Ceramics for engines

NASA Technical Reports Server (NTRS)

Kiser, James D.; Levine, Stanley R.; Dicarlo, James A.

1987-01-01

Structural ceramics were under nearly continuous development for various heat engine applications since the early 1970s. These efforts were sustained by the properties that ceramics offer in the areas of high-temperature strength, environmental resistance, and low density and the large benefits in system efficiency and performance that can result. The promise of ceramics was not realized because their brittle nature results in high sensitivity to microscopic flaws and catastrophic fracture behavior. This translated into low reliability for ceramic components and thus limited their application in engines. For structural ceramics to successfully make inroads into the terrestrial heat engine market requires further advances in low cost, net shape fabrication of high reliability components, and improvements in properties such as toughness, and strength. These advances will lead to very limited use of ceramics in noncritical applications in aerospace engines. For critical aerospace applications, an additional requirement is that the components display markedly improved toughness and noncatastrophic or graceful fracture. Thus the major emphasis is on fiber-reinforced ceramics.

Properties and Applications of High Emissivity Composite Films Based on Far-Infrared Ceramic Powder

PubMed Central

Xiong, Yabo; Huang, Shaoyun; Wang, Wenqi; Liu, Xinghai; Li, Houbin

2017-01-01

Polymer matrix composite materials that can emit radiation in the far-infrared region of the spectrum are receiving increasing attention due to their ability to significantly influence biological processes. This study reports on the far-infrared emissivity property of composite films based on far-infrared ceramic powder. X-ray fluorescence spectrometry, Fourier transform infrared spectroscopy, thermogravimetric analysis, and X-ray powder diffractometry were used to evaluate the physical properties of the ceramic powder. The ceramic powder was found to be rich in aluminum oxide, titanium oxide, and silicon oxide, which demonstrate high far-infrared emissivity. In addition, the micromorphology, mechanical performance, dynamic mechanical properties, and far-infrared emissivity of the composite were analyzed to evaluate their suitability for strawberry storage. The mechanical properties of the far-infrared radiation ceramic (cFIR) composite films were not significantly influenced (p ≥ 0.05) by the addition of the ceramic powder. However, the dynamic mechanical analysis (DMA) properties of the cFIR composite films, including a reduction in damping and shock absorption performance, were significant influenced by the addition of the ceramic powder. Moreover, the cFIR composite films showed high far-infrared emissivity, which has the capability of prolonging the storage life of strawberries. This research demonstrates that cFIR composite films are promising for future applications. PMID:29186047

Properties and Applications of High Emissivity Composite Films Based on Far-Infrared Ceramic Powder.

PubMed

Xiong, Yabo; Huang, Shaoyun; Wang, Wenqi; Liu, Xinghai; Li, Houbin

2017-11-29

Polymer matrix composite materials that can emit radiation in the far-infrared region of the spectrum are receiving increasing attention due to their ability to significantly influence biological processes. This study reports on the far-infrared emissivity property of composite films based on far-infrared ceramic powder. X-ray fluorescence spectrometry, Fourier transform infrared spectroscopy, thermogravimetric analysis, and X-ray powder diffractometry were used to evaluate the physical properties of the ceramic powder. The ceramic powder was found to be rich in aluminum oxide, titanium oxide, and silicon oxide, which demonstrate high far-infrared emissivity. In addition, the micromorphology, mechanical performance, dynamic mechanical properties, and far-infrared emissivity of the composite were analyzed to evaluate their suitability for strawberry storage. The mechanical properties of the far-infrared radiation ceramic (cFIR) composite films were not significantly influenced ( p ≥ 0.05) by the addition of the ceramic powder. However, the dynamic mechanical analysis (DMA) properties of the cFIR composite films, including a reduction in damping and shock absorption performance, were significant influenced by the addition of the ceramic powder. Moreover, the cFIR composite films showed high far-infrared emissivity, which has the capability of prolonging the storage life of strawberries. This research demonstrates that cFIR composite films are promising for future applications.

Ceramic high pressure gas path seal

NASA Technical Reports Server (NTRS)

Liotta, G. C.

1987-01-01

Stage 1 ceramic shrouds (high pressure turbine gas path seal) were developed for the GE T700 turbine helicopter engine under the Army/NASA Contract NAS3-23174. This contract successfully proved the viability and benefits of a Stage 1 ceramic shroud for production application. Stage 1 ceramic shrouds were proven by extensive component and engine testing. This Stage 1 ceramic shroud, plasma sprayed ceramic (ZrOs-BY2O3) and bond coating (NiCrAlY) onto a cast metal backing, offers significant engine performance improvement. Due to the ceramic coating, the amount of cooling air required is reduced 20% resulting in a 0.5% increase in horsepower and a 0.3% decrease in specific fuel consumption. This is accomplished with a component which is lower in cost than the current production shroud. Stage 1 ceramic shrouds will be introduced into field service in late 1987.

Processing and Material Characterization of Continuous Basalt Fiber Reinforced Ceramic Matrix Composites Using Polymer Derived Ceramics.

NASA Technical Reports Server (NTRS)

Cox, Sarah B.

2014-01-01

The need for high performance vehicles in the aerospace industry requires materials which can withstand high loads and high temperatures. New developments in launch pads and infrastructure must also be made to handle this intense environment with lightweight, reusable, structural materials. By using more functional materials, better performance can be seen in the launch environment, and launch vehicle designs which have not been previously used can be considered. The development of high temperature structural composite materials has been very limited due to the high cost of the materials and the processing needed. Polymer matrix composites can be used for temperatures up to 260C. Ceramics can take much higher temperatures, but they are difficult to produce and form in bulk volumes. Polymer Derived Ceramics (PDCs) begin as a polymer matrix, allowing a shape to be formed and cured and then to be pyrolized in order to obtain a ceramic with the associated thermal and mechanical properties. The use of basalt in structural and high temperature applications has been under development for over 50 years, yet there has been little published research on the incorporation of basalt fibers as a reinforcement in the composites. In this study, continuous basalt fiber reinforced PDCs have been fabricated and tested for the applicability of this composite system as a high temperature structural composite material. The oxyacetylene torch testing and three point bend testing have been performed on test panels and the test results are presented.

Recent Observations on the Performance of Hybrid Ceramic Tribo-Contacts

NASA Astrophysics Data System (ADS)

Buttery, M.; Cropper, M.; Wardzinski, B.; Lewis, S.; McLaren, S.; Kreuser, J.

2015-09-01

Hybrid ceramic ball bearings offer great promise in space applications but have not been rapidly adopted by industry perhaps partly due to the relatively low amount of published data on specific in-vacuum performance. Such bearings, having, typically, silicon nitride balls and 440C or high nitrogen steel (e.g. X30) raceways offer the potential for long life and low torque noise due a combination of chemical inertness, high hardness and the extremely smooth surfaces produced in ceramic balls. Though initial benefits were foreseen for high speed applications, the potential for reduced adhesive forces and wear in conditions of marginal lubrication, and for improvements in lubricant lifetime in long life applications limited by oil tribo-degradation render hybrid ceramic bearings more generally attractive.This paper draws together a number of experimental studies carried out at Pin-on-Disc (POD), Spiral Orbit Tribometer (SOT) and bearing-level recently at ESTL.

Development of lightweight ceramic ablators and arc-jet test results

NASA Technical Reports Server (NTRS)

Tran, Huy K.

1994-01-01

Lightweight ceramic ablators (LCA's) were recently developed at Ames to investigate the use of low density fibrous substrates and organic resins as high temperature, high strength ablative heat shields. Unlike the traditional ablators, LCA's use porous ceramic/carbon fiber matrices as substrates for structural support, and polymeric resins as fillers. Several substrates and resins were selected for the initial studies, and the best performing candidates were further characterized. Three arcjet tests were conducted to determine the LCA's thermal performance and ablation characteristics in a high enthalpy, hypersonic flow environment. Mass loss and recession measurements were obtained for each sample at post test, and the recession rates were determined from high speed motion films. Surface temperatures were also obtained from optical pyrometers.

Continuous Fiber Ceramic Composites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fareed, Ali; Craig, Phillip A.

2002-09-01

Fiber-reinforced ceramic composites demonstrate the high-temperature stability of ceramics--with an increased fracture toughness resulting from the fiber reinforcement of the composite. The material optimization performed under the continuous fiber ceramic composites (CFCC) included a series of systematic optimizations. The overall goals were to define the processing window, to increase the robustinous of the process, to increase process yield while reducing costs, and to define the complexity of parts that could be fabricated.

Fracture mechanics concepts in reliability analysis of monolithic ceramics

NASA Technical Reports Server (NTRS)

Manderscheid, Jane M.; Gyekenyesi, John P.

1987-01-01

Basic design concepts for high-performance, monolithic ceramic structural components are addressed. The design of brittle ceramics differs from that of ductile metals because of the inability of ceramic materials to redistribute high local stresses caused by inherent flaws. Random flaw size and orientation requires that a probabilistic analysis be performed in order to determine component reliability. The current trend in probabilistic analysis is to combine linear elastic fracture mechanics concepts with the two parameter Weibull distribution function to predict component reliability under multiaxial stress states. Nondestructive evaluation supports this analytical effort by supplying data during verification testing. It can also help to determine statistical parameters which describe the material strength variation, in particular the material threshold strength (the third Weibull parameter), which in the past was often taken as zero for simplicity.

Effect of hydrogen on the strength and microstructure of selected ceramics

NASA Technical Reports Server (NTRS)

Herbell, Thomas P.; Eckel, Andrew J.; Hull, David R.; Misra, Ajay K.

1990-01-01

Ceramics in monolithic form and as composite constituents in the form of fibers, matrices, and coatings are currently being considered for a variety of high-temperature applications in aeronautics and space. Many of these applications involve exposure to a hydrogen-containing environment. The compatibility of selected ceramics in gaseous high-temperature hydrogen is assessed. Environmental stability regimes for the long term use of ceramic materials are defined by the parameters of temperature, pressure, and moisture content. Thermodynamically predicted reactions between hydrogen and several monolithic ceramics are compared with actual performance in a controlled environment. Morphology of hydrogen attack and the corresponding strength degradation is reported for silicon carbide, silicon nitride, alumina, magnesia, and mullite.

Performance study of highly efficient 520 W average power long pulse ceramic Nd:YAG rod laser

NASA Astrophysics Data System (ADS)

Choubey, Ambar; Vishwakarma, S. C.; Ali, Sabir; Jain, R. K.; Upadhyaya, B. N.; Oak, S. M.

2013-10-01

We report the performance study of a 2% atomic doped ceramic Nd:YAG rod for long pulse laser operation in the millisecond regime with pulse duration in the range of 0.5-20 ms. A maximum average output power of 520 W with 180 J maximum pulse energy has been achieved with a slope efficiency of 5.4% using a dual rod configuration, which is the highest for typical lamp pumped ceramic Nd:YAG lasers. The laser output characteristics of the ceramic Nd:YAG rod were revealed to be nearly equivalent or superior to those of high-quality single crystal Nd:YAG rod. The laser pump chamber and resonator were designed and optimized to achieve a high efficiency and good beam quality with a beam parameter product of 16 mm mrad (M2˜47). The laser output beam was efficiently coupled through a 400 μm core diameter optical fiber with 90% overall transmission efficiency. This ceramic Nd:YAG laser will be useful for various material processing applications in industry.

Progress report

NASA Technical Reports Server (NTRS)

Abhiraman, A.; Collard, D.; Cardelino, B.; Bhatia, S.; Desai, P.; Harruna, I.; Khan, I.; Mariam, Y.; Mensah, T.; Mitchell, M.

1992-01-01

The NASA funding allowed Clark Atlanta University (CAU) to establish a High Performance Polymers And Ceramics (HiPPAC) Research Center. The HiPPAC Center is consolidating and expanding the existing polymer and ceramic research capabilities at CAU through the development of interdepartmental and interinstitutional research in: (1) polymer synthesis; (2) polymer characterization and properties; (3) polymer processing; (4) polymer-based ceramic synthesis; and (5) ceramic characterization and properties. This Center has developed strong interactions between scientists and materials scientists of CAU and their counterparts from sister institutions in the Atlanta University Center (AUC) and the Georgia Institute of Technology. As a component of the center, we have started to develop strong collaborations with scientists from other universities and the HBCU's, national and federal agency laboratories, and the private sector during this first year. During this first year we have refined the focus of the research in the HiPPAC Center to three areas with seven working groups that will start programmatic activities on January 1, 1993, as follows: (1) nonlinear optical properties of chitosan derivatives; (2) polymeric electronic materials; (3) nondestructive characterization and prediction of polyimide performance; (4) solution processing of high-performance materials; (5) processable polyimides for composite applications; (6) sol-gel based ceramic materials processing; and (7) synthetic based processing of pre-ceramic polymers.

Use of a Ceramic Membrane to Improve the Performance of Two-Separate-Phase Biocatalytic Membrane Reactor.

PubMed

Ranieri, Giuseppe; Mazzei, Rosalinda; Wu, Zhentao; Li, Kang; Giorno, Lidietta

2016-03-14

Biocatalytic membrane reactors (BMR) combining reaction and separation within the same unit have many advantages over conventional reactor designs. Ceramic membranes are an attractive alternative to polymeric membranes in membrane biotechnology due to their high chemical, thermal and mechanical resistance. Another important use is their potential application in a biphasic membrane system, where support solvent resistance is highly needed. In this work, the preparation of asymmetric ceramic hollow fibre membranes and their use in a two-separate-phase biocatalytic membrane reactor will be described. The asymmetric ceramic hollow fibre membranes were prepared using a combined phase inversion and sintering technique. The prepared fibres were then used as support for lipase covalent immobilization in order to develop a two-separate-phase biocatalytic membrane reactor. A functionalization method was proposed in order to increase the density of the reactive hydroxyl groups on the surface of ceramic membranes, which were then amino-activated and treated with a crosslinker. The performance and the stability of the immobilized lipase were investigated as a function of the amount of the immobilized biocatalytst. Results showed that it is possible to immobilize lipase on a ceramic membrane without altering its catalytic performance (initial residual specific activity 93%), which remains constant after 6 reaction cycles.

FIB/SEM and SEM/EDS microstructural analysis of metal-ceramic and zirconia-ceramic interfaces.

PubMed

Massimi, F; Merlati, G; Sebastiani, M; Battaini, P; Menghini, P; Bemporad, E

2012-01-10

Recently introduced FIB/SEM analysis in microscopy seems to provide a high-resolution characterization of the samples by 3D (FIB) cross-sectioning and (SEM) high resolution imaging. The aim of this study was to apply the FIB/SEM and SEM/EDS analysis to the interfaces of a metal-ceramic vs. two zirconia-ceramic systems. Plate samples of three different prosthetic systems were prepared in the dental lab following the manufacturers' instructions, where metal-ceramic was the result of a ceramic veneering (porcelain-fused-to-metal) and the two zirconia-ceramic systems were produced by the dedicated CAD-CAM procedures of the zirconia cores (both with final sintering) and then veneered by layered or heat pressed ceramics. In a FIB/SEM equipment (also called DualBeam), a thin layer of platinum (1 μm) was deposited on samples surface crossing the interfaces, in order to protect them during milling. Then, increasingly deeper trenches were milled by a focused ion beam, first using a relatively higher and later using a lower ion current (from 9 nA to 0.28 nA, 30KV). Finally, FEG-SEM (5KV) micrographs (1000-50,000X) were acquired. In a SEM the analysis of the morphology and internal microstructure was performed by 13KV secondary and backscattered electrons signals (in all the samples). The compositional maps were then performed by EDS probe only in the metal-ceramic system (20kV). Despite the presence of many voids in all the ceramic layers, it was possible to identify: (1) the grain structures of the metallic and zirconia substrates, (2) the thin oxide layer at the metal-ceramic interface and its interactions with the first ceramic layer (wash technique), (3) the roughness of the two different zirconia cores and their interactions with the ceramic interface, where the presence of zirconia grains in the ceramic layer was reported in two system possibly due to sandblasting before ceramic firing.

Net shaped high performance oxide ceramic parts by selective laser melting

NASA Astrophysics Data System (ADS)

Yves-Christian, Hagedorn; Jan, Wilkes; Wilhelm, Meiners; Konrad, Wissenbach; Reinhart, Poprawe

An additive manufacturing technique (AM) for ceramics, based on Al2O3-ZrO2 powder by means of Selective Laser Melting (SLM) is presented. Pure ceramic powder is completely melted by a laser beam yielding net-shaped specimens of almost 100% densities without any post-processing. Possible crack formation during the build-up process due to thermal stresses is prevented by a high-temperature preheating of above 1600 ∘C. Specimens with fine-grained nano-sized microstructures and flexural strengths of above 500 MPa are produced. The new technology allows for rapid freeform manufacture of complex net-shaped ceramics, thus, exploiting the outstanding mechanical and thermal properties for high-end medical and engineering disciplines.

Substitution of ceramics for high temperature alloys. [advantages of using silicon carbides and silicon nitrides in gas turbine engines

NASA Technical Reports Server (NTRS)

Probst, H. B.

1978-01-01

The high temperature capability of ceramics such as silicon nitride and silicon carbide can result in turbine engines of improved efficiency. Other advantages when compared to the nickel and cobalt alloys in current use are raw material availability, lower weight, erosion/corrosion resistance, and potentially lower cost. The use of ceramics in three different sizes of gas turbine is considered; these are the large utility turbines, advanced aircraft turbines, and small automotive turbines. Special consideration, unique to each of these applications, arise when one considers substituting ceramics for high temperature alloys. The effects of material substitutions are reviewed in terms of engine performance, operating economy, and secondary effects.

Lightweight high performance ceramic material

DOEpatents

Nunn, Stephen D [Knoxville, TN

2008-09-02

A sintered ceramic composition includes at least 50 wt. % boron carbide and at least 0.01 wt. % of at least one element selected from the group consisting of Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy Ho, Er, Tm, Yb, and Lu, the sintered ceramic composition being characterized by a density of at least 90% of theoretical density.

Thin film thermocouples for high temperature measurement on ceramic materials

NASA Technical Reports Server (NTRS)

Holanda, Raymond

1992-01-01

Thin film thermocouples have been developed for use on metal parts in jet engines to 1000 C. However, advanced propulsion systems are being developed that will use ceramic materials and reach higher temperatures. The purpose of this work is to develop thin film thermocouples for use on ceramic materials. The thin film thermocouples are Pt13Rh/Pt fabricated by the sputtering process. Lead wires are attached using the parallel-gap welding process. The ceramic materials are silicon nitride, silicon carbide, aluminum oxide, and mullite. Both steady state and thermal cycling furnace tests were performed in the temperature range to 1500 C. High-heating-rate tests were performed in an arc lamp heat-flux-calibration facility. The fabrication of the thin film thermocouples is described. The thin film thermocouple output was compared to a reference wire thermocouple. Drift of the thin film thermocouples was determined, and causes of drift are discussed. The results of high-heating-rate tests up to 2500 C/sec are presented. The stability of the ceramic materials is examined. It is concluded that Pt13Rh/Pt thin film thermocouples are capable of meeting lifetime goals of 50 hours or more up to temperatures of 1500 C depending on the stability of the particular ceramic substrate.

Investigation on Surface Insulation Strength of Machinable Ceramic Material under Pulsed Voltage in Vacuum

NASA Astrophysics Data System (ADS)

Zhang, Guan-Jun; Zhao, Wen-Bin; Ma, Xin-Pei; Li, Guang-Xin; Ma, Kui; Zheng, Nan; Yan, Zhang

Ceramic material has been widely used as insulator in vacuum. Their high hardness and brittle property brings some difficulty in the application. A new kind of machinable ceramic was invented recently. The ceramic can be machined easily and accurately after being sintered, which provides the possibility of making the insulator with fine and complicated configuration. The paper studies its surface insulation performance and flashover phenomena under pulsed excitation in vacuum. The ceramic samples with different crystallization parameters are tested under the vacuum level of 10-4 Pa. The machinable ceramic behaves better surface insulation performance than comparative the Al2O3 and glass sample. The effect of crystallization level on the trap density and flashover current is also presented. After flashover shots many times, the surface microscopic patterns of different samples are observed to investigate the damage status, which can be explained by the thermal damage mechanism.

High-temperature ceramic heat exchanger element for a solar thermal receiver

NASA Technical Reports Server (NTRS)

Strumpf, H. J.; Kotchick, D. M.; Coombs, M. G.

1982-01-01

A study has been completed on the development of a high-temperature ceramic heat exchanger element to be integrated into a solar reciver producing heated air. A number of conceptual designs were developed for heat exchanger elements of differing configuration. These were evaluated with respect to thermal performance, pressure drop, structural integrity, and fabricability. The final design selection identified a finned ceramic shell as the most favorable concept. The ceramic shell is surrounded by a larger metallic shell. The flanges of the two shells are sealed to provide a leak-tight pressure vessel. The ceramic shell is fabricated by an innovative combination of slip casting the receiver walls and precision casting the heat transfer finned plates. The fins are bonded to the shell during firing. Fabrication of a one-half scale demonstrator ceramic receiver has been completed.

Ceramic composite separators coated with moisturized ZrO(2) nanoparticles for improving the electrochemical performance and thermal stability of lithium ion batteries.

PubMed

Kim, Ki Jae; Kwon, Hyuk Kwon; Park, Min-Sik; Yim, Taeeun; Yu, Ji-Sang; Kim, Young-Jun

2014-05-28

We introduce a ceramic composite separator prepared by coating moisturized ZrO2 nanoparticles with a poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-12wt%HFP) copolymer on a polyethylene separator. The effect of moisturized ZrO2 nanoparticles on the morphology and the microstructure of the polymeric coating layer is investigated. A large number of micropores formed around the embedded ZrO2 nanoparticles in the coating layer as a result of the phase inversion caused by the adsorbed moisture. The formation of micropores highly affects the ionic conductivity and electrolyte uptake of the ceramic composite separator and, by extension, the rate discharge properties of lithium ion batteries. In particular, thermal stability of the ceramic composite separators coated with the highly moisturized ZrO2 nanoparticles (a moisture content of 16 000 ppm) is dramatically improved without any degradation in electrochemical performance compared to the performance of pristine polyethylene separators.

Demonstrating the potential of yttrium-doped barium zirconate electrolyte for high-performance fuel cells.

PubMed

Bae, Kiho; Jang, Dong Young; Choi, Hyung Jong; Kim, Donghwan; Hong, Jongsup; Kim, Byung-Kook; Lee, Jong-Ho; Son, Ji-Won; Shim, Joon Hyung

2017-02-23

In reducing the high operating temperatures (≥800 °C) of solid-oxide fuel cells, use of protonic ceramics as an alternative electrolyte material is attractive due to their high conductivity and low activation energy in a low-temperature regime (≤600 °C). Among many protonic ceramics, yttrium-doped barium zirconate has attracted attention due to its excellent chemical stability, which is the main issue in protonic-ceramic fuel cells. However, poor sinterability of yttrium-doped barium zirconate discourages its fabrication as a thin-film electrolyte and integration on porous anode supports, both of which are essential to achieve high performance. Here we fabricate a protonic-ceramic fuel cell using a thin-film-deposited yttrium-doped barium zirconate electrolyte with no impeding grain boundaries owing to the columnar structure tightly integrated with nanogranular cathode and nanoporous anode supports, which to the best of our knowledge exhibits a record high-power output of up to an order of magnitude higher than those of other reported barium zirconate-based fuel cells.

High-Performance Flexible Single-Crystalline Silicon Nanomembrane Thin-Film Transistors with High- k Nb2O5-Bi2O3-MgO Ceramics as Gate Dielectric on a Plastic Substrate.

PubMed

Qin, Guoxuan; Zhang, Yibo; Lan, Kuibo; Li, Lingxia; Ma, Jianguo; Yu, Shihui

2018-04-18

A novel method of fabricating flexible thin-film transistor based on single-crystalline Si nanomembrane (SiNM) with high- k Nb 2 O 5 -Bi 2 O 3 -MgO (BMN) ceramic gate dielectric on a plastic substrate is demonstrated in this paper. SiNMs are successfully transferred to a flexible polyethylene terephthalate substrate, which has been plated with indium-tin-oxide (ITO) conductive layer and high- k BMN ceramic gate dielectric layer by room-temperature magnetron sputtering. The BMN ceramic gate dielectric layer demonstrates as high as ∼109 dielectric constant, with only dozens of pA current leakage. The Si-BMN-ITO heterostructure has only ∼nA leakage current at the applied voltage of 3 V. The transistor is shown to work at a high current on/off ratio of above 10 4 , and the threshold voltage is ∼1.3 V, with over 200 cm 2 /(V s) effective channel electron mobility. Bending tests have been conducted and show that the flexible transistors have good tolerance on mechanical bending strains. These characteristics indicate that the flexible single-crystalline SiNM transistors with BMN ceramics as gate dielectric have great potential for applications in high-performance integrated flexible circuit.

Large size crystalline vs. co-sintered ceramic Yb(3+):YAG disk performance in diode pumped amplifiers.

PubMed

Albach, Daniel; Chanteloup, Jean-Christophe

2015-01-12

A comprehensive experimental benchmarking of Yb(3+):YAG crystalline and co-sintered ceramic disks of similar thickness and doping level is presented in the context of high average power laser amplifier operation. Comparison is performed considering gain, depolarization and wave front deformation quantitative measurements and analysis.

An insight into current concepts and techniques in resin bonding to high strength ceramics.

PubMed

Luthra, R; Kaur, P

2016-06-01

Reliable bonding between high strength ceramics and resin composite cement is difficult to achieve because of their chemical inertness and lack of silica content. The aim of this review was to assess the current literature describing methods for resin bonding to ceramics with high flexural strength such as glass-infiltrated alumina and zirconia, densely sintered alumina and yttria-partially stabilized tetragonal zirconia polycrystalline ceramic (Y-TZP) with respect to bond strength and bond durability. Suitable peer reviewed publications in the English language were identified through searches performed in PubMed, Google Search and handsearches. The keywords or phrases used were 'resin-ceramic bond', 'silane coupling agents', 'air particle abrasion', 'zirconia ceramic' and 'resin composite cements'. Studies from January 1989 to June 2015 were included. The literature demonstrated that there are multiple techniques available for surface treatments but bond strength testing under different investigations have produced conflicting results. Within the scope of this review, there is no evidence to support a universal technique of ceramic surface treatment for adhesive cementation. A combination of chemical and mechanical treatments might be the recommended solution. The hydrolytic stability of the resin ceramic bond should be enhanced. © 2016 Australian Dental Association.

Alumina ceramic based high-temperature performance of wireless passive pressure sensor

NASA Astrophysics Data System (ADS)

Wang, Bo; Wu, Guozhu; Guo, Tao; Tan, Qiulin

2016-12-01

A wireless passive pressure sensor equivalent to inductive-capacitive (LC) resonance circuit and based on alumina ceramic is fabricated by using high temperature sintering ceramic and post-fire metallization processes. Cylindrical copper spiral reader antenna and insulation layer are designed to realize the wireless measurement for the sensor in high temperature environment. The high temperature performance of the sensor is analyzed and discussed by studying the phase-frequency and amplitude-frequency characteristics of reader antenna. The average frequency change of sensor is 0.68 kHz/°C when the temperature changes from 27°C to 700°C and the relative change of twice measurements is 2.12%, with high characteristic of repeatability. The study of temperature-drift characteristic of pressure sensor in high temperature environment lays a good basis for the temperature compensation methods and insures the pressure signal readout accurately.

The Processing and Mechanical Properties of High Temperature/High Performance Composites. Book 5. Interface Effects

DTIC Science & Technology

1994-04-01

Interfacial Mechanical Properties in Fiber Reinforced Ceramic Composites," 1. Am. Ceram. Soc., 70 (1987) 542-48. [25] P.D. Jero, R.J. Kerans and T.A...Mater., 40 [611251-57 (1992). [16] D.B. Marshall and W. Oliver, "Measurement of Interfacial Mechanical Properties in Fiber-Reinforced Ceramic...Charlottesville. VA 22903, U.S.A. (Received 14 July 1993;fl/al version acepted IS AustrW 1993) Abstract-The interfacial structure / property relationships of a

Ultrahigh Piezoelectric Properties in Textured (K,Na)NbO3 -Based Lead-Free Ceramics.

PubMed

Li, Peng; Zhai, Jiwei; Shen, Bo; Zhang, Shujun; Li, Xiaolong; Zhu, Fangyuan; Zhang, Xingmin

2018-02-01

High-performance lead-free piezoelectric materials are in great demand for next-generation electronic devices to meet the requirement of environmentally sustainable society. Here, ultrahigh piezoelectric properties with piezoelectric coefficients (d 33 ≈700 pC N -1 , d 33 * ≈980 pm V -1 ) and planar electromechanical coupling factor (k p ≈76%) are achieved in highly textured (K,Na)NbO 3 (KNN)-based ceramics. The excellent piezoelectric properties can be explained by the strong anisotropic feature, optimized engineered domain configuration in the textured ceramics, and facilitated polarization rotation induced by the intermediate phase. In addition, the nanodomain structures with decreased domain wall energy and increased domain wall mobility also contribute to the ultrahigh piezoelectric properties. This work not only demonstrates the tremendous potential of KNN-based ceramics to replace lead-based piezoelectrics but also provides a good strategy to design high-performance piezoelectrics by controlling appropriate phase and crystallographic orientation. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Ceramic Processing

DOE Office of Scientific and Technical Information (OSTI.GOV)

EWSUK,KEVIN G.

1999-11-24

Ceramics represent a unique class of materials that are distinguished from common metals and plastics by their: (1) high hardness, stiffness, and good wear properties (i.e., abrasion resistance); (2) ability to withstand high temperatures (i.e., refractoriness); (3) chemical durability; and (4) electrical properties that allow them to be electrical insulators, semiconductors, or ionic conductors. Ceramics can be broken down into two general categories, traditional and advanced ceramics. Traditional ceramics include common household products such as clay pots, tiles, pipe, and bricks, porcelain china, sinks, and electrical insulators, and thermally insulating refractory bricks for ovens and fireplaces. Advanced ceramics, also referredmore » to as ''high-tech'' ceramics, include products such as spark plug bodies, piston rings, catalyst supports, and water pump seals for automobiles, thermally insulating tiles for the space shuttle, sodium vapor lamp tubes in streetlights, and the capacitors, resistors, transducers, and varistors in the solid-state electronics we use daily. The major differences between traditional and advanced ceramics are in the processing tolerances and cost. Traditional ceramics are manufactured with inexpensive raw materials, are relatively tolerant of minor process deviations, and are relatively inexpensive. Advanced ceramics are typically made with more refined raw materials and processing to optimize a given property or combination of properties (e.g., mechanical, electrical, dielectric, optical, thermal, physical, and/or magnetic) for a given application. Advanced ceramics generally have improved performance and reliability over traditional ceramics, but are typically more expensive. Additionally, advanced ceramics are typically more sensitive to the chemical and physical defects present in the starting raw materials, or those that are introduced during manufacturing.« less

Grain-Size-Dependent Thermoelectric Properties of SrTiO3 3D Superlattice Ceramics

NASA Astrophysics Data System (ADS)

Zhang, Rui-zhi; Koumoto, Kunihito

2013-07-01

The thermoelectric (TE) performance of SrTiO3 (STO) 3D superlattice ceramics with 2D electron gas grain boundaries (GBs) was theoretically investigated. The grain size dependence of the power factor, lattice thermal conductivity, and ZT value were calculated by using Boltzmann transport equations. It was found that nanostructured STO ceramics with smaller grain size have larger ZT value. This is because the quantum confinement effect, energy filtering effect, and interfacial phonon scattering at GBs all become stronger with decreasing grain size, resulting in higher power factor and lower lattice thermal conductivity. These findings will aid the design of nanostructured oxide ceramics with high TE performance.

Polymer, metal and ceramic matrix composites for advanced aircraft engine applications

NASA Technical Reports Server (NTRS)

Mcdanels, D. L.; Serafini, T. T.; Dicarlo, J. A.

1985-01-01

Advanced aircraft engine research within NASA Lewis is being focused on propulsion systems for subsonic, supersonic, and hypersonic aircraft. Each of these flight regimes requires different types of engines, but all require advanced materials to meet their goals of performance, thrust-to-weight ratio, and fuel efficiency. The high strength/weight and stiffness/weight properties of resin, metal, and ceramic matrix composites will play an increasingly key role in meeting these performance requirements. At NASA Lewis, research is ongoing to apply graphite/polyimide composites to engine components and to develop polymer matrices with higher operating temperature capabilities. Metal matrix composites, using magnesium, aluminum, titanium, and superalloy matrices, are being developed for application to static and rotating engine components, as well as for space applications, over a broad temperature range. Ceramic matrix composites are also being examined to increase the toughness and reliability of ceramics for application to high-temperature engine structures and components.

Electromechanical properties of A-site (LiCe)-modified sodium bismuth titanate (Na0.5Bi4.5Ti4O15) piezoelectric ceramics at elevated temperature

NASA Astrophysics Data System (ADS)

Wang, Chun-Ming; Wang, Jin-Feng; Zhang, Shujun; Shrout, Thomas R.

2009-05-01

The Aurivillius-type bismuth layer-structured (NaBi)0.46(LiCe)0.04Bi4Ti4O15 (NBT-LiCe) piezoelectric ceramics were synthesized using conventional solid-state processing. Phase analysis was performed by x-ray diffraction and microstructural morphology was assessed by scanning electron microscopy. The dielectric, piezoelectric, ferroelectric, and electromechanical properties of NBT-LiCe ceramics were investigated. The piezoelectric activities were found to be significantly enhanced compared to NBT ceramics, which can be attributed to the lattice distortion and the presence of bismuth vacancies. The dielectric and electromechanical properties of NBT-LiCe ceramics at elevated temperature were investigated in detail. The excellent piezoelectric, dielectric, and electromechanical properties, coupled with high Curie temperature (Tc=660 °C), demonstrated that the NBT-LiCe ceramics are the promising candidates for high temperature applications.

Environmental Barrier Coatings for Turbine Engines: A Design and Performance Perspective

NASA Technical Reports Server (NTRS)

Zhu, Dongming; Fox, Dennis S.; Ghosn, Louis; Smialek, James L.; Miller, Robert A.

2009-01-01

Ceramic thermal and environmental barrier coatings (TEBC) for SiC-based ceramics will play an increasingly important role in future gas turbine engines because of their ability to effectively protect the engine components and further raise engine temperatures. However, the coating long-term durability remains a major concern with the ever-increasing temperature, strength and stability requirements in engine high heat-flux combustion environments, especially for highly-loaded rotating turbine components. Advanced TEBC systems, including nano-composite based HfO2-aluminosilicate and rare earth silicate coatings are being developed and tested for higher temperature capable SiC/SiC ceramic matrix composite (CMC) turbine blade applications. This paper will emphasize coating composite and multilayer design approach and the resulting performance and durability in simulated engine high heat-flux, high stress and high pressure combustion environments. The advances in the environmental barrier coating development showed promise for future rotating CMC blade applications.

Thermal and Environmental Barrier Coatings for Advanced Propulsion Engine Systems

NASA Technical Reports Server (NTRS)

Zhu, Dong-Ming; Miller, Robert A.

2004-01-01

Ceramic thermal and environmental barrier coatings (TEBCs) are used in gas turbine engines to protect engine hot-section components in the harsh combustion environments, and extend component lifetimes. For future high performance engines, the development of advanced ceramic barrier coating systems will allow these coatings to be used to simultaneously increase engine operating temperature and reduce cooling requirements, thereby leading to significant improvements in engine power density and efficiency. In order to meet future engine performance and reliability requirements, the coating systems must be designed with increased high temperature stability, lower thermal conductivity, and improved thermal stress and erosion resistance. In this paper, ceramic coating design and testing considerations will be described for high temperature and high-heat-flux engine applications in hot corrosion and oxidation, erosion, and combustion water vapor environments. Further coating performance and life improvements will be expected by utilizing advanced coating architecture design, composition optimization, and improved processing techniques, in conjunction with modeling and design tools.

Lightweight Ceramics for Aeroacoustic Applications

NASA Technical Reports Server (NTRS)

Kwan, H. W.; Spamer, G. T.; Yu, J.; Yasukawa, B.

1997-01-01

The use of a HTP (High Temperature Performance) ceramic foam for aeroacoustic applications is investigated. HTP ceramic foam is a composition of silica and alumina fibers developed by LMMS. This foam is a lightweight high-temperature fibrous bulk material with small pore size, ultra high porosity, and good strength. It can be used as a broadband noise absorber at both room and high temperature (up to 1800 F). The investigation included an acoustic assessment as well as material development, and environmental and structural evaluations. The results show that the HTP ceramic foam provides good broadband noise absorbing capability and adequate strength when incorporating the HTP ceramic foam system into a honeycomb sandwich structure. On the other hand, the material is sensitive to Skydrol and requires further improvements. Good progress has been made in the impedance model development. A relationship between HTP foam density, flow resistance, and tortuosity will be established in the near future. Additional effort is needed to investigate the coupling effects between face sheet and HTP foam material.

Tribology of ceramics: Report of the Committee on Tribology of Ceramics

NASA Technical Reports Server (NTRS)

1988-01-01

The current state of knowledge of ceramic surface structures, composition, and reactivity is reviewed. The tribological requirements of advanced mechanical systems now being deployed (in particular, heat engines) exceed the capabilities of traditional metallic-based materials because of the high temperatures encountered. Advanced ceramic materials for such applications are receiving intense scrutiny, but there is a lack of understanding of the properties and behavior of ceramic surfaces and the influence of processing on the properties of ceramics is described. The adequacy of models, ranging form atomic to macro, to describe and to predict ceramic friction and wear are discussed, as well as what is known about lubrication at elevated temperatures. From this analysis, recommendations are made for coordination, research, and development that will lead to better performance of ceramic materials in tribological systems.

Investigation on the effect of sintering temperature on kaolin hollow fibre membrane for dye filtration.

PubMed

Mohtor, Nur Hamizah; Othman, Mohd Hafiz Dzarfan; Ismail, Ahmad Fauzi; Rahman, Mukhlis A; Jaafar, Juhana; Hashim, Nur Awanis

2017-07-01

Despite its extraordinary price, ceramic membrane can still be able to surpass polymeric membrane in the applications that require high temperature and pressure conditions, as well as harsh chemical environment. In order to alleviate the high cost of ceramic material that still becomes one of the major factors that contributes to the high production cost of ceramic membrane, various attempts have been made to use low cost ceramic materials as alternatives to well-known expensive ceramic materials such as alumina, silica, and zirconia in the fabrication of ceramic membrane. Thus, local Malaysian kaolin has been chosen as the ceramic material in this study for the preparation of kaolin hollow fibre membrane since it is inexpensive and naturally abundant in Malaysia. Due to the fact that the sintering process plays a prominent role in obtaining the desired morphology, properties, and performances of prepared ceramic membrane, the aim of this work was to study the effect of different sintering temperatures applied (ranging from 1200 to 1500 °C) in the preparation of kaolin hollow fibre membrane via dry/wet phase inversion-based spinning technique and sintering process. The morphology and properties of membrane were then characterised by SEM, AFM, FTIR, XRD, and three-point bending test, while the performances of membrane were investigated by conducting water permeation and Reactive Black 5 (RB5) dye rejection tests. From the experimental results obtained, the sintering temperature of 1400 °C could be selected as the optimum sintering temperature in preparing the kaolin hollow fibre membrane with the dense sponge-like structure of separation layer that resulted in the good mechanical strength of 70 MPa with the appreciable water permeation of 75 L/h m 2  bar and RB5 rejection of 68%.

The uniformity and imaging properties of some new ceramic scintillators

NASA Astrophysics Data System (ADS)

Chac, George T. L.; Miller, Brian W.; Shah, Kanai; Baldoni, Gary; Domanik, Kenneth J.; Bora, Vaibhav; Cherepy, Nerine J.; Seeley, Zachary; Barber, H. Bradford

2012-10-01

Results are presented of investigations into the composition, uniformity and gamma-ray imaging performance of new ceramic scintillators with synthetic garnet structure. The ceramic scintillators were produced by a process that uses flame pyrolysis to make nanoparticles which are sintered into a ceramic and then compacted by hot isostatic compression into a transparent material. There is concern that the resulting ceramic scintillator might not have the uniformity of composition necessary for use in gamma-ray spectroscopy and gamma-ray imaging. The compositional uniformity of four samples of three ceramic scintillator types (GYGAG:Ce, GLuGAG:Ce and LuAG:Pr) was tested using an electron microprobe. It was found that all samples were uniform in elemental composition to the limit of sensitivity of the microprobe (few tenths of a percent atomic) over distance scales from ~ 1 cm to ~ 1 um. The light yield and energy resolution of all ceramic scintillator samples were mapped with a highly collimated 57Co source (122 keV) and performance was uniform at mapping scale of 0.25 mm. Good imaging performance with single gamma-ray photon detection was demonstrated for all samples using a BazookaSPECT system, and the imaging spatial resolution, measured as the FWHM of a LSF was 150 um.

Ceramic fibers for matrix composites in high-temperature engine applications

PubMed

Baldus; Jansen; Sporn

1999-07-30

High-temperature engine applications have been limited by the performance of metal alloys and carbide fiber composites at elevated temperatures. Random inorganic networks composed of silicon, boron, nitrogen, and carbon represent a novel class of ceramics with outstanding durability at elevated temperatures. SiBN(3)C was synthesized by pyrolysis of a preceramic N-methylpolyborosilazane made from the single-source precursor Cl(3)Si-NH-BCl(2). The polymer can be processed to a green fiber by melt-spinning, which then undergoes an intermediate curing step and successive pyrolysis. The ceramic fibers, which are presently produced on a semitechnical scale, combine several desired properties relevant for an application in fiber-reinforced ceramic composites: thermal stability, mechanical strength, high-temperature creep resistivity, low density, and stability against oxidation or molten silicon.

Influence of electrical resistivity and machining parameters on electrical discharge machining performance of engineering ceramics.

PubMed

Ji, Renjie; Liu, Yonghong; Diao, Ruiqiang; Xu, Chenchen; Li, Xiaopeng; Cai, Baoping; Zhang, Yanzhen

2014-01-01

Engineering ceramics have been widely used in modern industry for their excellent physical and mechanical properties, and they are difficult to machine owing to their high hardness and brittleness. Electrical discharge machining (EDM) is the appropriate process for machining engineering ceramics provided they are electrically conducting. However, the electrical resistivity of the popular engineering ceramics is higher, and there has been no research on the relationship between the EDM parameters and the electrical resistivity of the engineering ceramics. This paper investigates the effects of the electrical resistivity and EDM parameters such as tool polarity, pulse interval, and electrode material, on the ZnO/Al2O3 ceramic's EDM performance, in terms of the material removal rate (MRR), electrode wear ratio (EWR), and surface roughness (SR). The results show that the electrical resistivity and the EDM parameters have the great influence on the EDM performance. The ZnO/Al2O3 ceramic with the electrical resistivity up to 3410 Ω·cm can be effectively machined by EDM with the copper electrode, the negative tool polarity, and the shorter pulse interval. Under most machining conditions, the MRR increases, and the SR decreases with the decrease of electrical resistivity. Moreover, the tool polarity, and pulse interval affect the EWR, respectively, and the electrical resistivity and electrode material have a combined effect on the EWR. Furthermore, the EDM performance of ZnO/Al2O3 ceramic with the electrical resistivity higher than 687 Ω·cm is obviously different from that with the electrical resistivity lower than 687 Ω·cm, when the electrode material changes. The microstructure character analysis of the machined ZnO/Al2O3 ceramic surface shows that the ZnO/Al2O3 ceramic is removed by melting, evaporation and thermal spalling, and the material from the working fluid and the graphite electrode can transfer to the workpiece surface during electrical discharge machining ZnO/Al2O3 ceramic.

[Relative fracture toughness of differents dental ceramics].

PubMed

Pagani, Clovis; Miranda, Carolina Baptista; Bottino, Marco Cícero

2003-03-01

Although ceramics present high compressive strength, they are brittle materials due to their low tensile strength so they have lower capacity to absorb shocks. This study evaluated the fracture toughness of different ceramic systems, which refers to the ability of a friable material to absorb defformation energy. Three ceramic systems were investigated. Ten cylindrical samples (5,0mm x 3,0mm), were obtained from each ceramic material as follows: G1- 10 samples of Vitadur Alpha (Vita-Zahnfabrik); G2- 10 samples of IPS Empress2 (Ivoclar-Vivadent); G3- 10 samples of In-Ceram Alumina (Vita-Zahnfabrik). Fracture toughness values were collected upon indentation tests that were performed under a heavy load. A microhardness tester (Digital Microhardness Tester FM) utilized a 500gf load cell during 10seconds to perform four impressions on each sample. Statistically significant results were observed (ANOVA and Kruskal-Wallis tests). In-Ceram Alumina presented the highest median toughness values (2,96N/m3/2), followed by Vitadur Alpha (2,08N/m3/2) and IPS Empress2 (1,05N/m3/2). It may be concluded that different ceramic systems present distinct fracture toughness values, thus In-Ceram is capable of absorbing superior stress when compared to Vitadur Alpha and IPS Empress2.

Critical Needs for Robust and Reliable Database for Design and Manufacturing of Ceramic Matrix Composites

NASA Technical Reports Server (NTRS)

Singh, M.

1999-01-01

Ceramic matrix composite (CMC) components are being designed, fabricated, and tested for a number of high temperature, high performance applications in aerospace and ground based systems. The critical need for and the role of reliable and robust databases for the design and manufacturing of ceramic matrix composites are presented. A number of issues related to engineering design, manufacturing technologies, joining, and attachment technologies, are also discussed. Examples of various ongoing activities in the area of composite databases. designing to codes and standards, and design for manufacturing are given.

Manufacturing aspheric mirrors made of zero thermal expansion cordierite ceramics using Magnetorheological Finishing (MRF)

NASA Astrophysics Data System (ADS)

Sugawara, Jun; Maloney, Chris

2016-07-01

NEXCERATM cordierite ceramics, which have ultra-low thermal expansion properties, are perfect candidate materials to be used for light-weight satellite mirrors that are used for geostationary earth observation and for mirrors used in ground-based astronomical metrology. To manufacture the high precision aspheric shapes required, the deterministic aspherization and figure correction capabilities of Magnetorheological Finishing (MRF) are tested. First, a material compatibility test is performed to determine the best method for achieving the lowest surface roughness of RMS 0.8nm on plano surfaces made of NEXCERATM ceramics. Secondly, we will use MRF to perform high precision figure correction and to induce a hyperbolic shape into a conventionally polished 100mm diameter sphere.

A high temperature testing system for ceramic composites

NASA Technical Reports Server (NTRS)

Hemann, John

1994-01-01

Ceramic composites are presently being developed for high temperature use in heat engine and space power system applications. The operating temperature range is expected to be 1090 to 1650 C (2000 F to 3000 F). Very little material data is available at these temperatures and, therefore, it is desirable to thoroughly characterize the basic unidirectional fiber reinforced ceramic composite. This includes testing mainly for mechanical material properties at high temperatures. The proper conduct of such characterization tests requires the development of a tensile testing system includes unique gripping, heating, and strain measuring devices which require special considerations. The system also requires an optimized specimen shape. The purpose of this paper is to review various techniques for measuring displacements or strains, preferably at elevated temperatures. Due to current equipment limitations it is assumed that the specimen is to be tested at a temperature of 1430 C (2600F) in an oxidizing atmosphere. For the most part, previous high temperature material characterization tests, such as flexure and tensile tests, have been performed in inert atmospheres. Due to the harsh environment in which the ceramic specimen is to be tested, many conventional strain measuring techniques can not be applied. Initially a brief description of the more commonly used mechanical strain measuring techniques is given. Major advantages and disadvantages with their application to high temperature tensile testing of ceramic composites are discussed. Next, a general overview is given for various optical techniques. Advantages and disadvantages which are common to these techniques are noted. The optical methods for measuring strain or displacement are categorized into two sections. These include real-time techniques. Finally, an optical technique which offers optimum performance with the high temperature tensile testing of ceramic composites is recommended.

Ceramic Integration Technologies for Advanced Energy Systems: Critical Needs, Technical Challenges, and Opportunities

NASA Technical Reports Server (NTRS)

Singh, Mrityunjay

2010-01-01

Advanced ceramic integration technologies dramatically impact the energy landscape due to wide scale application of ceramics in all aspects of alternative energy production, storage, distribution, conservation, and efficiency. Examples include fuel cells, thermoelectrics, photovoltaics, gas turbine propulsion systems, distribution and transmission systems based on superconductors, nuclear power generation and waste disposal. Ceramic integration technologies play a key role in fabrication and manufacturing of large and complex shaped parts with multifunctional properties. However, the development of robust and reliable integrated systems with optimum performance requires the understanding of many thermochemical and thermomechanical factors, particularly for high temperature applications. In this presentation, various needs, challenges, and opportunities in design, fabrication, and testing of integrated similar (ceramic ceramic) and dissimilar (ceramic metal) material www.nasa.gov 45 ceramic-ceramic-systems have been discussed. Experimental results for bonding and integration of SiC based Micro-Electro-Mechanical-Systems (MEMS) LDI fuel injector and advanced ceramics and composites for gas turbine applications are presented.

Novel, Ceramic Membrane System For Hydrogen Separation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Elangovan, S.

2012-12-31

Separation of hydrogen from coal gas represents one of the most promising ways to produce alternative sources of fuel. Ceramatec, teamed with CoorsTek and Sandia National Laboratories has developed materials technology for a pressure driven, high temperature proton-electron mixed conducting membrane system to remove hydrogen from the syngas. This system separates high purity hydrogen and isolates high pressure CO{sub 2} as the retentate, which is amenable to low cost capture and transport to storage sites. The team demonstrated a highly efficient, pressure-driven hydrogen separation membrane to generate high purity hydrogen from syngas using a novel ceramic-ceramic composite membrane. Recognizing themore » benefits and limitations of present membrane systems, the all-ceramic system has been developed to address the key technical challenges related to materials performance under actual operating conditions, while retaining the advantages of thermal and process compatibility offered by the ceramic membranes. The feasibility of the concept has already been demonstrated at Ceramatec. This project developed advanced materials composition for potential integration with water gas shift rectors to maximize the hydrogenproduction.« less

Textured Na x CoO2 Ceramics Sintered from Hydrothermal Platelet Nanocrystals: Growth Mechanism and Transport Properties

NASA Astrophysics Data System (ADS)

Zhang, Wei; Liu, Pengcheng; Wang, Yifeng; Zhu, Kongjun; Tai, Guoan; Liu, Jinsong; Wang, Jing; Yan, Kang; Zhang, Jianhui

2018-05-01

Nanostructuring is an effective approach to improve thermoelectric (TE) performance, which is caused by the interface and quantum effects on electron and phonon transport. For a typical layered structure such as sodium cobalt (NCO), a highly textured ceramic with nanostructure is beneficial for the carrier transport properties due to the strong anisotropy. In this paper, we established a textured NCO ceramic with highly oriented single crystals in nanoscale. The Na0.6CoO2 platelet crystals were prepared by a one-step hydrothermal method. The growth mechanism was revealed to involve dissolution-recrystallization and exchange reactions. NCO TE ceramics fabricated by a press-aided spark plasma sintering method showed a high degree of texturing, with the platelet crystals basically lying along the in-plane direction perpendicular to the press direction. TE properties of the textured NCO ceramics showed a strong anisotropic behavior. The in-plane electrical conductivity was considerably larger than the out-of-plane data because of fewer grain boundaries and interfaces that existed in the in-plane direction. Moreover, the in-plane Seebeck coefficient was higher because of the anisotropic electronic nature of NCO. Although the in-plane thermal conductivity was high, a prior ZT value was enabled for these NCO ceramics along this direction because of the dominant electrical transport. This finding provides a new approach to prepare highly oriented ceramics.

Loading capacity of zirconia implant supported hybrid ceramic crowns.

PubMed

Rohr, Nadja; Coldea, Andrea; Zitzmann, Nicola U; Fischer, Jens

2015-12-01

Recently a polymer infiltrated hybrid ceramic was developed, which is characterized by a low elastic modulus and therefore may be considered as potential material for implant supported single crowns. The purpose of the study was to evaluate the loading capacity of hybrid ceramic single crowns on one-piece zirconia implants with respect to the cement type. Fracture load tests were performed on standardized molar crowns milled from hybrid ceramic or feldspar ceramic, cemented to zirconia implants with either machined or etched intaglio surface using four different resin composite cements. Flexure strength, elastic modulus, indirect tensile strength and compressive strength of the cements were measured. Statistical analysis was performed using two-way ANOVA (p=0.05). The hybrid ceramic exhibited statistically significant higher fracture load values than the feldspar ceramic. Fracture load values and compressive strength values of the respective cements were correlated. Highest fracture load values were achieved with an adhesive cement (1253±148N). Etching of the intaglio surface did not improve the fracture load. Loading capacity of hybrid ceramic single crowns on one-piece zirconia implants is superior to that of feldspar ceramic. To achieve maximal loading capacity for permanent cementation of full-ceramic restorations on zirconia implants, self-adhesive or adhesive cements with a high compressive strength should be used. Copyright © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Development of Thin Film Thermocouples on Ceramic Materials for Advanced Propulsion System Applications

NASA Technical Reports Server (NTRS)

Holanda, R.

1992-01-01

Thin film thermocouples have been developed for use on metal parts in jet engines to 1000 c. However, advanced propulsion systems are being developed that will use ceramic materials and reach higher temperatures. The purpose of this work is to develop thin film thermocouples for use on ceramic materials. The new thin film thermocouples are Pt13Rh/Pt fabricated by the sputtering process. Lead wires are attached using the parallel-gap welding process. The ceramic materials tested are silicon nitride, silicon carbide, aluminum oxide, and mullite. Both steady state and thermal cycling furnace tests were performed in the temperature range to 1500 C. High-heating-rate tests were performed in an arc lamp heat-flux-calibration facility. The fabrication of the thin film thermocouples is described. The thin film thermocouple output was compared to a reference wire thermocouple. Drift of the thin film thermocouples was determined, and causes of drift are discussed. The results of high heating rate tests up to 2500 C/sec are presented. The stability of the ceramic materials is examined. It is concluded that Pt13Rh/Pt thin film thermocouples are capable of meeting lifetime goals of 50 hours or more up to temperature of 1500 C depending on the stability of the particular ceramic substrate.

Development of thin film thermocouples on ceramic materials for advanced propulsion system applications

NASA Technical Reports Server (NTRS)

Holanda, Raymond

1993-01-01

Thin film thermocouples were developed for use on metal parts in jet engines to 1000 C. However, advanced propulsion systems are being developed that will use ceramic materials and reach higher temperatures. The purpose is to develop thin film thermocouples for use on ceramic materials. The new thin film thermocouples are Pt13Rh/Pt fabricated by the sputtering process. Lead wires are attached using the parallel-gap welding process. The ceramic materials tested are silicon nitride, silicon carbide, aluminum oxide, and mullite. Both steady state and thermal cycling furnace tests were performed in the temperature range to 1500 C. High-heating-rate tests were performed in an arc lamp heat-flux-calibration facility. The fabrication of the thin film thermocouples is described. The thin film thermocouple output was compared to a reference wire thermocouple. Drift of the thin film thermocouples was determined, and causes of drift are discussed. The results of high heating rate tests up to 2500 C/sec are presented. The stability of the ceramic materials is examined. It is concluded that Pt13Rh/Pt thin film thermocouples are capable of meeting lifetime goals of 50 hr or more up to temperatures of 1500 C depending on the stability of the particular ceramic substrate.

Application of a low cost ceramic filter to a membrane bioreactor for greywater treatment.

PubMed

Hasan, Md Mahmudul; Shafiquzzaman, Md; Nakajima, Jun; Ahmed, Abdel Kader T; Azam, Mohammad Shafiul

2015-03-01

The performance of a low cost and simple ceramic filter to a membrane bioreactor (MBR) process was evaluated for greywater treatment. The ceramic filter was submerged in an acrylic cylindrical column bioreactor. Synthetic greywater (prepared by shampoo, dish cleaner and laundry detergent) was fed continuously into the reactor. The filter effluent was obtained by gravitational pressure. The average flux performance was observed to be 11.5 LMH with an average hydraulic retention time of 1.7 days. Complete biodegradation of surfactant (methylene blue active substance removal: 99-100%) as well as high organic removal performance (biochemical oxygen demand: 97-100% and total organic carbon: >88%) was obtained. The consistency of flux (11.5 LMH) indicated that the filter can be operated for a long time without fouling. The application of this simple ceramic filter would make MBR technology cost-effective in developing countries for greywater reclamation and reuse.

Carbon nanotube, graphene and boron nitride nanotube reinforced bioactive ceramics for bone repair.

PubMed

Gao, Chengde; Feng, Pei; Peng, Shuping; Shuai, Cijun

2017-10-01

The high brittleness and low strength of bioactive ceramics have severely restricted their application in bone repair despite the fact that they have been regarded as one of the most promising biomaterials. In the last few years, low-dimensional nanomaterials (LDNs), including carbon nanotubes, graphene and boron nitride nanotubes, have gained increasing attention owing to their favorable biocompatibility, large surface specific area and super mechanical properties. These qualities make LDNs potential nanofillers in reinforcing bioactive ceramics. In this review, the types, characteristics and applications of the commonly used LDNs in ceramic composites are summarized. In addition, the fabrication methods for LDNs/ceramic composites, such as hot pressing, spark plasma sintering and selective laser sintering, are systematically reviewed and compared. Emphases are placed on how to obtain the uniform dispersion of LDNs in a ceramic matrix and maintain the structural stability of LDNs during the high-temperature fabrication process of ceramics. The reinforcing mechanisms of LDNs in ceramic composites are then discussed in-depth. The in vitro and in vivo studies of LDNs/ceramic in bone repair are also summarized and discussed. Finally, new developments and potential applications of LDNs/ceramic composites are further discussed with reference to experimental and theoretical studies. Despite bioactive ceramics having been regarded as promising biomaterials, their high brittleness and low strength severely restrict their application in bone scaffolds. In recent years, low-dimensional nanomaterials (LDNs), including carbon nanotubes, graphene and boron nitride nanotubes, have shown great potential in reinforcing bioactive ceramics owing to their unique structures and properties. However, so far it has been difficult to maintain the structural stability of LDNs during fabrication of LDNs/ceramic composites, due to the lengthy, high-temperature process involved. This review presents a comprehensive overview of the developments and applications of LDNs in bioactive ceramics. The newly-developed fabrication methods for LDNs/ceramic composites, the reinforcing mechanisms and the in vitro and in vivo performance of LDNs are also summarized and discussed in detail. Copyright © 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Ultralight and fire-resistant ceramic nanofibrous aerogels with temperature-invariant superelasticity.

PubMed

Si, Yang; Wang, Xueqin; Dou, Lvye; Yu, Jianyong; Ding, Bin

2018-04-01

Ultralight aerogels that are both highly resilient and compressible have been fabricated from various materials including polymer, carbon, and metal. However, it has remained a great challenge to realize high elasticity in aerogels solely based on ceramic components. We report a scalable strategy to create superelastic lamellar-structured ceramic nanofibrous aerogels (CNFAs) by combining SiO 2 nanofibers with aluminoborosilicate matrices. This approach causes the random-deposited SiO 2 nanofibers to assemble into elastic ceramic aerogels with tunable densities and desired shapes on a large scale. The resulting CNFAs exhibit the integrated properties of flyweight densities of >0.15 mg cm -3 , rapid recovery from 80% strain, zero Poisson's ratio, and temperature-invariant superelasticity to 1100°C. The integral ceramic nature also provided the CNFAs with robust fire resistance and thermal insulation performance. The successful synthesis of these fascinating materials may provide new insights into the development of ceramics in a lightweight, resilient, and structurally adaptive form.

Ultralight and fire-resistant ceramic nanofibrous aerogels with temperature-invariant superelasticity

PubMed Central

Wang, Xueqin; Dou, Lvye; Yu, Jianyong

2018-01-01

Ultralight aerogels that are both highly resilient and compressible have been fabricated from various materials including polymer, carbon, and metal. However, it has remained a great challenge to realize high elasticity in aerogels solely based on ceramic components. We report a scalable strategy to create superelastic lamellar-structured ceramic nanofibrous aerogels (CNFAs) by combining SiO2 nanofibers with aluminoborosilicate matrices. This approach causes the random-deposited SiO2 nanofibers to assemble into elastic ceramic aerogels with tunable densities and desired shapes on a large scale. The resulting CNFAs exhibit the integrated properties of flyweight densities of >0.15 mg cm−3, rapid recovery from 80% strain, zero Poisson’s ratio, and temperature-invariant superelasticity to 1100°C. The integral ceramic nature also provided the CNFAs with robust fire resistance and thermal insulation performance. The successful synthesis of these fascinating materials may provide new insights into the development of ceramics in a lightweight, resilient, and structurally adaptive form. PMID:29719867

Conversion of hydrophilic SiOC nanofibrous membrane to robust hydrophobic materials by introducing palladium

NASA Astrophysics Data System (ADS)

Wu, Nan; Wan, Lynn Yuqin; Wang, Yingde; Ko, Frank

2017-12-01

Hydrophobic ceramic nanofibrous membranes have wide applications in the fields of high-temperature filters, oil/water separators, catalyst supports and membrane reactors, for their water repellency property, self-cleaning capability, good environmental stability and long life span. In this work, we fabricated an inherently hydrophobic ceramic nanofiber membrane without any surface modification through pyrolysis of electrospun polycarbosilane nanofibers. The hydrophobicity was introduced by the hierarchical microstructure formed on the surface of the nanofibers and the special surface composition by the addition of trace amounts of palladium. Furthermore, the flexible ceramic mats demonstrated robust chemical resistance properties with consistent hydrophobicity over the entire pH value range and effective water-in-oil emulsion separation performance. Interestingly, a highly cohesive force was found between water droplet and the ceramic membranes, suggesting their great potentials in micro-liquid transportation. This work provides a new route for adjusting the composition of ceramic surface and flexible, recyclable and multifunctional ceramic fibrous membranes for utilization in harsh environments.

Electromechanical properties of A-site (LiCe)-modified sodium bismuth titanate (Na{sub 0.5}Bi{sub 4.5}Ti{sub 4}O{sub 15}) piezoelectric ceramics at elevated temperature

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang Chunming; Wang Jinfeng; Zhang Shujun

2009-05-01

The Aurivillius-type bismuth layer-structured (NaBi){sub 0.46}(LiCe){sub 0.04}Bi{sub 4}Ti{sub 4}O{sub 15} (NBT-LiCe) piezoelectric ceramics were synthesized using conventional solid-state processing. Phase analysis was performed by x-ray diffraction and microstructural morphology was assessed by scanning electron microscopy. The dielectric, piezoelectric, ferroelectric, and electromechanical properties of NBT-LiCe ceramics were investigated. The piezoelectric activities were found to be significantly enhanced compared to NBT ceramics, which can be attributed to the lattice distortion and the presence of bismuth vacancies. The dielectric and electromechanical properties of NBT-LiCe ceramics at elevated temperature were investigated in detail. The excellent piezoelectric, dielectric, and electromechanical properties, coupled with high Curiemore » temperature (T{sub c}=660 deg. C), demonstrated that the NBT-LiCe ceramics are the promising candidates for high temperature applications.« less

Performance of europium-doped strontium iodide, transparent ceramics and bismuth-loaded polymer scintillators

NASA Astrophysics Data System (ADS)

Cherepy, N. J.; Payne, S. A.; Sturm, B. W.; O'Neal, S. P.; Seeley, Z. M.; Drury, O. B.; Haselhorst, L. K.; Rupert, B. L.; Sanner, R. D.; Thelin, P. A.; Fisher, S. E.; Hawrami, R.; Shah, K. S.; Burger, A.; Ramey, J. O.; Boatner, L. A.

2011-09-01

Recently discovered scintillators for gamma ray spectroscopy - single-crystal SrI2(Eu), GYGAG(Ce) transparent ceramic and Bismuth-loaded plastics - offer resolution and fabrication advantages compared to commercial scintillators, such as NaI(Tl) and standard PVT plastic. Energy resolution at 662 keV of 2.7% is obtained with SrI2(Eu), while 4.5% is obtained with GYGAG(Ce). A new transparent ceramic scintillator for radiographic imaging systems, GLO(Eu), offers high light yield of 70,000 Photons/MeV, high stopping, and low radiation damage. Implementation of single-crystal SrI2(Eu), Gd-based transparent ceramics, and Bi-loaded plastic scintillators can advance the state-of-the art in ionizing radiation detection systems.

Energy efficient engine high pressure turbine ceramic shroud support technology report

NASA Technical Reports Server (NTRS)

Nelson, W. A.; Carlson, R. G.

1982-01-01

This work represents the development and fabrication of ceramic HPT (high pressure turbine) shrouds for the Energy Efficient Engine (E3). Details are presented covering the work performed on the ceramic shroud development task of the NASA/GE Energy Efficient Engine (E3) component development program. The task consists of four phases which led to the selection of a ZrO2-BY2O3 ceramic shroud material system, the development of an automated plasma spray process to produce acceptable shroud structures, the fabrication of select shroud systems for evaluation in laboratory, component, and CF6-50 engine testing, and finally, the successful fabrication of ZrO2-8Y2O3/superpeg, engine quality shrouds for the E3 engine.

Performance of Europium-Doped Strontium Iodide, Transparent Ceramics and Bismuth-loaded Polymer Scintillators

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cherepy, N J; Payne, S A; Sturm, B W

2011-08-30

Recently discovered scintillators for gamma ray spectroscopy, single crystal SrI{sub 2}(Eu), GYGAG(Ce) transparent ceramic and Bismuth-loaded plastics, offer resolution and fabrication advantages compared to commercial scintillators, such as NaI(Tl) and standard PVT plastic. Energy resolution at 662 keV of 2.7% is obtained with SrI{sub 2}(Eu), while 4.5% is obtained with GYGAG(Ce). A new transparent ceramic scintillator for radiographic imaging systems, GLO(Eu) offers high light yield of 70,000 Photons/MeV, high stopping, and low radiation damage. Implementation of single crystal SrI{sub 2}(Eu), Gd-based transparent ceramics, and Bi-loaded plastic scintillators can advance the state-of-the art in ionizing radiation detection systems.

High impact resistant ceramic composite

DOEpatents

Derkacy, J.A.

1991-07-16

A ceramic material and a method of forming a ceramic material which possesses a high impact resistance are disclosed. The material comprises: (a) a first continuous phase of [beta]-SiC; and (b) a second phase of about 25-40 vol % TiB[sub 2]. Al[sub 2]O[sub 3] is preferably used as a densification aid. The material is formed by hot-pressing the mixture at a temperature from greater than about 1800 C to less than the transition temperature of [beta]-SiC to [alpha]-SiC. The hot-pressing is performed at a pressure of about 2000 psi to about 4000 psi in an inert atmosphere for several hours and results in the formation of a two phase sintered ceramic composite material. 6 figures.

High impact resistant ceramic composite

DOEpatents

Derkacy, James A.

1991-07-16

A ceramic material and a method of forming a ceramic material which possesses a high impact resistance. The material comprises: (a) a first continuous phase of .beta.-SiC; and (b) a second phase of about 25-40 vol % TiB.sub.2. Al.sub.2 O.sub.3 is preferably used as a densification aid. The material is formed by hot-pressing the mixture at a temperature from greater than about 1800.degree. C. to less than the transition temperature of .beta.-SiC to .alpha.-SiC. The hot-pressing is performed at a pressure of about 2000 psi to about 4000 psi in an inert atmosphere for several hours and results in the formation of a two phase sintered ceramic composite material.

Investigation on emission characteristics of metal-ceramic cathode applied to industrial X-ray diode.

PubMed

Xun, Ma; Jianqiang, Yuan; Hongwei, Liu; Hongtao, Li; Lingyun, Wang; Ping, Jiang

2016-06-01

The industrial x-ray diode with high impedance configuration is usually adopted to generate repetitive x-ray, but its performance would be worsened due to lower electric field on the cathode of diode when a voltage of several hundreds of kV is applied. To improve its performance, a novel metal-ceramic cathode is proposed in this paper. Key factors (width, relative permittivity of ceramic, and so on) affecting electric field distribution on triple points are analyzed by electrostatic field calculation program, so as to optimize the design of this novel cathode. Experiments are done to study the characteristics including emission current of cathode, diode voltage duration, diode mean dynamic impedance, and diode impedance drop velocity within diode power duration. The results show that metal-ceramic cathode could improve diode performance by enhancing emission current and stabling impedance; the impedance drop velocity of diode with spoke-shaped metal-ceramic cathode was reduced to -5 Ω ns(-1) within diode power duration, comparing to -15 Ω ns(-1) with metal foil cathode.

Highly durable, coking and sulfur tolerant, fuel-flexible protonic ceramic fuel cells.

PubMed

Duan, Chuancheng; Kee, Robert J; Zhu, Huayang; Karakaya, Canan; Chen, Yachao; Ricote, Sandrine; Jarry, Angelique; Crumlin, Ethan J; Hook, David; Braun, Robert; Sullivan, Neal P; O'Hayre, Ryan

2018-05-01

Protonic ceramic fuel cells, like their higher-temperature solid-oxide fuel cell counterparts, can directly use both hydrogen and hydrocarbon fuels to produce electricity at potentially more than 50 per cent efficiency 1,2 . Most previous direct-hydrocarbon fuel cell research has focused on solid-oxide fuel cells based on oxygen-ion-conducting electrolytes, but carbon deposition (coking) and sulfur poisoning typically occur when such fuel cells are directly operated on hydrocarbon- and/or sulfur-containing fuels, resulting in severe performance degradation over time 3-6 . Despite studies suggesting good performance and anti-coking resistance in hydrocarbon-fuelled protonic ceramic fuel cells 2,7,8 , there have been no systematic studies of long-term durability. Here we present results from long-term testing of protonic ceramic fuel cells using a total of 11 different fuels (hydrogen, methane, domestic natural gas (with and without hydrogen sulfide), propane, n-butane, i-butane, iso-octane, methanol, ethanol and ammonia) at temperatures between 500 and 600 degrees Celsius. Several cells have been tested for over 6,000 hours, and we demonstrate excellent performance and exceptional durability (less than 1.5 per cent degradation per 1,000 hours in most cases) across all fuels without any modifications in the cell composition or architecture. Large fluctuations in temperature are tolerated, and coking is not observed even after thousands of hours of continuous operation. Finally, sulfur, a notorious poison for both low-temperature and high-temperature fuel cells, does not seem to affect the performance of protonic ceramic fuel cells when supplied at levels consistent with commercial fuels. The fuel flexibility and long-term durability demonstrated by the protonic ceramic fuel cell devices highlight the promise of this technology and its potential for commercial application.

Process Development of Porcelain Ceramic Material with Binder Jetting Process for Dental Applications

NASA Astrophysics Data System (ADS)

Miyanaji, Hadi; Zhang, Shanshan; Lassell, Austin; Zandinejad, Amirali; Yang, Li

2016-03-01

Custom ceramic structures possess significant potentials in many applications such as dentistry and aerospace where extreme environments are present. Specifically, highly customized geometries with adequate performance are needed for various dental prostheses applications. This paper demonstrates the development of process and post-process parameters for a dental porcelain ceramic material using binder jetting additive manufacturing (AM). Various process parameters such as binder amount, drying power level, drying time and powder spread speed were studied experimentally for their effect on geometrical and mechanical characteristics of green parts. In addition, the effects of sintering and printing parameters on the qualities of the densified ceramic structures were also investigated experimentally. The results provide insights into the process-property relationships for the binder jetting AM process, and some of the challenges of the process that need to be further characterized for the successful adoption of the binder jetting technology in high quality ceramic fabrications are discussed.

Laser-diode pumped 40-W Yb:YAG ceramic laser.

PubMed

Hao, Qiang; Li, Wenxue; Pan, Haifeng; Zhang, Xiaoyi; Jiang, Benxue; Pan, Yubai; Zeng, Heping

2009-09-28

We demonstrated a high-power continuous-wave (CW) polycrystalline Yb:YAG ceramic laser pumped by fiber-pigtailed laser diode at 968 nm with 400 mum fiber core. The Yb:YAG ceramic laser performance was compared for different Yb(3+) ion concentrations in the ceramics by using a conventional end-pump laser cavity consisting of two flat mirrors with output couplers of different transmissions. A CW laser output of 40 W average power with M(2) factor of 5.8 was obtained with 5 mol% Yb concentration under 120 W incident pump power. This is to the best of our knowledge the highest output power in end-pumped bulk Yb:YAG ceramic laser.

Ceramic technology for solar thermal receivers

NASA Technical Reports Server (NTRS)

Kudirka, A. A.; Smoak, R. H.

1981-01-01

The high-temperature capability, resistance to corrosive environments and non-strategic nature of ceramics have prompted applications in the solar thermal field whose advantages over metallic devices of comparable performance may begin to be assessed. It is shown by a survey of point-focusing receiver designs employing a variety of ceramic compositions and fabrication methods that the state-of-the-art in structural ceramics is not sufficiently advanced to fully realize the promised benefits of higher temperature capabilities at lower cost than metallic alternatives. The ceramics considered include alumina, berylia, magnesia, stabilized zirconia, fused silica, silicon nitride, silicon carbide, mullite and cordierite, processed by such methods as isostatic pressing, dry pressing, slip casting, extrusion, calendaring and injection molding.

High-temperature ceramic heat exchanger element for a solar thermal receiver

NASA Technical Reports Server (NTRS)

Strumpf, H. J.; Kotchick, D. M.; Coombs, M. G.

1982-01-01

A study was performed by AiResearch Manufacturing Company, a division of The Garrett Corporation, on the development a high-temperature ceramic heat exchanger element to be integrated into a solar receiver producing heated air. A number of conceptual designs were developed for heat exchanger elements of differing configuration. These were evaluated with respect to thermal performance, pressure drop, structural integrity, and fabricability. The final design selection identified a finned ceramic shell as the most favorable concept. The shell is surrounded by a larger metallic shell. The flanges of the two shells are sealed to provide a leak-tight pressure vessel. The ceramic shell is to be fabricated by an innovative combination of slip casting the receiver walls and precision casting the heat transfer finned plates. The fins are bonded to the shell during firing. The unit is sized to produce 2150 F ar at 2.7 atm pressure, with a pressure drop of about 2 percent of the inlet pressure. This size is compatible with a solar collector providing a receiver input of 85 kw(th). Fabrication of a one-half scale demonstrator ceramic receiver has been completed.

A high performance ceramic-polymer separator for lithium batteries

NASA Astrophysics Data System (ADS)

Kumar, Jitendra; Kichambare, Padmakar; Rai, Amarendra K.; Bhattacharya, Rabi; Rodrigues, Stanley; Subramanyam, Guru

2016-01-01

A three-layered (ceramic-polymer-ceramic) hybrid separator was prepared by coating ceramic electrolyte [lithium aluminum germanium phosphate (LAGP)] over both sides of polyethylene (PE) polymer membrane using electron beam physical vapor deposition (EB-PVD) technique. Ionic conductivities of membranes were evaluated after soaking PE and LAGP/PE/LAGP membranes in a 1 Molar (1M) lithium hexafluroarsenate (LiAsF6) electrolyte in ethylene carbonate (EC), dimethyl carbonate (DMC) and ethylmethyl carbonate (EMC) in volume ratio (1:1:1). Scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques were employed to evaluate morphology and structure of the separators before and after cycling performance tests to better understand structure-property correlation. As compared to regular PE separator, LAGP/PE/LAGP hybrid separator showed: (i) higher liquid electrolyte uptake, (ii) higher ionic conductivity, (iii) lower interfacial resistance with lithium and (iv) lower cell voltage polarization during lithium cycling at high current density of 1.3 mA cm-2 at room temperature. The enhanced performance is attributed to higher liquid uptake, LAGP-assisted faster ion conduction and dendrite prevention. Optimization of density and thickness of LAGP layer on PE or other membranes through manipulation of PVD deposition parameters will enable practical applications of this novel hybrid separator in rechargeable lithium batteries with high energy, high power, longer cycle life, and higher safety level.

Are we all doing it wrong? Influence of stripping and cleaving methods of laser fibers on laser lithotripsy performance.

PubMed

Kronenberg, Peter; Traxer, Olivier

2015-03-01

We assessed whether stripping and cleaving the laser fiber tip with specialized tools, namely laser fiber strippers, or ceramic or metal scissors, would influence lithotripsy performance. Laser fiber tips were stripped with a specialized laser fiber stripper or remained coated. The tips were then cleaved with metal or ceramic scissors. Laser lithotripsy experiments were performed with the 4 fiber tip combinations using an automated laser fragmentation testing system with artificial stones made of plaster of Paris or BegoStone Plus (Bego, Lincoln, Rhode Island). High frequency-low pulse energy (20 Hz and 0.5 J) and low frequency-high pulse energy (5 Hz and 2.0 J) settings were used for 30 seconds. Fissure width, depth and volume, and laser fiber tip photos were analyzed. Coated laser fiber tips always achieved significantly higher ablation volumes (sometimes greater than 50%) than stripped laser fiber tips (p <0.00001) regardless of cleaving scissor type, stone material or lithotripter setting. Coated fiber tips cleaved with metal scissors ablated as well as those cleaved with ceramic scissors (p = 0.16). However, stripped fibers were much less ablative when they were cut with metal scissors compared to ceramic scissors (p <0.00001). Harder stone material decreased ablation volume (p <0.00001). Low frequency-high pulse energy settings were an average of 3 times more ablative than high frequency-low pulse energy settings (p <0.00001). Stripping the fibers, a harder stone material and low frequency-high pulse energy settings were associated with increased fiber tip degradation. Coated laser fibers provided better lithotripsy performance and metal scissors were as good as ceramic scissors to cleave coated fibers. This knowledge may improve and simplify the way that laser lithotripsy procedures are done worldwide. Copyright © 2015 American Urological Association Education and Research, Inc. Published by Elsevier Inc. All rights reserved.

Interfacial microstructure and shear strength of reactive air brazed oxygen transport membrane ceramic-metal alloy joints

NASA Astrophysics Data System (ADS)

FR, Wahid Muhamad; Yoon, Dang-Hyok; Raju, Kati; Kim, Seyoung; Song, Kwang-sup; Yu, Ji Haeng

2018-01-01

To fabricate a multi-layered structure for maximizing oxygen production, oxygen transport membrane (OTM) ceramics need to be joined or sealed hermetically metal supports for interfacing with the peripheral components of the system. Therefore, in this study, Ag-10 wt% CuO was evaluated as an effective filler material for the reactive air brazing of dense Ce0.9Gd0.1O2-δ-La0.7Sr0.3MnO3±δ (GDC-LSM) OTM ceramics. Thermal decomposition in air and wetting behavior of the braze filler was performed. Reactive air brazing was performed at 1050 °C for 30 min in air to join GDC-LSM with four different commercially available high temperature-resistant metal alloys, such as Crofer 22 APU, Inconel 600, Fecralloy, and AISI 310S. The microstructure and elemental distribution of the ceramic-ceramic and ceramic-metal interfaces were examined from polished cross-sections. The mechanical shear strength at room temperature for the as-brazed and isothermally aged (800 °C for 24 h) joints of all the samples was compared. The results showed that the strength of the ceramic-ceramic joints was decreased marginally by aging; however, in the case of metal-ceramic joints, different decreases in strengths were observed according to the metal alloy used, which was explained based on the formation of different oxide layers at the interfaces.

The precursors effects on biomimetic hydroxyapatite ceramic powders.

PubMed

Yoruç, Afife Binnaz Hazar; Aydınoğlu, Aysu

2017-06-01

In this study, effects of the starting material on chemical, physical, and biological properties of biomimetic hydroxyapatite ceramic powders (BHA) were investigated. Characterization and chemical analysis of BHA powders were performed by using XRD, FT-IR, and ICP-AES. Microstructural features such as size and morphology of the resulting BHA powders were characterized by using BET, nano particle sizer, pycnometer, and SEM. Additionally, biological properties of the BHA ceramic powders were also investigated by using water-soluble tetrazolium salts test (WST-1). According to the chemical analysis of BHA ceramic powders, chemical structures of ceramics which are prepared under different conditions and by using different starting materials show differences. Ceramic powders which are produced at 80°C are mainly composed of hydroxyapatite, dental hydroxyapatite (contain Na and Mg elements in addition to Ca), and calcium phosphate sulfide. However, these structures are altered at high temperatures such as 900°C depending on the features of starting materials and form various calcium phosphate ceramics and/or their mixtures such as Na-Mg-hydroxyapatite, hydroxyapatite, Mg-Whitlockit, and chloroapatite. In vitro cytotoxicity studies showed that amorphous ceramics produced at 80°C and ceramics containing chloroapatite structure as main or secondary phases were found to be extremely cytotoxic. Furthermore, cell culture studies showed that highly crystalline pure hydroxyapatite structures were extremely cytotoxic due to their high crystallinity values. Consequently, the current study indicates that the selection of starting materials which can be used in the production of calcium phosphate ceramics is very important. It is possible to produce calcium phosphate ceramics which have sufficient biocompatibility at physiological pH values and by using appropriate starting materials. Copyright © 2017 Elsevier B.V. All rights reserved.

Refractory Materials for Flame Deflector Protection System Corrosion Control: Refractory Ceramics Literature Survey

NASA Technical Reports Server (NTRS)

Calle, Luz Marina; Hintze, Paul E.; Parlier, Christopher R.; Curran, Jerome P.; Kolody, Mark; Perusich, Stephen; Whitten, Mary C.; Trejo, David; Zidek, Jason; Sampson, Jeffrey W.;

Photopyroelectric response of PTCa∕PEEK composite.

PubMed

Estevam, Giuliano Pierre; de Melo, Washington Luiz Barros; Sakamoto, Walter Katsumi

2011-02-01

A pyroelectric composite made of calcium modified lead titanate ceramic and polyether-ether-ketone high performance polymer was obtained in the film form by hot pressing the ceramic/polymer mixture into the desired composition. After polarization with a suitable electric field, a ceramic composite film (60% vol.) exhibited a pyroelectric figure of merit three times higher than that of a lead zirconate titanate ceramic. The material was used as infrared radiation sensor. The voltage responsivity decreases with the inverse of the frequency showing the same behavior of the thermally thick sensor. The reproducibility of the sensor responses was observed.

A floating macro/mesoporous crystalline anatase TiO2 ceramic with enhanced photocatalytic performance for recalcitrant wastewater degradation.

PubMed

Xing, Zipeng; Zhou, Wei; Du, Fan; Qu, Yang; Tian, Guohui; Pan, Kai; Tian, Chungui; Fu, Honggang

2014-01-14

A macro/mesoporous anatase TiO2 ceramic floating photocatalyst has been successfully synthesized using highly thermally stable mesoporous TiO2 powder as a precursor, followed by a camphene-based freeze-casting process and high-temperature calcinations. The ceramics are characterized in detail by X-ray diffraction, Raman spectra, scanning electron microscopy, transmission electron microscopy and N2 adsorption-desorption isotherms. The results indicate that the TiO2 ceramics present hierarchical macro/mesoporous structures, which maintain high porosity and high compressive strength at the optimal sintering temperature of 800 °C. The ordered mesoporous TiO2 network still possesses high thermal stability and inhibits the anatase-to-rutile phase transformation during calcinations. The obtained ceramics exhibit good adsorptive and photocatalytic activity for the degradation of octane and rhodamine B, and the total organic carbon removal ratio is up to 98.8% and 98.6% after photodegradation for 3 h, respectively. The roles of active species in the photocatalytic process are compared using different types of active species scavengers, and the degradation mechanism is also proposed. Furthermore, the ceramics are recyclable, and no clear changes are observed after ten cycles. In addition, the ceramics are also active in the photodegradation of phenol, thiobencarb, and atrazine. Therefore, these novel floating photocatalysts will have wide applications, including the removal of floating organic pollutants from the wastewater surfaces or the removal of soluble organic pollutants from wastewater.

Fiber reinforced glasses and glass-ceramics for high performance applications

NASA Technical Reports Server (NTRS)

Prewo, K. M.; Brennan, J. J.; Layden, G. K.

1986-01-01

The development of fiber reinforced glass and glass-ceramic matrix composites is described. The general concepts involved in composite fabrication and resultant composite properties are given for a broad range of fiber and matrix combinations. It is shown that composite materials can be tailored to achieve high levels of toughness, strength, and elastic stiffness, as well as wear resistance and dimensional stability.

Performance of Carbon/Polytetrafluoroethylene (PTFE) Air Cathodes from pH 0 to 14 for Li-Air Batteries

DTIC Science & Technology

2007-12-01

aqueous and aqueous electrolytes are kept separate by a non-electronically conducting ceramic membrane impervious to water, but with a high ionic...thought of as being solvated by the ceramic membrane as it passes from non-aqueous to aqueous electrolyte. The half-cell reaction at the lithium...overall charge in the reaction, positive lithium ions flow through an ionically conducting ceramic membrane from the non-aqueous anode compartment to

[A ten-year clinical study of cracked teeth restored with glass ceramic crowns].

PubMed

Luo, X P; Yuan, Y; Shi, Y J; Qian, D D

2016-10-09

Objective: To evaluate the clinic performance of high strength glass ceramic crowns for the painful cracked teeth during a 10-year observation period. Methods: Forty-two posterior teeth from 36 patients were diagnosed as having a crack, biting painful and sensitivity to cold were selected in the Department of Prosthodontic, Institute and Hospital of Stomatology, Nanjing University Medical School. The lost-wax hot pressed glass ceramic crowns were bonded on the minimally invasive prepared teeth by modern adhesive technology. Patients were interviewed and went through clinic examination after one week, one month, and every six months. Results: The effectiveness of 42 glass ceramic crowns for cracked teeth was evaluated for a mean observation time over 10-year. At the first week, 29(81%) patients were free of pain, three still had sensitivity to cold and chewing pain, three still had sensitivity to cold, one had painful to cold and hot. After one month, two patients still had chewing pain, and one tooth needed endodontic treatment after six months. In 10 years, 2(5%) all ceramic crowns were broken, the other 40 restorations kept good clinical performances with a 10-year survival rate of 95%. Conclusions: The high strength glass ceramic crowns are very effective and successful in treating the cracked teeth and then keep the good mastication function and appearance.

Electrical and dielectric properties of Na1/2La1/2Cu3Ti4O12 ceramics prepared by high energy ball-milling and conventional sintering

NASA Astrophysics Data System (ADS)

Mahfoz Kotb, H.; Ahmad, Mohamad M.

2016-12-01

We report on the measurements of the electrical and dielectric properties of Na1/2La1/2Cu3Ti4O12 (NLCTO) ceramics prepared by high energy ball-milling and conventional sintering without any calcination steps. The x-ray powder diffraction analysis shows that pure perovskite-like CCTO phase is obtained after sintering at 1025 °C-1075 °C. Higher sintering temperatures result in multi-phase ceramics due to thermal decomposition. Scanning electron microscope observations reveal that the grain size is in a range of ˜3 μm-5μm for these ceramics. Impedance spectroscopy measurements performed in a wide frequency range (1 Hz-10 MHz) and at various temperatures (120 K-470 K) are used to study the dielectric and electrical properties of NLCTO ceramics. A good compromise between high ɛ‧ (5.7 × 103 and 4.1 × 103 at 1.1 kHz and 96 kHz, respectively) and low tan δ (0.161 and 0.126 at 1.1 kHz and 96 kHz, respectively) is obtained for the ceramic sintered at 1050 °C. The observed high dielectric constant behavior is explained in terms of the internal barrier layer capacitance effect.

Influence of Electrical Resistivity and Machining Parameters on Electrical Discharge Machining Performance of Engineering Ceramics

PubMed Central

Ji, Renjie; Liu, Yonghong; Diao, Ruiqiang; Xu, Chenchen; Li, Xiaopeng; Cai, Baoping; Zhang, Yanzhen

2014-01-01

Engineering ceramics have been widely used in modern industry for their excellent physical and mechanical properties, and they are difficult to machine owing to their high hardness and brittleness. Electrical discharge machining (EDM) is the appropriate process for machining engineering ceramics provided they are electrically conducting. However, the electrical resistivity of the popular engineering ceramics is higher, and there has been no research on the relationship between the EDM parameters and the electrical resistivity of the engineering ceramics. This paper investigates the effects of the electrical resistivity and EDM parameters such as tool polarity, pulse interval, and electrode material, on the ZnO/Al2O3 ceramic's EDM performance, in terms of the material removal rate (MRR), electrode wear ratio (EWR), and surface roughness (SR). The results show that the electrical resistivity and the EDM parameters have the great influence on the EDM performance. The ZnO/Al2O3 ceramic with the electrical resistivity up to 3410 Ω·cm can be effectively machined by EDM with the copper electrode, the negative tool polarity, and the shorter pulse interval. Under most machining conditions, the MRR increases, and the SR decreases with the decrease of electrical resistivity. Moreover, the tool polarity, and pulse interval affect the EWR, respectively, and the electrical resistivity and electrode material have a combined effect on the EWR. Furthermore, the EDM performance of ZnO/Al2O3 ceramic with the electrical resistivity higher than 687 Ω·cm is obviously different from that with the electrical resistivity lower than 687 Ω·cm, when the electrode material changes. The microstructure character analysis of the machined ZnO/Al2O3 ceramic surface shows that the ZnO/Al2O3 ceramic is removed by melting, evaporation and thermal spalling, and the material from the working fluid and the graphite electrode can transfer to the workpiece surface during electrical discharge machining ZnO/Al2O3 ceramic. PMID:25364912

Development of seals for a geothermal downhole intensifier. Progress report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Captain, K.M.; Harvey, A.C.; Caskey, B.C.

1985-08-01

A system using high-velocity fluid jets in conjunction with a rotary diamond bit is currently considered as the best candidate for reducing the cost of drilling geothermal wells. Technical, safety and cost considerations indicate that the required jet supply pressure can best be established by a downhole pressure intensifier. Key intensifier components are the check valve and plunger seals, which must prevent leakage of the high-pressure, high-temperature abrasive fluid (drilling mud). To achieve the required performance, novel ceramic seals are currently being developed. The check valve seal includes a tapered polymeric plug and ceramic stop acting against a ceramic seat.more » The ceramic plunger seal is a variant of the ''stepped-joint'' piston ring and is designed to minimize contact pressure and abrasive wear. Initial testing of these seals in the laboratory shows encouraging results; design refinement and further testing is in progress. 2 refs., 6 figs., 3 tabs.« less

High performance Aurivillius phase sodium-potassium bismuth titanate lead-free piezoelectric ceramics with lithium and cerium modification

NASA Astrophysics Data System (ADS)

Wang, Chun-Ming; Wang, Jin-Feng

2006-11-01

The piezoelectric properties of the lithium and cerium modified A-site vacancies sodium-potassium bismuth titanate (NKBT) lead-free piezoceramics are investigated. The piezoelectric activity of NKBT ceramics is significantly improved by the modification of lithium and cerium. The Curie temperature TC, piezoelectric coefficient d33, and mechanical quality factor Qm for the NKBT ceramics modified with 0.10mol% (LiCe) are found to be 660°C, 25pC/N, and 3135, respectively. The Curie temperature gradually decreases from 675to650°C with the increase of (LiCe) modification. The dielectric spectroscopy shows that all the samples possess stable piezoelectric properties, demonstrating that the (LiCe) modified NKBT-based ceramics are the promising candidates for high temperature applications.

Analysis of machining damage in engineering ceramics by fracture mechanics, fractography and x-ray diffraction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hollstein, T.; Pfeiffer, W.; Rombach, M.

1996-12-31

The cost for final machining covers a significant percentage of the whole cost of a ceramic component. This is due to the difficult machining of the high performance ceramics. The high values of hardness and wear resistance, which are desired in many applications, hinder the process of machining. Only a few machining procedures are applicable to engineering ceramics e.g. grinding, polishing or ultrasonic lapping, and the rate of material removal is considerably lower than for metals. In addition crack generation in the surface regions during machining is easily possible due to the brittleness of the ceramics. The material removal duringmore » grinding, which is the most important machining procedure of engineering ceramics, takes place mainly by brittle fracture processes but also by ductile material removal. The complex stress conditions in the work piece below or in the vicinity of the grinding grits lead to a variability of cracks and crack systems like median cracks, lateral cracks or radial cracks, which extend in general {le} 50 {mu}m and which lead to the strength anisotropy of ground ceramics, if certain grinding parameters are used e.g..« less

Synthesis of Highly Uniform and Compact Lithium Zinc Ferrite Ceramics via an Efficient Low Temperature Approach.

PubMed

Xu, Fang; Liao, Yulong; Zhang, Dainan; Zhou, Tingchuan; Li, Jie; Gan, Gongwen; Zhang, Huaiwu

2017-04-17

LiZn ferrite ceramics with high saturation magnetization (4πM s ) and low ferromagnetic resonance line widths (ΔH) represent a very critical class of material for microwave ferrite devices. Many existing approaches emphasize promotion of the grain growth (average size is 10-50 μm) of ferrite ceramics to improve the gyromagnetic properties at relatively low sintering temperatures. This paper describes a new strategy for obtaining uniform and compact LiZn ferrite ceramics (average grains size is ∼2 μm) with enhanced magnetic performance by suppressing grain growth in great detail. The LiZn ferrites with a formula of Li 0.415 Zn 0.27 Mn 0.06 Ti 0.1 Fe 2.155 O 4 were prepared by solid reaction routes with two new sintering strategies. Interestingly, results show that uniform, compact, and pure spinel ferrite ceramics were synthesized at a low temperature (∼850 °C) without obvious grain growth. We also find that a fast second sintering treatment (FSST) can further improve their gyromagnetic properties, such as higher 4πM s and lower ΔH. The two new strategies are facile and efficient for densification of LiZn ferrite ceramics via suppressing grain growth at low temperatures. The sintering strategy reported in this study also provides a referential experience for other ceramics, such as soft magnetism ferrite ceramics or dielectric ceramics.

Enhancing steel properties through in situ formation of ultrahard ceramic surface

PubMed Central

Pahlevani, Farshid; Kumar, Rahul; Gorjizadeh, Narjes; Hossain, Rumana; Cholake, Sagar T; Privat, Karen; Sahajwalla, Veena

2016-01-01

Abrasion and corrosion resistant steel has attracted considerable interest for industrial application as a means of minimising the costs associated with product/component failures and/or short replacement cycles. These classes of steels contain alloying elements that increase their resistance to abrasion and corrosion. Their benefits, however, currently come at a potentially prohibitive cost; such high performance steel products are both more technically challenging and more expensive to produce. Although these methods have proven effective in improving the performance of more expensive, high-grade steel components, they are not economically viable for relatively low cost steel products. New options are needed. In this study, a complex industrial waste stream has been transformed in situ via precisely controlled high temperature reactions to produce an ultrahard ceramic surface on steel. This innovative ultrahard ceramic surface increases both the hardness and compressive strength of the steel. Furthermore, by modifying the composition of the waste input and the processing parameters, the ceramic surface can be effectively customised to match the intended application of the steel. This economical new approach marries industry demands for more cost-effective, durable steel products with global imperatives to address resource depletion and environmental degradation through the recovery of resources from waste. PMID:27929096

High charge-discharge performance of Pb{sub 0.98}La{sub 0.02}(Zr{sub 0.35}Sn{sub 0.55}Ti{sub 0.10}){sub 0.995}O{sub 3} antiferroelectric ceramics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu, Chenhong; University of the Chinese Academy of Sciences, Beijing 100049; Liu, Zhen

2016-08-21

The energy storage performance and charge-discharge properties of Pb{sub 0.98}La{sub 0.02}(Zr{sub 0.35}Sn{sub 0.55}Ti{sub 0.10}){sub 0.995}O{sub 3} (PLZST) antiferroelectric ceramics were investigated through directly measuring the hysteresis loops and pulse discharge current-time curves. The energy density only varies 0.2% per degree from 25 °C to 85 °C, and the energy efficiency maintains at about 90%. Furthermore, an approximate calculating model of maximum power density p{sub max} was established for the discharge process. Under a relatively high working electric field (8.2 kV/mm), this ceramics possess a greatly enhanced power density of 18 MW/cm{sup 3}. Moreover, the pulse power properties did not show degradation until 1500 timesmore » of charge-discharge cycling. The large released energy density, high energy efficiency, good temperature stability, greatly enhanced power density, and excellent fatigue endurance combined together make this PLZST ceramics an ideal candidate for pulse power applications.« less

Enhancing steel properties through in situ formation of ultrahard ceramic surface.

PubMed

Pahlevani, Farshid; Kumar, Rahul; Gorjizadeh, Narjes; Hossain, Rumana; Cholake, Sagar T; Privat, Karen; Sahajwalla, Veena

2016-12-08

Abrasion and corrosion resistant steel has attracted considerable interest for industrial application as a means of minimising the costs associated with product/component failures and/or short replacement cycles. These classes of steels contain alloying elements that increase their resistance to abrasion and corrosion. Their benefits, however, currently come at a potentially prohibitive cost; such high performance steel products are both more technically challenging and more expensive to produce. Although these methods have proven effective in improving the performance of more expensive, high-grade steel components, they are not economically viable for relatively low cost steel products. New options are needed. In this study, a complex industrial waste stream has been transformed in situ via precisely controlled high temperature reactions to produce an ultrahard ceramic surface on steel. This innovative ultrahard ceramic surface increases both the hardness and compressive strength of the steel. Furthermore, by modifying the composition of the waste input and the processing parameters, the ceramic surface can be effectively customised to match the intended application of the steel. This economical new approach marries industry demands for more cost-effective, durable steel products with global imperatives to address resource depletion and environmental degradation through the recovery of resources from waste.

A controlled wet-spinning and dip-coating process for preparation of high-permeable TiO2 hollow fiber membranes.

PubMed

Zhang, Qi; Wang, Hua; Fan, Xinfei; Chen, Shuo; Yu, Hongtao; Quan, Xie

2016-01-01

In order to improve the permeate flux of photocatalytic membranes, we present an approach for coupling TiO2 with ceramic hollow fiber membranes. The ceramic hollow fiber membranes with high permeate flux were fabricated by a controlled wet-spinning process using polyethersulfone (PESf) and ceramic powder as precursors and 1-methyl-2-pyrrolidinone as solvent, and the subsequent TiO2 coating was performed by a dip-coating process using tetra-n-butyl titanate as precursor. It has been found that the PESf/ceramic powder ratio could influence the structure of the membranes. Here the as-prepared TiO2 hollow fiber membranes had a pure water flux of 4,450 L/(m(2)·h). The performance of the TiO2 hollow fiber membrane was evaluated using humic acid (HA) as a test substance. The results demonstrated that this membrane exhibited a higher permeate flux under UV irradiation than in the dark and the HA removal efficiency was enhanced. The approach described here provides an operable route to the development of high-permeable photocatalytic membranes for water treatment.

Characterization of an Ultra-High Temperature Ceramic Composite

NASA Technical Reports Server (NTRS)

Levine, Stanley R.; Opila, Elizabeth J.; Robinson, Raymond C.; Lorincz, Jonathan A.

2004-01-01

Ultra-high temperature ceramics (UHTC) are of interest for hypersonic vehicle leading edge applications. Monolithic UHTCs are of concern because of their low fracture toughness and brittle behavior. UHTC composites (UHTCC) are being investigated as a possible approach to overcome these deficiencies. In this study a small sample of a UHTCC was evaluated by limited mechanical property tests, furnace oxidation exposures, and oxidation exposures in a flowing environment generated by an oxy-acetylene torch. The composite was prepared from a carbon fiber perform using ceramic particulates and a pre-cerns about microcracking due to thermal expansion mismatch between the matrix and the carbon fiber reinforcements, and about the oxidation resistance of the HfB2-SiC coating layer and the composite constituents. However, positive performance in the torch test warrants further study of this concept.

Recent advancements in transparent ceramics and crystal fibers for high power lasers

NASA Astrophysics Data System (ADS)

Kim, W.; Baker, C.; Villalobos, G.; Florea, C.; Gibson, D.; Shaw, L. B.; Bowman, S.; Bayya, S.; Sadowski, B.; Hunt, M.; Askins, C.; Peele, J.; Aggarwal, I. D.; Sanghera, J. S.

2013-05-01

In this paper, we present our recent progress in the development of rare-earth (Yb3+ or Ho3+) doped Lu2O3 and Y2O3 sesquioxides for high power solid state lasers. We have fabricated high quality transparent ceramics using nano-powders synthesized by a co-precipitation method. This was accomplished by developments in high purity powder synthesis and low temperature scalable sintering technology developed at NRL. The optical, spectral and morphological properties as well as the lasing performance from our highly transparent ceramics are presented. In the second part of the paper, we discuss our recent research effort in developing cladded-single crystal fibers for high power single frequency fiber lasers has the potential to significantly exceed the capabilities of existing silica fiber based lasers. Single crystal fiber cores with diameters as small as 35μm have been drawn using high purity rare earth doped ceramic or single crystal feed rods by the Laser Heated Pedestal Growth (LHPG) process. Our recent results on the development of suitable claddings on the crystal fiber core are discussed.

Advanced ceramic material for high temperature turbine tip seals

NASA Technical Reports Server (NTRS)

Vogan, J. W.; Solomon, N. G.; Stetson, A. R.

1980-01-01

Forty-one material systems were evaluated for potential use in turbine blade tip seal applications at 1370 C. Both ceramic blade tip inserts and abradable ceramic tip shoes were tested. Hot gas erosion, impact resistance, thermal stability, and dynamic rub performance were the criteria used in rating the various materials. Silicon carbide and silicon nitride were used, both as blade tips and abradables. The blade tip inserts were fabricated by hot pressing while low density and honeycomb abradables were sintered or reaction bonded.

Method to fabricate high performance tubular solid oxide fuel cells

DOEpatents

Chen, Fanglin; Yang, Chenghao; Jin, Chao

2013-06-18

In accordance with the present disclosure, a method for fabricating a solid oxide fuel cell is described. The method includes forming an asymmetric porous ceramic tube by using a phase inversion process. The method further includes forming an asymmetric porous ceramic layer on a surface of the asymmetric porous ceramic tube by using a phase inversion process. The tube is co-sintered to form a structure having a first porous layer, a second porous layer, and a dense layer positioned therebetween.

Transparent ceramic scintillators for gamma spectroscopy and radiography

NASA Astrophysics Data System (ADS)

Cherepy, N. J.; Kuntz, J. D.; Seeley, Z. M.; Fisher, S. E.; Drury, O. B.; Sturm, B. W.; Hurst, T. A.; Sanner, R. D.; Roberts, J. J.; Payne, S. A.

2010-08-01

Transparent ceramics combine the scintillation performance of single crystals with the ruggedness and processability of glass. We have developed a versatile, scaleable fabrication method, wherein nanoparticle feedstock is consolidated at temperatures well below melting to form inch-scale phase-pure transparent ceramics with optical scatter of α <0.1 cm-1. We have fabricated Cerium-doped Gadolinium Garnets with light yields of ~50,000 Ph/MeV and energy resolution of <5% at 662 keV. We have also developed methods to form sheets of the high-Z ceramic scintillator, Europium-doped Lutetium Oxide Bixbyite, producing ~75,000 Ph/MeV for radiographic imaging applications.

Doped sesquioxide ceramic for eye-safe solid state laser materials

NASA Astrophysics Data System (ADS)

Kim, Woohong; Baker, Colin; Florea, Catalin; Frantz, Jesse; Villalobos, Guillermo; Shaw, Brandon; Bowman, Steve; O'Connor, Shawn; Sadowski, Bryan; Hunt, Michael; Aggalwar, Ishwar; Sanghera, Jasbinder

2013-03-01

In this paper, we present our recent results in the development of Ho3+ doped sesquioxides for eye-safe solid state lasers. We have synthesized optical quality Lu2O3 nanopowders doped with concentrations of 0.1, 1.0, 2.0, and 5% Ho3+. The powders were synthesized by a co-precipitation method beginning with nitrates of holmium and lutetium. The nanopowders were hot pressed into optical quality ceramic discs. The optical transmission of the ceramic discs is excellent, nearly approaching the theoretical limit. The optical, spectral and morphological properties as well as the lasing performance from highly transparent ceramics are presented.

Supersaturating Silicon with Titanium by Continuous-Wave Laser Irradiation of Sputtered Titanium Film on Silicon

NASA Astrophysics Data System (ADS)

Bao-Dian, Fan; Yu, Qiu; Rong, Chen; Miao, Pan; Li-Han, Cai; Jiang-Hui, Zheng; Chao, Chen

2016-02-01

Not Available Supported by the National Natural Science Foundation of China under Grant No 61076056, and the Opening Project of State Key Laboratory of High Performance Ceramics and Superfine Microstructure of Shanghai Institute of Ceramics of Chinese Academy of Sciences under Grant No SKL201404SIC.

Evaluation of a novel multiple phase veneering ceramic.

PubMed

Sinthuprasirt, Pannapa; van Noort, Richard; Moorehead, Robert; Pollington, Sarah

2015-04-01

To produce a new veneering ceramic based on the production of a multiple phase glass-ceramic with improved performance in terms of strength and toughness. A composition of 60% leucite, 20% diopside and 20% feldspathic glass was prepared, blended and a heat treatment schedule of 930°C for 5 min was derived from differential thermal analysis (DTA) of the glasses. X-ray diffraction (XRD) and SEM analysis determined the crystalline phases and microstructure. Chemical solubility, biaxial flexural strength (BFS), fracture toughness, hardness, total transmittance and coefficient of thermal expansion (CTE) were all measured in comparison to a commercial veneering ceramic (VITA VM9). Thermal shock resistance of the leucite-diopside and VITA VM9 veneered onto a commercial high strength zirconia (Vita In-Ceram YZ) was also assessed. Statistical analysis was undertaken using Independent Samples t-test. Weibull analysis was employed to examine the reliability of the strength data. The mean chemical solubility was 6 μg/cm(2) for both ceramics (P=1.00). The mean BFS was 109 ± 8 MPa for leucite-diopside ceramic and 79 ± 11 MPa for VITA VM9 ceramic (P=0.01). Similarly, the leucite-diopside ceramic demonstrated a significantly higher fracture toughness and hardness. The average total transmittance was 46.3% for leucite-diopside ceramic and 39.8% for VITA VM9 (P=0.01). The leucite-diopside outperformed the VITA VM9 in terms of thermal shock resistance. Significance This novel veneering ceramic exhibits significant improvements in terms of mechanical properties, yet retains a high translucency and is the most appropriate choice as a veneering ceramic for a zirconia base core material. Copyright © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

High Temperature Piezoelectric Drill

NASA Technical Reports Server (NTRS)

Bao, Xiaoqi; Scott, James; Boudreau, Kate; Bar-Cohen, Yoseph; Sherrit, Stewart; Badescu, Mircea; Shrout, Tom; Zhang, Shujun

2009-01-01

The current NASA Decadal mission planning effort has identified Venus as a significant scientific target for a surface in-situ sampling/analyzing mission. The Venus environment represents several extremes including high temperature (460 deg C), high pressure (9 MPa), and potentially corrosive (condensed sulfuric acid droplets that adhere to surfaces during entry) environments. This technology challenge requires new rock sampling tools for these extreme conditions. Piezoelectric materials can potentially operate over a wide temperature range. Single crystals, like LiNbO3, have a Curie temperature that is higher than 1000 deg C and the piezoelectric ceramics Bismuth Titanate higher than 600 deg C. A study of the feasibility of producing piezoelectric drills that can operate in the temperature range up to 500 deg C was conducted. The study includes the high temperature properties investigations of engineering materials and piezoelectric ceramics with different formulas and doping. The drilling performances of a prototype Ultrasonic/Sonic Drill/Corer (USDC) using high temperate piezoelectric ceramics and single crystal were tested at temperature up to 500 deg C. The detailed results of our study and a discussion of the future work on performance improvements are presented in this paper.

Optimization of the Processing Parameters of High Temperature Superconducting Glass-Ceramics: Center Director's Discretionary Fund Final Report

NASA Technical Reports Server (NTRS)

Ethridge, E. C.; Kaukler, W. F.

1993-01-01

A number of promising glass forming compositions of high Tc superconducting Ba-Sr-Ca-Cu-O (BSCCO) materials were evaluated for their glass-ceramic crystallization ability. The BSCCO ceramics belonging to the class of superconductors in the Ba-Sr-Ca-Cu-O system were the focus of this study. By first forming the superconducting material as a glass, subsequent devitrification into the crystalline (glass-ceramic) superconductor can be performed by thermal processing of the glass preform body. Glass formability and phase formation were determined by a variety of methods in another related study. This study focused on the nucleation and crystallization of the materials. Thermal analysis during rapid cooling aids in the evaluation of nucleation and crystallization behavior. Melt viscosity is used to predict glass formation ability.

Ensuring near-optimum homogeneity and densification levels in nano-reinforced ceramics

NASA Astrophysics Data System (ADS)

Dassios, Konstantinos G.; Barkoula, Nektaria-Marianthi; Alafogianni, Panagiota; Bonnefont, Guillaume; Fantozzi, Gilbert; Matikas, Theodore E.

2016-04-01

The development of a new generation of high temperature ceramic materials for aerospace applications, reinforced at a scale closer to the molecular level and three orders of magnitude less than conventional fibrous reinforcements, by embedded carbon nanotubes, has recently emerged as a uniquely challenging scientific effort. The properties of such materials depend strongly on two main factors: i) the homogeneity of the dispersion of the hydrophobic medium throughout the ceramic volume and ii) the ultimate density of the resultant product after sintering of the green body at the high-temperatures and pressures required for ceramic consolidation. The present works reports the establishment of two independent experimental strategies which ensure achievement of near perfect levels of tube dispersion homogeneity and fully dense final products. The proposed methodologies are validated across non-destructive evaluation data of materials performance.

Low-loss electromagnetic composites for RF and microwave applications.

PubMed

Wang, Hong; Yang, Haibo; Xiang, Feng; Yao, Xi

2011-09-01

Low-loss electromagnetic composites with high permittivity and permeability will benefit the miniaturization and multifunctional of RF devices. A kind of low-loss dielectric-magnetic ceramic-ceramic composite was developed by hybrid processing technology with the goal of integrating the dielectric properties and magnetic properties. The hybrid processing technology exhibits the advantage of lowered sintering temperatures for the composites while retaining good microstructure and high performance. By introducing elastomer as matrix, a kind of flexible low-loss dielectric-magnetic ceramic-polymer composite was prepared and studied. The obtained flexible dielectric-magnetic ceramic-polymer composite exhibited low loss and good mechanical properties. The results show good effects on lowering the dielectric loss and extending the cut-off magnetic frequency of the electromagnetic composite. Methods for tailoring the properties of the multifunctional composites were proposed and discussed.

London University Search Instrument: a combinatorial robot for high-throughput methods in ceramic science.

PubMed

Wang, Jian; Evans, Julian R G

2005-01-01

This paper describes the design, construction, and operation of the London University Search Instrument (LUSI) which was recently commissioned to create and test combinatorial libraries of ceramic compositions. The instrument uses commercially available powders, milled as necessary to create thick-film libraries by ink-jet printing. Multicomponent mixtures are prepared by well plate reformatting of ceramic inks. The library tiles are robotically loaded into a flatbed furnace and, when fired, transferred to a 2-axis high-resolution measurement table fitted with a hot plate where measurements of, for example, optical or electrical properties can be made. Data are transferred to a dedicated high-performance computer. The possibilities for remote interrogation and search steering are discussed.

Enhanced lithium battery with polyethylene oxide-based electrolyte containing silane-Al2 O3 ceramic filler.

PubMed

Zewde, Berhanu W; Admassie, Shimelis; Zimmermann, Jutta; Isfort, Christian Schulze; Scrosati, Bruno; Hassoun, Jusef

2013-08-01

A solid polymer electrolyte prepared by using a solvent-free, scalable technique is reported. The membrane is formed by low-energy ball milling followed by hot-pressing of dry powdered polyethylene oxide polymer, LiCF3 SO3 salt, and silane-treated Al2 O3 (Al2 O3 -ST) ceramic filler. The effects of the ceramic fillers on the properties of the ionically conducting solid electrolyte membrane are characterized by using electrochemical impedance spectroscopy, XRD, differential scanning calorimeter, SEM, and galvanostatic cycling in lithium cells with a LiFePO4 cathode. We demonstrate that the membrane containing Al2 O3 -ST ceramic filler performs well in terms of ionic conductivity, thermal properties, and lithium transference number. Furthermore, we show that the lithium cells, which use the new electrolyte together with the LiFePO4 electrode, operate within 65 and 90 °C with high efficiency and long cycle life. Hence, the Al2 O3 -ST ceramic can be efficiently used as a ceramic filler to enhance the performance of solid polymer electrolytes in lithium batteries. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Ceramic membrane defouling (cleaning) by air Nano Bubbles.

PubMed

Ghadimkhani, Aliasghar; Zhang, Wen; Marhaba, Taha

2016-03-01

Ceramic membranes are among the most promising technologies for membrane applications, owing to their excellent resistance to mechanical, chemical, and thermal stresses. However, membrane fouling is still an issue that hampers the applications at large scales. Air Nano Bubbles (NBs), due to high mass transfer efficiency, could potentially prevent fouling of ceramic membrane filtration processes. In this study, bench and pilot scale ceramic membrane filtration was performed with air NBs to resist fouling. To simulate fouling, humic acid, as an organic foulant, was applied to the membrane flat sheet surface. Complete membrane clogging was achieved in less than 6 h. Membrane defouling (cleaning) was performed by directly feeding of air NBs to the membrane cells. The surface of the ceramic membrane was superbly cleaned by air NBs, as revealed by atomic force microscope (AFM) images before and after the treatment. The permeate flux recovered to its initial level (e.g., 26.7 × 10(-9) m(3)/m(2)/s at applied pressure of 275.8 kPa), which indicated that NBs successfully unclogged the pores of the membrane. The integrated ceramic membrane and air NBs system holds potential as an innovative sustainable technology. Copyright © 2015 Elsevier Ltd. All rights reserved.

Behaviour of Li 2ZrO 3 and Li 2TiO 3 pebbles relevant to their utilization as ceramic breeder for the HCPB blanket

NASA Astrophysics Data System (ADS)

Lulewicz, J. D.; Roux, N.; Piazza, G.; Reimann, J.; van der Laan, J.

2000-12-01

Li 2ZrO 3 and Li 2TiO 3 pebbles are being investigated at Commissariat à l'Energie Atomique as candidate alternative ceramics for the European helium-cooled pebble bed (HCPB) blanket. The pebbles are fabricated using the extrusion-spheronization-sintering process and are optimized regarding composition, geometrical characteristics, microstructural characteristics, and material purity. Tests were designed and are being performed with other organizations so as to check the functional performance of the pebbles and pebble beds with respect to the HCPB blanket requirements, and, finally, to make the selection of the most appropriate ceramic for the HCPB blanket. Tests include high temperature long-term annealing, thermal shock, thermal cycling, thermal mechanical behaviour of pebble beds, thermal conductivity of pebble beds, and tritium extraction. Current results indicate the attractiveness of these ceramics pebbles for the HCPB blanket.

Uniformly Porous Nanocrystalline CaMgFe1.33Ti3O12 Ceramic Derived Electro-Ceramic Nanocomposite for Impedance Type Humidity Sensor

PubMed Central

Tripathy, Ashis; Pramanik, Sumit; Manna, Ayan; Shasmin, Hanie Nadia; Radzi, Zamri; Abu Osman, Noor Azuan

2016-01-01

Since humidity sensors have been widely used in many sectors, a suitable humidity sensing material with improved sensitivity, faster response and recovery times, better stability and low hysteresis is necessary to be developed. Here, we fabricate a uniformly porous humidity sensor using Ca, Ti substituted Mg ferrites with chemical formula of CaMgFe1.33Ti3O12 as humidity sensing materials by solid-sate step-sintering technique. This synthesis technique is useful to control the grain size with increased porosity to enhance the hydrophilic characteristics of the CaMgFe1.33Ti3O12 nanoceramic based sintered electro-ceramic nanocomposites. The highest porosity, lowest density and excellent surface-hydrophilicity properties were obtained at 1050 °C sintered ceramic. The performance of this impedance type humidity sensor was evaluated by electrical characterizations using alternating current (AC) in the 33%–95% relative humidity (RH) range at 25 °C. Compared with existing conventional resistive humidity sensors, the present sintered electro-ceramic nanocomposite based humidity sensor showed faster response time (20 s) and recovery time (40 s). This newly developed sensor showed extremely high sensitivity (%S) and small hysteresis of <3.4%. Long-term stability of the sensor had been determined by testing for 30 consecutive days. Therefore, the high performance sensing behavior of the present electro-ceramic nanocomposites would be suitable for a potential use in advanced humidity sensors. PMID:27916913

Custom ceramic microchannel-cooled array for high-power fiber-coupled application

NASA Astrophysics Data System (ADS)

Junghans, Jeremy; Feeler, Ryan; Stephens, Ed

2018-03-01

A low-SWaP (Size, Weight and Power) diode array has been developed for a high-power fiber-coupled application. High efficiency ( 65%) diodes enable high optical powers while minimizing thermal losses. A large amount of waste heat is still generated and must be extracted. Custom ceramic microchannel-coolers (MCCs) are used to dissipate the waste heat. The custom ceramic MCC was designed to accommodate long cavity length diodes and micro-lenses. The coolers provide similar thermal performance as copper MCCs however they are not susceptible to erosion and can be cooled with standard filtered water. The custom ceramic micro-channel cooled array was designed to be a form/fit replacement for an existing copperbased solution. Each array consisted of three-vertically stacked MCCs with 4 mm CL, 976 nm diodes and beamshaping micro-optics. The erosion and corrosion resistance of ceramic array is intended to mitigate the risk of copperbased MCC corrosion failures. Elimination of the water delivery requirements (pH, resistivity and dissolved oxygen control) further reduces the system SWaP while maintaining reliability. The arrays were fabricated and fully characterized. This work discusses the advantages of the ceramic MCC technology and describes the design parameters that were tailored for the fiber-coupled application. Additional configuration options (form/fit, micro-lensing, alternate coolants, etc.) and on-going design improvements are also discussed.

Analysis of Effect of Zn(O,S) Buffer Layer Properties on CZTS Solar Cell Performance Using AMPS

NASA Astrophysics Data System (ADS)

Lin, Ling-Yan; Qiu, Yu; Zhang, Yu; Zhang, Hao

2016-10-01

Not Available Supported by the Guiding Project of Strategic Emerging Industries of Fujian Provincial Department of Science and Technology under Grant No 2015H0010, the Opening Project of State Key Laboratory of High Performance Ceramics and Superfine Microstructure of Shanghai Institute of Ceramics of Chinese Academy of Sciences under Grant No SKL201404SIC, and the Natural Science Foundation of Fujian Province under Grant No 2016J01751.

A novel biomimetic approach to the design of high-performance ceramic/metal composites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Launey, Maximilien E.; Munch, Etienne; Alsem, Daan Hein

2009-08-01

The prospect of extending natural biological design to develop new synthetic ceramic-metal composite materials is examined. Using ice-templating of ceramic suspensions and subsequent metal infiltration, we demonstrate that the concept of ordered hierarchical design can be applied to create fine-scale laminated ceramic-metal (bulk) composites that are inexpensive, lightweight and display exceptional damage-tolerance properties. Specifically, Al{sub 2}O{sub 3}/Al-Si laminates with ceramic contents up to approximately 40 vol% and with lamellae thicknesses down to 10 {micro}m were processed and characterized. These structures achieve an excellent fracture toughness of 40 MPa{radical}m at a tensile strength of approximately 300 MPa. Salient toughening mechanisms aremore » described together with further toughening strategies.« less

Performance Evaluations of Ceramic Wafer Seals

NASA Technical Reports Server (NTRS)

Dunlap, Patrick H., Jr.; DeMange, Jeffrey J.; Steinetz, Bruce M.

2006-01-01

Future hypersonic vehicles will require high temperature, dynamic seals in advanced ramjet/scramjet engines and on the vehicle airframe to seal the perimeters of movable panels, flaps, and doors. Seal temperatures in these locations can exceed 2000 F, especially when the seals are in contact with hot ceramic matrix composite sealing surfaces. NASA Glenn Research Center is developing advanced ceramic wafer seals to meet the needs of these applications. High temperature scrub tests performed between silicon nitride wafers and carbon-silicon carbide rub surfaces revealed high friction forces and evidence of material transfer from the rub surfaces to the wafer seals. Stickage between adjacent wafers was also observed after testing. Several design changes to the wafer seals were evaluated as possible solutions to these concerns. Wafers with recessed sides were evaluated as a potential means of reducing friction between adjacent wafers. Alternative wafer materials are also being considered as a means of reducing friction between the seals and their sealing surfaces and because the baseline silicon nitride wafer material (AS800) is no longer commercially available.

Advanced composites in Japan

NASA Technical Reports Server (NTRS)

Diefendorf, R. Judd; Hillig, William G.; Grisaffe, Salvatore J.; Pipes, R. Byron; Perepezko, John H.; Sheehan, James E.

1994-01-01

The JTEC Panel on Advanced Composites surveyed the status and future directions of Japanese high-performance ceramic and carbon fibers and their composites in metal, intermetallic, ceramic, and carbon matrices. Because of a strong carbon and fiber industry, Japan is the leader in carbon fiber technology. Japan has initiated an oxidation-resistant carbon/carbon composite program. With its outstanding technical base in carbon technology, Japan should be able to match present technology in the U.S. and introduce lower-cost manufacturing methods. However, the panel did not see any innovative approaches to oxidation protection. Ceramic and especially intermetallic matrix composites were not yet receiving much attention at the time of the panel's visit. There was a high level of monolithic ceramic research and development activity. High temperature monolithic intermetallic research was just starting, but notable products in titanium aluminides had already appeared. Matrixless ceramic composites was one novel approach noted. Technologies for high temperature composites fabrication existed, but large numbers of panels or parts had not been produced. The Japanese have selected aerospace as an important future industry. Because materials are an enabling technology for a strong aerospace industry, Japan initiated an ambitious long-term program to develop high temperature composites. Although just starting, its progress should be closely monitored in the U.S.

CEMCAN Software Enhanced for Predicting the Properties of Woven Ceramic Matrix Composites

NASA Technical Reports Server (NTRS)

Murthy, Pappu L. N.; Mital, Subodh K.; DiCarlo, James A.

2000-01-01

Major advancements are needed in current high-temperature materials to meet the requirements of future space and aeropropulsion structural components. Ceramic matrix composites (CMC's) are one class of materials that are being evaluated as candidate materials for many high-temperature applications. Past efforts to improve the performance of CMC's focused primarily on improving the properties of the fiber, interfacial coatings, and matrix constituents as individual phases. Design and analysis tools must take into consideration the complex geometries, microstructures, and fabrication processes involved in these composites and must allow the composite properties to be tailored for optimum performance. Major accomplishments during the past year include the development and inclusion of woven CMC micromechanics methodology into the CEMCAN (Ceramic Matrix Composites Analyzer) computer code. The code enables one to calibrate a consistent set of constituent properties as a function of temperature with the aid of experimentally measured data.

Permittivity and performance of dielectric pads with sintered ceramic beads in MRI: early experiments and simulations at 3 T.

PubMed

Luo, Wei; Lanagan, Michael T; Sica, Christopher T; Ryu, Yeunchul; Oh, Sukhoon; Ketterman, Matthew; Yang, Qing X; Collins, Christopher M

2013-07-01

Passive dielectric materials have been used to improve aspects of MRI by affecting the distribution of radiofrequency electromagnetic fields. Recently, interest in such materials has increased with the number of high-field MRI sites. Here, we introduce a new material composed of sintered high-permittivity ceramic beads in deuterated water. This arrangement maintains the ability to create flexible pads for conforming to individual subjects. The properties of the material are measured and the performance of the material is compared to previously used materials in both simulation and experiment at 3 T. Results show that both permittivity of the beads and effect on signal-to-noise ratio and required transmit power in MRI are greater than those of materials consisting of ceramic powder in water. Importantly, use of beads results in both higher permittivity and lower conductivity than use of powder. Copyright © 2012 Wiley Periodicals, Inc.

Next Generation Ceramic Substrate Fabricated at Room Temperature.

PubMed

Kim, Yuna; Ahn, Cheol-Woo; Choi, Jong-Jin; Ryu, Jungho; Kim, Jong-Woo; Yoon, Woon-Ha; Park, Dong-Soo; Yoon, Seog-Young; Ma, Byungjin; Hahn, Byung-Dong

2017-07-26

A ceramic substrate must not only have an excellent thermal performance but also be thin, since the electronic devices have to become thin and small in the electronics industry of the next generation. In this manuscript, a thin ceramic substrate (thickness: 30-70 µm) is reported for the next generation ceramic substrate. It is fabricated by a new process [granule spray in vacuum (GSV)] which is a room temperature process. For the thin ceramic substrates, AlN GSV films are deposited on Al substrates and their electric/thermal properties are compared to those of the commercial ceramic substrates. The thermal resistance is significantly reduced by using AlN GSV films instead of AlN bulk-ceramics in thermal management systems. It is due to the removal of a thermal interface material which has low thermal conductivity. In particular, the dielectric strengths of AlN GSV films are much higher than those of AlN bulk-ceramics which are commercialized, approximately 5 times. Therefore, it can be expected that this GSV film is a next generation substrate in thermal management systems for the high power application.

Preparation, characterization and application of novel proton conducting ceramics

NASA Astrophysics Data System (ADS)

Wang, Siwei

Due to the immediate energy shortage and the requirement of environment protection nowadays, the efficient, effective and environmental friendly use of current energy sources is urgent. Energy conversion and storage is thus an important focus both for industry and academia. As one of the hydrogen energy related materials, proton conducting ceramics can be applied in solid oxide fuel cells and steam electrolysers, as well as high temperature hydrogen separation membranes and hydrogen sensors. For most of the practical applications, both high proton conductivity and chemical stability are desirable. However, the state-of-the-art proton conducting ceramics are facing great challenges in simultaneously fulfilling conductivity and stability requirements for practical applications. Consequently, understanding the properties for the proton conducting ceramics and developing novel materials that possess both high proton conductivity and enhanced chemical stability have both scientific and practical significances. The objective of this study is to develop novel proton conducting ceramics, either by evaluating the doping effects on the state-of-the-art simple perovskite structured barium cerates, or by investigating novel complex perovskite structured Ba3Ca1.18Nb1.82O 9-delta based proton conductors as potential proton conducting ceramics with improved proton conductivity and enhanced chemical stability. Different preparation methods were compared, and their influence on the structure, including the bulk and grain boundary environment has been investigated. In addition, the effects of microstructure on the electrical properties of the proton conducting ceramics have also been characterized. The solid oxide fuel cell application for the proton conducting ceramics performed as electrolyte membranes has been demonstrated.

Heat treatment of transparent Yb:YAG and YAG ceramics and its influence on laser performance

NASA Astrophysics Data System (ADS)

Fujioka, Kana; Mochida, Tetsuo; Fujimoto, Yasushi; Tokita, Shigeki; Kawanaka, Junji; Maruyama, Momoko; Sugiyama, Akira; Miyanaga, Noriaki

2018-05-01

Composite transparent ceramic materials are promising for improving the performance of high-average-power lasers. A combination of room-temperature bonding via surface treatment by a fast atom beam and diffusion bonding via heating, which effectively controls the ion diffusion distance near the interface, makes the laser materials suitable for a variety of oscillator/amplifier. During the heat treatment of yttrium aluminum garnet (YAG) ceramics, the Si ions in the solid solution of the sintering aid incorporated within the grains were seen to segregate at the grain boundary, resulting in an increase of scattering sites. The number density and size of the scattering sites strongly depended on the post-heating temperature rather than the heating time. Specifically, heating at 1300 °C did not affect the transmittance of the YAG ceramic, whereas both the size and number of scattering sites substantially increased with a heat treatment at 1400 °C. The laser oscillation experiment using cryogenically-cooled Yb:YAG ceramics exhibited heating temperature dependence of the slope efficiency owing to the increasing scattering loss.

Interdisciplinary research and development on the effects of the nature and properties of ceramic materials in the design of advanced structural components

NASA Technical Reports Server (NTRS)

1978-01-01

An educational development and supportive research program on ceramic materials established to advance design methodology, improve materials, and develop engineers knowledgable in design with and use of high performance ceramic materials is described. Emphasis is on the structures and related materials problems in a ceramic turbine engine, but applications in coal gasification, solar conversion, and magnetohydrodynamic technologies are considered. Progress of various research projects in the areas of new materials, processing, characterization, and nondestructive testing is reported. Fracture toughness determination, extended X-ray absorption fine structure measurements, and grain boundary effects in beta-alumina are among the topics covered.

Silver Niobate Lead-Free Antiferroelectric Ceramics: Enhancing Energy Storage Density by B-Site Doping.

PubMed

Zhao, Lei; Gao, Jing; Liu, Qing; Zhang, Shujun; Li, Jing-Feng

2018-01-10

Lead-free dielectric ceramics with high recoverable energy density are highly desired to sustainably meet the future energy demand. AgNbO 3 -based lead-free antiferroelectric ceramics with double ferroelectric hysteresis loops have been proved to be potential candidates for energy storage applications. Enhanced energy storage performance with recoverable energy density of 3.3 J/cm 3 and high thermal stability with minimal energy density variation (<10%) over a temperature range of 20-120 °C have been achieved in W-modified AgNbO 3 ceramics. It is revealed that the W 6+ cations substitute the B-site Nb 5+ and reduce the polarizability of B-site cations, leading to the enhanced antiferroelectricity, which is confirmed by the polarization hysteresis and dielectric tunability. It is believed that the polarizability of B-site cations plays a dominant role in stabilizing the antiferroelectricity in AgNbO 3 system, in addition to the tolerance factor, which opens up a new design approach to achieve stable antiferroelectric materials.

Ceramic Borehole Seals for Nuclear Waste Disposal Applications

NASA Astrophysics Data System (ADS)

Lowry, B.; Coates, K.; Wohletz, K.; Dunn, S.; Patera, E.; Duguid, A.; Arnold, B.; Zyvoloski, G.; Groven, L.; Kuramyssova, K.

2015-12-01

Sealing plugs are critical features of the deep borehole system design. They serve as structural platforms to bear the weight of the backfill column, and as seals through their low fluid permeability and bond to the borehole or casing wall. High hydrostatic and lithostatic pressures, high mineral content water, and elevated temperature due to the waste packages and geothermal gradient challenge the long term performance of seal materials. Deep borehole nuclear waste disposal faces the added requirement of assuring performance for thousands of years in large boreholes, requiring very long term chemical and physical stability. A high performance plug system is being developed which capitalizes on the energy of solid phase reactions to form a ceramic plug in-situ. Thermites are a family of self-oxidized metal/oxide reactions with very high energy content and the ability to react under water. When combined with engineered additives the product exhibits attractive structural, sealing, and corrosion properties. In the initial phase of this research, exploratory and scaled tests demonstrated formulations that achieved controlled, fine grained, homogeneous, net shape plugs composed predominantly of ceramic material. Laboratory experiments produced plug cores with confined fluid permeability as low as 100 mDarcy, compressive strength as high as 70 MPa (three times the strength of conventional well cement), with the inherent corrosion resistance and service temperature of ceramic matrices. Numerical thermal and thermal/structural analyses predicted the in-situ thermal performance of the reacted plugs, showing that they cooled to ambient temperature (and design strength) within 24 to 48 hours. The current development effort is refining the reactant formulations to achieve desired performance characteristics, developing the system design and emplacement processes to be compatible with conventional well service practices, and understanding the thermal, fluid, and structural effects the plug will have on surrounding media. This paper will report on the state of the development effort and plans for a field demonstration in early 2016 in a cased well with traditional plug seal and strength measurements.

High performance cermet electrodes

DOEpatents

Isenberg, Arnold O.; Zymboly, Gregory E.

1986-01-01

Disclosed is a method of increasing the operating cell voltage of a solid oxide electrochemical cell having metal electrode particles in contact with an oxygen-transporting ceramic electrolyte. The metal electrode is heated with the cell, and oxygen is passed through the oxygen-transporting ceramic electrolyte to the surface of the metal electrode particles so that the metal electrode particles are oxidized to form a metal oxide layer between the metal electrode particles and the electrolyte. The metal oxide layer is then reduced to form porous metal between the metal electrode particles and the ceramic electrolyte.

Diode-pumped high power 2.7 μm Er:Y2O3 ceramic laser at room temperature

NASA Astrophysics Data System (ADS)

Wang, Li; Huang, Haitao; Shen, Deyuan; Zhang, Jian; Chen, Hao; Tang, Dingyuan

2017-09-01

Investigation of room temperature laser performance of the polycrystalline Er:Y2O3 ceramic at 2.7 μm with respect to dopant concentrations was conducted. With 7 at.% Er3+ concentration Er:Y2O3 ceramic as laser gain medium, over 2.05 W of CW output power at 2.7 μm was generated with a slope efficiency of 11.1% with respect to the absorbed LD pump power. The prospects for improvement in lasing efficiency and output power are considered.

Ceramic Transactions. Volume 21. Proceedings of the Symposium on Microwave Theory and Application in Materials Processing Annual Meeting of the American Ceramic Society (23rd) Held in Cincinnati, Ohio on April 29-May 3 1991

DTIC Science & Technology

1992-04-27

spectrum analysis . 4. CONCLUSIONS * The nonthermal synthesis of crystalline nanoparticles of aluminum nitride, silicon carbide and silicon nitride is...51 R.E. Newnham, S.J. Jang, M. Xu, and F. Jones Theory of Microwave Interactions with Ceramic Mz terials .... 69 V.M. Kenkre An Analysis of the...the Performance of Microwave Process Systems Which Utilize High Q Cavities ............ 667 J.F. Gerling and G. Fournier Microwave Thermogravimetric

Joining of ceramics for high performance energy systems. Mid-term progress report, August 1, 1979-March 31, 1980

DOE Office of Scientific and Technical Information (OSTI.GOV)

Smeltzer, C E; Metcalfe, A G

The subject program is primarily an exploratory and demonstration study of the use of silicate glass-based adhesives for bonding silicon-base refractory ceramics (SiC, Si/sub 3/N/sub 4/). The projected application is 1250 to 2050/sup 0/F relaxing joint service in high-performance energy conversion systems. The five program tasks and their current status are as follows. Task 1 - Long-Term Joint Stability. Time-temperature-transformation studies of candidate glass adhesives, out to 2000 hours simulated service exposure, are half complete. Task 2 - Environmental and Service Effects on Joint Reliability. Start up delayed due to late delivery of candidate glass fillers and ceramic specimens. Taskmore » 3 - Viscoelastic Damping of Glass Bonded Ceramics. Promising results obtained over approximately the same range of glass viscosity required for joint relaxation function (10/sup 7.5/ to 10/sup 9.5/ poise). Work is 90% complete. Task 4 - Crack Arrest and Crack Diversion by Joints. No work started due to late arrival of materials. Task 5 - Improved Joining and Fabrication Methods. Significant work has been conducted in the area of refractory pre-glazing and the application and bonding of high-density candidate glass fillers (by both hand-artisan and slip-spray techniques). Work is half complete.« less

Room temperature impact deposition of ceramic by laser shock wave

NASA Astrophysics Data System (ADS)

Jinno, Kengo; Tsumori, Fujio

2018-06-01

In this paper, a direct fine patterning of ceramics at room temperature combining 2 kinds of laser microfabrication methods is proposed. The first method is called laser-induced forward transfer and the other is called laser shock imprinting. In the proposed method, a powder material is deposited by a laser shock wave; therefore, the process is applicable to a low-melting-point material, such as a polymer substrate. In the process, a carbon layer plays an important role in the ablation by laser irradiation to generate a shock wave. This shock wave gives high shock energy to the ceramic particles, and the particles would be deposited and solidified by high-speed collision with the substrate. In this study, we performed deposition experiments by changing the thickness of the carbon layer, laser energy, thickness of the alumina layer, and gap substrates. We compared the ceramic deposits after each experiment.

High speed infrared radiation thermometer, system, and method

DOEpatents

Markham, James R.

2002-01-01

The high-speed radiation thermometer has an infrared measurement wavelength band that is matched to the infrared wavelength band of near-blackbody emittance of ceramic components and ceramic thermal barrier coatings used in turbine engines. It is comprised of a long wavelength infrared detector, a signal amplifier, an analog-to-digital converter, an optical system to collect radiation from the target, an optical filter, and an integral reference signal to maintain a calibrated response. A megahertz range electronic data acquisition system is connected to the radiation detector to operate on raw data obtained. Because the thermometer operates optimally at 8 to 12 .mu.m, where emittance is near-blackbody for ceramics, interferences to measurements performed in turbine engines are minimized. The method and apparatus are optimized to enable mapping of surface temperatures on fast moving ceramic elements, and the thermometer can provide microsecond response, with inherent self-diagnostic and calibration-correction features.

Lattice Thermal Conductivity of Ultra High Temperature Ceramics (UHTC) ZrB2 and HfB2 from Atomistic Simulations

NASA Technical Reports Server (NTRS)

Lawson, JOhn W.; Daw, Murray S.; Bauschlicher, Charles W.

2011-01-01

Ultra high temperature ceramics (UHTC) including ZrB2 and HfB2 are candidate materials for applications in extreme environments because of their high melting point, good mechanical properties and reasonable oxidation resistance. Unlike many ceramics, these materials have high thermal conductivity which can be advantageous, for example, to reduce thermal shock. Recently, we developed Tersoff style interatomic potentials for both ZrB2 and HfB2 appropriate for atomistic simulations. As an application, Green-Kubo molecular dynamics simulations were performed to evaluate the lattice thermal conductivity for single crystals of ZrB2 and HfB2. The atomic mass difference in these binary compounds leads to oscillations in the time correlation function of the heat current. Results at room temperature and at elevated temperatures will be reported.

Lattice Thermal Conductivity of Ultra High Temperature Ceramics ZrB2 and HfB2 from Atomistic Simulations

NASA Technical Reports Server (NTRS)

Lawson, John W.; Murray, Daw S.; Bauschlicher, Charles W., Jr.

2011-01-01

Atomistic Green-Kubo simulations are performed to evaluate the lattice thermal conductivity for single crystals of the ultra high temperature ceramics ZrB2 and HfB2 for a range of temperatures. Recently developed interatomic potentials are used for these simulations. Heat current correlation functions show rapid oscillations which can be identified with mixed metal-Boron optical phonon modes. Agreement with available experimental data is good.

Chemistry-driven structural alterations in short-term retrieved ceramic-on-metal hip implants: Evidence for in vivo incompatibility between ceramic and metal counterparts.

PubMed

Zhu, Wenliang; Pezzotti, Giuseppe; Boffelli, Marco; Chotanaphuti, Thanainit; Khuangsirikul, Saradej; Sugano, Nobuhiko

2017-08-01

Ceramic-on-metal (CoM) hip implants were reported to experience lower wear rates in vitro as compared to metal-on-metal (MoM) bearings, thus hinting metal-ion release at lower levels in vivo. In this article, we show a spectroscopic study of two short-term retrieval cases of zirconia-toughened alumina (ZTA) femoral heads belonging to CoM hip prostheses, which instead showed poor wear performances in vivo. Metal contamination and abnormally high fractions of tetragonal-to-monoclinic (t→m) polymorphic transformation of the zirconia phase could be found on both ZTA heads, which contrasted with the optimistic predictions of in vitro experiments. At the molecular scale, incorporation of metal ions into the ceramic lattices could be recognized as due to frictionally assisted phenomena occurring at the ceramic surface. Driven by abnormal friction, diffusion of metal ions induced lattice shrinkage in the zirconia phases, while residual stress fields became stored at the surface of the femoral head. Diffusional alterations destabilized the chemistry of the ceramic surface and resulted in an abnormal increase in t→m phase transformation in vivo. Frictionally driven metal transfer to the ceramic lattice thus hinders the in vivo performance of CoM prostheses. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 1469-1480, 2017. © 2016 Wiley Periodicals, Inc.

Effects of improved process for CuO-doped NKN lead-free ceramics on high-power piezoelectric transformers.

PubMed

Yang, Song-Ling; Tsai, Cheng-Che; Liou, Yi-Cheng; Hong, Cheng-Shong; Li, Bing-Jing; Chu, Sheng-Yuan

2011-12-01

In this paper, the effects of the electrical proper- ties of CuO-doped (Na(0.5)K(0.5))NbO(3) (NKN) ceramics prepared separately using the B-site oxide precursor method (BO method) and conventional mixed-oxide method (MO method) on high-power piezoelectric transformers (PTs) were investigated. The performances of PTs made with these two substrates were compared. Experimental results showed that the output power and temperature stability of PTs could be enhanced because of the lower resonant impedance of the ceramics prepared using the BO method. In addition, the output power of PTs was more affected by the resonant impedance than by the mechanical quality factor (Q(m)) of the ceramics. The PTs fabricated with ceramics prepared using the BO method showed a high efficiency of more than 94% and a maximum output power of 8.98 W (power density: 18.3 W/cm(3)) with temperature increase of 3°C under the optimum load resistance (5 kΩ) and an input voltage of 150 V(pp). This output power of the lead-free disk-type PTs is the best reported so far.

Design and Development for Capacitive Humidity Sensor Applications of Lead-Free Ca,Mg,Fe,Ti-Oxides-Based Electro-Ceramics with Improved Sensing Properties via Physisorption

PubMed Central

Tripathy, Ashis; Pramanik, Sumit; Manna, Ayan; Bhuyan, Satyanarayan; Azrin Shah, Nabila Farhana; Radzi, Zamri; Abu Osman, Noor Azuan

2016-01-01

Despite the many attractive potential uses of ceramic materials as humidity sensors, some unavoidable drawbacks, including toxicity, poor biocompatibility, long response and recovery times, low sensitivity and high hysteresis have stymied the use of these materials in advanced applications. Therefore, in present investigation, we developed a capacitive humidity sensor using lead-free Ca,Mg,Fe,Ti-Oxide (CMFTO)-based electro-ceramics with perovskite structures synthesized by solid-state step-sintering. This technique helps maintain the submicron size porous morphology of the developed lead-free CMFTO electro-ceramics while providing enhanced water physisorption behaviour. In comparison with conventional capacitive humidity sensors, the presented CMFTO-based humidity sensor shows a high sensitivity of up to 3000% compared to other materials, even at lower signal frequency. The best also shows a rapid response (14.5 s) and recovery (34.27 s), and very low hysteresis (3.2%) in a 33%–95% relative humidity range which are much lower values than those of existing conventional sensors. Therefore, CMFTO nano-electro-ceramics appear to be very promising materials for fabricating high-performance capacitive humidity sensors. PMID:27455263

Advanced SiC/SiC Ceramic Composites For Gas-Turbine Engine Components

NASA Technical Reports Server (NTRS)

Yun, H. M.; DiCarlo, J. A.; Easler, T. E.

2004-01-01

NASA Glenn Research Center (GRC) is developing a variety of advanced SiC/SiC ceramic composite (ASC) systems that allow these materials to operate for hundreds of hours under stress in air at temperatures approaching 2700 F. These SiC/SiC composite systems are lightweight (approximately 30% metal density) and, in comparison to monolithic ceramics and carbon fiber-reinforced ceramic composites, are able to reliably retain their structural properties for long times under aggressive gas-turbine engine environments. The key for the ASC systems is related first to the NASA development of the Sylramic-iBN Sic fiber, which displays higher thermal stability than any other SiC- based ceramic fibers and possesses an in-situ grown BN surface layer for higher environmental durability. This fiber is simply derived from Sylramic Sic fiber type that is currently produced at ATK COI Ceramics (COIC). Further capability is then derived by using chemical vapor infiltration (CVI) and/or polymer infiltration and pyrolysis (PIP) to form a Sic-based matrix with high creep and rupture resistance as well as high thermal conductivity. The objectives of this study were (1) to optimize the constituents and processing parameters for a Sylramic-iBN fiber reinforced ceramic composite system in which the Sic-based matrix is formed at COIC almost entirely by PIP (full PIP approach), (2) to evaluate the properties of this system in comparison to other 2700 F Sylramic-iBN systems in which the matrix is formed by full CVI and CVI + PIP, and (3) to examine the pros and cons of the full PIP approach for fabricating hot-section engine components. A key goal is the development of a composite system with low porosity, thereby providing high modulus, high matrix cracking strength, high interlaminar strength, and high thermal conductivity, a major property requirement for engine components that will experience high thermal gradients during service. Other key composite property goals are demonstration at high temperatures of high environmental resistance and high creep resistance, which in turn will result in long component life. Data are presented from a variety of laboratory tests on simple two-dimensional panels that examine these properties and compare the performance of the optimized full PIP system with those of the full CVI and CVI + PIP hybrid systems. Underlying mechanisms for performance differences in the various systems are discussed. Remaining issues for further property enhancement and for application of the full PIP approach for engine components are also discussed, as well as on-going approaches at NASA to solve these issues.

Performance and Selectivity of Ceramic Membranes in the Ultrafiltration of Model Emulsion in Saline

NASA Astrophysics Data System (ADS)

Ćwirko, Konrad; Kalbarczyk-Jedynak, Agnieszka

2017-06-01

Oily wastewaters from different onshore and offshore installations and from maritime transport pose a serious threat to the environment so they must be treated by multistage separation also including membrane processes. The main advantages of such membranes are high performance and selectivity, high resistance for temperature and pressure, resistance for acids, bases and solvents, long service life and for application - significant reduction of industries and transport environmental impact. This work presents the results of the process of separation of oil from the emulsion with NaCl addition. Research was performed with a use of laboratory installation with ceramic 300 kDa membrane. The analysis concerned performance and selectivity of a membrane in the function of time and test results have been subsequently compared with the requirements of the IMO.

Thermal Conductivity of Advanced Ceramic Thermal Barrier Coatings Determined by a Steady-state Laser Heat-flux Approach

NASA Technical Reports Server (NTRS)

Zhu, Dong-Ming; Miller, Robert A.

2004-01-01

The development of low conductivity and high temperature capable thermal barrier coatings requires advanced testing techniques that can accurately and effectively evaluate coating thermal conductivity under future high-performance and low-emission engine heat-flux conditions. In this paper, a unique steady-state CO2 laser (wavelength 10.6 microns) heat-flux approach is described for determining the thermal conductivity and conductivity deduced cyclic durability of ceramic thermal and environmental barrier coating systems at very high temperatures (up to 1700 C) under large thermal gradients. The thermal conductivity behavior of advanced thermal and environmental barrier coatings for metallic and Si-based ceramic matrix composite (CMC) component applications has also been investigated using the laser conductivity approach. The relationships between the lattice and radiation conductivities as a function of heat flux and thermal gradient at high temperatures have been examined for the ceramic coating systems. The steady-state laser heat-flux conductivity approach has been demonstrated as a viable means for the development and life prediction of advanced thermal barrier coatings for future turbine engine applications.

Strain rate sensitivity of the tensile strength of two silicon carbides: experimental evidence and micromechanical modelling

NASA Astrophysics Data System (ADS)

Zinszner, Jean-Luc; Erzar, Benjamin; Forquin, Pascal

2017-01-01

Ceramic materials are commonly used to design multi-layer armour systems thanks to their favourable physical and mechanical properties. However, during an impact event, fragmentation of the ceramic plate inevitably occurs due to its inherent brittleness under tensile loading. Consequently, an accurate model of the fragmentation process is necessary in order to achieve an optimum design for a desired armour configuration. In this work, shockless spalling tests have been performed on two silicon carbide grades at strain rates ranging from 103 to 104 s-1 using a high-pulsed power generator. These spalling tests characterize the tensile strength strain rate sensitivity of each ceramic grade. The microstructural properties of the ceramics appear to play an important role on the strain rate sensitivity and on the dynamic tensile strength. Moreover, this experimental configuration allows for recovering damaged, but unbroken specimens, giving unique insight on the fragmentation process initiated in the ceramics. All the collected data have been compared with corresponding results of numerical simulations performed using the Denoual-Forquin-Hild anisotropic damage model. Good agreement is observed between numerical simulations and experimental data in terms of free surface velocity, size and location of the damaged zones along with crack density in these damaged zones. This article is part of the themed issue 'Experimental testing and modelling of brittle materials at high strain rates'.

Strain rate sensitivity of the tensile strength of two silicon carbides: experimental evidence and micromechanical modelling.

PubMed

Zinszner, Jean-Luc; Erzar, Benjamin; Forquin, Pascal

2017-01-28

Ceramic materials are commonly used to design multi-layer armour systems thanks to their favourable physical and mechanical properties. However, during an impact event, fragmentation of the ceramic plate inevitably occurs due to its inherent brittleness under tensile loading. Consequently, an accurate model of the fragmentation process is necessary in order to achieve an optimum design for a desired armour configuration. In this work, shockless spalling tests have been performed on two silicon carbide grades at strain rates ranging from 10 3 to 10 4  s -1 using a high-pulsed power generator. These spalling tests characterize the tensile strength strain rate sensitivity of each ceramic grade. The microstructural properties of the ceramics appear to play an important role on the strain rate sensitivity and on the dynamic tensile strength. Moreover, this experimental configuration allows for recovering damaged, but unbroken specimens, giving unique insight on the fragmentation process initiated in the ceramics. All the collected data have been compared with corresponding results of numerical simulations performed using the Denoual-Forquin-Hild anisotropic damage model. Good agreement is observed between numerical simulations and experimental data in terms of free surface velocity, size and location of the damaged zones along with crack density in these damaged zones.This article is part of the themed issue 'Experimental testing and modelling of brittle materials at high strain rates'. © 2016 The Author(s).

Strain rate sensitivity of the tensile strength of two silicon carbides: experimental evidence and micromechanical modelling

PubMed Central

Erzar, Benjamin

2017-01-01

Ceramic materials are commonly used to design multi-layer armour systems thanks to their favourable physical and mechanical properties. However, during an impact event, fragmentation of the ceramic plate inevitably occurs due to its inherent brittleness under tensile loading. Consequently, an accurate model of the fragmentation process is necessary in order to achieve an optimum design for a desired armour configuration. In this work, shockless spalling tests have been performed on two silicon carbide grades at strain rates ranging from 103 to 104 s−1 using a high-pulsed power generator. These spalling tests characterize the tensile strength strain rate sensitivity of each ceramic grade. The microstructural properties of the ceramics appear to play an important role on the strain rate sensitivity and on the dynamic tensile strength. Moreover, this experimental configuration allows for recovering damaged, but unbroken specimens, giving unique insight on the fragmentation process initiated in the ceramics. All the collected data have been compared with corresponding results of numerical simulations performed using the Denoual–Forquin–Hild anisotropic damage model. Good agreement is observed between numerical simulations and experimental data in terms of free surface velocity, size and location of the damaged zones along with crack density in these damaged zones. This article is part of the themed issue ‘Experimental testing and modelling of brittle materials at high strain rates’. PMID:27956504

Integration Science and Technology of Silicon-Based Ceramics and Composites:Technical Challenges and Opportunities

NASA Technical Reports Server (NTRS)

Singh, M.

2013-01-01

Ceramic integration technologies enable hierarchical design and manufacturing of intricate ceramic and composite parts starting with geometrically simpler units that are subsequently joined to themselves and/or to metals to create components with progressively higher levels of complexity and functionality. However, for the development of robust and reliable integrated systems with optimum performance for high temperature applications, detailed understanding of various thermochemical and thermomechanical factors is critical. Different technical approaches are required for the integration of ceramic to ceramic and ceramic to metal systems. Active metal brazing, in particular, is a simple and cost-effective method to integrate ceramic to metallic components. Active braze alloys usually contain a reactive filler metal (e.g., Ti, Cr, V, Hf etc) that promotes wettability and spreading by inducing chemical reactions with the ceramics and composites. In this presentation, various examples of brazing of silicon nitride to themselves and to metallic systems are presented. Other examples of joining of ceramic composites (C/SiC and SiC/SiC) using ceramic interlayers and the resulting microstructures are also presented. Thermomechanical characterization of joints is presented for both types of systems. In addition, various challenges and opportunities in design, fabrication, and testing of integrated similar (ceramic-ceramic) and dissimilar (ceramic-metal) material systems will be discussed. Potential opportunities and need for the development of innovative design philosophies, approaches, and integrated system testing under simulated application conditions will also be presented.

Advanced Environmental Barrier Coating Development for SiC/SiC Ceramic Matrix Composites: NASA's Perspectives

NASA Technical Reports Server (NTRS)

Zhu, Dongming

2016-01-01

This presentation reviews NASA environmental barrier coating (EBC) system development programs and the coating materials evolutions for protecting the SiC/SiC Ceramic Matrix Composites in order to meet the next generation engine performance requirements. The presentation focuses on several generations of NASA EBC systems, EBC-CMC component system technologies for SiC/SiC ceramic matrix composite combustors and turbine airfoils, highlighting the temperature capability and durability improvements in simulated engine high heat flux, high pressure, high velocity, and with mechanical creep and fatigue loading conditions. The current EBC development emphasis is placed on advanced NASA 2700F candidate environmental barrier coating systems for SiC/SiC CMCs, their performance benefits and design limitations in long-term operation and combustion environments. Major technical barriers in developing environmental barrier coating systems, the coating integrations with next generation CMCs having the improved environmental stability, erosion-impact resistance, and long-term fatigue-environment system durability performance are described. The research and development opportunities for advanced turbine airfoil environmental barrier coating systems by utilizing improved compositions, state-of-the-art processing methods, and simulated environment testing and durability modeling are discussed.

Adjusting dental ceramics: An in vitro evaluation of the ability of various ceramic polishing kits to mimic glazed dental ceramic surface.

PubMed

Steiner, René; Beier, Ulrike S; Heiss-Kisielewsky, Irene; Engelmeier, Robert; Dumfahrt, Herbert; Dhima, Matilda

2015-06-01

During the insertion appointment, the practitioner is often faced with the need to adjust ceramic surfaces to fit a restoration to the adjacent or opposing dentition and soft tissues. The purpose of this study was to assess the ceramic surface smoothness achieved with various commercially available ceramic polishing kits on different commonly used ceramic systems. The reliability of the cost of a polishing kit as an indicator of improved surface smoothness was assessed. A total of 350 ceramic surfaces representing 5 commonly available ceramic systems (IPS Empress Esthetic, IPS e.max Press, Cergo Kiss, Vita PM 9, Imagine PressX) were treated with 5 types of ceramic polishing systems (Cerapreshine, 94006C, Ceramiste, Optrafine, Zenostar) by following the manufacturers' guidelines. The surface roughness was measured with a profilometer (Taylor Hobson; Precision Taylor Hobson Ltd). The effects of ceramic systems and polishing kits of interest on surface roughness were analyzed by 2-way ANOVA, paired t test, and Bonferroni corrected significance level. The ceramic systems and polishing kits statistically affected surface roughness (P<.001).The polishing kit Zenostar on IPS e.max Press created the smoothest ceramic surface. No correlation could be established between the high cost of the polishing kit and low surface roughness. None of the commonly used ceramic polishing kits could create a surface smoother than that of glazed ceramic (P<.001). The inclusion of a diamond polishing paste step is recommended to improve surface smoothness (P<.001). The cost of ceramic polishing kits is not recommended as a reliable indicator of better performance of ceramic polishing kits (P>.30). Copyright © 2015 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

Pre-Combustion Carbon Dioxide Capture by a New Dual Phase Ceramic-Carbonate Membrane Reactor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lin, Jerry Y. S.

2015-01-31

This report documents synthesis, characterization and carbon dioxide permeation and separation properties of a new group of ceramic-carbonate dual-phase membranes and results of a laboratory study on their application for water gas shift reaction with carbon dioxide separation. A series of ceramic-carbonate dual phase membranes with various oxygen ionic or mixed ionic and electronic conducting metal oxide materials in disk, tube, symmetric, and asymmetric geometric configurations was developed. These membranes, with the thickness of 10 μm to 1.5 mm, show CO 2 permeance in the range of 0.5-5×10 -7 mol·m -2·s -1·Pa -1 in 500-900°C and measured CO 2/N 2more » selectivity of up to 3000. CO 2 permeation mechanism and factors that affect CO 2 permeation through the dual-phase membranes have been identified. A reliable CO 2 permeation model was developed. A robust method was established for the optimization of the microstructures of ceramic-carbonate membranes. The ceramic-carbonate membranes exhibit high stability for high temperature CO 2 separations and water gas shift reaction. Water gas shift reaction in the dual-phase membrane reactors was studied by both modeling and experiments. It is found that high temperature syngas water gas shift reaction in tubular ceramic-carbonate dual phase membrane reactor is feasible even without catalyst. The membrane reactor exhibits good CO 2 permeation flux, high thermal and chemical stability and high thermal shock resistance. Reaction and separation conditions in the membrane reactor to produce hydrogen of 93% purity and CO 2 stream of >95% purity, with 90% CO 2 capture have been identified. Integration of the ceramic-carbonate dual-phase membrane reactor with IGCC process for carbon dioxide capture was analyzed. A methodology was developed to identify optimum operation conditions for a membrane tube of given dimensions that would treat coal syngas with targeted performance. The calculation results show that the dual-phase membrane reactor could improve IGCC process efficiency but the cost of the membrane reactor with membranes having current CO 2 permeance is high. Further research should be directed towards improving the performance of the membranes and developing cost-effective, scalable methods for fabrication of dual-phase membranes and membrane reactors.« less

Comparison and simulation of salt-ceramic composites for use in high temperature concentrated solar power

NASA Astrophysics Data System (ADS)

Fossile, Lauren Michelle

Due to the inherently intermittent nature of solar energy caused by cloud cover among other sources, thermal storage systems are needed to make solar energy more consistent. This same technology could be used to prolong the daily number of useful hours of solar energy power plants. Salt-ceramic materials are a relatively new prospect for heat storage, but have been researched mostly with magnesium oxide and several different carbonate salts. Salt ceramics are a phase change material where the salt changes phase inside the ceramic structure allowing for the system to use the sensible heat of both materials and the latent heat of the salt to store thermal energy. Capillary forces within the ceramic structure hold in the salt when the salt melts. The focus here is on the possibility of creating a low-cost salt-ceramic storage material for high temperature solar energy applications. A theoretical analysis of the resulting materials is performed. While most of the existing salt ceramics have been made from magnesium oxide, aluminum oxide is more readily available from various companies in the area. Magnesium oxide is often considered a custom ceramic, so it is more expensive. A cost and material property comparison has been completed between these two materials to determine which is better suited for solar storage. Many of the existing salt-ceramics use carbonate salts, but nitrate salts are commonly used in graphite/salt composites. Therefore, a cost and theoretical performance comparison is between these materials also. For comparisons' sake, zirconia and graphite have also been analyzed as the filler in the composite. Each combination of salt and ceramic or graphite has been analyzed. In order to make the use of salt-ceramics more cost-effective and available to Nevada's energy providers, research has been done into which ceramics have high availability in Nevada, low cost, and the best material properties for this application. The thermal properties and cost of these materials have been compared to the price that Nevada's energy utilities are willing to pay per unit of stored energy, which was approximated through a survey conducted by the National Science Foundation (NSF) - Experimental Project to Stimulate Competitive Research (EPSCoR) at the University of Nevada, Las Vegas. The surveys were completed on Nevadan energy purveyors concerning climate change attitudes, but included questions regarding the usefulness and cost of solar storage. The cost per unit of energy has also been calculated and whether the utilities would be willing to pay for each combination will be determined using information obtained from the surveys mentioned above. This information will dictate which combination will be best for use in the state of Nevada at solar energy power plants.

Effects of Compression, Staging, and Braid Angle on Braided Rope Seal Performance

NASA Technical Reports Server (NTRS)

Steinetz, Bruce M.; Adams, Michael L.

1997-01-01

Future turbine engines and industrial systems will be operating at increased temperatures to achieve more demanding efficiency and performance goals. In the highest temperature sections of the engine new material systems such as ceramics and intermetallics are being considered to withstand the harsh thermal environment. Components constructed of these low expansion-rate materials experience thermal strains and a resulting reduction of life when rigidly attached to high expansion-rate, superalloy support structures. Seals are being designed to both seal and to serve as compliant mounts allowing for relative thermal growths between high temperature but brittle primary structures and the surrounding support structures. Previous seal research yielded several braided rope seal designs which demonstrated the ability to both seal and serve as a compliant mount. The hybrid seal was constructed of an all-ceramic (alumina-silica) core overbraided with a superalloy wire sheath (cobalt based superalloy). The all ceramic seal was constructed of an all-ceramic (alumina-silica) core overbraided with multiple ceramic (alumina-silica) sheath layers. Program goals for braided rope seals are to improve flow resistance and/or seal resilience. To that end, the current report studies the test results of: baseline and modified hybrid seals; two stage hybrid and two stage all-ceramic seal configurations; and single stage hybrid and single stage all-ceramic seal configurations for a range of seal crush conditions. Hybrid seal modifications include increasing the sheath braid angle and core coverage. For the same percent seal cross-sectional crush, results show that increasing the hybrid seal braid angle increased seal stiffness and seal unit load, resulting in flows approximately one third of the baseline hybrid seal flows. For both hybrid and all-ceramic seals, two stage seal configurations significantly outperformed single stage configurations. Two stage seal flows were at least 30% less than the single stage seal flows for the same seal crush. Furthermore, test results of single stage seals indicate that for both all-ceramic and hybrid seals, a specific seal crush condition exists at which minimum flows are achieved (i.e. increasing seal crush beyond a certain point does not result in better flow performance). Flow results are presented for a range of pressures and temperatures from ambient to 1300 F, before and after scrubbing. Compression tests results show that for both all-ceramic and hybrid seals, seal preload and stiffness increase with seal crush, but residual seal interference remains constant.

Systematic approach to preparing ceramic-glass composites with high translucency for dental restorations.

PubMed

Yoshimura, Humberto N; Chimanski, Afonso; Cesar, Paulo F

2015-10-01

Ceramic composites are promising materials for dental restorations. However, it is difficult to prepare highly translucent composites due to the light scattering that occurs in multiphase ceramics. The objective of this work was to verify the effectiveness of a systematic approach in designing specific glass compositions with target properties in order to prepare glass infiltrated ceramic composites with high translucency. First it was necessary to calculate from literature data the viscosity of glass at the infiltration temperature using the SciGlass software. Then, a glass composition was designed for targeted viscosity and refractive index. The glass of the system SiO2-B2O3-Al2O3-La2O3-TiO2 prepared by melting the oxide raw materials was spontaneously infiltrated into porous alumina preforms at 1200°C. The optical properties were evaluated using a refractometer and a spectrophotometer. The absorption and scattering coefficients were calculated using the Kubelka-Munk model. The light transmittance of prepared composite was significantly higher than a commercial ceramic-glass composite, due to the matching of glass and preform refractive indexes which decreased the scattering, and also to the decrease in absorption coefficient. The proposed systematic approach was efficient for development of glass infiltrated ceramic composites with high translucency, which benefits include the better aesthetic performance of the final prosthesis. Copyright © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Performance comparison between ceramic Ce:GAGG and single crystal Ce:GAGG with digital-SiPM

NASA Astrophysics Data System (ADS)

Park, C.; Kim, C.; Kim, J.; Lee, Y.; Na, Y.; Lee, K.; Yeom, J. Y.

2017-01-01

The Gd3Al2Ga3O12 (Ce:GAGG) is a new inorganic scintillator known for its attractive properties such as high light yield, stopping power and relatively fast decay time. In this study, we fabricated a ceramic Ce:GAGG scintillator as a cost-effective alternative to single crystal Ce:GAGG and, for the first time, investigated their performances when coupled to the digital silicon photomultiplier (dSiPM)—a new type of photosensor designed for applications in medical imaging, high energy and astrophysics. Compared to 3 × 3 × 2 mm3 sized single crystal Ce:GAGG, the translucent ceramic Ce:GAGG, which has a much lower transmittance than the single crystal, was determined to give an output signal amplitude that is approximately 61% of single crystal Ce:GAGG. The energy resolution of the 511 keV annihilation peak of a 22Na source was measured to be 9.9 ± 0.2% and 13.0 ± 0.3% for the single and ceramic scintillators respectively. On the other hand, the coincidence resolving time (CRT) of ceramic Ce:GAGG was 307 ± 23 ps, better than the 465 ± 37 ps acquired with single crystals—probably attributed to its slightly faster decay time and higher proportion of the fast decay component. The ceramic Ce:GAGG may be a promising cost-effective candidate for applications that do not require thick scintillators such as x-ray detectors and charged particle detectors, and those that require time-of-flight capabilities.

In vivo biofilm formation on different dental ceramics.

PubMed

Bremer, Felicia; Grade, Sebastian; Kohorst, Philipp; Stiesch, Meike

2011-01-01

To investigate the formation of oral biofilm on various dental ceramics in vivo. Five different ceramic materials were included: a veneering glass- ceramic, a lithium disilicate glass-ceramic, a yttrium-stabilized zirconia (Y-TZP), a hot isostatically pressed (HIP) Y-TZP ceramic, and an HIP Y-TZP ceramic with 25% alumina. Test specimens were attached to individually designed acrylic appliances; five volunteers wore these appliances for 24 hours in the maxillary arch. After intraoral exposure, the samples were removed from the appliances and the adhering biofilms vitally stained. Then, the two-dimensional surface coating and thickness of the adhering biofilm were determined by confocal laser scanning microscopy. Statistical analysis was performed using one-way ANOVA with the level of significance set at .05. Significant differences (P < .001) in the bacterial surface coating and in the thickness of the biofilm were found between the various ceramic materials. The lowest surface coating (19.0%) and biofilm thickness (1.9 Μm) were determined on the HIP Y-TZP ceramic; the highest mean values were identified with the lithium disilicate glass-ceramic (46.8%, 12.6 Μm). Biofilm formation on various types of dental ceramics differed significantly; in particular, zirconia exhibited low plaque accumulation. In addition to its high strength, low plaque accumulation makes zirconia a promising material for various indications (including implant abutments and telescopic crowns) that previously were met only with metal-based materials.

Electrostatic Assembly Preparation of High-Toughness Zirconium Diboride-Based Ceramic Composites with Enhanced Thermal Shock Resistance Performance.

PubMed

Zhang, Baoxi; Zhang, Xinghong; Hong, Changqing; Qiu, Yunfeng; Zhang, Jia; Han, Jiecai; Hu, PingAn

2016-05-11

The central problem of using ceramic as a structural material is its brittleness, which associated with rigid covalent or ionic bonds. Whiskers or fibers of strong ceramics such as silicon carbide (SiC) or silicon nitride (Si3N4) are widely embedded in a ceramic matrix to improve the strength and toughness. The incorporation of these insulating fillers can impede the thermal flow in ceramic matrix, thus decrease its thermal shock resistance that is required in some practical applications. Here we demonstrate that the toughness and thermal shock resistance of zirconium diboride (ZrB2)/SiC composites can be improved simultaneously by introducing graphene into composites via electrostatic assembly and subsequent sintering treatment. The incorporated graphene creates weak interfaces of grain boundaries (GBs) and optimal thermal conductance paths inside composites. In comparison to pristine ZrB2-SiC composites, the toughness of (2.0%) ZrB2-SiC/graphene composites exhibited a 61% increasing (from 4.3 to 6.93 MPa·m(1/2)) after spark plasma sintering (SPS); the retained strength after thermal shock increased as high as 74.8% at 400 °C and 304.4% at 500 °C. Present work presents an important guideline for producing high-toughness ceramic-based composites with enhanced thermal shock properties.

A high temperature ceramic heat exchanger element for a solar thermal receiver

NASA Technical Reports Server (NTRS)

Strumpf, H. J.; Kotchick, D. M.; Coombs, M. G.

1982-01-01

The development of a high-temperature ceramic heat exchanger element to be integrated into a solar receiver producing heated air was studied. A number of conceptual designs were developed for heat exchanger elements of differing configuration. These were evaluated with respect to thermal performance, pressure drop, structural integrity, and fabricability. The final design selection identified a finned ceramic shell as the most favorable concept. The shell is surrounded by a larger metallic shell. The flanges of the two shells are sealed to provide a leak-tight pressure vessel. The ceramic shell is to be fabricated by a innovative combination of slip casting the receiver walls and precision casting the heat transfer finned plates. The fins are bonded to the shell during firing. The unit is sized to produce 2150 F air at 2.7 atm pressure, with a pressure drop of about 2 percent of the inlet pressure. This size is compatible with a solar collector providing a receiver input of 85 kw(th). Fabrication of a one-half scale demonstrator ceramic receiver was completed.

Actuator Feasibility Study for Active Control of Ducted Axial Fan Noise

NASA Technical Reports Server (NTRS)

Simonich, John C.

1994-01-01

A feasibility study was performed to investigate actuator technology which is relevant for a particular application of active noise control for gas turbine stator vanes. This study investigated many different classes of actuators and ranked them on the order of applicability. The most difficult requirements the actuators had to meet were high frequency response, large amplitude deflections, and a thin profile. Based on this assessment, piezoelectric type actuators were selected as the most appropriate actuator class. Specifically, Rainbows (a new class of high performance piezoelectric actuators), and unimorphs (a ceramic/metal composite) appeared best suited to the requirements. A benchtop experimental study was conducted. The performance of a variety of different actuators was examined, including high polymer films, flextensional actuators, miniature speakers, unimorphs, and Rainbows. The displacement/frequency response and phase characteristics of the actuators were measured. Physical limitations of actuator operation were also examined. This report includes the first known, high displacement, dynamic data obtained for Rainbow actuators. A new "hard" ceramic Rainbow actuator which does not appear to be limited in operation by self heating as "soft" ceramic Rainbows was designed, constructed and tested. The study concludes that a suitable actuator for active noise control in gas turbine engines can be achieved with state of the art materials and processing.

The Influence of Grain Refiners on the Efficiency of Ceramic Foam Filters

NASA Astrophysics Data System (ADS)

Towsey, Nicholas; Schneider, Wolfgang; Krug, Hans-Peter; Hardman, Angela; Keegan, Neil J.

An extensive program of work has been carried out to evaluate the efficiency of ceramic foam filters under carefully controlled conditions. Work reported at previous TMS meetings showed that in the absence of grain refiners, ceramic foam filters have the capacity for high filtration efficiency and consistent, reliable performance. The current phase of the investigation focuses on the impact grain refiner additions have on filter performance. The high filtration efficiencies obtained using 50 or 80ppi CFF's in the absence of grain refiners diminish when Al-3%Ti-1%B grain refiners are added. This, together with the impact of incoming inclusion loading on filter performance and the level of grain refiner addition are considered in detail. The new generation Al-3%Ti-0.15%C grain refiner has also been included. At typical addition levels (1kg/tonne) the effect on filter efficiency is similar to that for TiB2based grain refiners. The work was again conducted on a production scale using AA1050 alloy. Metal quality was determined using LiMCA and PoDFA. Spent filters were also analysed.

Coating system to permit direct brazing of ceramics

DOEpatents

Cadden, Charles H.; Hosking, F. Michael

2003-01-01

This invention relates to a method for preparing the surface of a ceramic component that enables direct brazing using a non-active braze alloy. The present invention also relates to a method for directly brazing a ceramic component to a ceramic or metal member using this method of surface preparation, and to articles produced by using this brazing method. The ceramic can be high purity alumina. The method comprises applying a first coating of a silicon-bearing oxide material (e.g. silicon dioxide or mullite (3Al.sub.2 O.sub.3.2SiO.sub.2) to the ceramic. Next, a thin coating of active metal (e.g. Ti or V) is applied. Finally, a thicker coating of a non-active metal (e.g. Au or Cu) is applied. The coatings can be applied by physical vapor deposition (PVD). Alternatively, the active and non-active metals can be co-deposited (e.g. by sputtering a target made of mullite). After all of the coatings have been applied, the ceramic can be fired at a high temperature in a non-oxidizing environment to promote diffusion, and to enhance bonding of the coatings to the substrate. After firing, the metallized ceramic component can be brazed to other components using a conventional non-active braze alloy. Alternatively, the firing and brazing steps can be combined into a single step. This process can replace the need to perform a "moly-manganese" metallization step.

Randomized, Controlled Clinical Trial of Bilayer Ceramic and Metal-Ceramic Crown Performance

PubMed Central

Esquivel-Upshaw, Josephine; Rose, William; Oliveira, Erica; Yang, Mark; Clark, Arthur E.; Anusavice, Kenneth

2013-01-01

Purpose Analyzing the clinical performance of restorative materials is important, as there is an expectation that these materials and procedures will restore teeth and do no harm. The objective of this research study was to characterize the clinical performance of metal-ceramic crowns, core ceramic crowns, and core ceramic/veneer ceramic crowns based on 11 clinical criteria. Materials and Methods An IRB-approved, randomized, controlled clinical trial was conducted as a single-blind pilot study. The following three types of full crowns were fabricated: (1) metal-ceramic crown (MC) made from a Pd-Au-Ag-Sn-In alloy (Argedent 62) and a glass-ceramic veneer (IPS d.SIGN veneer); (2) non-veneered (glazed) lithium disilicate glass-ceramic crown (LDC) (IPS e.max Press core and e.max Ceram Glaze); and (3) veneered lithia disilicate glass-ceramic crown (LDC/V) with glass-ceramic veneer (IPS Empress 2 core and IPS Eris). Single-unit crowns were randomly assigned. Patients were recalled for each of 3 years and were evaluated by two calibrated clinicians. Thirty-six crowns were placed in 31 patients. A total of 12 crowns of each of the three crown types were studied. Eleven criteria were evaluated: tissue health, marginal integrity, secondary caries, proximal contact, anatomic contour, occlusion, surface texture, cracks/chips (fractures), color match, tooth sensitivity, and wear (of crowns and opposing enamel). Numerical rankings ranged from 1 to 4, with 4 being excellent, and 1 indicating a need for immediate replacement. Statistical analysis of the numerical rankings was performed using a Fisher’s exact test. Results There was no statistically significant difference between performance of the core ceramic crowns and the two veneered crowns at year 1 and year 2 (p > 0.05). All crowns were rated either as excellent or good for each of the clinical criteria; however, between years 2 and 3, gradual roughening of the occlusal surface occurred in some of the ceramic-ceramic crowns, possibly caused by dissolution and wear of the glaze. Statistically significant differences in surface texture (p = 0.0013) and crown wear (p = 0.0078) were found at year 3 between the metal-ceramic crowns and the lithium-disilicate-based crowns. Conclusion Based on the 11 criteria, the clinical performance of ceramic-ceramic crowns was comparable to that of the metal-ceramic crowns after 2 years; however, gradual roughening occurred between years 2 and 3, which resulted in differences in surface texture and wear. PMID:22978697

Optimization of the injection molding process for development of high performance calcium oxide -based ceramic cores

NASA Astrophysics Data System (ADS)

Zhou, P. P.; Wu, G. Q.; Tao, Y.; Cheng, X.; Zhao, J. Q.; Nan, H.

2018-02-01

The binder composition used for ceramic injection molding plays a crucial role on the final properties of sintered ceramic and to avoid defects on green parts. In this study, the effects of binder compositions on the rheological, microstructures and the mechanical properties of CaO based ceramic cores were investigated. It was found that the optimized formulation for dispersant, solid loading was 1.5 wt% and 84 wt%, respectively. The microstructures, such as porosity, pore size distribution and grain boundary density were closely related to the plasticizer contents. The decrease of plasticizer contents can enhance the strength of the ceramic cores but with decreased shrinkage. Meanwhile, the creep resistance of ceramic cores was enhanced by decreasing of plasticizer contents. The flexural strength of the core was found to decrease with the increase of the porosity, the improvement of creep resistance is closely related to the decrease of porosity and grain boundary density.

A Randomized Trial Comparing Ceramic-on-Ceramic Bearing vs Ceramic-on-Crossfire-Polyethylene Bearing Surfaces in Total Hip Arthroplasty.

PubMed

Beaupre, Lauren A; Al-Houkail, Amro; Johnston, Donald William C

2016-06-01

Bearing surfaces in total hip arthroplasty (THA) may affect implant longevity and hence patient outcomes. This randomized clinical trial determined how ceramic-on-ceramic (CERAMIC) bearing THA affected joint-specific pain, function, and stiffness and prosthesis fixation/longevity over 10 postoperative years compared with ceramic-on-highly-crosslinked-polyethylene (POLYETHYLENE) bearing THA. This is a follow-up to previously reported 5-year outcomes. Subjects aged <61 years were randomized to CERAMIC (n = 48) or POLYETHYLENE (n = 44) THA. Subjects were assessed using the Western Ontario McMaster Osteoarthritis Index and the RAND 12-Item Health Survey preoperatively, and at 1, 5, and 10 years postoperatively. Plain radiographs were evaluated at 10 years for fixation, and medical records were reviewed for revisions. Of 92 subjects, 6 (7%) died within 10 years; 68 (79%) survivors provided radiographic and/or clinical follow-up at 10 years postoperatively. Improvements seen at 5 years in both the Western Ontario McMaster Osteoarthritis Index and RAND 12-Item Health Survey were retained at 10 years with no group differences (P > .48). There were no failures or loss of fixation related to bearing surfaces/wear in either group. Over 10 years, 3 subjects in the POLYETHYLENE group had revisions that were related to recurrent dislocation; 2 revisions were performed within 2 years of surgery, and one further subject underwent revision at 7 years postoperatively. This is one of the first randomized clinical trials to examine 10-year outcomes between CERAMIC and POLYETHYLENE bearing THAs. Both bearing surfaces performed well out to 10 years in subjects who were <61 years at time of surgery. Copyright © 2015 Elsevier Inc. All rights reserved.

All-ceramic or metal-ceramic tooth-supported fixed dental prostheses (FDPs)? A systematic review of the survival and complication rates. Part I: Single crowns (SCs).

PubMed

Sailer, Irena; Makarov, Nikolay Alexandrovich; Thoma, Daniel Stefan; Zwahlen, Marcel; Pjetursson, Bjarni Elvar

2015-06-01

To assess the 5-year survival of metal-ceramic and all-ceramic tooth-supported single crowns (SCs) and to describe the incidence of biological, technical and esthetic complications. Medline (PubMed), Embase, Cochrane Central Register of Controlled Trials (CENTRAL) searches (2006-2013) were performed for clinical studies focusing on tooth-supported fixed dental prostheses (FDPs) with a mean follow-up of at least 3 years. This was complimented by an additional hand search and the inclusion of 34 studies from a previous systematic review [1,2]. Survival and complication rates were analyzed using robust Poisson's regression models to obtain summary estimates of 5-year proportions. Sixty-seven studies reporting on 4663 metal-ceramic and 9434 all-ceramic SCs fulfilled the inclusion criteria. Seventeen studies reported on metal-ceramic crowns, and 54 studies reported on all-ceramic crowns. Meta-analysis of the included studies indicated an estimated survival rate of metal-ceramic SCs of 94.7% (95% CI: 94.1-96.9%) after 5 years. This was similar to the estimated 5-year survival rate of leucit or lithium-disilicate reinforced glass ceramic SCs (96.6%; 95% CI: 94.9-96.7%), of glass infiltrated alumina SCs (94.6%; 95% CI: 92.7-96%) and densely sintered alumina and zirconia SCs (96%; 95% CI: 93.8-97.5%; 92.1%; 95% CI: 82.8-95.6%). In contrast, the 5-year survival rates of feldspathic/silica-based ceramic crowns were lower (p<0.001). When the outcomes in anterior and posterior regions were compared feldspathic/silica-based ceramic and zirconia crowns exhibited significantly lower survival rates in the posterior region (p<0.0001), the other crown types performed similarly. Densely sintered zirconia SCs were more frequently lost due to veneering ceramic fractures than metal-ceramic SCs (p<0.001), and had significantly more loss of retention (p<0.001). In total higher 5 year rates of framework fracture were reported for the all-ceramic SCs than for metal-ceramic SCs. Survival rates of most types of all-ceramic SCs were similar to those reported for metal-ceramic SCs, both in anterior and posterior regions. Weaker feldspathic/silica-based ceramics should be limited to applications in the anterior region. Zirconia-based SCs should not be considered as primary option due to their high incidence of technical problems. Copyright © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Ballistic Performance of Porous-Ceramic, Thermal Protection Systems to 9 km/s

NASA Technical Reports Server (NTRS)

Miller, Joshua E.; Bohl, William E.; Foreman, Cory D.; Christiansen, Eric C.; Davis, Bruce A.

2010-01-01

Porous-ceramic, thermal protection systems are used heavily in current reentry vehicles like the Orbiter, and they are currently being proposed for the next generation of US manned spacecraft, Orion. These materials insulate the structural components and sensitive components of a spacecraft against the intense thermal environments of atmospheric reentry. These materials are also highly exposed to solid particle space environment hazards. This paper discusses recent impact testing up to 9.65 km/s on ceramic tiles similar to those used on the Orbiter. These tiles are a porous-ceramic insulator of nominally 8 lb/ft(exp 3) alumina-fiber-enhanced-thermal-barrier (AETB8) coated with a damage-resistant, toughened-unipiece-fibrous-insulation/reaction-cured-glass layer (TUFI/RCG).

[Multiply upconversion emission in oxyfluoride ceramics].

PubMed

Xiao, Si-guo; Yang, Xiao-liang; Liu, Zhen-wei

2003-02-01

Oxyfluoride ceramics with the host composition of SiO2 and PbF2 have been prepared. X-ray diffraction analysis of the ceramics revealed that fluoride type beta-PbF2 solid solution regions are precipitated in the glass matrix. Rare earth ions in the beta-PbF2 solid solution show highly efficient upconversion performance due to the very small multi-phonon relaxation rates. Eight upconversion emission bands whose central wavelength are 846, 803, 665, 549, 523, 487, 456 and 411 nm have been observed when the sample was excited with 930 nm diode light. Four possible energy transfer processes between Er3+ and Yb3+ cause the electronic population of high energy level of Er3+ and realize the abound upconversion luminescence bands.

Current status of ceramic-based membranes for oxygen separation from air.

PubMed

Hashim, Salwa Meredith; Mohamed, Abdul Rahman; Bhatia, Subhash

2010-10-15

There has been tremendous progress in membrane technology for gas separation, in particular oxygen separation from air in the last 20 years. It provides an alternative route to the existing conventional separation processes such as cryogenic distillation and pressure swing adsorption as well as cheaper production of oxygen with high purity. This review presents the recent advances of ceramic membranes for the separation of oxygen from air at high temperature. It covers the issues and problems with respect to the selectivity and separation performance. The paper also presents different approaches applied to overcome these challenges. The future directions of ceramic-based membranes for oxygen separation from air are also presented. Copyright © 2010 Elsevier B.V. All rights reserved.

Longevity of metal-ceramic crowns cemented with self-adhesive resin cement: a prospective clinical study

PubMed

Brondani, Lucas Pradebon; Pereira-Cenci, Tatiana; Wandsher, Vinicius Felipe; Pereira, Gabriel Kalil; Valandro, Luis Felipe; Bergoli, César Dalmolin

2017-04-10

Resin cements are often used for single crown cementation due to their physical properties. Self-adhesive resin cements gained widespread due to their simplified technique compared to regular resin cement. However, there is lacking clinical evidence about the long-term behavior of this material. The aim of this prospective clinical trial was to assess the survival rates of metal-ceramic crowns cemented with self-adhesive resin cement up to six years. One hundred and twenty-nine subjects received 152 metal-ceramic crowns. The cementation procedures were standardized and performed by previously trained operators. The crowns were assessed as to primary outcome (debonding) and FDI criteria. Statistical analysis was performed using Kaplan-Meier statistics and descriptive analysis. Three failures occurred (debonding), resulting in a 97.6% survival rate. FDI criteria assessment resulted in scores 1 and 2 (acceptable clinical evaluation) for all surviving crowns. The use of self-adhesive resin cement is a feasible alternative for metal-ceramic crowns cementation, achieving high and adequate survival rates.

Synthesis and characterization of a BaGdF5:Tb glass ceramic as a nanocomposite scintillator for x-ray imaging.

PubMed

Lee, Gyuhyon; Struebing, Christian; Wagner, Brent; Summers, Christopher; Ding, Yong; Bryant, Alex; Thadhani, Naresh; Shedlock, Daniel; Star-Lack, Josh; Kang, Zhitao

2016-05-20

Transparent glass ceramics with embedded light-emitting nanocrystals show great potential as low-cost nanocomposite scintillators in comparison to single crystal and transparent ceramic scintillators. In this study, cubic structure BaGdF5:Tb nanocrystals embedded in an aluminosilicate glass matrix are reported for potential high performance MeV imaging applications. Scintillator samples with systematically varied compositions were prepared by a simple conventional melt-quenching method followed by annealing. Optical, structural and scintillation properties were characterized to guide the design and optimization of selected material systems, aiming at the development of a system with higher crystal volume and larger crystal size for improved luminosity. It is observed that enhanced scintillation performance was achieved by tuning the glass matrix composition and using GdF3 in the raw materials, which served as a nucleation agent. A 26% improvement in light output was observed from a BaGdF5:Tb glass ceramic with addition of GdF3.

Prepreg and Melt Infiltration Technology Developed for Affordable, Robust Manufacturing of Ceramic Matrix Composites

NASA Technical Reports Server (NTRS)

Singh, Mrityunjay; Petko, Jeannie F.

2004-01-01

Affordable fiber-reinforced ceramic matrix composites with multifunctional properties are critically needed for high-temperature aerospace and space transportation applications. These materials have various applications in advanced high-efficiency and high-performance engines, airframe and propulsion components for next-generation launch vehicles, and components for land-based systems. A number of these applications require materials with specific functional characteristics: for example, thick component, hybrid layups for environmental durability and stress management, and self-healing and smart composite matrices. At present, with limited success and very high cost, traditional composite fabrication technologies have been utilized to manufacture some large, complex-shape components of these materials. However, many challenges still remain in developing affordable, robust, and flexible manufacturing technologies for large, complex-shape components with multifunctional properties. The prepreg and melt infiltration (PREMI) technology provides an affordable and robust manufacturing route for low-cost, large-scale production of multifunctional ceramic composite components.

Improved performance of diatomite-based dental nanocomposite ceramics using layer-by-layer assembly

PubMed Central

Lu, Xiaoli; Xia, Yang; Liu, Mei; Qian, Yunzhu; Zhou, Xuefeng; Gu, Ning; Zhang, Feimin

2012-01-01

To fabricate high-strength diatomite-based ceramics for dental applications, the layer-by-layer technique was used to coat diatomite particles with cationic [poly(allylamine hydrochloride)] and anionic [poly(sodium 4-styrenesulfonate)] polymers to improve the dispersion and adsorption of positively charged nano-ZrO2 (zirconia) as a reinforcing agent. The modified diatomite particles had reduced particle size, narrower size distribution, and were well dispersed, with good adsorption of nano-ZrO2. To determine the optimum addition levels for nano-ZrO2, ceramics containing 0, 20, 25, 30, and 35 wt% nano-ZrO2 were sintered and characterized by the three-point bending test and microhardness test. In addition to scanning electron microscopy, propagation phase-contrast synchrotron X-ray microtomography was used to examine the internal structure of the ceramics. The addition of 30 wt% nano-ZrO2 resulted in the highest flexural strength and fracture toughness with reduced porosity. Shear bond strength between the core and veneer of our diatomite ceramics and the most widely used dental ceramics were compared; the shear bond strength value for the diatomite-based ceramics was found to be significantly higher than for other groups (P < 0.05). Our results show that diatomite-based nanocomposite ceramics are good potential candidates for ceramic-based dental materials. PMID:22619551

Improved performance of diatomite-based dental nanocomposite ceramics using layer-by-layer assembly.

PubMed

Lu, Xiaoli; Xia, Yang; Liu, Mei; Qian, Yunzhu; Zhou, Xuefeng; Gu, Ning; Zhang, Feimin

2012-01-01

To fabricate high-strength diatomite-based ceramics for dental applications, the layer-by-layer technique was used to coat diatomite particles with cationic [poly(allylamine hydrochloride)] and anionic [poly(sodium 4-styrenesulfonate)] polymers to improve the dispersion and adsorption of positively charged nano-ZrO(2) (zirconia) as a reinforcing agent. The modified diatomite particles had reduced particle size, narrower size distribution, and were well dispersed, with good adsorption of nano-ZrO(2). To determine the optimum addition levels for nano-ZrO(2), ceramics containing 0, 20, 25, 30, and 35 wt% nano-ZrO(2) were sintered and characterized by the three-point bending test and microhardness test. In addition to scanning electron microscopy, propagation phase-contrast synchrotron X-ray microtomography was used to examine the internal structure of the ceramics. The addition of 30 wt% nano-ZrO(2) resulted in the highest flexural strength and fracture toughness with reduced porosity. Shear bond strength between the core and veneer of our diatomite ceramics and the most widely used dental ceramics were compared; the shear bond strength value for the diatomite-based ceramics was found to be significantly higher than for other groups (P < 0.05). Our results show that diatomite-based nanocomposite ceramics are good potential candidates for ceramic-based dental materials.

Wear of Selected Oxide Ceramics and Coatings

NASA Technical Reports Server (NTRS)

Miyoshi, K.; Sayir, A.; Farmer, S. C.

2005-01-01

The use of oxide ceramics and coatings for moving mechanical components operating in high-temperature, oxidizing environments creates a need to define the tribological performance and durability of these materials. Results of research focusing on the wear behavior and properties of Al2O3/ZrO2 (Y2O3) eutectics and coatings under dry sliding conditions are discussed. The importance of microstructure and composition on wear properties of directionally solidified oxide eutectics is illustrated. Wear data of selected oxide-, nitride-, and carbide-based ceramics and coatings are given for temperatures up to 973K in air.

Implementation Challenges for Sintered Silicon Carbide Fiber Bonded Ceramic Materials for High Temperature Applications

NASA Technical Reports Server (NTRS)

Singh, M.

2011-01-01

During the last decades, a number of fiber reinforced ceramic composites have been developed and tested for various aerospace and ground based applications. However, a number of challenges still remain slowing the wide scale implementation of these materials. In addition to continuous fiber reinforced composites, other innovative materials have been developed including the fibrous monoliths and sintered fiber bonded ceramics. The sintered silicon carbide fiber bonded ceramics have been fabricated by the hot pressing and sintering of silicon carbide fibers. However, in this system reliable property database as well as various issues related to thermomechanical performance, integration, and fabrication of large and complex shape components has yet to be addressed. In this presentation, thermomechanical properties of sintered silicon carbide fiber bonded ceramics (as fabricated and joined) will be presented. In addition, critical need for manufacturing and integration technologies in successful implementation of these materials will be discussed.

Transparent Lu 2 O 3 :Eu ceramics by sinter and HIP optimization

NASA Astrophysics Data System (ADS)

Seeley, Z. M.; Kuntz, J. D.; Cherepy, N. J.; Payne, S. A.

2011-09-01

Evolution of porosity and microstructure was observed during densification of lutetium oxide ceramics doped with europium (Lu 2O 3:Eu) fabricated via vacuum sintering and hot isostatic pressing (HIP'ing). Nano-scale starting powder was uniaxially pressed and sintered under high vacuum at temperatures between 1575 and 1850 °C to obtain densities ranging between 94% and 99%, respectively. Sintered compacts were then subjected to 200 MPa argon gas at 1850 °C to reach full density. Vacuum sintering above 1650 °C led to rapid grain growth prior to densification, rendering the pores immobile. Sintering between 1600 and 1650 °C resulted in closed porosity yet a fine grain size to allow the pores to remain mobile during the subsequent HIP'ing step, resulting in a fully-dense highly transparent ceramic without the need for subsequent air anneal. Light yield performance was measured and Lu 2O 3:Eu showed ˜4 times higher light yield than commercially used scintillating glass indicating that this material has the potential to improve the performance of high energy radiography devices.

Thermal and Environmental Barrier Coating Development for Advanced Propulsion Engine Systems

NASA Technical Reports Server (NTRS)

Zhu, Dongming; Miller, Robert A.; Fox, Dennis S.

2008-01-01

Ceramic thermal and environmental barrier coatings (TEBCs) are used in gas turbine engines to protect engine hot-section components in the harsh combustion environments, and extend component lifetimes. Advanced TEBCs that have significantly lower thermal conductivity, better thermal stability and higher toughness than current coatings will be beneficial for future low emission and high performance propulsion engine systems. In this paper, ceramic coating design and testing considerations will be described for turbine engine high temperature and high-heat-flux applications. Thermal barrier coatings for metallic turbine airfoils and thermal/environmental barrier coatings for SiC/SiC ceramic matrix composite (CMC) components for future supersonic aircraft propulsion engines will be emphasized. Further coating capability and durability improvements for the engine hot-section component applications can be expected by utilizing advanced modeling and design tools.

Effect of binder burnout on the sealing performance of glass ceramics for solid oxide fuel cells

NASA Astrophysics Data System (ADS)

Ertugrul, Tugrul Y.; Celik, Selahattin; Mat, Mahmut D.

2013-11-01

The glass ceramics composite sealants are among few materials suitable for the solid oxide fuel cells (SOFC) due to their high operating temperatures (600 °C-850 °C). The glass ceramics chemically bond to both the metallic interconnector and the ceramic electrolyte and provide a gas tight connection. A careful and several stages manufacturing procedure is required to obtain a gas tight sealing. In this study, effects of binder burnout process on the sealing performance are investigated employing commercially available glass ceramic powders. The glass ceramic laminates are produced by mixing glass ceramic powders with the organic binders and employing a tape casting method. The laminates are sandwiched between the metallic interconnectors of an SOFC cell. The burnout and subsequent sealing quality are analyzed by measuring leakage rate and final macrostructure of sealing region. The effects of heating rate, dead weight load, solid loading, carrier gas and their flow rates are investigated. It is found that sealing quality is affected from all investigated parameters. While a slower heating rate is required for a better burnout, the mass flow rate of sweep gas must be adequate for removal of the burned gas. The leakage rate is reduced to 0.1 ml min-1 with 2 °C min-1 + 1 °C min-1 heating rate, 86.25% solid loading, 200 N dead weight load and 500 ml min-1 sweep gas flow rate.

Temperature Distributions in Semitransparent Coatings: A Special Two-Flux Solution

NASA Technical Reports Server (NTRS)

Siegel, Robert; Spuckler, Charles M.

1995-01-01

Radiative transfer is analyzed in a semitransparent coating on an opaque substrate and in a semitransparent layer for evaluating thermal protection behavior and ceramic component performance in high temperature applications. Some ceramics are partially transparent for radiative transfer, and at high temperatures internal emission and reflections affect their thermal performance. The behavior is examined for a ceramic component for which interior cooling is not provided. Two conditions are considered: (1) the layer is heated by penetration of radiation from hot surroundings while its external surface is simultaneously film cooled by convection, and (2) the surface is heated by convection while the semitransparent material cools from within by radiant emission leaving through the surface. By using the two-flux method, which has been found to yield good accuracy in previous studies, a special solution is obtained for these conditions. The analytical result includes isotropic scattering and requires only an integration to obtain the temperature distribution within the semitransparent material. Illustrative results are given to demonstrate the nature of the thermal behavior.

SiC Fibers and SiCf/SiC Ceramic Matrix Minicomposites Damage Behavior

NASA Technical Reports Server (NTRS)

Almansour, Amjad S.

2017-01-01

Silicon Carbide based Ceramic Matrix Composites (CMCs) are attractive materials for use in high-temperature applications in the aerospace industry. Performance and durability of CMCs depend on the properties of its constituents such as fibers and matrix. Therefore, CMCs constituents limitations and damage mechanisms are discussed and characterized in representative simulated application conditions and dominant damage mechanisms are identified at elevated temperatures. In this work, the initiation and evolution of damage in Hi-Nicalon type S fiber-reinforced minicomposites with different interphases thicknesses from different manufacturers were investigated employing several nondestructive evaluation techniques such as acoustic emission, electrical resistance and microscopy. Moreover, the tensile creep behavior of single Hi-Nicalon Type S SiC fibers were tested and characterized and creep parameters were extracted. Fibers creep tests were performed in air or vacuum at 1200-1482 C under high stresses. Creep parameters was then used in understanding load sharing and lifing of ceramic matrix minicomposites. Future work plans will be reviewed.

Microwave assisted synthesis and characterization of barium titanate nanoparticles for multi layered ceramic capacitor applications.

PubMed

Thirumalai, Sundararajan; Shanmugavel, Balasivanandha Prabu

2011-01-01

Barium titanate is a common ferroelectric electro-ceramic material having high dielectric constant, with photorefractive effect and piezoelectric properties. In this research work, nano-scale barium titanate powders were synthesized by microwave assisted mechano-chemical route. Suitable precursors were ball milled for 20 hours. TGA studies were performed to study the thermal stability of the powders. The powders were characterized by XRD, SEM and EDX Analysis. Microwave and Conventional heating were performed at 1000 degrees C. The overall heating schedule was reduced by 8 hours in microwave heating thereby reducing the energy and time requirement. The nano-scale, impurity-free and defect-free microstructure was clearly evident from the SEM micrograph and EDX patterns. LCR meter was used to measure the dielectric constant and dielectric loss values at various frequencies. Microwave heated powders showed superior dielectric constant value with low dielectric loss which is highly essential for the fabrication of Multi Layered Ceramic Capacitors.

New Oxide Ceramic Developed for Superior High-Temperature Wear Resistance

NASA Technical Reports Server (NTRS)

Sayir, Ali; Miyoshi, Kazuhisa; Farmer, Serene C.

2003-01-01

Ceramics, for the most part, do not have inherently good tribological properties. For example friction coefficients in excess of 0.7 have been reported for silicon nitride sliding on silicon nitride or on bearing steel (ref. 1). High friction is always accompanied by considerable wear. Despite their inherently poor tribological properties, the high strength and high toughness of silicon nitride (Si3N4) ceramics has led to their successful use in tribological applications (refs. 1 to 4). The upper temperature limit for the application of Si3N4 as wear-resistant material is limited by reaction with the tribological environment (ref. 3). Silicon nitride is known to produce a thin silicon dioxide film with easy shear capability that results in low friction and low wear in a moist environment (ref. 5). At elevated temperatures, the removal of the reaction product that acts as lubricant causes the friction coefficient to increase and, consequently, the wear performance to become poor. New materials are sought that will have wear resistance superior to that of Si3N4 at elevated temperatures and in harsh environments. A new class of oxide ceramic materials has been developed with potential for excellent high-temperature wear resistance. The new material consists of a multicomponent oxide with a two-phase microstructure, in which the wear resistance of the mixed oxide is significantly higher than that of the individual constituents. This is attributed to the strong constraining effects provided by the interlocking microstructures at different length scales, to the large aspect ratio of the phases, to the strong interphase bonding, and to the residual stresses. Fretting wear tests were conducted by rubbing the new ceramic material against boron carbide (B4C). The new ceramic material produced a wear track groove on B4C, suggesting significantly higher wear resistance for the oxide ceramic. The new material did not suffer from any microstructural degradation after the wear test. The wear rate of the new ceramic material at 600 C was determined to be on the order of 10-10 mm3/N-m, which is 3 to 5 orders of magnitude lower than that for the current state-of-theart wear-resistant materials (Si3N4and B4C). The friction coefficient of the new ceramic materials is on the order of 0.4, which is significantly lower than that of silicon nitride. This new class of oxide materials has shown considerable potential for applications requiring high wear resistance at high temperatures and in harsh environments. New understanding of the wear behavior of ceramic materials is emerging as a result of the surprisingly high wear resistance of two-phase oxide ceramics. There is excellent potential for further improvements in the wear resistance of oxide ceramics through optimizing the microstructure and altering the crystallographic properties of specific oxide materials as a second phase to reduce the coefficient of friction at elevated temperatures.

Methods for Producing High-Performance Silicon Carbide Fibers, Architectural Preforms, and High-Temperature Composite Structures

NASA Technical Reports Server (NTRS)

Yun, Hee-Mann (Inventor); DiCarlo, James A. (Inventor)

2014-01-01

Methods are disclosed for producing architectural preforms and high-temperature composite structures containing high-strength ceramic fibers with reduced preforming stresses within each fiber, with an in-situ grown coating on each fiber surface, with reduced boron within the bulk of each fiber, and with improved tensile creep and rupture resistance properties tier each fiber. The methods include the steps of preparing an original sample of a preform formed from a pre-selected high-strength silicon carbide ceramic fiber type, placing the original sample in a processing furnace under a pre-selected preforming stress state and thermally treating the sample in the processing furnace at a pre-selected processing temperature and hold time in a processing gas having a pre-selected composition, pressure, and flow rate. For the high-temperature composite structures, the method includes additional steps of depositing a thin interphase coating on the surface of each fiber and forming a ceramic or carbon-based matrix within the sample.

Boosting the Recoverable Energy Density of Lead-Free Ferroelectric Ceramic Thick Films through Artificially Induced Quasi-Relaxor Behavior.

PubMed

Peddigari, Mahesh; Palneedi, Haribabu; Hwang, Geon-Tae; Lim, Kyung Won; Kim, Ga-Yeon; Jeong, Dae-Yong; Ryu, Jungho

2018-06-20

Dielectric ceramic film capacitors, which store energy in the form of electric polarization, are promising for miniature pulsed power electronic device applications. For a superior energy storage performance of the capacitors, large recoverable energy density, along with high efficiency, high power density, fast charge/discharge rate, and good thermal/fatigue stability, is desired. Herein, we present highly dense lead-free 0.942[Na 0.535 K 0.480 NbO 3 ]-0.058LiNbO 3 (KNNLN) ferroelectric ceramic thick films (∼5 μm) demonstrating remarkable energy storage performance. The nanocrystalline KNNLN thick film fabricated by aerosol deposition (AD) process and annealed at 600 °C displayed a quasi-relaxor ferroelectric behavior, which is in contrast to the typical ferroelectric nature of the KNNLN ceramic in its bulk form. The AD film exhibited a large recoverable energy density of 23.4 J/cm 3 , with an efficiency of over 70% under the electric field of 1400 kV/cm. Besides, an ultrahigh power density of 38.8 MW/cm 3 together with a fast discharge speed of 0.45 μs, good fatigue endurance (up to 10 6 cycles), and thermal stability in a wide temperature range of 20-160 °C was also observed. Using the AD process, we could make a highly dense microstructure of the film containing nano-sized grains, which gave rise to the quasi-relaxor ferroelectric characteristics and the remarkable energy storage properties.

Aerospace Ceramic Materials: Thermal, Environmental Barrier Coatings and SiC/SiC Ceramic Matrix Composites for Turbine Engine Applications

NASA Technical Reports Server (NTRS)

Zhu, Dongming

2018-01-01

Ceramic materials play increasingly important roles in aerospace applications because ceramics have unique properties, including high temperature capability, high stiffness and strengths, excellent oxidation and corrosion resistance. Ceramic materials also generally have lower densities as compared to metallic materials, making them excellent candidates for light-weight hot-section components of aircraft turbine engines, rocket exhaust nozzles, and thermal protection systems for space vehicles when they are being used for high-temperature and ultra-high temperature ceramics applications. Ceramic matrix composites (CMCs), including non-oxide and oxide CMCs, are also recently being incorporated in gas turbine engines for high pressure and high temperature section components and exhaust nozzles. However, the complexity and variability of aerospace ceramic processing methods, compositions and microstructures, the relatively low fracture toughness of the ceramic materials, still remain the challenging factors for ceramic component design, validation, life prediction, and thus broader applications. This ceramic material section paper presents an overview of aerospace ceramic materials and their characteristics. A particular emphasis has been placed on high technology level (TRL) enabling ceramic systems, that is, turbine engine thermal and environmental barrier coating systems and non-oxide type SiC/SiC CMCs. The current status and future trend of thermal and environmental barrier coatings and SiC/SiC CMC development and applications are described.

Creep performance of oxide ceramic fiber materials at elevated temperature in air and in steam

NASA Astrophysics Data System (ADS)

Armani, Clinton J.

Structural aerospace components that operate in severe conditions, such as extreme temperatures and detrimental environments, require structural materials that have superior long-term mechanical properties and that are thermochemically stable over a broad range of service temperatures and environments. Ceramic matrix composites (CMCs) capable of excellent mechanical performance in harsh environments are prime candidates for such applications. Oxide ceramic materials have been used as constituents in CMCs. However, recent studies have shown that high-temperature mechanical performance of oxide-oxide CMCs deteriorate in a steam-rich environment. The degradation of strength at elevated temperature in steam has been attributed to the environmentally assisted subcritical crack growth in the oxide fibers. Furthermore, oxide-oxide CMCs have shown significant increases in steady-state creep rates in steam. The present research investigated the effects of steam on the high-temperature creep and monotonic tension performance of several oxide ceramic materials. Experimental facilities were designed and configured, and experimental methods were developed to explore the influence of steam on the mechanical behaviors of ceramic fiber tows and of ceramic bulk materials under temperatures in the 1100--1300°C range. The effects of steam on creep behavior of Nextel(TM)610 and Nextel(TM)720 fiber tows were examined. Creep rates at elevated temperatures in air and in steam were obtained for both types of fibers. Relationships between creep rates and applied stresses were modeled and underlying creep mechanisms were identified. For both types of fiber tows, a creep life prediction analysis was performed using linear elastic fracture mechanics and a power-law crack velocity model. These results have not been previously reported and have critical design implications for CMC components operating in steam or near the recommended design limits. Predictions were assessed and validated via comparisons with experimental results. Additionally, the utility of the Monkman-Grant relationship to predicting creep-rupture life of the fiber tows at elevated temperature in air and in steam was demonstrated. Furthermore, the effects of steam on the compressive creep performance of bulk ceramic materials were also studied. Performance of fine grained, polycrystalline alumina (Al2O3) was investigated at 1100 and 1300°C in air and in steam. To evaluate the effect of silica doping during material processing both undoped and silica doped polycrystalline alumina specimens were tested. Finally, compressive creep performance of yttrium aluminum garnet (YAG, Y3Al5O12) was evaluated at 1300°C in air and in steam. Both undoped and silica doped YAG specimens were included in the study. YAG is being considered as the next-generation oxide fiber material. However, before considerable funding and effort are invested in a fiber development program, it is necessary to evaluate the creep performance of YAG at elevated temperature in steam. Results of this research demonstrated that both the undoped YAG and the silica doped YAG exhibited exceptional creep resistance at 1300°C in steam for grain sizes ˜1 microm. These results supplement the other promising features of YAG that make it a strong candidate material for the next generation ceramic fiber.

Surface preparation for high purity alumina ceramics enabling direct brazing in hydrogen atmospheres

DOEpatents

Cadden, Charles H.; Yang, Nancy Yuan Chi; Hosking, Floyd M.

2001-01-01

The present invention relates to a method for preparing the surface of a high purity alumina ceramic or sapphire specimen that enables direct brazing in a hydrogen atmosphere using an active braze alloy. The present invention also relates to a method for directly brazing a high purity alumina ceramic or sapphire specimen to a ceramic or metal member using this method of surface preparation, and to articles produced by this brazing method. The presence of silicon, in the form of a SiO.sub.2 -containing surface layer, can more than double the tensile bond strength in alumina ceramic joints brazed in a hydrogen atmosphere using an active Au-16Ni-0.75 Mo-1.75V filler metal. A thin silicon coating applied by PVD processing can, after air firing, produce a semi-continuous coverage of the alumina surface with a SiO.sub.2 film. Room temperature tensile strength was found to be proportional to the fraction of air fired surface covered by silicon-containing films. Similarly, the ratio of substrate fracture versus interface separation was also related to the amount of surface silicon present prior to brazing. This process can replace the need to perform a "moly-manganese" metallization step.

Metal-Matrix/Hollow-Ceramic-Sphere Composites

NASA Technical Reports Server (NTRS)

Baker, Dean M.

2011-01-01

A family of metal/ceramic composite materials has been developed that are relatively inexpensive, lightweight alternatives to structural materials that are typified by beryllium, aluminum, and graphite/epoxy composites. These metal/ceramic composites were originally intended to replace beryllium (which is toxic and expensive) as a structural material for lightweight mirrors for aerospace applications. These materials also have potential utility in automotive and many other terrestrial applications in which there are requirements for lightweight materials that have high strengths and other tailorable properties as described below. The ceramic component of a material in this family consists of hollow ceramic spheres that have been formulated to be lightweight (0.5 g/cm3) and have high crush strength [40.80 ksi (.276.552 MPa)]. The hollow spheres are coated with a metal to enhance a specific performance . such as shielding against radiation (cosmic rays or x rays) or against electromagnetic interference at radio and lower frequencies, or a material to reduce the coefficient of thermal expansion (CTE) of the final composite material, and/or materials to mitigate any mismatch between the spheres and the matrix metal. Because of the high crush strength of the spheres, the initial composite workpiece can be forged or extruded into a high-strength part. The total time taken in processing from the raw ingredients to a finished part is typically 10 to 14 days depending on machining required.

High Ionic Conductivity of Composite Solid Polymer Electrolyte via In Situ Synthesis of Monodispersed SiO2 Nanospheres in Poly(ethylene oxide).

PubMed

Lin, Dingchang; Liu, Wei; Liu, Yayuan; Lee, Hye Ryoung; Hsu, Po-Chun; Liu, Kai; Cui, Yi

2016-01-13

High ionic conductivity solid polymer electrolyte (SPE) has long been desired for the next generation high energy and safe rechargeable lithium batteries. Among all of the SPEs, composite polymer electrolyte (CPE) with ceramic fillers has garnered great interest due to the enhancement of ionic conductivity. However, the high degree of polymer crystallinity, agglomeration of ceramic fillers, and weak polymer-ceramic interaction limit the further improvement of ionic conductivity. Different from the existing methods of blending preformed ceramic particles with polymers, here we introduce an in situ synthesis of ceramic filler particles in polymer electrolyte. Much stronger chemical/mechanical interactions between monodispersed 12 nm diameter SiO2 nanospheres and poly(ethylene oxide) (PEO) chains were produced by in situ hydrolysis, which significantly suppresses the crystallization of PEO and thus facilitates polymer segmental motion for ionic conduction. In addition, an improved degree of LiClO4 dissociation can also be achieved. All of these lead to good ionic conductivity (1.2 × 10(-3) S cm(-1) at 60 °C, 4.4 × 10(-5) S cm(-1) at 30 °C). At the same time, largely extended electrochemical stability window up to 5.5 V can be observed. We further demonstrated all-solid-state lithium batteries showing excellent rate capability as well as good cycling performance.

Light Weight Ceramic Ablators for Mars Follow-on Mission Vehicle Thermal Protection System

NASA Technical Reports Server (NTRS)

Tran, Huy K.; Rasky, Daniel J.; Hsu, Ming-Ta; Turan, Ryan

1994-01-01

New Light Weight Ceramic Ablators (LCA) were produced by using ceramic and carbon fibrous substrates, impregnated with silicone and phenolic resins. The special infiltration techniques (patent pending) were developed to control the amount of organic resins in the highly porous fiber matrices so that the final densities of LCA's range from 0.22 to 0.24 g/cc. This paper presents the thermal and ablative performance of the Silicone Impregnated Reusable Ceramic Ablators (SIRCA) in simulated entry conditions for Mars-Pathfinder in the Ames 60 MW Interaction Heating Facility (I HF). Arc jet test results yielded no evidence of char erosion and mass loss at high stagnation pressures to 0.25 atm. Minimal silica melt was detected on surface char at a stagnation pressure of 0.31 atm. Four ceramic substrates were used in the production of SIRCA's to obtain the effective of boron oxide present in substrate so the thermal performance of SIRCA's. A sample of SIRCA was also exposed to the same heating condition for five cycles and no significant mass loss or recession was observed. Tensile testing established that the SIRCA tensile strength is about a factor of two higher than that of the virgin substrates. Thermogravimetric Analysis (TGA) of the char in nitrogen and air showed no evidence of free carbon in the char. Scanning Electron Microscopy of the post test sample showed that the char surface consists of a fibrous structure that was sealed with a thin layer of silicon oxide melt.

Origin of colossal permittivity in (In1/2Nb1/2)TiO2via broadband dielectric spectroscopy.

PubMed

Zhao, Xiao-gang; Liu, Peng; Song, Yue-Chan; Zhang, An-ping; Chen, Xiao-ming; Zhou, Jian-ping

2015-09-21

(In1/2Nb1/2)TiO2 (IN-T) ceramics were prepared via a solid-state reaction route. X-ray diffraction (XRD) and Raman spectroscopy were used for the structural and compositional characterization of the synthesized compounds. The results indicated that the sintered ceramics have a single phase of rutile TiO2. Dielectric spectroscopy (frequency range from 20 Hz to 1 MHz and temperature range from 10 K to 270 K) was performed on these ceramics. The IN-T ceramics showed extremely high permittivities of up to ∼10(3), which can be referred to as colossal permittivity, with relatively low dielectric losses of ∼0.05. Most importantly, detailed impedance data analyses of IN-T demonstrated that electron-pinned defect-dipoles, interfacial polarization and polaron hopping polarization contribute to the colossal permittivity at high temperatures (270 K); however, only the complexes (pinned electron) and polaron hopping polarization are active at low temperatures (below 180 K), which is consistent with UDR analysis.

Topological design of all-ceramic dental bridges for enhancing fracture resistance.

PubMed

Zhang, Zhongpu; Chen, Junning; Li, Eric; Li, Wei; Swain, Michael; Li, Qing

2016-06-01

Layered all-ceramic systems have been increasingly adopted in major dental prostheses. However, ceramics are inherently brittle, and they often subject to premature failure under high occlusion forces especially in the posterior region. This study aimed to develop mechanically sound novel topological designs for all-ceramic dental bridges by minimizing the fracture incidence under given loading conditions. A bi-directional evolutionary structural optimization (BESO) technique is implemented within the extended finite element method (XFEM) framework. Extended finite element method allows modeling crack initiation and propagation inside all-ceramic restoration systems. Following this, BESO searches the optimum distribution of two different ceramic materials, namely porcelain and zirconia, for minimizing fracture incidence. A performance index, as per a ratio of peak tensile stress to material strength, is used as a design objective. In this study, the novel XFEM based BESO topology optimization significantly improved structural strength by minimizing performance index for suppressing fracture incidence in the structures. As expected, the fracture resistance and factor of safety of fixed partial dentures structure increased upon redistributing zirconia and porcelain in the optimal topological configuration. Dental CAD/CAM systems and the emerging 3D printing technology were commercially available to facilitate implementation of such a computational design, exhibiting considerable potential for clinical application in the future. Copyright © 2015 John Wiley & Sons, Ltd. Copyright © 2015 John Wiley & Sons, Ltd.

Application of ceramic membranes with pre-ozonation for treatment of secondary wastewater effluent.

PubMed

Lehman, S Geno; Liu, Li

2009-04-01

Membrane fouling is an inevitable problem when microfiltration (MF) and ultrafiltraion (UF) are used to treat wastewater treatment plant (WWTP) effluent. While historically the use of MF/UF for water and wastewater treatment has been almost exclusively focused on polymeric membranes, new generation ceramic membranes were recently introduced in the market and they possess unique advantages over currently available polymeric membranes. Ceramic membranes are mechanically superior and are more resistant to severe chemical and thermal environments. Due to the robustness of ceramic membranes, strong oxidants such as ozone can be used as pretreatment to reduce the membrane fouling. This paper presents results of a pilot study designed to investigate the application of new generation ceramic membranes for WWTP effluent treatment. Ozonation and coagulation pretreatment were evaluated to optimize the membrane operation. The ceramic membrane demonstrated stable performance at a filtration flux of 100 gfd (170LMH) at 20 degrees C with pretreatment using PACl (1mg/L as Al) and ozone (4 mg/L). To understand the effects of ozone and coagulation pretreatment on organic foulants, natural organic matter (NOM) in four waters - raw, ozone treated, coagulation treated, and ozone followed by coagulation treated wastewaters - were characterized using high performance size exclusion chromatography (HPSEC). The HPSEC analysis demonstrated that ozone treatment is effective at degrading colloidal NOMs which are likely responsible for the majority of membrane fouling.

Synthesis and Luminescence Properties of Transparent Nanocrystalline GdF3:Tb Glass-Ceramic Scintillator.

PubMed

Lee, Gyuhyon; Savage, Nicholas; Wagner, Brent; Zhang, Yuelan; Jacobs, Benjamin; Menkara, Hisham; Summers, Christopher; Kang, Zhitao

2014-03-01

Transparent glass-ceramic containing rare-earth doped halide nanocrystals exhibits enhanced luminescence performance. In this study, a glass-ceramic with Tb doped gadolinium fluoride nanocrystals embedded in an aluminosilicate glass matrix is investigated for X-ray imaging applications. The nanocrystalline glass-ceramic scintillator was prepared by a melt-quench method followed by an anneal. The GdF 3 :Tb nanocrystals precipitated within the oxide glass matrix during the processing and their luminescence and scintillation properties were investigated. In this nanocomposite scintillator system, the incorporation of high atomic number Gd compound into the glass matrix increases the X-ray stopping power of the glass scintillator, and effective energy transfer between Gd 3+ and Tb 3+ ions in the nanocrystals enhances the scintillation efficiency.

Controlling the leakage of liquid bismuth cathode elements in ceramic crucibles used for the electrowinning process in pyroprocessing

NASA Astrophysics Data System (ADS)

Kim, Dae-Young; Hwang, Il-Soon; Lee, Jong-Hyeon

2016-09-01

Pyroprocessing has shown promise as an alternative to wet processing for the recycling of transuranics with a high proliferation resistance. However, a critical issue for pyroprocessing is the ceramic crucibles used in the electrowinning process. These ceramic crucibles are frequently damaged by thermal stress, which results in significant volumes of crucible waste that must be properly disposed. Transuranic waste (TRU) elements intrude throughout the pores of a damaged crucible. The volume of generated radioactive waste is a concern when dealing with nuclear power plants and decontamination issues. In this study, laser treatment and sintering were performed on the crucibles to minimize the TRU elements trapped within. Secondary ion mass spectroscopy was used to measure the intrusion depth of Li in the surface-treated ceramics.

Synthesis and Luminescence Properties of Transparent Nanocrystalline GdF3:Tb Glass-Ceramic Scintillator

PubMed Central

Lee, Gyuhyon; Savage, Nicholas; Wagner, Brent; Zhang, Yuelan; Jacobs, Benjamin; Menkara, Hisham; Summers, Christopher; Kang, Zhitao

2014-01-01

Transparent glass-ceramic containing rare-earth doped halide nanocrystals exhibits enhanced luminescence performance. In this study, a glass-ceramic with Tb doped gadolinium fluoride nanocrystals embedded in an aluminosilicate glass matrix is investigated for X-ray imaging applications. The nanocrystalline glass-ceramic scintillator was prepared by a melt-quench method followed by an anneal. The GdF3:Tb nanocrystals precipitated within the oxide glass matrix during the processing and their luminescence and scintillation properties were investigated. In this nanocomposite scintillator system, the incorporation of high atomic number Gd compound into the glass matrix increases the X-ray stopping power of the glass scintillator, and effective energy transfer between Gd3+ and Tb3+ ions in the nanocrystals enhances the scintillation efficiency. PMID:24610960

Evaluation Of Shielding Efficacy Of A Ferrite Containing Ceramic Material

DOE Office of Scientific and Technical Information (OSTI.GOV)

Verst, C.

2015-10-12

The shielding evaluation of the ferrite based Mitsuishi ceramic material has produced for several radiation sources and possible shielding sizes comparative dose attenuation measurements and simulated projections. High resolution gamma spectroscopy provided uncollided and scattered photon spectra at three energies, confirming theoretical estimates of the ceramic’s mass attenuation coefficient, μ/ρ. High level irradiation experiments were performed using Co-60, Cs-137, and Cf-252 sources to measure penetrating dose rates through steel, lead, concrete, and the provided ceramic slabs. The results were used to validate the radiation transport code MCNP6 which was then used to generate dose rate attenuation curves as a functionmore » of shielding material, thickness, and mass for photons and neutrons ranging in energy from 200 keV to 2 MeV.« less

Plasma gun with coaxial powder feed and adjustable cathode

NASA Technical Reports Server (NTRS)

Zaplatynsky, Isidor (Inventor)

1991-01-01

An improved plasma gun coaxially injects particles of ceramic materials having high melting temperatures into the central portion of a plasma jet. This results in a more uniform and higher temperature and velocity distribution of the sprayed particles. The position of the cathode is adjustable to facilitate optimization of the performance of the gun wherein grains of the ceramic material are melted at lower power input levels.

Sample Size Induced Brittle-to-Ductile Transition of Single-Crystal Aluminum Nitride

DTIC Science & Technology

2015-08-01

exhibit many distinctive physical and mechanical properties, compared to metallic and polymeric materials, but the propensity toward brittle fracture ...micromechanism for the plastic deformation of ductile metals while the mechanical performance of high-strength ceramics is often dominated by brittle fracture at...SUPPLEMENTARY NOTES A reprint from Acta Materialia 88 (2015) 252–259 14. ABSTRACT Ceramics are known to be mechanically hard, chemically inert and

Enhancement of Dielectric Breakdown Strength and Energy Conversion Efficiency of Niobate Glass-Ceramics by Sc2O3 Doping

NASA Astrophysics Data System (ADS)

Xiao, Shi; Xiu, Shaomei; Yang, Ke; Shen, Bo; Zhai, Jiwei

2018-01-01

Niobate glass-ceramics K2O-SrO-Nb2O5-B2O3-Al2O3-SiO2 (KSN-BAS) doped with different amounts of Sc2O3 have been prepared through a melt quenching/controlled crystallization method, and the influence of the Sc2O3 content on their phase composition, microstructure, dielectric performance, and charge-discharge properties investigated. X-ray powder diffraction results showed that the peak positions of the KSr2Nb5O15 phase shifted to higher angle and the glass-ceramic microstructures were significantly improved by Sc2O3 addition. Based on these results, 0.5 mol.% Sc2O3 doping was found to achieve remarkable enhancement in energy storage density, which reached 9.63 ± 0.39 J/cm3 at dielectric breakdown strength of 1450.38 ± 29.01 kV/cm with high conversion efficiency of ˜ 92.1%. For pulsed power applications, discharge speed of 17 ns and power density of 0.48 MW/cm3 were obtained in the glass-ceramic with 0.5 mol.% Sc2O3. These results could provide a new design strategy for high-performance dielectric capacitors.

Comparison of catalytic converter performance in internal combustion engine fueled with Ron 95 and Ron 97 gasoline

NASA Astrophysics Data System (ADS)

Leman, A. M.; Rahman, Fakhrurrazi; Jajuli, Afiqah; Feriyanto, Dafit; Zakaria, Supaat

2017-09-01

Generating ideal stability between engine performance, fuel consumption and emission is one of the main challenges in the automotive industry. The characteristics of engine combustion and creation of emission might simply change with different types of operating parameters. This study aims in investigating the relationship between two types of fuels on the performance and exhaust emission of internal combustion engine using ceramic and metallic catalytic converters. Experimental tests were performed on Mitsubishi 4G93 engine by applying several ranges of engine speeds to determine the conversion of pollutant gases released by the engine. The obtained results specify that the usage of RON 97 equipped with metallic converters might increase the conversion percentage of 1.31% for CO and 126 ppm of HC gases. The metallic converters can perform higher conversion compared to ceramic because in the high space velocities, metallic has higher surface geometry area and higher amount of transverse Peclet number (Pi). Ceramic converters achieved conversion at 2496 ppm of NOx gas, which is higher than the metallic converter.

[Spectroscopic Research on Slag Nanocrystal Glass Ceramics Containing Rare Earth Elements].

PubMed

Ouyang, Shun-li; Li, Bao-wei; Zhang, Xue-feng; Jia, Xiao-lin; Zhao, Ming; Deng, Lei-bo

2015-08-01

The research group prepared the high-performance slag nanocrystal glass ceramics by utilizing the valuable elements of the wastes in the Chinese Bayan Obo which are characterized by their symbiotic or associated existence. In this paper, inductively coupled plasma emission spectroscopy (ICP), X-ray diffraction (XRD), Raman spectroscopy (Raman) and scanning electron microscopy (SEM) are all used in the depth analysis for the composition and structure of the samples. The experiment results of ICP, XRD and SEM showed that the principal crystalline phase of the slag nanocrystal glass ceramics containing rare earth elements is diopside, its grain size ranges from 45 to 100 nm, the elements showed in the SEM scan are basically in consistent with the component analysis of ICP. Raman analysis indicated that its amorphous phase is a three-dimensional network structure composed by the structural unit of silicon-oxy tetrahedron with different non-bridging oxygen bonds. According to the further analysis, we found that the rare earth microelement has significant effect on the network structure. Compared the nanocrystal slag glass ceramic with the glass ceramics of similar ingredients, we found that generally, the Raman band wavenumber for the former is lower than the later. The composition difference between the glass ceramics and the slag nanocrystal with the similar ingredients mainly lies on the rare earth elements and other trace elements. Therefore, we think that the rare earth elements and other trace elements remains in the slag nanocrystal glass ceramics have a significant effect on the network structure of amorphous phase. The research method of this study provides an approach for the relationship among the composition, structure and performance of the glass ceramics.

Enhanced electrocaloric analysis and energy-storage performance of lanthanum modified lead titanate ceramics for potential solid-state refrigeration applications.

PubMed

Zhang, Tian-Fu; Huang, Xian-Xiong; Tang, Xin-Gui; Jiang, Yan-Ping; Liu, Qiu-Xiang; Lu, Biao; Lu, Sheng-Guo

2018-01-10

The unique properties and great variety of relaxer ferroelectrics make them highly attractive in energy-storage and solid-state refrigeration technologies. In this work, lanthanum modified lead titanate ceramics are prepared and studied. The giant electrocaloric effect in lanthanum modified lead titanate ceramics is revealed for the first time. Large refrigeration efficiency (27.4) and high adiabatic temperature change (1.67 K) are achieved by indirect analysis. Direct measurements of electrocaloric effect show that reversible adiabatic temperature change is also about 1.67 K, which exceeds many electrocaloric effect values in current direct measured electrocaloric studies. Both theoretical calculated and direct measured electrocaloric effects are in good agreements in high temperatures. Temperature and electric field related energy storage properties are also analyzed, maximum energy-storage density and energy-storage efficiency are about 0.31 J/cm 3 and 91.2%, respectively.

High-temperature properties of ceramic fibers and insulations for thermal protection of atmospheric entry and hypersonic cruise vehicles

NASA Technical Reports Server (NTRS)

Kourtides, Demetrius A.; Pitts, William C.; Araujo, Myrian; Zimmerman, R. S.

1988-01-01

Multilayer insulations (MIs) which will operate in the 500 to 1000 C temperature range are being considered for possible applications on aerospace vehicles subject to convective and radiative heating during atmospheric entry. The insulations described consist of ceramic fibers, insulations, and metal foils quilted together with ceramic thread. As these types of insulations have highly anisotropic properties, the total heat transfer characteristics must be determined. Data are presented on the thermal diffusivity and thermal conductivity of four types of MIs and are compared to the baseline Advanced Flexible Reusable Surface Insulation currently used on the Space Shuttle Orbiter. In addition, the high temperature properties of the fibers used in these MIs are discussed. The fibers investigated included silica and three types of aluminoborosilicate (ABS). Static tension tests were performed at temperatures up to 1200 C and the ultimate strain, tensile strength, and tensile modulus of single fibers were determined.

The Effect of Sintering Temperature on Linear and Nonlinear Optical Properties of YAG Nanoceramics

NASA Astrophysics Data System (ADS)

Gayvoronsky, V. Ya.; Popov, A. S.; Brodyn, M. S.; Uklein, A. V.; Multian, V. V.; Shul'zhenko, O. O.

Recent improvements in powder synthesis and ceramics sintering made it possible to fabricate high-quality optical materials. The work is devoted to the structural and optical characterization of the ({Y_3}{Al_5}{O_{12}}, YAG) ceramics prepared by high-pressure low-temperature technique. The structural properties of the studied ceramic samples was obtained by X-ray diffraction. The studies of the total and in-line transmittance as well as optical scattering indicatrices were performed in visible and NIR ranges. The scatterer size ˜200 nm was estimated by Rayleigh-Gans-Debye model. It was shown that the studied samples demonstrate high transparency at 1064 nm. The nonlinear optical characterization of the samples was done by the self-action of the picosecond laser pulses at 1064 nm. The measured nonlinear optical response (χ^(3)) ˜ 10^{-11} esu) showed significant dependence on the sintering temperature variation.

High temperature properties of ceramic fibers and insulations for thermal protection of atmospheric entry and hypersonic cruise vehicles

NASA Technical Reports Server (NTRS)

Kourtides, Demetrius A.; Pitts, William C.; Araujo, Myrian; Zimmerman, R. S.

1988-01-01

Multilayer insulations (MIs) which will operate in the 500 to 1000 C temperature range are being considered for possible applications on aerospace vehicles subject to convective and radiative heating during atmospheric entry. The insulations described consist of ceramic fibers, insulations, and metal foils quilted together with ceramic thread. As these types of insulations have highly anisotropic properties, the total heat transfer characteristics must be determined. Data are presented on the thermal diffusivity and thermal conductivity of four types of MIs and are compared to the baseline Advanced Flexible Reusable Surface Insulation currently used on the Space Shuttle Orbiter. In addition, the high temperature properties of the fibers used in these MIs are discussed. The fibers investigated included silica and three types of aluminoborosilicate (ABS). Static tension tests were performed at temperatures up to 1200 C and the ultimate strain, tensile strength, and tensile modulus of single fibers were determined.

Performance analysis of advanced spacecraft TPS

NASA Technical Reports Server (NTRS)

Pitts, William C.

1991-01-01

Spacecraft entering a planetary atmosphere require a very sophisticated thermal protection system. The materials used must be tailored to each specific vehicle based on its planned mission profiles. Starting with the Space Shuttle, many types of ceramic insulation with various combinations of thermal properties have been developed by others. The development of two new materials is described: A Composite Flexible Blanket Insulation which has a significantly lower effective thermal conductivity than other ceramic blankets; and a Silicon Matrix Composite which has applications at high temperature locations such as wing leading edges. Also, a systematic study is described that considers the application of these materials for a proposed Personnel Launch System. The study shows how most of these available ceramic materials would perform during atmospheric entry of this vehicle. Other specific applications of these thermal protection materials are discussed.

Thermomechanical Performance of Si-Ti-C-O and Sintered SiC Fiber-Bonded Ceramics at High Temperatures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Matsunaga, Tadashi; Lin, Hua-Tay; Singh, Mrityunjay

2011-01-01

The stress-temperature-lifetime response of Si-Ti-C-O fiber-bonded ceramic (Tyrannohex ) and sintered SiC fiber-bonded ceramic (SA-Tyrannohex ) materials were investigated in air from 500 to 1150 C and 500 to 1400 C, respectively. The apparent threshold stress of Si-Ti-C-O fiber-bonded ceramic was about 175 MPa in the 500-1150 C temperature range. When the applied stress of the sintered SiC fiber-bonded ceramic was below an apparent threshold stress (e.g., ~225MPa) for tests conducted 1150 C, no failures were observed for lifetimes up to 1000h. In the case of sintered SiC fiber-bonded ceramic, at the temperature of 1300 C, the apparent threshold stressmore » decreased to 175 MPa. The decrease in strength seemed to be caused by grain growth which was confirmed from the SEM fractography. Both fiber-bonded ceramics exhibited much higher durability than a commercial SiC/SiC composite at temperatures above 500 C. In addition, results suggested that the sintered SiC fiber-bonded ceramic (SA-Tyrannohex) is more stable than a Hi-Nicalon/MI SiC composite with BN/SiC fiber coating at temperatures above 1300 C.« less

Development of a ceramic surface replacement for the hip. An experimental Sialon model.

PubMed

Clarke, I C; Phillips, W; McKellop, H; Coster, I R; Hedley, A; Amstutz, H C

1979-01-01

The objective of this study was to investigate the design and fixation advantages of Sialon ceramic surface replacements implanted without acrylic bone cement. The biocompatibility and friction and wear properties of Sialon ceramic were compared with more conventional prosthetic materials such as stainless steel and alumina. A functional load-bearing canine hip surface replacement model was established to test Sialon femoral cups designed for fixation by bone ingrowth. The results of the polyethylene wear tests on highly polished ceramic and stainless steel counterfaces were essentially similar. These laboratory data indicated that the in-vivo polyethylene wear performance on metal or ceramic prosthetic surfaces could be expected to be indistinguishable, i.e. the ceramic/polyethylene combination would not offer any improved wear resistance in-vivo. It was found possible to get bone ingrowth into the macrokeying areas of the ceramic femoral cups but not into the microporous surfaces due to the presence of a fibrous membrane lining their internal surfaces. The biocompatability specimens also appeared to be invested with a fibrous membrane. Further studies are under way to determine the relationship between reaming procedures, micro motion at the interfaces and Sialon biocompatibility.

Letter report on PCT/Monolith glass ceramic corrosion tests

DOE Office of Scientific and Technical Information (OSTI.GOV)

Crawford, Charles L.

2015-09-24

The Savannah River National Laboratory (SRNL) is collaborating with personnel from Pacific Northwest National Laboratory (PNNL) to study advanced waste form glass ceramics for immobilization of waste from Used Nuclear Fuel (UNF) separations processes. The glass ceramic waste forms take advantage of both crystalline and glassy phases where ‘troublesome’ elements (e.g., low solubility in glass or very long-lived) partition to highly durable ceramic phases with the remainder of elements residing in the glassy phase. The ceramic phases are tailored to create certain minerals or unique crystalline structures that can host the radionuclides by binding them in their specific crystalline networkmore » while not adversely impacting the residual glass network (Crum et al., 2011). Glass ceramics have been demonstrated using a scaled melter test performed in a pilot scale (1/4 scale) cold crucible induction melter (CCIM) (Crum et al., 2014; Maio et al., 2015). This report summarizes recent results from both Phase I and Phase II bench scale tests involving crucible fabrication and corrosion testing of glass ceramics using the Product Consistency Test (PCT). Preliminary results from both Phase I and Phase II bench scale tests involving statistically designed matrices have previously been reported (Crawford, 2013; Crawford, 2014).« less

Mechanical fatigue degradation of ceramics versus resin composites for dental restorations.

PubMed

Belli, Renan; Geinzer, Eva; Muschweck, Anna; Petschelt, Anselm; Lohbauer, Ulrich

2014-04-01

For posterior partial restorations an overlap of indication exists where either ceramic or resin-based composite materials can be successfully applied. The aim of this study was to compare the fatigue resistance of modern dental ceramic materials versus dental resin composites in order to address such conflicts. Bar specimens of five ceramic materials and resin composites were produced according to ISO 4049 and stored for 14 days in distilled water at 37°C. The following ceramic materials were selected for testing: a high-strength zirconium dioxide (e.max ZirCAD, Ivoclar), a machinable lithium disilicate (e.max CAD, Ivoclar), a pressable lithium disilicate ceramic (e-max Press, Ivoclar), a fluorapatite-based glass-ceramic (e.max Ceram, Ivoclar), and a machinable color-graded feldspathic porcelain (Trilux Forte, Vita). The composite materials selected were: an indirect machinable composite (Lava Ultimate, 3M ESPE) and four direct composites with varying filler nature (Clearfil Majesty Posterior, Kuraray; GrandioSO, Voco; Tetric EvoCeram, Ivoclar-Vivadent; and CeramX Duo, Dentsply). Fifteen specimens were tested in water for initial strength (σin) in 4-point bending. Using the same test set-up, the residual flexural fatigue strength (σff) was determined using the staircase approach after 10(4) cycles at 0.5 Hz (n=25). Weibull parameters σ0 and m were calculated for the σin specimens, whereas the σff and strength loss in percentage were obtained from the fatigue experiment. The zirconium oxide ceramic showed the highest σin and σff (768 and 440 MPa, respectively). Although both lithium disilicate ceramics were similar in the static test, the pressable version showed a significantly higher fatigue resistance after cyclic loading. Both the fluorapatite-based and the feldspathic porcelain showed equivalent initial and cyclic fatigue properties. From the composites, the highest filled direct material Clearfil Majesty Posterior showed superior fatigue performance. From all materials, e.max Press and Clearfil Majesty Posterior showed the lowest strength loss (29.6% and 32%, respectively), whereas the other materials lost between 41% and 62% of their flexural strength after cyclic loading. Dental ceramics and resin composite materials show equivalent fatigue strength degradation at loads around 0.5σin values. Apart from the zirconium oxide and the lithium disilicate ceramics, resin composites generally showed better σff after 10,000 cycles than the fluorapatite glass-ceramic and the feldspathic porcelain. Resin composite restorations may be used as an equivalent alternative to glass-rich-ceramic inlays regarding mechanical performance. Copyright © 2014 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Manufacture of high-density ceramic sinters

NASA Technical Reports Server (NTRS)

Hibata, Y.

1986-01-01

High density ceramic sinters are manufactured by coating premolded or presintered porous ceramics with a sealing material of high SiO2 porous glass or nitride glass and then sintering by hot isostatic pressing. The ceramics have excellent abrasion and corrosion resistances. Thus LC-10 (Si3N2 powder) and Y2O3-Al2O3 type sintering were mixed and molded to give a premolded porous ceramic (porosity 37%, relative bulk density 63%). The ceramic was dipped in a slurry containing high SiO2 porous glass and an alcohol solution of cellulose acetate and dried. The coated ceramic was treated in a nitrogen atmosphere and then sintered by hot isostatic pressing to give a dense ceramic sinter.

Adhesive strength of total knee endoprostheses to bone cement - analysis of metallic and ceramic femoral components under worst-case conditions.

PubMed

Bergschmidt, Philipp; Dammer, Rebecca; Zietz, Carmen; Finze, Susanne; Mittelmeier, Wolfram; Bader, Rainer

2016-06-01

Evaluation of the adhesive strength of femoral components to the bone cement is a relevant parameter for predicting implant safety. In the present experimental study, three types of cemented femoral components (metallic, ceramic and silica/silane-layered ceramic) of the bicondylar Multigen Plus knee system, implanted on composite femora were analysed. A pull-off test with the femoral components was performed after different load and several cementing conditions (four groups and n=3 components of each metallic, ceramic and silica/silane-layered ceramic in each group). Pull-off forces were comparable for the metallic and the silica/silane-layered ceramic femoral components (mean 4769 N and 4298 N) under standard test condition, whereas uncoated ceramic femoral components showed reduced pull-off forces (mean 2322 N). Loading under worst-case conditions led to decreased adhesive strength by loosening of the interface implant and bone cement using uncoated metallic and ceramic femoral components, respectively. Silica/silane-coated ceramic components were stably fixed even under worst-case conditions. Loading under high flexion angles can induce interfacial tensile stress, which could promote early implant loosening. In conclusion, a silica/silane-coating layer on the femoral component increased their adhesive strength to bone cement. Thicker cement mantles (>2 mm) reduce adhesive strength of the femoral component and can increase the risk of cement break-off.

AGT 100 automotive gas turbine system development

NASA Technical Reports Server (NTRS)

Helms, H. E. G.

1982-01-01

General Motors is developing an automotive gas turbine system that can be an alternate powerplant for future automobiles. Work sponsored by DOE and administered by NASA Lewis Research Center is emphasizing small component aerodynamics and high-temperature structural ceramics. Reliability requirements of the AGT 100 turbine system include chemical and structural ceramic component stability in the gas turbine environment. The power train system, its configuration and schedule are presented, and its performance tested. The aerodynamic component development is reviewed with discussions on the compressor, turbine, regenerator, interturbine duct and scroll, and combustor. Ceramic component development is also reviewed, and production cost and required capital investment are taken into consideration.

Study on coming out of the shaft from ceramic sleeve in terms of the residual displacement

NASA Astrophysics Data System (ADS)

Zhang, G. W.; Noda, N.-A.; Sano, Y.; Sakai, H.

2018-06-01

Ceramic roller can be used in the heating furnace conveniently because of its high temperature resistance. However, the coming out of the shaft may often happen from the ceramic sleeve under repeated load. In this paper, a two-dimensional shrink fitted structure is considered by replacing the shaft with the inner plate and by replacing the sleeve with the outer plate. Based on the model with stopper, the FEM simulation is performed under alternate loading with certain intervals newly added. The analysis results show that the coming out failure can be explained from the residual displacement accumulation during these intervals.

Challenges and Opportunities in Design, Fabrication, and Testing of High Temperature Joints in Ceramics and Ceramic Composites

NASA Technical Reports Server (NTRS)

Singh, M.; Levine, S. R. (Technical Monitor)

2001-01-01

Ceramic joining has been recognized as an enabling technology for successful utilization of advanced ceramics and composite materials. A number of joint design and testing issues have been discussed for ceramic joints in silicon carbide-based ceramics and fiber-reinforced composites. These joints have been fabricated using an affordable, robust ceramic joining technology (ARCJoinT). The microstructure and good high temperature mechanical capability (compressive and flexural strengths) of ceramic joints in silicon carbide-based ceramics and composite materials are reported.

Positively charged microporous ceramic membrane for the removal of Titan Yellow through electrostatic adsorption.

PubMed

Cheng, Xiuting; Li, Na; Zhu, Mengfu; Zhang, Lili; Deng, Yu; Deng, Cheng

2016-06-01

To develop a depth filter based on the electrostatic adsorption principle, positively charged microporous ceramic membrane was prepared from a diatomaceous earth ceramic membrane. The internal surface of the highly porous ceramic membrane was coated with uniformly distributed electropositive nano-Y2O3 coating. The dye removal performance was evaluated through pressurized filtration tests using Titan Yellow aqueous solution. It showed that positively charged microporous ceramic membrane exhibited a flow rate of 421L/(m(2)·hr) under the trans-membrane pressure of 0.03bar. Moreover it could effectively remove Titan Yellow with feed concentration of 10mg/L between pH3 to 8. The removal rate increased with the enhancement of the surface charge properties with a maximum rejection of 99.6%. This study provides a new and feasible method of removing organic dyes in wastewater. It is convinced that there will be a broad market for the application of charged ceramic membrane in the field of dye removal or recovery from industry wastewater. Copyright © 2016. Published by Elsevier B.V.

Environmental Barrier Coating Fracture, Fatigue and High-Heat-Flux Durability Modeling and Stochastic Progressive Damage Simulation

NASA Technical Reports Server (NTRS)

Zhu, Dongming; Nemeth, Noel N.

2017-01-01

Advanced environmental barrier coatings will play an increasingly important role in future gas turbine engines because of their ability to protect emerging light-weight SiC/SiC ceramic matrix composite (CMC) engine components, further raising engine operating temperatures and performance. Because the environmental barrier coating systems are critical to the performance, reliability and durability of these hot-section ceramic engine components, a prime-reliant coating system along with established life design methodology are required for the hot-section ceramic component insertion into engine service. In this paper, we have first summarized some observations of high temperature, high-heat-flux environmental degradation and failure mechanisms of environmental barrier coating systems in laboratory simulated engine environment tests. In particular, the coating surface cracking morphologies and associated subsequent delamination mechanisms under the engine level high-heat-flux, combustion steam, and mechanical creep and fatigue loading conditions will be discussed. The EBC compostion and archtechture improvements based on advanced high heat flux environmental testing, and the modeling advances based on the integrated Finite Element Analysis Micromechanics Analysis Code/Ceramics Analysis and Reliability Evaluation of Structures (FEAMAC/CARES) program will also be highlighted. The stochastic progressive damage simulation successfully predicts mud flat damage pattern in EBCs on coated 3-D specimens, and a 2-D model of through-the-thickness cross-section. A 2-parameter Weibull distribution was assumed in characterizing the coating layer stochastic strength response and the formation of damage was therefore modeled. The damage initiation and coalescence into progressively smaller mudflat crack cells was demonstrated. A coating life prediction framework may be realized by examining the surface crack initiation and delamination propagation in conjunction with environmental degradation under high-heat-flux and environment load test conditions.

Grinding model and material removal mechanism of medical nanometer zirconia ceramics.

PubMed

Zhang, Dongkun; Li, Changhe; Jia, Dongzhou; Wang, Sheng; Li, Runze; Qi, Xiaoxiao

2014-01-01

Many patents have been devoted to developing medical nanometer zirconia ceramic grinding techniques that can significantly improve both workpiece surface integrity and grinding quality. Among these patents is a process for preparing ceramic dental implants with a surface for improving osseo-integration by sand abrasive finishing under a jet pressure of 1.5 bar to 8.0 bar and with a grain size of 30 µm to 250 µm. Compared with other materials, nano-zirconia ceramics exhibit unmatched biomedical performance and excellent mechanical properties as medical bone tissue and dentures. The removal mechanism of nano-zirconia materials includes brittle fracture and plastic removal. Brittle fracture involves crack formation, extension, peeling, and chipping to completely remove debris. Plastic removal is similar to chip formation in metal grinding, including rubbing, ploughing, and the formation of grinding debris. The materials are removed in shearing and chipping. During brittle fracture, the grinding-led transverse and radial extension of cracks further generate local peeling of blocks of the material. In material peeling and removal, the mechanical strength and surface quality of the workpiece are also greatly reduced because of crack extension. When grinding occurs in the plastic region, plastic removal is performed, and surface grinding does not generate grinding fissures and surface fracture, producing clinically satisfactory grinding quality. With certain grinding conditions, medical nanometer zirconia ceramics can be removed through plastic flow in ductile regime. In this study, we analyzed the critical conditions for the transfer of brittle and plastic removal in nano-zirconia ceramic grinding as well as the high-quality surface grinding of medical nanometer zirconia ceramics by ELID grinding.

Clinical efficacy of composite versus ceramic inlays and onlays: a systematic review.

PubMed

Fron Chabouis, Hélène; Smail Faugeron, Violaine; Attal, Jean-Pierre

2013-12-01

Large tooth substance losses are frequent in posterior teeth because of primary caries or aging restorations. Inlays and onlays are often the minimal invasive solution in such cases, but the efficacy of the composite and ceramic materials used is unknown. We performed a systematic review of randomized controlled trials comparing the efficacy of composite and ceramic inlays or onlays. MEDLINE, Embase and the Cochrane Central Register of Controlled Trials were searched without any restriction on date or language, as were references of eligible studies and ClinicalTrials.gov. Eligible studies were randomized trials comparing the clinical efficacy of composite to ceramic inlays or onlays in adults with any clinical outcome for at least 6 months. From 172 records identified, we examined reports of 2 randomized controlled trials involving 138 inlays (no onlays evaluated) in 80 patients and exhibiting a high-risk of bias. Outcomes were clinical scores and major failures. The 3-year overall failure risk ratio was 2 [0.38-10.55] in favor of ceramic inlays although not statistically significant. The reported clinical scores (United States Public Health Services and Californian Dental Association) showed considerable heterogeneity between trials and could not be combined. We have very limited evidence that ceramics perform better than composite material for inlays in the short term. However, this result may not be valid in the long term, and other trials are needed. Trials should follow Fédération dentaire internationale recommendations and enhance their methodology. Trials comparing composite and ceramic onlays are needed. Copyright © 2013 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Performance and Durability of Environmental Barrier Coatings on SiC/SiC Ceramic Matrix Composites

NASA Technical Reports Server (NTRS)

Zhu, Dongming; Harder, Bryan; Bhatt, Ramakrishna

2016-01-01

This presentation highlights advanced environmental barrier coating (EBC) and SiC-SiC Ceramic Matrix Composites (CMC) systems for next generation turbine engines. The emphasis will be placed on fundamental coating and CMC property evaluations; and the integrated system performance and degradation mechanisms in simulated laboratory turbine engine testing environments. Long term durability tests in laser rig simulated high heat flux the rmomechanical creep and fatigue loading conditions will also be presented. The results can help improve the future EBC-CMC system designs, validating the advanced EBC-CMC technologies for hot section turbine engine applications.

Design study of a kinematic Stirling engine for dispered solar electric power systems

NASA Technical Reports Server (NTRS)

1980-01-01

The concept evaluation shows that the four cylinder double acting U type Stirling engine with annular regenerators is the most suitable engine type for the 15 kW solar application with respect to design, performance and cost. Results show that near term performance for a metallic Stirling engine is 42% efficiency. Further improved components show an impact on efficiency of the future metallic engine to 45%. Increase of heater temperature, through the introduction of ceramic components, contribute the greatest amount to achieve high efficiency goals. Future ceramic Stirling engines for solar applications show an efficiency of around 50%.

Single crystals and nonlinear process for outstanding vibration-powered electrical generators.

PubMed

Badel, Adrien; Benayad, Abdelmjid; Lefeuvre, Elie; Lebrun, Laurent; Richard, Claude; Guyomar, Daniel

2006-04-01

This paper compares the performances of vibration-powered electrical generators using a piezoelectric ceramic and a piezoelectric single crystal associated to several power conditioning circuits. A new approach of the piezoelectric power conversion based on a nonlinear voltage processing is presented, leading to three novel high performance power conditioning interfaces. Theoretical predictions and experimental results show that the nonlinear processing technique may increase the power harvested by a factor of 8 compared to standard techniques. Moreover, it is shown that, for a given energy harvesting technique, generators using single crystals deliver 20 times more power than generators using piezoelectric ceramics.

Effect of high-power-laser with and without graphite coating on bonding of resin cement to lithium disilicate ceramic.

PubMed

Feitosa, Fernanda A; de Araújo, Rodrigo M; Tay, Franklin R; Niu, Lina; Pucci, César R

2017-12-12

The present study evaluated the effect of different high-power-laser surface treatments on the bond strength between resin cement and disilicate ceramic. Lithium disilicate ceramic specimens with truncated cones shape were prepared and divided into 5 groups: HF (hydrofluoric acid-etching), Er:YAG laser + HF, Graphite + Er:YAG laser + HF, Nd:YAG laser + HF, and Graphite + Nd:YAG laser + HF. The treated ceramic surfaces were characterized with scanning electron microscopy and surface roughness measurement. Hourglasses-shaped ceramic- resin bond specimens were prepared, thermomechanically cycled and stressed to failure under tension. The results showed that for both the factors "laser" and "graphite", statistically significant differences were observed (p < 0.05). Multiple-comparison tests performed on the "laser" factor were in the order: Er:YAG > Nd:YAG (p < 0.05), and on the "graphite" factor were in the order: graphite coating < without coating (p < 0.05). The Dunnett test showed that Er:YAG + HF had significantly higher tensile strength (p = 0.00). Higher surface roughness was achieved after Er:YAG laser treatment. Thus Er:YAG laser treatment produces higher bond strength to resin cement than other surface treatment protocols. Surface-coating with graphite does not improve bonding of the laser-treated lithium disilicate ceramic to resin cement.

Optimisation of oxygen ion transport in materials for ceramic membrane devices.

PubMed

Kilner, J A

2007-01-01

Oxygen transport in ceramic oxide materials has received much attention over the past few decades. Much of this interest has stemmed from the desire to construct high temperature electrochemical devices for energy conversion, an example being the solid oxide fuel cell. In order to achieve high performance for these devices, insights are needed in how to achieve optimum performance from the functional components such as the electrolytes and electrodes. This includes the optimisation of oxygen transport through the crystal lattice of electrode and electrolyte materials and across the homogeneous (grain boundary) and heterogeneous interfaces that exist in real devices. Strategies are discussed for the optimisation of these quantities and current problems in the characterisation of interfacial transport are explored.

Exploratory evaluation of ceramics for automobile thermal reactors

NASA Technical Reports Server (NTRS)

Stone, P. L.; Blankenship, C. P.

1972-01-01

An exploratory evaluation of ceramics for automobile thermal reactors was conducted. Potential ceramic materials were evaluated in several reactor designs using both engine dynamometer and vehicle road tests. Silicon carbide contained in a corrugated metal support structure exhibited the best performance lasting over 800 hours in engine dynamometer tests and over 15,000 miles (24,200 km) of vehicle road tests. Reactors containing glass-ceramic components did not perform as well as silicon carbide. But the glass-ceramics still offer good potential for reactor use. The results of this study are considered to be a reasonable demonstration of the potential use of ceramics in thermal reactors.

Evaluation of the ICET Test Stand to Assess the Performance of a Range of Ceramic Media Filter Elements in Support of ASME AG-1 Subsection FO

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schemmel, A.

High Efficiency Particulate Air (HEPA) filters are defined as extended-medium, dry-type filters with: (1) a minimum particle removal efficiency of no less than 99.97 percent for 0.3 micrometer particles, (2) a maximum, clean resistance of 1.0 inch water column (in. WC) when operated at 1,000 cubic feet per minute (CFM), and (3) a rigid casing that extends the full depth of the medium. Specifically, ceramic media HEPA filters provide better performance at elevated temperatures, are moisture resistant and nonflammable, can perform their function if wetted and exposed to greater pressures, and can be cleaned and reused. This paper describes themore » modification and design of a large scale test stand which properly evaluates the filtration characteristics of a range of ceramic media filters challenged with a nuclear aerosol agent in order to develop Section FO of ASME AG-1.« less

Novel ultra-low temperature co-fired microwave dielectric ceramic at 400 degrees and its chemical compatibility with base metal

PubMed Central

Di, Zhou; Li-Xia, Pang; Ze-Ming, Qi; Biao-Bing, Jin; Xi, Yao

2014-01-01

A novel NaAgMoO4 material with spinel-like structure was synthesized by using the solid state reaction method and the ceramic sample was well densified at an extreme low sintering temperature about 400°C. Rietveld refinement of the crystal structure was performed using FULLPROF program and the cell parameters are a = b = c = 9.22039 Å with a space group F D −3 M (227). High performance microwave dielectric properties, with a permittivity ~7.9, a Qf value ~33,000 GHz and a temperature coefficient of resonant frequency ~−120 ppm/°C, were obtained. From X-ray diffraction (XRD) and Energy Dispersive Spectrometer (EDS) analysis of the co-fired sample, it was found that the NaAgMoO4 ceramic is chemically compatible with both silver and aluminum at the sintering temperature and this makes it a promising candidate for the ultra-low temperature co-fired ceramics technology. Analysis of infrared and THz spectra indicated that dielectric polarizability at microwave region of the NaAgMoO4 ceramic was equally contributed by ionic displasive and electronic polarizations. Its small microwave dielectric permittivity can also be explained well by the Shannon's additive rule. PMID:25099530

Environmental Barrier Coatings for Ceramics and Ceramic Composites

NASA Technical Reports Server (NTRS)

Lee, Kang N.; Fox, Dennis; Eldridge, Jeffrey; Robinson, R. Craig; Bansal, Narottam

2004-01-01

One key factor that limits the performance of current gas turbine engines is the temperature capability of hot section structural components. Silicon-based ceramics, such as SiC/SiC composites and monolithic Si3N4, are leading candidates to replace superalloy hot section components in the next generation gas turbine engines due to their excellent high temperature properties. A major stumbling block to realizing Si-based ceramic hot section components is the recession of Si-based ceramics in combustion environments due to the volatilization of silica scale by water vapor. An external environmental barrier coating (EBC) is the most promising approach to preventing the recession. Current EBCs are based on silicon, mullite (3A12O3-2SiO2) and BSAS (barium strontium aluminum silicate with celsian structure). Volatility of BSAS, BSAS-silica chemical reaction, and low melting point of silicon limit the durability and temperature capability of current EBCs. Research is underway to develop EBCs with longer life and enhanced temperature capability. Understanding key issues affecting the performance of current EBCs is necessary for successful development of advanced EBCs. These issues include stress, chemical compatibility, adherence, and water vapor stability. Factors that affect stress are thermal expansion mismatch, phase stability, chemical stability, elastic modulus, etc. The current understanding on these issues will be discussed.

Boron/Carbon/Silicon/Nitrogen Ceramics And Precursors

NASA Technical Reports Server (NTRS)

Riccitiello, Salvatore; Hsu, Ming TA; Chen, Timothy S.

1996-01-01

Ceramics containing various amounts of boron, carbon, silicon, and nitrogen made from variety of polymeric precursors. Synthesized in high yield from readily available and relatively inexpensive starting materials. Stable at room temperature; when polymerized, converted to ceramics in high yield. Ceramics resist oxidation and other forms of degradation at high temperatures; used in bulk to form objects or to infiltrate other ceramics to obtain composites having greater resistance to oxidation and high temperatures.

Dramatically improve the Safety Performance of Li ion Battery Separators and Reduce the Manufacturing Cost Using Ultraviolet Curing and High Precision Coating Technologies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Voelker, Gary; Arnold, John

The objective of this project was to improve the safety of operation of Lithium ion batteries (LIB)and at the same time significantly reduce the manufacturing cost of LIB separators. The project was very successful in demonstrating the improved performance and reduced cost attributed to using UV curable binder and high speed printing technology to place a very thin and precisely controlled ceramic layer on the surface of base separators made of polyolefins such as Polyethylene, Polypropylene and combinations of the two as well as cellulosic base separators. The underlying need for this new technology is the recently identified potential ofmore » fire in large format Lithium ion batteries used in hybrid, plug-in hybrid and electric vehicles. The primary potential cause of battery fire is thermal runaway caused by several different electrical or mechanical mechanisms; such as, overcharge, puncture, overheating, compaction, and internal short circuit. During thermal runaway, the ideal separator prevents ion flow and continues to physically separate the anode from the cathode. If the temperature of the battery gets higher, the separator may melt and partially clog the pores and help prevent ion flows but it also can shrink which can result in physical contact of the electrodes and accelerate thermal run-away even further. Ceramic coated separators eliminate many of the problems related to the usage of traditional separators. The ceramic coating provides an electrically insulating layer that retains its physical integrity at high temperature, allows for more efficient thermal heat transfer, helps reduce thermal shrinkage, and inhibits dendrite growth that could create a potential short circuit. The use of Ultraviolet (UV) chemistry to bind fine ceramic particles on separators is a unique and innovative approach primarily because of the instant curing of the UV curable binder upon exposure to UV light. This significant reduction in drying/curing time significantly reduces the cost of a ceramic coating. Another innovation is high precision, high speed, printing techniques that can apply a unique pattern of ceramic particles on base separators. The pattern will maximize ionic conductivity and minimize ceramic coating weight and thickness, while retaining the benefits of increased puncture strength, reduced thermal shrinkage and no decomposition. This project has met all of its goals and has been successfully completed. This successful completion has enabled Miltec UV to take the final steps leading to the commercialization of an innovative technology that will result in ceramic coated separators that can be manufactured and sold from the US, with increased production capacity, reduced cost, and improved battery safety.« less

Simulation of automotive wrist pin joint and tribological studies of tin coated Al-Si alloy, metal matrix composites and nitrogen ceramics under mixed lubrication

NASA Astrophysics Data System (ADS)

Wang, Qian

Development of automotive engines with high power output demands the application of high strength materials with good tribological properties. Metal matrix composites (MMC's) and some nitrogen ceramics are of interest to replace some conventional materials in the piston/pin/connecting rod design. A simulation study has been developed to explore the possibility to employ MMC's as bearing materials and ceramics as journal materials, and to investigate the related wear mechanisms and the possible journal bearing failure mechanisms. Conventional tin coated Al-Si alloy (Al-Si/Sn) have been studied for the base line information. A mixed lubrication model for journal bearing with a soft coating has been developed and applied to the contact and temperature analysis of the Al-Si/Sn bearing. Experimental studies were performed to reveal the bearing friction and wear behavior. Tin coating exhibited great a advantage in friction reduction, however, it suffered significant wear through pitting and debonding. When the tin wore out, the Al-Si/steel contact experienced higher friction. A cast and P/M MMC's in the lubricated contact with case hardened steel and ceramic journals were studied experimentally. Without sufficient material removal in the conformal contact situation, MMC bearings in the MMC/steel pairs gained weight due to iron transfer and surface tribochemical reactions with the lubricant additives and contact failure occurred. However, the MMC/ceramic contacts demonstrated promising tribological behavior with low friction and high wear resistance, and should be considered for new journal bearing design. Ceramics are wear resistant. Ceramic surface roughness is very crucial when the journals are in contact with the tin coated bearings. In contact with MMC bearings, ceramic surface quality and fracture toughness seem to play some important roles in affecting the friction coefficient. The wear of silicon nitride and beta sialon (A) journals is pitting due to grain boundary fracture and grain pull-out.

Large Electrocaloric Effect in Lead-Free (Ba0.85Ca0.15)(Zr0.1Ti0.9)O3 Ceramics Prepared via Citrate Route

PubMed Central

Shi, Jing; Zhu, Rongfeng; Liu, Xing; Yuan, Ningyi; Ding, Jianning; Luo, Haosu

2017-01-01

The 1 wt % Li-doped (Ba0.85Ca0.15)(Zr0.1Ti0.9)O3 (BCZT-Li) ceramics prepared by the citrate method exhibit improved phase purity, densification and electrical properties, which provide prospective possibility to develop high-performance electrocaloric materials. The electrocaloric effect was evaluated by phenomenological method, and the BCZT-Li ceramics present large electrocaloric temperature change ∆T, especially large electrocaloric responsibility ξ = ∆Tmax/∆Emax, which can be comparable to the largest values reported in the lead-free piezoelectric ceramics. The excellent electrocaloric effect is considered as correlating with the coexistence of polymorphic ferroelectric phases, which are detected by the Raman spectroscopy. The large ξ value accompanied by decreased Curie temperature (around 73 °C) of the BCZT-Li ceramics prepared by the citrate method presents potential applications as the next-generation solid-state cooling devices. PMID:28927004

Large Electrocaloric Effect in Lead-Free (Ba0.85Ca0.15)(Zr0.1Ti0.9)O₃ Ceramics Prepared via Citrate Route.

PubMed

Shi, Jing; Zhu, Rongfeng; Liu, Xing; Fang, Bijun; Yuan, Ningyi; Ding, Jianning; Luo, Haosu

2017-09-18

The 1 wt % Li-doped (Ba 0.85 Ca 0.15 )(Zr 0.1 Ti 0.9 )O₃ (BCZT-Li) ceramics prepared by the citrate method exhibit improved phase purity, densification and electrical properties, which provide prospective possibility to develop high-performance electrocaloric materials. The electrocaloric effect was evaluated by phenomenological method, and the BCZT-Li ceramics present large electrocaloric temperature change ∆ T , especially large electrocaloric responsibility ξ = ∆ T max /∆ E max , which can be comparable to the largest values reported in the lead-free piezoelectric ceramics. The excellent electrocaloric effect is considered as correlating with the coexistence of polymorphic ferroelectric phases, which are detected by the Raman spectroscopy. The large ξ value accompanied by decreased Curie temperature (around 73 °C) of the BCZT-Li ceramics prepared by the citrate method presents potential applications as the next-generation solid-state cooling devices.

(Tribology conferences and forums)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yust, C.S.

The principal meeting attended during this trip was the Japan International Tribology Conference Nagoya 1990. The conference encompassed a wide range of topics, including the tribology of ceramics, the tribology in high-performance automobiles, and many aspects of lubrication technology. Associated forums were also held on the tribology of advanced ceramics, on solid lubrication, and on automotive lubricants. Presentations made during the latter forum discussed anticipated trends in engine development and anticipated improvements in lubricants required for the next generation of engines. In addition to meetings, site visits were made to five industrial organizations to discuss ceramic tribology. Nippon Steel Corporationmore » and Toshiba Corporation are both very active in the ceramic area, Nippon Steel from their interest in research on new materials and Toshiba from both an interest in new materials and in support of their work in electronic devices. Two engine manufacturers were also visited, Toyota Motor Corporation, and Nissan Motor Co., Ltd. These companies were somewhat reserved in their discussion of progress in the utilization of ceramics in automobile engines.« less

Acousto-Ultrasonic analysis of failure in ceramic matrix composite tensile specimens

NASA Technical Reports Server (NTRS)

Kautz, Harold E.; Chulya, Abhisak

1993-01-01

Three types of acousto-ultrasonic (AU) measurements, stress-wave factor (SWF), lowest antisymmetric plate mode group velocity (VS), and lowest symmetric plate mode group velocity (VL), were performed on specimens before and after tensile failure. Three different Nicalon fiber architectures with ceramic matrices were tested. These composites were categorized as 1D (unidirectional fiber orientation) SiC/CAS glass ceramic, and 2D and 3D woven SiC/SiC ceramic matrix materials. SWF was found to be degraded after tensile failure in all three material categories. VS was found to be degraded only in the 1D SiC/CAS. VL was difficult to determine on the irregular specimen surfaces but appeared unchanged on all failed specimens. 3D woven specimens with heat-treatment at high temperature exhibited degradation only in SWF.

Thermo-mechanical performance of precision C/SiC mounts

NASA Astrophysics Data System (ADS)

Goodman, William A.; Mueller, Claus E.; Jacoby, Marc T.; Wells, Jim D.

2001-12-01

For complex shaped, lightweight, high precision opto- mechanical structures that must operate in adverse environments and over wide ranges of temperature, we consider IABG's optical grade silicon carbide composite ceramic (C/SiC) as the material of choice. C/SiC employs conventional NC machining/milling equipment to rapidly fabricate near-net shape parts, providing substantial schedule, cost, and risk savings for high precision components. Unlike powder based SiC ceramics, C/SiC does not experience significant shrinkage during processing, nor does it suffer from incomplete densification. If required, e.g. for large-size components, a fully-monolithic ceramic joining technique can be applied. Generally, the thermal and mechanical properties of C/SiC are tunable in certain ranges by modifying certain process steps. This paper focuses on the thermo-mechanical performance of new, high precision mounts designed by Schafer Corporation and manufactured by IABG. The mounts were manufactured using standard optical grade C/SiC (formulation internally called A-3). The A-3 formulation has a near-perfect CTE match with silicon, making it the ideal material to athermally support Schafer produced Silicon Lightweight Mirrors (SLMs) that will operate in a cryogenic environment. Corresponding thermo- mechanical testing and analysis is presented in this manuscript.

Environmental Stability and Oxidation Behavior of HfO2-Si and YbGd(O) Based Environmental Barrier Coating Systems for SiCSiC Ceramic Matrix Composites

NASA Technical Reports Server (NTRS)

Zhu, Dongming; Farmer, Serene; McCue, Terry R.; Harder, Bryan; Hurst, Janet B.

2017-01-01

Ceramic environmental barrier coatings (EBC) and SiCSiC ceramic matrix composites (CMCs) will play a crucial role in future aircraft propulsion systems because of their ability to significantly increase engine operating temperatures, improve component durability, reduce engine weight and cooling requirements. Advanced EBC systems for SiCSiC CMC turbine and combustor hot section components are currently being developed to meet future turbine engine emission and performance goals. One of the significant material development challenges for the high temperature CMC components is to develop prime-reliant, environmental durable environmental barrier coating systems. In this paper, the durability and performance of advanced Electron Beam-Physical Vapor Deposition (EB-PVD) NASA HfO2-Si and YbGdSi(O) EBC bond coat top coat systems for SiCSiC CMC have been summarized. The high temperature thermomechanical creep, fatigue and oxidation resistance have been investigated in the laboratory simulated high-heat-flux environmental test conditions. The advanced NASA EBC systems showed promise to achieve 1500C temperature capability, helping enable next generation turbine engines with significantly improved engine component temperature capability and durability.

Compact Ceramic Microchannel Heat Exchangers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lewinsohn, Charles

The objective of the proposed work was to demonstrate the feasibility of a step change in power plant efficiency at a commercially viable cost, by obtaining performance data for prototype, compact, ceramic microchannel heat exchangers. By performing the tasks described in the initial proposal, all of the milestones were met. The work performed will advance the technology from Technology Readiness Level 3 (TRL 3) to Technology Readiness Level 4 (TRL 4) and validate the potential of using these heat exchangers for enabling high efficiency solid oxide fuel cell (SOFC) or high-temperature turbine-based power plants. The attached report will describe howmore » this objective was met. In collaboration with The Colorado School of Mines (CSM), specifications were developed for a high temperature heat exchanger for three commercial microturbines. Microturbines were selected because they are a more mature commercial technology than SOFC, they are a low-volume and high-value target for market entry of high-temperature heat exchangers, and they are essentially scaled-down versions of turbines used in utility-scale power plants. Using these specifications, microchannel dimensions were selected to meet the performance requirements. Ceramic plates were fabricated with microchannels of these dimensions. The plates were tested at room temperature and elevated temperature. Plates were joined together to make modular, heat exchanger stacks that were tested at a variety of temperatures and flow rates. Although gas flow rates equivalent to those in microturbines could not be achieved in the laboratory environment, the results showed expected efficiencies, robust operation under significant temperature gradients at high temperature, and the ability to cycle the stacks. Details of the methods and results are presented in this final report.« less

Zirconia-magnesia inert matrix fuel and waste form: Synthesis, characterization and chemical performance in an advanced fuel cycle

NASA Astrophysics Data System (ADS)

Holliday, Kiel Steven

There is a significant buildup in plutonium stockpiles throughout the world, because of spent nuclear fuel and the dismantling of weapons. The radiotoxicity of this material and proliferation risk has led to a desire for destroying excess plutonium. To do this effectively, it must be fissioned in a reactor as part of a uranium free fuel to eliminate the generation of more plutonium. This requires an inert matrix to volumetrically dilute the fissile plutonium. Zirconia-magnesia dual phase ceramic has been demonstrated to be a favorable material for this task. It is neutron transparent, zirconia is chemically robust, magnesia has good thermal conductivity and the ceramic has been calculated to conform to current economic and safety standards. This dissertation contributes to the knowledge of zirconia-magnesia as an inert matrix fuel to establish behavior of the material containing a fissile component. First, the zirconia-magnesia inert matrix is synthesized in a dual phase ceramic containing a fissile component and a burnable poison. The chemical constitution of the ceramic is then determined. Next, the material performance is assessed under conditions relevant to an advanced fuel cycle. Reactor conditions were assessed with high temperature, high pressure water. Various acid solutions were used in an effort to dissolve the material for reprocessing. The ceramic was also tested as a waste form under environmental conditions, should it go directly to a repository as a spent fuel. The applicability of zirconia-magnesia as an inert matrix fuel and waste form was tested and found to be a promising material for such applications.

Femtosecond laser inscribed cladding waveguides in Nd:YAG ceramics: fabrication, fluorescence imaging and laser performance.

PubMed

Liu, Hongliang; Jia, Yuechen; Vázquez de Aldana, Javier Rodríguez; Jaque, Daniel; Chen, Feng

2012-08-13

We report on the fabrication of depressed cladding waveguide lasers in Nd:YAG (neodymium doped yttrium aluminum garnet, Nd:Y3Al5O12) ceramics microstructured by femtosecond laser pulses. Full control over the confined light spatial distribution is demonstrated by the fabrication of high contrast waveguides with hexagonal, circular and trapezoidal configurations. The confocal fluorescence measurements of the waveguides reveal that the original luminescence features of Nd3+ ions are well-preserved in the waveguide regions. Under optical pump at 808 nm, cladding waveguides showed continuous wave efficient laser oscillation. The maximum output power obtained at 1064.5 nm is ~181 mW with a slope efficiency as high as 44%, which suggests that the fabricated Nd:YAG ceramic waveguides are promising candidates for efficient integrated laser sources.

High performance zeolite LTA pervaporation membranes on ceramic hollow fibers by dipcoating-wiping seed deposition.

PubMed

Wang, Zhengbao; Ge, Qinqin; Shao, Jia; Yan, Yushan

2009-05-27

We demonstrate for the first time that by one single hydrothermal synthesis a zeolite LTA membrane with a high flux of 9.0 kg/m(2) h and high water/ethanol separation factor of 10,000 could be formed on a ceramic hollow fiber that is known for its ability to form a compact module. The flux is the highest reported in the literatures. A novel seeding method, dipcoating-wiping, is key to obtaining zeolite membranes with high separation performance because it reproducibly produces a uniform and trace seed layer on the support. This new seeding method is expected to have serious implications for making defect-free zeolite films and membranes for many applications. The membranes reported here have the potential to solve the key problems that have prevented zeolite membranes from widespread use for biofuel production.

Affordable Manufacturing Technologies Being Developed for Actively Cooled Ceramic Components

NASA Technical Reports Server (NTRS)

Bhatt, Ramakrishna T.

1999-01-01

Efforts to improve the performance of modern gas turbine engines have imposed increasing service temperature demands on structural materials. Through active cooling, the useful temperature range of nickel-base superalloys in current gas turbine engines has been extended, but the margin for further improvement appears modest. Because of their low density, high-temperature strength, and high thermal conductivity, in situ toughened silicon nitride ceramics have received a great deal of attention for cooled structures. However, high processing costs have proven to be a major obstacle to their widespread application. Advanced rapid prototyping technology, which is developing rapidly, offers the possibility of an affordable manufacturing approach.

Characterization of natural organic matter treated by iron oxide nanoparticle incorporated ceramic membrane-ozonation process.

PubMed

Park, Hosik; Kim, Yohan; An, Byungryul; Choi, Heechul

2012-11-15

In this study, changes in the physical and structural properties of natural organic matter (NOM) were observed during hybrid ceramic membrane processes that combined ozonation with ultrafiltration ceramic membrane (CM) or with a reactive ceramic membrane (RM), namely, an iron oxide nanoparticles (IONs) incorporated-CM. NOM from feed water and NOM from permeate treated with hybrid ceramic membrane processes were analyzed by employing several NOM characterization techniques. Specific ultraviolet absorbance (SUVA), high-performance size exclusion chromatography (HPSEC) and fractionation analyses showed that the hybrid ceramic membrane process effectively removed and transformed relatively high contents of aromatic, high molecular weight and hydrophobic NOM fractions. Fourier transform infrared spectroscopy (FTIR) and 3-dimensional excitation-emission matrix (EEM) fluorescence spectroscopy revealed that this process caused a significant decrease of the aromaticity of humic-like structures and an increase in electron withdrawing groups. The highest removal efficiency (46%) of hydroxyl radical probe compound (i.e., para-Chlorobenzoic acid (pCBA)) in RM-ozonation process compared with that in CM without ozonation process (8%) revealed the hydroxyl radical formation by the surface-catalyzed reaction between ozone and IONs on the surface of RM. In addition, experimental results on flux decline showed that fouling of RM-ozonation process (15%) was reduced compared with that of CM without ozonation process (30%). These results indicated that the RM-ozonation process enhanced the destruction of NOM and reduced the fouling by generating hydroxyl radicals from the catalytic ozonation in the RM-ozonation process. Copyright © 2012 Elsevier Ltd. All rights reserved.

A Hybrid Actuation System Demonstrating Significantly Enhanced Electromechanical Performance

NASA Technical Reports Server (NTRS)

Su, Ji; Xu, Tian-Bing; Zhang, Shujun; Shrout, Thomas R.; Zhang, Qiming

2004-01-01

A hybrid actuation system (HYBAS) utilizing advantages of a combination of electromechanical responses of an electroactive polymer (EAP), an electrostrictive copolymer, and an electroactive ceramic single crystal, PZN-PT single crystal, has been developed. The system employs the contribution of the actuation elements cooperatively and exhibits a significantly enhanced electromechanical performance compared to the performances of the device made of each constituting material, the electroactive polymer or the ceramic single crystal, individually. The theoretical modeling of the performances of the HYBAS is in good agreement with experimental observation. The consistence between the theoretical modeling and experimental test make the design concept an effective route for the development of high performance actuating devices for many applications. The theoretical modeling, fabrication of the HYBAS and the initial experimental results will be presented and discussed.

Investigation of Re-X glass ceramic for acceleration insulating columns

NASA Astrophysics Data System (ADS)

Faltens, A.; Rosenblum, S.

1985-05-01

In an induction linac the accelerating voltage appears along a voltage-graded vacuum insulator column which is a performance limiting and major cost component. Re-X glass ceramic insulators have the long-sought properties of allowing cast-in gradient electrodes, good breakdown characteristics, and compatibility with high vacuum systems. Re-X is a glass ceramic developed by General Electric for use in the manufacture of electrical apparatus, such as vacuum arc interrupters. We have examined vacuum outgassing behavior and voltage breakdown in vacuum and find excellent performance. The housings are in the shape of tubes with type 430 stainless steel terminations. Due to a matched coefficient of thermal expansion between metal and insulator, no vacuum leaks have resulted from any welding operation. The components should be relatively inexpensive to manufacture in large sizes and appear to be a very attractive accelerator column. We are planning to use a standard GE housing in our MBE-4 induction linac.

Design Concepts for Cooled Ceramic Matrix Composite Turbine Vanes

NASA Technical Reports Server (NTRS)

Boyle, Robert

2014-01-01

This project demonstrated that higher temperature capabilities of ceramic matrix composites (CMCs) can be used to reduce emissions and improve fuel consumption in gas turbine engines. The work involved closely coupling aerothermal and structural analyses for the first-stage vane of a high-pressure turbine (HPT). These vanes are actively cooled, typically using film cooling. Ceramic materials have structural and thermal properties different from conventional metals used for the first-stage HPT vane. This project identified vane configurations that satisfy CMC structural strength and life constraints while maintaining vane aerodynamic efficiency and reducing vane cooling to improve engine performance and reduce emissions. The project examined modifications to vane internal configurations to achieve the desired objectives. Thermal and pressure stresses are equally important, and both were analyzed using an ANSYS® structural analysis. Three-dimensional fluid and heat transfer analyses were used to determine vane aerodynamic performance and heat load distributions.

Electromagnetic interference shielding performance of nano-layered Ti3SiC2 ceramics at high-temperatures

NASA Astrophysics Data System (ADS)

Li, Sigong; Tan, Yongqiang; Xue, Jiaxiang; Liu, Tong; Zhou, Xiaosong; Zhang, Haibin

2018-01-01

The X-band electromagnetic interference (EMI) shielding properties of nano-layered Ti3SiC2 ceramics were evaluated from room temperature up to 800°C in order to explore the feasibility of Ti3SiC2 as efficient high temperature EMI shielding material. It was found that Ti3SiC2 exhibits satisfactory EMI shielding effectiveness (SE) close to 30 dB at room temperature and the EMI SE shows good temperature stability. The remarkable EMI shielding properties of Ti3SiC2 can be mainly attributed to high electrical conductivity, high dielectric loss and more importantly the multiple reflections due to the layered structure.

Improved performance of silicon nitride-based high temperature ceramics

NASA Technical Reports Server (NTRS)

Ashbrook, R. L.

1977-01-01

Recent progress in the production of Si3N4 based ceramics is reviewed: (1) high temperature strength and toughness of hot pressed Si3N4 were improved by using high purity powder and a stabilized ZrO2 additive, (2) impact resistance of hot pressed Si3N4 was increased by the use of a crushable energy absorbing layer, (3) the oxidation resistance and strength of reaction sintered Si3N4 were increased by impregnating reaction sintered silicon nitride with solutions that oxidize to Al2O3 or ZrO2, (4) beta prime SiA1ON compositions and sintering aids were developed for improved oxidation resistance or improved high temperature strength.

Sealing glass-ceramics with near-linear thermal strain, Part II: Sequence of crystallization and phase stability

DOE PAGES

Rodriguez, Mark A.; Griego, James J. M.; Dai, Steve

2016-08-22

The sequence of crystallization in a recrystallizable lithium silicate sealing glass-ceramic Li 2O–SiO 2–Al 2O 3–K 2O–B 2O 3–P 2O 5–ZnO was analyzed by in situ high-temperature X-ray diffraction (HTXRD). Glass-ceramic specimens have been subjected to a two-stage heat-treatment schedule, including rapid cooling from sealing temperature to a first hold temperature 650°C, followed by heating to a second hold temperature of 810°C. Notable growth and saturation of Quartz was observed at 650°C (first hold). Cristobalite crystallized at the second hold temperature of 810°C, growing from the residual glass rather than converting from the Quartz. The coexistence of quartz and cristobalitemore » resulted in a glass-ceramic having a near-linear thermal strain, as opposed to the highly nonlinear glass-ceramic where the cristobalite is the dominant silica crystalline phase. HTXRD was also performed to analyze the inversion and phase stability of the two types of fully crystallized glass-ceramics. While the inversion in cristobalite resembles the character of a first-order displacive phase transformation, i.e., step changes in lattice parameters and thermal hysteresis in the transition temperature, the inversion in quartz appears more diffuse and occurs over a much broader temperature range. Furthermore, localized tensile stresses on quartz and possible solid-solution effects have been attributed to the transition behavior of quartz crystals embedded in the glass-ceramics.« less

Enhanced texture evolution and piezoelectric properties in CuO-doped Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 grain-oriented ceramics

NASA Astrophysics Data System (ADS)

Chang, Yunfei; Watson, Beecher; Fanton, Mark; Meyer, Richard J.; Messing, Gary L.

2017-12-01

In this work, both crystallographic texture and doping engineering strategies were integrated to develop relaxor-PbTiO3 (PT) based ternary ferroelectric ceramics with enhanced texture evolution and superior electromechanical properties. CuO-doped Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 (PIN-PMN-PT) piezoelectric ceramics with [001]c texture fraction ≥97% were synthesized by templated grain growth. The addition of CuO significantly promotes densification and oriented grain growth in the templated ceramics, leading to full texture development at dramatically reduced times and temperatures. Moreover, the CuO dopant remarkably enhances the piezoelectric properties of the textured ceramics while maintaining high phase transition temperatures and large coercive fields. Doping 0.125 wt. % CuO yields the electromechanical properties of d33 = 927 pC/N, d33* = 1510 pm/V, g33 = 43.2 × 10-3 Vm/N, Kp = 0.87, Ec=8.8 kV/cm, and tan δ = 1.3%, which are the best values reported so far in PIN-PMN-PT based ceramics. The high piezoelectric coefficient is mainly from the reversible piezoelectric response, with the irreversible contribution being on the order of 13.1%. We believe that this work not only facilitates closing the performance gap between ceramics and single crystals but also can expand relaxor-PT based piezoelectric application fields.

Environmental Barrier Coating Development for SiC/SiC Ceramic Matrix Composites: Recent Advances and Future Directions

NASA Technical Reports Server (NTRS)

Zhu, Dongming

2016-01-01

This presentation briefly reviews the SiC/SiC major environmental and environment-fatigue degradations encountered in simulated turbine combustion environments, and thus NASA environmental barrier coating system evolution for protecting the SiC/SiC Ceramic Matrix Composites for meeting the engine performance requirements. The presentation will review several generations of NASA EBC materials systems, EBC-CMC component system technologies for SiC/SiC ceramic matrix composite combustors and turbine airfoils, highlighting the temperature capability and durability improvements in simulated engine high heat flux, high pressure, high velocity, and with mechanical creep and fatigue loading conditions. This paper will also focus on the performance requirements and design considerations of environmental barrier coatings for next generation turbine engine applications. The current development emphasis is placed on advanced NASA candidate environmental barrier coating systems for SiC/SiC CMCs, their performance benefits and design limitations in long-term operation and combustion environments. The efforts have been also directed to developing prime-reliant, self-healing 2700F EBC bond coat; and high stability, lower thermal conductivity, and durable EBC top coats. Major technical barriers in developing environmental barrier coating systems, the coating integrations with next generation CMCs having the improved environmental stability, erosion-impact resistance, and long-term fatigue-environment system durability performance will be described. The research and development opportunities for turbine engine environmental barrier coating systems by utilizing improved compositions, state-of-the-art processing methods, and simulated environment testing and durability modeling will be briefly discussed.

Silk coating on a bioactive ceramic scaffold for bone regeneration: effective enhancement of mechanical and in vitro osteogenic properties towards load-bearing applications.

PubMed

Li, Jiao Jiao; Roohani-Esfahani, Seyed-Iman; Kim, Kyungsook; Kaplan, David L; Zreiqat, Hala

2017-06-01

Bioactive ceramic scaffolds represent competitive choices for clinical bone reconstruction, but their widespread use is restricted by inherent brittleness and weak mechanical performance under load. This study reports the development of strong and tough bioactive scaffolds suitable for use in load-bearing bone reconstruction. A strong and bioactive ceramic scaffold (strontium-hardystonite-gahnite) is combined with single and multiple coating layers of silk fibroin to enhance its toughness, producing composite scaffolds which match the mechanical properties of cancellous bone and show enhanced capacity to promote in vitro osteogenesis. Also reported for the first time is a comparison of the coating effects obtained when a polymeric material is coated on ceramic scaffolds with differing microstructures, namely the strontium-hardystonite-gahnite scaffold with high-density struts as opposed to a conventional ceramic scaffold, such as biphasic calcium phosphate, with low-density struts. The results show that silk coating on a unique ceramic scaffold can lead to simple and effective enhancement of its mechanical and biological properties to suit a wider range of applications in clinical bone reconstruction, and also establish the influence of ceramic microstructure on the effectiveness of silk coating as a method of reinforcement when applied to different types of ceramic bone graft substitutes. Copyright © 2015 John Wiley & Sons, Ltd. Copyright © 2015 John Wiley & Sons, Ltd.

High resolution ceramic gun for projection CRT

NASA Astrophysics Data System (ADS)

Muchi, T.; Tagami, S.; Saito, T.

1995-08-01

A ceramic resistor with high-resistivity and a low thermal coefficient has been developed. The use of this ceramic material as a cylindrical electrode realizes an electrostatic lens with low spherical aberration. A ceramic electron gun based on a new concept has been developed for high resolution projection CRTs.

In vitro study of fracture load and fracture pattern of ceramic crowns: a finite element and fractography analysis.

PubMed

Campos, Roberto Elias; Soares, Carlos José; Quagliatto, Paulo S; Soares, Paulo Vinícius; de Oliveira, Osmir Batista; Santos-Filho, Paulo Cesar Freitas; Salazar-Marocho, Susana M

2011-08-01

This in vitro study investigated the null hypothesis that metal-free crowns induce fracture loads and mechanical behavior similar to metal ceramic systems and to study the fracture pattern of ceramic crowns under compressive loads using finite element and fractography analyses. Six groups (n = 8) with crowns from different systems were compared: conventional metal ceramic (Noritake) (CMC); modified metal ceramic (Noritake) (MMC); lithium disilicate-reinforced ceramic (IPS Empress II) (EMP); leucite-reinforced ceramic (Cergogold) (CERG); leucite fluoride-apatite reinforced ceramic (IPS d.Sign) (SIGN); and polymer crowns (Targis) (TARG). Standardized crown preparations were performed on bovine roots containing NiCr metal dowels and resin cores. Crowns were fabricated using the ceramics listed, cemented with dual-cure resin cement, and submitted to compressive loads in a mechanical testing machine at a 0.5-mm/min crosshead speed. Data were submitted to one-way ANOVA and Tukey tests, and fractured specimens were visually inspected under a stereomicroscope (20×) to determine the type of fracture. Maximum principal stress (MPS) distributions were calculated using finite element analysis, and fracture origin and the correlation with the fracture type were determined using fractography. Mean values of fracture resistance (N) for all groups were: CMC: 1383 ± 298 (a); MMC: 1691 ± 236 (a); EMP: 657 ± 153 (b); CERG: 546 ± 149 (bc); SIGN: 443 ± 126 (c); TARG: 749 ± 113 (b). Statistical results showed significant differences among groups (p < 0.05) represented by different lowercase letters. Metal ceramic crowns presented fracture loads significantly higher than the others. Ceramic specimens presented high incidence of fractures involving either the core or the tooth, and all fractures of polymer crown specimens involved the tooth in a catastrophic way. Based on stress and fractographic analyses it was determined that fracture occurred from the occlusal to the cervical direction. Within the limitations of this study, the results indicated that the use of ceramic and polymer crowns without a core reinforcement should be carefully evaluated before clinical use due to the high incidence of failure with tooth involvement. This mainly occurred for the polymer crown group, although the fracture load was higher than normal occlusal forces. High tensile stress concentrations were found around and between the occlusal loading points. Fractographic analysis indicated fracture originating from the load point and propagating from the occlusal surface toward the cervical area, which is the opposite direction of that observed in clinical situations. © 2011 by The American College of Prosthodontists.

Decontamination of Explosives-Contaminated Range Scrap Using A Transportable Hot Gas Decontamination (HGD) System: Cost & Performance Report

DTIC Science & Technology

2007-01-01

nonirritating, and a 9-micron diameter fiber nonrespirable, making handling safe and easy. • Basalt Mat, manufactured by BGF Industries (bgf.com). High...temperature mineral wool ( basalt fiber wool) mat blanket good to 1,500oF. Product is still under development as of 2002 but shows promise. 6.3...hazard to range technicians. • The Cerablanket® (manufactured by Thermal Ceramics) contains refractory ceramic fibers , which can potentially cause

Biomechanical behavior of a cemented ceramic knee replacement under worst case scenarios

NASA Astrophysics Data System (ADS)

Kluess, D.; Mittelmeier, W.; Bader, R.

2009-12-01

In connection with technological advances in the manufacturing of medical ceramics, a newly developed ceramic femoral component was introduced in total knee arthroplasty (TKA). The motivation to consider ceramics in TKA is based on the allergological and tribological benefits as proven in total hip arthroplasty. Owing to the brittleness and reduced fracture toughness of ceramic materials, the biomechanical performance has to be examined intensely. Apart from standard testing, we calculated the implant performance under different worst case scenarios including malposition, bone defects and stumbling. A finite-element-model was developed to calculate the implant performance in situ. The worst case conditions revealed principal stresses 12.6 times higher during stumbling than during normal gait. Nevertheless, none of the calculated principal stress amounts were above the critical strength of the ceramic material used. The analysis of malposition showed the necessity of exact alignment of the implant components.

Biomechanical behavior of a cemented ceramic knee replacement under worst case scenarios

NASA Astrophysics Data System (ADS)

Kluess, D.; Mittelmeier, W.; Bader, R.

2010-03-01

In connection with technological advances in the manufacturing of medical ceramics, a newly developed ceramic femoral component was introduced in total knee arthroplasty (TKA). The motivation to consider ceramics in TKA is based on the allergological and tribological benefits as proven in total hip arthroplasty. Owing to the brittleness and reduced fracture toughness of ceramic materials, the biomechanical performance has to be examined intensely. Apart from standard testing, we calculated the implant performance under different worst case scenarios including malposition, bone defects and stumbling. A finite-element-model was developed to calculate the implant performance in situ. The worst case conditions revealed principal stresses 12.6 times higher during stumbling than during normal gait. Nevertheless, none of the calculated principal stress amounts were above the critical strength of the ceramic material used. The analysis of malposition showed the necessity of exact alignment of the implant components.

Lead-free piezoceramics.

PubMed

Saito, Yasuyoshi; Takao, Hisaaki; Tani, Toshihiko; Nonoyama, Tatsuhiko; Takatori, Kazumasa; Homma, Takahiko; Nagaya, Toshiatsu; Nakamura, Masaya

2004-11-04

Lead has recently been expelled from many commercial applications and materials (for example, from solder, glass and pottery glaze) owing to concerns regarding its toxicity. Lead zirconium titanate (PZT) ceramics are high-performance piezoelectric materials, which are widely used in sensors, actuators and other electronic devices; they contain more than 60 weight per cent lead. Although there has been a concerted effort to develop lead-free piezoelectric ceramics, no effective alternative to PZT has yet been found. Here we report a lead-free piezoelectric ceramic with an electric-field-induced strain comparable to typical actuator-grade PZT. We achieved this through the combination of the discovery of a morphotropic phase boundary in an alkaline niobate-based perovskite solid solution, and the development of a processing route leading to highly <001> textured polycrystals. The ceramic exhibits a piezoelectric constant d33 (the induced charge per unit force applied in the same direction) of above 300 picocoulombs per newton (pC N(-1)), and texturing the material leads to a peak d33 of 416 pC N(-1). The textured material also exhibits temperature-independent field-induced strain characteristics.

Chemical and microstructural analyses for heavy metals removal from water media by ceramic membrane filtration.

PubMed

Ali, Asmaa; Ahmed, Abdelkader; Gad, Ali

2017-01-01

This study aims to investigate the ability of low cost ceramic membrane filtration in removing three common heavy metals namely; Pb 2+ , Cu 2+ , and Cd 2+ from water media. The work includes manufacturing ceramic membranes with dimensions of 15 by 15 cm and 2 cm thickness. The membranes were made from low cost materials of local clay mixed with different sawdust percentages of 0.5%, 2.0%, and 5.0%. The used clay was characterized by X-ray diffraction (XRD) and X-ray fluorescence analysis. Aqueous solutions of heavy metals were prepared in the laboratory and filtered through the ceramic membranes. The influence of the main parameters such as pH, initial driving pressure head, and concentration of heavy metals on their removal efficiency by ceramic membranes was investigated. Water samples were collected before and after the filtration process and their heavy metal concentrations were determined by chemical analysis. Moreover, a microstructural analysis using scanning electronic microscope (SEM) was performed on ceramic membranes before and after the filtration process. The chemical analysis results showed high removal efficiency up to 99% for the concerned heavy metals. SEM images approved these results by showing adsorbed metal ions on sides of the internal pores of the ceramic membranes.

Additive Manufacturing for Cost Efficient Production of Compact Ceramic Heat Exchangers and Recuperators

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shulman, Holly; Ross, Nicole

2015-10-30

An additive manufacture technique known as laminated object manufacturing (LOM) was used to fabricate compact ceramic heat exchanger prototypes. LOM uses precision CO2 laser cutting of ceramic green tapes, which are then precision stacked to build a 3D object with fine internal features. Modeling was used to develop prototype designs and predict the thermal response, stress, and efficiency in the ceramic heat exchangers. Build testing and materials analyses were used to provide feedback for the design selection. During this development process, laminated object manufacturing protocols were established. This included laser optimization, strategies for fine feature integrity, lamination fluid control, greenmore » handling, and firing profile. Three full size prototypes were fabricated using two different designs. One prototype was selected for performance testing. During testing, cross talk leakage prevented the application of a high pressure differential, however, the prototype was successful at withstanding the high temperature operating conditions (1300 °F). In addition, analysis showed that the bulk of the part did not have cracks or leakage issues. This led to the development of a module method for next generation LOM heat exchangers. A scale-up cost analysis showed that given a purpose built LOM system, these ceramic heat exchangers would be affordable for the applications.« less

Creep and stress relaxation modeling of polycrystalline ceramic fibers

NASA Technical Reports Server (NTRS)

Dicarlo, James A.; Morscher, Gregory N.

1994-01-01

A variety of high performance polycrystalline ceramic fibers are currently being considered as reinforcement for high temperature ceramic matrix composites. However, under mechanical loading about 800 C, these fibers display creep related instabilities which can result in detrimental changes in composite dimensions, strength, and internal stress distributions. As a first step toward understanding these effects, this study examines the validity of a mechanism-based empirical model which describes primary stage tensile creep and stress relaxation of polycrystalline ceramic fibers as independent functions of time, temperature, and applied stress or strain. To verify these functional dependencies, a simple bend test is used to measure stress relaxation for four types of commercial ceramic fibers for which direct tensile creep data are available. These fibers include both nonoxide (SCS-6, Nicalon) and oxide (PRD-166, FP) compositions. The results of the Bend Stress Relaxation (BSR) test not only confirm the stress, time, and temperature dependencies predicted by the model, but also allow measurement of model empirical parameters for the four fiber types. In addition, comparison of model tensile creep predictions based on the BSR test results with the literature data show good agreement, supporting both the predictive capability of the model and the use of the BSR text as a simple method for parameter determination for other fibers.

Creep and stress relaxation modeling of polycrystalline ceramic fibers

NASA Technical Reports Server (NTRS)

Dicarlo, James A.; Morscher, Gregory N.

1991-01-01

A variety of high performance polycrystalline ceramic fibers are currently being considered as reinforcement for high temperature ceramic matrix composites. However, under mechanical loading above 800 C, these fibers display creep-related instabilities which can result in detrimental changes in composite dimensions, strength, and internal stress distributions. As a first step toward understanding these effects, this study examines the validity of mechanistic-based empirical model which describes primary stage tensile creep and stress relaxation of polycrystalline ceramic fibers as independent functions of time, temperature, and applied stress or strain. To verify these functional dependencies, a simple bend test is used to measure stress relaxation for four types of commercial ceramic fibers for which direct tensile creep data are available. These fibers include both nonoxide (SCS-6, Nicalon) and oxide (PRD-166, FP) compositions. The results of the bend stress relaxation (BSR) test not only confirm the stress, time, and temperature dependencies predicted by the model but also allow measurement of model empirical parameters for the four fiber types. In addition, comparison of model predictions and BSR test results with the literature tensile creep data show good agreement, supporting both the predictive capability of the model and the use of the BSR test as a simple method for parameter determination for other fibers.

Main Clinical Outcomes of Feldspathic Porcelain and Glass-Ceramic Laminate Veneers: A Systematic Review and Meta-Analysis of Survival and Complication Rates.

PubMed

Morimoto, Susana; Albanesi, Rafael Borges; Sesma, Newton; Agra, Carlos Martins; Braga, Mariana Minatel

2016-01-01

The aim of this study was to perform a systematic review and meta-analysis based on clinical trials that evaluated the main outcomes of glass-ceramic and feldspathic porcelain laminate veneers. A systematic search was carried out in Cochrane and PubMed databases. From the selected studies, the survival rates for porcelain and glass-ceramic veneers were extracted, as were complication rates of clinical outcomes: debonding, fracture/chipping, secondary caries, endodontic problems, severe marginal discoloration, and influence of incisal coverage and enamel/dentin preparation. The Cochran Q test and the I(2) statistic were used to evaluate heterogeneity. Out of the 899 articles initially identified, 13 were included for analysis. Metaregression analysis showed that the types of ceramics and follow-up periods had no influence on failure rate. The estimated overall cumulative survival rate was 89% (95% CI: 84% to 94%) in a median follow-up period of 9 years. The estimated survival for glass-ceramic was 94% (95% CI: 87% to 100%), and for feldspathic porcelain veneers, 87% (95% CI: 82% to 93%). The meta-analysis showed rates for the following events: debonding: 2% (95% CI: 1% to 4%); fracture/chipping: 4% (95% CI: 3% to 6%); secondary caries: 1% (95% CI: 0% to 3%); severe marginal discoloration: 2% (95% CI: 1% to 10%); endodontic problems: 2% (95% CI: 1% to 3%); and incisal coverage odds ratio: 1.25 (95% CI: 0.33 to 4.73). It was not possible to perform meta-analysis of the influence of enamel/dentin preparation on failure rates. Glass-ceramic and porcelain laminate veneers have high survival rates. Fracture/ chipping was the most frequent complication, providing evidence that ceramic veneers are a safe treatment option that preserve tooth structure.

Design and evaluation of experimental ceramic automobile thermal reactors

NASA Technical Reports Server (NTRS)

Stone, P. L.; Blankenship, C. P.

1974-01-01

The paper summarizes the results obtained in an exploratory evaluation of ceramics for automobile thermal reactors. Candidate ceramic materials were evaluated in several reactor designs using both engine dynamometer and vehicle road tests. Silicon carbide contained in a corrugated metal support structure exhibited the best performance, lasting 1100 hours in engine dynamometer tests and for more than 38,600 kilimeters (24,000 miles) in vehicle road tests. Although reactors containing glass-ceramic components did not perform as well as silicon carbide, the glass-ceramics still offer good potential for reactor use with improved reactor designs.

Design and evaluation of experimental ceramic automobile thermal reactors

NASA Technical Reports Server (NTRS)

Stone, P. L.; Blankenship, C. P.

1974-01-01

The results obtained in an exploratory evaluation of ceramics for automobile thermal reactors are summarized. Candidate ceramic materials were evaluated in several reactor designs by using both engine-dynamometer and vehicle road tests. Silicon carbide contained in a corrugated-metal support structure exhibited the best performance, lasting 1100 hr in engine-dynamometer tests and more than 38,600 km (24000 miles) in vehicle road tests. Although reactors containing glass-ceramic components did not perform as well as those containing silicon carbide, the glass-ceramics still offer good potential for reactor use with improved reactor designs.

Fabrication of PVDF-TrFE based bilayered PbTiO3/PVDF-TrFE films capacitor

NASA Astrophysics Data System (ADS)

Nurbaya, Z.; Wahid, M. H.; Rozana, M. D.; Annuar, I.; Alrokayan, S. A. H.; Khan, H. A.; Rusop, M.

2016-07-01

Development of high performance capacitor is reaching towards new generation where the ferroelectric materials take places as the active dielectric layer. The motivation of this study is to produce high capacitance device with long life cycle. This was configured by preparing bilayered films where lead titanate as an active dielectric layer and stacked with the top dielectric layer, poly(vinyledenefluoride-trifluoroethylene). Both of them are being referred that have one in common which is ferroelectric behavior. Therefore the combination of ceramic and polymer ferroelectric material could perform optimum dielectric characteristic for capacitor applications. The fabrication was done by simple sol-gel spin coating method that being varied at spinning speed property for polymer layers, whereas maintaining the ceramic layer. The characterization of PVDF-TrFE/PbTiO3 was performed according to metal-insulator-metal stacked capacitor measurement which includes structural, dielectric, and ferroelectric measurement.

Ceramic regenerator program

NASA Technical Reports Server (NTRS)

Franklin, Jerrold E.

1991-01-01

The feasibility of fabricating an Air Turbo Ramjet (ATR) regenerator containing intricate hydraulic passages from a ceramic material in order to allow operation with high temperature combustion gas and to reduce weight as compared with metallic materials was demonstrated. Platelet technology, ceramic tape casting, and multilayer ceramic packaging techniques were used in this fabrication of subscale silicon nitride components. Proof-of-concept demonstrations were performed to simulate a methane cooled regenerator for an ATR engine. The regenerator vane was designed to operate at realistic service conditions, i.e., 600 psi in a 3500 R (3040 F), 500 fps combustion gas environment. A total of six regenerators were fabricated and tested. The regenerators were shown to be able to withstand internal pressurization to 1575 psi. They were subjected to testing in 500 fps, 3560 R (3100 F) air/propane combustion products and were operated satisfactorily for an excess of 100 hr and 40 thermal cycles which exceeded 2460 R (2000 F).

Fabrication of Porous Ceramic-Geopolymer Based Material to Improve Water Absorption and Retention in Construction Materials: A Review

NASA Astrophysics Data System (ADS)

Jamil, N. H.; Ibrahim, W. M. A. W.; Abdullah, M. M. A. B.; Sandu, A. V.; Tahir, M. F. M.

2017-06-01

Porous ceramic nowadays has been investigated for a variety of its application such as filters, lightweight structural component and others due to their specific properties such as high surface area, stability and permeability. Besides, it has the properties of low thermal conductivity. Various formation techniques making these porous ceramic properties can be tailored or further fine-tuned to obtain the optimum characteristic. Porous materials also one of the good candidate for absorption properties. Conventional construction materials are not design to have good water absorption and retention that lead to the poor performance on these criteria. Temperature is a major driving force for moisture movement and influences sorption characteristics of many constructions materials. The effect of elevated temperatures on the water absorption coefficient and retention remain as critical issue that need to be investigated. Therefore, this paper will review the process parameters in fabricating porous ceramic for absorption properties.

Creep, Fatigue and Fracture Behavior of Environmental Barrier Coating and SiC-SiC Ceramic Matrix Composite Systems: The Role of Environment Effects

NASA Technical Reports Server (NTRS)

Zhu, Dongming; Ghosn, Louis J.

2015-01-01

Advanced environmental barrier coating (EBC) systems for low emission SiCSiC CMC combustors and turbine airfoils have been developed to meet next generation engine emission and performance goals. This presentation will highlight the developments of NASAs current EBC system technologies for SiC-SiC ceramic matrix composite combustors and turbine airfoils, their performance evaluation and modeling progress towards improving the engine SiCSiC component temperature capability and long-term durability. Our emphasis has also been placed on the fundamental aspects of the EBC-CMC creep and fatigue behaviors, and their interactions with turbine engine oxidizing and moisture environments. The EBC-CMC environmental degradation and failure modes, under various simulated engine testing environments, in particular involving high heat flux, high pressure, high velocity combustion conditions, will be discussed aiming at quantifying the protective coating functions, performance and durability, and in conjunction with damage mechanics and fracture mechanics approaches.

Environmental durability of ceramics and ceramic composites

NASA Technical Reports Server (NTRS)

Fox, Dennis S.

1992-01-01

An account is given of the current understanding of the environmental durability of both monolithic ceramics and ceramic-matrix composites, with a view to the prospective development of methods for the characterization, prediction, and improvement of ceramics' environmental durability. Attention is given to the environmental degradation behaviors of SiC, Si3N4, Al2O3, and glass-ceramic matrix compositions. The focus of corrosion prevention in Si-based ceramics such as SiC and Si3N4 is on the high and low sulfur fuel combustion-product effects encountered in heat engine applications of these ceramics; sintering additives and raw material impurities are noted to play a decisive role in ceramics' high temperature environmental response.

An evaluation of strain measuring devices for ceramic composites

NASA Technical Reports Server (NTRS)

Gyekenyesi, John Z.; Bartolotta, Paul A.

1991-01-01

A series of tensile tests was conducted on SiC/reaction bonded silicon nitrides (RBSN) composites using different methods of strain measurement. The tests were used to find the optimum strain sensing device for use with continuous fiber reinforced ceramic matrix composites in ambient and high temperature environments. Bonded resistance gages were found to offer excellent performance for room temperature tests. The clip-on gage offers the same performance, but less time is required for mounting it to the specimen. Low contact force extensometers track the strain with acceptable results at high specimen temperatures. Silicon carbide rods with knife edges are preferred. The edges must be kept sharp. The strain measuring devices should be mounted on the flat side of the specimen. This is in contrast to mounting on the rough thickness side.

An evaluation of strain measuring devices for ceramic composites

NASA Technical Reports Server (NTRS)

Gyekenyesi, John Z.; Bartolotta, Paul A.

1992-01-01

A series of tensile tests were conducted on SiC/RBSN composites using different methods of strain measurement. The tests were used to find the optimum strain sensing device for use with continuous fiber reinforced ceramic matrix composites in ambient and high temperature environments. Bonded resistance strain gages were found to offer excellent performance for room temperature tests. The clip-on gage offers the same performance but significantly less time is required for mounting it to the specimen. Low contact force extensometers track the strain with acceptable results at high specimen temperatures. Silicon carbide rods with knife edges are preferred. The edges must be kept sharp. The strain measuring devices should be mounted on the flat side of the specimen. This is in contrast to mounting on the rough thickness side.

Optimization Method of a Low Cost, High Performance Ceramic Proppant by Orthogonal Experimental Design

NASA Astrophysics Data System (ADS)

Zhou, Y.; Tian, Y. M.; Wang, K. Y.; Li, G.; Zou, X. W.; Chai, Y. S.

2017-09-01

This study focused on optimization method of a ceramic proppant material with both low cost and high performance that met the requirements of Chinese Petroleum and Gas Industry Standard (SY/T 5108-2006). The orthogonal experimental design of L9(34) was employed to study the significance sequence of three factors, including weight ratio of white clay to bauxite, dolomite content and sintering temperature. For the crush resistance, both the range analysis and variance analysis reflected the optimally experimental condition was weight ratio of white clay to bauxite=3/7, dolomite content=3 wt.%, temperature=1350°C. For the bulk density, the most important factor was the sintering temperature, followed by the dolomite content, and then the ratio of white clay to bauxite.

Plasma-sprayed zirconia gas path seal technology: A state-of-the-art review

NASA Technical Reports Server (NTRS)

Bill, R. C.

1979-01-01

The benefits derived from application of ceramic materials to high pressure turbine gas path seal components are described and the developmental backgrounds of various approaches are reviewed. The most fully developed approaches are those employing plasma sprayed zirconium oxide as the ceramic material. Prevention of cracking and spalling of the zirconium oxide under cyclic thermal shock conditions imposed by the engine operating cycle is the most immediate problem to be solved before implementation is undertaken. Three promising approaches to improving cyclic thermal shock resistance are described and comparative rig performance of each are reviewed. Advanced concepts showing potential for performance improvements are described.

DSC and TG Analysis of a Blended Binder Based on Waste Ceramic Powder and Portland Cement

NASA Astrophysics Data System (ADS)

Pavlík, Zbyšek; Trník, Anton; Kulovaná, Tereza; Scheinherrová, Lenka; Rahhal, Viviana; Irassar, Edgardo; Černý, Robert

2016-03-01

Cement industry belongs to the business sectors characteristic by high energy consumption and high {CO}2 generation. Therefore, any replacement of cement in concrete by waste materials can lead to immediate environmental benefits. In this paper, a possible use of waste ceramic powder in blended binders is studied. At first, the chemical composition of Portland cement and ceramic powder is analyzed using the X-ray fluorescence method. Then, thermal and mechanical characterization of hydrated blended binders containing up to 24 % ceramic is carried out within the time period of 2 days to 28 days. The differential scanning calorimetry and thermogravimetry measurements are performed in the temperature range of 25°C to 1000°C in an argon atmosphere. The measurement of compressive strength is done according to the European standards for cement mortars. The thermal analysis results in the identification of temperature and quantification of enthalpy and mass changes related to the liberation of physically bound water, calcium-silicate-hydrates dehydration and portlandite, vaterite and calcite decomposition. The portlandite content is found to decrease with time for all blends which provides the evidence of the pozzolanic activity of ceramic powder even within the limited monitoring time of 28 days. Taking into account the favorable results obtained in the measurement of compressive strength, it can be concluded that the applied waste ceramic powder can be successfully used as a supplementary cementing material to Portland cement in an amount of up to 24 mass%.

Comparative effectiveness of ceramic-on-ceramic implants in stemmed hip replacement: a multinational study of six national and regional registries.

PubMed

Sedrakyan, Art; Graves, Stephen; Bordini, Barbara; Pons, Miquel; Havelin, Leif; Mehle, Susan; Paxton, Elizabeth; Barber, Thomas; Cafri, Guy

2014-12-17

The rapid decline in use of conventional total hip replacement with a large femoral head size and a metal-on-metal bearing surface might lead to increased popularity of ceramic-on-ceramic bearings as another hard-on-hard alternative that allows implantation of a larger head. We sought to address comparative effectiveness of ceramic-on-ceramic and metal-on-HXLPE (highly cross-linked polyethylene) implants by utilizing the distributed health data network of the ICOR (International Consortium of Orthopaedic Registries), an unprecedented collaboration of national and regional registries and the U.S. FDA (Food and Drug Administration). A distributed health data network was developed by the ICOR and used in this study. The data from each registry are standardized and provided at a level of aggregation most suitable for the detailed analysis of interest. The data are combined across registries for comprehensive assessments. The ICOR coordinating center and study steering committee defined the inclusion criteria for this study as total hip arthroplasty performed without cement from 2001 to 2010 in patients forty-five to sixty-four years of age with osteoarthritis. Six national and regional registries (Kaiser Permanente and HealthEast in the U.S., Emilia-Romagna region in Italy, Catalan region in Spain, Norway, and Australia) participated in this study. Multivariate meta-analysis was performed with use of linear mixed models, with survival probability as the unit of analysis. We present the results of the fixed-effects model and include the results of the random-effects model in an appendix. SAS version 9.2 was used for all analyses. We first compared femoral head sizes of >28 mm and ≤28 mm within ceramic-on-ceramic implants and then compared ceramic-on-ceramic with metal-on-HXLPE. A total of 34,985 patients were included; 52% were female. We found a lower risk of revision associated with use of ceramic-on-ceramic implants when a larger head size was used (HR [hazard ratio] = 0.73, 95% CI [confidence interval] = 0.60 to 0.88, p = 0.001). Use of smaller-head-size ceramic-on-ceramic bearings was associated with a higher risk of failure compared with metal-on-HXLPE bearings (HR = 1.36, 95% CI = 1.09 to 1.68, p = 0.006). Use of large-head-size ceramic-on-ceramic bearings was associated with a small protective effect relative to metal-on-HXLPE bearings (not subdivided by head size) in years zero to two, but this difference dissipated over the longer term. Our multinational study based on a harmonized, distributed network showed that use of ceramic-on-ceramic implants with a smaller head size in total hip arthroplasty without cement was associated with a higher risk of revision compared with metal-on-HXLPE and >28-mm ceramic-on-ceramic implants. These findings warrant careful reflection by regulatory and clinical communities and wide dissemination to patients for informed decision-making regarding such surgery. Copyright © 2014 by The Journal of Bone and Joint Surgery, Incorporated.

Fabrication of piezoelectric ceramic micro-actuator and its reliability for hard disk drives.

PubMed

Jing, Yang; Luo, Jianbin; Yang, Wenyan; Ju, Guoxian

2004-11-01

A new U-type micro-actuator for precisely positioning a magnetic head in high-density hard disk drives was proposed and developed. The micro-actuator is composed of a U-type stainless steel substrate and two piezoelectric ceramic elements. Using a high-d31 piezoelectric coefficient PMN-PZT ceramic plate and adopting reactive ion etching process fabricate the piezoelectric elements. Reliability against temperature was investigated to ensure the practical application to the drive products. The U-type substrate attached to each side via piezoelectric elements also was simulated by the finite-element method and practically measured by a laser Doppler vibrometer in order to testify the driving mechanics of it. The micro-actuator coupled with two piezoelectric elements featured large displacement of 0.875 microm and high-resonance frequency over 22 kHz. The novel piezoelectric micro-actuators then possess a useful compromise performance to displacement, resonance frequency, and generative force. The results reveal that the new design concept provides a valuable alternative for multilayer piezoelectric micro-actuators.

Mechanical behavior of high strength ceramic fibers at high temperatures

NASA Technical Reports Server (NTRS)

Tressler, R. E.; Pysher, D. J.

1991-01-01

The mechanical behavior of commercially available and developmental ceramic fibers, both oxide and nonoxide, has been experimentally studied at expected use temperatures. In addition, these properties have been compared to results from the literature. Tensile strengths were measured for three SiC-based and three oxide ceramic fibers for temperatures from 25 C to 1400 C. The SiC-based fibers were stronger but less stiff than the oxide fibers at room temperature and retained more of both strength and stiffness to high temperatures. Extensive creep and creep-rupture experiments have been performed on those fibers from this group which had the best strengths above 1200 C in both single filament tests and tests of fiber bundles. The creep rates for the oxides are on the order of two orders of magnitude faster than the polymer derived nonoxide fibers. The most creep resistant filaments available are single crystal c-axis sapphire filaments. Large diameter CVD fabricated SiC fibers are the most creep and rupture resistant nonoxide polycrystalline fibers tested to date.

Energy efficient engine pin fin and ceramic composite segmented liner combustor sector rig test report

NASA Technical Reports Server (NTRS)

Dubiel, D. J.; Lohmann, R. P.; Tanrikut, S.; Morris, P. M.

1986-01-01

Under the NASA-sponsored Energy Efficient Engine program, Pratt and Whitney has successfully completed a comprehensive test program using a 90-degree sector combustor rig that featured an advanced two-stage combustor with a succession of advanced segmented liners. Building on the successful characteristics of the first generation counter-parallel Finwall cooled segmented liner, design features of an improved performance metallic segmented liner were substantiated through representative high pressure and temperature testing in a combustor atmosphere. This second generation liner was substantially lighter and lower in cost than the predecessor configuration. The final test in this series provided an evaluation of ceramic composite liner segments in a representative combustor environment. It was demonstrated that the unique properties of ceramic composites, low density, high fracture toughness, and thermal fatigue resistance can be advantageously exploited in high temperature components. Overall, this Combustor Section Rig Test program has provided a firm basis for the design of advanced combustor liners.

Development of all-solid lithium-ion battery using Li-ion conducting glass-ceramics

NASA Astrophysics Data System (ADS)

Inda, Yasushi; Katoh, Takashi; Baba, Mamoru

We have developed a high performance lithium-ion conducting glass-ceramics. This glass-ceramics has the crystalline form of Li 1+ x+ yAl xTi 2- xSi yP 3- yO 12 with a NASICON-type structure, and it exhibits a high lithium-ion conductivity of 10 -3 S cm -1 or above at room temperature. Moreover, since this material is stable in the open atmosphere and even to exposure to moist air, it is expected to be applied for various uses. One of applications of this material is as a solid electrolyte for a lithium-ion battery. Batteries were developed by combining a LiCoO 2 positive electrode, a Li 4Ti 5O 12 negative electrode, and a composite electrolyte. The battery using the composite electrolyte with a higher conductivity exhibited a good charge-discharge characteristic.

A new large area scintillator screen for X-ray imaging

NASA Astrophysics Data System (ADS)

Nagarkar, V. V.; Miller, S. R.; Tipnis, S. V.; Lempicki, A.; Brecher, C.; Lingertat, H.

2004-01-01

We report on the development of a new, large area, powdered scintillator screen based on Lu 2O 3(Eu). As reported earlier, the transparent ceramic form of this material has a very high density of 9.4 g/cm 3, a high light output comparable to that of CsI(Tl), and emits in a narrow spectral band centered at about 610 nm. Research into fabrication of this ceramic scintillator in a large area format is currently underway, however the process is not yet practical for large scale production. Here we have explored fabrication of large area screens using precursor powders from which the ceramics are fabricated. To date we have produced up to 16 × 16 cm 2 area screens with thickness in the range of 18 mg/cm 2. This paper outlines the screen fabrication technique and presents its imaging performance in comparison with a commercial Gd 2O 2S:Tb (GOS) screen.

Effect of Mechanical and Thermal Loading Histories on Residual Properties of SiCf/SiC Ceramic Matrix Composites

NASA Technical Reports Server (NTRS)

Almansour, Amjad; Kiser, Doug; Smith, Craig; Bhatt, Ram; Gorican, Dan; Phillips, Ron; McCue, Terry R.

2017-01-01

Silicon Carbide based Ceramic Matrix Composites (CMCs) are attractive materials for use in high-temperature structural applications in the aerospace and nuclear industries. Under high stresses and temperatures, creep degradation is the dominant damage mechanism in CMCs. Consequently, chemical vapor infiltration (CVI) SiCf/SiC ceramic matrix composites (CMC) incorporating SylramicTM-iBN SiC fibers coated with boron nitride (BN) interphase and CVI-SiC matrix were tested to examine creep behavior in air at a range of elevated temperatures of (2200 - 2700 F). Samples that survived creep tests were evaluated via RT fast fracture tensile tests to determine residual properties, with the use of acoustic emission (AE) to assess stress dependent damage initiation and progression. Microscopy of regions within the gage section of the tested specimens was performed. Observed material degradation mechanisms are discussed.

Improving tribological and anti-bacterial properties of titanium external fixation pins through surface ceramic conversion.

PubMed

Dong, Huan; Mukinay, Tatiana; Li, Maojun; Hood, Richard; Soo, Sein Leung; Cockshott, Simon; Sammons, Rachel; Li, Xiaoying

2017-01-01

In this study, an advanced ceramic conversion surface engineering technology has been applied for the first time to self-drilling Ti6Al4V external fixation pins to improve their performance in terms of biomechanical, bio-tribological and antibacterial properties. Systematic characterisation of the ceramic conversion treated Ti pins was carried out using Scanning electron microscope, X-ray diffraction, Glow-discharge optical emission spectroscopy, nano- and micro-indentation and scratching; the biomechanical and bio-tribological properties of the surface engineered Ti pins were evaluated by insertion into high density bone simulation material; and the antibacterial behaviour was assessed with Staphylococcus aureus NCTC 6571. The experimental results have demonstrated that the surfaces of Ti6Al4V external fixation pins were successfully converted into a TiO 2 rutile layer (~2 μm in thickness) supported by an oxygen hardened case (~15 μm in thickness) with very good bonding due to the in-situ conversion nature. The maximum insertion force and temperature were reduced from 192N and 31.2 °C when using the untreated pins to 182N and 26.1 °C when the ceramic conversion treated pins were tested. This is mainly due to the significantly increased hardness (more than three times) and the effectively enhanced wear resistance of the cutting edge of the self-drilling Ti pins following the ceramic conversion treatment. The antibacterial tests also revealed that there was a significantly reduced number of bacteria isolated from the ceramic conversion treated pins compared to the untreated pins of around 50 % after 20 h incubation, P < 0.01 (0.0024). The results reported are encouraging and could pave the way towards high-performance anti-bacterial titanium external fixation pins with reduced pin-track infection and pin loosing.

[Comparison of early clinical effects of two hip prosthesis designs between ceramics to ceramics and metal to polyethylene].

PubMed

Yang, Li-qing; Li, Xi; Fu, Qin; Wang, Cheng

2013-07-01

To retrospectively study early therapeutic effects of the ceramics to ceramics prosthesis design in treating hip disease. From October 2007 to September 2010, 42 patients (44 hips) with hip disease underwent replacement of total hip. Hip prosthesis designs included the Pinnacle ceramics to ceramics and the Duraloc metal to polyethylene,produced by DePuy Company, all were non-bone cement type of artificial hip joint. Twenty patients (22 hips) were performed with ceramics to ceramics total hip prosthesis (CoC group, there were 12 males and 8 females, aged from 21 to 49 years) and 22 patients (22 hips) were performed with metal to polyethylene total hip prosthesis (MoP group, there were 13 males and 9 females, aged from 42 to 55 years). All the surgical approachs were posterolateral, and the routine anticoagulation and the corresponding functional exercise were performed after operation. The follow-up time was 6 months at least including clinical and radiographic observation. Measured the motion of joint and evaluated the function of hip joint according to Harris classification. All clinical effects were satisfactory and no dislocation ,loosening,infection, deep venous thrombosis and other complications occurred. There was no statistical significance in Harris scoring and the motion of joint between two groups before and after operation (P>0.05). The clinical effect of ceramics to ceramics prosthesis design in improving clinical symptoms and the motion of joint is coordinate with metal to polyethylene total hip prosthesis, however, its advantages and long-term efficacy need further observing. The ceramics to ceramics prosthesis design may be a good choice for the young patients with hip disease because of its good wear resistance.

Characterization of Thick and Thin Film SiCN for Pressure Sensing at High Temperatures

PubMed Central

Leo, Alfin; Andronenko, Sergey; Stiharu, Ion; Bhat, Rama B.

2010-01-01

Pressure measurement in high temperature environments is important in many applications to provide valuable information for performance studies. Information on pressure patterns is highly desirable for improving performance, condition monitoring and accurate prediction of the remaining life of systems that operate in extremely high temperature environments, such as gas turbine engines. A number of technologies have been recently investigated, however these technologies target specific applications and they are limited by the maximum operating temperature. Thick and thin films of SiCN can withstand high temperatures. SiCN is a polymer-derived ceramic with liquid phase polymer as its starting material. This provides the advantage that it can be molded to any shape. CERASET™ also yields itself for photolithography, with the addition of photo initiator 2, 2-Dimethoxy-2-phenyl-acetophenone (DMPA), thereby enabling photolithographical patterning of the pre-ceramic polymer using UV lithography. SiCN fabrication includes thermosetting, crosslinking and pyrolysis. The technology is still under investigation for stability and improved performance. This work presents the preparation of SiCN films to be used as the body of a sensor for pressure measurements in high temperature environments. The sensor employs the phenomenon of drag effect. The pressure sensor consists of a slender sensitive element and a thick blocking element. The dimensions and thickness of the films depend on the intended application of the sensors. Fabrication methods of SiCN ceramics both as thin (about 40–60 μm) and thick (about 2–3 mm) films for high temperature applications are discussed. In addition, the influence of thermosetting and annealing processes on mechanical properties is investigated. PMID:22205871

In vitro evaluation of the mutagenic and carcinogenic power of high purity zirconia ceramic.

PubMed

Covacci, V; Bruzzese, N; Maccauro, G; Andreassi, C; Ricci, G A; Piconi, C; Marmo, E; Burger, W; Cittadini, A

1999-02-01

Tetragonal zirconia polycrystal (TZP) is a new interesting ceramic for the manufacture of medical devices. Its wide use in orthopedic and odontoiatric implants was limited till now by the high chemical and radiochemical impurities of the raw materials. Purification processes now available allow to obtain high purity ceramic grade powders suitable for TZP ceramics manufacture, even if their possible mutagenic and transforming effects are still unclear. The aim of this work is to study in vitro the mutagenic and oncogenic effects of a new zirconia ceramic stabilized by yttria (Y-TZP). This ceramic was sintered from high purity powders obtained by a process developed under a project carried out within the Brite EuRam programme. For comparison, ceramics made from unpurified zirconia powder were also tested. Fibroblasts irradiated by a linear accelerator were used as positive control. The results obtained show that Y-TZP ceramic does not elicit either mutagenic or transforming effect on C3H/10T(1/2) (10T(1/2)) cells and demonstrate that ceramic from high purity powders can be considered suitable for biomedical applications from the point of view of the effects of its radioactive impurity content.

High-Performance Protonic Ceramic Fuel Cells with Thin-Film Yttrium-Doped Barium Cerate-Zirconate Electrolytes on Compositionally Gradient Anodes.

PubMed

Bae, Kiho; Lee, Sewook; Jang, Dong Young; Kim, Hyun Joong; Lee, Hunhyeong; Shin, Dongwook; Son, Ji-Won; Shim, Joon Hyung

2016-04-13

In this study, we used a compositionally gradient anode functional layer (AFL) consisting of Ni-BaCe(0.5)Zr(0.35)Y(0.15)O(3-δ) (BCZY) with increasing BCZY contents toward the electrolyte-anode interface for high-performance protonic ceramic fuel cells. It is identified that conventional homogeneous AFLs fail to stably accommodate a thin film of BCZY electrolyte. In contrast, a dense 2 μm thick BCZY electrolyte was successfully deposited onto the proposed gradient AFL with improved adhesion. A fuel cell containing this thin electrolyte showed a promising maximum peak power density of 635 mW cm(-2) at 600 °C, with an open-circuit voltage of over 1 V. Impedance analysis confirmed that minimizing the electrolyte thickness is essential for achieving a high power output, suggesting that the anode structure is important in stably accommodating thin electrolytes.

Experimental studies on a new highly porous hydroxyapatite matrix for obliterating open mastoid cavities.

PubMed

Punke, Christoph; Zehlicke, Thorsten; Boltze, Carsten; Pau, Hans Wilhelm

2008-09-01

In an initial preliminary study, the applicability of a new high-porosity hydroxyapatite (HA) ceramic for obliterating large open mastoid cavities was proven and tested in an animal model (bulla of guinea pig). Experimental study. NanoBone, a highly porous matrix consisting of 76% hydroxyl apatite and 24% silicone dioxide fabricated in a sol-gel technique, was administered unilaterally into the opened bullae of 30 guinea pigs. In each animal, the opposite bulla was filled with Bio-Oss, a bone substitute consisting of a portion of mineral bovine bone. Histologic evaluations were performed 1, 2, 3, 4, 5, and 12 weeks after the implantation. After an initial phase in which the ceramic granules were surrounded by inflammatory cells (1-2 wk), there were increasing signs of vascularization. Osteoneogenesis and-at the same time-resorption of the HA ceramic were observed after the third week. No major difference in comparison to the bovine bone material could be found. Our results confirm the favorable qualities of the new ceramic reported in association with current maxillofacial literature. Conventional HA granules used for mastoid obliteration to date often showed problems with prolonged inflammatory reactions and, finally, extrusions. In contrast to those ceramics, the new material seems to induce more osteoneogenesis and undergoes early resorption probably due to its high porosity. Overall, it is similar to the bovine bone substance tested on the opposite ear in each animal. Further clinical studies may reveal whether NanoBone can be an adequate material for obliterating open mastoid cavities in patients.

Magnetic-field sensing coil embedded in ceramic for measuring ambient magnetic field

DOEpatents

Takahashi, Hironori

2004-02-10

A magnetic pick-up coil for measuring magnetic field with high specific sensitivity, optionally with an electrostatic shield (24), having coupling elements (22) with high winding packing ratio, oriented in multiple directions, and embedded in ceramic material for structural support and electrical insulation. Elements of the coil are constructed from green ceramic sheets (200) and metallic ink deposited on surfaces and in via holes of the ceramic sheets. The ceramic sheets and the metallic ink are co-fired to create a monolithic hard ceramic body (20) with metallized traces embedded in, and placed on exterior surfaces of, the hard ceramic body. The compact and rugged coil can be used in a variety of environments, including hostile conditions involving ultra-high vacuum, high temperatures, nuclear and optical radiation, chemical reactions, and physically demanding surroundings, occurring either individually or in combinations.

Synthesis of high performance ceramic fibers by chemical vapor deposition for advanced metallics reinforcing

NASA Technical Reports Server (NTRS)

Revankar, Vithal; Hlavacek, Vladimir

1991-01-01

The chemical vapor deposition (CVD) synthesis of fibers capable of effectively reinforcing intermetallic matrices at elevated temperatures which can be used for potential applications in high temperature composite materials is described. This process was used due to its advantage over other fiber synthesis processes. It is extremely important to produce these fibers with good reproducible and controlled growth rates. However, the complex interplay of mass and energy transfer, blended with the fluid dynamics makes this a formidable task. The design and development of CVD reactor assembly and system to synthesize TiB2, CrB, B4C, and TiC fibers was performed. Residual thermal analysis for estimating stresses arising form thermal expansion mismatch were determined. Various techniques to improve the mechanical properties were also performed. Various techniques for improving the fiber properties were elaborated. The crystal structure and its orientation for TiB2 fiber is discussed. An overall view of the CVD process to develop CrB2, TiB2, and other high performance ceramic fibers is presented.

Experimental Equipment Design and Fabrication Study for Delta-G Experiment

NASA Technical Reports Server (NTRS)

1997-01-01

The Research Machine Shop at UAH did not develop any new technology in the performance of the following tasks. All tasks were performed as specified.UAH RMS shall design and fabricate a "poor" model of a silicon-carbide high-temperature crucible with dimensions of 8 inches in diameter and 4 inches high-temperature crucible for pouring liquid ceramic materials at 1200 C into molds from heating ovens. The crucible shall also be designed with a manipulation fixture to facilitate holding and pouring of the heated liquid material. UAH RMS shall investigate the availability of 400 Hz, high-current (65 volts @ 100 amperes) power systems for use in high-speed rotating disk experiments, UAH RMS shall investigate, develop a methodology, and experiment on the application of filament-wound carbon fibers to the periphery of ceramic superconductors to withstand high levels of rotational g-forces. UAH RMS shall provide analytical data to verify the resulting improved disc with carbon composite fibers.

Ceramic Matrix Composite Vane Subelement Burst Testing

NASA Technical Reports Server (NTRS)

Brewer, David N.; Verrilli, Michael; Calomino, Anthony

2006-01-01

Burst tests were performed on Ceramic Matrix Composite (CMC) vane specimens, manufactured by two vendors, under the Ultra Efficient Engine Technology (UEET) project. Burst specimens were machined from the ends of 76mm long vane sub-elements blanks and from High Pressure Burner Rig (HPBR) tested specimens. The results of burst tests will be used to compare virgin specimens with specimens that have had an Environmental Barrier Coating (EBC) applied, both HPBR tested and untested, as well as a comparison between vendors.

Silicon carbide sewing thread

NASA Technical Reports Server (NTRS)

Sawko, Paul M. (Inventor)

1995-01-01

Composite flexible multilayer insulation systems (MLI) were evaluated for thermal performance and compared with currently used fibrous silica (baseline) insulation system. The systems described are multilayer insulations consisting of alternating layers of metal foil and scrim ceramic cloth or vacuum metallized polymeric films quilted together using ceramic thread. A silicon carbide thread for use in the quilting and the method of making it are also described. These systems provide lightweight thermal insulation for a variety of uses, particularly on the surface of aerospace vehicles subject to very high temperatures during flight.

Development of 10×10 Matrix-anode MCP-PMT

NASA Astrophysics Data System (ADS)

Yang, Jie; Li, Yongbin; Xu, Pengxiao; Zhao, Wenjin

2018-02-01

10×10 matrix-anode is developed by high-temperature co-fired ceramics (HTCC) technology. Based on the new matrix-anode, a new kind of photon counting imaging detector - 10×10 matrix-anode MCP-PMT is developed, and its performance parameters are tested. HTCC technology is suitable for the MCP-PMT's air impermeability and its baking process. Its response uniformity is better than the metal-ceramic or metal-glass sealing anode, and it is also a promising method to realize a higher density matrix-anode.

Radiation-Thermal Sintering of Zirconia Powder Compacts Under Conditions of Bilateral Heating Using Beams of Low-Energy Electrons

NASA Astrophysics Data System (ADS)

Ghyngazov, S. A.; Frangulyan, T. S.; Chernyavskii, A. V.; Goreev, A. K.; Naiden, E. P.

2015-06-01

Comparative experiments on sintering zirconia ceramics are performed using colliding beams of low-energy electrons and under conditions of thermal heating. The density and microhardness of ceramic materials manufactured via different processes are determined. The use of a regime of bilateral heating by high-intensity,low-energy electron beams is shown to intensify the sintering process and yield material specimens with improved characteristics compared to those formed by thermal sintering.

Transient Heating and Thermomechanical Stress Modeling of Ceramic HEPA Filters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bogle, Brandon; Kelly, James; Haslam, Jeffrey

The purpose of this report is to showcase an initial finite-element analysis model of a ceramic High-Efficiency Particulate (HEPA) Air filter design. Next generation HEPA filter assemblies are being developed at LLNL to withstand high-temperature fire scenarios by use of ceramics and advanced materials. The filters are meant for use in radiological and nuclear facilities, and are required to survive 500°C fires over an hour duration. During such conditions, however, collecting data under varying parameters can be challenging; therefore, a Finite Element Analysis model of the filter was conducted using COMSOL ® Multiphysics to analyze the effects of fire. Finitemore » Element Analysis (FEA) modelling offers several opportunities: researchers can quickly and easily consider impacts of potential design changes, material selection, and flow characterization on filter performance. Specifically, this model provides stress references for the sealant at high temperatures. Modeling of full filter assemblies was deemed inefficient given the computational requirements, so a section of three tubes from the assembly was modeled. The model looked at the transient heating and thermomechanical stress development during a 500°C air flow at 6 CFM. Significant stresses were found at the ceramic-metal interfaces of the filter, and conservative temperature profiles at locations of interest were plotted. The model can be used for the development of sealants that minimize stresses at the ceramic-metal interface. Further work on the model would include the full filter assembly and consider heat losses to make more accurate predictions.« less

Effect of ceramic coating of JT8D combustor liner on maximum liner temperatures and other combustor performance parameters

NASA Technical Reports Server (NTRS)

Butze, H. F.; Liebert, C. H.

1976-01-01

The effect of ceramic coating of a JT8D combustor liner was investigated at simulated cruise and takeoff conditions with two fuels of widely different aromatic contents. Substantial decreases in maximum liner temperatures and flame radiation values were obtained with the ceramic-coated liner. Small reductions in exhaust gas smoke concentrations were observed with the ceramic-coated liner. Other performance parameters such as combustion efficiency and emissions of unburned hydrocarbons, CO, and NOx were not affected significantly. No deterioration of the ceramic coating was observed after about 6 hours of cyclic operation including several startups and shutdowns.

Modeling the Mechanical Behavior of Ceramic Matrix Composite Materials

NASA Technical Reports Server (NTRS)

Jordan, William

1998-01-01

Ceramic matrix composites are ceramic materials, such as SiC, that have been reinforced by high strength fibers, such as carbon. Designers are interested in using ceramic matrix composites because they have the capability of withstanding significant loads while at relatively high temperatures (in excess of 1,000 C). Ceramic matrix composites retain the ceramic materials ability to withstand high temperatures, but also possess a much greater ductility and toughness. Their high strength and medium toughness is what makes them of so much interest to the aerospace community. This work concentrated on two different tasks. The first task was to do an extensive literature search into the mechanical behavior of ceramic matrix composite materials. This report contains the results of this task. The second task was to use this understanding to help interpret the ceramic matrix composite mechanical test results that had already been obtained by NASA. Since the specific details of these test results are subject to the International Traffic in Arms Regulations (ITAR), they are reported in a separate document (Jordan, 1997).

Laser ultrasonics for bulk-density distribution measurement on green ceramic tiles

NASA Astrophysics Data System (ADS)

Revel, G. M.; Cavuto, A.; Pandarese, G.

2016-10-01

In this paper a Laser Ultrasonics (LUT) system is developed and applied to measure bulk density distribution of green ceramic tiles, which are porous materials with low heat conductivity. Bulk density of green ceramic bodies is a fundamental parameter to be kept under control in the industrial production of ceramic tiles. The LUT system proposed is based on a Nd:YAG pulsed laser for excitation and an air-coupled electro-capacitive transducer for detection. The paper reports experimental apparent bulk-density measurements on white ceramic bodies after a calibration procedures. The performances observed are better than those previously achieved by authors using air-coupled ultrasonic probes for both emission and detection, allowing to reduce average uncertainty down to about ±6 kg/m3 (±0.3%), thanks to the increase in excitation efficiency and lateral resolution, while maintaining potential flexibility for on-line application. The laser ultrasonic procedure proposed is available for both on-line and off-line application. In this last case it is possible to obtain bulk density maps with high spatial resolution by a 2D scan without interrupting the production process.

Electric-Field-Directed Parallel Alignment Architecting 3D Lithium-Ion Pathways within Solid Composite Electrolyte.

PubMed

Liu, Xueqing; Peng, Sha; Gao, Shuyu; Cao, Yuancheng; You, Qingliang; Zhou, Liyong; Jin, Yongcheng; Liu, Zhihong; Liu, Jiyan

2018-05-09

It is of great significance to seek high-performance solid electrolytes via a facile chemistry and simple process for meeting the requirements of solid batteries. Previous reports revealed that ion conducting pathways within ceramic-polymer composite electrolytes mainly occur at ceramic particles and the ceramic-polymer interface. Herein, one facile strategy toward ceramic particles' alignment and assembly induced by an external alternating-current (AC) electric field is presented. It was manifested by an in situ optical microscope that Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 particles and poly(ethylene glycol) diacrylate in poly(dimethylsiloxane) (LATP@PEGDA@PDMS) assembled into three-dimensional connected networks on applying an external AC electric field. Scanning electron microscopy revealed that the ceramic LATP particles aligned into a necklacelike assembly. Electrochemical impedance spectroscopy confirmed that the ionic conductivity of this necklacelike alignment was significantly enhanced compared to that of the random one. It was demonstrated that this facile strategy of applying an AC electric field can be a very effective approach for architecting three-dimensional lithium-ion conductive networks within solid composite electrolyte.

Observation of rare-earth segregation in silicon nitride ceramics at subnanometre dimensions.

PubMed

Shibata, Naoya; Pennycook, Stephen J; Gosnell, Tim R; Painter, Gayle S; Shelton, William A; Becher, Paul F

2004-04-15

Silicon nitride (Si3N4) ceramics are used in numerous applications because of their superior mechanical properties. Their intrinsically brittle nature is a critical issue, but can be overcome by introducing whisker-like microstructural features. However, the formation of such anisotropic grains is very sensitive to the type of cations used as the sintering additives. Understanding the origin of dopant effects, central to the design of high-performance Si3N4 ceramics, has been sought for many years. Here we show direct images of dopant atoms (La) within the nanometre-scale intergranular amorphous films typically found at grain boundaries, using aberration corrected Z-contrast scanning transmission electron microscopy. It is clearly shown that the La atoms preferentially segregate to the amorphous/crystal interfaces. First-principles calculations confirm the strong preference of La for the crystalline surfaces, which is essential for forming elongated grains and a toughened microstructure. Whereas principles of micrometre-scale structural design are currently used to improve the mechanical properties of ceramics, this work represents a step towards the atomic-level structural engineering required for the next generation of ceramics.

Experimental Evaluation of Hot Films on Ceramic Substrates for Skin-Friction Measurement

NASA Technical Reports Server (NTRS)

Noffz, Gregory K.; Lavine, Adrienne S.; Hamory, Philip J.

2003-01-01

An investigation has been performed on the use of low-thermal conductivity, ceramic substrates for hot films intended to measure skin friction. Hot films were deposited on two types of ceramic substrates. Four hot films used composite-ceramic substrates with subsurface thermocouples (TCs), and two hot films were deposited on thin Macor(R) substrates. All six sensors were tested side by side in the wall of the NASA Glenn Research Center 8-ft by 6-ft Supersonic Wind Tunnel (SWT). Data were obtained from zero flow to Mach 1.98 in air. Control measurements were made with three Preston tubes and two boundary-layer rakes. The tests were repeated at two different hot film power levels. All hot films and subsurface TCs functioned throughout the three days of testing. At zero flow, the films on the high-thermal conductivity Macor(R) substrates required approximately twice the power as those on the composite-ceramic substrates. Skin-friction results were consistent with the control measurements. Estimates of the conduction heat losses were made using the embedded TCs but were hampered by variability in coating thicknesses and TC locations.

Rietveld refinement and dielectric properties of (Na{sub 0.5}Bi{sub 0.5}TiO{sub 3})-(Bi{sub 0.8}Ba{sub 0.2}FeO{sub 3}) ceramics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kaswan, Kavita, E-mail: kaswan.kavita@gmail.com; Agarwal, Ashish; Sanghi, Sujata

2015-06-24

(1-x)(Na{sub 0.5}Bi{sub 0.5}TiO{sub 3})-x(Bi{sub 0.8}Ba{sub 0.2}FeO{sub 3}) lead free ceramics (NBT, NBT-BBFO; x = 0.0, 0.1 respectively) have been synthesized by conventional solid state reaction method. Crystalline phase of sintered ceramics was investigated at room temperature using X-ray diffraction. Rietveld refinement of XRD data performed by FullProf revealed that both the samples exhibited rhombohedral structure with R3c space group. Dielectric properties of these ceramics were studied at different temperatures in a wide frequency range using impedance analyzer. Dielectric constant and dielectric loss were found to be increase with increase of BBFO content. The prepared ceramics exhibit a broad maximum inmore » dielectric permittivity at 593K and dispersive permittivity at high temperatures. The NBT-BBFO sample shows a relaxor ferroelectric behavior at different frequencies.« less

History of fast reactor fuel development

NASA Astrophysics Data System (ADS)

Kittel, J. H.; Frost, B. R. T.; Mustelier, J. P.; Bagley, K. Q.; Crittenden, G. C.; Van Dievoet, J.

1993-09-01

The first fast breeder reactors, constructed in the 1945-1960 time period, used metallic fuels composed of uranium, plutonium, or their alloys. They were chosen because most existing reactor operating experience had been obtained on metallic fuels and because they provided the highest breeding ratios. Difficulties in obtaining adequate dimensional stability in metallic fuel elements under conditions of high fuel burnup led in the 1960s to the virtual worldwide choice of ceramic fuels. Although ceramic fuels provide lower breeding performance, this objective is no longer an important consideration in most national programs. Mixed uranium and plutonium dioxide became the ceramic fuel that has received the widest use. The more advanced ceramic fuels, mixed uranium and plutonium carbides and nitrides, continue under development. More recently, metal fuel elements of improved design have joined ceramic fuels in achieving goal burnups of 15 to 20 percent. Low-swelling fuel cladding alloys have also been continuously developed to deal with the unexpected problem of void formation in stainless steels subjected to fast neutron irradiation, a phenomenon first observed in the 1960s.

SiAlON COATINGS OF SILICON NITRIDE AND SILICON CARBIDE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jan W. Nowok; John P. Hurley; John P. Kay

2000-06-01

The need for new engineering materials in aerospace applications and in stationary power turbine blades for high-efficiency energy-generating equipment has led to a rapid development of ceramic coatings. They can be tailored to have superior physical (high specific strength and stiffness, enhanced high-temperature performance) and chemical (high-temperature corrosion resistance in more aggressive fuel environments) properties than those of monolithic ceramic materials. Among the major chemical properties of SiAlON-Y ceramics are their good corrosion resistance against aggressive media combined with good thermal shock behavior. The good corrosion resistance results from the yttria-alumina-garnet (YAG), Al{sub 5}Y{sub 3}O{sub 12}, formed during the corrosionmore » process of SiAlON-Y ceramics in combustion gases at 1300 C. The interfacial chemical precipitation of the YAG phase is beneficial. This phase may crystallize in cubic and/or tetragonal modifications and if formed in SiAlON-Y ceramic may simultaneously generate residual stress. Also, this phase can contain a large number of point defects, which is a consequence of the large unit cell and complexity of the YAG structure because it has no close-packed oxygen planes. Therefore, the need exists to elucidate the corrosion mechanism of a multilayered barrier with respect to using SiAlON-YAG as a corrosion-protective coating. Stress corrosion cracking in the grain boundary of a silicon nitride (Si{sub 3}N{sub 4}) ceramic enriched in a glassy phase such as SiAlON can significantly affect its mechanical properties. It has been suggested that the increased resistance of the oxynitride glass to stress corrosion is related to the increased surface potential of the fracture surface created in the more durable and highly cross-linked oxynitride glass network structure. We expect that either increased or decreased surface potential of the intergranular glassy phase is brought about by changes in the residual stress of the SiAlON-Y ceramic and/or creation of a space-charge region at the SiAlON-YAG interface. Both features originate from a secondary phase of YAG formed during the SiAlON-Y glass corrosion process. Conventional oxidation-protection coatings for metallic materials in high-temperature corrosive environments are typically formed by applying a slurry mixture to the surface followed by a high-temperature furnace cure. During the cure, the coating reacts with the alloy to form a layer typically 25 to 50 {micro}m{sup 3} thick. Generally, coating thickness is one critical microstructural parameter that influences its performance; therefore, its optimization is an important aspect of coating technology. The aim of the present research program is (1) to produce a thin SiAlON-YAG ceramic coating with a high quality of interface, (2) to understand the major experimental characteristics for creating a good bonding between a substrate and a thin coating, and (3) to explain why the Al{sub 5}Y{sub 3}O{sub 12} phase increases SiAlON-Y ceramic alkali corrosion resistance. To produce the SiAlON-Y coating on silicon nitride ceramic with a YAG layer, a slurry mixture of SiAlON-Y components was designed. The research program was extended to Y{sub 2}SiO{sub 5} coating to get preliminary information on the Si{sub 3}N{sub 4}-Y{sub 2}SiO{sub 5} interface microstructure. It was expected that this phase would have a very low porosity. Generally, coatings that contain ductile phases such as Y{sub 2}SiO{sub 5} can produce low-porosity coatings.« less

Comparison of the bacterial removal performance of silver nanoparticles and a polymer based quaternary amine functiaonalized silsesquioxane coated point-of-use ceramic water filters.

PubMed

Zhang, Hongyin; Oyanedel-Craver, Vinka

2013-09-15

This study compares the disinfection performance of ceramic water filters impregnated with two antibacterial compounds: silver nanoparticles and a polymer based quaternary amine functiaonalized silsesquioxane (poly(trihydroxysilyl) propyldimethyloctadecyl ammonium chloride (TPA)). This study evaluated these compounds using ceramic disks manufactures with clay obtained from a ceramic filter factory located in San Mateo Ixtatan, Guatemala. Instead of using full size ceramic water filters, manufactured 6.5 cm diameter ceramic water filter disks were used. Results showed that TPA can achieve a log bacterial reduction value of 10 while silver nanoparticles reached up to 2 log reduction using a initial concentration of bacteria of 10(10)-10(11)CFU/ml. Similarly, bacterial transport demonstrated that ceramic filter disks painted with TPA achieved a bacterial log reduction value of 6.24, which is about 2 log higher than the values obtained for disks painted with silver nanoparticles (bacterial log reduction value: 4.42). The release of both disinfectants from the ceramic materials to the treated water was determined measuring the effluent concentrations in each test performed. Regarding TPA, about 3% of the total mass applied to the ceramic disks was released in the effluent over 300 min, which is slightly lower than the release percentage for silver nanoparticles (4%). This study showed that TPA provides a comparable disinfection performance than silver nanoparticles in ceramic water filter. Another advantage of using TPA is the cost as the price of TPA is considerable lower than silver nanoparticles. In spite of the use of TPA in several medical related products, there is only partial information regarding the health risk associated with the ingestion of this compound. Additional long-term toxicological information for TPA should be evaluated before its future application in ceramic water filters. Copyright © 2013 Elsevier B.V. All rights reserved.

High temperature composites. Status and future directions

NASA Technical Reports Server (NTRS)

Signorelli, R. A.

1982-01-01

A summary of research investigations of manufacturing methods, fabrication methods, and testing of high temperature composites for use in gas turbine engines is presented. Ceramic/ceramic, ceramic/metal, and metal/metal composites are considered. Directional solidification of superalloys and eutectic alloys, fiber reinforced metal and ceramic composites, ceramic fibers and whiskers, refractory coatings, metal fiber/metal composites, matrix metal selection, and the preparation of test specimens are discussed.

Sandblasting nozzle

NASA Technical Reports Server (NTRS)

Perkins, G. S.; Pawlik, E. V.; Phillips, W. M. (Inventor)

1981-01-01

A nozzle for use with abrasive and/or corrosive materials is formed of sintered ceramic compositions having high temperature oxidation resistance, high hardness and high abrasion and corrosion resistance. The ceramic may be a binary solid solution of a ceramic oxide and silicon nitride, and preferably a ternary solid solution of a ceramic oxide, silicon nitride and aluminum nitride. The ceramic oxide is selected from a group consisting of Al2O3, Y2O3 and Cr2O3, or mixtures of those compounds. Titanium carbide particles are dispersed in the ceramic mixture before sintering. The nozzles are encased for protection from external forces while in use by a metal or plastic casing.

Cements and adhesives for all-ceramic restorations.

PubMed

Manso, Adriana P; Silva, Nelson R F A; Bonfante, Estevam A; Pegoraro, Thiago A; Dias, Renata A; Carvalho, Ricardo M

2011-04-01

Dental cements are designed to retain restorations, prefabricated or cast posts and cores, and appliances in a stable, and long-lasting position in the oral environment. Resin-based cements were developed to overcome drawbacks of nonresinous materials, including low strength, high solubility, and opacity. Successful cementation of esthetic restorations depends on appropriate treatment to the tooth substrate and intaglio surface of the restoration, which in turn, depends on the ceramic characteristics. A reliable resin cementation procedure can only be achieved if the operator is aware of the mechanisms involved to perform the cementation and material properties. This article addresses current knowledge of resin cementation concepts, exploring the bonding mechanisms that influence long-term clinical success of all-ceramic systems. Copyright © 2011 Elsevier Inc. All rights reserved.

Unirradiated testing of the demonstration-scale ceramic waste form at ANL-West

DOE Office of Scientific and Technical Information (OSTI.GOV)

Goff, K.M.; Simpson, M.F.; Bateman, K.J.

1997-12-01

The ceramic waste form is being developed by Argonne National Laboratory (ANL) as part of the demonstration of the electrometallurgical treatment of spent nuclear fuel for disposal. The alkali, alkaline earth, halide, and rare earth fission products are stabilized in zeolite, which is combined with glass and processed in a hot isostatic press (HIP) to form a ceramic composite. The transuranics, including plutonium, are also stabilized in this high-level waste. Most of the laboratory-scale development work is performed in the Chemical Technology Division of ANL in Illinois. At ANL-West in Idaho, this technology is being demonstrated on an engineering scalemore » before implementation with irradiated materials in a remote environment.« less

Ballistic Performance of Porous Ceramic Thermal Protection Systems at 9 km/s

NASA Technical Reports Server (NTRS)

Miller, Joshua E.; Bohl, W. E.; Foreman, C. D.; Christiansen, Eric L.; Davis, B. A.

2009-01-01

Porous-ceramic, thermal-protection-systems are used heavily in current reentry vehicles like the Orbiter, and they are currently being proposed for the next generation of manned spacecraft, Orion. These materials insulate the structural components and sensitive electronic components of a spacecraft against the intense thermal environments of atmospheric reentry. Furthermore, these materials are also highly exposed to space environmental hazards like meteoroid and orbital debris impacts. This paper discusses recent impact testing up to 9 km/s on ceramic tiles similar to those used on the Orbiter. These tiles have a porous-batting of nominally 8 lb/cubic ft alumina-fiber-enhanced-thermal-barrier (AETB8) insulating material coated with a damage-resistant, toughened-unipiece-fibrous-insulation (TUFI) layer.

Laminated composite of magnetic alloy powder and ceramic powder and process for making same

DOEpatents

Moorhead, Arthur J.; Kim, Hyoun-Ee

1999-01-01

A laminated composite structure of alternating metal powder layers, and layers formed of an inorganic bonding media powder, and a method for manufacturing same are discosed. The method includes the steps of assembling in a cavity alternating layers of a metal powder and an inorganic bonding media of a ceramic, glass, and glass-ceramic. Heat, with or without pressure, is applied to the alternating layers until the particles of the metal powder are sintered together and bonded into the laminated composite structure by the layers of sintered inorganic bonding media to form a strong composite structure. The method finds particular application in the manufacture of high performance magnets wherein the metal powder is a magnetic alloy powder.

Laminated composite of magnetic alloy powder and ceramic powder and process for making same

DOEpatents

Moorhead, A.J.; Kim, H.

1999-08-10

A laminated composite structure of alternating metal powder layers, and layers formed of an inorganic bonding media powder, and a method for manufacturing same are disclosed. The method includes the steps of assembling in a cavity alternating layers of a metal powder and an inorganic bonding media of a ceramic, glass, and glass-ceramic. Heat, with or without pressure, is applied to the alternating layers until the particles of the metal powder are sintered together and bonded into the laminated composite structure by the layers of sintered inorganic bonding media to form a strong composite structure. The method finds particular application in the manufacture of high performance magnets wherein the metal powder is a magnetic alloy powder. 9 figs.

Applications in the Nuclear Industry for Thermal Spray Amorphous Metal and Ceramic Coatings

NASA Astrophysics Data System (ADS)

Blink, J.; Farmer, J.; Choi, J.; Saw, C.

2009-06-01

Amorphous metal and ceramic thermal spray coatings have been developed with excellent corrosion resistance and neutron absorption. These coatings, with further development, could be cost-effective options to enhance the corrosion resistance of drip shields and waste packages, and limit nuclear criticality in canisters for the transportation, aging, and disposal of spent nuclear fuel. Iron-based amorphous metal formulations with chromium, molybdenum, and tungsten have shown the corrosion resistance believed to be necessary for such applications. Rare earth additions enable very low critical cooling rates to be achieved. The boron content of these materials and their stability at high neutron doses enable them to serve as high efficiency neutron absorbers for criticality control. Ceramic coatings may provide even greater corrosion resistance for waste package and drip shield applications, although the boron-containing amorphous metals are still favored for criticality control applications. These amorphous metal and ceramic materials have been produced as gas-atomized powders and applied as near full density, nonporous coatings with the high-velocity oxy-fuel process. This article summarizes the performance of these coatings as corrosion-resistant barriers and as neutron absorbers. This article also presents a simple cost model to quantify the economic benefits possible with these new materials.

Dilatometric shrinkage study on magnesium titanate-based ceramic systems

NASA Astrophysics Data System (ADS)

Ermawati, F. U.; Suasmoro, S.

2018-03-01

The development of dielectric materials for applications in the microwave frequencies has been increasing with rapid progress in mobile and satellite communication systems. Magnesium titanate (MgTiO3)-based ceramics have been the favourite candidates for such applications due to their excellent dielectric characteristics, i.e. a moderate level of dielectric constant together with a high-quality factor and high-temperature stability. These outstanding performance, however, can only be achieved when the ceramics are highly dense. The work reported in this paper discussed the study on the dilatometric shrinkage behaviour of pure and zinc-doped magnesium titanate (Mg1–xZn x TiO3 for x = 0–0.5) ceramic systems after the systems following the heating passage up to 1300 °C. The results were discussed based on the phase formation data recorded from powder X-ray diffraction (XRD). An additional 2 wt. % V2O5 to the MZT0.2 system has increased the shrinkage of the system, and hence the relative density. The V2O5 addition also prevented the grain growth and did not alter the structure. From 100 Hz to 20 MHz, the dielectric permittivity is constant; which varies from (15.4 – 17.0) ± 0.1 % throughout the samples, these values are therefore frequency independent.

Evaluation of an innovative high temperature ceramic wafer seal for hypersonic engine applications. Ph.D. Thesis, 1991

NASA Technical Reports Server (NTRS)

Steinetz, Bruce M.

1992-01-01

A critical mechanical system in advanced hypersonic engines is the panel-edge seal system that seals gaps between the articulating engine panels and the adjacent engine splitter walls. Significant advancements in seal technology are required to meet the extreme demands placed on the seals, including the simultaneous requirements of low leakage, conformable, high temperature, high pressure, sliding operation. In this investigation, the design, development, analytical and experimental evaluation of a new ceramic wafer seal that shows promise of meeting these demands will be addressed. A high temperature seal test fixture was designed and fabricated to measure static seal leakage performance under engine simulated conditions. Ceramic wafer seal leakage rates are presented for engine-simulated air pressure differentials (up to 100 psi), and temperature (up to 1350 F), sealing both flat and distorted wall conditions, where distortions can be as large as 0.15 inches in only an 18 inch span. Seal leakage rates are low, meeting an industry-established tentative leakage limit for all combinations of temperature, pressure and wall conditions considered. A seal leakage model developed from externally-pressurized gas film bearing theory is also presented. Predicted leakage rates agree favorably with the measured data for nearly all conditions of temperature and pressure. Discrepancies noted at high engine pressure and temperature are attributed to thermally-induced, non-uniform changes in the size and shape of the leakage gap condition. The challenging thermal environment the seal must operate in places considerable demands on the seal concept and material selection. Of the many high temperature materials considered in the design, ceramics were the only materials that met the many challenging seal material design requirements. Of the aluminum oxide, silicon carbide, and silicon nitride ceramics considered in the material ranking scheme developed herein, the silicon nitride class of ceramics ranked the highest because of their high temperature strength; resistance to the intense heating rates; resistance to hydrogen damage; and good structural properties. Baseline seal feasibility has been established through the research conducted in this investigation. Recommendations for future work are also discussed.

Three-year clinical evaluation of two ceramic crown systems: a preliminary study.

PubMed

Etman, Maged K; Woolford, M J

2010-02-01

The clinical performance and failure mechanisms of recently introduced ceramic crown systems used to restore posterior teeth have not been adequately examined. The purpose of this prospective clinical study was to evaluate and compare the clinical performance of 2 new ceramic crown systems with that of metal ceramic crowns using modified United States Public Health Services (USPHS) criteria. Ninety posterior teeth requiring crown restorations in 48 patients were randomized into 3 equal groups (n=30) for which different crown systems were used: an experimental hot-pressed glass ceramic based on a modified lithium disilicate ceramic (IPS e.max Press), an alumina-coping-based ceramic (Procera AllCeram), and a metal ceramic (Simidur S 2 veneered with IPS Classic Porcelain). The crowns were assessed over 3 years using the modified USPHS criteria. Crowns that developed visible cracks were sectioned and removed, and the surfaces were analyzed using a scanning electron microscope (SEM). The data were analyzed using the Kruskal-Wallis nonparametric statistical test, followed by the Mann-Whitney test with Bonferroni correction (alpha=.05). USPHS evaluation showed that the IPS e.max Press and metal ceramic crowns experienced fewer clinical changes than Procera AllCeram. Visible roughness, wear, and deformity were noticed in occlusal contact areas of Procera AllCeram crowns. SEM images showed well defined wear facets in both ceramic crown systems. Kruskal-Wallis tests showed a significant difference (P<.05) in Alpha scores among the 3 crown systems. Mann-Whitney tests showed significant differences among groups. IPS e.max Press crowns demonstrated clinical behavior comparable to Procera AllCeram and metal ceramic crowns, but the wear resistance of this crown type was superior to the Procera AllCeram crowns, according to modified USPHS criteria.

High-throughput method to predict extrusion pressure of ceramic pastes.

PubMed

Cao, Kevin; Liu, Yang; Tucker, Christopher; Baumann, Michael; Grit, Grote; Lakso, Steven

2014-04-14

A new method was developed to measure the rheology of extrudable ceramic pastes using a Hamilton MicroLab Star liquid handler. The Hamilton instrument, normally used for high throughput liquid processing, was expanded to function as a low pressure capillary rheometer. Diluted ceramic pastes were forced through the modified pipettes, which produced pressure drop data that was converted to standard rheology data. A known ceramic paste containing cellulose ether was made and diluted to various concentrations in water. The most dilute paste samples were tested in the Hamilton instrument and the more typical, highly concentrated, ceramic paste were tested with a hydraulic ram extruder fitted with a capillary die and pressure measurement system. The rheology data from this study indicates that the dilute high throughput method using the Hamilton instrument correlates to, and can predict, the rheology of concentrated ceramic pastes normally used in ceramic extrusion production processes.

Light-weight ceramic insulation

NASA Technical Reports Server (NTRS)

Hsu, Ming-Ta S. (Inventor); Chen, Timothy S. (Inventor)

2002-01-01

Ultra-high temperature, light-weight, ceramic insulation such as ceramic tile is obtained by pyrolyzing a siloxane gel derived from the reaction of at least one organo dialkoxy silane and at least one tetralkoxy silane in an acid or base liquid medium. The reaction mixture of the tetra- and dialkoxy silanes may contain also an effective amount of a mono- or trialkoxy silane to obtain the siloxane gel. The siloxane gel is dried at ambient pressures to form a siloxane ceramic precursor without significant shrinkage. The siloxane ceramic precursor is subsequently pyrolyzed, in an inert atmosphere, to form the black ceramic insulation comprising atoms of silicon, carbon and oxygen. The ceramic insulation, can be characterized as a porous, uniform ceramic tile resistant to oxidation at temperatures ranging as high as 1700.degree. C. and is particularly useful as lightweight tiles for spacecraft and other high-temperature insulation applications.

Characterization, optical properties and laser ablation behavior of epoxy resin coatings reinforced with high reflectivity ceramic particles

NASA Astrophysics Data System (ADS)

Li, Wenzhi; Kong, Jing; Wu, Taotao; Gao, Lihong; Ma, Zhuang; Liu, Yanbo; Wang, Fuchi; Wei, Chenghua; Wang, Lijun

2018-04-01

Thermal damage induced by high power energy, especially high power laser, significantly affects the lifetime and performance of equipment. High-reflectance coating/film has attracted considerable attention due to its good performance in the damage protection. Preparing a high-reflectance coating with high reaction endothermal enthalpy will effectively consume a large amount of incident energy and in turn protect the substrate from thermal damage. In this study, a low temperature process was used to prepare coatings onto substrate with complex shape and avoid thermal effect during molding. An advanced high reflection ceramic powder, La1‑xSrxTiO3+δ , was added in the epoxy adhesive matrix to improve the reflectivity of coating. The optical properties and laser ablation behaviors of coatings with different ceramic additive ratio of La1‑xSrxTiO3+δ and modified epoxy-La1‑xSrxTiO3+δ with ammonium polyphosphate coatings were investigated, respectively. We found that the reflectivity of coatings is extremely high due to mixed high-reflection La1‑xSrxTiO3+δ particles, up to 96% at 1070 nm, which can significantly improve the laser resistance. In addition, the ammonium polyphosphate modifies the residual carbon structure of epoxy resin from discontinuous fine particles structure to continuous and porous structure, which greatly enhances the thermal-insulation property of coating. Furthermore, the laser ablation threshold is improved obviously, which is from 800 W cm‑2 to 1000 W cm‑2.

Robust Joining and Integration of Advanced Ceramics and Composites: Challenges, Opportunities, and Realities

NASA Technical Reports Server (NTRS)

Singh, Mrityunjay

2006-01-01

Advanced ceramics and fiber reinforced composites are under active consideration for use in a wide variety of high temperature applications within the aeronautics, space transportation, energy, and nuclear industries. The engineering designs of ceramic and composite components require fabrication and manufacturing of large and complex shaped parts of various thicknesses. In many instances, it is more economical to build up complex shapes by joining simple geometrical shapes. In addition, these components have to be joined or assembled with metallic sub-components. Thus, joining and attachment have been recognized as enabling technologies for successful utilization of ceramic components in various demanding applications. In this presentation, various challenges and opportunities in design, fabrication, and testing of high temperature joints in advanced ceramics and ceramic matrix composites will be presented. Silicon carbide based advanced ceramics and fiber reinforced composites in different shapes and sizes, have been joined using an affordable, robust ceramic joining technology. In addition, some examples of metal-ceramic brazing will also be presented. Microstructure and high temperature mechanical properties of joints in silicon carbide ceramics and composites will be reported. Various joint design philosophies and design issues in joining of ceramics and composites will be discussed.

High-Power Characteristics of Thickness Shear Mode for Textured SrBi2Nb2O9 Ceramics

NASA Astrophysics Data System (ADS)

Ogawa, Hirozumi; Kawada, Shinichiro; Kimura, Masahiko; Higuchi, Yukio; Takagi, Hiroshi

2009-09-01

The high-power piezoelectric characteristics of the thickness shear mode for <00l> oriented ceramics of bismuth layer structured ferroelectrics (BLSF), SrBi2Nb2O9 (SBN), were studied by the constant current driving method. These textured ceramics were fabricated by the templated grain growth (TGG) method, and the Lotgering factor was 95%. The vibration of the thickness shear mode in the textured SBN ceramics was stable at the vibration velocity of 2.0 m/s. The resonant frequency was almost constant with increasing vibration velocity in the textured SBN ceramics, however, it decreased with increasing vibration velocity in the randomly oriented SBN ceramics. In the case of Pb(Mn,Nb)O3-Pb(Zr,Ti)O3 ceramics, the vibration velocity of the thickness shear mode was saturated at more than 0.3 m/s, and the resonant frequency decreased at lower vibration velocity than in the case of SBN ceramics. The dissipation power density of the textured SBN ceramics was the lowest among those of the randomly oriented SBN and Pb(Mn,Nb)O3-PZT ceramics. The thickness shear mode of textured SBN ceramics is a good candidate for high-power piezoelectric applications.

A new method for achieving enhanced dielectric response over a wide temperature range

DOE PAGES

Maurya, Deepam; Sun, Fu -Chang; Pamir Alpay, S.; ...

2015-10-19

We report a novel approach for achieving high dielectric response over a wide temperature range. In this approach, multilayer ceramic heterostructures with constituent compositions having strategically tuned Curie points (TC) were designed and integrated with varying electrical connectivity. Interestingly, these multilayer structures exhibited different dielectric behavior in series and parallel configuration due to variations in electrical boundary conditions resulting in the differences in the strength of the electrostatic coupling. The results are explained using nonlinear thermodynamic model taking into account electrostatic interlayer interaction. We believe that present work will have huge significance in design of high performance ceramic capacitors.

A new method for achieving enhanced dielectric response over a wide temperature range

PubMed Central

Maurya, Deepam; Sun, Fu-Chang; Pamir Alpay, S.; Priya, Shashank

2015-01-01

We report a novel approach for achieving high dielectric response over a wide temperature range. In this approach, multilayer ceramic heterostructures with constituent compositions having strategically tuned Curie points (TC) were designed and integrated with varying electrical connectivity. Interestingly, these multilayer structures exhibited different dielectric behavior in series and parallel configuration due to variations in electrical boundary conditions resulting in the differences in the strength of the electrostatic coupling. The results are explained using nonlinear thermodynamic model taking into account electrostatic interlayer interaction. We believe that present work will have huge significance in design of high performance ceramic capacitors. PMID:26477391

Analytical design of an advanced radial turbine. [automobile engines

NASA Technical Reports Server (NTRS)

Large, G. D.; Finger, D. G.; Linder, C. G.

1981-01-01

The aerodynamic and mechanical potential of a single stage ceramic radial inflow turbine was evaluated for a high temperature single stage automotive engine. The aerodynamic analysis utilizes a turbine system optimization technique to evaluate both radial and nonradial rotor blading. Selected turbine rotor configurations were evaluated mechanically with three dimensional finite element techniques. Results indicate that exceptionally high rotor tip speeds (2300 ft/sec) and performance potential are feasible with radial bladed rotors if the projected ceramic material properties are realized. Nonradial rotors reduced tip speed requirements (at constant turbine efficiency) but resulted in a lower cumulative probability of success due to higher blade and disk stresses.

Characterization of fatigue behavior of 2-D woven fabric reinforced ceramic matrix composite at elevated temperature. Final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Groner, D.J.

This study investigated the fatigue behavior and associated damage mechanisms in notched and unnotched enhanced SiC/SiC ceramic matrix composite specimens at 1100 deg C. Stiffness degradation, strain variation, and hysteresis were evaluated to characterize material behavior. Microscopic examination was performed to characterize damage mechanisms. During high cycle/low stress fatigue tests, far less fiber/matrix interface debond was evident than in low cycle/high stress fatigue tests. Notched specimens exhibited minimal stress concentration during monotonic tensile testing and minimal notch sensitivity during fatigue testing. Damage mechanisms were also similar to unnotched.

Correlation of compressive stress with spalling of plasma sprayed ceramic materials

NASA Technical Reports Server (NTRS)

Mullen, R. L.; Mcdonald, G.; Hendricks, R. C.; Hofle, M. M.

1983-01-01

Ceramics on metal substrates for potential use as high temperature seals or other applications are exposed to forces originating from differences in thermal expansion between the ceramic and the metal substrate. This report develops a relationship between the difference in expansion of the ceramic and the substrate, defines conditions under which shear between the ceramic and the substrate occurs, and those under which bending forces are produced in the ceramic. The off-axis effect of compression forces resulting from high temperature plastic flow of the ceramic producing buckling of the ceramic is developed. Shear is associated with the edge or boundary stresses on the component while bending is associated with the distortion of an interior region. Both modes are significant in predicting life of the ceramic.

High-Power Piezoelectric Vibration Characteristics of Textured SrBi2Nb2O9 Ceramics

NASA Astrophysics Data System (ADS)

Kawada, Shinichiro; Ogawa, Hirozumi; Kimura, Masahiko; Shiratsuyu, Kosuke; Niimi, Hideaki

2006-09-01

The high-power piezoelectric vibration characteristics of textured SrBi2Nb2O9 (SBN) ceramics, that is bismuth-layer-structured ferroelectrics, were studied in the longitudinal mode (33-mode) by constant current driving method and compared with those of ordinary randomly oriented SBN and widely used Pb(Ti,Zr)O3 (PZT) ceramics. In the case of textured SBN ceramics, resonant properties are stable up to a vibration velocity of 2.6 m/s. Vibration velocity at resonant frequency increases proportionally with the applied electric field, and resonant frequency is almost constant in high-vibration-velocity driving. On the other hand, in the case of randomly oriented SBN and PZT ceramics, the increase in vibration velocity is not proportional to the applied high electric field, and resonant frequency decreases with increasing vibration velocity. The resonant sharpness Q of textured SBN ceramics is about 2000, even at a vibration velocity of 2.6 m/s. Therefore, textured SBN ceramics are good candidates for high-power piezoelectric applications.

Ceramic automotive Stirling engine program

NASA Technical Reports Server (NTRS)

1986-01-01

The Ceramic Automotive Stirling Engine Program evaluated the application of advanced ceramic materials to an automotive Stirling engine. The objective of the program was to evaluate the technical feasibility of utilizing advanced ceramics to increase peak engine operating temperature, and to evaluate the performance benefits of such an increase. Manufacturing cost estimates were also developed for various ceramic engine components and compared with conventional metallic engine component costs.

Microwave sintering of ceramic materials

NASA Astrophysics Data System (ADS)

Karayannis, V. G.

2016-11-01

In the present study, the potential of microwave irradiation as an innovative energy- efficient alternative to conventional heating technologies in ceramic manufacturing is reviewed, addressing the advantages/disadvantages, while also commenting on future applications of possible commercial interest. Ceramic materials have been extensively studied and used due to several advantages they exhibit. Sintering ceramics using microwave radiation, a novel technology widely employed in various fields, can be an efficient, economic and environmentally-friendlier approach, to improve the consolidation efficiency and reduce the processing cycle-time, in order to attain substantial energy and cost savings. Microwave sintering provides efficient internal heating, as energy is supplied directly and penetrates the material. Since energy transfer occurs at a molecular level, heat is generated throughout the material, thus avoiding significant temperature gradients between the surface and the interior, which are frequently encountered at high heating rates upon conventional sintering. Thus, rapid, volumetric and uniform heating of various raw materials and secondary resources for ceramic production is possible, with limited grain coarsening, leading to accelerated densification, and uniform and fine-grained microstructures, with enhanced mechanical performance. This is particularly important for manufacturing large-size ceramic products of quality, and also for specialty ceramic materials such as bioceramics and electroceramics. Critical parameters for the process optimization, including the electromagnetic field distribution, microwave-material interaction, heat transfer mechanisms and material transformations, should be taken into consideration.

Fabrication and properties of radially <001>C textured PMN-PT cylinders for transducer applications

NASA Astrophysics Data System (ADS)

Poterala, Stephen F.; Meyer, Richard J.; Messing, Gary L.

2012-07-01

<001>C Textured PMN-PT ceramics have electromechanical properties (d33 = 850-1050 pm/V, k33 = 0.79-0.83) between those of conventional PZT ceramics and relaxor PMN-PT crystals. In this work, we tailor crystallographic orientation in textured PMN-PT ceramics for transducer designs with non-planar poling surfaces. Specifically, omni-directional cylindrical transducer elements were fabricated using monolithic, radially <001>C textured and poled PMN-PT ceramic. Texture was produced by templated grain growth using NBT-PT templates, which were oriented radially by wrapping green ceramic tapes around a cylindrical mandrel. Finished transducer elements measure ˜5 cm in diameter by ˜2.5 cm in height and demonstrate scalability of textured ceramic fabrication techniques. The fabricated cylinders are ˜50 vol. % textured and show high 31-mode electromechanical properties compared to PZT ceramics (d31 = -259 pm/V, k31 = 0.43, ɛT33 = 3000, and Qm = 350). Frequency bandwidth is related to the square of the hoop mode coupling coefficient kh2, which is ˜60% higher in textured PMN-PT cylinders compared to PZT 5H. Finite element simulations show that this parameter may be further increased by improving texture quality to ≥90 vol. %. Radially textured PMN-PT may thus improve performance in omni-directional cylindrical transducers while avoiding the need for segmented single crystal designs.

Influence of hot isostatic pressing on ZrO2-CaO dental ceramics properties.

PubMed

Gionea, Alin; Andronescu, Ecaterina; Voicu, Georgeta; Bleotu, Coralia; Surdu, Vasile-Adrian

2016-08-30

Different hot isostatic pressing conditions were used to obtain zirconia ceramics, in order to assess the influence of HIP on phase transformation, compressive strength, Young's modulus and density. First, CaO stabilized zirconia powder was synthesized through sol-gel method, using zirconium propoxide, calcium isopropoxide and 2-metoxiethanol as precursors, then HIP treatment was applied to obtain final dense ceramics. Ceramics were morphologically and structurally characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Density measurements, compressive strength and Young's modulus tests were also performed in order to evaluate the effect of HIP treatment. The zirconia powders heat treated at 500°C for 2h showed a pure cubic phase with average particle dimension about 70nm. The samples that were hot isostatic pressed presented a mixture of monoclinic-tetragonal or monoclinic-cubic phases, while for pre-sintered samples, cubic zirconia was the single crystalline form. Final dense ceramics were obtained after HIP treatment, with relative density values higher than 94%. ZrO2-CaO ceramics presented high compressive strength, with values in the range of 500-708.9MPa and elastic behavior with Young's modulus between 1739MPa and 4372MPa. Finally zirconia ceramics were tested for biocompatibility allowing the normal development of MG63 cells in vitro. Copyright © 2015 Elsevier B.V. All rights reserved.

Significantly enhanced piezoelectricity in low-temperature sintered Aurivillius-type ceramics with ultrahigh Curie temperature of 800 °C

NASA Astrophysics Data System (ADS)

Cai, Kai; Huang, Chengcheng; Guo, Dong

2017-04-01

We report an Aurivillius-type piezoelectric ceramic (Ca1-2x (LiCe) x Bi4Ti3.99Zn0.01O15) that has an ultrahigh Curie temperature (T c) around 800 °C and a significantly enhanced piezoelectric coefficient (d 33), comparable to that of textured ceramics fabricated using the complicated templating method. Surprisingly, the highest d 33 of 26 pC/N was achieved at an unexpectedly low sintering temperature (T s) of only 920 °C (~200 °C lower than usual) despite the non-ideal density. Study of different synthesized samples indicates that a relatively low T s is crucial for suppressing Bi evaporation and abnormal grain growth, which are indispensable for high resistivity and effective poling due to decreased carrier density and restricted anisotropic conduction. Because the layered structure is sensitive to lattice defects, controlled Bi loss is considered to be crucial for maintaining structural order and spontaneous polarization. This low-T s system is very promising for practical applications due to its high piezoelectricity, low cost and high reproducibility. Contrary to our usual understanding, the results reveal that a delicate balance of density, Bi loss and grain morphology achieved by adjusting the sintering temperature is crucial for the enhancing performance in Aurivillius-type high-T c ceramics.

Thermal Cyclic Behavior of Thermal and Environmental Barrier Coatings Investigated Under High-Heat-Flux Conditions

NASA Technical Reports Server (NTRS)

Zhu, Dongming; Lee, Kang N.; Miller, Robert A.

2002-01-01

Environmental barrier coatings (EBC's) have been developed to protect silicon-carbide- (SiC) based ceramic components in gas turbine engines from high-temperature environmental attack. With continuously increasing demands for significantly higher engine operating temperature, future EBC systems must be designed for both thermal and environmental protection of the engine components in combustion gases. In particular, the thermal barrier functions of EBC's become a necessity for reducing the engine-component thermal loads and chemical reaction rates, thus maintaining the required mechanical properties and durability of these components. Advances in the development of thermal and environmental barrier coatings (TBC's and EBC's, respectively) will directly impact the successful use of ceramic components in advanced engines. To develop high-performance coating systems, researchers must establish advanced test approaches. In this study, a laser high-heat-flux technique was employed to investigate the thermal cyclic behavior of TBC's and EBC's on SiC-reinforced SiC ceramic matrix composite substrates (SiC/SiC) under high thermal gradient and thermal cycling conditions. Because the laser heat flux test approach can monitor the coating's real-time thermal conductivity variations at high temperature, the coating thermal insulation performance, sintering, and delamination can all be obtained during thermal cycling tests. Plasma-sprayed yttria-stabilized zirconia (ZrO2-8 wt% Y2O3) thermal barrier and barium strontium aluminosilicate-based environmental barrier coatings (BSAS/BSAS+mullite/Si) on SiC/SiC ceramic matrix composites were investigated in this study. These coatings were laser tested in air under thermal gradients (the surface and interface temperatures were approximately 1482 and 1300 C, respectively). Some coating specimens were also subject to alternating furnace cycling (in a 90-percent water vapor environment at 1300 C) and laser thermal gradient cycling tests (in air), to investigate the water vapor effect. All cyclic tests were conducted using a 60-min hot-time temperature.

Properties and Clinical Application of Three Types of Dental Glass-Ceramics and Ceramics for CAD-CAM Technologies

PubMed Central

Ritzberger, Christian; Apel, Elke; Höland, Wolfram; Peschke, Arnd; Rheinberger, Volker M.

2010-01-01

The main properties (mechanical, thermal and chemical) and clinical application for dental restoration are demonstrated for three types of glass-ceramics and sintered polycrystalline ceramic produced by Ivoclar Vivadent AG. Two types of glass-ceramics are derived from the leucite-type and the lithium disilicate-type. The third type of dental materials represents a ZrO2 ceramic. CAD/CAM technology is a procedure to manufacture dental ceramic restoration. Leucite-type glass-ceramics demonstrate high translucency, preferable optical/mechanical properties and an application as dental inlays, onlays and crowns. Based on an improvement of the mechanical parameters, specially the strength and toughness, the lithium disilicate glass-ceramics are used as crowns; applying a procedure to machine an intermediate product and producing the final glass-ceramic by an additional heat treatment. Small dental bridges of lithium disilicate glass-ceramic were fabricated using a molding technology. ZrO2 ceramics show high toughness and strength and were veneered with fluoroapatite glass-ceramic. Machining is possible with a porous intermediate product.

Corrosion of Ceramic Materials

NASA Technical Reports Server (NTRS)

Opila, Elizabeth J.; Jacobson, Nathan S.

1999-01-01

Non-oxide ceramics are promising materials for a range of high temperature applications. Selected current and future applications are listed. In all such applications, the ceramics are exposed to high temperature gases. Therefore it is critical to understand the response of these materials to their environment. The variables to be considered here include both the type of ceramic and the environment to which it is exposed. Non-oxide ceramics include borides, nitrides, and carbides. Most high temperature corrosion environments contain oxygen and hence the emphasis of this chapter will be on oxidation processes.

Properties of Miniature Cantilever-Type Ultrasonic Motor Using Lead-Free Array-Type Multilayer Piezoelectric Ceramics of (Sr,Ca)2NaNb5O15 under High Input Power

NASA Astrophysics Data System (ADS)

Doshida, Yutaka; Shimizu, Hiroyuki; Mizuno, Youich; Tamura, Hideki

2012-07-01

The properties of miniature cantilever-type ultrasonic motors using lead-free array-type multilayer piezoelectric ceramics of (Sr,Ca)2NaNb5O15 (SCNN) developed using the design rule were investigated under high input power by comparison with the high-power properties of SCNN ceramics. The frequency dependence of the revolution speed reflected the nonlinear behavior of SCNN ceramics with the hard-spring effect and showed a mirror-reversed image relative to that of the motor of Pb(Zr,Ti)O3 (PZT) ceramics. The output power increased linearly with increasing input power up to 110 mW without heat generation, and the driving properties were almost the same as the expectations under low input power. The output power density characteristics of the motors were high in comparison with those of the commercialized motors of PZT ceramics. It appeared that the motors have a high potential as an environmental friendly piezoelectric device with excellent properties, reflecting the high-power properties of SCNN ceramics.

Lead-free BNT-based composite materials: enhanced depolarization temperature and electromechanical behavior.

PubMed

Bai, Wangfeng; Zheng, Peng; Wen, Fei; Zhang, Jingji; Chen, Daqin; Zhai, Jiwei; Ji, Zhenguo

2017-11-14

The development of (Bi 0.5 Na 0.5 )TiO 3 -based solid solutions with both high depolarization temperature T d and excellent piezoelectric and electromechanical properties for practical application is intractable because improved thermal stability is usually accompanied by a deterioration in piezoelectric and electromechanical performance. Herein, we report a 0-3 type 0.93(Bi 0.5 Na 0.5 )TiO 3 -0.07BaTiO 3  : 30 mol%ZnO composite (BNT-7BT : 0.3ZnO), in which the ZnO nanoparticles exist in two forms, to resolve the abovementioned long-standing obstacle. In this composite, Zn ions fill the boundaries of BNT-7BT grains, and residual Zn ions diffuse into the BNT-7BT lattice, as confirmed by XRD, Raman spectroscopy, and microstructure analysis. The BNT-7BT composite ceramics with a 0-3 type connectivity exhibited enhanced frequency-dependent electromechanical properties, fatigue characteristics, and thermal stabilities. More importantly, low poling field-driven large piezoelectric properties were observed for the composite ceramics as compared to the case of the pure BNT-7BT solid solution. A mechanism related to the ZnO-driven phase transition from the rhombohedral to tetragonal phase and built-in electric field to partially compensate the depolarization field was proposed to explain the achieved outstanding piezoelectric performance. This is the first time that the thermal stability, electromechanical behavior, and low poling field-driven high piezoelectric performance of BNT-based ceramics have been simultaneously optimized. Thus, our study provides a referential methodology to achieve novel piezoceramics with excellent piezoelectricity by composite engineering and opens up a new development window for the utilization of conventional BNT-based and other lead-free ceramics in practical applications.

Application of exopolysaccharides to improve the performance of ceramic bodies in the unidirectional dry pressing process

NASA Astrophysics Data System (ADS)

Caneira, Inês; Machado-Moreira, Bernardino; Dionísio, Amélia; Godinho, Vasco; Neves, Orquídia; Dias, Diamantino; Saiz-Jimenez, Cesareo; Miller, Ana Z.

2015-04-01

Ceramic industry represents an important sector of economic activity in the European countries and involves complex and numerous manufacturing processes. The unidirectional dry pressing process includes milling and stirring of raw materials (mainly clay and talc minerals) in aqueous suspensions, followed by spray drying to remove excess water obtaining spray-dried powders further subjected to dry pressing process (conformation). However, spray-dried ceramic powders exhibit an important variability in their performance when subjected to the dry pressing process, particularly in the adhesion to the mold and mechanical strength, affecting the quality of the final conformed ceramic products. Therefore, several synthetic additives (deflocculants, antifoams, binders, lubricants and plasticizers) are introduced in the ceramic slips to achieve uniform and homogeneous pastes, conditioning their rheological properties. However, an important variability associated with the performance of the conformed products is still reported. Exopolysaccharides or Extracellular Polymeric Substances (EPS) are polymers excreted by living organisms, such as bacteria, fungi and algae, which may confer unique and potentially interesting properties with potential industrial uses, such as viscosity control, gelation, and flocculation. Polysaccharides, such as pullulan, gellan, carrageenan and xanthan have found a wide range of applications in food, pharmaceutical, petroleum, and in other industries. The aim of this study was the assessment of exopolysaccharides as natural additives to optimize the performance of spray-dried ceramic powders during the unidirectional dry pressing process, replacing the synthetic additives used in the ceramic production process. Six exopolysaccharides, namely pullulan, gellan, xanthan gum, κappa- and iota-carrageenan, and guar gum were tested in steatite-based spray-dried ceramic powders at different concentrations. Subsequently, these ceramic powders were submitted to unidirectional dry pressing process (conformation) and the green conformed bodies were tested on the following properties: mechanical flexural strength and adhesion/disaggregation of the conformed material. The binding state of polysaccharides and mineral grains was evaluated by field emission scanning electron microscopy (FESEM). Our data showed that xanthan gum and pullulan were the most effective polysaccharides in improving the performance of spray-dried ceramic powders during unidirectional dry pressing process, in comparison to the control steatite-based ceramic bodies containing synthetic additives. In addition, these polysaccharides yielded the best cost-benefit relationship, representing an eco-friendly and cost-effective alternative to synthetic additives used in technical ceramics industry. Hence, this study has contributed to define a new and sustainable strategy to improve the performance of ceramic materials during unidirectional dry pressing process, reduce production costs and minimize environmental impact. Acknowledgments: This study was financed by Portuguese funds through FCT- Fundação para a Ciência e a Tecnologia (project EXPL/CTM-CER/0637/2012) and supported by Rauschert Portuguesa, SA.

Dynamic, High-Temperature, Flexible Seal

NASA Technical Reports Server (NTRS)

Steinetz, Bruce M.; Sirocky, Paul J.

1989-01-01

New seal consists of multiple plies of braided ceramic sleeves filled with small ceramic balls. Innermost braided sleeve supported by high-temperature-wire-mesh sleeve that provides both springback and preload capabilities. Ceramic balls reduce effect of relatively high porosity of braided ceramic sleeves by acting as labyrinth flow path for gases and thereby greatly increasing pressure gradient seal can sustain. Dynamic, high-temperature, flexible seal employed in hypersonic engines, two-dimensional convergent/divergent and vectorized-thrust exhaust nozzles, reentry vehicle airframes, rocket-motor casings, high-temperature furnaces, and any application requiring non-asbestos high-temperature gaskets.

Corrosion Issues for Ceramics in Gas Turbines

NASA Technical Reports Server (NTRS)

Jacobson, Nathan S.; Fox, Dennis S.; Smialek, James L.; Opila, Elizabeth J.; Tortorelli, Peter F.; More, Karren L.; Nickel, Klaus G.; Hirata, Takehiko; Yoshida, Makoto; Yuri, Isao

2000-01-01

The requirements for hot-gas-path materials in gas turbine engines are demanding. These materials must maintain high strength and creep resistance in a particularly aggressive environment. A typical gas turbine environment involves high temperatures, rapid gas flow rates, high pressures, and a complex mixture of aggressive gases. Figure 26.1 illustrates the requirements for components of an aircraft engine and critical issues [1]. Currently, heat engines are constructed of metal alloys, which meet these requirements within strict temperature limits. In order to extend these temperature limits, ceramic materials have been considered as potential engine materials, due to their high melting points and stability at high temperatures. These materials include oxides, carbides, borides, and nitrides. Interest in using these materials in engines appears to have begun in the 1940s with BeO-based porcelains [2]. During the 1950s, the efforts shifted to cermets. These were carbide-based materials intended to exploit the best properties of metals and ceramics. During the 1960s and 1970s, the silicon-based ceramics silicon carbide (SiC) and silicon nitride (Si3N4) were extensively developed. Although the desirable high-temperature properties of SiC and Si3N4 had long been known, consolidation of powders into component-sized bodies required the development of a series of specialized processing routes [3]. For SiC, the major consolidation routes are reaction bonding, hot-pressing, and sintering. The use of boron and carbon as additives which enable sintering was a particularly noteworthy advance [4]. For Si3N4 the major consolidation routes are reaction bonding and hot pressing [5]. Reaction-bonding involves nitridation of silicon powder. Hot pressing involves addition of various refractory oxides, such as magnesia (MgO), alumina (Al2O3), and yttria (y2O3). Variations on these processes include a number of routes including Hot Isostatic Pressing (HIP), gas-pressure sintering, sinter-HIPing, and Encapsulation-HIPing. It is important to note that each process involves the addition of secondary elements, which later were shown to dramatically influence oxidation and corrosion behavior. As dense bodies of silicon-based ceramics became more readily available, their desirable high temperature properties were confirmed. These materials retained strength to very high temperatures (i.e. 1300-1400 C). Further, they were lightweight and made from abundant materials. SiC and Si3N4 therefore emerged as leading ceramic candidates for components in heat engines, designed to operate at higher temperatures for better performance and fuel efficiency. The first US programs for ceramics in heat engines have been reviewed [6]. Selected programs on ceramic engine parts are summarized here in regard to their contributions to understanding the corrosion behavior of a heat engine environment.

A Low Temperature Co-fired Ceramics Manufactured Power Inductor Based on A Ternary Hybrid Material System

NASA Astrophysics Data System (ADS)

Xie, Yunsong; Chen, Ru

Low temperature co-fired ceramics (LTCC) is one of the most important techniques to produce circuits with high working frequency, multi-functionality and high integration. We have developed a methodology to enable a ternary hybrid material system being implemented into the LTCC manufacturing process. The co-firing sintering process can be divided into a densification and cooling process. In this method, a successful ternary hybrid material densification process is achieved by tuning the sintering profile of each material to match each other. The system integrity is maintained in the cooling process is obtained by develop a strong bonding at the interfaces of each materials. As a demonstration, we have construct a power inductor device made of the ternary material system including Ag, NiCuZn ferrite and non-magnetic ceramic. The power inductors well maintains its physical integrity after sintering. The microscopic images show no obvious sign of cracks or structural deformation. More importantly, despite the bonding between the ferrite and ceramic is enhanced by non-magnetic element diffusion, the undesired magnetic elements diffusion is effectively suppressed. The electric performance shows that the power handling capability is comparable to the current state of art device.

Experimental and Numerical Study of Ceramic Foam Filtration

NASA Astrophysics Data System (ADS)

Laé, E.; Duval, H.; Rivière, C.; Le Brun, P.; Guillot, J.-B.

Ceramic foam filtration is widely used to enable removal of non metallic inclusions from liquid aluminium. Its performances have been largely studied in the literature and some discrepancies remain amongst the published results. Consequently, a research program was deployed to evaluate the performances of a range of ceramic foam filters used under various conditions and to understand the inclusions capture mechanisms.

Dependences of microstructure on electromagnetic interference shielding properties of nano-layered Ti3AlC2 ceramics.

PubMed

Tan, Yongqiang; Luo, Heng; Zhou, Xiaosong; Peng, Shuming; Zhang, Haibin

2018-05-21

The microstructure dependent electromagnetic interference (EMI) shielding properties of nano-layered Ti 3 AlC 2 ceramics were presented in this study by comparing the shielding properties of various Ti 3 AlC 2 ceramics with distinct microstructures. Results indicate that Ti 3 AlC 2 ceramics with dense microstructure and coarse grains are more favourable for superior EMI shielding efficiency. High EMI shielding effectiveness over 40 dB at the whole Ku-band frequency range was achieved in Ti 3 AlC 2 ceramics by microstructure optimization, and the high shielding effectiveness were well maintained up to 600 °C. A further investigation reveals that only the absorption loss displays variations upon modifying microstructure by allowing more extensive multiple reflections in coarse layered grains. Moreover, the absorption loss of Ti 3 AlC 2 was found to be much higher than those of highly conductive TiC ceramics without layered structure. These results demonstrate that nano-layered MAX phase ceramics are promising candidates of high-temperature structural EMI shielding materials and provide insightful suggestions for achieving high EMI shielding efficiency in other ceramic-based shielding materials.

Design Protocols and Analytical Strategies that Incorporate Structural Reliability Models

NASA Technical Reports Server (NTRS)

Duffy, Stephen F.

1997-01-01

Ceramic matrix composites (CMC) and intermetallic materials (e.g., single crystal nickel aluminide) are high performance materials that exhibit attractive mechanical, thermal and chemical properties. These materials are critically important in advancing certain performance aspects of gas turbine engines. From an aerospace engineer's perspective the new generation of ceramic composites and intermetallics offers a significant potential for raising the thrust/weight ratio and reducing NO(x) emissions of gas turbine engines. These aspects have increased interest in utilizing these materials in the hot sections of turbine engines. However, as these materials evolve and their performance characteristics improve a persistent need exists for state-of-the-art analytical methods that predict the response of components fabricated from CMC and intermetallic material systems. This need provided the motivation for the technology developed under this research effort. Continuous ceramic fiber composites exhibit an increase in work of fracture, which allows for "graceful" rather than catastrophic failure. When loaded in the fiber direction, these composites retain substantial strength capacity beyond the initiation of transverse matrix cracking despite the fact that neither of its constituents would exhibit such behavior if tested alone. As additional load is applied beyond first matrix cracking, the matrix tends to break in a series of cracks bridged by the ceramic fibers. Any additional load is born increasingly by the fibers until the ultimate strength of the composite is reached. Thus modeling efforts supported under this research effort have focused on predicting this sort of behavior. For single crystal intermetallics the issues that motivated the technology development involved questions relating to material behavior and component design. Thus the research effort supported by this grant had to determine the statistical nature and source of fracture in a high strength, NiAl single crystal turbine blade material; map a simplistic failure strength envelope of the material; develop a statistically based reliability computer algorithm, verify the reliability model and computer algorithm, and model stator vanes for rig tests. Thus establishing design protocols that enable the engineer to analyze and predict the mechanical behavior of ceramic composites and intermetallics would mitigate the prototype (trial and error) approach currently used by the engineering community. The primary objective of the research effort supported by this short term grant is the continued creation of enabling technologies for the macroanalysis of components fabricated from ceramic composites and intermetallic material systems. The creation of enabling technologies aids in shortening the product development cycle of components fabricated from the new high technology materials.

Design Protocols and Analytical Strategies that Incorporate Structural Reliability Models

NASA Technical Reports Server (NTRS)

Duffy, Stephen F.

1997-01-01

Ceramic matrix composites (CMC) and intermetallic materials (e.g., single crystal nickel aluminide) are high performance materials that exhibit attractive mechanical, thermal, and chemical properties. These materials are critically important in advancing certain performance aspects of gas turbine engines. From an aerospace engineers perspective the new generation of ceramic composites and intermetallics offers a significant potential for raising the thrust/weight ratio and reducing NO(sub x) emissions of gas turbine engines. These aspects have increased interest in utilizing these materials in the hot sections of turbine engines. However, as these materials evolve and their performance characteristics improve a persistent need exists for state-of-the-art analytical methods that predict the response of components fabricated from CMC and intermetallic material systems. This need provided the motivation for the technology developed under this research effort. Continuous ceramic fiber composites exhibit an increase in work of fracture, which allows for 'graceful' rather than catastrophic failure. When loaded in the fiber direction these composites retain substantial strength capacity beyond the initiation of transverse matrix cracking despite the fact that neither of its constituents would exhibit such behavior if tested alone. As additional load is applied beyond first matrix cracking, the matrix tends to break in a series of cracks bridged by the ceramic fibers. Any additional load is born increasingly by the fibers until the ultimate strength of the composite is reached. Thus modeling efforts supported under this research effort have focused on predicting this sort of behavior. For single crystal intermetallics the issues that motivated the technology development involved questions relating to material behavior and component design. Thus the research effort supported by this grant had to determine the statistical nature and source of fracture in a high strength, NiAl single crystal turbine blade material; map a simplistic future strength envelope of the material; develop a statistically based reliability computer algorithm; verify the reliability model and computer algorithm-, and model stator vanes for rig tests. Thus establishing design protocols that enable the engineer to analyze and predict the mechanical behavior of ceramic composites and intermetallics would mitigate the prototype (trial and error) approach currently used by the engineering community. The primary objective of the research effort supported by this short term grant is the continued creation of enabling technologies for the macro-analysis of components fabricated from ceramic composites and intermetallic material systems. The creation of enabling technologies aids in shortening the product development cycle of components fabricated from the new high technology materials.

Advanced Turbine Technology Applications Project (ATTAP) 1993 annual report

NASA Technical Reports Server (NTRS)

1994-01-01

This report summarizes work performed by AlliedSignal Engines, a unit of AlliedSignal Aerospace Company, during calendar year 1993, toward development and demonstration of structural ceramic technology for automotive gas turbine engines. This work was performed for the U.S. Department of Energy (DOE) under National Aeronautics and Space Administration (NASA) Contract DEN3-335, Advanced Turbine Technology Applications Project (ATFAP). During 1993, the test bed used to demonstrate ceramic technology was changed from the AlliedSignal Engines/Garrett Model AGT101 regenerated gas turbine engine to the Model 331-200(CT) engine. The 331-200(CT) ceramic demonstrator is a fully-developed test platform based on the existing production AlliedSignal 331-200(ER) gas turbine auxiliary power unit (APU), and is well suited to evaluating ceramic turbine blades and nozzles. In addition, commonality of the 331-200(CT) engine with existing gas turbine APU's in commercial service provides the potential for field testing of ceramic components. The 1993 ATTAP activities emphasized design modifications of the 331-200 engine test bed to accommodate ceramic first-stage turbine nozzles and blades, fabrication of the ceramic components, ceramic component proof and rig tests, operational tests of the test bed equipped with the ceramic components, and refinement of critical ceramic design technologies.

High pressure ceramic joint

DOEpatents

Ward, M.E.; Harkins, B.D.

1993-11-30

Many recuperators have components which react to corrosive gases and are used in applications where the donor fluid includes highly corrosive gases. These recuperators have suffered reduced life, increased service or maintenance, and resulted in increased cost. The present joint when used with recuperators increases the use of ceramic components which do not react to highly corrosive gases. Thus, the present joint used with the present recuperator increases the life, reduces the service and maintenance, and reduces the increased cost associated with corrosive action of components used to manufacture recuperators. The present joint is comprised of a first ceramic member, a second ceramic member, a mechanical locking device having a groove defined in one of the first ceramic member and the second ceramic member. The joint and the mechanical locking device is further comprised of a refractory material disposed in the groove and contacting the first ceramic member and the second ceramic member. The present joint mechanically provides a high strength load bearing joint having good thermal cycling characteristics, good resistance to a corrosive environment and good steady state strength at elevated temperatures. 4 figures.

High pressure ceramic joint

DOEpatents

Ward, Michael E.; Harkins, Bruce D.

1993-01-01

Many recuperators have components which react to corrosive gases and are used in applications where the donor fluid includes highly corrosive gases. These recuperators have suffered reduced life, increased service or maintenance, and resulted in increased cost. The present joint when used with recuperators increases the use of ceramic components which do not react to highly corrosive gases. Thus, the present joint used with the present recuperator increases the life, reduces the service and maintenance, and reduces the increased cost associated with corrosive action of components used to manufacture recuperators. The present joint is comprised of a first ceramic member, a second ceramic member, a mechanical locking device having a groove defined in one of the first ceramic member and the second ceramic member. The joint and the mechanical locking device is further comprised of a refractory material disposed in the groove and contacting the first ceramic member and the second ceramic member. The present joint mechanically provides a high strength load bearing joint having good thermal cycling characteristics, good resistance to a corrosive environment and good steady state strength at elevated temperatures.

Correlation of compressive and shear stress with spalling of plasma-sprayed ceramic materials

NASA Technical Reports Server (NTRS)

Mullen, R. L.; Mcdonald, G.; Hendricks, R. C.; Hofle, M. M.

1983-01-01

Ceramics on metal substrates for potential use as high temperature seals or other applications are exposed to forces originating from differences in thermal expansion between the ceramic and the metal substrate. This report develops a relationship between the difference in expansion of the ceramic and the substrate, defines conditions under which shear between the ceramic and the substrate occurs, and those under which bending forces are produced in the ceramic. The off-axis effect of compression forces resulting from high temperature plastic flow of the ceramic producing buckling of the ceramic is developed. Shear is associated with the edge or boundary stresses on the component while bending is associated with the distortion of an interior region. Both modes are significant in predicting life of the ceramic. Previously announced in STAR as N83-27016

Advances in Ceramic Matrix Composite Blade Damping Characteristics for Aerospace Turbomachinery Applications

NASA Technical Reports Server (NTRS)

Min, James B.; Harris, Donald L.; Ting, J. M.

2011-01-01

For advanced aerospace propulsion systems, development of ceramic matrix composite integrally-bladed turbine disk technology is attractive for a number of reasons. The high strength-to-weight ratio of ceramic composites helps to reduce engine weight and the one-piece construction of a blisk will result in fewer parts count, which should translate into reduced operational costs. One shortcoming with blisk construction, however, is that blisks may be prone to high cycle fatigue due to their structural response to high vibration environments. Use of ceramic composites is expected to provide some internal damping to reduce the vibratory stresses encountered due to unsteady flow loads through the bladed turbine regions. A goal of our research was to characterize the vibration viscous damping behavior of C/SiC composites. The vibration damping properties were measured and calculated. Damping appeared to decrease with an increase in the natural frequency. While the critical damping amount of approximately 2% is required for typical aerospace turbomachinery engines, the C/SiC damping at high frequencies was less than 0.2% from our study. The advanced high-performance aerospace propulsion systems almost certainly will require even more damping than what current vehicles require. A purpose of this paper is to review some work on C/SiC vibration damping by the authors for the NASA CMC turbine blisk development program and address an importance of the further investigation of the blade vibration damping characteristics on candidate CMC materials for the NASA s advanced aerospace turbomachinery engine systems.

Development of a double-layered ceramic filter for aerosol filtration at high-temperatures: the filter collection efficiency.

PubMed

de Freitas, Normanda L; Gonçalves, José A S; Innocentini, Murilo D M; Coury, José R

2006-08-25

The performance of double-layered ceramic filters for aerosol filtration at high temperatures was evaluated in this work. The filtering structure was composed of two layers: a thin granular membrane deposited on a reticulate ceramic support of high porosity. The goal was to minimize the high pressure drop inherent of granular structures, without decreasing their high collection efficiency for small particles. The reticulate support was developed using the technique of ceramic replication of polyurethane foam substrates of 45 and 75 pores per inch (ppi). The filtering membrane was prepared by depositing a thin layer of granular alumina-clay paste on one face of the support. Filters had their permeability and fractional collection efficiency analyzed for filtration of an airborne suspension of phosphatic rock in temperatures ranging from ambient to 700 degrees C. Results revealed that collection efficiency decreased with gas temperature and was enhanced with filtration time. Also, the support layer influenced the collection efficiency: the 75 ppi support was more effective than the 45 ppi. Particle collection efficiency dropped considerably for particles below 2 microm in diameter. The maximum collection occurred for particle diameters of approximately 3 microm, and decreased again for diameters between 4 and 8 microm. Such trend was successfully represented by the proposed correlation, which is based on the classical mechanisms acting on particle collection. Inertial impaction seems to be the predominant collection mechanism, with particle bouncing/re-entrainment acting as detachment mechanisms.

The effect of abrading and cutting instruments on machinability of dental ceramics.

PubMed

Sakoda, Satoshi; Nakao, Noriko; Watanabe, Ikuya

2018-03-16

The aim was to investigate the effect of machining instruments on machinability of dental ceramics. Four dental ceramics, including two zirconia ceramics were machined by three types (SiC, diamond vitrified, and diamond sintered) of wheels with a hand-piece engine and two types (diamond and carbide) of burs with a high-speed air turbine. The machining conditions used were abrading speeds of 10,000 and 15,000 r.p.m. with abrading force of 100 gf for the hand-piece engine, and a pressure of 200 kPa and a cutting force of 80 gf for the air-turbine hand-piece. The machinability efficiency was evaluated by volume losses after machining the ceramics. A high-abrading speed had high-abrading efficiency (high-volume loss) compared to low-abrading speed in all abrading instruments used. The diamond vitrified wheels demonstrated higher volume loss for two zirconia ceramics than those of SiC and diamond sintered wheels. When the high-speed air-turbine instruments were used, the diamond points showed higher volume losses compared to the carbide burs for one ceramic and two zirconia ceramics with high-mechanical properties. The results of this study indicated that the machinability of dental ceramics depends on the mechanical and physical properties of dental ceramics and machining instruments. The abrading wheels show autogenous action of abrasive grains, in which ground abrasive grains drop out from the binder during abrasion, then the binder follow to wear out, subsequently new abrasive grains come out onto the instrument surface (autogenous action) and increase the grinding amount (volume loss) of grinding materials.

Ceramic Coatings for Clad (The C 3 Project): Advanced Accident-Tolerant Ceramic Coatings for Zr-Alloy Cladding

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sickafus, Kurt E.; Wirth, Brian; Miller, Larry

The goal of this NEUP-IRP project is to develop a fuel concept based on an advanced ceramic coating for Zr-alloy cladding. The coated cladding must exhibit demonstrably improved performance compared to conventional Zr-alloy clad in the following respects: During normal service, the ceramic coating should decrease cladding oxidation and hydrogen pickup (the latter leads to hydriding and embrittlement). During a reactor transient (e.g., a loss of coolant accident), the ceramic coating must minimize or at least significantly delay oxidation of the Zr-alloy cladding, thus reducing the amount of hydrogen generated and the oxygen ingress into the cladding. The specific objectivesmore » of this project are as follows: To produce durable ceramic coatings on Zr-alloy clad using two possible routes: (i) MAX phase ceramic coatings or similar nitride or carbide coatings; and (ii) graded interface architecture (multilayer) ceramic coatings, using, for instance, an oxide such as yttria-stabilized zirconia (YSZ) as the outer protective layer. To characterize the structural and physical properties of the coated clad samples produced in 1. above, especially the corrosion properties under simulated normal and transient reactor operating conditions. To perform computational analyses to assess the effects of such coatings on fuel performance and reactor neutronics, and to perform fuel cycle analyses to assess the economic viability of modifying conventional Zr-alloy cladding with ceramic coatings. This project meets a number of the goals outlined in the NEUP-IRP call for proposals, including: Improve the fuel/cladding system through innovative designs (e.g. coatings/liners for zirconium-based cladding) Reduce or eliminate hydrogen generation Increase resistance to bulk steam oxidation Achievement of our goals and objectives, as defined above, will lead to safer light-water reactor (LWR) nuclear fuel assemblies, due to improved cladding properties and built-in accident resistance, as well as the possibilities for enhanced fuel/clad system performance and longevity.« less

Towards a high thermoelectric performance in rare-earth substituted SrTiO3: effects provided by strongly-reducing sintering conditions.

PubMed

Kovalevsky, A V; Yaremchenko, A A; Populoh, S; Thiel, P; Fagg, D P; Weidenkaff, A; Frade, J R

2014-12-28

Donor-substituted strontium titanate ceramics demonstrate one of the most promising performances among n-type oxide thermoelectrics. Here we report a marked improvement of the thermoelectric properties in rare-earth substituted titanates Sr0.9R0.1TiO3±δ (R = La, Ce, Pr, Nd, Sm, Gd, Dy, Y) to achieve maximal ZT values of as high as 0.42 at 1190 K < T < 1225 K, prepared via a conventional solid state route followed by sintering under strongly reducing conditions (10%H2-90%N2, 1773 K). As a result of complex defect chemistry, both electrical and thermal properties were found to be dependent on the nature of the rare-earth cation and exhibit an apparent correlation with the unit cell size. High power factors of 1350-1550 μW m(-1) K(-2) at 400-550 K were observed for R = Nd, Sm, Pr and Y, being among the largest reported so far for n-type conducting bulk-ceramic SrTiO3-based materials. Attractive ZT values at high temperatures arise primarily from low thermal conductivity, which, in turn, stem from effective phonon scattering in oxygen-deficient perovskite layers formed upon reduction. The results suggest that highly-reducing conditions are essential and should be employed, whenever possible, in other related micro/nanostructural engineering approaches to suppress the thermal conductivity in target titanate-based ceramics.

Design, Fabrication and Characterization of High Temperature Joints in Ceramic Composites

NASA Technical Reports Server (NTRS)

Singh, M.

1999-01-01

Ceramic joining has been recognized as one of the enabling technologies for the successful utilization of ceramic components in a number of demanding, high temperature applications. Various joint design philosophies and design issues have been discussed along with an affordable, robust ceramic joining technology (ARCJoinT). A wide variety of silicon carbide-based composite materials, in different shapes and sizes, have been joined using this technology. This technique is capable of producing joints with tailorable thickness and composition. The room and high temperature mechanical properties and fractography of ceramic joints have been reported. These joints maintain their mechanical strength up to 1200 C in air. This technology is suitable for the joining of large and complex shaped ceramic composite components and with certain modifications, can be applied to repair of ceramic components damaged in service.

Design, Fabrication, and Characterization of High Temperature Joints in Ceramic Composites

NASA Technical Reports Server (NTRS)

Singh, M.

1999-01-01

Ceramic joining has been recognized as one of the enabling technologies for the successful utilization of ceramic components in a number of demanding, high temperature applications. Various joint design philosophies and design issues have been discussed along with an affordable, robust ceramic joining technology (ARCJoinT). A wide variety of silicon carbide-based composite materials, in different shapes and sizes, have been joined using this technology. This technique is capable of producing joints with tailorable thickness and composition. The room and high temperature mechanical properties and fractography of ceramic joints have been reported. These joints maintain their mechanical strength up to 1200C in air. This technology is suitable for the joining of large and complex shaped ceramic composite components and with certain modifications, can be applied to repair of ceramic components damaged in service.

Nonaqueous slip casting of high temperature ceramic superconductors using an investment casting technique

NASA Technical Reports Server (NTRS)

Hooker, Matthew W. (Inventor); Taylor, Theodore D. (Inventor); Wise, Stephanie A. (Inventor); Buckley, John D. (Inventor); Vasquez, Peter (Inventor); Buck, Gregory M. (Inventor); Hicks, Lana P. (Inventor)

1993-01-01

A process for slip casting ceramic articles that does not employ parting agents and affords the casting of complete, detailed, precision articles that do not possess parting lines is presented. This process is especially useful for high temperature superconductors and water-sensitive ceramics. A wax pattern for a shell mold is provided, and an aqueous mixture of a calcium sulfate-bonded investment material is applied as a coating to the wax pattern. The coated wax pattern is then dried, followed by curing to vaporize the wax pattern and leave a shell mold of the calcium sulfate-bonded investment material. The shell mold is cooled to room temperature, and a ceramic slip, created by dispersing a ceramic powder in an organic liquid, is poured therein. After a ceramic shell of desired thickness or a solid article has set up in the shell mold, excess ceramic slip is poured out. The shell mold is misted with water and peeled away from the ceramic article, after which the ceramic is fired to provide a complete, detailed, precision, high temperature superconductive ceramic article without parting lines. The casting technique may take place in the presence of a magnetic field to orient the ceramic powders during the casting process.

Experimental validation of prototype high voltage bushing

NASA Astrophysics Data System (ADS)

Shah, Sejal; Tyagi, H.; Sharma, D.; Parmar, D.; M. N., Vishnudev; Joshi, K.; Patel, K.; Yadav, A.; Patel, R.; Bandyopadhyay, M.; Rotti, C.; Chakraborty, A.

2017-08-01

Prototype High voltage bushing (PHVB) is a scaled down configuration of DNB High Voltage Bushing (HVB) of ITER. It is designed for operation at 50 kV DC to ensure operational performance and thereby confirming the design configuration of DNB HVB. Two concentric insulators viz. Ceramic and Fiber reinforced polymer (FRP) rings are used as double layered vacuum boundary for 50 kV isolation between grounded and high voltage flanges. Stress shields are designed for smooth electric field distribution. During ceramic to Kovar brazing, spilling cannot be controlled which may lead to high localized electrostatic stress. To understand spilling phenomenon and precise stress calculation, quantitative analysis was performed using Scanning Electron Microscopy (SEM) of brazed sample and similar configuration modeled while performing the Finite Element (FE) analysis. FE analysis of PHVB is performed to find out electrical stresses on different areas of PHVB and are maintained similar to DNB HV Bushing. With this configuration, the experiment is performed considering ITER like vacuum and electrical parameters. Initial HV test is performed by temporary vacuum sealing arrangements using gaskets/O-rings at both ends in order to achieve desired vacuum and keep the system maintainable. During validation test, 50 kV voltage withstand is performed for one hour. Voltage withstand test for 60 kV DC (20% higher rated voltage) have also been performed without any breakdown. Successful operation of PHVB confirms the design of DNB HV Bushing. In this paper, configuration of PHVB with experimental validation data is presented.

Affordable, Robust Ceramic Joining Technology (ARCJoinT) for High Temperature Applications

NASA Technical Reports Server (NTRS)

Singh, M.

1998-01-01

Ceramic joining is recognized as one of the enabling technologies for the successful utilization of silicon carbide-based monolithic ceramic and fiber reinforced composite components in a number of demanding and high temperature applications in aerospace and ground-based systems. An affordable, robust ceramic joining technology (ARCJoinT) for joining of silicon carbide-based ceramics and fiber reinforced composites has been developed. This technique is capable of producing joints with tailorable thickness and composition. A wide variety of silicon carbide-based ceramics and composites, in different shapes and sizes, have been joined using this technique. The room and high temperature mechanical properties and fractography of ceramic joints have been reported. In monolithic silicon carbide ceramics, these joints maintain their mechanical strength up to 1350 C in air. There is no change in the mechanical strength of joints in silicon carbide matrix composites up to 1200 C in air. In composites, simple butt joints yield only about 20% of the ultimate strength of the parent materials. This technology is suitable for the joining of large and complex shaped ceramic and composite components, and with certain modifications, can be applied to repair of ceramic components damaged in service.

Synthesis and characterisation of novel low temperature ceramic and its implementation as substrate in dual segment CDRA

NASA Astrophysics Data System (ADS)

Kumari, Preeti; Tripathi, Pankaj; Sahu, Bhagirath; Singh, S. P.; Parkash, Om; Kumar, Devendra

2018-02-01

Li2O-(2-3x)MgO-(x)Al2O3-P2O5 (LMAP) (x = 0.00-0.08) ceramic system was prepared through solid state synthesis route at different sintering temperatures (800-925 °C). A small addition of Al2O3 (x = 0.02) in LMAP ceramics lowers the sintering temperature by more than 100 °C with good relative density of 94.13%. The sintered samples were characterized in terms of density, apparent porosity, water absorption, crystal structure, micro-structure and microwave dielectric properties. Silver compatibility test is also performed for its use as electrode material in low temperature co-fired ceramic (LTCC) application. To check the performance of the prepared LTCC as substrate, a microstrip-fed aperture-coupled dual segment cylindrical dielectric resonator antenna (DS-CDRA) is designed using LMAP (x = 0.02) ceramic as substrate material and Barium Strontium Titanate with 10 wt% of PbO-BaO-B2O3-SiO2 glass (BSTG) and Teflon as the components of resonating material. The simulation study of the DS-CDRA is performed using the Ansys High Frequency Structure Simulator (HFSS) software. A conductive coating of silver is used on the substrate. The simulated and measured -10 dB reflection coefficient bandwidths of 910 MHz (9.07-9.98 GHz at resonant frequency of 9.49 GHz) and 1080 MHz (8.68-9.76 GHz at resonant frequency of 9.36 GHz), respectively are achieved. The measured results of the fabricated antenna are found in good agreement with the simulation results. The prepared material can find potential applications in radar and radio navigation as well as radio astronomy and military satellite communication.

High-temperature testing of glass/ceramic matrix composites

NASA Technical Reports Server (NTRS)

Mandell, John F.; Grande, Dodd H.; Dannemann, Kathryn A.

1989-01-01

Recent advances in ceramic and other high-temperature composites have created a need for test methods that can be used at 1000 C and above. Present test methods usually require adhesively bonded tabs that cannot be used at high temperatures. This paper discusses some of the difficulties with high-temperature test development and describes several promising test methods. Stress-strain data are given for Nicalon ceramic fiber reinforced glass and glass-ceramic matrix composites tested in air at temperatures up to 1000 C.

Machinability of IPS Empress 2 framework ceramic.

PubMed

Schmidt, C; Weigl, P

2000-01-01

Using ceramic materials for an automatic production of ceramic dentures by CAD/CAM is a challenge, because many technological, medical, and optical demands must be considered. The IPS Empress 2 framework ceramic meets most of them. This study shows the possibilities for machining this ceramic with economical parameters. The long life-time requirement for ceramic dentures requires a ductile machined surface to avoid the well-known subsurface damages of brittle materials caused by machining. Slow and rapid damage propagation begins at break outs and cracks, and limits life-time significantly. Therefore, ductile machined surfaces are an important demand for machine dental ceramics. The machining tests were performed with various parameters such as tool grain size and feed speed. Denture ceramics were machined by jig grinding on a 5-axis CNC milling machine (Maho HGF 500) with a high-speed spindle up to 120,000 rpm. The results of the wear test indicate low tool wear. With one tool, you can machine eight occlusal surfaces including roughing and finishing. One occlusal surface takes about 60 min machining time. Recommended parameters for roughing are middle diamond grain size (D107), cutting speed v(c) = 4.7 m/s, feed speed v(ft) = 1000 mm/min, depth of cut a(e) = 0.06 mm, width of contact a(p) = 0.8 mm, and for finishing ultra fine diamond grain size (D46), cutting speed v(c) = 4.7 m/s, feed speed v(ft) = 100 mm/min, depth of cut a(e) = 0.02 mm, width of contact a(p) = 0.8 mm. The results of the machining tests give a reference for using IPS Empress(R) 2 framework ceramic in CAD/CAM systems. Copyright 2000 John Wiley & Sons, Inc.

Mechanical behavior of a ceramic matrix composite material. M.S. Thesis Final Report

NASA Technical Reports Server (NTRS)

Grosskopf, Paul P.; Duke, John C., Jr.

1991-01-01

Monolithic ceramic materials have been used in industry for hundreds of years. These materials have proven their usefulness in many applications, yet, their potential for critical structural applications is limited. The existence of an imperfection in a monolithic ceramic on the order of several microns in size may be critical, resulting in catastrophic failure. To overcome this extreme sensitivity to small material imperfections, reinforced ceramic materials were developed. A ceramic matrix which has been reinforced with continuous fibers is not only less sensitive to microscopic flaws, but is also able to sustain significant damage without suffering catastrophic failure. A borosilicate glass reinforced with several layers of plain weave silicon carbide cloth (Nicalon) was studied. The mechanical testing which was performed included both flexural and tensile loading configurations. This testing was done not only to determine the material properties, but also to initiate a controlled amount of damage within each specimen. Several nondestructive testing techniques, including acousto-ultrasonics (AU), were performed on the specimens periodically during testing. The AU signals were monitored through the use of an IBM compatible personal computer with a high speed data acquisition board. Software was written which manipulates the AU signals in both the time and frequency domains, resulting in quantitative measures of the mechanical response of the material. The measured AU parameters are compared to both the mechanical test results and data from other nondestructive methods including ultrasonic C-scans and penetrant enhanced x ray radiography.

Improved Slip Casting Of Ceramic Models

NASA Technical Reports Server (NTRS)

Buck, Gregory M.; Vasquez, Peter; Hicks, Lana P.

1994-01-01

Improved technique of investment slip casting developed for making precise ceramic wind-tunnel models. Needed in wind-tunnel experiments to verify predictions of aerothermodynamical computer codes. Ceramic materials used because of their low heat conductivities and ability to survive high temperatures. Present improved slip-casting technique enables casting of highly detailed models from aqueous or nonaqueous solutions. Wet shell molds peeled off models to ensure precise and undamaged details. Used at NASA Langley Research Center to form superconducting ceramic components from nonaqueous slip solutions. Technique has many more applications when ceramic materials developed further for such high-strength/ temperature components as engine parts.

Effect of the microstructure on the lifetime of dental ceramics.

PubMed

Borba, Márcia; de Araújo, Maico D; Fukushima, Karen A; Yoshimura, Humberto N; Cesar, Paulo F; Griggs, Jason A; Della Bona, Alvaro

2011-07-01

To evaluate the effect of the microstructure on the Weibull and slow crack growth (SCG) parameters and on the lifetime of three ceramics used as framework materials for fixed partial dentures (FPDs) (YZ - Vita In-Ceram YZ; IZ - Vita In-Ceram Zirconia; AL - Vita In-Ceram AL) and of two veneering porcelains (VM7 and VM9). Bar-shaped specimens were fabricated according to the manufacturer's instructions. Specimens were tested in three-point flexure in 37°C artificial saliva. Weibull analysis (n=30) and a constant stress-rate test (n=10) were used to determine the Weibull modulus (m) and SCG coefficient (n), respectively. Microstructural and fractographic analyzes were performed using SEM. ANOVA and Tukey's test (α=0.05) were used to statistically analyze data obtained with both microstructural and fractographic analyzes. YZ and AL presented high crystalline content and low porosity (0.1-0.2%). YZ had the highest characteristic strength (σ(0)) value (911MPa) followed by AL (488MPa) and IZ (423MPa). Lower σ(0) values were observed for the porcelains (68-75MPa). Except for IZ and VM7, m values were similar among the ceramic materials. Higher n values were found for YZ (76) and AL (72), followed by IZ (54) and the veneering materials (36-44). Lifetime predictions showed that YZ was the material with the best mechanical performance. The size of the critical flaw was similar among the framework materials (34-48μm) and among the porcelains (75-86μm). The microstructure influenced the mechanical and SCG behavior of the studied materials and, consequently, the lifetime predictions. Copyright © 2011 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Light-weight black ceramic insulation

NASA Technical Reports Server (NTRS)

Hsu, Ming-Ta S. (Inventor); Chen, Timothy S. (Inventor)

2003-01-01

Ultra-high temperature, light-weight, black ceramic insulation having a density ranging from about 0.12 g/cc. to 0.6 g/cc. such as ceramic tile is obtained by pyrolyzing siloxane gels derived from the reaction of at least one organo dialkoxy silane and at least one tetralkoxy silane in an acid or base liquid medium. The reaction mixture of the tetra- and dialkoxy silanes also may contain an effective amount of a mono- or trialkoxy silane to obtain the siloxane gels. The siloxane gels are dried at ambient temperatures and pressures to form siloxane ceramic precursors without significant shrinkage. The siloxane ceramic precursors are subsequently pyrolyzed, in an inert atmosphere, to form the black ceramic insulation comprising atoms of silicon, carbon and oxygen. The ceramic insulation can be characterized as a porous, uniform ceramic tile resistant to oxidation at temperatures ranging as high as 1700.degree. C., and particularly useful as lightweight tiles for spacecraft and other high-temperature insulation applications.

Characterization of TiN coating layers using ultrasonic backward radiation.

PubMed

Song, Sung-Jin; Yang, Dong-Joo; Kim, Hak-Joon; Kwon, Sung D; Lee, Young-Ze; Kim, Ji-Yoon; Choi, Song-Chun

2006-12-22

Since ceramic layers coated on machinery components inevitably experience the changes in their properties it is necessary to evaluate the characteristics of ceramic coating layers nondestructively for the reliable use of coated components and the remaining life prediction. To address such a need, in the present study, the ultrasonic backward radiation technique is applied to examine the very thin TiN ceramic layers coated on AISI 1045 steel or austenitic 304 steel substrate. Specifically, the ultrasonic backward radiation profiles have been measured with variations in specimen preparation conditions such as coating layer thickness and sliding loading. In the experiments performed in the current study, the peak angle and the peak amplitude of ultrasonic backward radiation profile varied sensitively according to two specimen preparation conditions. In fact, this result demonstrates a high possibility of the ultrasonic backward radiation as an effective tool for the nondestructive characterization of the TiN ceramic coating layers even in such a thin regime.

Composite Flexible Blanket Insulation

NASA Technical Reports Server (NTRS)

Kourtides, Demetrius A. (Inventor); Pitts, William C. (Inventor); Goldstein, Howard E. (Inventor); Sawko, Paul M. (Inventor)

1991-01-01

Composite flexible multilayer insulation systems (MLI) were evaluated for thermal performance and compared with the currently used fibrous silica (baseline) insulation system. The systems described are multilayer insulations consisting of alternating layers of metal foil and scrim ceramic cloth or vacuum metallized polymeric films quilted together using ceramic thread. A silicon carbide thread for use in the quilting and the method of making it are also described. These systems are useful in providing lightweight insulation for a variety of uses, particularly on the surface of aerospace vehicles subject to very high temperatures during flight.

Hugoniot equation of state and dynamic strength of boron carbide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Grady, Dennis E.

Boron carbide ceramics have been particularly problematic in attempts to develop adequate constitutive model descriptions for purposes of analysis of dynamic response in the shock and impact environment. Dynamic strength properties of boron carbide ceramic differ uniquely from comparable ceramics. Furthermore, boron carbide is suspected, but not definitely shown, to undergoing polymorphic phase transformation under shock compression. In the present paper, shock-wave compression measurements conducted over the past 40 years are assessed for the purpose of achieving improved understanding of the dynamic equation of state and strength of boron carbide. In particular, attention is focused on the often ignored Losmore » Alamos National Laboratory (LANL) Hugoniot measurements performed on porous sintered boron carbide ceramic. The LANL data are shown to exhibit two compression anomalies on the shock Hugoniot within the range of 20–60 GPa that may relate to crystallographic structure transitions. More recent molecular dynamics simulations on the compressibility of the boron carbide crystal lattice reveal compression transitions that bear similarities to the LANL Hugoniot results. The same Hugoniot data are complemented with dynamic isentropic compression data for boron carbide extracted from Hugoniot measurements on boron carbide and copper granular mixtures. Other Hugoniot measurements, however, performed on near-full-density boron carbide ceramic differ markedly from the LANL Hugoniot data. These later data exhibit markedly less compressibility and tend not to show comparable anomalies in compressibility. Alternative Hugoniot anomalies, however, are exhibited by the near-full-density data. Experimental uncertainty, Hugoniot strength, and phase transformation physics are all possible explanations for the observed discrepancies. It is reasoned that experimental uncertainty and Hugoniot strength are not likely explanations for the observed differences. The notable mechanistic difference in the processes of shock compression between the LANL data and that of the other studies is the markedly larger inelastic deformation and dissipation experienced in the shock event brought about by compaction of the substantially larger porosity LANL test ceramics. High-pressure diamond anvil cell experiments reveal extensive amorphization, reasoned to be a reversion product of a higher-pressure crystallographic phase, which is a consequence of application of both high pressure and shear deformation to the boron carbide crystal structure. A dependence of shock-induced high-pressure phase transformation in boron carbide on the extent of shear deformation experienced in the shock process offers a plausible explanation for the differences observed in the LANL Hugoniot data on porous ceramic and that of other shock data on near-full-density boron carbide.« less

Fibre-matrix bond strength studies of glass, ceramic, and metal matrix composites

NASA Technical Reports Server (NTRS)

Grande, D. H.; Mandell, J. F.; Hong, K. C. C.

1988-01-01

An indentation test technique for compressively loading the ends of individual fibers to produce debonding has been applied to metal, glass, and glass-ceramic matrix composites; bond strength values at debond initiation are calculated using a finite-element model. Results are correlated with composite longitudinal and interlaminar shear behavior for carbon and Nicalon fiber-reinforced glasses and glass-ceramics including the effects of matrix modifications, processing conditions, and high-temperature oxidation embrittlement. The data indicate that significant bonding to improve off-axis and shear properties can be tolerated before the longitudinal behavior becomes brittle. Residual stress and other mechanical bonding effects are important, but improved analyses and multiaxial interfacial failure criteria are needed to adequately interpret bond strength data in terms of composite performance.

Reuse of hazardous calcium fluoride sludge from the integrated circuit industry.

PubMed

Zhu, Ping; Cao, Zhenbang; Ye, YiLi; Qian, Guangren; Lu, Bo; Zhou, Ming; Zhou, Jin

2013-11-01

The Chinese integrated circuit industry has been transformed from a small state-owned sector into a global competitor, but chip manufacturing produces large amounts of calcium fluoride sludges (CFS). In China, landfill is a current option for treating CFS. In order to solve the problem of unavailable landfill sites and prevent fluorine from dissolved CFS polluting water sources, CFS was tested as a component for a ceramic product made with sodium borate, sodium phosphate and waste alumina using a low-temperature sintering technology, and the effects of various factors on characteristics of the ceramic were investigated to optimize the process. The best sintering temperature was controlled at 700°C, and the optimal raw material ratio of the ceramic was 11% sodium borate, 54% sodium phosphate, 30% CFS and 5% waste alumina. The CFS ceramic was characterized by a morphological structure and X-ray diffraction. The results indicated that CFS was transformed into Na2Ca(PO4)F as an inert and a main crystalline phase in the ceramic, which was enclosed by the borophosphate glass. Toxicity characteristic leaching procedure, corrosion resistance and compressive strength tests verified CFS ceramic as a qualified construction ceramic material, and the fluorine from CFS was solidified in the inert crystalline phase, which would not be released to cause secondary pollution. This novel technology not only avoids the CFS hydrolyzing reaction forming harmful hydrofluoric acid gas at 800°C and above, but also produces high-performance ceramics as a construction material, in accordance with the concept of sustainable development.

Method for producing ceramic composition having low friction coefficient at high operating temperatures

DOEpatents

Lankford, Jr., James

1988-01-01

A method for producing a stable ceramic composition having a surface with a low friction coefficient and high wear resistance at high operating temperatures. A first deposition of a thin film of a metal ion is made upon the surface of the ceramic composition and then a first ion implantation of at least a portion of the metal ion is made into the near surface region of the composition. The implantation mixes the metal ion and the ceramic composition to form a near surface composite. The near surface composite is then oxidized sufficiently at high oxidizing temperatures to form an oxide gradient layer in the surface of the ceramic composition.

Joining and Assembly of Silicon Carbide-based Advanced Ceramics and Composites for High Temperature Applications

NASA Technical Reports Server (NTRS)

Singh, M.

2004-01-01

Silicon carbide based advanced ceramics and fiber reinforced composites are under active consideration for use in wide variety of high temperature applications within the aeronautics, space transportation, energy, and nuclear industries. The engineering designs of ceramic and composite component require fabrication and manufacturing of large and complex shaped parts of various thicknesses. In many instances, it is more economical to build up complex shapes by joining simple geometrical shapes. In addition these components have to be joined or assembled with metallic sub-components. Thus, joining and attachment have been recognized as enabling technologies for successful utilization of ceramic components in various demanding applications. In this presentation, various challenges and opportunities in design, fabrication, and testing o high temperature joints in ceramic matrix composites will be presented. Silicon carbide based advanced ceramics (CVD and hot pressed), and C/SiC and SiC/SiC composites, in different shapes and sizes, have been joined using an affordable, robust ceramic joining technology (ARCJoinT). Microstructure and high temperature mechanical properties of joints in silicon carbide ceramics and CVI and melt infiltrated SiC matrix composites will,be reported. Various joint design philosophies and design issues in joining of ceramics and composites well be discussed.

Fabrication of PVDF-TrFE based bilayered PbTiO{sub 3}/PVDF-TrFE films capacitor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nurbaya, Z., E-mail: nurbayazainal@gmail.com; Razak School of Engineering and Advanced Technology, Universiti Teknologi Malaysia, 54100 Kuala Lumpur; Wahid, M. H.

2016-07-06

Development of high performance capacitor is reaching towards new generation where the ferroelectric materials take places as the active dielectric layer. The motivation of this study is to produce high capacitance device with long life cycle. This was configured by preparing bilayered films where lead titanate as an active dielectric layer and stacked with the top dielectric layer, poly(vinyledenefluoride-trifluoroethylene). Both of them are being referred that have one in common which is ferroelectric behavior. Therefore the combination of ceramic and polymer ferroelectric material could perform optimum dielectric characteristic for capacitor applications. The fabrication was done by simple sol-gel spin coatingmore » method that being varied at spinning speed property for polymer layers, whereas maintaining the ceramic layer. The characterization of PVDF-TrFE/PbTiO3 was performed according to metal-insulator-metal stacked capacitor measurement which includes structural, dielectric, and ferroelectric measurement.« less

Segmented lasing tube for high temperature laser assembly

DOEpatents

Sawicki, Richard H.; Alger, Terry W.; Finucane, Raymond G.; Hall, Jerome P.

1996-01-01

A high temperature laser assembly capable of withstanding operating temperatures in excess of 1500.degree. C. is described comprising a segmented cylindrical ceramic lasing tube having a plurality of cylindrical ceramic lasing tube segments of the same inner and outer diameters non-rigidly joined together in axial alignment; insulation of uniform thickness surround the walls of the ceramic lasing tube; a ceramic casing, preferably of quartz, surrounding the insulation; and a fluid cooled metal jacket surrounds the ceramic casing. In a preferred embodiment, the inner surface of each of the ceramic lasing tube segments are provided with a pair of oppositely spaced grooves in the wall thereof parallel to the center axis of the segmented cylindrical ceramic lasing tube, and both of the grooves and the center axis of the segmented cylindrical ceramic lasing tube lie in a common plane, with the grooves in each ceramic lasing tube segment in circumferential alignment with the grooves in the adjoining ceramic lasing tube segments; and one or more ceramic plates, all lying in a common plane to one another and with the central axis of the segmented ceramic lasing tube, are received in the grooves to provide additional wall area in the segmented ceramic lasing tube for collision and return to ground state of metastable metal atoms within the segmented ceramic lasing tube.

Nano-Ceramic Coated Plastics

NASA Technical Reports Server (NTRS)

Cho, Junghyun

2013-01-01

Plastic products, due to their durability, safety, and low manufacturing cost, are now rapidly replacing cookware items traditionally made of glass and ceramics. Despite this trend, some still prefer relatively expensive and more fragile ceramic/glassware because plastics can deteriorate over time after exposure to foods, which can generate odors, bad appearance, and/or color change. Nano-ceramic coatings can eliminate these drawbacks while still retaining the advantages of the plastic, since the coating only alters the surface of the plastic. The surface coating adds functionality to the plastics such as self-cleaning and disinfectant capabilities that result from a photocatalytic effect of certain ceramic systems. These ceramic coatings can also provide non-stick surfaces and higher temperature capabilities for the base plastics without resorting to ceramic or glass materials. Titanium dioxide (TiO2) and zinc oxide (ZnO) are the candidates for a nano-ceramic coating to deposit on the plastics or plastic films used in cookware and kitchenware. Both are wide-bandgap semiconductors (3.0 to 3.2 eV for TiO2 and 3.2 to 3.3 eV for ZnO), so they exhibit a photocatalytic property under ultraviolet (UV) light. This will lead to decomposition of organic compounds. Decomposed products can be easily washed off by water, so the use of detergents will be minimal. High-crystalline film with large surface area for the reaction is essential to guarantee good photocatalytic performance of these oxides. Low-temperature processing (<100 C) is also a key to generating these ceramic coatings on the plastics. One possible way of processing nanoceramic coatings at low temperatures (< 90 C) is to take advantage of in-situ precipitated nanoparticles and nanostructures grown from aqueous solution. These nanostructures can be tailored to ceramic film formation and the subsequent microstructure development. In addition, the process provides environment- friendly processing because of the aqueous solution. Low-temperature processing has also shown versatility to generate various nanostructures. The growth of low-dimensional nanostructures (0-D, 1-D) provides a means of enhancing the crystallinity of the solution-prepared films that is of importance for photocatalytic performance. This technology can generate durable, fully functional nano-ceramic coatings (TiO2, ZnO) on plastic materials (silicone, Teflon, PET, etc.) that can possess both photocatalytic oxide properties and flexible plastic properties. Processing cost is low and it does not require any expensive equipment investment. Processing can be scalable to current manufacturing infrastructure.

Energy harvesting performance of piezoelectric ceramic and polymer nanowires.

PubMed

Crossley, Sam; Kar-Narayan, Sohini

2015-08-28

Energy harvesting from ubiquitous ambient vibrations is attractive for autonomous small-power applications and thus considerable research is focused on piezoelectric materials as they permit direct inter-conversion of mechanical and electrical energy. Nanogenerators (NGs) based on piezoelectric nanowires are particularly attractive due to their sensitivity to small-scale vibrations and may possess superior mechanical-to-electrical conversion efficiency when compared to bulk or thin-film devices of the same material. However, candidate piezoelectric nanowires have hitherto been predominantly analyzed in terms of NG output (i.e. output voltage, output current and output power density). Surprisingly, the corresponding dynamical properties of the NG, including details of how the nanowires are mechanically driven and its impact on performance, have been largely neglected. Here we investigate all realizable NG driving contexts separately involving inertial displacement, applied stress T and applied strain S, highlighting the effect of driving mechanism and frequency on NG performance in each case. We argue that, in the majority of cases, the intrinsic high resonance frequencies of piezoelectric nanowires (∼tens of MHz) present no barrier to high levels of NG performance even at frequencies far below resonance (<1 kHz) typically characteristic of ambient vibrations. In this context, we introduce vibrational energy harvesting (VEH) coefficients ηS and ηT, based on intrinsic materials properties, for comparing piezoelectric NG performance under strain-driven and stress-driven conditions respectively. These figures of merit permit, for the first time, a general comparison of piezoelectric nanowires for NG applications that takes into account the nature of the mechanical excitation. We thus investigate the energy harvesting performance of prototypical piezoelectric ceramic and polymer nanowires. We find that even though ceramic and polymer nanowires have been found, in certain cases, to have similar energy conversion efficiencies, ceramics are more promising in strain-driven NGs while polymers are more promising for stress-driven NGs. Our work offers a viable means of comparing NG materials and devices on a like-for-like basis that may be useful for designing and optimizing nanoscale piezoelectric energy harvesters for specific applications.

Thermo-optical and spectroscopic properties of Nd:YAG fine grain ceramics: towards a better performance than the Nd:YAG laser crystals

NASA Astrophysics Data System (ADS)

Santos, W. Q.; Benayas, A.; Jaque, D.; García-Solé, J.; Catunda, T.; Jacinto, C.

2016-02-01

In this work, we investigated the thermo-optical properties of highly Nd3+ doped YAG ceramics. The normalized lifetime thermal lens method was used to obtain the fluorescence quantum efficiency (η) versus Nd3+ concentration (N t) and to study the energy transfer microparameters C DD and C DA. The N t dependence of η was compared to the results of the previous literature. The C DA found is very similar to those of the previous literature, while the C DD is very different and higher than C DA, although the main dependence of η with N t is assigned to C DA. The figure of merit (η.N t versus N t) indicated a maximum around 3.8 at.% Nd2O3, which in addition to the very low ds/dT value, evidences the YAG ceramic as an excellent material for an ultra-high-power microchip laser system and for devices requiring minimum pump-induced local heating generation.

Development ceramic composites based on Al2O3, SiO2 and IG-017 additive

NASA Astrophysics Data System (ADS)

Kurovics, E.; Shmakova, A.; Kanev, B.; Gömze, L. A.

2017-02-01

Based on high purity alumina and quartz powders and IG-017 bio-original additives the authors have developed new ceramic composite materials for different industrial purposes. The main goal was to fine a material and morphological structures of high performance ceramic composites as frames for development complex materials for extreme consumptions in the future. For this the mixed powders of Al2O3 , SiO2 and IG-017 bio-original additive were uniaxially pressed at different compaction pressures into disc shapes and were sintered in electric kiln under air (1) and nitrogrn (2) atmosphere. The grain size distributions of the raw materials were determined by laser granulometry. There thermo-physical properties were also determined by derivatography. The prepared and sintered specimens were tested on geometrical sizes, microstructure and morphology by scanning electron microscopy, porosity and water absorption. In this work the authors present the results of their research and investigation.

Design Concepts for Cooled Ceramic Composite Turbine Vane

NASA Technical Reports Server (NTRS)

Boyle, Robert J.; Parikh, Ankur H.; Nagpal, VInod K.

2015-01-01

The objective of this work was to develop design concepts for a cooled ceramic vane to be used in the first stage of the High Pressure Turbine(HPT). To insure that the design concepts were relevant to the gas turbine industry needs, Honeywell International Inc. was subcontracted to provide technical guidance for this work. The work performed under this contract can be divided into three broad categories. The first was an analysis of the cycle benefits arising from the higher temperature capability of Ceramic Matrix Composite(CMC) compared with conventional metallic vane materials. The second category was a series of structural analyses for variations in the internal configuration of first stage vane for the High Pressure Turbine(HPT) of a CF6 class commercial airline engine. The third category was analysis for a radial cooled turbine vanes for use in turboshaft engine applications. The size, shape and internal configuration of the turboshaft engine vanes were selected to investigate a cooling concept appropriate to small CMC vanes.

Testing of felt-ceramic materials for combustor applications

NASA Technical Reports Server (NTRS)

Venkat, R. S.; Roffe, G.

1983-01-01

The feasibility of using composite felt ceramic materials as combustor liners was experimentally studied. The material consists of a porous felt pad sandwiched between a layer of ceramic and one of solid metal. Flat, rectangular test panels, which encompassed several design variations of the basic composite material, were tested, two at a time, in a premixed gas turbine combustor as sections of the combustor wall. Tests were conducted at combustor inlet conditions of 0.5 MPa and 533 K with a reference velocity of 25 m/s. The panels were subjected to a hot gas temperature of 2170 K with 1% of the total airflow used to film cool the ceramic surface of the test panel. In general, thin ceramic layers yield low ceramic stress levels with high felt ceramic interface temperatures. On the other hand, thick ceramic layers result in low felt ceramic interface temperatures but high ceramic stress levels. Extensive thermal cycling appears to cause material degradation, but for a limited number of cycles, the survivability of felt ceramic materials, even under extremely severe combustor operating conditions, was conclusively demonstrated.

Ceramic strengthening by tuning the elastic moduli of resin-based luting agents.

PubMed

Spazzin, Aloísio O; Bacchi, Ataís; Alessandretti, Rodrigo; Santos, Mateus B; Basso, Gabriela R; Griggs, Jason; Moraes, Rafael R

2017-03-01

Resin-based luting agents (RBLAs) with tuned elastic moduli (E) were prepared and their influence on the strengthening, reliability, and mode of failure of luted feldspar ceramic was investigated. RBLAs with low E (2.6GPa), intermediate E (6.6GPa), and high E (13.3GPa) were prepared and used to coat acid-etched ceramic disks. Positive (untreated ceramic) and negative (acid-etched ceramic) control groups were tested. The response variables (n=30) were biaxial flexural strength (σ bf , MPa), characteristic strength (σ 0 , MPa), and Weibull modulus at the ceramic surface (z=0) and luting agent surface (z=-t 2 ). A 3D finite element analysis simulated the biaxial flexural test. Fractographic analysis and morphology of the bonded interfaces were analyzed using scanning electron microscopy. The RBLAs improved σ bf and σ 0 at z=0, particularly those with intermediate and high E, whereas the mechanical reliability was only affected in the negative control. At z=-t 2 , differences between all RBLAs were observed but the structural reliability was independent of the RBLA tested. Increasing E of the RBLA was associated with increased stress concentration at the RBLA and reduced stresses reaching the ceramic. Failures originated on the ceramic surface at the ceramic-cement interface. In the high E group, failure sometimes originated from the RBLA free surface. All RBLAs completely filled the ceramic irregularities. Increased E of the RBLA reduced the variability of strength, the stress reaching the ceramic structure, and sometimes altered the origin of failure. The use of high E RBLAs seems beneficial for luting feldspar ceramics. Copyright © 2017 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Robust Joining and Integration Technologies for Advanced Metallic, Ceramic, and Composite Systems

NASA Technical Reports Server (NTRS)

Singh, M.; Shpargel, Tarah; Morscher, Gregory N.; Halbig, Michael H.; Asthana, Rajiv

2006-01-01

Robust integration and assembly technologies are critical for the successful implementation of advanced metallic, ceramic, carbon-carbon, and ceramic matrix composite components in a wide variety of aerospace, space exploration, and ground based systems. Typically, the operating temperature of these components varies from few hundred to few thousand Kelvin with different working times (few minutes to years). The wide ranging system performance requirements necessitate the use of different integration technologies which includes adhesive bonding, low temperature soldering, active metal brazing, diffusion bonding, ARCJoinT, and ultra high temperature joining technologies. In this presentation, a number of joining examples and test results will be provided related to the adhesive bonding and active metal brazing of titanium to C/C composites, diffusion bonding of silicon carbide to silicon carbide using titanium interlayer, titanium and hastelloy brazing to silicon carbide matrix composites, and ARCJoinT joining of SiC ceramics and SiC matrix composites. Various issues in the joining of metal-ceramic systems including thermal expansion mismatch and resulting residual stresses generated during joining will be discussed. In addition, joint design and testing issues for a wide variety of joints will be presented.

A Brief Research Review for Improvement Methods the Wettability between Ceramic Reinforcement Particulate and Aluminium Matrix Composites

NASA Astrophysics Data System (ADS)

Razzaq, Alaa Mohammed; Majid, Dayang Laila Abang Abdul; Ishak, M. R.; B, Uday M.

2017-05-01

The development of new methods for addition fine ceramic powders to Al aluminium alloy melts, which would lead to more uniform distribution and effective incorporation of the reinforcement particles into the aluminium matrix alloy. Recently the materials engineering research has moved to composite materials from monolithic, adapting to the global need for lightweight, low cost, quality, and high performance advanced materials. Among the different methods, stir casting is one of the simplest ways of making aluminium matrix composites. However, it suffers from poor distribution and combination of the reinforcement ceramic particles in the metal matrix. These problems become significantly effect to reduce reinforcement size, more agglomeration and tendency with less wettability for the ceramic particles in the melt process. Many researchers have carried out different studies on the wettability between the metal matrix and dispersion phase, which includes added wettability agents, fluxes, preheating the reinforcement particles, coating the reinforcement particles, and use composting techniques. The enhancement of wettability of ceramic particles by the molten matrix alloy and the reinforcement particles distribution improvement in the solidified matrix is the main objective for many studies that will be discussed in this paper.

Ceramics Curriculum: What Has It Been? What Could it Be?

ERIC Educational Resources Information Center

Sessions, Billie

1999-01-01

Reviews the traditional approach to ceramics education that focuses on studio-based, formalist curriculum and Modernist concerns. Argues for a comprehensive, or contextual, ceramics education in high school classrooms that would include contextual information about ceramic objects. Discusses example ceramic objects by various artists. (CMK)

Luminescence properties of lustre decorated majolica

NASA Astrophysics Data System (ADS)

Galli, A.; Martini, M.; Sibilia, E.; Padeletti, G.; Fermo, P.

Luminescence measurements have been performed on several Italian Renaissance ceramic shards produced in central Italy, as well as on some others from Hispano-Moresque and Fatimid periods. The aim of this study was the characterisation of the raw materials used to manufacture lustre decorated majolica. At first, the thermoluminescence (TL) dating of all ceramic bodies was performed, because the shards lacked sure chronological attribution, having been provided by private collectors, or found during emergency restoration works or archaeological surveys. To characterise the defects and the recombination centers of the different components of the ceramics (ceramic body, glaze, glaze, and lustre), radioluminescence (RL) measurements have been performed on samples representative of each historical period. The dating results are reported, as well as the preliminary RL results.

Dielectric and varistor properties of rare-earth-doped ZnO and CaCu3Ti4O12 composite ceramics

NASA Astrophysics Data System (ADS)

Lu, Huafei; Lin, Yuanhua; Yuan, Jiancong; Nan, Cewen; Chen, Kexin

2013-02-01

To investigate the multi-functional ceramics with both high permittivity and large nonlinear coefficient, we have prepared rare-earth Tb-and-Co doped ZnO and TiO2-rich CaCu3Ti4O12 (TCCTO) powders by chemical co-precipitation and sol-gel methods respectively, and then obtained the TCCTO/ZnO composite ceramics, sintered at 1100°C for 3 h in air. Analyzing the composite ceramics of the microstructure and phase composition indicated that the composite ceramics were composed of the main phases of ZnO and CaCu3Ti4O12 (CCTO). Our results revealed that the TCCTO/ZnO composite ceramics showed both high dielectric and good nonlinear electrical behaviors. The composite ceramic of TCCTO: ZnO = 0.3 exhibited a high dielectric constant of 210(1 kHz) with a nonlinear coefficient of 11. The dielectric behavior of TCCTO/ZnO composite could be explained by the mixture rule. With the high dielectric permittivity and tunable varistor behaviors, the composite ceramics has a potential application for the higher voltage transportation devices.

Ultrasonic/Sonic Drill for High Temperature Application

NASA Technical Reports Server (NTRS)

Bao, Xiaoqi; Bar-Cohen, Yoseph; Scott, James; Sherrit, Stewart; Widholm, Scott; Badescu, Mircea; Shrout, Tom; Jones, Beth

2010-01-01

Venus is one of the many significant scientific targets for NASA. New rock sampling tools with the ability to be operated at high temperatures of the order of 460 deg C are required for surface in-situ sampling/analysis missions. Piezoelectric materials such as LiNbO? crystals and Bismuth Titanate are potentially operational at the temperature range found on the surface of Venus. A study of the feasibility of producing piezoelectric drills for a temperature up to 500 deg C was conducted. The study includes investigation of the high temperature properties of piezoelectric crystals and ceramics with different formulas and doping. Several prototypes of Ultrasonic/Sonic Drill/Corers (USDC) driven by transducers using the high temperate piezoelectric ceramics and single LiNbO? crystal were fabricated. The transducers were analyzed by scanning the impedance at room temperature and 500 deg C under both low and high voltages. The drilling performances were tested at temperature up to 500 deg C. Preliminary results were previously reported [Bao et al, 2009]. In this paper, the progress is presented and the future works for performance improvements are discussed.

High temperature ceramic/metal joint structure

DOEpatents

Boyd, Gary L.

1991-01-01

A high temperature turbine engine includes a hybrid ceramic/metallic rotor member having ceramic/metal joint structure. The disclosed joint is able to endure higher temperatures than previously possible, and aids in controlling heat transfer in the rotor member.

Research on self-propagating high temperature synthesis prepared ZrC-ZrB2 composite ceramic

NASA Astrophysics Data System (ADS)

Yong, Cheng; Xunjia, Su; Genliang, Hou; YaKun, Xing

2013-03-01

ZrC-ZrB2 composite ceramic material is prepared by self-propagating high temperature synthesis, using Zr powders, CrO2 powders and Al powders as raw materials. Samples are studied by XRD and SEM, the results show that: ZrC-ZrB2 composite ceramic is attained after self-propagating high-temperature reaction, with Zr+ B4C as the main reactive system, and which is added respectively different content (CrO3 + Al) system. The study finds that the ceramic composite products are mainly composed of ZrC and ZrB2 phase, and other subphase. Compared to the main reactive system composite ceramic, composite ceramic grains grow up obviously, after introduction of the highly exothermic system (CrO3 + Al) in the main reactive system, and with the gradual increase of the content (CrO3 + Al).

A Novel Electro-Thermal Laminated Ceramic with Carbon-Based Layer

PubMed Central

Ji, Yi; Huang, Bin; Rao, Pinggen

2017-01-01

A novel electro-thermal laminated ceramic composed of ceramic tile, carbon-based layer, dielectric layer, and foaming ceramic layer was designed and prepared by tape casting. The surface temperature achieved at an applied voltage of 10 V by the laminated ceramics was 40.3 °C when the thickness of carbon-based suspension was 1.0 mm and the adhesive strength between ceramic tile and carbon-based layer was 1.02 ± 0.06 MPa. In addition, the thermal aging results at 100 °C up to 192 h confirmed the high thermal stability and reliability of the electro-thermal laminated ceramics. The development of this laminated ceramic with excellent electro-thermal properties and safety provides a new individual heating device which is highly expected to be widely applied in the field of indoor heat supply. PMID:28773006

A Novel Electro-Thermal Laminated Ceramic with Carbon-Based Layer.

PubMed

Ji, Yi; Huang, Bin; Rao, Pinggen

2017-06-12

A novel electro-thermal laminated ceramic composed of ceramic tile, carbon-based layer, dielectric layer, and foaming ceramic layer was designed and prepared by tape casting. The surface temperature achieved at an applied voltage of 10 V by the laminated ceramics was 40.3 °C when the thickness of carbon-based suspension was 1.0 mm and the adhesive strength between ceramic tile and carbon-based layer was 1.02 ± 0.06 MPa. In addition, the thermal aging results at 100 °C up to 192 h confirmed the high thermal stability and reliability of the electro-thermal laminated ceramics. The development of this laminated ceramic with excellent electro-thermal properties and safety provides a new individual heating device which is highly expected to be widely applied in the field of indoor heat supply.

Oxidation and Corrosion of Ceramics and Ceramic Matrix Composites

NASA Technical Reports Server (NTRS)

Jacobson, Nathan S.; Opila, Elizabeth J.; Lee, Kang N.

2000-01-01

Ceramics and ceramic matrix composites are candidates for numerous applications in high temperature environments with aggressive gases and possible corrosive deposits. There is a growing realization that high temperature oxidation and corrosion issues must be considered. There are many facets to these studies, which have been extensively covered in some recent reviews. The focus of this paper is on current research, over the past two years. In the authors' view, the most important oxidation and corrosion studies have focused on four major areas during this time frame. These are; (I) Oxidation of precursor-based ceramics; (II) Studies of the interphase material in ceramic matrix composites; (III) Water vapor interactions with ceramics, particularly in combustion environments; and (IV) Development of refractory oxide coatings for silicon-based ceramics. In this paper, we shall explore the most current work in each of these areas.

[Ceramic-on-ceramic bearings in total hip arthroplasty (THA)].

PubMed

Sentürk, U; Perka, C

2015-04-01

The main reason for total hip arthroplasty (THA) revision is the wear-related aseptic loosening. Younger and active patients after total joint replacement create high demands, in particular, on the bearings. The progress, especially for alumina ceramic-on-ceramic bearings and mixed ceramics have solved many problems of the past and lead to good in vitro results. Modern ceramics (alumina or mixed ceramics containing alumina) are extremely hard, scratch-resistant, biocompatible, offer a low coefficient of friction, superior lubrication and have the lowest wear rates in comparison to all other bearings in THA. The disadvantage of ceramic is the risk of material failure, i.e., of ceramic fracture. The new generation of mixed ceramics (delta ceramic), has reduced the risk of head fractures to 0.03-0.05 %, but the risk for liner fractures remains unchanged at about 0.02 %. Assuming a non-impinging component implantation, ceramic-on-ceramic bearings have substantial advantages over all other bearings in THA. Due to the superior hardness, ceramic bearings produce less third body wear and are virtually impervious to damage from instruments during the implantation process. A specific complication for ceramic-on-ceramic bearings is "squeaking". The high rate of reported squeaking (0.45 to 10.7 %) highlights the importance of precise implant positioning and the stem and patient selection. With precise implant positioning this problem is rare with many implant designs and without clinical relevance. The improved tribology and the presumable resulting implant longevity make ceramic-on-ceramic the bearing of choice for young and active patients. Georg Thieme Verlag KG Stuttgart · New York.

International Standards for Properties and Performance of Advanced Ceramics - 30 years of Excellence

NASA Technical Reports Server (NTRS)

Jenkins, Michael G.; Salem, Jonathan A.; Helfinstine, John; Quinn, George D.; Gonczy, Stephen T.

2016-01-01

Mechanical and physical properties/performance of brittle bodies (e.g., advanced ceramics and glasses) can be difficult to measure correctly unless the proper techniques are used. For three decades, ASTM Committee C28 on Advanced Ceramics, has developed numerous full-consensus standards (e.g., test methods, practices, guides, terminology) to measure various properties and performance of a monolithic and composite ceramics and coatings that, in some cases, may be applicable to glasses. These standards give the "what, how, how not, why, why not, etc." for many mechanical, physical, thermal, properties and performance of advanced ceramics. Use of these standards provides accurate, reliable, repeatable and complete data. Involvement in ASTM Committee C28 has included users, producers, researchers, designers, academicians, etc. who write, continually update, and validate through round robin test programmes, more than 45 standards in the 30 years since the Committee's inception in 1986. Included in this poster is a pictogram of the ASTM Committee C28 standards and how to obtain them either as i) individual copies with full details or ii) a complete collection in one volume. A listing of other ASTM committees of interest is included. In addition, some examples of the tangible benefits of standards for advanced ceramics are employed to demonstrate their practical application.

Residual stress measurement in veneering ceramic by hole-drilling.

PubMed

Mainjot, Amélie K; Schajer, Gary S; Vanheusden, Alain J; Sadoun, Michaël J

2011-05-01

Mismatch in thermal expansion properties between veneering ceramic and metallic or high-strength ceramic cores can induce residual stresses and initiate cracks when combined with functional stresses. Knowledge of the stress distribution within the veneering ceramic is a key factor for understanding and predicting chipping failures, which are well-known problems with Yttria-tetragonal-zirconia-polycrystal based fixed partial dentures. The objectives of this study are to develop a method for measuring the stress profile in veneering ceramics and to compare ceramic-fused-to-metal compounds to veneered Yttria-tetragonal-zirconia-polycrystal ceramic. The hole-drilling method, often used for engineering measurements, was adapted for use with veneering ceramic. Because of the high sensitivity needed in comparison with industrial applications, a high sensitivity electrical measurement chain was developed. All samples exhibited the same type of stress vs. depth profile, starting with compressive at the ceramic surface, decreasing with depth and becoming tensile at 0.5-1.0mm from the surface, and then becoming slightly compressive again. The zirconia samples exhibited a stress depth profile of larger magnitude. The hole drilling method was shown be a practical tool for measuring residual stresses in veneering ceramics. Copyright © 2010 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

High Temperature Resistant Organopolysiloxane Coating for Protecting and Repairing Rigid Thermal Insulation

NASA Technical Reports Server (NTRS)

Leiser, Daniel B. (Inventor); Hsu, Ming-Ta S. (Inventor); Chen, Timothy S. (Inventor)

1999-01-01

Ceramics are protected from high temperature degradation, including high temperature, oxidative, aeroconvective degradation by a high temperature and oxidation resistant coating of a room temperature curing, hydrolyzed and partially condensed liquid polyorganosiloxane to the surface of the ceramic. The liquid polyorganosiloxane is formed by the hydrolysis and partial condensation of an alkyltrialkoxysilane with water or a mixture of an alkyltrialkoxysilane and a dialkyldialkoxysilane with water. The liquid polyorganosiloxane cures at room temperature on the surface of the ceramic to form a hard, protective, solid coating which forms a high temperature environment, and is also used as an adhesive for adhering a repair plug in major damage to the ceramic. This has been found useful for protecting and repairing porous, rigid ceramics of a type used on reentry space vehicles.

Determination of the slow crack growth susceptibility coefficient of dental ceramics using different methods.

PubMed

Gonzaga, Carla Castiglia; Cesar, Paulo Francisco; Miranda, Walter Gomes; Yoshimura, Humberto Naoyuki

2011-11-01

This study compared three methods for the determination of the slow crack growth susceptibility coefficient (n) of two veneering ceramics (VM7 and d.Sign), two glass-ceramics (Empress and Empress 2) and a glass-infiltrated alumina composite (In-Ceram Alumina). Discs (n = 10) were prepared according to manufacturers' recommendations and polished. The constant stress-rate test was performed at five constant stress rates to calculate n(d) . For the indentation fracture test to determine n(IF) , Vickers indentations were performed and the crack lengths were measured under an optical microscope. For the constant stress test (performed only for d.Sign for the determination of n(s) ) four constant stresses were applied and held constant until the specimens' fracture and the time to failure was recorded. All tests were performed in artificial saliva at 37°C. The n(d) values were 17.2 for Empress 2, followed by d.Sign (20.5), VM7 (26.5), Empress (30.2), and In-Ceram Alumina (31.1). In-Ceram Alumina and Empress 2 showed the highest n(IF) values, 66.0 and 40.2, respectively. The n(IF) values determined for Empress (25.2), d.Sign (25.6), and VM7 (20.1) were similar. The n(s) value determined for d.Sign was 31.4. It can be concluded that the n values determined for the dental ceramics evaluated were significantly influenced by the test method used. 2011 Wiley Periodicals, Inc.

Effect of SiC Content on the Ablation and Oxidation Behavior of ZrB2-Based Ultra High Temperature Ceramic Composites

PubMed Central

Hu, Ping; Gui, Kaixuan; Yang, Yang; Dong, Shun; Zhang, Xinghong

2013-01-01

The ablation and oxidation of ZrB2-based ultra high temperature ceramic (UHTC) composites containing 10%, 15% and 30% v/v SiC were tested under different heat fluxes in a high frequency plasma wind tunnel. Performance was significantly affected by the surface temperature, which was strongly dependent on the composition. Composites containing 10% SiC showed the highest surface temperature (>2300 °C) and underwent a marked degradation under both conditions. In contrast, composites with 30% SiC exhibited the lowest surface temperature (<2000 °C) and demonstrated excellent ablation resistance. The surface temperature of UHTCs in aerothermal testing was closely associated with the dynamic evolution of the surface and bulk oxide properties, especially for the change in chemical composition on the exposed surface, which was strongly dependent on the material composition and testing parameters (i.e., heat flux, enthalpy, pressure and test time), and in turn affected its oxidation performance. PMID:28809239

Effect of SiC Content on the Ablation and Oxidation Behavior of ZrB₂-Based Ultra High Temperature Ceramic Composites.

PubMed

Hu, Ping; Gui, Kaixuan; Yang, Yang; Dong, Shun; Zhang, Xinghong

2013-04-29

The ablation and oxidation of ZrB₂-based ultra high temperature ceramic (UHTC) composites containing 10%, 15% and 30% v/v SiC were tested under different heat fluxes in a high frequency plasma wind tunnel. Performance was significantly affected by the surface temperature, which was strongly dependent on the composition. Composites containing 10% SiC showed the highest surface temperature (>2300 °C) and underwent a marked degradation under both conditions. In contrast, composites with 30% SiC exhibited the lowest surface temperature (<2000 °C) and demonstrated excellent ablation resistance. The surface temperature of UHTCs in aerothermal testing was closely associated with the dynamic evolution of the surface and bulk oxide properties, especially for the change in chemical composition on the exposed surface, which was strongly dependent on the material composition and testing parameters ( i.e. , heat flux, enthalpy, pressure and test time), and in turn affected its oxidation performance.

Feature selection for neural network based defect classification of ceramic components using high frequency ultrasound.

PubMed

Kesharaju, Manasa; Nagarajah, Romesh

2015-09-01

The motivation for this research stems from a need for providing a non-destructive testing method capable of detecting and locating any defects and microstructural variations within armour ceramic components before issuing them to the soldiers who rely on them for their survival. The development of an automated ultrasonic inspection based classification system would make possible the checking of each ceramic component and immediately alert the operator about the presence of defects. Generally, in many classification problems a choice of features or dimensionality reduction is significant and simultaneously very difficult, as a substantial computational effort is required to evaluate possible feature subsets. In this research, a combination of artificial neural networks and genetic algorithms are used to optimize the feature subset used in classification of various defects in reaction-sintered silicon carbide ceramic components. Initially wavelet based feature extraction is implemented from the region of interest. An Artificial Neural Network classifier is employed to evaluate the performance of these features. Genetic Algorithm based feature selection is performed. Principal Component Analysis is a popular technique used for feature selection and is compared with the genetic algorithm based technique in terms of classification accuracy and selection of optimal number of features. The experimental results confirm that features identified by Principal Component Analysis lead to improved performance in terms of classification percentage with 96% than Genetic algorithm with 94%. Copyright © 2015 Elsevier B.V. All rights reserved.

Treatment of food waste recycling wastewater using anaerobic ceramic membrane bioreactor for biogas production in mainstream treatment process of domestic wastewater.

PubMed

Jeong, Yeongmi; Hermanowicz, Slawomir W; Park, Chanhyuk

2017-10-15

A bench-scale anaerobic membrane bioreactor (AnMBR) equipped with submerged flat-sheet ceramic membranes was operated at mesophilic conditions (30-35 °C) treating domestic wastewater (DWW) supplemented with food wasterecycling wastewater (FRW) to increase the organic loading rate (OLR) for better biogas production. Coupling ceramic membrane filtration with AnMBR treatment provides an alternative strategy for high organic wastewater treatment at short hydraulic retention times (HRTs) with the potential benefits of membrane fouling because they have a high hydrophilicity and more robust at extreme conditions. The anaerobic ceramic MBR (AnCMBR) treating mixture of actual FRW with DWW (with an influent chemical oxygen demand (COD) of 2,115 mg/L) was studied to evaluate the treatment performance in terms of organic matter removal and methane production. COD removal during actual FRW with DWW operation averaged 98.3 ± 1.0% corresponding to an average methane production of 0.21 ± 0.1 L CH 4 /g COD removed . Biogas sparging, relaxation and permeate back-flushing were concurrently employed to manage membrane fouling. A flux greater than 9.2 L m -2  h -1 (LMH) was maintained at 13 h HRT for approximately 200 days without chemical cleaning at an OLR of 2.95 kg COD m -3  d -1 . On day 100, polyvinyl alcohol (PVA)-gel beads were added into the AnCMBR to alleviate the membrane fouling, suggesting that their mechanical scouring effect contributed positively in reducing the fouling index (FI). Although these bio-carriers might accelerate the breaking up of bio-flocs, which released a higher amount of soluble microbial products (SMP), a 95.4% SMP rejection was achieved. Although the retention efficiency of dissolved organic carbons (DOC) was 91.4% across the ceramic membrane, a meaningful interpretation of organic carbon detection (OCD) fingerprints was conducted to better understand the ceramic membrane performance. Copyright © 2017 Elsevier Ltd. All rights reserved.

Method of making contamination-free ceramic bodies

NASA Technical Reports Server (NTRS)

Philipp, Warren H. (Inventor)

1991-01-01

Ceramic structures having high strength at temperatures above 1000 C after sintering are made by mixing ceramic powders with binder deflocculants such as guanidine salts of polymeric acids, guanidine salts of aliphatic organic carboxylic acids or guanidine alkylsulfates with the foregoing guanidine salts. The novelty of the invention appears to lie in the substitution of guanidine salts for the alkalai metal salt components or organic fatty acids of the prior art binder-deflocculant, ceramic processing aids whereby no undesirable metal contaminants are present in the final ceramic structure. Guanidine alkylsulfates also replace the Na or K alkylsulfates commonly used with binder-deflocculants in making high temperature ceramic structures.

Boron Nitride Nanotubes Synthesized by Pressurized Reactive Milling Process

NASA Technical Reports Server (NTRS)

Hurst, Janet B.

2004-01-01

Nanotubes, because of their very high strength, are attractive as reinforcement materials for ceramic matrix composites (CMCs). Recently there has been considerable interest in developing and applying carbon nanotubes for both electronic and structural applications. Although carbon nanotubes can be used to reinforce composites, they oxidize at high temperatures and, therefore, may not be suitable for ceramic composites. Boron nitride, because it has a higher oxidation resistance than carbon, could be a potential reinforcement material for ceramic composites. Although boron nitride nanotubes (BNnT) are known to be structurally similar to carbon nanotubes, they have not undergone the same extensive scrutiny that carbon nanotubes have experienced in recent years. This has been due to the difficulty in synthesizing this material rather than lack of interest in the material. We expect that BNnTs will maintain the high strength of carbon nanotubes while offering superior performance for the high-temperature and/or corrosive applications of interest to NASA. At the NASA Glenn Research of preparing BN-nTs were investigated and compared. These include the arc jet process, the reactive milling process, and chemical vapor deposition. The most successful was a pressurized reactive milling process that synthesizes BN-nTs of reasonable quantities.

Strong, tough and stiff bioinspired ceramics from brittle constituents

NASA Astrophysics Data System (ADS)

Bouville, Florian; Maire, Eric; Meille, Sylvain; van de Moortèle, Bertrand; Stevenson, Adam J.; Deville, Sylvain

2014-05-01

High strength and high toughness are usually mutually exclusive in engineering materials. In ceramics, improving toughness usually relies on the introduction of a metallic or polymeric ductile phase, but this decreases the material’s strength and stiffness as well as its high-temperature stability. Although natural materials that are both strong and tough rely on a combination of mechanisms operating at different length scales, the relevant structures have been extremely difficult to replicate. Here, we report a bioinspired approach based on widespread ceramic processing techniques for the fabrication of bulk ceramics without a ductile phase and with a unique combination of high strength (470 MPa), high toughness (22 MPa m1/2), and high stiffness (290 GPa). Because only mineral constituents are needed, these ceramics retain their mechanical properties at high temperatures (600 °C). Our bioinspired, material-independent approach should find uses in the design and processing of materials for structural, transportation and energy-related applications.

High temperature ceramics for automobile gas turbines. Part 2: Development of ceramic components

NASA Technical Reports Server (NTRS)

Walzer, P.; Koehler, M.; Rottenkolber, P.

1978-01-01

The development of ceramic components for automobile gas turbine engines is described with attention given to the steady and unsteady thermal conditions the ceramics will experience, and their anti-corrosion and strain-resistant properties. The ceramics considered for use in the automobile turbines include hot-pressed Si3N4, reaction-sintered, isostatically pressed Si3N4, hot-pressed SiC, reaction-bonded SiC, and glass ceramics. Attention is given to the stress analysis of ceramic structures and the state of the art of ceramic structural technology is reviewed, emphasizing the use of ceramics for combustion chambers and ceramic shrouded turbomachinery (a fully ceramic impeller).

Insulated laser tube structure and method of making same

DOEpatents

Dittbenner, Gerald R.

1999-01-01

An insulated high temperature ceramic laser tube having substantially uniform insulation along the length of the tube is disclosed having particulate ceramic insulation positioned between the outer wall of the ceramic laser tube and the inner surface of tubular ceramic fiber insulation which surrounds the ceramic laser tube. The particulate ceramic insulation is preferably a ceramic capable of sintering to the outer surface of the ceramic laser tube and to the inner surface of the tubular ceramic fiber insulation. The addition of the particulate ceramic insulation to fill all the voids between the ceramic laser tube and the fibrous ceramic insulation permits the laser tube to be operated at a substantially uniform temperature throughout the length of the laser tube.

Material requirements for the High Speed Civil Transport

NASA Technical Reports Server (NTRS)

Stephens, Joseph R.; Hecht, Ralph J.; Johnson, Andrew M.

1993-01-01

Under NASA-sponsored High Speed Research (HSR) programs, the materials and processing requirements have been identified for overcoming the environmental and economic barriers of the next generation High Speed Civil Transport (HSCT) propulsion system. The long (2 to 5 hours) supersonic cruise portion of the HSCT cycle will place additional durability requirements on all hot section engine components. Low emissions combustor designs will require high temperature ceramic matrix composite liners to meet an emission goal of less than 5g NO(x) per Kg fuel burned. Large axisymmetric and two-dimensional exhaust nozzle designs are now under development to meet or exceed FAR 36 Stage III noise requirements, and will require lightweight, high temperature metallic, intermetallic, and ceramic matrix composites to reduce nozzle weight and meet structural and acoustic component performance goals. This paper describes and discusses the turbomachinery, combustor, and exhaust nozzle requirements of the High Speed Civil Transport propulsion system.

In vivo and in vitro assessment of an intraoral dental colorimeter.

PubMed

Karaagaclioglu, Lale; Terzioglu, Hakan; Yilmaz, Burak; Yurdukoru, Bengul

2010-06-01

The purpose of this study was to assess the performance of an intraoral dental colorimeter. In vivo repeatability of an intraoral colorimeter was assessed by performing color measurements of 30 individuals' right maxillary central incisor. Three consecutive measurements from each individual were made. In the in vitro part of the study, 25 metal-ceramic and 25 all-ceramic specimens were prepared. Five shades of metal-ceramic and all-ceramic specimens were selected for color determination. A widely recognized in vitro colorimeter was used as the control group for the in vitro performance assessment of the in vivo colorimeter. The color differentiation capability of two colorimeters was compared with the readings obtained from ceramic specimens. DeltaE values between shade groups of ceramic specimens were calculated and statistically analyzed with Student's t-test. The repeatability of the intraoral instrument was evaluated statistically with Intraclass correlation coefficient. The in vivo evaluation results showed that the overall repeatability coefficient values of L*, a*, and b* notations of the intraoral colorimeter were "excellent." The color differences (DeltaE) calculated between the colorimeters were significant only between shades A(1)-B(1) for metal-ceramic specimens (p= 0.002); however, from 5 of 10 shade couples of all-ceramic specimens, the color differences obtained from the readings of the in vivo colorimeter were significantly different from that of the in vitro colorimeter (p < 0.001). For all specimens, the differences between DeltaE values were within clinically acceptable limits (<3.5). Within the limitations of this study, the intraoral colorimeter exhibited successful in vivo repeatability; however, the color difference detection performance of the device varied depending on the translucency of the specimens.

Non-planar pad-printed thick-film focused high-frequency ultrasonic transducers for imaging and therapeutic applications.

PubMed

Lethiecq, Marc; Lou-Moeller, Rasmus; Ketterling, Jeffrey; Levassort, Franck; Tran-Huu-Hue, Louis Pascal; Filoux, Erwan; Silverman, Ronald H; Wolny, Wanda W

2012-09-01

Pad-printed thick-film transducers have been shown to be an interesting alternative to lapped bulk piezoceramics, because the film is deposited with the required thickness, size, and geometry, thus avoiding any subsequent machining to achieve geometrical focusing. Their electromechanical properties are close to those of bulk ceramics with similar composition despite having a higher porosity. In this paper, padprinted high-frequency transducers based on a low-loss piezoceramic composition are designed and fabricated. High-porosity ceramic cylinders with a spherical top surface are used as the backing substrate. The transducers are characterized in view of imaging applications and their imaging capabilities are evaluated with phantoms containing spherical inclusions and in different biological tissues. In addition, the transducers are evaluated for their capability to produce high-acoustic intensities at frequencies around 20 MHz. High-intensity measurements, obtained with a calibrated hydrophone, show that transducer performance is promising for applications that would require the same device to be used for imaging and for therapy. Nevertheless, the transducer design can be improved, and simulation studies are performed to find a better compromise between low-power and high-power performance. The size, geometry, and constitutive materials of optimized configurations are proposed and their feasibility is discussed.

Preparation of Co-Zn ferrite nano-based materials and their enhanced magnetic performance via inverse miniemulsion method

NASA Astrophysics Data System (ADS)

Ji, Juejin; Zhang, Zhenqian; Fang, Bijun; Ding, Jianning

2017-11-01

The well dispersed CZF/PAM nanoparticles were prepared by the inverse miniemulsion method, which present high calcining and sintering activity for preparing Co0.875Zn0.125Fe2O4 (CZF) films, powders and ceramics at rather low temperatures. The prepared CZF/PAM inverse miniemulsion exhibits excellent film-formation performance, which is feasible for coating CZF films. XRD and FT-IR measurements confirmed that phase pure spinel structure and well crystalline CZF powders can be prepared calcined at the least temperature of 400 °C. The 450 °C-calcined CZF powders exhibit nearly spherical shape grains with average particle size 20-30 nm accompanied by apparent conglomeration. Improved external magnetic performance and electrical properties are obtained in the synthesized CZF powders and ceramics, which provide versatile promising applications.

MHD oxidant intermediate temperature ceramic heater study

NASA Technical Reports Server (NTRS)

Carlson, A. W.; Chait, I. L.; Saari, D. P.; Marksberry, C. L.

1981-01-01

The use of three types of directly fired ceramic heaters for preheating oxygen enriched air to an intermediate temperature of 1144K was investigated. The three types of ceramic heaters are: (1) a fixed bed, periodic flow ceramic brick regenerative heater; (2) a ceramic pebble regenerative heater. The heater design, performance and operating characteristics under conditions in which the particulate matter is not solidified are evaluated. A comparison and overall evaluation of the three types of ceramic heaters and temperature range determination at which the particulate matter in the MHD exhaust gas is estimated to be a dry powder are presented.

High Temperature Deformation Behavior of YBa2Cu3O6+x Superconducting Ceramic Materials

DTIC Science & Technology

1993-05-15

Mocellin , High Tech. Ceramics, ed P. Vinvinzini, Pub. Elsevier Science Publisher (1986). 15. F. Wakai, S. Sakaguchi and M. Matsuno, Adv. Ceram. Mater...Soc., 68r101, 552 (1985). 18. C. Carry and A. Mocellin , J. Amer. Ceram. Soc., 69f91, C215 (1986). 19. P. C. Panda, E. R. Seydal and R. Raj, US Patent

High pressure ceramic heat exchanger

DOEpatents

Harkins, Bruce D.; Ward, Michael E.

1998-01-01

Many recuperators have components which react to corrosive gases and are used in applications where the donor fluid includes highly corrosive gases. These recuperators have suffered reduced life, increased service or maintenance, and resulted in increased cost. The present header assembly when used with recuperators reduces the brittle effect of a portion of the ceramic components. Thus, the present header assembly used with the present recuperator increases the life, reduces the service and maintenance, and reduces the increased cost associated with corrosive action of components used to manufacture recuperators. The present header assembly is comprised of a first ceramic member, a second ceramic member, a strengthening reinforcing member being in spaced relationship to the first ceramic member and the second ceramic member. The header assembly is further comprised of a refractory material disposed in contacting relationship with the first ceramic member, the second ceramic member and the strengthening reinforcing member. The present header assembly provides a high strength load bearing header assembly having good thermal cycling characteristics, good resistance to a corrosive environment and good steady state strength at elevated temperatures.

High pressure ceramic heat exchanger

DOEpatents

Harkins, Bruce D.; Ward, Michael E.

1999-01-01

Many recuperators have components which react to corrosive gases and are used in applications where the donor fluid includes highly corrosive gases. These recuperators have suffered reduced life, increased service or maintenance, and resulted in increased cost. The present header assembly when used with recuperators reduces the brittle effect of a portion of the ceramic components. Thus, the present header assembly used with the present recuperator increases the life, reduces the service and maintenance, and reduces the increased cost associated with corrosive action of components used to manufacture recuperators. The present header assembly is comprised of a first ceramic member, a second ceramic member, a reinforcing member being in spaced relationship to the first ceramic member and the second ceramic member. The header assembly is further comprised of a refractory material disposed in contacting relationship with the first ceramic member, the second ceramic member and the reinforcing member and having a strengthening member wrapped around the refractory material. The present header assembly provides a high strength load bearing header assembly having good thermal cycling characteristics, good resistance to a corrosive environment and good steady state strength at elevated temperatures.

High pressure ceramic heat exchanger

DOEpatents

Harkins, B.D.; Ward, M.E.

1998-09-22

Many recuperators have components which react to corrosive gases and are used in applications where the donor fluid includes highly corrosive gases. These recuperators have suffered reduced life, increased service or maintenance, and resulted in increased cost. The present header assembly when used with recuperators reduces the brittle effect of a portion of the ceramic components. Thus, the present header assembly used with the present recuperator increases the life, reduces the service and maintenance, and reduces the increased cost associated with corrosive action of components used to manufacture recuperators. The present header assembly is comprised of a first ceramic member, a second ceramic member, a strengthening reinforcing member being in spaced relationship to the first ceramic member and the second ceramic member. The header assembly is further comprised of a refractory material disposed in contacting relationship with the first ceramic member, the second ceramic member and the strengthening reinforcing member. The present header assembly provides a high strength load bearing header assembly having good thermal cycling characteristics, good resistance to a corrosive environment and good steady state strength at elevated temperatures. 5 figs.

Shock-activated reaction synthesis and high pressure response of titanium-based ternary carbide and nitride ceramics

NASA Astrophysics Data System (ADS)

Jordan, Jennifer Lynn

The objectives of this study were to (a) investigate the effect of shock activation of precursor powders for solid-state reaction synthesis of Ti-based ternary ceramics and (b) to determine the high pressure phase stability and Hugoniot properties of Ti3SiC2. Dynamically densified compacts of Ti, SiC, and graphite precursor powders and Ti and AlN precursor powders were used to study the shock-activated formation of Ti 3SiC2 and Ti2AlN ternary compounds, respectively, which are considered to be novel ceramics having high stiffness but low hardness. Gas gun and explosive loading techniques were used to obtain a range of loading conditions resulting in densification and activation. Measurements of fraction reacted as a function of time and temperature and activation energies obtained from DTA experiments were used to determine the degree of activation caused by shock compression and its subsequent effect on the reaction mechanisms and kinetics. In both systems, shock activation led to an accelerated rate of reaction at temperatures less than 1600°C and, above that temperature, it promoted the formation of almost 100% of the ternary compound. A kinetics-based mathematical model based on mass and thermal transport was developed to predict the effect of shock activation and reaction synthesis conditions that ensure formation of the ternary compounds. Model predictions revealed a transition temperature above which the reaction is taken over by the "run-away" combustion-type mode. The high pressure phase stability of pre-alloyed Ti 3SiC2 compound was investigated by performing Hugoniot shock and particle velocity measurements using the facilities at the National Institute for Materials Science (Tsukuba, Japan). Experiments performed at pressures of 95--120 GPa showed that the compressibility of Ti3SiC 2 at these pressures deviates from the previously reported compressibility of the material under static high pressure loading. The deviation in compressibility behavior is indicative of the transformation of the Ti3 SiC2 ceramic to a high pressure, high density phase.

Ceramic components for the AGT 100 engine

NASA Technical Reports Server (NTRS)

Helms, H. E.; Heitman, P. W.

1983-01-01

Historically, automotive gas turbines have not been able to meet requirements of the marketplace with respect to cost, performance, and reliability. However, the development of appropriate ceramic materials has overcome problems related to a need for expensive superalloy components and to limitations regarding the operating temperature. An automotive gas turbine utilizing ceramic components has been developed by a U.S. automobile manufacturer. A 100-horsepower, two-shaft, regenerative engine geometry was selected because it is compatible with manual, automatic, and continuously variable transmissions. Attention is given to the ceramic components, the ceramic gasifier turbine rotor development, the ceramic gasifier scroll, ceramic component testing, and the use of advanced nondestructive techniques for the evaluation of the engine components.

Barium Titanate Nanoparticles: Highly Cytocompatible Dispersions in Glycol-chitosan and Doxorubicin Complexes for Cancer Therapy

NASA Astrophysics Data System (ADS)

Ciofani, Gianni; Danti, Serena; D'Alessandro, Delfo; Moscato, Stefania; Petrini, Mario; Menciassi, Arianna

2010-07-01

In the latest years, innovative nanomaterials have attracted a dramatic and exponentially increasing interest, in particular for their potential applications in the biomedical field. In this paper, we reported our findings on the cytocompatibility of barium titanate nanoparticles (BTNPs), an extremely interesting ceramic material. A rational and systematic study of BTNP cytocompatibility was performed, using a dispersion method based on a non-covalent binding to glycol-chitosan, which demonstrated the optimal cytocompatibility of this nanomaterial even at high concentration (100 μg/ml). Moreover, we showed that the efficiency of doxorubicin, a widely used chemotherapy drug, is highly enhanced following the complexation with BTNPs. Our results suggest that innovative ceramic nanomaterials such as BTNPs can be realistically exploited as alternative cellular nanovectors.

Packaging Technologies for 500 C SiC Electronics and Sensors: Challenges in Material Science and Technology

NASA Technical Reports Server (NTRS)

Chen, Liang-Yu; Neudeck, Philip G.; Behelm, Glenn M.; Spry, David J.; Meredith, Roger D.; Hunter, Gary W.

2015-01-01

This paper presents ceramic substrates and thick-film metallization based packaging technologies in development for 500C silicon carbide (SiC) electronics and sensors. Prototype high temperature ceramic chip-level packages and printed circuit boards (PCBs) based on ceramic substrates of aluminum oxide (Al2O3) and aluminum nitride (AlN) have been designed and fabricated. These ceramic substrate-based chip-level packages with gold (Au) thick-film metallization have been electrically characterized at temperatures up to 550C. The 96 alumina packaging system composed of chip-level packages and PCBs has been successfully tested with high temperature SiC discrete transistor devices at 500C for over 10,000 hours. In addition to tests in a laboratory environment, a SiC junction field-effect-transistor (JFET) with a packaging system composed of a 96 alumina chip-level package and an alumina printed circuit board was tested on low earth orbit for eighteen months via a NASA International Space Station experiment. In addition to packaging systems for electronics, a spark-plug type sensor package based on this high temperature interconnection system for high temperature SiC capacitive pressure sensors was also developed and tested. In order to further significantly improve the performance of packaging system for higher packaging density, higher operation frequency, power rating, and even higher temperatures, some fundamental material challenges must be addressed. This presentation will discuss previous development and some of the challenges in material science (technology) to improve high temperature dielectrics for packaging applications.

High temperature turbine engine structure

DOEpatents

Boyd, Gary L.

1991-01-01

A high temperature turbine engine includes a rotor portion having axially stacked adjacent ceramic rotor parts. A ceramic/ceramic joint structure transmits torque between the rotor parts while maintaining coaxial alignment and axially spaced mutually parallel relation thereof despite thermal and centrifugal cycling.

Laboratory studies on the tribology of hard bearing hip prostheses: ceramic on ceramic and metal on metal.

PubMed

Vassiliou, K; Scholes, S C; Unsworth, A

2007-01-01

Total hip replacements offer relief to a great many patients every year around the world. With an expected service life of around 25 years on most devices, and with younger and younger patients undergoing this surgery, it is of great importance to understand the mechanisms of their function. Tribological testing of both conventional and hard bearing joint combinations have been conducted in many centres throughout the world, and, after being initially abandoned owing to premature failures, hard bearing combinations have been revisited as viable options for joint replacements. Improved design, manufacturing procedures, and material compositions have led to improved performance over first-generation designs in both metal-on-metal and ceramic-on-ceramic hip prostheses. This paper offers a review of the work conducted in an attempt to highlight the most important factors affecting joint performance and tribology of hard bearing combinations. The tribological performance of these joints is superior to that of conventional metal- or ceramic-on-polymer designs.

Method of making a continuous ceramic fiber composite hot gas filter

DOEpatents

Hill, Charles A.; Wagner, Richard A.; Komoroski, Ronald G.; Gunter, Greg A.; Barringer, Eric A.; Goettler, Richard W.

1999-01-01

A ceramic fiber composite structure particularly suitable for use as a hot gas cleanup ceramic fiber composite filter and method of making same from ceramic composite material has a structure which provides for increased strength and toughness in high temperature environments. The ceramic fiber composite structure or filter is made by a process in which a continuous ceramic fiber is intimately surrounded by discontinuous chopped ceramic fibers during manufacture to produce a ceramic fiber composite preform which is then bonded using various ceramic binders. The ceramic fiber composite preform is then fired to create a bond phase at the fiber contact points. Parameters such as fiber tension, spacing, and the relative proportions of the continuous ceramic fiber and chopped ceramic fibers can be varied as the continuous ceramic fiber and chopped ceramic fiber are simultaneously formed on the porous vacuum mandrel to obtain a desired distribution of the continuous ceramic fiber and the chopped ceramic fiber in the ceramic fiber composite structure or filter.

Environmental Barrier Coatings for Silicon-Based Ceramics

NASA Technical Reports Server (NTRS)

Lee, Kang N.; Fox, Dennis S.; Robinson, Raymond C.; Bansal, Narottam P.

2001-01-01

Silicon-based ceramics, such as SiC fiber-reinforced SiC (SiC/SiC ceramic matrix composites (CMC) and monolithic silicon nitride (Si3N4), are prime candidates for hot section structural components of next generation gas turbine engines. Silicon-based ceramics, however, suffer from rapid surface recession in combustion environments due to volatilization of the silica scale via reaction with water vapor, a major product of combustion. Therefore, application of silicon-based ceramic components in the hot section of advanced gas turbine engines requires development of a reliable method to protect the ceramic from environmental attack. An external environmental barrier coating (EBC) is considered a logical approach to achieve protection and CP long-term stability. The first generation EBC consisted of two layers, mullite (3Al2O3-2SiO2) bond coat and yttria-stabilized zirconia (YSZ, ZrO2-8 Wt.% Y2O3) top coat. Second generation EBCs, with substantially improved performance compared with the first generation EBC, were developed in the NASA High Speed Research-Enabling Propulsion Materials (HSR-EPM) Program. The first generation EBC consisted of two layers, mullite (3Al2O3-2SiO2) bond coat and yttria-stabilized zirconia (YSZ, ZrO2-8 wt.% Y2O3) top coat. Second generation EBCs, with substantially improved performance compared with the first generation EBC, were developed in the NASA High Speed Research-Enabling Propulsion Materials (HSR-EPM) Program (5). They consist of three layers, a silicon first bond coat, a mullite or a mullite + BSAS (BaO(1-x)-SrO(x)-Al2O3-2SiO2) second bond coat, and a BSAS top coat. The EPM EBCs were applied on SiC/SiC CMC combustor liners in three Solar Turbines (San Diego, CA) Centaur 50s gas turbine engines. The combined operation of the three engines has accumulated over 24,000 hours without failure (approximately 1,250 C maximum combustor liner temperature), with the engine in Texaco, Bakersfield, CA, accumulating about 14,000 hours. As the commercialization of Si-based ceramic components in gas turbines is on the horizon, a major emphasis is placed on EBCs for two reasons. First, they are absolute necessity for the protection of Si-based ceramics from water vapor. Second, they can enable a major enhancement in the performance of gas turbines by creating temperature gradients with the incorporation of a low thermal conductivity layer. Thorough understanding of current state-of-the-art EBCs will provide the foundation upon which development of future EBCs will be based. Phase stability and thermal conductivity of EPM EBCs are published elsewhere. This paper will discuss the chemical/environmental durability and silica volatility of EPM EBCs and their impact on the coating's upper temperature limit.

78 FR 44315 - Spring 2013 Regulatory Agenda

Federal Register 2010, 2011, 2012, 2013, 2014

2013-07-23

... Structural Clay Products Manufacturing and Clay Ceramics Manufacturing. 238 Standards of Performance 2060... (NESHAP): Brick and Structural Clay Products Manufacturing and Clay Ceramics Manufacturing Legal Authority... pollutants (HF, HCl, and metals) emitted from brick and clay ceramics kilns, as well as dryers and glazing...

Removal of phosphorus by the core-shell bio-ceramic/Zn-layered double hydroxides (LDHs) composites for municipal wastewater treatment in constructed rapid infiltration system.

PubMed

Zhang, Xiangling; Guo, Lu; Huang, Hualing; Jiang, Yinghe; Li, Meng; Leng, Yujie

2016-06-01

Constructed rapid infiltration systems (CRIS) are a reasonable option for treating wastewater, owing to their simplicity, low cost and low energy consumption. Layered double hydroxides (LDHs), novel materials with high surface area and anion exchange capacity, faced the problem of the application in CRIS due to the powdered form. To overcome this shortcoming, Zn-LDHs (FeZn-LDHs, CoZn-LDHs, AlZn-LDHs) were prepared by co-precipitation method and in-situ coated on the surface of the natural bio-ceramic to synthesize the core-shell bio-ceramic/Zn-LDHs composites. Characterization by Scanning Electron Microscope (SEM) and X-ray Fluorescence Spectrometer (XRFS) indicated that the Zn-LDHs were successful loaded on the natural bio-ceramic. Column tests experiments indicated that the bio-ceramic/Zn-LDHs efficiently enhanced the removal performance of phosphorus. The efficiently removal rates of bio-ceramic/FeZn-LDHs were 71.58% for total phosphorous (TP), 74.91% for total dissolved phosphorous (TDP), 82.31% for soluble reactive phosphorous (SRP) and 67.58% for particulate phosphorus (PP). Compared with the natural bio-ceramic, the average removal rates were enhanced by 32.20% (TP), 41.33% (TDP), 49.06% (SRP) and 10.50% (PP), respectively. Adsorption data of phosphate were better described by the Freundlich model for the bio-ceramic/Zn-LDHs and natural bio-ceramic, except for the bio-ceramic/CoZn-LDHs. The maximum adsorption capacity of bio-ceramic/AlZn-LDHs (769.23 mg/kg) was 1.77 times of the natural bio-ceramic (434.78 mg/kg). The effective desorption of phosphate could achieve by using a mixed solution of 5 M NaCl + 0.1 M NaOH, it outperformed the natural bio-ceramic of 18.95% for FeZn-LDHs, 7.59% for CoZn-LDHs and 12.66% for AlZn-LDHs. The kinetic data of the bio-ceramic/Zn-LDHs were better described by the pseudo-second-order equation. Compared the removal amount of phosphate by the natural bio-ceramic, the physical effects were improved little, but the chemical effects were enhanced for 112.49% for FeZn-LDHs, 111.89% for CoZn-LDHs and 122.67% for AlZn-LDHs. Therefore, the way of coating Zn-LDHs on the bio-ceramic efficiently improved the chemical effects in phosphate removal, supporting that it can use as potential substrates for the removal of phosphorus in CRIS. Copyright © 2016 Elsevier Ltd. All rights reserved.

Preparation of Ceramic-Bonded Carbon Block for Blast Furnace

NASA Astrophysics Data System (ADS)

Li, Yiwei; Li, Yawei; Sang, Shaobai; Chen, Xilai; Zhao, Lei; Li, Yuanbing; Li, Shujing

2014-01-01

Traditional carbon blocks for blast furnaces are mainly produced with electrically calcined anthracite owing to its good hot metal corrosion resistance. However, this kind of material shows low thermal conductivity and does not meet the demands for cooling of the hearth and the bottom of blast furnaces. In this article, a new kind of a high-performance carbon block has been prepared via ceramic-bonded carbon (CBC) technology in a coke bed at 1673 K (1400 °C) using artificial graphite aggregate, alumina, metallic aluminum, and silicon powders as starting materials. The results showed that artificial graphite aggregates were strongly bonded by the three-dimensional network of ceramic phases in carbon blocks. In this case, the good resistance of the CBC blocks against erosion/corrosion by the hot metal is provided by the ceramic matrix and the high thermal conductivity by the graphite aggregates. The microstructure of this carbon block resembles that of CBC composites with a mean pore size of less than 0.1 μm, and up to 90 pct of the porosity shows a pore size <1 μm. Its thermal conductivity is higher than 30 W · m-1 · K-1 [293 K (20 °C)]. Meanwhile, its hot metal corrosion resistance is better than that of traditional carbon blocks.

Single Side Electrolytic In-Process Dressing (ELID) Grinding with Lapping Kinematics of Silicon Carbide

NASA Astrophysics Data System (ADS)

Khoshaim, Ahmed Bakr

The demand for Silicon Carbide ceramics (SiC) has increased significantly in the last decade due to its reliable physical and chemical properties. The silicon carbide is widely used for aerospace segments in addition to many uses in the industry. Sometimes, a single side grinding is preferable than conventional grinding, for it has the ability to produce flat ceramics. However, the manufacturing cost is still high because of the high tool wear and long machining time. Part of the solution is to use electrolytic in process dressing (ELID) to reduce the processing time. The study on ELID single side grinding of ceramics has never been attempted before. The study involves four variables with three levels each. One of the variables, which is the eccentricity, is being investigated for the first time on ceramics. A full factorial design, for both the surface roughness and material removal rate, guides to calculate mathematical models that can predict future results. Three grinding wheel mesh sizes are used. An investigation of the influence of different grain size on the results can then be evaluated. The kinematics of the process was studied based on eccentricity in order to optimize the pattern of the diamond grains. The experiment is performed with the assist of the proposed specialized ELID fluid, TRIM C270E.

Wear properties of alumina/zirconia composite ceramics for joint prostheses measured with an end-face apparatus.

PubMed

Morita, Yusuke; Nakata, Kenichi; Kim, Yoon-Ho; Sekino, Tohru; Niihara, Koichi; Ikeuchi, Ken

2004-01-01

While only alumina is applied to all-ceramic joint prostheses at present, a stronger ceramic is required to prevent fracture and chipping due to impingement and stress concentration. Zirconia could be a potential substitute for alumina because it has high strength and fracture toughness. However, the wear of zirconia/zirconia combination is too high for clinical use. Although some investigations on composite ceramics revealed that mixing of different ceramics was able to improve the mechanical properties of ceramics, there are few reports about wear properties of composite ceramics for joint prosthesis. Since acetabular cup and femoral head of artificial hip joint are finished precisely, they indicate high geometric conformity. Therefore, wear test under flat contact was carried out with an end-face wear testing apparatus for four kinds of ceramics: alumina monolith, zirconia monolith, alumina-based composite ceramic, and zirconia based composite ceramic. Mean contact pressure was 10 MPa and sliding velocity was 40 mm/s. The wear test continued for 72 hours and total sliding distance was 10 km. After the test, the wear factor was calculated. Worn surfaces were observed with a scanning electron micrograph (SEM). The results of this wear test show that the wear factors of the both composite ceramics are similarly low and their mechanical properties are much better than those of the alumina monolith and the zirconia monolith. According to these results, it is predicted that joint prostheses of the composite ceramics are safer against break down and have longer lifetime compared with alumina/alumina joint prostheses.

Needs assessment for nondestructive testing and materials characterization for improved reliability in structural ceramics for heat engines

DOE Office of Scientific and Technical Information (OSTI.GOV)

Johnson, D.R.; McClung, R.W.; Janney, M.A.

1987-08-01

A needs assessment was performed for nondestructive testing and materials characterization to achieve improved reliability in ceramic materials for heat engine applications. Raw materials, green state bodies, and sintered ceramics were considered. The overall approach taken to improve reliability of structural ceramics requires key inspections throughout the fabrication flowsheet, including raw materials, greed state, and dense parts. The applications of nondestructive inspection and characterization techniques to ceramic powders and other raw materials, green ceramics, and sintered ceramics are discussed. The current state of inspection technology is reviewed for all identified attributes and stages of a generalized flowsheet for advanced structuralmore » ceramics, and research and development requirements are identified and listed in priority order. 164 refs., 3 figs.« less

Film Cooled Recession of SiC/SiC Ceramic Matrix Composites: Test Development, CFD Modeling and Experimental Observations

NASA Technical Reports Server (NTRS)

Zhu, Dongming; Sakowski, Barbara A.; Fisher, Caleb

2014-01-01

SiCSiC ceramic matrix composites (CMCs) systems will play a crucial role in next generation turbine engines for hot-section component applications because of their ability to significantly increase engine operating temperatures, reduce engine weight and cooling requirements. However, the environmental stability of Si-based ceramics in high pressure, high velocity turbine engine combustion environment is of major concern. The water vapor containing combustion gas leads to accelerated oxidation and corrosion of the SiC based ceramics due to the water vapor reactions with silica (SiO2) scales forming non-protective volatile hydroxide species, resulting in recession of the ceramic components. Although environmental barrier coatings are being developed to help protect the CMC components, there is a need to better understand the fundamental recession behavior of in more realistic cooled engine component environments.In this paper, we describe a comprehensive film cooled high pressure burner rig based testing approach, by using standardized film cooled SiCSiC disc test specimen configurations. The SiCSiC specimens were designed for implementing the burner rig testing in turbine engine relevant combustion environments, obtaining generic film cooled recession rate data under the combustion water vapor conditions, and helping developing the Computational Fluid Dynamics (CFD) film cooled models and performing model validation. Factors affecting the film cooled recession such as temperature, water vapor concentration, combustion gas velocity, and pressure are particularly investigated and modeled, and compared with impingement cooling only recession data in similar combustion flow environments. The experimental and modeling work will help predict the SiCSiC CMC recession behavior, and developing durable CMC systems in complex turbine engine operating conditions.

A High-Performing Sulfur-Tolerant and Redox-Stable Layered Perovskite Anode for Direct Hydrocarbon Solid Oxide Fuel Cells

PubMed Central

Ding, Hanping; Tao, Zetian; Liu, Shun; Zhang, Jiujun

2015-01-01

Development of alternative ceramic oxide anode materials is a key step for direct hydrocarbon solid oxide fuel cells (SOFCs). Several lanthanide based layered perovskite-structured oxides demonstrate outstanding oxygen diffusion rate, favorable electronic conductivity, and good oxygen surface exchange kinetics, owing to A-site ordered structure in which lanthanide and alkali-earth ions occupy alternate (001) layers and oxygen vacancies are mainly located in [LnOx] planes. Here we report a nickel-free cation deficient layered perovskite, (PrBa)0.95(Fe0.9Mo0.1)2O5 + δ (PBFM), for SOFC anode, and this anode shows an outstanding performance with high resistance against both carbon build-up and sulfur poisoning in hydrocarbon fuels. At 800 °C, the layered PBFM showed high electrical conductivity of 59.2 S cm−1 in 5% H2 and peak power densities of 1.72 and 0.54 W cm−2 using H2 and CH4 as fuel, respectively. The cell exhibits a very stable performance under a constant current load of 1.0 A cm−2. To our best knowledge, this is the highest performance of ceramic anodes operated in methane. In addition, the anode is structurally stable at various fuel and temperature conditions, suggesting that it is a feasible material candidate for high-performing SOFC anode. PMID:26648509

A High-Performing Sulfur-Tolerant and Redox-Stable Layered Perovskite Anode for Direct Hydrocarbon Solid Oxide Fuel Cells

NASA Astrophysics Data System (ADS)

Ding, Hanping; Tao, Zetian; Liu, Shun; Zhang, Jiujun

2015-12-01

Development of alternative ceramic oxide anode materials is a key step for direct hydrocarbon solid oxide fuel cells (SOFCs). Several lanthanide based layered perovskite-structured oxides demonstrate outstanding oxygen diffusion rate, favorable electronic conductivity, and good oxygen surface exchange kinetics, owing to A-site ordered structure in which lanthanide and alkali-earth ions occupy alternate (001) layers and oxygen vacancies are mainly located in [LnOx] planes. Here we report a nickel-free cation deficient layered perovskite, (PrBa)0.95(Fe0.9Mo0.1)2O5 + δ (PBFM), for SOFC anode, and this anode shows an outstanding performance with high resistance against both carbon build-up and sulfur poisoning in hydrocarbon fuels. At 800 °C, the layered PBFM showed high electrical conductivity of 59.2 S cm-1 in 5% H2 and peak power densities of 1.72 and 0.54 W cm-2 using H2 and CH4 as fuel, respectively. The cell exhibits a very stable performance under a constant current load of 1.0 A cm-2. To our best knowledge, this is the highest performance of ceramic anodes operated in methane. In addition, the anode is structurally stable at various fuel and temperature conditions, suggesting that it is a feasible material candidate for high-performing SOFC anode.

A High-Performing Sulfur-Tolerant and Redox-Stable Layered Perovskite Anode for Direct Hydrocarbon Solid Oxide Fuel Cells.

PubMed

Ding, Hanping; Tao, Zetian; Liu, Shun; Zhang, Jiujun

2015-12-09

Development of alternative ceramic oxide anode materials is a key step for direct hydrocarbon solid oxide fuel cells (SOFCs). Several lanthanide based layered perovskite-structured oxides demonstrate outstanding oxygen diffusion rate, favorable electronic conductivity, and good oxygen surface exchange kinetics, owing to A-site ordered structure in which lanthanide and alkali-earth ions occupy alternate (001) layers and oxygen vacancies are mainly located in [LnOx] planes. Here we report a nickel-free cation deficient layered perovskite, (PrBa)0.95(Fe0.9Mo0.1)2O5 + δ (PBFM), for SOFC anode, and this anode shows an outstanding performance with high resistance against both carbon build-up and sulfur poisoning in hydrocarbon fuels. At 800 °C, the layered PBFM showed high electrical conductivity of 59.2 S cm(-1) in 5% H2 and peak power densities of 1.72 and 0.54 W cm(-2) using H2 and CH4 as fuel, respectively. The cell exhibits a very stable performance under a constant current load of 1.0 A cm(-2). To our best knowledge, this is the highest performance of ceramic anodes operated in methane. In addition, the anode is structurally stable at various fuel and temperature conditions, suggesting that it is a feasible material candidate for high-performing SOFC anode.

Trends of microwave dielectric materials for antenna application

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sulong, T. A. T., E-mail: tuanamirahtuansulong@gmail.com; Osman, R. A. M., E-mail: rozana@unimap.edu.my; Idris, M. S., E-mail: sobri@unimap.edu.my

Rapid development of a modern microwave communication system requires a high quality microwave dielectric ceramic material to be used as mobile and satellite communication. High permittivity of dielectric ceramics leads to fabrication of compact device for electronic components. Dielectric ceramics which used for microwave applications required three important parameters such as high or appropriate permittivity (ε{sub r}), high quality factor (Q {sub f} ≥ 5000 GH z) and good temperature coefficient of resonant frequency (τ{sub f}). This paper review of various dielectric ceramic materials used as microwave dielectric materials and related parameters for antenna applications.

Development and evaluation of magnesium oxide-based ceramics for chamber parts in mass-production plasma etching equipment

NASA Astrophysics Data System (ADS)

Kasashima, Yuji; Tsutsumi, Kota; Mitomi, Shinzo; Uesugi, Fumihiko

2017-06-01

In mass-production plasma etching equipment, the corrosion of ceramic chamber parts reduces the production yield of LSI and overall equipment effectiveness (OEE) owing to contamination, short useful life, and particle generation. Novel ceramics that can improve the production yield and OEE are highly required. We develop magnesium oxide (MgO)-based ceramics and evaluate them under mass-production plasma etching conditions. The results of this study indicate that the developed MgO-based ceramics with high mechanical properties and low electric resistivity have a higher resistance to corrosion in plasma etching using CF4 gas than Si and conventional ceramic materials such as aluminum oxide and yttrium oxide.

An evaluation of the electric arc spray and (HPPS) processes for the manufacturing of high power plasma spraying MCrAIY coatings

NASA Astrophysics Data System (ADS)

Sacriste, D.; Goubot, N.; Dhers, J.; Ducos, M.; Vardelle, A.

2001-06-01

The high power plasma torch (PlazJet) can be used to spray refractory ceramics with high spray rates and deposition efficiency. It can provide dense and hard coating with high bond strengths. When manufacturing thermal barrier coatings, the PlazJet gun is well adapted to spraying the ceramic top coat but not the MCrAIY materials that are used as bond coat. Arc spraying can compete with plasma spraying for metallic coatings since cored wires can be used to spray alloys and composites. In addition, the high production rate of arc spraying enables a significant decrease in coating cost. This paper discusses the performances of the PlazJet gun, and a twin-wire are spray system, and compares the properties and cost of MCrAIY coatings made with these two processes. For arc spraying, the use of air or nitrogen as atomizing gas is also investigated.

Dynamic plasticity and failure of high-purity alumina under shock loading.

PubMed

Chen, M W; McCauley, J W; Dandekar, D P; Bourne, N K

2006-08-01

Most high-performance ceramics subjected to shock loading can withstand high failure strength and exhibit significant inelastic strain that cannot be achieved under conventional loading conditions. The transition point from elastic to inelastic response prior to failure during shock loading, known as the Hugoniot elastic limit (HEL), has been widely used as an important parameter in the characterization of the dynamic mechanical properties of ceramics. Nevertheless, the underlying micromechanisms that control HEL have been debated for many years. Here we show high-resolution electron microscopy of high-purity alumina, soft-recovered from shock-loading experiments. The change of deformation behaviour from dislocation activity in the vicinity of grain boundaries to deformation twinning has been observed as the impact pressures increase from below, to above HEL. The evolution of deformation modes leads to the conversion of material failure from an intergranular mode to transgranular cleavage, in which twinning interfaces serve as the preferred cleavage planes.

High-power piezoelectric characteristics of textured bismuth layer structured ferroelectric ceramics.

PubMed

Ogawa, Hirozumi; Kawada, Shinichiro; Kimura, Masahiko; Shiratsuyu, Kousuke; Sakabe, Yukio

2007-12-01

Abstract-The high-power piezoelectric characteristics in h001i oriented ceramics of bismuth layer structured ferroelectrics (BLSF), SrBi(2)Nb(2)O(9) (SBN), (Bi,La)(4)Ti(3)O(12) (BLT), and CaBi(4)Ti(4)O(15) (CBT), were studied by a constant voltage driving method. These textured ceramics were fabricated by a templated grain growth (TGG) method, and their Lotgering factors were 95%, 97%, and 99%, respectively. The vibration velocities of the longitudinal mode (33-mode) increased proportionally to an applied electric field up to 2.5 m/s in these textured BLSF ceramics, although, the vibration velocity of the 33-mode was saturated at more than 1.0 m/s in the Pb(Mn,Nb)O(3)-PZT ceramics. The resonant frequencies were constant up to the vibration velocity of 2.5 m/s in the SBN and CBT textured ceramics; however, the resonant frequency decreased with increasing over the vibration velocity of 1.5 m/s in the BLT textured ceramics. The dissipation power density of the BLT was almost the same as that of the Pb(Mn,Nb)O(3)-PZT ceramics. However, the dissipation power densities of the SBN and CBT were lower than those of the BLT and Pb(Mn,Nb)O(3)-PZT ceramics. The textured SBN and CBT ceramics are good candidates for high-power piezoelectric applications.

Evaluation of a Silver-Embedded Ceramic Tablet as a Primary and Secondary Point-of-Use Water Purification Technology in Limpopo Province, S. Africa

PubMed Central

Ehdaie, Beeta; Rento, Chloe T.; Son, Veronica; Turner, Sydney S.; Samie, Amidou; Dillingham, Rebecca A.

2017-01-01

The World Health Organization (WHO) recognizes point-of-use water treatment (PoUWT) technologies as effective means to improve water quality. This paper investigates long-term performance and social acceptance of a novel PoUWT technology, a silver-infused ceramic tablet, in Limpopo Province, South Africa. When placed in a water storage container, the silver-embedded ceramic tablet releases silver ions into water, thereby disinfecting microbial pathogens and leaving the water safe for human consumption. As a result of its simplicity and efficiency, the silver-embedded ceramic tablet can serve as a stand-alone PoUWT method and as a secondary PoUWT to improve exisitng PoUWT methods, such as ceramic water filters. In this paper, three PoUWT interventions were conducted to evaluate the silver-embedded ceramic tablet: (1) the silver-embedded ceramic tablet as a stand-alone PoUWT method, (2) ceramic water filters stand-alone, and (3) a filter-tablet combination. The filter-tablet combination evaluates the silver-embedded ceramic tablet as a secondary PoUWT method when placed in the lower reservoir of the ceramic water filter system to provide residual disinfection post-filtration. Samples were collected from 79 households over one year and analyzed for turbidity, total silver levels and coliform bacteria. Results show that the silver-embedded ceramic tablet effectively reduced total coliform bacteria (TC) and E. coli when used as a stand-alone PoUWT method and when used in combination with ceramic water filters. The silver-embedded ceramic tablet’s performance as a stand-alone PoUWT method was comparable to current inexpensive, single-use PoUWT methods, demonstrating 100% and 75% median reduction in E. coli and TC, respectively, after two months of use. Overall, the the filter-tablet combination performed the best of the three interventions, providing a 100% average percent reduction in E. coli over one year. User surveys were also conducted and indicated that the silver-embedded ceramic tablet was simple to use and culturally appropriate. Also, silver levels in all treated water samples remained below 20 μg/L, significantly lower than the drinking water standard of 100 μg/L, making it safe for consumption. Long-term data demonstrates that the silver-embedded ceramic tablet has beneficial effects even after one year of use. This study demonstrates that the silver-embedded ceramic tablet can effectively improve water quality when used alone, or with ceramic water filters, to reduce rates of recontamination. Therefore, the tablet has the potential to provide a low-cost means to purify water in resource-limited settings. PMID:28095435

Evaluation of a Silver-Embedded Ceramic Tablet as a Primary and Secondary Point-of-Use Water Purification Technology in Limpopo Province, S. Africa.

PubMed

Ehdaie, Beeta; Rento, Chloe T; Son, Veronica; Turner, Sydney S; Samie, Amidou; Dillingham, Rebecca A; Smith, James A

2017-01-01

The World Health Organization (WHO) recognizes point-of-use water treatment (PoUWT) technologies as effective means to improve water quality. This paper investigates long-term performance and social acceptance of a novel PoUWT technology, a silver-infused ceramic tablet, in Limpopo Province, South Africa. When placed in a water storage container, the silver-embedded ceramic tablet releases silver ions into water, thereby disinfecting microbial pathogens and leaving the water safe for human consumption. As a result of its simplicity and efficiency, the silver-embedded ceramic tablet can serve as a stand-alone PoUWT method and as a secondary PoUWT to improve exisitng PoUWT methods, such as ceramic water filters. In this paper, three PoUWT interventions were conducted to evaluate the silver-embedded ceramic tablet: (1) the silver-embedded ceramic tablet as a stand-alone PoUWT method, (2) ceramic water filters stand-alone, and (3) a filter-tablet combination. The filter-tablet combination evaluates the silver-embedded ceramic tablet as a secondary PoUWT method when placed in the lower reservoir of the ceramic water filter system to provide residual disinfection post-filtration. Samples were collected from 79 households over one year and analyzed for turbidity, total silver levels and coliform bacteria. Results show that the silver-embedded ceramic tablet effectively reduced total coliform bacteria (TC) and E. coli when used as a stand-alone PoUWT method and when used in combination with ceramic water filters. The silver-embedded ceramic tablet's performance as a stand-alone PoUWT method was comparable to current inexpensive, single-use PoUWT methods, demonstrating 100% and 75% median reduction in E. coli and TC, respectively, after two months of use. Overall, the the filter-tablet combination performed the best of the three interventions, providing a 100% average percent reduction in E. coli over one year. User surveys were also conducted and indicated that the silver-embedded ceramic tablet was simple to use and culturally appropriate. Also, silver levels in all treated water samples remained below 20 μg/L, significantly lower than the drinking water standard of 100 μg/L, making it safe for consumption. Long-term data demonstrates that the silver-embedded ceramic tablet has beneficial effects even after one year of use. This study demonstrates that the silver-embedded ceramic tablet can effectively improve water quality when used alone, or with ceramic water filters, to reduce rates of recontamination. Therefore, the tablet has the potential to provide a low-cost means to purify water in resource-limited settings.

Porous zirconia ceramic as an alternative to dentin for in vitro dentin barriers cytotoxicity test.

PubMed

Hu, Meng-Long; Lin, Hong; Jiang, Ruo-Dan; Dong, Li-Min; Huang, Lin; Zheng, Gang

2018-06-01

This study assessed the potential of porous zirconia ceramic as an alternative to dentin via an in vitro dentin barrier cytotoxicity test. The permeability of dentin and porous zirconia ceramic was measured using a hydraulic-conductance system, and their permeability was divided into two groups: high and low. Using an in vitro dentin barrier test, the cytotoxicity of dental materials by dentin and porous zirconia ceramic was compared within the same permeability group. The L-929 cell viability was assessed by MTT assay. The mean (SD) permeability of the high and low group for dentin was 0.334 (0.0873) and 0.147 (0.0377) μl min -1  cm -2  cm H 2 O -1 and for zirconia porous ceramic was 0.336 (0.0609) and 0.146 (0.0340) μl min -1  cm -2  cm H 2 O -1 . The cell viability of experimental groups which are the low permeability group was higher than that of the high permeability group for both dentin and porous zirconia ceramic as a barrier except for Maxcem Elite ™ by porous zirconia ceramic. There was no significant difference between dentin and porous zirconia ceramic in cell viability, within either the high or low permeability group for all materials. The SD for cell viability of the porous zirconia ceramic was less than that of the dentin, across all materials within each permeability group, except for Maxcem Elite ™ in the high permeability group. Porous zirconia ceramic, having similar permeability to dentin at the same thickness, can be used as an alternative to dentin for in vitro dentin barrier cytotoxicity tests. In vitro dentin barrier cytotoxicity tests when a standardized porous zirconia ceramic was used as a barrier could be useful for assessing the potential toxicity of new dental materials applied to dentin before applying in clinical and may resolve the issue of procuring human teeth when testing proceeds.

Fracture Toughness and Reliability in High-Temperature Structural Ceramics and Composites: Prospects and Challenges for the 21st Century

NASA Technical Reports Server (NTRS)

Dutta, Sunil

1999-01-01

The importance of high fracture toughness and reliability in Si3N4, and SiC-based structural ceramics and ceramic matrix composites is reviewed. The potential of these ceramics and ceramic matrix composites for high temperature applications in defense and aerospace applications such as gas turbine engines, radomes, and other energy conversion hardware have been well recognized. Numerous investigations were pursued to improve fracture toughness and reliability by incorporating various reinforcements such as particulate-, whisker-, and continuous fiber into Si3N4 and SiC matrices. All toughening mechanisms, e.g. crack deflection, crack branching, crack bridging, etc., essentially redistribute stresses at the crack tip and increase the energy needed to propagate a crack through the composite material, thereby resulting in improved fracture toughness and reliability. Because of flaw insensitivity, continuous fiber reinforced ceramic composite (CFCC) was found to have the highest potential for higher operating temperature and longer service conditions. However, the ceramic fibers should display sufficient high temperature strength and creep resistance at service temperatures above 1000 'C. The greatest challenge to date is the development of high quality ceramic fibers with associate coatings able to maintain their high strength in oxidizing environment at high temperature. In the area of processing, critical issues are, preparation of optimum matrix precursors, precursor infiltration into fiber array, and matrix densification at a temperature, where grain crystallization and fiber degradation do not occur. A broad scope of effort is required for improved processing and properties with a better understanding of all candidate composite systems.

Analysis of grinding of superalloys and ceramics for off-line process optimization

NASA Astrophysics Data System (ADS)

Sathyanarayanan, G.

The present study has compared the performances of resinoid, vitrified, and electroplated CBN wheels in creep feed grinding of M42 and D2 tool steels. Responses such as a specific energy, normal and tangential forces, and surface roughness were used as measures of performance. It was found that creep feed grinding with resinoid, vitrified, and electroplated CBN wheels has its own advantages, but no single wheel could provide good finish, lower specific energy, and high material removal rates simultaneously. To optimize the CBN grinding with different bonded wheels, a Multiple Criteria Decision Making (MCDM) methodology was used. Creep feed grinding of superalloys, Ti-6Al-4V and Inconel 718, has been modeled by utilizing neural networks to optimize the grinding process. A parallel effort was directed at creep feed grinding of alumina ceramics with diamond wheels to investigate the influence of process variables on responses based on experimental results and statistical analysis. The conflicting influence of variables was observed. This led to the formulation of ceramic grinding process as a multi-objective nonlinear mixed integer problem.

Microstructure and High Temperature Oxidation Property of Fe-Cr-B Based Metal/Ceramic Composite Manufactured by Powder Injection Molding Process

NASA Astrophysics Data System (ADS)

Joo, Yeun-Ah; Kim, Young-Kyun; Yoon, Tae-Sik; Lee, Kee-Ahn

2018-03-01

This study investigated the microstructure and high temperature oxidation property of Fe-Cr-B metal/ceramic composite manufactured using powder injection molding process. Observations of initial microstructure showed a unique structure where α-Fe and (Cr, Fe)2B form a continuous three-dimensional network. High temperature oxidation tests were performed at 900, 1000 and 1100 °C, for 24 h, and the oxidation weight gain according to each temperature condition was 0.13, 0.84 and 6.4 mg/cm2, respectively. The oxidation results according to time at 900 and 1000 °C conditions represented parabolic curves, and at 1100 °C condition formed a rectilinear curve. Observation and phase analysis results of the oxides identified Cr2O3 and SiO2 at 900 and 1000 °C. In addition to Cr2O3 and SiO2, CrBO3 and FeCr2O4 formed due to phase decomposition of boride were identified at 1100 °C. Based on the findings above, this study suggested the high temperature oxidation mechanism of Fe-Cr-B metal/ceramic composite manufactured using powder injection molding, and the possibility of its application as a high temperature component material was also discussed.

JTEC panel report on advanced composites in Japan

NASA Technical Reports Server (NTRS)

Diefendorf, R. J.; Grisaffe, S. J.; Hillig, W. B.; Perepezko, J. H.; Pipes, R. B.; Sheehan, J. E.

1991-01-01

The JTEC Panel on Advanced Composites visited Japan and surveyed the status and future directions of Japanese high performance ceramic and carbon fibers and their composites in metal, intermetallic, ceramic and carbon matrices. The panel's interests included not only what composite systems were chosen, but also how these systems were developed. A strong carbon and fiber industry makes Japan the leader in carbon fiber technology. Japan has initiated an oxidation resistant carbon/carbon composite program. The goals for this program are ambitious, and it is just starting, but its progress should be closely monitored in the United States.

Performance enhancement of direct ethanol fuel cell using Nafion composites with high volume fraction of titania

NASA Astrophysics Data System (ADS)

Matos, B. R.; Isidoro, R. A.; Santiago, E. I.; Fonseca, F. C.

2014-12-01

The present study reports on the performance enhancement of direct ethanol fuel cell (DEFC) at 130 °C with Nafion-titania composite electrolytes prepared by sol-gel technique and containing high volume fractions of the ceramic phase. It is found that for high volume fractions of titania (>10 vol%) the ethanol uptake of composites is largely reduced while the proton conductivity at high-temperatures is weakly dependent on the titania content. Such tradeoff between alcohol uptake and conductivity resulted in a boost of DEFC performance at high temperatures using Nafion-titania composites with high fraction of the inorganic phase.

Challenges and Opportunities in Reactive Processing and Applications of Advanced Ceramic Materials

NASA Technical Reports Server (NTRS)

Singh, Mrityunjay

2003-01-01

Recently, there has been a great deal of interest in the research, development, and commercialization of innovative synthesis and processing technologies for advanced ceramics and composite materials. Reactive processing approaches have been actively considered due to their robustness, flexibility, and affordability. A wide variety of silicon carbide-based advanced ceramics and composites are currently being fabricated using the processing approaches involving reactive infiltration of liquid and gaseous species into engineered fibrous or microporous carbon performs. The microporous carbon performs have been fabricated using the temperature induced phase separation and pyrolysis of two phase organic (resin-pore former) mixtures and fiber reinforcement of carbon and ceramic particulate bodies. In addition, pyrolyzed native plant cellulose tissues also provide unique carbon templates for manufacturing of non-oxide and oxide ceramics. In spite of great interest in this technology due to their affordability and robustness, there is a lack of scientific basis for process understanding and many technical challenges still remain. The influence of perform properties and other parameters on the resulting microstructure and properties of final material is not well understood. In this presentation, mechanism of silicon-carbon reaction in various systems and the effect of perform microstructure on the mechanical properties of advanced silicon carbide based materials will be discussed. Various examples of applications of reactively processed advanced silicon carbide ceramics and composite materials will be presented.

Innovative manufacturing and materials for low cost lithium ion batteries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Carlson, Steven

2015-12-29

This project demonstrated entirely new manufacturing process options for lithium ion batteries with major potential for improved cost and performance. These new manufacturing approaches are based on the use of the new electrode-coated separators instead of the conventional electrode-coated metal current collector foils. The key enabler to making these electrode-coated separators is a new and unique all-ceramic separator with no conventional porous plastic separator present. A simple, low cost, and high speed manufacturing process of a single coating of a ceramic pigment and polymer binder onto a re-usable release film, followed by a subsequent delamination of the all-ceramic separator andmore » any layers coated over it, such as electrodes and metal current collectors, was utilized. A suitable all-ceramic separator was developed that demonstrated the following required features needed for making electrode-coated separators: (1) no pores greater than 100 nanometer (nm) in diameter to prevent any penetration of the electrode pigments into the separator; (2) no shrinkage of the separator when heated to the high oven heats needed for drying of the electrode layer; and (3) no significant compression of the separator layer by the high pressure calendering step needed to densify the electrodes by about 30%. In addition, this nanoporous all-ceramic separator can be very thin at 8 microns thick for increased energy density, while providing all of the performance features provided by the current ceramic-coated plastic separators used in vehicle batteries: improved safety, longer cycle life, and stability to operate at voltages up to 5.0 V in order to obtain even more energy density. The thin all-ceramic separator provides a cost savings of at least 50% for the separator component and by itself meets the overall goal of this project to reduce the cell inactive component cost by at least 20%. The all-ceramic separator also enables further cost savings by its excellent heat stability with no shrinkage at up to 220oC. This allows vacuum drying of the dry cell just before filling with the electrolyte and thereby can reduce the size of the cell assembly dry room by 50%. Once the electrode-coated separator is produced, there are many different approaches for adding the metal current collector layers and making and connecting the tabs of the cells. These approaches include: (1) laminating the electrode side of the electrode-coated separator to both sides of a metal current collector; and (2) making a full coated electrode stack by coating or depositing a current collector layer on the electrode side and then coating a second electrode layer onto the current collector. Further cost savings are available from using lower cost and/or thinner and lighter current collectors and from using a separator coating manufacturing process at widths of 1.5 meters (m) or more and at high production line speeds of up to 125 meters per minute (mpm), both of which are well above the conventional coating widths and line speeds presently used in manufacturing electrodes for lithium ion batteries.« less

Structure and electrical properties of <001> textured (Ba0.85Ca0.15)(Ti0.9Zr0.1)O3 lead-free piezoelectric ceramics

NASA Astrophysics Data System (ADS)

Ye, S. K.; Fuh, J. Y. H.; Lu, L.

2012-06-01

<001> textured (Ba0.85Ca0.15)(Ti0.9Zr0.1)O3 (BCTZ) lead-free piezoelectric ceramics were prepared by templated-grain growth method using BaTiO3 as template. The degree of orientation and the microstructure of the ceramics with different amount of template were investigated. The electrical properties of the textured-ceramics in the optimized condition were dramatically enhanced compared with randomly-oriented BCTZ ceramics. The textured BCTZ ceramics showed high piezoelectric constants d33 = 470 pC/N and d31 = -170 pC/N, and high electromechanical coupling factors kp = 44% and k31 = 22%. In addition, the Curie point of the textured ceramics revealed an increase with the template content.

A comparative study of progressive wear of four dental monolithic, veneered glass-ceramics.

PubMed

Zhang, Zhenzhen; Yi, Yuanping; Wang, Xuesong; Guo, Jiawen; Li, Ding; He, Lin; Zhang, Shaofeng

2017-10-01

This study evaluated the wear performance and wear mechanisms of four dental glass-ceramics, based on the microstructure and mechanical properties in the progressive wear process. Bar (N = 40, n = 10) and disk (N = 32, n = 8) specimens were prepared from (A) lithium disilicate glass-ceramic (LD), (B) leucite reinforced glass-ceramic (LEU), (C) feldspathic glass-ceramic (FEL), and (D) fluorapatite glass-ceramic (FLU). The bar specimens were tested for three-point flexural strength, hardness, fracture toughness and elastic modulus. The disk specimens paired with steatite antagonists were tested in a pin-on-disk tribometer with 10N up to 1000,000 wear cycles. The wear analysis of glass-ceramics was performed using a 3D profilometer after every 200,000 wear cycles. Wear loss of steatite antagonists was calculated by measuring the weight and density using sensitive balance and Archimedes' method. Wear morphologies and microstructures were analyzed by scanning electron microscopy (SEM). The crystalline phase compositions were determined using X-ray diffraction (XRD). One-way analysis of variance (ANOVA) was used to analyze the data. Multiple pair-wise comparison of means was performed by Tukey's post-hoc test. LD showed the highest fracture toughness, flexural strength, elastic modulus and crystallinity, followed by LEU and FEL, and FLU showed the lowest. However, the hardness of LD was lower than all the other three types of ceramics. For steatite antagonists, LD produced the least wear loss of antagonist, followed by LEU and FEL, and FLU had the most wear loss. For glass-ceramic materials, LD exhibited similar wear loss as LEU, but more than FLU and FEL did. Moreover, fracture occurred on the wear surface of FLU. In the progressive wear process, veneering porcelains showed better wear resistance but fluorapatite veneering porcelains appeared fracture surface. Monolithic lithium disilicate glass-ceramics with higher mechanical properties showed more wear loss, however, they did not fracture and produced less wear loss of antagonists. Copyright © 2017 Elsevier Ltd. All rights reserved.

Practice-based clinical evaluation of ceramic single crowns after at least five years.

PubMed

Dhima, Matilda; Paulusova, Vladimira; Carr, Alan B; Rieck, Kevin L; Lohse, Christine; Salinas, Thomas J

2014-02-01

Long-term practice-based clinical evaluations of various contemporary ceramic crown restorations from multiple practitioners are limited. The aims of this study were to evaluate the clinical performance of ceramic single crowns and to identify factors that influence their clinical performance. Ceramic single crowns that had been placed at the Mayo Clinic and in function since 2005 were identified and included in the study. The restorations were examined clinically, radiographically, and with photographs. Modified United States Public Health Services criteria were used for the clinical evaluation. The ceramic systems evaluated were bilayer and monolayer. Fifty-nine patients (41 women, 18 men) with 226 single teeth and implants restored with single ceramic crowns were identified. The mean duration from insertion date to study examination date was 6.1 years. Thirteen restorations (6%) were replaced at a mean 3.3 years after insertion date (range, 0.1-6.1 years). Estimated replacement-free survival rates (95% confidence interval [CI]; number of teeth/implants still at risk) at 5 years after insertion date were 95.1% (95% CI, 92.2-98.1; 153) and at 10 years were 92.8% (95% CI, 89.1-96.8; 8). The most common reason for replacement was fracture to the core of posterior layered ceramic crowns. The most commonly used luting agent was resin-modified ionomer cement. Most restorations exhibited clinically acceptable marginal integrity, shade, no caries recurrence, and no periapical pathology. The clinical performance of ceramic single crowns at 5 and 10 years supports their application in all areas of the mouth. With the majority of fractures to the core occurring early in the lifetime of layered ceramic posterior crowns, consideration of other monolithic ceramic systems for posterior crowns is advised. Copyright © 2014 Editorial Council for the Journal of Prosthetic Dentistry. Published by Mosby, Inc. All rights reserved.

Cement-based piezoelectric ceramic composites for sensor applications in civil engineering

NASA Astrophysics Data System (ADS)

Dong, Biqin

The objectives of this thesis are to develop and apply a new smart composite for the sensing and actuation application of civil engineering. Piezoelectric ceramic powder is incorporated into cement-based composite to achieve the sensing and actuation capability. The research investigates microstructure, polarization and aging, material properties and performance of cement-based piezoelectric ceramic composites both theoretically and experimentally. A hydrogen bonding is found at the interface of piezoelectric ceramic powder and cement phase by IR (Infrared Ray), XPS (X-ray Photoelectron Spectroscopy) and SIMS (Secondary Ion Mass Spectroscopy). It largely affects the material properties of composites. A simple first order model is introduced to explain the poling mechanism of composites and the dependency of polarization is discussed using electromechanical coupling coefficient kt. The mechanisms acting on the aging effect is explored in detail. Dielectrical, piezoelectric and mechanical properties of the cement-based piezoelectric ceramic composites are studied by experiment and theoretical calculation based on modified cube model (n=1) with chemical bonding . A complex circuit model is proposed to explain the unique feature of impedance spectra and the instinct of high-loss of cement-based piezoelectric ceramic composite. The sensing ability of cement-based piezoelectric ceramic composite has been evaluated by using step wave, sine wave, and random wave. It shows that the output of the composite can reflects the nature and characteristics of mechanical input. The work in this thesis opens a new direction for the current actuation/sensing technology in civil engineering. The materials and techniques, developed in this work, have a great potential in application of health monitoring of buildings and infrastructures.

Effect of processing induced particle alignment on the fracture toughness and fracture behavior of multiphase dental ceramics.

PubMed

Gonzaga, Carla C; Okada, Cristina Yuri; Cesar, Paulo F; Miranda, Walter G; Yoshimura, Humberto N

2009-11-01

To investigate the processing induced particle alignment on fracture behavior of four multiphase dental ceramics (one porcelain, two glass-ceramics and a glass-infiltrated-alumina composite). Disks (Ø12 mm x 1.1mm-thick) and bars (3 mm x 4 mm x 20 mm) of each material were processed according to manufacturer instructions, machined and polished. Fracture toughness (K(Ic)) was determined by the indentation strength method using 3-point bending and biaxial flexure fixtures for the fracture of bars and disks, respectively. Microstructural and fractographic analyses were performed with scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction. The isotropic microstructure of the porcelain and the leucite-based glass-ceramic resulted in similar fracture toughness values regardless of the specimen geometry. On the other hand, materials containing second-phase particles with high aspect ratio (lithium disilicate glass-ceramic and glass-infiltrated-alumina composite) showed lower fracture toughness for disk specimens compared to bars. For the lithium disilicate glass-ceramic disks, it was demonstrated that the occurrence of particle alignment during the heat-pressing procedure resulted in an unfavorable pattern that created weak microstructural paths during the biaxial test. For the glass-infiltrated-alumina composite, the microstructural analysis showed that the large alumina platelets tended to align their large surfaces perpendicularly to the direction of particle deposition during slip casting of green preforms. The fracture toughness of dental ceramics with anisotropic microstructure should be determined by means of biaxial testing, since it results in lower values.

Tribomaterial factors in space mechanism brake performance

NASA Technical Reports Server (NTRS)

Hawthorne, H. M.

1990-01-01

The asbestos/phenolic pads of Shuttle Remote Manipulator System (SRMS) brakes are unsuitable for use in long life space mechanisms because their friction decreases on extended sliding in high vacuum. Dehydration of the material and accumulation of wear debris in the conforming interface of this tribosystem induces the permanent friction changes. Other polymer and some ceramic based materials exhibit similar frictional torque behavior due to the development of minimal contact patches by the interfacial debris. In contrast, high friction occurs when other ceramics form many small contacts throughout fine debris beds. Generating this latter interfacial structure during run-in ensures that the in-vacuo friction remains stable thereafter. Such materials with low wear rates are potential candidates for friction elements in SSRMS and similar mechanisms.

Reconfigurable all-dielectric metamaterial frequency selective surface based on high-permittivity ceramics

NASA Astrophysics Data System (ADS)

Li, Liyang; Wang, Jun; Wang, Jiafu; Ma, Hua; Du, Hongliang; Zhang, Jieqiu; Qu, Shaobo; Xu, Zhuo

2016-04-01

Based on effective medium theory and dielectric resonator theory, we propose the design of reconfigurable all-dielectric metamaterial frequency selective surfaces (FSSs) using high-permittivity ceramics. The FSS is composed of ceramic resonators with different band stop responses under front and side incidences. By mechanically tuning the orientation of the ceramic resonators, reconfigurable electromagnetic (EM) responses between two adjacent stopbands can be achieved. The two broad stopbands originate from the first two resonant modes of the ceramic resonators. As an example, a reconfigurable FSS composed of cross-shaped ceramic resonators is demonstrated. Both numerical and experimental results show that the FSS can switch between two consecutive stopbands in 3.55-4.60 GHz and 4.54-4.94 GHz. The design method can be readily extended to the design of FSSs in other frequencies for high-power applications.

Reconfigurable all-dielectric metamaterial frequency selective surface based on high-permittivity ceramics

PubMed Central

Li, Liyang; Wang, Jun; Wang, Jiafu; Ma, Hua; Du, Hongliang; Zhang, Jieqiu; Qu, Shaobo; Xu, Zhuo

2016-01-01

Based on effective medium theory and dielectric resonator theory, we propose the design of reconfigurable all-dielectric metamaterial frequency selective surfaces (FSSs) using high-permittivity ceramics. The FSS is composed of ceramic resonators with different band stop responses under front and side incidences. By mechanically tuning the orientation of the ceramic resonators, reconfigurable electromagnetic (EM) responses between two adjacent stopbands can be achieved. The two broad stopbands originate from the first two resonant modes of the ceramic resonators. As an example, a reconfigurable FSS composed of cross-shaped ceramic resonators is demonstrated. Both numerical and experimental results show that the FSS can switch between two consecutive stopbands in 3.55–4.60 GHz and 4.54–4.94 GHz. The design method can be readily extended to the design of FSSs in other frequencies for high-power applications. PMID:27052098

Modified Ion-Conducting Ceramics Based on Lanthanum Gallate: Synthesis, Structure, and Properties

NASA Astrophysics Data System (ADS)

Kaleva, G. M.; Politova, E. D.; Mosunov, A. V.; Sadovskaya, N. V.

2018-06-01

A review is presented of the synthesis and complex investigation of modified ion-conducting ceramics based on heterosubstituted lanthanum gallate as a promising electrolyte material for solid oxide fuel cells. The effect the composition of multicomponent complex oxides has on the structure, microstructure, and electrophysical properties of ceramics is examined. Samples of ceramics with new compositions are produced via solid-state synthesis and modified with lithium fluoride. A drop is observed in the sintering temperature of the ceramics, caused by the liquid phase mechanism of sintering as a result of the low-melting superstoichiometric quantities of the additive. The effect lithium fluoride has on the process of phase formation, microstructure, and conductivity of the ceramics is investigated. It is found that samples modified with lithium fluoride display high density, dense grain packing, and high values of electrical conductivity at high temperatures.

Ceramic applications in the advanced Stirling automotive engine

NASA Technical Reports Server (NTRS)

Tomazic, W. A.; Cairelli, J. E.

1977-01-01

The ideal cycle, its application to a practical machine, and the specific advantages of high efficiency, low emissions, multi-fuel capability, and low noise of the stirling engine are discussed. Certain portions of the Stirling engine must operate continuously at high temperature. Ceramics offer the potential of cost reduction and efficiency improvement for advanced engine applications. Potential applications for ceramics in Stirling engines, and some of the special problems pertinent to using ceramics in the Stirling engine are described. The research and technology program in ceramics which is planned to support the development of advanced Stirling engines is outlined.

On the feasibility of the Chevron Notch Beam method to measure fracture toughness of fine-grained zirconia ceramics.

PubMed

Kailer, Andreas; Stephan, Marc

2016-10-01

The fracture toughness determination of fine-grained zirconia ceramics using the chevron notched beam method (CNB) was investigated to assess the feasibility of this method for quality assurance and material characterization. CNB tests were performed using four different yttria-stabilized zirconia ceramics under various testing modes and conditions, including displacement-controlled and load-rate-controlled four point bending to assess the influence of slow crack growth and identify most suitable test parameters. For comparison, tests using single-edge V-notch beams (SEVNB) were conducted. It was observed that the CNB method yields well-reproducible results. However, slow crack growth effects significantly affect the measured KIC values, especially when slow loading rates are used. To minimize the effect of slow crack growth, the application of high loading rates is recommended. Despite a certain effort needed for setting up a sample preparation routine, the CNB method is considered to be very useful for measuring and controlling the fracture toughness of zirconia ceramics. Copyright © 2016 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Multi-susceptibile Single-Phased Ceramics with Both Considerable Magnetic and Dielectric Properties by Selectively Doping

PubMed Central

Liu, Chuyang; Zhang, Yujing; Jia, Jingguo; Sui, Qiang; Ma, Ning; Du, Piyi

2015-01-01

Multiferroic ceramics with extraordinary susceptibilities coexisting are vitally important for the multi-functionality and integration of electronic devices. However, multiferroic composites, as the most potential candidates, will introduce inevitable interface deficiencies and thus dielectric loss from dissimilar phases. In this study, single-phased ferrite ceramics with considerable magnetic and dielectric performances appearing simultaneously were fabricated by doping target ions in higher valence than that of Fe3+, such as Ti4+, Nb5+ and Zr4+, into BaFe12O19. In terms of charge balance, Fe3+/Fe2+ pair dipoles are produced through the substitution of Fe3+ by high-valenced ions. The electron hopping between Fe3+ and Fe2+ ions results in colossal permittivity. Whilst the single-phased ceramics doped by target ions exhibit low dielectric loss naturally due to the diminishment of interfacial polarization and still maintain typical magnetic properties. This study provides a convenient method to attain practicable materials with both outstanding magnetic and dielectric properties, which may be of interest to integration and multi-functionality of electronic devices. PMID:25835175

Dielectric properties of Y and Nb co-doped TiO2 ceramics.

PubMed

Wang, Xianwei; Zhang, Bihui; Xu, Linhai; Wang, Xiaoer; Hu, Yanchun; Shen, Gaohang; Sun, Lingyun

2017-08-17

In this work, the (Y 0.5 Nb 0.5 ) x Ti 1-x O 2 (x = 0.001, 0.01, 0.02, 0.04, 0.06 and 0.1) ceramics (as called YNTO) were fabricated by synthesized through a standard solid-state reaction. As revealed by the X-ray diffraction (XRD) spectra, the YNTOs exhibit tetragonal rutile structure. Meanwhile, the grain size of YNTO ceramics increased and then decreased with the increase of x value, and the largest value reached when x = 0.02. All the YNTO samples display colossal permittivity (~10 2 -10 5 ) over a wide temperature and frequency range. Moreover, the optimal ceramic, (Y 0.5 Nb 0.5 ) 0.02 Ti 0.98 O 2 , exhibits high performance over a broad temperature range from 20 °C to 180 °C; specifically, at 1 kHz, the dielectric constant and dielectric loss are 6.55 × 10 4 and 0.22 at room temperature, and they are 1.03 × 10 5 and 0.11 at 180 °C, respectively.

Multi-susceptibile single-phased ceramics with both considerable magnetic and dielectric properties by selectively doping.

PubMed

Liu, Chuyang; Zhang, Yujing; Jia, Jingguo; Sui, Qiang; Ma, Ning; Du, Piyi

2015-04-02

Multiferroic ceramics with extraordinary susceptibilities coexisting are vitally important for the multi-functionality and integration of electronic devices. However, multiferroic composites, as the most potential candidates, will introduce inevitable interface deficiencies and thus dielectric loss from dissimilar phases. In this study, single-phased ferrite ceramics with considerable magnetic and dielectric performances appearing simultaneously were fabricated by doping target ions in higher valence than that of Fe(3+), such as Ti(4+), Nb(5+) and Zr(4+), into BaFe12O19. In terms of charge balance, Fe(3+)/Fe(2+) pair dipoles are produced through the substitution of Fe(3+) by high-valenced ions. The electron hopping between Fe(3+) and Fe(2+) ions results in colossal permittivity. Whilst the single-phased ceramics doped by target ions exhibit low dielectric loss naturally due to the diminishment of interfacial polarization and still maintain typical magnetic properties. This study provides a convenient method to attain practicable materials with both outstanding magnetic and dielectric properties, which may be of interest to integration and multi-functionality of electronic devices.

Multi-susceptibile Single-Phased Ceramics with Both Considerable Magnetic and Dielectric Properties by Selectively Doping

NASA Astrophysics Data System (ADS)

Liu, Chuyang; Zhang, Yujing; Jia, Jingguo; Sui, Qiang; Ma, Ning; Du, Piyi

2015-04-01

Multiferroic ceramics with extraordinary susceptibilities coexisting are vitally important for the multi-functionality and integration of electronic devices. However, multiferroic composites, as the most potential candidates, will introduce inevitable interface deficiencies and thus dielectric loss from dissimilar phases. In this study, single-phased ferrite ceramics with considerable magnetic and dielectric performances appearing simultaneously were fabricated by doping target ions in higher valence than that of Fe3+, such as Ti4+, Nb5+ and Zr4+, into BaFe12O19. In terms of charge balance, Fe3+/Fe2+ pair dipoles are produced through the substitution of Fe3+ by high-valenced ions. The electron hopping between Fe3+ and Fe2+ ions results in colossal permittivity. Whilst the single-phased ceramics doped by target ions exhibit low dielectric loss naturally due to the diminishment of interfacial polarization and still maintain typical magnetic properties. This study provides a convenient method to attain practicable materials with both outstanding magnetic and dielectric properties, which may be of interest to integration and multi-functionality of electronic devices.

Current perspectives of bio-ceramic technology in endodontics: calcium enriched mixture cement - review of its composition, properties and applications

PubMed Central

Nawal, Ruchika Roongta; Talwar, Sangeeta; Verma, Mahesh

2015-01-01

Advancements in bio-ceramic technology has revolutionised endodontic material science by enhancing the treatment outcome for patients. This class of dental materials conciliates excellent biocompatibility with high osseoconductivity that render them ideal for endodontic care. Few recently introduced bio-ceramic materials have shown considerable clinical success over their early generations in terms of good handling characteristics. Calcium enriched mixture (CEM) cement, Endosequence sealer, and root repair materials, Biodentine and BioAggregate are the new classes of bio-ceramic materials. The aim of this literature review is to present investigations regarding properties and applications of CEM cement in endodontics. A review of the existing literature was performed by using electronic and hand searching methods for CEM cement from January 2006 to December 2013. CEM cement has a different chemical composition from that of mineral trioxide aggregate (MTA) but has similar clinical applications. It combines the biocompatibility of MTA with more efficient characteristics, such as significantly shorter setting time, good handling characteristics, no staining of tooth and effective seal against bacterial leakage. PMID:25671207

Fixed partial dentures investigated by optical coherent tomography

NASA Astrophysics Data System (ADS)

Sinescu, Cosmin; Negrutiu, Meda; Todea, Carmen; Hughes, Mike; Tudorache, Florin; Podoleanu, Adrian G.

2008-02-01

Fixed partial prostheses as integral ceramics, integral polymers, metal ceramics or metal polymers bridges, are mainly used in the frontal part of the dental arch (especially the integral bridges). They have to satisfy high stress requirements as well as esthetic. The masticatory stress may induce fractures of the bridges. These may be triggered by initial materials defects or by alterations of the technological process. The fractures of these bridges lead to functional, esthetic and phonetic disturbances which finally render the prosthetic treatment inefficient. The purpose of this study is to evaluate the capability of en-face optical coherence tomography (OCT) in detection and analysis of possible fractures in several integral fixed partial dentures. The materials used were represented by several fixed partial prostheses, integral ceramics, integral polymers, metal ceramics and metal polymers bridges. In order to discover the defects, scanning was performed from incisal, vestibular, oral and cervical directions material defects such as fractures and pores were investigated using OCT. In conclusion, en-face OCT has proven as a valuable non invasive method to investigate fixed partial prostheses before their insertion in the oral cavity.

Effect of Different Ceramic Crown Preparations on Tooth Structure Loss: An In Vitro Study

NASA Astrophysics Data System (ADS)

Ebrahimpour, Ashkan

Objective: To quantify and compare the amount of tooth-structure reduction following the full-coverage preparations for crown materials of porcelain-fused-to-metal, lithium disilicate glass-ceramic and yttria-stabilized tetragonal zirconia polycrystalline for three tooth morphologies. Methods: Groups of resin teeth of different morphologies were individually weighed to high precision, then prepared following the preparation guidelines. The teeth were re-weighed after preparation and the amount of structural reduction was calculated. Statistical analyses were performed to find out if there was a significant difference among the groups. Results: Amount of tooth reduction for zirconia crown preparations was the lowest and statistically different compared with the other two materials. No statistical significance was found between the amount of reduction for porcelain-fused-to-metal and lithium disilicate glass-ceramic crowns. Conclusion: Within the limitations of this study, more tooth structure can be saved when utilizing zirconia full-coverage restorations compared with lithium disilicate glass-ceramic and porcelain-fused-to-metal crowns in maxillary central incisors, first premolars and first molars.

Evaluation of ceramics for stator application: Gas turbine engine report

NASA Technical Reports Server (NTRS)

Trela, W.; Havstad, P. H.

1978-01-01

Current ceramic materials, component fabrication processes, and reliability prediction capability for ceramic stators in an automotive gas turbine engine environment are assessed. Simulated engine duty cycle testing of stators conducted at temperatures up to 1093 C is discussed. Materials evaluated are SiC and Si3N4 fabricated from two near-net-shape processes: slip casting and injection molding. Stators for durability cycle evaluation and test specimens for material property characterization, and reliability prediction model prepared to predict stator performance in the simulated engine environment are considered. The status and description of the work performed for the reliability prediction modeling, stator fabrication, material property characterization, and ceramic stator evaluation efforts are reported.

Fabrication of highly dense SiN4 ceramics without additives by high pressure sintering

NASA Technical Reports Server (NTRS)

Takatori, K.; Shimade, M.; Koizumi, M.

1984-01-01

Silicon nitride (Si3N4) is one of candidate materials for the engineering ceramics which is used at high temperatures. The mechanical strengths of hot pressed or sintered Si2N4 ceramics containing some amount of additives, however, are deteriorated at elevated temperatures. To improve the high temperature strength of Si3N4 ceramics, an attempt to consolidate Si3N4 without additives was made by high pressure sintering technique. Scanning electron micrographs of fracture surfaces of the sintered bodies showed the bodies had finely grained and fully self-bonded sintered bodies were 310N sq m at room temperature and 174N/sq m at 1200 C.

Addition of a pontic to all-ceramic Turkom-Cera fixed partial denture restorations.

PubMed

Uludag, Bulent; Tokar, Emre; Polat, Serdar

2013-04-01

High-strength all-ceramic materials are commonly used in dentistry. When complications occur in an all-ceramic restoration, the restoration is usually replaced. This article describes the time-saving ability and cost-effectiveness of this novel technique for the addition of a pontic in two complicated clinical cases. Turkom-Cera(™) [Turkom-Ceramic (M) Sdn. Bhd.] with aluminum oxide (99.98%) is an all-ceramic system that offers the option of addition of a new pontic to the sintered framework. The new pontic was cut off from an alumina blank [Turkom-Ceramic (M) Sdn. Bhd.], moistened, and attached to the framework using alumina gel [Turkom-Ceramic (M) Sdn. Bhd.]. The framework was veneered with veneering porcelain (Vita VM 7; VITA Zahnfabrik). The two cases presented here involving the addition of a pontic to sintered framework were followed up for at least 1 year. No complication was detected or reported by the patients. Alumina- and zirconia-based ceramics are particularly suitable for for all-ceramic restorations in high-stress bearing areas. However, replacement of a failed all-ceramic restoration is not the most practical solution, considering both cost and tooth-related factors. This attractive feature of the Turkom-Cera allows the repair of a fractured ceramic coping or the addition of a new pontic to restorations.

Addition of a pontic to all-ceramic Turkom-Cera fixed partial denture restorations

PubMed Central

Uludag, Bulent; Tokar, Emre; Polat, Serdar

2013-01-01

High-strength all-ceramic materials are commonly used in dentistry. When complications occur in an all-ceramic restoration, the restoration is usually replaced. This article describes the time-saving ability and cost-effectiveness of this novel technique for the addition of a pontic in two complicated clinical cases. Turkom-Cera™ [Turkom-Ceramic (M) Sdn. Bhd.] with aluminum oxide (99.98%) is an all-ceramic system that offers the option of addition of a new pontic to the sintered framework. The new pontic was cut off from an alumina blank [Turkom-Ceramic (M) Sdn. Bhd.], moistened, and attached to the framework using alumina gel [Turkom-Ceramic (M) Sdn. Bhd.]. The framework was veneered with veneering porcelain (Vita VM 7; VITA Zahnfabrik). The two cases presented here involving the addition of a pontic to sintered framework were followed up for at least 1 year. No complication was detected or reported by the patients. Alumina- and zirconia-based ceramics are particularly suitable for for all-ceramic restorations in high-stress bearing areas. However, replacement of a failed all-ceramic restoration is not the most practical solution, considering both cost and tooth-related factors. This attractive feature of the Turkom-Cera allows the repair of a fractured ceramic coping or the addition of a new pontic to restorations. PMID:24883033

Hydroxyapatite ceramic implants for cranioplasty in children: a single-center experience.

PubMed

Zaccaria, Laura; Tharakan, Sasha Job; Altermatt, Stefan

2017-02-01

The use of hydroxyapatite ceramic (HAC) implants for the treatment of skull defects in pediatric patients started 2010 at our institution. Ceramic implants facilitate osteoblast migration and therefore optimize osteointegration with the host bone. The purpose of this study is to report a single-center experience with this treatment modality. A retrospective review of all patients from July 2010 through June 2014 undergoing a cranioplasty using hydroxyapatite ceramic implant and managed at a single institution was performed. Indication for cranioplasty, the hospital course, and follow-up were reviewed. Bone density was measured in Hounsfield Units (HU) and osteointegration was calculated using Mimics Software® (Mimics Innovation Suite v17.0 Medical, Materialize, Leuven, Belgium). Over the 4-year period, six patients met criteria for the study. Five patients had an osteointegration of nearly 100%. One patient had an incomplete osteointegration with a total bone-implant contact area of 69%. The mean bone density was 2800 HU (2300-3000 HU). Bone density alone is estimated to have a Hounsfield value between 400 and 2000 HU depending on the body region and bone quality. There were no major complications, and the patients were highly satisfied with the esthetical result. Hydroxyapatite ceramic implants for cranioplasty in pediatric patients are a good choice for different indications. The implants show excellent osteointegration and esthetical results.

The effect of micro-structure on upconversion luminescence of Nd3+/Yb3+ co-doped La2O3-TiO2-ZrO2 glass-ceramics

NASA Astrophysics Data System (ADS)

Zhang, Minghui; Wen, Haiqin; Pan, Xiuhong; Yu, Jianding; Jiang, Meng; Yu, Huimei; Tang, Meibo; Gai, Lijun; Ai, Fei

2018-03-01

Nd3+/Yb3+ co-doped La2O3-TiO2-ZrO2 glasses have been prepared by aerodynamic levitation method. The glasses show high refractive index of 2.28 and Abbe number of 18.3. Glass-ceramics heated at 880 °C for 50 min perform the strongest upconversion luminescence. X-ray diffraction patterns of glass-ceramics with different depths indicate that rare earth ions restrain crystallization. Body crystallization mechanism mixed with surface crystallization is confirmed in the heat treatment. Surface crystals achieve priority to grow, resulting in important effects on upconversion luminescence. The results of atomic force microscope and scanning electron microscope indicate that crystal particles with uniform size distribute densely and homogenously on the surface and large amount of glass matrix exists in the glass ceramics heated at 880 °C for 50 min. Crystals in the glass-ceramics present dense structure and strong boundaries, which can reduce the mutual nonradiative relaxation rate among rare earth ions and then improve upconversion luminescence effectively. Based on micro-structural study, the mechanism that upconversion luminescence can be improved by heat treatment has been revealed. The results of micro-structural analysis agree well with the spectra.

Two-year clinical evaluation of IPS Empress II ceramic onlays/inlays.

PubMed

Tagtekin, D A; Ozyöney, G; Yanikoglu, F

2009-01-01

The stronger the ceramic material, the longer the restoration stays in the mouth. The current study evaluated the two-year clinical performance of a strong ceramic system, IPS Empress II, with increased strength on onlay/inlay restorations of molars. Teeth from 35 patients, including three premolars and 32 molars, were prepared for 28 onlay and seven inlay restorations with IPS Empress II ceramics. The restorations were cemented with a highly viscous, dual-curing luting composite cement (Bifix) and evaluated by two examiners using USPHS criteria at baseline (one week following insertion), six months, one year and two years. The baseline scores and recalls were assessed by Wilcoxon signed rank test. Statistically significant marginal discoloration at the Bravo level was found at the 12- and 24-month recalls (p=0.046). One debonding was statistically insignificant. No changes were observed with respect to anamnesis, such as any symptom from the TMJ or masticatory muscles. No restorations were replaced due to hypersensitivity or were missing at the two-year evaluation. Any wear on the restoration, antagonist tooth or any changes of proximal contacts were not observed. IPS Empress II Ceramics were found to be appropriate as onlay/inlay restorations for clinical use under the conditions of the current study.

Fully Ceramic Microencapsulated Fuel Development for LWR Applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Snead, Lance Lewis; Besmann, Theodore M; Terrani, Kurt A

2012-01-01

The concept, fabrication, and key feasibility issues of a new fuel form based on the microencapsulated (TRISO-type) fuel which has been specifically engineered for LWR application and compacted within a SiC matrix will be presented. This fuel, the so-called fully ceramic microencapsulated fuel is currently undergoing development as an accident tolerant fuel for potential UO2 replacement in commercial LWRs. While the ability of this fuel to facilitate normal LWR cycle performance is an ongoing effort within the program, this will not be a focus of this paper. Rather, key feasibility and performance aspects of the fuel will be presented includingmore » the ability to fabricate a LWR-specific TRISO, the need for and route to a high thermal conductivity and fully dense matrix that contains neutron poisons, and the performance of that matrix under irradiation and the interaction of the fuel with commercial zircaloy clad.« less

Development and mechanical properties of construction materials from lunar simulants

NASA Technical Reports Server (NTRS)

Desai, Chandra S.

1990-01-01

The development of construction materials such as concrete from lunar soils without the use of water requires a different methodology than that used for conventional terrestrial concrete. Currently, this research involves two aspects: (1) liquefaction of lunar simulants with various additives in a furnace so as to produce a construction material like an intermediate ceramic; and (2) cyclic loading of simulant with different initial vacuums and densities with respect to the theoretical maximum densities (TMD). In both cases, bending, triaxial compression, extension, and hydrostatic tests will be performed to define the stress-strain strength response of the resulting materials. In the case of the intermediate ceramic, bending and available multiaxial test devices will be used, while for the compacted case, tests will be performed directly in the new device. The tests will be performed by simulating in situ confining conditions. A preliminary review of high-purity metal is also conducted.

X-ray shielding behaviour of kaolin derived mullite-barites ceramic

NASA Astrophysics Data System (ADS)

Ripin, A.; Mohamed, F.; Choo, T. F.; Yusof, M. R.; Hashim, S.; Ghoshal, S. K.

2018-03-01

Mullite-barite ceramic (MBC) is an emergent material for effective shielding of redundant ionizing radiation exposure. The composition dependent mechanical, thermal, and microstructure properties of MBC that makes MBC a high performing novel radiation shielding candidate remained unexplored. This paper examines the possibility of exploiting Malaysian kaolin (AKIM-35) and barite (BaSO4) derived ceramic (MBC) system for X-ray shielding operation. Using conventional pressing and sintering method six ceramic samples are prepared by mixing AKIM-35 with barite at varying contents (0, 10, 20, 30, 40 and 50 wt%). Synthesized pressed mixtures are calcined at 400 °C for 30 min and then sintered to 1300 °C for 120 min at a heating rate of 10 °C/min. Sintered samples are characterized via X-ray Diffraction (XRD), Field Emission Scanning Electron Microscope (FESEM), lead equivalent (LE), uniformity and dose reduction analyses. XRD pattern of prepared ceramics revealed the presence of monoclinic barium alumino-silicate (BAS) and orthorhombic mullite as major shielding phases together with other minor phase of barite and hexagonal quartz (SiO2) structures. Furthermore, FESEM images of ceramics (between 0 and 30 wt%) displayed the existence of compacted monoclinic plate of BAS and acicular mullite morphology (ceramics at 40 and 50 wt%). Radiation tests displayed the capacity of ceramics (at 0 and 10 wt%) to shield the X-ray radiation emanated at tube potential range of 50-120 kV. The highest radiation attenuation is ascertained at 70 kV where the dose is reduced remarkably between 99.11% and 97.42%. Ceramics at 0 and 10 wt% demonstrated the highest lead (Pb) equivalent thickness (LE) of 0.44 mm and 0.34 mm, respectively. It is established that such MBC may contribute towards the development of shielding material against ionizing radiation in diagnostic radiology (X-ray) dose range.

Durability of feldspathic veneering ceramic on glass-infiltrated alumina ceramics after long-term thermocycling.

PubMed

Mesquita, A M M; Ozcan, M; Souza, R O A; Kojima, A N; Nishioka, R S; Kimpara, E T; Bottino, M A

2010-01-01

This study compared the bond strength durability of a feldspathic veneering ceramic to glass-infiltrated reinforced ceramics in dry and aged conditions. Disc shaped (thickness: 4 mm, diameter: 4 mm) of glass-infiltrated alumina (In-Ceram Alumina) and glass-infiltrated alumina reinforced by zirconia (In-Ceram Zirconia) core ceramic specimens (N=48, N=12 per groups) were constructed according to the manufacturers' recommendations. Veneering ceramic (VITA VM7) was fired onto the core ceramics using a mold. The core-veneering ceramic assemblies were randomly divided into two conditions and tested either immediately after specimen preparation (Dry) or following 30000 thermocycling (5-55 ºC±1; dwell time: 30 seconds). Shear bond strength test was performed in a universal testing machine (cross-head speed: 1 mm/min). Failure modes were analyzed using optical microscope (x20). The bond strength data (MPa) were analyzed using ANOVA (α=0.05). Thermocycling did not decrease the bond strength results for both In-Ceram Alumina (30.6±8.2 MPa; P=0.2053) and In-Ceram zirconia (32.6±9 MPa; P=0.3987) core ceramic-feldspathic veneering ceramic combinations when compared to non-aged conditions (28.1±6.4 MPa, 29.7±7.3 MPa, respectively). There were also no significant differences between adhesion of the veneering ceramic to either In-Ceram Alumina or In-Ceram Zirconia ceramics (P=0.3289). Failure types were predominantly a mixture of adhesive failure between the veneering and the core ceramic together with cohesive fracture of the veneering ceramic. Long-term thermocycling aging conditions did not impair the adhesion of the veneering ceramic to the glass-infiltrated alumina core ceramics tested.

Ceramic Single Phase High-Level Nuclear Waste Forms: Hollandite, Perovskite, and Pyrochlore

NASA Astrophysics Data System (ADS)

Vetter, M.; Wang, J.

2017-12-01

The lack of viable options for the safe, reliable, and long-term storage of nuclear waste is one of the primary roadblocks of nuclear energy's sustainable future. The method being researched is the incorporation and immobilization of harmful radionuclides (Cs, Sr, Actinides, and Lanthanides) into the structure of glasses and ceramics. Borosilicate glasses are the main waste form that is accepted and used by today's nuclear industry, but they aren't the most efficient in terms of waste loading, and durability is still not fully understood. Synroc-phase ceramics (i.e. hollandite, perovskite, pyrochlore, zirconolite) have many attractive qualities that glass waste forms do not: high waste loading, moderate thermal expansion and conductivity, high chemical durability, and high radiation stability. The only downside to ceramics is that they are more complex to process than glass. New compositions can be discovered by using an Artificial Neural Network (ANN) to have more options to optimize the composition, loading for performance by analyzing the non-linear relationships between ionic radii, electronegativity, channel size, and a mineral's ability to incorporate radionuclides into its structure. Cesium can be incorporated into hollandite's A-site, while pyrochlore and perovskite can incorporate actinides and lanthanides into their A-site. The ANN is used to predict new compositions based on hollandite's channel size, as well as the A-O bond distances of pyrochlore and perovskite, and determine which ions can be incorporated. These new compositions will provide more options for more experiments to potentially improve chemical and thermodynamic properties, as well as increased waste loading capabilities.

A New High-Temperature Ultrasonic Transducer for Continuous Inspection.

PubMed

Amini, Mohammad Hossein; Sinclair, Anthony N; Coyle, Thomas W

2016-03-01

A novel design of piezoelectric ultrasonic transducer is introduced, suitable for operation at temperatures of up to 700 °C-800 °C. Lithium niobate single crystal is chosen as the piezoelectric element primarily due to the high Curie temperature of 1200 °C. A backing element based on a porous ceramic is designed for which the pore volume fraction and average pore diameter in the ceramic matrix can be controlled in the manufacturing process; this enables the acoustic impedance and attenuation to be selected to match their optimal values as predicted by a one-dimensional transducer model of the entire transducer. Porous zirconia is selected as the ceramic matrix material of the backing element to obtain an ultrasonic signal with center frequency of 2.7-3 MHz, and 3-dB bandwidth of 90%-95% at the targeted operating temperature. Acoustic coupling of the piezocrystal to the backing element and matching layer is investigated using commercially available high-temperature adhesives and brazing alloys. The performance of the transducer as a function of temperature is studied. Stable bonding and clear signals were obtained using an aluminum brazing alloy as the bonding agent.

Ceramic Parts for Turbines

NASA Technical Reports Server (NTRS)

Jones, R. D.; Carpenter, Harry W.; Tellier, Jim; Rollins, Clark; Stormo, Jerry

1987-01-01

Abilities of ceramics to serve as turbine blades, stator vanes, and other elements in hot-gas flow of rocket engines discussed in report. Ceramics prime candidates, because of resistance to heat, low density, and tolerance of hostile environments. Ceramics considered in report are silicon nitride, silicon carbide, and new generation of such ceramic composites as transformation-toughened zirconia and alumina and particulate- or whisker-reinforced matrices. Report predicts properly designed ceramic components viable in advanced high-temperature rocket engines and recommends future work.

Final Project Report CFA-14-6357: A New Paradigm for Understanding Multiphase Ceramic Waste Form Performance

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brinkman, Kyle; Bordia, Rajendra; Reifsnider, Kenneth

This project fabricated model multiphase ceramic waste forms with processing-controlled microstructures followed by advanced characterization with synchrotron and electron microscopy-based 3D tomography to provide elemental and chemical state-specific information resulting in compositional phase maps of ceramic composites. Details of 3D microstructural features were incorporated into computer-based simulations using durability data for individual constituent phases as inputs in order to predict the performance of multiphase waste forms with varying microstructure and phase connectivity.

Method of preparing a high solids content, low viscosity ceramic slurry

DOEpatents

Tiegs, Terry N.; Wittmer, Dale E.

1995-01-01

A method for producing a high solids content, low viscosity ceramic slurry composition comprises turbomilling a dispersion of a ceramic powder in a liquid to form a slurry having a viscosity less than 100 centipoise and a solids content equal to or greater than 48 volume percent.

Method of preparing a high solids content, low viscosity ceramic slurry

DOEpatents

Tiegs, T.N.; Wittmer, D.E.

1995-10-10

A method for producing a high solids content, low viscosity ceramic slurry composition comprises turbomilling a dispersion of a ceramic powder in a liquid to form a slurry having a viscosity less than 100 centipoise and a solids content equal to or greater than 48 volume percent.

Ballistic Performance of Porous-Ceramic, Thermal-Protection-Systems

NASA Technical Reports Server (NTRS)

Christiansen, E. L.; Davis, B. A.; Miller, J. E.; Bohl, W. E.; Foreman, C. D.

2009-01-01

Porous-ceramic, thermal protection systems are used heavily in current reentry vehicles like the Space Shuttle and are currently being proposed for the next generation of manned spacecraft, Orion. These materials insulate the structural components of a spacecraft against the intense thermal environments of atmospheric reentry. Furthermore, these materials are also highly exposed to space environmental hazards like meteoroid and orbital debris impacts. This paper discusses recent impact testing up to 9 km/s, and the findings of the influence of material equation-of-state on the simulation of the impact event to characterize the ballistic performance of these materials. These results will be compared with heritage models1 for these materials developed from testing at lower velocities. Assessments of predicted spacecraft risk based upon these tests and simulations will also be discussed.

The depolarization performances of 0.97PbZrO3-0.03Ba(Mg1/3Nb2/3)O3 ceramics under hydrostatic pressure

NASA Astrophysics Data System (ADS)

Su, Rigu; Nie, Hengchang; Liu, Zhen; Peng, Ping; Cao, Fei; Dong, Xianlin; Wang, Genshui

2018-02-01

Several 0.97PbZrO3-0.03Ba(Mg1/3Nb2/3)O3 (0.97PZ-0.03BMN) ceramics were prepared via the columbite precursor method. Their microstructures and pressure-dependent ferroelectric and depolarization performances were then studied. The X-ray diffraction patterns of ground and fresh samples indicate that a main rhombohedral symmetry crystal structure is present in the bulk and that it sits alongside a trace quantity of an orthorhombic antiferroelectric phase that results from the effect of grinding on the surface. The remanent polarization (Pr) of the 0.97PZ-0.03BMN reached 32.4 μC/cm2 at 4.5 kV/mm and ambient pressure. In an in situ pressure-induced current measurement, more than 91% of the retained Pr of the pre-poled sample was released when the pressure was increased from 194 MPa to 238 MPa. That this pressure-driven depolarization should be attributed to the pressure-induced ferroelectric-antiferroelectric phase transition is supported by the emergence of double P-E loops at high hydrostatic pressures. Moreover, the 0.97PZ-0.03BMN ceramics exhibit no temperature-induced phase transitions and little related polarization loss up to 125 °C, which suggests that Pr has excellent thermal stability. The sharp depolarization behavior at low pressures and excellent temperature stability reveal that our 0.97PZ-0.03BMN ceramics exhibit superior performances in mechanical-electrical energy conversion applications.

Ceramic-based microelectrode arrays: recording surface characteristics and topographical analysis

PubMed Central

Talauliker, Pooja M.; Price, David A.; Burmeister, Jason J.; Nagari, Silpa; Quintero, Jorge E.; Pomerleau, Francois; Huettl, Peter; Hastings, J. Todd; Gerhardt, Greg A.

2011-01-01

Amperometric measurements using microelectrode arrays (MEAs) provide spatially and temporally resolved measures of neuromolecules in the central nervous system of rats, mice and non-human primates. Multi-site MEAs can be mass fabricated on ceramic (Al2O3) substrate using photolithographic methods, imparting a high level of precision and reproducibility in a rigid but durable recording device. Although the functional capabilities of MEAs have been previously documented for both anesthetized and freely-moving paradigms, the performance enabling intrinsic physical properties of the MEA device have not heretofore been presented. In these studies, spectral analysis confirmed that the MEA recording sites were primarily composed of elemental platinum (Pt°). In keeping with the precision of the photolithographic process, scanning electron microscopy revealed that the Pt recording sites have unique microwell geometries post-fabrication. Atomic force microscopy demonstrated that the recording surfaces have nanoscale irregularities in the form of elevations and depressions, which contribute to increased current per unit area that exceeds previously reported microelectrode designs. The ceramic substrate on the back face of the MEA was characterized by low nanoscale texture and the ceramic sides consisted of an extended network of ridges and cavities. Thus, individual recording sites have a unique Pt° composition and surface profile that has not been previously observed for Pt-based microelectrodes. These features likely impact the physical chemistry of the device, which may influence adhesion of biological molecules and tissue as well as electrochemical recording performance post-implantation. This study is a necessary step towards understanding and extending the performance abilities of MEAs in vivo. PMID:21513736

Fracture performance of computer-aided manufactured zirconia and alloy crowns.

PubMed

Rosentritt, Martin; Behr, Michael; Thaller, Christian; Rudolph, Heike; Feilzer, Albert

2009-09-01

To compare the fracture resistance and fracture performance of CAD/CAM zirconia and alloy crowns. One electrophoretic deposition alumina ceramic (Wolceram, Wolceram) and 4 zirconia-based systems (ce.novation, ce.novation; Cercon, DeguDent; Digizon, Amann Girrbach; and Lava, 3M ESPE) were investigated. A porcelain-fused-to-metal method (Academy, Bego Medical) was used in either conventional casting technique or laser sintering. Sixteen crowns of each material were fabricated and veneered with glass-ceramic as recommended by the manufacturers. Crown and root dimensions were measured, and 8 crowns of each system were adhesively bonded or conventionally cemented. After the crowns were artificially aged in a simulated oral environment (1,200,000 mechanical loads with 50 N; 3,000 thermal cycles with distilled water between 5 degrees C and 55 degrees C; 2 minutes per cycle), fracture resistance and fracture patterns were determined and defect sizes investigated. The fracture force varied between 1,111 N and 2,038 N for conventional cementation and between 1,181 N and 2,295 N for adhesive bonding. No significant differences were found between adhesive and conventional cementations. Fracture patterns presented mostly as a chipping of the veneering, in single cases as a fracture of the core, and in 1 case as a fracture of the tooth. Crown material and cementation do not have any significant influence on the fracture force and fracture performance of all-ceramic and metal-based crowns. Therefore, it may be concluded that adhesive bonding is not necessary for the application of high-strength ceramics.

High Performance Composites. "Designed" Materials for the New Millennium. 2nd Module in a Series on Advanced Materials. Resources in Technology.

ERIC Educational Resources Information Center

Jacobs, James A.

1994-01-01

This learning module on composites such as polymer matrix, metal matrix, ceramic matrix, particulate, and laminar includes a design brief giving context, objectives, evaluation, student outcomes, and quiz. (SK)

High-Temperature Wettability and Interactions between Y-Containing Ni-Based Alloys and Various Oxide Ceramics.

PubMed

Li, Jinpeng; Zhang, Huarui; Gao, Ming; Li, Qingling; Bian, Weidong; Tao, Tongxiang; Zhang, Hu

2018-05-07

To obtain appropriate crucible materials for vacuum induction melting of MCrAlY alloys, four different oxide ceramics, including MgO, Y₂O₃, Al₂O₃, and ZrO₂, with various microstructures were designed and characterized. The high-temperature wettability and interactions between Ni-20Co-20Cr-10Al-1.5Y alloys and oxide ceramics were studied by sessile drop experiments under vacuum. The results showed that all the systems exhibited non-wetting behavior. The contact angles were stable during the melting process of alloys and the equilibrium contact angles were 140° (MgO), 148° (Y₂O₃), 154° (Al₂O₃), and 157° (ZrO₂), respectively. The interfacial reaction between the ceramic substrates and alloys occurred at high temperature. Though the ceramics had different microstructures, similar continuous Y₂O₃ reaction layer with thicknesses of about 25 μm at the alloy-ceramic interface in MgO, Al₂O₃, and ZrO₂ systems formed. The average area percentage of oxides in the alloy matrices were 0.59% (MgO), 0.11% (Al₂O₃), 0.09% (ZrO₂), and 0.02% (Y₂O₃), respectively. The alloys, after reacting with MgO ceramic, had the highest inclusion content, while those with the lowest content were in the Y₂O₃ system. Y₂O₃ ceramic was the most beneficial for vacuum induction melting of high-purity Y-containing Ni-based alloys.

Ceramic synthesis of 0.08BiGaO3-0.90BaTiO3-0.02LiNbO3 under high pressure and high temperature

NASA Astrophysics Data System (ADS)

Hui, Jin; Yong, Li; Mou-Sheng, Song; Lin, Chen; Xiao-Peng, Jia; Hong-An, Ma

2016-07-01

In this paper, the preparation of 0.08BiGaO3-0.90BaTiO3-0.02LiNbO3 is investigated at pressure 3.8 GPa and temperature 1100-1200 °C. Experimental results indicate that not only is the sintered rate more effective, but also the sintered temperature is lower under high pressure and high temperature than those of under normal pressure. It is thought that the adscititious pressure plays the key role in this process, which is discussed in detail. The composition and the structure of the as-prepared samples are recorded by XRD patterns. The result shows that the phases of BaTiO3, BaBiO2.77, and Ba2Bi4Ti5O18 with piezoelectric ceramic performance generate in the sintered samples. Furthermore, the surface morphology characteristics of the typical samples are also investigated using a scanning electron microscope. It indicates that the grain size and surface structure of the samples are closely related to the sintering temperature and sintering time. It is hoped that this study can provide a new train of thought for the preparation of lead-free piezoelectric ceramics with excellent performance. Project supported by the National Natural Science Foundation of China (Grant No. 51172089), the Natural Science Foundation of Education Department of Guizhou Province, China (Grant Nos. KY [2013]183 and LH [2015]7232), and the Research Fund for the Doctoral Program of Tongren University, China (Grant No. DS1302).