Ceramic-metal composite article and joining method

DOEpatents

Kang, Shinhoo; Selverian, John H.; Kim, Hans J.; Dunn, Edmund M.; Kim, Kyung S.

1992-01-01

A ceramic-metal article including a ceramic rod, a metal rod, and a braze joining the ceramic and metal rods at a braze area of a coaxial bore in the metal rod. The bore gradually decreases in diameter, having an inward seat area sized for close sliding fit about the ceramic, a larger brazing area near the joint end, and a void area intermediate the braze and seat areas. The ceramic is seated without brazing in the bore seat area. The side wall between the brazing area and the metal outer surface is about 0.030-0.080 inch. The braze includes an inner braze layer, an outer braze layer, and an interlayer about 0.030-0.090 inch thick. A shoulder between the brazing and void areas supports the interlayer during bonding while preventing bonding between the void area and the ceramic member, leaving a void space between the void area and the ceramic member. A venting orifice extends generally radially through the metal member from the outer surface to the void space. The braze layers are palladium, platinum, gold, silver, copper, nickel, indium, chromium, molybdenum, niobium, iron, aluminum, or alloys thereof. Preferred is a gold-palladium-nickel brazing alloy. The interlayer is nickel, molybdenum, copper, tantalum, tungsten, niobium, aluminum, cobalt, iron, or an alloy thereof.

Ceramic-metal composite article and joining method

DOEpatents

Kang, S.; Selverian, J.H.; Kim, H.J.; Dunn, E.M.; Kim, K.S.

1992-04-28

A ceramic-metal article including a ceramic rod, a metal rod, and a braze joining the ceramic and metal rods at a braze area of a coaxial bore in the metal rod is described. The bore gradually decreases in diameter, having an inward seat area sized for close sliding fit about the ceramic, a larger brazing area near the joint end, and a void area intermediate the braze and seat areas. The ceramic is seated without brazing in the bore seat area. The side wall between the brazing area and the metal outer surface is about 0.030-0.080 inch. The braze includes an inner braze layer, an outer braze layer, and an interlayer about 0.030-0.090 inch thick. A shoulder between the brazing and void areas supports the interlayer during bonding while preventing bonding between the void area and the ceramic member, leaving a void space between the void area and the ceramic member. A venting orifice extends generally radially through the metal member from the outer surface to the void space. The braze layers are palladium, platinum, gold, silver, copper, nickel, indium, chromium, molybdenum, niobium, iron, aluminum, or alloys thereof. Preferred is a gold-palladium-nickel brazing alloy. The interlayer is nickel, molybdenum, copper, tantalum, tungsten, niobium, aluminum, cobalt, iron, or an alloy thereof. 4 figs.

Braze material for joining ceramic to metal and ceramic to ceramic surfaces and joined ceramic to metal and ceramic to ceramic article

DOEpatents

Hunt, T.K.; Novak, R.F.

1991-05-07

An improved active metal braze filler material is provided in which the coefficient of thermal expansion of the braze filler is more closely matched with that of the ceramic and metal, or two ceramics, to provide ceramic to metal, or ceramic to ceramic, sealed joints and articles which can withstand both high temperatures and repeated thermal cycling without failing. The braze filler material comprises a mixture of a material, preferably in the form of a powder, selected from the group consisting of molybdenum, tungsten, silicon carbide and mixtures thereof, and an active metal filler material selected from the group consisting of alloys or mixtures of nickel and titanium, alloys or mixtures of nickel and zirconium, alloys or mixtures of nickel, titanium, and copper, alloys or mixtures of nickel, titanium, and zirconium, alloys or mixtures of niobium and nickel, alloys or mixtures of niobium and zirconium, alloys or mixtures of niobium and titanium, alloys or mixtures of niobium, titanium, and nickel, alloys or mixtures of niobium, zirconium, and nickel, and alloys or mixtures of niobium, titanium, zirconium, and nickel. The powder component is selected such that its coefficient of thermal expansion will effect the overall coefficient of thermal expansion of the braze material so that it more closely matches the coefficients of thermal expansion of the ceramic and metal parts to be joined. 3 figures.

Braze material for joining ceramic to metal and ceramic to ceramic surfaces and joined ceramic to metal and ceramic to ceramic article

DOEpatents

Hunt, Thomas K.; Novak, Robert F.

1991-01-01

An improved active metal braze filler material is provided in which the coefficient of thermal expansion of the braze filler is more closely matched with that of the ceramic and metal, or two ceramics, to provide ceramic to metal, or ceramic to ceramic, sealed joints and articles which can withstand both high temperatures and repeated thermal cycling without failing. The braze filler material comprises a mixture of a material, preferably in the form of a powder, selected from the group consisting of molybdenum, tungsten, silicon carbide and mixtures thereof, and an active metal filler material selected from the group consisting of alloys or mixtures of nickel and titanium, alloys or mixtures of nickel and zirconium, alloys or mixtures of nickel, titanium, and copper, alloys or mixtures of nickel, titanium, and zirconium, alloys or mixtures of niobium and nickel, alloys or mixtures of niobium and zirconium, alloys or mixtures of niobium and titanium, alloys or mixtures of niobium, titanium, and nickel, alloys or mixtures of niobium, zirconium, and nickel, and alloys or mixtures of niobium, titanium, zirconium, and nickel. The powder component is selected such that its coefficient of thermal expansion will effect the overall coefficient of thermal expansion of the braze material so that it more closely matches the coefficients of thermal expansion of the ceramic and metal parts to be joined.

Preparation of a dense, polycrystalline ceramic structure

DOEpatents

Cooley, Jason; Chen, Ching-Fong; Alexander, David

2010-12-07

Ceramic nanopowder was sealed inside a metal container under a vacuum. The sealed evacuated container was forced through a severe deformation channel at an elevated temperature below the melting point of the ceramic nanopowder. The result was a dense nanocrystalline ceramic structure inside the metal container.

High temperature ceramic articles having corrosion resistant coating

DOEpatents

Stinton, David P.; Lee, Woo Y.

1997-01-01

A ceramic article which includes a porous body of SiC fibers, Si.sub.3 N.sub.4 fibers, SiC coated fibers or Si.sub.3 N.sub.4 coated fibers, having at least one surface, the article having a coating of AlN adherently disposed throughout at least a portion of the porous body.

High temperature ceramic articles having corrosion resistant coating

DOEpatents

Stinton, D.P.; Lee, W.Y.

1997-09-30

A ceramic article is disclosed which includes a porous body of SiC fibers, Si{sub 3}N{sub 4} fibers, SiC coated fibers or Si{sub 3}N{sub 4} coated fibers, having at least one surface, the article having a coating of AlN adherently disposed throughout at least a portion of the porous body. 1 fig.

Ionic Conduction in Nanocrystalline Materials

DTIC Science & Technology

2000-02-10

In the following, we review studies performed films prepared by a polymer precursor process on on stabilized zirconia ceramics with grain sizes alumina ... titania , is reviewed. While it remains too early to make firm conclusions, the following observations are made. Additives which contribute to ion blocking...Keywords: Ionic conductivity; Nanocrystalline; Zirconia; Ceria; Titania ; Defects 1. Introduction tivity by nearly two orders of magnitude [6]. Given the

Low Density Resin Impregnated Ceramic Article Having an Average Density of 0.15 to 0.40 G/CC

NASA Technical Reports Server (NTRS)

Tran, Huy K. (Inventor); Henline, William D. (Inventor); Hsu, Ming-ta S. (Inventor); Rasky, Daniel J. (Inventor); Riccitiello, Salvatore R. (Inventor)

1996-01-01

A low-density resin impregnated ceramic article advantageously employed as a structural ceramic ablator comprising a fired preform of ceramic fibers. The fibers of the ceramic preform are coated with an organic resin film. The organic resin can be a thermoplastic resin or a cured thermosetting resin. In one embodiment, the resin is uniformly distributed within the ceramic article. In a second embodiment, the resin is distributed so as to provide a density gradient along at least one direction of the ceramic article. The resin impregnated ceramic article is prepared by providing a fired preform of ceramic fibers; immersing the preform of ceramic fibers in a solution of a solvent and an organic resin infiltrant; and removing the solvent to form a resin film on the ceramic fibers.

Method for making glass-ceramic articles exhibiting high frangibility

DOEpatents

Beall, George H.; Brydges, III., William T.; Ference, Joseph; Kozlowski, Theodore R.

1976-02-03

This invention is concerned with glass-ceramic articles having compositions within a very narrowly-delimited area of the MgO-Al.sub.2 O.sub.3 -B.sub.2 O.sub.3 -SiO.sub.2 field and having alpha-quartz and sapphirine as the principal crystal phases, resulting from nucleation through a combination of TiO.sub.2 and ZrO.sub.2. Upon contacting such articles with lithium ions at an elevated temperature, said lithium ions will replace magnesium ions on a two Li.sup.+-for-one Mg.sup..sup.+2 basis within the crystal structures, thereby providing a unitary glass-ceramic article having an integral surface layer wherein the principal crystal phase is a lithium-stuffed beta-quartz solid solution. That transformation of crystal phases results in compressive stresses being set up within the surface layer as the articles are cooled. Through the careful control of composition, crystallization treatment, and the parameters of the replacement reaction in the crystal structures, a tremendous degree of stored elastic energy can be developed within the articles such that they will demonstrate frangibility when fractured but will not exhibit undesirable spontaneous breakage and/or spalling.

Microwave sintering of nanophase ceramics without concomitant grain growth

DOEpatents

Eastman, Jeffrey A.; Sickafus, Kurt E.; Katz, Joel D.

1993-01-01

A method of sintering nanocrystalline material is disclosed wherein the nanocrystalline material is microwaved to heat the material to a temperature less than about 70% of the melting point of the nanocrystalline material expressed in degrees K. This method produces sintered nanocrystalline material having a density greater than about 95% of theoretical and an average grain size not more than about 3 times the average grain size of the nanocrystalline material before sintering. Rutile TiO.sub.2 as well as various other ceramics have been prepared. Grain growth of as little as 1.67 times has resulted with densities of about 90% of theoretical.

A device for microwave sintering large ceramic articles

DOEpatents

Kimrey, H.D. Jr.

1987-07-24

A microwave sintering system is provided for uniform sintering of large and/or irregular shapes ceramic articles at microwave frequencies of at least 28 GHz in the hundreds of kilowatts power range in an untuned cavity. A 28 GHz, 200 kw gyrotron with variable power output is used as the microwave source connected to an untuned microwave cavity formed of an electrically conductive housing. The part to be sintered is placed in the cavity and supported on a removable high temperature table in a central location within the cavity. The part is surrounded by a microwave transparent bulk insulating material to reduce thermal heat loss at the part surfaces and maintain more uniform temperature. The cavity may be operated at a high vacuum to aid in preventing arcing. The system allows controlled increased heating rates of greater than 200/degree/C/min to provide rapid heating of a ceramic part to a selected sintering temperature where it is maintained by regulating the microwave power applied to the part. As a result of rapid heating, the extent on non-isothermal processes such as segregation of impurities to the grain boundaries are minimized and exaggerated grain growth is reduced, thereby strengthening the mechanical properties of the ceramic part being sintered. 1 fig.

Synthesis of new 2-amino-4H-pyran-3,5-dicarboxylate derivatives using nanocrystalline MIIZr4(PO4)6 ceramics as reusable and robust catalysts under microwave irradiation

NASA Astrophysics Data System (ADS)

Safaei-Ghomi, Javad; Javidan, Abdollah; Ziarati, Abolfazl; Shahbazi-Alavi, Hossein

2015-08-01

In the present paper, we report the successful synthesis of nanocrystalline MIIZr4(PO4)6 ceramics (M: Mn, Ni, Fe, Co). These nano-structures were characterized by X-ray diffraction, scanning electron microscopy, and vibrating sample magnetometer (VSM). Size of nano-structures was in the range of 20-150 nm. Nano-MIIZr4(PO4)6 as an efficient and green catalyst has been used for the preparation of 2-amino-4H-pyran-3,5-dicarboxylate derivatives by the three-component condensation reaction of ethyl cyanoacetate, ethyl acetoacetate, and various aromatic aldehydes under microwave irradiation. Extraordinarily, the best results were obtained using MnZr4(PO4)6 nanocrystallines as an efficient catalyst. This method provides several advantages including easy work-up, excellent yields, short reaction times, using of microwave as green method, recoverability of the catalyst, and little catalyst loading.

Crystallographic and magnetic properties of nanocrystalline perovskite structure SmFeO3 orthoferrite

NASA Astrophysics Data System (ADS)

Kumar, Ashwini; Shen, Jingdong; Zhao, Huihui; Zhengjian, Qi; Li, Qi

2018-05-01

In this article, we present the structural and magnetic studies of pristine SmFeO3 nanocrystalline ceramic samples as sintered at temperature 850 °C and 1000 °C. X-ray powder diffraction data confirm the existence of single-phase nature with orthorhombic (Pbnm) structure of the samples. The SEM image reveals spherical particles with a size range of 60-130 nm for SFO-850 and SFO-1000 samples. X-ray absorption spectroscopy studies on Fe L3,2 and O K-edges of SmFeO3 sample revealed the homo-valence state of Fe in these materials. From magnetization studies it has been observed the materials exhibit ferromagnetic and antiferromagnetic (canted spin structure) sub-lattices, which results strong magnetic anisotropy in the system.

Compression deformation of WC: atomistic description of hard ceramic material

NASA Astrophysics Data System (ADS)

Feng, Qing; Song, Xiaoyan; Liu, Xuemei; Liang, Shuhua; Wang, Haibin; Nie, Zuoren

2017-11-01

The deformation characteristics of WC, as a typical hard ceramic material, were studied on the nanoscale using atomistic simulations for both the single-crystal and polycrystalline forms under uniaxial compression. In particular, the effects of crystallographic orientation, grain boundary coordination and grain size on the origin of deformation were investigated. The deformation behavior of the single-crystal and polycrystalline WC both depend strongly on the orientation towards the loading direction. The grain boundaries play a significant role in the deformation coordination and the potential high fracture toughness of the nanocrystalline WC. In contrast to conventional knowledge of ceramics, maximum strength was obtained at a critical grain size corresponding to the turning point from a Hall-Petch to an inverse Hall-Petch relationship. For this the mechanism of the combined effect of dislocation motion within grains and the coordination of stress concentration at the grain boundaries were proposed. The present work has moved forward our understanding of plastic deformability and the possibility of achieving a high strength of nanocrystalline ceramic materials.

Compression deformation of WC: atomistic description of hard ceramic material.

PubMed

Feng, Qing; Song, Xiaoyan; Liu, Xuemei; Liang, Shuhua; Wang, Haibin; Nie, Zuoren

2017-11-24

The deformation characteristics of WC, as a typical hard ceramic material, were studied on the nanoscale using atomistic simulations for both the single-crystal and polycrystalline forms under uniaxial compression. In particular, the effects of crystallographic orientation, grain boundary coordination and grain size on the origin of deformation were investigated. The deformation behavior of the single-crystal and polycrystalline WC both depend strongly on the orientation towards the loading direction. The grain boundaries play a significant role in the deformation coordination and the potential high fracture toughness of the nanocrystalline WC. In contrast to conventional knowledge of ceramics, maximum strength was obtained at a critical grain size corresponding to the turning point from a Hall-Petch to an inverse Hall-Petch relationship. For this the mechanism of the combined effect of dislocation motion within grains and the coordination of stress concentration at the grain boundaries were proposed. The present work has moved forward our understanding of plastic deformability and the possibility of achieving a high strength of nanocrystalline ceramic materials.

Method for preparing thin-walled ceramic articles of configuration

DOEpatents

Holcombe, C.E.; Powell, G.L.

1975-11-01

A method for preparing a hollow thin-walled ceramic product is described. Ceramic powder is plasma-sprayed onto a concave surface of a substrate having a coefficient of thermal expansion less than that of the ceramic. The coated substrate is heated to sinter the ceramic and then cooled to effect a separation of the ceramic product from the substrate. (auth)

Method and device for microwave sintering large ceramic articles

DOEpatents

Kimrey, Jr., Harold D.

1990-01-01

A microwave sintering system and method are provided for extremely uniform sintering of large and/or irregular shaped ceramic articles at microwave frequencies of at least 28 GHz in the hundreds of kilowatts power range in an untuned cavity. A 28 GHz, 200 kw gyrotron with variable power output is used as the microwave source connected to an untuned microwave cavity formed of an electrically conductive housing through an overmoded waveguide arrangement which acts in conjunction with a mode promoter within the cavity to achieve unexpected field uniformity. The part to be sintered is placed in the cavity and supported on a removable high temperature table in a central location within the cavity. The part is surrounded by a microwave transparent bulk insulating material to reduce thermal heat loss at the part surfaces and maintain more uniform temperature. The cavity may be operated at a high vacuum to aid in preventing arcing. The system allows controlled increased heating rates of greater than 200.degree. C./min to provide rapid heating of a ceramic part to a selected sintering temperature where it is maintained by regulating the microwave power applied to the part. As a result of rapid heating, the extent of non-isothermal processes such as segregation of impurities to the grain boundaries are minimized and exaggerated grain growth is reduced, thereby strengthening the mechanical properties of the ceramic part being sintered.

Investigations of Nanocrystalline Alloy Electrospark Coating Made of Nanocrystalline Alloy Based on 5БДCP Ferrum

NASA Astrophysics Data System (ADS)

Kolomeichenko, A. V.; Kuznetsov, I. S.; Izmaylov, A. Yu; Solovyev, R. Yu; Sharifullin, S. N.

2017-09-01

The article describes the properties of wear resistant electrospark coating made of nanocrystalline alloy of type 5БДCP (Finemet). It is proved that electrospark coating has nanocrystalline structure which is like amorphous matrix with nanocrystals α - Fe. Coating thickness is 33 μm, micro-hardness is 8461 - 11357 MPa, wear resistance is 0,55×104s/g. Coating ofnanocrystalline alloy of type 5БДCP can be used to increase wear resistance of machinery working surfaces.

Fabrication of GaN doped ZnO nanocrystallines by laser ablation.

PubMed

Gopalakrishnan, N; Shin, B C; Bhuvana, K P; Elanchezhiyan, J; Balasubramanian, T

2008-08-01

Here, we present the fabrication of pure and GaN doped ZnO nanocrystallines on Si(111) substrates by KrF excimer laser. The targets for the ablation have been prepared by conventional ceramic method. The fabricated nanocrystallines have been investigated by X-ray diffraction, photoluminescence and atomic force microscopy. The X-ray diffraction analysis shows that the crystalline size of pure ZnO is 36 nm and it is 41 nm while doped with 0.8 mol% of GaN due to best stoichiometry between Zn and O. Photoluminescence studies reveal that intense deep level emissions have been observed for pure ZnO and it has been suppressed for the GaN doped ZnO structures. The images of atomic force microscope show that the rms surface roughness is 27 nm for pure ZnO and the morphology is improved with decrease in rms roughness, 18 nm with fine crystallines while doped with 1 mol% GaN. The improved structural, optical and morphological properties of ZnO nanocrystalline due to GaN dopant have been discussed in detail.

Synthesis of Nanocrystalline CaWO4 as Low-Temperature Co-fired Ceramic Material: Processing, Structural and Physical Properties

NASA Astrophysics Data System (ADS)

Vidya, S.; Solomon, Sam; Thomas, J. K.

2013-01-01

Nanocrystalline scheelite CaWO4, a promising material for low-temperature co-fired ceramic (LTCC) applications, has been successfully synthesized through a single-step autoignition combustion route. Structural analysis of the sample was performed by powder x-ray diffraction (XRD), Fourier-transform infrared spectroscopy, and Raman spectroscopy. The XRD analysis revealed that the as-prepared sample was single phase with scheelite tetragonal structure. The basic optical properties and optical constants of the CaWO4 nanopowder were studied using ultraviolet (UV)-visible absorption spectroscopy, which showed that the material was a wide-bandgap semiconductor with bandgap of 4.7 eV at room temperature. The sample showed poor transmittance in the ultraviolet region but maximum transmission in the visible/near-infrared regions. The photoluminescence spectra recorded at different temperatures showed intense emission in the green region. The particle size estimated from transmission electron microscopy was 23 nm. The feasibility of CaWO4 for LTCC applications was studied from its sintering behavior. The sample was sintered at a relatively low temperature of 810°C to high density, without using any sintering aid. The surface morphology of the sintered sample was analyzed by scanning electron microscopy. The dielectric constant and loss factor of the sample measured at 5 MHz were found to be 10.50 and 1.56 × 10-3 at room temperature. The temperature coefficient of the dielectric constant was -88.71 ppm/°C. The experimental results obtained in this work demonstrate the potential of nano-CaWO4 as a low-temperature co-fired ceramic as well as an excellent luminescent material.

Method for preparing configured silicon carbide whisker-reinforced alumina ceramic articles

DOEpatents

Tiegs, Terry N.

1987-01-01

A ceramic article of alumina reinforced with silicon carbide whiskers suitable for the fabrication into articles of complex geometry are provided by pressureless sintering and hot isostatic pressing steps. In accordance with the method of the invention a mixture of 5 to 10 vol. % silicon carbide whiskers 0.5 to 5 wt. % of a sintering aid such as yttria and the balance alumina powders is ball-milled and pressureless sintered in the desired configuration in the desired configuration an inert atmosphere at a temperature of about 1800.degree. C. to provide a self-supporting configured composite of a density of at least about 94% theoretical density. The composite is then hot isostatically pressed at a temperature and pressure adequate to provide configured articles of at least about 98% of theoretical density which is sufficient to provide the article with sufficient strength and fracture toughness for use in most structural applications such as gas turbine blades, cylinders, and other components of advanced heat engines.

Method of sintering ceramic materials

DOEpatents

Holcombe, Cressie E.; Dykes, Norman L.

1992-01-01

A method for sintering ceramic materials is described. A ceramic article is coated with layers of protective coatings such as boron nitride, graphite foil, and niobium. The coated ceramic article is embedded in a container containing refractory metal oxide granules and placed within a microwave oven. The ceramic article is heated by microwave energy to a temperature sufficient to sinter the ceramic article to form a densified ceramic article having a density equal to or greater than 90% of theoretical density.

Method of sintering ceramic materials

DOEpatents

Holcombe, C.E.; Dykes, N.L.

1992-11-17

A method for sintering ceramic materials is described. A ceramic article is coated with layers of protective coatings such as boron nitride, graphite foil, and niobium. The coated ceramic article is embedded in a container containing refractory metal oxide granules and placed within a microwave oven. The ceramic article is heated by microwave energy to a temperature sufficient to sinter the ceramic article to form a densified ceramic article having a density equal to or greater than 90% of theoretical density. 2 figs.

Template-assisted formation of microsized nanocrystalline CeO2 tubes and their catalytic performance in the carboxylation of methanol

PubMed Central

Naumann, Meike; Schäfer, Christian; Brandner, Armin; Hofmann, Heiko J; Claus, Peter

2011-01-01

Summary Polymethylmethacrylate (PMMA)/ceria composite fibres were synthesized by using a sequential combination of polymer electrospinning, spray-coating with a sol, and a final calcination step to yield microstructured ceria tubes, which are composed of nanocrystalline ceria particles. The PMMA template is removed from the organic/inorganic hybrid material by radio frequency (rf) plasma etching followed by calcination of the ceramic green-body fibres. Microsized ceria (CeO2) tubes, with a diameter of ca. 0.75 µm, composed of nanocrystalline agglomerated ceria particles were thus obtained. The 1-D ceramic ceria material was characterized by X-ray diffraction, scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), UV–vis and photoluminescence spectroscopy (PL), as well as thermogravimetric analysis (TGA). Its catalytic performance was studied in the direct carboxylation of methanol with carbon dioxide leading to dimethyl carbonate [(CH3O)2CO, DMC], which is widely employed as a phosgene and dimethyl sulfate substitute, and as well as a fuel additive. PMID:22259761

Method of making a modified ceramic-ceramic composite

DOEpatents

Weaver, Billy L.; McLaughlin, Jerry C.; Stinton, David P.

1995-01-01

The present invention provides a method of making a shaped ceramic-ceramic composite articles, such as gas-fired radiant heat burner tubes, heat exchangers, flame dispersers, and other furnace elements, having a formed-on ceramic-ceramic composite thereon.

Microstructure and physical properties of laser Zn modified amorphous-nanocrystalline coating on a titanium alloy

NASA Astrophysics Data System (ADS)

Li, Jia-Ning; Gong, Shui-Li; Shi, Yi-Ning; Suo, Hong-Bo; Wang, Xi-Chang; Deng, Yun-Hua; Shan, Fei-Hu; Li, Jian-Quan

2014-02-01

A Zn modified amorphous-nanocrystalline coating was fabricated on a Ti-6Al-4V alloy by laser cladding of the Co-Ti-B4C-Zn-Y2O3 mixed powders. Such coating was researched by means of a scanning electron microscope (SEM) and a high resolution transmission electron microscope (HRTEM), etc. Experimental results indicated that the Co5Zn21 and TiB2 nanocrystalline phases were produced through in situ metallurgical reactions, which blocked the motion of dislocation, and TiB2 grew along (010), (111) and (024). The Co5Zn21 nanocrystals were produced attached to the ceramics, which mainly consisted of the Co nanoparticles embedded in a heterogeneous zinc, and had varied crystalline orientations.

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

Proton conducting ceramics in membrane separations

DOEpatents

Brinkman, Kyle S; Korinko, Paul S; Fox, Elise B; Chen, Frank

2015-04-14

Perovskite materials of the general formula SrCeO.sub.3 and BaCeO.sub.3 are provided having improved conductivity while maintaining an original ratio of chemical constituents, by altering the microstructure of the material. A process of making Pervoskite materials is also provided in which wet chemical techniques are used to fabricate nanocrystalline ceramic materials which have improved grain size and allow lower temperature densification than is obtainable with conventional solid-state reaction processing.

Mechanical properties of nanocrystalline cobalt

NASA Astrophysics Data System (ADS)

Karimpoor, Amir A.; Erb, Uwe

2006-05-01

Due to their excellent wear and corrosion properties, nanocrystalline cobalt and several cobalt alloys made by electrodeposition are currently being developed as environmentally benign replacement coatings for hard chromium electrodeposits. The focus of this study is on the mechanical properties of nanocrystalline cobalt, which are currently not well understood. A comparison is presented for hardness, tensile properties, Charpy impact properties and fracture surface analysis of both nanocrystalline (grain size: 12 nm) and conventional polycrystalline (grain size: 4.8 m) cobalt. It is shown that the hardness and tensile strength of nanocrystalline cobalt is 2-3 times higher than for polycrystalline cobalt. However, in contrast to other nanocrystalline materials tested previously, nanocrystalline cobalt retains considerable ductility with elongation to fracture values up to 7%.

Site Directed Nucleation and Growth of Ceramic Films on Metallic Surfaces

DTIC Science & Technology

2009-04-30

ceramics and other nanoscale composite materials research with the ultimate goal being the cell-free, nanocrystalline assembly of adaptive bioceramic...for high temperature or high wear environments. Other applications/technology developments for this research include adaptive materials, wear...bound vesicles that form the surface membrane of gastropod nacre. 19 Folia formation was observed by recovering titanium and aluminum disc implants

Preparation of Nanocrystalline Powders of ZrO2, Stabilized by Y2O3 Dobs for Ceramics

NASA Astrophysics Data System (ADS)

Petrunin, V. F.; Korovin, S. A.

The purpose of this study was to develop a synthesis conditions and produce samples of nanocrystalline zirconia powder in a high-temperature phase state. To increase the stability of this state at room temperature, Y2O3 was used as a dop in the two-stages chemical method including coprecipitation mixture of the corresponding hydroxides and air drying. To reduce agglomeration of nanoparticles during heat treatment of precursors the microwave oven instead of a muffle was used. Different characterisation methods have been used to determine that the obtained powders are nano-scale corresponds to a high-temperature tetragonal phase of ZrO2. It is shown that such nanocrystalline powders may be used to produce highly-dense nanoceramics.

Biomimetic nanocrystalline apatites: Emerging perspectives in cancer diagnosis and treatment.

PubMed

Al-Kattan, Ahmed; Girod-Fullana, Sophie; Charvillat, Cédric; Ternet-Fontebasso, Hélène; Dufour, Pascal; Dexpert-Ghys, Jeannette; Santran, Véronique; Bordère, Julie; Pipy, Bernard; Bernad, José; Drouet, Christophe

2012-02-14

Nanocrystalline calcium phosphate apatites constitute the mineral part of hard tissues, and the synthesis of biomimetic analogs is now well-mastered at the lab-scale. Recent advances in the fine physico-chemical characterization of these phases enable one to envision original applications in the medical field along with a better understanding of the underlying chemistry and related pharmacological features. In this contribution, we specifically focused on applications of biomimetic apatites in the field of cancer diagnosis or treatment. We first report on the production and first biological evaluations (cytotoxicity, pro-inflammatory potential, internalization by ZR-75-1 breast cancer cells) of individualized luminescent nanoparticles based on Eu-doped apatites, eventually associated with folic acid, for medical imaging purposes. We then detail, in a first approach, the preparation of tridimensional constructs associating nanocrystalline apatite aqueous gels and drug-loaded pectin microspheres. Sustained releases of a fluorescein analog (erythrosin) used as model molecule were obtained over 7 days, in comparison with the ceramic or microsphere reference compounds. Such systems could constitute original bone-filling materials for in situ delivery of anticancer drugs. Copyright © 2011 Elsevier B.V. All rights reserved.

Structures and properties of alumina-based ceramic for reconstructive oncology

NASA Astrophysics Data System (ADS)

Grigoriev, M. V.; Kulkov, S. N.

2016-08-01

The microstructure of alumina ceramics based on powders with a varying grain size has been investigated. Both commercial alumina powders and those fabricated by denitration of aluminum salts in high-frequency discharge plasma were used. It is shown that the variation of the sintering temperature and morphology of the initial powders of the particles leads to a change of the pore structure of ceramics from pore isolated clusters to a structure consisting of a ceramic skeleton and a large pore space. Changing the type of pore structure occurs at about 50% of porosity. The ceramic pore size distribution is bimodal. Dependencies final density vs initial density are linear; at the same time with increasing temperature, inclination of changes from positive to negative, indicating the change of sealing mechanisms. Extrapolation of these curves showed that they intersect with the values of density of about 2 g/cm3, which indicates the possibility of producing non-shrink ceramics. It is shown that the strength increases with increasing nanocrystalline alumina content in powder mixture. A change in the character the pore structure is accompanied by a sharp decrease in strength, which corresponds to the percolation transition in ceramics. These results showed that it is possible to obtain ceramic materials with the structure and properties similar to natural bone.

Superhard Nanocrystalline Homometallic Stainless Steel on Steel for Seamless Coatings

NASA Technical Reports Server (NTRS)

Tobin, Eric J.; Hafley, R. (Technical Monitor)

2002-01-01

The objective of this work is to deposit nanocrystalline stainless steel onto steel substrates (homometallic) for enhanced wear and corrosion resistance. Homometallic coatings provide superior adhesion, and it has been shown that ultrafine-grained materials exhibit the increased hardness and decreased permeability desired for protective coatings. Nanocrystals will be produced by controlling nucleation and growth and use of an ion beam during deposition by e-beam evaporation or sputtering. Phase I is depositing 31 6L nanocrystalline stainless steel onto 31 6L stainless steel substrates. These coatings exhibit hardnesses comparable to those normally obtained for ceramic coatings such ZrO2, and possess the superior adhesion of seamless, homometallic coatings. Hardening the surface with a similar material also enhances adhesion, by avoiding problems associated with thermal and lattice mismatch. So far we have deposited nanocrystalline homometallic 316L stainless steel coatings by varying the ions and the current density of the ion beams. For all deposition conditions we have produced smooth, uniform, superhard coatings. All coatings exhibit hardness of at least 200% harder than that of bulk materials. Our measurements indicate that there is a direct relationship between nanohardness and the current density of the ion beam. Stress measurements indicate that stress in the films is increasingly proportional to current density of the ion beam. TEM, XPS, and XRD results indicate that the coated layers consist of FCC structure nanocrystallites with a dimension of about 10 to 20 nm. The Ni and Mo concentration of these coating are lower than those of bulk 316L but the concentration of Cr is higher.

Organometallic Precursor Routes to Si-C-Al-O-N Ceramics

DTIC Science & Technology

1991-05-15

Pyrolysis Chemistry of Polymeric Precursors to SiC and Si3 N 4", Kluwer Academic Publishers, Dordrecht, NATO Workshop or Organometallic Polymers with Special...the polymer to a preceramic SiC . Thus the IR and H CRAMPS spectra confirm the decreasing concentration of hydrogen with increasing pyrolysis ...generality of this polymer pyrolysis route to nanocrystalline composites of refractory nitride and carbide ceramics. Investigation of AlN Precursors Our

Hip Squeaking after Ceramic-on-ceramic Total Hip Arthroplasty

PubMed Central

Wu, Guo-Liang; Zhu, Wei; Zhao, Yan; Ma, Qi; Weng, Xi-Sheng

2016-01-01

Objective: The present study aimed to review the characteristics and influencing factors of squeaking after ceramic-on-ceramic (CoC) total hip arthroplasty (THA) and to analyze the possible mechanisms of the audible noise. Data Sources: The data analyzed in this review were based on articles from PubMed and Web of Science. Study Selection: The articles selected for review were original articles and reviews found based on the following search terms: “total hip arthroplasty”, “ceramic-on-ceramic”, “hip squeaking”, and “hip noise.” Results: The mechanism of the squeaking remains unknown. The possible explanations included stripe wear, edge loading, a third body, fracture of the ceramic liner, and resonance of the prosthesis components. Squeaking occurrence is influenced by patient, surgical, and implant factors. Conclusions: Most studies indicated that squeaking after CoC THA was the consequence of increasing wear or impingement, caused by prosthesis design, patient characteristics, or surgical factors. However, as conflicts exist among different articles, the major reasons for the squeaking remain to be identified. PMID:27453238

Dense high temperature ceramic oxide superconductors

DOEpatents

Landingham, Richard L.

1993-01-01

Dense superconducting ceramic oxide articles of manufacture and methods for producing these articles are described. Generally these articles are produced by first processing these superconducting oxides by ceramic processing techniques to optimize materials properties, followed by reestablishing the superconducting state in a desired portion of the ceramic oxide composite.

Dense high temperature ceramic oxide superconductors

DOEpatents

Landingham, R.L.

1993-10-12

Dense superconducting ceramic oxide articles of manufacture and methods for producing these articles are described. Generally these articles are produced by first processing these superconducting oxides by ceramic processing techniques to optimize materials properties, followed by reestablishing the superconducting state in a desired portion of the ceramic oxide composite.

"Bulk" Nanocrystalline Metals: Review of the Current State of the Art and Future Opportunities for Copper and Copper Alloys

NASA Astrophysics Data System (ADS)

Tschopp, M. A.; Murdoch, H. A.; Kecskes, L. J.; Darling, K. A.

2014-06-01

It is a new beginning for innovative fundamental and applied science in nanocrystalline materials. Many of the processing and consolidation challenges that have haunted nanocrystalline materials are now more fully understood, opening the doors for bulk nanocrystalline materials and parts to be produced. While challenges remain, recent advances in experimental, computational, and theoretical capability have allowed for bulk specimens that have heretofore been pursued only on a limited basis. This article discusses the methodology for synthesis and consolidation of bulk nanocrystalline materials using mechanical alloying, the alloy development and synthesis process for stabilizing these materials at elevated temperatures, and the physical and mechanical properties of nanocrystalline materials with a focus throughout on nanocrystalline copper and a nanocrystalline Cu-Ta system, consolidated via equal channel angular extrusion, with properties rivaling that of nanocrystalline pure Ta. Moreover, modeling and simulation approaches as well as experimental results for grain growth, grain boundary processes, and deformation mechanisms in nanocrystalline copper are briefly reviewed and discussed. Integrating experiments and computational materials science for synthesizing bulk nanocrystalline materials can bring about the next generation of ultrahigh strength materials for defense and energy applications.

Physics of the multi-functionality of lanthanum ferrite ceramics

NASA Astrophysics Data System (ADS)

Bhargav, K. K.; Ram, S.; Majumder, S. B.

2014-05-01

In the present work, we have illustrated the physics of the multifunctional characteristics of nano-crystalline LaFeO3 powder prepared using auto-combustion synthesis. The synthesized powders were phase pure and crystallized into centro-symmetric Pnma space group. The temperature dependence of dielectric constant of pure LaFeO3 exhibits dielectric maxima similar to that observed in ferroelectric ceramics with non-centrosymmetric point group. The dielectric relaxation of LaFeO3 correlates well with small polaron conduction. The occurrence of polarization hysteresis in LaFeO3 (with centro-symmetric Pnma space group) is thought to be spin current induced type. The canting of the Fe3+ spins induce weak ferromagnetism in nano-crystalline LaFeO3. Room temperature saturation magnetization of pure LaFeO3 is reported to be 3.0 emu/g. Due to the presence of both ferromagnetic as well as polarization ordering, LaFeO3 behaves like a single phase multiferroic ceramics. The magneto-electric coupling in this system has been demonstrated through the magneto-dielectric measurements which yield about 0.8% dielectric tuning (at 10 kHz) with the application of 2 T magnetic field. As a typical application of the synthesized nano-crystalline LaFeO3 powder, we have studied its butane sensing characteristics. The efficient butane sensing characteristics have been correlated to their catalytic activity towards oxidation of butane. Through X-ray photoelectron spectroscopy analyses, we detect the surface adsorbed oxygen species on LaFeO3 surface. Surface adsorbed oxygen species play major role in their low temperature butane sensing. Finally, we have hypothesized that the desorbed H2O and O2 (originate from surface adsorbed hydroxyl and oxygen) initiate the catalytic oxidative dehydrogenation of n-butane resulting in weakening of the electrostatics of the gas molecules.

Mechanism of γ-irradiation induced phase transformations in nanocrystalline Mn{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4} ceramics

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

Jagadeesha Angadi, V.; Anupama, A.V.; Choudhary, Harish K.

The structural, infrared absorption and magnetic property transformations in nanocrystalline Mn{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4} samples irradiated with different doses (0, 15, 25 and 50 kGy) of γ-irradiation were investigated in this work and a mechanism of phase transformation/decomposition is provided based on the metastable nature of the Mn-atoms in the spinel lattice. The nano-powder sample was prepared by solution combustion route and the pellets of the sample were exposed to γ-radiation. Up to a dose of 25 kGy of γ-radiation, the sample retained the single phase cubic spinel (Fd-3m) structure, but the disorder in the sample increased. On irradiatingmore » the sample with 50 kGy γ-radiation, the spinel phase decomposed into new stable phases such as α-Fe{sub 2}O{sub 3} and ZnFe{sub 2}O{sub 4} phases along with amorphous MnO phase, leading to a change in the surface morphology of the sample. Along with the structural transformations the magnetic properties deteriorated due to breakage of the ferrimagnetic order with higher doses of γ-irradiation. Our results are important for the understanding of the stability, durability and performance of the Mn-Zn ferrite based devices used in space applications. - Graphical abstract: The nanocrystalline Mn{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4} ceramic sample transforms to crystalline α-Fe{sub 2}O{sub 3} and ZnFe{sub 2}O{sub 4} phases (and amorphous MnO phase) at a γ-irradiation dose of 50 kGy, as MnO goes out of the spinel lattice. The high energy γ-irradiation causes structural damage to the nanomaterials leading to change in morphology of the sample as seen in the SEM images. - Highlights: • Mn atoms are more unstable in the Mn-Zn ferrite spinel lattice than Zn-atoms. • Displacement of Mn atoms by γ-radiation from the lattice renders phase transformation. • In Mn{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4}, Mn-ferrite cell transforms to crystalline α-Fe{sub 2}O{sub 3} and amorphous MnO. • The stable Zn

Thermally Stable Nanocrystalline Steel

NASA Astrophysics Data System (ADS)

Hulme-Smith, Christopher Neil; Ooi, Shgh Woei; Bhadeshia, Harshad K. D. H.

2017-10-01

Two novel nanocrystalline steels were designed to withstand elevated temperatures without catastrophic microstructural changes. In the most successful alloy, a large quantity of nickel was added to stabilize austenite and allow a reduction in the carbon content. A 50 kg cast of the novel alloy was produced and used to verify the formation of nanocrystalline bainite. Synchrotron X-ray diffractometry using in situ heating showed that austenite was able to survive more than 1 hour at 773 K (500 °C) and subsequent cooling to ambient temperature. This is the first reported nanocrystalline steel with high-temperature capability.

Crystallization Kinetics in Fluorochloroziroconate Glass-Ceramics

NASA Astrophysics Data System (ADS)

Alvarez, Carlos J.

Annealing fluorochlorozirconate (FCZ) glasses nucleates BaCl2 nanocrystals in the glass matrix, resulting in a nanocomposite glass-ceramic that has optical properties suitable for use as a medical X-ray imaging plate. Understanding the way in which the BaCl¬2 nanocrystal nucleation, growth and phase transformation processes proceed is critical to controlling the optical behavior. However, there is a very limited amount of information about the formation, morphology, and distribution of the nanocrystalline particles in FCZ glass-ceramics. In this thesis, the correlation between the microstructure and the crystallization kinetics of FCZ glass-ceramics, are studied in detail. In situ X-ray diffraction and transmission electron microscopy annealing experiments are used to analyze the crystal structure, size and distribution of BaCl 2 nanocrystals in FCZ glass-ceramics as a function of annealing rate and temperature. Microstructural analysis of the early stages on nucleation identified the formation of both BaCl2 and BaF2 nanocrystals. Annealing FCZ glass-ceramics above 280°C can cause the formation of additional glass matrix phase crystals, their microstructure and the annealing parameters required for their growth are identified. As the crystalline phases grow directly from the glass, small variations in processing of the glass can have a profound influence on the crystallization process. The information obtained from these experiments improves the understanding of the nucleation, growth and phase transformation process of the BaCl¬2 nanocrystals and additional crystalline phases that form in FCZ glass-ceramics, and may help expedite the implementation of FCZ glass-ceramics as next-generation X-ray detectors. Lastly, as these glass-ceramics may one day be commercialized, an investigation into their degradation in different environmental conditions was also performed. The effects of direct contact with water or prolonged exposure to humid environments on the

Rapid room-temperature synthesis of nanocrystalline spinels as oxygen reduction and evolution electrocatalysts.

PubMed

Cheng, Fangyi; Shen, Jian; Peng, Bo; Pan, Yuede; Tao, Zhanliang; Chen, Jun

2011-01-01

Spinels can serve as alternative low-cost bifunctional electrocatalysts for oxygen reduction/evolution reactions (ORR/OER), which are the key barriers in various electrochemical devices such as metal-air batteries, fuel cells and electrolysers. However, conventional ceramic synthesis of crystalline spinels requires an elevated temperature, complicated procedures and prolonged heating time, and the resulting product exhibits limited electrocatalytic performance. It has been challenging to develop energy-saving, facile and rapid synthetic methodologies for highly active spinels. In this Article, we report the synthesis of nanocrystalline M(x)Mn(3-x)O(4) (M = divalent metals) spinels under ambient conditions and their electrocatalytic application. We show rapid and selective formation of tetragonal or cubic M(x)Mn(3-x)O(4) from the reduction of amorphous MnO(2) in aqueous M(2+) solution. The prepared Co(x)Mn(3-x)O(4) nanoparticles manifest considerable catalytic activity towards the ORR/OER as a result of their high surface areas and abundant defects. The newly discovered phase-dependent electrocatalytic ORR/OER characteristics of Co-Mn-O spinels are also interpreted by experiment and first-principle theoretical studies.

[Ceramic posts].

PubMed

Mainjot, Amélie; Legros, Caroline; Vanheusden, Alain

2006-01-01

As a result of ceramics and all-ceram technologies development esthetic inlay core and abutments flooded the market. Their tooth-colored appearance enhances restoration biomimetism principally on the marginal gingiva area. This article reviews indications and types of cores designed for natural teeth and implants.

Ceramic Honeycomb Structures and Method Thereof

NASA Technical Reports Server (NTRS)

Cagliostro, Domenick E.; Riccitiello, Salvatore R.

1989-01-01

The present invention relates to a method for producing ceramic articles and the articles, the process comprising the chemical vapor deposition (CVD) and/or chemical vapor infiltration (CVI) of a honeycomb structure. Specifically the present invention relates to a method for the production of a ceramic honeycomb structure, including: (a) obtaining a loosely woven fabric/binder wherein the fabric consists essentially of metallic, ceramic or organic fiber and the binder consists essentially of an organic or inorganic material wherein the fabric/binder has and retains a honeycomb shape, with the proviso that when the fabric is metallic or ceramic the binder is organic only; (b) substantially evenly depositing at least one layer of a ceramic on the fabric/binder of step (a); and (c) recovering the ceramic coated fiber honeycomb structure. In another aspect, the present invention relates to a method for the manufacture of a lightweight ceramic-ceramic composite honeycomb structure, which process comprises: (d) pyrolyzing a loosely woven fabric a honeycomb shaped and having a high char yield and geometric integrity after pyrolysis at between about 700 degrees and 1,100 degrees Centigrade; (e) substantially evenly depositing at least one layer of ceramic material on the pyrolyzed fabric of step (a); and (f) recovering the coated ceramic honeycomb structure. The ceramic articles produced have enhanced physical properties and are useful in aircraft and aerospace uses.

Etching process for improving the strength of a laser-machined silicon-based ceramic article

DOEpatents

Copley, Stephen M.; Tao, Hongyi; Todd-Copley, Judith A.

1991-01-01

A process for improving the strength of laser-machined articles formed of a silicon-based ceramic material such as silicon nitride, in which the laser-machined surface is immersed in an etching solution of hydrofluoric acid and nitric acid for a duration sufficient to remove substantially all of a silicon film residue on the surface but insufficient to allow the solution to unduly attack the grain boundaries of the underlying silicon nitride substrate. This effectively removes the silicon film as a source of cracks that otherwise could propagate downwardly into the silicon nitride substrate and significantly reduce its strength.

Etching process for improving the strength of a laser-machined silicon-based ceramic article

DOEpatents

Copley, S.M.; Tao, H.; Todd-Copley, J.A.

1991-06-11

A process is disclosed for improving the strength of laser-machined articles formed of a silicon-based ceramic material such as silicon nitride, in which the laser-machined surface is immersed in an etching solution of hydrofluoric acid and nitric acid for a duration sufficient to remove substantially all of a silicon film residue on the surface but insufficient to allow the solution to unduly attack the grain boundaries of the underlying silicon nitride substrate. This effectively removes the silicon film as a source of cracks that otherwise could propagate downwardly into the silicon nitride substrate and significantly reduce its strength. 1 figure.

Structural Ceramic Nanocomposites: A Review of Properties and Powders’ Synthesis Methods

PubMed Central

Palmero, Paola

2015-01-01

Ceramic nanocomposites are attracting growing interest, thanks to new processing methods enabling these materials to go from the research laboratory scale to the commercial level. Today, many different types of nanocomposite structures are proposed in the literature; however, to fully exploit their exceptional properties, a deep understanding of the materials’ behavior across length scales is necessary. In fact, knowing how the nanoscale structure influences the bulk properties enables the design of increasingly performing composite materials. A further key point is the ability of tailoring the desired nanostructured features in the sintered composites, a challenging issue requiring a careful control of all stages of manufacturing, from powder synthesis to sintering. This review is divided into four parts. In the first, classification and general issues of nanostructured ceramics are reported. The second provides basic structure–property relations, highlighting the grain-size dependence of the materials properties. The third describes the role of nanocrystalline second-phases on the mechanical properties of ordinary grain sized ceramics. Finally, the fourth part revises the mainly used synthesis routes to produce nanocomposite ceramic powders, underlining when possible the critical role of the synthesis method on the control of microstructure and properties of the sintered ceramics. PMID:28347029

A comparison of different powder compaction processes adopted for synthesis of lead-free piezoelectric ceramics

NASA Astrophysics Data System (ADS)

Mahesh, M. L. V.; Bhanu Prasad, V. V.; James, A. R.

2016-04-01

Barium zirconium titanate, Ba(Zr0.15Ti0.85)O3 nano-crystalline powders were synthesized using high energy ball milling. The calcined powders were compacted adopting two different approaches viz. the conventional uniaxial pressing and cold-isostatic pressing (CIP) and the compacts were sintered at 1350 °C. A single phase perovskite structure was observed in both cases. BZT ceramics compacted using CIP technique exhibited enhanced dielectric and ferroelectric properties compared to ceramics compacted by uniaxial pressing. The polarization current peaks have been used in this paper as an experimental evidence to prove the existence of ferroelectricity in the BZT ceramics under study. The peak polarization current was found to be ~700% higher in case of cold iso-statically compacted ceramics. Similarly electric field induces strain showed a maximum strain ( S max) of 0.08% at an electric field of 28 kV/cm. The dielectric and ferroelectric properties observed are comparable to single crystals of the same material.

A new classification system for all-ceramic and ceramic-like restorative materials.

PubMed

Gracis, Stefano; Thompson, Van P; Ferencz, Jonathan L; Silva, Nelson R F A; Bonfante, Estevam A

2015-01-01

Classification systems for all-ceramic materials are useful for communication and educational purposes and warrant continuous revisions and updates to incorporate new materials. This article proposes a classification system for ceramic and ceramic-like restorative materials in an attempt to systematize and include a new class of materials. This new classification system categorizes ceramic restorative materials into three families: (1) glass-matrix ceramics, (2) polycrystalline ceramics, and (3) resin-matrix ceramics. Subfamilies are described in each group along with their composition, allowing for newly developed materials to be placed into the already existing main families. The criteria used to differentiate ceramic materials are based on the phase or phases present in their chemical composition. Thus, an all-ceramic material is classified according to whether a glass-matrix phase is present (glass-matrix ceramics) or absent (polycrystalline ceramics) or whether the material contains an organic matrix highly filled with ceramic particles (resin-matrix ceramics). Also presented are the manufacturers' clinical indications for the different materials and an overview of the different fabrication methods and whether they are used as framework materials or monolithic solutions. Current developments in ceramic materials not yet available to the dental market are discussed.

Radiation tolerance of nanocrystalline ceramics: insights from Yttria Stabilized Zirconia.

PubMed

Dey, Sanchita; Drazin, John W; Wang, Yongqiang; Valdez, James A; Holesinger, Terry G; Uberuaga, Blas P; Castro, Ricardo H R

2015-01-13

Materials for applications in hostile environments, such as nuclear reactors or radioactive waste immobilization, require extremely high resistance to radiation damage, such as resistance to amorphization or volume swelling. Nanocrystalline materials have been reported to present exceptionally high radiation-tolerance to amorphization. In principle, grain boundaries that are prevalent in nanomaterials could act as sinks for point-defects, enhancing defect recombination. In this paper we present evidence for this mechanism in nanograined Yttria Stabilized Zirconia (YSZ), associated with the observation that the concentration of defects after irradiation using heavy ions (Kr(+), 400 keV) is inversely proportional to the grain size. HAADF images suggest the short migration distances in nanograined YSZ allow radiation induced interstitials to reach the grain boundaries on the irradiation time scale, leaving behind only vacancy clusters distributed within the grain. Because of the relatively low temperature of the irradiations and the fact that interstitials diffuse thermally more slowly than vacancies, this result indicates that the interstitials must reach the boundaries directly in the collision cascade, consistent with previous simulation results. Concomitant radiation-induced grain growth was observed which, as a consequence of the non-uniform implantation, caused cracking of the nano-samples induced by local stresses at the irradiated/non-irradiated interfaces.

Radiation Tolerance of Nanocrystalline Ceramics: Insights from Yttria Stabilized Zirconia

PubMed Central

Dey, Sanchita; Drazin, John W.; Wang, Yongqiang; Valdez, James A.; Holesinger, Terry G.; Uberuaga, Blas P.; Castro, Ricardo H. R.

2015-01-01

Materials for applications in hostile environments, such as nuclear reactors or radioactive waste immobilization, require extremely high resistance to radiation damage, such as resistance to amorphization or volume swelling. Nanocrystalline materials have been reported to present exceptionally high radiation-tolerance to amorphization. In principle, grain boundaries that are prevalent in nanomaterials could act as sinks for point-defects, enhancing defect recombination. In this paper we present evidence for this mechanism in nanograined Yttria Stabilized Zirconia (YSZ), associated with the observation that the concentration of defects after irradiation using heavy ions (Kr+, 400 keV) is inversely proportional to the grain size. HAADF images suggest the short migration distances in nanograined YSZ allow radiation induced interstitials to reach the grain boundaries on the irradiation time scale, leaving behind only vacancy clusters distributed within the grain. Because of the relatively low temperature of the irradiations and the fact that interstitials diffuse thermally more slowly than vacancies, this result indicates that the interstitials must reach the boundaries directly in the collision cascade, consistent with previous simulation results. Concomitant radiation-induced grain growth was observed which, as a consequence of the non-uniform implantation, caused cracking of the nano-samples induced by local stresses at the irradiated/non-irradiated interfaces. PMID:25582769

Radiation tolerance of nanocrystalline ceramics: Insights from yttria stabilized zirconia

DOE PAGES

Dey, Sanchita; Drazin, John W.; Wang, Yongqiang; ...

2015-01-13

Materials for applications in hostile environments, such as nuclear reactors or radioactive waste immobilization, require extremely high resistance to radiation damage, such as resistance to amorphization or volume swelling. Nanocrystalline materials have been reported to present exceptionally high radiation-tolerance to amorphization. In principle, grain boundaries that are prevalent in nanomaterials could act as sinks for point-defects, enhancing defect recombination. In this paper we present evidence for this mechanism in nanograined Yttria Stabilized Zirconia (YSZ), associated with the observation that the concentration of defects after irradiation using heavy ions (Kr⁺, 400 keV) is inversely proportional to the grain size. HAADF imagesmore » suggest the short migration distances in nanograined YSZ allow radiation induced interstitials to reach the grain boundaries on the irradiation time scale, leaving behind only vacancy clusters distributed within the grain. Because of the relatively low temperature of the irradiations and the fact that interstitials diffuse thermally more slowly than vacancies, this result indicates that the interstitials must reach the boundaries directly in the collision cascade, consistent with previous simulation results. Concomitant radiation-induced grain growth was observed which, as a consequence of the non-uniform implantation, caused cracking of the nano-samples induced by local stresses at the irradiated/non-irradiated interfaces.« less

Solid state consolidation nanocrystalline copper-tungsten using cold spray

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

Hall, Aaron Christopher; Sarobol, Pylin; Argibay, Nicolas

It is well known that nanostructured metals can exhibit significantly improved properties compared to metals with conventional grain size. Unfortunately, nanocrystalline metals typically are not thermodynamically stable and exhibit rapid grain growth at moderate temperatures. This severely limits their processing and use, making them impractical for most engineering applications. Recent work has shown that a number of thermodynamically stable nanocrystalline metal alloys exist. These alloys have been prepared as powders using severe plastic deformation (e.g. ball milling) processes. Consolidation of these powders without compromise of their nanocrystalline microstructure is a critical step to enabling their use as engineering materials. Wemore » demonstrate solid-state consolidation of ball milled copper-tantalum nanocrystalline metal powder using cold spray. Unfortunately, the nanocrystalline copper-tantalum powder that was consolidated did not contain the thermodynamically stable copper-tantalum nanostructure. Nevertheless, this does this demonstrates a pathway to preparation of bulk thermodynamically stable nanocrystalline copper-tantalum. Furthermore, it demonstrates a pathway to additive manufacturing (3D printing) of nanocrystalline copper-tantalum. Additive manufacturing of thermodynamically stable nanocrystalline metals is attractive because it enables maximum flexibility and efficiency in the use of these unique materials.« less

FOREWORD: Focus on Advanced Ceramics Focus on Advanced Ceramics

NASA Astrophysics Data System (ADS)

Ohashi, Naoki

2011-06-01

Much research has been devoted recently to developing technologies for renewable energy and improving the efficiency of the processes and devices used in industry and everyday life. Efficient solutions have been found using novel materials such as platinum and palladium-based catalysts for car exhaust systems, samarium-cobalt and neodymium-iron-boron permanent magnets for electrical motors, and so on. However, their realization has resulted in an increasing demand for rare elements and in their deficit, the development of new materials based on more abundant elements and new functionalities of traditional materials. Moreover, increasing environmental and health concerns demand substitution of toxic or hazardous substances with nature-friendly alternatives. In this context, this focus issue on advanced ceramics aims to review current trends in ceramics science and technology. It is related to the International Conference on Science and Technology of Advanced Ceramics (STAC) held annually to discuss the emerging issues in the field of ceramics. An important direction of ceramic science is the collaboration between experimental and theoretical sciences. Recent developments in density functional theory and computer technology have enabled the prediction of physical and chemical properties of ceramics, thereby assisting the design of new materials. Therefore, this focus issue includes articles devoted to theory and advanced characterization techniques. As mentioned above, the potential shortage of rare elements is becoming critical to the industry and has resulted in a Japanese government initiative called the 'Ubiquitous Element Strategy'. This focus issue also includes articles related to this strategy and to the associated topics of energy conversion, such as phosphors for high-efficiency lighting and photocatalysts for solar-energy harvesting. We hope that this focus issue will provide a timely overview of current trends and problems in ceramics science and

Micromechanics Modeling of Fracture in Nanocrystalline Metals

NASA Technical Reports Server (NTRS)

Glaessgen, E. H.; Piascik, R. S.; Raju, I. S.; Harris, C. E.

2002-01-01

Nanocrystalline metals have very high theoretical strength, but suffer from a lack of ductility and toughness. Therefore, it is critical to understand the mechanisms of deformation and fracture of these materials before their full potential can be achieved. Because classical fracture mechanics is based on the comparison of computed fracture parameters, such as stress intlmsity factors, to their empirically determined critical values, it does not adequately describe the fundamental physics of fracture required to predict the behavior of nanocrystalline metals. Thus, micromechanics-based techniques must be considered to quanti@ the physical processes of deformation and fracture within nanocrystalline metals. This paper discusses hndamental physicsbased modeling strategies that may be useful for the prediction Iof deformation, crack formation and crack growth within nanocrystalline metals.

Direct synthesis and characterization of optically transparent conformal zinc oxide nanocrystalline thin films by rapid thermal plasma CVD

NASA Astrophysics Data System (ADS)

Pedersen, Joachim D.; Esposito, Heather J.; Teh, Kwok Siong

2011-10-01

We report a rapid, self-catalyzed, solid precursor-based thermal plasma chemical vapor deposition process for depositing a conformal, nonporous, and optically transparent nanocrystalline ZnO thin film at 130 Torr (0.17 atm). Pure solid zinc is inductively heated and melted, followed by ionization by thermal induction argon/oxygen plasma to produce conformal, nonporous nanocrystalline ZnO films at a growth rate of up to 50 nm/min on amorphous and crystalline substrates including Si (100), fused quartz, glass, muscovite, c- and a-plane sapphire (Al2O3), gold, titanium, and polyimide. X-ray diffraction indicates the grains of as-deposited ZnO to be highly textured, with the fastest growth occurring along the c-axis. The individual grains are observed to be faceted by (103) planes which are the slowest growth planes. ZnO nanocrystalline films of nominal thicknesses of 200 nm are deposited at substrate temperatures of 330°C and 160°C on metal/ceramic substrates and polymer substrates, respectively. In addition, 20-nm- and 200-nm-thick films are also deposited on quartz substrates for optical characterization. At optical spectra above 375 nm, the measured optical transmittance of a 200-nm-thick ZnO film is greater than 80%, while that of a 20-nm-thick film is close to 100%. For a 200-nm-thick ZnO film with an average grain size of 100 nm, a four-point probe measurement shows electrical conductivity of up to 910 S/m. Annealing of 200-nm-thick ZnO films in 300 sccm pure argon at temperatures ranging from 750°C to 950°C (at homologous temperatures between 0.46 and 0.54) alters the textures and morphologies of the thin film. Based on scanning electron microscope images, higher annealing temperatures appear to restructure the ZnO nanocrystalline films to form nanorods of ZnO due to a combination of grain boundary diffusion and bulk diffusion. PACS: films and coatings, 81.15.-z; nanocrystalline materials, 81.07.Bc; II-VI semiconductors, 81.05.Dz.

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

PubMed Central

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

2016-01-01

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

Laser-Aided Ceramic Bracket Debonding: A Comprehensive Review

PubMed Central

Ghazanfari, Rezvaneh; Nokhbatolfoghahaei, Hanieh; Alikhasi, Marzieh

2016-01-01

Different techniques have been introduced for the removal of ceramic brackets. Since the early 1990s, lasers have been used experimentally for debonding ceramic brackets. The goal of this study is to give a comprehensive literature review on laser-aided ceramic bracket debonding. PubMed and Google Scholar databases were used to identify dental articles with the following combination of key words: Ceramic brackets, Debonding, and Laser. Sixteen English articles from 2004 to 2015 were selected. The selected studies were categorized according to the variables investigated including the intrapulpal temperature, shear bond strength, debonding time, enamel damage and bracket failure. Most articles reported decreased shear bond strength and debonding time following laser irradiation without any critical and irritating increase in pulpal temperature. There were no reports of bracket failure or enamel damage. Laser irradiation is an efficient way to reduce shear bond strength of ceramic bracket and debonding time. This technique is a safe way for removing ceramic bracket with minimal impact on intrapulpal temperature and enamel surface and it reduces ceramic bracket failure. PMID:27330690

Synthesis, characterization, and photocatalytic properties of nanocrystalline NZO thin films

NASA Astrophysics Data System (ADS)

Aryanto, D.; Hastuti, E.; Husniya, N.; Sudiro, T.; Nuryadin, B. W.

2018-03-01

Nanocrystalline Ni-doped ZnO (NZO) thin films were synthesized on glass substrate using sol-gel spin coating methods. The effect of annealing on the structural and optical properties of nanocrystalline thin film was studied using X-ray diffractometer (XRD), field emission scanning electron microscopy (FESEM), UV-VIS spectrophotometry, and photoluminescence (PL). The results showed that the annealing temperature strongly influenced the physical properties of nanocrystalline NZO thin films. The photocatalytic properties of nanocrystalline NZO thin films were evaluated using an aqueous solution of Rhodamine-B. The photocatalytic activity of nanocrystalline NZO thin films increased with the increase of annealing temperature. The results indicated that the structure, morphology, and band gap energy of nanocrystalline NZO thin films played an important role in photocatalytic activity.

Transient liquid phase ceramic bonding

DOEpatents

Glaeser, Andreas M.

1994-01-01

Ceramics are joined to themselves or to metals using a transient liquid phase method employing three layers, one of which is a refractory metal, ceramic or alloy. The refractory layer is placed between two metal layers, each of which has a lower melting point than the refractory layer. The three layers are pressed between the two articles to be bonded to form an assembly. The assembly is heated to a bonding temperature at which the refractory layer remains solid, but the two metal layers melt to form a liquid. The refractory layer reacts with the surrounding liquid and a single solid bonding layer is eventually formed. The layers may be designed to react completely with each other and form refractory intermetallic bonding layers. Impurities incorporated into the refractory metal may react with the metal layers to form refractory compounds. Another method for joining ceramic articles employs a ceramic interlayer sandwiched between two metal layers. In alternative embodiments, the metal layers may include sublayers. A method is also provided for joining two ceramic articles using a single interlayer. An alternate bonding method provides a refractory-metal oxide interlayer placed adjacent to a strong oxide former. Aluminum or aluminum alloys are joined together using metal interlayers.

Zirconia-coated carbonyl-iron-particle-based magnetorheological fluid for polishing optical glasses and ceramics.

PubMed

Shafrir, Shai N; Romanofsky, Henry J; Skarlinski, Michael; Wang, Mimi; Miao, Chunlin; Salzman, Sivan; Chartier, Taylor; Mici, Joni; Lambropoulos, John C; Shen, Rui; Yang, Hong; Jacobs, Stephen D

2009-12-10

We report on magnetorheological finishing (MRF) spotting experiments performed on glasses and ceramics using a zirconia-coated carbonyl-iron (CI)-particle-based magnetorheological (MR) fluid. The zirconia-coated magnetic CI particles were prepared via sol-gel synthesis in kilogram quantities. The coating layer was approximately 50-100 nm thick, faceted in surface structure, and well adhered. Coated particles showed long-term stability against aqueous corrosion. "Free" nanocrystalline zirconia polishing abrasives were cogenerated in the coating process, resulting in an abrasive-charged powder for MRF. A viable MR fluid was prepared simply by adding water. Spot polishing tests were performed on a variety of optical glasses and ceramics over a period of nearly three weeks with no signs of MR fluid degradation or corrosion. Stable material removal rates and smooth surfaces inside spots were obtained.

The Bulk Nanocrystalline zn Produced by Mechanical Attrition

NASA Astrophysics Data System (ADS)

Zhu, X. K.; Zhao, K. Y.; Li, C. J.; Tao, J. M.; Chan, T. L.; Koch, C. C.

The purpose of experiment was to produce bulk nanocrystalline Zn by mechanical attrition. The bulk nanocrystalline Zn produced by mechanical attrition was studied. The microstructural evolution during cryomilling and subsequent room temperature milling was characterized using scanning electron microscopy (SEM) and X-ray diffraction (XRD). In this paper, Nanocrystalline Zn was produced by insitu consolidation of Zn elemental powder using mechanical attrition at liquid nitrogen and room temperature. For the samples studied, the longest elongation of 65% and highest stress of 200 MPa is obtained in nanocrystalline Zn during tensile testing at the condition of strain rate (10-3 sec-1) and 20°C which is equal to 0.43 Tm (Tm is the melting temperature of pure Zn).

Giant electrocaloric and energy storage performance of [(K0.5Na0.5)NbO3](1-x)-[LiSbO3] x nanocrystalline ceramics.

PubMed

Kumar, Raju; Singh, Satyendra

2018-02-16

Electrocaloric (EC) refrigeration, an EC effect based technology has been accepted as an auspicious way in the development of next generation refrigeration due to high efficiency and compact size. Here, we report the results of our experimental investigations on electrocaloric response and electrical energy storage properties in lead-free nanocrystalline (1 - x)K 0.5 Na 0.5 NbO 3 -xLiSbO 3 (KNN-xLS) ceramics in the range of 0.015 ≤ x ≤ 0.06 by the indirect EC measurements. Doping of LiSbO 3 has lowered both the transitions (T C and T O-T ) of KNN to the room temperature side effectively. A maximal value of EC temperature change, ΔT = 3.33 K was obtained for the composition with x = 0.03 at 345 K under an external electric field of 40 kV/cm. The higher value of EC responsivity, ζ = 8.32 × 10 -7  K.m/V is found with COP of 8.14 and recoverable energy storage of 0.128 J/cm 3 with 46% efficiency for the composition of x = 0.03. Our investigations show that this material is a very promising candidate for electrocaloric refrigeration and energy storage near room temperature.

Method for treating beta-spodumene ceramics

DOEpatents

Day, J. Paul; Hickman, David L.

1994-09-27

A vapor-phase method for treating a beta-spodumene ceramic article to achieve a substitution of exchangeable hydrogen ions for the lithium present in the beta-spodumene crystals, wherein a barrier between the ceramic article and the source of exchangeable hydrogen ions is maintained in order to prevent lithium contamination of the hydrogen ion source and to generate highly recoverable lithium salts, is provided.

Nonaqueous slip casting of high temperature ceramic superconductors using an investment casting technique

NASA Technical Reports Server (NTRS)

Hooker, Matthew W. (Inventor); Taylor, Theodore D. (Inventor); Wise, Stephanie A. (Inventor); Buckley, John D. (Inventor); Vasquez, Peter (Inventor); Buck, Gregory M. (Inventor); Hicks, Lana P. (Inventor)

1993-01-01

A process for slip casting ceramic articles that does not employ parting agents and affords the casting of complete, detailed, precision articles that do not possess parting lines is presented. This process is especially useful for high temperature superconductors and water-sensitive ceramics. A wax pattern for a shell mold is provided, and an aqueous mixture of a calcium sulfate-bonded investment material is applied as a coating to the wax pattern. The coated wax pattern is then dried, followed by curing to vaporize the wax pattern and leave a shell mold of the calcium sulfate-bonded investment material. The shell mold is cooled to room temperature, and a ceramic slip, created by dispersing a ceramic powder in an organic liquid, is poured therein. After a ceramic shell of desired thickness or a solid article has set up in the shell mold, excess ceramic slip is poured out. The shell mold is misted with water and peeled away from the ceramic article, after which the ceramic is fired to provide a complete, detailed, precision, high temperature superconductive ceramic article without parting lines. The casting technique may take place in the presence of a magnetic field to orient the ceramic powders during the casting process.

A neutron scintillator based on transparent nanocrystalline CaF{sub 2}:Eu glass ceramic

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

Struebing, Christian; Kang, Zhitao, E-mail: zhitao.kang@gtri.gatech.edu; School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332

2016-04-11

There are no efficient Eu{sup 2+} doped glass neutron scintillators reported due to low doping concentrations of Eu{sup 2+} and the amorphous nature of the glass matrix. In this work, an efficient CaF{sub 2}:Eu glass ceramic neutron scintillator was prepared by forming CaF{sub 2}:Eu nanocrystals in a {sup 6}Li-containing glass matrix. Through appropriate thermal treatments, the scintillation light yield of the transparent glass ceramic was increased by a factor of at least 46 compared to the as-cast amorphous glass. This improvement was attributed to more efficient energy transfer from the CaF{sub 2} crystals to the Eu{sup 2+} emitting centers. Furthermore » light yield improvement is expected if the refractive index of the glass matrix can be matched to the CaF{sub 2} crystal.« less

Zirconia-coated carbonyl-iron-particle-based magnetorheological fluid for polishing optical glasses and ceramics

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

Shafrir, Shai N.; Romanofsky, Henry J.; Skarlinski, Michael

2009-12-10

We report on magnetorheological finishing (MRF) spotting experiments performed on glasses and ceramics using a zirconia-coated carbonyl-iron (CI)-particle-based magnetorheological (MR) fluid. The zirconia-coated magnetic CI particles were prepared via sol-gel synthesis in kilogram quantities. The coating layer was {approx}50-100 nm thick, faceted in surface structure, and well adhered. Coated particles showed long-term stability against aqueous corrosion. ''Free'' nanocrystalline zirconia polishing abrasives were cogenerated in the coating process, resulting in an abrasive-charged powder for MRF. A viable MR fluid was prepared simply by adding water. Spot polishing tests were performed on a variety of optical glasses and ceramics over a periodmore » of nearly three weeks with no signs of MR fluid degradation or corrosion. Stable material removal rates and smooth surfaces inside spots were obtained.« less

Molten Salt Synthesis and Structural Characterization of BaTiO3 Nanocrystal Ceramics

NASA Astrophysics Data System (ADS)

Ahda, S.; Misfadhila, S.; Parikin, P.; Putra, T. Y. S. P.

2017-02-01

A new synthesis route to obtain high-purity barium titanate powder, BaTiO3, using the molten salt method by reacting the raw materials (BaCO3 and TiO2) in an atmosphere of molten NaCl and KCl, has been developed. The synthesized BaTiO3 ceramic particles have been successfully carried out at the sintering temperature 950°C for 4 hours. The Rietveld refinement of the XRD diffraction patterns was employed to characterize the structural information of the nanocrystalline BaTiO3 ceramics. The lattice parameters (a=4.0043 Å, b=4.0308Å with space group P4mm) of tetragonal perovskite structure, as an indication of piezoelectric characteristics, have been successfully determined by the Rietveld refinement. While the crystallitte particle size and strains have been obtained for the values of 110.6 nm and 0.74 % respectively

Low temperature biosynthesis of Li2O-MgO-P2O5-TiO2 nanocrystalline glass with mesoporous structure exhibiting fast lithium ion conduction.

PubMed

Du, Xiaoyong; He, Wen; Zhang, Xudong; Ma, Jinyun; Wang, Chonghai; Li, Chuanshan; Yue, Yuanzheng

2013-04-01

We demonstrate a biomimetic synthesis methodology that allows us to create Li2O-MgO-P2O5-TiO2 nanocrystalline glass with mesoporous structure at lower temperature. We design a 'nanocrystal-glass' configuration to build a nanoarchitecture by means of yeast cell templates self-assembly followed by the controlled in-situ biomineralization of materials on the cell wall. Electrochemically active nanocrystals are used as the lamellar building blocks of mesopores, and the semiconductive glass phase can act both as the 'glue' between nanocrystals and functionalized component. The Li2O-MgO-P2O5-TiO2 nanocrystalline glass exhibits outstanding thermal stability, high conductivity and wide potential window. This approach could be applied to many other multicomponent glass-ceramics to fabricate mesoporous conducting materials for solid-state lithium batteries. Copyright © 2012 Elsevier B.V. All rights reserved.

Aging of Nanocrystalline Mackinawite (FeS): Mineralogical and Physicochemical Properties

NASA Astrophysics Data System (ADS)

Jeong, H. Y.; Lee, H.

2011-12-01

Due to the extraordinary physical properties and high surface areas, nanocrystalline minerals have been widely investigated for their potential uses in treating contaminated groundwaters and surface waters. Most previous studies in this field have focused on either preparation of nanocrystalline minerals or measurement of their reactivity with environmental contaminants. Nanocrystalline minerals, due to the inherent thermodynamic instability, tend to change the physicochemical and mineralogical properties over time, usually resulting in the decreased reactivity. Thus, to better assess the long-term effectiveness of nanocrystalline minerals in field applications, such "aging" effects should be clearly delineated. In the present work, we have investigated the aging impact on nanocrystalline mackinawite (FeS), the ubiquitous Fe-bearing mineral in anoxic sulfidic sediments. Mackinawite (FeS) is known to be an effective scavenger for metal pollutants and a strong reducing reagent for chromate and chlorinated organic compounds. Our preliminary results indicate that nanocrystalline FeS ages via Ostwald ripening, particle aggregation, or mineralogical transformation. By X-ray diffraction (XRD) analysis, aging of nanocrystalline FeS via Ostwald ripening is found to be dominant at acidic pH. Cryogenic transmission electron microscopy (TEM) shows that particle aggregation is most evident at neutral pH. Transformation of nanosized FeS into a more thermodynamically stable greigite (Fe3S4) is observed in the presence of folic acid at acidic pH. The pH-dependent aging process may be linked with changes in the apparent solubility and surface charge of FeS with pH. The Ostwald ripening or particle aggregation of nanocrystalline FeS leads to the decrease surface area, thus causing the decreased reactivity. Given the less reactivity of greigite, the transformation of nanocrystalline FeS to greigite is also expected to result in the decreased reactivity.

Ceramic thermal barrier coating for rapid thermal cycling applications

DOEpatents

Scharman, Alan J.; Yonushonis, Thomas M.

1994-01-01

A thermal barrier coating for metal articles subjected to rapid thermal cycling includes a metallic bond coat deposited on the metal article, at least one MCrAlY/ceramic layer deposited on the bond coat, and a ceramic top layer deposited on the MCrAlY/ceramic layer. The M in the MCrAlY material is Fe, Ni, Co, or a mixture of Ni and Co. The ceramic in the MCrAlY/ceramic layer is mullite or Al.sub.2 O.sub.3. The ceramic top layer includes a ceramic with a coefficient of thermal expansion less than about 5.4.times.10.sup.-6 .degree.C.sup.-1 and a thermal conductivity between about 1 J sec.sup.-1 m.sup.-1 .degree.C.sup.-1 and about 1.7 J sec.sup.-1 m.sup.-1 .degree.C.sup.-1.

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.

Nanocrystalline heterojunction materials

DOEpatents

Elder, Scott H.; Su, Yali; Gao, Yufei; Heald, Steve M.

2003-07-15

Mesoporous nanocrystalline titanium dioxide heterojunction materials are disclosed. In one disclosed embodiment, materials comprising a core of titanium dioxide and a shell of a molybdenum oxide exhibit a decrease in their photoadsorption energy as the size of the titanium dioxide core decreases.

Synthesis of Nano-Crystalline Gamma-TiAl Materials

NASA Technical Reports Server (NTRS)

Hales, Stephen J.; Vasquez, Peter

2003-01-01

One of the principal problems with nano-crystalline materials is producing them in quantities and sizes large enough for valid mechanical property evaluation. The purpose of this study was to explore an innovative method for producing nano-crystalline gamma-TiAl bulk materials using high energy ball milling and brief secondary processes. Nano-crystalline powder feedstock was produced using a Fritsch P4(TM) vario-planetary ball mill recently installed at NASA-LaRC. The high energy ball milling process employed tungsten carbide tooling (vials and balls) and no process control agents to minimize contamination. In a collaborative effort, two approaches were investigated, namely mechanical alloying of elemental powders and attrition milling of pre-alloyed powders. The objective was to subsequently use RF plasma spray deposition and short cycle vacuum hot pressing in order to effect consolidation while retaining nano-crystalline structure in bulk material. Results and discussion of the work performed to date are presented.

Initial stage corrosion of nanocrystalline copper particles and thin films

NASA Astrophysics Data System (ADS)

Tao, Weimin

1997-12-01

Corrosion behavior is an important issue in nanocrystalline materials research and development. A very fine grain size is expected to have significant effects on the corrosion resistance of these novel materials. However, both the macroscopic corrosion properties and the corresponding structure evolution during corrosion have not been fully studied. Under such circumstances, conducting fundamental research in this area is important and necessary. In this study, high purity nanocrystalline and coarse-grained copper were selected as our sample material, sodium nitrite aqueous solution at room temperature and air at a high temperature were employed as corrosive environments. The weight loss testing and electrochemical methods were used to obtain the macroscopic corrosion properties, whereas the high resolution transmission electron microscope was employed for the structure analysis. The weight loss tests indicate that the corrosion rate of nanocrystalline copper is about 5 times higher than that of coarse-grained copper at the initial stage of corrosion. The electrochemical measurements show that the corrosion potential of the nanocrystalline copper has a 230 mV negative shift in comparison with that of the coarse-grained copper. The nanocrystalline copper also exhibits a significantly higher exchange current density than the coarse-grained copper. High resolution TEM revealed that the surface structure changes at the initial stage of corrosion. It was found that the first copper oxide layer formed on the surface of nanocrystalline copper thin film contains a large density of high angle grain boundaries, whereas that formed on the surface of coarse-grained copper shows highly oriented oxide nuclei and appears to show a strong tendency for forming low angle grain boundaries. A correlation between the macroscopic corrosion properties and the structure characteristics is proposed for the nanocrystalline copper based on the concept of the "apparent" exchange current

Application of micro- and nanocrystalline cellulose

NASA Astrophysics Data System (ADS)

Sotnikova, Yu S.; Demina, T. S.; Istomin, A. V.; Goncharuk, G. P.; Grandfils, Ch; Akopova, T. A.; Zelenetskii, A. N.; Babayevsky, P. G.

2018-04-01

Micro- and nanocrystalline forms of cellulose were extracted from flax stalks and evaluated in terms of their applicability for various materials science tasks. It was revealed that both form of cellulose had anisometric morphology with length of 27.1 μm and 159 nm; diameter of 8.7 μm and 85 nm, respectively. They were used as reinforcing fillers for fabrication of composite films based on hydroxyethylcellulose. Film-forming and mechanical properties of the composite materials were significantly varied in dependence on filler content (0–10 wt.%) and size. As a second option of micro- and nanocrystalline cellulose application, a study of their effectiveness as stabilizing agents for oil/water Pickering emulsions was carried out. In contrast to micron-sized cellulose the nanocrystalline form appeared to be successful in the process of CH2Cl2/water interface stabilization and fabrication of polylactide microparticles via oil/water Pickering emulsion solvent evaporation technique.

Characterization of Nanocrystalline Aluminum Alloy 5083 Powders Produced by Cryogenic Attrition

DTIC Science & Technology

2014-11-01

Characterization of Nanocrystalline Aluminum Alloy 5083 Powders Produced by Cryogenic Attrition by Tiffany Ngo ARL-TN-0643...November 2014 Characterization of Nanocrystalline Aluminum Alloy 5083 Powders Produced by Cryogenic Attrition Tiffany Ngo Weapons and...3. DATES COVERED (From - To) August 2014 4. TITLE AND SUBTITLE Characterization of Nanocrystalline Aluminum Alloy 5083 Powders Produced by

Nanocrystalline cellulose from coir fiber: preparation, properties, and applications

USDA-ARS?s Scientific Manuscript database

Nanocrystalline cellulose derived from various botanical sources offers unique and potentially useful characteristics. In principle, any cellulosic material can be considered as a potential source of a nanocrystalline material, including crops, crop residues, and agroindustrial wastes. Because of t...

Mechanical properties and rapid low-temperature consolidation of nanocrystalline Cu-ZrO2 composites by pulsed current activated heating

NASA Astrophysics Data System (ADS)

Kang, Bo-Ram; Yoon, Jin-kook; Hong, Kyung-Tae; Shon, In-Jin

2015-07-01

Metal-ceramic compositr can be obtained with an optimum combination of low density, high oxidation resistance, and high hardness of the ceramic and toughness of the metal. Therefore, metal matrix composites are recognized as candidates for aerospace, automotive, biomaterials, and defense applications. Despite its many attractive properties, the low fracture toughness of ZrO2 limits its wide application. One of the most obvious tactics to improve the mechanical properties has been to fabricate a nanostructured material and composite material. Nano-powders of Cu and ZrO2 were synthesized from 2CuO and Zr powders by high-energy ball milling. Nanocrystalline 2Cu-ZrO2 composite was consolidated within 5 minutes from mechanically synthesized powders of ZrO2 and 2Cu at low temperature, by a pulsed current activated sintering method. The relative density of the composite was 98.5%. The fracture toughness of 2Cu-ZrO2 composite in this study is higher than that of monolithic ZrO2, without great decrease of hardness.

Nanocrystalline Heterojunction Materials

DOEpatents

Elder, Scott H.; Su, Yali; Gao, Yufei; Heald, Steve M.

2004-02-03

Mesoporous nanocrystalline titanium dioxide heterojunction materials and methods of making the same are disclosed. In one disclosed embodiment, materials comprising a core of titanium dioxide and a shell of a molybdenum oxide exhibit a decrease in their photoadsorption energy as the size of the titanium dioxide core decreases.

Methods for preparation of nanocrystalline rare earth phosphates for lighting applications

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

Comanzo, Holly Ann; Manoharan, Mohan; Martins Loureiro, Sergio Paulo

Disclosed here are methods for the preparation of optionally activated nanocrystalline rare earth phosphates. The optionally activated nanocrystalline rare earth phosphates may be used as one or more of quantum-splitting phosphor, visible-light emitting phosphor, vacuum-UV absorbing phosphor, and UV-emitting phosphor. Also disclosed herein are discharge lamps comprising the optionally activated nanocrystalline rare earth phosphates provided by these methods.

Making Ceramic Cameras

ERIC Educational Resources Information Center

Squibb, Matt

2009-01-01

This article describes how to make a clay camera. This idea of creating functional cameras from clay allows students to experience ceramics, photography, and painting all in one unit. (Contains 1 resource and 3 online resources.)

Nanocrystalline cerium oxide materials for solid fuel cell systems

DOEpatents

Brinkman, Kyle S

2015-05-05

Disclosed are solid fuel cells, including solid oxide fuel cells and PEM fuel cells that include nanocrystalline cerium oxide materials as a component of the fuel cells. A solid oxide fuel cell can include nanocrystalline cerium oxide as a cathode component and microcrystalline cerium oxide as an electrolyte component, which can prevent mechanical failure and interdiffusion common in other fuel cells. A solid oxide fuel cell can also include nanocrystalline cerium oxide in the anode. A PEM fuel cell can include cerium oxide as a catalyst support in the cathode and optionally also in the anode.

Verification of Ceramic Structures

NASA Astrophysics Data System (ADS)

Behar-Lafenetre, Stephanie; Cornillon, Laurence; Rancurel, Michael; De Graaf, Dennis; Hartmann, Peter; Coe, Graham; Laine, Benoit

2012-07-01

In the framework of the “Mechanical Design and Verification Methodologies for Ceramic Structures” contract [1] awarded by ESA, Thales Alenia Space has investigated literature and practices in affiliated industries to propose a methodological guideline for verification of ceramic spacecraft and instrument structures. It has been written in order to be applicable to most types of ceramic or glass-ceramic materials - typically Cesic®, HBCesic®, Silicon Nitride, Silicon Carbide and ZERODUR®. The proposed guideline describes the activities to be performed at material level in order to cover all the specific aspects of ceramics (Weibull distribution, brittle behaviour, sub-critical crack growth). Elementary tests and their post-processing methods are described, and recommendations for optimization of the test plan are given in order to have a consistent database. The application of this method is shown on an example in a dedicated article [7]. Then the verification activities to be performed at system level are described. This includes classical verification activities based on relevant standard (ECSS Verification [4]), plus specific analytical, testing and inspection features. The analysis methodology takes into account the specific behaviour of ceramic materials, especially the statistical distribution of failures (Weibull) and the method to transfer it from elementary data to a full-scale structure. The demonstration of the efficiency of this method is described in a dedicated article [8]. The verification is completed by classical full-scale testing activities. Indications about proof testing, case of use and implementation are given and specific inspection and protection measures are described. These additional activities are necessary to ensure the required reliability. The aim of the guideline is to describe how to reach the same reliability level as for structures made of more classical materials (metals, composites).

Fatigue stress concentration and notch sensitivity in nanocrystalline metals

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

Furnish, Timothy A.; Boyce, Brad L.; Sharon, John A.

Recent studies have shown the potential for nanocrystalline metals to possess excellent fatigue resistance compared to their coarse-grained counterparts. Although the mechanical properties of nanocrystalline metals are believed to be particularly susceptible to material defects, a systematic study of the effects of geometric discontinuities on their fatigue performance has not yet been performed. In the present work, nanocrystalline Ni–40 wt%Fe containing both intrinsic and extrinsic defects were tested in tension–tension fatigue. The defects were found to dramatically reduce the fatigue resistance, which was attributed to the relatively high notch sensitivity in the nanocrystalline material. Microstructural analysis within the crack-initiation zonesmore » underneath the defects revealed cyclically-induced abnormal grain growth (AGG) as a predominant deformation and crack initiation mechanism during high-cycle fatigue. Furthermore, the onset of AGG and the ensuing fracture is likely accelerated by the stress concentrations, resulting in the reduced fatigue resistance compared to the relatively defect-free counterparts.« less

Fatigue stress concentration and notch sensitivity in nanocrystalline metals

DOE PAGES

Furnish, Timothy A.; Boyce, Brad L.; Sharon, John A.; ...

2016-03-11

Recent studies have shown the potential for nanocrystalline metals to possess excellent fatigue resistance compared to their coarse-grained counterparts. Although the mechanical properties of nanocrystalline metals are believed to be particularly susceptible to material defects, a systematic study of the effects of geometric discontinuities on their fatigue performance has not yet been performed. In the present work, nanocrystalline Ni–40 wt%Fe containing both intrinsic and extrinsic defects were tested in tension–tension fatigue. The defects were found to dramatically reduce the fatigue resistance, which was attributed to the relatively high notch sensitivity in the nanocrystalline material. Microstructural analysis within the crack-initiation zonesmore » underneath the defects revealed cyclically-induced abnormal grain growth (AGG) as a predominant deformation and crack initiation mechanism during high-cycle fatigue. Furthermore, the onset of AGG and the ensuing fracture is likely accelerated by the stress concentrations, resulting in the reduced fatigue resistance compared to the relatively defect-free counterparts.« less

Studies on the sensing behaviour of nanocrystalline CuGa(2)O(4) towards hydrogen, liquefied petroleum gas and ammonia.

PubMed

Biswas, Soumya Kanti; Sarkar, Arpita; Pathak, Amita; Pramanik, Panchanan

2010-06-15

In the present article, the gas sensing behaviour of nanocrystalline CuGa(2)O(4) towards H(2), liquefied petroleum gas (LPG) and NH(3) has been reported for the first time. Nanocrystalline powders of CuGa(2)O(4) having average particle sizes in the range of 30-60nm have been prepared through thermal decomposition of an aqueous precursor solution comprising copper nitrate, gallium nitrate and triethanol amine (TEA), followed by calcination at 750 degrees C for 2h. The synthesized nanocrystalline CuGa(2)O(4) powders have been characterised through X-ray diffraction (XRD), transmission electron microscopy (TEM), field-emission scanning electron microscopy (FESEM) study, energy dispersive X-ray (EDX) analysis and BET (Brunauer-Emmett-Teller) surface area measurement. The synthesized CuGa(2)O(4) having spinel structure with specific surface area of 40m(2)/g exhibits maximum sensitivity towards H(2), LPG, and NH(3) at 350 degrees C.

Flexible Ceramic-Metal Insulation Composite and Method of Making

NASA Technical Reports Server (NTRS)

Rasky, Daniel J. (Inventor); Sawko, Paul M. (Inventor); Kilodziej, Paul (Inventor); Kourtides, Demetrius A. (Inventor)

1998-01-01

A method for joining a woven flexible ceramic fabric and a thin metal sheet creating an integral metal surfaced flexible thermal protection article, which methods compress: placing multiple dots of high temperature metallic or fabric and the thin metal sheet in a random or organized pattern, with the proviso that the brazing material covers about 10% or less of the surface of one flat side of the metal sheet; heating the flexible ceramic fabric, brazing material and thin metal sheet for a predetermined period of time to integrally connect the same; and cooling the formed flexible article to ambient temperature. Preferably the flexible ceramic is selected from fibers comprising atoms of silicon, carbon, nitrogen, boron, oxygen or combinations thereof. The flexible thermal protection article produced is also part of the present invention. The thin metal sheet is comprised of titanium, aluminum, chromium, niobium or alloys or combinations thereof. The brazing material is selected from copper/silver or copper/gold or is a ceramic brazing or adhesive material.

Electric field-assisted sintering of nanocrystalline hydroxyapatite for biomedical applications

NASA Astrophysics Data System (ADS)

Tran, Tien Bich

As the main inorganic component of bone, hydroxyapatite (HA, Ca 10(PO4)6(OH)2) should be an ideal candidate in biomaterials selection. When grain sizes are in the nanometric regime, protein adsorption and cell adhesion are enhanced, while strength, hardness, and wear resistance are improved. Unfortunately, low phase stability, poor sinterability, and a tendency towards exaggerated grain coarsening challenge full densification of nanocrystalline hydroxyapatite by conventional sintering methods. The field-assisted sintering technique (FAST) has successfully consolidated a variety of nanocrystalline metals and ceramics in dramatically reduced times. The sintering enhancements observed during FAST can be attributed to thermal and athermal effects. The rapid heating rates (up to ˜1000ºC/min) afforded by FAST contribute a significant thermal effect. Since fast heating rates reduce powder exposure to sub-sintering temperatures, non-densifying surface diffusion is limited. The athermal effects of FAST are less well understood and can include plasma generation, dielectric breakdown, particle surface cleaning, grain boundary pinning, and space charge effects. Applying the field-assisted sintering technique to nanocrystalline hydroxyapatite yielded surprising results. Deviations from conventional densification behavior were observed, with dehydroxylation identified as the most deleterious process to densification as well as mechanical and biological performance. Since hydroxyapatite is not a stable phase at high temperatures and low water partial pressure atmospheres, desintering due to dehydroxylation-related pore formation became apparent during Stage III sintering. In fact, the degree of desintering and pore formation increased with the extent of Stage III sintering and grain growth. The atomic rearrangements taking place during grain boundary migration are believed to favor the formation of more-stable oxyapatite through hydroxyapatite dehydroxylation. This behavior was

[All-ceramic peripheral restorations: crowns and bridges].

PubMed

Legros, Caroline; Vanheusden, Alain

2006-01-01

Over the last years, current technologies in dental ceramics are strongly improved, constantly producing new materials for the restoration of the single or plural teeth. Feldspathic porcelains fused to a cast metal substructure, the so-called "metal-ceramic crown," has been long time the gold standard; this is primarily due to their predictable long-term strength characteristics. All-ceramic systems are a focus of interest, because they offer aesthetic results that may be difficult to achieve with metal-ceramic systems. Nowadays, the new ceramics associate aesthetic and good mechanical qualities, biocompatibility, accurate marginal fit and low invasive preparations. Thanks to the diversification of all-ceram processes, materials properties and clinical situations are now the prime criteria which determine the practitioner's choice. In this article, we try to summarize different clinical concepts for peripheric all-ceram restoration, such as crowns and bridges used in a daily dental practice.

Some aspects of pulsed laser deposition of Si nanocrystalline films

NASA Astrophysics Data System (ADS)

Polyakov, B.; Petruhins, A.; Butikova, J.; Kuzmin, A.; Tale, I.

2009-11-01

Nanocrystalline silicon films were deposited by a picosecond laser ablation on different substrates in vacuum at room temperature. A nanocrystalline structure of the films was evidenced by atomic force microscopy (AFM), optical and Raman spectroscopies. A blue shift of the absorption edge was observed in optical absorption spectra, and a decrease of the optical phonon energy at the Brillouin zone centre was detected by Raman scattering. Early stages of nanocrystalline film formation on mica and HOPG substrates were studied by AFM. Mechanism of nanocrystal growth on substrate is discussed. in here

Electrodeposition of Nanocrystalline Co-P Coatings as a Hard Chrome Alternative

DTIC Science & Technology

2009-09-02

Electrodeposition  of Nanocrystalline Co‐P  Coatings as a Hard Chrome Alternative Report Documentation Page Form ApprovedOMB No. 0704-0188 Public reporting burden...AND SUBTITLE Electrodeposition of Nanocrystalline Co‐P Coatings as a Hard Chrome Alternative 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c...Defense Conference – 2 September 2009 Conventional  Electrodeposits Polycrystalline (10‐100 µm) Electrodeposited Nanocrystalline Materials Pulsed

Structural, optical and magnetic behaviour of nanocrystalline Volborthite

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

Arvind, Hemant K., E-mail: hemantarvind@gmail.com; Kumar, Sudhish, E-mail: skmlsu@gmail.com; Kalal, Sangeeta

2016-05-06

Nanocrystalline sample of Volborthite (Copper Pyrovanadate: Cu{sub 3}V{sub 2} (OH){sub 2}O{sub 7}.2H{sub 2}O) has been synthesized using wet chemical route and characterized by XRD, SEM, FTIR, UV-Vis-NIR spectroscopic and magnetization measurements. Room temperature X-ray diffraction analysis confirms the single phase monoclinic structure and nanocrystalline nature of Volborthite. The UV-Visible optical absorption spectrum displays two broad absorption peaks in the range of 200-350 nm and 400-1000 nm. The direct band gap is found to be E{sub g}= ∼2.74 eV. Bulk Volborthite was reported to be a natural frustrated antiferromagnet, however our nanocrystalline Volborthite display week ferromagnetic hysteresis loop with very small coercivity andmore » retentivity at room temperature.« less

Methods for providing ceramic matrix composite components with increased thermal capacity

NASA Technical Reports Server (NTRS)

Steibel, James Dale (Inventor); Utah, David Alan (Inventor)

2001-01-01

A method for enhancing the cooling capability of a turbine component made from a ceramic matrix composite. The method improves the thermal performance of the component by producing a surface having increased cooling capacity, thereby allowing the component to operate at a higher temperature. The method tailors the available surface area on the cooling surface of the composite component by depositing a particulate layer of coarse grained ceramic powders of preselected size onto the surface of the ceramic matrix composite component. The size of the particulate is selectively tailored to match the desired surface finish or surface roughness of the article. The article may be designed to have different surface finishes for different locations, so that the application of different sized powders can provide different cooling capabilities at different locations, if desired. The compositions of the particulates are chemically compatible with the ceramic material comprising the outer surface or portion of the ceramic matrix composite. The particulates are applied using a slurry and incorporated into the article by heating to an elevated temperature without melting the matrix, the particulates or the fiber reinforcement.

Method to produce nanocrystalline powders of oxide-based phosphors for lighting applications

DOEpatents

Loureiro, Sergio Paulo Martins; Setlur, Anant Achyut; Williams, Darryl Stephen; Manoharan, Mohan; Srivastava, Alok Mani

2007-12-25

Some embodiments of the present invention are directed toward nanocrystalline oxide-based phosphor materials, and methods for making same. Typically, such methods comprise a steric entrapment route for converting precursors into such phosphor material. In some embodiments, the nanocrystalline oxide-based phosphor materials are quantum splitting phosphors. In some or other embodiments, such nanocrystalline oxide based phosphor materials provide reduced scattering, leading to greater efficiency, when used in lighting applications.

Nanocrystalline Aluminum Truss Cores for Lightweight Sandwich Structures

NASA Astrophysics Data System (ADS)

Schaedler, Tobias A.; Chan, Lisa J.; Clough, Eric C.; Stilke, Morgan A.; Hundley, Jacob M.; Masur, Lawrence J.

2017-12-01

Substitution of conventional honeycomb composite sandwich structures with lighter alternatives has the potential to reduce the mass of future vehicles. Here we demonstrate nanocrystalline aluminum-manganese truss cores that achieve 2-4 times higher strength than aluminum alloy 5056 honeycombs of the same density. The scalable fabrication approach starts with additive manufacturing of polymer templates, followed by electrodeposition of nanocrystalline Al-Mn alloy, removal of the polymer, and facesheet integration. This facilitates curved and net-shaped sandwich structures, as well as co-curing of the facesheets, which eliminates the need for extra adhesive. The nanocrystalline Al-Mn alloy thin-film material exhibits high strength and ductility and can be converted into a three-dimensional hollow truss structure with this approach. Ultra-lightweight sandwich structures are of interest for a range of applications in aerospace, such as fairings, wings, and flaps, as well as for the automotive and sports industries.

Three-dimensional analysis by electron diffraction methods of nanocrystalline materials.

PubMed

Gammer, Christoph; Mangler, Clemens; Karnthaler, Hans-Peter; Rentenberger, Christian

2011-12-01

To analyze nanocrystalline structures quantitatively in 3D, a novel method is presented based on electron diffraction. It allows determination of the average size and morphology of the coherently scattering domains (CSD) in a straightforward way without the need to prepare multiple sections. The method is applicable to all kinds of bulk nanocrystalline materials. As an example, the average size of the CSD in nanocrystalline FeAl made by severe plastic deformation is determined in 3D. Assuming ellipsoidal CSD, it is deduced that the CSD have a width of 19 ± 2 nm, a length of 18 ± 1 nm, and a height of 10 ± 1 nm.

Nanocrystalline copper films are never flat

NASA Astrophysics Data System (ADS)

Zhang, Xiaopu; Han, Jian; Plombon, John J.; Sutton, Adrian P.; Srolovitz, David J.; Boland, John J.

2017-07-01

We used scanning tunneling microscopy to study low-angle grain boundaries at the surface of nearly planar copper nanocrystalline (111) films. The presence of grain boundaries and their emergence at the film surface create valleys composed of dissociated edge dislocations and ridges where partial dislocations have recombined. Geometric analysis and simulations indicated that valleys and ridges were created by an out-of-plane grain rotation driven by reduction of grain boundary energy. These results suggest that in general, it is impossible to form flat two-dimensional nanocrystalline films of copper and other metals exhibiting small stacking fault energies and/or large elastic anisotropy, which induce a large anisotropy in the dislocation-line energy.

Syntheses of nanocrystalline BaTiO3 and their optical properties

NASA Astrophysics Data System (ADS)

Yu, J.; Chu, J.; Zhang, M.

Stoichiometric and titanium-excess nanocrystalline barium titanates were synthesized using a hydrothermal process at various hydrothermal temperatures and with further heat treatment at 500 °C and 900 °C. Owing to the different process conditions, the excess titanium exists in different states and configurations within the nanocrystalline BaTiO3 matrix; this was demonstrated by X-ray diffraction, Raman scattering, and photoluminescence. In these nanocrystalline BaTiO3, the 590, 571, 543 and 694 nm light emission bands were observed; mechanisms leading to such emissions were also discussed.

Distinctive glial and neuronal interfacing on nanocrystalline diamond.

PubMed

Bendali, Amel; Agnès, Charles; Meffert, Simone; Forster, Valérie; Bongrain, Alexandre; Arnault, Jean-Charles; Sahel, José-Alain; Offenhäusser, Andreas; Bergonzo, Philippe; Picaud, Serge

2014-01-01

Direct electrode/neuron interfacing is a key challenge to achieve high resolution of neuronal stimulation required for visual prostheses. Neuronal interfacing on biomaterials commonly requires the presence of glial cells and/or protein coating. Nanocrystalline diamond is a highly mechanically stable biomaterial with a remarkably large potential window for the electrical stimulation of tissues. Using adult retinal cell cultures from rats, we found that glial cells and retinal neurons grew equally well on glass and nanocrystalline diamond. The use of a protein coating increased cell survival, particularly for glial cells. However, bipolar neurons appeared to grow even in direct contact with bare diamond. We investigated whether the presence of glial cells contributed to this direct neuron/diamond interface, by using purified adult retinal ganglion cells to seed diamond and glass surfaces with and without protein coatings. Surprisingly, these fully differentiated spiking neurons survived better on nanocrystalline diamond without any protein coating. This greater survival was indicated by larger cell numbers and the presence of longer neurites. When a protein pattern was drawn on diamond, neurons did not grow preferentially on the coated area, by contrast to their behavior on a patterned glass. This study highlights the interesting biocompatibility properties of nanocrystalline diamond, allowing direct neuronal interfacing, whereas a protein coating was required for glial cell growth.

Distinctive Glial and Neuronal Interfacing on Nanocrystalline Diamond

PubMed Central

Bendali, Amel; Agnès, Charles; Meffert, Simone; Forster, Valérie; Bongrain, Alexandre; Arnault, Jean-Charles; Sahel, José-Alain; Offenhäusser, Andreas; Bergonzo, Philippe; Picaud, Serge

2014-01-01

Direct electrode/neuron interfacing is a key challenge to achieve high resolution of neuronal stimulation required for visual prostheses. Neuronal interfacing on biomaterials commonly requires the presence of glial cells and/or protein coating. Nanocrystalline diamond is a highly mechanically stable biomaterial with a remarkably large potential window for the electrical stimulation of tissues. Using adult retinal cell cultures from rats, we found that glial cells and retinal neurons grew equally well on glass and nanocrystalline diamond. The use of a protein coating increased cell survival, particularly for glial cells. However, bipolar neurons appeared to grow even in direct contact with bare diamond. We investigated whether the presence of glial cells contributed to this direct neuron/diamond interface, by using purified adult retinal ganglion cells to seed diamond and glass surfaces with and without protein coatings. Surprisingly, these fully differentiated spiking neurons survived better on nanocrystalline diamond without any protein coating. This greater survival was indicated by larger cell numbers and the presence of longer neurites. When a protein pattern was drawn on diamond, neurons did not grow preferentially on the coated area, by contrast to their behavior on a patterned glass. This study highlights the interesting biocompatibility properties of nanocrystalline diamond, allowing direct neuronal interfacing, whereas a protein coating was required for glial cell growth. PMID:24664111

Extreme creep resistance in a microstructurally stable nanocrystalline alloy

NASA Astrophysics Data System (ADS)

Darling, K. A.; Rajagopalan, M.; Komarasamy, M.; Bhatia, M. A.; Hornbuckle, B. C.; Mishra, R. S.; Solanki, K. N.

2016-09-01

Nanocrystalline metals, with a mean grain size of less than 100 nanometres, have greater room-temperature strength than their coarse-grained equivalents, in part owing to a large reduction in grain size. However, this high strength generally comes with substantial losses in other mechanical properties, such as creep resistance, which limits their practical utility; for example, creep rates in nanocrystalline copper are about four orders of magnitude higher than those in typical coarse-grained copper. The degradation of creep resistance in nanocrystalline materials is in part due to an increase in the volume fraction of grain boundaries, which lack long-range crystalline order and lead to processes such as diffusional creep, sliding and rotation. Here we show that nanocrystalline copper-tantalum alloys possess an unprecedented combination of properties: high strength combined with extremely high-temperature creep resistance, while maintaining mechanical and thermal stability. Precursory work on this family of immiscible alloys has previously highlighted their thermo-mechanical stability and strength, which has motivated their study under more extreme conditions, such as creep. We find a steady-state creep rate of less than 10-6 per second—six to eight orders of magnitude lower than most nanocrystalline metals—at various temperatures between 0.5 and 0.64 times the melting temperature of the matrix (1,356 kelvin) under an applied stress ranging from 0.85 per cent to 1.2 per cent of the shear modulus. The unusual combination of properties in our nanocrystalline alloy is achieved via a processing route that creates distinct nanoclusters of atoms that pin grain boundaries within the alloy. This pinning improves the kinetic stability of the grains by increasing the energy barrier for grain-boundary sliding and rotation and by inhibiting grain coarsening, under extremely long-term creep conditions. Our processing approach should enable the development of

Luminescence and related properties of nanocrystalline porous silicon

NASA Astrophysics Data System (ADS)

Koshida, N.

This document is part of subvolume C3 'Optical Properties' of volume 34 'Semiconductor quantum structures' of Landolt-Börnstein, Group III, Condensed Matter, on the optical properties of quantum structures based on group IV semiconductors. It discusses luminescence and related properties of nanocrystalline porous silicon. Topics include an overview of nanostructured silicon, its fabrication technology, and properties of nanocrystalline porous silicon such as confinement effects, photoluminescence, electroluminesce, carrier charging effects, ballistic transport and emission, and thermally induced acoustic emission.

Mid-term results of the BIOLOX delta ceramic-on-ceramic total hip arthroplasty.

PubMed

Lee, Y K; Ha, Y C; Yoo, J-I; Jo, W L; Kim, K-C; Koo, K H

2017-06-01

We conducted a prospective study of a delta ceramic total hip arthroplasty (THA) to determine the rate of ceramic fracture, to characterise post-operative noise, and to evaluate the mid-term results and survivorship. Between March 2009 and March 2011, 274 patients (310 hips) underwent cementless THA using a delta ceramic femoral head and liner. At each follow-up, clinical and radiological outcomes were recorded. A Kaplan-Meier analysis was undertaken to estimate survival. Four patients (four hips) died and 18 patients (20 hips) were lost to follow-up within five years. The remaining 252 patients (286 hips) were followed for a mean of 66.5 months (60 to 84). There were 144 men (166 hips) and 108 women (120 hips) with a mean age of 49.7 years (16 to 83) at surgery. The mean pre-operative Harris Hip Score of 47.1 points improved to 93.8 points at final follow-up. Six patients reported squeaking in seven hips; however, none were audible. Radiolucent lines involving Gruen zones one and/or seven were seen in 52 hips (18.2%). No hip had detectable wear, focal osteolysis or signs of loosening. One hip was revised because of fracture of the ceramic liner, which occurred due to an undetected malseating of the ceramic liner at the time of surgery. One hip was revised for a periprosthetic fracture of the femur, and one hip was treated for periprosthetic joint infection. The six-year survivorship with re-operation for any reason as the endpoint was 99.0% (95% confidence interval 97.8% to 100%). The rate of delta ceramic fracture was 0.3% (one of 286). While ceramic head fracture was dominant in previous ceramic-on-ceramic THA, fracture of the delta ceramic liner due to malseating is a concern. Cite this article: Bone Joint J 2017;99-B:741-8. ©2017 The British Editorial Society of Bone & Joint Surgery.

Stability analysis of multipoint tool equipped with metal cutting ceramics

NASA Astrophysics Data System (ADS)

Maksarov, V. V.; Khalimonenko, A. D.; Matrenichev, K. G.

2017-10-01

The article highlights the issues of determining the stability of the cutting process by a multipoint cutting tool equipped with cutting ceramics. There were some recommendations offered on the choice of parameters of replaceable cutting ceramic plates for milling based of the conducted researches. Ceramic plates for milling are proposed to be selected on the basis of value of their electrical volume resistivity.

Articles for high temperature service and methods for their manufacture

DOEpatents

Sarrafi-Nour, Reza; Meschter, Peter Joel; Johnson, Curtis Alan; Luthra, Krishan Lal; Rosenzweig, Larry Steven

2016-06-14

An article for use in aggressive environments is presented. In one embodiment, the article comprises a substrate and a self-sealing and substantially hermetic sealing layer comprising an alkaline-earth aluminosilicate disposed over the bondcoat. The substrate may be any high-temperature material, including, for instance, silicon-bearing ceramics and ceramic matrix composites. A method for making such articles is also presented. The method comprises providing a substrate; disposing a self-sealing alkaline-earth aluminosilicate layer over the substrate; and heating the sealing layer to a sealing temperature at which at least a portion of the sealing layer will flow.

Gigacycle fatigue behavior by ultrasonic nanocrystalline surface modification.

PubMed

Ahn, D G; Amanov, A; Cho, I S; Shin, K S; Pyoun, Y S; Lee, C S; Park, I G

2012-07-01

Nanocrystalline surface layer up to 84 microm in thick is produced on a specimen made of Al6061-T6 alloy by means of surface treatment called ultrasonic nanocrystalline surface modification (UNSM) technique. The refined grain size is produced in the top-layer and it is increased with increasing depth from the top surface. Vickers microhardness measurement for each nanocrystalline surface layer is performed and measurement results showed that the microhardness is increased from 116 HV up to 150 HV, respectively. In this study, fatigue behavior of Al6061-T6 alloy was studied up to 10(7)-10(9) cycles by using a newly developed ultrasonic fatigue testing (UFT) rig. The fatigue results of the UNSM-treated Al6061-T6 alloy specimens were compared with those of the untreated specimens. The microstructure of the untreated and UNSM-treated specimens was characterized by means of scanning electron microscopey (SEM) and transmission electron microscopey (TEM).

Synthesis of Mesoporous Nanocrystalline Zirconia by Surfactant-Assisted Hydrothermal Approach.

PubMed

Nath, Soumav; Biswas, Ashik; Kour, Prachi P; Sarma, Loka S; Sur, Ujjal Kumar; Ankamwar, Balaprasad G

2018-08-01

In this paper, we have reported the chemical synthesis of thermally stable mesoporous nanocrystalline zirconia with high surface area using a surfactant-assisted hydrothermal approach. We have employed different type of surfactants such as CTAB, SDS and Triton X-100 in our synthesis. The synthesized nanocrystalline zirconia multistructures exhibit various morphologies such as rod, mortar-pestle with different particle sizes. We have characterized the zirconia multistructures by X-ray diffraction study, Field emission scanning electron microscopy, Attenuated total refection infrared spectroscopy, UV-Vis spectroscopy and photoluminescence spectroscopy. The thermal stability of as synthesized zirconia multistructures was studied by thermo gravimetric analysis, which shows the high thermal stability of nanocrystalline zirconia around 900 °C temperature.

Covalent attachment and growth of nanocrystalline films of photocatalytic TiOF2

NASA Astrophysics Data System (ADS)

Zhu, Jian; Lv, Fujian; Xiao, Shengxiong; Bian, Zhenfeng; Buntkowsky, Gerd; Nuckolls, Colin; Li, Hexing

2014-11-01

This manuscript describes a synthesis of nanocrystalline TiOF2 film. The nanocrystalline TiOF2 becomes chemically attached to the surface of the glass slide. These films are robust and can be recycled as photocatalysts for the degradation of organic dyes and solvents. These films also have significant antibacterial properties upon irradiation.This manuscript describes a synthesis of nanocrystalline TiOF2 film. The nanocrystalline TiOF2 becomes chemically attached to the surface of the glass slide. These films are robust and can be recycled as photocatalysts for the degradation of organic dyes and solvents. These films also have significant antibacterial properties upon irradiation. Electronic supplementary information (ESI) available: Methods for sample preparation, characterization and Fig. S1-S8. See DOI: 10.1039/c4nr05598e

Biologically inspired rosette nanotubes and nanocrystalline hydroxyapatite hydrogel nanocomposites as improved bone substitutes

NASA Astrophysics Data System (ADS)

Zhang, Lijie; Rodriguez, Jose; Raez, Jose; Myles, Andrew J.; Fenniri, Hicham; Webster, Thomas J.

2009-04-01

Today, bone diseases such as bone fractures, osteoporosis and bone cancer represent a common and significant public health problem. The design of biomimetic bone tissue engineering materials that could restore and improve damaged bone tissues provides exciting opportunities to solve the numerous problems associated with traditional orthopedic implants. Therefore, the objective of this in vitro study was to create a biomimetic orthopedic hydrogel nanocomposite based on the self-assembly properties of helical rosette nanotubes (HRNs), the osteoconductive properties of nanocrystalline hydroxyapatite (HA), and the biocompatible properties of hydrogels (specifically, poly(2-hydroxyethyl methacrylate), pHEMA). HRNs are self-assembled nanomaterials that are formed from synthetic DNA base analogs in water to mimic the helical nanostructure of collagen in bone. In this study, different geometries of nanocrystalline HA were controlled by either hydrothermal or sintering methods. 2 and 10 wt% nanocrystalline HA particles were well dispersed into HRN hydrogels using ultrasonication. The nanocrystalline HA and nanocrystalline HA/HRN hydrogels were characterized by x-ray diffraction, transmission electron microscopy, and scanning electron microscopy. Mechanical testing studies revealed that the well dispersed nanocrystalline HA in HRN hydrogels possessed improved mechanical properties compared to hydrogel controls. In addition, the results of this study provided the first evidence that the combination of either 2 or 10 wt% nanocrystalline HA and 0.01 mg ml-1 HRNs in hydrogels greatly increased osteoblast (bone-forming cell) adhesion up to 236% compared to hydrogel controls. Moreover, this study showed that HRNs stimulated HA nucleation and mineralization along their main axis in a way that is very reminiscent of the HA/collagen assembly pattern in natural bone. In summary, the presently observed excellent properties of the biomimetic nanocrystalline HA/HRN hydrogel composites

The effect of spark plasma sintering on lithium disilicate glass-ceramics.

PubMed

Al Mansour, Fatima; Karpukhina, Natalia; Grasso, Salvatore; Wilson, Rory M; Reece, Mike J; Cattell, Michael J

2015-10-01

To evaluate the effects of spark plasma sintering (SPS) on the microstructure of lithium disilicate glass-ceramics. IPS e.max CAD glass-ceramic samples were processed using spark plasma sintering (SPS) and conventionally sintered (CS) as a comparison. Specimens were sintered at varying temperatures (T1: 840°C, T2: 820°C, T3: 800°C), heating rates (HR1: 150°C/min, HR2: 300°C/min, HR3: 500°C/min) and pressures (P1: 15MPa, P2: 50MPa, P3: 70MPa). IPS e.max Press glass powder samples were densified at 750 and 800°C (50 or 200MPa pressure). Samples were characterized using XRD, HTXRD, and SEM and quantitative image analysis. There was a significant increase in median crystal size (MCS) between the CS and the SPS T1 groups. A statistical difference (p>0.05) in MCS between SPS T1 and SPS T2 groups was observed. The SPS HR3 sample produced a smaller MCS than the CS, SPS HR1 and HR2 groups (p<0.05). The SPS P3 sample had a reduction in MCS compared with the CS group (p<0.05). XRD of the SPS samples revealed major lithium disilicate/lithium metasilicate phases and minor lithium orthophosphate and cristobalite/quartz phases. Densified IPS e.max Press glass samples resulted in fine fibrils or graduated lithium disilicate crystals. The effects of SPS were used to refine the microstructure of IPS e.max CAD lithium disilicate glass-ceramics. Densification by SPS of IPS e.max Press glass resulted in textured and fine nano-crystalline microstructures. SPS generated glass-ceramic microstructures may have unique properties and could be useful in the production of CAD/CAM materials for dentistry. Copyright © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Electrical impedance spectroscopy of neutron-irradiated nanocrystalline silicon carbide (3C-SiC)

NASA Astrophysics Data System (ADS)

Huseynov, Elchin M.

2018-01-01

It the present work, impedance spectra of nanocrystalline 3C-SiC particles have been comparatively analyzed before and after neutron irradiation. Resonance states and shifts were observed at the impedance spectra of nanocrystalline 3C-SiC particles after neutron irradiation. Relaxation time has been calculated from interdependence of real and imaginary parts of impedance of nanocrystalline 3C-SiC particles. Calculated relaxation times have been investigated as a function of neutron irradiation period. Neutron transmutation (31P isotopes production) effects on the impedance spectra and relaxation times have been studied. Moreover, influence of agglomeration and amorphous transformation to the impedance spectra and relaxation times of nanocrystalline 3C-SiC particles have been investigated.

Silver film on nanocrystalline TiO{sub 2} support: Photocatalytic and antimicrobial ability

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

Vukoje, Ivana D., E-mail: ivanav@vinca.rs; Tomašević-Ilić, Tijana D., E-mail: tommashev@gmail.com; Zarubica, Aleksandra R., E-mail: zarubica2000@yahoo.com

Highlights: • Simple photocatalytic rout for deposition of Ag on nanocrystalline TiO{sub 2} films. • High antibactericidal efficiency of deposited Ag on TiO{sub 2} support. • Improved photocatalytic performance of TiO{sub 2} films in the presence of deposited Ag. - Abstract: Nanocrystalline TiO{sub 2} films were prepared on glass slides by the dip coating technique using colloidal solutions consisting of 4.5 nm particles as a precursor. Photoirradiation of nanocrystalline TiO{sub 2} film modified with alanine that covalently binds to the surface of TiO{sub 2} and at the same time chelate silver ions induced formation of metallic silver film. Optical andmore » morphological properties of thin silver films on nanocrystalline TiO{sub 2} support were studied by absorption spectroscopy and atomic force microscopy. Improvement of photocatalytic performance of nanocrystalline TiO{sub 2} films after deposition of silver was observed in degradation reaction of crystal violet. Antimicrobial ability of deposited silver films on nanocrystalline TiO{sub 2} support was tested in dark as a function of time against Escherichia coli, Staphylococcus aureus, and Candida albicans. The silver films ensured maximum cells reduction of both bacteria, while the fungi reduction reached satisfactory 98.45% after 24 h of contact.« less

Direct Coating of Nanocrystalline Diamond on Steel

NASA Astrophysics Data System (ADS)

Tsugawa, Kazuo; Kawaki, Shyunsuke; Ishihara, Masatou; Hasegawa, Masataka

2012-09-01

Nanocrystalline diamond films have been successfully deposited on stainless steel substrates without any substrate pretreatments to promote diamond nucleation, including the formation of interlayers. A low-temperature growth technique, 400 °C or lower, in microwave plasma chemical vapor deposition using a surface-wave plasma has cleared up problems in diamond growth on ferrous materials, such as the surface graphitization, long incubation time, substrate softening, and poor adhesion. The deposited nanocrystalline diamond films on stainless steel exhibit good adhesion and tribological properties, such as a high wear resistance, a low friction coefficient, and a low aggression strength, at room temperature in air without lubrication.

Defect studies of nanocrystalline zirconia powders and sintered ceramics

NASA Astrophysics Data System (ADS)

Čížek, Jakub; Melikhova, Oksana; Procházka, Ivan; Kuriplach, Jan; Kužel, Radomír; Brauer, Gerhard; Anwand, Wolfgang; Konstantinova, Tatyana E.; Danilenko, Igor A.

2010-01-01

The main objective of the present paper is to communicate a study of defects behavior in zirconia-based nanomaterials—pressure-compacted yttria-stabilized zirconia (YSZ) nanopowders with different contents of Y2O3 and ceramics obtained by sintering the YZS nanopowders. In addition, YZS single crystals were also investigated. Positron annihilation techniques including positron lifetime and coincidence Doppler broadening with a conventional positron source and Doppler broadening experiments on a monoenergetic positron beam were involved in this study as the principal tools. These techniques were supplemented with transmission electron microscopy and x-ray diffraction observations. In order to get better support of the experimental data interpretation, the state-of-art theoretical calculations of positron parameters were performed for the perfect ZrO2 lattice and selected defect configurations in the YSZ. Theoretical calculations have indicated that neither the oxygen vacancies nor their neutral complexes with substitutional yttrium atoms are capable of positron trapping. On the other hand, the zirconium vacancies are deep positron traps and obviously are responsible for the saturated positron trapping observed in the YSZ single crystals. In the compacted YSZ nanopowders, a majority of positrons is trapped either in the vacancylike defects situated in the negative space-charge layers along grain boundaries (τ1≈185ps) or in vacancy clusters at intersections of grain boundaries (τ2≈370ps) . The intensity ratio I2/I1 was found to be correlated with the mean grain size d as I2/I1˜d-2 . A small fraction of positrons (≈10%) form positronium in large pores (τ3≈2ns,τ4≈30ns) . A significant grain growth during sintering of the YSZ nanopowders above 1000°C was observed.

Structural characterization of nanocrystalline cadmium sulphide powder prepared by solvent evaporation technique

NASA Astrophysics Data System (ADS)

Pandya, Samir; Tandel, Digisha; Chodavadiya, Nisarg

2018-05-01

CdS is one of the most important compounds in the II-VI group of semiconductor. There are numerous applications of CdS in the form of nanoparticles and nanocrystalline. Semiconductors nanoparticles (also known as quantum dots), belong to state of matter in the transition region between molecules and solids, have attracted a great deal of attention because of their unique electrical and optical properties, compared to bulk materials. In the field of optoelectronic, nanocrystalline form utilizes mostly in the field of catalysis and fluid technology. Considering these observations, presented work had been carried out, i.e. based on the nanocrystalline material preparation. In the present work CdS nano-crystalline powder was synthesized by a simple and cost effective chemical technique to grow cadmium sulphide (CdS) nanoparticles at 200 °C with different concentrations of cadmium. The synthesis parameters were optimized. The synthesized powder was structurally characterized by X-ray diffraction and particle size analyzer. In the XRD analysis, Micro-structural parameters such as lattice strain, dislocation density and crystallite size were analysed. The broadened diffraction peaks indicated nanocrystalline particles of the film material. In addition to that the size of the prepared particles was analyzed by particle size analyzer. The results show the average size of CdS particles ranging from 80 to 100 nm. The overall conclusion of the work can be very useful in the synthesis of nanocrystalline CdS powder.

Bulk Nanocrystalline Metals: Review of the Current State of the Art and Future Opportunities for Copper and Copper Alloys

DTIC Science & Technology

2014-05-13

nanocrystalline materials using mechanical alloying, the alloy development and synthesis process for stabilizing these materials at elevated temperatures, and...the physical and mechanical properties of nanocrystalline materials with a focus throughout on nanocrystalline copper and a nanocrystalline Cu-Ta...approaches as well as experimental results for grain growth, grain boundary processes, and deformation mechanisms in nanocrystalline copper are

Electrode characteristics of nanocrystalline AB{sub 5} compounds prepared by mechanical alloying

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

Chen, Z.; Chen, Z.; Zhou, D.

1998-10-01

Nanocrystalline LaNi{sub 5} and LaNi{sub 4.5}Si{sub 0.5} synthesized by mechanical alloying were used as negative materials for Ni-MH batteries. It was found that the electrodes prepared with the nanocrystalline powders had similar discharge capacities, better activation behaviors, and longer cycle lifetimes, compared with the negative electrode prepared with polycrystalline coarse-grained LaNi{sub 5} alloy. The properties of the electrodes prepared with these nanocrystalline materials were attributed to the structural characteristics of the compounds caused by mechanical alloying.

Synthesis of nanocrystalline ZnO thin films by electron beam evaporation

NASA Astrophysics Data System (ADS)

Kondkar, V.; Rukade, D.; Bhattacharyya, V.

2018-05-01

Nanocrystalline ZnO thin films have potential for applications in variety of optoelectronic devices. In the present study, nanocrystalline thin films of ZnO are grown on fused silica substrate using electron beam (e-beam) evaporation technique. Phase identification is carried out using Glancing angle X-ray diffraction (GAXRD) and Raman spectroscopy. Ultraviolet-Visible (UV-Vis) spectroscopic analysis is carried out to calculate energy band gap of the ZnO film. Surface morphology of the film is investigated using atomic force microscopy (AFM) and field emission scanning electron microscopy (FESEM). Highly quality nanocrystalline thin films of hexagonal wurtzite ZnO are synthesized using e-beam evaporation technique.

A historical perspective of synthetic ceramic and traditional feldspathic porcelain.

PubMed

Chu, Stephen; Ahmad, Irfan

2005-10-01

Ceramics were invented by the Chinese during the T'ang Dynasty, where they quickly became a precious commodity. By the early 18th Century, ceramics found its way into dentistry due to its high strength, biocompatibility, and malleability. Today, ceramic materials are a staple in dentistry, available in both naturally based and partially synthetic formulas. Most recently they have become available as quartz-glass synthetic materials manufactured under controlled conditions to eliminate the inconsistencies and impurities inherent in the naturally based counterpart. This article details the discovery of porcelain and its role as a precious substance throughout the world and time, from its initial use as ornamental earthenware to its practical application in modern dentistry. Upon reading this article, the reader should: Understand the historical significance of porcelain. Recognize the fundamental constituents and physical properties of both natural feldspathic porcelains and fully synthetic ceramics used in dentistry.

Deposition and characterization of ZnSe nanocrystalline thin films

NASA Astrophysics Data System (ADS)

Temel, Sinan; Gökmen, F. Özge; Yaman, Elif; Nebi, Murat

2018-02-01

ZnSe nanocrystalline thin films were deposited at different deposition times by using the Chemical Bath Deposition (CBD) technique. Effects of deposition time on structural, morphological and optical properties of the obtained thin films were characterized. X-ray diffraction (XRD) analysis was used to study the structural properties of ZnSe nanocrystalline thin films. It was found that ZnSe thin films have a cubic structure with a preferentially orientation of (111). The calculated average grain size value was about 28-30 nm. The surface morphology of these films was studied by the Field Emission Scanning Electron Microscope (FESEM). The surfaces of the thin films were occurred from small stacks and nano-sized particles. The band gap values of the ZnSe nanocrystalline thin films were determined by UV-Visible absorption spectrum and the band gap values were found to be between 2.65-2.86 eV.

Method for producing melt-infiltrated ceramic composites using formed supports

DOEpatents

Corman, Gregory Scot; Brun, Milivoj Konstantin; McGuigan, Henry Charles

2003-01-01

A method for producing shaped articles of ceramic composites provides a high degree of dimensional tolerance to these articles. A fiber preform is disposed on a surface of a stable formed support, a surface of which is formed with a plurality of indentations, such as grooves, slots, or channels. Precursors of ceramic matrix materials are provided to the fiber preform to infiltrate from both sides of the fiber preform. The infiltration is conducted under vacuum at a temperature not much greater than a melting point of the precursors. The melt-infiltrated composite article substantially retains its dimension and shape throughout the fabrication process.

Growth characteristics of nanocrystalline silicon films fabricated by using chlorinated precursors at low temperatures.

PubMed

Huang, Rui; Ding, Honglin; Song, Jie; Guo, Yanqing; Wang, Xiang; Lin, Xuanying

2010-11-01

We employed plasma enhanced chemical vapor deposition technique to fabricate nanocrystalline Si films at a low temperature of 250 degrees C by using SiCl4 and H2 as source gases. The evolution of microstructure of the films with deposition periods shows that nanocrystalline Si can be directly grown on amorphous substrate at the initial growth process, which is in contrast to the growth behavior observed in the SiH4/H2 system. Furthermore, it is interesting to find that the area density of nanocrystalline Si as well as grain size can be controlled by modulating the concentration of SiCl4. By decreasing the SiCl4 concentration, the area density of nanocrystalline Si can be enhanced up to 10(11) cm(-2), while the grain size is shown to decrease down to 10 nm. It is suggested that Cl plays an important role in the low-temperature growth of nanocrystalline Si.

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.

Grain Size Threshold for Enhanced Irradiation Resistance in Nanocrystalline and Ultrafine Tungsten

DOE PAGES

El Atwani, Osman; Hinks, Jonathan; Greaves, Graeme; ...

2017-02-21

Nanocrystalline metals are considered highly radiation-resistant materials due to their large grain boundary areas. Here, the existence of a grain size threshold for enhanced irradiation resistance in high-temperature helium-irradiated nanocrystalline and ultrafine tungsten is demonstrated. Average bubble density, projected bubble area and the corresponding change in volume were measured via transmission electron microscopy and plotted as a function of grain size for two ion fluences. Nanocrystalline grains of less than 35 nm size possess ~10–20 times lower change in volume than ultrafine grains and this is discussed in terms of the grain boundaries defect sink efficiency.

Updating Classifications of Ceramic Dental Materials: A Guide to Material Selection.

PubMed

McLaren, Edward A; Figueira, Johan

2015-06-01

The indications for and composition of today's dental ceramic materials serve as the basis for determining the appropriate class of ceramics to use for a given case. By understanding the classifications, composition, and characteristics of the latest all-ceramic materials, which are presented in this article in order of most to least conservative, dentists and laboratory technicians can best determine the ideal material for a particular treatment.

Nanocrystalline Iron-Ore-Based Catalysts for Fischer-Tropsch Synthesis.

PubMed

Yong, Seok; Park, Ji Chan; Lee, Ho-Tae; Yang, Jung-Il; Hong, SungJun; Jung, Heon; Chun, Dong Hyun

2016-02-01

Nanocrystalline iron ore particles were fabricated by a wet-milling process using an Ultra Apex Mill, after which they were used as raw materials of iron-based catalysts for low-temperature Fischer-Tropsch synthesis (FTS) below 280 degrees C, which usually requires catalysts with a high surface area, a large pore volume, and a small crystallite size. The wet-milling process using the Ultra Apex Mill effectively destroyed the initial crystallite structure of the natural iron ores of several tens to hundreds of nanometers in size, resulting in the generation of nanocrystalline iron ore particles with a high surface area and a large pore volume. The iron-ore-based catalysts prepared from the nanocrystalline iron ore particles effectively catalyzed the low-temperature FTS, displaying a high CO conversion (about 90%) and good C5+ hydrocarbon productivity (about 0.22 g/g(cat)(-h)). This demonstrates the feasibility of using the iron-ore-based catalysts as inexpensive and disposable catalysts for the low-temperature FTS.

Nanocrystalline copper films are never flat.

PubMed

Zhang, Xiaopu; Han, Jian; Plombon, John J; Sutton, Adrian P; Srolovitz, David J; Boland, John J

2017-07-28

We used scanning tunneling microscopy to study low-angle grain boundaries at the surface of nearly planar copper nanocrystalline (111) films. The presence of grain boundaries and their emergence at the film surface create valleys composed of dissociated edge dislocations and ridges where partial dislocations have recombined. Geometric analysis and simulations indicated that valleys and ridges were created by an out-of-plane grain rotation driven by reduction of grain boundary energy. These results suggest that in general, it is impossible to form flat two-dimensional nanocrystalline films of copper and other metals exhibiting small stacking fault energies and/or large elastic anisotropy, which induce a large anisotropy in the dislocation-line energy. Copyright © 2017 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.

Hot pressing of nanocrystalline tantalum using high frequency induction heating and pulse plasma sintering

NASA Astrophysics Data System (ADS)

Jakubowicz, J.; Adamek, G.; Sopata, M.; Koper, J. K.; Siwak, P.

2017-12-01

The paper presents the results of nanocrystalline powder tantalum consolidation using hot pressing. The authors used two different heating techniques during hot pressing: high-frequency induction heating (HFIH) and pulse plasma sintering (PPS). A comparison of the structure, microstructure, mechanical properties and corrosion resistance of the bulk nanocrystalline tantalum obtained in both techniques was performed. The nanocrystalline powder was made to start from the microcrystalline one using the high-energy ball milling process. The nanocrystalline powder was hot-pressed at 1000 °C, whereas, for comparison, the microcrystalline powder was hot pressed up to 1500 °C for proper consolidation. The authors found that during hot pressing, the powder partially reacts with the graphite die covered by boron nitride, which facilitated punches and powder displacement in the die during densification. Tantalum carbide and boride in the nanocrystalline material was found, which can improve the mechanical properties. The hardness of the HFIH and PPS nanocrystalline tantalum was as high as 625 and 615 HV, respectively. The microstructure was more uniform in the PPS nanomaterial. The corrosion resistance in both cases deteriorated, in comparison to the microcrystalline material, while the PPS material corrosion resistance was slightly better than that of the HFIH one.

Microstructures and mechanical properties of nanocrystalline NiTi intermetallics formed by mechanosynthesis

NASA Astrophysics Data System (ADS)

Arunkumar, S.; Kumaravel, P.; Velmurugan, C.; Senthilkumar, V.

2018-01-01

The formulation of nanocrystalline NiTi shape memory alloys has potential effects in mechanical stimulation and medical implantology. The present work elucidates the effect of milling time on the product's structural characteristics, chemical composition, and microhardness for NiTi synthesized by mechanical alloying for different milling durations. Increasing the milling duration led to the formation of a nanocrystalline NiTi intermetallic at a higher level. The formation of nanocrystalline materials was directed through cold fusion, fracturing, and the development of a steady state, which were influenced by the accumulation of strain energy. In the morphological study, uninterrupted cold diffusion and fracturing were visualized using transmission electron microscopy. Particle size analysis revealed that the mean particle size was reduced to 93 μm after 20 h of milling. The mechanical strength was enhanced by the formation of a nanocrystalline intermetallic phase at longer milling time, which was confirmed by the results of Vickers hardness analyses.

Polymer blend of PLA/PHBV based bionanocomposites reinforced with nanocrystalline cellulose for potential application as packaging material.

PubMed

Dasan, Y K; Bhat, A H; Ahmad, Faiz

2017-02-10

The current research discusses the development of poly (lactic acid) (PLA) and poly-(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) reinforced nanocrystalline cellulose bionanocomposites. The nanocrystalline cellulose was derived from waste oil palm empty fruit bunch fiber by acid hydrolysis process. The resulting nanocrystalline cellulose suspension was then surface functionalized by TEMPO-mediated oxidation and solvent exchange process. Furthermore, the PLA/PHBV/nanocrystalline cellulose bionanocomposites were produced by solvent casting method. The effect of the addition of nanocrystalline cellulose on structural, morphology, mechanical and barrier properties of bionanocomposites was investigated. The results revealed that the developed bionanocomposites showed improved mechanical properties and decrease in oxygen permeability rate. Therefore, the developed bio-based composite incorporated with an optimal composition of nanocrystalline cellulose exhibits properties as compared to the polymer blend. Copyright © 2016 Elsevier Ltd. All rights reserved.

Ceramic honeycomb structures and the method thereof

NASA Technical Reports Server (NTRS)

Riccitiello, Salvatore R. (Inventor); Cagliostro, Domenick E. (Inventor)

1987-01-01

The subject invention pertains to a method of producing an improved composite-composite honeycomb structure for aircraft or aerospace use. Specifically, the subject invention relates to a method for the production of a lightweight ceramic-ceramic composite honeycomb structure, which method comprises: (1) pyrolyzing a loosely woven fabric/binder having a honeycomb shape and having a high char yield and geometric integrity after pyrolysis at between about 700 and 1,100 C; (2) substantially evenly depositing at least one layer of ceramic material on the pyrolyzed fabric/binder of step (1); (3) recovering the coated ceramic honeycomb structure; (4) removing the pyrolyzed fabric/binder of the structure of step (3) by slow pyrolysis at between 700 and 1000 C in between about a 2 to 5% by volume oxygen atmosphere for between about 0.5 and 5 hr.; and (5) substantially evenly depositing on and within the rigid hollow honeycomb structure at least one additional layer of the same or a different ceramic material by chemical vapor deposition and chemical vapor infiltration. The honeycomb shaped ceramic articles have enhanced physical properties and are useful in aircraft and aerospace uses.

Framework Stability of Nanocrystalline NaY in Aqueous Solution at Varying pH

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

Petushkov, Anton; Freeman, Jasmine; Larsen, Sarah C.

Nanocrystalline zeolites (with crystal sizes of less than 50 nm) are versatile, porous nanomaterials with potential applications in a broad range of areas including bifunctional catalysis, drug delivery, environmental protection, and sensing, to name a few. The characterization of the properties of nanocrystalline zeolites on a fundamental level is critical to the realization of these innovative applications. Nanocrystalline zeolites have unique surface chemistry that is distinct from conventional microcrystalline zeolite materials and that will result in novel applications. In the proposed work, magnetic resonance techniques (solid state nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR)) will be used tomore » elucidate the structure and reactivity of nanocrystalline zeolites and to motivate bifunctional applications. Density functional theory (DFT) calculations will enhance data interpretation through chemical shift, quadrupole coupling constant, g-value and hyperfine calculations.« less

[The classification of ceramics according to its chemical nature and its method of production].

PubMed

Moureau, Thomas; Bouhy, Alice; Raepsaet, Nicolas; Vanheusden, Alain

2006-01-01

Nowadays, we find on the market a huge amount of design and manufactured system that allows the realisation of all-ceramics restorations, using different ceramics. The purpose of this article is suggesting a classification of mostly used ceramics and a few laboratory process used in our university.

Electrodeposition of Nanocrystalline Cobalt Phosphorous Coatings as a Hard Chrome Alternative

DTIC Science & Technology

2014-11-01

1 ASETSDefense 2014 Electrodeposition of Nanocrystalline Cobalt Phosphorous Coatings as a Hard Chrome Alternative Ruben A. Prado, CEF...COVERED 00-00-2014 to 00-00-2014 4. TITLE AND SUBTITLE Electrodeposition of Nanocrystalline Cobalt Phosphorous Coatings as a Hard Chrome Alternative...coatings as a Hard Chrome (EHC) electroplating alternative for DoD manufacturing and repair. – Fully define deposition parameters and properties

Model for temperature-dependent magnetization of nanocrystalline materials

NASA Astrophysics Data System (ADS)

Bian, Q.; Niewczas, M.

2015-01-01

A magnetization model of nanocrystalline materials incorporating intragrain anisotropies, intergrain interactions, and texture effects has been extended to include the thermal fluctuations. The method relies on the stochastic Landau-Lifshitz-Gilbert theory of magnetization dynamics and permits to study the magnetic properties of nanocrystalline materials at arbitrary temperature below the Currie temperature. The model has been used to determine the intergrain exchange constant and grain boundary anisotropy constant of nanocrystalline Ni at 100 K and 298 K. It is found that the thermal fluctuations suppress the strength of the intergrain exchange coupling and also reduce the grain boundary anisotropy. In comparison with its value at 2 K, the interparticle exchange constant decreases by 16% and 42% and the grain boundary anisotropy constant decreases by 28% and 40% at 100 K and 298 K, respectively. An application of the model to study the grain size-dependent magnetization indicates that when the thermal activation energy is comparable to the free energy of grains, the decrease in the grain size leads to the decrease in the magnetic permeability and saturation magnetization. The mechanism by which the grain size influences the magnetic properties of nc-Ni is discussed.

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.

Recent Advances on Carbon Nanotubes and Graphene Reinforced Ceramics Nanocomposites

PubMed Central

Ahmad, Iftikhar; Yazdani, Bahareh; Zhu, Yanqiu

2015-01-01

Ceramics suffer the curse of extreme brittleness and demand new design philosophies and novel concepts of manufacturing to overcome such intrinsic drawbacks, in order to take advantage of most of their excellent properties. This has been one of the foremost challenges for ceramic material experts. Tailoring the ceramics structures at nanometre level has been a leading research frontier; whilst upgrading via reinforcing ceramic matrices with nanomaterials including the latest carbon nanotubes (CNTs) and graphene has now become an eminent practice for advanced applications. Most recently, several new strategies have indeed improved the properties of the ceramics/CNT nanocomposites, such as by tuning with dopants, new dispersions routes and modified sintering methods. The utilisation of graphene in ceramic nanocomposites, either as a solo reinforcement or as a hybrid with CNTs, is the newest development. This article will summarise the recent advances, key difficulties and potential applications of the ceramics nanocomposites reinforced with CNTs and graphene. PMID:28347001

Multifunctionality of nanocrystalline lanthanum ferrite

NASA Astrophysics Data System (ADS)

Rai, Atma; Thakur, Awalendra K.

2016-05-01

Nanocrystalline lanthanum ferrite has been synthesized by adopting modified Pechini route. No evidence of impurity or secondary phase has been detected up to the detection of error limit of X-ray diffractometer (XRD). Rietveld refinement of X-ray diffraction pattern reveals orthorhombic crystal system with space group Pnma (62).Crystallite size and lattice strain was found to be ˜42.8nm and 0.306% respectively. Optical band gap was found to be 2.109 eV, by UV-Visible diffused reflectance spectrum (DRS). Brunauer-Emmet-Teller (BET) surface area was found to be ˜3.45 m2/g. Magnetization-hysteresis (M-H) loop was recorded at room temperature (300K) reveals weak ferromagnetism in Nanocrystalline lanthanum ferrite. The weak ferromagnetism in lanthanum ferrite is due to the uncompensated antiferromagnetic spin ordering. Ferroelectric loop hysteresis observed at room temperature at 100Hz depicts the presence of ferroelectric ordering in LaFeO3.Simultanious presence of magnetic and ferroelectric ordering at room temperature makes it suitable candidate of Multiferroic family.

Multifunctionality of nanocrystalline lanthanum ferrite

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

Rai, Atma, E-mail: atma@iitp.ac.in; Thakur, Awalendra K.; Centre for Energy and Environment, Indian Institute of Technology Patna 800013 India

2016-05-06

Nanocrystalline lanthanum ferrite has been synthesized by adopting modified Pechini route. No evidence of impurity or secondary phase has been detected up to the detection of error limit of X-ray diffractometer (XRD). Rietveld refinement of X-ray diffraction pattern reveals orthorhombic crystal system with space group Pnma (62).Crystallite size and lattice strain was found to be ∼42.8nm and 0.306% respectively. Optical band gap was found to be 2.109 eV, by UV-Visible diffused reflectance spectrum (DRS). Brunauer-Emmet-Teller (BET) surface area was found to be ∼3.45 m{sup 2}/g. Magnetization-hysteresis (M-H) loop was recorded at room temperature (300K) reveals weak ferromagnetism in Nanocrystalline lanthanummore » ferrite. The weak ferromagnetism in lanthanum ferrite is due to the uncompensated antiferromagnetic spin ordering. Ferroelectric loop hysteresis observed at room temperature at 100Hz depicts the presence of ferroelectric ordering in LaFeO{sub 3}.Simultanious presence of magnetic and ferroelectric ordering at room temperature makes it suitable candidate of Multiferroic family.« less

Nanocarbon Allotropes-Graphene and Nanocrystalline Diamond-Promote Cell Proliferation.

PubMed

Verdanova, Martina; Rezek, Bohuslav; Broz, Antonin; Ukraintsev, Egor; Babchenko, Oleg; Artemenko, Anna; Izak, Tibor; Kromka, Alexander; Kalbac, Martin; Hubalek Kalbacova, Marie

2016-05-01

Two profoundly different carbon allotropes - nanocrystalline diamond and graphene - are of considerable interest from the viewpoint of a wide range of biomedical applications including implant coating, drug and gene delivery, cancer therapy, and biosensing. Osteoblast adhesion and proliferation on nanocrystalline diamond and graphene are compared under various conditions such as differences in wettability, topography, and the presence or absence of protein interlayers between cells and the substrate. The materials are characterized in detail by means of scanning electron microscopy, atomic force microscopy, photoelectron spectroscopy, Raman spectroscopy, and contact angle measurements. In vitro experiments have revealed a significantly higher degree of cell proliferation on graphene than on nanocrystalline diamond and a tissue culture polystyrene control material. Proliferation is promoted, in particular, by hydrophobic graphene with a large number of nanoscale wrinkles independent of the presence of a protein interlayer, i.e., substrate fouling is not a problematic issue in this respect. Nanowrinkled hydrophobic graphene, thus, exhibits superior characteristics for those biomedical applications where high cell proliferation is required under differing conditions. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Influence of voids distribution on the deformation behavior of nanocrystalline palladium

NASA Astrophysics Data System (ADS)

Bachurin, D. V.

2018-07-01

Uniaxial deformation of three-dimensional nanocrystalline palladium containing porosity in the form of voids was investigated by means of molecular dynamics method. Simulations were performed at temperature of 300 K and at a constant strain rate of 108s-1. Two cases of voids distribution were considered: random and at triple or quadrupole junctions. It has been revealed that both the voids distribution and subsequent annealing at elevated temperature influence the deformation behavior of nanocrystalline palladium. In particular, the presence of voids at grain junctions results in a reduction of the Young's modulus and more pronounced softening effect during plastic deformation. The subsequent annealing evokes shrinkage of voids and strengthening effect. Contribution of grain boundary accommodation processes into both elastic and plastic deformation of nanocrystalline materials is discussed.

Electrode characteristics of nanocrystalline (Zr, Ti)(V, Cr, Ni) 2.41 compound

NASA Astrophysics Data System (ADS)

Majchrzycki, W.; Jurczyk, M.

The electrochemical properties of nanocrystalline Zr 0.35Ti 0.65V 0.85Cr 0.26Ni 1.30 alloy, which has the hexagonal C14 type structure, have been investigated. This material has been prepared using mechanical alloying (MA) followed by annealing. The amorphous phase forms directly from the starting mixture of the elements, without other phase formation. Heating the MA samples at 1070 K for 0.5 h resulted in the creation of ordered alloy. This alloy was used as negative electrode for Ni-MH x battery. The electrochemical results show very little difference between the nanocrystalline and polycrystalline powders, as compared with the substantial difference between these and the amorphous powder. In the annealed nanocrystalline Zr 0.35Ti 0.65V 0.85Cr 0.26Ni 1.30 powders discharging capacities up to 150 mA h g -1 (at 160 mA g -1 discharging current) have been measured. The properties of nanocrystalline electrode were attributed to the structural characteristics of the compound caused by mechanical alloying.

Ceramic nanoparticles: Recompense, cellular uptake and toxicity concerns.

PubMed

Singh, Deependra; Singh, Satpal; Sahu, Jageshwari; Srivastava, Shikha; Singh, Manju Rawat

2016-01-01

Over the past few years, nanoparticles and their role in drug delivery have been the centre of attraction as new drug delivery systems. Various forms of nanosystems have been designed, such as nanoclays, scaffolds and nanotubes, having numerous applications in areas such as drug loading, target cell uptake, bioassay and imaging. The present study discusses various types of nanoparticles, with special emphasis on ceramic nanocarriers. Ceramic materials have high mechanical strength, good body response and low or non-existing biodegradability. In this article, the various aspects concerning ceramic nanoparticles, such as their advantages over other systems, their cellular uptake and toxicity concerns are discussed in detail.

Controlling Directional Liquid Motion on Micro- and Nanocrystalline Diamond/β-SiC Composite Gradient Films.

PubMed

Wang, Tao; Handschuh-Wang, Stephan; Huang, Lei; Zhang, Lei; Jiang, Xin; Kong, Tiantian; Zhang, Wenjun; Lee, Chun-Sing; Zhou, Xuechang; Tang, Yongbing

2018-01-30

In this Article, we report the synthesis of micro- and nanocrystalline diamond/β-SiC composite gradient films, using a hot filament chemical vapor deposition (HFCVD) technique and its application as a robust and chemically inert means to actuate water and hazardous liquids. As revealed by scanning electron microscopy, the composition of the surface changed gradually from pure nanocrystalline diamond (hydrophobic) to a nanocrystalline β-SiC surface (hydrophilic). Transmission electron microscopy and Raman spectroscopy were employed to determine the presence of diamond, graphite, and β-SiC phases. The as-prepared gradient films were evaluated for their ability to actuate water. Indeed, water was transported via the gradient from the hydrophobic (hydrogen-terminated diamond) to the hydrophilic side (hydroxyl-terminated β-SiC) of the gradient surface. The driving distance and velocity of water is pivotally influenced by the surface roughness. The nanogradient surface showed significant promise as the lower roughness combined with the longer gradient yields in transport distances of up to 3.7 mm, with a maximum droplet velocity of nearly 250 mm/s measured by a high-speed camera. As diamond and β-SiC are chemically inert, the gradient surfaces can be used to drive hazardous liquids and reactive mixtures, which was signified by the actuation of hydrochloric acid and sodium hydroxide solution. We envision that the diamond/β-SiC gradient surface has high potential as an actuator for water transport in microfluidic devices, DNA sensors, and implants, which induce guided cell growth.

Fracture strength of three all-ceramic systems: Top-Ceram compared with IPS-Empress and In-Ceram.

PubMed

Quran, Firas Al; Haj-Ali, Reem

2012-03-01

The purpose of this study was to investigate the fracture loads and mode of failure of all-ceramic crowns fabricated using Top-Ceram and compare it with all-ceramic crowns fabricated from well-established systems: IPS-Empress II, In-Ceram. Thirty all-ceramic crowns were fabricated; 10 IPS-Empress II, 10 In-Ceram alumina and 10 Top-Ceram. Instron testing machine was used to measure the loads required to introduce fracture of each crown. Mean fracture load for In-Ceram alumina [941.8 (± 221.66) N] was significantly (p > 0.05) higher than those of Top-Ceram and IPS-Empress II. There was no statistically significant difference between Top-Ceram and IPS-Empress II mean fracture loads; 696.20 (+222.20) and 534 (+110.84) N respectively. Core fracture pattern was highest seen in Top- Ceram specimens.

Nanocrystalline High-Entropy Alloys: A New Paradigm in High-Temperature Strength and Stability.

PubMed

Zou, Yu; Wheeler, Jeffrey M; Ma, Huan; Okle, Philipp; Spolenak, Ralph

2017-03-08

Metals with nanometer-scale grains or nanocrystalline metals exhibit high strengths at ambient conditions, yet their strengths substantially decrease with increasing temperature, rendering them unsuitable for usage at high temperatures. Here, we show that a nanocrystalline high-entropy alloy (HEA) retains an extraordinarily high yield strength over 5 GPa up to 600 °C, 1 order of magnitude higher than that of its coarse-grained form and 5 times higher than that of its single-crystalline equivalent. As a result, such nanostructured HEAs reveal strengthening figures of merit-normalized strength by the shear modulus above 1/50 and strength-to-density ratios above 0.4 MJ/kg, which are substantially higher than any previously reported values for nanocrystalline metals in the same homologous temperature range, as well as low strain-rate sensitivity of ∼0.005. Nanocrystalline HEAs with these properties represent a new class of nanomaterials for high-stress and high-temperature applications in aerospace, civilian infrastructure, and energy sectors.

Surface Properties of a Nanocrystalline Fe-Ni-Nb-B Alloy After Neutron Irradiation

NASA Astrophysics Data System (ADS)

Pavùk, Milan; Sitek, Jozef; Sedlačková, Katarína

2014-09-01

The effect of neutron radiation on the surface properties of the nanocrystalline (Fe0.25Ni0.75)81Nb7B12 alloy was studied. Firstly, amorphous (Fe0.25Ni0.75)81Nb7B12 ribbon was brought by controlled annealing to the nanocrystalline state. After annealing, the samples of the nanocrystalline ribbon were irradiated in a nuclear reactor with neutron fluences of 1×1016cm-2 and 1 × 1017cm-2 . By utilizing the magnetic force microscopy (MFM), topography and a magnetic domain structure were recorded at the surface of the ribbon-shaped samples before and after irradiation with neutrons. The results indicate that in terms of surface the nanocrystalline (Fe0.25Ni0.75)81Nb7B12 alloy is radiation-resistant up to a neutron fluence of 1 × 1017cm-2 . The changes in topography observed for both irradiated samples are discussed

Production of nanocrystalline metal powders via combustion reaction synthesis

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

Frye, John G.; Weil, Kenneth Scott; Lavender, Curt A.

Nanocrystalline metal powders comprising tungsten, molybdenum, rhenium and/or niobium can be synthesized using a combustion reaction. Methods for synthesizing the nanocrystalline metal powders are characterized by forming a combustion synthesis solution by dissolving in water an oxidizer, a fuel, and a base-soluble, ammonium precursor of tungsten, molybdenum, rhenium, or niobium in amounts that yield a stoichiometric burn when combusted. The combustion synthesis solution is then heated to a temperature sufficient to substantially remove water and to initiate a self-sustaining combustion reaction. The resulting powder can be subsequently reduced to metal form by heating in a reducing gas environment.

Grain growth in nanocrystalline iron and Fe-Al alloys

NASA Astrophysics Data System (ADS)

Mirzadeh, Hamed; Zomorodian, Amir

2010-02-01

The effects of the annealing temperature and time, cryomilling in liquid nitrogen, and the addition of aluminum powder on the thermal stability and grain growth behavior of nanocrystalline iron were modeled using the Artificial Neural Network (ANN) technique. The developed model can be used as a guide for the quantification of the grain growth by considering the effects of annealing temperature and time. The model also quantified the effect of Al on the thermal stability of cryomilled nanocrystalline Fe. The model results showed that the cryomilling of Fe has a tangible effect on the stabilization of the nanostructure.

Glasses, ceramics, and composites from lunar materials

NASA Technical Reports Server (NTRS)

Beall, George H.

1992-01-01

A variety of useful silicate materials can be synthesized from lunar rocks and soils. The simplest to manufacture are glasses and glass-ceramics. Glass fibers can be drawn from a variety of basaltic glasses. Glass articles formed from titania-rich basalts are capable of fine-grained internal crystallization, with resulting strength and abrasion resistance allowing their wide application in construction. Specialty glass-ceramics and fiber-reinforced composites would rely on chemical separation of magnesium silicates and aluminosilicates as well as oxides titania and alumina. Polycrystalline enstatite with induced lamellar twinning has high fracture toughness, while cordierite glass-ceramics combine excellent thermal shock resistance with high flexural strengths. If sapphire or rutile whiskers can be made, composites of even better mechanical properties are envisioned.

Induced superhydrophobic and antimicrobial character of zinc metal modified ceramic wall tile surfaces

NASA Astrophysics Data System (ADS)

Özcan, Selçuk; Açıkbaş, Gökhan; Çalış Açıkbaş, Nurcan

2018-04-01

Hydrophobic surfaces are also known to have antimicrobial effect by restricting the adherence of microorganisms. However, ceramic products are produced by high temperature processes resulting in a hydrophilic surface. In this study, an industrial ceramic wall tile glaze composition was modified by the inclusion of metallic zinc powder in the glaze suspension applied on the pre-sintered wall tile bodies by spraying. The glazed tiles were gloss fired at industrially applicable peak temperatures ranging from 980 °C to 1100 °C. The fired tile surfaces were coated with a commercial fluoropolymer avoiding water absorption. The surfaces were characterized with SEM, EDS, XRD techniques, roughness, sessile water drop contact angle, surface energy measurements, and standard antimicrobial tests. The surface hydrophobicity and the antimicrobial activity results were compared with that of unmodified, uncoated gloss fired wall tiles. A superhydrophobic contact angle of 150° was achieved at 1000 °C peak temperature due to the formation of micro-structured nanocrystalline zinc oxide granules providing a specific surface topography. At higher peak temperatures the hydrophobicity was lost as the specific granular surface topography deteriorated with the conversion of zinc oxide granules to the ubiquitous willemite crystals embedded in the glassy matrix. The antimicrobial efficacy also correlated with the hydrophobic character.

[Ceramic-on-ceramic bearings in total hip arthroplasty (THA)].

PubMed

Sentürk, U; Perka, C

2015-04-01

The main reason for total hip arthroplasty (THA) revision is the wear-related aseptic loosening. Younger and active patients after total joint replacement create high demands, in particular, on the bearings. The progress, especially for alumina ceramic-on-ceramic bearings and mixed ceramics have solved many problems of the past and lead to good in vitro results. Modern ceramics (alumina or mixed ceramics containing alumina) are extremely hard, scratch-resistant, biocompatible, offer a low coefficient of friction, superior lubrication and have the lowest wear rates in comparison to all other bearings in THA. The disadvantage of ceramic is the risk of material failure, i.e., of ceramic fracture. The new generation of mixed ceramics (delta ceramic), has reduced the risk of head fractures to 0.03-0.05 %, but the risk for liner fractures remains unchanged at about 0.02 %. Assuming a non-impinging component implantation, ceramic-on-ceramic bearings have substantial advantages over all other bearings in THA. Due to the superior hardness, ceramic bearings produce less third body wear and are virtually impervious to damage from instruments during the implantation process. A specific complication for ceramic-on-ceramic bearings is "squeaking". The high rate of reported squeaking (0.45 to 10.7 %) highlights the importance of precise implant positioning and the stem and patient selection. With precise implant positioning this problem is rare with many implant designs and without clinical relevance. The improved tribology and the presumable resulting implant longevity make ceramic-on-ceramic the bearing of choice for young and active patients. Georg Thieme Verlag KG Stuttgart · New York.

Portfolio: Ceramics.

ERIC Educational Resources Information Center

Hardy, Jane; And Others

1982-01-01

Describes eight art activities using ceramics. Elementary students created ceramic tiles to depict ancient Egyptian and medieval European art, made ceramic cookie stamps, traced bisque plates on sketch paper, constructed clay room-tableaus, and designed clay relief masks. Secondary students pit-fired ceramic pots and designed ceramic Victorian…

NDE of ceramics and ceramic composites

NASA Technical Reports Server (NTRS)

Vary, Alex; Klima, Stanley J.

1991-01-01

Although nondestructive evaluation (NDE) techniques for ceramics are fairly well developed, they are difficult to apply in many cases for high probability detection of the minute flaws that can cause failure in monolithic ceramics. Conventional NDE techniques are available for monolithic and fiber reinforced ceramic matrix composites, but more exact quantitative techniques needed are still being investigated and developed. Needs range from flaw detection to below 100 micron levels in monolithic ceramics to global imaging of fiber architecture and matrix densification anomalies in ceramic composites. NDE techniques that will ultimately be applicable to production and quality control of ceramic structures are still emerging from the lab. Needs are different depending on the processing stage, fabrication method, and nature of the finished product. NDE techniques are being developed in concert with materials processing research where they can provide feedback information to processing development and quality improvement. NDE techniques also serve as research tools for materials characterization and for understanding failure processes, e.g., during thermomechanical testing.

Thermal conductivity of amorphous and nanocrystalline silicon films prepared by hot-wire chemical-vapor deposition

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

Jugdersuren, B.; Kearney, B. T.; Queen, D. R.

We report 3..omega.. thermal conductivity measurements of amorphous and nanocrystalline silicon thin films from 85 to 300 K prepared by hot-wire chemical-vapor deposition, where the crystallinity of the films is controlled by the hydrogen dilution during growth. The thermal conductivity of the amorphous silicon film is in agreement with several previous reports of amorphous silicon prepared by a variety of deposition techniques. The thermal conductivity of the as-grown nanocrystalline silicon film is 70% higher and increases 35% more after an anneal at 600 degrees C. They all have similarly weak temperature dependence. Structural analysis shows that the as-grown nanocrystalline siliconmore » is approximately 60% crystalline, nanograins and grain boundaries included. The nanograins, averaging 9.1 nm in diameter in the as-grown film, are embedded in an amorphous matrix. The grain size increases to 9.7 nm upon annealing, accompanied by the disappearance of the amorphous phase. We extend the models of grain boundary scattering of phonons with two different non-Debye dispersion relations to explain our result of nanocrystalline silicon, confirming the strong grain size dependence of heat transport for nanocrystalline materials. However, the similarity in thermal conductivity between amorphous and nanocrystalline silicon suggests the heat transport mechanisms in both structures may not be as dissimilar as we currently understand.« less

Effects of oxide distributed in grain boundaries on microstructure stability of nanocrystalline metals

NASA Astrophysics Data System (ADS)

Zhou, Kai; Li, Hui; Biao Pang, Jin; Wang, Zhu

2013-06-01

Nanocrystalline copper and zinc prepared by high-pressure compaction method have been studied by positron lifetime spectroscopy associated with X-ray diffraction. For nanocrystalline Cu, mean grain sizes of the samples decrease after being annealed at 900 °C and increase during aging at 180 °C, revealing that the atoms exchange between the two regions. The positron lifetime results indicate that the vacancy clusters formed in the annealing process are unstable and decomposed at the aging time below 6 hours. In addition, the partially oxidized surfaces of the nanoparticles hinder the grain growth during the ageing at 180 °C, and the vacancy clusters inside the disorder regions which are related to Cu2O need longer aging time to decompose. In the case of nanocrystalline Zn, the open volume defect (not larger than divacancy) is dominant according to the high relative intensity for the short positron lifetime (τ1). The oxide (ZnO) inside the grain boundaries has been found having an effect to hinder the decrease of average positron lifetime (τav) during the annealing, which probably indicates that the oxide stabilizes the microstructure of the grain boundaries. For both nanocrystalline copper and zinc, the oxides in grain boundaries enhance the thermal stability of the microstucture, in spite of their different crystal structures. This effect is very important for the nanocrystalline materials using as radiation resistant materials.

Silicone Resin Applications for Ceramic Precursors and Composites

PubMed Central

Narisawa, Masaki

2010-01-01

This article reviews the applications of silicone resins as ceramic precursors. The historical background of silicone synthesis chemistry is introduced to explain the production costs and supply availability of various silicones. Thermal degradation processes of silicones are classified in terms of the main chain structure and cyclic oligomer expulsion process, which determine the resulting ceramic yield and the chemical composition. The high temperature decomposition of Si-O-C beyond 1,400 °C in an inert atmosphere and formation of a protective silica layer on material surfaces beyond 1,200 °C in an oxidative atmosphere are discussed from the viewpoints of the wide chemical composition of the Si-O-C materials. Applications of the resins for binding agents, as starting materials for porous ceramics, matrix sources with impregnation, fiber spinning and ceramic adhesions are introduced. The recent development of the process of filler or cross-linking agent additions to resin compounds is also introduced. Such resin compounds are useful for obtaining thick coatings, MEMS parts and bulk ceramics, which are difficult to obtain by pyrolysis of simple organometallic precursors without additives.

Cathodic electrodeposition of ceramic and organoceramic materials. Fundamental aspects.

PubMed

Zhitomirsky, I

2002-03-29

Electrodeposition of ceramic materials can be performed by electrophoretic (EPD) or electrolytic (ELD) deposition. Electrophoretic deposition is achieved via motion of charged particles towards an electrode under an applied electric field. Electrolytic deposition produces colloidal particles in cathodic reactions for subsequent deposition. Various electrochemical strategies and deposition mechanisms have been developed for electrodeposition of ceramic and organoceramic films, and are discussed in the present article. Electrode-position of ceramic and organoceramic materials includes mass transport, accumulation of particles near the electrode and their coagulation to form a cathodic deposit. Various types of interparticle forces that govern colloidal stability in the absence and presence of processing additives are discussed. Novel theoretical contributions towards an interpretation of particle coagulation near the electrode surface are reviewed. Background information is given on the methods of particle charging, stabilization of colloids in aqueous and non-aqueous media, electrophoretic mobility of ceramic particles and polyelectrolytes, and electrode reactions. This review also covers recent developments in the electrodeposition of ceramic and organoceramic materials.

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.

Comparative study of structural and magnetic properties of nano-crystalline Li 0.5Fe 2.5O 4 prepared by various methods

NASA Astrophysics Data System (ADS)

Verma, Vivek; Pandey, Vibhav; Singh, Sukhveer; Aloysius, R. P.; Annapoorni, S.; Kotanala, R. K.

2009-08-01

Lithium ferrite has been considered as one of the highly strategic magnetic material. Nano-crystalline Li 0.5Fe 2.5O 4 was prepared by four different techniques and characterized by X-ray diffraction, vibrating sample magnetometer (VSM), transmission electron microscope (TEM) and Fourier transform infrareds (FTIR). The effect of annealing temperature (700, 900 and 1050 °C) on microstructure has been correlated to the magnetic properties. From X-ray diffraction patterns, it is confirmed that the pure phase of lithium ferrite began to form at 900 °C annealing. The particle size of as-prepared lithium ferrite was observed around 40, 31, 22 and 93 nm prepared by flash combustion, sol-gel, citrate precursor and standard ceramic technique, respectively. Lithium ferrite prepared by citrate precursor method shows a maximum saturation magnetization 67.6 emu/g at 5 KOe.

Characteristics of W Doped Nanocrystalline Carbon Films Prepared by Unbalanced Magnetron Sputtering.

PubMed

Park, Yong Seob; Park, Chul Min; Kim, Nam-Hoon; Kim, Jae-Moon

2016-05-01

Nanocrystalline tungsten doped carbon (WC) films were prepared by unbalanced magnetron sputtering. Tungsten was used as the doping material in carbon thin films with the aim of application as a contact strip in an electric railway. The structural, physical, and electrical properties of the fabricated WC films with various DC bias voltages were investigated. The films had a uniform and smooth surface. Hardness and frication characteristics of the films were improved, and the resistivity and sheet resistance decreased with increasing negative DC bias voltage. These results are associated with the nanocrystalline WC phase and sp(2) clusters in carbon networks increased by ion bombardment enhanced with increasing DC bias voltage. Consequently, the increase of sp(2) clusters containing WC nanocrystalline in the carbon films is attributed to the improvement in the physical and electrical properties.

Isolation of bacterial cellulose nanocrystalline from pineapple peel waste: Optimization of acid concentration in the hydrolysis method

NASA Astrophysics Data System (ADS)

Anwar, Budiman; Rosyid, Nurul Huda; Effendi, Devi Bentia; Nandiyanto, Asep Bayu Dani; Mudzakir, Ahmad; Hidayat, Topik

2016-02-01

Isolation of needle-shaped bacterial cellulose nanocrystalline with a diameter of 16-64 nm, a fiber length of 258-806 nm, and a degree of crystallinity of 64% from pineapple peel waste using an acid hydrolysis process was investigated. Experimental showed that selective concentration of acid played important roles in isolating the bacterial cellulose nanocrystalline from the cellulose source. To achieve the successful isolation of bacterial cellulose nanocrystalline, various acid concentrations were tested. To confirm the effect of acid concentration on the successful isolation process, the reaction conditions were fixed at a temperature of 50°C, a hydrolysis time of 30 minutes, and a bacterial cellulose-to-acid ratio of 1:50. Pineapple peel waste was used as a model for a cellulose source because to the best of our knowledge, there is no report on the use of this raw material for producing bacterial cellulose nanocrystalline. In fact, this material can be used as an alternative for ecofriendly and cost-free cellulose sources. Therefore, understanding in how to isolate bacterial cellulose nanocrystalline from pineapple peel waste has the potential for large-scale production of inexpensive cellulose nanocrystalline.

Structural Ceramics Database

National Institute of Standards and Technology Data Gateway

SRD 30 NIST Structural Ceramics Database (Web, free access)   The NIST Structural Ceramics Database (WebSCD) provides evaluated materials property data for a wide range of advanced ceramics known variously as structural ceramics, engineering ceramics, and fine ceramics.

Improve oxidation resistance at high temperature by nanocrystalline surface layer

NASA Astrophysics Data System (ADS)

Xia, Z. X.; Zhang, C.; Huang, X. F.; Liu, W. B.; Yang, Z. G.

2015-08-01

An interesting change of scale sequence occurred during oxidation of nanocrystalline surface layer by means of a surface mechanical attrition treatment. The three-layer oxide structure from the surface towards the matrix is Fe3O4, spinel FeCr2O4 and corundum (Fe,Cr)2O3, which is different from the typical two-layer scale consisted of an Fe3O4 outer layer and an FeCr2O4 inner layer in conventional P91 steel. The diffusivity of Cr, Fe and O is enhanced concurrently in the nanocrystalline surface layer, which causes the fast oxidation in the initial oxidation stage. The formation of (Fe,Cr)2O3 inner layer would inhabit fast diffusion of alloy elements in the nanocrystalline surface layer of P91 steel in the later oxidation stage, and it causes a decrease in the parabolic oxidation rate compared with conventional specimens. This study provides a novel approach to improve the oxidation resistance of heat resistant steel without changing its Cr content.

Synthesis and characterization of nanocrystalline mesoporous zirconia using supercritical drying.

PubMed

Tyagi, Beena; Sidhpuria, Kalpesh; Shaik, Basha; Jasra, Raksh Vir

2006-06-01

Synthesis of nano-crystalline zirconia aerogel was done by sol-gel technique and supercritical drying using n-propanol solvent at and above supercritical temperature (235-280 degrees C) and pressure (48-52 bar) of n-propanol. Zirconia xerogel samples have also been prepared by conventional thermal drying method to compare with the super critically dried samples. Crystalline phase, crystallite size, surface area, pore volume, and pore size distribution were determined for all the samples in detail to understand the effect of gel drying methods on these properties. Supercritical drying of zirconia gel was observed to give thermally stable, nano-crystalline, tetragonal zirconia aerogels having high specific surface area and porosity with narrow and uniform pore size distribution as compared to thermally dried zirconia. With supercritical drying, zirconia samples show the formation of only mesopores whereas in thermally dried samples, substantial amount of micropores are observed along with mesopores. The samples prepared using supercritical drying yield nano-crystalline zirconia with smaller crystallite size (4-6 nm) as compared to higher crystallite size (13-20 nm) observed with thermally dried zirconia.

[Posterior ceramic bonded partial restorations].

PubMed

Mainjot, Amélie; Vanheusden, Alain

2006-01-01

Posterior ceramic bonded partial restorations are conservative and esthetic approaches for compromised teeth. Overlays constitute a less invasive alternative for tooth tissues than crown preparations. With inlays and onlays they are also indicated in case of full arch or quadrant rehabilitations including several teeth. This article screens indications and realization of this type of restorations.

Self-composite comprised of nanocrystalline diamond and a non-diamond component useful for thermoelectric applications

DOEpatents

Gruen, Dieter M.

2012-09-04

One provides nanocrystalline diamond material that comprises a plurality of substantially ordered diamond crystallites that are sized no larger than about 10 nanometers. One then disposes a non-diamond component within the nanocrystalline diamond material. By one approach this non-diamond component comprises an electrical conductor that is formed at the grain boundaries that separate the diamond crystallites from one another. The resultant nanowire is then able to exhibit a desired increase with respect to its ability to conduct electricity while also preserving the thermal conductivity behavior of the nanocrystalline diamond material.

Self-composite comprised of nanocrystalline diamond and a non-diamond component useful for thermoelectric applications

DOEpatents

Gruen, Dieter M [Downers Grove, IL

2009-08-11

One provides nanocrystalline diamond material that comprises a plurality of substantially ordered diamond crystallites that are sized no larger than about 10 nanometers. One then disposes a non-diamond component within the nanocrystalline diamond material. By one approach this non-diamond component comprises an electrical conductor that is formed at the grain boundaries that separate the diamond crystallites from one another. The resultant nanowire is then able to exhibit a desired increase with respect to its ability to conduct electricity while also preserving the thermal conductivity behavior of the nanocrystalline diamond material.

Bioactive and inert dental glass-ceramics.

PubMed

Montazerian, Maziar; Zanotto, Edgar Dutra

2017-02-01

The global market for dental materials is predicted to exceed 10 billion dollars by 2020. The main drivers for this growth are easing the workflow of dentists and increasing the comfort of patients. Therefore, remarkable research projects have been conducted and are currently underway to develop improved or new dental materials with enhanced properties or that can be processed using advanced technologies, such as CAD/CAM or 3D printing. Among these materials, zirconia, glass or polymer-infiltrated ceramics, and glass-ceramics (GCs) are of great importance. Dental glass-ceramics are highly attractive because they are easy to process and have outstanding esthetics, translucency, low thermal conductivity, high strength, chemical durability, biocompatibility, wear resistance, and hardness similar to that of natural teeth, and, in certain cases, these materials are bioactive. In this review article, we divide dental GCs into the following two groups: restorative and bioactive. Most restorative dental glass-ceramics (RDGCs) are inert and biocompatible and are used in the restoration and reconstruction of teeth. Bioactive dental glass-ceramics (BDGCs) display bone-bonding ability and stimulate positive biological reactions at the material/tissue interface. BDGCs are suggested for dentin hypersensitivity treatment, implant coating, bone regeneration and periodontal therapy. Throughout this paper, we elaborate on the history, processing, properties and applications of RDGCs and BDGCs. We also report on selected papers that address promising types of dental glass-ceramics. Finally, we include trends and guidance on relevant open issues and research possibilities. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 619-639, 2017. © 2016 Wiley Periodicals, Inc.

Magnetorheological materials, method for making, and applications thereof

DOEpatents

Shen, Rui; Yang, Hong; Shafrir, Shai N.; Miao, Chunlin; Wang, Mimi; Mici, Joni; Lambropoulos, John C.; Jacobs, Stephen D.

2014-08-19

A magnetorheological material comprises a magnetic particle and a ceramic material, wherein the magnetorheological material is in a dried form and further wherein a portion of the ceramic material is in the form of a nanocrystalline coating over the entire exterior surface of the magnetic particle and another portion of the ceramic material is in the form of a free nanocrystal. A magnetorheological material comprises a magnetic particle having a ceramic material coating over an external surface thereof as a result of a coating process, and a free nanocrystal of the ceramic material in the form of a residual by-product of the coating process. A sol-gel process for making a magnetorheological product comprises providing a sol of a desired ceramic coating material; combining a desired quantity of carbonyl iron (CI) particles with the sol to coat the CI particles with the ceramic coating material; creating a resulting quantity of nanocrystalline ceramic material-coated CI particles and a quantity of free nanocrystals of the ceramic material; and, drying the resulting quantity of coated CI particles and free nanocrystals to a moisture content equal to or less than 2 wt %.

Nanocrystalline CuNi alloys: improvement of mechanical properties and thermal stability

NASA Astrophysics Data System (ADS)

Nogues, Josep; Varea, A.; Pellicer, E.; Sivaraman, K. M.; Pane, S.; Nelson, B. J.; Surinach, S.; Baro, M. D.; Sort, J.

2014-03-01

Nanocrystalline metallic films are known to benefit from novel and enhanced physical and chemical properties. In spite of these outstanding properties, nanocrystalline metals typically show relatively poor thermal stability which leads to deterioration of the properties due to grain coarsening. We have studied nanocrystalline Cu1-xNix (0.56 < x < 1) thin films (3 μm-thick) electrodeposited galvanostatically onto Cu/Ti/Si (100) substrates. CuNi thin films exhibit large values of hardness (6.15 < H < 7.21 GPa), which can be tailored by varying the composition. However, pure Ni films (x = 1) suffer deterioration of their mechanical and magnetic properties after annealing during 3 h at relatively low temperatures (TANN > 475 K) due to significant grain growth. Interestingly, alloying Ni with Cu clearly improves the thermal stability of the material because grain coarsening is delayed due to segregation of a Cu-rich phase at grain boundaries, thus preserving both the mechanical and magnetic properties up to higher TANN.

Transition from Irradiation-Induced Amorphization to Crystallization in Nanocrystalline Silicon Carbide

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

Jiang, Weilin; Jiao, Liang; Wang, Haiyan

2011-12-01

Response to irradiation of nanocrystalline 3C-SiC is studied using 2 MeV Au+ ions near the critical temperature for amorphization and is compared to the behavior of its monocrystalline counterpart under the identical irradiation conditions. The irradiated samples have been characterized using in-situ ion channeling, ex-situ x-ray diffraction, and helium ion microscopy. Compared to monocrystalline 3C-SiC, a faster amorphization process in the nanocrystalline material (average grain size = 3.3 nm) is observed at 500 K. However, the nanograin grows with increasing ion fluence at 550 K and the grain size tends to saturate at high fluences. The striking contrast demonstrates amore » sharp transition from irradiation-induced interface-driven amorphization at 500 K to crystallization at 550 K. The results could show potential impacts of nanocrystalline SiC on nuclear fuel cladding and structural components of next-generation nuclear energy systems.« less

Method of making a hydrogen transport membrane, and article

DOEpatents

Schwartz, Joseph M.; Corpus, Joseph M.; Lim, Hankwon

2015-07-21

The present invention relates to a method of manufacturing a hydrogen transport membrane and the composite article itself. More specifically, the invention relates to producing a membrane substrate, wherein the ceramic substrate is coated with a metal oxide slurry, thereby eliminating the need for an activation step prior to plating the ceramic membrane through an electroless plating process. The invention also relates to modifying the pore size and porosity of the substrate by oxidation or reduction of the particles deposited by the metal oxide slurry.

Preparation of high-quality ultrathin transmission electron microscopy specimens of a nanocrystalline metallic powder.

PubMed

Riedl, Thomas; Gemming, Thomas; Mickel, Christine; Eymann, Konrad; Kirchner, Alexander; Kieback, Bernd

2012-06-01

This article explores the achievable transmission electron microscopy specimen thickness and quality by using three different preparation methods in the case of a high-strength nanocrystalline Cu-Nb powder alloy. Low specimen thickness is essential for spatially resolved analyses of the grains in nanocrystalline materials. We have found that single-sided as well as double-sided low-angle Ar ion milling of the Cu-Nb powders embedded into epoxy resin produced wedge-shaped particles of very low thickness (<10 nm) near the edge. By means of a modified focused ion beam lift-out technique generating holes in the lamella interior large micrometer-sized electron-transparent regions were obtained. However, this lamella displayed a higher thickness at the rim of ≥30 nm. Limiting factors for the observed thicknesses are discussed including ion damage depths, backscattering, and surface roughness, which depend on ion type, energy, current density, and specimen motion. Finally, sections cut by ultramicrotomy at low stroke rate and low set thickness offered vast, several tens of square micrometers uniformly thin regions of ∼10-nm minimum thickness. As major drawbacks, we have detected a thin coating on the sections consisting of epoxy deployed as the embedding material and considerable nanoscale thickness variations. Copyright © 2011 Wiley Periodicals, Inc.

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

Failure of a novel ceramic-on-ceramic hip resurfacing prosthesis.

PubMed

Matharu, Gulraj S; Daniel, Joseph; Ziaee, Hena; McMinn, Derek J W

2015-03-01

We report the early failure of five ceramic-on-ceramic hip resurfacings (CoCHRs). The ceramic used for the acetabular liner was a novel ceramic-composite (two thirds polyurethane and one third alumina ceramic). All cases were revised for increasing metal ion levels (blood cobalt 3.93-208.0 μg/l and chromium 1.57-17.5 μg/l) due to ceramic liner fracture and/or accelerated wear of the ceramic femoral head coating. Patients underwent bearing exchange and revision using primary hip arthroplasty implants at a mean of 3.0 years following CoCHR. Intraoperatively all patients had metallosis. At 1 to 2 years of follow-up blood metal ions normalized with no complications. We do not recommend this particular type of ceramic-on-ceramic bearing for hip resurfacing. Copyright © 2014 Elsevier Inc. All rights reserved.

High Temperature Stable Nanocrystalline SiGe Thermoelectric Material

NASA Technical Reports Server (NTRS)

Yang, Sherwin (Inventor); Matejczyk, Daniel Edward (Inventor); Determan, William (Inventor)

2013-01-01

A method of forming a nanocomposite thermoelectric material having microstructural stability at temperatures greater than 1000 C. The method includes creating nanocrystalline powder by cryomilling. The method is particularly useful in forming SiGe alloy powder.

Consumable core for manufacture of composite articles and related method

DOEpatents

Taxacher, Glenn Curtis; de Diego, Peter; Gray, Paul Edward; Monaghan, Philip Harold

2017-09-05

Systems, methods and devices adapted to ease manufacture of composite articles (e.g., ceramic composite articles), particularly composite articles which include a hollow feature are disclosed. In one embodiment, a system includes: a consumable core formed to be disposed within an inner portion of a composite precursor, the consumable core adapted to convert into an infiltrant during a manufacturing process and infiltrate the composite precursor.

In-situ TEM observation of the response of ultrafine- and nanocrystalline-grained tungsten to extreme irradiation environments

PubMed Central

El-Atwani, O.; Hinks, J. A.; Greaves, G.; Gonderman, S.; Qiu, T.; Efe, M.; Allain, J. P.

2014-01-01

The accumulation of defects, and in particular He bubbles, can have significant implications for the performance of materials exposed to the plasma in magnetic-confinement nuclear fusion reactors. Some of the most promising candidates for deployment into such environments are nanocrystalline materials as the engineering of grain boundary density offers the possibility of tailoring their radiation resistance properties. In order to investigate the microstructural evolution of ultrafine- and nanocrystalline-grained tungsten under conditions similar to those in a reactor, a transmission electron microscopy study with in situ 2 keV He+ ion irradiation at 950°C has been completed. A dynamic and complex evolution in the microstructure was observed including the formation of defect clusters, dislocations and bubbles. Nanocrystalline grains with dimensions less than around 60 nm demonstrated lower bubble density and greater bubble size than larger nanocrystalline (60–100 nm) and ultrafine (100–500 nm) grains. In grains over 100 nm, uniform distributions of bubbles and defects were formed. At higher fluences, large faceted bubbles were observed on the grain boundaries, especially on those of nanocrystalline grains, indicating the important role grain boundaries can play in trapping He and thus in giving rise to the enhanced radiation tolerance of nanocrystalline materials. PMID:24796578

Coating system to permit direct brazing of ceramics

DOEpatents

Cadden, Charles H.; Hosking, F. Michael

2003-01-01

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

Stabilizing Nanocrystalline Oxide Nanofibers at Elevated Temperatures by Coating Nanoscale Surface Amorphous Films.

PubMed

Yao, Lei; Pan, Wei; Luo, Jian; Zhao, Xiaohui; Cheng, Jing; Nishijima, Hiroki

2018-01-10

Nanocrystalline materials often exhibit extraordinary mechanical and physical properties but their applications at elevated temperatures are impaired by the rapid grain growth. Moreover, the grain growth in nanocrystalline oxide nanofibers at high temperatures can occur at hundreds of degrees lower than that would occur in corresponding bulk nanocrystalline materials, which would eventually break the fibers. Herein, by characterizing a model system of scandia-stabilized zirconia using hot-stage in situ scanning transmission electron microscopy, we discover that the enhanced grain growth in nanofibers is initiated at the surface. Subsequently, we demonstrate that coating the fibers with nanometer-thick amorphous alumina layer can enhance their temperature stability by nearly 400 °C via suppressing the surface-initiated grain growth. Such a strategy can be effectively applied to other oxide nanofibers, such as samarium-doped ceria, yttrium-stabilized zirconia, and lanthanum molybdate. The nanocoatings also increase the flexibility of the oxide nanofibers and stabilize the high-temperature phases that have 10 times higher ionic conductivity. This study provides new insights into the surface-initiated grain growth in nanocrystalline oxide nanofibers and develops a facile yet innovative strategy to improve the high-temperature stability of nanofibers for a broad range of applications.

Boron-carbon-silicon polymers and the ceramic thereof

NASA Technical Reports Server (NTRS)

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

1991-01-01

The present invention relates to a process for the production of an organoborosilicon preceramic polymer. The prepolymer is pyrolyzed to produce a ceramic article useful in high temperature (e.g., aerospace) or extreme environmental applications.

[In-vitro research on the thermal debonding of ceramic brackets].

PubMed

Bäzner, B; Ettwein, K H; Röhlcke, F; Sernetz, F

1991-12-01

The mechanical debonding of ceramic brackets using special instruments involves the use of a degree of force that is damaging to the enamel. For this reason, the authors have developed the Ceramic Debonding Unit for the thermal debonding of ceramic brackets. The unit reduces the force necessary for debonding, without overheating the tooth. The present article explains the principle of the unit. The influence on the temperature increase in the pulpa of the mechanical torque applied during debonding, and the time taken for debonding was investigated in extracted teeth (lower central incisors). Tests on ceramic brackets made by various manufacturers showed that safe debonding is possible if the debonding time does not exceed 3 seconds at a torque of 100 Nnm. The temperature increase in the pulpa will not exceed 5 degrees C when the Ceramic Debonding Unit is used under these conditions, so that harmful overheating of healthy teeth does not occur.

Evidence of a temperature transition for denuded zone formation in nanocrystalline Fe under He irradiation

DOE PAGES

El-Atwani, Osman; Nathaniel II, James E.; Leff, Asher C.; ...

2016-10-18

Nanocrystalline materials are radiation-tolerant materials’ candidates due to their high defect sink density. Here, nanocrystalline iron films were irradiated with 10 keV helium ions in situ in a transmission electron microscope at elevated temperatures. Grain-size-dependent bubble density changes and denuded zone occurrence were observed at 700 K, but not at 573 K. This transition, attributed to increased helium–vacancy migration at elevated temperatures, suggests that nanocrystalline microstructures are more resistant to swelling at 700 K due to decreased bubble density. Finally, denuded zone formation had no correlation with grain size and misorientation angle under the conditions studied.

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.

Comparison of high pressure homogenization and stirred bead milling for the production of nano-crystalline suspensions.

PubMed

Nakach, Mostafa; Authelin, Jean-René; Perrin, Marc-Antoine; Lakkireddy, Harivardhan Reddy

2018-05-19

Currently, the two technologies primarily used for the manufacturing of nano-crystalline suspensions using top down process (i.e. wet milling) are high pressure homogenization (HPH) and stirred bead milling (SBM). These two technologies are based upon different mechanisms, i.e., cavitation forces for HPH and shear forces for stirred bead milling. In this article, the HPH and SBM technologies are compared in terms of the impact of the suspension composition the process parameters and the technological configuration on milling performances and physical quality of the suspensions produced. The data suggested that both HPH and SBM are suitable for producing nano-crystalline suspensions, although SBM appeared more efficient than HPH, since the limit of milling (d 50 ) for SBM was found to be lower than that obtained with HPH (100 nm vs 200 nm). For both these technologies, regardless of the process parameters used for milling and the scale of manufacturing, the relationship of d 90 versus d 50 could be described by a unique master curve (technology signature of milling pathway) outlining that the HPH leads to more uniform particle size distribution as compared to SBM. Copyright © 2018 Elsevier B.V. All rights reserved.

Method to grow pure nanocrystalline diamond films at low temperatures and high deposition rates

DOEpatents

Carlisle, John A [Plainfield, IL; Gruen, Dieter M [Downers Grove, IL; Auciello, Orlando [Bolingbrook, IL; Xiao, Xingcheng [Woodridge, IL

2009-07-07

A method of depositing nanocrystalline diamond film on a substrate at a rate of not less than about 0.2 microns/hour at a substrate temperature less than about 500.degree. C. The method includes seeding the substrate surface with nanocrystalline diamond powder to an areal density of not less than about 10.sup.10sites/cm.sup.2, and contacting the seeded substrate surface with a gas of about 99% by volume of an inert gas other than helium and about 1% by volume of methane or hydrogen and one or more of acetylene, fullerene and anthracene in the presence of a microwave induced plasma while maintaining the substrate temperature less than about 500.degree. C. to deposit nanocrystalline diamond on the seeded substrate surface at a rate not less than about 0.2 microns/hour. Coatings of nanocrystalline diamond with average particle diameters of less than about 20 nanometers can be deposited with thermal budgets of 500.degree. C.-4 hours or less onto a variety of substrates such as MEMS devices.

Development of Nanocrystalline Zeolite Materials for the Decontamination of Chemical Warfare Agents

DTIC Science & Technology

2008-11-17

phosphite (CH3O)2P(O)H or DMP. There is -40-20020406080100 In te ns ity ppm a) b) c) d) * ** ** ** * * 33 37 1225 9 Figure 6. 31P MAS NMR spectra...The main objective of this research is to use novel nanocrystalline zeolite materials synthesized in our laboratories for the decontamination of...nanocrystalline zeolite materials. In these studies, we have focused our attention on the decontamination of 2-CEES and DMMP, two simulants for mustard gas

Method of forming a ceramic matrix composite and a ceramic matrix component

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

de Diego, Peter; Zhang, James

A method of forming a ceramic matrix composite component includes providing a formed ceramic member having a cavity, filling at least a portion of the cavity with a ceramic foam. The ceramic foam is deposited on a barrier layer covering at least one internal passage of the cavity. The method includes processing the formed ceramic member and ceramic foam to obtain a ceramic matrix composite component. Also provided is a method of forming a ceramic matrix composite blade and a ceramic matrix composite component.

Preparation of Cu2ZnSnS4 nano-crystalline powder by mechano-chemical method

NASA Astrophysics Data System (ADS)

Alirezazadeh, Farzaneh; Sheibani, Saeed; Rashchi, Fereshteh

2018-01-01

Copper zinc tin sulfide (Cu2ZnSnS4, CZTS) is one of the most promising ceramic materials as an absorber layer in solar cells due to its suitable band gap, high absorption coefficient and non-toxic and environmental friendly constituent elements. In this work, nano-crystalline CZTS powder was synthesized by mechanical milling. Elemental powders of Cu, Zn, Sn and were mixed in atomic ratio of 2:1:1:4 according to the stoichiometry of Cu2ZnSnS4 and then milled in a planetary high energy ball mill under argon atmosphere. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and diffusion reflectance spectroscopy (DRS). XRD results confirm the formation of single-phase CZTS with kesterite structure after 20 h of milling. Also, the mean crystallite size was about 35 nm. SEM results show that after 20 h of milling, the product has a relatively uniform particle size distribution. Optical properties of the product indicate that the band gap of prepared CZTS is 1.6 eV which is near to the optimum value for photovoltaic solar cells showing as a light absorber material in solar energy applications.

Joining engineering ceramics

NASA Astrophysics Data System (ADS)

Loehman, Ronald E.

Methods for joining ceramics are outlined with attention given to their fundamental properties, and some examples of ceramic bonding in engineering ceramic systems are presented. Ceramic-ceramic bonds using no filler material include diffusion and electric-field bonding and ceramic welding, and bonds with filler materials can be provided by Mo-Mn brazing, microwave joining, and reactive nonmetallic liquid bonding. Ceramic-metal joints can be effected with filler material by means of the same ceramic-ceramic processes and without filler material by means of use of molten glass or diffusion bonding. Key properties of the bonding processes include: bonds with discontinuous material properties, energies that are positive relative to the bulk material, and unique chemical and mechanical properties. The processes and properties are outlined for ceramic-metal joints and for joining silicon nitride, and the factors that control wetting, adhesion, and reaction on the atomic scale are critical for establishing successful joints.

Grain growth behavior at absolute zero during nanocrystalline metal indentation

NASA Astrophysics Data System (ADS)

Sansoz, F.; Dupont, V.

2006-09-01

The authors show using atomistic simulations that stress-driven grain growth can be obtained in the athermal limit during nanocrystalline aluminum indentation. They find that the grain growth results from rotation of nanograins and propagation of shear bands. Together, these mechanisms are shown to lead to the unstable migration of grain boundaries via process of coupled motion. An analytical model is used to explain this behavior based on the atomic-level shear stress acting on the interfaces during the shear band propagation. This study sheds light on the atomic mechanism at play during the abnormal grain coarsening observed at low temperature in nanocrystalline metals.

Multilayer Article Characterized by Low Coefficient of Thermal Expansion Outer Layer

NASA Technical Reports Server (NTRS)

Lee, Kang N. (Inventor)

2004-01-01

A multilayer article comprises a substrate comprising a ceramic or a silicon-containing metal alloy. The ceramic is a Si-containing ceramic or an oxide ceramic with or without silicon. An outer layer overlies the substrate and at least one intermediate layer is located between the outer layer and thc substrate. An optional bond layer is disposed between thc 1 least one intermediate layer and thc substrate. The at least one intermediate layer may comprise an optional chemical barrier layer adjacent the outer layer, a mullite-containing layer and an optional chemical barrier layer adjacent to the bond layer or substrate. The outer layer comprises a compound having a low coefficient of thermal expansion selected from one of the following systems: rare earth (RE) silicates; at least one of hafnia and hafnia-containing composite oxides; zirconia-containing composite oxides and combinations thereof.

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

PubMed

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

2018-06-20

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

Nanocrystalline sp{sup 2} and sp{sup 3} carbons: CVD synthesis and applications

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

Terranova, M. L.; Rossi, M.; Tamburri, E., E-mail: emanuela.tamburri@uniroma2.it

The design and production of innovative materials based on nanocrystalline sp{sup 2}- and sp{sup 3}-coordinated carbons is presently a focus of the scientific community. We present a review of the nanostructures obtained in our labs using a series of synthetic routes, which make use of chemical vapor deposition (CVD) techniques for the selective production of non-planar graphitic nanostructures, nanocrystalline diamonds, and hybrid two-phase nanostructures.

Impedance spectroscopic and dielectric properties of nanosized Y2/3Cu3Ti4O12 ceramic

NASA Astrophysics Data System (ADS)

Sharma, Sunita; Yadav, Shiv Sundar; Singh, M. M.; Mandal, K. D.

2014-11-01

Yttrium Copper Titanate (Y2/3Cu3Ti4O12) nanoceramic is structurally analogous to CaCu3Ti4O12 (CCTO). X-ray diffraction (XRD) of Y2/3Cu3Ti4O12 (YCTO) shows the presence of all normal peaks of CCTO. SEM micrograph exhibits the presence of bimodal grains of size ranging from 1-2 μm. Bright field TEM image clearly displays nanocrystalline particle which is supported by presence of a few clear rings in the corresponding selected area electron diffraction (SAED) pattern. It exhibits a high value of dielectric constant (ɛ‧ = 8434) at room temperature and 100 Hz frequency with characteristic relaxation peaks. Impedance and modulus studies revealed the presence of temperature-dependent Maxwell-Wagner type of relaxation in the ceramic.

Remakes of Colorlogic and IPS Empress ceramic restorations in general practice.

PubMed

Hekland, Helge; Riise, Trond; Berg, Einar

2003-01-01

The aim of this article was to study frequencies and distribution of remakes of all-ceramic inlays/onlays, veneers, and crowns occurring before and after cementation. A total of 2,069 sintered feldspathic ceramic restorations (Colorlogic) and 1,136 pressure-molded ceramic restorations (IPS Empress 1 and 2) were produced during the study period by one dental laboratory. The laboratory gave an unqualified and unlimited guarantee for their ceramic restorations. The outcome variable was reports from the clinicians to the dental laboratory about any problems related to the restoration, necessitating remake. Problems occurring before cementation occurred in 4.4% of the restorations. Veneers were remade more frequently than the other types of restorations (6.6%). After cementation, the overall 2-year rate of remakes was 1%, indicating a survival rate of the ceramic restorations of 99%, with inlays/onlays exhibiting the highest (99.8%) and crowns the lowest (98.4%) rates. This difference in rates was significant. No significant differences in remakes between ceramics or tooth categories were found. There were few problems in a short- to medium-term perspective that, in the opinion of general practitioners, necessitated remakes of all-ceramic restorations.

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

Application of ASTAR(TM)/Precession Electron Diffraction Technique to Quantitatively Study Defects in Nanocrystalline Metallic Materials

NASA Astrophysics Data System (ADS)

Ghamarian, Iman

Nanocrystalline metallic materials have the potential to exhibit outstanding performance which leads to their usage in challenging applications such as coatings and biomedical implant devices. To optimize the performance of nanocrystalline metallic materials according to the desired applications, it is important to have a decent understanding of the structure, processing and properties of these materials. Various efforts have been made to correlate microstructure and properties of nanocrystalline metallic materials. Based on these research activities, it is noticed that microstructure and defects (e.g., dislocations and grain boundaries) play a key role in the behavior of these materials. Therefore, it is of great importance to establish methods to quantitatively study microstructures, defects and their interactions in nanocrystalline metallic materials. Since the mechanisms controlling the properties of nanocrystalline metallic materials occur at a very small length scale, it is fairly difficult to study them. Unfortunately, most of the characterization techniques used to explore these materials do not have the high enough spatial resolution required for the characterization of these materials. For instance, by applying complex profile-fitting algorithms to X-ray diffraction patterns, it is possible to get an estimation of the average grain size and the average dislocation density within a relatively large area. However, these average values are not enough for developing meticulous phenomenological models which are able to correlate microstructure and properties of nanocrystalline metallic materials. As another example, electron backscatter diffraction technique also cannot be used widely in the characterization of these materials due to problems such as relative poor spatial resolution (which is 90 nm) and the degradation of Kikuchi diffraction patterns in severely deformed nano-size grain metallic materials. In this study, ASTAR(TM)/precession electron

Dispersed metal-toughened ceramics and ceramic brazing

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

Moorhead, A.J.; Tiegs, T.N.; Lauf, R.J.

1983-01-01

An alumina (Al/sub 2/O/sub 3/) based material that contains approximately 1 vol % finely dispersed platinum or chromium was developed for use in high temperature thermal-shock resistant electrical insulators. The work at ORNL is divided into two areas: (1) development of DMT ceramics; and (2) development of brazing filler metals suitable for making ceramic-to-ceramic and ceramic-to-metal brazements. The DMT ceramics and brazements are intended for service at elevated temperatures and at high stress levels in the dirty environments of advanced heat engines. The development and characterization of DMT ceramics includes processing (powder preparation, densification and heat treatment) and detailed measurementmore » of mechanical and physical properties (strength, fracture toughness, and thermal conductivity). The brazing work includes: (1) the formulation and melting of small quantities of experimental brazing filler metals; (2) evaluation of the wetting and bonding behavior of these filler metals on Al/sub 2/O/sub 3/, partially stabilized zirconia and ..cap alpha..-SiC in a sessile drop apparatus; and (3) determine the short-term strength and fracture toughness of brazements.« less

Method of producing silicon carbide articles

DOEpatents

Milewski, John V.

1985-01-01

A method of producing articles comprising reaction-bonded silicon carbide (SiC) and graphite (and/or carbon) is given. The process converts the graphite (and/or carbon) in situ to SiC, thus providing the capability of economically obtaining articles made up wholly or partially of SiC having any size and shape in which graphite (and/or carbon) can be found or made. When the produced articles are made of an inner graphite (and/or carbon) substrate to which SiC is reaction bonded, these articles distinguish SiC-coated graphite articles found in the prior art by the feature of a strong bond having a gradual (as opposed to a sharply defined) interface which extends over a distance of mils. A method for forming SiC whisker-reinforced ceramic matrices is also given. The whisker-reinforced articles comprise SiC whiskers which substantially retain their structural integrity.

Stability of nanocrystalline Ni-based alloys: coupling Monte Carlo and molecular dynamics simulations

NASA Astrophysics Data System (ADS)

Waseda, O.; Goldenstein, H.; Silva, G. F. B. Lenz e.; Neiva, A.; Chantrenne, P.; Morthomas, J.; Perez, M.; Becquart, C. S.; Veiga, R. G. A.

2017-10-01

The thermal stability of nanocrystalline Ni due to small additions of Mo or W (up to 1 at%) was investigated in computer simulations by means of a combined Monte Carlo (MC)/molecular dynamics (MD) two-steps approach. In the first step, energy-biased on-lattice MC revealed segregation of the alloying elements to grain boundaries. However, the condition for the thermodynamic stability of these nanocrystalline Ni alloys (zero grain boundary energy) was not fulfilled. Subsequently, MD simulations were carried out for up to 0.5 μs at 1000 K. At this temperature, grain growth was hindered for minimum global concentrations of 0.5 at% W and 0.7 at% Mo, thus preserving most of the nanocrystalline structure. This is in clear contrast to a pure Ni model system, for which the transformation into a monocrystal was observed in MD simulations within 0.2 μs at the same temperature. These results suggest that grain boundary segregation of low-soluble alloying elements in low-alloyed systems can produce high-temperature metastable nanocrystalline materials. MD simulations carried out at 1200 K for 1 at% Mo/W showed significant grain boundary migration accompanied by some degree of solute diffusion, thus providing additional evidence that solute drag mostly contributed to the nanostructure stability observed at lower temperature.

Molten salt synthesis of nanocrystalline phase of high dielectric constant material CaCu3Ti4O12.

PubMed

Prakash, B Shri; Varma, K B R

2008-11-01

Nanocrystalline powders of giant dielectric constant material, CaCu3Ti4O12 (CCTO), have been prepared successfully by the molten salt synthesis (MSS) using KCl at 750 degrees C/10 h, which is significantly lower than the calcination temperature (approximately 1000 degrees C) that is employed to obtain phase pure CCTO in the conventional solid-state reaction route. The water washed molten salt synthesized powder, characterized by X-ray powder diffraction (XRD), Scanning electron microscopy (SEM), and Transmission electron microscopy (TEM) confirmed to be a phase pure CCTO associated with approximately 150 nm sized crystallites of nearly spherical shape. The decrease in the formation temperature/duration of CCTO in MSS method was attributed to an increase in the diffusion rate or a decrease in the diffusion length of reacting ions in the molten salt medium. As a consequence of liquid phase sintering, pellets of as-synthesized KCl containing CCTO powder exhibited higher sinterability and grain size than that of KCl free CCTO samples prepared by both MSS method and conventional solid-state reaction route. The grain size and the dielectric constant of KCl containing CCTO ceramics increased with increasing sintering temperature (900 degrees C-1050 degrees C). Indeed the dielectric constants of these ceramics were higher than that of KCl free CCTO samples prepared by both MSS method and those obtained via the solid-state reaction route and sintered at the same temperature. Internal barrier layer capacitance (IBLC) model was invoked to correlate the observed dielectric constant with the grain size in these samples.

FAST TRACK COMMUNICATION: Nanocrystalline silicon film growth morphology control through RF waveform tailoring

NASA Astrophysics Data System (ADS)

Johnson, Erik V.; Verbeke, Thomas; Vanel, Jean-Charles; Booth, Jean-Paul

2010-10-01

We demonstrate the application of RF waveform tailoring to generate an electrical asymmetry in a capacitively coupled plasma-enhanced chemical vapour deposition system, and its use to control the growth mode of hydrogenated amorphous and nanocrystalline silicon thin films deposited at low temperature (150 °C). A dramatic shift in the dc bias potential at the powered electrode is observed when simply inverting the voltage waveform from 'peaks' to 'troughs', indicating an asymmetric distribution of the sheath voltage. By enhancing or suppressing the ion bombardment energy at the substrate (situated on the grounded electrode), the growth of thin silicon films can be switched between amorphous and nanocrystalline modes, as observed using in situ spectroscopic ellipsometry. The effect is observed at pressures sufficiently low that the collisional reduction in average ion bombardment energy is not sufficient to allow nanocrystalline growth (<100 mTorr).

Ceramic Laser Materials

PubMed Central

Sanghera, Jasbinder; Kim, Woohong; Villalobos, Guillermo; Shaw, Brandon; Baker, Colin; Frantz, Jesse; Sadowski, Bryan; Aggarwal, Ishwar

2012-01-01

Ceramic laser materials have come a long way since the first demonstration of lasing in 1964. Improvements in powder synthesis and ceramic sintering as well as novel ideas have led to notable achievements. These include the first Nd:yttrium aluminum garnet (YAG) ceramic laser in 1995, breaking the 1 KW mark in 2002 and then the remarkable demonstration of more than 100 KW output power from a YAG ceramic laser system in 2009. Additional developments have included highly doped microchip lasers, ultrashort pulse lasers, novel materials such as sesquioxides, fluoride ceramic lasers, selenide ceramic lasers in the 2 to 3 μm region, composite ceramic lasers for better thermal management, and single crystal lasers derived from polycrystalline ceramics. This paper highlights some of these notable achievements. PMID:28817044

Thermal stability and chemical resistance of (Ti,Al)N-Cu and (Ti,Al)N-Ni metal-ceramic nanostructured coatings

NASA Astrophysics Data System (ADS)

Belov, D. S.; Blinkov, I. V.; Volkhonskii, A. O.; Kuznetsov, D. V.; Kiryukhantsev-Korneev, F. V.; Pustov, Yu. A.; Sergevnin, V. S.

2016-12-01

This work represents the results of research on thermal stability, oxidation resistance at temperatures of up to 800 °C and electrochemical behaviour of (Ti,Al)N-(∼3 at.%)Cu and (Ti,Al)N-(∼8 at.%)Ni nanocrystalline coatings in acidic and alkaline media. The coatings were deposited by the arc-PVD method with a thickness of approximately 4 μm and crystallite size of less than 20 nm. It has been demonstrated that the composition and properties of the coating structures do not change when the coatings are heated in 10-4 Pa vacuum at temperatures of 600, 700 °C for 1.5 h. Heating up to 800 °C caused an increase of crystallite size and reduction microstrain in the crystal lattice of the ceramic phase. The process is accompanied by deterioration of the coating hardness from 48 to 52 to 33-36 GPa. The (Ti,Al)N-Cu and (Ti,Al)N-Ni metal-ceramic nanostructured coatings are characterized by heat resistance up to the temperatures of 700 and 800 °C respectively. The coatings under study have tendency for self-passivation and resistance to pitting corrosion.

Stacking fault energies and slip in nanocrystalline metals.

PubMed

Van Swygenhoven, H; Derlet, P M; Frøseth, A G

2004-06-01

The search for deformation mechanisms in nanocrystalline metals has profited from the use of molecular dynamics calculations. These simulations have revealed two possible mechanisms; grain boundary accommodation, and intragranular slip involving dislocation emission and absorption at grain boundaries. But the precise nature of the slip mechanism is the subject of considerable debate, and the limitations of the simulation technique need to be taken into consideration. Here we show, using molecular dynamics simulations, that the nature of slip in nanocrystalline metals cannot be described in terms of the absolute value of the stacking fault energy-a correct interpretation requires the generalized stacking fault energy curve, involving both stable and unstable stacking fault energies. The molecular dynamics technique does not at present allow for the determination of rate-limiting processes, so the use of our calculations in the interpretation of experiments has to be undertaken with care.

Ceramic inspection system

DOEpatents

Werve, Michael E [Modesto, CA

2006-05-16

A system for inspecting a ceramic component. The ceramic component is positioned on a first rotary table. The first rotary table rotates the ceramic component. Light is directed toward the first rotary table and the rotating ceramic component. A detector is located on a second rotary table. The second rotary table is operably connected to the first rotary table and the rotating ceramic component. The second rotary table is used to move the detector at an angle to the first rotary table and the rotating ceramic component.

Recent Progress in Using Advanced Characterization and Modeling Approaches to Study Radiation Effects in Oxide Ceramics

DOE PAGES

Bai, Xian-Ming

2014-10-23

I serve as a Guest Editor for the Nuclear Materials Committee of the TMS Structural Materials Division, and coordinated the topic ‘‘Radiation Effects in Oxide Ceramics and Novel LWR Fuels" for JOM in the December 2014 issue. I selected five articles related this topic. These articles talk about some recent progress of using advanced experimental and modeling tools to study radiation effects in oxide ceramics at atomistic scale and mesoscale. In this guest editor commentary article, I summarize the novel aspects of these papers and also provide some suggestions for future research directions.

Deformation-induced localized solid-state amorphization in nanocrystalline nickel.

PubMed

Han, Shuang; Zhao, Lei; Jiang, Qing; Lian, Jianshe

2012-01-01

Although amorphous structures have been widely obtained in various multi-component metallic alloys, amorphization in pure metals has seldom been observed and remains a long-standing scientific curiosity and technological interest. Here we present experimental evidence of localized solid-state amorphization in bulk nanocrystalline nickel introduced by quasi-static compression at room temperature. High-resolution electron microscope observations illustrate that nano-scale amorphous structures present at the regions where severe deformation occurred, e.g. along crack paths or surrounding nano-voids. These findings have indicated that nanocrystalline structures are highly desirable for promoting solid-state amorphization, which may provide new insights for understanding the nature of the crystalline-to-amorphous transformation and suggested a potential method to produce elemental metallic glasses that have hardly been available hitherto through rapid solidification.

Deformation-induced localized solid-state amorphization in nanocrystalline nickel

PubMed Central

Han, Shuang; Zhao, Lei; Jiang, Qing; Lian, Jianshe

2012-01-01

Although amorphous structures have been widely obtained in various multi-component metallic alloys, amorphization in pure metals has seldom been observed and remains a long-standing scientific curiosity and technological interest. Here we present experimental evidence of localized solid-state amorphization in bulk nanocrystalline nickel introduced by quasi-static compression at room temperature. High-resolution electron microscope observations illustrate that nano-scale amorphous structures present at the regions where severe deformation occurred, e.g. along crack paths or surrounding nano-voids. These findings have indicated that nanocrystalline structures are highly desirable for promoting solid-state amorphization, which may provide new insights for understanding the nature of the crystalline-to-amorphous transformation and suggested a potential method to produce elemental metallic glasses that have hardly been available hitherto through rapid solidification. PMID:22768383

Grain boundary and triple junction diffusion in nanocrystalline copper

NASA Astrophysics Data System (ADS)

Wegner, M.; Leuthold, J.; Peterlechner, M.; Song, X.; Divinski, S. V.; Wilde, G.

2014-09-01

Grain boundary and triple junction diffusion in nanocrystalline Cu samples with grain sizes, , of ˜35 and ˜44 nm produced by spark plasma sintering were investigated by the radiotracer method using the 63Ni isotope. The measured diffusivities, Deff, are comparable with those determined previously for Ni grain boundary diffusion in well-annealed, high purity, coarse grained, polycrystalline copper, substantiating the absence of a grain size effect on the kinetic properties of grain boundaries in a nanocrystalline material at grain sizes d ≥ 35 nm. Simultaneously, the analysis predicts that if triple junction diffusion of Ni in Cu is enhanced with respect to the corresponding grain boundary diffusion rate, it is still less than 500ṡDgb within the temperature interval from 420 K to 470 K.

Faceted ceramic fibers, tapes or ribbons and epitaxial devices therefrom

DOEpatents

Goyal, Amit

2013-07-09

A crystalline article includes a single-crystal ceramic fiber, tape or ribbon. The fiber, tape or ribbon has at least one crystallographic facet along its length, which is generally at least one meter long. In the case of sapphire, the facets are R-plane, M-plane, C-plane or A-plane facets. Epitaxial articles, including superconducting articles, can be formed on the fiber, tape or ribbon.

Faceted ceramic fibers, tapes or ribbons and epitaxial devices therefrom

DOEpatents

Goyal, Amit [Knoxville, TN

2012-07-24

A crystalline article includes a single-crystal ceramic fiber, tape or ribbon. The fiber, tape or ribbon has at least one crystallographic facet along its length, which is generally at least one meter long. In the case of sapphire, the facets are R-plane, M-plane, C-plane or A-plane facets. Epitaxial articles, including superconducting articles, can be formed on the fiber, tape or ribbon.

Addition of a pontic to all-ceramic Turkom-Cera fixed partial denture restorations.

PubMed

Uludag, Bulent; Tokar, Emre; Polat, Serdar

2013-04-01

High-strength all-ceramic materials are commonly used in dentistry. When complications occur in an all-ceramic restoration, the restoration is usually replaced. This article describes the time-saving ability and cost-effectiveness of this novel technique for the addition of a pontic in two complicated clinical cases. Turkom-Cera(™) [Turkom-Ceramic (M) Sdn. Bhd.] with aluminum oxide (99.98%) is an all-ceramic system that offers the option of addition of a new pontic to the sintered framework. The new pontic was cut off from an alumina blank [Turkom-Ceramic (M) Sdn. Bhd.], moistened, and attached to the framework using alumina gel [Turkom-Ceramic (M) Sdn. Bhd.]. The framework was veneered with veneering porcelain (Vita VM 7; VITA Zahnfabrik). The two cases presented here involving the addition of a pontic to sintered framework were followed up for at least 1 year. No complication was detected or reported by the patients. Alumina- and zirconia-based ceramics are particularly suitable for for all-ceramic restorations in high-stress bearing areas. However, replacement of a failed all-ceramic restoration is not the most practical solution, considering both cost and tooth-related factors. This attractive feature of the Turkom-Cera allows the repair of a fractured ceramic coping or the addition of a new pontic to restorations.

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.

Anti-inflammatory activity of nanocrystalline silver-derived solutions in porcine contact dermatitis

PubMed Central

2010-01-01

Background Nanocrystalline silver dressings have anti-inflammatory activity, unlike solutions containing Ag+ only, which may be due to dissolution of multiple silver species. These dressings can only be used to treat surfaces. Thus, silver-containing solutions with nanocrystalline silver properties could be valuable for treating hard-to-dress surfaces and inflammatory conditions of the lungs and bowels. This study tested nanocrystalline silver-derived solutions for anti-inflammatory activity. Methods Inflammation was induced on porcine backs using dinitrochlorobenzene. Negative and positive controls were treated with distilled water. Experimental groups were treated with solutions generated by dissolving nanocrystalline silver in distilled water adjusted to starting pHs of 4 (using CO2), 5.6 (as is), 7, and 9 (using Ca(OH)2). Solution samples were analyzed for total silver. Daily imaging, biopsying, erythema and oedema scoring, and treatments were performed for three days. Biopsies were processed for histology, immunohistochemistry (for IL-4, IL-8, IL-10, TNF-α, EGF, KGF, KGF-2, and apoptotic cells), and zymography (MMP-2 and -9). One-way ANOVAs with Tukey-Kramer post tests were used for statistical analyses. Results Animals treated with pH 7 and 9 solutions showed clear visual improvements. pH 9 solutions resulted in the most significant reductions in erythema and oedema scores. pH 4 and 7 solutions also reduced oedema scores. Histologically, all treatment groups demonstrated enhanced re-epithelialisation, with decreased inflammation. At 24 h, pMMP-2 expression was significantly lowered with pH 5.6 and 9 treatments, as was aMMP-2 expression with pH 9 treatments. In general, treatment with silver-containing solutions resulted in decreased TNF-α and IL-8 expression, with increased IL-4, EGF, KGF, and KGF-2 expression. At 24 h, apoptotic cells were detected mostly in the dermis with pH 4 and 9 treatments, nowhere with pH 5.6, and in both the epidermis and dermis

A general higher-order nonlocal couple stress based beam model for vibration analysis of porous nanocrystalline nanobeams

NASA Astrophysics Data System (ADS)

Ebrahimi, Farzad; Barati, Mohammad Reza

2017-12-01

This paper develops a higher order refined beam model with a parabolic shear strain function for vibration analysis of porous nanocrystalline nanobeams based on nonlocal couple stress theory. Nanocrystalline nanobeam is composed from three phases which are nano-grains, nano-voids and interface. Nano-voids or porosities inside the material have a stiffness-softening impact on the nanobeam. Nonlocal elasticity theory of Eringen is applied in analysis of nanocrystalline nanobeams for the first time. Also, modified couple stress theory is employed to capture grains rigid rotations. The governing equations obtained from Hamilton's principle are solved applying an analytical approach which satisfies various boundary conditions. The reliability of present approach is verified by comparing obtained results with those provided in literature. Finally the influences of nonlocal parameter, couple stress, grain size, porosities and shear deformation on the vibration characteristics of nanocrystalline nanobeams are explored.

Understanding the low temperature electrical properties of nanocrystalline tin oxide for gas sensor applications

NASA Astrophysics Data System (ADS)

Drake, Christina Hartsell

Nanocrystalline metal/metal oxide is an important class of transparent and electronic materials due to its potential use in many applications, including gas sensors. At the nanoscale, many of the phenomena observed that give nanocrystalline semiconducting oxide enhanced performance as a gas sensor material over other conventional engineering materials is still poorly understood. This study is aimed at understanding the low temperature electrical and chemical properties of nanocrystalline SnO2 that makes it suitable for room temperature gas detectors. Studies were carried out in order to understand how various synthesis methods affect the surfaces on the nano-oxides, interactions of a target gas (in this study hydrogen) with different surface species, and changes in the electrical properties as a function of dopants and grain size. A correlation between the surface reactions and the electrical response of doped nanocrystalline metal-oxide-semiconductors exposed to a reducing gas is established using Fourier Transform Infrared (FTIR) Spectroscopy attached to a specially built custom designed catalytic cell. First principle calculations of oxygen vacancy concentrations from absorbance spectra are presented. FTIR is used for effectively screening of these nanostructures for gas sensing applications. The effect of processing temperature on the microstructural evolution and on the electronic properties of nanocrystalline trivalent doped-SnO 2 is also presented. This study includes the effect of dopants (In and Ce) on the growth of nano-SnO2, as well as their effects on the electronic properties and gas sensor behavior of the nanomaterial at room temperature. Band bending affects are also investigated for this system and are related to enhanced low temperature gas sensing. The role and importance of oxygen vacancies in the electronic and chemical behavior of surface modified nanocrystalline SnO2 are explored in this study. A generalized explanation for the low temperature

Functional materials based on nanocrystalline cellulose

NASA Astrophysics Data System (ADS)

Surov, O. V.; Voronova, M. I.; Zakharov, A. G.

2017-10-01

The data on the synthesis of functional materials based on nanocrystalline cellulose (NCC) published over the past 10 years are analyzed. The liquid-crystal properties of NCC suspensions, methods of investigation of NCC suspensions and films, conditions for preserving chiral nematic structure in the NCC films after removal of the solvent and features of templated sol-gel synthesis of functional materials based on NCC are considered. The bibliography includes 106 references.

Controlled removal of ceramic surfaces with combination of ions implantation and ultrasonic energy

DOEpatents

Boatner, Lynn A.; Rankin, Janet; Thevenard, Paul; Romana, Laurence J.

1995-01-01

A method for tailoring or patterning the surface of ceramic articles is provided by implanting ions to predetermined depth into the ceramic material at a selected surface location with the ions being implanted at a fluence and energy adequate to damage the lattice structure of the ceramic material for bi-axially straining near-surface regions of the ceramic material to the predetermined depth. The resulting metastable near-surface regions of the ceramic material are then contacted with energy pulses from collapsing, ultrasonically-generated cavitation bubbles in a liquid medium for removing to a selected depth the ion-damaged near-surface regions containing the bi-axially strained lattice structure from the ceramic body. Additional patterning of the selected surface location on the ceramic body is provided by implanting a high fluence of high-energy, relatively-light ions at selected surface sites for relaxing the bi-axial strain in the near-surface regions defined by these sites and thereby preventing the removal of such ion-implanted sites by the energy pulses from the collapsing ultrasonic cavitation bubbles.

Efficient Second-Harmonic Generation in Nanocrystalline Silicon Nanoparticles.

PubMed

Makarov, Sergey V; Petrov, Mihail I; Zywietz, Urs; Milichko, Valentin; Zuev, Dmitry; Lopanitsyna, Natalia; Kuksin, Alexey; Mukhin, Ivan; Zograf, George; Ubyivovk, Evgeniy; Smirnova, Daria A; Starikov, Sergey; Chichkov, Boris N; Kivshar, Yuri S

2017-05-10

Recent trends to employ high-index dielectric particles in nanophotonics are motivated by their reduced dissipative losses and large resonant enhancement of nonlinear effects at the nanoscale. Because silicon is a centrosymmetric material, the studies of nonlinear optical properties of silicon nanoparticles have been targeting primarily the third-harmonic generation effects. Here we demonstrate, both experimentally and theoretically, that resonantly excited nanocrystalline silicon nanoparticles fabricated by an optimized laser printing technique can exhibit strong second-harmonic generation (SHG) effects. We attribute an unexpectedly high yield of the nonlinear conversion to a nanocrystalline structure of nanoparticles supporting the Mie resonances. The demonstrated efficient SHG at green light from a single silicon nanoparticle is 2 orders of magnitude higher than that from unstructured silicon films. This efficiency is significantly higher than that of many plasmonic nanostructures and small silicon nanoparticles in the visible range, and it can be useful for a design of nonlinear nanoantennas and silicon-based integrated light sources.

Fabrication of a metal-ceramic crown to fit an existing partial removable dental prosthesis using ceramic pressed to metal technique: a clinical report

PubMed Central

Seo, Jae-Min

2014-01-01

Fabricating a crown to retrofit an existing abutment tooth for a partial removable dental prosthesis (PRDP) is one of the most time-consuming and labor-intensive clinical procedures. In particular, when the patient is concerned with esthetic aspects of restoration, the task of fabricating becomes more daunting. Many techniques for the fabrication of all-metallic or metal-ceramic crowns have been discussed in the literature. This article was aimed to describe a simple fabrication method in which a retrofitting crown was fabricated for a precise fit using a ceramic-pressed-to-metal system. PMID:25006389

High temperature ceramics for automobile gas turbines. Part 2: Development of ceramic components

NASA Technical Reports Server (NTRS)

Walzer, P.; Koehler, M.; Rottenkolber, P.

1978-01-01

The development of ceramic components for automobile gas turbine engines is described with attention given to the steady and unsteady thermal conditions the ceramics will experience, and their anti-corrosion and strain-resistant properties. The ceramics considered for use in the automobile turbines include hot-pressed Si3N4, reaction-sintered, isostatically pressed Si3N4, hot-pressed SiC, reaction-bonded SiC, and glass ceramics. Attention is given to the stress analysis of ceramic structures and the state of the art of ceramic structural technology is reviewed, emphasizing the use of ceramics for combustion chambers and ceramic shrouded turbomachinery (a fully ceramic impeller).

Influence of Weak External Magnetic Field on Amorphous and Nanocrystalline Fe-based Alloys

NASA Astrophysics Data System (ADS)

Degmová, J.; Sitek, J.

2010-07-01

Nanoperm, Hitperm and Finamet amorphous and nanocrystalline alloys were measured by Mössbauer spectrometry in a weak external magnetic field of 0.5 T. It was shown that the most sensitive parameters of Mössbauer spectra are the intensities of the 2nd and the 5th lines. Rather small changes were observed also in the case of internal magnetic field values. The spectrum of nanocrystalline Nanoperm showed the increase in A23 parameter (ratio of line intensities) from 2.4 to 3.7 and decrease of internal magnetic field from 20 to 19 T for amorphous subspectrum under the influence of magnetic field. Spectrum of nanocrystalline Finemet shown decrease in A23 parameter from 3.5 to 2.6 almost without a change in the internal magnetic field value. In the case of amorphous Nanoperm and Finemet samples, the changes are almost negligible. Hitperm alloy showed the highest sensitivity to the weak magnetic field, when the A23 parameter increased from 0.4 to 2.5 in the external magnetic fields. The A23 parameter of crystalline subspectrum increased from 2.7 to 3.8 and the value of internal magnetic field corresponding to amorphous subspectrum increased from 22 to 24 T. The behavior of nanocrystalline alloys under weak external magnetic field was analyzed within the three-level relaxation model of magnetic dynamics in an assembly of single-domain particles.

Comparison of the load at fracture of Turkom-Cera to Procera AllCeram and In-Ceram all-ceramic restorations.

PubMed

AL-Makramani, Bandar M A; Razak, Abdul A A; Abu-Hassan, Mohamed I

2009-08-01

This study investigated the occlusal fracture resistance of Turkom-Cerafused alumina compared to Procera AllCeram and In-Ceram all-ceramic restorations. Sixmaster dies were duplicated from the prepared maxillary first premolar tooth using nonprecious metal alloy (Wiron 99). Ten copings of 0.6 mm thickness were fabricated from each type of ceramic, for a total of thirty copings. Two master dies were used for each group, and each of them was used to lute five copings. All groups were cemented with resin luting cement Panavia F according to manufacturer's instructions and received a static load of 5 kg during cementation. After 24 hours of distilled water storage at 37 degrees C, the copings were vertically compressed using a universal testing machine at a crosshead speed of 1 mm/min. The results of the present study showed the following mean loads at fracture: Turkom-Cera (2184 +/- 164 N), In-Ceram (2042 +/- 200 N), and Procera AllCeram (1954 +/- 211 N). ANOVA and Scheffe's post hoc test showed that the mean load at fracture of Turkom-Cera was significantly different from Procera AllCeram (p < 0.05). Scheffe's post hoc test showed no significant difference between the mean load at fracture of Turkom-Cera and In-Ceram or between the mean load at fracture of In-Ceram and Procera AllCeram. Because Turkom-Cera demonstrated equal to or higher loads at fracture than currently accepted all-ceramic materials, it would seem to be acceptable for fabrication of anterior and posterior ceramic crowns.

Optical properties of transparent glass–ceramics containing lithium–mica nanocrystals: Crystallization effect

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

Khani, V.; Alizadeh, P., E-mail: p-alizadeh@modares.ac.ir; Shakeri, M.S.

2013-09-01

Graphical abstract: Optical properties of transparent Li{sub 2}O–MgO–Al{sub 2}O{sub 3}–SiO{sub 2}–F glasses containing lithium–mica nanocrystals are studied and crystallization condition has been evaluated and optimized to produce transparent glass–ceramics. Crystallization temperatures were determined by differential thermal analysis and crystalline phases were identified and quantified by X-ray diffraction. Scanning electron microscopy was used for morphological variations and UV–vis absorption spectroscopy for comparative analysis of transparency. In order to investigate the optical properties of transparent glass–ceramics, optical band gap, Fermi energy level and Urbach energy are calculated. The results of the investigation illustrate that band gap is reduced with increases in crystallizationmore » time and temperature. Enhanced orderliness in the arrangement of atoms might be regarded as possible reasons for the above changes. - Highlights: • The optimum temperature and time of crystallization were determined. • Li–mica nanocrystals with size of <30 nm were formed using a two-step heat-treatment. • Optical band gap and Fermi energy of nanocrystalline materials decreased with increasing of crystallization temperature and time. • Urbach band tailing was decreased with increasing of crystallization condition. - Abstract: Optical properties of transparent Li{sub 2}O–MgO–Al{sub 2}O{sub 3}–SiO{sub 2}–F glasses containing lithium–mica nanocrystals were studied. The crystallization condition of these glasses was evaluated and optimized to produce transparent glass–ceramics. Crystallization temperatures were determined by differential thermal analysis and crystalline phases were identified and quantified by X-ray diffraction. Scanning electron microscopy was used to detect morphological changes and UV–vis absorption spectroscopy was used for comparative analysis of transparency. In order to investigate the optical properties

Ceramic-ceramic shell tile thermal protection system and method thereof

NASA Technical Reports Server (NTRS)

Riccitiello, Salvatore R. (Inventor); Smith, Marnell (Inventor); Goldstein, Howard E. (Inventor); Zimmerman, Norman B. (Inventor)

1986-01-01

A ceramic reusable, externally applied composite thermal protection system (TPS) is proposed. The system functions by utilizing a ceramic/ceramic upper shell structure which effectively separates its primary functions as a thermal insulator and as a load carrier to transmit loads to the cold structure. The composite tile system also prevents impact damage to the atmospheric entry vehicle thermal protection system. The composite tile comprises a structurally strong upper ceramic/ceramic shell manufactured from ceramic fibers and ceramic matrix meeting the thermal and structural requirements of a tile used on a re-entry aerospace vehicle. In addition, a lightweight high temperature ceramic lower temperature base tile is used. The upper shell and lower tile are attached by means effective to withstand the extreme temperatures (3000 to 3200F) and stress conditions. The composite tile may include one or more layers of variable density rigid or flexible thermal insulation. The assembly of the overall tile is facilitated by two or more locking mechanisms on opposing sides of the overall tile assembly. The assembly may occur subsequent to the installation of the lower shell tile on the spacecraft structural skin.

Remediation of arsenic and lead with nanocrystalline zinc sulfide.

PubMed

Piquette, Alan; Cannon, Cody; Apblett, Allen W

2012-07-27

Nanocrystalline (1.7 ± 0.3 nm) zinc sulfide with a specific surface area up to 360 m(2) g(-1) was prepared from the thermal decomposition of a single-source precursor, zinc ethylxanthate. Zinc ethylxanthate decomposes to cubic zinc sulfide upon exposure to temperatures greater than or equal to 125 °C. The resulting zinc sulfide was tested as a water impurity extractant. The target impurities used in this study were As(5+), As(3+), and Pb(2+). The reaction of the nanocrystalline ZnS with Pb(2+) proceeds as a replacement reaction where solid PbS is formed and Zn(2+) is released into the aqueous system. Removal of lead to a level of less than two parts per billion is achievable. The results of a detailed kinetics experiment between the ZnS and Pb(2+) are included in this study. Unlike the instance of lead, both As(5+) and As(3+) adsorb on the surface of the ZnS extractant as opposed to an ion-exchange process. An uptake capacity of > 25 mg g(-1) for the removal of As(5+) is possible. The uptake of As(3+) appears to proceed by a slower process than that of the As(5+) with a capacity of nearly 20 mg g(-1). The nanocrystalline zinc sulfide was extremely successful for the removal of arsenic and lead from simulated oil sand tailing pond water.

Solid state amorphization of nanocrystalline nickel by cryogenic laser shock peening

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

Ye, Chang, E-mail: cye@uakron.edu; Ren, Zhencheng; Zhao, Jingyi

2015-10-07

In this study, complete solid state amorphization in nanocrystalline nickel has been achieved through cryogenic laser shock peening (CLSP). High resolution transmission electron microscopy has revealed the complete amorphous structure of the sample after CLSP processing. A molecular dynamic model has been used to investigate material behavior during the shock loading and the effects of nanoscale grain boundaries on the amorphization process. It has been found that the initial nanoscale grain boundaries increase the initial Gibbs free energy before plastic deformation and also serve as dislocation emission sources during plastic deformation to contribute to defect density increase, leading to themore » amorphization of pure nanocrystalline nickel.« less

Ceramic ware waste as coarse aggregate for structural concrete production.

PubMed

García-González, Julia; Rodríguez-Robles, Desirée; Juan-Valdés, Andrés; Morán-Del Pozo, Julia M; Guerra-Romero, M Ignacio

2015-01-01

The manufacture of any kind of product inevitably entails the production of waste. The quantity of waste generated by the ceramic industry, a very important sector in Spain, is between 5% and 8% of the final output and it is therefore necessary to find an effective waste recovery method. The aim of the study reported in the present article was to seek a sustainable means of managing waste from the ceramic industry through the incorporation of this type of waste in the total replacement of conventional aggregate (gravel) used in structural concrete. Having verified that the recycled ceramic aggregates met all the technical requirements imposed by current Spanish legislation, established in the Code on Structural Concrete (EHE-08), then it is prepared a control concrete mix and the recycled concrete mix using 100% recycled ceramic aggregate instead of coarse natural aggregate. The concretes obtained were subjected to the appropriate tests in order to conduct a comparison of their mechanical properties. The results show that the concretes made using ceramic sanitary ware aggregate possessed the same mechanical properties as those made with conventional aggregate. It is therefore possible to conclude that the reuse of recycled ceramic aggregate to produce recycled concrete is a feasible alternative for the sustainable management of this waste.

Probing nanocrystalline grain dynamics in nanodevices

PubMed Central

Yeh, Sheng-Shiuan; Chang, Wen-Yao; Lin, Juhn-Jong

2017-01-01

Dynamical structural defects exist naturally in a wide variety of solids. They fluctuate temporally and hence can deteriorate the performance of many electronic devices. Thus far, the entities of these dynamic objects have been identified to be individual atoms. On the other hand, it is a long-standing question whether a nanocrystalline grain constituted of a large number of atoms can switch, as a whole, reversibly like a dynamical atomic defect (that is, a two-level system). This is an emergent issue considering the current development of nanodevices with ultralow electrical noise, qubits with long quantum coherence time, and nanoelectromechanical system sensors with ultrahigh resolution. We demonstrate experimental observations of dynamic nanocrystalline grains that repeatedly switch between two or more metastable coordinate states. We study temporal resistance fluctuations in thin ruthenium dioxide (RuO2) metal nanowires and extract microscopic parameters, including relaxation time scales, mobile grain sizes, and the bonding strengths of nanograin boundaries. These material parameters are not obtainable by other experimental approaches. When combined with previous in situ high-resolution transmission electron microscopy, our electrical method can be used to infer rich information about the structural dynamics of a wide variety of nanodevices and new two-dimensional materials. PMID:28691094

Raman and dielectric studies of GdMnO3 bulk ceramics synthesized from nano powders

NASA Astrophysics Data System (ADS)

Samantaray, S.; Mishra, D. K.; Roul, B. K.

2017-05-01

Nanocrystalline GdMnO3 (GMO) powders has been synthesized by a simple chemical route i. e. pyrophoric reaction technique and then sintered in the form of bulk pellet at 850°C for 24 hours by adopting slow step sintering schedule. It is observed that by reducing the particles size, chemical route enhances the mixing process as well as decreasing the sintering temperature to get single phase material system in compared to the polycrystalline sample prepared directly from the micron sized commercial powder. Raman spectroscopic studies confirm that the sample is in single phase without any detectable impurity. Frequency dependent dielectric properties i.e., dielectric constant (K) and dielectric loss (tanδ) of GMO ceramics sintered at 850°C for 24 hours were studied at room temperature. The sample showed high K value (˜2736) in the frequency of 100 Hz at room temperature.

Subtractive Plasma-Assisted-Etch Process for Developing High Performance Nanocrystalline Zinc-Oxide Thin-Film-Transistors

DTIC Science & Technology

2015-03-26

THIN - FILM - TRANSISTORS THESIS Thomas M. Donigan, First Lieutenant, USAF AFIT-ENG-MS-15-M-027 DEPARTMENT OF THE AIR FORCE AIR UNIVERSITY AIR...DEVELOPING HIGH PERFORMANCE NANOCRYSTALLINE ZINC-OXIDE THIN - FILM - TRANSISTORS THESIS Presented to the Faculty Department of Electrical and...15-M-027 SUBTRACTIVE PLASMA-ASSISTED-ETCH PROCESS FOR DEVELOPING HIGH PERFORMANCE NANOCRYSTALLINE ZINC-OXIDE THIN - FILM - TRANSISTORS

Integrally cored ceramic investment casting mold fabricated by ceramic stereolithography

NASA Astrophysics Data System (ADS)

Bae, Chang-Jun

Superalloy airfoils are produced by investment casting (IC), which uses ceramic cores and wax patterns with ceramic shell molds. Hollow cored superalloy airfoils in a gas turbine engine are an example of complex IC parts. The complex internal hollow cavities of the airfoil are designed to conduct cooling air through one or more passageways. These complex internal passageways have been fabricated by a lost wax process requiring several processing steps; core preparation, injection molding for wax pattern, and dipping process for ceramic shell molds. Several steps generate problems such as high cost and decreased accuracy of the ceramic mold. For example, costly tooling and production delay are required to produce mold dies for complex cores and wax patterns used in injection molding, resulting in a big obstacle for prototypes and smaller production runs. Rather than using separate cores, patterns, and shell molds, it would be advantageous to directly produce a mold that has the casting cavity and the ceramic core by one process. Ceramic stereolithography (CerSLA) can be used to directly fabricate the integrally cored ceramic casting mold (ICCM). CerSLA builds ceramic green objects from CAD files from many thin liquid layers of powder in monomer, which are solidified by polymerization with a UV laser, thereby "writing" the design for each slice. This dissertation addresses the integrally cored casting ceramic mold (ICCM), the ceramic core with a ceramic mold shell in a single patternless construction, fabricated by ceramic stereolithography (CerSLA). CerSLA is considered as an alternative method to replace lost wax processes, for small production runs or designs too complex for conventional cores and patterns. The main topic is the development of methods to successfully fabricate an ICCM by CerSLA from refractory silica, as well as related issues. The related issues are the segregation of coarse fused silica powders in a layer, the degree of segregation parameter to

Grain boundary character distribution in nanocrystalline metals produced by different processing routes

DOE PAGES

Bober, David B.; Kumar, Mukal; Rupert, Timothy J.; ...

2015-12-28

Nanocrystalline materials are defined by their fine grain size, but details of the grain boundary character distribution should also be important. Grain boundary character distributions are reported for ball-milled, sputter-deposited, and electrodeposited Ni and Ni-based alloys, all with average grain sizes of ~20 nm, to study the influence of processing route. The two deposited materials had nearly identical grain boundary character distributions, both marked by a Σ3 length percentage of 23 to 25 pct. In contrast, the ball-milled material had only 3 pct Σ3-type grain boundaries and a large fraction of low-angle boundaries (16 pct), with the remainder being predominantlymore » random high angle (73 pct). Furthermore, these grain boundary character measurements are connected to the physical events that control their respective processing routes. Consequences for material properties are also discussed with a focus on nanocrystalline corrosion. As a whole, the results presented here show that grain boundary character distribution, which has often been overlooked in nanocrystalline metals, can vary significantly and influence material properties in profound ways.« less

Effects of Bi Addition on the Microstructure and Mechanical Properties of Nanocrystalline Ag Coatings.

PubMed

Wang, Yuxin; Cheng, Guang; Tay, See Leng; Guo, Yunxia; Sun, Xin; Gao, Wei

2017-08-10

In this study we investigated the effects of Bi addition on the microstructure and mechanical properties of an electrodeposited nanocrystalline Ag coating. Microstructural features were investigated with transmission electron microscopy (TEM). The results indicate that the addition of Bi introduced nanometer-scale Ag-Bi solid solution particles and more internal defects to the initial Ag microstructures. The anisotropic elastic-plastic properties of the Ag nanocrystalline coating with and without Bi addition were examined with nanoindentation experiments in conjunction with the recently-developed inverse method. The results indicate that the as-deposited nanocrystalline Ag coating contained high mechanical anisotropy. With the addition of 1 atomic percent (at%) Bi, the anisotropy within Ag-Bi coating was very small, and yield strength of the nanocrystalline Ag-Bi alloy in both longitudinal and transverse directions were improved by over 100% compared to that of Ag. On the other hand, the strain-hardening exponent of Ag-Bi was reduced to 0.055 from the original 0.16 of the Ag coating. Furthermore, the addition of Bi only slightly increased the electrical resistivity of the Ag-Bi coating in comparison to Ag. Results of our study indicate that Bi addition is a promising method for improving the mechanical and physical performances of Ag coating for electrical contacts.

Addition of a pontic to all-ceramic Turkom-Cera fixed partial denture restorations

PubMed Central

Uludag, Bulent; Tokar, Emre; Polat, Serdar

2013-01-01

High-strength all-ceramic materials are commonly used in dentistry. When complications occur in an all-ceramic restoration, the restoration is usually replaced. This article describes the time-saving ability and cost-effectiveness of this novel technique for the addition of a pontic in two complicated clinical cases. Turkom-Cera™ [Turkom-Ceramic (M) Sdn. Bhd.] with aluminum oxide (99.98%) is an all-ceramic system that offers the option of addition of a new pontic to the sintered framework. The new pontic was cut off from an alumina blank [Turkom-Ceramic (M) Sdn. Bhd.], moistened, and attached to the framework using alumina gel [Turkom-Ceramic (M) Sdn. Bhd.]. The framework was veneered with veneering porcelain (Vita VM 7; VITA Zahnfabrik). The two cases presented here involving the addition of a pontic to sintered framework were followed up for at least 1 year. No complication was detected or reported by the patients. Alumina- and zirconia-based ceramics are particularly suitable for for all-ceramic restorations in high-stress bearing areas. However, replacement of a failed all-ceramic restoration is not the most practical solution, considering both cost and tooth-related factors. This attractive feature of the Turkom-Cera allows the repair of a fractured ceramic coping or the addition of a new pontic to restorations. PMID:24883033

Durability of feldspathic veneering ceramic on glass-infiltrated alumina ceramics after long-term thermocycling.

PubMed

Mesquita, A M M; Ozcan, M; Souza, R O A; Kojima, A N; Nishioka, R S; Kimpara, E T; Bottino, M A

2010-01-01

This study compared the bond strength durability of a feldspathic veneering ceramic to glass-infiltrated reinforced ceramics in dry and aged conditions. Disc shaped (thickness: 4 mm, diameter: 4 mm) of glass-infiltrated alumina (In-Ceram Alumina) and glass-infiltrated alumina reinforced by zirconia (In-Ceram Zirconia) core ceramic specimens (N=48, N=12 per groups) were constructed according to the manufacturers' recommendations. Veneering ceramic (VITA VM7) was fired onto the core ceramics using a mold. The core-veneering ceramic assemblies were randomly divided into two conditions and tested either immediately after specimen preparation (Dry) or following 30000 thermocycling (5-55 ºC±1; dwell time: 30 seconds). Shear bond strength test was performed in a universal testing machine (cross-head speed: 1 mm/min). Failure modes were analyzed using optical microscope (x20). The bond strength data (MPa) were analyzed using ANOVA (α=0.05). Thermocycling did not decrease the bond strength results for both In-Ceram Alumina (30.6±8.2 MPa; P=0.2053) and In-Ceram zirconia (32.6±9 MPa; P=0.3987) core ceramic-feldspathic veneering ceramic combinations when compared to non-aged conditions (28.1±6.4 MPa, 29.7±7.3 MPa, respectively). There were also no significant differences between adhesion of the veneering ceramic to either In-Ceram Alumina or In-Ceram Zirconia ceramics (P=0.3289). Failure types were predominantly a mixture of adhesive failure between the veneering and the core ceramic together with cohesive fracture of the veneering ceramic. Long-term thermocycling aging conditions did not impair the adhesion of the veneering ceramic to the glass-infiltrated alumina core ceramics tested.

Comparative study on corrosion resistance and in vitro biocompatibility of bulk nanocrystalline and microcrystalline biomedical 304 stainless steel.

PubMed

Nie, F L; Wang, S G; Wang, Y B; Wei, S C; Zheng, Y F

2011-07-01

SUS 304 stainless steels have been widely used in orthodontics and implants such as archwires, brackets, and screws. The purpose of present study was to investigate the biocompatibility of both the commercial microcrystalline biomedical 304 stainless steel (microcrystalline 304ss) and novel-fabricated nanocrystalline 304 stainless steel (nanocrystalline 304ss). Bulk nanocrystalline 304ss sheets had been successfully prepared by microcrystalline 304ss plates using severe rolling technique. The electrochemical corrosion and ion release behavior immersion in artificial saliva were measured to evaluate the property of biocorrosion in oral environment. The cell lines of murine and human cell lines from oral and endothelial environment were co-cultured with extracts to evaluate the cytotoxicity and provide referential evidence in vivo. The polarization resistance trials indicated that nanocrystalline 304ss is more corrosion resistant than the microcrystalline 304ss in oral-like environment with higher corrosion potential, and the amount of toxic ions released into solution after immersion is lower than that of the microcrystalline 304ss and the daily dietary intake level. The cytotoxicity results also elucidated that nanocrystalline 304ss is biologically compatible in vitro, even better than that of microcrystalline 304ss. Based on the much higher mechanical and physical performances, nanocrystalline 304ss with enhanced biocorrosion property, well-behaved in vitro cytocompatibility can be a promising alternative in orthodontics and fixation fields in oral cavity. Copyright © 2011 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Ceramic-on-ceramic bearing fractures in total hip arthroplasty: an analysis of data from the National Joint Registry.

PubMed

Howard, D P; Wall, P D H; Fernandez, M A; Parsons, H; Howard, P W

2017-08-01

risk of ceramic bearing fracture. Cite this article: Bone Joint J 2017;99-B:1012-19. ©2017 The British Editorial Society of Bone & Joint Surgery.

Solution-processed nanocrystalline PbS on paper substrate with pencil traced electrodes as visible photodetector

NASA Astrophysics Data System (ADS)

Vankhade, Dhaval; Chaudhuri, Tapas K.

2018-04-01

Paper-based PbS photodetector sensitive in the visible spectrum is reported. Nanocrystalline PbS-on-paper devices are fabricated by a spin coating method on white paper (300 GSM) from a methanolic precursor solution. Photodetector cells of gap 0.2 cm and length 0.5 cm are prepared by drawing contacts by monolithic cretacolor 8B pencil. X-ray diffractometer confirmed the deposition of nanocrystalline PbS films with 14 nm crystallites. The SEM illustrated the uniform coating of nanocrystalline PbS thin films on cellulose fibres of papers having an average thickness of fibres are 10 µm. The linear J-V characteristics in dark and under illumination of light using graphite trace on nanocrystalline PbS-on-paper shows good ohmic contact. The resistivity of pencil trace is 30 Ω.cm. Spectral response measurements of photodetector reveal the excellent sensitivity from 400 to 700 nm with a peak at 550 nm. The best responsivity anddetectivity are 0.7 A/W and 1.4 × 1012 Jones respectively. These paper-based low-cost photodetectors devices have fast photoresponse and recovery without baseline deviation.

Thermal transport in nanocrystalline Si and SiGe by ab initio based Monte Carlo simulation.

PubMed

Yang, Lina; Minnich, Austin J

2017-03-14

Nanocrystalline thermoelectric materials based on Si have long been of interest because Si is earth-abundant, inexpensive, and non-toxic. However, a poor understanding of phonon grain boundary scattering and its effect on thermal conductivity has impeded efforts to improve the thermoelectric figure of merit. Here, we report an ab-initio based computational study of thermal transport in nanocrystalline Si-based materials using a variance-reduced Monte Carlo method with the full phonon dispersion and intrinsic lifetimes from first-principles as input. By fitting the transmission profile of grain boundaries, we obtain excellent agreement with experimental thermal conductivity of nanocrystalline Si [Wang et al. Nano Letters 11, 2206 (2011)]. Based on these calculations, we examine phonon transport in nanocrystalline SiGe alloys with ab-initio electron-phonon scattering rates. Our calculations show that low energy phonons still transport substantial amounts of heat in these materials, despite scattering by electron-phonon interactions, due to the high transmission of phonons at grain boundaries, and thus improvements in ZT are still possible by disrupting these modes. This work demonstrates the important insights into phonon transport that can be obtained using ab-initio based Monte Carlo simulations in complex nanostructured materials.

Thermal transport in nanocrystalline Si and SiGe by ab initio based Monte Carlo simulation

PubMed Central

Yang, Lina; Minnich, Austin J.

2017-01-01

Nanocrystalline thermoelectric materials based on Si have long been of interest because Si is earth-abundant, inexpensive, and non-toxic. However, a poor understanding of phonon grain boundary scattering and its effect on thermal conductivity has impeded efforts to improve the thermoelectric figure of merit. Here, we report an ab-initio based computational study of thermal transport in nanocrystalline Si-based materials using a variance-reduced Monte Carlo method with the full phonon dispersion and intrinsic lifetimes from first-principles as input. By fitting the transmission profile of grain boundaries, we obtain excellent agreement with experimental thermal conductivity of nanocrystalline Si [Wang et al. Nano Letters 11, 2206 (2011)]. Based on these calculations, we examine phonon transport in nanocrystalline SiGe alloys with ab-initio electron-phonon scattering rates. Our calculations show that low energy phonons still transport substantial amounts of heat in these materials, despite scattering by electron-phonon interactions, due to the high transmission of phonons at grain boundaries, and thus improvements in ZT are still possible by disrupting these modes. This work demonstrates the important insights into phonon transport that can be obtained using ab-initio based Monte Carlo simulations in complex nanostructured materials. PMID:28290484

Structural Ceramics

NASA Technical Reports Server (NTRS)

1986-01-01

This publication is a compilation of abstracts and slides of papers presented at the NASA Lewis Structural Ceramics Workshop. Collectively, these papers depict the scope of NASA Lewis' structural ceramics program. The technical areas include monolithic SiC and Si3N4 development, ceramic matrix composites, tribology, design methodology, nondestructive evaluation (NDE), fracture mechanics, and corrosion.

Fluid casting of particle-based articles

DOEpatents

Menchhofer, Paul

1995-01-01

A method for the production of articles made of a particle-based material; e.g., ceramics and sintered metals. In accordance with one aspect of the invention, a thermally settable slurry containing a relatively high concentration of the particles is introduced into an immiscible, heated fluid. The slurry sets or hardens into a shape determined by the physical characteristics of the fluid and the manner of introduction of the slurry into the fluid. For example, the slurry is pulse injected into the fluid to provide spherical articles. The hardened spheres may then be sintered to consolidate the particles and provide a high density product.

Fluid casting of particle-based articles

DOEpatents

Menchhofer, P.

1995-03-28

A method is disclosed for the production of articles made of a particle-based material; e.g., ceramics and sintered metals. In accordance with one aspect of the invention, a thermally settable slurry containing a relatively high concentration of the particles is introduced into an immiscible, heated fluid. The slurry sets hardens into a shape determined by the physical characteristics of the fluid and the manner of introduction of the slurry into the fluid. For example, the slurry is pulse injected into the fluid to provide spherical articles. The hardened spheres may then be sintered to consolidate the particles and provide a high density product. 1 figure.

The Effects of an Unexpected Ceramic Coating Phase at the Head of a Pipe on Joining and Postprocessing of a Ceramic-Lined Composite Pipe

NASA Astrophysics Data System (ADS)

Mahmoodian, R.; Rahbari, R. G.; Hamdi, M.; Hassan, M. A.; Sparham, Mahdi

2013-01-01

Produced ceramic-lined steel pipe using the self-propagating high-temperature synthesis (SHS) method has found uses in many applications. A SHS-centrifugal machine was designed to produce a ceramic-lined steel pipe from ferric oxide and aluminum powder (thermite mixture) under high centrifugal acceleration. The obtained products are expected to be Al2O3 ceramic in the innermost layer and a Fe layer in a region between the outer steel pipes. In the present work, specific regions of a pipe was particularly observed to investigate the stuck (dead) spaces at the pipe head because of its importance in further processes (joining, welding, etc.) which may affect the quality of the next operations. In this article, the product's composition, phase separation, microhardness, and surface finish were studied on three zones of the pipe.

Ceramic-glass-ceramic seal by microwave heating

DOEpatents

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

1983-10-04

A method for producing a ceramic-glass-ceramic seal by microwaving, mixes a slurry of glass sealing material and coupling agent and applies same to ceramic workpieces. The slurry and workpieces are placed together, insulated and then microwaved at a power, time and frequency sufficient to cause a liquid phase reaction in the slurry. The reaction of the glass sealing material forms a chemically different seal than that which would be formed by conventional heating because it is formed by a diffusion rather than by wetting of the reactants.

Ceramic-glass-ceramic seal by microwave heating

DOEpatents

Meek, Thomas T.; Blake, Rodger D.

1985-01-01

A method for producing a ceramic-glass-ceramic seal by microwaving, mixes a slurry of glass sealing material and coupling agent and applies same to ceramic workpieces. The slurry and workpieces are placed together, insulated and then microwaved at a power, time and frequency sufficient to cause a liquid phase reaction in the slurry. The reaction of the glass sealing material forms a chemically different seal than that which would be formed by conventional heating because it is formed by a diffusion rather than by wetting of the reactants.

Ceramic Stereolithography: Additive Manufacturing for Ceramics by Photopolymerization

NASA Astrophysics Data System (ADS)

Halloran, John W.

2016-07-01

Ceramic stereolithography and related additive manufacturing methods involving photopolymerization of ceramic powder suspensions are reviewed in terms of the capabilities of current devices. The practical fundamentals of the cure depth, cure width, and cure profile are related to the optical properties of the monomer, ceramic, and photo-active components. Postpolymerization steps, including harvesting and cleaning the objects, binder burnout, and sintering, are discussed and compared with conventional methods. The prospects for practical manufacturing are discussed.

Ingot selection for aesthetic restorations using contemporary pressed ceramics.

PubMed

Ritter, Robert G; Culp, Lee

2002-08-01

Accurate communication among the patient, clinician, and laboratory technician is critical to the development of a functional, aesthetic restoration. The use of pressed ceramic restorations has provided a durable, consistent alternative for full-coverage crowns, veneers, onlays, and short-span fixed partial dentures. This article discusses the importance of proper ingot selection in the fabrication of aesthetic restorations and in the realization of patients' expectations for smile design. Ceramic ingots are available in a variety of colors and opacities that provide the clinician and laboratory technician with the latitude to select an ingot that will ultimately ensure patient satisfaction.

Properties of nanocrystalline Si layers embedded in structure of solar cell

NASA Astrophysics Data System (ADS)

Jurečka, Stanislav; Imamura, Kentaro; Matsumoto, Taketoshi; Kobayashi, Hikaru

2017-12-01

Suppression of spectral reflectance from the surface of solar cell is necessary for achieving a high energy conversion efficiency. We developed a simple method for forming nanocrystalline layers with ultralow reflectance in a broad range of wavelengths. The method is based on metal assisted etching of the silicon surface. In this work, we prepared Si solar cell structures with embedded nanocrystalline layers. The microstructure of embedded layer depends on the etching conditions. We examined the microstructure of the etched layers by a transmission electron microscope and analysed the experimental images by statistical and Fourier methods. The obtained results provide information on the applied treatment operations and can be used to optimize the solar cell forming procedure.

Solvothermal synthesis of nanocrystalline TiO 2 in toluene with surfactant

NASA Astrophysics Data System (ADS)

Kim, Chung-Sik; Moon, Byung Kee; Park, Jong-Ho; Choi, Byung-Chun; Seo, Hyo-Jin

2003-10-01

Synthesis of narrow-dispersed nanocrystalline TiO 2 was investigated by surfactant-aided solvothermal synthetic method in toluene solutions. Titanium isopropoxide (TIP) was used as precursor, which was decomposed at high temperature in the surfactant-dissolved solution. After the solution was thermally treated at 250°C for 20 h in an autoclave, low-dispersed TiO 2 nanocrystalline particles with average size of <6 nm were synthesized. When sufficient amount of TIP or surfactant was added in the solution, long dumbbell-shaped nanorods were formed, which may be due to the oriented growth of particles along [0 0 1] axis. Characterization of products was investigated by X-ray diffraction and transmission electron microscopy.

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

PubMed Central

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

2013-01-01

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

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

PubMed

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

2015-06-01

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

Opportunities for Fluorochlorozirconate and Other Glass-Ceramic Detectors in Medical Imaging Devices

PubMed Central

Johnson, Jacqueline A.; Leonard, Russell L.; Lubinsky, AR; Schweizer, Stefan

2017-01-01

This article gives an overview of fluorochlorozirconate glass-ceramic scintillators and storage phosphor materials: how they are synthesized, what their properties are, and how they can be used in medical imaging. Such materials can enhance imaging in x-ray radiography, especially mammography and dental imaging, computed tomography, and positron emission tomography. Although focusing on fluorochlorozirconate materials, the reader will find the discussion is relevant to other luminescent glass and glass-ceramic systems. PMID:28890955

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.

[Increasing the safety of ceramic femoral heads for hip prostheses].

PubMed

Willmann, G; Pfaff, H G; Richter, H G

1995-12-01

Since 1974 Biolox ceramic femoral ball heads have been used successfully for artificial modular hip joints. The revision rate due to ball head fracture is lower than 0.02%. This is an extremely low value. In this article it is shown how the safety of a ceramic ball head can be improved using the procedures of HIPing, engraving by laser technique, and 100% proof testing. By applying these means the materials properties density, grain size, grain size distribution, and the strength of the ball head, i.e. the fracture load can be improved significantly.

Temperature dependence of the radiation tolerance of nanocrystalline pyrochlores A 2Ti 2O 7 (A = Gd, Ho and Lu)

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

Wen, J.; Sun, C.; Dholabhai, P. P.

A potentially enhanced radiation resistance of nanocrystalline materials, as a consequence of the high density of interfaces and surfaces, has attracted much attention both to understand the fundamental role of these defect sinks and to develop them for high-radiation environments. Here, irradiation response of nanocrystalline A 2Ti 2O 7 (A = Gd, Ho and Lu) pyrochlore powders with grain sizes of 20–30 nm was investigated by 1-MeV Kr 2+ ion bombardment. In situ transmission electron microscopy (TEM) revealed that the critical amorphization fluence for each nanocrystalline compound at room temperature was greater than that for their coarse-grained counterparts, indicating anmore » enhanced amorphization resistance. The effect of temperature on the irradiation response of one of these compounds, nanocrystalline Lu 2Ti 2O 7, was further examined by performing ion irradiation at an elevated temperature range of 480–600 K. The critical amorphization temperature (T c) was found to be noticeably higher in nanocrystalline Lu 2Ti 2O 7 (610 K) than its coarse-grained counterpart (480 K), revealing that nanocrystalline Lu 2Ti 2O 7 is less resistant to amorphization compared to its coarse-grained phase under high temperatures. We interpret these results with the aid of atomistic simulations. Molecular statics calculations find that cation antisite defects are less energetically costly to form near surfaces than in the bulk, suggesting that the nanocrystalline form of these materials is generally less susceptible to amorphization than coarse-grained counterparts at low temperatures where defect kinetics are negligible. In contrast, at high temperatures, the annealing efficiency of antisite defects by cation interstitials is significantly reduced due to the sink properties of the surfaces in the nanocrystalline pyrochlore, which contributes to the observed higher amorphization temperature in the nano-grained phase than in coarse-grained counterpart. Altogether, these

Temperature dependence of the radiation tolerance of nanocrystalline pyrochlores A 2Ti 2O 7 (A = Gd, Ho and Lu)

DOE PAGES

Wen, J.; Sun, C.; Dholabhai, P. P.; ...

2016-03-21

A potentially enhanced radiation resistance of nanocrystalline materials, as a consequence of the high density of interfaces and surfaces, has attracted much attention both to understand the fundamental role of these defect sinks and to develop them for high-radiation environments. Here, irradiation response of nanocrystalline A 2Ti 2O 7 (A = Gd, Ho and Lu) pyrochlore powders with grain sizes of 20–30 nm was investigated by 1-MeV Kr 2+ ion bombardment. In situ transmission electron microscopy (TEM) revealed that the critical amorphization fluence for each nanocrystalline compound at room temperature was greater than that for their coarse-grained counterparts, indicating anmore » enhanced amorphization resistance. The effect of temperature on the irradiation response of one of these compounds, nanocrystalline Lu 2Ti 2O 7, was further examined by performing ion irradiation at an elevated temperature range of 480–600 K. The critical amorphization temperature (T c) was found to be noticeably higher in nanocrystalline Lu 2Ti 2O 7 (610 K) than its coarse-grained counterpart (480 K), revealing that nanocrystalline Lu 2Ti 2O 7 is less resistant to amorphization compared to its coarse-grained phase under high temperatures. We interpret these results with the aid of atomistic simulations. Molecular statics calculations find that cation antisite defects are less energetically costly to form near surfaces than in the bulk, suggesting that the nanocrystalline form of these materials is generally less susceptible to amorphization than coarse-grained counterparts at low temperatures where defect kinetics are negligible. In contrast, at high temperatures, the annealing efficiency of antisite defects by cation interstitials is significantly reduced due to the sink properties of the surfaces in the nanocrystalline pyrochlore, which contributes to the observed higher amorphization temperature in the nano-grained phase than in coarse-grained counterpart. Altogether, these

Cements and adhesives for all-ceramic restorations.

PubMed

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

2011-04-01

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

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.

Effects of Bi Addition on the Microstructure and Mechanical Properties of Nanocrystalline Ag Coatings

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

Wang, Yuxin; Cheng, Guang; Tay, See Leng

Here in this study we investigated the effects of Bi addition on the microstructure and mechanical properties of an electrodeposited nanocrystalline Ag coating. Microstructural features were investigated with transmission electron microscopy (TEM). The results indicate that the addition of Bi introduced nanometer-scale Ag-Bi solid solution particles and more internal defects to the initial Ag microstructures. The anisotropic elastic-plastic properties of the Ag nanocrystalline coating with and without Bi addition were examined with nanoindentation experiments in conjunction with the recently-developed inverse method. The results indicate that the as-deposited nanocrystalline Ag coating contained high mechanical anisotropy. With the addition of 1 atomicmore » percent (at%) Bi, the anisotropy within Ag-Bi coating was very small, and yield strength of the nanocrystalline Ag-Bi alloy in both longitudinal and transverse directions were improved by over 100% compared to that of Ag. On the other hand, the strain-hardening exponent of Ag-Bi was reduced to 0.055 from the original 0.16 of the Ag coating. Furthermore, the addition of Bi only slightly increased the electrical resistivity of the Ag-Bi coating in comparison to Ag. Lastly, results of our study indicate that Bi addition is a promising method for improving the mechanical and physical performances of Ag coating for electrical contacts.« less

Effects of Bi Addition on the Microstructure and Mechanical Properties of Nanocrystalline Ag Coatings

DOE PAGES

Wang, Yuxin; Cheng, Guang; Tay, See Leng; ...

2017-08-10

Here in this study we investigated the effects of Bi addition on the microstructure and mechanical properties of an electrodeposited nanocrystalline Ag coating. Microstructural features were investigated with transmission electron microscopy (TEM). The results indicate that the addition of Bi introduced nanometer-scale Ag-Bi solid solution particles and more internal defects to the initial Ag microstructures. The anisotropic elastic-plastic properties of the Ag nanocrystalline coating with and without Bi addition were examined with nanoindentation experiments in conjunction with the recently-developed inverse method. The results indicate that the as-deposited nanocrystalline Ag coating contained high mechanical anisotropy. With the addition of 1 atomicmore » percent (at%) Bi, the anisotropy within Ag-Bi coating was very small, and yield strength of the nanocrystalline Ag-Bi alloy in both longitudinal and transverse directions were improved by over 100% compared to that of Ag. On the other hand, the strain-hardening exponent of Ag-Bi was reduced to 0.055 from the original 0.16 of the Ag coating. Furthermore, the addition of Bi only slightly increased the electrical resistivity of the Ag-Bi coating in comparison to Ag. Lastly, results of our study indicate that Bi addition is a promising method for improving the mechanical and physical performances of Ag coating for electrical contacts.« less

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

NASA Technical Reports Server (NTRS)

1988-01-01

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

Ceramics for engines

NASA Technical Reports Server (NTRS)

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

1987-01-01

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

Effect of Ceramic Particle Velocity on Cold Spray Deposition of Metal-Ceramic Coatings

NASA Astrophysics Data System (ADS)

Sova, A.; Kosarev, V. F.; Papyrin, A.; Smurov, I.

2011-01-01

In this paper, metal-ceramic coatings are cold sprayed taking into account the spray parameters of both metal and ceramic particles. The effect of the ceramic particle velocity on the process of metal-ceramic coating formation and the coating properties is analyzed. Copper and aluminum powders are used as metal components. Two fractions of aluminum oxide and silicon carbide are sprayed in the tests. The ceramic particle velocity is varied by the particle injection into different zones of the gas flow: the subsonic and supersonic parts of the nozzle and the free jet after the nozzle exit. The experiments demonstrated the importance of the ceramic particle velocity for the stability of the process: Ceramic particles accelerated to a high enough velocity penetrate into the coating, while low-velocity ceramic particles rebound from its surface.

Effect of rapid thermal annealing on nanocrystalline TiO2 thin films synthesized by swift heavy ion irradiation

NASA Astrophysics Data System (ADS)

Thakurdesai, Madhavi; Kanjilal, D.; Bhattacharyya, Varsha

2012-08-01

Irradiation by swift heavy ions (SHI) is unique tool to synthesize nanocrystalline thin films. We have reported transformation of 100 nm thick amorphous films into nanocrystalline film due to irradiation by 100 MeV Ag ion beam. Oblate shaped nanoparticles having anatase phase of TiO2 were formed on the surface of the irradiated films. In the present investigation, these films are annealed at 350 °C for 2 min in oxygen atmosphere by Rapid Thermal Annealing (RTA) method. During RTA processing, the temperature rises abruptly and this thermal instability is expected to alter surface morphology, structural and optical properties of nanocrystalline TiO2 thin films. Thus in the present work, effect of RTA on SHI induced nanocrystalline thin films of TiO2 is studied. The effect of RTA processing on the shape and size of TiO2 nanoparticles is studied by Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM). Glancing Angle X-ray Diffraction (GAXRD) studies are carried to investigate structural changes induced by RTA processing. Optical characterization is carried out by UV-vis spectroscopy and photoluminescence (PL) spectroscopy. The changes observed in structural and optical properties of nanocrystalline TiO2 thin films after RTA processing are attributed to the annihilation of SHI induced defects.

Influence of coating on nanocrystalline magnetic properties during high temperature thermal ageing

NASA Astrophysics Data System (ADS)

Lekdim, Atef; Morel, Laurent; Raulet, Marie-Ange

2017-05-01

Since their birth or mergence the late 1980s, the nanocrystalline ultrasoft magnetic materials are taking a great importance in power electronic systems conception. One of the main advantages that make them more attractive nowadays is their ability to be packaged since the reduction of the magnetostrictive constant to almost zero. In aircraft applications, due to the high component compactness and to their location (for example near the jet engine), the operating temperature increases and may reach easily 200 °C and more. Consequently, the magnetic thermal ageing may occur but is, unfortunately, weakly studied. This paper focuses on the influence of the coating (packaging type) on the magnetic nanocrystalline performances during a thermal ageing. This study is based on monitoring the magnetic characteristics of two types of nanocrystalline cores (naked and coated) during a thermal activated ageing (100, 150 and 200 °C). Based on a dedicated monitoring protocol, a large magnetic characterization has been done and analyzed. Elsewhere, X-Ray Diffraction and magnetostriction measurements were carried out to support the study of the anisotropy energies evolution with ageing. This latter is discussed in this paper to explain and give hypothesis about the ageing phenomena.

Temperature effects on luminescence properties of Cr3+ ions in alkali gallium silicate nanostructured media

NASA Astrophysics Data System (ADS)

Lipinska-Kalita, Kristina E.; Krol, Denise M.; Hemley, Russell J.; Kalita, Patricia E.; Gobin, Cedric L.; Ohki, Yoshimichi

2005-09-01

We have investigated the optical properties of Cr3+ ions in an alkali gallium silicate glass system and in two glass-based nanocomposites with nucleated β-Ga2O3 nanocrystals. The nucleation and growth of the nanocrystalline phase in the host glass matrix were monitored by Raman scattering spectroscopy and angle-dispersive x-ray diffraction. A broadband luminescence, associated with the 4T2-4A2 transition from the weak crystal field of octahedral Cr3+ sites, dominated the emission of the precursor as-quenched glass. The luminescence spectra of the synthesized glass-ceramic nanocomposites revealed a crystal-like 2E-4A2 strong emission and indicated that the major fraction of Cr3+ ions was located within the nanocrystalline environment. The variable-temperature studies of the nanocomposites demonstrated that the fluorescence of Cr3+ ions can be transformed from sharp R lines of the 2E-4A2 transition to a combination of R lines and of the broad band of the 4T2-4A2 transition. We propose a simple distribution model where the major part of Cr3+ ions is located in the nanocrystalline phase of the glass-ceramic composites in the octahedral environment, substituting the gallium atoms in the β-Ga2O3 crystal structure. The developed nanocrystalline glass-ceramics are a promising class of Cr3+-doped oxide glass-based optically active composite materials.

Study on the corrosion properties of nanocrystalline nickel electrodepositied by reverse pulse current

NASA Astrophysics Data System (ADS)

Cheng, Wen; Ge, Wen; Yang, Qian; Qu, Xinxin

2013-07-01

Nanocrystalline nickel coatings were produced by the method of reverse pulse electrodepositing on the surface of steel sheets. The crystallite size of nanocrystalline nickel coatings was determined by X-ray diffraction (XRD). The effect of saccharin concentration on the crystallite size of the coatings was studied. The average crystallite sizes were diminished as a result of increasing saccharin concentration. CHI660C electrochemical workstation was used to determine the Tafel polarization curves and electrochemical impedance spectroscopy (EIS) of the coatings. The value of corrosion potential, natural corrosion current density, polarizaiton resistance and impedance was calculated, the results suggested that smaller grain size led to higher polarization resistance. EIS gave the charge transfer resistance Rct and pore resistance Rpo variation trend from beginning to 30 min. Scanning electron microscopy (SEM) examination showed the surface morphology of the nickel coatings after the neutral salt spray (NSS) test or bathing in 10% HCl. The images indicated that the corrosion behavior of nanocrystalline nickel coatings was pitting corrosion, the mechanism was also discussed.

New twinning route in face-centered cubic nanocrystalline metals.

PubMed

Wang, Lihua; Guan, Pengfei; Teng, Jiao; Liu, Pan; Chen, Dengke; Xie, Weiyu; Kong, Deli; Zhang, Shengbai; Zhu, Ting; Zhang, Ze; Ma, Evan; Chen, Mingwei; Han, Xiaodong

2017-12-15

Twin nucleation in a face-centered cubic crystal is believed to be accomplished through the formation of twinning partial dislocations on consecutive atomic planes. Twinning should thus be highly unfavorable in face-centered cubic metals with high twin-fault energy barriers, such as Al, Ni, and Pt, but instead is often observed. Here, we report an in situ atomic-scale observation of twin nucleation in nanocrystalline Pt. Unlike the classical twinning route, deformation twinning initiated through the formation of two stacking faults separated by a single atomic layer, and proceeded with the emission of a partial dislocation in between these two stacking faults. Through this route, a three-layer twin was nucleated without a mandatory layer-by-layer twinning process. This route is facilitated by grain boundaries, abundant in nanocrystalline metals, that promote the nucleation of separated but closely spaced partial dislocations, thus enabling an effective bypassing of the high twin-fault energy barrier.

Ferroelectric Polarization in Nanocrystalline Hydroxyapatite Thin Films on Silicon

PubMed Central

Lang, S. B.; Tofail, S. A. M.; Kholkin, A. L.; Wojtaś, M.; Gregor, M.; Gandhi, A. A.; Wang, Y.; Bauer, S.; Krause, M.; Plecenik, A.

2013-01-01

Hydroxyapatite nanocrystals in natural form are a major component of bone- a known piezoelectric material. Synthetic hydroxyapatite is widely used in bone grafts and prosthetic pyroelectric coatings as it binds strongly with natural bone. Nanocrystalline synthetic hydroxyapatite films have recently been found to exhibit strong piezoelectricity and pyroelectricity. While a spontaneous polarization in hydroxyapatite has been predicted since 2005, the reversibility of this polarization (i.e. ferroelectricity) requires experimental evidence. Here we use piezoresponse force microscopy to demonstrate that nanocrystalline hydroxyapatite indeed exhibits ferroelectricity: a reversal of polarization under an electrical field. This finding will strengthen investigations on the role of electrical polarization in biomineralization and bone-density related diseases. As hydroxyapatite is one of the most common biocompatible materials, our findings will also stimulate systematic exploration of lead and rare-metal free ferroelectric devices for potential applications in areas as diverse as in vivo and ex vivo energy harvesting, biosensing and electronics. PMID:23884324

Ferroelectric Polarization in Nanocrystalline Hydroxyapatite Thin Films on Silicon

NASA Astrophysics Data System (ADS)

Lang, S. B.; Tofail, S. A. M.; Kholkin, A. L.; Wojtaś, M.; Gregor, M.; Gandhi, A. A.; Wang, Y.; Bauer, S.; Krause, M.; Plecenik, A.

2013-07-01

Hydroxyapatite nanocrystals in natural form are a major component of bone- a known piezoelectric material. Synthetic hydroxyapatite is widely used in bone grafts and prosthetic pyroelectric coatings as it binds strongly with natural bone. Nanocrystalline synthetic hydroxyapatite films have recently been found to exhibit strong piezoelectricity and pyroelectricity. While a spontaneous polarization in hydroxyapatite has been predicted since 2005, the reversibility of this polarization (i.e. ferroelectricity) requires experimental evidence. Here we use piezoresponse force microscopy to demonstrate that nanocrystalline hydroxyapatite indeed exhibits ferroelectricity: a reversal of polarization under an electrical field. This finding will strengthen investigations on the role of electrical polarization in biomineralization and bone-density related diseases. As hydroxyapatite is one of the most common biocompatible materials, our findings will also stimulate systematic exploration of lead and rare-metal free ferroelectric devices for potential applications in areas as diverse as in vivo and ex vivo energy harvesting, biosensing and electronics.

Ferroelectric polarization in nanocrystalline hydroxyapatite thin films on silicon.

PubMed

Lang, S B; Tofail, S A M; Kholkin, A L; Wojtaś, M; Gregor, M; Gandhi, A A; Wang, Y; Bauer, S; Krause, M; Plecenik, A

2013-01-01

Hydroxyapatite nanocrystals in natural form are a major component of bone--a known piezoelectric material. Synthetic hydroxyapatite is widely used in bone grafts and prosthetic pyroelectric coatings as it binds strongly with natural bone. Nanocrystalline synthetic hydroxyapatite films have recently been found to exhibit strong piezoelectricity and pyroelectricity. While a spontaneous polarization in hydroxyapatite has been predicted since 2005, the reversibility of this polarization (i.e. ferroelectricity) requires experimental evidence. Here we use piezoresponse force microscopy to demonstrate that nanocrystalline hydroxyapatite indeed exhibits ferroelectricity: a reversal of polarization under an electrical field. This finding will strengthen investigations on the role of electrical polarization in biomineralization and bone-density related diseases. As hydroxyapatite is one of the most common biocompatible materials, our findings will also stimulate systematic exploration of lead and rare-metal free ferroelectric devices for potential applications in areas as diverse as in vivo and ex vivo energy harvesting, biosensing and electronics.

Visualizing decoupling in nanocrystalline alloys: A FORC-temperature analysis

NASA Astrophysics Data System (ADS)

Rivas, M.; Martínez-García, J. C.; Gorria, P.

2016-02-01

Devitrifying ferromagnetic amorphous precursors in the adequate conditions may give rise to disordered assemblies of densely packed nanocrystals with extraordinary magnetic softness well explained by the exchange coupling among multiple crystallites. Whether the magnetic exchange interaction is produced by direct contact or mediated by the intergranular amorphous matrix has a strong influence on the behaviour of the system above room temperature. Multi-phase amorphous-nanocrystalline systems dramatically harden when approaching the amorphous Curie temperature (TC) due to the hard grains decoupling. The study of the thermally induced decoupling of nanosized crystallites embedded in an amorphous matrix has been performed in this work by the first-order reversal curves (FORCs) analysis. We selected a Fe-rich amorphous alloy with TC = 330 K, in order to follow the evolution of the FORC diagrams obtained below and above such temperature in samples with different percentages of nanocrystalline phase. The existence of up to four regions exhibiting unlike magnetic behaviours is unambiguously determined from the temperature evolution of the FORC.

Laser debonding of ceramic brackets: a comprehensive review.

PubMed

Azzeh, Ezz; Feldon, Paul J

2003-01-01

Since the invention of the ruby laser in the early 1960s, tremendous advances have been made in optic laser technology. Orthodontists have found various uses for lasers, including the debonding of ceramic brackets. Laser energy degrades the adhesive resin used to bond brackets. Consequently, lower forces can be used than when mechanical debonding is performed, reducing the risk of enamel damage. However, the heat produced by some lasers can damage the tooth pulp. Selecting the appropriate laser, resin, and bracket combination can minimize risks and make debonding more efficient. The purpose of this article is to give the clinician an up-to-date, comprehensive literature review about the clinical characteristics of debonding ceramic brackets with lasers.

Ceramic nanocarriers: versatile nanosystem for protein and peptide delivery.

PubMed

Singh, Deependra; Dubey, Pooja; Pradhan, Madhulika; Singh, Manju Rawat

2013-02-01

Proteins and peptides have been established to be the potential drug candidate for various human diseases. But, delivery of these therapeutic protein and peptides is still a challenge due to their several unfavorable properties. Nanotechnology is expanding as a promising tool for the efficient delivery of proteins and peptides. Among numerous nano-based carriers, ceramic nanoparticles have proven themselves as a unique carrier for protein and peptide delivery as they provide a more stable, bioavailable, readily manufacturable, and acceptable proteins and polypeptide formulation. This article provides an overview of the various aspects of ceramic nanoparticles including their classification, methods of preparation, latest advances, and applications as protein and peptide delivery carriers. Ceramic nanocarriers seem to have potential for preserving structural integrity of proteins and peptides, thereby promoting a better therapeutic effect. This approach thus provides pharmaceutical scientists with a new hope for the delivery of proteins and peptides. Still, considerable study on ceramic nanocarrier is necessary with respect to pharmacokinetics, toxicology, and animal studies to confirm their efficiency as well as safety and to establish their clinical usefulness and scale-up to industrial level.

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.

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

PubMed

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

2017-08-01

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

Characterization techniques to predict mechanical behaviour of green ceramic bodies fabricated by ceramic microstereolithography

NASA Astrophysics Data System (ADS)

Adake, Chandrashekhar V.; Bhargava, Parag; Gandhi, Prasanna

2018-02-01

Ceramic microstereolithography (CMSL) has emerged as solid free form (SFF) fabrication technology in which complex ceramic parts are fabricated from ceramic suspensions which are formulated by dispersing ceramic particles in UV curable resins. Ceramic parts are fabricated by exposing ceramic suspension to computer controlled UV light which polymerizes resin to polymer and this polymer forms rigid network around ceramic particles. A 3-dimensional part is created by piling cured layers one over the other. These ceramic parts are used to build microelectromechanical (MEMS) devices after thermal treatment. In many cases green ceramic parts can be directly utilized to build MEMS devices. Hence characterization of these parts is essential in terms of their mechanical behaviour prior to their use in MEMS devices. Mechanical behaviour of these green ceramic parts depends on cross link density which in turn depends on chemical structure of monomer, concentrations of photoinitiator and UV energy dose. Mechanical behaviour can be determined with the aid of nanoindentation. And extent of crosslinking can be verified with the aid of DSC. FTIR characterization is used to analyse (-C=C-) double bond conversion. This paper explains characterization tools to predict the mechanical behaviour of green ceramic bodies fabricated in CMSL

Evidence that abnormal grain growth precedes fatigue crack initiation in nanocrystalline Ni-Fe

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

Furnish, Timothy A.; Bufford, Daniel C.; Ren, Fang

Prior studies on the high-cycle fatigue behavior of nanocrystalline metals have shown that fatigue fracture is associated with abnormal grain growth (AGG). However, those previous studies have been unable to determine if AGG precedes fatigue crack initiation, or vice-versa. The present study shows that AGG indeed occurs prior to crack formation in nanocrystalline Ni-Fe by using a recently developed synchrotron X-ray diffraction modality that has been adapted for in-situ analysis. The technique allows fatigue tests to be interrupted at the initial signs of the AGG process, and subsequent microscopy reveals the precursor damage state preceding crack initiation.

Superparamagnetic nanocrystalline ZnFe2O4 with a very high Curie temperature.

PubMed

Deka, Sasanka; Joy, P A

2008-08-01

Studies on the magnetic properties of nanocrystalline ZnFe2O4 synthesized by an autocombustion method are reported. Superparamagnetic behavior is observed for the nanocrystalline materials with particle sizes of 8 nm and 17 nm, with superparamagnetic blocking temperatures of 65 K and 75 K, respectively. Magnetic hysteresis with very large coercivities of 533 Oe and 325 Oe, respectively, are observed at 12 K. Studies on the temperature variation of the magnetization above room temperature indicate that the Curie temperature is as high as approximately 800 K when compared to the paramagnetic nature of bulk zinc ferrite at room temperature.

Evidence that abnormal grain growth precedes fatigue crack initiation in nanocrystalline Ni-Fe

DOE PAGES

Furnish, Timothy A.; Bufford, Daniel C.; Ren, Fang; ...

2018-09-06

Prior studies on the high-cycle fatigue behavior of nanocrystalline metals have shown that fatigue fracture is associated with abnormal grain growth (AGG). However, those previous studies have been unable to determine if AGG precedes fatigue crack initiation, or vice-versa. The present study shows that AGG indeed occurs prior to crack formation in nanocrystalline Ni-Fe by using a recently developed synchrotron X-ray diffraction modality that has been adapted for in-situ analysis. The technique allows fatigue tests to be interrupted at the initial signs of the AGG process, and subsequent microscopy reveals the precursor damage state preceding crack initiation.

Method of making metal matrix composites reinforced with ceramic particulates

DOEpatents

Cornie, James A.; Kattamis, Theodoulos; Chambers, Brent V.; Bond, Bruce E.; Varela, Raul H.

1989-01-01

Composite materials and methods for making such materials are disclosed in which dispersed ceramic particles are at chemical equilibrium with a base metal matrix, thereby permitting such materials to be remelted and subsequently cast or otherwise processed to form net weight parts and other finished (or semi-finished) articles while maintaining the microstructure and mechanical properties (e.g. wear resistance or hardness) of the original composite. The composite materials of the present invention are composed of ceramic particles in a base metal matrix. The ceramics are preferably carbides of titanium, zirconium, tungsten, molybdenum or other refractory metals. The base metal can be iron, nickel, cobalt, chromium or other high temperature metal and alloys thereof. For ferrous matrices, alloys suitable for use as the base metal include cast iron, carbon steels, stainless steels and iron-based superalloys.

Method of making metal matrix composites reinforced with ceramic particulates

DOEpatents

Cornie, J.A.; Kattamis, T.; Chambers, B.V.; Bond, B.E.; Varela, R.H.

1989-08-01

Composite materials and methods for making such materials are disclosed in which dispersed ceramic particles are at chemical equilibrium with a base metal matrix, thereby permitting such materials to be remelted and subsequently cast or otherwise processed to form net weight parts and other finished (or semi-finished) articles while maintaining the microstructure and mechanical properties (e.g. wear resistance or hardness) of the original composite. The composite materials of the present invention are composed of ceramic particles in a base metal matrix. The ceramics are preferably carbides of titanium, zirconium, tungsten, molybdenum or other refractory metals. The base metal can be iron, nickel, cobalt, chromium or other high temperature metal and alloys thereof. For ferrous matrices, alloys suitable for use as the base metal include cast iron, carbon steels, stainless steels and iron-based superalloys. 2 figs.

Thermal shock and erosion resistant tantalum carbide ceramic material

NASA Technical Reports Server (NTRS)

Honeycutt, L., III; Manning, C. R. (Inventor)

1978-01-01

Ceramic tantalum carbide artifacts with high thermal shock and mechanical erosion resistance are provided by incorporating tungsten-rhenium and carbon particles in a tantalum carbide matrix. The mix is sintered by hot pressing to form the ceramic article which has a high fracture strength relative to its elastic modulus and thus has an improved thermal shock and mechanical erosion resistance. The tantalum carbide is preferable less than minus 100 mesh, the carbon particles are preferable less than minus 100 mesh, and the tungsten-rhenium particles are preferable elongate, having a length to thickness ratio of at least 2/1. Tungsten-rhenium wire pieces are suitable as well as graphite particles.

Synthesis and characterization of nanocrystalline LaMnO3 modified BaTiO3 ferroelectric ceramics prepared by chemical route

NASA Astrophysics Data System (ADS)

Dhak, Prasanta; Adak, Mrinal Kanti; Dhak, Debasis

2016-02-01

Nanocrystalline Ba1-3xTi1-3xLa2xMn4xO3, [x = 0.006, 0.008, 0.01 and 0.05] (abbreviated hereafter as BTLM) by chemical route. The phase formation and purity were checked by X-ray diffraction (XRD) study and transmission electron microscopy (TEM). The grain morphology after sintering was studied by scanning electron microscopy (SEM). The crystallite sizes range from 21 nm to 30 nm, while the particle size ranges between 27 nm and 38 nm. The grain size 212 nm and grain density 96.8% were found to be maximum for BTLM x = 0.05 and x = 0.01, respectively. The temperature dependence of dielectric constants was found to be more diffused and the peak value of the dielectric constant was decreased and more flat with the increase of the substituent concentration. The tangent loss was found to be decreased and reached to the minimum value of 0.032 for BTLM x = 0.05. The remnant polarization Pr, was 10 μC/cm2 for BTLM x = 0.01.

Nanocrystallinity effects on osteoblast and osteoclast response to silicon substituted hydroxyapatite.

PubMed

Casarrubios, Laura; Matesanz, María Concepción; Sánchez-Salcedo, Sandra; Arcos, Daniel; Vallet-Regí, María; Portolés, María Teresa

2016-11-15

Silicon substituted hydroxyapatites (SiHA) are highly crystalline bioceramics treated at high temperatures (about 1200°C) which have been approved for clinical use with spinal, orthopedic, periodontal, oral and craniomaxillofacial applications. The preparation of SiHA with lower temperature methods (about 700°C) provides nanocrystalline SiHA (nano-SiHA) with enhanced bioreactivity due to higher surface area and smaller crystal size. The aim of this study has been to know the nanocrystallinity effects on the response of both osteoblasts and osteoclasts (the two main cell types involved in bone remodelling) to silicon substituted hydroxyapatite. Saos-2 osteoblasts and osteoclast-like cells (differentiated from RAW-264.7 macrophages) have been cultured on the surface of nano-SiHA and SiHA disks and different cell parameters have been evaluated: cell adhesion, proliferation, viability, intracellular content of reactive oxygen species, cell cycle phases, apoptosis, cell morphology, osteoclast-like cell differentiation and resorptive activity. This comparative in vitro study evidences that nanocrystallinity of SiHA affects the cell/biomaterial interface inducing bone cell apoptosis by loss of cell anchorage (anoikis), delaying osteoclast-like cell differentiation and decreasing the resorptive activity of this cell type. These results suggest the potential use of nano-SiHA biomaterial for preventing bone resorption in treatment of osteoporotic bone. Copyright © 2016 Elsevier Inc. All rights reserved.

Wear behavior of Cu-Zn alloy by ultrasonic nanocrystalline surface modification.

PubMed

Cho, In Shik; Amanov, Auezhan; Ahn, Deok Gi; Shin, Keesam; Lee, Chang Soon; Pyoun, Young-Shik; Park, In-Gyu

2011-07-01

The ultrasonic nanocrystalline surface modification (UNSM) was applied to disk specimens made of Cu-Zn alloy in order to investigate the UNSM effects under five various conditions on wear of deformation twinning. In this paper, ball-on-disk test was conducted, and the results of UNSM-treated specimens showed that surface layer dislocation density and multi-directional twins were abruptly increased, and the grain size was altered into nano scale. UNSM delivers force onto the workpiece surface 20,000 times per second with 1,000 to 4,000 contact counts per square millimeter. The UNSM technology creates nanocrystalline and deformation twinning on the workpiece surface. One of the main concepts of this study is that defined phenomena of the UNSM technology, and the results revealed that nanocrystalline and deformation twinning depth might be controlled by means of impact energy of UNSM technology. EBSD and TEM analyses showed that deformation layer was increased up to 268 microm, and initial twin density was 0.001 x 10(6) cm(-2) and increased up to 0.343 x 10(6) cm(-2). Wear volume loss was also decreased from 703 x 10(3) mm3 to 387 x 10(3) mm3. Wear behavior according to deformation depth was observed under three different combinations. This is related to deformation depth which was created by UNSM technology.

[Comparison of color reappearance between metal-ceram restoration and foundry-ceram restoration using crystaleye spectrophotometer].

PubMed

Shi, Tao; Zhang, Ning; Kong, Fan-wen; Zhan, De-song

2010-10-01

To study the color reappearance effect of metal-ceram restoration and foundry-ceram restoration using Crystaleye spectrophotometer. 58 metal-ceram restorations and 58 foundry-ceram restorations according to the result of the Crystaleye spectrophotometer were made respectively. The deltaE between restorations and natural teeth as referenced were analyzed. And satisfaction of dentists and patients were evaluated. The deltaE between metal-ceram restorations and natural teeth was 7.13 +/- 0.74. The deltaE between foundry-ceram restorations and teeth was 1.47 +/- 0.84. There were statistical differences between the deltaE (P < 0.01). The satisnatural faction of dentists and patients to the foundry-ceram restorations were higher than to the metal-ceram restorations (P < 0.05). Crystaleye spectrophotometer can provide accurate reference for foundry-ceram restoration, but for metal-ceram restoration it is not accurate.

Ceramic Parts for Turbines

NASA Technical Reports Server (NTRS)

Jones, R. D.; Carpenter, Harry W.; Tellier, Jim; Rollins, Clark; Stormo, Jerry

1987-01-01

Abilities of ceramics to serve as turbine blades, stator vanes, and other elements in hot-gas flow of rocket engines discussed in report. Ceramics prime candidates, because of resistance to heat, low density, and tolerance of hostile environments. Ceramics considered in report are silicon nitride, silicon carbide, and new generation of such ceramic composites as transformation-toughened zirconia and alumina and particulate- or whisker-reinforced matrices. Report predicts properly designed ceramic components viable in advanced high-temperature rocket engines and recommends future work.

Eu-doped ZnO-HfO2 hybrid nanocrystal-embedded low-loss glass-ceramic waveguides

NASA Astrophysics Data System (ADS)

Ghosh, Subhabrata; N, Shivakiran Bhaktha B.

2016-03-01

We report on the sol-gel fabrication, using a dip-coating technique, of low-loss Eu-doped 70SiO2 -(30-x) HfO2-xZnO (x = 2, 5, 7 and 10 mol%) ternary glass-ceramic planar waveguides. Transmission electron microscopy and grazing incident x-ray diffraction experiments confirm the controlled growth of hybrid nanocrystals with an average size of 3 nm-25 nm, composed of ZnO encapsulated by a thin layer of nanocrystalline HfO2, with an increase of ZnO concentration from x = 2 mol% to 10 mol% in the SiO2-HfO2 composite matrix. The effect of crystallization on the local environment of Eu ions, doped in the ZnO-HfO2 hybrid nanocrystal-embedded glass-ceramic matrix, is studied using photoluminescence spectra, wherein an intense mixed-valence state (divalent as well as trivalent) emission of Eu ions is observed. The existence of Eu2+ and Eu3+ in the SiO2-HfO2-ZnO ternary matrix is confirmed by x-ray photoelectron spectroscopy. Importantly, the Eu{}2+,3+-doped ternary waveguides exhibit low propagation losses (0.3 ± 0.2 dB cm-1 at 632.8 nm) and optical transparency in the visible region of the electromagnetic spectrum, which makes ZnO-HfO2 nanocrystal-embedded SiO2-HfO2-ZnO waveguides a viable candidate for the development of on-chip, active, integrated optical devices.

Intrinsic ferromagnetism in nanocrystalline Mn-doped ZnO depending on Mn concentration.

PubMed

Subramanian, Munisamy; Tanemura, Masaki; Hihara, Takehiko; Soga, Tetsuo; Jimbo, Takashi

2011-04-01

The physical properties of Zn(1-x)Mn(x)O nanoparticles synthesized by thermal decomposition are extensively investigated by X-ray diffraction (XRD), Transmission Electron Microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Raman light scattering and Hysteresis measurements. XRD and XPS spectra reveal the absence of secondary phase in nanocrystalline ZnO doped with 5% or less Mn; and, later confirms that the valance state of Mn to be 2+ for all the samples. Raman spectra exhibit a peak at 660 cm(-1) which we attribute to the intrinsic lattice defects of ZnO with increasing Mn concentration. Overall, our results demonstrate that ferromagnetic properties can be realized while Mn-doped ZnO obtained in the nanocrystalline form.

Analysis of a nanocrystalline polymer dispersion of ebselen using solid-state NMR, Raman microscopy, and powder X-ray diffraction.

PubMed

Vogt, Frederick G; Williams, Glenn R

2012-07-01

Nanocrystalline drug-polymer dispersions are of significant interest in pharmaceutical delivery. The purpose of this work is to demonstrate the applicability of methods based on two-dimensional (2D) and multinuclear solid-state NMR (SSNMR) to a novel nanocrystalline pharmaceutical dispersion of ebselen with polyvinylpyrrolidone-vinyl acetate (PVP-VA), after initial characterization with other techniques. A nanocrystalline dispersion of ebselen with PVP-VA was prepared and characterized by powder X-ray diffraction (PXRD), confocal Raman microscopy and mapping, and differential scanning calorimetry (DSC), and then subjected to detailed 1D and 2D SSNMR analysis involving ¹H, ¹³C, and ⁷⁷Se isotopes and ¹H spin diffusion. PXRD was used to show that dispersion contains nanocrystalline ebselen in the 35-60 nm size range. Confocal Raman microscopy and spectral mapping were able to detect regions where short-range interactions may occur between ebselen and PVP-VA. Spin diffusion effects were analyzed using 2D SSNMR experiments and are able to directly detect interactions between ebselen and the surrounding PVP-VA. The methods used here, particularly the 2D SSNMR methods based on spin diffusion, provided detailed structural information about a nanocrystalline polymer dispersion of ebselen, and should be useful in other studies of these types of materials.

Investigating the Thermal and Phase Stability of Nanocrystalline Ni-W Produced by Electrodeposition, Sputtering, and Mechanical Alloying

NASA Astrophysics Data System (ADS)

Marvel, Christopher Jonathan

The development of nanocrystalline materials has been increasingly pursued over the last few decades. They have been shown to exhibit superior properties compared to their coarse-grain counterparts, and thus present a tremendous opportunity to revolutionize the performance of nanoscale devices or bulk structural materials. However, nanocrystalline materials are highly prone to grain growth, and if the nanocrystalline grains coarsen, the beneficial properties are lost. There is a strong effort to determine the most effective thermal stability mechanisms to avoid grain growth, but the physical nature of nanocrystalline grain growth is still unclear due to a lack of detailed understanding of nanocrystalline microstructures. Furthermore, the influence of contamination has scarcely been explored with advanced transmission electron microscopy techniques, nor has there been a direct comparison of alloys fabricated with different bulk processes. Therefore, this research has applied aberration-corrected scanning transmission electron microscopy to characterize nanocrystalline Ni-W on the atomic scale and elucidate the physical grain growth behavior. Three primary objectives were pursued: (1) explore the thermal stability mechanisms of nanocrystalline Ni-W, (2) evaluate the phase stability of Ni-W and link any findings to grain growth behavior, and (3) compare the influences of bulk fabrication processing, including electrodeposition, DC magnetron sputtering, and mechanical alloying, on the thermal stability and phase stability of Ni-W. Several thermal stability mechanisms were identified throughout the course of this research. First and foremost, W-segregation was scarcely observed to grain boundaries, and it is unclear if W-segregation improves thermal stability contrary to most reports in the 2 literature. Long-range Ni4W chemical ordering was observed in alloys with more than 20 at.% W, and it is likely Ni4W domains reduce grain boundary mobility. In addition, lattice

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

Direct Observation of Sink-Dependent Defect Evolution in Nanocrystalline Iron under Irradiation

DOE PAGES

El Atwani, Osman; Nathaniel, James; Leff, Asher C.; ...

2017-05-12

Crystal defects generated during irradiation can result in severe changes in morphology and an overall degradation of mechanical properties in a given material. Nanomaterials have been proposed as radiation damage tolerant materials, due to the hypothesis that defect density decreases with grain size refinement due to the increase in grain boundary surface area. The lower defect density should arise from grain boundary-point defect absorption and enhancement of interstitial-vacancy annihilation. In this study, low energy helium ion irradiation on free-standing iron thin films were performed at 573 K. Interstitial loops of a 0 /2 [111] Burgers vector were directly observed asmore » a result of the displacement damage. Loop density trends with grain size demonstrated an increase in the nanocrystalline (<100 nm) regime, but scattered behavior in the transition from the nanocrystalline to the ultra-fine regime (100–500 nm). To examine the validity of such trends, loop density and area for different grains at various irradiation doses were compared and revealed efficient defect absorption in the nanocrystalline grain size regime, but loop coalescence in the ultra-fine grain size regime. Lastly, a relationship between the denuded zone formation, a measure of grain boundary absorption efficiency, grain size, grain boundary type and misorientation angle is determined.« less

Direct Observation of Sink-Dependent Defect Evolution in Nanocrystalline Iron under Irradiation

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

El Atwani, Osman; Nathaniel, James; Leff, Asher C.

Crystal defects generated during irradiation can result in severe changes in morphology and an overall degradation of mechanical properties in a given material. Nanomaterials have been proposed as radiation damage tolerant materials, due to the hypothesis that defect density decreases with grain size refinement due to the increase in grain boundary surface area. The lower defect density should arise from grain boundary-point defect absorption and enhancement of interstitial-vacancy annihilation. In this study, low energy helium ion irradiation on free-standing iron thin films were performed at 573 K. Interstitial loops of a 0 /2 [111] Burgers vector were directly observed asmore » a result of the displacement damage. Loop density trends with grain size demonstrated an increase in the nanocrystalline (<100 nm) regime, but scattered behavior in the transition from the nanocrystalline to the ultra-fine regime (100–500 nm). To examine the validity of such trends, loop density and area for different grains at various irradiation doses were compared and revealed efficient defect absorption in the nanocrystalline grain size regime, but loop coalescence in the ultra-fine grain size regime. Lastly, a relationship between the denuded zone formation, a measure of grain boundary absorption efficiency, grain size, grain boundary type and misorientation angle is determined.« less

Light-weight ceramic insulation

NASA Technical Reports Server (NTRS)

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

2002-01-01

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

Influence of ceramic thickness and ceramic materials on fracture resistance of posterior partial coverage restorations.

PubMed

Bakeman, E M; Rego, N; Chaiyabutr, Y; Kois, J C

2015-01-01

This study evaluated the influence of ceramic thickness and ceramic materials on fracture resistance of posterior partial coverage ceramic restorations. Forty extracted molars were allocated into four groups (n=10) to test for two variables: 1) the thickness of ceramic (1 mm or 2 mm) and 2) the ceramic materials (a lithium disilicate glass-ceramic [IPS e.max] or leucite-reinforced glass ceramic [IPS Empress]). All ceramic restorations were luted with resin cement (Variolink II) on the prepared teeth. These luted specimens were loaded to failure in a universal testing machine, in the compression mode, with a crosshead speed of 1.0 mm/min. The data were analyzed using two-way analysis of variance and the Tukey Honestly Significantly Different multiple comparison test (α =0.05). The fracture resistance revealed a significant effect for materials (p<0.001); however, the thickness of ceramic was not significant (p=0.074), and the interaction between the thickness of ceramic and the materials was not significant (p=0.406). Mean (standard deviation) fracture resistance values were as follows: a 2-mm thickness of a lithium disilicate bonded to tooth structure (2505 [401] N) revealed a significantly higher fracture resistance than did a 1-mm thickness of leucite-reinforced (1569 [452] N) and a 2-mm thickness of leucite-reinforced ceramic bonded to tooth structure (1716 [436] N) (p<0.05). There was no significant difference in fracture resistance values between a lithium disilicate ceramic at 1-mm thickness (2105 [567] N) and at 2-mm thickness. Using a lithium disilicate glass ceramic for partial coverage restoration significantly improved fracture resistance compared to using a leucite-reinforced glass ceramic. The thickness of ceramic had no significant effect on fracture resistance when the ceramics were bonded to the underlying tooth structure.

Y-TZP ceramic processing from coprecipitated powders: a comparative study with three commercial dental ceramics.

PubMed

Lazar, Dolores R R; Bottino, Marco C; Ozcan, Mutlu; Valandro, Luiz Felipe; Amaral, Regina; Ussui, Valter; Bressiani, Ana H A

2008-12-01

(1) To synthesize 3mol% yttria-stabilized zirconia (3Y-TZP) powders via coprecipitation route, (2) to obtain zirconia ceramic specimens, analyze surface characteristics, and mechanical properties, and (3) to compare the processed material with three reinforced dental ceramics. A coprecipitation route was used to synthesize a 3mol% yttria-stabilized zirconia ceramic processed by uniaxial compaction and pressureless sintering. Commercially available alumina or alumina/zirconia ceramics, namely Procera AllCeram (PA), In-Ceram Zirconia Block (CAZ) and In-Ceram Zirconia (IZ) were chosen for comparison. All specimens (6mmx5mmx5mm) were polished and ultrasonically cleaned. Qualitative phase analysis was performed by XRD and apparent densities were measured on the basis of Archimedes principle. Ceramics were also characterized using SEM, TEM and EDS. The hardness measurements were made employing Vickers hardness test. Fracture toughness (K(IC)) was calculated. Data were analyzed using one-way analysis of variance (ANOVA) and Tukey's test (alpha=0.05). ANOVA revealed that the Vickers hardness (p<0.0001) and fracture toughness (p<0.0001) were affected by the ceramic materials composition. It was confirmed that the PA ceramic was constituted of a rhombohedral alumina matrix, so-called alpha-alumina. Both CAZ and IZ ceramics presented tetragonal zirconia and alpha-alumina mixture of phases. The SEM/EDS analysis confirmed the presence of aluminum in PA ceramic. In the IZ and CAZ ceramics aluminum, zirconium and cerium in grains involved by a second phase containing aluminum, silicon and lanthanum were identified. PA showed significantly higher mean Vickers hardness values (H(V)) (18.4+/-0.5GPa) compared to vitreous CAZ (10.3+/-0.2GPa) and IZ (10.6+/-0.4GPa) ceramics. Experimental Y-TZP showed significantly lower results than that of the other monophased ceramic (PA) (p<0.05) but it showed significantly higher fracture toughness (6.0+/-0.2MPam(1/2)) values when compared to the

Thermal Stability of Nanocrystalline Copper for Potential Use in Printed Wiring Board Applications

NASA Astrophysics Data System (ADS)

Woo, Patrick Kai Fai

Copper is a widely used conductor in the manufacture of printed wiring boards (PWB). The trends in miniaturization of electronic devices create increasing challenges to all electronic industries. In particular PWB manufacturers face great challenges because the increasing demands in greater performance and device miniaturization pose enormous difficulties in manufacturing and product reliability. Nanocrystalline and ultra-fine grain copper can potentially offer increased reliability and functionality of the PWB due to the increases in strength and achievable wiring density by reduction in grain size. The first part of this thesis is concerned with the synthesis and characterization of nanocrystalline and ultra-fine grain-sized copper for potential applications in the PWB industry. Nanocrystalline copper with different amounts of sulfur impurities (25-230ppm) and grain sizes (31-49nm) were produced and their hardness, electrical resistivity and etchability were determined. To study the thermal stability of nanocrystalline copper, differential scanning calorimetry and isothermal heat treatments combined with electron microscopy techniques for microstructural analysis were used. Differential scanning calorimetry was chosen to continuously monitor the grain growth process in the temperature range from 40?C to 400?C. During isothermal annealing experiments samples were annealed at 23?C, 100?C and 300?C to study various potential thermal issues for these materials in PWB applications such as the long-term room temperature thermal stability as well as for temperature excursions above the operation temperature and peak temperature exposure during the PWB manufacturing process. From all annealing experiments the various grain growth events and the overall stability of these materials were analyzed in terms of driving and dragging forces. Experimental evidence is presented which shows that the overall thermal stability, grain boundary character and texture evolution of

Tribological properties of structural ceramics

NASA Technical Reports Server (NTRS)

Buckley, D. H.; Miyoshi, K.

1985-01-01

The tribological and lubricated behavior of both oxide and nonoxide ceramics are reviewed in this chapter. Ceramics are examined in contact with themselves, other harder materials and metals. Elastic, plastic and fracture behavior of ceramics in solid state contact is discussed. The contact load necessary to initiate fracture in ceramics is shown to be appreciably reduced with tangential motion. Both friction and wear of ceramics are anisotropic and relate to crystal structure as has been observed with metals. Grit size effects in two and three body abrasive wear are observed for ceramics. Both free energy of oxide formation and the d valence bond character of metals are related to the friction and wear characteristics for metals in contact with ceramics. Surface contaminants affect friction and adhesive wear. For example, carbon on silicon carbide and chlorine on aluminum oxide reduce friction while oxygen on metal surfaces in contact with ceramics increases friction. Lubrication increases the critical load necessary to initiate fracture of ceramics both in indentation and with sliding or rubbing. Ceramics compositions both as coatings and in composites are described for the high temperature lubrication of both alloys and ceramics.

On Ceramics.

ERIC Educational Resources Information Center

School Arts, 1982

1982-01-01

Presents four ceramics activities for secondary-level art classes. Included are directions for primitive kiln construction and glaze making. Two ceramics design activities are described in which students make bizarrely-shaped lidded jars, feet, and footwear. (AM)

Nanocrystalline silicon: Lattice dynamics and enhanced thermoelectric properties

DOE PAGES

Claudio, Tania; Stein, Niklas; Stroppa, Daniel G.; ...

2014-12-21

In this study, silicon has several advantages when compared to other thermoelectric materials, but until recently it was not used for thermoelectric applications due to its high thermal conductivity, 156 W K -1 m -1 at room temperature. Nanostructuration as means to decrease thermal transport through enhanced phonon scattering has been a subject of many studies. In this work we have evaluated the effects of nanostructuration on the lattice dynamics of bulk nanocrystalline doped silicon. The samples were prepared by gas phase synthesis, followed by current and pressure assisted sintering. The heat capacity, density of phonons states, and elastic constantsmore » were measured, which all reveal a significant, ≈25%, reduction in the speed of sound. The samples present a significantly decreased lattice thermal conductivity, ≈25 W K -1 m -1, which, combined with a very high carrier mobility, results in a dimensionless figure of merit with a competitive value that peaks at ZT ≈ 0.57 at 973 °C. Due to its easily scalable and extremely low-cost production process, nanocrystalline Si prepared by gas phase synthesis followed by sintering could become the material of choice for high temperature thermoelectric generators.« less

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

Nanocrystalline Nb-Al-Ge mixtures fabricated using wet mechanical milling

NASA Astrophysics Data System (ADS)

Pusceddu, E.; Charlton, S.; Hampshire, D. P.

2008-02-01

An investigation into Nb-Al-Ge mixtures is presented with special attention to the superconducting compounds Nb3(Al1-xGex) with x = 0, 0.3 and 1, which are reported to provide the highest upper critical field values for Nb-based compounds. Wet mechanical milling using copper milling media and distilled water as a process control agent (PCA) was used with the intention of improving the yield, properties and the performance of these materials. Very high yields of nanocrystalline material were achieved but significant copper contamination occurred - confirmed using inductively-coupled-plasma atomic-emission-spectroscopy. Simultaneous thermogravimetric measurements and differential scanning calorimetry were performed on powders milled for up to 20 h with different PCA content, to quantify the work done on the powders. A typical grain size of a few nm was obtained for the Nb-Al-Ge mixtures after several hours milling. Powder ground for 20 h with 5% PCA was processed using a hot isostatic press (HIP) operating at 2000 atm and temperatures up to 750 °C. The room temperature resistivity decreased as the temperature of the HIPing increased. Unfortunately, despite the nanocrystalline microstructure of the powders and the high HIP temperatures, if superconducting material was formed it was below the detection level of resistivity, Ac. susceptibility and SQUID measurements. We conclude that during milling there was widespread contamination of the powders by the PCA so that milling with distilled water as a PCA is not to be recommended for fabricating nanocrystalline Nb3(Al1-xGex) A15 superconducting compounds.

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.

Measuring Fracture Times Of Ceramics

NASA Technical Reports Server (NTRS)

Shlichta, Paul J.; Bister, Leo; Bickler, Donald G.

1989-01-01

Electrical measurements complement or replace fast cinematography. Electronic system measures microsecond time intervals between impacts of projectiles on ceramic tiles and fracture tiles. Used in research on ceramics and ceramic-based composite materials such as armor. Hardness and low density of ceramics enable them to disintegrate projectiles more efficiently than metals. Projectile approaches ceramic tile specimen. Penetrating foil squares of triggering device activate display and recording instruments. As ceramic and resistive film break oscilloscope plots increase in electrical resistance of film.

Ceramic electrolyte coating methods

DOEpatents

Seabaugh, Matthew M.; Swartz, Scott L.; Dawson, William J.; McCormick, Buddy E.

2004-10-12

Processes for preparing aqueous suspensions of a nanoscale ceramic electrolyte material such as yttrium-stabilized zirconia. The invention also includes a process for preparing an aqueous coating slurry of a nanoscale ceramic electrolyte material. The invention further includes a process for depositing an aqueous spray coating slurry including a ceramic electrolyte material on pre-sintered, partially sintered, and unsintered ceramic substrates and products made by this process.

[Ceramic-ceramic articulation in uncemented total hip arthroplasty].

PubMed

Synder, Marek; Drobniewski, Marek; Kozłowski, Piotr; Grzegorzewski, Andrzej

2005-01-01

The main problem in total hip arthroplasty (THA) surgery is aseptic loosening of prosthesis components. In most cases the phagocytes reaction against the wear particle during the hip movement is responsible for aseptic prosthesis loosening. To prevent this reaction different hip articulation are invented to reduce this reaction. One of these solutions is ceramic-ceramic hip prosthesis articulation. The aim of this study was to evaluate the long-term results in patients who were treated because of coxarthrosis by means of ceramic-ceramic hip prosthesis. We analyzed 258 primary THA (222 patients, 116 women and 106 men) who were treated because of advanced coxarthrosis by Mittelmeier type hip endoprosthesis (ceramic-ceramic articulation). The mean age of patients at the surgery was 45.6 years and a mean follow-up 10.2 years. In most of our cases the idiopathic, traumatic and dysplastic coxarthrosis was noted. For clinical evaluation the classification system proposed by Merle d'Aubigne and Postel with Charnley modification was used. For radiological evaluation of the steam implantation the classification system proposed by De Lee and Charnley was used and for the cup implantation the system by Gruen and Moreland. In 87 patients (33.7%) the final results was graded as very good, in 96 (37.2%) as good, in 47 (18.2%) as satisfactory and in 28 patients (10.9%) the final results was poor. In analyzed group in 13 patients (5.0%) the revision surgery was necessary. The long-term results of THA with the use of Mittelmeier type of hip prosthesis presented a very low percentage of aseptic loosening. This type of prosthesis gives very high patients satisfaction.

Ceramic gas turbine shroud

DOEpatents

Shi, Jun; Green, Kevin E.

2014-07-22

An example gas turbine engine shroud includes a first annular ceramic wall having an inner side for resisting high temperature turbine engine gasses and an outer side with a plurality of radial slots. A second annular metallic wall is positioned radially outwardly of and enclosing the first annular ceramic wall and has a plurality of tabs in communication with the slot of the first annular ceramic wall. The tabs of the second annular metallic wall and slots of the first annular ceramic wall are in communication such that the first annular ceramic wall and second annular metallic wall are affixed.

Nanocrystalline NiNd0.01Fe1.99O4 as a gas sensor

NASA Astrophysics Data System (ADS)

Shinde, Tukaram J.; Gadkari, Ashok B.; Jadhav, Sarjerao R.; Kumar, Surender; Dalawai, Sanjeev P.; Vasambekar, Pramod N.

2015-06-01

Nanocrystalline NiNd0.01Fe1.99O4 has been synthesized by oxalate co-precipitation method and was characterized by X-ray diffraction technique. X-ray diffraction analysis confirms the formation of single phase cubic spinel structure. Crystallite size of the ferrite lies in the nano-particle range. The gas sensing properties of nanocrystalline ferrite were studied for gases like Cl2, LPG and C2H5OH. It was observed that NiNd0.01Fe1.99O4 is more sensitive towards chlorine followed by LPG at an operating temperature 277 °C compared to ethanol.

Ceramic electrolyte coating and methods

DOEpatents

Seabaugh, Matthew M [Columbus, OH; Swartz, Scott L [Columbus, OH; Dawson, William J [Dublin, OH; McCormick, Buddy E [Dublin, OH

2007-08-28

Aqueous coating slurries useful in depositing a dense coating of a ceramic electrolyte material (e.g., yttrium-stabilized zirconia) onto a porous substrate of a ceramic electrode material (e.g., lanthanum strontium manganite or nickel/zirconia) and processes for preparing an aqueous suspension of a ceramic electrolyte material and an aqueous spray coating slurry including a ceramic electrolyte material. The invention also includes processes for depositing an aqueous spray coating slurry including a ceramic electrolyte material onto pre-sintered, partially sintered, and unsintered ceramic substrates and products made by this process.

The history of ceramic filters.

PubMed

Fujishima, S

2000-01-01

The history of ceramic filters is surveyed. Included is the history of piezoelectric ceramics. Ceramic filters were developed using technology similar to that of quartz crystal and electro-mechanical filters. However, the key to this development involved the theoretical analysis of vibration modes and material improvements of piezoelectric ceramics. The primary application of ceramic filters has been for consumer-market use. Accordingly, a major emphasis has involved mass production technology, leading to low-priced devices. A typical ceramic filter includes monolithic resonators and capacitors packaged in unique configurations.

Anisotropic nanocrystalline MnBi with high coercivity at high temperature

NASA Astrophysics Data System (ADS)

Yang, J. B.; Yang, Y. B.; Chen, X. G.; Ma, X. B.; Han, J. Z.; Yang, Y. C.; Guo, S.; Yan, A. R.; Huang, Q. Z.; Wu, M. M.; Chen, D. F.

2011-08-01

Magnetic hard nanocrystalline MnBi has been prepared by melt spinning and subsequent low temperature annealing. A coercivity of 2.5 T can be achieved at 540 K for MnBi with an average grain size of about 20-30 nm. The coercivity iHc, mainly controlled by the coherent magnetization rotation, shows a strong dependence on the time of grinding and exhibits a positive temperature coefficient from 100 up to 540 K. The unique temperature dependent behavior of the coercivity (magnetocrystalline anisotropy) has a relationship with the variations in the crystal lattice ratio of c/a with temperatures. In addition, discontinuity can not be found in the lattice parameters of a, c, and c/a ratio at the magnetostructural transition temperature. The nanocrystalline MnBi powder fixed in an epoxy resin and under an applied magnetic field of 24 kOe shows a maximum energy product of 7.1 MGOe at room temperature and shows anisotropic characteristics with high Mr/Ms ratio up to 560 K.

Performance characteristics of nanocrystalline diamond vacuum field emission transistor array

NASA Astrophysics Data System (ADS)

Hsu, S. H.; Kang, W. P.; Davidson, J. L.; Huang, J. H.; Kerns, D. V.

2012-06-01

Nitrogen-incorporated nanocrystalline diamond (ND) vacuum field emission transistor (VFET) with self-aligned gate is fabricated by mold transfer microfabrication technique in conjunction with chemical vapor deposition (CVD) of nanocrystalline diamond on emitter cavity patterned on silicon-on-insulator (SOI) substrate. The fabricated ND-VFET demonstrates gate-controlled emission current with good signal amplification characteristics. The dc characteristics of the ND-VFET show well-defined cutoff, linear, and saturation regions with low gate turn-on voltage, high anode current, negligible gate intercepted current, and large dc voltage gain. The ac performance of the ND-VFET is measured, and the experimental data are analyzed using a modified small signal circuit model. The experimental results obtained for the ac voltage gain are found to agree with the theoretical model. A higher ac voltage gain is attainable by using a better test setup to eliminate the associated parasitic capacitances. The paper reveals the amplifier characteristics of the ND-VFET for potential applications in vacuum microelectronics.

Performance characteristics of nanocrystalline diamond vacuum field emission transistor array

NASA Astrophysics Data System (ADS)

Hsu, S. H.; Kang, W. P.; Davidson, J. L.; Huang, J. H.; Kerns, D. V.

2012-05-01

Nitrogen-incorporated nanocrystalline diamond (ND) vacuum field emission transistor (VFET) with self-aligned gate is fabricated by mold transfer microfabrication technique in conjunction with chemical vapor deposition (CVD) of nanocrystalline diamond on emitter cavity patterned on silicon-on-insulator (SOI) substrate. The fabricated ND-VFET demonstrates gate-controlled emission current with good signal amplification characteristics. The dc characteristics of the ND-VFET show well-defined cutoff, linear, and saturation regions with low gate turn-on voltage, high anode current, negligible gate intercepted current, and large dc voltage gain. The ac performance of the ND-VFET is measured, and the experimental data are analyzed using a modified small signal circuit model. The experimental results obtained for the ac voltage gain are found to agree with the theoretical model. A higher ac voltage gain is attainable by using a better test setup to eliminate the associated parasitic capacitances. The paper reveals the amplifier characteristics of the ND-VFET for potential applications in vacuum microelectronics.

Ultra-thin nanocrystalline diamond membranes as pressure sensors for harsh environments

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

Janssens, S. D., E-mail: stoffel.d.janssens@gmail.com; Haenen, K., E-mail: ken.haenen@uhasselt.be; IMOMEC, IMEC vzw, Wetenschapspark 1, B-3590 Diepenbeek

2014-02-17

Glass and diamond are suitable materials for harsh environments. Here, a procedure for fabricating ultra-thin nanocrystalline diamond membranes on glass, acting as an electrically insulating substrate, is presented. In order to investigate the pressure sensing properties of such membranes, a circular, highly conductive boron-doped nanocrystalline diamond membrane with a resistivity of 38 mΩ cm, a thickness of 150 nm, and a diameter of 555 μm is fabricated in the middle of a Hall bar structure. During the application of a positive differential pressure under the membrane (0–0.7 bar), four point piezoresistive effect measurements are performed. From these measurements, it can be concluded that the resistancemore » response of the membrane, as a function of differential pressure, is highly linear and sensitive.« less

High pressure ceramic joint

DOEpatents

Ward, Michael E.; Harkins, Bruce D.

1993-01-01

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

Thin film ceramic thermocouples

NASA Technical Reports Server (NTRS)

Gregory, Otto (Inventor); Fralick, Gustave (Inventor); Wrbanek, John (Inventor); You, Tao (Inventor)

2011-01-01

A thin film ceramic thermocouple (10) having two ceramic thermocouple (12, 14) that are in contact with each other in at least on point to form a junction, and wherein each element was prepared in a different oxygen/nitrogen/argon plasma. Since each element is prepared under different plasma conditions, they have different electrical conductivity and different charge carrier concentration. The thin film thermocouple (10) can be transparent. A versatile ceramic sensor system having an RTD heat flux sensor can be combined with a thermocouple and a strain sensor to yield a multifunctional ceramic sensor array. The transparent ceramic temperature sensor that could ultimately be used for calibration of optical sensors.

Ceramic tamper-revealing seals

DOEpatents

Kupperman, David S.; Raptis, Apostolos C.; Sheen, Shuh-Haw

1992-01-01

A flexible metal or ceramic cable with composite ceramic ends, or a u-shaped ceramic connecting element attached to a binding element plate or block cast from alumina or zirconium, and connected to the connecting element by shrink fitting.

Production of hydrogen using nanocrystalline protein-templated catalysts on m13 phage.

PubMed

Neltner, Brian; Peddie, Brian; Xu, Alex; Doenlen, William; Durand, Keith; Yun, Dong Soo; Speakman, Scott; Peterson, Andrew; Belcher, Angela

2010-06-22

For decades, ethanol has been in use as a fuel for the storage of solar energy in an energy-dense, liquid form. Over the past decade, the ability to reform ethanol into hydrogen gas suitable for a fuel cell has drawn interest as a way to increase the efficiency of both vehicles and stand-alone power generators. Here we report the use of extremely small nanocrystalline materials to enhance the performance of 1% Rh/10% Ni@CeO(2) catalysts in the oxidative steam reforming of ethanol with a ratio of 1.7:1:10:11 (air/EtOH/water/argon) into hydrogen gas, achieving 100% conversion of ethanol at only 300 degrees C with 60% H(2) in the product stream and less than 0.5% CO. Additionally, nanocrystalline 10% Ni@CeO(2) was shown to achieve 100% conversion of ethanol at 400 degrees C with 73% H(2), 2% CO, and 2% CH(4) in the product stream. Finally, we demonstrate the use of biological templating on M13 to improve the resistance of this catalyst to deactivation over 52 h tests at high flow rates (120 000 h(-1) GHSV) at 450 degrees C. This study suggests that the use of highly nanocrystalline, biotemplated catalysts to improve activity and stability is a promising route to significant gains over traditional catalyst manufacture methods.

Ceramic heat exchanger

DOEpatents

LaHaye, Paul G.; Rahman, Faress H.; Lebeau, Thomas P. E.; Severin, Barbara K.

1998-01-01

A tube containment system. The tube containment system does not significantly reduce heat transfer through the tube wall. The contained tube is internally pressurized, and is formed from a ceramic material having high strength, high thermal conductivity, and good thermal shock resistance. The tube containment system includes at least one ceramic fiber braid material disposed about the internally pressurized tube. The material is disposed about the tube in a predetermined axial spacing arrangement. The ceramic fiber braid is present in an amount sufficient to contain the tube if the tube becomes fractured. The tube containment system can also include a plurality of ceramic ring-shaped structures, in contact with the outer surface of the tube, and positioned between the tube and the ceramic fiber braid material, and/or at least one transducer positioned within tube for reducing the internal volume and, therefore, the energy of any shrapnel resulting from a tube fracture.

Ceramic heat exchanger

DOEpatents

LaHaye, P.G.; Rahman, F.H.; Lebeau, T.P.; Severin, B.K.

1998-06-16

A tube containment system is disclosed. The tube containment system does not significantly reduce heat transfer through the tube wall. The contained tube is internally pressurized, and is formed from a ceramic material having high strength, high thermal conductivity, and good thermal shock resistance. The tube containment system includes at least one ceramic fiber braid material disposed about the internally pressurized tube. The material is disposed about the tube in a predetermined axial spacing arrangement. The ceramic fiber braid is present in an amount sufficient to contain the tube if the tube becomes fractured. The tube containment system can also include a plurality of ceramic ring-shaped structures, in contact with the outer surface of the tube, and positioned between the tube and the ceramic fiber braid material, and/or at least one transducer positioned within tube for reducing the internal volume and, therefore, the energy of any shrapnel resulting from a tube fracture. 6 figs.

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.

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.

Method of producing novel silicon carbide articles. [Patent application

DOEpatents

Milewski, J.V.

1982-06-18

A method of producing articles comprising reaction-bonded silicon carbide (SiC) and graphite (and/or carbon) is given. The process converts the graphite (and/or carbon) in situ to SiC, thus providing the capability of economically obtaining articles made up wholly or partially of SiC having any size and shape in which graphite (and/or carbon) can be found or made. When the produced articles are made of an inner graphite (and/or carbon) substrate to which SiC is reaction bonded, these articles distinguish SiC-coated graphite articles found in the prior art by the feature of a strong bond having a gradual (as opposed to a sharply defined) interface which extends over a distance of mils. A method for forming SiC whisker-reinforced ceramic matrices is also given. The whisker-reinforced articles comprise SiC whiskers which substantially retain their structural integrity.

Ceramic tamper-revealing seals

DOEpatents

Kupperman, D.S.; Raptis, A.C.; Sheen, S.H.

1992-12-08

A flexible metal or ceramic cable is described with composite ceramic ends, or a U-shaped ceramic connecting element attached to a binding element plate or block cast from alumina or zirconium, and connected to the connecting element by shrink fitting. 7 figs.

Nano-glass ceramic cathodes for Li+/Na+ mixed-ion batteries

NASA Astrophysics Data System (ADS)

He, Wen; Zhang, Xudong; Jin, Chao; Wang, Yaoyao; Mossin, Susanne; Yue, Yuanzheng

2017-02-01

Electrode materials can display superior electrochemical performances and behavior via the nanoscale design. Here, the low-temperature synthesis of nano-glass ceramics (NGCs) is based on inheriting the network structure of yeast polyphosphate metabolism. The NGCs-3 sample synthesized with a molar ratio of Fe/V = 7:6 is composed of nano-domains of semiconducting oxide glass (Li2O-Na2O-Fe2O3-V2O5-P2O5, LNFVP), nanocrystalline particles (Li9Fe3P8O29, Li0.6V1.67O3.67 and VOPO4), and nanopores connected by interfaces. We have clarified the mixing ion transport mechanism and the electrochemical reactions, and the influences of molar ratio of Fe/V on the structure and electrochemical properties of NGCs. This nanoscale design offers a new possibility improved the electrochemical performances of Li+/Na+ mixed-ion batteries (LNMIBs). The NGCs-3 electrode exhibits a higher discharge capacity (145 mAh g-1) and energy storage density (525 Whkg-1) at 5C, and the capacity retention reaches 70% after 1000 cycles. More importantly, we have established a direct relationship between the electrochemical kinetics and nanostructure of NGC electrode materials.

Ceramic hot-gas filter

DOEpatents

Connolly, Elizabeth Sokolinski; Forsythe, George Daniel; Domanski, Daniel Matthew; Chambers, Jeffrey Allen; Rajendran, Govindasamy Paramasivam

1999-01-01

A ceramic hot-gas candle filter having a porous support of filament-wound oxide ceramic yarn at least partially surrounded by a porous refractory oxide ceramic matrix, and a membrane layer on at least one surface thereof. The membrane layer may be on the outer surface, the inner surface, or both the outer and inner surface of the porous support. The membrane layer may be formed of an ordered arrangement of circularly wound, continuous filament oxide ceramic yarn, a ceramic filler material which is less permeable than the filament-wound support structure, or some combination of continuous filament and filler material. A particularly effective membrane layer features circularly wound filament with gaps intentionally placed between adjacent windings, and a filler material of ceramic particulates uniformly distributed throughout the gap region. The filter can withstand thermal cycling during backpulse cleaning and is resistant to chemical degradation at high temperatures.

Ceramic hot-gas filter

DOEpatents

Connolly, E.S.; Forsythe, G.D.; Domanski, D.M.; Chambers, J.A.; Rajendran, G.P.

1999-05-11

A ceramic hot-gas candle filter is described having a porous support of filament-wound oxide ceramic yarn at least partially surrounded by a porous refractory oxide ceramic matrix, and a membrane layer on at least one surface thereof. The membrane layer may be on the outer surface, the inner surface, or both the outer and inner surface of the porous support. The membrane layer may be formed of an ordered arrangement of circularly wound, continuous filament oxide ceramic yarn, a ceramic filler material which is less permeable than the filament-wound support structure, or some combination of continuous filament and filler material. A particularly effective membrane layer features circularly wound filament with gaps intentionally placed between adjacent windings, and a filler material of ceramic particulates uniformly distributed throughout the gap region. The filter can withstand thermal cycling during back pulse cleaning and is resistant to chemical degradation at high temperatures.

Fundamental tribological properties of ceramics

NASA Technical Reports Server (NTRS)

Buckley, D. H.; Miyoshi, K.

1985-01-01

When a ceramic is brought into contact with itself, another ceramic, or a metal, strong bond forces can develop between the materials. Adhesion between a ceramic and itself or another solid are discussed from a theoretical consideration of the nature of the surfaces and experimentally by relating bond forces to the interface resulting from solid state contact. Elastic, plastic, and fracture behavior of ceramics in solid-state contact are discussed as they relate to friction and wear. The contact load necessary to initiate fracture in ceramics is shown to be appreciably reduced with tangential motion. Both friction and wear of ceramics are anisotropic and relate to crystal structure as with metals. Both free energy of oxide formation and the d valence bond character of metals are related to the friction and wear characteristics for metals in contact with ceramics. Lubrication is found to increase the critical load necessary to initiate fracture of ceramics with sliding or rubbing contact.

The High performance of nanocrystalline CVD diamond coated hip joints in wear simulator test.

PubMed

Maru, M M; Amaral, M; Rodrigues, S P; Santos, R; Gouvea, C P; Archanjo, B S; Trommer, R M; Oliveira, F J; Silva, R F; Achete, C A

2015-09-01

The superior biotribological performance of nanocrystalline diamond (NCD) coatings grown by a chemical vapor deposition (CVD) method was already shown to demonstrate high wear resistance in ball on plate experiments under physiological liquid lubrication. However, tests with a close-to-real approach were missing and this constitutes the aim of the present work. Hip joint wear simulator tests were performed with cups and heads made of silicon nitride coated with NCD of ~10 μm in thickness. Five million testing cycles (Mc) were run, which represent nearly five years of hip joint implant activity in a patient. For the wear analysis, gravimetry, profilometry, scanning electron microscopy and Raman spectroscopy techniques were used. After 0.5 Mc of wear test, truncation of the protruded regions of the NCD film happened as a result of a fine-scale abrasive wear mechanism, evolving to extensive plateau regions and highly polished surface condition (Ra<10nm). Such surface modification took place without any catastrophic features as cracking, grain pullouts or delamination of the coatings. A steady state volumetric wear rate of 0.02 mm(3)/Mc, equivalent to a linear wear of 0.27 μm/Mc favorably compares with the best performance reported in the literature for the fourth generation alumina ceramic (0.05 mm(3)/Mc). Also, squeaking, quite common phenomenon in hard-on-hard systems, was absent in the present all-NCD system. Copyright © 2015 Elsevier Ltd. All rights reserved.

Exposure to lead and cadmium released from ceramics and glassware intended to come into contact with food.

PubMed

Rebeniak, Małgorzata; Wojciechowska-Mazurek, Maria; Mania, Monika; Szynal, Tomasz; Strzelecka, Agnieszka; Starska, Krystyna

2014-01-01

The dietary intake of harmful elements, particularly lead and cadmium constitutes a health threat and essential measures should be undertaken to reduce consumer exposure. The latest risk assessments by the European Food Safety Authority (EFSA) and Joint FAO/WHO Expert Committee on Food Additives (JECFA) have indicated that the Provisional Tolerable Weekly Intake (PTWI) for lead and cadmium do not ensure health safety and their review had to be undertaken. Migration from ceramics and glassware intended for food contact is an important source of lead and cadmium intake. To study the release of lead and cadmium from ceramics and glassware (including decorated products) intended for food contact that are available on the Polish market and to assess the resulting health risk to the consumer. Ceramics and glassware (mainly decorated) were sampled from the Polish market during 2010- 2012 throughout the country by staff of the Sanitary-Epidemiological Stations in accordance with monitoring procedures and guidelines designed by the National Institute of Public Health-National Institute of Hygiene. Migration of lead and cadmium was measured by incubating the samples with 4% acetic acid for 24 hours at a temperature of 22±2ºC in the dark. Flame Atomic Absorption Spectrometry (FAAS) was used to measure these elements in food simulant according to a validated and accredited method (PN-EN ISO/IEC 17025). 1273 samples of ceramics and glass wares were analysed in 2010-2012. Lead and cadmium release were usually found to be below analytical detection limits. Permissible migration limits (as prescribed by the legislation) of these metals were rarely exceeded and were reported mainly in articles imported from outside the EU. Two imported and decorated ceramic flat plates released lead at 0.9 and 11.9 mg/dm2 (limit 0.8 mg/dm2) and 5 imported deep plates gave migration values of 4.7 mg/L, 4.9 mg/L, 5.6 mg/L, 6.1 mg/L, 8.6 mg/L (limit 4.0 mg/L). Lead migrations from ceramic ware rims

Nonlinear fracture of concrete and ceramics

NASA Technical Reports Server (NTRS)

Kobayashi, Albert S.; Du, Jia-Ji; Hawkins, Niel M.; Bradt, Richard C.

1989-01-01

The nonlinear fracture process zones in an impacted unnotched concrete bend specimen, a prenotched ceramic bend specimen, and an unnotched ceramic/ceramic composite bend specimen were estimated through hybrid experimental numerical analysis. Aggregate bridging in concrete, particulate bridging in ceramics, and fiber bridging in ceramic/ceramic composite are modeled by Barenblatt-type cohesive zones which are incorporated into the finite-element models of the bend specimens. Both generation and propagation analyses are used to estimate the distribution of crack closure stresses in the nonlinear fracture process zones. The finite-element models are then used to simulate fracture tests consisting of rapid crack propagation in an impacted concrete bend specimen, and stable crack growth and strain softening in a ceramic and ceramic/ceramic composite bend specimens.

Metal to ceramic sealed joint

DOEpatents

Lasecki, J.V.; Novak, R.F.; McBride, J.R.

1991-08-27

A metal to ceramic sealed joint which can withstand wide variations in temperature and maintain a good seal is provided for use in a device adapted to withstand thermal cycling from about 20 to about 1000 degrees C. The sealed joint includes a metal member, a ceramic member having an end portion, and an active metal braze forming a joint to seal the metal member to the ceramic member. The joint is positioned remote from the end portion of the ceramic member to avoid stresses at the ends or edges of the ceramic member. The sealed joint is particularly suited for use to form sealed metal to ceramic joints in a thermoelectric generator such as a sodium heat engine where a solid ceramic electrolyte is joined to metal parts in the system. 11 figures.

Metal to ceramic sealed joint

DOEpatents

Lasecki, John V.; Novak, Robert F.; McBride, James R.

1991-01-01

A metal to ceramic sealed joint which can withstand wide variations in temperature and maintain a good seal is provided for use in a device adapted to withstand thermal cycling from about 20 to about 1000 degrees C. The sealed joint includes a metal member, a ceramic member having an end portion, and an active metal braze forming a joint to seal the metal member to the ceramic member. The joint is positioned remote from the end portion of the ceramic member to avoid stresses at the ends or edges of the ceramic member. The sealed joint is particularly suited for use to form sealed metal to ceramic joints in a thermoelectric generator such as a sodium heat engine where a solid ceramic electrolyte is joined to metal parts in the system.

Examining the influence of grain size on radiation tolerance in the nanocrystalline regime

DOE PAGES

Barr, Christopher M.; Li, Nan; Boyce, Brad L.; ...

2018-05-01

Here, nanocrystalline materials have been proposed as superior radiation tolerant materials in comparison to coarse grain counterparts. However, there is still a limited understanding whether a particular nanocrystalline grain size is required to obtain significant improvements in key deleterious effects resulting from energetic irradiation. This work employs the use of in-situ heavy ion irradiation transmission electron microscopy experiments coupled with quantitative defect characterization and precession electron diffraction to explore the sensitivity of defect size and density within the nanocrystalline regime in platinum. Under the explored experimental conditions, no significant change in either the defect size or density between grain sizesmore » of 20 and 100 nm was observed. Furthermore, the in-situ transmission electron microscopy irradiations illustrate stable sessile defect clusters of 1–3 nm adjacent to most grain boundaries, which are traditionally treated as strong defect sinks. The stability of these sessile defects observed in-situ in small, 20–40 nm, grains is the proposed primary mechanism for a lack of defect density trends. Lastly, this scaling breakdown in radiation improvement with decreasing grain size has practical importance on nanoscale grain boundary engineering approaches for proposed radiation tolerant alloys.« less

Examining the influence of grain size on radiation tolerance in the nanocrystalline regime

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

Barr, Christopher M.; Li, Nan; Boyce, Brad L.

Here, nanocrystalline materials have been proposed as superior radiation tolerant materials in comparison to coarse grain counterparts. However, there is still a limited understanding whether a particular nanocrystalline grain size is required to obtain significant improvements in key deleterious effects resulting from energetic irradiation. This work employs the use of in-situ heavy ion irradiation transmission electron microscopy experiments coupled with quantitative defect characterization and precession electron diffraction to explore the sensitivity of defect size and density within the nanocrystalline regime in platinum. Under the explored experimental conditions, no significant change in either the defect size or density between grain sizesmore » of 20 and 100 nm was observed. Furthermore, the in-situ transmission electron microscopy irradiations illustrate stable sessile defect clusters of 1–3 nm adjacent to most grain boundaries, which are traditionally treated as strong defect sinks. The stability of these sessile defects observed in-situ in small, 20–40 nm, grains is the proposed primary mechanism for a lack of defect density trends. Lastly, this scaling breakdown in radiation improvement with decreasing grain size has practical importance on nanoscale grain boundary engineering approaches for proposed radiation tolerant alloys.« less

High pressure ceramic joint

DOEpatents

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

1993-11-30

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

Ceramic Electron Multiplier

DOE PAGES

Comby, G.

1996-10-01

The Ceramic Electron Multipliers (CEM) is a compact, robust, linear and fast multi-channel electron multiplier. The Multi Layer Ceramic Technique (MLCT) allows to build metallic dynodes inside a compact ceramic block. The activation of the metallic dynodes enhances their secondary electron emission (SEE). The CEM can be used in multi-channel photomultipliers, multi-channel light intensifiers, ion detection, spectroscopy, analysis of time of flight events, particle detection or Cherenkov imaging detectors. (auth)

The impact of diamond nanocrystallinity on osteoblast functions.

PubMed

Yang, Lei; Sheldon, Brian W; Webster, Thomas J

2009-07-01

Nanocrystalline diamond has been proposed as an anti-abrasive film on orthopedic implants. In this study, osteoblast (bone forming cells) functions including adhesion (up to 4h), proliferation (up to 5 days) and differentiation (up to 21 days) on different diamond film topographies were systematically investigated. In order to exclude interferences from changes in surface chemistry and wettability (energy), diamond films with nanometer and micron scale topographies were fabricated through microwave plasma enhanced chemical-vapor-deposition and hydrogen plasma treatment. Scanning electron microscopy (SEM), atomic force microscopy (AFM), Raman spectroscopy and water contact angle measurements verified the similar surface chemistry and wettability but varied topographies for all of the diamond films prepared on silicon in this study. Cytocompatibility assays demonstrated enhanced osteoblast functions (including adhesion, proliferation, intracellular protein synthesis, alkaline phosphatase activity and extracellular calcium deposition) on nanocrystalline diamond compared to submicron diamond grain size films for all time periods tested up to 21 days. An SEM study of osteoblast attachment helped to explain the topographical impact diamond had on osteoblast functions by showing altered filopodia extensions on the different diamond topographies. In summary, these results provided insights into understanding the role diamond nanotopography had on osteoblast interactions and more importantly, the application of diamond films to improve orthopedic implant lifetimes.

Change of magnetic properties of nanocrystalline alloys under influence of external factors

NASA Astrophysics Data System (ADS)

Sitek, Jozef; Holková, Dominika; Dekan, Julius; Novák, Patrik

2016-10-01

Nanocrystalline (Fe3Ni1)81Nb7B12 alloys were irradiated using different types of radiation and subsequently studied by Mössbauer spectroscopy. External magnetic field of 0.5 T, electron-beam irradiation up to 4 MGy, neutron irradiation up to 1017 neutrons/cm2 and irradiation with Cu ions were applied on the samples. All types of external factors had an influence on the magnetic microstructure manifested as a change in the direction of the net magnetic moment, intensity of the internal magnetic field and volumetric fraction of the constituent phases. The direction of the net magnetic moment was the most sensitive parameter. Changes of the microscopic magnetic parameters were compared after different external influence and results of nanocrystalline samples were compared with their amorphous precursors.

Ceramic Surface Treatment with a Single-component Primer: Resin Adhesion to Glass Ceramics.

PubMed

Prado, Mayara; Prochnow, Catina; Marchionatti, Ana Maria Estivalete; Baldissara, Paolo; Valandro, Luiz Felipe; Wandscher, Vinicius Felipe

2018-04-19

To evaluate the microshear bond strength (μSBS) of composite cement bonded to two machined glass ceramics and its durability, comparing conventional surface conditioning (hydrofluoric acid + silane) to a one-step primer (Monobond Etch & Prime). Machined slices of lithium disilicate ceramic (LDC) (IPS e.max CAD) and feldspathic ceramic (FC) (VITA Mark II) glass ceramics were divided into two groups (n = 10) according to two factors: 1. surface treatment: HF+S (ca 5% hydrofluoric acid [IPS Ceramic Etching GEL] + silane coupling agent [SIL; Monobond Plus]) or MEP (single-component ceramic conditioner; Monobond Etch & Prime); 2. storage condition: baseline (without aging; tested 24 h after cementing) or aged (70 days of water storage + 12,000 thermal cycles). Composite cement (Multilink Automix, Ivoclar Vivadent) was applied to starch matrices on the treated ceramic surfaces and photoactivated. A μSBS test was performed (0.5 mm/min) and the failure pattern was determined. Contact angle and micromorphological analyses were also performed. Data were analyzed with Student's t-test (α = 5%). For both ceramic materials, HF+S resulted in higher mean μSBS (MPa) at baseline (LDC: HF+S 21.2 ± 2.2 > MEP 10.4 ± 2.4; FC: HF+S 19.6 ± 4.3 > MEP 13.5 ± 5.4) and after aging (LDC: HF+S 14.64 ± 2.31 > MEP 9 ± 3.4; FC HF+S: 14.73 ± 3.33 > MEP 11.1 ± 3.3). HF+S resulted in a statistically significant decrease in mean μSBS after aging (p = 0.0001), while MEP yielded no significant reduction. The main failure type was adhesive between composite cement and ceramic. HF+S resuted in the lowest contact angle. Hydrofluoric acid + silane resulted in higher mean μSBS than Monobond Etch & Prime for both ceramics; however, Monobond Etch & Prime had stable bonding after aging.

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.

Defect structure in electrodeposited nanocrystalline Ni layers with different Mo concentrations

NASA Astrophysics Data System (ADS)

Kapoor, Garima; Péter, László; Fekete, Éva; Gubicza, Jenő

2018-05-01

The effect of molybdenum (Mo) alloying on the lattice defect structure in electrodeposited nanocrystalline nickel (Ni) films was studied. The electrodeposited layers were prepared on copper substrate at room temperature, with a constant current density and pH value. The chemical composition of these layers was determined by EDS. In addition, X-ray diffraction line profile analysis was carried out to study the microstructural parameters such as the crystallite size, the dislocation density and the stacking fault probability. It was found that the higher Mo content yielded more than one order of magnitude larger dislocation density while the crystallite size was only slightly smaller. In addition, the twin boundary formation activity during deposition increased with increasing Mo concentration. The results obtained on electrodeposited layers were compared with previous research carried out on bulk nanocrystalline Ni-Mo materials with similar compositions but processed by severe plastic deformation.

Ultrahigh hardness and high electrical resistivity in nano-twinned, nanocrystalline high-entropy alloy films

NASA Astrophysics Data System (ADS)

Huo, Wenyi; Liu, Xiaodong; Tan, Shuyong; Fang, Feng; Xie, Zonghan; Shang, Jianku; Jiang, Jianqing

2018-05-01

Nano-twinned, nanocrystalline CoCrFeNi high-entropy alloy films were produced by magnetron sputtering. The films exhibit a high hardness of 8.5 GPa, the elastic modulus of 161.9 GPa and the resistivity as high as 135.1 μΩ·cm. The outstanding mechanical properties were found to result from the resistance of deformation created by nanocrystalline grains and nano-twins, while the electrical resistivity was attributed to the strong blockage effect induced by grain boundaries and lattice distortions. The results lay a solid foundation for the development of advanced films with structural and functional properties combined in micro-/nano-electronic devices.

Multiple magnetic scattering in small-angle neutron scattering of Nd-Fe-B nanocrystalline magnet.

PubMed

Ueno, Tetsuro; Saito, Kotaro; Yano, Masao; Ito, Masaaki; Shoji, Tetsuya; Sakuma, Noritsugu; Kato, Akira; Manabe, Akira; Hashimoto, Ai; Gilbert, Elliot P; Keiderling, Uwe; Ono, Kanta

2016-06-20

We have investigated the influence of multiple scattering on the magnetic small-angle neutron scattering (SANS) from a Nd-Fe-B nanocrystalline magnet. We performed sample-thickness- and neutron-wavelength-dependent SANS measurements, and observed the scattering vector dependence of the multiple magnetic scattering. It is revealed that significant multiple scattering exists in the magnetic scattering rather than the nuclear scattering of Nd-Fe-B nanocrystalline magnet. It is considered that the mean free path of the neutrons for magnetic scattering is rather short in Nd-Fe-B magnets. We analysed the SANS data by the phenomenological magnetic correlation model considering the magnetic microstructures and obtained the microstructural parameters.

Multiple magnetic scattering in small-angle neutron scattering of Nd–Fe–B nanocrystalline magnet

PubMed Central

Ueno, Tetsuro; Saito, Kotaro; Yano, Masao; Ito, Masaaki; Shoji, Tetsuya; Sakuma, Noritsugu; Kato, Akira; Manabe, Akira; Hashimoto, Ai; Gilbert, Elliot P.; Keiderling, Uwe; Ono, Kanta

2016-01-01

We have investigated the influence of multiple scattering on the magnetic small-angle neutron scattering (SANS) from a Nd–Fe–B nanocrystalline magnet. We performed sample-thickness- and neutron-wavelength-dependent SANS measurements, and observed the scattering vector dependence of the multiple magnetic scattering. It is revealed that significant multiple scattering exists in the magnetic scattering rather than the nuclear scattering of Nd–Fe–B nanocrystalline magnet. It is considered that the mean free path of the neutrons for magnetic scattering is rather short in Nd–Fe–B magnets. We analysed the SANS data by the phenomenological magnetic correlation model considering the magnetic microstructures and obtained the microstructural parameters. PMID:27321149

From amorphous to nanocrystalline: the effect of nanograins in amorphous matrix on the thermal conductivity of hot-wire chemical-vapor deposited silicon films

DOE PAGES

Kearney, B. T.; Jugdersuren, B.; Queen, D. R.; ...

2017-12-28

Here, we have measured the thermal conductivity of amorphous and nanocrystalline silicon films with varying crystalline content from 85K to room temperature. The films were prepared by the hot-wire chemical-vapor deposition, where the crystalline volume fraction is determined by the hydrogen (H2) dilution ratio to the processing silane gas (SiH4), R=H2/SiH4. We varied R from 1 to 10, where the films transform from amorphous for R < 3 to mostly nanocrystalline for larger R. Structural analyses show that the nanograins, averaging from 2 to 9nm in sizes with increasing R, are dispersed in the amorphous matrix. The crystalline volume fractionmore » increases from 0 to 65% as R increases from 1 to 10. The thermal conductivities of the two amorphous silicon films are similar and consistent with the most previous reports with thicknesses no larger than a few um deposited by a variety of techniques. The thermal conductivities of the three nanocrystalline silicon films are also similar, but are about 50-70% higher than those of their amorphous counterparts. The heat conduction in nanocrystalline silicon films can be understood as the combined contribution in both amorphous and nanocrystalline phases, where increased conduction through improved nanocrystalline percolation path outweighs increased interface scattering between silicon nanocrystals and the amorphous matrix.« less

From amorphous to nanocrystalline: the effect of nanograins in amorphous matrix on the thermal conductivity of hot-wire chemical-vapor deposited silicon films

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

Kearney, B. T.; Jugdersuren, B.; Queen, D. R.

Here, we have measured the thermal conductivity of amorphous and nanocrystalline silicon films with varying crystalline content from 85K to room temperature. The films were prepared by the hot-wire chemical-vapor deposition, where the crystalline volume fraction is determined by the hydrogen (H2) dilution ratio to the processing silane gas (SiH4), R=H2/SiH4. We varied R from 1 to 10, where the films transform from amorphous for R < 3 to mostly nanocrystalline for larger R. Structural analyses show that the nanograins, averaging from 2 to 9nm in sizes with increasing R, are dispersed in the amorphous matrix. The crystalline volume fractionmore » increases from 0 to 65% as R increases from 1 to 10. The thermal conductivities of the two amorphous silicon films are similar and consistent with the most previous reports with thicknesses no larger than a few um deposited by a variety of techniques. The thermal conductivities of the three nanocrystalline silicon films are also similar, but are about 50-70% higher than those of their amorphous counterparts. The heat conduction in nanocrystalline silicon films can be understood as the combined contribution in both amorphous and nanocrystalline phases, where increased conduction through improved nanocrystalline percolation path outweighs increased interface scattering between silicon nanocrystals and the amorphous matrix.« less

Ceramic and non-ceramic hydroxyapatite as a bone graft material: a brief review.

PubMed

Dutta, S R; Passi, D; Singh, P; Bhuibhar, A

2015-03-01

Treatment of dental, craniofacial and orthopedic defects with bone graft substitutes has shown promising result achieving almost complete bone regeneration depending on product resorption similar to human bone's physicochemical and crystallographic characteristics. Among these, non-ceramic and ceramic hydroxyapatite being the main inorganic salt of bone is the most studied calcium phosphate material in clinical practices ever since 1970s and non-ceramic since 1985. Its "chemical similarity" with the mineralized phase of biologic bone makes it unique. Hydroxyapatite as an excellent carrier of osteoinductive growth factors and osteogenic cell populations is also useful as drug delivery vehicle regardless of its density. Porous ceramic and non-ceramic hydroxyapatite is osteoconductive, biocompatible and very inert. The need for bone graft material keeps on increasing with increased age of the population and the increased conditions of trauma. Recent advances in genetic engineering and doping techniques have made it possible to use non-ceramic hydroxyapatite in larger non-ceramic crystals and cluster forms as a successful bone graft substitute to treat various types of bone defects. In this paper we have mentioned some recently studied properties of hydroxyapatite and its various uses through a brief review of the literatures available to date.

Mounting for ceramic scroll

DOEpatents

Petty, Jack D.

1993-01-01

A mounting for a ceramic scroll on a metal engine block of a gas turbine engine includes a first ceramic ring and a pair of cross key connections between the first ceramic ring, the ceramic scroll, and the engine block. The cross key connections support the scroll on the engine block independent of relative radial thermal growth and for bodily movement toward an annular mounting shoulder on the engine. The scroll has an uninterrupted annular shoulder facing the mounting shoulder on the engine block. A second ceramic ring is captured between mounting shoulder and the uninterrupted shoulder on the scroll when the latter is bodily shifted toward the mouting shoulder to define a gas seal between the scroll and the engine block.

Fabrication of ceramic substrate-reinforced and free forms by mandrel plasma spraying metal-ceramic composites

NASA Technical Reports Server (NTRS)

Quentmeyer, R. J.; Mcdonald, G.; Hendricks, R. C.

1985-01-01

Components fabricated of, or coated with, ceramics have lower parasitic cooling requirements. Techniques are discussed for fabricating thin-shell ceramic components and ceramic coatings for applications in rocket or jet engine environments. Thin ceramic shells with complex geometric forms involving convolutions and reentrant surfaces were fabricated by mandrel removal. Mandrel removal was combined with electroplating or plasma spraying and isostatic pressing to form a metal support for the ceramic. Rocket engine thrust chambers coated with 0.08 mm (3 mil) of ZrO2-8Y2O3 had no failures and a tenfold increase in engine life. Some measured mechanical properties of the plasma-sprayed ceramic are presented.

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

PubMed Central

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

2010-01-01

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

[Preparation of porous ceramics based on waste ceramics and its Ni2+ adsorption characteristics].

PubMed

Zhang, Yong-Li; Wang, Cheng-Zhi; Shi, Ce; Shang, Ling-Ling; Ma, Rui; Dong, Wan-Li

2013-07-01

The preparation conditions of porous ceramics were determined by SEM, XRD and FT-IR characterizations as well as the nickel removal ability of porous ceramics to be: the mass fraction w of sesbania powder doped was 4%, and the calcination temperature was 800 degrees C. SEM and pore structure characterization illustrated that calcination caused changes in the structure and morphology of waste ceramics. With the increase of calcination temperature, the specific surface area and pore volume decreased, while the aperture increased. EDS analyses showed that the main elements of both the original waste porcelain powder and the porous ceramics were Si, Al and O. The SEM, XRD and FT-IR characterization of porous ceramics illustrated that the structure of porous ceramics was stable before and after adsorption. The series of experiments of Ni2+ adsorption using these porous ceramics showed that when the dosage of porous ceramics was 10 g x L(-1), the adsorption time was 60 min, the pH value was 6.32, and the concentration of nickel-containing wastewater was below 100 mg x L(-1), the Ni2+ removal of wastewater reached 89.7%. Besides, the porous ceramics showed higher removal efficiency on nickel in the wastewater. The Ni(2+)-containing wastewater was processed by the porous ceramics prepared, and the adsorption dynamics and adsorption isotherms of Ni2+ in wastewater by porous ceramics were investigated. The research results showed that the Ni2+ adsorption process of porous ceramics was in accordance with the quasi second-order kinetic model (R2 = 0.999 9), with Q(e) of 9.09 mg x g(-1). The adsorption process can be described by the Freundlich equation and Langmuir equation, and when the temperature increased from 20 degrees C to 40 degrees C, the maximum adsorption capacity Q(m) increased from 14.49 mg x g(-1) to 15.38 mg x g(-1).

High surface area nanocrystalline hausmannite synthesized by a solvent-free route

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

Herrera-Miranda, Daniel; Ponrouch, Alexandre; Pons, Josefina

Highlights: ► High surface area Mn{sub 3}O{sub 4} nanoparticles obtained by a solvent-free low temperature route. ► 3,6,9-Trioxadecanoic acid allows to obtain nanocrystalline hausmannite. ► Tape casted electrodes show up to 300 mAh g{sup −1} capacity after more than 40 cycles at a C/3 rate. ► Upper cut off voltage strongly influences capacity retention upon cycling at high C rates. -- Abstract: Nanocrystalline high surface area Mn{sub 3}O{sub 4} powder was obtained at low temperature by a solvent-free route. The precursor was a mixture of manganese (II) acetate, 3,6,9-trioxadecanoic acid (TODA) and ammonium acetate that were intimately mixed by groundingmore » in an agate mortar. Nanocrystalline Mn{sub 3}O{sub 4} was obtained by thermal treatment at 120 °C. Powder X-ray diffraction, selected area electron diffraction, high resolution transmission electron microscopy, and Fourier transformed infrared characterization confirmed the formation of the hausmannite phase. The as-prepared mesoporous material has high specific surface area (120 m{sup 2} g{sup −1}). The performances of tape casted Mn{sub 3}O{sub 4} nanopowder electrodes were investigated as anode material for lithium ion batteries. High capacity values were achieved at diverse C rates. Capacity fading was found to be dependent on the upper cut off voltage, the presence of a plateau at 2.25 V vs. Li{sup +}/Li being detrimental for long term cyclability.« less

Experimental and Modeling Studies on the Microstructures and Properties of Oxidized Aluminum Nitride Ceramic Substrates

NASA Astrophysics Data System (ADS)

Cao, Ye; Xu, Haixian; Zhan, Jun; Zhang, Hao; Wei, Xin; Wang, Jianmin; Cui, Song; Tang, Wenming

2018-05-01

Oxidation of aluminum nitride (AlN) ceramic substrates doped with 2 wt.% Y2O3 was performed in air at temperatures ranging from 1000 to 1300 °C for various lengths of time. Microstructure, bending strength, and thermal conductivity of the oxidized AlN substrates were studied experimentally and also via mathematical models. The results show that the oxide layer formed on the AlN substrates is composed of α-Al2O3 nanocrystallines and interconnected micropores. Longitudinal and transverse cracks are induced in the oxide layer under tensile and shear stresses, respectively. Intergranular oxidation of the AlN grains close to the oxide layer/AlN interface also occurs, leading to widening and cracking of the AlN grain boundaries. These processes result in the monotonous degradation of bending strength and thermal conductivity of the oxidized AlN substrates. Two mathematic models concerning these properties of the oxidized AlN substrates versus the oxide layer thickness were put forward. They fit well with the experimental results.

Synthesis of functional ceramic supports by ice templating and atomic layer deposition

NASA Astrophysics Data System (ADS)

Klotz, Michaela; Weber, Matthieu; Deville, Sylvain; Oison, Didier; Iatsunskyi, Igor; Coy, Emerson; Bechelany, Mikhael

2018-05-01

In this work, we report an innovative route for the manufacturing of functional ceramic supports, by combining ice templating of yttria stabilized zirconia (YSZ) and atomic layer deposition (ALD) of Al2O3 processes. Ceramic YSZ monoliths are prepared using the ice-templating process, which is based on the controlled crystallization of water following a thermal gradient. Sublimation of the ice and the sintering of the material reveal the straight micrometer sized pores shaped by the ice crystal growth. The high temperature sintering allows for the ceramic materials to present excellent mechanical strength and porosities of 67%. Next, the conformality benefit of ALD is used to deposit an alumina coating at the surface of the YSZ pores, in order to obtain a functional material. The Al2O3 thin films obtained by ALD are 100 nm thick and conformally deposited within the macroporous ceramic supports, as shown by SEM and EDS analysis. Mercury intrusion experiments revealed a reduction of the entrance pore diameter, in line with the growth per cycle of 2 Å of the ALD process. In addition to the manufacture of the innovative ceramic nanomaterials, this article also describes the fine characterization of the coatings obtained using mercury intrusion, SEM and XRD analysis.

Ceramic combustor mounting

DOEpatents

Hoffman, Melvin G.; Janneck, Frank W.

1982-01-01

A combustor for a gas turbine engine includes a metal engine block including a wall portion defining a housing for a combustor having ceramic liner components. A ceramic outlet duct is supported by a compliant seal on the metal block and a reaction chamber liner is stacked thereon and partly closed at one end by a ceramic bypass swirl plate which is spring loaded by a plurality of circumferentially spaced, spring loaded guide rods and wherein each of the guide rods has one end thereof directed exteriorly of a metal cover plate on the engine block to react against externally located biasing springs cooled by ambient air and wherein the rod spring support arrangement maintains the stacked ceramic components together so that a normal force is maintained on the seal between the outlet duct and the engine block under all operating conditions. The support arrangement also is operative to accommodate a substantial difference in thermal expansion between the ceramic liner components of the combustor and the metal material of the engine block.

Tribological Properties of Structural Ceramics

NASA Technical Reports Server (NTRS)

Buckley, Donald H.; Miyoshi, Kazuhisa

1987-01-01

Paper discusses tribological properties of structural ceramics. Function of tribological research is to bring about reduction in adhesion, friction, and wear of mechanical components; to prevent failures; and to provide long, reliable component life, through judicious selection of materials, operating parameters, and lubricants. Paper reviews adhesion, friction, wear, and lubrication of ceramics; anisotropic friction and wear behavior; and effects of surface films and interactions between ceramics and metals. Analogies with metals are made. Both oxide and nonoxide ceramics, including ceramics used as high temperature lubricants, are dicussed.

Randomized clinical trial of implant-supported ceramic-ceramic and metal-ceramic fixed dental prostheses: preliminary results.

PubMed

Esquivel-Upshaw, Josephine F; Clark, Arthur E; Shuster, Jonathan J; Anusavice, Kenneth J

2014-02-01

The aim of this study was to determine the survival rates over time of implant-supported ceramic-ceramic and metal-ceramic prostheses as a function of core-veneer thickness ratio, gingival connector embrasure design, and connector height. An IRB-approved, randomized, controlled clinical trial was conducted as a single-blind pilot study involving 55 patients missing three teeth in either one or two posterior areas. These patients (34 women; 21 men; age range 52-75 years) were recruited for the study to receive a three-unit implant-supported fixed dental prosthesis (FDP). Two implants were placed for each of the 72 FDPs in the study. The implants (Osseospeed, Astra Tech), which were made of titanium, were grit blasted. A gold-shaded, custom-milled titanium abutment (Atlantis, Astra Tech), was secured to each implant body. Each of the 72 FDPs in 55 patients were randomly assigned based on one of the following options: (1) A. ceramic-ceramic (Yttria-stabilized zirconia core, pressable fluorapatite glass-ceramic, IPS e.max ZirCAD, and ZirPress, Ivoclar Vivadent) B. metal-ceramic (palladium-based noble alloy, Capricorn, Ivoclar Vivadent, with press-on leucite-reinforced glass-ceramic veneer, IPS InLine POM, Ivoclar Vivadent); (2) occlusal veneer thickness (0.5, 1.0, and 1.5 mm); (3) curvature of gingival embrasure (0.25, 0.5, and 0.75 mm diameter); and (4) connector height (3, 4, and 5 mm). FDPs were fabricated and cemented with dual-cure resin cement (RelyX, Universal Cement, 3M ESPE). Patients were recalled at 6 months, 1 year, and 2 years. FDPs were examined for cracks, fracture, and general surface quality. Recall exams of 72 prostheses revealed 10 chipping fractures. No fractures occurred within the connector or embrasure areas. Two-sided Fisher's exact tests showed no significant correlation between fractures and type of material system (p = 0.51), veneer thickness (p = 0.75), radius of curvature of gingival embrasure (p = 0.68), and connector height (p = 0

Randomized Clinical Trial of Implant-Supported Ceramic-Ceramic and Metal-Ceramic Fixed Dental Prostheses: Preliminary Results

PubMed Central

Esquivel-Upshaw, Josephine F.; Clark, Arthur E.; Shuster, Jonathan J.; Anusavice, Kenneth J.

2013-01-01

Purpose The aim of this study was to determine the survival rates over time of implant-supported ceramic-ceramic and metal-ceramic prostheses as a function of core-veneer thickness ratio, gingival connector embrasure design, and connector height. Materials and Methods An IRB-approved, randomized, controlled clinical trial was conducted as a single-blind pilot study involving 55 patients missing three teeth in either one or two posterior areas. These patients (34 women; 21 men; age range 52–75 years) were recruited for the study to receive a 3-unit implant-supported fixed dental prosthesis (FDP). Two implants were placed for each of the 72 FDPs in the study. The implants (Osseospeed, Astra Tech), which were made of titanium, were grit blasted. A gold-shaded, custom-milled titanium abutment (Atlantis, Astra Tech), was secured to each implant body. Each of the 72 FDPs in 55 patients were randomly assigned based on one of the following options: (1) A. Material: ceramic-ceramic (Yttria-stabilized zirconia core, pressable fluorapatite glass-ceramic, IPS e.max ZirCAD and ZirPress, Ivoclar Vivadent) B. metal-ceramic (palladium-based noble alloy, Capricorn, Ivoclar Vivadent, with press-on leucite-reinforced glass-ceramic veneer, IPS InLine POM, Ivoclar Vivadent); (2) occlusal veneer thickness (0.5, 1.0, and 1.5 mm); (3) curvature of gingival embrasure (0.25, 0.5, and 0.75 mm diameter); and (4) connector height (3, 4, and 5 mm). FDPs were fabricated and cemented with dual-cure resin cement (RelyX, Universal Cement, 3M ESPE). Patients were recalled at 6 months, 1 year, and 2 years. FDPs were examined for cracks, fracture, and general surface quality. Results Recall exams of 72 prostheses revealed 10 chipping fractures. No fractures occurred within the connector or embrasure areas. Two-sided Fisher’s exact tests showed no significant correlation between fractures and type of material system (p = 0.51), veneer thickness (p = 0.75), radius of curvature of gingival embrasure

Exploring biosensor applications with cotton cellulose nanocrystalline protein and peptide conjugates

USDA-ARS?s Scientific Manuscript database

Sensor I: Nano-crystalline preparations were produced through acid hydrolysis and mechanical breakage of the cotton fibers from a scoured and bleached cotton fabric and a scoured and bleached, mercerized fabric, which was shown to produce cellulose I (NCI) and cellulose II (NCII) crystals respective...

Softening due to Grain Boundary Cavity Formation and its Competition with Hardening in Helium Implanted Nanocrystalline Tungsten

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

Cunningham, W. Streit; Gentile, Jonathan M.; El-Atwani, Osman

The unique ability of grain boundaries to act as effective sinks for radiation damage plays a significant role in nanocrystalline materials due to their large interfacial area per unit volume. Leveraging this mechanism in the design of tungsten as a plasma-facing material provides a potential pathway for enhancing its radiation tolerance under fusion-relevant conditions. In this study, we explore the impact of defect microstructures on the mechanical behavior of helium ion implanted nanocrystalline tungsten through nanoindentation. Softening was apparent across all implantation temperatures and attributed to bubble/cavity loaded grain boundaries suppressing the activation barrier for the onset of plasticity viamore » grain boundary mediated dislocation nucleation. An increase in fluence placed cavity induced grain boundary softening in competition with hardening from intragranular defect loop damage, thus signaling a new transition in the mechanical behavior of helium implanted nanocrystalline tungsten.« less

Softening due to Grain Boundary Cavity Formation and its Competition with Hardening in Helium Implanted Nanocrystalline Tungsten

DOE PAGES

Cunningham, W. Streit; Gentile, Jonathan M.; El-Atwani, Osman; ...

2018-02-13

The unique ability of grain boundaries to act as effective sinks for radiation damage plays a significant role in nanocrystalline materials due to their large interfacial area per unit volume. Leveraging this mechanism in the design of tungsten as a plasma-facing material provides a potential pathway for enhancing its radiation tolerance under fusion-relevant conditions. In this study, we explore the impact of defect microstructures on the mechanical behavior of helium ion implanted nanocrystalline tungsten through nanoindentation. Softening was apparent across all implantation temperatures and attributed to bubble/cavity loaded grain boundaries suppressing the activation barrier for the onset of plasticity viamore » grain boundary mediated dislocation nucleation. An increase in fluence placed cavity induced grain boundary softening in competition with hardening from intragranular defect loop damage, thus signaling a new transition in the mechanical behavior of helium implanted nanocrystalline tungsten.« less

CP/MAS ¹³C NMR study of pulp hornification using nanocrystalline cellulose as a model system.

PubMed

Idström, Alexander; Brelid, Harald; Nydén, Magnus; Nordstierna, Lars

2013-01-30

The hornification process of paper pulp was investigated using solid-state (13)C NMR spectroscopy. Nanocrystalline cellulose was used to serve as a model system of the crystalline parts of the fibrils in pulp fibers. Characterization of the nanocrystalline cellulose dimensions was carried out using scanning electron microscopy. The samples were treated by drying and wetting cycles prior to NMR analysis where the hornification phenomenon was recorded by spectral changes of the cellulose C-4 carbon signals. An increase of the crystalline signal and a decrease of the signals corresponding to the accessible amorphous domains were found for both paper pulp and nanocrystalline cellulose. These spectral changes grew stronger with repeating drying and wetting cycles. The results show that cellulose co-crystallization contribute to hornification. Another conclusion is that the surfaces of higher hydrophobicity in cellulose fibrils have an increased preference for aggregation. Copyright © 2012 Elsevier Ltd. All rights reserved.

Corrosion of Ceramic Materials

NASA Technical Reports Server (NTRS)

Opila, Elizabeth J.; Jacobson, Nathan S.

1999-01-01

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

Free-standing oxide superconducting articles

DOEpatents

Wu, X.D.; Muenchausen, R.E.

1993-12-14

A substrate-free, free-standing epitaxially oriented superconductive film including a layer of a template material and a layer of a ceramic superconducting material is provided together with a method of making such a substrate-free ceramic superconductive film by coating an etchable material with a template layer, coating the template layer with a layer of a ceramic superconductive material, coating the layer of ceramic superconductive material with a protective material, removing the etchable material by an appropriate means so that the etchable material is separated from a composite structure including the template layer.

Water as probe molecule for midgap states in nanocrystalline strontium titanate by conventional and synchronous luminescence spectroscopy under ambient conditions

NASA Astrophysics Data System (ADS)

Taylor, Sean; Samokhvalov, Alexander

2017-03-01

Alkaline earth metal titanates are broad bandgap semiconductors with applications in electronic devices, as catalysts, photocatalysts, sorbents, and sensors. Strontium titanate SrTiO3 is of interest in electronic devices, sensors, in the photocatalytic hydrogen generation, as catalyst and sorbent. Both photocatalysis and operation of electronic devices rely upon the pathways of relaxation of excited charge in the semiconductor, including relaxation through the midgap states. We report characterization of nanocrystalline SrTiO3 at room temperature by "conventional" vs. synchronous luminescence spectroscopy and complementary methods. We determined energies of radiative transitions in the visible range through the two midgap states in the nanocrystalline SrTiO3. Further, adsorption and desorption of vapor of water as "probe molecule" for midgap states in the nanocrystalline SrTiO3 was studied, for the first time, by luminescence spectroscopy under ambient conditions. Emission of visible light from the nanocrystalline SrTiO3 is significantly increased upon desorption of water and decreased (quenched) upon adsorption of water vapor, due to interactions with the surface midgap states.

Atomistic modeling of La 3+ doping segregation effect on nanocrystalline yttria-stabilized zirconia

DOE PAGES

Zhang, Shenli; Sha, Haoyan; Castro, Ricardo H. R.; ...

2018-01-01

The effect of La 3+ doping on the structure and ionic conductivity change in nanocrystalline yttria-stabilized zirconia (YSZ) was studied using a combination of Monte Carlo and molecular dynamics simulations.

Biomimetic three-dimensional nanocrystalline hydroxyapatite and magnetically synthesized single-walled carbon nanotube chitosan nanocomposite for bone regeneration

PubMed Central

Im, Owen; Li, Jian; Wang, Mian; Zhang, Lijie Grace; Keidar, Michael

2012-01-01

Background Many shortcomings exist in the traditional methods of treating bone defects, such as donor tissue shortages for autografts and disease transmission for allografts. The objective of this study was to design a novel three-dimensional nanostructured bone substitute based on magnetically synthesized single-walled carbon nanotubes (SWCNT), biomimetic hydrothermally treated nanocrystalline hydroxyapatite, and a biocompatible hydrogel (chitosan). Both nanocrystalline hydroxyapatite and SWCNT have a biomimetic nanostructure, excellent osteoconductivity, and high potential to improve the load-bearing capacity of hydrogels. Methods Specifically, three-dimensional porous chitosan scaffolds with different concentrations of nanocrystalline hydroxyapatite and SWCNT were created to support the growth of human osteoblasts (bone-forming cells) using a lyophilization procedure. Two types of SWCNT were synthesized in an arc discharge with a magnetic field (B-SWCNT) and without a magnetic field (N-SWCNT) for improving bone regeneration. Results Nanocomposites containing magnetically synthesized B-SWCNT had superior cytocompatibility properties when compared with nonmagnetically synthesized N-SWCNT. B-SWCNT have much smaller diameters and are twice as long as their nonmagnetically prepared counterparts, indicating that the dimensions of carbon nanotubes can have a substantial effect on osteoblast attachment. Conclusion This study demonstrated that a chitosan nanocomposite with both B-SWCNT and 20% nanocrystalline hydroxyapatite could achieve a higher osteoblast density when compared with the other experimental groups, thus making this nanocomposite promising for further exploration for bone regeneration. PMID:22619545

Study of magnetic and electrical properties of nanocrystalline Mn doped NiO.

PubMed

Raja, S Philip; Venkateswaran, C

2011-03-01

Diluted Magnetic Semiconductors (DMS) are intensively explored in recent years for its applications in spintronics, which is expected to revolutionize the present day information technology. Nanocrystalline Mn doped NiO samples were prepared using chemical co-precipitation method with an aim to realize room temperature ferromagnetism. Phase formation of the samples was studied using X-ray diffraction-Rietveld analysis. Scanning electron microscopy and Energy dispersive X-ray analysis results reveal the nanocrystalline nature of the samples, agglomeration of the particles, considerable particle size distribution and the near stoichiometry. Thermomagnetic curves confirm the single-phase formation of the samples up to 1% doping of Mn. Vibrating Sample Magnetometer measurements indicate the absence of ferromagnetism at room temperature. This may be due to the low concentration of Mn2+ ions having weak indirect coupling with Ni2+ ions. The lack of free carriers is also expected to be the reason for the absence of ferromagnetism, which is in agreement with the results of resistivity measurements using impedance spectroscopy. Arrhenius plot shows the presence of two thermally activated regions and the activation energy for the nanocrystalline Mn doped sample was found to be greater than that of undoped NiO. This is attributed to the doping effect of Mn. However, the dielectric constant of the samples was found to be of the same order of magnitude very much comparable with that of undoped NiO.

Effect of structural evolution of ZnO/HfO2 nanocrystals on Eu2+/Eu3+ emission in glass-ceramic waveguides for photonic applications

NASA Astrophysics Data System (ADS)

Ghosh, Subhabrata; N, Shivakiran Bhaktha B.

2018-06-01

Eu-doped 70SiO2–23HfO2–7ZnO (mol%) glass-ceramic waveguides have been fabricated by sol-gel method as a function of heat-treatment temperatures for on-chip blue-light emitting source applications. Structural evolution of spherical ZnO and spherical as well as rod-like HfO2 nanocrystalline structures have been observed with heat-treatments at different temperatures. Initially, in the as-prepared samples at 900 ◦C, both, Eu2+ as well as Eu3+ ions are found to be present in the ternary matrix. With controlled heat-treatments of up to 1000 ◦C for 2 h, local environment of Eu-ions become more crystalline in nature and the reduction of Eu3+ to Eu2+ takes place in such ZnO/HfO2 crystalline environments. In these ternary glass-ceramic waveguides, heat-treated at higher temperatures, the blue-light emission characteristic, which is the signature of 4f 65d \\to 4f 7 energy level transition of Eu2+ ions is found to be greatly enhanced. The as-prepared glass-ceramic waveguides exhibit a propagation loss of 0.4 ± 0.2 dB cm‑1 at 632.8 nm. Though the propagation losses increase with the growth of nanocrystals, the added functionalities achieved in the optimally heat-treated Eu-doped 70SiO2–23HfO2–7ZnO (mol%) waveguides, make them a viable functional optical material for the fabrication of on-chip blue-light emitting sources for integrated optic applications.

Effect of structural evolution of ZnO/HfO2 nanocrystals on Eu2+/Eu3+ emission in glass-ceramic waveguides for photonic applications.

PubMed

Ghosh, Subhabrata; Bhaktha B N, Shivakiran

2018-06-01

Eu-doped 70SiO 2 -23HfO 2 -7ZnO (mol%) glass-ceramic waveguides have been fabricated by sol-gel method as a function of heat-treatment temperatures for on-chip blue-light emitting source applications. Structural evolution of spherical ZnO and spherical as well as rod-like HfO 2 nanocrystalline structures have been observed with heat-treatments at different temperatures. Initially, in the as-prepared samples at 900 ◦ C, both, Eu 2+ as well as Eu 3+ ions are found to be present in the ternary matrix. With controlled heat-treatments of up to 1000 ◦ C for 2 h, local environment of Eu-ions become more crystalline in nature and the reduction of Eu 3+ to Eu 2+ takes place in such ZnO/HfO 2 crystalline environments. In these ternary glass-ceramic waveguides, heat-treated at higher temperatures, the blue-light emission characteristic, which is the signature of 4f 6 5d [Formula: see text] 4f 7 energy level transition of Eu 2+ ions is found to be greatly enhanced. The as-prepared glass-ceramic waveguides exhibit a propagation loss of 0.4 ± 0.2 dB cm -1 at 632.8 nm. Though the propagation losses increase with the growth of nanocrystals, the added functionalities achieved in the optimally heat-treated Eu-doped 70SiO 2 -23HfO 2 -7ZnO (mol%) waveguides, make them a viable functional optical material for the fabrication of on-chip blue-light emitting sources for integrated optic applications.

Formation of nanocrystalline SiGe in Polycrystalline-Ge/Si thin film without any metal induced crystallization

NASA Astrophysics Data System (ADS)

Tah, Twisha; Singh, Ch. Kishan; Madapu, K. K.; Polaki, S. R.; Ilango, S.; David, C.; Dash, S.; Panigrahi, B. K.

2017-05-01

The formation of nanocrystalline SiGe without the aid of metal induced crystallization is reported. Re-crystallization of the as-deposited poly-Ge film (deposited at 450 °C) leads to development of regions with depleted Ge concentration upon annealing at 500 °C. Clusters with crystalline facet containing both nanocrystalline SiGe and crystalline Ge phase starts appearing at 600 °C. The structural phase characteristics were investigated by X-ray diffraction (XRD) and Raman spectroscopy. The stoichiometry of the SiGe phase was estimated from the positions of the Raman spectral peaks.

Thermal desorption spectroscopy of high fluence irradiated ultrafine and nanocrystalline tungsten: helium trapping and desorption correlated with morphology

NASA Astrophysics Data System (ADS)

El-Atwani, O.; Taylor, C. N.; Frishkoff, J.; Harlow, W.; Esquivel, E.; Maloy, S. A.; Taheri, M. L.

2018-01-01

Microstructural changes due to displacement damage and helium desorption are two phenomena that occur in tungsten plasma facing materials in fusion reactors. Nanocrystalline metals are being investigated as radiation tolerant materials that can mitigate these microstructural changes and better trap helium along their grain boundaries. Here, we investigate the performance of three tungsten grades (nanocrystalline, ultrafine and ITER grade tungsten), exposed to a high fluence of 4 keV helium at both RT and 773 K, during a thermal desorption spectroscopy (TDS) experiment. An investigation of the microstructure in pre-and post-TDS sample sets was performed. The amount of desorbed helium was shown to be highest in the ITER grade tungsten and lowest in the nanocrystalline tungsten. Correlating the desorption spectra and the microstructure (grain boundaries decorated with nanopores and crack formation) and comparing with previous literature on coarse grained tungsten samples at similar irradiation and TDS conditions, revealed the importance of grain boundaries in trapping helium and limiting helium desorption up to a high temperature of 1350 K in agreement with transmission electron microscopy studies on helium irradiated tungsten which showed preferential and large facetted bubble formation along the grain boundaries in the nanocrystalline tungsten grade.

Thermal desorption spectroscopy of high fluence irradiated ultrafine and nanocrystalline tungsten: helium trapping and desorption correlated with morphology

DOE PAGES

El-Atwani, Osman; Taylor, Chase N.; Frishkoff, James; ...

2017-11-09

Here, microstructural changes due to displacement damage and helium desorption are two phenomena that occur in tungsten plasma facing materials in fusion reactors. Nanocrystalline metals are being investigated as radiation tolerant materials that can mitigate these microstructural changes and better trap helium along their grain boundaries. Here, we investigate the performance of three tungsten grades (nanocrystalline, ultrafine and ITER grade tungsten), exposed to a high fluence of 4 keV helium at both RT and 773 K, during a thermal desorption spectroscopy (TDS) experiment. An investigation of the microstructure in pre-and post-TDS sample sets was performed. The amount of desorbed heliummore » was shown to be highest in the ITER grade tungsten and lowest in the nanocrystalline tungsten. Correlating the desorption spectra and the microstructure (grain boundaries decorated with nanopores and crack formation) and comparing with previous literature on coarse grained tungsten samples at similar irradiation and TDS conditions, revealed the importance of grain boundaries in trapping helium and limiting helium desorption up to a high temperature of 1350 K in agreement with transmission electron microscopy studies on helium irradiated tungsten which showed preferential and large facetted bubble formation along the grain boundaries in the nanocrystalline tungsten grade.« less

Light-weight black ceramic insulation

NASA Technical Reports Server (NTRS)

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

2003-01-01

Ultra-high temperature, light-weight, black ceramic insulation having a density ranging from about 0.12 g/cc. to 0.6 g/cc. such as ceramic tile is obtained by pyrolyzing siloxane gels derived from the reaction of at least one organo dialkoxy silane and at least one tetralkoxy silane in an acid or base liquid medium. The reaction mixture of the tetra- and dialkoxy silanes also may contain an effective amount of a mono- or trialkoxy silane to obtain the siloxane gels. The siloxane gels are dried at ambient temperatures and pressures to form siloxane ceramic precursors without significant shrinkage. The siloxane ceramic precursors are subsequently pyrolyzed, in an inert atmosphere, to form the black ceramic insulation comprising atoms of silicon, carbon and oxygen. The ceramic insulation can be characterized as a porous, uniform ceramic tile resistant to oxidation at temperatures ranging as high as 1700.degree. C., and particularly useful as lightweight tiles for spacecraft and other high-temperature insulation applications.

Alternating current transport and dielectric relaxation of nanocrystalline graphene oxide

NASA Astrophysics Data System (ADS)

Zedan, I. T.; El-Menyawy, E. M.

2018-07-01

Graphene oxide (GO) has been synthesized from natural graphite using modified Hummer's method and is subjected to sonication for 1 h. X-ray diffraction (XRD) showed that the prepared GO has nanocrystalline structure with particle size of about 5 nm and high-resolution transmission electron microscope showed that it had a layered structure. The nanocrystalline GO powder was pressed as a disk and the alternating current (AC) electrical conductivity, σAC, and dielectric properties have been investigated in the frequency range 50Hz-5 MHz and temperature range 298-523K using parallel plate spectroscopic technique. Analysis of σ AC as a function of frequency shows that the relation follows Jonscher's universal law with frequency exponent decreases with increasing temperature in which the correlated barrier hopping model is applicable to describe the behavior. The dielectric constant and dielectric loss are studied as functions of frequency and temperature. The dielectric modulus formalism is used for describing the relaxation process in which the relaxation time and its activation energy were evaluated.

Deformation-mechanism map for nanocrystalline metals by molecular-dynamics simulation.

PubMed

Yamakov, V; Wolf, D; Phillpot, S R; Mukherjee, A K; Gleiter, H

2004-01-01

Molecular-dynamics simulations have recently been used to elucidate the transition with decreasing grain size from a dislocation-based to a grain-boundary-based deformation mechanism in nanocrystalline f.c.c. metals. This transition in the deformation mechanism results in a maximum yield strength at a grain size (the 'strongest size') that depends strongly on the stacking-fault energy, the elastic properties of the metal, and the magnitude of the applied stress. Here, by exploring the role of the stacking-fault energy in this crossover, we elucidate how the size of the extended dislocations nucleated from the grain boundaries affects the mechanical behaviour. Building on the fundamental physics of deformation as exposed by these simulations, we propose a two-dimensional stress-grain size deformation-mechanism map for the mechanical behaviour of nanocrystalline f.c.c. metals at low temperature. The map captures this transition in both the deformation mechanism and the related mechanical behaviour with decreasing grain size, as well as its dependence on the stacking-fault energy, the elastic properties of the material, and the applied stress level.

New atom probe approaches to studying segregation in nanocrystalline materials.

PubMed

Samudrala, S K; Felfer, P J; Araullo-Peters, V J; Cao, Y; Liao, X Z; Cairney, J M

2013-09-01

Atom probe is a technique that is highly suited to the study of nanocrystalline materials. It can provide accurate atomic-scale information about the composition of grain boundaries in three dimensions. In this paper we have analysed the microstructure of a nanocrystalline super-duplex stainless steel prepared by high pressure torsion (HPT). Not all of the grain boundaries in this alloy display obvious segregation, making visualisation of the microstructure challenging. In addition, the grain boundaries present in the atom probe data acquired from this alloy have complex shapes that are curved at the scale of the dataset and the interfacial excess varies considerably over the boundaries, making the accurate characterisation of the distribution of solute challenging using existing analysis techniques. In this paper we present two new data treatment methods that allow the visualisation of boundaries with little or no segregation, the delineation of boundaries for further analysis and the quantitative analysis of Gibbsian interfacial excess at boundaries, including the capability of excess mapping. Copyright © 2013 Elsevier B.V. All rights reserved.

Voltammetric and impedance behaviours of surface-treated nano-crystalline diamond film electrodes

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

Liu, F. B.; Jing, B.; Cui, Y.

2015-04-15

The electrochemical performances of hydrogen- and oxygen-terminated nano-crystalline diamond film electrodes were investigated by cyclic voltammetry and AC impedance spectroscopy. In addition, the surface morphologies, phase structures, and chemical states of the two diamond films were analysed by scanning probe microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy, respectively. The results indicated that the potential window is narrower for the hydrogen-terminated nano-crystalline diamond film than for the oxygen-terminated one. The diamond film resistance and capacitance of oxygen-terminated diamond film are much larger than those of the hydrogen-terminated diamond film, and the polarization resistances and double-layer capacitance corresponding to oxygen-terminated diamond filmmore » are both one order of magnitude larger than those corresponding to the hydrogen-terminated diamond film. The electrochemical behaviours of the two diamond film electrodes are discussed.« less

Structural analysis of nanocrystalline ZnTe alloys synthesized by melt quenching technique

NASA Astrophysics Data System (ADS)

Singh, Harinder; Singh, Tejbir; Thakur, Anup; Sharma, Jeewan

2018-05-01

Nanocrystalline ZnxTe100-x (x=0, 5, 20, 30, 40, 50) alloys have been synthesized using melt quenching technique. Energy-dispersive X-Ray spectroscopy (EDS) has been used to verify the elemental composition of samples. Various absorption modes are recorded from Fourier transform infrared spectroscopy (FTIR) confirming the formation of ZnTe. The structural study has been performed using X-Ray Diffraction (XRD) method. All synthesized samples have been found to be nanocrystalline in nature with average crystallite size in the range from 49.3 nm to 77.1 nm. Results have shown that Zn0Te100 exhibits hexagonal phase that transforms into a cubic ZnTe phase as the amount of zinc is increased. Pure ZnTe phase has been obtained for x = 50. The texture coefficient (Tc) has been calculated to find the prominent orientations of different planes.

Resolving the nanostructure of plasma-enhanced chemical vapor deposited nanocrystalline SiOx layers for application in solar cells

NASA Astrophysics Data System (ADS)

Klingsporn, M.; Kirner, S.; Villringer, C.; Abou-Ras, D.; Costina, I.; Lehmann, M.; Stannowski, B.

2016-06-01

Nanocrystalline silicon suboxides (nc-SiOx) have attracted attention during the past years for the use in thin-film silicon solar cells. We investigated the relationships between the nanostructure as well as the chemical, electrical, and optical properties of phosphorous, doped, nc-SiO0.8:H fabricated by plasma-enhanced chemical vapor deposition. The nanostructure was varied through the sample series by changing the deposition pressure from 533 to 1067 Pa. The samples were then characterized by X-ray photoelectron spectroscopy, spectroscopic ellipsometry, Raman spectroscopy, aberration-corrected high-resolution transmission electron microscopy, selected-area electron diffraction, and a specialized plasmon imaging method. We found that the material changed with increasing pressure from predominantly amorphous silicon monoxide to silicon dioxide containing nanocrystalline silicon. The nanostructure changed from amorphous silicon filaments to nanocrystalline silicon filaments, which were found to cause anisotropic electron transport.

Performance of Ceramics in Severe Environments

NASA Technical Reports Server (NTRS)

Jacobson, Nathan S.; Fox, Dennis S.; Smialek, James L.; Deliacorte, Christopher; Lee, Kang N.

2005-01-01

Ceramics are generally stable to higher temperatures than most metals and alloys. Thus the development of high temperature structural ceramics has been an area of active research for many years. While the dream of a ceramic heat engine still faces many challenges, niche markets are developing for these materials at high temperatures. In these applications, ceramics are exposed not only to high temperatures but also aggressive gases and deposits. In this chapter we review the response of ceramic materials to these environments. We discuss corrosion mechanisms, the relative importance of a particular corrodent, and, where available, corrosion rates. Most of the available corrosion information is on silicon carbide (SIC) and silicon nitride (Si3N4) monolithic ceramics. These materials form a stable film of silica (SO2) in an oxidizing environment. We begin with a discussion of oxidation of these materials and proceed to the effects of other corrodents such as water vapor and salt deposits. We also discuss oxidation and corrosion of other ceramics: precurser derived ceramics, ceramic matrix composites (CMCs), ceramics which form oxide scales other than silica, and oxide ceramics. Many of the corrosion issues discussed can be mitigated with refractory oxide coatings and we discuss the current status of this active area of research. Ultimately, the concern of corrosion is loss of load bearing capability. We discuss the effects of corrosive environments on the strength of ceramics, both monolithic and composite. We conclude with a discussion of high temperature wear of ceramics, another important form of degradation at high temperatures.

Mechanism of γ-irradiation induced phase transformations in nanocrystalline Mn0.5Zn0.5Fe2O4 ceramics

NASA Astrophysics Data System (ADS)

Jagadeesha Angadi, V.; Anupama, A. V.; Choudhary, Harish K.; Kumar, R.; Somashekarappa, H. M.; Mallappa, M.; Rudraswamy, B.; Sahoo, B.

2017-02-01

The structural, infrared absorption and magnetic property transformations in nanocrystalline Mn0.5Zn0.5Fe2O4 samples irradiated with different doses (0, 15, 25 and 50 kGy) of γ-irradiation were investigated in this work and a mechanism of phase transformation/decomposition is provided based on the metastable nature of the Mn-atoms in the spinel lattice. The nano-powder sample was prepared by solution combustion route and the pellets of the sample were exposed to γ-radiation. Up to a dose of 25 kGy of γ-radiation, the sample retained the single phase cubic spinel (Fd-3m) structure, but the disorder in the sample increased. On irradiating the sample with 50 kGy γ-radiation, the spinel phase decomposed into new stable phases such as α-Fe2O3 and ZnFe2O4 phases along with amorphous MnO phase, leading to a change in the surface morphology of the sample. Along with the structural transformations the magnetic properties deteriorated due to breakage of the ferrimagnetic order with higher doses of γ-irradiation. Our results are important for the understanding of the stability, durability and performance of the Mn-Zn ferrite based devices used in space applications.

Advanced Ceramic Armor Materials

DTIC Science & Technology

1990-05-11

materials, toughened alumina, fiber -reinforced glass matrix composites, and multilayer-gradient materials for ballistic testing. Fabrication and...material systems: Multilayer advanced armor materials consisting of a hard ceramic faceplate bonded to a graphite fiber -reinforced glass matrix...toughened alumina, and fiber - applied studies of advanced reinforced ceramic matrix glass and glass -ceramic composites for ballistic testing. technologies

Controllable nonlinear refraction characteristics in hydrogenated nanocrystalline silicon

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

Zheng, D. Q.; Ye, Q. H.; Shen, W. Z., E-mail: wzshen@sjtu.edu.cn

2014-02-07

Nonlinear refraction (NLR) of hydrogenated nanocrystalline silicon (nc-Si:H) has been investigated through the close aperture Z-scan method. We demonstrate a significant NLR and a unique feature of controllable NLR characteristics between saturable and Kerr NLR with the incident photon energy. We numerically evaluate the proportion of these two mechanisms in different wavelengths by a modified NLR equation. The band tail of nc-Si:H appears to play a crucial role in such NLR responses.

Nanocrystalline SiC film thermistors for cryogenic applications

NASA Astrophysics Data System (ADS)

Mitin, V. F.; Kholevchuk, V. V.; Semenov, A. V.; Kozlovskii, A. A.; Boltovets, N. S.; Krivutsa, V. A.; Slepova, A. S.; Novitskii, S. V.

2018-02-01

We developed a heat-sensitive material based on nanocrystalline SiC films obtained by direct deposition of carbon and silicon ions onto sapphire substrates. These SiC films can be used for resistance thermometers operating in the 2 K-300 K temperature range. Having high heat sensitivity, they are relatively low sensitive to the magnetic field. The designs of the sensors are presented together with a discussion of their thermometric characteristics and sensitivity to magnetic fields.

Ultrasonic Emission from Nanocrystalline Porous Silicon

NASA Astrophysics Data System (ADS)

Shinoda, Hiroyuki; Koshida, Nobuyoshi

A simple layer structure composed of a metal thin film and a porous silicon layer on a silicon substrate generates intense and wide-band airborne ultrasounds. The large-bandwidth and the fidelity of the sound reproduction are leveraged in applications varying from sound-based measurement to a scientific study of animal ecology. This chapter describes the basic principle of the ultrasound generation. The macroscopic properties of the low thermal conductivity and the small heat capacity of nanocrystalline porous silicon thermally induce ultrasonic emission. The state-of-the-art of the achievable sound pressure and sound signal properties is introduced, with the technological and scientific applications of the devices.

Technopotters and Webs of Clay: Digital Possibilities for Teaching Ceramics

ERIC Educational Resources Information Center

Weida, Courtney Lee

2007-01-01

In this article, the author examines ways in which the Internet is changing the way ceramicists teach, learn, and work. She addresses the curricular issue of how Web resources may supplement ceramic art history and extend student-centered learning. The author also explores the nature of the interplay between computer technology and clay. (Contains…

Analyses of fine paste ceramics

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

Sabloff, J A

1980-01-01

Four chapters are included: history of Brookhaven fine paste ceramics project, chemical and mathematical procedures employed in Mayan fine paste ceramics project, and compositional and archaeological perspectives on the Mayan fine paste ceramics. (DLC)

Frequency-dependent failure mechanisms of nanocrystalline gold interconnect lines under general alternating current

NASA Astrophysics Data System (ADS)

Luo, X. M.; Zhang, B.; Zhang, G. P.

2014-09-01

Thermal fatigue failure of metallization interconnect lines subjected to alternating currents (AC) is becoming a severe threat to the long-term reliability of micro/nanodevices with increasing electrical current density/power. Here, thermal fatigue failure behaviors and damage mechanisms of nanocrystalline Au interconnect lines on the silicon glass substrate have been investigated by applying general alternating currents (the pure alternating current coupled with a direct current (DC) component) with different frequencies ranging from 0.05 Hz to 5 kHz. We observed both thermal fatigue damages caused by Joule heating-induced cyclic strain/stress and electromigration (EM) damages caused by the DC component. Besides, the damage formation showed a strong electrically-thermally-mechanically coupled effect and frequency dependence. At lower frequencies, thermal fatigue damages were dominant and the main damage forms were grain coarsening with grain boundary (GB) cracking/voiding and grain thinning. At higher frequencies, EM damages took over and the main damage forms were GB cracking/voiding of smaller grains and hillocks. Furthermore, the healing effect of the reversing current was considered to elucidate damage mechanisms of the nanocrystalline Au lines generated by the general AC. Lastly, a modified model was proposed to predict the lifetime of the nanocrystalline metal interconnect lines, i.e., that was a competing drift velocity-based approach based on the threshold time required for reverse diffusion/healing to occur.

History and trends of bioactive glass-ceramics.

PubMed

Montazerian, Maziar; Dutra Zanotto, Edgar

2016-05-01

The interest around bioactive glass-ceramics (GCs) has grown significantly over the last two decades due to their appropriate biochemical and mechanical properties. The intense research effort in this field has led to some new commercial products for biomedical applications. This review article begins with the basic concepts of GC processing and development via controlled heat treatments of monolithic pieces or sinter-crystallization of powdered glasses. We then go on to describe the processing, properties, and applications of some commercial bioactive GCs and discuss selected valuable reported researches on several promising types of bioactive GCs. The article finishes with a section on open relevant research directions for bioactive GC development. © 2016 Wiley Periodicals, Inc.

Antibacterial studies of ZnO nanoparticle coatings on nanocrystalline YSZ irradiated with femtosecond laser light

NASA Astrophysics Data System (ADS)

Alvarez, Crysthal; Garcia, Valeria; Cuando, Natanael; Aguilar, Guillermo

2018-02-01

Recently, efforts have been made to create a transparent ceramic cranial implant comprised of nanocrystalline yttriastabilized zirconia (nc-YSZ) that will provide optical access to the brain. This has been referred to as Window to the Brain (WttB) in the literature. WttB will allow the use of laser and photonic treatments and diagnostics in areas with difficult optical access in the brain. Nevertheless, infection is still one of the frequent cranial implant complications. In most cases a second surgery is required to replace the infected implant. To address potential infections in the WttB platform, we have studied the antibacterial effect of a Zinc Oxide (ZnO) nanoparticles coating on nc-YSZ. After coating with ZnO nanoparticles, the implant was irradiated with infrared femtosecond laser light. We synthesized ZnO nanoparticles through the Laser Ablation of Solids in Liquids (LASL) method, using a Zinc solid target in a liquid medium (water/acetone). Antibacterial coatings were obtained by air brush, using a precursor solution of ZnO nanoparticles in distilled water. Escherichia coli (E. coli) have been used as representative, clinical relevant bacteria to probe the antibacterial effect of the coating. Our previous studies suggested that the use of ZnO nanoparticles inhibit bacterial growth. Laser irradiation treatment alone also offers inhibition of bacterial growth, up to 70%. The incorporation of nanoparticles offers an additional 20% inhibition. Thus, this work represents the next step towards the development of a clinically-oriented transparent cranial implant.

Synthesis, characterization, and photocatalytic properties of core/shell mesoporous silica nanospheres supporting nanocrystalline titania

NASA Astrophysics Data System (ADS)

Cendrowski, K.; Chen, X.; Zielinska, B.; Kalenczuk, R. J.; Rümmeli, M. H.; Büchner, B.; Klingeler, R.; Borowiak-Palen, E.

2011-11-01

The facile bulk synthesis of silica nanospheres makes them an attractive support for the transport of chemical compounds such as nanocrystalline titanium dioxide. In this contribution we present a promising route for the synthesis of mesoporous silica nanospheres (m-SiO2) with diameter in range 200 nm, which are ideal supports for nanocrystalline titanium dioxide (TiO2). The detailed microscopic and spectroscopic characterizations of core/shell structure (m-SiO2/TiO2) were conducted. Moreover, the photocatalytic potential of the nanostructures was investigated via phenol decomposition and hydrogen generation. A clear enhancement of photoactivity in both reactions as compared to commercial TiO2-Degussa P25 catalyst is detected.

Field electron emission enhancement in lithium implanted and annealed nitrogen-incorporated nanocrystalline diamond films

NASA Astrophysics Data System (ADS)

Sankaran, K. J.; Srinivasu, K.; Yeh, C. J.; Thomas, J. P.; Drijkoningen, S.; Pobedinskas, P.; Sundaravel, B.; Leou, K. C.; Leung, K. T.; Van Bael, M. K.; Schreck, M.; Lin, I. N.; Haenen, K.

2017-06-01

The field electron emission (FEE) properties of nitrogen-incorporated nanocrystalline diamond films were enhanced due to Li-ion implantation/annealing processes. Li-ion implantation mainly induced the formation of electron trap centers inside diamond grains, whereas post-annealing healed the defects and converted the a-C phase into nanographite, forming conduction channels for effective transport of electrons. This resulted in a high electrical conductivity of 11.0 S/cm and enhanced FEE performance with a low turn-on field of 10.6 V/μm, a high current density of 25.5 mA/cm2 (at 23.2 V/μm), and a high lifetime stability of 1,090 min for nitrogen incorporated nanocrystalline diamond films.

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.

Enhanced magnetoelectric effects in composite of piezoelectric ceramics, rare-earth iron alloys, and shape-optimized nanocrystalline alloys.

PubMed

Zhang, Jitao; Li, Ping; Wen, Yumei; He, Wei; Yang, Aichao; Lu, Caijiang

2014-03-01

An enhancement for magnetoelectric (ME) effects is studied in a three-phase ME architecture consisting of two magnetostrictive Terfenol-D (Tb(0.3)Dy(0.7)Fe(1.92)) plates, a piezoelectric PZT (Pb(Zr,Ti)O3) plate, and a pair of shape-optimized FeCuNbSiB nanocrystalline alloys. By modifying the conventional shape of the magnetic flux concentrator, the shape-optimized flux concentrator has an improved effective permeability (μ(eff)) due to the shape-induced demagnetizing effect at its end surface. The flux concentrator concentrates and amplifies the external magnetic flux into Terfenol-D plate by means of changing its internal flux concentrating manner. Consequently, more flux lines can be uniformly concentrated into Terfenol-D plates. The effective piezomagnetic coefficients (d(33m)) of Terfenol-D plate and the ME voltage coefficients (α(ME)) can be further improved under a lower magnetic bias field. The dynamic magneto-elastic properties and the effective magnetic induction of Terfenol-D are taken into account to derive the enhanced effective ME voltage coefficients (α(ME,eff)), the consistency of experimental results and theoretical analyses verifies this enhancement. The experimental results demonstrate that the maximum d(33m) in our proposed architecture achieves 22.48 nm/A under a bias of 114 Oe. The maximum α(ME) in the bias magnetic range 0-900 Oe reaches 84.73 mV/Oe under the low frequency of 1 kHz, and 2.996 V/Oe under the resonance frequency of 102.3 kHz, respectively. It exhibits a 1.43 times larger piezomagnetic coefficient and a 1.87 times higher ME voltage coefficient under a smaller magnetic bias of 82 Oe than those of a conventional Terfenol-D/PZT/Terfenol-D composite. These shape-induced magnetoelectric behaviors provide the possibility of using this ME architecture in ultra-sensitive magnetic sensors.

Controlling the sol–gel process of nano-crystalline lithium-mica glass-ceramic by its chemical composition and synthesis parameters

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

Tohidifar, M.R., E-mail: tohidifar@znu.ac.ir; Alizadeh, P.; Aghaei, A.R.

2015-01-15

This paper aims to explore the impact of the parameters such as pH of the system, refluxing temperature, water quantity and chemical composition on the sol–gel synthesis of lithium-mica glass-ceramic nano-powder. The synthesis process was accomplished using two chemical composition formula (Li{sub (1+x)}Mg{sub 3}AlSi{sub 3(1+x)}O{sub 10+6.5x}F{sub 2} and LiMg{sub 3}AlSi{sub 3(1+x)}O{sub 10+6x}F{sub 2}). X-ray diffraction, Brunauer–Emmett–Teller surface area measurement and scanning electron microscopy techniques were applied to evaluate a variety of as-synthesized samples. Consequently, a transparent homogeneous sol was obtained under the conditions as pH ≤ 4, synthesis temperature ≤ 50 °C, and mol ratio of water to chemicals ≤more » 2. The prepared nano-powders under such conditions were in the range of 60–100 nm. The results also revealed that the mica glass-ceramics prepared based on the composition Li{sub (1+x)}Mg{sub 3}AlSi{sub 3(1+x)}O{sub 10+6.5x}F{sub 2} possessed finer powders due to their slow hydrolysis process. Moreover, any reduction in the stoichiometric deviation of lithium mica (x) leads to acquiring finer powders. - Highlights: • A transparent homogeneous sol leads to prepare nanopowders in the range of 60–100 nm. • The particles synthesized at lower temperatures possess finer sizes. • The acquired product which is prepared with excessive water offers larger sizes. • Any reduction in stoichiometric deviation leads to acquiring finer powders. • Taking synthesis composition as Li{sub (1+x)}Mg{sub 3}AlSi{sub 3(1+x)}O{sub 10+6.5x}F{sub 2} offers finer powders.« less

Factors affecting the shear bond strength of metal and ceramic brackets bonded to different ceramic surfaces.

PubMed

Abu Alhaija, Elham S J; Abu AlReesh, Issam A; AlWahadni, Ahed M S

2010-06-01

The aims of this study were to evaluate the shear bond strength (SBS) of metal and ceramic brackets bonded to two different all-ceramic crowns, IPS Empress 2 and In-Ceram Alumina, to compare the SBS between hydrofluoric acid (HFA), phosphoric acid etched, and sandblasted, non-etched all-ceramic surfaces. Ninety-six all-ceramic crowns were fabricated resembling a maxillary left first premolar. The crowns were divided into eight groups: (1) metal brackets bonded to sandblasted 9.6 per cent HFA-etched IPS Empress 2 crowns; (2) metal brackets bonded to sandblasted 9.6 per cent HFA-etched In-Ceram crowns; (3) ceramic brackets bonded to sandblasted 9.6 per cent HFA-etched IPS Empress 2 crowns; (4) ceramic brackets bonded to sandblasted 9.6 per cent HFA-etched In-Ceram crowns; (5) metal brackets bonded to sandblasted 37 per cent phosphoric acid-etched IPS Empress 2 crowns; (6) metal brackets bonded to sandblasted 37 per cent phosphoric acid-etched In-Ceram crowns; (7) metal brackets bonded to sandblasted, non-etched IPS Empress 2 crowns; and (8) metal brackets bonded to sandblasted, non-etched In-Ceram crowns. Metal and ceramic orthodontic brackets were bonded using a conventional light polymerizing adhesive resin. An Instron universal testing machine was used to determine the SBS at a crosshead speed of 0.1 mm/minute. Comparison between groups was performed using a univariate general linear model and chi-squared tests. The highest mean SBS was found in group 3 (120.15 +/- 45.05 N) and the lowest in group 8 (57.86 +/- 26.20 N). Of all the variables studied, surface treatment was the only factor that significantly affected SBS (P < 0.001). Acid etch application to sandblasted surfaces significantly increased the SBS in groups 1, 2, 5, and 6. The SBS of metal brackets debonded from groups 1, 3, and 5 were not significantly different from those of groups 2, 4, and 6. All debonded metal brackets revealed a similar pattern of bond failure at the adhesive-restorative interface

Vitrified chemically bonded phosphate ceramics for immobilization of radioisotopes

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

Wagh, Arun S.

2016-04-05

A method of immobilizing a radioisotope and vitrified chemically bonded phosphate ceramic (CBPC) articles formed by the method are described. The method comprises combining a radioisotope-containing material, MgO, a source of phosphate, and optionally, a reducing agent, in water at a temperature of less than 100.degree. C. to form a slurry; curing the slurry to form a solid intermediate CBPC article comprising the radioisotope therefrom; comminuting the intermediate CBPC article, mixing the comminuted material with glass frits, and heating the mixture at a temperature in the range of about 900 to about 1500.degree. C. to form a vitrified CBPC articlemore » comprising the radioisotope immobilized therein.« less

Ceramic automotive Stirling engine program

NASA Technical Reports Server (NTRS)

1986-01-01

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

Combining Hard with Soft Materials in Nanoscale Under High-Pressure High-Temperature Conditions

NASA Technical Reports Server (NTRS)

Palosz, B.; Gierlotka, S.; Swiderska-Sroda, A.; Fietkiewicz, K.; Kalisz, G.; Grzanka, E.; Stel'makh, S.; Palosz, W.

2004-01-01

Nano-composites with a primary nanocrystalline ceramic matrix and a secondary nanocrystalline material (metal or semiconductor) were synthesized by infiltration of an appropriate liquid into ceramic compacts under pressures of up to 8 GPa and temperatures of up to 2000 K. The purpose of our work is to obtain nanocomposites which constitute homoger?ous mixtures of two phases, both forming nano- grains of about 10 nm in size. The high pressure is used to bring the porosity of the compacted powders down to the nano-scale and force a given liquid into the nano-sized pores. The advantage of the infiltration technique is that, in a single, continuous process, we start with a nanocrystalline powder, compress it to form the matrix of the composite, and crystallize and/or synthesize a second nanomaterial in the matrix pores. The key limitation of this technology is, that the pores in the matrix need to stay open during the entire process of infiltration. Thus the initial powder should form a rigid skeleton, otherwise the so-called self-stop process can limit cr block a further flow of the liquid phase and hinder the process of the composite formation. Therefore powders of only very hard ceramic materials like diamond, Sic, or Alz03, which can withstand a substantial external load without undesired deformation, can be used as the primary phase. With this technique, using diamond and S i c ceramic powders infiltrated by liquid metals (AI, Zn, Sn, Ag, Au) and semiconductors (Si, Ge, GaAs, CdTe), we obtained nano-composites with the grain size in the range of 10 - 30 nm. Our work addresses the key problem in manufacturing bulk nanocrystalline materials, i.e. preservation of nano-scale during the fabrication process. In this paper we discuss basic technical and methodological problems associated with nano-infiltration based on the results obtained for Zn-Sic composites.

Analysis of Short and Long Range Atomic Order in Nanocrystalline Diamonds with Application of Powder Diffractometry

NASA Technical Reports Server (NTRS)

Palosz, B.; Grzanka, E.; Stelmakh, S.; Pielaszek, R.; Bismayer, U.; Neuefiend, J.; Weber, H.-P.; Proffen, T.; VonDreele, R.; Palosz, W.;

Production of biofuel from waste cooking palm oil using nanocrystalline zeolite as catalyst: process optimization studies.

PubMed

Taufiqurrahmi, Niken; Mohamed, Abdul Rahman; Bhatia, Subhash

2011-11-01

The catalytic cracking of waste cooking palm oil to biofuel was studied over different types of nano-crystalline zeolite catalysts in a fixed bed reactor. The effect of reaction temperature (400-500 °C), catalyst-to-oil ratio (6-14) and catalyst pore size of different nanocrystalline zeolites (0.54-0.80 nm) were studied over the conversion of waste cooking palm oil, yields of Organic Liquid Product (OLP) and gasoline fraction in the OLP following central composite design (CCD). The response surface methodology was used to determine the optimum value of the operating variables for maximum conversion as well as maximum yield of OLP and gasoline fraction, respectively. The optimum reaction temperature of 458 °C with oil/catalyst ratio=6 over the nanocrystalline zeolite Y with pore size of 0.67 nm gave 86.4 wt% oil conversion, 46.5 wt% OLP yield and 33.5 wt% gasoline fraction yield, respectively. The experimental results were in agreement with the simulated values within an experimental error of less than 5%. Copyright © 2011 Elsevier Ltd. All rights reserved.

Method for producing ceramic-glass-ceramic seals by microwave heating

DOEpatents

Blake, Rodger D.; Meek, Thomas T.

1986-01-01

Method for producing a ceramic-glass-ceramic seal by the use of microwave energy, and a sealing mixture which comprises a glass sealing material, a coupling agent, and an oxidizer. The seal produced exhibits greater strength due to its different microstructure. Sodium nitrate is the most preferred oxidizer.

Ceramic applications in turbine engines

NASA Technical Reports Server (NTRS)

Byrd, J. A.; Janovicz, M. A.; Thrasher, S. R.

1981-01-01

Development testing activities on the 1900 F-configuration ceramic parts were completed, 2070 F-configuration ceramic component rig and engine testing was initiated, and the conceptual design for the 2265 F-configuration engine was identified. Fabrication of the 2070 F-configuration ceramic parts continued, along with burner rig development testing of the 2070 F-configuration metal combustor in preparation for 1132 C (2070 F) qualification test conditions. Shakedown testing of the hot engine simulator (HES) rig was also completed in preparation for testing of a spin rig-qualified ceramic-bladed rotor assembly at 1132 C (2070 F) test conditions. Concurrently, ceramics from new sources and alternate materials continued to be evaluated, and fabrication of 2070 F-configuration ceramic component from these new sources continued. Cold spin testing of the critical 2070 F-configuration blade continued in the spin test rig to qualify a set of ceramic blades at 117% engine speed for the gasifier turbine rotor. Rig testing of the ceramic-bladed gasifier turbine rotor assembly at 108% engine speed was also performed, which resulted in the failure of one blade. The new three-piece hot seal with the nickel oxide/calcium fluoride wearface composition was qualified in the regenerator rig and introduced to engine operation wiwth marginal success.

High pressure ceramic heat exchanger

DOEpatents

Harkins, Bruce D.; Ward, Michael E.

1998-01-01

Many recuperators have components which react to corrosive gases and are used in applications where the donor fluid includes highly corrosive gases. These recuperators have suffered reduced life, increased service or maintenance, and resulted in increased cost. The present header assembly when used with recuperators reduces the brittle effect of a portion of the ceramic components. Thus, the present header assembly used with the present recuperator increases the life, reduces the service and maintenance, and reduces the increased cost associated with corrosive action of components used to manufacture recuperators. The present header assembly is comprised of a first ceramic member, a second ceramic member, a strengthening reinforcing member being in spaced relationship to the first ceramic member and the second ceramic member. The header assembly is further comprised of a refractory material disposed in contacting relationship with the first ceramic member, the second ceramic member and the strengthening reinforcing member. The present header assembly provides a high strength load bearing header assembly having good thermal cycling characteristics, good resistance to a corrosive environment and good steady state strength at elevated temperatures.

High pressure ceramic heat exchanger

DOEpatents

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

1998-09-22

Many recuperators have components which react to corrosive gases and are used in applications where the donor fluid includes highly corrosive gases. These recuperators have suffered reduced life, increased service or maintenance, and resulted in increased cost. The present header assembly when used with recuperators reduces the brittle effect of a portion of the ceramic components. Thus, the present header assembly used with the present recuperator increases the life, reduces the service and maintenance, and reduces the increased cost associated with corrosive action of components used to manufacture recuperators. The present header assembly is comprised of a first ceramic member, a second ceramic member, a strengthening reinforcing member being in spaced relationship to the first ceramic member and the second ceramic member. The header assembly is further comprised of a refractory material disposed in contacting relationship with the first ceramic member, the second ceramic member and the strengthening reinforcing member. The present header assembly provides a high strength load bearing header assembly having good thermal cycling characteristics, good resistance to a corrosive environment and good steady state strength at elevated temperatures. 5 figs.

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.

Positron annihilation in transparent ceramics

NASA Astrophysics Data System (ADS)

Husband, P.; Bartošová, I.; Slugeň, V.; Selim, F. A.

2016-01-01

Transparent ceramics are emerging as excellent candidates for many photonic applications including laser, scintillation and illumination. However achieving perfect transparency is essential in these applications and requires high technology processing and complete understanding for the ceramic microstructure and its effect on the optical properties. Positron annihilation spectroscopy (PAS) is the perfect tool to study porosity and defects. It has been applied to investigate many ceramic structures; and transparent ceramics field may be greatly advanced by applying PAS. In this work positron lifetime (PLT) measurements were carried out in parallel with optical studies on yttrium aluminum garnet transparent ceramics in order to gain an understanding for their structure at the atomic level and its effect on the transparency and light scattering. The study confirmed that PAS can provide useful information on their microstructure and guide the technology of manufacturing and advancing transparent ceramics.

Manufacture of high-density ceramic sinters

NASA Technical Reports Server (NTRS)

Hibata, Y.

1986-01-01

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

Strain isolated ceramic coatings

NASA Technical Reports Server (NTRS)

Tolokan, R. P.; Brady, J. B.; Jarrabet, G. P.

1985-01-01

Plasma sprayed ceramic coatings are used in gas turbine engines to improve component temperature capability and cooling air efficiency. A compliant metal fiber strain isolator between a plasma sprayed ceramic coating and a metal substrate improves ceramic durability while allowing thicker coatings for better insulation. Development of strain isolated coatings has concentrated on design and fabrication of coatings and coating evaluation via thermal shock testing. In thermal shock testing, five types of failure are possible: buckling failure im compression on heat up, bimetal type failure, isothermal expansion mismatch failure, mudflat cracking during cool down, and long term fatigue. A primary failure mode for thermally cycled coatings is designated bimetal type failure. Bimetal failure is tensile failure in the ceramic near the ceramic-metal interface. One of the significant benefits of the strain isolator is an insulating layer protecting the metal substrate from heat deformation and thereby preventing bimetal type failure.

Coexistence of colossal stress and texture gradients in sputter deposited nanocrystalline ultra-thin metal films

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

Kuru, Yener; Welzel, Udo; Mittemeijer, Eric J.

2014-12-01

This paper demonstrates experimentally that ultra-thin, nanocrystalline films can exhibit coexisting colossal stress and texture depth gradients. Their quantitative determination is possible by X-ray diffraction experiments. Whereas a uniform texture by itself is known to generally cause curvature in so-called sin{sup 2}ψ plots, it is shown that the combined action of texture and stress gradients provides a separate source of curvature in sin{sup 2}ψ plots (i.e., even in cases where a uniform texture does not induce such curvature). On this basis, the texture and stress depth profiles of a nanocrystalline, ultra-thin (50 nm) tungsten film could be determined.

Acanthite–argentite transformation in nanocrystalline silver sulfide and the Ag{sub 2}S/Ag nanoheterostructure

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

Gusev, A. I., E-mail: gusev@ihim.uran.ru; Sadovnikov, S. I.

Nanocrystalline acanthite-structured silver sulfide of the monoclinic structure and a Ag{sub 2}S/Ag nanoheterostructure are produced. The high-temperature X-ray diffraction technique is applied to the in situ study of the (acanthite α-Ag{sub 2}S)–(argentite β-Ag{sub 2}S) phase transformation in nanocrystalline silver sulfide. The crystal structure of argentite is refined, and it is found that the content of vacant sites in the metal sublattice of argentite exceeds 92%. A model of a resistive switch, whose operation is based on the reversible acanthite–argentite transformation in a Ag{sub 2}S/Ag heterostructure, is considered.

Oxidation resistant nanocrystalline MCrAl(Y) coatings and methods of forming such coatings

DOEpatents

Cheruvu, Narayana S.; Wei, Ronghua

2014-07-29

The present disclosure relates to an oxidation resistant nanocrystalline coating and a method of forming an oxidation resistant nanocrystalline coating. An oxidation resistant coating comprising an MCrAl(Y) alloy may be deposited on a substrate, wherein M, includes iron, nickel, cobalt, or combinations thereof present greater than 50 wt % of the MCrAl(Y) alloy, chromium is present in the range of 15 wt % to 30 wt % of the MCrAl(Y) alloy, aluminum is present in the range of 6 wt % to 12 wt % of the MCrAl(Y) alloy and yttrium, is optionally present in the range of 0.1 wt % to 0.5 wt % of the MCrAl(Y) alloy. In addition, the coating may exhibit a grain size of 200 nm or less as deposited.

Rheology of Organodispersions of Alumina Nanopowders Used in Producing Articles from Engineering Ceramics

NASA Astrophysics Data System (ADS)

Palcevskis, E.; Faitelson, L.; Jakobsons, E.

2005-05-01

The rheological properties of molding suspensions of alumina nanopowder in paraffin have been studied. Powders with specific surface areas of 32 and 55 m2/g and the surface-active substances oleic acid and Hypermer LP1 were used. The Hamaker constant for alumina particles in paraffin wax was estimated. A rough calculation showed that a gel should arise in the suspensions studied. The linearly viscoelastic characteristics determined by the method of small-amplitude periodic shear (on the frequency range from 0.063 to 157 s-1) confirmed this conclusion. The flow curves of the molding feedstock, determined over a broad range of shear rates (from 0.018 to 1070 s-1), point to a pseudoplastic character of the flow. From the rheological studies it follows that, in manufacturing engineering ceramics by injection molding from the suspensions investigated and in designing or selecting the forming equipment, the realization of maximum high shear strains must be ensured, which will promote a qualitative filling of intricately shaped and small-size molds.

Interphase for ceramic matrix composites reinforced by non-oxide ceramic fibers

NASA Technical Reports Server (NTRS)

DiCarlo, James A. (Inventor); Bhatt, Ramakrishna (Inventor); Morscher, Gregory N. (Inventor); Yun, Hee-Mann (Inventor)

2008-01-01

A ceramic matrix composite material is disclosed having non-oxide ceramic fibers, which are formed in a complex fiber architecture by conventional textile processes; a thin mechanically weak interphase material, which is coated on the fibers; and a non-oxide or oxide ceramic matrix, which is formed within the interstices of the interphase-coated fiber architecture. During composite fabrication or post treatment, the interphase is allowed to debond from the matrix while still adhering to the fibers, thereby providing enhanced oxidative durability and damage tolerance to the fibers and the composite material.

High prevalence of noise following Delta ceramic-on-ceramic total hip arthroplasty.

PubMed

Salo, P P; Honkanen, P B; Ivanova, I; Reito, A; Pajamäki, J; Eskelinen, A

2017-01-01

We evaluated the short-term functional outcome and prevalence of bearing-specific generation of audible noise in 301 patients (336 hips) operated on with fourth generation (Delta) medium diameter head, ceramic-on-ceramic (CoC) total hip arthroplasties (THAs). There were 191 female (63%) and 110 male patients (37%) with a mean age of 61 years (29 to 78) and mean follow-up of 2.1 years (1.3 to 3.4). Patients completed three questionnaires: Oxford Hip Score (OHS), Research and Development 36-item health survey (RAND-36) and a noise-specific symptom questionnaire. Plain radiographs were also analysed. A total of three hips (0.9%) were revised. There were 52 patients (54 hips, 17%) who reported noise, and in 25 (48%) of them the noise was frequently heard. In the multiple regression analysis, the only independent risk factor for noise was a specific THA brand, with a threefold increased risk (95% confidence intervals 1.39 to 6.45, p = 0.005) of noise compared with the reference THA brand. Patients with noisy hips had lower median OHS (43 versus 46.5, p = 0.002) and their physical functioning (p = 0.021) subscale in RAND-36 was reduced. Noise was surprisingly common in this population. Cite this article: Bone Joint J 2017;99-B:44-50. ©2017 The British Editorial Society of Bone & Joint Surgery.

Improved ceramic slip casting technique. [application to aircraft model fabrication

NASA Technical Reports Server (NTRS)

Buck, Gregory M. (Inventor); Vasquez, Peter (Inventor)

1993-01-01

mold of the calcium sulfate-bonded investment material. The shell mold is cooled to room temperature, and a ceramic slip is poured therein. After a ceramic shell of desired thickness has set up in the shell mold, excess ceramic slip is poured out. While still wet, the shell mold is peeled from the ceramic shell to expose any delicate or detailed parts, after which the ceramic shell is cured to provide a complete, detailed, precision ceramic article without parting lines.

Survival Rate of Resin and Ceramic Inlays, Onlays, and Overlays: A Systematic Review and Meta-analysis.

PubMed

Morimoto, S; Rebello de Sampaio, F B W; Braga, M M; Sesma, N; Özcan, M

2016-08-01

This systematic review and meta-analysis aimed to evaluate the survival rate of ceramic and resin inlays, onlays, and overlays and to identify the complication types associated with the main clinical outcomes. Two reviewers searched PubMed, EMBASE, and the Cochrane Central Register of Controlled Trials for articles published between 1983 through April 2015, conforming to Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines for systematic reviews. Clinical studies meeting the following criteria were included: 1) studies related to resin and ceramic inlays, onlays, and overlays; 2) prospective, retrospective, or randomized controlled trials conducted in humans; 3) studies with a dropout rate of less than 30%; and 4) studies with a follow-up longer than 5 y. Of 1,389 articles, 14 met the inclusion criteria. The meta-regression indicated that the type of ceramic material (feldspathic porcelain vs. glass-ceramic), study design (retrospective vs. prospective), follow-up time (5 vs. 10 y), and study setting (university vs. private clinic) did not affect the survival rate. Estimated survival rates for glass-ceramics and feldspathic porcelain were between 92% and 95% at 5 y (n = 5,811 restorations) and were 91% at 10 y (n = 2,154 restorations). Failures were related to fractures/chipping (4%), followed by endodontic complications (3%), secondary caries (1%), debonding (1%), and severe marginal staining (0%). Odds ratios (95% confidence intervals) were 0.19 (0.04 to 0.96) and 0.54 (0.17 to 1.69) for pulp vitality and type of tooth involved (premolars vs. molars), respectively. Ceramic inlays, onlays, and overlays showed high survival rates at 5 y and 10 y, and fractures were the most frequent cause of failure. © International & American Associations for Dental Research 2016.

Influence of ceramic surface texture on the wear of gold alloy and heat-pressed ceramics.

PubMed

Saiki, Osamu; Koizumi, Hiroyasu; Nogawa, Hiroshi; Hiraba, Haruto; Akazawa, Nobutaka; Matsumura, Hideo

2014-01-01

The purpose of this study was to evaluate the influence of ceramic surface texture on the wear of rounded rod specimens. Plate specimens were fabricated from zirconia (ZrO2), feldspathic porcelain, and lithium disilicate glass ceramics (LDG ceramics). Plate surfaces were either ground or polished. Rounded rod specimens with a 2.0-mm-diameter were fabricated from type 4 gold alloy and heat-pressed ceramics (HP ceramics). Wear testing was performed by means of a wear testing apparatus under 5,000 reciprocal strokes of the rod specimen with 5.9 N vertical loading. The results were statistically analyzed with a non-parametric procedure. The gold alloy showed the maximal height loss (90.0 µm) when the rod specimen was abraded with ground porcelain, whereas the HP ceramics exhibited maximal height loss (49.8 µm) when the rod specimen was abraded with ground zirconia. There was a strong correlation between height loss of the rod and surface roughness of the underlying plates, for both the gold alloy and HP ceramics.

Water-soluble nanocrystalline cellulose films with highly transparent and oxygen barrier properties

NASA Astrophysics Data System (ADS)

Cheng, Shaoling; Zhang, Yapei; Cha, Ruitao; Yang, Jinliang; Jiang, Xingyu

2015-12-01

By mixing a guar gum (GG) solution with a nanocrystalline cellulose (NCC) dispersion using a novel circular casting technology, we manufactured biodegradable films as packaging materials with improved optical and mechanical properties. These films could act as barriers for oxygen and could completely dissolve in water within 5 h. We also compared the effect of nanocomposite films and commercial food packaging materials on the preservation of food.By mixing a guar gum (GG) solution with a nanocrystalline cellulose (NCC) dispersion using a novel circular casting technology, we manufactured biodegradable films as packaging materials with improved optical and mechanical properties. These films could act as barriers for oxygen and could completely dissolve in water within 5 h. We also compared the effect of nanocomposite films and commercial food packaging materials on the preservation of food. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr07647a

Surface grafting of reduced graphene oxide using nanocrystalline cellulose via click reaction

NASA Astrophysics Data System (ADS)

Kabiri, Roya; Namazi, Hassan

2014-07-01

Reduced graphene oxide (RGO) sheet was functionalized with nanocrystalline cellulose (NCC) via click coupling between azide-functionalized graphene oxide (GO-N3) and terminal propargyl-functionalized nanocrystalline cellulose (PG-NCC). First, the reactive azide groups were introduced on the surface of GO with azidation of 2-chloroethyl isocyanate-treated graphene oxide (GO-Cl). Then, the resulted compounds were reacted with PG-NCC utilizing copper-catalyzed azide-alkyne cycloaddition. During the click reaction, GO was simultaneously reduced to graphene. The coupling was confirmed by Fourier transform infrared, Raman, DEPT135, and 13C NMR spectroscopy, and the complete exfoliation of graphene in the NCC matrix was confirmed with X-ray diffraction measurement. The degree of functionalization from the gradual mass loss of RGO-NCC suggests that around 23 mass % has been functionalized covalently. The size of both NCC and GO was found to be in nanometric range, which decreased after click reaction.

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

NASA Astrophysics Data System (ADS)

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

2009-06-01

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

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.

Health hazards of ceramic artists.

PubMed

Dorevitch, S; Babin, A

2001-01-01

Ceramic artists can be exposed to many hazards including metals (such as lead), fibrogenic dusts (such as silica), heat, repetitive motion, radiation, and toxic emissions from kilns. The health risks of these exposures have not been well characterized among artists, although limited information is available from commercial potteries. Adverse health effects may be prevented by using less hazardous materials (such as lead-free glazes), improved ventilation, and proper work practices. Special precautions must be in place if children have access to the ceramics studio. The use of glazed ceramic dishes can be a risk for lead toxicity. Food should not be stored in glazed ceramics, and pregnant women should avoid daily use of ceramic mugs for drinking hot beverages.

Corrosion resistant ceramic materials

DOEpatents

Kaun, Thomas D.

1995-01-01

Ceramic materials which exhibit stability in severely-corrosive environments having high alkali-metal activity, high sulfur/sulfide activity and/or molten halides at temperatures of 200.degree.-550.degree. C. or organic salt (including SO.sub.2 and SO.sub.2 Cl.sub.2) at temperatures of 25.degree.-200.degree. C. These sulfide ceramics form stoichiometric (single-phase) compounds with sulfides of Ca, Li, Na, K, Al, Mg, Si, Y, La, Ce, Ga, Ba, Zr and Sr and show melting-points that are sufficiently low and have excellent wettability with many metals (Fe, Ni, Mo) to easily form metal/ceramic seals. Ceramic compositions are also formulated to adequately match thermal expansion coefficient of adjacent metal components.

Corrosion resistant ceramic materials

DOEpatents

Kaun, Thomas D.

1996-01-01

Ceramic materials which exhibit stability in severely-corrosive environments having high alkali-metal activity, high sulfur/sulfide activity and/or molten halides at temperatures of 200.degree.-550.degree. C. or organic salt (including SO.sub.2 and SO.sub.2 Cl.sub.2) at temperatures of 25.degree.-200.degree. C. These sulfide ceramics form stoichiometric (single-phase) compounds with sulfides of Ca, Li, Na, K, Al, Mg, Si, Y, La, Ce, Ga, Ba, Zr and Sr and show melting-points that are sufficiently low and have excellent wettability with many metals (Fe, Ni, Mo) to easily form metal/ceramic seals. Ceramic compositions are also formulated to adequately match thermal expansion coefficient of adjacent metal components.

Corrosion resistant ceramic materials

DOEpatents

Kaun, T.D.

1996-07-23

Ceramic materials are disclosed which exhibit stability in severely-corrosive environments having high alkali-metal activity, high sulfur/sulfide activity and/or molten halides at temperatures of 200--550 C or organic salt (including SO{sub 2} and SO{sub 2}Cl{sub 2}) at temperatures of 25--200 C. These sulfide ceramics form stoichiometric (single-phase) compounds with sulfides of Ca, Li, Na, K, Al, Mg, Si, Y, La, Ce, Ga, Ba, Zr and Sr and show melting-points that are sufficiently low and have excellent wettability with many metals (Fe, Ni, Mo) to easily form metal/ceramic seals. Ceramic compositions are also formulated to adequately match thermal expansion coefficient of adjacent metal components. 1 fig.

High pressure ceramic heat exchanger

DOEpatents

Harkins, Bruce D.; Ward, Michael E.

1999-01-01

Many recuperators have components which react to corrosive gases and are used in applications where the donor fluid includes highly corrosive gases. These recuperators have suffered reduced life, increased service or maintenance, and resulted in increased cost. The present header assembly when used with recuperators reduces the brittle effect of a portion of the ceramic components. Thus, the present header assembly used with the present recuperator increases the life, reduces the service and maintenance, and reduces the increased cost associated with corrosive action of components used to manufacture recuperators. The present header assembly is comprised of a first ceramic member, a second ceramic member, a reinforcing member being in spaced relationship to the first ceramic member and the second ceramic member. The header assembly is further comprised of a refractory material disposed in contacting relationship with the first ceramic member, the second ceramic member and the reinforcing member and having a strengthening member wrapped around the refractory material. The present header assembly provides a high strength load bearing header assembly having good thermal cycling characteristics, good resistance to a corrosive environment and good steady state strength at elevated temperatures.

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.

Ceramic transactions: Fractography of glasses and ceramics III. Volume 64

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

Varner, J.R.; Frechette, V.D.; Quinn, G.D.

1996-12-31

Reports are presented from the Third Annual Conference on the Fractography of Glasses and Ceramics. Topics include ceramics fracture mode, damage analysis, defect origin, deformation, crack evolution, and the use of laser raman spectroscopy for analysis of residual surface strains. Individual projects have been processed separately for the United States Department of Energy databases.

Migration studies of nickel and chromium from ceramic and glass tableware into food simulants.

PubMed

Szynal, Tomasz; Rebeniak, Małgorzata; Mania, Monika

nickel was found. The validated methods for measuring chromium achieved the following parameters; 0.02 to 0.80 mg/L operating range, 0.01 mg/L detection limit, 0.02 mg/L limit of quantification, 6% repeatability, 2.8% accuracy, 102% average recovery and 11% uncertainty. For the nickel method the corresponding parameters were 0.02 to 0.80 mg/L work- ing range, 0.02 mg/L limit of quantification, 0.01 mg/L detection limit, 5% repeatability, 6.5% accuracy, 101% average recovery and 12% uncertainty. The tested ceramics and glassware did not pose a threat to human health regarding migration of nickel and chromium, and thus any potential exposure to these metals released from these products into food will be small. However, due to the toxicity of these metals, the migration of nickel and chromium is still required for articles coming into contact with food, which includes metalware. ceramic tableware, ceramics, glassware, food contact articles, nickel, chromium leaching, migration.

Thermal Stability of Nanocrystalline Alloys by Solute Additions and A Thermodynamic Modeling

NASA Astrophysics Data System (ADS)

Saber, Mostafa

Nanocrystalline alloys show superior properties due to their exceptional microstructure. Thermal stability of these materials is a critical aspect. It is well known that grain boundaries in nanocrystalline microstructures cause a significant increase in the total free energy of the system. A driving force provided to reduce this excess free energy can cause grain growth. The presence of a solute addition within a nanocrystalline alloy can lead to the thermal stability. Kinetic and thermodynamic stabilization are the two basic mechanisms with which stability of a nanoscale grain size can be achieved at high temperatures. The basis of this thesis is to study the effect of solute addition on thermal stability of nanocrystalline alloys. The objective is to determine the effect of Zr addition on the thermal stability of mechanically alloyed nanocrysatillne Fe-Cr and Fe-Ni alloys. In Fe-Cr-Zr alloy system, nanoscale grain size stabilization was maintained up to 900 °C by adding 2 at% Zr. Kinetic pinning by intermetallic particles in the nanoscale range was identified as a primary mechanism of thermal stabilization. In addition to the grain size strengthening, intermetallic particles also contribute to strengthening mechanisms. The analysis of microhardness, XRD data, and measured grain sizes from TEM micrographs suggested that both thermodynamic and kinetic mechanisms are possible mechanisms. It was found that alpha → gamma phase transformation in Fe-Cr-Zr system does not influence the grain size stabilization. In the Fe-Ni-Zr alloy system, it was shown that the grain growth in Fe-8Ni-1Zr alloy is much less than that of pure Fe and Fe-8Ni alloy at elevated temperatures. The microstructure of the ternary Fe-8Ni-1Zr alloy remains in the nanoscale range up to 700 °C. Using an in-situ TEM study, it was determined that drastic grain growth occurs when the alpha → gamma phase transformation occurs. Accordingly, there can be a synergistic relationship between grain growth

Transparent nanocrystalline diamond coatings and devices

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

Sumant, Anirudha V.; Khan, Adam

2017-08-22

A method for coating a substrate comprises producing a plasma ball using a microwave plasma source in the presence of a mixture of gases. The plasma ball has a diameter. The plasma ball is disposed at a first distance from the substrate and the substrate is maintained at a first temperature. The plasma ball is maintained at the first distance from the substrate, and a diamond coating is deposited on the substrate. The diamond coating has a thickness. Furthermore, the diamond coating has an optical transparency of greater than about 80%. The diamond coating can include nanocrystalline diamond. The microwavemore » plasma source can have a frequency of about 915 MHz.« less

Ceramic susceptor for induction bonding of metals, ceramics, and plastics

NASA Technical Reports Server (NTRS)

Fox, Robert L.; Buckley, John D.

1991-01-01

A thin (.005) flexible ceramic susceptor (carbon) was discovered. It was developed to join ceramics, plastics, metals, and combinations of these materials using a unique induction heating process. Bonding times for laboratory specimens comparing state of the art technology to induction bonding were cut by a factor of 10 to 100 times. This novel type of carbon susceptor allows for applying heat directly and only to the bondline without heating the entire structure, supports, and fixtures of a bonding assembly. The ceramic (carbon film) susceptor produces molten adhesive or matrix material at the bond interface. This molten material flows through the perforated susceptor producing a fusion between the two parts to be joined, which in many instances has proven to be stronger than the parent material. Bonding can be accomplished in 2 minutes on areas submitted to the inductive heating. Because a carbon susceptor is used in bonding carbon fiber reinforced plastics and ceramics, there is no radar signature or return making it an ideal process for joining advanced aerospace composite structures.

Ceramic technology for automotive turbines

NASA Technical Reports Server (NTRS)

Mclean, A. F.

1982-01-01

The paper presents an update on ceramic technology for automotive turbines. Progress in research and development of improved ceramics is reviewed, including approaches for assessing time-dependent strength characteristics. Processes for making shapes are discussed, and the design and testing of selected ceramic turbine components are reviewed.

Superconductive articles including cerium oxide layer

DOEpatents

Wu, Xin D.; Muenchausen, Ross E.

1993-01-01

A ceramic superconductor comprising a metal oxide substrate, a ceramic high temperature superconductive material, and a intermediate layer of a material having a cubic crystal structure, said layer situated between the substrate and the superconductive material is provided, and a structure for supporting a ceramic superconducting material is provided, said structure comprising a metal oxide substrate, and a layer situated over the surface of the substrate to substantially inhibit interdiffusion between the substrate and a ceramic superconducting material deposited upon said structure.