A Dual-Phase Ceramic Membrane with Extremely High H2 Permeation Flux Prepared by Autoseparation of a Ceramic Precursor.

PubMed

Cheng, Shunfan; Wang, Yanjie; Zhuang, Libin; Xue, Jian; Wei, Yanying; Feldhoff, Armin; Caro, Jürgen; Wang, Haihui

2016-08-26

A novel concept for the preparation of multiphase composite ceramics based on demixing of a single ceramic precursor has been developed and used for the synthesis of a dual-phase H2 -permeable ceramic membrane. The precursor BaCe0.5 Fe0.5 O3-δ decomposes on calcination at 1370 °C for 10 h into two thermodynamically stable oxides with perovskite structures: the cerium-rich oxide BaCe0.85 Fe0.15 O3-δ (BCF8515) and the iron-rich oxide BaCe0.15 Fe0.85 O3-δ (BCF1585), 50 mol % each. In the resulting dual-phase material, the orthorhombic perovskite BCF8515 acts as the main proton conductor and the cubic perovskite BCF1585 as the main electron conductor. The dual-phase membrane shows an extremely high H2 permeation flux of 0.76 mL min(-1)  cm(-2) at 950 °C with 1.0 mm thickness. This auto-demixing concept should be applicable to the synthesis of other ionic-electronic conducting ceramics. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Hydroxyapatite-based porous aggregates: physico-chemical nature, structure, texture and architecture.

PubMed

Fabbri, M; Celotti, G C; Ravaglioli, A

1995-02-01

At the request of medical teams from the maxillofacial sector, a highly porous ceramic support based on hydroxyapatite of around 70-80% porosity was produced with a pore size distribution similar to bone texture (< 10 microns, approximately 3 vol%; 10-150 microns, approximately 110 vol%; > 150 microns, approximately 86 vol%). The ceramic substrates were conceived not only as a fillers for bone cavities, but also for use as drug dispensers and as supports to host cells to produce particular therapeutic agents. A method is suggested to obtain a substrate of high porosity, exploiting the impregnation of spongy substrate with hydroxyapatite ceramic particles. X-ray and scanning electron microscopy analyses were carried out to evaluate the nature of the new ceramic support in comparison with the most common commercial product; pore size distribution and porosity were controlled to known hydroxyapatite ceramic architecture for the different possible uses.

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.

Effect of surface acid etching on the biaxial flexural strength of two hot-pressed glass ceramics.

PubMed

Hooshmand, Tabassom; Parvizi, Shaghayegh; Keshvad, Alireza

2008-07-01

The purpose of this study was to assess the effect of surface acid etching on the biaxial flexural strength of two hot-pressed glass ceramics reinforced by leucite or lithium disilicate crystals. Forty glass ceramic disks (14-mm diameter, 2-mm thick) consisting of 20 leucite-based ceramic disks (IPS Empress) and 20 lithia disilicate-based ceramic (IPS Empress 2) were produced by hot-pressing technique. All specimens were polished and then cleaned ultrasonically in distilled water. Ten specimens of each ceramic group were then etched with 9% hydrofluoric (HF) acid gel for 2 minutes and cleaned ultrasonically again. The biaxial flexural strength was measured by the piston-on-three-ball test in a universal testing machine. Data based on ten specimens in each group were analyzed by two-way ANOVA (alpha= 0.05). Microstructure of ceramic surfaces before and after acid etching was also examined by a scanning electron microscope. The mean biaxial flexural strength values for each group tested were (in MPa): nonetched IPS Empress = 118.6 +/- 25.5; etched IPS Empress = 102.9 +/- 15.4; nonetched IPS Empress 2 = 283.0 +/- 48.5; and etched IPS Empress 2 = 250.6 +/- 34.6. The results showed that the etching process reduced the biaxial flexural strengths significantly for both ceramic types (p= 0.025). No significant interaction between the ceramic type and etching process was found (p= 0.407). From the results, it was concluded that surface HF acid etching could have a weakening effect on hot-pressed leucite or lithia disilicate-based glass ceramic systems.

In-situ formation of multiphase electron beam physical vapor deposited barrier coatings for turbine components

DOEpatents

Subramanian, Ramesh

2001-01-01

A turbine component (10), such as a turbine blade, is provided which is made of a metal alloy (22) and a base columnar thermal barrier coating (20) on the alloy surface, where a heat resistant ceramic oxide sheath material (32' or 34') covers the columns (28), and the sheath material is the reaction product of a precursor ceramic oxide sheath material and the base thermal barrier coating material.

Engineering of III-Nitride Semiconductors on Low Temperature Co-fired Ceramics.

PubMed

Mánuel, J M; Jiménez, J J; Morales, F M; Lacroix, B; Santos, A J; García, R; Blanco, E; Domínguez, M; Ramírez, M; Beltrán, A M; Alexandrov, D; Tot, J; Dubreuil, R; Videkov, V; Andreev, S; Tzaneva, B; Bartsch, H; Breiling, J; Pezoldt, J; Fischer, M; Müller, J

2018-05-02

This work presents results in the field of advanced substrate solutions in order to achieve high crystalline quality group-III nitrides based heterostructures for high frequency and power devices or for sensor applications. With that objective, Low Temperature Co-fired Ceramics has been used, as a non-crystalline substrate. Structures like these have never been developed before, and for economic reasons will represent a groundbreaking material in these fields of Electronic. In this sense, the report presents the characterization through various techniques of three series of specimens where GaN was deposited on this ceramic composite, using different buffer layers, and a singular metal-organic chemical vapor deposition related technique for low temperature deposition. Other single crystalline ceramic-based templates were also utilized as substrate materials, for comparison purposes.

Analysis of Shear Bond Strength and Morphology of Er:YAG Laser-Recycled Ceramic Orthodontic Brackets.

PubMed

Han, Ruo-qiao; Yang, Kai; Ji, Ling-fei; Ling, Chen

2016-01-01

The aim of this study was to compare the recycling of deboned ceramic brackets via an Er:YAG laser or via the traditional chairside processing methods of flaming and sandblasting; shear bond strength and morphological changes were evaluated in recycled brackets versus new brackets. 3M Clarity Self-Ligating Ceramic Brackets with a microcrystalline base were divided into groups subjected to flaming, sandblasting, or exposure to an Er:YAG laser. New ceramic brackets served as a control group. Shear bond strengths were determined with an Electroforce test machine and tested for statistical significance through analysis of variance. Morphological examinations of the recycled ceramic bracket bases were conducted with scanning electron microscopy and confocal laser scanning microscopy. Residue on the bracket base was analyzed with Raman spectroscopy. Faded, dark adhesive was left on recycled bracket bases processed via flaming. Adhesive was thoroughly removed by both sandblasting and exposure to an Er:YAG laser. Compared with new brackets, shear bond strength was lower after sandblasting (p < 0.05), but not after exposure to an Er:YAG laser. The Er:YAG laser caused no damage to the bracket. Er:YAG lasers effectively remove adhesive from the bases of ceramic brackets without damaging them; thus, this method may be preferred over other recycling methods.

Advanced Plasma Propulsion

DTIC Science & Technology

2011-11-01

within these cusps where electrons collide with the ceramic insulator lining the channel. In the MIT design, the overall magnetic field strength...allow compression of the anode spring (Sp), which holds the anode insulator (AI) flush with the base core (1). The anode stem and anode (A) are...case Aluminum bulk material 3 Insulator Cone HP-BN St. Gobain/ Ferro- Ceramic Grinding Inc. M1-M3 Permanent

Cleanability evaluation of ceramic glazes with nanometer far-infrared materials using contact angle measurement.

PubMed

Wang, Lijuan; Liang, Jinsheng; Di, Xingfu; Tang, Qingguo

2014-05-01

The cleanability of easy-to-clean ceramic glazes doped with nanometer far-infrared materials was compared with that of some high-quality household ceramic glazes from the market. The cleanability was evaluated by the contact angle measurement using a sessile drop method with a Dataphysics OCA-30 contact angle analyzer. The results showed that the difference of contact angles of water on the glazes before soiling and after cleaning could be used as a parameter for evaluating the cleanability of the glazes. The relationship between cleanability and surface properties, such as surface free energy and surface topography, was investigated. The surface free energy of the samples and their components were calculated using van Oss acid-base approach. By measuring advancing and receding contact angles, the contact angle hysteresis of the ceramic glazes due to the surface topography was investigated. It was shown that the cleanability of ceramic glazes containing nanometer far-infrared materials (NFIM) is better than that of household ceramic glazes from market, due to a higher ratio of electron-acceptor parameter to electron-donor parameter, which led to the effect of water hydration as well as better hydrophilic property and increased smoothness. The contact angle measurement not only accurately evaluates the cleanability of the ceramic glazes, but also has a contribution to the study of cleanability theory. Moreover, this method is simple, convenient and less sample-consumption.

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.

Computer-aided study of key factors determining high mechanical properties of nanostructured surface layers in metal-ceramic composites

NASA Astrophysics Data System (ADS)

Konovalenko, Igor S.; Shilko, Evgeny V.; Ovcharenko, Vladimir E.; Psakhie, Sergey G.

2017-12-01

The paper presents the movable cellular automaton method. It is based on numerical models of surface layers of the metal-ceramic composite NiCr-TiC modified under electron beam irradiation in inert gas plasmas. The models take into account different geometric, concentration and mechanical parameters of ceramic and metallic components. The authors study the contributions of key structural factors in mechanical properties of surface layers and determine the ranges of their variations by providing the optimum balance of strength, strain hardening and fracture toughness.

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.

The plasma electrolytic oxidation micro-discharge channel model and its microstructure characteristic based on Ti tracer

NASA Astrophysics Data System (ADS)

Gao, Fangyuan; Hao, Li; Li, Guang; Xia, Yuan

2018-02-01

This study focuses on the individual discharge channel of ceramic coating prepared by plasma electrolytic oxidation (PEO), and attempts to reveal the mechanism of breakdown discharge at low voltage. Titanium (Ti) was employed as a substrate with the layer of aluminum deposited on it (aluminized Ti). The shape and microstructure of the discharge channels in PEO coatings were investigated using transmission electron microscope (TEM) and scanning electron microscopy (SEM). A schematic model of the individual discharge channel was proposed based on Ti tracer method. The shape of the discharge channel was mainly cylinder-shaped in the compact coating, with a groove-like oxidation region existed at the coating/substrate interface. In the groove-like oxidation region, the phase composition mainly composed of amorphous and mixed polycrystalline (aluminum titanate and mullite). β-Al2O3 was found in the ceramic coating. TEM morphology showed that nanometer sized micro channels existed in the ceramic coatings.

Corrosion Resistance of a Cast-Iron Material Coated With a Ceramic Layer Using Thermal Spray Method

NASA Astrophysics Data System (ADS)

Florea, C. D.; Bejinariu, C.; Munteanu, C.; Istrate, B.; Toma, S. L.; Alexandru, A.; Cimpoesu, R.

2018-06-01

Cast-iron 250 used for breake systems present many corrosion signs after a mean usage time based on the environment conditions they work. In order to improve them corrosion resistance we propose to cover the active part of the material using a ceramic material. The deposition process is an industrial deposition system based on thermal spraying that can cover high surfaces in low time. In this articol we analyze the influence of a ceramic layer (40-50 µm) on the corrosion resistance of FC250 cast iron. The results were analyzed using scanning electron microscopy (SEM), X-ray energy dispersive (EDS) and linear and cyclic potentiometry.

Marginal and Internal Discrepancies of Posterior Zirconia-Based Crowns Fabricated with Three Different CAD/CAM Systems Versus Metal-Ceramic.

PubMed

Ortega, Rocio; Gonzalo, Esther; Gomez-Polo, Miguel; Suárez, María J

2015-01-01

The aim of this study was to analyze the marginal and internal fit of metalceramic and zirconia-based crowns. Forty standardized steel specimens were prepared to receive posterior crowns and randomly divided into four groups (n = 10): (1) metal-ceramic, (2) NobelProcera Zirconia, (3) Lava Zirconia, and (4) VITA In-Ceram YZ. All crowns were cemented with glass-ionomer agent and sectioned buccolingually. A scanning electron microscope was used for measurements. Kruskal-Wallis and Wilcoxon signed rank test (α = .05) statistical analyses were conducted. Significant differences (P < .0001) in marginal discrepancies were observed between metal-ceramic and zirconia groups. No differences were found for the axial wall fit (P = .057). Significant differences were shown among the groups in discrepancies at the occlusal cusp (P = .0012) and at the fossa (P = .0062). No differences were observed between surfaces. All zirconia groups showed better values of marginal discrepancies than the metal-ceramic group. Procera Zirconia showed the lowest gaps.

Computational evidence for stable inorganic fullerene-like structures of ceramic and semiconductor materials

NASA Astrophysics Data System (ADS)

Chang, Ch; Patzer, A. B. C.; Sedlmayr, E.; Steinke, T.; Sülzle, D.

2001-12-01

Theoretical electronic structure techniques have become an indispensible and powerful means for predicting molecular properties and designing new materials. Based on a density functional approach and guided by geometric considerations we provide evidence for some specific inorganic fullerene-like cage molecules of ceramic and semiconductor materials which exhibit high energetic stability and point group symmetry as well as nearly perfect spherical shape.

Preliminary results on complex ceramic layers deposition by atmospheric plasma spraying

NASA Astrophysics Data System (ADS)

Florea, Costel; Bejinariu, Costicǎ; Munteanu, Corneliu; Cimpoeşu, Nicanor

2017-04-01

In this article we obtain thin layers from complex ceramic powders using industrial equipment based on atmospheric plasma spraying. We analyze the influence of the substrate material roughness on the quality of the thin layers using scanning electron microscopy (SEM) and X-ray dispersive energy analyze (EDAX). Preliminary results present an important dependence between the surface state and the structural and chemical homogeneity.

Chemistry of electronic ceramic materials. Proceedings of the International Conference on the Chemistry of Electronic Ceramic Materials

NASA Technical Reports Server (NTRS)

Davies, P. K.; Roth, R. S.

1991-01-01

The conference was held at Jackson Hole, Wyoming from August 17 to 22, 1990, and in an attempt to maximize the development of this rapidly moving, multidisciplinary field, this conference brought together major national and international researchers to bridge the gap between those primarily interested in the pure chemistry of inorganic solids and those interested in the physical and electronic properties of ceramics. With the many major discoveries that have occurred over the last decade, one of the goals of this meeting was to evaluate the current understanding of the chemistry of electronic ceramic materials, and to assess the state of a field that has become one of the most important areas of advanced materials research. The topics covered include: crystal chemistry; dielectric ceramics; low temperature synthesis and characterization; solid state synthesis and characterization; surface chemistry; superconductors; theory and modeling.

Analysis of Shear Bond Strength and Morphology of Er:YAG Laser-Recycled Ceramic Orthodontic Brackets

PubMed Central

Han, Ruo-qiao; Ji, Ling-fei; Ling, Chen

2016-01-01

Objective. The aim of this study was to compare the recycling of deboned ceramic brackets via an Er:YAG laser or via the traditional chairside processing methods of flaming and sandblasting; shear bond strength and morphological changes were evaluated in recycled brackets versus new brackets. Materials and Methods. 3M Clarity Self-Ligating Ceramic Brackets with a microcrystalline base were divided into groups subjected to flaming, sandblasting, or exposure to an Er:YAG laser. New ceramic brackets served as a control group. Shear bond strengths were determined with an Electroforce test machine and tested for statistical significance through analysis of variance. Morphological examinations of the recycled ceramic bracket bases were conducted with scanning electron microscopy and confocal laser scanning microscopy. Residue on the bracket base was analyzed with Raman spectroscopy. Results. Faded, dark adhesive was left on recycled bracket bases processed via flaming. Adhesive was thoroughly removed by both sandblasting and exposure to an Er:YAG laser. Compared with new brackets, shear bond strength was lower after sandblasting (p < 0.05), but not after exposure to an Er:YAG laser. The Er:YAG laser caused no damage to the bracket. Conclusion. Er:YAG lasers effectively remove adhesive from the bases of ceramic brackets without damaging them; thus, this method may be preferred over other recycling methods. PMID:27047964

Characterization of ion beam modified ceramic wear surfaces using Auger electron spectroscopy

NASA Technical Reports Server (NTRS)

Wei, W.; Lankford, J.

1987-01-01

An investigation of the surface chemistry and morphology of the wear surfaces of ceramic material surfaces modified by ion beam mixing has been conducted using Auger electron spectroscopy and secondary electron microscopy. Studies have been conducted on ceramic/ceramic friction and wear couples made up of TiC and NiMo-bonded TiC cermet pins run against Si3N4 and partially stabilized zirconia disc surfaces modified by the ion beam mixing of titanium and nickel, as well as ummodified ceramic/ceramic couples in order to determine the types of surface changes leading to the improved friction and wear behavior of the surface modified ceramics in simulated diesel environments. The results of the surface analyses indicate that the formation of a lubricating oxide layer of titanium and nickel, is responsible for the improvement in ceramic friction and wear behavior. The beneficial effect of this oxide layer depends on several factors, including the adherence of the surface modified layer or subsequently formed oxide layer to the disc substrate, the substrate materials, the conditions of ion beam mixing, and the environmental conditions.

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.

Final Technical Report - 300°C Capable Electronics Platform and Temperature Sensor System For Enhanced Geothermal Systems

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

Chen, Cheng-Po; Shaddock, David; Sandvik, Peter

2012-11-30

A silicon carbide (SiC) based electronic temperature sensor prototype has been demonstrated to operate at 300°C. We showed continuous operation of 1,000 hours with SiC operational amplifier and surface mounted discreet resistors and capacitors on a ceramic circuit board. This feasibility demonstration is a major milestone in the development of high temperature electronics in general and high temperature geothermal exploration and well management tools in particular. SiC technology offers technical advantages that are not found in competing technologies such as silicon-on-insulator (SOI) at high temperatures of 200°C to 300°C and beyond. The SiC integrated circuits and packaging methods can bemore » used in new product introduction by GE Oil and Gas for high temperature down-hole tools. The existing SiC fabrication facility at GE is sufficient to support the quantities currently demanded by the marketplace, and there are other entities in the United States and other countries capable of ramping up SiC technology manufacturing. The ceramic circuit boards are different from traditional organic-based electronics circuit boards, but the fabrication process is compatible with existing ceramic substrate manufacturing. This project has brought high temperature electronics forward, and brings us closer to commercializing tools that will enable and reduce the cost of enhanced geothermal technology to benefit the public in terms of providing clean renewable energy at lower costs.« less

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.

Economic analysis of crystal growth in space

NASA Technical Reports Server (NTRS)

Ulrich, D. R.; Chung, A. M.; Yan, C. S.; Mccreight, L. R.

1972-01-01

Many advanced electronic technologies and devices for the 1980's are based on sophisticated compound single crystals, i.e. ceramic oxides and compound semiconductors. Space processing of these electronic crystals with maximum perfection, purity, and size is suggested. No ecomonic or technical justification was found for the growth of silicon single crystals for solid state electronic devices in space.

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.

Microstructure and wear resistance of Al2O3-M7C3/Fe composite coatings produced by laser controlled reactive synthesis

NASA Astrophysics Data System (ADS)

Tan, Hui; Luo, Zhen; Li, Yang; Yan, Fuyu; Duan, Rui

2015-05-01

Based on the principle of thermite reaction of Al and Fe2O3 powders, the Al2O3 ceramic reinforced Fe-based composite coatings were fabricated on a steel substrate by laser controlled reactive synthesis and cladding. The effects of different additions of thermite reactants on the phase transition, microstructure evolution, microhardness and wear resistance of the composite coatings were investigated by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Vickers microhardness and block-on-ring wear test, respectively. The results show that Al2O3 ceramic and M7C3 carbide are in situ synthesized via the laser controlled reactive synthesis. The Al2O3 ceramic and M7C3 carbides prefer to distribute along the γ-Fe phase boundary continuously, which separates the γ-Fe matrix and is beneficial to the grain refinement. With the increase of thermite reactants, the amount of Al2O3 ceramic and M7C3 carbide in the composite coatings increases gradually. Moreover the cladding layer changes from dendritic structure to columnar structure and martensite structure in the heat affected zone becomes coarse. The increased thermite reactants improve the microhardness and wear resistance of the in situ composite coatings obviously and enhance the hardness of the heat affected zone, which should be ascribed to the grain refinement, ceramic and carbide precipitation and solid solution strengthening.

Laser profilometer module based on a low-temperature cofired ceramic substrate

NASA Astrophysics Data System (ADS)

Heikkinen, Veli; Heikkinen, Mikko; Keranen, Kimmo; Mitikka, Risto S.; Putila, Veli-Pekka; Tukkiniemi, Kari

2005-09-01

We realized a laser profilometer module using low temperature cofired ceramics technology. The device consists of a vertical-cavity surface-emitting laser as the light source and a complementary metal oxide semiconductor image sensor as the detector. The laser transmitter produces a thin light stripe on the measurable object, and the receiver calculates the distance profile using triangulation. Because the design of optoelectronic modules, such as the laser profilometer, is usually carried out using specialized software, its electronic compatibility is very important. We developed a data transmission network using commercial optical, electrical, and mechanical design software, which enabled us to electronically transfer data between the designers. The module electronics were realized with multilayer ceramics technology that eases component assembly by providing precision alignment features in the substrate. The housing was manufactured from aluminum using electronic data transfer from the mechanical design software to the five-axis milling workstation. Target distance profiles were obtained from 100 points with an accuracy varying from 0.1 mm at a 5-cm distance to 2 cm at 1.5 m. The module has potential for distance measurement in portable devices where small size, light weight, and low power consumption are important.

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.

Monolithic LTCC seal frame and lid

DOEpatents

Krueger, Daniel S.; Peterson, Kenneth A.; Stockdale, Dave; Duncan, James Brent; Riggs, Bristen

2016-06-21

A method for forming a monolithic seal frame and lid for use with a substrate and electronic circuitry comprises the steps of forming a mandrel from a ceramic and glass based material, forming a seal frame and lid block from a ceramic and glass based material, creating a seal frame and lid by forming a compartment and a plurality of sidewalls in the seal frame and lid block, placing the seal frame and lid on the mandrel such that the mandrel fits within the compartment, and cofiring the seal frame and lid block.

Synthesis, morphological, electromechanical characterization of (CaMgFex)Fe1-xTi3O12-δ/PDMS nanocomposite thin films for energy storage application

NASA Astrophysics Data System (ADS)

Tripathy, Ashis; Sharma, Priyaranjan; Sahoo, Narayan

2018-03-01

At the present time, flexible and stretchable electronics has intended to use the new cutting-edge technologies for advanced electronic application. Currently, Polymers are being employed for such applications but they are not effective due to their low dielectric constant. To enhance the dielectric properties of polymer for energy storage application, it is necessary to add ceramic material of high dielectric constant to synthesize a polymer-ceramic composite. Therefore, a novel attempt has been made to enhance the dielectric properties of the Polydimethylsiloxane (PDMS) polymer by adding (CaMgFex)Fe1-xTi3O12-δ(0 90%), which can make it a potential material for advanced flexible electronic devices, energy storage and biomedical applications.

Ab initio modeling of complex amorphous transition-metal-based ceramics.

PubMed

Houska, J; Kos, S

2011-01-19

Binary and ternary amorphous transition metal (TM) nitrides and oxides are of great interest because of their suitability for diverse applications ranging from high-temperature machining to the production of optical filters or electrochromic devices. However, understanding of bonding in, and electronic structure of, these materials represents a challenge mainly due to the d electrons in their valence band. In the present work, we report ab initio calculations of the structure and electronic structure of ZrSiN materials. We focus on the methodology needed for the interpretation and automatic analysis of the bonding structure, on the effect of the length of the calculation on the convergence of individual quantities of interest and on the electronic structure of materials. We show that the traditional form of the Wannier function center-based algorithm fails due to the presence of d electrons in the valence band. We propose a modified algorithm, which allows one to analyze bonding structure in TM-based systems. We observe an appearance of valence p states of TM atoms in the electronic spectra of such systems (not only ZrSiN but also NbO(x) and WAuO), and examine the importance of the p states for the character of the bonding as well as for facilitating the bonding analysis. The results show both the physical phenomena and the computational methodology valid for a wide range of TM-based ceramics.

Analysis of the Atomic-Scale Defect Chemistry at Interfaces in Fluorite Structured Oxides by Electron Energy Loss Spectroscopy

DTIC Science & Technology

2001-11-01

electronic properties, i.e. oxygen coordination and cation valence at grain boundaries of the fluorite structured Gdo]2Ceo.gO 2_x ceramic membrane material...required to obtain a detailed understanding of the atomic scale phenomena in ceramics, as the polycrystalline nature of Gdo.2Ceo.802- ceramic membrane material

Influence of a cellulosic ether carrier on the structure of biphasic calcium phosphate ceramic particles in an injectable composite material.

PubMed

Dupraz, A; Nguyen, T P; Richard, M; Daculsi, G; Passuti, N

1999-04-01

An injectable composite material based on biphasic calcium phosphate (BCP) and a nonionic cellulose ether has been elaborated for use in percutaneous surgery for spine fusion. This paper reports the characterization results of this material by spectroscopic techniques including X-ray diffraction (XRD), infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) fitted with an energy dispersive X-Ray analysis system and high-resolution transmission electron microscopy (HR-TEM). From FTIR and XPS results, it was observed that the adhesion between the polymer and the ceramic might be insured by oxygen bridging developed through an ionic bonding between calcium ions and (C-O) groups of the polymer. Moreover, XPS showed attraction of Ca2+ ions in the polymer matrix, while the ceramic surface was modified in a HPO4(2-) -rich layer. These results suggest a possible dissolution/precipitation process at the interface ceramic/polymer. HR-TEM observations supported this hypothesis, showing a light contrasted fringe at the surface of the ceramic grains in the composite paste. As well, changes in the XRD spectra could indicate a small decrease in the crystal size of the BCP powder through the contact to polymer solution. In addition, SEM observation showed a decrease of the initial BCP granulometry. Aggregates of 80-200 microm seemed to be mostly dissociated in micrograins. The ceramic grains were coated with and bonded between each other by the polymer matrix, which acted as spacer in between the ceramic grains, creating a macroporous-like material structure.

Thin-Film Ceramic Thermocouples Fabricated and Tested

NASA Technical Reports Server (NTRS)

Wrbanek, John D.; Fralick, Gustave C.; Farmer, Serene C.; Sayir, Ali; Gregory, Otto J.; Blaha, Charles A.

2004-01-01

The Sensors and Electronics Technology Branch of the NASA Glenn Research Center is developing thin-film-based sensors for surface measurement in propulsion system research. Thin-film sensors do not require special machining of the components on which they are mounted, and they are considerably thinner than wire- or foil-based sensors. One type of sensor being advanced is the thin-film thermocouple, specifically for applications in high-temperature combustion environments. Ceramics are being demonstrated as having the potential to meet the demands of thin-film thermocouples in advanced aerospace environments. The maximum-use temperature of noble metal thin-film thermocouples, 1500 C (2700 F), may not be adequate for components used in the increasingly harsh conditions of advanced aircraft and next-generation launch vehicles. Ceramic-based thermocouples are known for their high stability and robustness at temperatures exceeding 1500 C, but are typically in the form of bulky rods or probes. As part of ASTP, Glenn's Sensors and Electronics Technology Branch is leading an in-house effort to apply ceramics as thin-film thermocouples for extremely high-temperature applications as part of ASTP. Since the purity of the ceramics is crucial for the stability of the thermocouples, Glenn's Ceramics Branch and Case Western Reserve University are developing high-purity ceramic sputtering targets for fabricating high-temperature sensors. Glenn's Microsystems Fabrication Laboratory, supported by the Akima Corporation, is using these targets to fabricate thermocouple samples for testing. The first of the materials used were chromium silicide (CrSi) and tantalum carbide (TaC). These refractory materials are expected to survive temperatures in excess of 1500 C. Preliminary results indicate that the thermoelectric voltage output of a thin-film CrSi versus TaC thermocouple is 15 times that of the standard type R (platinum-rhodium versus platinum) thermocouple, producing 20 mV with a 200 C temperature gradient. The photograph on the left shows the CrSi-TaC thermocouple in a test fixture at Glenn, and the resulting output signal is shown on the right. The temperature differential across the sample, from the center of the sample inside the oven to the sample mount outside the oven, is measured using a type R thermocouple on the sample.

Electrode array for neural stimulation

DOEpatents

Wessendorf, Kurt O [Albuquerque, NM; Okandan, Murat [Edgewood, NM; Stein, David J [Albuquerque, NM; Yang, Pin [Albuquerque, NM; Cesarano, III, Joseph; Dellinger, Jennifer [Albuquerque, NM

2011-08-16

An electrode array for neural stimulation is disclosed which has particular applications for use in a retinal prosthesis. The electrode array can be formed as a hermetically-sealed two-part ceramic package which includes an electronic circuit such as a demultiplexer circuit encapsulated therein. A relatively large number (up to 1000 or more) of individually-addressable electrodes are provided on a curved surface of a ceramic base portion the electrode array, while a much smaller number of electrical connections are provided on a ceramic lid of the electrode array. The base and lid can be attached using a metal-to-metal seal formed by laser brazing. Electrical connections to the electrode array can be provided by a flexible ribbon cable which can also be used to secure the electrode array in place.

Transparent athermal glass-ceramics in Li2O-Al2O3-SiO2 system

NASA Astrophysics Data System (ADS)

Himei, Yusuke; Nagakane, Tomohiro; Sakamoto, Akihiko; Kitamura, Naoyuki; Fukumi, Kohei; Nishii, Junji; Hirao, Kazuyuki

2005-04-01

An attempt has been conducted to develop multicomponent transparent glass-ceramics which have athermal property better than silica glass. Transparent Li2O-Al2O3-SiO2 (LAS) glass-ceramics with small thermal expansion coefficient was chosen as a candidate. Athermal property of the glass-ceramics was improved by the independent control of temperature coefficients of electronic polarizability and thermal expansion coefficient, both of which govern the temperature coefficient of optical path length. It was found that temperature coefficient of electronic polarizability and thermal expansion coefficient of the LAS glass-ceramics were controllable by the additives and crystallization conditions. The doping of B2O3 and the crystallization under a hydrostatic pressure of 196 MPa were very effective to reduce temperature coefficient of electronic polarizability without a remarkable increase in thermal expansion coefficient. It was deduced that the reduction in temperature coefficient of electronic polarizability by the crystallization under 196 MPa resulted from the inhibition of the precipitation of beta-spodumene solid solution. The relative temperature coefficients of optical path length of B2O3-doped glass-ceramic crystallized under 196 MPa was 11.7 x 10-6/°C, which was slightly larger than that of silica glass. Nevertheless, the thermal expansion coefficient of this glass-ceramic was smaller than that of silica glass.

Microstructure and properties of ceramics

NASA Technical Reports Server (NTRS)

Hamano, K.

1984-01-01

The history of research into the microstructure and properties of ceramic ware is discussed; methods of producing ceramics with particular characteristics are investigated. Bubbles, sintering, cracks, and electron microscopy are discussed.

Ceramic transactions - Materials processing and design: Grain-boundary-controlled properties of fine ceramics II. Volume 44

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

Niihara, Koichi; Ishizaki, Kozo; Isotani, Mitsuo

This volume contains selected papers presented at a workshop by the Japan Fine Ceramics Center, `Materials Processing and Design Through Better Control of Grain Boundaries: Emphasizing Fine Ceramics II,` which was held March 17-19, 1994, in Koda-cho, Aichi, Japan. The focus of the workshop was the application of grain boundary phenomena to materials processing and design. The topics covered included electronic materials, evaluation methods, structural materials, and interfaces. Also included is an illuminating overview of the current status of work on grain boundary assisted materials processing and design, particularly for fine ceramics. The volume`s chapter titles are: Electron Microscopy, Evaluation,more » Grain Boundary Control and Design, Functional Ceramics, Composite Materials, Synthesis and Sintering, and Mechanical Properties.« less

Modification of Structure and Tribological Properties of the Surface Layer of Metal-Ceramic Composite under Electron Irradiation in the Plasmas of Inert Gases

NASA Astrophysics Data System (ADS)

Ovcharenko, V. E.; Ivanov, K. V.; Mohovikov, A. A.; Yu, B.; Xu, Yu; Zhong, L.

2018-01-01

Metal-ceramic composites are the main materials for high-load parts in tribomechanical systems. Modern approaches to extend the operation life of tribomechanical systems are based on increasing the strength and tribological properties of the surface layer having 100 to 200 microns in depth. The essential improvement of the properties occurs when high dispersed structure is formed in the surface layer using high-energy processing. As a result of the dispersed structure formation the more uniform distribution of elastic stresses takes place under mechanical or thermal action, the energy of stress concentrators emergence significantly increases and the probability of internal defects formation reduces. The promising method to form the dispersed structure in the surface layer is pulse electron irradiation in the plasmas of inert gases combining electron irradiation and ion bombardment in one process. The present work reports upon the effect of pulse electron irradiation in plasmas of different inert gases with different atomic mass and ionization energy on the structure and tribological properties of the surface layer of TiC/(Ni-Cr) metal-ceramic composite with the volume ratio of the component being 50:50. It is experimentally shown that high-dispersed heterophase structure with a fraction of nanosized particles is formed during the irradiation. Electron microscopy study reveals that refining of the initial coarse TiC particles occurs via their dissolution in the molten metal binder followed by the precipitation of secondary fine particles in the interparticle layers of the binder. The depth of modified layer and the fraction of nanosized particles increase when the atomic number of the plasma gas increases and ionization energy decreases. The wear resistance of metal-ceramic composite improves in accordance to the formation of nanocrystalline structure in the surface layer.

Crystal phase analysis of SnO{sub 2}-based varistor ceramic using the Rietveld method

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

Moreira, M.L.; Pianaro, S.A.; Andrade, A.V.C.

2006-09-15

A second addition of l mol% of CoO to a pre calcined SnO{sub 2}-based ceramic doped with 1.0 mol% of CoO, 0.05 mol% of Nb{sub 2}O{sub 5} and 0.05 mol% of Cr{sub 2}O{sub 3} promotes the appearance of a secondary phase, Co{sub 2}SnO{sub 4}, besides the SnO{sub 2} cassiterite phase, when the ceramic was sintered at 1350 deg. C/2 h. This was observed using X-ray powder diffraction, scanning electron microscopy and energy dispersive X-ray techniques. Rietveld refinement was carried out to quantify the phases present in the ceramic system. The results of the quantitative analysis were 97 wt.% SnO{sub 2}more » and 3 wt.% Co{sub 2}SnO{sub 4}. The microstructural analysis showed that a certain amount of cobalt ion remains into cassiterite grains.« less

High-energy electron beams for ceramic joining

NASA Astrophysics Data System (ADS)

Turman, Bob N.; Glass, S. J.; Halbleib, J. A.; Helmich, D. R.; Loehman, Ron E.; Clifford, Jerome R.

1995-03-01

Joining of structural ceramics is possible using high melting point metals such as Mo and Pt that are heated with a high energy electron beam, with the potential for high temperature joining. A 10 MeV electron beam can penetrate through 1 cm of ceramic, offering the possibility of buried interface joining. Because of transient heating and the lower heat capacity of the metal relative to the ceramic, a pulsed high power beam has the potential for melting the metal without decomposing or melting the ceramic. We have demonstrated the feasibility of the process with a series of 10 MeV, 1 kW electron beam experiments. Shear strengths up to 28 MPa have been measured. This strength is comparable to that reported in the literature for bonding silicon nitride (Si3N4) to molybdenum with copper-silver-titanium braze, but weaker than that reported for Si3N4 - Si3N4 with gold-nickel braze. The bonding mechanism appears to be formation of a thin silicide layer. Beam damage to the Si3N4 was also assessed.

Influence of CAD/CAM systems and cement selection on marginal discrepancy of zirconia-based ceramic crowns.

PubMed

Martínez-Rus, Francisco; Suárez, María J; Rivera, Begoña; Pradíes, Guillermo

2012-04-01

To analyze the effect of ceramic manufacturing technique and luting cement selection on the marginal adaptation of zirconium oxide-based all-ceramic crowns. An extracted mandibular first premolar was prepared for a complete coverage restoration and subsequently duplicated 40 times in a liquid crystal polymer (LCP). All-ceramic crowns (n = 10) were fabricated on LCP models using the following systems: glass-infiltrated zirconia-toughened alumina (In-Ceram Zirconia) and yttrium cation-doped tetragonal zirconia polycrystals (In-Ceram YZ, Cercon, and Procera Zirconia). The restorations (n = 5) were cemented on their respective dies with glass-ionomer cement (Ketac Cem Aplicap) and resin cement (Panavia 21). The absolute marginal discrepancy of the crowns was measured before and after cementation by scanning electronic microscopy at 160 points along the circumferential margin. The data were analyzed using one-way ANOVA for repeated measures and for independent samples, Scheffé's multiple range post hoc test, and Student's t-test (alpha = 0.05). There were statistical differences in the mean marginal openings among the four all-ceramic systems before and after luting (P < 0.0001). The Procera restorations had the lowest pre- and post-cementation values (P < 0.0001). A significant increase in the marginal gap size caused by luting media occurred in all tested groups (P < 0.0001). Resin cement resulted in larger marginal discrepancies than glass-ionomer cement (P < 0.0001).

Superconductive radiofrequency window assembly

DOEpatents

Phillips, Harry Lawrence; Elliott, Thomas S.

1998-01-01

The present invention is a superconducting radiofrequency window assembly for use in an electron beam accelerator. The srf window assembly (20) has a superconducting metal-ceramic design. The srf window assembly (20) comprises a superconducting frame (30), a ceramic plate (40) having a superconducting metallized area, and a superconducting eyelet (50) for sealing plate (40) into frame (30). The plate (40) is brazed to eyelet (50) which is then electron beam welded to frame (30). A method for providing a ceramic object mounted in a metal member to withstand cryogenic temperatures is also provided. The method involves a new metallization process for coating a selected area of a ceramic object with a thin film of a superconducting material. Finally, a method for assembling an electron beam accelerator cavity utilizing the srf window assembly is provided. The procedure is carried out within an ultra clean room to minimize exposure to particulates which adversely affect the performance of the cavity within the electron beam accelerator.

Superconductive radiofrequency window assembly

DOEpatents

Phillips, H.L.; Elliott, T.S.

1998-05-19

The present invention is a superconducting radiofrequency window assembly for use in an electron beam accelerator. The SRF window assembly has a superconducting metal-ceramic design. The SRF window assembly comprises a superconducting frame, a ceramic plate having a superconducting metallized area, and a superconducting eyelet for sealing plate into frame. The plate is brazed to eyelet which is then electron beam welded to frame. A method for providing a ceramic object mounted in a metal member to withstand cryogenic temperatures is also provided. The method involves a new metallization process for coating a selected area of a ceramic object with a thin film of a superconducting material. Finally, a method for assembling an electron beam accelerator cavity utilizing the SRF window assembly is provided. The procedure is carried out within an ultra clean room to minimize exposure to particulates which adversely affect the performance of the cavity within the electron beam accelerator. 11 figs.

Superconducting radiofrequency window assembly

DOEpatents

Phillips, Harry L.; Elliott, Thomas S.

1997-01-01

The present invention is a superconducting radiofrequency window assembly for use in an electron beam accelerator. The srf window assembly (20) has a superconducting metal-ceramic design. The srf window assembly (20) comprises a superconducting frame (30), a ceramic plate (40) having a superconducting metallized area, and a superconducting eyelet (50) for sealing plate (40) into frame (30). The plate (40) is brazed to eyelet (50) which is then electron beam welded to frame (30). A method for providing a ceramic object mounted in a metal member to withstand cryogenic temperatures is also provided. The method involves a new metallization process for coating a selected area of a ceramic object with a thin film of a superconducting material. Finally, a method for assembling an electron beam accelerator cavity utilizing the srf window assembly is provided. The procedure is carried out within an ultra clean room to minimize exposure to particulates which adversely affect the performance of the cavity within the electron beam accelerator.

Superconducting radiofrequency window assembly

DOEpatents

Phillips, H.L.; Elliott, T.S.

1997-03-11

The present invention is a superconducting radiofrequency window assembly for use in an electron beam accelerator. The srf window assembly has a superconducting metal-ceramic design. The srf window assembly comprises a superconducting frame, a ceramic plate having a superconducting metallized area, and a superconducting eyelet for sealing plate into frame. The plate is brazed to eyelet which is then electron beam welded to frame. A method for providing a ceramic object mounted in a metal member to withstand cryogenic temperatures is also provided. The method involves a new metallization process for coating a selected area of a ceramic object with a thin film of a superconducting material. Finally, a method for assembling an electron beam accelerator cavity utilizing the srf window assembly is provided. The procedure is carried out within an ultra clean room to minimize exposure to particulates which adversely affect the performance of the cavity within the electron beam accelerator. 11 figs.

Packaging Technologies for High Temperature Electronics and Sensors

NASA Technical Reports Server (NTRS)

Chen, Liang-Yu; Hunter, Gary W.; Neudeck, Philip G.; Beheim, Glenn M.; Spry, David J.; Meredith, Roger D.

2013-01-01

This paper reviews ceramic substrates and thick-film metallization based packaging technologies in development for 500 C 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 550 C. A 96% alumina based edge connector for a PCB level subsystem interconnection has also been demonstrated recently. The 96% alumina packaging system composed of chip-level packages and PCBs has been tested with high temperature SiC devices at 500 C for over 10,000 hours. In addition to tests in a laboratory environment, a SiC JFET with a packaging system composed of a 96% alumina chip-level package and an alumina printed circuit board mounted on a data acquisition circuit board was launched as a part of the MISSE-7 suite to the International Space Station via a Shuttle mission. This packaged SiC transistor was successfully tested in orbit for eighteen months. A spark-plug type sensor package designed for high temperature SiC capacitive pressure sensors was developed. This sensor package combines the high temperature interconnection system with a commercial high temperature high pressure stainless steel seal gland (electrical feed-through). Test results of a packaged high temperature capacitive pressure sensor at 500 C are also discussed. In addition to the pressure sensor package, efforts for packaging high temperature SiC diode-based gas chemical sensors are in process.

Packaging Technologies for High Temperature Electronics and Sensors

NASA Technical Reports Server (NTRS)

Chen, Liangyu; Hunter, Gary W.; Neudeck, Philip G.; Beheim, Glenn M.; Spry, David J.; Meredith, Roger D.

2013-01-01

This paper reviews ceramic substrates and thick-film metallization based packaging technologies in development for 500degC 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 chiplevel packages with gold (Au) thick-film metallization have been electrically characterized at temperatures up to 550degC. A 96% alumina based edge connector for a PCB level subsystem interconnection has also been demonstrated recently. The 96% alumina packaging system composed of chip-level packages and PCBs has been tested with high temperature SiC devices at 500degC for over 10,000 hours. In addition to tests in a laboratory environment, a SiC JFET with a packaging system composed of a 96% alumina chip-level package and an alumina printed circuit board mounted on a data acquisition circuit board was launched as a part of the MISSE-7 suite to the International Space Station via a Shuttle mission. This packaged SiC transistor was successfully tested in orbit for eighteen months. A spark-plug type sensor package designed for high temperature SiC capacitive pressure sensors was developed. This sensor package combines the high temperature interconnection system with a commercial high temperature high pressure stainless steel seal gland (electrical feed-through). Test results of a packaged high temperature capacitive pressure sensor at 500degC are also discussed. In addition to the pressure sensor package, efforts for packaging high temperature SiC diode-based gas chemical sensors are in process.

Single-source-precursor synthesis of dense SiC/HfCxN1-x-based ultrahigh-temperature ceramic nanocomposites

NASA Astrophysics Data System (ADS)

Wen, Qingbo; Xu, Yeping; Xu, Binbin; Fasel, Claudia; Guillon, Olivier; Buntkowsky, Gerd; Yu, Zhaoju; Riedel, Ralf; Ionescu, Emanuel

2014-10-01

A novel single-source precursor was synthesized by the reaction of an allyl hydrido polycarbosilane (SMP10) and tetrakis(dimethylamido)hafnium(iv) (TDMAH) for the purpose of preparing dense monolithic SiC/HfCxN1-x-based ultrahigh temperature ceramic nanocomposites. The materials obtained at different stages of the synthesis process were characterized via Fourier transform infrared (FT-IR) as well as nuclear magnetic resonance (NMR) spectroscopy. The polymer-to-ceramic transformation was investigated by means of MAS NMR and FT-IR spectroscopy as well as thermogravimetric analysis (TGA) coupled with in situ mass spectrometry. Moreover, the microstructural evolution of the synthesized SiHfCN-based ceramics annealed at different temperatures ranging from 1300 °C to 1800 °C was characterized by elemental analysis, X-ray diffraction, Raman spectroscopy and transmission electron microscopy (TEM). Based on its high temperature behavior, the amorphous SiHfCN-based ceramic powder was used to prepare monolithic SiC/HfCxN1-x-based nanocomposites using the spark plasma sintering (SPS) technique. The results showed that dense monolithic SiC/HfCxN1-x-based nanocomposites with low open porosity (0.74 vol%) can be prepared successfully from single-source precursors. The average grain size of both HfC0.83N0.17 and SiC phases was found to be less than 100 nm after SPS processing owing to a unique microstructure: HfC0.83N0.17 grains were embedded homogeneously in a β-SiC matrix and encapsulated by in situ formed carbon layers which acted as a diffusion barrier to suppress grain growth. The segregated Hf-carbonitride grains significantly influenced the electrical conductivity of the SPS processed monolithic samples. While Hf-free polymer-derived SiC showed an electrical conductivity of ca. 1.8 S cm-1, the electrical conductivity of the Hf-containing material was analyzed to be ca. 136.2 S cm-1.A novel single-source precursor was synthesized by the reaction of an allyl hydrido polycarbosilane (SMP10) and tetrakis(dimethylamido)hafnium(iv) (TDMAH) for the purpose of preparing dense monolithic SiC/HfCxN1-x-based ultrahigh temperature ceramic nanocomposites. The materials obtained at different stages of the synthesis process were characterized via Fourier transform infrared (FT-IR) as well as nuclear magnetic resonance (NMR) spectroscopy. The polymer-to-ceramic transformation was investigated by means of MAS NMR and FT-IR spectroscopy as well as thermogravimetric analysis (TGA) coupled with in situ mass spectrometry. Moreover, the microstructural evolution of the synthesized SiHfCN-based ceramics annealed at different temperatures ranging from 1300 °C to 1800 °C was characterized by elemental analysis, X-ray diffraction, Raman spectroscopy and transmission electron microscopy (TEM). Based on its high temperature behavior, the amorphous SiHfCN-based ceramic powder was used to prepare monolithic SiC/HfCxN1-x-based nanocomposites using the spark plasma sintering (SPS) technique. The results showed that dense monolithic SiC/HfCxN1-x-based nanocomposites with low open porosity (0.74 vol%) can be prepared successfully from single-source precursors. The average grain size of both HfC0.83N0.17 and SiC phases was found to be less than 100 nm after SPS processing owing to a unique microstructure: HfC0.83N0.17 grains were embedded homogeneously in a β-SiC matrix and encapsulated by in situ formed carbon layers which acted as a diffusion barrier to suppress grain growth. The segregated Hf-carbonitride grains significantly influenced the electrical conductivity of the SPS processed monolithic samples. While Hf-free polymer-derived SiC showed an electrical conductivity of ca. 1.8 S cm-1, the electrical conductivity of the Hf-containing material was analyzed to be ca. 136.2 S cm-1. Electronic supplementary information (ESI) available: Raman spectroscopy characterization of the SiHfCN-based ceramics. See DOI: 10.1039/c4nr03376k

Polymer Assisted Functional Ceramic Nanofibrous Structures for Potential Optoelectronic and Photocatalytic Applications

NASA Astrophysics Data System (ADS)

Aykut, Yakup

The use of fossil fuels adversely effects the environment and hence increases global warming. On the other hand the lack of fuel reservoirs triggers people to find environmentally friendly new energy sources. Solar cell technology is one of the developing energy production technologies in green productions. Currently, many solar cells are made of highly purified silicon crystals. However silicon based solar cells have high energy conversion efficiency, they are highly brittle, expensive, and time consuming during the fabrication process. Organic and metal oxide based photovoltaic materials are a more cost-effective alternative to silicon based solar cells. In ceramic materials, Titanium dioxide (TiO2), zinc oxide (ZnO) and magnesium zinc oxide (MgxZn 1-xO) have intensive research interest owing to their optoelectronic and photocatalytic properties, and they have been used in dye sensitized solar cells as electron acceptor layer due to their high band gap properties and having low conduction band levels than electron donor dye molecules or quantum dots. On the other hand, energy band levels of the ceramic materials are considerable affected by their crystal microstructures, shapes and doping materials. Because of their high surface to volume ratio, nanofibers are suitable as active energy conversions layers in organic and dye sensitized solar cells. Using nanofibrous ceramic structure instead of film provides higher energy conversion efficiency since the high surface areas of the electrospun mats may accommodate a greater concentration of dye molecules or quantum dots, which could result in greater efficiency of electron transfer within the material, as compared to traditional film-based technologies. Also, the continuous structure of nanofibers may allow for effective electron transfer as a result of the direct conduction pathway of the photoelectrons along the fibers. Moreover, 3D structures of nanofibrous mat allow scattering and absorbing the photons multiple times. Sol-Gel electrospinning procedure has been widely used to obtain ceramic nanofibers. Briefly, at sol-gel electrospinning procedure, a carrier polymer and ceramic precursor is dissolved in an appropriate solvent, and polymer/ceramic precursor composite nanofibers are produced with a following electrospinning process. Then, as spun nanofibers are calcined at high temperatures to remove polymer and other organic residues from the fibers and convert ceramic precursor into ceramic nanofibers. We investigate temperature dependent crystal phase transformations of electrospun TiO2 nanofibers regardless of other parameters and observed their microstructures and optical properties due to different calcination temperatures. Quantum dots are semi conductive metallic nanocrystals with very wide light absorption range in UV, visible and even in near-infrared regions depending on the size of the quantum dots. On the other hand, TiO2 is a high band gap semiconductor material and absorbs the light in UV range that limits its photovoltaic applications. In order to extend its light absorption through visible region, we sensitized and incorporated low band gap CdSe quantum dot on electrospun TiO2 nanofibers. Zinc oxide (ZnO) is another high band gap ceramic materials with promising optical properties have been used for photonic applications. Intrinsic lattice defects in ZnO are one of the main limitation factors that affect the device performance tremendously and could be controlled due to fabrication process. We investigated the effect of different type of surfactants with different charge groups on fiber morphology, microstructure and optical properties of sol-gel electrospun ZnO nanofibers. Finally, in order to tune band gap energy level of ZnO nanofibers to higher values, we doped Mg2+ into ZnO nanofibers. Because Zn2+ and Mg2+ have similar atomic radii, some of Zn2+ ions are replaced with Mg 2+ ions in the structure to produce different "x" value of MgxZn1-xO due to amount of Mg content. We produced tuned band gap MgxZn1-xO nanofibers via sol-gel electrospinning.

Different effects of a novel CaO-MgO-SiO₂-based multiphase glass-ceramic on cell behaviors of normal and cancer cells in vitro.

PubMed

Zhang, Mengjiao; Chen, Xianchun; Pu, Ximing; Liao, Xiaoming; Huang, Zhongbing; Yin, Guangfu

2014-04-01

The effects in vitro of a novel multiphase glass-ceramic (with nominal composition of 43.19% CaO, 7.68% MgO, and 49.13% SiO2 in weight percent) on cell adhesion, proliferation, differentiation and ultrastructure of human osteosarcoma cell line MG63, mouse fibroblasts L929, and human lung adenocarcinoma epithelial cell line A549 were investigated in this research. Scanning electron microscopy (SEM) micrographs revealed that the surface morphology of this glass-ceramic was beneficial to cell adhesion. The glass-ceramic extracts at certain concentrations could stimulate the proliferation and differentiation of MG63 and L929 cells, whereas inhibit A549 proliferation, which might be resulted from the released Si ions. In addition, when cultured with 0.1mg/mL glass-ceramic powder suspension, the cell ultrastructure of MG63 showed abundant organelles and L929 displayed the phenomena of cellular stress response. While more interestingly, A549 exhibited chromatin condensation, mitochondria swell and RER expansion, which was presumed to be early signs of apoptosis. These results suggest that this novel CaO-MgO-SiO2-based multiphase glass-ceramic has potential for bone regeneration and tissue engineering applications. Copyright © 2013 Elsevier B.V. All rights reserved.

Study on electrostatic and electromagnetic probes operated in ceramic and metallic depositing plasmas

NASA Astrophysics Data System (ADS)

Styrnoll, T.; Bienholz, S.; Lapke, M.; Awakowicz, P.

2014-04-01

This paper discusses plasma probe diagnostics, namely the multipole resonance probe (MRP) and Langmuir probe (LP), operated in depositing plasmas. The aim of this work is to show that the combination of both probes provides stable and robust measurements and clear determination of plasma parameters for metallic and ceramic coating processes. The probes use different approaches to determine plasma parameters, e.g. electron density ne and electron temperature Te. The LP is a well-established plasma diagnostic, and its applicability in technological plasmas is well documented. The LP is a dc probe that performs a voltage sweep and analyses the measured current, which makes it insensitive against conductive metallic coating. However, once the LP is dielectrically coated with a ceramic film, its functionality is constricted. In contrast, the MRP was recently presented as a monitoring tool, which is insensitive to coating with dielectric ceramics. It is a new plasma diagnostic based on the concept of active plasma resonance spectroscopy, which uses the universal characteristic of all plasmas to resonate on or near the electron plasma frequency. The MRP emits a frequency sweep and the absorption of the signal, the |S11| parameter, is analysed. Since the MRP concept is based on electromagnetic waves, which are able to transmit dielectrics, it is insensitive to dielectric coatings. But once the MRP is metallized with a thin conductive film, no undisturbed RF-signal can be emitted into the plasma, which leads to falsified plasma parameter. In order to compare both systems, during metallic or dielectric coating, the probes are operated in a magnetron CCP, which is equipped with a titanium target. We present measurements in metallic and dielectric coating processes with both probes and elaborate advantages and problems of each probe operated in each coating environment.

Ferroelectric ceramics in a pyroelectric accelerator

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

Shchagin, A. V., E-mail: shchagin@kipt.kharkov.ua; Belgorod State University, Belgorod 308015; Miroshnik, V. S.

2015-12-07

The applicability of polarized ferroelectric ceramics as a pyroelectric in a pyroelectric accelerator is shown by experiments. The spectra of X-ray radiation of energy up to tens of keV, generated by accelerated electrons, have been measured on heating and cooling of the ceramics in vacuum. It is suggested that curved layers of polarized ferroelectric ceramics be used as elements of ceramic pyroelectric accelerators. Besides, nanotubes and nanowires manufactured from ferroelectric ceramics are proposed for the use in nanometer-scale ceramic pyroelectric nanoaccelerators for future applications in nanotechnologies.

Polymer-Ceramic Composite Scaffolds: The Effect of Hydroxyapatite and β-tri-Calcium Phosphate

PubMed Central

Caetano, Guilherme; Vyas, Cian; Diver, Carl; Bártolo, Paulo

2018-01-01

The design of bioactive scaffolds with improved mechanical and biological properties is an important topic of research. This paper investigates the use of polymer-ceramic composite scaffolds for bone tissue engineering. Different ceramic materials (hydroxyapatite (HA) and β-tri-calcium phosphate (TCP)) were mixed with poly-ε-caprolactone (PCL). Scaffolds with different material compositions were produced using an extrusion-based additive manufacturing system. The produced scaffolds were physically and chemically assessed, considering mechanical, wettability, scanning electron microscopy and thermal gravimetric tests. Cell viability, attachment and proliferation tests were performed using human adipose derived stem cells (hADSCs). Results show that scaffolds containing HA present better biological properties and TCP scaffolds present improved mechanical properties. It was also possible to observe that the addition of ceramic particles had no effect on the wettability of the scaffolds. PMID:29342890

Development of highly porous scaffolds based on bioactive silicates for dental tissue engineering

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

Goudouri, O.M., E-mail: menti.goudouri@ww.uni-erlangen.de; Department of Physics, Aristotle University of Thessaloniki, 54124 Thessaloniki; Theodosoglou, E.

Graphical abstract: - Highlights: • Synthesis of an Mg-based glass-ceramic via the sol–gel technique. • The heat treatment of the glass-ceramic promoted the crystallization of akermanite. • Akermanite scaffolds coated with gelatin were successfully fabricated. • An HCAp layer was developed on the surface of all scaffolds after 9 days in SBF. - Abstract: Various scaffolding materials, ceramics and especially Mg-based ceramic materials, including akermanite (Ca{sub 2}MgSi{sub 2}O{sub 7}) and diopside (CaMgSi{sub 2}O{sub 6}), have attracted interest for dental tissue regeneration because of their improved mechanical properties and controllable biodegradation. The aim of the present work was the synthesis ofmore » an Mg-based glass-ceramic, which would be used for the construction of workable akermanite scaffolds. The characterization of the synthesized material was performed by Fourier Transform Infrared Spectroscopy (FTIR) X-Ray Diffractometry (XRD) and Scanning Electron Microscopy (SEM). Finally, the apatite forming ability of the scaffolds was assessed by immersion in simulated body fluid. The scaffolds were fabricated by the foam replica technique and were subsequently coated with gelatin to provide a functional surface for increased cell attachment. Finally, SEM microphotographs and FTIR spectra of the scaffolds after immersion in SBF solution indicated the inorganic bioactive character of the scaffolds suitable for the intended applications in dental tissue engineering.« less

Effect of zircon-based tricolor pigments on the color, microstructure, flexural strength and translucency of a novel dental lithium disilicate glass-ceramic.

PubMed

Yuan, Kun; Wang, Fu; Gao, Jing; Sun, Xiang; Deng, Zai-Xi; Wang, Hui; Jin, Lei; Chen, Ji-Hua

2014-01-01

The purpose of this study was to investigate the effect of zircon-based tricolor pigments (praseodymium zircon yellow, ferrum zircon red, and vanadium zircon blue) on the color, thermal property, crystalline phase composition, microstructure, flexural strength, and translucency of a novel dental lithium disilicate glass-ceramic. The pigments were added to the glass frit, milled, pressed, and sintered. Ninety monochrome samples were prepared and the colors were analyzed. The effect of the pigments on thermal property, crystalline phase composition, and microstructure were determined by differential scanning calorimetry (DSC), X-ray diffraction (XRD), and scanning electron microscopy (SEM), respectively. Addition of the pigments resulted in the acquisition of subtractive primary colors as well as tooth-like colors, and did not demonstrate significant effects on the thermal property, crystalline phase composition, microstructure, and flexural strength of the experimental glass-ceramic. Although significant differences (p < 0.01) were observed between the translucencies of the uncolored and 1.0 wt % zircon-based pigment colored ceramics, the translucencies of the latter were sufficient to fabricate dental restorations. These results indicate that the zircon-based tricolor pigments can be used with dental lithium disilicate glass-ceramic to produce abundant and predictable tooth-like colors without significant adverse effects, if mixed in the right proportions. Copyright © 2013 Wiley Periodicals, Inc.

An Investigation into the Use of 3D Scanning and Printing Technologies in the Navy Collaborative Product Lifecycle Management

DTIC Science & Technology

2013-12-01

starches ) are simple. One example is the use of 3DP to fabricate Ti3SiC2 (titanium silicon carbide)- based ceramics (Nan, Yin, Zhang, & Cheng, 2011...These ceramics are highly valued in high-temperature and electronic applications because of characteristics such as high oxidation resistance , low...electrical resistance , and low density; however, it also has low strength and fracture toughness, making it difficult to manufacture. Nan et al. (2011

High-Temperature, Thin-Film Ceramic Thermocouples Developed

NASA Technical Reports Server (NTRS)

Sayir, Ali; Blaha, Charles A.; Gonzalez, Jose M.

2005-01-01

To enable long-duration, more distant human and robotic missions for the Vision for Space Exploration, as well as safer, lighter, quieter, and more fuel efficient vehicles for aeronautics and space transportation, NASA is developing instrumentation and material technologies. The high-temperature capabilities of thin-film ceramic thermocouples are being explored at the NASA Glenn Research Center by the Sensors and Electronics Branch and the Ceramics Branch in partnership with Case Western Reserve University (CWRU). Glenn s Sensors and Electronics Branch is developing thin-film sensors for surface measurement of strain, temperature, heat flux, and surface flow in propulsion system research. Glenn s Ceramics Branch, in conjunction with CWRU, is developing structural and functional ceramic technology for aeropropulsion and space propulsion.

Additive Manufacturing of Silicon Carbide-Based Ceramic Matrix Composites: Technical Challenges and Opportunities

NASA Technical Reports Server (NTRS)

Singh, Mrityunjay; Halbig, Michael C.; Grady, Joseph E.

2016-01-01

Advanced SiC-based ceramic matrix composites offer significant contributions toward reducing fuel burn and emissions by enabling high overall pressure ratio (OPR) of gas turbine engines and reducing or eliminating cooling air in the hot-section components, such as shrouds, combustor liners, vanes, and blades. Additive manufacturing (AM), which allows high value, custom designed parts layer by layer, has been demonstrated for metals and polymer matrix composites. However, there has been limited activity on additive manufacturing of ceramic matrix composites (CMCs). In this presentation, laminated object manufacturing (LOM), binder jet process, and 3-D printing approaches for developing ceramic composite materials are presented. For the laminated object manufacturing (LOM), fiber prepreg laminates were cut into shape with a laser and stacked to form the desired part followed by high temperature heat treatments. For the binder jet, processing optimization was pursued through silicon carbide powder blending, infiltration with and without SiC nano powder loading, and integration of fibers into the powder bed. Scanning electron microscopy was conducted along with XRD, TGA, and mechanical testing. Various technical challenges and opportunities for additive manufacturing of ceramics and CMCs will be presented.

Laboratory evaluations on thermal debonding of ceramic brackets.

PubMed

Sernetz, F; Kraut, J

1991-01-01

The purpose of this laboratory study was to define the working parameters and physiological safety and efficacy of the Dentaurum Ceramic Debonding Unit. Extracted mandibular incisors were utilized because of their low thermal mass and low heat sensitivity. The teeth were embedded in plastic and placed on a turning force measuring apparatus. An electrothermal element was placed in the pulp chamber (filled with a conducting paste). The thermoelement temperature was registered on y-t recorder as was the turning momentum required to remove the ceramic brackets with the Dentaurum Ceramic Debonding Unit. Ceramic brackets from GAC (Allure III), Unitek (Transcend) and Dentaurum (Fascination) using one and two component adhesives (Monolok, Concise), were tested. Scanning electron microscopic views taken after debonding showed predictable (and favorable) adhesive failure at the bracket base/resin interface. No enamel damage was demonstrated. All brackets were removable under three seconds with a clinically reproducible turning force of 85-100 Nmm allowing for intrapulpal temperature increases under the 5 degrees C biocompatible threshold. The Dentaurum Ceramic Debonding Unit provided a safe, reliable, efficient modality of removing ceramic brackets while maintaining a physiologically acceptable rise in pulpal temperature without damage to tooth enamel or pulpal tissue.

A fractographic study of clinically retrieved zirconia-ceramic and metal-ceramic fixed dental prostheses.

PubMed

Pang, Zhen; Chughtai, Asima; Sailer, Irena; Zhang, Yu

2015-10-01

A recent 3-year randomized controlled trial (RCT) of tooth supported three- to five-unit zirconia-ceramic and metal-ceramic posterior fixed dental prostheses (FDPs) revealed that veneer chipping and fracture in zirconia-ceramic systems occurred more frequently than those in metal-ceramic systems [1]. This study seeks to elucidate the underlying mechanisms responsible for the fracture phenomena observed in this RCT using a descriptive fractographic analysis. Vinyl-polysiloxane impressions of 12 zirconia-ceramic and 6 metal-ceramic FDPs with veneer fractures were taken from the patients at the end of a mean observation of 40.3±2.8 months. Epoxy replicas were produced from these impressions [1]. All replicas were gold coated, and inspected under the optical microscope and scanning electron microscope (SEM) for descriptive fractography. Among the 12 zirconia-ceramic FDPs, 2 had small chippings, 9 had large chippings, and 1 exhibited delamination. Out of 6 metal-ceramic FDPs, 5 had small chippings and 1 had large chipping. Descriptive fractographic analysis based on SEM observations revealed that fracture initiated from the wear facet at the occlusal surface in all cases, irrespective of the type of restoration. Zirconia-ceramic and metal-ceramic FDPs all fractured from microcracks that emanated from occlusal wear facets. The relatively low fracture toughness and high residual tensile stress in porcelain veneer of zirconia restorations may contribute to the higher chipping rate and larger chip size in zirconia-ceramic FDPs relative to their metal-ceramic counterparts. The low veneer/core interfacial fracture energy of porcelain-veneered zirconia may result in the occurrence of delamination in zirconia-ceramic FDPs. Copyright © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

A fractographic study of clinically retrieved zirconia–ceramic and metal–ceramic fixed dental prostheses

PubMed Central

Pang, Zhen; Chughtai, Asima; Sailer, Irena; Zhang, Yu

2015-01-01

Objectives A recent 3-year randomized controlled trial (RCT) of tooth supported three- to five-unit zirconia–ceramic and metal–ceramic posterior fixed dental prostheses (FDPs) revealed that veneer chipping and fracture in zirconia–ceramic systems occurred more frequently than those in metal–ceramic systems [1]. This study seeks to elucidate the underlying mechanisms responsible for the fracture phenomena observed in this RCT using a descriptive fractographic analysis. Methods Vinyl-polysiloxane impressions of 12 zirconia–ceramic and 6 metal–ceramic FDPs with veneer fractures were taken from the patients at the end of a mean observation of 40.3 ± 2.8 months. Epoxy replicas were produced from these impressions [1]. All replicas were gold coated, and inspected under the optical microscope and scanning electron microscope (SEM) for descriptive fractography. Results Among the 12 zirconia–ceramic FDPs, 2 had small chippings, 9 had large chippings, and 1 exhibited delamination. Out of 6 metal–ceramic FDPs, 5 had small chippings and 1 had large chipping. Descriptive fractographic analysis based on SEM observations revealed that fracture initiated from the wear facet at the occlusal surface in all cases, irrespective of the type of restoration. Significance Zirconia–ceramic and metal–ceramic FDPs all fractured from microcracks that emanated from occlusal wear facets. The relatively low fracture toughness and high residual tensile stress in porcelain veneer of zirconia restorations may contribute to the higher chipping rate and larger chip size in zirconia–ceramic FDPs relative to their metal–ceramic counterparts. The low veneer/core interfacial fracture energy of porcelain-veneered zirconia may result in the occurrence of delamination in zirconia–ceramic FDPs. PMID:26233469

Enhanced strain effect of aged acceptor-doped BaTiO3 ceramics with clamping domain structures

NASA Astrophysics Data System (ADS)

Wang, Lei; Zhou, Zhiyong; Zhao, Xiaobo; Liu, Zhen; Liang, Ruihong; Dong, Xianlin

2017-03-01

A clamping domain structure is proposed to improve the amount of non-180° domain switching in BaTiO3 based piezoelectric ceramics. Experimental results show a large unipolar strain of 0.23% at 5 kV/mm in aged 0.5 mol. % Mn doped BaTiO3 ceramics with clamping domain structures, and the normalized strain (d33*= Smax/Emax) reaches 600 pm/V at low electric fields of 2 or 3 kV/mm. In contrast, pure BaTiO3 ceramics with clamping domain structures exhibit no clear polarization constriction or strain enhancement at 3 kV/mm. Electron paramagnetic resonance spectra verify the existence of titanium vacancies, Mn2+ and Mn4+, in 0.5 mol. % Mn doped BaTiO3 ceramics. These results indicate that the enhanced strain effect can be attributed to the combined effect of the clamping domain structure and stabilization of defect dipoles. This method provides a general way to obtain large strain in ferroelectrics.

On the electron density localization in elemental cubic ceramic and FCC transition metals by means of a localized electrons detector.

PubMed

Aray, Yosslen; Paredes, Ricardo; Álvarez, Luis Javier; Martiz, Alejandro

2017-06-14

The electron density localization in insulator and semiconductor elemental cubic materials with diamond structure, carbon, silicon, germanium, and tin, and good metallic conductors with face centered cubic structure such as α-Co, Ni, Cu, Rh, Pd, Ag, Ir, Pt, and Au, was studied using a localized electrons detector defined in the local moment representation. Our results clearly show an opposite pattern of the electron density localization for the cubic ceramic and transition metal materials. It was found that, for the elemental ceramic materials, the zone of low electron localization is very small and is mainly localized on the atomic basin edges. On the contrary, for the transition metals, there are low-valued localized electrons detector isocontours defining a zone of highly delocalized electrons that extends throughout the material. We have found that the best conductors are those in which the electron density at this low-value zone is the lowest.

Engulfment of ceramic particles by fibroblasts does not alter cell behavior.

PubMed

Faye, Pierre-Antoine; Roualdes, Olivier; Rossignol, Fabrice; Hartmann, Daniel Jean; Desmoulière, Alexis

2017-02-17

Despite many studies, the impact of ceramic particles on cell behavior remains unclear. The aim of the present study was to investigate the effects of nano-sized ceramic particles on fibroblastic cells. Fibroblasts (dermal fibroblasts freshly isolated from skin samples and WI26 fibroblastic cells) were cultured in a monolayer in the presence of alumina or cerium-zirconia particles (≈50 nm diameter) at two concentrations (100 or 500 μg ml -1 ). Fluorescent alumina particles were also used. The following properties were analyzed: cell morphology, cytoplasmic ceramic incorporation (using confocal and transmission electron microscopy) and migration (using a silicon insert). Sedimentation field-flow fractionation (SdFFF) was also used to evaluate the rate of incorporation of ceramic particles into the cells. Finally, after treatment with various concentrations of ceramic particles, fibroblasts were also included in a collagen type I lattice constituting a dermal equivalent (DE), and the collagen lattice retraction and cell proliferation were evaluated. In monolayer conditions, the presence of both alumina and cerium-zirconia ceramic particles did not cause any deleterious effects on cultured cells (dermal fibroblast and WI26 cells) and cell fate was not affected in any way by the presence of ceramic particles in the cytoplasm. Confocal (using fluorescent alumina particles) and electron microscopy (using both alumina and cerium-zirconia particles) showed that ceramic particles were internalized in the WI26 cells. Using fluorescent membrane labeling and fluorescent alumina particles, a membrane was observed around the particle-containing vesicles present in the cytoplasm. Electron microscopy on WI26 cells showed the presence of a classical bilayer membrane around the ceramic particles. Interestingly, SdFFF confirmed that some dermal fibroblasts contained many alumina ceramic particles while others contained very few; in WI26 cells, the uptake of alumina ceramic was more homogeneous. In DE, collagen lattice retraction and cell proliferation were unchanged when WI26 fibroblastic cells contained alumina or cerium-zirconia ceramic particles. Our data suggest that ceramic particles are internalized in the cells by endocytosis. The presence of ceramic particles in the cytoplasm has no affect on cell behavior, confirming the excellent biocompatibility of this material and anticipating a minimal harmful effect of potential wear debris.

Membranes in Lithium Ion Batteries

PubMed Central

Yang, Min; Hou, Junbo

2012-01-01

Lithium ion batteries have proven themselves the main choice of power sources for portable electronics. Besides consumer electronics, lithium ion batteries are also growing in popularity for military, electric vehicle, and aerospace applications. The present review attempts to summarize the knowledge about some selected membranes in lithium ion batteries. Based on the type of electrolyte used, literature concerning ceramic-glass and polymer solid ion conductors, microporous filter type separators and polymer gel based membranes is reviewed. PMID:24958286

The structure and properties of boron carbide ceramics modified by high-current pulsed electron-beam

NASA Astrophysics Data System (ADS)

Ivanov, Yuri; Tolkachev, Oleg; Petyukevich, Maria; Teresov, Anton; Ivanova, Olga; Ikonnikova, Irina; Polisadova, Valentina

2016-01-01

The present work is devoted to numerical simulation of temperature fields and the analysis of structural and strength properties of the samples surface layer of boron carbide ceramics treated by the high-current pulsed electron-beam of the submillisecond duration. The samples made of sintered boron carbide ceramics are used in these investigations. The problem of calculating the temperature field is reduced to solving the thermal conductivity equation. The electron beam density ranges between 8…30 J/cm2, while the pulse durations are 100…200 μs in numerical modelling. The results of modelling the temperature field allowed ascertaining the threshold parameters of the electron beam, such as energy density and pulse duration. The electron beam irradiation is accompanied by the structural modification of the surface layer of boron carbide ceramics either in the single-phase (liquid or solid) or two-phase (solid-liquid) states. The sample surface of boron carbide ceramics is treated under the two-phase state (solid-liquid) conditions of the structural modification. The surface layer is modified by the high-current pulsed electron-beam produced by SOLO installation at the Institute of High Current Electronics of the Siberian Branch of the Russian Academy of Sciences, Tomsk, Russia. The elemental composition and the defect structure of the modified surface layer are analyzed by the optical instrument, scanning electron and transmission electron microscopes. Mechanical properties of the modified layer are determined measuring its hardness and crack resistance. Research results show that the melting and subsequent rapid solidification of the surface layer lead to such phenomena as fragmentation due to a crack network, grain size reduction, formation of the sub-grained structure due to mechanical twinning, and increase of hardness and crack resistance.

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.

The materials processing research base of the Materials Processing Center

NASA Technical Reports Server (NTRS)

Flemings, M. C.; Bowen, H. K.; Kenney, G. B.

1980-01-01

The goals and activities of the center are discussed. The center activities encompass all engineering materials including metals, ceramics, polymers, electronic materials, composites, superconductors, and thin films. Processes include crystallization, solidification, nucleation, and polymer synthesis.

Clinical application of bio ceramics

NASA Astrophysics Data System (ADS)

Anu, Sharma; Gayatri, Sharma

2016-05-01

Ceramics are the inorganic crystalline material. These are used in various field such as biomedical, electrical, electronics, aerospace, automotive and optical etc. Bio ceramics are the one of the most active areas of research. Bio ceramics are the ceramics which are biocompatible. The unique properties of bio ceramics make them an attractive option for medical applications and offer some potential advantages over other materials. During the past three decades, a number of major advances have been made in the field of bio ceramics. This review focuses on the use of these materials in variety of clinical scenarios.

Clinical application of bio ceramics

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

Anu, Sharma, E-mail: issaranu@gmail.com; Gayatri, Sharma, E-mail: sharmagayatri@gmail.com

Ceramics are the inorganic crystalline material. These are used in various field such as biomedical, electrical, electronics, aerospace, automotive and optical etc. Bio ceramics are the one of the most active areas of research. Bio ceramics are the ceramics which are biocompatible. The unique properties of bio ceramics make them an attractive option for medical applications and offer some potential advantages over other materials. During the past three decades, a number of major advances have been made in the field of bio ceramics. This review focuses on the use of these materials in variety of clinical scenarios.

A solvated electron lithium electrode for secondary batteries

NASA Astrophysics Data System (ADS)

Sammells, A. F.; Semkow, K. W.

1986-09-01

Attention is given to a novel method for the achievement of high electro-chemical reversibility in Li-based nonaqueous cells, using a liquid negative electrode that consists of Li dissolved in liquid ammonia as a solvated electron Li electrode. The containment of this liquid negative active material from direct contact to a liquid nonaqueous electrolyte in the positive electrode compartment was realized through the use of a Li-intercalated, electronically conducting ceramic membrane.

Potential for EMU Fabric Damage by Electron Beam and Molten Metal During Space Welding for the International Space Welding Experiment

NASA Technical Reports Server (NTRS)

Fragomeni, James M.

1998-01-01

As a consequence of preparations concerning the International Space Welding Experiment (ISWE), studies were performed to better understand the effect of molten metal contact and electron beam impingement with various fabrics for space suit applications. The question arose as to what would occur if the electron beam from the Ukrainian Universal Hand Tool (UHT) designed for welding in space were to impinge upon a piece of Nextel AF-62 ceramic cloth designed to withstand temperatures up to 1427 C. The expectation was that the electron beam would lay down a static charge pattern with no damage to the ceramic fabric. The electron beam is capable of spraying the fabric with enough negative charge to repel further electrons from the fabric before significant heating occurs. The static charge pattern would deflect any further charge accumulation except for a small initial amount of leakage to the grounded surface of the welder. However, when studies were made of the effect of the electron beam on the insulating ceramic fabric it was surprisingly found that the electron beam did indeed burn through the ceramic fabric. It was also found that the shorter electron beam standoff distances had longer burnthrough times than did some greater electron beam standoff distances. A possible explanation for the longer burnthrough times for the small electron beam standoff distance would be outgassing of the fabric which caused the electron beam hand-tool to cycle on and off to provide some protection for the cathodes. The electron beam hand tool was observed to cycle off at the short standoff distance of two inches likely due to vapors being outgassed. During the electron beam welding process there is an electron leakage, or current leakage, flow from the fabric. A static charge pattern is initially laid down by the electron beam current flow. The static charge makes up the current leakage flow which initially slightly heats up the fabric. The initially laid down surface charge leaks a small amount of current. The rate at which the current charge leaks from the fabric controls how fast the fabric heats up. As the ceramic fabric is heated it begins to outgass primarily from contamination/impurities atoms or molecules on and below the fabric surface. The contaminant gases ionize to create extra charge carriers and multiply a current of electrons. The emitted gas which ionized in the electron leakage flow promotes further leakage. Thus, the small leakage of charge from the fabric surface is enhanced by outgassing. When the electron beam current makes up the lost current, the incoming electrons heat the fabric and further enhance the outgassing. The additional leakage promotes additional heating up of the ceramic fabric. The electrons bound to the ceramic fabric surface leak off more and more as the surface gets hotter promoting even greater leakage. The additional electrons that result also gain energy in the field and produce further electrons. Eventually the process becomes unstable and accelerates to the point where a hole is burned through the fabric.

Investigation of failure mechanism of thermal barrier coatings (TBCs) deposited by EB-PVD technique

NASA Astrophysics Data System (ADS)

Shahid, M. R.; Abbas, Musharaf

2013-06-01

Failure mechanism of thermal barrier coatings (TBCs) prepared by electron beam physical vapor deposition (EB-PVD) technique owing to formation of micro cracks was investigated. The TBCs were deposited on the Ni-based super alloy IN-100 and the micro cracks were observed within the top ceramic coat of thermally cycled TBCs at 1050°C. It was observed that these cracks propagate in the ceramic coat in the direction normal to interface while no cracks were observed in the bond coat. SEM/EDS studies revealed that some non-uniform oxides were formed on the interface between ceramic top and metallic bond coat just below the cracks. Study proposed that the cracks were initiated due to stress owing to big difference in Pilling-Bed worth ratio of non-uniform oxides as well as thermal stress, which caused the formation of cracks in top ceramic coat leading to failure of TBCs

Direct cooled power electronics substrate

DOEpatents

Wiles, Randy H [Powell, TN; Wereszczak, Andrew A [Oak Ridge, TN; Ayers, Curtis W [Kingston, TN; Lowe, Kirk T [Knoxville, TN

2010-09-14

The disclosure describes directly cooling a three-dimensional, direct metallization (DM) layer in a power electronics device. To enable sufficient cooling, coolant flow channels are formed within the ceramic substrate. The direct metallization layer (typically copper) may be bonded to the ceramic substrate, and semiconductor chips (such as IGBT and diodes) may be soldered or sintered onto the direct metallization layer to form a power electronics module. Multiple modules may be attached to cooling headers that provide in-flow and out-flow of coolant through the channels in the ceramic substrate. The modules and cooling header assembly are preferably sized to fit inside the core of a toroidal shaped capacitor.

A new active solder for joining electronic components

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

SMITH,RONALD W.; VIANCO,PAUL T.; HERNANDEZ,CYNTHIA L.

Electronic components and micro-sensors utilize ceramic substrates, copper and aluminum interconnect and silicon. The joining of these combinations require pre-metallization such that solders with fluxes can wet such combinations of metals and ceramics. The paper will present a new solder alloy that can bond metals, ceramics and composites. The alloy directly wets and bonds in air without the use flux or premetallized layers. The paper will present typical processing steps and joint microstructures in copper, aluminum, aluminum oxide, aluminum nitride, and silicon joints.

Bio/Nano Electronic Devices and Sensors

DTIC Science & Technology

2008-10-01

Microscopy and Microanalysis 2006 Meeting, Chicago, IL, July 30 - August 3, 2006 4) S. Khizroev, "Three-dimensional Magnetic Memory," presented at US Air...ABSTRACT This effort consists of five research thrusts: (1) Dense Memory Devices-(1)3-D magnetic recording was enhanced using patterned soft underlayers...and interlayer, (2) Cold cathode microwave generator and ceramic electron multiplier-ceramic multiplier using a novel secondary electron yield

Electron-induced electron yields of uncharged insulating materials

NASA Astrophysics Data System (ADS)

Hoffmann, Ryan Carl

Presented here are electron-induced electron yield measurements from high-resistivity, high-yield materials to support a model for the yield of uncharged insulators. These measurements are made using a low-fluence, pulsed electron beam and charge neutralization to minimize charge accumulation. They show charging induced changes in the total yield, as much as 75%, even for incident electron fluences of <3 fC/mm2, when compared to an uncharged yield. The evolution of the yield as charge accumulates in the material is described in terms of electron recapture, based on the extended Chung and Everhart model of the electron emission spectrum and the dual dynamic layer model for internal charge distribution. This model is used to explain charge-induced total yield modification measured in high-yield ceramics, and to provide a method for determining electron yield of uncharged, highly insulating, high-yield materials. A sequence of materials with progressively greater charge susceptibility is presented. This series starts with low-yield Kapton derivative called CP1, then considers a moderate-yield material, Kapton HN, and ends with a high-yield ceramic, polycrystalline aluminum oxide. Applicability of conductivity (both radiation induced conductivity (RIC) and dark current conductivity) to the yield is addressed. Relevance of these results to spacecraft charging is also discussed.

Uses of ceramics in microelectronics: A survey

NASA Technical Reports Server (NTRS)

Bratschun, W. R.; Mountvala, A. J.; Pincus, A. G.

1971-01-01

The properties and behavior of ceramic materials used in components for electronic circuitry are examined to appraise the present and future directions for microelectronics, and to suggest further product development, and how innovations may be useful in other technologies. Ceramic and glass insulators, resistors, capacitors, and the use of ceramics and glasses in microcircuitry are discussed along with technology transfer to nonaerospace uses.

Essential Factors Influencing the Bonding Strength of Cold-Sprayed Aluminum Coatings on Ceramic Substrates

NASA Astrophysics Data System (ADS)

Drehmann, R.; Grund, T.; Lampke, T.; Wielage, B.; Wüstefeld, C.; Motylenko, M.; Rafaja, D.

2018-02-01

The present work summarizes the most important results of a research project dealing with the comprehensive investigation of the bonding mechanisms between cold-sprayed Al coatings and various poly- and monocrystalline ceramic substrates (Al2O3, AlN, Si3N4, SiC, MgF2). Due to their exceptional combination of properties, metallized ceramics are gaining more and more importance for a wide variety of applications, especially in electronic engineering. Cold spray provides a quick, flexible, and cost-effective one-step process to apply metallic coatings on ceramic surfaces. However, since most of the existing cold-spray-related publications focus on metallic substrates, only very little is known about the bonding mechanisms acting between cold-sprayed metals and ceramic substrates. In this paper, the essential factors influencing the bonding strength in such composites are identified. Besides mechanical tensile strength testing, a thorough analysis of the coatings and especially the metal/ceramic interfaces was conducted by means of HRTEM, FFT, STEM, EDX, EELS, GAXRD, and EBSD. The influence of substrate material, substrate temperature, and particle size is evaluated. The results suggest that, apart from mechanical interlocking, the adhesion of cold-sprayed metallic coatings on ceramics is based on a complex interplay of different mechanisms such as quasiadiabatic shearing, static recrystallization, and heteroepitaxial growth.

Phase modification and dielectric properties of a cullet-paper ash-kaolin clay-based ceramic

NASA Astrophysics Data System (ADS)

Samah, K. A.; Sahar, M. R.; Yusop, M.; Omar, M. F.

2018-03-01

Novel ceramics from waste material made of ( x) paper ash-(80 - x) cullet-20 kaolin clay (10wt% ≤ x ≤ 30wt%) were successfully synthesized using a conventional solid-state reaction technique. Energy-dispersive X-ray analysis confirmed the presence of Si, Ca, Al, and Fe in the waste material for preparing these ceramics. The influence of the cullet content on the phase structures and the dielectric properties of these ceramics were systematically investigated. The impedance spectra were verified in the range from 1 Hz to 10 MHz at room temperature. The phase of the ceramics was found to primarily consist of wollastonite (CaSiO3), along with minor phases of γ-dicalcium silicate (Ca2SiO4) and quartz (SiO2). The sample with a cullet content of 55wt% possessed the optimum wollastonite structure and exhibited good dielectric properties. An increase of the cullet content beyond 55wt% resulted in a structural change from wollastonite to dicalcium silicate, a decrease in dielectric constant, and an increase in dielectric loss. All experimental results suggested that these novel ceramics from waste are applicable for electronic devices.

Simulation and performance study of ceramic THGEM

NASA Astrophysics Data System (ADS)

Yan, Jia-Qing; Xie, Yu-Guang; Hu, Tao; Lu, Jun-Guang; Zhou, Li; Qu, Guo-Pu; Cai, Xiao; Niu, Shun-Li; Chen, Hai-Tao

2015-06-01

THGEMs based on a ceramic substrate have been successfully developed for neutron and single photon detection. The influences on thermal neutron scattering and internal radioactivity of both ceramic and FR-4 substrates were studied and compared. The ceramic THGEMs are homemade, of 200 μm hole diameter, 600 μm pitch, 200 μm thickness, 80 μm rim, and 50 mm×50 mm sensitive area. FR-4 THGEMs with the same geometry were used as a reference. The gas gain, energy resolution and gain stability were measured in different gas mixtures using 5.9 keV X-rays. The maximum gain of a single layer ceramic THGEM reaches 6×104 and 1.5×104 at Ne+CH4=95:5 and Ar + i-C4H10 = 97:3, respectively. The energy resolution is better than 24%. Good gain stability was obtained during a more than 100 hour continuous test in Ar+CO2 = 80:20. By using a 239Pu source, the alpha deposited energy spectrum and gain curve of the ceramic THGEM were measured. Supported by National Natural Science Foundation of China (11205173) and State Key Laboratory of Particle Detection and Electronics (H9294206TD)

Fabrication and Characterization of Dense Zirconia and Zirconia-Silica Ceramic Nanofibers

PubMed Central

Guo, Guangqing; Fan, Yuwei

2011-01-01

The objective of this study was to prepare dense zirconia-yttria (ZY), zirconia-silica (ZS) and zirconia-yttria-silica (ZYS) nanofibers as reinforcing elements for dental composites. Zirconium (IV) propoxide, yttrium nitrate hexahydrate, and tetraethyl orthosilicate (TEOS) were used as precursors for the preparation of zirconia, yttria, and silica sols. A small amount (1–1.5 wt%) of polyethylene oxide (PEO) was used as a carry polymer. The sols were preheated at 70 °C before electrospinning and their viscosity was measured with a viscometer at different heating time. The gel point was determined by viscosity–time (η–t) curve. The ZY, ZS and ZYS gel nanofibers were prepared using a special reactive electrospinning device under the conditions near the gel point. The as-prepared gel nanofibers had diameters between 200 and 400 nm. Dense (nonporous) ceramic nanofibers of zirconia-yttria (96/4), zirconia-silica (80/20) and zirconia-yttria-silica (76.8/3.2/20) with diameter of 100–300 nm were obtained by subsequent calcinations at different temperatures. The gel and ceramic nanofibers obtained were characterized by scanning electron microscope (SEM), high-resolution field-emission scanning electron microscope (FE-SEM), thermogravimetric analyzer (TGA), differential scanning calorimeter (DSC), Fourier transform infrared spectrometer (FT-IR), and X-ray diffraction (XRD). SEM micrograph revealed that ceramic ZY nanofibers had grained structure, while ceramic ZS and ZYS nanofibers had smooth surfaces, both showing no visible porosity under FE-SEM. Complete removal of the polymer PEO was confirmed by TGA/DSC and FT-IR. The formation of tetragonal phase of zirconia and amorphous silica was proved by XRD. In conclusion, dense zirconia-based ceramic nanofibers can be fabricated using the new reactive sol–gel electrospinning technology with minimum organic polymer additives. PMID:21133090

Bonding of Resin Cement to Zirconia with High Pressure Primer Coating

PubMed Central

Wang, Ying-jie; Jiao, Kai; Liu, Yan; Zhou, Wei; Shen, Li-juan; Fang, Ming; Li, Meng; Zhang, Xiang; Tay, Franklin R.; Chen, Ji-hua

2014-01-01

Objectives To investigate the effect of air-drying pressure during ceramic primer coating on zirconia/resin bonding and the surface characteristics of the primed zirconia. Methods Two ceramic primers (Clearfil Ceramic Primer, CCP, Kuraray Medical Inc. and Z-Prime Plus, ZPP, Bisco Inc.) were applied on the surface of air-abraded zirconia (Katana zirconia, Noritake) and dried at 4 different air pressures (0.1–0.4 MPa). The primed zirconia ceramic specimens were bonded with a resin-based luting agent (SA Luting Cement, Kuraray). Micro-shear bond strengths of the bonded specimens were tested after 3 days of water storage or 5,000× thermocycling (n = 12). Failure modes of the fractured specimens were examined with scanning electron miscopy. The effects of air pressure on the thickness of the primer layers and the surface roughness (Sa) of primed zirconia were evaluated using spectroscopic ellipsometry (n = 6), optical profilometry and environmental scanning electron microscopy (ESEM) (n = 6), respectively. Results Clearfil Ceramic Primer air-dried at 0.3 and 0.4 MPa, yielding significantly higher µSBS than gentle air-drying subgroups (p<0.05). Compared to vigorous drying conditions, Z-Prime Plus air-dried at 0.2 MPa exhibited significantly higher µSBS (p<0.05). Increasing air-drying pressure reduced the film thickness for both primers. Profilometry measurements and ESEM showed rougher surfaces in the high pressure subgroups of CCP and intermediate pressure subgroup of ZPP. Conclusion Air-drying pressure influences resin/zirconia bond strength and durability significantly. Higher air-drying pressure (0.3-0.4 MPa) for CCP and intermediate pressure (0.2 MPa) for ZPP are recommended to produce strong, durable bonds between resin cement and zirconia ceramics. PMID:24992678

Theoretical studies of the electronic properties of ceramic materials

NASA Astrophysics Data System (ADS)

Ching, W. Y.

1990-11-01

The first-principles orthogonalized linear combination of atomic orbitals (OLCAO) method for electronic structure studies has been applied to a variety of complex inorganic crystals. The theory and the practice of the OLCAO method in the local density approximation are discussed in detail. Recent progress in the study of electronic and optical properties of a large list of ceramic systems are summarized. Eight selected topics on different ceramic crystals focusing on specific points of interest are presented as examples. The materials discussed are AlN, Cu2O, beta-Si3N4, Y2O3, LiB3O5, ferroelectric crystals, Fe-B compounds, and the YBa2Cu3O7 superconductor.

Joining and Integration of Silicon Carbide-Based Materials for High Temperature Applications

NASA Technical Reports Server (NTRS)

Halbig, Michael C.; Singh, Mrityunjay

2016-01-01

Advanced joining and integration technologies of silicon carbide-based ceramics and ceramic matrix composites are enabling for their implementation into wide scale aerospace and ground-based applications. The robust joining and integration technologies allow for large and complex shapes to be fabricated and integrated with the larger system. Potential aerospace applications include lean-direct fuel injectors, thermal actuators, turbine vanes, blades, shrouds, combustor liners and other hot section components. Ground based applications include components for energy and environmental systems. Performance requirements and processing challenges are identified for the successful implementation different joining technologies. An overview will be provided of several joining approaches which have been developed for high temperature applications. In addition, various characterization approaches were pursued to provide an understanding of the processing-microstructure-property relationships. Microstructural analysis of the joint interfaces was conducted using optical, scanning electron, and transmission electron microscopy to identify phases and evaluate the bond quality. Mechanical testing results will be presented along with the need for new standardized test methods. The critical need for tailoring interlayer compositions for optimum joint properties will also be highlighted.

Combinatorial and High Throughput Discovery of High Temperature Piezoelectric Ceramics

DTIC Science & Technology

2011-10-10

the known candidate piezoelectric ferroelectric perovskites. Unlike most computational studies on crystal chemistry, where the starting point is some...studies on crystal chemistry, where the starting point is some form of electronic structure calculation, we use a data driven approach to initiate our...experimental measurements reported in the literature. Given that our models are based solely on crystal and electronic structure data and did not

Radiopaque Strontium Fluoroapatite Glass-Ceramics.

PubMed

Höland, Wolfram; Schweiger, Marcel; Dittmer, Marc; Ritzberger, Christian

2015-01-01

The controlled precipitation of strontium fluoroapatite crystals was studied in four base glass compositions derived from the SiO2-Al2O3-Y2O3-SrO-Na2O-K2O/Rb2O/Cs2O-P2O5-F system. The crystal phase formation of these glasses and the main properties of the glass-ceramics, such as thermal and optical properties and radiopacity were compared with a fifth, a reference glass-ceramic. The reference glass-ceramic was characterized as Ca-fluoroapatite glass-ceramic. The four strontium fluoroapatite glass-ceramics showed the following crystal phases: (a) Sr5(PO4)3F - leucite, KAlSi2O6, (b) Sr5(PO4)3F - leucite, KAlSi2O6, and nano-sized NaSrPO4, (c) Sr5(PO4)3F - pollucite, CsAlSi2O6, and nano-sized NaSrPO4, and (d) Sr5(PO4)3F - Rb-leucite, RbAlSi2O6, and nano-sized NaSrPO4. The proof of crystal phase formation was possible by X-ray diffraction. The microstructures, which were studied using scanning electron microscopy, demonstrated a uniform distribution of the crystals in the glass matrix. The Sr-fluoroapatites were precipitated based on an internal crystallization process, and the crystals demonstrated a needle-like morphology. The study of the crystal growth of needle-like Sr-fluoroapatites gave a clear evidence of an Ostwald ripening mechanism. The formation of leucite, pollucite, and Rb-leucite was based on a surface crystallization mechanism. Therefore, a twofold crystallization mechanism was successfully applied to develop these types of glass-ceramics. The main focus of this study was the controlled development of glass-ceramics exhibiting high radiopacity in comparison to the reference glass-ceramic. This goal could be achieved with all four glass-ceramics with the preferred development of the Sr-fluoroapatite - pollucite-type glass-ceramic. In addition to this main development, it was possible to control the thermal properties. Especially the Rb-leucite containing glass-ceramic showed the highest coefficient of thermal expansion (CTE). These glass-ceramics allow optical properties, especially the translucency and color, to be tailored to the needs of biomaterials for dental applications. The authors conclude that it is possible to use twofold crystallization processes to develop glass-ceramic biomaterials featuring different properties, such as specific radiopacity values, CTEs, and optical characteristics.

Radiopaque Strontium Fluoroapatite Glass-Ceramics

PubMed Central

Höland, Wolfram; Schweiger, Marcel; Dittmer, Marc; Ritzberger, Christian

2015-01-01

The controlled precipitation of strontium fluoroapatite crystals was studied in four base glass compositions derived from the SiO2–Al2O3–Y2O3–SrO–Na2O–K2O/Rb2O/Cs2O–P2O5–F system. The crystal phase formation of these glasses and the main properties of the glass-ceramics, such as thermal and optical properties and radiopacity were compared with a fifth, a reference glass-ceramic. The reference glass-ceramic was characterized as Ca-fluoroapatite glass-ceramic. The four strontium fluoroapatite glass-ceramics showed the following crystal phases: (a) Sr5(PO4)3F – leucite, KAlSi2O6, (b) Sr5(PO4)3F – leucite, KAlSi2O6, and nano-sized NaSrPO4, (c) Sr5(PO4)3F – pollucite, CsAlSi2O6, and nano-sized NaSrPO4, and (d) Sr5(PO4)3F – Rb-leucite, RbAlSi2O6, and nano-sized NaSrPO4. The proof of crystal phase formation was possible by X-ray diffraction. The microstructures, which were studied using scanning electron microscopy, demonstrated a uniform distribution of the crystals in the glass matrix. The Sr-fluoroapatites were precipitated based on an internal crystallization process, and the crystals demonstrated a needle-like morphology. The study of the crystal growth of needle-like Sr-fluoroapatites gave a clear evidence of an Ostwald ripening mechanism. The formation of leucite, pollucite, and Rb-leucite was based on a surface crystallization mechanism. Therefore, a twofold crystallization mechanism was successfully applied to develop these types of glass-ceramics. The main focus of this study was the controlled development of glass-ceramics exhibiting high radiopacity in comparison to the reference glass-ceramic. This goal could be achieved with all four glass-ceramics with the preferred development of the Sr-fluoroapatite – pollucite-type glass-ceramic. In addition to this main development, it was possible to control the thermal properties. Especially the Rb-leucite containing glass-ceramic showed the highest coefficient of thermal expansion (CTE). These glass-ceramics allow optical properties, especially the translucency and color, to be tailored to the needs of biomaterials for dental applications. The authors conclude that it is possible to use twofold crystallization processes to develop glass-ceramic biomaterials featuring different properties, such as specific radiopacity values, CTEs, and optical characteristics. PMID:26528470

Cervical and Incisal Marginal Discrepancy in Ceramic Laminate Veneering Materials: A SEM Analysis

PubMed Central

Ranganathan, Hemalatha; Ganapathy, Dhanraj M.; Jain, Ashish R.

2017-01-01

Context: Marginal discrepancy influenced by the choice of processing material used for the ceramic laminate veneers needs to be explored further for better clinical application. Aims: This study aimed to evaluate the amount of cervical and incisal marginal discrepancy associated with different ceramic laminate veneering materials. Settings and Design: This was an experimental, single-blinded, in vitro trial. Subjects and Methods: Ten central incisors were prepared for laminate veneers with 2 mm uniform reduction and heavy chamfer finish line. Ceramic laminate veneers fabricated over the prepared teeth using four different processing materials were categorized into four groups as Group I - aluminous porcelain veneers, Group II - lithium disilicate ceramic veneers, Group III - lithium disilicate-leucite-based veneers, Group IV - zirconia-based ceramic veneers. The cervical and incisal marginal discrepancy was measured using a scanning electron microscope. Statistical Analysis Used: ANOVA and post hoc Tukey honest significant difference (HSD) tests were used for statistical analysis. Results: The cervical and incisal marginal discrepancy for four groups was Group I - 114.6 ± 4.3 μm, 132.5 ± 6.5 μm, Group II - 86.1 ± 6.3 μm, 105.4 ± 5.3 μm, Group III - 71.4 ± 4.4 μm, 91.3 ± 4.7 μm, and Group IV - 123.1 ± 4.1 μm, 142.0 ± 5.4 μm. ANOVA and post hoc Tukey HSD tests observed a statistically significant difference between the four test specimens with regard to cervical marginal discrepancy. The cervical and incisal marginal discrepancy scored F = 243.408, P < 0.001 and F = 180.844, P < 0.001, respectively. Conclusion: This study concluded veneers fabricated using leucite reinforced lithium disilicate exhibited the least marginal discrepancy followed by lithium disilicate ceramic, aluminous porcelain, and zirconia-based ceramics. The marginal discrepancy was more in the incisal region than in the cervical region in all the groups. PMID:28839415

Cervical and Incisal Marginal Discrepancy in Ceramic Laminate Veneering Materials: A SEM Analysis.

PubMed

Ranganathan, Hemalatha; Ganapathy, Dhanraj M; Jain, Ashish R

2017-01-01

Marginal discrepancy influenced by the choice of processing material used for the ceramic laminate veneers needs to be explored further for better clinical application. This study aimed to evaluate the amount of cervical and incisal marginal discrepancy associated with different ceramic laminate veneering materials. This was an experimental, single-blinded, in vitro trial. Ten central incisors were prepared for laminate veneers with 2 mm uniform reduction and heavy chamfer finish line. Ceramic laminate veneers fabricated over the prepared teeth using four different processing materials were categorized into four groups as Group I - aluminous porcelain veneers, Group II - lithium disilicate ceramic veneers, Group III - lithium disilicate-leucite-based veneers, Group IV - zirconia-based ceramic veneers. The cervical and incisal marginal discrepancy was measured using a scanning electron microscope. ANOVA and post hoc Tukey honest significant difference (HSD) tests were used for statistical analysis. The cervical and incisal marginal discrepancy for four groups was Group I - 114.6 ± 4.3 μm, 132.5 ± 6.5 μm, Group II - 86.1 ± 6.3 μm, 105.4 ± 5.3 μm, Group III - 71.4 ± 4.4 μm, 91.3 ± 4.7 μm, and Group IV - 123.1 ± 4.1 μm, 142.0 ± 5.4 μm. ANOVA and post hoc Tukey HSD tests observed a statistically significant difference between the four test specimens with regard to cervical marginal discrepancy. The cervical and incisal marginal discrepancy scored F = 243.408, P < 0.001 and F = 180.844, P < 0.001, respectively. This study concluded veneers fabricated using leucite reinforced lithium disilicate exhibited the least marginal discrepancy followed by lithium disilicate ceramic, aluminous porcelain, and zirconia-based ceramics. The marginal discrepancy was more in the incisal region than in the cervical region in all the groups.

Properties and Crystallization Phenomena in Li2Si2O5–Ca5(PO4)3F and Li2Si2O5–Sr5(PO4)3F Glass–Ceramics Via Twofold Internal Crystallization

PubMed Central

Rampf, Markus; Dittmer, Marc; Ritzberger, Christian; Schweiger, Marcel; Höland, Wolfram

2015-01-01

The combination of specific mechanical, esthetic, and chemical properties is decisive for the application of materials in prosthodontics. Controlled twofold crystallization provides a powerful tool to produce special property combinations for glass–ceramic materials. The present study outlines the potential of precipitating Ca5(PO4)3F as well as Sr5(PO4)3F as minor crystal phases in Li2Si2O5 glass–ceramics. Base glasses with different contents of CaO/SrO, P2O5, and F− were prepared within the glasses of the SiO2–Li2O–K2O–CaO/SrO–Al2O3–P2O5–F system. Preliminary studies of nucleation by means of XRD and scanning electron microscopy (SEM) of the nucleated base glasses revealed X-ray amorphous phase separation phenomena. Qualitative and quantitative crystal phase analyses after crystallization were conducted using XRD in combination with Rietveld refinement. As a main result, a direct proportional relationship between the content of apatite-forming components in the base glasses and the content of apatite in the glass–ceramics was established. The microstructures of the glass–ceramics were investigated using SEM. Microstructural and mechanical properties were found to be dominated by Li2Si2O5 crystals and quite independent of the content of the apatite present in the glass–ceramics. Biaxial strengths of up to 540 MPa were detected. Ca5(PO4)3F and Sr5(PO4)3F influence the translucency of the glass–ceramics and, hence, help to precisely tailor the properties of Li2Si2O5 glass–ceramics. The authors conclude that the twofold crystallization of Li2Si2O5–Ca5(PO4)3F or Li2Si2O5–Sr5(PO4)3F glass–ceramics involves independent solid-state reactions, which can be controlled via the chemical composition of the base glasses. The influence of the minor apatite phase on the optical properties helps to achieve new combinations of features of the glass–ceramics and, hence, displays new potential for dental applications. PMID:26389112

Properties and Crystallization Phenomena in Li2Si2O5-Ca5(PO4)3F and Li2Si2O5-Sr5(PO4)3F Glass-Ceramics Via Twofold Internal Crystallization.

PubMed

Rampf, Markus; Dittmer, Marc; Ritzberger, Christian; Schweiger, Marcel; Höland, Wolfram

2015-01-01

The combination of specific mechanical, esthetic, and chemical properties is decisive for the application of materials in prosthodontics. Controlled twofold crystallization provides a powerful tool to produce special property combinations for glass-ceramic materials. The present study outlines the potential of precipitating Ca5(PO4)3F as well as Sr5(PO4)3F as minor crystal phases in Li2Si2O5 glass-ceramics. Base glasses with different contents of CaO/SrO, P2O5, and F(-) were prepared within the glasses of the SiO2-Li2O-K2O-CaO/SrO-Al2O3-P2O5-F system. Preliminary studies of nucleation by means of XRD and scanning electron microscopy (SEM) of the nucleated base glasses revealed X-ray amorphous phase separation phenomena. Qualitative and quantitative crystal phase analyses after crystallization were conducted using XRD in combination with Rietveld refinement. As a main result, a direct proportional relationship between the content of apatite-forming components in the base glasses and the content of apatite in the glass-ceramics was established. The microstructures of the glass-ceramics were investigated using SEM. Microstructural and mechanical properties were found to be dominated by Li2Si2O5 crystals and quite independent of the content of the apatite present in the glass-ceramics. Biaxial strengths of up to 540 MPa were detected. Ca5(PO4)3F and Sr5(PO4)3F influence the translucency of the glass-ceramics and, hence, help to precisely tailor the properties of Li2Si2O5 glass-ceramics. The authors conclude that the twofold crystallization of Li2Si2O5-Ca5(PO4)3F or Li2Si2O5-Sr5(PO4)3F glass-ceramics involves independent solid-state reactions, which can be controlled via the chemical composition of the base glasses. The influence of the minor apatite phase on the optical properties helps to achieve new combinations of features of the glass-ceramics and, hence, displays new potential for dental applications.

Effect of Powder Characteristics on Microstructure and Properties in Alkoxide Prepared PZT Ceramics.

DTIC Science & Technology

1984-12-01

Effect of pH of precipitating solution on the pressed and fired densities (9500 C/ h) of PZT (+ 0.25 wt% V2o5 ). * Figure 12. Plot of dielectric...Lectures: a) Electronic Cermics/Dielectrics Properties, b) Glasses and Substrates in Electronics, c) Thick Film Hybrid Circuits; d) Nagnetic Ceramics

Transmission electron microscopy: direct observation of crystal structure in refractory ceramics.

PubMed

Shaw, T M; Thomas, G

1978-11-10

Using high-resolution multibeam interference techniques in the transmission electron microscope, images have been obtained that make possible a real-space structure analysis of a beryllium-silicon-nitrogen compound. The results illustrate the usefulness of lattice imaging in the analysis of local crystal structure in these technologically promising ceramic materials.

Influences of PZT addition on phase formation and magnetic properties of perovskite Pb(Fe0.5Nb0.5)O3-based ceramics

NASA Astrophysics Data System (ADS)

Amonpattaratkit, P.; Jantaratana, P.; Ananta, S.

2015-09-01

In this work, the investigation of phase formation, crystal structure, microstructure, microchemical composition and magnetic properties of perovskite (1-x)PFN-xPZT (x=0.1-0.5) multiferroic ceramics derived from a combination of perovskite stabilizer PZT and a wolframite-type FeNbO4 B-site precursor was carried out by using a combination of X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) analyzer and vibrating sample magnetometer (VSM) techniques. The addition of PZT phase and its concentration have been found to have pronounced effects on the perovskite phase formation, densification, grain growth and magnetic properties of the sintered ceramics. XRD spectra from these ceramics reveal transformation of the (pseudo) cubic into the tetragonal perovskite structure. When increasing PZT content, the degree of perovskite phase formation and the tetragonality value of the ceramics increase gradually accompanied with the variation of cell volume, the M-H hysteresis loops, however, become narrower accompanied by the decrease of maximum magnetization (Mmax), remanent polarization (Mr), and coercive field (HC).

New functionalities in abundant element oxides: ubiquitous element strategy

PubMed Central

Hosono, Hideo; Hayashi, Katsuro; Kamiya, Toshio; Atou, Toshiyuki; Susaki, Tomofumi

2011-01-01

While most ceramics are composed of ubiquitous elements (the ten most abundant elements within the Earth's crust), many advanced materials are based on rare elements. A ‘rare-element crisis’ is approaching owing to the imbalance between the limited supply of rare elements and the increasing demand. Therefore, we propose a ‘ubiquitous element strategy’ for materials research, which aims to apply abundant elements in a variety of innovative applications. Creation of innovative oxide materials and devices based on conventional ceramics is one specific challenge. This review describes the concept of ubiquitous element strategy and gives some highlights of our recent research on the synthesis of electronic, thermionic and structural materials using ubiquitous elements. PMID:27877391

Dense ceramic membranes for converting methane to syngas

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

Balachandran, U.; Dusek, J.T.; Picciolo, J.J.

1995-07-01

Dense mixed-oxide ceramics capable of conducting both electrons and oxygen ions are promising materials for partial oxygenation of methane to syngas. We are particularly interested in an oxide based on the Sr-Fe-Co-O system. Dense ceramic membrane tubes have been fabricated by a plastic extrusion technique. The sintered tubes were then used to selectively transport oxygen from air through the membrane to make syngas without the use of external electrodes. The sintered tubes have operated for >1000 h, and methane conversion efficiencies of >98% have been observed. Mechanical properties, structural integrity of the tubes during reactor operation, results of methane conversion,more » selectivity of methane conversion products, oxygen permeation, and fabrication of multichannel configurations for large-scale production of syngas will be presented.« less

Nd:AlN polycrystalline ceramics: A candidate media for tunable, high energy, near IR lasers

NASA Astrophysics Data System (ADS)

Wieg, A. T.; Grossnickle, M. J.; Kodera, Y.; Gabor, N. M.; Garay, J. E.

2016-09-01

We present processing and characterization of Nd-doped aluminum nitride (Nd:AlN) polycrystalline ceramics. We compare ceramics with significant segregation of Nd to those exhibiting minimal segregation. Spatially resolved photoluminescence maps reveal a strong correlation between homogeneous Nd doping and spatially homogeneous light emission. The spectroscopically resolved light emission lines show excellent agreement with the expected Nd electronic transitions. Notably, the lines are significantly broadened, producing near IR emission (˜1077 nm) with a remarkable ˜100 nm bandwidth at room temperature. We attribute the broadened lines to a combination of effects: multiple Nd-sites, anisotropy of AlN and phonon broadening. These broadened, overlapping lines in a media with excellent thermal conductivity have potential for Nd-based, tunable lasers with high average power.

EPR of radiation defects in lithium-oxyfluoride glass ceramics

NASA Astrophysics Data System (ADS)

Fedotovs, A.; Rogulis, U.; Sarakovskis, A.; Dimitrocenko, L.

2010-11-01

We studied oxyfluoride composites based on lithium silicate glasses with yttrium fluorides and rare-earth dopants. The electron paramagnetic resonance (EPR) has been used to obtain information about radiation induced defects in these materials. Spectra have been measured before and after X-ray irradiation at room temperature and at liquid nitrogen temperature. Fluoride crystallites within samples were created by means of thermal treatment at specific temperatures. EPR spectra of radiation induced defects in oxyfluoride glass ceramics, in which crystallites have not been yet created, show no explicit hfs interaction of fluorine nuclei. However, in glass ceramics, which already contains fluoride crystallites, the hfs characteristic to fluorine nuclei appears in the EPR spectra. EPR hyperfine structure could be explained within a model of an F-type centre in YF3 crystalline phase.

Industrial Ceramics: Secondary Schools.

ERIC Educational Resources Information Center

New York City Board of Education, Brooklyn, NY. Bureau of Curriculum Development.

The expanding use of ceramic products in today's world can be seen in the areas of communications, construction, aerospace, textiles, metallurgy, atomic energy, and electronics. The demands of science have brought ceramics from an art to an industry using mass production and automated processes which requires the services of great numbers as the…

Fabrication of compact electron gun for 6 MeV X-ray source

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

Ghodke, S.R.; Barnwal, Rajesh; Kumar, Mahendra, E-mail: ghodke_barc@yahoo.co.in

The 6 MeV X-Ray source for container cargo scanning application has been designed and developed by the Accelerator and Pulse Power Division, BARC, Mumbai. This compact linac has been designed as a mobile system, to be mounted on a moving container. In linac-based cargo-scanning system, to work electron gun on a movable container, it has to be robust. Electron gun is to work at 10{sup -7} mbar vacuum and 2000 degree Celsius temperature. An effort is made to engineer the gun assembly to make it more robust and aligned. The linac acts as the source of X-rays, which fall onmore » the cargo and are then detected by the detector system. Many components are indigenously developed like grid, insulating ring, Tungsten filament and filament guide, which are made from alumina ceramic and Tantalum which is to work at 1500 degree Celsius. Filament connector is made from Invar to reduce heat loss and to make rigid connection. It was CNC machined and wire cut by EDM. Invar and Copper electrode feed through is shrink fitted with the help of liquid Nitrogen. Shrink fit tolerances of 15 micrometer are achieved by jig boring machining processes. Tantalum cup for LaB6 cathode and heat shield are made from die and punch mechanism. For alignment of electron emitter with beam axis this Tantalum cup is a crucial component. Electron gun is assembled and aligned its components with the help of precision jigs. The whole assembly was Helium leak tested by MSLD up to 4 x 10{sup -10} mbar.l/s vacuum, no leak was found. This paper will describe the machining, Tantalum cup forming, ceramic components development, heat shields, ceramic feed through etc of electron gun. (author)« less

Center for Cement Composite Materials

DTIC Science & Technology

1990-01-31

metal-oxygen structures G. Kordas MSE-Ceramics Electron paramagnetic resonance W. M. Kriven MSE-Ceramics Electron microscopy Microstructural...SPONSORING iSb. OFFICE SYMBOL 9. PROWIREMENT INSTRUMENT IDENTIFICATION NUMBER ORGANIZATION (If applicable) C S(2is _ _ _- r_,__’ Contract F49620-87-C...novel in-situ technique involving nuclear magnetic resonance . Fiber- matrix interactions in MDF laminates were also studied. Characterization of DSP

Advanced Sensor and Packaging Technologies for Intelligent Adaptive Engine Controls (Preprint)

DTIC Science & Technology

2013-05-01

combination of micro-electromechanical systems (MEMS) sensor technology, novel ceramic materials, high - temperature electronics, and advanced harsh...with simultaneous pressure measurements up to 1,000 psi. The combination of a high - temperature , high -pressure-ratio compressor system, and adaptive...combination of micro-electromechanical systems (MEMS) sensor technology, novel ceramic materials, high temperature electronics, and advanced harsh

Electronically conductive ceramics for high temperature oxidizing environments

DOEpatents

Kucera, Gene H.; Smith, James L.; Sim, James W.

1986-01-01

A high temperature, ceramic composition having electronic conductivity as measured by resistivity below about 500 ohm-cm, chemical stability particularly with respect to cathode conditions in a molten carbonate fuel cell, and composed of an alkali metal, transition metal oxide containing a dopant metal in the crystalline structure to replace a portion of the alkali metal or transition metal.

NASA/CARES dual-use ceramic technology spinoff applications

NASA Technical Reports Server (NTRS)

Powers, Lynn M.; Janosik, Lesley A.; Gyekenyesi, John P.; Nemeth, Noel N.

1994-01-01

NASA has developed software that enables American industry to establish the reliability and life of ceramic structures in a wide variety of 21st Century applications. Designing ceramic components to survive at higher temperatures than the capability of most metals and in severe loading environments involves the disciplines of statistics and fracture mechanics. Successful application of advanced ceramics material properties and the use of a probabilistic brittle material design methodology. The NASA program, known as CARES (Ceramics Analysis and Reliability Evaluation of Structures), is a comprehensive general purpose design tool that predicts the probability of failure of a ceramic component as a function of its time in service. The latest version of this software, CARESALIFE, is coupled to several commercially available finite element analysis programs (ANSYS, MSC/NASTRAN, ABAQUS, COSMOS/N4, MARC), resulting in an advanced integrated design tool which is adapted to the computing environment of the user. The NASA-developed CARES software has been successfully used by industrial, government, and academic organizations to design and optimize ceramic components for many demanding applications. Industrial sectors impacted by this program include aerospace, automotive, electronic, medical, and energy applications. Dual-use applications include engine components, graphite and ceramic high temperature valves, TV picture tubes, ceramic bearings, electronic chips, glass building panels, infrared windows, radiant heater tubes, heat exchangers, and artificial hips, knee caps, and teeth.

Ab initio Computations of the Electronic, Mechanical, and Thermal Properties of Ultra High Temperature Ceramics (UHTC) ZrB2 and HfB2

NASA Technical Reports Server (NTRS)

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

2011-01-01

Refractory materials such as metallic borides, often considered as ultra high temperature ceramics (UHTC), are characterized by high melting point, high hardness, and good chemical inertness. These materials have many applications which require high temperature materials that can operate with no or limited oxidation. Ab initio, first principles methods are the most accurate modeling approaches available and represent a parameter free description of the material based on the quantum mechanical equations. Using these methods, many of the intrinsic properties of these material can be obtained. We performed ab initio calculations based on density functional theory for the UHTC materials ZrB2 and HfB2. Computational results are presented for structural information (lattice constants, bond lengths, etc), electronic structure (bonding motifs, densities of states, band structure, etc), thermal quantities (phonon spectra, phonon densities of states, specific heat), as well as information about point defects such as vacancy and antisite formation energies.

Effect of Sintering Temperature on Structural, Dielectric, and Magnetic Properties of Multiferroic YFeO₃ Ceramics Fabricated by Spark Plasma Sintering.

PubMed

Wang, Meng; Wang, Ting; Song, Shenhua; Ma, Qing; Liu, Renchen

2017-03-07

Based on precursor powders with a size of 200-300 nm prepared by the low-temperature solid reaction method, phase-pure YFeO₃ ceramics are fabricated using spark plasma sintering (SPS) at different temperatures. X-ray diffraction (XRD) and scanning electron microscopy (SEM) reveal that the high-purity YFeO₃ ceramics can be prepared using SPS, while the results from X-ray photoelectron spectroscopy (XPS) show that the concentration of oxygen vacancies resulting from transformation from Fe 3+ to Fe 2+ is low. The relative density of the 1000 °C-sintered sample is as high as 97.7%, which is much higher than those of the samples sintered at other temperatures. The present dielectric and magnetic properties are much better than those of the samples fabricated by conventional methods. These findings indicate that the YFeO₃ ceramics prepared by the low temperature solid reaction and SPS methods possess excellent dielectric and magnetic properties, making them suitable for potential applications involving magnetic storage.

Ceramic MEMS Designed for Wireless Pressure Monitoring in the Industrial Environment

PubMed Central

Pavlin, Marko; Belavic, Darko; Novak, Franc

2012-01-01

This paper presents the design of a wireless pressure-monitoring system for harsh-environment applications. Two types of ceramic pressure sensors made with a low-temperature cofired ceramic (LTCC) were considered. The first type is a piezoresistive strain gauge pressure sensor. The second type is a capacitive pressure sensor, which is based on changes of the capacitance values between two electrodes: one electrode is fixed and the other is movable under an applied pressure. The design was primarily focused on low power consumption. Reliable operation in the presence of disturbances, like electromagnetic interference, parasitic capacitances, etc., proved to be contradictory constraints. A piezoresistive ceramic pressure sensor with a high bridge impedance was chosen for use in a wireless pressure-monitoring system and an acceptable solution using energy-harvesting techniques has been achieved. The described solution allows for the integration of a sensor element with an energy harvester that has a printed thick-film battery and complete electronics in a single substrate packaged inside a compact housing. PMID:22368471

PREFACE: Symposium 1: Advanced Structure Analysis and Characterization of Ceramic Materials

NASA Astrophysics Data System (ADS)

Yashima, Masatomo

2011-05-01

Preface to Symposium 1 (Advanced Structure Analysis and Characterization of Ceramic Materials) of the International Congress of Ceramics III, held 14-18 November 2010 in Osaka, Japan Remarkable developments have been made recently in the structural analysis and characterization of inorganic crystalline and amorphous materials, such as x-ray, neutron, synchrotron and electron diffraction, x-ray/neutron scattering, IR/Raman scattering, NMR, XAFS, first-principle calculations, computer simulations, Rietveld analysis, the maximum-entropy method, in situ measurements at high temperatures/pressures and electron/nuclear density analysis. These techniques enable scientists to study not only static and long-range periodic structures but also dynamic and short-/intermediate-range structures. Multi-scale characterization from the electron to micrometer levels is becoming increasingly important as a means of understanding phenomena at the interfaces, grain boundaries and surfaces of ceramic materials. This symposium has discussed the structures and structure/property relationships of various ceramic materials (electro, magnetic and optical ceramics; energy and environment related ceramics; bio-ceramics; ceramics for reliability secure society; traditional ceramics) through 38 oral presentations including 8 invited lectures and 49 posters. Best poster awards were given to six excellent poster presentations (Y-C Chen, Tokyo Institute of Technology; C-Y Chung, Tohoku University; T Stawski, University of Twente; Y Hirano, Nagoya Institute of Technology; B Bittova, Charles University Prague; Y Onodera, Kyoto University). I have enjoyed working with my friends in the ICC3 conference. I would like to express special thanks to other organizers: Professor Scott T Misture, Alfred University, USA, Professor Xiaolong Chen, Institute of Physics, CAS, China, Professor Takashi Ida, Nagoya Institute of Technology, Japan, Professor Isao Tanaka, Kyoto University, Japan. I also acknowledge the invited speakers, all the participants and organizing committee of the ICC3. I am pleased to publish the Proceedings of the Symposium 1 of ICC3. I hope that the papers contained in these Proceedings will prove helpful to Professors, researchers and students in improving the fields of Structure Analysis and Characterization of Ceramic Materials. Masatomo Yashima April 2011 Department of Chemistry and Materials Science, Graduate School of Science and Engineering, Tokyo Institute of Technology, Japan

Degree of conversion and bond strength of resin-cements to feldspathic ceramic using different curing modes.

PubMed

Novais, Veridiana Resende; Raposo, Luís Henrique Araújo; Miranda, Rafael Resende de; Lopes, Camila de Carvalho Almança; Simamoto, Paulo Cézar; Soares, Carlos José

2017-01-01

The aim of this study was to assess the performance of resin cements when different curing modes are used, by evaluating the degree of conversion and bond strength to a ceramic substrate. Three resin cements were evaluated, two dual-cured (Variolink II and RelyX ARC) and one light-cured (Variolink Veneer). The dual-cured resin cements were tested by using the dual activation mode (base and catalyst) and light-activation mode (base paste only). For degree of conversion (DC) (n=5), a 1.0 mm thick feldspathic ceramic disc was placed over the resin cement specimens and the set was light activated with a QTH unit. After 24 h storage, the DC was measured with Fourier transform infrared spectroscopy (FTIR). For microshear bond strength testing, five feldspathic ceramic discs were submitted to surface treatment, and three cylindrical resin cement specimens were bonded to each ceramic surface according to the experimental groups. After 24 h, microshear bond testing was performed at 0.5 mm/min crosshead speed until the failure. Data were submitted to one-way ANOVA followed by Tukey test (p<0.05). Scanning electron microscopy (SEM) was used for classifying the failure modes. Higher DC and bond strength values were shown by the resin cements cured by using the dual activation mode. The Variolink II group presented higher DC and bond strength values when using light-activation only when compared with the Variolink Veneer group. The base paste of dual-cured resin cements in light-activation mode can be used for bonding translucent ceramic restorations of up to or less than 1.0 mm thick.

Correlation of electron backscatter diffraction and piezoresponse force microscopy for the nanoscale characterization of ferroelectric domains in polycrystalline lead zirconate titanate

NASA Astrophysics Data System (ADS)

Burnett, T. L.; Weaver, P. M.; Blackburn, J. F.; Stewart, M.; Cain, M. G.

2010-08-01

The functional properties of ferroelectric ceramic bulk or thin film materials are strongly influenced by their nanostructure, crystallographic orientation, and structural geometry. In this paper, we show how, by combining textural analysis, through electron backscattered diffraction, with piezoresponse force microscopy, quantitative measurements of the piezoelectric properties can be made at a scale of 25 nm, smaller than the domain size. The combined technique is used to obtain data on the domain-resolved effective single crystal piezoelectric response of individual crystallites in Pb(Zr0.4Ti0.6)O3 ceramics. The results offer insight into the science of domain engineering and provide a tool for the future development of new nanostructured ferroelectric materials for memory, nanoactuators, and sensors based on magnetoelectric multiferroics.

The effect of sintering temperature on electrical characteristics of Fe2TiO5/Nb2O5 ceramics for NTC thermistor

NASA Astrophysics Data System (ADS)

Wiendartun, Risdiana, Fitrilawati, Siregar, R. E.

2016-02-01

A study on the fabrication of Iron Titanium Oxide (Fe2TiO5) ceramics for negative temperature coefficient (NTC) thermistors has been carried out, in order to know the effect of sintering temperature on the electrical characteristic of 1.0 % mole Nb2O5 doped Fe2TiO5 ceramics.These ceramics were made by mixing commercial powders of Fe2O3, TiO2 and Nb2O5 with proportional composition to produce Fe2TiO5 based ceramic. The raw pellet was sintered at 1000 °C, 1100 °C and 1200 °C temperature for 2 hours in air. Analysis of the microstructure and crystal structure were performed by using a scanning electron microscope (SEM) and x-ray diffraction (XRD) respectively. XRD spectra showed that the crystal structure of all ceramics of Fe2TiO5 made at various sintering temperatures are orthorhombic. The SEM images showed that the grain size of pellet ceramics increase with increasing sintering temperatures. From electrical resistances data that was measured at temperature 30-300 °C, it is found that the value of thermistor constant (B), activation energy (Ea), thermistor sensitivity (α) and room temperature resistance (RRT) decreases with respect to the increasing of sintering temperature. The fabricated Fe2TiO5 ceramics have thermistor constants (B = 6394-6959 K). This can be applied as temperature sensor, and will fulfill the market requirement.

Ultralight, scalable, and high-temperature-resilient ceramic nanofiber sponges.

PubMed

Wang, Haolun; Zhang, Xuan; Wang, Ning; Li, Yan; Feng, Xue; Huang, Ya; Zhao, Chunsong; Liu, Zhenglian; Fang, Minghao; Ou, Gang; Gao, Huajian; Li, Xiaoyan; Wu, Hui

2017-06-01

Ultralight and resilient porous nanostructures have been fabricated in various material forms, including carbon, polymers, and metals. However, the development of ultralight and high-temperature resilient structures still remains extremely challenging. Ceramics exhibit good mechanical and chemical stability at high temperatures, but their brittleness and sensitivity to flaws significantly complicate the fabrication of resilient porous ceramic nanostructures. We report the manufacturing of large-scale, lightweight, high-temperature resilient, three-dimensional sponges based on a variety of oxide ceramic (for example, TiO 2 , ZrO 2 , yttria-stabilized ZrO 2 , and BaTiO 3 ) nanofibers through an efficient solution blow-spinning process. The ceramic sponges consist of numerous tangled ceramic nanofibers, with densities varying from 8 to 40 mg/cm 3 . In situ uniaxial compression in a scanning electron microscope showed that the TiO 2 nanofiber sponge exhibits high energy absorption (for example, dissipation of up to 29.6 mJ/cm 3 in energy density at 50% strain) and recovers rapidly after compression in excess of 20% strain at both room temperature and 400°C. The sponge exhibits excellent resilience with residual strains of only ~1% at 800°C after 10 cycles of 10% compression strain and maintains good recoverability after compression at ~1300°C. We show that ceramic nanofiber sponges can serve multiple functions, such as elasticity-dependent electrical resistance, photocatalytic activity, and thermal insulation.

Ultralight, scalable, and high-temperature–resilient ceramic nanofiber sponges

PubMed Central

Wang, Haolun; Zhang, Xuan; Wang, Ning; Li, Yan; Feng, Xue; Huang, Ya; Zhao, Chunsong; Liu, Zhenglian; Fang, Minghao; Ou, Gang; Gao, Huajian; Li, Xiaoyan; Wu, Hui

2017-01-01

Ultralight and resilient porous nanostructures have been fabricated in various material forms, including carbon, polymers, and metals. However, the development of ultralight and high-temperature resilient structures still remains extremely challenging. Ceramics exhibit good mechanical and chemical stability at high temperatures, but their brittleness and sensitivity to flaws significantly complicate the fabrication of resilient porous ceramic nanostructures. We report the manufacturing of large-scale, lightweight, high-temperature resilient, three-dimensional sponges based on a variety of oxide ceramic (for example, TiO2, ZrO2, yttria-stabilized ZrO2, and BaTiO3) nanofibers through an efficient solution blow-spinning process. The ceramic sponges consist of numerous tangled ceramic nanofibers, with densities varying from 8 to 40 mg/cm3. In situ uniaxial compression in a scanning electron microscope showed that the TiO2 nanofiber sponge exhibits high energy absorption (for example, dissipation of up to 29.6 mJ/cm3 in energy density at 50% strain) and recovers rapidly after compression in excess of 20% strain at both room temperature and 400°C. The sponge exhibits excellent resilience with residual strains of only ~1% at 800°C after 10 cycles of 10% compression strain and maintains good recoverability after compression at ~1300°C. We show that ceramic nanofiber sponges can serve multiple functions, such as elasticity-dependent electrical resistance, photocatalytic activity, and thermal insulation. PMID:28630915

Synthesis of β-tricalcium phosphate.

PubMed

Chaair, H; Labjar, H; Britel, O

2017-09-01

Ceramics play a key role in several biomedical applications. One of them is bone grafting, which is used for treating bone defects caused by injuries or osteoporosis. Calcium-phosphate based ceramic are preferred as bone graft biomaterials in hard tissue surgery because their chemical composition is close to the composition of human bone. They also have a marked bioresorbability and bioactivity. In this work, we have developed methods for synthesis of β-tricalcium phosphate apatite (β-TCP). These products were characterized by different techniques such as X-ray diffraction, infrared spectroscopy, scanning electron microscopy and chemical analysis. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

Ceramic component for electrodes

DOEpatents

Marchant, David D.

1979-01-01

A ceramic component suitable for preparing MHD generator electrodes consists of HfO.sub.2 and sufficient Tb.sub.4 O.sub.7 to stabilize at least 60 volume percent of the HfO.sub.2 into the cubic structure. The ceramic component may also contain a small amount of PrO.sub.2, Yb.sub.2 O.sub.3 or a mixture of both to improve stability and electronic conductivity of the electrode. The component is highly resistant to corrosion by molten potassium seed and molten coal slag in the MHD fluid and exhibits both ionic and electronic conductivity.

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.

About structural phase state of coating based on zirconium oxide formed by microplasma oxidation method

NASA Astrophysics Data System (ADS)

Gubaidulina, Tatiana A.; Sergeev, Viktor P.; Kuzmin, Oleg S.; Fedorischeva, Marina V.; Kalashnikov, Mark P.

2017-12-01

The oxide-ceramic coating based of zirconium oxide is formed by the method of microplasma oxidation. The producing modes of the oxide layers on E110 zirconium alloy are under testing. It was found that using microplasma treatment of E110 zirconium in aluminosilicate electrolyte makes possible the formation of porous oxide-ceramic coatings based on zirconium alloyed by aluminum and niobium. The study is focused on the modes how to form heat-shielding coatings with controlled porosity and minimal amount of microcracks. The structural-phase state of the coating is studied by X-ray diffraction analysis and scanning electron microscopy (SEM). It was found that the ratio of the monoclinic and tetragonal phases changes with the change occurring in the coating formation modes.

Preparation of Oxidation-Resistant Ultra High Melting Temperature Materials and Structures Using Laser Method

DTIC Science & Technology

2009-06-06

sample within a small ceramic muffle. The microwave absorption coefficient of most ceramics is low, but increases with temperature. Thus, as the...increased using additives with higher absorption 7 coefficients . Silicon carbide has a higher loss tangent at 2.4 GHz than most ceramics, and thus...electron beam sintering. Microwave heating works well for large volumes, but ceramics normally have a low dielectric absorption constant at room

Fracture Toughness (KIC) of Lithography Based Manufactured Alumina Ceramic

NASA Astrophysics Data System (ADS)

Nindhia, T. G. T.; Schlacher, J.; Lube, T.

2018-04-01

Precision shaped ceramic components can be obtained by an emerging technique called Lithography based Ceramic Manufacturing (LCM). A green part is made from a slurry consisting of a ceramic powder in a photocurable binder with addition of dispersant and plasticizer. Components are built in a layer–by-layer way by exposing the desired cross- sections to light. The parts are subsequently sintered to their final density. It is a challenge to produce ceramic component with this method that yield the same mechanical properties in all direction. The fracture toughness (KIc) of of LCM-alumina (prepared at LITHOZ GmbH, Austria) was tested by using the Single-Edge-V-Notched Beam (SEVNB) method. Notches are made into prismatic bend-bars in all three direction X, Y and Z to recognize the value of fracture toughness of the material in all three directions. The microstructure was revealed with optical microscopy as well as Scanning Electron Microscopy (SEM). The results indicate that the fracture toughness in Y-direction has the highest value (3.10 MPam1/2) that is followed by the one in X-direction which is just a bit lower (2.90 MPam1/2). The Z-direction is found to have a similar fracture toughness (2.95 MPam1/2). This is supported by a homogeneous microstructure showing no hint of the layers used during production.

Extended glaze firing on ceramics for hard machining: Crack healing, residual stresses, optical and microstructural aspects.

PubMed

Aurélio, Iana L; Dorneles, Lucio S; May, Liliana G

2017-02-01

To evaluate the effect of extended and conventional (manufacturer-recommended) glaze firings on crack healing, residual stresses, optical characteristics and crystalline structure of four ceramics for hard machining. Rectangular specimens were obtained by sectioning densely sintered feldspathic (FEL), leucite- (LEU), lithium disilicate- (DIS), and zirconia-reinforced lithium silicate-based (ZLS) prefabricated ceramic blocks and divided into groups according to the applied glaze firing (n=5): conventional glaze/manufacturer-recommended (G), extended glaze (EG) and control/no heat treatment (C). Defects generated by indentation were analyzed by scanning electron microscopy before and after firing (n=1) to evaluate crack healing. Residual stresses were determined by the indentation technique. Color differences (ΔE) after firing were measured by CIEDE2000 formula, and translucency variations were quantified by contrast ratio. Stability of crystalline microstructure was analyzed by X-ray diffraction. Regardless of the material, EG had greater ability than G to heal defects, and produced compressive residual stresses, while G generated tensile stresses. Color differences produced by EG were: imperceptible for FEL and LEU ceramics; perceptible, but still clinically acceptable for DIS; clinically unacceptable for ZLS. G produced no perceptible color change. The DIS and ZLS ceramics became ≈1% more opaque after G, ≈4% and ≈15%, respectively, after EG. The crystalline phase of all the ceramics remained stable after G and EG. Extended glaze firing could be an alternative to finish feldspathic, leucite-, and lithium disilicate-based ceramic restorations, since it provides greater crack healing than the conventional glaze firing. It develops tolerable residual stresses, and produces clinically acceptable color alterations, without altering the microstructure of these materials. Copyright © 2016 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Nearly full-dense and fine-grained AZO:Y ceramics sintered from the corresponding nanoparticles

PubMed Central

2012-01-01

Aluminum-doped zinc oxide ceramics with yttria doping (AZO:Y) ranging from 0 to 0.2 wt.% were fabricated by pressureless sintering yttria-modified nanoparticles in air at 1,300°C. Scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction analysis, a physical property measurement system, and a densimeter were employed to characterize the precursor nanoparticles and the sintered AZO ceramics. It was shown that a small amount of yttria doping can remarkably retard the growth of the as-received precursor nanoparticles, further improve the microstructure, refine the grain size, and enhance the density for the sintered ceramic. Increasing the yttria doping to 0.2 wt.%, the AZO:Y nanoparticles synthetized by a coprecipitation process have a nearly sphere-shaped morphology and a mean particle diameter of 15.1 nm. Using the same amount of yttria, a fully dense AZO ceramic (99.98% of theoretical density) with a grain size of 2.2 μm and a bulk resistivity of 4.6 × 10−3 Ω·cm can be achieved. This kind of AZO:Y ceramic has a potential to be used as a high-quality sputtering target to deposit ZnO-based transparent conductive films with better optical and electrical properties. PMID:22929049

Surface treatment of alumina-based ceramics using combined laser sources

NASA Astrophysics Data System (ADS)

Triantafyllidis, D.; Li, L.; Stott, F. H.

2002-01-01

Alumina-based refractory materials are extensively used as linings in incinerators and furnaces. These materials are subject to molten salt corrosion and chemical degradation because of the existence of porosity and material inhomogeneity. Efforts to improve the performance of these materials have so far concentrated mainly on the optimisation of the manufacturing processes (e.g. producing denser refractory bricks) and in-service monitoring. Laser surface treatment has also been used to improve performance. The main problem identified with laser surface treatment is solidification cracking due to the generation of very large temperature gradients. The aim of this paper is to investigate the surface modification of alumina-based ceramics by using two combined laser sources in order to control the thermal gradients and cooling rates during processing so that crack formation can be eliminated. The material under investigation is 85% alumina refractory ceramic, used as lining material in incineration plants. The surface morphology and cross-section of the treated samples are analysed using optical and scanning electron microscopy (SEM) and compared with single laser beam treated samples.

Influence of low concentration acid treatment on lithium disilicate core/veneer ceramic bond strength

PubMed Central

Garcia, Rudan P.; Conti, Paulo CR.; Pereira, Jefferson R.; Valle, Accácio Ld.

2013-01-01

Objective: This study evaluated the influence of low concentration acid treatment on the shear bond strength between lithium disilicate (LD) infrastructure and veneering porcelain. The surface morphology characteristic after this acid treatment was also examined. Study Design: LD reinforced ceramic cylinders (n=10) (IPS e.max Press, Ivoclar-Vivadent, Schaan, Liechtenstein) were treated (LD-treated) with a low concentration acid solution (Invex Liquid – Ivoclar-Vivadent, Schaan, Liechtenstein) or not treated with the acid solution (LD-untreated). They were veneered with a glass ceramic (IPS e.max Ceram, Ivoclar-Vivadent, Schaan, Liechtenstein). A metal ceramic group (CoCr) was tested as control. Shear bond strength (SBS) was conducted using a universal testing machine at 0.5 mm/min. Surface morphology characteristics after acid treatment were analyzed using scanning electron microscopy. Results: The acid treatment at low concentrations did not influence the SBS of the LD/veneering porcelain interface. The CoCr group showed the significant higher SBS value (35.59 ± 5.97 MPa), followed by LD-untreated group (27.76 ± 3.59 MPa) and LD-treated (27.02 ± 4.79 MPa). The fracture modes were predominantly adhesive for CoCr group and cohesive within the infrastructure for DL groups. Scanning Electron Microscopy (SEM) analysis showed no morphological differences between treated and untreated LD surfaces. Conclusions: Low concentration acid treatment did not improved SBS of veneering ceramic to LD and did not cause morphological changes on the LD surface. Key words:Lithium disilicate, glass ceramics, acid etching, shear bond strength, scanning electron microscopy. PMID:24455073

Biaxial flexural strength of CAD/CAM ceramics.

PubMed

Buso, L; Oliveira-Júnior, O B; Hiroshi Fujiy, F; Leão Lombardo, G H; Ramalho Sarmento, H; Campos, F; Assunção Souza, R O

2011-06-01

Aim of the study was to evaluate the biaxial flexural strength of ceramics processed using the Cerec inLab system. The hypothesis was that the flexural strength would be influenced by the type of ceramic. Ten samples (ISO 6872) of each ceramic (N.=50/n.=10) were made using Cerec inLab (software Cerec 3D) (Ø:15 mm, thickness: 1.2 mm). Three silica-based ceramics (Vita Mark II [VM], ProCad [PC] and e-max CAD ECAD]) and two yttria-stabilized tetragonal-zirconia-polycrystalline ceramics (Y-TZP) (e-max ZirCad [ZrCAD] and Vita In-Ceram 2000 YZ Cubes [VYZ]) were tested. The samples were finished with wet silicone carbide papers up to 1 200-grit and polished in a polishing machine with diamond paste (3 µm). The samples were then submitted to biaxial flexural strength testing in a universal testing machine (EMIC), 1 mm/min. The data (MPa) were analyzed using the Kruskal-Wallis and Dunn (5%) tests. Scanning electronic microscopy (SEM) was performed on a representative sample from each group. The values (median, mean±sd) obtained for the experimental groups were: VM (101.7, 102.1±13.65 MPa), PC (165.2, 160±34.7 MPa), ECAD (437.2, 416.1±50.1 MPa), ZrCAD (804.2, 800.8±64.47 MPa) and VYZ (792.7, 807±100.7 MPa). The type of ceramic influenced the flexural strength values (P=0.0001). The ceramics ECADa, e-max ZrCADa and VYZa presented similar flexural strength values which were significantly higher than the other groups (PCb and VM IIb), which were similar statistically between them (Dunn's test). The hypothesis was accepted. The polycrystalline ceramics (Y-TZP) should be material chosen for make FPDs because of their higher flexural strength values.

Electronically conductive ceramics for high temperature oxidizing environments

DOEpatents

Kucera, G.H.; Smith, J.L.; Sim, J.W.

1983-11-10

This invention pertains to a high temperature, ceramic composition having electronic conductivity as measured by resistivity below about 500 ohm-cm, chemical stability particularly with respect to cathode conditions in a molten carbonate fuel cell, and composed of an alkali metal, transition metal oxide containing a dopant metal in the crystalline structure to replace a portion of the alkali metal or transition metal.

Mixture for producing fracture-resistant, fiber-reinforced ceramic material by microwave heating

DOEpatents

Meek, T.T.; Blake, R.D.

1985-04-03

A fracture-resistant, fiber-reinforced ceramic substrate is produced by a method which involves preparing a ceramic precursor mixture comprising glass material, a coupling agent, and resilient fibers, and then exposing the mixture to microwave energy. The microwave field orients the fibers in the resulting ceramic material in a desired pattern wherein heat later generated in or on the substrate can be dissipated in a desired geometric pattern parallel to the fiber pattern. Additionally, the shunt capacitance of the fracture-resistant, fiber-reinforced ceramic substrate is lower which provides for a quicker transit time for electronic pulses in any conducting pathway etched into the ceramic substrate.

Mixture for producing fracture-resistant, fiber-reinforced ceramic material by microwave heating

DOEpatents

Meek, Thomas T.; Blake, Rodger D.

1987-01-01

A fracture-resistant, fiber-reinforced ceramic substrate is produced by a method which involves preparing a ceramic precursor mixture comprising glass material, a coupling agent, and resilient fibers, and then exposing the mixture to microwave energy. The microwave field orients the fibers in the resulting ceramic material in a desired pattern wherein heat later generated in or on the substrate can be dissipated in a desired geometric pattern parallel to the fiber pattern. Additionally, the shunt capacitance of the fracture-resistant, fiber-reinforced ceramic substrate is lower which provides for a quicker transit time for electronic pulses in any conducting pathway etched into the ceramic substrate.

Hermetic electronic packaging of an implantable brain-machine-interface with transcutaneous optical data communication.

PubMed

Schuettler, Martin; Kohler, Fabian; Ordonez, Juan S; Stieglitz, Thomas

2012-01-01

Future brain-computer-interfaces (BCIs) for severely impaired patients are implanted to electrically contact the brain tissue. Avoiding percutaneous cables requires amplifier and telemetry electronics to be implanted too. We developed a hermetic package that protects the electronic circuitry of a BCI from body moisture while permitting infrared communication through the package wall made from alumina ceramic. The ceramic package is casted in medical grade silicone adhesive, for which we identified MED2-4013 as a promising candidate.

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.

[Interface bond and compatibility between Mark II machining ceramic and vita VM9 veneering porcelain].

PubMed

Liu, Tian-Shuang; Li, Zhen-Chun; Chen, Xiao-Dong

2009-04-01

To investigate the interface bond and thermal compatibility between Mark II machining ceramic and Vita VM9 veneering porcelain. A bar shaped specimen (30 mm x 15 mm x 1 mm in size) of Mark II block was prepared, with 0.5 mm-deep notch (vertical to the long axis of specimen) at the middle of the bottom surface. The upper surface was veneered with 0.3 mm VM9 dentin base porcelain. Then the specimen was fractured from the notching site and the fracture surface was examined under scanning electron microscope (SEM) and electron microprobe analyzer (EMPA) with electron beam of 1 microm in diameter. Another ten specimens (30 mm x 15 mm x 1.5 mm in size) were fabricated and the temperature of thermal shock resistance were tested. SEM observation showed tight bond between these two materials and EMPA results showed penetration of Al element from Mark II block into veneering porcelain and Ca element from veneering porcelain into Mark II block occurred after sintering baking. The average temperature of thermal shock resistance for specimens in this study was (194.0+/-10.3) degrees C. Cracks were mainly distributed in veneering porcelain. Chemical bond exists between the Mark II machining ceramic and Vita VM9 veneering porcelain, and there is good thermal compatibility between them.

Percolative theories of strongly disordered ceramic high-temperature superconductors.

PubMed

Phillips, J C

2010-01-26

Optimally doped ceramic superconductors (cuprates, pnictides, etc.) exhibit transition temperatures T(c) much larger than strongly coupled metallic superconductors like Pb (T(c) = 7.2 K, E(g)/kT(c) = 4.5) and exhibit many universal features that appear to contradict the Bardeen, Cooper, and Schrieffer theory of superconductivity based on attractive electron-phonon pairing interactions. These complex materials are strongly disordered and contain several competing nanophases that cannot be described effectively by parameterized Hamiltonian models, yet their phase diagrams also exhibit many universal features in both the normal and superconductive states. Here we review the rapidly growing body of experimental results that suggest that these anomalously universal features are the result of marginal stabilities of the ceramic electronic and lattice structures. These dual marginal stabilities favor both electronic percolation of a dopant network and rigidity percolation of the deformed lattice network. This "double percolation" model has previously explained many features of the normal-state transport properties of these materials and is the only theory that has successfully predicted strict lowest upper bounds for T(c) in the cuprate and pnictide families. Here it is extended to include Coulomb correlations and percolative band narrowing, as well as an angular energy gap equation, which rationalizes angularly averaged gap/T(c) ratios, and shows that these are similar to those of conventional strongly coupled superconductors.

New ZnO-Based Glass Ceramic Sensor for H2 and NO2 Detection

PubMed Central

Afify, Ahmed S.; Ataalla, Mohamed

2017-01-01

In this study, a glass ceramic with a nominal composition 58ZnO:4Bi2O3:4WO3:33.3B2O3 was synthesized by melt quenching technique. A gas sensor was then manufactured using a ZnO sol-gel phase as a permanent binder of the glass–ceramic to an alumina substrate having interdigitated electrodes. The film sensitivity towards humidity, NH3, H2 and NO2 was studied at different temperatures. X-ray diffraction technique (XRD), field emission- scanning electron microscopy (FE-SEM) and differential thermal analysis (DTA) were used to characterize the prepared material. Though the response in the sub-ppm NO2 concentration range was not explored, the observed results are comparable with the latest found in the literature. PMID:29099781

Non-hermetic encapsulation for implantable electronic devices based on epoxy.

PubMed

Boeser, Fabian; Ordonez, Juan S; Schuettler, Martin; Stieglitz, Thomas; Plachta, Dennis T T

2015-08-01

Hermetic and non-hermetic implant packaging are the two strategies to protect electronic systems from the humid conditions inside the human body. Within the scope of this work twelve different material combinations for a non-hermetic, high-reliable epoxy based encapsulation technique were characterized. Three EPO-TEK (ET) epoxies and one low budget epoxy were chosen for studies with respect to their processability, water vapor transmission rate (WVTR) and adhesion to two different ceramic-based substrates as well as to one standard FR4-substrate. Setups were built to analyze the mentioned properties for at least 30 days using an aging test in a moist environment. As secondary test subjects, commercially available USB flash drives (UFD) were successfully encapsulated inside the epoxies, soaked in phosphate buffered saline (PBS, pH=7.4), stored in an incubator (37°C) and tested for 256 days without failure. By means of epoxy WVTR (0.0278 g/day/m(2)) and degrease of adhesion (24.59 %) during 30 days in PBS, the combination of the standard FR4-substrate and the epoxy ET 301-2 was found to feature the best encapsulation properties. If a ceramic-based electronic system has to be used, the most promising combination consists of the alumina substrate and the epoxy ET 302-3M (WVTR: 0.0588 g/day/m(2); adhesion drop: 49.58 %).

Hybrid membrane-microfluidic components using a novel ceramic MEMS technology

NASA Astrophysics Data System (ADS)

Lutz, Brent J.; Polyakov, Oleg; Rinaldo, Chris

2012-03-01

A novel hybrid nano/microfabrication technology has been employed to produce unique MEMS and microfluidic components that integrate nanoporous membranes. The components are made by micromachining a self-organized nanostructured ceramic material that is biocompatible and amenable to surface chemistry modification. Microfluidic structures, such as channels and wells, can be made with a precision of <2 microns. Thin-film membranes can be integrated into the bottom of these structures, featuring a wide range of possible thicknesses, from 100 micron to <50 nm. Additionally, these membranes may be non-porous or porous (with controllable pore sizes from 200 nm to <5 nm), for sophisticated size-based separations. With previous and current support from the NIH SBIR program, we have built several unique devices, and demonstrated improved separations, cell culturing, and imaging (optical and electron microscopy) versus standard products. Being ceramic, the material is much more robust to demanding environments (e.g. high and low temperatures and organic solvents), compared to polymer-based devices. Additionally, we have applied multiple surface modification techniques, including atomic layer deposition, to manipulate properties such as electrical conductivity. This microfabrication technology is highly scaleable, and thus can yield low-cost, reliable, disposable microcomponents and devices. Specific applications that can benefit from this technology includes cell culturing and assays, imaging by cryo-electron tomography, environmental sample processing, as well as many others.

Temperature-dependent electron paramagnetic resonance detect oxygen vacancy defects and Cr valence of tetragonal Ba(Ti1-xCrx)O3 ceramics

NASA Astrophysics Data System (ADS)

Han, Dan-Dan; Lu, Da-Yong; Meng, Fan-Ling; Yu, Xin-Yu

2018-03-01

Temperature-dependent electron paramagnetic resonance (EPR) study was employed to detect oxygen vacancy defects in the tetragonal Ba(Ti1-xCrx)O3 (x = 5%) ceramic for the first time. In the rhombohedral phase below -150 °C, an EPR signal at g = 1.955 appeared in the insulating Ba(Ti1-xCrx)O3 (x = 5%) ceramic with an electrical resistivity of 108 Ω cm and was assigned to ionized oxygen vacancy defects. Ba(Ti1-xCrx)O3 ceramics exhibited a tetragonal structure except Ba(Ti1-xCrx)O3 (x = 10%) with a tetragonal-hexagonal mixed phase and a first-order phase transition dielectric behavior (ε‧m > 11,000). Mixed valence Cr ions could coexist in ceramics, form CrTi‧-VOrad rad or CrTirad-TiTi‧ defect complexes and make no contribution to a dielectric peak shift towards low temperature.

Carbon/PTFE Electrode for Lithium/Air-Water Batteries

DTIC Science & Technology

2007-03-01

non-electronically conducting ceramic membrane impervious to water but with a high ionic conductivity for lithium-ions. LiTixAly(PO4)3 is one such...example of a ceramic composition that has been used in this manner. The lithium ion can be thought of as being solvated by the ceramic membrane as it...through 5) provides current. To balance the overall charge in the reaction, positive lithium ions flow 1 through an ionically conducting ceramic

Proceedings of the seventh international conference on high voltage electron microscopy

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

Fisher, R.M.; Gronsky, R.; Westmacott, K.H.

1983-01-01

Eight-four papers are arranged under the following headings: high resolution, techniques and instrumentation, radiation effects, in-situ and phase transformations, minerals and ceramics, and semiconductors and thin films. Twenty-three papers were abstracted separately for the data base; three of the remainder had previously been abstracted. (DLC)

Effect of Er:YAG Laser and Sandblasting in Recycling of Ceramic Brackets.

PubMed

Yassaei, Soghra; Aghili, Hossein; Hosseinzadeh Firouzabadi, Azadeh; Meshkani, Hamidreza

2017-01-01

Introduction: This study was performed to determine the shear bond strength of rebonded mechanically retentive ceramic brackets after recycling with Erbium-Doped Yttrium Aluminum Garnet (Er:YAG) laser or sandblasting. Methods: Twenty-eight debonded ceramic brackets plus 14 intact new ceramic brackets were used in this study. Debonded brackets were randomly divided into 2 groups of 14. One group was treated by Er:YAG laser and the other with sandblasting. All the specimens were randomly bonded to 42 intact human upper premolars. The shear bond strength of all specimens was determined with a universal testing machine at a crosshead speed of 0.5 mm/min until bond failure occurred. The recycled bracket base surfaces were observed under a scanning electron microscope (SEM). Analysis of variance (ANOVA) and Tukey tests were used to compare the shear bond strength of the 3 groups. Fisher exact test was used to evaluate the differences in adhesive remnant index (ARI) scores. Results: The highest bond strength belonged to brackets recycled by Sandblasting (16.83 MPa). There was no significant difference between the shear bond strength of laser and control groups. SEM photographs showed differences in 2 recycling methods. The laser recycled bracket appeared to have as well-cleaned base as the new bracket. Although the sandblasted bracket photographs showed no remnant adhesives, remarkable micro-roughening of the base of the bracket was apparent. Conclusion: According to the results of this study, both Er:YAG laser and sandblasting were efficient to mechanically recondition retentive ceramic brackets. Also, Er:YAG laser did not change the design of bracket base while removing the remnant adhesives which might encourage its application in clinical practice.

Effect of Er:YAG Laser and Sandblasting in Recycling of Ceramic Brackets

PubMed Central

Yassaei, Soghra; Aghili, Hossein; Hosseinzadeh Firouzabadi, Azadeh; Meshkani, Hamidreza

2017-01-01

Introduction: This study was performed to determine the shear bond strength of rebonded mechanically retentive ceramic brackets after recycling with Erbium-Doped Yttrium Aluminum Garnet (Er:YAG) laser or sandblasting. Methods: Twenty-eight debonded ceramic brackets plus 14 intact new ceramic brackets were used in this study. Debonded brackets were randomly divided into 2 groups of 14. One group was treated by Er:YAG laser and the other with sandblasting. All the specimens were randomly bonded to 42 intact human upper premolars. The shear bond strength of all specimens was determined with a universal testing machine at a crosshead speed of 0.5 mm/min until bond failure occurred. The recycled bracket base surfaces were observed under a scanning electron microscope (SEM). Analysis of variance (ANOVA) and Tukey tests were used to compare the shear bond strength of the 3 groups. Fisher exact test was used to evaluate the differences in adhesive remnant index (ARI) scores. Results: The highest bond strength belonged to brackets recycled by Sandblasting (16.83 MPa). There was no significant difference between the shear bond strength of laser and control groups. SEM photographs showed differences in 2 recycling methods. The laser recycled bracket appeared to have as well-cleaned base as the new bracket. Although the sandblasted bracket photographs showed no remnant adhesives, remarkable micro-roughening of the base of the bracket was apparent. Conclusion: According to the results of this study, both Er:YAG laser and sandblasting were efficient to mechanically recondition retentive ceramic brackets. Also, Er:YAG laser did not change the design of bracket base while removing the remnant adhesives which might encourage its application in clinical practice. PMID:28912939

Quantitative analysis of enamel on debonded orthodontic brackets.

PubMed

Cochrane, Nathan J; Lo, Thomas W G; Adams, Geoffrey G; Schneider, Paul M

2017-09-01

Iatrogenic damage to the tooth surface in the form of enamel tearouts can occur during removal of fixed orthodontic appliances. The aim of this study was to assess debonded metal and ceramic brackets attached with a variety of bonding materials to determine how frequently this type of damage occurs. Eighty-one patients close to finishing fixed orthodontic treatment were recruited. They had metal brackets bonded with composite resin and a 2-step etch-and-bond technique or ceramic brackets bonded with composite resin and a 2-step etch-and- bond technique, and composite resin with a self-etching primer or resin-modified glass ionomer cement. Debonded brackets were examined by backscattered scanning electron microscopy with energy dispersive x-ray spectroscopy to determine the presence and area of enamel on the base pad. Of the 486 brackets collected, 26.1% exhibited enamel on the bonding material on the bracket base pad. The incidences of enamel tearouts for each group were metal brackets, 13.3%; ceramic brackets, 30.2%; composite resin with self-etching primer, 38.2%; and resin-modified glass ionomer cement, 21.2%. The percentage of the bracket base pad covered in enamel was highly variable, ranging from 0% to 46.1%. Enamel damage regularly occurred during the debonding process with the degree of damage being highly variable. Damage occurred more frequently when ceramic brackets were used (31.9%) compared with metal brackets (13.3%). Removal of ceramic brackets bonded with resin-modified glass ionomer cement resulted in less damage compared with the resin bonding systems. Copyright © 2017 American Association of Orthodontists. Published by Elsevier Inc. All rights reserved.

Effects of Polarization on Mechanical Properties of Lead Zirconate Titanate Ceramics Evaluated by Modified Small Punch Tests

NASA Astrophysics Data System (ADS)

Deng, Qihuang; Fan, Yuchi; Wang, Lianjun; Xiong, Zhi; Wang, Hongzhi; Li, Yaogang; Zhang, Qinghong; Kawasaki, Akira; Jiang, Wan

2012-01-01

Pb(Zr,Ti)O3 (PZT) ceramics were prepared by the conventional mixed oxide method, and the strength of the resultant PZT ceramics was evaluated using modified small punch (MSP) tests. Load-displacement curve test results showed that the crack-initiation and fracture strengths of PZT ceramics decreased after polarization. The effect of the polarization accelerated the fatigue properties of PZT ceramics. Scanning electron microscopy (SEM) results showed that microcracks were formed before the maximum load in the MSP test, and the first load drop corresponded to crack initiation.

Evaluation of sol-gel based magnetic 45S5 bioglass and bioglass-ceramics containing iron oxide.

PubMed

Shankhwar, Nisha; Srinivasan, A

2016-05-01

Multicomponent oxide powders with nominal compositions of (45-x)·SiO2·24.5CaO·24.5Na2O·6P2O5xFe2O3 (in wt.%) were prepared by a modified sol-gel procedure. X-ray diffraction (XRD) patterns and high resolution transmission electron microscope images of the sol-gel products show fully amorphous structure for Fe2O3 substitutions up to 2 wt.%. Sol-gel derived 43SiO2·24.5CaO·24.5Na2O·6P2O5·2Fe2O3 glass (or bioglass 45S5 with SiO2 substituted with 2 wt.% Fe2O3), exhibited magnetic behavior with a coercive field of 21 Oe, hysteresis loop area of 33.25 erg/g and saturation magnetization of 0.66 emu/g at an applied field of 15 kOe at room temperature. XRD pattern of this glass annealed at 850 °C for 1h revealed the formation of a glass-ceramic containing sodium calcium silicate and magnetite phases in nanocrystalline form. Temperature dependent magnetization and room temperature electron spin resonance data have been used to obtain information on the magnetic phase and distribution of iron ions in the sol-gel glass and glass-ceramic samples. Sol-gel derived glass and glass-ceramic exhibit in-vitro bioactivity by forming a hydroxyapatite surface layer under simulated physiological conditions and their bio-response is superior to their melt quenched bulk counterparts. This new form of magnetic bioglass and bioglass ceramics opens up new and more effective biomedical applications. Copyright © 2016 Elsevier B.V. All rights reserved.

Nanoelectric Materials Laboratory Development

NASA Technical Reports Server (NTRS)

Allen, Lee; Hill, Curtis

2015-01-01

The Ultracapacitor Research and Development project is a collaborative effort between the NASA Marshall Space Flight Center's (MSFC's) ES43 Parts, Packaging, and Fabrication Branch and the EM41 Nonmetallic Materials Branch. NASA's Ultracapacitor Research is an effort to develop solid-state energy storage devices through processing of ceramic materials into printable dielectric inks, which can be formed and treated to produce solid state ultracapacitor cells capable of exceeding lithium-ion battery energy density at a fraction of the weight. Research and development efforts into solid state ultracapacitors have highlighted a series of technical challenges such as understanding as-received nature of ceramic powders, treatment and optimization of ceramic powders, dielectric and conductor ink formulation, and firing of printed (green) ultracapacitor cells. Two facilities have been continually developed since project inception: the Additive Electronics Lab in Bldg. 4487 and the Nanoelectric Materials Lab in Bldg. 4602. The Nanoelectric Materials Lab has become a unique facility at MSFC, capable of custom processing a wide range of media for additive electronics. As research has progressed, it was discovered that additional in-house processing was necessary to achieve smaller, more uniform particle diameters. A vibratory mill was obtained that can agitate powder and media in three directions, which has shown to be much more effective than ball milling. However, in order to understand the effects of milling, a particle size analysis system has been installed to characterize as-received and milled materials Continued research into the ultracapacitor technology included advanced milling and optimization of ceramic nanoparticles, fluidized bed treatment of atomic-layer deposition- (ALD-) coated ceramic particles, custom development of dielectric and conductor inks, as well as custom ink precursors such as polyvinylidene diflouride- (PVDF-) loaded vehicles. Experiments with graphene-based inks were also conducted.

Development and Characterization of the Bonding and Integration Technologies Needed for Fabricating Silicon Carbide Based Injector Components

NASA Technical Reports Server (NTRS)

Halbig,Michael C.; Singh, Mrityunjay

2008-01-01

Advanced ceramic bonding and integration technologies play a critical role in the fabrication and application of silicon carbide based components for a number of aerospace and ground based applications. One such application is a lean direct injector for a turbine engine to achieve low NOx emissions. Ceramic to ceramic diffusion bonding and ceramic to metal brazing technologies are being developed for this injector application. For the diffusion bonding technology, titanium interlayers (coatings and foils) were used to aid in the joining of silicon carbide (SiC) substrates. The influence of such variables as surface finish, interlayer thickness, and processing time were investigated. Electron microprobe analysis was used to identify the reaction formed phases. In the diffusion bonds, an intermediate phase, Ti5Si3Cx, formed that is thermally incompatible in its thermal expansion and caused thermal stresses and cracking during the processing cool-down. Thinner interlayers of pure titanium and/or longer processing times resulted in an optimized microstructure. Tensile tests on the joined materials resulted in strengths of 13-28 MPa depending on the SiC substrate material. Nondestructive evaluation using ultrasonic immersion showed well formed bonds. For the joining technology of brazing Kovar fuel tubes to silicon carbide, preliminary development of the joining approach has begun. Various technical issues and requirements for the injector application are addressed.

Radiation effects in cubic zirconia: A model system for ceramic oxides

NASA Astrophysics Data System (ADS)

Thomé, L.; Moll, S.; Sattonnay, G.; Vincent, L.; Garrido, F.; Jagielski, J.

2009-06-01

Ceramics are key engineering materials for electronic, space and nuclear industry. Some of them are promising matrices for the immobilization and/or transmutation of radioactive waste. Cubic zirconia is a model system for the study of radiation effects in ceramic oxides. Ion beams are very efficient tools for the simulation of the radiations produced in nuclear reactors or in storage form. In this article, we summarize the work made by combining advanced techniques (RBS/C, XRD, TEM, AFM) to study the structural modifications produced in ion-irradiated cubic zirconia single crystals. Ions with energies in the MeV-GeV range allow exploring the nuclear collision and electronic excitation regimes. At low energy, where ballistic effects dominate, the damage exhibits a peak around the ion projected range; it accumulates with a double-step process by the formation of a dislocation network. At high energy, where electronic excitations are favored, the damage profiles are rather flat up to several micrometers; the damage accumulation is monotonous (one step) and occurs through the creation and overlap of ion tracks. These results may be generalized to many nuclear ceramics.

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

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.

Effects of Ceramic Density and Sintering Temperature on the Mechanical Properties of a Novel Polymer-Infiltrated Ceramic-Network Zirconia Dental Restorative (Filling) Material.

PubMed

Li, Weiyan; Sun, Jian

2018-05-10

BACKGROUND Polymer-infiltrated ceramic-network (PICN) dental material is a new and practical development in orthodontics. Sintering is the process of forming a stable solid mass from a powder by heating without melting. The aim of this study was to evaluate the effects of sintering temperature on the mechanical properties of a PICN zirconia dental material. MATERIAL AND METHODS A dense zirconia ceramic and four PICN zirconia dental materials, with varying porosities, were sintered at three different temperatures; 12 PICN zirconia dental materials based on these porous ceramics were prepared, as well as a pure polymer. After the specimen preparation, flexural strength and elastic modulus values were measured using the three-point bending test, and fracture toughness were determined by the single-edge notched beam (SENB) method. The Vickers hardness test method was used with an indentation strength (IS) test. Scanning electron microscopy (SEM) was used to examine the microstructure of the ceramic surface and the fracture surface. RESULTS Mechanical properties of the PICN dental materials, including flexural strength, elastic modulus, fracture toughness, and hardness, were more similar to the properties of natural teeth when compared with traditional dental ceramic materials, and were affected by the density and sintering temperature. SEM showed that the porous ceramic network became cohesive and that the length of cracks in the PICN dental material was reduced. CONCLUSIONS PICN zirconia dental materials were characterized by similar mechanical properties to natural dental tissues, but further studies are required continue to improve the similarities with natural human enamel and dentin.

Effects of Ceramic Density and Sintering Temperature on the Mechanical Properties of a Novel Polymer-Infiltrated Ceramic-Network Zirconia Dental Restorative (Filling) Material

PubMed Central

Li, Weiyan

2018-01-01

Background Polymer-infiltrated ceramic-network (PICN) dental material is a new and practical development in orthodontics. Sintering is the process of forming a stable solid mass from a powder by heating without melting. The aim of this study was to evaluate the effects of sintering temperature on the mechanical properties of a PICN zirconia dental material. Material/Methods A dense zirconia ceramic and four PICN zirconia dental materials, with varying porosities, were sintered at three different temperatures; 12 PICN zirconia dental materials based on these porous ceramics were prepared, as well as a pure polymer. After the specimen preparation, flexural strength and elastic modulus values were measured using the three-point bending test, and fracture toughness were determined by the single-edge notched beam (SENB) method. The Vickers hardness test method was used with an indentation strength (IS) test. Scanning electron microscopy (SEM) was used to examine the microstructure of the ceramic surface and the fracture surface. Results Mechanical properties of the PICN dental materials, including flexural strength, elastic modulus, fracture toughness, and hardness, were more similar to the properties of natural teeth when compared with traditional dental ceramic materials, and were affected by the density and sintering temperature. SEM showed that the porous ceramic network became cohesive and that the length of cracks in the PICN dental material was reduced. Conclusions PICN zirconia dental materials were characterized by similar mechanical properties to natural dental tissues, but further studies are required continue to improve the similarities with natural human enamel and dentin. PMID:29746449

Tribochemical Glass Ceramic Coating as a New Approach for Resin Adhesion to Zirconia.

PubMed

Wandscher, Vinícius Felipe; Fraga, Sara; Pozzobon, João Luiz; Soares, Fabio Zovico Maxnuck; Foletto, Edson Luiz; May, Liliana Gressler; Valandro, Luiz Felipe

To investigate the effects of a novel tribochemical silica coating technique with powders made from feldspathic ceramic and leucite-based ceramic on the bond strength of zirconia to resin cement before and after aging. Zirconia blocks were divided into 3 groups according to the material used for airborne-particle abrasion: 1) SP (control): silica-coated alumina particles; 2) FP: feldspathic ceramic powder; 3) LP: leucite glass-ceramic powder. After silanization, composite resin cylinders were cemented on the zirconia surface using a dual-curing resin cement. Prior to the shear bond strength (SBS) test, half of the samples (n = 15) were stored in distilled water for 24 h; the other half (n = 15) were submitted to aging (10,000 thermocycles of 5°C to 55°C; 150 days of water storage). The bond strength data were analyzed using two-way ANOVA and Tukey's test (α = 0.05). Scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and x-ray diffraction analysis were performed. The initial bond strengths did not differ significantly between the groups (p = 0.053). However, after aging procedures, airborne-particle abrasion with feldspathic ceramic powder (FP) resulted in higher values of bond strength (p = 0.0001). SEM and EDS indicated that all the treatments promoted silica deposition on the Y-TZP surface ceramic. Airborne-particle abrasion with FP and LP induced a lower percentage of the monoclinic phase. Airborne abrasion with fine feldspathic ceramic particles is a novel tribochemical technique and appears to be suitable for improving the bond strength between zirconia and resin cements.

Mixture for producing fracture-resistant, fiber-reinforced ceramic material by microwave heating

DOEpatents

Meek, T.T.; Blake, R.D.

1987-09-22

A fracture-resistant, fiber-reinforced ceramic substrate is produced by a method which involves preparing a ceramic precursor mixture comprising glass material, a coupling agent, and resilient fibers, and then exposing the mixture to microwave energy. The microwave field orients the fibers in the resulting ceramic material in a desired pattern wherein heat later generated in or on the substrate can be dissipated in a desired geometric pattern parallel to the fiber pattern. Additionally, the shunt capacitance of the fracture-resistant, fiber-reinforced ceramic substrate is lower which provides for a quicker transit time for electronic pulses in any conducting pathway etched into the ceramic substrate. 2 figs.

Single-source-precursor synthesis of dense SiC/HfC(x)N(1-x)-based ultrahigh-temperature ceramic nanocomposites.

PubMed

Wen, Qingbo; Xu, Yeping; Xu, Binbin; Fasel, Claudia; Guillon, Olivier; Buntkowsky, Gerd; Yu, Zhaoju; Riedel, Ralf; Ionescu, Emanuel

2014-11-21

A novel single-source precursor was synthesized by the reaction of an allyl hydrido polycarbosilane (SMP10) and tetrakis(dimethylamido)hafnium(iv) (TDMAH) for the purpose of preparing dense monolithic SiC/HfC(x)N(1-x)-based ultrahigh temperature ceramic nanocomposites. The materials obtained at different stages of the synthesis process were characterized via Fourier transform infrared (FT-IR) as well as nuclear magnetic resonance (NMR) spectroscopy. The polymer-to-ceramic transformation was investigated by means of MAS NMR and FT-IR spectroscopy as well as thermogravimetric analysis (TGA) coupled with in situ mass spectrometry. Moreover, the microstructural evolution of the synthesized SiHfCN-based ceramics annealed at different temperatures ranging from 1300 °C to 1800 °C was characterized by elemental analysis, X-ray diffraction, Raman spectroscopy and transmission electron microscopy (TEM). Based on its high temperature behavior, the amorphous SiHfCN-based ceramic powder was used to prepare monolithic SiC/HfC(x)N(1-x)-based nanocomposites using the spark plasma sintering (SPS) technique. The results showed that dense monolithic SiC/HfC(x)N(1-x)-based nanocomposites with low open porosity (0.74 vol%) can be prepared successfully from single-source precursors. The average grain size of both HfC0.83N0.17 and SiC phases was found to be less than 100 nm after SPS processing owing to a unique microstructure: HfC0.83N0.17 grains were embedded homogeneously in a β-SiC matrix and encapsulated by in situ formed carbon layers which acted as a diffusion barrier to suppress grain growth. The segregated Hf-carbonitride grains significantly influenced the electrical conductivity of the SPS processed monolithic samples. While Hf-free polymer-derived SiC showed an electrical conductivity of ca. 1.8 S cm(-1), the electrical conductivity of the Hf-containing material was analyzed to be ca. 136.2 S cm(-1).

Electron beam gun with kinematic coupling for high power RF vacuum devices

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

Borchard, Philipp

An electron beam gun for a high power RF vacuum device has components joined by a fixed kinematic coupling to provide both precise alignment and high voltage electrical insulation of the components. The kinematic coupling has high strength ceramic elements directly bonded to one or more non-ductile rigid metal components using a high temperature active metal brazing alloy. The ceramic elements have a convex surface that mates with concave grooves in another one of the components. The kinematic coupling, for example, may join a cathode assembly and/or a beam shaping focus electrode to a gun stem, which is preferably composedmore » of ceramic. The electron beam gun may be part of a high power RF vacuum device such as, for example, a gyrotron, klystron, or magnetron.« less

The effects of PbZn1/3Nb2/3O3-doping on structural, thermal, optical, dielectric, and ferroelectric properties of BaTiO3 ceramics

NASA Astrophysics Data System (ADS)

Suchanicz, J.; Świerczek, K.; Sitko, D.; Czaja, P.; Marchet, P.; Czternastek, H.; Majda, D.

2017-09-01

Low-lead (1-x)BT-xPZN (x = 0, 0.025, 0.05, 0.075, 0.10, 0.125, and 0.15) ceramics were successfully synthesized by the spark-plasma-sintering method for the first time. Their phase transition behavior as well as structural, thermal, optical, and electrical properties was investigated. These materials exhibit the structure of perovskite-type solid solutions and undergo a sequence of phase transitions, typical of pure BaTiO3 (BT). The dielectric test results revealed that with the increase in the PbZn1/3Nb2/3O3 (PZN) content, the frequency dispersion of electric permittivity increases, whilst the dielectric/ferroelectric properties tend to deteriorate, which is characteristic of relaxor-type behavior. Therefore, it is reasonable to suppose that these ceramics progressively lack long-range ordering. These effects are due to the competition between lone-pair electrons' induced changes in the A-O band upon Pb2+ addition and ionic size differences. In general, the transition temperatures observed by dielectric analyses are in good agreement with those obtained from X-ray diffraction and differential scanning calorimetry measurements. The BT-PZN system may help to understand why relaxor behavior appears in perovskite-based materials. It appears that these materials can become a good starting point for the development of new low-lead electronic ceramics.

Strength and fatigue properties of three-step sintered dense nanocrystal hydroxyapatite bioceramics

NASA Astrophysics Data System (ADS)

Guo, Wen-Guang; Qiu, Zhi-Ye; Cui, Han; Wang, Chang-Ming; Zhang, Xiao-Jun; Lee, In-Seop; Dong, Yu-Qi; Cui, Fu-Zhai

2013-06-01

Dense hydroxyapatite (HA) ceramic is a promising material for hard tissue repair due to its unique physical properties and biologic properties. However, the brittleness and low compressive strength of traditional HA ceramics limited their applications, because previous sintering methods produced HA ceramics with crystal sizes greater than nanometer range. In this study, nano-sized HA powder was employed to fabricate dense nanocrystal HA ceramic by high pressure molding, and followed by a three-step sintering process. The phase composition, microstructure, crystal dimension and crystal shape of the sintered ceramic were examined by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Mechanical properties of the HA ceramic were tested, and cytocompatibility was evaluated. The phase of the sintered ceramic was pure HA, and the crystal size was about 200 nm. The compressive strength and elastic modulus of the HA ceramic were comparable to human cortical bone, especially the good fatigue strength overcame brittleness of traditional sintered HA ceramics. Cell attachment experiment also demonstrated that the ceramics had a good cytocompatibility.

Post-fatigue fracture resistance of metal core crowns: press-on metal ceramic versus a conventional veneering system

PubMed Central

Agustín-Panadero, Rubén; Campos-Estellés, Carlos; Labaig-Rueda, Carlos

2015-01-01

Background The aim of this in vitro study was to compare the mechanical failure behavior and to analyze fracture characteristics of metal ceramic crowns with two veneering systems – press-on metal (PoM) ceramic versus a conventional veneering system – subjected to static compressive loading. Material and Methods Forty-six crowns were constructed and divided into two groups according to porcelain veneer manufacture. Group A: 23 metal copings with porcelain IPS-InLine veneering (conventional metal ceramic). Group B: 23 metal copings with IPS-InLine PoM veneering porcelain. After 120,000 fatigue cycles, the crowns were axially loaded to the moment of fracture with a universal testing machine. The fractured specimens were examined under optical stereomicroscopy and scanning electron microscope. Results Fracture resistance values showed statistically significant differences (Student’s t-test) regarding the type of ceramic veneering technique (p=0.001): Group A (conventional metal ceramics) obtained a mean fracture resistance of 1933.17 N, and Group B 1325.74N (Press-on metal ceramics). The most common type of fracture was adhesive failure (with metal exposure) (p=0.000). Veneer porcelain fractured on the occlusal surface following a radial pattern. Conclusions Metal ceramic crowns made of IPS InLine or IPS InLine PoM ceramics with different laboratory techniques all achieved above-average values for clinical survival in the oral environment according to ISO 6872. Crowns made with IPS InLine by conventional technique resisted fracture an average of 45% more than IPS InLine PoM fabricated with the press-on technique. Key words:Mechanical failure, conventional feldspathic, pressable ceramic, chewing simulator, thermocycling, compressive testing, fracture types, scanning electron microscope. PMID:26155346

Improved DC Gun and Insulator Assembly

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

Neubauer, Michael

Many user facilities such as synchrotron radiation light sources and free electron lasers rely on DC high voltage photoguns with internal field gradients as high as 10 to 15 MV/m. These high gradients often lead to field emission which poses serious problems for the photocathode used to generate the electron beam and the ceramic insulators used to bias the photocathode at high voltage. Ceramic insulators are difficult to manufacture, require long commissioning times, and have poor reliability, in part because energetic electrons bury themselves in the ceramic causing a buildup of charge and eventual puncture, and also because large diametermore » ceramics are difficult to braze reliably. The lifetimes of photo cathodes inside high current DC guns exhibiting field emission are limited to less than a hundred hours. Reducing the surface gradients on the metals reduces the field emission, which serves to maintain the required ultrahigh vacuum condition. A novel gun design with gradients around 5 MV/m and operating at 350 kV, a major improvement over existing designs, was proposed that allows for the in-situ replacement of photo cathodes in axially symmetric designs using inverted ceramics. In this project, the existing JLAB CEBAF asymmetric gun design with an inverted ceramic support was modeled and the beam dynamics characterized. An improved structure was designed that reduces the surface gradients and improves the beam optics. To minimize the surface gradients, a number of electrostatic gun designs were studied to determine the optimum configuration of the critical electrodes within the gun structure. Coating experiments were carried out to create a charge dissipative coating for cylindrical ceramics. The phase II proposal, which was not granted, included the design and fabrication of an axially symmetric DC Gun with an inverted ceramic that would operate with less than 5 MV/m at 350 kV and would be designed with an in-situ replaceable photo-cathode.« less

Wear and Reactivity Studies of Melt infiltrated Ceramic Matrix Composite

NASA Technical Reports Server (NTRS)

Jarmon, David C.; Ojard, Greg; Brewer, David N.

2013-01-01

As interest grows in the use of ceramic matrix composites (CMCs) for critical gas turbine engine components, the effects of the CMCs interaction with the adjoining structure needs to be understood. A series of CMC/material couples were wear tested in a custom elevated temperature test rig and tested as diffusion couples, to identify interactions. Specifically, melt infiltrated silicon carbide/silicon carbide (MI SiC/SiC) CMC was tested in combination with a nickel-based super alloy, Waspaloy, a thermal barrier coating, Yttria Stabilized Zirconia (YSZ), and a monolithic ceramic, silicon nitride (Si3N4). To make the tests more representative of actual hardware, the surface of the CMC was kept in the as-received state (not machined) with the full surface features/roughness present. Test results include: scanning electron microscope characterization of the surfaces, micro-structural characterization, and microprobe analysis.

Effect of etching with distinct hydrofluoric acid concentrations on the flexural strength of a lithium disilicate-based glass ceramic.

PubMed

Prochnow, Catina; Venturini, Andressa B; Grasel, Rafaella; Bottino, Marco C; Valandro, Luiz Felipe

2017-05-01

This study examined the effects of distinct hydrofluoric acid concentrations on the mechanical behavior of a lithium disilicate-based glass ceramic. Bar-shaped specimens were produced from ceramic blocks (e.max CAD, Ivoclar Vivadent). The specimens were polished, chamfered, and sonically cleaned in distilled water. The specimens were randomly divided into five groups (n = 23). The HF1, HF3, HF5, and HF10 specimens were etched for 20 s with acid concentrations of 1%, 3%, 5%, and 10%, respectively, while the SC (control) sample was untreated. The etched surfaces were evaluated using a scanning electron microscope and an atomic force microscope. Finally, the roughness was measured, and 3-point bending flexural tests were performed. The data were analyzed using one-way analysis of variance (ANOVA) and Tukey's test (α = 0.05). The Weibull modulus and characteristic strength were also determined. No statistical difference in the roughness and flexural strength was determined among the groups. The structural reliabilities (Weilbull moduli) were similar for the tested groups; however, the characteristic strength of the HF1 specimen was greater than that of the HF10 specimen. Compared with the untreated ceramic, the surface roughness and flexural strength of the ceramic were unaffected upon etching, regardless of the acid concentration. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 885-891, 2017. © 2016 Wiley Periodicals, Inc.

Additive Manufacturing of SiC Based Ceramics and Ceramic Matrix Composites

NASA Technical Reports Server (NTRS)

Halbig, Michael Charles; Singh, Mrityunjay

2015-01-01

Silicon carbide (SiC) ceramics and SiC fiber reinforcedSiC ceramic matrix composites (SiCSiC CMCs) offer high payoff as replacements for metals in turbine engine applications due to their lighter weight, higher temperature capability, and lower cooling requirements. Additive manufacturing approaches can offer game changing technologies for the quick and low cost fabrication of parts with much greater design freedom and geometric complexity. Four approaches for developing these materials are presented. The first two utilize low cost 3D printers. The first uses pre-ceramic pastes developed as feed materials which are converted to SiC after firing. The second uses wood containing filament to print a carbonaceous preform which is infiltrated with a pre-ceramic polymer and converted to SiC. The other two approaches pursue the AM of CMCs. The first is binder jet SiC powder processing in collaboration with rp+m (Rapid Prototyping+Manufacturing). Processing optimization was pursued through SiC powder blending, infiltration with and without SiC nano powder loading, and integration of nanofibers into the powder bed. The second approach was laminated object manufacturing (LOM) in which fiber prepregs and laminates are cut to shape by a laser and stacked to form the desired part. Scanning electron microscopy was conducted on materials from all approaches with select approaches also characterized with XRD, TGA, and bend testing.

Enhanced Multiferroic Properties of YMnO3 Ceramics Fabricated by Spark Plasma Sintering Along with Low-Temperature Solid-State Reaction

PubMed Central

Wang, Meng; Wang, Ting; Song, Shenhua; Ravi, Muchakayala; Liu, Renchen; Ji, Shishan

2017-01-01

Based on precursor powders with a size of 200–300 nm prepared by the low-temperature solid-state reaction method, phase-pure YMnO3 ceramics are fabricated using spark plasma sintering (SPS). X-ray diffraction (XRD) and scanning electron microscopy (SEM) reveal that the high-purity YMnO3 ceramics can be prepared by SPS at 1000 °C for 5 minutes with annealing at 800 °C for 2 h. The relative density of the sample is as high as 97%, which is much higher than those of the samples sintered by other methods. The present dielectric and magnetic properties are much better than those of the samples fabricated by conventional methods and SPS with ball-milling precursors, and the ferroelectric loops at room temperature can be detected. These findings indicate that the YMnO3 ceramics prepared by the low temperature solid reaction method and SPS possess excellent dielectric lossy ferroelectric properties at room temperature, and magnetic properties at low temperature (10 K), making them suitable for potential multiferroic applications. PMID:28772832

Application of Recycled Ceramic Aggregates for the Production of Mineral-Asphalt Mixtures.

PubMed

Andrzejuk, Wojciech; Barnat-Hunek, Danuta; Siddique, Rafat; Zegardło, Bartosz; Łagód, Grzegorz

2018-04-24

This paper describes a method of designing and producing innovative mineral⁻asphalt mixtures, which utilize waste aggregate from the recycling of sanitary ceramics. The work presents the basic properties of the ceramic material, the investigation concerning the microstructure of the aggregate obtained from the grinding of waste, and a comparison with the images obtained for the aggregates usually employed in mineral⁻asphalt mixtures. The mixtures were designed for the application in the wearing course. Four series of mixtures were prepared. In the first and second, the ceramic aggregate constituted a partial substitute for dolomite, whereas in the third, we substituted granodiorite, and the fourth series contained only dolomite. The mixtures were examined for the content of soluble binder, the bulk density of samples, the presence of voids, the space filled with binder, and the susceptibility to water and frost corrosion. The obtained results were compared with the standard requirements. The microstructure as well as the contact zone in the considered mineral⁻asphalt mixtures are presented based on research conducted by means of a scanning electron microscope (SEM).

Application of Recycled Ceramic Aggregates for the Production of Mineral-Asphalt Mixtures

PubMed Central

Andrzejuk, Wojciech; Barnat-Hunek, Danuta; Siddique, Rafat; Zegardło, Bartosz; Łagód, Grzegorz

2018-01-01

This paper describes a method of designing and producing innovative mineral–asphalt mixtures, which utilize waste aggregate from the recycling of sanitary ceramics. The work presents the basic properties of the ceramic material, the investigation concerning the microstructure of the aggregate obtained from the grinding of waste, and a comparison with the images obtained for the aggregates usually employed in mineral–asphalt mixtures. The mixtures were designed for the application in the wearing course. Four series of mixtures were prepared. In the first and second, the ceramic aggregate constituted a partial substitute for dolomite, whereas in the third, we substituted granodiorite, and the fourth series contained only dolomite. The mixtures were examined for the content of soluble binder, the bulk density of samples, the presence of voids, the space filled with binder, and the susceptibility to water and frost corrosion. The obtained results were compared with the standard requirements. The microstructure as well as the contact zone in the considered mineral–asphalt mixtures are presented based on research conducted by means of a scanning electron microscope (SEM). PMID:29695115

Effect of Sintering Temperature on Structural, Dielectric, and Magnetic Properties of Multiferroic YFeO3 Ceramics Fabricated by Spark Plasma Sintering

PubMed Central

Wang, Meng; Wang, Ting; Song, Shenhua; Ma, Qing; Liu, Renchen

2017-01-01

Based on precursor powders with a size of 200–300 nm prepared by the low-temperature solid reaction method, phase-pure YFeO3 ceramics are fabricated using spark plasma sintering (SPS) at different temperatures. X-ray diffraction (XRD) and scanning electron microscopy (SEM) reveal that the high-purity YFeO3 ceramics can be prepared using SPS, while the results from X-ray photoelectron spectroscopy (XPS) show that the concentration of oxygen vacancies resulting from transformation from Fe3+ to Fe2+ is low. The relative density of the 1000 °C-sintered sample is as high as 97.7%, which is much higher than those of the samples sintered at other temperatures. The present dielectric and magnetic properties are much better than those of the samples fabricated by conventional methods. These findings indicate that the YFeO3 ceramics prepared by the low temperature solid reaction and SPS methods possess excellent dielectric and magnetic properties, making them suitable for potential applications involving magnetic storage. PMID:28772626

The Microstructure and Physical Properties of Incinerated Paper-Cullet-Clay Ceramics

NASA Astrophysics Data System (ADS)

Sahar, M. R.; Hamzah, K.; Rohani, M. S.; Samah, K. A.; Razi, M. M.

A series of ceramic based on (x) incinerated recycle paper - (80-x) cullet - 20 Kaolin clay (where 10×45 wt%) has successfully been made by slip casting technique followed by sintering at 1000 °C. The actual composition of ceramic is analyzed using Energy Dispersive of X-Ray (EDAX) while the phase existence is determined using X-Ray Diffraction (XRD) technique. Their microstructural morphology is observed under Scanning Electron Microscope (SEM) and the physical properties are measured in term of their thermal shrinkage and hardness. It is found that the ceramic contain mostly of Silica and the phase is dominated by the existence of Quartz (SiO2), Wollastonite (CaSiO3) and Anorthite (Ca(Al2SiO8)). The SEM micrograph shows that the morphology is dominated by the existence of granular structure, and then become smoother as the cullet level is further increased. It is also found out that the thermal shrinkage is in the range 18% - 6.5% while the hardness is in the range of 152MPa- 1.463 GPa depending on composition.

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.

Spectroscopic properties of Nd3+ doped transparent oxyfluoride glass ceramics.

PubMed

Yu, Yunlong; Chen, Daqin; Ma, En; Wang, Yuansheng; Hu, Zhongjian

2007-07-01

In this paper, the spectroscopic properties of Nd(3+) doped transparent oxyfluoride glass ceramics containing LaF(3) nano-crystals were systematically studied. The formation and distribution of LaF(3) nano-crystals in the glass matrix were investigated by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Based on Judd-Ofelt theory, the intensity parameters Omega(t) (t=2, 4, 6), spontaneous emission probability, radiative lifetime, radiative quantum efficiency, width of the emission line and stimulated emission cross-section of Nd(3+) were evaluated. Particularly, the effect of Nd(3+) doping level on them was discussed. With the increase of Nd(3+) concentration in the glass ceramic, the experimental luminescence lifetime, radiative quantum efficiency and stimulated emission cross-section vary from 353.4 micros, 78.3% and 1.86 x 10(-20)cm(2) to 214.7 micros, 39.9% and 1.52 x 10(-20)cm(2), respectively. The comparative study of Nd(3+) spectroscopic parameters in different hosts suggests that the investigated glass ceramic system is potentially applicable as laser materials for 1.06 microm emission.

Synthesis and electrical properties of (LiCo 3/5Fe 1/5Mn 1/5)VO 4 ceramics

NASA Astrophysics Data System (ADS)

Ram, Moti

2010-03-01

(LiCo 3/5Fe 1/5Mn 1/5)VO 4 ceramic was synthesized via solution-based chemical method. X-ray diffraction analysis was carried out on the synthesized powder sample at room temperature, which confirms the orthorhombic structure with the lattice parameters of a = 10.3646 (20) Å, b = 3.7926 (20) Å, c = 9.2131 (20) Å. Field emission scanning electron microscopic analysis was carried out on the sintered pellet sample that indicates grains of unequal sizes (˜0.1 to 2 μm) presents average grains size with polydisperse distribution on the surface of the ceramic. Complex impedance spectroscopy (CIS) technique is used for the study of electrical properties. CIS analysis identifies: (i) grain interior, grain boundary and electrode-material interface contributions to electrical response (ii) the presence of temperature dependent electrical relaxation phenomena in the ceramics. Detailed conductivity study indicates that electrical conduction in the material is a thermally activated process. The variation of A.C. conductivity with frequency at different temperatures obeys Jonscher's universal law.

Joining Dental Ceramic Layers With Glass

PubMed Central

Saied, MA; Lloyd, IK; Haller, WK; Lawn, BR

2011-01-01

Objective Test the hypothesis that glass-bonding of free-form veneer and core ceramic layers can produce robust interfaces, chemically durable and aesthetic in appearance and, above all, resistant to delamination. Methods Layers of independently produced porcelains (NobelRondo™ Press porcelain, Nobel BioCare AB and Sagkura Interaction porcelain, Elephant Dental) and matching alumina or zirconia core ceramics (Procera alumina, Nobel BioCare AB, BioZyram yttria stabilized tetragonal zirconia polycrystal, Cyrtina Dental) were joined with designed glasses, tailored to match thermal expansion coefficients of the components and free of toxic elements. Scanning electron microprobe analysis was used to characterize the chemistry of the joined interfaces, specifically to confirm interdiffusion of ions. Vickers indentations were used to drive controlled corner cracks into the glass interlayers to evaluate the toughness of the interfaces. Results The glass-bonded interfaces were found to have robust integrity relative to interfaces fused without glass, or those fused with a resin-based adhesive. Significance The structural integrity of the interfaces between porcelain veneers and alumina or zirconia cores is a critical factor in the longevity of all-ceramic dental crowns and fixed dental prostheses. PMID:21802131

Colossal permittivity and the polarization mechanism of (Mg, Mn) co-doped LaGaO3 ceramics

NASA Astrophysics Data System (ADS)

Luo, Tingting; Liu, Zhifu; Zhang, Faqiang; Li, Yongxiang

2018-03-01

Mg and Mn co-doped LaGa0.7-xMgxMn0.3O3 (x = 0, 0.05, 0.10, 0.15) ceramics were prepared by a solid-state reaction method. The electrical properties of the LaGa0.7-xMgxMn0.3O3 ceramics were studied in detail by dielectric spectra, impedance spectra, and I-V characteristic analysis. Colossal permittivity up to 104 could be obtained across the frequency range up to 104 Hz. The impedance analysis of the co-doped LaGaO3 ceramics indicated that the Mott's variable range hopping (VRH) polarization should be the main origin of colossal permittivity. Mg and Mn co-doping suppressed the formation of Mn3+ and enhanced the VRH polarization, resulting in increased permittivity. Partial localization of electrons by Mg reduced the long-range electron hopping and led to the decrease in dielectric loss.

Defect Complex Effect in Nb Doped TiO2 Ceramics with Colossal Permittivity

NASA Astrophysics Data System (ADS)

Li, Fuchao; Shang, Baoqiang; Liang, Pengfei; Wei, Lingling; Yang, Zupei

2016-10-01

Donor-doped Nb x Ti1- x O2 ( x = 1%, 2%, 4%, 6%, and 8%) ceramics with giant permittivity (>104) and a very low dielectric loss (˜0.05) were sintered under flowing N2 at 1400°C for 10 h. By increasing Nb doping concentration, two different dielectric responses were evidenced in the frequency dependence of dielectric properties of Nb doped TiO2 ceramics, which corresponded to the space charge polarization and the electron-pinned defect-dipoles effect, respectively. Especially, combined with the x-ray photoelectron spectroscopy results, the electron-pinned defect-dipoles induced by the 2({Nb}^{5 + } )_{{Ti}}^{ bullet } to 4({Ti}^{3 + } )^'_{{Ti}} leftarrow {V}_{{o}}^{ bullet bullet } defect complex were further confirmed to give rise to both their high ɛr and low tan δ in the high frequency range for the Nb x Ti1- x O2 ceramics with x > 4%.

Joining of Silicon Carbide Through the Diffusion Bonding Approach

NASA Technical Reports Server (NTRS)

Halbig, Michael .; Singh, Mrityunjay

2009-01-01

In order for ceramics to be fully utilized as components for high-temperature and structural applications, joining and integration methods are needed. Such methods will allow for the fabrication the complex shapes and also allow for insertion of the ceramic component into a system that may have different adjacent materials. Monolithic silicon carbide (SiC) is a ceramic material of focus due to its high temperature strength and stability. Titanium foils were used as an interlayer to form diffusion bonds between chemical vapor deposited (CVD) SiC ceramics with the aid of hot pressing. The influence of such variables as interlayer thickness and processing time were investigated to see which conditions contributed to bonds that were well adhered and crack free. Optical microscopy, scanning electron microscopy, and electron microprobe analysis were used to characterize the bonds and to identify the reaction formed phases.

Preparation and Characterization of Niobium Doped Lead-Telluride Glass Ceramics

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

Sathish, M.; Eraiah, B.; Anavekar, R. V.

2011-07-15

Niobium-lead-telluride glass ceramics of composition xNb{sub 2}O{sub 5}-(20-x) pbO-80TeO{sub 2}(where x = 0.1 mol% to 0.5 mol%) were prepared by using conventional melt quenching method. The prepared glass samples were initially amorphous in nature after annealed at 400 deg. c all samples were crystallized. This was confined by X-ray diffraction and scanning electron microscopy. The particle size of these glass ceramics have been calculated by using Debye-Scherer formula and the particle size is in the order of 15 nm to 60 nm. The scanning electron microscopy (SEM) photograph shows the presence of needle-like crystals in these samples.

Evaluation of surface roughness and polishing techniques for new ceramic materials.

PubMed

Campbell, S D

1989-05-01

The surface roughness of crown and bridge materials should be minimized to obtain optimal biocompatability. This study used scanning electron microscopy to evaluate the effect of polishing procedures on two all-ceramic crown materials (Dicor and Cerestore). The "as formed," unpolished specimens of both Dicor and Cerestore materials presented a rough surface. It was found that any attempt to polish the Cerestore coping material resulted in an extremely rough surface. Finishing of the Dicor ceramic resulted in a smoother but pitted surface. Polishing of both ceramic materials resulted in a surface that was rougher than the glazed metal ceramic controls. The smoothest finish was obtained when the glazed veneer (Cerestore) and shading porcelain (Dicor) were applied to the all-ceramic materials.

A new generation of high temperature oxygen sensors

NASA Astrophysics Data System (ADS)

Spirig, John V.

Potentiometric internal reference oxygen sensors were created by embedding a metal/metal oxide mixture within an yttria-stabilized zirconia oxygen-conducting ceramic superstructure. A static internal reference oxygen pressure was produced inside the reference chamber of the sensor at the target application temperature. The metal/metal oxide-containing reference chamber was sealed within the stabilized zirconia ceramic superstructure by a high pressure (3-6 MPa) and high temperature (1200-1300°C) bonding method that initiated grain boundary sliding between the ceramic components. The bonding method created ceramic joints that were pore-free and indistinguishable from the bulk ceramic. The oxygen sensor presented in this study is capable of long-term operation and is resistant to the strains of thermal cycling. The temperature ceiling of this device was limited to 800°C by the glass used to seal the sensor package where the lead wire breached the inner-to-outer environment. Were it possible to create a gas-tight joint between an electron carrier and stabilized zirconia, additional sealing agents would not be necessary during sensor construction. In order to enable this enhancement it is necessary to make a gas-tight joint between two dissimilar materials: a ceramic electrolyte and an efficient ceramic electron carrier. Aluminum-doped lanthanum strontium manganese oxide, La0.77Sr 0.20Al0.9Mn0.1O3, was joined to stabilized tetragonal zirconia polymorph YTZP (ZrO2)0.97(Y 2O3)0.03 by a uniaxial stress (3-6 MPa) and high-temperature (1250-1350°C) bonding method that initiated grain-boundary sliding between the ceramic components. An analysis of reactivity between different Al-dopings of LaxSr1-xAlyMn1-yO3 indicated that the Al:Mn ratio must be high to diminish the reaction between LaxSr1-xAlyMn1-yO3 and stabilized zirconia. While the resulting compound, La0.77Sr 0.20Al0.9Mn0.1O3, was an inefficient electron carrier, the successful bond between an aluminum-doped manganate perovskite and stabilized zirconia, served as a model system for joining electron carriers to an electrolyte without the creation of undesirable interlayers. Electron microscopy confirmed that intergranular penetration occurred at the joining plane leading to effective bonding between the two dissimilar ceramics. Raman spectral maps of the joining planes obtained with 2-D Raman microscopy demonstrated the absence of any new phases at the interface. A conducting perovskite with a lower Al:Mn ratio, but compensating A-site deficiency, La0.69Sr0.18Al0.45Mn0.55 O3, was joined to YTZP at 1250°C. X-ray diffraction was used to gain structural information on this A-site deficient perovskite. Room temperature resistivity measurements of the electroceramics were performed on joined and unjoined samples to determine the extent to which joining altered electron conduction within the LSAM. Electron microscopy confirmed that intergranular penetration occurred at the joining plane leading to effective bonding between the two dissimilar ceramics. Raman spectral maps of the joined samples demonstrated that joining temperature determines the extent to which interlayers begin to form in the joining plane. X-ray microdiffraction of the joining planes confirmed a threshold temperature for operation of a device created from these materials at 1350°C. A new material with diminished reactivity and high conductivity is presented to serve as a replacement for metal electrodes. In this manner, the model for a new generation of high-temperature oxygen sensors with internal references and ceramic wires is elucidated.

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.

Scanning electron microscope comparative surface evaluation of glazed-lithium disilicate ceramics under different irradiation settings of Nd:YAG and Er:YAG lasers.

PubMed

Viskic, Josko; Jokic, Drazen; Jakovljevic, Suzana; Bergman, Lana; Ortolan, Sladana Milardovic; Mestrovic, Senka; Mehulic, Ketij

2018-01-01

To evaluate the surface of glazed lithium disilicate dental ceramics after irradiation under different irradiation settings of Nd:YAG and Er:YAG lasers using a scanning electron microscope (SEM). Three glazed-press lithium disilicate ceramic discs were treated with HF, Er:YAG, and Nd:YAG, respectively. The laser-setting variables tested were laser mode, repetition rate (Hz), power (W), time of exposure (seconds), and laser energy (mJ). Sixteen different variable settings were tested for each laser type, and all the samples were analyzed by SEM at 500× and 1000× magnification. Surface analysis of the HF-treated sample showed a typical surface texture with a homogenously rough pattern and exposed ceramic crystals. Er:YAG showed no effect on the surface under any irradiation setting. The surface of Nd:YAG-irradiated samples showed cracking, melting, and resolidifying of the ceramic glaze. These changes became more pronounced as the power increased. At the highest power setting (2.25 W), craters on the surface with large areas of melted or resolidified glaze surrounded by globules were visible. However, there was little to no exposure of ceramic crystals or visible regular surface roughening. Neither Er:YAG nor Nd:YAG dental lasers exhibited adequate surface modification for bonding of orthodontic brackets on glazed lithium disilicate ceramics compared with the control treated with 9.5% HF.

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

Ivanov, Yuri, E-mail: yufi55@mail.ru; National Research Tomsk State University, 36 Lenina Str., Tomsk, 634050; National Research Tomsk Polytechnic University, 30 Lenina Str., Tomsk, 634050

The present work is devoted to numerical simulation of temperature fields and the analysis of structural and strength properties of the samples surface layer of boron carbide ceramics treated by the high-current pulsed electron-beam of the submillisecond duration. The samples made of sintered boron carbide ceramics are used in these investigations. The problem of calculating the temperature field is reduced to solving the thermal conductivity equation. The electron beam density ranges between 8…30 J/cm{sup 2}, while the pulse durations are 100…200 μs in numerical modelling. The results of modelling the temperature field allowed ascertaining the threshold parameters of the electronmore » beam, such as energy density and pulse duration. The electron beam irradiation is accompanied by the structural modification of the surface layer of boron carbide ceramics either in the single-phase (liquid or solid) or two-phase (solid-liquid) states. The sample surface of boron carbide ceramics is treated under the two-phase state (solid-liquid) conditions of the structural modification. The surface layer is modified by the high-current pulsed electron-beam produced by SOLO installation at the Institute of High Current Electronics of the Siberian Branch of the Russian Academy of Sciences, Tomsk, Russia. The elemental composition and the defect structure of the modified surface layer are analyzed by the optical instrument, scanning electron and transmission electron microscopes. Mechanical properties of the modified layer are determined measuring its hardness and crack resistance. Research results show that the melting and subsequent rapid solidification of the surface layer lead to such phenomena as fragmentation due to a crack network, grain size reduction, formation of the sub-grained structure due to mechanical twinning, and increase of hardness and crack resistance.« less

Microstructure, tribological and strength properties of the surface layer in metal-ceramic composite nano-structured by electron irradiation

NASA Astrophysics Data System (ADS)

Ovcharenko, V. E.; Ivanov, K. V.; Mokhovikov, A. A.

2017-12-01

Exemplified by metal-ceramic composite TiC-(Ni-Cr) with the ratio of components 50:50, the paper presents findings of the study on patterns of nanoscale structural-phase state formation in the surface layer of the composite under pulsed electron irradiation in inert gas plasmas with different ionization energies and atomic weights and their influence on tribological and strength properties of the surface layer.

Fabrication of porous hierarchical polymer/ceramic composites by electron irradiation of organic/inorganic polymers: route to a highly durable, large-area superhydrophobic coating.

PubMed

Lee, Eun Je; Kim, Jae Joon; Cho, Sung Oh

2010-03-02

Polymer/ceramic composite films with micro- and nanocombined hierarchical structures are fabricated by electron irradiation of poly(methyl methacrylate) (PMMA) microspheres/silicone grease. Electron irradiation induces volume contraction of PMMA microspheres and simultaneously transforms silicone grease into a ceramic material of silicon oxycarbide with many nanobumps. As a result, highly porous structures that consist of micrometer-sized pores and microparticles decorated with nanobumps are created. The fabricated films with the porous hierarchical structure exhibit good superhydrophobicity with excellent self-cleaning and antiadhesion properties after surface treatment with fluorosilane. In addition, the porous hierarchical structures are covered with silicon oxycarbide, and thus the superhydrophobic coatings have high hardness and strong adhesion to the substrate. The presented technique provides a straightforward route to producing large-area, mechanically robust superhydrophobic films on various substrate materials.

[Analysis and prevention of dust pollution caused by 5 common prosthetic materials].

PubMed

Yang, Xiang-Wen; Wei, Bin; Zhu, Cao-Yun; Qian, Liang; Li, Yi-Han

2017-10-01

To analyze and evaluate dust pollution in prosthodontic clinic and make proposal for reasonable protection. This study analyzed the particle size, element composition and dust concentration of 5 materials which were commonly used in dental restorations (veneering ceramics, cobalt-chromium alloy, photosensitive plastic, hard base resin, advanced artificial teeth) by using scanning electron microscopy (SEM), X-ray energy dispersive spectrometer（EDS） and dust concentration laser tester, in order to assess the effects of prosthodontic dust posed on medical staff health and put forward reasonable suggestions for prevention and control of dust pollution. The particle size of veneering ceramics, cobalt-chromium alloy, photosensitive plastic, hard base resin and advanced artificial teeth was (2.15±3.00), (33.78±24.33), (7.78±11.86), (31.16±44.35) and (28.45±39.21)μm, respectively. The time weighted average respirable dust concentration of veneering ceramics was 0.393 mg/m 2 which was beyond the scope of national security. Dust pollution is serious in prosthodontic clinic to which we should pay more attention and take appropriate prevention measures.

All ceramic structure for molten carbonate fuel cell

DOEpatents

Smith, James L.; Kucera, Eugenia H.

1992-01-01

An all-ceramic molten carbonate fuel cell having a composition formed of a multivalent metal oxide or oxygenate such as an alkali metal, transition metal oxygenate. The structure includes an anode and cathode separated by an electronically conductive interconnect. The electrodes and interconnect are compositions ceramic materials. Various combinations of ceramic compositions for the anode, cathode and interconnect are disclosed. The fuel cell exhibits stability in the fuel gas and oxidizing environments. It presents reduced sealing and expansion problems in fabrication and has improved long-term corrosion resistance.

[Biological activity evaluation of porous HA ceramics using NH4 HCO3/PVA as pore-creating agents].

PubMed

Wang, Songquan; Zhang, Dekun

2010-12-01

Porous HA ceramics were prepared by using NH4 HCO3/PVA as pore-formed material along with biological glass as intensifier, and these ceramics were immersed in Locke's Physiological Saline and Simulate Body Fluid (SBF). The changes of phase composition, grain size and crystallinity of porous HA ceramics before and after immersion were investigated by X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). The biological activity was evaluated. The porous HA ceramics showed various degrees of decomposition after immersion in the two solution systems, but there was no evident change in respect to crystallinity. Besides, the impact of different degrees of solution systems on the change of grain size and planar preferred orientation was observed. The TCP phase of the ceramics immersed in Locke's Physiological Saline decomposed and there was no crystal growth on the surface of ceramics; however, the grain size of ceramics immersed in SBF became refined in certain degree and the surface of ceramics took on the new crystal growth.

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.

A Novel Technique for the Connection of Ceramic and Titanium Implant Components Using Glass Solder Bonding

PubMed Central

Mick, Enrico; Tinschert, Joachim; Mitrovic, Aurica; Bader, Rainer

2015-01-01

Both titanium and ceramic materials provide specific advantages in dental implant technology. However, some problems, like hypersensitivity reactions, corrosion and mechanical failure, have been reported. Therefore, the combining of both materials to take advantage of their pros, while eliminating their respective cons, would be desirable. Hence, we introduced a new technique to bond titanium and ceramic materials by means of a silica-based glass ceramic solder. Cylindrical compound samples (Ø10 mm × 56 mm) made of alumina toughened zirconia (ATZ), as well as titanium grade 5, were bonded by glass solder on their end faces. As a control, a two-component adhesive glue was utilized. The samples were investigated without further treatment, after 30 and 90 days of storage in distilled water at room temperature, and after aging. All samples were subjected to quasi-static four-point-bending tests. We found that the glass solder bonding provided significantly higher bending strength than adhesive glue bonding. In contrast to the glued samples, the bending strength of the soldered samples remained unaltered by the storage and aging treatments. Scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) analyses confirmed the presence of a stable solder-ceramic interface. Therefore, the glass solder technique represents a promising method for optimizing dental and orthopedic implant bondings. PMID:28793440

Corrosion Behavior of Ceramic Cup of Blast Furnace Hearth by Liquid Iron and Slag

NASA Astrophysics Data System (ADS)

Li, Yanglong; Cheng, Shusen; Wang, Zhifeng

2016-10-01

Three kinds of sample bricks of ceramic cups for blast furnace hearth were studied by dynamic corrosion tests based on different corrosion systems, i.e., liquid iron system, liquid slag system and liquid iron-slag system. Considering the influence of temperature and sample rotational speed, the corrosion profiles and mass loss of the samples were analyzed. In addition, the microstructure of the corroded samples was observed by optical microscope (OM) and scanning electron microscope (SEM). It was found that the corrosion profiles could be divided into iron corrosion region, slag corrosion region and iron-slag corrosion region via corrosion degree after iron-slag corrosion experiment. The most serious corrosion occurred in iron-slag corrosion region. This is due to Marangoni effect, which promotes a slag film formed between liquid iron and ceramic cup and results in local corrosion. The corrosion of the samples deepened with increasing temperature of liquid iron and slag from 1,623 K to 1,823 K. The variation of slag composition had greater influence on the erosion degree than that of rotational speed in this experiment. Taking these results into account the ceramic cup composition should be close to slag composition to decrease the chemical reaction. A microporous and strong material should be applied for ceramic cup.

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

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.

Influence of fluoride additions on biological and mechanical properties of Na2O-CaO-SiO2-P2O5 glass-ceramics.

PubMed

Li, H C; Wang, D G; Hu, J H; Chen, C Z

2014-02-01

Two series of Na2O-CaO-SiO2-P2O5 glass-ceramics doped with NH4HF2 (G-NH4HF2) or CaF2 (G-CaF2) have been prepared by sol-gel method. The glass-ceramic phase composition and morphology were characterized by X-ray diffraction (XRD) and scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS). The mechanical properties and thermal expansion coefficient were measured by a microhardness tester, an electronic tensile machine and a thermal expansion coefficient tester. The structure difference between these two glass-ceramics was investigated by Fourier transform infrared spectroscopy (FTIR), and the in vitro bioactivity of the glass-ceramics was determined by in vitro simulated body fluid (SBF) immersion test. The hemolysis test, in vitro cytotoxicity test, systemic toxicity test and the implanted experiment in animals were used to evaluate the biocompatibility of the glass-ceramics. The mechanical properties of sample G-NH4HF2 are lower than that of sample G-CaF2, and the bioactivity of sample G-NH4HF2 is better than that of sample G-CaF2. The thermal expansion coefficients of these two glass-ceramics are all closer to that of Ti6Al4V. After 7 days of SBF immersion, apatites were induced on glass-ceramic surface, indicating that the glass-ceramics have bioactivity. The hemolysis test, in vitro cytotoxicity test and systemic toxicity test demonstrate that the glass-ceramics do not cause hemolysis reaction, and have no toxicity to cell and living animal. The implanted experiment in animals shows that bone tissue can form a good osseointegration with the implant after implantation for two months, indicating that the glass-ceramics are safe to serve as implants. Copyright © 2013 Elsevier B.V. All rights reserved.

Giant dielectric response and low dielectric loss in Al{sub 2}O{sub 3} grafted CaCu{sub 3}Ti{sub 4}O{sub 12} ceramics

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

Rajabtabar-Darvishi, A.; Center for Surface and Nanoanalytics; Bayati, R., E-mail: reza.bayati@intel.com, E-mail: mbayati@ncsu.edu, E-mail: wdfei@hit.edu.cn

2015-03-07

This study sheds light on the effect of alumina on dielectric constant and dielectric loss of novel CaCu{sub 3}Ti{sub 4}O{sub 12} composite ceramics. Alumina, at several concentrations, was deposited on the surface of CaCu{sub 3}Ti{sub 4}O{sub 12} particles via sol-gel technique. The dielectric constant significantly increased for all frequencies and the dielectric loss substantially decreased for low and intermediate frequencies. These observations were attributed to the change in characteristics of grains and grain boundaries. It was found that the insulating properties of the grain boundaries are improved following the addition of Al{sub 2}O{sub 3}. The relative density of CaCu{sub 3}Ti{submore » 4}O{sub 12}/Al{sub 2}O{sub 3} composite ceramics decreased compared to the pure CaCu{sub 3}Ti{sub 4}O{sub 12} and the grain size was greatly changed with the alumina content affecting the dielectric properties. With the addition of alumina into CaCu{sub 3}Ti{sub 4}O{sub 12}, tighter interfaces formed. The 6%- and 10%-alumina ceramics showed the minimum dielectric loss and the maximum dielectric constant, respectively. Both the dielectric constant and loss tangent decreased in the 20%-alumina ceramic due to the formation of CuO secondary phase. It was revealed that Al serves as an electron acceptor decreasing the electron concentration, if Al{sup 3+} ions substitute for Ti{sup 4+} ions, and as an electron donor increasing the electron concentration, if Al{sup 3+} ions substitute for Ca{sup 2+} ions. We established a processing-microstructure-properties paradigm which opens new avenues for novel applications of CaCu{sub 3}Ti{sub 4}O{sub 12}/Al{sub 2}O{sub 3} composite ceramics.« less

Soviet Developments in High Temperature Ceramics No. 1, January-December 1975

DTIC Science & Technology

1976-02-25

in microstructure and granulometric composition of silicon nitride in the process of hot pressing were studied by optical and electron micrographic...and on the laboratory-made a-alumina specimens^have shown that densely- sintered ceramics can be produced by a simplified process using a- Al -O...dusting of the powdered ceramic materials, spinel slurry deposition and subsequent fusion by a plasma jet traveling along the coated surface at

Advanced Lithium Anodes for Li/Air and Li/Water Batteries

DTIC Science & Technology

2005-10-05

µm thick protective glass- ceramic membrane . The value of Li discharged capacity in this experiment is significantly larger than the Li thickness...polarization solid-state cell used for determination of electronic current across glass- ceramic membrane Final Report Page 27 of 45 10/05/2005...Li anode/aqueous electrolyte interface without destruction of the 50 µm thick protective glass- ceramic membrane . The thickness of the Li foil used in

Phase Equilibria and Crystallography of Ceramic Oxides

PubMed Central

Wong-Ng, W.; Roth, R. S.; Vanderah, T. A.; McMurdie, H. F.

2001-01-01

Research in phase equilibria and crystallography has been a tradition in the Ceramics Division at National Bureau of Standards/National Institute of Standatrds and Technology (NBS/NIST) since the early thirties. In the early years, effort was concentrated in areas of Portland cement, ceramic glazes and glasses, instrument bearings, and battery materials. In the past 40 years, a large portion of the work was related to electronic materials, including ferroelectrics, piezoelectrics, ionic conductors, dielectrics, microwave dielectrics, and high-temperature superconductors. As a result of the phase equilibria studies, many new compounds have been discovered. Some of these discoveries have had a significant impact on US industry. Structure determinations of these new phases have often been carried out as a joint effort among NBS/NIST colleagues and also with outside collaborators using both single crystal and neutron and x-ray powder diffraction techniques. All phase equilibria diagrams were included in Phase Diagrams for Ceramists, which are collaborative publications between The American Ceramic Society (ACerS) and NBS/NIST. All x-ray powder diffraction patterns have been included in the Powder Diffraction File (PDF). This article gives a brief account of the history of the development of the phase equilibria and crystallographic research on ceramic oxides in the Ceramics Division. Represented systems, particularly electronic materials, are highlighted. PMID:27500068

Comparative analysis of electrophysical properties of ceramic tantalum pentoxide coatings, deposited by electron beam evaporation and magnetron sputtering methods

NASA Astrophysics Data System (ADS)

Donkov, N.; Mateev, E.; Safonov, V.; Zykova, A.; Yakovin, S.; Kolesnikov, D.; Sudzhanskaya, I.; Goncharov, I.; Georgieva, V.

2014-12-01

Ta2O5 ceramic coatings have been deposited on glass substrates by e-beam evaporation and magnetron sputtering methods. For the magnetron sputtering process Ta target was used. X-ray diffraction measurements show that these coatings are amorphous. XPS survey spectra of the ceramic Ta2O5 coatings were obtained. All spectra consist of well-defined XPS lines of Ta 4f, 4d, 4p and 4s; O 1s; C 1s. Ta 4f doublets are typical for Ta2O5 coatings with two main peaks. Scanning electron microscopy and atomic force microscopy images of the e-beam evaporated and magnetron sputtered Ta2O5 ceramic coatings have revealed a relatively flat surface with no cracks. The dielectric properties of the tantalum pentoxide coatings have been investigated in the frequency range of 100 Hz to 1 MHz. The electrical behaviour of e-beam evaporated and magnetron sputtered Ta2O5 ceramic coatings have also been compared. The deposition process conditions principally effect the structure parameters and electrical properties of Ta2O5 ceramic coatings. The coatings deposited by different methods demonstrate the range of dielectric parameters due to the structural and stoichiometric composition changes

Multifunctional Ceramic Nanostructured Coatings

DTIC Science & Technology

2010-12-01

silicon carbide composites // J. Europ. Cer. Soc. − 2004. − Vol. 24. − P. 2169−2179. 22. Yu. P. Udalov, E. E. Valova, S. S. Ordanian. Fabrication and...by the titanium and tungsten borides and carbides . The analysis was done using the X-ray and electron-optical methods. This information expands our...coating compositions should be based on limited solubility materials. Such systems include carbides , nitrides, borides and silicides based on

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.

Bond strength of selected composite resin-cements to zirconium-oxide ceramic

PubMed Central

Fons-Font, Antonio; Amigó-Borrás, Vicente; Granell-Ruiz, María; Busquets-Mataix, David; Panadero, Rubén A.; Solá-Ruiz, Maria F.

2013-01-01

Objectives: The aim of this study was to evaluate bond strengths of zirconium-oxide (zirconia) ceramic and a selection of different composite resin cements. Study Design: 130 Lava TM cylinders were fabricated. The cylinders were sandblasted with 80 µm aluminium oxide or silica coated with CoJet Sand. Silane, and bonding agent and/or Clearfil Ceramic Primer were applied. One hundred thirty composite cement cylinders, comprising two dual-polymerizing (Variolink II and Panavia F) and two autopolymerizing (Rely X and Multilink) resins were bonded to the ceramic samples. A shear test was conducted, followed by an optical microscopy study to identify the location and type of failure, an electron microscopy study (SEM and TEM) and statistical analysis using the Kruskal-Wallis test for more than two independent samples and Mann-Whitney for two independent samples. Given the large number of combinations, Bonferroni correction was applied (α=0.001). Results: Dual-polymerizing cements provided better adhesion values (11.7 MPa) than the autopolymerizing (7.47 MPa) (p-value M-W<0.001). The worst techniques were Lava TM + sandblasting + Silane + Rely X; Lava TM + sandblasting + Silane + Multilink and Lava TM + CoJet + silane + Multilink. Adhesive failure (separation of cement and ceramic) was produced at a lesser force than cohesive failure (fracture of cement) (p-value M-W<0.001). Electron microscopy confirmed that the surface treatments modified the zirconium-oxide ceramic, creating a more rough and retentive surface, thus providing an improved micromechanical interlocking between the cement and the ceramic. Key words:Shear bond strength, silica coating, surface treatment, zirconia ceramics, phosphate monomer. PMID:22926485

Frequency domain kinetic of positron-electron annihilation in the MgO-Al2O3 spinel-type ceramics

NASA Astrophysics Data System (ADS)

Fl'unt, Orest; Klym, Halyna; Ingram, Adam

2018-03-01

In this work, the kinetic of positron-electron annihilation in the MgO-Al2O3 spinel-type ceramics sintered at different temperatures (1100, 1200 and 1400 °C) has been calculated and analyzed in a frequency domain. The spectra of real (in-phase) and imaginary (quadrature) components of positron-electron annihilation kinetic have been obtained numerically from usual temporal characteristics using integral Fourier transform. The numerical calculations were carried out using cubic spline interpolation of the pulse characteristics of MgO-Al2O3 ceramics in time domain with following analytical calculations of integrals. The obtained spectra as real so imaginary part of MgO-Al2O3 ceramics in frequency domain almost good obey a Debye law denying correlation between elementary positron annihilation processes. Complex diagrams of frequency domain responses of as-prepared samples have a shape of semicircles with close characteristic frequencies. Some deviation on low-frequency side of the semicircles is observed confirming an availability of longer time kinetic processes. Sintering temperature dependencies of the relaxation times and characteristic frequencies of positron-electron annihilation processes have been obtained. It is shown that position of large maxima on the frequency dependencies of imaginary part corresponds to fast average relaxation lifetime representing the most intensive interaction process of positrons with small cavity traps in solids.

Surfaces and interfaces of glass and ceramics; Proceedings of the International Symposium on Special Topics in Ceramics, Alfred University, Alfred, N.Y., August 27-29, 1973

NASA Technical Reports Server (NTRS)

Frechette, V. D. (Editor); Lacourse, W. C.; Burdick, V. L.

1974-01-01

The characterization of surfaces and interfaces is considered along with the infrared spectra of several N-containing compounds absorbed on montmorillonites, applications of surface characterization techniques to glasses, the observation of electronic spectra in glass and ceramic surfaces, a method for determining the preferred orientation of crystallites normal to a surface, and the friction and wear behavior of glasses and ceramics. Attention is given to the wear behavior of cast surface composites, an experimental investigation of the dynamic and thermal characteristics of the ceramic stock removal process, a dynamic elastic model of ceramic stock removal, and the structure and properties of solid surfaces. Individual items are announced in this issue.

Room-temperature ductile inorganic semiconductor.

PubMed

Shi, Xun; Chen, Hongyi; Hao, Feng; Liu, Ruiheng; Wang, Tuo; Qiu, Pengfei; Burkhardt, Ulrich; Grin, Yuri; Chen, Lidong

2018-05-01

Ductility is common in metals and metal-based alloys, but is rarely observed in inorganic semiconductors and ceramic insulators. In particular, room-temperature ductile inorganic semiconductors were not known until now. Here, we report an inorganic α-Ag 2 S semiconductor that exhibits extraordinary metal-like ductility with high plastic deformation strains at room temperature. Analysis of the chemical bonding reveals systems of planes with relatively weak atomic interactions in the crystal structure. In combination with irregularly distributed silver-silver and sulfur-silver bonds due to the silver diffusion, they suppress the cleavage of the material, and thus result in unprecedented ductility. This work opens up the possibility of searching for ductile inorganic semiconductors/ceramics for flexible electronic devices.

Technological study of ancient ceramics produced in Casteldurante (central Italy) during the Renaissance

NASA Astrophysics Data System (ADS)

Padeletti, G.; Fermo, P.; Gilardoni, S.; Galli, A.

In order to recover the ancient tradition concerning the materials used for the decoration, majolica shards produced during the Renaissance period in Casteldurante, a famous centre for ceramic production in Italy (Marche), have been examined. In the present study, pigments used for the decorations have been investigated by means of inductively coupled plasma optical emission spectrometry (ICP-OES), scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM-EDX) and diffuse-reflectance UV-Vis spectroscopy. Ochre, lead antimonate yellow, copper-based pigment and smalt have been used as colourants to obtain respectively yellow-orange, yellow, green and blue decorations in accordance with what is reported by the ancient recipes.

Room-temperature ductile inorganic semiconductor

NASA Astrophysics Data System (ADS)

Shi, Xun; Chen, Hongyi; Hao, Feng; Liu, Ruiheng; Wang, Tuo; Qiu, Pengfei; Burkhardt, Ulrich; Grin, Yuri; Chen, Lidong

2018-05-01

Ductility is common in metals and metal-based alloys, but is rarely observed in inorganic semiconductors and ceramic insulators. In particular, room-temperature ductile inorganic semiconductors were not known until now. Here, we report an inorganic α-Ag2S semiconductor that exhibits extraordinary metal-like ductility with high plastic deformation strains at room temperature. Analysis of the chemical bonding reveals systems of planes with relatively weak atomic interactions in the crystal structure. In combination with irregularly distributed silver-silver and sulfur-silver bonds due to the silver diffusion, they suppress the cleavage of the material, and thus result in unprecedented ductility. This work opens up the possibility of searching for ductile inorganic semiconductors/ceramics for flexible electronic devices.

Tropical sea snail shells: Possible exotic sources for ceramic biomaterial synthesis

NASA Astrophysics Data System (ADS)

Oktar, F. N.; Kiyici, I. A.; Gökçe, H.; Aǧaogulları, D.; Kayali, E. S.

2013-12-01

In this study, chemical and structural properties of sea snail shell based bioceramic materials (i.e. hydroxyapatite, whitlockite and other phases) are produced by using mechano-chemical (ultrasonic) conversion method. For this purpose, differential thermal and gravimetric analysis (DTA/TG), X-ray diffraction, infra-red (IR) and scanning electron microscope (SEM) studies are performed.

Microstructure of Transparent Strontium Fresnoite Glass-Ceramics

PubMed Central

Wisniewski, Wolfgang; Takano, Kazuya; Takahashi, Yoshihiro; Fujiwara, Takumi; Rüssel, Christian

2015-01-01

Glass-ceramics grown from a glass of the composition Sr2TiSi2.45O8.9 (STS 45) are analyzed by scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD). Oriented nucleation with the c-axes preferably perpendicular to the surface is detected. A very strong 001-texture is observed after only 10 μm of growth into the bulk, making this the first system in which an orientation preferred during nucleation prevails during growth into the bulk in glass-ceramics. Piezoelectric measurements are performed and d33-values presented and discussed. The obtained results are critically viewed with respect to the two growth models describing Sr2TiSi2O8 growth in glasses. PMID:25780988

New insights on the synthesis and electronic transport in bulk polycrystalline Pr-doped SrTiO3-δ

NASA Astrophysics Data System (ADS)

Dehkordi, Arash Mehdizadeh; Bhattacharya, Sriparna; Darroudi, Taghi; Alshareef, Husam N.; Tritt, Terry M.

2015-02-01

Recently, we have reported a significant enhancement in the electronic and thermoelectric properties of bulk polycrystalline SrTiO3 ceramics via praseodymium doping. This improvement was originated from the simultaneous enhancement in the thermoelectric power factor and reduction in thermal conductivity, which was contributed to the non-uniform distribution of Pr dopants. In order to further understand the underlying mechanism, we herein investigate the role of praseodymium doping source (Pr2O3 versus Pr6O11) on the synthesis and electronic transport in Pr-doped SrTiO3 ceramics. It was observed that the high-temperature electronic transport properties are independent of the choice of praseodymium doping source for samples prepared following our synthesis strategy. Theoretical calculations were also performed in order to estimate the maximum achievable power factor and the corresponding optimal carrier concentration. The result suggests the possibility of further improvement of the power factor. This study should shed some light on the superior electronic transport in bulk polycrystalline Pr-doped SrTiO3 ceramics and provide new insight on further improvement of the thermoelectric power factor.

Effect of various additives on microstructure, mechanical properties, and in vitro bioactivity of sodium oxide-calcium oxide-silica-phosphorus pentoxide glass-ceramics.

PubMed

Li, H C; Wang, D G; Hu, J H; Chen, C Z

2013-09-01

The partial substitution of MgO, TiO2, or CaF2 for CaO in the Na2O-CaO-SiO2-P2O5 (45S5) system was conducted by the sol-gel method and a comparative study on structural, mechanical properties, and bioactivity of the glasses was reported. Based on thermogravimetric and differential thermal analysis, the gels were sintered with a suitable heat treatment procedure. The glass-ceramic properties were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) and so on, and the bioactivity of the glass-ceramic was evaluated by in vitro assays in simulated body fluid (SBF). Results indicate that with the partial substitution of MgO, TiO2, CaF2 for CaO in glass composition, the mechanical properties of the glass-ceramics have been significantly improved. Furthermore, CaF2 promotes glass crystallization and the crystallization does not inhibit the glass-ceramic bioactivity. All samples possess bioactivity; however, the bioactivity of these glass-ceramics is quite different. Compared with 45S5, the introduction of MgO decreases the ability of apatite induction. The addition of TiO2 does not significantly improve the bioactivity, and the replacement of CaO by CaF2 shows a higher bioactivity. Copyright © 2013 Elsevier Inc. All rights reserved.

DEVELOPMENT OF A CERAMIC TAMPER INDICATING SEAL: SRNL CONTRIBUTIONS

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

Krementz, D.; Brinkman, K.; Martinez-Rodriguez, M.

2013-06-03

Savannah River National Laboratory (SRNL) and Sandia National Laboratories (SNL) are collaborating on development of a Ceramic Seal, also sometimes designated the Intrinsically Tamper Indicating Ceramic Seal (ITICS), which is a tamper indicating seal for international safeguards applications. The Ceramic Seal is designed to be a replacement for metal loop seals that are currently used by the IAEA and other safeguards organizations. The Ceramic Seal has numerous features that enhance the security of the seal, including a frangible ceramic body, protective and tamper indicating coatings, an intrinsic unique identifier using Laser Surface Authentication, electronics incorporated into the seal that providemore » cryptographic seal authentication, and user-friendly seal wire capture. A second generation prototype of the seal is currently under development whose seal body is of Low Temperature Co-fired Ceramic (LTCC) construction. SRNL has developed the mechanical design of the seal in an iterative process incorporating comments from the SNL vulnerability review team. SRNL is developing fluorescent tamper indicating coatings, with recent development focusing on optimizing the durability of the coatings and working with a vendor to develop a method to apply coatings on a 3-D surface. SRNL performed a study on the effects of radiation on the electronics of the seal and possible radiation shielding techniques to minimize the effects. SRNL is also investigating implementation of Laser Surface Authentication (LSA) as a means of unique identification of each seal and the effects of the surface coatings on the LSA signature.« less

Monolithic ceramic capacitors for high reliability applications

NASA Technical Reports Server (NTRS)

Thornley, E. B.

1981-01-01

Monolithic multi-layer ceramic dielectric capacitors are widely used in high reliability applications in spacecraft, launch vehicles, and military equipment. Their relatively low cost, wide range of values, and package styles are attractive features that result in high usage in electronic circuitry in these applications. Design and construction of monolithic ceramic dielectric capacitors, defects that can lead to failure, and methods for defect detection that are being incorporated in military specifications are discussed.

Electrospun Ceramic Nanofiber Mats Today: Synthesis, Properties, and Applications

PubMed Central

Esfahani, Hamid; Ramakrishna, Seeram

2017-01-01

Ceramic nanofibers (NFs) have recently been developed for advanced applications due to their unique properties. In this article, we review developments in electrospun ceramic NFs with regard to their fabrication process, properties, and applications. We find that surface activity of electrospun ceramic NFs is improved by post pyrolysis, hydrothermal, and carbothermal processes. Also, when combined with another surface modification methods, electrospun ceramic NFs result in the advancement of properties and widening of the application domains. With the decrease in diameter and length of a fiber, many properties of fibrous materials are modified; characteristics of such ceramic NFs are different from their wide and long (bulk) counterparts. In this article, electrospun ceramic NFs are reviewed with an emphasis on their applications as catalysts, membranes, sensors, biomaterials, fuel cells, batteries, supercapacitors, energy harvesting systems, electric and magnetic parts, conductive wires, and wearable electronic textiles. Furthermore, properties of ceramic nanofibers, which enable the above applications, and techniques to characterize them are briefly outlined. PMID:29077074

Electrospun Ceramic Nanofiber Mats Today: Synthesis, Properties, and Applications.

PubMed

Esfahani, Hamid; Jose, Rajan; Ramakrishna, Seeram

2017-10-27

Ceramic nanofibers (NFs) have recently been developed for advanced applications due to their unique properties. In this article, we review developments in electrospun ceramic NFs with regard to their fabrication process, properties, and applications. We find that surface activity of electrospun ceramic NFs is improved by post pyrolysis, hydrothermal, and carbothermal processes. Also, when combined with another surface modification methods, electrospun ceramic NFs result in the advancement of properties and widening of the application domains. With the decrease in diameter and length of a fiber, many properties of fibrous materials are modified; characteristics of such ceramic NFs are different from their wide and long (bulk) counterparts. In this article, electrospun ceramic NFs are reviewed with an emphasis on their applications as catalysts, membranes, sensors, biomaterials, fuel cells, batteries, supercapacitors, energy harvesting systems, electric and magnetic parts, conductive wires, and wearable electronic textiles. Furthermore, properties of ceramic nanofibers, which enable the above applications, and techniques to characterize them are briefly outlined.

Bismuth Sodium Titanate Based Materials for Piezoelectric Actuators

PubMed Central

Reichmann, Klaus; Feteira, Antonio; Li, Ming

2015-01-01

The ban of lead in many electronic products and the expectation that, sooner or later, this ban will include the currently exempt piezoelectric ceramics based on Lead-Zirconate-Titanate has motivated many research groups to look for lead-free substitutes. After a short overview on different classes of lead-free piezoelectric ceramics with large strain, this review will focus on Bismuth-Sodium-Titanate and its solid solutions. These compounds exhibit extraordinarily high strain, due to a field induced phase transition, which makes them attractive for actuator applications. The structural features of these materials and the origin of the field-induced strain will be revised. Technologies for texturing, which increases the useable strain, will be introduced. Finally, the features that are relevant for the application of these materials in a multilayer design will be summarized. PMID:28793724

Transmission of ˜ 10 keV electron beams through thin ceramic foils: Measurements and Monte Carlo simulations of electron energy distribution functions

NASA Astrophysics Data System (ADS)

Morozov, A.; Heindl, T.; Skrobol, C.; Wieser, J.; Krücken, R.; Ulrich, A.

2008-07-01

Electron beams with particle energy of ~10 keV were sent through 300 nm thick ceramic (Si3N4 + SiO2) foils and the resulting electron energy distribution functions were recorded using a retarding grid technique. The results are compared with Monte Carlo simulations performed with two publicly available packages, Geant4 and Casino v2.42. It is demonstrated that Geant4, unlike Casino, provides electron energy distribution functions very similar to the experimental distributions. Both simulation packages provide a quite precise average energy of transmitted electrons: we demonstrate that the maximum uncertainty of the calculated values of the average energy is 6% for Geant4 and 8% for Casino, taking into account all systematic uncertainties and the discrepancies in the experimental and simulated data.

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.

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.

The friction and wear of ceramic/ceramic and ceramic/metal combinations in sliding contact

NASA Technical Reports Server (NTRS)

Sliney, Harold E.; Dellacorte, Christopher

1993-01-01

The tribological characteristics of ceramics sliding on ceramics are compared to those of ceramics sliding on a nickel based turbine alloy. The friction and wear of oxide ceramics and silicon-based ceramics in air at temperatures from room ambient to 900 C (in a few cases to 1200 C) were measured for a hemispherically-tipped pin on a flat sliding contact geometry. In general, especially at high temperature, friction and wear were lower for ceramic/metal combinations than for ceramic/ceramic combinations. The better tribological performance for ceramic/metal combinations is attributed primarily to the lubricious nature of the oxidized surface of the metal.

Synthesis and electrical characterization of BaZr0.9Ho0.1O3-δ electrolyte ceramic for IT - SOFCs

NASA Astrophysics Data System (ADS)

Saini, Deepash S.; Singh, Lalit K.; Bhattacharya, D.

2018-04-01

A cost-effective modified combustion method using citric acid and glycine has recently been developed to synthesize high quality, and nanosized BaZr0.9Ho0.1O3 ceramic powder. BaZr0.9Ho0.1O3-δ ceramic powder was characterized by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM) and field emission scanning electron microscopy (FESEM). XRD pattern of BaZr0.9Ho0.1O3-δ ceramic sintered at 1600 °C has shown that pure phase of BaZr0.9Ho0.1O3-δ with cubic Pm3¯m space group symmetry. The transmission electron microscopic investigation has shown that the particle size of the powder calcined at 1100 °C was in the range 30-80 nm. The FESEM image of sintered pellet at 1600 °C for 4 h reveals porous nature of BaZr0.9Ho0.1O3-δ with 83.7 relative density. Impedance analysis reveal three type relaxations in the temperature range 250 °C to 500 °C as studied at different frequencies over 100 Hz to 1 MHz in air. The grain boundary conductivity of BaZr0.9Ho0.1O3-δ ceramic is found lower then grain (bulk) conductivity due to core-space charge layer behavior in grain boundary.

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.

Ceramic Translations. Volume 41. Grain Boundaries and Interfacial Phenomena in Electronic Ceramics

DTIC Science & Technology

1994-01-01

will be dealt with below. EXPERIMENTAL PROCEDURE Two BaTiO 3 powders were examined. The first was a commercially prepared hydrothermal powder whilst...the second was hydrothermally grown in the present work to an average particle size (0.28 To the extent authorized under the laws of the United States...program [14]. Particle sizes were determined with a JEOL JXA-840 scanning electron microscope running at 15 keV. Fresh commercial hydrothermal BaTiO 3

Enhanced Actuation Performance and Reduced Heat Generation in Shear-Bending Mode Actuator at High Temperature.

PubMed

Chen, Jianguo; Liu, Guoxi; Cheng, Jinrong; Dong, Shuxiang

2016-08-01

The actuation performance, strain hysteresis, and heat generation of the shear-bending mode actuators based on soft and hard BiScO3-PbTiO3 (BS-PT) ceramics were investigated under different thermal (from room temperature to 300 °C) and electrical loadings (from 2 to 10 kV/cm and from 1 to 1000 Hz). The actuator based on both soft and hard BS-PT ceramics worked stably at the temperature as high as 300 °C. The maximum working temperature of this shear-bending actuators is 150 °C higher than those of the traditional piezoelectric actuators based on commercial Pb(Zr, Ti)O3 materials. Furthermore, although the piezoelectric properties of soft-type ceramics based on BS-PT ceramics were superior to those of hard ceramics, the maximum displacement of the actuator based on hard ceramics was larger than that fabricated by soft ceramics at high temperature. The maximum displacement of the actuator based on hard ceramics was [Formula: see text] under an applied electric field of 10 kV/cm at 300 °C. The strain hysteresis and heat generation of the actuator based on hard ceramics was smaller than those of the actuator based on soft ceramics in the wide temperature range. These results indicated that the shear-bending actuator based on hard piezoelectric ceramics was more suitable for high-temperature piezoelectric applications.

Rietveld refinement, electronic structure and ionic conductivity of Sr{sub 4}La{sub 6}(SiO{sub 4}){sub 6}F{sub 2} and Sr{sub 4}La{sub 6}(SiO{sub 4}){sub 6}O ceramics

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

Boughzala, Khaled, E-mail: khaledboughzala@gmail.com; Preparatory Institute for Engineering Studies, 5000 Monastir; Debbichi, Mourad

In this paper, we report the effect of the tunnel anions on the ionic conductivity of Strontium-Lanthanum silicate apatites. The Sr{sub 4}La{sub 6}(SiO{sub 4}){sub 6}F{sub 2} and Sr{sub 4}La{sub 6}(SiO{sub 4}){sub 6}O ceramics were prepared by the solid state reaction method. X-ray diffraction, NMR spectroscopy and Raman measurements were performed to investigate the crystal structure and vibrational active modes. Moreover, the electronic structures of the crystals were evaluated by the first-principles quantum mechanical calculation based on the density functional theory. Finally, the ionic conductivity was studied according to the complex impedance method. - Graphical abstract: The relaxed primitive unit cellmore » for Sr{sub 4}La{sub 6}Fap. Display Omitted.« less

Surface analysis of mixed-conducting ferrite membranes by the conversion-electron Mössbauer spectroscopy

NASA Astrophysics Data System (ADS)

Waerenborgh, J. C.; Tsipis, E. V.; Yaremchenko, A. A.; Kharton, V. V.

2011-09-01

Conversion-electron Mössbauer spectroscopy analysis of iron surface states in the dense ceramic membranes made of 57Fe-enriched SrFe 0.7Al 0.3O 3- δ perovskite, shows no traces of reductive decomposition or carbide formation in the interfacial layers after operation under air/CH 4 gradient at 1173 K, within the limits of experimental uncertainty. The predominant trivalent state of iron cations at the membrane permeate-side surface exposed to flowing dry methane provides evidence of the kinetic stabilization mechanism, which is only possible due to slow oxygen-exchange kinetics and enables long-term operation of the ferrite-based ceramic reactors for natural gas conversion. At the membrane feed-side surface exposed to air, the fractions of Fe 4+ and Fe 3+ are close to those in the powder equilibrated at atmospheric oxygen pressure, suggesting that the exchange limitations to oxygen transport are essentially localized at the partially reduced surface.

Synthesis of SiCN@TiO2 core-shell ceramic microspheres via PDCs method

NASA Astrophysics Data System (ADS)

Liu, Hongli; Wei, Ning; Li, Jing; Zhang, Haiyuan; Chu, Peng

2018-02-01

A facile and effective polymer-derived ceramics (PDCs) emulsification-crosslinking-pyrolysis method was developed to fabricate SiCN@TiO2 core-shell ceramic microspheres with polyvinylsilazane (PVSZ) and tetrabutyl titanate (TBT) as precursors. The TBT: PVSZ mass ratios, emulsifier concentrations and the pyrolysis temperature were examined as control parameters to tune the size and morphology of microspheres. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) confirmed the synthesized SiCN@TiO2 microspheres to be comprised of SiCN core coated with TiO2 crystals, with an average size of 0.88 μm when pyrolyzed at 1400 °C. The analysis of Fourier transform infrared spectroscopy (FT-IR), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) ensured that SiCN@TiO2 core-shell ceramic microspheres composed of rutile TiO2, β-SiC and Si3N4 crystalline phases, The thermal properties were characterized by thermogravimetric analysis (TGA). The obtained SiCN@TiO2 core-shell ceramic microspheres were the promising candidate of the infrared opacifier in silica aerogels and this technique can be extended to other preceramic polymers.

Performance of universal adhesives on bonding to leucite-reinforced ceramic.

PubMed

Kim, Ryan Jin-Young; Woo, Jung-Soo; Lee, In-Bog; Yi, Young-Ah; Hwang, Ji-Yun; Seo, Deog-Gyu

2015-01-01

This study aimed to investigate the microshear bond strength of universal bonding adhesives to leucite-reinforced glass-ceramic. Leucite-reinforced glass-ceramic blocks were polished and etched with 9.5% hydrofluoric acid for 1 min. The specimens were assigned to one of four groups based on their surface conditioning (n = 16): 1) NC: negative control with no further treatment; 2) SBU: Single Bond Universal (3M ESPE); 3) ABU: ALL-BOND Universal (Bisco); and 4) PC: RelyX Ceramic Primer and Adper Scotchbond Multi-Purpose Adhesive (3M ESPE) as a positive control. RelyX Ultimate resin cement (3M ESPE) was placed on the pretreated ceramic and was light cured. Eight specimens from each group were stored in water for 24 h, and the remaining eight specimens were thermocycled 10,000 times prior to microshear bond strength evaluation. The fractured surfaces were examined by stereomicroscopy and scanning electron microscopy (SEM). After water storage and thermocycling, the microshear bond strength values decreased in the order of PC > SBU and ABU > NC (P < 0.05). Thermocycling significantly reduced the microshear bond strength, regardless of the surface conditioning used (P < 0.05). Cohesive failure in the ceramic and mixed failure in the ceramic and resin cement were observed in the fractured specimens. The percentage of specimens with cohesive failure after 24 h of water storage was: NC (50%), SBU (75%), ABU (75%), and PC (87%). After thermocycling, the percentage of cohesive failure in NC decreased to 25%; however, yet the percentages of the other groups remained the same. Although the bond strength between resin and hydrofluoric acid-etched glass ceramic was improved when universal adhesives were used, conventional surface conditioning using a separate silane and adhesive is preferable to a simplified procedure that uses only a universal adhesive for cementation of leucite-reinforced glass-ceramic.

The Effect of MnO2 Content and Sintering Atmosphere on The Electrical Properties of Iron Titanium Oxide NTC Thermistors using Yarosite

NASA Astrophysics Data System (ADS)

Wiendartun; Gustaman Syarif, Dani

2017-02-01

The effect of MnO2 content and sintering atmosphere on the characteristics of Fe2TiO5 ceramics for Negative Thermal Coefficient (NTC) thermistors by using Fe2O3 derived from yarosite has been studied. The ceramics were produced by pressing a homogeneous mixture of Fe2O3, TiO2 and MnO2 (0-2.0 w/o) powders in appropriate proportions to produce Fe2TiO5 based ceramics and sintering the pressed powder at 1100-1200°C for 3 hours in air, O2 and N2 gas. Electrical characterization was done by measuring electrical resistivity of the sintered ceramics at various temperatures from 30°C to 200°C. Microstructure and structural analyses were also carried out by using an scanning electron microscope (SEM) and x-ray diffraction (XRD). The XRD data showed that the pellets crystallize in orthorhombic. The presence of second phase could not be identified from the XRD analyses. The SEM images showed that the grain size of pellet ceramics increase with increasing of MnO2 addition, and the grains size of the ceramic sintered in oxygen gas is smaller than sintered in nitrogen gas. Electrical data showed that the value of room temperature resistance (RRT) tend to decrease with respect to the increasing of MnO2 addition and the pellet ceramics sintered in oxygen gas had the largest thermistor constant (B), activation energy (Ea), sensitivity (α) and room temperature resistance (RRT), compared to the sintered in nitrogen gas. From the electrical characteristics data, it was known that the electrical characteristics of the Fe2TiO5 pellet ceramics followed the NTC characteristic. The fabricated Fe2TiO5 ceramics have thermistor constants (B = 2207-7145K). This can be applied as temperature sensor, and will fulfill the market requirement.

Study on Microstructures and Properties of Porous TiC Ceramics Fabricated by Powder Metallurgy

NASA Astrophysics Data System (ADS)

Ma, Yana; Bao, Chonggao; Han, Longhao; Chen, Jie

2017-02-01

Powder metallurgy process was used to fabricate porous titanium carbide (TiC) ceramics, in which TiC powders were taken as the raw materials, nickel was used as the metallic binder and urea was the space-holder. Microstructure, composition and phase of porous TiC ceramics were characterized by scanning electron microscopy (SEM) and x-ray diffraction (XRD). Flexure strength of the porous TiC ceramics was tested by a three-point bending method. The results show that macropores and micropores coexist in the prepared porous TiC ceramics. Moreover, the pore number, size and distribution in porous TiC ceramics can be controlled on demand. Particularly, the factors such as the number or size of space-holder, compacting pressure and Ni content have significant effect on the porosity and flexure strength.

Nd:YAG Laser-aided ceramic brackets debonding: Effects on shear bond strength and enamel surface

NASA Astrophysics Data System (ADS)

Han, Xianglong; Liu, Xiaolin; Bai, Ding; Meng, Yao; Huang, Lan

2008-11-01

In order to evaluate the efficiency of Nd:YAG laser-aided ceramic brackets debonding technique, both ceramic brackets and metallic brackets were bonded with orthodontic adhesive to 30 freshly extracted premolars. The specimens were divided into three groups, 10 in each, according to the brackets employed and the debonding techniques used: (1) metallic brackets with shear debonding force, (2) ceramic brackets with shear debonding force, and (3) ceramic brackets with Nd:YAG laser irradiation. The result showed that laser irradiation could diminish shear bond strength (SBS) significantly and produce the most desired ARI scores. Moreover, scanning electron microscopy investigation displayed that laser-aided technique induced little enamel scratch or loss. It was concluded that Nd:YAG laser could facilitate the debonding of ceramic brackets and diminish the amount of remnant adhesive without damaging enamel structure.

Predictive Surface Roughness Model for End Milling of Machinable Glass Ceramic

NASA Astrophysics Data System (ADS)

Mohan Reddy, M.; Gorin, Alexander; Abou-El-Hossein, K. A.

2011-02-01

Advanced ceramics of Machinable glass ceramic is attractive material to produce high accuracy miniaturized components for many applications in various industries such as aerospace, electronics, biomedical, automotive and environmental communications due to their wear resistance, high hardness, high compressive strength, good corrosion resistance and excellent high temperature properties. Many research works have been conducted in the last few years to investigate the performance of different machining operations when processing various advanced ceramics. Micro end-milling is one of the machining methods to meet the demand of micro parts. Selecting proper machining parameters are important to obtain good surface finish during machining of Machinable glass ceramic. Therefore, this paper describes the development of predictive model for the surface roughness of Machinable glass ceramic in terms of speed, feed rate by using micro end-milling operation.

Sintering and crystallization behavior of CaMgSi{sub 2}O{sub 6}-NaFeSi{sub 2}O{sub 6} based glass-ceramics

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

Goel, Ashutosh; Kansal, Ishu; Dipartimento di Ingegneria dei Materiali e dell'Ambiente, Facolta di Ingegneria, Universita di Modena e Reggio Emilia, 41100 Modena

2009-11-01

We report on the synthesis, sintering, and crystallization behaviors of a glass with a composition corresponding to 90 mol % CaMgSi{sub 2}O{sub 6}-10 mol % NaFeSi{sub 2}O{sub 6}. The investigated glass composition crystallized superficially immediately after casting of the melt and needs a high cooling rate (rapid quenching) in order to produce an amorphous glass. Differential thermal analysis and hot-stage microscopy were employed to investigate the glass forming ability, sintering behavior, relative nucleation rate, and crystallization behavior of the glass composition. The crystalline phase assemblage in the glass-ceramics was studied under nonisothermal heating conditions in the temperature range of 850-950more » deg. C in both air and N{sub 2} atmosphere. X-ray diffraction studies adjoined with the Rietveld-reference intensity ratio method were employed to quantify the amount of crystalline phases, while electron microscopy was used to shed some light on the microstructure of the resultant glass-ceramics. Well sintered glass-ceramics with diopside as the primary crystalline phase were obtained where the amount of diopside varied with the heating conditions.« less

FAST TRACK COMMUNICATION: Mechanical, electrical and micro-structural properties of La0.6Sr0.4Co0.2Fe0.8O3 perovskite-based ceramic foams

NASA Astrophysics Data System (ADS)

Gupta, Ravindra K.; Kim, Eun Yi; Noh, Ho Sung; Whang, Chin Myung

2008-02-01

Mechanical, electrical and micro-structural properties of new electronic conducting ceramic foams are reported. Ceramic foams are prepared using the slurry of La0.6Sr0.4Co0.2Fe0.8O3 (LSCF) by the polymeric sponge method, which is followed by spray coating for increasing the number of coatings-sinterings on polyurethane foams of 30, 45 and 60 ppi (pores per linear inch). An increase in the number of coatings-sinterings and ppi improved the compressive strength, density and electrical conductivity by decreasing the porosity to ~76%, as also observed by the SEM study. The three-times coated-sintered ceramic foams (60 ppi) exhibited optimum values of compressive strength of ~1.79 MPa and relative density of ~0.24 at 25 °C and electrical conductivity of ~22 S cm-1 at 600 °C with an activation energy of ~0.22 eV indicating its suitability as a solid oxide fuel cell current collector. The experimental results are discussed in terms of the Gibson and Ashby theoretical model.

Preparation of Ferroelectric KNbO3 Based Borate Glass System.

PubMed

Kruea-In, Chatchai; Intawin, Pratthana; Leenakul, Wilaiwan

2015-11-01

The incorporation method was employed to produce ferroelectric glass ceramics from the K2O-Nb2O5-B2O3 glass system. The nanocrystalline potassium niobate (KNbO3) was first prepared using a simple mixed oxide method, where the B2O3 was initially mixed and then melted to form glass. The successfully produced optically transparent glass was then subjected to a heat treatment schedule for further crystallization at temperatures ranging from 500 to 650 degrees C, which resulted in the precipitation of the KNbO3 phase, together with the K3B2Nb3O12 phase. Scanning electron microscopy (SEM) showed the presence of randomly oriented KNbO3 crystals dispersed in a continuous glass matrix. It was found that the glass ceramics subjected to the heat treatment at temperatures higher than 545 degrees C were opaque, while the lower gave a highly transparent glass ceramics. The crystal size and crystallinity were found to increase with increasing heat treatment temperature, which in turn plays an important role in controlling the properties of the glass ceramics, including physical, optical, and dielectric properties.

Modeling & processing of ceramic and polymer precursor ceramic matrix composite materials

NASA Astrophysics Data System (ADS)

Wang, Xiaolin

Synthesis and processing of novel materials with various advanced approaches have attracted much attention of engineers and scientists for the past thirty years. Many advanced materials display a number of exceptional properties and can be produced with different novel processing techniques. For example, AlN is a promising candidate for electronic, optical and opto-electronic applications due to its high thermal conductivity, high electrical resistivity, high acoustic wave velocity and large band gap. Large bulk AlN crystal can be produced by sublimation of AlN powder. Novel nonostructured multicomponent refractory metal-based ceramics (carbides, borides and nitrides) show a lot of exceptional mechanical, thermal and chemical properties, and can be easily produced by pyrolysis of suitable preceramic precursors mixed with metal particles. The objective of this work is to study sublimation and synthesis of AlN powder, and synthesis of SiC-based metal ceramics. For AlN sublimation crystal growth, we will focus on modeling the processes in the powder source that affect significantly the sublimation growth as a whole. To understand the powder porosity evolution and vapor transport during powder sublimation, the interplay between vapor transport and powder sublimation will be studied. A physics-based computational model will be developed considering powder sublimation and porosity evolution. Based on the proposed model, the effect of a central hole in the powder on the sublimation rate is studied and the result is compared to the case of powder without a hole. The effect of hole size on the sublimation rate will be studied. The effects of initial porosity, particle size and driving force on the sublimation rate are also studied. Moreover, the optimal growth condition for large diameter crystal quality and high growth rate will be determined. For synthesis of SiC-based metal ceramics, we will focus on developing a multi-scale process model to describe the dynamic behavior of filler particle reaction, microstructure evolution, at the microscale as well as transient fluid flow, heat transfer, and species transport at the macroscale. The model comprises of (i) a microscale model and (ii) a macroscale transport model, and aims to provide optimal conditions for the fabrication process of the ceramics. The porous media macroscale model for SiC-based metal-ceramic materials processing will be developed to understand the thermal polymer pyrolysis, chemical reaction of active fillers and transport phenomena in the porous media. The macroscale model will include heat and mass transfer, curing, pyrolysis, chemical reaction and crystallization in a mixture of preceramic polymers and submicron/nano-sized metal particles of uranium, zirconium, niobium, or hafnium. The effects of heating rate, sample size, size and volume ratio of the metal particles on the reaction rate and product uniformity will be studied. The microscale model will be developed for modeling the synthesis of SiC matrix and metal particles. The macroscale model provides thermal boundary conditions to the microscale model. The microscale model applies to repetitive units in the porous structure and describes mass transport, composition changes and motion of metal particles. The unit-cell is the representation unit of the source material, and it consists of several metal particles, SiC matrix and other components produced from the synthesis process. The reactions between different components, the microstructure evolution of the product will be considered. The effects of heating rate and metal particle size on species uniformity and microstructure are investigated.

Carbon nanotube-ceramic nanocomposites: Synthesis and characterization

NASA Astrophysics Data System (ADS)

Clark, Michael David

Ceramic materials are widely used in modern society for a variety of applications including fuel cell electrolytes, bio-medical implants, and jet turbines. However, ceramics are inherently brittle making them excellent candidates for mechanical reinforcement. In this work, the feasibility of dispersing multi-walled carbon nanotubes into a silicon carbide matrix for mechanical property enhancement is explored. Prior to dispersing, nanotubes were purified using an optimized, three step methodology that incorporates oxidative treatment, acid sonication, and thermal annealing rendering near-superhydrophobic behavior in synthesized thin films. Alkyl functionalized nanotube dispersability was characterized in various solvents. Dispersability was contingent on fostering polar interactions between the functionalized nanotubes and solvent despite the purely dispersive nature of the aliphatic chains. Interpretation of these results yielded values of 45.6 +/- 1.2, 0.78 +/- 0.04, and 2 4 +/- 0.9 mJ/m2 for the Lifshitz-van der Waals, electron acceptor and electron donor surface energy components respectively. Aqueous nanotube dispersions were prepared using a number of surfactants to examine surfactant concentration and pH effects on nanotube dispersability. Increasing surfactant concentrations resulted in a solubility plateau, which was independent of the surfactant's critical micelle concentration. Deviations from neutral pH demonstrated negligible influence on non-ionic surfactant adsorption while, ionic surfactants showed substantial pH dependent behavior. These results were explained in the context of nanotube surface ionization and Debye length variation. Successful MWNT dispersion into a silicon carbide based matrix is reported by in-situ ceramic formation using two routes; sol-gel chemistry and pre-ceramic polymeric precursor workup. For the former, nanotube dispersion was assisted by PluronicRTM surfactants. Pyrolytic treatment and consolidation of formed powders yielded ceramic silicon oxycarbide glasses (SiO1.1 C0.6) attributed to incomplete carbothermal reduction. Microhardness and dynamic moduli measurements were consistent with silicon oxycarbide glasses and unaffected by nanotube loading up to 0.11 wt. %. Pyrolysis and densification of poly(methylsilyne) yielded a high density ceramic material (2.45-2.63 g/cm 3). Nanotube introduction was achieved using two separate alkylation techniques; alkyllithium replacement and organic peroxide workup. Bulk mechanical testing was deemed unreliable as powder consolidation introduced chemical inhomogeneity with pellet edges being largely composed of polycrystalline silicon and silicon carbide, while the center contained substantial oxygen contamination.

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

The effects of composition and sintering temperature on the silica foam fabricated by slurry method

NASA Astrophysics Data System (ADS)

Baharom, Syazwani; Ahmad, Sufizar; Taib, Hariati; Muda, Rizamarhaiza

2016-07-01

Reticulated ceramic or open pore ceramic foam is a well-known material which exhibits extremely high porosities, with a significant degree of interconnectivity that makes them desirable in a wide range of applications. There were broad types of ceramic foam fabrication method such as polymeric sponge method, direct foaming, and starch consolidation. In this study, the slurry method has been chosen to fabricate Silica (SiO2) foam. In this process, Polyurethane (PU) foam template was dipped into ceramic slurry and followed by drying and sintering to obtain foam which contains porosity in the range of 50% to 70%. The compositions of SiO2 were varied starting from 55 wt.%, 60 wt.%, 65 wt.% and 70 wt.%. The samples of SiO2 that have been dipped and dried were sintered at 900°C, 1000°C, 1100°C, and 1250°C. The sintered SiO2 ceramic foam samples were characterized to observe their morphology, and physical properties. Thus, the microstructure of the SiO2 ceramic foams samples was examined by Scanning Electron Microscopy (SEM), and Electron Dispersive Spectroscopy (EDS). Meanwhile, the physical properties of the SiO2 ceramic foam samples such as the total porosity (%) and bulk density were determined using Archimedes method. It was found that the density of ceramic foam produced was in the range of 0.25 g/cm3 up to 0.75 g/cm3, whereas the level of porosity percentage was in the range of 61.81% to 82.18% with the size of open pore or window cells were in between 141 µm up to 626 µm.

Reverse Engineering of Corinthian Pigment Processing and Firing Technologies on Archaic Polychrome Ceramics

NASA Astrophysics Data System (ADS)

Klesner, Catherine Elizabeth

Decorative, polychrome ceramics from Corinth, Greece, produced during the 8th-6th centuries B.C.E. are luxury goods that were widely traded throughout Greece and the Mediterranean. The decorated ceramics were produced in a variety of shapes, including aryballos, alabastron, and olpe. They were decorated with slip-glazes in distinctive white, black, red, yellow, and purple colors, and in a variety of surface finishes, matte, semi-matte and glossy. Artisans in Corinthian workshops experimented to change the colors of the slips by varying the type and amount of iron-rich raw materials. They also varied the composition of the clay used as a binder and the amount of flux used as a sintering aid to promote glass formation. This research reconstructs the technology used by the Corinthian craftsmen to produce the Archaic polychrome ceramics, and shows how these technologies differed from the production of better known, more prestigious Athenian black-figure and red-figure ceramics. Through microstructural examination of archaeological samples and replication experiments, this thesis proposes that the purple iron oxide pigment is the result of acid treatment and oxidation of iron metal. The firing temperature range of the Corinthian polychrome ceramics was determined experimentally to be 925-1025°C, which is higher than previously reported and similar to that reported for Corinthian transport amphoras. The firing range is higher by 50-150°C than the Athenian black-figure and red-figure ceramics. Samples of Corinthian polychrome and Athenian black-figure ceramics from the Marie Farnsworth collection at the University of Arizona were tested and compared to Corinthian clay collections. Analytical techniques included Fourier-transform infrared spectroscopy (FTIR), scanning-electron microscopy with energy-dispersive spectroscopy (SEM-EDS), micro-Raman spectroscopy, and wavelength-dispersive electron microprobe (EPMA with BSE-SEM).

The effects of composition and sintering temperature on the silica foam fabricated by slurry method

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

Baharom, Syazwani, E-mail: hd140001@siswa.uthm.edu.my; Ahmad, Sufizar, E-mail: sufizar@uthm.edu.my; Taib, Hariati, E-mail: hariati@uthm.edu.my

Reticulated ceramic or open pore ceramic foam is a well-known material which exhibits extremely high porosities, with a significant degree of interconnectivity that makes them desirable in a wide range of applications. There were broad types of ceramic foam fabrication method such as polymeric sponge method, direct foaming, and starch consolidation. In this study, the slurry method has been chosen to fabricate Silica (SiO{sub 2}) foam. In this process, Polyurethane (PU) foam template was dipped into ceramic slurry and followed by drying and sintering to obtain foam which contains porosity in the range of 50% to 70%. The compositions ofmore » SiO{sub 2} were varied starting from 55 wt.%, 60 wt.%, 65 wt.% and 70 wt.%. The samples of SiO{sub 2} that have been dipped and dried were sintered at 900°C, 1000°C, 1100°C, and 1250°C. The sintered SiO{sub 2} ceramic foam samples were characterized to observe their morphology, and physical properties. Thus, the microstructure of the SiO{sub 2} ceramic foams samples was examined by Scanning Electron Microscopy (SEM), and Electron Dispersive Spectroscopy (EDS). Meanwhile, the physical properties of the SiO{sub 2} ceramic foam samples such as the total porosity (%) and bulk density were determined using Archimedes method. It was found that the density of ceramic foam produced was in the range of 0.25 g/cm{sup 3} up to 0.75 g/cm{sup 3}, whereas the level of porosity percentage was in the range of 61.81% to 82.18% with the size of open pore or window cells were in between 141 µm up to 626 µm.« less

In vitro biocompatibility of a ferrimagnetic glass-ceramic for hyperthermia application.

PubMed

Bretcanu, Oana; Miola, Marta; Bianchi, Claudia L; Marangi, Ida; Carbone, Roberta; Corazzari, Ingrid; Cannas, Mario; Verné, Enrica

2017-04-01

Ferrimagnetic glass-ceramics containing magnetite crystals were developed for hyperthermia applications of solid neoplastic tissue. The present work is focused on in vitro evaluation of the biocompatibility of these materials, before and after soaking in a simulated body fluid (SBF). X-ray diffraction, scanning electron microscopy, atomic absorption spectrophotometry, X-ray photoelectron spectrometry and pH measurements were employed in glass-ceramic characterisation. The free-radical mediated reactivity of the glass-ceramic was evaluated by Electron Paramagnetic Resonance (EPR) spin trapping. Cell adhesion and proliferation tests were carried out by using 3T3 murine fibroblasts. Cytotoxicity was performed by qualitative evaluation of human bone osteosarcoma cells U2OS cell line. The results show that almost two times more 3T3 cells proliferated on the samples pre-treated in SBF, compared with the untreated specimens. Moreover a decrease of confluence was observed at 48 and 72h for U2OS cells exposed to the untreated glass-ceramic, while the powder suspensions of glass-ceramic pre-treated in SBF did not influence the cell morphology up to 72h of exposition. The untreated glass-ceramic exhibited Fenton-like reactivity, as well as reactivity towards formate molecule. After pre-treatment with SBF the reactivity towards formate was completely suppressed. The concentration of iron released into the SBF solution was below 0.1ppm at 37°C, during one month of soaking. The different in vitro behaviour of the samples before and after SBF treatment has been correlated to the bioactive glass-ceramic surface modifications as detected by morphological, structural and compositional analyses. Copyright © 2016 Elsevier B.V. All rights reserved.

Aspects of bonding between resin luting cements and glass ceramic materials.

PubMed

Tian, Tian; Tsoi, James Kit-Hon; Matinlinna, Jukka P; Burrow, Michael F

2014-07-01

The bonding interface of glass ceramics and resin luting cements plays an important role in the long-term durability of ceramic restorations. The purpose of this systematic review is to discuss the various factors involved with the bond between glass ceramics and resin luting cements. An electronic Pubmed, Medline and Embase search was conducted to obtain laboratory studies on resin-ceramic bonding published in English and Chinese between 1972 and 2012. Eighty-three articles were included in this review. Various factors that have a possible impact on the bond between glass ceramics and resin cements were discussed, including ceramic type, ceramic crystal structure, resin luting cements, light curing, surface treatments, and laboratory test methodology. Resin-ceramic bonding has been improved substantially in the past few years. Hydrofluoric acid (HF) etching followed by silanizaiton has become the most widely accepted surface treatment for glass ceramics. However, further studies need to be undertaken to improve surface preparations without HF because of its toxicity. Laboratory test methods are also required to better simulate the actual oral environment for more clinically compatible testing. Copyright © 2014 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

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.

[Effect of porcelain firing cycle on microstructure and corrosion resistance of 4 metal ceramic alloys].

PubMed

Chen, Lei; Cai, Hui; Xu, Guo-fu; Fang, Chang-yun

2006-06-01

To determine the effect of porcelain firing cycle on microstructure of 4 metal ceramic alloys, and to analyze the changes of their corrosion resistance in the artificial saliva. We simulated the process of firing and repolishing when fabricating porcelain-fused-to-metal restoration in clinic,and then observed the microstructures of Ni-Cr, Ni-Cr-Ti, Co-Cr alloys and high gold alloy by field emission scanning electron microscopy and energy dispersive spectroscopy. The electrochemical corrosion behavior of alloys in artificial saliva was analyzed by polarization curves and corrview 2 corrosion analysis software. The data of self-corrosion potential and transpassive potential were obtained and analyzed. After the porcelain firing cycle, the surface composition changed slightly, and the morphological in the 3 predominate base metal alloys also changed. The self-corrosion potential turned to more negative, and the transpassive potential declined. The procedure of porcelain firing cycle can affect the surface microstructure and increase the corrosion of 4 metal-ceramic alloys.

Microgravity science and applications: Apparatus and facilities

NASA Technical Reports Server (NTRS)

1989-01-01

NASA support apparatus and facilities for microgravity research are summarized in fact sheets. The facilities are ground-based simulation environments for short-term experiments, and the shuttle orbiter environment for long duration experiments. The 17 items of the microgravitational experimental apparatus are described. Electronic materials, alloys, biotechnology, fluid dynamics and transport phenomena, glasses and ceramics, and combustion science are among the topics covered.

Novel Materials for 3D Printing by Photopolymerization.

PubMed

Layani, Michael; Wang, Xiaofeng; Magdassi, Shlomo

2018-05-13

The field of 3D printing, also known as additive manufacturing (AM), is developing rapidly in both academic and industrial research environments. New materials and printing technologies, which enable rapid and multimaterial printing, have given rise to new applications and utilizations. However, the main bottleneck for achieving many more applications is the lack of materials with new physical properties. Here, some of the recent reports on novel materials in this field, such as ceramics, glass, shape-memory polymers, and electronics, are reviewed. Although new materials have been reported for all three main printing approaches-fused deposition modeling, binder jetting or laser sintering/melting, and photopolymerization-based approaches, apparently, most of the novel physicochemical properties are associated with materials printed by photopolymerization approaches. Furthermore, the high resolution that can be achieved using this type of 3D printing, together with the new properties, has resulted in new implementations such as microfluidic, biomedical devices, and soft robotics. Therefore, the focus here is on photopolymerization-based additive manufacturing including the recent development of new methods, novel monomers, and photoinitiators, which result in previously inaccessible applications such as complex ceramic structures, embedded electronics, and responsive 3D objects. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Ceramic Defects in Metal-Ceramic Fixed Dental Prostheses Made from Co-Cr and Au-Pt Alloys: A Retrospective Study.

PubMed

Mikeli, Aikaterini; Boening, Klaus W; Lißke, Benjamin

2015-01-01

Ceramic defects in porcelain-fused-to-metal (PFM) restorations may depend on framework alloy type. This study assessed ceramic defects on cobalt-chromium- (Co-Cr-) and gold-platinum- (Au-Pt-) based PFM restorations. In this study, 147 Co-Cr-based and 168 Au-Pt-based PFM restorations inserted between 1998 and 2010 (139 patients) were examined for ceramic defects. Detected defects were assigned to three groups according to clinical defect relevance. Ceramic defect rates (Co-Cr-based: 12.9%; Au-Pt-based: 7.2%) revealed no significant difference but a strong statistical trend (U test, P = .082). Most defects were of little clinical relevance. Co-Cr PFM restorations may be at higher risk for ceramic defects compared to Au-Pt-based restorations.

Highly sensitive nonlinear luminescent ceramics for volumetric and multilayer data carriers

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

Martynovich, E F; Dresvyanskiy, V P; Voitovich, A P

2015-10-31

The interaction of optical ceramics based on wide-bandgap crystals with near-IR femtosecond laser radiation is studied experimentally. The formation of luminescent centres in LiF and MgF{sub 2} ceramics under the action of single laser pulses is considered. Two interaction regimes are used. In the regime of low-aperture focusing of laser radiation (800 nm, 30 fs, 0.3 mJ), multiple selffocusing and filamentation in the samples are observed. The luminescent centres are formed in thin channels induced by light filaments. The average effective self-focusing length is ∼100 μm; the formation of luminescent centres begins at this length and ceases at a wavelengthmore » of about 380 mm. The luminescent trace (spur) induced by a single laser filament was ∼30 μm long and 1.3 μm in diameter. The second regime of light interaction with the sample was based on high-aperture focusing with a simultaneous decrease in the laser pulse energy. This led to the formation of single pits with a diameter smaller than the optical diffraction limit. The luminescent centres induced by the laser radiation were aggregated colour centres. The mechanism of their creation included the highly-nonlinear generation of electron – hole pairs in the filamentation region, their recombination with the formation of anion excitons and the decay of excitons into Fresnel defects by the Lushchik – Vitol – Hersh – Pooley mechanism, as well as their recharging, migration and aggregation. (laser applications and other topics in quantum electronics)« less

Machinability of lithium disilicate glass ceramic in in vitro dental diamond bur adjusting process.

PubMed

Song, Xiao-Fei; Ren, Hai-Tao; Yin, Ling

2016-01-01

Esthetic high-strength lithium disilicate glass ceramics (LDGC) are used for monolithic crowns and bridges produced in dental CAD/CAM and oral adjusting processes, which machinability affects the restorative quality. A machinability study has been made in the simulated oral clinical machining of LDGC with a dental handpiece and diamond burs, regarding the diamond tool wear and chip control, machining forces and energy, surface finish and integrity. Machining forces, speeds and energy in in vitro dental adjusting of LDGC were measured by a high-speed data acquisition and force sensor system. Machined LDGC surfaces were assessed using three-dimensional non-contact chromatic confocal optical profilometry and scanning electron microscopy (SEM). Diamond bur morphology and LDGC chip shapes were also examined using SEM. Minimum tool wear but significant LDGC chip accumulations were found. Machining forces and energy significantly depended on machining conditions (p<0.05) and were significantly higher than other glass ceramics (p<0.05). Machining speeds dropped more rapidly with increased removal rates than other glass ceramics (p<0.05). Two material machinability indices associated with the hardness, Young's modulus and fracture toughness were derived based on the normal force-removal rate relations, which ranked LDGC the most difficult to machine among glass ceramics. Surface roughness for machined LDGC was comparable for other glass ceramics. The removal mechanisms of LDGC were dominated by penetration-induced brittle fracture and shear-induced plastic deformation. Unlike most other glass ceramics, distinct intergranular and transgranular fractures of lithium disilicate crystals were found in LDGC. This research provides the fundamental data for dental clinicians on the machinability of LDGC in intraoral adjustments. Copyright © 2015 Elsevier Ltd. All rights reserved.

Mechanical behavior of single-layer ceramized zirconia abutments for dental implant prosthetic rehabilitation

PubMed Central

Jiménez-Melendo, Manuel; Llena-Blasco, Oriol; Bruguera, August; Llena-Blasco, Jaime; Yáñez-Vico, Rosa-María; García-Calderón, Manuel; Vaquero-Aguilar, Cristina; Velázquez-Cayón, Rocío; Gutiérrez-Pérez, José-Luis

2014-01-01

Objectives: This study was undertaken to characterize the mechanical response of bare (as-received) and single-layer ceramized zirconia abutments with both internal and external connections that have been developed to enhanced aesthetic restorations. Material and Methods: Sixteen zirconia implant abutments (ZiReal Post®, Biomet 3i, USA) with internal and external connections have been analyzed. Half of the specimens were coated with a 0.5mm-thick layer of a low-fusing fluroapatite ceramic. Mechanical tests were carried out under static (constant cross-head speed of 1mm/min until fracture) and dynamic (between 100 and 400N at a frequency of 1Hz) loading conditions. The failure location was identified by electron microscopy. The removal torque of the retaining screws after testing was also evaluated. Results: The average fracture strength was above 300N for all the abutments, regardless of connection geometry and coating. In most of the cases (94%), failure occurred by abutment fracture. No significant differences were observed either in fatigue behavior and removal torque between the different abutment groups. Conclusions: Mechanical behavior of Zireal zirconia abutments is independent of the type of internal/external connection and the presence/absence of ceramic coating. This may be clinically valuable in dental rehabilitation to improve the aesthetic outcome of zirconia-based dental implant systems. Key words:Dental implant, zirconia, ceramic structure, mechanical properties. PMID:25674313

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.

Dephosphorization of complexly alloyed nickel melts under vacuum induction melting conditions: II. Experimental results and their interpretation

NASA Astrophysics Data System (ADS)

Burtsev, V. T.; Anuchkin, S. N.; Sidorov, V. V.; Rigin, V. E.

2013-05-01

The activities of the components of BaO-BaF2-BaCl2-NiO and CaO-CaF2-CaCl2-NiO slags systems, which were considered as a phase having a collective electron system, are calculated, and it is shown that the barium, calcium, and oxygen activities at 1600°C are maximal in the BaO- and CaO-based systems depending on the main oxide content. The dephosphorization of three types of nickel-based melts by slags of 14 compositions in crucibles made of Al2O3, MgO, and MgO-Al2O3 (80-20 wt %) is experimentally studied, and the degree of dephosphorization is shown to depend on the phosphorus content in a metal, the slag composition, and the crucible material (degree of dephosphorization is maximal in Al2O3 crucibles). The forming slag is assimilated by Al2O3 and MgO-Al2O3 ceramics with a porosity of about 30%. If 4-10 wt % NiO are present in a slag, the wettability of the Al2O3 ceramic is significantly higher than that of the MgO-based ceramic.

Clinically used adhesive ceramic bonding methods: a survey in 2007, 2011, and in 2015.

PubMed

Klosa, K; Meyer, G; Kern, M

2016-09-01

The objective of the study is to evaluate practices of dentists regarding adhesive cementation of all-ceramic restorations over a period of 8 years. The authors developed a questionnaire regarding adhesive cementation procedures for all-ceramic restorations. Restorations were distinguished between made out of silicate ceramic or oxide ceramic. The questionnaire was handed out to all dentists participating in a local annual dental meeting in Northern Germany. The returned questionnaires were analyzed to identify incorrect cementation procedures based upon current evidence-based technique from the scientific dental literature. The survey was conducted three times in 2007, 2011, and 2015 and their results were compared. For silicate ceramic restorations, 38-69 % of the participants used evidence-based bonding procedures; most of the incorrect bonding methods did not use a silane containing primer. In case of oxide ceramic restorations, most participants did not use air-abrasion prior to bonding. Only a relatively low rate (7-14 %) of dentists used evidence-based dental techniques for bonding oxide ceramics. In adhesive cementation of all-ceramic restorations, the practices of surveyed dentists in Northern Germany revealed high rates of incorrect bonding. During the observation period, the values of evidence-based bonding procedures for oxide ceramics improved while the values for silicate ceramics declined. Based on these results, some survey participants need additional education for adhesive techniques. Neglecting scientifically accepted methods for adhesive cementation of all-ceramic restorations may result in reduced longevity of all-ceramic restorations.

Stabilized chromium oxide film

DOEpatents

Nyaiesh, A.R.; Garwin, E.L.

1986-08-04

Stabilized air-oxidized chromium films deposited on high-power klystron ceramic windows and sleeves having a thickness between 20 and 150A are useful in lowering secondary electron emission yield and in avoiding multipactoring and window failure due to overheating. The ceramic substrate for the film is chosen from alumina, sapphire or beryllium oxide.

Stabilized chromium oxide film

DOEpatents

Garwin, Edward L.; Nyaiesh, Ali R.

1988-01-01

Stabilized air-oxidized chromium films deposited on high-power klystron ceramic windows and sleeves having a thickness between 20 and 150.ANG. are useful in lowering secondary electron emission yield and in avoiding multipactoring and window failure due to overheating. The ceramic substrate for the film is chosen from alumina, sapphire or beryllium oxide.

Analysis of Al2O3 Nanostructure Using Scanning Microscopy

PubMed Central

Kubica, Marek; Bara, Marek

2018-01-01

It has been reported that the size and shape of the pores depend on the structure of the base metal, the type of electrolyte, and the conditions of the anodizing process. The paper presents thin Al2O3 oxide layer formed under hard anodizing conditions on a plate made of EN AW-5251 aluminum alloy. The oxidation of the ceramic layer was carried out for 40–80 minutes in a three-component SAS electrolyte (aqueous solution of acids: sulphuric 33 ml/l, adipic 67 g/l, and oxalic 30 g/l) at a temperature of 293–313 K, and the current density was 200–400 A/m2. Presented images were taken by a scanning microscope. A computer analysis of the binary images of layers showed different shapes of pores. The structure of ceramic Al2O3 layers is one of the main factors determining mechanical properties. The resistance to wear of specimen-oxide coating layer depends on porosity, morphology, and roughness of the ceramic layer surface. A 3D oxide coating model, based on the computer analysis of images from a scanning electron microscope (Philips XL 30 ESEM/EDAX), was proposed. PMID:29861823

Advanced Material-Ordered Nanotubular Ceramic Membranes Covalently Capped with Single-Wall Carbon Nanotubes.

PubMed

Al-Gharabli, Samer; Hamad, Eyad; Saket, Munib; Abu El-Rub, Ziad; Arafat, Hassan; Kujawski, Wojciech; Kujawa, Joanna

2018-05-07

Advanced ceramic materials with a well-defined nano-architecture of their surfaces were formed by applying a two-step procedure. Firstly, a primary amine was docked on the ordered nanotubular ceramic surface via a silanization process. Subsequently, single-wall carbon nanotubes (SWCNTs) were covalently grafted onto the surface via an amide building block. Physicochemical (e.g., hydrophobicity, and surface free energy (SFE)), mechanical, and tribological properties of the developed membranes were improved significantly. The design, preparation, and extended characterization of the developed membranes are presented. Tools such as high-resolution transmission electron microscopy (HR-TEM), single-area electron diffraction (SAED) analysis, microscopy, tribology, nano-indentation, and Raman spectroscopy, among other techniques, were utilized in the characterization of the developed membranes. As an effect of hydrophobization, the contact angles (CAs) changed from 38° to 110° and from 51° to 95° for the silanization of ceramic membranes 20 (CM20) and CM100, respectively. SWCNT functionalization reduced the CAs to 72° and 66° for ceramic membranes carbon nanotubes 20 (CM-CNT-20) and CM-CNT-100, respectively. The mechanical properties of the developed membranes improved significantly. From the nanotribological study, Young’s modulus increased from 3 to 39 GPa for CM-CNT-20 and from 43 to 48 GPa for pristine CM-CNT-100. Furthermore, the nanohardness increased by about 80% after the attachment of CNTs for both types of ceramics. The proposed protocol within this work for the development of functionalized ceramic membranes is both simple and efficient.

Development of Ultra-Low Power Metal Oxide Sensors and Arrays for Embedded Applications

NASA Astrophysics Data System (ADS)

Lutz, Brent; Wind, Rikard; Kostelecky, Clayton; Routkevitch, Dmitri; Deininger, Debra

2011-09-01

Metal oxide semiconductor sensors are widely used as individual sensors and in arrays, and a variety of designs for low power microhotplates have been demonstrated.1 Synkera Technologies has developed an embeddable chemical microsensor platform, based on a unique ceramic MEMS technology, for practical implementation in cell phones and other mobile electronic devices. Key features of this microsensor platform are (1) small size, (2) ultra-low power consumption, (3) high chemical sensitivity, (4) accurate response to a wide-range of threats, and (5) low cost. The sensor platform is enabled by a combination of advances in ceramic micromachining, and precision deposition of sensing films inside the high aspect ratio pores of anodic aluminum oxide (AAO).

A comparison of the microstructure and properties of the IPS Empress 2 and the IPS Empress glass-ceramics.

PubMed

Höland, W; Schweiger, M; Frank, M; Rheinberger, V

2000-01-01

The aim of this report is to analyze the microstructures of glass-ceramics of the IPS Empress 2 and IPS Empress systems by scanning electron microscopy. The main properties of the glass-ceramics were determined and compared to each other. The flexural strength of the pressed glass-ceramic (core material) was improved by a factor of more than three for IPS Empress 2 (lithium disilicate glass-ceramic) in comparison with IPS Empress (leucite glass-ceramic). For the fracture toughness, the K(IC) value was measured as 3.3 +/- 0.3 MPa. m(0.5) for IPS Empress 2 and 1.3 +/- 0.1 MPa. m(0.5) for IPS Empress. Abrasion behavior, chemical durability, and optical properties such as translucency of all glass-ceramics fulfill the dental standards. The authors concluded that IPS Empress 2 can be used to fabricate 3-unit bridges up to the second premolar. Copyright 2000 John Wiley & Sons, Inc.

[Cytocompatibility of nanophase hydroxyapatite ceramics].

PubMed

Wen, Bo; Chen, Zhi-qing; Jiang, Yin-shan; Yang, Zheng-wen; Xu, Yong-zhong

2004-12-01

To evaluate the cytocompatibility of nanophase hydroxyapatite ceramics in vitro. Hydroxyapatite (HA) was prepared via wet method. The grain size of the hydroxyapatite in the study was determined by scanning electron microscope and atomic force microscope with image analysis software. Primary osteoblast culture was established from rat calvaria. Cell adherence and proliferation on nanophase hydroxyapatite ceramics and conventional hydroxyapatite ceramics were examined at 1, 3, 5, 7 days. Morphology of the cells was observed by microscope. The average grain size of the nanophase and conventional HA was 55 nm and 780 nm, respectively. Throughout 7 days period, osteoblast proliferation on the HA was similar to that on tissue culture borosilicate glass controls, osteoblasts could attach, spread and proliferate on HA. However, compared to conventional ceramics, osteoblast proliferation on nanophase HA was significantly better after 1, 3, 5 and 7 days. Cytocompatibility of nanophase HA was significantly better than conventional ceramics.

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.

Capacitor Test, Evaluation. and Modeling Within NASA Electronic Parts and Packaging (NEPP) Program. "Why Ceramic Capacitors Fracture During Manual Soldering and How to Avoid Failures"

NASA Technical Reports Server (NTRS)

Teverovsky, Alexander

2011-01-01

Presentation discusses: (1) Why Multi-Layer Ceramic Capacitors(MLCCs) crack during manual soldering? Workmanship and parts issues. (2) Do existing qualification requirements assure crack-free soldering? MIL-spec Thermal Shock (TS) testing. MIL-spec Resistance to Soldering Heat (RSH) test. (3) What test can assure reliable soldering? Mechanical characteristics of ceramics. Comparison of three TS techniques: LND, TSD, and IWT. (4) Simulation of TS conditions.

Strategic Defense Initiative Program: Extent of Foreign Participation

DTIC Science & Technology

1990-02-07

the Air Force to a West German company, . Chemical Lasers project, for fabrication of a lightweight hig mirror . The firished product will be a 70...centimeter mirror lightweight, uncool"P glass ceramic material with no tus.rm. Two contracts, totaling $1.7 million, were au-arded under th Definition...Ground-Based Free The ground-based laser system concept is to fire a free electrru Electron Laser Project beam generated on the ground to a mirror relay

Characterization of Ultra-high Temperature Ceramics via Transmission Electron Microscopy Relevant ZrB2-based Composites, TaC-based Composites and Oxides Containing SiC Chopped Fibers

DTIC Science & Technology

2015-03-06

was formed by ZrO2 rounded grains containing W traces and covered by H3BO3 acicular crystals deriving from hydration of B2O3 after exposure to...TaSi2 grains tended to form large pockets as wide as 3-8 m. Other spurious phases formed upon decomposition of the additive, were identified as SiC

Effects of BiAlO{sub 3}-doping on dielectric and ferroelectric properties of 0.93Na{sub 0.5}Bi{sub 0.5}TiO{sub 3}–0.07BaTiO{sub 3} lead-free ceramics

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

Wang, Jian; Chen, Xiao-ming, E-mail: xmchen-snnu@163.com; Zhao, Xu-mei

2015-07-15

Highlights: • BiAlO{sub 3}-doped BNT-based ceramics were synthesized via a conventional solid state reaction method. • T% values are 56%, 32%, 37%, and 37% for the ceramics with x = 0, 0.01, 0.02 and 0.06, respectively. • The mean grain sizes of the ceramics with x = 0, 0.01, 0.02 and 0.06 are about 1.1, 0.9, 0.8 and 0.7 μm, respectively. • Dielectric anomalies in the ϵ{sub r}–T curves are close related to the BiAlO{sub 3} amounts. • The ceramic with x = 0.01 shows the P{sub m} of 32.5 μC/cm{sup 2}, P{sub r} of 24.1 μC/cm{sup 2}, E{sub c}more » of 20.0 kV/cm and d{sub 33} of 166 pC/N. - Abstract: (1 − x)(0.93Na{sub 0.5}Bi{sub 0.5}TiO{sub 3}–0.07BaTiO{sub 3})–xBiAlO{sub 3} (BNBT-xBA, x = 0, 0.01, 0.02, 0.06) lead-free ceramics were synthesized via a conventional solid state reaction method. Crystallite structure, microstructure, dielectric and ferroelectric properties of the BNBT–xBA ceramics were studied in detail. X-ray diffraction results show that all ceramics exhibit typical diffraction peaks of ABO{sub 3} perovskite structure. Scanning electron microscope images show that all samples have fine microstructures. Both Curie temperature and maximum dielectric constant vary with the change in the BiAlO{sub 3} amounts. The values of hysteresis loop squareness were calculated to be 1.26, 0.81, 0.51 and 0.36 for the ceramics with x = 0, 0.01, 0.02 and 0.06, respectively, indicating a decreased switching behavior of polarization. The changes in dielectric and ferroelectric properties of the ceramics are also discussed.« less

Silver-hafnium braze alloy

DOEpatents

Stephens, Jr., John J.; Hosking, F. Michael; Yost, Frederick G.

2003-12-16

A binary allow braze composition has been prepared and used in a bonded article of ceramic-ceramic and ceramic-metal materials. The braze composition comprises greater than approximately 95 wt % silver, greater than approximately 2 wt % hafnium and less than approximately 4.1 wt % hafnium, and less than approximately 0.2 wt % trace elements. The binary braze alloy is used to join a ceramic material to another ceramic material or a ceramic material, such as alumina, quartz, aluminum nitride, silicon nitride, silicon carbide, and mullite, to a metal material, such as iron-based metals, cobalt-based metals, nickel-based metals, molybdenum-based metals, tungsten-based metals, niobium-based metals, and tantalum-based metals. A hermetic bonded article is obtained with a strength greater than 10,000 psi.

Effect of Jig Design and Assessment of Stress Distribution in Testing Metal-Ceramic Adhesion.

PubMed

Özcan, Mutlu; Kojima, Alberto Noriyuki; Nishioka, Renato Sussumu; Mesquita, Alfredo Mikail Melo; Bottino, Marco Antonio; Filho, Gilberto Duarte

2016-12-01

In testing adhesion using shear bond test, a combination of shear and tensile forces occur at the interface, resulting in complex stresses. The jig designs used for this kind of test show variations in published studies, complicating direct comparison between studies. This study evaluated the effect of different jig designs on metal-ceramic bond strength and assessed the stress distribution at the interface using finite element analysis (FEA). Metal-ceramic (Metal: Ni-Cr, Wiron 99, Bego; Ceramic: Vita Omega 900, Vita) specimens (N = 36) (diameter: 4 mm, veneer thickness: 4 mm; base diameter: 5 mm, thickness: 1 mm) were fabricated and randomly divided into three groups (n = 12 per group) to be tested using one of the following jig designs: (a) chisel (CH) (ISO 11405), (b) steel strip (SS), (c) piston (PI). Metal-ceramic interfaces were loaded under shear until debonding in a universal testing machine (0.5 mm/min). Failure types were evaluated using scanning electron microscopy (SEM). FEA was used to study the stress distribution using different jigs. Metal-ceramic bond strength data (MPa) were analyzed using ANOVA and Tukey's tests (α = 0.05). The jig type significantly affected the bond results (p = 0.0001). PI type of jig presented the highest results (MPa) (p < 0.05) (58.2 ± 14.8), followed by CH (38.7 ± 7.6) and SS jig type (23.3 ± 4.2) (p < 0.05). Failure types were exclusively a combination of cohesive failure in the opaque ceramic and adhesive interface failure. FEA analysis indicated that the SS jig presented slightly more stress formation than with the CH jig. The PI jig presented small stress concentration with more homogeneous force distribution compared to the CH jig where the stress concentrated in the area where the force was applied. Metal-ceramic bond strength was affected by the jig design. Accordingly, the results of in vitro studies on metal-ceramic adhesion should be evaluated with caution. When adhesion of ceramic materials to metals is evaluated in in vitro studies, it should be noted that the loading jig type affects the results. Clinical observations should report on the location and type of ceramic fractures in metal-ceramic reconstructions so that the most relevant test method can be identified. © 2015 by the American College of Prosthodontists.

Structure and bioactivity studies of new polysiloxane-derived materials for orthopedic applications

NASA Astrophysics Data System (ADS)

Paluszkiewicz, Czesława; Gumuła, Teresa; Podporska, Joanna; Błażewicz, Marta

2006-07-01

The aim of this work was to examine the structure of new calcium silicate bioactive ceramic implant material for bone surgery applications. The bioceramic material was obtained by thermal treatment of active fillers-containing organosilicon polymer precursor. Different ceramic active fillers, namely Ca(OH) 2, CaCO 3, Na 2HPO 4 and SiO 2 powders were used. The phase composition of ceramic samples obtained by thermal transformation of active fillers containing polysiloxane was investigated. Morphology and structure of ceramic phases were characterized by means of scanning electron microscopy (SEM) with EDS point analysis, FTIR spectroscopy and XRD analysis. It was found that thermal treatment of active fillers-containing organosilicon precursor lead to the formation of wollastonite-containing ceramic material. This ceramic material showed bioactivity in 'in vitro' conditions studied by immersing the samples in simulated body fluid (SBF). The surface of wollastonite-containing ceramic before and after immersion in SBF was analysed. It can be concluded that this kind of ceramic material may be useful as bone substitute. FTIR spectroscopy is an adequate device for the determination of such derived materials structure.

Process for strengthening silicon based ceramics

DOEpatents

Kim, Hyoun-Ee; Moorhead, A. J.

1993-01-01

A process for strengthening silicon based ceramic monolithic materials and omposite materials that contain silicon based ceramic reinforcing phases that requires that the ceramic be exposed to a wet hydrogen atmosphere at about 1400.degree. C. The process results in a dense, tightly adherent silicon containing oxide layer that heals, blunts , or otherwise negates the detrimental effect of strength limiting flaws on the surface of the ceramic body.

Process for strengthening silicon based ceramics

DOEpatents

Kim, Hyoun-Ee; Moorhead, A. J.

1993-04-06

A process for strengthening silicon based ceramic monolithic materials and omposite materials that contain silicon based ceramic reinforcing phases that requires that the ceramic be exposed to a wet hydrogen atmosphere at about 1400.degree. C. The process results in a dense, tightly adherent silicon containing oxide layer that heals, blunts , or otherwise negates the detrimental effect of strength limiting flaws on the surface of the ceramic body.

Potassium Sodium Niobate-Based Lead-Free Piezoelectric Multilayer Ceramics Co-Fired with Nickel Electrodes.

PubMed

Kawada, Shinichiro; Hayashi, Hiroyuki; Ishii, Hideki; Kimura, Masahiko; Ando, Akira; Omiya, Suetake; Kubodera, Noriyuki

2015-11-03

Although lead-free piezoelectric ceramics have been extensively studied, many problems must still be overcome before they are suitable for practical use. One of the main problems is fabricating a multilayer structure, and one solution attracting growing interest is the use of lead-free multilayer piezoelectric ceramics. The paper reviews work that has been done by the authors on lead-free alkali niobate-based multilayer piezoelectric ceramics co-fired with nickel inner electrodes. Nickel inner electrodes have many advantages, such as high electromigration resistance, high interfacial strength with ceramics, and greater cost effectiveness than silver palladium inner electrodes. However, widely used lead zirconate titanate-based ceramics cannot be co-fired with nickel inner electrodes, and silver palladium inner electrodes are usually used for lead zirconate titanate-based piezoelectric ceramics. A possible alternative is lead-free ceramics co-fired with nickel inner electrodes. We have thus been developing lead-free alkali niobate-based multilayer ceramics co-fired with nickel inner electrodes. The normalized electric-field-induced thickness strain ( S max / E max ) of a representative alkali niobate-based multilayer ceramic structure with nickel inner electrodes was 360 pm/V, where S max denotes the maximum strain and E max denotes the maximum electric field. This value is about half that for the lead zirconate titanate-based ceramics that are widely used. However, a comparable value can be obtained by stacking more ceramic layers with smaller thicknesses. In the paper, the compositional design and process used to co-fire lead-free ceramics with nickel inner electrodes are introduced, and their piezoelectric properties and reliabilities are shown. Recent advances are introduced, and future development is discussed.

Potassium Sodium Niobate-Based Lead-Free Piezoelectric Multilayer Ceramics Co-Fired with Nickel Electrodes

PubMed Central

Kawada, Shinichiro; Hayashi, Hiroyuki; Ishii, Hideki; Kimura, Masahiko; Ando, Akira; Omiya, Suetake; Kubodera, Noriyuki

2015-01-01

Although lead-free piezoelectric ceramics have been extensively studied, many problems must still be overcome before they are suitable for practical use. One of the main problems is fabricating a multilayer structure, and one solution attracting growing interest is the use of lead-free multilayer piezoelectric ceramics. The paper reviews work that has been done by the authors on lead-free alkali niobate-based multilayer piezoelectric ceramics co-fired with nickel inner electrodes. Nickel inner electrodes have many advantages, such as high electromigration resistance, high interfacial strength with ceramics, and greater cost effectiveness than silver palladium inner electrodes. However, widely used lead zirconate titanate-based ceramics cannot be co-fired with nickel inner electrodes, and silver palladium inner electrodes are usually used for lead zirconate titanate-based piezoelectric ceramics. A possible alternative is lead-free ceramics co-fired with nickel inner electrodes. We have thus been developing lead-free alkali niobate-based multilayer ceramics co-fired with nickel inner electrodes. The normalized electric-field-induced thickness strain (Smax/Emax) of a representative alkali niobate-based multilayer ceramic structure with nickel inner electrodes was 360 pm/V, where Smax denotes the maximum strain and Emax denotes the maximum electric field. This value is about half that for the lead zirconate titanate-based ceramics that are widely used. However, a comparable value can be obtained by stacking more ceramic layers with smaller thicknesses. In the paper, the compositional design and process used to co-fire lead-free ceramics with nickel inner electrodes are introduced, and their piezoelectric properties and reliabilities are shown. Recent advances are introduced, and future development is discussed. PMID:28793646

Chemical and Microstructural Changes in Metallic and Ceramic Materials Exposed to Venusian Surface Conditions

NASA Technical Reports Server (NTRS)

Costa, Gustavo C. C.; Jacobson, Nathan S.; Lukco, Dorothy; Hunter, Gary W.; Nakley, Leah; Radoman-Shaw, Brandon G.; Harvey, Ralph P.

2017-01-01

The chemical and microstructural behavior of steels (304, 310, 316, and 1018), nickel-based alloys (beta-NiAl, G30, and 625), gold, coatings (4YSZ, SilcoNert(TradeMark) 1040 (SilcoTek Co.), Dursan(TradeMark)? (SilcoTek Co.), and porcelain), and bulk ceramics (alpha-Al2O3, fused quartz, beta-SiC, and alpha-Si3N4) were probed after exposure to supercritical fluid with temperature, pressure, and composition mimicking the Venus lower atmosphere. Exposures were carried out in the Glenn Extreme Environments Rig (GEER) chamber with the Venusian gas mixture (96.5% CO2, 3.5% N2, 30 ppm H2O, 150 ppm SO2, 28 ppm CO, 15 ppm OCS, 3 ppm H2S, 0.5 ppm HCl, and 5 ppb HF) at 92 bar (1330 psi) and 467 C (873 F) for durations of 10 and 42 days. An additional 21-day exposure was done to stainless steel uncoated and coated with SilcoNert(TradeMark) and Dursan(TradeMark). Samples were characterized before and after the experiment by gravimetric analysis, X-ray diffraction, X-ray photoelectron and Auger electron spectroscopies, and cross section electron microscopy analysis. All steels exposed for 10 and 42 days formed double-layered scales consisting mainly of metal (Cr, Fe, Ni) oxides and sulfides showing different chemistry, microstructure, and crystalline phases. The alloys G30 and 625 formed double-layered scales consisting mainly of nickel sulfides. After 10 days, the beta-NiAl exhibited no detectable scale, suggesting only a very thin film was formed. The 304 and 316 stainless steels coated with 4YSZ that were exposed for 10 and 42 days exhibited no significant oxidation. Steel 1018 coated with 4YSZ exhibited a corrosion scale of iron and/or chromium oxide formed at the base of the alloy. The 304 steel coated with porcelain did not exhibit corrosion, although the coating exhibited recession. SilcoNert(TradeMark) exposed for 10 and 42 days exhibited recession, although no oxidation was found to occur at the base of the alloy. Stainless steel 316 coated with Dursan(TradeMark) ? exhibited corrosion at the base of the alloy. All ceramics tested showed no clear evidence of reaction. The weight-gain-per-area performance of the materials exposed in the GEER for 10 and 42 days are reported from the lowest to the highest weight gain per area as follows: gold did not exhibit any weight change; nickel-based alloys: beta- NiAl < G30 < 625; steels: 304 < 310 < 316 < 1018; ceramics: considering the experimental uncertainties, no weight change was observed for all ceramics of this work (alpha-Al2O3, Si3N4, SiC, and amorphous SiO2).

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.

Influence of nanogold additives on phase formation, microstructure and dielectric properties of perovskite BaTiO3 ceramics

NASA Astrophysics Data System (ADS)

Nonkumwong, Jeeranan; Ananta, Supon; Srisombat, Laongnuan

2015-06-01

The formation of perovskite phase, microstructure and dielectric properties of nanogold-modified barium titanate (BaTiO3) ceramics was examined as a function of gold nanoparticle contents by employing a combination of X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray, Archimedes principle and dielectric measurement techniques. These ceramics were fabricated from a simple mixed-oxide method. The amount of gold nanoparticles was found to be one of the key factors controlling densification, grain growth and dielectric response in BaTiO3 ceramics. It was found that under suitable amount of nanogold addition (4 mol%), highly dense perovskite BaTiO3 ceramics with homogeneous microstructures of refined grains (~0.5-3.1 μm) and excellence dielectric properties can be produced.

Method of making sulfur tolerant composite cermet electrodes for solid oxide electrochemical cells

DOEpatents

Isenberg, Arnold O.

1989-01-01

An electrochemical apparatus is made containing an exterior electorde bonded to the exterior of a tubular, solid, oxygen ion conducting electrolyte where the electrolyte is also in contact with an interior electrode, said exterior electrode comprising particles of an electronic conductor contacting the electrolyte, where a ceramic metal oxide coating partially surrounds the particles and is bonded to the electrolyte, and where a coating of an ionic-electronic conductive material is attached to the ceramic metal oxide coating and to the exposed portions of the particles.

Sulfur tolerant composite cermet electrodes for solid oxide electrochemical cells

DOEpatents

Isenberg, Arnold O.

1987-01-01

An electrochemical apparatus is made containing an exterior electrode bonded to the exterior of a tubular, solid, oxygen ion conducting electrolyte where the electrolyte is also in contact with an interior electrode, said exterior electrode comprising particles of an electronic conductor contacting the electrolyte, where a ceramic metal oxide coating partially surrounds the particles and is bonded to the electrolyte, and where a coating of an ionic-electronic conductive material is attached to the ceramic metal oxide coating and to the exposed portions of the particles.

Assessment of Bracket Surface Morphology and Dimensional Change

PubMed Central

Radhakrishnan, Pillai Devu; Sapna Varma, N. K.; Ajith, V. V.

2017-01-01

Objective: The objective of this study was to compare the surface morphology and dimensional stability of the bracket slot at the onset of treatment and after 12 months of intraoral exposure. The study also compared the amount of calcium at the bracket base which indicates enamel loss among the three orthodontic brackets following debonding after 12 months of intraoral exposure. Materials and Methods: The sample consisted of 60 (0.022” MBT) canine brackets. They were divided into three groups: self-ligating, ceramic bracket with metal slot, and stainless steel (SS) brackets. The slot dimensions, micromorphologic characteristics of as-received and retrieved brackets were measured with a stereomicroscope and scanning electron microscope (SEM), respectively. The amount of calcium at the bracket base which indicates enamel damage was quantified using energy-dispersive X-ray spectrometry (EDX). Results: The results showed statistically significant alterations (P < 0.05) in the right vertical dimension, internal tie wing width (cervical), right and left depth of the slot (Kruskal–Wallis test). Multiple comparison using Mann–Whitney test showed that ceramic brackets underwent (P < 0.05) minimal alterations in the right vertical dimension, internal tie wing width (cervical), right and left depth of the slot (0.01 mm, −0.003 mm, 0.006 mm, −0.002 mm, respectively) when compared with the changes seen in SS and self-ligating brackets. SEM analysis revealed an increase in the surface roughness of ceramic with metal slot brackets and self-ligating bracket showed the least irregularity. The presence of calcium was noted on all evaluated brackets under EDX, but ceramic with metal slot brackets showed a significantly greater amount of enamel loss (P = 0.001). Conclusion: Ceramic brackets were found to be dimensionally stable when compared to SS and self-ligating. Self-ligating bracket showed minimal surface irregularity. Ceramic with metal slot brackets showed a greater amount of enamel loss following debonding. PMID:28566855

Mixed ionic and electronic conducting ceramic membranes for hydrocarbon processing

DOEpatents

Van Calcar, Pamela; Mackay, Richard; Sammells, Anthony F.

2002-01-01

The invention relates to mixed phase materials for the preparation of catalytic membranes which exhibit ionic and electronic conduction and which exhibit improved mechanical strength compared to single phase ionic and electronic conducting materials. The mixed phase materials are useful for forming gas impermeable membranes either as dense ceramic membranes or as dense thin films coated onto porous substrates. The membranes and materials of this invention are useful in catalytic membrane reactors in a variety of applications including synthesis gas production. One or more crystalline second phases are present in the mixed phase material at a level sufficient to enhance the mechanical strength of the mixture to provide membranes for practical application in CMRs.

Phase transformation in multiferroic Bi5Ti3FeO15 ceramics by temperature-dependent ellipsometric and Raman spectra: An interband electronic transition evidence

NASA Astrophysics Data System (ADS)

Jiang, P. P.; Duan, Z. H.; Xu, L. P.; Zhang, X. L.; Li, Y. W.; Hu, Z. G.; Chu, J. H.

2014-02-01

Thermal evolution and an intermediate phase between ferroelectric orthorhombic and paraelectric tetragonal phase of multiferroic Bi5Ti3FeO15 ceramic have been investigated by temperature-dependent spectroscopic ellipsometry and Raman scattering. Dielectric functions and interband transitions extracted from the standard critical-point model show two dramatic anomalies in the temperature range of 200-873 K. It was found that the anomalous temperature dependence of electronic transition energies and Raman mode frequencies around 800 K can be ascribed to intermediate phase transformation. Moreover, the disappearance of electronic transition around 3 eV at 590 K is associated with the conductive property.

Bioactivity and cell proliferation in radiopaque gel-derived CaO-P2O5-SiO2-ZrO2 glass and glass-ceramic powders.

PubMed

Montazerian, Maziar; Yekta, Bijan Eftekhari; Marghussian, Vahak Kaspari; Bellani, Caroline Faria; Siqueira, Renato Luiz; Zanotto, Edgar Dutra

2015-10-01

In this study, 10 mol% ZrO2 was added to a 27CaO-5P2O5-68SiO2 (mol%) base composition synthesized via a simple sol-gel method. This composition is similar to that of a frequently investigated bioactive gel-glass. The effects of ZrO2 on the in vitro bioactivity and MG-63 cell proliferation of the glass and its derivative polycrystalline (glass-ceramic) powder were investigated. The samples were characterized using thermo-gravimetric and differential thermal analysis (TG/DTA), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) coupled to energy dispersive X-ray spectroscopy (EDS). Release of Si, Ca, P and Zr into simulated body fluid (SBF) was determined by inductively coupled plasma (ICP). Upon heat treatment at 1000 °C, the glass powder crystallized into an apatite-wollastonite-zirconia glass-ceramic powder. Hydroxycarbonate apatite (HCA) formation on the surface of the glass and glass-ceramic particles containing ZrO2 was confirmed by FTIR and SEM. Addition of ZrO2 to the base glass composition decreased the rate of HCA formation in vitro from one day to three days, and hence, ZrO2 could be employed to control the rate of apatite formation. However, the rate of HCA formation on the glass-ceramic powder containing ZrO2 crystal was equal to that in the base glassy powder. Tests with a cultured human osteoblast-like MG-63 cells revealed that the glass and glass-ceramic materials stimulated cell proliferation, indicating that they are biocompatible and are not cytotoxic in vitro. Moreover, zirconia clearly increased osteoblast proliferation over that of the Zr-free samples. This increase is likely associated with the lower solubility of these samples and, consequently, a smaller variation in the media pH. Despite the low solubility of these materials, bioactivity was maintained, indicating that these glassy and polycrystalline powders are potential candidates for bone graft substitutes and bone cements with the special feature of radiopacity. Copyright © 2015 Elsevier B.V. All rights reserved.

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

Matsuoka, T., E-mail: ta-matsuoka@mg.ngkntk.co.jp; Kozuka, H.; Kitamura, K.

A (K,Na)NbO₃-based lead-free piezoelectric ceramic was successfully densified. It exhibited an enhanced electromechanical coupling factor of kₚ=0.52, a piezoelectric constant d₃₃=252 pC/N, and a frequency constant Nₚ=3170 Hz m because of the incorporation of an elaborate secondary phase composed primarily of KTiNbO₅. The ceramic's nominal composition was 0.92K₀.₄₂Na₀.₄₄Ca₀.₀₄Li₀.₀₂Nb₀.₈₅O₃–0.047K₀.₈₅Ti₀.₈₅Nb₁.₁₅O₅–0.023BaZrO₃ –0.0017Co₃O₄–0.002Fe₂O₃–0.005ZnO, abbreviated herein as KNN–NTK composite. The KNN–NTK ceramic exhibited a dense microstructure with few microvoids which significantly degraded its piezoelectric properties. Elemental maps recorded using transmission electron microscopy with energy-dispersive X-ray spectroscopy (TEM–EDS) revealed regions of high concentrations of Co and Zn inside the NTK phase. In addition, X-ray diffraction patternsmore » confirmed that a small portion of the NTK phase was converted into K₂(Ti,Nb,Co,Zn)₆O₁₃ or CoZnTiO₄ by a possible reaction between Co and Zn solutes and the NTK phase during a programmed sintering schedule. TEM studies also clarified a distortion around the KNN/NTK interfaces. Such an NTK phase filled voids between KNN particles, resulting in an improved chemical stability of the KNN ceramic. The manufacturing process was subsequently scaled to 100 kg per batch for granulated ceramic powder using a spray-drying technique. The properties of the KNN–NTK composite ceramic produced using the scaled-up method were confirmed to be identical to those of the ceramic prepared by conventional solid-state reaction sintering. Consequently, slight changes in the NTK phase composition and the distortion around the KNN/NTK interfaces affected the KNN–NTK composite ceramic's piezoelectric characteristics.« less

TEM Analysis of Diffusion-Bonded Silicon Carbide Ceramics Joined Using Metallic Interlayers

NASA Technical Reports Server (NTRS)

Ozaki, T.; Hasegawa, Y.; Tsuda, H.; Mori, S.; Halbig, M. C.; Asthana, R.; Singh, M.

2017-01-01

SiC fiber-bonded ceramics (SA-Tyrannohex: SA-THX) diffusion-bonded with TiCu metallic interlayers were investigated. Thin samples of the ceramics were prepared with a focused ion beam (FIB) and the interfacial microstructure of the prepared samples was studied by transmission electron microscopy (TEM) and scanning TEM (STEM). In addition to conventional microstructure observation, for detailed analysis of reaction compounds in diffusion-bonded area, we performed STEM-EDS measurements and selected area electron diffraction (SAD) experiments. The TEM and STEM experiments revealed the diffusion-bonded area was composed of only one reaction layer, which was characterized by TiC precipitates in Cu-Si compound matrix. This reaction layer was in good contact with the SA-THX substrates, and it is concluded that the joint structure led to the excellent bonding strength.

Process for strengthening aluminum based ceramics and material

DOEpatents

Moorhead, Arthur J.; Kim, Hyoun-Ee

2000-01-01

A process for strengthening aluminum based ceramics is provided. A gaseous atmosphere consisting essentially of silicon monoxide gas is formed by exposing a source of silicon to an atmosphere consisting essentially of hydrogen and a sufficient amount of water vapor. The aluminum based ceramic is exposed to the gaseous silicon monoxide atmosphere for a period of time and at a temperature sufficient to produce a continuous, stable silicon-containing film on the surface of the aluminum based ceramic that increases the strength of the ceramic.

Practical colloidal processing of multication ceramics

DOE PAGES

Bell, Nelson S.; Monson, Todd C.; Diantonio, Christopher; ...

2015-09-07

The use of colloidal processing principles in the formation of ceramic materials is well appreciated for developing homogeneous material properties in sintered products, enabling novel forming techniques for porous ceramics or 3D printing, and controlling microstructure to enable optimized material properties. The solution processing of electronic ceramic materials often involves multiple cationic elements or dopants to affect microstructure and properties. Material stability must be considered through the steps of colloidal processing to optimize desired component properties. This review provides strategies for preventing material degradation in particle synthesis, milling processes, and dispersion, with case studies of consolidation using spark plasma sinteringmore » of these systems. The prevention of multication corrosion in colloidal dispersions can be achieved by utilizing conditions similar to the synthesis environment or by the development of surface passivation layers. The choice of dispersing surfactants can be related to these surface states, which are of special importance for nanoparticle systems. A survey of dispersant chemistries related to some common synthesis conditions is provided for perovskite systems as an example. Furthermore, these principles can be applied to many colloidal systems related to electronic and optical applications.« less

Packaging Technologies for 500C SiC Electronics and Sensors

NASA Technical Reports Server (NTRS)

Chen, Liang-Yu

2013-01-01

Various SiC electronics and sensors are currently under development for applications in 500C high temperature environments such as hot sections of aerospace engines and the surface of Venus. In order to conduct long-term test and eventually commercialize these SiC devices, compatible packaging technologies for the SiC electronics and sensors are required. This presentation reviews packaging technologies developed for 500C SiC electronics and sensors to address both component and subsystem level packaging needs for high temperature environments. The packaging system for high temperature SiC electronics includes ceramic chip-level packages, ceramic printed circuit boards (PCBs), and edge-connectors. High temperature durable die-attach and precious metal wire-bonding are used in the chip-level packaging process. A high temperature sensor package is specifically designed to address high temperature micro-fabricated capacitive pressure sensors for high differential pressure environments. This presentation describes development of these electronics and sensor packaging technologies, including some testing results of SiC electronics and capacitive pressure sensors using these packaging technologies.

Temperature and energy effects on secondary electron emission from SiC ceramics induced by Xe17+ ions.

PubMed

Zeng, Lixia; Zhou, Xianming; Cheng, Rui; Wang, Xing; Ren, Jieru; Lei, Yu; Ma, Lidong; Zhao, Yongtao; Zhang, Xiaoan; Xu, Zhongfeng

2017-07-25

Secondary electron emission yield from the surface of SiC ceramics induced by Xe 17+ ions has been measured as a function of target temperature and incident energy. In the temperature range of 463-659 K, the total yield gradually decreases with increasing target temperature. The decrease is about 57% for 3.2 MeV Xe 17+ impact, and about 62% for 4.0 MeV Xe 17+ impact, which is much larger than the decrease observed previously for ion impact at low charged states. The yield dependence on the temperature is discussed in terms of work function, because both kinetic electron emission and potential electron emission are influenced by work function. In addition, our experimental data show that the total electron yield gradually increases with the kinetic energy of projectile, when the target is at a constant temperature higher than room temperature. This result can be explained by electronic stopping power which plays an important role in kinetic electron emission.

Photocatalysis-assisted water filtration: using TiO2-coated vertically aligned multi-walled carbon nanotube array for removal of Escherichia coli O157:H7.

PubMed

Oza, Goldie; Pandey, Sunil; Gupta, Arvind; Shinde, Sachin; Mewada, Ashmi; Jagadale, Pravin; Sharon, Maheshwar; Sharon, Madhuri

2013-10-01

A porous ceramic was coated with vertically aligned multi-walled carbon nanotubes (MWCNTs) by spray pyrolysis. Titanium dioxide (TiO2) nanoparticles were then coated onto this densely aligned MWCNT. The presence of TiO2/MWCNT interfacial arrays was confirmed by X-ray diffraction (XRD), scanning electron microscope-energy dispersive analysis of X-ray (SEM-EDAX) and transmission electron microscope (TEM). This is a novel report in which water loaded with a most dreadful enterohemorrhagic pathogenic strain of Escherichia coli O157:H7 was filtered through TiO2/MWCNT coated porous ceramic filter and then analysed. Bacterial removal performance was found to be significantly lower in control i.e. plain porous ceramic (P<0.05) as compared to TiO2/MWCNT coated ceramic. The photocatalytic killing rate constant for TiO2-ceramic and MWCNT/TiO2-ceramic under fluorescent light was found be 1.45×10(-2) min(-1) and 2.23×10(-2) min(-1) respectively. Further, when I-V characteristics were performed for TiO2/MWCNT composite, it was corroborated that the current under light irradiation is comparatively higher than that in dark, thus proving it to be photocatalytically efficient system. The enhanced photocatalysis may be a contribution of increased surface area and charge transfer rate as a consequence of aligned MWCNT network. © 2013 Elsevier B.V. All rights reserved.

The influence of crystallised Fe3O4 on the magnetic properties of coprecipitation-derived ferrimagnetic glass-ceramics.

PubMed

Bretcanu, O; Spriano, S; Verné, E; Cöisson, M; Tiberto, P; Allia, P

2005-07-01

Ferrimagnetic glass-ceramics are potential candidates for magnetic induction hyperthermia, which is one form of inducing deep-regional hyperthermia, by using a magnetic field. The aim of this work was to analyse the influence of the amount of crystallised magnetite on the magnetic properties of glass-ceramic samples. Thus, two different ferrimagnetic glass-ceramics with the composition of the system Na(2)O-CaO-SiO(2)-P(2)O(5)-FeO-Fe(2)O(3) were prepared by melting at 1500 degrees C for 30 min of the coprecipitation-derived starting products. The X-ray diffraction patterns show the presence of nanometric magnetite crystals in a glassy matrix after cooling from melting temperature. The estimated amount of crystallised magnetite varies between 20 and 45 wt.%, as a function of the chemical composition. The morphology of the crystals was studied by scanning electron micrography and transmission electron micrography. Glass transition temperature and thermal stability were investigated by differential thermal analysis. Magnetic hysteresis cycles were analysed using a vibrating sample magnetometer with a maximum applied field of 17 kOe, at room temperature, in quasi-static conditions. Calorimetric measurements were carried out using a magnetic induction furnace. The power losses estimated from calorimetric measurements under a magnetic field of 40 kA/m and 440 kHz are 65 W/g for the glass-ceramic with lower iron oxides content and 25 W/g for the glass-ceramic with higher iron oxide content.

Characterization of 3D interconnected microstructural network in mixed ionic and electronic conducting ceramic composites

NASA Astrophysics Data System (ADS)

Harris, William M.; Brinkman, Kyle S.; Lin, Ye; Su, Dong; Cocco, Alex P.; Nakajo, Arata; Degostin, Matthew B.; Chen-Wiegart, Yu-Chen Karen; Wang, Jun; Chen, Fanglin; Chu, Yong S.; Chiu, Wilson K. S.

2014-04-01

The microstructure and connectivity of the ionic and electronic conductive phases in composite ceramic membranes are directly related to device performance. Transmission electron microscopy (TEM) including chemical mapping combined with X-ray nanotomography (XNT) have been used to characterize the composition and 3-D microstructure of a MIEC composite model system consisting of a Ce0.8Gd0.2O2 (GDC) oxygen ion conductive phase and a CoFe2O4 (CFO) electronic conductive phase. The microstructural data is discussed, including the composition and distribution of an emergent phase which takes the form of isolated and distinct regions. Performance implications are considered with regards to the design of new material systems which evolve under non-equilibrium operating conditions.The microstructure and connectivity of the ionic and electronic conductive phases in composite ceramic membranes are directly related to device performance. Transmission electron microscopy (TEM) including chemical mapping combined with X-ray nanotomography (XNT) have been used to characterize the composition and 3-D microstructure of a MIEC composite model system consisting of a Ce0.8Gd0.2O2 (GDC) oxygen ion conductive phase and a CoFe2O4 (CFO) electronic conductive phase. The microstructural data is discussed, including the composition and distribution of an emergent phase which takes the form of isolated and distinct regions. Performance implications are considered with regards to the design of new material systems which evolve under non-equilibrium operating conditions. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr06684c

Method for producing chemically bonded phosphate ceramics and for stabilizing contaminants encapsulated therein utilizing reducing agents

DOEpatents

Singh, Dileep; Wagh, Arun S.; Jeong, Seung-Young

2000-01-01

Known phosphate ceramic formulations are improved and the ability to produce iron-based phosphate ceramic systems is enabled by the addition of an oxidizing or reducing step during the acid-base reactions that form the phosphate ceramic products. The additives allow control of the rate of the acid-base reactions and concomitant heat generation. In an alternate embodiment, waste containing metal anions are stabilized in phosphate ceramic products by the addition of a reducing agent to the phosphate ceramic mixture. The reduced metal ions are more stable and/or reactive with the phosphate ions, resulting in the formation of insoluble metal species within the phosphate ceramic matrix, such that the resulting chemically bonded phosphate ceramic product has greater leach resistance.

Gamma radiation in ceramic capacitors: a study for space missions

NASA Astrophysics Data System (ADS)

dos Santos Ferreira, Eduardo; Sarango Souza, Juliana

2017-10-01

We studied the real time effects of the gamma radiation in ceramic capacitors, in order to evaluate the effects of cosmic radiation on these devices. Space missions have electronic circuits with various types of devices, many studies have been done on semiconductor devices exposed to gamma radiation, but almost no studies for passive components, in particular ceramic capacitors. Commercially sold ceramic capacitors were exposed to gamma radiation, and the capacitance was measured before and after exposure. The results clearly show that the capacitance decreases with exposure to gamma radiation. We confirmed this observation in a real time capacitance measurement, obtained using a data logging system developed by us using the open source Arduino platform.

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.

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.

Metal/ceramic interface structures and segregation behavior in aluminum-based composites

DOE PAGES

Zhang, Xinming; Hu, Tao; Rufner, Jorgen F.; ...

2015-06-14

Trimodal Al alloy (AA) matrix composites consisting of ultrafine-­grained (UFG) and coarse-­ grained (CG) Al phases and micron-­sized B 4C ceramic reinforcement particles exhibit combinations of strength and ductility that render them useful for potential applications in the aerospace, defense and automotive industries. Tailoring of microstructures with specific mechanical properties requires a detailed understanding of interfacial structures to enable strong interface bonding between ceramic reinforcement and metal matrix, and thereby allow for effective load transfer. Trimodal AA metal matrix composites typically show three characteristics that are noteworthy: nanocrystalline grains in the vicinity of the B4C reinforcement particles; Mg segregation atmore » AA/B 4C interfaces; and the presence of amorphous interfacial layers separating nanocrystalline grains from B 4C particles. Interestingly, however, fundamental information related to the mechanisms responsible for these characteristics as well as information on local compositions and phases are absent in the current literature. Here in this study, we use high-­resolution transmission electron microscopy, energy-­dispersive X-­ray spectroscopy, electron energy-­loss spectroscopy, and precession assisted electron diffraction to gain fundamental insight into the mechanisms that affect the characteristics of AA/B 4C interfaces. Specifically, we determined interfacial structures, local composition and spatial distribution of the interfacial constituents. Near atomic resolution characterization revealed amorphous multilayers and a nanocrystalline region between Al phase and B 4C reinforcement particles. The amorphous multilayers consist of nonstoichiometric Al xO y, while the nanocrystalline region is comprised of MgO nanograins. The experimental results are discussed in terms of the possible underlying mechanisms at AA/B 4C interfaces.« less

[Study on friction and wear properties of dental zirconia ceramics processed by microwave and conventional sintering methods].

PubMed

Guoxin, Hu; Ying, Yang; Yuemei, Jiang; Wenjing, Xia

2017-04-01

This study evaluated the wear of an antagonist and friction and wear properties of dental zirconia ceramic that was subjected to microwave and conventional sintering methods. Ten specimens were fabricated from Lava brand zirconia and randomly assigned to microwave and conventional sintering groups. A profile tester for surface roughness was used to measure roughness of the specimens. Wear test was performed, and steatite ceramic was used as antagonist. Friction coefficient curves were recorded, and wear volume were calculated. Finally, optical microscope was used to observe the surface morphology of zirconia and steatite ceramics. Field emission scanning electron microscopy was used to observe the microstructure of zirconia. Wear volumes of microwave and conventionally sintered zirconia were (6.940±1.382)×10⁻², (7.952±1.815) ×10⁻² mm³, respectively. Moreover, wear volumes of antagonist after sintering by the considered methods were (14.189±4.745)×10⁻², (15.813±3.481)×10⁻² mm³, correspondingly. Statistically significant difference was not observed in the wear resistance of zirconia and wear volume of steatite ceramic upon exposure to two kinds of sintering methods. Optical microscopy showed that ploughed surfaces were apparent in zirconia. The wear surface of steatite ceramic against had craze, accompanied by plough. Scanning electron microscopy showed that zirconia was sintered compactly when subjected to both conventional sintering and microwave methods, whereas grains of zirconia sintered by microwave alone were smaller and more uniform. Two kinds of sintering methods are successfully used to produce dental zirconia ceramics with similar friction and wear properties.
.

Additive colours approach for dental ceramics translucency characteristics made from Sumatra and Java natural sands

NASA Astrophysics Data System (ADS)

Takarini, V.; Gunawan, J.; Hasratiningsih, Z.; Rudyawan, A.

2018-04-01

Translucency is one of dental ceramics desirable aesthetic characteristics, which can be used as an indirect restoration. Dental ceramics can also be made using Computed Aided Design/Computer Aided Manufacturing (CAD/CAM) unit that can create variety blocks as an ingot into a customized restoration. This paper presents the results of self-synthesized porcelain blocks generated from natural sand of Sumatera and Java Islands to promote national independency. This research aims to determine the translucency of dental ceramics made from Indonesia’s natural sand. Six samples each of two different synthesized temperatures, 1150 °C and 1200 °C, were made. To analyse translucency of the sample, their image was taken in bright light background in a black box, then additive green and blue colours histogram channel with range 0 (opaque) to 255 (transparent) were evaluated using Matlab R2015B. The result revealed that mean of green peaks on 1150 °C has an average translucency value of 41%, compared to 34% of blue peaks. Lower percentage of translucency, 31% and 25% on the green and blue channel respectively were attained in samples synthesized in 1200 °C. These suggest that 1150 °C is the optimum temperature for translucency for these ceramic samples from natural sands as they contain leucite crystals shown by the XRD analyses as a result of silica-undersaturated mixture indicated by the Electron Dispersive Spectroscopy. SEM (Scanning Electron Microscope) results show remnant of air pocket in the samples sintered at higher temperature.In conclusion, natural sand from Sumatera and Java can be considered as reliable, cheap basic material options in developing self-synthesized dental ceramics with a desirable translucency. These preliminary results indicate that better balance between strength and translucency could potentially be achieved by making nano-sized dental ceramics.

Effect of an internal coating technique on tensile bond strengths of resin cements to zirconia ceramics.

PubMed

Kitayama, Shuzo; Nikaido, Toru; Maruoka, Rena; Zhu, Lei; Ikeda, Masaomi; Watanabe, Akihiko; Foxton, Richard M; Miura, Hiroyuki; Tagami, Junji

2009-07-01

This study was conducted to enhance the tensile bond strengths of resin cements to zirconia ceramics. Fifty-six zirconia ceramic specimens (Cercon Base) and twenty-eight silica-based ceramic specimens (GN-1, GN-1 Ceramic Block) were air-abraded using alumina. Thereafter, the zirconia ceramic specimens were divided into two subgroups of 28 each according to the surface pretreatment; no pretreatment (Zr); and the internal coating technique (INT). For INT, the surface of zirconia was coated by fusing silica-based ceramics (Cercon Ceram Kiss). Ceramic surfaces were conditioned with/without a silane coupling agent followed by bonding with one of two resin cements; Panavia F 2.0 (PF) and Superbond C&B (SB). After 24 hours storage in water, the tensile bond strengths were tested (n=7). For both PF and SB, silanization significantly improved the bond strength to GN-1 and INT (p<0.05). The INT coating followed by silanizaton demonstrated enhancement of bonding to zirconia ceramics.

Effect of ceramic thickness and composite bases on stress distribution of inlays--a finite element analysis.

PubMed

Durand, Letícia Brandão; Guimarães, Jackeline Coutinho; Monteiro Junior, Sylvio; Baratieri, Luiz Narciso

2015-01-01

The purpose of this study was to determine the effect of cavity depth, ceramic thickness, and resin bases with different elastic modulus on von Mises stress patterns of ceramic inlays. Tridimensional geometric models were developed with SolidWorks image software. The differences between the models were: depth of pulpal wall, ceramic thickness, and presence of composite bases with different thickness and elastic modulus. The geometric models were constrained at the proximal surfaces and base of maxillary bone. A load of 100 N was applied. The stress distribution pattern was analyzed with von Mises stress diagrams. The maximum von Mises stress values ranged from 176 MPa to 263 MPa and varied among the 3D-models. The highest von Mises stress value was found on models with 1-mm-thick composite resin base and 1-mm-thick ceramic inlay. Intermediate values (249-250 MPa) occurred on models with 2-mm-thick composite resin base and 1-mm-thick ceramic inlay and 1-mm-thick composite resin base and 2-mm-thick ceramic inlay. The lowest values were observed on models restored exclusively with ceramic inlay (176 MPa to 182 MPa). It was found that thicker inlays distribute stress more favorably and bases with low elastic modulus increase stress concentrations on the internal surface of the ceramic inlay. The increase of ceramic thickness tends to present more favorable stress distribution, especially when bonded directly onto the cavity without the use of supporting materials. When the use of a composite base is required, composite resin with high elastic modulus and reduced thickness should be preferred.

Joining and Integration of Silicon Nitride Ceramics for Aerospace and Energy Systems

NASA Technical Reports Server (NTRS)

Singh, M.; Asthana, R.

2009-01-01

Light-weight, creep-resistant silicon nitride ceramics possess excellent high-temperature strength and are projected to significantly raise engine efficiency and performance when used as turbine components in the next-generation turbo-shaft engines without the extensive cooling that is needed for metallic parts. One key aspect of Si3N4 utilization in such applications is its joining response to diverse materials. In an ongoing research program, the joining and integration of Si3N4 ceramics with metallic, ceramic, and composite materials using braze interlayers with the liquidus temperature in the range 750-1240C is being explored. In this paper, the self-joining behavior of Kyocera Si3N4 and St. Gobain Si3N4 using a ductile Cu-based active braze (Cu-ABA) containing Ti will be presented. Joint microstructure, composition, hardness, and strength as revealed by optical microscopy, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), Knoop microhardness test, and offset compression shear test will be presented. Additionally, microstructure, composition, and joint strength of Si3N4/Inconel 625 joints made using Cu-ABA, will be presented. The results will be discussed with reference to the role of chemical reactions, wetting behavior, and residual stresses in joints.

Synthesis and acid digestion of biomorphic ceramics: determination of alkaline and alkaline earth ions.

PubMed

Bosch Ojeda, Catalina; Sánchez Rojas, Fuensanta; Cano Pavón, José Manuel

2007-09-01

Ceramic and glass are some of the more recent engineering materials and those that are most resistant to environmental conditions. They belong to advanced materials in that they are being developed for the aerospace and electronics industries. In the last decade, a new class of ceramic materials has been the focus of particular attention. The materials were produced with natural, renewable resources (wood or wood-based products). In this work, we have synthesised a new biomorphic ceramic material from oak wood and Si infiltration. After the material characterization, we have optimized the dissolution of the sample by acid attack in an oven under microwave irradiation. Experimental designs were used as a multivariate strategy for the evaluation of the effects of varying several variables at the same time. The optimization was performed in two steps using factorial design for preliminary evaluation and a Draper-Lin design for determination of the critical experimental conditions. Five variables (time, power, volume of HNO3, volume H2SO4 and volume of HF) were considered as factors and as a response the concentration of different metal ions in the optimization process. Interactions between analytical factors and their optimal levels were investigated using a Draper-Lin design.

Interfacial characterization of ceramic core materials with veneering porcelain for all-ceramic bi-layered restorative systems.

PubMed

Tagmatarchis, Alexander; Tripodakis, Aris-Petros; Filippatos, Gerasimos; Zinelis, Spiros; Eliades, George

2014-01-01

The aim of the study was to characterize the elemental distribution at the interface between all-ceramic core and veneering porcelain materials. Three groups of all-ceramic cores were selected: A) Glass-ceramics (Cergo, IPS Empress, IPS Empress 2, e-max Press, Finesse); B) Glass-infiltrated ceramics (Celay Alumina, Celay Zirconia) and C) Densely sintered ceramics (Cercon, Procera Alumina, ZirCAD, Noritake Zirconia). The cores were combined with compatible veneering porcelains and three flat square test specimens were produced for each system. The core-veneer interfaces were examined by scanning electron microscopy and energy dispersive x-ray microanalysis. The glass-ceramic systems showed interfacial zones reach in Si and O, with the presence of K, Ca, Al in core and Ca, Ce, Na, Mg or Al in veneer material, depending on the system tested. IPS Empress and IPS Empress 2 demonstrated distinct transitional phases at the core-veneer interface. In the glassinfiltrated systems, intermixing of core (Ce, La) with veneer (Na, Si) elements occurred, whereas an abrupt drop of the core-veneer elemental concentration was documented at the interfaces of all densely sintered ceramics. The results of the study provided no evidence of elemental interdiffusion at the core-veneer interfaces in densely sintered ceramics, which implies lack of primary chemical bonding. For the glass-containing systems (glassceramics and glass-infiltrated ceramics) interdiffusion of the glass-phase seems to play a critical role in establishing a primary bonding condition between ceramic core and veneering porcelain.

Ceramic debris in hip prosthesis: correlation between synovial fluid and joint capsule.

PubMed

De Pasquale, Dalila; Stea, Susanna; Beraudi, Alina; Montesi, Monica; Squarzoni, Stefano; Toni, Aldo

2013-05-01

Detection of ceramic particles in synovial fluids allows early diagnosis of ceramic damage, but there is no evidence of a relationship between ceramic debris in the articular space and in the joint capsule. The aim of the present study is to verify if the particles isolated in the synovial fluid are comparable with those stored in the capsular tissue. Twenty-one patients were enrolled. Both synovial fluid and capsular samples were collected during revision surgery and ceramic particles were isolated and analyzed by scanning electron microscopy and energy-dispersive X-ray microanalysis. It resulted a significant correlation between the samples couples (18 out of 21). This study confirms that the synovial fluid analysis can give a clear definition of the presence of particles in the joint capsule. Copyright © 2013 Elsevier Inc. All rights reserved.

Thermal barrier coating life prediction model development, phase 2

NASA Technical Reports Server (NTRS)

Meier, Susan Manning; Sheffler, Keith D.; Nissley, David M.

1991-01-01

The objective of this program was to generate a life prediction model for electron-beam-physical vapor deposited (EB-PVD) zirconia thermal barrier coating (TBC) on gas turbine engine components. Specific activities involved in development of the EB-PVD life prediction model included measurement of EB-PVD ceramic physical and mechanical properties and adherence strength, measurement of the thermally grown oxide (TGO) growth kinetics, generation of quantitative cyclic thermal spallation life data, and development of a spallation life prediction model. Life data useful for model development was obtained by exposing instrumented, EB-PVD ceramic coated cylindrical specimens in a jet fueled burner rig. Monotonic compression and tensile mechanical tests and physical property tests were conducted to obtain the EB-PVD ceramic behavior required for burner rig specimen analysis. As part of that effort, a nonlinear constitutive model was developed for the EB-PVD ceramic. Spallation failure of the EB-PVD TBC system consistently occurred at the TGO-metal interface. Calculated out-of-plane stresses were a small fraction of that required to statically fail the TGO. Thus, EB-PVD spallation was attributed to the interfacial cracking caused by in-plane TGO strains. Since TGO mechanical properties were not measured in this program, calculation of the burner rig specimen TGO in-plane strains was performed by using alumina properties. A life model based on maximum in-plane TGO tensile mechanical strain and TGO thickness correlated the burner rig specimen EB-PVD ceramic spallation lives within a factor of about plus or minus 2X.

Ceramic thermal barrier coatings for commercial gas turbine engines

NASA Technical Reports Server (NTRS)

Meier, Susan Manning; Gupta, Dinesh K.; Sheffler, Keith D.

1991-01-01

The paper provides an overview of the short history, current status, and future prospects of ceramic thermal barrier coatings for gas turbine engines. Particular attention is given to plasma-sprayed and electron beam-physical vapor deposited yttria-stabilized (7 wt pct Y2O3) zirconia systems. Recent advances include improvements in the spallation life of thermal barrier coatings, improved bond coat composition and spraying techniques, and improved component design. The discussion also covers field experience, life prediction modeling, and future directions in ceramic coatings in relation to gas turbine engine design.

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.

Geopolymers for Structural Ceramic Applications

DTIC Science & Technology

2006-08-31

Applications of geopolymers have included ceramic matrix composites ,ŕ, 3 waste encapsulation 9-11and alternative cements.7,12,14 As adhesives... compositions of the geopolymer adhesive interfaces were studied with scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). Durable...after thermal shock testing. In response, chopped-fiber reinforced geopolymer composites were processed as possible candidate mold materials for casting

Surface reactivity and hydroxyapatite formation on Ca5MgSi3O12 ceramics in simulated body fluid

NASA Astrophysics Data System (ADS)

Xu, Jian; Wang, Yaorong; Huang, Yanlin; Cheng, Han; Seo, Hyo Jin

2017-11-01

In this work, the new calcium-magnesium-silicate Ca5MgSi3O12 ceramic was made via traditional solid-state reaction. The bioactivities were investigated by immerging the as-made ceramics in simulated body fluid (SBF) for different time at body temperature (37 °C). Then the samples were taken to measure X-ray powder diffraction (XRD), Scanning electron microscopy (SEM), X-ray energy-dispersive spectra (EDS), and Fourier transform infrared spectroscopy (FT-IR) measurements. The bone-like hydroxyapatite nanoparticles formation was observed on the ceramic surfaces after the immersion in SBF solutions. Ca5MgSi3O12 ceramics possess the Young's modulus and the bending strength and of 96.3 ± 1.2 GPa and 98.7 ± 2.3 MPa, respectively. The data suggest that Ca5MgSi3O12 ceramics can quickly induce HA new layers after soaking in SBF. Ca5MgSi3O12 ceramics are potential to be used as biomaterials for bone-tissue repair. The cell adherence and proliferation experiments are conducted confirming the reliability of the ceramics as a potential candidate.

Scanning and Transmission Electron Microscopy of High Temperature Materials

NASA Technical Reports Server (NTRS)

1994-01-01

Software and hardware updates to further extend the capability of the electron microscope were carried out. A range of materials such as intermetallics, metal-matrix composites, ceramic-matrix composites, ceramics and intermetallic compounds, based on refractory elements were examined under this research. Crystal structure, size, shape and volume fraction distribution of various phases which constitute the microstructures were examined. Deformed materials were studied to understand the effect of interfacial microstructure on the deformation and fracture behavior of these materials. Specimens tested for a range of mechanical property requirements, such as stress rupture, creep, low cycle fatigue, high cycle fatigue, thermomechanical fatigue, etc. were examined. Microstructural and microchemical stability of these materials exposed to simulated operating environments were investigated. The EOIM Shuttle post-flight samples were also examined to understand the influence of low gravity processing on microstructure. In addition, fractographic analyses of Nb-Zr-W, titanium aluminide, molybdenum silicide and silicon carbide samples were carried out. Extensive characterization of sapphire fibers in the fiber-reinforced composites made by powder cloth processing was made. Finally, pressure infiltration casting of metal-matrix composites was carried out.

Microstructural Analysis and Transport Properties of Thermally Sprayed Multiple-Layer Ceramic Coatings

NASA Astrophysics Data System (ADS)

Wang, Hsin; Muralidharan, Govindarajan; Leonard, Donovan N.; Haynes, J. Allen; Porter, Wallace D.; England, Roger D.; Hays, Michael; Dwivedi, Gopal; Sampath, Sanjay

2018-02-01

Multilayer, graded ceramic/metal coatings were prepared by an air plasma spray method on Ti-6Al-4V, 4140 steel and graphite substrates. The coatings were designed to provide thermal barriers for diesel engine pistons to operate at higher temperatures with improved thermal efficiency and cleaner emissions. A systematic, progressive variation in the mixture of yttria-stabilized zirconia and bondcoat alloys (NiCoCrAlYHfSi) was designed to provide better thermal expansion match with the substrate and to improve thermal shock resistance and cycle life. Heat transfer through the layers was evaluated by a flash diffusivity technique based on a model of one-dimensional heat flow. The aging effect of the as-sprayed coatings was captured during diffusivity measurements, which included one heating and cooling cycle. The hysteresis of thermal diffusivity due to aging was not observed after 100-h annealing at 800 °C. The measurements of coatings on substrate and freestanding coatings allowed the influence of interface resistance to be evaluated. The microstructure of the multilayer coating was examined using scanning electron microscope and electron probe microanalysis.

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

NASA Astrophysics Data System (ADS)

Wang, Mao-Hua; Ma, Xiao-Yu; Zhang, Bo; Zhou, Fu

2014-11-01

CaCu3Ti4O12 (CCTO) powders coated with carbon were synthesized by using a high-energy ball milling method. The obtained samples were characterized by x-ray diffraction, transmission electron microscopy and scanning electron microscopy. The carbon-coated CCTO particles had a rough surface, which resulted from the growth of the carbon coating on the CCTO particles. It was found that the CCTO phase was observed as the major phase and no reaction occurred between the carbon and CCTO during the sintering process. The grain size of the CCTO ceramics decreased with the increase in carbon content, which indicated that carbon inhibits grain growth of CCTO ceramics. Specially, the dielectric constant decreased with the increase in carbon content. And CCTO1 ceramic (mass ratio of CCTO: carbon = 10:1) showed a lower dielectric constant (3.74 × 104), with the dielectric loss value (0.04) much lower than that of CCTO at 20°C (10 k Hz).

Synthesis and microstructural TEM investigation of CaCu 3Ru 4O 12 ceramic and thin film

NASA Astrophysics Data System (ADS)

Brizé, Virginie; Autret-Lambert, Cécile; Wolfman, Jérôme; Gervais, Monique; Gervais, François

2011-10-01

CaCu 3Ru 4O 12 (CCRO) is a conductive oxide having the same structure as CaCu 3Ti 4O 12 (CCTO) and close lattice parameters. The later compound is strongly considered for high density parallel plates capacitors application due to its so-called colossal dielectric constant. The need for an electrode inducing CCTO epitaxial growth with a clean and sharp interface is therefore necessary, and CCRO is a good potential candidate. In this paper, the synthesis of monophasic CCRO ceramic is reported, as well as pulsed laser deposition of CCRO thin film onto (001) NdCaAlO 4 substrate. Structural and physical properties of bulk CCRO were studied by transmission electron microscopy and electron spin resonance. CCRO films and ceramic exhibited a metallic behavior down to low temperature. CCRO films were (001) oriented and promoted a CCTO film growth with the same orientation.

Figure of merit comparison of PP-based electret and PVDF-based piezoelectric polymer energy harvesters

NASA Astrophysics Data System (ADS)

Mrlík, M.; Leadenham, S.; AlMaadeed, M. A.; Erturk, A.

2016-04-01

The harvesting of mechanical strain and kinetic energy has received great attention over the past two decades in order to power wireless electronic components such as those used in passive and active monitoring applications. Piezoelectric ceramics, such as PZT (lead zirconate titanate), constitute the most commonly used electromechanical interface in vibration energy harvesters. However, there are applications in which piezoelectric ceramics cannot be used due to their low allowable curvature and brittle nature. Soft polymer PVDF (polyvinylidene fluoride) is arguably the most popular non-ceramic soft piezoelectric energy harvester material for such scenarios. Another type of polymer that has received less attention is PP (polypropylene) for electret-based energy harvesting using the thickness mode (33- mode). This work presents figure of merit comparison of PP versus PVDF for off-resonant energy harvesting in thickness mode operation, revealing substantial advantage of PP over PVDF. For thickness mode energy harvesting scenarios (e.g. dynamic compression) at reasonable ambient vibration frequencies, the figure of merit for the maximum power output is proportional to the square of the effective piezoelectric strain constant divided by the effective permittivity constant. Under optimal conditions and for the same volume, it is shown that PP can generate more than two orders of magnitude larger electrical power as compared to PVDF due to the larger effective piezoelectric strain constant and lower permittivity of the former.

Effect of sintering temperature on physical, structural and optical properties of wollastonite based glass-ceramic derived from waste soda lime silica glasses

NASA Astrophysics Data System (ADS)

Almasri, Karima Amer; Sidek, Hj. Ab Aziz; Matori, Khamirul Amin; Zaid, Mohd Hafiz Mohd

The impact of different sintering temperatures on physical, optical and structural properties of wollastonite (CaSiO3) based glass-ceramics were investigated for its potential application as a building material. Wollastonite based glass-ceramics was provided by a conventional melt-quenching method and followed by a controlled sintering process. In this work, soda lime silica glass waste was utilized as a source of silicon. The chemical composition and physical properties of glass were characterized by using Energy Dispersive X-ray Fluorescence (EDXRF) and Archimedes principle. The Archimedes measurement results show that the density increased with the increasing of sintering temperature. The generation of CaSiO3, morphology, size and crystal phase with increasing the heat-treatment temperature were examined by field emission scanning electron microscopy (FESEM), Fourier transforms infrared reflection spectroscopy (FTIR), and X-ray diffraction (XRD). The average calculated crystal size gained from XRD was found to be in the range 60 nm. The FESEM results show a uniform distribution of particles and the morphology of the wollastonite crystal is in relict shapes. The appearance of CaO, SiO2, and Ca-O-Si bands disclosed from FTIR which showed the formation of CaSiO3 crystal phase. In addition to the calculation of the energy band gap which found to be increased with increasing sintering temperature.

Fabrication of silica ceramic membrane via sol-gel dip-coating method at different nitric acid amount

NASA Astrophysics Data System (ADS)

Kahlib, N. A. Z.; Daud, F. D. M.; Mel, M.; Hairin, A. L. N.; Azhar, A. Z. A.; Hassan, N. A.

2018-01-01

Fabrication of silica ceramics via the sol-gel method has offered more advantages over other methods in the fabrication of ceramic membrane, such as simple operation, high purity homogeneous, well defined-structure and complex shapes of end products. This work presents the fabrication of silica ceramic membrane via sol-gel dip-coating methods by varying nitric acid amount. The nitric acid plays an important role as catalyst in fabrication reaction which involved hydrolysis and condensation process. The tubular ceramic support, used as the substrate, was dipped into the sol of Tetrethylorthosilicate (TEOS), distilled water and ethanol with the addition of nitric acid. The fabricated silica membrane was then characterized by (Field Emission Scanning Electron Microscope) FESEM and (Fourier transform infrared spectroscopy) FTIR to determine structural and chemical properties at different amount of acids. From the XRD analysis, the fabricated silica ceramic membrane showed the existence of silicate hydrate in the final product. FESEM images indicated that the silica ceramic membrane has been deposited on the tubular ceramic support as a substrate and penetrate into the pore walls. The intensity peak of FTIR decreased with increasing of amount of acids. Hence, the 8 ml of acid has demonstrated the appropriate amount of catalyst in fabricating good physical and chemical characteristic of silica ceramic membrane.

Characterization of the Materials Synthesized by High Pressure-High Temperature Treatment of a Polymer Derived t-BC₂N Ceramic.

PubMed

Matizamhuka, Wallace R; Sigalas, Iakovos; Herrmann, Mathias; Dubronvinsky, Leonid; Dubrovinskaia, Natalia; Miyajima, Nobuyoshi; Mera, Gabriela; Riedel, Ralf

2011-11-29

Bulk B-C-N materials were synthesized under static high thermobaric conditions (20 GPa and 2,000 °C) in a multianvil apparatus from a polymer derived t-BC 1.97 N ceramic. The bulk samples were characterised using X-ray synchrotron radiation and analytical transmission electron microscopy in combination with electron energy loss spectroscopy. Polycrystalline B-C-N materials with a cubic type structure were formed under the applied reaction conditions, but the formation of a ternary cubic diamond-like c-BC₂N compound, could not be unambiguously confirmed.

Method of forming a dense, high temperature electronically conductive composite layer on a porous ceramic substrate

DOEpatents

Isenberg, A.O.

1992-04-21

An electrochemical device, containing a solid oxide electrolyte material and an electrically conductive composite layer, has the composite layer attached by: (A) applying a layer of LaCrO[sub 3], YCrO[sub 3] or LaMnO[sub 3] particles, on a portion of a porous ceramic substrate, (B) heating to sinter bond the particles to the substrate, (C) depositing a dense filler structure between the doped particles, (D) shaving off the top of the particles, and (E) applying an electronically conductive layer over the particles as a contact. 7 figs.

Auger spectroscopy of fracture surfaces of ceramics

NASA Technical Reports Server (NTRS)

Marcus, H. L.; Harris, J. M.; Szalkowski, F. J.

1974-01-01

Results of Auger electron spectroscopy (AES) studies of fracture surfaces in a series of ceramic materials, including Al2O3, MgO, and Si3N4, which were formed using different processing techniques. AES on the fractured surface of a lunar sample is also discussed. Scanning electron micrograph fractography is used to relate the surface chemistry to the failure mode. Combined argon ion sputtering and AES studies demonstrate the local variations in chemistry near the fracture surface. The problems associated with doing AES in insulators are also discussed, and the experimental techniques directed toward solving them are described.

Supersonic laser spray of aluminium alloy on a ceramic substrate

NASA Astrophysics Data System (ADS)

Riveiro, A.; Lusquiños, F.; Comesaña, R.; Quintero, F.; Pou, J.

2007-12-01

Applying a ceramic coating onto a metallic substrate to improve its wear resistance or corrosion resistance has attracted the interest of many researchers during decades. However, only few works explore the possibility to apply a metallic layer onto a ceramic material. This work presents a novel technique to coat ceramic materials with metals: the supersonic laser spraying. In this technique a laser beam is focused on the surface of the precursor metal in such a way that the metal is transformed to the liquid state in the beam-metal interaction zone. A supersonic jet expels the molten material and propels it to the surface of the ceramic substrate. In this study, we present the preliminary results obtained using the supersonic laser spray to coat a commercial cordierite ceramic plate with an Al-Cu alloy using a 3.5 kW CO 2 laser and a supersonic jet of Argon. Coatings were characterized by scanning electron microscopy (SEM) and interferometric profilometry.

Characterization of Low Firing Temperature Ceramic Glaze Using Phuket MSW and Soda Lime Cullet

NASA Astrophysics Data System (ADS)

Ketboonruang, P.; Jinawat, S.; Kashima, D. P.; Wasanapiarnpong, T.; Sujaridworakun, P.; Buggakuptav, W.; Traipol, N.; Jiemsirilers, S.

2011-10-01

The normal firing temperature of ceramic products is around 1200 °C. In order to reduce firing temperature, industrial wastes were utilized in ceramic glaze. Phuket municipal solid waste (MSW), soda lime cullet, and borax were used as raw materials for low firing temperature glazes. The glaze compositions were designed using a triaxial diagram. Stoneware ceramic body was glazed then fired at 1000 and 1150 °C for 15 minutes. Morphology and phase composition of glazes were analyzed by Scanning electron microscopy (SEM-EDS) and X-ray diffraction (XRD). Thermal expansion compatibility of Stoneware body and glazes were investigated using a dilatometer. Melting behaviour of selected glaze was analyzed by heating stage microscopy. Phuket MSW and Soda lime glass cullet can be used in high percentage as major raw materials for low firing temperature ceramic glaze that show good texture and vitrified at lower firing temperature without using any commercial ceramic frits. The firing temperature can be reduced up to 150 °C in this study.

Effect of engraving speeds of CO₂ laser irradiation on In-Ceram Alumina roughness: a pilot study.

PubMed

Ersu, Bahadır; Ersoy, Orkun; Yuzugullu, Bulem; Canay, Senay

2015-05-01

The aim of the study was to determine the effect of CO₂ laser on surface roughness of In-Ceram-Alumina-ceramic. Four aluminum-oxide ceramic disc specimens were prepared of In-Ceram Alumina. Discs received CO₂ laser irradiation with different engraving speeds (100, 400, 600 and 800 mm/min) as a surface treatment. The roughness of the surfaces was measured on digital elevation models reconstructed from stereoscopic images acquired by scanning-electron-microscope. Surface roughness data were analyzed with One-Way-Analysis-of-Variance at a significance level of p<0.05. There was no significant difference between the roughness values (p=0.82). Due to higher laser durations, partial melting signs were observed on the surfaces. Tearing, smearing and swelling occurred on melted surfaces. Swelling accompanying melting increased the surface roughness, while laser power was fixed and different laser engraving speeds were applied. Although different laser irradiation speeds did not affect the roughness of ceramic surfaces, swelling was observed which led to changes on surfaces.

Ceramics with Different Additives

NASA Astrophysics Data System (ADS)

Wang, Juanjuan; Feng, Lajun; Lei, Ali; Zhao, Kang; Yan, Aijun

2014-09-01

Li2CO3, MgCO3, BaCO3, and Bi2O3 dopants were introduced into CaCu3Ti4O12 (CCTO) ceramics in order to improve the dielectric properties. The CCTO ceramics were prepared by conventional solid-state reaction method. The phase structure, microstructure, and dielectric behavior were carefully investigated. The pure structure without any impurity phases can be confirmed by the x-ray diffraction patterns. Scanning Electron Microscopy (SEM) analysis illuminated that the grains of Ca0.90Li0.20Cu3Ti4O12 ceramics were greater than that of pure CCTO. It was important for the properties of the CCTO ceramics to study the additives in complex impedance spectroscopy. It was found that the Ca0.90Li0.20Cu3Ti4O12 ceramics had the higher permittivity (>45000), the lower dielectric loss (<0.025) than those of CCTO at 1 kHz at room temperature and good temperature stability from -30 to 75 °C.

[Experimental research on the effect of nanophase ceramics on osteoblasts functions].

PubMed

Wen, Bo; Chen, Zhiqing; Jiang, Yinshan; Yang, Zhengwen; Xu, Yongzhong

2005-06-01

In order to study the cytocompatibility of nanophase hydroxyapatite ceramic in vitro, we prepared hydroxyapatite by use of the wet chemistry techniques. The grain size of hydroxyapatite of interest to the present study was determined by scanning electron microscopy and atomic force microscopy with image analysis software. Primary culture of osteoblast from rat calvaria was established. Protein content, synthesis of alkaline phosphatase and deposition of calcium-containing mineral by osteoblasts cultured on nanophase hydroxyapatite ceramics and on conventional hydroxyapatite ceramics for 7, 14, 21 and 28 days were examined. The results showed that the average surface grain size of the nanophase and that of the conventional HA compact formulations was 55 (nanophase) and 780 (conventional) nm, respectively. More importantly, compared to the synthesis of alkaline phosphatase and deposition of calcium-containing mineral by osteoblasts cultured on nanophase was significantly greater than that on conventional ceramics after 21 and 28 days. The cytocompatibility was significantly greater on nanophase HA than on conventional formulations of the same ceramic.

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

Preparation of ceramic coating on Ti substrate by Plasma electrolytic oxidation in different electrolytes and evaluation of its corrosion resistance

NASA Astrophysics Data System (ADS)

Shokouhfar, M.; Dehghanian, C.; Baradaran, A.

2011-01-01

Ceramic oxide coatings (titania) were produced on Ti by micro-arc oxidation in different aluminate and carbonate based electrolytes. This process was conducted under constant pulsed DC voltage condition. The effect of KOH and NaF in aluminate based solution was also studied. The surface morphology, growth and phase composition of coatings were investigated using scanning electron microscope and X-ray diffraction. Corrosion behavior of the coatings was also examined by potentiodynamic polarization and electrochemical impedance spectroscopy. It was found that the sparking initiation voltage (spark voltage) had a significant effect on the form and properties of coatings. Coatings obtained from potassium aluminate based solution had a lower spark voltage, higher surface homogeneity and a better corrosion resistance than the carbonate based solution. Addition of NaF instead of KOH had improper effects on the homogeneity and adhesion of coatings which in turn caused a poor corrosion protection behavior of the oxide layer. AC impedance curves showed two time constants which is an indication of the coatings with an outer porous layer and an inner compact layer.

The recycling of incinerated sewage sludge ash as a raw material for CaO-Al2O3-SiO2-P2O5 glass-ceramic production.

PubMed

Zhang, Zhikun; Zhang, Lei; Yin, Yulei; Liang, Xuanye; Li, Aimin

2015-01-01

In this paper, the recycling of incinerated sewage sludge ash (ISSA) into glass-ceramic materials by a two-stage sintering cycle of nucleation stage and crystallization stage without any pressure and binder is presented. The parent glasses were subjected to the following nucleation/crystallization temperature and time level: (A) 790°C, 1.0 h/870°C, 1.0-3.0 h; (B) 790°C, 1.0 h/945°C, 1.0-3.0 h and (C) 790°C, 1.0 h/1065°C, 1.0-3.0 h. X-ray power diffraction analysis results revealed that multiple crystalline phases coexisted in the glass-ceramic materials and the crystalline phase compositions were more affected by crystallization temperature than crystallization time. Scanning electron microscopy analysis showed an interlocking microstructure of glass phases and crystals with different sizes and spatial distribution. The glass-ceramics crystallized at 945°C for 2.0 h exhibited optimal properties of density of 2.88±0.08 g/cm3, compression strength of 247±12 MPa, bending strength of 118±14 MPa and water absorption of 0.42±0.04. The leaching concentrations of heavy metals were far lower than the limits required by the regulatory standard of EPA. This paper provides a feasible, low-cost and promising method to produce ISSA-based glass-ceramics and highlights the principal characteristics that must be taken into account to use ISSA correctly in glass-ceramics.

Determining efficacy of monitoring devices on ceramic bond to resin composite

PubMed Central

Osorio, Estrella; Aguilera, Fátima S.; Osorio, Raquel; García-Godoy, Franklin; Cabrerizo-Vilchez, Miguel A.; Toledano, Manuel

2012-01-01

Objectives: This paper aims to assess the effectiveness of 3D nanoroughness and 2D microroughness evaluations, by their correlation with contact angle measurements and shear bond strength test, in order to evaluate the effect of two different acids conditioning on the bonding efficacy of a leucite-based glass-ceramic to a composite resin. Study Design: Ceramic (IPS Empress) blocks were treated as follows: 1) no treatment, 2) 37% phosphoric acid (H3PO4), 15 s, 3) 9% hydrofluoric acid (HF), 5 min. Micro- and nano-roughness were assessed with a profilometer and by means of an atomic force microscopy (AFM). Water contact angle (CA) measurements were determined to assess wettability of the ceramic surfaces with the asixymetric drop shape analysis contact diameter technique. Shear bond strength (SBS) was tested to a resin composite (Z100) with three different adhesive systems (Scotchbond Multipurpose Plus, Clearfil New Bond, ProBOND). Scanning electron microscopy (SEM) images were performed. Results: Nanoroughness values assessed in 50x50 μm areas were higher for the HF group, these differences were not detected by profilometric analysis. HF treatment created the nano- roughest surfaces and the smallest CA (p<0.05), producing the highest SBS to the composite resin with all tested adhesive systems (p<0.05). No differences existed between the SBS produced by the adhesive systems evaluated with any of the surface treatments tested. Conclusions: Nano-roughness obtained in a 50x50 µm scan size areas was the most reliable data to evaluate the topographical changes produced by the different acid treatments on ceramic surfaces. Key words:Dental ceramic, acid etching, bonding efficacy, resin composite, adhesive systems, contact angle, roughness. PMID:22549693

Spectrophotometric Determination of the Hole Concentration in the Superconductor YBa2Cu3O(sub 7-x)

ERIC Educational Resources Information Center

Hoppe, Jack I.; Malati, Mounir A.

2005-01-01

An experimental study of ceramic superconductors namely YBa2Cu3O(sub 7-x), which illustrates the use of spectrophotometry, based on the electronic spectra of complexes of Fe(II), Fe(III) and Cu(II) to better understand the stoichiometry of YBCO is described. The results from this experiment are in good agreement with those obtained by the…

Catalytic reforming of methane to syngas in an oxygen-permeative membrane reactor

NASA Astrophysics Data System (ADS)

Urano, Takeshi; Kubo, Keiko; Saito, Tomoyuki; Hitomi, Atsushi

2011-05-01

For fuel cell applications, partial oxidative reforming of methane to syngas, hydrogen and carbon monoxide, was performed via a dense oxygen-permeative ceramic membrane composed by both ionic and electronic conductive materials. The modification of Ni-based catalyst by noble metals was investigated to increase oxygen permeation flux and decrease carbon deposition during reforming reaction. The role of each component in catalyst was also discussed.

High efficiency aqueous and hybrid lithium-air batteries enabled by Li1.5Al0.5Ge1.5(PO4)3 ceramic anode-protecting membranes

NASA Astrophysics Data System (ADS)

Safanama, Dorsasadat; Adams, Stefan

2017-02-01

Due to their extremely high specific energy, rechargeable Li-air batteries could meet the demand for large-scale storage systems to integrate renewable sources into the power grid. Li-air batteries with aqueous catholytes with high solubility of discharge products have a higher potential to reach their slightly lower theoretical limits in practical devices. In this work, we demonstrate aqueous and hybrid Li-air batteries with NASICON-type Li1+xAxGe2-x(PO4)3 ceramic as anode-protecting membrane. The LAGP ceramic pellets with room temperature conductivity >10-4 S cm-1 are synthesized by melt quenching and subsequently annealed based on our optimized heat treatment cycle. Hybrid Li-air batteries are assembled by sandwiching LAGP membranes between Li-anode chamber and catholyte solutions (of various pH values) with CNT/Pt as air-cathode. When the two electron reduction mechanism prevails, overpotentials below 0.2 V are achieved for currents up to 0.07 mA cm-2 leading to energy efficiencies exceeding 98%.

RETRACTED: Chemical densification of plasma sprayed yttria stabilized zirconia (YSZ) coatings for high temperature wear and corrosion resistance

NASA Astrophysics Data System (ADS)

Ye, Yaping; Fehr, Karl Thomas; Faulstich, Martin; Wolf, Gerhard

2012-12-01

Plasma-sprayed yttria stabilized zirconia (YSZ) ceramic coatings have been widely used as wear- and corrosion-resistant coatings in high temperature applications and an aggressive environment due to their high hardness, wear resistance, heat and chemical resistance, and low thermal conductivity. The highly porous structure of plasma-sprayed ceramic coatings and their poor adhesion to the substrate usually lead to the coating degradation and failure. In this study, a two-layer system consisting of atmospheric plasma-sprayed 8 wt.% yttria-stabilized zirconia (8YSZ) and Ni-based alloy coatings was post-treated by means of a novel chemical sealing process at moderate temperatures of 600-800 °C. Microstructure characteristics of the YSZ coatings were studied using an electron probe micro-analyzer (EPMA). Results revealed that the ceramic top coat was densified by the precipitated zirconia in the open pores. Therefore, the sealed YSZ coatings exhibit reduced porosity, higher hardness and a better adhesion onto the bond coat. The mechanisms for the sealing process were also proposed.

Putty-like bone fillers based on CaP ceramics or Biosilicate® combined with carboxymethylcellulose: Characterization, optimization, and evaluation.

PubMed

Gabbai-Armelin, Paulo R; Renno, Ana Cm; Crovace, Murilo C; Magri, Angela Mp; Zanotto, Edgar D; Peitl, Oscar; Leeuwenburgh, Sander Cg; Jansen, John A; van den Beucken, Jeroen Jjp

2017-08-01

Calcium phosphates and bioactive glass ceramics have been considered promising biomaterials for use in surgeries. However, their moldability should be further enhanced. We here thereby report the handling, physicochemical features, and morphological characteristics of formulations consisting of carboxymethylcellulose-glycerol and hydroxyapatite-tricalcium phosphate or Biosilicate® particles. We hypothesized that combining either material with carboxymethylcellulose-glycerol would improve handling properties, retaining their bioactivity. In addition to scanning electron microscopy, cohesion, mineralization, pH, and viscoelastic properties of the novel formulations, cell culture experiments were performed to evaluate the cytotoxicity and cell proliferation. Putty-like formulations were obtained with improved cohesion and moldability. Remarkably, mineralization in simulated body fluid of hydroxyapatite-tricalcium phosphate/carboxymethylcellulose-glycerol formulations was enhanced compared to pure hydroxyapatite-tricalcium phosphate. Cell experiments showed that all formulations were noncytotoxic and that HA-TCP60 and BGC50 extracts led to an increased cell proliferation. We conclude that combining carboxymethylcellulose-glycerol with either hydroxyapatite-tricalcium phosphate or Biosilicate® allows for the generation of moldable putties, improves handling properties, and retains the ceramic bioactivity.

An Experimental Investigation towards Improvement of Thermoelectric Properties of Strontium Titanate Ceramics

NASA Astrophysics Data System (ADS)

Mehdizadeh Dehkordi, Arash

The direct energy conversion between heat and electricity based on thermoelectric effects is a topic of long-standing interest in condensed matter materials science. Experimental and theoretical investigations in order to understand the mechanisms involved and to improve the materials properties and conversion efficiency have been ongoing for more than half a century. While significant achievements have been accomplished in improving the properties of conventional heavy element based materials (such as Bi2Te 3 and PbTe) as well as the discovery of new materials systems for the close-to-room temperature and intermediate temperatures, high-temperature applications of thermoelectrics is still limited to one materials system, namely SiGe. Recently, oxides have exhibited great potential to be investigated for high-temperature thermoelectric power generation. The objective of this dissertation is to synthesize and investigate both electronic and thermal transport in strontium titanate (SrTiO3) ceramics in order to experimentally realize its potential and to ultimately investigate the possibility of further improvement of the thermoelectric performance of this perovskite oxide for mid- to high temperature applications. Developing a synthesis strategy and tuning various synthesis parameters to benefit the thermoelectric transport form the foundation of this study. It is worth mentioning that the results of this study has been employed to prepare targets for pulsed-laser deposition (PLD) to study the thermoelectric properties of corresponding thin films and superlattice structures at Dr. Husam Alshareef's group at King Abdullah University of Science and Technology (KAUST), Saudi Arabia. Considering the broad range of functionality of SrTiO3, the findings of this work will surely benefit other fields of research and application of this functional oxide such as photoluminescence, ferroelectricity or mixed-ionic electronic conductivity. This dissertation will ultimately attempt to answer the question, "Is it possible to further improve the thermoelectric properties of SrTiO 3-based ceramics?". The organization of the dissertation is as follows: In Chapter 1, the fundamental concepts in the thermoelectric theory is explained. Second, we briefly review the characteristics of "good" thermoelectric materials and highlight the differences exist between SrTiO3 and conventional thermoelectric materials. In Chapter 2, SrTiO3 is introduced and the electronic and thermal properties arising from its crystal structure are discussed. Chapter 3 is dedicated to the fundamentals of measurements of the electronic and thermal transport properties which are the backbone of the current work. Our experimental results are presented in Chapter 4 and 5. The synthesis and processing techniques to prepare doped SrTiO3 powder and bulk polycrystalline ceramic are presented in Chapter 3. The optimizations of the synthesis and densification parameters involved are presented and discussed in this chapter as well. Significant improvement achieved in the thermoelectric figure of merit of Pr-doped SrTiO3 and the studies performed to understand the results are presented in Chapter 5. Concluding remarks and future work are discussed in Chapter 6.

Facile synthesis of mesoporous silica sublayer with hierarchical pore structure on ceramic membrane using anionic polyelectrolyte.

PubMed

Kang, Taewook; Oh, Seogil; Kim, Honggon; Yi, Jongheop

2005-06-21

A facile method for introducing mesoporous silica sublayer onto the surface of a ceramic membrane for use in liquid-phase separation is described. To reduce the electrostatic repulsion between the mesoporous silica sol and the ceramic membrane in highly acidic conditions (pH < 2), thus facilitating the approach of hydrolyzed silica sol to the surface of the membrane, poly(sodium 4-styrenesulfonate) (Na+PSS-, denoted as PSS-) was used as an ionic linker. The use of PSS- led to a significant reduction in positive charge on the ceramic membrane, as confirmed by experimental titration data. Consistent with the titration results, the amount of mesoporous silica particles on the surface of the ceramic membrane was low, in the absence of PSS- treatment, whereas mesoporous silica sublayer with hierarchical pore structure was produced, when 1 wt % PSS- was used. The results show that mesoporous silica grows in the confined surface, eventually forming a multistacked surface architecture. The mesoporous silica sublayer contained uniform, ordered (P6 mm) mesopores of ca. 7.5 nm from mesoporous silica as well as macropores ( approximately mum) from interparticle voids, as evidenced by transmission electron microscopy and scanning electron microscopy analyses. The morphologies of the supported mesoporous silica could be manipulated, thus permitting the generation of uniform needlelike forms or uniform spheroid particles by varying the concentration of PSS-.

Domain disruption and defect accumulation during unipolar electric fatigue in a BZT-BCT ceramic

NASA Astrophysics Data System (ADS)

Fan, Zhongming; Zhou, Chao; Ren, Xiaobing; Tan, Xiaoli

2017-12-01

0.5Ba(Zr0.2Ti0.8)O30.5(Ba0.7Ca0.3)TiO3 (BZT-BCT) is a promising lead-free piezoelectric ceramic with excellent piezoelectric properties (e.g., d33 > 600 pC/N). As potential device applications are considered, the electric fatigue resistance of the ceramic must be evaluated. In this Letter, electric-field in situ transmission electron microscopy is employed to study the microstructural evolution in the BZT-BCT polycrystalline ceramic during unipolar cycling. It is shown that the large ferroelectric domains are disrupted and replaced with accumulated defect clusters and fragmented domains after 5 × 104 unipolar cycles. In this fatigued state, the grain becomes nonresponsive to applied voltages.

Sintering and microstructure of silicon carbide ceramic with Y3Al5O12 added by sol-gel method*

PubMed Central

Guo, Xing-zhong; Yang, Hui

2005-01-01

Silicon carbide (SiC) ceramic with YAG (Y3Al5O12) additive added by sol-gel method was liquid-phase sintered at different sintering temperatures, and the sintering mechanism and microstructural characteristics of resulting silicon carbide ceramics were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and elemental distribution of surface (EDS). YAG (yttrium aluminum garnet) phase formed before the sintering and its uniform distribution in the SiC/YAG composite powder decreased the sintering temperature and improved the densification of SiC ceramic. The suitable sintering temperature was 1860 °C with the specimen sintered at this temperature having superior sintering and mechanical properties, smaller crystal size and fewer microstructure defects. Three characteristics of improved toughness of SiC ceramic with YAG added by sol-gel method were microstructural densification, main-crack deflection and crystal ‘bridging’. PMID:15682507

Synthesis, characterization, bioactivity and antibacterial studies of silver doped calcium borosilicate glass-ceramics

NASA Astrophysics Data System (ADS)

Kumar, Alesh; Mariappan, C. R.

2018-04-01

Bioactive glass-ceramics 45.8 mol% SiO- 45.8 CaO - 8.4 B2O3 doped with Ag2O were synthesized by sol-gel method. The glass-ceramic nature of samples was confirmed by X-ray diffraction (XRD) and transmission electron microscopy (TEM) analysis. Fourier transform infrared (FT-IR) spectra reveal the probable stretching and bending vibration modes of silicate and borate groups. UV-Visible spectra reveal the presence of Ag+ ions and metallic Ag in the glass matrix for Ag2O doped ceramic sample. Biocompatibility of the glass nature of samples was studied by soaking of samples in Dulbecco's Modified Eagle's Medium (DMEM) with subsequent XRD studies. It was found that bone-like apatite formation on the glasses after soaked in DMEM. Antibacterial studies of glass ceramics powder against gram positive and negative microorganisms were carried out.

Microwave dielectric properties of BaO-2CeO{sub 2}-nTiO{sub 2} ceramics

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

Sreemoolanadhan, H.; Sebastian, M.T.; Ratheesh, R.

2004-11-01

The BaO-2CeO{sub 2}-nTiO{sub 2} ceramics with n=3, 4 and 5 have been prepared with CeO{sub 2} as starting material. The ceramics have been characterized using scanning electron microscopy, X-ray diffraction, Raman and X-ray photoelectron spectroscopy techniques. The microwave dielectric properties have been measured using standard dielectric resonator techniques. BaO-2CeO{sub 2}-3TiO{sub 2} (123), BaO-2CeO{sub 2}-4TiO{sub 2} (124) and BaO-2CeO{sub 2}-5TiO{sub 2} (125) ceramics showed dielectric constants of 38, 27 and 32, respectively. All the ceramics showed fairly good unloaded Q-factors. 124 and 125 compounds exhibited low {tau}f values, while 123 showed a high {tau}f value.

Influence of interface point defect on the dielectric properties of Y doped CaCu3Ti4O12 ceramics

NASA Astrophysics Data System (ADS)

Deng, Jianming; Sun, Xiaojun; Liu, Saisai; Liu, Laijun; Yan, Tianxiang; Fang, Liang; Elouadi, Brahim

2016-04-01

CaCu3Ti4-xYxO12 (0≤x≤0.12) ceramics were fabricated with conventional solid-state reaction method. Phase structure and microstructure of prepared ceramics were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The impedance and modulus tests both suggested the existence of two different relaxation behavior, which were attributed to bulk and grain boundary response. In addition, the conductivity and dielectric permittivity showed a step-like behavior under 405K. Meanwhile, frequency independence of dc conduction became dominant when above 405K. In CCTO ceramic, rare earth element Y3+ ions as an acceptor were used to substitute Ti sites, decreasing the concentration of oxygen vacancy around grain-electrode and grain boundary. The reason to the reduction of dielectric behavior in low frequencies range was associated with the Y doping in CCTO ceramic.

Friction and Wear Behavior of Selected Dental Ceramics

NASA Astrophysics Data System (ADS)

Park, Jongee; Pekkan, Gurel; Ozturk, Abdullah

The purpose of this study was to determine the friction coefficients and wear rates of six commercially available dental ceramics including IPS Empress 2 (E2), Cergo Pressable Ceramic (CPC), Cercon Ceram (CCS) and Super porcelain EX-3 (SPE). Bovine enamel (BE) was also tested as a reference material for comparison purposes. Samples of the dental ceramics were prepared according to the instructions described by the manufacturers in disk-shape with nominal dimensions of 12 mm × 2 mm. The wear tests were performed by means of a pin-on-disk type tribometer. The friction coefficients and specific wear rates of the materials were determined at a load of 10 N and rotating speed of 0.25 cm/s without lubrication. Surface morphology of the wear tracks was examined using a scanning electron microscope. Statistical analyses were made using one-way ANOVA and Turkey's HSD (P < 0.05).

X-ray absorption fine structure analysis of molybdenum added to BaTiO3-based ceramics used for multilayer ceramic capacitors

NASA Astrophysics Data System (ADS)

Ogata, Yoichiro; Shimura, Tetsuo; Ryu, Minoru; Iwazaki, Yoshiki

2017-04-01

The effect of slight molybdenum doping of perovskite-type BaTiO3-based ceramics on the reliability of a multilayer ceramic capacitor (MLCC) and on the valence state of molybdenum in the BaTiO3-based ceramics has been investigated by highly accelerated lifetime tests and X-ray absorption fine structure analysis. The molybdenum added to the BaTiO3-based ceramics is located at Ti sites and improves the highly accelerated lifetime and lowers the initial dielectric resistivity in MLCCs. Through sintering in a reducing atmosphere, which is an important process in the fabrication of BaTiO3-based MLCCs, the oxidation state of the molybdenum added could be adjusted from +6 to a value close to +4.

Influence of surface treatments on bond strength of metal and ceramic brackets to a novel CAD/CAM hybrid ceramic material.

PubMed

Elsaka, Shaymaa E

2016-01-01

This study evaluated the effect of four different surface treatments methods on the shear bond strength (SBS) of ceramic and metal brackets to Vita Enamic (VE) CAD/CAM hybrid ceramic. A total of 240 plates (10 mm × 10 mm × 3 mm) were cut from VE ceramic blocks and divided into two groups. In each group, four subgroups were prepared by hydrofluoric acid (HF); phosphoric acid (H3PO4); diamond ceramic grinding bur; and silica coating using CoJet system (CJ). Maxillary central incisor metal (Victory Series) and ceramic (Clarity) brackets were bonded with light-cure composite and then stored in artificial saliva for 1 week and thermocycled. The SBS test was performed, and the failure types were classified with adhesive remnant index scores. Surface morphology of the ceramic was characterized after treatment using a scanning electron microscope. Data were analyzed using two-way ANOVA, Tukey HSD test, and Weibull analysis. SBS was significantly affected by the type of bracket and by type of treatment (P < 0.001). Specimens treated with CJ presented with significantly higher SBS compared to other groups (P < 0.05). Improvements in SBS values (MPa) were found in the following order: CJ > HF > Bur > H3PO4. Ceramic bracket showed higher SBS compared to metal bracket. Adhesive failures between the ceramic and composite resin were the predominant mode of failure in all groups. Surface treatment of VE CAD/CAM hybrid ceramic with silica coating enhanced the adhesion with ceramic and metal brackets.

Glass-ceramic coating material for the CO2 laser based sintering of thin films as caries and erosion protection.

PubMed

Bilandžić, Marin Dean; Wollgarten, Susanne; Stollenwerk, Jochen; Poprawe, Reinhart; Esteves-Oliveira, Marcella; Fischer, Horst

2017-09-01

The established method of fissure-sealing using polymeric coating materials exhibits limitations on the long-term. Here, we present a novel technique with the potential to protect susceptible teeth against caries and erosion. We hypothesized that a tailored glass-ceramic material could be sprayed onto enamel-like substrates to create superior adhesion properties after sintering by a CO 2 laser beam. A powdered dental glass-ceramic material from the system SiO 2 -Na 2 O-K 2 O-CaO-Al 2 O 3 -MgO was adjusted with individual properties suitable for a spray coating process. The material was characterized using X-ray fluorescence analysis (XRF), heating microscopy, dilatometry, scanning electron microscopy (SEM), grain size analysis, biaxial flexural strength measurements, fourier transform infrared spectroscopy (FTIR), and gas pycnometry. Three different groups of samples (each n=10) where prepared: Group A, powder pressed glass-ceramic coating material; Group B, sintered hydroxyapatite specimens; and Group C, enamel specimens (prepared from bovine teeth). Group B and C where spray coated with glass-ceramic powder. All specimens were heat treated using a CO 2 laser beam process. Cross-sections of the laser-sintered specimens were analyzed using laser scanning microscopy (LSM), energy dispersive X-ray analysis (EDX), and SEM. The developed glass-ceramic material (grain size d50=13.1mm, coefficient of thermal expansion (CTE)=13.310 -6 /K) could be spray coated on all tested substrates (mean thickness=160μm). FTIR analysis confirmed an absorption of the laser energy up to 95%. The powdered glass-ceramic material was successfully densely sintered in all sample groups. The coating interface investigation by SEM and EDX proved atomic diffusion and adhesion of the glass-ceramic material to hydroxyapatite and to dental enamel. A glass-ceramic material with suitable absorption properties was successfully sprayed and laser-sintered in thin films on hydroxyapatite as well as on bovine enamel. The presented novel technique of tooth coating with a dental glass-ceramic using a CO 2 -laser holds a great potential as a possible method to protect susceptible teeth against caries and erosion. Copyright © 2017 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Electron paramagnetic resonance of Nb-doped BaTiO3 ceramics with positive temperature coefficient of resistivity

NASA Astrophysics Data System (ADS)

Jida, Shin'suke; Miki, Toshikatsu

1996-11-01

Paramagnetic centers in Nb-doped BaTiO3 ceramics are measured at 77-500 K by electron paramagnetic resonance (EPR) for investigating the role of the centers on the well-known positive temperature coefficient of resistivity (PTCR) effect (PTCR at the Curie temperature). EPR detects four signals; an anisotropically broad singlet signal at g=2.005, a sextet signal due to Mn2+, a Cr3+ signal, and a Ti3+ signal. The former two signals arise in the rhombohedral and cubic phases, but disappear in the tetragonal and orthorhombic phases. The Cr3+ signal appears in all of the phases, while the Ti3+ signal is detected only at low temperatures. The singlet signal also arises in undoped, barium-deficient BaTiO3 ceramics, therefore the signal is attributable to barium-vacancy-associated centers rather than Nb4+ ions or Fe3+ ions proposed by several authors. In this article, we propose that the singlet signal is due to vacancy-pairs of VBa-F+ type, i.e., the vacancy pair of VBa-VO capturing one electron. The electrical resistivity data show a polaronic character of low-temperature conduction and a high resistivity jump around the Curie temperature. The low-temperature polaronic conduction is explained in terms of electron-hopping between Ti4+ and Ti3+ ions. The resistivity jump at the Curie temperature occurs along with the EPR intensity increase of the singlet signal, the Mn2+ signal and the Cr3+ signal. We conclude that the PTCR of Nb-doped BaTiO3 ceramics is strongly associated with the trap activation of the VBa-VO vacancy-pairs and manganese centers at the tetragonal-to-cubic transition.

In-situ High Temperature Phase Transformations in Ceramics

DTIC Science & Technology

2009-07-28

microscopy - SEM and transmission electron microscopy - TEM), have identified important microstructural considerations, such as the critical ...particularly with judicial design of the critical particle size and microstructure.12, 47, 48 Likewise, preliminary work indicates the possibility of high...toughening of fiber reinforced, fibrous monolithic or laminated ceramic matrix composites.49, 50 enstatite was above a 7 μm critical grain size

Adequacy of surface analytical tools for studying the tribology of ceramics

NASA Technical Reports Server (NTRS)

Sliney, H. E.

1986-01-01

Surface analytical tools are very beneficial in tribological studies of ceramics. Traditional methods of optical microscopy, XRD, XRF, and SEM should be combined with newer surface sensitive techniques especially AES and XPS. ISS and SIMS can also be useful in providing additional compositon details. Tunneling microscopy and electron energy loss spectroscopy are less known techniques that may also prove useful.

The Electrospun Ceramic Hollow Nanofibers

PubMed Central

Davoudpour, Yalda; Habibi, Youssef; Elbahri, Mady

2017-01-01

Hollow nanofibers are largely gaining interest from the scientific community for diverse applications in the fields of sensing, energy, health, and environment. The main reasons are: their extensive surface area that increases the possibilities of engineering, their larger accessible active area, their porosity, and their sensitivity. In particular, semiconductor ceramic hollow nanofibers show greater space charge modulation depth, higher electronic transport properties, and shorter ion or electron diffusion length (e.g., for an enhanced charging–discharging rate). In this review, we discuss and introduce the latest developments of ceramic hollow nanofiber materials in terms of synthesis approaches. Particularly, electrospinning derivatives will be highlighted. The electrospun ceramic hollow nanofibers will be reviewed with respect to their most widely studied components, i.e., metal oxides. These nanostructures have been mainly suggested for energy and environmental remediation. Despite the various advantages of such one dimensional (1D) nanostructures, their fabrication strategies need to be improved to increase their practical use. The domain of nanofabrication is still advancing, and its predictable shortcomings and bottlenecks must be identified and addressed. Inconsistency of the hollow nanostructure with regard to their composition and dimensions could be one of such challenges. Moreover, their poor scalability hinders their wide applicability for commercialization and industrial use. PMID:29120403

A study on wear resistance and microcrack of the Ti 3Al/TiAl + TiC ceramic layer deposited by laser cladding on Ti-6Al-4V alloy

NASA Astrophysics Data System (ADS)

Li, Jianing; Chen, Chuanzhong; Squartini, Tiziano; He, Qingshan

2010-12-01

Laser cladding of the Al + TiC alloy powder on Ti-6Al-4V alloy can form the Ti 3Al/TiAl + TiC ceramic layer. In this study, TiC particle-dispersed Ti 3Al/TiAl matrix ceramic layer on the Ti-6Al-4V alloy by laser cladding has been researched by means of X-ray diffraction, scanning electron microscope, electron probe micro-analyzer, energy dispersive spectrometer. The main difference from the earlier reports is that Ti 3Al/TiAl has been chosen as the matrix of the composite coating. The wear resistance of the Al + 30 wt.% TiC and the Al + 40 wt.% TiC cladding layer was approximately 2 times greater than that of the Ti-6Al-4V substrate due to the reinforcement of the Ti 3Al/TiAl + TiC hard phases. However, when the TiC mass percent was above 40 wt.%, the thermal stress value was greater than the materials yield strength limit in the ceramic layer, the microcrack was present and its wear resistance decreased.

Thermoelectric properties and figure of merit of perovskite-type Ba1-xLaxSnO3 with x=0.002-0.008

NASA Astrophysics Data System (ADS)

Yasukawa, Masahiro; Kono, Toshio; Ueda, Kazushige; Yanagi, Hiroshi; Wng Kim, Sung; Hosono, Hideo

2013-10-01

Thermoelectric properties and figure of merit were evaluated from the Seebeck coefficient S, electrical conductivity σ, and thermal conductivity κ measured at high temperatures for perovskite-type ceramics of Ba1-xLaxSnO3 with x=0.002, 0.005, and 0.008, which were prepared by a polymerized complex method and a subsequent spark plasma sintering technique. All the polycrystalline dense ceramics showed n-type degenerate semiconducting behavior in the temperature range of 373-1073 K. The La content dependence of the S values revealed successful increase in the electron carriers with the La doping in this x range. The κ values remained almost unchanged with x showing ~9.6 Wm-1 K-1 at room temperature and decreased with increasing temperature. The electronic thermal conductivities calculated by the Wiedemann-Franz law as well as the T-1 dependence of the κ values indicate that the phonon thermal conductivity was dominant. The dimensionless figure of merit ZT increased with increasing temperature for all the ceramics and showed ~0.1 at 1073 K for the ceramics with x=0.002 and 0.005.

Effect of Ceramic Surface Treatments After Machine Grinding on the Biaxial Flexural Strength of Different CAD/CAM Dental Ceramics.

PubMed

Bagheri, Hossein; Hooshmand, Tabassom; Aghajani, Farzaneh

2015-09-01

This study aimed to evaluate the effect of different ceramic surface treatments after machining grinding on the biaxial flexural strength (BFS) of machinable dental ceramics with different crystalline phases. Disk-shape specimens (10mm in diameter and 1.3mm in thickness) of machinable ceramic cores (two silica-based and one zirconia-based ceramics) were prepared. Each type of the ceramic surfaces was then randomly treated (n=15) with different treatments as follows: 1) machined finish as control, 2) machined finish and sandblasting with alumina, and 3) machined finish and hydrofluoric acid etching for the leucite and lithium disilicate-based ceramics, and for the zirconia; 1) machined finish and post-sintered as control, 2) machined finish, post-sintered, and sandblasting, and 3) machined finish, post-sintered, and Nd;YAG laser irradiation. The BFS were measured in a universal testing machine. Data based were analyzed by ANOVA and Tukey's multiple comparisons post-hoc test (α=0.05). The mean BFS of machined finish only surfaces for leucite ceramic was significantly higher than that of sandblasted (P=0.001) and acid etched surfaces (P=0.005). A significantly lower BFS was found after sandblasting for lithium disilicate compared with that of other groups (P<0.05). Sandblasting significantly increased the BFS for the zirconia (P<0.05), but the BFS was significantly decreased after laser irradiation (P<0.05). The BFS of the machinable ceramics was affected by the type of ceramic material and surface treatment method. Sandblasting with alumina was detrimental to the strength of only silica-based ceramics. Nd:YAG laser irradiation may lead to substantial strength degradation of zirconia.

Effect of Ceramic Surface Treatments After Machine Grinding on the Biaxial Flexural Strength of Different CAD/CAM Dental Ceramics

PubMed Central

Bagheri, Hossein; Aghajani, Farzaneh

2015-01-01

Objectives: This study aimed to evaluate the effect of different ceramic surface treatments after machining grinding on the biaxial flexural strength (BFS) of machinable dental ceramics with different crystalline phases. Materials and Methods: Disk-shape specimens (10mm in diameter and 1.3mm in thickness) of machinable ceramic cores (two silica-based and one zirconia-based ceramics) were prepared. Each type of the ceramic surfaces was then randomly treated (n=15) with different treatments as follows: 1) machined finish as control, 2) machined finish and sandblasting with alumina, and 3) machined finish and hydrofluoric acid etching for the leucite and lithium disilicate-based ceramics, and for the zirconia; 1) machined finish and post-sintered as control, 2) machined finish, post-sintered, and sandblasting, and 3) machined finish, post-sintered, and Nd;YAG laser irradiation. The BFS were measured in a universal testing machine. Data based were analyzed by ANOVA and Tukey’s multiple comparisons post-hoc test (α=0.05). Results: The mean BFS of machined finish only surfaces for leucite ceramic was significantly higher than that of sandblasted (P=0.001) and acid etched surfaces (P=0.005). A significantly lower BFS was found after sandblasting for lithium disilicate compared with that of other groups (P<0.05). Sandblasting significantly increased the BFS for the zirconia (P<0.05), but the BFS was significantly decreased after laser irradiation (P<0.05). Conclusions: The BFS of the machinable ceramics was affected by the type of ceramic material and surface treatment method. Sandblasting with alumina was detrimental to the strength of only silica-based ceramics. Nd:YAG laser irradiation may lead to substantial strength degradation of zirconia. PMID:27148372

Crack tip fracture toughness of base glasses for dental restoration glass-ceramics using crack opening displacements.

PubMed

Deubener, J; Höland, M; Höland, W; Janakiraman, N; Rheinberger, V M

2011-10-01

The critical stress intensity factor, also known as the crack tip toughness K(tip), was determined for three base glasses, which are used in the manufacture of glass-ceramics. The glasses included the base glass for a lithium disilicate glass-ceramic, the base glass for a fluoroapatite glass-ceramic and the base glass for a leucite glass-ceramic. These glass-ceramic are extensively used in the form of biomaterials in restorative dental medicine. The crack tip toughness was established by using crack opening displacement profiles under experimental conditions. The crack was produced by Vickers indentation. The crack tip toughness parameters determined for the three glass-ceramics differed quite significantly. The crack tip parameters of the lithium disilicate base glass and the leucite base glass were higher than that of the fluoroapatite base glass. This last material showed glass-in-glass phase separation. The discussion of the results clearly shows that the droplet glass phase is softer than the glass matrix. Therefore, the authors conclude that a direct relationship exists between the chemical nature of the glasses and the crack tip parameter. Copyright © 2011 Elsevier Ltd. All rights reserved.

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

Microwave emission from lead zirconate titanate induced by impulsive mechanical load

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

Aman, A., E-mail: alexander.aman@ovgu.de; Packaging Group, Institute of Micro- and Sensorsytems, Otto-von-Guericke University, Universitätsplatz 2, 39106 Magdeburg; Majcherek, S.

2015-10-28

This paper focuses on microwave emission from Lead zirconate titanate Pb [Zr{sub x}Ti{sub 1−x}] O{sub 3} (PZT) induced by mechanical stressing. The mechanical stress was initiated by impact of a sharp tungsten indenter on the upper surface of PZT ceramic. The sequences of microwave and current impulses, which flew from indenter to electric ground, were detected simultaneously. The voltage between the upper and lower surface of ceramic was measured to obtain the behavior of mechanical force acting on ceramic during the impact. It was found that the amplitude, form, and frequency of measured microwave impulses were different by compression andmore » restitution phase of impact. Two different mechanisms of electron emission, responsible for microwave impulse generation, were proposed based on the dissimilar impulse behavior. The field emission from tungsten indenter is dominant during compression, whereas ferroemission dominates during restitution phase. Indeed, it was observed that the direction of the current flow, i.e., sign of current impulses is changed by transitions from compression to restitution phase of impact. The observed dissimilar behavior of microwave impulses, caused by increasing and decreasing applied force, can be used to calculate the contact time and behavior of mechanical force during mechanical impact on ceramic surface. It is shown that the generation of microwave impulses exhibits high reproducibility, impulse intensity, a low damping factor, and high mechanical failure resistance. Based on these microwave emission properties of PZT, the development of new type of stress sensor with spatial resolution of few microns becomes possible.« less

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.

Composition and microstructure of maiolica from the museum of ceramics in Ascoli Piceno (Italy): evidences by electron microscopy and microanalysis

NASA Astrophysics Data System (ADS)

Gulmini, M.; Scognamiglio, F.; Roselli, G.; Vaggelli, G.

2015-09-01

The present work focuses on majolica objects from the collection of the museum of ceramic in Ascoli Piceno (Italy). The scientific investigation was performed on fragments detached from seven maiolicas attributed to the Castelli production (Abruzzi region) and one majolica from the Ascoli Piceno production (Marche region). The Castelli artifacts (late sixteenth-early eighteenth century) belong to the decorated style known as " compendiario." The piece from Ascoli Piceno recalls the decoration style of the other considered objects and is attributable to the "Paci" manufacture (first half of the nineteenth century). The selected objects were investigated by fiber optics reflectance spectroscopy, micro-X-ray fluorescence spectroscopy and scanning electron microscopy coupled with electron-dispersive X-ray spectrometry. The ceramic bodies of all objects are calcareous, whereas the glazes are lead-alkali type opacified by tin dioxide. Blue and purplish-red decorations were obtained by cobalt and manganese compounds dissolved in the glaze, respectively. Yellow and orange decorations were obtained by particles of lead antimonate and hematite. Finally, black decorations were obtained using compounds rich in manganese and iron. The study contributes to knowledge on the production of Castelli ceramics and presents first archaeometric data on the maiolica production from Ascoli Piceno. The scientific examination highlights continuity with the Renaissance production, and the joint contribution of the three analytical techniques suggests distinctive features among different productions, thus integrating and refining the information obtained by the art-historical study.

Ceramic Technology Project semiannual progress report, April 1992--September 1992

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

Johnson, D.R.

1993-07-01

This project was developed to meet the ceramic technology requirements of the DOE Office of Transportation Systems` automotive technology programs. Significant progress in fabricating ceramic components for DOE, NASA, and DOE advanced heat engine programs show that operation of ceramic parts in high-temperature engines is feasible; however, addition research is needed in materials and processing, design, and data base and life prediction before industry will have a sufficient technology base for producing reliable cost-effective ceramic engine components commercially. A 5-yr project plan was developed, with focus on structural ceramics for advanced gas turbine and diesel engines, ceramic bearings and attachments,more » and ceramic coatings for thermal barrier and wear applications in these engines.« less

Magnetic properties of Y3+ doped Bi4-xTi2FeO12 aurivillius phase ceramics

NASA Astrophysics Data System (ADS)

Tirupathi, Patri; Reddy, H. Satish Kumar; Babu, P. D.

2018-05-01

In the present paper reports a comprehensive investigation of structural, microstructural and magnetic phase transition in Y3+ doped BITF Aurivillius phase compounds. The study of surface morphology by scanning electron microscope reveals the growth of plate-like grains and further the grain size increase with increasing Y3+ composition. Low temperature magnetic studies reveals enhanced magnetic property with doping of Y3+ in BITF. It was explained by considering exchange interaction between the neighboring Fe+3 ions via electron trapped electrons at oxygen vacancies. Temperature dependent dc-magnetic studies exhibit a magnetic transitions TC = 750 K for x=0.0 TC ˜ 674 K for x=1.0 & TC ˜ 645 K for x=1.50 ceramics respectively in high temperature magnetization studies

Packaging Technology Developed for High-Temperature Silicon Carbide Microsystems

NASA Technical Reports Server (NTRS)

Chen, Liang-Yu; Hunter, Gary W.; Neudeck, Philip G.

2001-01-01

High-temperature electronics and sensors are necessary for harsh-environment space and aeronautical applications, such as sensors and electronics for space missions to the inner solar system, sensors for in situ combustion and emission monitoring, and electronics for combustion control for aeronautical and automotive engines. However, these devices cannot be used until they can be packaged in appropriate forms for specific applications. Suitable packaging technology for operation temperatures up to 500 C and beyond is not commercially available. Thus, the development of a systematic high-temperature packaging technology for SiC-based microsystems is essential for both in situ testing and commercializing high-temperature SiC sensors and electronics. In response to these needs, researchers at Glenn innovatively designed, fabricated, and assembled a new prototype electronic package for high-temperature electronic microsystems using ceramic substrates (aluminum nitride and aluminum oxide) and gold (Au) thick-film metallization. Packaging components include a ceramic packaging frame, thick-film metallization-based interconnection system, and a low electrical resistance SiC die-attachment scheme. Both the materials and fabrication process of the basic packaging components have been tested with an in-house-fabricated SiC semiconductor test chip in an oxidizing environment at temperatures from room temperature to 500 C for more than 1000 hr. These test results set lifetime records for both high-temperature electronic packaging and high-temperature electronic device testing. As required, the thick-film-based interconnection system demonstrated low (2.5 times of the room-temperature resistance of the Au conductor) and stable (decreased 3 percent in 1500 hr of continuous testing) electrical resistance at 500 C in an oxidizing environment. Also as required, the electrical isolation impedance between printed wires that were not electrically joined by a wire bond remained high (greater than 0.4 GW) at 500 C in air. The attached SiC diode demonstrated low (less than 3.8 W/mm2) and relatively consistent dynamic resistance from room temperature to 500 C. These results indicate that the prototype package and the compatible die-attach scheme meet the initial design standards for high-temperature, low-power, and long-term operation. This technology will be further developed and evaluated, especially with more mechanical tests of each packaging element for operation at higher temperatures and longer lifetimes.

[Preliminary study of bonding strength between diatomite-based dental ceramic and veneering porcelains].

PubMed

Lu, Xiao-li; Gao, Mei-qin; Cheng, Yu-ye; Zhang, Fei-min

2015-04-01

In order to choose the best veneering porcelain for diatomite-based dental ceramic substrate, the bonding strength between diatomite-based dental ceramics and veneering porcelains was measured, and the microstructure and elements distribution of interface were analyzed. The coefficient of thermal expansion (CTE) of diatomite-based dental ceramics was detected by dilatometry. Three veneering porcelain materials were selected with the best CTE matching including alumina veneering porcelain (group A), titanium porcelain veneering porcelain (group B), and E-max veneering porcelain (group C). Shear bonding strength was detected. SEM and EDS were used to observe the interface microstructure and element distribution. Statistical analysis was performed using SPSS 17.0 software package. The CTE of diatomite-based dental ceramics at 25-500 degrees centigrade was 8.85×10-6K-1. The diatomite-based substrate ceramics combined best with group C. Shear bonding strength between group A and C and group B and C both showed significant differences(P<0.05). SEM and EDS showed that the interface of group C sintered tightly and elements permeated on both sides of the interface. The diatomite-based substrate ceramics combines better with E-max porcelain veneer.

Flight-vehicle materials, structures, and dynamics - Assessment and future directions. Vol. 3 - Ceramics and ceramic-matrix composites

NASA Technical Reports Server (NTRS)

Levine, Stanley R. (Editor)

1992-01-01

The present volume discusses ceramics and ceramic-matrix composites in prospective aerospace systems, monolithic ceramics, transformation-toughened and whisker-reinforced ceramic composites, glass-ceramic matrix composites, reaction-bonded Si3N4 and SiC composites, and chemical vapor-infiltrated composites. Also discussed are the sol-gel-processing of ceramic composites, the fabrication and properties of fiber-reinforced ceramic composites with directed metal oxidation, the fracture behavior of ceramic-matrix composites (CMCs), the fatigue of fiber-reinforced CMCs, creep and rupture of CMCs, structural design methodologies for ceramic-based materials systems, the joining of ceramics and CMCs, and carbon-carbon composites.

Humidity Testing of PME and BME Ceramic Capacitors with Cracks

NASA Technical Reports Server (NTRS)

Teverovsky, Alexander A.; Herzberger, Jaemi

2014-01-01

Cracks in ceramic capacitors are one of the major causes of failures during operation of electronic systems. Humidity testing has been successfully used for many years to verify the absence of cracks and assure quality of military grade capacitors. Traditionally, only precious metal electrode (PME) capacitors were used in high reliability applications and the existing requirements for humidity testing were developed for this type of parts. With the advance of base metal electrode (BME) capacitors, there is a need for assessment of the applicability of the existing techniques for the new technology capacitors. In this work, variety of different PME and BME capacitors with introduced cracks were tested in humid environments at different voltages and temperatures. Analysis of the test results indicates differences in the behavior and failure mechanisms for BME and PME capacitors and the need for different testing conditions.

The lanthanum gallate-based mixed conducting perovskite ceramics

NASA Astrophysics Data System (ADS)

Politova, E. D.; Stefanovich, S. Yu.; Aleksandrovskii, V. V.; Kaleva, G. M.; Mosunov, A. V.; Avetisov, A. K.; Sung, J. S.; Choo, K. Y.; Kim, T. H.

2005-01-01

The structure, microstructure, dielectric, and transport properties of the anion deficient perovskite solid solutions (La,Sr)(Ga,Mg,M)O3- with M=Fe, Ni have been studied. Substitution of iron and nickel for gallium up to about 20 and 40 at.% respectively, leads to the perovskite lattice contraction due to the cation substitutions by the transition elements. The transition from pure ionic to mixed ionic-electronic conductivity was observed for both the systems studied. Both the enhancement of total conductivity and increasing in the thermal expansion coefficient values has been proved to correlate with the increasing amount of weakly bounded oxygen species in the Fe or Ni-doped ceramics. The oxygen ionic conductivity has been estimated from the kinetic experiments using the dc-conductivity and dilatometry methods under the condition of the stepwise change of the atmosphere from nitrogen to oxygen.

Characterization of the Materials Synthesized by High Pressure-High Temperature Treatment of a Polymer Derived t-BC2N Ceramic

PubMed Central

Matizamhuka, Wallace R.; Sigalas, Iakovos; Herrmann, Mathias; Dubronvinsky, Leonid; Dubrovinskaia, Natalia; Miyajima, Nobuyoshi; Mera, Gabriela; Riedel, Ralf

2011-01-01

Bulk B-C-N materials were synthesized under static high thermobaric conditions (20 GPa and 2,000 °C) in a multianvil apparatus from a polymer derived t-BC1.97N ceramic. The bulk samples were characterised using X-ray synchrotron radiation and analytical transmission electron microscopy in combination with electron energy loss spectroscopy. Polycrystalline B-C-N materials with a cubic type structure were formed under the applied reaction conditions, but the formation of a ternary cubic diamond-like c-BC2N compound, could not be unambiguously confirmed. PMID:28824124

Electride Mediated Surface Enhanced Raman Scattering (SERS)

NASA Technical Reports Server (NTRS)

Anderson, Mark S. (Inventor)

2016-01-01

An electride may provide surface enhanced Raman scattering (SERS). The electride, a compound where the electrons serve as anions, may be a ceramic electride, such as a conductive ceramic derived from mayenite, or an organic electride, for example. The textured electride surface or electride particles may strongly enhance the Raman scattering of organic or other Raman active analytes. This may also provide a sensitive method for monitoring the chemistry and electronic environment at the electride surface. The results are evidence of a new class of polariton (i.e., a surface electride-polariton resonance mechanism) that is analogous to the surface plasmon-polariton resonance that mediates conventional SERS.

Method of forming a dense, high temperature electronically conductive composite layer on a porous ceramic substrate

DOEpatents

Isenberg, Arnold O.

1992-01-01

An electrochemical device, containing a solid oxide electrolyte material and an electrically conductive composite layer, has the composite layer attached by: (A) applying a layer of LaCrO.sub.3, YCrO.sub.3 or LaMnO.sub.3 particles (32), on a portion of a porous ceramic substrate (30), (B) heating to sinter bond the particles to the substrate, (C) depositing a dense filler structure (34) between the doped particles (32), (D) shaving off the top of the particles, and (E) applying an electronically conductive layer over the particles (32) as a contact.

Disposable chemical sensors and biosensors made on cellulose paper.

PubMed

Kim, Joo-Hyung; Mun, Seongcheol; Ko, Hyun-U; Yun, Gyu-Young; Kim, Jaehwan

2014-03-07

Most sensors are based on ceramic or semiconducting substrates, which have no flexibility or biocompatibility. Polymer-based sensors have been the subject of much attention due to their ability to collect molecules on their sensing surface with flexibility. Beyond polymer-based sensors, the recent discovery of cellulose as a smart material paved the way to the use of cellulose paper as a potential candidate for mechanical as well as electronic applications such as actuators and sensors. Several different paper-based sensors have been investigated and suggested. In this paper, we review the potential of cellulose materials for paper-based application devices, and suggest their feasibility for chemical and biosensor applications.

Novel Approach for Positioning Sensor Lead Wires on SiC-Based Monolithic Ceramic and FRCMC Components/Subcomponents Having Flat and Curved Surfaces

NASA Technical Reports Server (NTRS)

Kiser, J. Douglas; Singh, Mrityunjay; Lei, Jin-Fen; Martin, Lisa C.

1999-01-01

A novel attachment approach for positioning sensor lead wires on silicon carbide-based monolithic ceramic and fiber reinforced ceramic matrix composite (FRCMC) components has been developed. This approach is based on an affordable, robust ceramic joining technology, named ARCJoinT, which was developed for the joining of silicon carbide-based ceramic and fiber reinforced composites. The ARCJoinT technique has previously been shown to produce joints with tailorable thickness and good high temperature strength. In this study, silicon carbide-based ceramic and FRCMC attachments of different shapes and sizes were joined onto silicon carbide fiber reinforced silicon carbide matrix (SiC/ SiC) composites having flat and curved surfaces. Based on results obtained in previous joining studies. the joined attachments should maintain their mechanical strength and integrity at temperatures up to 1350 C in air. Therefore they can be used to position and secure sensor lead wires on SiC/SiC components that are being tested in programs that are focused on developing FRCMCs for a number of demanding high temperature applications in aerospace and ground-based systems. This approach, which is suitable for installing attachments on large and complex shaped monolithic ceramic and composite components, should enhance the durability of minimally intrusive high temperature sensor systems. The technology could also be used to reinstall attachments on ceramic components that were damaged in service.

Nd3+-doped TeO2-Bi2O3-ZnO transparent glass ceramics for laser application at 1.06 μm

NASA Astrophysics Data System (ADS)

Hu, Xiaolin; Luo, Zhiwei; Liu, Taoyong; Lu, Anxian

2017-04-01

The high crystallinity transparent glass ceramics based on Nd3+-doped 70TeO2-15Bi2O3-15ZnO (TBZ) compositions were successfully prepared by two-step heat treatment process. The effects of Nd2O3 content on the thermal, structural, mechanical, and optical properties of TBZ glass ceramics were studied. The incorporation of Nd2O3 enhanced the crystallization tendency in the matrix glass composition. The crystal phase and morphology of Bi2Te4O11 in the glass ceramics were confirmed by X-ray diffraction and field emission scanning electron microscopy. Due to precipitate more crystal phase, the hardness values increased from 3.21 to 3.66 GPa. Eight absorption peaks were observed from 400 to 900 nm and three emission bands appeared in the range of 850-1400 nm. With the increasing of Nd2O3 content from 0.5 to 2.5 wt%, the intensity of absorption peaks enhanced and the emission intensity increased up to 1.0 wt% and then fell down for further dopant concentration. The fluorescence decay lifetime decreased rapidly starting from 1.5 wt% Nd2O3 content due to the obvious energy migration among Nd3+. According to the extreme strong emission band around 1062 nm and the optimum Nd2O3 content (1.0 wt%), N10 glass ceramic was considered as a potential material for 1.06 μm laser applications.

NASA Tech Briefs, February 1989. Volume 13, No. 2

NASA Technical Reports Server (NTRS)

1989-01-01

This issue contains a special feature on shaping the future with Ceramics. Other topics include: Electronic Components & and Circuits. Electronic Systems, Physical Sciences, Materials, Computer Programs, Mechanics, Machinery, Fabrication Technology, Mathematics and Information Sciences, and Life Sciences,

Emerging Ceramic-based Materials for Dentistry

PubMed Central

Denry, I.; Kelly, J.R.

2014-01-01

Our goal is to give an overview of a selection of emerging ceramics and issues for dental or biomedical applications, with emphasis on specific challenges associated with full-contour zirconia ceramics, and a brief synopsis on new machinable glass-ceramics and ceramic-based interpenetrating phase composites. Selected fabrication techniques relevant to dental or biomedical applications such as microwave sintering, spark plasma sintering, and additive manufacturing are also reviewed. Where appropriate, the authors have added their opinions and guidance. PMID:25274751

The Effect of Water or Wax-based Binders on the Chemical and Morphological Characteristics of the Margin Ceramic-Framework Interface.

PubMed

Güler, Umut; de Queiroz, José Renato Cavalcanti; de Oliveira, Luiz Fernando Cappa; Canay, Senay; Ozcan, Mutlu

2015-09-01

This study evaluated the effect of binder choice in mixing ceramic powder on the chemical and morphological features between the margin ceramic-framework interfaces. Titanium and zirconia frameworks (15 x 5 x 0.5 mm3) were veneered with margin ceramics prepared with two different binders, namely a) water/conventional or b) wax-based. For each zirconia framework material, four different margin ceramics were used: a- Creation Zi (Creation Willi Geller International); b- GC Initial Zr (GC America); Triceram (Dentaurum); and d- IPS emax (voclar Vivadent). For the titanium framework, three different margin ceramics were used: a- Creation Ti (Creation Willi Geller International); b- Triceram (Dentaurum); and c- VITA Titaniumkeramik (Vita Zahnfabrik). The chemical composition of the framework-margin ceramic interface was analyzed using Energy Dispersive X-ray Spectroscopy (EDS) and porosity level was quantified within the margin ceramic using an image program (ImageJ) from four random areas (100 x 100 pixels) on each SEM image. EDS analysis showed the presence of Carbon at the margin ceramic-framework interface in the groups where wax-based binder technique was used with the concentration being the highest for the IPS emax ZirCAD group. While IPS system (IPS ZirCAD and IPS Emax) presented higher porosity concentration using wax binder, in the other groups wax-based binder reduced the porosity of margin ceramic, except for Titanium - Triceram combination.

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.

Reduced wear of enamel with novel fine and nano-scale leucite glass-ceramics.

PubMed

Theocharopoulos, Antonios; Chen, Xiaohui; Hill, Robert; Cattell, Michael J

2013-06-01

Leucite glass-ceramics used to produce all-ceramic restorations can suffer from brittle fracture and wear the opposing teeth. High strength and fine crystal sized leucite glass-ceramics have recently been reported. The objective of this study is to investigate whether fine and nano-scale leucite glass-ceramics with minimal matrix microcracking are associated with a reduction in in vitro tooth wear. Human molar cusps (n=12) were wear tested using a Bionix-858 testing machine (300,000 simulated masticatory cycles) against experimental fine crystal sized (FS), nano-scale crystal sized (NS) leucite glass-ceramics and a commercial leucite glass-ceramic (Ceramco-3, Dentsply, USA). Wear was imaged using Secondary Electron Imaging (SEI) and quantified using white-light profilometry. Both experimental groups were found to produce significantly (p<0.05) less volume and mean-height tooth loss compared to Ceramco-3. The NS group had significantly (p<0.05) less tooth mean-height loss and less combined (tooth and ceramic) loss than the FS group. Increased waviness and damage was observed on the wear surfaces of the Ceramco-3 glass-ceramic disc/tooth group in comparison to the experimental groups. This was also indicated by higher surface roughness values for the Ceramco-3 glass-ceramic disc/tooth group. Fine and nano-sized leucite glass-ceramics produced a reduction in in vitro tooth wear. The high strength low wear materials of this study may help address the many problems associated with tooth enamel wear and restoration failure. Copyright © 2013 Elsevier Ltd. All rights reserved.

Fabrication of Ce3+ doped Gd3Ga3Al2O12 ceramics by reactive sintering method

NASA Astrophysics Data System (ADS)

Ye, Yong; Liu, Peng; Yan, Dongyue; Xu, Xiaodong; Zhang, Jian

2017-09-01

Ce3+ doped Gd3Ga3Al2O12 (Ce:GGAG) ceramics were fabricated by solid state reactive sintering method in this study. The ceramics were pre-sintered in normal muffle furnace in air at various temperature range from 1410 °C to 1550 °C for 10 h and post-treated by hot isostatic press at 1400 °C/2 h in 200 MPa Ar. The phase and microstructure evolution of Ce: GGAG samples during the densification process were investigated by X-ray diffraction and scanning electron microscope. Pure GGAG phase appeared with the temperature increased to 1200 °C. The fully dense and translucent GGAG ceramics were fabricated by pre-sintering at 1450 °C and followed by HIP treatment.

Micro-Raman and FT-IR spectroscopic studies of ceramic shards excavated from ancient Stratonikeia city at Eskihisar village in West-South Turkey

NASA Astrophysics Data System (ADS)

Bahçeli, Semiha; Güleç, Gamze; Erdoğan, Hasan; Söğüt, Bilal

2016-02-01

In this study, micro-Raman and Fourier transformed infrared (FT-IR) spectroscopies, X-ray diffraction (XRD) and scanning electron microscope with energy dispersive X-ray (SEM-EDX) were used to characterize the mineralogical structures of pigments of four ceramic fragments in which one of them belongs to Hellenistic period (1st - IVth century BC) and other three ceramic shards belong to Early Rome (IVth century BC- 1st century AD) excavated from Stratonikeia ancient city. In the results of investigations on these four ceramic fragments, the various phases were identified: quartz, kaolinite, albit (or Na-feldspar), calcite, anastase, hematite and magnetite. Furthermore, the obtained findings indicate that firing temperature is about 800-850 °C for all the shards.

Synthesis and characterization of cerium containing iron phosphate based glass-ceramics

NASA Astrophysics Data System (ADS)

Deng, Yi; Liao, Qilong; Wang, Fu; Zhu, Hanzhen

2018-02-01

The structure and properties of xCeO2-(100-x)(40Fe2O3-60P2O5), where x = 0, 2, 4, 6 and 8 mol%, glass-ceramics prepared by melting and slow cooling method have been investigated by using X-ray diffraction (XRD), scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), differential thermal analysis (DTA) and the Product Consistency Test (PCT). The results show that the 40Fe2O3-60P2O5 sample is homogeneously amorphous and the sample containing 2 mol% CeO2 has a small amount of FePO4 phase embedded. For the sample containing up to 4 mol% CeO2, monazite CePO4 and a small amount of FePO4 appear. Spectra analysis show that the structure networks of the glass-ceramics mainly consist of orthophosphate, along with pyrophosphate and a small amount of metaphosphate units. Moreover, the leaching rates of Fe and Ce are about 3.5 × 10-5 g m-2 d-1 and 5.0 × 10-5 g m-2 d-1 respectively after immersion in deionized water at 90 °C for 56 days, indicating their good chemical durability. The conclusions imply that the prepared method may be a promising process to immobilize nuclear waste into glass-ceramic matrix.

Tailoring the surface chemical bond states of the NbN films by doping Ag: Achieving hard hydrophobic surface

NASA Astrophysics Data System (ADS)

Ren, Ping; Zhang, Kan; Du, Suxuan; Meng, Qingnan; He, Xin; Wang, Shuo; Wen, Mao; Zheng, Weitao

2017-06-01

Robust hydrophobic surfaces based on ceramics capable of withstanding harsh conditions such as abrasion, erosion and high temperature, are required in a broad range of applications. The metal cations with coordinative saturation or low electronegativity are commonly chosen to achieve the intrinsically hydrophobic ceramic by reducing Lewis acidity, and thus the ceramic systems are limited. In this work, we present a different picture that robust hydrophobic surface with high hardness (≥20 GPa) can be fabricated through doping Ag atoms into intrinsically hydrophilic ceramic film NbN by reactive co-sputtering. The transition of wettability from hydrophilic to hydrophobic of Nb-Ag-N films induced by Ag doping results from the appearance of Ag2O groups on the films surfaces through self-oxidation, because Ag cations (Ag+) in Ag2O are the filled-shell (4d105S0) electronic structure with coordinative saturation that have no tendency to interact with water. The results show that surface Ag2O benefited for hydrophobicity comes from the solute Ag atoms rather than precipitate metal Ag, in which the more Ag atoms incorporated into Nb-sublattice are able to further improve the hydrophobicity, whereas the precipitation of Ag nanoclusters would worsen it. The present work opens a window for fabricating robust hydrophobic surface through tailoring surface chemical bond states by doping Ag into transition metal nitrides.

Role of sublayers in mechanical response of pulsed electron beam irradiated surface layers to contact load

NASA Astrophysics Data System (ADS)

Konovalenko, Igor S.

2017-12-01

Here we develop the movable cellular automaton method based a numerical model of surface layers in a NiCr-TiC metal ceramic composite modified by pulsed electron beam irradiation in inert gas plasmas. The model explicitly takes into account the presence of several sublayers differing in structure and mechanical properties. The contribution of each sublayer to the mechanical response of the modified surface to contact loading is studied. It is shown that the maximum strength and fracture toughness are achieved in surface layers containing thin and stiff external sublayers and a more ductile thick internal sublayer.

Mechanics of hard films on soft substrates

NASA Astrophysics Data System (ADS)

Lu, Nanshu

2009-12-01

Flexible electronics have been developed for various applications, including paper-like electronic readers, rollable solar cells, electronic skins etc., with the merits of light weight, low cost, large area, and ruggedness. The systems may be subject to one-time or repeated large deformation during manufacturing and application. Although organic materials can be highly deformable, currently they are not able to fulfill every electronic function. Therefore flexible electronic devices are usually made as organic/inorganic hybrids, with diverse materials, complex architecture, and micro features. While the polymer substrates can recover from large deformations, thin films of electronic materials such as metals, silicon, oxides, and nitrides fracture at small strains, usually less than a few percent. Mechanics of hard films on soft substrates hence holds the key to build high-performance and highly reliable flex circuits. This thesis investigates the deformability and failure mechanisms of thin films of metallic and ceramic materials supported by soft polymeric substrates through combined experimental, theoretical, and numerical methods. When subject to tension, micron-thick metal films with stable microstructure and strong interfacial adhesion to the substrate can be stretched beyond 50% without forming cracks. They eventually rupture by a ductile transgranular fracture which involves simultaneous necking and debonding. When metal films become nanometer-thick, intergranular fracture dominates the failure mode at elongations of only a few percent. Unannealed films show unstable microstructure at room temperature when subject to mechanical loading. In this case, films also rupture at small strains but by three concurrent mechanisms: deformation-induced grain growth, strain localization at large grains, and simultaneous debonding. In contrast to metal films, ceramic films rupture by brittle mechanisms. The only way to prevent rupture of ceramic films is to reduce the strain they are subject to. Instead of using blanket films that fail at strains less than i%, we have patterned ceramic films into a lattice of periodic, isolated islands. Failure modes such as channel cracking, debonding, and wrinkling have been identified. Island behaviors are controlled by factors such as island size, thickness, and elastic mismatch with the substrate. A very soft interlayer between the islands and the underlying polyimide substrate reduces strains in the islands by orders of magnitude. Using this approach, substrates with arrays of 200 x 200 mum2 large SiNx islands were stretched beyond 20% without cracking or debonding the islands. In summary, highly stretchable thin metal films and ceramic island arrays supported by polymer substrates have been achieved, along with mechanistic understandings of their deformation and failure mechanisms.

[Compatibility between high-strength dental ceramic (type A) and vintage AL veneering porcelain].

PubMed

Cui, Jun; Chao, Yong-lie; Meng, Yu-kun

2006-05-01

To investigate the interface bond strength and compatibility between High-Strength Dental Ceramic (type A) and Vintage AL veneering porcelain. Twenty bar-shape specimens (ten Vintage AL and ten Vitadur alpha) were fabricated, and shear test was conducted to determine the bond strength. A bilayered composite (1 mm core ceramic and 0.8 mm Vintage AL) was prepared and then fractured for scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) analysis. Ten all-ceramic anterior crowns were fabricated and the temperatures of thermal shock resistance were tested. The mean values of the bond strength measured were (55.52 +/- 14.64) MPa and (59.37 +/- 13.93) MPa for Vintage AL and Vitadur alpha respectively (P>0.05). SEM showed tight connection between the High-Strength Dental Ceramic (type A) and the veneering porcelain. Element diffusion was also confirmed by energy dispersive spectroscopy (EDS) analysis. The temperature of thermal shock resistance of this system was (179 +/- 15) degrees C. Vintage AL veneering porcelain has good thermal and chemical compatibility with High-Strength Dental Ceramic (type A).

Manipulating electronic and mechanical properties at metal-ceramic interfaces with a nanomolecular layer

NASA Astrophysics Data System (ADS)

Kwan, Matthew P.

This work demonstrates that inserting nanomolecular layers (NMLs) can profoundly change and/or lead to novel electronic and mechanical properties of metal-ceramic interfaces. The first set of results demonstrate that organophosphonate NMLs up to 1.8 nm thick can alter metal work functions by +/- 0.6 eV. This work function change is a strong function of the NML terminal groups (methyl, mercaptan, carboxylic acid, or phosphonic acid), morphology (up right, lying down, or mixed orientation), and the nature of the bonding (covalent, polar, or Van der Waals) between NML and the adjacent layers. Additionally, while NML-ceramic bond type and strength can influence and counteract the effect of NML morphology, the metal-NML bond appears to be independent of the morphology of the NML underlayer. The second set of results demonstrate that inserting an organosilane NML at a metal-ceramic interface can lead to multifold fracture toughening under both static (stress corrosion) and cyclic loads (fatigue) tested in four-point bend. Nanolayer-induced interface strengthening during static loading activates metal plasticity above the metal yield strength, leading to two-fold fracture toughening. Metal plasticity-induced toughening increases as temperature is increased up to 85 °C due to decreasing yield stress. In the fatigue fracture tests I report for the first time a loading-frequency-dependent tripling in fracture toughening in the 75-300 Hz range upon inserting a mercapto-silane NML at the weakest interface of a ceramic-polymer-metal-ceramic stack. This unusual behavior arises from the NML strengthened interface enabling load transfer to- and plasticity in the polymer layer, while the fatigue toughening magnitude and frequency range are determined by polymer rheology.

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.

Environment Conscious Ceramics (Ecoceramics): An Eco-Friendly Route to Advanced Ceramic Materials

NASA Technical Reports Server (NTRS)

Singh, M.

2001-01-01

Environment conscious ceramics (Ecoceramics) are a new class of materials, which can be produced with renewable natural resources (wood) or wood wastes (wood sawdust). This technology provides an eco-friendly route to advanced ceramic materials. Ecoceramics have tailorable properties and behave like ceramic materials manufactured by conventional approaches. Silicon carbide-based ecoceramics have been fabricated by reactive infiltration of carbonaceous preforms by molten silicon or silicon-refractory metal alloys. The fabrication approach, microstructure, and mechanical properties of SiC-based ecoceramics are presented.

Gold/silver coated nanoporous ceramic membranes: a new substrate for SERS studies

NASA Astrophysics Data System (ADS)

Kassu, A.; Robinson, P.; Sharma, A.; Ruffin, P. B.; Brantley, C.; Edwards, E.

2010-08-01

Surface Enhanced Raman Scattering (SERS) is a recently discovered powerful technique which has demonstrated sensitivity and selectivity for detecting single molecules of certain chemical species. This is due to an enhancement of Raman scattered light by factors as large as 1015. Gold and Silver-coated substrates fabricated by electron-beam lithography on Silicon are widely used in SERS technique. In this paper, we report the use of nanoporous ceramic membranes for SERS studies. Nanoporous membranes are widely used as a separation membrane in medical devices, fuel cells and other studies. Three different pore diameter sizes of commercially available nanoporous ceramic membranes: 35 nm, 55nm and 80nm are used in the study. To make the membranes SERS active, they are coated with gold/silver using sputtering techniques. We have seen that the membranes coated with gold layer remain unaffected even when immersed in water for several days. The results show that gold coated nanoporous membranes have sensitivity comparable to substrates fabricated by electron-beam lithography on Silicon substrates.

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)

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.

Effect of Acidic Agents on Surface Roughness of Dental Ceramics

PubMed Central

Kukiattrakoon, Boonlert; Hengtrakool, Chanothai; Kedjarune-Leggat, Ureporn

2011-01-01

Background: An increase in surface roughness of ceramics may decrease strength and affect the clinical success of ceramic restorations. However, little is known about the effect of acidic agents on ceramic restorations. The aim of this study was to evaluate the surface roughness of dental ceramics after being immersed in acidic agents. Methods: Eighty-three ceramic disk specimens (12.0 mm in diameter and 2.0 mm in thickness) were made from four types of ceramics (VMK 95, Vitadur Alpha, IPS Empress Esthetic, and IPS e.max Ceram). Baseline data of surface roughness were recorded by profilometer. The specimens were then immersed in acidic agents (citrate buffer solution, pineapple juice and green mango juice) and deionized water (control) at 37°C for 168 hours. One group was immersed in 4% acetic acid at 80°C for 168 hours. After immersion, surface roughness was evaluated by a profilometer at intervals of 24, 96, and 168 hours. Surface characteristics of specimens were studied using scanning electron microscopy (SEM). Data were analyzed using two-way repeated ANOVA and Tukey's multiple comparisons (α = 0.05). Results: For all studied ceramics, all surface roughness parameters were significantly increased after 168 hours immersion in all acidic agents (P < 0.05). After 168 hours in 4% acetic acid, there were significant differences for all roughness parameters from other acidic agents of all evaluated ceramics. Among all studied ceramics, Vitadur Alpha showed significantly the greatest values of all surface roughness parameters after immersion in 4% acetic acid (P < 0.001). SEM photomicrographs also presented surface destruction of ceramics in varying degrees. Conclusion: Acidic agents used in this study negatively affected the surface of ceramic materials. This should be considered when restoring the eroded tooth with ceramic restorations in patients who have a high risk of erosive conditions. PMID:22132009

Pre-form ceramic matrix composite cavity and a ceramic matrix composite component

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

Monaghan, Philip Harold; Delvaux, John McConnell; Taxacher, Glenn Curtis

A pre-form CMC cavity and method of forming pre-form CMC cavity for a ceramic matrix component includes providing a mandrel, applying a base ply to the mandrel, laying-up at least one CMC ply on the base ply, removing the mandrel, and densifying the base ply and the at least one CMC ply. The remaining densified base ply and at least one CMC ply form a ceramic matrix component having a desired geometry and a cavity formed therein. Also provided is a method of forming a CMC component.

Light Weight Biomorphous Cellular Ceramics from Cellulose Templates

NASA Technical Reports Server (NTRS)

Singh, Mrityunjay; Yee, Bo-Moon; Gray, Hugh R. (Technical Monitor)

2003-01-01

Bimorphous ceramics are a new class of materials that can be fabricated from the cellulose templates derived from natural biopolymers. These biopolymers are abundantly available in nature and are produced by the photosynthesis process. The wood cellulose derived carbon templates have three- dimensional interconnectivity. A wide variety of non-oxide and oxide based ceramics have been fabricated by template conversion using infiltration and reaction-based processes. The cellular anatomy of the cellulose templates plays a key role in determining the processing parameters (pyrolysis, infiltration conditions, etc.) and resulting ceramic materials. The processing approach, microstructure, and mechanical properties of the biomorphous cellular ceramics (silicon carbide and oxide based) have been discussed.

PLZT Ceramic Driving Rotary Micro-mirror Based on Photoelectric-electrostatic Mechanism

NASA Astrophysics Data System (ADS)

Tang, Yujuan; Yang, Zhong; Chen, Yusong; Wang, Xinjie

2017-12-01

Based on the anomalous photovoltaic effect of PLZT, a rotary micro-mirror driven by hybrid photoelectric-electrostatic actuation of PLZT ceramic is proposed. Firstly, the mathematical modelling of coupled multi-physics fields of PLZT ceramic is established during illumination and light off phases. Then, the relationship between the rotation angle and the photovoltage of PLZT ceramics is established. In addition, the feasibility of rotary micro-mirror with hybrid photoelectric-electrostatic driving is verified via closed-loop control for photo-induced voltage of PLZT ceramic. The experimental results show that the photo-induced voltage of PLZT ceramics has good dynamic control precision using on-off closed-loop control method.

Identification of light elements in silicon nitride by aberration-corrected scanning transmission electron microscopy.

PubMed

Idrobo, Juan C; Walkosz, Weronika; Klie, Robert F; Oğüt, Serdar

2012-12-01

In silicon nitride structural ceramics, the overall mechanical and thermal properties are controlled by the atomic and electronic structures at the interface between the ceramic grains and the amorphous intergranular films (IGFs) formed by various sintering additives. In the last ten years the atomic arrangements of heavy elements (rare-earths) at the Si(3)N(4)/IGF interfaces have been resolved. However, the atomic position of light elements, without which it is not possible to obtain a complete description of the interfaces, has been lacking. This review article details the authors' efforts to identify the atomic arrangement of light elements such as nitrogen and oxygen at the Si(3)N(4)/SiO(2) interface and in bulk Si(3)N(4) using aberration-corrected scanning transmission electron microscopy. Published by Elsevier B.V.

High temperature solid electrolyte fuel cell with ceramic electrodes

DOEpatents

Marchant, David D.; Bates, J. Lambert

1984-01-01

A solid oxide electrolyte fuel cell is described having a central electrolyte comprised of a HfO.sub.2 or ZrO.sub.2 ceramic stabilized and rendered ionically conductive by the addition of Ca, Mg, Y, La, Nd, Sm, Gd, Dy Er, or Yb. The electrolyte is sandwiched between porous electrodes of a HfO.sub.2 or ZrO.sub.2 ceramic stabilized by the addition of a rare earth and rendered electronically conductive by the addition of In.sub.2 O.sub.3. Alternatively, the anode electrode may be made of a metal such as Co, Ni, Ir Pt, or Pd.

High temperature solid electrolyte fuel cell with ceramic electrodes

DOEpatents

Bates, J.L.; Marchant, D.D.

A solid oxide electrolyte fuel cell is described having a central electrolyte comprised of a HfO/sub 2/ or ZrO/sub 2/ ceramic stabilized and rendered ionically conductive by the addition of Ca, Mg, Y, La, Nd, Sm, Gd, Dy Er, or Yb. The electrolyte is sandwiched between porous electrodes of a HfO/sub 2/ or ZrO/sub 2/ ceramic stabilized by the addition of a rare earth and rendered electronically conductive by the addition of In/sub 2/O/sub 3/. Alternatively, the anode electrode may be made of a metal such as Co, Ni, Ir Pt, or Pd.

Aging of ceramic carbonized hydroxyapatite at room temperature

NASA Astrophysics Data System (ADS)

Tkachenko, M. V.; Kamzin, A. S.

2016-08-01

The process of aging of ceramic carbonized hydroxyapatite (CHA) produced in a dry carbon dioxide atmosphere at temperatures of 800-1200°C has been studied by chemical and X-ray structural analysis, infrared spectroscopy, and scanning electron microscopy methods. The phase composition and structure of initial prepared ceramics samples and those aged for a year have been compared. It has been shown that relaxation of internal stresses occurring during pressed sample sintering causes plastic deformation of crystallites at room temperature, accompanied by redistribution of carbonate ions between A1, A2, B1, and B2 sites and CHA decomposition with the formation of CaO separations.

Chemical Vapor Deposition of Turbine Thermal Barrier Coatings

NASA Technical Reports Server (NTRS)

Haven, Victor E.

1999-01-01

Ceramic thermal barrier coatings extend the operating temperature range of actively cooled gas turbine components, therefore increasing thermal efficiency. Performance and lifetime of existing ceram ic coatings are limited by spallation during heating and cooling cycles. Spallation of the ceramic is a function of its microstructure, which is determined by the deposition method. This research is investigating metalorganic chemical vapor deposition (MOCVD) of yttria stabilized zirconia to improve performance and reduce costs relative to electron beam physical vapor deposition. Coatings are deposited in an induction-heated, low-pressure reactor at 10 microns per hour. The coating's composition, structure, and response to the turbine environment will be characterized.

Emergency Dosimetry Using Ceramic Components in Personal Electronic Devices

NASA Astrophysics Data System (ADS)

Kouroukla, E. C.; Bailiff, I. K.; Terry, I.

2014-02-01

The rapid assessment of radiation dose to members of the public exposed to significant levels of ionizing radiation during a radiological incident presents a significant difficulty in the absence of planned radiation monitoring. However, within most personal electronic devices components such as resistors with alumina substrates can be found that have potentially suitable properties as solid state dosimeters using luminescence measurement techniques. The suitability of several types of ceramic-based components (e.g., resonators, inductors and resistors) has been previously examined using optically stimulated luminescence (OSL) and thermoluminescence (TL) techniques to establish their basic characteristics for the retrospective determination of absorbed dose. In this paper, we present results obtained with aluminum oxide surface mount resistors extracted from mobile phones that further extend this work. Very encouraging results have been obtained related to the measurement of luminescence sensitivity, dose response, reusability, limit of detection, signal reproducibility and known-dose recovery. However, the alumina exhibits a rapid loss of the latent luminescence signal with time following irradiation attributed to athermal (or anomalous) fading. The issues related to obtaining a reliable correction protocol for this loss and the detailed examinations required of the fading behavior are discussed.

Microstructural Analysis and Transport Properties of Thermally Sprayed Multiple-Layer Ceramic Coatings

DOE PAGES

Wang, Hsin; Muralidharan, Govindarajan; Leonard, Donovan N.; ...

2018-01-04

In this paper, multilayer, graded ceramic/metal coatings were prepared by an air plasma spray method on Ti-6Al-4V, 4140 steel and graphite substrates. The coatings were designed to provide thermal barriers for diesel engine pistons to operate at higher temperatures with improved thermal efficiency and cleaner emissions. A systematic, progressive variation in the mixture of yttria-stabilized zirconia and bondcoat alloys (NiCoCrAlYHfSi) was designed to provide better thermal expansion match with the substrate and to improve thermal shock resistance and cycle life. Heat transfer through the layers was evaluated by a flash diffusivity technique based on a model of one-dimensional heat flow.more » The aging effect of the as-sprayed coatings was captured during diffusivity measurements, which included one heating and cooling cycle. The hysteresis of thermal diffusivity due to aging was not observed after 100-h annealing at 800 °C. The measurements of coatings on substrate and freestanding coatings allowed the influence of interface resistance to be evaluated. Finally, the microstructure of the multilayer coating was examined using scanning electron microscope and electron probe microanalysis.« less

Microstructural Analysis and Transport Properties of Thermally Sprayed Multiple-Layer Ceramic Coatings

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

Wang, Hsin; Muralidharan, Govindarajan; Leonard, Donovan N.

In this paper, multilayer, graded ceramic/metal coatings were prepared by an air plasma spray method on Ti-6Al-4V, 4140 steel and graphite substrates. The coatings were designed to provide thermal barriers for diesel engine pistons to operate at higher temperatures with improved thermal efficiency and cleaner emissions. A systematic, progressive variation in the mixture of yttria-stabilized zirconia and bondcoat alloys (NiCoCrAlYHfSi) was designed to provide better thermal expansion match with the substrate and to improve thermal shock resistance and cycle life. Heat transfer through the layers was evaluated by a flash diffusivity technique based on a model of one-dimensional heat flow.more » The aging effect of the as-sprayed coatings was captured during diffusivity measurements, which included one heating and cooling cycle. The hysteresis of thermal diffusivity due to aging was not observed after 100-h annealing at 800 °C. The measurements of coatings on substrate and freestanding coatings allowed the influence of interface resistance to be evaluated. Finally, the microstructure of the multilayer coating was examined using scanning electron microscope and electron probe microanalysis.« less

Effect of Powder Grain Size on Microstructure and Magnetic Properties of Hexagonal Barium Ferrite Ceramic

NASA Astrophysics Data System (ADS)

Shao, Li-Huan; Shen, Si-Yun; Zheng, Hui; Zheng, Peng; Wu, Qiong; Zheng, Liang

2018-05-01

Compact hexagonal barium ferrite (BaFe12O19, BaM) ceramics with excellent magnetic properties have been prepared from powder with the optimal grain size. The dependence of the microstructure and magnetic properties of the ceramics on powder grain size was studied in detail. Single-phase hexagonal barium ferrite powder with grain size of 177 nm, 256 nm, 327 nm, and 454 nm was obtained by calcination under different conditions. Scanning electron microscopy revealed that 327-nm powder was beneficial for obtaining homogeneous grain size and compact ceramic. In addition, magnetic hysteresis loops and complex permeability spectra demonstrated that the highest saturation magnetization (67.2 emu/g) and real part of the permeability (1.11) at 1 GHz were also obtained using powder with grain size of 327 nm. This relationship between the powder grain size and the properties of the resulting BaM ceramic could be significant for development of microwave 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

Cu3Mo2O9: An Ultralow-Firing Microwave Dielectric Ceramic with Good Temperature Stability and Chemical Compatibility with Aluminum

NASA Astrophysics Data System (ADS)

Wen, Wangxi; Li, Chunchun; Sun, Yihua; Tang, Ying; Fang, Liang

2018-02-01

An ultralow-firing microwave dielectric ceramic Cu3Mo2O9 with orthorhombic structure has been fabricated via a solid-state reaction method. X-ray diffraction analysis, Rietveld refinement, Raman spectroscopy, energy-dispersive spectrometry, and scanning electron microscopy were employed to explore the phase purity, crystal structure, and microstructure. Pure and dense Cu3Mo2O9 ceramics could be obtained in the sintering temperature range from 580°C to 680°C. The sample sintered at 660°C for 4 h exhibited the highest relative density (˜ 97.2%) and best microwave dielectric properties with ɛ r = 7.2, Q × f = 19,300 GHz, and τ f = - 7.8 ppm/°C. Chemical compatibility with aluminum electrodes was also confirmed. All the results suggest that Cu3Mo2O9 ceramic is a promising candidate for use in ultralow-temperature cofired ceramic applications.

Thermal Cycle Reliability and Failure Mechanisms of CCGA and PBGA Assemblies with and without Corner Staking

NASA Technical Reports Server (NTRS)

Ghaffarian, Reza

2008-01-01

Area array packages (AAPs) with 1.27 mm pitch have been the packages of choice for commercial applications; they are now starting to be implemented for use in military and aerospace applications. Thermal cycling characteristics of plastic ball grid array (PBGA) and chip scale package assemblies, because of their wide usage for commercial applications, have been extensively reported on in literature. Thermal cycling represents the on-off environmental condition for most electronic products and therefore is a key factor that defines reliability.However, very limited data is available for thermal cycling behavior of ceramic packages commonly used for the aerospace applications. For high reliability applications, numerous AAPs are available with an identical design pattern both in ceramic and plastic packages. This paper compares assembly reliability of ceramic and plastic packages with the identical inputs/outputs(I/Os) and pattern. The ceramic package was in the form of ceramic column grid array (CCGA) with 560 I/Os peripheral array with the identical pad design as its plastic counterpart.

Characterization of the bioactive and mechanical behavior of dental ceramic/sol-gel derived bioactive glass mixtures.

PubMed

Abbasi, Zahra; Bahrololoum, Mohammad E; Bagheri, Rafat; Shariat, Mohammad H

2016-02-01

Dental ceramics can be modified by bioactive glasses in order to develop apatite layer on their surface. One of the benefits of such modification is to prolong the lifetime of the fixed dental prosthesis by preventing the formation of secondary caries. Dental ceramic/sol-gel derived bioactive glass mixture is one of the options for this modification. In the current study, mixtures of dental ceramic/bioactive glass with different compositions were successfully produced. To evaluate their bioactive behavior, prepared samples were immersed in a simulated body fluid at various time intervals. The prepared and soaked specimens were characterized using Fourier transform infrared spectroscopy, X-ray diffractometry and scanning electron microscopy. Since bioactive glasses have deleterious effects on the mechanical properties of dental ceramics, 3-point bending tests were used to evaluate the flexural strength, flexural strain, tangent modulus of elasticity and Weibull modulus of the specimens in order to find the optimal relationship between mechanical and bioactive properties. Copyright © 2015 Elsevier Ltd. All rights reserved.

Onset of multiferroicity in nickel and lithium co-substituted barium titanate ceramics

NASA Astrophysics Data System (ADS)

Alkathy, Mahmoud S.; James Raju, K. C.

2018-04-01

The structural, magnetic and ferroelectric properties of nickel and lithium co-substituted barium titanate were investigated in this work. Ba(1-x)LixNix/2TiO3 (x = 0, 0.02, 0.04 and 0.08) ceramics were synthesized via solid-state reaction with the assistance of microwave heating of the starting materials. The tetragonal structure has been observed in all samples, and it is confirmed by the Rietveld refinement study. The morphological study has been carried out by FE-SEM. Electron spin resonance (ESR) has been used to study the electron interaction and to verify the magnetism behavior of present samples. No resonance signal was observed in pure BaTiO3 samples. However, the resonance signal has appeared in the co-substituted samples. The result shows that the electron interactions are strongly affected by Ni2+ and Li+ concentrations. M-H loop was traced using VSM at room temperature. The results confirm that the sample with x = 0 shows an anti-ferromagnetic response. However, a ferromagnetic hysteresis loop arises with co-substitution. The emergence of M-H loops confirms the appearance of magnetic properties in Ni2+ and Li+ co-substituted BaTiO3 ceramics. The origin of magnetic behavior could be due to the carrier-mediated exchange interactions. Room temperature P-E hysteresis loop has been investigated at an applied electric field of 35 kV/cm and 33 Hz frequency. Measurements of room temperature ferroelectric and magnetic hysteresis loops indicate that the Ni2+ and Li+ co-substituted BaTiO3 ceramics show ferroelectricity and ferromagnetism simultaneously.

In-situ formation of multiphase deposited thermal barrier coatings

DOEpatents

Subramanian, Ramesh

2004-01-13

A multiphase ceramic thermal barrier coating is provided. The coating is adapted for use in high temperature applications in excess of about 1200.degree. C., for coating superalloy components of a combustion turbine engine. The coating comprises a ceramic single or two oxide base layer disposed on the substrate surface; and a ceramic oxide reaction product material disposed on the base layer, the reaction product comprising the reaction product of the base layer with a ceramic single or two oxide overlay layer.

Compressive Strength and Indentation Damage in Ceramic Materials.

DTIC Science & Technology

1978-05-31

The extent of the plastically deformed region associated with indentation in silicon carbide is determined by means of selected area electron...microfracture mechanisms responsible for the temperature-sensitive compressive strength behavior of polycrystalline Al2O3 and alpha-SiC. It is determined ...that the early stages of damage can be related to the presence or absence of microplasticity , depending upon the ceramic. Further, local plastic flow in

Workshop on High Temperature Metal-Ceramic Composites Held in Aurora, New York on 10-11 September 1990

DTIC Science & Technology

1990-12-26

to mechanical properties , atomic structure , electronic bonding, and long term stability of interfaces at high temperature. The objective of this...discussion. The subjects were measurement of the local mechanical properties of-interfaces, constrained deformation, reactions at metal ceramic...as a function of oxygen activity and the effect of these reactions on mechanical properties understood, (iv) local deformation on the scale of

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.

Low-temperature Spin Spray Deposited Ferrite/piezoelectric Thin Film Magnetoelectric Heterostructures with Strong Magnetoelectric Coupling

DTIC Science & Technology

2014-01-08

more energy efficient, lightweight, compact, and less noisy. Studies on ME heterostructures are mostly based on complex oxide piezoelectric ceramic or...except for a recent demonstration of a spin spray deposited ZnO films [17, 18]. ZnO is a typical piezoelectric material , which makes it a good...erties which makes it applicable in a wide variety of electron, optoelectronic, spintronics and nanodevices [17, 18]. The piezoelectric properties of

High Temperature Studies of La-Monazite

DTIC Science & Technology

2004-07-01

Hay, E. Boakeye, M. D. Petry, Y. Berta, K. Von Lehmden, and J. Welch, " 5 A. Meldrum , L. A. Boatner, and R. C. Ewing, "Electron-Irradiation-Induced... Meldrum , L. A. Boatner, and R. C. Ewing, "A Comparison of Radiation Alumina-based Fiber for High Temperature Composite Reinforcement," Ceram. Eng... acid . The processing included procedures that allowed the La/P ratio to be controlled to be very close to the stoichiometric value of unity (within less

Synthesis of the Novel Type of Bimodal Ceramic Nanowires from Polymer and Composite Fibrous Mats

PubMed Central

Matysiak, Wiktor

2018-01-01

The purpose of this paper was to produce SiO2 and TiO2 nanowires via the electrospinning process from a polyvinylpyrrolidone (PVP)/Tetraethyl orthosilicate (TEOS)/Titanium (IV) butoxide (TNBT)/dimethylformamide (DMF) and ethanol (EtOH) solution. The as-obtained nanofibers were calcined at temperatures ranging from 400 °C to 600 °C in order to remove the organic phase. The one-dimensional ceramic nanostructures were studied using a scanning electron microscope (SEM) and a transmission electron microscope (TEM) to analyze the influence of the used temperature on the morphology and structures of the obtained ceramic nanomaterials. In order to examine the chemical structure of the nanowires, energy dispersive spectrometry (EDX) and Fourier-Transform Infrared spectroscopy (FTIR) were used. The optical property analysis was performed on the basis of UV-Vis spectra of absorbance as a function of the wavelength. Using the modified Swanepoel method, which the authors proposed and the recorded absorbance spectra allowed to determine the banded refractive index n, real n′ and imaginary k part of the refractive index as a function of the wavelength, complex dielectric permeability ε, and real and imaginary part εr and εi of the dielectric permeability as a function of the radiation energy of the produced ceramic nanowires. PMID:29558456

Influence of Europium Doping on Various Electrical Properties of Low-Temperature Sintered 0.5Ba0.90Ca0.10TiO3-0.5BaTi0.88Zr0.12O3-0.1%CuO- xEu Lead-Free Ceramics

NASA Astrophysics Data System (ADS)

Tian, Yongshang; Li, Shuiyun; Sun, Shulin; Gong, Yansheng; Li, Tiantian; Yu, Yongshang; Jing, Qiangshan

2018-01-01

0.5Ba0.90Ca0.10TiO3-0.5BaTi0.88Zr0.12O3-0.1%CuO- xEu (BCT-BZT-Cu- xEu; x = 0-0.90%) lead-free ceramics were sintered at 1220°C with as-synthesized nanoparticles by a modified Pechini method. The structural characteristics and electrical properties of the ceramics that were influenced by varying europium-doping were investigated. All the ceramics featured high densification (relative density: ˜ 96%). X-ray powder diffraction results indicated the samples possessed pure orthorhombic phase. The maximum relative permittivity ( ɛ r, 10869) was found at x around 0.30%. Europium ions could dope on different substitution sites in the ABO3 lattice, which evidently influenced electrical properties with various volumes of oxygen vacancy. Moreover, the formation mechanisms of oxygen vacancy and defect electron complexes were stated. The piezoelectric properties were impacted by defect electron complexes, internal stress, ionic electronegativity, etc. The optimal electrical properties, i.e., d 33 = 384 pC/N, Q m = 92, and k p = 0.36, were detected at x = 0.45%.

Processing and characterization of multi-cellular monolithic bioceramics for bone regenerative scaffolds

NASA Astrophysics Data System (ADS)

Ari-Wahjoedi, Bambang; Ginta, Turnad Lenggo; Parman, Setyamartana; Abustaman, Mohd Zikri Ahmad

2014-10-01

Multicellular monolithic ceramic body is a ceramic material which has many gas or liquid passages partitioned by thin walls throughout the bulk material. There are many currently known advanced industrial applications of multicellular ceramics structures i.e. as supports for various catalysts, electrode support structure for solid oxide fuel cells, refractories, electric/electronic materials, aerospace vehicle re-entry heat shields and biomaterials for dental as well as orthopaedic implants by naming only a few. Multicellular ceramic bodies are usually made of ceramic phases such as mullite, cordierite, aluminum titanate or pure oxides such as silica, zirconia and alumina. What make alumina ceramics is excellent for the above functions are the intrinsic properties of alumina which are hard, wear resistant, excellent dielectric properties, resists strong acid and alkali attacks at elevated temperatures, good thermal conductivities, high strength and stiffness as well as biocompatible. In this work the processing technology leading to truly multicellular monolithic alumina ceramic bodies and their characterization are reported. Ceramic slip with 66 wt.% solid loading was found to be optimum as impregnant to the polyurethane foam template. Mullitic ceramic composite of alumina-sodium alumino disilicate-Leucite-like phases with bulk and true densities of 0.852 and 1.241 g cm-3 respectively, pore linear density of ±35 cm-1, linear and bulk volume shrinkages of 7-16% and 32 vol.% were obtained. The compressive strength and elastic modulus of the bioceramics are ≈0.5-1.0 and ≈20 MPa respectively.

Silica coating on alumina ceramic: comparison of three chairside air-abrasion devices working for different times and distances.

PubMed

Pestana Passos, S; Dias Vanderlei, A; Ozcan, M; Felipe Valandro, L F; Felipe Valandro, L

2011-03-01

This study evaluated, by scanning electron microscope (SEM) and EDS, the effect of different strategies for silica coating (sandblasters, time and distance) of a glass-infiltrated ceramic (In-Ceram Alumina). Forty-one ceramic blocks were produced. For comparison of the three air-abrasion devices, 15 ceramic samples were divided in three groups (N.=5): Bioart, Microetcher and Ronvig (air-abrasion parameters: 20 s at a distance of 10 mm). For evaluation of the time and distance factors, ceramic samples (N.=5) were allocated in groups considering three applied times (5 s, 13 s and 20 s) and two distances (10 mm and 20 mm), using the Ronvig device. In a control sample, no surface treatment was performed. After that, the micro-morphologic analyzes of the ceramic surfaces were made using SEM. EDS analyzes were carried out to detect the % of silica on representative ceramic surface. ANOVA and Tukey tests were used to analyze the results. One-way ANOVA showed the silica deposition was different for different devices (P=0.0054). The Ronvig device promoted the highest silica coating compared to the other devices (Tukey test). Two-way ANOVA showed the distance and time factors did not affect significantly the silica deposition (application time and distance showed no statistical difference). The Ronvig device provided the most effective silica deposition on glass-infiltrated alumina ceramic surface and the studied time and distance for air-abrasion did not affect the silica coating.

Alumina-based ceramic composite

DOEpatents

Alexander, Kathleen B.; Tiegs, Terry N.; Becher, Paul F.; Waters, Shirley B.

1996-01-01

An improved ceramic composite comprising oxide ceramic particulates, nonoxide ceramic particulates selected from the group consisting of carbides, borides, nitrides of silicon and transition metals and mixtures thereof, and a ductile binder selected from the group consisting of metallic, intermetallic alloys and mixtures thereof is described. The ceramic composite is made by blending powders of the ceramic particulates and the ductile to form a mixture and consolidating the mixture of under conditions of temperature and pressure sufficient to produce a densified ceramic composite.

Effects of single pulse energy on the properties of ceramic coating prepared by micro-arc oxidation on Ti alloy

NASA Astrophysics Data System (ADS)

Wang, Jun-Hua; Wang, Jin; Lu, Yan; Du, Mao-Hua; Han, Fu-Zhu

2015-01-01

The effects of single pulse energy on the properties of ceramic coating fabricated on a Ti-6Al-4V alloy via micro-arc oxidation (MAO) in aqueous solutions containing aluminate, phosphate, and some additives are investigated. The thickness, micro-hardness, surface and cross-sectional morphology, surface roughness, and compositions of the ceramic coating are studied using eddy current thickness meter, micro-hardness tester, JB-4C Precision Surface roughness meter, scanning electron microscopy (SEM) and X-ray diffraction (XRD). Single pulse energy remarkably influences the ceramic coating properties. The accumulative time of impulse width is an important parameter in the scientific and rational measurement of the film forming law of ceramic coating. The ceramic coating thickness approximately linearly increases with the cumulative time of impulse width. Larger impulse width resulted in higher single pulse energy, film forming rates and thicker ceramic coating thickness. The sizes of oxide particles, micro-pores and micro-cracks slightly increase with impulse width and single pulse energy. The main surface conversion products generated during MAO process in aqueous solutions containing aluminate are rutile TiO2, anatase TiO2, and a large amount of Al2TiO5. The effects of single pulse energy on the micro-hardness and phase composition of ceramic coating are not as evident as those of frequency and duty cycle.

Luminescent properties of Eu{sup 2+}-doped BaGdF{sub 5} glass ceramics a potential blue phosphor for ultra-violet light-emitting diode

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

Zhang, Weihuan; Zhang, Yuepin, E-mail: zhangyuepin@nbu.edu.cn; Ouyang, Shaoye

2015-01-14

Eu{sup 2+} doped transparent oxyfluoride glass ceramics containing BaGdF{sub 5} nanocrystals were successfully fabricated by melt-quenching technique under a reductive atmosphere. The structure of the glass and glass ceramics were investigated by differential scanning calorimetry, X-ray diffraction (XRD), and transmission electron microscopy (TEM). The luminescent properties were investigated by transmission, excitation, and emission spectra. The decay time of the Gd{sup 3+} ions at 312 nm excited with 275 nm were also investigated. The results of XRD and TEM indicated the existence of BaGdF5 nanocrystals in the transparent glass ceramics. The excitation spectra of Eu{sup 2+} doped glass ceramics showed an excellent overlapmore » with the main emission region of an ultraviolet light-emitting diode (UV-LED). Compared with the as-made glass, the emission of glass ceramics is much stronger by a factor of increasing energy transfer efficiency from Gd{sup 3+} to Eu{sup 2+} ions, the energy transfer efficiency from Gd{sup 3+} to Eu{sup 2+} ions was discussed. In addition, the chromaticity coordinates of glass and glass ceramics specimens were also discussed, which indicated that the Eu{sup 2+} doped BaGdF{sub 5} glass ceramics may be used as a potential blue-emitting phosphor for UV-LED.« less

Ceramic membrane fouling during ultrafiltration of oil/water emulsions: roles played by stabilization surfactants of oil droplets.

PubMed

Lu, Dongwei; Zhang, Tao; Ma, Jun

2015-04-07

Oil/water (O/W) emulsion stabilized by surfactants is the part of oily wastewater that is most difficult to handle. Ceramic membrane ultrafiltration presently is an ideal process to treat O/W emulsions. However, little is known about the fouling mechanism of the ceramic membrane during O/W emulsion treatment. This paper investigated how stabilization surfactants of O/W emulsions influence the irreversible fouling of ceramic membranes during ultrafiltration. An unexpected phenomenon observed was that irreversible fouling was much less when the charge of the stabilization surfactant of O/W emulsions is opposite to the membrane. The less ceramic membrane fouling in this case was proposed to be due to a synergetic steric effect and demulsification effect which prevented the penetration of oil droplets into membrane pores and led to less pore blockage. This proposed mechanism was supported by cross section images of fouled and virgin ceramic membranes taken with scanning electron microscopy, regression results of classical fouling models, and analysis of organic components rejected by the membrane. Furthermore, this mechanism was also verified by the existence of a steric effect and demulsification effect. Our finding suggests that ceramic membrane oppositely charged to the stabilization surfactant should be applied in ultrafiltration of O/W emulsions to alleviate irreversible membrane fouling. It could be a useful rule for ceramic membrane ultrafiltration of oily wastewater.

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.

Nanocrystallization in Fluorochlorozirconate Glass-Ceramics.

PubMed

Alvarez, Carlos J; Liu, Yuzi; Leonard, Russell L; Johnson, Jacqueline A; Petford-Long, Amanda K

2013-11-01

Heat treating fluorochlorozirconate (FCZ) glasses nucleates nanocrystals in the glass matrix, resulting in a nanocomposite glass-ceramic that has optical properties suitable for use as a medical imaging plate. Understanding the way in which the nanocrystal nucleation proceeds is critical to controlling the optical behavior. The nucleation and growth of nanocrystals in FCZ glass-ceramics was investigated with in situ transmission electron microscopy heating experiments. The experiments showed the nucleation and growth of previously unreported BaF 2 nanocrystals in addition to the expected BaCl 2 nanocrystals. Chemical analysis of the BaF 2 nanocrystals shows an association with the optically active dopant previously thought only to interact with BaCl 2 nanocrystals. The association of the dopant with BaF 2 crystals suggests that it plays a role in the photoluminescent (PL) properties of FCZ glass-ceramics.

A High-Average-Power Free Electron Laser for Microfabrication and Surface Applications

NASA Technical Reports Server (NTRS)

Dylla, H. F.; Benson, S.; Bisognano, J.; Bohn, C. L.; Cardman, L.; Engwall, D.; Fugitt, J.; Jordan, K.; Kehne, D.; Li, Z.;

Fractographic Investigation of Micromechanisms of Fracture in Alumina Ceramics

DTIC Science & Technology

1981-11-30

mechanisms flaw linking work of fracture electron channeling crack branching environmental effects 20. A07 ACT (Continue an reverse side Of necessary and...CLASSIFICATION OF THIS PAGE(I hm Date "ftn.,a environments using multiple techniques such as SEM, TEM, selected area electron channeling , and...94 Selected area electron channeling (SAEC) .. .... ........ 99 V. CONCLUSIONS. .. ............................ 100 VI. REFERENCES

Internal coating of zirconia restoration with silica-based ceramic improves bonding of resin cement to dental zirconia ceramic.

PubMed

Kitayama, Shuzo; Nikaido, Toru; Ikeda, Masaomi; Alireza, Sadr; Miura, Hiroyuki; Tagami, Junji

2010-01-01

Resin bonding to zirconia ceramic cannot be established by standard methods that are utilized for conventional silica-based dental ceramics. This study was aimed to examine the tensile bond strength of resin cement to zirconia ceramic using a new laboratory technique. Sixty-four zirconia ceramic specimens were air-abraded using Al2O3 particles and divided into two groups; the control group with no pretreatment (Control), and the group pretreated using the internal coating technique (INT), in which the surface of the zirconia specimens were thinly coated by fusing silica-based ceramic and air-abraded in the same manner. The specimens in each group were further divided into two subgroups according to the silane coupling agents applied; a mixture of dentin primer/silane coupling agent (Clearfil SE Bond Primer/Porcelain Bond Activator) or a newly developed single-component silane coupling agent (Clearfil Ceramic Primer). After bonding with dual-cured resin cement (Panavia F 2.0), they were stored in water for 24 h and half of them were additionally subjected to thermal cycling. The tensile bond strengths were tested using a universal testing machine. ANOVAs revealed significant influence of ceramic surface pretreatment (p<0.001), silane coupling agent (p<0.001) and thermal cycling (p<0.001); the INT coating technique significantly increased the bond strengths of resin cement to zirconia ceramic, whereas thermal cycling significantly decreased the bond strengths. The use of a single-component silane coupling agent demonstrated significantly higher bond strengths than that of a mixture of dentin primer/silane coupling agent. The internal coating of zirconia dental restorations with silica-based ceramic followed by silanization may be indicated in order to achieve better bonding for the clinical success.

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.

CoO-doped MgO-Al2O3-SiO2-colored transparent glass-ceramics with high crystallinity

NASA Astrophysics Data System (ADS)

Tang, Wufu; Zhang, Qian; Luo, Zhiwei; Yu, Jingbo; Gao, Xianglong; Li, Yunxing; Lu, Anxian

2018-02-01

To obtain CoO-doped MgO-Al2O3-SiO2 (MAS)-colored transparent glass-ceramics with high crystallinity, the glass with the composition 21MgO-21Al2O3-54SiO2-4B2O3-0.2CoO (in mol %) was prepared by conventional melt quenching technique and subsequently thermal treated at several temperatures. The crystallization behavior of the glass, the precipitated crystalline phases and crystallinity were analyzed by X-ray diffraction (XRD). The microstructure of the glass-ceramics was characterized by field emission scanning electron microscopy (FSEM). The transmittance of glass-ceramic was measured by UV spectrophotometer. The results show that a large amount of α-cordierite (indianite) with nano-size was precipitated from the glass matrix after treatment at 1020 °C for 3 h. The crystallinity of the transparent glass-ceramic reached up to 97%. Meanwhile, the transmittance of the glass-ceramic was 74% at 400 nm with a complex absorption band from 450 nm to 700 nm. In addition, this colored transparent glass-ceramic possessed lower density (2.469 g/cm3), lower thermal expansion coefficient (1.822 × 10-6 /℃), higher Vickers hardness (9.1 GPa) and higher bending strength (198 MPa) than parent glass.

Tooth wear against ceramic crowns in posterior region: a systematic literature review

PubMed Central

Hmaidouch, Rim; Weigl, Paul

2013-01-01

The objective of this systematic review was to assess tooth wear against ceramic crowns in posterior region in vitro and in vivo. An electronic PubMed search was conducted to identify studies on tooth wear against ceramic crowns in posterior region. The selected studies were analyzed in regard to type of crowns, natural antagonist, measuring protocol and outcome. From a yield of 1 000 titles, 43 articles were selected for full-text analysis; finally, no in vitro and only five in vivo studies met the inclusion criteria. As there is heterogeneity in design, used measuring method, ceramics and analysis-form, a meta-analysis was not possible. Results of these studies are very controversial which makes a scientifically valid comparison impossible. This review indicated that some all-ceramic crowns are as wear friendly as metal-ceramic crowns. Up to now, it has been impossible to associate tooth wear with any specific causal agent. The role of ceramic surface treatment that might be responsible for the changing in rate of tooth wear seems undetermined as yet through clinical trials. The literature reveals that studies on this topic are subject to a substantial amount of bias. Therefore, additional clinical studies, properly designed to diminish bias, are warranted. PMID:24136675

Effect of Tourmaline-Doped on the Far Infrared Emission of Iron Ore Tailings Ceramics.

PubMed

Liu, Jie; Meng, Junping; Liang, Jinsheng; Zhang, Hongchen; Gu, Xiaoyang

2016-04-01

Iron ore tailings as secondary resources have been of great importance to many countries in the world. Their compositions are similar to that of infrared emission ceramics, but there are few reports about it. In addition, tourmaline has high infrared emission properties due to its unique structure. With the purpose of expanding functional utilization of iron ore tailings, as well as reducing the production cost of far infrared ceramics, a new kind of far infrared emission ceramics was prepared by using iron ore tailings, calcium carbonate, silica, and natural tourmaline. The ceramics powders were characterized by Fourier transform infrared spectroscope, X-ray diffraction and scanning electron microscopy, respectively. The results show that after being sintered at 1065 °C, the percentage of pseudobrookite and lattice strain of samples increased with increasing the elbaite content. Furthermore, the added tourmaline was conducive to the densification sintering of ceramics. The appearance of Li-O vibration at 734.73 cm-1, as well as the strengthened Fe-O vibration at 987.68 cm-1 were attributed to the formation of Li0.375Fe1.23Ti1.4O5 solid solution, which led the average far infrared emissivity of ceramics increase from 0.861 to 0.906 within 8-14 µm.

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.

Characterization of composite materials based on cement-ceramic powder blended binder

NASA Astrophysics Data System (ADS)

Kulovaná, Tereza; Pavlík, Zbyšek

2016-06-01

Characterization of newly developed composite mortars with incorporated ceramic powder coming from precise brick cutting as partial Portland cement replacement up to 40 mass% is presented in the paper. Fine ceramic powder belongs to the pozzolanic materials. Utilization of pozzolanic materials is accompanied by lower request on energy needed for Portland clinker production which generally results in lower production costs of blended binder and lower CO2 emission. In this paper, the ceramic powder is used in cement based mortar composition in amount of 8, 16, 24, 32, and 40 mass% of cement. Chemical composition of ceramic powder is analyzed by X-Ray Fluorescence and X-Ray Diffraction. The particle size distribution of ceramics is accessed on laser diffraction principle. For 28 days cured mortar samples, basic physical and mechanical properties are experimentally determined. The obtained results demonstrate that ceramic powder has potential to replace a part of Portland cement in composition of cement based composites and to reduce negative environmental impact of their production.

Characterization of composite materials based on cement-ceramic powder blended binder

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

Kulovaná, Tereza; Pavlík, Zbyšek

Characterization of newly developed composite mortars with incorporated ceramic powder coming from precise brick cutting as partial Portland cement replacement up to 40 mass% is presented in the paper. Fine ceramic powder belongs to the pozzolanic materials. Utilization of pozzolanic materials is accompanied by lower request on energy needed for Portland clinker production which generally results in lower production costs of blended binder and lower CO{sub 2} emission. In this paper, the ceramic powder is used in cement based mortar composition in amount of 8, 16, 24, 32, and 40 mass% of cement. Chemical composition of ceramic powder is analyzedmore » by X-Ray Fluorescence and X-Ray Diffraction. The particle size distribution of ceramics is accessed on laser diffraction principle. For 28 days cured mortar samples, basic physical and mechanical properties are experimentally determined. The obtained results demonstrate that ceramic powder has potential to replace a part of Portland cement in composition of cement based composites and to reduce negative environmental impact of their production.« less

Comparative dielectric studies of nanostructured BaTiO{sub 3}, CaCu{sub 3}Ti{sub 4}O{sub 12} and 0.5BaTiO{sub 3}⋅ 0.5CaCu{sub 3}Ti{sub 4}O{sub 12} nano-composites synthesized by modified sol–gel and solid state methods

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

Singh, Laxman; Rai, Uma Shanker; Mandal, Kam Deo

2014-10-15

BaTiO{sub 3} (BTO), CaCu{sub 3}Ti{sub 4}O{sub 12} (CCTO) and 0.5BaTiO{sub 3}·0.5CaCu{sub 3}Ti{sub 4}O{sub 12} (BTO–CCTO), as a new nano-composite ceramic, were successfully designed and fabricated by a semi-wet gel route and a modified solid state method. The dielectric properties of the BTO–CCTO ceramic were compared to those of the BTO and CCTO ceramics at lower sintering temperatures and durations. The X-ray diffraction analysis revealed that the BTO and CCTO ceramics form a single crystalline phase and the average crystalline sizes calculated from X-ray diffraction data were in the range of 40–65 nm. The particle sizes of the BTO, CCTO, andmore » BTO–CCTO ceramics obtained from transmission electron microscopy images were in the ranges of 40–65 nm, 80–110 nm, and 70–95 nm, respectively. The phase composition and microstructure were studied by X-ray diffraction and scanning electron microscopy. The energy dispersive X-ray results demonstrated the purity and stoichiometry of the BTO–CCTO nano-composite. The grain sizes of the BTO, CCTO and BTO–CCTO ceramics were found to be in the ranges of 500 nm–1 μm, 4–24 μm, and 250 nm–4 μm, respectively. The AC conductivity as a function of frequency confirmed the semiconducting nature of all of the ceramics and obeyed the Jonscher's power law. The impedance spectrum measurement result showed that the CCTO ceramic possessed an exceptional grain boundary resistance, which supports the internal barrier layer capacitance (IBLC) mechanism present in this ceramic and is responsible for the high ε{sub r} values. - Highlights: • Nanostructured BaTiO{sub 3}, CaCu{sub 3}Ti{sub 4}O{sub 12}, and 0.5BaTiO{sub 3}⋅ 0.5CaCu{sub 3}Ti{sub 4}O{sub 12} have been synthesized. • XRD and TEM analysis confirmed the formation of nanoparticles, 40–65 and 50–90 nm. • Impedance analysis shows high grain-boundary resistance present in CCTO ceramic. • AC conductivity as a function of frequency confirms the semiconducting nature.« less

Ceramic-like wear behaviour of human dental enamel.

PubMed

Arsecularatne, J A; Hoffman, M

2012-04-01

This paper reports a transmission electron microscopy (TEM) analysis of subsurfaces of enamel specimens following in vitro reciprocating wear tests with an enamel cusp sliding on a flat enamel specimen under hydrated conditions. The obtained results show that crack formation occurred in the wear scar subsurface. The path followed by these cracks seems to be dictated either by the histological structure of enamel or by the contact stress field. Moreover, the analysis of a set of enamel wear results obtained from the literature and application of fracture-based models, originally developed for ceramics, correlate well, confirming the similar wear processes taking place in these materials. This analysis also reveals a marked influence of coefficient of friction on the enamel wear rate: for a higher coefficient of friction value, enamel wear can be severe even under forces generated during normal operation of teeth. Copyright © 2011 Elsevier Ltd. All rights reserved.

Preparation, Microstructure and Performance of Nanoscale Ceramics Reinforced Hard Composite Coating

NASA Astrophysics Data System (ADS)

Li, Peng

2014-11-01

This paper is based on the dry sliding wear of Stellite SF12-B4C-TiN-Mo composite coating deposited on a pure Ti using a laser cladding technique, the parameters of which provide almost crack-free composites with low porosity. To the best of our knowledge, it is the first time that Stellite SF12-B4C-TiN-Mo mixed powders are deposited as the hard composites by a laser cladding technique. Scanning electron microscope images indicate that the nanoscale particles are produced in such coating. The fact that due to the sufficiently rapid heating and cooling rates of the laser cladding technique, the ceramics, such as TiC or TiB2 did not have enough time to grow up, resulting in the formation of the nanoscale particles. Compared with a pure Ti substrate, the increments of the micro-hardness and wear resistance are obtained for such composite coating.

An experimental investigation of damage evolution in a ceramic matrix composite

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

Walter, M.E.; Ravichandran, G.

The mechanical behavior of a glass-ceramic matrix composite, SiC/CAS (calcium aluminosilicate reinforced with unidirectional SiC fibers), is studied. Results based on uniaxial tension experiments are presented for specimens with fibers aligned in the loading direction. Axial and transverse strain gages on all four gage section surfaces and in situ acoustic emission and ultrasonic wave speed measurements were used to monitor the evolution of damage. All measurements were made with high-resolution, continuous data acquisition. Post-test optical and scanning electron microscopy was also used to identify the various micromechanisms of damage. The experimental results demonstrate the existence of zones of deformation'' whichmore » are associated with the onset of different damage mechanisms. It is shown that the observed stress-strain behavior can be explained in terms of the material properties of the matrix and the fiber, the material processing, and the postulated zones of deformation.« less

Corrosion properties of zirconium-based ceramic coatings for micro-bearing and biomedical applications

NASA Astrophysics Data System (ADS)

Walkowicz, J.; Zavaleyev, V.; Dobruchowska, E.; Murzynski, D.; Donkov, N.; Zykova, A.; Safonov, V.; Yakovin, S.

2016-03-01

Ceramic oxide ZrO2 and oxynitride ZrON coatings are widely used as protective coatings against diffusion and corrosion. The enhancement of the coatings' mechanical properties, as well as their wear and corrosion resistance, is very important for their tribological performance. In this work, ZrO2 and ZrON coatings were deposited by magnetron sputtering on stainless steel (AISI 316) substrates. The adhesion, hardness and elastic properties were evaluated by standard methods. The surface structure of the deposited coatings was observed by electron scanning microscopy (SEM) and atomic force microscopy (AFM). The composition of the coatings was analyzed by X-ray photoelectron spectroscopy (XPS) and energy dispersive X-ray spectroscopy (EDS). The corrosion resistance properties were evaluated using the potentiodynamic method. The results show that the corrosion parameters are significantly increased in the cases of both oxynitride and oxide coatings in comparison with the stainless steel (AISI 316) substrates.

Pre-form ceramic matrix composite cavity and method of forming and method of forming a ceramic matrix composite component

DOEpatents

Monaghan, Philip Harold; Delvaux, John McConnell; Taxacher, Glenn Curtis

2015-06-09

A pre-form CMC cavity and method of forming pre-form CMC cavity for a ceramic matrix component includes providing a mandrel, applying a base ply to the mandrel, laying-up at least one CMC ply on the base ply, removing the mandrel, and densifying the base ply and the at least one CMC ply. The remaining densified base ply and at least one CMC ply form a ceramic matrix component having a desired geometry and a cavity formed therein. Also provided is a method of forming a CMC component.

Alumina-based ceramic composite

DOEpatents

Alexander, K.B.; Tiegs, T.N.; Becher, P.F.; Waters, S.B.

1996-07-23

An improved ceramic composite comprising oxide ceramic particulates, nonoxide ceramic particulates selected from the group consisting of carbides, borides, nitrides of silicon and transition metals and mixtures thereof, and a ductile binder selected from the group consisting of metallic, intermetallic alloys and mixtures thereof is described. The ceramic composite is made by blending powders of the ceramic particulates and the ductile to form a mixture and consolidating the mixture of under conditions of temperature and pressure sufficient to produce a densified ceramic composite. 5 figs.

Multi-signal FIB/SEM tomography

NASA Astrophysics Data System (ADS)

Giannuzzi, Lucille A.

2012-06-01

Focused ion beam (FIB) milling coupled with scanning electron microscopy (SEM) on the same platform enables 3D microstructural analysis of structures using FIB for serial sectioning and SEM for imaging. Since FIB milling is a destructive technique, the acquisition of multiple signals from each slice is desirable. The feasibility of collecting both an inlens backscattered electron (BSE) signal and an inlens secondary electron (SE) simultaneously from a single scan of the electron beam from each FIB slice is demonstrated. The simultaneous acquisition of two different SE signals from two different detectors (inlens vs. Everhart-Thornley (ET) detector) is also possible. Obtaining multiple signals from each FIB slice with one scan increases the acquisition throughput. In addition, optimization of microstructural and morphological information from the target is achieved using multi-signals. Examples of multi-signal FIB/SEM tomography from a dental implant will be provided where both material contrast from the bone/ceramic coating/Ti substrate phases and porosity in the ceramic coating will be characterized.

Marginal fit of all-ceramic crowns fabricated using two extraoral CAD/CAM systems in comparison with the conventional technique.

PubMed

Alqahtani, Fawaz

2017-01-01

The purpose of this study was to determine the effect of two extraoral computer-aided design (CAD) and computer-aided manufacturing (CAM) systems, in comparison with conventional techniques, on the marginal fit of monolithic CAD/CAM lithium disilicate ceramic crowns. This is an in vitro interventional study. The study was carried out at the Department of Prosthodontics, School of Dentistry, Prince Sattam Bin Abdul-Aziz University, Saudi Arabia, from December 2015 to April 2016. A marginal gap of 60 lithium disilicate crowns was evaluated by scanning electron microscopy. In total, 20 pressable lithium disilicate (IPS e.max Press [Ivoclar Vivadent]) ceramic crowns were fabricated using the conventional lost-wax technique as a control group. The experimental all-ceramic crowns were produced based on a scan stone model and milled using two extraoral CAD/CAM systems: the Cerec group was fabricated using the Cerec CAD/CAM system, and the Trios group was fabricated using Trios CAD and milled using Wieland Zenotec CAM. One-way analysis of variance (ANOVA) and the Scheffe post hoc test were used for statistical comparison of the groups (α=0.05). The mean (±standard deviation) of the marginal gap of each group was as follows: the Control group was 91.15 (±15.35) µm, the Cerec group was 111.07 (±6.33) µm, and the Trios group was 60.17 (±11.09) µm. One-way ANOVA and the Scheffe post hoc test showed a statistically significant difference in the marginal gap between all groups. It can be concluded from the current study that all-ceramic crowns, fabricated using the CAD/CAM system, show a marginal accuracy that is acceptable in clinical environments. The Trios CAD group displayed the smallest marginal gap.

Fatigue Behavior of Crystalline-Reinforced Glass-Ceramics.

PubMed

Vicari, Carolina Barbosa; Magalhães, Bárbara de Oliveira; Griggs, Jason Alan; Borba, Márcia

2018-01-03

To evaluate the fatigue behavior of two crystalline-reinforced ceramics: leucite-reinforced (VL) and lithium disilicate-based (VD) glass-ceramics. Bar-shaped specimens (16 × 4 × 1.2 mm) were produced for each ceramic using prefabricated CAD/CAM blocks. For each group, 30 specimens were subjected to a three-point flexural strength test in a universal testing machine. For VL and VD, 36 and 41 specimens were subjected to a cyclic fatigue test, respectively. The cyclic fatigue test was performed with a pneumatic mechanical cycling machine (1 Hz; 37°C distilled water). Specimens were tested at two stress levels for each preset lifetime (10 3 and 10 4 cycles for VL; 10 4 and 10 5 cycles for VD) following the boundary technique. Fractography was performed with a scanning electron microscope. Data were analyzed with Weibull analysis. There were significant differences among groups for characteristic strength (σ 0 ) and Weibull modulus (m), as the confidence intervals did not overlap. The VD group presented the highest values of σ 0 , but the lowest Weibull modulus. Both groups showed a reduction of approximately 60% of the initial flexural strength (σ f ) after cycling for 10 4 cycles. For VD tested in fatigue, there was no degradation of σ f when the number of cycles was increased from 10 4 to 10 5 . The VL group showed an 18% decrease in σ f when the number of cycles increased from 10 3 to 10 4 . Flexural strength values estimated for a 5% probability of failure were 36 MPa for VL and 55 MPa for VD, after 10 4 cycles. Both glass-ceramics showed similar strength degradation (60%) after a lifetime of 10 4 cycles, despite their distinct mechanical properties. Mechanical cycling in humid conditions proved to be an important factor for the degradation of the mechanical properties of crystalline-reinforced glass-ceramics. © 2018 by the American College of Prosthodontists.

The effect of TiO2 concentration on properties of apatite-mullite glass-ceramics for dental use.

PubMed

Fathi, Hawa M; Johnson, Anthony

2016-02-01

The aim of this study was to evaluate the effect of TiO2 concentration on the properties of apatite-mullite glass-ceramics namely strength and the chemical solubility to comply with the ISO standard recommendations for dental ceramics (BS EN ISO 6872-2008). Ten novel glass-ceramic materials were produced based on the general formula (4.5SiO2-3Al2O3-1.5P2O5-3CaO-CaF2-xTiO2) where x varied from 0.5 to 5 wt%. Glass with no TiO2 added (HG1T0.0) was used as a reference. Discs of 12 mm diameter and 1.6 mm (±0.2 mm) thickness were prepared for both biaxial flexural strength (BFS) and chemical solubility testing, in accordance with the BS EN ISO 6872-2008 for dental ceramics. All produced materials were investigated using differential thermal analysis (DTA), X-ray diffraction (XRD), and scanning electron microscopy (SEM). Energy dispersive X-ray analysis (EDS) was also carried out on some samples to identify the element composition of samples. Increasing the concentration of TiO2 from 0.5 wt% to 2 wt% significantly (P<0.05) increased the chemical solubility of the material. With the material containing 2.5 wt% of TiO2, the solubility significantly reduced (P<0.05) and resulted in a solubility value of 228.3 μm/cm(2) and BFS value of 197.9 MPa. Increasing the TiO2 concentration more than 2.5 wt%, led to a significant (P<0.05) increase in solubility and a reduction in BFS. TiO2 is an effective agent for improving the durability and the mechanical properties of an apatite-mullite glass-ceramic only up to 2.5 wt% concentration. Copyright © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Enhanced Thermoelectric Performance of n-type Bi2O2Se Ceramics Induced by Ge Doping

NASA Astrophysics Data System (ADS)

Ruleova, P.; Plechacek, T.; Kasparova, J.; Vlcek, M.; Benes, L.; Lostak, P.; Drasar, C.

2018-02-01

Ceramic samples with the composition Bi2- x Ge x O2Se1.01 ( x = 0, 0.05, 0.075, and 0.1) were synthesized by solid-state reaction and compacted using a hot-pressing technique. The prepared materials were characterized by x-ray diffraction analysis, electron microscopy, and measurements of electrical conductivity σ, Seebeck coefficient S, and thermal conductivity in the temperature range 300-780 K. Ge in the Bi2O2Se host structure led to an increase of the free electron concentration compared to pristine Bi2O2Se1.01. The donor effect is attributed to point substitutional defects in the Bi sublattice— {Ge}_{{Bi}}^{ + }, and oxygen vacancies {V}_{{O}}^{ + 2} producing free electrons. As a result, we observe an increase in the electrical conductivity and decrease in Seebeck coefficient while thermal conductivity κ changes slightly. The highest value of the dimensionless figure of merit ZT = σS 2 T/ κ reaches 0.25 for the composition Bi1.95Ge0.05O2Se1.01 at T = 723 K, which is, to date, the highest ZT value reported for Bi2O2Se ceramics. Our results suggest that Bi2O2Se is still worth exploring.

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.

Perovskite- and Heusler based materials for thermoelectric converters

NASA Astrophysics Data System (ADS)

Weidenkaff, Anke

2015-03-01

The broad application of thermoelectric converters in future energy technologies requires the development of active, stable, low cost and sustainable materials. Semiconductors based on perovskite and heusler structures show substantial potential for thermoelectric energy conversion processes. Their good performance can be explained based on their suitable band structure, adjusted charge carrier density, mass and mobility, limited phonon transport, electron filtering possibilities, strongly correlated electronic systems, etc. These properties are widely tuneable by following theoretical concepts and a deep composition-structure-property understanding to change the composition, structure and size of the crystallites in innovative scalable synthesis procedures. Improved thermoelectric materials are developed, synthesised and tested in diverse high temperature applications to improve the efficiency and energy density of the thermoelectric conversion process. The lecture will provide a summary on the field of advanced perovskite-type ceramics and Heusler compounds gaining importance for a large number of future energy technologies.

Spacecraft ceramic protective shield

NASA Technical Reports Server (NTRS)

Larriva, Rene F. (Inventor); Nelson, Anne (M.); Czechanski, James G. (Inventor); Poff, Ray E. (Inventor)

1995-01-01

A low areal density protective shield apparatus, and method for making same, for protecting spacecraft structures from impact with hypervelocity objects, including a bumper member comprising a bumper ceramic layer, a bumper shock attenuator layer, and a bumper confining layer. The bumper ceramic layer can be SiC or B.sub.4 C; the bumper shock attenuator layer can be zirconia felt; and the bumper confining layer can be aluminum. A base armor member can be spaced from the bumper member and a ceramic fiber-based curtain can be positioned between the bumper and base armor members.

[The bonding mechanisms of base metals for metal-ceramic crown microstructure analysis of bonding agent and gold bond between porcelain and base metals].

PubMed

Wang, C C; Hsu, C S

1996-06-01

The use of base metal alloys for porcelain fused to a metal crown and bridges has increased recently because of lower price, high hardness, high tensile strength and high elastic modulus. The addition of beryllium to base metal alloys increased fluidity and improved casting fitness. Beryllium also controlled surface oxidation and bonding strength. The bonding agent and gold bonding agent also affected the bonding strength between porcelain and metal alloys. Four commercially available ceramic base alloys were studied (two alloys contained beryllium element, another two did not). The purpose of this investigation was to study the microstructure between porcelain matrix, bonding agent and alloy matrix interfaces. A scanning electron micro-probe analyzer and energy dispersive X-ray spectroscopy (EDXS) were used to study the distribution of elements (Ni, Cr, Mo, Cu, O, Si, Sn, Al) in four base alloys. The following results were obtained: 1. The thickness of the oxidized layer of Rexillium III alloy and Unitbond alloy (contained beryllium) was thinner than Unibond alloy and Wiron 88 alloy (no beryllium). 2. The thickness of the oxidized layer of alloys in air (10 minutes and 30 minutes) was thinner in Unitbond (2.45 microns and 3.80 microns) and thicker in Wiron 88 (4.39 microns and 5.96 microns). 3. The thickness of the oxidized layer occurring for a duration of ten minutes (in vaccum) showed that the Rexillium III alloy was the thinnest (1.93 microns), and Wiron 88 alloy was the thickest (2.30 microns). But in thirty minutes (vacuum), Unitbond alloy was the thinnest (3.37 microns), and Wiron 88 alloy was the thickest (5.51 microns). 4. The intensity of Cr elements was increased obviously near the interface between Unitbond alloy, Wiron 88 alloy (no beryllium) and oxidized layer, but the intensity of Ni and Mo elements was slightly increased. The intensity of Cr element was not increased markedly between Rexillium III alloy, Unitbond alloy (beryllium) and oxidized layer. 5. A white-grayish oxidized layer appeared at the metal-ceramic interfaces but the thickness of oxidized layer was not obviously different. 6. The use of bonding agent at metal-ceramic interface leads to the deposition of many Sn elements at about 40 microns range within the porcelain surface. 7. Second interaction phases at the porcelain layer appeared when gold bonding agent was used, and a 50-100 microns microleakage occurred at the metal-ceramic interface.

Thermal barrier coating resistant to sintering

DOEpatents

Subramanian, Ramesh; Seth, Brij B.

2004-06-29

A device (10) is made, having a ceramic thermal barrier coating layer (16) characterized by a microstructure having gaps (18) with a sintering inhibiting material (22) disposed on the columns (20) within the gaps (18). The sintering resistant material (22) is stable over the range of operating temperatures of the device (10), is not soluble with the underlying ceramic layer (16) and is applied by a process that is not an electron beam physical vapor deposition process.

Characterization and surface treatment effects on topography of a glass-infiltrated alumina/zirconia-reinforced ceramic.

PubMed

Della Bona, Alvaro; Donassollo, Tiago A; Demarco, Flávio F; Barrett, Allyson A; Mecholsky, John J

2007-06-01

Characterize the microstructure, composition and some physical properties of a glass-infiltrated alumina/zirconia-reinforced ceramic (IZ) and the effect of surface treatment on topography. IZ ceramic specimens were fabricated according to ISO6872 instructions and polished through 1 microm alumina abrasive. Quantitative and qualitative analyses were performed using scanning electron microscopy (SEM), backscattered imaging (BSI), electron dispersive spectroscopy (EDS) and stereology. The elastic modulus (E) and Poisson's ratio (nu) were determined using ultrasonic waves, and the density (rho) using a helium pycnometer. The following ceramic surface treatments were used: AP-as-polished; HF-etching with 9.5% hydrofluoric acid for 90 s; SB-sandblasting with 25 microm aluminum oxide particles for 15s and SC-blasting with 30 microm aluminum oxide particles modified by silica (silica coating) for 15s. An optical profilometer was used to examine the surface roughness (Ra) and SEM-EDS were used to measure the amount of silica after all treatments. The IZ mean property values were as follows: rho=4.45+/-0.01 g/cm(3); nu=0.26 and E=245 GPa. Mean Ra values were similar for AP- and HF-treated IZ but significantly increased after either SC or SB treatment (p

Effect of raw material ratios on the compressive strength of magnesium potassium phosphate chemically bonded ceramics.

PubMed

Wang, Ai-juan; Yuan, Zhi-long; Zhang, Jiao; Liu, Lin-tao; Li, Jun-ming; Liu, Zheng

2013-12-01

The compressive strength of magnesium potassium phosphate chemically bonded ceramics is important in biomedical field. In this work, the compressive strength of magnesium potassium phosphate chemically bonded ceramics was investigated with different liquid-to-solid and MgO-to-KH2PO4 ratios. X-ray diffractometer was applied to characterize its phase composition. The microstructure was imaged using a scanning electron microscope. The results showed that the compressive strength of the chemically bonded ceramics increased with the decrease of liquid-to-solid ratio due to the change of the packing density and the crystallinity of hydrated product. However, with the increase of MgO-to-KH2PO4 weight ratio, its compressive strength increased firstly and then decreased. The low compressive strength in lower MgO-to-KH2PO4 ratio might be explained by the existence of the weak phase KH2PO4. However, the low value of compressive strength with the higher MgO-to-KH2PO4 ratio might be caused by lack of the joined phase in the hydrated product. Besides, it has been found that the microstructures were different in these two cases by the scanning electron microscope. Colloidal structure appeared for the samples with lower liquid-to-solid and higher MgO-to-KH2PO4 ratios possibly because of the existence of amorphous hydrated products. The optimization of both liquid-to-solid and MgO-to-KH2PO4 ratios was important to improve the compressive strength of magnesium potassium phosphate chemically bonded ceramics. © 2013.

Study on effect of plasma surface treatments for diamond deposition by DC arc plasmatron.

PubMed

Kang, In-Je; Joa, Sang-Beom; Lee, Heon-Ju

2013-11-01

To improve the thermal conductivity and wear resistance of ceramic materials in the field of renewable energy technologies, diamond coating by plasma processing has been carried out in recent years. This study's goal is to improve diamond deposition on Al2O3 ceramic substrates by plasma surface treatments. Before diamond deposition was carried out in a vacuum, plasma surface treatments using Ar gas were conducted to improve conditions for deposition. We also conducted plasma processing for diamond deposition on Al2O3 ceramic substrates using a DC arc Plasmatron. The Al2O3 ceramic substrates with diamond film (5 x 15 mm2), were investigated by SEM (Scanning Electron Microscopy), AFM (Atomic Force Microscopy) and XRD (X-ray Diffractometer). Then, the C-H stretching of synthetic diamond films by FTIR (Fourier Transform Infrared Spectroscopy) was studied. We identified nanocrystalline diamond films on the Al2O3 ceramic substrates. The results showed us that the deposition rate of diamond films was 2.3 microm/h after plasma surface treatments. Comparing the above result with untreated ceramic substrates, the deposition rate improved with the surface roughness of the deposited diamond films.

In vivo bone tissue response to a canasite glass-ceramic.

PubMed

da Rocha Barros, V M; Salata, L A; Sverzut, C E; Xavier, S P; van Noort, R; Johnson, A; Hatton, P V

2002-07-01

The aim of this study was to determine the biocompatibility and osteoconductive potential of a high-strength canasite glass ceramic. Glass-ceramic rods were produced using the lost-wax casting technique and implanted in the mid-shafts rabbit femurs. Implants were harvested at 4, 13 and 22 weeks and prepared for light and electron microscopy. Hydroxyapatite was used as a control material. Hydroxyapatite implants were surrounded by new mineralised bone tissue after 4 weeks of implantation. The amount of bone surrounding the implant increased slightly at 13 weeks. In contrast, canasite glass and glass ceramic implants were almost entirely surrounded by soft tissue during all the time periods. Close contact between bone and canasite glass-ceramic implant without the intervening fibrous tissue was observed in only a few regions. The canasite formulation evaluated was not osteoconductive and appeared to degrade in the biological environment. It was therefore concluded that the canasite formulation used was unsuitable for use as implant. Further work is required to improve the biocompatibility of these materials with bone tissue. It is possible that this could be achieved by reducing the solubility of the glass and glass ceramic.

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

Raj, C. Justin, E-mail: cjustinraj@gmail.com; Paramesh, G.; Prakash, B. Shri

Highlights: • Mg doped zinc oxide ceramics were fabricated by co-precipitation/solid state reaction. • MZO ceramics shown a Debye type and colossal dielectric response. • Physical absorption of atmospheric water vapor contributes these high permittivity. • The fabricated ceramic shows Maxwell–Wagner type of relaxation. - Abstract: Zn{sub 1−x}Mg{sub x}O ( ≤ x ≤ 0.1) ceramics were fabricated by conventional solid-state reaction of co-precipitated zinc oxide and magnesium hydroxide nanoparticles. Structural and morphological properties of the fabricated ceramics were studied using X-ray diffraction and scanning electron microscopic analysis. The dielectric measurements of the ceramics were carried out as a function ofmore » frequency and temperature respectively. Interestingly, Mg doped ZnO (MZO) samples exhibited colossal dielectric response (∼1 × 10{sup 4} at 1 kHz) with Debye like relaxation. The detailed dielectric studies and thermal analyses showed that the unusual dielectric response of the samples were originated from the defected grain and grain boundary (GB) conductivity relaxations due to the absorbed atmospheric water vapor (moisture). Impedance spectroscopy was employed to determine the defected grain and GB resistances, capacitances and which supported Maxwell–Wagner type relaxation phenomena.« less

Grain-Boundary Engineering for Aging and Slow-Crack-Growth Resistant Zirconia.

PubMed

Zhang, F; Chevalier, J; Olagnon, C; Batuk, M; Hadermann, J; Van Meerbeek, B; Vleugels, J

2017-07-01

Ceramic materials are prone to slow crack growth, resulting in strength degradation over time. Although yttria-stabilized zirconia (Y-TZP) ceramics have higher crack resistance than other dental ceramics, their aging susceptibility threatens their long-term performance in aqueous environments such as the oral cavity. Unfortunately, increasing the aging resistance of Y-TZP ceramics normally reduces their crack resistance. Our recently conducted systematic study of doping 3Y-TZP with various trivalent cations revealed that lanthanum oxide (La 2 O 3 ) and aluminum oxide (Al 2 O 3 ) have the most potent effect to retard the aging kinetics of 3Y-TZP. In this study, the crack-propagation behavior of La 2 O 3 and Al 2 O 3 co-doped 3Y-TZP ceramics was investigated by double-torsion methods. The grain boundaries were examined using scanning transmission electron microscopy and energy-dispersive spectroscopy (STEM-EDS). Correlating these analytic data with hydrothermal aging studies using different doping systems, a strategy to strongly bind the segregated dopant cations with the oxygen vacancies at the zirconia-grain boundary was found to improve effectively the aging resistance of Y-TZP ceramics without affecting the resistance to crack propagation.

Bonding to oxide ceramics—laboratory testing versus clinical outcome.

PubMed

Kern, Matthias

2015-01-01

Despite a huge number of published laboratory bonding studies on dental oxide ceramics clinical long-term studies on resin bonded oxide ceramic restorations are rare. The purpose of this review is to present the best available clinical evidence for successful bonding of dental oxide ceramic restorations. Clinical trials with resin-bonded restorations that had no or only limited mechanical retention and were made from alumina or zirconia ceramic were identified using an electronic search in PubMed database. Overall 10 publications with clinical trials could be identified. Their clinical outcome was compared with that laboratory bond strength studies. Clinical data provide strong evidence that air-abrasion at a moderate pressure in combination with using phosphate monomer containing primers and/or luting resins provide long-term durable bonding to glass-infiltrated alumina and zirconia ceramic under the humid and stressful oral conditions. As simple and clinically reliable bonding methods to oxide ceramics exist, the rationale for development of alternative bonding methods might be reconsidered especially when these methods are more time consuming or require rather complicated and/or technique sensitive procedures. Copyright © 2014 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

A quantitative acoustic emission study on fracture processes in ceramics based on wavelet packet decomposition

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

Ning, J. G.; Chu, L.; Ren, H. L., E-mail: huilanren@bit.edu.cn

2014-08-28

We base a quantitative acoustic emission (AE) study on fracture processes in alumina ceramics on wavelet packet decomposition and AE source location. According to the frequency characteristics, as well as energy and ringdown counts of AE, the fracture process is divided into four stages: crack closure, nucleation, development, and critical failure. Each of the AE signals is decomposed by a 2-level wavelet package decomposition into four different (from-low-to-high) frequency bands (AA{sub 2}, AD{sub 2}, DA{sub 2}, and DD{sub 2}). The energy eigenvalues P{sub 0}, P{sub 1}, P{sub 2}, and P{sub 3} corresponding to these four frequency bands are calculated. Bymore » analyzing changes in P{sub 0} and P{sub 3} in the four stages, we determine the inverse relationship between AE frequency and the crack source size during ceramic fracture. AE signals with regard to crack nucleation can be expressed when P{sub 0} is less than 5 and P{sub 3} more than 60; whereas AE signals with regard to dangerous crack propagation can be expressed when more than 92% of P{sub 0} is greater than 4, and more than 95% of P{sub 3} is less than 45. Geiger location algorithm is used to locate AE sources and cracks in the sample. The results of this location algorithm are consistent with the positions of fractures in the sample when observed under a scanning electronic microscope; thus the locations of fractures located with Geiger's method can reflect the fracture process. The stage division by location results is in a good agreement with the division based on AE frequency characteristics. We find that both wavelet package decomposition and Geiger's AE source locations are suitable for the identification of the evolutionary process of cracks in alumina ceramics.« less

Time-dependent fracture probability of bilayer, lithium-disilicate-based, glass-ceramic, molar crowns as a function of core/veneer thickness ratio and load orientation.

PubMed

Anusavice, Kenneth J; Jadaan, Osama M; Esquivel-Upshaw, Josephine F

2013-11-01

Recent reports on bilayer ceramic crown prostheses suggest that fractures of the veneering ceramic represent the most common reason for prosthesis failure. The aims of this study were to test the hypotheses that: (1) an increase in core ceramic/veneer ceramic thickness ratio for a crown thickness of 1.6mm reduces the time-dependent fracture probability (Pf) of bilayer crowns with a lithium-disilicate-based glass-ceramic core, and (2) oblique loading, within the central fossa, increases Pf for 1.6-mm-thick crowns compared with vertical loading. Time-dependent fracture probabilities were calculated for 1.6-mm-thick, veneered lithium-disilicate-based glass-ceramic molar crowns as a function of core/veneer thickness ratio and load orientation in the central fossa area. Time-dependent fracture probability analyses were computed by CARES/Life software and finite element analysis, using dynamic fatigue strength data for monolithic discs of a lithium-disilicate glass-ceramic core (Empress 2), and ceramic veneer (Empress 2 Veneer Ceramic). Predicted fracture probabilities (Pf) for centrally loaded 1.6-mm-thick bilayer crowns over periods of 1, 5, and 10 years are 1.2%, 2.7%, and 3.5%, respectively, for a core/veneer thickness ratio of 1.0 (0.8mm/0.8mm), and 2.5%, 5.1%, and 7.0%, respectively, for a core/veneer thickness ratio of 0.33 (0.4mm/1.2mm). CARES/Life results support the proposed crown design and load orientation hypotheses. The application of dynamic fatigue data, finite element stress analysis, and CARES/Life analysis represent an optimal approach to optimize fixed dental prosthesis designs produced from dental ceramics and to predict time-dependent fracture probabilities of ceramic-based fixed dental prostheses that can minimize the risk for clinical failures. Copyright © 2013 Academy of Dental Materials. All rights reserved.

Time-dependent fracture probability of bilayer, lithium-disilicate-based glass-ceramic molar crowns as a function of core/veneer thickness ratio and load orientation

PubMed Central

Anusavice, Kenneth J.; Jadaan, Osama M.; Esquivel–Upshaw, Josephine

2013-01-01

Recent reports on bilayer ceramic crown prostheses suggest that fractures of the veneering ceramic represent the most common reason for prosthesis failure. Objective The aims of this study were to test the hypotheses that: (1) an increase in core ceramic/veneer ceramic thickness ratio for a crown thickness of 1.6 mm reduces the time-dependent fracture probability (Pf) of bilayer crowns with a lithium-disilicate-based glass-ceramic core, and (2) oblique loading, within the central fossa, increases Pf for 1.6-mm-thick crowns compared with vertical loading. Materials and methods Time-dependent fracture probabilities were calculated for 1.6-mm-thick, veneered lithium-disilicate-based glass-ceramic molar crowns as a function of core/veneer thickness ratio and load orientation in the central fossa area. Time-dependent fracture probability analyses were computed by CARES/Life software and finite element analysis, using dynamic fatigue strength data for monolithic discs of a lithium-disilicate glass-ceramic core (Empress 2), and ceramic veneer (Empress 2 Veneer Ceramic). Results Predicted fracture probabilities (Pf) for centrally-loaded 1,6-mm-thick bilayer crowns over periods of 1, 5, and 10 years are 1.2%, 2.7%, and 3.5%, respectively, for a core/veneer thickness ratio of 1.0 (0.8 mm/0.8 mm), and 2.5%, 5.1%, and 7.0%, respectively, for a core/veneer thickness ratio of 0.33 (0.4 mm/1.2 mm). Conclusion CARES/Life results support the proposed crown design and load orientation hypotheses. Significance The application of dynamic fatigue data, finite element stress analysis, and CARES/Life analysis represent an optimal approach to optimize fixed dental prosthesis designs produced from dental ceramics and to predict time-dependent fracture probabilities of ceramic-based fixed dental prostheses that can minimize the risk for clinical failures. PMID:24060349

Electronic and structural properties of micro-and nanometre-sized crystalline copper monoxide ceramics investigated by positron annihilation

NASA Astrophysics Data System (ADS)

Druzhkov, A. P.; Gizhevskii, B. A.; Arbuzov, V. L.; Kozlov, E. A.; Shalnov, K. V.; Naumov, S. V.; Perminov, D. A.

2002-09-01

Electronic and structural properties of copper monoxide (CuO) sintered as a common ceramic and nanoceramic are studied by positron annihilation spectroscopy. A CuO nanoceramic with crystallite size ranging from 15 to 90 nm was prepared from a common one by shock-wave loading. It is found that the momentum distribution of valence electrons in CuO is shifted, as compared with metallic copper, towards higher momentum values. This result is related to the effect of the Cu 3d-O 2p hybridization in the Cu-O ionic covalent bond formation. It is found that open volumes, identified mainly as small agglomerates of oxygen vacancies, appear at the nanoceramic crystallite interfaces. The degree of the Cu-O bond covalency decreases locally at the crystallite interfaces because of an oxygen deficit. The nanocrystalline state in CuO is shown to be thermally stable up to 700 K.

In situ TEM of radiation effects in complex ceramics.

PubMed

Lian, Jie; Wang, L M; Sun, Kai; Ewing, Rodney C

2009-03-01

In situ transmission electron microscopy (TEM) has been extensively applied to study radiation effects in a wide variety of materials, such as metals, ceramics and semiconductors and is an indispensable tool in obtaining a fundamental understanding of energetic beam-matter interactions, damage events, and materials' behavior under intense radiation environments. In this article, in situ TEM observations of radiation effects in complex ceramics (e.g., oxides, silicates, and phosphates) subjected to energetic ion and electron irradiations have been summarized with a focus on irradiation-induced microstructural evolution, changes in microchemistry, and the formation of nanostructures. New results for in situ TEM observation of radiation effects in pyrochlore, A(2)B(2)O(7), and zircon, ZrSiO(4), subjected to multiple beam irradiations are presented, and the effects of simultaneous irradiations of alpha-decay and beta-decay on the microstructural evolution of potential nuclear waste forms are discussed. Furthermore, in situ TEM results of radiation effects in a sodium borosilicate glass subjected to electron-beam exposure are introduced to highlight the important applications of advanced analytical TEM techniques, including Z-contrast imaging, energy filtered TEM (EFTEM), and electron energy loss spectroscopy (EELS), in studying radiation effects in materials microstructural evolution and microchemical changes. By combining ex situ TEM and advanced analytical TEM techniques with in situ TEM observations under energetic beam irradiations, one can obtain invaluable information on the phase stability and response behaviors of materials under a wide range of irradiation conditions. (c) 2009 Wiley-Liss, Inc.

Orientation and phase mapping in the transmission electron microscope using precession-assisted diffraction spot recognition: state-of-the-art results.

PubMed

Viladot, D; Véron, M; Gemmi, M; Peiró, F; Portillo, J; Estradé, S; Mendoza, J; Llorca-Isern, N; Nicolopoulos, S

2013-10-01

A recently developed technique based on the transmission electron microscope, which makes use of electron beam precession together with spot diffraction pattern recognition now offers the possibility to acquire reliable orientation/phase maps with a spatial resolution down to 2 nm on a field emission gun transmission electron microscope. The technique may be described as precession-assisted crystal orientation mapping in the transmission electron microscope, precession-assisted crystal orientation mapping technique-transmission electron microscope, also known by its product name, ASTAR, and consists in scanning the precessed electron beam in nanoprobe mode over the specimen area, thus producing a collection of precession electron diffraction spot patterns, to be thereafter indexed automatically through template matching. We present a review on several application examples relative to the characterization of microstructure/microtexture of nanocrystalline metals, ceramics, nanoparticles, minerals and organics. The strengths and limitations of the technique are also discussed using several application examples. ©2013 The Authors. Journal of Microscopy published by John Wiley & Sons Ltd on behalf of Royal Microscopical Society.

Composite mixed oxide ionic and electronic conductors for hydrogen separation

DOEpatents

Gopalan, Srikanth [Westborough, MA; Pal, Uday B [Dover, MA; Karthikeyan, Annamalai [Quincy, MA; Hengdong, Cui [Allston, MA

2009-09-15

A mixed ionic and electronic conducting membrane includes a two-phase solid state ceramic composite, wherein the first phase comprises an oxygen ion conductor and the second phase comprises an n-type electronically conductive oxide, wherein the electronically conductive oxide is stable at an oxygen partial pressure as low as 10.sup.-20 atm and has an electronic conductivity of at least 1 S/cm. A hydrogen separation system and related methods using the mixed ionic and electronic conducting membrane are described.

Current Issues with Environmental Barrier Coatings for Ceramics and Ceramic Composites

NASA Technical Reports Server (NTRS)

Lee, Kang N.

2004-01-01

The environmental barrier coating (EBC) for SiC/SiC ceramic matrix composites and Si3N4 ceramics is an emerging field as the application of silicon-based ceramics in the gas turbine engine hot section is on the horizon, both for aero and industrial gas turbines. EBC is an enabling technology for silicon-based ceramics because these materials without an EBC cannot be used in combustion environments due to rapid surface recession. Significant progress in EBC development has been made during the last decade through various government-sponsored programs. Current EBCs are based on silicon, mullite (3Al2O3-2SiO2) and BSAS (barium strontium aluminum silicate with celsian structure). Volatility of BSAS, BSAS-silica chemical reaction, and low melting point of silicon limit temperature capability of current EBCs to about 1350 C for long-term applications. There is a need for higher temperature EBCs as the temperature capability of silicon-based ceramics continue to increase. Therefore, research is underway to develop EBCs with improved temperature capability compared to current EBCs. The current status and issues with the advanced EBC development efforts will be discussed.

[Study of relationship between powder-size gradation and mechanical properties of Zirconia toughened glass infiltrated nanometer-ceramic composite powder].

PubMed

Chai, Feng; Xu, Ling; Liao, Yun-mao; Chao, Yong-lie

2003-07-01

The fabrication of all-ceramic dental restorations is challenged by ceramics' relatively low flexural strength and intrinsic poor resistance to fracture. This paper aimed at investigating the relationships between powder-size gradation and mechanical properties of Zirconia toughened glass infiltrated nanometer-ceramic composite (Al(2)O(3)-nZrO(2)). Al(2)O(3)-nZrO(2) ceramics powder (W) was processed by combination methods of chemical co-precipitation and ball milling with addition of different powder-sized ZrO(2). Field-emission scanning electron microscopy was used to determine the particle size distribution and characterize the particle morphology of powders. The matrix compacts were made by slip-casting technique and sintered to 1,450 degrees C and flexural strength and the fracture toughness of them were measured. 1. The particle distribution of Al(2)O(3)-nZrO(2) ceramics powder ranges from 0.02 - 3.5 micro m and among them the superfine particles almost accounted for 20%. 2. The ceramic matrix samples with addition of nZrO(2) (W) showed much higher flexural strength (115.434 +/- 5.319) MPa and fracture toughness (2.04 +/- 0.10) MPa m(1/2) than those of pure Al(2)O(3) ceramics (62.763 +/- 7.220 MPa; 1.16 +/- 0.02 MPa m(1/2)). The particle size of additive ZrO(2) may impose influences on mechanical properties of Al(2)O(3)-nZrO(2) ceramics matrix. Good homogeneity and reasonable powder-size gradation of ceramic powder can improve the mechanical properties of material.

CO2 and Nd:YAP laser interaction with lithium disilicate and Zirconia dental ceramics: A preliminary study

NASA Astrophysics Data System (ADS)

Rocca, Jean-Paul; Fornaini, Carlo; Brulat-Bouchard, Nathalie; Bassel Seif, Samy; Darque-Ceretti, Evelyne

2014-04-01

Lithium disilicate and Zirconia ceramics offer a high level of accuracy when used in prosthetic dentistry. Their bonding using different resins is highly dependent on micro-mechanical interlocking and adhesive chemical bonding. Investigation of the performances of high strength ceramics when their surface is modified for chemical and mechanical bonding is then required. The aim of this study is to investigate the possibility of using laser for surface treatment of different high strength CAD/CAM ceramics and thus to improve their mechanical and chemical properties. Thirty two CAD/CAM ceramic discs were divided into two different groups: lithium disilicate ceramics (IPS e.max CAD®, Ivoclar, Vivadent, Italy) and Zirconia ceramics (IPS e.max ZirCAD®, Ivoclar, Vivadent, Italy). The Laser surface treatment was performed by Carbon Dioxide laser (Dream Pulse Laser®, Daeshin Enterprise Corp., Korea) at 20 W, 25 W and 30 W CW and by Neodymium Yttrium Aluminum Perovskite laser (Nd:YAP Lokki®, Lobel Medical, France) at 10 W and 30 Hz. Physical modifications of the irradiated ceramic discs were observed by scanning electron microscopy (SEM) and chemically analyzed by Energy-Dispersive Spectroscopy (EDS). Surface wettability was tested using the water drop test and the crystalline structure was investigated using X-ray diffraction (XRD). The macroscopic observation showed a shinier structure in all the groups, while at the SEM observation only CO2 25 W and 30 W treated groups showed cracks and fissures. In the conditions of this study, CO2 laser and Nd:YAP laser with the parameters used create chemical and physical surface modifications of the ceramics, indicating the possibility of an improvement in adhesion of the tested ceramics.

Physicochemical properties of precursors of Al2O3-ZrO2 oxide ceramics prepared by electrochemical method

NASA Astrophysics Data System (ADS)

Petrova, E. V.; Dresvyannikov, A. F.; Ahmadi Daryakenari, M.; Khairullina, A. I.

2016-05-01

Scanning electron microscopy, X-ray, and thermal analysis are used to examine the structure and properties of dispersive systems based on aluminum and zirconium oxides prepared electrochemically. The effect the conditions of synthesis have on the structure and morphology of Al2O3-ZrO2 particles is studied. It is shown that the effect of an electric field on the reaction medium allows us to adjust the physicochemical properties and morphology.

Fiber Strength of Hi Nicalon(TM) S After Oxidation and Scale Crystallization in Si(OH)4 Saturated Steam (Postprint)

DTIC Science & Technology

2017-02-06

conducted for the longest times because the fibers would completely oxidize. The SiO2 tube would warp during experiments run at temperatures over 1200° C ...Chollon, G.; Labrugere, C .; Lahaye, M.; Guette, A.; Bruneel, J . L.; Couzi, M.; Naslain, R.; Jiang, D. L., Characterization of Nearly Stoichiometric...Electron Beam Irradiation Curing - A Review. J . Ceram. Soc. Japan 2006, 114, 455-460. 8. Sauder, C .; Lamon, J ., Tensile Creep Behavior of SiC-Based Fibers

Interfacial adhesion of dental ceramic-resin systems

NASA Astrophysics Data System (ADS)

Della Bona, Alvaro

The clinical success of resin bonding procedures for indirect ceramic restorations and ceramic repairs depends on the quality and durability of the bond between the ceramic and the resin. The quality of this bond will depend upon the bonding mechanisms that are controlled in part by the surface treatment that promotes micromechanical and/or chemical bonding to the substrate. The objective of this study is to correlate interfacial toughness (K A) with fracture surface morphological parameters of the dental ceramic-resin systems as a function of ceramic surface treatment. The analytical procedures focused on characterizing the microstructure and fracture properties of EmpressRTM ceramics (a leucite-based core ceramic, two lithia disilicate-based core ceramics, and a glass veneer) and determining the ceramic-resin adhesion zone bond strength characteristics. Microstructure and composition are controlling factors in the development of micromechanical retention produced by etching. Silane treated ceramics negated the effect of surface roughening produced by etching, inducing lower surface energy of the ceramic and, reduced bonding effectiveness. There was a positive correlation between WA, tensile bond strength (a), and KA, i.e., higher mean WA value, and higher mean sigma and KA values. This study suggests that (1) the sigma and KA values for ceramic bonded to resin are affected by the ceramic microstructure and the ceramic surface treatments; (2) the definition of the adhesion zone is essential to classify the modes of failure, which should be an integral component of all failure analyses; (3) the microtensile test may be preferable to conventional shear or flexural tests as an indicator of composite-ceramic bond quality; and (4) careful microscopic analysis of fracture surfaces and an x-ray dot map can produce a more consistent and complete description of the fracture process and interpretation of the modes of failure. The mode of failure and fractographic analyses provide important a more comprehensive assessment of mechanisms that control the survival times of dental adhesive systems. Thus, the quality of the bond should not be assessed based on bond strength data alone.

Durability Testing of Commercial Ceramic Materials

NASA Technical Reports Server (NTRS)

Schienle, J. L.

1996-01-01

Technical efforts by AlliedSignal Engines in DOE/NASA-funded project from February, 1978 through December, 1995 are reported in the fields ceramic materials for gas turbine engines and cyclic thermal durability testing. A total of 29 materials were evaluated in 40 cyclic oxidation exposure durability tests. Ceramic test bars were cyclically thermally exposed to a hot combustion environment at temperatures up to 1371 C (2500 F) for periods of up to 3500 hours, simulating conditions typically encountered by hot flowpath components in an automotive gas turbine engine. Before and after exposure, quarter-point flexure strength tests were performed on the specimens, and fractography examinations including scanning electron microscopy (SEM) were performed to determine failure origins.

Implementation of a Non-Metallic Barrier in an Electric Motor

NASA Technical Reports Server (NTRS)

M'Sadoques, George A. (Inventor); Carra, Michael R. (Inventor); Beringer, Durwood M. (Inventor)

2013-01-01

A motor for use in a volatile environment includes a rotor exposed to the volatile environment, electronics for rotating the rotor, an impervious ceramic barrier separating the electronics and the rotor, and a flexible seal for preventing the volatile environment from contacting the electronics and for minimizing vibratory and twisting loads upon the barrier to minimize damage to the barrier.

Processing and characterization of multi-cellular monolithic bioceramics for bone regenerative scaffolds

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

Ari-Wahjoedi, Bambang, E-mail: bambang-ariwahjoedi@petronas.com.my; Centre for Intelligent Signal and Imaging Research, Universiti Teknologi PETRONAS, Bandar Seri Iskandar; Ginta, Turnad Lenggo

2014-10-24

Multicellular monolithic ceramic body is a ceramic material which has many gas or liquid passages partitioned by thin walls throughout the bulk material. There are many currently known advanced industrial applications of multicellular ceramics structures i.e. as supports for various catalysts, electrode support structure for solid oxide fuel cells, refractories, electric/electronic materials, aerospace vehicle re-entry heat shields and biomaterials for dental as well as orthopaedic implants by naming only a few. Multicellular ceramic bodies are usually made of ceramic phases such as mullite, cordierite, aluminum titanate or pure oxides such as silica, zirconia and alumina. What make alumina ceramics ismore » excellent for the above functions are the intrinsic properties of alumina which are hard, wear resistant, excellent dielectric properties, resists strong acid and alkali attacks at elevated temperatures, good thermal conductivities, high strength and stiffness as well as biocompatible. In this work the processing technology leading to truly multicellular monolithic alumina ceramic bodies and their characterization are reported. Ceramic slip with 66 wt.% solid loading was found to be optimum as impregnant to the polyurethane foam template. Mullitic ceramic composite of alumina-sodium alumino disilicate-Leucite-like phases with bulk and true densities of 0.852 and 1.241 g cm{sup −3} respectively, pore linear density of ±35 cm{sup −1}, linear and bulk volume shrinkages of 7-16% and 32 vol.% were obtained. The compressive strength and elastic modulus of the bioceramics are ≈0.5-1.0 and ≈20 MPa respectively.« less

Ceramic applications in turbine engines

NASA Technical Reports Server (NTRS)

Helms, H. E.; Heitman, P. W.; Lindgren, L. C.; Thrasher, S. R.

1984-01-01

The application of ceramic components to demonstrate improved cycle efficiency by raising the operating temperature of the existing Allison IGI 404 vehicular gas turbine engine is discussed. This effort was called the Ceramic Applications in Turbine Engines (CATE) program and has successfully demonstrated ceramic components. Among these components are two design configurations featuring stationary and rotating caramic components in the IGT 404 engine. A complete discussion of all phases of the program, design, materials development, fabrication of ceramic components, and testing-including rig, engine, and vehicle demonstation test are presented. During the CATE program, a ceramic technology base was established that is now being applied to automotive and other gas turbine engine programs. This technology base is outlined and also provides a description of the CATE program accomplishments.

[Fractographic analysis of clinically failed anterior all ceramic crowns].

PubMed

DU, Qian; Zhou, Min-bo; Zhang, Xin-ping; Zhao, Ke

2012-04-01

To identify the site of crack initiation and propagation path of clinically failed all ceramic crowns by fractographic analysis. Three clinically failed anterior IPS Empress II crowns and two anterior In-Ceram alumina crowns were retrieved. Fracture surfaces were examined using both optical stereo and scanning electron microscopy. Fractographic theory and fracture mechanics principles were applied to disclose the damage characteristics and fracture mode. All the crowns failed by cohesive failure within the veneer on the labial surface. Critical crack originated at the incisal contact area and propagated gingivally. Porosity was found within the veneer because of slurry preparation and the sintering of veneer powder. Cohesive failure within the veneer is the main failure mode of all ceramic crown. Veneer becomes vulnerable when flaws are present. To reduce the chances of chipping, multi-point occlusal contacts are recommended, and layering and sintering technique of veneering layer should also be improved.

Bluish-green color emitting Ba2Si3O8:Eu2+ ceramic phosphors for white light-emitting diodes.

PubMed

Xiao, F; Xue, Y N; Zhang, Q Y

2009-10-15

This paper reports on the structural and optical properties of Eu(2+) activated Ba(2)Si(3)O(8) ceramic phosphors synthesized by a sol-gel method. The ceramic phosphors have been characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM) and fluorescence measurements. The structural characterization results suggest that the as-prepared phosphors are of single phase monoclinic Ba(2)Si(3)O(8) with rod-like morphology. A broad excitation band ranging from 300 to 410 nm matches well with the ultraviolet (UV) radiation of light-emitting diodes (LEDs). Upon 380 nm UV light excitation, these phosphors emit bluish-green emission centered at 500 nm with color coordination (x=0.25, y=0.40). All the obtained results indicate that the Ba(2)Si(3)O(8):Eu(2+) ceramic phosphors are promising bluish-green candidates for the phosphor-converted white LEDs.

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.

Using laser radiation for the formation of capillary structure in flat ceramic heat pipes

NASA Astrophysics Data System (ADS)

Nikolaenko, Yu. E.; Rotner, S. M.

2012-12-01

The possibility of using laser radiation with a wavelength of 1.064 μm for the formation of a capillary structure in the evaporation zone of flat ceramic heat pipes has been experimentally confirmed. Using a technological regime with established parameters, a capillary structure was formed in AlN and Al2O3 ceramic plates with a thickness of 1-2 mm and lateral dimensions of 48 × 60 and 100 × 100 mm, which ensured absorption of heat-transfer fluids (distilled water, ethyl alcohol, acetone) to a height of 100 mm against gravity forces. The thermal resistance of flat ceramic heat pipes with this capillary structure reaches 0.07°C/W, which is quite acceptable for their use as heat sinks in systems of thermal regime control for electronic components and as heat exchange plates for large-size thermoelectric conversion units.

The ceramics of Malpaís of Zacapu, Michoacán, Mexico, during the Early and Middle Postclassic periods (900-1450 AD): Micro-chemical characterization of surface paintings

NASA Astrophysics Data System (ADS)

Jadot, E.; Schiavon, N.; Manso, M.

2016-05-01

Tarascan ceramic sherds from two Postclassical archaeological sites (900-1450 AD) at the Malpaís of Zacapu, Michoacán, Mexico, were investigated by combining Back-Scattered Scanning Electron Microscopy and Energy Dispersive Spectroscopy (BSEM-EDS), μ-X-Ray Diffractometry (μ-XRD), μ-X-ray Fluorescence Spectroscopy (μ-XRF) and μ-Raman Spectroscopy. These sherds are famous for their forms and decorations although the composition of its raw materials remains so far unknown and focused only on the composition of the ceramic paste. For the purpose of surface decoration characterization, the pigments used in slips and paintings were identified as hematite, magnetite, amorphous carbon, graphite and lignite. Furthermore chemical and molecular structure determination allowed the identification of technological aspects such as the firing temperatures and atmospheres used in ceramics production.

Low Cost CaTiO3 Perovskite Synthesized from Scallop (Anadara granosa) Shell as Antibacterial Ceramic Material

NASA Astrophysics Data System (ADS)

Fatimah, Is; Nur Ilahi, Rico; Pratami, Rismayanti

2018-01-01

Research on perovskite CaTiO3 synthesis from scallop (Anadara granosa) shell and its test as material for antibacterial ceramic application have been conducted. The synthesis was performed by calcium extraction from the scallop shell followed by solid-solid reaction of obtained calcium with TiO2. Physicochemical character of the perovskite wasstudied by measurement of crystallinity using x-ray diffraction (XRD), diffuse-reflectance UV Visible spectrophotometry, scanning electrone microscope-energy dispersive x-ray (SEM-EDX) and Fourier-Transform InfraRed. Considering the future application of the perovskite as antibacterial agent, laboratory test of the peroskite as material in antibacterial ceramic preparation was also conducted. Result of research indicated that perovskite formation was obtained and the material demonstrated photocatalytic activity as identified by band gap energy (Eg) value. The significant activity was also reflected by the antibacterial action of formed ceramic.

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.