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Sample records for preparing ceramic nitrides

  1. Preparation and dielectric properties of porous silicon nitride ceramics

    Institute of Scientific and Technical Information of China (English)

    LI Jun-qi; LUO Fa; ZHU Dong-mei; ZHOU Wan-cheng

    2006-01-01

    Porous silicon nitride ceramics with difference volume fractions of porosity from 34.1% to 59.2% were produced by adding different amount of the pore-forming agent into initial silicon nitride powder. The microwave dielectric property of these ceramics at a frequency of 9.36 GHz was studied. The crystalline phases of the samples were determined by X-ray diffraction analysis. The influence of porosity on the dielectric properties was evaluated. The results show that α-Si3N4 crystalline phase exists in all the samples while the main crystalline phase of the samples is β-Si3N4,indicating that the a/b transformation happens during the preparation of samples and the transformation is incomplete. There is a dense matrix containing large pores and cavities with needle-shaped and flaky β-Si3N4 grains distributing. The dielectric constant of the ceramics reduces with the increase of porosity.

  2. Low-Cost Preparation of Boron Nitride Ceramic Powders

    Institute of Scientific and Technical Information of China (English)

    LI Duan; ZHANG Changrui; LI Bin; CAO Feng; WANG Siqing; LIU Kun; FANG Zhenyu

    2012-01-01

    The amorphous boron nitride ceramic powders were prepared at 750-950 ℃ by the lowcost urea route,and the effects of preparation temperatures,molar ratios of the raw materials and oxidation treatment on the composition,structure and surface morphology of the products were investigated through FTIR,XRD and SEM.The results show that the products ceramize and crystallize gradually with the increase of the temperature.When the molar ratio and reaction temperature are 3:2 and 850 ℃,respectively,the products have high purity,compact structure and nice shape.The oxidation treatment at 450 ℃ will not impair the composition and structure of boron nitfide but effectively remove the impurities.

  3. Preparation and Properties of Macroporous Silicon Nitride Ceramics by Gelcasting and Carbonthermal Reaction

    Institute of Scientific and Technical Information of China (English)

    Wen ZHANG; Hongjie WANG; Zhihao JIN

    2005-01-01

    Macroporous silicon nitride (Si3N4) ceramics with high strength, uniform structure and relatively high porosity were obtained by gelcasting and carbonthermal reaction in a two-step sintering technique. Microstructure and composition were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction(XRD). Open porosity, pore size distribution and basic mechanical performance were measured by Archimedes method,mercury intrusion porosimetry and three-point bending methods, respectively. SEM and TEM results revealed that pores were formed by elongated β-Si3N4. SADP measurement proved the formation of SiC particles. The SiC granules were beneficial for the formation of high ratio elongated β-Si3N4, and at proper amount, they also acted as reinforcement phase. Thermodynamic analysis indicated that the mechanisms of the reactions were mainly associated with liquid-solid reaction and gas-liquid reaction.

  4. Reticulated porous silicon nitride-based ceramics

    OpenAIRE

    Mazzocchi, Mauro; Medri, Valentina; Guicciardi, Stefano

    2012-01-01

    The interest towards the production of porous silicon nitride originates from the unique combination of light weight, of mechanical and physical properties typical of this class of ceramics that make them attractive for many engineering applications. Although pores are generally believed to deteriorate the mechanical properties of ceramics (the strength of porous ceramics decreases exponentially with an increase of porosity), the recent literature reports that porous silicon nitride can exhib...

  5. 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.

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

    Institute of Scientific and Technical Information of China (English)

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

    2016-01-01

    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 aver-age 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.

  7. Preparation and Application of Silicon Nitride Ceramics%氮化硅陶瓷的制备与应用

    Institute of Scientific and Technical Information of China (English)

    孙亚光; 贺胜利; 刘荣安; 金昊; 杨文龙; 张宇航

    2016-01-01

    论述了氮化硅陶瓷在航天军工、机械工程、超细研磨、轴承制造、汽车配件等领域的应用,对氮化硅陶瓷的生产技术发展与市场应用进行了分析,展望了我国氮化硅行业的发展方向。%The wide applications of silicon nitride ceramics to the aerospace and defense industry, mechanic engineering, superifne grinding, bearing manufacturing, automotive parts, etc are introduced, the development of their production technology and their market are analyzed, and their industrial trends are China are predicted.

  8. Development of high-thermal-conductivity silicon nitride ceramics

    Directory of Open Access Journals (Sweden)

    You Zhou

    2015-09-01

    Full Text Available Silicon nitride (Si3N4 with high thermal conductivity has emerged as one of the most promising substrate materials for the next-generation power devices. This paper gives an overview on recent developments in preparing high-thermal-conductivity Si3N4 by a sintering of reaction-bonded silicon nitride (SRBSN method. Due to the reduction of lattice oxygen content, the SRBSN ceramics could attain substantially higher thermal conductivities than the Si3N4 ceramics prepared by the conventional gas-pressure sintering of silicon nitride (SSN method. Thermal conductivity could further be improved through increasing the β/α phase ratio during nitridation and enhancing grain growth during post-sintering. Studies on fracture resistance behaviors of the SRBSN ceramics revealed that they possessed high fracture toughness and exhibited obvious R-curve behaviors. Using the SRBSN method, a Si3N4 with a record-high thermal conductivity of 177 Wm−1K−1 and a fracture toughness of 11.2 MPa m1/2 was developed. Studies on the influences of two typical metallic impurity elements, Fe and Al, on thermal conductivities of the SRBSN ceramics revealed that the tolerable content limits for the two impurities were different. While 1 wt% of impurity Fe hardly degraded thermal conductivity, only 0.01 wt% of Al caused large decrease in thermal conductivity.

  9. Silicon nitride ceramic having high fatigue life and high toughness

    Science.gov (United States)

    Yeckley, Russell L.

    1996-01-01

    A sintered silicon nitride ceramic comprising between about 0.6 mol % and about 3.2 mol % rare earth as rare earth oxide, and between about 85 w/o and about 95 w/o beta silicon nitride grains, wherein at least about 20% of the beta silicon nitride grains have a thickness of greater than about 1 micron.

  10. Synthesis of boron nitride from boron containing poly(vinyl alcohol) as ceramic precursor

    Indian Academy of Sciences (India)

    M Das; S Ghatak

    2012-02-01

    A ceramic precursor, prepared by condensation reaction from poly(vinyl alcohol) (PVA) and boric acid (H3BO3) in 1:1, 2:1 and 4:1 molar ratios, was synthesized as low temperature synthesis route for boron nitride ceramic. Samples were pyrolyzed at 850°C in nitrogen atmosphere followed by characterization using Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD).

  11. Microstructure of Spark Plasma-Sintered Silicon Nitride Ceramics

    Science.gov (United States)

    Lukianova, O. A.; Novikov, V. Yu.; Parkhomenko, A. A.; Sirota, V. V.; Krasilnikov, V. V.

    2017-04-01

    The microstructure and phase composition of the high-content Al2O3-Y2O3-doped spark plasma-sintered silicon nitride were investigated. Fully dense silicon nitride ceramics with a typical α-Si3N4 equiaxed structure with average grain size from 200 to 530 nm, high elastic modulus of 288 GPa, and high hardness of 2038 HV were spark plasma sintered (SPSed) at 1550 °C. Silicon nitride with elongated β-Si3N4 grains, higher hardness of 1800 HV, density of 3.25 g/cm3, and Young's modulus 300 GPa SPSed at 1650 °C was also reviewed.

  12. Continuous Fiber Ceramic Composite (CFCC) Program: Gaseous Nitridation

    Energy Technology Data Exchange (ETDEWEB)

    R. Suplinskas G. DiBona; W. Grant

    2001-10-29

    Textron has developed a mature process for the fabrication of continuous fiber ceramic composite (CFCC) tubes for application in the aluminum processing and casting industry. The major milestones in this project are System Composition; Matrix Formulation; Preform Fabrication; Nitridation; Material Characterization; Component Evaluation

  13. Interface Structure and Atomic Bonding Characteristics in Silicon Nitride Ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Ziegler, A; Idrobo, J C; Cinibulk, M K; Kisielowski, C; Browning, N D; Ritchie, R O

    2004-10-12

    This investigation examines the interface atomic structure and bonding characteristics in an advanced ceramic, obtaining new and unique experimental information that will help to understand and improve the properties of ceramics. Unique direct atomic resolution images have been obtained that illustrate how a range of rare-earth atoms bond to the interface between the intergranular phase and the matrix grains in an advanced silicon nitride ceramic. It has been found that each rare-earth atom bonds to the interface at a different location, depending on atom size, electronic configuration and the presence of oxygen at the interface. This is the key factor to understanding the origin of the mechanical properties in these ceramics and will enable precise tailoring in the future to critically improve the materials performance in wide-ranging applications.

  14. Fabrication of hexagonal boron nitride based ceramics by combustion synthesis

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Pure h-BN (hexagonal boron nitride) and h-BN based ceramic parts were fabricated by combustion synthesis technique, i.e. self-propagating high-temperature synthesis (SHS). Components were manufactured by the combustion reaction of 80  MPa nitrogen and the compact made by cool isostatic pressing. In h-BN based ceramic parts, h-BN powder was used as diluent and SiO2 powder as reinforcing phase. The density of pure h-BN and h-BN-based ceramic parts were 58% and 78% of theoretical density, respectively. With XRD and SEM, phases and microstructures of ceramic parts were analyzed. Mechanical properties were also tested.

  15. Preparation of Bauxite Ceramic Microsphere

    Institute of Scientific and Technical Information of China (English)

    CHENG Xiaosu; LIU Pingan; LI Xiuyan; SHUI Anze; ZENG Lingke

    2007-01-01

    Ceramic microspheres were prepared by using Chinese bauxite as raw materials through the centrifugal spray drying method. The control technology of microsphere size, degree of sphericity was researched. The ceramic microspheres were sintered by a double sintering process. The microstructure and composition of ceramic microsphere were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray energy spectroscopy. The results show that the degree of sphericity of the ceramic microsphere was good and the particle size was 10-100 μm. The XRD analysis reveals that the main crystalline phase of the ceramic microsphere was α- Al2O3 and mullite (3Al2O3·2SiO2). The product can be used as reinforced material for composite material, especially for antiskid and hard wearing aluminum alloy coating.

  16. Development of the microstructure of the silicon nitride based ceramics

    Directory of Open Access Journals (Sweden)

    Bressiani J.C.

    1999-01-01

    Full Text Available Basic regularities of silicon nitride based materials microstructure formation and development in interrelation with processing conditions, type of sintering additives, and starting powders properties are discussed. Models of abnormal or exaggerated grain growth are critically reassessed. Results of several model experiments conducted in order to determine the most important factors directing the microstructure formation processes in RE-fluxed Si3N4 ceramics are reviewed. Existing data on the mechanisms governing the microstructure development of Si3N4-based ceramics are analyzed and several principles of microstructure tailoring are formulated.

  17. Method for preparing ceramic composite

    Science.gov (United States)

    Alexander, Kathleen B.; Tiegs, Terry N.; Becher, Paul F.; Waters, Shirley B.

    1996-01-01

    A process for preparing ceramic composite comprising blending TiC particulates, Al.sub.2 O.sub.3 particulates and nickle aluminide and consolidating the mixture at a temperature and pressure sufficient to produce a densified ceramic composite having fracture toughness equal to or greater than 7 MPa m.sup.1/2, a hardness equal to or greater than 18 GPa.

  18. Preparation and characteristics of porous ceramics

    Institute of Scientific and Technical Information of China (English)

    Dongmei SHAO; Peiping ZHANG; Liyan MA; Juanjuan LIU

    2007-01-01

    Pyrophyllite is always used for making porous ceramics. In order to design the preparation technics of porous ceramics with pyrophyllite reasonably we must know the classifications, characteristics, properties and applications of porous ceramics. The classification and characteristics of porous ceramics are reviewed in this article; and several common preparations with their advantages and disadvantages are also introduced. The authors discussed the problems existing in researching and developing process for porous ceramics, and forecasted the development prospect of porous ceramics.

  19. Solvothermal synthesis: a new route for preparing nitrides

    CERN Document Server

    Demazeau, G; Denis, A; Largeteau, A

    2002-01-01

    Solvothermal synthesis appears to be an interesting route for preparing nitrides such as gallium nitride and aluminium nitride, using ammonia as solvent. A nitriding additive is used to perform the reaction and, in the case of gallium nitride, is encapsulated by melt gallium. The syntheses are performed in the temperature range 400-800 deg. C and in the pressure range 100-200 MPa. The synthesized powders are characterized by x-ray diffraction and scanning electron microscopy. Finely divided gallium nitride GaN and aluminium nitride AlN, both with wurtzite-type structure, can be obtained by this route.

  20. 三维打印结合反应烧结制备多孔氮化硅陶瓷%Porous Silicon Nitride Ceramics Prepared by 3D Printing and Reaction Sintering

    Institute of Scientific and Technical Information of China (English)

    翁作海; 曾庆丰; 谢聪伟; 彭军辉; 张瑾

    2013-01-01

    Using silicon powder as starting material and dextrin as binder, porous silicon green body was prepared via 3D printing technology, and then highly porous silicon nitride ceramic was obtained by reaction sintering. The influence of sintering process on the property of the 3DP porous Si3N4 was investigated. The results show that, when the silicon green body was prepared by the 3D printer followed by the step-by-step heating process, porous Si3N4 ceramic with flexural strength of (5. 1 + 0. 3) MPa and porosity of (74. 3 + 0. 6) % was obtained. After reaction sintering, the linear shrinkages of the samples were smaller than 2. 0%. Ceramic parts with complex shapes can be ma-nufactured by such hybrid 3DP and reaction sintering technology with free-form and near-net-shape features.%以硅粉(Si)为起始原料,糊精为粘结剂,采用三维打印(3DP)快速成型技术制备出多孔硅坯体,通过反应烧结得到高孔隙率的氮化硅(Si3N4)陶瓷.研究了反应烧结工艺对3DP多孔Si3N4陶瓷性能的影响.结果表明:3DP成型的硅坯体采用阶梯式升温机制,可得到抗弯强度为(5.1±0.3)MPa,孔隙率达(74.3±0.6)%的多孔Si3 N4陶瓷.反应烧结后,样品的线收缩率小于2.O%.三维打印结合反应烧结法实现了复杂形状陶瓷构件的无模制造与净尺寸成型.

  1. Preparation and characterization of porous Si3N4 ceramics prepared by compression molding and slip casting methods

    Indian Academy of Sciences (India)

    Yu Fangli; Wang Huanrui; Bai Yu; Yang Jianfeng

    2010-10-01

    Porous silicon nitride (Si3N4) ceramics were fabricated by compression molding and slip casting methods using petroleum coke as pore forming agent, and Y2O3–Al2O3 as sintering additives. Microstructure, mechanical properties and gas permeability of porous Si3N4 ceramics were investigated. The mechanical properties and microstructure of porous Si3N4 ceramics prepared by compression molding were better than those which were prepared by slip casting method, whereas slip casting method is suitable for the preparation of porous Si3N4 ceramics with higher porosity and excellent gas permeability.

  2. Ceramic veneers with minimum preparation.

    Science.gov (United States)

    da Cunha, Leonardo Fernandes; Reis, Rachelle; Santana, Lino; Romanini, Jose Carlos; Carvalho, Ricardo Marins; Furuse, Adilson Yoshio

    2013-10-01

    The aim of this article is to describe the possibility of improving dental esthetics with low-thickness glass ceramics without major tooth preparation for patients with small to moderate anterior dental wear and little discoloration. For this purpose, a carefully defined treatment planning and a good communication between the clinician and the dental technician helped to maximize enamel preservation, and offered a good treatment option. Moreover, besides restoring esthetics, the restorative treatment also improved the function of the anterior guidance. It can be concluded that the conservative use of minimum thickness ceramic laminate veneers may provide satisfactory esthetic outcomes while preserving the dental structure.

  3. Ceramic processing of boron nitride insulators

    Energy Technology Data Exchange (ETDEWEB)

    Morgan, C. S.; McCulloch, R. W.

    1977-01-01

    Fuel pin simulators (FPS) are the prime elements of several test facilities at the Oak Ridge National Laboratory (ORNL). These experimental facilities are used to conduct out-of-reactor thermal-hydraulic and mechanical interaction safety tests for both light-water and breeder reactor programs. The FPS units simulate the geometry, heat flux profiles, and operational capabilities of a reactor core element under steady-state and transient conditions. They are subjected to temperatures as high as 1600/sup 0/C (2900/sup 0/F) and power levels as high as 57.5 kW/m (17.5 kW/ft) as well as severe thermal stresses during transient tests. The insulating material in the narrow annulus between the heating coil and the FPS sheath is subjected to very rigorous conditions. Accuracy of the reactor safety test information and validity of the test data depend on the heat flux uniformity under all test conditions and on the reliable operation of all fuel pin simulators and their internal thermocouples. Boron nitride (BN), because of its high degree of chemical inertness combined with its relatively unique properties of high thermal conductivity and low electrical conductivity, is the most suitable insulating material for FPS. The important BN properties, thermal conductivity and electrical resistance, are strongly influenced by crystallite orientation and by impurities. The article describes new BN powder processing techniques, which optimize these properties.

  4. Ceramic veneers with minimum preparation

    OpenAIRE

    da Cunha, Leonardo Fernandes; Reis, Rachelle; Santana, Lino; Romanini, Jose Carlos; de CARVALHO, Ricardo Marins; Furuse, Adilson Yoshio

    2013-01-01

    The aim of this article is to describe the possibility of improving dental esthetics with low-thickness glass ceramics without major tooth preparation for patients with small to moderate anterior dental wear and little discoloration. For this purpose, a carefully defined treatment planning and a good communication between the clinician and the dental technician helped to maximize enamel preservation, and offered a good treatment option. Moreover, besides restoring esthetics, the restorative t...

  5. Sintering of silicon nitride ceramics with magnesium silicon nitride and yttrium oxide as sintering aids

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, J; Xu, J Y [Shanghai Institute of Technology, Shanghai 200235 (China); Peng, G H [Guangxi Normal University, Guilin 541004, Guangxi (China); Zhuang, H R; Li, W L; Xu, S Y [Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China); Mao, Y J, E-mail: guojianjiang@sit.edu.cn [Shanghai University, Shanghai 200444 (China)

    2011-10-29

    Silicon nitride (Si{sub 3}N{sub 4}) ceramics had been produced through pressureless sintering and hot-pressing sintering with MgSiN{sub 2}-Y{sub 2}O{sub 3} or only MgSiN{sub 2} as sintering aids. The influences of the amount of MgSiN{sub 2} and Y{sub 2}O{sub 3} and sintering methods on the properties of Si{sub 3}N{sub 4} ceramics were investigated. The results show that the bend strength of Si{sub 3}N{sub 4} ceramic fabricated through pressureless sintering at 1820 deg. C for 4 h with 5.6 wt.% MgSiN{sub 2}-15.8 wt.% Y{sub 2}O{sub 3} as sintering additive could achieve 839 MPa. However, the bend strength of Si{sub 3}N{sub 4} ceramic produced by hot-pressing sintering at 1750 deg. C for 1 h under uniaxial pressure of 20 MPa with 4.76 wt.% MgSiN{sub 2} was 1149 MPa. The thermal conductivity of the Si{sub 3}N{sub 4} ceramic 2 3 4 could reach to 129 W{center_dot}m{sup -1{center_dot}}K{sup 1}. The present work demonstrated that MgSiN{sub 2} aids and hot-pressing sintering were effective to improve the thermal conductivity of Si{sub 3}N{sub 4} ceramic.

  6. Indentation fatigue in silicon nitride, alumina and silicon carbide ceramics

    Indian Academy of Sciences (India)

    A K Mukhopadhyay

    2001-04-01

    Repeated indentation fatigue (RIF) experiments conducted on the same spot of different structural ceramics viz. a hot pressed silicon nitride (HPSN), sintered alumina of two different grain sizes viz. 1 m and 25 m, and a sintered silicon carbide (SSiC) are reported. The RIF experiments were conducted using a Vicker’s microhardness tester at various loads in the range 1–20 N. Subsequently, the gradual evolution of the damage was characterized using an optical microscope in conjunction with the image analysing technique. The materials were classified in the order of the decreasing resistance against repeated indentation fatigue at the highest applied load of 20 N. It was further shown that there was a strong influence of grain size on the development of resistance against repeated indentation fatigue on the same spot. Finally, the poor performance of the sintered silicon carbide was found out to be linked to its previous thermal history.

  7. Freeze granulation for the processing of silicon nitride ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Lyckfeldt, O. [Swedish Ceramic Inst., Goeteborg (Sweden); Rundgren, K. [Permascand AB, Ljungaverk (Sweden); Sjoestedt, M. [PowderPro HB, Hisings Backa (Sweden)

    2004-07-01

    Freeze granulation (LS-2, PowderPro HB, Sweden) has been demonstrated as a favourable alternative to conventional granulation methods (spray drying, sieve granulation etc) in the production of granules for the pressing of high-performance ceramic powders. Freeze granulation/freeze drying prevents the migration of pressing aids or particle fines to the granule surface, as is the case in spray drying. This ensures granule homogeneity and an easy breakdown of granules during pressing. This, in turn, results in defect minimisation and optimal conditions for the sintering and the development of the desired material properties. In this study silicon nitride materials have been produced using freeze granulation, pressing and sintering to validate the performance. Materials with competitive properties were manufactured based on medium-cost, direct-nitrided powders (SicoNide P95, Permascand AB, Sweden), various pressing and sintering aid compositions as well as various pressing and sintering schedules. MgO vs Fe{sub 2}O{sub 3} as sintering aid, PEG vs PVA as binder and higher pressure at the initial uniaxial pressing were found to promote the sintering performance. (orig.)

  8. Modelling structure and properties of amorphous silicon boron nitride ceramics

    Directory of Open Access Journals (Sweden)

    Johann Christian Schön

    2011-06-01

    Full Text Available Silicon boron nitride is the parent compound of a new class of high-temperature stable amorphous ceramics constituted of silicon, boron, nitrogen, and carbon, featuring a set of properties that is without precedent, and represents a prototypical random network based on chemical bonds of predominantly covalent character. In contrast to many other amorphous materials of technological interest, a-Si3B3N7 is not produced via glass formation, i.e. by quenching from a melt, the reason being that the binary components, BN and Si3N4, melt incongruently under standard conditions. Neither has it been possible to employ sintering of μm-size powders consisting of binary nitrides BN and Si3N4. Instead, one employs the so-called sol-gel route starting from single component precursors such as TADB ((SiCl3NH(BCl2. In order to determine the atomic structure of this material, it has proven necessary to simulate the actual synthesis route.Many of the exciting properties of these ceramics are closely connected to the details of their amorphous structure. To clarify this structure, it is necessary to employ not only experimental probes on many length scales (X-ray, neutron- and electron scattering; complex NMR experiments; IR- and Raman scattering, but also theoretical approaches. These address the actual synthesis route to a-Si3B3N7, the structural properties, the elastic and vibrational properties, aging and coarsening behaviour, thermal conductivity and the metastable phase diagram both for a-Si3B3N7 and possible silicon boron nitride phases with compositions different from Si3N4: BN = 1 : 3. Here, we present a short comprehensive overview over the insights gained using molecular dynamics and Monte Carlo simulations to explore the energy landscape of a-Si3B3N7, model the actual synthesis route and compute static and transport properties of a-Si3BN7.

  9. Experimental Research on Residual Stress in Surface of Silicon Nitride Ceramic Balls

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The influence of the residual stress in surface of ceramic balls on the fatigue life is large, because the life of silicon nitride ball bearings is more sensitive to the load acted on the bearings than the life of all-steel ball bearings. In this paper, the influence of thermal stress produced in sintering and mechanical stress formed in lapping process on residual stress in surface of silicon nitride ceramic balls was discussed. The residual compress stress will be formed in the surface of silicon nitride ...

  10. Progress in preparation, properties and application of boron nitride nanomaterials

    Science.gov (United States)

    Wang, Youjun; Han, Jiaqi; Li, Yanjiao; Chen, Hao

    2017-08-01

    Boron nitride nanomaterials have attracted much and more interest in scientific research workers because of their excellent physical and chemical properties. They have become an important research hotspot in today's materials field. In this paper, boron nitride nanoparticles, "fullerenes", nanotubes, nanoribbons and Nano sheets were reviewed in terms of preparation methods, properties and potential applications.

  11. Use of additives to improve microstructures and fracture resistance of silicon nitride ceramics

    Science.gov (United States)

    Becher, Paul F.; Lin, Hua-Tay

    2011-06-28

    A high-strength, fracture-resistant silicon nitride ceramic material that includes about 5 to about 75 wt-% of elongated reinforcing grains of beta-silicon nitride, about 20 to about 95 wt-% of fine grains of beta-silicon nitride, wherein the fine grains have a major axis of less than about 1 micron; and about 1 to about 15 wt-% of an amorphous intergranular phase comprising Si, N, O, a rare earth element and a secondary densification element. The elongated reinforcing grains have an aspect ratio of 2:1 or greater and a major axis measuring about 1 micron or greater. The elongated reinforcing grains are essentially isotropically oriented within the ceramic microstructure. The silicon nitride ceramic exhibits a room temperature flexure strength of 1,000 MPa or greater and a fracture toughness of 9 MPa-m.sup.(1/2) or greater. The silicon nitride ceramic exhibits a peak strength of 800 MPa or greater at 1200 degrees C. Also included are methods of making silicon nitride ceramic materials which exhibit the described high flexure strength and fracture-resistant values.

  12. Precursors in the preparation of transition metal nitrides and transition metal carbonitrides and their reaction intermediates

    Science.gov (United States)

    Maya, Leon

    1991-01-01

    A process for making ammonolytic precursors to nitride and carbonitride ceramics. Extreme reaction conditions are not required and the precursor is a powder-like substance that produces ceramics of improved purity and morphology upon pyrolysis.

  13. Method of preparation of uranium nitride

    Science.gov (United States)

    Kiplinger, Jaqueline Loetsch; Thomson, Robert Kenneth James

    2013-07-09

    Method for producing terminal uranium nitride complexes comprising providing a suitable starting material comprising uranium; oxidizing the starting material with a suitable oxidant to produce one or more uranium(IV)-azide complexes; and, sufficiently irradiating the uranium(IV)-azide complexes to produce the terminal uranium nitride complexes.

  14. Application of Silicon Nitride (Si3N4) Ceramics in Ball Bearing

    OpenAIRE

    2016-01-01

    This paper is discus about silicon nitride ceramics in application to ball bearing. Silicon nitride (Si3N4) have advance properties such as consistent at temperature operation up to 1000°C, greater thermal shock resistance, lower density and low thermal expansion. This properties gives some benefit for ball bearing material such as higher running speed, reduce vibration of the shaft, will improve the life time and maintenance cost, lower heat generated, less energy consumption, lower wear ...

  15. Preparation and properties of dental zirconia ceramics

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Y2O3-stabilized tetragonal zireonia polyerystalline (Y-TZP) ceramics with high-performance were prepared for dental application by use of the micro-emulsion and two-step sintering method.The crystal phase,morphology,and microstructure of the reaction products were characterized by X-ray diffraction (XRD),scanning electron microscopy (SEM),and transmission electron microscopy (TEM).XRD results show that the ceramics mainly consist of tetragonal zirconia.Physical and mechanical properties test results show that the bending strength,fracture toughness,and the density of full sintered Y-TZP ceramics are llS0 MPa,5.53 crown machined with this material by CAD/CAM system exhibits a verisimilitude configuration and the material's expansion coefficient well matches that of the glaze.These results further indicate that the product can be used as a promising new ceramic material

  16. Reaction hot-pressing and property-composition relationships of modified sialon - boron nitride hetero-modulus ceramics

    Science.gov (United States)

    Wang, Y.; Shabalin, I. L.; Zhang, L.; Zhdanov, V. B.

    2011-10-01

    Hetero-modulus ceramics (HMC) present the combination of a ceramic matrix with inclusions of a dispersed phase with considerably lower values of Young's modulus, resulting in a material with significantly advanced properties. Densified '-Si6-xAlxOxN8-x based HMC materials, with various volume contents of low-modulus α-BN phase and modifiers such as TiN or ZrO2 in sialon matrix, were prepared by high-temperature reaction hot-pressing in nitrogen atmosphere. The pristine blend composition for reaction hot-pressing consisted of mixed fine powders of Si, Al, B, Ti nitrides and Al, Zr oxides. Statistical design of 25-2 fractional factorial and third-order simplex-grid types was used for the experimental studies to estimate the effects of some technological factors on the densification of hot-pressed products and the property-composition relationships of modified HMC materials.

  17. Thermal Effect of Ceramic Nanofiller Aluminium Nitride on Polyethylene Properties

    Directory of Open Access Journals (Sweden)

    Omer Bin Sohail

    2012-01-01

    Full Text Available Ethylene polymerization was done to form polyethylene nano-composite with nanoaluminum nitride using zirconocene catalysts. Results show that the catalytic activity is maximum at a filler loading of 15 mg nanoaluminum nitride. Differential scanning calorimeter (DSC and X-ray diffraction (XRD results show that percentage crystallinity was also marginally higher at this amount of filler. Thermal behavior of polyethylene nanocomposites (0, 15, 30, and 45 mg was studied by DSC and thermal gravimetric analyzer (TGA. Morphology of the component with 15 mg aluminium nitride is more fibrous as compared to 0 mg aluminium nitride and higher filler loading as shown by SEM images. In order to understand combustibility behavior, tests were performed on microcalorimeter. Its results showed decrease in combustibility in polyethylene nanocomposites as the filler loading increases.

  18. Preparation of Crystallized Carbon Nitride Based on Microwave Plasma CVD

    National Research Council Canada - National Science Library

    Masatoshi INOUE; Yukihiro SAKAMOTO; Matsufumi TAKAYA

    2010-01-01

    ... on. To obtain this material, generally CH4 is used as a carbon source. Therefore, to make clear the effects of the reaction gas on the preparation of carbon nitride, we tried to use C2H4 as a carbon source instead of CH4...

  19. PREPARATION OF HIGH PURITY MULLITE CERAMICS

    OpenAIRE

    Rodrigo, P.; Boch, P.

    1986-01-01

    Preparation of mullite ceramics by reaction-sintering of alumina silica shows the necessity of favoring densification over mullitisation. Different Al2O3/SiO2 ratios have been studied. The influence of additives, iron oxide and zirconium oxide, has been examined.

  20. Preparation and Instability of Nanocrystalline Cuprous Nitride.

    Science.gov (United States)

    Reichert, Malinda D; White, Miles A; Thompson, Michelle J; Miller, Gordon J; Vela, Javier

    2015-07-06

    Low-dimensional cuprous nitride (Cu3N) was synthesized by nitridation (ammonolysis) of cuprous oxide (Cu2O) nanocrystals using either ammonia (NH3) or urea (H2NCONH2) as the nitrogen source. The resulting nanocrystalline Cu3N spontaneously decomposes to nanocrystalline CuO in the presence of both water and oxygen from air at room temperature. Ammonia was produced in 60% chemical yield during Cu3N decomposition, as measured using the colorimetric indophenol method. Because Cu3N decomposition requires H2O and produces substoichiometric amounts of NH3, we conclude that this reaction proceeds through a complex stoichiometry that involves the concomitant release of both N2 and NH3. This is a thermodynamically unfavorable outcome, strongly indicating that H2O (and thus NH3 production) facilitate the kinetics of the reaction by lowering the energy barrier for Cu3N decomposition. The three different Cu2O, Cu3N, and CuO nanocrystalline phases were characterized by a combination of optical absorption, powder X-ray diffraction, transmission electron microscopy, and electronic density of states obtained from electronic structure calculations on the bulk solids. The relative ease of interconversion between these interesting and inexpensive materials bears possible implications for catalytic and optoelectronic applications.

  1. Fabrication of silicon nitride nanoceramics—Powder preparation and sintering: A review

    Directory of Open Access Journals (Sweden)

    Toshiyuki Nishimura et al

    2007-01-01

    Full Text Available Fine-grained silicon nitride ceramics were investigated mainly for their high-strain-rate plasticity. The preparation and densification of fine silicon nitride powder were reviewed. Commercial sub-micrometer powder was used as raw powder in the "as-received" state and then used after being ground and undergoing classification operation. Chemical vapor deposition and plasma processes were used for fabricating nanopowder because a further reduction in grain size caused by grinding had limitations. More recently, nanopowder has also been obtained by high-energy milling. This process in principle is the same as conventional planetary milling. For densification, primarily hot pressing was performed, although a similar process known as spark plasma sintering (SPS has also recently been used. One of the advantages of SPS is its high heating rate. The high heating rate is advantageous because it reduces sintering time, achieving densification without grain growth. We prepared silicon nitride nanopowder by high-energy milling and then obtained nanoceramics by densifying the nanopowder by SPS.

  2. 含硅聚硼氮烷裂解转化制备氮化硼陶瓷纤维%Preparation of Boron Nitride Ceramic Fibers by Pyrolysis of Silicon-containing Polyborazine

    Institute of Scientific and Technical Information of China (English)

    李文华; 王军; 谢征芳; 王浩; 唐云

    2012-01-01

    以低活性含硅聚硼氮烷为先驱体,经熔融纺丝,BCl3脱硅不熔化处理以及在氨气气氛中高温裂解制备的氮化硼纤维仍含有硅元素,这主要是含硅聚硼氮烷结构中的B-N(SiMe3)2和B-N(SiMe3)-B由于位阻与BCl3反应脱除SiMe3不完全所致.而采用HCl首先与含硅聚硼氮烷反应减少其位阻,再通过BCl3进一步脱硅不熔化处理制备的氮化硼陶瓷纤维经FT-IR、X射线衍射(XRD)分析表明纤维基本不含硅元素,并且扫描电子显微镜(SEM)表明得到的氮化硼陶瓷纤维直径约为11μm,断面致密无孔,室温下抗拉强度为0.45 GPa.%ilicon still exists in boron nitride(BN) ceramic fibers which were prepared by melt-spinning,curing with BCl3 and pyrolysis under NH3 of a preceramic silicon-containing polyborazine.That is because B-N(SiMe3)2 and B-N(SiMe3)-B could not react with BCl3 completely for the steric hindrance.So HCl was used to react with silicon-containing polyborazine first to reduce its steric hindrance.Then,BCl3 reacted with silicon-containing polyborazine to remove the residual SiMe3.After pyrolysis under NH3,BN ceramic fibers without silicon were obtained which was proved by FT-IR and X-ray diffraction.The obtained BN ceramic fibers with diameter of about 11 μm were dense which was demonstrated by scanning electron mi-croscopy(SEM) and the fibers showed room temperature mechanical property with average tensile strength of 0.45 GPa.

  3. Preparation of carbon-nitride bulk samples in the presence of seed carbon-nitride films

    Energy Technology Data Exchange (ETDEWEB)

    Kim, J. I. [Korea University of Technology and Education, Chonan (Korea, Republic of); Zorov, N. B. [Moscow State University, Moscow (Russian Federation)

    2004-05-15

    A procedure was developed for preparing bulk carbon-nitride crystals from polymeric alpha-C{sub 3}N{sub 4.2} at high pressure and high temperature in the presence of seeds of crystalline carbon-nitride films prepared by using a high-voltage discharge plasma combined with pulsed laser ablation of a graphite target. The samples were evaluated by using X-ray photoelectron spectroscopy (XPS), infrared (IR) spectroscopy, Auger electron spectroscopy (AES), secondary-ion mass spectrometry (SIMS), scanning electron microscopy (SEM) and X-ray diffraction (XRD). Notably, XPS studies of the film composition before and after thermobaric treatments demonstrated that the nitrogen composition in the alpha-C{sub 3}N{sub 4.2} material, which initially contained more than 58 % nitrogen, decreased during the annealing process and reached a common, stable composition of approx 45 %. The thermobaric experiments were performed at 10 - 77 kbar and 350 - 1200 .deg. C.

  4. Light element ceramics

    OpenAIRE

    Rao, KJ; Varma, KBR; Raju, AR

    1988-01-01

    An overview of a few structually important light element ceramics is presented. Included in the overview are silicon nitide, sialon, aluminium nitride, boron carbide and silicon carbide. Methods of preparation, characterization and industrial applications of these ceramics are summarized. Mechanical properties, industrial production techniques and principal uses of these ceramics are emphasized.

  5. Application of Silicon Nitride (Si3N4 Ceramics in Ball Bearing

    Directory of Open Access Journals (Sweden)

    Wijianto Wijianto

    2016-08-01

    operation up to 1000°C, greater thermal shock resistance, lower density and low thermal expansion. This properties gives some benefit for ball bearing material such as higher running speed, reduce vibration of the shaft, will improve the life time and maintenance cost, lower heat generated, less energy consumption, lower wear rate, reducing noise level and reduce of using lubricant. The sintering methods are used to produce ball bearing from silicon nitride. Some techniques can be applied to increase ceramics strength which are reduce porosity, reduce grain size, reduce surface flaw and proof stressing. The surface finishing of the ceramic bearing is very important because silicon nitride as a brittle material, its strength is limited to the flaw sizes especially the flaw at the surface.

  6. Waste conversion into high-value ceramics: Carbothermal nitridation synthesis of titanium nitride nanoparticles using automotive shredder waste.

    Science.gov (United States)

    Mayyas, Mohannad; Pahlevani, Farshid; Maroufi, Samane; Liu, Zhao; Sahajwalla, Veena

    2017-03-01

    Environmental concern about automotive shredder residue (ASR) has increased in recent years due to its harmful content of heavy metals. Although several approaches of ASR management have been suggested, these approaches remain commercially unproven. This study presents an alternative approach for ASR management where advanced materials can be generated as a by-product. In this approach, titanium nitride (TiN) has been thermally synthesized by nitriding pressed mixture of automotive shredder residue (ASR) and titanium oxide (TiO2). Interactions between TiO2 and ASR at non-isothermal conditions were primarily investigated using thermogravimetric analysis (TGA) and differential scanning calorimetry. Results indicated that TiO2 influences and catalyses degradation reactions of ASR, and the temperature, at which reduction starts, was determined around 980 °C. The interaction between TiO2 and ASR at isothermal conditions in the temperature range between 1200 and 1550 °C was also studied. The pressed mixture of both materials resulted in titanium nitride (TiN) ceramic at all given temperatures. Formation kinetics were extracted using several models for product layer diffusion-controlled solid-solid and solid-fluid reactions. The effect of reactants ratio and temperature on the degree of conversion and morphology was investigated. The effect of reactants ratio was found to have considerable effect on the morphology of the resulting material, while temperature had a lesser impact. Several unique structures of TiN (porous nanostructured, polycrystalline, micro-spherical and nano-sized structures) were obtained by simply tuning the ratio of TiO2 to ASR, and a product with appreciable TiN content of around 85% was achieved after only one hour nitridation at 1550 °C.

  7. Preparation of graphitic carbon nitride by electrodeposition

    Institute of Scientific and Technical Information of China (English)

    LI Chao; CAO Chuanbao; ZHU Hesun

    2003-01-01

    The CNx thin film was deposited on Si(100) substrate from a saturated acetone solution of cyanuric trichloride and melamine (cyanuric trichloride/melamine=1︰1.5) at room temperature. X-ray diffraction (XRD) results showed that the diffraction peaks in the pattern coincided well with those of graphite-like carbon nitride calculated in the literature. The lattice constants (a=4.79 A, c=6.90 A) for g-C3N4 matched with those of ab initio calculations (a=4.74 A, c=6.72 A) quite well. X-ray photoelectron spectroscopy (XPS) measurements indicated that the elements in the deposited films were mostly of C and N (N/C=0.75), and N (400.00 eV) bonded with C (287.72 eV) in the form of six-member C3N3 ring. The peaks at 800 cm-1, 1310 cm-1 and 1610 cm-1 in the Fourier transform infrared (FTIR) spectrum indicated that triazine ring existed in the product. These results demonstrated that crystalline g-C3N4 was obtained in the CNx film.

  8. Numerical Simulation of Ballistic Impact of Layered Aluminum Nitride Ceramic

    Science.gov (United States)

    2015-09-01

    configuration simulated in this work duplicates that examined in experiments of Yadav and Ravichandran.1 As shown in Fig. 1a, a WHA (tungsten heavy alloy... WHA ) 157 c aJohnson GR, Holmquist TJ, Beissel SR. Response of aluminum nitride (including a phase change) to large strains, high strain rates, and...results cannot be isolated in the present set of simulations, but possibilities include the following: the WHA material may be weaker than that

  9. Effect of Grinding and Polishing on the Residual Stress and Bending Strength of a Silicon Nitride Ceramic

    Institute of Scientific and Technical Information of China (English)

    GAO Ling; YANG Haitao; DU Daming; ZHAO Shikun; LI Huaping; YUAN Runzhang

    2005-01-01

    The residual stresses on the surface of the differently ground and polished silicon nitride ceramics were measured using X-ray diffraction and identified by SEM.The effect of the residual stress on the bending strength was investigated.The investigations show that the grinding process can introduce subatantial tensile residual stresses up to 290MPa on the surface of silicon nitride ceramics,which has a significant effect on reducing the bending strength of the ceramics after grinding.Thus,in comparison with the ceramics with a rough surface,the ceramics with a mirror image surface may have a lower strength.Polishing can smooth the residual stresses.When we evaluate the quality of the ceramic components after grinding,we must take residual stress into consideration. The grinding methods and grinding conditions must be carefully selected in order to get the favorite residual stress as well as the surface smoothness.

  10. Preparation and Characterization of Yb - doped YAG Ceramics

    OpenAIRE

    2011-01-01

    Rare-earth doped yttrium aluminum garnet (YAG) ceramics are among the most widely produced transparent ceramics for laser applications. Yb:YAG ceramics are an interesting IR laser material [1], which allows significantly higher doping compared to the generally more used Nd:YAG [2,3]. This work presents the preparation of polycrystalline Yb:YAG ceramics with dopant concentration from 0 up to 20 at.% via solid state reactive sintering. Samples were prepared via cold isostatic pressing of spray ...

  11. Polymer-Derived Boron Nitride: A Review on the Chemistry, Shaping and Ceramic Conversion of Borazine Derivatives

    Directory of Open Access Journals (Sweden)

    Samuel Bernard

    2014-11-01

    Full Text Available Boron nitride (BN is a III-V compound which is the focus of important research since its discovery in the early 19th century. BN is electronic to carbon and thus, in the same way that carbon exists as graphite, BN exists in the hexagonal phase. The latter offers an unusual combination of properties that cannot be found in any other ceramics. However, these properties closely depend on the synthesis processes. This review states the recent developments in the preparation of BN through the chemistry, shaping and ceramic conversion of borazine derivatives. This concept denoted as Polymer-Derived Ceramics (PDCs route allows tailoring the chemistry of precursors to elaborate complex BN shapes which cannot be obtained by conventional process. The effect of the chemistry of the molecular precursors, i.e., borazine and trichloroborazine, and their polymeric derivatives i.e., polyborazylene and poly[tri(methylaminoborazine], in which the specific functional groups and structural motifs determine the shaping potential by conventional liquid-phase process and plastic-forming techniques is discussed. Nanotubes, nano-fibers, coatings, monoliths and fiber-reinforced matrix composites are especially described. This leads to materials which are of significant engineering interest.

  12. Studies of aluminium nitride ceramics for application in UV dosimetry

    DEFF Research Database (Denmark)

    Trinkler, L.; Bøtter-Jensen, L.; Christensen, P.

    2000-01-01

    The study is reported of the ceramic material AlN-Y2O3 as a potential luminescence dosemeter for the detection of UV radiation. Both the thermoluminescence and the optically stimulated luminescence properties of the material have been studied after exposure to UV radiation and compared with those...... of the widely used dosemeter material Al2O3:C. It has been shown that AlN-Y2O3 ceramics exhibit three orders of magnitude higher sensitivity to UV radiation than does Al2O3,:C over a broad spectral region. The thermoluminescence from AlN-Y2O3 is characterised by linear dose dependence over a wide range...

  13. Chemical interaction silicon nitride ceramics and iron alloys

    Directory of Open Access Journals (Sweden)

    Oliveira, F. J.

    2000-12-01

    Full Text Available Metal/ceramic diffusion experiments are helpful to study bonding mechanisms or the effect of metal composition on the chemical wear of ceramic cutting tools. The reaction kinetics of Fe alloys/Si3 N4 ceramic diffusion couples was investigated in the temperature range 1050ºC-1250ºC, for 0.5h to 80h, under inert atmosphere. Optical microscopy, SEM and EPMA were carried out in cross sections of the reacted pairs. Si3N4 decomposes into Si and N that dissolve and diffuse through the metal. Both the diffusion zone on the metal side and the reaction zone on the ceramic side obey parabolic growth laws of time, with activation energies in the range Q=310-460kJmol-1. The amount of dissolved Si, the length of the diffusion zone and thus the reactivity of the ceramic increase as the alloy carbon content decreases. Due to Si accumulation, the α-Fe solid solution is stabilised at the reaction temperature and a steep decrease in the Si concentration is observed beyond the diffusion zone. The reinforcement of the Si3N4 composites with A12O3 platelets enhances the chemical resistance of the ceramic due to the inertness of this oxide and to the partial crystallisation of the intergranular phase. Other dispersoids such as HfN, BN and TiN do not improve the chemical resistance of the matrix by iron attack.

    Los experimentos de difusión metal/cerámica permiten estudiar mecanismos de unión y analizar el efecto de la composición del metal en el desgaste químico de herramientas de corte cerámicas. En este trabajo se investigó la cinética de reacción en pares de difusión aleaciones de Fe/Si3N4 a temperaturas entre 1050ºC-1250ºC, tiempos entre 0.5h a 80h, en atmósfera inerte. Las secciones transversales de los pares de difusión se analizaron mediante microscopía óptica, SEM y microsonda electrónica. El Si3N4 se descompone en Si y N que se disuelven y difunden en el metal. Tanto la zona de difusión en el metal como la zona de reacción en la cer

  14. 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.

  15. Hard carbon nitride and method for preparing same

    Science.gov (United States)

    Haller, E.E.; Cohen, M.L.; Hansen, W.L.

    1992-05-05

    Novel crystalline [alpha](silicon nitride-like)-carbon nitride and [beta](silicon nitride-like)-carbon nitride are formed by sputtering carbon in the presence of a nitrogen atmosphere onto a single crystal germanium or silicon, respectively, substrate. 1 figure.

  16. Static tensile and tensile creep testing of four boron nitride coated ceramic fibers at elevated temperatures

    Science.gov (United States)

    Coguill, Scott L.; Adams, Donald F.; Zimmerman, Richard S.

    1989-01-01

    Six types of uncoated ceramic fibers were static tensile and tensile creep tested at various elevated temperatures. Three types of boron nitride coated fibers were also tested. Room temperature static tensile tests were initially performed on all fibers, at gage lengths of 1, 2, and 4 inches, to determine the magnitude of end effects from the gripping system used. Tests at one elevated temperature, at gage lengths of 8 and 10 inches, were also conducted, to determine end effects at elevated temperatures. Fiber cross sectional shapes and areas were determined using scanning electron microscopy. Creep testing was typically performed for 4 hours, in an air atmosphere.

  17. Reaction hot-pressing and property-composition relationships of modified sialon - boron nitride hetero-modulus ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Y; Shabalin, I L [Materials and Physics Research Centre, University of Salford, Salford, Greater Manchester, M5 4WT (United Kingdom); Zhang, L [Department of Ceramic and Glass Engineering, CICECO, University of Aveiro, Aveiro 3810-193 (Portugal); Zhdanov, V B, E-mail: i.shabalin@salford.ac.uk [Department of Less-Common Metals, Ural State Technical University, Yekaterinburg 620002 (Russian Federation)

    2011-10-29

    Hetero-modulus ceramics (HMC) present the combination of a ceramic matrix with inclusions of a dispersed phase with considerably lower values of Young's modulus, resulting in a material with significantly advanced properties. Densified '-Si{sub 6-x}Al{sub x}O{sub x}N{sub 8-x} based HMC materials, with various volume contents of low-modulus {alpha}-BN phase and modifiers such as TiN or ZrO{sub 2} in sialon matrix, were prepared by high-temperature reaction hot-pressing in nitrogen atmosphere. The pristine blend composition for reaction hot-pressing consisted of mixed fine powders of Si, Al, B, Ti nitrides and Al, Zr oxides. Statistical design of 2{sup 5-2} fractional factorial and third-order simplex-grid types was used for the experimental studies to estimate the effects of some technological factors on the densification of hot-pressed products and the property-composition relationships of modified HMC materials.

  18. Preparation and characteristic of NASICON ceramics

    Institute of Scientific and Technical Information of China (English)

    ZHU Dongmei; LUO Fa; XIE Zhanglong; ZHOU Wancheng

    2006-01-01

    Hot-pressed sintering was employed to prepare the sodium super ionic conductor (Na1+xZr2SixP3-xO12,1.8≤x≤2.2)ceramics and compare with the sample obtained from normal-press sintering. The phase formation, density, and conductivity of the hot-press sintered and the normal-press sintered samples were investigated in detail. Results show that the density of NASICON ceramics and the degree of crystallization can be improved by hot-press process efficiently. The density of the sample sintered by normal sintering is obviously lower than that sintered by hot press. XRD analysis indicates all the hot press sintered samples contain mainly monoclinic NASICON and no ZrO2 phase was found. The ionic conductivity of normal-press sintered sample is much lower than that of hot-press sintered sample. When the composition is close to Na3Zr2Si2PO12 , the dc conductivities of the hot press sintered samples were in the order of 10-3 S·cm-1.The variation of the ac conductivity with frequency in the high frequency region agrees with the power law feature of σ(ω) ∝ωn(0<n<1).

  19. A New Method for Preparation of Nanocrystalline Molybdenum Nitride

    Institute of Scientific and Technical Information of China (English)

    SHEN Long-Hai; CUI Qi-Liang; ZHANG Jian; LI Xue-Fei; ZHOU Qiang; ZOU Guang-Tian

    2005-01-01

    @@ Nanocrystalline molybdenum nitride (γ-Mo2N) with the cubic structure is prepared by the direct-current arc discharge method in N2 gas, using metal Mo or W rod as a cathode. The x-ray diffraction (XRD) and transmission electron microscopy (TEM) are used to characterize the product. It is found that the conversion of Mo to γ-Mo2N and affinity of Mo to N2 are determined by the nitrogen pressur e. Moreover, we compare the effect of Mo and W rod as a cathode for preparing γ-Mo2N. The average size of γ-Mo2N particles is about 5nm. The rapid quenching mechanism can be used to explain the formation of nanocrystalline γ-Mo2N.

  20. Control of interface fracture in silicon nitride ceramics: influence of different rare earth elements

    Energy Technology Data Exchange (ETDEWEB)

    Sun, E.Y.; Becher, P.F.; Waters, S.B.; Hsueh, Chun-Hway; Plucknett, K.P. [Oak Ridge National Lab., TN (United States); Hoffmann, M.J. [Karlsruhe Univ. (T.H.) (Germany). Inst. fuer Keramik im Maschinenbau

    1996-10-01

    The toughness of self-reinforced silicon nitride ceramics is improved by enhancing crack deflection and crack bridging mechanisms. Both mechanisms rely on the interfacial debonding process between the elongated {Beta}-Si{sub 3}N{sub 4} grains and the intergranular amorphous phases. The various sintering additives used for densification may influence the interfacial debonding process by modifying the thermal and mechanical properties of the intergranular glasses, which will result in different residual thermal expansion mismatch stresses; and the atomic bonding structure across the {Beta}-Si{sub 3}N{sub 4} glass interface. Earlier studies indicated that self-reinforced silicon nitrides sintered with different rare earth additives and/or different Y{sub 2}O{sub 3}:AI{sub 2}0{sub 3} ratios could exhibit different fracture behavior that varied from intergranular to transgranular fracture. No studies have been conducted to investigate the influence of sintering additives on the interfacial fracture in silicon nitride ceramics. Because of the complexity of the material system and the extremely small scale, it is difficult to conduct quantitative analyses on the chemistry and stress states of the intergranular glass phases and to relate the results to the bulk properties. The influence of different sintering additives on the interfacial fracture behavior is assessed using model systems in which {Beta}-Si{sub 3}N{sub 4}whiskers are embedded in SIAIRE (RE: rare-earth) oxynitride glasses. By systematically varying the glass composition, the role of various rare-earth additives on interfacial fracture has been examined. Specifically, four different additives were investigated: Al{sub 2}0{sub 3}, Y{sub 2}0{sub 3}, La{sub 2}O{sub 3}, and Yb{sub 2}O{sub 3}. In addition, applying the results from the model systems, the R- curve behavior of self-reinforced silicon nitride ceramics sintered with different Y{sub 2}0{sub 3}:AI{sub 2}0{sub 3} ratios was characterized.

  1. 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.

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

    Science.gov (United States)

    Singh, M.; Asthana, R.

    2009-01-01

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

  3. Preparation of nanocrystalline BaTiO3 ceramics

    Institute of Scientific and Technical Information of China (English)

    DENG XiangYun; LI DeJun; LI JianBao; WANG XiaoHui; LI LongTu

    2009-01-01

    The high-dense nanocrystalline BaTiO3 (BT) ceramics with grain size smaller than 100 nm have been successfully prepared by the two step sintering and the spark plasma sintering (SPS) process. The successive transitions in nanograin BT ceramics from rhombohedrel to orthorhombic, tetragonal and cubic transitions, similar to those in coarse BT ceramics, were revealed by in-situ temperature dependent Raman spectrum. The multiphase coexistence and the diffused phase transition character were demonstrated in the 8 nm nanocrystalline BT ceramics.

  4. Preparation and Chiral Selectivity of BSA-Modified Ceramic Membrane

    Institute of Scientific and Technical Information of China (English)

    Cai Lian SU; Rong Ji DAI; Bin TONG; Yu Lin DENG

    2006-01-01

    An affinity-transport system, containing porous ceramic membranes bound with bovine serum albumin (BSA) was used for chiral separation of racemic tryptophan. The preparation of BSA modified ceramic membrane included three steps. Firstly, the membrane was modified with amino group using silanization with an amino silane. Secondly, the amino group modified membrane was bound with aldehyde group using gluteraldehyde. Finally, BSA was covalently bound on the surface of the ceramic membrane. Efficient separation of racemic tryptophan was carried out by performing permeation cell experiments, with BSA modified, porous ceramic membranes.

  5. Preparation of nanocrystalline BaTiO3 ceramics

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    The high-dense nanocrystalline BaTiO3(BT)ceramics with grain size smaller than 100nm have been successfully prepared by the two step sintering and the spark plasma sintering(SPS)process.The successive transitions in nanograin BT ceramics from rhombohedral to orthorhombic,tetragonal and cubic transitions,similar to those in coarse BT ceramics,were revealed by in-situ temperature dependent Raman spectrum.The multiphase coexistence and the diffused phase transition character were demonstrated in the 8nm nanocrystalline BT ceramics.

  6. Preparation and characterization of boron nitride/carbon fiber composite with high specific surface area

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Yan; Fan, Mingwen [Wuhan Univ. (China). Key Laboratory for Oral Biomedical Engineering; Yuan, Songdong; Xiong, Kun; Hu, Kunpeng; Luo, Yi [Hubei Univ. of Technology, Wuhan (China). School of Chemistry and Chemical Engineering; Li, Dong [Hubei Univ. of Technology, Wuhan (China). School of Chemistry and Chemical Engineering; Oxford Univ. (United Kingdom). Chemistry Research Lab.

    2014-06-15

    Boron nitride can be used as a good catalyst carrier because of its high thermal conductivity and chemical stability. However, a high specific surface area of boron nitride is still desirable. In this work, a carbon fiber composite coated with boron nitride villous nano-film was prepared, and was also characterized by means of scanning electron microscopy, high resolution transmission electron microscopy, Fourier transform infrared spectroscopy, and Brunauer-Emmett-Teller analysis. The results indicated that the carbon fibers were covered by uniform villous boron nitride films whose thickness was about 150 - 200 nm. The specific surface area of the boron nitride/carbon fiber composite material was 96 m{sup 2} g{sup -1}, which was markedly improved compared with conventional boron nitride materials. (orig.)

  7. Atomic resolution transmission electron microscopy of the intergranular structure of a Y{sub 2}O{sub 3}-silicon nitride ceramic

    Energy Technology Data Exchange (ETDEWEB)

    Ziegler, A.; Kisielowski, C.; Hoffmann, M.J.; Ritchie, R.O.

    2002-05-01

    High-resolution transmission electron microscopy (HRTEM) employing focus-variation phase-reconstruction methods is used to image the atomic structure of grain boundaries in a silicon nitride ceramic at a resolution of 0.8 Angstrom

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

    Science.gov (United States)

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

    2013-07-01

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

  9. Ablation and radar-wave transmission performances of the nitride ceramic matrix composites

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The 2.5 dimensional silica fiber reinforced nitride matrix composites (2.5D SiO2f/Si3N4-BN) were prepared through the preceramic polymer impregnation pyro- lysis (PIP) method. The ablation and radar-wave transparent performances of the composite at high temperature were evaluated under arc jet. The composition and ablation surface microstructures were studied by X-ray diffraction (XRD) and scanning electron microscope (SEM). The results show that the 2.5D SiO2f/Si3N4-BN composites have a linear ablation rate of 0.33 mm/s and high radar-wave trans- parent ratio of 98.6%. The fused layer and the matrix are protected by each other, and no fused layer accumulates on the ablation surface. The nitride composite is a high-temperature ablation resistivity and microwave transparent material.

  10. Ablation and radar-wave transmission performances of the nitride ceramic matrix composites

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The 2.5 dimensional silica fiber reinforced nitride matrix composites (2.5D SiO2f/Si3N4-BN) were prepared through the preceramic polymer impregnation pyrolysis (PIP) method. The ablation and radar-wave transparent performances of the composite at high temperature were evaluated under arc jet. The composition and ablation surface microstructures were studied by X-ray diffraction (XRD) and scanning electron microscope (SEM). The results show that the 2.5D SiO2f/Si3N4-BN composites have a linear ablation rate of 0.33 mm/s and high radar-wave transparent ratio of 98.6%. The fused layer and the matrix are protected by each other, and no fused layer accumulates on the ablation surface. The nitride composite is a high-temperature ablation resistivity and microwave transparent material.

  11. Preparation of High Strength Silicon Nitride Ceramic Fibers From Polycarbosilane Fibers byγ-Ray Irradiation and Thermal Cross-Linking%γ辐照联合热交联聚碳硅烷先驱丝热解制备高强度氮化硅陶瓷纤维

    Institute of Scientific and Technical Information of China (English)

    黎阳; 高家诚; 许云书

    2014-01-01

    在空气气氛中采用γ射线辐照处理聚碳硅烷(PCS)先驱丝,辐照先驱丝经 Ar中热交联、NH3中热解氨化、N2中高温氮化处理制备了氮化硅陶瓷纤维。研究了热交联处理对辐照先驱丝化学结构、凝胶含量、氨化陶瓷产率、抗拉强度、微观形貌及氧含量的影响。结果表明:热交联处理生成了 Si—CH2—Si 和 Si—O—Si 桥连结构,桥连结构使PCS先驱丝实现凝胶化;热交联处理不仅大幅提高了辐照 PCS先驱丝的氨化陶瓷产率,还提高了热解所得氮化硅陶瓷纤维的抗拉强度,而且还降低了陶瓷纤维的氧含量;吸收剂量为1.0 MGy的辐照丝经热交联处理后,其热解所得氮化硅陶瓷纤维抗拉强度达2.05 GPa,氧质量分数仅为9.5%。%Polycarbosilane (PCS)precursor fibers were irradiated byγ-ray in air.Silicon nitride ceramic fibers were obtained from the irradiated PCS fibers by process of thermal cross-linking treatment in Ar,ammoniation pyrolysis in NH3 and high temperature nitriding treatment in N2 .The effects of thermal cross-linking treatment on chemical structure,gel content,ammoniation ceramic yield,tensile strength,microstructure and oxygen content were studied.The results show that bridge structures of Si—CH2—Si and Si—O—Si are formed in the PCS fibers by thermal cross-linking treatment and make the PCS fibers become gelling.The ammoniation ceramic yield of the irradiated PCS fibers increases sharply after thermal cross-linking treatment.The tensile strength of the silicon nitride ceramic fibers increases sharply, while the oxygen content decreases. After thermal cross-linking treatment,the tensile strength of the silicon nitride ceramic fibers derived from the PCS fibers with absorbed dose of 1.0 MGy reaches 2.05 GPa and the oxygen mass fraction is 9.5%.

  12. Improved photoluminescence of silicon nanocrystals in silicon nitride prepared by ammonia sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Ma, K; Feng, J Y; Zhang, Z J [Department of Materials Science and Engineering, Key Laboratory of Advanced Materials, Tsinghua University, Beijing 100084 (China)

    2006-09-28

    In the present work we investigated the photoluminescence property of silicon nanocrystals in silicon nitride prepared by ammonia sputtering. Silicon nanocrystals were demonstrated to form even after thermal annealing at 700 deg. C. Compared with the control sample using N{sub 2} as the reactive gas, the luminescence intensity of silicon nanocrystals in silicon nitride prepared by NH{sub 3} sputtering was greatly increased. The improvement in photoluminescence was attributed to the introduction of hydrogen-related bonds, which could well passivate the nonradiative defects existing at the interface between silicon nanocrystals and the silicon nitride matrix.

  13. Fuzzy sets predict flexural strength and density of silicon nitride ceramics

    Science.gov (United States)

    Cios, Krzysztof J.; Sztandera, Leszek M.; Baaklini, George Y.; Vary, Alex

    1993-01-01

    In this work, we utilize fuzzy sets theory to evaluate and make predictions of flexural strength and density of NASA 6Y silicon nitride ceramic. Processing variables of milling time, sintering time, and sintering nitrogen pressure are used as an input to the fuzzy system. Flexural strength and density are the output parameters of the system. Data from 273 Si3N4 modulus of rupture bars tested at room temperature and 135 bars tested at 1370 C are used in this study. Generalized mean operator and Hamming distance are utilized to build the fuzzy predictive model. The maximum test error for density does not exceed 3.3 percent, and for flexural strength 7.1 percent, as compared with the errors of 1.72 percent and 11.34 percent obtained by using neural networks, respectively. These results demonstrate that fuzzy sets theory can be incorporated into the process of designing materials, such as ceramics, especially for assessing more complex relationships between the processing variables and parameters, like strength, which are governed by randomness of manufacturing processes.

  14. Preparation of Ultra-fine Aluminum Nitride in Thermal Plasma

    Institute of Scientific and Technical Information of China (English)

    漆继红; 罗义文; 印永祥; 代晓雁

    2002-01-01

    Ultra-fine aluminum nitride has been synthesized by the evaporation of aluminum powder at atmospheric-pressure nitrogen plasma in a hot-wall reactor. The average size of aluminum nitride particle is 0.11μm measured by scanning electric mirror (SEM), and the purity is at least over 90% evaluated by X-Ray diffraction (XRD). The conversion of Al powder to aluminum nitride is strongly depended on the injection of NH3. Typical experimental parameters such as the feed rate of raw material, the flow rate of ammonia and the position of injecting aluminum powder into the reactor are given.

  15. Preparation and Structure of Rainbow Piezoelectric Ceramics

    Institute of Scientific and Technical Information of China (English)

    SHEN Xing

    2003-01-01

    Rainbow piezoelectric ceramics are a new type of stress-biased, oxide-reduced composite ferroelectric ceramics, which have a special dome structure. The have shown excellent properties such as ultra-high displacement under an applied electric field and enhanced load-bearing capability. In this article, their manufacture,structures and properties were discussed in detail by combining experiments and theory analysis. The resuts show that the optimal conditions for producing Rainbow samples from PLZT ceramics were determined to be 900℃ for 1 to 1.5 hours. A number of different phases have been found in the reduced layer of Rainbow ceramics by XRD analyses . The phases found include metallic lead and other oxide phases , such cs PbO , ZrO2 and TiO2 . The original PLZT phase was not observed. The reduced layer was transgranularly fractured while the unreduced ceramic was intergranularly fractured. Two kinds of fracture types can be seen at the interface , which denotes the different degrees of reduction. It is shown that the Pb grains ( about 0.2 μm ) constitute a continuous phase in the reduced layer, which accounts for the good electrical condnctivity.

  16. Preparation of Glass Ceramic Based on Granulated Slag and Cullet

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The glass-ceramic was prepared on the basis of materials of granulated slag containing high-calcium oxide and cullet.The content of granulated slag ranges from 50%-60%wt in the glass compositions. The samples were analyzed by DTA, SEM and XRD.The results show that the main crystal phase of the glass-ceramic is β-CaSiO3,Which is in scattering fiber or column form.The applying properties have also been measured.

  17. Liquid Phase Sintering (LPS) and Dielectric Constant of α-Silicon Nitride Ceramic

    Institute of Scientific and Technical Information of China (English)

    CHEN Changlian; CHEN Fei; SHEN Qiang; ZHANG Lianmeng; YAN Faqiang

    2006-01-01

    The spark plasma sintering (SPS) was applied to prepare α-Si3N4 ceramics of different densities with magnesia, silicon dioxide, alumina as the sintering aids. The mechanism of liquid phase sintering (LPS) was discussed and the factors influencing the density of the prepared samples were analyzed. The dielectric constant of sintered samples was tested. The experimental results show that the density can be controlled from 2.48 g/cm3 to 3.09 g/cm3 while the content of the sintering aids and the sintering temperature alter and the dielectric constant is closely dependent on the density of obtained samples.

  18. Preparation and Microstructure of Bauxite-Based Sialon by Reduction Nitridation

    Institute of Scientific and Technical Information of China (English)

    ZHANG Haijun; LIU Zhanjie; ZHONG Xiangchong

    2004-01-01

    The phase compostition and microstructure of Sialon prepared from Chinese bauxite have been studied.The use of Si powder is more effective than that of activated carbon for reduction-nitridation.For bauxite specimens with 40~50% Si addition,more than 90% of Sialon may be obtained when nitrided at 1450~1500℃;the main crystalline phase is O'-Sialon(Z=0.2).

  19. Influence of additive system (Al2O3-RE2O3 , RE = Y, La, Nd, Dy, Yb on microstructure and mechanical properties of silicon nitride-based ceramics

    Directory of Open Access Journals (Sweden)

    Juliana Marchi

    2009-06-01

    Full Text Available Silicon nitride based ceramics have been widely used as structural ceramics, due mainly to their thermo-mechanical properties such as high density, high thermal shock resistance, corrosion resistance and chemical stability. The aim of this study was to determine the influence of rare earth and aluminum oxide additions as sintering aids on densification, microstructure and mechanical properties of silicon nitride. Silicon nitride mixtures with 91 wt. (% Si3N4 and 9% wt. (% additives were prepared and sintered. The density, microstructure and mechanical properties of the sintered specimens of these mixtures were determined. In most specimens, scanning electron microscopic examination and X ray diffraction analysis revealed elongated grains of β-Si3N4 with aspect ratio of about 2.0 and dispersed in a glassy phase. The density of the sintered specimens was higher than 94% of the theoretical density (td and specimens with La2O3 and Al2O3 additions exhibited the highest value. The results of this investigation indicate that the rare earth ion size influences densification of silicon nitride, but this correlation was not observed in specimens containing two different rare earth oxides. The hardness values varied in direct proportion to the density of the specimens and the fracture toughness values were influenced by the composition of the intergranular glassy phase.

  20. The preparation of high-adsorption, spherical, hexagonal boron nitride by template method

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Ning, E-mail: zhangning5832@163.com; Liu, Huan; Kan, Hongmin; Wang, Xiaoyang; Long, Haibo; Zhou, Yonghui

    2014-11-15

    Highlights: • The high-adsorption, spherical, hexagonal boron nitride powders were prepared. • The influence mechanism of template content on the micro-morphology and adsorption was explored. • At appropriate synthesis temperature, higher adsorption mesoporous spheres h-BN began to form. - Abstract: This research used low-cost boric acid and borax as a source of boron, urea as a nitrogen source, dodecyl-trimethyl ammonium chloride (DTAC) as a template, and thus prepared different micro-morphology hexagonal boron nitride powders under a flowing ammonia atmosphere at different nitriding temperatures. The effects of the template content and nitriding temperature on the micro-morphology of hexagonal boron nitride were studied and the formation mechanism analysed. The influences of the template content and nitriding temperature on adsorption performance were also explored. The results showed that at a nitriding temperature of 675 °C, the micro-morphologies of h-BN powder were orderly, inhomogeneous spherical, uniform spherical, beam, and pie-like with increasing template content. The micro-morphology was inhomogeneous spherical at a DTAC dose of 7.5%. The micro-morphology was uniform spherical at a DTAC dose of 10%. At a DTAC dose of 12%, the micro-morphology was a mixture of beam and pie-like shapes. At a certain template content (DTAC at 10%) and at lower nitriding temperatures (625 °C and 650 °C), spherical shell structures with surface subsidence began to form. The porous spheres would appear at a nitriding temperature of 675 °C, and the ball diameter thus formed was approximately 500–600 nm. The ball diameter was about 600–700 nm when the nitriding temperature was 700 °C. At a nitriding temperature of 725 °C, the ball diameter was between 800 and 1000 nm and sintering necking started to form. When the relative pressure was higher, previously closed pores opened and connected with the outside world: the adsorption then increased significantly. The

  1. Preparation, Characterization and Performance of Conch Ceramics Added With Shell

    Directory of Open Access Journals (Sweden)

    Wang Qingyu

    2016-01-01

    Full Text Available The conch ceramics bodies with different ratios were prepared by compression moulding technology using shell, kaolin, and calcium oxide etc. as the raw materials, and then calcined at the high temperature to obtain the conch ceramics. The effects of raw material ratios and calcination temperatures on the performance of conch ceramics were investigated by rotational viscometer, vernier caliper, digital display whiteness meter, thermal analyzer, and Fourier transform infrared spectrometer(FT-IR. The results indicated that the viscosity, line shrinkage rate, and whiteness of the conch ceramics were 1.29 Pa·s, 17.9%, and 54.1%, respectively, when the content of the shell powder was 20 wt% and kaolin was 65 wt%. The density of the conch ceramics was the largest (3.8 g/cm3 when calcination temperature was 1200 °C. The results of FT-IR spectrum showed that the addition of the shell powders changed the structure of the ceramic body, which improved the performance of the conch ceramics.

  2. Influence of additives on anisotropic grain growth in silicon nitride ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Becher, P.F. [Metals and Ceramics Division, Oak Ridge National Laboratory, Oak Ridge, TN (United States)]. E-mail: becherpf@ornl.gov; Painter, G.S. [Metals and Ceramics Division, Oak Ridge National Laboratory, Oak Ridge, TN (United States); Shibata, N. [Institute for Engineering Innovation, University of Tokyo, Tokyo (Japan); Satet, R.L. [Institute for Ceramics in Mechanical Engineering, University of Karlsruhe, Karlsruhe (Germany); Hoffmann, M.J. [Institute for Ceramics in Mechanical Engineering, University of Karlsruhe, Karlsruhe (Germany); Pennycook, S.J. [Condensed Matter Science Division, Oak Ridge National Laboratory, Oak Ridge, TN (United States)

    2006-04-25

    Tailoring microstructure and composition are critical components for obtaining high-performance silicon nitride (Si{sub 3}N{sub 4}) ceramics. Anisotropic growth behavior of Si{sub 3}N{sub 4} grains can be used to form very elongated grains, which serve to reinforce the matrix analogous to whisker-reinforcement of ceramics. The Si{sub 3}N{sub 4} grain morphology is known to be very sensitive to the particular additive used, especially in the case of the oxides of the rare earths (RE) and Group III elements. However, the atomistic mechanisms by which this occurs has not been understood until now. A first-principles model, the differential binding energy, has been developed to characterize the competition between RE and Si for migrating to the {beta}-Si{sub 3}N{sub 4} grain surfaces. The theory predicts that, of the RE, La should have the strongest and Lu the weakest preferential segregation to the grain surfaces. Additional calculations define the adsorption sites and their binding strengths for each of the REs on the prismatic plane of the Si{sub 3}N{sub 4} grains. These predictions are confirmed by unique atomic-resolution images obtained by aberration-corrected Z-contrast scanning transmission electron microscopy (STEM). The combined theoretical and STEM studies reveal that the elements that induce the greatest observed grain anisotropy are those with the strongest preferential segregation plus high binding strength to the prismatic grain surface. Advances now allow one to use first principles calculations to determine the chemical affinity and bonding of the rare earths, as well as other elements, at the grain interfaces; atomistic factors that actually control the growth anisotropy as opposed to the commonly considered ion size, which at best, only provides a trend.

  3. Preparation of Porous Silica Ceramics with Low Dielectric Constant

    Institute of Scientific and Technical Information of China (English)

    MAO Xiao-jian; WANG Shi-wei; SHIMAI Shun-zo

    2006-01-01

    Porous silica ceramics has been prepared with the starch consolidation casting method. Slurries with various fractions of starch added in were prepared by ball-milling. The evaluation of the microstructures was done through two techniques: Hg porosimetry and SEM investigation. The bending strength of the sintered samples varied within the range of 10 MPa-20 MPa and the low dielectric constant within the range of 2.0-2.4 correspondent with the porosity of 42%-56%. The ceramics holds a brilliant promise of being a kind of core material used in sandwich-like electromagnetic windows.

  4. 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.

  5. Indentation strength of silicon nitride ceramics processed by spark plasma sintering technique

    Energy Technology Data Exchange (ETDEWEB)

    Azeggagh, N. [Université de Lyon, INSA-Lyon, LaMCoS CNRS UMR5259, F-69621 Villeurbanne (France); Université de Lyon, INSA-Lyon, MATEIS CNRS UMR5510, F-69621 Villeurbanne (France); Tohoku University, 6-6-11, Aza-Aoba, Aramaki, Aobaku, Sendai 980-8579 (Japan); Joly-Pottuz, L., E-mail: lucile.joly-pottuz@insa-lyon.fr [Université de Lyon, INSA-Lyon, MATEIS CNRS UMR5510, F-69621 Villeurbanne (France); Chevalier, J. [Université de Lyon, INSA-Lyon, MATEIS CNRS UMR5510, F-69621 Villeurbanne (France); Omori, M.; Hashida, T. [Tohoku University, 6-6-11, Aza-Aoba, Aramaki, Aobaku, Sendai 980-8579 (Japan); Nélias, D. [Université de Lyon, INSA-Lyon, LaMCoS CNRS UMR5259, F-69621 Villeurbanne (France)

    2015-09-17

    We investigated the influence of the microstructure on the true stress–strain curve of silicon nitride based ceramics. The materials were processed by spark plasma sintering technique. Si{sub 3}N{sub 4} with fine, average and coarse microstructures were obtained. Load versus displacement curves (P–h) were obtained by means of instrumented indentation technique using diamond coni-spherical tip. The experimental data were coupled with a minimization method based on the Levenberg–Marquardt algorithm and the non-linear part of the mechanical response was identified. Based on the obtained stress–strain curves, rolling contact simulations were performed. In addition, the nature of Hertzian contact damage was examined in the material with coarse microstructure using diamond indenters of radii 0.2 and 1 mm. The surface damage was observed under optical microscopy while Focused Ion Beam Sectioning technique permitted to image the subsurface damage. An evident size effect was noticed: fracture consisting of classical ring cracks dominated at large scale while distributed microcracks beneath the indent dominated at small scale.

  6. Preparation of porous hydroxyapatite ceramics with starch additives

    Institute of Scientific and Technical Information of China (English)

    YANG Lei; NING Xiao-shan; CHEN Ke-xin; XIAO Qun-fang; ZHOU He-ping

    2005-01-01

    Porous ceramics prepared from nano-sized hydroxyapatite powders by adding water soluble starch and insoluble starch were investigated. The results show that small pores of several micrometers or less can be produced by adding water soluble starch as a pore former. Two kinds of starch have different pore forming mechanisms. The permeability of the porous ceramics can be greatly improved by adding the insoluble starch to channel the small pores rather than solely using water soluble starch. The control of permeability can be achieved by adjusting the content ratio of water soluble starch to insoluble starch. Strength tests show the ceramics have rather high strength. Therefore a kind of porous filtering material with small pores, controllable permeability and good strength can be prepared by using starch additives.

  7. Effects of Phase Composition on Microstructure and Mechanical Properties of Lu2O3-doped Porous Silicon Nitride Ceramics

    Institute of Scientific and Technical Information of China (English)

    Quan Li; Xiaowei Yin

    2011-01-01

    Porous silicon nitride ceramics (Si3N4) were fabricated by pressureless sintering using different particle size of silicon nitride powder. Lu2O3 was used as sintering additive. According to phase relationships in the ternary system Si3N4-SiO2-Lu2O3, porous Si3N4 ceramics with different phase composition were designed through the change of the content of SiO2 which was formed by the oxidation at 800℃ in air. Porous Si3N4 with different phase compositions was obtained after sintering at 1800℃in N2atmosphere. A small content of SiO2 favored the formation of secondary phase Lu4Si2O7N2, while large content of SiO2 favored the formation of secondary phase Lu2Si2O7 and Si2N2O. Porous Si3N4 ceramics with secondary phase Lu4Si2O7N2 had a flexural strength of 207 MPa, while that with secondary phase Si2N2O and Lu2Si2O7 had lower flexural strength.

  8. Transparent ceramics and methods of preparation thereof

    Science.gov (United States)

    Hollingsworth, Joel P.; Kuntz, Joshua D.; Seeley, Zachary M.; Soules, Thomas F.

    2012-12-25

    A method for forming a transparent ceramic preform in one embodiment includes forming a suspension of oxide particles in a solvent, wherein the suspension includes a dispersant, with the proviso that the suspension does not include a gelling agent; and uniformly curing the suspension for forming a preform of gelled suspension. A method according to another embodiment includes creating a mixture of inorganic particles, a solvent and a dispersant, the inorganic particles having a mean diameter of less than about 2000 nm; agitating the mixture; adding the mixture to a mold; and curing the mixture in the mold for gelling the mixture, with the proviso that no gelling agent is added to the mixture.

  9. 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.

  10. Epitaxial ternary nitride thin films prepared by a chemical solution method

    Energy Technology Data Exchange (ETDEWEB)

    Luo, Hongmei [Los Alamos National Laboratory; Feldmann, David M [Los Alamos National Laboratory; Wang, Haiyan [TEXAS A& M; Bi, Zhenxing [TEXAS A& M

    2008-01-01

    It is indispensable to use thin films for many technological applications. This is the first report of epitaxial growth of ternary nitride AMN2 films. Epitaxial tetragonal SrTiN2 films have been successfully prepared by a chemical solution approach, polymer-assisted deposition. The structural, electrical, and optical properties of the films are also investigated.

  11. Chemical Structure of Carbon Nitride Films Prepared by MW-ECR Plasma Enhanced Magnetron Sputtering

    Institute of Scientific and Technical Information of China (English)

    XUJun,GAOPeng; DINGWan-yu; LIXin; DENGXin-lu; DONGChuang

    2004-01-01

    Amorphous carbon nitride thin films were prepared by plasma-enhanced DC magnetron sputtering using twinned microwave electron cyclotron resonance plasma sources. Chemical structure of deposited films was investigated using X-ray photoelectron spectroscopy and Fourier transtorm infrared spectroscopy. The results indicate that the deposition rate is strongly affected by direct current bias, and the films are mainly composed of a single amorphous carbon nitride phase with N/C ratio close to C3N4, and the bonding is predominantly of C-N type.

  12. Preparation and properties of unidirectional boron nitride fibre reinforced boron nitride matrix composites via precursor infiltration and pyrolysis route

    Energy Technology Data Exchange (ETDEWEB)

    Li Duan, E-mail: whataboutduan@gmail.com [State Key Laboratory of Advanced Ceramic Fibres and Composites, College of Aerospace and Materials Engineering, National University of Defense Technology, Changsha 410073 (China); Zhang Changrui; Li Bin; Cao Feng; Wang Siqing; Li Junsheng [State Key Laboratory of Advanced Ceramic Fibres and Composites, College of Aerospace and Materials Engineering, National University of Defense Technology, Changsha 410073 (China)

    2011-10-25

    Highlights: {yields} BN fibres degrade little when exposed at elevated temperatures. {yields} Precursor infiltration and pyrolysis route is useful to prepare BNf/BN composites. {yields} Few reports have related to the preparation and properties of BNf/BN composites. {yields} BNf/BN composites have desirable high-temperature mechanical properties. {yields} BNf/BN composites have excellent dielectric properties at 2-18 GHz. - Abstract: The unidirectional boron nitride fibre reinforced boron nitride matrix (BN{sub f}/BN) composites were prepared via the precursor infiltration and pyrolysis (PIP) route, and the structure, composition, mechanical and dielectric properties were studied. The composites have a high content and fine crystallinity of BN. The density is 1.60 g cm{sup -3} with a low open porosity of 4.66%. The composites display good mechanical properties with the average flexural strength, elastic modulus and fracture toughness being 53.8 MPa, 20.8 GPa and 6.88 MPa m{sup 1/2}, respectively. Lots of long fibres pull-out from the fracture surface, suggesting a good fibre/matrix interface. As temperature increases, both of the flexural strength and elastic modulus exhibit a decreasing trend, with the lowest values being 36.2 MPa and 8.6 GPa at 1000 deg. C, respectively. The desirable residual ratios of the flexural strength and elastic modulus at 1000 deg. C are 67.3% and 41.3%, respectively. The composites have excellent dielectric properties, with the average dielectric constant and loss tangent being 3.07 and 0.0044 at 2-18 GHz, respectively.

  13. A new class of boron nitride fibers with tunable properties by combining an electrospinning process and the polymer-derived ceramics route.

    Science.gov (United States)

    Salles, Vincent; Bernard, Samuel; Brioude, Arnaud; Cornu, David; Miele, Philippe

    2010-02-01

    Novel boron nitride (BN) fibers have been developed with diameters ranging from the nano- to microscale by thermal conversion of as-electrospun fibers from polyacrylonitrile and poly[B-(methylamino)borazine] blend solutions. Such a new class of ceramic fibers is seen as potential candidate for thermal management applications and filtration systems in harsh environments.

  14. Preparation and Easy-Cleaning Property of Rare Earth Composite Ceramic

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Rare earth and far-infrared mineral composite materials were added to ceramic glazes to prepare easy-cleaning ceramic. The morphology of easy-cleaning ceramic was observed by SEM. The influence of easy-cleaning ceramic on water surface tension and contact angles of water were investigated. Through calculation of ceramic surface free energy and observation of oil drop on ceramic surface in water, the easy-cleaning mechanism of rare earth composite ceramic was studied. It is found that the rare earth composite ceramic can make water surface tension decrease. The surface free energy and the polar component of rare earth composite ceramic are increased. The rare earth composite ceramics have the easy-cleaning property.

  15. The all-ceramic, inlay supported fixed partial denture. Part 1. Ceramic inlay preparation design: a literature review.

    Science.gov (United States)

    Thompson, M C; Thompson, K M; Swain, M

    2010-06-01

    The effect of cavity design is a controversial and underrated factor in the clinical success of ceramic inlays and inlay supported prosthesis. Many articles and studies have been conducted into the advantages and disadvantages of isolated aspects of preparation design, but lacking is a review of the most relevant papers which bring together a consensus on all the critical features. Hence, a review and analysis of cavity depth, width, preparation taper and internal line angles is warranted in our attempts to formulate preparation guidelines that will lead to clinically successful, all-ceramic inlay restorations and ceramic inlay supported prosthesis.

  16. Compressive creep of silicon nitride with additives; Fluencia por compressao de nitreto de silicio aditivado

    Energy Technology Data Exchange (ETDEWEB)

    Shibuya, Newton Hissao; Cavalcanti, Celso Berilo Cidade; Piorino Neto, Francisco; Silva, Vitor Alexandre da; Silva, Cosme Roberto Moreira da [Centro Tecnico Aeroespacial (CTA), Sao Jose dos Campos, SP (Brazil). Inst. de Aeronautica e Espaco

    1995-12-31

    Manufacturing of engine and turbine components made of silicon nitride based ceramics requires knowledge of thermochemical properties such as resistance to compressive creep. In order to characterize this property a compressive creep apparatus was assembled at AMR/IAE/CTA, able to work at 1450 deg C in a continuous mode. Test pieces were prepared from mixtures of silicon nitride with rare earth carbonate and aluminium nitride. These test pieces were pressureless sintered at 1750 deg C for 30 minutes under nitrogen atmosphere. Experiments showed that rare earth carbonate and aluminium nitride are suitable additives for silicon nitride. (author) 1 fig., 2 tabs.

  17. Preparation of Ceramic-Bonded Carbon Block for Blast Furnace

    Science.gov (United States)

    Li, Yiwei; Li, Yawei; Sang, Shaobai; Chen, Xilai; Zhao, Lei; Li, Yuanbing; Li, Shujing

    2014-01-01

    Traditional carbon blocks for blast furnaces are mainly produced with electrically calcined anthracite owing to its good hot metal corrosion resistance. However, this kind of material shows low thermal conductivity and does not meet the demands for cooling of the hearth and the bottom of blast furnaces. In this article, a new kind of a high-performance carbon block has been prepared via ceramic-bonded carbon (CBC) technology in a coke bed at 1673 K (1400 °C) using artificial graphite aggregate, alumina, metallic aluminum, and silicon powders as starting materials. The results showed that artificial graphite aggregates were strongly bonded by the three-dimensional network of ceramic phases in carbon blocks. In this case, the good resistance of the CBC blocks against erosion/corrosion by the hot metal is provided by the ceramic matrix and the high thermal conductivity by the graphite aggregates. The microstructure of this carbon block resembles that of CBC composites with a mean pore size of less than 0.1 μm, and up to 90 pct of the porosity shows a pore size <1 μm. Its thermal conductivity is higher than 30 W · m-1 · K-1 [293 K (20 °C)]. Meanwhile, its hot metal corrosion resistance is better than that of traditional carbon blocks.

  18. Alumina ceramics prepared with new pore-forming agents

    Directory of Open Access Journals (Sweden)

    Zuzana Živcová

    2008-06-01

    Full Text Available Porous ceramics have a wide range of applications at all length scales, ranging from fi ltration membranes and catalyst supports to biomaterials (scaffolds for bone ingrowths and thermally or acoustically insulating bulk materials or coating layers. Organic pore-forming agents (PFAs of biological origin can be used to control porosity, pore size and pore shape. This work concerns the characterization and testing of several less common pore-forming agents (lycopodium, coffee, fl our and semolina, poppy seed, which are of potential interest from the viewpoint of size, shape or availability. The performance of these new PFAs is compared to that of starch, which has become a rather popular PFA for ceramics during the last decade. The PFAs investigated in this work are in the size range from 5 μm (rice starch to approximately 1 mm (poppy seed, all with more or less isometric shape. The burnout behavior of PFAs is studied by thermal analysis, i.e. thermogravimetry and differential thermal analysis. For the preparation of porous alumina ceramics from alumina suspensions containing PFAs traditional slip casting (into plaster molds and starch consolidation casting (using metal molds are used in this work. The resulting microstructures are investigated using optical microscopy, combined with image analysis, as well as other methods (Archimedes method of double-weighing in water, mercury intrusion porosimetry.

  19. Effects of rare earth oxide additives on the thermal behaviors of aluminum nitride ceramics

    Institute of Scientific and Technical Information of China (English)

    YAO Yijun; WANG Ling; LI Chuncheng; JIANG Xiaolong; QIU Tai

    2009-01-01

    The effects of Y_2O_3 and Er_2O_3 on the sintering behaviors, thermal properties and microstructure of AIN ceramics were investigated. The ex-perimental results show that the sintering temperature can be decreased; the relative density and thermal behavior can be improved by adding rare earth oxide in AIN ceramics. For AIN ceramics with 3 wt.% Er_2O_3 additive, the relative density is 98.8%, and the thermal conductivity reaches 106 W·m~(-1)·K~(-1). The microstructure research found that no obvious aluminum erbium oxide was found in AIN ceramics doped with 3 wt.% Er_2O_3, which favored the improvement of the thermal conductivity of AIN ceramics.

  20. Tantalum (oxy)nitrides: preparation, characterisation and enhancement of photo-Fenton-like degradation of atrazine under visible light.

    Science.gov (United States)

    Du, Yingxun; Zhao, Lu; Su, Yaling

    2011-11-15

    Tantalum (oxy)nitrides were prepared by the nitridation of Ta(2)O(5) and were added to a photo-Fenton-like system to enhance Fe(3+) reduction and atrazine degradation under visible light. The samples were characterized by XRD, XPS, DRS and BET analyses. XPS analysis showed that the nitrogen content of the tantalum (oxy)nitride samples increased noticeably with the nitridation temperature and nitridation time but slightly with the flow rate of NH(3). XRD results showed Ta(2)O(5) was first converted to TaON and then to Ta(3)N(5) when the nitridation temperature increased. DRS analysis showed that the sample obtained at 800°C displayed the strongest absorption of visible light. However, the ability of the tantalum (oxy)nitrides to reduce Fe(3+) did not increase continuously with the nitrogen content. Sample 7 (700°C, [Formula: see text] , 6h) showed the highest level of photocatalytic activity for Fe(3+) reduction. This is because the photocatalytic activity of TaON for Fe(3+) reduction is higher than that of Ta(3)N(5). And a slight synergetic effect was observed between TaON and Ta(3)N(5). With the addition of sample 7, H(2)O(2) decomposition and atrazine degradation were significantly accelerated in a photo-Fenton-like system under visible light. The regenerated tantalum (oxy)nitrides catalyst displayed considerably stable performance for atrazine degradation.

  1. Catalytic self-assembly preparation and characterization of carbon nitride nanotubes by a solvothermal method

    Institute of Scientific and Technical Information of China (English)

    HUANG Fuling; CAO Chuanbao; ZHU Hesun

    2005-01-01

    A solvothermal reaction of anhydrous C3N3Cl3 and sodium using cyclohexane as solvent and NiCl2 as catalyst precursor has been carried out to prepare carbon nitride nanotubes successfully at 230℃ and 1.8 MPa. The carbon nitride nanotubes were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), electron diffraction (ED), electron energy loss spectrum (EELS) and Raman spectrum. SEM and TEM results indicated that the tubes have a length of 20-30 μm, a uniform outer diameter of about 50-60 nm, an inner diameter of 30-40 nm and are highly ordered assembled as bundles. The EELS measurement indicated that the ratio of N/C was about 1.00. The ED and XRD analyses revealed that the tube may have a new CN crystalline structure. The growth mechanism of nanotubes was discussed.

  2. The production of silicon carbon nitride ceramic fibres from poly-silazane polymers. Herstellung von Siliciumcarbonitrid-Keramikfasern aus Polysilazan-Polymeren

    Energy Technology Data Exchange (ETDEWEB)

    Holzinger, R.

    1994-07-14

    The investigations carried out in this work can be divided into two main points. One, the process technique branch, goes along the polymer precursor route. This includes the melt spinning of the poly-silazane polymers, the stabilisation of the green fibres and finally pyrolysis to silicon-carbon nitride ceramic fibres. Starting from the polymers, all the reactions and structural changes during the individual steps are examined. These experiments represent the second main part of the work. The optimisation criterion is always the tensile strength of the resulting ceramic fibres. (orig.)

  3. A new class of boron nitride fibers with tunable properties by combining an electrospinning process and the polymer-derived ceramics route

    Science.gov (United States)

    Salles, Vincent; Bernard, Samuel; Brioude, Arnaud; Cornu, David; Miele, Philippe

    2010-02-01

    Novel boron nitride (BN) fibers have been developed with diameters ranging from the nano- to microscale by thermal conversion of as-electrospun fibers from polyacrylonitrile and poly[B-(methylamino)borazine] blend solutions. Such a new class of ceramic fibers is seen as potential candidate for thermal management applications and filtration systems in harsh environments.Novel boron nitride (BN) fibers have been developed with diameters ranging from the nano- to microscale by thermal conversion of as-electrospun fibers from polyacrylonitrile and poly[B-(methylamino)borazine] blend solutions. Such a new class of ceramic fibers is seen as potential candidate for thermal management applications and filtration systems in harsh environments. Electronic supplementary information (ESI) available: Experimental details and EDX results. See DOI: 10.1039/b9nr00185a

  4. Ceramic joining

    Energy Technology Data Exchange (ETDEWEB)

    Loehman, R.E. [Sandia National Lab., Albuquerque, NM (United States)

    1996-04-01

    This paper describes the relation between reactions at ceramic-metal interfaces and the development of strong interfacial bonds in ceramic joining. Studies on a number of systems are described, including silicon nitrides, aluminium nitrides, mullite, and aluminium oxides. Joints can be weakened by stresses such as thermal expansion mismatch. Ceramic joining is used in a variety of applications such as solid oxide fuel cells.

  5. Space-confined preparation of high surface area tungsten oxide and tungsten nitride inside the pores of mesoporous silica SBA-15

    DEFF Research Database (Denmark)

    Meyer, Simon; Beyer, Hans; Köhler, Klaus

    2015-01-01

    For the direct preparation of high surface area nitride materials, a lack of suitable precursors exists. Indirect preparation by gas phase nitridation (e.g. by ammonia) requires high temperatures and often results in sintering. The present work demonstrates that the space-confined preparation of ...

  6. Gallium nitride epitaxy on silicon: Importance of substrate preparation

    Energy Technology Data Exchange (ETDEWEB)

    Martin, G.A.; Sverdlov, B.N.; Botchkarev, A.; Morkoc, H.; Thompson, W.H.; Nayfeh, M.H. [Univ. of Illinois, Urbana, IL (United States); Smith, D.J.; Tsen, S.C.Y. [Arizona State Univ., Tempe, AZ (United States)

    1996-11-01

    Hexagonal GaN films grown on non-isomorphic substrates are usually characterized by numerous threading defects which are essentially boundaries between wurtzite GaN domains where the stacking sequences do not align. One origin of these defects is irregularities on the substrate surface such as surface steps. Using Si <111> substrates and a substrate preparation procedure that makes wide atomically flat terraces, the authors demonstrate that reduction of these irregularities greatly improves the crystalline and luminescent quality of GaN films grown by plasma-enhanced molecular beam epitaxy. X-ray rocking curve width decreases from over 1 degree to less than 20 minutes, while PL halfwidth decreases from over 15 meV to less than 10 meV.

  7. Engineering of silicon-based ceramic fibers: Novel SiTaC(O) ceramic fibers prepared from polytantalosilane

    Energy Technology Data Exchange (ETDEWEB)

    Xie, Z., E-mail: xiezhengfang@163.com [State Key Laboratory of Advanced Ceramic Fibers and Composites, National University of Defense Technology, Changsha 410073 (China); Cao, S.; Wang, J. [State Key Laboratory of Advanced Ceramic Fibers and Composites, National University of Defense Technology, Changsha 410073 (China); Yan, X. [State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); Bernard, S., E-mail: Samuel.Bernard@univ-lyon1.fr [Laboratoire des Multimateriaux et Interfaces (UMR CNRS 5615), Universite de Lyon, Universite Lyon1, 43 bd du 11 Novembre 1918, 69622 Villeurbanne Cedex (France); Miele, P. [Laboratoire des Multimateriaux et Interfaces (UMR CNRS 5615), Universite de Lyon, Universite Lyon1, 43 bd du 11 Novembre 1918, 69622 Villeurbanne Cedex (France)

    2010-10-15

    Research highlights: {yields} This paper reports the preparation and characterization of a novel variety of silicon-based ceramic fibers. {yields} In the present paper, we provide a detailed picture of the preparation process of SiTaC(O) ceramic fibers from a polytantalosilane. {yields} We have fully characterized the polymer by FT-IR, NMR, chemical composition, GPC and TGA as well as the chemical composition, the structure, the texture, and the mechanical properties of the ceramic fibers by XPS, SEM, X-ray diffraction (XRD), and mechanical tests. - Abstract: A novel variety of silicon-based ceramic fibers has been prepared from a preceramic organosilicon polymers called polytantalocarbosilane (PTaCS). This melt-spinnable polymer has been synthesized by thermally induced reactions between tantalum (V) tetraethoxyacetylacetonate (Ta(Acac)(OEt){sub 4}) and polysilacarbosilane (PSCS). The polymer in which [-Si-C-]{sub n} chains are crosslinked via Ta-containing bridges as identified by infrared spectroscopy, XPS and NMR, is decomposed in high ceramic yield (76%) and can be spun in the molten state into fibers to be cured in air then pyrolyzed in flowing nitrogen at 1200 deg. C into amorphous SiTaC(O) fibers. Complete characterization of this new generation of silicon-based ceramic fibers was made based on mechanical tests, XRD and SEM. These fibers exhibit relatively good mechanical properties and excellent high-temperature stability with good oxidation resistance.

  8. Ultramicro molybdenum nitride powder prepared using high-energy mechanochemical method

    Institute of Scientific and Technical Information of China (English)

    AN Geng; LIU Gaojie

    2008-01-01

    Using the specially designed mechanochemical ball-mill equipment, ultramicro molybdenum nitride powders were prepared from pure molybdenum powders in ammonia atmosphere at room temperature by high-energy ball milling. The structure and the particle size of the powders were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The results show that the mass ratio of grinding media to powder was 8:1, after milling for 30h the Mo2N of fcc structure was obtained, and the average particle size of the powders was around 100 nm. It is found that the chemisorption of ammonia onto the fresh molybdenum surfaces created by milling was the predominant process during solid-gas reaction, and the energy input due to introduction of highly dense grain boundaries and lattice defects offered the activation energy for the transition from Mo-N chemisorption to molybdenum nitride. In addition, the change of Mo electronic undersaturation induced by the grain refining accelerated the bonding between Mo and N. The mechanism model of whole nitriding reaction was given. During the high-energy ball milling processing, the rotational speed of milling played a critical role in determining the overall reaction speed.

  9. Preparation and Microstructure of Glass-ceramics and Ceramic Composite Materials

    Institute of Scientific and Technical Information of China (English)

    HE Feng; XIE Junlin; HAN Da

    2008-01-01

    The technology and microstructure of glass-ceramics and ceramic composite materials were studied.A suitable ceramic body was chosen on the basis of the sintering temperature of CaO-Al2O3-SiO2 system glass-ceramics.According to the expansion coefficient of the ceramic body,that of CaO-Al2O3-SiO2 system glass-ceramics was adjusted.a-wollastonite was found present as the major crystalline phase in glass-ceramic.The CaO-Al2O3-SiO2 system glass-ceramic layer and ceramic body could be sintered together by adjusting the sintering period.The compositions of glass-ceramic layer and ceramic body diffuse mutually at 1100℃.resulting in an interface between them.To achieve good sintered properties of glass-ceramics and the chosen ceramic body,at least a four-hour sintering time is used.

  10. Research Progress on Preparation for Biomass-based SiC Ceramic

    Directory of Open Access Journals (Sweden)

    CUI He-shuai

    2017-08-01

    Full Text Available Silicon carbide (SiC ceramics prepared by the conventional process has excellent properties and wide application prospects, but the increased cost of high-temperature preparation process restricts its further development. In contrast, the abundant porous structure of biomass makes itself to be ideal replacement of SiC ceramic prepared at low temperature. This paper reviewed the structure characteristics, preparation methods, pyrolysis mechanism and influence parameters of biomass-based SiC ceramic, and eventually explored the current problems and development trends of the pretreatment of carbon source and silicon source, the pyrolysis process and the application research on the preparation for biomass-based SiC ceramic.

  11. Experimental investigation of laser surface processing of flexure silicon nitride ceramic

    Institute of Scientific and Technical Information of China (English)

    SUN Li; A. P. MALSHE; JIANG Wen-ping; P. H. MCCLUSKEY

    2006-01-01

    A continuous wave carbon dioxide (CO2) laser (λ=10.6μm) was employed to treat the surface of Si3N4 MOR (modulus of rupture) bars. The effects of the CO2 laser process on physical and mechanical properties of ground Si3N4 samples were investigated. Scanning electron microscopy (SEM) analysis shows that the area occupied by cavities and fracture is decreased by about 49.4% after laser treatments. Cross-sectional metallography results indicate that the secondary YSiAlON phase in the Si3N4 ceramic is softened/melted and flowed into the defects. Four-point bending tests show that the flexural strength of the treated samples is improved to 10.9%. Fractographic analysis show that the fracture origins move from the surface to subsurface. It is concluded that laser surface processing have significant effects on fracture behavior of flexure Si3N4 ceramic.

  12. Modelling and analysis of CVD processes in porous media for ceramic composite preparation

    NARCIS (Netherlands)

    Lin, Y.S.; Burggraaf, A.J.

    1991-01-01

    A continuum phenomenological model is presented to describe chemical vapour deposition (CVD) of solid product inside porous substrate media for the preparation of reinforced ceramic-matrix composites [by the chemical vapour infiltration (CVI) process] and ceramic membrane composites (by a modified C

  13. Influence of sintering temperature on microstructure and properties of SiO{sub 2} ceramic incorporated with boron nitride nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Du Ming [Key Laboratory for Liquid-Solid Structure Evolution and Processing of Materials (Ministry of Education), Shandong University, Jinan 250061 (China); Engineering Ceramics Key Laboratory of Shandong Province, Shandong University, Jinan 250061 (China); Bi Jianqiang, E-mail: bjq1969@163.com [Key Laboratory for Liquid-Solid Structure Evolution and Processing of Materials (Ministry of Education), Shandong University, Jinan 250061 (China) and Engineering Ceramics Key Laboratory of Shandong Province, Shandong University, Jinan 250061 (China) and Faculty of Engineering, Department of Physics and Astronomy, and Nanoscience and Engineering Center, University of Georgia, Athens, GA 30602 (United States); Wang Weili; Sun Xiaolin; Long Nana [Key Laboratory for Liquid-Solid Structure Evolution and Processing of Materials (Ministry of Education), Shandong University, Jinan 250061 (China); Engineering Ceramics Key Laboratory of Shandong Province, Shandong University, Jinan 250061 (China)

    2012-05-01

    Highlights: Black-Right-Pointing-Pointer SiO{sub 2} matrix containing 5 wt% BNNTs was fabricated at 1300-1450 Degree-Sign C. Black-Right-Pointing-Pointer Microstructure and properties (mechanical and dielectric) were investigated. Black-Right-Pointing-Pointer The most superior mechanical and dielectric properties were attained at 1400 Degree-Sign C. - Abstract: Silica (SiO{sub 2}) ceramic containing 5 wt% boron nitride nanotubes (BNNTs) was fabricated by hot pressing at 1200-1450 Degree-Sign C. The influences of the sintering temperature on phase composition, relative density, microstructure and mechanical and dielectric properties were investigated, respectively. As the increase of sintering temperature, mechanical properties varied dramatically, while the relative density and dielectric constant increased during the range of sintering temperature. The composite sintered at 1400 Degree-Sign C exhibited superior properties, attaining flexure strength of 120.5 MPa, fracture toughness of 1.21 MPa m{sup 1/2}, dielectric constant of 4 and relative density of 92%. Particularly, flexure strength and fracture toughness were about 230.8% and 208.6% higher than those of monolithic SiO{sub 2}, respectively.

  14. Sonogels in the Preparation of Advanced Glass and Ceramic Materials

    Science.gov (United States)

    1992-10-20

    1 In0 f 7;ra Products) ceramic fibres . -using other yreinforcing phases in the. form of 7’T02 (7YF- 100 ,Zircar Products) and A1203 (MAFTEC) ceramic...usd we -r, made friom ceramic fibres . In both cases t ,- fi bris were I anrgel y continuous and random], oriented in p1lanes parallel Io tahe layers...gives the relative densities for the CT15 ’ A1203 composites . They are designated as CT15Av , where y is the volume fract ion of alt]mina ceramic

  15. Synthesis and Thermal Conductivity of Exfoliated Hexagonal Boron Nitride/Alumina Ceramic Composite

    Science.gov (United States)

    Hung, Ching-cheh; Hurst, Janet; Santiago, Diana; Lizcano, Maricela; Kelly, Marisabel

    2017-01-01

    Exfoliated hexagonal boron nitride (hBN)/alumina composite can be fabricated by following the process of (1) heating a mixture of hBN, AlCl3, and NaF in nitrogen for intercalation; (2) heating the intercalated product in air for exfoliation and at the same time converting the intercalate (AlCl3) into Al2O3, (3) rinsing the oxidized product, (4) coating individual exfoliated hBN platelets that contain Al2O3 with new layers of aluminum oxide, and finally, (5) hot pressing the product into the composite. The composite thus obtained has a composition of approximately 60 percent by weight hBN and 40 percent by weight alumina. Its in-plane and through-plane thermal conductivity were measured to be 86 and 18 watts per meter Kelvin, respectively, at room temperature.

  16. Preparation and evaluation of silicon nitride matrices for silicon nitride-SiC fiber composites. M.S. Thesis Final Technical Report

    Science.gov (United States)

    Axelson, Scott R.

    1988-01-01

    Continuous silicon carbide (SiC) fiber was added to three types of silicon nitride (Si3N4) matrices. Efforts were aimed at producing a dense Si3N4 matrix from reaction-bonded silicon nitride (RBSN) by hot-isostatic-pressing (HIP) and pressureless sintering, and from Si3N4 powder by hot-pressing. The sintering additives utilized were chosen to allow for densification, while not causing severe degradation of the fiber. The ceramic microstructures were evaluated using scanning optical microscopy. Vickers indentation was used to determine the microhardness and fracture toughness values of the matrices. The RBSN matrices in this study did not reach more than 80 percent of theoretical density after sintering at various temperatures, pressures, and additive levels. Hot-pressing Si3N4 powder produced the highest density matrices; hardness and toughness values were within an order of magnitude of the best literature values. The best sintering aid composition chosen included Y2O3, SiO2, and Al2O3 or AlN. Photomicrographs demonstrate a significant reduction of fiber attack by this additive composition.

  17. Optimization of dispersing agents for preparing YAG transparent ceramics

    Institute of Scientific and Technical Information of China (English)

    BA Xuewei; LI Jiang; PAN Yubai; LIU Jing; JIANG Benxue; LIU Wenbin; KOU Huamin

    2013-01-01

    The suspensions of the powder mixture of yttria and alumina were prepared by the aqueous tape casting method.Rodia DP270,Dolapix CE64,citric acid and Dammonium 3008 were used as dispersing agents.The morphologies of the powders and the fiacture surface of the green body were observed by scanning electron microscopy (SEM).The zeta potential test was employed to characterize the surface charge states of different suspensions.The dispersion of the suspensions was analyzed by the rheological tests and the sedimentation experiments.The results indicated that the yttria and alumina powder mixtures were well dispersed by the dispersing agents.The rheological curves showed shear thinning behavior.The most efficient dispersing agent was Dammonium 3008.The optimum usage of Dammonium 3008 was 1.0 wt.%.The green body was dense and no interface between the adjacent layers was found.The in-line transmittance of the as-sintered YAG ceramic was higher than 80% between 400 and 1100 nm.

  18. Preparation and characterization of the porous ceramics from fly ash

    Institute of Scientific and Technical Information of China (English)

    REN Xiang-jun; ZHANG Xue-bin; MENG Guang-yao; LIU Xing-qin

    2007-01-01

    Porous ceramics was made from coal fly ash,and the microstructure and other properties were characterized as a function of the amount of the pore-forming agent and firing temperature.The results indicated that the proper sintering temperature for the useful ceramic materials is 1250 ℃.and a liquid-phase was involved in the dansification process.

  19. Properties of Al-doped Copper Nitride Films Prepared by Reactive Magnetron Sputtering

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Cu3N and AlxCu3N films were prepared with reactive magnetron sputtering method. The two films were deposited on glass substrates at 0.8 Pa N2 partial pressure and 100 ℃ substrate temperature by using a pure Cu and Al target, respectively. X-ray diffraction (XRD) measurements show that the un-doped film was composed of Cu3N crystallites with anti-ReO3 structure and adopted [111] preferred orientation. XRD shows that the growth of Al-doped copper nitride films (AlxCu3N) was affected strongly by doping Al, the intensity of [111] peak decreases with increasing the concentration of Al and the high concentration of Al could prevent the Cu3N from crystallization. AFM shows that the surface of AlxCu3N film is smoother than that of Cu3N film. Compared with the Cu3N films, the resistivities of the Al-doped copper nitride films (AlxCu3N) have been reduced, and the microhardness has been enhanced.

  20. Fabrication and secondary-phase crystallization of rare-earth disilicate-silicon nitride ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Cinibulk, M.K.; Thomas, G. (Lawrence Berkeley Lab., CA (United States). Center for Advanced Materials); Johnson, S.M. (SRI International, Menlo Park, CA (United States). Materials Research Lab.)

    1992-08-01

    In this paper, the fabrication and intergranular-phase devitrification of silicon nitride densified with rare-earth (RE) oxide additives is investigated. The additions of the oxides of Sm, Gd, Dy, Er, and Yb, having high melting points and behaving similarly to Y[sub 2]O[sub 3], were compositionally controlled to tailor a microstructure with a crystalline secondary phase of RE[sub 2]Si[sub 2]O[sub 7]. The lanthanide oxides were found to be ass effective as Y[sub 2]O[sub 3] in densifying Si[sub 3]N[sub 4], resulting in identical microstructures and densities of 98-99% of theoretical density. The crystallization behavior of all six disilicates was similar, characterized by a limited nucleation and rapid growth mechanism resulting in large single crystals. Complete crystallization of the intergranular phase was obtained with the exception of a thin residual amorphous film which was observed at interfaces and believed to be rich in impurities, the cause of incomplete devitrification.

  1. Processing of Silicon Nitride Ceramics from Concentrated Aqueous Suspensions by Robocasting

    Energy Technology Data Exchange (ETDEWEB)

    HE,GUOPING; HIRSCHFELD,DEIDRE A.; CESARANO III,JOSEPH; STUECKER,JOHN N.

    2000-08-14

    The optimization of concentrated AlliedSignal GS-44 silicon nitride aqueous slurries for robocasting was investigated. The dispersion mechanisms of GS-44 Si{sub 3}N{sub 4} aqueous suspensions with and without polyacrylate were analyzed. The zero point of charge (ZPC) was at about pH 6. Well-dispersed GS-44 suspensions were obtained in the pH range from 7 to 11 by the addition of Darvan 821A. The influence of pH, amount of Darvan 821A and solids loading on the theological behavior of GS-44 aqueous suspensions was determined. A coagulant, aluminum nitrate, was used to control the yield stress and shear thinning behavior of highly loaded Si{sub 3}N{sub 4} slurries. Homogeneous and stable suspensions of 52 vol% GS-44 Si{sub 3}N{sub 4} were robocast successfully at pH 7.8 to pH 8.5. The sintering process, mechanical properties and microstructural characteristics of robocast GS-44 bars were determined.

  2. Preparation of Si3N4 Form Diatomite via a Carbothermal Reduction-Nitridation Process

    Science.gov (United States)

    Ma, Bin; Huang, Zhaohui; Mei, Lefu; Fang, Minghao; Liu, Yangai; Wu, Xiaowen; Hu, Xiaozhi

    2016-05-01

    Si3N4 was produced using diatomite and sucrose as silicon and carbon sources, respectively. The effect of the C/SiO2 molar ratio, heating temperature and soaking time on the morphology and phase compositions of the final products was investigated by scanning electron microscopy, x-ray diffraction analysis and energy dispersive spectroscopy. The phase equilibrium relationships of the system at different heating temperatures were also investigated based on the thermodynamic analysis. The results indicate that the phase compositions depended on the C/SiO2 molar ratio, heating temperature and soaking time. Fabrication of Si3N4 from the precursor via carbothermal reduction nitridation was achieved at 1550°C for 1-8 h using a C/SiO2 molar ratio of 3.0. The as-prepared Si3N4 contained a low amount of Fe3Si (<1 wt.%).

  3. Preparation of silicon carbide nitride films on Si substrate by pulsed high-energy density plasma

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Thin films of silicon carbide nitride (SiCN) were prepared on (111) oriented silicon substrates by pulsed high-energy density plasma (PHEDP). The evolution of the chemical bonding states between silicon, nitrogen and carbon was investigated as a function of discharge voltage using X-ray photoelectron spectroscopy. With an increase in discharge voltage both the C1s and N 1s spectra shift to lower binding energy due to the formation of C-Si and N-Si bonds. The Si-C-N bonds were observed in the deconvolved C1s and N 1s spectra. The X-ray diffractometer (XRD) results show that there were no crystals in the films. The thickness of the films was approximately 1-2 μm with scanning electron microscopy (SEM).

  4. Electrical and optical properties of indium nitride and indium-rich nitrides prepared by molecular beam epitaxy for opto-electronics applications

    Science.gov (United States)

    Lu, Hai

    Great interest in III-nitride semiconductors has been driven by the significant technological importance of this material system. GaN and its alloy have been used in the fabrication of a range of electronic and photonic devices. Blue light emitting diode and laser diode with InGaN as the active layer have been commercialized for several years. Due to such technological importance, considerable research efforts have been made to understand the fundamental properties of III-N semiconductors. However, unlike the intensively studied GaN, InGaN and other nitride compounds, InN, which is also an important component of the III-N system, remains the least studied nitride material. This is mainly due to the difficulty in preparation of high-quality InN epilayers. Two of the main difficulties are the lack of suitable substrate material and the low dissociation temperature of InN. As a result, many fundamental parameters of InN were adopted from some very early reports based on polycrystalline InN films produced by RF sputtering method. Those reports are seemingly good but have never been repeated. This thesis reports epitaxial growth of InN and In-rich nitrides by molecular beam epitaxy. The optimum growth conditions of InN were investigated, which results in the best electrical properties of InN film reported in recent years. For the first time, non-degenerate InN film was produced and the surface charge accumulation of InN films was identified. Detailed and original structural characterizations were carried out. By collaborating with outside labs, many fundamentals properties of InN were measured or rediscovered. One of the main accomplishments in the study is the discovery of the narrow fundamental bandgap of InN, which is around 0.7 eV instead of the widely accepted 1.9 eV. This significant result provides new research guidance for the scientific community. By further preparing In-rich nitrides, the bowing parameters of InGaN and InAIN were first accurately measured. For

  5. Preparation and characterization of photo chromic effect for ceramic tiles

    Energy Technology Data Exchange (ETDEWEB)

    Atay, B.; Goktas, A.; Dogan, A.

    2011-07-01

    Ceramic tile industry is developing due to the technological researches in scientific area and new tiles which are not only a traditional ceramic also have many multiple functionalities have been marketed nowadays. These tiles like photo catalytic, photovoltaic, antibacterial and etc. improve the quality of life and provide lots of benefits such as self cleaning, energy production, climate control. The goal of this study was to enhance the photo chromic function on ceramic tiles which is the attitude of changing color in a reversible way by electromagnetic radiation and widely used in many areas because of its aesthetic and also functional properties. High response time of photo chromic features of ceramic tiles have been achieved by employing of polymeric gel with additives of photoactive dye onto the ceramic surface. Photo chromic layer with a thickness of approximately 45- 50 {mu}m was performed by using spray coating technique which provided homogeneous deposition on surface. Photo chromic ceramic tiles with high photo chromic activity such as reversibly color change between {delta}E= 0.29 and 26.31 were obtained successfully. The photo chromic performance properties and coloring-bleaching mechanisms were analyzed by spectrophotometer. The microstructures of coatings were investigated both by stereo microscopy and scanning electron microscopy (SEM). (Author) 13 refs.

  6. Preparation of Machinable Y-TZP/LaPO4 Composite Ceramics by Liquid Precursor Infiltration

    Institute of Scientific and Technical Information of China (English)

    周振君; 杨正方; 袁启明; 李秀华

    2002-01-01

    A machinable Y-TZP/LaPO4 composite ceramic was prepared by infiltrating LaPO4 liquid precursor into Y-TZP porous ceramic. Sintered Y-TZP ceramic preformed with 35% (volume fraction) open pore volume was made by adding graphite (30%, volume fraction). The Y-TZP/LaPO4 composite ceramics containing different LaPO4 contents were obtained by infiltration and pyrolysis cycles. The machinability and mechanical properties of materials were investigated. The results show that the machinable Y-TZP/LaPO4 composite ceramics containing 2.3% to 7.5% (volume fraction) LaPO4 has good machinability as well as outstanding mechanical properties.

  7. Preparation and Luminescence of Er3+ Doped Oxyfluoride Glass Ceramics Containing LaF3 Nanocrystals

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Er3+ doped transparent oxyfluoride glass ceramics containing LaF3 nanocrystals were prepared and the up-con-version and near infrared luminescence behavior of Er3+ in glasses and glass ceramics were investigated. With increasing heat-treating time and temperature, the size (varied from 0 to 19 nm) and crystallinity (varied from 0 to 47%) of LaF3 nanocrystals in the glass ceramics are increased. The up-conversion luminescence intensity of Er3+ ions in the glass ceramics is much stronger than that in the glasses and increased significantly with increasing heat-treating time and temperature. The near infrared emission of Er3+ ions in the glass ceramics is found to be similar to that in the glasses.

  8. Fracture toughness of zirconia ceramic crowns made by feather-edge tooth preparation design

    Directory of Open Access Journals (Sweden)

    Mirković Nemanja

    2012-01-01

    Full Text Available Background/Aim. Fracture toughness determines functional crown strenght and prevents damages on ceramics during mastication. There is a lack of relevant literature data about fracture toughness of crowns made by feather-edge preparation. Mechanical testing of ceramic samples is supposed to show if feather-edge tooth preparation is a successful method for making ceramic crowns without any risk of reduction of their mechanical properties. This research was done to establish effects of feather-edge tooth preparation on fracture toughness of single zirconia ceramic crowns. Methods. The research was performed as an experimental study. Sixty (60 ceramic crowns were made on non-carious extracted human premolars. Thirty (30 crowns were made on the basis of feather-edge preparation (experimental group I. The group II included 30 crowns made on 1 mm rounded shoulder. Crowns fabrication was executed on a copy mill production system “Zirkonzahn” (Zirkonzahn GMBH, Gais, Germany. The spherical compression test was used to determine fracture toughness, using 6 mm diameter ceramic ball. Fracture load for damaging ceramic crown was recorded on a universal testing machine - Zwick, type 1464, with the speed of 0.05 mm/min. Results. The results of this research introduced significant differences between fracture toughness of ceramic samples in every examined group. However, fracture toughness of crowns from both group was above 2 000 N, what was double beyond a recommended value. The mean value of fracture toughness in the feather-edge group was 2 090 N, and in shoulder group it was 2 214 N. Conclusion. This research showed a high fracture toughness of zirconia crowns made on feather-edge preparation. The examined crowns showed a fracture resistance at a sufficient distance in relation to the minimum values of functional loads. Further research of functional loads of these crown is necessary, as well as research of marginal adaptation of cemented crowns and

  9. In-situ multi-information measurement system for preparing gallium nitride photocathode

    Institute of Scientific and Technical Information of China (English)

    Fu Xiao-Qian; Chang Ben-Kang; Qian Yun-Sheng; Zhang Jun-Ju

    2012-01-01

    We introduce the first domestic in-situ multi-information measurement system for a gallium nitride (GaN) photocathode.This system can successfully fulfill heat cleaning and activation for GaN in an ultrahigh vacuum environment and produce a GaN photocathode with a negative electron affinity (NEA) status.Information including the heat cleaning temperature,vacuum degree,photocurrent,electric current of cesium source,oxygen source,and the most important information about the spectral response,or equivalently,the quantum efficiency (QE) can be obtained during preparation.The preparation of a GaN photocathode with this system indicates that the optimal heating temperature in a vacuum is about 700 ℃.We also develop a method of quickly evaluating the atomically clean surface with the vacuum degree versus wavelength curve to prevent possible secondary contamination when the atomic level cleaning surface is tested with X-ray photoelectron spectroscopy.The photocurrent shows a quick enhancement when the current ratio between the cesium source and oxygen source is 1.025.The spectral response of the GaN photocathode is fiat in a wavelength range from 240 nm to 365 nm,and an abrupt decline is observed at 365 nm,which demonstrates that with the in-situ multi-information measurement system the NEA GaN photocathode can be successfully prepared.

  10. In-situ multi-information measurement system for preparing gallium nitride photocathode

    Science.gov (United States)

    Fu, Xiao-Qian; Chang, Ben-Kang; Qian, Yun-Sheng; Zhang, Jun-Ju

    2012-03-01

    We introduce the first domestic in-situ multi-information measurement system for a gallium nitride (GaN) photocathode. This system can successfully fulfill heat cleaning and activation for GaN in an ultrahigh vacuum environment and produce a GaN photocathode with a negative electron affinity (NEA) status. Information including the heat cleaning temperature, vacuum degree, photocurrent, electric current of cesium source, oxygen source, and the most important information about the spectral response, or equivalently, the quantum efficiency (QE) can be obtained during preparation. The preparation of a GaN photocathode with this system indicates that the optimal heating temperature in a vacuum is about 700 °C. We also develop a method of quickly evaluating the atomically clean surface with the vacuum degree versus wavelength curve to prevent possible secondary contamination when the atomic level cleaning surface is tested with X-ray photoelectron spectroscopy. The photocurrent shows a quick enhancement when the current ratio between the cesium source and oxygen source is 1.025. The spectral response of the GaN photocathode is flat in a wavelength range from 240 nm to 365 nm, and an abrupt decline is observed at 365 nm, which demonstrates that with the in-situ multi-information measurement system the NEA GaN photocathode can be successfully prepared.

  11. Tantalum (oxy)nitrides: Preparation, characterisation and enhancement of photo-Fenton-like degradation of atrazine under visible light

    Energy Technology Data Exchange (ETDEWEB)

    Du, Yingxun, E-mail: yxdu@niglas.ac.cn [Nanjing Institute of Geography and Limnology, State Key Laboratory of Lake Science and Environment, Chinese Academy of Sciences, Nanjing 210008 (China); Zhao, Lu; Su, Yaling [Nanjing Institute of Geography and Limnology, State Key Laboratory of Lake Science and Environment, Chinese Academy of Sciences, Nanjing 210008 (China)

    2011-11-15

    Highlights: {yields} The photocatalytic activity of TaON for Fe{sup 3+} reduction is higher than that of Ta{sub 3}N{sub 5}. {yields} Atrazine degradation was accelerated significantly by tantalum (oxy)nitrides sample. {yields} The regenerated catalyst displays considerably stable performance for atrazine degradation. - Abstract: Tantalum (oxy)nitrides were prepared by the nitridation of Ta{sub 2}O{sub 5} and were added to a photo-Fenton-like system to enhance Fe{sup 3+} reduction and atrazine degradation under visible light. The samples were characterized by XRD, XPS, DRS and BET analyses. XPS analysis showed that the nitrogen content of the tantalum (oxy)nitride samples increased noticeably with the nitridation temperature and nitridation time but slightly with the flow rate of NH{sub 3}. XRD results showed Ta{sub 2}O{sub 5} was first converted to TaON and then to Ta{sub 3}N{sub 5} when the nitridation temperature increased. DRS analysis showed that the sample obtained at 800 {sup o}C displayed the strongest absorption of visible light. However, the ability of the tantalum (oxy)nitrides to reduce Fe{sup 3+} did not increase continuously with the nitrogen content. Sample 7 (700 {sup o}C, Q{sub NH{sub 3}}=0.3L/min, 6 h) showed the highest level of photocatalytic activity for Fe{sup 3+} reduction. This is because the photocatalytic activity of TaON for Fe{sup 3+} reduction is higher than that of Ta{sub 3}N{sub 5}. And a slight synergetic effect was observed between TaON and Ta{sub 3}N{sub 5}. With the addition of sample 7, H{sub 2}O{sub 2} decomposition and atrazine degradation were significantly accelerated in a photo-Fenton-like system under visible light. The regenerated tantalum (oxy)nitrides catalyst displayed considerably stable performance for atrazine degradation.

  12. 新型耐高温氮化物陶瓷纤维研究进展%Research progress in new high temperature resistant nitride ceramic fiber

    Institute of Scientific and Technical Information of China (English)

    彭雨晴; 韩克清; 赵曦; 袁佳; 余木火

    2011-01-01

    介绍了耐高温氮化物陶瓷纤维的种类及制备方法即有机聚合物先驱体转化法;综述了Si3N4,BN,SiBN,SiBN(C)陶瓷纤维的研究进展;重点介绍了SiBN(C)陶瓷纤维的研究现状,并与SiC纤维进行性能对比.指出具有耐高温、透波性等功能结构一体化的SiBN(C)陶瓷纤维是陶瓷纤维的重要发展方向,简化先驱体的合成过程及降低制备成本是技术关键,聚合物分子结构设计和纺丝工艺还有待深入研究.%Hie variety and the production technology, I.e. Organic polymer precursor conversion method, of high temperature resistant nitride ceramic fiber was introduced. The research progress in Si3N4, BN, SiBN and SiBN(C) ceramic fibers was reviewed. The research situation of SiBN(C) ceramic fiber was emphatically introduced. And the properties of SiBN( C) ceramic fiber were compared with those of SiC fiber. It was pointed out that the development trend of ceramic fibers would focus on the function-structure integrated SiBN(C) ceramic fiber with high temperature resistance and wave transmissivity, the key technology should be the simplification of precursor synthesis process and the reduction of production cost, and the polymer molecular structure design and the spinning process should be studied further.

  13. Preparation of Machinable Bioactive Glass-ceramics by Sol-gel Method

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    The purpose of this research was to prepare machinable bioactive glass-ceramics by sol-gel method. A multi-component composite sol with great uniformity and stability was first prepared by a 2-step method.The composite sol was then transformed into gel by aging under different temperatures. The gel was dried finally by super critically drying method and sintered to obtain the machinable bioactive glass-ceramics. Effect of thermal treatment on crystallization of the glass-ceramics was investigated by X-ray diffraction (XRD) analysis. Microstructure of the glass-ceramics was observed by Scanning Electron Microscopy (SEM) and the mechanism of machinability was discussed. Phlogopite and hydroxylapatite were identified as main crystal phases by XRD analysis under thermal treatment at 750 ℃ and 950 ℃ for 1.5 h separately. The relative bulk density could achieve 99%under 1050 ℃ for 4 h. Microstructure of the glass-ceramics showed that the randomly distributed phlogopite and hydroxylapatite phases were favorable to the machinability of the glass-ceramics. A mean bending strength of about 160-180 MPa and a fracture toughness parameter KIC of about 2.1-2.3 were determined for the glass-ceramics.

  14. Preparation of high-pressure phase boron nitride films by physical vapor deposition

    CERN Document Server

    Zhu, P W; Zhao, Y N; Li, D M; Liu, H W; Zou Guang Tian

    2002-01-01

    The high-pressure phases boron nitride films together with cubic, wurtzic, and explosive high-pressure phases, were successfully deposited on the metal alloy substrates by tuned substrate radio frequency magnetron sputtering. The percentage of cubic boron nitride phase in the film was about 50% as calculated by Fourier transform infrared measurements. Infrared peak position of cubic boron nitride at 1006.3 cm sup - sup 1 , which is close to the stressless state, indicates that the film has very low internal stress. Transition electron microscope micrograph shows that pure cubic boron nitride phase exits on the surface of the film. The growth mechanism of the BN films was also discussed.

  15. Preparation and Sintering Effect in Quartz-Barium Titanate Porous Ceramics and Permeability Modulation Using an Implanted Electrode

    Directory of Open Access Journals (Sweden)

    Ernesto Suaste Gómez

    2014-01-01

    Full Text Available Barium titanate and quartz mixed in different proportions were used to create porous piezoelectric ceramics. Three different sintering temperatures were used for the ceramics preparation; a nichrome wire was used as internal electrode in porous ceramics. Characteristics as porous area, porosity, and its relationship with quartz percentage and sintering temperatures were studied. Porous ceramics with an implanted electrode were created, by applying an alternating voltage in the internal electrode that controlled the liquid permeability coefficient, calculated by the Darcy Law.

  16. Preparation and Application of New Porous Environmental Ceramics Filter Medium

    Institute of Scientific and Technical Information of China (English)

    LI Meng; WU Jianfeng; JIN Jianhua; LIU Xinming

    2005-01-01

    A new kind of environmental ceramics medium which was made of industrial solid wastes discharged by Shandong Alum Corporation has been used in the process of drinking water treatment. New techniques were introduced to ensure its remarkable advantages such as high porosity and strength. The results of practical application show that this sort of filter medium has shorter filtration run, shorter mature period and higher filter deposit capability compared with traditional sand filter medium. Moreover, up to 25%- 30% of the daily running costs are expected to be reduced by using this ceramics medium.

  17. Preparation and properties of hexagonal boron nitride fibers used as high temperature membrane filter

    Energy Technology Data Exchange (ETDEWEB)

    Hou, Xinmei, E-mail: houxinmei@ustb.edu.cn; Yu, Ziyou; Li, Yang; Chou, Kuo-Chih

    2014-01-01

    Graphical abstract: - Highlights: • h-BN fibers were successfully fabricated using H{sub 3}BO{sub 3} and C{sub 3}H{sub 6}N{sub 6} as raw materials. • The obtained BN fibers were polycrystalline and uniform in morphology. • It exhibited good oxidation resistance and low thermal expansion coefficient. - Abstract: Hexagonal boron nitride fibers were synthesized via polymeric precursor method using boric acid (H{sub 3}BO{sub 3}) and melamine (C{sub 3}H{sub 6}N{sub 6}) as raw materials. The precursor fibers were synthesized by water bath and BN fibers were prepared from the precursor at 1873 K for 3 h in flowing nitrogen atmosphere. The crystalline phase and microstructures of BN fibers were examined by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy and high resolution electron microscopy. The results showed that h-BN fibers with uniform morphology were successfully fabricated. The well-synthesized BN fibers were polycrystalline with 0.4–1.5 μm in diameter and 200–500 μm in length. The as-prepared samples exhibited good oxidation resistance and low thermal expansion coefficient at high temperature.

  18. Preparation of Titanium Nitride Nanoparticles from a Novel Refiuxing Derived Precursor

    Institute of Scientific and Technical Information of China (English)

    LIU Fei; LIANG Xiaofeng; LI Yongdi; YAO Yadong; ZHANG Hao; SHAO Wei; KANG Yunqing; YIN Guangfu; HUANG Zhongbing; LIAO Xiaoming

    2011-01-01

    Titanium nitride (TiN) nanoparticles were prepared from a novel refiuxing-derived precursor.The organic/inorganic hybrid precursor was prepared by a two-stage refluxing method using hydrous TiO2 as titania source and n-dodecane as carbon source. The precursor was heat-treated to 1 200 ℃ in flowing ammonia (NH3) to get TiN nanoparticles. The phase and chemical compositions were investigated by means of XRD,Raman spectroscopy and XPS. Samples microstructure was studied by means of SEM, TEM and SEAD. XRD pattern indicated that the product was face-centered cubic TiN with a lattice constant a = 4.236(A) and average crystallite sizes of 35.2 nm. Raman spectra indicated that long time refluxing results in Alkane dehydrogenation and the formation of coke on TiO2 nanoparticles. Oxygen presence in TiN lattice was confirmed by XPS investigation. The particle size that was showed by Electron microscopy photographs ranged from 20 to 60 nm.

  19. Novel methods of powder preparation and ceramic forming for improving reliability of multilayer ceramic actuators

    Science.gov (United States)

    Near, Craig D.; Dawson, William J.; Swartz, Scott L.; Issartel, Jean P.

    1993-07-01

    Critical components of many smart systems employ multilayer piezoelectric actuators based on lead zirconate titanate (PZT) ceramics. Applications include active vibration systems, noise suppression, acoustic camouflage, actuated structures, reconfigurable surfaces, and structural health monitoring. Two strategies involving novel materials processing techniques are discussed for improving the performance and reliability of PZT ceramic components. The first is the use of an advanced powder synthesis, which was recently developed for a range of DoD specification materials. The second strategy involves two improved ceramic manufacturing routes designed to replace the current tape casting and co-firing method. One is the use of roll- compaction for tape forming. The other is the application of the infiltrated electrode approach. Both of these methods provide improved electrical and mechanical performances and superior reliability.

  20. Fine yellow α-SiAlON:Eu phosphors for white LEDs prepared by the gas-reduction–nitridation method

    Directory of Open Access Journals (Sweden)

    Hui-Li Li et al

    2007-01-01

    Full Text Available Yellow-emitting α-SiAlON:Eu2+ phosphors were synthesized by the gas reduction and nitridation of a homogeneous oxide precursor in a CaO–Al2O3–SiO2–Eu2O3 system at 1400–1450 °C using an NH3–CH4 mixture gas as a reduction–nitridation agent. The precursor was prepared by a sol–gel process using a low-cost nitrate, tetraethyl orthosilicate and citric acid as the starting materials. The effects of reaction parameters such as heating rate, temperature, holding time and CH4 content on the composition, microstructure and photoluminescence of the prepared powders were investigated. Nearly single-phase α-SiAlON was successfully synthesized by the one-step gas reduction and nitridation without the need for post-annealing at a higher temperature. The prepared powders consisted of relatively well-dispersed and uniform crystals with a hexagonal shape. The photoluminescence spectra of Eu-doped Ca-α-SiAlON phosphors excited by near-ultraviolet or blue light showed a broad, yellow emission band at 500–700 nm, which agrees well with that obtained from phosphors prepared by the conventional solid-state reaction.

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

    Science.gov (United States)

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

    2015-10-01

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

  2. Preparation of high performance ceramic tiles using waste tile granules and ceramic polishing powder

    Institute of Scientific and Technical Information of China (English)

    WANG Gong-xun; SU Da-gen

    2008-01-01

    This paper presents an innovative approach to reusing waste tile granules (TG) and ceramic polishing powder (PP) to produce high performance ceramic tiles. We studied formulations each with a TG mass fraction of 25.0% and a different PP mass fraction between 1.0% and 7.0%. The formulations included a small amount of borax additive of a mass fracton between 0.2%and 1.2%. The effects of these industrial by-products on compressive strength, water absorption and microstructure of the new ceramic tiles were investigated. The results indicate that the compressive strength decreases and water absorption increases when TG with a mass fraction of 25.0% are added. Improvement of the compressive strength may be achieved when TG (up to 25.0%)and PP (up to 2.0%) are both used at the same time. In particular, the compressive strength improvement can be maximized and water absorption reduced when a borax additive of up to 0.5% is used as a flux. Scanning electron microscopy reveals that a certain amount of fine PP granules and a high content of fluxing oxides from borax avail the formation of glassy phase that fills up the pores in the new ceramic tiles, resulting in a dense product with high compressive strength and low water absorption.

  3. Preparation and Characterization of Nanotitanium Dioxide Coating Film Doped with Fe3+ Ions on Porous Ceramic

    Institute of Scientific and Technical Information of China (English)

    Kejing Xu

    2005-01-01

    The nanotitanium dioxide (TiO2) photocatalytic and porous ceramic filtering technique is one of the advanced methods to effectively treat organic wastewater. The TiO2 sol doped with Fe3+ ions was prepared by sol-gel processing. The influences of the process conditions of coating nanophotocatalytic material-Fe3+-TiO2 film on the surface of porous ceramic filter by dipping-lift method on the performance of porous ceramic filter were studied. The porous ceramic filters have two functions at the same time,filtration and photocatalytic degradation. The results of this study showed that the pH and viscosity of the sol,amount of Fe3+ ions doped as well as the coating times greatly affect the quality of coating film,the performance parameters and the photocatalytic activity of the porous ceramic filter. When the pH of the sol is 3-4,the viscosity is about 6 mPa·S,the amount of doped Fe3+ ions is about 2.0 g/L,the porous ceramic filter has been shown to have the best filtering performance and photocatalytic activity. In this condition,the porosity of porous ceramic is about 42.5%,the pore diameter is 8-10μm. The degradation of methyl-orange is 74.76% under lighting for 120 min.

  4. Comparison of load-fatigue performance of posterior ceramic onlay restorations under different preparation designs.

    Science.gov (United States)

    Kois, Dean E; Chaiyabutr, Yada; Kois, John C

    2012-06-01

    The objective of this study was to evaluate the load-fatigue performance of posterior ceramic onlay restorations relative to two variables: preparation design (with or without buccal veneers); and the existing amount of tooth structure (non-worn tooth, worn tooth). Sixty extracted third molars were divided into five groups. One group received a mesial-occlusal-distal (MOD) gold onlay restoration (control). The other four experimental groups were prepared for ceramic onlay restorations. Two of the groups additionally received 2-mm occlusal reduction to simulate occlusal wear. All restored teeth were subjected to thermocycling prior to fatigue testing. A fatigue load of 150 N was applied on the occlusal surface at a frequency of 1.2 hz, at an angle of 135 degrees to the long axis of the tooth. Specimen failure was defined as the occurrence of crack propagation in the luting cement layer. This was monitored by the strain gauge on the specimen. All specimens restored on worn tooth had significantly lower fatigue failure cycle counts than those of non-worn tooth. The fracture mode analysis revealed that ceramic fracture tended to be demonstrated only in the group of worn tooth groups. The addition of a buccal veneer component had no significant effect on the load-fatigue performance of posterior ceramic onlay restorations, but the existing amount of tooth structure did have a significant effect on the load-fatigue performance of posterior ceramic onlay restorations. Catastrophic failures (ceramic fracture) occurred only in the group of worn tooth.

  5. Compound transparent ceramics and methods of preparation thereof

    Science.gov (United States)

    Hollingsworth, Joel P.; Kuntz, Joshua D.; Soules, Thomas F.; Landingham, Richard L.

    2012-12-11

    According to one embodiment, a method for forming a composite transparent ceramic preform includes forming a first suspension of oxide particles in a first solvent which includes a first dispersant but does not include a gelling agent, adding the first suspension to a first mold of a desired shape, and uniformly curing the first suspension in the first mold until stable. The method also includes forming a second suspension of oxide particles in a second solvent which includes a second dispersant but does not include a gelling agent, adding the second suspension to the stable first suspension in a second mold of a desired shape encompassing the first suspension and the second suspension, and uniformly curing the second suspension in the second mold until stable. Other methods for forming a composite transparent ceramic preform are also described according to several other embodiments. Structures are also disclosed.

  6. Preparation and properties of highly porous, biomorphic YSZ ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Rambo, C.R.; Cao, J.; Sieber, H

    2004-10-15

    Highly porous, biomorphic YSZ (yttria-stabilized zirconia) ceramics were manufactured by infiltration of zirconium-oxychloride (ZrOCl{sub 2}{center_dot}8H{sub 2}O) sol into biological template structures derived from rattan and pine wood. 3-5 mol% yttrium nitrate (Y(NO{sub 3}){sub 3}{center_dot}5H{sub 2}O) was added to the sol to stabilize the tetragonal ZrO{sub 2} phase. After vacuum-assisted infiltration, the specimens were pyrolysed at 800 deg. C in N{sub 2} atmosphere. Repeated infiltrations and subsequent annealing in air at temperatures up to 1550 deg. C yields the burn out of the biocarbon template and resulted in the formation of biomorphous YSZ ceramics, which maintained the microstructural features of the biological preform. Depending on the type of the biological template as well as the processing parameters, biomorphic ZrO{sub 2} ceramics with an unidirected pore morphology and a large variety of microstructures can be obtained.

  7. Preparation and Crystal Structure of Lithium Nitride Chloride Li 4NCl

    Science.gov (United States)

    Marx, Rupert

    1997-02-01

    Li4NCl was prepared from Li3N and dry OH-free LiCl at 450°C. It is found to be the more nitrogen-rich of two compounds in the quasi-binary system Li3-2xN1-xClx. Following unit cell indexing using laboratory X-ray powder data, the previously unknown structure of the title compound was solved from neutron powder diffraction data recorded using the flat-cone and powder diffractometer E2 at the Berlin BERII reactor. Li4NCl crystallizes in the hexagonal rhombohedral space groupRoverline3=m(No. 166),a=366.225(4),c=1977.18(4) pm with three formula units per unit cell. Its structure comprises a 1:1-ordering variant of a cubic close anion packing, N3-and Cl-forming layers perpendicular to [001]. Li atoms occupy all the triangular voids of the N layers and all the NCl3-tetrahedral holes. Nitrogen is in lithium nitride-like hexagonal bipyramidal coordination by Li, the equatorial six-membered ring being slightly puckered, while Cl is in distorted octahedral coordination. Calculation of the Madelung part of the lattice energy shows that the nitrogen hexagonal bipyramidal coordination polyhedron, peculiar for Li4NCl and the Li3N parent structure, is in agreement with a simple ionic picture and does not imply any covalent bonding.

  8. Preparation and Microstructure of Porous ZrB2 Ceramics Using Reactive Spark Plasma Sintering Method

    Institute of Scientific and Technical Information of China (English)

    YUAN Huiping; LI Junguo; SHEN Qiang; ZHANG Lianmeng

    2015-01-01

    Zirconium oxide (ZrO2) and boron carbide (B4C) were added to ZrB2 raw powders to prepare ZrB2 porous ceramics by reactive spark plasma sintering (RSPS). The reactions between ZrO2 and B4C which produce ZrB2 and gas (such as CO and B2O3) result in pore formation. X-Ray Diffraction results indicated that the products phase was ZrB2 and the reaction was completed after the RSPS process. The porosity could be controlled by changing the ratio of synthesized ZrB2 to raw ZrB2 powders. The porosity of porous ceramics with 20 wt% and 40 wt% synthsized ZrB2 are 0.185 and 0.222, respectivly. And dense ZrB2-SiC ceramic with a porosity of 0.057 was prepared under the same conditions for comparison. The pores were homogeneously distributed within the microstructure of the porous ceramics. The results indicate a promising method for preparing porous ZrB2-based ceramics.

  9. Preparation of Long-Lasting Phosphorescence (LLP) Glass-Ceramic Materials

    Institute of Scientific and Technical Information of China (English)

    李成宇; 苏锵; 王淑彬

    2004-01-01

    Three kinds of glass-ceramics, i.e., Mn2+ doped zinc borosilicate, Eu2+, Dy3+ co-doped strontium aluminoborate and Eu2+, Nd3+ co-doped calcium aluminoborate were prepared, whose phosphorescence emission band peaks at 525, 516 and 464 nm, respectively. In preparation of these glass-ceramics the base glasses were gained by heating the mixed starting materials at high temperature to get the transparent glasses; then those glasses were heat-treated and turned to opaque glass-ceramics. X-ray diffraction(XRD) shows that the crystallites are ZnSiO4, SrAl2O4 and α-CaAl2B2O7, respectively. It is a useful way to get new LLP materials by the method reported in this work that may be considered as "from glass to crystal".

  10. Effect of Y2O3 and Dy2O3 on Microstructure and Mechanical Behaviors of Aluminum Nitride Ceramics

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The effects of two types of additives, Y2O3 and Dy2O3, on the sintering and mechanical behaviors of AlN ceramics were investigated. The experimental results show that the sintering temperature can be decreased and the mechanical behavior can be improved by adding rare earth in AlN ceramics. The strength of AlN ceramics with Y2O3 and Dy2O3 are 326 and 320 MPa, respectively, which are 97.6% and 93.9% higher than the un-doped AlN ceramics. The fracture behavior on the fracture surfaces of rare earth oxide AlN ceramics was found to be a mixed mode of transgranular fracture and intergranular fracture. As a result, it is concluded that the improvement of bending strength of AlN ceramics with Y2O3 and Dy2O3 addition are mainly achieved by strengthening the grain boundary.

  11. Preparation and characterization of photochromic effect for ceramic tiles

    Directory of Open Access Journals (Sweden)

    Atay, B.

    2011-08-01

    Full Text Available Ceramic tile industry is developing due to the technological researches in scientific area and new tiles which are not only a traditional ceramic also have many multiple functionalities have been marketed nowadays. These tiles like photocatalytic, photovoltaic, antibacterial and etc. improve the quality of life and provide lots of benefits such as self cleaning, energy production, climate control. The goal of this study was to enhance the photochromic function on ceramic tiles which is the attitude of changing color in a reversible way by electromagnetic radiation and widely used in many areas because of its aesthetic and also functional properties. High response time of photochromic features of ceramic tiles have been achieved by employing of polymeric gel with additives of photoactive dye onto the ceramic surface. Photochromic layer with a thickness of approximately 45- 50 µm was performed by using spray coating technique which provided homogeneous deposition on surface. Photochromic ceramic tiles with high photochromic activity such as reversibly color change between ΔE= 0.29 and 26.31 were obtained successfully. The photochromic performance properties and coloring-bleaching mechanisms were analyzed by spectrophotometer. The microstructures of coatings were investigated both by stereo microscopy and scanning electron microscopy (SEM.

    La industria de baldosa cerámica se está desarrollando debido a las investigaciones tecnológicas en el área científica y los nuevos azulejos no son sólo de cerámica tradicional, sino que también tienen múltiples funcionalidades que son valiosas en el mercado hoy en día. Estos azulejos tipo fotocatalítico, fotovoltáico, anti-bacteriano, entre otros, mejoran la calidad de vida y proporcionan muchos beneficios como la limpieza fácil o de uno mismo, la producción energética y el control del clima. La meta de este estudio es realzar la función fotocrómatica en las baldosas cerámicas y la

  12. Defect production in ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Zinkle, S.J. [Oak Ridge National Lab., TN (United States); Kinoshita, C. [Kyushu Univ. (Japan)

    1997-08-01

    A review is given of several important defect production and accumulation parameters for irradiated ceramics. Materials covered in this review include alumina, magnesia, spinel silicon carbide, silicon nitride, aluminum nitride and diamond. Whereas threshold displacement energies for many ceramics are known within a reasonable level of uncertainty (with notable exceptions being AIN and Si{sub 3}N{sub 4}), relatively little information exists on the equally important parameters of surviving defect fraction (defect production efficiency) and point defect migration energies for most ceramics. Very little fundamental displacement damage information is available for nitride ceramics. The role of subthreshold irradiation on defect migration and microstructural evolution is also briefly discussed.

  13. Transmission Electron Microscopy Specimen Preparation Method for Multiphase Porous Functional Ceramics

    DEFF Research Database (Denmark)

    Zhang, Wei; Kuhn, Luise Theil; Jørgensen, Peter Stanley

    2013-01-01

    An optimum method is proposed to prepare thin foil transmission electron microscopy (TEM) lamellae of multiphase porous functional ceramics: prefilling the pore space of these materials with an epoxy resin prior to focused ion beam milling. Several advantages of epoxy impregnation are demonstrate...

  14. Bismuth oxide based ceramics with improved electrical and mechanical properties: Part I. Preparation and characterisation

    NARCIS (Netherlands)

    Kruidhof, H.; Seshan, K.; Lippens Jr., B.C.; Gellings, P.J.; Burggraaf, A.J.

    1987-01-01

    A study of the preparative variables in the synthesis of ceramics based on Bi2O3-Er2O3 solid solutions has shown that the best results are obtained with a coprecipitation method. Critical parameters in the synthesis are found to be i) wet milling of the precalcined powder with an appropriate liquid

  15. Preparation and Drug-release Behavior of β-TCP Ceramics Drug Carrier in vitro

    Institute of Scientific and Technical Information of China (English)

    ZHANG Qihuan; YAN Xin; YAN Yuhua; DAI Honglian; JIANG Xin; LI Shipu

    2012-01-01

    β-TCP ceramics drug carrier was first prepared and characterized.SEM showed that β-TCP carrier was in porous amorphous structure with diameters around 10 μm.The physical properties including apparent porosity,volume-weight,tensile strength and the permeability were measured and the results indicated those properties fit the clinical usage of β-TCP drug carrier.Furthermore,drug release experiment in vitro showed that the carrier could prolong drug release in simulated body fluid which provides basis for the clinical use of β-TCP ceramics as drug carrier.

  16. 氮化硅基多孔陶瓷的制备技术、孔隙结构及其相关性能%Silicon Nitride Based Porous Ceramics:Preparation Technologies, Porous Structure and Properties

    Institute of Scientific and Technical Information of China (English)

    苏睿; 黄志锋; 李飞宇; 陈斐; 沈强

    2016-01-01

    氮化硅多孔陶瓷是近年来得到广泛关注的一类新型的结构-功能一体化陶瓷材料,在航空航天、机械、化工、海洋工程等重要领域有着广阔的应用前景。本文介绍了氮化硅基多孔陶瓷的主要制备技术,回顾了氮化硅基多孔陶瓷力学性能和介电性能的研究进展。考虑到高孔隙率氮化硅基多孔陶瓷力学性能难以提高,磷酸盐结合氮化硅基多孔陶瓷已经逐渐成为新的研究热点,因此,本文进一步对磷酸盐结合氮化硅基多孔陶瓷的制备技术、力学性能、介电性能、热学性能进行了综合评述,并对氮化硅基多孔陶瓷的应用前景进行了展望。%Silicon nitride porous ceramics is an advanced type of structure –function integration ceramic materials which is popular in recently, and it has profound application prospect in aerospace, machinery, chemistry, oceanographic engineering and other significant domain. In this article, the main preparation technologies of porous Si3N4 ceramics have been summarized, and the research progress about the mechanical and dielectric properties of porous Si3N4 ceramics have been reviewed in this paper. Further, consider about the problem that it is hard to improve the mechanical properties of porous Si3N4 ceramics with high porosity, the research hotspot is moving on porous Si3N4 ceramics with phosphate binder. Therefore, their preparation technologies, mechanical, dielectric and thermal properties have been analyzed in further, and the potential application of porous Si3N4 ceramics was discussed.

  17. Heat treatment of piezoelectric Pb(ZrTi)O3 ceramic fibers prepared with continuous spinning

    Science.gov (United States)

    Xiong, Z. X.; Pan, J.; Xue, H.; Mai, M. F.; Qiu, H.; Chen, L. F.

    2009-07-01

    Ceramic of Pb(ZrTi)O3 is one kind of typical smart materials, with excellent ferroelectric and piezoelectric properties. In this paper, a novel heat treatment was applied for the ceramic fibers prepared via sol-gel route with continuous spinning. Aided with microwave energy, dense ceramic fibers are obtained after treated at around 900°C for 1h, in which the diameters of the fibers are between 5μm and 30μm. The samples were also characterized with thermal analysis, FTIR spectroscopy and X-ray diffraction. By using of a scanning electron microscope, SEM, it was observed that a dense microstructure of the fiber was reached.

  18. Preparation of cross-sectional specimens of ceramic thermal barrier coatings for transmission electron microscopy.

    Science.gov (United States)

    Unal, O; Heuer, A H; Mitchell, T E

    1990-04-01

    During the microstructural examination of ceramic thermal barrier coatings by transmission electron microscopy (TEM), initial efforts for the preparation of cross-sectional thin foils from interface regions by conventional means were mostly failures. Delamination of the Y2O3-stabilized ZrO2 ceramic coating from the nickel-base alloy substrate sometimes occurred during fine polishing at around 80 microns thickness but mostly occurred during dimpling. Because of this sensitivity, special techniques for mechanical handling were developed so that ion milling could give thin enough regions of the metal-ceramic interface. TEM showed convincingly that the highly fragile nature of the coatings is in fact due to the extensive porosity at the interface developed as a result of heat treatment.

  19. Cross-sectional AEM preparation technique for ceramic-coated WC-Co cutting tools.

    Science.gov (United States)

    Ostreicher, K; Sung, C

    1993-04-15

    The preparation of cross-sectional specimens for AEM studies of materials such as ceramic coated tungsten carbide presents some unique problems. Pieces joined by the use of epoxides often separate at the interface between the WC and ceramic coating during the initial mechanical grinding and subsequent thinning process as a result of the vibration and physical strain placed on the sample. These problems have been overcome through the use of a preparation process which essentially encapsulates the sample within the confines of an epoxy filled quartz tube. This preparation process has allowed for facile AEM cross-sectional analysis of TiN/TiCN coatings on WC-Co substrates, and has revealed two distinct grain morphologies within the TiCN coating.

  20. Sintering of anorthite based ceramics prepared from kaolin DD2 and calcite

    Energy Technology Data Exchange (ETDEWEB)

    Zaiou, S.; Harabi, A.; Harabi, E.; Guechi, A.; Karboua, N.; Benhassine, M.-T.; Zouai, S.; Guerfa, F., E-mail: Zaiou_21@yahoo.fr, E-mail: harabi52@gmail.com, E-mail: semouni84@gmail.com, E-mail: guechia@yahoo.fr, E-mail: kanour17@yahoo.fr, E-mail: mtb25dz@gmail.com, E-mail: zouaisouheila@yahoo.fr, E-mail: guerfatiha@gmail.com [Ceramics Lab., Faculty of Exact Science, Physics Department, Mentouri University of Constantine (Algeria)

    2016-10-15

    In this work, the preparation of anorthite based ceramics using a modified milling system and 80 wt% kaolin (DD2 type) and 20 wt% calcium oxide extracted from CaCO{sub 3} is shown. The choice of these raw materials was dictated by their natural abundance. Previous studies have shown that a simple and vibratory multidirectional milling system using a bimodal distribution of highly resistant ceramics can be successfully used for obtaining fine powders. The prepared samples were sintered at different temperatures ranging between 800 and 1100 °C. It has been found that the relative density of samples sintered at 900 °C for 1 h with a heating rate of 5 °C/min was about 96% of the theoretical density of anorthite (2.75 g/cm{sup 3} ). Finally, the prepared samples were also characterized by scanning electron microscopy, X-ray diffraction and Raman spectroscopy. (author)

  1. Preparation and Characteristic of Glass-Ceramics with Super Low Thermal Expansion Coefficient

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The preparation technics of glass-ceramics with super low coefficient of thermal expansion containing β-quartz solid solution as a main crystal phase based on the glass in the system Li2O-Al2O3-SiO2 was introduced. The composition of base glass, technics of melting and heat treatment effecting on characteristic of glass-ceramics was described. Specimens were prepared by melting, anneal and controlled two steps heat treatment. Crystal phase, microstructure and elementary distributing were studied by using XRD, SEM and EDS respectively. Prepared specimens show excellent transparency and super low thermal expansion coefficient of 2×10-8 ·K-1, which reaches international advanced level.

  2. Novel band gap-tunable K–Na co-doped graphitic carbon nitride prepared by molten salt method

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Jiannan [Institute of Eco-environmental Sciences, Liaoning Shihua University, Fushun 113001 (China); School of Environmental and Biological Engineering, Liaoning Shihua University, Fushun 113001 (China); Ma, Lin [School of Petrochemical Engineering, Liaoning Shihua University, Fushun 113001 (China); Wang, Haoying; Zhao, Yanfeng [School of Environmental and Biological Engineering, Liaoning Shihua University, Fushun 113001 (China); Zhang, Jian [School of Petrochemical Engineering, Liaoning Shihua University, Fushun 113001 (China); Hu, Shaozheng, E-mail: hushaozhenglnpu@163.com [Institute of Eco-environmental Sciences, Liaoning Shihua University, Fushun 113001 (China)

    2015-03-30

    Graphical abstract: K and Na ions co-doped into g-C{sub 3}N{sub 4} crystal lattice can tune the position of CB and VB potentials, influence the structural and optical properties, and thus improve the photocatalytic degradation and mineralization ability. - Highlights: • K, Na co-doped g-C{sub 3}N{sub 4} was prepared in KCl/NaCl molten salt system. • The structural and optical properties of g-C{sub 3}N{sub 4} were greatly influenced by co-doping. • The position of VB and CB can be tuned by controlling the weight ratio of eutectic salts to melamine. • Co-doped g-C{sub 3}N{sub 4} showed outstanding photodegradation ability, mineralization ability, and catalytic stability. - Abstract: Novel band gap-tunable K–Na co-doped graphitic carbon nitride was prepared by molten salt method using melamine, KCl, and NaCl as precursor. X-ray diffraction (XRD), N{sub 2} adsorption, Scanning electron microscope (SEM), UV–vis spectroscopy, Photoluminescence (PL), and X-ray photoelectron spectroscopy (XPS) were used to characterize the prepared catalysts. The CB and VB potentials of graphitic carbon nitride could be tuned from −1.09 and +1.55 eV to −0.29 and +2.25 eV by controlling the weight ratio of eutectic salts to melamine. Besides, ions doping inhibited the crystal growth of graphitic carbon nitride, enhanced the surface area, and increased the separation rate of photogenerated electrons and holes. The visible-light-driven Rhodamine B (RhB) photodegradation and mineralization performances were significantly improved after K–Na co-doping.

  3. Cervical end preparation design on collarless metal ceramic crown to the decrease of bacterial colony

    Directory of Open Access Journals (Sweden)

    Edy Machmud

    2010-09-01

    Full Text Available Background: Cervical end preparation design is an important procedure in fixed partial denture. If the cervical end preparation design is inadequate, dental plaque will easily be formed and this may indicate the beginning of periodontal disease. Purpose: This study was aimed to analyze the effect of cervical end preparation design on collarless metal ceramic crown towards the decrease of bacterium colony number. Methods: This study was quasi-experimental study applying pre and post test on a control group involving 48 subjects with shoulder, bevel shoulder, and deep chamfer cervical end preparation. The bacterium colonies were examined on the 1st, 7th, and 21st days after the insertion of collarless metal ceramic crown. Results: The study showed that bacterium colony increased significantly in deep chamfer and bevel shoulder preparation design between the treatment group and the control group (p<0.05. In shoulder preparation there was not significant different between the treatment group and the control group (p>0.05. Conclusion: Compared to the bevel shoulder and deep chamfer, shoulder design is the best design for collarless metal ceramic crown restoration.Latar belakang: Desain preparasi tepi servikal merupakan suatu tahap yang sangat menentukan dalam pembuatan gigi tiruan cekat. Apabila desain preparasi tepi servikal tidak adekuat dapat menyebabkan pembentukan plak gigi pada daerah tersebut. Keadaan ini merupakan tahap awal terjadinya penyakit periodontal. Tujuan: Untuk menganalisis pengaruh desain preparasi tepi servikal yang dibuat pada mahkota collarless metal ceramic untuk mengurangi jumlah bakterium koloni. Metode: Penelitian ini adalah penelitian eksperimental semu dengan metode pre and post test dan kelompok kontrol terhadap 48 subyek penelitian. Dilakukan preparasi gigi dan pembuatan akhiran preparasi tepi servikal shoulder, bevel shoulder, dan deep chamfer pada subyek penelitian. Pemeriksaan koloni bakteri dilakukan pada hari ke-1

  4. Preparation and characterization of nanocrystalline barium ferrite ceramic

    Science.gov (United States)

    Saeedi, Majid; Abdellahi, Majid; Rahimi, Alireza; Khandan, Amirsalar

    2016-09-01

    In this work, nanocrystalline BaFe12O19 hexaferrite ceramic was synthesized via high-energy ball milling and subsequent sintering from the mixed powders of Fe2O3 and BaCO3. X-ray diffraction (XRD), X-ray photoemission spectroscopy (XPS), differential thermal analysis (DTA) and scanning electron microscopy (SEM) were utilized to understand the structural evolution during the synthesis process. Vibrating sample magnetometer (VSM) was also used to investigate the magnetic properties of the samples as a function of sintering process. DTA analysis suggested that the initial high-energy milling of the precursors helps the formation of single domain magnetic particles. According to the results obtained, BaFe12O19 can be formed via two main steps, during which BaFe2O4 is formed initially that eventually turns into BaFe12O19. VSM-based findings showed that the ratio of remanent magnetization to magnetization value (Mr/Ms) is around 0.5 which is the expected value for randomly oriented assembly of uniaxial single-domain particles undergoing magnetization reversal by coherent rotation. The observed magnetic parameters (Mr and Ms) are much higher than the previously reported values, due to the reduction in particle size as a result of ball milling.

  5. Structural, dielectric and magnetic properties of cobalt ferrite prepared using auto combustion and ceramic route

    Energy Technology Data Exchange (ETDEWEB)

    Murugesan, C., E-mail: murugesanscience@gmail.com; Perumal, M.; Chandrasekaran, G.

    2014-09-01

    Cobalt ferrite is synthesized by using low temperature auto combustion and high temperature ceramic methods. The prepared samples have values of lattice constant equal to 8.40 Å and 8.38 Å for auto combustion and ceramic methods respectively. The FTIR spectrum of samples of the auto combustion method shows a high frequency vibrational band at 580 cm{sup −1} assigned to tetrahedral site and a low frequency vibrational band at 409 cm{sup −1} assigned to octahedral site which are shifted to 590 cm{sup −1} and 412 cm{sup −1} for the ceramic method sample. SEM micrographs of samples show a substantial difference in surface morphology and size of the grains between the two methods. The frequency dependent dielectric constant and ac conductivity of the samples measured from 1 Hz to 2 MHz at room temperature are reported. The room temperature magnetic hysteresis parameters of the samples are measured using VSM. The measured values of saturation magnetization, coercivity and remanent magnetization are 42 emu/g, 1553 Oe, 18.5 emu/g for the auto combustion method, 66.7 emu/g, 379.6 Oe, and 17.3 emu/g for the ceramic method, respectively. The difference in preparation methods and size of the grains causes interesting changes in electrical and magnetic properties.

  6. Biomorphous SiC ceramics prepared from cork oak as precursor

    Science.gov (United States)

    Yukhymchuk, V. O.; Kiselov, V. S.; Valakh, M. Ya.; Tryus, M. P.; Skoryk, M. A.; Rozhin, A. G.; Kulinich, S. A.; Belyaev, A. E.

    2016-04-01

    Porous ceramic materials of SiC were synthesized from carbon matrices obtained via pyrolysis of natural cork as precursor. We propose a method for the fabrication of complex-shaped porous ceramic hardware consisting of separate parts prepared from natural cork. It is demonstrated that the thickness of the carbon-matrix walls can be increased through their impregnation with Bakelite phenolic glue solution followed by pyrolysis. This decreases the material's porosity and can be used as a way to modify its mechanical and thermal characteristics. Both the carbon matrices (resulted from the pyrolysis step) and the resultant SiC ceramics are shown to be pseudomorphous to the structure of initial cork. Depending on the synthesis temperature, 3C-SiC, 6H-SiC, or a mixture of these polytypes, could be obtained. By varying the mass ratio of initial carbon and silicon components, stoichiometric SiC or SiC:C:Si, SiC:C, and SiC:Si ceramics could be produced. The structure, as well as chemical and phase composition of the prepared materials were studied by means of Raman spectroscopy and scanning electron microscopy.

  7. Preparation of Ln3-xEuxS4 (Ln=Ce,Pr,and Nd) ceramics by pressureless sintering

    Institute of Scientific and Technical Information of China (English)

    YUAN HaiBin; ZHANG JianHui; YU RuiJin; SU Oiang

    2009-01-01

    The preparation of ternary rare earth sulfides of Ln3-xEuxS4(Ln = Ce,Pr,and Nd) ceramics was investigated,and the effect of Eu substitution on Ln3-xEuxS4 ceramics was also studied.Ln3-xEuxS4 powders were synthesized by the sulfurization of their oxide powders using carbon disulfide gas.Ln3-xEuxS4 ceramics were sintered by pressure-less sintering method.All pressureless sintered Ln3-xEuxS4 ceramics crystallized in y-phase.It was found that Eu substitution could improve the density of Ln3-xEuxS4 ceramics.Furthermore,Eu substitution might narrow the optical band gaps of Ln3-xEuxS4 ceramics.

  8. Preparation of AZO Nanoparticles, Ceramic Targets and Thin Films by a Co-precipitaition Method

    Institute of Scientific and Technical Information of China (English)

    XIU Sanmu; WEI Tiefeng; YANG Ye; ZHANG Ting; LI Jia; SONG Weijie

    2015-01-01

    We comprehensively study the co-precipitation preparation of aluminum doped zinc oxide (AZO) nanoparticles, ceramic target and thin iflm deposition. The nanoparticles calcined below 700℃possessed pure wurtzite structure of ZnO. When the calcination temperature exceeded 700℃, ZnAl2O4 phase appeared. The resistivity and relative density of the AZO target pressed from nanoparticles were 3×10-3Ω∙cm and 99.1%, respectively. The minimum resistivity of AZO thin films prepared by DC sputtering of the ceramic target reached 4.1×10–4Ω∙cm with the mobility of 33 cm2/v∙s and the carrier concentration of 4.5 ×1020 cm-3. The average optical transmittance of the AZO thin iflms in the visible wavelength range (400-800 nm) was more than 80%.

  9. Fourier transform infrared analysis of ceramic powders: Quantitative determination of alpha, beta, and amorphous phases of silicon nitride

    Energy Technology Data Exchange (ETDEWEB)

    Trout, T.K.; Bellama, J.M.; Brinckman, F.E.; Faltynek, R.A.

    1989-03-01

    Fourier transform infrared spectroscopy (FT-IR) forms the basis for determining the morphological composition of mixtures containing alpha, beta, and amorphous phases of silicon nitride. The analytical technique, involving multiple linear regression treatment of Kubelka-Munk absorbance values from diffuse reflectance measurements, yields specific percent composition data for the amorphous phase as well as the crystalline phases in ternary mixtures of 0--1% by weight Si/sub 3/N/sub 4/ in potassium bromide.

  10. Coal Fly Ash Ceramics: Preparation, Characterization, and Use in the Hydrolysis of Sucrose

    Directory of Open Access Journals (Sweden)

    Ricardo Pires dos Santos

    2014-01-01

    Full Text Available Coal ash is a byproduct of mineral coal combustion in thermal power plants. This residue is responsible for many environmental problems because it pollutes soil, water, and air. Thus, it is important to find ways to reuse it. In this study, coal fly ash, obtained from the Presidente Médici Thermal Power Plant, was utilized in the preparation of ceramic supports for the immobilization of the enzyme invertase and subsequent hydrolysis of sucrose. Coal fly ash supports were prepared at several compaction pressures (63.66–318.30 MPa and sintered at 1200°C for 4 h. Mineralogical composition (by X-ray diffraction and surface area were studied. The ceramic prepared with 318.30 MPa presented the highest surface area (35 m2/g and amount of immobilized enzyme per g of support (76.6 mg/g. In assays involving sucrose inversion, it showed a high degree of hydrolysis (around 81% even after nine reuses and 30 days’ storage. Therefore, coal fly ash ceramics were demonstrated to be a promising biotechnological alternative as an immobilization support for the hydrolysis of sucrose.

  11. Study of Large-Scale Aluminium-Doped Zinc Oxide Ceramic Targets Prepared by Slip Casting

    Directory of Open Access Journals (Sweden)

    Ling-yun Han

    2016-01-01

    Full Text Available Aluminium-doped zinc oxide (AZO ceramic green compacts at a size of 170 × 340 × 17 mm have been prepared by slip casting. An AZO slurry with good fluidity and viscosity was obtained when 1.2 wt% of dispersant was added, which indicates that the slurry prepared with micrometre particles is more suitable for slip casting. The densification and electrical properties of the AZO targets prepared by particles with different sizes were investigated after sintering from 1380 to 1460°C. The results showed that the relative density of the AZO target prepared with 45 nm particles could reach nearly 98% at 1380°C; the resistivity of the AZO target prepared with nanometre particles could be as low as 1.6 × 10−3 Ω·cm at 1400°C; and the average transmittance of the AZO film prepared with nanometre particles could reach a maximum value of 93.73% in the visible region at 250 W. In this study, the correlation between the density, resistivity, and grain growth of AZO ceramic green compacts was studied.

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

    Science.gov (United States)

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

    2016-05-11

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

  13. Preparation and Photocatalytic Property of TiO2/Diatomite-Based Porous Ceramics Composite Materials

    Directory of Open Access Journals (Sweden)

    Shuilin Zheng

    2012-01-01

    Full Text Available The diatomite-based porous ceramics was made by low-temperature sintering. Then the nano-TiO2/diatomite-based porous ceramics composite materials were prepared by hydrolysis deposition method with titanium tetrachloride as the precursor of TiO2 and diatomite-based porous as the supporting body of the nano-TiO2. The structure and microscopic appearance of nano-TiO2/diatomite-based porous ceramics composite materials was characterized by XRD and SEM. The photocatalytic property of the composite was investigated by the degradation of malachite green. Results showed that, after calcination at 550°C, TiO2 thin film loaded on the diatomite-based porous ceramics is anatase TiO2 and average grain size of TiO2 is about 10 nm. The degradation ratio of the composite for 5 mg/L malachite green solution reached 86.2% after irradiation for 6 h under ultraviolet.

  14. Preparation of Neodymium-Doped Yttrium Aluminum Garnet Transparent Ceramics by Homogeneous Precipitation Method

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    Neodymium doped-yttrium aluminum garnet (Nd: YAG) transparent polycrystalline ceramics already become substitutes of single crystals because they are provided with easy fabrication, low cost, large size, highly doped concentration, high heat conductivity, mass fabrication, multi-layers and multi-functions. The Nd: YAG precursor powders with loosely dispersed, slightly agglomerated, super fine and YAG cubic crystal phase were synthesized at 1100 ℃ by the hocal stabilizer, TEOS as sintering additive. The Nd:YAG transparent ceramics were prepared after being vacuum sintered at 1700 ℃ for 5 h. The Nd:YAG ceramic materials were characterized by the TG-DTA, XRD, FT-IR, TEM, FEG-ESEM and FT-PL. The results show that the crystallization temperature of YAG is 850 ℃ and the intermediate crystal phase YAP forming during the heat treatment transforms to YAG cubic crystal phase at 1050 ℃. The lasing wavelength of (Nd0.01Y0.99)3Al5O12 transparent ceramics is 1.065 μm and there exists a slight red-shift compared to the single crystal with the same chemical composition. The optical transmittance is 45% in the visible light and 58% in the near infrared light and the optical transmittance descends with the decreasing the wavelength.

  15. All- Ceramic Crown Preparation and the Remained wall Thickness of the Pulp Chamber

    Directory of Open Access Journals (Sweden)

    Mohammadzadeh Akhlaghi N.

    2012-12-01

    Full Text Available tatement of Problem: A minimally invasive method of preparation is essential to prevent tooth structure weakening and pulp irritation; especially for mandibular anterior single-tooth all-ceramic crowns. According to many investigations, one of the most important reasons of pulp injury caused by tooth preparation for different restorative procedures is reduced “remained wall thickness” (RWT. In order to protect the pulp from irritation, it is necessary to maintain a 0.5 mm of RWT.Purpose: The purpose of the present study was to evaluate the effect of all-ceramic crown preparation on pulp chamber RWT of mandibular incisors.Materials and Method: Mesiodistal and buccolingual initial images of 24 ex-tracted mandibular incisors were provided. The pulp chamber initial wall thick-nesses of buccal, lingual and proximal surfaces of cervical, 1and 2 mm above the cervical areas and also the incisal surfaces of incisal sections were measured using digital radiography and Photoshop software. After all-ceramic crown preparation, images were provided at the same initial positions. The initial and remained pulp chamber wall thicknesses were statistically evaluated and analyzed by ANOVA, paired t-test and a post hoc Tukey test.Results: Repeated measures ANOVA showed that the mean of pre- or post-preparation wall thicknesses were not significantly different for each surface at the three horizontal levels (p> 0.05. However, there were significant differences between the surfaces for each section. Comparison of pre- and post-preparation wall thicknesses revealed significant differences (p< 0.05. Proximal surfaces of cervical sections had the least RWT (0.42±0.12.Conclusion: According to the results of the present study, the least amount of initial and remained wall thicknesses of pulp chamber were related to the proximal surfaces, particularly in cervical areas. Therefore a reduction of preparation to 0.7 mm is suggested to prevent future pulp injury for

  16. Analysis of recovery process of low-dose neutron irradiation-induced defects in silicon nitride-based ceramics by thermal annealing

    Energy Technology Data Exchange (ETDEWEB)

    Rueanngoen, Areerak, E-mail: areerak_k@yahoo.com [Department of Nuclear Engineering, Graduate School of Science and Engineering, Tokyo Institute of Technology, O-okayama, Meguro-ku, Tokyo 152-8550 (Japan); Kanazawa, Koumei [Department of Nuclear Engineering, Graduate School of Science and Engineering, Tokyo Institute of Technology, O-okayama, Meguro-ku, Tokyo 152-8550 (Japan); Imai, Masamitsu; Yoshida, Katsumi; Yano, Toyohiko [Research Laboratory for Nuclear Reactors, Tokyo Institute of Technology, O-okayama, Meguro-ku, Tokyo 152-8550 (Japan)

    2014-12-15

    Two kinds of silicon nitride ceramics consisting of different polymorphs were neutron-irradiated up to 8.5 × 10{sup 24} n/m{sup 2} (E > 0.1 MeV) at 563 K, and their annealing behaviors were compared to those of previously reported SiAlON polymorphs subjected to the same irradiation condition. The macroscopic length change of α- and β-Si{sub 3}N{sub 4} and α- and β-SiAlON were 0.11%, 0.06%, 0.12% and 0.14%, respectively. Based on swelling data and microstructural observations, the low dose neutron irradiation-induced defects in silicon nitride-based ceramics were considered to be primarily point defects. In order to investigate the kinetics of defect recovery, these irradiated specimens were isothermally and isochronally annealed continuously up to 1473 K. Macroscopic length change decreased gradually with increasing annealing temperature. Recovery curves of isochronal annealing of α-Si{sub 3}N{sub 4} and α-SiAlON were similar, and those of β-Si{sub 3}N{sub 4} and β-SiAlON were also similar. The recombination rate constant as a first-order reaction increased with the increasing of the isothermal annealing temperature. A two-stage recovery process was considered between the irradiation temperature and 1473 K. The activation energies at higher temperatures were almost double those at lower temperatures in both Si{sub 3}N{sub 4} and SiAlON. At lower temperatures range the recovery should occur by annihilation of close-spaced Frenkel pairs. On the other hand, at higher temperatures, the recovery process may be governed by the annihilation of separated Frenkel pairs. In addition, the activation energies for defect recovery in Si{sub 3}N{sub 4} were larger than defects in SiAlON. Recovery characteristics of α- and β-phases were different in both crystals that are suggested to be due to differences in crystal structures.

  17. Experimental studies of superhard materials carbon nitride CNx prepared by ion-beam synthesis method

    Institute of Scientific and Technical Information of China (English)

    辛火平; 林成鲁; 许华平; 邹世昌; 石晓红; 吴兴龙; 朱宏; P.L.FHemment

    1996-01-01

    Formation of superhard materials carbon nitride CNt by using ion-beam synthesis method is reported.100-keV high-dose N+ ions were implanted into carbon thin films at different temperatures.The samples were evaluated by X-ray photoelectron spectroscopy (XPS),Fourier transformation-infrared absorption spectroscopy (FTIR),Raman spectroscopy,cross-sectional transmission electron microscopy (XTEM),Rutherford backscattering spectroscopy (RBS).X-ray diffraction analysis (XRD) and Vickers microhardness measurement.The results show that the buried carbon nitride CN> layer has been successfully formed by using 100-keV high-dose N+ ions implantation into carbon thin film.Implantation of reactive ions into silicon (IRIS) computer program has been used to simulate the formation of the buried β-C3N4 layer as N+ ions are implanted into carbon.A good agreement between experimental measurements and IRIS simulation is found.

  18. Preparation technology and anti-corrosion performances of black ceramic coatings formed by micro-arc oxidation on aluminum alloys

    Institute of Scientific and Technical Information of China (English)

    CHEN Ling; HAN Jing; YU Shengxue

    2006-01-01

    In order to prepare ornamental and anti-corrosive coating on aluminum alloys, preparation technology of black micro-arc ceramic coatings on Al alloys in silicate based electrolyte was studied.The influence of content of Na2WO4 and combination additive in solution on the performance of black ceramic coatings was studied; the anticorrosion performances of black ceramic coatings were evaluated through whole-immersion test and electrochemical method in 3.5% NaCl solution at different pH value; SEM and XRD were used to analyze the surface morphology and phase constitutes of the black ceramic coatings.Experimental results indicated that, without combination additives, with the increasing of Na2WO4 content in the electrolyte, ceramic coating became darker and thicker, but the color was not black; after adding combination additive, the coating turned to be black; the black ceramic coating was multi-hole form in surface.There was a small quantity of tungsten existing in the black ceramic coating beside α-Al2O3 phase and β-Al2O3 phase.And aluminum alloy with black ceramic coating exhibited excellent anti-corrosion property in acid, basic and neutral 3.5% NaCl solution.

  19. Preparation of Zeolite X Membranes on Porous Ceramic Substrates with Zeolite Seeds

    Institute of Scientific and Technical Information of China (English)

    Zhongqiang Xu; Qingling Chen; Guanzhong Lu

    2002-01-01

    Zeolite X membranes were investigated by in-situ hydrothermal synthesis on porous ceramic tubes precoated with zeolite X seeds or precursor amorphous aluminosilicate, and porous α-Al2O3 ceramic tubes with a pore size of 50 200 nm were employed as supports. Zeolite X crystals were synthesized by the classic method and mixed into deionized water as a slurry with a concentration of 0.2 0.5wt%, having a range of crystal sizes from 0.2 to 2μm. Crystal seeds were pressed into the pores near the inner surface of the ceramic tubes, and crystallization took place at 95℃ for 24-96 h. It was also investigated that Boehmite sol added with zeolite X seeds was precoated on ceramic supports to form a layer of γ-Al2O3 by heating, and hydrothermal crystallization could then take place to prepare the zeolite membranes on the composite ceramic tubes. The crystal species were characterized by XRD, and the morphology of the supports subjected to crystallization was characterized by SEM. The composite zeolite membranes have zeolitic top-layers with a thickness of 10-25 μm, and zeolite crystals can be intruded into pores of the supports as deeply as 100μm. The experimental results indicate that the precoating of zeolitic seeds on supports is beneficial to crystallization by shortening the synthesis time and improving the membrane strength. The resulting zeolite X membrane shows permselectivity to tri-n-butylamine((C4H9)3N) over perfluro-tributyl-amine ((C4Fg)3N), and a permeance ratio of 57 for ((C4Hg)3N to (C4F9)3N could be reached at 350℃. Permeances of BZ, EB and TIPB through the zeolite membrane were also measured and were found to slightly increase with temperature.

  20. Investigation of pitch-sulphur mixtures used as binder in the preparation of black ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Clausse, V.; Bastien, T.; Hoppe, S.; Mareche, J.F.; Fierro, V.; Celzard, A. [Nancy University, Nancy (France)

    2009-08-15

    Since tens of years, sulphur is a very classical additive in the composition of black ceramics because, if added in small amounts (i.e., less than 10 wt.% of the binder), it improves their mechanical properties without strongly degrading their graphitability and their conductivity. Macroscopic properties of black ceramics strongly depend on the quality of the interfaces between grains of solid filler (graphite, carbon black) and coke originating from the pyrolysis of the binder; thus, the binder should correctly wet the filler prior to the carbonisation process. Coal-tar pitch usually exhibits a high affinity for carbon grains. In the effect of the amount of sulphur on the viscosity of the molten binder and on the way the present work, it wets the solid filler was investigated. For that purpose, the penetration of mixtures of coal-tar pitch and sulphur inside a bed of carbon particles was studied as a function of temperature. The influence of the sulphur content on composition, optical texture, and transport properties of the derived black ceramics, as well as the way it was mixed with the other constituents, were also examined. It was found that the preparation of black ceramics may be achieved easily and in safe conditions, without evolution of H{sub 2}S, using pitch-sulphur mixtures first molten in a bladed mixer, and having sulphur contents within the range 10-20 wt.%. The presence of sulphur increases the coke yield but lowers the ability to graphitise, thus limiting the transport properties of the resultant black ceramic. The optimal concentration of sulphur should thus be a compromise between mechanical strength and other physical properties.

  1. Preparation of Lanthanum-Doped Pb(Zr,Ti)O3 Ceramics Sheets by Tape Casting

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The physical and electrical properties of lanthanum doped Pb(Zr,Ti)O3 ceramic sheets (PLZT) which were prepared by tape casting method were carried out. Tape casting of lanthanum modified PZT was performed using commercial cellulose acetate binders and poly(ethylene glycol) plasticizers in ethanol solvent. Tapes from these slips were casted on a polymer substrate. The PLZT green tapes were stacked for 5 units and sintered in air at 1050℃ for 1 h with heating rate 5℃/min. SEM micrographs show that the tape is dense (90.26% of theoretical density) and rather uniform with grain size of approximately 1.1 ? m. The dielectric permittivity and loss tangent of PLZT ceramics as a function of temperature at 1 kHz suggest that the compounds exhibit a phase transition of diffuse type. The transition temperature (Tm) and piezoelectric coefficient (d33) were 110℃ and 117 pC/N, respectively.

  2. Preparation and luminescence properties of Ce3+/Dy3+-codoped fluorosilicate glass ceramics

    Institute of Scientific and Technical Information of China (English)

    CUI Shuo; ZHAO Daliang; Huang Jinglu; FU Hengyi; QIAN Jiangyun; LUO Qun; Qiao Xusheng; FAN Xianping; ZHANG Xianghua

    2012-01-01

    The Ce3+and Dy3+ co-doped fluorosilicate glass and glass ceramics containing SrF2 or CeF3 nanocrystals were prepared under reducing atmosphere.The precipitated nano-crystalline phase shifted from cubic SrF2 to hexagonal CeF3 gradually with the heat treatment temperature increasing from 620 to 680 ℃.The glass and glass ceramics emitted white light,deriving from a combination of the Ce3+ blue and the Dy3+ yellow light.The CIE coordinates could be tuned by adjusting the ratio of Ce3+/Dy3+ concentration.The luminescence could be enhanced significantly by annealing the samples at the temperatures lower than 640 ℃.

  3. Students’ evaluation of preclinical simulation for all ceramic preparation (In Faculty of Dentistry Universiti Kebangsaan Malaysia

    Directory of Open Access Journals (Sweden)

    Natasya Ahmad Tarib

    2008-06-01

    Full Text Available The purpose of the study is to evaluate all ceramic crown (ACC preparations those were made by dental undergraduate students during the preclinical sessions. 104 plastic teeth were prepared by 4th year dental undergraduates during the preclinical session for ACC crown examined. The teeth were placed on the frasaco arches and were mounted in the frasaco head. The preparations were examined for the tapering, presence of undercuts, incisal and cingulum reductions as well as preparation of shoulder margin. Preparations were examined using hand instruments and visual. The sample size was 92 plastic teeth. Most of the preparations were acceptable with acceptable placement and types of margins, adequate axial and incisal reductions and acceptable tapered of the axial walls. On the other hand, most of the teeth showed absence of cingulum wall. Most of the crowns prepared by the students were acceptable. It showed that they understood the principles of crown preparation. Cingulum wall preparation has to be given greater emphasis as it is important in the retention and resistance of the restoration.

  4. Influence of cavity preparation design on fracture resistance of posterior Leucite-reinforced ceramic restorations.

    Science.gov (United States)

    Soares, Carlos Jose; Martins, Luis Roberto Marcondes; Fonseca, Rodrigo Borges; Correr-Sobrinho, Lourenco; Fernandes Neto, Alfredo Julio

    2006-06-01

    Controversy exists concerning the preferred cavity design for posterior ceramic restorations to improve their resistance to fracture under occlusal load. The aim of this study was to assess the resistance to fracture of leucite-reinforced ceramic restorations placed on molars with different cavity preparation designs. Ninety noncarious molars were selected, stored in 0.2% thymol solution, and divided into 9 groups (n = 10): IT, intact teeth; CsI, conservative inlay; ExI, extensive inlay; CsO/mb, conservative onlay with mesio-buccal cusp coverage; ExO/mb, entensive onlay with mesio-buccal cusp coverage; CsO/b, conservative onlay with buccal cusp coverage; ExO/b, entensive onlay with buccal cusp coverage; CsO/t, conservative onlay with total cusp coverage; ExO/t, extensive onlay with total cusp coverage. Teeth were restored with a Leucite-reinforced ceramic (Cergogold). The fracture resistance (N) was assessed under compressive load in a universal testing machine. The data were analyzed with 1-way and 2-way analyses of variance, followed by the Tukey HSD test (alpha = .05). Fracture modes were recorded, based on the degree of tooth structure and restoration damage. One-way analysis showed that intact teeth had the highest fracture resistance values. Two-way analyses showed no significant differences for the isthmus extention factor, but showed a significant difference for the preparation design type of fracture (P = .03), and also for the interaction between both factors (P = .013). The fracture mode observed in all groups tended to involve only restorations. Within the limitations of this study, it was observed that cuspal coverage does not increase fracture resistance of the posterior tooth-restoration complex restored with leucite-reinforced ceramics.

  5. Ultra high strain properties of lanthanum substituted PZT electro-ceramics prepared via mechanical activation

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Ajeet, E-mail: jkajeet@yahoo.co.in [Ceramics and Composites Group, Defence Metallurgical Research Laboratory, Hyderabad 500058 (India); School of Physics, University of Hyderabad, Hyderabad 500046 (India); Bhanu Prasad, V.V., E-mail: bhanu@dmrl.drdo.in [Ceramics and Composites Group, Defence Metallurgical Research Laboratory, Hyderabad 500058 (India); James Raju, K.C., E-mail: kcjrsp@yahoo.com [School of Physics, University of Hyderabad, Hyderabad 500046 (India); James, A.R., E-mail: james@dmrl.drdo.in [Ceramics and Composites Group, Defence Metallurgical Research Laboratory, Hyderabad 500058 (India)

    2014-06-25

    Highlights: • PLZT comparable with PMN–PT and their hot-pressed counterparts synthesized. • HEM applied for ceramic preparation at reduced sintering temperature. • Strain value (0.27%) comparable to previous reported values for PLZT 8/60/40. • The electric field induced (strain) hysteresis loss was also found to be very less. - Abstract: Substitution of lanthanum at the A sites of perovskite lead zirconate titanate ceramics shows an improvement in the structural and electrical properties. (Pb{sub 0.92}La{sub 0.08})(Zr{sub 0.60}Ti{sub 0.40})O{sub 3} (PLZT 8/60/40) was prepared using high energy mechano-chemical milling. The effect of milling on the microstructure and electrical properties of PLZT 8/60/40 has been studied. X-ray diffraction shows the phase formation after milling itself. TEM was used to measure the particle size. The SEM image of the sintered pellet shows a dense microstructure and the average grain size was found to be <1.5 μm. Electrical properties of the ceramics were characterized. Piezoelectric charge coefficient (d{sub 33}) was found to be 561 pC/N. Resonance studies were performed on poled ceramics and the electromechanical coupling factor was calculated by the resonance method. The PLZT 8/60/40 composition showed a well saturated and uniform P–E hysteresis loop with remanent polarization (P{sub r}) of 33.29 μC/cm{sup 2} and a coercive field (E{sub c}) of 10.57 kV/cm. Electric field induced strain (S–E loop) shows a value of ∼0.27% with minimum loss.

  6. Preparation of thin ceramic monofilaments for TEM observation with novel embedding processes

    Energy Technology Data Exchange (ETDEWEB)

    Li, Siwei [College of Materials, Key Laboratory of High Performance Ceramic Fibers (Xiamen University), Ministry of Education, Xiamen 361005 (China); National Key Laboratory of Thermostructure Composite Materials, Northwestern Polytechnical University, Xi' an 710072 (China); Feng, Zude, E-mail: zdfeng@xmu.edu.cn [College of Materials, Key Laboratory of High Performance Ceramic Fibers (Xiamen University), Ministry of Education, Xiamen 361005 (China); Zhang, Litong [National Key Laboratory of Thermostructure Composite Materials, Northwestern Polytechnical University, Xi' an 710072 (China); Wang, Yanyan; Chen, Lifu [College of Materials, Key Laboratory of High Performance Ceramic Fibers (Xiamen University), Ministry of Education, Xiamen 361005 (China)

    2011-01-15

    An applicable method to prepare transmission electron microscopy specimens from ceramic fibers for longitudinal and cross-sectional observations is investigated. The method includes novel embedding processes to fix fibers, a polishing process using a self-manufactured device to get uniformly low thickness (40 {mu}m for L-fiber, 60 {mu}m for C-fiber), a one-side dimpling process to grind the specimen to near electron transparency (about 5 {mu}m in thickness for both L-fiber and C-fiber) and an efficient ion milling process using calculated parameters. These techniques are reliable to accomplish the preparation with high quality in a relatively short time. Many factors related to the preparation processes are discussed. -- Research Highlights: {yields}We develop an applicable method to prepare TEM specimens from thin ceramic fibers. {yields}We develop novel embedding processes to enhance the polishing efficiency. {yields}A self-manufactured device is used to get uniformly low thickness. {yields}One-side dimpling method and calculated ion milling process are introduced. {yields}Samples with large thin area for longitudinal and cross-sectional view are obtained.

  7. Preparation of thin ceramic monofilaments for TEM observation with novel embedding processes.

    Science.gov (United States)

    Li, Siwei; Feng, Zude; Zhang, Litong; Wang, Yanyan; Chen, Lifu

    2011-01-01

    An applicable method to prepare transmission electron microscopy specimens from ceramic fibers for longitudinal and cross-sectional observations is investigated. The method includes novel embedding processes to fix fibers, a polishing process using a self-manufactured device to get uniformly low thickness (40 μm for L-fiber, 60 μm for C-fiber), a one-side dimpling process to grind the specimen to near electron transparency (about 5 μm in thickness for both L-fiber and C-fiber) and an efficient ion milling process using calculated parameters. These techniques are reliable to accomplish the preparation with high quality in a relatively short time. Many factors related to the preparation processes are discussed.

  8. Thermal stability of tungsten sub-nitride thin film prepared by reactive magnetron sputtering

    Science.gov (United States)

    Zhang, X. X.; Wu, Y. Z.; Mu, B.; Qiao, L.; Li, W. X.; Li, J. J.; Wang, P.

    2017-03-01

    Tungsten sub-nitride thin films deposited on silicon samples by reactive magnetron sputtering were used as a model system to study the phase stability and microstructural evolution during thermal treatments. XRD, SEM&FIB, XPS, RBS and TDS were applied to investigate the stability of tungsten nitride films after heating up to 1473 K in vacuum. At the given experimental parameters a 920 nm thick crystalline film with a tungsten and nitrogen stoichiometry of 2:1 were achieved. The results showed that no phase and microstructure change occurred due to W2N film annealing in vacuum up to 973 K. Heating up to 1073 K led to a partial decomposition of the W2N phase and the formation of a W enrichment layer at the surface. Increasing the annealing time at the same temperature, the further decomposition of the W2N phase was negligible. The complete decomposition of W2N film happened as the temperature reached up to 1473 K.

  9. The Effect of Molar Preparation Axial Height on Retention of Adhesively-luted CAD/CAM Ceramic Crowns

    Science.gov (United States)

    2015-04-29

    Retention of Adhesively -luted CAD/CAM Ceramic Crowns 7. Intended publication/meeting: International Association of Dental Research Annual Meeting...Postgraduate Dental School The Effect of Molar Preparation Axial Height on Retention of Adhesively -luted CAD/CAM Ceramic Crowns Robert E...Capt (Dr.) Robert Wake 2. Academic Title: AEGD Dental Resident 3. School/Department/Center: AF Postgraduate Dental School, Keesler AFB. MS 4 . Phone

  10. Mechanical properties of anorthite based ceramics prepared from kaolin DD2 and calcite

    Directory of Open Access Journals (Sweden)

    A. Harabi

    Full Text Available Abstract Good quality ceramics costs a lot that has limited their use in developing countries. This work was devoted to prepare low-cost and good quality anorthite based ceramics. The proposed composition was 80 wt% kaolin (DD2 type and 20 wt% calcium oxide (CaO. The choice of these raw materials was dictated by their natural abundance coupled with a modified milling system, as another interesting advantage. Previous studies have shown that a simple vibratory multidirectional milling system using bimodal distribution of highly resistant ceramic milling elements has been successfully applied for obtaining fine powders. The influence of the relatively lower sintering temperature, ranging from 800 to 1100 °C, on the porosity and the average pore size (APS have been investigated. The APS and the porosity values of samples sintered at 950 °C were about 1 μm and 4%, respectively. The best Vickers microhardness and 3-point bending strength values for these sintered samples, using this proposed milling system, were 7.1 GPa and 203 MPa, respectively. Finally, the crystalline phase evolution during heat treatment was investigated by X-ray diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy techniques.

  11. In Situ Preparation of Titanium Carbide Ceramic Layer on Grey Cast Iron

    Directory of Open Access Journals (Sweden)

    Lisheng ZHONG

    2015-11-01

    Full Text Available In this article, we report the in situ synthesis of TiC ceramic layer between titanium plate and graphite phases in grey cast iron using heat treatment method. The microstructure of the compound region was characterized by X-ray diffraction (XRD and scanning electron microscopy (SEM, and the kinetics of the TiC ceramic layer was analyzed. The results revealed that the as-prepared TiC samples were irregularly shaped particles with a size of 1 ~ 8 μm and gradient distribution on the surface of grey cast iron. The thickness of the reaction layers increased gradually as the incubation continued, which were 62, 81, 95 and 108 μm after incubation at 1164 °C for 1, 2, 3 and 4 hours, respectively. Also, it can be recognized that the layer thickness changes in a parabolic style with incubation duration. The formation process of TiC ceramic layer consists of diffusion and in situ reaction of carbon and titanium atoms.DOI: http://dx.doi.org/10.5755/j01.ms.21.4.9700

  12. Effect of endodontic access cavity preparation on monolithic and ceramic veneered zirconia restorations.

    Science.gov (United States)

    Grobecker-Karl, Tanja; Christian, Mirko; Karl, Matthias

    2016-01-01

    Due to the high chipping rates observed in veneered zirconia ceramic restorations, the use of monolithic zirconia restorations has been recommended. This study tried to compare veneered and monolithic zirconia fixed dental prostheses (FDPs) with respect to the amount of damage induced by endodontic access preparation. Monolithic and ceramic veneered (n = 10) three-unit restorations (retainers: first premolar and first molar; pontic: second premolar) were subject to endodontic access cavity preparation in both retainers using a diamond rotary instrument under continuous water cooling. The number of chipping fractures and microfractures detected using the fluorescent penetrant method were recorded. Statistical analysis was based on Wilcoxon rank sum tests with Bonferroni correction (level of significance α = .05). Only one microfracture could be identified in the group of monolithic FDPs while a maximum of seven microfractures and three chipping fractures per retainer crown were recorded in the group of veneered restorations. At the premolar site, the veneered restorations showed significantly more microfractures (P = .0055) and chipping fractures (P = .0008). At the molar site, no significant difference with respect to microfractures could be detected (P = .0767), while significantly more chipping fractures occurred in the veneered samples (P = .0293). Monolithic zirconia restorations seem to be less susceptible to damage when endodontic access cavities have to be prepared as compared to veneered zirconia reconstructions. However, no conclusions can be drawn on the long-term performance of a specific restoration based on this study.

  13. The preparation of dental glass-ceramic composites with controlled fraction of leucite crystals

    Directory of Open Access Journals (Sweden)

    Martina Mrázová

    2008-06-01

    Full Text Available This work is dealing with synthesis of leucite powder, which can be used for the preparation of dental glassceramic composites by subsequent thermal treatment. Newly developed procedure is based on preparation of dental raw material as a mixture of two separate compounds: the crystalline leucite powder prepared at relatively low temperature and a commercial matrix powder.Hydrothermal synthesis of tetragonal leucite particles (KAlSi2O6 with the average size of about 3 μm was developed in our laboratory. The leucite dental raw material was prepared by mixing of 20 wt.% of synthetic tetragonal leucite with commercial matrix. Dental composites were prepared from the dental raw material by uniaxial pressing and firing up to 960°C. Dilatometric measurements confirmed that the coefficient of thermal expansion increased by 32% when 20 wt.% of the tetragonal leucite was added into the basic matrix. In addition, it was showed that the synthesized leucite powder was suitable for the preparation of leucite composites with controlled coefficient of thermal expansion. High value of the thermal expansion coefficient enables application of prepared composite in metal-ceramics restorations.

  14. All-ceramic single-tooth restorations: choosing the material to match the preparation--preparing the tooth to match the material.

    Science.gov (United States)

    Baltzer, A

    2008-01-01

    The shape of a crown preparation is the prime determinant for the choice of material for an all-ceramic restoration. One essential factor is the available space for the restoration, which requires a certain occlusal thickness. The dentist's preparation design determines the available vertical clearance, and the dental technician has the responsibility of advising the dentist with regard to either choosing the right material to match the preparation or to preparing the tooth to match the material. Assuming a minimum static fracture strength of > 2000 N, the following materials can be used for all-ceramic crowns: Laboratory surveys have shown that in most situations, the available occlusal clearance in clinical reality is only 0.8 to 0.9 mm (after cementing). This shows that the available space will often be insufficient for providing monoblock crowns and still on the tight side for veneered oxide ceramics (In Ceram, zirconia, etc.). However, crowns made of veneered oxide ceramics are much more complex to fabricate and much more expensive. By simply providing a minimal occlusal thickness of 1.5 mm, the treatment provider could therefore easily facilitate the use of the much more economical monoblock crowns without compromising either esthetics or strength. Actually, crowns with veneered oxide ceramic copings do not offer any higher fracture resistance compared to Mark II crowns as long as the minimum thickness requirements are met. The flexural strength of CAD/CAM-fabricated lithium disilicate rods is about twice that of CAD/CAM-fabricated Mark II rods. When used for crowns with a wall thickness of 1.5 mm, however, both materials exhibit the same fracture strength of between 2000 and 2500 N. This is related to the different reinforcing action of the adhesive luting agent, which is essentially required for both these materials. When choosing a material, preparation shapes, technical complexity and cost should be thoroughly compared and scrutinized and should figure

  15. Characterization of Ceramic Composite-Membranes Prepared by ORMOSIL Coating Sol

    Institute of Scientific and Technical Information of China (English)

    Goo-Dae Kim; Tae-Bong Kim

    2004-01-01

    Sol-gel methods offer many advantages over conventional slip-casting, including the ability to produce ceramic membranes. They are purer, more homogeneous, more reactive and contain a wider variety of compositions. We produced ormosil sol using sol-gel process under different molecular weight of polymer species [polyethylene glycol (PEG) ] in total system [Tetraethyl ortho silicate(TEOS)-polyethylene glycol (PEG)]. The properties of as-prepared ormosil sol such as,viscosity, gelation time were characterized. Also, the ceramic membrane was prepared by dip-coating with synthetic sol and its micro-structure was observed by scanning electron microscopy. The permeability and rejection efficiency of membrane for oil/water emulsion were evaluated as cross-flow apparatus. The ormosil sol coated Membrane is easily formed by steric effect of polymer and it improves flux efficiency because infiltration into porous support decreased. Its flux efficiency is elevated about 200(1/m2·h) compared with colloidal sol coated membrane at point of five minutes from starting test.

  16. Preparation of BN/SiO2 ceramics by PIP method

    Institute of Scientific and Technical Information of China (English)

    WANG Jing; WEN Guang-wu; MENG Qing-chang

    2005-01-01

    The precursor infiltration and pyrolysis(PIP) method for preparation of BN/SiO2 composites was used to improve mechanical properties, dielectric properties and feasibility of high temperature dielectric parts with large dimensions and complex shapes. In the processing procedure, the porous BN ceramic matrix was first successfully prepared by compacting the mixed powders of B and BN and then sintering them at a certain temperature under normal pressure of N2.The polycarbosilane(PCS) solution was vacuum infiltrated into porous BN ceramics at the room temperature and then at 800 ℃ in the air to depolimerize out amorphous SiO2, and sintered further at 1 300 ℃ in N2 to get BN/SiO2 composites. The microstructure of materials was studied by means of X-ray diffraction and electron probe micro analysis. The thermo-decomposition mechanism of PCS was investigated by a TG-DTA and infrared (IR) spectrum analysis. The flexural strengths were measured by the three-point bending method. The dielectric constant and the loss tangent were measured by the wave-guide method. The results show BN/SiO2 composites were fabricated. The obtained composites posses a flexural strength of 61.9693.31 MPa, the dielectric constant in the range of 3.503.78 and the order of magnitude of the loss tangent at 10-3, which are good for the high temperature dielectric parts with large size and complex shapes.

  17. Eco prep: the economical preparation of ceramic bodies; Ecoprep: la preparacion rentable de masas ceramicas

    Energy Technology Data Exchange (ETDEWEB)

    Luders, M.; Walter, H. J.; Nold, P.; Lobe, R.; Muller, M.; Gerl, S.

    2012-07-01

    Eco prep (Economic Preparation) is the sustainable technology for preparing ceramic bodies with a minimum consumption of resources. It has a huge impact on the energy balance and eliminates the need for additives to generate a high-quality slip to make granules. In consequence Eco prep delivers a significant reduction in production costs, bringing an investment in this technology to the break-even point after a very short time. Reduction in water consumption and additives and the use of new raw materials are other advantages that impulse the implementation of this production technology, as well as important reduction of CO{sub 2} emissions, contributing to meeting the goals of the Kyoto Protocol. In short: A technology already successfully applied in different industries for decades, that includes a compendium of measures based on saving reductions in a range from 66% (energy, water,) and 100% (additives, deflocculants, etc.) and will mark the future in micro granulation processes also in the ceramic industry. (Author)

  18. Preparation and characterization of silicon nitride (Si−N)-coated carbon fibers and their effects on thermal properties in composites

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Hyeon-Hye [R& D Division, Korea Institute of Carbon Convergence Technology, Jeonju 561-844 (Korea, Republic of); Nano& Advanced Materials Engineering, Jeonju University, Jeonju 560-759 (Korea, Republic of); Han, Woong [R& D Division, Korea Institute of Carbon Convergence Technology, Jeonju 561-844 (Korea, Republic of); Lee, Hae-seong [Nano& Advanced Materials Engineering, Jeonju University, Jeonju 560-759 (Korea, Republic of); Min, Byung-Gak [Department of Polymer Science & Engineering, Korea National University of Transportation, Chungju 380-702 (Korea, Republic of); Kim, Byung-Joo, E-mail: ap2-kbj@hanmail.net [R& D Division, Korea Institute of Carbon Convergence Technology, Jeonju 561-844 (Korea, Republic of)

    2015-10-15

    Graphical abstract: We report preparation and characterization of silicon nitride (Si−N)-coated carbon fibers and their effects on thermal properties in composites. Thermally composites showed enhanced thermal conductivity increasing from up to 59% by the thermal network. - Highlights: • A new method of Si−N coating on carbon fibers was reported. • Silane layer were successfully converted to Si−N layer on carbon fiber surface. • Si−N formation was confirmed by FT-IR, XPS, and EDX. • Thermal conductivity of Si−N coated CF composites were enhanced to 0.59 W/mK. - Abstract: This study investigates the effect of silicon nitride (Si−N)-coated carbon fibers on the thermal conductivity of carbon-fiber-reinforced epoxy composite. The surface properties of the Si−N-coated carbon fibers (SiNCFs) were observe using Fourier transform infrared spectroscopy, scanning electron microscopy, energy dispersive spectroscopy, and X-ray photoelectron spectroscopy, and the thermal stability was analyzed using thermogravimetric analysis. SiNCFs were fabricated through the wet thermal treatment of carbon fibers (Step 1: silane finishing of the carbon fibers; Step 2: high-temperature thermal treatment in a N{sub 2}/NH{sub 3} environment). As a result, the Si−N belt was exhibited by SEM. The average thickness of the belt were 450–500 nm. The composition of Si−N was the mixture of Si−N, Si−O, and C−Si−N as confirmed by XPS. Thermal residue of the SiNCFs in air was enhanced from 3% to 50%. Thermal conductivity of the composites increased from 0.35 to 0.59 W/mK after Si−N coating on carbon surfaces.

  19. Property of Uranium Nitride Ceramic Pellet by Hot Press Sintering%热压烧结 UN 陶瓷芯块的性能

    Institute of Scientific and Technical Information of China (English)

    尹邦跃; 屈哲昊

    2014-01-01

    Uranium nitride nuclear fuel has lots of advantages ,such as high uranium density ,high melt point ,high thermal conductivity ,low thermal expansion coefficient and high irradiation stability ,so it is an important candidate fuel for the future nuclear energy systems including space nuclear reactor ,nuclear rocket ,fast reactor and ADS . In this research ,U2N3 powders were fabricated by nitriding reaction of nitrogen and uranium powders .UN ceramic pellets with density of 93.5% TD (theory density) have a little residual metal uranium when U2 N3 powders with median particle size of 38.3 μm were hot press sintered in vacuum at 1 600 ℃ .But UN ceramic pellets can be vacuum hot press sintered to 96 .1% TD at 1 550 ℃ by 18.1 μm U2 N3 powders ,without residual uranium ,in w hich the total mass content of U and N is 99.57% ,the impurity content of each heavy metal is less than 50 μg/g ,the oxygen content is 1 048 μg/g ,and the car-bon content is 502 μg/g .U2 N3 will completely be decomposed into UN above 1 027 ℃ , and UN will also be decomposed above 1 627 ℃ .%UN燃料具有铀密度高、熔点高、热导率高、热膨胀系数低、辐照稳定性好等优点,是未来空间核电源、核火箭、快堆和ADS的重要候选燃料。本文采用金属铀粉与氮气在300~400℃直接发生化合反应,制得单相U2 N3粉末。粒度为38.3μm的 U2 N3粉末在1600℃真空热压烧结,制得相对密度为93.5%、存在少量金属铀相的U N陶瓷;而18.1μm的U2 N3粉末在1550℃真空热压烧结,制得相对密度为96.1%、不残留金属铀相的 U N陶瓷,U与N的总质量分数为99.57%,每个金属杂质含量均低于50μg/g ,氧含量为1048μg/g ,碳含量为502μg/g。U2 N3在1027℃以上将会完全分解成UN ,UN在1627℃以上也会发生分解。

  20. Development of high-temperature resistant, noncorrodible, nonmetallic ceramic materials, especially silicon nitride in gas turbine application. Entwicklung von hochwarmfesten, korrosionsbestaendigen, nichtmetallischen keramischen Werkstoffen, insbesondere Siliciumnitrid fuer den Gasturbinenbau

    Energy Technology Data Exchange (ETDEWEB)

    Blecha, M.; Pohlmann, H.J.

    1985-03-01

    The report under review is part of the project 'Ceramic Materials for Automobile Gas Turbines', which has been sponsored by the Ministry for Research and Technology of the Federal Republic of Germany since 1974 and describes the works in the years from 1980 to 1983. Special effort has been made in the improvement of silicon nitride concerning oxidation resistance and strength, suitable production techniques such as foil casting, injection moulding, extrusion and isostatic pressing as well as the manufacturing of structural components with improved material data for test purposes. With this the tight connection of production techniques, construction and testing in simulated application conditions was proved.

  1. History of ``NANO''-Scale VERY EARLY Solid-State (and Liquid-State) Physics/Chemistry/Metallurgy/ Ceramics; Interstitial-Alloys Carbides/Nitrides/Borides/...Powders and Cermets, Rock Shocks, ...

    Science.gov (United States)

    Maiden, Colin; Siegel, Edward

    History of ``NANO'': Siegel-Matsubara-Vest-Gregson[Mtls. Sci. and Eng. 8, 6, 323(`71); Physica Status Solidi (a)11,45(`72)] VERY EARLY carbides/nitrides/borides powders/cermets solid-state physics/chemistry/metallurgy/ ceramics FIRST-EVER EXPERIMENTAL NANO-physics/chemistry[1968 ->Physica Status Solidi (a)11,45(`72); and EARLY NANO-``physics''/NANO-``chemistry'' THEORY(after: Kubo(`62)-Matsubara(`60s-`70s)-Fulde (`65) [ref.: Sugano[Microcluster-Physics, Springer('82 `98)

  2. Ceramic fibers from Si-B-C polymer precursors

    Science.gov (United States)

    Riccitiello, S. R.; Hsu, M. S.; Chen, T. S.

    1993-01-01

    Non-oxide ceramics such as silicon carbide (SiC), silicon nitride (Si3N4), and silicon borides (SiB4, SiB6) have thermal stability, oxidation resistance, hardness, and varied electrical properties. All these materials can be prepared in a fiber form from a suitable polymer precursor. The above mentioned fibers, when tested over a temperature range from 25 to 1400 C, experience degradation at elevated temperatures. Past work in ceramic materials has shown that the strength of ceramics containing both carbides and borides is sustained at elevated temperatures, with minimum oxidation. The work presented here describes the formation of ceramic fibers containing both elements, boron and silicon, prepared via the polymer precursor route previously reported by the authors, and discusses the fiber mechanical properties that are retained over the temperature range studied.

  3. A novel BN–MAS system composite ceramics with greatly improved mechanical properties prepared by low temperature hot-pressing

    Energy Technology Data Exchange (ETDEWEB)

    Cai, Delong; Yang, Zhihua, E-mail: zhyang@hit.edu.cn; Duan, Xiaoming; Liang, Bin; Li, Qian; Jia, Dechang, E-mail: dcjia@hit.edu.cn; Zhou, Yu

    2015-05-01

    A novel composite ceramics with excellent mechanical properties was fabricated by means of low temperature hot-pressing using hexagonal boron nitride (h-BN) and magnesium aluminum silicate (MAS) as raw materials. The influences of starting MAS content on the microstructural evolution and mechanical properties of the composites were investigated. The results indicate that the effective enhancement of relative density of composites has been achieved, which shows that MAS is an effective liquid-phase sintering aid during the hot-pressing. MAS also can improve the structural ordering of h-BN flakes. On the other hand, h-BN exhibits significant inhibiting effect on the crystallization of α-Cordierite. Furthermore, h-BN flakes with layered structure can play a role in strengthening the MAS matrix. So h-BN and MAS are considered to be co-enhanced by each other, resulting in better sintering ability and the mechanical properties of composite ceramics are better than that of both h-BN and MAS. Composite ceramics incorporated with 50 wt% MAS exhibits the highest bending strength and fracture toughness of 213±25 MPa and 2.49±0.35 MPa m{sup 1/2}, respectively.

  4. Preparation and luminescence of new Nd 3+ doped chloro-sulphide glass-ceramics

    Science.gov (United States)

    Seznec, Vincent; Ma, Hong Li; Zhang, Xiang Hua; Nazabal, Virginie; Adam, Jean-Luc; Qiao, X. S.; Fan, X. P.

    2006-12-01

    Chalcogenide glass-ceramics containing rare earth have been studied. A reproducible process has been established for making transparent glass-ceramics. The presence of micro-crystals inside the chalco-halide glass-ceramics induces scattering at the short wavelengths. Photoluminescence of rare earth has been greatly increased in glass-ceramics. To our best knowledge, this is the first paper on rare-earth-doped glass-ceramics based on chalcogenide.

  5. Visible light induced electron transfer process over nitrogen doped TiO(2) nanocrystals prepared by oxidation of titanium nitride.

    Science.gov (United States)

    Wu, Zhongbiao; Dong, Fan; Zhao, Weirong; Guo, Sen

    2008-08-30

    Nitrogen doped TiO(2) nanocrystals with anatase and rutile mixed phases were prepared by incomplete oxidation of titanium nitride at different temperatures. The as-prepared samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), core level X-ray photoelectron spectroscopy (CL XPS), valence band X-ray photoelectron spectroscopy (VB XPS), UV-vis diffuse reflectance spectra (UV-vis DRS), and visible light excited photoluminescence (PL). The photocatalytic activity was evaluated for photocatalytic degradation of toluene in gas phase under visible light irradiation. The visible light absorption and photoactivities of these nitrogen doped TiO(2) nanocrystals can be clearly attributed to the change of the additional electronic (N(-)) states above the valence band of TiO(2) modified by N dopant as revealed by the VB XPS and visible light induced PL. A band gap structure model was established to explain the electron transfer process over nitrogen doped TiO(2) nanocrystals under visible light irradiation, which was consistent with the previous theoretical and experimental results. This model can also be applied to understand visible light induced photocatalysis over other nonmetal doped TiO(2).

  6. Facile preparation and applications of graphitic carbon nitride coating in solid-phase microextraction.

    Science.gov (United States)

    Xu, Na; Wang, Yiru; Rong, Mingcong; Ye, Zhifeng; Deng, Zhuo; Chen, Xi

    2014-10-17

    In this study, graphitic carbon nitride (g-C3N4) was used as a coating material for solid-phase microextraction (SPME) applications. Coupled to gas chromatography (GC), the extraction ability of the SPME fiber was investigated and compared with the commercial fibers of 100 μm PDMS and 85 μm CAR/PDMS using six target analytes including deltamethrin, nerolidol, amphetamine, dodecane, ametryn and acrylamide. The g-C3N4 coating revealed excellent extraction ability and durability comparing with those of the commercial fibers due to its loose structure and unique physicochemical properties. The repeatability for each single fiber was found to be 3.46% and reproducibility for fiber to fiber was 8.53%. The g-C3N4 SPME fiber was applied to the determination of acrylamide in potato chips, the linearity and detection limit was 0.5-250 μg g(-1) and 0.018 μg g(-1), respectively.

  7. Preparation and characterization of boron nitride coatings on carbon fibers from borazine by chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Li Junsheng, E-mail: charlesljs@163.com [State Key Laboratory of Advanced Ceramic Fibers and Composites, College of Aerospace and Materials Engineering, National University of Defense Technology, Changsha, 410073 (China); Zhang Changrui; Li Bin [State Key Laboratory of Advanced Ceramic Fibers and Composites, College of Aerospace and Materials Engineering, National University of Defense Technology, Changsha, 410073 (China)

    2011-06-15

    Boron nitride (BN) coatings were deposited on carbon fibers by chemical vapor deposition (CVD) using borazine as single source precursor. The deposited coatings were characterized by scanning electron microscopy (SEM), Auger electron spectroscopy (AES), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy. The effect of temperatures on growth kinetics, morphology, composition and structure of the coatings was investigated. In the low temperature range of 900 deg. C-1000 deg. C, the growth rate increased with increasing temperature complying with Arrhenius law, and an apparent active energy of 72 kJ/mol was calculated. The coating surface was smooth and compact, and the coatings uniformly deposited on individual fibers of carbon fiber bundles. The growth was controlled by surface reaction. At 1000 deg. C, the deposition rate reached a maximum (2.5 {mu}m/h). At the same time, the limiting step of the growth translated to be mass-transportation. Above 1100 deg. C, the growth rate decreased drastically due to the occurrence of gas-phase nucleation. Moreover, the coating surface became loose and rough. Composition and structure examinations revealed that stoichiometric BN coatings with turbostratic structure were obtained below 1000 deg. C, while hexagonal BN coatings were deposited above 1100 deg. C. A penetration of carbon element from the fibers to the coatings was observed.

  8. Surface Preparation and Deposited Gate Oxides for Gallium Nitride Based Metal Oxide Semiconductor Devices

    Directory of Open Access Journals (Sweden)

    Paul C. McIntyre

    2012-07-01

    Full Text Available The literature on polar Gallium Nitride (GaN surfaces, surface treatments and gate dielectrics relevant to metal oxide semiconductor devices is reviewed. The significance of the GaN growth technique and growth parameters on the properties of GaN epilayers, the ability to modify GaN surface properties using in situ and ex situ processes and progress on the understanding and performance of GaN metal oxide semiconductor (MOS devices are presented and discussed. Although a reasonably consistent picture is emerging from focused studies on issues covered in each of these topics, future research can achieve a better understanding of the critical oxide-semiconductor interface by probing the connections between these topics. The challenges in analyzing defect concentrations and energies in GaN MOS gate stacks are discussed. Promising gate dielectric deposition techniques such as atomic layer deposition, which is already accepted by the semiconductor industry for silicon CMOS device fabrication, coupled with more advanced physical and electrical characterization methods will likely accelerate the pace of learning required to develop future GaN-based MOS technology.

  9. Effects of single pulse energy on the properties of ceramic coating prepared by micro-arc oxidation on Ti alloy

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Jun-Hua [Department of Mechanical Engineering, Tsinghua University, Beijing 100084 (China); School of Materials Science and Engineering, Henan University of Science and Technology, Luoyang 471023 (China); Faculty of Mechanical and Electrical Engineering, Kunming University of Science and Technology, Kunming 650500 (China); Wang, Jin [Department of Mechanical Engineering, Tsinghua University, Beijing 100084 (China); Beijing Key Lab of Precision/Ultra-precision Manufacturing Equipments and Control, Beijing 100084 (China); Lu, Yan [School of Materials Science and Engineering, Henan University of Science and Technology, Luoyang 471023 (China); Du, Mao-Hua [Faculty of Mechanical and Electrical Engineering, Kunming University of Science and Technology, Kunming 650500 (China); Han, Fu-Zhu, E-mail: hanfuzhu@mail.tsinghua.edu.cn [Department of Mechanical Engineering, Tsinghua University, Beijing 100084 (China); Beijing Key Lab of Precision/Ultra-precision Manufacturing Equipments and Control, Beijing 100084 (China)

    2015-01-01

    Highlights: • Single pulse energy remarkably influences the properties of ceramic coating prepared by MAO on Ti alloy. • The accumulative time of impulse width is an important parameter in the scientific and rational measurement of the film forming law of ceramic coating. • The ceramic coating thickness approximately linearly increases with the cumulative time of impulse width. • Larger impulse width resulted in higher single pulse energy, film forming rates and thicker ceramic coating thickness. • The effects of single pulse energy on the micro-hardness and phase composition of ceramic coating are not as evident as those of frequency and duty cycle. - Abstract: The effects of single pulse energy on the properties of ceramic coating fabricated on a Ti–6Al–4V alloy via micro-arc oxidation (MAO) in aqueous solutions containing aluminate, phosphate, and some additives are investigated. The thickness, micro-hardness, surface and cross-sectional morphology, surface roughness, and compositions of the ceramic coating are studied using eddy current thickness meter, micro-hardness tester, JB-4C Precision Surface roughness meter, scanning electron microscopy (SEM) and X-ray diffraction (XRD). Single pulse energy remarkably influences the ceramic coating properties. The accumulative time of impulse width is an important parameter in the scientific and rational measurement of the film forming law of ceramic coating. The ceramic coating thickness approximately linearly increases with the cumulative time of impulse width. Larger impulse width resulted in higher single pulse energy, film forming rates and thicker ceramic coating thickness. The sizes of oxide particles, micro-pores and micro-cracks slightly increase with impulse width and single pulse energy. The main surface conversion products generated during MAO process in aqueous solutions containing aluminate are rutile TiO{sub 2}, anatase TiO{sub 2}, and a large amount of Al{sub 2}TiO{sub 5}. The effects of

  10. Preparation and Optical Properties of Infrared Transparent 3Y-TZP Ceramics

    Directory of Open Access Journals (Sweden)

    Chuanfeng Wang

    2017-04-01

    Full Text Available In the present study, a tough tetragonal zirconia polycrystalline (Y-TZP material was developed for use in high-speed infrared windows and domes. The influence of the preparation procedure and the microstructure on the material’s optical properties was evaluated by SEM and FT-IR spectroscopy. It was revealed that a high transmittance up to 77% in the three- to five-micrometer IR region could be obtained when the sample was pre-sintered at 1225 °C and subjected to hot isostatic pressing (HIP at 1275 °C for two hours. The infrared transmittance and emittance at elevated temperature were also examined. The in-line transmittance remained stable as the temperature increased to 427 °C, with degradation being observed only near the infrared cutoff edge. Additionally, the emittance property of 3Y-TZP ceramic at high temperature was found to be superior to those of sapphire and spinel. Overall, the results indicate that Y-TZP ceramic is a potential candidate for high-speed infrared windows and domes.

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

    Science.gov (United States)

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

    2015-03-01

    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 (Zn2+0.17Fe3+0.83)[Fe3+1.17Fe2+0.06Ni2+0.77]O4 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.

  12. Creep in ceramics

    CERN Document Server

    Pelleg, Joshua

    2017-01-01

    This textbook is one of its kind, since there are no other books on Creep in Ceramics. The book consist of two parts: A and B. In part A general knowledge of creep in ceramics is considered, while part B specifies creep in technologically important ceramics. Part B covers creep in oxide ceramics, carnides and nitrides. While covering all relevant information regarding raw materials and characterization of creep in ceramics, the book also summarizes most recent innovations and developments in this field as a result of extensive literature search.

  13. Influence of temporary organic bond nature on the properties of compacts and ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Ditts, A., E-mail: ditts@tpu.ru; Revva, I., E-mail: revva@tpu.ru; Pogrebenkov, V.; Kosolapov, A. [National Research Tomsk Polytechnic University, 30, Lenin Ave., Tomsk, 634050 (Russian Federation); Galashov, E. [Novosibirsk State University, 2, Pirogova Str., 630090, Novosibirsk (Russian Federation); Nepochatov, Y. [Holding JSC “NEVZ-Soyuz”, 220, Krasny Avenue, Novosibirsk, 634050 (Russian Federation)

    2016-01-15

    This work contains results of investigation of obtaining high thermally conductive ceramics from commercial powders of aluminum nitride and yttrium oxide by the method of monoaxial compaction of granulate. The principal scheme of preparation is proposed and technological properties of granulate are defined. Compaction conditions for simple items to use as heat removal in microelectronics and power electrical engineering have been established. Investigations of thermophysical properties of obtained ceramics and its structure by the XRD and SEM methods have been carried out. Ceramics with thermal conductivity from 172 to 174 W/m·K has been obtained as result of this work.

  14. PROCESSING AND CHARACTERIZATION OF TUBULAR CERAMIC SUPPORT FOR MICROFILTRATION MEMBRANE PREPARED FROM PYROPHYLLITE CLAY

    Directory of Open Access Journals (Sweden)

    Abedallah Talidi

    2011-09-01

    Full Text Available Tubular macroporous support for ceramic microfiltration membranes were prepared by extrusion followed by sintering of the low cost pyrophyllite clay. Clay powders mixed with some organic additives can be extruded to form a porous tubular support. The average pore size of the membrane is observed to increase from 5 µm to 10.8 µm when sintering temperature increase from 900 °C to 1200 °C. However, with the increase in temperature from 900 °C to 1200 °C, the support porosity is reduced from 47% to 30% and flexural strength is increased from 4 MPa to 17 MPa. The fabricated macro-porous supports are expected to have potential applications in the pre-treatment and also can be used like support for membranes of ultra-filtration.

  15. Preparation and Mechanical Properties of Al2O3/Al Laminated Ceramic Matrix Composites

    Institute of Scientific and Technical Information of China (English)

    HUANG Kangming; LI Weixin; XIE Binhuan; RAO Pinggen; PENG Cheng; CHEN Dabo; WU Jianqing

    2011-01-01

    Three series of Al2O3/Al laminated ceramic matrix composites,named SPA,SPV and HP,were fabricated by different methods.SPA and SPV were prepared using Al2O3 slices and Al slurry via screen printing and subsequent heat treatment in air or vacuum.HP samples were made by hot pressing the layered stack of Al foils and Al2O3 slices.SEM and XRD were applied to analyze the microstructure and the interlayer crystal phase.The bending strength,fracture toughness and fracture work of the samples made by the three methods were measured and compared.The results show that the composites have much better toughness and higher fracture work than the Al2O3 slice.Among the samples made by the three methods,the samples made by hot pressing have the optimum mechanical performance.The displacement-load curves and fracture mechanism were analyzed.

  16. Low Temperature Preparation and Cold Manufacturing Techniques for Femoral Head of Al2O3 Ceramic

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    The hip joint femoral head prosthesis was prepared using the Al2O3 material, which was synthesized by high purity alumina micro-powder and Mg- Zr- Y composite additives, the cold manufacturing techniques of lathe turning, grade polishing and the matching size correction of the sintered femoral head were studied. The results showed, after being pressed under 200 MPa cold isostatic pressure and being pre-sintered at 1 150 ℃, the biscuit' s strength can meet the demands of lathe turning; After being grade polished by SiC micro-powder and diamond abrading agent and being size corrected by special instruments, the femoral head prosthesis of Al2O3 ceramic has good surface degree of finish and articulates tightly with femoral handle.

  17. Preparation for femur prosthesis of ceramic-metal combination artificial hip joint

    Institute of Scientific and Technical Information of China (English)

    王欣宇; 李世普; 陈晓明; 贺建华

    2002-01-01

    Al2O3 material was synthesized by using high purity alumina micro-powder and Mg-Zr-Y composite additives at temperature of 1600℃, which had good mechanics property of 416MPa bending strength and 5.46MPa*m1/2 fracture toughness. Femur head prosthesis of hip joint was prepared by using this material; Ti alloy femur handle was sprayed bioactive hydroxyapatite (HA) by plasma on surface, which improves the chemistry stability and biocompatibility of Ti alloy; ceramic-metal combination artificial hip joint femur prosthesis was made by combining Al2O3 femur head with Ti alloy femur handle, so the manufacturing process is improved and the property and application flexibility are advanced.

  18. Characterization of Green-Emitting Translucent Zinc Oxide Ceramics Prepared Via Spark Plasma Sintering

    Energy Technology Data Exchange (ETDEWEB)

    Hong, Mei [University of California; DeVito, David M [ORNL; Howe, Jane Y [ORNL; Yang, Xiaocheng [West Virginia University; Giles, Nancy C. [Air Force Institute of Technology; Neal, John S [ORNL; Munir, Zuhair [University of California

    2011-01-01

    Translucent, green-emitting zinc oxide (ZnO) bodies, 19 mm in diameter and 0.72 mm in thickness, have been prepared via spark plasma sintering method. The consolidation of ZnO powders was investigated over the temperature range of 550-1050 C and the pressure range of 55-530 MPa. Samples sintered at temperatures >850 C and pressures of {approx}120 MPa were translucent and had densities of {approx}100%. Samples sintered at 950 C and 130 MPa showed a higher maximum transmittance than the samples sintered at higher or lower temperatures or pressures, with an excellent in-line transmission of 70% in the IR region around 2330 nm. The dense ZnO ceramics exhibited a strong green emission and a weak ultraviolet emission, and the relative intensity of the green emission increased with increasing sintering temperature.

  19. 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.

  20. Correlation of photothermal conversion on the photo-induced deformation of amorphous carbon nitride films prepared by reactive sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Harata, T.; Aono, M., E-mail: aono@nda.ac.jp; Kitazawa, N.; Watanabe, Y. [Department of Materials Science and Engineering, National Defense Academy, 1-10-20 Hashirimizu, Yokosuka, Kanagawa 239-8686 (Japan)

    2014-08-04

    The photo-induced deformation of hydrogen-free amorphous carbon nitride (a-CN{sub x}) films was investigated under visible-light illumination. The films gave rise to photothermal conversion by irradiation. In this study, we investigated the effects of thermal energy generated by irradiation on the deformation of a-CN{sub x}/ultrathin substrate bimorph specimens. The films were prepared on both ultrathin Si and SiO{sub 2} substrates by reactive radio-frequency magnetron sputtering from a graphite target in the presence of pure nitrogen gas. The temperature of the film on the SiO{sub 2} substrate increased as the optical band-gap of the a-CN{sub x} was decreased. For the film on Si, the temperature remained constant. The deformation degree of the films on Si and SiO{sub 2} substrates were approximately the same. Thus, the deformation of a-CN{sub x} films primarily induced by photon energy directly.

  1. A Study of Ceramic-Lined Composite Steel Pipes Prepared by SHS Centrifugal-Thermite Process

    National Research Council Canada - National Science Library

    Yuxin Li; Letao Jiang; Qing Lu; Peikang Bai; Bin Liu; Jianhong Wang

    2016-01-01

    .... The result showed the ceramic lined pipe is composed of the three main layers of various compositions, which were subsequently determined to be Fe layer, the transition layer and the ceramic layer...

  2. Boron Nitride Nanotubes

    Science.gov (United States)

    Smith, Michael W. (Inventor); Jordan, Kevin (Inventor); Park, Cheol (Inventor)

    2012-01-01

    Boron nitride nanotubes are prepared by a process which includes: (a) creating a source of boron vapor; (b) mixing the boron vapor with nitrogen gas so that a mixture of boron vapor and nitrogen gas is present at a nucleation site, which is a surface, the nitrogen gas being provided at a pressure elevated above atmospheric, e.g., from greater than about 2 atmospheres up to about 250 atmospheres; and (c) harvesting boron nitride nanotubes, which are formed at the nucleation site.

  3. Structure property relationships of nitride superlattice hard coatings prepared by pulsed laser deposition

    Science.gov (United States)

    Patel, Nitin

    Today, more than 40% of all cutting tools used in machining applications are covered with coatings. Coatings improve wear resistance, increase tool life, enable use at higher speed, and broaden the application range. Superlattices, where thin layers (typically deposited in an alternating fashion, are widely used commercially. Importantly, the hardness value of a superlattice (e.g. TiN/AlN) can significantly exceed the rule of mixture value. Superlattice coatings built from crystallographically dissimilar materials are not widely studied but hold promise for improvements in performance by allowing for both hardness and toughness to be simultaneously optimized. This is what this thesis is concerned with: a structure-property comparison of isostructural superlattices with corresponding non-isostructural superlattices. In order to grow both isostructural and non-isostructural superlattices from the same set of materials, it is necessary to grow monolithic films in different phases. Towards this end, the synthesis of different phases of AlN, (Ti,Al)N, TaN, and TiN was investigated. Films were grown by pulsed laser deposition in two different chambers that had different base pressures to study the effect of background gases on the phases and orientations of the films. Growth of AlN and (Ti,Al)N films is strongly affected in a chamber that had a base pressure of 10-6 Torr, but the films adopt their stable nitride structures in a chamber with the lower base pressure of 10-8 Torr. TaN adopts either the cubic rock salt structure or its stable hexagonal structure, depending on the growth temperature, while TiN grows as rock salt in all conditions. Single crystal epitaxial superlattices were then grown with different compositions, periodicities, and crystallographic orientations to compare the effect of chemistry, nanostructure, and crystallographic texture on hardness. Finally, the structure-property relationships of non-isostructural (cubic/hexagonal) superlattices are

  4. Density variation and piezoelectric properties of Ba(Ti1−Sn)O3 ceramics prepared from nanocrystalline powders

    Indian Academy of Sciences (India)

    A K Nath; Nirmali Medhi

    2012-10-01

    Nanocrystalline powders of tin-doped barium titanate with different concentrations of tin have been synthesized by a combination of solid state reaction and high-energy ball milling. The average particle size of the milled powders as determined from TEM analysis was about 5.96 nm. Analysis of all the milled powders using X-ray diffraction method showed single phase perovskite structure. The density variation of the ceramics with sintering temperature has been studied by sintering the samples at different temperatures. Density variation results show that 1350°C is the optimum sintering temperature for tin-doped barium titanate ceramics. SEM micrographs show high density and increasing trend of grain size with increasing content of Sn. The ferroelectricity decreases with increasing concentration of Sn. The electromechanical coupling coefficient also decreases with increasing Sn content corroborating decreasing trend of ferroelectricity. The bipolar strain curves show piezoelectric properties of the prepared ceramics.

  5. INFLUENCE OF REOXIDATION ON SILICA-CONTAINING BARIUM TITANATE CERAMICS FOR PTCR THERMISTORS PREPARED BY TAPE CASTING

    Directory of Open Access Journals (Sweden)

    Jianqiao Liu

    2016-03-01

    Full Text Available Silica-containing barium-rich BaTiO₃ ceramics for thermistors with a positive temperature coefficient of resistance are prepared by a tape-casting technique. The ceramics are sintered in a reducing atmosphere at low temperatures of 1175-1225°C. The influences of reoxidation are investigated after the reduced ceramics are reoxidized in air at 700-900°C. An anomalous correlation is illustrated between room temperature resistivity and reoxidation temperature. The anomaly results from the ferroelectricity rebuilding mechanism, which includes the spontaneous polarization theory and the ferroelectricity degradation caused by oxygen vacancies. The acceptor-state densities are estimated from the temperature-dependent resistivity. A critical temperature of 750-800°C is concluded for the grain boundary reoxidation.

  6. Preparation,Characterization and Dielectric Property of Sr5LaTi3Nb7O30 Ceramic

    Institute of Scientific and Technical Information of China (English)

    ZHUO Rong-hui; ZHANG Hui; YANG Jun-feng; HUANG Tao-hua; YUAN Run-zhang

    2004-01-01

    Sr5LaTi3Nb7O30 ceramic was prepared by the conventional high temperature solid-state reaction route. The sintered samples were characterized by X-ray diffraction, scanning electron microscopy (SEM), differential thermal calorimetry (DSC) and dielectric measurements.The results show Sr5LaTi3Nb7O30 belongs to paraelectric phase of filled tetragonal TB structure at room temperature, and undergoes a diffuse phase transition in the temperature range of -54-34 ℃.And Sr5LaTi3Nb7O30 ceramic shows a high dielectric constant of 479 with a low dielectric loss of 0.005 at 1MHz. In comparison with Ba-based ceramics with TB structure, the temperature coefficients of the dielectric constant (τε) is significantly reduced.

  7. [Preparation and photoluminescence study of Er3+ : Y2O3 transparent ceramics].

    Science.gov (United States)

    Luo, Jun-ming; Li, Yong-xiu; Deng, Li-ping

    2008-10-01

    Y2O3 acted as the matrix material, which was doped with different concentrations of Er3+, Er3+ : Y2O3 nanocrystalline powder was prepared by co-precipitation method, and Er3+ : Y2O3 transparent ceramics was fabricated by vacuum sintering at 1700 degrees C, 1 x 10(-3) Pa for 8 h. By using the X-ray diffraction (D/MAX-RB), transmission electron microscopy(Philips EM420), automatic logging spectrophotometer(DMR-22), fluorescence analyzer (F-4500) and 980 nm diode laser, the structural, morphological and luminescence properties of the sample were investigated. The results show that Er3+ dissolved completely in the Y2O3 cubic phase, the precursor was amorphous, weak diffraction peaks appeared after calcination at 400 degrees C, and if calcined at 700 degrees C, the precursor turned to pure cubic phase. With increasing the calcining temperature, the diffraction peaks became sharp quickly, and when the calcining temperature reached 1100 degrees C, the diffraction peaks became very sharp, indicating that the grains were very large. The particles of Er+ : Y2O3 is homogeneous and nearly spherical, the average diameter of the particles is in the range of 40-60 nm after being calcined at 1000 degrees C for 2 h. The relative density of Er3+ : Y2O3 transparent ceramics is 99.8%, the transmittance of the Er2+ : Y2O3 transparent ceramics is markedly lower than the single crystal at the short wavelength, but the transmittance is improved noticeably with increasing the wavelength, and the transmittance exceeds 60% at the wavelength of 1200 nm. Excited under the 980 nm diode laser, there are two main up-conversion emission bands, green emission centers at 562 nm and red emission centers at 660 nm, which correspond to (4)S(3/2) / (2)H(11/2) - (4)I(15/2) and (4)F(9/2) - (4)I(15/2) radiative transitions respectively. By changing the doping concentrations of Er3+, the color of up-conversion luminescence can be tuned from green to red gradually. The luminescence intensity is not reinforce

  8. Preparation and performance of thin-layered PdAu/ceramic composite membranes

    Energy Technology Data Exchange (ETDEWEB)

    Shi, Lei; Goldbach, Andreas; Zeng, Gaofeng; Xu, Hengyong [Dalian Institute of Chemical Physics, Chinese Academy of Science, Zhongshan Road 457, Dalian 116023 (China)

    2010-05-15

    Preparation of 3-5 {mu}m thick, hydrogen-selective PdAu layers via sequential electroless plating of Pd and Au onto ceramic microfiltration membranes was investigated employing a cyanide-free Au plating bath. The Au deposition rate was strongly dependent on bath temperature and alkalinity reaching an optimum at 333 K and pH 10. Homogenous alloying of the separate metal layers under atmospheric H{sub 2} proved to be a protracted process and required approximately a week at 873 K for a PdAu layer as thin as 3 {mu}m. After 300 h annealing at 823 K the 5 {mu}m thick PdAu layer of a composite membrane still exhibited a Au gradient declining from 7.4 at.% at the top surface to 5.5 at.% at the support interface despite that the H{sub 2} permeation rate had become stable. Nonetheless, the membrane exhibited a very high H{sub 2} permeability of e.g. 1.3 x 10{sup -8} mol m m{sup -2} s{sup -1} Pa{sup -0.5} at 673 K, but it decreased much faster with temperature below 573 K than above, likely due to a change from bulk H diffusion-controlled to H{sub 2} adsorption or desorption-limited transport. The composite membrane withstood cycling between 523 and 723 K in H{sub 2} well showing that differing thermal expansion of the joined metallic and ceramic materials stayed within the tolerance range up to 723 K. (author)

  9. Structural, dielectric and piezoelectric properties of aluminium doped PLZT ceramics prepared by sol-gel route

    Energy Technology Data Exchange (ETDEWEB)

    Dutta, Soma [Department of Physics and Meteorology, Indian Institute of Technology Kharagpur, Kharagpur 721302 (India)]. E-mail: dutta_som@yahoo.co.in; Choudhary, R.N.P. [Department of Physics and Meteorology, Indian Institute of Technology Kharagpur, Kharagpur 721302 (India); Sinha, P.K. [Department of Aerospace Engineering, Indian Institute of Technology Kharagpur, Kharagpur 721302 (India)

    2007-03-14

    Nanosized piezoelectric ceramics for vibration sensor applications have been prepared by mixing the ferroelectric PLZT (8:60:40) with variable doping fractions of trivalent aluminium ion (Al{sup 3+}). Samples have been prepared through a standard sol-gel route. X-ray diffraction and scanning electron microscopy (SEM) have been used to determine the phase and morphological modifications. Transmission electron microscopy (TEM) studies reveal the microstructure with nanosized well-dispersed homogeneous spherical particles. The vibrational infra-red (IR) spectroscopy record is taken to locate the position of the doping Al{sup 3+} ion. Using electrical impedance spectroscopy, the resonance and anti-resonance frequencies of the Al modified PLZT system have been determined and analysed. Al addition in PLZT has left a profound effect in its dielectric and piezoelectric properties. An interpretation of the role of Al addition is proposed in terms of structure modification. The sensing power of the investigated material was found useful for the vibration control of a cantilever beam.

  10. Crystallization behavior of three-dimensional silica fiber reinforced silicon nitride composite

    Science.gov (United States)

    Qi, Gongjin; Zhang, Changrui; Hu, Haifeng; Cao, Feng; Wang, Siqing; Jiang, Yonggang; Li, Bin

    2005-10-01

    The crystallization behavior of a new type of ceramic matrix composites, three-dimensional silica fiber reinforced silicon nitride matrix composite prepared by perhydropolysilazane infiltration and pyrolysis, was investigated by X-ray diffractometry and Fourier transform infrared spectroscopy. With the post-annealing treatment of the amorphous as-received composite at elevated tempertures of 1400 and 1600 °C in nitrogen atmosphere, there was remarkable suppression of the crystallization of polymer-derived silicon nitride ceramic matrix into α-Si 3N 4 and silica fibers into α-cristobalite, which was probably attributed to the phase of silicon oxynitrides originating from the strong fiber/matrix interfacial chemical reaction.

  11. Copper ion implanted aluminum nitride dilute magnetic semiconductors (DMS) prepared by molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Shah, A., E-mail: attaullah77@yahoo.com [National Institute of Lasers and Optronics (NILOP), PO Nilore, Islamabad (Pakistan); DMME, Pakistan Institute of Engineering and Applied Science (PIEAS), PO Nilore, Islamabad (Pakistan); Ahmad, Jamil [DMME, Pakistan Institute of Engineering and Applied Science (PIEAS), PO Nilore, Islamabad (Pakistan); Ahmad, Ishaq [Experimental Physics Lab, National Center for Physics (NCP), Islamabad (Pakistan); Mehmood, Mazhar [DMME, Pakistan Institute of Engineering and Applied Science (PIEAS), PO Nilore, Islamabad (Pakistan); Mahmood, Arshad [National Institute of Lasers and Optronics (NILOP), PO Nilore, Islamabad (Pakistan); Rasheed, Muhammad Asim [DMME, Pakistan Institute of Engineering and Applied Science (PIEAS), PO Nilore, Islamabad (Pakistan)

    2014-10-30

    Highlights: • AlN:Cu dilute magnetic semiconductors were successfully prepared by molecular beam epitaxy followed by Cu{sup +} implantation. • Room temperature ferromagnetism was observed after annealing the samples at appropriate temperature. • XRD and Raman spectrometry excluded the possibility of formation of any secondary phases. • By doping intrinsically nonmagnetic dopants (Cu), it has been proved experimentally that their precipitates do not contribute to ferromagnetism. • The reason for ferromagnetism in Cu-doped AlN as observed was explained on the basis of p–d hybridization mechanism (Wu et al.). - Abstract: Diluted magnetic semiconductor (DMS) AlN:Cu films were fabricated by implanting Cu{sup +} ions into AlN thin films at various ion fluxes. AlN films were deposited on c-plane sapphire by molecular beam epitaxy followed by Cu{sup +} ion implantation. The structural and magnetic characterization of the samples was performed through Rutherford backscattering and channeling spectrometry (RBS/C), X-ray diffraction (XRD), Raman spectroscopy, vibrating sample magnetometer (VSM) and SQUID. Incorporation of copper into the AlN lattice was confirmed by RBS, while XRD revealed that no new phase was formed as a result of ion implantation. RBS also indicated formation of defects as a result of implantation process and the depth and degree of damage increased with an increase in ion fluence. Raman spectra showed only E{sub 2} (high) and A{sub 1} (LO) modes of wurtzite AlN crystal structure and confirmed that no secondary phases were formed. It was found that both Raman modes shift with Cu{sup +} fluences, indicating that Cu ion may go to interstitial or substitutional sites resulting in distortion or damage of lattice. Although as implanted samples showed no magnetization, annealing of the samples resulted in appearance of room temperature ferromagnetism. The saturation magnetization increased with both the annealing temperature as well as with ion

  12. Effect of applied dc bias voltage on composition, chemical bonding and mechanical properties of carbon nitride films prepared by PECVD

    Institute of Scientific and Technical Information of China (English)

    LI Hong-xuan; XU Tao; HAO Jun-ying; CHEN Jian-min; ZHOU Hui-di; XUE Qun-ji; LIU Hui-wen

    2004-01-01

    Carbon nitride films were deposited on Si (100) substrates using plasma-enhanced chemical vapor deposition (PECVD) technique from CH4 and N2 at different applied dc bias voltage. The microstructure, composition and chemical bonding of the resulting films were characterized by Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). The mechanical properties such as hardness and elastic modulus of the films were evaluated using nano-indentation. As the results, the Raman spectra, showing the G and D bands, indicate the amorphous structure of the films. XPS and FTIR measurements demonstrate the existence of various carbon-nitride bonds in the films and the hydrogenation of carbon nitride phase. The composition ratio of N to C, the nano-hardness and the elastic modulus of the carbon nitride films increase with increasing dc bias voltage and reach the maximums at a dc bias voltage of 300 V, then they decrease with further increase of the dc bias voltage. Moreover, the XRD analyses indicate that the carbon nitride film contains some polycrystalline C3N4 phase embedded in the amorphous matrix at optimized deposition condition of dc bias voltage of 300 V.

  13. Lithium ceramics: sol-gel preparation and tritium release; Ceramiques lithiees: elaboration sol-gel et relachement du tritium

    Energy Technology Data Exchange (ETDEWEB)

    Renoult, O.

    1994-04-01

    Ceramics based on lithium aluminate (LiA1O{sub 2}), lithium zirconate (Li{sub 2}ZrO{sub 3}) and lithium titanate (Li{sub 2}TiO{sub 3}) are candidates as tritium breeder blanket materials for forthcoming nuclear fusion reactors. Lithium silico-aluminate Li{sub 4+x}A1{sub 4-3x}Si{sub 2x}O{sub 8} (0 {<=} x {<=} 0,25) powders were synthetized from alkoxyde-hydroxyde sol-gel route. By direct sintering at 850-1100 deg C (without prior calcination), ceramics with controlled stoichiometry and homogenous microstructure were obtained. We have also prepared, using a comparable method, Li{sub 2}Zr{sub 1-x}Ti{sub x}O{sub 3} (x = 0, x = 0,1 et x = 1) materials. All these ceramics, with different microstructures and compositions, have been tested in out-of-reactor experiments. Concerning lithium aluminate microporous ceramics, the silicon substitution leads to a significant improvement of the tritrium release. Classical models taking into account independent surface mechanisms are not able to describe correctly the observed tritium release kinetics. We show, using a simple model, that the release kinetics is in fact limited by an intergranular diffusion followed by a desorption. The delay in tritium release, which occurs when the ceramic compacity increases, is explained in terms of an enhancement of the ionic T{sup +} diffusion path length. The energy required for desorption includes a leading term independent of hydrogen contained in the sweep gas. This term is attributed to the limiting recombination step of T{sup +} in molecular species HTO. For similar microstructures, the facility of tritium release for the different studied materials is explained by three properties: the crystal structure of the ceramic, the acidity of oxides and finally the presence of electronic non-stoichiometric defects. (author). 89 refs., 50 figs., 2 tabs., 1 annexe.

  14. Research Progress of Cu-base Brazing Filler Metals for Brazing Silicon Nitride Ceramics%钎焊氮化硅陶瓷的 Cu 基钎料的研究进展

    Institute of Scientific and Technical Information of China (English)

    栗慧

    2014-01-01

    陶瓷连接技术是结构陶瓷实用化的有效手段,焊料成分对连接体的性能具有决定性作用。文章主要从焊料成分的角度,重点总结了钎焊Si3 N4陶瓷的Cu基钎焊材料的发展现状。%Joining technology of silicon nitride based materials is the most effective means for practical application.The chemical composition of adhesive has significant influence on the joining strength.The re-cent development in brazing of Si3 N4 ceramics Cu-base brazing fillers is emphatically reviewed in this paper from the point of chemical composition.

  15. Preparation,Electrochemical Behavior and Electrocatalytic Activity of a Copper Hexacyanoferrate Modified Ceramic Carbon Electrode

    Institute of Scientific and Technical Information of China (English)

    YU,Hao; ZHENG,Jian-Bin

    2007-01-01

    A copper hexacyanoferrate modified ceramic carbon electrode(CuHCF/CCE)had been prepared by two-step sol-gel technique and characterized using electrochemical methods.The resulting modified electrode showed a pair of well-defined surface waves in the potential range of 0.40 to 1.0 V with the formal potential of 0.682 V (vs.SCE)in 0.050 mol·dm-3 HOAc-NaOAc buffer containing 0.30 mol·dm-3 KCI.The charge transfer coefficient (α) and charge transfer rate constant(Ks)for the modified electrode were calculated.The electrocatalytic activity of this modified electrode to hydrazine was also investigated,and chronoamperometry was exploited to conveniently determine the diffusion coefficient(D)of hydrazine in solution and the catalytic rate constant(Kcat).Finally,hydrazine was determined with amperometry using the resulting modified electrode.The calibration plot for hydrazine determination was linear in 3.0×10-6-7.5×10-4 mol·dm-3 with the detection limit of 8.0×10-7 mol·dm-3.This modified electrode had some advantages over the modified film electrodes constructed by the conventional methods,such as renewable surface,good long-term stability,excellent catalytic activity and short response time to hydrazine.

  16. Semiconducting barium titanate ceramics prepared by using yttrium hexaboride as sintering aid

    Energy Technology Data Exchange (ETDEWEB)

    Wang, X.X.; Chan, H.L.W.; Pang, G.K.H.; Choy, C.L

    2003-07-25

    Nb-doped BaTiO{sub 3} semiconducting ceramics have been prepared at 1150 deg. C by employing YB{sub 6} as the sintering aid. The low-temperature sintered samples exhibit a positive temperature coefficient of resistivity (PTCR) effect. The room-temperature resistivity and the magnitude of PTCR effect depend on the amount of YB{sub 6} added, the Nb{sub 2}O{sub 5} content and the sintering conditions. At 1 mol% of YB{sub 6}, the sample has a low room-temperature resistivity and a resistivity jump of about 10{sup 4}. Transmission electron microscope studies revealed that the intergranular region between the crystalline BaTiO{sub 3} grains has an amorphous structure. Y, Ba and Ti are present in the intergranular region but no Y is detectable in the crystalline grains. A liquid phase is believed to be present during sintering and it helps to facilitate the densification process and to enhance the PTCR effect.

  17. Waste water purification using new porous ceramics prepared by recycling waste glass and bamboo charcoal

    Science.gov (United States)

    Nishida, Tetsuaki; Morimoto, Akane; Yamamoto, Yoshito; Kubuki, Shiro

    2017-04-01

    New porous ceramics (PC) prepared by recycling waste glass bottle of soft drinks (80 mass%) and bamboo charcoal (20 mass%) without any binder was applied to the waste water purification under aeration at 25 °C. Artificial waste water (15 L) containing 10 mL of milk was examined by combining 15 mL of activated sludge and 750 g of PC. Biochemical oxygen demand (BOD) showed a marked decrease from 178 to 4.0 (±0.1) mg L-1 in 5 days and to 2.0 (±0.1) mg L-1 in 7 days, which was equal to the Environmental Standard for the river water (class A) in Japan. Similarly, chemical oxygen demand (COD) decreased from 158 to 3.6 (±0.1) mg L-1 in 5 days and to 2.2 (±0.1) mg L-1 in 9 days, which was less than the Environmental Standard for the Seawater (class B) in Japan: 3.0 mg L-1. These results prove the high water purification ability of the PC, which will be effectively utilized for the purification of drinking water, fish preserve water, fish farm water, etc.

  18. Preparation and antimicrobial assay of ceramic brackets coated with TiO2 thin films

    Science.gov (United States)

    Cao, Shuai; Wang, Ye; Cao, Lin; Wang, Yu; Lin, Bingpeng; Lan, Wei

    2016-01-01

    Objective Different methods have been utilized to prevent enamel demineralization and other complications during orthodontic treatment. However, none of these methods can offer long-lasting and effective prevention of orthodontic complications or interventions after complications occur. Considering the photocatalytic effect of TiO2 on organic compounds, we hoped to synthesize a novel bracket with a TiO2 thin film to develop a photocatalytic antimicrobial effect. Methods The sol-gel dip coating method was used to prepare TiO2 thin films on ceramic bracket surfaces. Twenty groups of samples were composed according to the experimental parameters. Crystalline structure and surface morphology were characterized by X-ray diffraction and scanning electron microscopy, respectively; film thickness was examined with a surface ellipsometer. The photocatalytic properties under ultraviolet (UV) light irradiation were analyzed by evaluating the degradation ratio of methylene blue (MB) at a certain time. Antibacterial activities of selected thin films were also tested against Lactobacillus acidophilus and Candida albicans. Results Films with 5 coating layers annealed at 700℃ showed the greatest photocatalytic activity in terms of MB decomposition under UV light irradiation. TiO2 thin films with 5 coating layers annealed at 700℃ exhibited the greatest antimicrobial activity under UV-A light irradiation. Conclusions These results provide promising guidance in prevention of demineralization by increasing antimicrobial activities of film coated brackets. PMID:27226960

  19. Structural and Magnetic Characterizations of Nano Sized Grain Zinc Ferrite/Hydroxyapatite Ceramic Prepared by Solid State Reaction Route.

    Science.gov (United States)

    Pankaew, Piyapong; Klumdoung, Pattarinee

    2015-11-01

    A promising composite of bioactive hydroxyapatite (HAp) and zinc ferrite (ZnFe2O4) has potentials for future bone reinforcing formation. In present study, HAp and ZnFe2O4 composite ceramic was prepared by solid state reaction route for easier control of structural and magnetic characteristics and with low cost. HAp powder was synthesized by precipitation method from chicken eggshell. Mixed powders with varying ZnFe2O4/HAp weight ratios from 2-10 wt% were milled together and uniaxially pressed and then sintered at 1200 degrees C for 3 hours. The XRD results showing no other phases of composite ceramics with only HAp and ZnFe2O4 phases were identified, indicating high stability of HAp property. Phase fractions of ZnFe2O4 were found to increase from 10.8 to 18.73 wt% with increasing content of ZnFe2O4. FT-IR results were only revealed vibration bands of standard HAp phase. SEM results revealed primary grains sizes of the prepared ceramics in nano scale. The BET surface area and pore volume increased with increasing content of ZnFe2O4 in composite ceramics. The VSM results of composites with increasing ZnFe2O4 content had been shown with increasing magnetization from 0.05 to 1.85 emu/g while their coercivities were decreased from 44 to 24 Oe. Higher magnetization as well as higher super paramagnetic behavior could be achieved with increasing the studied ZnFe2O4 weight ratios in ZnFe2O4/HAp composite ceramics, which can be tailored for specific applications.

  20. Method of preparing a high solids content, low viscosity ceramic slurry

    Science.gov (United States)

    Tiegs, Terry N.; Wittmer, Dale E.

    1995-01-01

    A method for producing a high solids content, low viscosity ceramic slurry composition comprises turbomilling a dispersion of a ceramic powder in a liquid to form a slurry having a viscosity less than 100 centipoise and a solids content equal to or greater than 48 volume percent.

  1. A study of ceramic-lined composite steel pipes prepared by SHS centrifugal-thermite process

    Directory of Open Access Journals (Sweden)

    Li Yuxin

    2016-01-01

    Full Text Available Al2O3 ceramic-lined steel pipe was produced by self-propagating high-temperature synthesis centrifugal thermite process (SHS C-T process from Fe2O3 and Al as the raw materials. The composition, phase separation and microstructures were investigated. The result showed the ceramic lined pipe is composed of the three main layers of various compositions, which were subsequently determined to be Fe layer, the transition layer and the ceramic layer. Fe layer is composed of austenite and ferrite, the transition layer consisted of Al2O3 ceramic and Fe, the ceramic layer consisted of the dendritic-shaped Al2O3 and the spinel-shaped structured FeAl2O4.

  2. Dielectric properties of the BaTi0.85Zr 0.15O3 ceramics prepared by different techniques

    Directory of Open Access Journals (Sweden)

    Lavinia Petronela Curecheriu

    2008-12-01

    Full Text Available Three different processing routes, i.e. the classical solid state reaction technique the sol-precipitation method and the oxalate route, were employed for preparing BaTi0.85Zr0.15O3 ceramics. The dielectric properties of these ceramics are comparatively analyzed. The obtained results show that the dielectric properties of these ceramics, even having the same composition, are highly sensitive to the preparation route, causing differences in the microstructures and in the local electrical inhomogeneity, thus, causing complicated dielectric relaxation phenomena.

  3. Nd-doped barium titanate ceramics with various Ti/Ba ratios prepared by sol-gel method

    Institute of Scientific and Technical Information of China (English)

    SHI Qizhen; CUI Bin; WANG Hui; TIAN Jing; CHANG Zhuguo; HOU Yudong

    2005-01-01

    The Nd-doped BaTiO3 nanocrystalline powders and ceramics with different Ti/Ba ratios were prepared by sol-gel method. Phases and microstructures of the Nd-doped BaTiO3based powders and ceramics were characterized by XRD, SEM and TEM methods. The results revealed that the powders synthesized by sol-gel method were nanometer scale (30-60 nm)and were mainly composed of cubic BaTiO3 with a small amount of BaCO3. After sintering at high temperature, both cubic BaTiO3 and BaCO3 were transformed into tetrahedron BaTiO3 phase.The dielectric properties of the ceramics were also determined and the influence of Ti/Ba ratio on the dielectric properties was discussed. The Tc did not change with the variation of Ti/Ba ratio,while the εmax increased firstly and then decreased. The excess TiO2 is benefit for the modification of ceramics' microstructure and dielectric properties.

  4. Antibacterial Properties of TiO_2 Ceramic Pellets Prepared Using Nano TiO_2 Powder

    Institute of Scientific and Technical Information of China (English)

    YAO Yadong; LI Yongdi; SHAO Wei; KANG Yunqing; WANG Hongjing; HUANG Zhongbin; LIAO Xiaoming; YIN Guangfu

    2009-01-01

    Titanium dioxide(TiO_2)porous ceramic pellets with three dimension nano-structure were prepared using nano TiO_2 powder.The TiO_2 porous ceramic pellets were composed of TiO_2 nanoparticles with 14-16 nm in diameter and had porosity of 74.85%.The mean pore size of the TiO_2 porous ceramic pellets was 20.73 nm and the main pore size ranged from 3 to 16 nm.The mass loss of the TiO_2 ceramic pellets was less than 5%after 20 d immersion in water.The antibacterial properties of the TiO_2 pellets were studied.The sterilization rate of Colibacillus(hospital polluted water with bacterium)can reach 99%after 3 h photocatalytic process and these TiO_2 pellets are easy to be re-activated and cyclically be used.The shaping mechanism and photocatalysis sterilization mechanism of the TiO_2 pellets were discussed.

  5. Crystallization evolution, microstructure and properties of sewage sludge-based glass-ceramics prepared by microwave heating.

    Science.gov (United States)

    Tian, Yu; Zuo, Wei; Chen, Dongdong

    2011-11-30

    A Microwave Melting Reactor (MMR) was designed in this study which improved the microwave adsorption of sewage sludge to prepare glass-ceramics. Differential scanning calorimetry (DSC), X-ray diffraction (XRD), and scanning electron microscopy (SEM) were used for the study of crystallization behavior and microstructure of the developed glass-ceramics. DSC and XRD analysis revealed that crystallization of the nucleated specimen in the region of 900-1000°C resulted in the formation of two crystalline phases: anorthite and wollastonite. When the crystallization temperature increased from 900 to 1000°C, the tetragonal wollastonite grains were subjected to tensile microstresses, causing the cracking of crystal. Al ions substituted partially Si ions and occupied tetrahedral sites, giving rise to the formation of anorthite. The relationship between microwave irradiation and crystal growth was studied and the result indicated that the microwave selective heating suppressed the crystal growth, giving apparent improvements in the properties of the glass-ceramics. The glass-ceramics products exhibited bending strength of 86.5-93.4 MPa, Vickers microhardness of 6.12-6.54 GPa and thermal expansion coefficient of 5.29-5.75 × 10(-6)/°C. The best chemical durability in acid and alkali solutions was 1.32-1.61 and 0.41-0.58 mg/cm(2), respectively, showing excellent durability in alkali solution. Copyright © 2011 Elsevier B.V. All rights reserved.

  6. Influence of preparation design and ceramic thicknesses on fracture resistance and failure modes of premolar partial coverage restorations.

    Science.gov (United States)

    Guess, Petra C; Schultheis, Stefan; Wolkewitz, Martin; Zhang, Yu; Strub, Joerg R

    2013-10-01

    Preparation designs and ceramic thicknesses are key factors for the long-term success of minimally invasive premolar partial coverage restorations. However, only limited information is presently available on this topic. The purpose of this in vitro study was to evaluate the fracture resistance and failure modes of ceramic premolar partial coverage restorations with different preparation designs and ceramic thicknesses. Caries-free human premolars (n=144) were divided into 9 groups. Palatal onlay preparation comprised reduction of the palatal cusp by 2 mm (Palatal Onlay Standard), 1 mm (Palatal-Onlay-Thin), or 0.5 mm (Palatal Onlay Ultrathin). Complete-coverage onlay preparation additionally included the buccal cusp (Occlusal Onlay Standard; Occlusal Onlay Thin; Occlusal Onlay Ultrathin). Labial surface preparations with chamfer reductions of 0.8 mm (Complete-Veneer-Standard), 0.6 mm (Complete-Veneer-Thin), and 0.4 mm (Complete Veneer Ultrathin) were implemented for complete veneer restorations. Restorations were fabricated from a pressable lithium disilicate ceramic (IPS-e.max-Press) and cemented adhesively (Syntac-Classic/Variolink-II). All specimens were subjected to cyclic mechanical loading (F=49 N, 1.2 million cycles) and simultaneous thermocycling (5°C to 55°C) in a mouth-motion simulator. After fatigue, restorations were exposed to single-load-to-failure. Two-way ANOVA was used to identify statistical differences. Pair-wise differences were calculated and P-values were adjusted by the Tukey-Kramer method (α=.05). All specimens survived fatigue. Mean (SD) load to failure values (N) were as follows: 837 (320/Palatal-Onlay-Standard), 1055 (369/Palatal-Onlay-Thin), 1192 (342/Palatal-Onlay-Ultrathin), 963 (405/Occlusal-Onlay-Standard), 1108 (340/Occlusal-Onlay-Thin), 997 (331/Occlusal-Onlay-Ultrathin), 1361 (333/Complete-Veneer-Standard), 1087 (251/Complete-Veneer-Thin), 883 (311/Complete-Veneer-Ultrathin). Palatal-onlay restorations revealed a significantly

  7. Preparation and properties of bisphenol-F based boron-phenolic resin/modified silicon nitride composites and their usage as binders for grinding wheels

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Chun-Te [Department of Polymer Engineering, National Taiwan University of Science and Technology, 43, Sec 4, Keelung Rd, Taipei 106, Taiwan (China); Lee, Hsun-Tsing [Department of Materials Science and Engineering, Vanung University, Chung-Li, Tao-Yuan, Taiwan (China); Chen, Jem-Kun, E-mail: jkchen@mail.ntust.edu.tw [Department of Polymer Engineering, National Taiwan University of Science and Technology, 43, Sec 4, Keelung Rd, Taipei 106, Taiwan (China)

    2015-03-01

    Highlights: • Bisphenol-F based boron-phenolic resins (B-BPF) with B−O bonds were synthesized. • The modified silicon nitride (m-SiN) was well dispersed and adhered in the B-BPF. • B-BPF/m-SiN composites have good thermal resistance and mechanical properties. • The grinding wheels bound by B-BPF/m-SiN have excellent grinding quality. - Abstract: In this study, phenolic resins based on bisphenol-F (BPF) were synthesized. Besides, ammonium borate was added in the synthesis process of BPF to form the bisphenol-F based boron-phenolic resins (B-BPF). The glass transition temperature, thermal resistance, flexural strength and hardness of B-BPF are respectively higher than those of BPF. This is due to the presence of new cross-link B−O bonds in the B-BPF. In addition, the 3-aminopropyltriethoxysilane modified silicon nitride powders (m-SiN) were fully mixed with B-BPF to form the B-BPF/m-SiN composites. The thermal resistance and mechanical properties of the B-BPF/m-SiN are promoted by the well-dispersed and well-adhered m-SiN in these novel polymer/ceramics composites. The results of grinding experiments indicate that the grinding wheels bound by the B-BPF/m-SiN have better grinding quality than those bound by the BPF. Thus the B-BPF/m-SiN composites are better binding media than the BPF resins.

  8. Fabrication and properties of graphene reinforced silicon nitride composite materials

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Yaping; Li, Bin, E-mail: libin@nudt.edu.cn; Zhang, Changrui; Wang, Siqing; Liu, Kun; Yang, Bei

    2015-09-17

    Silicon nitride (Si{sub 3}N{sub 4}) ceramic composites reinforced with graphene platelets (GPLs) were prepared by hot pressed sintering and pressureless sintering respectively. Adequate intermixing of the GPLs and the ceramic powders was achieved in nmethyl-pyrrolidone (NMP) under ultrasonic vibration followed by ball-milling. The microstructure and phases of the Si{sub 3}N{sub 4} ceramic composites were investigated by Field Emission Scanning Electron Microscopy (SEM) and X-ray diffraction (XRD). The effects of GPLs on the composites' mechanical properties were analyzed. The results showed that GPLs were well dispersed in the Si{sub 3}N{sub 4} ceramic matrix. β-Si{sub 3}N{sub 4,} O′-sialon and GPLs were present in the hot-pressed composites while pressureless sintered composites contain β-Si{sub 3}N{sub 4}, Si, SiC and GPLs. Graphene has the potential to improve the mechanical properties of both the hot pressed and pressureless sintered composites. Toughening effect of GPLs on the pressureless sintered composites appeared more effective than that on the hot pressed composites. Toughening mechanisms, such as pull-out, crack bridging and crack deflection induced by GPLs were observed in the composites prepared by the two methods.

  9. Preparation of ceramic-corrosion-cell fillers and application for cyclohexanone industry wastewater treatment in electrobath reactor

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Suqing; Qi, Yuanfeng; Gao, Yue; Xu, Yunyun; Gao, Fan; Yu, Huan; Lu, Yue [Shandong Key Laboratory of Water Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Shandong University, 250100 Jinan (China); Yue, Qinyan, E-mail: qyyue58@yahoo.com.cn [Shandong Key Laboratory of Water Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Shandong University, 250100 Jinan (China); Li, Jinze [Shandong Key Laboratory of Water Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Shandong University, 250100 Jinan (China)

    2011-11-30

    Highlights: Black-Right-Pointing-Pointer Dried sewage sludge and scrap iron used as raw materials for sintering ceramics. Black-Right-Pointing-Pointer The new media ceramics used as fillers in electrobath of micro-electrolysis. Black-Right-Pointing-Pointer Modified micro-electrolysis used in cyclohexanone industry wastewater treatment. Black-Right-Pointing-Pointer This modified micro-electrolysis could avoid failure of the electrobath reactor. - Abstract: As new media, ceramic-corrosion-cell fillers (Cathode Ceramic-corrosion-cell Fillers - CCF, and Anode Ceramic-corrosion-cell Fillers - ACF) employed in electrobath were investigated for cyclohexanone industry wastewater treatment. 60.0 wt% of dried sewage sludge and 40.0 wt% of clay, 40.0 wt% of scrap iron and 60.0 wt% of clay were utilized as raw materials for the preparation of raw CCF and ACF, respectively. The raw CCF and ACF were respectively sintered at 400 Degree-Sign C for 20 min in anoxic conditions. The physical properties (bulk density, grain density and water absorption), structural and morphological characters and toxic metal leaching contents were tested. The influences of pH, hydraulic retention time (HRT) and the media height on removal of COD{sub Cr} and cyclohexanone were studied. The results showed that the bulk density and grain density of CCF and ACF were 869.0 kg m{sup -3} and 936.3 kg m{sup -3}, 1245.0 kg m{sup -3} and 1420.0 kg m{sup -3}, respectively. The contents of toxic metal (Cu, Zn, Cd, Pb, Cr, Ba, Ni and As) were all below the detection limit. When pH of 3-4, HRT of 6 h and the media height of 60 cm were applied, about 90% of COD{sub cr} and cyclohexanone were removed.

  10. Preparation of α-Al2O3 base ceramic coating on aluminum alloy via thermo-decomposition of diaspore

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The aim of this work is to describe the possibilities of preparing a corundum coating onaluminum alloy through in-situ chemical reaction at a relative low temperature. The transformationconditions of diaspore (β-AIOOH) to corundum (α-Al2O3 ) are studied using X-ray diffraction analy-sis. Temperature and heating time are two main factors influencing the transformation. Suitableheating parameters can lower the transformation temperature. On this basis, a new process isdeveloped to produce corundum ceramic coating on an aluminum alloy substrate. The phasecomposition and microstructure of the coating are studied using X-ray diffraction analysis andScanning Electron Microscopy. Abrasion properties of the coating are evaluated by ring-block tri-botester. The results show that it is feasible to obtain ceramic coatings on aluminum alloy sub-strates by means of thermo-decomposition of diaspore.

  11. PREPARATION MICRO-FILTRATION CERAMIC MEMBRANE FROM NATURAL ZEOLITE FOR PROCION RED MX8B AND METHYLENE BLUE FILTRATION

    Directory of Open Access Journals (Sweden)

    Dyah Choiriyah

    2015-12-01

    Full Text Available The study of ceramic membrane fabrication from natural zeolite and its utilization for filtration of procion red MX8B and methylene blue has been investigated. The purposes of this study are to determine the effect of pressure on membrane permeability and selectivity and utilize natural zeolite as ceramic membranes procion red MX8B and methylene blue filtration. The membrane was prepared by metide press pellets and then calcined at 850 oC. The membranes were characterized by mechanical test, flux and rejection of dye. The compression test of the membrane found the values of 1369.178 psi in dry conditions to 1388.933 psi in wet conditions. The flux test found that the higher the pressure applied, the flux was increase. However, the high pressure also decreased the selectivity. Rejection test found that the rejection of methylene blue filtration up to 70 %. Meanwhile, procion red MX8B filtration has rejectivity less than 20 %.

  12. Effect of particle size on microstructure and strength of porous spinel ceramics prepared by pore-forming in situ technique

    Indian Academy of Sciences (India)

    Wen Yan; Nan Li; Yuanyuan Li; Guangping Liu; Bingqiang Han; Juliang Xu

    2011-08-01

    The porous spinel ceramics were prepared from magnesite and bauxite by the pore-forming in situ technique. The characterization of porous spinel ceramics was determined by X-ray diffractometer (XRD), scanning electron microscopy(SEM), mercury porosimetry measurement etc and the effects of particle size on microstructure and strength were investigated. It was found that particle size affects strongly on the microstructure and strength. With decreasing particle size, the pore size distribution occurs from multi-peak mode to bi-peak mode, and lastly to mono-peak mode; the porosity decreases but strength increases. The most apposite mode is the specimens from the grinded powder with a particle size of 6.53 m, which has a high apparent porosity (40%), a high compressive strength (75.6MPa), a small average pore size (2.53 m) and a homogeneous pore size distribution.

  13. FIBROUS CERAMIC-CERAMIC COMPOSITE MATERIALS PROCESSING AND PROPERTIES

    OpenAIRE

    1986-01-01

    The introduction of continuous fibers in a ceramic matrix can improve its toughness, if the fiber-matrix bonding is weak enough, due to matrix microcracking and fiber pull-out. Ceramic-ceramic composite materials are processed according to liquid or gas phase techniques. The most important are made of glass, carbide, nitride or oxide matrices reinforced with carbon, SiC or Al2O3 fibers.

  14. Rapid preparation of ceramic moulds for medium-sized superalloy castings with magnesia-phosphate-bonded bauxite-mullite investments

    Directory of Open Access Journals (Sweden)

    Li Tingzhong

    2010-11-01

    Full Text Available Phosphate-bonded investments have already been widely utilized in dental restoration and micro-casting of artistic products for its outstanding rapid setting and high strength. However, the rapid setting rate of investment slurry has up to now been a barrier to extend the use of such slurry in preparation of medium-sized ceramic moulds. This paper proposes a new process of rapid fabrication of magnesia-phosphate-bonded investment ceramic moulds for medium-sized superalloy castings utilizing bauxite and mullite as refractory aggregates. In order to determine the properties of magnesia-phosphate-bonded bauxite-mullite investments (MPBBMI, a series of experiments were conducted, including modification of the workable time of slurry by liquid(mL/powder(g(L/P ratio and addition of boric acid as retard agent and sodium tri-polyphosphate (STP as strengthening agent, and adjustment of bauxite (g/mullite(g(B/M ratio for mechanical strength. Mechanical vibration was applied to improve initial setting time and fluidity when pouring investment slurry; then an intermediate size ceramic mould for superalloy castings was manufactured by means of this rapid preparing process with MPBBMI material. The results showed that the MPBBMI slurry exhibits proper initial setting time and excellent fluidity when the L/P ratio is 0.64 and the boric acid content is 0.88wt.%. The fired specimens made from the MPBBMI material demonstrated adequate compression strength to withstand impact force of molten metal when the B/M ratio is 0.89 and the STP content is 0.92wt.%. The experimental results confirmed the feasibility of the proposed rapid fabricating process for medium-sized ceramic moulds with MPBBMI material by appropriate measures.

  15. Studies on plutonium-zirconium co-precipitation and carbothermal reduction in the internal gelation process for nitride fuel preparation

    Science.gov (United States)

    Hedberg, Marcus; Ekberg, Christian

    2016-10-01

    Sol-gel based techniques are one way to lower the handling of highly radioactive powders when producing transuranium-containing fuel. In this work inert matrix (Zr0.6,Pu0.4)N fuel has been produced by internal gelation followed by carbothermal reduction. No co-gelation was observed during internal gelation and a two phase material could be detected by scanning electron microscopy in the nitrided microspheres. Sintering has been performed in both Ar and N2. X-ray diffraction revealed that sintering in N2 produced a solid solution, while sintering in Ar did not. The final metal composition in the microspheres was determined by ICP-MS to be about 41% Pu and 59% Zr. Vegard's law was applied to estimate the nitride purity in the solid solution pellet to be Zr0.6Pu0.4N0.87C0.13 making the final material more of a carbonitride than a pure nitride.

  16. Slip Casting and Green Body Evaluation of 6% Yttria, 2% Alumina Silicon Nitride

    Science.gov (United States)

    1991-12-01

    Some Properrie of Aqucouw Silicon Nitride SuN- pensons. Ponrahkovaya Metallurgrya. no. 3 (159), March 1976, p. 37. 7. GREIL. P., NAGEL. A., STADELMANN ...H., and PETZOW, G. Revie%, Colloidal Proce=ing of Silicon Nitride Ceramics. Ceramic Materi- als and Componenls for Engines, p. 319. 8. STADELMANN II

  17. Study on Physical and Chemical Behaviors of Rare Earths in Preparing Ceramic Tube Supported Palladium Film by Electroless Plating

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The rare earths of ytterbium, lanthanum, praseodymium, neodymium and their binary mixtures were respectively added into the traditional electroless plating solution to prepare thin palladium film on the inner surface of porous ceramic tube. The experimental results shows that the addition of rare earths increases palladium deposition rates and the binary mixtures are superior to the single rare earths and the mixture of ytterbium-lanthanum is the most efficient. Adding the mixture of ytterbium-lanthanum can also reduce the plating temperature by 10~20 ℃, shrink the metal crystal size and improve the film densification compared to those by traditional electroless plating. A thin palladium film with 5 μm was prepared and the film made a highly pure hydrogen with a molar fraction of more than 99.97% from a H2-N2 gas mixture. More attentions were paid to analyze the physical and chemical behaviors of the rare earths in palladium film preparation.

  18. The effect of preparation under vacuum and microwave drying on the mechanical properties of porcelain ceramic foam via polymeric sponge method

    Science.gov (United States)

    Shahatha, S. H.; Mohammed, M. A.

    2016-04-01

    In this paper was demonstrated the effect of preparation condition under vacuum and microwave drying on the mechanical properties of porcelain ceramic foam. The study was based on five different polymeric foam templates with thickness ranging from 0.5 to 4 cm. The templates were impregnated in ceramic slurry with solid loading ranging from 35 to 55 wt. % under vacuum pressure 10-1 Torr and then sintered to 1250°C. Effects of polymeric foam template thickness and solid loading quantity were evaluated based on porosity, density and mechanical properties (compressive and flexural strengths) of the ceramic foam.

  19. Preparation and laser performance of Nd-doped yttrium lanthanum oxide transparent ceramic

    Science.gov (United States)

    Yang, Qiuhong; Lu, Shenzhou; Zhang, Bin; Zhang, Haojia; Zhou, Jun; Yuan, Zhijun; Qi, Yunfeng; Lou, Qihong

    2011-03-01

    1.5 at.% Nd:Y 1.8La 0.2O 3 transparent ceramic was fabricated by a solid-state reaction method and sintered at 1650-1700 °C for 40-50 h under H 2 atmosphere. The spectroscopic properties were investigated at room temperature. The transparent ceramic has excellent spectroscopic properties, with the absorption cross section of 1.50 × 10 -20 cm 2 and broad full width at half maximum (FWHM) of about 8 nm at LD wavelength 806 nm, the emission cross section of 2.03 × 10 -20 cm 2 at 1079 nm, and the decay lifetime of 200 μs. Laser performance was carried out using an uncoated Nd:Y 1.8La 0.2O 3 ceramic plate under laser diode end-pumping without any water cooling device. The room temperature thermal conductivity of this ceramic is 6.20 W/mK. For Nd:Y 1.8La 0.2O 3 ceramic laser, a maximum output power of 62 mW was obtained at 1079 nm under a 808 nm diode pump.

  20. Effect of Sintering Temperature on the Properties of Fused Silica Ceramics Prepared by Gelcasting

    Science.gov (United States)

    Wan, Wei; Huang, Chun-e.; Yang, Jian; Zeng, Jinzhen; Qiu, Tai

    2014-07-01

    Fused silica ceramics were fabricated by gelcasting, by use of a low-toxicity N' N-dimethylacrylamide gel system, and had excellent properties compared with those obtained by use of the low-toxicity 2-hydroxyethyl methacrylate and toxic acrylamide systems. The effect of sintering temperature on the microstructure, mechanical and dielectric properties, and thermal shock resistance of the fused silica ceramics was investigated. The results showed that sintering temperature has a critical effect. Use of an appropriate sintering temperature will promote densification and improve the strength, thermal shock resistance, and dielectric properties of fused silica ceramics. However, excessively high sintering temperature will greatly facilitate crystallization of amorphous silica and result in more cristobalite in the sample, which will cause deterioration of these properties. Fused silica ceramics sintered at 1275°C have the maximum flexural strength, as high as 81.32 MPa, but, simultaneously, a high coefficient of linear expansion (2.56 × 10-6/K at 800°C) and dramatically reduced residual flexural strength after thermal shock (600°C). Fused silica ceramics sintered at 1250°C have excellent properties, relatively high and similar flexural strength before (67.43 MPa) and after thermal shock (65.45 MPa), a dielectric constant of 3.34, and the lowest dielectric loss of 1.20 × 10-3 (at 1 MHz).

  1. Review of corrosion behavior of ceramic heat exchanger materals: Corrosion characteristics of silicon carbide and silicon nitride. Final report, September 11, 1992--March 11, 1993

    Energy Technology Data Exchange (ETDEWEB)

    Munro, R.G.; Dapkunas, S.J.

    1993-09-01

    The present work is a review of the substantial effort that has been made to measure and understand the effects of corrosion with respect to the properties, performance, and durability of various forms of silicon carbide and silicon nitride. The review encompasses corrosion in diverse environments, usually at temperatures of 1000C or higher. The environments include dry and moist oxygen, mixtures of hot gaseous vapors, molten salts, molten metals, and complex environments pertaining to coal ashes and slags.

  2. Preparation and properties of bisphenol-F based boron-phenolic resin/modified silicon nitride composites and their usage as binders for grinding wheels

    Science.gov (United States)

    Lin, Chun-Te; Lee, Hsun-Tsing; Chen, Jem-Kun

    2015-03-01

    In this study, phenolic resins based on bisphenol-F (BPF) were synthesized. Besides, ammonium borate was added in the synthesis process of BPF to form the bisphenol-F based boron-phenolic resins (B-BPF). The glass transition temperature, thermal resistance, flexural strength and hardness of B-BPF are respectively higher than those of BPF. This is due to the presence of new cross-link Bsbnd O bonds in the B-BPF. In addition, the 3-aminopropyltriethoxysilane modified silicon nitride powders (m-SiN) were fully mixed with B-BPF to form the B-BPF/m-SiN composites. The thermal resistance and mechanical properties of the B-BPF/m-SiN are promoted by the well-dispersed and well-adhered m-SiN in these novel polymer/ceramics composites. The results of grinding experiments indicate that the grinding wheels bound by the B-BPF/m-SiN have better grinding quality than those bound by the BPF. Thus the B-BPF/m-SiN composites are better binding media than the BPF resins.

  3. Preparation and properties of gradient Al2O3-ZrO2 ceramic foam by centrifugal slip casting method

    Directory of Open Access Journals (Sweden)

    Li Qiang

    2012-11-01

    Full Text Available The aim of the present research is to provide a novel technique for preparing gradient Al2O3-ZrO2 ceramic foams. This technique used epispastic polystyrene spheres to array templates and centrifugal slip casting to obtain cell struts with gradient distribution of Al2O3 and ZrO2 particles and high packing density. Aqueous Al2O3-20vol.% ZrO2 slurries with 20vol.% solid contents were prepared and the dispersion and rheological characteristics of the slurries were investigated. The settling velocity and mass segregation of Al2O3 and ZrO2 particles at different centrifugal accelerations were calculated and studied. The drying behavior, macrostructure, microstructure, compressive property and resistance to thermal shock of the sintered products were also investigated. The results show that the difference of settling velocity of Al2O3 and ZrO2 particles increases and mass segregation becomes acute with an increase in centrifugal acceleration. The cell struts prepared at a centrifugal acceleration of 1,690 g have high sintered density (99.0% TD and continuous gradient distribution of Al2O3 and ZrO2 particles. When sintered at 1,550 oC for 2 h, the cell size of gradient Al2O3-ZrO2 foam is approximately uniform, about 1.1 mm. With the porosity of gradient Al2O3-ZrO2 ceramic foams increasing from 75.3% to 83.0%, the compressive strength decreases from 4.4 to 2.4 MPa, and the ceramic foams can resist 8-11 repeated thermal shock from 1,100 oC to room temperature.

  4. Influence of porcelain firing and cementation on the marginal adaptation of metal-ceramic restorations prepared by different methods.

    Science.gov (United States)

    Kaleli, Necati; Saraç, Duygu

    2017-05-01

    Marginal adaptation plays an important role in the survival of metal-ceramic restorations. Porcelain firings and cementation may affect the adaptation of restorations. Moreover, conventional casting procedures and casting imperfections may cause deteriorations in the marginal adaptation of metal-ceramic restorations. The purpose of this in vitro study was to compare the marginal adaptation after fabrication of the framework, porcelain application, and cementation of metal-ceramic restorations prepared by using the conventional lost-wax technique, milling, direct metal laser sintering (DMLS), and LaserCUSING, a direct process powder-bed system. Alterations in the marginal adaptation of the metal frameworks during the fabrication stages and the precision of fabrication methods were evaluated. Forty-eight metal dies simulating prepared premolar and molar abutment teeth were fabricated to investigate marginal adaptation. They were divided into 4 groups (n=12) according to the fabrication method used (group C serving as the control group: lost-wax method; group M: milling method; group LS: DMLS method; group DP: direct process powder-bed method). Sixty marginal discrepancy measurements were recorded separately on each abutment tooth after fabrication of the framework, porcelain application, and cementation by using a stereomicroscope. Thereafter, each group was divided into 3 subgroups according to the measurements recorded in each fabrication stage: subgroup F (framework), subgroup P (porcelain application), and subgroup C (cementation). Data were statistically analyzed with univariate analysis of variance (followed by 1-way ANOVA and Tamhane T2 test (α=.05). The lowest marginal discrepancy values were observed in restorations prepared by using the direct process powder-bed method, and this was significantly different (Pdirect process powder-bed method is quite successful in terms of marginal adaptation. The marginal discrepancy increased after porcelain application

  5. Comparative study of dielectric properties of MgNb2O6 prepared by molten salt and ceramic method

    Indian Academy of Sciences (India)

    Vishnu Shanker; Ashok K Ganguli

    2003-12-01

    Magnesium niobate (MgNb2O6) powder was synthesized by the conventional ceramic route as well as by the molten salt route using a eutectic mixture of NaCl–KCl as the salt and Mg(NO3)$_2\\cdot$6H2O and TiO2 as the starting materials. Pure phase of MgNb2O6 could be obtained by the molten salt method at 1100°C. However, in ceramic method the pure phase of MgNb2O6 was obtained by heating at 1025°C for 20 h. On sintering at 1100°C the dielectric constant and dielectric loss of MgNb2O6 obtained by the molten salt method was found to be 19.5 and 0.004 at 100 kHz at room temperature. Lower values were obtained for these oxides prepared by the ceramic route, 16.6 and 0.000518, respectively. In both cases the dielectric constant was quite stable with frequency.

  6. Preparation of ceramic-corrosion-cell fillers and application for cyclohexanone industry wastewater treatment in electrobath reactor.

    Science.gov (United States)

    Wu, Suqing; Qi, Yuanfeng; Gao, Yue; Xu, Yunyun; Gao, Fan; Yu, Huan; Lu, Yue; Yue, Qinyan; Li, Jinze

    2011-11-30

    As new media, ceramic-corrosion-cell fillers (Cathode Ceramic-corrosion-cell Fillers - CCF, and Anode Ceramic-corrosion-cell Fillers - ACF) employed in electrobath were investigated for cyclohexanone industry wastewater treatment. 60.0 wt% of dried sewage sludge and 40.0 wt% of clay, 40.0 wt% of scrap iron and 60.0 wt% of clay were utilized as raw materials for the preparation of raw CCF and ACF, respectively. The raw CCF and ACF were respectively sintered at 400°C for 20 min in anoxic conditions. The physical properties (bulk density, grain density and water absorption), structural and morphological characters and toxic metal leaching contents were tested. The influences of pH, hydraulic retention time (HRT) and the media height on removal of COD(Cr) and cyclohexanone were studied. The results showed that the bulk density and grain density of CCF and ACF were 869.0 kg m(-3) and 936.3 kg m(-3), 1245.0 kg m(-3) and 1420.0 kg m(-3), respectively. The contents of toxic metal (Cu, Zn, Cd, Pb, Cr, Ba, Ni and As) were all below the detection limit. When pH of 3-4, HRT of 6h and the media height of 60 cm were applied, about 90% of COD(cr) and cyclohexanone were removed.

  7. Ceramic Technology Project database: March 1990 summary report. DOE/ORNL Ceramic Technology Project

    Energy Technology Data Exchange (ETDEWEB)

    Keyes, B.L.P.

    1992-07-01

    This report is the fifth in a series of semiannual data summary reports on information being stored in the Ceramic Technology Project (CTP) database. The overall system status as of March 31, 1990, is summarized, and the latest additions of ceramic mechanical properties data are given for zirconia, silicon carbide, and silicon nitride ceramic mechanical properties data, including some properties on brazed specimens.

  8. Preparation of Silver- and Zinc-Doped Mullite-Based Ceramics Showing Anti-Bacterial Biofilm Properties

    Directory of Open Access Journals (Sweden)

    Suhair Saleh

    2011-03-01

    Full Text Available Zinc- and silver-doped mullite ceramic discs were prepared and tested as potentially resistant materials against bacterial adhesion and biofilm formation. Elemental analysis and X-ray diffraction studies showed that zinc ions were incorporated in the structural framework of the mullite, while silver ions remained outside the mullite crystal lattice, which allowed their slow (0.02 ppm/24 hours leaching into the surrounding aqueous environment. In agreement with this behavior, silver-doped mullite showed potent resistance against surface attachment of Pseudomonas aeruginosa, while on the other hand, zinc-doped mullite failed to stop bacterial attachment.

  9. Preparation and properties of nano-composite ceramic coating by thermo chemical reaction method

    Institute of Scientific and Technical Information of China (English)

    MA Zhuang; SUN Fang-hong; LI Zhi-chao

    2007-01-01

    Nano-composite ceramic coating was fabricated on Q235 steel through thermo chemical reaction method. Structure of the coating was analyzed and the properties were tested. The results show that a few of new ceramic phases, such as MgAl2O4, ZnAl2O4,Al2SiO5, Ni3Fe and Fe3Al, are formed on the coating during the process of solidifying at 600 ℃. The ceramic coating is dense and the high bonding strength is obtained. The average bonding strength between the coating and matrix could be 14.22 MPa. The acid resistance of the coating increase by 8.8 times, the alkali resistance by 4.1 times, the salt resistance by 10.3 times, and the wear resistance by 2.39 times.

  10. Research on Abrasives in the Chemical Mechanical Polishing Process for Silicon Nitride Balls

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Silicon nitride (Si 3N 4) has been the main material for balls in ceramic ball bearings, for its lower density, high strength, high hardness, fine thermal stability and anticorrosive, and is widely used in various fields, such as high speed and high temperature areojet engines, precision machine tools and chemical engineer machines. Silicon nitride ceramics is a kind of brittle and hard material that is difficult to machining. In the traditional finishing process of silicon nitride balls, balls are lapped...

  11. Preparation of Gd2O2S:Pr Scintillation Ceramics by Pressureless Reaction Sintering Method

    Institute of Scientific and Technical Information of China (English)

    Jingbao Lian; Xudong Sun; Tie Gao; Qiang Li; Xiaodong Li; Zhigang Liu

    2009-01-01

    Fabrication of Gd2O2S:Pr scintillation ceramics by pressureless reaction sintering was investigated. The 2Gd2O3.(Gd,Pr)2(SO4)3.mH2O precursor was made by hydrotherrnal reaction using commercially available Gd2O3, Pr6O11 and H2SO4 as the starting materials. Then single phase Gd2O2SO4:Pr powder was obtained by calcining the precursor at 750℃ for 2 h. The Gd2O2SO4:Pr powder compacts can be sintered to single phase Gd2O2S:Pr ceramics with a relative density of 99% and mean grain size of 30 μm at 1750℃ for 2 h in flowing hydrogen atmosphere. Densification and microstructural development of the Gd2O2S:Pr ceramics were examined. Luminescence spectra of the Gd2O2S:Pr ceramic under 309 nm UV excitation and X-ray excitation show a green emission at 511 nm as the most prominent peak, which corresponds to the 3P0-ZH4 transition of Pr3+ ions.

  12. Preparation of Biomorphic SiC/C Ceramics from Pine Wood via Supercritical Ethanol Infiltration

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Biomorphic (wood derived) carbide ceramics with an overall composition in the SiC/C was produced by supercritical ethanol infiltration of low viscosity tetraethylorthosilicate/supercritical ethanol into biologically derived carbon templates (CB-templates) and in situ hydrolysis into Si(OH)4-gel, the Si(OH)4-gel was calcined at 1400℃ to promote the polycondensation of Si(OH)4-gel into SiO2-phase and then carbonthermal reduction of the SiO2 with the biocarbon template into highly porous, biomorphic SiC/C ceramics. The phases and morphology conversion mechanism of resulting porous SiC/C ceramics have been investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Fourier transform infrared spectroscopy (FT-IR). Experimental results showed that the biomorphic cellular morphology of pinewood charcoal was remained in the porous SiC/C ceramic with high precision that consisted of β-SiC with minority of α-SiC and the remain free carbon existed in amorphous phase.

  13. Preparation and luminescence properties of Eu3+ doped oxyfluoride borosilicate glass ceramics

    Institute of Scientific and Technical Information of China (English)

    LI Yanhong; ZHAO Li; ZHANG Yongming; MA Jing

    2012-01-01

    Oxyfluoride borosilicate glass with the molar composition of60SiO2-15B2O3-15Na2O-8CaF2-2NaF-0.25Eu2O3 was synthesized by a traditional glass melting method.Glass ceramics containing CaF2 nanocrystals were preparcd by heat treating the glass samples at a temperature in the range of 620-680℃.The results of X-ray diffraction (XRD) indicated that the average crystallite size and the lattice constant of CaF2 nanocrystals increased with the heat treatment temperature incrcasing.The luminescence spectra showed that the emission intensity of Eu3+ doped glass ceramics was stronger than that of the glass matrix,and increased with the heat treatment temperature increasing.The left edge of excitation band shifted to shorter wavelength in the glass ceramics.The local environments of Eu3+ ions in the glass and glass ceramics were different.

  14. Preparation of TiN Ceramic Collector for Sodium Sulfur Battery

    Institute of Scientific and Technical Information of China (English)

    ZHANG; Hao; MA; Jun-ping; TANG; Xian

    2015-01-01

    As an energy storage technology,sodium sulfur battery is used in many areas.It uses beta alumina ceramic as electrolytes,sodium and sulfur as electrode,the working temperature is350℃,which can get heat from radioisotopes.Traditional battery uses stainless steel and Al as collector,which are easily eroded by sodium.As

  15. Pyrochlore free 0.67PMN-0.33PT ceramics prepared by particle-coating method

    Energy Technology Data Exchange (ETDEWEB)

    Chu, Ruiqing; Li, Yan [College of Materials Science and Engineering, Liaocheng University, Liaocheng 252059 (China); Gong, Shuwen [College of Chemistry and Chemical Engineering, Liaocheng University, Liaocheng 252059 (China); Liu, Yong [College of Materials Science and Engineering, Liaocheng University, Liaocheng 252059 (China); Li, Guorong [The State Key Lab of High Performance Ceramics and Superfinemicrostructure, Shanghai Institute of Ceramics, Chinese Academy of Science, Shanghai 200050 (China); Xu, Zhijun, E-mail: zhjxu@lcu.edu.cn [College of Materials Science and Engineering, Liaocheng University, Liaocheng 252059 (China)

    2012-08-20

    Highlights: Black-Right-Pointing-Pointer Pyrochlore-free PMN-PT powders were obtained by two-step particle-coating method. Black-Right-Pointing-Pointer Mg-citric acid polymeric complex coatings avoid the formation of pyrochlore phase. Black-Right-Pointing-Pointer Pyrochlore-free PMN-PT powders have been successfully prepared at 800 Degree-Sign C. Black-Right-Pointing-Pointer The PMN-PT ceramics sintered at 1150 Degree-Sign C exhibited excellent electrical properties. - Abstract: In present study, pyrochlore-free 0.67Pb(Mg{sub 1/3}Nb{sub 2/3})O{sub 3}-0.33PbTiO{sub 3} (0.67PMN-0.33PT) powders and ceramics have been successfully prepared. Using oxides as raw materials, pyrochlore-free 0.67PMN-0.33PT powders were obtained by two-step particle-coating method. The XRD and EDS results confirmed that the Mg-citric acid polymeric complex coatings effectively prevent the direct contact between PbO and Nb{sub 2}O{sub 5} and thus avoid the formation of pyrochlore phase. The obtained pyrochlore-free 0.67PMN-0.33PT powders at 800 Degree-Sign C showed uniform and even grain size. The 0.67PMN-0.33PT ceramics sintered at 1150 Degree-Sign C for 2 h exhibited 99% of relative density and a piezoelectric coefficient (d{sub 33}) of 576pC/N, a remnant polarization (P{sub r}) of 28.4 {mu}C/cm{sup 2}, a planar electromechanical coupling factor (k{sub p}) of 0.55 and a mechanical quality factor (Q{sub m}) of 90.

  16. Effect of kaolin particle size and loading on the characteristics of kaolin ceramic support prepared via phase inversion technique

    Directory of Open Access Journals (Sweden)

    Siti Khadijah Hubadillah

    2016-06-01

    Full Text Available In this study, low cost ceramic supports were prepared from kaolin via phase inversion technique with two kaolin particle sizes, which are 0.04–0.6 μm (denoted as type A and 10–15 μm (denoted as type B, at different kaolin contents ranging from 14 to 39 wt.%, sintered at 1200 °C. The effect of kaolin particle sizes as well as kaolin contents on membrane structure, pore size distribution, porosity, mechanical strength, surface roughness and gas permeation of the support were investigated. The support was prepared using kaolin type A induced asymmetric structure by combining macroporous voids and sponge-like structure in the support with pore size of 0.38 μm and 1.05 μm, respectively, and exhibited ideal porosity (27.7%, great mechanical strength (98.9 MPa and excellent gas permeation. Preliminary study shows that the kaolin ceramic support in this work is potential to gas separation application at lower cost.

  17. Preparation of LuAG Powders with Single Phase and Good Dispersion for Transparent Ceramics Using Co-Precipitation Method

    Directory of Open Access Journals (Sweden)

    Liangjie Pan

    2015-08-01

    Full Text Available The synthesis of pure and well dispersed lutetium aluminum garnet (LuAG powder is crucial and important for the preparation of LuAG transparent ceramics. In this paper, high purity and well dispersed LuAG powders have been synthesized via co-precipitation method with lutetium nitrate and aluminum nitrate as raw materials. Ammonium hydrogen carbonate (AHC was used as the precipitant. The influence of aging time, pH value, and dripping speed on the prepared LuAG powders were investigated. It showed that long aging duration (>15 h with high terminal pH value (>7.80 resulted in segregation of rhombus Lu precipitate and Al precipitate. By decreasing the initial pH value or accelerating the dripping speed, rhombus Lu precipitate was eliminated and pure LuAG nano powders were synthesized. High quality LuAG transparent ceramics with transmission >75% at 1064 nm were fabricated using these well dispersed nano LuAG powders.

  18. Effect of organic additives on mechanical properties of SiC ceramics prepared by a modified gelcasting method

    Directory of Open Access Journals (Sweden)

    Feng Wang

    2016-12-01

    Full Text Available A novel and simple gel system of isobutylene and maleic anhydride (PIBM was used to prepare SiC ceramics. The rheological behaviour of the SiC slurries was investigated as function of organic additives. The SiC slurries with 0.2 wt.% PIBM and 0.2 wt.% tetramethylammonium hydroxide (TMAH showed low viscosity, which was favourable for casting SiC green bodies. In order to obtain homogeneous green bodies, polyvinyl alcohol (PVA was used to assist the dispersion of carbon black in the slurries, and polyethylene glycol (PEG was added to inhibit the surface exfoliation of green bodies. The content of PVA was controlled carefully to avoid the warpage of green bodies during the drying process. Finally, homogeneous defect-free SiC green bodies were successfully fabricated via aqueous gelcasting. The SiC ceramics sintered at 2100 °C (prepared from slurries with solid content of 60 wt.% showed an average flexural strength of 305.7 MPa with porosity of 19.92%.

  19. Reduced leakage current and improved ferroelectricity in magneto-electric composite ceramics prepared with microwave assisted radiant hybrid sintering

    Directory of Open Access Journals (Sweden)

    Sanjay Kumar Upadhyay

    2015-04-01

    Full Text Available Structural, electrical and magnetic properties of magneto-electric composite ceramics viz., 0.9 BaTi0.95Sn0.05O3 (BTSO- 0.1 Ni0.8Zn0.2Fe2O4 (NZFO prepared with microwave assisted radiant hybrid sintering (MARH are reported. Phase purity and isovalent substitution of Ti4+ by Sn4+ of the samples is confirmed from x-ray diffraction and 119Sn Mossbauer measurements respectively. Significant suppression of leakage current and improvement of ferroelectricity is observed for the composites prepared with MARH. The observed results are explained in terms of uniform dispersion of ferrite (NZFO phase in the ferroelectric (BTSO matrix as evidenced from back-scattered scanning electron micrographs.

  20. Heuristic Analysis Model of Nitrided Layers' Formation Consisting of the Image Processing and Analysis and Elements of Artificial Intelligence

    National Research Council Canada - National Science Library

    Tomasz Wójcicki; Michal Nowicki

    2016-01-01

    .... The objectives of the analyses of the materials for gas nitriding technology are described. The methods of the preparation of nitrided layers, the steps of the process and the construction and operation of devices for gas nitriding are given...

  1. Preparation of a sol-gel-derived carbon nanotube ceramic electrode by microwave irradiation and its application for the determination of adenine and guanine

    Energy Technology Data Exchange (ETDEWEB)

    Abbaspour, Abdolkarim, E-mail: abbaspour@chem.susc.ac.i [Department of Chemistry, College of Sciences, Shiraz University, Shiraz, Fars 71456-85464 (Iran, Islamic Republic of); Ghaffarinejad, Ali [Department of Chemistry, College of Sciences, Shiraz University, Shiraz, Fars 71456-85464 (Iran, Islamic Republic of)

    2010-01-01

    In this study, microwave irradiation was used for the fast preparation (min) of a sol-gel-derived carbon nanotube ceramic electrode (MW-CNCE). For confirmation of the preparation of the ceramic by MW irradiation, Fourier transform infrared, X-ray diffraction spectra and scanning electron microscopy images of the produced ceramic were compared with those of conventional ceramic (which is produced by drying the ceramic in air for 48 h). The electrochemical behavior of MW-CNCE in nicotinamide adenine dinucleotide, L-cysteine, adenine and guanine was compared with that of a conventional sol-gel-derived carbon nanotube ceramic electrode (CNCE). In all systems, similar peak potentials and lower background currents were obtained with respect to CNCE. Finally, the MW-CNCE was used for the simultaneous determination of adenine and guanine using differential pulse voltammetry. The linear ranges of 0.1-10 and 0.1-20 muM were obtained for adenine and guanine, respectively. These results are comparable with some modified electrodes that have recently been reported for the determination of adenine and guanine, with the advantage that the proposed electrode did not contain modifier. In addition, the proposed electrode was successfully used for the oxidation of adenine and guanine in DNA, and the detection limit for this measurement was 0.05 mug mL{sup -1} DNA.

  2. Fracture toughness of advanced alumina ceramics and alumina matrix composites used for cutting tool edges

    Directory of Open Access Journals (Sweden)

    M. Szutkowska

    2012-10-01

    Full Text Available Purpose: Specific characteristics in fracture toughness measurements of advanced alumina ceramics and alumina matrix composites with particular reference to α-Al2O3, Al2O3-ZrO2, Al2O3-ZrO2-TiC and Al2O3-Ti(C,N has been presented.Design/methodology/approach: The present study reports fracture toughness obtained by means of the conventional method and direct measurements of the Vickers crack length (DCM method of selected tool ceramics based on alumina: pure alumina, alumina-zirconia composite with unstabilized and stabilized zirconia, alumina–zirconia composite with addition of TiC and alumina–nitride-carbide titanium composite with 2wt% of zirconia. Specimens were prepared from submicro-scale trade powders. Vicker’s hardness (HV1, fracture toughness (KIC at room temperature, the indentation fracture toughness, Young’s modulus and apparent density were also evaluated. The microstructure was observed by means of scanning electron microscopy (SEM.Findings: The lowest value of KIC is revealed by pure alumina ceramics. The addition of (10 wt% unstabilized zirconia to alumina or a small amount (5 wt% of TiC to alumina–zirconia composite improve fracture toughness of these ceramics in comparison to alumina ceramics. Alumina ceramics and alumina-zirconia ceramics reveal the pronounced character of R-curve because of an increasing dependence on crack growth resistance with crack extension as opposed to the titanium carbide-nitride reinforced composite based on alumina. R-curve has not been observed for this composite.Practical implications: The results show the method of fracture toughness improvement of alumina tool ceramics.Originality/value: Taking into account the values of fracture toughness a rational use of existing ceramic tools should be expected.

  3. Preparation of MgTiO3 Ceramics by High Energy Ball Milling

    Institute of Scientific and Technical Information of China (English)

    TAO Zhendong; ZHANG Ying; YANG Zhongxi; WANG Yingzi; MENG Shanshan; TENG Tieli

    2006-01-01

    MgTiO3 precursor was mechanochemically synthesized by high-energy ball milling of MgO and TiO2. The sintering characteristic of the resulted MgTiO3 precursor was investigated. The experimental results indicate that particles of both MgO and TiO2 powders become smaller rapidly, and then the crystalline structures of MgO and TiO2 change significantly. MgTiO3 was observed by XRD after 30 hours of ball milling. Strong diffraction peaks of MgTiO3 were observed after 50 hours of ball milling. HRTEM observation proves that dense MgTiO3 ceramics with a compact crystalline structure can be sintered from mechanochemically activated MgTiO3 precursor, the volume density of the resulting ceramic is as high as 95% of the theoretical density, the porosity and average pore diameter of the ceramic are measured as 4.95% and 50 nm respectively, and the transverse strength exceeded 500 MPa.

  4. Properties of ceramics prepared using dry discharged waste to energy bottom ash dust.

    Science.gov (United States)

    Bourtsalas, Athanasios; Vandeperre, Luc; Grimes, Sue; Themelis, Nicolas; Koralewska, Ralf; Cheeseman, Chris

    2015-09-01

    The fine dust of incinerator bottom ash generated from dry discharge systems can be transformed into an inert material suitable for the production of hard, dense ceramics. Processing involves the addition of glass, ball milling and calcining to remove volatile components from the incinerator bottom ash. This transforms the major crystalline phases present in fine incinerator bottom ash dust from quartz (SiO(2)), calcite (CaCO(3)), gehlenite (Ca(2)Al(2)SiO(7)) and hematite (Fe(2)O(3)), to the pyroxene group minerals diopside (CaMgSi(2)O(6)), clinoenstatite (MgSi(2)O(6)), wollastonite (CaSiO(3)) together with some albite (NaAlSi(3)O(8)) and andradite (Ca(3)Fe(2)Si(3)O(12)). Processed powders show minimal leaching and can be pressed and sintered to form dense (>2.5 g cm(-3)), hard ceramics that exhibit low firing shrinkage (ceramic tiles that have potential for use in a range of industrial applications.

  5. Properties of sintered glass-ceramics prepared from plasma vitrified air pollution control residues.

    Science.gov (United States)

    Roether, J A; Daniel, D J; Rani, D Amutha; Deegan, D E; Cheeseman, C R; Boccaccini, A R

    2010-01-15

    Air pollution control (APC) residues, obtained from a major UK energy from waste (EfW) plant, processing municipal solid waste, have been blended with silica and alumina and melted using DC plasma arc technology. The glass produced was crushed, milled, uni-axially pressed and sintered at temperatures between 750 and 1150 degrees C, and the glass-ceramics formed were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Mechanical properties assessed included Vickers's hardness, flexural strength, Young's modulus and thermal shock resistance. The optimum sintering temperature was found to be 950 degrees C. This produced a glass-ceramic with high density (approximately 2.58 g/cm(3)), minimum water absorption (approximately 2%) and relatively high mechanical strength (approximately 81+/-4 MPa). Thermal shock testing showed that 950 degrees C sintered samples could withstand a 700 degrees C quench in water without micro-cracking. The research demonstrates that glass-ceramics can be readily formed from DC plasma treated APC residues and that these have comparable properties to marble and porcelain. This novel approach represents a technically and commercially viable treatment option for APC residues that allow the beneficial reuse of this problematic waste.

  6. Preparation of transparent Y2O3 ceramic by slip casting and vacuum sintering

    Institute of Scientific and Technical Information of China (English)

    HUO Di; ZHENG Yanchun; SUN Xudong; LI Xiaodong; LIU Shaohong

    2012-01-01

    In the present work transparent Y2O3 ceramics were made by slip casting and vacuum sintering of nanopowders with sodium polyacrylic acid (PAA-Na) as dispersant.The rheological properties of Y2O3 nanopowder slurry were investigated using different amounts of dispersant and solid contents.The microstructures and transmittance of the sintered ceramics were also studied by means of scauning electron microscopy (SEM) and ultra-violet visible spectrometry.The results showed that rheological behaviors of the Y2O3 nanopowder slurry were effectively promoted by sodium polyacrylic acid.Highly dispersive and stable slurries were obtained as the dispersant was added over 1.0dwb% under the fixed conditions of pH 11 and 45 wt.% solid content.All the slip cast green bodies were sintered into highly dense ceramics after sintering at 1700 ℃ for 5 h in vacuum,wherein the sample added with 1.1% sodium polyacrylic acid exhibited the highest relative density of 99.36% and transmission of 30% at 800 nm wavelength.

  7. Transparent polycrystalline cubic silicon nitride

    Science.gov (United States)

    Nishiyama, Norimasa; Ishikawa, Ryo; Ohfuji, Hiroaki; Marquardt, Hauke; Kurnosov, Alexander; Taniguchi, Takashi; Kim, Byung-Nam; Yoshida, Hidehiro; Masuno, Atsunobu; Bednarcik, Jozef; Kulik, Eleonora; Ikuhara, Yuichi; Wakai, Fumihiro; Irifune, Tetsuo

    2017-01-01

    Glasses and single crystals have traditionally been used as optical windows. Recently, there has been a high demand for harder and tougher optical windows that are able to endure severe conditions. Transparent polycrystalline ceramics can fulfill this demand because of their superior mechanical properties. It is known that polycrystalline ceramics with a spinel structure in compositions of MgAl2O4 and aluminum oxynitride (γ-AlON) show high optical transparency. Here we report the synthesis of the hardest transparent spinel ceramic, i.e. polycrystalline cubic silicon nitride (c-Si3N4). This material shows an intrinsic optical transparency over a wide range of wavelengths below its band-gap energy (258 nm) and is categorized as one of the third hardest materials next to diamond and cubic boron nitride (cBN). Since the high temperature metastability of c-Si3N4 in air is superior to those of diamond and cBN, the transparent c-Si3N4 ceramic can potentially be used as a window under extremely severe conditions. PMID:28303948

  8. OPTIMAL PREPARATION JUNCTIONS FOR ALL-CERAMIC FIXED RESTORATIONS MADE BY CAM 5 – S 2 IMPRESSION, VHF

    Directory of Open Access Journals (Sweden)

    Angelina Vlahova

    2015-12-01

    Full Text Available Introduction: The type of the preparation junction is determined by a number of factors that need to be taken in consideration with CAD/CAM Fixed Prosthodontics: the material of which the construction will be made; the type and condition of the retainer teeth, of their periodontium and the occlusion; the design software, the CAM setting and the type of drills; the working protocol; the type of the cement and the method of cementation.Purpose: The aim of this publication is to describe the optimal preparation junctions for all-ceramic crown and bridge restorations made by CAM 5 - S 2 Impression, VHF.Materials and methods: Suitable are chamfer and shoulder preparation junction with rounded inner angle (width 1 - 1, 5 mm. Trimming of 1.5 – 2 mm dental tissues is necessary on the occlusal surface. The homothetic reduction of teeth is optimal.Results and discussion: The width depends on the size and vitality of the tooth. In stained teeth and those built with metal pins the removal of more tissues provides a greater volume needed to disguise the dark color. Vestibular preparation under the level of the gingiva is preferable to ensure optimal aesthetics. Preparation junction is determined also by the CAD/CAM technology - the type of drills and protocol of impression taking (classical or digital. The creation of a working model with TRIOS, 3Shape intraoral scanner is greatly facilitated by preparation junctions made above the gingival margin.Conclusion: Knowledge about the criteria for selection the preparation junctions is essential for fabrication accurate and aesthetic CAD/CAM restorations.

  9. Surface enhanced Raman scattering activity of TiN thin film prepared via nitridation of sol-gel derived TiO2 film

    Science.gov (United States)

    Dong, Zhanliang; Wei, Hengyong; Chen, Ying; Wang, Ruisheng; Zhao, Junhong; Lin, Jian; Bu, Jinglong; Wei, Yingna; Cui, Yi; Yu, Yun

    2015-10-01

    Surface-enhanced Raman scattering (SERS) is a powerful and non-destructive analytical technique tool for chemical and biological sensing applications. Metal-free SERS substrates have recently been developed by using semiconductor nanostructures. The optical property of TiN film is similar to that of gold. Besides that, its good chemical inertness and thermodynamic stability make TiN thin film an excellent candidate for SERS. In order to investigate its SERS activity, the TiN thin film was successfully prepared via direct nitridation of the sol-gel derived TiO2 thin film on the quartz substrate using ammonia gas as reducing agent. The crystallite structures and morphology of TiN thin film were determined by XRD, RAMAN and FE-SEM. The results show that the thin film obtained is cubic titanium nitride with a lattice parameter of 4.2349 Å. The surface of TiN thin film is rough and with the particles of 50 nm in average sizes. The thickness of TiN thin film is about 130 nm. The TiN thin film displays a surface Plasmon resonance absorption peak at around 476 nm, which can lead to a strong enhancement of the EM field on the interface. The Raman signal of the probe molecule R6G was greatly enhanced through TiN thin film substrates. The enhancement factor is about 4.1×103 and the detection limit achieves 10-6 M for R6G. The TiN thin film substrate also shows a good reproducibility of SERS performance. The results indicate that TiN thin film is an attractive material with potential application in SERS substrates.

  10. Thin film ceramic thermocouples

    Science.gov (United States)

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

    2011-01-01

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

  11. Preparation and photo-catalytic activity of TiO2-coated medical stone-based porous ceramics

    Science.gov (United States)

    Gao, Ru-qin; Hou, Xin-mei

    2013-06-01

    Medical stone-based porous ceramics as a carrier were prepared by ultra-fine grinding and low-temperature sintering method. Nano-TiO2 thin films were loaded on the carrier by chemical liquid deposition method using titanium tetrachloride as a precursor. The micro-morphology and microstructure of the synthesized samples were characterized using X-ray diffraction, scanning electron microscopy with energy dispersive spectrometry, and mercury injection method. The photo-catalytic activity of the TiO2 thin films was investigated by degrading formaldehyde. The main crystalline phase in the TiO2 thin films calcined at 550°C is anatase with the average particle size about 10 nm. The specific surface area of the carrier-coated nano-TiO2 increases from 3.68 to 5.32 m2/g. The formaldehyde removal rate of the TiO2/medical stone-based porous ceramics irradiated under an ultraviolet lamp for 120 min reaches 85.6%.

  12. ZrC Ceramics Prepared by Self-propagating High-temperature Synthesis/Single Action Pressing

    Directory of Open Access Journals (Sweden)

    CHENG Yong

    2017-01-01

    Full Text Available ZrC ceramics were prepared by mechanical axial compression of self-propagating high-temperature synthesis/single action pressing (SHS/SAP.The effects of pressure on microstructure and densification of the products,as well as the relationship between displacement/variation of the load curve and SHS reaction,were studied.The structure and properties of the products were investigated by XRD and SEM.In addition,the density was measured by the drain away liquid method.Meanwhile,universal testing machine was used to record the displacement and load curve alternations.The results indicate that products are mainly composed of ZrC phase,the process of exhaust are accelerated as the increasing of pressure as well,leading to the smaller size of porosity and crystal particles.Density manifested as an increasing pattern by the elevated pressure with no longer change at 80MPa.Due to the strong attenuation of pressure at the peak of temperature,the density of the production is only 65.7% in 120MPa.The end point of the SHS reaction and the plastic time of the products can be monitored by displacement and load curve.The results provide evidence for the application of self-propagating high-temperature synthesis/pseudo-hot isostatic pressing to further improve the density of ceramics.

  13. Processing, Mechanical and Optical Properties of Additive-Free ZrC Ceramics Prepared by Spark Plasma Sintering

    Directory of Open Access Journals (Sweden)

    Clara Musa

    2016-06-01

    Full Text Available In the present study, nearly fully dense monolithic ZrC samples are produced and broadly characterized from microstructural, mechanical and optical points of view. Specifically, 98% dense products are obtained by Spark Plasma Sintering (SPS after 20 min dwell time at 1850 °C starting from powders preliminarily prepared by Self-propagating High-temperature Synthesis (SHS followed by 20 min ball milling. A prolonged mechanical treatment up to 2 h of SHS powders does not lead to appreciable benefits. Vickers hardness of the resulting samples (17.5 ± 0.4 GPa is reasonably good for monolithic ceramics, but the mechanical strength (about 250 MPa up to 1000 °C could be further improved by suitable optimization of the starting powder characteristics. The very smoothly polished ZrC specimen subjected to optical measurements displays high absorption in the visible-near infrared region and low thermal emittance at longer wavelengths. Moreover, the sample exhibits goodspectral selectivity (2.1–2.4 in the 1000–1400 K temperature range. These preliminary results suggest that ZrC ceramics produced through the two-step SHS/SPS processing route can be considered as attractive reference materials for the development of innovative solar energy absorbers.

  14. Preparation of Silicon Carbide Reticulated Ceramics%碳化硅网眼多孔陶瓷的制备

    Institute of Scientific and Technical Information of China (English)

    朱新文; 江东亮; 谭寿洪

    2000-01-01

    本工作采用有机泡沫浸渍工艺制备了具有相互贯通气孔的碳化硅网眼多孔陶瓷.通过选择合适的流变剂获得了对海绵具有良好涂覆性能的浆料.探讨了粘结剂对网眼多孔陶瓷性能的影响,结果表明:硅溶胶是一种比较理想的粘结剂.XRD、SEM研究了烧结制品的晶相组成及显微结构,同时还对烧结制品的孔筋密度、气孔率、力学性能等进行了表征.本工作在1450℃下保温1h获得了气孔率为75%~85%、抗弯强度达2.5MPa以上的碳化硅网眼多孔陶瓷,其主要晶相由α-SiC、α-Al2O3、方石英和莫来石组成.%The open cell silicon carbide reticulated ceramics were prepared by impregnating a polyurethane sponge with aqueous ceramic slurry. TG-DTA analysis of the polyurethane sponge was used to determine the global thermal cycle for the consolidation of the porous ceramic bodies.A thixotropical slurry by adding effective rheological agents was optimized to uniformly coat the polyurethane sponge. The effect of processing conditions on properties of the sintered was studied.The effect of binders on processing was discussed in detail and it was found that colloidal silica is an effective binder. The structure of the sintered bodies were characterized by SEM and the phases of the sintered bodies were determined by XRD. Some properties including bulk density,strut density, porosity and strength of the sintered bodies, were characterized. The SiC reticulated ceramics, having 75%~85% porosity and bending strength as high as 2.5MPa, can be obtained under firing temperature 1450℃ for lh. The phases of the fired bodies are composed of α-SiC,α-Al2O3, cristobalite and mullite.

  15. Microstructure of reactive sintered Al bonded Si3N4-SiC ceramics

    Institute of Scientific and Technical Information of China (English)

    CUI Chong; WANG Yuan-ting; JIANG Jin-guo; CHEN Guang; SUN Qiang-jin

    2006-01-01

    Aluminium nitride-silicon nitride-silicon carbide (AlN-Si3N4-SiC) composite ceramics were prepared to increase the bending strength and improve the phase structure of Si3N4-based ceramics. The ceramics were made by reactive sintering in N2 atmosphere at 1 360 ℃, using Al as sintering additive. The phase composing of ceramics was identified with an X-ray diffractometer and the microstructure of the materials was studied by scanning electron microscopy. The results indicate that the phase structure is affected remarkably and the interface modality is changed. The interface between Si3N4 and SiC becomes blurry and that between SiC and AlN matches more better at the same time. But the liquid-phase appears during the reactive sintering along with the addition of Al by which the melting point of Si is decreased. The appearance of liquid Si decreases the bending strength of the ceramics. Lower temperature nitrification technic was introduced to avoid the appearance of liquid-phase Si. The optimum addition of Al was investigated by XRD and SEM analysis in order to obtain the maximal bending strength of materials.

  16. STUDY OF CERAMIC TILE PREPARATION WITH HIGH CONTENT OF CINDER%高掺量煤渣制备陶瓷釉面砖的研究

    Institute of Scientific and Technical Information of China (English)

    程小苏; 陈倩

    2011-01-01

    Ceramic glazed tile was prepared by low temperature biscuit fire and high temperature glost fire using cinder from a ceramic factory' coal gasifier as the ceramic raw material. The phase composition and microstructure of ceramic glazed tile were analyzed by testing strength, water absorption, X-ray diffraction (XRD) and scanning electron microscopy (SEM). The effects of Albite and Black Talc to strength of ceramic body were discussed. When the content of cinder was 50%, the strength of ceramic tile was more than 35Mpa.%以煤气发生炉的煤渣为主要原料,辅以钠长石和黑滑石等其他原料,经低温素烧、高温釉烧的二次烧结工艺在辊道窑烧制成陶瓷釉面砖.测试其强度和吸水率,并采用X射线衍射(XRD)仪和扫描电子显微镜(SEM)分析了煤渣陶瓷釉面砖的物相组成及微观结构,探讨了配方中钠长石和黑滑石含量对陶瓷坯体强度的影响,制备出的陶瓷釉面砖强度大于35Mpa,且煤渣利用量可达50%.

  17. Investigation on Structural and Optical Properties of Willemite Doped Mn2+ Based Glass-Ceramics Prepared by Conventional Solid-State Method

    Directory of Open Access Journals (Sweden)

    Nur Farhana Samsudin

    2015-01-01

    Full Text Available Mn-doped willemite (Zn2SiO4:Mn2+ glass-ceramics derived from ZnO-SLS glass system were prepared by a conventional melt-quenching technique followed by a controlled crystallization step employing the heat treatment process. Soda lime silica (SLS glass waste, ZnO, and MnO were used as sources of silicon, zinc, and manganese, respectively. The obtained glass-ceramic samples were characterized using the X-ray diffraction (XRD, Field Emission Scanning Electron Microscopy (FESEM, Fourier Transform Infrared (FTIR, UV-Visible (UV-Vis, and photoluminescence (PL spectroscopy. The results of XRD revealed that ZnO crystal and willemite (β-Zn2SiO4 were presented as major embedded crystalline phases. This observation was consistent with the result of FESEM which showed the presence of irregularity in shape and size of willemite crystallites. FTIR spectroscopy exhibits the structural evolution of willemite based glass-ceramics. The optical band gap shows a decreasing trend as the Mn-doping content increased. Photoluminescent technique was applied to characterize the role of Mn2+ ions when entering the willemite glass-ceramic structure. By measuring the excitation and emission spectra, the main emission peak of the glass-ceramic samples located at a wavelength of 585 nm after subjecting to 260 nm excitations. The following results indicate that the obtained glass-ceramics can be applied as phosphor materials.

  18. Preparation of CeO(2)-ZrO(2) ceramic fibers by electrospinning.

    Science.gov (United States)

    Zhang, Yanfei; Li, Jiayan; Li, Qin; Zhu, Ling; Liu, Xiangdong; Zhong, Xinghua; Meng, Jian; Cao, Xueqiang

    2007-03-15

    Electrospinning was employed to fabricate polymer-ceramic composite fibers from solutions containing poly(vinyl pyrrolidone) (PVP), Ce(NO(3))(3) x 6H(2)O and ZrOCl(2) x 8H(2)O. Upon firing the composite fibers at 1000 degrees C, Ce(0.67)Zr(0.33)O(2) fibers with diameters ranging from 0.4 to 2 microm were synthesized. These fibers exhibit strong resistance to sintering. They still have specific surface area around 11.8 m(2)/g after being heated at 1000 degrees C for 6 h.

  19. A Review on the Preparation of Borazine-derived Boron Nitride Nanoparticles and Nanopolyhedrons by Spray-pyrolysis and Annealing Process

    Directory of Open Access Journals (Sweden)

    Vincent Salles

    2016-01-01

    Full Text Available Boron nitride (BN nanostructures (= nanoBN are struc‐ tural analogues of carbon nanostructures but display different materials chemistry and physics, leading to a wide variety of structural, thermal, electronic, and optical applications. Proper synthesis routes and advanced structural design are among the great challenges for preparing nanoBN with such properties. This review provides an insight into the preparation and characteriza‐ tion of zero dimensional (0D nanoBN including nanopar‐ ticles and nanopolyhedrons from borazine, an economically competitive and attractive (from a technical point of view molecule, beginning with a concise intro‐ duction to hexagonal BN, followed by an overview on the past and current state of research on nanoparticles. Thus, a review of the spray-pyrolysis of borazine to form BN nanoparticles is firstly presented. The use of BN nanopar‐ ticles as precursors of BN nanopolyhedrons is then de‐ tailed. Applications and research perspectives for these 0D nanoBN are discussed in the conclusion.

  20. Preparation of CaO-SiO2 Glass-Ceramic Spheres by Electrospraying Combined with Sol-Gel Method

    Directory of Open Access Journals (Sweden)

    Hirotaka Maeda

    2013-01-01

    Full Text Available CaO-SiO2 glass-ceramic spheres were prepared by an electrospray method using hydrolyzed silicon alkoxide containing calcium nitrate. Crystalline calcium silicates, such as Ca2SiO4 and β-CaSiO3, formed around the surface of the spheres after heat treatment. The dissolution of the crystal phase of the spheres caused the release of Ca2+ and Si4+ ions during the initial stage of soaking in Tris-buffer solution, leading to the formation of nanosized pores at the sphere surface. The incorporation of Ca2+ ions into the glassy phase of the spheres suppressed the rapid pH increase during the initial stage of soaking in Tris-buffer solution.

  1. PZT压电纤维的制备及性能研究%Study on the Preparation and Properties of PZT Ceramic Fibers

    Institute of Scientific and Technical Information of China (English)

    杨杰; 刘兴钊

    2009-01-01

    以溶胶-凝胶(Sol-Gel)工艺制备的PZT陶瓷粉为原料,采用氧化物粉末装管法制备PZT压电陶瓷纤维.SEM分析显示,该陶瓷纤维呈圆柱型形貌,直径约为250 μm.分析了不同烧结温度下PZT陶瓷纤维的断面微结构及Pb含量变化,得出PZT陶瓷纤维的最佳烧结温度为1 000 ℃.XRD分析表明,此温度下烧结的陶瓷纤维呈单一的钙钛矿结构.实验结果表明,采用氧化物粉末装管法制备的陶瓷纤维大小均匀,结构致密,具有高长径比,克服了传统工艺不能制备结构致密的长纤维的缺陷.%Using the PZT ceramic powder prepared by Sol-Gel method as the raw material, the PZT piezoelectric ceramic fibers have been prepaared by using the Oxide Powder in Tube(OPTT)procedure.The SEM morphology showed that the PZT ceramic fibers had a cylindrical morphology with a diameter of about 250 μm.The sectional micro-structure and the content of Pb of the PZT ceramic fiber were analyzed at different sintering temperature. The result showed that the optimal sintering termperature of the PZT ceramic fiber was 1 000 ℃.The X-ray diffraction patterns showed that the ceramic fibers were pure perovskite structure.Compared with conventional fabrication process,PZT ceramic fibers prepared by the OPIT method have the advantage of dense ,uniform and high height-to-width ratio.

  2. Preparation and characterizations of bioglass ceramic cement/Ca-P coating on pure magnesium for biomedical applications.

    Science.gov (United States)

    Zhang, Xue; Li, Xiao-Wu; Li, Ji-Guang; Sun, Xu-Dong

    2014-01-08

    Magnesium has been recently recognized as a biodegradable metal for bone substitute applications. In order to improve the biocompatibility and osteointegration of pure Mg, two kinds of coatings, i.e., the Ca-P coating and bioglass ceramic cement (BGCC)/Ca-P coating, were prepared on the pure Mg ribbons in the present work. The Ca-P coating was obtained by aqueous solution method. Subsequently, Ca-P coated Mg was immersed into the BGCC slurry, which was prepared by the mix of SiO2-CaO-P2O5 bioglass ceramic (BGC) powders and phosphate liquid with a liquid-to-solid ratio (L/S) of 1.6, to obtain BGCC/Ca-P coating by a dipping-pulling method. The microstructures, morphologies, and compositions of these coatings have been characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) with energy-dispersive spectroscopy (EDS). The effect of these coatings on the mineralization activity of pure Mg has been investigated. The results indicated that both the Ca-P coating and BGCC/Ca-P coating could promote the nucleation of osteoconductive minerals, i.e., bone-like apatite, and the hydroxyapatite (HA) layer formed on the surface of the BGCC/Ca-P coating is obviously more dense, thick, and stable than that formed on the Ca-P coating after immersion in SBF solution for 15 days. The potentiodynamic polarization test indicated that the corrosion current density of the BGCC/Ca-P coated Mg is obviously lower than that of the Ca-P coating and 10 times lower than that of uncoated Mg. These results demonstrated that the BGCC/Ca-P coating can increase significantly the corrosion resistance of Mg and introduce a high biocompatibility of the bone-Mg substrate interface. In summary, the newly developed BGCC/Ca-P coated Mg has a good potential for biomedical applications.

  3. Preparation of Micro-Porous Alumina Sheet Support for Ceramic Membrane by Extrusion

    Science.gov (United States)

    Hemra, Khanthima; Atong, Duangduen; Aungkavattana, Pavadee

    Among several types of ceramic membrane developed for a half of century, alumina is the most extensive advantage. In this study, many types of alumina with different particle size distributions were used as a starting material for fabrication of support sheet ceramic membrane using extrusion process. The investigation focused on the alumina dough components composed of some organic binders and water. The organic binder of about 12 wt. % was required in order for dough to be easily extruded, while the amount of water added to the dough depended on the particle size of alumina powder. The particle size and size distribution of starting powder showed strong effects on pore size of sintered alumina support. The pore size decreased when smaller particle size of starting powder was used. In addition, the pore volume of the sintered alumina decreased with increasing the sintering temperature due to improvement in densification, while pore size remained the same. The mechanical strength of alumina supports was also influenced by the particle size of starting powder; the finer particle size resulted in the higher mechanical strength. However, in order to obtain a good flux for the membrane, a high mechanical strength of the support along with its effective porosity is critical concerns. In this work, the support sintered at 1450°C provided a proper porosity of approximately 40% with an acceptable mechanical strength of 30-45MPa.

  4. 墙地砖胶粘剂的研制%Preparation of ceramic tile adhesive

    Institute of Scientific and Technical Information of China (English)

    赵卫国; 俞永涵; 钱翠英; 蒋中南

    2001-01-01

    A fine water resisting styrene-acrylic emulsion was synthesized by adding silane coupling agent in the polymerization.By using this emulsion,a waterproof and weather fastness ceramic tile adhesive was produced successfully.The experimental results show that the silane dosage and its adding method have great effects on the product,and the property of the ceramic tile was good when using propylene-glycol butyl ether and methyl hydroxypropyl cellulose as film-forming agent and thickener respectively.%通过在聚合过程中加入硅烷偶联剂,制得一种耐水性优良的苯丙乳液,并用该乳液制得耐水、耐候性优良的即用型墙地砖胶粘剂。实验表明,硅烷偶联剂的加入量和加入方式对产品耐水性的影响较大,同时,以丙二醇丁醚和甲基羟丙基纤维素分别作为产品的成膜助剂及增稠剂,产品的综合性能较佳。

  5. Optimization of the preparation conditions of ceramic products using drinking water treatment sludges.

    Science.gov (United States)

    Zamora, R M Ramirez; Ayala, F Espesel; Garcia, L Chavez; Moreno, A Duran; Schouwenaars, R

    2008-11-01

    The aim of this work is to optimize, via Response Surface Methodology, the values of the main process parameters for the production of ceramic products using sludges obtained from drinking water treatment in order to valorise them. In the first experimental stage, sludges were collected from a drinking water treatment plant for characterization. In the second stage, trials were carried out to elaborate thin cross-section specimens and fired bricks following an orthogonal central composite design of experiments with three factors (sludge composition, grain size and firing temperature) and five levels. The optimization parameters (Y(1)=shrinking by firing (%), Y(2)=water absorption (%), Y(3)=density (g/cm(3)) and Y(4)=compressive strength (kg/cm(2))) were determined according to standardized analytical methods. Two distinct physicochemical processes were active during firing at different conditions in the experimental design, preventing the determination of a full response surface, which would allow direct optimization of production parameters. Nevertheless, the temperature range for the production of classical red brick was closely delimitated by the results; above this temperature, a lightweight ceramic with surprisingly high strength was produced, opening possibilities for the valorisation of a product with considerably higher added value than what was originally envisioned.

  6. Proton conductivity in tungsten and antimony-modified titania ceramics prepared by the sol-gel method

    Energy Technology Data Exchange (ETDEWEB)

    Vichi, Flavio Maron [Departamento de Quimica Fundamental, Instituto de Quimica, Universidade de Sao Paulo, Av. Prof, Lineu Prestes, 748, Butanta, Sao Paulo, SP (Brazil); Tejedor-Tejedor, Maria Isabel; Anderson, Marc A. [Environmental Chemistry and Technology Program, University of Wisconsin-Madison, 660 N. Park St., Madison, WI 53706 (United States)

    2005-03-15

    Titania ceramic materials modified with 5% antimony and 5% tungsten were prepared by the sol-gel method. For the antimony-modified material, a treatment with H{sub 2}O{sub 2} was also performed, in order to obtain antimonic acid. The electric conductivity of the xerogels was measured at 25 {sup o}C in the relative humidity (RH) range 33-81%. At 25 {sup o}C, the electrical conductivity of the 'as prepared' 5% Sb ceramic varies from 2.02x10{sup -5} S cm{sup -1} at 33% RH to 1.12x10{sup -2} S cm{sup -1} at 81% R.H. For the material treated with H{sub 2}O{sub 2}, the conductivity varies from 1.56x10{sup -5} to 2.37x10{sup -2} S cm{sup -1} for 33% and 81% R.H., respectively. For the tungsten-modified material, the conductivity varies from 1.02x10{sup -5} to 2.66x10{sup -3} S cm{sup -1} for 33% and 81% R.H., respectively. The activation energies observed for proton conduction were 23.5 kJ mol{sup -1} for TiO{sub 2}/W 5%, 22.9 kJ mol{sup -1} for TiO{sub 2}/Sb 5% and 20.6 kJ mol{sup -1} for the material treated with H{sub 2}O{sub 2}. The highest activation energy was observed for untreated TiO{sub 2}:24.8 kJ mol{sup -1}. The conductivity values for the Sb-modified ceramics are superior to those reported previously for antimonic acid films, and approach the values reported for proton-conducting polymers, such as Nafion(R), making them a potential candidate for application as electrolytes in fuel cell systems.

  7. Ceramic Technology Project database: March 1990 summary report

    Energy Technology Data Exchange (ETDEWEB)

    Keyes, B.L.P.

    1992-07-01

    This report is the fifth in a series of semiannual data summary reports on information being stored in the Ceramic Technology Project (CTP) database. The overall system status as of March 31, 1990, is summarized, and the latest additions of ceramic mechanical properties data are given for zirconia, silicon carbide, and silicon nitride ceramic mechanical properties data, including some properties on brazed specimens.

  8. Preparation of high-content hexagonal boron nitride composite film and characterization of atomic oxygen erosion resistance

    Science.gov (United States)

    Zhang, Yu; Li, Min; Gu, Yizhuo; Wang, Shaokai; Zhang, Zuoguang

    2017-04-01

    Space aircrafts circling in low earth orbit are suffered from highly reactive atomic oxygen (AO). To shield AO, a flexible thin film with 80 wt.% hexagonal boron nitride (h-BN) and h-BN/epoxy film were fabricated through vacuum filtration and adding nanofibrillated cellulose fibers. H-BN nanosheets were hydroxylated for enhancing interaction in the films. Mass loss and erosion yield at accumulated AO fluence about 3.04 × 1020 atoms/cm2 were adopted to evaluate the AO resistance properties of the films. A carpet-like rough surface, chemical oxidations and change in crystal structure of h-BN were found after AO treatment, and the degrading mechanism was proposed. The mass loss and erosion yield under AO attack were compared between h-BN film and h-BN/epoxy film, and the comparison was also done for various types of shielding AO materials. Excellent AO resistance property of h-BN film is shown, and the reasons are analyzed.

  9. Ammonia Synthesis using Ti and Nb Nitride Nano-particles Prepared by Mesoporous Graphitic C3N4

    KAUST Repository

    Kumagai, Hiromu

    2015-01-22

    TiN and NbN nanoparticles were synthesized from mesoporous graphitic C3N4 (mpg-C3N4) as a reactive template and used as the catalyst for ammonia synthesis. The obtained TiN and NbN nanoparticles possess high surface areas of 299 and 275 m2 g-1, respectively, making them attractive in the use of catalysis and support. Although most of the TiN and NbN particles show no measurable activity for ammonia formation, the nanoparticles enabled an ammonia synthesis rate of 31 μmol h-1 g-cat-1 at 673 K and 0.1 MPa of synthesis gas (N2 + 3H2) for both TiN and NbN catalysts. It is evident that the formation of nanoparticles with high nitride surface area is essential for the materials to function as catalysts in ammonia synthesis. The addition of Fe to TiN enhanced the ammonia synthesis activity, whereas it had detrimental effects on the catalytic activity of NbN. The properties of these catalysts in ammonia synthesis are discussed.

  10. Recent progress in ceramic joining

    Energy Technology Data Exchange (ETDEWEB)

    Loehman, R.E.

    1998-09-01

    Both fundamental and practical aspects of ceramic joining are understood well enough for many, if not most, applications requiring moderate strengths at room temperature. This paper argues that the two greatest needs in ceramic joining are for techniques to join buried interfaces by selective heating, and methods for joining ceramics for use at temperatures of 800 to 1,200 C. Heating with microwave radiation or with high-energy electron beams has been used to join buried ceramic interfaces, for example SiC to SiC. Joints with varying levels of strength at temperatures of 600 to 1,000 C have been made using four techniques: (1) transient liquid phase bonding; (2) joining with refractory braze alloys; (3) joining with refractory glass compositions; and (4) joining using preceramic polymers. Joint strengths as high as 550 MPa at 1,000 C have been reported for silicon nitride-silicon nitride bonds tested in four-point flexure.

  11. Preparation and Application of Ceramic Coating on Magnesium Alloy%镁合金陶瓷涂层制备工艺及应用

    Institute of Scientific and Technical Information of China (English)

    赵斌; 李欣棉; 陶莹; 李智超

    2012-01-01

    The characteristics and research status of preparation technology of ceramic coating on Mg alloy (including methods of thermochemical reaction, thermal spray and so on) were introduced, and the application prospect of ceramic coating on Mg alloy in the production practice was pointed out.%介绍了镁合金陶瓷涂层的制备工艺(包括热化学反应法、热喷涂法及其他方法)的特点及研究现状,并指岀了镁合金陶瓷涂层在生产实践中的应用前景.

  12. 氮气压力对多孔氮化硅陶瓷显微组织和力学性能的影响%Effects of Nitrogen Pressure on Microstructure and Mechanical Performance of Porous Silicon Nitride Ceramics

    Institute of Scientific and Technical Information of China (English)

    张俊禧; 徐照芸; 王波; 秦毅; 杨建锋; 赵中坚; 胡伟; 施志伟

    2014-01-01

    Porous silicon nitride ceramic was fabricated by usingα-Si3N4 as raw material and Y2O3 as a sintering ad-ditive, with nitrogen pressure of 0.12 MPa, 0.32 MPa and 0.52 MPa. Effects of the nitrogen pressure on grain mor-phology and mechanical properties of the resultant porous Si3N4 ceramics were characterized by SEM, XRD and flex-ural strength. With the increasing of nitrogen pressure, sintering shrinkage decreased, with a corresponding increased porosity. Due to the increase of nitrogen pressure, the viscosity of liquid phase increased due to increased N solubility, leading to the low densification in the sintering. Fibrousβ-Si3N4 grains were developed in the porous microstructure and the grain morphology and aspect ratio were greatly affected by the nitrogen pressures. The high viscosity of the liquid phase in nitrogen at high pressure led to restraining of theβ-Si3N4 nucleation, and preferential growth ofβ-Si3N4. Due to the formation of elongatedβ-Si3N4, flexural strength of the porous Si3N4 ceramic was improved by the increase of nitrogen pressure, while decreased with the increase of porosity. The porous Si3N4 ceramics with porosity of 58%and flexural strength of 140 MPa were obtained at the nitrogen pressure of 0.52 MPa.%以α-Si3N4为原料, Y2O3为烧结助剂,在三种不同的氮气压力(0.12、0.32和0.52 MPa)下烧结制备了多孔氮化硅陶瓷。研究了氮气压力对氮化硅的烧结行为、显微组织和力学性能的影响,分别通过SEM观察显微组织并统计晶粒的长径比,通过 XRD 对物相进行分析,并对烧结试样进行三点弯曲强度测试。随着氮气压力的提高,多孔陶瓷的线收缩率降低、气孔率提高,这是由于低熔点的液相中N含量随氮气压力的提升而增加,导致了液相粘度提高,抑制陶瓷致密化。随着氮气压力的提高,组织中的棒状β-Si3N4生长良好,晶粒长径比增大,其原因是高的液相粘度抑制了β-Si3N4

  13. Facile and fast preparation of low-cost silica-supported graphitic carbon nitride for solid-phase extraction of fluoroquinolone drugs from environmental waters.

    Science.gov (United States)

    Speltini, Andrea; Maraschi, Federica; Govoni, Roberta; Milanese, Chiara; Profumo, Antonella; Malavasi, Lorenzo; Sturini, Michela

    2017-03-17

    The analytical application of silica-supported graphitic carbon nitride (g-C3N4@silica) for solid-phase extraction (SPE) of fluoroquinolone (FQ) pollutants from water is presented for the first time. g-C3N4@silica was easily and quickly prepared by one-pot thermal condensation of dicyandiamide and characterized by powder X-ray diffraction, thermogravimetric analysis, scanning electron microscopy, Fourier transform infrared spectroscopy and surface area measurements. The novel composite was applied as sorbent for SPE of FQs from water prior high-performance liquid chromatography with fluorescence detection. The extraction efficiency of g-C3N4 was tested in tap and surface waters at actual concentrations (10-100ngL(-1)). Quantitative adsorption was achieved using 100mg sorbent (20wt% g-C3N4) for pre-concentration of 50-500mL sample, at the native pH (∼7.5-8). Elution was performed with 25mM H3PO4 aqueous solution-acetonitrile (80:20), obtaining recoveries in the range 70-114%, enrichment factors up to 500 and inter-day RSDs≤12%. The batch-to-batch reproducibility was assessed on three independently synthesized g-C3N4@silica preparations (RSD 6-12%). g-C3N4 supported on silica microparticles proved to be of easy preparation, inexpensive, reusable for at least 4 extractions of raw surface waters, and suitable for determination in real matrices. Copyright © 2017 Elsevier B.V. All rights reserved.

  14. CARBON NITRIDE FILMS PREPARED AT DIFFERENT N2/Ar RATIOS BY CLOSED FIELD UNBALANCED REACTIVE MAGNETRON SPUTTERING

    Institute of Scientific and Technical Information of China (English)

    A. Vyas; K.Y. Li; Z.F. Zhou; Y.G. Shen

    2005-01-01

    Carbon nitride (CNx) thin films have been deposited onto Si(100) (for structural and mechanical analyses) and M42 high-speed-steel (for tribological measurements) substrates at room temperature by closed-field unbalanced magnetron sputtering. The mechanical and tribological properties of these films were highly dependent on the N/C concentration ratio that was adjusted by the F(N2)/F(Ar) flow-rate ratio at fixed substrate biasing of -60V during deposition. The films were characterized by employing scanning electron microscopy (SEM), atomic force microscopy(AFM), nano-indentation measurements, X-ray photoelectron spectroscopy (XPS), Raman scattering and Fourier transform infrared (FTIR) spectroscopy, pin-on-disc tribometer, scratch tester, and Rockwell-C tester. The results showed that the N content in the films increased with the N2 pressure. However, the maximum N/C ratio obtained was 0.25. The nanohardness was measured to be in the range of 11.7-20.8GPa depending on the N/C ratios. The XPS N 1s spectra showed the existence of both N-C sp2 and N-C sp3 bonds in films. Raman and FTIR spectra exhibited that N-C bonds were fewer when compared to other N-C bonds. The friction coefficient of the film deposited onto steel substrate with N/C=0.26 was measured to be ~0.08and for film with N/C=0.22 a high critical load of 70N was obtained. The tribological data also showed that the wear rates of these films were in the range of~10-16m3/Nm, indicating excellent wear resistance for CNxfilms.

  15. High sensitivity hydrogen sensing with Pt-decorated porous gallium nitride prepared by metal-assisted electroless etching.

    Science.gov (United States)

    Duan, Barrett K; Bohn, Paul W

    2010-05-01

    A unique hydrogen sensor structure based on Pt-decorated porous gallium nitride (PGaN) was fabricated by a two-step process consisting of metal-assisted electroless etching to produce PGaN with highly anisotropic pores followed by electroless deposition of Pt in the pores from an ammoniacal PtCl(6)(2-) solution. The Pt-decorated PGaN structure contains 50-100 nm diameter nanopores which are 400 nm to 1 microm deep and filled with Pt islands. Both electroless etching and deposition steps are done in solution and allow for large-scale production. An AC four-point probe conductivity measurement was implemented at f = 1 kHz, a frequency where the impedance of Pt-PGaN is nearly entirely resistive, and the change in conductance upon H(2) exposure was measured for three sample types: PGaN with a surface sputtered layer of Pt only; unetched GaN (CGaN) with both sputtered and electrolessly deposited Pt; and PGaN with both sputtered and electrolessly deposited Pt. The hydrogen sensing performance of the Pt-filled PGaN sensor was more than an order of magnitude better than either of the other two sample types under all experimental conditions, an observation attributed to the significant increase in Pt-GaN interfacial area in the electrolessly decorated PGaN samples, exhibiting a response to H2 concentrations as low as 1 ppm. The conductance changes are ascribed to adsorption-induced changes in interfacial polarization that produce changes in band bending and thus to the width of the space charge region near the Pt-GaN interface.

  16. Preparation and properties of Nd{sup 3+}:SrAlF{sub 5} nanocrystals embedded fluorophosphate transparent glass-ceramic with long fluorescence lifetime

    Energy Technology Data Exchange (ETDEWEB)

    Zheng, Ruilin; Wang, Jinlong; Zhang, Liaolin; Liu, Chunxiao; Wei, Wei [Nanjing University of Posts and Telecommunications, School of Optoelectronic Engineering, Nanjing (China)

    2016-07-15

    Nd{sup 3+}:SrAlF{sub 5} nanocrystals embedded fluorophosphate glass-ceramics were prepared by the melt quenching and subsequent thermal treatment method. The formation of SrAlF{sub 5} nanocrystals in the glass was confirmed by X-ray diffraction and scanning electron microscope. The fluorescence intensity and lifetime of the glass-ceramics increased with the increase of size of nanocrystals. Importantly, by controlling growth of nanocrystals, an obvious enhancement of lifetime (725 μs) emerged in the glass-ceramics heat-treated at 510 C and the transmittance can reach to 72.2 % at 1049 nm. The enhanced fluorescence intensity and lifetime were ascribed to the comfortable local environment to the Nd{sup 3+} ion and scattering of the nanoparticle embedded into the glass matrix. (orig.)

  17. A review of oxide, silicon nitride, and silicon carbide brazing

    Energy Technology Data Exchange (ETDEWEB)

    Santella, M.L.; Moorhead, A.J.

    1987-01-01

    There is growing interest in using ceramics for structural applications, many of which require the fabrication of components with complicated shapes. Normal ceramic processing methods restrict the shapes into which these materials can be produced, but ceramic joining technology can be used to overcome many of these limitations, and also offers the possibility for improving the reliability of ceramic components. One method of joining ceramics is by brazing. The metallic alloys used for bonding must wet and adhere to the ceramic surfaces without excessive reaction. Alumina, partially stabilized zirconia, and silicon nitride have high ionic character to their chemical bonds and are difficult to wet. Alloys for brazing these materials must be formulated to overcome this problem. Silicon carbide, which has some metallic characteristics, reacts excessively with many alloys, and forms joints of low mechanical strength. The brazing characteristics of these three types of ceramics, and residual stresses in ceramic-to-metal joints are briefly discussed.

  18. Functional properties of Sm{sub 2}NiMnO{sub 6} multiferroic ceramics prepared by spark plasma sintering

    Energy Technology Data Exchange (ETDEWEB)

    Gheorghiu, Felicia, E-mail: felicia.gheorghiu@uaic.ro [Dielectrics, Ferroelectrics & Multiferroics Group, Department of Physics, “Al. I. Cuza” Univ., 11 Blvd. Carol I, 700506 Iasi (Romania); RAMTECH Centre, Interdisciplinary Research Department-Field Science, “Al. I. Cuza” Univ., Blvd. Carol I, Nr. 11, 700506 Iasi (Romania); Curecheriu, Lavinia [Dielectrics, Ferroelectrics & Multiferroics Group, Department of Physics, “Al. I. Cuza” Univ., 11 Blvd. Carol I, 700506 Iasi (Romania); Lisiecki, Isabelle [CNRS, Univ Paris 06, UMR 7070, LM2N, bât. F, B.P. 52, 4 place Jussieu, Paris F-75231, Cedex 05 (France); Beaunier, Patricia [UPMC, Univ Paris 06, UMR 7197, LRS, Le Raphaël, 3 rue Galilée, 94200 Ivry (France); Feraru, Simona; Palamaru, Mircea N. [Faculty of Chemistry, “Al. I. Cuza” Univ., 11 Blvd. Carol I, 700506 Iasi (Romania); Musteata, Valentina [“Petru Poni” Institute of Macromolecular Chemistry, Aleea Grigore Ghica Voda 41A, 700487 Iasi (Romania); Lupu, Nicoleta [National Institute of Research and Development for Technical Physics, 700050 Iasi (Romania); Mitoseriu, Liliana, E-mail: lmtsr@uaic.ro [Dielectrics, Ferroelectrics & Multiferroics Group, Department of Physics, “Al. I. Cuza” Univ., 11 Blvd. Carol I, 700506 Iasi (Romania)

    2015-11-15

    In the present work, it was reported for the first time the new synthesis of Sm{sub 2}NiMnO{sub 6} double perovskite oxides by sol–gel auto-combustion method. The Rietveld analysis of the X-ray ceramics diffraction pattern recorded at room temperature for Sm{sub 2}NiMnO{sub 6} ceramics sintered at 1000 °C/5 min from powders obtained at 700 °C/7 h confirm the formation of the double perovskite with a monoclinic structure and the space group P2{sub 1}/n. The HRTEM analysis shows clear lattice fringes that confirm a high crystallinity level of the material corresponding to the monoclinic structure. The non-linear dielectric character was checked for the first time in Sm{sub 2}NiMnO{sub 6} double perovskite and the results reveals a strong nonlinearity and a small hysteretic behaviour. The present structural, magnetic and dielectric data make the Sm{sub 2}NiMnO{sub 6} system due to its multiferroic character a promising candidate to different modern electronic devices applications. - Highlights: • The Sm{sub 2}NiMnO{sub 6} double perovskite were prepared by sol–gel auto-combustion method. • The Rietveld and HRTEM analysis confirm a double perovskite monoclinic structure. • The non-linear character reveals a strong nonlinearity. • The magnetic transitions indicate a change in the spin ordering. • The Sm{sub 2}NiMnO{sub 6} system is a promising multiferroic candidate to modern applications.

  19. Preparation of a surface-grafted imprinted ceramic membrane for selective separation of molybdate anion from water solutions.

    Science.gov (United States)

    Zeng, Jianxian; Dong, Zhihui; Zhang, Zhe; Liu, Yuan

    2017-07-05

    A surface-grafted imprinted ceramic membrane (IIP-PVI/CM) for recognizing molybdate (Mo(VI)) anion was prepared by surface-initiated graft-polymerization. Firstly, raw alumina ceramic membrane (CM) was deposited with SiO2 active layer by situ hydrolysis deposition method. Subsequently, γ-methacryloxy propyl trimethoxyl silane (MPS) was used as a coupling agent to introduce double bonds onto the SiO2 layer (MPS-CM). Then, 1-vinylimidazole (VI) was employed as a functional monomer to graft-polymerization onto the MPS-CM (PVI-CM). During the graft-polymerization, the influence factors of grafting degree of PVI were investigated in detail. Under optimum conditions (monomer concentration 20wt%, temperature 70°C, initiator amount 1.1wt% and reaction time 8h), the grafting degree of 20.39g/100g was obtained. Further, Mo(VI) anion was used as a template to imprint in the PVI-CM by employing 1,6-dibromohexane as a cross-linking agent, and then Mo(VI) was removed, obtaining the IIP-PVI/CM with many imprinted cavities for Mo(VI). Thereafter, static adsorption and dynamic separation properties of IIP-PVI/CM for Mo(VI) were studied. Results indicate that IIP-PVI/CM shows a specific selectivity for Mo(VI) with the adsorption capacity of 0.69mmol/100g, and the selectivity coefficient of IIP-PVI/CM is 7.48 for molybdate to tungstate anions. During the dynamic separation, IIP-PVI/CM has also good selectivity for separation of Mo(VI) and W(VI) anions. Copyright © 2017 Elsevier B.V. All rights reserved.

  20. Microstructure, bonding strength and thermal shock resistance of ceramic coatings on steels prepared by plasma electrolytic oxidation

    Science.gov (United States)

    Wang, Yunlong; Jiang, Zhaohua; Yao, Zhongping

    2009-11-01

    Ceramic coatings were successfully prepared on steel by plasma electrolytic oxidation (PEO) in aluminate electrolyte and silicate electrolyte, respectively. The microstructure of the coatings including surface morphology, phase and element composition were studied by scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. The bonding strength between the ceramic coating and the substrate was tested using different methods including tensile tests and shearing tests. The thermal shock resistance of the coatings was also evaluated. The results indicated that coatings obtained in both electrolytes were porous and coarse. The average diameters of the pores were below 10 μm. PEO coatings obtained in aluminate electrolyte were composed of Fe 3O 4 and FeAl 2O 4, while those obtained in silicate electrolyte were in a noncrystal state. PEO coatings obtained in aluminate electrolyte showed similar change trend of tensile strength and shearing strength with increasing treating time, namely, a relatively high values with middle time treating and low value with short and long time treating. The best coating was the samples treated with 30 min, whose tensile strength was 20.6 MPa and shearing strength was 16 MPa. The tensile strength and shearing strength of coatings obtained in silicate electrolyte were not strongly influenced by the treating time, the values of which were range in 14 ± 2 MPa and 11 ± 2 MPa, respectively. Coatings obtained in both electrolytes showed the best thermal shock resistance with middle time treating. Coatings obtained in silicate electrolyte show a little better thermal shock resistance than those obtained in aluminate electrolyte.

  1. Preparation of Fe-Al Intermetallic / TiC-Al2O3 Ceramic Composites from Ilmenite by SHS

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Fe-Al intermetallic/TiC-Al2O3 ceramic composites were successfully prepared by self-propagating high-temperature synthesis (SHS) from natural ilmenite, aluminium and carbon as the raw materials. The effects of carbon sources, preheating time and heat treatment temperature on synthesis process and products were investigated in detail, and the reaction process of the FeTiO3-Al-C system was also discussed.It is shown that the temperature and velocity of the combustion wave are higher when graphite is used as the carbon source, which can reflect the effect of the carbon source structure on the combustion synthesis;Prolonging the preheating time or heat treatment temperature is beneficial to the formation of the ordered intermetallics; The temperature and velocity of the combustion wave arc improved, but the disordered alloys are difficult to eliminate with the preheating time prolonged. The compound powders mainly containing ordered Fe3Al intermetallic can be prepared through heat treatment at 750 ℃.

  2. Effect of nitrogen doping on the structural, optical and electrical properties of indium tin oxide films prepared by magnetron sputtering for gallium nitride light emitting diodes

    Science.gov (United States)

    Tian, Lifei; Cheng, Guoan; Wang, Hougong; Wu, Yulong; Zheng, Ruiting; Ding, Peijun

    2017-01-01

    The indium tin oxide (ITO) films are prepared by the direct current magnetron sputtering technology with an ITO target in a mixture of argon and nitrogen gas at room temperature. The blue transmittance at 455 nm rises from 63% to 83% after nitrogen doping. The resistivity of the ITO film reduces from 4.6 × 10-3 (undoped film) to 5.7 × 10-4 Ω cm (N-doped film). The X-ray photoelectron spectroscopy data imply that the binding energy of the In3d5/2 peak is declined 0.05 eV after nitrogen doping. The high resolution transmission electron microscope images show that the nitrogen loss density of the GaN/ITO interface with N-doped ITO film is smaller than that of the GaN/ITO interface with undoped ITO film. The forward turn-on voltage of gallium nitride light emitting diode reduces by 0.5 V after nitrogen doping. The fabrication of the N-doped ITO film is conducive to modify the N component of the interface between GaN and ITO layer.

  3. Preparation of graphitic carbon nitride with large specific surface area and outstanding N2 photofixation ability via a dissolve-regrowth process

    Science.gov (United States)

    Ma, Huiqiang; Shi, Zhenyu; Li, Qiang; Li, Shuang

    2016-12-01

    Nitrogen fixation is the second most important chemical process in nature next to photosynthesis. Here, we report a convenient dissolve-regrowth method for synthesizing graphitic carbon nitride (g-C3N4) with a large surface area and nitrogen vacancies by HCl treatment. XRD, N2adsorption, SEM, TEM, UV-Vis spectroscopy, EPR, N2-TPD, Photoluminescence and Photocurrent were used to characterize the prepared catalysts. The results indicate that HCl treatment does not influence the crystal phase of g-C3N4 but change the morphology and optical property, leading to the smaller particle size, larger surface area and increased bang gap energy. It is deduced by N2-TPD, Photoluminescence, Photocurrent and DFT simulations that the nitrogen vacancies formed by the HCl treatment not only serve as active sites to adsorb and activate N2 molecules but also promote interfacial charge transfer from g-C3N4to N2 molecules. The HCl treated g-C3N4 catalyst exhibits outstanding nitrogen photofixation ability under visible light, which is 13.4-fold higher than that of bulk g-C3N4 without nitrogen vacancy. The possible reaction mechanism is proposed.

  4. Preparation of Highly Thermally Conductive Polymer Composite at Low Filler Content via a Self-Assembly Process between Polystyrene Microspheres and Boron Nitride Nanosheets.

    Science.gov (United States)

    Wang, Xiongwei; Wu, Peiyi

    2017-06-14

    Rational distribution and orientation of boron nitride nanosheets (BNNSs) are very significant for a polymer/BNNS composite to obtain a high thermal conductivity at low filler content. In this paper, a high-performance thermal interface material based on exfoliated BNNSs and polystyrene (PS) microspheres was fabricated by latex blending and subsequent compression molding. In this case, BNNSs and PS microspheres first self-assembled to form the complex microspheres via strong electrostatic interactions between them. The as-prepared complex microspheres were further hot-pressed around the glass transition temperature, which brought the selective distribution of BNNSs at the interface of the deformed PS microspheres. As a consequence, a polymer composite with homogeneous dispersion and high in-plane orientation of BNNSs in PS matrix was obtained. Benefitted from this unique structure, the resultant composite exhibits a significant thermal conductivity enhancement of 8.0 W m(-1) K(-1) at a low filler content of 13.4 vol %. This facile method provides a new strategy to design and fabricate highly thermally conductive composites.

  5. Microstructure and wear resistance of Ti-Cu-N composite coating prepared via laser cladding/laser nitriding technology on Ti-6Al-4V alloy

    Science.gov (United States)

    Yang, Yuling; Cao, Shiyin; Zhang, Shuai; Xu, Chuan; Qin, Gaowu

    2017-07-01

    Ti-Cu-N coatings with three different Cu contents on Ti-6Al-4V alloy (TC4) were obtained via laser cladding together with laser nitriding (LC/LN) technology. Phase constituents, microstructure, microhardness, and wear resistance of the coatings were investigated. The evolution of the coefficients of friction for the three coatings was measured under dry sliding conditions as a function of the revolutions until the coating failure. The results show that the coatings are mainly composed of TiN, CuTi3 and some TiO6 phases dispersed in the matrix. A good metallurgical bonding between the coating and substrate has been successfully obtained. The prepared Ti-Cu-N composite coatings almost doubly enhance the microhardness of the TC4 alloy and reduce the friction down to 1/4-1/2 of the TC4 alloy, and thus significantly improve the wear resistance. The coefficient of friction depends on the Cu content in the coating.

  6. 流延成型用AlN无苯浆料的制备及其性能研究%Preparation and property of AlN ceramic slurries without xylene for tape casting

    Institute of Scientific and Technical Information of China (English)

    郭坚; 孙永健; 张洪武; 白锁; 王雪

    2015-01-01

    Aluminum nitride (AlN) ceramics have wide application prospect and have received a considerable attention owing to their excellent physical properties like thermal properties, electrical properties, mechanical properties and optical properties. Using ethanol-isopropanol mixtures as solvent, the influence of dispersant amount,Y value (the mass ratio bond to plasticizer), solide content and solvent constituent on the performance of AlN slurries were researched. When dispersant amount was 1.0% (mass fraction),Y value was 0.75, AlN slurries with 39.5% (volume fraction) and low viscosity were prepared without xylene, and AlN ceramics with thermal conductivity 178 W·m–1·K–1 and relative density 99.8% were prepared by sintering 1 825℃ for 4 h using tape casting.%氮化铝(AlN)陶瓷具有优良的热、电、力、光学性能,具有广阔的应用前景,已经引起了国内外研究者的广泛关注。以无水乙醇和异丙醇为混合溶剂,研究了分散剂添加量、Y值(表示粘结剂和增塑剂质量之比)、固含量及溶剂种类对AlN浆料性能的影响。在不添加二甲苯的前提下,当分散剂添加量为1.0%(质量分数)、Y值为0.75时,制备了固含量为39.5%(体积分数)的低黏度AlN浆料,并利用流延成型制备了AlN生坯,在氮气气氛中1825℃,保温4 h烧结后得到相对密度为99.8%、热导率为178 W·m–1·K–1的AlN陶瓷。

  7. Preparation and properties of CaO-Al2O3-SiO2 glass-ceramics by sintered frits particle from mining wastes

    Directory of Open Access Journals (Sweden)

    He F.

    2014-01-01

    Full Text Available The paper reports on some experimental results obtained from the production of glass-ceramics containing gold tailings powder (GTP. Frits particle sintered technology was used to prepare glass ceramic products. SiO2, CaO, ZnO, BaO and B2O3 were selected to adjust the composition of the glass. Based on the results of differential thermal analysis (DTA, the nucleation and crystallization temperature of parent glass samples with different schedule were identified, respectively. X-ray diffraction (XRD analysis of the produced glass-ceramics materials revealed that the main crystalline phase was β-wollastonite. With the increasing of CaO content, the intensity of crystal diffractive peaks also increases. The formation of β-wollastonite crystal could be accelerated by the increasing of CaO. The glass-ceramics with fine microstructure showed better physical, mechanical properties and chemical resistance. Overall results indicated that it was a feasible attempt to produce glass-ceramics for building and decorative materials from waste materials. The amount of GTP used in the glass batches was more than 65 wt% of the whole raw.

  8. Analysis of the properties of silicon nitride based ceramic (Si{sub 3}N{sub 4}) cutting tool using different addictive; Analise das propriedades de ferramenta de corte ceramicas de nitreto de silicio (Si{sub 3}N{sub 4}) usando diferentes aditivos

    Energy Technology Data Exchange (ETDEWEB)

    Pereira, Joaquim Lopes; Souza, Jose Vitor Candido de; Raymundo, Emerson Augusto [Centro Universitario de Volta Redonda (UNIFOA), Volta Redonda, RJ (Brazil); Silva, Oliverio Macedo Moreira [Centro Tecnico Aeroespacial (CTA), Sao Jose dos Campos, SP (Brazil)

    2013-06-15

    The constant search for new materials is part of the scientific and technological development of the industries. Ceramic been presenting important developments in terms of scientific and technological development, highlighting the predominance of covalent ceramics, which has important applications where abrasion resistance and hardness are required. Between covalent materials, several research papers in search of property improvements and cost reduction. However the production of ceramics of silicon nitride (Si{sub 3}N{sub 4}) with a reduced cost is possible only if used methods and different additives. The aim of this work is the development of compositions based on silicon nitride (Si{sub 3}N{sub 4}) using different additives such as Y{sub 2}O{sub 3}, CeO{sub 2}, Al{sub 2}O{sub 3} , and CTR{sub 2}O{sub 3} in varying amounts. For the development of ceramics, the mixtures were homogenized, dried, compacted and sintered using the sintering process of 1850°C for 1 hour, with a heating rate of 25°C/min. The characterizations were performed as a function of relative density by Archimedes method, the mass loss measured before and after sintering, phase analysis by X-ray diffraction, microstructure by scanning electron microscopy (SEM), and hardness and fracture toughness indentation method. The results showed relative density 97-98, Vickers hardness 17-19 GPa, fracture toughness from 5.6 to 6.8 MPa.m{sup 1/2}. The different phases were obtained depending on the types of additives used. The obtained results are promising for tribological applications. (author)

  9. Preparation and Characterization of Andalusite Ceramic Used for Solar Thermal Power Generation

    Institute of Scientific and Technical Information of China (English)

    WU Jianfeng; CHENG Hao; XU Xiaohong; ZHOU Yang; HE Dezhi; LIU Yi

    2014-01-01

    High-temperature thermal storage material is one of the critical materials of solar thermal power generation system. Andalusite, kaolin, talc,γ-Al2O3 and partially stabilized zirconia were used as the raw materials, and in-situ synthesis of cordierite was adopted to fabricate thermal storage material for solar thermal power generation via pressureless sintering. The phase compositions, microstructures and thermal shock resistances of the sintered samples were analyzed by XRD, SEM and EDS, and the corresponding mechanical properties were measured. The results show that the major phases of the samples are mullite and zirconium silicate, and the pores distribute uniformly. After being sintered at 1 460 ℃, A4 sample exhibits a better mechanical performance and thermal shock resistance, its loss rate of bending strength after 30 cycles thermal shock is 3.04%, the bulk density and bending strength are 2.86 g·cm-3 and 139.66 MPa, respectively. The better thermal shock resistance of the sample is closely related to the effect of zirconium silicate, such as its uniform distribution, nested growth with mullite, low thermal expansion coefficient, high thermal conductivity, etc. This ceramic can be widely used as one of potential thermal storage materials of solar thermal power generation system.

  10. Synthesis of ternary nitrides by mechanochemical alloying

    DEFF Research Database (Denmark)

    Jacobsen, C.J.H.; Zhu, J.J.; Lindelov, H.;

    2002-01-01

    Ternary metal nitrides ( of general formula MxM'N-y(z)) attract considerable interest because of their special mechanical, electrical, magnetic, and catalytic properties. Usually they are prepared by ammonolysis of ternary oxides (MxM'O-y(m)) at elevated temperatures. We show that ternary...... nitrides by mechanochemical alloying of a binary transition metal nitride (MxN) with an elemental transition metal. In this way, we have been able to prepare Fe3Mo3N and Co3Mo3N by ball-milling of Mo2N with Fe and Co, respectively. The transformation sequence from the starting materials ( the binary...

  11. PREPARATION OF RECYCLING CERAMIC TILES USING CERAMIC INDUSTRIAL WASTE%利用陶瓷工业废料制备再生陶瓷墙地砖

    Institute of Scientific and Technical Information of China (English)

    王功勋

    2011-01-01

    Recycling ceramic tile was made from raw materials using waste ceramic polishing powder(PP),and waste tiles,and using borax was added as a supplementary flux.Effects of PP sintering property on the strength of recycling ceramic tiles were investigated.Effects of PP on microstructure were detected by SEM tests.Results show that PP is beneficial to improve the sintering property because of its fine particle and glass phase.Strength of recycling ceramic tiles is increased by adding PP and borax compound.In the experimental,borax mass fraction of 0.5%,PP mass fraction of 2% and ceramic tile granule mass fraction of 25%,the strength of recycling ceramic tiles is the highest.This treatment technology features large integrated utilization efficiency for ceramic industrial waste and high strength of recycle ceramic tiles.%以废弃陶瓷抛光砖粉、陶瓷墙地砖烧成废料为原材料,硼砂作辅助熔剂制备再生陶瓷墙地砖,研究陶瓷抛光砖粉的高温烧结性能及其对再生墙地砖强度的影响,采用SEM测试分析陶瓷抛光砖粉对再生陶瓷制品微观结构的影响。结果表明:抛光砖粉含玻璃相、颗粒细小,有利坯体烧结密实;复掺少量抛光砖粉和硼砂,可提高制品强度。在硼砂掺量为0.5%,陶瓷抛光砖粉为2%、烧成废料为25%的实验条件下,所得再生陶瓷制品强度最高。该方法具有陶瓷工业废料的综合利用率高,制得的再生陶瓷制品强度高等特点。

  12. 直接氮化法制备AlN粉的工艺研究与性能表征%Synthesis Technique and Characterization of Aluminium Nitride Powders Prepared by Direct Nitridation

    Institute of Scientific and Technical Information of China (English)

    乐红志; 田贵山; 崔唐茵

    2011-01-01

    Aluminium nitride (A1N ) powder was synthesized by direct nitridation of Al powder, which was a simple-operational, large-scale and low-cost method. The effects of the temperature and holding time of nitriding reaction and the kind and percentage of ammonium salt additives on the phases were investigated. The synthesized powders were characterized by X-ray diffraction ( XRD) , field emission scanning electron microscope ( FESEM ) and X-ray energy dispersive spectrometer ( XEDS ). The results showed that ammonium chloride and ammonium fluoride could improve the nitridation quality and prevent the reactant Al particles from melting and coalescence, and nanosized A1N particles would be obtained. The presence of water vapor would have a great negative influence on nitridation, so it should be avoided.%本文采用一种操作简单、适合规模化且低成本的方法制备氮化铝粉末,研究了氮化烧成温度,铵盐的种类与用量对产物物相组成的影响.用X射线衍射仪(XRD)、场发射扫描电镜(SEM)、X射线能量散射能谱仪(XEDS)对制备的样品进行了分析表征.结果表明:氯化铵、氟化铵可较好改善铝粉氮化质量,避免铝粉熔融结块,并得到纳米尺寸的AlN颗粒;水汽的存在对氮化反应有严重的负面影响,须要避免.

  13. Microstructural changes in NiFe{sub 2}O{sub 4} ceramics prepared with powders derived from different fuels in sol-gel auto-combustion technique

    Energy Technology Data Exchange (ETDEWEB)

    Chauhan, Lalita, E-mail: chauhan.lalita5@gmail.com; Sreenivas, K. [Department of Physics & Astrophysics, University of Delhi, Delhi-110007 (India); Bokolia, Renuka

    2016-05-23

    Structural properties of Nickel ferrite (NiFe{sub 2}O{sub 4}) ceramics prepared from powders derived from sol gel auto-combustion method using different fuels (citric acid, glycine and Dl-alanine) are compared. Changes in the structural properties at different sintering temperatures are investigated. X-ray diffraction (XRD) confirms the formation of single phase material with cubic structure. Ceramics prepared using the different powders obtained from different fuels show that that there are no significant changes in lattice parameters. However increasing sintering temperatures show significant improvement in density and grain size. The DL-alanine fuel is found to be the most effective fuel for producing NIFe{sub 2}O{sub 4} powders by the sol-gel auto combustion method and yields highly crystalline powders in the as-burnt stage itself at a low temperature (80 °C). Subsequent use of the powders in ceramic manufacturing produces dense NiFe{sub 2}O{sub 4} ceramics with a uniform microstructure and a large grain size.

  14. Effect of the Fourth Element on Bonding of Silicon Nitride Ceramics with Y2O3-Al2O3-SiO2 Glass Solders

    Institute of Scientific and Technical Information of China (English)

    周飞

    2001-01-01

    Bonding of Si3N4 ceramic was performed with Y2O3-Al2O3-SiO2(YAS)-X glass solders,which were mixed with TiO2 (YT) and Si3N4 (YN), respectively. The effects of bonding conditions and interfacial reaction on the joint strength were studied. The joint strength in different bonding conditions was measured by four-point bending tests. The interfacial microstructures were observed and analyzed by SEM, EPMA and XRD. It is shown that with the increase of bonding temperature and holding time, the joint strength increases reaching a peak, and then decreases. When TiO2 is put into YAS solder,the bonding interface with Si3N4/(Y-Sialon glass+TiN)/TiN/Y-Sialon glass is formed. When YAS solder is mixed with Si3N4 powder, the interfacial residual thermal stress may be decreased, and then the joint strength is enhanced. According to microanalyses, the bonding strength is related to interfacial reaction.

  15. Preparation of Phosphorus Nitride Dichloride Oligomers%三聚磷腈的制备工艺

    Institute of Scientific and Technical Information of China (English)

    颜红侠; 宁荣昌; 马晓燕

    2001-01-01

    Hexachlorocyclotriphosphazene was prepared by reacting ammonium chloride and phosphorus pentachloride in an inert organic solvent at the presence of different metal compounds and pyridine. The conbination of MgCl2 · 6H2O with pyridine showed an ideal catalytic activity to give hexachlorocyclotriphosphazene in yield of 87% under the suitable conditions. The method is time saving.

  16. Minimally invasive preparation and design of a cantilevered, all-ceramic, resin-bonded, fixed partial denture in the esthetic zone: a case report and descriptive review.

    Science.gov (United States)

    Barwacz, Christopher A; Hernandez, Marcela; Husemann, R Henry

    2014-01-01

    Resin-bonded, fixed partial dentures have the potential to offer a minimally invasive, fixed-prosthetic approach to tooth replacement in patients who may not be candidates for implant therapy. However, traditional preparation protocols often recommend extensive preparation designs on two abutment teeth, thereby potentially compromising the long-term health of the adjacent abutments and often resulting in unilateral debonding of one of the retainers in the long term. In light of advances in high-strength ceramic systems capable of being reliably bonded to tooth structure and offering improved esthetic outcomes, as well as clinical and case-series research demonstrating improved survivability of cantilevered resin-bonded fixed partial dentures, new preparation designs and methodologies can be advocated. The following case report demonstrates the clinical application of sonoabrasion, coupled with a dental operating microscope, to minimally prepare a single abutment for a cantilevered, all-ceramic resin-bonded fixed partial denture. Relevant historic and contemporary literature regarding double versus single-retainer resin-bonded fixed partial dentures are reviewed, as well as clinical conditions that are most favorable for such restorations to have an optimal long-term prognosis. If appropriate clinical conditions exist, a cantilevered, all-ceramic, resin-bonded, fixed partial denture may be the most conservative means of tooth replacement in a patient who is not a candidate for an endosseous implant. © 2013 Wiley Periodicals, Inc.

  17. An In Vivo Evaluation of the Fit of Zirconium-Oxide Based, Ceramic Single Crowns with Vertical and Horizontal Finish Line Preparations.

    Science.gov (United States)

    Vigolo, Paolo; Mutinelli, Sabrina; Biscaro, Leonello; Stellini, Edoardo

    2015-12-01

    Different types of tooth preparations influence the marginal precision of zirconium-oxide based ceramic single crowns. In this in vivo study, the marginal fits of zirconium-oxide based ceramic single crowns with vertical and horizontal finish lines were compared. Forty-six teeth were chosen in eight patients indicated for extraction for implant placement. CAD/CAM technology was used for the production of 46 zirconium-oxide-based ceramic single crowns: 23 teeth were prepared with vertical finishing lines, 23 with horizontal finishing lines. One operator accomplished all clinical procedures. The zirconia crowns were cemented with glass ionomer cement. The teeth were extracted 1 month later. Marginal gaps along vertical planes were measured for each crown, using a total of four landmarks for each tooth by means of a microscope at 50× magnification. On conclusion of microscopic assessment, ESEM evaluation was completed on all specimens. The comparison of the gap between the two types of preparation was performed with a nonparametric test (two-sample Wilcoxon rank-sum test) with a level of significance fixed at p finish line preparations, the median value of the gap was 35.45 μm (Iqr, 0.33); for the vertical finish line group, the median value of the gap was 35.44 μm (Iqr, 0.40). The difference between the two groups was not statistically significant (two-sample Wilcoxon rank-sum test, p = 0.0872). Within the limitations of this study, the gaps of the zirconium-oxide-based ceramic CAD/CAM crowns with vertical and horizontal finish line preparations were not different. © 2015 by the American College of Prosthodontists.

  18. Ammonia Decomposition over Bimetallic Nitrides Supported on γ-Al2O3

    Institute of Scientific and Technical Information of China (English)

    Chun Shan LU; Xiao Nian LI; Yi Feng ZHU; Hua Zhang LIU; Chun Hui ZHOU

    2004-01-01

    A series of monometallic nitrides and bimetallic nitrides were prepared by temperature-programmed reaction with NH3. The effects of Co, Ni and Fe additives and the synergic action between Fe, Co, Ni and Mo on the ammonia decomposition activity were investigated. TPR-MS, XRD were also carried out to obtain better insight into the structure of the bimetallic nitride. The results of ammonia decomposition activity show that bimetallic nitrides are more active than monometallic nitrides or bimetallic oxides.

  19. Preparation Junctions for All-Ceramic CAD/CAM Crown and Bridge Restorations

    Directory of Open Access Journals (Sweden)

    Vlahova Angelina

    2016-07-01

    Full Text Available Background: The preparation junction type is determined by a number of factors that need to be taken in consideration with CAD/CAM Fixed Prosthodontics: the used material; the condition of the retainer teeth, their periodontium and the occlusion; the design software and the type of drills; the working protocol; the cement and the method of cementation.

  20. Microbial adherence to a nonprecious alloy after plasma nitriding process.

    Science.gov (United States)

    Sonugelen, Mehmet; Destan, Uhmut Iyiyapici; Lambrecht, Fatma Yurt; Oztürk, Berran; Karadeniz, Süleyman

    2006-01-01

    To investigate the microbial adherence to the surfaces of a nonprecious metal alloy after plasma nitriding. The plasma-nitriding process was performed to the surfaces of metals prepared from a nickel-chromium alloy. The microorganisms were labeled with technetium-99m. After the labeling procedure, 60 metal disks were treated with a microorganism for each use. The results revealed that the amount of adherence of all microorganisms on surfaces was changed by plasma-nitriding process; adherence decreased substantially (P plasma nitriding time were not significant (P> .05) With the plasma-nitriding process, the surface properties of nonprecious metal alloys can be changed, leading to decreased microbial adherence.

  1. Preparation and microwave characterization of BaNd{sub 2-x}Sm{sub x}Ti{sub 4}O{sub 12} (0 {<=} x {<=} 2) ceramics and their effect on the temperature coefficient of dielectric constant in polytetrafluoroethylene composites

    Energy Technology Data Exchange (ETDEWEB)

    Stanly Jacob, K.; Satheesh, R. [Centre for Materials for Electronics Technology, Department of Information Technology, Ministry of Communication and Information Technology, Govt. of India, M.G. Kavu, Athani P.O., Thrissur 680771, Kerala (India); Ratheesh, R., E-mail: ratheeshr@yahoo.com [Centre for Materials for Electronics Technology, Department of Information Technology, Ministry of Communication and Information Technology, Govt. of India, M.G. Kavu, Athani P.O., Thrissur 680771, Kerala (India)

    2009-10-15

    High dielectric and temperature-stable ceramic compositions have been prepared through solid-state ceramic route. The structure and microstructure of the ceramics have been studied using powder X-ray diffraction and scanning electron microscopic techniques. The dielectric properties of well-sintered ceramics are studied in the microwave frequency region using Hakki and Coleman post-resonator technique. The samples exhibited high dielectric constant (>77), relatively high quality factor (>1500) and near zero temperature coefficient of resonant frequency. Phase pure calcined ceramic materials are incorporated in the polytetrafluoroethylene matrix through a proprietary process comprising of sigma mixing, extrusion, calendering followed by hot pressing for the fabrication of planar circuit laminates. The effect of temperature coefficient of dielectric constant of the resultant polytetrafluoroethylene/ceramic composite materials is studied with respect to compositional variation of the filler materials.

  2. Characterization of Al{sub 2}O{sub 3} ceramic coatings on 6063 aluminum alloy prepared in borate electrolytes by micro-arc oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Li, H.X. [MOE Key Laboratory of Mechanical Manufacture and Automation, Zhejiang University of Technology, No. 6, Zhaohui District, Hangzhou 310014 (China); Rudnev, V.S. [Institute of Chemistry FEB RAS, Pr. 100 let Vladivostok, Vladivostok 690022 (Russian Federation); Zheng, X.H. [MOE Key Laboratory of Mechanical Manufacture and Automation, Zhejiang University of Technology, No. 6, Zhaohui District, Hangzhou 310014 (China); Yarovaya, T.P. [Institute of Chemistry FEB RAS, Pr. 100 let Vladivostok, Vladivostok 690022 (Russian Federation); Song, R.G. [MOE Key Laboratory of Mechanical Manufacture and Automation, Zhejiang University of Technology, No. 6, Zhaohui District, Hangzhou 310014 (China)], E-mail: songrg@zjut.edu.cn

    2008-08-25

    Al{sub 2}O{sub 3} ceramic coatings were directly prepared on 6063 aluminum alloy in borate electrolytes by micro-arc oxidation technique. The microstructure, phase composition, elemental distribution, and micro-hardness of Al{sub 2}O{sub 3} ceramic coatings were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX) and micro-hardness test. The fabricated samples were almost composed of {alpha}-Al{sub 2}O{sub 3} and {gamma}-Al{sub 2}O{sub 3}, also there existed pores and cracks on the surface of the coatings. Micro-hardness test shows that the prepared coatings are of high hardness, which can satisfy the requirements for the mechanical application.

  3. Preparation methodology and possible treatments for improved ceramics for high voltage vacuum applications

    CERN Document Server

    Tan, J

    1998-01-01

    The flashover characteristics of an insulator bridged high voltage vacuum gap can play an important role in the overall performance of a high voltage device, for example in the extreme environments of high energy particle accelerators. The detailed preparation of the insulators is, at present, governed by the commercial production methods and by standard bulk cleaning processes, which for a particular application may be far from optimum. The influence of the mechanical preparation, thermal history and particular cleaning technique have been investigated for commercially available alumina samples, with measurement of surface characteristics by scanning electron microscopy and laser diffraction, measurement of the secondary electron emission curve and analysis of the high voltage performance with the possibility of applied fields up to 200kV/cm. The results of the different measurements are discussed in the overall context of the problems encountered in the full sized high voltage devices, and suggestions are m...

  4. Functionalized boron nitride nanotubes

    Science.gov (United States)

    Sainsbury, Toby; Ikuno, Takashi; Zettl, Alexander K

    2014-04-22

    A plasma treatment has been used to modify the surface of BNNTs. In one example, the surface of the BNNT has been modified using ammonia plasma to include amine functional groups. Amine functionalization allows BNNTs to be soluble in chloroform, which had not been possible previously. Further functionalization of amine-functionalized BNNTs with thiol-terminated organic molecules has also been demonstrated. Gold nanoparticles have been self-assembled at the surface of both amine- and thiol-functionalized boron nitride Nanotubes (BNNTs) in solution. This approach constitutes a basis for the preparation of highly functionalized BNNTs and for their utilization as nanoscale templates for assembly and integration with other nanoscale materials.

  5. Crystalline boron nitride aerogels

    Science.gov (United States)

    Zettl, Alexander K.; Rousseas, Michael; Goldstein, Anna P.; Mickelson, William; Worsley, Marcus A.; Woo, Leta

    2017-04-04

    This disclosure provides methods and materials related to boron nitride aerogels. In one aspect, a material comprises an aerogel comprising boron nitride. The boron nitride has an ordered crystalline structure. The ordered crystalline structure may include atomic layers of hexagonal boron nitride lying on top of one another, with atoms contained in a first layer being superimposed on atoms contained in a second layer.

  6. Crystalline boron nitride aerogels

    Energy Technology Data Exchange (ETDEWEB)

    Zettl, Alexander K.; Rousseas, Michael; Goldstein, Anna P.; Mickelson, William; Worsley, Marcus A.; Woo, Leta

    2017-04-04

    This disclosure provides methods and materials related to boron nitride aerogels. In one aspect, a material comprises an aerogel comprising boron nitride. The boron nitride has an ordered crystalline structure. The ordered crystalline structure may include atomic layers of hexagonal boron nitride lying on top of one another, with atoms contained in a first layer being superimposed on atoms contained in a second layer.

  7. Processing and dielectric properties of ZnTiO3 ceramics prepared from nanopowder synthesised by sol-gel technique

    Directory of Open Access Journals (Sweden)

    Sophie d’Astorg

    2012-06-01

    Full Text Available ZnTiO3 nanopowders were obtained by sol-gel method. The nanopowders were characterised by means of TGA/DTA analysis, X-ray diffraction, TMA analysis and SEM characterisation. The results show that the crystalline structure of the sol-gel powders was obtained at 600 °C, with crystallite sizes of 10 nm. SEM shows that most of the prepared ZnTiO3 nanopowders are agglomerated. Since agglomeration plays an important role in the sintering of the ZnTiO3 ceramics, different deagglomeration techniques (ultrasonication, pulverisation and attrition milling were investigated. Dense ZnTiO3 structure was obtained from the attrition milled powder at 1050 °C and its dielectric characteristics were also investigated (εr =25, tε= -26 ppm/°C and tgδ < 10-3 at 1 MHz. The low sintering temperature and the good dielectric properties show promise for the manufacture of multilayered capacitors with internal copper electrodes.

  8. Novel texturing method for sputtered zinc oxide films prepared at high deposition rate from ceramic tube targets

    Directory of Open Access Journals (Sweden)

    Hüpkes J.

    2011-10-01

    Full Text Available Sputtered and wet-chemically texture etched zinc oxide (ZnO films on glass substrates are regularly applied as transparent front contact in silicon based thin film solar cells. In this study, chemical wet etching in diluted hydrofluoric acid (HF and subsequently in diluted hydrochloric acid (HCl on aluminum doped zinc oxide (ZnO:Al films deposited by magnetron sputtering from ceramic tube targets at high discharge power (~10 kW/m target length is investigated. Films with thickness of around 800 nm were etched in diluted HCl acid and HF acid to achieve rough surface textures. It is found that the etching of the films in both etchants leads to different surface textures. A two steps etching process, which is especially favorable for films prepared at high deposition rate, was systematically studied. By etching first in diluted hydrofluoric acid (HF and subsequently in diluted hydrochloric acid (HCl these films are furnished with a surface texture which is characterized by craters with typical diameter of around 500 − 1000 nm. The resulting surface structure is comparable to etched films sputtered at low deposition rate, which had been demonstrated to be able to achieve high efficiencies in silicon thin film solar cells.

  9. Effect of preparation method on the anti-corrosive properties of nanocrystalline Zn-CoO ceramic pigments

    Energy Technology Data Exchange (ETDEWEB)

    Rasouli, S. [Department of Nanotechnology, Institute for Color Science and Technology (ICST), 55 Vafamanesh Ave., HosseinAbad Square, Pasdaran St., 1668814811 Tehran (Iran, Islamic Republic of); Danaee, I. [Abadan Faculty of Petroleum, Petroleum University of Technology (PUT), Abadan (Iran, Islamic Republic of)

    2011-05-15

    Zn-CoO green ceramic pigments were synthesized by two different methods; high energy ball milling and solution combustion, with two different fuels; citric acid and glycine. Products were characterized by X-ray diffraction and scanning-transmission electron microscopy (TEM). The anti-corrosive properties of the obtained pigments were investigated by electrochemical impedance spectroscopy (EIS) techniques. Results have shown that either by solid state reaction or combustion by citric acid, a calcination step was needed to obtain the desired phase whereas by glycine fuel, pure ZnO phase was obtained directly. TEM showed particles with mean particle size of about 70, 150, and 180 nm for glycine, citric acid, and solid state reaction samples, respectively. The corrosion performance of the coating in 3% w/v NaCl solution was evaluated by EIS and polarization measurements. According to the measurements of EIS and electrochemical polarization, the coatings with glycine-based pigment showed the highest corrosion resistance among the prepared coatings. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  10. Preparation and characterization of lead zirconate titanate ceramic fibers with alkoxide-based sol-gel route

    Energy Technology Data Exchange (ETDEWEB)

    Mai Manfang; Lin Cheng; Xiong Zhaoxian; Xue Hao; Chen Lifu [Department of Materials Science and Engineering, College of Materials, Xiamen University, Xiamen 361005 (China)], E-mail: zxxiong@xmu.edu.cn

    2009-03-01

    Lead zirconate titanate (PZT) fibers with diameters from 10{mu}m to 40{mu}m were prepared via a sol-gel route. Several kinds of chemicals were used, including lead acetate trihydrate, zirconium n-butoxide and titanium n-butoxide, in addition to butanol as a solvent. As a water source for hydrolysis reaction, Pb(CH{sub 3}COO){sub 2}{center_dot}3H{sub 2}O was directly used without further adding of water or catalyst conventionally. Acetylacetonate and acetate were added as stabilization agents to obtain stable sols for fiber drawing. The gel-to-ceramic conversion was characterized with thermal analysis, infrared spectroscopy and X-ray diffraction. A pure perovskite phase was obtained after heat treatment at 650 deg. C for 1h. By using scanning electron microscope (SEM), it was observed that a lower rate of heat treatment resulted in a denser microstructure of the fibers. The relative permittivity and the P-E hysteresis loop of the crystalline PZT fibers were also measured and discussed in the paper.

  11. Preparation and characterization of lead zirconate titanate ceramic fibers with alkoxide-based sol-gel route

    Science.gov (United States)

    Mai, Manfang; Lin, Cheng; Xiong, Zhaoxian; Xue, Hao; Chen, Lifu

    2009-03-01

    Lead zirconate titanate (PZT) fibers with diameters from 10μm to 40μm were prepared via a sol-gel route. Several kinds of chemicals were used, including lead acetate trihydrate, zirconium n-butoxide and titanium n-butoxide, in addition to butanol as a solvent. As a water source for hydrolysis reaction, Pb(CH3COO)2·3H2O was directly used without further adding of water or catalyst conventionally. Acetylacetonate and acetate were added as stabilization agents to obtain stable sols for fiber drawing. The gel-to-ceramic conversion was characterized with thermal analysis, infrared spectroscopy and X-ray diffraction. A pure perovskite phase was obtained after heat treatment at 650°C for 1h. By using scanning electron microscope (SEM), it was observed that a lower rate of heat treatment resulted in a denser microstructure of the fibers. The relative permittivity and the P-E hysteresis loop of the crystalline PZT fibers were also measured and discussed in the paper.

  12. Effect of SiO2 on the Preparation and Properties of Pure Carbon Reaction Bonded Silicon Carbide Ceramics

    Institute of Scientific and Technical Information of China (English)

    WU Qi-de; GUO Bing-jian; YAN Yong-gao; ZHAO Xiu-jian; HONG Xiao-lin

    2004-01-01

    Effect of SiO2 content and sintering process on the composition and properties of Pure CarbonReaction Bonded Silicon Carbide (PCRBSC) ceramics prepared with C - SiO2 green body by infiltrating siliconwas presented. The infiltrating mechanism of C - SiO2 preform was also explored. The experimental results indicatethat the shaping pressure increases with the addition of SiO2 to the preform, and the pore size of the body turnedfiner and distributed in a narrower range, which is beneficial to decreasing the residual silicon content in the sin-tered materials and to avoiding shock off, thus increasing the conversion rate of SiC. SiO2 was deoxidized by car-bon at a high temperature and the gaseous SiO and CO produced are the main reason to the crack of the body atan elevated temperature. If the green body is deposited at 1800℃ in vacuum before infiltration crack will not beproduced in the preform and fully dense RBSC can be obtained. The ultimate material has the following properties:a density of3.05-3.12g/cm3 ,a strength of 580±32MPa and a hardness of (HRA)91-92.3.

  13. Thermal-stress analysis of ceramic laminate veneer restorations with different incisal preparations using micro-computed tomography-based 3D finite element models.

    Science.gov (United States)

    Celebi, Alper Tunga; Icer, Esra; Eren, Meltem Mert; Baykasoglu, Cengiz; Mugan, Ata; Yildiz, Esra

    2017-11-01

    Main objective of this study is to investigate the thermal behavior of ceramic laminate veneer restorations of the maxillary central incisor with different incisal preparations such as butt joint and palatinal chamfer using finite element method. In addition, it is also aimed to understand the effect of different thermal loads which simulates hot and cold liquid imbibing in the mouth. Three-dimensional solid models of the sound tooth and prepared veneer restorations were obtained using micro-computed tomography images. Each ceramic veneer restoration was made up of ceramic, luting resin cement and adhesive layer which were generated based on the scanned images using computer-aided design software. Our solid model also included the remaining dental tissues such as periodontal ligament and surrounding cortical and spongy bones. Time-dependent linear thermal analyses were carried out to compare temperature changes and stress distributions of the sound and restored tooth models. The liquid is firstly in contact with the crown area where the maximum stresses were obtained. For the restorations, stresses on palatinal surfaces were found larger than buccal surfaces. Through interior tissues, the effect of thermal load diminished and smaller stress distributions were obtained near pulp and root-dentin regions. We found that the palatinal chamfer restoration presents comparatively larger stresses than the butt joint preparation. In addition, cold thermal loading showed larger temperature changes and stress distributions than those of hot thermal loading independent from the restoration technique. Copyright © 2017 Elsevier Ltd. All rights reserved.

  14. Boron nitride composites

    Energy Technology Data Exchange (ETDEWEB)

    Kuntz, Joshua D.; Ellsworth, German F.; Swenson, Fritz J.; Allen, Patrick G.

    2017-02-21

    According to one embodiment, a composite product includes: a matrix material including hexagonal boron nitride and one or more borate binders; and a plurality of cubic boron nitride particles dispersed in the matrix material. According to another embodiment, a composite product includes: a matrix material including hexagonal boron nitride and amorphous boron nitride; and a plurality of cubic boron nitride particles dispersed in the matrix material.

  15. Plasma nitriding of steels

    CERN Document Server

    Aghajani, Hossein

    2017-01-01

    This book focuses on the effect of plasma nitriding on the properties of steels. Parameters of different grades of steels are considered, such as structural and constructional steels, stainless steels and tools steels. The reader will find within the text an introduction to nitriding treatment, the basis of plasma and its roll in nitriding. The authors also address the advantages and disadvantages of plasma nitriding in comparison with other nitriding methods. .

  16. 新型中空纤维陶瓷膜的制备方法%PREPARATION METHODS OF HOLLOW FIBER CERAMIC MEMBRANES

    Institute of Scientific and Technical Information of China (English)

    张小珍; 周健儿; 江瑜华

    2011-01-01

    Ceramic hollow fiber membranes have recently attracted considerable attention, due to the high active area/volume ratio provided by its high packing density, thin wall, high permeability and less material consumption. With the application of ceramic membranes in hollow fiber configuration, the separation equipment can be miniaturized. Ceramic hollow fiber membranes have potential applications in various fields, such as porous and dense ceramic membranes for separation, solid oxide fuel cells, microchannel-reactor, and supports of catalysts. This paper summarized the characteristics and progress in preparation methods of hollow fiber ceramic membranes. The emphasis was put on the comparison of different preparation methods. The phase inversion method was cost-effective, since the derived ceramic hollow fiber membranes with selfsupported asymmetric structure and thus high permeability can be obtained in one step. The application of phase inversion method could simplify the fabrication process of ceramic membranes and greatly reduce the production cost.%新型中空纤维陶瓷膜由于具有装填密度大、单位体积膜有效分离面积大、膜壁薄、渗透通量高和节省原料、易于实现分离设备小型化等独特优点而受到广泛关注,在用于多孔和致密陶瓷分离膜、固体氧化物燃料电池、微通道反应器、催化剂载体等方面都有着潜在的应用前景.本文在概括中空纤维陶瓷膜特点的基础上,综述了中空纤维陶瓷膜的制备方法及研究进展,着重分析比较了不同制备方法的优缺点.将相转化法应用于中空纤维陶瓷膜的制备,可实现通过一步成型制造具有自支撑非对称结构的复合陶瓷膜,有利于提高膜的渗透通量,简化膜制备工艺和显著降低制造成本.

  17. 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.

  18. Bonding lithium disilicate ceramic to feather-edge tooth preparations: a minimally invasive treatment concept.

    Science.gov (United States)

    Cortellini, Davide; Canale, Angelo

    2012-02-01

    To report the short-term clinical outcome of a new minimally invasive prosthetic approach utilizing monolithic lithium-disilicate full crowns bonded to feather-edge tooth preparations. 235 teeth, 136 anterior and 99 posterior, requiring a full crown were prepared with a feather-edge finish line providing a minimum space on the vertical walls of 0.3 mm at the margin, 0.5 mm along the axial walls, and an occlusal space of 1 to 1.5 mm to ensure sufficient resistance of the restoration. The dental technician manufactured the monolithic restorations using either CAD-CAM or pressed technology. The restorations were individualized with a staining technique to obtain the necessary esthetic characterization and bonded to the natural abutments using an adhesive cementation procedure. Out of 235 treated elements, only one monolithic restoration in a molar position fractured after 3 years of service. No biological or technical complications were observed. The final esthetic result was optimal. This procedure can be considered a further option for the conservative restorative treatment of single elements where a full crown is required.

  19. Structural and ferroelectrical properties of bismuth titanate ceramic powders prepared by mechanically assisted synthesis

    Directory of Open Access Journals (Sweden)

    Lazarević Z.Ž.

    2007-01-01

    Full Text Available Nanosized bismuth titanate, Bi4Ti3O12, was prepared via a high-energy ball milling process through mechanically assisted synthesis directly from the oxide mixture of Bi2O3 and TiO2. The Bi4Ti3O12 phase started to form after 1 h of milling. With increasing the milling time from 3 to 12 h, the particle size of formed Bi4Ti3O12 did not reduce significantly. The grain size was less than 16 nm and showed a strong tendency to agglomeration. The nucleation and phase formation of Bi4Ti3O12, crystal structure, microstructure, powder grain size and specific surface area were followed by XRD, Rietveld refinement analysis, SEM and the BET specific surface area measurements. Raman spectroscopy was used to explain the structural properties of Bi4Ti3O12 powder, prepared by mechanically assisted synthesis. Reduction in grain size with the increase of milling time was also noted (change in the position and relative intensity, which indicated changes in the structure, caused by nanodimension grains. The sample milled for 12 h and subsequently sintered at 1000°C for 24 h exhibited a hysteresis loop, confirming that the synthesized material possesses ferroelectric properties. .

  20. Preparation of continuous Si-Fe-C-O functional ceramic fibers

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    A new polymer named polyferrocarbosilane(PFCS) was prepared from polydimethylsilane and ferrocene. The spinnability of this polymer can be tailored by controlling the content of ferrocene in the polymer. The prepared polymer was spun into a continuous polymer fiber that was subsequently cured in air and heat-treated finally in N2 up to 1 350 ℃ for conversion into Si-Fe-C-O fibers. The resulted Si-Fe-C-O fibers display low specific resistance and magnetic property due to the existence of Fe,which also reduces the specific resistance significantly to 10-2 Ω·cm at room temperature when the amount of ferrocene in feed is as low as 3.0% (mass fraction). The resulted Si-Fe-C-O fibers, with C/Si molar ratio of about 1.3 and the maximum Fe content of about 2.0% (mole fraction), are composed of β-SiC and small amount of Fe3Si-like crystalline and have an average tensile strength of about 2.0 GPa.

  1. High Temperature Behavior of Ferro-Silicon Nitride Prepared by Flash Combustion Synthesis at Reducing Atmosphere%还原气氛下闪速燃烧合成氮化硅铁的高温行为

    Institute of Scientific and Technical Information of China (English)

    宋文; 陈俊红; 李勇; 孙加林

    2011-01-01

    为模拟闪速燃烧合成氮化硅铁在工作环境中的高温行为,研究了高温还原气氛下氮化硅铁的存在状态。根据热力学计算,采用在空气气氛中埋碳升温的方法,控制氧气分压在较低水平,将氮化硅铁样品分别升温至1 300℃及1 500℃,保温300 min后迅速水冷,以保存高温下样品的微观结构。采用X射线衍射和扫描电子显微镜表征样品的物相组成和微观结构。结果表明:室温下氮化硅铁的物相组成为α-Si3N4、β-Si3N4、SiO2和Fe3Si。在高温还原条件下,α-Si3N4转变为β-Si3N4,二氧化硅逐渐分解,而Fe3Si相未%This paper focused on the behaviors of ferro–silicon nitride at high temperature and reducing atmosphere to simulate the service environment of ferro–silicon nitride prepared by flash combustion synthesis.The specimen was sintered surrounded by the carbon in air to control partial pressure of oxygen at a low level on the basis of thermodynamic calculation.Ferro–silicon nitride was sintered at 1 300 ℃ and 1 500 ℃ separately and insulated for 300 min then got rapid hydrocooling to keep the microstructure at high temperature.Phase composition and microstructure of the specimens were studied by X-ray diffraction and scanning electron micro-scope.Results show that ferro–silicon nitride contained α-Si3N4,β-Si3N4,SiO2 and Fe3Si at room temperature.α-Si3N4 converted into β-Si3N4 and SiO2 decomposed at high temperature in reducing atmosphere,while Fe3Si was stable.Silicon nitride was decomposed into small grains with bigger specific surface area and reaction activity.And Si2N2O formed on the surface of silicon nitride.

  2. Additive Manufacturing of Dense Hexagonal Boron Nitride Objects

    Energy Technology Data Exchange (ETDEWEB)

    Marquez Rossy, Andres E [ORNL; Armstrong, Beth L [ORNL; Elliott, Amy M [ORNL; Lara-Curzio, Edgar [ORNL

    2017-05-12

    The feasibility of manufacturing hexagonal boron nitride objects via additive manufacturing techniques was investigated. It was demonstrated that it is possible to hot-extrude thermoplastic filaments containing uniformly distributed boron nitride particles with a volume concentration as high as 60% and that these thermoplastic filaments can be used as feedstock for 3D-printing objects using a fused deposition system. Objects 3D-printed by fused deposition were subsequently sintered at high temperature to obtain dense ceramic products. In a parallel study the behavior of hexagonal boron nitride in aqueous solutions was investigated. It was shown that the addition of a cationic dispersant to an azeotrope enabled the formulation of slurries with a volume concentration of boron nitride as high as 33%. Although these slurries exhibited complex rheological behavior, the results from this study are encouraging and provide a pathway for manufacturing hexagonal boron nitride objects via robocasting.

  3. Experimental studies of radiation resistance of boron nitride, C2C ceramics Al2O3 and carbon-fiber composites using a PF-1000 plasma-focus device

    Science.gov (United States)

    Gribkov, V. A.; Tuniz, C.; Demina, E. V.; Dubrovsky, A. V.; Pimenov, V. N.; Maslyaev, S. V.; Gaffka, R.; Gryaznevich, M.; Skladnik-Sadowska, E.; Sadowski, M. J.; Miklaszewski, R.; Paduch, M.; Scholz, M.

    2011-04-01

    This paper reports on experiments undertaken to compare the radiation resistance of two types of ceramics, boron nitride (BN) and pure alumina (Al2O3), which are used in a TAEA antenna coil installed in the MAST spherical tokamak. Samples of the investigated materials (bulk BN and a 20 μm film of Al2O3 on Al substrate) were exposed on the axis of the plasma-focus PF-1000 device, which can emit intense streams of hot plasma (v≈107 cm s-1 and Npl≈1018 cm-3) and fast deuteron beams (Ei≈100 keV). The most powerful plasma-ion pulse lasted 0.2-1.0 μs and its intensity decayed in about 100 μs. The irradiation process was diagnosed using fast optical cameras, laser interferometry and optical spectrometry. Experiments were performed at power flux densities equal to 109-1010 W cm-2 or 108-109 W cm-2 during the most powerful stage of the interaction process. The irradiated specimens were investigated by means of optical microscopy and x-ray structure analysis (XRSA). It was shown that at 1010 W cm-2 pulses the Al2O3 coating was completely evaporated, whereas a surface of the BN sample became smoother than in the virgin one. A direct comparison of both samples after the action of 108 W cm-2 pulses demonstrated a wave-like structure (more distinct on Al2O3). Weighing of these samples showed, however, that the evaporation of BN was about two times stronger than that of Al2O3 in spite of the lower irradiation flux; the XRSA showed no evidence of cracking of Al2O3 after these pulses. The insulation properties of Al2O3 did not decline, and the Al2O3 coating may be potentially more beneficial, provided that it is kept below its melting point. Characteristic features of damages of a material based on the carbon-fiber composite with additions of silicium carbide (SiC; 8-40% volumetric) were also investigated. It was found that at q=109 W cm-2, the surface erosion is associated with sputtering and evaporation. The degree of this erosion depends on the fibers' orientation in

  4. Formation mechanism and characteristics of lanthanum-doped BaTiO{sub 3} powders and ceramics prepared by the sol–gel process

    Energy Technology Data Exchange (ETDEWEB)

    Ianculescu, Adelina Carmen [Department of Oxide Materials Science and Engineering, Politehnica University of Bucharest, 17 Gh. Polizu, 011061 Bucharest (Romania); Vasilescu, Catalina Andreea, E-mail: katyvasilescu85@yahoo.com [Department of Oxide Materials Science and Engineering, Politehnica University of Bucharest, 17 Gh. Polizu, 011061 Bucharest (Romania); National Institute for Lasers, Plasma and Radiation Physics, P.O. Box MG54, 077125 Magurele (Romania); Crisan, Maria; Raileanu, Malina [Ilie Murgulescu Institute of Physical Chemistry, Romanian Academy, 202 Splaiul Independentei, 060021 Bucharest (Romania); Vasile, Bogdan Stefan; Calugaru, Mihai [Department of Oxide Materials Science and Engineering, Politehnica University of Bucharest, 17 Gh. Polizu, 011061 Bucharest (Romania); Crisan, Dorel; Dragan, Nicolae [Ilie Murgulescu Institute of Physical Chemistry, Romanian Academy, 202 Splaiul Independentei, 060021 Bucharest (Romania); Curecheriu, Lavinia; Mitoseriu, Liliana [Department of Physics, Al. I. Cuza University of Iasi, Blvd. Carol I 11, 700506 Iasi (Romania)

    2015-08-15

    Pure and lanthanum-doped barium titanate nanopowders described by two different formulae, as Ba{sub 1−x}La{sub x}TiO{sub 3}, for lower La concentrations (0 ≤ x ≤ 0.005) and Ba{sub 1−x}La{sub x}Ti{sub 1−x/4}O{sub 3} for higher La concentration (x = 0.025) were prepared by an alkoxide sol–gel method. Single phase compositions were obtained after annealing at 900 °C for 2 h, in air. The increase of the lanthanum content causes structural and morphological changes in the oxide powders, including the evolution of the unit cell from tetragonal toward a cubic symmetry, the particle size decrease and a higher aggregation tendency. SEM investigations of the ceramics sintered at 1300 °C for 4 h indicate significant changes of the microstructural features (strong decrease of the average grain size and increase of the intergranular porosity) with the raise of La amount. Lanthanum addition to barium titanate prepared by sol–gel induces a more significant shift of the Curie temperature toward lower values, than that one reported in literature for ceramics of similar compositions, but processed by the conventional solid state method. The compositions with smaller La amount (x ≤ 0.005) show semiconducting properties at room temperature and high relative dielectric permittivity values, while the undoped ceramics and those doped with higher La content (x = 0.025) are good dielectrics. The ceramic with x = 0.025 exhibits acceptable low losses, a very diffuse ferroelectric–paraelectric transition and Curie temperature closed to the room temperature, being thus susceptible for high tunability applications. - Highlights: • Ba{sub 1−x}La{sub x}TiO{sub 3} (x ≤ 0.005) and Ba{sub 1−x}La{sub x}Ti{sub 1−x/4}O{sub 3} (x = 0.025) were prepared by sol–gel. • Ceramics with x < 0.5 exhibit semiconductor and high dielectric properties. • Ceramic with x = 0.025 exhibits acceptable low losses and diffuse phase transition.

  5. Effects of single pulse energy on the properties of ceramic coating prepared by micro-arc oxidation on Ti alloy

    Science.gov (United States)

    Wang, Jun-Hua; Wang, Jin; Lu, Yan; Du, Mao-Hua; Han, Fu-Zhu

    2015-01-01

    The effects of single pulse energy on the properties of ceramic coating fabricated on a Ti-6Al-4V alloy via micro-arc oxidation (MAO) in aqueous solutions containing aluminate, phosphate, and some additives are investigated. The thickness, micro-hardness, surface and cross-sectional morphology, surface roughness, and compositions of the ceramic coating are studied using eddy current thickness meter, micro-hardness tester, JB-4C Precision Surface roughness meter, scanning electron microscopy (SEM) and X-ray diffraction (XRD). Single pulse energy remarkably influences the ceramic coating properties. The accumulative time of impulse width is an important parameter in the scientific and rational measurement of the film forming law of ceramic coating. The ceramic coating thickness approximately linearly increases with the cumulative time of impulse width. Larger impulse width resulted in higher single pulse energy, film forming rates and thicker ceramic coating thickness. The sizes of oxide particles, micro-pores and micro-cracks slightly increase with impulse width and single pulse energy. The main surface conversion products generated during MAO process in aqueous solutions containing aluminate are rutile TiO2, anatase TiO2, and a large amount of Al2TiO5. The effects of single pulse energy on the micro-hardness and phase composition of ceramic coating are not as evident as those of frequency and duty cycle.

  6. Silicon nitride equation of state

    Science.gov (United States)

    Brown, Robert C.; Swaminathan, Pazhayannur K.

    2017-01-01

    This report presents the development of a global, multi-phase equation of state (EOS) for the ceramic silicon nitride (Si3N4).1 Structural forms include amorphous silicon nitride normally used as a thin film and three crystalline polymorphs. Crystalline phases include hexagonal α-Si3N4, hexagonal β-Si3N4, and the cubic spinel c-Si3N4. Decomposition at about 1900 °C results in a liquid silicon phase and gas phase products such as molecular nitrogen, atomic nitrogen, and atomic silicon. The silicon nitride EOS was developed using EOSPro which is a new and extended version of the PANDA II code. Both codes are valuable tools and have been used successfully for a variety of material classes. Both PANDA II and EOSPro can generate a tabular EOS that can be used in conjunction with hydrocodes. The paper describes the development efforts for the component solid phases and presents results obtained using the EOSPro phase transition model to investigate the solid-solid phase transitions in relation to the available shock data that have indicated a complex and slow time dependent phase change to the c-Si3N4 phase. Furthermore, the EOSPro mixture model is used to develop a model for the decomposition products; however, the need for a kinetic approach is suggested to combine with the single component solid models to simulate and further investigate the global phase coexistences.

  7. Ferroelectric behaviour of 30 nm BaTiO3 ceramics prepared by high pressure assisted sintering

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Dense nanocrystalline BaTiO3 ceramics with a homogeneous grain size of 30 nm was obtained by pressure assistedsintering. The ferroelectric behaviour of the ceramics was characterized by the dielectric peak at around 120 ℃, the P-Ehysteresis loop and some ferroelectric domains. These experimental results indicate that the critical grain size for thedisappearance of ferroelectricity in nanocrystalline BaTiO3 ceramics fabricated by pressure assisted sintering is below 30 nm. The ferroelectric property decreasing with decreasing grain size can be explained by the lowered tetragonality and the 'dilution' effect of grain boundaries.

  8. PREPARATION OF ACTIVATED CARBON FROM SILK COTTON WOOD AND COCONUT SHELL BY PYROLISIS WITH CERAMIC FURNACE

    Directory of Open Access Journals (Sweden)

    Winarto Haryadi

    2010-06-01

    Full Text Available Preparation of activated carbon from silk cotton wood and coconut shell has been done. Carbon was made by pyrolysis process in the Muchalal furnace with 3000 watt electric power. The electric power was increased gradually from 1000, 2000 and then 3000 watt with interval 2 hours during 7 hours. Carbon was activated in Muchalal furnace with 4000 watt electric power during 2 hours and flowed with nitrogen gas. Product of the activated carbon was compared to standart product with several analysis including the surface area, acetic acid adsorption, iod adsorption and vapour adsorption. The results of analysis showed that surface area for silk cotton wood carbon, coconut shell carbon, and E.Merck product were 288.8072 m2/g, 222.9387 m2/g and 610.5543 m2/g, respectively. Acetic acid adsorption for silk cotton wood carbon, coconut shell carbon, and standart product were 157.391 mg/g, 132.791 mg/g, and 186.911 mg/g, respectively. Iodine adsorption for cotton wood carbon, coconut shell carbon, and standart product were 251.685 mg/g, 207.270 mg/g and 310.905 mg/g, respectively. Vapour adsorption for cotton wood carbon, coconut shell carbon and standart product were 12%, 4%,and 14%., respectively Key words : Activated carbon, pyrolysis, Muchalal furnace

  9. Dielectric properties of FeNbO4 ceramics prepared by the sol-gel method

    Science.gov (United States)

    Devesa, S.; Graça, M. P.; Henry, F.; Costa, L. C.

    2016-11-01

    In this work, FeNbO4 powders were prepared using the sol-gel method. The fine powder particles were pressed into pellets and sintered at temperatures between 500 and 1200 °C. The powder was studied by X-ray diffraction and Raman spectroscopy. The morphology of the grains was investigated by scanning electron microscopy. Heat-treatment of the particles results in higher crystallinity, larger grains, and a decrease in the porosity of the material. The dielectric properties were measured in the frequency range of 102-106 Hz, in function of temperature (200-370 K). In all samples the real (ε‧) and imaginary (ε″) parts of the complex permittivity increase with increasing annealing temperature. The sample heat treated at 1200 °C shows the highest ε‧, > 104 at 300 K. All samples show a dielectric relaxation phenomenon, analysed using the modulus formalism. The evolution of the ac conduction activation energy and of the activation energy associated with the relaxation mechanism, is directly related with the changes promoted by the heat treatment in the structure and in the morphology of the base powders.

  10. Preparation and oxygen permeation properties of SrFe(Cu)O3-δ dense ceramic membranes

    Institute of Scientific and Technical Information of China (English)

    Heng Zhang; Tingting Wang; Xinfa Dong; Weiming Lin

    2009-01-01

    Mixed oxygen-ionic and electronic conducting membranes of SrFe(Cu)O3-δ were prepared by solid-state reaction method.The crystal structure,oxygen nonstoichiometry,and phase stability of the materials were studied by TGA and XRD.Oxygen permeation fluxes through these membranes were studied at operating temperature ranging from 750 to 950 ℃.Results showed that doping Cu in SrFeO3-δ compound had a significant effect on the formation of single-phased perovskite structure.For SrFe1-xCuxO3-δ series materials,the oxygen nonstoichiometry and the oxygen permeation flux increased considerably with the increase of Cu-doping content (x = 0.1-0.3).The sintering property of the membrane decreased significantly when the Cu substitution amount reached 40%.SrFe0.7CU0.3O3-δ showed high oxygen permeation flux,but SrCuO2 and Sr2Fe2O5 phases formed in the compound after oxygen permeation test induced cracks in the membrane.

  11. Influence of preparation route and slip casting conditions on titania and barium titanate ceramics

    Institute of Scientific and Technical Information of China (English)

    Arvind K.Nikumbh; Parag V.Adhyapak

    2012-01-01

    Titania (TiO2) and barium titanate (BaTiO3) were synthesized using three different dicarboxylates,which included oxalate,malate and tartarate.These powders were characterized by X-ray powder diffraction,scanning electron micrographs,BET specific surface area and particle size distribution.Their properties depended to a great extent on the nature of the precursor.The titania and barium titanate powders obtained from the tartarate precursor were found to be good for slip casting.Slips of these oxides with different solids contents were prepared at different pH values using both distilled water and ethanol as the dispersing agent and also with and without deflocculant.The theological behaviors of the suspensions were then determined,and the slip,green and sedimentation bulk densities were measured.The minimum viscosities were observed at pH 8.2 for the TiO2-water and pH 10.2 for the BaTiO3-water system.

  12. PMNT热释电陶瓷材料的制备及性能研究%Preparation and Properties Study of PMNT Pyroelectric Ceramic Materaials

    Institute of Scientific and Technical Information of China (English)

    王实现; 张约品; 王冲; 章践立

    2011-01-01

    The PMNT ceramics with complex perovskite structure were prepared by the soft chemistry method. X-ray diffraction was used to detect the perovskite phase evolution and the presence of the pyrochlore phase in PMNT ceramics. The grain morphology was observed by scanning electron microscopy (SEM). The pyroelectric and piezoelectric properties of the ceramics were studied. The results show that the PMNT ceramics posses high densities and good pyroelectric properties. The pyroelectric coefficient of 0.67PMN-0.33PT ceramics is 5.5×10^-4C·m^-2.K^-1, Fd is 3.9× 10^-5 Pa^-1/2.%用软化学法合成了驰豫型复合钙钛矿结构铁电PMNT粉体,并将制备好的粉体压制成圆片状后放入硅碳棒炉中,于1150℃下烧结成致密热释电陶瓷材料.然后用x射线粉末衍射对合成材料进行物相分析,并用扫描电镜观察了晶粒形貌特征.结果表明:烧结后的陶瓷具有很好的致密性和热释电性,其中,0.67PMN.0.33PT组分热释电陶瓷的热释电系数为4.5×10^-4C·m^-2.K^-1,探测优值Fd为3.9×10^-5Pa^-1/2。

  13. αTCP ceramic doped with dicalcium silicate for bone regeneration applications prepared by powder metallurgy method: in vitro and in vivo studies.

    Science.gov (United States)

    Velasquez, Pablo; Luklinska, Zofia B; Meseguer-Olmo, Luis; Mate-Sanchez de Val, Jose E; Delgado-Ruiz, Rafael A; Calvo-Guirado, Jose L; Ramirez-Fernandez, Ma P; de Aza, Piedad N

    2013-07-01

    This study reports on the in vitro and in vivo behavior of α-tricalcium phosphate (αTCP) and also αTCP doped with either 1.5 or 3.0 wt % of dicalcium silicate (C2 S). The ceramics were successfully prepared by powder metallurgy method combined with homogenization and heat treatment procedures. All materials were composed of a single-phase, αTCP in the case of a pure material, or solid solution of C2 S in αTCP for the doped αTCP, which were stable at room temperature. The ceramics were tested for bioactivity in simulated body fluid, cell culture medium containing adult mesenchymal stem cells of human origin, and in animals. Analytical scanning electron microscopy combined with chemical elemental analysis was used and Fourier transform infrared and conventional histology methods. The in vivo behavior of the ceramics matched the in vitro results, independently of the C2 S content in αTCP. Carbonated hydroxyapatite (CHA) layer was formed on the surface and within the inner parts of the specimens in all cases. A fully mineralized new bone growing in direct contact with the implants was found under the in vivo conditions. The bioactivity and biocompatibility of the implants increased with the C2 S content in αTCP. The C2 S doped ceramics also favoured a phase transformation of αTCP into CHA, important for full implant integration during the natural bone healing processes. αTCP ceramic doped with 3.0 wt % C2 S showed the best bioactive in vitro and in vivo properties of all the compositions and hence could be of interest in specific applications for bone restorative purposes.

  14. Carbon nanofillers for machining insulating ceramics

    Directory of Open Access Journals (Sweden)

    Olivier Malek

    2011-10-01

    Full Text Available The implementation of ceramics in emerging applications is principally limited by the final machining process necessary for producing microcomponents with complex geometries. The addition of carbon nanotubes greatly enhances the electrical properties of insulating ceramics allowing electrical discharge machining to be used to manufacture intricate parts. Meanwhile other properties of the ceramic may be either preserved or even improved. For the first time, a silicon nitride/carbon nanotubes microgear is electrically discharge machined with a remarkably high material removal rate, low surface roughness, and low tool wear. This offers unprecedented opportunities for the manufacture of complicated ceramic parts by adding carbon nanotubes for new engineering and biomedical applications.

  15. Influences of Mechanical Vibration on Rapidly Solidified Al2O3/YSZ Ceramics Prepared by Combustion Synthesis

    Institute of Scientific and Technical Information of China (English)

    ZHAO Zhong-min; ZHANG Long; WANG Wei-guo; ZHANG Shi-yue

    2006-01-01

    Al2O3/YSZ composite ceramics was fabricated with combustion synthesis technology, and the influences of mechanical vibration on its microstructures and properties were investigated. It is found that under the mechanical vibration of ever-increasing frequency, increasing combustion temperature, accelerating ceramics/metal liquid-liquid separation and quickening ceramic solidification could not only reduce the average diameter and the size distribution of aligned ZrO2 nano-micron fibers in rod-shaped Al2O3 matrix grains, but also make the randomly-oriented rod-shaped grains finer and increase their aspect ratios. As a result, a remarkable increase in flexural strength and fracture toughness of the ceramics can be observed.

  16. Dielectric relaxation behaviour of Sr2SbMnO6 ceramics fabricated from nanocrystalline powders prepared by molten salt synthesis

    Indian Academy of Sciences (India)

    Antara Baral; K R S Preethi Meher; K B R Varma

    2011-02-01

    Double perovskite polycrystalline single phase and dense Sr2SbMnO6 (SSM) ceramics, fabricated using the nanocrystalline powders synthesized by molten salt method, exhibited high dielectric constant with low dielectric loss as compared to that of SSM ceramics obtained from the powders prepared by solid-state synthesis method. The dielectric data obtained over a wide frequency (100 Hz–1 MHz) and temperature (190 K–300 K) ranges exhibited distinct relaxations owing to both the grain and grain boundary. The dielectric dispersion was modeled using the Cole–Cole equation consisting of two separate relaxation terms corresponding to the grain and grain boundary. The grain and grain boundary relaxations observed in the Nyquist plots (' and ) were modeled by an equivalent circuit consisting of two parallel RC circuits connected in series with each other. A careful analysis of both the impedance ('' vs) and modulus ('' vs) behaviour corroborated the conclusions drawn fromthe dielectric data.

  17. Microstructure and Electrical Properties of Er2O3-Doped ZnO-Based Varistor Ceramics Prepared by High-Energy Ball Milling

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The microstructure, electrical properties and density of ZnO-based varistor ceramics with different Er2O3 content prepared by high-energy ball milling (HEBM) and sintered at 800 ℃ were investigated. With increasing Er2O3 content, the ZnO grain size decreases due to the Er-rich phases inhibiting grain growth;and nonlinear coefficient (α) decreases because of the decrease of barrier height (φB). The breakdown voltage (Eb) and density increase, whereas leakage current (IL) decreases with increasing Er2O3 content. The barrier height (φB), donor concentration (Nd), density of interface states (Ns) decrease and barrier width (ω) increases with increasing Er2O3 content due to acceptor effect of Er2O3 in varistor ceramics.

  18. Performance of Ceramics in Severe Environments

    Science.gov (United States)

    Jacobson, Nathan S.; Fox, Dennis S.; Smialek, James L.; Deliacorte, Christopher; Lee, Kang N.

    2005-01-01

    Ceramics are generally stable to higher temperatures than most metals and alloys. Thus the development of high temperature structural ceramics has been an area of active research for many years. While the dream of a ceramic heat engine still faces many challenges, niche markets are developing for these materials at high temperatures. In these applications, ceramics are exposed not only to high temperatures but also aggressive gases and deposits. In this chapter we review the response of ceramic materials to these environments. We discuss corrosion mechanisms, the relative importance of a particular corrodent, and, where available, corrosion rates. Most of the available corrosion information is on silicon carbide (SIC) and silicon nitride (Si3N4) monolithic ceramics. These materials form a stable film of silica (SO2) in an oxidizing environment. We begin with a discussion of oxidation of these materials and proceed to the effects of other corrodents such as water vapor and salt deposits. We also discuss oxidation and corrosion of other ceramics: precurser derived ceramics, ceramic matrix composites (CMCs), ceramics which form oxide scales other than silica, and oxide ceramics. Many of the corrosion issues discussed can be mitigated with refractory oxide coatings and we discuss the current status of this active area of research. Ultimately, the concern of corrosion is loss of load bearing capability. We discuss the effects of corrosive environments on the strength of ceramics, both monolithic and composite. We conclude with a discussion of high temperature wear of ceramics, another important form of degradation at high temperatures.

  19. Preparation of alumina ceramic membranes by electrophoresis%电泳沉积法制备氧化铝陶瓷膜的研究

    Institute of Scientific and Technical Information of China (English)

    陈晓晓; 魏刚; 张元晶; 付国柱; 乔宁

    2011-01-01

    以工业级陶瓷片为支撑体,氧化铝溶胶为电泳液,采用电泳沉积的方法制备了氧化铝陶瓷膜.当在30 V的电压条件下电泳3 min,经沉积-干燥-烧结工艺,反复进行3次后,即可得到氧化铝纳滤膜.采用SEM和液-液排除法等手段对纳滤膜进行表征,结果表明,膜厚在50 μm左右,孔隙率为31.51%,平均孔径为3.1nm,孔径分布为2.88 - 5.76 nm.性能测试表明,氧化铝纳滤膜对无机污染物和有机污染物均有强的截留作用,且性能较稳定.%Alumina ceramic membranes have been prepared by electrophoresis using an industrial ceramic as the electrophoretic matrix and alumina sol as the electrophoretic liquid. A nanofiltration membrane was prepared using the electrophoretic process and a coating-drying-sintering process repeated three times. The optimum electrophoresis time was found to be 3 min with a voltage of 30 V. The Al2O3 ceramic membrane obtained under these experimental conditions was characterized by SEM and liquid-liquid displacement methods. A ceramic membrane with a thickness of 50 μm had a porosity ratio of 31. 51% , a pore size of 3. 1 nm and a pore size distribution of 2. 88 nm to 5. 76 nm. Performance tests showed that the membrane had strong interception effects on both inorganic pollutants and organic pollutants.

  20. Ceramic material suitable for repair of a space vehicle component in a microgravity and vacuum environment, method of making same, and method of repairing a space vehicle component

    Science.gov (United States)

    Riedell, James A. (Inventor); Easler, Timothy E. (Inventor)

    2009-01-01

    A precursor of a ceramic adhesive suitable for use in a vacuum, thermal, and microgravity environment. The precursor of the ceramic adhesive includes a silicon-based, preceramic polymer and at least one ceramic powder selected from the group consisting of aluminum oxide, aluminum nitride, boron carbide, boron oxide, boron nitride, hafnium boride, hafnium carbide, hafnium oxide, lithium aluminate, molybdenum silicide, niobium carbide, niobium nitride, silicon boride, silicon carbide, silicon oxide, silicon nitride, tin oxide, tantalum boride, tantalum carbide, tantalum oxide, tantalum nitride, titanium boride, titanium carbide, titanium oxide, titanium nitride, yttrium oxide, zirconium diboride, zirconium carbide, zirconium oxide, and zirconium silicate. Methods of forming the ceramic adhesive and of repairing a substrate in a vacuum and microgravity environment are also disclosed, as is a substrate repaired with the ceramic adhesive.

  1. Low temperature sintering and performance of aluminum nitride/borosilicate glass

    Institute of Scientific and Technical Information of China (English)

    Hong-sheng ZHAO; Lei CHEN; Nian-zi GAO; Kai-hong ZHANG; Zi-qiang LI

    2009-01-01

    Aluminum nitride (AlN)/borosilicate glass composites were prepared by the tape casting process and hot-press sin-tered at 950 ℃ with AlN and SiO2-B2O3-ZnO-Al2O3-Li2O glass as starting materials. We characterized and analyzed the variation of the microstructure, bulk density, porosity, dielectric constant, thermal conductivity and thermal expansion coefficient (TEC) of the ceramic samples as a function of AlN content. Results show that AlN and SiO2-B2O3-ZnO-Al2O3-Li2O glass can be sintered at 950 ℃, and ZnAl2O4 and Zn2SiO4 phase precipitated to form glass-ceramic. The performance of the ceramic samples was de-termined by the composition and bulk density of the composites. Lower AlN content was found redounding to liquid phase sin-tering, and higher bulk density of composites can be accordingly obtained. With the increase of porosity, corresponding decreases were located in the dielectric constant, thermal conductivity and TEC of the ceramic samples. When the mass fraction of AlN was 40%, the ceramic samples possessed a low dielectric constant (4.5~5.0), high thermal conductivity (11.6 W/(m·K)) and a proper TEC (3.0×10K-1, which matched that of silicon). The excellent performance makes this kind of low temperature co-fired ce-ramic a promising candidate for application in the micro-electronics packaging industry.

  2. Toward Lower Overpotential through Improved Electron Transport Property: Hierarchically Porous CoN Nanorods Prepared by Nitridation for Lithium-Oxygen Batteries.

    Science.gov (United States)

    Xu, Shu-Mao; Zhu, Qian-Cheng; Harris, Michelle; Chen, Tong-Heng; Ma, Chao; Wei, Xiao; Xu, Hua-Sheng; Zhou, Yong-Xian; Cao, Yu-Cai; Wang, Kai-Xue; Chen, Jie-Sheng

    2016-09-14

    To lower the overpotential of a lithium-oxygen battery, electron transport at the solid-to-solid interface between the discharge product Li2O2 and the cathode catalyst is of great significance. Here we propose a strategy to enhance electron transport property of the cathode catalyst by the replace of oxygen atoms in the generally used metal oxide-based catalysts with nitrogen atoms to improve electron density at Fermi energy after nitridation. Hierarchically porous CoN nanorods were obtained by thermal treatment of Co3O4 nanorods under ammonia atmosphere at 350 °C. Compared with that of the pristine Co3O4 precursor before nitridation, the overpotential of the obtained CoN cathode was significantly decreased. Moreover, specific capacity and cycling stability of the CoN nanorods were enhanced. It is assumed that the discharged products with different morphologies for Co3O4 and CoN cathodes might be closely associated with the variation in the electronic density induced by occupancy of nitrogen atoms into interstitial sites of metal lattice after nitridation. The nitridation strategy for improved electron density proposed in this work is proved to be a simple but efficient way to improve the electrochemical performance of metal oxide based cathodes for lithium-oxygen batteries.

  3. Dielectric properties, impedance analysis and modulus behavior of CaTiO{sub 3} ceramic prepared by solid state reaction

    Energy Technology Data Exchange (ETDEWEB)

    Wong, Y.J., E-mail: yjeng_86@hotmail.com [Department of Physics, Faculty of Science, Universiti Putra Malaysia, 43400 Serdang, Selangor (Malaysia); Hassan, J., E-mail: jumiah@science.upm.edu.my [Department of Physics, Faculty of Science, Universiti Putra Malaysia, 43400 Serdang, Selangor (Malaysia); Advanced Materials and Nanotechnology Laboratory, Institute of Advanced Technology (ITMA), Universiti Putra Malaysia, 43400 Serdang, Selangor (Malaysia); Hashim, M., E-mail: mansor@science.upm.edu.my [Department of Physics, Faculty of Science, Universiti Putra Malaysia, 43400 Serdang, Selangor (Malaysia); Advanced Materials and Nanotechnology Laboratory, Institute of Advanced Technology (ITMA), Universiti Putra Malaysia, 43400 Serdang, Selangor (Malaysia)

    2013-09-15

    Highlights: •A single phase orthorhombic CaTiO{sub 3} structure with sub-micron grains is produced. •The frequency exponent ‘s’ is temperature dependent and explained by CBH model. •The dielectric constant and loss tangent are frequency and temperature dependent. •The modulus plot reveals the presence of thermally activated dielectric relaxation. •Cole-cole plot reveals two primary relaxation processes exist in the sample. -- Abstract: Calcium titanate (CaTiO{sub 3}) with the general formula for perovskites, ABO{sub 3}, is of technological importance, particularly with regard to dielectric properties. In this work, CaTiO{sub 3} ceramic material was prepared by the conventional solid state reaction method. The dielectric properties, impedance characteristics and modulus behavior of the CaTiO{sub 3} ceramic material sintered at 1240 °C were investigated in the frequency range of 10{sup −2}–10{sup 6} Hz and temperature range of 100–250 °C. The XRD analysis of the sintered CaTiO{sub 3} shows that it is an orthorhombic structure with lattice parameters a = 5.4398 Å, b = 7.6417 Å, and c = 5.3830 Å. The FESEM micrograph shows a significant difference in grain size distribution ranging from 0.26 to 2.32 μm. The AC conductivity, σ{sub AC}, is found to increase with increasing temperature within the frequency range of 10{sup −2}–10{sup 6} Hz confirming the hopping of electrons to be the conduction mechanism. Due to the decreasing values of the frequency exponent s with increasing temperature, the results of the σ{sub AC} are discussed using the correlated barrier height (CBH) model. For dielectric studies, the dielectric constant, ε′ is found to decrease with increasing frequency. In the whole temperature range of 100–250 °C, high and low frequency plateau are observed. Each converges at high frequency (>10{sup 5} Hz) for all the temperatures. The frequency dependence of loss tangent, tan δ, decreases with rise in temperature, with the

  4. Method of synthesizing cubic system boron nitride

    Energy Technology Data Exchange (ETDEWEB)

    Yuzu, S.; Sumiya, H.; Degawa, J.

    1987-10-13

    A method is described for synthetically growing cubic system boron nitride crystals by using boron nitride sources, solvents for dissolving the boron nitride sources, and seed crystals under conditions of ultra-high pressure and high temperature for maintaining the cubic system boron nitride stable. The method comprises the following steps: preparing a synthesizing vessel having at least two chambers, arrayed in order in the synthesizing vessel so as to be heated according to a temperature gradient; placing the solvents having different eutectic temperatures in each chamber with respect to the boron nitride sources according to the temperature gradient; placing the boron nitride source in contact with a portion of each of the solvents heated at a relatively higher temperature and placing at least a seed crystal in a portion of each of the solvents heated at a relatively lower temperature; and growing at least one cubic system boron nitride crystal in each of the solvents in the chambers by heating the synthesizing vessel for establishing the temperature gradient while maintaining conditions of ultra-high pressure and high temperature.

  5. Kaolinite as a Suspending Agent for Preparation of Porous BaTiO3 Ceramics via Freeze Casting

    Science.gov (United States)

    Li, Pin; Pu, Yongping; Dong, Zijing; Gao, Pan

    2014-02-01

    Porous barium titanate (BT) ceramics were fabricated by a freeze-casting technique with kaolinite as a suspending agent, and the effects of the kaolinite content on the microstructure and dielectric properties were investigated. The porous BT ceramics possessed high porosity and a unique two-dimensional pore structure along the freezing direction. The absolute value of the zeta potential and the viscosity of the slurry increased with increasing kaolinite content. The zeta potential plot and viscosity characterization results showed that a stable slurry was obtained when the kaolinite content was 8 wt.%. The porosity was substantially affected by the suspension effect and the fluxing action of the kaolinite. Porosity characterization showed that the porosity of the porous BT ceramic reached a maximum value for 8 wt.% addition of kaolinite. Scanning electron microscopy showed that the porous BT ceramics possessed a multilayered channel structure. The temperature dependence of the permittivity showed that the porous BT ceramics possessed good temperature stability of the dielectric constant.

  6. Evaluation of shear bond strength of metallic and ceramic brackets bonded to enamel prepared with self-etching primer.

    Science.gov (United States)

    Uysal, Tancan; Ustdal, Ayca; Kurt, Gokmen

    2010-04-01

    The aim of this in vitro study was to evaluate the shear bond strength (SBS) of different metallic and ceramic bracket bonding combinations using self-etching primers (SEPs). Eighty freshly extracted human premolar teeth were randomly divided into four equal groups for bonding with ceramic or metallic brackets as follows: group 1, metallic brackets bonded with conventional acid etching; group 2, metallic brackets bonded with Transbond Plus Self-Etching primer (TPSEP); group 3, ceramic brackets bonded as per group 1; group 4, ceramic brackets bonded as per group 2. The SBS of these brackets was measured and recorded in megapascals (MPa). The adhesive remnant index (ARI) scores were determined after bracket failure. Data were analyzed with the analysis of variance, Tukey, and chi-square tests. The bond strength of group 3 (mean: 36.7 +/- 11.8 MPa) was significantly higher than group 4 (mean: 26.6 +/- 8.9 MPa; P 0.05). Compared with conventional acid etching, SEPs significantly decreased the SBS of ceramic orthodontic brackets.

  7. 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.

  8. Preparation and electrical properties of FexCu0.10Ni0.66Mn2.24−xO4 (0 ≤ x ≤ 0.90) NTC ceramics

    NARCIS (Netherlands)

    Fang, Dao-lai; Chen, Chu-Sheng; Winnubst, A.J.A.

    2008-01-01

    In this paper, the dense FexCu0.10Ni0.66Mn2.24−xO4 (0 ≤ x ≤ 0.90) ceramics with accurate stoichiometry are prepared by the route of solid-state coordination reaction. The effect of Fe addition on the electrical properties of the ceramics has been investigated by powder X-ray diffraction (XRD), elec

  9. Preparation and characterization of new microwave dielectric ceramics Ba3-nLa1+nTinNb3-nO12

    Institute of Scientific and Technical Information of China (English)

    FANG Liang; MENG Sen-sen; ZHANG Hui; WU Bo-lin

    2006-01-01

    A series of new microwave dielectric ceramics Ba3-nLa1+nTinNb3-nO12 (n=0,1,2) were prepared in the BaO-La2O3-TiO2-Nb2O5 system by high temperature solid-state reaction route. The phase and structure of the ceramics were characterized by X-ray diffraction,scanning electron microscope,and microwave dielectric properties measurements. These samples were identified as single phase and adopted A4B3O12-type cation-deficient hexagonal perovskite structure,which can be described as consisting of identical perovskite-like blocks,three corner-sharing BO6 octahedra thick,separated by layers of vacant octahedral. These ceramics have high dielectric constants in the range of 48-42,high quality factors (Q×f ) up to 38 000 GHz,and low temperature coefficient of resonant frequencies (-f) in the range of (-40-+6)×10-6 ℃-1. With increasing content of La and Ti,the dielectric constants slightly decrease but -f gradually increases.

  10. 利用石墨尾矿制备建筑陶瓷%Preparation of Building Ceramic Tiles from Graphite Tailings

    Institute of Scientific and Technical Information of China (English)

    陈宝海; 杜高翔; 廖立兵; 杨敏

    2011-01-01

    Sintered ceramic tiles were prepared from the graphite tailings from Heilongjiang province, China. A proper amount of quartz and kaolin were added to the raw material to improve the properties of the ceramic tiles which were formed by pressing method. The influence of sintering temperature on properties of ceramic tiles was investigated. The results showed that the ceramic tiles possessed good color consistency and higher strength when the tiles were made with the raw materials containing 6%~8% of water, through pressing forming under 25 Mpa and sintering at 1060 -1080 ℃. The tiles are well conformed to the requirements of the national standard GB/T 4100-2006. The ceramic tiles have the highest strength when the firing temperature is 1060 ℃. Its bending strength and water absorptivity are 68.90 Mpa and 0.306%, respectively. The investigations with scanning electron microscope (SEM), thermogravimetric-differential thermal analysis (TG-DTA), and X-ray diffraction (XRD) shows that the anorthite begins to crystallize at about 950 °C and liquid appears at about 1050 ℃. The anorthite and glass phase are important to the sintering and strengthening of the ceramic tiles.%以黑龙江石墨尾矿为主要原料,辅以适量的石英和高岭土,采用压制成型法,制备烧结陶瓷砖.研究了烧成温度对陶瓷砖性能的影响.结果表明,当原料含水率为6%~8%、成型压力为25 MPa,烧成温度1060~1080℃时,制得的陶瓷砖为暗红色,颜色一致性好,强度较高,符合国家标准GB/T 4100-2006.当烧成温度为1060℃时,抗折强度最大,高达68.90 MPa,吸水率为0.306%.扫描电子显微镜、热重-差热和X射线衍射等方法分析结果表明,烧成温度为950℃左右时开始析出钙长石,1050℃左右时有大量的液相产生,钙长石和玻璃相对其成瓷及强度的提高起到了重要作用.

  11. Surface flaw detection in structural ceramics by scanning photoacoustic spectroscopy

    Science.gov (United States)

    Khandelwal, P. K.; Heitman, P. W.; Wakefield, T. D.; Silversmith, A. J.

    1980-01-01

    Laser-scanned photoacoustic spectroscopy has been used to detect tightly closed surface cracks in three structural ceramic materials: sintered silicon nitride, reaction-bonded silicon nitride, and sintered silicon carbide. It is found that the amplitude of the photoacoustic signal from the flaws is greater for the silicon nitrides than for silicon carbide, which is attributed to the lower thermal diffusivity of silicon nitride as well as differences in the grain size distribution and chemical composition. Signal amplitude, reproducibility, and signal-to-noise ratio are acceptable for effective flaw detection

  12. Portfolio: Ceramics.

    Science.gov (United States)

    Hardy, Jane; And Others

    1982-01-01

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

  13. Portfolio: Ceramics.

    Science.gov (United States)

    Hardy, Jane; And Others

    1982-01-01

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

  14. Fiscal 1996 report on the R and D result of industrial science and technology. R and D synergy ceramics (R and D on synergy ceramics); 1996 nendo sangyo kagaku gijutsu kenkyu kaihatsu seika hokokusho. Synergy ceramics no kenkyu kaihatsu (synergy ceramics no kenkyu kaihatsu)

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1998-03-01

    This paper summarizes the general survey mainly conducted by FCRA (Fine Ceramics Research Association) in fiscal 1996, and the joint research results with some universities, from some R and D on synergy ceramics. Silicon nitride based ceramics expressed the same high thermal conductivity as metal by seed crystal addition, grain growth control and orientation control of sheet lamination. For its practical use, study was made on control factors of material, formation and sintering. Ca2Y2Si2O9 single crystal was prepared by float-zone method to determine its crystal structure. No volume change due to high-temperature phase transition as thermal expansion was found. In carbothermal reduction- nitridation of SiO2, addition of Si3N4 seed powder increased a reaction rate and formed uniform particles with an isotropic shape. An average particle size was dependent on the size and number of fine particles in seed powder. Addition of both Si3N4 and Fe compound could change a particle shape from a spherical grain to an elongated grain. A spherical Fe-Si metal grain was found on the tip of an elongated grain. 66 refs., 73 figs., 13 tabs.

  15. Preparation of TiO2 photocatalysis antibacterial ceramic%TiO2光催化抗菌陶瓷的制备

    Institute of Scientific and Technical Information of China (English)

    陈前林; 吴建青; 王龙现

    2009-01-01

    制备了SiO2-Zr3(PO4)4改性的TiO2粉体,将其添加到陶瓷釉料中,研制出了TiO2光催化抗菌陶瓷,分别就改性TiO2粉体的光催化活性和TiO2光催化抗菌陶瓷的光催化抗菌机理进行了研究.研究表明,37.2%Zr3(PO4)4和11.5%SiO2改性的TiO2粉体经1323K处理后,仍具有较好的光催化活性,将其添加到陶瓷釉料中制备出的TiO2先催化抗菌陶瓷对大肠杆菌的抑菌率达98%.%TiO2 photocatalysis antibacterial ceramic was prepared by added TiO2 powder modified by SiO2-Zr3(PO4)4 in ceramic glaze. The photocatalysis mechanism of modified TiO2 powder and the photocatalysis antibac-terial mechanism of the ceramic have been investigated. Heat treated at 1323K, the modified TiO2 powder added 37.2% Zr3 (PO4)4 and 11.50%SiO2 showed a well photocatalysis activity,antibacterial ratio of the photocatalysis antibacterial ceramic to coliform have reached 98 %.

  16. Experimental studies of radiation resistance of boron nitride, C2C ceramics Al{sub 2}O{sub 3} and carbon-fiber composites using a PF-1000 plasma-focus device

    Energy Technology Data Exchange (ETDEWEB)

    Gribkov, V A; Demina, E V; Dubrovsky, A V; Pimenov, V N; Maslyaev, S V [Laboratory for Radiation Interaction with Metals, A A Baikov Institute of Metallurgy and Material Science, 119991 Moscow (Russian Federation); Tuniz, C [Multidisciplinary Laboratory, Abdus Salam International Centre for Theoretical Physics, 34014 Trieste (Italy); Gaffka, R; Gryaznevich, M [EURATOM/CCFE Fusion Association, Culham Science Centre, Abingdon OX14 3DB (United Kingdom); Skladnik-Sadowska, E; Sadowski, M J [Andrzej Soltan Institute for Nuclear Studies, 05-400 Otwock-Swierk n. Warsaw (Poland); Miklaszewski, R; Paduch, M; Scholz, M, E-mail: gribkovv@yahoo.com [Dense Magnetized Plasma Division, Institute of Plasma Physics and Laser Microfusion, 01-497 Warsaw (Poland)

    2011-04-15

    This paper reports on experiments undertaken to compare the radiation resistance of two types of ceramics, boron nitride (BN) and pure alumina (Al{sub 2}O{sub 3}), which are used in a TAEA antenna coil installed in the MAST spherical tokamak. Samples of the investigated materials (bulk BN and a 20 {mu}m film of Al{sub 2}O{sub 3} on Al substrate) were exposed on the axis of the plasma-focus PF-1000 device, which can emit intense streams of hot plasma (v{approx}10{sup 7} cm s{sup -1} and N{sub pl}{approx}10{sup 18} cm{sup -3}) and fast deuteron beams (E{sub i}{approx}100 keV). The most powerful plasma-ion pulse lasted 0.2-1.0 {mu}s and its intensity decayed in about 100 {mu}s. The irradiation process was diagnosed using fast optical cameras, laser interferometry and optical spectrometry. Experiments were performed at power flux densities equal to 10{sup 9}-10{sup 10} W cm{sup -2} or 10{sup 8}-10{sup 9} W cm{sup -2} during the most powerful stage of the interaction process. The irradiated specimens were investigated by means of optical microscopy and x-ray structure analysis (XRSA). It was shown that at 10{sup 10} W cm{sup -2} pulses the Al{sub 2}O{sub 3} coating was completely evaporated, whereas a surface of the BN sample became smoother than in the virgin one. A direct comparison of both samples after the action of 10{sup 8} W cm{sup -2} pulses demonstrated a wave-like structure (more distinct on Al{sub 2}O{sub 3}). Weighing of these samples showed, however, that the evaporation of BN was about two times stronger than that of Al{sub 2}O{sub 3} in spite of the lower irradiation flux; the XRSA showed no evidence of cracking of Al{sub 2}O{sub 3} after these pulses. The insulation properties of Al{sub 2}O{sub 3} did not decline, and the Al{sub 2}O{sub 3} coating may be potentially more beneficial, provided that it is kept below its melting point. Characteristic features of damages of a material based on the carbon-fiber composite with additions of silicium carbide (Si

  17. Negative permittivity of ZnO thin films prepared from aluminum and gallium doped ceramics via pulsed-laser deposition

    OpenAIRE

    M.A. Bodea; Sbarcea, G.; Naik, Gururaj V.; Boltasseva, Alexandra; Klar, T. A.; Pedarnig, J. D.

    2013-01-01

    Aluminum and gallium doped zinc oxide thin films with negative dielectric permittivity in the near infrared spectral range are grown by pulsed laser deposition. Composite ceramics comprising ZnO and secondary phase Al2O3 or Ga2O3 are employed as targets for laser ablation. Films deposited on glass from dense and small-grained ceramic targets show optical transmission larger than 70 % in the visible and reveal an onset of metallic reflectivity in the near infrared at 1100 nm and a crossover to...

  18. Negative permittivity of ZnO thin films prepared from aluminum and gallium doped ceramics via pulsed-laser deposition

    DEFF Research Database (Denmark)

    Bodea, M. A.; Sbarcea, G.; Naik, G. V.

    2013-01-01

    Aluminum and gallium doped zinc oxide thin films with negative dielectric permittivity in the near infrared spectral range are grown by pulsed laser deposition. Composite ceramics comprising ZnO and secondary phase Al2O3 or Ga2O3 are employed as targets for laser ablation. Films deposited on glass...... from dense and small-grained ceramic targets show optical transmission larger than 70 % in the visible and reveal an onset of metallic reflectivity in the near infrared at 1100 nm and a crossover to a negative real part of the permittivity at approximately 1500 nm. In comparison to noble metals, doped...

  19. Plasma etching a ceramic composite. [evaluating microstructure

    Science.gov (United States)

    Hull, David R.; Leonhardt, Todd A.; Sanders, William A.

    1992-01-01

    Plasma etching is found to be a superior metallographic technique for evaluating the microstructure of a ceramic matrix composite. The ceramic composite studied is composed of silicon carbide whiskers (SiC(sub W)) in a matrix of silicon nitride (Si3N4), glass, and pores. All four constituents are important in evaluating the microstructure of the composite. Conventionally prepared samples, both as-polished or polished and etched with molten salt, do not allow all four constituents to be observed in one specimen. As-polished specimens allow examination of the glass phase and porosity, while molten salt etching reveals the Si3N4 grain size by removing the glass phase. However, the latter obscures the porosity. Neither technique allows the SiC(sub W) to be distinguished from the Si3N4. Plasma etching with CF4 + 4 percent O2 selectively attacks the Si3N4 grains, leaving SiC(sub W) and glass in relief, while not disturbing the pores. An artifact of the plasma etching reaction is the deposition of a thin layer of carbon on Si3N4, allowing Si3N4 grains to be distinguished from SiC(sub W) by back scattered electron imaging.

  20. Design and Preparation of Ceramic Matrix in Metal Ceramic Heater%金属陶瓷发热体中陶瓷基体的设计和制备

    Institute of Scientific and Technical Information of China (English)

    邓腾飞; 贾倩

    2016-01-01

    以碳化硅、工业氢氧化铝、苏州土、钾长石、氧化钙为主要原料,设计了B系列配方。采用半干压成型和注凝成型两种不同的方法来制备金属陶瓷发热体基体,并确定最佳配方及制备工艺参数。以期在降低成本的同时,使其用途更加广泛。实验制备出了陶瓷基体并成功得到经二次烧成后内部镶嵌钨丝的样品。通过XRD和SEM等现代测试技术对材料的性能和微观结构进行了表征,相组成分析结果表明,样品的主晶相为碳化硅和方石英。显微结构分析表明,样品中生成了碳化硅晶粒且热导率与氧化铝陶瓷相比大大提高。%In this paper, using the SiC powder, industrial Al(OH)3, Suzhou kaolin, potash feldspar and CaO as the main raw materials, the metal ceramic heating body was prepared, and its optimum formulation and preparation process parameters were determined. In order to reduce the costs and make it more applicable, the properties and microstructure of the materials were characterized by XRD, SEM and other modern test techniques. The ceramic matrix was prepared by experiment. And the samples inlaid with tungsten wire were obtained successfully by double ifring. The phase composition analysis indicated that the main phases of samples were silicon carbide and cristobalite. The study results of microstructure showed that silicon carbide is gained in the samples. Compared with the alumina ceramics, the thermal conductivity of samples isgreatly improved.

  1. Preparation of Poly(p-phenylene sulfi de)/Carbon Composites with Enhanced Thermal Conductivity and Electrical Insulativity via Hybrids of Boron Nitride and Carbon Fillers

    Institute of Scientific and Technical Information of China (English)

    WU Jieli; WANG Jinwen; CHEN Feng

    2015-01-01

    The present work enhanced the thermal conductivity of poly(p-phenylene sulfi de)/expanded graphites and poly(p-phenylene sulfi de)/carbon nanotubes, by incorporating composites with hexagonal boron nitride, which simultaneously succeeded in raising the electrical conductivity of the systems. A two-step mechanical processing method which includes rotating solid-state premixing and inner mixing was adopted to improve dispersion of the hybrids, contributing to the formation of an interspered thermal conductive network. Similar synergic effect in thermal conductivity enhancement was discovered in the hybrid systems regardless of the dimension difference between the two carbonfi llers. Such is postulated to be the one satisfying advantage generated by the afore-mentioned network; the other is the insulativity of the hybrid systems given by the effective blockage of hexagonal boron nitride as an insulating material in our network.

  2. Dielectric, Electromagnetic Interference Shielding and Absorption Properties of Si3N4-PyC Composite Ceramics

    Institute of Scientific and Technical Information of China (English)

    Xuan Hao; Xiaowei Yin; Litong Zhang; Laifei Cheng

    2013-01-01

    Pyrolytic carbon (PyC) was infiltrated into silicon nitride (Si3N4) ceramics by precursor infiltration and pyrolysis (PIP) of phenolic resin,and Ni nanoparticles were added into the phenolic resin to change the electric conductivity of Si3N4-PyC composite ceramics.Dielectric permittivity,electromagnetic interference (EMI)shielding and absorption properties of Si3N4-PγC composite ceramics were studied as a function of Ni content at 8.2-12.4 GHz (X-band).When Ni nanoparticles were added into phenolic resin,the electric conductivity of the prepared composite ceramics decreased with increasing Ni content,which was attributed to the decrease of graphitization degree of PyC.The decrease in electric conductivity led to the decrease in both permittivity and EMI shielding effectiveness.Since too high permittivity is harmful to the impendence match and results in the strong reflection,the electromagnetic wave absorption property of Si3N4-PyC composite ceramics increases with increasing Ni content.When the content of Ni nanoparticles added into phenolic resin was 2 wt%,the composite ceramics possessed the lowest electric conductivity and displayed the most excellent absorption property with a minimum reflection loss as low as-28.9 dB.

  3. Formation and control of stoichiometric hafnium nitride thin films by direct sputtering of hafnium nitride target

    CERN Document Server

    Gotoh, Y; Ishikawa, J; Liao, M Y

    2003-01-01

    Hafnium nitride thin films were prepared by radio-frequency sputter deposition with a hafnium nitride target. Deposition was performed with various rf powers, argon pressures, and substrate temperatures, in order to investigate the influences of these parameters on the film properties, particularly the nitrogen composition. It was found that stoichiometric hafnium nitride films were formed at an argon gas pressure of less than 2 Pa, irrespective of the other deposition parameters within the range investigated. Maintaining the nitrogen composition almost stoichiometric, orientation, stress, and electrical resistivity of the films could be controlled with deposition parameters. (author)

  4. Preparation and Upconversion Luminescence of Y3Al5O12∶Yb3+, Er3+ Transparent Ceramics

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    YAG:1% (atom fraction) Yb3+, 0.5% (atom fraction) Er3+ transparent ceramics were fabricated by the solid state reaction method using high-purity Y2O3, Al2O3, Yb2O3, and Er2O3 powders as starting materials. The mixed powder compact was sintered at 1760 ℃ for 6 h in vacuum and annealed at 1500 ℃ for 10 h in an air atmosphere. The ceramics consisted of about 10 μm grains and exhibited a pore-free structure. The optical transmittance of the ceramics at 1064 nm was nearly 80%. Upconversion emissions were investigated on the ceramics pumped by a 980 nm continuous wave diode laser, and strong green emission centered at 523 and 559 nm and red emission centered at 669 nm were observed, which originated from the radiative transitions of 2H11/2→4I15/2, 4S3/2→4I15/2, and 4F9/2→4I15/2 of Er3+ ions, respectively.

  5. Waste-to-resource preparation of a porous ceramic membrane support featuring elongated mullite whiskers with enhanced porosity and permeance

    NARCIS (Netherlands)

    Zhu, Li; Dong, Yingchao; Hampshire, Stuart; Cerneaux, Sophie; Winnubst, Aloysius J.A.

    2015-01-01

    Different from traditional particle packing structure, a porous structure of ceramic membrane support was fabricated, featuring elongated mullitewhiskers with enhanced porosity, permeance and sufficient mechanical strength. The effect of additives (MoO3and AlF3) and sintering procedureon open porosi

  6. Dielectric and electrical design consideration of ceramics for fusion devices

    Science.gov (United States)

    Ohno, H.

    1991-03-01

    The research and development of high performance ceramics for nuclear applications are increasing their importance. Especially in nuclear development, innovative and application of ceramics are needed in fusion reactors. Summarized are the development of new materials such as silicon nitride with good mechanical and electrical properties and the application of zirconia-based ceramics for high temperature electrolysis of tritiated water in a tritium recycling system.

  7. Annual Conference on Composites and Advanced Ceramic Materials, 13th, Cocoa Beach, FL, Jan. 15-18, 1989, Collection of Papers. Parts 1 2

    Energy Technology Data Exchange (ETDEWEB)

    1989-10-01

    The present conference on advanced ceramics discusses topics in matrix-infiltration and processing techniques, the failure analysis of monolithic ceramics, the processing of polycrystalline oxide-matrix ceramic composites, the processing and properties of monolithic ceramics, ceramic composite interface phenomena, and ceramic NDE and characterization. Attention is given to chemical vapor infiltration for composites, dense ceramics via controlled melt oxidation, supertough silicon nitride, the properties of pressureless-sintered alumina-matrix/30 vol pct SiC composites, and toughening in metal particulate/glass-ceramic composites. Also discussed are the joining of silicon nitride for heat-engine applications, nitridation mechanisms in silicon powder compacts, the synthesis and properties of ceramic fibers, a technique for interfacial bond strength measurement, the degradation of SiC whiskers at elevated temperatures, and the correlation of NDE and fractography in Si3N4.

  8. Estimation of the risk of failure for an endodontically treated maxillary premolar with MODP preparation and CAD/CAM ceramic restorations.

    Science.gov (United States)

    Lin, Chun-Li; Chang, Yen-Hsiang; Pa, Che-An

    2009-10-01

    This study evaluated the risk of failure for an endodontically treated premolar with mesio occlusodistal palatal (MODP) preparation and 3 different computer-aided design/computer-aided manufacturing (CAD/CAM) ceramic restoration configurations. Three 3-dimensional finite element (FE) models designed with CAD/CAM ceramic onlay, endocrown, and conventional crown restorations were constructed to perform simulations. The Weibull function was incorporated with FE analysis to calculate the long-term failure probability relative to different load conditions. The results indicated that the stress values on the enamel, dentin, and luting cement for endocrown restoration were the lowest values relative to the other 2 restorations. Weibull analysis revealed that the individual failure probability in the endocrown enamel, dentin, and luting cement obviously diminished more than those for onlay and conventional crown restorations. The overall failure probabilities were 27.5%, 1%, and 1% for onlay, endocrown, and conventional crown restorations, respectively, in normal occlusal condition. This numeric investigation suggests that endocrown and conventional crown restorations for endodontically treated premolars with MODP preparation present similar longevity.

  9. Preparation and characterization of PbTi0{sub 3} ceramics modified by a natural mixture of rare earth oxides of xenotime

    Energy Technology Data Exchange (ETDEWEB)

    Baltazar-Rodrigues, Jair; Rodrigues Junior, Pedro; Cruz, Gerson K. da, E-mail: jbr@uepg.br [Universidade Estadual de Ponta Grossa (UEPG), PR (Brazil). Departamento de Fisica; Lente, Manuel H.; Eiras, Jose A. [Universidade Federal de Sao Carlos (UFSCar), SP (Brazil). Departamento de Fisica

    2014-01-15

    Lead titanate ceramics modified by xenotime (Xm) with nominal composition (Pb, Xm)TiO{sub 3}, Xm 10 or 15 mol %, were prepared by the conventional oxide mixture technique. Xenotime is a natural mineral consisting of a mixture of rare earth oxides. Thermal, structural and electric properties were investigated through differential and gravimetric thermal analysis, X-ray diffraction and dielectric measurements as a function of temperature. The results of both compositions revealed a higher density and free of cracks ceramic body, compared to pure PbTiO{sub 3} prepared by the same procedure. On the other hand, the structural characteristics and Curie temperature are nearly the same as those of pure PbTiO{sub 3}. The hysteresis loop measured at room temperature revealed a hard ferroelectric material with coercive field of 10.7 kV/cm and a remanent polarization of 0.2 μC/cm{sup 2}. These finding reveal a material with properties that highlight potential to be used as electronic devices that operate at high temperature and high frequencies. (author)

  10. Vapor-phase fabrication and properties of continuous-filament ceramic composites.

    Science.gov (United States)

    Besmann, T M; Sheldon, B W; Lowden, R A; Stinton, D P

    1991-09-06

    The continuous-filament ceramic composite is becoming recognized as necessary for new, high-temperature structural applications. Yet because of the susceptibility of the filaments to damage from traditional methods for the preparation of ceramics, vapor-phase infiltration has become the fabrication method of choice. The chemical vapor infiltration methods for producing these composites are now being studied in earnest, with the complexity of filament weaves and deposition chemistry being merged with standard heat and mass-transport relationships. Two of the most influential effects on the mechanical properties of these materials are the adhesion and frictional force between the fibers and the matrix, which can be controlled by a tailored interface coating. A variety of materials are available for producing these composites including carbide, nitride, boride, and oxide filaments and matrices. Silicon carbide-based materials are by far the most advanced and are already being used in aerospace applications.

  11. III Advanced Ceramics and Applications Conference

    CERN Document Server

    Gadow, Rainer; Mitic, Vojislav; Obradovic, Nina

    2016-01-01

    This is the Proceedings of III Advanced Ceramics and Applications conference, held in Belgrade, Serbia in 2014. It contains 25 papers on various subjects regarding preparation, characterization and application of advanced ceramic materials.

  12. 钻杆接头表面陶瓷膜层的制备和性能研究%Preparation and Characterization of Ceramic Film on Drilling Pipe Joint

    Institute of Scientific and Technical Information of China (English)

    黄本生; 刘阁; 江仲英; 尹文峰; 薛屺

    2015-01-01

    利用低压化学气相沉积技术(LPCVD),在钻杆接头表面制取Ti、Cr、A1的氮化物、碳化物和氧化物构成的金属陶瓷膜层.陶瓷膜的特性通过SEM、EDS和XRD分析.结合性能和腐蚀性能分别通过划痕试验和腐蚀实验测试.结果表明:陶瓷膜层致密而均匀,膜厚度在15 μm左右,且在膜层与基体之间还形成了一层厚5μm左右的过渡层.陶瓷复膜与基体材料结合性能良好,具有较好的致密性,不存在裂纹气孔等缺陷.陶瓷膜层有效阻隔了有害原子或离子与基体钢的接触,防止材料发生氢鼓泡、氢致开裂等,大大提高了钻杆接头材料的抗腐蚀性能.%A metallic ceramic film consisting of nitrides,carbides and oxides of Ti,Cr and A1 was prepared on the surface of a drilling pipe joint by low pressure chemical vapor deposition (LPCVD).The film was characterized by scanning electron microscopy (SEM),energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD).The adhesive ability and the corrosion resistance performance were evaluated by scratch test and corrosion test,respectively.The results show that the film is dense and homogeneous with 15 μm in thickness including a 5 μm transition layer.The film presents a good adherence to the substrate with no cracks and no pores.It could decrease electrochemical corrosion and chemical corrosion through separating the harmful atoms or ions from the substrate.Particularly,it could also effectively prevent H2S and CO2 from contacting the steel,avoiding hydrogen blistering (HB) and hydrogen to induce cracking (HIC).Consequently,the service life of drilling pipe can be greatly improved.

  13. 粉煤灰制备陶瓷地砖的研究%Study on ceramic floor tiles prepared from fly ash

    Institute of Scientific and Technical Information of China (English)

    王可桢; 王维

    2016-01-01

    本文目的在于研究原料粉末粒径大小对粉煤灰质陶瓷砖性能的影响。利用粉煤灰和滑石等普通陶瓷原料,经过模压成型成功制备了粉煤灰质陶瓷地砖。通过高倍电镜分析,研究了粒径大小对粉煤灰陶瓷地砖结晶和性能的影响规律。结果表明,粉煤灰质陶瓷坯体最佳烧成温度为1150℃,陶瓷原料粉末粒径小于250目,粉煤灰质陶瓷的性能最佳。粉煤灰中K2 O和Na2 O促进陶瓷晶化形核时生成透辉石相和降低烧成温度。本工作为粉煤灰大规模资源化及综合利用提出了新思路。%The objective of the present investigation was to study the effect of grain sizes on ceramic floor tiles prepared from fly ash .Green body of buildings ceramic can be produced from fly ash and talc by compression molding .The effect of grain sizes on crystal growth of fly ash -ceramic was studied by scanning electron microscopy ( SEM) .The result showed that when the optimal firing temperature is 1150℃.The particle size of the raw material powder being smaller than 250 mesh, the performance of the fly ash-ceramic is best .Sodium oxide and potassium oxide can improve the combining solid phase with liq-uid phase in the fly ash -ceramic successfully while crystallizing .This work is useful for the resourcing and comprehensive utilization of the red mud .

  14. Magnetic measurements of superconducting glass-ceramic fine rods in Bi sub 1 Ca sub 1 Sr sub 1 Cu sub 2 Al sub 0. 5 O sub x prepared under a temperature gradient

    Energy Technology Data Exchange (ETDEWEB)

    Higashida, Y.; Yokoyama, H.; Michishita, K.; Kubo, Y.; Yoshida, H. (R D Laboratory, Japan Fine Ceramics Center, Mutuno-cho, Atsuta-ku, Nagoya 456, Japan (JP)); Abe, Y.; Hosono, H. (Department of Materials Science and Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466, Japan)

    1989-10-09

    It is shown that the crystallization of the glass precursor under a temperature gradient is very effective for preparing the superconducting glass ceramics in the Bi-Ca-Sr-Cu-O system. The magnetization measurements show that the specimen prepared under a temperature gradient has a magnetization hysteresis several times larger at 4.2 K than that prepared under no temperature gradient; the coupling between superconducting grains of the former is stronger than that of the latter.

  15. Magnetic measurements of superconducting glass-ceramic fine rods in Bi1Ca1Sr1Cu2Al(0.5)O(x) prepared under a temperature gradient

    Science.gov (United States)

    Higashida, Yutaka; Yokoyama, Hisanori; Michishita, Kazuo; Kubo, Yukio; Yoshida, Hiroshi

    1989-10-01

    It is shown that the crystallization of the glass precursor under a temperature gradient is very effective for preparing the superconducting glass ceramics in the Bi-Ca-Sr-Cu-O system. The magnetization measurements show that the specimen prepared under a temperature gradient has a magnetization hysteresis several times larger at 4.2 K than that prepared under no temperature gradient; the coupling between superconducting grains of the former is stronger than that of the latter.

  16. 钛酸钾晶须耐碱多孔陶瓷的制备及表征%Preparation and Characterization of Alkaline Resistant Porous Ceramics from Potassium Titanate Whiskers

    Institute of Scientific and Technical Information of China (English)

    周亚新; 刘畅; 何明; 杨祝红; 冯新; 陆小华

    2007-01-01

    The preparation and characterization of alkaline resistant porous ceramics from potassium titanate whiskers are studied. K2Ti4O9 whiskers in the whisker preforms (mixtures of K2Ti6O13 and K2Ti4O9) were completely converted to K2Ti6O13 at 960℃. The alkaline resistance as well as the change in bending strength, porosity and permeability of the ceramics was investigated by altering the composition of the preforms in which the content of K2Ti6O13 whiskers was higher than 50% (molar fraction). The alkaline resistance of the porous K2Ti6O13 ceramics is found much higher than that of Al2O3 in caustic NaOH solutions, and further study indicates that the K2Ti6O13ceramics can be stably used in solutions of pH>2.0. The bending strength increases initially with the content of the raw K2Ti6O13 in the preforms up to 66% (molar fraction) and then decreases, contrary to the behaviors of porosity and permeability. The values of bending strength, porosity and permeability of the ceramics prepared from the precomparable to those of the porous Al2O3 ceramics.

  17. Effect of heat treatment on the optical properties of perovskite BaZr0.5Ce0.3Y0.2O3-δ ceramic prepared by spark plasma sintering

    Science.gov (United States)

    Xing, Bohang; Cheng, Zhi; Wang, Cao; Zhao, Zhe

    2017-09-01

    The effect of heat treatment on the in-line transmittance of BaZr0.5Ce0.3Y0.2O3-δ (BZCY532) ceramics prepared by spark plasma sintering method was investigated. The loss of Ba in transparent BZCY532 ceramics is the key reason for the loss of transmittance during the annealing process. This problem can be effectively alleviated by using a powder bed of BZCY532. Heat treatment atmospheres, wet air and dry air, were also found to be critical for obtaining high quality transparent ceramics. A highly transparent BZCY532 ceramic with the in-line transmittance (Tin) of 71.4% at 2000 nm can be obtained by using SPS method followed by an annealing in powder bed at 1500 °C in wet air.

  18. High temperature resistant cermet and ceramic compositions. [for thermal resistant insulators and refractory coatings

    Science.gov (United States)

    Phillips, W. M. (Inventor)

    1978-01-01

    High temperature oxidation resistance, high hardness and high abrasion and wear resistance are properties of cermet compositions particularly to provide high temperature resistant refractory coatings on metal substrates, for use as electrical insulation seals for thermionic converters. The compositions comprise a sintered body of particles of a high temperature resistant metal or metal alloy, preferably molybdenum or tungsten particles, dispersed in and bonded to a solid solution formed of aluminum oxide and silicon nitride, and particularly a ternary solid solution formed of a mixture of aluminum oxide, silicon nitride and aluminum nitride. Ceramic compositions comprising a sintered solid solution of aluminum oxide, silicon nitride and aluminum nitride are also described.

  19. 注凝成型制备莫来石-钛酸铝复相陶瓷%PREPARATION OF MULLITE-ALUMINIUM TITANATE CERAMIC COMPOSITES VIA GELCASTING

    Institute of Scientific and Technical Information of China (English)

    陆洪彬; 陈建华; 冯春霞; 焦宝祥; 孟祥康

    2009-01-01

    The mullite-aluminium titanate (MAT) ceramic composites were prepared via the gelcasting or dry pressing processes us- ing industrial mullite and aluminium titanate (Al2TiO5) powders with different mass ratios, that titanate was synthesized by doping the bi-component additive of 10% (in mole, the same below) MgO and 15% SiO2 relative to Al2O3. Effects of the bi-component additive on the phase composition and thermal stabilization of aluminium titanate powder were analyzed by X-ray diffraction and the micro- structures of MAT ceramic composites were characterized by scanning electron microscopy. The effects of aluminium titanate content on the bending strength and average thermal expansion coefficient (room temperature-1000 ℃) of the MAT ceramic composites pre- pared by dry pressing or gelcasting shaping processes were also investigated. The results show that the bi-component additive of MgO and SiO2 can promote the formation of Al2TiO5 and enhance its thermal stabilization. The MAT ceramic composites prepared by gel- casting process obtain more homogenous structure and higher bending strength than that prepared by dry pressing process. The MAT ceramic composite prepared by gelcasting process and containing 10% (mass fraction) Al2TiO5 has the maximum bending strength of 110.05 MPa.%引入10%(摩尔分数,相对于A12O3,下同)MgO和15%SiO2双组分添加剂合成了钛酸铝粉体.采用不同质量比的钛酸铝粉体和工业莫来石,用干压和注凝成型工艺制备了莫来石-钛酸铝(mullite-aluminium titanate,MAT)复相陶瓷.用X射线衍射分析了双组分添加剂对钛酸铝相组成和热稳定性的影响.通过扫描电镜表征了MAT复相陶瓷的微结构.研究了钛酸铝含量对采用于压、注凝2种成型工艺制备的MAT复相陶瓷的弯曲强度和平均热膨胀系数(室温~1 000℃)的影响.结果表明:MgO和SiO2双组分添加剂促进了钛酸铝的形成,增强了钛酸铝的热稳定性.通过注凝成型制备

  20. Properties of textile grade ceramic fibers

    Science.gov (United States)

    Pudnos, Eric

    1992-01-01

    The availability of textile grade ceramic fibers has sparked great interest for applications in composite reinforcement and high temperature insulation. This paper summarizes the properties of various small diameter textile grade ceramic fibers currently available. Room temperature mechanical and electrical properties of the fibers are discussed for three cases: ambient conditions, after heat aging in argon, and after heat aging in wet air. Dow Corning (R) HPZ Ceramic Fiber, a silicon nitride type fiber, is shown to have improved retention of mechanical and electrical properties above 1200 C.

  1. Improved electrical characteristics of Pr-doped BiFeO3 ceramics prepared by sol-gel route

    Science.gov (United States)

    Madolappa, Shivanand; Kundu, Swarup; Bhimireddi, Rajasekhar; Varma, K. B. R.

    2016-06-01

    Ceramics of Bi1-x Pr x FeO3 (x = 0-0.1) were fabricated using the nanocrystalline powders obtained via sol-gel route. X-ray powder diffraction studies confirmed that these belonged to rhombohedral perovskite structure associated with R3c space group. The dielectric properties of the ceramic samples as a function of frequency (100 Hz-10 MHz) and temperature (30 °C-250 °C) were studied. The dielectric constant increased while the loss decreased with the increase of Pr content. Dielectric dispersion in these samples was found to be poly dispersive Debye type relaxation as confirmed by invoking Cole-Cole relation. Impedance spectroscopy was employed to determine the electrical parameters associated with the grain and grain boundaries. Grain and grain boundary resistances were found to decrease with the increase of temperature for all the samples under study. The activation energies for the dielectric relaxation were evaluated by electric modulus spectra and these increase with the increase of Pr dopant level. The frequency dependent conductivity at various temperatures demonstrated the involvement of correlated barrier hopping conduction mechanism. The electrical conduction in these ceramics was ascribed to long and short range migration of oxygen ion vacancies as demonstrated by temperature dependent ac conductivity studies.

  2. Effect of nitrogen flow ratio on structure and properties of zirconium nitride films on Si(100) prepared by ion beam sputtering

    Indian Academy of Sciences (India)

    Shahab Norouzian; Majid Mojtahedzadeh Larijani; Reza Afzalzadeh

    2012-10-01

    In this study, zirconium nitride thin films were deposited on Si substrates by ion beam sputtering (IBS). Influence of N2/(N2+Ar) on the structural and physical properties of the films has been investigated with respect to the atomic ratio between nitrogen and zirconium. It was found that the thickness of layers decreased by increasing the F(N2). Moreover, crystalline plane peaks such as (111), (200) and (220) with (111) preferred orientation were observed due to strain energy which associate with (111) orientation in ZrN. Also, the fluctuation in nitrogen flow ratio results in colour and electrical resistivity of films.

  3. New Progress in the Preparation of Sintering and Application of Boron Carbide Ceramics%碳化硼陶瓷的烧结与应用新进展

    Institute of Scientific and Technical Information of China (English)

    杨亮亮; 谢志鹏; 刘维良; 魏红康; 赵琳; 宋明

    2015-01-01

    碳化硼陶瓷具有高硬度、高弹性模量、耐磨损、耐腐蚀等优点,是一种综合性能优异的结构材料。碳化硼陶瓷可通过有效添加剂、适当的温度与压力等条件实现致密化烧结,从而提高其综合性能,因此碳化硼的致密化烧结是其关键技术。本文论述了碳化硼陶瓷致密化烧结工艺的基本原理及烧结方法,在此基础上总结了碳化硼陶瓷在陶瓷装甲、核能和耐磨技术等重要领域的应用。%Boron carbide ceramics are typical structural materials with excellent comprehensive properties, due to their high hardness, high elastic modulus, excellent resistance to wear and corrosion, as well as other advantages. The densiifcation of boron carbide ceramics can be realized by effective additives, appropriate temperature and pressure to improve their mechanical behaviors. Thus, the sintering and densiifcation are the key steps in the entire preparing process. Here, the basic principle and routes of the sintering of boron carbide ceramics are summarized, and their applications in the ifeld of armor, nuclear power, and abrasives are presented.

  4. Preparation and properties of nanophase (Ce, Zr, PrO2-doped alumina coating on cordierite ceramic honeycomb for three-way catalysts

    Directory of Open Access Journals (Sweden)

    Jiuying Tian

    2012-03-01

    Full Text Available Nanophase (Ce, Zr, PrO2-doped alumina coatings were prepared by impregnating the cordierite ceramic honeycomb in the sol or in the slurry of already calcined powder, respectively. The effects of preparation methods on the crystal phase, texture, oxygen storage capacity (OSC, reducibility, surface morphology and thermal stability of coatings were investigated by X-ray diffraction (XRD, the Brunauer Emmet Teller (BET method, the oxygen pulsing technique, H2-temperature-programmed reduction (H2-TPR and scanning electron microscopy (SEM. These nanophase (Ce, Zr, PrO2-doped alumina coatings were used as supports to prepare Pd-only three-way catalysts, and evaluated with respect to catalytic activities. The results indicate that the nanophase (Ce, Zr, PrO2-doped alumina coatings prepared by the two methods have high thermal stability. However, the coating derived from the sol shows better crystalline structure, texture, reducibility and oxygen storage capacity than the coating derived from the slurry. SEM observation shows that the morphology of the coating derived from the sol is uniform and smooth. The Pd-only catalyst derived from the sol exhibits high three-way catalytic activity at low temperature and thermal stability, suggesting a great potential for applications.

  5. Preparation and properties of nanophase (Ce, Zr, Pr)O{sub 2}-doped alumina coating on cordierite ceramic honeycomb for three-way catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Tian, Jiuying; Lu, Jusheng [School of Chemistry and Chemical Engineering, Jiangsu Key Laboratory of Green Synthetic Chemistry for Functional Materials, Xuzhou Normal University, Xuzhou P.R. (China)

    2012-01-15

    Nanophase (Ce, Zr, Pr)O{sub 2}-doped alumina coatings were prepared by impregnating the cordierite ceramic honeycomb in the sol or in the slurry of already calcined powder, respectively. The effects of preparation methods on the crystal phase, texture, oxygen storage capacity (OSC), reducibility, surface morphology and thermal stability of coatings were investigated by X-ray diffraction (XRD), the Brunauer Emmet Teller (BET) method, the oxygen pulsing technique, H2-temperature-programmed reduction (H2-TPR) and scanning electron microscopy (SEM). These nanophase (Ce, Zr, Pr)O{sub 2}-doped alumina coatings were used as supports to prepare Pd-only three-way catalysts, and evaluated with respect to catalytic activities. The results indicate that the nanophase (Ce, Zr, Pr)O{sub 2}-doped alumina coatings prepared by the two methods have high thermal stability. However, the coating derived from the sol shows better crystalline structure, texture, reducibility and oxygen storage capacity than the coating derived from the slurry. SEM observation shows that the morphology of the coating derived from the sol is uniform and smooth. The Pd-only catalyst derived from the sol exhibits high three-way catalytic activity at low temperature and thermal stability, suggesting a great potential for applications. (author)

  6. UN{sub 2−x} layer formed on uranium metal by glow plasma nitriding

    Energy Technology Data Exchange (ETDEWEB)

    Long, Zhong [China Academy of Engineering Physics, P.O. Box 919-71, Mianyang 621907 (China); Hu, Yin [Science and Technology on Surface Physics and Chemistry Laboratory, P.O. Box 718-35, Mianyang 621907 (China); Chen, Lin [China Academy of Engineering Physics, P.O. Box 919-71, Mianyang 621907 (China); Luo, Lizhu [Science and Technology on Surface Physics and Chemistry Laboratory, P.O. Box 718-35, Mianyang 621907 (China); Liu, Kezhao, E-mail: liukz@hotmail.com [Science and Technology on Surface Physics and Chemistry Laboratory, P.O. Box 718-35, Mianyang 621907 (China); Lai, Xinchun, E-mail: lai319@yahoo.com [Science and Technology on Surface Physics and Chemistry Laboratory, P.O. Box 718-35, Mianyang 621907 (China)

    2015-01-25

    Highlights: • We used a very simple method to prepare nitride layer on uranium metal surface. • This modified layer is nitrogen-rich nitride, which should be written as UN{sub 2−x}. • TEM images show the nitride layer is composed of nano-sized grains. • XPS analysis indicates there is uranium with abnormal low valence in the nitride. - Abstract: Glow plasma nitriding is a simple and economical surface treatment method, and this technology was used to prepare nitride layer on the surface of uranium metal with thickness of several microns. The composition and structure of the nitride layer were analyzed by AES and XRD, indicating that this modified layer is nitrogen-rich uranium nitride, which should be written as UN{sub 2−x}. TEM images show the nitride layer is composed of nano-sized grains, with compact structure. And XPS analysis indicates there is uranium with abnormal low valence existing in the nitride. After the treated uranium storage in air for a long time, oxygen just entered the surface several nanometers, showing the nitride layer has excellent oxidation resistance. The mechanism of nitride layer formation and low valence uranium appearance is discussed.

  7. Growth of gallium nitride and indium nitride nanowires on conductive and flexible carbon cloth substrates.

    Science.gov (United States)

    Yang, Yi; Ling, Yichuan; Wang, Gongming; Lu, Xihong; Tong, Yexiang; Li, Yat

    2013-03-07

    We report a general strategy for synthesis of gallium nitride (GaN) and indium nitride (InN) nanowires on conductive and flexible carbon cloth substrates. GaN and InN nanowires were prepared via a nanocluster-mediated growth method using a home built chemical vapor deposition (CVD) system with Ga and In metals as group III precursors and ammonia as a group V precursor. Electron microscopy studies reveal that the group III-nitride nanowires are single crystalline wurtzite structures. The morphology, density and growth mechanism of these nanowires are determined by the growth temperature. Importantly, a photoelectrode fabricated by contacting the GaN nanowires through a carbon cloth substrate shows pronounced photoactivity for photoelectrochemical water oxidation. The ability to synthesize group III-nitride nanowires on conductive and flexible substrates should open up new opportunities for nanoscale photonic, electronic and electrochemical devices.

  8. Evaluation and comparison of the effect of different surface preparations on bond strength of glass ionomer cement with nickel-chrome metal-ceramic alloy: a laboratory study.

    Science.gov (United States)

    Hasti, Kalpana; Jagadeesh, H G; Patil, Narendra P

    2011-03-01

    Retention of fixed partial dentures is mostly dependent upon the bond between metal and cement as well as cement and tooth structure. However, most of the time clinical failure of bond has been observed at metal and cement interface. The treatment of metal surface, prior to luting, plays a crucial role in bonding cement with the metal. This study is conducted to evaluate and compare the effect of different surface preparations on the bond strength of resin-modified glass ionomer cement with nickel-chromium metal ceramic alloy. Fifty caries-free extracted molar teeth were made flat until the dentin of the occlusal surface was exposed. After fabrication of the wax patterns and subsequent castings, the castings were subjected to porcelain firing cycles. The nickel-chromium metal ceramic alloy discs were also divided into five groups and subjected to various surface treatments: (1) Unsandblasted (U), (2) sandblasted (S), (3) sandblasted and treated with 10% aqueous solution of KMnO4 (SK), (4) unsandblasted and roughened with diamond abrasive points (UD) and (5) unsandblasted and roughened with diamond abrasive points and treated with 10% aqueous solution of KMnO(4) (UDK). After surface treatments, the castings were cemented using Fuji PLUS encapsulated resin-modified glass ionomer cement. The obtained values of all the groups were subjected to statistical analysis for Tensile and Shear bond strength. Different surface treatments of the metal affects the bond strength values of resin-modified glass ionomer cement when used as luting agent.

  9. Preparation of In2O3-Sr2RuErO6 Composite Ceramics by the Spark Plasma Sintering and Their Thermoelectric Performance

    Institute of Scientific and Technical Information of China (English)

    Bo Cheng; Yuanhua Lin; Jinle Lan; Yong Liu; Cewen Nan

    2011-01-01

    In1.94Zn0.03Ge0.03O3 and Sr2RuErO6 composite ceramics have been prepared by the spark plasma sintering (SPS) technique. Microstructure studies show that the Sr2RuErO6 phases are randomly dispersed in the ln1.94Zn0.03Ge0.03O3 matrix. The results show that the Seebeck coefficient increases with increasing the amount of Sr2RuErO6, while the thermal conductivity of the composite samples is lower than that of the In1.94Zn0.03Ge0.03O3 ceramic. The thermal conductivity of the 7 vol.% Sr2RuErO6 sample can decrease to 2.15 W·m-1·K-1 at 973 K, and the evaluated maximum ZT value is 0.23 for 3 vol.% Sr2RuErO6 samples at 973 K, which makes them promising materials for the thermoelectric devices.

  10. Preparation and Performance of Al2TiO5-TiO2-SiO2 Honeycomb Ceramics by Doping Rare Earth

    Institute of Scientific and Technical Information of China (English)

    Zhu Shemin; Shen Yuesong; Wang Jialei; Zhang Yandong; Liu Yayun

    2007-01-01

    A preferable honeycomb ceramics of Al2TiO5-TiO2-SiO2 doped by CeO2 and Er2O3 with high performance was prepared by means of extrusion molding and the effects of CeO2 and Er2O3 on the mechanical strength, thermal stability, and sintering temperature of ATS ceramics were mainly investigated. The exp erimental results and the microscopic analysis by scanning electron microscope, X-ray powder diffraction, and TG-DSC showed that adding CeO2 and Er2O3 into ATS could prohibit the growth of their crystal grains and make their size uniform, which finally decrease its sintering temperature, and also enhance its mechanical performance as well as thermal stability. After the reforming, ATS doped by 0.5%CeO2+0.5%Er2O3 was sintered at 1250 ℃, its bending strength reached to 177.4 MPa and thermal expansion coefficient was 3.8×10-6/℃ at 25~1000 ℃, which provided a promising basis of making monolithic honeycomb catalyst of deNOx.

  11. PREPARATION OF ALUMINIUM OXIDE CERAMIC-CURVED PIPE BY SLIP CASTING%注浆成型法制备氧化铝陶瓷弯管

    Institute of Scientific and Technical Information of China (English)

    伍协; 陈振华; 李富营

    2011-01-01

    以氧化铝为主要原料,采用注浆成型法制备氧化铝陶瓷弯管。论文比较详细地研究了pH值、颗粒级配和有机粘结剂对产品性能的影响。结果表明:当pH值为1,粘结剂为2wt%获得的泥浆粘度最小;用颗粒大小4μm的100%α-Al2O3细粉制备的氧化铝陶瓷弯管气孔率最小、表观密度最大、显微结构最理想。%Based on aluminium oxide as main raw material, aluminium oxide ceramic-curved pipe was prepared by slip casting, pH, particle grading and binder were reshearched on the performance of aluminium oxide ceramic-curved pipe in detail.The results showed that. When the pH is 1 and binder is 2wt%, the viscosity of mud is smallest. The particle grading is 4 μ m 100% a-Al2O3 powder which porosity is the smallest, apparent density is the biggest, the microstructure is the most ideal.

  12. Preparation and catalytic performance of La0.8Sr0.2CoO3 supported on the mullite fiber ceramic

    Institute of Scientific and Technical Information of China (English)

    ZENG Lingke; LIU Yanchun; DUAN Bilin; LIU Ping'an; WANG Hui; SHUI Anze

    2007-01-01

    The perovskite-type La0.8Sr0.2CoO3 supported on the mullite fiber porous ceramics was prepared by means of the impregnating method,and was then characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD);thus we can come to the conclusion that the perovskite-type composite oxidant can disperse on the surface of mullite fiber ceramics.The catalytic activity of the La0.8Sr0.2CoO3 for NO and CO was evaluated.The effect of the doped 0.1 wt-% PdCl2 on the catalytic activity of the perovskite-type La0.8Sr0.2CoO3 was also discussed.The results show that the conversion rates of NO and CO respectively reaches 74.5% and 99% at 601℃ without doped Pd,and both reach 100% at 350℃ with a little doped Pd.

  13. Preparation and characterization of porous granular ceramic containing dispersed aluminum and iron oxides as adsorbents for fluoride removal from aqueous solution.

    Science.gov (United States)

    Chen, Nan; Zhang, Zhenya; Feng, Chuanping; Zhu, Dirui; Yang, Yingnan; Sugiura, Norio

    2011-02-15

    Porous granular ceramic adsorbents containing dispersed aluminum and iron oxides were synthesized by impregnating with salt solutions followed by precipitation at 600°C. In the present work detailed studies were carried out to investigate the effect of contact time, adsorbent dose, initial solution pH and co-existing anions. Characterization studies on the adsorbent by SEM, XRD, EDS, and BET analysis were carried out to clarify the adsorption mechanism. The adsorbents were sphere in shape, 2-3mm in particle size, highly porous and showed specific surface area of 50.69 sq m/g. The fluoride adsorption capacity of prepared adsorbent was 1.79 mg/g, and the maximum fluoride removal was obtained at pH 6. Both the Langmuir and Freundlich isotherm models were found to represent the measured adsorption data well. The experimental data were well explained with pseudo-second-order kinetic model. Results from this study demonstrated potential utility of Al/Fe dispersed in porous granular ceramics that could be developed into a viable technology for fluoride removal from aqueous solution. Copyright © 2010 Elsevier B.V. All rights reserved.

  14. Ceramic technology for advanced heat engines project

    Energy Technology Data Exchange (ETDEWEB)

    1990-09-01

    The Ceramic Technology for Advanced Heat Engines Project was developed by the Department of Energy's Office of Transportation Systems in Conservation and Renewable Energy. This project was developed to meet the ceramic technology requirements of the OTT's automotive technology programs. This project is managed by ORNL and is closely coordinated with complementary ceramics tasks funded by other DOE offices, NASA, DoD, and industry. Research is discussed under the following topics; Turbomilling of SiC Whiskers; microwave sintering of silicon nitride; and milling characterization; processing of monolithics; silicon nitride matrix; oxide matrix; silicate matrix; thermal and wear coatings; joining; design; contact interfaces; time-dependent behavior; environmental effects; fracture mechanics; nondestructive evaluation; and technology transfer. References, figures, and tables are included with each topic.

  15. Ceramic design methodology and the AGT-101

    Energy Technology Data Exchange (ETDEWEB)

    Boyd, G.L.; Carruthers, W.D.; Evershed, R.J.; Kidwell, J.R.

    1985-03-01

    The Garrett/Ford Advanced Gas Turbine (AGT101) technology project has made significant progress in the areas of ceramic component design, analysis, and test evaluation using an iterative approach. Design stress limits are being defined for state-of-the-art fine ceramics with good correlation between analytical predictions and empirical results. Recent tests in both rigs and engines are demonstrating the feasibility of high temperature/strength ceramic materials in the gas turbine environment. Component transient stress fields are being defined providing the data base for lower stress/longer life component design. Thermally induced transient stresses to 220 MPa (32 ksi) in reaction bonded silicon nitride (RBSN), 310 Mpa (45 ksi) in sintered alpha silicon carbide (SASC), and 345 MPa (50 ksi) in sintered silicon nitride (SSN) have been successfully demonstrated in AGT101 component screening and qualification test rigs.

  16. Preparation of Cristobalite-based Ceramics Using the Discarded Quartz Crucible%废弃石英坩埚资源化制备方石英质瓷

    Institute of Scientific and Technical Information of China (English)

    孙健; 李家科; 王艳香; 朱海翔

    2016-01-01

    Cristobalite-based ceramics were prepared using the discarded quartz crucible , kaolin, feldspar and bauxite as raw materials .The effects of batch formula and firing temperature on phase composition , microstructure , coefficient of thermal expansion and mechanical performances of cristobalite-based ceramics were investigated by XRD , SEM, thermal dilatometer and material testing machine .The results show that cristobalite-based ceramics with good mechanical performances are obtained when discarded quartz crucible 40%, kaolin 40%, feldspar 15% and bauxite 5% at 1300 ℃ for 30 min .Bending strength and coefficient of thermal expansion of cristobalite-based ceramic are 76.45 MPa and 7.16 × 10 -6℃-1 ( RT~600 ℃) ,respectively .And thermal shock resistance (△T ) is above 180 ℃.%以废弃石英坩埚、苏州土、长石和铝矾土等为原料制备方石英质瓷。采用XRD、SEM、热膨胀仪和材料试验机等测试方法,研究了配方组成和烧成温度对方石英质瓷的物相组成、微观形貌和机械性能影响规律。结果表明:当配料配方中废弃石英坩埚40%、苏州土40%、钾长石15%和铝矾土5%,在烧成温度1300℃、保温时间30 min条件下,可以获得机械性能较佳的方石英质瓷,其弯曲强度为76.45 MPa,热稳定性△T ≥180℃,热膨胀系数为7.16×10-6℃-1( RT~600℃)。

  17. Sol-gel derived ceramics

    OpenAIRE

    1990-01-01

    The synthesis of ceramic raw materials has become an important factor in ceramic technologies. The increasing demands to the performance of ceramic compounds has caused increased activities for the preparation of tailor-made raw materials. Amongst a variety of new syntheses like flame pyrolysis, reactive spray drying, plasma or laser assisted techniques, the sol-gel process plays an important and increasing role. The process describes the building up of an inorganic (in general an oxide) netw...

  18. Methods of forming boron nitride

    Science.gov (United States)

    Trowbridge, Tammy L; Wertsching, Alan K; Pinhero, Patrick J; Crandall, David L

    2015-03-03

    A method of forming a boron nitride. The method comprises contacting a metal article with a monomeric boron-nitrogen compound and converting the monomeric boron-nitrogen compound to a boron nitride. The boron nitride is formed on the same or a different metal article. The monomeric boron-nitrogen compound is borazine, cycloborazane, trimethylcycloborazane, polyborazylene, B-vinylborazine, poly(B-vinylborazine), or combinations thereof. The monomeric boron-nitrogen compound is polymerized to form the boron nitride by exposure to a temperature greater than approximately 100.degree. C. The boron nitride is amorphous boron nitride, hexagonal boron nitride, rhombohedral boron nitride, turbostratic boron nitride, wurzite boron nitride, combinations thereof, or boron nitride and carbon. A method of conditioning a ballistic weapon and a metal article coated with the monomeric boron-nitrogen compound are also disclosed.

  19. Methods of forming boron nitride

    Energy Technology Data Exchange (ETDEWEB)

    Trowbridge, Tammy L; Wertsching, Alan K; Pinhero, Patrick J; Crandall, David L

    2015-03-03

    A method of forming a boron nitride. The method comprises contacting a metal article with a monomeric boron-nitrogen compound and converting the monomeric boron-nitrogen compound to a boron nitride. The boron nitride is formed on the same or a different metal article. The monomeric boron-nitrogen compound is borazine, cycloborazane, trimethylcycloborazane, polyborazylene, B-vinylborazine, poly(B-vinylborazine), or combinations thereof. The monomeric boron-nitrogen compound is polymerized to form the boron nitride by exposure to a temperature greater than approximately 100.degree. C. The boron nitride is amorphous boron nitride, hexagonal boron nitride, rhombohedral boron nitride, turbostratic boron nitride, wurzite boron nitride, combinations thereof, or boron nitride and carbon. A method of conditioning a ballistic weapon and a metal article coated with the monomeric boron-nitrogen compound are also disclosed.

  20. Dynamic properties of ceramic materials

    Energy Technology Data Exchange (ETDEWEB)

    Grady, D.E. [Sandia National Labs., Albuquerque, NM (United States). Experimental Impact Physics Dept.

    1995-02-01

    The present study offers new data and analysis on the transient shock strength and equation-of-state properties of ceramics. Various dynamic data on nine high strength ceramics are provided with wave profile measurements, through velocity interferometry techniques, the principal observable. Compressive failure in the shock wave front, with emphasis on brittle versus ductile mechanisms of deformation, is examined in some detail. Extensive spall strength data are provided and related to the theoretical spall strength, and to energy-based theories of the spall process. Failure waves, as a mechanism of deformation in the transient shock process, are examined. Strength and equation-of-state analysis of shock data on silicon carbide, boron carbide, tungsten carbide, silicon dioxide and aluminum nitride is presented with particular emphasis on phase transition properties for the latter two. Wave profile measurements on selected ceramics are investigated for evidence of rate sensitive elastic precursor decay in the shock front failure process.

  1. Nitride Semiconductors Handbook on Materials and Devices

    CERN Document Server

    Ruterana, Pierre; Neugebauer, Jörg

    2003-01-01

    Semiconductor components based on silicon have been used in a wide range of applications for some time now. These elemental semiconductors are now well researched and technologically well developed. In the meantime the focus has switched to a new group of materials: ceramic semiconductors based on nitrides are currently the subject of research due to their optical and electronic characteristics. They open up new industrial possibilities in the field of photosensors, as light sources or as electronic components. This collection of review articles provides a systematic and in-depth overview of t

  2. 多孔陶瓷分离膜支撑体的制备%Preparation of Porous Ceramic Separation Membrane Supports

    Institute of Scientific and Technical Information of China (English)

    刘亚会; 汪建根

    2012-01-01

    采用氧化铝为主要原料制备出多孔陶瓷分离膜支撑体,对原料粉体做了TG/DSC曲线分析.研究了支撑体的烧结温度对收缩率的影响;烧结温度、保温时间和原料粉体粒径对孔结构、孔径的影响;造孔剂用量对孔隙率的影响.结果表明:在烧结温度1 200℃,保温时间4h,造孔剂用量(即造孔剂质量占原料总质量的百分数,下同)大于20%的条件下,制备出孔径分布均匀,孔隙率大于50%,符合透水要求的多孔陶瓷分离膜支撑体.%Porous ceramic separation membrane supports are prepared using alumina fine as the main raw materials, and the TG/DSC curves of the powder of raw materials are analyzed. The effect of the supports' sintering temperature on the shrinkage rate is studied. The effects of different sintering temperature, holding time and materials powder particle size on pore structure and size of the supports are also studied. The effect of the pore former dosage on porosity is also within the scope of study. The results show that porous ceramics separation membrane supports of uniform pore size distribution and with porosity more than 50% and pervious to water can be prepared under the following optimum conditions:sintering temperature being 1 200 ℃, holding time being 4 h, and porous agent being more than 20%.

  3. 日用陶瓷的低碳制备技术%LOW-CARBON PREPARATION TECHNOLOGY OF CERAMICS

    Institute of Scientific and Technical Information of China (English)

    王慧; 刘晓红; 郑卫东; 曾令可

    2011-01-01

    Global warming has become one of the world's most pressing problems, how to effectively prevent the emission of greenhouse gases are serious challenges what countries around the worm must face. For the high energy consumption, carbon dioxide emissions large ceramic industry, to achieve low-carbon production of ceramics is an important way to improve the competitiveness of enterprises.%全球气候变暖已成为当今世界最为严峻的问题之一,如何有效地防止温室气体的排放也是世界各国必须面临的严峻挑战。对于高能耗、二氧化碳排放量较大的陶瓷行业来说,实现陶瓷的低碳生产,是提高企业竞争力的一条重要途径。

  4. Synthesis mechanism of low-voltage praseodymium oxide doped zinc oxide varistor ceramics prepared through modified citrate gel coating.

    Science.gov (United States)

    Abdullah, Wan Rafizah Wan; Zakaria, Azmi; Ghazali, Mohd Sabri Mohd

    2012-01-01

    High demands on low-voltage electronics have increased the need for zinc oxide (ZnO) varistors with fast response, highly non-linear current-voltage characteristics and energy absorption capabilities at low breakdown voltage. However, trade-off between breakdown voltage and grain size poses a critical bottle-neck in the production of low-voltage varistors. The present study highlights the synthesis mechanism for obtaining praseodymium oxide (Pr(6)O(11)) based ZnO varistor ceramics having breakdown voltages of 2.8 to 13.3 V/mm through employment of direct modified citrate gel coating technique. Precursor powder and its ceramics were examined by means of TG/DTG, FTIR, XRD and FESEM analyses. The electrical properties as a function of Pr(6)O(11) addition were analyzed on the basis of I-V characteristic measurement. The breakdown voltage could be adjusted from 0.01 to 0.06 V per grain boundary by controlling the amount of Pr(6)O(11) from 0.2 to 0.8 mol%, without alteration of the grain size. The non-linearity coefficient, α, varied from 3.0 to 3.5 and the barrier height ranged from 0.56 to 0.64 eV. Breakdown voltage and α lowering with increasing Pr(6)O(11) content were associated to reduction in the barrier height caused by variation in O vacancies at grain boundary.

  5. Cu{sub 2}ZnSnSb(S,Se,Te){sub 4} film formation from selenization of sputtered self-prepared single ceramic target

    Energy Technology Data Exchange (ETDEWEB)

    Tsega, Moges, E-mail: mogestsega@yahoo.com [Department of Physics, University of the Free State (Qwaqwa campus), Private Bag X13, Phuthaditjhaba 9866 (South Africa); Kuo, Dong-Hau [Department of Materials Science and Engineering, National Taiwan University of Science and Technology, Taipei 10607, Taiwan (China); Dejene, F.B. [Department of Physics, University of the Free State (Qwaqwa campus), Private Bag X13, Phuthaditjhaba 9866 (South Africa)

    2015-08-31

    Single-layered Cu{sub 2}ZnSnSb(S,Se,Te){sub 4}(CZTASSeTe) thin films were prepared on Mo/glass substrate by radio frequency magnetron sputtering of a self-prepared single ceramic target. Successive selenization for the as-deposited film at a substrate temperature of 200 °C in Se-atmosphere was performed at various temperatures between 400 °C and 600 °C for 1 h. Structural investigation of the grown films revealed single-phase tetragonal structure corresponding to kesterite CZTSSe. All measured samples were found to exhibit p-type conductivity. An improved grain size and crystal quality with suitable atomic ratio [Cu/(Zn + Sb + Sn) = 0.89, Zn/Sn = 1.15, and metal/(S + Se + Te) = 1.02] obtained for CZTASSeTe film selenized at 600 °C. The Hall concentration increased from 1.06 to 5.8 × 10{sup 17} cm{sup −3}, mobility increased from 2.82 to 44.3 cm{sup 2} V{sup −1} s{sup −1}, and resistivity decreased from 20.92 to 0.24 Ω cm as the precursor film is selenized to 600 °C. An enhanced Hall mobility can be ascribed to the larger grains with better crystallinity and composition in the selenized film at 600 °C. Our large grain size and maximized mobility for CZTASSeTe film at the selenization temperature of 600 °C from single ceramic target can be useful for the fabrication of the CZTASSeTe absorber layer. - Highlights: • Cu{sub 2}ZnSnSb(S,Se,Te){sub 4} thin films were deposited by sputtering single ceramic target. • Structural and electrical properties of the films are presented. • Properties of CZTASSeTe thin films were related to Se vaporization temperature. • Selenized film at 600 °C presents the best crystal quality and enhanced Hall mobility.

  6. Temperature Compensation of Aluminum Nitride Lamb Wave Resonators Utilizing the Lowest-Order Symmetric Mode

    Science.gov (United States)

    2012-12-14

    82. D. P. Morgan, Surface- Wave Devices for Signal Processing, Holland: Elsevier, 1991. 83. L. E. McNeil, M. Grimsditch, and R. H. French ... Vibrational spectroscopy of aluminum nitride,” J. Am. Ceram. Soc., vol. 76, pp. 1132–1136, May 1993. 84. K. Hashimoto, Surface Acoustic Wave Devices in...Temperature Compensation of Aluminum Nitride Lamb Wave Resonators Utilizing the Lowest-Order Symmetric Mode Chih-Ming Lin Electrical Engineering and

  7. Ceramics in nuclear waste management

    Energy Technology Data Exchange (ETDEWEB)

    Chikalla, T D; Mendel, J E [eds.

    1979-05-01

    Seventy-three papers are included, arranged under the following section headings: national programs for the disposal of radioactive wastes, waste from stability and characterization, glass processing, ceramic processing, ceramic and glass processing, leaching of waste materials, properties of nuclear waste forms, and immobilization of special radioactive wastes. Separate abstracts were prepared for all the papers. (DLC)

  8. Ceramic Technology Project semiannual progress report, October 1992--March 1993

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, D.R.

    1993-09-01

    This project was developed to meet the ceramic technology requirements of the OTS`s automotive technology programs. Although progress has been made in developing reliable structural ceramics, further work is needed to reduce cost. The work described in this report is organized according to the following work breakdown structure project elements: Materials and processing (monolithics [Si nitride, carbide], ceramic composites, thermal and wear coatings, joining, cost effective ceramic machining), materials design methodology (contact interfaces, new concepts), data base and life prediction (structural qualification, time-dependent behavior, environmental effects, fracture mechanics, nondestructive evaluation development), and technology transfer.

  9. Synthesis Mechanism of Low-Voltage Praseodymium Oxide Doped Zinc Oxide Varistor Ceramics Prepared Through Modified Citrate Gel Coating

    Directory of Open Access Journals (Sweden)

    Wan Rafizah Wan Abdullah

    2012-04-01

    Full Text Available High demands on low-voltage electronics have increased the need for zinc oxide (ZnO varistors with fast response, highly non-linear current-voltage characteristics and energy absorption capabilities at low breakdown voltage. However, trade-off between breakdown voltage and grain size poses a critical bottle-neck in the production of low-voltage varistors. The present study highlights the synthesis mechanism for obtaining praseodymium oxide (Pr6O11 based ZnO varistor ceramics having breakdown voltages of 2.8 to 13.3 V/mm through employment of direct modified citrate gel coating technique. Precursor powder and its ceramics were examined by means of TG/DTG, FTIR, XRD and FESEM analyses. The electrical properties as a function of Pr6O11 addition were analyzed on the basis of I-V characteristic measurement. The breakdown voltage could be adjusted from 0.01 to 0.06 V per grain boundary by controlling the amount of Pr6O11 from 0.2 to 0.8 mol%, without alteration of the grain size. The non-linearity coefficient, α, varied from 3.0 to 3.5 and the barrier height ranged from 0.56 to 0.64 eV. Breakdown voltage and α lowering with increasing Pr6O11 content were associated to reduction in the barrier height caused by variation in O vacancies at grain boundary.

  10. Thermal stability of nanostructured titania and titania-ceria ceramic powders prepared by the sol-gel process

    NARCIS (Netherlands)

    Koebrugge, G.W.; Winnubst, A.J.A.; Burggraaf, A.J.

    1993-01-01

    The preparation and characterisation of nanometre TiO2 powder materials, prepared by the sol-gel method, are described. Controlled hydrolysis of a titanium-2-methyl-2-butoxide precursor was applied to obtain alcosols with particles (in alcohol) smaller than 5 nm. Powders obtained from this sol were

  11. On Ceramics.

    Science.gov (United States)

    School Arts, 1982

    1982-01-01

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

  12. Subtask 6.6 - SiAION Coatings for Alkali-Resistant Silicon Nitride. Topical report

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1997-02-25

    The efficiency of a gas turbine can be improved by increasing operating temperature. Construction materials should both meet high strength requirements and exhibit hot alkali corrosion resistance. Structural ceramics based on silicon nitride are promising candidates for high temperature engineering applications because of their high strength and good resistance to corrosion. Their performance varies significantly with the mechanical properties of boundary phases which, in turn, depend on their chemical composition, thickness of the amorphous phase, and the deformation process. To make silicon nitride ceramics tough, SiAlON ceramics were developed with controlled crystallization of the amorphous grain boundary phase. Crystallization of the grain boundary glass improves the high temperature mechanical properties of silicon nitride ceramics. Thus, the knowledge of silicon oxynitride ceramics corrosion behavior in Na{sub 2}SO{sub 4} becomes important for engineers in designing appropriate part for turbines working at high temperatures. So far there has been no report concerning alkali attack on SiAlON ceramics in the presence of SO{sub 2} and chlorine in flue gas. The goal of this project was to investigate alkali corrosion of SiAlON-Y structural ceramics under combustion conditions in the presence of sodium derived components.

  13. 不同电源模式下微弧氧化制备陶瓷膜的性能对比研究%The Performances of Ceramic Membrane Prepared by Micro Arc Oxidation Under Different Power Modes

    Institute of Scientific and Technical Information of China (English)

    韩勇; 王志义

    2012-01-01

    The ceramic coatings are prepared by micro arc oxidation on the ZL102 cast aluminum alloy,in the composite electrolyte of sodium silicate,tungsten,boric acid,sodium metaaluminate,and EDTA(Ethylene Diamine Tetraacetic Acid),using alternating current(AC) power and pulse power respectively.According to the observations with scanning electron microscopy(SEM),the pores on the surface of ceramic coating prepared by AC power are less than those prepared by pulse power,and with a better ceramic membrane morphology.The corrosion resistance of the ceramic layers is analyzed in the method of electrochemical,and the ceramic coating prepared by AC power supply has a better corrosion resistance.%在硅酸钠、钨酸钠、硼酸、偏铝酸钠和乙二胺四乙酸二钠的复合电解液中,分别采用交流电源和脉冲电源,利用微弧氧化方法,在ZL102铸造铝合金上制备了陶瓷膜层。通过扫描电镜(SEM)观察,交流电源模式制备的陶瓷膜层表面孔洞少,比用脉冲电源制备的陶瓷膜形貌好。利用电化学方法分析了陶瓷层的防腐蚀性能,交流电源制备的陶瓷膜层耐腐蚀性能好。

  14. Orientation control of (K,Na)NbO3 ceramics using platelike NaNbO3 templates prepared by single-step molten salt synthesis with mixed salt

    Science.gov (United States)

    Ishii, Keisuke; Tashiro, Shinjiro

    2016-10-01

    In order to shorten the firing time for sintering textured (K,Na)NbO3 system ceramics, the fabrication method of the single-step molten salt synthesis for preparing platelike NaNbO3 single-crystal particles was improved. An uneven shape was formed on the surfaces of platelike NaNbO3 single-crystal particles obtained by single-step molten salt synthesis in the mixed salts of KCl and NaCl. Using these single-crystal particles as the templates, textured (K,Na)NbO3 ceramics were fabricated. The sinterability of the textured ceramics and their piezoelectricity were compared between two kinds of templates synthesized in the mixed salt and in the conventional NaCl salt. The diffusivity of K atoms into these templates from the matrix powder of (K,Na)NbO3 during firing was also compared.

  15. Preparation and characterization of ceramic/carbon coated Fe₃O₄ magnetic nanoparticle nanocomposite as a solid-phase microextraction adsorbent.

    Science.gov (United States)

    Heidari, Hassan; Razmi, Habib; Jouyban, Abolghasem

    2012-07-06

    A novel solid-phase microextraction (SPME) fiber based on a glass tube coated with ceramic/carbon coated Fe₃O₄ magnetic nanoparticle nanocomposite (C-Fe₃O₄/C MNP) was prepared by sol-gel technique. The carbon coated Fe₃O₄ magnetic nanoparticles were synthesized by a simple hydrothermal reaction and the resultant powder was mixed with sol-gel precursors to prepare C-Fe₃O₄/C MNP. The prepared C-Fe₃O₄/C MNP was deposited on surface of glass tubes as new substrate with a simple method. The results revealed that this procedure was a simple and reproducible technique for the preparation of SPME fibers coated with magnetic nanoparticles. The scanning electron micrographs of the fiber surface revealed a three-dimensional structure which is suitable as SPME adsorbents. Some polycyclic aromatic hydrocarbons (PAHs) were selected as model compounds for evaluating performance of the designed SPME fiber. The analytes were extracted with SPME, and desorbed using acetonitrile via ultrasonication. The extracts were analyzed by high performance liquid chromatography (HPLC) with fluorescence detection. The results demonstrated that the proposed method based on the C-Fe₃O₄/C MNP fiber had wide dynamic linear range (0.01-350 μg L⁻¹) with good linearity (R²>0.990) and low detection limits (0.7-50 pg mL⁻¹). The relative standard deviation ranged from 6.9% to 12.2% for inter-day variations. These fibers were successfully used for the analysis of spiked water samples, which demonstrating the applicability of the home-made C-Fe₃O₄/C MNP fibers.

  16. Facility for low-temperature spin-polarized-scanning tunneling microscopy studies of magnetic/spintronic materials prepared in situ by nitride molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Wenzhi; Foley, Andrew; Alam, Khan; Wang, Kangkang; Liu, Yinghao; Chen, Tianjiao; Pak, Jeongihm; Smith, Arthur R., E-mail: smitha2@ohio.edu [Department of Physics and Astronomy, Nanoscale and Quantum Phenomena Institute, Ohio University, Athens, Ohio 45701 (United States)

    2014-04-15

    Based on the interest in, as well as exciting outlook for, nitride semiconductor based structures with regard to electronic, optoelectronic, and spintronic applications, it is compelling to investigate these systems using the powerful technique of spin-polarized scanning tunneling microscopy (STM), a technique capable of achieving magnetic resolution down to the atomic scale. However, the delicate surfaces of these materials are easily corrupted by in-air transfers, making it unfeasible to study them in stand-alone ultra-high vacuum STM facilities. Therefore, we have carried out the development of a hybrid system including a nitrogen plasma assisted molecular beam epitaxy/pulsed laser epitaxy facility for sample growth combined with a low-temperature, spin-polarized scanning tunneling microscope system. The custom-designed molecular beam epitaxy growth system supports up to eight sources, including up to seven effusion cells plus a radio frequency nitrogen plasma source, for epitaxially growing a variety of materials, such as nitride semiconductors, magnetic materials, and their hetero-structures, and also incorporating in situ reflection high energy electron diffraction. The growth system also enables integration of pulsed laser epitaxy. The STM unit has a modular design, consisting of an upper body and a lower body. The upper body contains the coarse approach mechanism and the scanner unit, while the lower body accepts molecular beam epitaxy grown samples using compression springs and sample skis. The design of the system employs two stages of vibration isolation as well as a layer of acoustic noise isolation in order to reduce noise during STM measurements. This isolation allows the system to effectively acquire STM data in a typical lab space, which during its construction had no special and highly costly elements included, (such as isolated slabs) which would lower the environmental noise. The design further enables tip exchange and tip coating without

  17. Facility for low-temperature spin-polarized-scanning tunneling microscopy studies of magnetic/spintronic materials prepared in situ by nitride molecular beam epitaxy.

    Science.gov (United States)

    Lin, Wenzhi; Foley, Andrew; Alam, Khan; Wang, Kangkang; Liu, Yinghao; Chen, Tianjiao; Pak, Jeongihm; Smith, Arthur R

    2014-04-01

    Based on the interest in, as well as exciting outlook for, nitride semiconductor based structures with regard to electronic, optoelectronic, and spintronic applications, it is compelling to investigate these systems using the powerful technique of spin-polarized scanning tunneling microscopy (STM), a technique capable of achieving magnetic resolution down to the atomic scale. However, the delicate surfaces of these materials are easily corrupted by in-air transfers, making it unfeasible to study them in stand-alone ultra-high vacuum STM facilities. Therefore, we have carried out the development of a hybrid system including a nitrogen plasma assisted molecular beam epitaxy/pulsed laser epitaxy facility for sample growth combined with a low-temperature, spin-polarized scanning tunneling microscope system. The custom-designed molecular beam epitaxy growth system supports up to eight sources, including up to seven effusion cells plus a radio frequency nitrogen plasma source, for epitaxially growing a variety of materials, such as nitride semiconductors, magnetic materials, and their hetero-structures, and also incorporating in situ reflection high energy electron diffraction. The growth system also enables integration of pulsed laser epitaxy. The STM unit has a modular design, consisting of an upper body and a lower body. The upper body contains the coarse approach mechanism and the scanner unit, while the lower body accepts molecular beam epitaxy grown samples using compression springs and sample skis. The design of the system employs two stages of vibration isolation as well as a layer of acoustic noise isolation in order to reduce noise during STM measurements. This isolation allows the system to effectively acquire STM data in a typical lab space, which during its construction had no special and highly costly elements included, (such as isolated slabs) which would lower the environmental noise. The design further enables tip exchange and tip coating without

  18. Alternative Liquid Fuel Effects on Cooled Silicon Nitride Marine Gas Turbine Airfoils

    Energy Technology Data Exchange (ETDEWEB)

    Holowczak, J.

    2002-03-01

    With prior support from the Office of Naval Research, DARPA, and U.S. Department of Energy, United Technologies is developing and engine environment testing what we believe to be the first internally cooled silicon nitride ceramic turbine vane in the United States. The vanes are being developed for the FT8, an aeroderivative stationary/marine gas turbine. The current effort resulted in further manufacturing and development and prototyping by two U.S. based gas turbine grade silicon nitride component manufacturers, preliminary development of both alumina, and YTRIA based environmental barrier coatings (EBC's) and testing or ceramic vanes with an EBC coating.

  19. [Key points in anterior esthetic restorations with all ceramic].

    Science.gov (United States)

    Luo, Xiaoping; Qian, Dongdong; Yuan, Yu; Meng, Xiangfeng

    2013-04-01

    This paper introduced the key points in fabricating anterior esthetic restorations with all ceramic materials, including pre-operative smile design, standard tooth preparation, provisional restoration fabrication, all ceramic materials selection, all ceramic restoration bonding, ceramic crack and fracture prevention. And then, the authors summarized and reviewed the clinical common problems in anterior esthetic restorations.

  20. Preparation and performance of ZnO nanowires modified carbon fibers reinforced NiFe{sub 2}O{sub 4} ceramic matrix composite

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Lei, E-mail: jwlzl77@163.com; Jiao, Wanli

    2013-12-25

    Highlights: •Unlike existing chemical modification, the liquid growth remains fiber’s strength. •ZnO nanowires array are grown on carbon fibers with controllable morphology. •ZnO nanowires array modified carbon fibers can reinforce the strength of ceramic matrix composite. •This research will provide a means to produce multifunctional composites. -- Abstract: The surface of carbon fibers was modified by ZnO nanowires using the liquid growth method. NiFe{sub 2}O{sub 4} ceramic matrix composites reinforced by the modified carbon fibers were prepared by a high-temperature solid-state reaction method at 1300 °C for 5 h in N{sub 2} atmosphere. The influences of modified carbon fibers on the mechanical performances of NiFe{sub 2}O{sub 4} composites were investigated. The crystal structure of modified carbon fibers and the morphology of modified carbon fibers surface and the NiFe{sub 2}O{sub 4} composites fracture cross-section were observed by meaning of X-ray diffraction (XRD) and scanning electron microscope (SEM), respectively. The results showed that hexagonal wurtzite ZnO nanowires array grew from the surface of carbon fibers vertically, with nanowires diameters ranging from 170 nm to 380 nm and lengths up to 2.8 μm. Unlike existing chemical modification and high temperature oxidation method, the liquid growth allowed morphology control and maintained the single fiber tensile strength substantially unchanged under certain growth procedures. Compared to pure NiFe{sub 2}O{sub 4} ceramic and bare carbon fibers reinforced NiFe{sub 2}O{sub 4} composite, the bending strength of NiFe{sub 2}O{sub 4} composite reinforced with ZnO nanowires surface modified carbon fibers was shown to increase by up to 70% and 45%, respectively. The development of an interphase offering control over the morphology will provide a means to produce multifunctional composites.

  1. Preparation of Ceramic Tiles with Electrolytic Manganese and Waste Glass Admicture%利用电解锰渣-废玻璃制备陶瓷砖

    Institute of Scientific and Technical Information of China (English)

    冉岚; 刘少友; 杨红芸; 张扬

    2015-01-01

    In order to solve the pollution of electrolytic manganese residue, the environment and improve the utilization of manganese slag, the preparation of ceramic tiles was studied by using electrolytic manganese and waste glass as the main raw material. The basic formulas were obtained in terms of the CaO-Al2O3-SiO2 termary system phase diagram, then they were optimized through a lot of experiments and the text of crystallization. The results indicated that the calcining temperature was 950℃electrolysis manganese when adding 32%electrolytic manganese and 10 g waste glass, the main crystals composition were quartz, cristobalite, mullite and anorthite, the shrinkage is 0.27%, it complied with the standard of GB/T 4100-2006 ceramic tiles.%为了解决电解锰渣对环境的污染,提高锰渣的利用率,研究了以电解锰渣-废玻璃为主要原料制备陶瓷砖。首先利用CaO-Al2O3-SiO2三相图获得初始配方,然后进行了大量的实验,并对产品的晶相进行分析,确定陶瓷砖的最优配方。结果证明,锰渣的添加量为32%,废玻璃含量为25%,煅烧温度为950℃,煅烧时间为30 min时,陶瓷坯的主晶相为石英、钙长石、莫来石和方石英,收缩率为0.27%,符合GB/T 4100-2006陶瓷砖的标准。

  2. Preparation and characterization of TiO2 and Si-doped octacalcium phosphate composite coatings on zirconia ceramics (Y-TZP) for dental implant applications

    Science.gov (United States)

    Bao, Lei; Liu, Jingxiao; Shi, Fei; Jiang, Yanyan; Liu, Guishan

    2014-01-01

    In order to prevent the low temperature degradation and improve the bioactivity of zirconia ceramic implants, TiO2 and Si-doped octacalcium phosphate composite coating was prepared on zirconia substrate. The preventive effect on low temperature degradation and surface morphology of the TiO2 layer were studied. Meanwhile, the structure and property changes of the bioactive coating after doping Si were discussed. The results indicate that the dense TiO2 layer, in spite of some microcracks, inhibited the direct contact of the water vapor with the sample's surface and thus prevented the low temperature degradation of zirconia substrates. The acceleration aging test shows that the ratio of the monoclinic phase transition decreased from 10% for the original zirconia substrate to 4% for the TiO2-coated substrate. As to the Si-doped octacalcium phosphate coating prepared by biomimetic method, the main phase composition of the coating was octacalcium phosphate. The morphology of the coating was lamellar-like, and the surface was uniform and continuous with no cracks being observed. It is suggested that Si was added into the coating both through substituting for PO43- and doping as NaSiO3.

  3. Bactericidal activity and silver release of porous ceramic candle filter prepared by sintering silica with silver nanoparticles/zeolite for water disinfection

    Science.gov (United States)

    Trinh Nguyen, Thuy Ai; Phu Dang, Van; Duy Nguyen, Ngoc; Le, Anh Quoc; Thanh Nguyen, Duc; Hien Nguyen, Quoc

    2014-09-01

    Porous ceramic candle filters (PCCF) were prepared by sintering silica from rice husk with silver nanoparticles (AgNPs)/zeolite A at about 1050 °C to create bactericidal PCCF/AgNPs for water disinfection. The silver content in PCCF/AgNPs was of 300-350 mg kg-1 determined by inductively coupled plasma-atomic emission spectroscopy (ICP-AES) and the average pore size of PCCF/AgNPs was of 50-70 Å measured by Brunauer-Emmett-Teller (BET) method. The bactericidal activity and silver release of PCCF/AgNPs have been investigated by flow test with water flow rate of 5 L h-1 and initial inoculation of E. coli in inlet water of 106 CFU/100 mL. The volume of filtrated water was collected up to 500 L. Results showed that the contamination of E. coli in filtrated water was water was low, far under the WHO guideline of 100 μg L-1 at maximum for drinking water. Based on the content of silver in PCCF/AgNPs and in filtrated water, it was estimated that one PCCF/AgNPs could be used to filtrate of ˜100 m3 water. Thus, as-prepared PCCF/AgNPs releases low content of silver into water and shows effectively bactericidal activity that is promising to apply as point-of-use water treatment technology for drinking water disinfection.

  4. Research on annihilation of cancer cells by glass-ceramics for cancer treatment with external magnetic field. I. Preparation and cytotoxicity.

    Science.gov (United States)

    Oh, S H; Choi, S Y; Lee, Y K; Kim, K N

    2001-03-05

    Ferrimagnetic glass-ceramics were prepared as a heating mediator for hyperthermia in cancer treatment. We prepared glasses in the system 40Fe2O3-30CaO-30SiO2 and precipitated ferrimagnetic crystallites through controlled two-step heat treatment. To improve the heating capability of ferrimagnetic crystallites, i.e., magnetite, generation of other crystalline phases should be prohibited. The addition of each 1% of P2O5 and B2O3 led to lowering the crystallization temperature of magnetite, which was useful to suppress the other crystalline formation. The maximum nucleating and crystal growth rates were 20.47 x 10(6)/mm2 x s at 690 degrees C and 8.125 nm/min(0.5) at 940 degrees C, respectively. After nucleation at 690 degrees C for 60 min prior to crystal growth at 940 degrees C for 2 h, samples exhibited the following properties: crystallite size of 90.5 nm, the maximum volumetric fraction of 31.1%, and saturation magnetization of 100 emu/cm2. The coercive forces were ranged between 382.0 and 388.2 Oe in all heat-treatment conditions. As a result of a preclinical evaluation of biocompatibility by agar diffusion test with L929 cells, both as-quenched and heat-treated glasses could be biocompatible.

  5. Use the Polishing Tile Waste to Prepare Thermal Insulation Ceramic Tile%抛光废料制备隔热保温陶瓷砖

    Institute of Scientific and Technical Information of China (English)

    刘华锋; 曾令可; 王慧; 冼志勇

    2014-01-01

    抛光废渣产生量大,回收利用率低,研究大量利用抛光废渣的新途径不仅能解决抛光废渣的处理问题,也将带来巨大的经济效益。本文分析了利用抛光废渣制备隔热保温陶瓷砖的背景、废弃原料处理、抛光渣发泡原理、制备工艺、性能影响因素等。%The production of polishing tile waste is so huge ,while with a low Recovery utilization rate. Research a new way that consuming a huge mass of polishing tile waste can not only solve the problem of waste processing ,but also produce huge economic benefits. This paper analyzed the back-ground ,the waste raw material processing ,the foaming principle ,the preparation technology ,the properties affecting factors of Preparation of Thermal Insulation ceramic tile with Polishing tile Waste.

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

    Science.gov (United States)

    Mahfoz Kotb, H.; Ahmad, Mohamad M.

    2016-12-01

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

  7. Boron nitride nanotubes radiolabeled with ⁹⁹mTc: preparation, physicochemical characterization, biodistribution study, and scintigraphic imaging in Swiss mice.

    Science.gov (United States)

    Soares, Daniel Crístian Ferreira; Ferreira, Tiago Hilário; Ferreira, Carolina de Aguiar; Cardoso, Valbert Nascimento; de Sousa, Edésia Martins Barros

    2012-02-28

    In the present study, boron nitride nanotubes (BNNTs) were synthesized from an innovative process and functionalized with a glycol chitosan polymer in CDTN (Centro de Desenvolvimento da Tecnologia Nuclear) laboratories. As a means of studying their in vivo biodistribution behavior, these nanotubes were radiolabeled with (99m)Tc and injected in mice. Their size, distribution, and homogeneity were determined by photon correlation spectroscopy (PCS), while their zeta potential was determined by laser Doppler anemometry. The morphology and structural organization were evaluated by scanning electron microscopy (SEM). The functionalization in the nanotubes was evaluated by thermogravimetry analysis (TGA) and Fourier transformer infrared spectroscopy. The results showed that BNNTs were obtained and functionalized successfully, reaching a mean size and dispersity deemed adequate for in vivo studies. The BNNTs were also evaluated by ex vivo biodistribution studies and scintigraphic imaging in healthy mice. The results showed that nanostructures, after 24h, having accumulated in the liver, spleen and gut, and eliminated via renal excretion. The findings from this study reveal a potential application of functionalized BNNTs as new potential drugs or radioisotope nanocarriers to be applied in therapeutic procedures.

  8. Microstructures and mechanical properties of carbon fiber reinforced silicon nitride composites prepared by gel-casting%凝胶注模法制备碳纤维/氮化硅复合材料的微观结构与力学性能

    Institute of Scientific and Technical Information of China (English)

    黄龙; 肖鹏; 罗衡; 周伟

    2014-01-01

    通过化学气相沉积在短碳纤维表面制备C/SiC复合涂层,然后采用凝胶注模法制备纤维体积分数分别为2%和4%的Cf/Si3N4复合材料,利用X射线衍射与扫描电镜对该材料的物相与组织结构进行分析,研究短碳纤维对Si3N4陶瓷力学性能的影响。结果表明:随碳纤维体积分数增加,Cf/Si3N4复合材料的密度和抗弯强度降低,但断裂韧性明显提高。当纤维体积分数为4%时,材料的断裂韧性达到8.91 MPa·m1/2,比氮化硅陶瓷提高1.6倍,材料主要由长柱状的β-Si3N4基体、C/SiC涂层及碳纤维组成,碳纤维表面的C/SiC双涂层可防止高温下碳纤维与氮化硅基体发生反应,使碳纤维与氮化硅基体界面结合良好,以提高材料韧性并保证有合适的强度,满足功能材料在一定条件下的使用要求。%Carbon fiber reinforced silicon nitride matrix composites (Cf/Si3N4) with short carbon fibers of 0%,2% and 4%(volume fraction)were prepared by gel-casting . The phase composition and microstructure of Cf/Si3N4 were studied by XRD and SEM. The effect of volume fraction of short carbon fiber on mechanical properties of the composites was investigated. The results show that: with increasing the content of short carbon fiber, the density and bending strength of Cf/Si3N4composites decrease, while the fracture toughness increases obviously. The fracture toughness is 8.91 MPa·m1/2 which is 1.6 times higher than that of single phase silicon nitride ceramics when the volume fraction of short carbon fibers is 4%. The composite is mainly composed of long cylindricalβ-Si3N4 matrix, C/SiC coatings and carbon fiber. The C/SiC double coating can prevent the reaction between carbon fiber and SiC matrix, which is beneficial to the bonding of the interface, and then increasing toughness and providing suitable strength.

  9. Synthesis of Sc{sub 2}O{sub 3} powders for preparation of transparent ceramics; Synthese de poudres de Sc{sub 2}O{sub 3} destinees a l'elaboration d'une ceramique transparente

    Energy Technology Data Exchange (ETDEWEB)

    Bravo, A.C.; Longuet, L.; Autissier, D. [CEA Centre d' Etudes du Ripault, 37 - Tours (France); Baumard, J.F. [Laboratoire Science des Procedes Ceramiques et de Traitements de Surfaces, SPCTS, UMR CNRS 6638, 87 - Limoges (France)

    2007-07-01

    Different precursors have been prepared by precipitation from scandium nitrates salts using ammonium hydrogeno-carbonate as precipitating agent. The influence of the precipitation technique, of the preparation temperature and of the 'precipitating agent/Sc{sup 3+}' molar ratio on the characteristics (nature, grain size...) of the synthesized precursors has been observed. A heat treatment at 700 C of these precursors has allowed to obtain thin and homogeneous Sc{sub 2}O{sub 3} powders well adapted for transparent ceramics preparation. (O.M.)

  10. Preparation, microstructure and oxidation resistance of SiCN ceramic matrix composites with glass-like carbon interface

    Directory of Open Access Journals (Sweden)

    Yi Xia

    2009-02-01

    Full Text Available Glass-like carbon (GC interface was successfully introduced into carbon fiber-reinforced SiCN ceramic matrix composite (C/GC/SiCN by polymer infiltration and pyrolysis using phenolic resin as precursor. In order to highlight the Oxidation resistance of GC interface, the Oxidation behavior of GC, carbon fiber (Cf containing approximately 0.3 μm GC coating and C/GC/SiCN was investigated by means of weight changes and residual strength ratio before and after oxidizing, and the results were also compared with that of Cf containing Pyrocarbon (PyC coating and C/PyC/SiCN composite. Scanning electron microscopy displays homogeneous, adherent GC coating on Cf. Weight loss rate of Cf containing GC coating is lower than that of Cf containing PyC coating. The residual stress ratio of C/GC/SiCN was higher than that of C/PyC/SiCN. The results indicate that GC interface can improve anti-oxidation of Cf-reinforced composite than PyC interface.

  11. Preparation, Characterization and Dielectric Properties of Ba6Mg0.67Nb9.33O30 Ceramic

    Institute of Scientific and Technical Information of China (English)

    ZHANG Hui; LIU Zaiquan; LIU Hongfei; FANG Liang; LIU Hanxing

    2005-01-01

    A new niobate Ba6Mg0.67Nb9.33O30 was synthesized in the BaO-MgO-Nb2O5 system by solid state reaction at 1350 ℃ for 48 h . The structure and dielectric properties of Ba6Mg0.67Nb9.33O30 were determined by X-ray powder diffraction, scanning electron microscopy and dielectric measurements. The results show that Ba6Mg0.67 Nb9.33O30 belongs to ferroelectric phase of filled tetragonal tungsten bronze structure at room temperature with unit cell parameters: a = 1.26052(4) nm, c = 0.40045(2) nm, space group P4bm, calculated density 5.707g·cm-3.Ba6Mg0.67Nb9.33O30 belongs to relaxor ferroelectrics undergoing diffusive phase transition,and the transition temperature ( Tc ) is 30 ℃ observed at 10 kHz. At room temperature, Ba6Mg0.67Nb9.33O30ceramic has a high dielectric constant 850 at 1 MHz and a low dielectric loss of 0. 0052.

  12. Synthesis of hexagonal boron nitride graphene-like few layers

    Science.gov (United States)

    Yuan, S.; Toury, B.; Journet, C.; Brioude, A.

    2014-06-01

    Self-standing highly crystallized hexagonal boron nitride (h-BN) mono-, bi- and few-layers have been obtained for the first time via the Polymer Derived Ceramics (PDCs) route by adding lithium nitride (Li3N) micropowders to liquid-state polyborazylene (PBN). Incorporation of Li3N as a crystallization promoter allows the onset of crystallization of h-BN at a lower temperature (1200 °C) than under classical conditions (1800 °C). The hexagonal structure was confirmed by both electron and X-ray diffraction.Self-standing highly crystallized hexagonal boron nitride (h-BN) mono-, bi- and few-layers have been obtained for the first time via the Polymer Derived Ceramics (PDCs) route by adding lithium nitride (Li3N) micropowders to liquid-state polyborazylene (PBN). Incorporation of Li3N as a crystallization promoter allows the onset of crystallization of h-BN at a lower temperature (1200 °C) than under classical conditions (1800 °C). The hexagonal structure was confirmed by both electron and X-ray diffraction. Electronic supplementary information (ESI) available: See DOI: 10.1039/c4nr01017e

  13. Engineered Nano-scale Ceramic Supports for PEM Fuel Cells. Tech Team Meeting Presentaion

    Energy Technology Data Exchange (ETDEWEB)

    Brosha, Eric L. [Los Alamos National Laboratory; Elbaz Alon, Lior [Los Alamos National Laboratory; Henson, Neil J. [Los Alamos National Laboratory; Rockward, Tommy [Los Alamos National Laboratory; Roy, Aaron [University of New Mexico; Serov, Alexey [University of New Mexico; Ward, Timothy [University of New Mexico

    2012-08-13

    Catalyst support durability is currently a technical barrier for commercialization of polymer electrolyte membrane (PEM) fuel cells, especially for transportation applications. Degradation and corrosion of the conventional carbon supports leads to losses in active catalyst surface area and, consequently, reduced performance. As a result, the goal of this work is to develop support materials that interact strongly with Pt, yet sustain bulk-like catalytic activities with very highly dispersed particles. Ceramic materials that are prepared using conventional solid-state methods have large grain sizes and low surface areas that can only be minimally ameliorated through grinding and ball milling. Other synthesis routes to produce ceramic materials must be investigated and utilized in order to obtain desired surface areas. In this work, several different synthesis methods are being utilized to prepare electronically conductive ceramic boride, nitride, and oxide materials with high surface areas and have the potential for use as PEMFC catalyst supports. Polymer-assisted deposition (PAD) and aerosol-through plasma (A-T-P) torch are among several methods used to obtain ceramic materials with surface areas that are equal to, or exceed Vulcan XC-72R supports. Cubic Mo-based ceramic phases have been prepared with average XRD-determined crystallite sizes as low as 1.6 nm (from full profile, XRD fitting) and a BET surface area exceeding 200 m{sup 2}/g. Additionally, black, sub-stoichiometric TiO{sub 2-x}, have been prepared with an average crystallite size in the 4 nm range and surface areas exceeding 250 m{sup 2}/gr. Pt disposition using an incipient wetness approach produced materials with activity for hydrogen redox reactions and ORR. Cyclic voltammetry data will be shown for a variety of potential Pt/ceramic catalysts. Initial experiments indicate enhanced Pt metal-support interactions as well. Plane wave periodic density functional calculations (VASP) are being used to

  14. Gallium nitride optoelectronic devices

    Science.gov (United States)

    Chu, T. L.; Chu, S. S.

    1972-01-01

    The growth of bulk gallium nitride crystals was achieved by the ammonolysis of gallium monochloride. Gallium nitride single crystals up to 2.5 x 0.5 cm in size were produced. The crystals are suitable as substrates for the epitaxial growth of gallium nitride. The epitaxial growth of gallium nitride on sapphire substrates with main faces of (0001) and (1T02) orientations was achieved by the ammonolysis of gallium monochloride in a gas flow system. The grown layers had electron concentrations in the range of 1 to 3 x 10 to the 19th power/cu cm and Hall mobilities in the range of 50 to 100 sq cm/v/sec at room temperature.

  15. Preparation of Nd-doped gadolinium-gallium garnet laser ceramic powder by sol-gel method

    Institute of Scientific and Technical Information of China (English)

    YAO Yan-ping; LIU Jing-he

    2006-01-01

    Preparation of Nd3+:Gd3Ga5O12 polycrystalline material by sol-gel method was preparated in this paper.The structure and the pattern of the sample were analyzed by thermogravimetric analysis and differential thermal analysis(TG-DTA),Infrared spectrum,XRD,TEM and electron spectrum,which indicated that the powder with good characteristics of 70-100 nm can be obtained by sintering at 1 000℃.It was shown that the chemical composition of the sample was agreed with experimental requirements by electron spectrum analysis.

  16. 苎麻织物制备多孔氧化铝遗态陶瓷%Preparation of porous alumina ceramics by morph-genetic process

    Institute of Scientific and Technical Information of China (English)

    王蒙; 刘江南; 贺辛亥; 王俊勃; 江燕; 李冰

    2014-01-01

    以苎麻织物为生物模板,聚合氯化铝溶液为浸渍液,经浸渍、干燥获得前驱体,将前驱体经有氧煅烧制备出具有苎麻织物结构的 Al2 O3遗态材料.采用 TG 、XRD 、TEM 、SEM 和比表面积等检测技术,分别对材料的热失重、物相组成和显微结构进行了表征与分析.结果表明,1200℃下制备的 Al2 O3陶瓷成功地保留了苎麻织物的结构.不同浓度下制得的 Al2 O3具有不同的微观形貌.Al2 O3比表面积为9.94~30.07m 2・ g-1;平均孔径为5.02~6.2nm .%Based on bio-templating ,a new kind of Al2 O3 morph-genetic ceramic materials with the struc-ture of ramie fibers was prepared by calcining under aerobic environment from precursors ,which were prepared by impregnating poly-aluminum chloride solution .The phase composition and micro-structure of the materials were analyzed and characterized respectively by using thermo -gravimetric analysis (TG) ,X-ray diffraction (XRD) ,transmission electron microscope (TEM ) ,scanning electron micro-scope (SEM ) and H-2000PS2 system .The experimental results show that the Al2 O3 morph-genetic ce-ramic successfully reserved the ramie fibers structure .Under different concentration of aluminum ,the products have different morphology . BET test shows that the specific surface area is 9.94 ~30.07m2 ・ g- 1 and the average pore diameter is 5.02 ~ 6.2nm .

  17. Boron nitride composites

    Science.gov (United States)

    Kuntz, Joshua D.; Ellsworth, German F.; Swenson, Fritz J.; Allen, Patrick G.

    2016-02-16

    According to one embodiment, a composite product includes hexagonal boron nitride (hBN), and a plurality of cubic boron nitride (cBN) particles, wherein the plurality of cBN particles are dispersed in a matrix of the hBN. According to another embodiment, a composite product includes a plurality of cBN particles, and one or more borate-containing binders.

  18. Boron nitride composites

    Energy Technology Data Exchange (ETDEWEB)

    Kuntz, Joshua D.; Ellsworth, German F.; Swenson, Fritz J.; Allen, Patrick G.

    2016-02-16

    According to one embodiment, a composite product includes hexagonal boron nitride (hBN), and a plurality of cubic boron nitride (cBN) particles, wherein the plurality of cBN particles are dispersed in a matrix of the hBN. According to another embodiment, a composite product includes a plurality of cBN particles, and one or more borate-containing binders.

  19. Processing and optimization of functional ceramic coatings and inorganic nanomaterials

    Science.gov (United States)

    Nyutu, Edward Kennedy G.

    Processing of functional inorganic materials including zero (0-D) dimensional (e.g. nanoparticles), 1-D (nanorods, nanofibers), and 2-D (films/coating) structures is of fundamental and technological interest. This research will have two major sections. The first part of section one focuses on the deposition of silicon dioxide onto a pre-deposited molybdenum disilicide coating on molybdenum substrates for both high (>1000 °C) and moderate (500-600 °C) temperature oxidation protection. Chemical vapor deposition (CVD/MOCVD) techniques will be utilized to deposit the metal suicide and oxide coatings. The focus of this study will be to establish optimum deposition conditions and evaluate the metal oxide coating as oxidation - thermal barriers for Mo substrates under both isothermal (static) and cyclic oxidation conditions. The second part of this section will involve a systematic evaluation of a boron nitride (BN) interface coating prepared by chemical vapor deposition. Ceramic matrix composites (CMCs) are prospective candidates for high (>1000 °C) temperature applications and fiber- matrix interfaces are the dominant design parameters in ceramic matrix composites (CMCs). An important goal of the study is to determine a set of process parameters, which would define a boron nitride (BN) interface coating by a chemical vapor deposition (CVD) process with respect to coating. In the first part of the second section, we will investigate a new approach to synthesize ultrafine metal oxides that combines microwave heating and an in-situ ultrasonic mixing of two or more liquid precursors with a tubular flow reactor. Different metal oxides such as nickel ferrite and zinc aluminate spinels will be studied. The synthesis of metal oxides were investigated in order to study the effects of the nozzle and microwave (INM process) on the purity, composition, and particle size of the resulting powders. The second part of this research section involves a study of microwave frequency

  20. Nanoscale multilayered and porous carbide interphases prepared by pressure-pulsed reactive chemical vapor deposition for ceramic matrix composites

    Energy Technology Data Exchange (ETDEWEB)

    Jacques, S., E-mail: jacques@lcts.u-bordeaux1.fr [LCTS, University of Bordeaux 1, CNRS, Herakles-Safran, CEA, 3 allee de la Boetie, F-33600 Pessac (France); Jouanny, I.; Ledain, O.; Maillé, L.; Weisbecker, P. [LCTS, University of Bordeaux 1, CNRS, Herakles-Safran, CEA, 3 allee de la Boetie, F-33600 Pessac (France)

    2013-06-15

    In Ceramic Matrix Composites (CMCs) reinforced by continuous fibers, a good toughness is achieved by adding a thin film called “interphase” between the fiber and the brittle matrix, which acts as a mechanical fuse by deflecting the matrix cracks. Pyrocarbon (PyC), with or without carbide sub-layers, is typically the material of choice to fulfill this role. The aim of this work was to study PyC-free nanoscale multilayered carbide coatings as interphases for CMCs. Nanoscale multilayered (SiC–TiC){sub n} interphases were deposited by pressure-Pulsed Chemical Vapor Deposition (P-CVD) on single filament Hi-Nicalon fibers and embedded in a SiC matrix sheath. The thicknesses of the carbide interphase sub-layers could be made as low as a few nanometers as evidenced by scanning and transmission electron microscopy. By using the P-ReactiveCVD method (P-RCVD), in which the TiC growth involves consumption of SiC, it was not only possible to obtain multilayered (SiC–TiC){sub n} films but also TiC films with a porous multilayered microstructure as a result of the Kirkendall effect. The porosity in the TiC sequences was found to be enhanced when some PyC was added to SiC prior to total RCVD consumption. Because the porosity volume fraction was still not high enough, the role of mechanical fuse of the interphases could not be evidenced from the tensile curves, which remained fully linear even when chemical attack of the fiber surface was avoided.

  1. Integrally cored ceramic investment casting mold fabricated by ceramic stereolithography

    Science.gov (United States)

    Bae, Chang-Jun

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

  2. Preparation of glasses and glass ceramics of heavy metal oxides containing silver: optical, structural and electrochemical properties; Preparacao de vidros e vitroceramicas de oxidos de metais pesados contendo prata: propriedades opticas, estruturais e eletroquimicas

    Energy Technology Data Exchange (ETDEWEB)

    Bregadiolli, Bruna A. [Departamento de Fisica, Faculdade de Ciencias, Universidade Estadual Paulista, Bauru - SP (Brazil); Souza, Ernesto R.; Sigoli, Fernando A. [Instituto de Quimica, Universidade Estadual de Campinas, Campinas - SP (Brazil); Caiut, Jose M.A. [Departamento de Quimica, Faculdade de Filosofia Ciencias e Letras de Ribeirao Preto, Universidade de Sao Paulo, Ribeirao Preto - SP (Brazil); Alencar, Monica A.S.; Benedetti, Assis V. [Instituto de Quimica, Universidade Estadual Paulista, Araraquara - SP (Brazil); Nalin, Marcelo, E-mail: mnalin@ufscar.br [Departamento de Quimica, Universidade Federal de Sao Carlos, SP, (Brazil)

    2012-07-01

    Silver containing heavy metal oxide glasses and glass ceramics of the system WO{sub 3}-SbPO{sub 4} -PbO-AgCl with different AgCl contents have been prepared and their thermal, structural and optical properties characterized. Glass ceramics containing metallic silver nanoparticles have been prepared by annealing glass samples at temperatures above the glass transition and analyzed by transmission electron microscopy and energy dispersive X-ray microanalysis. The presence of the metallic clusters has been also confirmed by the observation of a surface plasmon resonance band in the visible range. Cyclic voltammetric measurements indicated the presence of metallic silver into the glasses, even before to perform the thermal treatment. (author)

  3. Nitrogen Availability Of Nitriding Atmosphere In Controlled Gas Nitriding Processes

    Directory of Open Access Journals (Sweden)

    Michalski J.

    2015-06-01

    Full Text Available Parameters which characterize the nitriding atmosphere in the gas nitriding process of steel are: the nitriding potential KN, ammonia dissociation rate α and nitrogen availabilitymN2. The article discusses the possibilities of utilization of the nitriding atmosphere’s nitrogen availability in the design of gas nitriding processes of alloyed steels in atmospheres derived from raw ammonia, raw ammonia diluted with pre-dissociated ammonia, with nitrogen, as well as with both nitrogen and pre-dissociated ammonia. The nitriding processes were accomplished in four series. The parameters selected in the particular processes were: process temperature (T, time (t, value of nitriding potential (KN, corresponding to known dissociation rate of the ammonia which dissociates during the nitriding process (α. Variable parameters were: nitrogen availability (mN2, composition of the ingoing atmosphere and flow rate of the ingoing atmosphere (FIn.

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

    Science.gov (United States)

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

    2010-01-01

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

  5. Laser processing of ceramics for microelectronics manufacturing

    Science.gov (United States)

    Sposili, Robert S.; Bovatsek, James; Patel, Rajesh

    2017-03-01

    Ceramic materials are used extensively in the microelectronics, semiconductor, and LED lighting industries because of their electrically insulating and thermally conductive properties, as well as for their high-temperature-service capabilities. However, their brittleness presents significant challenges for conventional machining processes. In this paper we report on a series of experiments that demonstrate and characterize the efficacy of pulsed nanosecond UV and green lasers in machining ceramics commonly used in microelectronics manufacturing, such as aluminum oxide (alumina) and aluminum nitride. With a series of laser pocket milling experiments, fundamental volume ablation rate and ablation efficiency data were generated. In addition, techniques for various industrial machining processes, such as shallow scribing and deep scribing, were developed and demonstrated. We demonstrate that lasers with higher average powers offer higher processing rates with the one exception of deep scribes in aluminum nitride, where a lower average power but higher pulse energy source outperformed a higher average power laser.

  6. Physicochemical properties of precursors of Al2O3-ZrO2 oxide ceramics prepared by electrochemical method

    Science.gov (United States)

    Petrova, E. V.; Dresvyannikov, A. F.; Ahmadi Daryakenari, M.; Khairullina, A. I.

    2016-05-01

    Scanning electron microscopy, X-ray, and thermal analysis are used to examine the structure and properties of dispersive systems based on aluminum and zirconium oxides prepared electrochemically. The effect the conditions of synthesis have on the structure and morphology of Al2O3-ZrO2 particles is studied. It is shown that the effect of an electric field on the reaction medium allows us to adjust the physicochemical properties and morphology.

  7. Development of a dielectric ceramic based on diatomite-titania. Part one: powder preparation and sintering study

    Directory of Open Access Journals (Sweden)

    Tavares Elcio Correia de Souza

    1997-01-01

    Full Text Available This work presents powder preparation and sintering experiments of a mixture diatomite-titania. X-ray diffraction, DTA, TGA as well as chemical and microstructural analyses were made. The sintering process was investigated as a function of sintering temperature and time, mass variation, linear shrinkage and activation energy. The results show that sintering of diatomite-titania could be described by a viscous flow mechanism.

  8. Anisotropic Ferro- and Dielectric Properties of Textured Bi4Ti3O12 Ceramics Prepared by the Solid-State Reaction Based on Multiple Calcination

    Directory of Open Access Journals (Sweden)

    Xiangyu Mao

    2010-01-01

    Full Text Available The grain-oriented Bi4Ti3O12 (BIT samples were prepared by the solid-state reaction method with a multicalcination process. The grain-oriented BIT samples exhibit anisotropic structural, ferroelectric, piezoelectric, and dielectric properties. The remanent polarization (2Pr and the piezoelectric constant (d33 of a/b- and c-direction BIT ceramics are 49.5 μC cm−2, 22.2 pC N−1 and 6.7 μC cm−2 6.9 pC N−1, respectively. The dielectric anomalies of samples are observed around 157 K and 232 K. The dielectric anomalies at around 157 K are related to oxygen vacancies. The activation energy of the dielectric relaxation of this anomaly is estimated to be 1.36 eV. Another dielectric anomaly at around 232 K is related to polarizable domains and the viscous motion of domain walls.

  9. Liquid-phase non-thermal plasma-prepared N-doped TiO(2) for azo dye degradation with the catalyst separation system by ceramic membranes.

    Science.gov (United States)

    Cheng, Hsu-Hui; Chen, Shiao-Shing; Cheng, Yi-Wen; Tseng, Wei-Lun; Wang, Yi-Hui

    2010-01-01

    This study strived to improve the photocatalytic activity by using liquid-phase non-thermal plasma (LPNTP) technology for preparing N-doping TiO(2) as well as to separate/recover the N-dope TiO(2) particles by using ceramic ultrafiltration membrane process. The yellow color N-doped TiO(2) photocatalysts, obtained through the LPNTP process, were characterized with UV-Vis spectroscopy, X-ray diffraction (XRD), and electron spectroscopy for chemical analysis (ESCA). The UV-Vis spectrum of N-doped TiO(2) showed that the absorption band was shifted to 439 nm and the band gap was reduced to 2.82 eV. The structure analysis of XRD spectra showed that the peak positions and the crystal structure remained unchanged as anatase after plasma-treating at 13.5 W for 40 min. The photocatalytic activity of N-doped TiO(2) was evaluated by azo dyes under visible light, and 63% of them was degraded after 16 hours in a continuous-flow photocatalytic system. For membrane separation/recover system, the recovery efficiency reached 99.5% after the ultrafiltration had been carried out for 90 min, and the result indicated that the photocatalyst was able to be separated/recovered completely.

  10. Preparation and Electrical Properties of Ba2TiOSi2−xGexO7 (x=0.0 and 0.2 Ferroelectric Ceramics

    Directory of Open Access Journals (Sweden)

    S. K. Barbar

    2014-01-01

    Full Text Available Polycrystalline ceramic samples of pure and germanium (Ge4+ doped fresnoite of general formula Ba2TiOSi2−xGexO7 (x=0.0 and 0.2 have been prepared by solid state reaction technique. The formation of the single phase compound was confirmed by X-ray diffraction and the structural parameters were refined by the Rietveld refinement technique. The dc conductivity of both the materials has been measured as a function of temperature from room temperature to 753 K and activation energy was calculated using the relation σ = σoexp(-Ea/kt. The activation energy 4.74 eV obtained for the pure compound is very high in comparison with 1.47 eV of Ge4+-substituted compound. The frequency and temperature dependent dielectric behavior of both the compounds have been studied. The real and imaginary parts of the dielectric constant increase with the increase of temperature.

  11. Preparation of Cubic Boron Nitride Coating on WC-Co Substrate by Micro/Nanocrystalline Diamond Film Interlayer%基于微纳米金刚石过渡层的cBN刀具涂层制备

    Institute of Scientific and Technical Information of China (English)

    徐锋; 左敦稳; 张旭辉; 户海峰; 张骋; 王珉

    2013-01-01

    Cubic Boron Nitride(cBN) is a super-hard material, of which hardness is only less than diamond. But it has excellent chemical stability, especially no chemical reaction with ferrous materials. The cBN coating has irreplaceable function in the application of modern cutting tools. Research is carried out on the preparation of cBN coating on YG6 by micro/nanocrystalline diamond (M/NCD) film inter-layer. The micro/nanocrystalline diamond film is deposited in hot filament chemical vapor deposition system and cBN is deposited in radio frequency magnetron sputtering system. The scanning electron microscopy (SEM), Raman, atomic force microscopy(AFM), Fourier transferred infrared(FTIR) and in-denter are used to investigate the content, morphology and adhesion of the coating. The results show that the adhesion of cBN coating on WC-Co by micro/nanocrystalline diamond interlayer is much higher than that by nano diamond interlayer. The moderate bias voltage is important for the cBN film deposition in the magnetron sputtering process.%立方氮化硼(Cubic Boron Nitride,cBN)是仅次于金刚石的超硬材料,比金刚石具有更高的化学稳定性,可以胜任铁系金属的加工.本文在YG6硬质合金上基于微纳米金刚石过渡层开展cBN涂层的制备研究.本文在热丝化学气相沉积系统中制备微纳米金刚石过渡层(Micro/nanocrystalline diamond,M/NCD),在射频磁控溅射系统中制备cBN涂层,并对M/NCD与cBN涂层进行了成分、微观形貌与结合性能的研究.研究结果发现,在硬质合金基体上,M/NCD过渡层的结合性能明显优于NCD过渡层.磁控溅射制备cBN涂层过程中,存在适合cBN沉积的衬底偏压阈值,过高或过低的衬底偏压均不利于cBN含量的提高.

  12. Ceramic Processing

    Energy Technology Data Exchange (ETDEWEB)

    EWSUK,KEVIN G.

    1999-11-24

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

  13. Chem-prep PZT95/5 for neutron generator applications : the effect of pore former type and density on the depoling behavior of chemically prepared PZT 95/5 ceramics.

    Energy Technology Data Exchange (ETDEWEB)

    Lockwood, Steven John; Scofield, Timothy W.; Yang, Pin; Voigt, James A.; Tuttle, Bruce Andrew; Moore, Roger Howard

    2003-10-01

    The hydrostatically induced ferroelectric(FE)-to-antiferroelectric(AFE) phase transformation for chemically prepared niobium modified PZT 95/5 ceramics was studied as a function of density and pore former type (Lucite or Avicel). Special attention was placed on the effect of different pore formers on the charge release behavior associated with the FE-to-AFE phase transformation. Within the same density range (7.26 g/cm3 to 7.44 g/cm3), results showed that ceramics prepared with Lucite pore former exhibit a higher bulk modulus and a sharper polarization release behavior than those prepared with Avicel. In addition, the average transformation pressure was 10.7% greater and the amount of polarization released was 2.1% higher for ceramics with Lucite pore former. The increased transformation pressure was attributed to the increase of bulk modulus associated with Lucite pore former. Data indicated that a minimum volumetric transformational strain of -0.42% was required to trigger the hydrostatically induced FE-to-AFE phase transformation. This work has important implications for increasing the high temperature charge output for neutron generator power supply units.

  14. Annual Conference on Composites and Advanced Ceramic Materials, 12th, Cocoa Beach, FL, Jan. 17-22, 1988, Proceedings. Parts 1 and 2

    Energy Technology Data Exchange (ETDEWEB)

    1988-10-01

    The present conference discusses topics in the development status of advanced ceramics, the engineering applications of ceramic-matrix composites, modeling and theoretical considerations of engineering ceramics, the role of interfaces in ceramic-matrix composites, and polycrystalline oxide-matrix composites. Also discussed are glass- and glass-ceramic-matrix composites, carbide- and nitride-matrix composites, the synthesis methods as well as the properties and applications of ceramic matrix-reinforcing whiskers, fibers, and powders, and various SDI-related advanced ceramic materials for use in orbital systems.

  15. Composite treatment of ceramic tile armor

    Energy Technology Data Exchange (ETDEWEB)

    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.

  16. Composite treatment of ceramic tile armor

    Energy Technology Data Exchange (ETDEWEB)

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

    2012-01-02

    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.

  17. Preparation and properties of (K0.5Na0.5)NbO3-LiNbO3 ceramics

    Institute of Scientific and Technical Information of China (English)

    TANG Fu-sheng; DU Hong-liang; LI Zhi-min; ZHOU Wan-cheng; QU Shao-bo; PEI Zhi-bin

    2006-01-01

    The lead-free piezoelectric ceramics (1-x)(K0.5Na0.5)NbO3-xLiNbO3(abbreviated as KNLN) were synthesized by a traditional solid state reaction. The effects of Li+ on the sintering characteristic,the phase structure and piezoelectric properties of KNLN ceramics were investigated. The sintering temperature of KNN-based ceramics is decreased by doping Li+ and the range of the sintering temperature is narrow. The KNLN ceramics exhibit an enhanced piezoelectric properties with the piezoelectric constant d33 value of 180-200 pC/N,The electromechanical coupling coefficients kp is 35%-40%. The results show that (1-x)(K0.5Na0.5)- NbO3-xLiNbO3 (x=0.05,0.06) is a promising high-temperature lead free piezoelectric ceramic.

  18. Variation of crystallinity and stoichiometry in films of gallium oxide, gallium nitride and barium zirconate prepared by means of PLD; Variation von Kristallinitaet und Stoechiometrie in mittels PLD hergestellten Schichten aus Galliumoxid, Galliumnitrid und Bariumzirkonat

    Energy Technology Data Exchange (ETDEWEB)

    Brendt, Jochen

    2011-08-05

    Pulsed Laser Deposition (PLD) is an ablation technique for thin film preparation of many materials. The film properties can be well controlled by the process parameters. Therefore, in many cases a given material can be deposited with different properties by changing one or more process parameters. In this thesis thin films of gallium oxide, gallium nitride and barium zirconate were deposited with a large variation in structure and stoichiometry by means of Pulsed Laser Deposition. The characterization of the film crystallinity, phase purity and short range structural order was completed by means of X-ray diffraction and X-ray absorption spectroscopy. The stoichiometry was investigated using electron probe microanalysis. For analyzing the correlation between the structure and stoichiometry with the optical and electrical properties, optical absorption and electrical conductivity measurements were carried out. The investigation of all three material systems showed that very unique properties can be realized when combining an amorphous structure and a non-stoichiometric composition. For example, in amorphous and oxygen deficient gallium oxide an insulator-metal-transition can be induced by partial crystallization of the as prepared phase accomplished by annealing at about 400 C in argon atmosphere (as shown in literature). Furthermore, amorphous and highly non-stoichiometric barium zirconate has the ability to split water molecules to hydrogen and oxygen at room temperature. A detailed analysis of both phenomena has been performed by means of photoemission and transmission electron microscopy in the case of gallium oxide and via X-ray absorption spectroscopy and gas chromatography in the case of barium zirconate.

  19. Metal Nitrides for Plasmonic Applications

    DEFF Research Database (Denmark)

    Naik, Gururaj V.; Schroeder, Jeremy; Guler, Urcan;

    2012-01-01

    Metal nitrides as alternatives to metals such as gold could offer many advantages when used as plasmonic material. We show that transition metal nitrides can replace metals providing equally good optical performance for many plasmonic applications.......Metal nitrides as alternatives to metals such as gold could offer many advantages when used as plasmonic material. We show that transition metal nitrides can replace metals providing equally good optical performance for many plasmonic applications....

  20. Preparation of Hollow SiC Ceramic Microspheres With Drop-tower Technique%炉内成球法制备SiC空心陶瓷微球

    Institute of Scientific and Technical Information of China (English)

    李婧; 冯建鸿; 肖建建; 刘一杨; 李洁; 张占文; 李波

    2014-01-01

    采用干凝胶法,以聚碳硅烷(PCS )为原料,通过炉内成球技术制备了SiC空心陶瓷微球。并利用TG、IR、SEM、XRD等方法对陶瓷微球进行了成键结构、表面形貌等分析,讨论了有机聚合物的陶瓷化过程机理。结果表明,干凝胶成球技术能利用经纯化处理的聚碳硅烷在500~600℃下得到SiC空心陶瓷微球,采用乙醇作为发泡剂可使 PCS凝胶粒子得到良好发泡效果,提高载气中氦气含量至50%~80%可提高干凝胶粒子在吸热阶段的升温速率,微球经辐照后在850℃下碳化生成以β-SiC为主要相结构的球壳,球壳具有较好的表面平整度。%SiC ceramic microspheres were fabricated by drop-tower technique at low tem-perature using polycarbosilane (PCS ) as raw material . T he as-prepared microspheres were characterized by TG ,IR ,SEM and XRD .The reaction mechanism of organic poly-mer and the effects of process parameters (composition of furnace atmosphere and tem-perature) were investigated .The results show that ethanol as a blowing agent has a high blowing efficiency ,and the content of helium gas in the furnace atmosphere ranging rising to 50%-80% can increase the heating-up rate of gel particles in heat-absorbing stage .The high sphericity morphology is obtained at 500-600 ℃ .Moreover ,the SEM spectra indicate that irradiation can increase the surface finish quality and evenness of hollow SiC ceramic microspheres .