Preparation and Characterization of Microfiltration Ceramic Membranes Based on Natural Quartz Sand

Directory of Open Access Journals (Sweden)

Andrei Ivanets

2017-06-01

Full Text Available The effect of phase and chemical composition of natural quartz sand, binder and burnable additives was studied. The conditions of application of the membrane and biocide layers on the formation of porous ceramic and microfiltration membranes were investigated. It is shown that a crystalline oxide of Si(IV is determinant for obtaining the ceramic materials. The presence of carbonates (calcite, dolomite, aragonite, etc. and crystalline aluminosilicates (microcline, albite, phlogopit, etc. leads to a decrease in mechanical strength of ceramics. The biocide coating designed to protect the ceramic membrane surfaces from biofouling was applied and its anti-bacterial activity was shown.

CRYSTALLINE CERAMIC WASTE FORMS: REFERENCE FORMULATION REPORT

Energy Technology Data Exchange (ETDEWEB)

Brinkman, K.; Fox, K.; Marra, J.

2012-05-15

The research conducted in this work package is aimed at taking advantage of the long term thermodynamic stability of crystalline ceramics to create more durable waste forms (as compared to high level waste glass) in order to reduce the reliance on engineered and natural barrier systems. Durable ceramic waste forms that incorporate a wide range of radionuclides have the potential to broaden the available disposal options and to lower the storage and disposal costs associated with advanced fuel cycles. Assemblages of several titanate phases have been successfully demonstrated to incorporate radioactive waste elements, and the multiphase nature of these materials allows them to accommodate variation in the waste composition. Recent work has shown that they can be successfully produced from a melting and crystallization process. The objective of this report is to explain the design of ceramic host systems culminating in a reference ceramic formulation for use in subsequent studies on process optimization and melt property data assessment in support of FY13 melter demonstration testing. The waste stream used as the basis for the development and testing is a combination of the projected Cs/Sr separated stream, the Trivalent Actinide - Lanthanide Separation by Phosphorous reagent Extraction from Aqueous Komplexes (TALSPEAK) waste stream consisting of lanthanide fission products, the transition metal fission product waste stream resulting from the transuranic extraction (TRUEX) process, and a high molybdenum concentration with relatively low noble metal concentrations. In addition to the combined CS/LN/TM High Mo waste stream, variants without Mo and without Mo and Zr were also evaluated. Based on the results of fabricating and characterizing several simulated ceramic waste forms, two reference ceramic waste form compositions are recommended in this report. The first composition targets the CS/LN/TM combined waste stream with and without Mo. The second composition targets

The influence of glass composition on crystalline phase stability in glass-ceramic wasteforms

International Nuclear Information System (INIS)

Maddrell, Ewan; Thornber, Stephanie; Hyatt, Neil C.

2015-01-01

Highlights: • Crystalline phase formation shown to depend on glass matrix composition. • Zirconolite forms as the sole crystalline phase only for most aluminous glasses. • Thermodynamics indicate that low silica activity glasses stabilise zirconolite. - Abstract: Zirconolite glass-ceramic wasteforms were prepared using a suite of Na 2 O–Al 2 O 3 –B 2 O 3 –SiO 2 glass matrices with variable Al:B ratios. Zirconolite was the dominant crystalline phase only for the most alumina rich glass compositions. As the Al:B ratio decreased zirconolite was replaced by sphene, zircon and rutile. Thermodynamic data were used to calculate a silica activity in the glass melt below which zirconolite is the favoured crystalline phase. The concept of the crystalline reference state of glass melts is then utilised to provide a physical basis for why silica activity varies with the Al:B ratio

Deposition of Crystalline Hydroxyapatite Nanoparticles on Y-TZP Ceramic: A Potential Solution to Enhance Bonding Characteristics of Y-TZP Ceramics

Directory of Open Access Journals (Sweden)

Abbas Azari

2017-08-01

Full Text Available Objectives: Many advantages have been attributed to dental zirconia ceramics in terms of mechanical and physical properties; however, the bonding ability of this material to dental structure and/or veneering ceramics has always been a matter of concern. On the other hand, hydroxyapatite (HA shows excellent biocompatibility and good bonding ability to tooth structure, with mechanically unstable and brittle characteristics, that make it clinically unacceptable for use in high stress bearing areas. The main purpose of this study was to introduce two simple yet practical methods to deposit the crystalline HA nanoparticles on zirconia ceramics. Materials and Methods: zirconia blocks were treated with HA via two different deposition methods namely thermal coating and air abrasion. Specimens were analyzed by scanning electron microscopy, energy dispersive spectroscopy (EDS and X-ray diffraction (XRD.Results: In both groups, the deposition techniques used were successfully accomplished, while the substrate showed no structural change. However, thermal coating group showed a uniform deposition of crystalline HA but in air abrasion method, there were dispersed thin islands of HA.Conclusions: Thermal coating method has the potential to significantly alter the surface characteristics of zirconia. The simple yet practical nature of the proposed method may be able to shift the bonding paradigm of dental zirconia ceramics. This latter subject needs to be addressed in future investigations.Keywords: Zirconium Oxide; Hydroxyapatites; Dental Bonding; Microscopy, Electron, Scanning; X-Ray Diffraction; Spectrometry, X-Ray Emission

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

Science.gov (United States)

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

2012-01-01

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

Effect of Nano-crystalline Ceramic Coats Produced by Plasma Electrolytic Oxidation on Corrosion Behavior of AA5083 Aluminum Alloy

International Nuclear Information System (INIS)

Thayananth, T.; Muthupandi, V.; Rao, S. R. Koteswara

2010-01-01

High specific strength offered by aluminum and magnesium alloys makes them desirable in modern transportation industries. Often the restrictions imposed on the usage of these alloys are due to their poor tribological and corrosion properties. However, their corrosion properties can be further enhanced by synthesizing ceramic coating on the substrate through Plasma Electrolytic Oxidation (PEO) process. In this study, nano-crystalline alumina coatings were formed on the surface of AA5083 aluminum alloy test coupons using PEO process in aqueous alkali-silicate electrolyte with and without addition of sodium aluminate. X-ray diffraction (XRD) studies showed that the crystallite size varied between 38 and 46 nm and α- and γ- alumina were the dominant phases present in the coatings. Corrosion studies by potentiodynamic polarization tests in 3.5% NaCl revealed that the electrolyte composition has an influence on the corrosion resistance of nano-crystalline oxide layer formed.

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

Science.gov (United States)

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

2012-01-01

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

Quantitative analysis of crystalline and remaining glass phases in CaO-B2O3-SiO2 ternary system glass ceramics

International Nuclear Information System (INIS)

He Ming; Wu Mengqiang; Zhang Shuren; Zhou Xiaohua; Zhang Ting; Chen Song

2010-01-01

Research highlights: → As for CBS ternary system glass ceramics, due to the complex phase compositions, many methods could be difficult to determine quantitatively the absolute amounts of crystalline and remaining oxides. In this study, an available method based on the Rietveld method was used to quantitatively analyze the relative weight fraction and densities of crystalline phases. These above data are used to obtain a table of both relative weight fraction of crystalline phases and densities of all phases including CBS LTCC. Using volume additivity rule, it is possible to analysis quantitatively the absolute weight fraction of crystalline phases and also the oxides molar content in the remaining glass. - Abstract: Based on Rietveld method of X-ray techniques and volume additivity rule, a new method was developed to quantitatively analyze the phase composition of CaO-B 2 O 3 -SiO 2 ternary system glass ceramics. Lattice parameters, densities and relative weight fractions of crystalline phases in CaO-B 2 O 3 -SiO 2 ternary system were obtained by X-ray diffraction (XRD) refinement. According to the relative weight fraction of crystalline phases and densities of various components, the volume additivity rule was revealed by calculating the absolute weight fraction of crystalline phases of CaO-B 2 O 3 -SiO 2 glass ceramics. In addition, molar contents of the oxides in the remaining glass can also be determined by this method. Comparing this method with internal standard method, it is found that the maximum deviations of the crystallinity and the absolute weight fraction of crystalline phases are less than 2.6% and 2.9%, respectively. As a result, quantitative evaluation of CaO-B 2 O 3 -SiO 2 ternary system glass ceramics can be achieved using this method.

Thermal shock behavior of toughened gadolinium zirconate/YSZ double-ceramic-layered thermal barrier coating

International Nuclear Information System (INIS)

Zhong, Xinghua; Zhao, Huayu; Zhou, Xiaming; Liu, Chenguang; Wang, Liang; Shao, Fang; Yang, Kai; Tao, Shunyan; Ding, Chuanxian

2014-01-01

Highlights: • Gd 2 Zr 2 O 7 /YSZ DCL thermal barrier coating was designed and fabricated. • The Gd 2 Zr 2 O 7 top ceramic layer was toughened by addition of nanostructured 3YSZ. • Remarkable improvement in thermal shock resistance of the DCL coating was achieved. - Abstract: Double-ceramic-layered (DCL) thermal barrier coating system comprising of toughened Gadolinium zirconate (Gd 2 Zr 2 O 7 , GZ) as the top ceramic layer and 4.5 mol% Y 2 O 3 partially-stabilized ZrO 2 (4.5YSZ) as the bottom ceramic layer was fabricated by plasma spraying and thermal shock behavior of the DCL coating was investigated. The GZ top ceramic layer was toughened by addition of nanostructured 3 mol% Y 2 O 3 partially-stabilized ZrO 2 (3YSZ) to improve fracture toughness of the matrix. The thermal shock resistance of the DCL coating was enhanced significantly compared to that of single-ceramic-layered (SCL) GZ-3YSZ composite coating, which is believed to be primarily attributed to the two factors: (i) the increase in fracture toughness of the top ceramic layer by incorporating nanostructured YSZ particles and (ii) the improvement in strain tolerance through the utilization of 4.5YSZ as the bottom ceramic layer. In addition, the failure mechanisms are mainly attributed to the still low fracture toughness of the top ceramic layer and oxidation of the bond-coat

Illuminating light-dependent color shifts in core and veneer layers of dental all-ceramics

Science.gov (United States)

Lee, Yong-Keun; Cha, Hyun-Suk; Yu, Bin

2014-09-01

The color of an object is perceived differently depending on the ambient light conditions. Since dental all-ceramic restorations are fabricated by building up several layers to reproduce the tooth shade, the optical properties of each layer should be optimized for successful shade reproduction. This study aimed to determine the separate contributions of the color shifts in each of the core and veneer layers of all-ceramics by switching the illuminating lights on the color shifts of layered ceramics. Specimens of seven kinds of core ceramics and the corresponding veneer ceramics for each core were fabricated with a layered thickness of 1.5 mm. A sintering ceramic was used as a reference core material. The Commission Internationale de l'Eclairage (CIE) color coordinates of core, veneer, and layered specimens were measured with a spectroradiometer under the CIE illuminant D65 (daylight), A (incandescent lamp), and F9 (fluorescent lamp) simulating lights. Color shifts of the layered specimens were primarily determined by the CIE a* shifts (D65 to A switch) or by the CIE b* shifts (D65 to F9 switch) of the veneer layer. The color coordinates shifts in the constituent layers differentially influenced those of the layered specimens by the kind of switched lights. Therefore, the optical properties of the constituent layers of all-ceramics should be controlled to reflect these findings.

Joining Dental Ceramic Layers With Glass

Science.gov (United States)

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

2011-01-01

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

Formation of apatite layers on modified canasite glass-ceramics in simulated body fluid.

Science.gov (United States)

Miller, C A; Kokubo, T; Reaney, I M; Hatton, P V; James, P F

2002-03-05

Canasite glass-ceramics were modified by either increasing the concentration of calcium in the glass, or by the addition of P2O5. Samples of these novel materials were placed in simulated body fluid (SBF), along with a control material (commercial canasite), for periods ranging from 12 h to 28 days. After immersion, surface analysis was performed using thin film X-ray diffraction, Fourier transform infrared reflection spectroscopy, and scanning electron microscopy equipped with energy dispersive X-ray detectors. The concentrations of sodium, potassium, calcium, silicon, and phosphorus in the SBF solution were measured using inductively coupled plasma emission spectroscopy. No apatite was detected on the surface of commercial canasite, even after 28 days of immersion in SBF. A crystalline apatite layer was formed on the surface of a P2O5-containing canasite after 5 days, and after 3 days for calcium-enriched canasite. Ion release data suggested that the mechanism for apatite deposition was different for P2O5 and non-P2O5-containing glass-ceramics. Copyright 2001 John Wiley & Sons, Inc.

Microstructure examination of the interface of the glass-ceramic insulator of the molybdenum frame of a vacuum tube

International Nuclear Information System (INIS)

Spears, R.K.

1980-01-01

A common technique used in examining the structural integrity of a glass-ceramic insulator-molybdenum cylinder bond in a vacuum tube subassembly is to slit the outer molybdenum cylinder and separate it from the glass-ceramic insulator. Typically, a black glassy layer (0.001 to 0.002 in. thick) remains on the cylinder. This layer has been interpreted as a requirement for an adequate seal. A subassembly was found that did not exhibit this feature. Further investigation of approximately 100 subassemblies revealed four more parts lacking a black glassy layer. These parts were found to be from two production runs and from three glass-ceramic lots. A microstructural analysis showed that on those parts having a black glassy layer, the crystalline phase in the glass-ceramic grew to within one to two microns of the metal interface and then terminated. A dark region existed in the insulator between the interface and the termination of the crystalline phase. This was attributed to molybdenum oxide dissolved in the glass. On those parts where the glass-ceramic broke clean from the cylinder, the crystalline phase extended up to the metal. Also observed on these parts was the appearance of a dark region adjacent to the metal that extended approximately one to two microns into the glass-ceramic. This was assumed to be an oxide of molybdenum. This report presents information concerning the microstructure of the interface

Effect of layered manufacturing techniques, alloy powders, and layer thickness on metal-ceramic bond strength.

Science.gov (United States)

Ekren, Orhun; Ozkomur, Ahmet; Ucar, Yurdanur

2018-03-01

Direct metal laser sintering (DMLS) and direct metal laser melting (DMLM) have become popular for fabricating the metal frameworks of metal-ceramic restorations. How the type of layered manufacturing device, layer thickness, and alloy powder may affect the bond strength of ceramic to metal substructure is unclear. The purpose of this in vitro study was to evaluate the bond strength of dental porcelain to metal frameworks fabricated using different layered manufacturing techniques (DMLS and DMLM), Co-Cr alloy powders, and layer thicknesses and to evaluate whether a correlation exists between the bond strength and the number of ceramic remnants on the metal surface. A total of 75 bar-shaped metal specimens (n=15) were fabricated using either DMLS or DMLM. The powder alloys used were Keramit NP-S and EOS-Cobalt-Chrome SP-2 with layer thicknesses of 20 μm and 30 μm. After ceramic application, the metal-ceramic bond strength was evaluated with a 3-point-bend test. Three-way ANOVA followed by the Tukey honest significance difference test were used for statistical analysis (α=.05). De-bonding surface microstructure was observed with scanning electron microscopy. Energy dispersive spectroscopy analysis was conducted to evaluate the correlation between ceramic remnants on the metal surface and bond strength values. The mean bond strength value of DMLS was significantly higher than that of DMLM. While no statistically significant difference was found between layer thicknesses, alloy powders closely affected bond strength. Statistical comparisons revealed that the highest bond strength could be achieved with DMLS-Cobalt-Chrome SP2-20μm, and the lowest bond strength was observed in DMLS-Keramit NP-S-20μm (P≤.05). No correlation was found between porcelain remnants on the metal surface and bond strength values. The layered manufacturing device and the alloy powders evaluated in the current study closely affected the bond strength of dental porcelain to a metal framework

Oxidation studies of β-sialon ceramics containing amorphous and / or crystalline intergranular phases

International Nuclear Information System (INIS)

Persson, J.; Kall, P.O.; Jansson, K.; Nygren, M.

1992-01-01

β-sialon ceramics of equal overall compositions but containing amorphous, partly crystalline and almost completely crystalline intergranular phase(s) have been oxidized in oxygen at 1350 deg C for 20 hours. The obtained weight gain curves do not follow the parabolic rate law (ΔW/A 0 ) 2 = k p t + β. To the extent that crystallization occurs in the oxide scale during the oxidation experiment, the amorphous cross section area through which oxygen most easily diffuses will decrease with time. A brief description of this new rate law is given, and the obtained oxidation curves will be discussed within that framework. 4 refs., 2 tabs., 2 figs

Economic comparison of crystalline ceramic and glass waste forms for HLW disposal

International Nuclear Information System (INIS)

McKee, R.W.; Daling, P.M.; Wiles, L.E.

1983-05-01

A titanate-based, crystalline ceramic produced by hot isostatic pressing has been proposed as a potentially more stable and improved waste form for high-level nuclear waste disposal compared to the currently favored borosilicate glass waste form. This paper describes the results of a study to evaluate the relative costs for disposal of high-level waste from a 70,000 metric ton equivalent (MTE) system. The entire waste management system, including waste processing and encapsulation, transportation, and final repository disposal, was included in this analysis. The repository concept is based on the current basalt waste isolation project (BWIP) reference design. A range of design basis alternatives is considered to determine if this would influence the relative economics of the two waste forms. A thermal analysis procedure was utilized to define optimum canister sizes to assure that each waste form was compared under favorable conditions. Repository costs are found to favor the borosilicate glass waste form while transportation costs greatly favor the crystalline ceramic waste form. The determining component in the cost comparison is the waste processing cost, which strongly favors the borosilicate glass process because of its relative simplicity. A net cost advantage on the order of 12% to 15% on a waste management system basis is indicated for the glass waste form

Crystallinity of the double layer of cadmium arachidate films at the water surface

DEFF Research Database (Denmark)

Leveiller, F.; Jacquemain, D.; Lahav, M.

1991-01-01

A crystalline counterionic layer at the interface between an electrolyte solution and a charged layer of insoluble amphiphilic molecules was observed with grazing incidence synchrotron x-ray diffraction. Uncompressed arachidic films spread over 10(-3) molar cadmium chloride solution (pH 8.......8) spontaneously form crystalline clusters with coherence lengths of approximately 1000 angstroms at 9-degrees-C. Ten distinct diffraction peaks were observed, seven of which were attributed to scattering only from a crystalline Cd2+ layer and the other three to scattering primarily from the arachidate layer....... The reflections from the Cd2+ layer were indexed according to a 2 X 3 supercell of the arachidate lattice with three Cd2+ ions per cadmium unit cell....

The effects of sulfate content on crystalline phase, microstructure, and chemical durability of zirconolite−barium borosilicate glass-ceramics

Energy Technology Data Exchange (ETDEWEB)

Wu, Lang, E-mail: lang.wu@163.com [State Key Laboratory Cultivation Base for Nonmetal Composites and Functional Materials, Southwest University of Science and Technology, Mianyang 621010 (China); Wang, Xin; Li, Huidong; Teng, Yuancheng [State Key Laboratory Cultivation Base for Nonmetal Composites and Functional Materials, Southwest University of Science and Technology, Mianyang 621010 (China); Peng, Long [Sichuan Province Key Laboratory of Information Materials and Devices Application, Chengdu University of Information Technology, Chengdu 610225 (China)

2016-09-15

The effects of sulfate content on structure and chemical durability of barium borosilicate glass-ceramics were studied. The results show that the glass-ceramics with 0–1.10 mol% SO{sub 3} possess mainly CaZrTi{sub 2}O{sub 7}-2M phase along with a small amount of CaZrTi{sub 2}O{sub 7}-3T and ZrO{sub 2} phases. The hexagonal CaZrTi{sub 2}O{sub 7}-3T crystals crystallize on the surface of glass-ceramics. For the samples with 1.24–1.55 mol% SO{sub 3}, the main crystalline phases are CaTiSiO{sub 5} and CaZrTi{sub 2}O{sub 7}-2M in the bulk, while a separate sulfate layer containing Na{sub 2}SO{sub 4} and BaSO{sub 4} is observed on the surface. X-ray fluorescence analysis indicates that about 2/3 of the SO{sub 3} originally added has been lost by volatility. The normalized mass loss (NL{sub i}) for Na, B, Ca elements remains almost unchanged (∼10{sup −2} g/m{sup 2}) after 7 days for the samples with 0–1.10 mol% SO{sub 3}. The NL{sub i} for both Na and B increases gradually after 7 days when the SO{sub 3} content is 1.24 mol%. - Highlights: • Strip-shaped CaZrTi{sub 2}O{sub 7}-2M and plate-like CaTiSiO{sub 5} crystals crystallize in the bulk. • CaZrTi{sub 2}O{sub 7}-3T crystals crystallize on the surface for samples with 0–1.10 mol% SO{sub 3}. • A separate sulfate layer crystallizes on the surface when SO{sub 3} exceeds solubility.

Studies of void growth in a thin ductile layer between ceramics

DEFF Research Database (Denmark)

Tvergaard, Viggo

1997-01-01

The growth of voids in a thin ductile layer between ceramics is analysed numerically, using an axisymmetric cell model to represent an array of uniformly distributed spherical voids at the central plane of the layer. The purpose is to determine the full traction-separation law relevant to crack...... growth by a ductile mechanism along the thin layer. Plastic flow in the layer is highly constrained by the ceramics, so that a high. level of triaxial tension develops, leading in some cases to cavitation instabilities. The computations are continued to a state near the occurrence of void coalescence....

Numerical modelling of evaporation in a ceramic layer in the tape casting process

DEFF Research Database (Denmark)

Jabbaribehnam, Mirmasoud; Jambhekar, V. A.; Hattel, Jesper Henri

2016-01-01

Evaporation of water from a ceramic layer is a key phenomenon in the drying process for the manufacturing of tape cast ceramics. This process contains mass, momentum and energy exchange between the porous medium and the free-flow region. In order to analyze such interaction processes, a Represent......Evaporation of water from a ceramic layer is a key phenomenon in the drying process for the manufacturing of tape cast ceramics. This process contains mass, momentum and energy exchange between the porous medium and the free-flow region. In order to analyze such interaction processes...

Multi-layer SiC ceramics/Mo joints brazed using high-temperature solders

International Nuclear Information System (INIS)

Olesinska, W.; Kesik, J.

2003-01-01

The paper presents the results of studies on joining SiC ceramics with molybdenum, with the ceramic surface being activated by titanium, chromium or copper. Titanium or chromium were deposited by the sputtering technique, and copper - by the electro-chemical method. The microstructures of the SiC/Mo joints brazed with the CuMn13Ni3 solder and copper in a nitrogen atmosphere were examined and the results discussed. The joints, in which the ceramic surface was activated in addition with chromium, do not contain mechanical defects caused by the joining process, and the ceramic surface is covered with a continuous layer of the solder. A phase analysis of the interface surface identified an MeSiC phase. The mechanical strength of the joints in which the ceramic surface was modified by the Ti, Cr and Cu layers was markedly greater than that of the joints brazed directly to the uncoated ceramics with the use of active solders. (author)

Ceramic nanostructure materials, membranes and composite layers

NARCIS (Netherlands)

Burggraaf, A.J.; Keizer, Klaas; van Hassel, B.A.

1989-01-01

Synthesis methods to obtain nanoscale materials will be briefly discussed with a focus on sol-gel methods. Three types of nanoscale composites (powders, membranes and ion implanted layers) will be discussed and exemplified with recent original research results. Ceramic membranes with a thickness of

Development of crystalline ceramic for immobilization of TRU wastes in V.G. Khlopin Radium Institute

International Nuclear Information System (INIS)

Burakov, B.E.; Anderson, E.B.

1999-01-01

This paper discusses the Radium Institute's experience in the synthesis of crystalline ceramics based on two groups of actinide host-phases: 1) Zircon/zirconia-(Zn, Ac)SiO 4 /(Zr, Ac)O 2 , where Ac=Pu, Np, Am, Cm; 2) Garnet/perovskite-(Y, Gd, Ac) 3 (Al, Ga, Ac,..) 5 O 12 /(Y, Gd, Ac)(Al, Ga)O 3 . The zircon/zirconia ceramic was suggested as an universal waste form for the immobilization of TRU as well as weapon-grade Pu. Because the position of the Russian Ministry of Atomic Energy (Minatom) does not consider weapons Pu as a waste', the Radium Institute proposed the use of the same ceramic (mainly monophase zirconia ) as a Pu-fuel. The garnet/perovskite ceramic was suggested for the immobilization of military TRU wastes of complex chemical composition. The advantage of this ceramic is that Garnet and Perovskite host-phases can incorporate in their lattices not only actinides, but also other elements including neutron absorbers in a broad range of concentration and in different valence state. Sample of zircon/zirconia ceramic were prepared by hot uniaxial pressing (at temperature T=1300, 1400, 1500degC and pressure P=25 MPa) and sintering (at T=1450, 1490, 1500, 1600degC) methods using different types of initial precursor. Samples of garnet/perovskite ceramic were synthesized by melting method at T=2000degC. Ce, U, Gd were used as TRU stimulants for both types of ceramic. One sample of zircon/zirconia ceramic was doped with 10 wt.% of Pu 239 . Physico-chemical features of these ceramics are described. In conclusion we propose that the pressureless technology based on sintering or melting methods be used for the synthesis of ceramics for the immobilization of all types of TRU wastes. (author)

Magnetron deposition of metal-ceramic protective coatings on glasses of windows of space vehicles

OpenAIRE

Sergeev, Viktor Petrovich; Panin, Viktor Evgenyevich; Psakhie, Sergey Grigorievich; Chernyavskii, Alexandr; Svechkin, Valerii; Khristenko, Yurii; Kalashnikov, Mark Petrovich; Voronov, Andrei

2014-01-01

Transparent refractory metal-ceramic nanocomposite coatings with a high coefficient of elasticrecovery and microhardness on the basis of Ni/Si-Al-N are formed on a glass substrate by the pulse magnetron deposition method. The structure-phase states were investigated by TEM, SEM. It was established that the first layer consists of Ni nanograins with a fcc crystalline lattice, the second layer is two-phase: 5-10 nm nanocrystallites of the AlN phase with the hcp crystalline lattice in amorphous ...

Experimental Study on Layered Ice Bonded Abrasive Polishing of Glass-ceramics

Directory of Open Access Journals (Sweden)

Yuli SUN

2014-12-01

Full Text Available Layered ice bonded abrasive tools (LIBAT is a new kind of one which not only has the ability of lapping and polishing but also has the effect of self-dressing. In this paper, two kinds of layered ice bonded abrasive tools were designed and manufactured. Experimental studies on layered ice bonded abrasive (LIBA polishing of glass-ceramics were conducted. The results show that the surface topography of glass-ceramics polished by micro α-Al2O3-nano α-Al2O3 LIBAT is better than that of polished by micro α-Al2O3-nano SiO2 LIBAT. The surface roughness Sa of glass-ceramics polished by the two kinds of LIBAT is at the nanometer scale. The reasons of this phenomenon were analyzed. The experimental results illustrate that the LIBAT shows good effect and can be used in production practice. DOI: http://dx.doi.org/10.5755/j01.ms.20.4.6149

Crack Growth along Interfaces in Porous Ceramic Layers

DEFF Research Database (Denmark)

Sørensen, Bent F.; Horsewell, Andy

2001-01-01

Crack growth along porous ceramic layers was studied experimentally. Double cantilever beam sandwich specimens were loaded with pure bending moments to obtain stable crack growth. The experiments were conducted in an environmental scanning electron microscope enabling in situ observations...

Formation of calcium phosphate layer on ceramics with different reactivities

International Nuclear Information System (INIS)

Ribeiro, C.; Rigo, E.C.S.; Sepulveda, P.; Bressiani, J.C.; Bressiani, A.H.A.

2004-01-01

Biphasic ceramic samples of different biological reactivity are prepared by using hydroxyapatite (HAp) and tricalcium phosphate (TCP) in various ratios. Different parameters for sintering in an air atmosphere furnace were defined after dilatometric studies. An increased densification with decreased TCP content was observed. The sintered bodies were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The dissolution kinetics and in vitro reactivity were investigated using simulated body fluid (SBF) at 37 deg. C for a maximum period of 3 weeks. The surfaces of the ceramics were analyzed by Fourier transform infrared spectroscopy (FTIR) and SEM in order to observe the formation of a calcium phosphate layer, which indicates the samples bioactivity. Dissolution in SBF demonstrated that layers with different kinetics on the samples surface were formed during the immersion period. The biphasic ceramics show bioactive behavior, even if the resorbable TCP is incorporated

Graphene Quantum Dot Layers with Energy-Down-Shift Effect on Crystalline-Silicon Solar Cells.

Science.gov (United States)

Lee, Kyung D; Park, Myung J; Kim, Do-Yeon; Kim, Soo M; Kang, Byungjun; Kim, Seongtak; Kim, Hyunho; Lee, Hae-Seok; Kang, Yoonmook; Yoon, Sam S; Hong, Byung H; Kim, Donghwan

2015-09-02

Graphene quantum dot (GQD) layers were deposited as an energy-down-shift layer on crystalline-silicon solar cell surfaces by kinetic spraying of GQD suspensions. A supersonic air jet was used to accelerate the GQDs onto the surfaces. Here, we report the coating results on a silicon substrate and the GQDs' application as an energy-down-shift layer in crystalline-silicon solar cells, which enhanced the power conversion efficiency (PCE). GQD layers deposited at nozzle scan speeds of 40, 30, 20, and 10 mm/s were evaluated after they were used to fabricate crystalline-silicon solar cells; the results indicate that GQDs play an important role in increasing the optical absorptivity of the cells. The short-circuit current density was enhanced by about 2.94% (0.9 mA/cm(2)) at 30 mm/s. Compared to a reference device without a GQD energy-down-shift layer, the PCE of p-type silicon solar cells was improved by 2.7% (0.4 percentage points).

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

Science.gov (United States)

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

2018-05-21

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

Cold crucible induction melter test for crystalline ceramic waste form fabrication: A feasibility assessment

Energy Technology Data Exchange (ETDEWEB)

Amoroso, Jake W., E-mail: jake.amoroso@srnl.doe.gov [Savannah River National Laboratory, Aiken, SC 29808 (United States); Marra, James; Dandeneau, Christopher S. [Savannah River National Laboratory, Aiken, SC 29808 (United States); Brinkman, Kyle; Xu, Yun [Clemson University, Clemson, SC 29634 (United States); Tang, Ming [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Maio, Vince [Idaho National Laboratory, Idaho Falls, ID 83415 (United States); Webb, Samuel M. [Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, CA 94086 (United States); Chiu, Wilson K.S. [University of Connecticut, Storrs, Connecticut 06269-3139 (United States)

2017-04-01

The first scaled proof-of-principle cold crucible induction melter (CCIM) test to process a multiphase ceramic waste form from a simulated combined (Cs/Sr, lanthanide and transition metal fission products) commercial used nuclear fuel waste stream was recently conducted in the United States. X-ray diffraction, 2-D X-ray absorption near edge structure (XANES), electron microscopy, inductively coupled plasma-atomic emission spectroscopy (and inductively coupled plasma-mass spectroscopy for Cs), and product consistency tests were used to characterize the fabricated CCIM material. Characterization analyses confirmed that a crystalline ceramic with a desirable phase assemblage was produced from a melt using a CCIM. Primary hollandite, pyrochlore/zirconolite, and perovskite phases were identified in addition to minor phases rich in Fe, Al, or Cs. The material produced in the CCIM was chemically homogeneous and displayed a uniform phase assemblage with acceptable aqueous chemical durability.

Microstructural and Wear Behavior Characterization of Porous Layers Produced by Pulsed Laser Irradiation in Glass-Ceramics Substrates.

Science.gov (United States)

Sola, Daniel; Conde, Ana; García, Iñaki; Gracia-Escosa, Elena; de Damborenea, Juan J; Peña, Jose I

2013-09-09

In this work, wear behavior and microstructural characterization of porous layers produced in glass-ceramic substrates by pulsed laser irradiation in the nanosecond range are studied under unidirectional sliding conditions against AISI316 and corundum counterbodies. Depending on the optical configuration of the laser beam and on the working parameters, the local temperature and pressure applied over the interaction zone can generate a porous glass-ceramic layer. Material transference from the ball to the porous glass-ceramic layer was observed in the wear tests carried out against the AISI316 ball counterface whereas, in the case of the corundum ball, the wear volume loss was concentrated in the porous layer. Wear rate and friction coefficient presented higher values than expected for dense glass-ceramics.

Microstructural and Wear Behavior Characterization of Porous Layers Produced by Pulsed Laser Irradiation in Glass-Ceramics Substrates

Directory of Open Access Journals (Sweden)

Jose I. Peña

2013-09-01

Full Text Available In this work, wear behavior and microstructural characterization of porous layers produced in glass-ceramic substrates by pulsed laser irradiation in the nanosecond range are studied under unidirectional sliding conditions against AISI316 and corundum counterbodies. Depending on the optical configuration of the laser beam and on the working parameters, the local temperature and pressure applied over the interaction zone can generate a porous glass-ceramic layer. Material transference from the ball to the porous glass-ceramic layer was observed in the wear tests carried out against the AISI316 ball counterface whereas, in the case of the corundum ball, the wear volume loss was concentrated in the porous layer. Wear rate and friction coefficient presented higher values than expected for dense glass-ceramics.

Microindentation test for determining mechanical properties of corroded layers of ceramics

International Nuclear Information System (INIS)

Wakui, Takashi; Futakawa, Masatoshi; Tanabe, Yuji; Eto, Motokuni

1999-01-01

Microindentation tests on ceramics (Si-SiC, SiC, Al 2 O 3 and Si 3 N 4 ) immersed in boiling 95 wt% sulfuric acid for 100 or 1000 hours were performed to evaluate the mechanical properties of their corroded layers. The thickness (T) of corroded layer on ceramics was evaluated in terms of characteristic depth (d) which was determined from the point of inflection on the Depth-Load/Depth curve by the microindentation test. The relationship between T and d was found to be given as T nearly equal 10d. Finite element analyses were performed to validate the relationship and to clarify the effects of mechanical properties of corroded layer and the indenter tip radius on the relationship as well. The mechanical properties [Young's modulus (E f ) and yield stress (σ yf )] of corroded layers of Al 2 O 3 and Si 3 N 4 were identified by fitting the predicted Depth-Load/Depth curve to the experimental data. (author)

Effect of various intermediate ceramic layers on the interfacial stability of zirconia core and veneering ceramics.

Science.gov (United States)

Yoon, Hyung-In; Yeo, In-Sung; Yi, Yang-Jin; Kim, Sung-Hun; Lee, Jai-Bong; Han, Jung-Suk

2015-01-01

The purposes of this study were to evaluate the effects of intermediate ceramics on the adhesion between the zirconia core and veneer ceramics. The polished surfaces of fully sintered Y-TZP blocks received three different treatments: (1) connector (C), (2) liner (L) or (3) wash layer (W). All the treated zirconia blocks were veneered with either (a) fluorapatite glass-ceramic (E) or (b) feldspathic porcelain (V) and divided into four groups (CE, CV, LE and WV). For the control group, the testing surfaces of metal blocks were veneered with feldspathic porcelain (VM). A half of the samples in each group (n = 21) were exposed to thermocycling, while the other half of the specimens were stored at room temperature under dry conditions. All specimens were subjected to the shear test and the failed surfaces were microscopically examined. The elemental distribution at the zirconia core/veneer interface was analyzed. The specimens in Groups CE and CV exhibited significantly greater mean bond strength values than those in Groups LE and WV, respectively (p ceramic substances into the zirconia surface. A glass-ceramic based connector is significantly more favorable to core/veneer adhesion than the other intermediate ceramics evaluated in the study. However, thermal cycling affected the bond strength at the core/veneer interface differently according to the intermediate ceramics.

Deformation characteristics of the near-surface layers of zirconia ceramics implanted with aluminum ions

Science.gov (United States)

Ghyngazov, S. A.; Vasiliev, I. P.; Frangulyan, T. S.; Chernyavski, A. V.

2015-10-01

The effect of ion treatment on the phase composition and mechanical properties of the near-surface layers of zirconium ceramic composition 97 ZrO2-3Y2O3 (mol%) was studied. Irradiation of the samples was carried out by accelerated ions of aluminum with using vacuum-arc source Mevva 5-Ru. Ion beam had the following parameters: the energy of the accelerated ions E = 78 keV, the pulse current density Ji = 4mA / cm2, current pulse duration equal τ = 250 mcs, pulse repetition frequency f = 5 Hz. Exposure doses (fluence) were 1016 и 1017 ion/cm2. The depth distribution implanted ions was studied by SIMS method. It is shown that the maximum projected range of the implanted ions is equal to 250 nm. Near-surface layers were investigated by X-ray diffraction (XRD) at fixed glancing incidence angle. It is shown that implantation of aluminum ions into the ceramics does not lead to a change in the phase composition of the near-surface layer. The influence of implanted ions on mechanical properties of ceramic near-surface layers was studied by the method of dynamic nanoindentation using small loads on the indenter P=300 mN. It is shown that in ion- implanted ceramic layer the processes of material recovery in the deformed region in the unloading mode proceeds with higher efficiency as compared with the initial material state. The deformation characteristics of samples before and after ion treatment have been determined from interpretation of the resulting P-h curves within the loading and unloading sections by the technique proposed by Oliver and Pharr. It was found that implantation of aluminum ions in the near-surface layer of zirconia ceramics increases nanohardness and reduces the Young's modulus.

A facile method to enhance the uniformity and adhesion properties of water-based ceramic coating layers on hydrophobic polyethylene separators

Science.gov (United States)

Lee, Hoogil; Jeon, Hyunkyu; Gong, Seokhyeon; Ryou, Myung-Hyun; Lee, Yong Min

2018-01-01

To enhance the uniformity and adhesion properties of water-based ceramic coating layers on hydrophobic polyethylene (PE) separators, their surfaces were treated with thin and hydrophilic polydopamine layers. As a result, an aqueous ceramic coating slurry consisting of Al2O3 particles, carboxyl methyl cellulose (CMC) binders, and water solvent was easily spread on the separator surface, and a uniform ceramic layer was formed after solvent drying. Moreover, the ceramic coating layer showed greatly improved adhesion properties to the PE separator surface. Whereas the adhesion strength within the bulk coating layer (Fmid) ranged from 43 to 86 N m-1 depending on the binder content of 1.5-3.0 wt%, the adhesion strength at the interface between the ceramic coating layer and PE separator (Fsepa-Al2O3) was 245-360 N m-1, a value equivalent to an increase of four or five times. Furthermore, an additional ceramic coating layer of approximately 7 μm did not degrade the ionic conductivity and electrochemical properties of the bare PE separators. Thus, all the LiMn2O4/graphite cells with ceramic-coated separators delivered an improved cycle life and rate capability compared with those of the control cells with bare PE separators.

Nucleation and crystallization behaviors of nano-crystalline lithium–mica glass–ceramic prepared via sol–gel method

Energy Technology Data Exchange (ETDEWEB)

Tohidifar, M.R. [Department of Materials Science and Engineering, Tarbiat Modares University, P.O. Box 14115-143, Tehran (Iran, Islamic Republic of); Alizadeh, P., E-mail: p-alizadeh@modares.ac.ir [Department of Materials Science and Engineering, Tarbiat Modares University, P.O. Box 14115-143, Tehran (Iran, Islamic Republic of); Riello, P. [Department of Molecular Sciences and Nanosystems, University of Ca’Foscari, Venice (Italy)

2012-06-15

Graphical abstract: The effects of nucleation and crystallization treatments on nano-crystalline lithium–mica glass–ceramic, synthesized by sol–gel technique, were investigated. It was found that MgF{sub 2} crystals act as nuclei centers for the mica crystallization so that a large quantity of mica crystallites was obtained following nucleation process. The crystallization activation energy for both the un-nucleated and nucleated samples was measured as 400.2 and 229.6 kJ mol{sup −1}, respectively. The calculated Avrami exponents demonstrated that the growth mechanism of mica crystallites changes from the needle-like to three-dimensional growth with applying the appropriate nucleation treatment ▪. Highlights: ► Crystallization temperature shifts to 625 from 680 °C following nucleation process. ► Activation energy of crystallization for the nucleated specimen is 229.6 kJ mol{sup −1}. ► Crystallization activation energy for the un-nucleated specimen is 400.2 kJ mol{sup −1}. ► Needle-like growth is predominant growth mechanism for un-nucleated sample. ► Three-dimensional growth is predominant growth mechanism for nucleated sample. -- Abstract: The paper investigates the effects of nucleation and crystallization treatments on nano-crystalline lithium–mica glass–ceramics, taking the composition LiMg{sub 3}AlSi{sub 3(1+x)}O{sub 10+6x}F{sub 2} (x = 0.5) and 8 mass% MgF{sub 2} synthesized by sol–gel technique. Here, X-ray diffraction, thermal analysis and transmission electron microscopy were used to assess the structural evolutions of as-synthesized nano-crystalline lithium–mica glass–ceramics. It was found that MgF{sub 2} crystals perform as nuclei centers for the mica crystallization hence; a large quantity of mica crystallites obtained following the nucleation process at 400 °C for 12 h. For both the un-nucleated and nucleated samples, the crystallization activation energy was measured as 400.2 and 229.6 kJ mol{sup −1

High-power piezoelectric characteristics of textured bismuth layer structured ferroelectric ceramics.

Science.gov (United States)

Ogawa, Hirozumi; Kawada, Shinichiro; Kimura, Masahiko; Shiratsuyu, Kousuke; Sakabe, Yukio

2007-12-01

Abstract-The high-power piezoelectric characteristics in h001i oriented ceramics of bismuth layer structured ferroelectrics (BLSF), SrBi(2)Nb(2)O(9) (SBN), (Bi,La)(4)Ti(3)O(12) (BLT), and CaBi(4)Ti(4)O(15) (CBT), were studied by a constant voltage driving method. These textured ceramics were fabricated by a templated grain growth (TGG) method, and their Lotgering factors were 95%, 97%, and 99%, respectively. The vibration velocities of the longitudinal mode (33-mode) increased proportionally to an applied electric field up to 2.5 m/s in these textured BLSF ceramics, although, the vibration velocity of the 33-mode was saturated at more than 1.0 m/s in the Pb(Mn,Nb)O(3)-PZT ceramics. The resonant frequencies were constant up to the vibration velocity of 2.5 m/s in the SBN and CBT textured ceramics; however, the resonant frequency decreased with increasing over the vibration velocity of 1.5 m/s in the BLT textured ceramics. The dissipation power density of the BLT was almost the same as that of the Pb(Mn,Nb)O(3)-PZT ceramics. However, the dissipation power densities of the SBN and CBT were lower than those of the BLT and Pb(Mn,Nb)O(3)-PZT ceramics. The textured SBN and CBT ceramics are good candidates for high-power piezoelectric applications.

Nanomechanical properties of thick porous silicon layers grown on p- and p+-type bulk crystalline Si

International Nuclear Information System (INIS)

Charitidis, C.A.; Skarmoutsou, A.; Nassiopoulou, A.G.; Dragoneas, A.

2011-01-01

Highlights: → The nanomechanical properties of bulk crystalline Si. → The nanomechanical properties of porous Si. → The elastic-plastic deformation of porous Si compared to bulk crystalline quantified by nanoindentation data analysis. - Abstract: The nanomechanical properties and the nanoscale deformation of thick porous Si (PSi) layers of two different morphologies, grown electrochemically on p-type and p+-type Si wafers were investigated by the depth-sensing nanoindentation technique over a small range of loads using a Berkovich indenter and were compared with those of bulk crystalline Si. The microstructure of the thick PSi layers was characterized by field emission scanning electron microscopy. PSi layers on p+-type Si show an anisotropic mesoporous structure with straight vertical pores of diameter in the range of 30-50 nm, while those on p-type Si show a sponge like mesoporous structure. The effect of the microstructure on the mechanical properties of the layers is discussed. It is shown that the hardness and Young's modulus of the PSi layers exhibit a strong dependence on their microstructure. In particular, PSi layers with the anisotropic straight vertical pores show higher hardness and elastic modulus values than sponge-like layers. However, sponge-like PSi layers reveal less plastic deformation and higher wear resistance compared with layers with straight vertical pores.

What Is Crystalline Silica?

Science.gov (United States)

... and ceramic manufacturing and the tool and die, steel and foundry industries. Crystalline silica is used in manufacturing, household abrasives, adhesives, paints, soaps, and glass. Additionally, ...

An Experimental Study on Mechanical Modeling of Ceramics Based on Microstructure

Directory of Open Access Journals (Sweden)

Ya-Nan Zhang

2015-11-01

Full Text Available The actual grinding result of ceramics has not been well predicted by the present mechanical models. No allowance is made for direct effects of materials microstructure and almost all the mechanical models were obtained based on crystalline ceramics. In order to improve the mechanical models of ceramics, surface grinding experiments on crystalline ceramics and non-crystalline ceramics were conducted in this research. The normal and tangential grinding forces were measured to calculate single grit force and specific grinding energy. Grinding surfaces were observed. For crystalline alumina ceramics, the predictive modeling of normal force per grit fits well with the experimental result, when the maximum undeformed chip thickness is less than a critical depth, which turns out to be close to the grain size of alumina. Meanwhile, there is a negative correlation between the specific grinding energy and the maximum undeformed chip thickness. With the decreasing maximum undeformed chip thickness, the proportions of ductile removal and transgranular fracture increase. However, the grinding force models are not applicable for non-crystalline ceramic fused silica and the specific grinding energy fluctuates irregularly as a function of maximum undeformed chip thickness seen from the experiment.

Effect of added zinc on the properties of cobalt-containing ceramic pigments prepared from layered double hydroxides

International Nuclear Information System (INIS)

Perez-Bernal, M.E.; Ruano-Casero, R.J.; Rives, V.

2009-01-01

Layered double hydroxides (LDHs) with the hydrotalcite-type structure containing Co and Al, or Zn, Co and Al in the brucite-like layers and carbonate in the interlayer have been prepared by coprecipitation. The Zn/Co molar ratio was kept to 1 in all samples, while the divalent/trivalent molar ratio was varied from 2/1 to 1/2. The samples have been characterised by element chemical analysis, powder X-ray diffraction, differential thermal and thermogravimetric analysis, temperature-programmed reduction and FT-IR spectroscopy. A single hydrotalcite-like phase is formed for samples with molar ratio 2/1, which crystallinity decreases as the Al content is increased, developing small amounts of diaspore and dawsonite and probably an additional amorphous phase. Calcination at 1200 deg. C in air led to formation of spinels; a small amount of NaAlO 2 was observed in the Al-rich samples, which was removed by washing. The nature of the spinels formed (containing Co II , Co III , Al III and Zn II ) strongly depends on the cations molar ratio in the starting materials and the calcination treatment, leading to a partial oxidation of Co II species to Co III ones. Colour properties (L*a*b*) of the original and calcined solids have been measured. While the original samples show a pink colour (lighter for the series containing Zn), the calcined Co,Al samples show a dark blue colour and the Zn,Co,Al ones a green colour. Changes due to the different molar ratios within a given calcined series are less evident than between samples with the same composition in different series. These calcined materials could be usable as ceramic pigments. - Abstract: Mixed oxides from layered double hydroxides (LDHs) with the hydrotalcite-type structure containing Co and Al or Zn, Co and Al in the brucite-like layers are potential candidates for ceramic pigments with tunable colour properties. Display Omitted

Behaviour of ceramic and metallic layers in a H2O-H2S

International Nuclear Information System (INIS)

Furtuna, I.; Mihailescu, M.; Deaconu, M.; Dinu, A.; Cotolan, V; Nedelcu, L.; Titescu, Gh.

1996-01-01

In the installations for heavy water production there exist zones where the action of aggressive working conditions combined with a severe variable hydrodynamical regime lead to the destruction of the pyrite protecting layer. An alternating solution for the protection of these zones is to cover them with ceramic or metallic layers. This work presents the results of the preliminary tests on G28-52 steel samples, covered with ceramic and metallic layers, in the working environment (H 2 O-H 2 S) of the heavy water production installations and in severe hydrodynamical conditions. On the basis of the results obtained in the experiments and from the examination of the microstructure of the layers prior and after testing, a phenomenological model was developed to explain the behaviour of the deposed layers. On the basis of this model the conditions that the layers must satisfy have been deduced to improve their behaviour in the working environment

Injection molding of ceramic filled polypropylene: The effect of thermal conductivity and cooling rate on crystallinity

International Nuclear Information System (INIS)

Suplicz, A.; Szabo, F.; Kovacs, J.G.

2013-01-01

Highlights: • BN, talc and TiO 2 in 30 vol% were compounded with polypropylene matrix. • According to the DSC measurements, the fillers are good nucleating agents. • The thermal conductivity of the fillers influences the cooling rate of the melt. • The higher the cooling rate is, the lower the crystallinity in the polymer matrix. - Abstract: Three different nano- and micro-sized ceramic powders (boron-nitride (BN), talc and titanium-dioxide (TiO 2 )) in 30 vol% have been compounded with a polypropylene (PP) matrix. Scanning electron microscopy (SEM) shows that the particles are dispersed smoothly in the matrix and larger aggregates cannot be discovered. The cooling gradients and the cooling rate in the injection-molded samples were estimated with numerical simulations and finite element analysis software. It was proved with differential scanning calorimetry (DSC) measurements that the cooling rate has significant influence on the crystallinity of the compounds. At a low cooling rate BN works as a nucleating agent so the crystallinity of the compound is higher than that of unfilled PP. On the other hand, at a high cooling rate, the crystallinity of the compound is lower than that of unfilled PP because of its higher thermal conductivity. The higher the thermal conductivity is, the higher the real cooling rate in the material, which influences the crystallization kinetics significantly

Characterization and use of crystalline bacterial cell surface layers

Science.gov (United States)

Sleytr, Uwe B.; Sára, Margit; Pum, Dietmar; Schuster, Bernhard

2001-10-01

Crystalline bacterial cell surface layers (S-layers) are one of the most common outermost cell envelope components of prokaryotic organisms (archaea and bacteria). S-layers are monomolecular arrays composed of a single protein or glycoprotein species and represent the simplest biological membranes developed during evolution. S-layers as the most abundant of prokaryotic cellular proteins are appealing model systems for studying the structure, synthesis, genetics, assembly and function of proteinaceous supramolecular structures. The wealth of information existing on the general principle of S-layers have revealed a broad application potential. The most relevant features exploited in applied S-layer research are: (i) pores passing through S-layers show identical size and morphology and are in the range of ultrafiltration membranes; (ii) functional groups on the surface and in the pores are aligned in well-defined positions and orientations and accessible for chemical modifications and binding functional molecules in very precise fashion; (iii) isolated S-layer subunits from a variety of organisms are capable of recrystallizing as closed monolayers onto solid supports (e.g., metals, polymers, silicon wafers) at the air-water interface, on lipid films or onto the surface of liposomes; (iv) functional domains can be incorporated in S-layer proteins by genetic engineering. Thus, S-layer technologies particularly provide new approaches for biotechnology, biomimetics, molecular nanotechnology, nanopatterning of surfaces and formation of ordered arrays of metal clusters or nanoparticles as required for nanoelectronics.

Evaluating the Type of Light Transmittance in Mono Crystalline, Poly Crystalline and Sapphire Brackets- An Invitro Spectrofluorometer Study.

Science.gov (United States)

Mohamed, Jauhar P; Kommi, Pradeep Babu; Kumar, M Senthil; Hanumanth; Venkatesan; Aniruddh; Arvinth; Kumar, Arani Nanda

2016-08-01

Most of the patients seek orthodontic treatment to improve the smile, which improves the facial profile by means of fixed appliances i.e., brackets and wires. The brackets are of different types like stainless steel and ceramic. Ceramic brackets were considered as aesthetic appliance which was divided into mono-crystalline, polycrystalline and sapphire brackets. The light transmittance might influence the degree of curing adhesive material in mono crystalline, polycrystalline and sapphire brackets. The aim of the present study was to evaluate the translucency and intensity of three different aesthetic brackets (mono crystalline, poly crystalline and sapphire ceramic brackets) and to determine their influence on shear bond strength of the brackets. The adhesive remnant index was also measured after debonding of the brackets from the tooth surface. Twenty six samples each of monocrystalline, polycrystalline and sapphire brackets (total 78 ceramic brackets) were used for the study. The bracket samples were subjected to optical fluorescence test using spectrofluorometer to measure the intensity of the brackets. Seventy eight extracted premolar teeth were procured and divided into 3 groups. The brackets were then bonded to the tooth using Transbond XT (3M Unitek) light cure composite material and cured with new light cure unit (Light Emitting Diode) of wood pecker company (400-450nm) for 30 seconds, and these samples were subjected to shear bond strength test with Instron Universal Testing Machine (UNITEK-94100) with a load range between 0 to 100 KN with a maximum cross head speed of 0.5mm/min. ARI (Adhesive Remnant Index) scores were evaluated according to Artun and Bergland scoring system using stereomicroscope at 20x magnification. The light absorption values obtained from spectrofluorometeric study were 3300000-3500000 cps for group 1 (monocrystalline ceramic brackets), 6000000-6500000 cps for Group 2 (polycrystalline ceramic brackets) and 2700000 -3000000 cps for

Exoelectron emission from surface layer of Li2B4O7 glass ceramics

International Nuclear Information System (INIS)

Kawamoto, Takamichi; Katsube, Shizuko; Yanagisawa, Hideo; Kikuchi, Riichi; Kawanishi, Masaharu.

1984-01-01

The thermally stimulated exoelectron emission (TESS) of Li 2 B 4 O 7 glass ceramics was investigated for its application to the dosimetric use. It has been found the TSEE glow patterns of Li 2 B 4 O 7 glass ceramics and of the thin layer of LiF evaporated on Li 2 B 4 O 7 glass ceramics depend on the kind of radiations irradiated. The TSEE glow pattern of the duplicated structure sample indicated a possibility of determining the dose of each kind of radiation separately in the mixed radiation field. (author)

AFFORDABLE MULTI-LAYER CERAMIC (MLC) MANUFACTURING FOR POWER SYSTEMS (AMPS)

Energy Technology Data Exchange (ETDEWEB)

E.A. Barringer, Ph.D.

2002-11-27

McDermott Technology, Inc. (MTI) is attempting to develop high-performance, cost-competitive solid oxide fuel cell (SOFC) power systems. Recognizing the challenges and limitations facing the development of SOFC stacks comprised of electrode-supported cells and metallic interconnects, McDermott Technology, Inc. (MTI) has chosen to pursue an alternate path to commercialization. MTI is developing a multi-layer, co-fired, planar SOFC stack that will provide superior performance and reliability at reduced costs relative to competing designs. The MTI approach combines state-of-the-art SOFC materials with the manufacturing technology and infrastructure established for multi-layer ceramic (MLC) packages for the microelectronics industry. The rationale for using MLC packaging technology is that high quality, low-cost manufacturing has been demonstrated at high volumes. With the proper selection of SOFC materials, implementation of MLC fabrication methods offers unique designs for stacks (cells and interconnects) that are not possible through traditional fabrication methods. The MTI approach eliminates use of metal interconnects and ceramic-metal seals, which are primary sources of stack performance degradation. Co-fired cells are less susceptible to thermal cycling stresses by using material compositions that have closely matched coefficients of thermal expansion between the cell and the interconnect. The development of this SOFC stack technology was initiated in October 1999 under the DOE cosponsored program entitled ''Affordable Multi-layer Ceramic Manufacturing for Power Systems (AMPS)''. The AMPS Program was conducted as a two-phase program: Phase I--Feasibility Assessment (10/99--9/00); and Phase II--Process Development for Co-fired Stacks (10/00-3/02). This report provides a summary of the results from Phase I and a more detailed review of the results for Phase II. Phase I demonstrated the feasibility for fabricating multi-layer, co-fired cells and

A randomized controlled clinical trial of 3-unit posterior zirconia-ceramic fixed dental prostheses (FDP) with layered or pressed veneering ceramics: 3-year results.

Science.gov (United States)

Naenni, Nadja; Bindl, Andreas; Sax, Caroline; Hämmerle, Christoph; Sailer, Irena

2015-11-01

The aim of the present pilot study was to test whether or not posterior zirconia-ceramic fixed dental prostheses (FDPs) with pressed veneering ceramic exhibit less chipping than FDPs with layered veneering ceramics. Forty patients (13 female, 27 male; mean age 54 years (range 26.1-80.7 years) in need of one maxillary or mandibular three-unit FDP in the second premolar or molar region were recruited and treated at two separate centers at the University of Zurich according to the same study protocol. The frameworks were made out of zirconia using a CAD/CAM system (Cerec Sirona, Bensheim, Germany). The patients were randomly assigned to either the test group (zirconia frameworks veneered with pressed ceramic; IPS e.max ZirPress, Ivoclar Vivadent AG, Schaan, Liechtenstein; n=20) or the control group (layered veneering ceramic; IPS e.max Ceram, Ivoclar Vivadent AG, Schaan, Liechtenstein; n=20). All FDPs were adhesively cemented and evaluated at baseline (i.e., cementation), at 6 months and at 1 and 3 years of clinical service. The survival of the reconstruction was recorded. The technical outcome was assessed using modified United States Public Health Services (USPHS) criteria. The biologic parameters analyzed at abutment teeth and analogous non-restored teeth included probing pocket depth (PPD), plaque control record (PCR), bleeding on probing (BOP), and tooth vitality (CO2). Data was descriptively analyzed and survival was calculated using Kaplan-Meier statistics. 36 patients (25 female, 11 male; mean age 52.3 years) with 18 test and 18 control FDPs were examined after a mean follow-up of 36 months (95% CI: 32.6-39.1 months). Comparison of groups was done by Crosstabulation showing even distribution of the respective restored teeth amidst the groups. Survival rate was 100% for both test and control FDPs. Chipping of the veneering ceramic tended to occur more frequently in test (n=8; 40%) than in control (n=4; 20%) FDPs, albeit not significantly (p=0.3). No further

preparation, characterization and formulation of nano-ceramic materials to be used for the separation of some heavy metals

International Nuclear Information System (INIS)

Zayed, S.L.M.

2006-01-01

the synthesis of asymmetric composite and monolithic ceramic filters, with high performance quality, to be used in heavy metals separation is the aim of this study. asymmetric composite ceramic filter consisted of a macroporous or mesoporous substrate coated with several layers having lower pore size than the substrate usually microporous film. on the other hand, asymmetric monolithic ceramic filter is monolithic system having dual pore size distribution. ceramic filters synthesis was performed using polymeric sol-gel process. the optimization of synthesis parameters as well as the characterization was achieved to obtain ceramic filters with high separative properties. the synthesized ceramic filters were characterized using mercury porosimeter for pore size distribution analysis, BET method for specific surface areas measurements and BJH pore size distribution analysis, XRD analysis for crystalline phase identification and SEM for microstructure and morphology studies

Homogenized electromechanical properties of crystalline and ceramic relaxor ferroelectric 0.58Pb(Mg1/3Nb2/3)O3 0.42PbTiO3

Science.gov (United States)

Jayachandran, K. P.; Guedes, J. M.; Rodrigues, H. C.

2007-10-01

A modelling framework that incorporates the peculiarities of microstructural features, such as the spatial correlation of crystallographic orientations and morphological texture in piezoelectrics, is established. The mathematical homogenization theory of a piezoelectric medium is implemented using the finite element method by solving the coupled equilibrium electrical and mechanical fields. The dependence of the domain orientation on the macroscopic electromechanical properties of crystalline as well as polycrystalline ceramic relaxor ferroelectric 0.58Pb(Mg1/3Nb2/3)O3-0.42PbTiO3 (PMN-42% PT) is studied based on this model. The material shows large anisotropy in the piezoelectric coefficient ejK in its crystalline form. The homogenized electromechanical moduli of polycrystalline ceramic also exhibit significantly anisotropic behaviours. An optimum texture at which the piezoceramic exhibits its maximum longitudinal piezoelectric response is identified.

The Influence of Tool Composite's Structure During Process of Diamond Grinding of Ceramic Materials

Directory of Open Access Journals (Sweden)

Gawlik Józef

2014-12-01

Full Text Available This paper presents the results of the tests performed during the grinding process of the ceramic materials: – polycrystalline ceramics (Zirconium ZrO2 and mono-crystalline ceramics (sapphire α-Al2O3 by the diamond tools. Studies have shown that the concentration (thickening of the tool composite changes the tool's pore structure when using suitable wetted adamantine additives. Such modified composite has positive impact on tribological properties of the subsurface layer of the machined components. This is manifested by the reduction of the surface roughness and reduction of the vibration amplitude of the coefficient of friction. The possibilities of the positive effects when using wetted additives on the tool's composite during the pressing (briquetting stage confirm the study results.

Wonderland of ceramics superplasticity; Ceramics chososei no sekai

Energy Technology Data Exchange (ETDEWEB)

Wakai, F. [National Industrial Research Inst. of Nagoya, Nagoya (Japan)

1995-07-01

It has been ten years since it was found that ceramics, which is strong and hard at room temperatures and does not deform at all, may exhibit a superplasticity phenomenon at high temperatures that it endlessly elongates when pulled as if it were chewing gum. This phenomenon is one of peculiar behaviours which nano-crystal ceramics, pulverized to an extent that the crystalline particle size is on the order of nanometers, show. The application of superplasticity made the material engineers`s old dream come true that hard ceramics are arbitrarily deformed and machined like metal. Using as models materials such as silicone nitride, alumina and zirconia, this paper describes the history and deformation mechanism of ceramics superplasticity, material design aiming at superplasticization and application of ceramics superplasticity to the machining technology. Furthermore, it describes the trend and future development of international joint researches on the basic surveys on ceramics superplasticity. 25 refs., 11 figs.

Clinical application of bio ceramics

Energy Technology Data Exchange (ETDEWEB)

Anu, Sharma, E-mail: issaranu@gmail.com; Gayatri, Sharma, E-mail: sharmagayatri@gmail.com [Department of Chemistry, Govt. College of Engineering & Technology, Bikaner, Rajasthan (India)

2016-05-06

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

International Nuclear Information System (INIS)

Anu, Sharma; Gayatri, Sharma

2016-01-01

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.

Preparation and characterization of tempered tungsten layers on single crystalline silicon

International Nuclear Information System (INIS)

Nitzsche, K.; Knedlik, C.; Tippmann, H.; Spiess, L.; Harman, R.; Vanek, O.; Tvarozek, V.

1984-01-01

Tungsten layers have been deposited on single crystalline silicon by sputtering and characterized by measurements of the sheet resistance by a linear four point method and the van der Pauw method. The influence of tempering under argon on the resistance has been studied. By means of the RBS spectroscopy it was found that the increase in the specific resistance is caused by interdiffusion

Crystalline and magnetic ordering in the monoclinic phase of the layered perovskite PAMC

DEFF Research Database (Denmark)

Harris, P.; Lebech, B.; Achiwa, N.

1994-01-01

A single-crystal elastic neutron scattering experiment between 4.2 and 115 K has been performed on the low-temperature monoclinic zeta phase of the layered perovskite bis(propylammonium) manganesetetrachloride (PAMC). The crystalline structure is commensurately modulated, with a modulation vector...

EFFECTS OF INCORPORATING NATURAL MINERALS ON PRODUCTION AND BIOACTIVITY OF BIOACTIVE GLASS CERAMICS

Directory of Open Access Journals (Sweden)

Franco Matias Stabile

2016-07-01

Full Text Available Two glass-ceramics composition were produced from natural minerals. Quartzes and feldspars were pre-selected on the basis of their purities studied by X-ray diffraction (XRD and chemical analysis. Prepared compositions of glasses precursors were two different theoretical leucite (KAlSi₂O₆ /Bioglass 45S5 (L/Bg ratios. Transformations of raw materials mixtures and glass precursors were studied by differential thermal analyses. On the basis of thermal analysis results, glass ceramics were produced and characterized by XRD. Glass-ceramics were composed of two major crystalline phases, leucite and sodium calcium silicate. Bioactivity tests were performed submerging the glass-ceramics into simulated body fluid (SBF for different periods (1, 5 and 10 days. Bioactive behavior was monitored by XRD and scanning electron microscopy (SEM. Studied samples were found to be bioactive, in which hydroxyapatite layer was developed within 5 days of contact with SBF.

Oxygen recoil implant from SiO2 layers into single-crystalline silicon

International Nuclear Information System (INIS)

Wang, G.; Chen, Y.; Li, D.; Oak, S.; Srivastav, G.; Banerjee, S.; Tasch, A.; Merrill, P.; Bleiler, R.

2001-01-01

It is important to understand the distribution of recoil-implanted atoms and the impact on device performance when ion implantation is performed at a high dose through surface materials into single crystalline silicon. For example, in ultralarge scale integration impurity ions are often implanted through a thin layer of screen oxide and some of the oxygen atoms are inevitably recoil implanted into single-crystalline silicon. Theoretical and experimental studies have been performed to investigate this phenomenon. We have modified the Monte Carlo ion implant simulator, UT-Marlowe (B. Obradovic, G. Wang, Y. Chen, D. Li, C. Snell, and A. F. Tasch, UT-MARLOWE Manual, 1999), which is based on the binary collision approximation, to follow the full cascade and to dynamically modify the stoichiometry of the Si layer as oxygen atoms are knocked into it. CPU reduction techniques are used to relieve the demand on computational power when such a full cascade simulation is involved. Secondary ion mass spectrometry (SIMS) profiles of oxygen have been carefully obtained for high dose As and BF 2 implants at different energies through oxide layers of various thicknesses, and the simulated oxygen profiles are found to agree very well with the SIMS data. [copyright] 2001 American Institute of Physics

Ceramic hot-gas filter

Science.gov (United States)

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.

Ceramic hot-gas filter

Science.gov (United States)

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.

Synthesis of Functional Ceramic Supports by Ice Templating and Atomic Layer Deposition

Directory of Open Access Journals (Sweden)

Michaela Klotz

2018-05-01

Full Text Available 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.

Trace and surface analysis of ceramic layers of solid oxide fuel cells by mass spectrometry.

Science.gov (United States)

Becker, J S; Breuer, U; Westheide, J; Saprykin, A I; Holzbrecher, H; Nickel, H; Dietze, H J

1996-06-01

For the trace analysis of impurities in thick ceramic layers of a solid oxide fuel cell (SOFC) sensitive solid-state mass spectrometric methods, such as laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) and radiofrequency glow discharge mass spectrometry (rf-GDMS) have been developed and used. In order to quantify the analytical results of LA-ICP-MS, the relative sensitivity coefficients of elements in a La(0.6)Sr(0.35)MnO(3) matrix have been determined using synthetic standards. Secondary ion mass spectrometry (SIMS) - as a surface analytical method - has been used to characterize the element distribution and diffusion profiles of matrix elements on the interface of a perovskite/Y-stabilized ZrO(2) layer. The application of different mass spectrometric methods for process control in the preparation of ceramic layers for the SOFC is described.

A mechanical model for surface layer formation on self-lubricating ceramic composites

NARCIS (Netherlands)

Song, Jiupeng; Valefi, Mahdiar; de Rooij, Matthias B.; Schipper, Dirk J.

2010-01-01

To predict the thickness of a self-lubricating layer on the contact surface of ceramic composite material containing a soft phase during dry sliding test, a mechanical model was built to calculate the material transfer of the soft second phase in the composite to the surface. The tribological test,

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

Science.gov (United States)

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.

Structure and chemical durability of barium borosilicate glass–ceramics containing zirconolite and titanite crystalline phases

International Nuclear Information System (INIS)

Li, Huidong; Wu, Lang; Xu, Dong; Wang, Xin; Teng, Yuancheng; Li, Yuxiang

2015-01-01

In order to increase the solubility of actinides in the glass matrix, the effects of CaO, TiO 2 , and ZrSiO 4 addition (abbreviated as CTZ, in the mole ratio of 2:2:1) on crystalline phases, microstructure, and chemical durability of barium borosilicate glass–ceramics were investigated. The results show that the samples possess both zirconolite-2M and titanite phase when the CTZ content is greater than or equal to 45 wt.%. For the glass–ceramics with 45 wt.% CTZ (CTZ-45), only zirconolite-2M phase is observed after annealing at 680–740 °C for 2 h. The CTZ-45 possess zirconolite-2M and titanite phases after annealing at 700 °C first, and then annealing at 900–1050 °C for 2 h. Furthermore, the zirconolite-2M and titanite grains show a strip and brick shape, respectively. The CTZ-45 annealing at 950 °C shows the lower normalized leaching rates of B, Na and Nd when compared to that of CTZ-0 and CTZ-55. - Highlights: • CaO, TiO 2 , ZrSiO 4 (CTZ) as nucleating agents were added to barium borosilicate glass. • The samples with 45–55 wt% CTZ possess CaZrTi 2 O 7 -2M and CaTiSiO 5 crystalline phases. • CTZ-45 (45wt% CTZ) possesses only CaZrTi 2 O 7 -2M phase after annealing at 680–740 °C. • CTZ-45 possesses CaZrTi 2 O 7 -2M and CaTiSiO 5 phases after annealing at 900–1050 °C. • CTZ-45 annealing at 950 °C shows the lower leaching rates of B, Na and Nd than CTZ-0 and CTZ-55.

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

Science.gov (United States)

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

2017-12-01

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

High Gain and High Directive of Antenna Arrays Utilizing Dielectric Layer on Bismuth Titanate Ceramics

Directory of Open Access Journals (Sweden)

F. H. Wee

2012-01-01

Full Text Available A high gain and high directive microstrip patch array antenna formed from dielectric layer stacked on bismuth titanate (BiT ceramics have been investigated, fabricated, and measured. The antennas are designed and constructed with a combination of two-, four-, and six-BiT elements in an array form application on microwave substrate. For gain and directivity enhancement, a layer of dielectric was stacked on the BiT antenna array. We measured the gain and directivity of BiT array antennas with and without the dielectric layer and found that the gain of BiT array antenna with the dielectric layer was enhanced by about 1.4 dBi of directivity and 1.3 dB of gain over the one without the dielectric layer at 2.3 GHz. The impedance bandwidth of the BiT array antenna both with and without the dielectric layer is about 500 MHz and 350 MHz, respectively, which is suitable for the application of the WiMAX 2.3 GHz system. The utilization of BiT ceramics that covers about 90% of antenna led to high radiation efficiency, and small-size antennas were produced. In order to validate the proposed design, theoretical and measured results are provided and discussed.

Ceramic/metal nanocomposites by lyophilization: Processing and HRTEM study

International Nuclear Information System (INIS)

Gutierrez-Gonzalez, C.F.; Agouram, S.; Torrecillas, R.; Moya, J.S.; Lopez-Esteban, S.

2012-01-01

Highlights: ► A cryogenic route has been used to obtain ceramic/metal nanostructured powders. ► The powders present good homogeneity and dispersion of metal. ► The metal nanoparticle size distributions are centred in 17–35 nm. ► Both phases, ceramic and metal, present a high degree of crystallinity. ► Good metal/ceramic interfaces due to epitaxial growth, studied by HRTEM. -- Abstract: This work describes a wet-processing route based on spray-freezing and subsequent lyophilization designed to obtain nanostructured ceramic/metal powders. Starting from the ceramic powder and the corresponding metal salt, a water-based suspension is sprayed on liquid nitrogen. The frozen powders are subsequently freeze-dried, calcined and reduced. The material was analyzed using X-ray diffraction analysis at all stages. High resolution transmission electron microscopy studies showed a uniform distribution of metal nanoparticles on the ceramic grain surfaces, good interfaces and high crystallinity, with an average metal particle size in the nanometric range.

Testing method for ceramic armour and bare ceramic tiles

NARCIS (Netherlands)

Carton, E.P.; Roebroeks, G.H.J.J.

2016-01-01

TNO developed an alternative, more configuration independent ceramic test method than the Depth-of-Penetration test method. In this alternative test ceramic tiles and ceramic based armour are evaluated as target without a semi-infinite backing layer. An energy approach is chosen to evaluate and rank

Testing method for ceramic armor and bare ceramic tiles

NARCIS (Netherlands)

Carton, E.P.; Roebroeks, G.H.J.J.

2014-01-01

TNO has developed an alternative, more configuration independent ceramic test method than the standard Depth-of-Penetration test method. In this test ceramic tiles and ceramic based armor are evaluated as target without a semi-infinite backing layer. An energy approach is chosen to evaluate and rank

Photo-EMF sensitivity of porous silicon thin layer-crystalline silicon heterojunction to ammonia adsorption.

Science.gov (United States)

Vashpanov, Yuriy; Jung, Jae Il; Kwack, Kae Dal

2011-01-01

A new method of using photo-electromotive force in detecting gas and controlling sensitivity is proposed. Photo-electromotive force on the heterojunction between porous silicon thin layer and crystalline silicon wafer depends on the concentration of ammonia in the measurement chamber. A porous silicon thin layer was formed by electrochemical etching on p-type silicon wafer. A gas and light transparent electrical contact was manufactured to this porous layer. Photo-EMF sensitivity corresponding to ammonia concentration in the range from 10 ppm to 1,000 ppm can be maximized by controlling the intensity of illumination light.

Phase composition of yttrium-doped zirconia ceramics

Energy Technology Data Exchange (ETDEWEB)

Hennig, Christoph; Scheinost, Andreas C. [Helmholtz-Zentrum Dresden-Rossendorf e.V., Dresden (Germany). Molecular Structures; Weiss, Stephan [Helmholtz-Zentrum Dresden-Rossendorf e.V., Dresden (Germany). Surface Processes; Ikeda-Ohno, Atsushi [Helmholtz-Zentrum Dresden-Rossendorf e.V., Dresden (Germany). Chemistry of the F-Elements; Gumeniuk, R. [Technische Univ. Bergakademie Freiberg (Germany). Inst. fuer Experimentelle Physik

2017-06-01

Ceramic material might be an alternative to borosilicate glass for the immobilization of nuclear waste. The crystallinity of ceramic material increases the corrosion resistance over several magnitudes in relation to amorphous glasses. The stability of such ceramics depend on several parameters, among them the crystal phase composition. A reliable quantitative phase analysis is necessary to correlate the macroscopic material properties with structure parameters. We performed a feasibility study based on yttrium-doped zirconia ceramics as analogue for trivalent actinides to ascertain that the nanosized crystal phases in zirconia ceramics can be reliably determined.

Improved crystalline quality of AlN epitaxial layer on sapphire by introducing TMGa pulse flow into the nucleation stage

Science.gov (United States)

Wu, Hualong; Wang, Hailong; Chen, Yingda; Zhang, Lingxia; Chen, Zimin; Wu, Zhisheng; Wang, Gang; Jiang, Hao

2018-05-01

The crystalline quality of AlN epitaxial layers on sapphire substrates was improved by introducing trimethylgallium (TMGa) pulse flow into the growth of AlN nucleation layers. It was found that the density of both screw- and edge-type threading dislocations could be significantly reduced by introducing the TMGa pulse flow. With increasing TMGa pulse flow times, the lateral correlation length (i.e. the grain size) increases and the strain in the AlN epilayers changes from tensile state to compressive state. Unstrained AlN with the least dislocations and a smooth surface was obtained by introducing 2-times TMGa pulse flow. The crystalline improvement is attributed to enhanced lateral growth and improved crystalline orientation by the TMGa pulse flow.

Numerical modelling of evaporation in a ceramic layer in the tape casting process

Energy Technology Data Exchange (ETDEWEB)

Jabbari, M.; Hattel, J. H. [Process Modelling Group, Department of Mechanical Engineering, Technical University of Denmark, Nils Koppels Allé, 2800 Kgs. Lyngby (Denmark); Jambhekar, V. A.; Helmig, R. [Department of Hydromechanics and Modelling of Hydrosystems, Institute for Modelling Hydraulic and Environmental Systems, Universität Stuttgart, Stuttgart (Germany)

2016-06-08

Evaporation of water from a ceramic layer is a key phenomenon in the drying process for the manufacturing of tape cast ceramics. This process contains mass, momentum and energy exchange between the porous medium and the free–flow region. In order to analyze such interaction processes, a Representative Elementary Volume (REV)–scale model concept is presented for coupling non–isothermal multi–phase compositional porous–media flow and single–phase compositional laminar free–flow. The preliminary results show the typical expected evaporation behaviour from a porous medium initially saturated with water, and its transport to the free–flow region according to the existent results from the literature.

Phase relations in crystalline ceramic nuclear waste forms the system UO/sub 2 + x/-CeO2-ZrO2-ThO2 at 12000C in air

International Nuclear Information System (INIS)

Pepin, J.G.; McCarthy, G.J.

1981-01-01

Steady-state phase relations in the system UO/sub 2 + x/-CeO 2 -ZrO 2 -ThO 2 were determined for application to phase relations in the high-level crystalline ceramic nuclear waste form Supercalcine-Ceramics. Samples were treated at 1200 0 C at an oxygen partial pressure of 0.21 atm and a total pressure of 1 atm. Phase assemblages were found to be composed of cubic solid solutions of the flourite structure type, solid solutions based on ZrO 2 , and orthorhombic solid solutions based on U 3 O 8

Towards the synthesis of an experimental bioactive dental ceramic. Part I: Crystallinity characterization and bioactive behavior evaluation

International Nuclear Information System (INIS)

Goudouri, O.-M.; Kontonasaki, E.; Papadopoulou, L.; Kantiranis, N.; Lazaridis, N.K.; Chrissafis, K.; Chatzistavrou, X.; Koidis, P.; Paraskevopoulos, K.M.

2014-01-01

An attachment between the dental ceramic and the surrounding marginal tissues in fixed prosthetic restorations could eliminate secondary carries prevalence. The development of dental ceramics with apatite forming ability could provide the biological surface required for selective spread and attachment of specific cell types able to promote tissue attachment. Dental ceramics/bioactive glass composites synthesized by the sol gel method have been previously reported to develop carbonated hydroxyapatite (HCAp) in biomimetic solutions, requiring though a high amount of bioactive glass, which resulted in the compromise of their mechanical integrity. Thus, the aim of the present work was the synthesis and characterization of an experimental sol–gel derived dental ceramic with low amount of bioactive glass and the evaluation of its in vitro bioactivity. Differential thermal and thermogravimetric analysis (TG–DTA), Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffractometry (XRD), Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS) were used to evaluate the crystal structure and the in vitro apatite forming ability of the synthesized material. The results of this study indicated the successful sol–gel synthesis of an experimental dental ceramic containing low amount of bioactive glass that presented similar structural and morphological characteristics with a commercial feldspathic dental ceramic, while exhibiting in vitro bioactivity. The apatite forming ability of the experimental sol–gel derived feldspathic dental ceramic may trigger the appropriate cellular mechanisms towards the establishment of attachment with the surrounding connective tissue. This attachment could provide a barrier to oral bacteria penetration, prolonging the life expectation of the restorations. - Highlights: • Synthesis of a bioactive sol–gel dental ceramic for fixed prosthetic restorations. • The sol–gel technique promoted the crystallization of

Towards the synthesis of an experimental bioactive dental ceramic. Part I: Crystallinity characterization and bioactive behavior evaluation

Energy Technology Data Exchange (ETDEWEB)

Goudouri, O.-M. [Physics Department, Aristotle University of Thessaloniki, 54124 Thessaloniki (Greece); Kontonasaki, E. [School of Dentistry, Aristotle University of Thessaloniki, 54124 Thessaloniki (Greece); Papadopoulou, L.; Kantiranis, N. [Department of Geology, Aristotle University of Thessaloniki, 54124 Thessaloniki (Greece); Lazaridis, N.K. [Chemistry Department, Aristotle University of Thessaloniki, 54124 Thessaloniki (Greece); Chrissafis, K.; Chatzistavrou, X. [Physics Department, Aristotle University of Thessaloniki, 54124 Thessaloniki (Greece); Koidis, P. [School of Dentistry, Aristotle University of Thessaloniki, 54124 Thessaloniki (Greece); Paraskevopoulos, K.M., E-mail: kpar@auth.gr [Physics Department, Aristotle University of Thessaloniki, 54124 Thessaloniki (Greece)

2014-05-01

An attachment between the dental ceramic and the surrounding marginal tissues in fixed prosthetic restorations could eliminate secondary carries prevalence. The development of dental ceramics with apatite forming ability could provide the biological surface required for selective spread and attachment of specific cell types able to promote tissue attachment. Dental ceramics/bioactive glass composites synthesized by the sol gel method have been previously reported to develop carbonated hydroxyapatite (HCAp) in biomimetic solutions, requiring though a high amount of bioactive glass, which resulted in the compromise of their mechanical integrity. Thus, the aim of the present work was the synthesis and characterization of an experimental sol–gel derived dental ceramic with low amount of bioactive glass and the evaluation of its in vitro bioactivity. Differential thermal and thermogravimetric analysis (TG–DTA), Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffractometry (XRD), Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS) were used to evaluate the crystal structure and the in vitro apatite forming ability of the synthesized material. The results of this study indicated the successful sol–gel synthesis of an experimental dental ceramic containing low amount of bioactive glass that presented similar structural and morphological characteristics with a commercial feldspathic dental ceramic, while exhibiting in vitro bioactivity. The apatite forming ability of the experimental sol–gel derived feldspathic dental ceramic may trigger the appropriate cellular mechanisms towards the establishment of attachment with the surrounding connective tissue. This attachment could provide a barrier to oral bacteria penetration, prolonging the life expectation of the restorations. - Highlights: • Synthesis of a bioactive sol–gel dental ceramic for fixed prosthetic restorations. • The sol–gel technique promoted the crystallization of

Nature of radiation damage in ceramics

International Nuclear Information System (INIS)

Bunch, J.M.

1976-01-01

Efforts to determine the equivalence between different sources of radiation damage in ceramics are reviewed. The ways in which ceramics differ from metals are examined and proposed mechanisms for creation and stabilization of defects in insulators are outlined. Work on radiation damage in crystalline oxides is summarized and suggestions for further research are offered

Ceramic substrate including thin film multilayer surface conductor

Science.gov (United States)

Wolf, Joseph Ambrose; Peterson, Kenneth A.

2017-05-09

A ceramic substrate comprises a plurality of ceramic sheets, a plurality of inner conductive layers, a plurality of vias, and an upper conductive layer. The ceramic sheets are stacked one on top of another and include a top ceramic sheet. The inner conductive layers include electrically conductive material that forms electrically conductive features on an upper surface of each ceramic sheet excluding the top ceramic sheet. The vias are formed in each of the ceramic sheets with each via being filled with electrically conductive material. The upper conductive layer includes electrically conductive material that forms electrically conductive features on an upper surface of the top ceramic sheet. The upper conductive layer is constructed from a stack of four sublayers. A first sublayer is formed from titanium. A second sublayer is formed from copper. A third sublayer is formed from platinum. A fourth sublayer is formed from gold.

Characteristic electron energy loss spectra in SiC buried layers formed by C+ implantation into crystalline silicon

International Nuclear Information System (INIS)

Yan Hui; Chen Guanghua; Kwok, R.W.M.

1998-01-01

SiC buried layers were synthesized by a metal vapor vacuum arc ion source, with C + ions implanted into crystalline Si substrates. According to X-ray photoelectron spectroscopy, the characteristic electron energy loss spectra of the SiC buried layers were studied. It was found that the characteristic electron energy loss spectra depend on the profiles of the carbon content, and correlate well with the order of the buried layers

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

Science.gov (United States)

de Diego, Peter; Zhang, James

2017-05-30

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.

Synthesis of nucleated glass-ceramics using oil shale fly ash

International Nuclear Information System (INIS)

Luan Jingde; Li Aimin; Su Tong; Cui Xiaobo

2010-01-01

Nucleated glass-ceramics materials were produced from oil shale fly ash obtained from Huadian thermal power plant in China with the addition of analytic reagent CaO. On basis of differential thermal analysis (DTA) results, the nucleation and crystallization temperature of two parent glass samples with different alkalinity (Ak=m CaO /m SiO 2 ) were identified as Tn 1 = 810 deg. C, Tc 1 = 956 deg. C and Tn 2 = 824 o C, Tc 2 = 966 deg. C, respectively. X-ray diffraction (XRD) analysis of the produced nucleated glass-ceramics materials revealed that there was a coexistence phenomenon of multi-crystalline phase and the main crystalline phase was anorthite ([Ca,Na][AI,Si] 2 Si 2 O 8 ). The microstructure of the glass-ceramics materials was examined by scanning electron microscope (SEM). SEM observation indicated that there was an increase in the quantity of sphere-shaped crystals when crystallization time increased. Furthermore, the increase of alkalinity caused more amorphous phase occurring in glass-ceramics materials. Through the tests of physical and mechanical properties, the glass-ceramics materials with more crystalline phase and fine microstructure had high density, fine performance of resisting compression (328.92 MPa) and negligible water absorption. Through chemical resistance tests, the glass-ceramics samples showed strong corrosion resistance. Overall results indicated that it was a feasible attempt to produce nucleated glass-ceramics materials for building and decorative materials from oil shale fly ash.

Planar ceramic membrane assembly and oxidation reactor system

Science.gov (United States)

Carolan, Michael Francis; Dyer, legal representative, Kathryn Beverly; Wilson, Merrill Anderson; Ohm, Ted R.; Kneidel, Kurt E.; Peterson, David; Chen, Christopher M.; Rackers, Keith Gerard; Dyer, deceased, Paul Nigel

2007-10-09

Planar ceramic membrane assembly comprising a dense layer of mixed-conducting multi-component metal oxide material, wherein the dense layer has a first side and a second side, a porous layer of mixed-conducting multi-component metal oxide material in contact with the first side of the dense layer, and a ceramic channeled support layer in contact with the second side of the dense layer. The planar ceramic membrane assembly can be used in a ceramic wafer assembly comprising a planar ceramic channeled support layer having a first side and a second side; a first dense layer of mixed-conducting multi-component metal oxide material having an inner side and an outer side, wherein the inner side is in contact with the first side of the ceramic channeled support layer; a first outer support layer comprising porous mixed-conducting multi-component metal oxide material and having an inner side and an outer side, wherein the inner side is in contact with the outer side of the first dense layer; a second dense layer of mixed-conducting multi-component metal oxide material having an inner side and an outer side, wherein the inner side is in contact with the second side of the ceramic channeled layer; and a second outer support layer comprising porous mixed-conducting multi-component metal oxide material and having an inner side and an outer side, wherein the inner side is in contact with the outer side of the second dense layer.

Percolative ionic conduction in the LiAlSiO4 glass-ceramic system

International Nuclear Information System (INIS)

Biefeld, R.M.; Pike, G.E.; Johnson, R.T. Jr.

1977-01-01

The effect f crystallinity on the lithium ion conductivity in LiAlSiO 4 glass and glass-ceramic solid electrolytes has been determined. The ionic conductivity is thermally activated with an activation energy and pre-exponential factor that change in a marked and nonsimple manner as the volume fraction of crystallinity changes. These results are explained by using a continuum percolation model (effective-medium approximation) which assumes that ionic conduction in the glass-ceramic is almost entirely within the glass phase until the crystalline volume fraction rises above approx. 55%. The LiAlSiO 4 system would seem to be nearly ideal for application of percolation theory since the crystalline phase, β eucryptite, has nearly the same composition as the glass phase. Hence, as the crystallite volume fraction increases in the glass ceramic, the residual glass composition and conductivity remain the same. This is the first application of percolation theory to ionic transport in glass-ceramics and excellent agreement is obtained between theory and experiment for the LiAlSiO 4 system

Sol-gel applications for ceramic membrane preparation

Science.gov (United States)

Erdem, I.

2017-02-01

Ceramic membranes possessing superior properties compared to polymeric membranes are more durable under severe working conditions and therefore their service life is longer. The ceramic membranes are composed of some layers. The support is the layer composed of coarser ceramic structure and responsible for mechanical durability under filtration pressure and it is prepared by consolidation of ceramic powders. The top layer is composed of a finer ceramic micro-structure mainly responsible for the separation of components present in the fluid to be filtered and sol-gel method is a versatile tool to prepare such a tailor-made ceramic filtration structure with finer pores. Depending on the type of filtration (e.g. micro-filtration, ultra-filtration, nano-filtration) aiming separation of components with different sizes, sols with different particulate sizes should be prepared and consolidated with varying precursors and preparation conditions. The coating of sol on the support layer and heat treatment application to have a stable ceramic micro-structure are also important steps determining the final properties of the top layer. Sol-gel method with various controllable parameters (e.g. precursor type, sol formation kinetics, heat treatment conditions) is a practical tool for the preparation of top layers of ceramic composite membranes with desired physicochemical properties.

Grain Oriented Perovskite Layer Structure Ceramics for High-Temperature Piezoelectric Applications

Science.gov (United States)

Fuierer, Paul Anton

The perovskite layer structure (PLS) compounds have the general formula (A^{2+}) _2(B^{5+})_2 O_7, or (A^ {3+})_2(B^{4+ })_2O_7, and crystallize in a very anisotropic layered structure consisting of parallel slabs made up of perovskite units. Several of these compounds possess the highest Curie temperatures (T_{rm c} ) of any known ferroelectrics. Two examples are Sr_2Nb_2O _7 with T_{rm c} of 1342^circC, and La_2Ti_2O _7 with T_{rm c} of 1500^circC. This thesis is an investigation of PLS ceramics and their feasibility as a high temperature transducer material. Piezoelectricity in single crystals has been measured, but the containerless float zone apparatus necessary to grow high quality crystals of these refractory compounds is expensive and limited to a small number of research groups. Previous attempts to pole polycrystalline Sr_2Nb _2O_7 have failed, and to this point piezoelectricity has been absent. The initiative taken in this research was to investigate PLS ceramics by way of composition and processing schemes such that polycrystalline bodies could be electrically poled. The ultimate objective then was to demonstrate piezoelectricity in PLS ceramics, especially at high temperatures. Donor-doping of both La_2Ti _2O_7 and Sr_2Nb_2O _7 was found to increase volume resistivities at elevated temperatures, an important parameter to consider during the poling process. Sr_2Ta _2O_7 (T _{rm c} = -107 ^circC) was used to make solid solution compositions with moderately high Curie temperatures, of about 850^circC, and lower coercive fields. A hot-forging technique was employed to produce ceramics with high density (>99% of theoretical) and high degree of grain orientation (>90%). Texturing was characterized by x-ray diffraction and microscopy. Considerable anisotropy was observed in physical and electrical properties, including thermal expansion, resistivity, dielectric constant, and polarization. The direction perpendicular to the forging axis proved to be the

Investigation of charges carrier density in phosphorus and boron doped SiNx:H layers for crystalline silicon solar cells

International Nuclear Information System (INIS)

Paviet-Salomon, B.; Gall, S.; Slaoui, A.

2013-01-01

Highlights: ► We investigate the properties of phosphorus and boron-doped silicon nitride films. ► Phosphorus-doped layers yield higher lifetimes than undoped ones. ► The fixed charges density decreases when increasing the films phosphorus content. ► Boron-doped films feature very low lifetimes. ► These doped layers are of particular interest for crystalline silicon solar cells. -- Abstract: Dielectric layers are of major importance in crystalline silicon solar cells processing, especially as anti-reflection coatings and for surface passivation purposes. In this paper we investigate the fixed charge densities (Q fix ) and the effective lifetimes (τ eff ) of phosphorus (P) and boron (B) doped silicon nitride layers deposited by plasma-enhanced chemical vapour deposition. P-doped layers exhibit a higher τ eff than standard undoped layers. In contrast, B-doped layers exhibit lower τ eff . A strong Q fix decrease is to be seen when increasing the P content within the film. Based on numerical simulations we also demonstrate that the passivation obtained with P- and B-doped layers are limited by the interface states rather than by the fixed charges

In situ atomic layer nitridation on the top and down regions of the amorphous and crystalline high-K gate dielectrics

Energy Technology Data Exchange (ETDEWEB)

Tsai, Meng-Chen [Department of Materials Science and Engineering, National Taiwan University, Taipei 10617, Taiwan (China); Lee, Min-Hung [Institute of Electro-Optical Science and Technology, National Taiwan Normal University, Taipei 11677, Taiwan (China); Kuo, Chin-Lung; Lin, Hsin-Chih [Department of Materials Science and Engineering, National Taiwan University, Taipei 10617, Taiwan (China); Chen, Miin-Jang, E-mail: mjchen@ntu.edu.tw [Department of Materials Science and Engineering, National Taiwan University, Taipei 10617, Taiwan (China)

2016-11-30

Highlights: • The structural and electrical characteristics of the ZrO{sub 2} high-K dielectrics, treated with the in situ atomic layer doping of nitrogen into the top and down regions (top and down nitridation, TN and DN, respectively), were investigated. • The amorphous DN sample has a lower leakage current density (J{sub g}) than the amorphous TN sample, attributed to the formation of SiO{sub x}N{sub y} in the interfacial layer (IL). • The crystalline TN sample exhibited a lower CET and a similar J{sub g} as compared with the crystalline DN sample, which can be ascribed to the suppression of IL regrowth. • The crystalline ZrO{sub 2} with in situ atomic layer doping of nitrogen into the top region exhibited superior scaling limit, electrical characteristics, and reliability. - Abstract: Amorphous and crystalline ZrO{sub 2} gate dielectrics treated with in situ atomic layer nitridation on the top and down regions (top and down nitridation, abbreviated as TN and DN) were investigated. In a comparison between the as-deposited amorphous DN and TN samples, the DN sample has a lower leakage current density (J{sub g}) of ∼7 × 10{sup −4} A/cm{sup 2} with a similar capacitance equivalent thickness (CET) of ∼1.53 nm, attributed to the formation of SiO{sub x}N{sub y} in the interfacial layer (IL). The post-metallization annealing (PMA) leads to the transformation of ZrO{sub 2} from the amorphous to the crystalline tetragonal/cubic phase, resulting in an increment of the dielectric constant. The PMA-treated TN sample exhibits a lower CET of 1.22 nm along with a similar J{sub g} of ∼1.4 × 10{sup −5} A/cm{sup 2} as compared with the PMA-treated DN sample, which can be ascribed to the suppression of IL regrowth. The result reveals that the nitrogen engineering in the top and down regions has a significant impact on the electrical characteristics of amorphous and crystalline ZrO{sub 2} gate dielectrics, and the nitrogen incorporation at the top of crystalline

The radiolysis of lithium oxide ceramics

Energy Technology Data Exchange (ETDEWEB)

Tiliks, J; Supe, A; Kizane, G; Tiliks, J Jr [Latvia Univ., Riga (Latvia). Dept. of Chemistry; Grishmanov, V; Tanaka, S

1998-03-01

The radiolysis of Li{sub 2}O ceramics exposed to accelerated electrons (5 MeV) at 380 K was studied in the range of high absorbed doses up to 250 MGy. The formation of radiation defects (RD) and radiolysis products (RP) was demonstrated to occur simultaneously in the regions of (1) the regular crystalline lattice and (2) an enhanced content of the intrinsic defects and impurities. The production of the electronic RD and RP is more efficient in the region of the defected lattice than that at the site of the regular crystalline lattice. However, the stability of RD and RP formed in the region of the intrinsic defects is far less than those produced at the crystalline lattice, since most of the first mentioned RD and RP disappears with irradiation dose due to the radiation stimulated recombination. By this means the enhanced quantity of RD and RP is localized in the Li{sub 2}O ceramics irradiated to absorbed dose of 40-50 MGy, and hence this can influence the tritium release parameters. As soon as the intrinsic defects have been consumed in the production of RD and RP and the recombination of unstable electronic RD and RP takes place (at dose of {approx}100 MGy), the radiolysis of Li{sub 2}O ceramics occurs only at the crystalline lattice. Furthermore, the concentration of RD and RP increases monotonically and tends to the steady-state level. (author)

Net shape manufacturing of ceramic micro parts with tailored graded layers

Science.gov (United States)

Hassanin, H.; Jiang, K.

2014-01-01

Presented in this paper is a novel net shape manufacturing technology for making three-dimensional micro parts with functionally graded layers. Alumina/zirconia micro parts with either core-shell or top-bottom functionally graded material (FGM) profiles have been successfully fabricated by altering both the surface characteristics of polydimethylsiloxane (PDMS) micro moulds and ceramic suspensions composition. PDMS surface modifications were performed to achieve moulds with hydrophilic surfaces, which were used to form core/shell FGM green layers. On the other hand, moulds with hydrophobic surfaces were used to form top-bottom green layers. Cracks have been found between consecutive layers in both the green and sintered micro parts. It was found that, at dispersant concentration of about 9.0 mg g-1, the differences in the drying shrinkage between layers is less than 0.5%. In addition, layers of composition of 100% Al2O3-0% YSZ, 20% Al2O3-80% YSZ and 40% Al2O3-60% YSZ were found to produce less shrinkage difference during sintering. After optimization of both green and sintering layers, crack free core/shell and top-bottom alumina/zirconia FGM micro parts were successfully obtained. The proposed process enables the production of micro patterns tailored with functionally graded microstructures to locally enhance properties and performance.

A particle swarm-based algorithm for optimization of multi-layered and graded dental ceramics.

Science.gov (United States)

Askari, Ehsan; Flores, Paulo; Silva, Filipe

2018-01-01

The thermal residual stresses (TRSs) generated owing to the cooling down from the processing temperature in layered ceramic systems can lead to crack formation as well as influence the bending stress distribution and the strength of the structure. The purpose of this study is to minimize the thermal residual and bending stresses in dental ceramics to enhance their strength as well as to prevent the structure failure. Analytical parametric models are developed to evaluate thermal residual stresses in zirconia-porcelain multi-layered and graded discs and to simulate the piston-on-ring test. To identify optimal designs of zirconia-based dental restorations, a particle swarm optimizer is also developed. The thickness of each interlayer and compositional distribution are referred to as design variables. The effect of layers number constituting the interlayer between two based materials on the performance of graded prosthetic systems is also investigated. The developed methodology is validated against results available in literature and a finite element model constructed in the present study. Three different cases are considered to determine the optimal design of graded prosthesis based on minimizing (a) TRSs; (b) bending stresses; and (c) both TRS and bending stresses. It is demonstrated that each layer thickness and composition profile have important contributions into the resulting stress field and magnitude. Copyright © 2017 Elsevier Ltd. All rights reserved.

Development of a double-layered ceramic filter for aerosol filtration at high-temperatures: the filter collection efficiency.

Science.gov (United States)

de Freitas, Normanda L; Gonçalves, José A S; Innocentini, Murilo D M; Coury, José R

2006-08-25

The performance of double-layered ceramic filters for aerosol filtration at high temperatures was evaluated in this work. The filtering structure was composed of two layers: a thin granular membrane deposited on a reticulate ceramic support of high porosity. The goal was to minimize the high pressure drop inherent of granular structures, without decreasing their high collection efficiency for small particles. The reticulate support was developed using the technique of ceramic replication of polyurethane foam substrates of 45 and 75 pores per inch (ppi). The filtering membrane was prepared by depositing a thin layer of granular alumina-clay paste on one face of the support. Filters had their permeability and fractional collection efficiency analyzed for filtration of an airborne suspension of phosphatic rock in temperatures ranging from ambient to 700 degrees C. Results revealed that collection efficiency decreased with gas temperature and was enhanced with filtration time. Also, the support layer influenced the collection efficiency: the 75 ppi support was more effective than the 45 ppi. Particle collection efficiency dropped considerably for particles below 2 microm in diameter. The maximum collection occurred for particle diameters of approximately 3 microm, and decreased again for diameters between 4 and 8 microm. Such trend was successfully represented by the proposed correlation, which is based on the classical mechanisms acting on particle collection. Inertial impaction seems to be the predominant collection mechanism, with particle bouncing/re-entrainment acting as detachment mechanisms.

Crystalline Bioceramic Materials

Directory of Open Access Journals (Sweden)

de Aza, P. N.

2005-06-01

Full Text Available A strong interest in the use of ceramics for biomedical engineering applications developed in the late 1960´s. Used initially as alternatives to metallic materials in order to increase the biocompatibility of implants, bioceramics have become a diverse class of biomaterials, presently including three basic types: relatively bioinert ceramics; bioactive or surface reactive bioceramics and bioresorbable ceramics. This review will only refer to bioceramics “sensus stricto”, it is to say, those ceramic materials constituted for nonmetallic inorganic compounds, crystallines and consolidated by thermal treatments of powders to high temperatures. Leaving bioglasses, glass-ceramics and biocements apart, since, although all of them are obtained by thermal treatments to high temperatures, the first are amorphous, the second are obtained by desvitrification of a glass and in them vitreous phase normally prevails on the crystalline phases and the third are consolidated by means of a hydraulic or chemical reaction to room temperature. A review of the composition, physiochemical properties and biological behaviour of the principal types of crystalline bioceramics is given, based on the literature data and on the own experience of the authors.

A finales de los años sesenta se despertó un gran interés por el uso de los materiales cerámicos para aplicaciones biomédicas. Inicialmente utilizados como una alternativa a los materiales metálicos, con el propósito de incrementar la biocompatibilidad de los implantes, las biocerámicas se han convertido en una clase diversa de biomateriales, incluyendo actualmente tres tipos: cerámicas cuasi inertes; cerámicas bioactivas o reactivas superficialmente y cerámicas reabsorbibles o biodegradables. En la presente revisión se hace referencia a las biocerámicas en sentido estricto, es decir, a aquellos materiales constitutitos por compuestos inorgánicos no metálicos, cristalinos y consolidados

Electrical and thermal properties of lead titanate glass ceramics

International Nuclear Information System (INIS)

Shankar, J.; Deshpande, V.K.

2011-01-01

Glass samples with composition of (50-X)PbO-(25+X)TiO 2 -25B 2 O 3 (where X=0, 5, 10 and 12.5 mol%) were prepared using conventional quenching technique. The glass transition temperature, T g and crystallization temperature T c were determined from the DTA. These glass samples were converted to glass ceramics by following two stage heat treatment schedule. The glass ceramic samples were characterized by XRD, SEM and dielectric constant measurements. The XRD results revealed the formation of ferroelectric lead titanate (PT) as a major crystalline phase in the glass ceramics. The density increases and the CTE decreases for all glass ceramics with increase in X (mol%). This may be attributed to increase in PT phase. The SEM results which show rounded crystallites of lead titanate, also supports other results. Hysteresis loops observed at room temperature confirms the ferroelectric nature of glass ceramics. The optimized glass ceramic sample exhibits high dielectric constant which is of technical importance. -- Research Highlights: →Lead titanate glass ceramics prepared by conventional quenching technique. →Lead titanate is a major crystalline phase in the glass ceramics. →The ferroelectric nature of glass ceramics is confirmed by the hysteresis study. →The high value of ε observed at room temperature is quite promising in the study.

Ceramic Hosts for Fission Products Immobilization

Energy Technology Data Exchange (ETDEWEB)

Peter C Kong

2010-07-01

Natural spinel, perovskite and zirconolite rank among the most leach resistant of mineral forms. They also have a strong affinity for a large number of other elements and including actinides. Specimens of natural perovskite and zirconolite were radioisotope dated and found to have survived at least 2 billion years of natural process while still remain their loading of uranium and thorium . Developers of the Synroc waste form recognized and exploited the capability of these minerals to securely immobilize TRU elements in high-level waste . However, the Synroc process requires a relatively uniform input and hot pressing equipment to produce the waste form. It is desirable to develop alternative approaches to fabricate these durable waste forms to immobilize the radioactive elements. One approach is using a high temperature process to synthesize these mineral host phases to incorporate the fission products in their crystalline structures. These mineral assemblages with immobilized fission products are then isolated in a durable high temperature glass for periods measured on a geologic time scale. This is a long term research concept and will begin with the laboratory synthesis of the pure spinel (MgAl2O4), perovskite (CaTiO3) and zirconolite (CaZrTi2O7) from their constituent oxides. High temperature furnace and/or thermal plasma will be used for the synthesis of these ceramic host phases. Nonradioactive strontium oxide will be doped into these ceramic phases to investigate the development of substitutional phases such as Mg1-xSrxAl2O4, Ca1-xSrxTiO3 and Ca1-xSrxZrTi2O7. X-ray diffraction will be used to establish the crystalline structures of the pure ceramic hosts and the substitution phases. Scanning electron microscopy and energy dispersive X-ray analysis (SEM-EDX) will be performed for product morphology and fission product surrogates distribution in the crystalline hosts. The range of strontium doping is planned to reach the full substitution of the divalent

Preparation of basalt-based glass ceramics

Directory of Open Access Journals (Sweden)

MIHOVIL LOGAR

2003-06-01

Full Text Available Local and conventional raw materials–massive basalt from the Vrelo locality on Kopaonik mountain–have been used as starting materials to test their suitability for the production of glass-ceramics. Crystallization phenomena of glasses of the fused basalt rocks were studied by X-ray phase analysis, optical microscopy and other techniques. Various heat treatments were used, and their influences, on controlling the microstructures and properties of the products were studied with the aim of developing high strength glass-ceramic materials. Diopside CaMg(SiO32 and hypersthene ((Mg,FeSiO3 were identifies as the crystalline phases. The final products contained considerable amounts of a glassy phase. The crystalline size was in range of 8–480 mm with plate or needle shape. Microhardness, crashing strength and wears resistence of the glass-ceramics ranged from 6.5–7.5, from 2000–6300 kg/cm2 and from 0.1–0.2 g/cm, respectively.

Fabrication and characterization of glass–ceramics materials developed from steel slag waste

International Nuclear Information System (INIS)

He, Feng; Fang, Yu; Xie, Junlin; Xie, Jun

2012-01-01

Highlights: ► Steelmaking slag (SS) is one of the most common industrial wastes. ► Glass–ceramics produced from SS is observed to have good properties. ► A large volume of raw SS can be recycled. ► The utilization of SS could reduce solid waste pollution. -- Abstract: In this study, glass–ceramic materials were produced from SS (steel slag) obtained from Wuhan Iron and Steel Corporation in China. The amount of SS used in glass batch was about 31–41 wt.% of the total batch mixture. On basis of differential thermal analysis (DTA) results, the nucleation and crystallization temperature of the parent glass samples were identified, respectively. X-ray diffraction (XRD) revealed that multiple crystalline phases coexisted in the glass–ceramics, and the main crystalline phase was wollastonite (CaSiO 3 ). SEM observation indicated that there was an increase in the amount of crystalline phase in the glass–ceramics when the CaO content and crystallization time increased. It was also found that the glass–ceramics with fine microstructure enhance mechanical properties and erosion wear resistance. The obtained glass–ceramics showed a maximum bending strength of 145.6 MPa and very nice wear resistance. Therefore, it is feasible to produce nucleated glass–ceramics materials for building and decorative materials from SS.

Study of new CaO-SiO/sub 2/-P/sub 2/O/sub 5/CaF/sub 2/ bioactive ceramic

International Nuclear Information System (INIS)

Shamim, A.; Arif, I.; Siddiqi, S.A.; Shah, W.A.

1997-01-01

A new bioactive glass ceramic having, composition 48CaO-32SiO/sub 2/-16P/sub 2/O/sub 5/-4CaF/sub 2/ has been developed and studied for its physical and biological properties. Like the natural bone in which spastic particles are reinforced by collagen, in the present glass-ceramic, fine grained ceramic particles embedded in a glass matrix. X-ray diffraction analysis reveals wollastonite and oxyfluorapatite as the crystalline part of the glass-ceramic. Scanning electron microscopy of the samples has been carried out to see the grain size and grain distribution. Bending and compressive strength of the glass ceramic have been carried out to measured and found to be 208.60 m.Pa and 788.61 M.Pa respectively. Growth of apatite layer, which is responsible for bonding the broken part of a natural bone, on a bioactive glass-ceramic in a simulated body fluid has been studied. A small rectangular piece of this glass-ceramic has also been implanted successfully in a dog's tibia. (author)

Preparation and photocatalytic activity of chemically-bonded phosphate ceramics containing TiO2

Science.gov (United States)

Martins, Monize Aparecida; de Lima, Bruna de Oliveira; Ferreira, Leticia Patrício; Colonetti, Emerson; Feltrin, Jucilene; De Noni, Agenor

2017-05-01

Titanium dioxide was incorporated into chemically-bonded phosphate ceramic for use as photocatalytic inorganic coating. The coatings obtained were applied to unglazed ceramic tiles and cured at 350 °C. The surfaces were characterized by photocatalytic activity, determined in aqueous medium, based on the degradation of methylene blue dye. The effects of the percentage of TiO2 and the thickness of the layer on the photocatalytic efficiency were evaluated. The influence of the incorporation of TiO2 on the consolidation of the phosphate matrix coating was investigated using the wear resistance test. The crystalline phases of the coatings obtained were determined by XRD. The microstructure of the surfaces was analyzed by SEM. The thermal curing treatment did not cause a phase transition from anatase to rutile. An increase in the photocatalytic activity of the coating was observed with an increase in the TiO2 content. The dye degradation indices ranged from 14.9 to 44.0%. The photocatalytic efficiency was not correlated with the thickness of the coating layer deposited. The resistance to wear decreased with an increase in the TiO2 content. Comparison with a commercial photocatalytic ceramic coating indicated that there is a range of values for the TiO2 contents which offer potential for photocatalytic applications.

Hardness of ion implanted ceramics

International Nuclear Information System (INIS)

Oliver, W.C.; McHargue, C.J.; Farlow, G.C.; White, C.W.

1985-01-01

It has been established that the wear behavior of ceramic materials can be modified through ion implantation. Studies have been done to characterize the effect of implantation on the structure and composition of ceramic surfaces. To understand how these changes affect the wear properties of the ceramic, other mechanical properties must be measured. To accomplish this, a commercially available ultra low load hardness tester has been used to characterize Al 2 O 3 with different implanted species and doses. The hardness of the base material is compared with the highly damaged crystalline state as well as the amorphous material

Ceramics: Durability and radiation effects

Energy Technology Data Exchange (ETDEWEB)

Ewing, R.C.; Lutze, W. [Univ. of New Mexico, Albuquerque, NM (United States); Weber, W.J. [Pacific Northwest National Lab., Richland, WA (United States)

1996-05-01

At present, there are three seriously considered options for the disposition of excess weapons plutonium: (1) incorporation, partial burn-up and direct disposal of MOX-fuel; (2) vitrification with defense waste and disposal as glass {open_quotes}logs{close_quotes}; (3) deep borehole disposal. The first two options provide a safeguard due to the high activity of fission products in the irradiated fuel and the defense waste. The latter option has only been examined in a preliminary manner, and the exact form of the plutonium has not been identified. In this paper, we review the potential for the immobilization of plutonium in highly durable crystalline ceramics apatite, pyrochlore, zirconolite, monazite and zircon. Based on available data, we propose zircon as the preferred crystalline ceramic for the permanent disposition of excess weapons plutonium.

Structural and impedance characterization of ceramics prepared from NPK fertilizer

Directory of Open Access Journals (Sweden)

Diouma Kobor

2015-06-01

Full Text Available One of the main objectives of this work was to study the possibilities of valorising the phosphates through the development of a conductive ceramics using NPK fertilizer as a precursor. Phosphorus based powders were synthesized using solid state technique from NPK fertilizer, lithium chloride and iron chloride at different temperatures up to 900 °C and ceramic samples were prepared by the powder pressing and sintering at 1100 °C. XRD spectra of the calcined powders show various sharp peaks indicating a relatively high degree of crystallinity and presence of different crystalline phases, such as: phosphorus based crystalline compounds (AlPO4 and LiFePO4, ferrite (Fe3O4 and DyFeO3, CaSO4 and K3DyCl6. The prepared phosphorus based ceramics showed very interesting electrical and dielectric properties. Thus, in the future the obtained ceramics could find application in electronic or energy storage devices. However, further investigations are necessary to understand the exact chemical composition and structural characteristics of this material, to better understand the origin of the obtained electrical and dielectric behaviour.

Development of Ceramic Solid-State Laser Host Material

Science.gov (United States)

Prasad, Narasimha S.; Trivedi, Sudhir; Kutcher, Susan; Wang, Chen-Chia; Kim, Joo-Soo; Hommerich, Uwe; Shukla, Vijay; Sadangi, Rajendra

2009-01-01

Polycrystalline ceramic laser materials are gaining importance in the development of novel diode-pumped solid-state lasers. Compared to single-crystals, ceramic laser materials offer advantages in terms of ease of fabrication, shape, size, and control of dopant concentrations. Recently, we have developed Neodymium doped Yttria (Nd:Y2O3) as a solid-state ceramic laser material. A scalable production method was utilized to make spherical non agglomerated and monodisperse metastable ceramic powders of compositions that were used to fabricate polycrystalline ceramic material components. This processing technique allowed for higher doping concentrations without the segregation problems that are normally encountered in single crystalline growth. We have successfully fabricated undoped and Neodymium doped Yttria material up to 2" in diameter, Ytterbium doped Yttria, and erbium doped Yttria. We are also in the process of developing other sesquioxides such as scandium Oxide (Sc2O3) and Lutesium Oxide (Lu2O3) doped with Ytterbium, erbium and thulium dopants. In this paper, we present our initial results on the material, optical, and spectroscopic properties of the doped and undoped sesquioxide materials. Polycrystalline ceramic lasers have enormous potential applications including remote sensing, chem.-bio detection, and space exploration research. It is also potentially much less expensive to produce ceramic laser materials compared to their single crystalline counterparts because of the shorter fabrication time and the potential for mass production in large sizes.

Birnessite-type MnO2 nanosheets with layered structures under high pressure: elimination of crystalline stacking faults and oriented laminar assembly.

Science.gov (United States)

Sun, Yugang; Wang, Lin; Liu, Yuzi; Ren, Yang

2015-01-21

Squeezing out crystalline stacking faults: Birnessite-type δ-phase MnO2 microflowers containing interconnected ultrathin nanosheets are synthesized through a microwave-assisted hydrothermal process and exhibit a layered crystalline structure with significant stacking faults. Compressing these MnO2 nanosheets in a diamond anvil cell with high pressure up to tens of GPa effectively eliminates the crystalline stacking faults. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Crystalline Ceramic Waste Forms: Comparison Of Reference Process For Ceramic Waste Form Fabrication

Energy Technology Data Exchange (ETDEWEB)

Brinkman, K. S. [Savannah River National Laboratory; Marra, J. C. [Savannah River National Laboratory; Amoroso, J. [Savannah River National Laboratory; Tang, M. [Los Alamos National Laboratory

2013-08-22

The research conducted in this work package is aimed at taking advantage of the long term thermodynamic stability of crystalline ceramics to create more durable waste forms (as compared to high level waste glass) in order to reduce the reliance on engineered and natural barrier systems. Durable ceramic waste forms that incorporate a wide range of radionuclides have the potential to broaden the available disposal options and to lower the storage and disposal costs associated with advanced fuel cycles. Assemblages of several titanate phases have been successfully demonstrated to incorporate radioactive waste elements, and the multiphase nature of these materials allows them to accommodate variation in the waste composition. Recent work has shown that they can be produced from a melting and crystallization process. The objective of this report is to explore the phase formation and microstructural differences between lab scale melt processing in varying gas environments with alternative densification processes such as Hot Pressing (HP) and Spark Plasma Sintering (SPS). The waste stream used as the basis for the development and testing is a simulant derived from a combination of the projected Cs/Sr separated stream, the Trivalent Actinide - Lanthanide Separation by Phosphorous reagent Extraction from Aqueous Komplexes (TALSPEAK) waste stream consisting of lanthanide fission products, the transition metal fission product waste stream resulting from the transuranic extraction (TRUEX) process, and a high molybdenum concentration with relatively low noble metal concentrations. Melt processing as well as solid state sintering routes SPS and HP demonstrated the formation of the targeted phases; however differences in microstructure and elemental partitioning were observed. In SPS and HP samples, hollandite, pervoskite/pyrochlore, zirconolite, metallic alloy and TiO{sub 2} and Al{sub 2}O{sub 3} were observed distributed in a network of fine grains with small residual pores

Three-unit posterior zirconia-ceramic fixed dental prostheses (FDPs) veneered with layered and milled (CAD-on) veneering ceramics: 1-year follow-up of a randomized controlled clinical trial.

Science.gov (United States)

Grohmann, Philipp; Bindl, Andreas; Hämmerle, Christoph; Mehl, Albert; Sailer, Irena

2015-01-01

The aim of this multicenter randomized controlled clinical trial was to test posterior zirconia-ceramic fixed dental prostheses (FDPs) veneered with a computer-aided design/computer- assisted manufacture (CAD/CAM) lithium disilicate veneering ceramic (CAD-on) and manually layered zirconia veneering ceramic with respect to survival of the FDPs, and technical and biologic outcomes. Sixty patients in need of one posterior three-unit FDP were included. The zirconia frameworks were produced with a CAD/CAM system (Cerec inLab 3D/Cerec inEOS inLab). Thirty FDPs were veneered with a CAD/CAM lithium disilicate veneering ceramic (Cad-on) (test) and 30 were veneered with a layered zirconia veneering ceramic (control). For the clinical evaluation at baseline, 6, and 12 months, the United States Public Health Service (USPHS) criteria were used. The biologic outcome was judged by comparing the plaque control record (PCR), bleeding on probing (BOP), and probing pocket depth (PPD). Data were statistically analyzed. Fifty-six patients were examined at a mean follow-up of 13.9 months. At the 1-year follow-up the survival rate was 100% in the test and in the control group. No significant differences of the technical outcomes occurred. Major chipping occurred in the control group (n = 3) and predominantly minor chipping in the test group (minor n = 2, major n = 1). No biologic problems or differences were found. Both types of zirconia-ceramic FDPs exhibited very good clinical outcomes without differences between groups. Chipping occurred in both types of FDPs at small amounts, yet the extension of the chippings differed. The test FDPs predominantly exhibited minor chipping, the control FDPs major chipping.

Comparative study of transparent ceramic and single crystal Ce doped LuAG scintillators

International Nuclear Information System (INIS)

Yanagida, Takayuki; Fujimoto, Yutaka; Yokota, Yuui; Kamada, Kei; Yanagida, Satoko; Yoshikawa, Akira; Yagi, Hideki; Yanagitani, Takagimi

2011-01-01

Transparent ceramic Ce 0.5% doped Lu 3 Al 5 O 12 (LuAG) scintillator grown by the sintering method and single crystalline Ce doped LuAG grown by the Czochralski method are prepared. They are cut to the physical dimensions 4 × 4 × 2 mm 3 . Their transmittance and radio luminescence spectra are evaluated. They are both transmissive in wavelength longer than 500 nm and intense Ce 3+ 5d–4f emission appears around 520 nm. When 137 Cs γ-ray is irradiated, 662 keV photo-absorption peaks are clearly observed in each sample. The transparent ceramic one shows higher light yield than that of the single crystalline one. The absolute light yield of the ceramic sample is turned out to be 14800 ± 1500 ph/MeV. The decay time constants are evaluated under pulse X-ray excitation. The main component of the decay time of ceramic and single crystalline one are determined as 37 and 46 ns, respectively.

Atomic layer deposition of crystalline SrHfO3 directly on Ge (001) for high-k dielectric applications

International Nuclear Information System (INIS)

McDaniel, Martin D.; Ngo, Thong Q.; Ekerdt, John G.; Hu, Chengqing; Jiang, Aiting; Yu, Edward T.; Lu, Sirong; Smith, David J.; Posadas, Agham; Demkov, Alexander A.

2015-01-01

The current work explores the crystalline perovskite oxide, strontium hafnate, as a potential high-k gate dielectric for Ge-based transistors. SrHfO 3 (SHO) is grown directly on Ge by atomic layer deposition and becomes crystalline with epitaxial registry after post-deposition vacuum annealing at ∼700 °C for 5 min. The 2 × 1 reconstructed, clean Ge (001) surface is a necessary template to achieve crystalline films upon annealing. The SHO films exhibit excellent crystallinity, as shown by x-ray diffraction and transmission electron microscopy. The SHO films have favorable electronic properties for consideration as a high-k gate dielectric on Ge, with satisfactory band offsets (>2 eV), low leakage current (<10 −5 A/cm 2 at an applied field of 1 MV/cm) at an equivalent oxide thickness of 1 nm, and a reasonable dielectric constant (k ∼ 18). The interface trap density (D it ) is estimated to be as low as ∼2 × 10 12  cm −2  eV −1 under the current growth and anneal conditions. Some interfacial reaction is observed between SHO and Ge at temperatures above ∼650 °C, which may contribute to increased D it value. This study confirms the potential for crystalline oxides grown directly on Ge by atomic layer deposition for advanced electronic applications

Selective deposition contact patterning using atomic layer deposition for the fabrication of crystalline silicon solar cells

International Nuclear Information System (INIS)

Cho, Young Joon; Shin, Woong-Chul; Chang, Hyo Sik

2014-01-01

Selective deposition contact (SDC) patterning was applied to fabricate the rear side passivation of crystalline silicon (Si) solar cells. By this method, using screen printing for contact patterning and atomic layer deposition for the passivation of Si solar cells with Al 2 O 3 , we produced local contacts without photolithography or any laser-based processes. Passivated emitter and rear-contact solar cells passivated with ozone-based Al 2 O 3 showed, for the SDC process, an up-to-0.7% absolute conversion-efficiency improvement. The results of this experiment indicate that the proposed method is feasible for conversion-efficiency improvement of industrial crystalline Si solar cells. - Highlights: • We propose a local contact formation process. • Local contact forms a screen print and an atomic layer deposited-Al 2 O 3 film. • Ozone-based Al 2 O 3 thin film was selectively deposited onto patterned silicon. • Selective deposition contact patterning method can increase cell-efficiency by 0.7%

Irradiation induced crystalline to amorphous transition

International Nuclear Information System (INIS)

Bourgoin, J.

1980-01-01

Irradiation of a crystalline solid with energetic heavy particles results in cascades of defects which, with increasing dose, overlap and form a continuous disordered layer. In semiconductors the physical properties of such disordered layers are found to be similar to those of amorphous layers produced by evaporation. It is shown in the case of silicon, that the transition from a disordered crystalline (X) layer to an amorphous (α) layer occurs when the Gibbs energy of the X phase and of the defects it contains becomes larger than the Gibbs energy of the α phase. (author)

Crystalline phase, microstructure, and aqueous stability of zirconolite-barium borosilicate glass-ceramics for immobilization of simulated sulfate bearing high-level liquid waste

Science.gov (United States)

Wu, Lang; Xiao, Jizong; Wang, Xin; Teng, Yuancheng; Li, Yuxiang; Liao, Qilong

2018-01-01

The crystalline phase, microstructure, and aqueous stability of zirconolite-barium borosilicate glass-ceramics with different content (0-30 wt %) of simulated sulfate bearing high-level liquid waste (HLLW) were evaluated. The sulfate phase segregation in vitrification process was also investigated. The results show that the glass-ceramics with 0-20 wt% of HLLW possess mainly zirconolite phase along with a small amount baddeleyite phase. The amount of perovskite crystals increases while the amount of zirconolite crystals decreases when the HLLW content increases from 20 to 30 wt%. For the samples with 20-30 wt% HLLW, yellow phase was observed during the vitrification process and it disappeared after melting at 1150 °C for 2 h. The viscosity of the sample with 16 wt% HLLW (HLLW-16) is about 27 dPa·s at 1150 °C. The addition of a certain amount (≤20 wt %) of HLLW has no significant change on the aqueous stability of glass-ceramic waste forms. After 28 days, the 90 °C PCT-type normalized leaching rates of Na, B, Si, and La of the sample HLLW-16 are 7.23 × 10-3, 1.57 × 10-3, 8.06 × 10-4, and 1.23 × 10-4 g·m-2·d-1, respectively.

Composite metal foil and ceramic fabric materials

Science.gov (United States)

Webb, Brent J.; Antoniak, Zen I.; Prater, John T.; DeSteese, John G.

1992-01-01

The invention comprises new materials useful in a wide variety of terrestrial and space applications. In one aspect, the invention comprises a flexible cloth-like material comprising a layer of flexible woven ceramic fabric bonded with a layer of metallic foil. In another aspect, the invention includes a flexible fluid impermeable barrier comprising a flexible woven ceramic fabric layer having metal wire woven therein. A metallic foil layer is incontinuously welded to the woven metal wire. In yet another aspect, the invention includes a material comprising a layer of flexible woven ceramic fabric bonded with a layer of an organic polymer. In still another aspect, the invention includes a rigid fabric structure comprising a flexible woven ceramic fabric and a resinous support material which has been hardened as the direct result of exposure to ultraviolet light. Inventive methods for producing such material are also disclosed.

Sensitive Ceramics

DEFF Research Database (Denmark)

2014-01-01

Sensitive Ceramics is showing an interactive digital design tool for designing wall like composition with 3d ceramics. The experiment is working on two levels. One which has to do with designing compositions and patterns in a virtual 3d universe based on a digital dynamic system that responds on ...... with realizing the modules in ceramics by 3d printing directly in porcelain with a RapMan printer that coils up the 3d shape in layers. Finally the ceramic modules are mounted in a laser cut board that reflects the captured composition of the movement of the hands....

Zero lattice mismatch and twin-free single crystalline ScN buffer layers for GaN growth on silicon

Energy Technology Data Exchange (ETDEWEB)

Lupina, L.; Zoellner, M. H.; Dietrich, B.; Capellini, G. [IHP, Im Technologiepark 25, 15236 Frankfurt, Oder (Germany); Niermann, T.; Lehmann, M. [Technische Universität Berlin, Institut für Optik und Atomare Physik, Straße des 17. Juni 135, 10623 Berlin (Germany); Thapa, S. B.; Haeberlen, M.; Storck, P. [SILTRONIC AG, Hanns-Seidel-Platz 4, 81737 München (Germany); Schroeder, T. [IHP, Im Technologiepark 25, 15236 Frankfurt, Oder (Germany); BTU Cottbus, Konrad-Zuse-Str. 1, 03046 Cottbus (Germany)

2015-11-16

We report the growth of thin ScN layers deposited by plasma-assisted molecular beam epitaxy on Sc{sub 2}O{sub 3}/Y{sub 2}O{sub 3}/Si(111) substrates. Using x-ray diffraction, Raman spectroscopy, and transmission electron microscopy, we find that ScN films grown at 600 °C are single crystalline, twin-free with rock-salt crystal structure, and exhibit a direct optical band gap of 2.2 eV. A high degree of crystalline perfection and a very good lattice matching between ScN and GaN (misfit < 0.1%) makes the ScN/Sc{sub 2}O{sub 3}/Y{sub 2}O{sub 3} buffer system a very promising template for the growth of high quality GaN layers on silicon.

Room-temperature vacancy migration in crystalline Si from an ion-implanted surface layer

DEFF Research Database (Denmark)

Larsen, Arne Nylandsted; Christensen, Carsten; Petersen, Jon Wulff

1999-01-01

Migration of vacancies in crystalline, n-type silicon at room temperature from Ge+-implanted (150 keV, 5×109–1×1011 cm–2) surface layers was studied by tracing the presence of P–V pairs (E centers) in the underlying layer using deep level transient spectroscopy (DLTS). Under the conditions we have......–Et[approximate]0.15 eV that has donor character. It is argued that the center associated with this line is most probably the P2–V complex; it anneals at about 550 K. A lower limit of the RT-diffusion coefficient of the doubly charged, negative vacancy is estimated to be 4×10–11 cm2/s. ©1999 American Institute...

Atomic layer deposition of crystalline SrHfO{sub 3} directly on Ge (001) for high-k dielectric applications

Energy Technology Data Exchange (ETDEWEB)

McDaniel, Martin D.; Ngo, Thong Q.; Ekerdt, John G., E-mail: ekerdt@utexas.edu [Department of Chemical Engineering, The University of Texas at Austin, Austin, Texas 78712 (United States); Hu, Chengqing; Jiang, Aiting; Yu, Edward T. [Microelectronics Research Center, The University of Texas at Austin, Austin, Texas 78758 (United States); Lu, Sirong; Smith, David J. [Department of Physics, Arizona State University, Tempe, Arizona 85287 (United States); Posadas, Agham; Demkov, Alexander A. [Department of Physics, The University of Texas at Austin, Austin, Texas 78712 (United States)

2015-02-07

The current work explores the crystalline perovskite oxide, strontium hafnate, as a potential high-k gate dielectric for Ge-based transistors. SrHfO{sub 3} (SHO) is grown directly on Ge by atomic layer deposition and becomes crystalline with epitaxial registry after post-deposition vacuum annealing at ∼700 °C for 5 min. The 2 × 1 reconstructed, clean Ge (001) surface is a necessary template to achieve crystalline films upon annealing. The SHO films exhibit excellent crystallinity, as shown by x-ray diffraction and transmission electron microscopy. The SHO films have favorable electronic properties for consideration as a high-k gate dielectric on Ge, with satisfactory band offsets (>2 eV), low leakage current (<10{sup −5} A/cm{sup 2} at an applied field of 1 MV/cm) at an equivalent oxide thickness of 1 nm, and a reasonable dielectric constant (k ∼ 18). The interface trap density (D{sub it}) is estimated to be as low as ∼2 × 10{sup 12 }cm{sup −2 }eV{sup −1} under the current growth and anneal conditions. Some interfacial reaction is observed between SHO and Ge at temperatures above ∼650 °C, which may contribute to increased D{sub it} value. This study confirms the potential for crystalline oxides grown directly on Ge by atomic layer deposition for advanced electronic applications.

Thermal stability of double-ceramic-layer thermal barrier coatings with various coating thickness

International Nuclear Information System (INIS)

Dai Hui; Zhong Xinghua; Li Jiayan; Zhang Yanfei; Meng Jian; Cao Xueqiang

2006-01-01

Double-ceramic-layer (DCL) coatings with various thickness ratios composed of YSZ (6-8 wt.% Y 2 O 3 + ZrO 2 ) and lanthanum zirconate (LZ, La 2 Zr 2 O 7 ) were produced by the atmospheric plasma spraying. Chemical stability of LZ in contact with YSZ in DCL coatings was investigated by calcining powder blends at different temperatures. No obvious reaction was observed when the calcination temperature was lower than 1250 deg. C, implying that LZ and YSZ had good chemical applicability for producing DCL coating. The thermal cycling test indicate that the cycling lives of the DCL coatings are strongly dependent on the thickness ratio of LZ and YSZ, and the coatings with YSZ thickness between 150 and 200 μm have even longer lives than the single-layer YSZ coating. When the YSZ layer is thinner than 100 μm, the DCL coatings failed in the LZ layer close to the interface of YSZ layer and LZ layer. For the coatings with the YSZ thickness above 150 μm, the failure mainly occurs at the interface of the YSZ layer and the bond coat

Werkstoffwoche 98. Vol. 7. Symposium 9: Ceramics. Symposium 14: Simulation of ceramics

International Nuclear Information System (INIS)

Heinrich, J.; Ziegler, G.; Hermel, W.; Riedel, H.

1999-01-01

The leading subject of this proceedings volume is ceramic materials, with papers on the following subject clusters: Processing (infiltration, sintering, forming) - Physics and chemistry of ceramics (functional ceramics, SiC, ceramic precursors, microstructural properties) - Novel concepts (composites, damage induced by oxidation and mechanical stress, performance until damage under mechanical and thermal stress, layers, nanocomposites). 28 of the conference papers have been prepared for individual retrieval from the ENERGY database. (orig./CB) [de

Effect of p-layer properties on nanocrystalline absorber layer and thin film silicon solar cells

International Nuclear Information System (INIS)

Chowdhury, Amartya; Adhikary, Koel; Mukhopadhyay, Sumita; Ray, Swati

2008-01-01

The influence of the p-layer on the crystallinity of the absorber layer and nanocrystalline silicon thin film solar cells has been studied. Boron doped Si : H p-layers of different crystallinities have been prepared under different power pressure conditions using the plasma enhanced chemical vapour deposition method. The crystalline volume fraction of p-layers increases with the increase in deposition power. Optical absorption of the p-layer reduces as the crystalline volume fraction increases. Structural studies at the p/i interface have been done by Raman scattering studies. The crystalline volume fraction of the i-layer increases as that of the p-layer increases, the effect being more prominent near the p/i interface. Grain sizes of the absorber layer decrease from 9.2 to 7.2 nm and the density of crystallites increases as the crystalline volume fraction of the p-layer increases and its grain size decreases. With increasing crystalline volume fraction of the p-layer solar cell efficiency increases

The precursors effects on biomimetic hydroxyapatite ceramic powders.

Science.gov (United States)

Yoruç, Afife Binnaz Hazar; Aydınoğlu, Aysu

2017-06-01

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

Method for fabrication of ceramic dielectric films on copper foils

Science.gov (United States)

Ma, Beihai; Narayanan, Manoj; Dorris, Stephen E.; Balachandran, Uthamalingam

2015-03-10

The present invention provides a method for fabricating a ceramic film on a copper foil. The method comprises applying a layer of a sol-gel composition onto a copper foil. The sol-gel composition comprises a precursor of a ceramic material suspended in 2-methoxyethanol. The layer of sol-gel is then dried at a temperature up to about 250.degree. C. The dried layer is then pyrolyzed at a temperature in the range of about 300 to about 450.degree. C. to form a ceramic film from the ceramic precursor. The ceramic film is then crystallized at a temperature in the range of about 600 to about 750.degree. C. The drying, pyrolyzing and crystallizing are performed under a flowing stream of an inert gas. In some embodiments an additional layer of the sol-gel composition is applied onto the ceramic film and the drying, pyrolyzing and crystallizing steps are repeated for the additional layer to build up a thicker ceramic layer on the copper foil. The process can be repeated one or more times if desired.

Influence of Surface Properties of Filtration-Layer Metal Oxide on Ceramic Membrane Fouling during Ultrafiltration of Oil/Water Emulsion.

Science.gov (United States)

Lu, Dongwei; Zhang, Tao; Gutierrez, Leo; Ma, Jun; Croué, Jean-Philippe

2016-05-03

In this work, ceramic ultrafiltration membranes deposited with different metal oxides (i.e., TiO2, Fe2O3, MnO2, CuO, and CeO2) of around 10 nm in thickness and similar roughness were tested for O/W emulsion treatment. A distinct membrane fouling tendency was observed, which closely correlated to the properties of the filtration-layer metal oxides (i.e., surface hydroxyl groups, hydrophilicity, surface charge, and adhesion energy for oil droplets). Consistent with the distinct bond strength of the surface hydroxyl groups, hydrophilicity of these common metal oxides is quite different. The differences in hydrophilicity consequently lead to different adhesion of these metal oxides toward oil droplets, consistent with the irreversible membrane fouling tendency. In addition, the surface charge of the metal oxide opposite to that of emulsion can help to alleviate irreversible membrane fouling in ultrafiltration. Highly hydrophilic Fe2O3 with the lowest fouling tendency could be a potential filtration-layer material for the fabrication/modification of ceramic membranes for O/W emulsion treatment. To the best of our knowledge, this is the first study clearly showing the correlations between surface properties of filtration-layer metal oxides and ceramic membrane fouling tendency by O/W emulsion.

Influence of surface properties of filtration-layer metal oxide on ceramic membrane fouling during ultrafiltration of oil/water emulsion

KAUST Repository

Lu, Dongwei; Zhang, Tao; Gutierrez, Leo; Ma, Jun; Croue, Jean-Philippe

2016-01-01

In this work, ceramic ultrafiltration membranes deposited with different metal oxides (i.e., TiO2, Fe2O3, MnO2, CuO, and CeO2) of around 10 nm in thickness and similar roughness were tested for O/W emulsion treatment. Distinct membrane fouling tendency was observed, which closely correlated to the properties of the filtration-layer metal oxides (i.e. surface hydroxyl groups, hydrophilicity, surface charge, and adhesion energy for oil droplets). In consistent with the distinct bond strength of the surface hydroxyl groups, hydrophilicity of these common metal oxides are quite different. The differences in hydrophilicity consequently lead to different adhesion of these metal oxides towards oil droplets which consists very well with irreversible membrane fouling tendency. In addition, the surface charge of the metal oxide opposite to that of emulsion can help to alleviate irreversible membrane fouling in ultrafiltration. Highly hydrophilic Fe2O3 with lowest fouling tendency could be a potential filtration-layer material for the fabrication/modification of ceramic membranes for O/W emulsion treatment. To the best of our knowledge, this is the first study clearly showing the correlations between surface properties of filtration-layer metal oxides and ceramic membrane fouling tendency by O/W emulsion.

Influence of surface properties of filtration-layer metal oxide on ceramic membrane fouling during ultrafiltration of oil/water emulsion

KAUST Repository

Lu, Dongwei

2016-04-01

In this work, ceramic ultrafiltration membranes deposited with different metal oxides (i.e., TiO2, Fe2O3, MnO2, CuO, and CeO2) of around 10 nm in thickness and similar roughness were tested for O/W emulsion treatment. Distinct membrane fouling tendency was observed, which closely correlated to the properties of the filtration-layer metal oxides (i.e. surface hydroxyl groups, hydrophilicity, surface charge, and adhesion energy for oil droplets). In consistent with the distinct bond strength of the surface hydroxyl groups, hydrophilicity of these common metal oxides are quite different. The differences in hydrophilicity consequently lead to different adhesion of these metal oxides towards oil droplets which consists very well with irreversible membrane fouling tendency. In addition, the surface charge of the metal oxide opposite to that of emulsion can help to alleviate irreversible membrane fouling in ultrafiltration. Highly hydrophilic Fe2O3 with lowest fouling tendency could be a potential filtration-layer material for the fabrication/modification of ceramic membranes for O/W emulsion treatment. To the best of our knowledge, this is the first study clearly showing the correlations between surface properties of filtration-layer metal oxides and ceramic membrane fouling tendency by O/W emulsion.

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

Science.gov (United States)

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.

A combined SEM, CV and EIS study of multi-layered porous ceramic reactors for flue gas purification

DEFF Research Database (Denmark)

He, Zeming; Andersen, Kjeld Bøhm; Nygaard, Frederik Berg

2013-01-01

The effect of sintering temperature of 12-layered porous ceramic reactors (comprising 5 cells) was studied using scanning electron microscopy (SEM), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The difference in microstructures of the reactors was evaluated by SEM...

Plastic damage induced fracture behaviors of dental ceramic layer structures subjected to monotonic load.

Science.gov (United States)

Wang, Raorao; Lu, Chenglin; Arola, Dwayne; Zhang, Dongsheng

2013-08-01

The aim of this study was to compare failure modes and fracture strength of ceramic structures using a combination of experimental and numerical methods. Twelve specimens with flat layer structures were fabricated from two types of ceramic systems (IPS e.max ceram/e.max press-CP and Vita VM9/Lava zirconia-VZ) and subjected to monotonic load to fracture with a tungsten carbide sphere. Digital image correlation (DIC) and fractography technology were used to analyze fracture behaviors of specimens. Numerical simulation was also applied to analyze the stress distribution in these two types of dental ceramics. Quasi-plastic damage occurred beneath the indenter in porcelain in all cases. In general, the fracture strength of VZ specimens was greater than that of CP specimens. The crack initiation loads of VZ and CP were determined as 958 ± 50 N and 724 ± 36 N, respectively. Cracks were induced by plastic damage and were subsequently driven by tensile stress at the elastic/plastic boundary and extended downward toward to the veneer/core interface from the observation of DIC at the specimen surface. Cracks penetrated into e.max press core, which led to a serious bulk fracture in CP crowns, while in VZ specimens, cracks were deflected and extended along the porcelain/zirconia core interface without penetration into the zirconia core. The rupture loads for VZ and CP ceramics were determined as 1150 ± 170 N and 857 ± 66 N, respectively. Quasi-plastic deformation (damage) is responsible for crack initiation within porcelain in both types of crowns. Due to the intrinsic mechanical properties, the fracture behaviors of these two types of ceramics are different. The zirconia core with high strength and high elastic modulus has better resistance to fracture than the e.max core. © 2013 by the American College of Prosthodontists.

Microstructures and properties of ceramic particle-reinforced metal matrix composite layers produced by laser cladding

Science.gov (United States)

Zhang, Qingmao; He, Jingjiang; Liu, Wenjin; Zhong, Minlin

2005-01-01

Different weight ratio of titanium, zirconium, WC and Fe-based alloy powders were mixed, and cladded onto a medium carbon steel substrate using a 3kW continuous wave CO2 laser, aiming at producing Ceramic particles- reinforced metal matrix composites (MMCs) layers. The microstructures of the layers are typical hypoeutectic, and the major phases are Ni3Si2, TiSi2, Fe3C, FeNi, MC, Fe7Mo3, Fe3B, γ(residual austenite) and M(martensite). The microstructure morphologies of MMCs layers are dendrites/cells. The MC-type reinforcements are in situ synthesis Carbides which main compositions consist of transition elements Zr, Ti, W. The MC-type particles distributed within dendrite and interdendritic regions with different volume fractions for single and overlapping clad layers. The MMCs layers are dense and free of cracks with a good metallurgical bonding between the layer and substrate. The addition ratio of WC in the mixtures has the remarkable effect on the microhardness of clad layers.

TRIS buffer in simulated body fluid distorts the assessment of glass-ceramic scaffold bioactivity.

Science.gov (United States)

Rohanová, Dana; Boccaccini, Aldo Roberto; Yunos, Darmawati Mohamad; Horkavcová, Diana; Březovská, Iva; Helebrant, Aleš

2011-06-01

The paper deals with the characterisation of the bioactive phenomena of glass-ceramic scaffold derived from Bioglass® (containing 77 wt.% of crystalline phases Na(2)O·2CaO·3SiO(2) and CaO·SiO(2) and 23 wt.% of residual glass phase) using simulated body fluid (SBF) buffered with tris-(hydroxymethyl) aminomethane (TRIS). A significant effect of the TRIS buffer on glass-ceramic scaffold dissolution in SBF was detected. To better understand the influence of the buffer, the glass-ceramic scaffold was exposed to a series of in vitro tests using different media as follows: (i) a fresh liquid flow of SBF containing tris (hydroxymethyl) aminomethane; (ii) SBF solution without TRIS buffer; (iii) TRIS buffer alone; and (iv) demineralised water. The in vitro tests were provided under static and dynamic arrangements. SBF buffered with TRIS dissolved both the crystalline and residual glass phases of the scaffold and a crystalline form of hydroxyapatite (HAp) developed on the scaffold surface. In contrast, when TRIS buffer was not present in the solutions only the residual glassy phase dissolved and an amorphous calcium phosphate (Ca-P) phase formed on the scaffold surface. It was confirmed that the TRIS buffer primarily dissolved the crystalline phase of the glass-ceramic, doubled the dissolving rate of the scaffold and moreover supported the formation of crystalline HAp. This significant effect of the buffer TRIS on bioactive glass-ceramic scaffold degradation in SBF has not been demonstrated previously and should be considered when analysing the results of SBF immersion bioactivity tests of such systems. Copyright © 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Method for improving the performance of oxidizable ceramic materials in oxidizing environments

Science.gov (United States)

Nagaraj, Bangalore A. (Inventor)

2002-01-01

Improved adhesion of thermal barrier coatings to nonmetallic substrates using a dense layer of ceramic on an underlying nonmetallic substrate that includes at least one oxidizable component. The improved adhesion occurs because the application of the dense ceramic layer forms a diffusion barrier for oxygen. This diffusion barrier prevents the oxidizable component of the substrate from decomposing. The present invention applies ceramic by a process that deposits a relatively thick and dense ceramic layer on the underlying substrate. The formation of the dense layer of ceramic avoids the problem of void formation associated with ceramic formation by most prior art thermal decomposition processes. The formation of voids has been associated with premature spalling of thermal barrier layers and other protective layers applied to substrates.

Method of sintering ceramic materials

Science.gov (United States)

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.

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

Science.gov (United States)

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

2018-06-01

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

CVD synthesis of large-area, highly crystalline MoSe2 atomic layers on diverse substrates and application to photodetectors.

Science.gov (United States)

Xia, Jing; Huang, Xing; Liu, Ling-Zhi; Wang, Meng; Wang, Lei; Huang, Ben; Zhu, Dan-Dan; Li, Jun-Jie; Gu, Chang-Zhi; Meng, Xiang-Min

2014-08-07

Synthesis of large-area, atomically thin transition metal dichalcogenides (TMDs) on diverse substrates is of central importance for the large-scale fabrication of flexible devices and heterojunction-based devices. In this work, we successfully synthesized a large area of highly-crystalline MoSe2 atomic layers on SiO2/Si, mica and Si substrates using a simple chemical vapour deposition (CVD) method at atmospheric pressure. Atomic force microscopy (AFM) and Raman spectroscopy reveal that the as-grown ultrathin MoSe2 layers change from a single layer to a few layers. Photoluminescence (PL) spectroscopy demonstrates that while the multi-layer MoSe2 shows weak emission peaks, the monolayer has a much stronger emission peak at ∼ 1.56 eV, indicating the transition from an indirect to a direct bandgap. Transmission electron microscopy (TEM) analysis confirms the single-crystallinity of MoSe2 layers with a hexagonal structure. In addition, the photoresponse performance of photodetectors based on MoSe2 monolayer was studied for the first time. The devices exhibit a rapid response of ∼ 60 ms and a good photoresponsivity of ∼ 13 mA/W (using a 532 nm laser at an intensity of 1 mW mm(-2) and a bias of 10 V), suggesting that MoSe2 monolayer is a promising material for photodetection applications.

Ceramic Electron Multiplier

International Nuclear Information System (INIS)

Comby, G.

1996-01-01

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)

Electrical and physical characteristics for crystalline atomic layer deposited beryllium oxide thin film on Si and GaAs substrates

International Nuclear Information System (INIS)

Yum, J.H.; Akyol, T.; Lei, M.; Ferrer, D.A.; Hudnall, Todd W.; Downer, M.; Bielawski, C.W.; Bersuker, G.; Lee, J.C.; Banerjee, S.K.

2012-01-01

In a previous study, atomic layer deposited (ALD) BeO exhibited less interface defect density and hysteresis, as well as less frequency dispersion and leakage current density, at the same equivalent oxide thickness than Al 2 O 3 . Furthermore, its self-cleaning effect was better. In this study, the physical and electrical characteristics of ALD BeO grown on Si and GaAs substrates are further evaluated as a gate dielectric layer in III–V metal-oxide-semiconductor devices using transmission electron microscopy, selective area electron diffraction, second harmonic generation, and electrical analysis. An as-grown ALD BeO thin film was revealed as a layered single crystal structure, unlike the well-known ALD dielectrics that exhibit either poly-crystalline or amorphous structures. Low defect density in highly ordered ALD BeO film, less variability in electrical characteristics, and great stability under electrical stress were demonstrated. - Highlights: ► BeO is an excellent electrical insulator, but good thermal conductor. ► Highly crystalline film of BeO has been grown using atomic layer deposition. ► An ALD BeO precursor, which is not commercially available, has been synthesized. ► Physical and electrical characteristics have been investigated.

Graphene on insulating crystalline substrates

International Nuclear Information System (INIS)

Akcoeltekin, S; El Kharrazi, M; Koehler, B; Lorke, A; Schleberger, M

2009-01-01

We show that it is possible to prepare and identify ultra-thin sheets of graphene on crystalline substrates such as SrTiO 3 , TiO 2 , Al 2 O 3 and CaF 2 by standard techniques (mechanical exfoliation, optical and atomic force microscopy). On the substrates under consideration we find a similar distribution of single layer, bilayer and few-layer graphene and graphite flakes as with conventional SiO 2 substrates. The optical contrast C of a single graphene layer on any of those substrates is determined by calculating the optical properties of a two-dimensional metallic sheet on the surface of a dielectric, which yields values between C = -1.5% (G/TiO 2 ) and C = -8.8% (G/CaF 2 ). This contrast is in reasonable agreement with experimental data and is sufficient to make identification by an optical microscope possible. The graphene layers cover the crystalline substrate in a carpet-like mode and the height of single layer graphene on any of the crystalline substrates as determined by atomic force microscopy is d SLG = 0.34 nm and thus much smaller than on SiO 2 .

Liquid-like thermal conduction in intercalated layered crystalline solids

Science.gov (United States)

Li, B.; Wang, H.; Kawakita, Y.; Zhang, Q.; Feygenson, M.; Yu, H. L.; Wu, D.; Ohara, K.; Kikuchi, T.; Shibata, K.; Yamada, T.; Ning, X. K.; Chen, Y.; He, J. Q.; Vaknin, D.; Wu, R. Q.; Nakajima, K.; Kanatzidis, M. G.

2018-03-01

As a generic property, all substances transfer heat through microscopic collisions of constituent particles1. A solid conducts heat through both transverse and longitudinal acoustic phonons, but a liquid employs only longitudinal vibrations2,3. As a result, a solid is usually thermally more conductive than a liquid. In canonical viewpoints, such a difference also serves as the dynamic signature distinguishing a solid from a liquid. Here, we report liquid-like thermal conduction observed in the crystalline AgCrSe2. The transverse acoustic phonons are completely suppressed by the ultrafast dynamic disorder while the longitudinal acoustic phonons are strongly scattered but survive, and are thus responsible for the intrinsically ultralow thermal conductivity. This scenario is applicable to a wide variety of layered compounds with heavy intercalants in the van der Waals gaps, manifesting a broad implication on suppressing thermal conduction. These microscopic insights might reshape the fundamental understanding on thermal transport properties of matter and open up a general opportunity to optimize performances of thermoelectrics.

Ceramic Composite Thin Films

Science.gov (United States)

Ruoff, Rodney S. (Inventor); Stankovich, Sasha (Inventor); Dikin, Dmitriy A. (Inventor); Nguyen, SonBinh T. (Inventor)

2013-01-01

A ceramic composite thin film or layer includes individual graphene oxide and/or electrically conductive graphene sheets dispersed in a ceramic (e.g. silica) matrix. The thin film or layer can be electrically conductive film or layer depending the amount of graphene sheets present. The composite films or layers are transparent, chemically inert and compatible with both glass and hydrophilic SiOx/silicon substrates. The composite film or layer can be produced by making a suspension of graphene oxide sheet fragments, introducing a silica-precursor or silica to the suspension to form a sol, depositing the sol on a substrate as thin film or layer, at least partially reducing the graphene oxide sheets to conductive graphene sheets, and thermally consolidating the thin film or layer to form a silica matrix in which the graphene oxide and/or graphene sheets are dispersed.

Coating of carbon short fibers with thin ceramic layers by chemical vapor deposition

International Nuclear Information System (INIS)

Hackl, Gerrit; Gerhard, Helmut; Popovska, Nadejda

2006-01-01

Carbon short fiber bundles with a length of 6 mm were uniformly coated using specially designed, continuous chemical vapor deposition (CVD) equipment. Thin layers of titanium nitride, silicon nitride (SiC) and pyrolytic carbon (pyC) were deposited onto several kilograms of short fibers in this large scale CVD reactor. Thermo-gravimetric analyses and scanning electron microscopy investigations revealed layer thicknesses between 20 and 100 nm on the fibers. Raman spectra of pyC coated fibers show a change of structural order depending on the CVD process parameters. For the fibers coated with SiC, Raman investigations showed a deposition of amorphous SiC. The coated carbon short fibers will be applied as reinforcing material in composites with ceramic and metallic matrices

Melt processed crystalline ceramic waste forms for advanced nuclear fuel cycles: CRP T21027 1813: Processing technologies for high level waste, formulation of matrices and characterization of waste forms, Task 17208: Final report

Energy Technology Data Exchange (ETDEWEB)

Amoroso, J. W. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Marra, J. C. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

2015-08-26

A multi-phase ceramic waste form is being developed at the Savannah River National Laboratory (SRNL) for treatment of secondary waste streams generated by reprocessing commercial spent nuclear. The envisioned waste stream contains a mixture of transition, alkali, alkaline earth, and lanthanide metals. Ceramic waste forms are tailored (engineered) to incorporate waste components as part of their crystal structure based on knowledge from naturally found minerals containing radioactive and non-radioactive species similar to the radionuclides of concern in wastes from fuel reprocessing. The ability to tailor ceramics to mimic naturally occurring crystals substantiates the long term stability of such crystals (ceramics) over geologic timescales of interest for nuclear waste immobilization [1]. A durable multi-phase ceramic waste form tailored to incorporate all the waste components has the potential to broaden the available disposal options and thus minimize the storage and disposal costs associated with aqueous reprocessing. This report summarizes results from three years of work on the IAEA Coordinated Research Project on “Processing technologies for high level waste, formulation of matrices and characterization of waste forms” (T21027), and specific task “Melt Processed Crystalline Ceramic Waste Forms for Advanced Nuclear Fuel Cycles” (17208).

Melt processed crystalline ceramic waste forms for advanced nuclear fuel cycles: CRP T21027 1813: Processing technologies for high level waste, formulation of matrices and characterization of waste forms, task 17208: Final report

Energy Technology Data Exchange (ETDEWEB)

Amoroso, J. W. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Marra, J. C. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

2015-08-26

A multi-phase ceramic waste form is being developed at the Savannah River National Laboratory (SRNL) for treatment of secondary waste streams generated by reprocessing commercial spent nuclear. The envisioned waste stream contains a mixture of transition, alkali, alkaline earth, and lanthanide metals. Ceramic waste forms are tailored (engineered) to incorporate waste components as part of their crystal structure based on knowledge from naturally found minerals containing radioactive and non-radioactive species similar to the radionuclides of concern in wastes from fuel reprocessing. The ability to tailor ceramics to mimic naturally occurring crystals substantiates the long term stability of such crystals (ceramics) over geologic timescales of interest for nuclear waste immobilization [1]. A durable multi-phase ceramic waste form tailored to incorporate all the waste components has the potential to broaden the available disposal options and thus minimize the storage and disposal costs associated with aqueous reprocessing. This report summarizes results from three years of work on the IAEA Coordinated Research Project on “Processing technologies for high level waste, formulation of matrices and characterization of waste forms” (T21027), and specific task “Melt Processed Crystalline Ceramic Waste Forms for Advanced Nuclear Fuel Cycles” (17208).

Bioactivity and cytotoxicity of glass and glass-ceramics based on the 3CaO·P₂O₅--SiO₂--MgO system.

Science.gov (United States)

Daguano, Juliana K M F; Rogero, Sizue O; Crovace, Murilo C; Peitl, Oscar; Strecker, Kurt; Dos Santos, Claudinei

2013-09-01

The mechanical strength of bioactive glasses can be improved by controlled crystallization, turning its use as bulk bone implants viable. However, crystallization may affect the bioactivity of the material. The aim of this study was to develop glass-ceramics of the nominal composition (wt%) 52.75(3CaO·P₂O₅)-30SiO₂-17.25MgO, with different crystallized fractions and to evaluate their in vitro cytotoxicity and bioactivity. Specimens were heat-treated at 700, 775 and 975 °C, for 4 h. The major crystalline phase identified was whitlockite, an Mg-substituted tricalcium phosphate. The evaluation of the cytotoxicity was carried out by the neutral red uptake methodology. Ionic exchanges with the simulated body fluid SBF-K9 acellular solution during the in vitro bioactivity tests highlight the differences in terms of chemical reactivity between the glass and the glass-ceramics. The effect of crystallinity on the rates of hydroxycarbonate apatite (HCA) formation was followed by Fourier transformed infrared spectroscopy. Although all glass-ceramics can be considered bioactive, the glass-ceramic heat-treated at 775 °C (V775-4) presented the most interesting result, because the onset for HCA formation is at about 24 h and after 7 days the HCA layer dominates completely the spectrum. This occurs probably due to the presence of the whitlockite phase (3(Ca,Mg)O·P₂O₅). All samples were considered not cytotoxic.

Strategies for fracture toughness, strength and reliability optimisation of ceramic-ceramic laminates

Czech Academy of Sciences Publication Activity Database

Šestáková, L.; Bermejo, R.; Chlup, Zdeněk; Danzer, R.

2011-01-01

Roč. 102, č. 6 (2011), s. 613-626 ISSN 1862-5282 Institutional research plan: CEZ:AV0Z20410507 Keywords : Ceramic laminates * Layered ceramics * Residual stress * Fracture toughness * Threshold strength Subject RIV: JL - Materials Fatigue, Friction Mechanics Impact factor: 0.830, year: 2011

Preparation and spectral analysis of a new Tb3+-doped CaO-MgO-SiO2 glass ceramics

International Nuclear Information System (INIS)

Cheng Jinshu; Tian Peijing; Zheng Weihong; Xie Jun; Chen Zhenxia

2009-01-01

Tb 3+ -doped CaO-MgO-SiO 2 glass ceramics have been prepared and characterized. The structure and optical properties of the glass ceramics were studied by XRD, SEM, Raman, and fluorescence spectra. The precipitated crystalline phase in the glass ceramics was columnar CaMgSi 2 O 6 . Raman spectra showed the introduction of rare earth nearly had no influence on the sample structure. Fluorescence measurements showed that Tb 3+ ions entered into the diopside crystalline phase and induced a much stronger emission in the glass ceramics than that in the corresponding glass. With increase of Tb 3+ content and the introduction of Gd 3+ , the fluorescence intensity of the luminescent glass ceramic increased

Polyphase ceramic and glass-ceramic forms for immobilizing ICPP high-level nuclear waste

International Nuclear Information System (INIS)

Harker, A.B.; Flintoff, J.F.

1984-01-01

Polyphase ceramic and glass-ceramic forms have been consolidated from simulated Idaho Chemical Processing Plant wastes by hot isostatic pressing calcined waste and chemical additives by 1000 0 C or less. The ceramic forms can contain over 70 wt% waste with densities ranging from 3.5 to 3.85 g/cm 3 , depending upon the formulation. Major phases are CaF 2 , CaZrTi 207 , CaTiO 3 , monoclinic ZrO 2 , and amorphous intergranular material. The relative fraction of the phases is a function of the chemical additives (TiO 2 , CaO, and SiO 2 ) and consolidation temperature. Zirconolite, the major actinide host, makes the ceramic forms extremely leach resistant for the actinide simulant U 238 . The amorphous phase controls the leach performance for Sr and Cs which is improved by the addition of SiO 2 . Glass-ceramic forms were also consolidated by HIP at waste loadings of 30 to 70 wt% with densities of 2.73 to 3.1 g/cm 3 using Exxon 127 borosilicate glass frit. The glass-ceramic forms contain crystalline CaF 2 , Al 203 , and ZrSi 04 (zircon) in a glass matrix. Natural mineral zircon is a stable host for 4+ valent actinides. 17 references, 3 figures, 5 tables

Crystallization and properties of a spodumene-willemite glass ceramic

International Nuclear Information System (INIS)

Hu, A.M.; Li, M.; Dali, D.L. Mao; Liang, K.M.

2005-01-01

Spodumene-willemite glass ceramics were produced by replacement of Al 2 O 3 in lithium aluminium silicate by ZnO. With replacement of Al 2 O 3 by ZnO, the batch melting temperature, glass transition temperature (T g ) and crystallization temperature (T p ) all decreased. The main crystalline phases precipitated were eucriptite, β-spodumene and willemite (Zn 2 SiO 4 ). All compositions of glass ceramics showed bulk crystallization. As ZnO content increased, the grain sizes and thermal expansion coefficients increased, while the flexural strength and fracture toughness of the glass-ceramics increased first, and then decreased. The mechanical properties were correlated with crystallization and morphology of glass ceramics

A standardless method of quantitative ceramic analysis using X-ray powder diffraction

International Nuclear Information System (INIS)

Mazumdar, S.

1999-01-01

A new procedure using X-ray powder diffraction data for quantitative estimation of the crystalline as well as the amorphous phase in ceramics is described. Classification of the crystalline and amorphous X-ray scattering was achieved by comparison of the slopes at two successive points of the powder pattern at scattering angles at which the crystalline and amorphous phases superimpose. If the second slope exceeds the first by a stipulated value, the intensity is taken as crystalline; otherwise the scattering is considered as amorphous. Crystalline phase analysis is obtained by linear programming techniques using the concept that each observed X-ray diffraction peak has contributions from n component phases, the proportionate analysis of which is required. The method does not require the measurement of calibration data for use as an internal standard, but knowledge of the approximate crystal structure of each phase of interest in the mixture is necessary. The technique is also helpful in qualitative analysis because each suspected phase is characterized by the probability that it will be present when a reflection zone is considered in which the suspected crystalline phase could contribute. The amorphous phases are determined prior to the crystalline ones. The method is applied to ceramic materials and some results are presented. (orig.)

Crystallinity and superconductivity of as-grown MgB2 thin films with AlN buffer layers

International Nuclear Information System (INIS)

Tsujimoto, K.; Shimakage, H.; Wang, Z.; Kaya, N.

2005-01-01

The effects of aluminum nitride (AlN) buffer layers on the superconducting properties of MgB 2 thin film were investigated. The AlN buffer layers and as-grown MgB 2 thin films were deposited in situ using the multiple-target sputtering system. The best depositing condition for the AlN/MgB 2 bi-layer occurred when the AlN was deposited on c-cut sapphire substrates at 290 deg. C. The crystallinity of the AlN/MgB 2 bi-layer was studied using the XRD φ-scan and it showed that AlN and MgB 2 had the same in-plane alignment rotated at an angle of 30 deg. as compared to c-cut sapphire. The critical temperature of the MgB 2 film was 29.8 K and the resistivity was 50.0 μΩ cm at 40 K

Assessment of DNA damage in ceramic workers.

Science.gov (United States)

Anlar, Hatice Gul; Taner, Gokce; Bacanli, Merve; Iritas, Servet; Kurt, Turker; Tutkun, Engin; Yilmaz, Omer Hinc; Basaran, Nursen

2018-02-24

It is known that ceramic workers are potentially exposed to complex mixture of chemicals such as silica, inorganic lead, lime, beryllium and aluminum that can be associated with an increased risk of several diseases. All operations in the ceramic industries such as mixing, moulding, casting, shaking out and finishing jobs, have been associated with the higher exposure levels and in most of the silica-related industries, average overall exposure exceeded permissible exposure levels for respirable crystalline silica. The aim of this study was to evaluate the possible genotoxic damage in ceramic workers exposed to complex mixture of chemicals mainly crystalline silica. For this purpose, the blood and buccal epithelial cell samples were taken from the ceramic workers (n = 99) and their controls (n = 81). The genotoxicity was assessed by the alkaline comet assay in isolated lymphocytes and whole blood. Micronucleus (MN), binucleated (BN), pyknotic (PYC), condensed chromatin (CC), karyolytic (KYL), karyorrhectic (KHC) and nuclear bud (NBUD) frequencies in buccal epithelial cells and plasma 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) levels were also evaluated. In the study, 38 workers were diagnosed with silicosis, 9 workers were suspected to have silicosis, whereas 52 workers were found to be healthy. DNA damage in blood and lymphocytes; MN, CC + KHC, PYC frequencies in buccal epithelial cells and 8-oxodG levels in plasma were increased in workers compared to their controls. These results showed that occupational chemical mixture exposure in ceramic industry may cause genotoxic damage that can lead to important health problems in the workers.

Hot isostatically-pressed aluminosilicate glass-ceramic with natural crystalline analogues for immobilizing the calcined high-level nuclear waste at the Idaho Chemical Processing Plant

International Nuclear Information System (INIS)

Raman, S.

1993-12-01

The additives Si, Al, MgO, P 2 O 5 were mechanically blended with fluorinelsodium calcine in varying proportions. The batches were vacuum sealed in stainless steel canisters and hot isostatically pressed at 20,000 PSI and 1000 C for 4 hours. The resulting suite of glass-ceramic waste forms parallels the natural rocks in microstructural and compositional heterogeneity. Several crystalline phases ar analogous in composition and structure to naturally occurring minerals. Additional crystalline phases are zirconia and Ca-Mg borate. The glasses are enriched in silica and alumina. Approximately 7% calcine elements occur dissolved in this glass and the total glass content in the waste forms averages 20 wt%. The remainder of the calcine elements are partitioned into crystalline phases at 75 wt% calcine waste loading. The waste forms were tested for chemical durability in accordance with the MCC1-test procedure. The leach rates are a function of the relative proportions of additives and calcine, which in turn influence the composition and abundances of the glass and crystalline phases. The DOE leach rate criterion of less than 1 g/m 2 -day is met by all the elements B, Cs and Na are increased by lowering the melt viscosity. This is related to increased crystallization or devitrification with increases in MgO addition. This exploratory work has shown that the increases in waste loading occur by preferred partitioning of the calcine components among crystalline and glass phases. The determination of optimum processing parameters in the form of additive concentration levels, homogeneous blending among the components, and pressure-temperature stabilities of phases must be continued to eliminate undesirable effects of chemical composition, microstructure and glass devitrification

Elaboration of new ceramic composites containing glass fibre production wastes

International Nuclear Information System (INIS)

Rozenstrauha, I.; Sosins, G.; Krage, L.; Sedmale, G.; Vaiciukyniene, D.

2013-01-01

Two main by-products or waste from the production of glass fibre are following: sewage sludge containing montmorillonite clay as sorbent material and ca 50 % of organic matter as well as waste glass from aluminium borosilicate glass fibre with relatively high softening temperature (> 600 degree centigrade). In order to elaborate different new ceramic products (porous or dense composites) the mentioned by-products and illitic clay from two different layers of Apriki deposit (Latvia) with illite content in clay fraction up to 80-90 % was used as a matrix. The raw materials were investigated by differential-thermal (DTA) and XRD analysis. Ternary compositions were prepared from mixtures of 15 - 35 wt % of sludge, 20 wt % of waste glass and 45 - 65 wt % of clay and the pressed green bodies were thermally treated in sintering temperature range from 1080 to 1120 degree centigrade in different treatment conditions. Materials produced in temperature range 1090 - 1100 degree centigrade with the most optimal properties - porosity 38 - 52 %, water absorption 39 -47 % and bulk density 1.35 - 1.67 g/cm 3 were selected for production of porous ceramics and materials showing porosity 0.35 - 1.1 %, water absorption 0.7 - 2.6 % and bulk density 2.1 - 2.3 g/cm 3 - for dense ceramic composites. Obtained results indicated that incorporation up to 25 wt % of sewage sludge is beneficial for production of both ceramic products and glass-ceramic composites according to the technological properties. Structural analysis of elaborated composite materials was performed by scanning electron microscopy(SEM). By X-ray diffraction analysis (XRD) the quartz, diopside and anorthite crystalline phases were detected. (Author)

Ceramic to metal joining by using 1064 nm pulsed and CW laser energy source

International Nuclear Information System (INIS)

Lee, Young Min; Kim, Soo Won; Choi, Hae Woon; Kim, Joo Han

2013-01-01

A novel joining method for ceramic and metallic layers is proposed using laser drilling and surface tension driven liquid metal filling. A high intensity laser beam irradiated a 500 µm thick ceramic filter, and the irradiated laser drilled the ceramic layer. The pulsed or CW laser transmitted through the ceramic layer irradiated the bottom metallic layer; the molten metallic layer then filled the drilled ceramic holes by the capillary force between the liquid metal and ceramic layer. As process variables, average laser power, pulse duration, and the number of pulses were used. The scattering optical properties were also studied for both green and red lasers. There was no significant difference between the colors and the estimated extinction coefficients were -26.94 1/mm and -28.42 1/mm for the green and red lasers, respectively.

Factors controlling crystallization of miserite glass-ceramic.

Science.gov (United States)

Muhammed, Fenik K; Moorehead, Robert; van Noort, Richard; Pollington, Sarah

2015-12-01

The purpose of this study was to investigate a range of variables affecting the synthesis of a miserite glass-ceramic (GC). Miserite glass was synthesized by the melt quench technique. The crystallization kinetics of the glass were determined using Differential Thermal Analysis (DTA). The glasses were ground with dry ball-milling and then sieved to different particle sizes prior to sintering. These particle sizes were submitted to heat treatment regimes in a high temperature furnace to form the GC. The crystal phases of the GC were analyzed by X-ray diffraction (XRD). Scanning electron microscopy (SEM) was used to examine the microstructure of the cerammed glass. XRD analysis confirmed that the predominant crystalline phase of the GC was miserite along with a minor crystalline phase of cristobalite only when the particle size is <20 μm and the heat treatment at 1000°C was carried out for 4h and slowly cooled at the furnace rate. For larger particle sizes and faster cooling rates, a pseudowollastonite crystalline phase was produced. Short sintering times produced either a pseudowollastonite or xonotolite crystalline phase. The current study has shown that particle size and heat treatment schedules are major factors in controlling the synthesis of miserite GC. Copyright © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Electrical machining method of insulating ceramics

International Nuclear Information System (INIS)

Fukuzawa, Y.; Mohri, N.; Tani, T.

1999-01-01

This paper describes a new electrical discharge machining method for insulating ceramics using an assisting electrode with either a sinking electrical discharge machine or a wire electrical discharge machine. In this method, the metal sheet or mesh is attached to the ceramic surface as an assisting material for the discharge generation around the insulator surface. When the machining condition changes from the attached material to the workpiece, a cracked carbon layer is formed on the workpiece surface. As this layer has an electrical conductivity, electrical discharge occurs in working oil between the tool electrode and the surface of the workpiece. The carbon is formed from the working oil during this electrical discharge. Even after the material is machined, an electrical discharge occurs in the gap region between the tool electrode and the ceramic because an electrically conductive layer is generated continuously. Insulating ceramics can be machined by the electrical discharge machining method using the above mentioned surface modification phenomenon. In this paper the authors show a machined example demonstrating that the proposed method is available for machining a complex shape on insulating ceramics. Copyright (1999) AD-TECH - International Foundation for the Advancement of Technology Ltd

Glass Ceramic Waste Forms for Combined CS+LN+TM Fission Products Waste Streams

International Nuclear Information System (INIS)

Crum, Jarrod V.; Turo, Laura A.; Riley, Brian J.; Tang, Ming; Kossoy, Anna; Sickafus, Kurt E.

2010-01-01

In this study, glass ceramics were explored as an alternative waste form for glass, the current baseline, to be used for immobilizing alkaline/alkaline earth + lanthanide (CS+LN) or CS+LN+transition metal (TM) fission-product waste streams generated by a uranium extraction (UREX+) aqueous separations type process. Results from past work on a glass waste form for the combined CS+LN waste streams showed that as waste loading increased, large fractions of crystalline phases precipitated upon slow cooling.(1) The crystalline phases had no noticeable impact on the waste form performance by the 7-day product consistency test (PCT). These results point towards the development of a glass ceramic waste form for treating CS+LN or CS+LN+TM combined waste streams. Three main benefits for exploring glass ceramics are: (1) Glass ceramics offer increased solubility of troublesome components in crystalline phases as compared to glass, leading to increased waste loading; (2) The crystalline network formed in the glass ceramic results in higher heat tolerance than glass; and (3) These glass ceramics are designed to be processed by the same melter technology as the current baseline glass waste form. It will only require adding controlled canister cooling for crystallization into a glass ceramic waste form. Highly annealed waste form (essentially crack free) with up to 50X lower surface area than a typical High-Level Waste (HLW) glass canister. Lower surface area translates directly into increased durability. This was the first full year of exploring glass ceramics for the Option 1 and 2 combined waste stream options. This work has shown that dramatic increases in waste loading are achievable by designing a glass ceramic waste form as an alternative to glass. Table S1 shows the upper limits for heat, waste loading (based on solubility), and the decay time needed before treatment can occur for glass and glass ceramic waste forms. The improvements are significant for both combined waste

Glass Ceramic Waste Forms for Combined CS+LN+TM Fission Products Waste Streams

Energy Technology Data Exchange (ETDEWEB)

Crum, Jarrod V.; Turo, Laura A.; Riley, Brian J.; Tang, Ming; Kossoy, Anna; Sickafus, Kurt E.

2010-09-23

In this study, glass ceramics were explored as an alternative waste form for glass, the current baseline, to be used for immobilizing alkaline/alkaline earth + lanthanide (CS+LN) or CS+LN+transition metal (TM) fission-product waste streams generated by a uranium extraction (UREX+) aqueous separations type process. Results from past work on a glass waste form for the combined CS+LN waste streams showed that as waste loading increased, large fractions of crystalline phases precipitated upon slow cooling.[1] The crystalline phases had no noticeable impact on the waste form performance by the 7-day product consistency test (PCT). These results point towards the development of a glass ceramic waste form for treating CS+LN or CS+LN+TM combined waste streams. Three main benefits for exploring glass ceramics are: (1) Glass ceramics offer increased solubility of troublesome components in crystalline phases as compared to glass, leading to increased waste loading; (2) The crystalline network formed in the glass ceramic results in higher heat tolerance than glass; and (3) These glass ceramics are designed to be processed by the same melter technology as the current baseline glass waste form. It will only require adding controlled canister cooling for crystallization into a glass ceramic waste form. Highly annealed waste form (essentially crack free) with up to 50X lower surface area than a typical High-Level Waste (HLW) glass canister. Lower surface area translates directly into increased durability. This was the first full year of exploring glass ceramics for the Option 1 and 2 combined waste stream options. This work has shown that dramatic increases in waste loading are achievable by designing a glass ceramic waste form as an alternative to glass. Table S1 shows the upper limits for heat, waste loading (based on solubility), and the decay time needed before treatment can occur for glass and glass ceramic waste forms. The improvements are significant for both combined waste

Low-Temperature Crystalline Titanium Dioxide by Atomic Layer Deposition for Dye-Sensitized Solar Cells

KAUST Repository

Chandiran, Aravind Kumar

2013-04-24

Low-temperature processing of dye-sensitized solar cells (DSCs) is crucial to enable commercialization with low-cost, plastic substrates. Prior studies have focused on mechanical compression of premade particles on plastic or glass substrates; however, this did not yield sufficient interconnections for good carrier transport. Furthermore, such compression can lead to more heterogeneous porosity. To circumvent these problems, we have developed a low-temperature processing route for photoanodes where crystalline TiO2 is deposited onto well-defined, mesoporous templates. The TiO2 is grown by atomic layer deposition (ALD), and the crystalline films are achieved at a growth temperature of 200 C. The ALD TiO2 thickness was systematically studied in terms of charge transport and performance to lead to optimized photovoltaic performance. We found that a 15 nm TiO2 overlayer on an 8 μm thick SiO2 film leads to a high power conversion efficiency of 7.1% with the state-of-the-art zinc porphyrin sensitizer and cobalt bipyridine redox mediator. © 2013 American Chemical Society.

Tuning Eu"3"+ emission in europium sesquioxide films by changing the crystalline phase

International Nuclear Information System (INIS)

Mariscal, A.; Quesada, A.; Camps, I.; Palomares, F.J.; Fernández, J.F.; Serna, R.

2016-01-01

Highlights: • PLD production of high quality europium sesquioxide (Eu_2O_3) films. • The deposition of Al_2O_3 capping and/or buffer layers modifies the crystallization for Eu_2O_3 films upon annealing. • The formation of cubic or monoclinic phases can be favored. • Eu"3"+ emission tuning is achieved as a consequence of crystal field effects. - Abstract: We report the growth of europium sesquioxide (Eu_2O_3) thin films by pulsed laser deposition (PLD) in vacuum at room temperature from a pure Eu_2O_3 ceramic bulk target. The films were deposited in different configurations formed by adding capping and/or buffer layers of amorphous aluminum oxide (a-Al_2O_3). The optical properties, refractive index and extinction coefficient of the as deposited Eu_2O_3 layers were obtained. X-ray photoelectron spectroscopy (XPS) measurements were done to assess its chemical composition. Post-deposition annealing was performed at 500 °C and 850 °C in air in order to achieve the formation of crystalline films and to accomplish photoluminescence emission. According to the analysis of X-ray diffraction (XRD) spectra, cubic and monoclinic phases were formed. It is found that the relative amount of the phases is related to the different film configurations, showing that the control over the crystallization phase can be realized by adequately designing the structures. All the films showed photoluminescence emission peaks (under excitation at 355 nm) that are attributed to the intra 4f-transitions of Eu"3"+ ions. The emission spectral shape depends on the crystalline phase of the Eu_2O_3 layer. Specifically, changes in the hypersensitive "5D_0 → "7F_2 emission confirm the strong influence of the crystal field effect on the Eu"3"+ energy levels.

Sintering mechanism of blast furnace slag-kaolin ceramics

International Nuclear Information System (INIS)

Mostafa, Nasser Y.; Shaltout, Abdallah A.; Abdel-Aal, Mohamed S.; El-maghraby, A.

2010-01-01

A general ceramics processing scheme by cold uniaxial pressing and conventional sintering process have been used to prepare ceramics from mixtures of blast furnace slag (BFS) and kaolin (10%, 30% and 50% kaolin). The properties of the ceramics were studied by measuring linear shrinkage, bulk density, apparent porosity and mechanical properties of samples heated at temperatures from 800 o C to 1100 o C. The formed crystalline phases were characterized using X-ray diffraction (XRD) and scanning electron microscope (SEM). Slag melt formed at relatively low temperatures (800-900 o C) modified the sintering process to liquid phase sintering mechanism. Combination of BFS with 10% kaolin gave the highest mechanical properties, densification and shrinkage at relatively low firing temperatures. The crystalline phases were identified as gehlenite (Ca 2 Al 2 SiO 7 ) in both BFS and BFS with 10% kaolin samples. Anorthite (CaAl 2 Si 2 O 8 ) phase increased with increasing kaolin contents. In the case of kaolin-rich mixtures (30% and 50% kaolin), increased expansion took place during firing at temperatures in the range 800-1000 o C. This effect could be attributed to the entrapment of released gases.

Understanding the edge crack phenomenon in ceramic laminates

Directory of Open Access Journals (Sweden)

O. Ševeček

2015-10-01

Full Text Available Layered ceramic materials (also referred to as “ceramic laminates” are becoming one of the most promising areas of materials technology aiming to improve the brittle behavior of bulk ceramics. The utilization of tailored compressive residual stresses acting as physical barriers to crack propagation has already succeeded in many ceramic systems. Relatively thick compressive layers located below the surface have proven very effective to enhance the fracture resistance and provide a minimum strength for the material. However, internal compressive stresses result in out-of plane stresses at the free surfaces, what can cause cracking of the compressive layer, forming the so-called edge cracks. Experimental observations have shown that edge cracking may be associated with the magnitude of the compressive stresses and with the thickness of the compressive layer. However, an understanding of the parameters related to the onset and extension of such edge cracks in the compressive layers is still lacking. In this work, a 2D parametric finite element model has been developed to predict the onset and propagation of an edge crack in ceramic laminates using a coupled stress-energy criterion. This approach states that a crack is originated when both stress and energy criteria are fulfilled simultaneously. Several designs with different residual stresses and a given thickness in the compressive layers have been computed. The results predict the existence of a lower bound, below no edge crack will be observed, and an upper bound, beyond which the onset of an edge crack would lead to the complete fracture of the layer

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

Science.gov (United States)

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

2018-01-01

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

Electronic Conductivity of Vanadium-Tellurite Glass-Ceramics

DEFF Research Database (Denmark)

Kjeldsen, Jonas; Yue, Yuanzheng; Bragatto, Caio B.

2013-01-01

In this paper, we investigate the electronic conductivity of 2TeO2-V2O5 glass-ceramics with crystallinity ranging from 0 to 100 wt.%, i.e., from entirely amorphous to completely crystalline. The glass is prepared by the melt quenching technique, and the crystal is prepared by subsequent heat...... spectroscopy. We find similar activation energies for both glass and crystal, implying that they have similar conduction mechanisms, i.e., thermally activated hopping. The electronic conductivity of 2TeO2-V2O5 glass is about one order of magnitude higher than that of the corresponding crystal......, and a percolation phenomenon occurs at a glass fraction of 61 wt.%, increasing from a lower conductivity in the crystal to a higher conductivity in the glass. We explain the behavior of electronic conduction in the 2TeO2-V2O5 glass-ceramics by considering constriction effects between particles as well...

Opalescence of all-ceramic core and veneer materials.

Science.gov (United States)

Cho, Moon-Sang; Yu, Bin; Lee, Yong-Keun

2009-06-01

The enamel of natural teeth is opalescent, where there is light scattering of the shorter wavelengths of the visible spectrum, giving a tooth a bluish appearance in the reflected color and an orange/brown appearance in the transmitted color. The objective of this study was to determine the opalescence of all-ceramic core, veneer and layered specimens with a color measuring spectrophotometer. Colors of core (A2-corresponding shade), veneer (A2- and A3-corresponding shades) and layered (A2- and A3-layered) ceramics for all-ceramic restorations in clinically relevant thicknesses were measured in the reflectance and transmittance modes. The opalescence parameter (OP), which was calculated as the difference in blue-yellow coordinate (Deltab(*)) and red-green coordinate (Deltaa(*)), and the differences in blue-yellow coordinate (Deltab(*)) and in color (DeltaE(ab)(*)) between the reflected and transmitted colors were calculated. One-way ANOVA was performed for the OP values of the core, veneer and layered specimens by the kind of materials. Regression analysis was performed between the OP and Deltab(*), and the OP and DeltaE(ab)(*) values. The range of the OP value was 1.6-6.1, 2.0-7.1, 1.3-5.0 and 1.6-4.2 for the core, veneer, A2- and A3-layered specimens, respectively, all of which were significantly influenced by the kind of materials (pOpalescence varied by kind of ceramics. The OP values of ceramics were lower than those of tooth enamel. All-ceramic materials that can simulate the opalescence of natural teeth should be developed.

Autophobicity and layering behavior of thin liquid-crystalline polymer films.

NARCIS (Netherlands)

Wielen, van der M.W.J.; Cohen Stuart, M.A.; Fleer, G.J.

1998-01-01

The stability against breaking-up of thin spin-coated films of liquid-crystalline polymers depends on the film thickness and annealing temperature. This study concerns side-chain liquid-crystalline polymers, based on alternating copolymers of maleic anhydride and mesogenic alkenes. The mesogenic

Microstructure and properties of Ti-Al intermetallic/Al2O3 layers produced on Ti6Al2Mo2Cr titanium alloy by PACVD method

Science.gov (United States)

Sitek, R.; Bolek, T.; Mizera, J.

2018-04-01

The paper presents investigation of microstructure and corrosion resistance of the multi-component surface layers built of intermetallic phases of the Ti-Al system and an outer Al2O3 ceramic sub-layer. The layers were produced on a two phase (α + β) Ti6Al2Mo2Cr titanium alloy using the PACVD method with the participation of trimethylaluminum vapors. The layers are characterized by a high surface hardness and good corrosion, better than that of these materials in the starting state. In order to find the correlation between their structure and properties, the layers were subjected to examinations using optical microscopy, X-ray diffraction analysis (XRD), surface analysis by XPS, scanning electron microscopy (SEM), and analyses of the chemical composition (EDS). The properties examined included: the corrosion resistance and the hydrogen absorptiveness. Moreover growth of the Al2O3 ceramic layer and its influence on the residual stress distribution was simulated using finite element method [FEM]. The results showed that the produced layer has amorphous-nano-crystalline structure, improved corrosion resistance and reduces the permeability of hydrogen as compared with the base material of Ti6Al2Mo2Cr -titanium alloy.

Interaction at interface between superconducting yttrium ceramics and copper or niobium

International Nuclear Information System (INIS)

Karpov, M.I.; Korzhov, V.P.; Medved', N.V.; Myshlyaeva, M.M.

1992-01-01

Light metallography, scanning electron microscopy and local energy dispersion analysis have been used to study the interaction of Y-ceramics with copper and niobium. Samples in the form of wire of two types were employed, that is, consisting of ceramic core YBaCuO and Cu shell or a ceramic core YBaCuO and bimetallic Cu/Nb shell. The interaction of the ceramics with the shell metal began already at 500 deg with the formation at the interafaces Cu-YBaCuO of oxide layers containing ceramic elements, and in the ceramic core - nonsuperconducting phases. A thin Al-layer placed between the ceramics and the shell appreciably decreased the reactability of the ceramics with respect to copper and niobium

Producing ceramic laminate composites by EPD

International Nuclear Information System (INIS)

Nicholson, P.S.; Sarkar, P.; Datta, S.

1996-01-01

The search for tough structural ceramics to operate at high temperatures in hostile environments has led to the development of ceramic composites. This class of material includes laminar ceramic-ceramic composites, continuous-fiber-reinforced ceramic composites and functionally graded materials. The present authors developed electrophoretic deposition (EPD) to synthesize lamellar, fiber-reinforced and functionally graded composites. This paper briefly describes the synthesis and characterization of these EPD composites and introduces a novel class of lamellar composites with nonplanar layers. The synthesis of the latter demonstrates the facility of the EPD process for the synthesis of ceramic composites. The process is totally controllable via suspension concentration, deposition current, voltage and time

Nanomembrane structures having mixed crystalline orientations and compositions

Science.gov (United States)

Lagally, Max G.; Scott, Shelley A.; Savage, Donald E.

2014-08-12

The present nanomembrane structures include a multilayer film comprising a single-crystalline layer of semiconductor material disposed between two other single-crystalline layers of semiconductor material. A plurality of holes extending through the nanomembrane are at least partially, and preferably entirely, filled with a filler material which is also a semiconductor, but which differs from the nanomembrane semiconductor materials in composition, crystal orientation, or both.

Impedance spectroscopy of Li2CO3 doped (Ba,Sr)TiO3 ceramic

Science.gov (United States)

Ham, Yong-Su; Koh, Jung-Hyuk

2013-02-01

(BaxSr1-x)TiO3-based ceramic has been considered as one of the most important electronic materials widely employed in microwave passive device applications. Many researches have been performed to lower the high sintering temperature, by adding various dopants such as B2O3, La2O3, etc. In our previous study, by adding Li2CO3 to (Ba0.5,Sr0.5)TiO3 ceramics, the sintering temperature of Li2CO3 doped (Ba0.5,Sr0.5)TiO3 ceramics decreased from 1350 to 900 °C. This study observed the crystalline structure and electrical properties of Li2CO3 doped (Ba0.5,Sr0.5)TiO3 ceramics. In scanning the crystalline structure of Li2CO3 doped (Ba0.5,Sr0.5)TiO3 ceramics, no pyro phase was observed by X-ray diffraction analysis. To investigate the electrical properties of Li2CO3 doped (Ba0.5,Sr0.5)TiO3 ceramics, real and imaginary parts of the impedances were analyzed. Complex impedance data were measured from 100 Hz to 1 MHz at various temperature ranges.

Spectroscopic Properties of Neodymium and Erbium-Doped Magnesium Oxide Ceramics

Science.gov (United States)

2015-09-01

universally >99% of theoretical. Powder x-ray diffraction (XRD) analysis was employed to determine the crystalline phases in doped MgO ceramics after the...different sintering steps. Powders of sintered pellets were prepared by grinding fragments in a glass mortar and pestle to avoid crystalline...than anticipated for the doped MgO. Somewhat more conclusive information on the extent of successful RE doping was derived from the XRD analysis

Microstructure and thermochromic properties of VOX-WOX-VOX ceramic thin films

International Nuclear Information System (INIS)

Khamseh, S.; Ghahari, M.; Araghi, H.; Faghihi Sani, M.A.

2016-01-01

W-doped VO 2 films have been synthesized via oxygen annealing of V-W-V (vanadium-tungsten-vanadium) multilayered films. The effects of middle layer's thickness of V-W-V multilayered film on structure and properties of VO X -WO X -VO X ceramic thin films were investigated. The as-deposited V-W-V multilayered film showed amorphous-like structure when mixed structure of VO 2 (M) and VO 2 (B) was formed in VO X -WO X -VO X ceramic thin films. Tungsten content of VO X -WO X -VO X ceramic thin films increased with increasing middle layer's thickness. With increasing middle layer's thickness, room temperature square resistance (R sq ) of VO X -WO X -VO X ceramic thin films increased from 65 to 86 kΩ/sq. The VO X -WO X -VO X ceramic thin film with the thinnest middle layer showed significant SMT (semiconductor-metal transition) when SMT became negligible on increasing middle layer's thickness. (orig.)

Improvement in IBC-silicon solar cell performance by insertion of highly doped crystalline layer at heterojunction interfaces

International Nuclear Information System (INIS)

Bashiri, Hadi; Azim Karami, Mohammad; Mohammadnejad, Shahramm

2017-01-01

By inserting a thin highly doped crystalline silicon layer between the base region and amorphous silicon layer in an interdigitated back-contact (IBC) silicon solar cell, a new passivation layer is investigated. The passivation layer performance is characterized by numerical simulations. Moreover, the dependence of the output parameters of the solar cell on the additional layer parameters (doping concentration and thickness) is studied. By optimizing the additional passivation layer in terms of doping concentration and thickness, the power conversion efficiency could be improved by a factor of 2.5%, open circuit voltage is increased by 30 mV and the fill factor of the solar cell by 7.4%. The performance enhancement is achieved due to the decrease of recombination rate, a decrease in solar cell resistivity and improvement of field effect passivation at heterojunction interface. The above-mentioned results are compared with reported results of the same conventional interdigitated back-contact silicon solar cell structure. Furthermore, the effect of a-Si:H/c-Si interface defect density on IBC silicon solar cell parameters with a new passivation layer is studied. The additional passivation layer also reduces the sensitivity of output parameter of solar cell to interface defect density. (paper)

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

Science.gov (United States)

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

Nano-Ceramic Coated Plastics

Science.gov (United States)

Cho, Junghyun

2013-01-01

Plastic products, due to their durability, safety, and low manufacturing cost, are now rapidly replacing cookware items traditionally made of glass and ceramics. Despite this trend, some still prefer relatively expensive and more fragile ceramic/glassware because plastics can deteriorate over time after exposure to foods, which can generate odors, bad appearance, and/or color change. Nano-ceramic coatings can eliminate these drawbacks while still retaining the advantages of the plastic, since the coating only alters the surface of the plastic. The surface coating adds functionality to the plastics such as self-cleaning and disinfectant capabilities that result from a photocatalytic effect of certain ceramic systems. These ceramic coatings can also provide non-stick surfaces and higher temperature capabilities for the base plastics without resorting to ceramic or glass materials. Titanium dioxide (TiO2) and zinc oxide (ZnO) are the candidates for a nano-ceramic coating to deposit on the plastics or plastic films used in cookware and kitchenware. Both are wide-bandgap semiconductors (3.0 to 3.2 eV for TiO2 and 3.2 to 3.3 eV for ZnO), so they exhibit a photocatalytic property under ultraviolet (UV) light. This will lead to decomposition of organic compounds. Decomposed products can be easily washed off by water, so the use of detergents will be minimal. High-crystalline film with large surface area for the reaction is essential to guarantee good photocatalytic performance of these oxides. Low-temperature processing (nano-ceramic coatings (TiO2, ZnO) on plastic materials (silicone, Teflon, PET, etc.) that can possess both photocatalytic oxide properties and flexible plastic properties. Processing cost is low and it does not require any expensive equipment investment. Processing can be scalable to current manufacturing infrastructure.

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

Science.gov (United States)

Thirumalai, Sundararajan; Shanmugavel, Balasivanandha Prabu

2011-01-01

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

The In Vitro Bioactivity, Degradation, and Cytotoxicity of Polymer-Derived Wollastonite-Diopside Glass-Ceramics

Directory of Open Access Journals (Sweden)

Amanda De Castro Juraski

2017-04-01

Full Text Available Ca-Mg silicates are receiving a growing interest in the field of bioceramics. In a previous study, wollastonite-diopside (WD glass-ceramics were successfully prepared by a new processing route, consisting of the heat treatment of a silicone resin embedding reactive oxide particles and a Ca/Mg-rich glass. The in vitro degradation, bioactivity, and cell response of these new WD glass-ceramics, fired at 900–1100 °C for 1 h, as a function of the Ca/Mg-rich glass content, are the aim of this investigation The results showed that WD glass-ceramics from formulations comprising different glass contents (70–100% at 900 °C, 30% at 1100 °C exhibit the formation of an apatite-like layer on their surface after immersion in SBF for seven days, thus confirming their surface bioactivity. The XRD results showed that these samples crystallized, mainly forming wollastonite (CaSiO3 and diopside (CaMgSi2O6, but combeite (Na2Ca2Si3O9 crystalline phase was also detected. Besides in vitro bioactivity, cytotoxicity and osteoblast adhesion and proliferation tests were applied after all characterizations, and the formulation comprising 70% glass was demonstrated to be promising for further in vivo studies.

The In Vitro Bioactivity, Degradation, and Cytotoxicity of Polymer-Derived Wollastonite-Diopside Glass-Ceramics

Science.gov (United States)

Juraski, Amanda De Castro; Dorion Rodas, Andrea Cecilia; Elsayed, Hamada; Bernardo, Enrico; Oliveira Soares, Viviane; Daguano, Juliana

2017-01-01

Ca-Mg silicates are receiving a growing interest in the field of bioceramics. In a previous study, wollastonite-diopside (WD) glass-ceramics were successfully prepared by a new processing route, consisting of the heat treatment of a silicone resin embedding reactive oxide particles and a Ca/Mg-rich glass. The in vitro degradation, bioactivity, and cell response of these new WD glass-ceramics, fired at 900–1100 °C for 1 h, as a function of the Ca/Mg-rich glass content, are the aim of this investigation The results showed that WD glass-ceramics from formulations comprising different glass contents (70–100% at 900 °C, 30% at 1100 °C) exhibit the formation of an apatite-like layer on their surface after immersion in SBF for seven days, thus confirming their surface bioactivity. The XRD results showed that these samples crystallized, mainly forming wollastonite (CaSiO3) and diopside (CaMgSi2O6), but combeite (Na2Ca2Si3O9) crystalline phase was also detected. Besides in vitro bioactivity, cytotoxicity and osteoblast adhesion and proliferation tests were applied after all characterizations, and the formulation comprising 70% glass was demonstrated to be promising for further in vivo studies. PMID:28772783

Quantum efficiencies of near-infrared emission from Ni2+-doped glass-ceramics

International Nuclear Information System (INIS)

Suzuki, Takenobu; Arai, Yusuke; Ohishi, Yasutake

2008-01-01

A systematic method to evaluate potentials of Ni 2+ -doped transparent glass-ceramics as a new broadband optical gain media is presented. At first, near-infrared emission of various ceramics were investigated to explore the suitable crystalline phase to be grown in the glass-ceramics. The quantum efficiency of Ni 2+ near-infrared emission estimated by the Struck-Fonger analysis was higher than 95% for spinel-type structure gallate crystals MgGa 2 O 4 and LiGa 5 O 8 at room temperature. Transparent glass-ceramics containing Ni 2+ :LiGa 5 O 8 could be prepared and the quantum efficiency for the glass-ceramics was measured to be about 10%. This value shows a potential of Ni-doped transparent glass-ceramics as a broadband gain media

Presence of Fe-Al binary oxide adsorbent cake layer in ceramic membrane filtration and their impact for removal of HA and BSA.

Science.gov (United States)

Kim, Kyung-Jo; Jang, Am

2018-04-01

To enhance the removal of natural organic matter (NOM) in ceramic (Ce) membrane filtration, an iron-aluminum binary oxide (FAO) was applied to the ceramic membrane surface as the adsorbent cake layer, and it was compared with heated aluminum oxide (HAO) for the evaluation of the control of NOM. Both the HAO and FAO adsorbent cake layers efficiently removed the NOM regardless of NOM's hydrophobic/hydrophilic characteristics, and the dissolved organic carbon (DOC) removal in NOM for FAO was 1-1.12 times greater than that for HAO, which means FAO was more efficient in the removal of DOC in NOM. FAO (0.03 μm), which is smaller in size than HAO (0.4 μm), had greater flux reduction than HAO. The flux reduction increased as the filtration proceeded because most of the organic foulants (colloid/particles and soluble NOM) were captured by the adsorbent cake layer, which caused fouling between the membrane surface and the adsorbent cake layer. However, no chemically irreversible fouling was observed on the Ce membrane at the end of the FAO adsorbent cake layer filtration. This means that a stable adsorbent cake layer by FAO formed on the Ce membrane, and that the reduced pure water flux of the Ce membrane, resulting from the NOM fouling, can easily be recovered through physicochemical cleaning. Copyright © 2018 Elsevier Ltd. All rights reserved.

Structural analysis and thermal behavior of diopside-fluorapatite-wollastonite-based glasses and glass-ceramics.

Science.gov (United States)

Kansal, Ishu; Tulyaganov, Dilshat U; Goel, Ashutosh; Pascual, Maria J; Ferreira, José M F

2010-11-01

Glass-ceramics in the diopside (CaMgSi2O6)-fluorapatite (Ca5(PO4)3F)-wollastonite (CaSiO3) system are potential candidates for restorative dental and bone implant materials. The present study describes the influence of varying SiO2/CaO and CaF2/P2O5 molar ratio on the structure and thermal behavior of glass compositions in the CaO-MgO-SiO2-P2O5-Na2O-CaF2 system. The structural features and properties of the glasses were investigated by nuclear magnetic resonance (NMR), infrared spectroscopy, density measurements and dilatometry. Sintering and crystallization behavior of the glass powders were studied by hot-stage microscopy and differential thermal analysis, respectively. The microstructure and crystalline phase assemblage in the sintered glass powder compacts were studied under non-isothermal heating conditions at 825 °C. X-ray diffraction studies combined with the Rietveld-reference intensity ratio (R.I.R) method were employed to quantify the amount of amorphous and crystalline phases in the glass-ceramics, while scanning electron microscopy was used to shed some light on the microstructure of resultant glass-ceramics. An increase in CaO/SiO2 ratio degraded the sinterability of the glass powder compacts, resulting in the formation of akermanite as the major crystalline phase. On the other hand, an increase in P2O5/CaF2 ratio improved the sintering behavior of the glass-ceramics, while varying the amount of crystalline phases, i.e. diopside, fluorapatite and wollastonite. Copyright © 2010. Published by Elsevier Ltd.

A study on wear resistance and microcrack of the Ti3Al/TiAl + TiC ceramic layer deposited by laser cladding on Ti-6Al-4V alloy

International Nuclear Information System (INIS)

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

2010-01-01

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

Contact method to allow benign failure in ceramic capacitor having self-clearing feature

Science.gov (United States)

Myers, John D; Taylor, Ralph S

2012-06-26

A capacitor exhibiting a benign failure mode has a first electrode layer, a first ceramic dielectric layer deposited on a surface of the first electrode, and a second electrode layer disposed on the ceramic dielectric layer, wherein selected areas of the ceramic dielectric layer have additional dielectric material of sufficient thickness to exhibit a higher dielectric breakdown voltage than the remaining majority of the dielectric layer. The added thickness of the dielectric layer in selected areas allows lead connections to be made at the selected areas of greater dielectric thickness while substantially eliminating a risk of dielectric breakdown and failure at the lead connections, whereby the benign failure mode is preserved.

Machining of insulation ZrO2 ceramics by EDM using graphite electrode

International Nuclear Information System (INIS)

Tani, T.; Okada, M.; Fukuzawa, Y.; Mohri, N.

1998-01-01

As we proposed and reported before, insulating ceramics may be made into machinable materials with electrical discharge machining method by using an assisting electrode method. The machining properties depend on the formation mechanism of carbonization layer which has electrical conductivity on the ceramics surface during discharge. A big difference in machinability occurs between oxide and non-oxide ceramics. When ZrO 2 ceramics are machined with a copper tool electrode which was used for a machining of the non-oxide ceramics Si 3 N 4 , the electrical conductive layer is not formed on the machined surface uniformly. In this paper, in order to activate a carbonization reaction on the ceramics surface during discharge, the use of a porous graphite tool electrode is described. As a result of that, carbonized reaction occurs actively on the discharge gap and the uniform carbonized layer adheres to the machined surface. The surface roughness is much improved compared with previous machining conditions. Copyright (1998) Australasian Ceramic Society

Production and Characterization of Glass-Ceramic Materials for Potential Use in Dental Applications: Thermal and Mechanical Properties, Microstructure, and In Vitro Bioactivity

Directory of Open Access Journals (Sweden)

Francesco Baino

2017-12-01

Full Text Available Multicomponent silicate glasses and their corresponding glass-ceramic derivatives were prepared and tested for potential applications in dentistry. The glasses were produced via a melting-quenching process, ground and sieved to obtain fine-grained powders that were pressed in the form of small cylinders and thermally treated to obtain sintered glass-ceramic samples. X-ray diffraction investigations were carried out on the materials before and after sintering to detect the presence of crystalline phases. Thermal analyses, mechanical characterizations (assessment of bending strength, Young’s modulus, Vickers hardness, fracture toughness, and in vitro bioactivity tests in simulated body fluid were performed. On the basis of the acquired results, different potential applications in the dental field were discussed for the proposed glass-ceramics. The use of such materials can be suggested for either restorative dentistry or dental implantology, mainly depending on their peculiar bioactive and mechanical properties. At the end of the work, the feasibility of a novel full-ceramic bilayered implant was explored and discussed. This implant, comprising a highly bioactive layer expected to promote osteointegration and another one mimicking the features of tooth enamel, can have an interesting potential for whole tooth substitution.

Elaboration of optical glass-ceramic for frequency doubling

International Nuclear Information System (INIS)

Vigouroux, H.

2012-01-01

The High power laser development required the need of materials with nonlinear properties. Glass materials can be considered as ideal materials as they can be transparent and elaborated in very large dimension. Precipitation of non-centro symmetric crystalline particles in bulk glass leads to a material with bulk nonlinear properties. This glass-ceramic should be then easily integrated in such laser facilities. In this thesis, the results concerning the precipitation of the phase LiNbO 3 in the glassy-matrix 35 Li 2 O - 25 Nb 2 O 5 - 40 SiO 2 are detailed. The crystallization mechanism of this phase is studied through thermal analysis, optical and electronic microscopy as well as in-situ analyses. These studies reveal glass-ceramics are obtained through a precipitation of the lithium niobate crystalline phase in spherulite shape. The nonlinear optical properties are investigated on this materials and an original, isotropic Second Harmonic Generation Signal (SHG) is registered in the bulk glass-ceramic. A complete study using a multi-scale approach allows the correlation between the spherulite structure and the nonlinear optical properties. A mechanism at the origin of the SHG signal is proposed. This leads to a new approach for transparent inorganic materials development for isotropic SHG conversion. (author) [fr

Basic research in crystalline and noncrystalline ceramic systems. Annual report, August 1, 1980-October 31, 1981

International Nuclear Information System (INIS)

1981-01-01

The Basic Research Programs in Ceramics sponsored by the US Department of Energy supports a significant fraction of the research effort and graduate student training in ceramics at MIT. Various research activities involving ceramic materials include electrical properties; kinetic studies; defect structures, defect interactions, grain boundaries and surfaces; sintering studies; and mechanical properties

Sol-gel technology applied to crystalline ceramic nuclear waste forms

International Nuclear Information System (INIS)

Angelini, P.; Bond, W.D.; Caputo, A.J.; Mack, J.E.; Lackey, W.J.; Lee, D.A.; Stinton, D.P.

1980-01-01

The sol-gel process is being developed for the solidification and isolation of high-level nuclear fuel waste. Three gelation methods are being developed for producing alternative waste forms. These include internal gelation for producing spheres of up to 1 mm diam suitable for coating, external gelation, and water extraction methods for producing material suitable for alternate ceramic processing. In this study internal gelation has been used to produce ceramic spheres of various alternative nuclear waste compositions. A gelation system capable of producing 100-g batches has been assembled and used for development. Waste forms containing up to 70 wt % simulated Savannah River Plant waste have been produced. Dopants such as Cs, Sr, Nd, Ru, and Mo were used in some experiments to observe side waste streams and sintering effects. Synroc microspheres were coated with both low-density carbon, high-density impermeable carbon, high-temperature dense SiC, and SiC deposited at temperatures near 900 0 C. Other gelation methods and other alternative waste forms are being developed

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

Science.gov (United States)

Bagheri, Hossein; Hooshmand, Tabassom; Aghajani, Farzaneh

2015-09-01

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

Analysis of current-driven oscillatory dynamics of single-layer homoepitaxial islands on crystalline conducting substrates

Science.gov (United States)

Dasgupta, Dwaipayan; Kumar, Ashish; Maroudas, Dimitrios

2018-03-01

We report results of a systematic study on the complex oscillatory current-driven dynamics of single-layer homoepitaxial islands on crystalline substrate surfaces and the dependence of this driven dynamical behavior on important physical parameters, including island size, substrate surface orientation, and direction of externally applied electric field. The analysis is based on a nonlinear model of driven island edge morphological evolution that accounts for curvature-driven edge diffusion, edge electromigration, and edge diffusional anisotropy. Using a linear theory of island edge morphological stability, we calculate a critical island size at which the island's equilibrium edge shape becomes unstable, which sets a lower bound for the onset of time-periodic oscillatory dynamical response. Using direct dynamical simulations, we study the edge morphological dynamics of current-driven single-layer islands at larger-than-critical size, and determine the actual island size at which the migrating islands undergo a transition from steady to time-periodic asymptotic states through a subcritical Hopf bifurcation. At the highest symmetry of diffusional anisotropy examined, on {111} surfaces of face-centered cubic crystalline substrates, we find that more complex stable oscillatory states can be reached through period-doubling bifurcation at island sizes larger than those at the Hopf points. We characterize in detail the island morphology and dynamical response at the stable time-periodic asymptotic states, determine the range of stability of these oscillatory states terminated by island breakup, and explain the morphological features of the stable oscillating islands on the basis of linear stability theory.

Thermal resistance of buffer layer in a ceramic wall of MHD generation channel

International Nuclear Information System (INIS)

Nomura, Osami; Ebata, Yoshihiro; Hijikata, Kenichi.

1982-01-01

A wal l model is composed for obtaining the thermal resistance of the buffer layer. A buffer layer of the model is consisted to an adhesive layer and a buffer body. The adhesive layer is made of a copper plate, which is 0.3 mm thick, and adhered to the element by Refractory Method. The adhesive layer is consisted to three layers, i.e., Cu, Cu 2 O and CuO. These three layers seems to give rise to the thermal resistance. The buffer body is made of nickel wires of which radious is 0.4 mm and purity is 99.7%. All of the nickel wires are assembled in one direction which is parallel to a center line of the element, and bundled all together. Occupation ratio of nickel is about 78% in a sectional area of the buffer body. One end of the buffer body is soldered to adhesive layer by silver solder and opposite and is soldered to holder by lead solder. An element of the model is made of magnesia ceramics of which purity is about 99.9% and porosity is about 3%. A holder of the model is made of copper block. Results are as follows: (1) Thermal resistance of the buffer layer is from 1.9 to 2.5K/(W/cm 2 ). (2) Thermal resistance of the adhesive layer is from 0.43 to 0.87K/(W/cm 2 ). (3) Thermal resistance of the buffer body is calculated to about 0.7K/(W/cm 2 ) under the estimation at which the heat flows in the nickel wires only. (4) From above results, thermal resistance of silver soldering layer seems to be same as that of the adhesive layers. The buffer layer needs more value of the thermal resistance in order to apply to the MHD generation channel. Value of the thermal resistance is easily satisfied by changing of material of the buffer body, increase of thickness of the buffer layer and etc. Then this wall appears to be useful to an MHD generation channel wall. (author)

Quantitative firing transformations of a triaxial ceramic by X-ray diffraction methods

Directory of Open Access Journals (Sweden)

M. S. Conconi

2014-12-01

Full Text Available The firing transformations of traditional (clay based ceramics are of technological and archeological interest, and are usually reported qualitatively or semiquantitatively. These kinds of systems present an important complexity, especially for X-ray diffraction techniques, due to the presence of fully crystalline, low crystalline and amorphous phases. In this article we present the results of a qualitative and quantitative X-ray diffraction Rietveld analysis of the fully crystalline (kaolinite, quartz, cristobalite, feldspars and/or mullite, the low crystalline (metakaolinite and/or spinel type pre-mullite and glassy phases evolution of a triaxial (clay-quartz-feldspar ceramic fired in a wide temperature range between 900 and 1300 ºC. The employed methodology to determine low crystalline and glassy phase abundances is based in a combination of the internal standard method and the use of a nanocrystalline model where the long-range order is lost, respectively. A preliminary sintering characterization was carried out by contraction, density and porosity evolution with the firing temperature. Simultaneous thermo-gravimetric and differential thermal analysis was carried out to elucidate the actual temperature at which the chemical changes occur. Finally, the quantitative analysis based on the Rietveld refinement of the X-ray diffraction patterns was performed. The kaolinite decomposition into metakaolinite was determined quantitatively; the intermediate (980 ºC spinel type alumino-silicate formation was also quantified; the incongruent fusion of the potash feldspar was observed and quantified together with the final mullitization and the amorphous (glassy phase formation.The methodology used to analyze the X-ray diffraction patterns proved to be suitable to evaluate quantitatively the thermal transformations that occur in a complex system like the triaxial ceramics. The evaluated phases can be easily correlated with the processing variables and

Quantitative firing transformations of a triaxial ceramic by X-ray diffraction methods

International Nuclear Information System (INIS)

Conconi, M.S.; Gauna, M.R.; Serra, M.F.; Suarez, G.; Aglietti, E.F.; Rendtorff, N.M.

2014-01-01

The firing transformations of traditional (clay based) ceramics are of technological and archaeological interest, and are usually reported qualitatively or semi quantitatively. These kinds of systems present an important complexity, especially for X-ray diffraction techniques, due to the presence of fully crystalline, low crystalline and amorphous phases. In this article we present the results of a qualitative and quantitative X-ray diffraction Rietveld analysis of the fully crystalline (kaolinite, quartz, cristobalite, feldspars and/or mullite), the low crystalline (metakaolinite and/or spinel type pre-mullite) and glassy phases evolution of a triaxial (clay-quartz-feldspar) ceramic fired in a wide temperature range between 900 and 1300 deg C. The employed methodology to determine low crystalline and glassy phase abundances is based in a combination of the internal standard method and the use of a nanocrystalline model where the long-range order is lost, respectively. A preliminary sintering characterization was carried out by contraction, density and porosity evolution with the firing temperature. Simultaneous thermo-gravimetric and differential thermal analysis was carried out to elucidate the actual temperature at which the chemical changes occur. Finally, the quantitative analysis based on the Rietveld refinement of the X-ray diffraction patterns was performed. The kaolinite decomposition into metakaolinite was determined quantitatively; the intermediate (980 deg C) spinel type alumino-silicate formation was also quantified; the incongruent fusion of the potash feldspar was observed and quantified together with the final mullitization and the amorphous (glassy) phase formation.The methodology used to analyze the X-ray diffraction patterns proved to be suitable to evaluate quantitatively the thermal transformations that occur in a complex system like the triaxial ceramics. The evaluated phases can be easily correlated with the processing variables and materials

Quantitative firing transformations of a triaxial ceramic by X-ray diffraction methods

Energy Technology Data Exchange (ETDEWEB)

Conconi, M.S.; Gauna, M.R.; Serra, M.F. [Centro de Tecnologia de Recursos Minerales y Ceramica (CETMIC), Buenos Aires (Argentina); Suarez, G.; Aglietti, E.F.; Rendtorff, N.M., E-mail: rendtorff@cetmic.unlp.edu.ar [Universidad Nacional de La Plata (UNLP), Buenos Aires (Argentina). Fac. de Ciencias Exactas. Dept. de Quimica

2014-10-15

The firing transformations of traditional (clay based) ceramics are of technological and archaeological interest, and are usually reported qualitatively or semi quantitatively. These kinds of systems present an important complexity, especially for X-ray diffraction techniques, due to the presence of fully crystalline, low crystalline and amorphous phases. In this article we present the results of a qualitative and quantitative X-ray diffraction Rietveld analysis of the fully crystalline (kaolinite, quartz, cristobalite, feldspars and/or mullite), the low crystalline (metakaolinite and/or spinel type pre-mullite) and glassy phases evolution of a triaxial (clay-quartz-feldspar) ceramic fired in a wide temperature range between 900 and 1300 deg C. The employed methodology to determine low crystalline and glassy phase abundances is based in a combination of the internal standard method and the use of a nanocrystalline model where the long-range order is lost, respectively. A preliminary sintering characterization was carried out by contraction, density and porosity evolution with the firing temperature. Simultaneous thermo-gravimetric and differential thermal analysis was carried out to elucidate the actual temperature at which the chemical changes occur. Finally, the quantitative analysis based on the Rietveld refinement of the X-ray diffraction patterns was performed. The kaolinite decomposition into metakaolinite was determined quantitatively; the intermediate (980 deg C) spinel type alumino-silicate formation was also quantified; the incongruent fusion of the potash feldspar was observed and quantified together with the final mullitization and the amorphous (glassy) phase formation.The methodology used to analyze the X-ray diffraction patterns proved to be suitable to evaluate quantitatively the thermal transformations that occur in a complex system like the triaxial ceramics. The evaluated phases can be easily correlated with the processing variables and materials

Method of forming an oxide superconducting thin film having an R1A2C3 crystalline phase over an R2A1C1 crystalline phase

International Nuclear Information System (INIS)

Lelental, M.; Romanofsky, H.J.

1992-01-01

This patent describes a process which comprises forming a mixed rare earth alkaline earth copper oxide layer on a substrate and converting the mixed rare earth alkaline earth copper oxide layer to an electrically conductive layer. It comprises crystalline R 1 A 2 C 3 oxide phase by heating in the presence of oxygen, wherein rare earth and R is in each instance chosen from among yttrium, lanthanum, samarium, europium, gadolinium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium and alkaline earth and A is in each instance chosen from among calcium, strontium and barium, characterized in that a crystalline R 2 A 1 C 1 oxide phase is first formed as a layer on the substrate and the crystalline R 1 A 2 C 3 oxide phase is formed over the crystalline R 2 A 1 C 1 oxide phase by coating a mixed rare earth alkaline earth copper oxide on the crystalline R 2 A 1 C 1 oxide phase and heating the mixed rare earth alkaline earth copper oxide to a temperature of at least 1000 degrees C

Surface analysis applied to metal-ceramic and bioceramic interfacial bonding

International Nuclear Information System (INIS)

Smart, R.St.C.; Arora, P.S.; Steveson, M.; Kawashima, N.; Cavallaro, G.P.; Ming, H.; Skinner, W.M.

1999-01-01

Full text: Low temperature plasma reactions, combined with sol-gel coatings, have been used to produce a variety of ceramic surface layers on metal substrates and interfacial layers between metals and oxides or other ceramics. These layers can be designed to be compositionally and functionally graded from the metal to bulk ceramic material, eg. silica, alumina, hydroxyapatite. The graded layers are generally <50nm thick, continuous, fully bonded to the substrate and deformable without disbonding. The objectives in design of these layers have been to produce: metal surfaces protected from oxidation, corrosion and acid attack; improved metal-ceramic bonding; and bioceramic titanium-based interfaces to bioactive hydroxyapatite for improved dental and medical implants. Modified Auger parameter studies for Si in XPS spectra show that the structure on the metal surfaces grades from amorphous, dehydroxylated silica on the outer surface through layer silicates, chain silicates, pyrosilicates to orthosilicates close to the metal interface. At the metal interface, detached grains of the metal are imaged with interpenetration of the oxide and silicate species linking the layer to the oxidised metal surface. The ∼30nm layer has a substantially increased frictional load compared with the untreated oxidised metal, i.e. behaviour consistent with either stronger adhesion of the coating to the substrate or a harder surface. The composition, structure and thickness of these layers can be controlled by the duration of each plasma reaction and the choice of the final reagent. The mechanisms of reaction in each process step have been elucidated with a combination of XPS, TOF-SIMS, TEM, SEM and FTIR. Similar, graded titanium/oxide/silicate/silica ceramic surface layers have been shown to form using the low temperature plasma reactions on titanium alloys used in medical and dental implants. Thicker (i.e. μm) overlayers of ceramic materials can be added to the graded surface layers

Structural and dielectric properties of four - layer Aurivillius - type Ba0.25Sr0.75Bi4Ti4O15 ceramics

International Nuclear Information System (INIS)

Goyal, Parveen K.; Khokhar, Anita; Sreenivas, K.

2013-01-01

In the present study, a barium strontium bismuth titanate (Ba 0.25 Sr 0.75 Bi 4 Ti 4 O 15 , BSBT) ceramic composition has been prepared by conventional solid-state reaction. In order to study the structure of as synthesized BSBT ceramics, the X-ray powder diffraction (XRD), Raman and FTIR studies have been carried out on the powdered sample. X-ray diffraction analysis confirms the formation of a single phase four-layer Aurivillius-type ceramics that crystallizes in an orthorhombic structure with A2 1 am space group. The dielectric properties of the ceramics have been studied in the temperature range 30 - 600℃ temperature range at various frequencies (100 Hz to 1 MHz). A sharp dielectric anomaly was observed at ∼ 485℃ at all the frequencies corresponding to the ferroelectric to paraelectric phase transition. The ferroelectric behavior is confirmed from the Curie-Weiss law fitting of the dielectric data. (author)

Improvement of the long term stability in the high temperature solid oxide fuel cell using functional layers

Energy Technology Data Exchange (ETDEWEB)

Brueckner, B.; Guenther, C.; Ruckdaeschel, R. [Siemens AG, Erlangen (Germany)] [and others

1996-12-31

In the planar Siemens design of the solid oxide fuel cell a metallic interconnector is used to seperate the ceramic single cells. A disadvantage of the metallic bipolar plate which consists of a chromium alloy is the formation of high volatile Cr-oxides and hydroxides at the surface at the cathode side. The reaction products evaporate and are reduced at the cathode/electrolyte interface to form new crystalline phases. This process gives rise to long term cell degradation. Protective coatings might be successful in preventing the chromium oxide evaporation. The required properties of the protective layers are (I) high electrical conductivity, (II) similar coefficients of thermal expansion to the bipolar plate (III), chemical compatibility to the bipolar plate and cathode material, (IV) a low diffusion coefficient of Cr and (V) chemical stability up to 1223K under oxygen atmosphere. Furthermore, during operation at 1223K an electrical contact between the metallic plate and the electrodes has to be maintained. This problem could be solved using ceramic layer between the metallic plate and the single cells.

Synthesis and luminescent properties of Eu{sup 3+}/Eu{sup 2+} co-doped calcium aluminosilicate glass–ceramics

Energy Technology Data Exchange (ETDEWEB)

Bouchouicha, H. [Institut Lumière Matière, UMR5306 Université Lyon 1-CNRS, Université de Lyon, 69622 Villeurbanne Cedex (France); Panczer, G., E-mail: gerard.panczer@univ-lyon1.fr [Institut Lumière Matière, UMR5306 Université Lyon 1-CNRS, Université de Lyon, 69622 Villeurbanne Cedex (France); Ligny, D. de [Universität Erlangen-Nürnberg, Department Werkstoffwissenschaften, Lehrstuhl für Glas und Keramik, D-91058 Erlangen (Germany); Guyot, Y. [Institut Lumière Matière, UMR5306 Université Lyon 1-CNRS, Université de Lyon, 69622 Villeurbanne Cedex (France); Baesso, M.L. [Departemento de Fisica, Universidade Estadual de Maringa, 87020-900 Maringa, PR (Brazil); Andrade, L.H.C.; Lima, S.M. [Grupo de Espectroscopia Óptica e Fototérmica, Universidade Estadual de Mato Grosso do Sul – UEMS, C.P. 351, Dourados, MS (Brazil); Ternane, R. [Laboratoire d' Application de la Chimie aux Ressources et Substances Naturelles et à l' Environnement (LACReSNE), Université de Carthage, Faculté des Sciences de Bizerte, 7021 Zarzouna, Bizerte (Tunisia)

2016-01-15

Eu{sup 3+} and Eu{sup 2+} co-doped calcium aluminosilicate glass–ceramics have been prepared by devitrification of calcium aluminosilicate glass using heat-treatment. Control of crystallization in the glass–ceramics was studied by X-ray diffraction (XRD) and Raman spectroscopy. The results showed that crystalline phases in glass–ceramic belong to the family of melilite Ca{sub 2}Mg{sub 0.25}Al{sub 1.5}Si{sub 1.25}O{sub 7} as the major phase and anorthite CaAl{sub 2}Si{sub 2}O{sub 8} as the minor phase. Luminescent properties were investigated by emission; lifetime and the color points were calculated. Emission spectra showed that Eu{sup 2+} entered into the crystalline phase in a two steps mechanism: first as Eu{sup 3+} which is then reduced to Eu{sup 2+}. This incorporation in the crystal enhanced Eu{sup 2+} emission with increasing time of heat-treatment and therefore crystallization. - Highlights: • Crystallization of doped glass–ceramics by heat-treatment controlled by microRaman. • Crystalline phases consist of melilite and anorthite. • Eu{sup 3+} and Eu{sup 2+} emissions characterized by their lifetime and color indexes. • Crystallization process modified efficiently the emission color point.

Enhancing crystalline silicon solar cell efficiency with SixGe1-x layers

Science.gov (United States)

Ali, Adnan; Cheow, S. L.; Azhari, A. W.; Sopian, K.; Zaidi, Saleem H.

Crystalline silicon (c-Si) solar cell represents a cost effective, environment-friendly, and proven renewable energy resource. Industrially manufacturing of c-Si solar has now matured in terms of efficiency and cost. Continuing cost-effective efficiency enhancement requires transition towards thinner wafers in near term and thin-films in the long term. Successful implementation of either of these alternatives must address intrinsic optical absorption limitation of Si. Bandgap engineering through integration with SixGe1-x layers offers an attractive, inexpensive option. With the help of PC1D software, role of SixGe1-x layers in conventional c-Si solar cells has been intensively investigated in both wafer and thin film configurations by varying Ge concentration, thickness, and placement. In wafer configuration, increase in Ge concentration leads to enhanced absorption through bandgap broadening with an efficiency enhancement of 8% for Ge concentrations of less than 20%. At higher Ge concentrations, despite enhanced optical absorption, efficiency is reduced due to substantial lowering of open-circuit voltage. In 5-25-μm thickness, thin-film solar cell configurations, efficiency gain in excess of 30% is achievable. Therefore, SixGe1-x based thin-film solar cells with an order of magnitude reduction in costly Si material are ideally-suited both in terms of high efficiency and cost. Recent research has demonstrated significant improvement in epitaxially grown SixGe1-x layers on nanostructured Si substrates, thereby enhancing potential of this approach for next generation of c-Si based photovoltaics.

Valorization of sugarcane bagasse ash: producing glass-ceramic materials.

Science.gov (United States)

Teixeira, S R; Magalhães, R S; Arenales, A; Souza, A E; Romero, M; Rincón, J M

2014-02-15

Some aluminosilicates, for example mullite and wollastonite, are very important in the ceramic and construction industries. The most significant glass-ceramic for building applications has wollastonite as the main crystal phase. In this work we report on the use of sugarcane bagasse ash (SCBA) to produce glass-ceramics with silicates as the major crystalline phases. The glasses (frits) were prepared by mixing ash, limestone (calcium and magnesium carbonates) and potassium carbonate as the fluxing agent. X-ray fluorescence was used to determine the chemical composition of the glasses and their crystallization was assessed by using thermal analysis (DTA/DSC/TGA) and X-ray diffraction. The results showed that glass-ceramic material can be produced with wollastonite as the major phase, at a temperature lower than 900 °C. Copyright © 2014 Elsevier Ltd. All rights reserved.

Effect of Nb doping on sintering and dielectric properties of PZT ceramics

Directory of Open Access Journals (Sweden)

Ali Mirzaei

2016-09-01

Full Text Available The extensive use of piezoelectric ceramics such as lead zirconate titanate (PZT in different applications became possible with the development of donor or acceptor dopants. Therefore, studies on the effect of dopants on the properties of PZT ceramics are highly demanded. In this study undoped and 2.4 mol% Nb-doped PZT (PZTN powders were successfully obtained by a solid-state reaction and calcination at 850 °C for 2 h. Crystallinity and phase formation of the prepared powders were studied using X-ray diffraction (XRD. In order to study morphology of powders, scanning electron microscopy (SEM was performed. The crystalline PZT and Nb-doped PZT powders were pelleted into discs and sintered at 1100, 1150 and 1200 °C, with a heating rate of 10 °C/min, and holding time of 1–6 h to find the optimum combination of temperature and time to produce high density ceramics. Microstructural characterization was conducted on the fractured ceramic surfaces using SEM. Density measurements showed that maximal density of 95% of the theoretical density was achieved after sintering of PZT and PZTN ceramics at 1200 °C for 2 h and 4 h, respectively. However, the results of dielectric measurements showed that PZTN ceramics have higher relative permittivity (εr ∼17960 with lower Curie temperature (∼358 °C relative to PZT (εr = 16000 at ∼363 °C as a result of fine PZTN structure as well as presence of vacancies. In addition, dielectric loss (at 1 kHz of PZT and PZTN ceramics with 95% theoretical density was 0.0087 and 0.02, respectively. The higher dielectric loss in PZTN was due to easier domain wall motions in PZTN ceramics.

Microstructure and fracture analysis of fully ceramic microencapsulated fuel

International Nuclear Information System (INIS)

Lee, H. G.; Kim, D. J.; Park, J. Y.; Kim, W. J.; Lee, S. J.

2015-01-01

Nuclear fuel enhancing the accident tolerance is satisfied two parts. First, the performance has to be retained compared to the existing UO 2 nuclear fuel and zircaloy cladding system under the normal operation condition. Second, under the severe accident condition, the high temperature structural integrity has to be kept and the generation rate of hydrogen has to be reduced largely. FCM nuclear fuel is composed of tristructural isotropic(TRISO) fuel particle and SiC ceramic matrix. SiC ceramic matrix play an essential part in protecting fission product. In the FCM fuel concept, fission product is doubly protected by TRISO coating layer and SiC ceramic matrix compared to the current commercial UO 2 fuel system. SiC ceramic has excellent properties for fuel application. SiC ceramic has low neutron absorption cross-section, excellent irradiation resistivity and high thermal conductivity. Additionally, the relative thermal conductivity of the SiC ceramic as compared to UO 2 is quite good, reducing operational release of fission products form the fuel. TRISO coating layer which is deposited on UO 2 kernel is consists of PyC/SiC/PyC trialyer and buffer PyC layer. SiC matrix composite with TRISO particle was fabricated by hot pressing. 3 to 20 wt.% of sintering additives were added to investigate reaction between sintering additives and outer PyC layer of TRISO coating layer. The relative densities of all specimens show above 92%. The reaction between sintering additives and PyC is observed in most TRISO particles, the thickness of reactants shows about ten micrometers. The thermal shock resistance of SiC matrix composite was investigated

Ceramic component with reinforced protection against radiations

International Nuclear Information System (INIS)

Dubuisson, J.; Laville, H.; Le Gal, P.

1986-01-01

Ceramic components hardened against radiations are claimed (for example capacitors or ceramic substrates for semiconductors). They are prepared with a sintered ceramic containing a high proportion of heavy atoms (for instance barium titanate and a bismuth salt) provided with a glass layer containing a high proportion of light atoms. The two materials are joined by vitrification producing a diffusion zone at the interface [fr

Production of coloured glass-ceramics from incinerator ash using thermal plasma technology.

Science.gov (United States)

Cheng, T W; Huang, M Z; Tzeng, C C; Cheng, K B; Ueng, T H

2007-08-01

Incineration is a major treatment process for municipal solid waste in Taiwan. It is estimated that over 1.5 Mt of incinerator ash are produced annually. This study proposes using thermal plasma technology to treat incinerator ash. Sintered glass-ceramics were produced using quenched vitrified slag with colouring agents added. The experimental results showed that the major crystalline phases developed in the sintered glass-ceramics were gehlenite and wollastonite, but many other secondary phases also appeared depending on the colouring agents added. The physical/mechanical properties, chemical resistance and toxicity characteristic leaching procedure of the coloured glass-ceramics were satisfactory. The glass-ceramic products obtained from incinerator ash treated with thermal plasma technology have great potential for building applications.

Crystallization and dielectric properties of PbTiO3 based glass ceramics

Science.gov (United States)

Shankar, J.; Rani, G. Neeraja; Deshpande, V. K.

2018-04-01

Glass samples with composition (50 - X) PbO - (25 + X) TiO2 - 25 B2O3 (where X = 0, 5, 10 and 12.5 mol %) were prepared using conventional quenching technique. These glass samples were converted to glass ceramics by following two stage heat treatment schedule. The XRD results in the glass ceramics revealed the formation of tetragonal lead titanate as a major crystalline phase. The SEM results show rounded crystallite of lead titanate. The ferroelectric nature of all the glass ceramic samples is confirmed by P - E hysteresis measurements. The extended heat treatment of glass ceramic samples at 593K for 10 h exhibited saturated hysteresis loops with higher values of remnant polarization.

Blending crystalline/liquid crystalline small molecule semiconductors: A strategy towards high performance organic thin film transistors

Science.gov (United States)

He, Chao; He, Yaowu; Li, Aiyuan; Zhang, Dongwei; Meng, Hong

2016-10-01

Solution processed small molecule polycrystalline thin films often suffer from the problems of inhomogeneity and discontinuity. Here, we describe a strategy to solve these problems through deposition of the active layer from a blended solution of crystalline (2-phenyl[1]benzothieno[3,2-b][1]benzothiophene, Ph-BTBT) and liquid crystalline (2-(4-dodecylphenyl) [1]benzothieno[3,2-b]benzothiophene, C12-Ph-BTBT) small molecule semiconductors with the hot spin-coating method. Organic thin film transistors with average hole mobility approaching 1 cm2/V s, much higher than that of single component devices, have been demonstrated, mainly due to the improved uniformity, continuity, crystallinity, and stronger intermolecular π-π stacking in blend thin films. Our results indicate that the crystalline/liquid crystalline semiconductor blend method is an effective way to enhance the performance of organic transistors.

Fabrication of GaN epitaxial thin film on InGaZnO4 single-crystalline buffer layer

International Nuclear Information System (INIS)

Shinozaki, Tomomasa; Nomura, Kenji; Katase, Takayoshi; Kamiya, Toshio; Hirano, Masahiro; Hosono, Hideo

2010-01-01

Epitaxial (0001) films of GaN were grown on (111) YSZ substrates using single-crystalline InGaZnO 4 (sc-IGZO) lattice-matched buffer layers by molecular beam epitaxy with a NH 3 source. The epitaxial relationships are (0001) GaN //(0001) IGZO //(111) YSZ in out-of-plane and [112-bar 0] GaN //[112-bar 0] IGZO //[11-bar 0] YSZ in in-plane. This is different from those reported for GaN on many oxide crystals; the in-plane orientation of GaN crystal lattice is rotated by 30 o with respect to those of oxide substrates except for ZnO. Although these GaN films showed relatively large tilting and twisting angles, which would be due to the reaction between GaN and IGZO, the GaN films grown on the sc-IGZO buffer layers exhibited stronger band-edge photoluminescence than GaN grown on a low-temperature GaN buffer layer.

Epitaxial growth of silicon for layer transfer

Science.gov (United States)

Teplin, Charles; Branz, Howard M

2015-03-24

Methods of preparing a thin crystalline silicon film for transfer and devices utilizing a transferred crystalline silicon film are disclosed. The methods include preparing a silicon growth substrate which has an interface defining substance associated with an exterior surface. The methods further include depositing an epitaxial layer of silicon on the silicon growth substrate at the surface and separating the epitaxial layer from the substrate substantially along the plane or other surface defined by the interface defining substance. The epitaxial layer may be utilized as a thin film of crystalline silicon in any type of semiconductor device which requires a crystalline silicon layer. In use, the epitaxial transfer layer may be associated with a secondary substrate.

An evaluation of the processing conditions, structure, and properties (biaxial flexural strength and antibacterial efficacy) of sintered strontium-zinc-silicate glass ceramics.

Science.gov (United States)

Looney, Mark; Shea, Helen O'; Gunn, Lynda; Crowley, Dolores; Boyd, Daniel

2013-05-01

The use of artificial bone grafts has increased in order to satisfy a growing demand for bone replacement materials. Initial mechanical stability of synthetic bone grafts is very advantageous for certain clinical applications. Coupled with the advantage of mechanical strength, a material with inherent antibacterial properties would be very beneficial. A series of strontium-doped zinc silicate (Ca-Sr-Na-Zn-Si) glass ceramics have been characterized in terms of their crystalline structure, biaxial flexural strength and antibacterial efficacy based on the identification of optimum sintering conditions. All three glass ceramics, namely, BT110, BT111, and BT112 were found to be fully crystalline, with BT111 and BT112 comprising of biocompatible crystalline phases. The biaxial flexural strengths of the three glass ceramics ranged from 70 to 149 MPa and were shown to be superior to those of clinically established ceramics in dry conditions and following incubation in simulated physiological conditions. The bacteriostatic effect for each glass ceramic was also established, where BT112 showed an inhibitory effect against three of the most common bacteria found at implantation sites, namely, Enterococcus faecalis, methicillin-resistant Staphylococcus aureus (MRSA), and Pseudomonas aeruginosa. The results of the evaluation suggest that the materials studied offer advantages over current clinical materials and indicate the potential suitability of the glass ceramics as therapeutic bone grafts.

Synthesis, deposition and crystal growth of CZTS nanoparticles onto ceramic tiles

Directory of Open Access Journals (Sweden)

Ivan Calvet

2015-09-01

Full Text Available The work presents a simple solvothermal method for CZTS nanoparticles preparation using hexadecylamine (HDA as a capping agent. The as-prepared CZTS powder was deposited as ink using Doctor Blade technique onto ceramic tile, as a substrate substituting the typical soda-lime glass. The as-prepared film was thermal treated at different temperatures in order to enhance the thin film crystallinity. CZTS crystal growth onto ceramic tile was obtained successfully for the first time.

Masking ability of bi- and tri- laminate all-ceramic veneers on tooth-colored ceramic discs.

Science.gov (United States)

Farhan, Daniel; Sukumar, Smitha; von Stein-Lausnitz, Axel; Aarabi, Ghazal; Alawneh, Ahmad; Reissmann, Daniel R

2014-01-01

A predictable esthetic outcome is imperative when placing ceramic veneers. Discolored teeth pose a major challenge as sufficient material thickness is required to achieve a good esthetic result. There is limited evidence in the literature that compares the masking ability of multi-laminate veneers. The aim of this in-vitro study was to compare the masking ability of bi-laminate (BL) and tri-laminate (TL) all-ceramic veneers cemented on tooth-colored ceramic discs. A total of 40 veneers (shade A1, 10-mm diameter, 0.8-mm thick) were manufactured-20 BL veneers (0.4-mm pressable ceramic coping veneered with 0.4-mm thick enamel layer) and 20 TL veneers (0.4-mm coping veneered with 0.2-mm thick opaque interlayer and 0.2-mm thick enamel layer). A bonding apparatus was utilized to adhesively cement all veneers on the ceramic discs (shade A1), simulating teeth of light and dark color. The resulting groups (N = 10 each) were the reference groups (shade A1 ceramic base) BL-1 and TL-1 veneers, and the test groups (shade A4 ceramic base) BL-4 and TL-4 veneers. The color of the cemented veneers was measured using a spectrophotometer. The data were converted to CIE L*a*b* coordinates, and ΔE* were calculated to allow for statistical analysis. The color differences between the samples with the A1 and A4 ceramic bases were significantly lower when covered with TL veneers (mean ΔE*: 3.2 units) than with BL veneers (mean ΔE*: 4.0 units: p bi-laminate veneers. Patients with discolored/darker teeth may benefit from a more predictable esthetic result when teeth restored with tri-laminate rather than bi-laminate veneers. © 2014 Wiley Periodicals, Inc.

Low cost sol–gel derived SiC–SiO{sub 2} nanocomposite as anti reflection layer for enhanced performance of crystalline silicon solar cells

Energy Technology Data Exchange (ETDEWEB)

Jannat, Azmira [School of Semiconductor and Chemical Engineering, Solar Energy Research Center, Chonbuk National University, Jeonju, Jeonbuk 54896 (Korea, Republic of); Solar Energy Engineering, Chonbuk National University, Jeonju, Jeonbuk 54896 (Korea, Republic of); Lee, Woojin [School of Semiconductor and Chemical Engineering, Solar Energy Research Center, Chonbuk National University, Jeonju, Jeonbuk 54896 (Korea, Republic of); Akhtar, M. Shaheer, E-mail: shaheerakhtar@jbnu.ac.kr [School of Semiconductor and Chemical Engineering, Solar Energy Research Center, Chonbuk National University, Jeonju, Jeonbuk 54896 (Korea, Republic of); New & Renewable Energy Materials Development Center (NewREC), Chonbuk National University, Jeonbuk (Korea, Republic of); Li, Zhen Yu [School of Semiconductor and Chemical Engineering, Solar Energy Research Center, Chonbuk National University, Jeonju, Jeonbuk 54896 (Korea, Republic of); Yang, O.-Bong, E-mail: obyang@jbnu.ac.kr [School of Semiconductor and Chemical Engineering, Solar Energy Research Center, Chonbuk National University, Jeonju, Jeonbuk 54896 (Korea, Republic of); New & Renewable Energy Materials Development Center (NewREC), Chonbuk National University, Jeonbuk (Korea, Republic of)

2016-04-30

Graphical abstract: - Highlights: • Sol–gel derived SiC–SiO{sub 2} nanocomposite was prepared. • It effectively coated as AR layer on p-type Si-wafer. • SiC–SiO{sub 2} layer on Si solar cells exhibited relatively low reflectance of 7.08%. • Fabricated Si solar cell attained highly comparable performance of 16.99% to commercial device. - Abstract: This paper describes the preparation, characterizations and the antireflection (AR) coating application in crystalline silicon solar cells of sol–gel derived SiC–SiO{sub 2} nanocomposite. The prepared SiC–SiO{sub 2} nanocomposite was effectively applied as AR layer on p-type Si-wafer via two step processes, where the sol–gel of precursor solution was first coated on p-type Si-wafer using spin coating at 2000 rpm and then subjected to annealing at 450 °C for 1 h. The crystalline, and structural observations revealed the existence of SiC and SiO{sub 2} phases, which noticeably confirmed the formation of SiC–SiO{sub 2} nanocomposite. The SiC–SiO{sub 2} layer on Si solar cells was found to be an excellent AR coating, exhibiting the low reflectance of 7.08% at wavelengths ranging from 400 to 1000 nm. The fabricated crystalline Si solar cell with SiC–SiO{sub 2} nanocomposite AR coating showed comparable power conversion efficiency of 16.99% to the conventional Si{sub x}N{sub x} AR coated Si solar cell. New and effective sol–gel derived SiC–SiO{sub 2} AR layer would offer a promising technique to produce high performance Si solar cells with low-cost.

The impact of core-shell nanotube structures on fracture in ceramic nanocomposites

International Nuclear Information System (INIS)

Liang, Xin; Yang, Yingchao; Lou, Jun; Sheldon, Brian W.

2017-01-01

Multi-wall carbon nanotubes (MWCNTs) can be used to create ceramic nanocomposites with improved fracture toughness. In the present work, atomic layer deposition (ALD) was employed to deposit thin oxide layers on MWCNTs. These core-shell structures were then used to create nanocomposites by using a polymer derived ceramic (PDC) to produce the matrix. Variations in both the initial MWCNT structure and the oxide layers led to substantial differences in fiber-pullout behavior. Single tube pullout tests also showed that the oxide coatings led to stronger bonding with the ceramic matrix. With high defect density MWCNTs, this led to shorter pull-out lengths which is consistent with the conventional understanding of fracture in ceramic matrix composites. However, with low defect density MWCNTs longer pullout lengths were observed with the oxide layers. To interpret the different trends that were observed, we believe that the ALD coatings should not be viewed simply as a means of altering the interfacial properties. Instead, the coated MWCNTs should be viewed as more complex core-shell fibers where both interface and internal properties can be controlled with the ALD layers. - Graphical abstract: Fracture properties of core-shell nanotubes reinforced ceramic nanocomposites.

Tough hybrid ceramic-based material with high strength

International Nuclear Information System (INIS)

Guo, Shuqi; Kagawa, Yutaka; Nishimura, Toshiyuki

2012-01-01

This study describes a tough and strong hybrid ceramic material consisting of platelet-like zirconium compounds and metal. A mixture of boron carbide and excess zirconium powder was heated to 1900 °C using a liquid-phase reaction sintering technique to produce a platelet-like ZrB 2 -based hybrid ceramic bonded by a thin zirconium layer. The platelet-like ZrB 2 grains were randomly present in the as-sintered hybrid ceramic. Relative to non-hybrid ceramics, the fracture toughness and flexural strength of the hybrid ceramic increased by approximately 2-fold.

Phase constituents and microstructure of laser cladding Al2O3/Ti3Al reinforced ceramic layer on titanium alloy

International Nuclear Information System (INIS)

Li Jianing; Chen Chuanzhong; Lin Zhaoqing; Squartini, Tiziano

2011-01-01

Research highlights: → In this study, Fe 3 Al has been chosen as cladding powder due to its excellent properties of wear resistance and high strength, etc. → Laser cladding of Fe 3 Al + TiB 2 /Al 2 O 3 pre-placed alloy powder on Ti-6Al-4V alloy substrate can form the Ti 3 Al/Fe 3 Al + TiB 2 /Al 2 O 3 ceramic layer, which can increase wear resistance of substrate. → In cladding process, Al 2 O 3 can react with TiB 2 leading to formation of Ti 3 Al and B. → This principle can be used to improve the Fe 3 Al + TiB 2 laser-cladded coating. - Abstract: Laser cladding of the Fe 3 Al + TiB 2 /Al 2 O 3 pre-placed alloy powder on Ti-6Al-4V alloy can form the Ti 3 Al/Fe 3 Al + TiB 2 /Al 2 O 3 ceramic layer, which can greatly increase wear resistance of titanium alloy. In this study, the Ti 3 Al/Fe 3 Al + TiB 2 /Al 2 O 3 ceramic layer has been researched by means of electron probe, X-ray diffraction, scanning electron microscope and micro-analyzer. In cladding process, Al 2 O 3 can react with TiB 2 leading to formation of amount of Ti 3 Al and B. This principle can be used to improve the Fe 3 Al + TiB 2 laser cladded coating, it was found that with addition of Al 2 O 3 , the microstructure performance and micro-hardness of the coating was obviously improved due to the action of the Al-Ti-B system and hard phases.

Disposal costs for SRP high-level wastes in borosilicate glass and crystalline ceramic waste forms

International Nuclear Information System (INIS)

Rozsa, R.B.; Campbell, J.H.

1982-01-01

Purpose of this document is to compare and contrast the overall burial costs of the glass and ceramic waste forms, including processing, storage, transportation, packaging, and emplacement in a repository. Amount of waste will require approximately 10,300 standard (24 in. i.d. x 9-5/6 ft length) canisters of waste glass, each containing about 3260 lb of waste at 28% waste loading. The ceramic waste form requires about one-third the above number of standard canisters. Approximately $2.5 billion is required to process and dispose of this waste, and the total cost is independent of waste form (glass or ceramic). The major cost items (about 80% of the total cost) for all cases are capital and operating expenses. The capital and 20-year operating costs for the processing facility are the same order of magnitude, and their sum ranges from about one-half of the total for the reference glass case to two-thirds of the total for the ceramic cases

Impact of GaN transition layers in the growth of GaN epitaxial layer on silicon

International Nuclear Information System (INIS)

Zhao Danmei; Zhao Degang; Jiang Desheng; Liu Zongshun; Zhu Jianjun; Chen Ping; Liu Wei; Li Xiang; Shi Ming

2015-01-01

A method for growing GaN epitaxial layer on Si (111) substrate is investigated. Due to the large lattice mismatch between GaN and AlN, GaN grown directly above an AlN buffer layer on the Si substrate turns out to be of poor quality. In this study, a GaN transition layer is grown additionally on the AlN buffer before the GaN epitaxial growth. By changing the growth conditions of the GaN transition layer, we can control the growth and merging of islands and control the transfer time from 3D to 2D growth mode. With this method, the crystalline quality of the GaN epitaxial layer can be improved and the crack density is reduced. Here, we have investigated the impact of a transition layer on the crystalline quality and stress evolution of a GaN epitaxial layer with methods of X-ray diffraction, optical microscopy and in situ reflectivity trace. With the increasing thickness of transition layer, the crack decreases and the crystalline quality is improved. But when the transition layer exceeds a critical thickness, the crystalline quality of the epilayer becomes lower and the crack density increases. (paper)

Prediction of crack propagation in layered ceramics with strong interfaces

Czech Academy of Sciences Publication Activity Database

Náhlík, Luboš; Šestáková, L.; Hutař, Pavel; Bermejo, R.

2010-01-01

Roč. 77, č. 11 (2010), s. 2192-2199 ISSN 0013-7944 R&D Projects: GA AV ČR(CZ) KJB200410803; GA ČR GA101/09/1821 Institutional research plan: CEZ:AV0Z20410507 Keywords : Ceramic laminate * Crack propagation direction * Residual stress * Flaw tolerant ceramics * Optimal design Subject RIV: JL - Materials Fatigue, Friction Mechanics Impact factor: 1.571, year: 2010

Effect of the processing parameters on the crystalline structure of lanthanide ortho tantalates

Energy Technology Data Exchange (ETDEWEB)

Siqueira, Kisla P.F.; Dias, Anderson, E-mail: anderson_dias@iceb.ufop.br [Universidade Federal de Ouro Preto (UFOP), MG (Brazil). Dept. de Quimica

2014-08-15

The influence of the synthesis parameters on the crystalline structures of ortho tantalate ceramics has been investigated. Powder materials were prepared by the solid-state reaction route. X-ray diffraction and Raman scattering measurements were employed to investigate the crystal structure of the produced materials. In this work, we analyzed three different examples in which the temperature and time were decisive on the final crystal structure of LnTaO{sub 4} compounds besides the lanthanide ionic size. Firstly, the thermal evolution for NdTaO{sub 4} samples showed that mixed crystal phases are formed up to 1100 °C, while well-crystallized M-NdTaO{sub 4} (I2/a) materials are obtained in temperatures higher than 1200 °C. Also, the influence of the synthesis time was investigated for the LaTaO{sub 4} ceramics: it was necessary 14 h to obtain samples in the P2{sub 1}/c structure. Finally, two polymorphs could be obtained for the DyTaO{sub 4} ceramics: P2/a and I2/a space groups were obtained at 1300 °C and 1500 °C, respectively. This study indicated that the temperature, time and lanthanide size are directly correlated with the crystalline arrangement of the ortho tantalate materials.(author)

Estimation of stepwise crack propagation in ceramic laminates with strong interfaces

Directory of Open Access Journals (Sweden)

K. Štegnerová

2015-10-01

Full Text Available During the last years many researchers put so much effort to design layered structures combining different materials in order to improve low fracture toughness and mechanical reliability of the ceramics. It has been proven, that an effective way is to create layered ceramics with strongly bonded interfaces. After the cooling process from the sintering temperature, due to the different coefficients of thermal expansion of individual constituents of the composite, significant internal residual stresses are developed within the layers. These stresses can change the crack behaviour. This results to the higher value of so-called apparent fracture toughness, i.e. higher resistance of the ceramic laminate to the crack propagation. The contribution deals with a description of the specific crack behaviour in the layered alumina-zirconia ceramic laminate. The main aim is to clarify crack behaviour in the compressive layer and provide computational tools for estimation of crack behaviour in the field of strong residual stresses. The crack propagation was investigated on the basis of linear elastic fracture mechanics. Fracture parameters were computed numerically and by author’s routines. Finite element models were developed in order to obtain a stress distribution in the laminate containing a crack and to simulate crack propagation. The sharp change of the crack propagation direction was estimated using Sih’s criterion based on the strain energy density factor. Estimated crack behaviour is qualitatively in a good agreement with experimental observations. Presented approach contributes to the better understanding of the toughening mechanism of ceramic laminates and can be advantageously used for design of new layered ceramic composites and for better prediction of their failure.

Heavy ion irradiation effects of brannerite-type ceramics

International Nuclear Information System (INIS)

Lian, J.; Wang, L.M.; Lumpkin, G.R.; Ewing, R.C.

2002-01-01

Brannerite, UTi 2 O 6 , occurs in polyphase Ti-based, crystalline ceramics that are under development for plutonium immobilization. In order to investigate radiation effects caused by α-decay events of Pu, a 1 MeV Kr + irradiation on UTi 2 O 6 , ThTi 2 O 6 , CeTi 2 O 6 and a more complex material, composed of Ca-containing brannerite and pyrochlore, was performed over a temperature range of 25-1020 K. The ion irradiation-induced crystalline-to-amorphous transformation was observed in all brannerite samples. The critical amorphization temperatures of the different brannerite compositions are: 970 K, UTi 2 O 6 ; 990 K, ThTi 2 O 6 ; 1020 K, CeTi 2 O 6 . The systematic increase in radiation resistance from Ce-, Th- to U-brannerite is related to the difference of mean atomic mass of A-site cation in the structure. As compared with the pyrochlore structure-type, brannerite phases are more susceptible to ion irradiation-induced amorphization. The effects of structure and chemical compositions on radiation resistance of brannerite-type and pyrochlore-type ceramics are discussed

Characterization of crystallinity of Ge{sub 1−x}Sn{sub x} epitaxial layers grown using metal-organic chemical vapor deposition

Energy Technology Data Exchange (ETDEWEB)

Inuzuka, Yuki [Department of Crystalline Materials Science, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); Ike, Shinichi; Asano, Takanori [Department of Crystalline Materials Science, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); Japan Society for the Promotion of Science, Chiyoda-ku, Tokyo 102-8472 (Japan); Takeuchi, Wakana [Department of Crystalline Materials Science, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); Nakatsuka, Osamu, E-mail: nakatuka@alice.xtal.nagoya-u.ac.jp [Department of Crystalline Materials Science, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); Zaima, Shigeaki [Department of Crystalline Materials Science, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); EcoTopia Science Institute, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan)

2016-03-01

The epitaxial growth of a Ge{sub 1−x}Sn{sub x} layer was examined using metal-organic chemical vapor deposition (MOCVD) with two types of Ge precursors; tetra-ethyl-germane (TEGe) and tertiary-butyl-germane (TBGe); and the Sn precursor tri-butyl-vinyl-tin (TBVSn). Though the growth of a Ge{sub 1−x}Sn{sub x} layer on a Ge(001) substrate by MOCVD has been reported, a high-Sn-content Ge{sub 1−x}Sn{sub x} layer and the exploration of MO material combinations for Ge{sub 1−x}Sn{sub x} growth have not been reported. Therefore, the epitaxial growth of a Ge{sub 1−x}Sn{sub x} layer on Ge(001) and Si(001) substrates was examined using these precursors. The Ge{sub 1−x}Sn{sub x} layers were pseudomorphically grown on a Ge(001) substrate, while the Ge{sub 1−x}Sn{sub x} layer with a high degree of strain relaxation was obtained on a Si(001) substrate. Additionally, it was found that the two Ge precursors have different growth temperature ranges, where the TBGe could realize a higher growth rate at a lower growth temperature than the TEGe. The Ge{sub 1−x}Sn{sub x} layers grown using a combination of TBGe and TBVSn exhibited a higher crystalline quality and a smoother surface compared with the Ge{sub 1−x}Sn{sub x} layer prepared by low-temperature molecular beam epitaxy. In this study, a Ge{sub 1−x}Sn{sub x} epitaxial layer with a Sn content as high as 5.1% on a Ge(001) substrate was achieved by MOCVD at 300 °C. - Highlights: • Tertiary-butyl-germane and tri-butyl-vinyl-tin are suitable for Ge{sub 1−x}Sn{sub x} MOCVD growth. • We achieved a Sn content of 5.1% in Ge{sub 1−x}Sn{sub x} epitaxial layer on Ge(001). • The Ge{sub 1−x}Sn{sub x} layers grown on Ge and Si by MOCVD have high crystalline quality.

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

Energy Technology Data Exchange (ETDEWEB)

Li Jianing, E-mail: ljnljn1022@163.com [Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials (Ministry of Education), Department of Materials Science, Shandong University, Jing Shi Road 17923, Jinan 250061, Shandong (China); Chen Chuanzhong [Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials, Ministry of Education, Department of Materials Science, Shandong University, Jing Shi Road 17923, Jinan 250061, Shandong (China); Squartini, Tiziano [INFM-Department of Physics, Siena University, Siena 53100 (Italy); He Qingshan [Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials, Ministry of Education, Department of Materials Science, Shandong University, Jing Shi Road 17923, Jinan 250061, Shandong (China)

2010-12-15

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

Crystalline and lattice matched Ba0.7Si0.3O layers on plane and vicinal Si(001) surfaces

International Nuclear Information System (INIS)

Zachariae, J.

2006-01-01

In this work the low temperature growth conditions of epitaxial and lattice-matched Ba 0.7 Sr 0.3 O layers on Si(100) were investigated using the combination of low energy electron diffraction (LEED), x-ray photoemission (XPS) and electron energy loss spectroscopy (EELS). With these methods crystallinity, stoichiometry and electronic structure of both occupied and unoccupied levels were studied as a function of layer thickness. Oxide layers were generated by evaporating the metals in oxygen ambient pressure with the sample at room temperature. Perfect crystallinity and lattice matching was only obtained starting with a preadsorbed monolayer (ML) of Sr or Ba at a concentration close to one monolayer. The XPS analysis shows that Ba 0.7 Sr 0.3 O as a high-K gate dielectric offers an adequate band gap, an appropriate band alignment and a atomically sharp interface to the Si(001) substrate. No silicide and silicate species, or SiO 2 formation at the interface after oxidation were found. To show that Ba 0.7 Sr 0.3 O is really appropriate to replace SiO 2 as a gate dielectric, first C-V and I-V curves of MOS-diodes with SrO, BaO and Ba 0.7 Sr 0.3 O as gateoxide were measured under ambient conditions. Besides other results, it turns out that the measured dielectric constant of Ba 0.7 Sr 0.3 O conforms with the expected value of ε ∼ 25 - 30. Exploring ways for self-organized structuring of insulating films, the possibility to produce replicas of step trains, given by a vicinal Si(001)-4 [110] surface, in layers of crystalline and perfectly lattice matched Ba 0.7 Sr 0.3 O were investigated. For this purpose high-resolution spot profile analyses in low-energy electron diffraction (SPA-LEED) both on flat Si(001) and on vicinal Si(001)-4 [110] were carried out. The G(S) analysis of these mixed oxide layers reveals a strong influence of local compositional fluctuations of Sr and Ba ions and their respective scattering phases, which appears as an unphysically large variation

Chemical treatment and biomimetic coating evaluating in zirconia-alumina ceramics

International Nuclear Information System (INIS)

Aguiar, Amanda Abati

2007-01-01

Ceramic materials, as alumina and zirconia have been explored along the years as biomaterials application. The bio inert nature has been stimulating the development of new alternatives, as chemical treatments to improve the biological application of these ceramics. The biomimetic process of bio inert ceramics for coating apatite is based on soaking the implant in a simulated body fluid, SBF, with ion concentrations nearly equal to those of human blood plasma. The bioactivity of the material is related with the formation of a layer constituted of hydroxyapatite low crystalline, similar to the biological apatite. The biocompatibility associated to the structural properties of the alumina and zirconia has been stimulating the clinical use of these materials, mainly in areas of larger mechanical requests, places not recommended for bioactive hydroxyapatite, for instance. In this work samples of alumina, zirconia doped with Yttria (3% mol) and composites of alumina and zirconia doped with Yttria (3% mol) were prepared by co-precipitation method, calcinate, sintered, chemically treated with solutions of acid phosphoric and sodium hydroxide and them immersed in 1.0 M and 1.5 M SBF. The calcinate powders were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), gas adsorption (BET) and laser diffraction. The XRD results indicate that the samples are low crystalline. It was observed for BET that the samples present high specific surface area. The results of laser diffraction and SEM showed that the powders are agglomerates. The sintered samples were analyzed by XRD, SEM and X-ray fluorescence (XRF). The phases quantified by Rietveld method were: cubic, tetragonal and monoclinic of the zirconia, besides the phase alpha of the alumina. The chemical treatment with phosphoric acid didn't present a tendency of larger apatite formation in relation to the samples no chemically treated. The treatment with sodium hydroxide provoked accentuated transformation of

Different in vitro behavior of two Ca3(PO42 based biomaterials, a glass-ceramic and a ceramic, having the same chemical composition

Directory of Open Access Journals (Sweden)

M. Cristina Guerrero-Lecuona

2015-09-01

The reactivity in simulated body fluid and Tris–HCl solutions was studied. Both materials showed bioactive behavior, but the glass-ceramic dissolved faster, releasing large proportion of Ca and P ions, which afterwards nucleated and precipitated. However, the ceramic was more stable under the same conditions in these solutions. Glass-ceramic composite has a more open structure and allowed the faster formation of a bone-like apatite layer than the ceramic.

Ageing of low-firing prehistoric ceramics in hydrothermal conditions

Directory of Open Access Journals (Sweden)

Petra Zemenová

2012-03-01

Full Text Available Remains of a prehistoric ceramic object, a moon-shaped idol from the Bronze Age found in archaeological site Zdiby near Prague in the Czech Republic, were studied especially in terms of the firing temperature. Archaeological ceramics was usually fired at temperatures below 1000 °C. It contained unstable non-crystalline products, residua after calcination of clay components of a ceramic material. These products as metakaolinite can undergo a reverse rehydration to a structure close to kaolinite. The aim of this work was to prove whether the identified kaolinite in archaeological ceramics is a product of rehydration. The model compound containing high amount of kaolinite was prepared in order to follow its changes during calcination and hydrothermal treatment. Archaeological ceramics and the model compound were treated by hydrothermal ageing and studied by XRF, XRD and IR analyses. It was proved that the presence of kaolinite in the border-parts of the archaeological object was not a product of rehydration, but that it originated from the raw materials.

Laser synthesis of nanostructured ceramics from liquid precursors

International Nuclear Information System (INIS)

Wilden, Johannes; Fischer, Georg

2007-01-01

The free-form net shape laser synthesis of nanostructured ceramics from liquid precursors enables a residual stress-free production of high temperature resistant ceramic units and components for the use in microsystem engineering. Due to the use of molecular compounded liquid, ceramic precursors the resulting ceramic components show outstanding properties, for example high purity and a nanostructured material design. The use of pulsed lasers enables a defined input of energy required to pyrolyse the precursor material into a crystalline ceramic, so the active volume can be reduced significantly compared to other processes, for example pyrolysis by furnace. In this paper several methods for a further minimization of the active volume are presented. The investigations determined different factors affecting the process. Realizing selective experiments allows a determination of their influencing level and the definition of a working area to produce three-dimensional components with high aspect ratio. By several studies, e.g., scanning electron microscopy, transmission electron microscopy as well as X-ray diffraction analysis, the atomic structure and composition of the created components were analyzed and valued, so the different reaction processes can be described extensively

Temperature variation in metal ceramic technology analyzed using time domain optical coherence tomography

Science.gov (United States)

Sinescu, Cosmin; Topala, Florin I.; Negrutiu, Meda Lavinia; Duma, Virgil-Florin; Podoleanu, Adrian G.

2014-01-01

The quality of dental prostheses is essential in providing good quality medical services. The metal ceramic technology applied in dentistry implies ceramic sintering inside the dental oven. Every ceramic material requires a special sintering chart which is recommended by the producer. For a regular dental technician it is very difficult to evaluate if the temperature inside the oven remains the same as it is programmed on the sintering chart. Also, maintaining the calibration in time is an issue for the practitioners. Metal ceramic crowns develop a very accurate pattern for the ceramic layers depending on the temperature variation inside the oven where they are processed. Different patterns were identified in the present study for the samples processed with a variation in temperature of +30 °C to +50 °C, respectively - 30 0°C to -50 °C. The OCT imagistic evaluations performed for the normal samples present a uniform spread of the ceramic granulation inside the ceramic materials. For the samples sintered at a higher temperature an alternation between white and darker areas between the enamel and opaque layers appear. For the samples sintered at a lower temperature a decrease in the ceramic granulation from the enamel towards the opaque layer is concluded. The TD-OCT methods can therefore be used efficiently for the detection of the temperature variation due to the ceramic sintering inside the ceramic oven.

Contribution to the joining technique of SiC-ceramic using metallic interlayers

International Nuclear Information System (INIS)

Gottselig, B.; Gyarmati, E.; Naoumidis, A.; Nickel, H.

1989-07-01

For ceramics to be feasible for technical uses suitable joining techniques must be developed that allow reliable ceramic-ceramic and ceramic-metal connections. As yet such procedures exist, based only on empirical studies omitting the reaction behaviour of the joining materials and the specific properties of the reaction products. For this reason the reaction behaviour of silicon carbide with selected metals and subsequently the compatibility of these reaction layers with the ceramic substrate were investigated. The results gained were then applied to silicon carbide joints using intermediate metallic layers. With the reaction phase Ti 3 SiC 2 , found to be the most suitable in basic experiments, joining strengths could be obtained relative tc the mean strength and Weibull modulus comparable to those of the ceramic starting material. (orig.) [de

Calcium titanium silicate based glass-ceramic for nuclear waste immobilisation

Science.gov (United States)

Sharma, K.; Srivastav, A. P.; Goswami, M.; Krishnan, Madangopal

2018-04-01

Titanate based ceramics (synroc) have been studied for immobilisation of nuclear wastes due to their high radiation and thermal stability. The aim of this study is to synthesis glass-ceramic with stable phases from alumino silicate glass composition and study the loading behavior of actinides in glass-ceramics. The effects of CaO and TiO2 addition on phase evolution and structural properties of alumino silicate based glasses with nominal composition x(10CaO-9TiO2)-y(10Na2O-5 Al2O3-56SiO2-10B2O3); where z = x/y = 1.4-1.8 are reported. The glasses are prepared by melt-quench technique and characterized for thermal and structural properties using DTA and Raman Spectroscopy. Glass transition and peak crystallization temperatures decrease with increase of CaO and TiO2 content, which implies the weakening of glass network and increased tendency of glasses towards crystallization. Sphene (CaTiSiO5) and perovskite (CaTiO3) crystalline phases are confirmed from XRD which are well known stable phase for conditioning of actinides. The microsturcture and elemental analysis indicate the presence of actinide in stable crystalline phases.

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

Science.gov (United States)

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

2014-01-01

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

Composite of ceramic-coated magnetic alloy particles

Science.gov (United States)

Moorhead, Arthur J.; Kim, Hyoun-Ee

2000-01-01

A composite structure and method for manufacturing same, the composite structure being comprised of metal particles and an inorganic bonding media. The method comprises the steps of coating particles of a metal powder with a thin layer of an inorganic bonding media selected from the group of powders consisting of a ceramic, glass, and glass-ceramic. The particles are assembled in a cavity and heat, with or without the addition of pressure, is thereafter applied to the particles until the layer of inorganic bonding media forms a strong bond with the particles and with the layer of inorganic bonding media on adjacent particles. The resulting composite structure is strong and remains cohesive at high temperatures.

Tuning Eu{sup 3+} emission in europium sesquioxide films by changing the crystalline phase

Energy Technology Data Exchange (ETDEWEB)

Mariscal, A., E-mail: antonio.mariscal@csic.es [Laser Processing Group, Instituto de Óptica, CSIC, C/ Serrano 121, 28006 Madrid (Spain); Quesada, A. [Ceramics for Smart Systems Group, Instituto de Cerámica y Vidrio, C/ Kelsen 5, 28049 Madrid (Spain); Camps, I. [Laser Processing Group, Instituto de Óptica, CSIC, C/ Serrano 121, 28006 Madrid (Spain); Palomares, F.J. [Instituto de Ciencia de Materiales de Madrid, C/ Sor Juana Inés de la Cruz 3, 28049 Madrid (Spain); Fernández, J.F. [Ceramics for Smart Systems Group, Instituto de Cerámica y Vidrio, C/ Kelsen 5, 28049 Madrid (Spain); Serna, R. [Laser Processing Group, Instituto de Óptica, CSIC, C/ Serrano 121, 28006 Madrid (Spain)

2016-06-30

Highlights: • PLD production of high quality europium sesquioxide (Eu{sub 2}O{sub 3}) films. • The deposition of Al{sub 2}O{sub 3} capping and/or buffer layers modifies the crystallization for Eu{sub 2}O{sub 3} films upon annealing. • The formation of cubic or monoclinic phases can be favored. • Eu{sup 3+} emission tuning is achieved as a consequence of crystal field effects. - Abstract: We report the growth of europium sesquioxide (Eu{sub 2}O{sub 3}) thin films by pulsed laser deposition (PLD) in vacuum at room temperature from a pure Eu{sub 2}O{sub 3} ceramic bulk target. The films were deposited in different configurations formed by adding capping and/or buffer layers of amorphous aluminum oxide (a-Al{sub 2}O{sub 3}). The optical properties, refractive index and extinction coefficient of the as deposited Eu{sub 2}O{sub 3} layers were obtained. X-ray photoelectron spectroscopy (XPS) measurements were done to assess its chemical composition. Post-deposition annealing was performed at 500 °C and 850 °C in air in order to achieve the formation of crystalline films and to accomplish photoluminescence emission. According to the analysis of X-ray diffraction (XRD) spectra, cubic and monoclinic phases were formed. It is found that the relative amount of the phases is related to the different film configurations, showing that the control over the crystallization phase can be realized by adequately designing the structures. All the films showed photoluminescence emission peaks (under excitation at 355 nm) that are attributed to the intra 4f-transitions of Eu{sup 3+} ions. The emission spectral shape depends on the crystalline phase of the Eu{sub 2}O{sub 3} layer. Specifically, changes in the hypersensitive {sup 5}D{sub 0} → {sup 7}F{sub 2} emission confirm the strong influence of the crystal field effect on the Eu{sup 3+} energy levels.

Multilayer Ceramic Regenerator Materials for 4 K Cooling

International Nuclear Information System (INIS)

Numazawa, T.; Kamiya, K.; Satoh, T.; Nozawa, H.; Yanagitani, T.

2006-01-01

The ceramics oxide magnetic materials have shown excellent properties for use as regenerator materials used in 4 K crycoolers. Currently four kinds of oxide magnetic materials GdVO4, GAP=GdAlO3, GOS=Gd2O2S and Tb2O2S are available for applications for regenerators or thermal anchors from 2 K to 8 K. This paper focused on controlling the heat capacity of the (GdxTb1-x)2O2S system to cover the refrigeration temperatures between 6 K and 8 K. A concept of multilayer regenerator material consisting of multicomponent magnetic materials has been proposed and investigated. Two-layer ceramic material including two kinds of magnetic materials (Gd0.1Tb0.9)2O2S+Tb2O2S was successfully fabricated in the form of regenerator particles with an average diameter of 0.25 mm. Measured heat capacity data showed that it had twin peaks relating to those of (Gd0.1Tb0.9)2O2S and Tb2O2S, and the entire curve became broader and wider. The mechanical properties of strength and hardness of the two-layer ceramic material were the same as other ceramic regenerator materials like GOS. Thus, it is concluded that the multilayer ceramic material is very useful to control the heat capacity of the regenerator particles. The cooling tests using the two-layer ceramic material with HoCu2 and GOS have been done to investigate the 2nd stage regenerator configuration

Effect of pH values on surface modification and solubility of phosphate bioglass-ceramics in the CaO-P 2O 5-Na 2O-SrO-ZnO system

Science.gov (United States)

Li, Xudong; Cai, Shu; Zhang, Wenjuang; Xu, Guohua; Zhou, Wei

2009-08-01

The bioactive glass-ceramics in the CaO-P 2O 5-Na 2O-SrO-ZnO system were synthesized by the sol-gel technique, and then chemically treated at different pH values to study the solubility and surface modification. Samples sintered at 650 °C for 4 h consisted of the crystalline phase β-Ca 2P 2O 7 and the glass matrix. After soaking in the solution at pH 1.0, the residual glass matrix on the surface appeared entirely dissolved and no new phase could be detected. Whereas at pH 3.0, web-like layer exhibiting peaks corresponding to CaP 2O 6 was formed and covered the entire surface of the sample. When conducted at pH 10.0, only part of the glass matrix was dissolved and a new phase Ca 4P 6O 19 was precipitated, forming the petaline layer. The chemical treatment can easily change the surface morphologies and phase composition of this bioactive glass-ceramics. The higher level of surface roughness resulting from the new-formed layer would improve the interface bonding and benefit for cell adhesion.

Rare earth ion controlled crystallization of mica glass-ceramics

International Nuclear Information System (INIS)

Garai, Mrinmoy; Karmakar, Basudeb

2016-01-01

In understanding the effects of rare earth ions to control the crystallization and microstructure of alkaline boroaluminosilicate system, the CeO_2, Nd_2O_3, Sm_2O_3 and Gd_2O_3 doped K_2O−MgO−B_2O_3−Al_2O_3−SiO_2−F glasses were synthesized by melt-quenching at 1550 °C. Higher density (2.82–3.06 g cm"−"3) and thermal stability (glass phase) is experiential on addition of rare earth content, which also affects in increasing the glass transition temperature (T_g) and crystallization temperature (T_c). Decrease of thermal expansion in glasses with rare earth ion content is maintained by the stabilization of glass matrix owing to their large cationic field strength. A significant change in the non-isothermal DSC thermogram observed at 750–1050 °C is attributed to fluorophlogopite crystallization. Opaque glass-ceramics were prepared from such glasses by single step heat-treatment at 1050 °C; and the predominant crystalline phases are identified as fluorophlogopite mica, KMg_3(AlSi_3O_1_0)F_2 by XRD and EDX analysis. The compact glass-ceramic microstructure by the agglomeration of fluorophlogopite mica crystallites (crystal size ∼ 100–500 nm, FESEM) is achieved in attendance of rare earth ion; and such microstructure controlled the variation of density, thermal expansion and microhardness value. Higher thermal expansion (11.11–14.08 × 10"−"6/K at 50–800 °C and 50–900 °C) of such glass-ceramics approve that these rare earth containing glasses can be useful for high temperature vacuum sealing application with metal or solid electrolyte. The increase of Vickers microhardness (5.27–5.61 GPa) in attendance of rare earth ions is attributed to the compact crystallinity of fluorophlogopite mica glass-ceramic microstructure. - Highlights: • Synthesis of rare earth oxide doped alkaline boroaluminosilicate glasses. • Development of opaque fluorophlogopite mica glass-ceramics by single-step heat treatment. • Nanocrystalline glass-ceramic

Microstructure of gross chill-mark defect in a glass-ceramic preform

International Nuclear Information System (INIS)

Spears, R.K.

1980-01-01

The microstructure of a vacuum tube glass-ceramic preform containing gross chill-marks on the top and bottom surfaces as well as on the sides was analyzed. The preform was ceramed in a graphite mold and examined using SEM. The glass-ceramic had an extremely dense and fine crystalline structure except where the chill-marks were located. In those areas of matrix glass following the chill-mark plane were evident. It is concluded that gross chill-marks will affect the microstructure by disrupting the chemistry or nucleating characteristics in such a way that a chill-mark regon would appear to be depleted of crystallites. Although the crystallites in this region are larger, the quantity is lower than in the base glass-ceramic. The affected area caused by the chill-mark left a band of matrix glass approximately 100 μ wide. It is believed that planar defects of this size will degrade the mechanical and permeation properties of the glass-ceramic

Radioactive waste immobilization in protective ceramic forms by the HIP method at high pressures

International Nuclear Information System (INIS)

Sayenko, S.Yu.; Kantsedal, V.P.; Tarasov, R.V.; Starchenko, V.A.; Lyubtsev, R.I.

1993-01-01

Intense research activities have been carried out in recent years at the Kharkov Institute of Physics and Technology (KIPT) to develop the method of hot isostatic pressing (HIP) for immobilizing radioactive (primarily, high-level) wastes. With this method, the radioactive material is immobilized in a matrix under the simultaneous action of high pressures (up to 6,000 atm) and appropriate temperatures. The process has 2 variants: (1) radioactive wastes are treated as powders of oxides resulting from calcination during chemical treatment of spent fuel. In this case the radioactive material enters into the crystalline structure of the immobilized matrix or is distributed in the matrix as a homogeneous mixture; (2) protective barrier layers are pressed on spent fuel rods or their pieces as radioactive wastes, by the HIP method (fuel rod encapsulation in a protective form). Based on numerous results from various studies, the authors suggest that various ceramic compositions should be used as protective materials. Here the authors report two trends of their investigations: (1) development of ecologically clean process equipments for radioactive waste treatment by the HIP method; (2) manufacture of promising protective ceramic compositions and investigation of their physico-mechanical properties

A comparative study of progressive wear of four dental monolithic, veneered glass-ceramics.

Science.gov (United States)

Zhang, Zhenzhen; Yi, Yuanping; Wang, Xuesong; Guo, Jiawen; Li, Ding; He, Lin; Zhang, Shaofeng

2017-10-01

This study evaluated the wear performance and wear mechanisms of four dental glass-ceramics, based on the microstructure and mechanical properties in the progressive wear process. Bar (N = 40, n = 10) and disk (N = 32, n = 8) specimens were prepared from (A) lithium disilicate glass-ceramic (LD), (B) leucite reinforced glass-ceramic (LEU), (C) feldspathic glass-ceramic (FEL), and (D) fluorapatite glass-ceramic (FLU). The bar specimens were tested for three-point flexural strength, hardness, fracture toughness and elastic modulus. The disk specimens paired with steatite antagonists were tested in a pin-on-disk tribometer with 10N up to 1000,000 wear cycles. The wear analysis of glass-ceramics was performed using a 3D profilometer after every 200,000 wear cycles. Wear loss of steatite antagonists was calculated by measuring the weight and density using sensitive balance and Archimedes' method. Wear morphologies and microstructures were analyzed by scanning electron microscopy (SEM). The crystalline phase compositions were determined using X-ray diffraction (XRD). One-way analysis of variance (ANOVA) was used to analyze the data. Multiple pair-wise comparison of means was performed by Tukey's post-hoc test. LD showed the highest fracture toughness, flexural strength, elastic modulus and crystallinity, followed by LEU and FEL, and FLU showed the lowest. However, the hardness of LD was lower than all the other three types of ceramics. For steatite antagonists, LD produced the least wear loss of antagonist, followed by LEU and FEL, and FLU had the most wear loss. For glass-ceramic materials, LD exhibited similar wear loss as LEU, but more than FLU and FEL did. Moreover, fracture occurred on the wear surface of FLU. In the progressive wear process, veneering porcelains showed better wear resistance but fluorapatite veneering porcelains appeared fracture surface. Monolithic lithium disilicate glass-ceramics with higher mechanical properties showed more wear loss, however

Electrical properties of pseudo-single-crystalline Ge films grown by Au-induced layer exchange crystallization at 250 °C

Science.gov (United States)

Higashi, H.; Kudo, K.; Yamamoto, K.; Yamada, S.; Kanashima, T.; Tsunoda, I.; Nakashima, H.; Hamaya, K.

2018-06-01

We study the electrical properties of pseudo-single-crystalline Ge (PSC-Ge) films grown by a Au-induced layer exchange crystallization method at 250 °C. By inserting the SiNx layer between PSC-Ge and SiO2, we initiatively suppress the influence of the Ge/SiO2 interfacial defective layers, which have been reported in our previous works, on the electrical properties of the PSC-Ge layers. As a result, we can detect the influence of the ionized Au+ donors on the temperature-dependent hole concentration and Hall mobility. To further examine their electrical properties in detail, we also fabricate p-thin-film transistors (TFTs) with the PSC-Ge layer. Although the off-state leakage currents are suppressed by inserting the SiNx layer, the value of on/off ratio remains poor (leakage current although a nominal field effect mobility is enhanced up to ˜25 cm2/V s. Considering these features, we conclude that the Au contaminations into the PSC-Ge layer can affect the electrical properties and device performances despite a low-growth temperature of 250 °C. To achieve further high-performance p-TFTs, we have to suppress the Au contaminations into PSC-Ge during the Au-induced crystallization growth.

Sintering and crystallization behavior of CaMgSi2O6-NaFeSi2O6 based glass-ceramics

International Nuclear Information System (INIS)

Goel, Ashutosh; Kansal, Ishu; Ferrari, Anna Maria; Pascual, Maria J.; Barbieri, Luisa; Bondioli, Federica; Lancellotti, Isabella; Ribeiro, Manuel J.; Ferreira, Jose M. F.

2009-01-01

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

[Microstructure and mechanical property of a new IPS-Empress 2 dental glass-ceramic].

Science.gov (United States)

Luo, Xiao-ping; Watts, D C; Wilson, N H F; Silsons, N; Cheng, Ya-qin

2005-03-01

To investigate the microstructure and mechanical properties of a new IPS-Empress 2 dental glass-ceramic. AFM, SEM and XRD were used to analyze the microstructure and crystal phase of IPS-Empress 2 glass-ceramic. The flexural strength and fracture toughness were tested using 3-point bending method and indentation method respectively. IPS-Empress 2 glass-ceramic mainly consisted of lithium disilicate crystal, lithium phosphate and glass matrix, which formed a continuous interlocking structure. The crystal phases were not changed before and after hot-pressed treatment. AFM showed nucleating agent particles of different sizes distributed on the highly polished ceramic surface. The strength and fracture toughness were 300 MPa and 3.1 MPam(1/2). The high strength and fracture toughness of IPS-Empress 2 glass ceramic are attributed to the fine lithium disilicate crystalline, interlocking microstructure and crack deflection.

Immobilization of gadolinium in iron borophosphate glasses and iron borophosphate based glass-ceramics: Implications for the immobilization of plutonium(Ⅲ)

Energy Technology Data Exchange (ETDEWEB)

Wang, Fu, E-mail: wangfu@swust.edu.cn; Liao, Qilong, E-mail: liaoqilong@swust.edu.cn; Dai, Yunya; Zhu, Hanzhen

2016-08-15

Immobilization of gadolinium (Gd), a nonradioactive surrogate for Pu{sup 3+}, in iron borophosphate glasses/glass-ceramics (IBP glasses/glass-ceramics) has been investigated. The IBP glass containing 4 mol% Gd{sub 2}O{sub 3} is homogeneously amorphous. At higher Gd{sub 2}O{sub 3} concentrations, additional Gd is retained in the glasses as crystalline inclusions of monazite GdPO{sub 4} crystalline phase detected with X-ray diffraction. Moreover, Gd{sub 2}O{sub 3} addition increases the T{sub g} of the IBP glasses in glass formation range, which is consistent with the structural modification of the glasses. The structure of the Gd{sub 2}O{sub 3}-loaded IBP glasses/glass-ceramics is mainly based on pyrophosphate units. The chemical durability of Gd{sub 2}O{sub 3}-loaded IBP glasses/glass-ceramics is comparable to widely used borosilicate glass waste forms and the existence of monazite GdPO{sub 4} crystalline phase does not degrade the aqueous chemical durability of the IBP glasses/glass-ceramics. The Gd-loading results imply that the solubility should not be a limiting factor in processing nuclide Pu{sup 3+} if the formed crystalline phase(s) have high chemical durability. - Highlights: • Monazite GdPO{sub 4} are identified in the IBP glasses containing up to 6 mol% Gd{sub 2}O{sub 3}. • R{sub L} of the Gd{sub 2}O{sub 3}-loaded IBP glasses/glass-ceramics are about 10{sup −2} g m{sup −2} d{sup −1}. • Existence of GdPO{sub 4} does not degrade aqueous chemical durability of the IBP glass. • T{sub g} increases with increasing Gd{sub 2}O{sub 3} content in glass formation range. • IBP glasses are potential hosts for the immobilization of Pu{sup 3+} containing HLWs.

Evaluation of a novel multiple phase veneering ceramic.

Science.gov (United States)

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

2015-04-01

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

Upconversion studies of Er3+/Yb3+ doped SrO.TiO2 borosilicate glass ceramic system

International Nuclear Information System (INIS)

Maheshwari, Aditya; Om Prakash; Kumar, Devendra; Rai, S.B.

2011-01-01

Upconversion behaviour has been studied in various matrices and fine powders of SrTiO 3 by previous workers. In present work, Er 3+ /Yb 3+ were doped in appropriate ratio in SrO.TiO 2 borosilicate glass ceramic system to study the upconversion phenomenon. Dielectric properties of this class of glass ceramic system have been extensively investigated by Thakur et al. It has been observed that both upconversion efficiency and dielectric constant increases with transformation of glass into glass ceramic. Therefore, present investigation is based upon the study of optical as well as the electrical properties of same glass ceramic system. In order to prepare different crystalline matrices, two different Er 3+ /Yb 3+ :SrO.TiO 2 borosilicate glasses with same amount of Er 2 O 3 and Yb 2 O 3 were prepared by melt quench method. Glasses were transparent with light-wine colour. Glass ceramics were prepared from the glasses by heat treatment based on DTA (Differential thermal analysis) results. Glass ceramics were fully opaque with brownish-cream colour. Powder X-ray diffraction (XRD) patterns confirmed that two different crystalline matrices, Sr 3 Ti 2 O 7 , Ti 10 O 19 and SrTiO 3 , TiO 2 were present in two glass ceramic samples respectively. Luminescence properties of glass and glass ceramic samples with 976nm laser irradiation showed that the intensities of the green and red emission increased multiple times in glass ceramic than that of the glass. Possible mechanisms responsible for upconversion eg. Energy Transfer (ET) and Excited State Absorption (ESA), were studied through laser pumping power log dependence

CERAMIC WASTE FORM DATA PACKAGE

Energy Technology Data Exchange (ETDEWEB)

Amoroso, J.; Marra, J.

2014-06-13

The purpose of this data package is to provide information about simulated crystalline waste forms that can be used to select an appropriate composition for a Cold Crucible Induction Melter (CCIM) proof of principle demonstration. Melt processing, viscosity, electrical conductivity, and thermal analysis information was collected to assess the ability of two potential candidate ceramic compositions to be processed in the Idaho National Laboratory (INL) CCIM and to guide processing parameters for the CCIM operation. Given uncertainties in the CCIM capabilities to reach certain temperatures throughout the system, one waste form designated 'Fe-MP' was designed towards enabling processing and another, designated 'CAF-5%TM-MP' was designed towards optimized microstructure. Melt processing studies confirmed both compositions could be poured from a crucible at 1600{degrees}C although the CAF-5%TM-MP composition froze before pouring was complete due to rapid crystallization (upon cooling). X-ray diffraction measurements confirmed the crystalline nature and phase assemblages of the compositions. The kinetics of melting and crystallization appeared to vary significantly between the compositions. Impedance spectroscopy results indicated the electrical conductivity is acceptable with respect to processing in the CCIM. The success of processing either ceramic composition will depend on the thermal profiles throughout the CCIM. In particular, the working temperature of the pour spout relative to the bulk melter which can approach 1700{degrees}C. The Fe-MP composition is recommended to demonstrate proof of principle for crystalline simulated waste forms considering the current configuration of INL's CCIM. If proposed modifications to the CCIM can maintain a nominal temperature of 1600{degrees}C throughout the melter, drain, and pour spout, then the CAF-5%TM-MP composition should be considered for a proof of principle demonstration.

Calcium fluoride whispering gallery mode optical resonator with reduced thermal sensitivity

Science.gov (United States)

Savchenkov, Anatoliy; Matsko, Andrey

2018-03-01

We demonstrate a crystalline CaF2 resonator with thermal sensitivity of the optical modes approaching zero. The resonator is made by laminating a calcium fluoride layer forming an optical monolithic cavity with ceramic compensation layers. The ceramics is characterized with negative thermal expansion coefficient achievable in a certain temperature range. The thermally compensated resonator has a potential application for laser frequency stabilization.

Mechanical performance of a biocompatible biocide soda-lime glass-ceramic.

Science.gov (United States)

López-Esteban, S; Bartolomé, J F; Dí Az, L A; Esteban-Tejeda, L; Prado, C; López-Piriz, R; Torrecillas, R; Moya, J S

2014-06-01

A biocompatible soda-lime glass-ceramic in the SiO2-Na2O-Al2O3-CaO-B2O3 system containing combeite and nepheline as crystalline phases, has been obtained at 750°C by two different routes: (i) pressureless sintering and (ii) Spark Plasma Sintering. The SPS glass-ceramic showed a bending strength, Weibull modulus, and toughness similar values to the cortical human bone. This material had a fatigue limit slightly superior to cortical bone and at least two times higher than commercial dental glass-ceramics and dentine. The in vitro studies indicate that soda-lime glass-ceramic is fully biocompatible. The in vivo studies in beagle jaws showed that implanted SPS rods presented no inflammatory changes in soft tissues surrounding implants in any of the 10 different cases after four months implantation. The radiological analysis indicates no signs of osseointegration lack around implants. Moreover, the biocide activity of SPS glass-ceramic versus Escherichia coli, was found to be >4log indicating that it prevents implant infections. Because of this, the SPS new glass-ceramic is particularly promising for dental applications (inlay, crowns, etc). Copyright © 2014 Elsevier Ltd. All rights reserved.

Ceramic and glass radioactive waste forms

Energy Technology Data Exchange (ETDEWEB)

Readey, D.W.; Cooley, C.R. (comps.)

1977-01-01

This report contains 14 individual presentations and 6 group reports on the subject of glass and polycrystalline ceramic radioactive waste forms. It was the general consensus that the information available on glass as a waste form provided a good basis for planning on the use of glass as an initial waste form, that crystalline ceramic forms could also be good waste forms if much more development work were completed, and that prediction of the chemical and physical stability of the waste form far into the future would be much improved if the basic synergistic effects of low temperature, radiation and long times were better understood. Continuing development of the polycrystalline ceramic forms was recommended. It was concluded that the leach rate of radioactive species from the waste form is an important criterion for evaluating its suitability, particularly for the time period before solidified waste is permanently placed in the geologic isolation of a Federal repository. Separate abstracts were prepared for 12 of the individual papers; the remaining two were previously abstracted.

Integral ceramic superstructure evaluation using time domain optical coherence tomography

Science.gov (United States)

Sinescu, Cosmin; Bradu, Adrian; Topala, Florin I.; Negrutiu, Meda Lavinia; Duma, Virgil-Florin; Podoleanu, Adrian G.

2014-02-01

Optical Coherence Tomography (OCT) is a non-invasive low coherence interferometry technique that includes several technologies (and the corresponding devices and components), such as illumination and detection, interferometry, scanning, adaptive optics, microscopy and endoscopy. From its large area of applications, we consider in this paper a critical aspect in dentistry - to be investigated with a Time Domain (TD) OCT system. The clinical situation of an edentulous mandible is considered; it can be solved by inserting 2 to 6 implants. On these implants a mesostructure will be manufactured and on it a superstructure is needed. This superstructure can be integral ceramic; in this case materials defects could be trapped inside the ceramic layers and those defects could lead to fractures of the entire superstructure. In this paper we demonstrate that a TD-OCT imaging system has the potential to properly evaluate the presence of the defects inside the ceramic layers and those defects can be fixed before inserting the prosthesis inside the oral cavity. Three integral ceramic superstructures were developed by using a CAD/CAM technology. After the milling, the ceramic layers were applied on the core. All the three samples were evaluated by a TD-OCT system working at 1300 nm. For two of the superstructures evaluated, no defects were found in the most stressed areas. The third superstructure presented four ceramic defects in the mentioned areas. Because of those defects the superstructure may fracture. The integral ceramic prosthesis was send back to the dental laboratory to fix the problems related to the material defects found. Thus, TD-OCT proved to be a valuable method for diagnosing the ceramic defects inside the integral ceramic superstructures in order to prevent fractures at this level.

A new effect on the dependence of Tc on the number of Cu-O layers in the non-rare-earth ceramic superconductors

International Nuclear Information System (INIS)

Chela-Flores, J.; Martin, P.; Rodriguez-Nunez, J.J.

1988-08-01

We argue from the experimental evidence that the superconductivity in the non-rare-earth compounds is confined to two inequivalent layers of Cu-O planes where electron pairing occurs. This conjecture leads us to a set of phenomenological equations in terms of two order parameters that correctly describe the characteristic lengths of the copper oxide ceramics. The formalism developed indicates that samples with a larger number of Cu-O layers may have higher transition temperatures. The formalism suggests that in a multilayered Cu-O compound increments of T c as a function of the doping parameter will be more pronounced the larger the number of layers. (author). 12 refs

New Hypothesis for SOFC Ceramic Oxygen Electrode Mechanisms

DEFF Research Database (Denmark)

Mogensen, Mogens Bjerg; Chatzichristodoulou, Christodoulos; Graves, Christopher R.

2016-01-01

A new hypothesis for the electrochemical reaction mechanism in solid oxide cell ceramic oxygen electrodes is proposed based on literature including our own results. The hypothesis postulates that the observed thin layers of SrO-La2O3 on top of ceramic perovskite and other Ruddlesden-Popper...

Bi-layered zirconia/fluor-apatite bridges supported by ceramic dental implants: a prospective case series after thirty months of observation.

Science.gov (United States)

Spies, Benedikt Christopher; Witkowski, Siegbert; Butz, Frank; Vach, Kirstin; Kohal, Ralf-Joachim

2016-10-01

The aim of this study was to determine the success and survival rate of all-ceramic bi-layered implant-supported three-unit fixed dental prostheses (IS-FDPs) 3 years after implant placement. Thirteen patients (seven males, six females; age: 41-78 years) received two one-piece ceramic implants (alumina-toughened zirconia) each in the region of the premolars or the first molar and were finally restored with adhesively cemented bi-layered zirconia-based IS-FDPs (3 in the maxilla, 10 in the mandible) composed of CAD/CAM-fabricated zirconia frameworks pressed-over with fluor-apatite glass-ceramic ingots. At prosthetic delivery and the follow-ups after 1, 2 and 3 years, the restorations were evaluated using modified United States Public Health Service (USPHS) criteria. Restorations with minor veneer chippings, a small-area occlusal roughness, slightly soundable restoration margins, minimal contour deficiencies and tolerable color deviations were regarded as success. In case of more distinct defects that could, however, be repaired to a clinically acceptable level, IS-FDPs were regarded as surviving. Kaplan-Meier plots were used for the success/survival analyses. To verify an impact on subjective patients' perceptions, satisfaction was evaluated by visual analog scales (VAS). All patients were seen 3 years after implant installation. No IS-FDP had to be replaced, resulting in 100% survival after a mean observation period of 29.5 months (median: 30.7). At the 3-year follow-up, 7/13 IS-FDPs showed a veneer chipping, 13/13 an occlusal roughness and 12/13 minimal deficiencies of contour/color. Since six restorations showed a major chipping and/or a major occlusal roughness, the Kaplan-Meier success rate was 53.8%. However, patients' significantly improved perceptions of function, esthetics, sense, and speech at prosthetic delivery remained stable over time. Bi-layered zirconia/fluor-apatite IS-FDPs entirely survived the observation period but showed a high frequency of

Influence of Silver and Gold Nanoparticles and Thin Layers on Charge Carrier Generation in InGaN/GaN Multiple Quantum Well Structures and Crystalline Zinc Oxide Films

Science.gov (United States)

Mezdrogina, M. M.; Vinogradov, A. Ya.; Kozhanova, Yu. V.; Levitskii, V. S.

2018-04-01

It has been shown that Ag and Au nanoparticles and thin layers influence charge carrier generation in InGaN/GaN multiple quantum well structures and crystalline ZnO films owing to the surface morphology heterogeneity of the semiconductors. When nanoparticles 10 films, the radiation intensity has turned out to grow considerably because of a plasmon resonance with the participation of localized plasmons. The application of Ag or Au layers on the surface of the structures strongly attenuates the radiation. When Ag and Au nanoparticles are applied on crystalline ZnO films obtained by rf magnetron sputtering, the radiation intensity in the short-wavelength part of the spectrum increases insignificantly because of their highly heterogeneous surface morphology.

Influence of aluminium nitride as a foaming agent on the preparation of foam glass-ceramics from high-titanium blast furnace slag

Science.gov (United States)

Shi, Huan; Feng, Ke-qin; Wang, Hai-bo; Chen, Chang-hong; Zhou, Hong-ling

2016-05-01

To effectively reuse high-titanium blast furnace slag (TS), foam glass-ceramics were successfully prepared by powder sintering at 1000°C. TS and waste glass were used as the main raw materials, aluminium nitride (AlN) as the foaming agent, and borax as the fluxing agent. The influence of the amount of AlN added (1wt%-5wt%) on the crystalline phases, microstructure, and properties of the produced foam glass-ceramics was studied. The results showed that the main crystal phases were perovskite, diopside, and augite. With increasing AlN content, a transformation from diopside to augite occurred and the crystallinity of the pyroxene phases slightly decreased. Initially, the average pore size and porosity of the foam glass-ceramics increased and subsequently decreased; similarly, their bulk density and compressive strength decreased and subsequently increased. The optimal properties were obtained when the foam glass-ceramics were prepared by adding 4wt% AlN.

Corrosion protection of SiC-based ceramics with CVDMullite coatings

Energy Technology Data Exchange (ETDEWEB)

Sarin, V.; Auger, M. [Boston Univ., MA (United States)

1997-05-01

Silicon carbide ceramics are the leading candidate materials for use as heat exchangers in advanced combined cycle power plants because of their unique combination of high temperature strength, high thermal conductivity, excellent thermal shock resistance, and good high temperature stability and oxidation resistance. Ceramic coatings are being considered for diesel engine cylinder liners, piston caps, valve faces and seats, piston rings, and for turbine components such as combustors, blades, stators, seals, and bearings. Under such conditions ceramics are better suited to high temperature environments than metals. For the first time, adherent crystalline mullite coatings have been chemically vapor deposited onto SiC substrates to enhance its corrosion/oxidation resistance. Thermodynamic and kinetic considerations have been utilized to produce mullite coatings with a variety of growth rates, compositions, and morphologies. The flexibility of processing can be exploited to produce coated ceramics with properties tailored to specific applications and varied corrosive environments. These corrosive environments include thermal, Na{sub 2}SO{sub 4}, O{sub 2} and coal slag.

Performance of double-layer biofilter packed with coal fly ash ceramic granules in treating highly polluted river water.

Science.gov (United States)

Jing, Zhaoqian; Li, Yu-You; Cao, Shiwei; Liu, Yuyu

2012-09-01

To improve trickling filters' denitrification efficiency, a biofilter with a trickling upper layer and a submerged lower layer was developed and applied in treating highly polluted river water. It was packed with porous coal fly ash ceramic granules. Its start-up characteristics, influence of hydraulic loading rates (HLR), carbon/nitrogen (C/N) ratio and filter depth on pollutants removal were investigated. The results indicated this biofilter was started quickly in 16 days with river sediment as inoculum. Alternating nitrification and denitrification were achieved when water flowed downwards. COD and nitrogen were mainly removed in the upper layer and the lower layer, respectively. With HLR of 4.0-5.0m(3)/(m(2)d), chemical oxygen demand (COD), ammonium (NH(4)(+)-N) and total nitrogen (TN) in the effluent were below 50, 5 and 15 mg/L, respectively. This biofilter removed more than 80% of COD, 85% of NH(4)(+)-N and 60% of TN with C/N ratios ranging from 6 to 10. Copyright © 2012 Elsevier Ltd. All rights reserved.

The preparation of HfC/C ceramics via molecular design.

Science.gov (United States)

Inzenhofer, Kathrin; Schmalz, Thomas; Wrackmeyer, Bernd; Motz, Günter

2011-05-07

Polymer derived ceramics have received lots of attention throughout the last few decades. Unfortunately, only a few precursor systems have been developed, focusing on silicon based polymers and ceramics, respectively. Herein, the synthesis of novel hafnium containing organometallic polymers by two different approaches is reported. Dialkenyl substituted hafnocene monomers were synthesized and subsequently polymerized via a free radical mechanism. Salt metathesis reactions of hafnocene dichloride with bifunctional linkers led to the formation of polymeric materials. NMR spectroscopic methods--in solution as well as in the solid state--were used to characterize the organometallic polymers. Ceramics were finally obtained after cross-linking and thermal treatment under argon (T(max) = 1800 °C). SEM investigations, elemental analyses, Raman spectroscopy and XRD investigations identified the pyrolyzed products as partially crystalline HfC/C mixed phases.

Detoxification and immobilization of chromite ore processing residue in spinel-based glass-ceramic

Energy Technology Data Exchange (ETDEWEB)

Liao, Chang-Zhong [Guangdong Key Laboratory of Agricultural Environment Pollution Integrated Control, Guangdong Institute of Eco-Environmental and Soil Sciences, Guangzhou 510650 (China); Department of Civil Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong Special Administrative Region (China); Tang, Yuanyuan [School of Environmental Science and Engineering, South University of Science and Technology of China, Shenzhen 518055 (China); Lee, Po-Heng [Department of Civil & Environmental Engineering, The Hong Kong Polytechnic University, Hong Kong Special Administrative Region (China); Liu, Chengshuai, E-mail: csliu@soil.gd.cn [Guangdong Key Laboratory of Agricultural Environment Pollution Integrated Control, Guangdong Institute of Eco-Environmental and Soil Sciences, Guangzhou 510650 (China); State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550009 (China); Shih, Kaimin, E-mail: kshih@hku.hk [Department of Civil Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong Special Administrative Region (China); Li, Fangbai [Guangdong Key Laboratory of Agricultural Environment Pollution Integrated Control, Guangdong Institute of Eco-Environmental and Soil Sciences, Guangzhou 510650 (China)

2017-01-05

Graphical abstract: Schematic illustration of detoxification and immobilization of chromite ore processing residue in spinel-based glass-ceramic matrix. All Cr(VI) species is reduced to Cr(III) and most chromium contents are incorporated into spinel structure where the residual chromium are resided in the glass networks. - Highlights: • COPR was detoxified and immobilized in a spinel-based glass-ceramic matrix. • Cr-rich crystalline phase was determined to be MgCr{sub 1.32}Fe{sub 0.19}Al{sub 0.49}O{sub 4} spinel. • The partitioning ratio of Cr into spinel in the glass-ceramic can be up to 77%. • No Cr(VI) was observed after conversion of COPR into a glass-ceramic. • TCLP results demonstrate the superiority of the final product in immobilizing Cr. - Abstract: A promising strategy for the detoxification and immobilization of chromite ore processing residue (COPR) in a spinel-based glass-ceramic matrix is reported in this study. In the search for a more chemically durable matrix for COPR, the most critical crystalline phase for Cr immobilization was found to be a spinel solid solution with a chemical composition of MgCr{sub 1.32}Fe{sub 0.19}Al{sub 0.49}O{sub 4}. Using Rietveld quantitative X-ray diffraction analysis, we identified this final product is with the phases of spinel (3.5 wt.%), diopside (5.2 wt.%), and some amorphous contents (91.2 wt.%). The partitioning ratio of Cr reveals that about 77% of the Cr was incorporated into the more chemically durable spinel phase. The results of Cr K-edge X-ray absorption near-edge spectroscopy show that no Cr(VI) was observed after conversion of COPR into a glass-ceramic, which indicates successful detoxification of Cr(VI) into Cr(III) in the COPR-incorporated glass-ceramic. The leaching performances of Cr{sub 2}O{sub 3} and COPR-incorporated glass-ceramic were compared with a prolonged acid-leaching test, and the results demonstrate the superiority of the COPR-incorporated glass-ceramic matrix in the

Detoxification and immobilization of chromite ore processing residue in spinel-based glass-ceramic

International Nuclear Information System (INIS)

Liao, Chang-Zhong; Tang, Yuanyuan; Lee, Po-Heng; Liu, Chengshuai; Shih, Kaimin; Li, Fangbai

2017-01-01

Graphical abstract: Schematic illustration of detoxification and immobilization of chromite ore processing residue in spinel-based glass-ceramic matrix. All Cr(VI) species is reduced to Cr(III) and most chromium contents are incorporated into spinel structure where the residual chromium are resided in the glass networks. - Highlights: • COPR was detoxified and immobilized in a spinel-based glass-ceramic matrix. • Cr-rich crystalline phase was determined to be MgCr 1.32 Fe 0.19 Al 0.49 O 4 spinel. • The partitioning ratio of Cr into spinel in the glass-ceramic can be up to 77%. • No Cr(VI) was observed after conversion of COPR into a glass-ceramic. • TCLP results demonstrate the superiority of the final product in immobilizing Cr. - Abstract: A promising strategy for the detoxification and immobilization of chromite ore processing residue (COPR) in a spinel-based glass-ceramic matrix is reported in this study. In the search for a more chemically durable matrix for COPR, the most critical crystalline phase for Cr immobilization was found to be a spinel solid solution with a chemical composition of MgCr 1.32 Fe 0.19 Al 0.49 O 4 . Using Rietveld quantitative X-ray diffraction analysis, we identified this final product is with the phases of spinel (3.5 wt.%), diopside (5.2 wt.%), and some amorphous contents (91.2 wt.%). The partitioning ratio of Cr reveals that about 77% of the Cr was incorporated into the more chemically durable spinel phase. The results of Cr K-edge X-ray absorption near-edge spectroscopy show that no Cr(VI) was observed after conversion of COPR into a glass-ceramic, which indicates successful detoxification of Cr(VI) into Cr(III) in the COPR-incorporated glass-ceramic. The leaching performances of Cr 2 O 3 and COPR-incorporated glass-ceramic were compared with a prolonged acid-leaching test, and the results demonstrate the superiority of the COPR-incorporated glass-ceramic matrix in the immobilization of Cr. The overall results suggest that

Process of producing a ceramic matrix composite article and article formed thereby

Science.gov (United States)

Corman, Gregory Scot [Ballston Lake, NY; McGuigan, Henry Charles [Duanesburg, NY; Brun, Milivoj Konstantin [Ballston Lake, NY

2011-10-25

A CMC article and process for producing the article to have a layer on its surface that protects a reinforcement material within the article from damage. The method entails providing a body containing a ceramic reinforcement material in a matrix material that contains a precursor of a ceramic matrix material. A fraction of the reinforcement material is present and possibly exposed at a surface of the body. The body surface is then provided with a surface layer formed of a slurry containing a particulate material but lacking the reinforcement material of the body. The body and surface layer are heated to form the article by converting the precursor within the body to form the ceramic matrix material in which the reinforcement material is contained, and by converting the surface layer to form the protective layer that covers any fraction of the reinforcement material exposed at the body surface.

Spectroscopic ellipsometry characterization of amorphous and crystalline TiO2 thin films grown by atomic layer deposition at different temperatures

Science.gov (United States)

Saha, D.; Ajimsha, R. S.; Rajiv, K.; Mukherjee, C.; Gupta, M.; Misra, P.; Kukreja, L. M.

2014-10-01

TiO2 thin films of widely different structural and morphological characteristics were grown on Si (1 0 0) substrates using Atomic Layer Deposition (ALD) by varying the substrate temperature (Ts) in a wide range (50 °C ≤ Ts ≤ 400 °C). Spectroscopic ellipsometry (SE) measurements were carried out to investigate the effect of growth temperature on the optical properties of the films. Measured SE data were analyzed by considering double layer optical model for the sample together with the single oscillator Tauc-Lorentz dispersion relation. Surface roughness was taken into consideration due to the columnar growths of grains in crystalline films. The refractive index was found to be increased from amorphous (Ts ≤ 150 °C) to the nanocrystalline films (2500 < Ts ≤ 400 °C). The pronounced surface roughening for the large-grained anatase film obtained at the amorphous to crystalline phase transformation temperature of 200 °C, impeded SE measurement. The dispersions of refractive indices below the interband absorption edge were found to be strongly correlated with the single oscillator Wemple-DiDomenico (WD) model. The increase in dispersion energy parameter in WD model from disordered amorphous to the more ordered nanocrystalline films was found to be associated with the increase in the film density and coordination number.

Mullite-alumina functionally gradient ceramics

International Nuclear Information System (INIS)

Pena, P.; Bartolome, J.; Requena, J.; Moya, J.S.

1993-01-01

Cracks free mullite-alumina Functionally Gradient Ceramics (FGC) have been obtained by sequential slip casting of Mullite-alumina slurries with different mullite/alumina ratios. These slurries were prepared with 65 % solids content and viscosities ranging from 10 to 40 mPa.s. The presence of cracks perpendicular to the FGC layers have been attributed to residual stresses developed because of the mismatch in thermal expansion between layers. The microstructure of the different layers, and de residual stress value σ R in each layer was also determined. (orig.)

Hardness of basaltic glass-ceramics

DEFF Research Database (Denmark)

Jensen, Martin; Smedskjær, Morten Mattrup; Estrup, Maja

2009-01-01

The dependence of the hardness of basaltic glass-ceramics on their degree of crystallisation has been explored by means of differential scanning calorimetry, optical microscopy, x-ray diffraction, and Vickers indentation. Different degrees of crystallisation in the basaltic glasses were achieved...... by varying the temperature of heat treatment. The predominant crystalline phase in the glass was identified as augite. It was found that the hardness of the glass phase decreased slightly with an increase in the degree of crystallisation, while that of the augite phase drastically decreased....

Technology for bonding silicon nitride ceramics. Heat treatment technology to improve diffusion bonding strength; Chikka keiso ceramics no setsugo gijutsu. Kakusan setsugo kyodo kaizen no tame no metsushori gijutsu

Energy Technology Data Exchange (ETDEWEB)

Nakamura, M.; Shigematsu, K. [National Industrial Research Institute of Nagoya,Nagoya (Japan)

1999-01-25

Silicon nitride ceramics is a structural ceramics with excellent high temperature strength and tenacity, being expected of expansion of application as a high temperature material. However, its processibility is poor, and special sintering technique is required to manufacture members of complex shapes. Therefore, development has been made on a technology to manufacture bonded materials with high mechanical strength, by which diffusion bonding in high temperature nitrogen gas and heat treatment are combined, and crystalline structure in the vicinity of bonding interface is controlled. (translated by NEDO)

EFFECT OF CaO/SiO₂ AND HEAT TREATMENT ON THE MICROSTRUCTURE OF GLASS-CERAMICS FROM BLAST FURNACE SLAG

Directory of Open Access Journals (Sweden)

Chunshai Xie

2016-05-01

Full Text Available Glass-ceramics, with molten blast furnace (BF slag as the major raw material, were prepared successfully by the melting method. The effect of the CaO/SiO₂ ratio in the molten BF slag and heat treatment on the viscosity and microstructure of glass-ceramics produced from BF slag were traced using the melt property tester, DSC, XRD and SEM. The results showed that increasing the CaO/SiO₂ ratio of BF slag caused a decrease not only in the viscosity of the BF slag at high temperature but also in the nucleation and crystallization temperature for the preparation of glass-ceramics. The content of akermanite-gehlenite increased as the CaO/SiO₂ ratio increased from 0.30 to 0.63. With increasing nucleation and crystallization temperature, the crystalline phases remain unchanged, but the crystal shape changes from granular to flaky. The optimum CaO/SiO₂ ratio was found to be 0.44, resulting in diopside as the main crystalline phase, augite as the secondary crystalline phase and a small mount of akermanite-gehlenite after appropriate heat treatment i.e. nucleation at 775°C and crystallization at 920°C.

Influence of thermal expansion mismatch on residual stress profile in veneering ceramic layered on zirconia: Measurement by hole-drilling.

Science.gov (United States)

Mainjot, Amélie K; Najjar, Achref; Jakubowicz-Kohen, Boris D; Sadoun, Michaël J

2015-09-01

Mismatch in thermal expansion coefficient between core and veneering ceramic (Δα=αcore-αveneer, ppm/°C) is reported as a crucial parameter influencing veneer fractures with Yttria-tetragonal-zirconia-polycrystal (Y-TZP) prostheses, which still constitutes a misunderstood problem. However, the common positive Δα concept remains empirical. The objective of this study is to investigate the Δα dependence of residual stress profiles in veneering ceramic layered on Y-TZP frameworks. The stress profile was measured with the hole-drilling method in bilayered disc samples of 20mm diameter with a 0.7mm thick Y-TZP framework and a 1.5mm thick veneer layer. 3 commercial and 4 experimental veneering ceramics (n=3 per group) were used to obtain different Δα varying from -1.3ppm/°C to +3.2ppm/°C, which were determined by dilatometric analyses. Veneer fractures were observed in samples with Δα≥+2.3 or ≤-0.3ppm/°C. Residual stress profiles measured in other groups showed compressive stresses in the surface, these stresses decreasing with depth and then becoming more compressive again near the interface. Small Δα variations were shown to induce significant changes in residual stress profiles. Compressive stress near the framework was found to decrease inversely to Δα. Veneer CTE close to Y-TZP (+0.2ppm/°C Δα) gived the most favorable stress profile. Yet, near the framework, Δα-induced residual stress varied inversely to predictions. This could be explained by the hypothesis of structural changes occurrence within the Y-TZP surface. Consequently, the optimum Δα value cannot be determined before understanding Y-TZP's particular behavior when veneered. Copyright © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Enhancement of Compatibility between Ultrahigh-Molecular-Weight Polyethylene Particles and Butadiene.Nitrile Rubber Matrix with Nanoscale Ceramic Particles and Characterization of Evolving Layer

International Nuclear Information System (INIS)

Shadrinov, Nikolay V.; Sokolova, Marina D.; Cho, Jinho; Okhlopkova, A. A.; Lee, Jungkeun; Jeong, Daeyong

2013-01-01

This article examines the modification of surface properties of ultrahigh-molecular-weight polyethylene (UHMWPE) with nanoscale ceramic particles to fabricate an improved composite with butadiene.nitrile rubber (BNR). Adhesion force data showed that ceramic zeolite particles on the surface of UHMWPE modulated the surface state of the polymer and increased its compatibility with BNR. Atomic force microscopy phase images showed that UHMWPE made up the microphase around the zeolite particles and formed the evolving layer with a complex interface. The complex interface resulted in improvements in the mechanical properties of the composite, especially its low-temperature resistance coefficients, thereby improving its performance in low-temperature applications

Talc-silicon glass-ceramic waste forms for immobilization of high- level calcined waste

International Nuclear Information System (INIS)

Vinjamuri, K.

1993-06-01

Talc-silicon glass-ceramic waste forms are being evaluated as candidates for immobilization of the high level calcined waste stored onsite at the Idaho Chemical Processing Plant. These glass-ceramic waste forms were prepared by hot isostatically pressing a mixture of simulated nonradioactive high level calcined waste, talc, silicon and aluminum metal additives. The waste forms were characterized for density, chemical durability, and glass and crystalline phase compositions. The results indicate improved density and chemical durability as the silicon content is increased

Investigation of optical and magneto-optical constants and their surface-oxide-layer effects of single-crystalline GdCo2

International Nuclear Information System (INIS)

Lee, S.J.; Kim, K.J.; Canfield, P.C.; Lynch, D.W.

2000-01-01

We investigated the optical and magneto-optical properties of single-crystalline GdCo 2 by spectroscopic ellipsometry (SE) and magneto-optical Kerr spectrometry (MOKS). The diagonal component of the optical conductivity tensor of the compound was obtained by SE in the 1.5-5.5 eV region and the off-diagonal component by using the measured magneto-optical parameters (Kerr rotation and ellipticity) by MOKS and the SE data. The measured spectra were corrected for the surface oxide layer by employing a three-phase model treating the oxide layer as nonmagnetic with constant refractive index. The magnitude of the diagonal component becomes enhanced and the optical transition structures of the off-diagonal component become more pronounced by the oxide correction. The overall optical and magneto-optical data are discussed in terms of the calculated spin-polarized band structure and optical absorption of the compound and the effect of the surface oxide layer

Numerical investigation on anti-penetration behavior of ceramic/metal target under ballistic impact

International Nuclear Information System (INIS)

Mei, H; Wang, Y C; Liu, X; Cao, D F; Liu, L S

2013-01-01

In the paper, we used the LS-DYNA FE code to simulate the bullet penetration against the target plate with different ceramic-steel ratio of thickness. The main stages of the bullet penetration and damage contours of the target were studied by analyzing the residual velocity-time curves. We also studied energy absorption of the ceramic/metal target. Considering curves of residual velocity-time, we reckon the process of penetration contains four stages. Ceramic performed good resistance before the formation of damage cone of ceramic. But after the damage cone formed, the anti-penetration behavior kept declining. When the bullet started to penetrate the layer of metal, the anti-penetration behavior of target rose slightly. Compared with thickness ratio of 0.4 and 0.6, ceramic with 0.2 absorbed more energy and works longer. Of several different thicknesses, layers of ceramic and steel were studied. Steel per cm absorbed more energy than ceramic per cm.

Investigation of vitreous and crystalline ceramic materials for immobilization of alpha-contaminated residues

International Nuclear Information System (INIS)

Palmer, C.R.; Mellinger, G.B.; Rusin, J.M.

1981-01-01

Experimental investigations of two alternatives for immobilizing dispersible solid wastes contaminated with alpha-emitting radionuclides are reviewed. Borosilicate glasses and sintered silicate ceramics are being studied for such wastes, and results so far indicate both may offer attractive alternatives to waste generators. Waste oxide solubilities, de-vitrification behaviour and effects of residual carbon are examined for glasses incorporating incinerator ash and hydrated ferric oxide sludge. Glasses will accommodate these wastes at loadings of 30-60 wt% while maintaining good performance characteristics. A brief comparative evaluation of cold-pressed and sintered ceramics is also described. The effects on process and product properties of the choice of additives, waste loading and sintering temperature were determined. This approach also appears to promise economic waste loadings while achieving relatively durable waste forms. (author)

Bonding silicon nitride using glass-ceramic

International Nuclear Information System (INIS)

Dobedoe, R.S.

1995-01-01

Silicon nitride has been successfully bonded to itself using magnesium-aluminosilicate glass and glass-ceramic. For some samples, bonding was achieved using a diffusion bonder, but in other instances, following an initial degassing hold, higher temperatures were used in a nitrogen atmosphere with no applied load. For diffusion bonding, a small applied pressure at a temperature below which crystallisation occurs resulted in intimate contact. At slightly higher temperatures, the extent of the reaction at the interface and the microstructure of the glass-ceramic joint was highly sensitive to the bonding temperature. Bonding in a nitrogen atmosphere resulted in a solution-reprecipitation reaction. A thin layer of glass produced a ''dry'', glass-free joint, whilst a thicker layer resulted in a continuous glassy join across the interface. The chromium silicide impurities within the silicon nitride react with the nucleating agent in the glass ceramic, which may lead to difficulty in producing a fine glass-ceramic microstructure. Slightly lower temperatures in nitrogen resulted in a polycrystalline join but the interfacial contact was poor. It is hoped that one of the bonds produced may be developed to eventually form part of a graded joint between silicon nitride and a high temperature nickel alloy. (orig.)

Laser treatment of dental ceramic/cement layers: transmitted energy, temperature effects and surface characterisation.

Science.gov (United States)

Pich, Olena; Franzen, René; Gutknecht, Norbert; Wolfart, Stefan

2015-02-01

In the present paper, we investigate the behaviour of different dental materials under laser irradiation. We have used e.max Ceram, e.max ZirCAD, and e.max Press dental ceramics and glass ionomer cement Ketac Cem in the present study. The dental ceramics were prepared in the form of samples with thickness of 0.5-2 mm. We used two lasers [solid-state laser (Er:YAG, Fidelis III+, Fotona) and an 810- nm diode laser (FOX, A.R.C)] for the transillumination of ceramic samples. It has been shown that the laser energy transmitted through the ceramic material decreases to 30-40% of the original values along with an increase in the thickness of the irradiated sample. Pigmented ceramic samples show more laser energy loss compared to the samples containing no pigment. We investigated the temperature evolution in composite sandwiched ceramic/cement samples under laser treatment. The increase in the irradiation time and laser power led to a temperature increase of up to 80 °C. The surfaces of irradiated ceramic samples were examined with X-ray photoelectron spectroscopy to evaluate changes in chemical composition, such as a decrease in the C signal, accompanied by a strong increase in the Zr peak for the Er:YAG laser, while the 810-nm diode laser showed no change in the ratio of elements on the surface.

Glass Ceramic Formulation Data Package

International Nuclear Information System (INIS)

Crum, Jarrod V.; Rodriguez, Carmen P.; McCloy, John S.; Vienna, John D.; Chung, Chul-Woo

2012-01-01

A glass ceramic waste form is being developed for treatment of secondary waste streams generated by aqueous reprocessing of commercial used nuclear fuel (Crum et al. 2012b). The waste stream contains a mixture of transition metals, alkali, alkaline earths, and lanthanides, several of which exceed the solubility limits of a single phase borosilicate glass (Crum et al. 2009; Caurant et al. 2007). A multi-phase glass ceramic waste form allows incorporation of insoluble components of the waste by designed crystallization into durable heat tolerant phases. The glass ceramic formulation and processing targets the formation of the following three stable crystalline phases: (1) powellite (XMoO4) where X can be (Ca, Sr, Ba, and/or Ln), (2) oxyapatite Yx,Z(10-x)Si6O26 where Y is alkaline earth, Z is Ln, and (3) lanthanide borosilicate (Ln5BSi2O13). These three phases incorporate the waste components that are above the solubility limit of a single-phase borosilicate glass. The glass ceramic is designed to be a single phase melt, just like a borosilicate glass, and then crystallize upon slow cooling to form the targeted phases. The slow cooling schedule is based on the centerline cooling profile of a 2 foot diameter canister such as the Hanford High-Level Waste canister. Up to this point, crucible testing has been used for glass ceramic development, with cold crucible induction melter (CCIM) targeted as the ultimate processing technology for the waste form. Idaho National Laboratory (INL) will conduct a scaled CCIM test in FY2012 with a glass ceramic to demonstrate the processing behavior. This Data Package documents the laboratory studies of the glass ceramic composition to support the CCIM test. Pacific Northwest National Laboratory (PNNL) measured melt viscosity, electrical conductivity, and crystallization behavior upon cooling to identify a processing window (temperature range) for melter operation and cooling profiles necessary to crystallize the targeted phases in the

Dynamic fatigue on repolarization of lead zirconate-titanate base ceramics with various ferroelectric hardness

International Nuclear Information System (INIS)

Gavrilyachenko, V.G.; Semenchev, A.F.; Sklyarova, E.N.; Kuznetsova, E.M.

2006-01-01

One studied experimentally changes of the residual polarization in lead zirconate-titanate base ceramics with various ferroelectric hardness under the effect of a strong varying field. The twinning and untwinning of crystallites accompanying repolarization is assumed to be the basic mechanism of propagation of the crystalline structure defects governing the fatigue rates of the ferroelectric-soft ceramics. In ferroelectric-hard ceramics crystallites the stable configurations of mechanical twins, the result of the secondary twinning, are formed when the hysteresis loop is formed. At repolarization in the mentioned structures one observes no motion of the twin boundaries, and the fatigue rates are low ones [ru

Ceramic impregnated superabrasives

Science.gov (United States)

Radtke, Robert P.; Sherman, Andrew

2009-02-10

A superabrasive fracture resistant compact is formed by depositing successive layers of ceramic throughout the network of open pores in a thermally stable self-bonded polycrystalline diamond or cubic boron nitride preform. The void volume in the preform is from approximately 2 to 10 percent of the volume of the preform, and the average pore size is below approximately 3000 nanometers. The preform is evacuated and infiltrated under at least about 1500 pounds per square inch pressure with a liquid pre-ceramic polymerizable precursor. The precursor is infiltrated into the preform at or below the boiling point of the precursor. The precursor is polymerized into a solid phase material. The excess is removed from the outside of the preform, and the polymer is pyrolized to form a ceramic. The process is repeated at least once more so as to achieve upwards of 90 percent filling of the original void volume. When the remaining void volume drops below about 1 percent the physical properties of the compact, such as fracture resistance, improve substantially. Multiple infiltration cycles result in the deposition of sufficient ceramic to reduce the void volume to below 0.5 percent. The fracture resistance of the compacts in which the pores are lined with formed in situ ceramic is generally at least one and one-half times that of the starting preforms.

Rare earth ion controlled crystallization of mica glass-ceramics

Energy Technology Data Exchange (ETDEWEB)

Garai, Mrinmoy; Karmakar, Basudeb, E-mail: basudebk@cgcri.res.in

2016-09-05

In understanding the effects of rare earth ions to control the crystallization and microstructure of alkaline boroaluminosilicate system, the CeO{sub 2}, Nd{sub 2}O{sub 3}, Sm{sub 2}O{sub 3} and Gd{sub 2}O{sub 3} doped K{sub 2}O−MgO−B{sub 2}O{sub 3}−Al{sub 2}O{sub 3}−SiO{sub 2}−F glasses were synthesized by melt-quenching at 1550 °C. Higher density (2.82–3.06 g cm{sup −3}) and thermal stability (glass phase) is experiential on addition of rare earth content, which also affects in increasing the glass transition temperature (T{sub g}) and crystallization temperature (T{sub c}). Decrease of thermal expansion in glasses with rare earth ion content is maintained by the stabilization of glass matrix owing to their large cationic field strength. A significant change in the non-isothermal DSC thermogram observed at 750–1050 °C is attributed to fluorophlogopite crystallization. Opaque glass-ceramics were prepared from such glasses by single step heat-treatment at 1050 °C; and the predominant crystalline phases are identified as fluorophlogopite mica, KMg{sub 3}(AlSi{sub 3}O{sub 10})F{sub 2} by XRD and EDX analysis. The compact glass-ceramic microstructure by the agglomeration of fluorophlogopite mica crystallites (crystal size ∼ 100–500 nm, FESEM) is achieved in attendance of rare earth ion; and such microstructure controlled the variation of density, thermal expansion and microhardness value. Higher thermal expansion (11.11–14.08 × 10{sup −6}/K at 50–800 °C and 50–900 °C) of such glass-ceramics approve that these rare earth containing glasses can be useful for high temperature vacuum sealing application with metal or solid electrolyte. The increase of Vickers microhardness (5.27–5.61 GPa) in attendance of rare earth ions is attributed to the compact crystallinity of fluorophlogopite mica glass-ceramic microstructure. - Highlights: • Synthesis of rare earth oxide doped alkaline boroaluminosilicate glasses. • Development of opaque

Microstructural Characterization of Reaction-Formed Silicon Carbide Ceramics. Materials Characterization

Science.gov (United States)

Singh, M.; Leonhardt, T. A.

1995-01-01

Microstructural characterization of two reaction-formed silicon carbide ceramics has been carried out by interference layering, plasma etching, and microscopy. These specimens contained free silicon and niobium disilicide as minor phases with silicon carbide as the major phase. In conventionally prepared samples, the niobium disilicide cannot be distinguished from silicon in optical micrographs. After interference layering, all phases are clearly distinguishable. Back scattered electron (BSE) imaging and energy dispersive spectrometry (EDS) confirmed the results obtained by interference layering. Plasma etching with CF4 plus 4% O2 selectively attacks silicon in these specimens. It is demonstrated that interference layering and plasma etching are very useful techniques in the phase identification and microstructural characterization of multiphase ceramic materials.

Light trapping of crystalline Si solar cells by use of nanocrystalline Si layer plus pyramidal texture

Energy Technology Data Exchange (ETDEWEB)

Imamura, Kentaro; Nonaka, Takaaki; Onitsuka, Yuya; Irishika, Daichi; Kobayashi, Hikaru, E-mail: h.kobayashi@sanken.osaka-u.ac.jp

2017-02-15

Highlights: • Ultralow reflectivity Si wafers with light trapping effect can be obtained by forming a nanocrystalline Si layer on pyramidal textured Si surfaces. • Surface passivation using phosphosilicate glass improved minority carrier lifetime of the nanocrystalline Si layer/Si structure. • A high photocurrent density of 40.1 mA/cm{sup 2}, and a high conversion efficiency of 18.5% were achieved. - Abstract: The surface structure chemical transfer (SSCT) method has been applied to fabrication of single crystalline Si solar cells with 170 μm thickness. The SSCT method, which simply involves immersion of Si wafers in H{sub 2}O{sub 2} plus HF solutions and contact of Pt catalyst with Si taking only ∼30 s for 6 in. wafers, can decrease the reflectivity to less than 3% by the formation of a nanocrystalline Si layer. However, the reflectivity of the nanocrystalline Si layer/flat Si surface/rear Ag electrode structure in the wavelength region longer than 1000 nm is high because of insufficient absorption of incident light. The reflectivity in the long wavelength region is greatly decreased by the formation of the nanocrystalline Si layer on pyramidal textured Si surfaces due to an increase in the optical path length. Deposition of phosphosilicate glass (PSG) on the nanocrystalline Si layer for formation of pn-junction does not change the ultralow reflectivity because the surface region of the nanocrystalline Si layer possesses a refractive index of 1.4 which is nearly the same as that of PSG of 1.4–1.5. The PSG layer is found to passivate the nanocrystalline Si layer, which is evident from an increase in the minority carrier lifetime from 12 to 44 μs. Hydrogen treatment at 450 °C further increases the minority carrier lifetime approximately to a doubled value. The solar cells with the layer/pyramidal Si substrate/boron-diffused back surface field/Ag rear electrode> structure show a high conversion efficiency of 18

Characterization of a wollastonite glass-ceramic material prepared using sugar cane bagasse ash (SCBA) as one of the raw materials

Energy Technology Data Exchange (ETDEWEB)

Teixeira, Silvio R., E-mail: rainho@fct.unesp.br [Universidade Estadual Paulista — UNESP, Faculdade de Ciências e Tecnologia — FCT, 19060-900 Presidente Prudente — SP (Brazil); Souza, Agda E. [Universidade Estadual Paulista — UNESP, Faculdade de Ciências e Tecnologia — FCT, 19060-900 Presidente Prudente — SP (Brazil); Carvalho, Claudio L.; Reynoso, Victor C.S. [Universidade Estadual Paulista — UNESP, Faculdade de Engenharia de Ilha Solteira — FEIS, 15385-000 Ilha Solteira – SP (Brazil); Romero, Maximina; Rincón, Jesús Ma. [Instituto de Ciencias de la Construccion Eduardo Torroja — IETCC, CSIC, 28033 Madrid (Spain)

2014-12-15

Glass-ceramic material prepared with sugar cane bagasse ash as one of the raw materials was characterized to determine some important properties for its application as a coating material. X-ray diffraction patterns showed that wollastonite-2M (CaSiO{sub 3}) was the major glass-ceramic phase. The Rietveld method was used to quantify the crystalline (60 wt.%) and vitreous (40 wt.%) phases in the glass-ceramic. The microstructure (determined by scanning electron microscopy) of this material had a marble appearance, showing a microporous network of elongated crystals with some areas with dendritic, feather-like ordering. Microhardness data gave a mean hardness value of 564.4 HV (Vickers-hardness), and light microscopy disclosed a greenish brown colored material with a vitreous luster. - Highlights: • We studied the properties of a glass-ceramic material obtained from sugarcane ash. • This material has the appearance and hardness of natural stones. • A refining method gave information about its amorphous and crystalline phases. • This material has potential to be used as coating plates for buildings.

Characterization of a wollastonite glass-ceramic material prepared using sugar cane bagasse ash (SCBA) as one of the raw materials

International Nuclear Information System (INIS)

Teixeira, Silvio R.; Souza, Agda E.; Carvalho, Claudio L.; Reynoso, Victor C.S.; Romero, Maximina; Rincón, Jesús Ma.

2014-01-01

Glass-ceramic material prepared with sugar cane bagasse ash as one of the raw materials was characterized to determine some important properties for its application as a coating material. X-ray diffraction patterns showed that wollastonite-2M (CaSiO 3 ) was the major glass-ceramic phase. The Rietveld method was used to quantify the crystalline (60 wt.%) and vitreous (40 wt.%) phases in the glass-ceramic. The microstructure (determined by scanning electron microscopy) of this material had a marble appearance, showing a microporous network of elongated crystals with some areas with dendritic, feather-like ordering. Microhardness data gave a mean hardness value of 564.4 HV (Vickers-hardness), and light microscopy disclosed a greenish brown colored material with a vitreous luster. - Highlights: • We studied the properties of a glass-ceramic material obtained from sugarcane ash. • This material has the appearance and hardness of natural stones. • A refining method gave information about its amorphous and crystalline phases. • This material has potential to be used as coating plates for buildings

Optical properties of pre-colored dental monolithic zirconia ceramics.

Science.gov (United States)

Kim, Hee-Kyung; Kim, Sung-Hun

2016-12-01

The purposes of this study were to evaluate the optical properties of recently marketed pre-colored monolithic zirconia ceramics and to compare with those of veneered zirconia and lithium disilicate glass ceramics. Various shades of pre-colored monolithic zirconia, veneered zirconia, and lithium disilicate glass ceramic specimens were tested (17.0×17.0×1.5mm, n=5). CIELab color coordinates were obtained against white, black, and grey backgrounds with a spectrophotometer. Color differences of the specimen pairs were calculated by using the CIEDE2000 (ΔE 00 ) formula. The translucency parameter (TP) was derived from ΔE 00 of the specimen against a white and a black background. X-ray diffraction was used to determine the crystalline phases of monolithic zirconia specimens. Data were analyzed with 1-way ANOVA, Scheffé post hoc, and Pearson correlation testing (α=0.05). For different shades of the same ceramic brand, there were significant differences in L * , a * , b * , and TP values in most ceramic brands. With the same nominal shade (A2), statistically significant differences were observed in L * , a * , b * , and TP values among different ceramic brands and systems (Pceramics of the corresponding nominal shades ranged beyond the acceptability threshold. Due to the high L * values and low a * and b * values, pre-colored monolithic zirconia ceramics can be used with additional staining to match neighboring restorations or natural teeth. Due to their high value and low chroma, unacceptable color mismatch with adjacent ceramic restorations might be expected. Copyright © 2016 Elsevier Ltd. All rights reserved.

Coating of ceramic powders by chemical vapor deposition techniques (CVD)

International Nuclear Information System (INIS)

Haubner, R.; Lux, B.

1997-01-01

New ceramic materials with selected advanced properties can be designed by coating of ceramic powders prior to sintering. By variation of the core and coating material a large number of various powders and ceramic materials can be produced. Powders which react with the binder phase during sintering can be coated with stable materials. Thermal expansion of the ceramic materials can be adjusted by varying the coating thickness (ratio core/layer). Electrical and wear resistant properties can be optimized for electrical contacts. A fluidized bed reactor will be designed which allow the deposition of various coatings on ceramic powders. (author)

Fabrication and characterization of Er+3 doped SiO2/SnO2 glass-ceramic thin films for planar waveguide applications

Science.gov (United States)

Guddala, S.; Chiappini, A.; Armellini, C.; Turell, S.; Righini, G. C.; Ferrari, M.; Narayana Rao, D.

2015-02-01

Glass-ceramics are a kind of two-phase materials constituted by nanocrystals embedded in a glass matrix and the respective volume fractions of crystalline and amorphous phase determine the properties of the glass-ceramics. Among these properties transparency is crucial in particular when confined structures, such as, dielectric optical waveguides, are considered. Moreover, the segregation of dopant rare-earth ions, like erbium, in low phonon energy crystalline medium makes these structures more promising in the development of waveguide amplifiers. Here we are proposing a new class of low phonon energy tin oxide semiconductor medium doped silicate based planar waveguides. Er3+ doped (100-x) SiO2-xSnO2 (x= 10, 20, 25 and 30mol%), glass-ceramic planar waveguide thin films were fabricated by a simple sol-gel processing and dip coating technique. XRD and HRTEM studies indicates the glass-ceramic phase of the film and the dispersion of ~4nm diameter of tin oxide nanocrystals in the amorphous phase of silica. The spectroscopic assessment indicates the distribution of the dopant erbium ions in the crystalline medium of tin oxide. The observed low losses, 0.5±0.2 dB/cm, at 1.54 μm communication wavelength makes them a quite promising material for the development of high gain integrated optical amplifiers.

Enhanced green upconversion by controlled ceramization of Er3+–Yb3+ co-doped sodium niobium tellurite glass–ceramics for low temperature sensors

International Nuclear Information System (INIS)

Suresh Kumar, J.; Pavani, K.; Graça, M.P.F.; Soares, M.J.

2014-01-01

Highlights: • Upconversion luminescence improved in glass–ceramics compared to host glass. • Judd–Ofelt and radiative parameters calculated. • NIR decay curve results concur the results of improved luminescence. • Temperature dependent upconversion support the use of materials for sensors. - Abstract: Tellurite based glasses are well-known for their upconversion properties besides having a disadvantage of low mechanical strength dragging them away from practical applications. The present work deals with preparation of sodium niobium tellurite (SNT) glasses using melt quenching method, in which small quantities of boron and silicon in the form of oxides are added to improve their mechanical properties. Controlled heat treatment is performed to ceramize the prepared glasses based on the thermal data given by DTA. XRD and SEM profiles of the glass–ceramics which confirmed the formation of crystalline monoclinic Sodium Tellurium Niobium Oxide (Na 1.4 Nb 3 Te 4.9 O 18 ) phase (JCPDS card No. 04–011-7556). Upconversion measurements in the visible region were made for the prepared Er 3+ –Yb 3+ co-doped glasses and glass–ceramics with 980 nm laser excitation varying the laser power and concentration of Er 3+ ions. Results showed that the upconversion luminescence intensity was enhanced by ten times in SNT glass–ceramics compared to that in the SNT glasses. Decay curves give evidence of high performance of glass–ceramics compared to glasses due to ceramization and structural changes. Temperature dependent visible upconversion was performed to test the ability of efficient SNT glass–ceramic at low temperatures and variation of upconversion intensities was studied

Transparent ceramics for armor and EM window applications

OpenAIRE

Patel, Parimal J.; Gilde, Gary A.; Dehmer, Peter G.; McCauley, James W.

2000-01-01

Recently, the U.S. Army Research Laboratory (ARL) has focused increased attention on the development of transparent armor material systems for a variety of applications. Future combat and non-combat environments will require lightweight, threat adjustable, multifunctional, and affordable armor. Current glass/polycarbonate technologies are not expected to meet the increased requirements. Results over the past few years indicate that the use of transparent crystalline ceramics greatly improve t...

Corundum ceramic materials modified with silica nanopowders: structure and mechanical properties

International Nuclear Information System (INIS)

Kostytsyn, M. A.; Muratov, D. S.; Lysov, D. V.; Chuprunov, K. O.; Yudin, A. G.; Leybo, D. V.

2016-01-01

Filtering elements are often used in the metallurgy of rare earth metals. Corundum ceramic is one of the most suitable materials for this purpose. The process of formation and the properties of nanomodified ceramic materials, which are proposed as filtering materials with tunable effective porosity, are described. A silica nanopowder is used as a porosity-increasing agent. Vortex layer apparatus is used for mixing of precursor materials. The obtained results show that nanomodification with the vortex layer apparatus using 0.04 wt. % silica nanopowder as a modifying agent leads to an increase in the compression strength of corundum ceramic by the factor of 1.5. (paper)

Methods of three-dimensional electrophoretic deposition for ceramic and cermet applications and systems thereof

Science.gov (United States)

Rose, Klint Aaron; Kuntz, Joshua D.; Worsley, Marcus

2016-09-27

A ceramic, metal, or cermet according to one embodiment includes a first layer having a gradient in composition, microstructure and/or density in an x-y plane oriented parallel to a plane of deposition of the first layer. A ceramic according to another embodiment includes a plurality of layers comprising particles of a non-cubic material, wherein each layer is characterized by the particles of the non-cubic material being aligned in a common direction. Additional products and methods are also disclosed.

In situ characterization of delamination and crack growth of a CGO–LSM multi-layer ceramic sample investigated by X-ray tomographic microscopy

DEFF Research Database (Denmark)

Bjørk, Rasmus; Esposito, Vincenzo; Lauridsen, Erik Mejdal

2014-01-01

The densification, delamination and crack growth behavior in a Ce0.9Gd0.1O1.95 (CGO) and (La0.85Sr0.15)0.9MnO3 (LSM) multi-layer ceramic sample was studied using in situ X-ray tomographic microscopy (microtomography) to investigate the critical dynamics of crack propagation and delamination...... in a multilayered sample. Naturally occurring defects, caused by the sample preparation process, are shown not to be critical in sample degradation. Instead defects are nucleated during the debinding step. Crack growth is significantly faster along the material layers than perpendicular to them, and crack growth...

Microimpurity composition of superconducting ceramics

International Nuclear Information System (INIS)

Zhiglov, Yu.S.; Poltoratskij, Yu.B.; Protsenko, A.N.; Tuchin, O.V.

1989-01-01

Using laser mass spectrometry, the microimpurity composition of YBa 2 Cu 3 O 7-y superconducting ceramics, prepared by routine solid-phase synthesis from extremely pure yttrium and copper oxides and BaCO 3 , is determined. The presence of F, Na, Al, P, Cl, S, K, Ca impurities, which concentration in specimens varies within 10 -3 +5x10 -3 at.% and also Si, Sr, Fe of about 1x10 -1 at.% is established. It is difficult to determine concentrations of C, N, H 2 O impurities because of the presence of background signals of residual gases in the chamber. Using the method of Auger electron spectroscopy, a surface layer of HTSC ceramics grain is studied. The availability of chlorine impurity, which amount considerably exceeds its volume concentration, is determined in near the surface layer. 2 refs.; 2 figs

Fatigue of dental ceramics.

Science.gov (United States)

Zhang, Yu; Sailer, Irena; Lawn, Brian R

2013-12-01

Clinical data on survival rates reveal that all-ceramic dental prostheses are susceptible to fracture from repetitive occlusal loading. The objective of this review is to examine the underlying mechanisms of fatigue in current and future dental ceramics. The nature of various fatigue modes is elucidated using fracture test data on ceramic layer specimens from the dental and biomechanics literature. Failure modes can change over a lifetime, depending on restoration geometry, loading conditions and material properties. Modes that operate in single-cycle loading may be dominated by alternative modes in multi-cycle loading. While post-mortem examination of failed prostheses can determine the sources of certain fractures, the evolution of these fractures en route to failure remains poorly understood. Whereas it is commonly held that loss of load-bearing capacity of dental ceramics in repetitive loading is attributable to chemically assisted 'slow crack growth' in the presence of water, we demonstrate the existence of more deleterious fatigue mechanisms, mechanical rather than chemical in nature. Neglecting to account for mechanical fatigue can lead to gross overestimates in predicted survival rates. Strategies for prolonging the clinical lifetimes of ceramic restorations are proposed based on a crack-containment philosophy. Copyright © 2013 Elsevier Ltd. All rights reserved.

Low-temperature atomic layer epitaxy of AlN ultrathin films by layer-by-layer, in-situ atomic layer annealing.

Science.gov (United States)

Shih, Huan-Yu; Lee, Wei-Hao; Kao, Wei-Chung; Chuang, Yung-Chuan; Lin, Ray-Ming; Lin, Hsin-Chih; Shiojiri, Makoto; Chen, Miin-Jang

2017-01-03

Low-temperature epitaxial growth of AlN ultrathin films was realized by atomic layer deposition (ALD) together with the layer-by-layer, in-situ atomic layer annealing (ALA), instead of a high growth temperature which is needed in conventional epitaxial growth techniques. By applying the ALA with the Ar plasma treatment in each ALD cycle, the AlN thin film was converted dramatically from the amorphous phase to a single-crystalline epitaxial layer, at a low deposition temperature of 300 °C. The energy transferred from plasma not only provides the crystallization energy but also enhances the migration of adatoms and the removal of ligands, which significantly improve the crystallinity of the epitaxial layer. The X-ray diffraction reveals that the full width at half-maximum of the AlN (0002) rocking curve is only 144 arcsec in the AlN ultrathin epilayer with a thickness of only a few tens of nm. The high-resolution transmission electron microscopy also indicates the high-quality single-crystal hexagonal phase of the AlN epitaxial layer on the sapphire substrate. The result opens a window for further extension of the ALD applications from amorphous thin films to the high-quality low-temperature atomic layer epitaxy, which can be exploited in a variety of fields and applications in the near future.

Effect of ZnO on phase emergence, microstructure and surface modifications of calcium phosphosilicate glass/glass-ceramics having iron oxide

Energy Technology Data Exchange (ETDEWEB)

Sharma, K.; Dixit, A.; Bhattacharya, S.; Jagannath [Technical Physics and Prototype Engineering Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India); Deo, M.N. [High Pressure Physics Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India); Kothiyal, G.P., E-mail: gpkoth@barc.gov.in [Technical Physics and Prototype Engineering Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India)

2010-03-01

The effect of ZnO on phase emergence and microstructure properties of glass and glass-ceramics with composition 25SiO{sub 2}-50CaO-15P{sub 2}O{sub 5}-(10 - x)Fe{sub 2}O{sub 3}-xZnO (where x = 0, 2, 5, 7 mol%) has been studied. They have been characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). Surface modifications of these glass-ceramics in simulated body fluid have been studied using Fourier transform infrared reflection spectroscopy (FTIR), XPS and SEM. Results have shown a decrease in the fraction of non-bridging oxygen with increase in zinc oxide content. Emergence of crystalline phases in glass-ceramics at different heat treatment temperatures was studied using XRD. When glass is heat treated at 800 deg. C calcium phosphate, hematite and magnetite are developed as major phases in the glass-ceramics samples with ZnO up to 5 mol%. In addition to these, calcium silicate (Ca{sub 3}Si{sub 2}O{sub 7}) phase is also observed when glass is heat treated at 1000 deg. C. The microstructure of the glass-ceramics heat treated at 800 deg. C exhibits the formation of nano-size (40-50 nm) grains. On heat treatment at 1000 deg. C crystallites grow to above 50 nm size and more than one phase are observed in the microstructure. The formation of thin flake-like structure with coarse particles is observed at high zinc oxide concentration (x = 7 mol%). In vitro studies have shown the surface modifications and formation of Ca-P-rich layer on the glass-ceramics when immersed in simulated body fluids (SBF) for different durations. The bioactive response was found to depend on ZnO content.

Effect of ZnO on phase emergence, microstructure and surface modifications of calcium phosphosilicate glass/glass-ceramics having iron oxide

International Nuclear Information System (INIS)

Sharma, K.; Dixit, A.; Bhattacharya, S.; Jagannath; Deo, M.N.; Kothiyal, G.P.

2010-01-01

The effect of ZnO on phase emergence and microstructure properties of glass and glass-ceramics with composition 25SiO 2 -50CaO-15P 2 O 5 -(10 - x)Fe 2 O 3 -xZnO (where x = 0, 2, 5, 7 mol%) has been studied. They have been characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). Surface modifications of these glass-ceramics in simulated body fluid have been studied using Fourier transform infrared reflection spectroscopy (FTIR), XPS and SEM. Results have shown a decrease in the fraction of non-bridging oxygen with increase in zinc oxide content. Emergence of crystalline phases in glass-ceramics at different heat treatment temperatures was studied using XRD. When glass is heat treated at 800 deg. C calcium phosphate, hematite and magnetite are developed as major phases in the glass-ceramics samples with ZnO up to 5 mol%. In addition to these, calcium silicate (Ca 3 Si 2 O 7 ) phase is also observed when glass is heat treated at 1000 deg. C. The microstructure of the glass-ceramics heat treated at 800 deg. C exhibits the formation of nano-size (40-50 nm) grains. On heat treatment at 1000 deg. C crystallites grow to above 50 nm size and more than one phase are observed in the microstructure. The formation of thin flake-like structure with coarse particles is observed at high zinc oxide concentration (x = 7 mol%). In vitro studies have shown the surface modifications and formation of Ca-P-rich layer on the glass-ceramics when immersed in simulated body fluids (SBF) for different durations. The bioactive response was found to depend on ZnO content.

Use of sugar-cane bagasse ash to produce glass-ceramic material in the system Ca O-SiO2-Na2O

International Nuclear Information System (INIS)

Teixeira, S.R.; Santos, G.T.A.; Magalhaes, R.S.; Rincon, J.Ma.; Romero, M.; Carvalho, C.L.

2009-01-01

A bottom ash was used as raw material to obtain glass which was crystallized to form glass-ceramic material. The characterization of the ash shows that it consists mainly of crystalline materials, predominantly quartz, with oxides of iron, potassium and aluminum as minor elements. The glass was obtained from the mixing of ash with calcium and sodium carbonates. The glass and the glass-ceramic were examined using differential thermal analysis (DTA), X-ray fluorescence (XRF), X-ray diffraction (XRD) and scanning electron microscopy (SEM). XRD and DTA data show that Wollastonita is the only crystalline phase present in the material crystallized at 1050 deg C. Part of the glass was synthesized at this temperature for one hour, resulting in a green/brown hard material glass-ceramic. The images of SEM show morphology of spherilithic growth indicating volumetric crystallization mechanism. (author)

Use of solid waste from sand beneficiation process in the ceramic tile industry and its influence on the physical properties of the ceramic products

International Nuclear Information System (INIS)

Biff, Sergio; Silva, Manoel Ribeiro da

2016-01-01

The current paper had as main aim characterize and assess the use viability of a solid waste from sand beneficiation process in the production of ceramic tiles. To determine the main components the solid waste was characterized by X-ray fluorescence and the main crystalline phases were determined by X-ray diffraction. To evaluate the addition effects of the solid waste over the solid waste was introduced into a ceramic composition in proportions of 5% and 10%. The ceramics materials obtained were subjected to the linear retraction, water absorption and flexural strength analysis according to the Brazilian standard NBR 13818 (1997). Additionally, the solid waste and the ceramic materials obtained in this study were classified according to the Brazilian standard NBR 10004 (2004) to assess the potential environmental impact. The main solid waste constituents identified were silicon dioxide and aluminum oxide, respectively 50.2% e 19.2%, distributed in the crystal forms of quartz and kaolinite. The ceramic materials obtained after firing at 1100 deg C, without and with 10% of solid waste presented respectively flexural strength of 13.86 MPa and 14,52Mpa. The results of water absorption without and with addition of 10% of solid waste were respectively 16.96% and 16.63%, both appropriate performances for use in ceramic tiles according to the Brazilian standard NBR 13818 (1997). On the other hand, the ceramic materials obtained with the addition of 10% of solid waste were classified as inert materials according to Brazilian standard NBR 10004 (2004), showing the capability of incorporating solid waste in ceramic materials. (author)

Improved ionic conductivity of lithium-zinc-tellurite glass-ceramic electrolytes

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W. Widanarto

Full Text Available An enhancement in the secondary battery safety demands the optimum synthesis of glass-ceramics electrolytes with modified ionic conductivity. To achieve improved ionic conductivity and safer operation of the battery, we synthesized Li2O included zinc-tellurite glass-ceramics based electrolytes of chemical composition (85-xTeO2·xLi2O·15ZnO, where x = 0, 5, 10, 15 mol%. Samples were prepared using the melt quenching method at 800 °C followed by thermal annealing at 320 °C for 3 h and characterized. The effects of varying temperature, alternating current (AC frequency and Li2O concentration on the structure and ionic conductivity of such glass-ceramics were determined. The SEM images of the annealed glass-ceramic electrolytes displayed rough surface with a uniform distribution of nucleated crystal flakes with sizes less than 1 μm. X-ray diffraction analysis confirmed the well crystalline nature of achieved electrolytes. Incorporation of Li2O in the electrolytes was found to generate some new crystalline phases including hexagonal Li6(TeO6, monoclinic Zn2Te3O8 and monoclinic Li2Te2O5. The estimated crystallite size of the electrolyte was ranged from ≈40 to 80 nm. AC impedance measurement revealed that the variation in the temperatures, Li2O contents, and high AC frequencies have a significant influence on the ionic conductivity of the electrolytes. Furthermore, electrolyte doped with 15 mol% of Li2O exhibited the optimum performance with an ionic conductivity ≈2.4 × 10−7 S cm−1 at the frequency of 54 Hz and in the temperature range of 323–473 K. This enhancement in the conductivity was attributed to the sizable alteration in the ions vibration and ruptures of covalent bonds in the electrolytes network structures. Keywords: Zinc-tellurite, Glass-ceramics, X-ray diffraction, Ionic conductivity, Lithium oxide

Flexural strength and microstructure of two lithium disilicate glass ceramics for CAD/CAM restoration in the dental clinic

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Suk-Ho Kang

2013-08-01

Full Text Available Objectives There has been a growing interest in glass ceramic systems with good esthetics, high fracture resistance and bonding durability, and simplified fabrication techniques using CAD/CAM. The aim of this study is to compare flexural strength before and after heat treatment of two lithium disilicate CAD/CAM blocks, IPS e.max CAD (Ivoclar Vivadent and Rosetta SM (Hass, and to observe their crystalline structures. Materials and Methods Biaxial flexural strength was tested according to ISO 6872 with 20 disc form specimens sliced from each block before and after heat treatment. Also, the crystalline structures were observed using field-emission scanning microscopy (FE-SEM, Hitachi and x-ray diffraction (XRD, Rigaku analysis. The mean values of the biaxial flexural strength were analyzed by the Mann-Whitney U test at a significance level of p = 0.05. Results There were no statistically significant differences in flexural strength between IPS e.max CAD and Rosetta SM either before heat treatment or after heat treatment. For both ceramics, the initial flexural strength greatly increased after heat treatment, with significant differences (p < 0.05. The FE-SEM images presented similar patterns of crystalline structure in the two ceramics. In the XRD analysis, they also had similar patterns, presenting high peak positions corresponding to the standard lithium metasilicate and lithium disilicate at each stage of heat treatment. Conclusions IPS e.max CAD and Rosetta SM showed no significant differences in flexural strength. They had a similar crystalline pattern and molecular composition.

Spectroscopic ellipsometry characterization of amorphous and crystalline TiO{sub 2} thin films grown by atomic layer deposition at different temperatures

Energy Technology Data Exchange (ETDEWEB)

Saha, D., E-mail: babaisps@rrcat.gov.in [Laser Materials Processing Division, Raja Ramanna Centre for Advanced Technology, Indore 452013 (India); Ajimsha, R.S. [Laser Materials Processing Division, Raja Ramanna Centre for Advanced Technology, Indore 452013 (India); Rajiv, K.; Mukherjee, C. [Mechanical and Optical Support Section, Raja Ramanna Centre for Advanced Technology, Indore 452013 (India); Gupta, M. [UGC-DAE Consortium, Indore Centre, Khandwa Road, Indore 452017 (India); Misra, P.; Kukreja, L.M. [Laser Materials Processing Division, Raja Ramanna Centre for Advanced Technology, Indore 452013 (India)

2014-10-01

Highlights: • Refractive index was found to be increased from amorphous to the nanocrystalline films. • Refractive index was found to be inversely proportional with growth per cycle. • Large-grained anatase films showed lower refractive indices than the amorphous films. • Roughness was taken into consideration due to the columnar growths of crystalline films. - Abstract: TiO{sub 2} thin films of widely different structural and morphological characteristics were grown on Si (1 0 0) substrates using Atomic Layer Deposition (ALD) by varying the substrate temperature (T{sub s}) in a wide range (50 °C ≤ T{sub s} ≤ 400 °C). Spectroscopic ellipsometry (SE) measurements were carried out to investigate the effect of growth temperature on the optical properties of the films. Measured SE data were analyzed by considering double layer optical model for the sample together with the single oscillator Tauc-Lorentz dispersion relation. Surface roughness was taken into consideration due to the columnar growths of grains in crystalline films. The refractive index was found to be increased from amorphous (T{sub s} ≤ 150 °C) to the nanocrystalline films (250{sup 0} < T{sub s} ≤ 400 °C). The pronounced surface roughening for the large-grained anatase film obtained at the amorphous to crystalline phase transformation temperature of 200 °C, impeded SE measurement. The dispersions of refractive indices below the interband absorption edge were found to be strongly correlated with the single oscillator Wemple–DiDomenico (WD) model. The increase in dispersion energy parameter in WD model from disordered amorphous to the more ordered nanocrystalline films was found to be associated with the increase in the film density and coordination number.

Sacrificial Paste for Fabrication of Ceramic Materials by Layer-By-Layer Method

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Falkowski P.

2016-09-01

Full Text Available The aim of the work was to develop a sacrificial paste suitable for securing channels during shaping of ceramic materials with internal structures via combination of tape casting and soft lithography. Poly(ethylene glycol methyl ether and polyethylene glycols with different molecular weight were selected as a main components of a sacrificial paste due to their compatibility to UV curable dispersion. The research shows that sacrificial paste should be characterized by proper melting point. This goal was achieved by using a composition of PEG600 with 15wt.%PEG20000 and 10wt.% carbon. The invented sacrificial paste solidify beyond 27°C (melting point. After heating up to 80°C the viscosity of paste is low enough and easily fills the channels with diameter of 150-300μm. What is more, the operational time during free cooling from 80°C to solidification is around 8 minutes what gives enough time for application. Carbon was added as a modifier of rheological properties and as a black dye that helps in visual evaluation of a degree of filling channel. The first test proved that proposed method of preparation of ceramic samples with application of invented sacrificial paste is reliable and can be practically applied.

Microstructure and thermochromic properties of VO{sub X}-WO{sub X}-VO{sub X} ceramic thin films

Energy Technology Data Exchange (ETDEWEB)

Khamseh, S.; Ghahari, M. [Institute for Color Science and Technology, Department of Nanomaterial and Nanocoatings, Tehran (Iran, Islamic Republic of); Araghi, H. [Islamic Azad University, Department of Materials Engineering, Science and Research Branch, Tehran (Iran, Islamic Republic of); Faghihi Sani, M.A. [Sharif University of Technology, Department of Materials Science and Engineering, Tehran (Iran, Islamic Republic of)

2016-03-15

W-doped VO{sub 2} films have been synthesized via oxygen annealing of V-W-V (vanadium-tungsten-vanadium) multilayered films. The effects of middle layer's thickness of V-W-V multilayered film on structure and properties of VO{sub X}-WO{sub X}-VO{sub X} ceramic thin films were investigated. The as-deposited V-W-V multilayered film showed amorphous-like structure when mixed structure of VO{sub 2} (M) and VO{sub 2} (B) was formed in VO{sub X}-WO{sub X}-VO{sub X} ceramic thin films. Tungsten content of VO{sub X}-WO{sub X}-VO{sub X} ceramic thin films increased with increasing middle layer's thickness. With increasing middle layer's thickness, room temperature square resistance (R{sub sq}) of VO{sub X}-WO{sub X}-VO{sub X} ceramic thin films increased from 65 to 86 kΩ/sq. The VO{sub X}-WO{sub X}-VO{sub X} ceramic thin film with the thinnest middle layer showed significant SMT (semiconductor-metal transition) when SMT became negligible on increasing middle layer's thickness. (orig.)

A small angle neutron scattering study of mica based glass-ceramics with applications in dentistry

International Nuclear Information System (INIS)

Kilcoyne, S.H.; Bentley, P.M.; Al-Jawad, M.; Bubb, N.L.; Al-Shammary, H.A.O.; Wood, D.J.

2004-01-01

We are currently developing machinable and load-bearing mica-based glass-ceramics for use in restorative dental surgery. In this paper we present the results of an ambient temperature small angle neutron scattering (SANS) study of several such ceramics with chemical compositions chosen to optimise machinability and strength. The SANS spectra are all dominated by scattering from the crystalline-amorphous phase interface and exhibit Q -4 dependence (Porod scattering) indicating that, on a 100 A scale, the surface of the crystals is smooth

Structural and Chemical Analysis of the Zirconia-Veneering Ceramic Interface.

Science.gov (United States)

Inokoshi, M; Yoshihara, K; Nagaoka, N; Nakanishi, M; De Munck, J; Minakuchi, S; Vanmeensel, K; Zhang, F; Yoshida, Y; Vleugels, J; Naert, I; Van Meerbeek, B

2016-01-01

The interfacial interaction of veneering ceramic with zirconia is still not fully understood. This study aimed to characterize morphologically and chemically the zirconia-veneering ceramic interface. Three zirconia-veneering conditions were investigated: 1) zirconia-veneering ceramic fired on sandblasted zirconia, 2) zirconia-veneering ceramic on as-sintered zirconia, and 3) alumina-veneering ceramic (lower coefficient of thermal expansion [CTE]) on as-sintered zirconia. Polished cross-sectioned ceramic-veneered zirconia specimens were examined using field emission gun scanning electron microscopy (Feg-SEM). In addition, argon-ion thinned zirconia-veneering ceramic interface cross sections were examined using scanning transmission electron microscopy (STEM)-energy dispersive X-ray spectrometry (EDS) at high resolution. Finally, the zirconia-veneering ceramic interface was quantitatively analyzed for tetragonal-to-monoclinic phase transformation and residual stress using micro-Raman spectroscopy (µRaman). Feg-SEM revealed tight interfaces for all 3 veneering conditions. High-resolution transmission electron microscopy (HRTEM) disclosed an approximately 1.0-µm transformed zone at sandblasted zirconia, in which distinct zirconia grains were no longer observable. Straight grain boundaries and angular grain corners were detected up to the interface of zirconia- and alumina-veneering ceramic with as-sintered zirconia. EDS mapping disclosed within the zirconia-veneering ceramic a few nanometers thick calcium/aluminum-rich layer, touching the as-sintered zirconia base, with an equally thick silicon-rich/aluminum-poor layer on top. µRaman revealed t-ZrO2-to-m-ZrO2 phase transformation and residual compressive stress at the sandblasted zirconia surface. The difference in CTE between zirconia- and the alumina-veneering ceramic resulted in residual tensile stress within the zirconia immediately adjacent to its interface with the veneering ceramic. The rather minor chemical

Feasibility of ceramic joining with high energy electron beams

International Nuclear Information System (INIS)

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

1995-01-01

Joining structural ceramics is possible using high melting point metals such as Mo and Pt that are heated with a high energy electron beam, with the potential for producing joints with high temperature capability. A 10 MeV electron beam can penetrate through 1 cm of ceramic, offering the possibility of buried interface joining. Because of transient heating and the lower heat capacity of the metal relative to the ceramic, a pulsed high power beam has the potential for melting the metal without decomposing or melting the adjacent ceramic. The authors have demonstrated the feasibility of the process with a series of 10 MeV, 1 kW electron beam experiments. Shear strengths up to 28 NTa have been measured for Si 3 N 4 -Mo-Si 3 N 4 . These modest strengths are due to beam non-uniformity and the limited area of bonding. The bonding mechanism appears to be a thin silicide reaction layer. Si 3 N 4 -Si 3 N 4 joints with no metal layer were also produced, apparently bonded an yttrium apatite grain boundary phase

Three-Point Bending Tests of Zirconia Core/Veneer Ceramics for Dental Restorations

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Massimo Marrelli

2013-01-01

Full Text Available Introduction. The mechanical strength and the surface hardness of commercially available yttrium-doped zirconia were investigated. Furthermore, a comparative study of eight different ceramic veneers, to be used for the production of two-layered all-ceramic restorative systems, was carried out. Materials and Methods. Four types of zirconia specimens were analyzed, according to a standard ISO procedure (ISO 6872. Besides, two-layered zirconia-veneer specimens were prepared for three-point bending tests. Results. A strong effect of the surface roughness on the mechanical strength of zirconia specimens was observed. Finally, a comparative study of eight commercially available veneering ceramics shows different modes of failure between the selected veneers. Conclusion. The results indicate that close attention should be paid to the preparation of zirconia-based crowns and bridges by CAD/CAM process, because surface roughness has an important effect on the mechanical strength of the material. Finally, the results of the mechanical tests on two-layered specimens represent an important support to the choice of the veneering ceramic.

Electrical response of electron selective atomic layer deposited TiO2‑x heterocontacts on crystalline silicon substrates

Science.gov (United States)

Ahiboz, Doğuşcan; Nasser, Hisham; Aygün, Ezgi; Bek, Alpan; Turan, Raşit

2018-04-01

Integration of oxygen deficient sub-stoichiometric titanium dioxide (TiO2‑x) thin films as the electron transporting-hole blocking layer in solar cell designs are expected to reduce fabrication costs by eliminating high temperature processes while maintaining high conversion efficiencies. In this paper, we conducted a study to reveal the electrical properties of TiO2‑x thin films grown on crystalline silicon (c-Si) substrates by atomic layer deposition (ALD) technique. Effect of ALD substrate temperature, post deposition annealing, and doping type of the c-Si substrate on the interface states and TiO2‑x bulk properties were extracted by performing admittance (C-V, G-V) and current-voltage (J-V) measurements. Moreover, the asymmetry in C-V and J-V measurements between the p-n type and n-n TiO2‑x-c-Si heterojunction types were examined and the electron transport selectivity of TiO2‑x was revealed.

Electrical characterization of strontium titanate borosilicate glass ceramics system with bismuth oxide addition using impedance spectroscopy

International Nuclear Information System (INIS)

Thakur, O.P.; Kumar, Devendra; Parkash, Om; Pandey, Lakshman

2003-01-01

The ac electrical data, measured in the frequency range 0.1 kHz-1 MHz, were used to study the electrical response of strontium titanate borosilicate glass ceramic system with bismuth oxide addition. Complex plane plots from these electrical data for various glass ceramic samples reveal contributions from simultaneously operating polarization mechanisms to overall dielectric behavior. The complex modulus (M * ) representation of electrical data for various glass ceramic samples were found to be more informative. Equivalent circuit models, which represent the electrical behavior of glass ceramic samples, were determined using complex non-linear least square (CNLS) fitting. An attempt has been made to understand the dielectric behavior of various glass ceramics in terms of contributions arising from different polarization processes occurring at glassy matrix, crystalline phases, glass to crystal interface region and blocking electrodes. Glass ceramics containing SrTiO 3 and TiO 2 (rutile) phases show thermally stable dielectric behavior

Improved ionic conductivity of lithium-zinc-tellurite glass-ceramic electrolytes

Science.gov (United States)

Widanarto, W.; Ramdhan, A. M.; Ghoshal, S. K.; Effendi, M.; Cahyanto, W. T.; Warsito

An enhancement in the secondary battery safety demands the optimum synthesis of glass-ceramics electrolytes with modified ionic conductivity. To achieve improved ionic conductivity and safer operation of the battery, we synthesized Li2O included zinc-tellurite glass-ceramics based electrolytes of chemical composition (85-x)TeO2·xLi2O·15ZnO, where x = 0, 5, 10, 15 mol%. Samples were prepared using the melt quenching method at 800 °C followed by thermal annealing at 320 °C for 3 h and characterized. The effects of varying temperature, alternating current (AC) frequency and Li2O concentration on the structure and ionic conductivity of such glass-ceramics were determined. The SEM images of the annealed glass-ceramic electrolytes displayed rough surface with a uniform distribution of nucleated crystal flakes with sizes less than 1 μm. X-ray diffraction analysis confirmed the well crystalline nature of achieved electrolytes. Incorporation of Li2O in the electrolytes was found to generate some new crystalline phases including hexagonal Li6(TeO6), monoclinic Zn2Te3O8 and monoclinic Li2Te2O5. The estimated crystallite size of the electrolyte was ranged from ≈40 to 80 nm. AC impedance measurement revealed that the variation in the temperatures, Li2O contents, and high AC frequencies have a significant influence on the ionic conductivity of the electrolytes. Furthermore, electrolyte doped with 15 mol% of Li2O exhibited the optimum performance with an ionic conductivity ≈2.4 × 10-7 S cm-1 at the frequency of 54 Hz and in the temperature range of 323-473 K. This enhancement in the conductivity was attributed to the sizable alteration in the ions vibration and ruptures of covalent bonds in the electrolytes network structures.

ION EXCHANGE IN GLASS-CERAMICS

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George Halsey Beall

2016-08-01

Full Text Available In the past few years ion-exchange in glasses has found a renewed interest with a lot of new development and research in industrial and academic labs and the commercialization of materials with outstanding mechanical properties. These glasses are now widely used in many electronic devices including hand-held displays and tablets. The exchange is generally conducted in a bath of molten salt below the transition temperature of the glass. The exchange at the surface of an alkali ion by a bigger one brings compressive stress at the surface. The mechanical properties are dependent on the stress level at the surface and the depth of penetration of the bigger ion. As compared to glasses, glass-ceramics have the interest to display a wide range of aspects (transparent to opaque and different mechanical properties (especially higher modulus and toughness. There has been little research on ion-exchange in glass-ceramics. In these materials the mechanisms are much more complex than in glasses because of their polyphasic nature: ion-exchange generally takes place mostly in one phase (crystalline phase or residual glass. The mechanism can be similar to what is observed in glasses with the replacement of an ion by another in the structure. But in some cases this ion-exchange leads to microstructural modifications (for example amorphisation or phase change.This article reviews these ion-exchange mechanisms using several transparent and opaque alumino-silicate glass-ceramics as examples. The effect of the ion exchange in the various glass-ceramics will be described, with particular emphasis on flexural strength.

Bonding strength of glass-ceramic trabecular-like coatings to ceramic substrates for prosthetic applications.

Science.gov (United States)

Chen, Qiang; Baino, Francesco; Pugno, Nicola M; Vitale-Brovarone, Chiara

2013-04-01

A new approach based on the concepts of quantized fracture mechanics (QFM) is presented and discussed in this paper to estimate the bonding strength of trabecular-like coatings, i.e. glass-ceramic scaffolds mimicking the architecture of cancellous bone, to ceramic substrates. The innovative application of glass-derived scaffolds as trabecular-like coatings is proposed in order to enhance the osteointegration of prosthetic ceramic devices. The scaffolds, prepared by polymeric sponge replication, are joined to alumina substrates by a dense glass-ceramic coating (interlayer) and the so-obtained 3-layer constructs are investigated from micro-structural, morphological and mechanical viewpoints. In particular, the fracture strengths of three different crack propagation modes, i.e. glass-derived scaffold fracture, interface delamination or mixed fracture, are predicted in agreement with those of experimental mechanical tests. The approach proposed in this work could have interesting applications towards an ever more rational design of bone tissue engineering biomaterials and coatings, in view of the optimization of their mechanical properties for making them actually suitable for clinical applications. Copyright © 2012 Elsevier B.V. All rights reserved.

Stereolithographic processing of ceramics: Photon diffusion in colloidal dispersion

Science.gov (United States)

Garg, Rajeev

The technique of ceramic stereolithography (CSL) has been developed for fabricating near net shape ceramic objects. In stereolithography, the three-dimensional computer design file of the object is sliced into thin layers. Each layer is physically fabricated by photocuring the surface of a liquid photo-polymerizable resin bath by raster scanning an ultra-violet laser across the surface of the resin. In CSL, the liquid resin is a high concentration colloidal dispersion in a solution of ultraviolet curable polymers. The ceramic green body fabricated by ceramic stereolithography technique is subjected to the post processing steps of drying, binder burnout and sintering to form a dense ceramic object. An aqueous alumina dispersion in photocuring polymers with particle volume fraction greater than 0.5 was formulated for CSL process. Low molecular weight solution polymers were found to be best suited for formulating ceramic resins due to their inherently low viscosity and favorable interactions with the ceramic dispersant. A hydroxyapatite ceramic resin was also developed for the use in the CSL technique. A model is developed to describe the photocuring process in concentrated ceramic dispersion. The curing profile in ceramic dispersion is governed by multiple scattering from the ceramic particles and absorption by the photocuring polymers. Diffusion theory of light transport is used to model the multiple scattering and absorption phenomena. It is found that diffusive transport adequately describes the phenomena of laser pulse propagation in highly concentrated colloidal dispersions. A model was developed to describe the absorption in highly concentrated ceramic dispersion. Various complex-shaped monolithic alumina and hydroxyapatite objects were fabricated by CSL and shown to possess uniform microstructure. The mechanical properties and sintering behavior of the parts fabricated by CSL are shown to be comparable to those fabricated by other ceramic processing technique

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

Science.gov (United States)

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

2018-02-01

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

Rotary Ultrasonic Machining of Poly-Crystalline Cubic Boron Nitride

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Kuruc Marcel

2014-12-01

Full Text Available Poly-crystalline cubic boron nitride (PCBN is one of the hardest material. Generally, so hard materials could not be machined by conventional machining methods. Therefore, for this purpose, advanced machining methods have been designed. Rotary ultrasonic machining (RUM is included among them. RUM is based on abrasive removing mechanism of ultrasonic vibrating diamond particles, which are bonded on active part of rotating tool. It is suitable especially for machining hard and brittle materials (such as glass and ceramics. This contribution investigates this advanced machining method during machining of PCBN.

Radiation damage in nuclear waste ceramics

International Nuclear Information System (INIS)

Turcotte, R.P.; Roberts, F.P.; Rusin, J.M.; Wald, J.W.

1982-01-01

The text contains a number of specific observations about the radiation-induced changes in glass, glass-ceramic, and supercalcine nuclear waste forms. Other, more general conclusions can be summarized: Radiation-induced property changes follow an exponential ingrowth curve to saturation. Actinide host phases in both crystalline waste forms become X-ray amorphous. The magnitudes of the waste-form density changes observed could not be directly related to observed changes in the primary actinide phases. Although large crystal-structure changes occur in the materials studied, obvious physical degradation was not observed

Preparation and characterization of novel glass–ceramic tile with microwave absorption properties from iron ore tailings

International Nuclear Information System (INIS)

Yao, Rui; Liao, SongYi; Dai, ChangLu; Liu, YuChen; Chen, XiaoYu; Zheng, Feng

2015-01-01

A novel glass–ceramic tile consisting of one glass–ceramic layer (GC) attaining microwave absorption properties atop ceramic substrate was prepared through quench-heat treatment route derived from iron ore tailings (IOTs) and commercial raw materials (purity range 73–99%). X-ray diffraction (XRD), SEM, Energy dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), Physical property measurement system (PPMS) and Vector network analyzer (VNA) measurements were carried out to investigate phase, microstructure, magnetic and microwave absorption aspects of the glass–ceramic layer. Roughly 80.6±1.7 wt% borosilicate glass and 19.4±1.7 wt% spinel ferrite with chemical formula of (Zn 2+ 0.17 Fe 3+ 0.83 )[Fe 3+ 1.17 Fe 2+ 0.06 Ni 2+ 0.77 ]O 4 were found among the tested samples. Absorption of Electromagnetic wave by 3 mm thick glass–ceramic layer at frequency of 2–18 GHz reached peak reflection loss (RL) of −17.61 dB (98.27% microwave absorption) at 10.31 GHz. Altering the thickness of the glass–ceramic layer can meet the requirements of different level of microwave absorption. - Highlights: • Iron ore tailings (IOTs) have been used as one of the main raw materials. • Glass–ceramic tile contains spinel ferrite has been prepared. • The cation distribution of the spinel ferrite has been calculated. • The intrinsic complex permeability and permittivity have been evaluated

Effect of paramagnetic manganese ions doping on frequency and high temperature dependence dielectric response of layered Na1.9Li0.1Ti3O7 ceramics

International Nuclear Information System (INIS)

Pal, Dharmendra; Pandey, J.L.

2010-01-01

The manganese doped layered ceramic samples (Na 1.9 Li 0.1 )Ti 3 O 7 : XMn (0.01 ≤ X ≤ 0.1) have been prepared using high temperature solid state reaction. The room temperature electron paramagnetic resonance (EPR) investigations exhibit that at lower percentage of doping the substitution of manganese ions occur as Mn 3+ at Ti 4+ sites, whereas for higher percentage of doping Mn 2+ ions occupy the two different interlayer sodium/lithium sites. In both cases, the charge compensation mechanism should operate to maintain the overall charge neutrality of the lattice. The manganese doped derivatives of layered Na 1.9 Li 0. 1Ti 3 O 7 (SLT) ceramics have been investigated through frequency dependence dielectric spectroscopy in this work. The results indicate that the dielectric losses in these ceramics are the collective contribution of electric conduction, dipole orientation and space charge polarization. Smeared peaks in temperature dependence of permittivity plots suggest diffuse nature of high temperature ferroelectric phase transition. The light manganese doping in SLT enhances the dielectric constant. However, manganese doping decreases dielectric loss due to inhibition of domain wall motion, enhances electron-hopping conduction, and impedes the interlayer ionic conduction as well. Manganese doping also gives rise to contraction of interlayer space. (author)

Processing and properties of pressable ceramic with non-uniform reinforcement for selective-toughening

Energy Technology Data Exchange (ETDEWEB)

Yi, Wei [School of Mechanical and Chemical Engineering, The University of Western Australia, Perth, WA 6009 (Australia); School of Dentistry, The University of Western Australia, WA 6009 (Australia); Key Laboratory for Anisotropy and Texture of Materials (Ministry of Education), Northeastern University, Shenyang 110004 (China); Hu, Xiaozhi, E-mail: xiao.zhi.hu@uwa.edu.au [School of Mechanical and Chemical Engineering, The University of Western Australia, Perth, WA 6009 (Australia); Ichim, Paul [School of Dentistry, The University of Western Australia, WA 6009 (Australia); Sun, Xudong [Key Laboratory for Anisotropy and Texture of Materials (Ministry of Education), Northeastern University, Shenyang 110004 (China)

2012-12-15

Brittle low-strength and low-toughness pressable dental ceramic can be reinforced by ductile elongated gold-particles (GP). A customized crown structure can be adequately strengthened by distributing GP only in critical sections of the crown, where high tensile stresses are experienced. In the present study, a non-uniformly structured ceramic-matrix composite with excellent interfacial bonding, twofold fracture toughness and strength at desired locations, is fabricated using pressable dental ceramic and GP. The layout pattern and sequence of different GP/ceramic powder mixtures, high-temperature flow properties of these mixtures during hot-pressing and the sample mold geometry are used to control the distribution and locations of GP for selective toughening and strengthening. Nano-crystalline structures of the pressable ceramic-matrix and the nano-scaled interfacial region around GP have been revealed by high-magnification field-emission scanning electron microscopy. Toughening and strengthening mechanisms of the elongated GP including residual stresses from composite processing and ductile fracture of GP are discussed together with SEM observations. Bulk flexural strength and local micro-indentation fracture and deformation characteristics of the selective-toughened ceramic/metal composite have been compared to those of the monolithic pressable ceramic to validate the toughening and strengthening mechanisms.

Silica intercalated crystalline zirconium phosphate-type materials

NARCIS (Netherlands)

1988-01-01

The present invention relates to intercalated crystalline zirconium phosphate-types compositions wherein the interlayers of said composition have been intercalated with three-dimensional silicon oxide pillars whereby the pillars comprise at least two silicon atom layers parallel to the clay

Enhancement of fatigue endurance in ferroelectric PZT ceramic by the addition of bismuth layered SBT

Science.gov (United States)

Namsar, O.; Pojprapai, S.; Watcharapasorn, A.; Jiansirisomboon, S.

2014-10-01

Electrical fatigue properties of (1-x)PZT-xSBT ceramics (x = 0-1.0 weight fraction) were characterized. It was found that pure PZT ceramic had severe polarization fatigue. This was mainly attributed to an occurrence of the macroscopic cracks at near-electrode regions. On the contrary, pure SBT ceramic exhibited excellent fatigue resistance, which was attributed primarily to weak domain wall pinning. As small amount of SBT (0.1 ≤ x ≤ 0.3) was added into PZT, a small reduction of remanent polarization after fatigue process was observed. This demonstrated that these ceramics had high stability during the repeated domain switching due to their low oxygen vacancy concentration. Therefore, these results suggested that this new ceramic PZT-SBT system seemed to be an alternative material for replacing pure PZT in ferroelectric memory applications.

Cr3+ and Cr4+ luminescence in glass ceramic silica

International Nuclear Information System (INIS)

Martines, Marco A.U.; Davolos, Marian R.; Jafelicci, Miguel Junior; Souza, Dione F. de; Nunes, Luiz A.O.

2008-01-01

This paper reports on the effect of glass ceramic silica matrix on [CrO 4 ] 4- and Cr 2 O 3 NIR and visible luminescence. Chromium-containing silica was obtained by precipitation from water-glass and chromium nitrate acid solution with thermal treatment at 1000 deg. C. From XRD results silica and silica-chromium samples are crystalline. The chromium emission spectrum presents two main broad bands: one in the NIR region (1.1-1.7μm) and other in the visible region (0.6-0.7μm) assigned to Cr 4+ and to Cr 3+ , respectively. This thermal treated glass ceramic silica-chromium sample stabilizes the [CrO 4 ] 4- where Cr 4+ substitutes for Si 4+ and also hexacoordinated Cr 3+ group probably as segregated phase in the system. It can be pointed out that luminescence spectroscopy is a powerful tool for detecting the two chromium optical centers in the glass ceramic silica

Development and characterization of basalt-glass ceramics for the immobilization of transuranic wastes

International Nuclear Information System (INIS)

Lokken, R.O.; Chick, L.A.; Thomas, L.E.

1982-09-01

Basalt-based waste forms were developed for the immobilization of transuranic (TRU) contaminated wastes. The specific waste studied is a 3:1 blend of process sludge and incinerator ash. Various amounts of TRU blended waste were melted with Pomona basalt powder. The vitreous products were subjected to a variety of heat treatment conditions to form glass ceramics. The total crystallinity of the glass ceramic, ranging from 20 to 45 wt %, was moderately dependent on composition and heat treatment conditions. Three parent glasses and four glass ceramics with varied composition and heat treatment were produced for detailed phase characterization and leaching. Both parent glasses and glass ceramics were mainly composed of a continuous, glassy matrix phase. This glass matrix entered into solution during leaching in both types of materials. The Fe-Ti rich dispersed glass phase was not significantly degraded by leaching. The glass ceramics, however, exhibited four to ten times less elemental releases during leaching than the parent glasses. The glass ceramic matrix probably contains higher Fe and Na and lower Ca and Mg relative to the parent glass matrix. The crystallization of augite in the glass ceramics is believed to contribute to the improved leach rates. Leach rates of the basalt glass ceramic are compared to those of other TRU nuclear waste forms containing 239 Pu

[Fractographic analysis of clinically failed anterior all ceramic crowns].

Science.gov (United States)

DU, Qian; Zhou, Min-bo; Zhang, Xin-ping; Zhao, Ke

2012-04-01

To identify the site of crack initiation and propagation path of clinically failed all ceramic crowns by fractographic analysis. Three clinically failed anterior IPS Empress II crowns and two anterior In-Ceram alumina crowns were retrieved. Fracture surfaces were examined using both optical stereo and scanning electron microscopy. Fractographic theory and fracture mechanics principles were applied to disclose the damage characteristics and fracture mode. All the crowns failed by cohesive failure within the veneer on the labial surface. Critical crack originated at the incisal contact area and propagated gingivally. Porosity was found within the veneer because of slurry preparation and the sintering of veneer powder. Cohesive failure within the veneer is the main failure mode of all ceramic crown. Veneer becomes vulnerable when flaws are present. To reduce the chances of chipping, multi-point occlusal contacts are recommended, and layering and sintering technique of veneering layer should also be improved.

Multilayer ultra-high-temperature ceramic coatings

Science.gov (United States)

Loehman, Ronald E [Albuquerque, NM; Corral, Erica L [Tucson, AZ

2012-03-20

A coated carbon-carbon composite material with multiple ceramic layers to provide oxidation protection from ultra-high-temperatures, where if the carbon-carbon composite material is uninhibited with B.sub.4C particles, then the first layer on the composite material is selected from ZrB.sub.2 and HfB.sub.2, onto which is coated a layer of SiC coated and if the carbon-carbon composite material is inhibited with B.sub.4C particles, then protection can be achieved with a layer of SiC and a layer of either ZrB.sub.2 and HfB.sub.2 in any order.

Stable glass-ceramic sealants for solid oxide fuel cells: Influence of Bi{sub 2}O{sub 3} doping

Energy Technology Data Exchange (ETDEWEB)

Goel, Ashutosh; Ferreira, Jose M.F. [Department of Ceramics and Glass Engineering, University of Aveiro, CICECO, 3810-193 Aveiro (Portugal); Pascual, Maria J. [Instituto de Ceramica y Vidrio (CSIC), Kelsen 5, Campus de Cantoblanco, 28049 Madrid (Spain)

2010-07-15

Diopside (CaMgSi{sub 2}O{sub 6}) based glass-ceramics in the system SrO-CaO-MgO-Al{sub 2}O{sub 3}-B{sub 2}O{sub 3}-La{sub 2}O{sub 3}-Bi{sub 2}O{sub 3}-SiO{sub 2} have been synthesized for sealing applications in solid oxide fuel cells (SOFC). The parent glass composition in the primary crystallization field of diopside has been doped with different amounts of Bi{sub 2}O{sub 3} (1, 3, 5 wt.%). The sintering behavior by hot-stage microscopy (HSM) reveals that all the investigated glass compositions exhibit a two-stage shrinkage behavior. The crystallization kinetics of the glasses has been studied by differential thermal analysis (DTA) while X-ray diffraction adjoined with Rietveld-R.I.R. analysis have been employed to quantify the amount of crystalline and amorphous phases in the glass-ceramics. Diopside and augite crystallized as the primary crystalline phases in all the glass-ceramics. The coefficient of thermal expansion (CTE) of the investigated glass-ceramics varied between (9.06-10.14) x 10{sup -6} K{sup -1} after heat treatment at SOFC operating temperature for a duration varying between 1 h and 200 h. Further, low electrical conductivity, good joining behavior and negligible reactivity with metallic interconnects (Crofer22 APU and Sanergy HT) in air indicate that the investigated glass-ceramics are suitable candidates for further experimentation as sealants in SOFC. (author)

Potential assisted fabrication of metal-ceramic composite coatings

International Nuclear Information System (INIS)

Knote, A.; Schindler, U.; Krueger, H.G.; Kern, H.

2003-01-01

A possibility to produce uniform metal-ceramic composite coatings with a high content of ceramic particles up to 60 vol.% will be presented in this study. This method includes a combination of electrophoretic deposition and electrolytic deposition by several steps. A yttria-stabilized zirconia coating (Tosoh TZ-8Y) was first electrophoretically deposited on a ferritic steel plate and then sintered by 1100 C to an open porous layer. In the next step nickel was electrodeposited into the pores of the layer. By a final annealing step it was possible to improve the bonding of the composit coating on the substrate by diffusion of the metal components. (Abstract Copyright [2003], Wiley Periodicals, Inc.) [de

Phase constituents and microstructure of laser cladding Al{sub 2}O{sub 3}/Ti{sub 3}Al reinforced ceramic layer on titanium alloy

Energy Technology Data Exchange (ETDEWEB)

Li Jianing [Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials (Ministry of Education), Department of Materials Science, Shandong University, Jing Shi Road 17923, Jinan 250061, Shandong (China); Chen Chuanzhong, E-mail: czchen@sdu.edu.cn [Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials (Ministry of Education), Department of Materials Science, Shandong University, Jing Shi Road 17923, Jinan 250061, Shandong (China); Lin Zhaoqing [Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials (Ministry of Education), Department of Materials Science, Shandong University, Jing Shi Road 17923, Jinan 250061, Shandong (China); Squartini, Tiziano [INFM - Department of Physics, Siena University, Siena 53100 (Italy)

2011-04-07

Research highlights: > In this study, Fe{sub 3}Al has been chosen as cladding powder due to its excellent properties of wear resistance and high strength, etc. > Laser cladding of Fe{sub 3}Al + TiB{sub 2}/Al{sub 2}O{sub 3} pre-placed alloy powder on Ti-6Al-4V alloy substrate can form the Ti{sub 3}Al/Fe{sub 3}Al + TiB{sub 2}/Al{sub 2}O{sub 3} ceramic layer, which can increase wear resistance of substrate. > In cladding process, Al{sub 2}O{sub 3} can react with TiB{sub 2} leading to formation of Ti{sub 3}Al and B. > This principle can be used to improve the Fe{sub 3}Al + TiB{sub 2} laser-cladded coating. - Abstract: Laser cladding of the Fe{sub 3}Al + TiB{sub 2}/Al{sub 2}O{sub 3} pre-placed alloy powder on Ti-6Al-4V alloy can form the Ti{sub 3}Al/Fe{sub 3}Al + TiB{sub 2}/Al{sub 2}O{sub 3} ceramic layer, which can greatly increase wear resistance of titanium alloy. In this study, the Ti{sub 3}Al/Fe{sub 3}Al + TiB{sub 2}/Al{sub 2}O{sub 3} ceramic layer has been researched by means of electron probe, X-ray diffraction, scanning electron microscope and micro-analyzer. In cladding process, Al{sub 2}O{sub 3} can react with TiB{sub 2} leading to formation of amount of Ti{sub 3}Al and B. This principle can be used to improve the Fe{sub 3}Al + TiB{sub 2} laser cladded coating, it was found that with addition of Al{sub 2}O{sub 3}, the microstructure performance and micro-hardness of the coating was obviously improved due to the action of the Al-Ti-B system and hard phases.

Luminescence and host lattice structure of crystalline micro and nanoparticles co-doped with lanthanide ions

International Nuclear Information System (INIS)

Zurba, Nadia Khaled; Ferreira, Jose Maria da Fonte

2012-01-01

This article reports the investigation of crystalline micro and nanoparticles codoped with lanthanide ions, aiming at correlate their host lattice structure and chemical composition to the luminescence features. For this purpose, five phosphors were characterized by X-ray diffraction (XRD), scanning electron microscopy coupled to energy dispersive X-ray (EDX) spectroscopy, and photoluminescence (PL) spectroscopy, namely performed by their chromatic coordinates, radiance, luminance and PL emission spectra. This type of investigation concerning the optical characterization of luminescent crystalline micro and nanoparticles doped with lanthanide ions might be useful for scientific and practical applications, such as in light-emitting devices, luminescent paintings, ceramics, sensors, in nanoscience and nanotechnology. (author)

Mechanical energy dissipation in natural ceramic composites.

Science.gov (United States)

Mayer, George

2017-12-01

Ceramics and glasses, in their monolithic forms, typically exhibit low fracture toughness values, but rigid natural marine ceramic and glass composites have shown remarkable resistance to mechanical failure. This has been observed in load-extension behavior by recognizing that the total area under the curve, notably the part beyond the yield point, often conveys substantial capacity to carry mechanical load. The mechanisms underlying the latter observations are proposed as defining factors for toughness that provide resistance to failure, or capability to dissipate energy, rather than fracture toughness. Such behavior is exhibited in the spicules of glass sponges and in mollusk shells. There are a number of similarities in the manner in which energy dissipation takes place in both sponges and mollusks. It was observed that crack diversion, a new form of crack bridging, creation of new surface area, and other important energy-dissipating mechanisms occur and aid in "toughening". Crack tolerance, key to energy dissipation in these natural composite materials, is assisted by promoting energy distribution over large volumes of loaded specimens by minor components of organic constituents that also serve important roles as adhesives. Viscoelastic deformation was a notable characteristic of the organic component. Some of these energy-dissipating modes and characteristics were found to be quite different from the toughening mechanisms that are utilized for more conventional structural composites. Complementary to those mechanisms found in rigid natural ceramic/organic composites, layered architectures and very thin organic layers played major roles in energy dissipation in these structures. It has been demonstrated in rigid natural marine composites that not only architecture, but also the mechanical behavior of the individual constituents, the nature of the interfaces, and interfacial bonding play important roles in energy dissipation. Additionally, the controlling

Meniscus-force-mediated layer transfer technique using single-crystalline silicon films with midair cavity: Application to fabrication of CMOS transistors on plastic substrates

Science.gov (United States)

Sakaike, Kohei; Akazawa, Muneki; Nakagawa, Akitoshi; Higashi, Seiichiro

2015-04-01

A novel low-temperature technique for transferring a silicon-on-insulator (SOI) layer with a midair cavity (supported by narrow SiO2 columns) by meniscus force has been proposed, and a single-crystalline Si (c-Si) film with a midair cavity formed in dog-bone shape was successfully transferred to a poly(ethylene terephthalate) (PET) substrate at its heatproof temperature or lower. By applying this proposed transfer technique, high-performance c-Si-based complementary metal-oxide-semiconductor (CMOS) transistors were successfully fabricated on the PET substrate. The key processes are the thermal oxidation and subsequent hydrogen annealing of the SOI layer on the midair cavity. These processes ensure a good MOS interface, and the SiO2 layer works as a “blocking” layer that blocks contamination from PET. The fabricated n- and p-channel c-Si thin-film transistors (TFTs) on the PET substrate showed field-effect mobilities of 568 and 103 cm2 V-1 s-1, respectively.

Carbon nanotubes-porous ceramic composite by in situ CCVD growth of CNTs

International Nuclear Information System (INIS)

Mazumder, Sangram; Sarkar, Naboneeta; Park, Jung Gyu; Han, In Sub; Kim, Ik Jin

2016-01-01

A novel approach towards the formation of Carbon nanotubes-porous alumina ceramic composite was attempted by the application of three different reaction techniques. Porous alumina ceramics having micrometer pore dimensions were developed using the direct foaming technique. NaA zeolites were simultaneously synthesized and coated within the porous ceramics by an in situ hydrothermal process and were subjected to a simple ion exchange reaction for preparing the suitable catalyst material for Carbon nanotubes (CNTs) synthesis. The catalytic chemical vapour deposition (CCVD) technique was used to grow CNTs within the porous ceramics and the effect of growth time on the synthesized CNTs were investigated. Phase compositions of the samples were analysed by X-ray diffractometer (XRD). Field Emission Scanning Electron Microscopy (FESEM) and Transmission Electron Microscopy (TEM) were used for morphology, surface quality and structural analysis. Crystallinity, defects and yield were studied by Raman spectroscopy and thermogravimetric analysis (TGA). - Highlights: • Novel processing route of MWCNTs grown on Cobalt-zeolites-porous ceramics by CCVD. • CCVD time of 120 min produced MWCNTs with most prominent tube-like structure. • 120 min produced highest yield (19.46%) of CNTs with an I_D/I_G ratio of 0.88.

Interfacial crystalline structures in injection over-molded polypropylene and bond strength.

Science.gov (United States)

Yan, Bowen; Wu, Hong; Jiang, Genjie; Guo, Shaoyun; Huang, Jian

2010-11-01

This paper describes interfacial crystalline structures found in injection overmolded polypropylene components and the relationship of these structures to bond strength between the components. The combined effects of the development of hierarchical gradient structures and the particular thermomechanical environment near the interface on the interfacial crystalline structures were investigated in detail by PLM, SEM, DSC, WAXD, and infrared dichroism spectroscopy. The experimental results showed that during molding there was competitive formation of interfacial crystalline structures consisted of "shish-kebab" layer (SKL) and a transcrystalline layers (TCL). Variation in shear stress (controlled by injection pressure and injection speed) plays an important role in the formation of the SKL. The formation of TCL is influenced by the thermal environment, namely melt temperature and mold temperature. Increasing within certain limits, interfacial temperature and the thermal gradient near the interface promotes β-iPP growth. The relationship between interfacial crystalline structures and interfacial bond strength was established by lap shear measurement. The interfacial bond strength is improved by enhancing the formation of TCL, but reduced if SKL predominates.

Composite treatment of ceramic tile armor

Science.gov (United States)

Hansen, James G. R. [Oak Ridge, TN; Frame, Barbara J [Oak Ridge, TN

2010-12-14

An improved ceramic tile armor has a core of boron nitride and a polymer matrix composite (PMC) facing of carbon fibers fused directly to the impact face of the tile. A polyethylene fiber composite backing and spall cover are preferred. The carbon fiber layers are cured directly onto the tile, not adhered using a separate adhesive so that they are integral with the tile, not a separate layer.

Enhanced green upconversion by controlled ceramization of Er{sup 3+}–Yb{sup 3+} co-doped sodium niobium tellurite glass–ceramics for low temperature sensors

Energy Technology Data Exchange (ETDEWEB)

Suresh Kumar, J., E-mail: suresh@ua.pt; Pavani, K.; Graça, M.P.F.; Soares, M.J.

2014-12-25

Highlights: • Upconversion luminescence improved in glass–ceramics compared to host glass. • Judd–Ofelt and radiative parameters calculated. • NIR decay curve results concur the results of improved luminescence. • Temperature dependent upconversion support the use of materials for sensors. - Abstract: Tellurite based glasses are well-known for their upconversion properties besides having a disadvantage of low mechanical strength dragging them away from practical applications. The present work deals with preparation of sodium niobium tellurite (SNT) glasses using melt quenching method, in which small quantities of boron and silicon in the form of oxides are added to improve their mechanical properties. Controlled heat treatment is performed to ceramize the prepared glasses based on the thermal data given by DTA. XRD and SEM profiles of the glass–ceramics which confirmed the formation of crystalline monoclinic Sodium Tellurium Niobium Oxide (Na{sub 1.4}Nb{sub 3}Te{sub 4.9}O{sub 18}) phase (JCPDS card No. 04–011-7556). Upconversion measurements in the visible region were made for the prepared Er{sup 3+}–Yb{sup 3+} co-doped glasses and glass–ceramics with 980 nm laser excitation varying the laser power and concentration of Er{sup 3+} ions. Results showed that the upconversion luminescence intensity was enhanced by ten times in SNT glass–ceramics compared to that in the SNT glasses. Decay curves give evidence of high performance of glass–ceramics compared to glasses due to ceramization and structural changes. Temperature dependent visible upconversion was performed to test the ability of efficient SNT glass–ceramic at low temperatures and variation of upconversion intensities was studied.

Preparation and characterization of novel glass–ceramic tile with microwave absorption properties from iron ore tailings

Energy Technology Data Exchange (ETDEWEB)

Yao, Rui; Liao, SongYi [School of Materials Science and Engineering, Central South University, Changsha 410083 (China); Dai, ChangLu [Guangdong Bode Fine Building Material Co. Ltd., Foshan 528000 (China); Liu, YuChen; Chen, XiaoYu [School of Materials Science and Engineering, Central South University, Changsha 410083 (China); Zheng, Feng, E-mail: fzheng@csu.edu.cn [School of Materials Science and Engineering, Central South University, Changsha 410083 (China); Phase diagrams and materials design center, Central South University, Changsha 410083 (China)

2015-03-15

A novel glass–ceramic tile consisting of one glass–ceramic layer (GC) attaining microwave absorption properties atop ceramic substrate was prepared through quench-heat treatment route derived from iron ore tailings (IOTs) and commercial raw materials (purity range 73–99%). X-ray diffraction (XRD), SEM, Energy dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), Physical property measurement system (PPMS) and Vector network analyzer (VNA) measurements were carried out to investigate phase, microstructure, magnetic and microwave absorption aspects of the glass–ceramic layer. Roughly 80.6±1.7 wt% borosilicate glass and 19.4±1.7 wt% spinel ferrite with chemical formula of (Zn{sup 2+}{sub 0.17}Fe{sup 3+}{sub 0.83})[Fe{sup 3+}{sub 1.17}Fe{sup 2+}{sub 0.06}Ni{sup 2+}{sub 0.77}]O{sub 4} were found among the tested samples. Absorption of Electromagnetic wave by 3 mm thick glass–ceramic layer at frequency of 2–18 GHz reached peak reflection loss (RL) of −17.61 dB (98.27% microwave absorption) at 10.31 GHz. Altering the thickness of the glass–ceramic layer can meet the requirements of different level of microwave absorption. - Highlights: • Iron ore tailings (IOTs) have been used as one of the main raw materials. • Glass–ceramic tile contains spinel ferrite has been prepared. • The cation distribution of the spinel ferrite has been calculated. • The intrinsic complex permeability and permittivity have been evaluated.

Porous ZrO_2-TiO_2 ceramics for applications as sensing elements in the air humidity monitoring

International Nuclear Information System (INIS)

Oliveira, Rodrigo de Matos; Nono, Maria do Carmo de Andrade

2011-01-01

The environmental monitoring requires versatile, reliable and lower cost instruments. The chemical superficial absorption/adsorption capability of water molecules by several ceramic oxides makes them excellent candidates for this application. In this way, many efforts have been made for the development of porous ceramics, manufactured from mechanical mixture of ZrO_2 and TiO_2 powders, for application as air humidity sensing elements. The sintered ceramics were characterized as for crystalline phases (X-ray diffraction) and pores structure (scanning electron microscopy and mercury porosimetry). The relative humidity curves for the ceramics were obtained from measurements with RLC bridge in climatic chamber. The behavior of these curves were comparatively analyzed with the aid of pores sizes distribution curves, obtained through mercury porosimetry. The results evidenced that the air humidity ceramic sensing elements are very promising ones. (author)

Vacuum tight sodium resistant compound between ThO2 ceramic and metal

International Nuclear Information System (INIS)

Reetz, T.

A method for evaluating the mechanical tensions for metal/ ceramic joinings was applied to the selection of metal components for a highly vacuum tight, sodium-resistant metal/ThO 2 ceramic solder joining. The metal component selected was the iron--nickel alloy Dilasil which is joined to the ceramic using a nickel-based solder. The wetting of the cearamic could be carried out using the titanium hydride technique or after the formation of a W-cerium layer on the surface of this ceramic. (U.S.)

Rotating Ceramic Water Filter Discs System for Water Filtration

Directory of Open Access Journals (Sweden)

Riyadh Z. Al Zubaidy

2017-04-01

Full Text Available This work aimed to design, construct and operate a new laboratory scale water filtration system. This system was used to examine the efficiency of two ceramic filter discs as a medium for water filtration. These filters were made from two different ceramic mixtures of local red clay, sawdust, and water. The filtration system was designed with two rotating interfered modules of these filters. Rotating these modules generates shear force between water and the surfaces of filter discs of the filtration modules that works to reduce thickness of layer of rejected materials on the filters surfaces. Each module consists of seven filtration units and each unit consists of two ceramic filter discs. The average measured hydraulic conductivity of the first module was 13.7mm/day and that for the second module was 50mm/day. Results showed that the water filtration system can be operated continuously with a constant flow rate and the filtration process was controlled by a skin thin layer of rejected materials. The ceramic water filters of both filtration modules have high removal efficiency of total suspended solids up to 100% and of turbidity up to 99.94%.

Fabrication and characterization of low temperature co-fired cordierite glass–ceramics from potassium feldspar

International Nuclear Information System (INIS)

Wu, Jianfang; Li, Zhen; Huang, Yanqiu; Li, Fei; Yang, Qiuran

2014-01-01

Highlights: • Low cost cordierite glass–ceramics were fabricated from potassium feldspar. • The glass–ceramics could be highly densified below 950 °C. • The glass–ceramics exhibit extraordinary properties. • The glass–ceramics can be used as LTCC substrates. • The excess SiO 2 improved the microstructure and properties of the glass–ceramics. -- Abstract: Cordierite glass–ceramics for low temperature co-fired ceramic (LTCC) substrates were fabricated successfully using potassium feldspar as the main raw material. The sintering and crystallization behaviors of the glass–ceramics were investigated by the differential scanning calorimetry (DSC), X-ray diffraction (XRD), and field emission scanning electron microscope (FESEM). The results indicated that the glass–ceramics could be highly densified at 850 °C and the cordierite was the main crystalline phase precipitated from the glasses in the temperature range between 900 and 925 °C. The study also evaluated the physical properties including dielectric properties, thermal expansion and flexural strength of the glass–ceramics. The glass–ceramics showed low dielectric constants in the range of 6–8 and low dielectric losses in the range of 0.0025–0.01. The coefficients of thermal expansion (CTEs) are between 4.32 and 5.48 × 10 −6 K −1 and flexural strength of the glass–ceramics are 90–130 MPa. All of those qualify the glass–ceramics for further research to be used as potential LTCC substrates in the multilayer electronic substrate field. Additionally, the excess SiO 2 acted as a great role in improving the sinterability of the glasses, and the microstructure and dielectric properties of the relevant glass–ceramics

EDXRF study of Tupiguarani archaeological ceramics

International Nuclear Information System (INIS)

Appoloni, C.R.; Aragao, P.H.A.; Santos, A.O. dos; Silva, L.M. da; Barbieri, P.F.; Espinoza Quinones, F.R.; Nascimento Filho, V.F. do

2000-01-01

A set of Indian Brazilian pottery fragments belonging to Tupi-Guarani tradition has been studied by EDXRF. The pottery fragments were accidentally discovered in the Santa Dalmacia farm in 1990, sited near Cambe city at the north of Parana Brazilian State. The main objective was to characterize the ceramic paste, as well as the superficial layer of the ceramic fragments, in order to get information about the pigment composition of the plastic decoration. The Energy Dispersive X-ray Fluorescence (EDXRF) methodology was employed to obtain the ceramic paste composition, as well as the superficial layer of the ceramic fragments. The measurements were carried out at CENA. The experimental set up consisted of 238 Pu, 55 Fe and 109 Cd radioactive sources, a X-ray tube (at 15 kV, 40 mA, Mo target and Zr filter), a Si(Li) detector (30 mm 2 , with a Be window ) and a multichannel analyzer. For detection of the elements within the ceramic paste, the fragments were irradiated at the center of the lateral section. While several superficial areas with remaining plastic decoration were also chosen and irradiated at the convex and concave sides of each fragment. X-ray spectra were analyzed at UEL using the AXIL program. A program based on the graphic polygonal representation method was developed and used to correlate the representative intensity data of each fragment. A low Ca content, and a systematic presence of relatively high concentrations of Fe can characterize the ceramic pastes. Ti and Zr are also always present at high levels, and Ni, Cu and in some cases Zn at level of traces; Rb, Sr, Ba and Y are also present at low concentration. The black pigment in the pottery plastic decoration is due to the presence of Mn, the red pigment is due to the presence of Fe, while the white pigment is characterized by the presence of Ba. Other qualitative and quantitative results were obtained for each kind of ceramic fragment groups. For the eleven fragments studied, the polygonal

Magnetic properties of bioactive glass-ceramics containing nanocrystalline zinc ferrite

International Nuclear Information System (INIS)

Singh, Rajendra Kumar; Srinivasan, A.

2011-01-01

Glass-ceramics with finely dispersed zinc ferrite (ZnFe 2 O 4 ) nanocrystallites were obtained by heat treatment of x(ZnO,Fe 2 O 3 )(65-x)SiO 2 20(CaO,P 2 O 5 )15Na 2 O (6≤x≤21 mole%) glasses. X-ray diffraction patterns of the glass-ceramic samples revealed the presence of calcium sodium phosphate [NaCaPO 4 ] and zinc ferrite [ZnFe 2 O 4 ] as major crystalline phases. Zinc ferrite present in nanocrystalline form contributes to the magnetic properties of the glass-ceramic samples. Magnetic hysteresis cycles of the glass-ceramic samples were obtained with applied magnetic field sweeps of ±20 kOe and ±500 Oe, in order to evaluate the potential of these glass-ceramics for hyperthermia treatment of cancer. The evolution of magnetic properties in these samples, viz., from a partially paramagnetic to fully ferrimagnetic nature has been explored using magnetometry and X-ray diffraction studies. - Research highlights: → The glass-ceramics contain bone mineral and magnetic phases. → Calcium sodium phosphate and zinc ferrite nanocrystallites have been identified in all the sample. → With an increase in ZnO and Fe2O3 content, magnetic property of samples evolved from partially paramagnetic to fully ferrimagnetic nature. → Large magnetic hysteresis loops have been obtained for samples with high ZnO+Fe2O3 content.

Crystallization behaviors and seal application of basalt based glass-ceramics

Science.gov (United States)

Ateş, A.; Önen, U.; Ercenk, E.; Yılmaz, Ş.

2017-02-01

Basalt based glass-ceramics were prepared by conventional melt-quenching technique and subsequently converted to glass-ceramics by a controlled nucleation and crystallization process. Glass materials were obtained by melt at 1500°C and quenched in cold water. The powder materials were made by milling and spin coating. The powders were applied on the 430 stainless steel interconnector material, and heat treatment was carried out. The interface characteristics between the glass-ceramic layer and interconnector were investigated by using X-ray diffraction analysis (XRD) and scanning electron microscopy (SEM). The results showed that the basalt base glass-ceramic sealant material exhibited promising properties to use for SOFC.

EPR of radiation defects in lithium-oxyfluoride glass ceramics

Energy Technology Data Exchange (ETDEWEB)

Fedotovs, A; Rogulis, U; Sarakovskis, A; Dimitrocenko, L, E-mail: andris-f@navigator.l [Institute of Solid State Physics, University of Latvia, Kengaraga st. 8, LV-1063, Riga (Latvia)

2010-11-01

We studied oxyfluoride composites based on lithium silicate glasses with yttrium fluorides and rare-earth dopants. The electron paramagnetic resonance (EPR) has been used to obtain information about radiation induced defects in these materials. Spectra have been measured before and after X-ray irradiation at room temperature and at liquid nitrogen temperature. Fluoride crystallites within samples were created by means of thermal treatment at specific temperatures. EPR spectra of radiation induced defects in oxyfluoride glass ceramics, in which crystallites have not been yet created, show no explicit hfs interaction of fluorine nuclei. However, in glass ceramics, which already contains fluoride crystallites, the hfs characteristic to fluorine nuclei appears in the EPR spectra. EPR hyperfine structure could be explained within a model of an F-type centre in YF{sub 3} crystalline phase.

EPR of radiation defects in lithium-oxyfluoride glass ceramics

Science.gov (United States)

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

2010-11-01

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

Characterization of magnesium phosphate ceramics incorporating off-gas filters

International Nuclear Information System (INIS)

Yang, Jae Hwan; Lee, Chang Hwa; Heo, Chul Min; Jeon, Min Ku; Kang, Kweon Ho

2011-01-01

Radioactive cesium (Cs-137) and technetium (Tc-99) are discharged from the spent fuel as gaseous forms during the head-end process in pyroprocess. These off-gases are safely trapped via porous ceramic filters made of fly ash and calcium based material. Spent filters have to be treated, converted into proper waste forms in order to be disposed safely at a repository. Conventional technology used to make waste forms such as vitrification requires high temperature and complex process. In this study, we report a promising method to stabilize spent filters containing cesium and technetium using magnesium phosphate ceramics. Simulated spent filters were fabricated by vaporizing nonradioactive cesium and rhenium (a surrogate of Tc) through the voloxidizer. The crushed filters were mixed with raw materials of magnesium phosphate ceramics, to be stabilized in the phosphate ceramic matrix. Characterization of the waste forms was made by the compressive strength test, apparent porosity, XRD analysis, and SEM analysis. The sample containing filters showed the excellent mechanical property, with the highest compressive strength of 38.1 MPa in the sample with 30 wt% of Cs-filter. Microstructural analysis suggests that wastes are embedded in the crystalline phase formed by an acid-base reaction. (author)

Low cost silicon-on-ceramic photovoltaic solar cells

Science.gov (United States)

Koepke, B. G.; Heaps, J. D.; Grung, B. L.; Zook, J. D.; Sibold, J. D.; Leipold, M. H.

1980-01-01

A technique has been developed for coating low-cost mullite-based refractory substrates with thin layers of solar cell quality silicon. The technique involves first carbonizing one surface of the ceramic and then contacting it with molten silicon. The silicon wets the carbonized surface and, under the proper thermal conditions, solidifies as a large-grained sheet. Solar cells produced from this composite silicon-on-ceramic material have exhibited total area conversion efficiencies of ten percent.

Improvement of the crystallinity and photocatalytic property of zinc oxide as calcination product of Zn–Al layered double hydroxide

International Nuclear Information System (INIS)

Ahmed, Abdullah Ahmed Ali; Talib, Zainal Abidin; Hussein, Mohd Zobir bin; Zakaria, Azmi

2012-01-01

Highlights: ► ZnO phase and ZnAl 2 O 4 spinel can be formed as Zn–Al–NO 3 –LDH calcination products. ► The crystallinity of ZnO phase increased with an increase of calcination temperature. ► The optical band gaps of ZnO were improved with an increase in temperature. ► The oxygen vacancies in ZnO and ZnAl 2 O 4 generated the ESR signals. - Abstract: Zinc oxide with different degrees of crystallinity can be formed as Zn–Al-layered double hydroxide (Zn–Al–NO 3 –LDH) calcination products. ZnAl 2 O 4 spinel is also formed in a range of calcination temperatures from 600 to 1000 °C from the LDH. X-ray diffraction patterns showed that the crystallinity of the ZnO phase increased as calcination temperatures increased. The LDH structure was fully collapsed at and above 400 °C. The photocatalytic activity was determined by UV–VIS–NIR diffuse reflectance spectroscopy. The band gap of the calcined samples increased as the calcination temperature increased. Electron spin resonance (ESR) spectra of the fresh and calcined LDH at room temperature demonstrated that oxygen vacancies in the ZnO and ZnAl 2 O 4 were responsible for the generation of ESR signals. One BET specific surface area increased from 1 m 2 /g for the LDH to a maximum at 400 °C (43 m 2 /g) and decreased thereafter down to 6 m 2 /g at 1000 °C.

Investment Casting vs Replicast CS Considered in Terms of the Ceramic Mould Making and Dimensional Accuracy of Castings

Directory of Open Access Journals (Sweden)

Karwiński A.

2014-03-01

Full Text Available The article presents an analysis of the applicability of the Replicast CS process as an alternative to the investment casting process, considered in terms of the dimensional accuracy of castings. Ceramic shell moulds were based on the Ekosil binder and a wide range of ceramic materials, such as crystalline quartz, fused silica, aluminosilicates and zirconium silicate. The linear dimensions were measured with a Zeiss UMC 550 machine that allowed reducing to minimum the measurement uncertainty

High temperature tribological properties of plasma-sprayed metallic coatings containing ceramic particles

International Nuclear Information System (INIS)

Dallaire, S.; Legoux, J.G.

1995-01-01

For sealing a moving metal component with a dense silica-based ceramic pre-heated at 800 C, coatings with a low coefficient of friction and moderate wear loss are required. As reported previously, plasma-sprayed coatings containing solid lubricants could reduce sliding wear in high-temperature applications. Plasma-sprayed metal-based coatings containing ceramic particles have been considered for high temperature sealing. Selected metal powders (NiCoCrAlY, CuNi, CuNiIn, Ag, Cu) and ceramic particles (boron nitride, Zeta-B ceramic) were agglomerated to form suitable spray powders. Plasma-sprayed composite coatings and reference materials were tested in a modified pin-on-disc apparatus in which the stationary disc consisted of a dense silica-based ceramic piece initially heated at 800 C and allowed to cool down during tests. The influence of single exposure and repeated contacts with a dense silica-based ceramic material pre-heated to 800 C on the coefficient of friction, wear loss and damage to the ceramic piece was evaluated. Being submitted to a single exposure at high temperature, coatings containing malleable metals such as indium, silver and copper performed well. The outstanding tribological characteristics of the copper-Zeta-B ceramic coating was attributed to the formation of a glazed layer on the surface of this coating which lasted over exposures to high temperature. This glazed layer, composed of fine oxidation products, provided a smooth and polished surface and helped maintaining the coefficient of friction low

Influence of resin cement shade on the color and translucency of ceramic veneers.

Science.gov (United States)

Hernandes, Daiana Kelly Lopes; Arrais, Cesar Augusto Galvão; Lima, Erick de; Cesar, Paulo Francisco; Rodrigues, José Augusto

2016-01-01

This in vitro study evaluated the effect of two different shades of resin cement (RC- A1 and A3) layer on color change, translucency parameter (TP), and chroma of low (LT) and high (HT) translucent reinforced lithium disilicate ceramic laminates. One dual-cured RC (Variolink II, A1- and A3-shade, Ivoclar Vivadent) was applied to 1-mm thick ceramic discs to create thin RC films (100 µm thick) under the ceramics. The RC was exposed to light from a LED curing unit. Color change (ΔE) of ceramic discs was measured according to CIEL*a*b* system with a standard illuminant D65 in reflectance mode in a spectrophotometer, operating in the light range of 360-740 nm, equipped with an integrating sphere. The color difference between black (B) and white (W) background readings was used for TP analysis, while chroma was calculated by the formula C*ab=(a*2+b*2)½. ΔE of 3.3 was set as the threshold of clinically unacceptable. The results were evaluated by two-way ANOVA followed by Tukey's post hoc test. HT ceramics showed higher ΔE and higher TP than LT ceramics. A3-shade RC promoted higher ΔE than A1-shade cement, regardless of the ceramic translucency. No significant difference in TP was noted between ceramic discs with A1- and those with A3-shade cement. Ceramic with underlying RC showed lower TP than discs without RC. HT ceramics showed lower chroma than LT ceramics, regardless of the resin cement shade. The presence of A3-shade RC resulted in higher chroma than the presence of A1-shade RC. Darker underlying RC layer promoted more pronounced changes in ceramic translucency, chroma, and shade of high translucent ceramic veneers. These differences may not be clinically differentiable.

Layered ceramic composites via control of electrophoretic deposition kinetics

Czech Academy of Sciences Publication Activity Database

Hadraba, Hynek; Drdlík, D.; Chlup, Zdeněk; Maca, K.; Dlouhý, Ivo; Cihlář, J.

2013-01-01

Roč. 33, č. 12 (2013), s. 2305-2312 ISSN 0955-2219 R&D Projects: GA ČR(CZ) GAP108/11/1644; GA MŠk(CZ) ED1.1.00/02.0068 Institutional support: RVO:68081723 Keywords : Alumina * Zirconia * Laminates * Electrophoretic deposition Subject RIV: JH - Ceramics, Fire-Resistant Materials and Glass Impact factor: 2.307, year: 2013

Glass-ceramic nuclear waste forms obtained by crystallization of SiO 2-Al 2O 3-CaO-ZrO 2-TiO 2 glasses containing lanthanides (Ce, Nd, Eu, Gd, Yb) and actinides (Th): Study of the crystallization from the surface

Science.gov (United States)

Loiseau, P.; Caurant, D.

2010-07-01

Glass-ceramic materials containing zirconolite (nominally CaZrTi 2O 7) crystals in their bulk can be envisaged as potential waste forms for minor actinides (Np, Am, Cm) and Pu immobilization. In this study such matrices are synthesized by crystallization of SiO 2-Al 2O 3-CaO-ZrO 2-TiO 2 glasses containing lanthanides (Ce, Nd, Eu, Gd, Yb) and actinides (Th) as surrogates. A thin partially crystallized layer containing titanite and anorthite (nominally CaTiSiO 5 and CaAl 2Si 2O 8, respectively) growing from glass surface is also observed. The effect of the nature and concentration of surrogates on the structure, the microstructure and the composition of the crystals formed in the surface layer is presented in this paper. Titanite is the only crystalline phase able to significantly incorporate trivalent lanthanides whereas ThO 2 precipitates in the layer. The crystal growth thermal treatment duration (2-300 h) at high temperature (1050-1200 °C) is shown to strongly affect glass-ceramics microstructure. For the system studied in this paper, it appears that zirconolite is not thermodynamically stable in comparison with titanite growing form glass surface. Nevertheless, for kinetic reasons, such transformation (i.e. zirconolite disappearance to the benefit of titanite) is not expected to occur during interim storage and disposal of the glass-ceramic waste forms because their temperature will never exceed a few hundred degrees.

Conductive ceramic composition and method of preparation

Science.gov (United States)

Smith, J.L.; Kucera, E.H.

1991-04-16

A ceramic anode composition is formed of a multivalent metal oxide or oxygenate such as an alkali metal, transition metal oxygenate. The anode is prepared as a non-stoichiometric crystalline structure by reaction and conditioning in a hydrogen gas cover containing minor proportions of carbon dioxide and water vapor. The structure exhibits a single phase and substantially enhanced electrical conductivity over that of the corresponding stoichiometric structure. Unexpectedly, such oxides and oxygenates are found to be stable in the reducing anode fuel gas of a molten carbonate fuel cell. 4 figures.

Corrosion protection of SiC-based ceramics with CVD mullite coatings

Energy Technology Data Exchange (ETDEWEB)

Auger, M.L.; Sarin, V.K. [Boston Univ., MA (United States). Dept. of Mfg. Engineering

1997-12-01

For the first time, crystalline mullite coatings have been chemically vapor deposited on SiC substrates to enhance its corrosion and oxidation resistance. Thermodynamic and kinetic considerations have been utilized to produce mullite coatings with a variety of growth rates, compositions, and morphologies. The flexibility of processing can be exploited to produce coated ceramics with properties tailored to specific applications and varied corrosive environments.

Kinetics of the oxidation of Ba2YCu3O/sub x/ ceramics

International Nuclear Information System (INIS)

O'Bryan, H.M.; Gallagher, P.K.

1988-01-01

The kinetics of the oxidation of dense and porous samples of Ba 2 YCu 3 O/sub x/ ceramic have been determined by gravimetric analysis at 400--700 0 C. At 600 0 C and above, the rate decreases as the thickness of the oxidized layer increases. At 500 0 C and below, the kinetics show a linear relation that indicates that the oxidized layer does not protect the ceramic. Dilatometric, microscopic, and high-temperature x-ray data suggest that fractures in the oxide layer at the lower temperatures are caused by the large volume decrease that accompanies the change in oxygen stoichiometry

Ceramic tape casting: A review of current methods and trends with emphasis on rheological behaviour and flow analysis

DEFF Research Database (Denmark)

Jabbaribehnam, Mirmasoud; Bulatova, Regina; Tok, A. I Y

2016-01-01

Tape casting has been used to produce thin layers of ceramics that can be used as single layers or can be stacked and laminated into multilayered structures. Today, tape casting is the basic fabrication process that provides multilayered capacitors and multilayered ceramic packages. In tape casti...

Variation in the Optical Properties of the SiC-SiO2 Composite Antireflection Layer in Crystalline Silicon Solar Cells by Annealing

Science.gov (United States)

Jannat, Azmira; Li, Zhen Yu; Akhter, M. Shaheer; Yang, O.-Bong

2017-11-01

This study showed the effects of annealing on a sol-gel-derived SiC-SiO2 composite antireflection (AR) layer and investigated the optical and photovoltaic properties of crystalline silicon (Si) solar cells. The SiC-SiO2 composite AR coating showed a considerable decrease in reflectance from 7.18% to 3.23% at varying annealing temperatures of 450-800°C. The refractive indices of the SiC-SiO2 composite AR layer were tuned from 2.06 to 2.45 with the increase in annealing temperature. The analysis of the current density-voltage characteristics indicated that the energy conversion efficiencies of the fabricated Si solar cells gradually increased from 16.99% to 17.73% with increasing annealing temperatures of 450-800°C. The annealing of the SiC-SiO2 composite AR layer in Si solar cells was crucial to improving the optical, morphological, and photovoltaic properties.

EDXRF study of Tupi-Guarani archaeological ceramics

Science.gov (United States)

Appoloni, C. R.; Espinoza Quiñones, F. R.; Aragão, P. H. A.; dos Santos, A. O.; da Silva, L. M.; Barbieri, P. F.; do Nascimento Filho, V. F.; Coimbra, M. M.

2001-06-01

A set of Indian Brazilian pottery fragments belonging to Tupi-Guarani tradition has been studied by EDXRF. The main objective was to characterize the ceramic paste, as well as the superficial layer of the ceramic fragments, in order to get qualitative information about the pigment composition of the plastic decoration. Energy Dispersive X-ray Fluorescence (EDXRF) methodology was employed to obtain the ceramic paste composition, as well as the superficial layer of the ceramic fragments. The experimental set-up consisted of 238Pu, 55Fe and 109Cd radioactive sources, a X-ray tube (at 15 kV, 40 mA, Mo target and Zr filter), a Si(Li) detector (30 mm 2, with a Be window) and a multichannel analyzer. X-ray spectra were analyzed using the AXIL program. A program based on the graphic polygonal representation method was developed and used to correlate the representative intensity data of each fragment. A low Ca content and a systematic presence of relatively high concentrations of Fe can characterize the ceramic pastes. Ti and Zr are also always present at high levels, and Ni, Cu and in some cases Zn at level of traces; Rb, Sr, Ba and Y are also present at low concentration. The black pigment in the pottery plastic decoration is due to the presence of Mn, the red pigment is due to the presence of Fe, while the white pigment is characterized by the presence of Ba. For the eleven fragments studied, the polygonal representation method points that the same materials were employed in the pottery production, and the pigments in the plastic decoration were obtained from different inorganic materials.

EDXRF study of Tupi-Guarani archaeological ceramics

Energy Technology Data Exchange (ETDEWEB)

Appoloni, C.R. E-mail: appoloni@uel.br; Espinoza Quinones, F.R.; Aragao, P.H.A.; Santos, A.O. dos; Silva, L.M. da; Barbieri, P.F.; Nascimento Filho, V.F. do; Coimbra, M.M

2001-06-01

A set of Indian Brazilian pottery fragments belonging to Tupi-Guarani tradition has been studied by EDXRF. The main objective was to characterize the ceramic paste, as well as the superficial layer of the ceramic fragments, in order to get qualitative information about the pigment composition of the plastic decoration. Energy Dispersive X-ray Fluorescence (EDXRF) methodology was employed to obtain the ceramic paste composition, as well as the superficial layer of the ceramic fragments. The experimental set-up consisted of 238Pu, 55Fe and 109Cd radioactive sources, a X-ray tube (at 15 kV, 40 mA, Mo target and Zr filter), a Si(Li) detector (30 mm{sup 2}, with a Be window) and a multichannel analyzer. X-ray spectra were analyzed using the AXIL program. A program based on the graphic polygonal representation method was developed and used to correlate the representative intensity data of each fragment. A low Ca content and a systematic presence of relatively high concentrations of Fe can characterize the ceramic pastes. Ti and Zr are also always present at high levels, and Ni, Cu and in some cases Zn at level of traces; Rb, Sr, Ba and Y are also present at low concentration. The black pigment in the pottery plastic decoration is due to the presence of Mn, the red pigment is due to the presence of Fe, while the white pigment is characterized by the presence of Ba. For the eleven fragments studied, the polygonal representation method points that the same materials were employed in the pottery production, and the pigments in the plastic decoration were obtained from different inorganic materials.

EDXRF study of Tupi-Guarani archaeological ceramics

International Nuclear Information System (INIS)

Appoloni, C.R.; Espinoza Quinones, F.R.; Aragao, P.H.A.; Santos, A.O. dos; Silva, L.M. da; Barbieri, P.F.; Nascimento Filho, V.F. do; Coimbra, M.M.

2001-01-01

A set of Indian Brazilian pottery fragments belonging to Tupi-Guarani tradition has been studied by EDXRF. The main objective was to characterize the ceramic paste, as well as the superficial layer of the ceramic fragments, in order to get qualitative information about the pigment composition of the plastic decoration. Energy Dispersive X-ray Fluorescence (EDXRF) methodology was employed to obtain the ceramic paste composition, as well as the superficial layer of the ceramic fragments. The experimental set-up consisted of 238Pu, 55Fe and 109Cd radioactive sources, a X-ray tube (at 15 kV, 40 mA, Mo target and Zr filter), a Si(Li) detector (30 mm 2 , with a Be window) and a multichannel analyzer. X-ray spectra were analyzed using the AXIL program. A program based on the graphic polygonal representation method was developed and used to correlate the representative intensity data of each fragment. A low Ca content and a systematic presence of relatively high concentrations of Fe can characterize the ceramic pastes. Ti and Zr are also always present at high levels, and Ni, Cu and in some cases Zn at level of traces; Rb, Sr, Ba and Y are also present at low concentration. The black pigment in the pottery plastic decoration is due to the presence of Mn, the red pigment is due to the presence of Fe, while the white pigment is characterized by the presence of Ba. For the eleven fragments studied, the polygonal representation method points that the same materials were employed in the pottery production, and the pigments in the plastic decoration were obtained from different inorganic materials

Sintered glass ceramic composites from vitrified municipal solid waste bottom ashes

International Nuclear Information System (INIS)

Aloisi, Mirko; Karamanov, Alexander; Taglieri, Giuliana; Ferrante, Fabiola; Pelino, Mario

2006-01-01

A glass ceramic composite was obtained by sinter-crystallisation of vitrified municipal solid waste bottom ashes with the addition of various percentages of alumina waste. The sintering was investigated by differential dilatometry and the crystallisation of the glass particles by differential thermal analysis. The crystalline phases produced by the thermal treatment were identified by X-ray diffraction analysis. The sintering process was found to be affected by the alumina addition and inhibited by the beginning of the crystal-phase precipitation. Scanning electron microscopy was performed on the fractured sintered samples to observe the effect of the sintering. Young's modulus and the mechanical strength of the sintered glass ceramic and composites were determined at different heating rates. The application of high heating rate and the addition of alumina powder improved the mechanical properties. Compared to the sintered glass ceramic without additives, the bending strength and the Young's modulus obtained at 20 deg. C/min, increased by about 20% and 30%, respectively

Ni-BaTiO3-Based Base-Metal Electrode (BME) Ceramic Capacitors for Space Applications

Science.gov (United States)

Liu, Donhang; Fetter, Lula; Meinhold, Bruce

2015-01-01

A multi-layer ceramic capacitor (MLCC) is a high-temperature (1350C typical) co-fired ceramic monolithic that is composed of many layers of alternately stacked oxide-based dielectric and internal metal electrodes. To make the dielectric layers insulating and the metal electrode layers conducting, only highly oxidation-resistant precious metals, such as platinum, palladium, and silver, can be used for the co-firing of insulating MLCCs in a regular air atmosphere. MLCCs made with precious metals as internal electrodes and terminations are called precious-metal electrode (PME) capacitors. Currently, all military and space-level applications only address the use of PME capacitors.

Towards III-V solar cells on Si: Improvement in the crystalline quality of Ge-on-Si virtual substrates through low porosity porous silicon buffer layer and annealing

International Nuclear Information System (INIS)

Calabrese, Gabriele; Baricordi, Stefano; Bernardoni, Paolo; Fin, Samuele; Guidi, Vincenzo; Vincenzi, Donato

2014-01-01

A comparison between the crystalline quality of Ge grown on bulk Si and on a low porosity porous Si (pSi) buffer layer using low energy plasma enhanced chemical vapor deposition is reported. Omega/2Theta coupled scans around the Ge and Si (004) diffraction peaks show a reduction of the Ge full-width at half maximum (FWHM) of 22.4% in presence of the pSi buffer layer, indicating it is effective in improving the epilayer crystalline quality. At the same time atomic force microscopy analysis shows an increase in root means square roughness for Ge grown on pSi from 38.5 nm to 48.0 nm, as a consequence of the larger surface roughness of pSi compared to bulk Si. The effect of 20 minutes vacuum annealing at 580°C is also investigated. The annealing leads to a FWHM reduction of 23% for Ge grown on Si and of 36.5% for Ge on pSi, resulting in a FWHM of 101 arcsec in the latter case. At the same time, the RMS roughness is reduced of 8.8% and of 46.5% for Ge grown on bulk Si and on pSi, respectively. The biggest improvement in the crystalline quality of Ge grown on pSi with respect to Ge grown on bulk Si observed after annealing is a consequence of the simultaneous reorganization of the Ge epilayer and the buffer layer driven by energy minimization. A low porosity buffer layer can thus be used for the growth of low defect density Ge on Si virtual substrates for the successive integration of III-V multijunction solar cells on Si. The suggested approach is simple and fast –thus allowing for high throughput-, moreover is cost effective and fully compatible with subsequent wafer processing. Finally it does not introduce new chemicals in the solar cell fabrication process and can be scaled to large area silicon wafers

Diffusion of transmutation isotope in YBaCuO ceramics

International Nuclear Information System (INIS)

Malkovich, R.Sh.

2005-01-01

The diffusion of a transmutation isotope generated in YBaCuO ceramics irradiated by high-energy charged particles is mathematically analyzed. The model is based on the assumption that copper isotope atoms created in subsurface layers of ceramic grains segregate at the grain boundaries in the course of subsequent annealing and then rapidly diffuse via intergranular regions in depth of the material and penetrate into the bulk of grains [ru

Synthesis of bioactive and machinable miserite glass-ceramics for dental implant applications.

Science.gov (United States)

Saadaldin, Selma A; Dixon, S Jeffrey; Costa, Daniel O; Rizkalla, Amin S

2013-06-01

To synthesize and characterize machinable, bioactive glass-ceramics (GCs) suitable for dental implant applications. A glass in the SiO2-Al2O3-CaO-CaF2-K2O-B2O3-La2O3 system was synthesized by wet chemical methods, followed by calcination, melting and quenching. Crystallization kinetics were determined by differential thermal analysis (DTA). GC discs were produced by cold pressing of the glass powder and sintered using schedules determined by DTA. The crystalline phases and microstructure of GC samples were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. Dynamic Young's modulus (E), true hardness (Ho), fracture toughness (KIC) and brittleness index (BI) were evaluated. Bioactivity was studied by examining the formation of hydroxyapatite (HA) on the GC surfaces after soaking in simulated body fluid (SBF). Attachment and proliferation of MC3T3-E1 osteoblastic cells were assessed in vitro. Miserite [KCa5(Si2O7)(Si6O15)(OH)F] was the main crystalline phase of the GC with additional secondary phases. Microstructural studies revealed interlocking lath-like crystalline morphology. E, Ho, and KIC values for the GCs were 96±3 GPa, 5.27±0.26 GPa and 4.77±0.27 MPa m(0.5), respectively. The BI was found to be 1.11±0.05 μm(-0.5), indicating outstanding machinability. An HA surface layer was formed on the GC surfaces when soaked in SBF, indicating potential bioactivity. MC3T3-E1 cells exhibited attachment, spreading and proliferation on GC surfaces, demonstrating excellent biocompatibility. We present a novel approach for the synthesis of miserite GC with the physical and biological properties required for non-metallic dental implant applications. Copyright © 2013 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

The Impedance of Multi-layer Vacuum Chambers

CERN Document Server

Vos, L

2003-01-01

Many components of the LHC vacuum chamber have multi-layered walls : the copper coated cold beam screen, the titanium coated ceramic chamber of the dump kickers, the ceramic chamber of the injection kickers coated with copper stripes, only to name a few. Theories and computer programs are available for some time already to evaluate the impedance of these elements. Nevertheless, the algorithm developed in this paper is more convenient in its application and has been used extensively in the design phase of multi-layer LHC vacuum chamber elements. It is based on classical transmission line theory. Closed expressions are derived for simple layer configurations, while beam pipes involving many layers demand a chain calculation. The algorithm has been tested with a number of published examples and was verified with experimental data as well.

Crystallization Kinetics and Characterization of Nanostructure Mica Glass-Ceramics with Optical Transparency

Directory of Open Access Journals (Sweden)

P. Alizadeh

2014-01-01

Full Text Available Transparent glasses in a system of Li2O-MgO-SiO2-Al2O3-Fchemical constituents were prepared by melt quenching method. In the fabrication of nanocrystal glass-ceramics, controlled nucleation and subsequent crystal growth were necessary to avoid loss of transparency. It was therefore important to understand thermal properties and crystallization kinetics of the glass ceramics. The crystallization behavior of the prepared glass was investigated by DTA, XRD and SEM. By crystallization heat-treatment, various crystalline phases, microstructure and transmittance were obtained. The sellaite was first precipitated as the nuclei before the crystallization of mica and then mica nanocrystals were precipitated with average size of

Calcium phosphate glass-ceramics for bioactive coating on a β-titanium alloy

International Nuclear Information System (INIS)

Kasuga, T.; Nogami, M.; Niinomi, M.

2003-01-01

The formation of a porous coating is the decisive feature for the bio-compatibility of silica-free calcium phosphate glass ceramics on alloy surfaces like the β-Ti structured Ti-29Nb-13Ta-4.6Zr used in this work. The ceramic composition is highly important: 50CaO-40P 2 O 5 -7Na 2 O-3TiO 2 glass powder produces a pore-free coating unable to bind hydroxyapatite, whereas 60CaO-30P 2 O 5 -7Na 2 O-3TiO 2 glass incorporates pores from which a crystalline hydroxyapatite phase can grow over the surface from simulated body fluid (see Figure). (Abstract Copyright [2003], Wiley Periodicals, Inc.)

Layered Manufacturing of Dental Ceramics: Fracture Mechanics, Microstructure, and Elemental Composition of Lithography-Sintered Ceramic.

Science.gov (United States)

Uçar, Yurdanur; Aysan Meriç, İpek; Ekren, Orhun

2018-02-11

To compare the fracture mechanics, microstructure, and elemental composition of lithography-based ceramic manufacturing with pressing and CAD/CAM. Disc-shaped specimens (16 mm diameter, 1.2 mm thick) were used for mechanical testing (n = 10/group). Biaxial flexural strength of three groups (In-Ceram alumina [ICA], lithography-based alumina, ZirkonZahn) were determined using the "piston on 3-ball" technique as suggested in test Standard ISO-6872. Vickers hardness test was performed. Fracture toughness was calculated using fractography. Results were statistically analyzed using Kruskal-Wallis test followed by Dunnett T3 (α = 0.05). Weibull analysis was conducted. Polished and fracture surface characterization was made using scanning electron microscope (SEM). Energy dispersive spectroscopy (EDS) was used for elemental analysis. Biaxial flexural strength of ICA, LCM alumina (LCMA), and ZirkonZahn were 147 ± 43 MPa, 490 ± 44 MPa, and 709 ± 94 MPa, respectively, and were statistically different (P ≤ 0.05). The Vickers hardness number of ICA was 850 ± 41, whereas hardness values for LCMA and ZirkonZahn were 1581 ± 144 and 1249 ± 57, respectively, and were statistically different (P ≤ 0.05). A statistically significant difference was found between fracture toughness of ICA (2 ± 0.4 MPa⋅m 1/2 ), LCMA (6.5 ± 1.5 MPa⋅m 1/2 ), and ZirkonZahn (7.7 ± 1 MPa⋅m 1/2 ) (P ≤ 0.05). Weibull modulus was highest for LCMA (m = 11.43) followed by ZirkonZahn (m = 8.16) and ICA (m = 5.21). Unlike LCMA and ZirkonZahn groups, a homogeneous microstructure was not observed for ICA. EDS results supported the SEM images. Within the limitations of this in vitro study, it can be concluded that LCM seems to be a promising technique for final ceramic object manufacturing in dental applications. Both the manufacturing method and the material used should be improved. © 2018 by the American College of Prosthodontists.

Temperature Dependence of the Resonant Magnetoelectric Effect in Layered Heterostructures

Directory of Open Access Journals (Sweden)

Dmitrii A. Burdin

2017-10-01

Full Text Available The dependence of the resonant direct magnetoelectric effect on temperature is studied experimentally in planar composite structures. Samples of rectangular shapes with dimensions of 5 mm × 20 mm employed ferromagnetic layers of either an amorphous (metallic glass alloy or nickel with a thickness of 20–200 μm and piezoelectric layers of single crystalline langatate material or lead zirconate titanate piezoelectric ceramics with a thickness of 500 μm. The temperature of the samples was varied in a range between 120 and 390 K by blowing a gaseous nitrogen stream around them. It is shown that the effective characteristics of the magnetoelectric effect—such as the mechanical resonance frequency fr, the quality factor Q and the magnitude of the magnetoelectric coefficient αE at the resonance frequency—are contingent on temperature. The interrelations between the temperature changes of the characteristics of the magnetoelectric effect and the temperature variations of the following material parameters—Young’s modulus Y, the acoustic quality factor of individual layers, the dielectric constant ε, the piezoelectric modulus d of the piezoelectric layer as well as the piezomagnetic coefficients λ(n of the ferromagnetic layer—are established. The effect of temperature on the characteristics of the nonlinear magnetoelectric effect is observed for the first time. The results can be useful for designing magnetoelectric heterostructures with specified temperature characteristics, in particular, for the development of thermally stabilized magnetoelectric devices.

Relation of lifetime to surface passivation for atomic-layer-deposited Al2O3 on crystalline silicon solar cell

International Nuclear Information System (INIS)

Cho, Young Joon; Song, Hee Eun; Chang, Hyo Sik

2015-01-01

Highlights: • We investigated the relation of potassium contamination on Si solar wafer to lifetime. • We deposited Al 2 O 3 layer by atomic layer deposition (ALD) on Si solar wafer after several cleaning process. • Potassium can be left on Si surface by incomplete cleaning process and degrade the Al 2 O 3 passivation quality. - Abstract: We investigated the relation of potassium contamination on a crystalline silicon (c-Si) surface after potassium hydroxide (KOH) etching to the lifetime of the c-Si solar cell. Alkaline solution was employed for saw damage removal (SDR), texturing, and planarization of a textured c-Si solar wafer prior to atomic layer deposition (ALD) Al 2 O 3 growth. In the solar-cell manufacturing process, ALD Al 2 O 3 passivation is utilized to obtain higher conversion efficiency. ALD Al 2 O 3 shows excellent surface passivation, though minority carrier lifetime varies with cleaning conditions. In the present study, we investigated the relation of potassium contamination to lifetime in solar-cell processing. The results showed that the potassium-contaminated samples, due to incomplete cleaning of KOH, had a short lifetime, thus establishing that residual potassium can degrade Al 2 O 3 surface passivation

Carbon nanotubes-porous ceramic composite by in situ CCVD growth of CNTs

Energy Technology Data Exchange (ETDEWEB)

Mazumder, Sangram; Sarkar, Naboneeta; Park, Jung Gyu [Institute of Processing and Application of Inorganic Materials (PAIM), Department of Materials Science and Engineering, Hanseo University, #360 Daegok-ri, Haemi-myeon, Seosan-si, Chungnam, 356-706 (Korea, Republic of); Han, In Sub [Korea Institute of Energy Research (KIER), #152 Gajeong-gu, Daejeon 305-343 (Korea, Republic of); Kim, Ik Jin, E-mail: ijkim@hanseo.ac.kr [Institute of Processing and Application of Inorganic Materials (PAIM), Department of Materials Science and Engineering, Hanseo University, #360 Daegok-ri, Haemi-myeon, Seosan-si, Chungnam, 356-706 (Korea, Republic of)

2016-03-01

A novel approach towards the formation of Carbon nanotubes-porous alumina ceramic composite was attempted by the application of three different reaction techniques. Porous alumina ceramics having micrometer pore dimensions were developed using the direct foaming technique. NaA zeolites were simultaneously synthesized and coated within the porous ceramics by an in situ hydrothermal process and were subjected to a simple ion exchange reaction for preparing the suitable catalyst material for Carbon nanotubes (CNTs) synthesis. The catalytic chemical vapour deposition (CCVD) technique was used to grow CNTs within the porous ceramics and the effect of growth time on the synthesized CNTs were investigated. Phase compositions of the samples were analysed by X-ray diffractometer (XRD). Field Emission Scanning Electron Microscopy (FESEM) and Transmission Electron Microscopy (TEM) were used for morphology, surface quality and structural analysis. Crystallinity, defects and yield were studied by Raman spectroscopy and thermogravimetric analysis (TGA). - Highlights: • Novel processing route of MWCNTs grown on Cobalt-zeolites-porous ceramics by CCVD. • CCVD time of 120 min produced MWCNTs with most prominent tube-like structure. • 120 min produced highest yield (19.46%) of CNTs with an I{sub D}/I{sub G} ratio of 0.88.

Core-shell structured ceramic nonwoven separators by atomic layer deposition for safe lithium-ion batteries

Science.gov (United States)

Shen, Xiu; Li, Chao; Shi, Chuan; Yang, Chaochao; Deng, Lei; Zhang, Wei; Peng, Longqing; Dai, Jianhui; Wu, Dezhi; Zhang, Peng; Zhao, Jinbao

2018-05-01

Safety is one of the most factors for lithium-ion batteries (LIBs). In this work, a novel kind of ceramic separator with high safety insurance is proposed. We fabricated the core-shell nanofiber separators for LIBs by atomic layer deposition (ALD) of 30 nm Al2O3 on the electrospinning nonwoven fiber of polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP). The separators show a pretty high heat resistance up to 200 °C without any shrinkage, an excellent fire-resistant property and a wide electrochemical window. Besides, with higher uptake and ionic conductivity, cells assembled with the novel separator shows better electrochemical performance. The ALD produced separators exhibit great potential in elaborate products like 3C communications and in energy field with harsh requirements for safety such as electric vehicles. The application of ALD on polymer fiber membranes brings a new strategy and opportunity for improving the safety of the advanced LIBs.

Modelling of fluid flow in tape casting of thin ceramics: Analytical approaches and numerical investigations

DEFF Research Database (Denmark)

Jabbaribehnam, Mirmasoud; Hattel, Jesper Henri

2016-01-01

Tape casting has been used to produce thin layers of ceramics that can be used as single layers or can be stacked and laminated into multilayered structures. Many startup products such as multilayered inductors, multilayered varistors, piezoelectrics, ceramic fuel cells and lithium ion battery...... components are dependent upon tape casting technology. One of the growing sciences in the processing of ceramics by tape casting is the use of fluid flow analysis to control and enhance the final tapes. The fluid dynamics analysis of the ceramic slurries during tape casting is an efficient mean to elucidate...... the physical parameters crucial to the process. A review of the development of the tape casting process with particular focus on modelling the material flow is presented and in this context the current status is examined and future potential discussed....

Hydrogen separation from high temperature CO-containing syn-gas flow using molecular ceramic membranes

Energy Technology Data Exchange (ETDEWEB)

Soudarev, A.; Konakov, G.; Souryaninov, A.; Molchanov, A. [Boyko Research Engineering Ceramic Heat Engines Center Ltd., St. Petersburg (Russian Federation); Lelait, L.; Stevens, P.H. [European Inst. for Power Studies, Karlsruhe (Germany)

2006-07-01

Poisoning of the platinum (Pt) metals used as catalysts for proton exchange membrane fuel cells (PEMFCs) can negatively impact on PEMFC operation efficiency. In order to address this issue, a supply of hydrogen with a carbon monoxide (CO) admixtures is required. This paper provided details of a new type of molecular ceramic membrane (MCM) that allows the separation of hydrogen (H{sub 2}) from the hydrocarbon fuel reforming products that contain CO and has higher temperature and pressure capacity than other membranes. After various tests, alumo-magnesium spinel (AMS) was selected as the most promising porous material for the ceramic multi-layer membrane. The crystalline structure of the AMS showed good thermo-dynamic stability during tests that ranged between 20 and 1400 degrees C, as well as a chemical resistance relative to the effects of the aggressive fuel cell environment, and no exposure to the oxidation-recovery processes in the CO and H{sub 2} flow. The macroporous substrate of the AMS and the membrane selection layers have the same composition. The formation of the carrier was conducted by a semi-dry molding on a hydraulic press. Formation of the nano-porous structure in the carrier macro-pores by the polysilicon acid sol solution treatment allowed the synthesis of the amorphous silica and crystobalite crystals with a developed surface and nano-dimension subporosity. Test results have shown that the MCM has optimum penetrability and selectivity values as well as admissible thermo-mechanical properties. H{sub 2} flow through the membrane was 1.5-1.7 times greater than the CO flow. It was concluded that the AMS-based membrane devices will increase the efficiency of the PEMFC power plants and reduce their degradation capacity. 2 refs., 1 tab., 1 fig.

Preparation of textured Bi3TiNbO9 ceramics

International Nuclear Information System (INIS)

Zhou Zhiyong; Cheng Baozhu; Li Yuchen; Dong Xianlin

2007-01-01

Single phase of textured Bi 3 TiNbO 9 (BTNO) ceramics were prepared by a two-step sintering method: synthesizing seed-crystal platelets by molten-salt method with oxide mixture as precursor and then sintering the platelets via hot-pressing method. Molten-salt-synthesized fine BTNO plate-like crystallines (∼400 nm) had an orientation degree of 0.42. After hot-pressed under different conditions, textured BTNO ceramics with different orientation degree were obtained and the orientation degree of textured BTNO ceramics increased with the applied pressure as well as the sintering temperature. X-ray diffraction (XRD) patterns of textured BTNO revealed that the face perpendicular to the hot-pressing axis (-perpendicular ) exhibits stronger (0 0 l) diffraction peaks, while the face parallel to the hot-pressing axis (-parallel ) shows stronger (0 2 0)/(2 0 0) and weaker (0 0 l) diffraction peaks, which also can be apparently observed from SEM images. Highly oriented BTNO with a degree of 0.78 was obtained under an applied pressure of 60 MPa at 1050 deg. C

Ceramic laminates with tailored residual stresses

Directory of Open Access Journals (Sweden)

Baudín, C.

2009-12-01

Full Text Available Severe environments imposed by new technologies demand new materials with better properties and ensured reliability. The intrinsic brittleness of ceramics has forced scientists to look for new materials and processing routes to improve the mechanical behaviour of ceramics in order to allow their use under severe thermomechanical conditions. The laminate approach has allowed the fabrication of a new family of composite materials with strength and reliability superior to those of monolithic ceramics with microstructures similar to those of the constituent layers. The different ceramic laminates developed since the middle 1970´s can be divided in two large groups depending on whether the development of residual stresses between layers is the main design tool. This paper reviews the developments in the control and tailoring of residual stresses in ceramic laminates. The tailoring of the thickness and location of layers in compression can lead to extremely performing structures in terms of strength values and reliability. External layers in compression lead to the strengthening of the structure. When relatively thin and highly compressed layers are located inside the material, threshold strength, crack bifurcation and crack arrest during fracture occur.

Las severas condiciones de trabajo de las nuevas aplicaciones tecnológicas exigen el uso de materiales con mejores propiedades y alta fiabilidad. La potencialidad de uso de materiales frágiles, como los cerámicos, en estas aplicaciones exige el desarrollo de nuevos materiales y métodos de procesamiento que mejoren su comportamiento mecánico. El concepto de material laminado ha permitido la fabricación de una nueva familia de materiales con tensiones de fractura y fiabilidad superiores a las de materiales monolíticos con microestructuras similares a las de las láminas que conforman el laminado. Los distintos materiales laminados desarrollados desde mediados de los años 70 se pueden

"Silicon millefeuille": From a silicon wafer to multiple thin crystalline films in a single step

Science.gov (United States)

Hernández, David; Trifonov, Trifon; Garín, Moisés; Alcubilla, Ramon

2013-04-01

During the last years, many techniques have been developed to obtain thin crystalline films from commercial silicon ingots. Large market applications are foreseen in the photovoltaic field, where important cost reductions are predicted, and also in advanced microelectronics technologies as three-dimensional integration, system on foil, or silicon interposers [Dross et al., Prog. Photovoltaics 20, 770-784 (2012); R. Brendel, Thin Film Crystalline Silicon Solar Cells (Wiley-VCH, Weinheim, Germany 2003); J. N. Burghartz, Ultra-Thin Chip Technology and Applications (Springer Science + Business Media, NY, USA, 2010)]. Existing methods produce "one at a time" silicon layers, once one thin film is obtained, the complete process is repeated to obtain the next layer. Here, we describe a technology that, from a single crystalline silicon wafer, produces a large number of crystalline films with controlled thickness in a single technological step.

Minimum additive waste stabilization using vitreous ceramics. Progress report, October 1994--September 1995

International Nuclear Information System (INIS)

Feng, X.; Hahn, W.K.; Gong, M.; Gong, W.; Wang, L.; Ewing, R.C.

1995-01-01

Vitreous ceramic waste forms are being developed at Pacific Northwest Laboratory to complement glass waste forms in implementing the Minimum Additive Waste Stabilization (MAWS) Program to support the US Department of Energy's environmental restoration efforts. These vitreous ceramics are composed of various metal-oxide crystalline phases embedded in a silicate-glass phase. This work extends the success of vitreous ceramic waste forms to treat wastes with both high metal and high alkali contents. Two successful approaches are discussed: developing high-durability alkali-binding crystals in a durable glassy matrix, and developing water-soluble crystals in a durable and continuous glassy matrix. Nepheline-vitreous ceramics were demonstrated for the immobilization of high-alkali wastes with alkali contents up to 21 wt%. The chemical durability of the nepheline-vitreous ceramics is better than the corresponding glasses, especially in over longer times. Vitreous ceramics with Cs 2 O loading up to 35.4 wt% have been developed. Vitreous ceramic waste forms were developed from 90 and 100% Oak Ridge National Laboratory K-25 pond sludge. Heat treatment resulted in targeted crystal formation of spinels, potassium feldspar, and Ca-P phases. The K-25 pond sludge vitreous ceramics were up to 42 times more durable than high-level environmental assessments (EA) glass. The toxicity characteristics leach procedure (TCLP) concentration of LVC-6 is at least 2,000 times lower than US Environmental Protection Agency limits. Idaho Chemical Process Plant (ICPP) calcined wastes were immobilized into vitreous ceramics with calcine loading up to 88%. These ICPP-vitreous ceramics were more durable than the EA glass by factors of 5 to 30. Vitreous ceramic waste forms are being developed to complement, not to replace, glass waste forms

Comparison of the microstructure and composition of aboriginal ceramics, from indigenous site Caninhas, with the obtained ones in the region

International Nuclear Information System (INIS)

Matos, C.C.; Nakano, F.P.; Taguchi, S.P.; Camargo-Vernilli, D.; Ribeiro, R.B.; Rosa, S.J. L.

2009-01-01

The archaeological site of Caninhas is made of funeral and combustion structures and various objects of aboriginal daily use. These parts and fragments were safe and inventoried, constituting approximately 4000 units. The objective of this project was to analyze the microstructure and composition of archaeological ceramics, and ceramics made of argil current of the zone. The crystalline phases were identified by X-Rays Diffraction (XRD), elementary composition was obtained by X-Rays Fluorescence (XRF) and Energy Dispersive Spectrometry (EDS), and the microstructure was evaluated by Scanning Electron Microscope (SEM). Composition and microstructure of archaeological ceramics are different of current ceramics, indicating the effect of lixiviation in function of the time and the microstructural evolution due different ceramic processing. These results are valuable for the archaeological area studies, mainly for the cultural denoting which represents. The relation between some studies is basic to add knowledge: use of the ceramic materials engineering for archaeology application. (author)

Thermal properties and crystallization of lithium–mica glass and glass-ceramics

International Nuclear Information System (INIS)

Nia, A. Faeghi

2013-01-01

Highlights: • Two groups of Li–mica glass-ceramics, have been compared. • By controlling the glass composition, crystalline lepidolite was obtained. • The T p of Li–mica was through the previous virgilite and eucryptite phase. - Abstract: The purpose of this study was the synthesis of two groups of Li–mica glass-ceramics denoted by lepidolite (Al 2.5 F 2 KLi 1.5 O 10 Si 3 ) and Li-phlogopite (LiMg 3 AlSi 3 O 10 F 2 ). The studied system was SiO 2 –Al 2 O 3 –MgO–K 2 O–Li 2 O. A total of 3 compositions were prepared. Bulk casted glasses and sintered glass-ceramics of Li-phlogopite and lepidolite systems, were prepared. Eucryptite and virgilite were two prior phases of lepidolite and Li-phlogopite crystallization. It was shown that the obtained glass-ceramics have lower TEC than corresponding glasses. Sinterability of lepidolite glass-ceramic was shown that improved by increasing the Al 2 O 3 content in glass composition. TEC and microhardness values were α = 6.08 × 10 −6 /°C, 755 ± 11.1, α = 7.86 × 10 −6 /°C, 739 ± 7.4 and α = 5.05 × 10 −6 /°C, 658 ± 6.2 HV for Li-lep, Klep1 and Klep2 glasses, respectively

Bone bonding ability of some borate bio-glasses and their corresponding glass-ceramic derivatives

Directory of Open Access Journals (Sweden)

Fatma H. Margha

2012-12-01

Full Text Available Ternary borate glasses from the system Na2O·CaO·B2O3 together with soda-lime-borate samples containing 5 wt.% of MgO, Al2O3, SiO2 or P2O5 were prepared. The obtained glasses were converted to their glass-ceramic derivatives by controlled heat treatment. X-ray diffraction was employed to investigate the separated crystalline phases in glass-ceramics after heat treatment of the glassy samples. The glasses and corresponding glass-ceramics after immersion in water or diluted phosphate solution for extended times were characterized by the grain method (adopted by several authors and recommended by ASTM and Fourier-transform infrared spectra to justify the formation of hydroxyapatite as an indication of the bone bonding ability. The influence of glass composition on bioactivity potential was discussed too.

Bioactive glasses and glass-ceramics

Directory of Open Access Journals (Sweden)

de Aza, P. N.

2007-04-01

Full Text Available Since the late 1960´s, a great interest in the use of bioceramic materials for biomedical applications has been developed. In a previous paper, the authors reviewed crystalline bioceramic materials “sensus stricto”, it is to say, those ceramic materials, constituted for non-metallic inorganic compounds, crystallines and consolidates by thermal treatment of powders at high temperature. In the present review, the authors deal with those called bioactive glasses and glassceramics. Although all of them are also obtained by thermal treatment at high temperature, the first are amorphous and the second are obtained by devitrification of a glass, although the vitreous phase normally prevails on the crystalline phases. After an introduction to the concept of bioactive materials, a short historical review of the bioactive glasses development is made. Its preparation, reactivity in physiological media, mechanism of bonding to living tissues and mechanical strength of the bone-implant interface is also reported. Next, the concept of glass-ceramic and the way of its preparation are exposed. The composition, physicochemical properties and biological behaviour of the principal types of bioactive glasses and glass-ceramic materials: Bioglass®, Ceravital®, Cerabone®, Ilmaplant® and Bioverit® are also reviewed. Finally, a short review on the bioactive-glass coatings and bioactive-composites and most common uses of bioactive-glasses and glass-ceramics are carried out too.

Desde finales de los años sesenta, se ha despertado un gran interés por el uso de los materiales biocerámicos para aplicaciones biomédicas. En un trabajo previo, los autores hicieron una revisión de los denominados materiales biocerámicos cristalinos en sentido estricto, es decir, de aquellos materiales, constituidos por compuestos inorgánicos no metálicos, cristalinos y consolidados mediante tratamientos térmicos a altas temperaturas. En el presente trabajo, los autores

Sensitive Ceramics_Pattern #1-#5

DEFF Research Database (Denmark)

2014-01-01

pattern of which are reflecting the position and speed of the hands. In that way the user is able to interact and model a responding pattern. The second level has to do with realizing the modules in ceramics by 3d printing directly in porcelain with a RapMan printer that coils up the 3d shape in layers...

Neodymium partitioning in zirconolite-based glass-ceramics designed for minor actinides immobilization

International Nuclear Information System (INIS)

Loiseau, P.; Caurant, D.; Baffier, N.; Fillet, C.

2000-01-01

This study deals with glass-ceramic matrices designed for the conditioning of minor actinides, in which zirconolite crystals (CaZrTi 2 O 7 ) are homogeneously dispersed in a residual glassy matrix. Good immobilization performances require a high enrichment of actinides in the crystalline phase (double containment principle). Glass-ceramics are obtained by controlled devitrification of an aluminosilicate parent glass containing large amounts of TiO 2 and ZrO 2 . Neodymium was selected to simulate the trivalent minor actinides. Crystallization was performed at 1200 deg. C for various Nd 2 O 3 contents (0 - 10 wt. %). In all cases, zirconolite crystallization is obtained in the bulk of glass-ceramics. The evolution of Nd 3+ location between the crystals and the residual glass was followed by electron spin resonance and optical absorption. Both techniques demonstrate that neodymium is partly incorporated in zirconolite crystals. Moreover, total Nd 2 O 3 content in parent glass has a strong effect on Nd 3+ ions distribution. (authors)

Testing of neutron-irradiated ceramic-to-metal seals

International Nuclear Information System (INIS)

Brown, R.D.; Clinard, F.W. Jr.; Lopez, M.R.; Martinez, H.; Romero, T.J.; Cook, J.H.; Barr, H.N.; Hittman, F.

1990-01-01

This paper reports on ceramic-to-metal seals prepared by sputtering a titanium metallizing layer onto ceramic disks and then brazing to metal tubes. The ceramics used were alumina, MACOR, spinel, AlON, and a mixture of Al 2 O 3 and Si 3 N 4 . Except for the MACOR, which was brazed to a titanium tube, the ceramics were brazed to niobium tubes. The seals were leak tested and then sent to Los Alamos National Laboratory, where they were irradiated using the spallation neutron source at the Los Alamos Meson Physics Facility. Following irradiation for ∼ 90 days to a fluence of 2.8 x 10 23 n/m 2 , the samples were moved to hot cells and again leak tested. Only the MACOR samples showed any measurable leaks. One set of samples was then pressurized to 6.9 MPa (1000 psi) and subsequently leak tested. No leaks were found. Bursting the seals required hydrostatic pressures of at least 34 MPa (5000 psi). The high seal strength and few leaks indicate that ceramic-to-metal seals can resist radiation-induced degradation

Bulk glass ceramics containing Yb{sup 3+}/Er{sup 3+}: β-NaGdF{sub 4} nanocrystals: Phase-separation-controlled crystallization, optical spectroscopy and upconverted temperature sensing behavior

Energy Technology Data Exchange (ETDEWEB)

Chen, Daqin, E-mail: dqchen@fjirsm.ac.cn [College of Materials & Environmental Engineering, Hangzhou Dianzi University, Hangzhou 310018 (China); Wan, Zhongyi; Zhou, Yan [College of Materials & Environmental Engineering, Hangzhou Dianzi University, Hangzhou 310018 (China); Huang, Ping, E-mail: phuang@fjirsm.ac.cn [Key Laboratory of Design and Assembly of Functional Nanostructures, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou 350002 (China); Zhong, Jiasong; Ding, Mingye [College of Materials & Environmental Engineering, Hangzhou Dianzi University, Hangzhou 310018 (China); Xiang, Weidong; Liang, Xiaojuan [College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou 325035 (China); Ji, Zhenguo, E-mail: jizg@hdu.edu.cn [College of Materials & Environmental Engineering, Hangzhou Dianzi University, Hangzhou 310018 (China)

2015-07-25

Highlights: • Hexagonal NaGdF{sub 4} nanocrystals embedded bulk glass ceramics were fabricated. • The incorporation of Ln{sup 3+} dopants into the β-NaGdF{sub 4} lattice was demonstrated. • Upconversion luminescence was highly intensified after glass crystallization. • Such glass ceramics had possible application in the optical temperature sensors. - Abstract: Lanthanide doped hexagonal β-NaGdF{sub 4} nanocrystals embedded transparent bulk glass ceramics were successfully fabricated via a phase-separation-controlled crystallization route. Elemental mapping in the scanning transmission electron microscope and optical spectroscopy analysis demonstrated the partition of the active centers into the β-NaGdF{sub 4} crystalline lattice. As a result, upconversion luminescence of the glass ceramic co-doped with Yb{sup 3+} and Er{sup 3+} is about 60 times as high as that of the precursor glass, attributing to the modification of Yb{sup 3+}/Er{sup 3+} surrounding from phase-separated amorphous nanoparticle to β-NaGdF{sub 4} crystalline lattice with low phonon energy and high crystallinity after crystallization. Furthermore, the temperature-dependent green upconversion emissions assigned to {sup 2}H{sub 11/2} → {sup 4}I{sub 15/2} (520 nm) and {sup 4}S{sub 3/2} → {sup 4}I{sub 15/2} (540 nm) transitions were investigated, and the corresponding fluorescence intensity ratio of these two thermally coupled emitting-states greatly enhanced with increase of temperature. Using such fabricated glass ceramic as an optical thermometric medium, the maximum sensitivity reached as high as 0.0037 K{sup −1} at 580 K. It is expected that the investigated Er{sup 3+}/Yb{sup 3+} codoped glass ceramic might be a very promising candidate for accurate optical temperature sensors.

Influence of resin cement shade on the color and translucency of ceramic veneers

Science.gov (United States)

HERNANDES, Daiana Kelly Lopes; ARRAIS, Cesar Augusto Galvão; de LIMA, Erick; CESAR, Paulo Francisco; RODRIGUES, José Augusto

2016-01-01

ABSTRACT Objective This in vitro study evaluated the effect of two different shades of resin cement (RC- A1 and A3) layer on color change, translucency parameter (TP), and chroma of low (LT) and high (HT) translucent reinforced lithium disilicate ceramic laminates. Material and Methods One dual-cured RC (Variolink II, A1- and A3-shade, Ivoclar Vivadent) was applied to 1-mm thick ceramic discs to create thin RC films (100 µm thick) under the ceramics. The RC was exposed to light from a LED curing unit. Color change (ΔE) of ceramic discs was measured according to CIEL*a*b* system with a standard illuminant D65 in reflectance mode in a spectrophotometer, operating in the light range of 360-740 nm, equipped with an integrating sphere. The color difference between black (B) and white (W) background readings was used for TP analysis, while chroma was calculated by the formula C* ab=(a*2+b*2)½. ΔE of 3.3 was set as the threshold of clinically unacceptable. The results were evaluated by two-way ANOVA followed by Tukey's post hoc test. Results HT ceramics showed higher ΔE and higher TP than LT ceramics. A3-shade RC promoted higher ΔE than A1-shade cement, regardless of the ceramic translucency. No significant difference in TP was noted between ceramic discs with A1- and those with A3-shade cement. Ceramic with underlying RC showed lower TP than discs without RC. HT ceramics showed lower chroma than LT ceramics, regardless of the resin cement shade. The presence of A3-shade RC resulted in higher chroma than the presence of A1-shade RC. Conclusions Darker underlying RC layer promoted more pronounced changes in ceramic translucency, chroma, and shade of high translucent ceramic veneers. These differences may not be clinically differentiable. PMID:27556211

Influence of resin cement shade on the color and translucency of ceramic veneers

Directory of Open Access Journals (Sweden)

Daiana Kelly Lopes HERNANDES

Full Text Available ABSTRACT Objective This in vitro study evaluated the effect of two different shades of resin cement (RC- A1 and A3 layer on color change, translucency parameter (TP, and chroma of low (LT and high (HT translucent reinforced lithium disilicate ceramic laminates. Material and Methods One dual-cured RC (Variolink II, A1- and A3-shade, Ivoclar Vivadent was applied to 1-mm thick ceramic discs to create thin RC films (100 µm thick under the ceramics. The RC was exposed to light from a LED curing unit. Color change (ΔE of ceramic discs was measured according to CIEL*a*b* system with a standard illuminant D65 in reflectance mode in a spectrophotometer, operating in the light range of 360-740 nm, equipped with an integrating sphere. The color difference between black (B and white (W background readings was used for TP analysis, while chroma was calculated by the formula C*ab=(a*2+b*2½. ΔE of 3.3 was set as the threshold of clinically unacceptable. The results were evaluated by two-way ANOVA followed by Tukey's post hoc test. Results HT ceramics showed higher ΔE and higher TP than LT ceramics. A3-shade RC promoted higher ΔE than A1-shade cement, regardless of the ceramic translucency. No significant difference in TP was noted between ceramic discs with A1- and those with A3-shade cement. Ceramic with underlying RC showed lower TP than discs without RC. HT ceramics showed lower chroma than LT ceramics, regardless of the resin cement shade. The presence of A3-shade RC resulted in higher chroma than the presence of A1-shade RC. Conclusions Darker underlying RC layer promoted more pronounced changes in ceramic translucency, chroma, and shade of high translucent ceramic veneers. These differences may not be clinically differentiable.

Treatment of domestic wastewater with an anaerobic ceramic membrane bioreactor (AnCMBR).

Science.gov (United States)

Yue, Xiaodi; Koh, Yoong Keat Kelvin; Ng, How Yong

2015-01-01

In this study, a ceramic membrane with a pore size of 80 nm was incorporated into an anaerobic membrane bioreactor for excellent stability and integrity. Chemical oxygen demand (COD) removal efficiencies by biodegradation reached 78.6 ± 6.0% with mixed liquor suspended solids (MLSS) of 12.8 ± 1.2 g/L. Even though the total methane generated was 0.3 ± 0.03 L/g CODutilized, around 67.4% of it dissolved in permeate and was lost beyond collection. As a result, dissolved methane was 2.7 times of the theoretical saturating concentration calculated from Henry's law. When transmembrane pressure (TMP) of the ceramic membrane reached 30 kPa after 25.3 d, 95.2% of the total resistance was attributed to the cake layer, which made it the major contributor to membrane fouling. Compared to the mixed liquor, cake layer was rich in colloids and soluble products that could bind the solids to form a dense cake layer. The Methanosarcinaceae family preferred to attach to the ceramic membranes.

The application of positron annihilation lifetime spectroscopy to the study of glassy and partially crystalline materials

International Nuclear Information System (INIS)

Zipper, M.D.; Hill, A.J.

1994-01-01

The use of positron annihilation lifetime spectroscopy (PALS) as a materials characterisation technique is discussed and is illustrated by examples from the authors' laboratory. A brief guide to interpretation of PALS results for metals, semiconductors, ionic solids and molecular solids is presented; however, the paper focuses on recent results for glassy and partially crystalline ionic and molecular solids. Case studies are presented in which the phenomena studied by PALS include miscibility of polymer blends, plasticization of solid polymer electrolytes, crystallinity in molecular and ionic solids, nanostructure of glass-ceramics, and refractivity of fluoride glasses. Future directions for PALS research of the electronic and defect structures of materials are discussed. 140 refs., 1 tab., 19 figs

Tetragonal zirconia ceramics in Zr O2-Ce O2 system (Ce-TZP): preparation, characterization and mechanical properties

International Nuclear Information System (INIS)

Andrade Nono, M.C. de.

1992-01-01

This paper describes and discusses the results achieved in a study about Ce-TZP ceramics prepared from conventional powder mixtures of Zr O 2 and Ce O 2 (with composition in the range of 8 to 16 mol% Ce O 2 ). Physical and chemical characteristics were related with the powder compaction behavior and with the sintering state. The sintered ceramics showed a level of high porosity (≅ 4%), mainly due to the fairly adequate powder characteristics and compaction. The crystalline phases were analysed from X-rays diffraction data and showed that these ceramics can present tetragonal-to-monoclinic stress induced transformation. The bending strength, fracture toughness and Vickers hardness results were influenced by Ce O 2 content microstructure and sintering temperature. These Ce-TZP ceramics showed mechanical strength results comparable to those published in the international literature. (author)

Evaluation of machinability and flexural strength of a novel dental machinable glass-ceramic.

Science.gov (United States)

Qin, Feng; Zheng, Shucan; Luo, Zufeng; Li, Yong; Guo, Ling; Zhao, Yunfeng; Fu, Qiang

2009-10-01

To evaluate the machinability and flexural strength of a novel dental machinable glass-ceramic (named PMC), and to compare the machinability property with that of Vita Mark II and human enamel. The raw batch materials were selected and mixed. Four groups of novel glass-ceramics were formed at different nucleation temperatures, and were assigned to Group 1, Group 2, Group 3 and Group 4. The machinability of the four groups of novel glass-ceramics, Vita Mark II ceramic and freshly extracted human premolars were compared by means of drilling depth measurement. A three-point bending test was used to measure the flexural strength of the novel glass-ceramics. The crystalline phases of the group with the best machinability were identified by X-ray diffraction. In terms of the drilling depth, Group 2 of the novel glass-ceramics proves to have the largest drilling depth. There was no statistical difference among Group 1, Group 4 and the natural teeth. The drilling depth of Vita MK II was statistically less than that of Group 1, Group 4 and the natural teeth. Group 3 had the least drilling depth. In respect of the flexural strength, Group 2 exhibited the maximum flexural strength; Group 1 was statistically weaker than Group 2; there was no statistical difference between Group 3 and Group 4, and they were the weakest materials. XRD of Group 2 ceramic showed that a new type of dental machinable glass-ceramic containing calcium-mica had been developed by the present study and was named PMC. PMC is promising for application as a dental machinable ceramic due to its good machinability and relatively high strength.