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Sample records for al2o3 depositadas sobre

  1. HIDRODENITROGENACION DE CARBAZOL SOBRE CATALIZADORES NiMo/Al2O3-SiO2(x

    Directory of Open Access Journals (Sweden)

    Felipe Sánchez-Minero

    2012-01-01

    Full Text Available En este trabajo se estudió la velocidad de reacción del carbazol sobre catalizadores NiMo soportados sobre Al2O3 modificada superficialmente con SiO2 (0 y 10 % en peso de SiO2 en el soporte. Los catalizadores fueron evaluados en un reactor intermitente a cuatro temperaturas (287, 300, 312 y 325oC, presión de 4.0 MPa y relación molar hidrogeno/carbazol de 2400. A partir de los resultados experimentales se realizó un estudio cinético utilizando ecuaciones del tipo Langmuir-Hinshelwood (L-H. Luego, los parámetros cinéticos fueron estimados mediante la minimización de Powell (programa Scientist de MicroMath. Los resultados muestran que el catalizador con sílice (NiMo-SAC 10 alcanza una mayor actividad para la HDN de carbazol debido a que presenta un mayor número de sitios activos (valor de A, así como una menor fuerza de adsorción entre el reactante y la superficie catalítica (valor de KN, lo cual posiblemente favorece una mejor regeneración de sitios activos.

  2. CATALIZADOR ESTRUCTURADO DE Pt/Al2O3 SOBRE UNA ESPUMA DE ACERO INOXIDABLE (AISI 314 PARA LA OXIDACIÓN DE CO

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    Juan P. Bortolozzi

    2011-01-01

    Full Text Available Se obtuvo un catalizador estructurado por recubrimiento de Pt/Al2O3 sobre las paredes de una espuma de acero inoxidable AISI 314. Para estabilizar térmicamente e incrementar la rugosidad de la superficie de la espuma original se realizó un tratamiento a 900°C por 2 h. El soporte, Al2O3, y el metal activo, Pt, se incorporaron por inmersión. Las técnicas de caracterización aplicadas, XRD, LRS y SEM-EDX, permiten concluir que el tratamiento térmico previo indujo la formación de óxido de cromo y de las espinelas Mn1+xCr2-xO4-x y FeCr2O4 como fases principales en las paredes del sustrato. El espesor de la capa formada es cercano a 1 μm y los cristales producidos tienen forma octaédrica. El cubrimiento de alúmina presentó en general una apariencia homogénea, sin interacción con los óxidos formados durante el tratamiento. El Pt se distribuyó de manera uniforme, resultando un catalizador muy activo para la reacción test elegida: oxidación de monóxido de carbono.

  3. Reforma catalítica do metano sobre 1,5%Ni/α-Al2O3 dopado com elementos metálicos diferentes Catalytic reforming of methane over 1.5%Ni/α-Al2O3 doped with different metallic elements

    Directory of Open Access Journals (Sweden)

    L. S. Neiva

    2012-06-01

    Full Text Available O objetivo deste trabalho é desenvolver catalisadores de Ni suportados em α-Al2O3 dopada com os seguintes elementos metálicos: ferro, zinco, cério e zircônio. Os suportes catalíticos de α-Al2O3 dopada foram obtidos por meio do método de síntese da reação de combustão e o níquel, na condição de espécie ativa catalítica, foi depositado sobre os suportes por meio do método de impregnação úmida. As caracterizações estruturais, bem como, a avaliação dos desempenhos catalíticos destes materiais cerâmicos na reação de reforma a vapor do metano fazem parte dos objetivos deste trabalho. Os suportes catalíticos sintetizados apresentaram estruturas cristalinas com dimensão de suas porosidades na faixa da microporosidade associada à presença de mesoporos. A avaliação catalítica das amostras obtidas neste trabalho, na reação de reforma a vapor do metano, revelou que o desempenho catalítico deste tipo de material é influenciado por suas características físicas, tais como, valor da área superficial das partículas que compõem a estrutura, como também, o valor médio dos diâmetros de poros da mesma. Dentre as quatro amostras desenvolvidas neste trabalho, a amostra de α-Al2O3 dopada com zinco contendo 1,5% de Ni como espécie ativa catalítica, apresentou valores percentuais de conversão do metano mais elevados que as demais amostras.The aim this work is to develop Ni catalysts supported on α-Al2O3 doped with the following metallic elements: iron, zinc, cerium and zirconium. The catalytic supports composed by α-Al2O3 doped were obtained by means method of synthesis of the combustion reaction and the nickel in the active catalytic species condition, was deposited over the supports by the method of wet impregnation. The structural characterizations, as well as the evaluation of performance of these ceramic materials in catalytic reaction of steam reforming of methane are among the objectives of this work. The

  4. HIDROGENACIÓN SELECTIVA EN FASE LIQUIDA DE 1-HEPTINO SOBRE Ni/Al2O3. EFECTO DE LA TEMPERATURA DE REACCIÓN

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    María J. Maccarrone

    2011-01-01

    Full Text Available En este trabajo fue evaluado el efecto de la temperatura de reacción en la hidrogenación selectiva de 1-heptino a 1-hepteno usando un catalizador de níquel soportado sobre γ -alúmina. Fueron estudiadas diferentes temperaturas operacionales (273, 303 y 323 K, obteniéndose mayor conversión total del reactivo a la mayor temperatura, con una selectividad próxima al 90%. El catalizador de níquel preparado puede considerarse como una alternativa más económica a nivel industrial frente a los ya conocidos catalizadores de paladio, no sólo debido al bajo costo del metal sino también debido a su bajo contenido metálico (3,6% en masa. El catalizador fue caracterizado por Difracción de Rayos X, Reducción a Temperatura Programada y Espectroscopía Fotoelectrónica de Rayos X. Estas indicaron la presencia de óxido de níquel a nivel másico con fuertes interacciones con el soporte y la existencia de especies electro-deficientes de níquel a nivel superficial quienes serían las especies activas durante la hidrogenación del alquino terminal.

  5. Al2O3/Al2O3 Joint Brazed with Al2O3-particulate-contained Composite Ag-Cu-Ti Filler Material

    Institute of Scientific and Technical Information of China (English)

    Jianguo YANG; Hongyuan FANG; Xin WAN

    2005-01-01

    Microstructure and interfacial reactions of Al2O3 joints brazed with Al2O3-particulate-contained composite Ag-Cu-Ti filler material were researched by scanning electron microscopy (SEM), electron probe microscopy analysis (EPMA),energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). The interfacial reaction layer thickness of joints brazed with conventional active filler metal and active composite filler materials with different volume fraction of Al2O3 particulate was also studied. The experimental results indicated although there were Al2O3 particulates added into active filler metals, the time dependence of interfacial layer growth of joints brazed with active composite filler material is t1/2 as described by Fickian law as the joints brazed with conventional active filler metal.

  6. Al2O3/Au/Al2O3 layered films as tritium permeation barrier%Al2O3/Au/Al2O3层状阻氚薄膜

    Institute of Scientific and Technical Information of China (English)

    汤波楷; 何业东; 曹江利; 唐涛; 饶咏初

    2012-01-01

    Single Al2O3 films, single Au films and Al2O3/Au/Al2O3 layered films were prepared on 316L stainless steel substrate by megnetron sputtering. Then vapour phase permeation experiment of deuterium through 316L substrate and its film materials were carried out at 500℃ with a partial pressure of deuterium 0. 06 MPa. The results indicate that morphology of the three films is good and no phenomenon of cracking and spalling is found after deuterium permeation. Deuterium permeation reduction factors (PRF) of these films are over one order of magnitude relative to clean 316L. The performance of barrying deuterium increases progressively in the order of single Al2O3 films, single Au films and Al2O3/Au/Al2O3 ayered films. Al2O3/Au/Al2O3 layered films exhibit excellent performance of barrying deuterium because the mechanical properties of the layered films are improved visibly by the ductile interlayer Au and the interdiffusion between Au and 316L substratc is hindered by Al2O3 layer, so Au can give full play to barry deuterium. The study shows that layered films like precious metal integrated with ceramics is a new way in the domain of tritium permeation barrier development.%采用磁控溅射法在316L不锈钢基体上分别沉积单层Al2O3,膜、单层Au膜以及Al2O3/Au/Al2O3层状薄膜。采用气相渗透法在500℃,氘分压为0.06MPa条件下测试了薄膜的阻氘性能。结果表明,3种薄膜氘渗透后,薄膜的形貌良好,无开裂、无剥落的现象,氘渗透率减低因子均比316L不锈钢基材增大一个数量级以上,阻氘效能按单层Al2O3,膜、单层Au膜以及Al2O3/Au/Al2O3层状薄膜依次递升。Al2O3/Au/Al2O3层状薄膜的优异阻氘效能可归因于,延性的Au夹层使层状薄膜的力学性能得到显著提高;Al2O3层能阻止Au与基体间互扩散,使Au能充分发挥阻氘效能。本研究表明,由贵金属与陶瓷阻氚材料构成的层状薄膜是发展阻氚涂层的新途径。

  7. Al2O3-Coated Nano-SiC Particles Reinforced Al2O3 Matrix Composites

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Properties of Al2O3-coated nano-SiC have been compared with those of as-received SiC. The isoelectric point (IEP)of SiC changed from pH3.4 to pH7.3 after coating with the alumina precursor, which is close to that of alumina.Because both surfaces of coated SiC and Al2O3 possess higher positive charge at pH=4.5~5.0, they are uniformly dispersed in the two-phase aqueous suspensions, Then a mixed powder containing nano-SiC dispersed homogeneously into the Al2O3 matrix was achieved from flocculating the two-phase suspension. Finally, Al2O3/SiC nanocomposites were obtained by coating nano-SiC with Al2O3, in which the majority of SiC particles were located within the Al2O3 grains. The observation by transmission electron microscopy (TEM) and the analysis by the X-ray photoelectron spectroscopy (XPS) showed that cracks propagated towards the intragranular SiC rather than along grain boundaries.

  8. Preparation and Characterization of Highly Flexible Al2O3/Al/Al2O3 Hybrid Composite

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    Zhijiang Wang

    2015-01-01

    Full Text Available The natural brittleness of oxide ceramics heavily inhibits their more extensive applications. In present research, a highly flexible Al2O3/Al/Al2O3 hybrid composite was fabricated by employing plasma electrolysis oxidation to in situ grow alumina layers on Al foil, in which an outside layer of nanostructured polycrystalline oxide ceramic was composed of nanosized grains with the size of around 17 nm. Due to shear band formation, nanosized circle bubbles prolonging the crack path, grain rotation, and deformation, the fabricated Al2O3/Al/Al2O3 hybrid composite contains no observable cracks even after being bent on a cylindrical bar with a curvature of 1.5 mm. The composite exhibits alumina stiffness at the elastic stage and aluminum ductility during plastic deformation, which provides high flexibility with the well-integrated properties of the components. In a synergistic interaction, the alumina on the outside exhibited a strain of 0.33% at room temperature, which was higher than optimum value of 0.25% presented by reported most flexible oxide ceramics. With the unique characteristics and properties, the Al2O3/Al/Al2O3 composite demonstrates a great potential for various engineering applications.

  9. Synthesis and thermal characterization of Al2O3 nanoparticles

    Science.gov (United States)

    Ismardi, A.; Rosadi, O. M.; Kirom, M. R.; Syarif, D. G.

    2016-11-01

    Al2O3 nanoparticle has been successfully synthesized using sol gel method from AlCl3. The obtained nanoparticles was then characterized for grain size measurement, the size of nanoparticles was 6 nm by using surface area meter (SAM) and Transmission Electron Microscopy (TEM). The crystallinity property of the product was then checked with XRD spectroscopy, the result shows that the diffraction peaks were match with the 10-0425 JCPDS database. Thermal property of the Al2O3 nanoparticles was then studied by mixing it with engine base fluid as nanofluid. The usage of nanofluid was expected to be heat absorber and woulo increase cooling process in cooling machine. The results showed that cooling time increases when the concentration of nanofluid was increased. Finally, it is concluded that thermal property of Al2O3 was studied and applicable to be mixed with engine coolant of cooler machine to reduce cooling time process.

  10. DEPTH PROFILING OF DEUTERIUM IN Al2O3

    Institute of Scientific and Technical Information of China (English)

    谈效华; 赵国庆; 等

    1995-01-01

    D2+ ions of 70 and 90keV were separately implanted into two thick samples of sintered alumina ceramic and the distribution of deuterium has been measured for three runs at an interval of 5 months using high energy proton backscattering and elastic recoil detection (ERD).The measured data show that there is little diffusion of dueterium in Al2O3 and the diffusion coefficient is deduced to be 1.1×10-17 cm2/s.The measured total concentration of implanted deuterium is 4.5×1018at.cm2.The profile of hydrogen adsorbed on the surface of Al2O3 samples was also observed by ERD and 1H(19E,αγ)16O analysis.The distribution range of 1H in Al2O3 after deuterium implantation is much larger than that before one.

  11. Catalytic Methane Decomposition over Fe-Al2O3

    KAUST Repository

    Zhou, Lu

    2016-05-09

    The presence of a Fe-FeAl2O4 structure over an Fe-Al2O3 catalysts is demonstrated to be vital for the catalytic methane decomposition (CMD) activity. After H2 reduction at 750°C, Fe-Al2O3 prepared by means of a fusion method, containing 86.5wt% FeAl2O4 and 13.5wt% Fe0, showed a stable CMD activity at 750°C for as long as 10h. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Surface modified Al2O3 in fluorinated polyimide/Al2O3 nanocomposites: Synthesis and characterization

    Indian Academy of Sciences (India)

    Zivar Ghezelbash; Davoud Ashouri; Saman Mousavian; Amir Hossein Ghandi; Yaghoub Rahnama

    2012-11-01

    Organic–inorganic hybrid materials consisting of inorganic materials and organic polymers are a new class of materials, which have received much attention in recent years. In the present investigation, at first, the surface of nano-alumina (Al2O3) was treated with a silane coupling agent of -aminopropyltriethoxysilane (KH550), which introduces organic functional groups on the surface of Al2O3 nanoparticles. Then fluorinated polyimide (PI) was synthesized from 4,4'-(hexafluoroisopropylidene) diphthalic anhydride and 4,4'-diaminodiphenylsulfone. Finally, PI/modified Al2O3 nanocomposite films having 3, 5, 7 and 10% of Al2O3 were successfully prepared by an in situ polymerization reaction through thermal imidization. The obtained nanocomposites were characterized by fourier transform infrared spectroscopy, thermogravimetry analysis, X-ray powder diffraction, UV-Vis spectroscopy, field emission scanning electron microscopy and transmission electron microscopy. The results show that the Al2O3 nanoparticles were dispersed homogeneously in PI matrix. According to thermogravimetry analysis results, the addition of these nanoparticles improved thermal stability of the obtained hybrid materials.

  13. Understanding $Al_2O_3:Er^{3+}$ device performance

    NARCIS (Netherlands)

    Agazzi, L.; Bradley, J.D.B.; Ay, F.; Wörhoff, K.; Pollnau, M.

    2010-01-01

    Al2O3:Er3+ thin films were deposited on Si wafers and subsequently structured. On-chip devices such as amplifiers, ring lasers and a loss-less splitter were fabricated; data transmission at 170 Gbits/s and monolithic integration with SOI waveguides were demonstrated. The discrepancy between device p

  14. Upconversion spectroscopy of $Al_2O_3:Er^{3+}$

    NARCIS (Netherlands)

    Agazzi, L.; Bradley, J.D.B.; Ay, F.; Kahn, A.; Scheife, H.; Petermann, K.; Huber, G.; Ridder, de R.M.; Wörhoff, K.; Pollnau, M.; Wörhoff, K.; Agazzi, L.; Ismail, N.; Leijtens, X.

    2008-01-01

    The spectroscopic properties of $Al_2O_3:Er^{3+}$ thin films have been investigated by lifetime measurements. The luminescence decay curves show an initial non-exponential component, followed by an exponential tail, whose decay time decreases with increasing $Er^{3+}$ concentration. This behavior ca

  15. Síntese e caracterização do compósito Al2O3 -YAG e do Al2O3-YAG e Al2O3 aditivados com Nb2O5 Synthesis and characterization of Al2O3 -YAG composite and Al2O3-YAG and Al2O3 with Nb2O5 additives

    Directory of Open Access Journals (Sweden)

    R. F. Cabral

    2012-03-01

    Full Text Available O compósito Al2O3-YAG possui alta resistência à corrosão e à fluência em ambientes agressivos, o que permite vislumbrar aplicações bastante atrativas, tais como aletas de motores a jato e de turbinas a gás. Este compósito também apresenta elevada dureza e alta resistência à abrasão possibilitando o seu emprego em blindagens balísticas. Nesse estudo os pós precursores de Al2O3, Y2O3 e Nb2O5 foram homogeneizados em moinho de bolas planetário por 4 h, secados em estufa a 120 ºC por 48 h, desaglomerados e peneirados. O compósito Al2O3-YAG foi produzido a partir das misturas de Al2O3-Y2O3 a 1300 ºC por 2 h. Foram produzidas amostras de Al2O3-YAG, Al2O3-YAG com Nb2O5 e Al2O3 com Nb2O5. Posteriormente os pós foram prensados uniaxialmente a 70 MPa. A sinterização foi feita a 1400 e 1450 ºC. Os pós como recebidos e os processados foram caracterizados quanto à área de superfície específica e ao tamanho médio de partícula. Os materiais sinterizados foram caracterizados por densidade e porosidade aparente pelo método de Arquimedes e avaliados quanto à retração e à perda de massa. Os resultados mostraram que são necessários ainda ajustes nas condições de sinterização da composição Al2O3-YAG com Nb2O5 para melhorar a densificação e a retração, que foram baixas, da ordem de 60 e 3%, respectivamente. O Al2O3 aditivado com Nb2O5, por sua vez, apresentou uma densificação satisfatória, de 96% e uma retração em torno de 15%.The Al2O3-YAG composite exhibits high corrosion and creep resistance in aggressive environments, which provides quite glimpse attractive applications such as jet engine vanes and as gas turbines. This composite also shows high hardness and wear resistance allowing its use in ballistic armor. In this study, precursor powders of Al2O3, Y2O3 and Nb2O5 were homogeneously mixed in a planetary ball mill for 4 h, dried in an oven at 120 ºC for 48 h, sieved and deagglomerated. The Al2O3-YAG composite

  16. HIGH PROTON CONDUCTIVITY OF MESOPOROUS Al2O3

    Science.gov (United States)

    Shen, Hangyan; Maekawa, Hideki; Fujimaki, Yutaka; Kawada, Koutaro; Yamamura, Tsutomu

    Mesoporous Al2O3 was synthesized by the sol-gel method and the pore size was controlled over the range of 3-15nm. Proton conductivity of these samples was examined, which was as high as 0.004 S·cm-1 at 25°C. A systematic dependence of conductivity upon pore size was observed, in which the conductivity increased with increasing the pore size. Meanwhile the conductivity increased with increasing the humidity. Two peaks were observed in 1H NMR spectra, assigned to a "mobile" and an "immobile" proton, respectively. It can be seen that the conductivity of mesoporous-Al2O3 increased with increasing the "mobile" proton concentration. From TG-DTA measurement, proton species were categorized into three groups. It is suggested the group II protons have close relation with the NMR observed "mobile" protons.

  17. Antibiotic properties of Al2O3 doping silver

    Institute of Scientific and Technical Information of China (English)

    ZHANG Hai-bin; LIU Qing-ju; ZHU Zhong-qi; ZHANG Jin; EU Xing-hui

    2005-01-01

    The preparation technique and properties of Ag-type inorganic antibiotic material carried by Al2 O3 were studied. The results show that the material has good antibiotic and safety properties, the acute toxicity taken by stomata is LD50 > 8 000 mg/kg (little and big white rats), and the normal quantity in subacute toxicity test is the optimal sintering temperature is from 1 000 ℃ to 1 100 ℃.

  18. Activity Enhancement of Pt/Ba/Al2O3 Mixed with Mn/Ba/Al2O3 for NOx Storage-reduction by Hydrogen

    Institute of Scientific and Technical Information of China (English)

    Jian Hua XIAO; Xue Hui LI; Sha DENG; Fu Rong WANG; Le Fu WANG

    2006-01-01

    Mn/Ba/Al2O3 catalyst for NO oxidation-storage and Pt/Ba/Al2O3 catalyst mixed with Mn/Ba/Al2O3 for NOx storage-reduction by hydrogen were investigated. The results showed that Mn/Ba/Al2O3 had large nitrogen oxides storage capacity (397.9 μmolg-1) under lean bum condition.When Pt/Ba/Al2O3 catalyst was mixed with Mn/Ba/Al2O3 in equal weight proportion, the NOx conversion increased between 250 ℃ and 500 ℃ under the dynamic lean-rich bum conditions, and the maximum NOx conversion increased from 95.4% to 98.2%. Mn/Ba/Al2O3 has promoted NOx storing in the lean stage and improved NOx reduction efficiency in the rich stage, these might result in higher NOx conversion over the low Pt loading content catalyst.

  19. Wear Behavior of Cold Pressed and Sintered Al2O3/TiC/CaF2Al2O3/TiC Laminated Ceramic Composite

    Institute of Scientific and Technical Information of China (English)

    Xuefeng YANG; Jian CHENG; Peilong SONG; Shouren WANG; Liying YANG; Yanjun WANG; Ken MAO

    2013-01-01

    A novel laminated Al2O3/TiC/CaF2-Al2O3/TiC sandwich ceramic composite was fabricated through cold pressing and sintering to achieve better anti-wear performance,such as low friction coefficient and low wear rate.Al2O3/TiC/CaF2 and Al2O3/TiC composites were alternatively built layer-by-layer to obtain a sandwich structure.Solid lubricant CaF2 was added evenly into the Al2O3/TiC/CaF2 layer to reduce the friction and wear.Al2O3/TiC ceramic was also cold pressed and sintered for comparison.Friction analysis of the two ceramics was then conducted via a wear-and-tear machine.Worn surface and surface compositions were examined by scanning electron microscopy and energy dispersion spectrum,respectively.Results showed that the laminated Al2O3/TiC/CaF2-Al2O3/TiC sandwich ceramic composite has lower friction coefficient and lower wear rate than those of Al2O3/TiC ceramic alone because of the addition of CaF2 into the laminated Al2O3/TiC/CaF2-Al2O3/TiC sandwich ceramic composite.Under the friction load,the tiny CaF2 particles were scraped from the Al2O3/TiC/CaF2 layer and spread on friction pairs before falling off into micropits.This process formed a smooth,self-lubricating film,which led to better anti-wear properties.Adhesive wear is the main wear mechanism of Al2O3/TiC/CaF2 layer and abrasive wear is the main wear mechanism of Al2O3/TiC layer.

  20. Al2O3-based nanofluids: a review.

    Science.gov (United States)

    Sridhara, Veeranna; Satapathy, Lakshmi Narayan

    2011-07-16

    Ultrahigh performance cooling is one of the important needs of many industries. However, low thermal conductivity is a primary limitation in developing energy-efficient heat transfer fluids that are required for cooling purposes. Nanofluids are engineered by suspending nanoparticles with average sizes below 100 nm in heat transfer fluids such as water, oil, diesel, ethylene glycol, etc. Innovative heat transfer fluids are produced by suspending metallic or nonmetallic nanometer-sized solid particles. Experiments have shown that nanofluids have substantial higher thermal conductivities compared to the base fluids. These suspended nanoparticles can change the transport and thermal properties of the base fluid. As can be seen from the literature, extensive research has been carried out in alumina-water and CuO-water systems besides few reports in Cu-water-, TiO2-, zirconia-, diamond-, SiC-, Fe3O4-, Ag-, Au-, and CNT-based systems. The aim of this review is to summarize recent developments in research on the stability of nanofluids, enhancement of thermal conductivities, viscosity, and heat transfer characteristics of alumina (Al2O3)-based nanofluids. The Al2O3 nanoparticles varied in the range of 13 to 302 nm to prepare nanofluids, and the observed enhancement in the thermal conductivity is 2% to 36%.

  1. Microstructure of the Al2O3/Al2O3 Joint Brazed with Cu-Zn-Ti Filler Metal

    Institute of Scientific and Technical Information of China (English)

    Hongyuan FANG; Jianguo YANG; Xiuyu YU

    2001-01-01

    Microstructure and interface reactions of Al2O3 joints brazed by Cu-Zn-Ti alloy were studied by using SEM, EDS and XRD. The effects of brazing temperature and Ti content on interfacial reactions and microstructure were investigated, and the action of adding Zn into brazing alloy was also studied. TiO, Ti3Al and CuTi were formed at the interface of ceramics and the filler metal, while CuTi, Cu3Ti and α-Cu were found in the brazing. The thickness of the reaction layer increased with increasing of brazing temperature, under the same brazing process, the thickness increased with the Ti content.

  2. Effect of Processing Parameters on Thermal Cycling Behavior of Al2O3-Al2O3 Brazed Joints

    Science.gov (United States)

    Dandapat, Nandadulal; Ghosh, Sumana; Guha, Bichitra Kumar; Datta, Someswar; Balla, Vamsi Krishna

    2016-10-01

    In the present study, alumina ceramics were active metal brazed at different temperatures ranging from 1163 K to 1183 K (890 °C to 910 °C) using TICUSIL (68.8Ag-26.7Cu-4.5Ti in wt pct) foil as filler alloy of different thicknesses. The brazed joints were subjected to thermal cycling for 100 cycles between 323 K and 873 K (50 °C and 600 °C). The microstructural and elemental composition analysis of the brazed joints were performed by scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) before and after thermal cycling. Helium (He) leak test and brazing strength measurement were also conducted after thermal cycling for 100 cycles. The joint could withstand up to 1 × 10-9 Torr pressure and brazing strength was higher than 20 MPa. The experimental results demonstrated that joints brazed at the higher temperature with thinner filler alloy produced strong Al2O3-Al2O3 joints.

  3. Storage-Reduction of NOx over Combined Catalysts of Pt/Ba/Al2O3-Mn/Ba/Al2O3: Carbon Monoxide as Reductant

    Institute of Scientific and Technical Information of China (English)

    Sha Deng; Xuehui Li; Jianhua Xiao; Furong Wang; Lefu Wang

    2007-01-01

    Storage-reduction of NOx by carbon monoxide was investigated over combined catalysts of Mn/Ba/Al2O3-Pt/Ba/Al2O3. Combination of Mn/Ba/Al2O3 and Pt/Ba/Al2O3 catalysts in different ways showed excellent NOx storage-reduction performance and the content of Pt could be reduced by 50%.Not only the addition of 5Mn/15Ba/Al2O3 to 1Pt/15Ba/Al2O3 could improve its storage ability, but also enhance the NOx conversion consequently. NOx conversion over the combined catalysts (the combined catalysts Ⅰ and Ⅱ) was increased under dynamic lean-rich burn conditions, the maximum NOx conversion increased from 69.4% to respectively 78.8% and 75.7% over two combined catalysts.

  4. Characteristics of ethylene glycol-Al2O3 nanofluids prepared by utilizing Al2O3 nanoparticles synthesized from local bauxite

    Science.gov (United States)

    Syarif, D. G.

    2016-11-01

    Nanoparticles of Al2O3 have been synthesized from local bauxite mineral, and ethylene glycol (EG)-Al2O3 nanofluids have been prepared. Powder Al(OOH) was extracted from local bauxite using bayer process, and heated at 600°C for 3 hours to get Al2O3 nanoparticles. XRD analyses showed that the Al2O3 nanoparticles crystallizes in γ-Al2O3 with crystallite size of 4.12 nm. The specific surface area of the ACO3 nanoparticles was 296.72 m2/gr. Viscosity of the EG-Al2O3 nanofluids was temperature dependent, and decreased with increasing temperature. The viscosity of the nanofluids increased with the concentration of the Al2O3 nanoparticles. Meanwhile, Critical Heat Flux (CHF) enhancement of the nanofluids increased with the concentration of the Al2O3 nanoparticles. The largest CHF enhancement was 54% at Al2O3 concentration of 0.095 vol %.

  5. Antimicrobial effect of Al2O3, Ag and Al2O3/Ag thin films on Escherichia coli and Pseudomonas putida

    Science.gov (United States)

    Angelov, O.; Stoyanova, D.; Ivanova, I.; Todorova, S.

    2016-10-01

    The influence of Al2O3, Ag and Al2O3/Ag thin films on bacterial growth of Gramnegative bacteria Pseudomonas putida and Escherichia coli is studied. The nanostructured thin films are deposited on glass substrates without intentional heating through r.f. magnetron sputtering in Ar atmosphere of Al2O3 and Ag targets or through sequential sputtering of Al2O3 and Ag targets, respectively. The individual Ag thin films (thickness 8 nm) have a weak bacteriostatic effect on Escherichia coli expressed as an extended adaptive phase of the bacteria up to 5 hours from the beginning of the experiment, but the final effect is only 10 times lower bacterial density than in the control. The individual Al2O3 film (20 nm) has no antibacterial effect against two strains E. coli - industrial and pathogenic. The Al2O3/Ag bilayer films (Al2O3 20 nm/Ag 8 nm) have strong bactericidal effect on Pseudomonas putida and demonstrate an effective time of disinfection for 2 hours. The individual films Al2O3 and Ag have not pronounced antibacterial effect on Pseudomonas putida. A synergistic effect of Al2O3/Ag bilayer films in formation of oxidative species on the surface in contact with the bacterial suspension could be a reason for their antimicrobial effect on E. coli and P. putida.

  6. Ni/Al2O3 catalysts for CO methanation: Effect of Al2O3 supports calcined at different temperatures

    Institute of Scientific and Technical Information of China (English)

    Jiajian; Gao; Chunmiao; Jia; Jing; Li; Meiju; Zhang; Fangna; Gu; Guangwen; Xu; Ziyi; Zhong; Fabing; Su

    2013-01-01

    The correlation between phase structures and surface acidity of Al2O3 supports calcined at different temperatures and the catalytic performance of Ni/Al2O3 catalysts in the production of synthetic natural gas(SNG) via CO methanation was systematically investigated. A series of 10 wt% NiO/Al2O3 catalysts were prepared by the conventional impregnation method, and the phase structures and surface acidity of Al2O3 supports were adjusted by calcining the commercial γ-Al2O3 at different temperatures(600–1200 C). CO methanation reaction was carried out in the temperature range of 300–600 C at different weight hourly space velocities(WHSV = 30000 and 120000 mL·g-1h-1) and pressures(0.1 and 3.0 MPa). It was found that high calcination temperature not only led to the growth in Ni particle size, but also weakened the interaction between Ni nanoparticles and Al2O3 supports due to the rapid decrease of the specific surface area and acidity of Al2O3 supports. Interestingly, Ni catalysts supported on Al2O3 calcined at 1200 C(Ni/Al2O3-1200) exhibited the best catalytic activity for CO methanation under different reaction conditions. Lifetime reaction tests also indicated that Ni/Al2O3-1200 was the most active and stable catalyst compared with the other three catalysts, whose supports were calcined at lower temperatures(600, 800 and 1000 C). These findings would therefore be helpful to develop Ni/Al2O3 methanation catalyst for SNG production.

  7. Abrasive wear characteristics and mechanisms of Al2O3/PA1010 composite coatings

    Institute of Scientific and Technical Information of China (English)

    JIA Xian; LING Xiaomei

    2004-01-01

    The abrasive wear characteristics of Al2O3/PA1010 composite coatings on the surface of quenched and low-temperature temper steel 45 were tested on the mmplate abrasive wear testing machine and the same uncoated steel 45 was used as a reference material. Experimental results showed that the abrasive wear resistance of Al2O3//PAl010 composite coatings has a good linear relationship with the volume fraction of Al2O3 particles in Al2O3/PAl010 composite coatings, and the linear correlative coefficient is 0.979. Under the experimental conditions, the size of Al2O3 particles (40.5-161.0 μm) has little influence on the abrasive wear resistance of Al2O3/PA l010 composite coatings. By treating the surface of Al2O3 particles with a suitable bonding agent, the distribution of Al2O3 particles in matrix PAl010 is more homogeneous and the bonding state between Al2O3 particles and matrix PAl010 is better. Therefore, the ml2O3 particles in Al2O3/PA1010 composite coatings make the Al2O3/PAl010 composite coatings have better abrasive wear resistance than PA1010 coatings. The wear resistance of Al2O3/PA 1010 composite coatings is about 45% compared with that of steel 45.

  8. Radiation endurance in Al2O3 nanoceramics

    Science.gov (United States)

    García Ferré, F.; Mairov, A.; Ceseracciu, L.; Serruys, Y.; Trocellier, P.; Baumier, C.; Kaïtasov, O.; Brescia, R.; Gastaldi, D.; Vena, P.; Beghi, M. G.; Beck, L.; Sridharan, K.; di Fonzo, F.

    2016-09-01

    The lack of suitable materials solutions stands as a major challenge for the development of advanced nuclear systems. Most issues are related to the simultaneous action of high temperatures, corrosive environments and radiation damage. Oxide nanoceramics are a promising class of materials which may benefit from the radiation tolerance of nanomaterials and the chemical compatibility of ceramics with many highly corrosive environments. Here, using thin films as a model system, we provide new insights into the radiation tolerance of oxide nanoceramics exposed to increasing damage levels at 600 °C -namely 20, 40 and 150 displacements per atom. Specifically, we investigate the evolution of the structural features, the mechanical properties, and the response to impact loading of Al2O3 thin films. Initially, the thin films contain a homogeneous dispersion of nanocrystals in an amorphous matrix. Irradiation induces crystallization of the amorphous phase, followed by grain growth. Crystallization brings along an enhancement of hardness, while grain growth induces softening according to the Hall-Petch effect. During grain growth, the excess mechanical energy is dissipated by twinning. The main energy dissipation mechanisms available upon impact loading are lattice plasticity and localized amorphization. These mechanisms are available in the irradiated material, but not in the as-deposited films.

  9. Microstructural development of protective Al2O3 scales

    Science.gov (United States)

    Smialek, J. L.

    1984-01-01

    Microstructural characteristics of Al2O3 scales grown as protective coatings on NiCrAl alloys used in jet engines are described. The alloys were pure or doped with 0.3 percent Zr or Y and oxidized in 1 atm air at 1100 C for 0.1, 1 or 20.0 hr. The scales were then examined under a microscope. Transient epitaxial scales, formed during the 0.1 hr treatment and containing Ni, Cr and Al, consisted of a mosaic of subgrains and precipitates of different phases. The Y and Zr dopants had no effect on the nucleation site locations. The appearance of intergranular porosity at 0.1 hr was exacerbated after the 1 hr treatment. A bimodal void distribution appeared after 20 hr, when no porosity was evident. The detection of local areas of preferred orientation is taken as a spur to further studies of scale growth to gain control of the grain size or even to produce single crystal scales.

  10. Trapped charge densities in Al2O3-based silicon surface passivation layers

    Science.gov (United States)

    Jordan, Paul M.; Simon, Daniel K.; Mikolajick, Thomas; Dirnstorfer, Ingo

    2016-06-01

    In Al2O3-based passivation layers, the formation of fixed charges and trap sites can be strongly influenced by small modifications in the stack layout. Fixed and trapped charge densities are characterized with capacitance voltage profiling and trap spectroscopy by charge injection and sensing, respectively. Al2O3 layers are grown by atomic layer deposition with very thin (˜1 nm) SiO2 or HfO2 interlayers or interface layers. In SiO2/Al2O3 and HfO2/Al2O3 stacks, both fixed charges and trap sites are reduced by at least a factor of 5 compared with the value measured in pure Al2O3. In Al2O3/SiO2/Al2O3 or Al2O3/HfO2/Al2O3 stacks, very high total charge densities of up to 9 × 1012 cm-2 are achieved. These charge densities are described as functions of electrical stress voltage, time, and the Al2O3 layer thickness between silicon and the HfO2 or the SiO2 interlayer. Despite the strong variation of trap sites, all stacks reach very good effective carrier lifetimes of up to 8 and 20 ms on p- and n-type silicon substrates, respectively. Controlling the trap sites in Al2O3 layers opens the possibility to engineer the field-effect passivation in the solar cells.

  11. Effect of Al2O3 on Structure and Wearability of Composite Coating

    Institute of Scientific and Technical Information of China (English)

    DING Hong-yan; ZHANG Yue

    2004-01-01

    The composite coating was prepared by thermal spray welding after making composite powder, which is composed of Ni-based self-melted alloy and Al2O3 ceramic powder including nano, sub-micron and micron powders. The influences of contents and sizes of Al2O3 on the structure and wearability were investigated. The results show that the wear resistance of the coating would be increased greatly by adding Al2O3, but the spray weldability decreases with increasing Al2O3 content. So there is an optimal content of Al2O3 powder. The composite coating with Al2O3 nano or sub-micron powder of 0.5 % has the best abrasive resistance, while the optimal content of Al2O3 micron powder is 1%.

  12. Strength and thermal stability of Cu-Al2O3 composite obtained by internal oxidation

    Directory of Open Access Journals (Sweden)

    Jovanovic, M. T.

    2010-12-01

    Full Text Available The objective of the work is to study the effects of the high-energy milling on strengthening, thermal stability and electrical conductivity of Cu-Al2O3 composite. The prealloyed copper powders, atomized in inert gas and containing 3 wt. % Al, were milled up to 20 h in the planetary ball mill to oxidize in situ aluminium with oxygen from the air. Composite compacts were obtained by hot-pressing in an argon atmosphere at 800 °C for 3 h under the pressure of 35MPa. The microstructural characterization was performed by the optical microscope, scanning electron microscope (SEM, transmission electron microscope (TEM and X-ray diffraction analysis (XRD. The microhardness, electrical conductivity and density measurements were also carried out. The effect of internal oxidation and high-energy milling on strengthening of Cu-Al2O3 composite was significant, The increase of the microhardness of composite compacts (292 HV is almost threefold comparing to compacts processed from the as-received Cu-3 wt. % Al powder (102 HV. The grain size of Cu-Al2O3 compacts processed from 5 and 20 h-milled powders was 75 and 45 nm, respectively. The small increase in the grain size and the small microhardness drop indicate the high thermal stability of Cu-Al2O3 composite during high-temperature exposure at 800 °C.El objetivo del trabajo es el estudio de los efectos de la pulverización con altas energías sobre la resistencia, estabilidad térmica y conductividad eléctrica del compuesto Cu-Al2O3. El polvo pre-aleado de cobre, obtenido a través de la atomización con gas inerte y con un contenido de 3wt. % Al, se molió durante 20 h en el molino planetario de bolas dando lugar a la oxidación in situ del aluminio con el oxígeno del aire. El compuesto compactado se ha obtenido mediante prensado en caliente en atmósfera de argón a 800 °C durante 3 h y a una presión de 35MPa. La caracterización microestructural se hizo a través de microscopia óptica, microscopia

  13. Microstructure and Mechanical Property of Hot-Pressed Al2O3-Ni-P Composites Using Ni-P-Coated Al2O3 Powders

    Directory of Open Access Journals (Sweden)

    Hyeong-Chul Kim

    2015-01-01

    Full Text Available Al2O3-Ni-P composite powders with Ni-P contents of 10.9, 14.4, and 20.4 wt.% were synthesized via the Ni-P electroless deposition process. The as-received Al2O3-Ni-P composite powders were composed of Ni-P particles and Ni-P coating layer. Some Ni-P particles randomly adhered to the Al2O3 powders, and their particle diameter ranged from 5 nm to 20 nm. The thin Ni-P layer had about 5 nm thick amorphous structure and directly bonded with Al2O3 powders. Using the Ni-P-coated Al2O3 powders, a dense Al2O3-Ni-P composite can be successfully obtained using the hot press process at 1,350°C for 1 hour in an Ar atmosphere under an applied pressure of 30 MPa. The hot-pressed Al2O3-15 wt.% Ni-P composite showed excellent material properties. Its relative density, Vickers hardness, and fracture toughness were comparatively high: about 99.1%, 2,360 Hv, and 6 MPa·m1/2, respectively. The fracture surface of the hot-pressed Al2O3-Ni-P composite showed a semiductile mode due to the mixed intergranular and transgranular fracture mode. In particular, the fracture toughness of the hot-pressed Al2O3-15 wt.% Ni-P composite was strongly enhanced by the combined action of the crack branching and the crack deflection.

  14. The MgO-Al2O3-SiO2 system - Free energy of pyrope and Al2O3-enstatite. [in earth mantle formation

    Science.gov (United States)

    Saxena, S. K.

    1981-01-01

    The model of fictive ideal components is used to determine Gibbs free energies of formation of pyrope and Al2O3-enstatite from the experimental data on coexisting garnet and orthopyroxene and orthopyroxene and spinel in the temperature range 1200-1600 K. It is noted that Al2O3 forms an ideal solution with MgSiO3. These thermochemical data are found to be consistent with the Al2O3 isopleths that could be drawn using most recent experimental data and with the reversed experimental data on the garnet-spinel field boundary.

  15. Dissolution mechanism of Al2O3 in refining slags containing Ce2O3

    Directory of Open Access Journals (Sweden)

    Wang L.J.

    2016-01-01

    Full Text Available In the present work, the rate of dissolution of Al2O3 rod in CaO-SiO2-Al2O3 and CaO-SiO2-Al2O3-Ce2O3 slags were carried out in the temperature range of 1793 K (1520ºC - 1853 K (1580ºC under static conditions. The cross section of the rod and the boundary layers were identified and analyzed by SEM-EDS. The dissolution of Al2O3 was favored with the increasing CaO/Al2O3 ratio, elevating temperatures as well as the addition of Ce2O3. An intermediate product 3CaO5Al2O3Ce2O3 was detected. The mechanism of dissolution of Al2O3 in the Ce2O3 containing slag were also proposed as three steps involved: 1 the formation of calcium aluminates CaO•Al2O3 at the interface 2 the formation of 3CaO5Al2O3Ce2O3 as the reaction progresses; and 3 the dissolution of 3CaO5Al2O3Ce2O3 into the slag.

  16. The effect of precursors salts on surface state of Pd/Al2O3 and Pd/CeO2/Al2O3 catalysts

    Directory of Open Access Journals (Sweden)

    André L. Guimarães

    2004-12-01

    Full Text Available The influence of the precursors on the promoting effect of ceria on Pd/Al2O3 catalyst, when ceria is coated over alumina was studied. The reaction of propane oxidation proceeded under different feed conditions and the surface active sites were characterized by X-ray photoelectron spectroscopy (XPS and in situ diffuse reflectance spectroscopy (DRS. XPS and DRS results show that PdO/Pd0 interface are the active sites independent of the precursor, while the catalysts containing CeO2 showed formation of palladium species in the highest oxidation state, probably PdO2 (338 eV after the oxidation of propane. Besides, the O/Al and O/Ce ratios evidenced the increase of oxygen storage in the presence of CeO2. In addition, the precursor acetylacetonate favors the oxygen storage in the lattice.Estudo da influência dos precursores sobre os catalisadores de Pd/Al2O3 promovidos com céria ancorado sobre a alumina. A oxidação do propano foi feita sob diferentes condições de alimentação sendo caracterizados os sítios superficiais por Espectroscopia Fotoeletrônica de raios X (XPS e por Refletância Difusa em ''situ''. Resultados de XPS e DRS mostraram a formação de interfaces de PdO/Pd0 como sendo os sítios ativos, independentes do precursor utilizado na preparação, enquanto que os catalisadores contendo CeO2 mostraram a formação de espécies de paládio com estado de oxidação mais altos, provavelmente PdO2 (338 eV após a oxidação do propano. Além disso, as razões O/Al e O/Ce evidenciaram um aumento de oxigênio armazenado na presença de CeO2. O precursor acetilacetonato favoreceu o armazenamento de oxigênio na rede.

  17. Preparation of γ-Al2O3 films by laser chemical vapor deposition

    Science.gov (United States)

    Gao, Ming; Ito, Akihiko; Goto, Takashi

    2015-06-01

    γ- and α-Al2O3 films were prepared by chemical vapor deposition using CO2, Nd:YAG, and InGaAs lasers to investigate the effects of varying the laser wavelength and deposition conditions on the phase composition and microstructure. The CO2 laser was found to mostly produce α-Al2O3 films, whereas the Nd:YAG and InGaAs lasers produced γ-Al2O3 films when used at a high total pressure. γ-Al2O3 films had a cauliflower-like structure, while the α-Al2O3 films had a dense and columnar structure. Of the three lasers, it was the Nd:YAG laser that interacted most with intermediate gas species. This promoted γ-Al2O3 nucleation in the gas phase at high total pressure, which explains the cauliflower-like structure of nanoparticles observed.

  18. Al2O3层状复合陶瓷的研究进展%PROGRESS IN RESEARCH ON LAMINATED Al2O3 CERAMIC MATRIX COMPOSITES

    Institute of Scientific and Technical Information of China (English)

    孙媛媛; 王芬; 周彦昭

    2004-01-01

    层状复合是目前增韧Al2O3陶瓷的有效途径,从层状复合材料的成型方法、增韧机制、结构设计等方面,论述了Al2O3体系层状复合陶瓷的研究进展及目前存在的问题.

  19. Effect of Ultrasonic Vibration on the Behavior of Antifriction and Wear Resistance of Al2O3/Al2O3 Ceramic Friction Pairs Under Oil Lubrication

    Science.gov (United States)

    Dong, X. Y.; Qiao, Y. L.; Zang, Y.; Cui, Q. S.

    The behavior of antifriction and wear resistance of Al2O3/Al2O3 ceramic friction pairs lubricated by four different lubrication oils under ultrasonic vibration was studied. The surface morphologies of wear scare was analyzed by metallographic microscope. The effect mechanism of ultrasonic vibration on frictional pairs under different lubrication oils was discussed. The studied results showed that, ultrasonic vibration would improve the behavior of antifriction and wear resistance of the Al2O3/Al2O3 ceramic friction pairs under various lubrication oils.The improving would be dramaticer when the viscosity of lubrication oil was low. Ultrasonic vibration decreased the friction coefficient and wear volume 12.9% and 38.7% respectively, when the lubrication oil was 6#,the viscosity of which is 39.77 mm2/s. When the lubrication oil was 150BS, the viscosity of which is 549.69 mm2/s, ultrasonic vibration made friction coefficient and wear volume decreased 4.6% and 11.6% respectively.The effect of ultrasonic vibration on the behavior of antifriction and wear resistance of Al2O3/Al2O3 ceramic friction pairs was determined by the formation and the destruction of oil film on the friction surface and the upward floatage created by ultrasonic vibration.

  20. Influences of Al2O3 grain size on high-temperature oxidation of nano-Ni/Al2O3 composites

    Directory of Open Access Journals (Sweden)

    Hai Vu Pham

    2016-03-01

    Full Text Available Two 5 vol% Ni/Al2O3 composites with the difference in Al2O3 grain size were fabricated by pulsed electric current sintering technique to investigate the influence of Al2O3 grain size on oxidation behavior of the composites. Average Al2O3 grain sizes of two fabricated composites were 1.1 μm and 0.5 μm after sintering. Oxidation tests were conducted at temperatures ranging from 1100 to 1350 °C for 1–48 h in air. A thin NiAl2O4 layer was observed in exposed surface of samples after oxidation. An oxidized zone that consisted of Al2O3 matrix and NiAl2O4 grains was defined. Growth of the oxidized zone obeyed the parabolic law. Influences of Al2O3 grain size on high-temperature oxidation of the composites were discussed.

  1. Sliding wear of ZrO2-Al2O3 composite ceramics

    NARCIS (Netherlands)

    He, Y.J.; Winnubst, A.J.A.; Burggraaf, A.J.; Verweij, H.; Varst, van de P.G.T.; With, de G.

    1997-01-01

    The friction and wear behaviour of two ZrO2-Al2O3 composite materials, ADZ (20 wt% Al2O3 dispersed in yttria-doped ZrO2 matrix) and ZTA (Al2O3-15 wt% ZrO2), were investigated. Sliding wear tests were carried out on these materials under dry conditions using a ball-on-plate configuration. The effects

  2. Cerium and Lanthanum Modified Pd/Al2O3 Catalysts for Methanol Decomposition

    Institute of Scientific and Technical Information of China (English)

    杨成; 任杰; 孙予罕

    2001-01-01

    CeO2 improves the activity and selectivity of Pd/Al2O3 catalyst for methanol decomposition. The interaction between Pd and CeO2 was then proposed to result in the promoting effect. The selectivity of CO and H2 is significantly improved by addition of La2O3 to either Pd/Al2O3 or Pd/CeO2/Al2O3 catalysts. Moreover, a synergistic promotion between CeO2 and La2O3 on γ-Al2O3 supported Pd catalysts was observed for the catalytic activity towards methanol decomposition into CO and H2.

  3. An Investigation of Laser Assisted Machining of Al_2O_3 Particle Reinforced Aluminum Matrix Composite

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The Al 2O 3 particles reinforced aluminum matrix composite (Al 2O 3p/Al) are more and more widely used for their excellent physical and chemical properties. However, their poor machinability leads to severe tool wear and bad machined surface. In this paper laser assisted machining is adopted in machining Al 2O 3p/Al composite and good result was obtained. The result of experiment shows in machining Al 2O 3p/Al composites the cutting force is reduced in 30%~50%, the tool wear is reduced in 20%~30% an...

  4. Model Research On Synthesis Of Al2O3-C Layers By MOCVD

    Directory of Open Access Journals (Sweden)

    Sawka A.

    2015-06-01

    Full Text Available These are model studies whose aim is to obtain information that would allow development of new technology for synthesizing monolayers of Al2O3-C with adjusted microstructure on cemented carbides. The Al2O3-C layer will constitute an intermediate layer on which the outer layer of Al2O3 without carbon is synthesized. The purpose of the intermediate layer is to block the cobalt diffusion to the synthesized outer layer of Al2O3 and to stop the diffusion of air oxygen to the substrate during the synthesis of the outer layer. This layer should be thin, continuous, dense and uniform in thickness.

  5. Oxidation precursor dependence of atomic layer deposited Al2O3 films in a-Si:H(i)/Al2O3 surface passivation stacks

    Science.gov (United States)

    Xiang, Yuren; Zhou, Chunlan; Jia, Endong; Wang, Wenjing

    2015-03-01

    In order to obtain a good passivation of a silicon surface, more and more stack passivation schemes have been used in high-efficiency silicon solar cell fabrication. In this work, we prepared a-Si:H(i)/Al2O3 stacks on KOH solution-polished n-type solar grade mono-silicon(100) wafers. For the Al2O3 film deposition, both thermal atomic layer deposition (T-ALD) and plasma enhanced atomic layer deposition (PE-ALD) were used. Interface trap density spectra were obtained for Si passivation with a-Si films and a-Si:H(i)/Al2O3 stacks by a non-contact corona C-V technique. After the fabrication of a-Si:H(i)/Al2O3 stacks, the minimum interface trap density was reduced from original 3 × 1012 to 1 × 1012 cm-2 eV-1, the surface total charge density increased by nearly one order of magnitude for PE-ALD samples and about 0.4 × 1012 cm-2 for a T-ALD sample, and the carrier lifetimes increased by a factor of three (from about 10 μs to about 30 μs). Combining these results with an X-ray photoelectron spectroscopy analysis, we discussed the influence of an oxidation precursor for ALD Al2O3 deposition on Al2O3 single layers and a-Si:H(i)/Al2O3 stack surface passivation from field-effect passivation and chemical passivation perspectives. In addition, the influence of the stack fabrication process on the a-Si film structure was also discussed in this study.

  6. MgAl2O4–-Al2O3 solid solution interaction: mathematical framework and phase separation of -Al2O3 at high temperature

    Indian Academy of Sciences (India)

    Soumen Pal; A K Bandyopadhyay; S Mukherjee; B N Samaddar; P G Pal

    2011-07-01

    Although existence of MgAl2O4–-Al2O3 solid solution has been reported in the past, the detailed interactions have not been explored completely. For the first time, we report here a mathematical framework for the detailed solid solution interactions of -Al2O3 in MgAl2O4 (spinel). To investigate the solid solubility of -Al2O3 in MgAl2O4, Mg–Al spinel (MgO–Al2O3; = 1, 1.5, 3, 4.5 and an arbitrary high value 30) precursors have been heat treated at 1000°C. Presence of only non-stoichiometric MgAl2O4 phase up to = 4.5 at 1000°C indicates that alumina (as -Al2O3) present beyond stoichiometry gets completely accommodated in MgAl2O4 in the form of solid solution. → alumina phase transformation and its subsequent separation from MgAl2O4 has been observed in the Mg–Al spinel powders ( > 1) when the 1000°C heat treated materials are calcined at 1200°C. In the mathematical framework, unit cell of MgAl2O4 (Mg8Al16O32) has been considered for the solid solution interactions (substitution of Mg2+ ions by Al3+ ions) with -Al2O3. It is suggested that combination of unit cells of MgAl2O4 takes part in the interactions when > 5 (MgO–Al2O3).

  7. Integrated Al2O3:Er3+ amplifiers: The impact of fast spectroscopic quenching processes

    NARCIS (Netherlands)

    Agazzi, L.; Bradley, J.D.B.; Wörhoff, K.; Pollnau, M.

    2011-01-01

    We report a number of recently demonstrated integrated Al2O3:Er3+ devices and present spectroscopic investigations revealing the presence of a fast quenching mechanism – undetected in typical luminescence decay measurements – which limits the Al2O3:Er3+ amplifier performance.

  8. Microstructure of Al2O3/SiO2 ceramic core nano-composites

    Institute of Scientific and Technical Information of China (English)

    赵红亮; 翁康荣; 关绍康; 楼琅洪; 李英敖; 赵惠田; 胡壮麒

    2004-01-01

    Al2O3/SiO2 ceramic core nano-composites were prepared and their microstructure was investigated by transmission electron microscope(TEM). The results show that intergranular nano-composites are achieved. The bonding between Al2O3 and SiO2 particles is well and the interface is even. Amorphous phases and nano crystals appear in the Al2O3/SiO2 ceramic core nano-composites, which both come into being during the cooling process after sintering. Glass phase does not appear between the Al2O3 and SiO2 particles and only appears among the Al2O3 particles, which can be explained with stress model. The quantity of the glass phase is not much and its influence on the high-temperature deformation of the ceramic core nano-composites is little.

  9. Photochemistry of the α-Al2O3-PETN Interface

    Directory of Open Access Journals (Sweden)

    Roman V. Tsyshevsky

    2016-02-01

    Full Text Available Optical absorption measurements are combined with electronic structure calculations to explore photochemistry of an α-Al2O3-PETN interface formed by a nitroester (pentaerythritol tetranitrate, PETN, C5H8N4O12 and a wide band gap aluminum oxide (α-Al2O3 substrate. The first principles modeling is used to deconstruct and interpret the α-Al2O3-PETN absorption spectrum that has distinct peaks attributed to surface F0-centers and surface—PETN transitions. We predict the low energy α-Al2O3 F0-center—PETN transition, producing the excited triplet state, and α-Al2O3 F0-center—PETN charge transfer, generating the PETN anion radical. This implies that irradiation by commonly used lasers can easily initiate photodecomposition of both excited and charged PETN at the interface. The feasible mechanism of the photodecomposition is proposed.

  10. Comparison of ALD and IBS Al2O3 films for high power lasers

    Science.gov (United States)

    Liu, Hao; Jensen, Lars; Becker, Jürgen; Wurz, Marc Christopher; Ma, Ping; Ristau, Detlev

    2016-12-01

    Atomic layer deposition (ALD) has been widely studied in Micro-electronics due to its self-terminating property. ALD also grows film coatings with precise thickness and nodular-free structure, which are desirable properties for high power coatings. The depositing process was studied to produce uniform, stable and economic Al2O3 single layers. The layer properties relevant to high power laser industry were studied and compared with IBS Al2O3 single layers. ALD Al2O3 showed a stable growth of 0.104 nm/cycle, band gap energy of 6.5 eV and tensile stress of about 480 MPa. It also showed a low absorption at wavelength 1064 nm within several ppm, and LIDT above 30 J/cm2. These properties are superior to the reference IBS Al2O3 single layers and indicate a high versatility of ALD Al2O3 for high power coatings.

  11. Epitaxial Al2O3 capacitors for low microwave loss superconducting quantum circuits

    Directory of Open Access Journals (Sweden)

    K.-H. Cho

    2013-10-01

    Full Text Available We have characterized the microwave loss of high-Q parallel plate capacitors fabricated from thin-film Al/Al2O3/Re heterostructures on (0001 Al2O3 substrates. The superconductor-insulator-superconductor trilayers were grown in situ in a hybrid deposition system: the epitaxial Re base and polycrystalline Al counterelectrode layers were grown by sputtering, while the epitaxial Al2O3 layer was grown by pulsed laser deposition. Structural analysis indicates a highly crystalline epitaxial Al2O3 layer and sharp interfaces. The measured intrinsic (low-power, low-temperature quality factor of the resonators is as high as 3 × 104. These results indicate that low-loss grown Al2O3 is an attractive candidate dielectric for high-fidelity superconducting qubit circuits.

  12. Characterization and prevention of humidity related degradation of atomic layer deposited Al2O3

    Science.gov (United States)

    Rückerl, Andreas; Zeisel, Roland; Mandl, Martin; Costina, Ioan; Schroeder, Thomas; Zoellner, Marvin H.

    2017-01-01

    Atomic layer deposited aluminum oxide (ALD-Al2O3) is a dielectric material, which is widely used in organic light emitting diodes in order to prevent their organic layers from humidity related degradation. Unfortunately, there are strong hints that in some cases, ALD-Al2O3 itself is suffering from humidity related degradation. Especially, high temperature and high humidity seem to enhance ALD-Al2O3 degradation strongly. For this reason, the degradation behavior of ALD-Al2O3 films at high temperature and high humidity was investigated in detail and a way to prevent it from degradation was searched. The degradation behavior is analyzed in the first part of this paper. Using infrared absorbance measurements and X-ray diffraction, boehmite (γ-AlOOH) was identified as a degradation product. In the second part of the paper, it is shown that ALD-Al2O3 films can be effectively protected from degradation using a silicon oxide capping. The deposition of very small amounts of silicon in a molecular beam epitaxy system and an X-ray photoelectron spectroscopy investigation of the chemical bonding between the silicon and the ALD-Al2O3 surface led to the conclusion that a silicon termination of the ALD-Al2O3 surface (Al*-O-SiOx) is able to stop humidity related degradation of the underlying ALD-Al2O3 films. The third part of the paper shows that the protection mechanism of the silicon termination is probably due to the strong tendency of silicic acid to resilificate exposed ALD-Al2O3 surfaces. The protective effect of a simple silicon source on an ALD-Al2O3 surface is shown exemplary and the related chemical reactions are presented.

  13. Microstructure and Properties of SCE-Al2O3/PES-MBAE Composite

    Directory of Open Access Journals (Sweden)

    Yufei Chen

    2014-01-01

    Full Text Available SCE-Al2O3 was the nano-Al2O3 modified by supercritical ethanol and the surface of SCE-Al2O3 was coated with active group. 4,4′-diaminodiphenylmethane bismaleimide (MBMI was used as matrix; 3,3′-diallyl bisphenol A (BBA and bisphenol-A diallyl ether (BBE were used as reactive diluent, polyethersulfone (PES as toughening agent, and SCE-Al2O3 as modifier; SCE-Al2O3/PES-MBAE nanocomposite was prepared through in situ sol-gel method. The mechanism of composite toughened by PES was observed and analyzed. FTIR indicated that the reaction between MBMI and allyl compound occurred and SCE-Al2O3 had doped into the polymer matrix. SEM showed that PES particle was inlaid in matrix and presented as a two-phase structure in matrix. The heat resistance, dielectric properties, and mechanical properties of SCE-Al2O3/PES-MBAE nanocomposites were evaluated. The results showed that with the incorporation of PES, although the toughness of the material improved, the heat resistance and dielectric properties of material declined, meanwhile. The adulteration of SCE-Al2O3 could remedy the harmful effect caused by PES, while the content of SCE-Al2O3 was reasonable. The decomposition temperature, dielectric constant, and dielectric loss of composite were 441.23°C, 3.63 (100 Hz, and 1.52 × 10−3 (100 Hz; the bending strength and impact strength were 129.22 MPa and 13.19 kJ/mm2, respectively, when the content of SCE-Al2O3 was 3 wt% and PES was 5 wt%.

  14. Robust Low Voltage Program-Erasable Cobalt-Nanocrystal Memory Capacitors with Multistacked Al2O3/HfO2/Al2O3 Tunnel Barrier

    Institute of Scientific and Technical Information of China (English)

    LIAO Zhong-Wei; GOU Hong-Yan; HUANG Yue; SUN Qing-Qing; DING Shi-Jin; ZHANG Wei; ZHANG Shi-Li

    2009-01-01

    An atomic-layer-deposited Al2O3/HfO2/Al2O3 (A/H/A) tunnel barrier is investigated for Co nanocrystal memory capacitors. Compared to a single Al2O3 tunnel barrier, the A/H/A barrier can significantly increase the hysteresis window, i.e., an increase by 9 V for ±12 V sweep range. This is attributed to a marked decrease in the energy barriers of charge injections for the A/H/A tunnel barrier. Further, the Co-nanocrystal memory capacitor with the A/H/A tunnel barrier exhibits a memory window as large as 4.1 V for 100 /us program/erase at a low voltage of ±7 V, which is due to fast charge injection rates, i.e., about 2.4 × 1016 cm-2s-1 for electrons and 1.9×1016 cm-2s-1 for holes.

  15. Preparation of mullite whiskers reinforced SiC/Al2O3 composites by microwave sintering

    Directory of Open Access Journals (Sweden)

    Wei Li

    2016-12-01

    Full Text Available Mullite whiskers reinforced SiC/Al2O3 composites were prepared by microwave sintering in a microwave chamber with TE666 resonant mode. Original SiC particles were coated with SiO2 using sol-gel processing and mixed with Al2O3 particles. Mullite was formed in the reaction between SiO2 and Al2O3. The isostatically pressed cylindrical pellets were sintered from 1350 °C to 1600 °C for 30 min. Physical and chemical responses were investigated by detecting changes in reflected power during the microwave sintering process. XRD was carried out to characterize the samples and showed that mullite could be formed at 1200 °C. Bridging of mullite whiskers between Al2O3 and SiC particles was observed by SEM and is due to a so-called local hot spot effect, which was the unique feature for microwave sintering. The optimized microwave sintering temperature was 1500 °C corresponding to the maximum amount of mullite whiskers within SiC/Al2O3 composites. The high electro-magnetic field enhanced the decomposition of mullite at higher temperatures above 1550 °C. The mechanical properties of mullite whiskers reinforced SiC/Al2O3 composites are much better than the SiC/Al2O3 composites without mullite whiskers.

  16. Al2O3 on Black Phosphorus by Atomic Layer Deposition: An in Situ Interface Study.

    Science.gov (United States)

    Zhu, Hui; McDonnell, Stephen; Qin, Xiaoye; Azcatl, Angelica; Cheng, Lanxia; Addou, Rafik; Kim, Jiyoung; Ye, Peide D; Wallace, Robert M

    2015-06-17

    In situ "half cycle" atomic layer deposition (ALD) of Al2O3 was carried out on black phosphorus ("black-P") surfaces with modified phosphorus oxide concentrations. X-ray photoelectron spectroscopy is employed to investigate the interfacial chemistry and the nucleation of the Al2O3 on black-P surfaces. This work suggests that exposing a sample that is initially free of phosphorus oxide to the ALD precursors does not result in detectable oxidation. However, when the phosphorus oxide is formed on the surface prior to deposition, the black-P can react with both the surface adventitious oxygen contamination and the H2O precursor at a deposition temperature of 200 °C. As a result, the concentration of the phosphorus oxide increases after both annealing and the atomic layer deposition process. The nucleation rate of Al2O3 on black-P is correlated with the amount of oxygen on samples prior to the deposition. The growth of Al2O3 follows a "substrate inhibited growth" behavior where an incubation period is required. Ex situ atomic force microscopy is also used to investigate the deposited Al2O3 morphologies on black-P where the Al2O3 tends to form islands on the exfoliated black-P samples. Therefore, surface functionalization may be needed to get a conformal coverage of Al2O3 on the phosphorus oxide free samples.

  17. High energy transmission of Al2O3 doped with light transition metals

    KAUST Repository

    Schuster, Cosima

    2012-01-31

    The transmission of transparent colored ceramics based on Al2O3doped with light transition metals is measured in the visible and infrared range. To clarify the role of the dopands we perform ab initiocalculations. We discuss the electronic structure and present optical spectra obtained in the independent particle approximation. We argue that the gross spectral features of Co- and Ni-doped Al2O3 samples are described by our model, while the validity of the approach is limited for Cr-doped Al2O3.

  18. Ultrasonically assisted intercalation of Ni in Al2O3 thin film prepared by SILAR technique

    Science.gov (United States)

    Dhanayat, Swapnali; Digraskar, Renuka; Gattu, Ketan; Upadhye, Deepak; Mahajan, Sandeep; Sharma, Ramphal; Ghule, Anil

    2013-06-01

    The Al2O3 thin film were prepared by successive ionic layer adsorption and reaction (SILAR) technique and annealed at 250 °C. Thereafter, Ni was ultrasonically intercalated in Al2O3 thin films for different sonication time period of 5 and 10s, and subsequently annealed at 250 °C to form NiO-Al2O3. The films were further characterized using scanning electron microscopy, energy dispersive X-ray analysis, UV-Vis spectrophotometer and I-V system, to study morphological, compositional, optical and electrical properties.

  19. 高耐用性轻质Al_2O_3-MgO-C砖

    Institute of Scientific and Technical Information of China (English)

    王振良; 吕冰; 王守权

    2011-01-01

    Al2O3-MgO-C砖广泛用于钢包内衬的金属线。品川白耐火材料有限公司开发出了一种高耐用性轻质Al2O3-MgO-C砖——CALEAD。CALEAD的质量比普通Al2O3-MgO-C砖低10%,导热系数和体积密度均低于普通产品,其他性能基本相同。

  20. Finite element analysis of WC-Al2O3 composites

    Science.gov (United States)

    Patel, Satyanarayan; Vaish, Rahul

    2014-02-01

    Object oriented finite element analysis (OOF2) is used to estimate the thermal and mechanical properties of WC-Al2O3 composites. In the present work, five compositions of 10%, 20%, 30%, 40% and 50% Al2O3 (by volume) are studied. Young's modulus, thermal conductivity and thermal expansion coefficient are estimated using OOF2 and compared with other known analytical methods. Stress and strain contours are plotted to study the thermal and mechanical behavior of composites. It is found that the stresses are largely concentrated at the interfaces of the WC-Al2O3 phases.

  1. Cathode encapsulation of OLEDs by atomic layer deposited Al2O3 films and Al2O3/a-SiNx:H stacks

    NARCIS (Netherlands)

    Keuning, W.; Van de Weijer, P.; Lifka, H.; Kessels, W.M.M.; Creatore, M.

    2011-01-01

    Al2O3 thin films synthesized by plasma-enhanced atomic layer deposition(ALD) at room temperature (25 ºC) have been tested as water vapor per-meation barriers for OLED devices. Silicon nitride films (a-SiNx:H)deposited by plasma-enhanced chemical vapor deposition (PE-CVD) servedas reference and were

  2. Effects of Al2O3 Particulates on the Thickness of Reaction Layer of Al2O3 Joints Brazed with Al2O3-Particulate-Contained Composite Filler Materials

    Institute of Scientific and Technical Information of China (English)

    Jianguo YANG; Jingwei WU; Hongyuan FANG

    2003-01-01

    In order to understand the rate-controlling process for the interfacial layer growth of brazing joints brazed with activecomposite filler materials, the thickness of brazing joints brazed with conventional active filler metal and activecomposite filler materials with different volume fraction of Al2O3 particulate was studied. The experimental resultsindicate although there are Al2O3 particulates added into active filler metals, the time dependence of interfacial layergrowth is t2 as described by Fickian law for the joints brazed with conventional active filler metal. It also shows thatthe key factor affecting the interfacial layer growth is the volume fraction of alumina in the composite filler materialcompared with the titanium weight fraction in the filler material.

  3. ESTUDIO ELIPSOMÉTRICO DE PELÍCULAS SEMITRANSPARENTES DE PLATA DEPOSITADAS SOBRE VIDRIO

    Directory of Open Access Journals (Sweden)

    Víctor Toranzos

    2014-01-01

    Full Text Available Uti lizando elipsometría , se caracteriza l a estructura de la película mediante los índices ópticos n, k (región visible, 450 nm <  < 580 nm y el espesor ( 15 < d < 35 nm. Los índices ópticos varían con la cantidad de plata depositada obteniéndose para los menores depósitos índices efectivos 1.0 < n < 1.8 y 1.6 < k < 2.6 que corresponden, de acuerdo a los modelos utilizados, a una fracción volumétrica entre 0.35 y 0.5 d e plata en aire. Al aumentar la fracción volumétrica de plata se observa primeramente una disminución del espesor óptico efectivo de la película y para mayor cantidad de plata depositada se observa un aumento del espe sor con índices que tienden a valores má s p róximos a los de la plata maciza . Se comparan los índices ópticos obtenidos con los que se obtienen mediante las teorías de medio efectivo.

  4. Optical properties of the Al2O3/SiO2 and Al2O3/HfO2/SiO2 antireflective coatings

    Science.gov (United States)

    Marszałek, Konstanty; Winkowski, Paweł; Jaglarz, Janusz

    2014-01-01

    Investigations of bilayer and trilayer Al2O3/SiO2 and Al2O3/HfO2/SiO2 antireflective coatings are presented in this paper. The oxide films were deposited on a heated quartz glass by e-gun evaporation in a vacuum of 5 × 10-3 [Pa] in the presence of oxygen. Depositions were performed at three different temperatures of the substrates: 100 °C, 200 °C and 300 °C. The coatings were deposited onto optical quartz glass (Corning HPFS). The thickness and deposition rate were controlled with Inficon XTC/2 thickness measuring system. Deposition rate was equal to 0.6 nm/s for Al2O3, 0.6 nm - 0.8 nm/s for HfO2 and 0.6 nm/s for SiO2. Simulations leading to optimization of the thin film thickness and the experimental results of optical measurements, which were carried out during and after the deposition process, have been presented. The optical thickness values, obtained from the measurements performed during the deposition process were as follows: 78 nm/78 nm for Al2O3/SiO2 and 78 nm/156 nm/78 nm for Al2O3/HfO2/SiO2. The results were then checked by ellipsometric technique. Reflectance of the films depended on the substrate temperature during the deposition process. Starting from 240 nm to the beginning of visible region, the average reflectance of the trilayer system was below 1 % and for the bilayer, minima of the reflectance were equal to 1.6 %, 1.15 % and 0.8 % for deposition temperatures of 100 °C, 200 °C and 300 °C, respectively.

  5. Excitation quenching in Er3-doped Al2O3 amplifiers

    NARCIS (Netherlands)

    Agazzi, L.; Wörhoff, K.; Pollnau, M.

    2011-01-01

    Spectroscopic investigations in Al2O3:Er waveguides demonstrate that fast quenching of a fraction of ions - undetected in typical lumescence decay measurements - limits the amplifier performance. With optimized parameters 3 dB/cm net gain is feasible.

  6. 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.

  7. Preparation and formation mechanism of Al2O3 nanoparticles by reverse microemulsion

    Institute of Scientific and Technical Information of China (English)

    HUANG Ke-long; YIN Liang-guo; LIU Su-qin; LI Chao-jian

    2007-01-01

    Al2O3 nanoparticles were prepared by polyethylene glycol octylphenyl ether(Triton X-100)/n-butyl alcohol/cyclohexane/ water W/O reverse microemulsion. The proper calcination temperature was determined at 1 150 ℃ by thermal analysis of the precursor products. The structures and morphologies of Al2O3 nanoparticles were characterized by X-ray diffraction, transmission electron microscopy and UV-Vis spectra. The influences of mole ratio of water to surfactant on the morphologies and the sizes of the Al2O3 nanoparticles were studied. With the increase of surfactant content, the particles size becomes larger. The agglomeration of nanoparticles was solved successfully. And the formation mechanisms of Al2O3 nanoparticles in the reverse microemulsion were also discussed.

  8. Sintering densification and properties of Al2O3/PSZ(3Y) ceramic composites

    Institute of Scientific and Technical Information of China (English)

    马伟民; 修稚萌; 闻雷; 孙旭东; 铁维麟

    2004-01-01

    The content of partially stabilized zirconia has remarkable influence on densification and mechanical properties of Al2 O3/PSZ(3Y) ceramic composites. When 15%PSZ(3Y) is added to Al2 O3, after vacuum sintering for 2h at 1 550 ℃, the fracture toughness and bending strength of the Al2O3/PSZ(3Y) ceramic composite reaches 8.2properties was investigated. The change of rn-ZrO2 and t-ZrO2 phases content before and after fracture was measured by X-ray diffraction quantitative phase analysis. It is confirmed that improvement in bending strength and fracture toughness of the Al2O3/PSZ(3Y) ceramic composite is due to the phase transformation toughening mechanism of PSZ(3Y).

  9. PREPARATION OF CUO/γ-Al2O3 CATALYSTS FOR CATALYTIC COMBUSTION VOCS VIA PLASMA

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    CuO/γ-Al2O3 catalysts were prepared by plasma treatment and conventional impregnation methods. The catalytic combustion of two kinds of volatile organic compounds (VOCs), toluene and benzene, were carried out over these CuO/γ-Al2O3 catalysts. The surface properties of these catalysts were characterized by X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). The experimental results showed that in catalytic combustion the activity of the CuO/γ-Al2O3 catalyst prepared via plasma was much higher than that of the CuO/γ-Al2O3 catalyst prepared by conventional impregnation method. XRD results showed that an enhanced dispersion had been achieved with the plasma treatment. SEM results indicated that the size became much smaller and the surface became more uniform with the plasma treatment.

  10. Thermal shock fatigue behavior of TiC/Al2O3 composite ceramics

    Institute of Scientific and Technical Information of China (English)

    SI Tingzhi; LIU Ning; ZHANG Qingan; YOU Xianqing

    2008-01-01

    The thermal shock fatigue behaviors of pure hot-pressed alumina and 30 wt. % TiC/Al2O3 composites were studied. The effect of TiC and Al2O3 starting particle size on the mechanical properties of the composites was discussed. Indentation-quench test was conducted to evaluate the effect of thermal fatigue temperature difference (ΔT) and number of thermal cycles (N) on fatigue crack growth (Δα). The mechanical properties and thermal fatigue resistance of TiC/Al2O3 composites are remarkably improved by the addition of TiC. The thermal shock fatigue of monolithic alumina and TiC/Al2O3 composites is due to a "true" cycling effect (thermal fatigue). Crack deflection and bridging are the predominant reasons for the improvement of thermal shock fatigue resistance of the composites.

  11. Research on Surface Modification of 96 Al2O3 by Ni Ion Implantation

    Institute of Scientific and Technical Information of China (English)

    WANG Xiao-hong; SUN Zhi; ZHU Xin; WANG Zhen-zhong

    2006-01-01

    A matrix of 96 Al2O3 ceramics was implanted with Ni ion of different dosages and energies using a MEVVA implanter. Then metallic structures of copper were made on the implanted ceramics, by using selective electroless copper plating. In addition, the characteristics and microstructure of the implanted layer were studied by using the SEM, RBS and XPS. The results show that: 1) the implanted Ni exits as Ni0 , Ni2+, and Ni3+ in the surface of Al2O3 and metal Ni particles precipitate on ceramics during implantation; 2) the concentration of Ni submits to the Gauss distribution along the direction of implantation on the surface of Al2O3 and high Ni concentration on the surface can be obtained if the Ni is implanted with low energy and a high dosage and 3) Ni ion implantation can activate the surface of Al2O3 and induce electroless copper plating on the ceramics.

  12. Synthesis of Al2O3/WC powder by aluminothermic reduction and carbonization method

    Institute of Scientific and Technical Information of China (English)

    韩兵强; 李楠

    2004-01-01

    Al2O3/WC powder was synthesized by means of aluminothermic reduction-carbonization with metallic Al powder, yellow tungsten oxide and carbon black or graphite as raw materials under the protection of coke granules.The effects of Al2O3 content, temperature, C/WO3 molar ratio, and atmosphere on the synthesis of Al2O3/WC powder were studied. The results show that the relative content of WC and W2C is strongly influenced by the factors mentioned-above. Carbon black has higher reactivity than graphite. Al2O3-WC composite is easier to obtain under the protection of coke granules than under argon atmosphere. The CO in the coke layer can easily react with tungsten to form WC and to transfer from W2 C to WC.

  13. Al2O3:Er3+ waveguide amplifiers at 1.5 μm

    NARCIS (Netherlands)

    Agazzi, L.; Bradley, J.D.B.; Ay, F.; Wörhoff, K.; Pollnau, M.

    2010-01-01

    We report optical amplification in Al2O3:Er3+ with a gain bandwidth of 80 nm and peak gain of 2.0 dB/cm at 1533 nm, data transmission at 170 Gbit/s without added bit-error penalty and monolithic integration of these active Al2O3:Er3+ waveguides with passive silicon-on-insulator waveguides.

  14. Influence of Al2O3 content and heat treatment temperature on corrosion resistance of Al2O3-SiO2 castables to molten aluminum%Al2O3含量及热处理温度对Al2O3-SiO2系浇注料抗铝液侵蚀性的影响

    Institute of Scientific and Technical Information of China (English)

    张三华; 王战民; 胡书禾; 李少飞; 石会营; 曹喜营; 喻枫

    2010-01-01

    采用坩埚法和浸泡法研究了不同Al2O3含量(质量分数分别为80%~85%、65%~70%、40%~45%、25%~30%)及不同温度(分别为110、800、1 100和1 400 ℃)热处理后的Al2O3-SiO2系浇注料的抗铝液侵蚀性,借助电镜和能谱分析研究了被850 ℃铝液侵蚀后试样的显微结构.结果表明:(1)随着Al2O3含量的增加,Al2O3-SiO2系浇注料的抗铝液侵蚀性增强;(2)在1 100 ℃热处理后,浇注料的抗铝液侵蚀性最差;(3)铝液渗入浇注料内部后,铝液中的Al和Mg与浇注料中的石英和莫来石相发生反应,将SiO2还原成Si,Al和Mg则氧化成Al2O3和MgO,MgO进而与Al2O3反应生成尖晶石,破坏试样的结构;(4)对于Al2O3含量较高的Al2O3-SiO2浇注料,尖晶石富集层较致密,可阻止铝液继续向浇注料内部渗透.

  15. Methane Coupling Using Hydrogen Plasma and Pt/γ-Al2O3 Catalyst

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    In this paper, methane coupling at ambient temperature, under atmospheric pressure and in the presence of hydrogen was firstly investigated by using pulse corona plasma and Pt/γ-Al2O3 catalyst. Experimental results showed that Pt/γ-Al2O3 catalyst has catalytic activity for methane coupling to C2H4. Over sixty percent of outcomes of C2 hydrocarbons were detected to be ethylene.

  16. Preparation of ultrafine a-Al2O3 using precipitation-azeotropic distillation method

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Ammonium aluminum carbonate hydroxide (AACH) was prepared by a precipitation-azeotropic distillation method,which uses aluminum sulfate as the Al source and ammonium carbonate as the precipitant.Then,AACH was calcined into ultrafine α-Al2O3 powder.The factors that influence the dispersion property of ultrafine α-Al2O3 powder are discussed in this paper,such as the methods of adding materials,surfactant,and drying methods.The changes of the structure and property of ultrafine alumina in the thermal treatment process are also studied.The morphological structure and properties of AACH are characterized by DTA/TGA,SEM,XRD,and ICP measurements.The results show that ultrafine α-Al2O3 powder with a uniform particle size and well-distributed property can be synthesized only after aluminum sulfate atomizes into ammonium carbonate,proper amount of PEG1000 is added as the dispersant,and the product is treated by azeotropic distillation.The phase transformation of alumina during the calcination process can be described as amorphous Al2O3→γ-Al2O3→θ-Al2O3→α-Al2O3.The crystal grain size and density of ultrafine alumina powder increase with the increase of the calcination temperature.After AACH has been calcined at 1200℃ for 2 h,the ultrafine α-Al2O3 with uniform particle size,spherical shape,and more than 99.97% purity is obtained and its powder is well dispersed.

  17. Synthesis of highly porous Al2O3-YAG composite ceramics

    Directory of Open Access Journals (Sweden)

    Egelja Adela

    2016-01-01

    Full Text Available Al2O3-YAG composite was obtained by sintering of porous Al2O3 preforms infiltrated with water solution of aluminium nitrate nonahydrate, Al(NO33•9H2O and yttrium nitrate hexahydrate, Y(NO33•6H2O. Al2O3 preforms with porosity varying from 26 to 50% were obtained after sintering at temperature ranging from 1100 to 1500°C. Sintering of the infiltrated Al2O3 preforms led to formation of YAG particles due to reaction between Y2O3 and Al2O3 at high temperature. It was found that variation of porosity of alumina preforms and sintering temperature is an effective way to fabricate Al2O3-YAG composite with an unusual combination of properties. Open porosity was in the range 15-35%, specific surface was 0.6-6.1 m2/g, pore size was 150-900 nm whereas compressive strength was from 50 to 250 MPa. The effect of sintering temperature on YAG formation and phase composition were investigated using X-ray diffractometry whereas microstructure of the composite was analysed by scanning electron microscopy. [Projekat Ministartsva nauke Republike Srbije, br. 45012

  18. Characteristic evaluation of Al2O3/CNTs hybrid materials for micro-electrical discharge machining

    Institute of Scientific and Technical Information of China (English)

    Hyun-Seok TAK; Chang-Seung HA; Ho-Jun LEE; Hyung-Woo LEE; Young-Keun JEONG; Myung-Chang KANG

    2011-01-01

    The characteristic evaluation of aluminum oxide (Al2O3)/carbon nanotubes (CNTs) hybrid composites for micro-electrical discharge machining (EDM) was described. Alumina matrix composites reinforced with CNTs were fabricated by a catalytic chemical vapor deposition method. Al2O3 composites with different CNT concentrations were synthesized. The electrical characteristic of Al2O3/CNTs composites was examined. These composites were machined by the EDM process according to the various EDM parameters, and the characteristics of machining were analyzed using field emission scanning electron microscope (FESEM). The electrical conductivity has a increasing tendency as the CNTs content is increased and has a critical point at 5% Al2O3 (volume fraction). In the machining accuracy, many tangles of CNT in Al2O3/CNTs composites cause violent spark. Thus, it causes the poor dimensional accuracy and circularity. The results show that conductivity of the materials and homogeneous distribution of CNTs in the matrix are important factors for micro-EDM of Al2O3/CNTs hybrid composites.

  19. Polystyrene-Al2O3 composite solid polymer electrolyte for lithium secondary battery

    Science.gov (United States)

    Lim, Yu-Jeong; An, Yu-Ha; Jo, Nam-Ju

    2012-01-01

    In a common salt-in-polymer electrolyte, a polymer which has polar groups in the molecular chain is necessary because the polar groups dissolve lithium salt and coordinate cations. Based on the above point of view, polystyrene [PS] that has nonpolar groups is not suitable for the polymer matrix. However, in this PS-based composite polymer-in-salt system, the transport of cations is not by segmental motion but by ion-hopping through a lithium percolation path made of high content lithium salt. Moreover, Al2O3 can dissolve salt, instead of polar groups of polymer matrix, by the Lewis acid-base interactions between the surface group of Al2O3 and salt. Notably, the maximum enhancement of ionic conductivity is found in acidic Al2O3 compared with neutral and basic Al2O3 arising from the increase of free ion fraction by dissociation of salt. It was revealed that PS-Al2O3 composite solid polymer electrolyte containing 70 wt.% salt and 10 wt.% acidic Al2O3 showed the highest ionic conductivity of 9.78 × 10-5 Scm-1 at room temperature.

  20. Fabrication and characterization of hydroxyapatite/Al2O3 biocomposite coating on titanium

    Institute of Scientific and Technical Information of China (English)

    WU Zhen-jun; HE Li-ping; CHEN Zong-zhang

    2006-01-01

    A novel biocomposite coating of hydroxyapatite/Al2O3 was fabricated on titanium using a multi-step technique including physical vapor deposition(PVD), anodization, electrodeposition and hydrothermal treatment. Anodic Al2O3 layer with micrometric pore diameter was formed by anodization of the PVD-deposited aluminum film on titanium and subsequent removal of part barrier Al2O3 layer. Hydroxyapatite coating was then electrodeposited onto the as-synthesized anodic Al2O3 on titanium. A hydrothermal process was finally applied to the fabricated biocomposite coating on titanium in alkaline medium. Scanning electron microscopy(SEM), energy dispersive spectrometry(EDS) and X-ray diffractometry(XRD) were employed to investigate the morphologies and compositions of the pre- and post-hydrothermally treated hydroxyapatite/Al2O3 biocomposite coatings. The results show that micrometric plate-like Ca-deficient hydroxyapatite (CDHA) coatings are directly electrodeposited onto anodic Al2O3 at constant current densities ranging from 1.2 to 2.0 mA/cm2 using NaH2PO4 as the phosphorous source. After hydrothermal treatment,the micrometric plate-like CDHA coating electrodeposited at 2.0 mA/cm2 is converted into nano-network Ca-rich hydroxyapatite (CRHA) one and the adhesion strength is improved from 9.5 MPa to 21.3 MPa. A mechanism of dissolution-recrystallization was also proposed for the formation of CRHA.

  1. Preparation and Photocatalytic Properties of TiO2-Al2O3 Composite Loaded Catalysts

    Directory of Open Access Journals (Sweden)

    Jianzhong Pei

    2015-01-01

    Full Text Available This paper presents an experimental approach to study catalytic effects of Fe3+ modified nanometer titanium dioxide (TiO2 loaded on aluminium oxide (Al2O3. Sol-gel method was used to prepare modified TiO2 loaded on carrier. Purification tests were conducted in a self-developed instrument to study catalytic effects of TiO2 loaded on Al2O3 with different contents through degradation rate. The modification mechanism was studied by scanning electron microscope (SEM. Results showed that loading on Al2O3 improved photocatalytic effect of TiO2 modified with Fe3+. The best photocatalytic effect was achieved under catalytic action of Al2O3 loaded with 10% TiO2 composite; the degradation rates were 6.9%, 13.8%, 21.4%, and 49.2%, respectively, 0.7%, 3.9%, 1.3%, and 15.1% larger than unloaded TiO2. SEM results of four catalysts showed that nanometer TiO2 was coated in form of grain on the surface of Al2O3. The optimal loading content was 10% at which the nanometer TiO2 grains were coated on the surface of Al2O3 uniformly.

  2. Postperovskite phase equilibria in the MgSiO3-Al2O3 system.

    Science.gov (United States)

    Tsuchiya, Jun; Tsuchiya, Taku

    2008-12-09

    We investigate high-P,T phase equilibria of the MgSiO(3)-Al(2)O(3) system by means of the density functional ab initio computation methods with multiconfiguration sampling. Being different from earlier studies based on the static substitution properties with no consideration of Rh(2)O(3)(II) phase, present calculations demonstrate that (i) dissolving Al(2)O(3) tends to decrease the postperovskite transition pressure of MgSiO(3) but the effect is not significant ( approximately -0.2 GPa/mol% Al(2)O(3)); (ii) Al(2)O(3) produces the narrow perovskite+postperovskite coexisting P,T area (approximately 1 GPa) for the pyrolitic concentration (x(Al2O3) approximately 6 mol%), which is sufficiently responsible to the deep-mantle D'' seismic discontinuity; (iii) the transition would be smeared (approximately 4 GPa) for the basaltic Al-rich composition (x(Al2O3) approximately 20 mol%), which is still seismically visible unless iron has significant effects; and last (iv) the perovskite structure spontaneously changes to the Rh(2)O(3)(II) with increasing the Al concentration involving small displacements of the Mg-site cations.

  3. Al2O3 sintered pellets as thermoluminescent dosimeters Pastillas sinterizadas de Al2O3 como dosímetros termoluminiscentes

    Directory of Open Access Journals (Sweden)

    Amalia Osorio

    2012-06-01

    Full Text Available Verification of the radiation doses received by the area exposed during medical treatment is essential for assessing any scheme radiotherapy. This workdescribes the characteristic thermoluminescent (TL of sintered Al2O3 pellets, for its use as dosimeter dose low. Sintered Al2O3 pellets under different calcinations with a diameter of 5 mm and a thickness of 1 mm, they were irradiated to different dose using an unit of60 Co Theratron 780Cr in air to ambient temperature. The reading was carried in a Harshaw TLD 4500. Themain dosimetric properties of the material (glow curve, response reproducibility, reutilization, linearity and fading have been studied in detail. The glowcurve of the thin sintered Al2O3 pellets presents an intense peak TL to about 165◦C, which can be used for dosimetry. The results show that the pellets canbe used in quality control programs as thermoluminescent dosimeter in therapeutic dose range. The importance of this work is that the aluminum oxide (α−Al2O3 is a promising alternative in TL materials used for dosimetry “in vivo” within quality control programs.La verificación de la dosis de radiación recibida por el área expuesta durante eltratamiento médico es esencial para la evaluación de cualquier régimen de radioterapia.Este trabajo describe las caracteríısticas termoluminiscentes (TLde pastillas sinterizadas de Al2O3, para su posible uso como dosímetro TL de baja dosis. Pastillas de Al2O3 sinterizadas bajo diferentes condiciones decalcinación, con un diámetro de 5 mm y un espesor de 1 mm, fueron irradiadasa diferentes dosis usando una unidad de 60Co Theratron 780Cr enaire a temperatura ambiente. La lectura se realizó en un Harshaw TLD 4500.Las principales propiedades dosimétricas del material (curva de brillo, reproducibilidadde la respuesta, reutilización, linealidad y decaimiento térmicohan sido estudiadas en detalle. La curva de brillo de las pastillas sinterizadasde Al2O3 presenta un intenso

  4. Comparative Study of Properties of ZnO/GaN/Al2O3 and ZnO/Al2O3 Films Grown by Low-Pressure Metal Organic Chemical Vapour Deposition

    Institute of Scientific and Technical Information of China (English)

    赵佰军; 杨洪军; 杜国同; 缪国庆; 杨天鹏; 张源涛; 高仲民; 王金忠; 方秀军; 刘大力; 李万成; 马燕; 杨晓天; 刘博阳

    2003-01-01

    ZnO films were deposited by low-pressure metal organic chemical vapour deposition on epi-GaN/Al2O3 films and c-Al2O3 substrates.The structure and optical properties of the ZnO/GaN/Al2O3 and ZnO/Al2O3 films have been investigated to determine the differences between the two substrates.ZnO films on GaN/Al2O3 show very strong emission features associated with exciton transitions,just as ZnO films on Al2O3,while the crystalline structural qualities for ZnO films on GaN/Al2O3 are much better than those for ZnO films directly grown on Al2O3 substrates.Zn and O elements in the deposited ZnO/GaN/Al2O3 and ZnO/Al2O3 films are investigated and compared by x-ray photoelectron spectroscopy.According to the statistical results,the Zn/O ratio changes from Zn-rich for ZnO/Al2O3 films to O-rich for ZnO/GaN/Al2O3 films.

  5. Pressure-Induced Shifts of Energy Spectra of α-Al2O3:Mn4+

    Institute of Scientific and Technical Information of China (English)

    MA Dong-Ping,; CHEN Ju-Rong; MA Ning

    2002-01-01

    By making use of the diagonalization of the complete d3 energy matrix in a trigonally distorted cubic-field and the theory of pressure-induced shifts (PS) of energy spectra, the whole energy spectrum of α-Al2 O3 :Mn4+ and PS of levels have been calculated. All the calculated results are in excellent agreement with the experimental data. The comparison between the results ofα-AlO3:Mn4+ and ruby has been made. It is found that on one hand, R1-line and R2line PS of α-Al2O3:Mn4+ and ruby are linear in pressure over 0 ~ 100 kbar, and their values of the principal parameter for PS are very close to each other. On the other hand, the sensitivities of R1-line and R2-line PS of α-Al2O3:Mn4+are higher than those of ruby respectively, which comes mainly from the difference between the values of parameters at normal pressure of two crystals; moreover, the expansion ofd-electron wavefunctions of α-Al2 O3 :Mn4+ with compression is slightly larger than the one of ruby, and the effective charge experienced by d-electrons of α-Al2O3:Mn4+ decreases with compression more rapidly than the one of ruby. In the final analysis, all these can be explained in terms of the facts that the two crystals are doped α-Al2O3 with two isoelectronic ions; the strengths of the crystal field and covalency of α-Al2O3 :Mn4+ are larger than those of ruby respectively, due to the charge of Mn4+ to be larger than that of Cr3+.

  6. Mechanical Properties and Electrical Conductivity of TiN-Al2O3 Composites

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    TIN-Al2O3 composite powders with different TiN contents (0,10 vol%,20 vol%,30 vol% and 40 vol%) were prepared with micrometer TiN and α-Al2O3 powder (their purities were 99%) as starting materials by wet ball milling for 5 h.TiN-Al2O3 com-posite were then prepared by pressing the above composite powders,drying at 200 ℃ for 12 h and firing at 1 800 ℃ for 3 h in nitrogen atmosphere in hot-pressing furnace.The influences of TiN content on mechanical properties and electrical conductivity of TiN-Al2O3 com-posites were studied.The results showed that the me-chanical properties of the composite increased with TiN content increasing,while the resistivity of composites de-creased.A composite with 40% TiN had 498 MPa ben-ding strength,4.285 MPa·m1/2 fracture toughness,1.34×10-3 Ω·cm resistivity.The SEM analysis showed that the fine TiN crystals distributed among the crystal boundary of Al2O3 matrix.They bonded together forming a net-like structure which played a role of re-straining Al2O3 grains from growing up,toughening and strengthening,so the mechanical properties of TIN -Al2O3 composite were enhanced.

  7. The impact of ultrathin Al2O3 films on the electrical response of p-Ge/Al2O3/HfO2/Au MOS structures

    Science.gov (United States)

    Botzakaki, M. A.; Skoulatakis, G.; Kennou, S.; Ladas, S.; Tsamis, C.; Georga, S. N.; Krontiras, C. A.

    2016-09-01

    It is well known that the most critical issue in Ge CMOS technology is the successful growth of high-k gate dielectrics on Ge substrates. The high interface quality of Ge/high-k dielectric is connected with advanced electrical responses of Ge based MOS devices. Following this trend, atomic layer deposition deposited ultrathin Al2O3 and HfO2 films were grown on p-Ge. Al2O3 acts as a passivation layer between p-Ge and high-k HfO2 films. An extensive set of p-Ge/Al2O3/HfO2 structures were fabricated with Al2O3 thickness ranging from 0.5 nm to 1.5 nm and HfO2 thickness varying from 2.0 nm to 3.0 nm. All structures were characterized by x-ray photoelectron spectroscopy (XPS) and AFM. XPS analysis revealed the stoichiometric growth of both films in the absence of Ge sub-oxides between p-Ge and Al2O3 films. AFM analysis revealed the growth of smooth and cohesive films, which exhibited minimal roughness (~0.2 nm) comparable to that of clean bare p-Ge surfaces. The electrical response of all structures was analyzed by C-V, G-V, C-f, G-f and J-V characteristics, from 80 K to 300 K. It is found that the incorporation of ultrathin Al2O3 passivation layers between p-Ge and HfO2 films leads to superior electrical responses of the structures. All structures exhibit well defined C-V curves with parasitic effects, gradually diminishing and becoming absent below 170 K. D it values were calculated at each temperature, using both Hill-Coleman and Conductance methods. Structures of p-Ge/0.5 nm Al2O3/2.0 nm HfO2/Au, with an equivalent oxide thickness (EOT) equal to 1.3 nm, exhibit D it values as low as ~7.4  ×  1010 eV-1 cm-2. To our knowledge, these values are among the lowest reported. J-V measurements reveal leakage currents in the order of 10-1 A cm-2, which are comparable to previously published results for structures with the same EOT. A complete mapping of the energy distribution of D its into the energy bandgap of p-Ge, from the valence band

  8. Effect of fluoride additives on production and characterization of nano--Al2O3 particles

    Indian Academy of Sciences (India)

    F Mirjalili

    2014-12-01

    Nano--Al2O3 particles were synthesized by a sol–gel method using aqueous solutions of aluminum isopropoxide and 0.5 Maluminum nitrate. Sodium dodecylbenzenesulfonate (SDBS) was used as surfactant stabilizing agents. The solution was stirred for 48 h at 60 °C. The microstructural observation showed that surfactant with 48 h stirring time nanoscale -Al2O3 powder was produced at 1200 °C in the range of 20–30 nm in the presence of SDBS as a surfactant with 48 h stirring time. Temperature reduction of -Al2O3 formation has been achieved by introducing fluoride in the alumina precursor. The effects of ZnF2 additive and milling on the phase transformation as well as micrograph of the prepared -Al2O3 particles were investigated. The samples were characterized by different techniques such as X-ray diffraction, thermogravimetry analysis, differential scanning calorimetry, Fourier transform infrared spectra, scanning electron microscopy and transmission electron microscopy. Results indicated that using zinc fluoride (ZnF2) additive accompanied by milling led to retardation of the transformation temperature and modification of the alumina particle shape. The finest size for nonagglomerated nano-plate-like -Al2O3 particles (15–20 nm) was achieved at 950 °C.

  9. Influence of mechanical activation of AL2O3 on synthesis of magnesium aluminate spinel

    Directory of Open Access Journals (Sweden)

    Zhihui Zhang

    2004-01-01

    Full Text Available Magnesium aluminate (MA spinel is synthesized by reaction sintering from alumina and magnesia. The effects of mechanical activation of Al2O3 on reaction sintering were investigated. Non-milled a - Al2O3 and a - Al2O3 high-energy ball milled for 12h, 24h and 36h were mixed with a MgO analytical reagent according to the stoichiometric MA ratio, respectively and pressed into billets with diameters of 20mm and height of 15mm. The green-body billets were then sintered at high temperature in an air atmosphere. The results show that bulk density, relative content of MA and grain size of MA increase with increasing high-energy ball milling time of Al2O3. However prolonged milling time over 24h has a small beneficial effect on the densification of MA. Bulk density and grain size of a sample of a- Al2O3 milled for 24h are 3.30g/cm3 and 4-5 mm, respectively.

  10. Elimination of formaldehyde over Cu-Al2O3 catalyst at room temperature

    Institute of Scientific and Technical Information of China (English)

    ZHANG Chang-bin; SHI Xiao-yan; GAO Hong-wei; HE Hong

    2005-01-01

    Catalytic elimination of formaldehyde(HCHO) was investigated over Cu-Al2O3 catalyst at room temperature. The results indicated that no oxidation of HCHO into CO2 occurs at room temperature, but the adsorption of HCHO occurs on the catalyst surface.With the increase of gas hourly space velocity (GHSV) and inlet HCHO concentration, the time to reach saturation was shortened proportionally. The results of the in situ DRIFTS, Density functional theory calculations and temperature programmed desorption(TPD)showed that HCHO was completely oxidized into HCOOH over Cu-Al2 O3 at room temperature. With increasing the temperature in a flow of helium, HCOOH was completely decomposed into CO2 over the catalyst surface, and the deactivated Cu-Al2 O3 is regenerated at the same time. In addition, although Cu had no obvious influence on the adsorption of HCHO on Al2 O3, Cu dramatically lowered the decomposition temperature of HCOOH into CO2. It was shown that Cu-Al2 O3 catalyst had a good ability for the removal of HCHO, and appeared to be promising for its application in destroying HCHO at room temperature.

  11. PVDF- g-PSSA and Al 2O 3 composite proton exchange membranes

    Science.gov (United States)

    Shen, Yi; Qiu, Xinping; Shen, Juan; Xi, Jingyu; Zhu, Wentao

    Poly(vinylidene fluoride) grafted polystyrene sulfonated acid (PVDF- g-PSSA) membranes doped with different amount of Al 2O 3 (PVDF/Al 2O 3- g-PSSA) were prepared based on the solution-grafting technique. The microstructure of the membranes was characterized by IR-spectra and scanning electron microscope (SEM). The thermal stability was measured by thermal gravity analysis (TGA). The degree of grafting, water-uptake, proton conductivity and methanol permeability were measured. The results show that the PVDF- g-PSSA membrane doped with 10% Al 2O 3 has a lower methanol permeability of 6.6 × 10 -8 cm 2 s -1, which is almost one-fortieth of that of Nafion-117, and this membrane has moderate proton conductivity of 4.5 × 10 -2 S cm -1. Tests on cells show that a DMFC with the PVDF/10%Al 2O 3- g-PSSA has a better performance than Nafion-117. Although Al 2O 3 has some influence on the stability of the membrane, it can still be used in direct methanol fuel cells in the moderate temperature.

  12. Synthesis, biocompatibility and mechanical properties of ZrO2-Al2O3 ceramics composites.

    Science.gov (United States)

    Nevarez-Rascon, Alfredo; González-Lopez, Santiago; Acosta-Torres, Laura Susana; Nevarez-Rascon, Martina Margarita; Orrantia-Borunda, Erasmo

    2016-01-01

    This study evaluated cell viability, microhardness and flexural strength of two ceramic composites systems (ZA and AZ), pure alumina and zirconia. There were prepared homogeneous mixtures of 78wt%Al2O3+20wt%3Y-TZP+2wt%Al2O3w (AZ) and 80wt%3YTZP+18wt%Al2O3+2wt%Al2O3w (ZA), as well as 3Y-TZP (Z), pure Al2O3 (A) and commercial monolithic 3Y-TZP (Zc). Also mouse fibroblast cells 3T3-L1 and a MTT test was carried out at 24, 48 and 72 h. The surfaces were observed with SEM and the microhardness and three-point flexural strength values were estimated. The absolute microhardness values were: A>AZ>Z>Zc>ZA. Flexural strength of Zc, Z, and ZA were around double than AZ and A. All groups showed high biocompatibility trough cell viability values at 24, 48 and 72 h. Factors like grain shape, grain size and homogeneous or heterogeneous grain distributions may play an important role in physical, mechanical and biological properties of the ceramic composites.

  13. Directionally solidified Al2O3/GAP eutectic ceramics by micro-pulling-down method

    Science.gov (United States)

    Cao, Xue; Su, Haijun; Guo, Fengwei; Tan, Xi; Cao, Lamei

    2016-11-01

    We reported a novel route to prepare directionally solidified (DS) Al2O3/GAP eutectic ceramics by micro-pulling-down (μ-PD) method. The eutectic crystallizations, microstructure characters and evolutions, and their mechanical properties were investigated in detail. The results showed that the Al2O3/GAP eutectic composites can be successfully fabricated through μ-PD method, possessed smooth surface, full density and large crystal size (the maximal size: φ90 mm × 20 mm). At the process of Diameter, the as-solidified Al2O3/GAP eutectic presented a combination of "Chinese script" and elongated colony microstructure with complex regular structure. Inside the colonies, the rod-type or lamellar-type eutectic microstructures with ultra-fine GAP surrounded by the Al2O3 matrix were observed. At an appropriate solidificational rate, the binary eutectic exhibited a typical DS irregular eutectic structure of "chinese script" consisting of interpenetrating network of α-Al2O3 and GAP phases without any other phases. Therefore, the interphase spacing was refined to 1-2 µm and the irregular microstructure led to an outstanding vickers hardness of 17.04 GPa and fracture toughness of 6.3 MPa × m1/2 at room temperature.

  14. Elimination of formaldehyde over Cu-Al2O3 catalyst at room temperature.

    Science.gov (United States)

    Zhang, Chang-Bin; Shi, Xiao-Yan; Gao, Hong-Wei; He, Hong

    2005-01-01

    Catalytic elimination of formaldehyde (HCHO) was investigated over Cu-Al2O3 catalyst at room temperature. The results indicated that no oxidation of HCHO into CO2 occurs at room temperature, but the adsorption of HCHO occurs on the catalyst surface. With the increase of gas hourly space velocity (GHSV) and inlet HCHO concentration, the time to reach saturation was shortened proportionally. The results of the in situ DRIFTS, Density functional theory calculations and temperature programmed desorption(TPD) showed that HCHO was completely oxidized into HCOOH over Cu-Al2O3 at room temperature. With increasing the temperature in a flow of helium, HCOOH was completely decomposed into CO2 over the catalyst surface, and the deactivated Cu-Al2O3 is regenerated at the same time. In addition, although Cu had no obvious influence on the adsorption of HCHO on Al2O3, Cu dramatically lowered the decomposition temperature of HCOOH into CO2. It was shown that Cu-Al2O3 catalyst had a good ability for the removal of HCHO, and appeared to be promising for its application in destroying HCHO at room temperature.

  15. Growth of crystalline Al2O3 via thermal atomic layer deposition: Nanomaterial phase stabilization

    Directory of Open Access Journals (Sweden)

    S. M. Prokes

    2014-03-01

    Full Text Available We report the growth of crystalline Al2O3 thin films deposited by thermal Atomic Layer Deposition (ALD at 200 °C, which up to now has always resulted in the amorphous phase. The 5 nm thick films were deposited on Ga2O3, ZnO, and Si nanowire substrates 100 nm or less in diameter. The crystalline nature of the Al2O3 thin film coating was confirmed using Transmission Electron Microscopy (TEM, including high-resolution TEM lattice imaging, selected area diffraction, and energy filtered TEM. Al2O3 coatings on nanowires with diameters of 10 nm or less formed a fully crystalline phase, while those with diameters in the 20–25 nm range resulted in a partially crystalline coating, and those with diameters in excess of 50 nm were fully amorphous. We suggest that the amorphous Al2O3 phase becomes metastable with respect to a crystalline alumina polymorph, due to the nanometer size scale of the film/substrate combination. Since ALD Al2O3 films are widely used as protective barriers, dielectric layers, as well as potential coatings in energy materials, these findings may have important implications.

  16. Laser micromachining of CNT/Fe/Al2O3 nanocomposites

    Institute of Scientific and Technical Information of China (English)

    Kwang-Ryul KIM; Byoung-Deog CHOI; Jun-Sin YI; Sung-Hak CHO; Yong-Ho CHOA; Dong-Soo SHIN; Dong-Ho BAE; Myung-Chang KANG; Young-Keun JEONG

    2009-01-01

    CNT/Fe/Al2O3 mixed powders were synthesized from Fe/Al2O3 nanopowders using thermal CVD for the homogeneous dispersion of carbon nanotubes CNTs. CNTs consisted of MWNT, and the diameter was approximately 20-30 nm. After sintering, CNTs were homogenously located throughout Al2O3 grain boundary and were buckled. A femto-second laser installed with special optical systems was used for micromachining of the nanocomposites. The relationship between material ablation rate and energy fluence was theoretically investigated and compared with experimental results from cross-sectional SEM analysis. The nanocomposites which have higher content of CNT show a fairly good machining result due to its higher thermal conductivity and smaller grain size as well as lower light transmittance.

  17. Electrical conductivity studies on CuBr containing Al2O3 particles

    Science.gov (United States)

    Dubec, P. M.; Wagner, J. B., Jr.

    1984-01-01

    The conductivity of CuBr was studied and the role of a second phase, Al2O3, dispersed in CuBr was tested. CuBr melts at 493 C and exhibits three phases in the solid state. CuBr is a good ionic conductor with a transport number for copper ions of virtually unity with weighed proportions of the appropriate chemicals used. The CuBr materials were heated above melting point of CuBr, and the samples were sandwiched between copper electrodes. The ac conductivity, was determined at 1 kHz between 25 and 440 C depending on the sample. It was shown that at low temperatures, the conductivity for CuBr (Al2O3) increased by as much as 100, whereas in the beta phase the conductivity of CuBr containing Al2O3 decreased. The electrical conductivity studies are in agreement with earlier data.

  18. Ionic conductivity and thermoelectric power of pure and Al2O3-dispersed AgI

    Science.gov (United States)

    Shahi, K.; Wagner, J. B., Jr.

    1981-01-01

    Ionic and electronic conductivities, and thermoelectric power have been measured for AgI and AgI containing a dispersion of submicron size Al2O3 particles. While the dispersion of Al2O3 enhances the ionic conductivity significantly, it does not affect the electronic properties of the matrix. The enhancement is a strong function of the size and concentration of the dispersoid. Various models have been tested to account for the enhanced conduction. However, the complex behavior of the present results points out the need for more sophisticated theoretical models. Ionic conduction and thermoelectric power data suggest that the dispersed Al2O3 generates an excess of cation vacancies and thereby enhances the conductivity and suppresses the thermoelectric power of the matrix. The individual heats of transport of cation interstitials and vacancies have been estimated and compared to their respective migration energies.

  19. FABRICATION OF Al/Al2O3 FGM ROTATING DISC

    Directory of Open Access Journals (Sweden)

    A. B. Sanuddin

    2012-06-01

    Full Text Available This study presents a method of fabricating a disc made of Al/Al2O3 functionally graded materials (FGM, using a powder metallurgy manufacturing process. The aim is to develop a processing method for a rotating disc made of FGM, by stacking the slurry, layer by layer in a radial direction. A three-layer functionally graded material of Al/Al2O3 is fabricated with compositions of 10, 20, 30 vol.% Al2O3. The ceramic composition increases from the discs inner (centre to the outer. The combination of these materials can offer the ability to withstand high temperature conditions whilst maintaining strength in extreme environments.

  20. Mechanochemical Synthesis and Rapid Consolidation of Nanocrystalline 3NiAl-Al2O3 Composites

    Directory of Open Access Journals (Sweden)

    In-Jin Shon

    2011-01-01

    Full Text Available Nanopowders of 3NiAl and Al2O3 were synthesized from 3NiO and 5Al powders by high-energy ball milling. Nanocrystalline Al2O3 reinforced composite was consolidated by high-frequency induction-heated sintering within 3 minutes from mechanochemically synthesized powders of Al2O3 and 3NiAl. The advantage of this process is that it allows very quick densification to near theoretical density and inhibition grain growth. Nanocrystalline materials have received much attention as advanced engineering materials with improved physical and mechanical properties. The relative density of the composite was 97%. The average Vickers hardness and fracture toughness values obtained were 804 kg/mm2 and 7.5 MPa⋅m1/2, respectively.

  1. Synthesis of -Al2O3 nanowires through a boehmite precursor route

    Indian Academy of Sciences (India)

    Qi Yang

    2011-04-01

    Crystalline -Al2O3 nanowires with diameter, 20–40 nm, length above 600 nm and aspect ratio above 30 have been successfully synthesized by thermal decomposition of boehmite (-AlOOH) precursors obtained via hydrothermal route by using AlCl3, NaOH and NH3 as starting materials. Thermogravimetric analysis (TG), differential thermal analysis (DTA), X-ray diffraction (XRD), transmission electron microscope (TEM), selected area electron diffraction (SAED) and high resolution transmission electron microscope (HRTEM) were used to characterize the features of the as-made -Al2O3 nanowires and their -AlOOH precursors. The pH value of the solution and the mixed precipitant play important roles in the formation of -AlOOH nanowires. After calcination at 500°C for 2 h, the orthorhombic -AlOOH transforms to cubic -Al2O3 and retains nanowire morphology.

  2. Preparation and Properties of Plasma Spraying Cu-Al2O3 Gradient Coatings

    Institute of Scientific and Technical Information of China (English)

    Ali LEI; Nan DONG; Lajun FENG

    2007-01-01

    In order to overcome the limitations of low adhesion strength and poor thermal-shock resistance of pure ceramic coatings, Cu-Al2O3 gradient coatings were fabricated by plasma spraying. The microstructure and distribution of Cu-Al2O3 gradient coatings were analyzed. The adhesion strength, thermal-shock resistance and porosity of the coatings were tested. The results show that the composition of the gradient coatings has a gradient distribution along the thickness of coatings. As copper has a relatively low melting point and the molten copper has good wettability on the surface of Al2O3, it can be melted sufficiently and could fill the interstices and pores among the spraying particles effectively, thus improves the adhesion strength, thermal shock resistance and reduces the porosity. The adhesion strength of the gradient coating is 15.2 MPa which is two times of that of the double-layer structure coating.

  3. SYNTHESIS AND ELECTRICAL PROPERTIES OF POLYIMIDE-Al2O3 COMPOSITES

    Institute of Scientific and Technical Information of China (English)

    Hong-yan Li; Shu-fan Ning; Hai-bing Hu; Bin Liu; Wei Chen; Shou-tian Chen

    2007-01-01

    Polyimide-alumina hybrid films were synthesized via in situ polymerization and thermal imidation process from a solution of polyimide precursor and nanosized alumina in N,N-dimethylacetamide, and the microstructure of the hybrid films was characterized by transmission electron microscope (TEM) and infra-red (IR) spectrometry. The dependence of thermal stability, tensile properties, dielectric properties and degradation endurance under corona on the nano-Al2O3 content of polyimide-alumina hybrid films was studied. The results show that with the increase of Al2O3 content, the thermal stability and the dielectric properties of the hybrids increase, while the tensile properties decrease. Better corona resistance can be achieved if the PI film is filled with α-Al2O3 nanometric particle.

  4. Strain Distribution of Au and Ag Nanoparticles Embedded in Al2O3 Thin Film

    Directory of Open Access Journals (Sweden)

    Honghua Huang

    2014-01-01

    Full Text Available Au and Ag nanoparticles embedded in amorphous Al2O3 matrix are fabricated by the pulsed laser deposition (PLD method and rapid thermal annealing (RTA technique, which are confirmed by the experimental high-resolution transmission electron microscope (HRTEM results, respectively. The strain distribution of Au and Ag nanoparticles embedded in the Al2O3 matrix is investigated by the finite-element (FE calculations. The simulation results clearly indicate that both the Au and Ag nanoparticles incur compressive strain by the Al2O3 matrix. However, the compressive strain existing on the Au nanoparticle is much weaker than that on the Ag nanoparticle. This phenomenon can be attributed to the reason that Young’s modulus of Au is larger than that of Ag. This different strain distribution of Au and Ag nanoparticles in the same host matrix may have a significant influence on the technological potential applications of the Au-Ag alloy nanoparticles.

  5. Corrosion behavior of Zn-Ni-Al2O3 composite coating

    Institute of Scientific and Technical Information of China (English)

    ZHENG Huanyu; AN Maozhong; LU Junfeng

    2006-01-01

    The corrosion behavior and anti-corrosion mechanism of the Zn-Ni-Al2O3 composite coating were investigated by SEM, EDS and XPS.The results indicate that the corrosion type of the Zn-Ni-Al2O3 coatings in neutral 5 wt.% NaCl solution is uniform corrosion.The presence of compact and uniformly dispersed nano alumina particles substantially inhibits the corrosion of Zn-Ni-Al2O3 composite coatings.In the initial corrosion stage, the corrosive products of Zn-Ni matrix form a compact ZnCl2·4Zn(OH)2 layer.With the development of corrosion, some nano alumina particles are embedded and form a Ni enrichment layer.In Ni enrichment layer, Ni presents as Ni and NiO.

  6. Hard α-Al2O3 Film Coating on Industrial Roller Using Aerosol Deposition Method

    Science.gov (United States)

    Seto, Naoki; Endo, Kazuteru; Sakamoto, Nobuo; Hirose, Shingo; Akedo, Jun

    2014-12-01

    It is well known that α-Al2O3 forms very hard, highly insulating, smooth films. There is demand for the use of such films instead of conventional hard, smooth films; For example, industrial rollers such as calendering rollers etc. are always required to have a harder and smoother surface than conventional rollers. Therefore, this work investigated the specification of α-Al2O3 films, e.g., their wear resistance and chemical stability, using various tests. This paper also discusses whether α-Al2O3 film can take the place of Cr plating film as a hard, smooth film by comparing their wear resistance and chemical stability.

  7. Laser assembly nanostructured Al2O3/TiO2 coating on cast aluminum surface

    Institute of Scientific and Technical Information of China (English)

    ZHANG Guang-jun; DAI Jian-qiang; WANG Hui-ping; YAN Min-jie; XI Wen-long; ZOU Chang-gu; GE Da-fang

    2004-01-01

    CO2 laser quick assembly technology is adopted on the surface of cast aluminum ZL104 to form a dense ceramic coating containing a great deal of nanometer Al2O3/TiO2 particles which eliminate cracks and porosities.The major phases of the coating are α-Al2O3 andβ-TiO2. The micro-hardness distribution of the coating is 1 813,1 504, 1 485 and 1 232 (HV0.05). The bonding strength of the coating LC1 is 11.4 N, which is 7.26 times higher than that of the conventional hot-spraying Al2O3/TiO2 coating. It has been proved by analysis that the bonding strength is achieved because of the effects of both super-quick laser consolidation and the nanometer effect of nanometer ceramic material.

  8. Structural and dynamic properties of LiNO3 + Al2O3 nanocomposites

    Science.gov (United States)

    Gafurov, M. M.; Rabadanov, K. Sh.; Ataev, M. B.; Amirov, A. M.; Kubataev, Z. Yu.; Kakagasanov, M. G.

    2015-10-01

    The structural and dynamic properties of lithium nitrate LiNO3 and its heterogeneous composites with a nanopowder of aluminum oxide Al2O3 at different temperatures, phase states, and concentrations of the Al2O3 nanopowder have been investigated using Raman scattering, differential thermal analysis, and X-ray diffraction. It has been shown that, in the (1- x)LiNO3 + xAl2O3 composites, an amorphous phase (for x ≥ 0.5) is formed, whose thermal effect is observed at 185°C. The calculations of the dynamic characteristics of vibrations of the nitrate ion, as well as the differential thermal and X-ray diffraction analyses, have demonstrated that the nanocomposite can be represented as a highly disordered "quasilattice" in which "sites" are occupied by nanoparticles with amorphous lithium nitrate shells and spaces between them (conventionally "interstitial sites") become channels of a facilitated flow of the ion current.

  9. Rapid fabrication of Al2O3 encapsulations for organic electronic devices

    Science.gov (United States)

    Ali, Kamran; Ali, Junaid; Mehdi, Syed Murtuza; Choi, Kyung-Hyun; An, Young Jin

    2015-10-01

    Organic electronics have earned great reputation in electronic industry yet they suffer technical challenges such as short lifetimes and low reliability because of their susceptibility to water vapor and oxygen which causes their fast degradation. This paper report on the rapid fabrication of Al2O3 encapsulations through a unique roll-to-roll atmospheric atomic layer deposition technology (R2R-AALD) for the life time enhancement of organic poly (4-vinylphenol) (PVP) memristor devices. The devices were then categorized into two sets. One was processed with R2R-AALD Al2O3 encapsulations at 50 °C and the other one was kept as un-encapsulated. The field-emission scanning electron microscopy (FESEM) results revealed that pin holes and other irregularities in PVP films with average arithmetic roughness (Ra) of 9.66 nm have been effectively covered by Al2O3 encapsulation having Ra of 0.92 nm. The X-ray photoelectron spectroscopy XPS spectrum for PVP film showed peaks of C 1s and O 1s at the binding energies of 285 eV and 531 eV, respectively. The respective appearance of Al 2p, Al 2s, and O 1s peaks at the binding energies of 74 eV, 119 eV, and 531 eV, confirms the fabrication of Al2O3 films. Electrical current-voltage (I-V) measurements confirmed that the Al2O3 encapsulation has a huge influence on the performance, robustness and life time of memristor devices. The Al2O3 encapsulated memristor performed with superior stability for four weeks whereas the un-encapsulated devices could only last for one week. The performance of encapsulated device had been promising after being subjected to bending test for 100 cycles and the variations in its stability were of minor concern confirming the mechanical robustness and flexibility of the devices.

  10. Antireflective bilayer coatings based on Al2O3 film for UV region

    Directory of Open Access Journals (Sweden)

    Marszałek Konstanty

    2015-03-01

    Full Text Available Bilayer antireflective coatings consisting of aluminium oxide Al2O3/MgF2 and Al2O3/SiO2 are presented in this paper. Oxide films were deposited by means of e-gun evaporation in vacuum of 5 × 10-3 Pa in the presence of oxygen, and magnesium fluoride was prepared by thermal evaporation on heated optical lenses made from quartz glass (Corning HPFS. Substrate temperature was maintained at 250 _C during the deposition. Thickness and deposition rate were controlled with a thickness measuring system Inficon XTC/2. The experimental results of the optical measurements carried out during and after the deposition process have been presented. Physical thickness measurements were made during the deposition process and resulted in 44 nm/52 nm for Al2O3/MgF2 and 44 nm/50 nm for Al2O3/SiO2 system. Optimization was carried out for ultraviolet region with minimum of reflectance at 300 nm. The influence of post deposition annealing on the crystal structure was determined by X-ray measurements. In the range from ultraviolet to the beginning of visible region, the reflectance of both systems decreased and reached minimum at 290 nm. The value of reflectance at this point, for the coating Al2O3/MgF2 was equal to R290nm = 0.6 % and for Al2O3/SiO2R290nm = 1.1 %. Despite the difference between these values both are sufficient for applications in the UV optical systems for medicine and UV laser technology.

  11. Narrow in-gap states in doped Al 2 O 3

    KAUST Repository

    Casas-Cabanas, Montse

    2011-10-01

    Based on XRD data testifying that the M ions occupy substitutional sites, transmittance measurement are discussed in comparison to electronic structure calculations for M-doped Al2O3 with M = V, Mn, and Cr. The M 3d states are found approximatively 2 eV above the top of the host valence band. The fundamental band gap of Al2O3 is further reduced in the V and Mn cases due to a splitting of the narrow band at the Fermi energy. Nevertheless the measured transmittance in the visible range remains high in all three cases. © 2011 Elsevier B.V. All rights reserved.

  12. Study of The Pd-B/γ-Al2O3 Amorphous Alloy Catalyst

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    The Pd-B/γ-Al2O3 amorphous alloy catalyst and Pd/γ-Al2O3 crystalline metal catalyst were prepared by KBH4 reduction and routine impregnation, respectively. Pd-B/γ-A12O3 and Pd/γ-A12O3 catalysts were characterized by XRD and SEM. It was found that the catalytic activity of the Pd-B/γ-A12O3 amorphous alloy catalyst was higher than that of the Pd/γ-A12O3crystalline metal catalyst in the anthraquinone hydrogenation.

  13. Antireflective bilayer coatings based on Al2O3 film for UV region

    OpenAIRE

    Marszałek Konstanty; Winkowski Paweł; Marszałek Marta

    2015-01-01

    Bilayer antireflective coatings consisting of aluminium oxide Al2O3/MgF2 and Al2O3/SiO2 are presented in this paper. Oxide films were deposited by means of e-gun evaporation in vacuum of 5 × 10-3 Pa in the presence of oxygen, and magnesium fluoride was prepared by thermal evaporation on heated optical lenses made from quartz glass (Corning HPFS). Substrate temperature was maintained at 250 _C during the deposition. Thickness and deposition rate were controlled with a thickness measuring syste...

  14. Surface passivation of gallium nitride by ultrathin RF-magnetron sputtered Al2O3 gate.

    Science.gov (United States)

    Quah, Hock Jin; Cheong, Kuan Yew

    2013-08-14

    An ultrathin RF-magnetron sputtered Al2O3 gate on GaN subjected to postdeposition annealing at 800 °C in O2 ambient was systematically investigated. A cross-sectional energy-filtered transmission electron microscopy revealed formation of crystalline Al2O3 gate, which was supported by X-ray diffraction analysis. Various current conduction mechanisms contributing to leakage current of the investigated sample were discussed and correlated with metal-oxide-semiconductor characteristics of this sample.

  15. Effects of Additives on Properties of Unburned MgO—Al2O3 Refractory

    Institute of Scientific and Technical Information of China (English)

    LIFang; TANLihua

    1999-01-01

    The influences of four kinds of additives added into the matrix of MgO-Al2O3 unbuned products were investigated,The results show that samples with proper MgO/Al2O3 ration and proper addition of Cr2O3(2%- 4%) have good thermal shock resistance and slag corrosion resistance as well,XRD and SEM determination results indicate that a kind of compound spinel(Mg,Al, Cr) O4 was formed and the microstucture of the samples are denser.

  16. Studies on the Structure and Properties of Multiphase Al2O3 Abrasion-resistant Ceramics

    Institute of Scientific and Technical Information of China (English)

    WU Ren-Ping; YU Yan; RUAN Yu-Zhong

    2006-01-01

    The Al2O3 abrasion-resistant ceramics is successfully prepared by using waste aluminum sludge as the main raw material with the addition of a little clay, talc and barium carbonate. The crystal structure and microstructure of ceramic are characterized by means of XRD,SEM, etc., and the physical and mechanical properties are also tested. The results show that besides the phase of corundum, a little mullite, Mg-Al spinel and hyalophane phases also exist in the product. These phases are produced via reaction in-situ, which can inhibit the overgrowth of Al2O3grain in grain boundary, and improve the integral property of the material.

  17. Study of the KNO3-Al2O3 system by differential scanning calorimetry

    Science.gov (United States)

    Amirov, A. M.; Gafurov, M. M.; Rabadanov, K. Sh.

    2016-09-01

    The structural and the thermodynamic properties of potassium nitrate KNO3 and its composites with nanosized aluminum oxide Al2O3 have been studied by differential scanning calorimetry. It has been found that an amorphous phase forms in composites (1- x)KNO3- x Al2O3. The thermal effect corresponding to this phase has been observed at 316°C. It has been found that the phase transition heats of potassium nitrate decreased as the aluminum oxide fraction increased.

  18. The Evolution of Al2O3 Content in Ancient Chinese Glasses

    Directory of Open Access Journals (Sweden)

    Wang Cheng-yu

    2016-01-01

    Full Text Available Based on the evidence from museums, collectors, the dug out of the grave, the evolution of Al2O3 content in Chinese glasses from Western Zhou to Qing dynasty was documented in this paper in detail. It was found that Al2O3 contents in ancient Chinese glasses were relatively higher than those of outside of China in the world. This is the character of the ancient Chinese glasses which is caused by not only the high Al contents in the raw materials but also by the Chinese people’s preference of the milky glasses similar to jade

  19. Study of LDPE/Al2O3 composite material as substrate for microstrip antenna

    Science.gov (United States)

    Sarmah, Debashis; Bhattacharyya, N. S.; Bhattacharyya, S.; Gogoi, J. P.

    2013-01-01

    Low density polyethylene (LDPE)/Alumina (Al2O3) composite systems have been studied as an alternate substrate for microstrip patch antennas (MPA). Morphological, thermal and microwave characterizations of the composites are carried out for different volume fractions of Al2O3 in the LDPE matrix. The size and the distribution of alumina particles are quite uniform in the composite. Enhancement of thermal and microwave properties of the composite over the parent polymer is observed. Simple rectangular MPA in X-band is fabricated on the composite material to verify its applicability as substrates for MPA. A return loss of ~ -26dB is observed at the design frequency.

  20. Effect of Nd-doping on the Thermal Stability and Pore-structure of Al2O3 Membranes

    Institute of Scientific and Technical Information of China (English)

    YU Jian-Chang; XU Wei-Jun; HUANG Qing-Ming; HU Sheng-Wei

    2005-01-01

    Unsupported Nd-doped Al2O3 membranes have been prepared with a sol-gel treatnt by using aluminium isopropoxide and Nd(NO3)3 as the main raw materials. The properties of Nd-doped Al2O3 membranes were characterized by XRD, DTA-TG, IR and N2 adsorption. The effects of Nd-doping on the phase composition, thermal stability as well as applications of pore- structure of Nd-doped Al2O3 membranes at high temperature were discussed. The results show that Nd-doping can raise the transition temperature rom γ-Al2O3 to α-Al2O3, enhance the thermal stability of Al2O3 membranes, and evidently improve the pore-structural parameters of Al2O3 mem- branes applied at higher temperatures.

  1. The Influence of Al2O3 Powder Morphology on the Properties of Cu-Al2O3 Composites Designed for Functionally Graded Materials (FGM)

    Science.gov (United States)

    Strojny-Nędza, Agata; Pietrzak, Katarzyna; Węglewski, Witold

    2016-08-01

    In order to meet the requirements of an increased efficiency applying to modern devices and in more general terms science and technology, it is necessary to develop new materials. Combining various types of materials (such as metals and ceramics) and developing composite materials seem to be suitable solutions. One of the most interesting materials includes Cu-Al2O3 composite and gradient materials (FGMs). Due to their potential properties, copper-alumina composites could be used in aerospace industry as rocket thrusters and components in aircraft engines. The main challenge posed by copper matrix composites reinforced by aluminum oxide particles is obtaining the uniform structure with no residual porosity (existing within the area of the ceramic phase). In the present paper, Cu-Al2O3 composites (also in a gradient form) with 1, 3, and 5 vol.% of aluminum oxide were fabricated by the hot pressing and spark plasma sintering methods. Two forms of aluminum oxide (αAl2O3 powder and electrocorundum) were used as a reinforcement. Microstructural investigations revealed that near fully dense materials with low porosity and a clear interface between the metal matrix and ceramics were obtained in the case of the SPS method. In this paper, the properties (mechanical, thermal, and tribological) of composite materials were also collected and compared. Technological tests were preceded by finite element method analyses of thermal stresses generated in the gradient structure, and additionally, the role of porosity in the formation process of composite properties was modeled. Based on the said modeling, technological conditions for obtaining FGMs were proposed.

  2. Wettability of silicon carbide ceramic by Al2O3/Dy2O3 and Al2O3/Yb2O3 systems

    Institute of Scientific and Technical Information of China (English)

    J.A.da Silva; B.M.Moreschi; G.C.R.Garcia; S.Ribeiro

    2013-01-01

    Wettability is an important phenomenon in the liquid phase sintering of silicon carbide (SiC) ceramics.This work involved a study of the wetting of SiC ceramics by two oxide systems,Al2O3/Dy2O3 and Al2O3/Yb2O3,which have so far not been studied for application in the sintering of SiC ceramics.Five mixtures of each system were prepared,with different compositions close to their respective eutectic ones.Samples of the mixtures were pressed into cylindrical specimens,which were placed on a SiC plate and subjected to temperatures above their melting points using a graphite resistance furnace.The behavior of the melted mixtures on the SiC plate was observed by means of an imaging system using a CCD camera and the sessile drop method was employed to determine the contact angle,the parameter that measures the degree of wettability.The results of variation in the contact angle as a function of temperature were plotted in graphic form which showed that the curves displayed a fast decline and good spreading.All the samples of the two systems presented final contact angles of 40° to 10° indicating their good wetting on SiC in the argon atmosphere.The melted/solidified area and interface between SiC and melted/solidified phase were evaluated by scanning electron microscopy (SEM) and their crystalline phases were identified by X-ray diffraction (DRX).The DRX analysis showed that Al2O3 and RE2O3 reacted and formed the Dy3Al5O12 (DyAg) and Yb3Al5O12 (YbAg) phases.The results indicated that the two systems had a promising potential as additives for the sintering of SiC ceramics.

  3. Study on AgCuTi Brazing Al2O3/Nb%AgCuTi钎焊Al2O3/Nb的研究

    Institute of Scientific and Technical Information of China (English)

    吴铭方; 于治水

    2000-01-01

    在钎焊温度1 043~1 393 K、钎焊时间3~60 min条件下,对Al2O3/(Ag72Cu28)97Ti3/Nb接头进行了钎焊试验.经SEM、EDS、XRD检测,界面产物为TiO、Ti2O.在1 093 K、15 min条件下,接头剪切强度最高可达223 MPa.

  4. Role of Al2O3 fiber in eutectic Al-Si alloy composites

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The effects of Al2O3 fiber on wear characteristics of eutectic Al-Si alloy composites were studied using a pin-on-disk tester under dry sliding condition. The results show that the Al2O3 fiber can make matrix grain be fine, specially the eutectic Si be finer and prevent the plastic flow of matrix and prohibit the crack propagation in the wear layer, thereby it can remarkably improve the mechanical property and the wear resistance of the MMCs. Since Al2O3 fiber plays a role of certain framework in protecting the matrix against crash, it can eliminate the severe wear of MMCs with higher φf of fiber from the beginning of test. At mild stage, when φf is in the range of 8%~10%, the wear rates are the lowest. With increasing φf of Al2O3 fiber, the wear mechanism of MMCs can be transformed from adhesive delamination to brittle breakaway.

  5. Al2O3 Passivation on c-si Surfaces for Low Temperature Solar Cell Applications

    Energy Technology Data Exchange (ETDEWEB)

    Saynova, D.S.; Janssen, G.J.M.; Burgers, A.R.; Mewe, A.A. [ECN Solar Energy, Westerduinweg 3, NL-1755 LE Petten (Netherlands); Cianci, E.; Seguini, G.; Perego, M. [Laboratorio MDM, IMM-CNR, Via C. Olivetti 2,I-20864 Agrate Brianza MB (Italy)

    2013-07-01

    Functional passivation of high resistivity p-type c-Si wafer surfaces was achieved using 10 nm Al2O3 layers and low temperatures for both the thermal ALD process and post-deposition anneal. Effective lifetime values higher than 1 ms were measured at excess carrier density {delta}n=1015 cm{sup -3}. This result was reached in combination with temperatures of 100C and 200C for the Al2O3 layer deposition and anneal, respectively. The Al2O3/c-Si interface was characterized using conductance-voltage and capacitance-voltage measurements. In particular, significantly reduced interface density of the electrically active defects Dit {approx} 2x1010 eV{sup -1}cm{sup -2} was detected, which enabled excellent chemical passivation. The measured density of fixed charges at the interface, Qf, after anneal were in the range +1x10{sup 12} to -1x10{sup 12} cm{sup -2} indicating that both inversion and accumulation conditions result in relevant field-effect passivation using Al2O3 layers and low temperature processes. Numerical simulations on representative test structures show that the uniform Qf effect can be understood in terms of a surface damage region (SDR) present near the interface in combination with asymmetry in the lifetime of holes and electrons in the SDR. The combination of low processing temperatures, thin layers and good passivation properties facilitate a technology for future low temperature solar cell applications.

  6. Optically stimulated luminescence response to Al2O3 to beta radiation

    DEFF Research Database (Denmark)

    Akselrod, A.; Akselrod, M.S.; Agersnap Larsen, N.

    1999-01-01

    High sensitivity dosemeters based on Al2O3:C have been prepared and tested for use as beta dosemeters using optically stimulated luminescence (OSL). Two types of sample were prepared and tested, namely unpolished thick, single crystal chips and thin powder layers on aluminium substrates...

  7. Optical observation of DNA translocation through Al2O3 sputtered silicon nanopores in porous membrane

    Science.gov (United States)

    Yamazaki, Hirohito; Ito, Shintaro; Esashika, Keiko; Taguchi, Yoshihiro; Saiki, Toshiharu

    2016-03-01

    Nanopore sensors are being developed as a platform for analyzing single DNA, RNA, and protein. In nanopore sensors, ionic current measurement is widely used and proof-of-concept of nanopore DNA sequencing by it has been demonstrated by previous studies. Recently, we proposed an alternative platform of nanopore DNA sequencing that incorporates ultraviolet light and porous silicon membrane to perform high-throughput measurement. In the development of our DNA sequencing platform, controlling nanopore size in porous silicon membrane is essential but remains a challenge. Here, we report on observation of DNA translocation through Al2O3 sputtered silicon nanopores (Al2O3 nanopores) by our optical scheme. Electromagnetic wave simulation was performed to analyze the excitation volume on Al2O3 nanopores generated by focused ultraviolet light. In the experiment, DNA translocation time through Al2O3 nanopores was compared with that of silicon nanopores and we examined the effect of nanopore density and thickness of membrane by supplementing the static electric field simulation.

  8. Enhanced Barrier Performance of Engineered Paper by Atomic Layer Deposited Al2O3 Thin Films.

    Science.gov (United States)

    Mirvakili, Mehr Negar; Van Bui, Hao; van Ommen, J Ruud; Hatzikiriakos, Savvas G; Englezos, Peter

    2016-06-01

    Surface modification of cellulosic paper is demonstrated by employing plasma assisted atomic layer deposition. Al2O3 thin films are deposited on paper substrates, prepared with different fiber sizes, to improve their barrier properties. Thus, a hydrophobic paper is created with low gas permeability by combining the control of fiber size (and structure) with atomic layer deposition of Al2O3 films. Papers are prepared using Kraft softwood pulp and thermomechanical pulp. The cellulosic wood fibers are refined to obtain fibers with smaller length and diameter. Films of Al2O3, 10, 25, and 45 nm in thickness, are deposited on the paper surface. The work demonstrates that coating of papers prepared with long fibers efficiently reduces wettability with slight enhancement in gas permeability, whereas on shorter fibers, it results in significantly lower gas permeability. Wettability studies on Al2O3 deposited paper substrates have shown water wicking and absorption over time only in papers prepared with highly refined fibers. It is also shown that there is a certain fiber size at which the gas permeability assumes its minimum value, and further decrease in fiber size will reverse the effect on gas permeability.

  9. Ir-Ru/Al2O3 catalysts used in satellite propulsion

    Directory of Open Access Journals (Sweden)

    T.G. Soares Neto

    2003-09-01

    Full Text Available Ir/Al2O3, Ir-Ru/Al2O3 and Ru/Al2O3, catalysts with total metal contents of 30% were prepared using the methods of incipient wetness and incipient coimpregnation wetness and were tested in a 2N microthruster. Their performances were then compared with that of the Shell 405 commercial catalyst (30% Ir/Al2O3. Tests were performed in continuous and pulsed regimes, where there are steep temperature and pressure gradients, from ambient values up to 650 ºC and 14 bar. Performance stability, thrust produced, temperature and stagnation pressure in the chamber and losses of mass were analyzed and compared to the corresponding parameters in Shell 405 tests. It was observed that the performance of all the above-mentioned catalysts was comparable to that of the commercial one, except for in loss of mass, where the values was higher, which was attributed to the lower mechanical resistance of the support.

  10. Classical Bahavior of Alumina (Al2O3) Nanofluids in Antifrogen N with Experimental Evidence

    NARCIS (Netherlands)

    Saleemi, M.; Vanapalli, S.; Nikkam, N.; Toprak, M.S.; Muhammed, M.

    2015-01-01

    A nanofluid is a suspension containing nanoparticles in conventional heat transfer fluids. This paper reports on an investigation of alumina (Al2O3) nanoparticles in Antifrogen N, also called AFN, which is a popular antifreeze coolant consisting primarily of ethylene glycol and other additives to im

  11. In-situ RHEED and characterization of ALD Al2O3 gate dielectrics

    NARCIS (Netherlands)

    Bankras, Radko Gerard

    2006-01-01

    In-situ RHEED en karakterisatie van ALD Al2O3 gate diëlektrica Sinds de introductie van de MOSFET transistor (metaal-oxide-silicium veldeffecttransistor) in 1960, heeft de halfgeleidertechnologie een snelle ontwikkeling doorgemaakt. Deze vooruitgang bestond hoofdzakelijk uit de mogelijkheid om trans

  12. Focused ion beam nano-structuring of photonic Bragg gratings in $Al_2O_3$ waveguides

    NARCIS (Netherlands)

    Uranga, Amaia; Ay, Feridun; Bradley, Jonathan D.B.; Ridder, de René M.; Wörhoff, Kerstin; Pollnau, Markus; Emplit, Ph.; Delqué, M.; Gorza, S.-P.; Kockaart, P.; Leijtens, X.

    2007-01-01

    Focused ion beam (FIB) etching is receiving increasing attention for the fabrication of active integrated optical components such as waveguide amplifiers and lasers. Si-technology compatible low-loss $Al_2O_3$ channel waveguides grown on thermally oxidized silicon substrates have been reported recen

  13. Focused ion beam nano-structuring of Bragg gratings in $Al_2O_3$ channel waveguides

    NARCIS (Netherlands)

    Ay, Feridun; Uranga, Amaia; Bradley, Jonathan D.B.; Wörhoff, Kerstin; Ridder, de René M.; Pollnau, Markus; Ridder, de R.M.; Ay, F.; Kauppinen, L.J.

    2008-01-01

    We report our recent results on an optimization study of focused ion beam (FIB) nano-structuring of Bragg gratings in $Al_2O_3$ channel waveguides. By optimizing FIB milling parameters such as ion current, dwell time, loop repetitions, scanning strategy, and applying a top metal layer for reducing c

  14. Widely wavelength-selective Al2O3:Er3+ ring laser

    NARCIS (Netherlands)

    Bradley, J.D.B.; Agazzi, L.; Ay, F.; Wörhoff, K.; Pollnau, M.; Stoffer, R.

    2010-01-01

    Integrated Al2O3:Er3+ channel waveguide ring lasers were realized on thermally oxidized silicon substrates. High pump power coupling into- and low output power coupling from the ring is achieved in a straightforward design. Wavelength selection in the range 1532 to 1557 nm was demonstrated by varyin

  15. Energy-transfer processes in $Al_2O_3:Er^{3+}$ waveguide amplifiers

    NARCIS (Netherlands)

    Agazzi, L.; Wörhoff, K.; Pollnau, M.

    2012-01-01

    The influence of migration-accelerated energy-transfer upconversion and fast luminescence quenching on $Al_2O_3:Er^{3+}$ waveguide amplifiers is investigated. Results indicate that the latter has the stronger impact on the amplifier small-signal gain.

  16. Preliminary Study on MgO· Al2O3 Spinel Fiber

    Institute of Scientific and Technical Information of China (English)

    YANG Daoyuan; GUO Xinrong; ZHONG Xiangchong

    2004-01-01

    MgO· Al2O3 spinel fibers may be obtained by thermal treatment of pressed specimens composed of Mg-Al-O materials with appropriate oxide-metal ratio at high temperature under controlled atmosphere. Their phase composition and microstructure have been examined.

  17. Preparation and catalytic behavior of CeO2 nanoparticles on Al2O3 crystal

    Science.gov (United States)

    Hattori, Takashi; Kobayashi, Katsutoshi; Ozawa, Masakuni

    2017-01-01

    In this work, we examined the preparation, morphology, and catalytic behavior of CeO2 nanoparticles (NPs) on Al2O3(0001) crystal substrates. A CeO2 NP layer was prepared by the dipping method using a CeO2 nanocrystal colloid solution. Even after heat treatment at 1000 °C, the CeO2 NP layer maintained the granular morphology of CeO2 with a grain diameter of less than 40 nm. CeO2 NPs on an Al2O3 crystal showed higher oxidation activity for gaseous hydrogen at moderate temperatures and enhanced oxygen release properties of CeO2, compared with CeO2 powder. This was due to the highly dispersed CeO2 NPs and the interaction between CeO2 NPs and Al2O3; this clarified the importance of the Al2O3 support for the CeO2 catalyst.

  18. Hydrogen generation from methanolysis of sodium borohydride over Co/Al2O3 catalyst

    Institute of Scientific and Technical Information of China (English)

    Dongyan Xu; Lin Zhao; Ping Dai; Shengfu Ji

    2012-01-01

    Co/Al2O3 catalyst is prepared with an impregnation-chemical reduction method and used to catalyze the methanolysis of sodium borohydride (NaBH4) for hydrogen generation.At solution temperature of 0℃,the methanolysis reaction can be effectively accelerated using Co/Al2O3 catalyst and provide a desirable hydrogen generation rate,which makes it suitable for apphcations under the circumstance of low environmental temperature.The byproduct of methanolysis reaction is analyzed by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR).The characterization results indicate that methanol can be easily recovered after methanolysis reaction by hydrolysis of the methanolysis byproduct,NaB(OCH3)4.The catalytic activity of Co/Al2O3 towards NaBH4 methanolysis can be further improved by appropriate calcination treatment.The catalytic methanolysis kinetics and catalyst reusability are also studied over the Co/Al2O3 catalyst calcined at the optimized temperature.

  19. Theory of Al2O3 incorporation in SiO2

    DEFF Research Database (Denmark)

    Lægsgaard, Jesper

    2002-01-01

    Different possible forms of Al2O3 units in a SiO2 network are studied theoretically within the framework of density-functional theory. Total-energy differences between the various configurations are obtained, and simple thermodynamical arguments are used to provide an estimate of their relative i...

  20. Transmission of 18 kev negative ions Cl- through nanocapillariesin Al2O3 membrane

    Institute of Scientific and Technical Information of China (English)

    Lü Xue-Yang; Yin Yong-Zhi; Wang Hong-Wei; Ji Ming-Chao; Chen Lin; Chen Xi-Meng; Jia Juan-Juan; Zhou Peng; Zhou Chun-Lin; Qiu Xi-Yu; Shao Jian-Xiong; Cui Ying

    2011-01-01

    We investigate the angular distribution of the transmitted 18kev negative ions Cl- through Al2O3 nanocapillaries of 50 nm in diameter and 10μm in length. Elastic scattering ions and inelastic scattering ions are obtained simultaneonsly. The experimental result is partially consistent with the guiding effect. We can qualitatively explain our experimental result through a dynamic process.

  1. MALEIC ANHYDRIDE HYDROGENATION OF PD/AL2O3 CATALYST UNDER SUPERCRITICAL CO2 MEDIUM

    Science.gov (United States)

    Hydrogenation of maleic anhydride (MA) to either y-butyrolactone of succinic anhydride over simple Pd/Al2O3 impregnated catalyst in supercritical CO2 medium has been studied at different temperatures and pressures. A comparison of the supercritical CO2 medium reaction with the c...

  2. Preparation and characterization of DLC/SiO2/Al2O3 nanofiltration membrane

    Indian Academy of Sciences (India)

    Jin-Su Jeong; Churl-Hee Cho; Jong-Oh Kim; Dong-Hun Yeo; Won-Youl Choi

    2013-12-01

    High quality ceramic thin films were fabricated by thin film deposition process in semiconductor field in order to fabricate high performance carbon/SiO2/Al2O3 membrane. -Al2O3 substrate was used as a supporting material. A severe thermal stress and rough surface for active ceramic top layer such as zeolite were observed. To overcome thermal stress, intermediate layer of SiO2 and diamond-like carbon (DLC) thin films were used. SiO2 and DLC thin films on porous alumina support were deposited using plasma-enhanced chemical vapour deposition (PECVD). Homogeneous and smooth surfaces and interfaces of DLC/SiO2/Al2O3 membrane were observed by FESEM. The phases of DLC and SiO2 thin films were identified by X-ray diffraction pattern. Gas permeabilities of the nanofiltration membrane with DLC/SiO2/Al2O3 were observed at various annealing temperatures. Mixed gas permeability of the membrane with 1 m-thick SiO2 and 2 m-thick DLC thin filmannealed at 200 °C was ∼18 ccm at 1018 mb back pressure.

  3. Gas-phase dehydration of glycerol over commercial Pt/γ-Al2O3 catalysts

    Institute of Scientific and Technical Information of China (English)

    Sergey Danov; Anton Esipovich; Artem Belousov; Anton Rogozhin

    2015-01-01

    Gas-phase dehydration of glycerol to produce acrolein was investigated over commercial catalysts based onγ-Al2O3, viz. A-64, A-56, I-62, AP-10, AP-56, AP-64 and KR-104. To understand the effect of Cl−anions, HCl-impregnated sup-ports have been investigated in the dehydration reaction of glycerol at 375 °C. For comparison, various H-zeolites were also examined. It was found that the glycerol conversion over the solid acid catalysts was strongly dependent on their acidity and surface area. And the relationship between the catalytic activity and the acidity of the catalysts was discussed. The outstanding properties of Pt/γ-Al2O3 catalyst systems for the dehydration of glycerol were revealed. Pt/γ-Al2O3 catalyst (AP-64) showed the highest catalytic activity after 50 h of reaction with an acrolein selectivity of 65%at a conversion of glycerol of 90%. Based on these results, catalysts based onγ-Al2O3 appear to be most promising for gas phase dehydration of glycerol.

  4. Analysis of the residual stress in Al2O3-SiC nanocomposites

    Institute of Scientific and Technical Information of China (English)

    王宏志; 高濂; 郭景坤

    1999-01-01

    The residual stress in Al2O3-SiC nanocomposites was measured by the X-ray diffraction method. A mode was established to calculate the residual stress, which accorded with the results measured by the XRD method. The strengthening and toughening mechanism was also discussed.

  5. Al2O3/Silicon NanoISFET with Near Ideal Nernstian Response

    NARCIS (Netherlands)

    Chen, Songyue; Bomer, Johan G.; Carlen, Edwin T.; Berg, van den Albert

    2011-01-01

    Nanoscale ISFET (ion sensitive field-effect transistor) pH sensors are presented that produce the well-known sub-Nernstian pH-response for silicon dioxide (SiO2) surfaces and near ideal Nernstian sensitivity for alumina (Al2O3) surfaces. Titration experiments of SiO2 surfaces resulted in a varying p

  6. Uniform Atomic Layer Deposition of Al2O3 on Graphene by Reversible Hydrogen Plasma Functionalization

    Science.gov (United States)

    2017-01-01

    A novel method to form ultrathin, uniform Al2O3 layers on graphene using reversible hydrogen plasma functionalization followed by atomic layer deposition (ALD) is presented. ALD on pristine graphene is known to be a challenge due to the absence of dangling bonds, leading to nonuniform film coverage. We show that hydrogen plasma functionalization of graphene leads to uniform ALD of closed Al2O3 films down to 8 nm in thickness. Hall measurements and Raman spectroscopy reveal that the hydrogen plasma functionalization is reversible upon Al2O3 ALD and subsequent annealing at 400 °C and in this way does not deteriorate the graphene’s charge carrier mobility. This is in contrast with oxygen plasma functionalization, which can lead to a uniform 5 nm thick closed film, but which is not reversible and leads to a reduction of the charge carrier mobility. Density functional theory (DFT) calculations attribute the uniform growth on both H2 and O2 plasma functionalized graphene to the enhanced adsorption of trimethylaluminum (TMA) on these surfaces. A DFT analysis of the possible reaction pathways for TMA precursor adsorption on hydrogenated graphene predicts a binding mechanism that cleans off the hydrogen functionalities from the surface, which explains the observed reversibility of the hydrogen plasma functionalization upon Al2O3 ALD.

  7. Thermally stimulated conductivity and thermoluminescence from Al2O3 : C

    DEFF Research Database (Denmark)

    Agersnap Larsen, N.; Bøtter-Jensen, L.; McKeever, S.W.S.

    1999-01-01

    Simultaneous measurements of thermoluminescence (TL) and thermally stimulated conductivity (TSC) are reported on single-crystal dosimetry-quality Al2O3:C following gamma irradiation at room temperature. Analysis of the data reveals a superposition of several first-order TL and TSC peaks caused...

  8. Guiding of low-energy electrons by highly ordered Al2 O3 nanocapillaries

    DEFF Research Database (Denmark)

    Milosavljević, A.R.; Víkor, G.; Pešić, Z.D.;

    2007-01-01

    We report an experimental study of guided transmission of low-energy (200-350 eV) electrons through highly ordered Al2 O3 nanocapillaries with large aspect ratio (140 nm diameter and 15 μm length). The nanochannel array was prepared using self-ordering phenomena during a two-step anodization proc...

  9. Al2O3-SiC-C Bricks for Hot Metal Pretreatment

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    @@ 1 Scope This standard specifies the classification,techni-cal requirements,test methods,inspection rules,packing,marking,transportation,storage and quality certificate of Al2O3-SiC-C bricks for hot metal pre-treatment.

  10. Al2O3 SiC-C Bricks for Hot Metal Pretreatment

    Institute of Scientific and Technical Information of China (English)

    Yu Lingyan; Peng Xigao

    2010-01-01

    @@ 1 Scope This standard specifies the classification,shape and dimensions,technical requirements,test methods,quality appraisal procedures,packing,marking,transportation,storage,and quality certificate of Al2O3SiC-C bricks for hot metal pretreatment.

  11. Current Tunnelling in MOS Devices with Al2O3/SiO2 Gate Dielectric

    Directory of Open Access Journals (Sweden)

    A. Bouazra

    2008-01-01

    Full Text Available With the continued scaling of the SiO2 thickness below 2 nm in CMOS devices, a large direct-tunnelling current flow between the gate electrode and silicon substrate is greatly impacting device performance. Therefore, higher dielectric constant materials are desirable for reducing the gate leakage while maintaining transistor performance for very thin dielectric layers. Despite its not very high dielectric constant (∼10, Al2O3 has emerged as one of the most promising high-k candidates in terms of its chemical and thermal stability as its high-barrier offset. In this paper, a theoretical study of the physical and electrical properties of Al2O3 gate dielectric is reported including I(V and C(V characteristics. By using a stack of Al2O3/SiO2 with an appropriate equivalent oxide thickness of gate dielectric MOS, the gate leakage exhibits an important decrease. The effect of carrier trap parameters (depth and width at the Al2O3/SiO2 interface is also discussed.

  12. Preparation and Properties of Crystallizable Glass/Al2O3 Composites for LTCC Material

    Institute of Scientific and Technical Information of China (English)

    SHAO Hui; ZHOU Hongling; ZHU Haihui; SHEN Xiaodong

    2011-01-01

    The investigated low temperature Co fired ceramics(LTCC) composite of 60wt% CaO-Al2O3-B2O3-SiO2 glass and 40wt% α-Al2O3 as a filler is a non-reactive system,which is a critical part of the low temperature Co fired ceramics process.Through a study on densification process,the phase transformation and microstructure can be revealed.Its composites typically consist of CaO-Al2O3-B2O3-SiO2 glass and α-Al2O3 powders of average particle size (D50=3.49 μm).The sintering behavior,phase evaluation,sintered morphology,and microwave dielectric properties were investigated.In the fire range of 800 to 900 ℃,the composites were crystallized after completion of densification.It is found that the composites start to densify at 825 ℃,simultaneously,the dielectric constant (εr) reaches its maximum.With increasing heat-treatment temperatures,due to the loose microstmcture of the material,tanδ increases slightly.The last of the sintered samples were identified as partly Anorthite at 850 ℃.At that temperature it has εr of 7.9 and tanδ less than 1 x 10-3,and can be used as a promising LTCC material.

  13. Erbium-ion implantation into various crystallographic cuts of Al2O3

    Science.gov (United States)

    Nekvindova, P.; Mackova, A.; Malinsky, P.; Cajzl, J.; Svecova, B.; Oswald, J.; Wilhelm, R. A.

    2015-12-01

    This paper reports on the importance of crystallographic cuts with a different orientation on the luminescent properties and structural changes of Al2O3 implanted with Er+ ions at 190 keV and with a fluence of 1.0 × 1016 cm-2. Post-implantation annealing at 1000 °C in oxygen atmosphere was also done. The chemical compositions and erbium concentration-depth profiles of implanted layers were studied by Rutherford Backscattering Spectrometry (RBS) and compared to SRIM simulations. The same value of the maximum erbium concentration (up to 2 at.%) was observed at a depth of about 40 nm for all crystallographic cuts. The structural properties of the prepared layers were characterised by RBS/channelling. The relative amount of disordered atoms of 70-80% was observed in the prepared implanted layers and discussed for various cuts. It has been found that erbium is positioned randomly in the Al2O3 crystalline matrix, and no preferential positions appeared even after the annealing procedure. Erbium luminescence properties were measured in the wavelength range of 1440-1650 nm for all samples. As-implanted Al2O3 samples had a significant luminescence band at 1530 nm. The best luminescence was repeatedly observed in the cut of Al2O3. The annealing procedure significantly improved the luminescent properties.

  14. Optical spectroscopic study of Al2O3:Ti3+ under hydrostatic pressure

    NARCIS (Netherlands)

    García-Revilla, S.; Rodríguez, F.; Hernández, I.; Valiente, R.; Pollnau, M.

    2002-01-01

    This work investigates the effect of hydrostatic pressure on the excitation, emission and lifetime of Ti3+-doped Al2O3 in the 0–110 kbar range. The application of pressure induces band shifts that are correlated with the corresponding local structural changes undergone by the TiO6 complex. The incre

  15. Electrochemical Impedance Studies on Tribocorrosion Behavior of Plasma-Sprayed Al2O3 Coatings

    Science.gov (United States)

    Liu, Zhe; Chu, Zhenhua; Chen, Xueguang; Dong, Yanchun; Yang, Yong; Li, Yingzhen; Yan, Dianran

    2015-06-01

    In this paper, the tribocorrosion of plasma-sprayed Al2O3 coatings in simulated seawater was investigated by electrochemical impedance spectroscopy (EIS) technique, complemented by scanning electron microscopy to observe the morphology of the tribocorrosion attack. Base on EIS of plasma-sprayed Al2O3 coatings undergoing long-time immersion in simulated seawater, the corrosion process of Al2O3 coatings can be divided into the earlier stage of immersion (up to 20 h) and the later stage (beyond 20 h). Then, the wear tests were carried out on the surface of Al2O3 coating undergoing different times of immersion to investigate the influence of wear on corrosion at different stages. The coexistence of wear and corrosion condition had been created by a boron nitride grinding head rotating on the surface of coatings corroded in simulated seawater. The measured EIS and the values of the fitting circuit elements showed that wear accelerated corrosion at the later stage, meanwhile, corrosion accelerated wear with the immersion time increasing.

  16. Al2O3 Extraction Technologies from Fly Ash on the Properties of Modified PP Resin%粉煤灰提取Al2O3工艺对PP改性性能的影响

    Institute of Scientific and Technical Information of China (English)

    董金虎

    2012-01-01

    Extract Al2O3 was extracted from fly ash using alkali high-temperature calcinations, obtain two different structures' Al2O3 were obtained by two different technologies at the phase of Al(OH), separated out,and two different A12O3 were used to modify PP resin. The results showed that, the tensile strength of PP modified by sheet Al2O3, was better than the PP modified by flocculent Al2O3, and the elongation and impact strength of PP modified by the two different Al2O3 could have the same modification effect, and the content of sheet AlO3 litter than flocculent Al2O3 when obtained the same modification effect. And when the content of Al2O3 was about 2% , the comprehensive performance of PP modified by sheet Al2O3 was better,and the tensile strength increased about 13 % , and the elongation increased about 18 % , and the impact strength increased 15 % .%采用碱焙烧法从粉煤灰中提取Al2O3,在Al(OH)3析出过程中采用两种不同的工艺方法,可以形成两种结构的Al2O3,并分别将两种Al2O3用于改性PP树脂.结果表明:片状Al2O3改性PP的拉伸强度好于絮状Al2O3,而两种Al2O3改性PP的断裂伸长率、冲击强度可以获得相当的改性效果,且片状Al2O3的用量少于絮状Al2O3.片状Al2O3用量为2%左右时,改性PP的综合性能较好,拉伸强度提高约13%,断裂伸长率提高约18%,冲击强度提高约15%.

  17. Structural optical correlated properties of SnO2/Al2O3 core@ shell heterostructure

    Science.gov (United States)

    Heiba, Zein K.; Imam, N. G.; Bakr Mohamed, Mohamed

    2016-07-01

    Nano size polycrystalline samples of the core@shell heterostructure of SnO2 @ xAl2O3 (x = 0, 25, 50, 75 wt.%) were synthesized by sol-gel technique. The resulting samples were characterized with fourier transform infrared spectroscopy (FT-IR), photoluminescence (PL) and X-ray powder diffraction (XRD). The XRD patterns manifest diffraction peaks of SnO2 as main phase with weak peaks corresponding to Al2O3 phase. The formation of core@ shell structure is confirmed by TEM images and Rietveld quantitative phase analysis which revealed that small part of Al2O3 is incorporated into the SnO2 lattice while the main part (shell) remains as a separate phase segregated on the grain boundary surface of SnO2 (core). It is found that the grain size of the mixed oxides SnO2 @ xAl2O3 is below 10 nm while for pure SnO2 it is over 41 nm, indicating that alumina can effectively prevent SnO2 from further growing up in the process of calcination. This is confirmed by the large increase in the specific surface area for mixed oxide samples. The PL emission showed great dependence on the structure properties analyzed by XRD and FTIR. The PL results recommend Al2O3@SnO2 core@shell heterostructure to be a promising short-wavelength luminescent optoelectronic devices for blue, UV, and laser light-emitting diodes.

  18. An Experimental Study of Sintered (Ni-Cr-xAl2O3 Composites

    Directory of Open Access Journals (Sweden)

    Alaa Abdulhasan Atiyah

    2016-09-01

    Full Text Available This paper deals with the (Ni-Cr- xAl2O3 metallic composites (MCCs. Restraining of of thermal expansion at adequate mechanical and corrosion properties is the main objective of this work. Composites are fabricated with four weight percentages of (x = 1, 2, 5 and 10% Al2O3. Compacting and sintering has accomplished at (636 MPa and 1250oC for 7 hrs. All sintered compacts were examined for phases and microstructure featuring. Results have indicated, the incorporation of Al2O3 with the matrix is due to the efficient sintering conditions, that diminishing the grain growth and increasing the softening temperature from 850°C to become 1350°C. Volume expansion appeared in the base sintered composites (NiCr-xAl2O3 due to pores evolution according to SEM observation. As, the Al2O3 has increased, the microhardness and corrosion resistance have improved. DSC results show a clear one exothermic and one endothermic reaction were occurred during the heating cycle. Corrosion behavior of fabricated composites was estimated by polarization curves using Potentiostat at scan rate 3 mV.sec-1. Potential-time measurements showed the formation of protective layer on surface composites compared with Ni-Cr base composite through an obtaining of the nobler open circuit potentials for composites. Corrosion parameters were estimated by the Tafel extrapolation method, these parameters indicated that the corrosion potential shifted toward a positive direction in addition to get lower corrosion current density especially for Ni-Cr/5%Alumina composite.

  19. Investigating the electronic properties of Al2O3/Cu(In,GaSe2 interface

    Directory of Open Access Journals (Sweden)

    R. Kotipalli

    2015-10-01

    Full Text Available Atomic layer deposited (ALD Al2O3 films on Cu(In,GaSe2 (CIGS surfaces have been demonstrated to exhibit excellent surface passivation properties, which is advantageous in reducing recombination losses at the rear metal contact of CIGS thin-film solar cells. Here, we report, for the first time, experimentally extracted electronic parameters, i.e. fixed charge density (Qf and interface-trap charge density (Dit, for as-deposited (AD and post-deposition annealed (PDA ALD Al2O3 films on CIGS surfaces using capacitance–voltage (C-V and conductance-frequency (G-f measurements. These results indicate that the AD films exhibit positive fixed charges Qf (approximately 1012 cm−2, whereas the PDA films exhibit a very high density of negative fixed charges Qf (approximately 1013 cm−2. The extracted Dit values, which reflect the extent of chemical passivation, were found to be in a similar range of order (approximately 1012 cm−2 eV−1 for both AD and PDA samples. The high density of negative Qf in the bulk of the PDA Al2O3 film exerts a strong Coulomb repulsive force on the underlying CIGS minority carriers (ns, preventing them to recombine at the CIGS/Al2O3 interface. Using experimentally extracted Qf and Dit values, SCAPS simulation results showed that the surface concentration of minority carriers (ns in the PDA films was approximately eight-orders of magnitude lower than in the AD films. The electrical characterization and estimations presented in this letter construct a comprehensive picture of the interfacial physics involved at the Al2O3/CIGS interface.

  20. Microstructure of Suspension Plasma Spray and Air Plasma Spray Al2O3-ZrO2 Composite Coatings

    Science.gov (United States)

    Chen, Dianying; Jordan, Eric H.; Gell, Maurice

    2009-09-01

    Al2O3-ZrO2 coatings were deposited by the suspension plasma spray (SPS) molecularly mixed amorphous powder and the conventional air plasma spray (APS) Al2O3-ZrO2 crystalline powder. The amorphous powder was produced by heat treatment of molecularly mixed chemical solution precursors below their crystallization temperatures. Phase composition and microstructure of the as-synthesized and heat-treated SPS and APS coatings were characterized by XRD and SEM. XRD analysis shows that the as-sprayed SPS coating is composed of α-Al2O3 and tetragonal ZrO2 phases, while the as-sprayed APS coating consists of tetragonal ZrO2, α-Al2O3, and γ-Al2O3 phases. Microstructure characterization revealed that the Al2O3 and ZrO2 phase distribution in SPS coatings is much more homogeneous than that of APS coatings.

  1. Effects of Al2O3-Particulate-Contained Composite Filler Materials on the Shear Strength of Alumina Joints

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    All2O3/Al2O3 joints were brazed with a new kind of filler materials, which were formed by adding Al2O3 particulates into Ag-Cu-Ti active filler metal. The results showed that the material parameters (the Ti content, Al2O3 particulate volume fraction) of the composite filler materials affected the shear strength of brazed joints. When the Ti content was 2 wt pct in the filler metal, the shear strength of brazing joints decreased with the increasing the volume ratio of Al2O3 particulate. When the Ti content was 3 wt pct in the filler metal, the shear strength of joints increased from 93.75 MPa(Al2O3p 0 vol. pct) to 135.32 MPa(Al2O3p 15 vol. pct).

  2. Characterization of Al2O3 Thin Films on GaAs Substrate Grown by Atomic Layer Deposition

    Institute of Scientific and Technical Information of China (English)

    LU Hong-Liang; LI Yan-Bo; XU Min; DING Shi-Jin; SUN Liang; ZHANG Wei; WANG Li-Kang

    2006-01-01

    @@ Al2O3 thin films are grown by atomic layer deposition on GaAs substrates at 300℃. The structural properties of the Al2O3 thin film and the Al2O3/GaAs interface are characterized using x-ray diffraction (XRD), highresolution transmission electron microscopy (HRTEM), and x-ray photoelectron spectroscopy (XPS). The XRD results show that the as-deposited Al2O3 film is amorphous. For 30 atomic layer deposition growth cycles, the thicknesses of the Al2O3 thin film and the interface layer from the HRTEM are 3.3nm and 0.5nm, respectively.XPS analyses reveal that the Al2O3/GaAs interface is almost free from As2O3.

  3. Effects of a second phase on the tribological properties of Al2O3 and ZrO2 ceramics

    NARCIS (Netherlands)

    He, Y.J.; Winnubst, A.J.A.; Schipper, D.J.; Burggraaf, A.J.; Verweij, H.

    1997-01-01

    The tribological properties of four different materials are investigated, tetragonal zirconia (Y-ZTP), Al2O3 dispersed in Y-TZP (ADZ), ZrO2 dispersed in Al2O3 (ZTA) and Al2O3 (with 300 ppm MgO). These materials are used as a cylinder sliding against a plate of Y-TZP (TZ-3Y)). Compared to Y-TZP, the

  4. Development and Application of Al2O3 - Si3N4 Refractories Used in Blast Furnace

    Institute of Scientific and Technical Information of China (English)

    LI Xianming; LI Yong; KANG Huarong; DONG Shengying; XUE Wendong; SONG Wen

    2008-01-01

    Newly developed Al2O3-Si3N4 composite refracto-ries used for blast furnace is introduced in this work.Al2O3-Si3N4 composite refractories attacked by alkali vapor and blast Jhrnace slag was investigated. High per-formance Al2O3 -Si3N4 composite refractories was pro-duced and used at both 2 560 m3 blast furnaces of Tan-gsteel and No. 5 blast furnace of Shaosteel.

  5. Study on Interface between Sub-micron Particles and Matrix n Al2O3p/Al Composites

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The microstructural characteristic of 1070Al matrix composites reinforced by 0.15 μm Al2O3 particles whose volume fraction was 40% was investigated by TEM and HREM. The results showed that the interface between the matrix and reinforcements was clean and bonded well, without any interfacial reaction products. There were some preferential crystallographic orientation relationships between Al matrix and Al2O3 particle because of the lattice imperfection on the surface of Al2O3 particles.

  6. Effect of Al2O3 Binder on the Precipitated Iron-Based Catalysts for Fischer-Tropsch Synthesis

    Institute of Scientific and Technical Information of China (English)

    Hai-Jun Wan; Bao-Shan Wu; Xia An; Ting-Zhen Li; Zhi-Chao Tao; Hong-Wei Xiang; Yong-Wang Li

    2007-01-01

    A series of iron-based Fischer-Tropsch synthesis (FTS) catalysts incorporated with Al2O3 binder were prepared by the combination of co-precipitation and spray drying technology. The catalyst samples were characterized by using N2 physical adsorption, temperature-programmed reduction/desorption (TPR/TPD) and M(o)ssbauer effect spectroscopy (MES) methods. The characterization results indicated that the BET surface area increases with increasing Al2O3 content and passes through a maximum at the Al2O3/Fe ratio of 10/100 (weight basis). After the point, it decreases with further increase in Al2O3 content. The incorporation of Al2O3 binder was found to weaken the surface basicity and suppress the reduction and carburization of iron-based catalysts probably due to the strong K-Al2O3 and Fe-Al2O3 interactions. Furthermore, the H2 adsorption ability of the catalysts is enhanced with increasing Al2O3 content. The FTS performances of the catalysts were tested in a slurry-phase continuously stirred tank reactor (CSTR) under the reaction conditions of 260 ℃, 1.5 MPa, 1000 h-1 and molar ratio of H2/CO 0.67 for 200 h. The results showed that the addition of small amounts of Al2O3 affects the activity of iron-based catalysts to a little extent. However, with further increase of Al2O3 content, the FTS activity and water gas shift reaction (WGS) activity are decreased severely. The addition of appropriate Al2O3 do not affect the product selectivity, but the catalysts incorporated with large amounts of Al2O3 have higher selectivity for light hydrocarbons and lower selectivity for heavy hydrocarbons.

  7. Electrical Discharge Machining of Al/7.5% Al2O3 MMCs Using Rotary Tool and Al2O3 Powder

    Science.gov (United States)

    Daneshmand, Saeed; Masoudi, Behnam; Monfared, Vahid

    Nowadays, composites are used in different parts of industries and it is one of the most important subjects. The most widely used reinforcements in metal matrix composites are Al2O3 and SiC fibers and particles which may be used in cutting-edge functional and structural applications of aerospace, defense, and automobile industries. Depending on the type of powder used, composite materials are difficult to machine by conventional cutting tools and methods. The most appropriate way for machining of these composites is electro discharge. For the reason of improving the surface quality, tool wear rate and material removal rate and reducing the cracks on the surface, Al2O3 powder was used. In this study, the effect of input parameters of EDM such as voltage, pulse current, pulse on-time and pulse off-time on output parameters like material removal rate, tool wear rate and surface roughness in both conditions of the rotary tool with powder mixed dielectric EDM and the stationary tool excluding powder mixed dielectric were investigated. The critical parameters were identified by variance analysis, while the optimum machining parameter settings were achieved via Taguchi method. Results show that using of powder mixed dielectric and rotary tool reduce the tool wear rate, surface roughness and the cracks on the surface significantly. It is found also that using of powder mixed dielectric and rotary tool improve the material removal rate due to improved flushing action and sparking efficiency. The analysis of variance showed that the pulse current and pulse on-time affected highly the MRR, TWR, surface roughness and surface cracks.

  8. Probing the Physical Conditions of Supernova Ejecta with the Measured Sizes of Presolar Al2O3 Grains

    OpenAIRE

    2015-01-01

    A few particles of presolar Al2O3 grains with sizes above 0.5 mum are believed to have been produced in the ejecta of core-collapse supernovae (SNe). In order to clarify the formation condition of such large Al2O3 grains, we investigate the condensation of Al2O3 grains for wide ranges of the gas density and cooling rate. We first show that the average radius and condensation efficiency of newly formed Al2O3 grains are successfully described by a non-dimensional quantity "Lambda_on" defined as...

  9. Effects of Surface Treatments on the Performances of Al2 O3 Nano-Particle/Polyimide adhesive

    Institute of Scientific and Technical Information of China (English)

    MA Shi-ning; ZHANG Shi-tang; QIAO Yu-lin

    2004-01-01

    The nano-Al2O3/polyimide composite adhesive was prepared by high-energy chemical and mechanical handing in this paper. The thermally curing process was preliminary determined, furthermore, the effects of n-Al2 O3 on the performance of polyimide adhesive were investigated using SEM. The results were showed that n-Al2 O3 particles were segregated from adhesive to the interface, especially bulk structural defect, which may be the reason why the performance of n-Al2O3/PI adhesive becomes better. However, the detailed mechanism is still to be discussed.

  10. Preparation and Characterization of Liquid Crystalline Polyurethane/Al2O3/Epoxy Resin Composites for Electronic Packaging

    Directory of Open Access Journals (Sweden)

    Shaorong Lu

    2012-01-01

    Full Text Available Liquid crystalline polyurethane (LCPU/Al2O3/epoxy resin composites were prepared by using LCPU as modifier. The mechanical properties, thermal stability, and electrical properties of the LCPU/Al2O3/epoxy resin composites were investigated systematically. The thermal oxidation analysis indicated that LCPU/Al2O3/epoxy resin composites can sustain higher thermal decomposition temperature. Meanwhile, coefficient of thermal expansion (CTE was also found to decrease with addition of LCPU and nano-Al2O3.

  11. Promotion Effect of CaO Modification on Mesoporous Al2O3-Supported Ni Catalysts for CO2 Methanation

    Directory of Open Access Journals (Sweden)

    Wen Yang

    2016-01-01

    Full Text Available The catalysts Ni/Al2O3 and CaO modified Ni/Al2O3 were prepared by impregnation method and applied for methanation of CO2. The catalysts were characterized by N2 adsorption/desorption, temperature-programmed reduction of H2 (H2-TPR, X-ray diffraction (XRD, and temperature-programmed desorption of CO2 and H2 (CO2-TPD and H2-TPD techniques, respectively. TPR and XRD results indicated that CaO can effectively restrain the growth of NiO nanoparticles, improve the dispersion of NiO, and weaken the interaction between NiO and Al2O3. CO2-TPD and H2-TPD results suggested that CaO can change the environment surrounding of CO2 and H2 adsorption and thus the reactants on the Ni atoms can be activated more easily. The modified Ni/Al2O3 showed better catalytic activity than pure Ni/Al2O3. Ni/CaO-Al2O3 showed high CO2 conversion especially at low temperatures compared to Ni/Al2O3, and the selectivity to CH4 was very close to 1. The high CO2 conversion over Ni/CaO-Al2O3 was mainly caused by the surface coverage by CO2-derived species on CaO-Al2O3 surface.

  12. Geant4 calculations for space radiation shielding material Al2O3

    Science.gov (United States)

    Capali, Veli; Acar Yesil, Tolga; Kaya, Gokhan; Kaplan, Abdullah; Yavuz, Mustafa; Tilki, Tahir

    2015-07-01

    Aluminium Oxide, Al2O3 is the most widely used material in the engineering applications. It is significant aluminium metal, because of its hardness and as a refractory material owing to its high melting point. This material has several engineering applications in diverse fields such as, ballistic armour systems, wear components, electrical and electronic substrates, automotive parts, components for electric industry and aero-engine. As well, it is used as a dosimeter for radiation protection and therapy applications for its optically stimulated luminescence properties. In this study, stopping powers and penetrating distances have been calculated for the alpha, proton, electron and gamma particles in space radiation shielding material Al2O3 for incident energies 1 keV - 1 GeV using GEANT4 calculation code.

  13. Geant4 calculations for space radiation shielding material Al2O3

    Directory of Open Access Journals (Sweden)

    Capali Veli

    2015-01-01

    Full Text Available Aluminium Oxide, Al2O3 is the most widely used material in the engineering applications. It is significant aluminium metal, because of its hardness and as a refractory material owing to its high melting point. This material has several engineering applications in diverse fields such as, ballistic armour systems, wear components, electrical and electronic substrates, automotive parts, components for electric industry and aero-engine. As well, it is used as a dosimeter for radiation protection and therapy applications for its optically stimulated luminescence properties. In this study, stopping powers and penetrating distances have been calculated for the alpha, proton, electron and gamma particles in space radiation shielding material Al2O3 for incident energies 1 keV – 1 GeV using GEANT4 calculation code.

  14. Luminescence study of nanosized Al2O3:Tb3+ obtained by gas-dispersed synthesis

    Science.gov (United States)

    Berezovskaya, I. V.; Poletaev, N. I.; Khlebnikova, M. E.; Zatovsky, I. V.; Bychkov, K. L.; Efryushina, N. P.; Khomenko, O. V.; Dotsenko, V. P.

    2016-09-01

    Terbium-doped Al2O3 samples were obtained by gas-dispersed synthesis. It was shown that the resulting powders, with particle sizes of 10-70 nm, consist of a mixture of transition aluminas, among which the δ *-polymorph is dominant. The luminescence properties of Al2O3:Tb3+ have been studied upon excitation in the UV-visible range of the spectrum. It was found that Tb3+ ions cause several groups of inhomogeneously broadened emission bands in the range of 470-640 nm, which are characteristic for disordered materials. In addition, the emission spectra contain a broad band at about 450 nm and several narrower ones in the 680-720 nm region. These features are attributed to surface defects and impurity Cr3+ ions occupying Al3+ octahedral positions, respectively.

  15. Preparation and Characterization of Fe2O3/Al2O3 Nano-composites

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Al2O3/Fe2O3 nano-composites were prepared by sol-gel route. The effect of Fe2O3 content on the structure, grain size and characterization of the composite were investigated through X-ray diffraction and M(o)ssbauer spectrum. The X-ray diffraction results show that Al2O3/Fe2O3 nano-composites with the Fe2O3, content of 40 wt% can be obtained after heat-treated at 900℃. The M(o)ssbauer effect results show that all samples exhibit clear super-paramagnetic phenomenon. Particles grow and defects reduce with the increasing of Fe2O3 conteni and some α-Fe2O3 stay magnetic order.

  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. TEM study of a hot-pressed Al2O3-NbC composite material

    Directory of Open Access Journals (Sweden)

    Wilson Acchar

    2005-03-01

    Full Text Available Alumina-based composites have been developed in order to improve the mechanical properties of the monolithic matrix and to replace the WC-Co material for cutting tool applications. Al2O3 reinforced with refractory carbides improves hardness, fracture toughness and wear resistance to values suitable for metalworking applications. Al2O3-NbC composites were uniaxially hot-pressed at 1650 °C in an inert atmosphere and their mechanical properties and microstructures were analyzed. Sintered density, average grain size, microhardness and fracture toughness measurements and microstructural features were evaluated. Results have shown that the mechanical properties of alumina-NbC are comparable to other carbide systems. Microstructural analysis has shown that the niobium carbide particles are mainly located at the grain boundaries of alumina grains, which is an evidence of the "pinning effect", produced by NbC particles.

  18. Improved real-time dosimetry using the radioluminescence signal from Al2O3:C

    DEFF Research Database (Denmark)

    Damkjær, Sidsel Marie Skov; Andersen, Claus Erik; Aznar, Marianne

    2008-01-01

    15th International Conference on Solid State Dosimetry Location: Delft Univ Technol, Delft, NETHERLANDS Date: JUL 08-13, 2007 Abstract: Carbon-doped aluminum oxide (Al2O3:C) is a highly sensitive luminescence material for ionizing radiation dosimetry, and it is well established that the optically...... to greatly reduce the influence of shallow traps in the range from 0 to 3 Gy and the RL dose-rate measurements with a time resolution of 0. 1 s closely matched dose-rate changes monitored with in ionization chamber. (c) 2007 Elsevier Ltd. All rights reserved.......15th International Conference on Solid State Dosimetry Location: Delft Univ Technol, Delft, NETHERLANDS Date: JUL 08-13, 2007 Abstract: Carbon-doped aluminum oxide (Al2O3:C) is a highly sensitive luminescence material for ionizing radiation dosimetry, and it is well established that the optically...

  19. Propane oxidation on Pt-WO3/g -AL2O3 catalytic systems

    Directory of Open Access Journals (Sweden)

    Silva M.A.Pereira da

    2003-01-01

    Full Text Available The oxidation of propane on was studied with Pt-xWO3/Al2O3 catalysts was studied ,by varying the concentration of tungsten sublayer. Thermal analysis and XRD in situ showed that the enrichment of tungsten at the surface is associated with the formation of HxWO3 bronze. FTIR results with C3H8 and O2 indicated that the catalyst surface properties and the interaction between W and Pt were modified. These modified surface complexes prevented the formation of acetates and formate species. The addition of W increased the activity of Pt/Al2O3 towards in C3H8 oxidation. Tungsten was the main responsible for the stability of the bimetallic catalysts in the presence of water.

  20. Fe-Al2O3 nanocomposites prepared by high-energy ball milling

    DEFF Research Database (Denmark)

    Linderoth, Søren; Pedersen, M.S.

    1994-01-01

    Nanocomposites of alpha-Fe and alpha-Al2O3, prepared by high-energy ball milling, exhibit coercivities which are enhanced by about two orders of magnitude with respect to the bulk value. The degree of enhancement depends on the volume fraction (x(upsilon)) of Fe, with a maximum for x(upsilon) alm......Nanocomposites of alpha-Fe and alpha-Al2O3, prepared by high-energy ball milling, exhibit coercivities which are enhanced by about two orders of magnitude with respect to the bulk value. The degree of enhancement depends on the volume fraction (x(upsilon)) of Fe, with a maximum for x......(upsilon) almost-equal-to 0.25. The effect is ascribed to the production of single-domain magnetic grains. Mossbauer spectroscopy reveals the presence of iron oxide phases which could not be seen by x-ray and electron diffraction measurements....

  1. Effect of sulfur removal on Al2O3 scale adhesion

    Science.gov (United States)

    Smialek, James L.

    1991-01-01

    The effect of removing sulfur impurity on the adhesion of Al2O3 scale to NiCrAl was investigated in four experiments. It was found that removing sulfur to concentration less than 1 ppm per weight is sufficient to produce a very significant degree of alpha-Al2O3 scale adhesion to undoped NiCrAl alloys. Results of experiments show that repeated oxidation, and polishing after each oxidation cycle, of pure NiCrAl alloy lowered sulfur content from 10 to 2 ppm by weight (presumably by removing the segregated interfacial layer after each cycle); thinner samples became adherent after fewer oxidation-polishing cycles because of more limited supply of sulfur. It was found that spalling in subsequent cyclic oxidation tests was a direct function of the initial sulfur content. The transition between the adherent and nonadherent behavior was modeled in terms of sulfur flux, sulfur content, and sulfur segregation.

  2. Adherent Al2O3 scales produced on undoped NiCrAl alloys

    Science.gov (United States)

    Smialek, James L.

    1986-01-01

    Repeated oxidation and polishing of high purity Ni-15Cr-13Al has dramatically changed its cyclic oxidation behavior from nonadherent to adherent. No apparent change in scale phase, morphology or interface structure occurred during this transition, dismissing any mechanism based on pegging, vacancy sink, or growth stress. The principle change that did occur was a reduction in the sulfur content from 10 ppmw to 3 ppmw after 25 cycles at 1120 C. These observations are used to support the model of Al2O3 scale adherence put forth by Smeggil et al. which claims that Al2O3 scale spallation occurs due to sulfur segregation and bond deterioration at the oxide-metal interface.

  3. Anormalous Optical Absorption in Porous Al_2O3 Host Matrix---Nano-Oxide Particle Nanocomposites

    Science.gov (United States)

    Zhang, Lide; Zhang, Biao; Mo, Chimei

    1996-03-01

    Porous Al_2O3 host matrix---nano-γ-Fe_2O3 particle composites (porous nanocomposite) were prepared by pyrolysis of Fe(NO_3)_39H_2O in porous nano- Al_2O3 matrix at 250^0C. Comparing with simple nanocomposites formed by mixing nano-γ-Fe_2O3 and compacting at room temperature, followed by annealing at 250^0C, the following anomalous optical behaviors were observed: for porous nanocomposite containing 5% Fe_2O_3, the aborption edge shifts obviously from 827nm to 543nm, and with increasing dopping amount of Fe_2O3 from 5% to 70%, blue shift phenomina decreases. Namely, the absorption edge moves from 543nm to 710nm. The mechanism of shift of the absorption edge is discussed.

  4. NO2 adsorption on BaO/Al2O3: the nature of nitrate species.

    Science.gov (United States)

    Szanyi, Janós; Kwak, Ja Hun; Kim, Do Heui; Burton, Sarah D; Peden, Charles H F

    2005-01-13

    Temperature programmed desorption, infrared spectroscopy, and (15)N solid state NMR spectroscopy were used to characterize the nature of the nitrate species formed on Al(2)O(3) and BaO/Al(2)O(3) NO(x) storage/reduction materials. Two distinctly different nitrate species were found: surface nitrates that are associated with a monolayer BaO on the alumina support, and a bulk-like nitrate that forms on this thin BaO layer. The surface nitrates desorb as NO(2) at lower temperatures than do the bulk-like nitrates, which decompose as NO+O(2) at higher temperatures. The amount of NO(x) stored in the monolayer nitrate is proportional to the surface area of the catalyst, while that in the bulk nitrate increases with BaO coverage.

  5. Versatile sputtering technology for Al2O3 gate insulators on graphene

    Directory of Open Access Journals (Sweden)

    Miriam Friedemann, Mirosław Woszczyna, André Müller, Stefan Wundrack, Thorsten Dziomba, Thomas Weimann and Franz J Ahlers

    2012-01-01

    Full Text Available We report a novel, sputtering-based fabrication method of Al2O3 gate insulators on graphene. Electrical performance of dual-gated mono- and bilayer exfoliated graphene devices is presented. Sputtered Al2O3 layers possess comparable quality to oxides obtained by atomic layer deposition with respect to a high relative dielectric constant of about 8, as well as low-hysteresis performance and high breakdown voltage. We observe a moderate carrier mobility of about 1000 cm2 V− 1 s−1 in monolayer graphene and 350 cm2 V− 1 s−1 in bilayer graphene, respectively. The mobility decrease can be attributed to the resonant scattering on atomic-scale defects, likely originating from the Al precursor layer evaporated prior to sputtering.

  6. Ni/Al2O3 catalysts for syngas methanation: Effect of Mn promoter

    Institute of Scientific and Technical Information of China (English)

    Anmin Zhao; Weiyong Ying; Haitao Zhang; Hongfang Ma; Dingye Fang

    2012-01-01

    Ni/Al2O3 catalysts with different amounts of manganese ranging from 1 to 3 wt% as promoter were prepared by co-impregnation method.The catalysts were characterized by N2 physisorption,XRD,TPR,SEM and TEM.Their catalytic activity towards syngas methanation reaction was also investigated using a fixed-bed integral reactor.It was demonstrated that the addition of manganese to Ni/Al2O3 catalysts can increase the catalyst surface area and average pore volume,but decrease NiO crystallite size,leading to higher activity and stability.The effects of reaction temperature,pressure and weight hourly space velocity (WHSV) on carbon oxides conversion and CH4 formation rate were also studied.High carbon oxides conversion,CH4 selectivity and formation rate were achieved at the reaction temperature range of 280-300 ℃.

  7. Protective Al2O3 scale formation on NbAl3-base alloys

    Science.gov (United States)

    Doychak, J.; Hebsur, M. G.

    1991-01-01

    The oxidation of NbAl3 with additions of Cr and Y was studied to determine the mechanisms of the beneficial effects of these elements upon oxidation. Cr additions to the binary NbAl3 alloy of up to 6.8 at. percent reduced the scale growth rates and promoted alpha-Al2O3 formation over much longer times relative to binary NbAl3. A major effect of Cr is to form a layer of AlNbCr at the metal/scale interface, which is inherently more oxidation-resistant than the matrix alloy in the long term. Yttrium additions to a Cr-containing alloy improved the scale growth rate and adherence and changed the scale microstructure to mimic that of a typical protective Al2O3 scale.

  8. Electrical characteristics of polycrystalline Si layers embedded into high- k Al 2O 3 gate layers

    Science.gov (United States)

    Park, Byoungjun; Cho, Kyoungah; Kim, Sangsig

    2008-09-01

    The electrical characteristics of polycrystalline Si (poly Si) layers embedded into high- k Al 2O 3 (alumina) gate layers are investigated in this work. The capacitance versus voltage ( C- V) curves obtained from the metal-alumina-polysilicon-alumina-silicon (MASAS) capacitors exhibit significant threshold voltage shifts, and the width of their hysteresis window is dependent on the range of the voltage sweep. The counterclockwise hysteresis observed in the C- V curves indicates that electrons originating from the p-type Si substrate in the inversion condition are trapped in the floating gate layer consisting of the poly Si layer present between the top and bottom Al 2O 3 layers in the MASAS capacitor. Also, current versus voltage ( I- V) measurements are performed to examine the electrical characteristics of the fabricated capacitors. The I- V measurements reveal that our MASAS capacitors show a very low leakage current density, compared to the previously reported results.

  9. Strength Properties and Microstructure of Diphase β—Sialon/Al2O3 Composites

    Institute of Scientific and Technical Information of China (English)

    LIYoufen; HONGYanruo; 等

    2000-01-01

    Study on modules of rupture and microstructure of xphase bearing diphase β-Sialon and diphase β-Sialon/Al2O3 composites shows that MOR increases with tempera-ture rise up to a maximum oint and then decreases,For diphase β-Sialon materials,the maximum strength reaches 130 MPa-170 MPa at 1200℃;whereas for diphase β-Sialon/Al2O3 composites,the maximum strength reaches 200MPa-300 MPa at 1000℃,In the microstructure of th composite ,oblong crystals of x-phase and hexagonal prismatic crystals of β-Sialon are interlaced in the skeleton structure of corundum.This struture creates a distinctly intensifying effect on the strength of the composite.

  10. Visible luminescence of Al2O3 nanoparticles embedded in silica glass host matrix

    Science.gov (United States)

    El Mir, L.; Amlouk, A.; Barthou, C.

    2006-11-01

    This paper deals with the sol gel elaboration and defects photoluminescence (PL) examination of Al2O3 nanocrystallites (size ˜30 nm) confined in glass based on silica aerogel. Aluminium oxide aerogels were synthesized using esterification reaction for hydrolysis of the precursor and supercritical conditions of ethyl alcohol for drying. The obtained nanopowder was incorporated in SiO2 host matrix. After heating under natural atmosphere at 1150 °C for 2 h, the composite Al2O3/SiO2 (AS) exhibited a strong PL bands at 400 600 and 700 900 nm in 78 300 K temperature range. PL excitation (PLE) measurements show different origins of the emission. It was suggested that OH-related radiative centres and non-bridging oxygen hole centres (NBOHCs) were responsible for the bands at 400 600 and 700 900 nm, respectively.

  11. Vacuum ultraviolet photochemical selective area atomic layer deposition of Al2O3 dielectrics

    Directory of Open Access Journals (Sweden)

    P. R. Chalker

    2015-01-01

    Full Text Available We report the photochemical atomic layer deposition of Al2O3 thin films and the use of this process to achieve area-selective film deposition. A shuttered vacuum ultraviolet (VUV light source is used to excite molecular oxygen and trimethyl aluminum to deposit films at 60°C. In-situ QCM and post-deposition ellipsometric measurements both show that the deposition rate is saturative as a function of irradiation time. Selective area deposition was achieved by projecting the VUV light through a metalized magnesium fluoride photolithographic mask and the selectivity of deposition on the illuminated and masked regions of the substrate is a logarithmic function of the UV exposure time. The Al2O3 films exhibit dielectric constants of 8 – 10 at 1 MHz after forming gas annealing, similar to films deposited by conventional thermal ALD.

  12. Space-charge-controlled field emission model of current conduction through Al2O3 films

    Science.gov (United States)

    Hiraiwa, Atsushi; Matsumura, Daisuke; Kawarada, Hiroshi

    2016-02-01

    This study proposes a model for current conduction in metal-insulator-semiconductor (MIS) capacitors, assuming the presence of two sheets of charge in the insulator, and derives analytical formulae of field emission (FE) currents under both negative and positive bias. Since it is affected by the space charge in the insulator, this particular FE differs from the conventional FE and is accordingly named the space-charge-controlled (SCC) FE. The gate insulator of this study was a stack of atomic-layer-deposition Al2O3 and underlying chemical SiO2 formed on Si substrates. The current-voltage (I-V) characteristics simulated using the SCC-FE formulae quantitatively reproduced the experimental results obtained by measuring Au- and Al-gated Al2O3/SiO2 MIS capacitors under both biases. The two sheets of charge in the Al2O3 films were estimated to be positive and located at a depth of greater than 4 nm from the Al2O3/SiO2 interface and less than 2 nm from the gate. The density of the former is approximately 1 × 1013 cm-2 in units of electronic charge, regardless of the type of capacitor. The latter forms a sheet of dipoles together with image charges in the gate and hence causes potential jumps of 0.4 V and 1.1 V in the Au- and Al-gated capacitors, respectively. Within a margin of error, this sheet of dipoles is ideally located at the gate/Al2O3 interface and effectively reduces the work function of the gate by the magnitude of the potential jumps mentioned above. These facts indicate that the currents in the Al2O3/SiO2 MIS capacitors are enhanced as compared to those in ideal capacitors and that the currents in the Al-gated capacitors under negative bias (electron emission from the gate) are more markedly enhanced than those in the Au-gated capacitors. The larger number of gate-side dipoles in the Al-gated capacitors is possibly caused by the reaction between the Al and Al2O3, and therefore gate materials that do not react with underlying gate insulators should be chosen

  13. Erbium and Al2O3 nanocrystals-doped silica optical fibers

    OpenAIRE

    2014-01-01

    Fibre lasers and inherently rare-earth-doped optical fibers nowadays pass through a new period of their progress aiming at high efficiency of systems and their high power. In this paper, we deal with the preparation of silica fibers doped with erbium and Al2O3 nanocrystals and the characterization of their optical properties. The fibers were prepared by the extended Modified Chemical Vapor Deposition (MCVD) method from starting chlorides or oxide nanopowders. Conventional as well as modified ...

  14. KINERJA KATALIS Ag/Al2O3 UNTUK REDUKSI NOx

    Directory of Open Access Journals (Sweden)

    Rakhman Sarwono

    2012-02-01

    Full Text Available NOx merupakan hasil samping dari suatu reaksi pembakaran. NOx merupakan gas yang beracun sangat berbahaya terhadap kesehatan manusia dan hewan bila terhirup pada waktu bernafas. Untuk mengurangi kadar NOx pada gas buang, banyak penelitian diarahkan pada reduksi NOx dengan katalis secara selektif dengan hidrokarbon dan oksigen berlebihan. Katalis yang digunakan adalah katalis alumina (Al2O3 yang didapat dari katalis komersial (AlO1-7 dan katalis hasil sintesa (ALOA. Katalis Ag/Al2O3 didapat dengan memasukkan logam Ag ke dalam alumina (Al2O3 dengan cara impregnasi dengan larutan perak nitrat. Katalis diuji aktifitasnya pada reaktor fixed bed yang diluarnya terdapat pemanas yang bisa diatur suhunya. Reaktan seperti gas NO, C2H4  dan oksigen dimasukkan kedalam reaktor dengan laju yang ditentukan. Hasil reaksi dianalisa dengan gas chromatography dan dicatat pada recorder, selanjutnya bisa ditentukan kuantitas dan prosentase konversinya. Katalis alumina  ALOA mempunyai kemampuan mereduksi NO dengan konversi  sekitar 40-45% gas NO menjadi N2. Loading logam perak (Ag kedalam Al2O3 sebesar 2-3% berat menambah daya reduksi NO menjadi sekitar 45-50% pada suhu 500oC. Pada umpan NO + C2H4  + O2  reaksi reduksi terjadi pada suhu 300oC, sedangkan pada umpan NO + C2H4   (tanpa oksigen reaksi reduksi baru terjadi pada suhu 450oC, dengan demikian adanya oksigen sangat berperan dalam proses reduksi NOx. Reaksi peruraian C2H4 menjadi COx berkebalikan dengan kinerja katalis pada proses reduksi NOx

  15. Modified Mechanism of Eutectic Silicon in Al2O3/Al-Si Alloy

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Al2O3/Al-Si alloy composite was manufactured by squeeze casting. The morphology of the eutectic silicon in the composite was observed by scanning electronic microscope (SEM), and the modified mechanism of eutectic silicon in the composite was approached. The alumina fiber in the composite can trigger twin during the growth of Al-Si eutectic and lead to the modification of eutectic silicon near the fiber.

  16. The temperature dependence of optically stimulated luminescence from α-Al2O3:C

    DEFF Research Database (Denmark)

    Markey, B.G.; McKeever, S.W.S.; Akselrod, M.S.;

    1996-01-01

    The results of experimental measurements and computer simulations on optically stimulated luminescence (OSL) from alpha-Al2O3:C are described. The intensity of the OSL observed during illumination of irradiated specimens with visible light is temperature dependent. Optical stimulation is observed...... from the main dosimetric traps, and from deep traps. The temperature dependence appears to be due to the presence of shallow traps, with a possible additional contribution from thermally assisted optical excitation....

  17. Temperature dependence of the Al2O3:C response in medical luminescence dosimetry

    DEFF Research Database (Denmark)

    Edmund, Jens Morgenthaler; Andersen, Claus Erik

    2007-01-01

    is not varied. The RL response only depends on the irradiation temperature. We recommend that calibration should be carried out at the same irradiation temperature at which the measurement is performed (i.e. at body temperature for in vivo measurements). The overall change in the integrated OSL and RL signals...... and detection wavelengths. The reported temperature dependence seems to be a general property of Al2O3:C. (C) 2006 Elsevier Ltd. All rights reserved....

  18. Numerical investigation of Al2O3/water nanofluid laminar convective heat transfer through triangular ducts

    OpenAIRE

    Zeinali Heris, Saeed; Noie, Seyyed Hossein; Talaii, Elham; Sargolzaei, Javad

    2011-01-01

    In this article, laminar flow-forced convective heat transfer of Al2O3/water nanofluid in a triangular duct under constant wall temperature condition is investigated numerically. In this investigation, the effects of parameters, such as nanoparticles diameter, concentration, and Reynolds number on the enhancement of nanofluids heat transfer is studied. Besides, the comparison between nanofluid and pure fluid heat transfer is achieved in this article. Sometimes, because of pressure drop limita...

  19. Frustration of Negative Capacitance in Al2O3/BaTiO3 Bilayer Structure

    Science.gov (United States)

    Kim, Yu Jin; Park, Min Hyuk; Lee, Young Hwan; Kim, Han Joon; Jeon, Woojin; Moon, Taehwan; Do Kim, Keum; Jeong, Doo Seok; Yamada, Hiroyuki; Hwang, Cheol Seong

    2016-01-01

    Enhancement of capacitance by negative capacitance (NC) effect in a dielectric/ferroelectric (DE/FE) stacked film is gaining a greater interest. While the previous theory on NC effect was based on the Landau-Ginzburg-Devonshire theory, this work adopted a modified formalism to incorporate the depolarization effect to describe the energy of the general DE/FE system. The model predicted that the SrTiO3/BaTiO3 system will show a capacitance boost effect. It was also predicted that the 5 nm-thick Al2O3/150 nm-thick BaTiO3 system shows the capacitance boost effect with no FE-like hysteresis behavior, which was inconsistent with the experimental results; the amorphous-Al2O3/epitaxial-BaTiO3 system showed a typical FE-like hysteresis loop in the polarization – voltage test. This was due to the involvement of the trapped charges at the DE/FE interface, originating from the very high field across the thin Al2O3 layer when the BaTiO3 layer played a role as the NC layer. Therefore, the NC effect in the Al2O3/BaTiO3 system was frustrated by the involvement of reversible interface charge; the highly stored charge by the NC effect of the BaTiO3 during the charging period could not be retrieved during the discharging process because integral part of the polarization charge was retained within the system as a remanent polarization.

  20. 气相氟化四氯乙烯的ZnF_2/Al_2O_3催化剂%Study on ZnF_2/Al_2O_3 catalysts for the vapor phase hydrofluorination of tetrachloroethylene

    Institute of Scientific and Technical Information of China (English)

    程永香; 谢遵运; 彭小波; 罗孟飞

    2012-01-01

    ZnF2/Al2O3 catalysts were prepared by an impregnation method.The effect of the Al2O3 support calcination temperature on catalytic performance for the vapor phase hydrofluorination of tetrachloroethylene was studied.The catalysts were characterized by XRD,Raman,NH3-TPD and BET techniques.The results show that-Al2O3 started to transform to-Al2O3 and α-Al2O3 at 900 ℃.-Al2O3 reaches to its maximum at 1100℃.By further increasing the calcination temperature,all-Al2O3 transformed to α-Al2O3.The highest activity was obtained on a ZnF2/Al2O3 catalyst with the Al2O3 support calcined at 1110 ℃.The conversion of tetrachloroethylene was 45.7% and the selectivity to HCFC-123(2,2-dichloro-1,1,1-three ethyl fluoride) and HCFC-124(2-chloro-1,1,1,2-tetrafluoroethane) was 48.2% at a reaction temperature of 300 ℃.%采用浸渍法制备了ZnO/Al2O3催化剂,考察了载体Al2O3的焙烧温度对催化剂性能的影响。并对催化剂进行了X射线衍射(XRD)、Raman光谱、氨气程序升温脱附(NH3-TPD)和BET表征。结果表明:随着Al2O3焙烧温度升高,从900℃开始,-Al2O3逐渐向-Al2O3和α-Al2O3转变,1100℃焙烧样品中-Al2O3的XRD峰强度达到最大。当温度继续升高,-Al2O3将转变成α-Al2O3Al2O3载体经过1100℃焙烧制得的ZnF2/Al2O3催化剂催化性能最高,当反应温度为300℃时,四氯乙烯的转化率为45.7%,HCFC-123(2,2-二氯-1,1,1-三氟乙烷)和HCFC-124(2-氯-1,1,1,2-四氟乙烷)的总选择性为48.2%。

  1. Er3+–Al2O3 nanoparticles doping of borosilicate glass

    Indian Academy of Sciences (India)

    Jonathan Massera; Laeticia Petit; Joona Koponen; Benoit Glorieux; Leena Hupa; Mikko Hupa

    2015-09-01

    Novel borosilicate glasses were developed by adding in the glass batch Er3+–Al2O3 nanoparticles synthetized by using a soft chemical method. A similar nanoparticle doping with modified chemical vapour deposition (MCVD) process was developed to increase the efficiency of the amplifying silica fibre in comparison to using MCVD and solution doping. It was shown that with the melt quench technique, a Er3+–Al22O3 nanoparticle doping neither leads to an increase in the Er3+ luminescence properties nor allows one to control the rare-earth chemical environment in a borosilicate glass. The site of Er3+ in the Er3+–Al2O3 nanoparticle containing glass seems to be similar as in glasses with the same composition prepared using standard raw materials. We suspect the Er3+ ions to diffuse from the nanoparticles into the glass matrix. There was no clear evidence of the presence of Al2O3 nanoparticles in the glasses after melting.

  2. Effect of adsorbed films on friction of Al2O3-metal systems

    Science.gov (United States)

    Pepper, S. V.

    1976-01-01

    The kinetic friction of polycrystalline Al2O3 sliding on Cu, Ni, and Fe in ultrahigh vacuum was studied as a function of the surface chemistry of the metal. Clean metal surfaces were exposed to O2, Cl2, C2H4, and C2H3Cl, and the change in friction due to the adsorbed species was observed. Auger electron spectroscopy assessed the elemental composition of the metal surface. It was found that the systems exposed to Cl2 exhibited low friction, interpreted as the van der Waals force between the Al2O3 and metal chloride. The generation of metal oxide by oxygen exposures resulted in an increase in friction, interpreted as due to strong interfacial bonds established by reaction of metal oxide with Al2O3 to form the complex oxide (spinel). The only effect of C2H4 was to increase the friction of the Fe system, but C2H3Cl exposures decreases friction in both Ni and Fe systems, indicating the dominance of the chlorine over the ethylene complex on the surface

  3. KINETIKA HIDRODESULFURISASI DIBENZOTHIOPHENE (HDS DBT MENGGUNAKAN KATALIS NiMo/γ-Al2O3

    Directory of Open Access Journals (Sweden)

    Subagjo Subagjo

    2014-12-01

    Full Text Available Evaluasi kinetika reaksi hidrodesulfurisasi (HDS dibenzothiophene dan simulasi nafta hydrotreater yang berada di PT. PERTAMINA Refinery Unit II Dumai menggunakan katalis NiMo/Al2O3 hasil pengembangan telah dilakukan. Kinetika reaksi HDS DBT dilakukan dalan sistem reaktor batch dengan variasi temperatur 280-320oC dan tekanan 30 bar. Data kinetika diolah dengan persamaan hukum pangkat (law power dan persamaan kinetik mekanistik (Langmuir Hinshelwood, LH. Berdasarkan model hukum pangkat, kinetika HDS DBT menggunakan NiMo/Al2O3 hasil pengembangan merupakan  orde satu  terhadap DBT dengan konstanta Arhenius  sebesar 165633 detik-1 dan energi aktivasi 69017 J/mol (16,56 kkal/mol. Model LH yang cocok untuk reaksi HDS DBT menggunakan NiMo/Al2O3 hasil pengembangan adalah model LH yang mengilustrasikan adanya kompetisi antara reaktan DBT dan H2 pada tipe pusat aktif yang sama, dengan DBT teradsorb secara kuat sedangkan H2 teradsorpsi secara lemah. Energi aktifasi dan konstanta Arhenius berdasarkan model LH ini ini berturut-turut adalah 81409 J/mol (19,34 kkal/mol dan 1658133 s-1. Dengan menggunakan persamaan laju reaksi hukum pangkat, model memberikan hasil konversi sulfur yang sama dengan hasil keluaran reaktor nafta hydrotreater RU II-Dumai, yaitu mencapai 98%.

  4. Kinetic Adsorption of Cd onto Nanometer Al2O3/Carbon Fibre

    Institute of Scientific and Technical Information of China (English)

    LI Yu; WANG Yue; HAN Wei; LI Su-wen; ZHAO Hui; ZHU Chang-yun; WANG Heng

    2005-01-01

    A new nanometer material, nano-Al2O3 with carbon fibre as the carrier, was employed for the removal of Cd with low concentrations from polluted water. The characterization of the material was carried out by means of SEM and TEM. Batch adsorption and elution experiments were carried out to determine the adsorption properties of Cd on the new adsorbent. The classical Thomas model was applied to estimating the equilibrium coefficients of Cd adsorption and the saturated adsorption ability. The results show that the Thomas model is fit for describing the kinetic adsorption process, and the maximum adsorption capacity of the nanometer Al2O3/carbon is 69.29 mg/g. The resulting information also indicates that the desorption of Cd eluted with de-ionized water at a rate of 9.8 mL/min can be neglected. With the advantage of a high adsorption capacity for removing low concentration Cd, the Al2O3/carbon fibre possesses the potentiality to be an effective adsorbent for the removal of Cd from polluted water.

  5. Micro mechanical properties of n-Al2O3/Ni composite coating by nanoindentation

    Institute of Scientific and Technical Information of China (English)

    WANG Hong-mei; XU Bin-shi; MA Shi-ning; DONG Shi-yun; LI Xiao-ying

    2004-01-01

    A new type of nano test system was introduced, the test principle and the indentation data analysis method were described. It was used to test the micro mechanical properties, such as hardness, elastic modulus and indentation creep property of n-Al2O3/Ni composite coating on steel prepared by brush plating, and the variety of mechanical properties with coating thickness was researched. The results show that the mechanical properties are basically identical within the whole coating, the hardness and modulus decrease in the defect fields, especially within the dendritic crystals, whereas the mechanical properties are not influenced greatly at the interspaces among dendritic crystals. The average hardness and elastic modulus of n-Al2O3/Ni coating are 6.34 GPa and 154 GPa respectively, and the hardness is 2.4 times higher than that of steel and the indentation creep curve of n-Al2O3/Ni coating is similar to that of the uniaxial compression creep, and the creep rate of steady-state is about 0. 104 nm/s. These results will supply useful data for process improvement, new type material development and application expansion.

  6. H2 assisted NH3-SCR over Ag/Al2O3 for automotive applications

    DEFF Research Database (Denmark)

    Fogel, Sebastian

    The up-coming strict emission legislation demands new and improved catalysts for diesel vehicle deNOx. The demand for low-temperature activity is especially challenging. H2-assisted NH3-SCR over Ag/Al2O3 has shown a very promising low-temperature activity and a combination of Ag/Al2O3 and Fe...... has been the preparation of monolithic catalyst bricks for the catalyst testing. A high SBET and higher Ag loading gave a high sulphur tolerance and activity. It was believed that the high SBET is needed to give a higher NH3 adsorption capacity, necessary for the SCR reaction. A higher Ag loading...... both in a sequential dual-bed layout and a dual-layer layout where the catalysts were coated on top of each other. The Ag/Al2O3 catalyst was also investigated with the aim of improving the sulphur tolerance and low-temperature activity by testing different alumina-supports. A large focus of this study...

  7. New technique of comprehensive utilization of spent Al2O3-based catalyst

    Institute of Scientific and Technical Information of China (English)

    FENG Qi-ming; CHEN Yun; SHAO Yan-hai; ZHANG Guo-fan; OU Le-ming; LU Yi-ping

    2006-01-01

    A new technology was developed to recover multiple valuable elements from the spent Al2O3-based catalyst by X-ray phase analysis and exploratory experiments. The experimental results show that in the condition of roasting temperature of 750 ℃ and roasting time of 30 min, molar ratio of Na2 O to Al2O3 of 1.2, the leaching rates of alumina, vanadium and molybdenum in the spent catalyst are 97.2 %, 95.80% and 98. 9 %, respectively. Vanadium and molybdenum in sodium aluminate solution can be recovered by precipitators A and B, and the precipitation rates of vanadium and molybdenum are 94.8% and 92.6%. Al(OH)3 was prepared from sodium aluminate solution in the carbonation decomposition process, and the purity of Al2O3 is 99.9% after calcination, the recovery of alumina reaches 90.6% in the whole process; the Ni-Co concentrate was leached by sulfuric acid, a nickel recovery of 98.2 % and cobalt recovery over 98.5 % can be obtained under the experimental condition of 30 % H2 SO4, 80 ℃, reaction time 4 h, mass ratio of liquid to solid 8, stirring rate 800 r/min.

  8. Effects of drying method on preparation of nanometer α-Al2O3

    Institute of Scientific and Technical Information of China (English)

    XIAO Jin; WAN Ye; DENG Hua; LI Jie; LIU Ye-xiang

    2007-01-01

    Ammonium aluminum carbonate hydroxide (AACH) precursor was synthesized by the precipitation reaction of aluminum sulfate and ammonium carbonate. Then the precursor was dealt with five drying methods including ordinary drying, alcohol exchange, vacuum freeze-drying, glycol distillation, n-butanol azeotropic distillation respectively and calcined at 1 200 ℃ for 2 h to get α-Al2O3. The effects of drying methods on preparation of nanometer α-Al2O3 were discussed, and the optimal drying method was confirmed. The structural properties of powders were characterized by XRD, SEM and BET measurements. The results show that vacuum freeze-drying, glycol distillation and n-butanol azeotropic distillation can prevent the powders from aggregating, and among them the n-butanol azeotropic distillation is the best method. The nanometer α-Al2O3 powder with non-aggregation can be manufactured using n-butanol azeotropic distillation and the average particle size is about 40 nm.

  9. Fabrication of Homogenous Dispersion TiB2-Al2O3 Composites

    Institute of Scientific and Technical Information of China (English)

    ZHANG Jinyong; TANG Wenjun; FU Zhengyi; WANG Weiming; ZHANG Qingjie

    2011-01-01

    In order to get a homogenous mixture and compact of TiB2-A12O3,hybridization as a surface modification method was used to prepare nano-scale Al2O3 coated TiB2 particles.PE-wax particles were first coated onto TiB2 particles by hybridization,and then the nano-scale Al2O3 particles were coated onto the surface of TiB2 coated by PE-wax particles again.SEM,TEM and EDS were used to characterize the microstructure of as-received core/shell particles and its compacts.The experimental results show that a particle-scale homogenous dispersion of TiB2 and Al2O3 can be formed not only in mixed powder but also in dewaxed compacts.The compacts then were sintered by gas-pressing sintering(GPS).Finial products show improved mechanic properties comparing with reference samples fabricated by normal ways.

  10. Theoretical insight into Cobalt subnano-clusters adsorption on α-Al2O3 (0001)

    Science.gov (United States)

    Gao, Fen-e.; Ren, Jun; Wang, Qiang; Li, Debao; Hou, Bo; Jia, Litao; Cao, Duanlin

    2017-02-01

    The investigation on the structural stability, nucleation, growth and interaction of cobalt cluster Con(n=2-7) on the α-Al2O3(0001) surface by using density functional theory methods has been reported. Energetically, the most favorable adsorption sites were identified and the strongest adsorption energy cluster is the tetrahedral Co4 cluster. On the other hand, the nucleation of Con(n=2-7) clusters on the surface is exothermic and thermodynamically favorable. Moreover, even-odd alternation was found with respect to clusters nucleation as a function of the number of cobalt atoms (for n=1-7). Meanwhile, the Con clusters can be adsorbed on the surface stably owing to the charge transfer from Co atoms to Al and O atoms of the Al2O3 substrate. In addition, we establish the crucial importance of monomer, dimer and trimer diffusion on the surface. The diffusion of the monomer cobalt from Al(3) to O(5) or O(5) to Al(4) site is quite easy on the Al2O3(0001) surface, whereas the diffusion of the Co2 dimer is thermodynamically unfavorable by compared with that of the Co adatom and Co3 trimer.

  11. Insight into the effects of different ageing protocols on Rh/Al2O3 catalyst

    Science.gov (United States)

    Zhao, Baohuai; Ran, Rui; Cao, Yidan; Wu, Xiaodong; Weng, Duan; Fan, Jun; Wu, Xueyuan

    2014-07-01

    In this work, a catalyst of Rh loaded on Al2O3 was prepared by impregnating method with rhodium nitrate aqueous solution as the Rh precursor. The catalyst was aged under different protocols (lean, rich, inert and cyclic) to obtain several aged samples. All the Rh/Al2O3 samples were characterized by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) method, CO-chemisorption, H2-temperature programmed reduction (H2-TPR), transmission electron microscope (TEM) and X-ray photoelectron spectroscopy (XPS). It was found that a specific ageing treatment could strongly affect the catalytic activity. The N2 aged and the H2 aged samples had a better catalytic activity for CO + NO reaction than the fresh sample while the air aged and the cyclic aged samples exhibited much worse activity. More surface Rh content and better reducibility were obtained in the N2 and the H2 aged samples and the Rh particles existed with an appropriate size, which were all favorable to the catalytic reaction. However, the air and the cyclic ageing protocols induced a strong interaction between Rh species and the Al2O3 support, which resulted in a severe sintering of particles of Rh species and the loss of active sites. The structure evolution scheme of the catalysts aged in different protocols was also established in this paper.

  12. Effect of Nb on the Interfacial Wettability in Al2O3/Medium Mn Steel

    Institute of Scientific and Technical Information of China (English)

    Sirong YU; Yaohui LIU; Zhenming HE

    2003-01-01

    To develop medium Mn steel (MMS) matrix composites reinforced by Al2O3 particles, the effect of Nb on the interracial wettability of Al2O3/MMS and its mechanism were investigated in this paper. The results show that the wetting angle of the specimens with different Nb contents are bigger than that of the specimen without Nb at the first stage, and then decreases with time at 1450℃. At certain time, the wetting angle is lower than that of the specimen without Nb. At 1550 and 1600℃, the wetting angle of the specimens containing Nb decreases quickly with time at first stage. After 10 min, the wetting angle reaches a steady state, and hardly changes with time. The mechanisms of Nb to improve the wettability can be attributed to the enrichment of Nb at the interface and Nb serves as surface active agent of MMS at T<1550℃, and as catalyzer for the interfacial reaction of Al2O3/MMS at T≥1550℃, and reduces the interfacial energies.

  13. PREPARATION AND CHARACTERIZATION OF CHITOSAN-ZnO/Al2O3 COMPOSITE

    Directory of Open Access Journals (Sweden)

    Dina Kartika Maharani

    2015-11-01

    Full Text Available The purpose of this research was to prepare novel composite based on biopolymer and nontoxic inorganic materials that can be applied for many uses such as coating agent on textile for antibacterial purposes. In this research, Chitosan-ZnO/ Al2O3 composites were prepared by mixing chitosan solution with ZnO particles and Al2O3 (alumina sol produced by sol-gel method. The products were characterized with Fourier Transform Infra Red (FTIR Spectrophotometer and X-Ray Diffractometer (XRD. The result of this research showed that composites exist as transparent solution that was suitable for coating agent application. The result of FTIR Spectrophotometer analysis showed that there were interactions between chitosan, ZnO particles and Al2O3 particles which indicated from absorption bands in the region of wave number 3500-3400 cm-1, 1600-1500 cm-1 and 600-450 cm-1. It mean that chitosan interacted to ZnO particles and alumina particles . The XRD analysis of composites showed that there were change in the diffraction peak in the 2 theta value of 10o and 19o which indicated interaction of chitosan with ZnO particles and alumina particles

  14. Impact of Al2O3 on the aggregation and deposition of graphene oxide.

    Science.gov (United States)

    Ren, Xuemei; Li, Jiaxing; Tan, Xiaoli; Shi, Weiqun; Chen, Changlun; Shao, Dadong; Wen, Tao; Wang, Longfei; Zhao, Guixia; Sheng, Guoping; Wang, Xiangke

    2014-05-20

    To assess the environmental behavior and impact of graphene oxide (GO) on living organisms more accurately, the aggregation of GO and its deposition on Al2O3 particles were systematically investigated using batch experiments across a wide range of solution chemistries. The results indicated that the aggregation of GO and its deposition on Al2O3 depended on the solution pH and the types and concentrations of electrolytes. MgCl2 and CaCl2 destabilized GO because of their effective charge screening and neutralization, and the presence of NaH2PO4 and poly(acrylic acid) (PAA) improved the stability of GO with the increase in pH values as a result of electrostatic interactions and steric repulsion. Specifically, the dissolution of Al2O3 contributed to GO aggregation at relatively low pH or high pH values. Results from this study provide critical information for predicting the fate of GO in aquatic-terrestrial transition zones, where aluminum (hydro)oxides are present.

  15. Preparation of Paraffin/γ-Al2O3Composites as Phase Change Energy Storage Materials%Preparation of Paraffin/γ-Al2O3 Composites as Phase Change Energy Storage Materials

    Institute of Scientific and Technical Information of China (English)

    ZHAO Liang; MARuiying; MENG Xianglan; WANG Gang; FANG Xiangchen

    2011-01-01

    Paraffin/γ-Al2O3 composites as phase change energy storage materials were prepared by absorbingparaffin in porous network of γ-Al2O3.In the composite materials,paraffin was used as a phase change material(PCM) for thermal energy storage,and γ-Al2O3 acted as supporting materials.Characterizations were conducted to evaluate the energy storage performance of the composites,and differential scanning calorimeter results showed that the PCM-3 composite has melting latent heat of 112.9 kJ/kg with a melting temperature of 62.9 ℃.Due to strong capillary force and surface tension between paraffin and γ-Al2O3,the leakage of melted paraffin from the composites can be effectively prevented.Therefore,the paraffin/γ-Al2O3 composites have a good thermal stability and can be used repeatedly.

  16. Dielectric Properties of Thermal and Plasma-Assisted Atomic Layer Deposited Al2O3 Thin Films

    NARCIS (Netherlands)

    Jinesh, K. B.; van Hemmen, J. L.; M. C. M. van de Sanden,; Roozeboom, F.; Klootwijk, J. H.; Besling, W. F. A.; Kessels, W. M. M.

    2011-01-01

    A comparative electrical characterization study of aluminum oxide (Al2O3) deposited by thermal and plasma-assisted atomic layer depositions (ALDs) in a single reactor is presented. Capacitance and leakage current measurements show that the Al2O3 deposited by the plasma-assisted ALD shows excellent d

  17. Influence of AlF3 and hydrothermal conditions on morphologies of α-Al2O3

    Institute of Scientific and Technical Information of China (English)

    FU Gao-feng; WANG Jing; KANG Jian

    2008-01-01

    Homogeneous α-Al2O3 platelets were synthesized by introducing AlF3 to alumina precursor.The effects of AlF3 additive on the phase transformation and morphology of the prepared α-Al2O3 platelets were investigated.The results show that a single phase of α-Al2O3 with an average particle size of 8μm can be obtained at 900℃ with 2% AlF3 additive.The transformation temperature decreasing IS attributed to introduction of Al3+ vacancy and to the formation of intermediate compound of AlOF,which is considered to accelerate the mass transportation from transitional Al2O3 to α-Al2O3.AlF3 concentration and hydrothermal temperature can also affect the morphology of α-Al2O3.When hydrothermal temperature is 120℃,the morphology of α-Al2O3 transforms from irregular to flat hexangular platelet with increasing AlF3 concentration.As hydrothermal temperature increases,the morphology of α-Al2O3 with 2% AlF3 additive changes from polyhedron to hexangular platelet and then to vermicular.

  18. Adsorption behavior of heavy metal ions by carbon nanotubes grown on microsized Al2O3 particles

    Institute of Scientific and Technical Information of China (English)

    Shu-Huei Hsieh; Jao-Jia Horng

    2007-01-01

    Carbon nanotubes (CNTs) were grown on the surface of microsized Al2O3 particles in CH4 atmosphere at 700 ℃ under the catalysis of Fe-Ni nanoparticles.The CNTs on Al2O3 were used for adsorbing Pb2+,Cu2+,and Cd2+ from the solution and the results were compared with active carbon powders,commercial carbon nanotubes,and Al2O3 particles.The as-grown CNTs/Al2O3 have demonstrated extraordinary absorption capacity with further treatment or oxidation,as well as hydrophilic ability that other CNTs lacked.The adsorption capacity of CNTs on Al2O3 is superior to other adsorbents and the preference order of adsorption on composite Al2O3 is Pb2+>Cu2+>Cd2+.It seemed that the adsorption of those Pb2+,Cu2+,and Cd2+ did not change the surface properties of composite particles.The adsorption behaviors of Pb2+,Cu2+,and Cd2+ by CNTs on Al2O3 match well with the Langmuir isothermal adsorption model and the second order kinetic model.The calculated saturation amount adsorbed by 1 g of CNTs on Al2O3 are 67.11,26.59,and 8.89 mg/g for Pb2+,Cu2+,and Cd2+ in single adsorption test,respectively.

  19. Sliding Wear Behavior of Plasma Sprayed Alumina-Based Composite Coatings against Al2O3 Ball

    Institute of Scientific and Technical Information of China (English)

    Minh-quy Le; Young-hun Chae; Seock-sam Kim

    2004-01-01

    The sliding wear behaviors of a single layer Al2O3-30 wt pct ZrO2, a double layer Al2O3-30 wt pct ZrO2/Ni-Cr and a single layer Al2O3-13 wt pct TiO2 coating deposited on low carbon steel by plasma spraying were investigated under lubricated conditions with various normal loads. The plastic deformation, detachment and pull out of splats were involved in the wear process of the studied coatings under test conditions. Crack propagation was found in Al2O3-13 wt pct TiO2 under loads of 70 and 100 N and in Al2O3-30 wt pct ZrO2/Ni-Cr under a load of 130 N.While increasing the normal load, the wear rates of Al2O3-30 wt pct ZrO2 and Al2O3-30 wt pct ZrO2/Ni-Cr slightly increased, the wear rate of Al2O3-13 wt pct TiO2 increased rapidly. The results showed that the Ni-Cr bonding layer improved the wear resistance of the coating system even it is relatively thin compared with the outer coating layer.The influence of this bonding layer on wear behavior of the coating increased as increasing the normal load.

  20. Coherent 3D nanostructure of γ-Al2O3: Simulation of whole X-ray powder diffraction pattern

    Science.gov (United States)

    Pakharukova, V. P.; Yatsenko, D. A.; Gerasimov, E. Yu.; Shalygin, A. S.; Martyanov, O. N.; Tsybulya, S. V.

    2017-02-01

    The structure and nanostructure features of nanocrystalline γ-Al2O3 obtained by dehydration of boehmite with anisotropic platelet-shaped particles were investigated. The original models of 3D coherent nanostructure of γ-Al2O3 were constructed. The models of nanostructured γ-Al2O3 particles were first confirmed by a direct simulation of powder X-Ray diffraction (XRD) patterns using the Debye Scattering Equation (DSE) with assistance of high-resolution transmission electron microscopy (HRTEM) study. The average crystal structure of γ-Al2O3 was shown to be tetragonally distorted. The experimental results revealed that thin γ-Al2O3 platelets were heterogeneous on a nanometer scale and nanometer-sized building blocks were separated by partially coherent interfaces. The XRD simulation results showed that a specific packing of the primary crystalline blocks in the nanostructured γ-Al2O3 particles with formation of planar defects on {001}, {100}, and {101} planes nicely accounted for pronounced diffuse scattering, anisotropic peak broadening and peak shifts in the experimental XRD pattern. The identified planar defects in cation sublattice seem to be described as filling cation non-spinel sites in existing crystallographic models of γ-Al2O3 structure. The overall findings provided an insight into the complex nanostructure, which is intrinsic to the metastable γ-Al2O3 oxide.

  1. Study on Sulfation of CeO2/γ-Al2O3 Sorbent in Simulated Flue Gas

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The sulfation of CeO2/γ-Al2O3 sorbent in simulated flue gas was studied. A series of CeO2/γ-Al2O3 sorbents with different CeO2 loadings were prepared by impregnation and characterized by X-ray diffraction. Thermogravimetric technique was used to study the sulfation of CeO2/γ-Al2O3 sorbents, mainly on the CeO2 loading, sulfation cycles, and intrinsic kinetics. The study revealed that monolayer coverage of CeO2 supported on γ-Al2O3 was 0.125 g CeO2/g (γ-Al2O3). Below monolayer coverage, CeO2 was highly dispersed on γ-Al2O3. The optimal CeO2 loading on sulfation was 0.03 g CeO2/g (γ-Al2O3). CeO2/γ-Al2O3 sorbent was recyclable by controlling sulfation time. Intrinsic kineticd equation was R=1.1394×10-4×exp (-1,508.39/T) mg·mg-1·s-1. Activation energy and reaction order were 12.54 kJ·mol-1 and first order, respectively.

  2. Negative charge and charging dynamics in Al2O3 films on Si characterized by second-harmonic generation

    Science.gov (United States)

    Gielis, J. J. H.; Hoex, B.; van de Sanden, M. C. M.; Kessels, W. M. M.

    2008-10-01

    Thin films of Al2O3 synthesized by atomic layer deposition provide an excellent level of interface passivation of crystalline silicon (c-Si) after a postdeposition anneal. The Al2O3 passivation mechanism has been elucidated by contactless characterization of c-Si/Al2O3 interfaces by optical second-harmonic generation (SHG). SHG has revealed a negative fixed charge density in as-deposited Al2O3 on the order of 1011 cm-2 that increased to 1012-1013 cm-2 upon anneal, causing effective field-effect passivation. In addition, multiple photon induced charge trapping dynamics suggest a reduction in recombination channels after anneal and indicate a c-Si/Al2O3 conduction band offset of 2.02±0.04 eV.

  3. Synthesis and characterization of PMMA/Al2O3 composite particles by in situ emulsion polymerization

    Institute of Scientific and Technical Information of China (English)

    Hui Liu; Hongqi Ye; Tianquan Lin; Tao Zhou

    2008-01-01

    In order to improve its dispersibility, superfine alumina (Al2O3) was encapsulated with poly (methyl methacrylate) (PMMA) by in situ emulsion polymerization. It was found that only when the concentration of sodium dodecyl sulfate (SDS) was much higher than its critical micelle concentration, could PMMA/Al2O3 composite particles with high percentage of grafting (PG) be prepared. The same results were obtained between the experimental and stoichiometric amounts of tris (dodecylbenzenesulfonate) isopropoxide (NDZ), indicating that single-molecule-layer adsorption had taken place between NDZ and Al2O3. Analysis using FTIR. TEM and XPS showed that PMMA/Al2O3 composite particles with core-shell structure had been successfully synthesized by in sire emulsion polymerization. Compared to Al2O3, thermal stability and dispersibility of the composite particles showed marked improvement.

  4. The Influence of Nano-Al2O3 Additive on the Adhesion between Epoxy Resin and Steel Substrate

    Institute of Scientific and Technical Information of China (English)

    ZHAI Lan-lan; LING Guo-ping

    2004-01-01

    The influence of nano-Al2O3 additive on the adhesion between epoxy resin and steel substrate has been investigated. The results of tensile testing indicated that the adhesion strength was increased dramatically by addition of Al2O3 nanoparticles in epoxy resin compared with that of the unmodified resin. The highest adhesion strength was obtained with 1 wt% nano-Al2O3 added in epoxy adhesive, more than two times higher than that of the unmodified. Scanning electronic microscope (SEM) revealed that a boundary layer exists between epoxy and steel substrate, energy spectrum analysis indicates there is enrichment of the nano-Al2O3 particle. Those results confirmed that the nano-Al2O3 additive was closely related to the change of interface morphology and the improvement of adhesion strength. The reason for adhesion improvement was also be discussed.

  5. The improvement of Al2O3/AlGaN/GaN MISHEMT performance by N2 plasma pretreatment

    Institute of Scientific and Technical Information of China (English)

    Feng Qian; Tian Yuan; Bi Zhi-Wei; Yue Yuan-Zheng; Ni Jin-Yu; Zhang Jin-Cheng; Hao Yue; Yang Lin-An

    2009-01-01

    This paper discusses the effect of N2 plasma treatment before dielectric deposition on the electrical performance of a Al2O3/AlGaN/GaN metal-insulator-semiconductor high electron mobility transistor (MISHEMT), with Al2O3deposited by atomic layer deposition. The results indicated that the gate leakage was decreased two orders of magnitude after the Al2O3/AlGaN interface was pretreated by N2 plasma. Furthermore, effects of N2 plasma pretreatment on the electrical properties of the AlGaN/Al2O3 interface were investigated by x-ray photoelectron spectroscopy measurements and the interface quality between Al2O3 and AlGaN film was improved.

  6. PROPERTIES OF TiC-Al2O3/Fe COMPOSITES PREPARED BY SHS/PHIP%SHS/PHIP制备TiC-Al2O3/Fe复合材料的性能

    Institute of Scientific and Technical Information of China (English)

    张卫方; 韩杰才; 杜善义; 习年生; 陶春虎

    2001-01-01

    对SHS/PHIP技术制备出的TiC-Al2O3/Fe复合材料的性能进行了测试和分析.结果表明,TiC-Al2O3/Fe复合材料具有良好的综合力学性能.材料具有很高的比刚度.金属Fe相的加入,较大地提高了材料的抗弯强度和断裂韧性.TiC-Al2O3复相陶瓷为典型的脆性断裂;随着Fe含量的增加,材料具有明显韧性断裂的特征.%The influence of Fe content on the properties of TiC-Al2O3/Fe composites prepared by SHS/PHIP was studied. The results show that the TiC-Al2O3/Fe cermets prepared by SHS/PHIP possess high mechanical properties such as well-improved flexural strength and fracture toughness owing to the addition of Fe, and highly special stiffness. The TiC-Al2O3 ceramic exhibits the typical brittle fracture behavior. However, the TiC-Al2O3/Fe cermets exhibit obvious characteristic of tough fracture with Fe content increasing.

  7. Teflon/Al2O3纳米复合膜的结构及微观摩擦学特性%Structure and Microtribological Properties of Teflon and Teflon/Al2O3 Micro-assembling Film

    Institute of Scientific and Technical Information of China (English)

    贾慧娟; 汤卉; 邵俊鹏

    2003-01-01

    为了提高聚四氟乙烯的耐磨损能力,用射频磁控溅射法交替溅射纯Teflon靶和Al2O3靶获得Teflon/Al2O3多层复合膜,通过PHI-5300ESCA型X射线光电子能谱及原子力显微镜(AFM)对其结构、力学性能和微观摩擦磨损特性研究表明:Teflon/Al2O3多层复合膜不但具有Al2O3膜的较高硬度和抗磨损性能,而且具有纯Teflon膜的减摩性和高承载能力.同Al2O3相比,复合膜的综合性能优于纯Al2O3膜和纯Teflon膜.Teflon/Al2O3多层复合膜的研制,解决了弹性金属塑料瓦耐磨损能力差的问题.

  8. ( Ni-P)-Al2O3纳米微粒复合镀层硬度和耐磨性测试%Hardness and Wear Resistance of (Ni-P)-Al2O3 Nanoparticle Composite Coating

    Institute of Scientific and Technical Information of China (English)

    常京龙; 吴庆利

    2011-01-01

    In order to improve the surface performance of steel, (Ni-P)-Al2O3 nanoparticle composite coating was prepared by composite plating technology on steel because of its unique physical and chemical properties. And the hardness and wear resistance of conventional Ni-P coating, (Ni-P)-Al2O3 nanoparticle composite coating before and after heat treatment were determined. The results show that the hardness and wear resistance of (Ni-P)-Al2O3 nanoparticle composite coating especially after heat treatment were greatly improved.%为了改进钢材表面性能,采用复合化学镀技术制备( Ni-P) -Al2O3纳米微粒复合镀层,由于纳米微粒独特的物理化学特性致使使得到的复合镀层具有多种优良性能.通过Ni-P合金镀层、(Ni-P) -Al2O3纳米微粒复合镀层和热处理后的(Ni-P) -Al2O3纳米微粒复合镀层硬度和耐磨性能测试,得出(Ni-P)-Al2O3纳米微粒复合镀层尤其是热处理后其硬度和耐磨性能得到很大的改善.

  9. Coking-resistant Ni-ZrO2/Al2O3 catalyst for CO methanation

    Institute of Scientific and Technical Information of China (English)

    Qing Liu; Fangna Gu; Jiajian Gao; Huifang Li; Guangwen Xu∗; Fabing Su∗

    2014-01-01

    Highly coke-resisting ZrO2-decorated Ni/Al2O3 catalysts for CO methanation were prepared by a two-step process. The support was first loaded with NiO by impregnating method and then modified with ZrO2 by deposition-precipitation method (IM-DP). Nitrogen adsorption-desorption, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis, H2 temperature-programmed reduction and desorption, NH3 temperature-programmed desorption, and zeta potential analysis were employed to characterize the samples. The results revealed that, compared with the catalysts with the same composition prepared by co-impregnation (CI) and sequential impregnation (SI) methods, the Ni/Al2O3 catalyst prepared by IM-DP showed much enhanced catalytic performance for syngas methanation under the condition of atmospheric pressure and a high weight hourly space velocity of 120000 mL·g−1·h−1. In a 80 h life time test under the condition of 300–600◦C and 3.0 MPa, this catalyst showed high stability and resistance to coking, and the amount of deposited carbon was only 0.4 wt%. On the contrary, the deposited carbon over the catalyst without ZrO2 reached 1.5 wt%after a 60 h life time test. The improved catalytic performance was attributed to the selective deposition of ZrO2 nanoparticles on the surface of NiO rather than Al2O3, which could be well controlled via changing the electrostatic interaction in the DP procedure. This unique structure could enhance the dissociation of CO2 and generate surface oxygen intermediates, thus preventing carbon deposition on the Ni particles in syngas methanation.

  10. Synthesis of γ-Al2O3 nanoparticles by chemical precipitation method

    Institute of Scientific and Technical Information of China (English)

    SONG Xiao-lan; QU Peng; YANG Hai-pin; HE Xi; QIU Guan-zhou

    2005-01-01

    Highly pure active γ-Al2O3 nanoparticles were synthesized from aluminum nitrate and ammonium carbonate with a little surfactant by chemical precipitation method. The factors affecting the synthesis process were studied. The properties of γ-Al2O3 nanoparticles were characterized by DTA, XRD, BET, TEM, laser granularity analysis and impurity content analysis. The results show that the amorphous precursor Al(OH)3 sols are produced by using 0.1 mol/L Al(NO3)3 ·9H2O and 0.16 mol/L (NH4)2CO3·H2O reaction solutions, according to the volume ratio 1.33, adding 0.024% (volume fraction) surfactant PEG600, and reacting at 40 ℃, 1 000 r/min stirring rate for 15 min. Then, after stabilizing for 24 h, the precursors were extracted and filtrated by vacuum, washed thoroughly with deionized water and dehydrated ethanol, dried in vacuum at 80 ℃ for 8 h, final calcined at 800 ℃ for 1 h in the air, and high purity active γ-Al2O3 nanoparticles can be prepared with cubic in crystal system, O7H-FD3M in space group, about 9 nm in crystal grain size, about 20 nm in particle size and uniform size distribution, 131.35 m2/g in BET specific surface area, 7-11 nm in pore diameter, and not lower than 99.93% in purity.

  11. Testing of Flame Sprayed Al2O3 Matrix Coatings Containing TiO2

    Directory of Open Access Journals (Sweden)

    Czupryński A.

    2016-09-01

    Full Text Available The paper presents the results of the properties of flame sprayed ceramic coatings using oxide ceramic materials coating of a powdered aluminium oxide (Al2O3 matrix with 3% titanium oxide (TiO2 applied to unalloyed S235JR grade structural steel. A primer consisting of a metallic Ni-Al-Mo based powder has been applied to plates with dimensions of 5×200×300 mm and front surfaces of Ø40×50 mm cylinders. Flame spraying of primer coating was made using a RotoTec 80 torch, and an external coating was made with a CastoDyn DS 8000 torch. Evaluation of the coating properties was conducted using metallographic testing, phase composition research, measurement of microhardness, substrate coating adhesion (acc. to EN 582:1996 standard, erosion wear resistance (acc. to ASTM G76-95 standard, and abrasive wear resistance (acc. to ASTM G65 standard and thermal impact. The testing performed has demonstrated that flame spraying with 97% Al2O3 powder containing 3% TiO2 performed in a range of parameters allows for obtaining high-quality ceramic coatings with thickness up to ca. 500 µm on a steel base. Spray coating possesses a structure consisting mainly of aluminium oxide and a small amount of NiAl10O16 and NiAl32O49 phases. The bonding primer coat sprayed with the Ni-Al-Mo powder to the steel substrate and external coating sprayed with the 97% Al2O3 powder with 3% TiO2 addition demonstrates mechanical bonding characteristics. The coating is characterized by a high adhesion to the base amounting to 6.5 MPa. Average hardness of the external coating is ca. 780 HV. The obtained coatings are characterized by high erosion and abrasive wear resistance and the resistance to effects of cyclic thermal shock.

  12. The FTIR studies of gels and thin films of Al2O3-TiO2 and Al2O3-TiO2-SiO2 systems.

    Science.gov (United States)

    Adamczyk, Anna; Długoń, Elżbieta

    2012-04-01

    In this work, samples in form of bulk ones and thin films were obtained using the sol-gel method. The bulk samples were heated at different temperatures (500 °C, 850 °C and 1100 °C) corresponding to the annealing process of coatings, deposited on different substrates by dipping and pulling out samples from the proper sol with the stable speed. Thin films of both Al2O3-TiO2 and Al2O3-TiO2-SiO2 systems were deposited on carbon, steel and titanium substrates in two different ways: as single layers obtained from Al2O3 sol, TiO2 sol and Al2O3 sol or deposited as mixed coatings from Al2O3-TiO2 sol as well as Al2O3-TiO2-SiO2 one. All bulk samples were studied by the FTIR spectroscopy and the X-ray diffractometry while thin films were also investigated by the electron microscopy. In the IR spectra of Al2O3-TiO2 samples, as well as gels and coatings, bands due to the vibrations of AlO bonds of the octahedrally and tetrahedrally coordinated aluminum were observed. The IR spectra of samples of Al2O3-TiO2-SiO2 system differ from that of Al2O3-TiO2 ones in presence of bands assigned to the SiO bond vibrations and in positions of bands due to AlO bond vibrations. In all spectra of bulk samples and coatings, the positions of TiO bond vibrations were ascribed basing on the IR spectra of the pure anatase and rutile.

  13. Sulfation and Desulfation Behavior of Pt-BaO/MgO-Al2O3 NOx Storage Reduction Catalyst.

    Science.gov (United States)

    Jeong, Soyeon; Kim, Do Heui

    2016-05-01

    The comparative study between Pt-BaO/Al2O3 and Pt-BaO/MgO-Al2O3 gives the information about the effect of MgO addition to Al2O3 support on the sulfation and desulfation behavior of Pt-BaO/MgO-Al2O3 NOx storage reduction catalyst. The sulfated two samples were analyzed by using element analysis (EA), X-ray diffraction (XRD), H2 temperature programmed reaction (H2 TPRX) and NOx uptake measurement. The amount of sulfur uptake on 2 wt% Pt-20 wt% BaO/Al2O3 and 2 wt% Pt-20 wt% BaO/MgO-Al2O3 are almost identical as 0.45 and 0.40 of S/Ba, respectively, which yields the drastic decrease in NOx uptake for both sulfated samples. However, after desulfa- tion with H2 at 600 degrees C, the residual sulfur amount on MgO-Al2O3 supported catalyst is three times larger than that on Al2O3 supported one, indicating that sulfur species formed on the former are more stable than those on the latter. It is also well corresponding to the H2 TPRX results where the main H2S peak from MgO-Al2O3 supported sample is observed at higher temperature than Al2O3 supported one, resulting in the lower NOx uptake activity of former sample than the latter one. Meanwhile, after desulfation of MgO-Al2O3 supported sample at 700 degrees C and 800 degrees C, the activity is recovered more significantly due to the removal of the large amount of sulfur while Al2O3 supported one decreases monotonically due to the sintering of Pt crystallite and the formation of BaAl2O4 phase. It is summarized that MgO-Al2O3 supported catalyst enhances the thermal stability of the catalyst, however, forms the stable sulfate species, which needs to be improved to develop the more sulfur resistant NSR catalyst system.

  14. Pt-Rh/g Al2O3 Benzene Hydrogenation Reaction as a Characterization Technique

    Directory of Open Access Journals (Sweden)

    Fonseca N.M. da

    1998-01-01

    Full Text Available Pt-Rh/Al2O3 catalysts prepared by successive incipient impregnations and coimpregnation were characterized by H2 chemisorption, temperature programmed reduction and benzene hydrogenation reaction in the vapor phase. The results showed that Rh plays the role of Pt reducting agent, which is very different from the effects of metal-metal interaction which appear mainly in solids with the highest metal contents. The most important parameter that results in bimetallic particles in the catalyst prepared by successive impregnation is the sequence of metal addition.

  15. Viscosity affected by nanoparticle aggregation in Al2O3-water nanofluids.

    Science.gov (United States)

    Duan, Fei; Kwek, Dingtian; Crivoi, Alexandru

    2011-03-22

    An investigation on viscosity was conducted 2 weeks after the Al2O3-water nanofluids having dispersants were prepared at the volume concentration of 1-5%. The shear stress was observed with a non-Newtonian behavior. On further ultrasonic agitation treatment, the nanofluids resumed as a Newtonian fluids. The relative viscosity increases as the volume concentrations increases. At 5% volume concentration, an increment was about 60% in the re-ultrasonication nanofluids in comparison with the base fluid. The microstructure analysis indicates that a higher nanoparticle aggregation had been observed in the nanofluids before re-ultrasonication.

  16. Radioluminescence in Al2O3: C - analytical and numerical simulation results

    DEFF Research Database (Denmark)

    Pagonis, V.; Lawless, J.; Chen, R.

    2009-01-01

    The phenomenon of radioluminescence (RL) has been reported in a number of materials including Al2O3 : C, which is one of the main dosimetric materials. In this work, we study RL using a kinetic model involving two trapping states and two kinds of recombination centres. The model has been previously....... The set of differential equations is also solved analytically by assuming dynamic balance during sample irradiation. Analytical expressions are obtained for the concentrations of traps and centres in the material during irradiation with short irradiation pulses, by assuming that quasi-steady conditions...

  17. Lanthanum Modified Ni/γ-Al2O3 Catalysts for Partial Oxidation of Methane

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    La modified Ni/γ-Al2O3 catalysts prepared by co-precipitation method using NaOH-Na2CO3 as a precipitator show high activity and selectivity for the partial oxidation of methane (POM). Meanwhile, the addition of La is beneficial for the formation of an active component and stability of support. We investigated some factors including calcining temperature, nickel content, and space velocity, which turned out to have a strong influence on catalytic activity and selectivity. By XRD and TPR, it is concluded that Ni0 reduced from amorphous NiAl2O4 is the major active component for POM.

  18. Ultrasonic Al2O3 Ceramic Thermometry in High-Temperature Oxidation Environment

    Directory of Open Access Journals (Sweden)

    Yanlong Wei

    2016-11-01

    Full Text Available In this study, an ultrasonic temperature measurement system was designed with Al2O3 high-temperature ceramic as an acoustic waveguide sensor and preliminarily tested in a high-temperature oxidation environment. The test results indicated that the system can indeed work stably in high-temperature environments. The relationship between the temperature and delay time of 26 °C–1600 °C ceramic materials was also determined in order to fully elucidate the high-temperature oxidation of the proposed waveguide sensor and to lay a foundation for the further application of this system in temperatures as high as 2000 °C.

  19. Preparation of ZnO-Al2O3 Particles in a Premixed Flame

    DEFF Research Database (Denmark)

    Jensen, Joakim Reimer; Johannessen, Tue; Wedel, Stig

    2000-01-01

    Zinc oxide (ZnO) and alumina (Al2O3) particles are synthesized by the combustion of their volatilized acetylacetonate precursors in a premixed air-methane flame reactor. The particles are characterized by XRD, transmission electron microscopy, scanning mobility particle sizing and by measurement...... with diameter 25-40 nm and specific surface area 27-43 m2/g. The crystallite size for both oxides, estimated from the XRD line broadening, is comparable to or slightly smaller than the primary particle diameter. The specific surface area increases and the primary particle size decreases with a decreasing flame...

  20. Temperature coefficients for in vivo RL and OSL dosimetry using Al2O3 : C

    DEFF Research Database (Denmark)

    Andersen, C.E.; Edmund, Jens Morgenthaler; Damkjaer, S.M.S.

    2008-01-01

    A radiotherapy dosimetry system based on radiolurninescence (RL) and optically stimulated luminescence (OSL) from small carbon-doped aluminum oxide (Al2O3:C) crystals attached to optical-fiber cables has been developed. To quantify the influence of temperature variations on clinical RL and OSL...... measurement results, we conducted an automated laboratory experiment involving threefold randomization of (1) irradiation temperature (10-45 degrees C), (2) stimulation temperature (10-45 degrees C), and (3) irradiation dose (0-4 Gy; 50 kV X-rays). We derived linear RL and OSL temperature coefficients using...

  1. Adherent Al2O3 scales formed on undoped NiCrAl alloys

    Science.gov (United States)

    Smialek, James L.

    1987-01-01

    Changes in the spalling behavior of Al2O3 scales formed on an undoped NiCrAl alloy are described. Two samples of Ni-15Cr-13Al (wt pct), one a control and the other sanded, were subjected to 25 oxidation cycles. It is observed that adherent scales formed on the sanded sample; however, the control sample had speckled, spalled scales. The data reveal that the adherent scales are caused by repeated removal of surface layers after each oxidation cycle. It is determined that interfacial segregation of sulfur influences spallation and sulfur removal increases bonding. The effect of moisture on scale adhesions is investigated.

  2. Ultra-low thermal conductivity in W/Al2O3 nanolaminates.

    Science.gov (United States)

    Costescu, R M; Cahill, D G; Fabreguette, F H; Sechrist, Z A; George, S M

    2004-02-13

    Atomic layer deposition and magnetron sputter deposition were used to synthesize thin-film multilayers of W/Al(2)O(3). With individual layers only a few nanometers thick, the high interface density produced a strong impediment to heat transfer, giving rise to a thermal conductivity of approximately 0.6 watts per meter per kelvin. This result suggests that high densities of interfaces between dissimilar materials may provide a route for the production of thermal barriers with ultra-low thermal conductivity.

  3. Texture Analyses of Ti/Al2O3 Nanocomposite Produced Using Friction Stir Processing

    Science.gov (United States)

    Shafiei-Zarghani, Aziz; Kashani-Bozorg, Seyed Farshid; Gerlich, Adrian P.

    2016-11-01

    The texture evolution of Ti/Al2O3 nanocomposite fabricated using friction stir processing (FSP) was investigated at both macroscopic and microscopic levels employing X-ray diffraction and electron backscattering diffraction techniques. The developed textures were compared with ideal shear textures of hexagonal close-packed (hcp) structure, revealing that the fabricated nanocomposite is dominated by the P 1 hcp (fiber { 10bar{1}1} continuous dynamic recrystallization as well as increasing the fraction of high-angle grain boundaries within the developed microstructure.

  4. Preparation of SiCp/Al2O3-Al Composites by Directed Metal Oxidation

    Institute of Scientific and Technical Information of China (English)

    LIN Ying; YANG Hai-bo; WANG Fen; ZHU Jian-feng

    2006-01-01

    SiCp/Al2O3-Al composites were synthesized by means of direct metal oxidation method. The composition and microstructures of the composites were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM) and metallurgical microscope. The effects of technical parameters on the properties of the product were analyzed. The results indicate that the composite possesses a dense microstructure, composed of three interpenetrated phases. Of them, SiO2 layer prohibits the powdering of the composites; Mg promotes the wetting and infiltration of the system and Si restricts the interfacial reaction while improving the wetting ability between reinforcement and matrix.

  5. CW-OSL measurement protocols using optical fibre Al2O3:C dosemeters

    DEFF Research Database (Denmark)

    Edmund, J.M.; Andersen, C.E.; Marckmann, C.J.

    2006-01-01

    A new system for in vivo dosimetry during radiotherapy has been introduced. Luminescence signals from a small crystal of carbon-doped aluminium oxide (Al2O3:C) are transmitted through an optical fibre cable to an instrument that contains optical filters, a photomultiplier tube and a green (532 nm......) laser. The prime output is continuous wave optically stimulated luminescence (CW-OSL) used for the measurement of the integrated dose. We demonstrate a measurement protocol with high reproducibility and improved linearity, which is suitable for clinical dosimetry. A crystal-specific minimum pre...

  6. RESEARCH ON ELECTROCHROMIC PROPERTIES OF Al2O3/ B-Al-NiO-BASED FILM%Al2O3/B-Al-Nio薄膜电致变色性能的研究

    Institute of Scientific and Technical Information of China (English)

    楼贤春; 周学东; 曾涛

    2009-01-01

    采用溶胶-凝胶法制备了B-Al-Nio和Al2O3/B-Al-NiO复合薄膜.采用扫描电镜,电化学测试和透过率测试分析Al2O3薄膜并对B-Al-NiO的变色性能和稳定性进行分析和表征.结果表明Al2O3薄膜对NiO基薄膜的变色效果影响不大,同时有效提高NiO基薄膜的稳定性.

  7. Microstructure and Wear Behaviors of In-situ Al2O3p/7075 Composites%原位Al2O3P/7075复合材料微观组织与磨损行为

    Institute of Scientific and Technical Information of China (English)

    刘慧敏; 杨树青; 许萍; 李进福

    2012-01-01

    采用原位反应近液相线铸造法制备具有不同质量分数的Al2O3P/7075复合材料,并对其进行干滑动磨损实验研究,通过OM,SEM,TEM等材料分析方法测试了材料的微观组织和磨损表面形貌.结果表明,原位Al2O3颗粒对7075铝合金的晶粒组织有明显细化效果,Al2O3P/7075复合材料的耐磨性比基体7075铝合金有明显的提高.原因是原位合成的复合材料界面结合良好,原位Al2O3颗粒在摩擦过程中起着抑制金属流动和支撑的双重作用.磨损表面形貌显示,原位Al2O3颗粒的加入,使磨损机制由黏着磨损变为磨粒磨损,从而改善了材料的耐磨性.%The Al2O3P/7075 Al composites were synthesized by in-situ reaction near-liquidus casting. The microstructure and dry sliding wear behavior of the prepared composites were analyzed using OM, SEM and TEM as well as wear friction testing. The results reveal that in-situ Al2O3 particle with average size of approximately <1μm is uniformly distributed in the matrix, which exhibits desirable refining effects on microstructure of 7075 Al alloy. The wear behavior of the composites is greatly superior to that of the matrix, which is attributed to the grain refining and formation of a compact interface of Al2O3P/7075 Al composites. In addition, in-situ Al2O3 particles exhibit coupling effects of inhibiting metal flow and bearing some load in process of friction. The wear mechanism of the matrix 7075A1 alloy is adhesive wear, while the wear surface of Al2O3p/7075 Al composites is superior to that of the matrix 7075 Al alloy. The wear mechanism of Al2O3P/7075 Al composites is abrasive wear, and wear resistance of Al2O3P/7075 Al is improved.

  8. ANTI-ELECTROLYTIC PROPERTIES OF PAA-PEO-α-Al2O3-H2O SUSPENSIONS%PAA-PEO-α-Al2O3-H2O悬浮液的抗电解质性能

    Institute of Scientific and Technical Information of China (English)

    张浩; 王晓莉; 郭露村

    2007-01-01

    The electrolytic effect on the rheological properties of a poly (acrylic acid) (PAA)-α-Al2O3-H2O suspension and the anti-electrolytic capability of a PAA-poly (ethylene oxide) (PEO)-α-Al2O3-H2O suspension were studied. The results show that the addition of an electrolyte (like NaCl or CaCl2) dramatically decreases the stability of PAA-α-Al2O3-H2O suspensions, and the influence of divalent ions (Ca2+) was more pronounced than that of univalent ions (Na+). The PAA-PEO-α-Al2O3-H2O systems can maintain inherent rheological properties in the presence of the electrolyte at same electrolytic concentrations. This behavior is attributed to the effective anti-electrolytic capability of PAA-PEO-α-Al2O3-H2O suspensions.%研究了电解质对聚丙烯酸[poly(acrylic acid),PAA]-α-Al2O3-H2O悬浮液流变性能的影响以及PAA-聚氧化乙烯[poly(ethylene oxide),PEO]-α-Al2O3-H2O悬浮液的抗电解质的性能.结果表明:PAA-α-Al2O3-H2O悬浮液的流变性能受NaCl和CaCl2等电解质的影响较大,并且二价盐CaCl2比一价盐NaCl对PAA-α-Al2O3悬浮液分散和稳定性的影响更明显,电解质造成Al2O3颗粒的絮凝,使浆料的稳定性能变差.在电解质浓度相同的条件下,PAA-PEO-α-Al2O3-H2O悬浮液基本不受电解质的影响,浆料始终保持稳定,PAA-PEO-α-Al2O3-H2O悬浮液具有很强的抗电解质能力.

  9. Fluência em filtros cerâmicos de Al2O3 Creep in Al2O3 ceramic filters

    Directory of Open Access Journals (Sweden)

    V. R. Salvini

    2001-12-01

    Full Text Available O comportamento de fluência em materiais cerâmicos sólidos é afetado pela sua microestrutura. Fundamentalmente, são três os parâmetros que influenciam o comportamento de fluência nestes materiais: o constituinte mineralógico, a fase vítrea e a porosidade. Além destes fatores microestruturais, a fluência em cerâmicas celulares depende também da sua macroestrutura, constituída de um arranjo tridimensional de filamentos sólidos interligados. Assim, a análise dos resultados de fluência nestes materiais compreende duas etapas: na primeira deve-se identificar o modo de deformação dos filamentos cerâmicos (macroestrutura e na segunda, identificar o(s mecanismo(s de fluência da microestrutura através dos parâmetros n (expoente da tensão aplicada e Q (energia de ativação do processo. Neste trabalho avaliou-se a fluência em filtros cerâmicos de Al2O3 de 10 ppi sob compressão de 0,034; 0,051 e 0,068 MPa às temperaturas de 1500, 1550 e 1600 ºC ao ar. De acordo com os resultados obtidos, supõe-se que o modo de deformação por flambagem dos filamentos paralelos a carga aplicada é um dos principais fatores que contribui para o aumento da taxa de deformação do filtro e, portanto, dos valores de n e Q. Além do modo de deformação dos filamentos, observou-se que o tipo de ensaio de fluência (com ou sem troca de carga também influencia a determinação dos valores de n e Q.The creep behavior of solid ceramics is strongly affected by the microstructure. Fundamentally, there are three microstructural features which influence the creep behavior: the mineral content, the flux content and the apparent porosity. Additionally, the creep of cellular ceramics also depends on their macrostructure constituted by a tridimensional array of struts. Therefore, the creep analysis of these materials should consist of two stages. Firstly, identification of the macrostructure deformation mode and secondly, determination of the stress exponent

  10. Anisotropic temperature-dependent thermal conductivity by an Al2O3 interlayer in Al2O3/ZnO superlattice films

    Science.gov (United States)

    Lee, Won-Yong; Lee, Jung-Hoon; Ahn, Jae-Young; Park, Tae-Hyun; Park, No-Won; Kim, Gil-Sung; Park, Jin-Seong; Lee, Sang-Kwon

    2017-03-01

    The thermal conductivity of superlattice films is generally anisotropic and should be studied separately in the in-plane and cross-plane directions of the films. However, previous works have mostly focused on the cross-plane thermal conductivity because the electrons and phonons in the cross-plane direction of superlattice films may result in much stronger interface scattering than that in the in-plane direction. Nevertheless, it is highly desirable to perform systematic studies on the effect of interface formation in semiconducting superlattice films on both in-plane and cross-plane thermal conductivities. In this study, we determine both the in-plane and cross-plane thermal conductivities of Al2O3 (AO)/ZnO superlattice films grown by atomic layer deposition (ALD) on SiO2/Si substrates in the temperature range of 50–300 K by the four-point-probe 3-ω method. Our experimental results indicate that the formation of an atomic AO layer (0.82 nm) significantly contributes to the decrease of the cross-plane thermal conductivity of the AO/ZnO superlattice films compared with that of AO/ZnO thin films. The cross-plane thermal conductivity (0.26–0.63 W m‑1 K‑1 of the AO/ZnO superlattice films (with an AO layer of ∼0.82 nm thickness) is approximately ∼150%–370% less than the in-plane thermal conductivity (0.96–1.19 W m‑1 K‑1) of the corresponding film, implying significant anisotropy. This indicates that the suppression of the cross-plane thermal conductivity is mainly attributed to the superlattice, rather than the nanograin columnar structure in the films. In addition, we theoretically analyzed strong anisotropic behavior of the in-plane and cross-plane thermal conductivities of the AO/ZnO superlattice films in terms of temperature dependence.

  11. Effect of polymorphism of Al2O3 on sintering and grain growth of magnesia aluminate spinel

    Directory of Open Access Journals (Sweden)

    Zhihui Z.

    2007-01-01

    Full Text Available The effect of polymorphism of Al2O3 on sintering and grain growth of magnesia aluminate spinel was studied. γ - Al2O3 and α - Al2O3 were mixed with MgO according to the stoichiometric MA ratio, respectively, and pressed into billets with a 20mm diameter and 15mm height, and then were sintered at temperature from 1250ºC to 1400ºC in air atmosphere. Bulk density, apparent porosity and grain size were measured. The results indicated that the grain size of MA with γ-Al2O3 is larger than the grain size of MA with α - Al2O3. This is because the activation energy of grain growth of magnesia aluminate spinel prepared by γ-Al2O3 is lower than that by α -Al2O3, the former is 159KJ/mol and the latter is 217KJ/mol.

  12. Structure and Mechanical Properties of Ni-P-Nano Al2O3 Composite Coatings Synthesized by Electroless Plating

    Institute of Scientific and Technical Information of China (English)

    ZHOU Guang-hong; DING Hong-yan; ZHOU Fei; ZHANG Yue

    2008-01-01

    Ni-P-nano Al2O3 composite coatings were deposited by electroless plating, and their microstructures were observed by SEM (scanning electron microscope). The microhardness and the wear resistance of the Ni-P-nano Al2O3 composite coatings were measured using microhardness tester and block-on-ring tribometer, respectively, and the comparison with those of Ni-P coatings or Ni-P-micro Al2O3 coating was given. The influences of aging temperature on their hardness and wear resistance were analyzed. The results showed that the nano Al2O3 particles were distributed uniformly in the Ni-P-Al2O3 coatings. Among three kinds of Ni-P based coatings, the hardness and wear resistance of Ni-P-nano Al2O3 coatings were largest, and the maximum values could be obtained at 400 ℃. This indicated that the precipitation of nano Al2O3 particles would improve the hardness and wear resistance of the Ni-P coatings.

  13. Fabrication and mechanical properties of WC-Co-Al2O3 nanocomposites by spark plasma sintering

    Institute of Scientific and Technical Information of China (English)

    SHEN Jun; ZHANG Fa-ming; SUN Jian-fei

    2005-01-01

    Small amounts of nanocrystalline Al2 O3 particles were doped in WC-Co nanocrystalline powders to study their reinforcing effects, and spark plasma sintering technique was used to fabricate the WC-Co-Al2 O3 nanocomposites. Experimental results show that the use of Al2 O3 nanoparticles as dispersions to reinforce WC-Co composites can increase the hardness, especially the transverse rupture strength of the WC-Co hardmetal. With addition of 0.5%(mass fraction) Al2O3 nanoparticles, the spark plasma sintered WC-7Co-0.5Al2O3 nanocomposites exhibit hardness of 21.22 GPa and transverse rupture strength of 3 548 MPa. The fracture surface of the WC-7Co-0.5Al2O3 nanocomposites mainly fracture with transcrystalline rupture mode. The reinforcing mechanism is maybe related to the hindrance effect of microcracks propagation and the pinning effect for the dislocations movement, as well as the residual compressive strength due to the Al2 O3 nanoparticles doped.

  14. Selective Oxidation of CO in Excess H2 over Ru/Al2O3 Catalysts Modified with Metal Oxide

    Institute of Scientific and Technical Information of China (English)

    Xirong Chen; Hanbo Zou; Shengzhou Chen; Xinfa Dong; Weiming Lin

    2007-01-01

    The RU/Al2O3 catalysts modified with metal oxide (K2O and La2Os) were prepared via incipient wetness impregnation method from RUCl3.nH2O mixed with nitrate loading on Al2O3 support. The activity of catalysts was evaluated under simulative conditions for the preferential oxidation of CO (CO-PROX) from the hydrogen-rich gas streams produced by reforming gas, and the performances of catalysts were investigated by XRD and TPR. The results showed that the activity temperature of the modified catalysts RU-K2O/Al2O3 and Ru-La2Oa/Al2O3 were lowered approximately 30 ℃ compared with pure RU/AI2O3, and the activity temperature range was widened. The conversion of CO on RU-K2O/Al2O3 and Ru-La2O3/Al2O3 was above 99% at 140-160 ℃, suitable to remove CO in a hydrogen-rich gas and the selectivity of Ru-La2O3/Al2O3 was higher than that of RU-K2O/AI2O3 in the active temperature range. Slight methanation reaction was detected at 220 ℃ and above.

  15. Broadband infrared emission from Er-Tm :Al2O3 thin films

    Science.gov (United States)

    Xiao, Zhisong; Serna, R.; Afonso, C. N.; Vickridge, I.

    2005-09-01

    Thin films of amorphous aluminum oxide (Al2O3) co-doped with Er3+ and Tm3+ have been synthesized by alternate pulsed laser deposition. When pumped at 794 nm a broad emission band over 1400-1700 nm is observed. Two peaks related to the 1540 nm band from Er3+ and to the 1640 nm band from Tm3+ are clearly distinguished. The photoluminescence intensity ratio of the 1640-1540 nm emissions has been controlled by modifying the Tm concentration. A spectrum with a fairly flat profile and a full width at half maximum of 230 nm is obtained for an Er concentration of 7.2×1019cm-3 and a [Tm]/[Er] concentration ratio of 3. It is found that the Er3+ to Tm3+ energy transfer processes play an important role in the definition of the luminescent response. The large width of the emission band and the excellent optical and thermomechanical properties of the Er-Tm co-doped Al2O3 signal this system as a potential candidate for the development of broadband integrated optical amplifiers.

  16. Ethanol gas sensing properties of Al2O3-doped ZnO thick film resistors

    Indian Academy of Sciences (India)

    D R Patil; L A Patil; D P Amalnerkar

    2007-12-01

    The characterization and ethanol gas sensing properties of pure and doped ZnO thick films were investigated. Thick films of pure zinc oxide were prepared by the screen printing technique. Pure zinc oxide was almost insensitive to ethanol. Thick films of Al2O3 (1 wt%) doped ZnO were observed to be highly sensitive to ethanol vapours at 300°C. Aluminium oxide grains dispersed around ZnO grains would result into the barrier height among the grains. Upon exposure of ethanol vapours, the barrier height would decrease greatly leading to drastic increase in conductance. It is reported that the surface misfits, calcination temperature and operating temperature can affect the microstructure and gas sensing performance of the sensor. The efforts are, therefore, made to create surface misfits by doping Al2O3 into zinc oxide and to study the sensing performance. The quick response and fast recovery are the main features of this sensor. The effects of microstructure and additive concentration on the gas response, selectivity, response time and recovery time of the sensor in the presence of ethanol vapours were studied and discussed.

  17. Effect of interface geometry on electron tunnelling in Al/Al2O3/Al junctions

    Science.gov (United States)

    Koberidze, M.; Feshchenko, A. V.; Puska, M. J.; Nieminen, R. M.; Pekola, J. P.

    2016-04-01

    We investigate how different interface geometries of an Al/Al2O3 junction, a common component of modern tunnel devices, affect electron transport through the tunnel barrier. We study six distinct Al/Al2O3 interfaces which differ in stacking sequences of the metal and the oxide surface atoms and the oxide termination. To construct model potential barrier profiles for each examined geometry, we rely on first-principles density-functional theory (DFT) calculations for the barrier heights and the shapes of the interface regions as well as on experimental data for the barrier widths. We show that even tiny variations in the atomic arrangement at the interface cause significant changes in the tunnel barrier parameters and, consequently, in electron transport properties. Especially, we find that variations in the crucial barrier heights and widths can be as large as 2 eV and 5 Å, respectively. Finally, to gain information about the average properties of the measured junction, we fit the conductance calculated within the Wentzel-Kramers-Brillouin approximation to the experimental data and interpret the fit parameters with the help of the DFT results.

  18. Separation of Fine Al2O3 Inclusion from Liquid Steel with Super Gravity

    Science.gov (United States)

    Li, Chong; Gao, Jintao; Wang, Zhe; Guo, Zhancheng

    2017-04-01

    An innovative approach of super gravity was proposed to separate fine Al2O3 inclusions from liquid steel in this study. To investigate the removal behaviors of inclusions, the effects of different gravity coefficients and time on separating the inclusions were studied. The results show that a large amount of Al2O3 inclusions gathered at the top of the sample obtained by super gravity, whereas there were almost no inclusions appearing at the bottom. The volume fraction and number density of inclusions presented a gradient distribution along the direction of the super gravity, which became steeper with increasing gravity coefficient and separating time. As a result of the collision between inclusions, a large amount of inclusions aggregated and grew during the moving process, which further decreased the removal time. The experimental required removal time of inclusions is close to the theoretical values calculated by Stokes law under gravity coefficient G ≤ 80, t ≤ 15 minutes, and the small deviation may be because the inclusion particles are not truly spherical. Under the condition of gravity coefficient G = 80, t = 15 minutes, the total oxygen content at the bottom of the sample (position of 5 cm) is only 8.4 ppm, and the removal rate is up to 95.6 pct compared with that under normal gravity.

  19. Decomposition of hexachlorobenzene over Al2O3 supported metal oxide catalysts

    Institute of Scientific and Technical Information of China (English)

    ZHANG Lifei; ZHENG Minghui; ZHANG Bing; LIU Wenbin; GAO Lirong; BA Te; REN Zhiyuan; SU Guijin

    2008-01-01

    Decomposition of hexachlorobenzene (HCB) was investigated over several metal oxides (i.e., MgO, CaO, BaO, La2O3,CeO2, MnO2, Fe2O3 and Co3O4) supported on Al2O3, which was achieved in closed system at a temperature of 300℃. Catalysts were prepared by incipient wetness impregnation with different metal oxides loading and impregnating solvents. The decomposition efficiency of different catalysts for this reaction depends on the nature of the metal oxide used, and Al2O3 supported La2O3 was found to be the most active one. Pentachlorobenzene (PeCB), and all tetrachlorobenzene (TeCB), trichlorobenzene (TrCB), and dichlorobenzene (DCB) isomers were detected after the decomposition reaction, indicating that the decomposition was mainly a dechlorination process. The detection of all lower chlorinated beazenes suggested the complexity of decomposition and the presence of more than one dechlodnation pathway.

  20. Effect of Treated Graphite on Properties of Al2 O3-SiC-C Castables

    Institute of Scientific and Technical Information of China (English)

    SHI Huiying; ZHANG Yang; BU Xiangjuan; CAO Xiying; HE Jiasong; WANG Lei

    2009-01-01

    Al2O3-SiC-C castables with 2 % pitch or 2 %,4% and 6% treated graphite,respectively,were prepared based on the basic formulation of traditional Al2O3-SiC-C castables.The flowability of castables,and bulk density,volume stability,strength,oxidation resistance and slag resistance of specimens fired at 110 ℃,1 100 ℃ and 1 500 ℃ respectively were comparatively studied.The results showed that:(1) With carbon source changing from pitch to treated graphite and the increase of treated graphite addition,water addition of castables increased,bulk density of specimens fired at different temperatures increased firstly and then decreased,strength after drying decreased obviously,strength after firing and oxidation resistance changed slightly,hot modulus of rupture increased obviously;(2) Slag resistance of specimen with treated graphite was worse than that of specimen with the same amount of pitch,but the former was obviously improved with the increase of treated graphite addition.

  1. Atomic Layer Deposition Al2O3 Thin Films in Magnetized Radio Frequency Plasma Source

    Science.gov (United States)

    Li, Xingcun; Chen, Qiang; Sang, Lijun; Yang, Lizhen; Liu, Zhongwei; Wang, Zhenduo

    Self-limiting deposition of aluminum oxide (Al2O3) thin films were accomplished by the plasma-enhanced chemical vapor deposition using trimethyl aluminum (TMA) and O2 as precursor and oxidant, respectively, where argon was kept flowing in whole deposition process as discharge and purge gas. In here we present a novel plasma source for the atomic layer deposition technology, magnetized radio frequency (RF) plasma. Difference from the commercial RF source, magnetic coils were amounted above the RF electrode, and the influence of the magnetic field strength on the deposition rate and morphology are investigated in detail. It concludes that a more than 3 Å/ purging cycle deposition rate and the good quality of ALD Al2O3 were achieved in this plasma source even without extra heating. The ultra-thin films were characterized by including Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectric spectroscopy (XPS), scanning electron microscopy (SEM), and atomic force microscopy (AFM). The high deposition rates obtained at ambient temperatures were analyzed after in-situ the diagnostic of plasmas by Langmuir probe.

  2. Chemical Quenching of Positronium in CUO/Al2O3 Catalysts

    Institute of Scientific and Technical Information of China (English)

    ZHANG Hong-Jun; LIU Zhe-Wen; CHEN Zhi-Quan; WANG Shao-Jie

    2011-01-01

    CuO/Al2O3 catalysts were prepared by mixing CuO and γ-Al2O3 nanopowders. Microstructure and chemical environment of the catalysts are characterized by positron annihilation spectroscopy. The positron annihilation lifetime measurements reveal two long lifetime components τ3 and τ4, which correspond to ortho-positronium (o-Ps) annihilating in microvoids and large pores, respectively. With increasing CuO content from 0 to 40 wt%, both τ4 and its intensity I4 show significant decrease, which indicates quenching effect of o-Ps. The para-positronium (p-Ps) intensities derived from multi-Gaussian fitting of the coincidence Doppler broadening spectra also decreases gradually with increasing CuO content. This excludes the possibility of spin-conversion of positronium. Therefore, the chemical quenching by CuO is probably responsible for the decrease of o-Ps lifetime. Variation in the o-Ps annihilation rate λ4 (1/τ4) as a function of CuO content can be well fitted by a straight line, and the slope of the fitting Jine is (1.83 ± 0.05) × 107 s-1.

  3. Structure and magnetism of granular Fe-Al 2O 3

    Science.gov (United States)

    Santos, A.; Ardisson, J. D.; Viegas, A. D. C.; Schmidt, J. E.; Persiano, A. I. C.; Macedo, W. A. A.

    2001-05-01

    The structural and magnetic properties of granular Fe-Al 2O 3 nanocomposite obtained starting from sol-gel processing are presented. Samples with nominal Fe content ranging from 20% to 62% in volume were prepared. The conversion of Fe oxides into metallic Fe was obtained by calcination at 800°C followed by reduction at 600°C for 2 h in H 2 atmosphere. After reduction, our results indicated up to 78% α-Fe, preserving the mean diameter of the metallic nanoparticles between 50 and 80 nm, ˜16% Fe oxides and ˜7% interstitial Fe 2+ and substitutional Fe 3+ cations in the Al 2O 3 lattice. Vibrating sample magnetometry at 300 K resulted in coercivity between 400 and 630 Oe and saturation magnetization between 40 and 134 emu/g. From transport measurements, the highest magnetoresistance, close to 2% at room temperature, was observed for samples with 25% α-Fe and 51 vol% total Fe.

  4. Spent wash decolourization using nano-Al2O3/kaolin photocatalyst: Taguchi and ANN approach

    Directory of Open Access Journals (Sweden)

    Charles David

    2015-09-01

    Full Text Available The intense colour of the spent wash effluent leads to crucial ecological issue when released untreated into the environment. The decolourization of distillery spent wash effluent is known to be a very challenging task. In this study, the degradation of organic pollutants in the form of colour was performed using nano photocatalyst prepared using aluminium oxide (Al2O3 nanoparticle and kaolin clay. As-synthesized nano-Al2O3/kaolin composites were used as photocatalyst for colour degradation of spent wash effluent. The process parameters such as dosage, pH, temperature and agitation were optimized to attain the maximum decolourization efficiency. The structural and the textural characteristics of the photocatalyst were analysed by X-ray diffraction (XRD, Brunauer–Emmett–Teller (BET surface area analysis, High Resolution Scanning Electron Microscope (HRSEM and Energy Dispersive X-ray (EDAX. Optimization of the process parameters using Taguchi Orthogonal Array (OA design resulted in a maximum of 80% spent wash decolourization. Using Artificial Neural Network (ANN, a two layered feedforward backpropagation model resulted as the best performance and predictive model for spent wash decolourization. The experimental data were found to be in excellent agreement with the predicted results from the ANN model.

  5. Superficial modifications in TiO2 and Al2O3 ceramics

    Directory of Open Access Journals (Sweden)

    Santos Flávio de Paula

    2003-01-01

    Full Text Available The properties of hydrophilicity or hydrophobicity of materials are defined mainly, though not exclusively, by their composition, morphology and surface energy. In this work, titanium dioxide (TiO2 and aluminum oxide-alumina (Al2O3 ceramics prepared by uniaxial pressing were studied in terms of surface energy. The surfaces of these ceramics were treated with nitrogen plasma, using a stainless steel reactor excited by a 13,6 MHz radio frequency operating at 50 W input power and 13 Pa nitrogen pressure. The surface morphology was investigated by scanning electron microscopy (SEM analysis. Surface energy and contact angle measurements were taken using a RAMÉ-HART goniometer. These measurements were taken as function of time, over a 21-day period. The contact angle and surface energy values were found to change by almost 34% in comparison to their initial values immediately following plasma treatment. Nonetheless, the hydrophilic character of the Al2O3 and TiO2 remained constant throughout the test period.

  6. Preparation of MWNTs/Al2O3 composites and their mechanical and electrical properties

    Institute of Scientific and Technical Information of China (English)

    FAN; Jinpeng; ZHAO; Daqing; XU; Zening; WU; Minsheng

    2005-01-01

    The mechanical and electrical properties of MWNTs/Al2O3 composite prepared fabricated by hot pressing are investigated. The relation between properties and microstructure of composites is also discussed. With 4wt% MWNTs as reinforcement, the fracture toughness of composite obtained reaches 5.55 Mpa·m1/2, which is 80% higher than that of pure Al2O3 obtained in the same conditions. The main toughening mechanism is CNTs' pinning alumina grain boundaries, and the pullout of CNTs takes effect also. Through adding 2wt% MWNTs and altering the mix method, the fracture toughness of the composite obtained is 3.97 Mpa·m1/2. Furthermore, the electrical resistivity is as low as 8.4×10-3Ω·m, decreasing by 14 orders of magnitude compared with pure alumina ceramics. The function of CNTs in composite is related to the distribution state of CNTs in composite, and the distribution state of CNTs in matrix is dependent on preparation procedures.

  7. Fractal analysis of crack paths in Al2O3-TiC-4%Co composites

    Institute of Scientific and Technical Information of China (English)

    LI Jing; YIN Yan-sheng; LIU Ying-cai; MA Lai-peng

    2006-01-01

    Al2O3-TiC-4%Co(volume fraction) composites(ATC) with high toughness (7.8±0.8 MPa·m1/2) and strength (782±60 MPa) were fabricated. In comparison with Al2O3-TiC composites(AT), the fracture toughness was significantly improved by 60%. The crack paths, generated by Vickers indentation on the polished surfaces of both composites, were analyzed from a fractal point of view to distinguish the possible toughening mechanisms involved. Quantitative evaluation of indentation cracks indicates that the crack deflection plays a more effective role. Cracks of the ATC composites show higher deflection angles and more deflections along the path. ATC composites present higher fractal dimension (D=1.07) than AT composites (D=1.02), which is directly related to the higher fracture toughness. A significant relationship between crack path and toughness is evident: the more irregular the geometry of the crack, the higher the fracture toughness.

  8. Some TEM observations of Al2O3 scales formed on NiCrAl alloys

    Science.gov (United States)

    Smialek, J.; Gibala, R.

    1979-01-01

    The microstructural development of Al2O3 scales on NiCrAl alloys has been examined by transmission electron microscopy. Voids have been observed within grains in scales formed on a pure NiCrAl alloy. Both voids and oxide grains grew measurably with oxidation time at 1100 C. The size and amount of porosity decreased towards the oxide-metal growth interface. It was postulated that the voids resulted from an excess number of oxygen vacancies near the oxide-metal interface. Short-circuit diffusion paths were discussed in reference to current growth stress models for oxide scales. Transient oxidations of pure, Y-doped, and Zr-doped NiCrAl was also examined. Oriented alpha-(Al,Cr)2O3 and Ni(Al,Cr)2O4 scales often coexisted in layered structures on all three alloys. Close-packed oxygen planes and directions in the corundum and spinel layers were parallel. The close relationships between oxide layers provided a gradual transition from initial transient scales to steady state Al2O3 growth.

  9. Density Measurements of Low Silica CaO-SiO2-Al2O3 Slags

    Science.gov (United States)

    Muhmood, Luckman; Seetharaman, Seshadri

    2010-08-01

    Density measurements of a low-silica CaO-SiO2-Al2O3 system were carried out using the Archimedes principle. A Pt 30 pct Rh bob and wire arrangement was used for this purpose. The results obtained were in good agreement with those obtained from the model developed in the current group as well as with other results reported earlier. The density for the CaO-SiO2 and the CaO-Al2O3 binary slag systems also was estimated from the ternary values. The extrapolation of density values for high-silica systems also showed good agreement with previous works. An estimation for the density value of CaO was made from the current experimental data. The density decrease at high temperatures was interpreted based on the silicate structure. As the mole percent of SiO2 was below the 33 pct required for the orthosilicate composition, discrete {text{SiO}}4^{4 - } tetrahedral units in the silicate melt would exist along with O2- ions. The change in melt expansivity may be attributed to the ionic expansions in the order of {text{Al}}^{ 3+ } - {text{O}}^{ 2- } < {text{Ca}}^{ 2+ } - {text{O}}^{ 2- } < {text{Ca}}^{ 2+ } - {text{O}}^{ - } Structural changes in the ternary slag also could be correlated to a drastic change in the value of enthalpy of mixing.

  10. Corrosion Resistance of Ni/Al2O3 Nanocomposite Coatings

    Directory of Open Access Journals (Sweden)

    Beata KUCHARSKA

    2016-05-01

    Full Text Available Nickel matrix composite coatings with ceramic disperse phase have been widely investigated due to their enhanced properties, such as higher hardness and wear resistance in comparison to the pure nickel. The main aim of this research was to characterize the structure and corrosion properties of electrochemically produced Ni/Al2O3 nanocomposite coatings. The coatings were produced in a Watts bath modified by nickel grain growth inhibitor, cationic surfactant and the addition of alumina particles (low concentration 5 g/L. The process has been carried out with mechanical and ultrasonic agitation. The Ni/Al2O3 nanocomposite coatings were characterized by SEM, XRD and TEM techniques. In order to evaluate corrosion resistance of produced coatings, the corrosion studies have been carried out by the potentiodynamic method in a 0.5 M NaCl solution. The corrosion current, corrosion potential and corrosion rate were determined. Investigations of the morphology, topography and corrosion damages of the produced surface layers were performed by scanning microscope techniques. DOI: http://dx.doi.org/10.5755/j01.ms.22.1.7407

  11. A light-scattering study of Al2O3 abrasives of various grit sizes

    Science.gov (United States)

    Heinson, Yuli W.; Chakrabarti, Amitabha; Sorensen, Christopher M.

    2016-09-01

    We report light scattering phase function measurements for irregularly shaped Al2O3 abrasive powders of various grit sizes. Q-space analysis is applied to the angular scattering to reveal a forward scattering regime, Guinier regime, power law regime with quantifiable exponents, and an enhanced backscattering regime. The exponents of the power laws for Al2O3 abrasives decrease with increasing internal coupling parameter ρ ‧ , which is in agreement with previous observations for other irregular particles. Unlike other dust particles previously studied showing single power laws under Q-space analysis, the largest three abrasives, for which ρ ‧ ≳ 100 , showed a kink in the power law, which is possibly due to the higher degree of symmetry for the abrasives than for all the particles studied previously. Direct comparison of the 1200, 1000, and 800 grit abrasive scattering to scattering by corresponding spheres shows that the scatterings approximately coincide at the spherical particle qR ≃ ρ ‧ crossover point. Furthermore, the scattering at the maximum qR = 2 kR by the irregularly shaped abrasives is close to the geometric centers of the glories of the spheres.

  12. Effects of temperature and ionization density in medical luminescence dosimetry using Al2O3:C

    DEFF Research Database (Denmark)

    Edmund, Jens Morgenthaler

    2007-01-01

    ) signal can be read out by stimulating the crystal with light. This thesis applies the initial part and the total area of the resulting OSL decay curve for dosimetry measurements and investigates the effects of temperature and proton energy, i.e. ionization density, on the RL and OSL signals from Al2O3:C...... by the combined efforts of energetic shallow traps and thermal excitation from intermediate states in deeper traps. In the study of ionization density, we investigated protons with energies between 10 and 60 MeV (4.57 to 1.08 keV/ìm in water). Experimentally, we observed that the initial OSL signal provided...... that the initial OSL signal is, in general, not LET independent which makes Al2O3:C unsuitable for OSL proton dosimetry. The initial OSL signal can, however, be combined with the total OSL signal to provide an LET independent response for a given dose and LET interval. On the basis of TST, we estimate a so...

  13. Tribological properties of Cu based composite materials strengthened with Al2O3 particles

    Directory of Open Access Journals (Sweden)

    J. W. Kaczmar

    2012-12-01

    Full Text Available In the present work copper was strenghtened with 20 and 30 vol. % of alumina particles characterized by diameter of 3-6μm. The copperbased composite materials were manufactured by the squeeze casting method. Preheated preforms made from Al2O3 particles were placedin the desired place in the heated cast die and the squeeze casting process with liquid copper was performed applying the infiltrationpressure of 90MPa and pressure was kept for 10-15s until solidification was complete. The microstructure and physical properties: Brinell hardness (HBW and density were characterized. Metallografic examinations showed that alumina particles were uniformly distributed in the copper matrix. Hardness of 208 HBW for composite materials containing 30 vol.% of particles was achieved. Wear investigations were performed applying the tribological pin-on-disc tester. Friction forces between copper based composite materials containing 20 and 30 vol. % of Al2O3 particles and cast iron were registered and wear was determined on the base of the specimen mass loss after 1.0, 3.5 and 8.5 km friction distance.

  14. Dissolution Behavior of Indium in CaO-SiO2-Al2O3 Slag

    Science.gov (United States)

    Ko, Kyu Yeol; Park, Joo Hyun

    2011-12-01

    The solubility of indium in a molten CaO-SiO2-Al2O3 system was measured at 1773 K (1500 °C) to establish the dissolution mechanism of indium under a highly reducing atmosphere. The solubility of indium increases with increasing oxygen potential, whereas it decreases with increased activity of basic oxide. Therefore, a dissolution mechanism of indium can be constructed according to the following equation: {{In}}({{s}}) + 1/4{{O}}2 ({{g}}) = ({{In}}^{ + } ) + 1/2({{O}}^{2 - } ) The relationship between indium capacity and sulfide capacity shows a good correlation that is consistent with theoretical expectations. The enthalpy change of the indium dissolution reaction is negative, which indicates that the dissolution is an exothermic reaction. The heat of dissolution into high-silica melts is greater than that into low-silica melts. The solubility of indium is strongly dependent on the silica content. The activity coefficient, and thus the excess free energy of In2O, decreases linearly with increasing silica content, indicating that the In2O is believed to behave as a weak basic oxide in the current CaO-SiO2-Al2O3 ternary system under reducing conditions.

  15. A thin layer fiber-coupled luminescence dosimeter based on Al2O3:C

    DEFF Research Database (Denmark)

    Klein, F.A.; Greilich, Steffen; Andersen, Claus Erik

    2011-01-01

    of the introduced polymer host matrix on the dosimetric properties was observed. Depth-dose measurements with the new detectors in a 142.66 MeV proton and 270.55 MeV/u carbon ion beam are presented as example applications. We used an RL protocol with saturated crystals allowing for time-effective measurements......In this paper we present a fiber-coupled luminescent Al2O3:C dosimeter probe with high spatial resolution (0.1 mm). It is based on thin layers of Al2O3:C crystal powder and a UV-cured acrylate monomer composition. The fabrication of the thin layers is described in detail. No influence...... without sensitivity corrections. For protons, a relative luminescence efficiency hHCP of 0.715 0.014 was found in the Bragg peak. For carbon ions, a value of 0.498 0.001 was found in the entrance channel, 0.205 0.015 in the Bragg peak, and a mean of 0.413 0.050 in the tail region. The mean range...

  16. Fabrication of Al2O3-W Functionally Graded Materials by Slipcasting Method

    Science.gov (United States)

    Katayama, Tomoyuki; Sukenaga, Sohei; Saito, Noritaka; Kagata, Hajime; Nakashima, Kunihiko

    2011-10-01

    We have successfully fabricated a functionally graded material (FGM) from tungsten and alumina powders by a slip-casting method. This FGM has applications as a sealing and conducting component for high-intensity discharge lamps (HiDLs) that have a translucent alumina envelope. Two types of W powder, with different oxidizing properties, were used as the raw powders for the Al2O3-W FGM. "Oxidized W" was prepared by heat-treatment at 200 °C for 180 min in air. Alumina and each of the W powders were mixed in ultrapure water by ultrasonic stirring. The slurry was then cast into a cylindrical acrylic mold, which had a base of porous alumina, under controlled pressure. The green compacts were subsequently dried, and then sintered using a vacuum furnace at 1600 °C for a fixed time. The microstructures of the FGMs were observed by scanning electron microscopy (SEM) of the polished section. The Al2O3-W FGM with the "oxidized W" powder resulted in a microscopic compositional gradient. However, the FGM with "as-received W" showed no compositional gradient. This result was mainly attributed to the difference between the ζ-potentials of the W powders with the different oxidizing conditions; basically "oxidized W" powder tends to disperse because of the larger ζ-potential of the oxide layer coated on the W powder core.

  17. Tribological properties of Al 7075 alloy based composites strengthened with Al2O3 fibres

    Directory of Open Access Journals (Sweden)

    K. Naplocha

    2011-04-01

    Full Text Available Wear resistance of 7075 aluminium alloy based composite materials reinforced with Al2O3 Saffil fibres was investigated. The measurementsof wear were performed applying the pin-on-disc method at dry friction conditions with the gray iron counterpart. The effects ofpressure of composite samples on the counterpart made of gray iron and the orientation of fibers in relation to the friction surface on wear rate were determined. The materials were produced by squeeze casting method where 80-90% porous ceramic preform were infiltrated.After T6 heat treatment hardness increased about 50-60% both for unreinforced alloy and composites containing strengthening Saffilfibres. Wear resistance of composite materials in relation to the unreinforced 7075 alloy was slightly worse at lower pressure of 0.8 MPa. Under higher pressure of 1.2 MPa wear resistance of unreinforced 7075 alloy was even better whereas no effect of orientation of fibers on wear in composite materials was observed. Additionally, significant wear of counterface in the presence of debris with fragmented Al2O3 fibres as abrasives was observed. Wear resistance improvement of composite materials was obtained when with alumina Saffil fibres Carbon C fibres in the preforms were applied.

  18. Separation of Fine Al2O3 Inclusion from Liquid Steel with Super Gravity

    Science.gov (United States)

    Li, Chong; Gao, Jintao; Wang, Zhe; Guo, Zhancheng

    2017-01-01

    An innovative approach of super gravity was proposed to separate fine Al2O3 inclusions from liquid steel in this study. To investigate the removal behaviors of inclusions, the effects of different gravity coefficients and time on separating the inclusions were studied. The results show that a large amount of Al2O3 inclusions gathered at the top of the sample obtained by super gravity, whereas there were almost no inclusions appearing at the bottom. The volume fraction and number density of inclusions presented a gradient distribution along the direction of the super gravity, which became steeper with increasing gravity coefficient and separating time. As a result of the collision between inclusions, a large amount of inclusions aggregated and grew during the moving process, which further decreased the removal time. The experimental required removal time of inclusions is close to the theoretical values calculated by Stokes law under gravity coefficient G ≤ 80, t ≤ 15 minutes, and the small deviation may be because the inclusion particles are not truly spherical. Under the condition of gravity coefficient G = 80, t = 15 minutes, the total oxygen content at the bottom of the sample (position of 5 cm) is only 8.4 ppm, and the removal rate is up to 95.6 pct compared with that under normal gravity.

  19. Crystalline gamma-Al2O3 physical vapour deposition-coating for steel thixoforging tools.

    Science.gov (United States)

    Bobzin, K; Hirt, G; Bagcivan, N; Khizhnyakova, L; Ewering, M

    2011-10-01

    The process of thixoforming, which has been part of many researches during the last decades, combines the advantages of forging and casting for the shaping of metallic components. But due to the high temperatures of semi-solid steel alloys high demands on the tools are requested. To resists the thermal and mechanical loads (wear, friction, thermal and thermomechanical fatigue) protecting thin films are necessary. In this regard crystalline gamma-Al2O3 deposited via Physical Vapour Deposition (PVD) is a promising candidate: It exhibits high thermal stability, high oxidation resistance and high hot hardness. In the present work the application of a (Ti, Al)N/gamma-Al2O3 coating deposited by means of Magnetron Sputter Ion Plating in an industrial coating unit is presented. The coating was analysed by means of Rockwell test, nanoindentation, and Scanning Electron Microscopy (SEM). The coated tool was tested in thixoforging experiments with steel grade X210CrW12 (AlSI D6). The surface of the coated dies was examined with Scanning Electron Microscope (SEM) after 22, 42, 90 and 170 forging cycles.

  20. Surface micromorphology of dental composites [CE-TZP]-[Al2O3] with Ca(+2) modifier.

    Science.gov (United States)

    Berezina, Sofia; Il'icheva, Alla Alexandrovna; Podzorova, Lyudmila Ivanovna; Ţălu, Ştefan

    2015-09-01

    The objective of this study was to characterize the three-dimensional (3D) surface micromorphology of the ceramics produced from nanoparticles of alumina and tetragonal zirconia (t-ZrO2) with addition of Ca(+2) for sintering improvement. The 3D surface roughness of samples was studied by atomic force microscopy (AFM), fractal analysis of the 3D AFM-images, and statistical analysis of surface roughness parameters. Cube counting method, based on the linear interpolation type, applied for AFM data was used for fractal analysis. The morphology of non-modified ceramic sample was characterized by the rather big (1-2 μm) grains of α-Al2O3 phase with a habit close to hexagonal drowned in solid solution of t-ZrO2 with smooth surface. The pattern surfaces of modified composite content a little amount of elongated prismatic grains with composition close to the phase of СаСеAl3О7 as well as hexahedral α-Al2O3-grains. Fractal dimension, D, as well as height values distribution have been determined for the surfaces of the samples with and without modifying. It can be concluded that the smoothest surface is of the modified samples with Ca(+2) modifier but the most regular one is of the non-modified samples. A connection was observed between the surface morphology and the physical properties as assessed in previous works.

  1. Plasma-Assisted ALD of an Al2O3 Permeation Barrier Layer on Plastic

    Institute of Scientific and Technical Information of China (English)

    雷雯雯; 李兴存; 陈强; 王正铎

    2012-01-01

    Atomic layer deposition (ALD) technique is used in the preparation of organic/inorganic layers, which requires uniform surfaces with their thickness down to several nanometers. For film with such thickness, the growth mode defined as the arrangement of clusters on the surface during the growth is of significance. In this work, Al2O3 thin film was deposited on various interfacial species of pre-treated polyethylene terephthalate (PET, 12 μm) by plasma assisted atomic layer deposition (PA-ALD), where trimethyl aluminium was used as the Al precursor and O2 as the oxygen source. The interracial species, -NH3, -OH, and -COOH as well as SiCHO (derived from monomer of HMDSO plasma), were grafted previously by plasma and chemical treatments. The growth mode of PA-ALD Al2O3 was then investigated in detail by combining results from in-situ diagnosis of spectroscopic ellipsometry (SE) and ex-situ characterization of as-deposited layers from the morphologies scanned by atomic force microscopy (AFM). In addition, the oxygen transmission rates (OTR) of the original and treated plastic films were measured. The possible reasons for the dependence of the OTR values on the surface species were explored.

  2. Characteristic parameters and operational curves of γ-Al2O3 nanofiltration membranes

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    The γ-Al2O3 nanofiltration membranes were manufactured by the sol-gel technique. The result of N2 adsorption and desorption test indicates that the characteristic parameters of the membranes: BJH desorption average pore diameter, BJH desorption cumulative volume of pores and BET surface area are about 3.9 nm, 0.33 cm3/g and 245 m2/g respectively, and the pore size distribution is very narrow. The operational curves of γ-Al2O3 nanofiltration membranes of the Ca2+ retention rate vs the trans-membrane pressure, feed concentration of solution treated and pH of solution treated were studied for the first time. It is found that the retention rate for Ca2+ increases with the transmembrane pressure increasing and decreases with the feed concentration of CaCl2 solution increasing. The retention of Ca2+ is very much dependent on the pH of the solution. Minimal Ca2+ retention rate is found at the isoelectric point (pH = 7.5).

  3. Application of the Solvothermal Process in the Synthesis of High-performance Ag/γ-Al2O3 Catalysts

    Institute of Scientific and Technical Information of China (English)

    TANG Qing; LI Rui-xing; YIN Shu; Shingo Goto; Daisuke Nagai; Tsugio Sato

    2006-01-01

    Ag/γ-Al2O3 is a kind of promising catalyst with the relatively lower cost compared with those using noble metals,good resistance against catalytic poisoning and excellent behaviour for NOx removal. In the present study, Ag/γ-Al2O3 catalysts were synthesized by the solvothermal process and characterized by XRD, TG-DTA, TEM, UV-Vis and FT-IR. It was found that high-performance Ag/γ-Al2O3 catalysts could be synthesized by properly selecting starting materials,controlling the composition of solvent and other reaction conditions. The microstructure evolution of the catalysts was also discussed.

  4. The effect of particle size on the electrical conductivity of CuCl (Al2O3) composites

    Science.gov (United States)

    Chang, M. R.-W.; Shahi, K.; Wagner, J. B., Jr.

    1984-01-01

    The conductivity of CuCl containing Al2O3 of 0.06, 0.3, 1, 3, 8, and 15 micron sized particles was measured between 25 and 390 C. Conductivity was enhanced for the 0.06 and 0.3 sized Al2O3 particles for temperatures below approximately 250 C. The maximum enhancement occurred at 10 m/o of 0.06 micron Al2O3 at 25 C. Uncertain degrees of agglomeration as well as the grain size of the matrix were found to be significant.

  5. Effects of a second phase on the tribological properties of Al2O3 and ZrO2 ceramics

    OpenAIRE

    Y. J. He; Winnubst, A.J.A.; Schipper, D.J.; Burggraaf, A.J.; Verweij, H.

    1997-01-01

    The tribological properties of four different materials are investigated, tetragonal zirconia (Y-ZTP), Al2O3 dispersed in Y-TZP (ADZ), ZrO2 dispersed in Al2O3 (ZTA) and Al2O3 (with 300 ppm MgO). These materials are used as a cylinder sliding against a plate of Y-TZP (TZ-3Y)). Compared to Y-TZP, the wear resistance of ADZ composites is increased by a factor of 4¿10. At a contact pressure of 230 MPa, a wear transition for Y-TZP is observed from plastic deformation to microchipping and microfrac...

  6. Preparation and Characterization of Zeolite Beta with Low SiO2/Al2O3 Ratio

    Institute of Scientific and Technical Information of China (English)

    Kang Shanjiao; Gong Yanjun; Dou Tao; Zhang Ying; Zheng Yanying

    2007-01-01

    Zeolite beta with a low SiO2/Al2O3 ratio was synthesized by a novel two-step process. The synthesized sample was characterized with XRD,SEM,FTIR,and N2 adsorption-desorption and solid-state MAS NMR. The results showed that aluminium species were inserted into the framework of zeolite beta. The BET surface area,volume,and particle size of the zeolite beta sample decreased with decreasing SiO2/Al2O3 ratio. Our process was proved an efficient route to synthesize zeolite beta with a low SiO2/Al2O3 ratio.

  7. High-temperature oxidation behavior of Al2O3/TiAl matrix composite in air

    Institute of Scientific and Technical Information of China (English)

    AI TaoTao; WANG Fen; FENG XiaoMing

    2009-01-01

    The oxidation behavior of Al2O3/TiAl in situ composites fabricated by hot-pressing technology was in-vestigated at 900℃ in static air. The results indicate that the mass gains of the composites samples decrease gradually with increasing Nb2O5 content and the inert Al2O3 dispersoids effectively increase the oxidation resistance of the composites. The higher the Al2O3 dispersoids content, the more pro-nounced the effect. The primary oxidation precesses obey approximately the linear laws, and the cyclic oxidation precesses follow the parabolic laws. The oxidized sample containing Ti2AIN and TiAI phases in the scales exhibits excellent oxidation resistance. The oxide scale formed after exposure at 900℃ for 120 h is multiple-layered, consisting mainly of an outer TiC2 layer, an intermediate Al2O3 layer, and an inner TiO2+Al2O3 mixed layer. From the outer layer to the inner layer, TiO2+Al2O3 mixed layer presents the transit of AI-rich oxide to Ti-rich oxide mixed layer. Near the substrate, cross-section micrograph shows a relatively loose layer, and micro- and macro-pores remain on this layer, which is a transition layer and transferres from Al2O3+TiO2 scale to substrate. The thickness of oxide layer is about 20 μm. It is also found that continuous protective alumina scales can not be observed on the surface of oxida-tion scales. Ti ions diffuse outwardly to form the outer TiC2 layer, while oxygen ions transport inwardly to form the inner TiO2+Al2O3 mixed layer. Under long-time intensive oxidation exposure, the internal Al2O3 scale has s good adhesiveness with the outer TiO2 scale. No obvious spallation of the oxide scales occurs. The increased oxidation resistance by the presence of in situ Al2O3 particulates is at-tributed to the enhanced alumina-forming tendency and thin and dense scale formation. Al2O3 particu-lates enhance the potential barrier of Ti ions from M/MO interface to O/MO interface, thereby the TiO2growth rate decreases, which is also beneficial to

  8. Atomic layer deposition of an Al2O3 dielectric on ultrathin graphite by using electron beam irradiation

    Institute of Scientific and Technical Information of China (English)

    Jiang Ran; Meng Lingguo; Zhang Xijian; Hyung-Suk Jung; Cheol Seong Hwang

    2012-01-01

    Atomic layer deposition ofan Al2O3 dielectric on ultrathin graphite is studied in order to investigate the integration of a high k dielectric with graphite-based substrates.Electron beam irradiation on the graphite surface is followed by a standard atomic layer deposition of Al2O3.Improvement of the Al2O3 layer deposition morphology was observed when using this radiation exposure on graphite.This result may be attributed to the amorphous change of the graphite layers during electron beam irradiation.

  9. Dense TiC-Al2O3 Composites Fabricated by SHS%致密 TiC-Al2O3复合陶瓷材料的自蔓延高温合成

    Institute of Scientific and Technical Information of China (English)

    张卫方; 韩杰才; 张幸红; 赫晓东; 杜善义

    1999-01-01

    本文通过自蔓延高温合成结合准热等静压法(SHS/PHIP)制崐备出了致密度为97.2%的TiC-Al2O3复合陶瓷. 分析了合成产物的结构、组织和性能. 结果表明,复合陶瓷由近乎球形的TiC颗粒和不规则的Al2O3相组成,TiC与Al2O3之间的界面光滑. TiC-Al2O3复合陶瓷的抗弯强度和硬度分别为510MPa和17.8GPa.

  10. 高炉出铁沟料中SiC、Al2O3的系统分析%Systematic Analysis of the SiC and Al2O3 in the Refractory for BF Lander

    Institute of Scientific and Technical Information of China (English)

    傅士刚; 王俊秀; 张小燕; 魏新晖; 王艳芹

    2014-01-01

    Utilizing the characteristic that SiO2, elemental Si, Al2O3 are soluble in hydrofluoric acid and nitric acid but SiC is insoluble in them, the simple was dissolved in hydrofluoric acid and nitric. The ashing and Filtering non melt matter together with the filter paper was incinerated and burned. The SiC content in lander material was determined by gravimetric method. Perchloric acid was added into the filtrate. By evaporating smoking, the residual fluoride ion effecting the measurement of the Al2O3 was removed. The Al2O3 content was analyzed by strong alkali separation, villiaumite replacement and EDTA titration method. The determination result is accurate and reliable and the relative standard deviations:SiC<0.134%and Al2O3<1.438%.%利用SiO2、单质Si、Al2O3易溶于氢氟酸、硝酸,而SiC不溶于氢氟酸、硝酸的特性,用氢氟酸、硝酸溶样,过滤的不熔物连同滤纸在瓷坩埚中灰化、灼烧,用重量法测定铁沟料中的SiC量。于滤液中加高氯酸蒸发冒烟除去残余氟离子对Al2O3分析的影响,用强碱沉淀分离、氟盐置换、EDTA滴定法分析Al2O3量。测定结果准确可靠,RSD:SiC<0.134%,Al2O3<1.438%。

  11. Role of support nature (γ-Al2O3 and SiO2-Al2O3) on the performances of rhenium oxide catalysts in the metathesis of ethylene and 2-pentene

    Institute of Scientific and Technical Information of China (English)

    Weena Phongsawat; Benjamas Netiworaruksa; Kongkiat Suriye; Siraprapha Dokjampa; Piyasan Praserthdam; Joongjai Panpranot

    2012-01-01

    The metathesis of ethylene and 2-pentene was studied as an alternative route for propylene production over Re2O7/γ-Al2O3 and Re2O7/SiO2-Al2O3 catalysts.Both NH3 temperature-programmed desorption (NH3-TPD) and H2 temperature-programmed reduction (H2-TPR) results showed that Re2O7/SiO2-Al2O3 exhibited stronger acidity and weaker metal-support interaction than Re2O7/γ-Al2O3.At 35-60 ℃,isomerization free metathesis was observed only over Re2O7/γ-Al2O3,suggesting that the formation of metal-carbene metathesis active sites required only weak acidity.Our results suggest that on the Re2O7/SiO2-Al2O3,hydrido-rhenium species ([Re]-H) were formed in addition to the metathesis active sites,resulting in the isomerization of the initial 1-butene product into 2-butenes.A subsequent secondary metathesis reaction between these 2-butenes and the excess ethylene could explain the enhanced yields of propylene observed.The results demonstrate the potential for high yield of propylene from alternative feedstocks.

  12. The Dielectic Properties of Polyimide/Nano-Al2O3 Composites Films%聚酰亚胺/纳米Al2O3复合薄膜的介电性能

    Institute of Scientific and Technical Information of China (English)

    李鸿岩; 郭磊; 刘斌; 陈维; 陈寿田

    2006-01-01

    为了提高聚酰亚胺(PI)的耐电晕性能,采用原位分散聚合法制备了聚酰亚胺/纳米Al2O3复合材料,并采用透射电子显微镜(TEM)对纳米Al2O3的分散状态进行了表征.研究了纳米Al2O3填加量对该复合材料耐电晕性能和其它介电性能的影响,结果表明,随着纳米Al2O3含量的增加,材料的耐电晕性能显著增强,在±910V(双极性)、15kHz条件下,纳米Al2O3质量分数为20%的PI薄膜的耐电晕寿命达到极大值,为纯PI薄膜寿命的25倍,聚酰亚胺/纳米Al2O3复合材料的体积电阻率和击穿场强没有明显的劣化,而相对介电常数和损耗角正切有所增加.

  13. The Modification of Sodium Polyacrylate Water Solution Cooling Properties by AL2O3

    Directory of Open Access Journals (Sweden)

    Wojciech Gęstwa

    2010-01-01

    Based on cooling curves, it can be concluded that for the water solution of sodium polyacrylate with AL2O3 nanoparticles in comparison to water and 10% polymer water solution lower cooling speed is obtained. The cooling medium containing nanoparticles provides lower cooling speed in the smallest surface austenite occurance (500–600 C in the charts of the CTP for most nonalloy structural steels and low-alloy steels. However lower cooling temperature at the beginning of martensitic transformation causes the formation of smaller internal stresses, leading to smaller dimensional changes and hardening deformation. For the quenching media the wetting angle was appointed by the drop-shape method. These studies showed the best wettability of polymer water solution (sodium polyacrylate with the addition of AL2O3 nanoparticles, whose wetting angle was about 65 degrees. Obtaining the smallest wetting angle for the medium containing nanoparticles suggests that the heat transfer to the cooling medium is larger. This allows slower cooling at the same time ensuring its homogeneity. The obtained values of wetting angle confirm the conclusions drawn on the basis of cooling curves and allowus to conclude that in the case of the heat transfer rate it will have a lower value than for water and 10% polymer water solution. In the research on hardened carburized steel samples C10 and 16MnCr5 surface hardness, impact strength and changes in the size of cracks in Navy C-ring sample are examined. On this basis of the obtained results it can be concluded that polymer water solution with nanoparticles allows to obtain a better impact strength at comparable hardness on the surface. Research on the dimensional changes on the basis of the sample of Navy C-ring also shows small dimensional changes for samples carburized and hardened in 10% polymer water solution with the addition of nanoparticles AL2O3. Smaller dimensional changes were obtained for samples of steel 16MnCr5 thanfar C10. The

  14. Catalytic Partial Oxidation of Methane over Ni/CeO2-ZrO2-Al2O3

    Institute of Scientific and Technical Information of China (English)

    Mei Dajiang; Chen Yaoqiang; Zhong Junbo; Wei Zhenling; Ma Di; Gong Maochu

    2007-01-01

    Nickel catalysts supported on CeO2-ZrO2-CeO2, ZrO2-Al2O3 and Al2O3 were prepared and characterized by means of X-ray diffraction (XRD), BET areas, H2 temperature-programmed reduction (H2-TPR), and X-ray photoelectron spectroscopy (XPS). Through the test of catalytic partial oxidation of methane (CPOM), Ni/CeO2-ZrO2-Al2O3 displayed the highest activity, which resulted from its largest BET area and best NiO dispersion. Furthermore, Ni/CeO2-ZrO2-Al2O3 maintained a long-time stability in CPOM, which was attributed to its best coking resistance among all the prepared catalysts.

  15. Catalytic activity of cerium-doped Ru/Al2O3 during ozonation of dimethyl phthalate

    Institute of Scientific and Technical Information of China (English)

    Yunrui ZHOU; Wanpeng ZHU; Xun CHEN

    2008-01-01

    In this paper, factors influencing the mineraliza-tion of dimethyl phthalate (DMP) during catalytic ozona-tion with a cerium-doped Ru/Al2O3 catalyst were studied. The catalytic contribution was calculated through the results of a companrison experiment. It showed that doping cerium significantly enhanced catalytic activity. The total organic carbon (TOC) removal over the doped catalyst at 100 rain reached 75.1%, 61.3% using Ru/Al2O3 catalyst and only 14.0% using ozone alone. Catalytic activity reached the maximum when 0.2% of ruthenium and 1.0% of cerium'were simultaneously loaded onto Al2O3 support. Results of experiments on oxidation by ozone alone, adsorption of the catalyst, Ce ion's and heterogeneous catalytic ozonation confirmed that the contribution of het-erogeneous catalytic ozonation was about 50%, which showed the obvious effect of Ru-Ce/Al2O3 on catalytic activity.

  16. Self-Propagating High- Temperature Reductive Synthesis of TiB2-Al2O3 Composite Powders

    Institute of Scientific and Technical Information of China (English)

    YU Zhiqiang; YANG Zhenguo

    2007-01-01

    TiB2-Al2O3 composite powders were produced by self-propagating high-temperature synthesis(SHS) method with reductive process from B2O3-TiO2-Al system. X-ray diffraction(XRD) and scanning electron microscopy(SEM) analyses show the presence of TiB2 and Al2O3 only in the composite powders produced by SHS. The powders are uniform and free-agglomerate. Transmission electron microscopy (TEM)and high resolution electron microscopy (HREM) observation of microstructure of the composite powders indicate that the interfaces of the TiB2-Al2O3 bond well, without any interfacial reaction products. It is proposed that the good interfacial bonding of the composite powders can be resulted from the TiB2 particles crystallizing and growing on the Al2O3 particles surface with surface defects acting as nucleation centers.

  17. Effects of Ce on catalytic combustion of methane over Pd-Pt/Al2O3 catalyst

    Institute of Scientific and Technical Information of China (English)

    Xing Fan; Fan Wang; Tianle Zhu; Hong He

    2012-01-01

    Activity and stability of 1%Pd-0.2%Pt/Al2O3 and 1%Pd-0.2%Pt/0.6%Ce/Al2O3 catalysts prepared by impregnation method for catalytic combustion of methane in air were investigated.The catalysts before and after reaction were characterized by BET,CO chemisorption,XRD and XPS techniques.Results showed that the presence of Ce significantly increased the activity and thermal stability of the Pd-Pt/Al2O3 catalyst towards methane combustion,which could be attributed to more highly-dispersed active PdO particles over the Pd-Pt/Ce/Al2O3 catalyst surface as well as the retarded sintering of PdO and the maintained oxidized state of surface Pd during the combustion process in the presence of Ce.

  18. Synthesis of CoFe/Al2O3 composite nanoparticles as the impedance matching layer of wideband multilayer absorber

    Science.gov (United States)

    Zhen, L.; Gong, Y. X.; Jiang, J. T.; Xu, C. Y.; Shao, W. Z.; Liu, P.; Tang, J.

    2011-04-01

    CoFe/Al2O3 composite nanoparticles were successfully prepared by hydrogen-thermally reducing cobalt aluminum ferrite. Compared with CoFe alloy nanoparticles, the permeability of CoFe/Al2O3 composite nanoparticles was remarkably enhanced and an improved impedance characteristic was achieved due to the introduction of insulated Al2O3. A multilayer absorber with CoFe/Al2O3 composite nanoparticles as the impedance matching layer and CoFe nanoflake as the dissipation layer was designed by using genetic algorithm, in which an ultrawide operation frequency bandwidth over 2.5-18 GHz was obtained. The microwave absorption performance in both normal and oblique incident case was evaluated by using electromagnetic simulator. The backward radar cross-section (RCS) was decreased at least 10 dB over a wide frequency range by covering the multilayer absorber on the surface of perfect electrical conductive plate.

  19. Thermal expansion and elastic anisotropy in single crystal Al2O3 and SiC reinforcements

    Science.gov (United States)

    Salem, Jonathan A.; Li, Zhuang; Bradt, Richard C.

    1994-01-01

    In single crystal form, SiC and Al2O3 are attractive reinforcing components for high temperature composites. In this study, the axial coefficients of thermal expansion and single crystal elastic constants of SiC and Al2O3 were used to determine their coefficients of thermal expansion and Young's moduli as a function of crystallographic orientation and temperature. SiC and Al2O3 exhibit a strong variation of Young's modulus with orientation; however, their moduli and anisotropies are weak functions of temperature below 1000 C. The coefficients of thermal expansion exhibit significant temperature dependence, and that of the non-cubic Al2O3 is also a function of crystallographic orientation.

  20. The Influence of Nano-Al2O3 Additive on the Adhesion between Epoxy Resin and Steel Substrate

    Institute of Scientific and Technical Information of China (English)

    ZHAILan-lan; LINGGuo-ping

    2004-01-01

    The influence of nano-A1203 additive on the adhesion between epoxy resin and steel substrate has been investigated. The results of tensile testing indicated that the adhesion strength was increased dramatically by addition of Al2O3 nanoparticles in epoxy resin compared with that of the unmodified resin. The highest adhesion strength was obtained with 1 wt% nano-Al2O3 added in epoxy adhesive, more than two times higher than that of the unmodified. Scanning electronic microscope (SEM) revealed that a boundary layer exists between epoxy and steel substrate, energy spectrum analysis indicates there is enrichment of the nano-Al2O3 particle. Those results confirmed that the nano-Al2O3 additive was closely related to the change of interface morphology and the improvement of adhesion strength. The reason for adhesion improvement was also be discussed.

  1. Choque térmico em filtros cerâmicos do sistema Al2O3-SiC Thermal shock on ceramic filters in the system Al2O3-SiC

    Directory of Open Access Journals (Sweden)

    V. R. Salvini

    2002-03-01

    Full Text Available Em diversas aplicações as cerâmicas celulares são submetidas a tensões térmicas severas, tal como na filtração de metais fundidos. Contudo, há poucos estudos sobre o desempenho ao choque térmico destes materiais. Uma das razões é que a metodologia para análise desta classe de materiais deve ser distinta daquela utilizada para os materiais cerâmicos densos. Isto porque no caso dos materiais celulares para filtração de metais fundidos o meio causador do choque térmico infiltra-se rapidamente na estrutura reticular de poros, reduzindo o gradiente de temperatura entre a superfície externa e a do interior do corpo. Neste contexto, a proposta do presente trabalho é verificar os efeitos de algumas propriedades dos filtros cerâmicos em seu comportamento mecânico durante testes de choque térmico em água. As propriedades consideradas são a permeabilidade, a condutividade térmica e a área superficial específica dos filtros. Para isto foram utilizados os filtros cerâmicos do sistema de Al2O3-SiC de 8, 10, 20 e 30 ppi (poros por polegada linear.In many applications, open-cell ceramics are expected to undergo severe thermal stresses, for instance, in their use as molten metal filters. However, only a few studies have considered the thermal shock behavior of these materials. One of the main reasons is the theoretical approach used for dense ceramics which may not be valid for porous materials. In this context, the aim of this work is to analyze the effects of permeability, specific surface area and thermal conductivity on the mechanical behavior of ceramic filters subjected to water quenching tests. Al2O3-SiC filters with nominal cell sizes, expressed as the number of pores per linear inch (ppi, ranged from 8 to 30 ppi were used in the experimental tests.

  2. On the Control of the Fixed Charge Densities in Al2O3-Based Silicon Surface Passivation Schemes.

    Science.gov (United States)

    Simon, Daniel K; Jordan, Paul M; Mikolajick, Thomas; Dirnstorfer, Ingo

    2015-12-30

    A controlled field-effect passivation by a well-defined density of fixed charges is crucial for modern solar cell surface passivation schemes. Al2O3 nanolayers grown by atomic layer deposition contain negative fixed charges. Electrical measurements on slant-etched layers reveal that these charges are located within a 1 nm distance to the interface with the Si substrate. When inserting additional interface layers, the fixed charge density can be continuously adjusted from 3.5 × 10(12) cm(-2) (negative polarity) to 0.0 and up to 4.0 × 10(12) cm(-2) (positive polarity). A HfO2 interface layer of one or more monolayers reduces the negative fixed charges in Al2O3 to zero. The role of HfO2 is described as an inert spacer controlling the distance between Al2O3 and the Si substrate. It is suggested that this spacer alters the nonstoichiometric initial Al2O3 growth regime, which is responsible for the charge formation. On the basis of this charge-free HfO2/Al2O3 stack, negative or positive fixed charges can be formed by introducing additional thin Al2O3 or SiO2 layers between the Si substrate and this HfO2/Al2O3 capping layer. All stacks provide very good passivation of the silicon surface. The measured effective carrier lifetimes are between 1 and 30 ms. This charge control in Al2O3 nanolayers allows the construction of zero-fixed-charge passivation layers as well as layers with tailored fixed charge densities for future solar cell concepts and other field-effect based devices.

  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. The effect of the gas composition on hydrogen-assisted NH3-SCR over Ag/Al2O3

    DEFF Research Database (Denmark)

    Tamm, Stefanie; Fogel, Sebastian; Gabrielsson, Pär;

    2013-01-01

    In addition to high activity in hydrocarbon-SCR, Ag/Al2O3 catalysts show excellent activity for NOx reduction for H2-assisted NH3-SCR already at 200°C. Here, we study the influence of different gas compositions on the activity of a pre-sulfated 6wt% Ag/Al2O3 catalyst for NOx reduction, and oxidat...

  5. Effect of Al2O3 on the friction performance of P/M composite materials for friction applications

    Science.gov (United States)

    Ivǎnuş, R. C.; ǎnuş, D., IV; Cǎlmuc, F.

    2010-06-01

    Bronze bearings are one of most used friction materials. In those applications where higher mechanical properties are needed, iron base bearings can be an alternative to bronze base materials, or other alloying elements added to bronze. The paper presents the results obtained in metal matrix composites field with friction characteristics, for automotive brakes, by P/M. The scope of these researches was the improvement of wear resistance and friction properties of metal matrix composites. Friction-wear properties of the Al2O3 reinforced samples were measured and compared with those of plain bronze based ones. For this purpose, density, hardness, friction coefficient wear behaviour of the samples were tested.Microstructures of samples before and after sintering and worn surfaces were also investigated by scanning electron microscopy (SEM), and the wear types were determined. The optimum friction-wear behaviour was obtained in the sample compacted at 500 MPa and sintered at 820°C. Density of the final samples decreased with increasing the amount of reinforcing elements (Al2O3) before presintering. However after sintering, there is no change in density of the samples including reinforcing elements (Al2O3). With increasing friction surface temperature, a reduction in the friction coefficient of the samples was observed. However, the highest reductions in the friction coefficients were observed in the as-received samples containing 0,5% reinforced Al2O3. The SEM images of the sample indicated that while bronze-based break lining material without Al2O3 showed abrasive wear behaviour, increasing the amount of Al2O3 resulted in a change of abrasive to adhesive wear mechanism. With increasing the amount of reinforcing Al2O3, wear resistance of the samples was increased. However samples reinforced with 5% and 6% Al2O3 showed the best results.

  6. Influence of the Al2O3 partial-monolayer number on the crystallization mechanism of TiO2 in ALD TiO2/Al2O3 nanolaminates and its impact on the material properties

    Science.gov (United States)

    Testoni, G. E.; Chiappim, W.; Pessoa, R. S.; Fraga, M. A.; Miyakawa, W.; Sakane, K. K.; Galvão, N. K. A. M.; Vieira, L.; Maciel, H. S.

    2016-09-01

    TiO2/Al2O3 nanolaminates are being investigated to obtain unique materials with chemical, physical, optical, electrical and mechanical properties for a broad range of applications that include electronic and energy storage devices. Here, we discuss the properties of TiO2/Al2O3 nanolaminate structures constructed on silicon (1 0 0) and glass substrates using atomic layer deposition (ALD) by alternatively depositing a TiO2 sublayer and Al2O3 partial-monolayer using TTIP-H2O and TMA-H2O precursors, respectively. The Al2O3 is formed by a single TMA-H2O cycle, so it is a partial-monolayer because of steric hindrance of the precursors, while the TiO2 sublayer is formed by several TTIP-H2O cycles. Overall, each nanolaminate incorporates a certain number of Al2O3 partial-monolayers with this number varying from 10-90 in the TiO2/Al2O3 nanolaminate grown during 2700 total reaction cycles of TiO2 at a temperature of 250 °C. The fundamental properties of the TiO2/Al2O3 nanolaminates, namely film thickness, chemical composition, microstructure and morphology were examined in order to better understand the influence of the number of Al2O3 partial-monolayers on the crystallization mechanism of TiO2. In addition, some optical, electrical and mechanical properties were determined and correlated with fundamental characteristics. The results show clearly the effect of Al2O3 partial-monolayers as an internal barrier, which promotes structural inhomogeneity in the film and influences the fundamental properties of the nanolaminate. These properties are correlated with gas phase analysis that evidenced the poisoning effect of trimethylaluminum (TMA) pulse during the TiO2 layer growth, perturbing the growth per cycle and consequently the overall film thickness. It was shown that the changes in the fundamental properties of TiO2/Al2O3 nanolaminates had little influence on optical properties such as band gap and transmittance. However, in contrast, electrical properties as resistivity

  7. Microstructure and mechanical properties of HIP diffusion bonded Al2 O3/Kovar joint%Al2O3/Kovar热等静压扩散层的组织与性能

    Institute of Scientific and Technical Information of China (English)

    李强; 王伟; 杨晓峰; 孙钊; 李启寿

    2014-01-01

    Al2 O3 ceramic and Kovar alloy were bonded by hot isostatic pressing ( HIP) diffusion with filler metal of Ti-Ni and Ag-Cu-Ti, respectively.Microstructure, interfacial reaction and shear strength of the Al 2O3/Kovar joints were tested and analyzed by optical microscope, scanning electronic microscope(SEM), energy dispersive spectrometer(EDS) and universal testing machine.The results show that no obvious cracks were observed in both of the Al 2 O3/Ti-Ni/Kovar interface and Al 2 O3/Ag-Cu-Ti/Kovar interface , however the shear strength and leakage rate of the Al 2 O3/Ag-Cu-Ti/Kovar joint are 85 MPa and less than 0.5 ×10 -10 Pa· m3/s, respectively, both are better than those of the Al2 O3/Ti-Ni/Kovar joint which shear strength is 67 MPa and leakage rate is about 2.0 ×10 -10 Pa· m3/s.%采用Ti-Ni及Ag-Cu-Ti为过渡层材料实现了Al2 O3陶瓷与Kovar合金的热等静压扩散连接。利用金相显微镜、SEM、EDS和万能试验机等测试分析了Al2 O3/Kovar扩散接头的显微组织、界面反应及剪切强度。结果表明,Al2 O3/Ti-Ni/Kovar接头连接界面处无孔洞等显微缺陷,但其强度及气密性较低,剪切强度及漏率分别为67 MPa及约2.0×10-10 Pa· m3/s;Al2 O3/Ag-Cu-Ti/Kovar接头之间界面连接良好,无明显显微缺陷,接头强度及气密性较高,剪切强度及漏率分别为85 MPa及<0.5×10-10 Pa· m3/s。

  8. Numerical Simulation of Water/Al2O3 Nanofluid Turbulent Convection

    Directory of Open Access Journals (Sweden)

    Vincenzo Bianco

    2010-01-01

    Full Text Available Turbulent forced convection flow of a water-Al2O3 nanofluid in a circular tube subjected to a constant and uniform temperature at the wall is numerically analyzed. The two-phase mixture model is employed to simulate the nanofluid convection, taking into account appropriate thermophysical properties. Particles are assumed spherical with a diameter equal to 38 nm. It is found that convective heat transfer coefficient for nanofluids is greater than that of the base liquid. Heat transfer enhancement is increasing with the particle volume concentration and Reynolds number. Comparisons with correlations present in the literature are accomplished and a very good agreement is found with Pak and Cho (1998. As for the friction factor, it shows a good agreement with the classical correlation used for normal fluid, such as Blasius formula.

  9. Influence of Sonication on the Stability and Thermal Properties of Al2O3 Nanofluids

    Directory of Open Access Journals (Sweden)

    Monir Noroozi

    2014-01-01

    Full Text Available Nanofluids containing Al2O3 nanoparticles (either 11 or 30 nm in size dispersed in distilled water at low concentrations (0.125–0.5 wt% were prepared using two different ultrasonic devices (a probe and a bath sonicator as the dispersant. The effect of the ultrasonic system on the stability and thermal diffusivity of the nanofluids was investigated. Thermal diffusivity measurements were conducted using a photopyroelectric technique. The dispersion characteristics and morphology of the nanoparticles, as well as the optical absorption properties of the nanofluids, were studied using photon cross correlation spectroscopy with a Nanophox analyzer, transmission electron microscopy, and ultraviolet-visible spectroscopy. At higher particle concentration, there was greater enhancement of the thermal diffusivity of the nanofluids resulting from sonication. Moreover, greater stability and enhancement of thermal diffusivity were obtained by sonicating the nanofluids with the higher power probe sonicator prior to measurement.

  10. Experimental Study of the Freezing Point of γ-Al2O3/Water Nanofluid

    Directory of Open Access Journals (Sweden)

    Thierry Maré

    2012-01-01

    Full Text Available Nanofluids are colloidal suspensions made of nanometer-sized particles dispersed in a conventional fluid. Their unusual thermal properties explain intensive investigations for several thermal and industrial applications. In this work, an experimental investigation was performed to measure the freezing point and to study the supercooling point made of alumina γ-Al2O3 nanoparticles with 30 nm diameter size and deionized water. Particles' volume fraction used in this work is ranging from 1% to 4%. The T-historic method based on the measurement of the point of inflexion was performed to measure the thermal properties such as the freezing point and the latent heat of solidification of the nanofluids for different concentrations. The results show that the supercooling degree decreases for the high particles volume concentrations and that the agglomeration does not influence the temperature of the freezing point. However, it makes the freezing process longer.

  11. Solidified structure and solute segregation in Al2O3/A356-La alloy composites

    Institute of Scientific and Technical Information of China (English)

    LIU Zheng; TU Tao

    2006-01-01

    Al2O3/A356-La alloy composites were fabricated by squeeze casting, and the effects of La on the solidified structure and the solute segregation during alloy solidification were studied. The results indicate that the structure of the matrix alloy becomes fine and small by the addition of La. La has been richened at the interface to help improve the wettability between the fiber and Al alloy, but there are no intermetallic compounds richening La found at the interface yet. There is no special influence of La on the Mg segregation in the matrix alloy. The distribution of Mg and La in the composites has been at the same position-near the interface.

  12. Pseudo-semi-solid thixoforging of cup shell with Al/Al2O3

    Institute of Scientific and Technical Information of China (English)

    LUO Shou-jing; CHENG Yuan-sheng; WANG Peng-xiang

    2006-01-01

    A new technology-the thixoforging of ceramics/metal composites in pseudo-semi-solid state was proposed based on the powder metallurgy technology combined with semi-solid metal forming process, and the cup shell of automobile piston with Al2O3/Al composites was prepared. It is proved through metallographic analyses and three-point bending tests that the technology is feasible for the ceramics/metal composites forming. The results show that the tough strength and the degree of hardness of the samples with certain plasticity are high. It will play a very large role in accelerating the ceramics composites and high melt point materials use in more fields and tamp the foundation for further studies of this technology.

  13. Surface Oxidation of Al2O3/SiC Nanocomposite: Phase Transformation and Microstructure

    Institute of Scientific and Technical Information of China (English)

    Cai Shu; Peng Zhenzhen; Feng Jie; Lu Feng

    2005-01-01

    The surface oxidation behavior of pressureless sintered Al2O3/SiC nanocomposite was studied from 1000 to 1400 ℃ for more than 10 h in air. Weight gain during the process of heat treatment was measured by TG analysis. Phase transformation and microstructure changes of these specimens due to oxidation were investigated with X-ray diffraction (XRD), SEM and EDX technology. Thermogravimetric analysis show that the weight gain as a result of oxidation of SiC become significant above 1200 ℃. In the range of 1000~1300 ℃, the SiC grits are usually coated with a layer of amorphous silica after oxidation. Above 1300 ℃, the amorphous silica reacted with alumina matrix and formed mullite or crystallized into cristobalite. The rate of oxidation depends on the formation of dense cristobalite film. Large amount of needle-like mullite and alumina crystals are formed on the surface after oxidation at 1400 ℃.

  14. Fabrication and properties of functionally graded NiAl/Al2O3 composites

    Science.gov (United States)

    Miller, D. P.; Lannutti, J. J.; Noebe, R. D.

    1993-01-01

    A modified sedimentation process was used in the production of a functionally gradient material (FGM), NiAl/Al2O3. A simple finite element model was used to guide our design and fabrication efforts by estimating residual stress states as a function of composite structure. This approach could lead to tailored designs that enhance or avoid specific residual stress states. Thermal cycling tests were factored into the model to predict time dependent or steady-state internal temperature and stress profiles. Four-point bend tests were conducted to establish the mechanical load-displacement behavior of a single interlayer FGM at room temperature, 800 and 1000 K. Room temperature bend strength of the FGM was 3-4 times that of the base NiAl. At elevated temperatures, composite fracture occurred in a gradual, noncatastrophic mode involving NiAl retardation of a succession of cracks originating in the alumina face.

  15. Effect of Metallic Zn Powder on Oxidation Resistance of Al2O3-C Refractories

    Institute of Scientific and Technical Information of China (English)

    LI Youqi; KE Changming; LI Yousheng; LI Nan

    2006-01-01

    Al2O3-C specimens were prepared by using tabular corundum,flaky graphite,Al,Si,and Zn powder as starting materials and phenolic formaldehyde resin as binder.Keeping the mass ratios of tabular corundum,flaky graphite,Al and Si constant,different contents of ZN(0,0.5%,1%,2%and 3%)were added respectively.The specimens were heat treated at 120-220℃ for 24h,and then fired at 1400℃ .for 3h in air atmosphere. The mass change rate, thickness of decarburization layer, apparent porosity, bulk density and microstructure of the products were determined and observed by means of SEM and EDX.The results show that the specimen with 2% Zn was characterized by minimum in thickness of decarburization layer and in apparent porosity and maximum in bulk density. Consequently, the specimen with 2% metal Zn is supposed to perform the best oxidation resistance.

  16. Wear Resistance of Aluminum Matrix Composites Reinforced with Al2O3 Particles After Multiple Remelting

    Science.gov (United States)

    Klasik, Adam; Pietrzak, Krystyna; Makowska, Katarzyna; Sobczak, Jerzy; Rudnik, Dariusz; Wojciechowski, Andrzej

    2016-08-01

    Based on previous results, the commercial composites of A359 (AlSi9Mg) alloy reinforced with 22 vol.% Al2O3 particles were submitted to multiple remelting by means of gravity casting and squeeze-casting procedures. The studies were focused on tribological tests, x-ray phase analyses, and microstructural examinations. More promising results were obtained for squeeze-casting method mainly because of the reduction of the negative microstructural effects such as shrinkage porosity or other microstructural defects and discontinuities. The results showed that direct remelting may be treated as economically well-founded and alternative way compared to other recycling processes. It was underlined that the multiple remelting method must be analyzed for any material separately.

  17. Magnesium Effect to the Hardness of Al2O3/Al Ceramic Matrix Composites

    Directory of Open Access Journals (Sweden)

    Eddy S. Siradj

    2009-04-01

    Full Text Available Composite is an alternative materialwhich has satisfying properties and can be accommodated for certain applications. Ceramic Matrix Composites (CMCsis one of the composite types that are very interesting in terms of high temperature applications material. In this paper,we investigate the effects of Mg addition on the hardness of Al2O3 Ceramic Matrix Composites which was produced bydirected metal oxidation (Dimox method. The CMCs material is made by placing Al ingot under mixture alumina andpercentage of Mg 5, 8, 10, and 12% wt. The processing temperature was 1100°C for 24 hours followed by cooling toroom temperature in the furnace. The results show that increasing of infiltration, the hardness increased to 1221 VHNmaximum at 8% wt Mg and then decrease again as the increment amount of Mg.

  18. CoFe2/Al2O3/PMNPT multiferroic heterostructures by atomic layer deposition

    Science.gov (United States)

    Zhou, Ziyao; Grocke, Garrett; Yanguas-Gil, Angel; Wang, Xinjun; Gao, Yuan; Sun, Nianxiang; Howe, Brandon; Chen, Xing

    2016-05-01

    Multiferroic materials and applications allow electric bias control of magnetism or magnetic bias control of polarization, enabling fast, compact, energy-efficient devices in RF/microwave communication systems such as filters, shifters, and antennas; electronics devices such as inductors and capacitors; and other magnetic material related applications including sensors and memories. In this manuscript, we utilize atomic layer deposition technology to grow magnetic CoFe metallic thin films onto PMNPT, with a ˜110 Oe electric field induced ferromagnetic resonance field shift in the CoFe/Al2O3/PMNPT multiferroic heterostructure. Our work demonstrates an atomic layer deposition fabricated multiferroic heterostructure with significant tunability and shows that the unique thin film growth mechanism will benefit integrated multiferroic application in near future.

  19. Usage of Porous Al2O3 Layers for RH Sensing

    CERN Document Server

    Timár-Horváth, Veronika; Vass-Várnai, András; Perlaky, Gergely

    2008-01-01

    At the Department of Electron Devices a cheap, more or less CMOS process compatible capacitive type RH sensor has been developed. Capacitive sensors are based on dielectric property changes of thin films upon water vapour uptake which depends on the surrounding media's relative humidity content. Because of the immense surface-to-volume ratio and the abundant void fraction, very high sensitivities can be obtained with porous ceramics. One of the ceramics to be used is porous Al2O3, obtained by electrochemical oxidation of aluminium under anodic bias. The average pore sizes are between 6...9 nm. In our paper we intend to demonstrate images representing the influence of the technological parameters on the porous structure and the device sensitivity.

  20. Process Optimization for Suppressing Cracks in Laser Engineered Net Shaping of Al2O3 Ceramics

    Science.gov (United States)

    Niu, F. Y.; Wu, D. J.; Yan, S.; Ma, G. Y.; Zhang, B.

    2017-03-01

    Direct additive manufacturing of ceramics (DAMC) without binders is a promising technique for rapidly fabricating high-purity components with good performance. Nevertheless, cracks are easily generated during fabrication as a result of the high intrinsic brittleness of ceramics and the great temperature gradients. Therefore, optimizing the DAMC process is a challenge. In this study, direct fabrication of Al2O3 single-bead wall structures are conducted with a laser engineered net shaping (LENS) system. A new process optimization method for suppressing cracks is proposed based on analytical models, and then the influence of process parameters on crack number is discussed experimentally. The results indicate that the crack number decreases obviously with the increase of scanning speed. Single-bead wall specimens without cracks are successfully fabricated by the optimized process.

  1. Joint Strength with Soldering of Al2O3 Ceramics After Ni-P Chemical Plating

    Institute of Scientific and Technical Information of China (English)

    邹贵生; 吴爱萍; 张德库; 孟繁明; 白海林; 张永清; 黎义; 巫世杰; 顾兆旃

    2004-01-01

    Ni-P alloy was chemically plated on Al2O3 ceramics to produce uniform alloy coatings at temperatures below 70℃. Cu metal was electroplated onto the Ni-P coating to facilitate the soldering and shorten the chemical plating time. Then, the electroplated ceramic specimens were soldered with 60 wt.% Sn-40 wt.% Pb solder in active colophony. The highest shear strength was acquired after the heat treatment at 170℃ for 15 min. The joint fractures mostly propagated along the interface between the ceramics and the Ni-P coating, with some fracture in both the ceramics and the Ni-P coating near the interface and some along the interface between the Cu and Ni-P coatings. The results show that ceramic surface roughness and the chemical plating parameters influence the coating quality, and that suitable heat treatment before the soldering also improves the adhesion between the ceramics and Ni-P coatings, thus strengthening the joints.

  2. AN EXPERIMENTAL STUDY ON HEAT TRANSFER AND FRICTION FACTOR OF AL2O3 NANOFLUID

    Directory of Open Access Journals (Sweden)

    K.V. Sharma

    2011-12-01

    Full Text Available L. Syam Sundar1 and K.V. Sharma2This paper reports experimental investigations of fully developed laminar convective heat transfer and friction factor characteristics of different volume concentrations of Al2O3 nanofluid in a plain tube, fitted with different twist ratios of twisted tape inserts. Experiments are conducted with water and nanofluid in the range of 700

  3. Bimodal substrate biasing to control \\gamma-Al2O3 deposition during reactive magnetron sputtering

    CERN Document Server

    Prenzel, Marina; Stein, Adrian; von Keudell, Achim; Nahif, Farwah; Schneider, Jochen M

    2013-01-01

    Al2O3 thin films have been deposited at substrate temperatures between 500{\\deg}C to 600{\\deg}C by reactive magnetron sputtering using an additional arbitrary substrate bias to tailor the energy distribution of the incident ions. The films were characterized by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The film structure being amorphous, nanocrystalline, or crystalline was correlated with characteristic ion energy distributions. The evolving crystalline structure is connected with different levels of displacements per atom (dpa) in the growing film as being derived from TRIM simulations. The boundary between the formation of crystalline films and amorphous or nanocrystalline films was at 0.9 dpa for a substrate temperature of 500{\\deg}C. This threshold shifts to 0.6 dpa for films grown at 550{\\deg}C.

  4. Sintering Behaviour of Al2O3-SiC-C Ramming Mix

    Institute of Scientific and Technical Information of China (English)

    WUXingrong; CAOFeng

    2004-01-01

    Silicon fines, boron acid solid powders and microfine SiO2 as sintering agents were incorporated into Al2O3-SiC-C ramming mix in order to investigated their effects on the microstructure , mechanical properties and sintering behavior of the ramming mix. Results show that all the three agents could improved both densification and mehanical properties markedly, compared to that of non-agent specimens and the effect of the composite of boron acid solid powders and microfine SiO2 is the best. The oxidation resistance increased with the addition of agents, which is supported by densification. Microstructures showed that agent powders could fill pores or produce liquid phases at high temperature, therefore, improve the sintering of the ramming mix.

  5. Sintering Behaviour of Al2O3-SiC-C Ramming Mix

    Institute of Scientific and Technical Information of China (English)

    WU Xingrong; CAO Feng

    2004-01-01

    Silicon fines, boron acid solid powders and microfine SiO2 as sintering agents were incorporated into Al2O3-SiC-C ramming mix in order to investigated their effects on the microstructue,mechanical properties and sintering be-havior of the ramming mix.Results show that all the three agents could improved both densification and mehanical properties markedly,compared to that of non-agent speci-mens and the effect of the composite of boron acid solid powders and microfine SiO2 is the best.The oxidation re-sistance increased with the addition of agents,which is supported by densification.Microstructures shoued that a-gent powders could fill pores or produce liquid phases at high temperatuer,therefore,improve the sintering of the ramming mix.

  6. Directed photoluminescent emission of ZnO tetrapods on biotemplated Al2O3

    Science.gov (United States)

    Rambo, Carlos R.; Hotza, Dachamir; Cunha, Carlo R. da; Zollfrank, Cordt

    2013-12-01

    In this work biomorphic Al2O3 with microcellular morphology was produced by biotemplating of rattan and coating with ZnO tetrapods (T-ZnO). The morphological features of the biomorphic ceramics were evaluated, as well as the photoluminescent properties of the final device. The T-ZnO-coated microvessels of rattan metaxylem acted as structural guides for the directional travel of light. Therefore, the intensity of the green emission was controlled through orientation of the device with respect to the microvessels axis. Microcellular ceramics coated with functional materials such as ZnO can be used to design novel optoelectronic sensing devices in applications that require control of the emitted luminescence signal.

  7. The Characteristics of the Surface Topography of Excimer Laser Processed Al2O3 Ceramic

    Institute of Scientific and Technical Information of China (English)

    LIUYing; WENShi-zhu

    2004-01-01

    Surface of Al2O3 ceramic was processed by an excimer laser and the characteristics of topography were examined based on the application of thesystem(MEMS). It is indicated that the statistic pararueters of surface topography processed by the excimer laser have an obvioas regularity. The arithmeticmean value Ro and the root-mean square value Rq change with the changing of processing parameters in the same step and trend, and there is a quantitative relation between them. A simplified nuuIel is proposed for the excimer laser processing surface profile, whose results of the analysis and calculation agree basically with the experimental data. Furthermore, the surfaces processed by excimer laser are greatly fiat. Skewness root-mean-square value Zq changed little with the change of the technological parameters. The above characteristics depend on the processing principle of excimer laser, quite different from the cutting processing.

  8. Dilatometric studies of Y2W3O12 with added Al2O3

    Indian Academy of Sciences (India)

    S Sumithra; A M Umarji

    2003-10-01

    Y2W3O12 exhibits negative thermal expansion along the three crystallographic directions due to the transverse thermal vibrations perpendicular to the Y-O-W linkage. It is highly hygroscopic and forms a trihydrate structure at room temperature. Dilatometric studies of Y2W3O12 show large thermal expansion hysteresis due to large grain size and a large initial positive thermal expansion due to the removal of water molecules. Al2O3 has been added to Y2W3O12 up to 10 wt% in an attempt to overcome the hygroscopicity and reduce the particle size and thereby the thermal expansion hysteresis. Thermo gravimetric, dilatometric and electron microscopic studies are presented to support these observations.

  9. Controlling Pore Size and its Distribution of γ-Al2O3 Nanofiltration Membranes

    Institute of Scientific and Technical Information of China (English)

    Rong Chun XIONG; Xiao Dong LEI; Gang WEI

    2003-01-01

    The preparation process of γ-Al2O3 nanofiltration membranes were studied by N2absorption and desorption test and retention rate vs thickness gradient curve method. It was foundthat template and thermal treatment were key factors for controlling pore size and its distribution.Under the optimized experimental conditions, the BJH (Barret-Joyner-Halenda) desorption averagepore diameter, BJH desorption cumulative volume of pores and BET (Brunauer-Emmett-Teller)surface area of obtained membranes were about 3.9 nm, 0.33 cm3/g and 245 m2/g respectively, thepore size distribution was very narrow. Pore size decreased with the increasing of thickness andno evident change after the dense top layer was formed. The optimum thickness can becontrolled by retention rate vs thickness gradient curve method.

  10. Probing the Physical Conditions of Supernova Ejecta with the Measured Sizes of Presolar Al2O3 Grains

    CERN Document Server

    Nozawa, Takaya; Hasegawa, Yasuhiro; Kozasa, Takashi

    2015-01-01

    A few particles of presolar Al2O3 grains with sizes above 0.5 mum are believed to have been produced in the ejecta of core-collapse supernovae (SNe). In order to clarify the formation condition of such large Al2O3 grains, we investigate the condensation of Al2O3 grains for wide ranges of the gas density and cooling rate. We first show that the average radius and condensation efficiency of newly formed Al2O3 grains are successfully described by a non-dimensional quantity "Lambda_on" defined as the ratio of the timescale with which the supersaturation ratio increases to the collision timescale of reactant gas species at dust formation. Then, we find that the formation of submicron-sized Al2O3 grains requires at least ten times higher gas densities than those presented by one-dimensional SN models. This indicates that presolar Al2O3 grains identified as a SN origin might be formed in dense gas clumps, allowing us to propose that the measured sizes of presolar grains can be a powerful tool to constrain the physic...

  11. Performance of Pd/CeO2-ZrO2-Al2O3 catalyst for motorcycle

    Institute of Scientific and Technical Information of China (English)

    ZHAO; Ming; CHEN; Shanhu; ZHANG; Xiaoyu; GONG; Maochu; CHE

    2009-01-01

    The Pd-only catalysts for motorcycle were prepared by impregnating CeO2-ZrO2-Al2O3 and CeO2-ZrO2+Al2O3 with PdCl2 aque-ous solution and characterized by X-ray diffraction (XRD), oxygen storage capacity (OSC) and H2-temperature-programmed reduction (H2-TPR) methods. The XRD result indicated that the CeO2-ZrO2-Al2O3 compound prepared by co-precipitation formed a single solid solu-tion and had good thermal stability, and Pd phase was not observed in all catalysts. The TPR results showed that the reduction temperature of Pd/CeO2-ZrO2-Al2O3 catalyst was lower than that of Pd/CeO2-ZrO2+Al2O3 catalyst whether they were fresh or aged catalysts. The Pd/CeO2-ZrO2-Al2O3 exhibited high three-way catalytic activity at low temperature, high thermal stability, and wide working window, sug-gesting a great potential for applications.

  12. Immuno-allergological properties of aluminium oxide (Al2O3) ceramics and nickel sulfate in humans.

    Science.gov (United States)

    Thomas, P; Barnstorf, S; Summer, B; Willmann, G; Przybilla, B

    2003-03-01

    For more than 30 years aluminium oxide (Al(2)O(3)) ceramics have been used for implants in maxillofacial and orthopaedic surgery. Up to now, there are no reports and also no investigations on hypersensitivity reactions. In order to evaluate the aspects of immuno-allergological reactivity to aluminium oxide ceramics, skin testing and in vitro lymphocyte activation studies were performed. The patch test reactivity to a standard series of contact allergens and to an aluminium oxide (Al(2)O(3)) disk was examined in a consecutive series of 250 patients frequenting a University Dermatology Clinic. Furthermore, peripheral blood mononuclear cells (PBMC) of 15 nickel-allergic and 15 non-allergic individuals were cultured with medium alone, with the pan T-cell mitogen phytohemagglutinine (PHA) or with nickel sulfate (NiSO(4)). By additional presence/absence of Al(2)O(3) disk its influence on the cytokine secretion pattern and proliferative response was investigated. The results show that in contrast to a high frequency of delayed-type hypersensitivity to standard contact allergens, no allergic skin reactions to Al(2)O(3) ceramics occured. The IL-4 and IFN-gamma production in vitro remained almost unchanged by the presence of Al(2)O(3) disk as well as the proliferative response of PBMC of non-allergic individuals. Cellular reactivity of nickel allergic and non-allergic donors was partly enhanced upon contact to Al(2)O(3) disks.

  13. Electroless Ni-P-PTFE-Al2O3 Dispersion Nanocomposite Coating for Corrosion and Wear Resistance

    Science.gov (United States)

    Sharma, Ankita; Singh, A. K.

    2014-01-01

    With the aim to produce a coating having good corrosion and wear resistance alongside hardness but lesser friction coefficient, Ni-P-PTFE-Al2O3 (NiPPA) dispersion coating was developed. This was achieved by introducing nanosized polytetrafluoroethylene (PTFE) and alumina (Al2O3) in the Ni-P matrix deposited on mild steel substrate. The coating was characterized using scanning electron microscopy, energy dispersive analysis of x-ray, and x-ray diffractrometry. Microhardness and wear resistance of the coating was measured using Vicker's hardness tester and Pin-on-Disc method, respectively. The corrosion behavior was measured using electrochemical polarization and immersion tests with and without exposure in 3.5% NaCl solution. It is observed that codeposition of Al2O3 and PTFE particles with Ni-P coating results in comparatively smooth surface with nodular grains. The NiPPA coating was observed to have moderate hardness between electroless Ni-P-PTFE and Ni-P-Al2O3 coating and good wear resistance with lubricating effect. Addition of both PTFE and Al2O3 is observed to enhance corrosion resistance of the Ni-P coating. However, improvement in corrosion resistance is more due to addition of Al2O3 than PTFE. Continuous exposure for 10-20 days in corrosive solution is found to deteriorate corrosion protection properties of the coating.

  14. Characterization of Al2O3 optically stimulated luminescence films for 2D dosimetry using a 6 MV photon beam

    Science.gov (United States)

    Ahmed, M. F.; Shrestha, N.; Schnell, E.; Ahmad, S.; Akselrod, M. S.; Yukihara, E. G.

    2016-11-01

    This work evaluates the dosimetric properties of newly developed optically stimulated luminescence (OSL) films, fabricated with either Al2O3:C or Al2O3:C,Mg, using a prototype laser scanning reader, a developed image reconstruction algorithm, and a 6 MV therapeutic photon beam. Packages containing OSL films (Al2O3:C and Al2O3:C,Mg) and a radiochromic film (Gafchromic EBT3) were irradiated using a 6 MV photon beam using different doses, field sizes, with and without wedge filter. Dependence on film orientation of the OSL system was also tested. Diode-array (MapCHECK) and ionization chamber measurements were performed for comparison. The OSLD film doses agreed with the MapCHECK and ionization chamber data within the experimental uncertainties (response was approximately linear from the MDD up to a few grays (the linearity correction was  response, resolution and dosimetric properties. The negligible background and potential simple calibration make these OSLD films suitable for remote audits. The characterization presented here may motivate further commercial development of a 2D dosimetry system based on the OSL from Al2O3:C or Al2O3:C,Mg.

  15. Performance of Pd/CeO_2-ZrO_2-Al_2O_3 catalyst for motorcycle

    Institute of Scientific and Technical Information of China (English)

    ZHAO Ming; CHEN Shanhu; ZHANG Xiaoyu; GONG Maochu; CHEN Yaoqiang

    2009-01-01

    The Pd-only catalysts for motorcycle were prepared by impregnating CeO_2-ZrO_2-Al_2O_3 and CeO_2-ZrO_2+Al_2O_3 with PdCl_2 aque-ous solution and characterized by X-ray diffraction (XRD), oxygen storage capacity (OSC) and H_2-temperature-programmed reduction (H_2-TPR) methods. The XRD result indicated that the CeO_2-ZrO_2-Al_2O_3 compound prepared by co-precipitation formed a single solid solu-tion and had good thermal stability, and Pd phase was not observed in all catalysts. The TPR results showed that the reduction temperature of Pd/CeO_2-ZrO_2-Al_2O_3 catalyst was lower than that of Pd/CeO_2-ZrO_2+Al_2O_3 catalyst whether they were fresh or aged catalysts. The Pd/CeO_2-ZrO_2-Al_2O_3 exhibited high three-way catalytic activity at low temperature, high thermal stability, and wide working window, sug-gesting a great potential for applications.

  16. SINTESIS DAN KARAKTERISASI GAMMA ALUMINA (γ-Al2O3 DARI KAOLIN ASAL TATAKAN, SELATAN BERDASARKAN VARIASI TEMPERATUR KALSINASI

    Directory of Open Access Journals (Sweden)

    Utami Irawati

    2013-05-01

    Full Text Available Sintesis dan karakterisasi gamma alumina (γ-Al2O3 dari kaolin asal Tatakan, Kalimantan Selatan berdasarkan variasi temperatur kalsinasi telah dilakukan. Gamma alumina (γ-Al2O3 diperoleh dengan metode sol-gel. Polyethylene glycol 6000 digunakan sebagai template pembentuk pori, presipitasi dilakukan dengan penambahan NH4OH 2,6 M hingga pH larutan 8-9 untuk memperoleh Al(OH3. Kalsinasi dilakukan pada temperatur 500, 600, 700 dan 800 0C. Gamma alumina (γ-Al2O3 hasil kalsinasi kemudian di analisis menggunakan Fourier Transform Infrared (FTIR dan X-Ray Diftraction (XRD. Hasil analisis karakterisasi FTIR menunjukkan pada masing-masing variasi temperatur terbentuknya kerangka gamma alumina (γ-Al2O3 dan hasil XRD menunjukkan fasa alumina yang terbentuk adalah gamma alumina (γ-Al2O3. Struktur terbaik dari gamma alumina (γ-Al2O3 berdasarkan kekristalannya yaitu pada temperatur kalsinasi 700 0C dengan nilai 2θ = 46,06; 60,07 dan 66,93.

  17. Friction and wear properties of ultra-high molecular mass polyethylene reinforced with Al2O3 nano-particle

    Institute of Scientific and Technical Information of China (English)

    FAN Dong-li; XIONG Dang-sheng

    2004-01-01

    The ultra-high molecular mass polyethylene (UHMMPE) as an artificial joint acetabular material was filled with nano-powder of Al2O3 of various mass fractions. The effect of Al2O3 mass fraction on the hardness, wetting property and tribological properties of the Al2O3-UHMMPE composites under dry friction sliding against both stainless steel and Ti-6Al-4V alloy was investigated. The morphologies of the worn surfaces of composites were observed with optical microscope. The results show that, wetting property and wear resistance of the composites are improved by filling Al2O3, while the friction coefficient is decreased largely under dry friction as compared with that of the unfilled UHMMPE. This is attributed to the reinforcing function of the nano-powder of Al2O3 in the composites. The wear of UHMMPE is dominated by plowing, plastic deformation and fatigue wear; while the Al2O3-UHMMPE composites are characterized by the mild fatigue wear.

  18. Microwave dielectric properties of CaCu3Ti4O12-Al2O3 composite

    Science.gov (United States)

    Rahman, Mohd Fariz Ab; Abu, Mohamad Johari; Karim, Saniah Ab; Zaman, Rosyaini Afindi; Ain, Mohd Fadzil; Ahmad, Zainal Arifin; Mohamed, Julie Juliewatty

    2016-07-01

    (1-x)CaCu3Ti4O12 + (x)Al2O3 composite (0 ≤ x ≤0.25) was prepared via conventional solid-state reaction method. The fabrication of sample was started with synthesizing stoichiometric CCTO from CaCO3, CuO and TiO2 powders, then wet-mixed in deionized water for 24 h. The process was continued with calcined CCTO powder at 900 °C for 12 h before sintered at 1040 °C for 10 h. Next, the calcined CCTO powder with different amount of Al2O3 were mixed for 24 h, then palletized and sintered at 1040 °C for 10. X-ray diffraction analysis on the sintered samples showed that CCTO powder was in a single phase, meanwhile the trace of secondary peaks which belong to CaAl2O4 and Corundum (Al2O3) could be observed in the other samples Scanning electron microscopy analysis showed that the grain size of the sample is firstly increased with addition of Al2O3 (x = 0.01), then become smaller with the x > 0.01. Microwave dielectric properties showed that the addition of Al2O3 (x = 0.01) was remarkably reduced the dielectric loss while slightly increased the dielectric permittivity. However, further addition of Al2O3 was reduced both dielectric loss and permittivity at least for an order of magnitude.

  19. Electrical characteristics of multilayered HfO2-Al2O3 charge trapping stacks deposited by ALD

    Science.gov (United States)

    Spassov, D.; Paskaleva, A.; Guziewicz, E.; Luka, G.; AKrajewski, T.; Kopalko, K.; Wierzbicka, A.; Blagoev, B.

    2016-10-01

    Electrical and charge trapping properties of atomic layer deposited HfO2-Al2O3 multilayer stacks with two different Al2O3 sublayer thicknesses were investigated regarding their implementation in charge trapping non-volatile memories. The effect of post deposition annealing in oxygen at 600°C is also studied. The decreasing Al2O3 thickness increases the stack's dielectric constant and the density of the initial positive oxide charge. The initial oxide charge increases after annealing to ∼6×1012 cm-2 and changes its sign to negative for the stacks with thicker Al2O3. The annealing enhances the dielectric constant of the stacks and reduces their thickness preserving the amorphous status. Nevertheless the annealing is not beneficial for the stacks with thicker Al2O3 as it considerably increases leakage currents. Conduction mechanisms in stacks were considered in terms of hopping conduction at low electric fields, and Fowler- Nordheim tunnelling, Schottky emission and Poole-Frenkel effect at higher ones. Maximum memory windows of about 12 and 16V were obtained for the as-grown structures with higher and lower Al2O3 content, respectively. In latter case additional improvement (the memory window increase up to 23V) is achieved by the annealing.

  20. Preparation of porous Al2O3-Ti-C perform by combustion synthesis

    Directory of Open Access Journals (Sweden)

    K.Granat

    2009-04-01

    Full Text Available Using combustion synthesis porous ceramic preforms for composite reinforcing were produced. Prepared mixture of alumina Saffilfibres, Ti powder and graphite flakes, after drying were placed in waveguide of microwave reactor. Supplied with constant power of 540Wmagnetron ignited and maintained reaction in flowing stream of CO2 gas. Al2O3 fibres should improve preliminary endurance of perform,whereas Ti powder processed to hard titanium carbides and oxides. During microwave heating ignited plasma additionally improveprocess and partly fused metallic Ti. Recorded temperature curves were similar for various samples. The highest synthesis temperature revealed samples containing 10% of Al2O3 , 10% of Ti and 5% of graphite, all percentages atomic. Microscopic observation showed considerable microstructure inhomogeneity of some samples. Both irregular component ordering and partly processed Ti particles inside preform exclude them for subsequent infiltration. Chemical analyze EDS of Ti based compounds partly confirmed work purpose, evidencing presence of Ti oxides and carbides. Independently of graphite content these compounds formed folded strips around solid or empty volume. Depends on CO2 availability, reaction could be slowed down resulting in more compacted Ti compounds. Created as a result of combustion synthesis Ti compound after infiltration with liquid metal properly bounded with the matrix. It could be assumed that redox reaction proceeded and on surface of Ti compound alumina and Al-Ti compounds were created. The preforms of proper strength and homogeneous structure were infiltrated with AlSi7Mg by squeeze casting method. In relation to typical composite reinforced only with fibres no significant increase of defects quantity was observed. Preliminary examination of mechanical properties confirmed that assumed work purpose is reasonable.

  1. Electric properties of hyperbranch liquid crystalline/Al2O3/epoxy resin composites%超支化液晶/Al2O3/环氧树脂复合材料电性能研究

    Institute of Scientific and Technical Information of China (English)

    班建峰; 庞起; 梁春杰; 覃利琴; 韦庆敏

    2012-01-01

    采用机械共混及模压成型工艺将Al2O3粉体,含H20哑铃状液晶化合物(HLCP)与环氧树脂(E-51)共混制备了HLCP/EP/Al2O3复合材料。研究了Al2O3含量对材料热稳定性、导电性能、导热性能及热膨胀的影响。结果表明:材料的导热系数、介电常数及热稳定性随Al2O3含量的增加而增大,当Al2O3粉体质量分数达到70%时,材料导热系数是纯环氧树脂的1.7倍;介电损耗、线膨胀系数随Al2O3含量的增加而减小,当Al2O3粉体质量分数为60%时,介电常数为3.71。同时,由于HLCP网格的存在,降低了材料的内耗,提高了复合材料的玻璃化转变温度,增强了电性能。%The EP/HCLP/Al2O3 composites were prepared by mchanical mixing and compression molding of Al2O3 powder,dumbbell-shaped liquid crystal compounds containing H20(HLCP) and epoxy resin(E-51).The effect of Al2O3 content on the thermal stability,electric properties,heat conducting property and thermal expansion of the composites were studied.The results showed that the thermal conductivity,dielectric constant and thermal stability were increased with the increasing of Al2O3 content.The thermal conductivity of the material with Al2O3 powder mass fraction of 70% was 1.7 times than that of pure epoxy resin.The dielectric loss and linear expansion coefficient were decreased with the increasing of Al2O3 content.The dielectric constant of the composite with Al2O3 powder mass fraction of 60% was 3.71.The same time,due to the existence of liquid crystal compound(HLCP) grid,the internal friction of the material was reduced.The composite glass transition temperature was improved and electrical properties were enhanced.

  2. 复合活性钎料钎焊Cu与Al2 O3的接头组织及性能%Microstructure and performance of the Cu/Al2O3 joint brazed with active composite filler

    Institute of Scientific and Technical Information of China (English)

    周英豪; 刘多; 雷玉珍; 宋晓国; 冯吉才

    2016-01-01

    为改善紫铜与Al2 O3陶瓷的连接强度,采用纳米-Al2 O3增强的AgCuTi复合钎料( AgCuTip )对紫铜与Al2 O3陶瓷进行了真空钎焊.采用扫描电镜、能谱分析以及剪切试验对钎焊接头微观组织及力学性能进行了分析.钎焊接头典型界面组织为紫铜/扩散层/铜基固溶体+银基固溶体+ Ti2 Cu + Ti3( Cu, Al)3 O/Al2 O3.纳米-Al2 O3的添加抑制了Al2 O3侧反应层的生长,并促进钎缝中形成弥散分布的Ti2Cu相.随着保温时间的延长,铜侧扩散层和Ti3(Cu, Al)3O反应层的厚度逐渐增大.保温时间为20 min时,铜母材向钎料过度溶解,降低了接头性能.当钎焊温度为880°C,保温10 min时,接头抗剪强度最高为82 MPa.纳米颗粒的加入细化了钎缝组织并降低了母材与钎缝热膨胀系数的不匹配,因此提高了接头的连接性能.保温时间可影响界面组织及反应层的厚度,进而影响接头的连接强度.%In order to improve the strength of Cu/Al2 O3 joint, vacuum brazing of copper to Al2 O3 ceramic was performed using nano -Al2O3 strengthened AgCuTi composite filler ( abbreviated as AgCuTip filler ). The microstructure and mechanical performance of the brazed joint were investigated by scanning electron microscope ( SEM ) , energy dispersive spectrometer ( EDS ) and shear strength test. Typical interfacial microstructure of Cu/AgCuTip/Al2O3 brazed joint is Cu/diffusion layer/Cu-based solid solution + Ag-based solid solution+Ti2 Cu +Ti3( Cu, Al) 3 O/Al2 O3 . The addition of nano-Al2 O3 can improve the interfacial microstructure by inhibiting the growth of reaction layer near Al2 O3 ceramic side, and promoting the formation of dispersed Ti2 Cu phase in brazing seam. Moreover, both thickness of diffusion layer and Ti3(Cu, Al)3O reaction layer thickened with an increasing holding time. Excessive dissolution of copper was occurred when holding time reached 20 min, which

  3. Study on technology of preparing high-purity α-Al2O3 powder%制备高纯度α-Al2O3粉体的工艺研究

    Institute of Scientific and Technical Information of China (English)

    吴沙沙; 王俊勃; 江燕; 王彦龙; 赵文杰; 杨尔慧

    2015-01-01

    The precursor Al(OH)3 of Al2 O3 were prepared by chemical precipitation with aluminium ni-trate and sal volatile under different concentration of aluminium nitrate,and Al2 O3 powders were getted through calcining precursor at different temperature. The powders were analyzed by the TG-DTG,XRD, BET and SEM. The results showed that the calcination temperature was an important factor to the crystal form of the Al2 O3 powder. The powders with good dispersing were obtained when the concentration of alu-minium nitrate was 0. 1 mol/ L. The sphere-like α-alumina powders with high purity were obtained when the calcination temperature was 1 200 ℃.%以硝酸铝和碳酸铵为原料,采用化学沉淀法,在不同硝酸铝浓度下制备 Al2 O3的前驱体 Al(OH)3,再经不同温度煅烧得到 Al2 O3粉体。利用 TG-DTG、XRD、BET 及 SEM 等分析手段对粉体的性能进行了表征。结果表明,煅烧温度对 Al2 O3的晶型有着重要的影响,硝酸铝浓度为0.1 mol/ L 时制备出的粉体分散性较好,经1200℃煅烧能制备出纯度较高的形貌类似球形的α-Al2 O3粉体。

  4. 不同形貌Ni/γ-Al2O3催化剂催化CO甲烷化反应的研究%CO methanation over Ni/γ-Al2 O3 catalysts with different morphologies

    Institute of Scientific and Technical Information of China (English)

    马胜利; 谭猗生; 张清德; 韩怡卓

    2011-01-01

    NiO with different morphologies were prepared by precipitation method and then the NiO/γ-Al2O3 catalysts were prepared from NiO and γ-Al2O3 by grind-mixing method. These catalysts were characterized by means of TEM, XRD and H2-TPR techniques. TEM images show that the morphologies of three NiO phases ( aNiO, b-NiO and c-NiO) obtained are in the shape of rod, granule and sheet, respectively. H2-TPR profiles show that the oxidabilities of these catalysts are in the order of b-NiO/γ-Al2O3 < a-NiO/γ-Al2O3 < c-NiO/γ-Al2O3.XRD patterns show that the crystalline sizes of Ni in these catalysts after reduction are in the order of b-Ni > a-Ni > c-Ni. CO methanation was carried out over the Ni/γ-Al2O3 catalysts in a continuous flow fixed-bed reactor and the effects of mixing method and morphology of active species on the catalysts perforce were investigated. It is found that the catalyst prepared from grind-mixing exhibits higher activity and stability than that obtained from simple-mixing. The catalytic activities of these catalysts with different morphologies for CO methanation follow the order of c-Ni/γ-Al2O3> a-Ni/γ-Al2O3> b-Ni/γ-Al2O3. Over the c-Ni/γ-Al2O3 catalyst (wNi = 15% ) under the conditions of atmospheric pressure, 593 K and a space velocity of 2 500 h-1 , the conversion of CO and the selectivity to CH4 reach 99.63% and 90.80%, respectively.%采用沉淀法分别以乙二醇、水、乙二醇-聚乙二醇600为修饰剂,制备了形貌分别为棒状(a-NiO)、粒状(b-NiO)和片状(c-NiO)结构的NiO催化剂,然后和γ-Al2O3通过研混法制得NiO/γ-Al2O3催化剂.采用XRD、TEM及H2-TPR等技术手段对催化剂进行了表征.TEM观察NiO的形貌分别为棒状、粒状和片状.H2-TPR结果表明,NiO/γ-Al2O3催化剂的氧化中心数量顺序为b-NiO/γ-Al2O3<a-NiO/γ-Al2O3<c-NiO/γ-Al2O3.XRD结果表明,NiO/γ-Al2O3催化剂还原后的Ni晶粒尺寸大小为b-Ni>a-Ni>c-Ni.在连续流动固定床反应装置上考察了Ni/γ-Al

  5. 轻质高强度C/Al2O3复合气凝胶的制备及表征%Synthesis and Characterization of Light and High-Strength C/Al2O3 Composite Aerogels

    Institute of Scientific and Technical Information of China (English)

    仲亚; 张君君; 沈晓冬; 崔升; 孔勇; 滕凯明

    2013-01-01

    采用溶胶-凝胶法和CO2超临界干燥工艺制备RF/Al2O3复合气凝胶,再经高温热处理过程得到轻质高强度C/Al2O3复合气凝胶,研究了不同热处理温度对气凝胶结构的影响,利用氮气吸附、X射线衍射、扫描电子显微镜和透射电子显微镜等手段对气凝胶的结构和性能进行了分析并且测试了不同热处理温度样品的压缩强度.实验结果表明:C/Al2O3复合气凝胶具有均匀的三维网络结构且成块性好,随着热处理温度的升高,气凝胶比表面积和强度均先增大后减小,当1 400℃时,C/Al2O3复合气凝胶比表面积最高,为831 m2·g-1,压缩强度最大,为9.5 MPa.%Resorcinol-formaldehyde/alumina composite (RF/Al2O3) aerogels were prepared using sol-gel techniques and supercritical fluid CO2 drying. RF/Al2O3 aerogels were successfully converted to light and high-strength carbon/alumina composite (C/Al2O3) aerogels after high temperature thermal treatment process. The effects of different thermal treatment temperature on the aerogels structures were studied. The structures and properties of aerogels were analyzed by means of BET, XRD, SEM, TEM and the compressive strengths were also measured. The experimental results showed that the as-synthesized C/Al2O3 aerogels with great monolithic morphology exhibited a three-dimensional network structure. With the increasing of thermal treatment temperature, both specific surface area and compressive strength of aerogels were first increase and then decrease. In particular, the C/Al2O3 aerogels treated by the thermal treatment temperature of 1 400℃ had the highest specific surface area and compressive strength (831 m2 · g-1 and 9.5 MPa, respectively).

  6. Microstructures of Porous Al2 O3 -ZrO2 Ceramics%多孔 Al2O3-ZrO2陶瓷的微观结构

    Institute of Scientific and Technical Information of China (English)

    杜红菊

    2015-01-01

    The low viscosity and high stability ceramic slurry were fabricated introducing Al2 O3 and ZrO2 ceramic powder as solute ,camphene as the solvent and Texaphor963 as additives .The por‐ous Al2 O3 -ZrO2 ceramics were prepared with high strength ceramic bodies by freezing casting meth‐od ,using pressureless sintering process .The microstructures of porous Al2 O3 -ZrO2 ceramics were studied in this paper .%以Al2 O3,ZrO2陶瓷粉体为溶质,以莰烯为溶剂,以Texaphor963作为添加剂,制备出低粘度高稳定性的陶瓷浆料,采用冷冻注模工艺制备出具有较高强度的陶瓷坯体,采用无压烧结工艺,得到了多孔Al2 O3-ZrO2陶瓷制品,并对其微观结构进行了研究。

  7. Influence of Na2O/Al2O3 and SiO2/Al2O3 ratios on the immobilization of Pb from electric arc furnace into the fly ash based geopolymers

    Directory of Open Access Journals (Sweden)

    Zejak R.

    2013-04-01

    Full Text Available Electric arc furnace dust (EAFD is by-product of iron and steel scrap remelting in electric arc furnace. This waste is classified as a hazardous material due to the leaching of heavy metals into the environment. Geopolymeryzation of fly ash into construction materials called - geopolymer is a considering as a possible way of immobilization of heavy metals from EAFD. Mechanical properties and chemical stability of geopolymers are mostly determined by the ratio between main oxides, Na2O, Al2O3 and SiO2. In this paper we have investigated possibility of Pb immobilization from EAFD into the fly ash based geopolymer. Geopolymers are synthesized at different Na2O/Al2O3 and SiO2/Al2O3 ratios. Compressive strength and chemical stability of geopolymers with respect to the leaching of Pb in water according to the EN 12457 regulation were tested. The results have shown that Na2O/Al2O3 and SiO2/Al2O3 ratios have influence on the compressive strength of geopolymers and Pb release in the water environment.

  8. Al2O3-H2O纳米悬浮液导热系数研究%Study on the Thermal Conductivity of Al2O3-H2O Nanosuspensions

    Institute of Scientific and Technical Information of China (English)

    李华; 朱冬生

    2010-01-01

    采用瞬变平面热源法测量了纳米Al2O3粉体分散于去离子水制备成的悬浮液的导热系数,分析了悬浮液的pH、分散剂的质量份额、纳米Al2O3粉体的质量份额等因素对悬浮液导热系数的影响.结果表明:在pH为8左右的时候,纳米Al2O3-H2O悬浮液的导热系数较大;悬浮液的导热系数随纳米Al2O3质量份额的增加而增加;在Al2O3纳米颗粒与SDBS分散剂质量分数比为1∶1时,悬浮液的导热系数较大,随着分散剂质量分数的增加,悬浮液的导热系数降低.

  9. DENSE TiC-Al2O3-Fe CERMET FABRICATED BY SHS%致密TiC-Al2O3-Fe金属陶瓷的自蔓延高温合成

    Institute of Scientific and Technical Information of China (English)

    张卫方; 韩杰才; 陈贵清; 尹京智; 陶春虎; 杜善义

    2000-01-01

    通过自蔓延高温合成结合准热等静压法(SHS/PHIP)制备出了致密的TiC-Al2O3-20Fe金属陶瓷.研究了延迟时间、高压持续时间、压力等工艺参数对金属陶瓷密实度的影响,分析了金属陶瓷的相组成、微观组织及性能.结果表明,燃烧合成过程中气体的排放和液相的存在是合成密实材料的关键,通过优化工艺合成了密实度为97.7%的TiC-Al2O3-20Fe金属陶瓷.金属陶瓷由TiC、Al2O3和Fe粘结相组成.粘结相Fe与Al2O3之间界面光滑,Fe与TiC之间有一较薄扩散层.TiC-Al2O3-20Fe金属陶瓷的抗弯强度和抗压强度分别为890 MPa和18.4 GPa.

  10. Viscosity and Structure Changes of CaO-SiO2-Al2 O3-CaF2 Melts with Substituting Al2 O3 for SiO2

    Institute of Scientific and Technical Information of China (English)

    Guo-hua ZHANG; Yu-lan ZHEN; Kuo-chih CHOU

    2016-01-01

    During the smelting process of the high Al steels,the reaction between SiO2 in molten slag and dissolved alumi-num in liquid steel always takes place.This aluminathermic reduction reaction will lead to the substitution of 1 mol SiO2 for 2/3 mol Al2 O3 .Therefore,the investigations about the influence of the ratio of Al2 O3 to SiO2 on viscosity and structure changes of mould flux during this process are very necessary.The viscosity variation of CaO-SiO2-Al2 O3-CaF2 melts was studied by changing compositions considering the aluminathermic reduction reaction.It was found that viscosity increased monotonously with gradually increasing the substitution extent.According to the Ra-man analysis,the substitution of Al2 O3 for SiO2 leads to the decrease of non-bridging oxygen but the increase of bridging oxygen.Therefore,degree of polymerization and viscosity increase as the substitution extent increases.By comparing the measured viscosities with the model calculated values,it was found that both the recently developed Zhang′s model and Roboud model could describe the viscosity variation behavior of CaO-SiO2-Al2 O3-CaF2 melts very well.

  11. Preparation of nanocomposite γ-Al2O3/polyethylene separator crosslinked by electron beam irradiation for lithium secondary battery

    Science.gov (United States)

    Nho, Young-Chang; Sohn, Joon-Yong; Shin, Junhwa; Park, Jong-Seok; Lim, Yoon-Mook; Kang, Phil-Hyun

    2017-03-01

    Although micro-porous membranes made of polyethylene (PE) offer excellent mechanical strength and chemical stability, they exhibit large thermal shrinkage at high temperature, which causes a short circuit between positive and negative electrodes in cases of unusual heat generation. We tried to develop a new technology to reduce the thermal shrinkage of PE separators by introducing γ-Al2O3 particles treated with coupling agent on PE separators. Nanocomposite γ-Al2O3/PE separators were prepared by the dip coating of polyethylene(PE) separators in γ-Al2O3/poly(vinylidenefluoride-hexafluoropropylene) (PVDF-HFP)/crosslinker (1,3,5-trially-1,3,5-triazine-2,4,6(1 H,3 H,5 H)-trione (TTT) solution with humidity control followed by electron beam irradiation. γ-Al2O3/PVDF-HFP/TTT (95/5/2)-coated PE separator showed the highest electrolyte uptake (157%) and ionic conductivity (1.3 mS/cm). On the basis of the thermal shrinkage test, the nanocomposite γ-Al2O3/PE separators containing TTT irradiated by electron beam exhibited a higher thermal resistance. Moreover, a linear sweep voltammetry test showed that the irradiated nanocomposite γ-Al2O3/PE separators have electrochemical stabilities of up to 5.0 V. In a battery performance test, the coin cell assembled with γ-Al2O3/PVDF-HFP/TTT-coated PE separator showed excellent discharge cycle performance.

  12. Effect of MgO on compositions of the system CaO-Al2O3-Fe2O3. Solubility

    Directory of Open Access Journals (Sweden)

    Palomo, Ángel

    1986-12-01

    Full Text Available Five different compositions belonging to the equilibrium system CaO-Al2O3-Fe2O3 were dopep with a fixed quantity of MgO (6,5% wt. The compositions, which lie in different primary fields of crystallization and in different triangles of compatibility, were submitted to several thermal treatments. Each composition, which had previously been melted, originates in its solidification the aluminates and ferrites which are usual in the interstitial phase of clinker Portland, although they are in different microstructural arrangements. The effect of MgO on the generated microstructures has been shown. Also, the solubility of MgO on the aluminic and ferritic phases has been measured.CCinco composiciones diferentes pertenecientes al sistema de equilibrio CaO-Al2O3-Fe2O3 fueron dopadas con una cantidad fija de MgO (6,5%. Las cinco composiciones, que están situadas sobre diferentes campos primarios de cristalización y/o sobre diferentes triángulos de compatibilidad, fueron sometidas a varios tratamientos térmicos. Cada composición (previamente fundida origina en su solidificación los aluminatos y ferritos habituales en la fase intersticial del clinker portland, aunque ordenados en microestructuras diferentes. Se ha comprobado el efecto del MgO sobre las microestructuras generadas, así como su solubilidad en las fases alumínicas y ferríticas.

  13. Preparation and Healing of Cracks in Al2O3-MgAION Composite

    Institute of Scientific and Technical Information of China (English)

    YANG Daoyuan; ZHU Kai; WU Juan

    2009-01-01

    The Al2O3-MgAION specimens with dimensions of φ20 mm×10 mm and 3 mm×4 mm×36 mm were pre-pared using corundum grains ( w( Al2O3) >98% , par-ticle size: 3-1 mm, ≤1 mm, ≤85 μm and ≤3 μm, respectively) and MgAION (particle size ≤ 2 μm ) as starting materials, PVA as binder, designing 3 formula-tions containing aggregate and 4 special formulations without aggregate, pressing under 150 Mpa and keep-ing for 5 s, firing at 1 500 ℃ for 2 h in nitrogen under normal pressure, and the cracks were prepared on the specimens by thermal shock method (air cooling at 1 100 ℃ for 10 cycles) and by Vickers method (29.4, 49.0 and 98.0 N, keeping for 25 s) , then holding at 1 100 ℃ and 1 550 ℃ for 6 h in nitrogen atmosphere for cracks healing, respectively. The influences of crack prefabricated method, grain composition, pressure of Vickers and pressure holding time on the shape and di-mension of cracks were studied. Effects of healing tem-perature on healing degree and MOR of specimens were investigated and the crack healing rate was calculated. The results showed that: (1) the cracks of MgAION specimens prepared by thermal shock method under nor-real pressure were of irregular shape and uncertain length; (2) the cracks prepared by Vickers method was approximate diamond-shape without slender cracks emit-ting from every vertex angle; but if composite specimens were fabricated by particles of several microns, the crack size, shape and its site, especially that obtained under 98.0 N for 25 s, could be controlled exactly under a Vickers hardometer, which made the crack healing re-search easy to conduct; (3) after healing treatment at 1 100 ℃ or 1 500 ℃, the cracks became shallower and smaller even disappeared, the strength of the specimen was recovered finally; (4) a formulation for crack heal-ing rate expressed by the cracked capacity was: V/ t = 1/3 C2v(1+ctg θ) Cv/ t.

  14. Influência de aditivos dispersantes nas propriedades de concretos refratários de Al2O3 e Al2O3-MgO Influence of dispersants in Al2O3 and Al2O3-MgO refractory castables

    Directory of Open Access Journals (Sweden)

    I. R. de Oliveira

    2004-03-01

    Full Text Available O estado de dispersão das partículas constituintes da matriz de concretos apresenta uma influência direta no comportamento reológico desses materiais, determinando as técnicas que podem ser usadas para a sua aplicação. Diferentes aditivos são utilizados visando uma dispersão eficiente, a qual constitui um requisito importante na otimização do empacotamento das partículas e da resistência mecânica de concretos. Entretanto, a influência desses aditivos nas propriedades de concretos tem sido muito pouco estudada. Neste trabalho investigou-se o efeito de três dispersantes nas propriedades e desempenho na secagem de diferentes composições refratárias. A presença de poliacrilato de sódio resultou em concretos com elevada permeabilidade e maior porosidade. Por outro lado, em composições no sistema Al2O3-MgO a presença de hexametafosfato de sódio proporcionou concretos com permeabilidade extremamente baixa acarretando numa secagem mais lenta, enquanto o ácido cítrico apresentou um desempenho intermediário. Tais efeitos nas propriedades dos concretos foram correlacionados às características intrínsecas dos aditivos.The state of dispersion of the castables matrix particles presents a direct influence in their rheological behavior, determining the techniques that can be used for their installation. Different additives have been used aiming an efficient dispersion, which constitutes an important requirement in the optimization of the particles packing and mechanical resistance of castables. However, the influence of those additives in the castables properties has not been extensively studied. In this work, the effect of 3 dispersants was investigated in the properties and drying behavior of different refractory compositions. The presence of sodium polyacrylate resulted in castables with higher permeability and larger porosity. On the other hand, in Al2O3-MgO compositions the presence of sodium hexametaphosphate provided

  15. Characterization of humic acid reactivity modifications due to adsorption onto α-Al 2O 3

    KAUST Repository

    Janot, Noémie

    2012-03-01

    Adsorption of purified Aldrich humic acid (PAHA) onto α-Al 2O 3 is studied by batch experiments at different pH, ionic strength and coverage ratios R (mg of PAHA by m 2 of mineral surface). After equilibration, samples are centrifuged and the concentration of PAHA in the supernatants is measured. The amount of adsorbed PAHA per m 2 of mineral surface is decreasing with increasing pH. At constant pH value, the amount of adsorbed PAHA increases with initial PAHA concentration until a pH-dependent constant value is reached. UV/Visible specific parameters such as specific absorbance SUVA 254, ratio of absorbance values E 2/E 3 and width of the electron-transfer absorbance band Δ ET are calculated for supernatant PAHA fractions of adsorption experiments at pH 6.8, to have an insight on the evolution of PAHA characteristics with varying coverage ratio. No modification is observed compared to original compound for R≥20mgPAHA/gα-Al2O3. Below this ratio, aromaticity decreases with initial PAHA concentration. Size-exclusion chromatography - organic carbon detection measurements on these supernatants also show a preferential adsorption of more aromatic and higher-sized fractions. Spectrophotometric titrations were done to estimate changes of reactivity of supernatants from adsorption experiments made at pH ≈6.8 and different PAHA concentrations. Evolutions of UV/Visible spectra with varying pH were treated to obtain titration curves that are interpreted within the NICA-Donnan framework. Protonation parameters of non-sorbed PAHA fractions are compared to those obtained for the PAHA before contact with the oxide. The amount of low proton-affinity type of sites and the value of their median affinity constant decrease after adsorption. From PAHA concentration in the supernatant and mass balance calculations, "titration curves" are experimentally proposed for the adsorbed fractions for the first time. These changes in reactivity to our opinion could explain the difficulty

  16. Investigation of TiC-Al2O3-Fe Cermet by SHS%TiC-Al2O3-Fe金属陶瓷的自蔓延高温合成研究

    Institute of Scientific and Technical Information of China (English)

    张化宇; 韩杰才; 张卫方; 杜善义

    1999-01-01

    通过自蔓延高温合成结合准热等静压法(SHS/PHIP)制备出了致密度为97.7%的TiC-Al2O3-20Fe金属陶瓷(TAF20).分析了金属陶瓷的相组成、微观组织及性能.结果表明:金属陶瓷由TiC,Al2O3陶瓷颗粒和Fe粘结相组成;粘结相中Fe与Al2O3之间的界面光滑,与TiC之间有一薄的扩散层;TAF20金属陶瓷的抗弯强度和抗压强度分别为890MPa和18.4GPa.

  17. 多孔α-Al2O3基陶瓷片状载体的制备与性能%Preparation and Properties of Porous α-Al2O3 Based Ceramic Disk Substrates

    Institute of Scientific and Technical Information of China (English)

    陈圣博; 刘旭光; 张宝泉

    2013-01-01

    采用干压成型法制备了多孔α-Al2O3基陶瓷片,研究了烧结温度和掺杂SiO2对其结构、形貌和性能的影响.提高烧结温度能增加α-Al2O3基陶瓷片的抗压强度,但收缩率也会随之增大.最佳烧结温度为1180℃,收缩率小于0.5%,抗压强度大于80 MPa.当掺杂SiO2粉体后,陶瓷片中的无定形SiO2在烧结过程中晶化形成方石英,能够促进α-A12O3陶瓷片的烧结.当SiO2含量为12wt%,并在1180℃下烧结时,陶瓷片的收缩率仅为1.2%,抗压强度大于110 MPa.与α-Al2O3陶瓷片相比,其孔径更小但孔径分布更宽.研究表明,α-Al2O3和SiO2/Al2O3陶瓷片均具有良好的分子筛膜生长活性.但由于载体具有不同的物化性质,所制备的ZSM-5分子筛膜具有不同的形貌和尺寸.%Porous α-Al2O3 based ceramics disks were prepared by dry pressure molding method.Influences of sintering temperature and SiO2 dopant on the structure,morphology and properties were investigated.It was founded that compressive strength and shrinkage ratio of αt-Al2O3 ceramic disk both increased with increasing sintering temperature.The shrinkage ratio and compressive strength was less than 0.5% and stronger than 80 MPa,respectively,while the optimum sintering temperature was chosen to be 1180℃.The sintering of αt-Al2O3 ceramic disk would be enhanced by doping SiO2,which crystallized into cristobalite phase from an amorphous phase during the sintering process.α-Al2O3 ceramic disk doped with 12wt% SiO2 sintered at 1180℃ exhibited a stronger compressive strength (110 MPa) and a shrinkage ratio of 1.2%.The ceramic disk possessed a smaller pore size but a wider pore size distribution than that of the pure α-Al2O3 ceramic disk.It was demonstrated that both α-Al2O3 and SiO2 doped α-Al2O3 ceramic disk substrates were favorable for the growth of ZSM-5 zeolite membranes.However,these ZSM-5 zeolite membranes showed different morphologies and crystal sizes,due to the difference in

  18. Catalytic wet air oxidation of phenol over RuO2/γ-Al2O3 catalyst

    Institute of Scientific and Technical Information of China (English)

    YANG Shaoxia; FENG Yujie; CAI Weimin; ZHU Wanpeng; JIANG Zhanpeng; WAN Jiafeng

    2004-01-01

    A kind of CWAO catalyst, RuO2/γ-Al2O3, was prepared by dipping Al2O3 into the aqueous solution of RuCl3.3H2O. XRD, SEM and TEM were used to determine the catalytic structure. Influences of the calcination temperature,the initial pH of the feed solution and degradation temperature on the activity of the RuO2/γ-Al2O3 catalyst were investigated and the reaction mechanism was preliminarily studied. Results showed that uniform dispersion of RuO2 crystallites was observed on the surface of the catalyst. The activity of the catalyst was higher at calcination temperature of 300℃ for 3 h and the particle reunion occurred and some large RuO2 crystallites were abundant at high calcination temperature of 500℃. The activity of the catalyst was better in the acid solution than in the alkaline solution. Increasing degradation temperature and using the catalyst could shorten the induction periods so that the phenol and COD removal were increased. For RuO2/γ-Al2O3 catalyst, the phenol and COD removal were respectively 98% and 80% in a temperature of 150℃, pH of 5.6 and pressure of 3 MPa after a 2 h reaction. This indicated that Ru/γ-Al2O3 catalyst had good activity.

  19. Meso-macroporous Al2O3 supported Ru catalysts for CO preferential oxidation in hydrogen-rich gases

    Institute of Scientific and Technical Information of China (English)

    Limiao Shen; Cheng Zhang; Yuan Liu

    2012-01-01

    Series of meso-macroporous Al2O3 supported Ru catalysts with different loadings were prepared by incipient wetness method and applied to preferential oxidation of CO in hydrogen-rich gases.N2 adsorption-desorption,SEM,XRD,TEM,CO chemisorption and H2-TPR techniques were employed to characterize the catalysts.The results indicate that Ru/Al2O3 catalysts have meso-macroporous structure,high surface area and high metal dispersion.The characterization results of XRD and CO chemisorption indicate the entry of Ru ions into Al2O3 lattice.The results of catalytic performance tests indicate that the meso-macroporous Al2O3 supported Ru catalysts for CO preferential oxidation showed good activity under high space velocity.It is proposed that the macropores in the Ru/Al2O3 catalyst favor mass transfer and mesopores help to improve the dispersion of metal,resulting in the excellent catalytic performance.

  20. Pt-Ti/ALD-Al2O3/p-Si MOS Capacitors for Future ULSI Technology

    Directory of Open Access Journals (Sweden)

    Ashok M. Mahajan

    2011-01-01

    Full Text Available The high dielectric constant (high-k thin film of Al2O3 was deposited by using Plasma enhanced atomic layer deposition (PE-ALD technique. The electron beam evaporation system was used to deposit the Pt-Ti metal to fabricate the Pt-Ti/Al2O3/Si MOS capacitors. Thickness measurement of Al2O3 gate dielectric was carried out with variable angle spectroscopic ellipsometry, which is measured to be 2.83 nm. The MOS capacitors were characterized to evaluate the electrical properties using capacitance voltage (C-V analyzer at different measurement frequencies. Capacitance voltage measurement shows that, dielectric constant k ranges from 7.87 to 10.44. In CV curve a slight negative shift is observed in the flatband voltage because of presence of trap charges in the Al2O3 MOS capacitor. A lower equivalent oxide thickness (EOT of 1.057 nm is obtained for the fabricated Pt-Ti/ Al2O3 /Si MOS capacitors.

  1. Methanobactin-Mediated Synthesis of Gold Nanoparticles Supported over Al2O3 toward an Efficient Catalyst for Glucose Oxidation

    Directory of Open Access Journals (Sweden)

    Jia-Ying Xin

    2014-11-01

    Full Text Available Methanobactin (Mb is a copper-binding peptide that appears to function as an agent for copper sequestration and uptake in methanotrophs. Mb can also bind and reduce Au(III to Au(0. In this paper, Au/Al2O3 catalysts prepared by a novel incipient wetness-Mb-mediated bioreduction method were used for glucose oxidation. The catalysts were characterized, and the analysis revealed that very small gold nanoparticles with a particle size <4 nm were prepared by the incipient wetness-Mb-mediated bioreduction method, even at 1.0% Au loading (w/w. The influence of Au loading, calcination temperature and calcination time on the specific activity of Au/Al2O3 catalysts was systematically investigated. Experimental results showed that decomposing the Mb molecules properly by calcinations can enhance the specific activity of Au/Al2O3 catalysts, though they acted as reductant and protective agents during the catalyst preparation. Au/Al2O3 catalysts synthesized by the method exhibited optimum specific activity under operational synthesis conditions of Au loading of 1.0 wt % and calcined at 450 °C for 2 h. The catalysts were reused eight times, without a significant decrease in specific activity. To our knowledge, this is the first attempt at the preparation of Au/Al2O3 catalysts by Mb-mediated in situ synthesis of gold nanoparticles.

  2. Hydrothermal synthesis of boehmites with various particle sizes and transition to α-Al2O3 powders by calcination

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    Boehmite powders with various particle sizes have been prepared by hydrothermal method and the α-Al2 O3 powders yielded after subsequent calcination have been studied. Dispersive crystalline boehmite powders of 30-100 nm, 0.4-0. 6μm and 1μm in size were obtained respectively by changing the hydrothermal precursors and the pH value of hydrothermal slurry. Calcination of boehmite powders of 30-100 nm at 1250℃ for 1h resulted in the formation of single-phase α-Al2O3,and the products consisted of vermicular particles. The boehmite powders of 0.4-0.6μm were also fully converted to α-Al2O3 at 1250℃, and the products consisted of plate-like particles with the same size of 0. 4-0. 6μm. The boehmite powders of 1μm calcined at 1350℃ for 2h were still composed of a little proportions of transition aluminas besides α-Al2 O3, and the particles sintered severely. The reaction processes for the formation of crystalline boehmites under hydrothermal conditions and α-Al2O3 powders during calcination have been discussed.

  3. Heat Transfer Enhancement in a Helically Coiled Tube with Al2O3/WATER Nanofluid Under Laminar Flow Condition

    Science.gov (United States)

    Kumar, P. C. Mukesh; Kumar, J.; Suresh, S.; Babu, K. Praveen

    2012-10-01

    In this experimental investigation, the heat transfer coefficients of a shell and helically coiled tube heat exchanger using Al2O3/water nanofluid under laminar flow condition were studied. The Al2O3 nanoparticles were characterized by X-Ray diffraction (XRD). The Al2O3/water nanofluid at 0.1%, 0.4% and 0.8% particle volume concentration were prepared by using two step method. The prepared nanofluid was characterized by scanning electron microscope (SEM). It is observed that the overall heat transfer coefficient, inner heat transfer coefficient and experimental inner Nusselt number increase while increasing particle volume concentration and increasing inner Dean number. The enhancement of overall heat transfer coefficient was found to be 7%, 16.9% and 24.2% at 0.1%, 0.4% and 0.8% Al2O3/water nanofluid respectively when compared with water. The enhancement of tube side experimental Nusselt number was found to be 17%, 22.9% and 28% at 0.1%, 0.4% and 0.8% particle volume concentration of Al2O3/water nanofluid respectively when compared with water at fixed Dean number. The tests were conducted in the range of 1600 tube.

  4. Fabrication of Al2O3-Cu Nanocomposites Using Rotary Chemical Vapor Deposition and Spark Plasma Sintering

    Directory of Open Access Journals (Sweden)

    Jianfeng Zhang

    2015-01-01

    Full Text Available A two-step rotary chemical vapor deposition technique was developed to uniformly mix Cu nanoparticles with the γAl2O3 powders, and then the as-obtained powders were consolidated to Al2O3-Cu nanocomposites by spark plasma sintering. In the RCVD process, the metal-organic precursor of copper dipivaloylmethanate (Cu(DPM2 reacted with O2 and then was reduced by H2 in order to erase the contamination of carbon. At 1473 K, the relative density of Al2O3-Cu increased with increasing CCu and the maximum value was 97.7% at CCu = 5.2 mass%. The maximum fracture toughness of Al2O3-Cu was 4.1 MPa m1/2 at CCu = 3.8 mass%, and 1 MPa m1/2 higher than that of monolithic Al2O3, validating the beneficial effects of Cu nanoparticles.

  5. Passivation Effect of Atomic Layer Deposition of Al2O3 Film on HgCdTe Infrared Detectors

    Science.gov (United States)

    Zhang, Peng; Ye, Zhen-Hua; Sun, Chang-Hong; Chen, Yi-Yu; Zhang, Tian-Ning; Chen, Xin; Lin, Chun; Ding, Ring-Jun; He, Li

    2016-09-01

    The passivation effect of atomic layer deposition of (ALD) Al2O3 film on a HgCdTe infrared detector was investigated in this work. The passivation effect of Al2O3 film was evaluated by measuring the minority carrier lifetime, capacitance versus voltage ( C- V) characteristics of metal-insulator-semiconductor devices, and resistance versus voltage ( R- V) characteristics of variable-area photodiodes. The minority carrier lifetime, C- V characteristics, and R- V characteristics of HgCdTe devices passivated by ALD Al2O3 film was comparable to those of HgCdTe devices passivated by e-beam evaporation of ZnS/CdTe film. However, the baking stability of devices passivated by Al2O3 film is inferior to that of devices passivated by ZnS/CdTe film. In future work, by optimizing the ALD Al2O3 film growing process and annealing conditions, it may be feasible to achieve both excellent electrical properties and good baking stability.

  6. Microstructure Investigation of Cu-Ni Base Al2O3 Nanocomposites: From Nanoparticles Synthesis to Consolidation

    Science.gov (United States)

    Ramos, M. I.; Suguihiro, N. M.; Brocchi, E. A.; Navarro, R.; Solorzano, I. G.

    2017-02-01

    Different compositions of Cu-Ni/Al2O3 nanocomposites were prepared by a chemical-based synthesis of co-formed oxides (CuO-NiO-Al2O3) nanoparticles followed by selective hydrogen reduction of the Cu and Ni oxides and finally by consolidation into pellets. The synthesized composites with both phases (metallic and oxide) containing nanoparticles in the 5 to 60 nm range have been systematically produced. Micro- and nanoscale characterization techniques were extensively employed in all stages of the process. X-ray diffraction (XRD) and transmission electron microscopy (TEM) analyses have shown a heterogeneous distribution of chemical elements resulting in the formation of Cu- and Ni-rich nanoparticles containing Al2O3 phase in a controlled low volume fraction, which later mostly dispersed between the metallic particle and, to a lesser extent, within metallic particles. After consolidation, under uniaxial pressure followed by sintering, the compacted nanocomposite observed in the transmission electron microscope (TEM) revealed that the Al2O3 have been more homogeneously distributed as such: the majority of it at the newly formed grain boundaries of the consolidated pellet and a small part of it within the metallic Cu-Ni matrix. Microhardness measurements demonstrate that dispersion of Al2O3 was successfully achieved as reinforcement phase, yielding up to 100 pct increase in hardness.

  7. Synthesis and Structural Characterization of Al2O3-Coated MoS2 Spheres for Photocatalysis Applications

    Directory of Open Access Journals (Sweden)

    S. V. Prabhakar Vattikuti

    2015-01-01

    Full Text Available This paper reports the synthesis of novel monodisperse Al2O3-coated molybdenum disulfide nanospheres (i.e., core-shell structures using a one-step facile hydrothermal method. XPS analysis confirmed the purity and stable structure of the Al2O3-coated MoS2 nanospheres. A possible growth mechanism of the core-shell structure is also reported, along with their influence on the photodegradation process of rhodamine B (RhB. The Al2O3-coated MoS2 nanospheres demonstrate good photocatalytic activity and chemical stability compared to MoS2 spheres. TG-DTA analysis provided insight into the decomposition process of the precursor solution and the stability of the nanoparticles. The enhanced photocatalytic activity makes the Al2O3-coated MoS2 nanospheres a promising candidate as a photocatalyst that could be used in place of traditional Al2O3/MoS2 photocatalyst for the removal of pollutants from waste water.

  8. Physico–chemical properties of CdO–Al2O3 catalysts. I – Structural characteristics

    Directory of Open Access Journals (Sweden)

    M.N. Alaya

    2014-11-01

    TG–DTA patterns of uncalcined samples were analyzed and the XRD of all 1000 °C-products and some selected samples calcined at 400–800 °C were investigated. The thermal behaviors of pure and mixed gels depend on the precipitating agent, pH of precipitation, chemical composition and method of preparation. Generally, calcination at temperatures below 800 °C gave poorly crystalline phases. Well crystalline phases are obtained at 800 and 1000 °C. For pure alumina γ-Al2O3 was shown as 400 °C-calcination product that transforms into the δ form around 900 °C and later to θ-Al2O3 as a major phase and α-Al2O3 as a minor phase at 1000 °C. CdO was shown by 500 °C-calcined cadmia gel that showed color changes with rise of calcination temperature. The most stable black cadmium oxide phase (Monteponite is obtained upon calcination at 1000 °C. Thousand degree celsius- calcined mixed oxides showed θ-Al2O3, α-Al2O3, CdAl2O4 and monteponite which dominate depending on the chemical composition.

  9. Assimilation Behavior of Calcium Ferrite and Calcium Diferrite with Sintered Al2O3 and MgO

    Science.gov (United States)

    Long, Hongming; Wu, Xuejian; Chun, Tiejun; Di, Zhanxia; Yu, Bin

    2016-10-01

    In this study, the assimilation behaviors between calcium ferrite (CF), calcium diferrite (CF2) and sintered Al2O3, and MgO were explored by an improved sessile drop technique, and the interfacial microstructure was discussed. The results indicated that the apparent contact angles of CF slag on Al2O3 and MgO substrate were 15.7 and 5.5 deg, and the apparent contact angles of CF2 slag on Al2O3 and MgO substrate were 17.9 and 7.2 deg, respectively. Namely, CF and CF2 slag were wetting well with Al2O3 and MgO substrate. The dissolution of Al2O3 substrate into the CF and CF2 slag was found to be the driving force of the wetting process. For the CF-MgO and CF2-MgO substrate systems, CaO contrarily distributed with MgO after wetting. For the CF-MgO system, after wetting, the slag was composed of CF and C2F, and most of the Fe2O3 permeated into substrate and formed two permeating layers.

  10. Tensile Strength and Microstructure of Al2O3-ZrO2 Hypo-Eutectic Fibers Studied

    Science.gov (United States)

    Farmer, Serene C.; Sayir, Ali

    2001-01-01

    Oxide eutectics offer high-temperature strength retention and creep resistance in oxidizing environments. Al2O3-ZrO2 eutectic strengths have been studied since the 1970's. Directionally solidified oxide eutectics exhibit improved resistance to slow crack growth and excellent strength retention at high temperatures up to 1400 C. Materials studied typically contain Y2O3 to metastably retain the high-temperature cubic and tetragonal polymorphs at room temperature. Al2O3-ZrO2 is of fundamental interest for creep studies because it combines a creep-resistant material, Al2O3, with a very low creep resistance material, ZrO2. Results on mechanical properties and microstructures of these materials will be used to define compositions for creep testing in future work. Substantial variations from the eutectic alumina to zirconia ratio can be tolerated without a loss in room-temperature strength. The effect of increasing Y2O3 addition on the room-temperature tensile strength of an Al2O3-ZrO2 material containing excess Al2O3 was examined at the NASA Glenn Research Center, where the materials were grown using Glenn's world-class laser growth facilities.

  11. Oxidation behavior of in-situ Al2O3/TiAl composites at 900℃ in static air

    Institute of Scientific and Technical Information of China (English)

    Tao-tao Ai; Fen Wang; Xiao-ming Feng

    2009-01-01

    In-situ Al2O3/TiAl composites were successfully synthesized from the starting powders of Ti, Al, TiO2 and Nb2O5. The oxidation behavior of the composites at 900℃ in static air was investigated. The results indicate that the composite samples present a much lower oxidation mass gain. Under long-time intensive oxidation exposure, the formed oxide scale is multi-layer. The formation of the outer TiO2 layer is fine and dense, the internal Al2O3 scale has good adhesiveness with the outer TiO2 scale, and the TiO2+Al2O3 mixed layer forming the protective oxide scale is favorable for the improvement of oxidation resistance. It is believed that the incorporation of Al2O3 particulates into the metal matrix decreases the coefficient of thermal expansion of the substrate, and forms a local three-dimensional network structure that can hold the oxide scale. The formation of the oxide scale with fmer particle size, stronger adherence, less micro-defects and slower growth rate can contribute to the improvement of oxidation resistance. Nb element plays an important role in reducing the internal oxidation action of the materials, restraining the growth of TiO2 crystals andpromoting thc stable formation of the Al 2O3-riched layer,which is benfeicial to improve the oxidation properties.

  12. MICROSTRUCTURES AND MECHANICAL PROPERTIES OF IN-SITU Al2O3/TiAl COMPOSITES BY EXOTHERMIC DISPERSION METHOD

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    In-situ Al2O3/TiAl composites were fabricated by pressure-assisted exothermic disper-sion (PAXD) method from elemental powder mixtures of Ti, Al, TiO2, and Nb2O5.The microstructures and mechanical properties of the as-sintered composites are in-vestigated. The results show that the as-sintered products consist of γ-TiAl, α2-Ti3Al,Al2O3, and NbAl3 phases. Microstrueture analysis indicates that Al2O3 particles tend to disperse on the grain boundaries. Application of a moderate pressure of 35 Mpa at 1200℃ yields Ab2O3/TiAl composites with fine Al2O3 reinforcement and a dis-continuous network linking by Al2O3 particles. The aluminide component has a fine submicron γ+α2 larnellar rnicrostructure. With increasing Nb2O5 content, A1203 par-ticles are dispersed uniformly in the matrix. The hardness of the composites increases gradually, and the bending strength and fracture toughness of the composites reach to the maximum value, respectively.

  13. Formation of Al2O3-HfO2 Eutectic EBC Film on Silicon Carbide Substrate

    Directory of Open Access Journals (Sweden)

    Kyosuke Seya

    2015-01-01

    Full Text Available The formation mechanism of Al2O3-HfO2 eutectic structure, the preparation method, and the formation mechanism of the eutectic EBC layer on the silicon carbide substrate are summarized. Al2O3-HfO2 eutectic EBC film is prepared by optical zone melting method on the silicon carbide substrate. At high temperature, a small amount of silicon carbide decomposed into silicon and carbon. The components of Al2O3 and HfO2 in molten phase also react with the free carbon. The Al2O3 phase reacts with free carbon and vapor species of AlO phase is formed. The composition of the molten phase becomes HfO2 rich from the eutectic composition. HfO2 phase also reacts with the free carbon and HfC phase is formed on the silicon carbide substrate; then a high density intermediate layer is formed. The adhesion between the intermediate layer and the substrate is excellent by an anchor effect. When the solidification process finished before all of HfO2 phase is reduced to HfC phase, HfC-HfO2 functionally graded layer is formed on the silicon carbide substrate and the Al2O3-HfO2 eutectic structure grows from the top of the intermediate layer.

  14. Preparation and properties characterization of Al2O3/ACF composite electrode materials%Al2O3/ACF复合电极材料的制备及性能表征

    Institute of Scientific and Technical Information of China (English)

    李海红; 杨洁; 郭雅妮; 强雪妮

    2015-01-01

    The activated carbon fiber (ACF) felt with H3PO4pretreatment was used as raw materials, adopting dipping calcination method to prepare Al2O3/ACF composite electrode materials. The micro-structure and electrochemical performance of the activated carbon fiber before and after loaded with Al2O3 were characterized by using scanning electron microscopy (SEM), Brunauer-Emmett-Teller gas adsorption method (BET), X-ray diffraction (XRD), energy X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR), respectively, and then using homemade improvised electric adsorption desalination device to test the electric adsorption performance for NaCl model wastewater. The results showed that Al2O3/ACF composite electrode materials were prepared with success by adopting the dipping calcination method. There was flocculent or granulate Al2O3 in the surface and pores of Al2O3/ACF complex, and the specific surface area was decreased from 1244.37 m2·g−1 to 974.59 m2·g−1. Meanwhile, the content of Al was 1.06% and Al2O3 with amorphous was existed on the surface of activated carbon fiber. The Al-O bonds were found on the surface of Al2O3/ACF electrode materials with increasing specific capacitance of 76.5% in comparison with the original activated carbon electrode. After loaded Al2O3,theelectric double layer capacity of ACF electrode materials was increased, the electric adsorption performance was improved, the desalination efficiency was promoted more than 2.3 times as original and the electrode was reproducible. Al2O3/ACF composite materials can be used as the electrode materials for the removal of the inorganic ions in wastewater.%以H3PO4预处理后的活性炭纤维(ACF)毡为原料,采用浸渍煅烧法制备Al2O3/ACF复合电极材料;通过扫描电镜(SEM)、比表面积及孔径分析仪(BET)、X射线衍射(XRD)、X射线光电子能谱(XPS)、傅里叶红外光谱分析仪(FTIR)对负载Al2O3前后活性炭

  15. Formation and surface characterization of nanostructured Al2O3–TiO2 coatings

    Indian Academy of Sciences (India)

    Vairamuthu Raj; Mohamed Sirajudeen Mumjitha

    2014-10-01

    One pot synthesis of Al2O3–TiO2 nanoceramic coatings from environment-friendly potassium titanium oxalate (PTO) electrolyte using facile electrochemical anodization has been reported for the first time. Systematic analysis of the anodization parameters such as applied current density and concentration of the PTO electrolyte influence on the morphology of the ceramic coatings was done. The textural properties of the coatings (thickness, growth rate, coating ratio) showed a linear regime with current density and electrolyte concentration decreases up to a certain level and then decreases. The growth process, distribution of chemical elements, phase constitutions and corrosion resistance of the coatings were investigated by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), Tafel polarization technique and electrochemical impedance spectroscopy (EIS). The relation between the corrosion resistivity of the anodic coating and the aforementioned anodization parameters is investigated. The mechanisms that are involved in the formation of the ceramic coatings are also discussed. The coatings formed from 30 g/L concentration of PTO and 0.02 A/cm2 current density show good morphology, textural properties and optimum corrosion resistance.

  16. Numerical investigation of Al2O3/water nanofluid laminar convective heat transfer through triangular ducts

    Directory of Open Access Journals (Sweden)

    Zeinali Heris Saeed

    2011-01-01

    Full Text Available Abstract In this article, laminar flow-forced convective heat transfer of Al2O3/water nanofluid in a triangular duct under constant wall temperature condition is investigated numerically. In this investigation, the effects of parameters, such as nanoparticles diameter, concentration, and Reynolds number on the enhancement of nanofluids heat transfer is studied. Besides, the comparison between nanofluid and pure fluid heat transfer is achieved in this article. Sometimes, because of pressure drop limitations, the need for non-circular ducts arises in many heat transfer applications. The low heat transfer rate of non-circular ducts is one the limitations of these systems, and utilization of nanofluid instead of pure fluid because of its potential to increase heat transfer of system can compensate this problem. In this article, for considering the presence of nanoparticl: es, the dispersion model is used. Numerical results represent an enhancement of heat transfer of fluid associated with changing to the suspension of nanometer-sized particles in the triangular duct. The results of the present model indicate that the nanofluid Nusselt number increases with increasing concentration of nanoparticles and decreasing diameter. Also, the enhancement of the fluid heat transfer becomes better at high Re in laminar flow with the addition of nanoparticles.

  17. Thermal conductivity and viscosity measurements of ethylene glycol-based Al2O3 nanofluids

    Science.gov (United States)

    Pastoriza-Gallego, María José; Lugo, Luis; Legido, José Luis; Piñeiro, Manuel M.

    2011-12-01

    The dispersion and stability of nanofluids obtained by dispersing Al2O3 nanoparticles in ethylene glycol have been analyzed at several concentrations up to 25% in mass fraction. The thermal conductivity and viscosity were experimentally determined at temperatures ranging from 283.15 K to 323.15 K using an apparatus based on the hot-wire method and a rotational viscometer, respectively. It has been found that both thermal conductivity and viscosity increase with the concentration of nanoparticles, whereas when the temperature increases the viscosity diminishes and the thermal conductivity rises. Measured enhancements on thermal conductivity (up to 19%) compare well with literature values when available. New viscosity experimental data yield values more than twice larger than the base fluid. The influence of particle size on viscosity has been also studied, finding large differences that must be taken into account for any practical application. These experimental results were compared with some theoretical models, as those of Maxwell-Hamilton and Crosser for thermal conductivity and Krieger and Dougherty for viscosity.

  18. Thermal conductivity and viscosity measurements of ethylene glycol-based Al2O3 nanofluids

    Directory of Open Access Journals (Sweden)

    Pastoriza-Gallego María

    2011-01-01

    Full Text Available Abstract The dispersion and stability of nanofluids obtained by dispersing Al2O3 nanoparticles in ethylene glycol have been analyzed at several concentrations up to 25% in mass fraction. The thermal conductivity and viscosity were experimentally determined at temperatures ranging from 283.15 K to 323.15 K using an apparatus based on the hot-wire method and a rotational viscometer, respectively. It has been found that both thermal conductivity and viscosity increase with the concentration of nanoparticles, whereas when the temperature increases the viscosity diminishes and the thermal conductivity rises. Measured enhancements on thermal conductivity (up to 19% compare well with literature values when available. New viscosity experimental data yield values more than twice larger than the base fluid. The influence of particle size on viscosity has been also studied, finding large differences that must be taken into account for any practical application. These experimental results were compared with some theoretical models, as those of Maxwell-Hamilton and Crosser for thermal conductivity and Krieger and Dougherty for viscosity.

  19. New battery strategies with a polymer/Al2O3 separator

    Science.gov (United States)

    Park, Kyusung; Cho, Joon Hee; Shanmuganathan, Kadhiravan; Song, Jie; Peng, Jing; Gobet, Mallory; Greenbaum, Steven; Ellison, Christopher J.; Goodenough, John B.

    2014-10-01

    A low-cost, thin, flexible, and mechanically robust alkali-ion electrolyte separator is shown to allow fabrication of a safe rechargeable alkali-ion battery with alternative cathode strategies. A Na-ion battery with an insertion host as cathode and a Li-ion battery with a redox flow-through cathode are demonstrated to cycle without significant fade. The separator membrane is a composite of Al2O3 particles and cross-linked ethylene-oxide chains; it can be fabricated at low cost into a large-area thin membrane that blocks dendrites from an alkali-metal anode. To block a soluble ferrocene redox molecule from crossing from the cathode side to the anode in a Li-ion battery with a redox-flow cathode, a thin mixed Li+/electronic-conducting film has been added to the cathode side of the composite separator. An osmosis issue was minimized by balancing concentrations of solutes on the two sides of the separator where the cathode side contains a soluble redox molecule.

  20. Acid-base properties of Ni-MgO-Al2O3 materials

    Science.gov (United States)

    Gac, Wojciech

    2011-01-01

    Ni-MgO-Al2O3 materials of different Ni/Mg ratios were prepared by the co-precipitation method. Acid-base properties of the samples after calcination and reduction were examined by the temperature programmed desorption of ammonia and carbon dioxide. Thermal treatment of the materials in air at 400 °C led to the formation of hydrotalcite-like phases. The increase of Ni/Mg ratio decreased the stability of the hydrotalcite structure. The number and the strength of acid and base sites were related to the Ni/Mg ratio and thermal treatment conditions of materials. It was found that the replacement of Ni with Mg decreased the acidity and increased basicity of the surface of oxide materials. Thermal treatment of the samples in hydrogen led to the structural changes. The presence of magnesia improved thermal stability. The ratio of the number of acid to base sites in the reduced samples gradually increased with the increase of magnesia content.

  1. Ni–Fe–Al$_2$O$_3$ electrodeposited nanocomposite coating with functionally graded microstructure

    Indian Academy of Sciences (India)

    V TORABINEJAD; A SABOUR ROUHAGHDAM; M ALIOFKHAZRAEI; M H ALLAHYARZADEH

    2016-06-01

    In this study, a Ni–Fe–Al$_2$O$_3$ nanocomposite coating was deposited on the substrate of low-carbon steel by electrodeposition from a sulphate-based bath. The effects of frequency and duty cycle were investigated to producethe functionally graded (FG) coating. For this purpose, first, the coatings with duty cycle-decreased method (DDM) were deposited in eight steps from 88 to 11%. At the second step, frequency-increased method (FIM) was utilized from 50 to 6400 Hz during eight steps. Assessing of coatings was carried out by scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), potentiodynamic test, Vickers microhardness test and wear test.Microstructure evaluations gained by SEM and EDS demonstrated that the continuous alterations of duty cycle contribute for manufacturing of FG coatings, so that the maximum particle fraction was in the free surface of the coating and its amount was gradually decreased to the interface. These investigations showed that FIM had no effect on production of graded structure. Corrosion and wear tests indicated high corrosion and wear resistance of DDM coatings in comparison to FIM coatings. Investigating the best coatings obtained from both above methods exhibited 50 and 20% reduction in corrosion current density and wear rate, respectively, for DDM specimen in comparison to FIM sample.

  2. Surface modification of g-Al2O3 by sodium ions

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    1H/23Na double resonance NMR techniques were employed to study the modification of surface hydroxyls on g-Al2O3 by sodium ions. 1H→23Na cross polarization (CP) experiment can resolve three kinds of sodium cations that are closely associated with surface hydroxyl groups, while the signal of deposited salt-Na2CO3, which is not connected to surface hydroxyl groups, is completely suppressed. 1H{23Na} spin echo double resonance experiments reveal the surface modification in more detail. At low Na+ coverage (5%, 10%), the acidic hydroxyl groups are preferentially coordinated with sodium ions, while both the acidic and the basic hydroxyl groups are accessible for sodium ions at high coordination that causes proton of the OH groups to be easily dissolved, which is evidenced by the fact that with calcination temperature of the catalysts increasing, the acidic hydroxyl groups are preferentially removed and only the basic hydroxyl groups remain when the calcination temperature is raised to 600℃.

  3. Structural considerations in friction welding of hybrid Al2O3-reinforced aluminum composites

    Institute of Scientific and Technical Information of China (English)

    In-Duck PARK; Choon-Tae LEE; Hyur-Soo KIM; Woo-Jin CHOI; Myung-Chang KANG

    2011-01-01

    Comparative studies on the relationship between the welding parameters and joining efficiency in the friction welding of hybrid Al2O3-reinforced aluminum composites were conducted. Metal matrix composites (MMCs) with 37% (volume fraction)aluminum particle were joined by friction welding. The results show that the effects of the rotation speed on the reduction rate of particle size are greater than those of the upset pressure, and the area of the MMC weld zone decreases as the joining efficiency increases, while it is considered that the joining efficiency does not increase as the reduction rate of particle size decreases. During the macro-examination of the bonding interface. a gray discolored region was observed on the bonding interface, and the center of the region was dark gray. After the micro-examination of the bonding interface, base metal made some second particulate formed by condensed alumina particulate but discoloration part distributed minute alumina particulate without second particulate. Consequently,it was also observed that rotational speed of 3 000 r/min and upset pressure of 63.6 MPa showed a very good joint.

  4. Composite material in the Al 2 O3 -20 vol% YAG system

    Directory of Open Access Journals (Sweden)

    Radosław Lach

    2010-03-01

    Full Text Available Within alumina particle suspension yttria precursor was precipitated with ammonium carbonate. Drying and calcination at 600°C resulted in the mixture of alumina and yttria particles, the latter being much finer than alumina particles. This mixture was additionally homogenized by short attrition milling in aqueous suspension of pH selected on the basis of zeta (ζ potential measurements. It was found that acidic conditions (realized with HNO3 resulted in hard agglomerates. Such powder shows poor sintering ability. Much better properties showed powders homogenized under basic conditions. They give dense materials composed of YAG inclusions within alumina matrix. YAG particles resulted from the reaction of Y2O3 with Al2O3 during heat treatment. Homogenization of the system mixed at pH=8, corresponding to the heterofloculation conditions, is slightly better than observed at pH=10. YAG inclusions (20 vol% increase hardness and fracture toughness of the material in comparison with pure alumina polycrystals.

  5. Surface reactions of dimethyl ether on γ-Al2O3

    Science.gov (United States)

    Bondarenko, G. N.; Volnina, E. A.; Kipnis, M. A.; Rodionov, A. S.; Samokhin, P. V.; Lin, G. I.

    2016-02-01

    The surface reactions of dimethyl ether (DME) on industrial alumina (γ-Al2O3) were studied by chromatographic analysis of the products at the outlet of the flow reactor and (independently) by diffuse reflectance IR spectroscopy. The major products of the reactions at 250°C were found to be methanol formed in the reaction of DME with hydroxyl groups (the 3720 and 3674 cm-1 bands in the diffuse reflectance spectrum) and various methoxy groups (the 1121, 1070, 695, and 670 cm-1 bands in the differential spectra). The presence of molecularly adsorbed methanol was confirmed by experiments with methanol fed in a high-temperature IR cell. The interaction of the resulting methanol molecule with the hydroxyl group led to the formation of a water molecule in the gas phase and a methoxy group on the oxide surface. Strong adsorption of molecular DME was revealed, which was favored by an increase in the temperature of the preliminary calcination of oxide from 250 to 450-500°C; treatment of alumina with water vapor after its preliminary contact with DME led to a recovery of the hydroxyl coating and a replacement of molecularly adsorbed DME with hydroxyl. The thermal effect recorded in a flow reactor was positive during the adsorption of DME and negative during the desorption of weakly bonded DME. Schemes of formation of methoxy groups in the interaction of DME and methanol with surface hydroxyls were suggested.

  6. n-Butane Oxidation over γ-Al2O3 Supported Vanadium Phosphate Catalysts

    Institute of Scientific and Technical Information of China (English)

    Y.H.Taufiq-Yap; L.K.Leong; R.Irmawati

    2007-01-01

    Four vanadium phosphate catalysts supported on γ-Al2O3(20 wt%)were synthesized via 75 h)at 673 K in a reaction flow of n-butane/air mixture.The samples calcined for 6 and 10 h produced only a single phase of(VO)2P2O7.However,the VOPO4 phase(β-VOPO4)was detected and became more prominent with only a minor pyrophosphate peaks were found after 30 h of calcination.All these pyrophosphate peaks disappeared after 75 h of calcination.The formation of V5+ phase Was also observed in the SEM micrographs.The redox properties and the nature of oxidants of the catalysts employed in this study were investigated by H2-TPR analysis.Selective oxidation of n-butane to maleic anhydride (MA) over these catalysts shows that the percentage of n-butane conversion decreases with the transformation of the catalysts from V4+ to V5+ phases.An appropriate ratio of V5+/V4+ can enhance the performance of the VPO catalyst.However,a higher amount of V5+ and its associated oxygen species are responsible to promote the MA selectivity.

  7. Effect of Sulfurization Temperature on Thioetheriifcation Performance of Mo-Ni/Al2O3 Catalyst

    Institute of Scientific and Technical Information of China (English)

    Shen Zhibing; Ke Ming; Ren Tao; Zhang Juntao; Liang Shengrong

    2015-01-01

    The Mo modiifed Ni/Al2O3 catalysts were prepared and sulifded at different temperatures, and their catalytic acti-vity for thioetheriifcation of mercaptans and oleifns (or dienes), hydrogenation of dienes and oleifns in the thioetheriifcation process using lfuidized catalytic cracking (FCC) naphtha as the feedstock was investigated. In order to disclose the correla-tion between the physicochemical characteristics of catalysts and their catalytic activity, the surface structures and properties of the catalysts sulifded at different temperatures were characterized by the high resolution transmission electronic micro-scopy (HRTEM), X-ray photoelectron spectroscopy (XPS) and H2-temperature programmed reduction (H2-TPR) technique. The results showed that an increase of sulfurization temperature not only could promote the sulfurization degree of active metals on the catalysts, but also could adjust the micro-morphology of active species. These changes could improve the catalytic performance of thioetheriifcation, and hydrogenation of dienes and oleifns. However, an excess sulfurization tem-perature was more easily to upgrade the ability of the catalyst for hydrogenation of oleifns, which could lead to a decrease of the octane number of the product. It was also showed that a moderate sulfurization temperature not only could improve the catalytic performance of thioetheriifcation and hydrogenation of dienes but also could control hydrogenation of oleifns.

  8. Thermal conductivity and viscosity measurements of ethylene glycol-based Al2O3 nanofluids.

    Science.gov (United States)

    Pastoriza-Gallego, María José; Lugo, Luis; Legido, José Luis; Piñeiro, Manuel M

    2011-03-15

    The dispersion and stability of nanofluids obtained by dispersing Al2O3 nanoparticles in ethylene glycol have been analyzed at several concentrations up to 25% in mass fraction. The thermal conductivity and viscosity were experimentally determined at temperatures ranging from 283.15 K to 323.15 K using an apparatus based on the hot-wire method and a rotational viscometer, respectively. It has been found that both thermal conductivity and viscosity increase with the concentration of nanoparticles, whereas when the temperature increases the viscosity diminishes and the thermal conductivity rises. Measured enhancements on thermal conductivity (up to 19%) compare well with literature values when available. New viscosity experimental data yield values more than twice larger than the base fluid. The influence of particle size on viscosity has been also studied, finding large differences that must be taken into account for any practical application. These experimental results were compared with some theoretical models, as those of Maxwell-Hamilton and Crosser for thermal conductivity and Krieger and Dougherty for viscosity.

  9. Wet foams hydrophobized by amphiphiles to give Al2O3 porous ceramics

    Science.gov (United States)

    Pokhrel, Ashish; Park, Jung Gyu; Kim, Ik Jin

    2012-05-01

    Wet chemical method to prepare ceramic foams with antecedent stability using inorganic particles (Al2O3,SiO2 etc.) which are in situ hydrophobized upon adsorption of short-chain amphiphilic molecules in the wet state and heightened mechanical property in the sintered state was developed. These wet foams are stable over several days and show no bubble coarsening nor drainage or creaming. This long-term stability is achieved through the irreversible adsorption of partially hydrophobized colloidal particles to the air-water interface using short-chain amphiphiles to in situ modify the wetting behavior of the particle surface based on the observations of Pickering emulsions. As a result, the suspension is foamed homogeneously throughout its entire volume and porous bulk materials can be produced upon drying and sintering. Wet foams featuring average bubble sizes between 30 and 300μm and sintered foams with porosity from 50 to 85% were obtained by adjusting the amphiphile - particle concentration, and additives in the initial suspension. Cells were mostly closed with an average size of approximately 150 μm. Single cells were separated by walls with minimum thicknesses of 1-3 μm.

  10. Classical Behavior of Alumina (Al2O3 Nanofluids in Antifrogen N with Experimental Evidence

    Directory of Open Access Journals (Sweden)

    M. Saleemi

    2015-01-01

    Full Text Available A nanofluid is a suspension containing nanoparticles in conventional heat transfer fluids. This paper reports on an investigation of alumina (Al2O3 nanoparticles in Antifrogen N, also called AFN, which is a popular antifreeze coolant consisting primarily of ethylene glycol and other additives to impede corrosion. The base carrier fluid is 50% by weight of water and 50% by weight of AFN. We systematically measured the nanomaterials and heat transfer data of nanofluids for four different size particles, namely, 20, 40, 150, and 250 nm alumina particles. The pH of all the nanofluids is adjusted to have a stable dispersion. The material characterizations include SEM and DLS particle measurements. We measured thermal conductivity, viscosity, and heat transfer coefficient in developing flow of the nanofluids. We observed that these nanofluids behave as any other classical fluids in thermally developing flow and classical heat transfer correlations can be used to completely describe the characteristics of these nanofluids.

  11. Al2O3/GdAlO3 fiber for dental porcelain reinforcement.

    Science.gov (United States)

    Medeiros, Igor S; Luz, Luciana A; Yoshimura, Humberto N; Cesar, Paulo F; Hernandes, Antonio C

    2009-10-01

    The aim of this study was to test the hypothesis that the addition of continuous or milled GdAlO3/Al2O3 fibers to a dental porcelain increases its mechanical properties. Porcelain bars without reinforcement (control) were compared to those reinforced with long fibers (30 vol%). Also, disk specimens reinforced with milled fibers were produced by adding 0 (control), 5 or 10 vol% of particles. The reinforcement with continuous fibers resulted in significant increase in the uniaxial flexural strength from 91.5 to 217.4 MPa. The addition of varied amounts of milled fibers to the porcelain did not significantly affect its biaxial flexural strength compared to the control group. SEM analysis showed that the interface between the continuous fiber and the porcelain was free of defects. On the other hand, it was possible to note the presence of cracks surrounding the milled fiber/porcelain interface. In conclusion, the reinforcement of the porcelain with continuous fibers resulted in an efficient mechanism to increase its mechanical properties; however the addition of milled fibers had no significant effect on the material because the porcelain was not able to wet the ceramic particles during the firing cycle.

  12. The Influence of impact on Composite Armour System Kevlar-29/polyester-Al2O3

    Science.gov (United States)

    Ramadhan, A. A.; Abu Talib, A. R.; Mohd Rafie, A. S.; Zahari, R.

    2012-09-01

    An experimental investigation of high velocity impact responses of composite laminated plates using a helium gas gun has been presented in this paper. The aim of this study was to develop the novel composite structure that meets the specific requirements of ballistic resistance which used for body protections, vehicles and other applications. Thus the high velocity impact tests were performed on composite Kevlar-29 fiber/polyester resin with alumina powder (Al2O3). The impact test was conducted by using a cylindrical steel projectile of 7.62mm diameter at a velocity range of 160-400 m/s. The results (shown in this work) are in terms of varying plate thickness and the amount of energy absorbed by the laminated plates meanwhile we obtained that the 12mm thickness of composite plate suitable for impact loading up to 200m/s impact velocity. Therefore this composite structure (it is used to reduce the amount of Kevlar) considered most economical armoure products. We used the ANSYS AUTODYN 3D- v.12 software for our simulations. The results have been obtained a4.1% maximum errors with experimental work of energy absorption.

  13. Ultrasonic investigations of some bismuth borate glasses doped with Al2O3

    Indian Academy of Sciences (India)

    Yasser B Saddeek; Moenis A Azooz; Amr Bakr Saddek

    2015-02-01

    The velocities of longitudinal and transverse ultrasonic waves in different compositions of 5Al2O3–29Na2O–(66−)B2O$_{3}−x$Bi2O3 glass system were measured at 4 MHz at room temperature using the pulse-echo technique. The velocity data were used to determine the elastic moduli and the dimensionality of the studied glasses. The observed changes in the elastic moduli of the glasses were related to the modifier role of Bi2O3 content. The results revealed that the density increased with increasing Bi2O3 content, which was attributed to the increase in the compactness and packing of the glass network. The ultrasonic data were analysed in terms of creation of new bonds of Bi2O3 attached to the structural units of the borate network. The new bonds decreased the average crosslink density and the number of network bonds per unit volume along with a weakening of the different modes of vibrations, which in its turn decreased the ultrasonic velocity. Quantitative analysis was carried out using Makishima–Mackenzie model in order to obtain more information about the rigidity of these glasses.

  14. Numerical investigation of Al2O3/water nanofluid laminar convective heat transfer through triangular ducts.

    Science.gov (United States)

    Zeinali Heris, Saeed; Noie, Seyyed Hossein; Talaii, Elham; Sargolzaei, Javad

    2011-02-28

    In this article, laminar flow-forced convective heat transfer of Al2O3/water nanofluid in a triangular duct under constant wall temperature condition is investigated numerically. In this investigation, the effects of parameters, such as nanoparticles diameter, concentration, and Reynolds number on the enhancement of nanofluids heat transfer is studied. Besides, the comparison between nanofluid and pure fluid heat transfer is achieved in this article. Sometimes, because of pressure drop limitations, the need for non-circular ducts arises in many heat transfer applications. The low heat transfer rate of non-circular ducts is one the limitations of these systems, and utilization of nanofluid instead of pure fluid because of its potential to increase heat transfer of system can compensate this problem. In this article, for considering the presence of nanoparticl: es, the dispersion model is used. Numerical results represent an enhancement of heat transfer of fluid associated with changing to the suspension of nanometer-sized particles in the triangular duct. The results of the present model indicate that the nanofluid Nusselt number increases with increasing concentration of nanoparticles and decreasing diameter. Also, the enhancement of the fluid heat transfer becomes better at high Re in laminar flow with the addition of nanoparticles.

  15. Autoreduction of promoted Ni/γ-Al 2O 3 during autothermal reforming of methane

    Science.gov (United States)

    Dias, Joelmir Augusto Costa; Assaf, José Mansur

    The addition of the noble metals Pt, Pd and Ir to the Ni/γ-Al 2O 3 catalyst used in the autothermal reforming of methane was investigated, with the aim of making the reaction ignite without previous reduction of the catalyst with H 2. In TPR-CH 4, the catalysts promoted with Pt and Ir chloride suffered reduction at temperatures lower than 500 °C, while the unpromoted catalyst and those promoted by addition of PdCl 2 did not suffer reduction. Pd promoted the reduction only when added as the nitrate. The catalytic tests of intermittent start-up, alternating with air flow, showed results consistent with those from the TPR-CH 4. Pt- and Ir-promoted catalysts were active in all the start-ups, producing a great quantity of hydrogen, while the sample promoted via paladium chloride did not produce hydrogen in significant quantity, converting methane only to CO 2 and water. The samples promoted via palladium nitrate were very active in autothermal reforming without previous reduction, producing a great quantity of hydrogen.

  16. Fuel purpose hydrotreating of sunflower oil on CoMo/Al2O3 catalyst.

    Science.gov (United States)

    Krár, Márton; Kovács, Sándor; Kalló, Dénes; Hancsók, Jeno

    2010-12-01

    The importance of the economical production and usage of new generation biofuels, the so-called bio gas oil (paraffins from triglycerides) and the results of the investigation for their productability on the CoMo/Al(2)O(3) catalyst, which was activated by reduction, are presented. The conversion of triglycerides, the yield of total organic fractions and the target product, furthermore the type and ratio of deoxygenation reactions were determined as a function of process parameters. The advantageous process parameters were found (380 degrees C, 40-60 bar, 500-600 Nm(3)/m(3) H(2)/sunflower oil ratio, 1.0 h(-1)), where the conversion of triglycerides was 100% and the yield of the target fraction [high paraffin containing (>99%) gas oil boiling range product] was relatively high (73.7-73.9%). The deoxygenation of triglycerides the reduction as well as the decarboxylation/decarbonylation reactions took place. The yield of the target fractions did not achieve the theoretical values (81.4-86.5%). That is why it is necessary to separate the target fraction and recirculate the heavy fraction.

  17. Structure and dynamics of PtSn/ γ Al 2 O 3

    Science.gov (United States)

    Vila, F. D.; Rehr, J. J.; Kelly, S. D.; Bare, S. R.

    2011-03-01

    Supported metal clusters have many industrial applications, especially in heterogeneous catalysis. Their activity and durability is determined by their internal atomic and electronic structure, as well as by their interaction with the support. We have previously shown that unusual phenomena such as large structural disorder and negative thermal expansion in supported Pt clusters can be understood by using a combination of MD and x-ray absorption spectroscopy simulations. Here we present results for prototypical Pt 10 Sn 10 alloy clusters on γ Al 2 O3 . Our simulations show that the internal structure and surface location of the clusters varies dynamically on a time scale of a few ps. While the Sn atoms are especially mobile, the clusters have well defined Pt-Pt and Pt-Sn coordination shells at ~ 2.75 AA. Moreover, at any instant there are between 2 and 5 bonds between the Pt/Sn and the O atoms in the surface. Finally, we present simulations of the XANES spectra and their relation to charge transfers between atoms in the cluster and between the cluster and the surface. Supported by NSF Grant PHY-0835543, UOP LLC, a Honeywell Company with computer support from NERSC.

  18. Molten Al and (0001) α-Al2O3 Single Crystal: Interface Stability

    Science.gov (United States)

    Aguilar-santillan, Joaquin

    2016-10-01

    The roughness on the " c"-plane (0001) sapphire single crystal reduces wetting of molten aluminum under Ar gas (99.999 pct) and PO2 10-15 Pa from 1073 K to 1473 K (800 °C to 1200 °C). The contact angle effect was partially understood by the roughness factor, R; however, the interfacial phenomenon involving this effect is yet a topic to study as it also depends, between other things, on the shape of droplet and the relationship to its substrate. The theory explains that the surface tension of liquid aluminum obtained by the sessile drop test can be determined just when a substrate is polished or free of any surface imperfection. However, roughness of sapphire (0001) surface promotes an apparent surface tension that exhibits different trends of wetting to that proposed in previous studies. This property adds to the interfacial wetting phenomena obtained from the Al-Al2O3 couple system and provides answers for contact angle trends toward a much more stable interface, which when coupled with thermodynamic conditions may help in the manufacturing, deterioration, and reliability of the system.

  19. Mixed Matrix Carbon Molecular Sieve and Alumina (CMS-Al2O3) Membranes

    Science.gov (United States)

    Song, Yingjun; Wang, David K.; Birkett, Greg; Martens, Wayde; Duke, Mikel C.; Smart, Simon; Diniz da Costa, João C.

    2016-07-01

    This work shows mixed matrix inorganic membranes prepared by the vacuum-assisted impregnation method, where phenolic resin precursors filled the pore of α-alumina substrates. Upon carbonisation, the phenolic resin decomposed into several fragments derived from the backbone of the resin matrix. The final stages of decomposition (>650 °C) led to a formation of carbon molecular sieve (CMS) structures, reaching the lowest average pore sizes of ~5 Å at carbonisation temperatures of 700 °C. The combination of vacuum-assisted impregnation and carbonisation led to the formation of mixed matrix of CMS and α-alumina particles (CMS-Al2O3) in a single membrane. These membranes were tested for pervaporative desalination and gave very high water fluxes of up to 25 kg m‑2 h‑1 for seawater (NaCl 3.5 wt%) at 75 °C. Salt rejection was also very high varying between 93–99% depending on temperature and feed salt concentration. Interestingly, the water fluxes remained almost constant and were not affected as feed salt concentration increased from 0.3, 1 and 3.5 wt%.

  20. Damage creation threshold of Al2O3 under swift heavy ion irradiation

    Science.gov (United States)

    Khalfaoui, N.; Stoquert, J. P.; Haas, F.; Traumann, C.; Meftah, A.; Toulemonde, M.

    2012-09-01

    Among insulators, sapphire (Al2O3) is less sensitive than any amorphizable oxides regarding the irradiation with heavy ions in the electronic energy loss regime. Earlier experimental results indicated a critical energy loss for damage creation of around of 20 keV/nm, while calculations based on the inelastic thermal spike model predict a value of ˜10 keV/nm. In order to clarify this discrepancy, additional irradiation experiments were performed with different ions between Ni and U covering electronic energy losses between 10 and 43 keV/nm and kinetic energies in the range from 1 to 11 MeV/u. Irradiation effects were characterized by atomic force microscopy (hillock formation), profilometry (swelling), and channeling Rutherford backscattering (near-surface disorder). Combining the results from these measurements, an electronic energy loss threshold of 9.5 ± 1.5 keV/nm is extracted, indicating that the earlier threshold was overestimated and confirming the predictive power of the inelastic thermal spike model. Threshold predictions based on thermal spike model calculations are given for lower and higher beam energies.

  1. Heat transfer performance of Al2O3/water nanofluids in a mini channel heat sink.

    Science.gov (United States)

    Dominic, A; Sarangan, J; Suresh, S; Sai, Monica

    2014-03-01

    The high density heat removal in electronic packaging is a challenging task of modern days. Finding compact, energy efficient and cost effective methods of heat removal is being the interest of researchers. In the present work, mini channel with forced convective heat transfer in simultaneously developing regime is investigated as the heat transfer coefficient is inversely proportional to hydraulic diameter. Mini channel heat sink is made from the aluminium plate of 30 mm square with 8 mm thickness. It has 15 mini channel of 0.9 mm width, 1.3 mm height and 0.9 mm of pitch. DI water and water based 0.1% and 0.2% volume fractions of Al2O3/water nanofluids are used as coolant. The flow rates of the coolants are maintained in such a way that it is simultaneously developing. Reynolds number is varied from 400 to 1600 and heat input is varied from 40 W to 70 W. The results showed that heat transfer coefficient is more than the heat transfer coefficient of fully developed flow. Also the heat transfer is more for nanofluids compared to DI water.

  2. Mixed Matrix Carbon Molecular Sieve and Alumina (CMS-Al2O3) Membranes.

    Science.gov (United States)

    Song, Yingjun; Wang, David K; Birkett, Greg; Martens, Wayde; Duke, Mikel C; Smart, Simon; Diniz da Costa, João C

    2016-07-29

    This work shows mixed matrix inorganic membranes prepared by the vacuum-assisted impregnation method, where phenolic resin precursors filled the pore of α-alumina substrates. Upon carbonisation, the phenolic resin decomposed into several fragments derived from the backbone of the resin matrix. The final stages of decomposition (>650 °C) led to a formation of carbon molecular sieve (CMS) structures, reaching the lowest average pore sizes of ~5 Å at carbonisation temperatures of 700 °C. The combination of vacuum-assisted impregnation and carbonisation led to the formation of mixed matrix of CMS and α-alumina particles (CMS-Al2O3) in a single membrane. These membranes were tested for pervaporative desalination and gave very high water fluxes of up to 25 kg m(-2) h(-1) for seawater (NaCl 3.5 wt%) at 75 °C. Salt rejection was also very high varying between 93-99% depending on temperature and feed salt concentration. Interestingly, the water fluxes remained almost constant and were not affected as feed salt concentration increased from 0.3, 1 and 3.5 wt%.

  3. Synthesis and catalytic property of Cu-Mn-Ce/ γ -Al2O3 complex oxide

    Institute of Scientific and Technical Information of China (English)

    黄可龙; 王红霞; 刘素琴; 桂客

    2002-01-01

    A new type of catalytic material for purification of automobile exhaust,Cu-Mn-Ce-O/ γ -Al2O3,has been studied.The factors affecting its catalytic activity,such as calcination temperature and the period of calcinations and so on have been investigated.Its catalytic activity after SO2-poisoning was determined in a fixed-bed reactor by exposing the sample to the atmosphere of 160 mL/min SO2/air.The study reveals that the catalyst has shown high catalytic activities for the conversion of NH3 oxidation by NO after sulfate.The conversion of NO reduction over the sulfated catalyst is somewhat higher than that over the fresh catalyst except that the optimum temperature has increased about 100 ℃.Also at the optimum process for the experiment,the selective catalytic oxidation of CO by NO is over 76% and the conversion of NO reduction is over 80% by NH3.

  4. Laminar convective heat transfer characteristic of Al2O3/water nanofluid in a circular microchannel

    Science.gov (United States)

    Trinavee, K.; Gogoi, T. K.; Pandey, M.

    2016-10-01

    In this study, laminar convective heat transfer characteristics Al2O3/water nanofluid in a circular microchannel is investigated using a two-phase (discrete phase) model. The computational fluid dynamic code FLUENT (ANSYS) is employed to solve the coupled momentum and energy equations with the boundary conditions of uniform wall heat flux and velocity at channel inlet. Detail analysis is done showing variation of wall temperature, fluid bulk mean temperature, heat transfer coefficient, Nusselt number, shear stress, friction, pressure drop, entropy generation etc. along the microchannel at two particle volume concentrations (1% and 4%) of the nanofluid. Comparison of results is provided between base and nanofluid and also for two cases, one with constant property and the other with variable temperature thermal conductivity and viscosity. Results show that heat transfer is enhanced in case of the nanofluid with low entropy generation and the heat transfer parameters increase with increase in nanoparticle volume concentration and Reynolds number. However, use of nanofluid also causes increase in pressure drop and shear stress. A comparison of the constant and variable property model showed that heat transfer is further enhanced; entropy, shear stress and pressure drop further decrease when temperature dependent properties of the nanofluid are considered instead of constant properties.

  5. Residual Stress in Brazing of Submicron Al2O3 to WC-Co

    Science.gov (United States)

    Grunder, T.; Piquerez, A.; Bach, M.; Mille, P.

    2016-07-01

    This study evaluated the residual stresses induced by brazing and grinding submicron Al2O3, using different methods. Energy dispersive x-ray spectrometry analysis (EDX) of 72Ag-Cu filler and filler/WC-Co interface showed evidence of atomic diffusion and possible formation of titanium oxide layers between the joint and the bonding materials. An analytical model supported by the finite element method (FEM) based on strain determination due to the difference in variation of thermal expansion was used to assess the stress distribution at the coupling interface and in bulk materials. The model took into account the evolution of the Young's modulus and of the thermal expansion with temperature. The model could be used to follow strain and stress evolutions of the bonded materials during the cooling cycle. The maximum stress rose above -300 MPa at the center of the 100 × 100 × 3 mm ceramic plates. The residual stresses on the external surface of ceramic were investigated by x-ray diffraction (XRD) and indentation fracture method (IFM). After brazing and grinding the plate, the principal stresses were 128.1 and 94.9 MPa, and the shear stress was -20.1 MPa. Microscopic examination revealed grain pull-out promoted by the global residual stresses induced by the brazing and grinding processes. The surface stresses evaluated by the different methods were reasonably correlated.

  6. Mercury cadmium telluride (HgCdTe) passivation by advanced thin conformal Al2O3 films

    Science.gov (United States)

    Fu, Richard; Pattison, James; Chen, Andrew; Nayfeh, Osama

    2012-06-01

    HgCdTe passivation process must be performed at low temperature in order to reduce Hg depletion. Low temperature plasma enhanced atomic layer deposition (PE-ALD) is an emerging deposition technology for thin highly conformal films to meet the demand. Room temperature PE-ALD Al2O3 film's passivation on HgCdTe has been studied. Conformal film was investigated through SEM images of the Al2O3 film deposited onto high aspect ratio features dry etched into HgCdTe. Minority carrier lifetime was measured and compared by photoconductive decay transients of HgCdTe before and after deposition. Room temperature ALD Al2O3 film increased the minority carrier lifetime of HgCdTe.

  7. Effective optimization of surface passivation on porous silicon carbide using atomic layer deposited Al2O3

    DEFF Research Database (Denmark)

    Lu, Weifang; Iwasa, Yoshimi; Ou, Yiyu

    2017-01-01

    of the PL intensity (up to 689%). The effect of thickness, annealing temperature, annealing duration and precursor purge time on the PL intensity of ALD Al2O3 films was investigated. In order to investigate the penetration depth and passivation effect in porous SiC, the samples were characterized by X......-ray photoelectron spectroscopy (XPS) and time-resolved PL. The optimized passivation conditions (20 nm Al2O3 deposited at 160 °C with purge time of 20 s, followed by an annealing for 5 min at 350 °C) for porous SiC were achieved and the results indicate that surface passivation by ALD Al2O3 thin films is a very...

  8. Transformation toughening of Al2O3/ZrO2 laminated ceramics with residual compressive stress

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    With the help of scanning electronic microscopy and X-ray diffraction, the relationships of microstmcture characteristics,phase assemblage, and fracture micrograph of Al2O3/ZrO2 laminated ceramics were studied. Compared with monolithic Al2O3/ZrO2 ceramics, the existence of surface compressive stresses greatly restrained the growth of ZrO2 and Al2O3 grains at high sinter temperature, fined the grain size, and increased the content of metastable t-ZrO2, which made the fracture transformation energy quantity 70% higher than that of the monolithic ceramics. The trans-granular and inter-granular fracture features were observed in the surface and center layers, which further verified that transformation toughening is the main mechanism, whereas, micro-crack toughening is helpful for enhancing fracture toughness.

  9. Selective hydrogenation of maleic anhydride over Pd/Al2O3 catalysts prepared via colloid deposition

    Indian Academy of Sciences (India)

    Hongjing Yuan; Chunlei Zhang; Weitao Huo; Chunli Ning; Yong Tang; Yi Zhang; Dequan Cong; Wenxiang Zhang; Jiahuan Luo; Su Li; Zhenlu Wang

    2014-01-01

    Pd/Al2O3 catalysts were prepared via colloid deposition and the performance of the catalysts was examined in the selective hydrogenation of maleic anhydride to succinic anhydride. When the reaction was carried on in a batch system with 1,4-dioxane as the solvent (353K and 1.0MPa), high conversion of maleic anhydride (>98%) and high selectivity (>99%) for succinic anhydride were observed after 5 h. The as-prepared Pd/Al2O3 catalyst also showed excellent performance in solvent-free system and fixed-bed systems. The maleic anhydride (MA) conversion was greater than 98%, and high selectivity (>99%) for succinic anhydride was obtained after 1600 h in a fixed bed reacter. The results showed that the activity of the Pd/Al2O3 catalysts was excellent due to its high active surface area.

  10. Thiophene hydrodesulfurization over CoMo/Al2O3-CuY catalysts: Temperature effect study

    Directory of Open Access Journals (Sweden)

    Yamina Boukoberine

    2016-09-01

    Full Text Available CoMo/γ-Al2O3-CuY catalysts are prepared by physically mixing CoMo/γ-Al2O3 catalyst with Cu-exchanged Y zeolite. The CuY zeolite is prepared by the solid state ion exchange technique. The thiophene hydrodesulfurization is performed in a fixed bed reactor at high temperature and atmospheric pressure. The results show that the presence of CuY zeolite particles in CoMo/Al2O3 catalyst can have a noticeable effect on both the conversion and product selectivities. An increasing zeolite loading in catalyst results in a decrease of the thiophene HDS activity. This decrease is probably caused by the formation of heavy compounds and the deactivation of the zeolite at high temperatures.

  11. Porous-Al2O3 thermal barrier coatings with dispersed Pt particles prepared by cathode plasma electrolytic deposition

    Institute of Scientific and Technical Information of China (English)

    Jin Zhang

    2016-01-01

    Porousa-Al2O3 thermal barrier coatings (TBCs) containing dispersed Pt particles were prepared by cathode plasma electrolytic deposition (CPED). The influence of the Pt particles on the microstructure of the coatings and the CPED process were studied. The prepared coatings were mainly composed ofα-Al2O3. The average thickness of the coatings was approximately 100μm. Such single-layer TBCs ex-hibited not only excellent high-temperature cyclic oxidation and spallation resistance, but also good thermal insulation properties. Porousa-Al2O3 TBCs inhibit further oxidation of alloy substrates because of their extremely low oxygen diffusion rate, provide good thermal insu-lation because of their porous structure, and exhibit excellent mechanical properties because of the toughening effect of the Pt particles and because of stress relaxation induced by deformation of the porous structure.

  12. Effect of Rare Earths on Mechanical Properties and Microstructure of TiCN/Al2O3 Ceramics

    Institute of Scientific and Technical Information of China (English)

    Li Xikun; Xiu Zhimeng; Sun Xundong

    2004-01-01

    The effects of Y on mechanical properties and microstructure of TiCN/Al2O3 ceramics were studied in details. The experimental results show that the mechanical properties and microstructure can be improved by adding rare earth in TiCN/Al2 O3 ceramics, flexural strength and fracture toughness of the composites increased when Y is doped by 18.99% and 18.58% than those of the matrix, respectively. Microstructure of cracks extension was observed through SEM and TEM. The mechanics of particles bridge, cracks branch and cracks deflection are enforced obviously during the processes of cracks extension because strong interfaces and weak interfaces coexist, so manifold mechanics of enforcement of toughness act upon together to increase fracture toughness of TiCN/Al2 O3 doped with Y.

  13. Estimation Model for Electrical Conductivity of CaF2-CaO-Al2O3 Slags

    Science.gov (United States)

    Shi, Guan-yong; Zhang, Ting-an; Dou, Zhi-he; Niu, Li-ping

    2016-09-01

    Electrical conductivity is one of the most important properties of molten slags. It has an important influence on process parameter selection of the electroslag remelting process. In the present work, a new model for estimating electrical conductivity of high-temperature slags has been proposed via calculating the conductivity by electrical conductivity of pure substances and interaction parameters between the different components in the slag has been proposed. In this model, the Arrhenius law is used to describe the relationship between electrical conductivity and temperature of slags. This model has been successfully applied to the CaF2-Al2O3, CaF2-CaO, and CaO-Al2O3, as well as CaF2-CaO-Al2O3 systems, and the calculated results are in good agreement with the measured values.

  14. Passivation of type II InAs/GaSb superlattice photodetectors with atomic layer deposited Al2O3

    Science.gov (United States)

    Salihoglu, Omer; Muti, Abdullah; Kutluer, Kutlu; Tansel, Tunay; Turan, Rasit; Kocabas, Coskun; Aydinli, Atilla

    2012-06-01

    We have achieved significant improvement in the electrical performance of the InAs/GaSb midwave infrared photodetector (MWIR) by using atomic layer deposited (ALD) aluminium oxide (Al2O3) as a passivation layer. Plasma free and low operation temperature with uniform coating of ALD technique leads to a conformal and defect free coverage on the side walls. This conformal coverage of rough surfaces also satisfies dangling bonds more efficiently while eliminating metal oxides in a self cleaning process of the Al2O3 layer. Al2O3 passivated and unpassivated diodes were compared for their electrical and optical performances. For passivated diodes the dark current density was improved by an order of magnitude at 77 K. The zero bias responsivity and detectivity was 1.33 A/W and 1.9 x 1013 Jones, respectively at 4 μm and 77 K. Quantum efficiency (QE) was determined as %41 for these detectors.

  15. Experiment and prediction on thermal conductivity of Al2O3/ZnO nano thin film interface structure

    Indian Academy of Sciences (India)

    Ping Yang; Liqiang Zhang; Haiying Yang; Dongjing Liu; Xialong Li

    2014-05-01

    We predict that there is a critical value of Al2O3/ZnO nano thin interface thickness based on two assumptions according to an interesting phenomenon, which the thermal conductivity (TC) trend of Al2O3/ZnO nano thin interface is consistent with that of relevant single nano thin interface when the nano thin interface thickness is > 300 nm; however, TC of Al2O3/ZnO nano thin interface is higher than that of relevant single nano thin interface when the thin films thickness is < 10 nm. This prediction may build a basis for the understanding of interface between two different oxide materials. It implies an idea for new generation of semiconductor devices manufacturing.

  16. Corrosion Behavior of Electrodepositing Ni/Al2O3 Composite Coatings under the Presence of NaCl Deposit

    Institute of Scientific and Technical Information of China (English)

    Xie Danyang; Liu Lin

    2007-01-01

    The morphology and corrosion behavior of Ni/Al2O3 composite coatings prepared using double-pulsed electrodepositing technique after oxidized under 800℃ NaCl deposit in air environment were analyzed by scanning electrical microscope (SEM), X-ray diffraction (XRD) and energy dispersive spectrum (EDS). The results showed that the corrosion of all composite coatings was accelerated under NaCl deposits, and the corrosion products were rather porous with poor adherence to the matrix. Al2)O3 particles in the coatings can refine the grain size and improve the high temperature corrosion resistance of the coatings. Within the test scope, the more Al2O3 particles in the coatings, the lower corrosion rates could be obtained, and the corrosion mechanism was also discussed.

  17. Preparation and mechanical properties of Fe3Al/Al2O3 nano-/micro-composite

    Institute of Scientific and Technical Information of China (English)

    尹衍升; 龚红宇; 范润华; 王昕; 谭训彦

    2003-01-01

    Al2O3 matrix composites reinforced with Fe3 Al nano-particles were fabricated by hot processing at 1 450-1 600℃.The effect of Fe3Al content on the densification,mechanical properties and microstructure of the composites was investigated.The results show that some elongated Al2 O3 grains are observed.Fe3 Al particles are mainly situated at grain boundaries of the matrix while smaller particles are trapped within the alumina grains.The addition of Fe3 Al nanoparticles improves the mechanical properties of alumina.The maximum strength and toughness of the Fe3Al/Al2O3 nanocomposites are 832 Mpa and 7.96 Mpa·m1/2,respectively.

  18. Growth and luminescence properties of Eu-doped HfO2/α-Al2O3 eutectic scintillator

    Institute of Scientific and Technical Information of China (English)

    Kei Kamada; Kosuke Hishinuma; Shunsuke Kurosawa; Akihiro Yamaji; Yasuhiro Shoji; Jan Pejchal; Yuji Ohashi; Yuui Yokota; Akira Yoshikawa

    2016-01-01

    HfO2/α-Al2O3 eutectics were grown by the micro-pulling down (μ-PD) method at the composition of 63.2 mol.%α-Al2O3, 35.512 mol.%HfO2, 0.92 mol.%Eu2O3 and 0.368 mol.%Y2O3. Rod phases with around 3–4μm diameter were observed on the transverse cross-section. The phase-separated scintillator fibers (PSSFs) structure with fibers of around 3–4μm diameter and 10–20μm length was observed. The electron back scattering patterns indicated crystal orientation of [101] for monoclinic HfO2 rod phase and [0001] forα-Al2O3 matrix in the transverse cross-section. Eu3+4f-4f emission was observed at 550–750 nm.

  19. Microwave Response of MgB2/Al2O3 Superconducting Thin Films by Microstrip Resonator Technique

    Institute of Scientific and Technical Information of China (English)

    SHI Li-Bin; ZHENG Yan; REN Jun-Yuan; LI Ming-Biao; ZHANG Feng-Yun; LI Bo-Xin; DONG Hai-Kuan

    2007-01-01

    Double-sided superconducting MgB2 thin films are deposited onto c-Al2O3 substrates by the hybrid physical chemical vapour deposition method. The microwave response of MgBz/Al2O3 is investigated by microstrip resonator technique. A grain-size model is introduced to the theory of microstrip resonators to analyse microwave properties of the films. We obtain effective penetration depth of the films at 0K (λe0 = 463 nm) and surface resistance (R3 = 1.52mΩ at 11 K and 8.73 GHz) by analysing the resonant frequency and unload quality factor of the microstrip resonator, which suggests that the impurities and disorders of grain boundaries of MgB2/Al2O3 result in increasing penetration depth and surface resistance of the films.

  20. A study on Al2O3 passivation in GaN MOS-HEMT by pulsed stress

    Institute of Scientific and Technical Information of China (English)

    Yue Yuan-Zheng; Hao Yue; Zhang Jin-Cheng; Feng Qian; Ni Jin-Yu; Ma Xiao-Hua

    2008-01-01

    This paper studies systematically the drain current collapse in AlGaN/GaN metal-oxide-semiconductor high electron mobility transistors (MOS-HEMTs) by applying pulsed stress to the device. Low-temperature layer of Al2O3 ultrathin film used as both gate dielectric and surface paasivation layer was deposited by atomic layer deposition (ALD).For HEMT, gate turn-on pulses induced large current collapse. However, for MOS-HEMT, no significant current collapse was found in the gate turn-on pulsing mode with different pulse widths, indicating the good passivation effect of ALD Al2O3. A small increase in Id in the drain pulsing mode is due to the relieving of self-heating effect. The comparison of synchronously dynamic pulsed Id - Vds characteristics of HEMT and MOS-HEMT further demonstrated the good passivation effect of ALD Al2O3.

  1. 纳米Al_2O_3颗粒增强新型铜基自润滑复合材料%Nano-Al_2O_3 particle reinforced Cu-based self-lubricating composites

    Institute of Scientific and Technical Information of China (English)

    陈岁元; 刘义杰; 刘常升; 孙桂芳

    2009-01-01

    以Cu-Ni-Y_2O_3-MoS_2-Graphite混合粉为基体, 加入质量分数分别为0%、1%、2%、3%、4%的纳米Al_20_3增强相, 采用粉末冶金方法制备纳米Al_2O_3增强新型铜基自润滑复合材料. 结果表明: 随着铜合金粉末中纳米Al_2O_3颗粒含量的增加, 所制备自润滑复合材料样品的密度下降, 但硬度和压溃强度先上升后下降, 在Al_2O_3含量为2%时硬度从HV 23. 7增加到HV 35. 1, 压溃强度从189 MPa提高到276 MPa. 由石墨和MoS2组成的混合固体自润滑材料的摩擦系数小且稳定, 约0.12. Al_2O_3质量分数为2%的样品磨损量最小, 是未加Al_2O_3试样磨损量的1/7~1/8. 铜基体经过镍、纳米Al_2O_3等弥散颗粒强化和固体润滑相石墨和MoS_2的加入, 所制备的材料已具有一定的自润滑性能.%Taking the mixture powders of Cu-Ni-Y_2O_3-MoS_2-Graphite as the matrix, and adding nano-Al_2O_3 mass fraction of 0%, 1%, 2%, 3% and 4% as the particle ment reinforce phase. Cu-based self-lubricating composite was prepared by powder metallurgy technology. The results show that the density of the samples decreases with increasing the content of nano-Al_2O_3, but the hardness and crushing strength of the samples increase firstly, then decrease. The hardness increas from HV 23. 7 to HV 35. 1 and the crushing strength increases from189 to 276 MPa with the increasing mass frautions of nano-Al_2O_3 from 0% to 2%. Friction coefficient of the materials with the mixture of graphite and MoS_2 is about 0.12. The least wear loss is 1/7~1/8 by contrasting thesample with non-nano-Al_2O_3. The copper-based self-lubricating composites reinforced with Ni and nano-Al_2O_3 by dispersion strengthening, and added with graphite and MoS_2 as solid lubricant, have definite self-lubricating properly.

  2. Al2O3绝缘栅SiC MIS结构基本特性的研究%Fundamental characteristics of SiC MIS structure with Al2O3 as gate dielectric

    Institute of Scientific and Technical Information of China (English)

    刘莉; 杨银堂; 马晓华

    2011-01-01

    采用原子层淀积(ALD)方法在4H-SiC(0001)8°N-/N+外延层上制备了超薄(~4 nm)Al2O3绝缘栅高介电常数SiC MIS电容.通过对Al2O3介质膜以及Al2O3/SiC界面微结构和电学特性分析表明,实验所得Al2O3介质膜具有较好的体特性和界面特性,Al2O3薄膜的击穿电场为25MV/cm,并且在可以接受的界面态密度(2×1013 cm-2)下具有较小的栅泄漏电流(8 MV/cm电场下漏电流密度为l×10-3A/cm-2).电流-电压测试分析表明,在FN隧穿条件下,SiC/A12O3之间的势垒高度为1.4 eV,已达到制作SiC MISFET器件的要求.同时,在整个栅压区域也受Frenkel-Poole和Schottkv机制的共同影响.%SiC MIS structure with ultra-thin Al2O3 as gate dielectric deposited by atomic layer deposition (ALD) on epitaxial layer of 4H-SiC(0001)8°N-/N+ substrate is fabricated.The microstructure and electrical characteristics analysis on the film and Al2O3/SiC interface has shown that Al2O3 deposited has a good bulk characteristics and a good quality between Al2O3 and SiC.The breakdown electrical field of Al2O3 film is 25 MV/cm; the MIS capacitor has a fairly low gate leakage current (current density of 1×10-3A/cm-2 with a electric field of 8 MV/cm) under acceptable interface effective charge (2× 1013 cm-2).Current-voltage measurement and analysis has shown that when the gate leakage current mechanism is dominated by FN tunneling, the barrier height of SiC/Al2O3 is 1.4 eV,which can meet the requirement of SiC MISFET devices.Besides this, the gate leakage current is co-influenced by both of Frenkel-Poole mechanism and Schottky emission.

  3. Characterization and Activity of Cu-MnOx/γ-Al2O3 Catalyst forHydrogenation of Carbon Dioxide

    Institute of Scientific and Technical Information of China (English)

    QI, Gong-Xin; ZHENG, Xiao-Ming; FEI, Jin-Hua; HOU, Zhao-Yin

    2001-01-01

    The effect of manganese on the dispersion, reduction behaviorand active states of surface of supported copper oxide catalysts have been investigated by XRD, temperature-programmed reduction and XPS. The activity of methanol synthesis from CO2/H2 was also investigated. The catalytic activity over CuO-MnOx/γ-Al2O3 catalyst for CO2 hydrogenation is higher than that of CuO/γ-Al2O3. The adding of manganese is beneficial in enhancing the dispersion of the supported copper oxide and make the TPR peak of the CuO-MnOx/γ-Al2O3 catalyst different from the individual supported coppper and manganese oxide catalysts, which indicates that there exists strong interaction between the copper and manganese oxide. For the CuO/γ-Al2O3 catalyst there are two reducible copper oxide species; α and β peaks are attributed to the reduction of highly dispersed copper oxide species and bulk CuO species, respectively. For the CuO-MnOx/γ-Al2O3 catalyst, four reduction peaks are observed, α peak is attributed to the dispersed copper oxide species; β peak is ascribed to the bulk CuO; γ peak is attributed to the reduction of high dispersed CuO interacting with manganese; δ peak may be the reduction of the manganese oxide interacting with copper oxide. XPS results show that Cu+ mostly existed on the working surface of the Cu-Mn/γ-Al2O3 catalysts. The activity was promoted by Cu with positive charge which was formed by means of long path exchange function between Cu-O-Mn. These results indicate that there is synergistic interaction between the copper and manganese oxide, which is responsible for the high activity of CO2 hydrogenation.

  4. Synthesis and Characterization of Biodegradable Ultrasonicated Films made from Chitosan/al2o3 Polymer Nanocomposites

    Science.gov (United States)

    Prakash, B.; Jothirajan, M. A.; Umapathy, S.; Amala, Viji

    Chitosan is a biopolymer which is biodegradable, biocompatible, non toxic and cationic in nature. Due to these interesting properties, it finds advanced applications in sensors, drug delivery vehicle and gene therapy etc., In this present work, the biocompatible Al2O3 Nano particles were embedded into Chitosan Polymer matrix by ultrasonication route. XRD and FTIR studies confirm the presence of Al2O3 nanoparticle in the Chitosan polymer matrix. The morphological, optical, electrical properties of the polymer nano composite films are carried out by employing scanning electron microscopy (SEM), UV- Vis, LCR and Impedance studies.

  5. Characterization of Al2O3 as CIGS surface passivation layer in high-efficiency CIGS solar cells

    OpenAIRE

    Joel, Jonathan

    2014-01-01

    In this thesis, a novel method of reducing the rear surface recombination in copper indium gallium (di) selenide (CIGS) thin film solar cells, using atomic layer deposited (ALD) Al2O3, has been evaluated via qualitative opto-electrical characterization. The idea stems from the silicon (Si) industry, where rear surface passivation layers are used to boost the open-circuit voltage and, hence, the cell efficiency. To enable a qualitative assessment of the passivation effect, Al/Al2O3/CIGS metal-...

  6. High Activity SnO2/Al2O3 Catalyst for NO Reduction in the Presence of Oxygen

    Institute of Scientific and Technical Information of China (English)

    Jun Hua LI; Ji Ming HAO; Li Xin FU; Tian Le ZHU; Zhi Ming LIU; Xiang Yu CUI

    2004-01-01

    The novel sol-gel SnO2/Al2O3 catalysts for selective catalytic reduction NO by propene under lean burn condition were investigated. The results showed that the maximum NO conversion was 82% on the SnO2/Al2O3 (5%Sn) catalyst, and the presence of H2O and SO2 improved the catalytic activity at low temperature. The catalytic activity of NO2 reduction by propene is much higher than that of NO at the entire temperature range, and the maximum NO2 conversion reached nearly 100% around the temperature 425℃.

  7. Contemplation of thermal characteristics by filling ratio of Al2O3 nanofluid in wire mesh heat pipe

    OpenAIRE

    R. Senthil; D. Ratchagaraja; R. Silambarasan; Manikandan, R.

    2016-01-01

    An experimental investigation on the thermal efficiency and thermal resistance with respect to the inclined angle using heat pipe was carried out. The working fluids used for this are Al2O3 nanofluid and deionized water. The performance of heat pipe in terms of overall heat transfer coefficient and thermal resistance is quantified by varying the volume of working fluid and the performance parameters are contemplated. For this purpose Al2O3 nanoparticles with a density of 9.8 g/cm3 and a volum...

  8. CeO2-Al2O3复合氧化物的制备与表征

    Institute of Scientific and Technical Information of China (English)

    彭友林; 王勇; 徐宾

    2015-01-01

    本文以Ce(NO3)3和Al(NO3)3为原料,柠檬酸为络合沉淀剂,聚乙二醇为分散剂,采用柠檬酸络合法合成了纯CeO2和CeO2-Al2O3复合氧化物,并且利用XRD手段对纯CeO2和CeO2-Al2O3复合氧化物进行了表征。

  9. Amplification of femtosecond pulses in Ti:Al2O3 using an injection-seeded laser

    Science.gov (United States)

    Lagasse, M. J.; Schoenlein, R. W.; Fujimoto, J. G.; Schulz, P. A.

    1989-12-01

    A 440-fsec, 0.1-pJ pulse from a dye laser is injected into a high-repetition-rate Ti:Al2O3 laser pumped by a copper-vapor laser to study the amplification and pulse broadening of femtosecond pulses in Ti:Al2O3. Gains of 2 x 10 to the 7th are achieved with output pulse durations of 1.1 psec. After recompression with a grating pair to compensate dispersion broadening, pulses as short as 275 fsec are obtained.

  10. Strengthening and Toughening Effect of Yttrium on Al2O3/TiCN Ceramic Tool Material

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The strengthening and toughening effect of yttrium on an advanced Al2O3/TiCN ceramic tool material was studied by means of SEM, TEM and energy spectrum analysis. Results showed that yttrium can react with the impurity elements such as W, Fe, Cr, etc. Thus, the interfaces between ceramic phases are purified and the interfacial binding strength is increased. As a result, the mechanical properties of the Al2O3/TiCN ceramic tool material reinforced with yttrium are improved significantly. In addition, the effect of yttrium on particle strengthening of the solid solution TiCN may partly contribute to the improvement of the mechanical properties.

  11. Studies on the properties of Al2O3:Cr2O3 (50:50) thin film

    Science.gov (United States)

    Ponmudi, S.; Sivakumar, R.; Sanjeeviraja, C.

    2016-05-01

    Aluminium oxide (Al2O3) and chromium oxide (Cr2O3) thin films have received great attention of researchers because of their unique properties of corrosion/oxidation resistance and high dielectric constant. In addition, chromium aluminium oxide has been considered as a best candidate for deep-ultraviolet optical masks. In the present work, thin films of Al2O3:Cr2O3 (50:50) were deposited on pre-cleaned microscopic glass substrate by RF magnetron sputtering technique. The substrate temperature and RF power induced changes in structural, surface morphological, compositional and optical properties of the films have been studied.

  12. The Influence of Mo Additive on the Microstructure and Property of Ti/Al2O3 Composite

    Institute of Scientific and Technical Information of China (English)

    WANG Zhi; LI Ming-ling; SHEN Qiang; ZHANG Lian-meng

    2003-01-01

    The influence of Mo on the microstructure, bending strength and HV of Ti/Al2O3 composite was studied, and the influence mechanism was analyzed . The results indicate that after the addition of Mo, the composite organization is finer and phases distribution is better-proportioned which make the microstructure denser , the bending strength and HV of composite are also increased to a degree . But the bending strength inceases first then decreases with the increasing of Mo content, so the appropriate Mo content for the Ti/Al2O3 composite is to be further confirmed.

  13. Microstructural characterization of Cu/ZnO/Al2O3 catalysts for the synthesis and steam reforming of methanol

    OpenAIRE

    2008-01-01

    Cu/ZnO/Al2O3 Katalysatoren stellen ein vielseitig einsetzbares Katalysatorsystem, wie z.B. für die Methanol Synthese sowie für die Methanol Dampfreformierung, dar. Letztere Reaktion kann formal auch als die Rückreaktion der Methanol Synthese ausgehend von CO2 und H2 betrachtet werden. In der vorliegenden Arbeit wurden unterschiedlich präparierte Cu/ZnO/Al2O3 Katalysatoren mittels in situ Röntgenbeugung sowie Röntgenabsorptionsspektroskopie hinsichtlich ihrer Mikrostruktur untersucht. Zusätzli...

  14. Microstructural characterization of Cu/ZnO/Al2O3 catalysts for the synthesis and steam reforming of methanol

    OpenAIRE

    2008-01-01

    Cu/ZnO/Al2O3 catalysts represent a versatile catalyst system for methanol chemistry, including the synthesis and steam reforming of methanol. Formally, the steam reforming of methanol is the reverse of methanol synthesis from CO2 and H2. In the present work a set of differently prepared Cu/ZnO/Al2O3 catalysts with a fixed composition of Cu/Zn/Al = 60:30:10 were investigated by in situ bulk techniques, X-ray diffraction, and X-ray absorption spectroscopy. Additionally, microscopic and morpholo...

  15. Elastic, dielectric, and piezoelectric properties of ceramic lead zirconate titanate/α-Al2O3 composites

    Science.gov (United States)

    Rybyanets, A. N.; Konstantinov, G. M.; Naumenko, A. A.; Shvetsova, N. A.; Makar'ev, D. I.; Lugovaya, M. A.

    2015-03-01

    The technology of producing ceramic lead zirconate titanate/α-Al2O3 composites has been developed. Elements of piezoactive composites containing from 0 to 60 vol % α-Al2O3 have been prepared. The elastic, dielectric, and piezoelectric parameters of the synthesized ceramic composites have been measured, and their microstructure has been studied. It has been found that the concentration dependences of the elastic and piezoelectric properties exhibit anomalies. The obtained data have been interpreted based on the percolation theory and the concept of microstructural constructing polycrystalline composition materials.

  16. Mechanical behaviour of Al/Al_2O_3 composite in pseudo-semi-solid state during isothermal compression

    Institute of Scientific and Technical Information of China (English)

    CHENG Yuan-sheng; LUO Shou-jing

    2009-01-01

    To gain a better understanding of thixoforging for the Al_2O_3-37%Al composite, its mechanical behavior in the pseudo-semi-solid state was studied by isothermal compression tests. The results show that the values of peak stress obviously decrease with increasing temperature and decreasing strain rate. The compressive true stress-strain curves of the Al_2O_3-37%Al composite can be divided into four stages. They are rapidly ascending, decreasing, steady and slowly ascending. Moreover, the main deformation mechanism controlling deformation of the composite in the pseudo-semi-solid state is the sliding or rotary movement between solid particles.

  17. Characterization of microstructure and properties of Al–Al$_3$Zr–Al$_2$O$_3$ composite

    Indian Academy of Sciences (India)

    ANUP MANDAL; KARABI DAS; SIDDHARTHA DAS

    2016-08-01

    Aluminium-based metal matrix composite strengthened by in situ Al$_2$O$_3$ and Al$_3$Zr particles were synthesized by powder metallurgy route. Phase analysis by X-ray diffraction and scanning electronmicroscopy revealed that the reaction between Al and ZrO$_2$ produced Al$_2$O$_3$ and Al$_3$Zr phases in the sintered composites. The hardness of the composite is a strong function of sintering temperature as well as the volume fraction of reinforcements. The dry sliding wear test results clearly indicated that increasing the volume fraction of zirconia particles in the compositeimproved the wear resistance. Microcutting, ploughing, delamination and oxidation were the main mechanisms of wear.

  18. Effect of Uniformly and Nonuniformly Coated Al2O3 Nanoparticles over Glass Tube Heater on Pool Boiling

    Directory of Open Access Journals (Sweden)

    Nitin Doifode

    2016-01-01

    Full Text Available Effect of uniformly and nonuniformly coated Al2O3 nanoparticles over plain glass tube heater on pool boiling heat transfer was studied experimentally. A borosilicate glass tube coated with Al2O3 nanoparticle was used as test heater. The boiling behaviour was studied by using high speed camera. Result obtained for pool boiling shows enhancement in heat transfer for nanoparticle coated surface heater and compared with plain glass tube heater. Also heat transfer coefficient for nonuniformly coated nanoparticles was studied and compared with uniformly coated and plain glass tube. Coating effect of nanoparticles over glass tube increases its surface roughness and thereby creates more nucleation sites.

  19. Formation of a 25 mol% Fe2O3-Al2O3 solid solution prepared by ball milling

    DEFF Research Database (Denmark)

    Jiang, Jianzhong; Mørup, Steen; Linderoth, Søren

    1996-01-01

    The phase transformation process of a 25 mol% Fe2O3-Al2O3 powder mixture during high-energy ball milling has been studied by x-ray diffraction and Mossbauer spectroscopy. A metastable solid solution of 25 mol % Fe2O3 in Al2O3 with corundum structure has successfully been prepared after a milling...... time of 122 h. This demonstrates that the high-energy ball milling technique is able to prepare metastable solid solutions with an extended range of compositions in ceramic/ceramic systems with a positive hear of mixing....

  20. Photoluminescence enhancement in porous SiC passivated by atomic layer deposited Al2O3 films

    DEFF Research Database (Denmark)

    Lu, Weifang; Iwasa, Yoshimi; Ou, Yiyu;

    2016-01-01

    Porous SiC co-doped with B and N was passivated by atomic layer deposited (ALD) Al2O3 films to enhance the photoluminescence. After optimizing the deposition conditions, as high as 14.9 times photoluminescence enhancement has been achieved.......Porous SiC co-doped with B and N was passivated by atomic layer deposited (ALD) Al2O3 films to enhance the photoluminescence. After optimizing the deposition conditions, as high as 14.9 times photoluminescence enhancement has been achieved....

  1. Microstructures of TiC-Al2O3-Fe Composites Prepared by SHS/PHIP%TiC-Al2O3-Fe复合材料的微观组织研究

    Institute of Scientific and Technical Information of China (English)

    张卫方; 陶春虎; 习年生; 韩杰才; 杜善义

    2001-01-01

    The microstructure of TiC-Al2O3-Fe composites prepared by SHS/PHIP was studied. As the Fe content was increased, the particle size of TiC decreased, and the distribution of Al2O3 became homogeneous. There existed a little of particle phase in TiC grains. While some of ε-(AlTi)Fe3Cx cellular phase with ε-AlFe3C0.69 structure was found in Fe-binder phase. A great deal of dislocation were observed in TiC grains because of the rapid pressing in the process of SHS/PHIP.%对SHS/PHIP技术制备出的TiC-Al2O3-Fe复合材料的微观组织结构进行了分析和研究. 结果表明,随着Fe含量的增加,TiC颗粒尺寸减小, Al2O3的分布趋于均匀. 在TiC晶粒中发现少量颗粒相;在Fe粘结相中发现具有ε-AlFe3C0.69型结构的胞状相;TiC晶粒中存在大量位错.

  2. Evalution on Surface Quality of n-Al2O3/Ni-P Composite Electroless Plating%n-Al2O3/Ni-P化学复合镀镀层表面质量评价

    Institute of Scientific and Technical Information of China (English)

    赵艺伟; 黄燕滨; 刘菲菲

    2009-01-01

    为了研究n-Al2O3/Ni-P化学复合镀层的表面质量,通过正交试验,得到n-Al2O3/Ni-P化学复合镀的最佳工艺参数为:温度86℃,pH值为5.2,搅拌量60L/h,纳米含量8g/L,表面活性剂A为2g/L,B为40mL.以镀层的硬度、孔隙率和表面粗糙度为评价标准,结果表明,n-Al2O3/Ni-P化学复合镀镀层的表面质量优于Ni-P化学镀:n-Al2O3/Ni-P化学复合镀镀层表面均匀致密,孔隙率等级为9级,硬度达到620HV,表面粗糙度Ra0.628μm.

  3. Anti-shrinkage finish of wool fabric with nano Al2O3/GPTMS Sol-gel%纳米Al2O3/GPTMS复合溶胶的羊毛防毡缩整理

    Institute of Scientific and Technical Information of China (English)

    林桂凤; 阎克路

    2006-01-01

    采用分散剂分散法、无机酸改性法和溶胶法制备纳米Al2O3颗粒分散体系,并对其粒径分布及储存稳定性进行了比较.将这三种方法制备的纳米Al2O3分别添加到GPTMS(3-缩水甘油醚氧丙基三甲氧基硅烷)溶胶中,采用轧烘焙工艺对羊毛织物进行防毡缩整理;测定织物的润湿性、接触角、定向摩擦效应、面积毡缩率;结合扫描电镜分析,评定和探讨纳米Al2O3/GPTMS复合溶胶中纳米Al2O3所起的作用.

  4. 用Pd-Cu-Pt/γ-Al2O3催化剂还原水中的硝酸盐%Catalytic Reduction of Nitrate in Water over Pd-Cu-Pt/γ-Al2O3 Catalyst

    Institute of Scientific and Technical Information of China (English)

    高建峰; 徐春彦; 王久芬; 庄源益

    2004-01-01

    以自制的高纯γ-Al2O3为载体,用双浸渍法制备了不同Pd/Cu比的Pd-Cu/γ-Al2O3催化剂,在间歇式反应器中直接处理含硝酸盐废水. 结果表明,利用不同Pd/Cu比的Pd-Cu/γ-Al2O3催化剂及Pd-Cu-Pt/γ-Al2O3催化剂,同时用甲酸为pH调节剂,在适合的条件下,于40 min内就能达到脱除硝酸盐的目的,氮脱除率可达95%. 这有可能发展成为一项有效和实用的水处理技术,特别是在以地下水作为饮用水源的农村地区.

  5. Ag2S/Al2O3纳米复合物的水热合成及表征%Hydrothermal Synthesis and Characterization of Ag2S/Al2O3 Nanocomposite

    Institute of Scientific and Technical Information of China (English)

    刘福红; 马新艳; 龚剑

    2011-01-01

    采用水热技术结合煅烧的方法,成功制备了Ag2 S/Al2O3纳米复合物.通过SEM、EDX、XRD等测试技术对产品进行了表征,证明得到的产品是Ag2S/Al2O3纳米复合物;无孔Al2O3和多孔Al2O3作反应模板得到的复合物的形态和分布不同.%Ag2 S/A12 03 nanocomposite was successfully prepared by hydrothermal method and calcination process. The structure and morphology of Ag2S/Al203 nanocomposite were characterized and confirmed by scanning electron microscopy(SEM) , energy-dispersive X-ray analysis ( EDX ) , and X-ray diffraction ( XRD ) patterns. The morphology and distribution of the product prepared with nonporous A12O3 and porous A12O3 as templates are different.

  6. Al2O3栅介质的制备工艺及其泄漏电流输运机制%Fabrication Process and Leakage Current Conduction Mechanisms of Al2O3 Gate Dielectric Thin Films

    Institute of Scientific and Technical Information of China (English)

    任驰; 杨红; 韩德栋; 康晋锋; 刘晓彦; 韩汝琦

    2003-01-01

    利用室温下反应磁控溅射结合炉退火的方法在P-Si(100)衬底上制备了Al2O3栅介质层,研究了不同的溅射气氛和退火条件对Al2O3栅介质层物理特性的影响.结果表明:在较高温度下N2气氛中退火有助于减小泄漏电流;在O2气氛中退火有助于减少Al2O3栅介质中的氧空位缺陷.对Al2O3栅介质泄漏电流输运机制的分析表明,在电子由衬底注入的情况下,泄漏电流主要由Schottky发射机制引起,而在电子由栅注入的情况下,泄漏电流可能由Schottky发射和Frenkel-Poole发射两种机制共同引起.

  7. Toughness enhancement in graphene nanoplatelet/SiC reinforced Al2O3 ceramic hybrid nanocomposites

    Science.gov (United States)

    Ahmad, Iftikhar; Islam, Mohammad; Subhani, Tayyab; Zhu, Yanqiu

    2016-10-01

    This paper elucidates the effect of silicon carbide nanoparticles (SiCNP) and graphene nanoplatelets (GNPs), on their own and together, on the densification behavior and fracture toughness of alumina (Al2O3) ceramic matrix. This was investigated by using the high-frequency induction heat sintering (HFIHS) process. While the addition of each nanostructure caused varying degrees of grain refinement and enhancement of mechanical properties, the incorporation of as little as 0.5 wt.% GNPs along with 5.0 wt.% SiCNP promoted uniform dispersion of the latter due to the lateral surface area of the graphene nanosheets with their two-dimensional morphology. There was an associated reduction in grain size from 1500 to 300 nm upon the addition of both types of nanoscale reinforcements. Extensive electron microscopy of the as-produced nanocomposites indicated the presence of SiCNP within, as well as at, the grain boundary areas whereas the 2D GNPs anchored between neighboring grains. Fractography of the samples revealed a transition from a mixed intergranular/transgranular mode for SiCNP or GNP-reinforced nanocomposites to transgranular fracture mode for the hybrid nanocomposites with improvements in fracture toughness and microhardness by 160 and 27%, respectively, largely due to the synergic role of the nanostructured reinforcements and their distinctly different toughening mechanisms. A new toughening model is proposed for the hybrid nanocomposites by taking into consideration crack deflection and pull-out effects due to SiCNP and the atomic level slip-stick driven GNPs inter-layer slithering. It was found that the addition of GNPs facilitates SiCNP dispersion that subsequently develops dense, fine-grained microstructures after a short-cycle, pressure-assisted consolidation process.

  8. Effect of microstructure on slag resistance of Al2 O3-Cr2 O3 bricks%Al2O3-Cr2O3砖显微结构对抗渣性能的影响

    Institute of Scientific and Technical Information of China (English)

    孙红刚; 李鹏涛; 付建莹; 闫双志; 王刚; 耿可明

    2014-01-01

    The slag resistance of two Al2 O3-Cr2 O3 bricks (with 10 mass%Cr2 O3 )A and B were researched using static crucible method and rotary slag method,respectively.The results show that,two Al2 O3-Cr2 O3 bricks have similar properties such as apparent porosity,bulk density,thermal shock resistance,and chem-ical compositions.Brick B has higher strength than brick A.Compared with brick B:brick A has smaller in-ner pores,because the white corundum aggregates in brick A are smoother and denser with continuous particle size distribution;Al2 O3-Cr2 O3 solid solution in brick A is smaller,crossing and forming net structure with small gaps,which reduces the penetration and wear of slag to refractories,meaning that brick A has better slag resistance than brick B.It’s obvious that optimizing microstructure is an effective way to im-prove the slag resistance of Al2 O3-Cr2 O3 materials.%分别采用静态坩埚抗渣法和回转抗渣法,对w(Cr2 O3)=10%的A和B两种Al2 O3-Cr2 O3砖进行了抗渣性能对比。结果发现:两种砖的化学组成、显气孔率、体积密度和抗热震性相近,B砖强度优于A砖的。但由于与B砖相比,A砖内部气孔尺寸更小,所用电熔白刚玉骨料形貌平滑,较为致密,粒度呈连续式分布,且A砖中Al2 O3-Cr2 O3固溶体发育较小,相互交错,形成了孔隙较小的空间网状结构,这种显微结构显著降低了熔渣对耐火材料的渗透和破坏,使A砖的抗渣性优于B砖的。因此,制备微气孔化结构的制品是提高Al2 O3-Cr2 O3材料抗渣性能的有效途径。

  9. Synthesis of Dimethyl Ether over C301/P-γ-Al2O3 Catalyst%C301/P-γ-Al2O3双功能催化剂一步合成二甲醚

    Institute of Scientific and Technical Information of China (English)

    陈樑; 章江洪; 张世玲; 谢磊磊

    2011-01-01

    利用磷酸浸渍改性甲醇脱水催化剂γ-Al2O3得到的P-γ-Al2O3与甲醇合成催化剂C301制备双功能催化剂(C301/P-γ-Al2O3).以C301/P-γ-Al2O3为催化剂,液体石蜡为溶剂,在浆态床反应器中研究合成气一步法制二甲醚(DME),考察了反应温度、压力、空速和合成气中的CO2含量对一步法制DME的影响.结果表明,反应温度、压力、空速及合成气中的CO2含量对合成DME均有较大影响,磷改性双功能催化剂可适应含CO2的合成气制DME,并可提高DME选择性,增加DME收率.在液体石蜡150 mL,催化剂用量为溶剂质量的7.3%,氢和一氧化碳物质的量之比为2,反应温度为270℃,反应压力4.3 MPa和空速为600 mL/(h·g)的条件下,CO单程转化率可达到93%以上,DME选择性大于60%.该催化剂的稳定性比较好,可承受较宽的温度、压力和空速的波动范围.%The bi-fiinction catalyst(C301/P-y-Al2O3) was prepared from P-y-Al2O3 obtained by modifying methanol dehydration catalyst y-Al2O3 through phosphorus acid dipping method and methanol synthesis catalyst C301. The effects of reaction temperature, reaction pressure, space velocity and CO2 content in the syngas on the catalytic performance of C301/P-y-Al2O3 for synthesis of dimethyl ether(DME) from syngas by one step method over C301/P-y-Al2O3(mass ratio of C301 to P-y-Al2O3 4) using liquid paraffin as solvent were investigated in the slurry bed. The results showed that the conversion of CO2 and the selectivity of DME reached 93% and 60%, respectively, under the conditions of liquid paraffin 150 mL, mass ratio of catalyst to liquid paraffin 7.3%, molar ratio of H2 to CO 2, reaction temperature 270 ℃, reaction temperature 4.3 Mpa, space velocity 600 mL/(hg). The conversion of total carbon(CO and CO2) and CO decreased, conversion of H2, selectivity and yield of DME increased when CO2 was added to syngas. The bi-function catalyst exhibited relatively stable catalytic performance in a wide

  10. 纳米Al2O3-SiO2的分散及颗粒间力的相互作用%DISPERSION AND MECHANIC INTERACTIONS OF NANOCRYSTALLINE Al2O3-SiO2 POWDER

    Institute of Scientific and Technical Information of China (English)

    张海军; 贾晓林; 刘战杰; 李文超

    2003-01-01

    研究了纳米γ-Al2O3, SiO2的分散行为及其同相与异相微粒间静电引力与斥力作用.采用Malvern Zetasize 3000HSA自动电位粒度仪测定了纳米γ-Al2O3和SiO2在不同pH下的表面电位.结果表明: 纳米γ-Al2O3的等电点为pH=8.23, 纳米SiO2的等电点为pH=1.58, 两种粉体混合后的等电点为pH=6.94.研究了悬浮液pH、表面活性剂对纳米粉体团聚体的影响, 结果表明: 添加FS20表面活性剂、 pH=12时, 两种粉体混合后的分散效果较好.采用DLVO(Derjaguin-Landau-Verwey-Overbeek)理论对γ-Al2O3, SiO2和γ-Al2O3-SiO2同相及异相纳米微粒间的分散过程进行了量化研究, 理论计算结果与实验结果吻合.

  11. Effects of Al2O3 Layer on Performance of Ultrathin Permalloy Films%Al2O3层对超薄各向异性磁电阻薄膜性能影响的研究

    Institute of Scientific and Technical Information of China (English)

    丁雷; 王乐; 滕蛟; 于广华

    2009-01-01

    各向异性磁电阻(AMR)薄膜材料被广泛应用于磁传感器和硬盘的读出磁头中.器件的小型化要求AMR薄膜材料必须做得很薄.采用磁控溅射的方法在玻璃基片上制备了Ta/NiFe/Ta磁电阻超薄薄膜,将几个纳米厚的Al2O3层插入Ta/NiFe/Ta薄膜的Ta/NiFe界面,研究该插层对超薄NiFe薄膜性能的影响.结果表明:由于Al2O3层的“镜面反射”作用,适当厚度和结构状态的Al2O3层可以提高薄膜的磁电阻值, 当NiFe薄膜厚度为5 nm时,通过在界面处插入约2nm的Al2O3层,薄膜的磁电阻值从0.65%提高到了0.80%,增加幅度超过20%.性能提高的主要原因是除纳米Al2O3插层的“镜面反射”作用外, 抑制Ta/NiFe的界面反应以及减少Ta层分流也是重要的影响因素.

  12. Study On Thermal Stability of Al2O3-ZrO2 Composite Membranes%Al2O3-ZrO2复合膜的热稳定性研究

    Institute of Scientific and Technical Information of China (English)

    郝艳霞; 杨绪杰; 陆路德; 汪信

    2002-01-01

      Al2O3-ZrO2 composite membranes were prepared by sol-gel process from aluminium iso-propoxide and zirconyl chloride as their precursors. The thermal stability, structure and appearance of composite membranes were characterized by thermogravimetric analysis and differential thermal analysis (TGA-DTA), X-ray diffraction (XRD), Fourier transform infrared spectroscope (FT-IR), scanning electron microscopy (SEM) and transmission electron micrographs (TEM), respectively. The results show that the thermal stability of composite membranes is better than those of pure Al2O3 or ZrO2 membranes. The crystal phase of composite membranes is tetragonal ZrO2 until 1100℃, but monoclinic ZrO2 and alpha Al2O3 appear at 1200℃. Investigation with SEM showed that the membranes were defect-free.%  以异丙醇铝和氯化氧锆为原料,用溶胶-凝胶法制备了Al2O3-ZrO2复合膜。应用TG、DTA、XRD、FT-IR、SEM、TEM等测试手段对复合膜的热稳定性、结构、形貌进行了表征。结果表明复合膜的热稳定性比单一由氧化铝或氧化锆制成的膜有显著地提高;在1100℃以下,复合膜以t-ZrO2存在,1200℃时,出现了m-ZrO2和α-Al2O3相。扫描电镜分析表明,膜表面完整、无缺陷。

  13. Pt-Rh/g Al2O3 Influence of Catalyst Preparation Methods on Metallic Particle Dispersion and Size Distribution

    Directory of Open Access Journals (Sweden)

    N.M. da Fonseca

    1998-06-01

    Full Text Available - Pt-Rh/Al2O3 catalysts were prepared by successive incipient impregnations or coimpregnation. Characterization was achieved by H2 chemisorption and transmission electron microscopy. It was verified that method of preparation, ratio of metal weights and sequence of deposition are factors that result in very distinct catalysts.

  14. Al 2O 3 supported Ru catalysts prepared by thermolysis of Ru 3(CO) 12 for catalytic wet air oxidation

    Science.gov (United States)

    Yu, Chaoying; Zhao, Peiqing; Chen, Gexin; Hu, Bin

    2011-06-01

    Low loading catalysts Ru/γ-Al 2O 3 and Ru-Ce/γ-Al 2O 3 were prepared by thermolysis of Ru 3(CO) 12 on γ-Al 2O 3. The catalysts were characterized by XPS, XRD and SEM. Two new Ru species (Ru A and Ru B) were detected during the Ru 3(CO) 12 decomposition process due to chemical interaction with the active OH groups on the surface of Al 2O 3 support, and the reduction of them can lead to more dispersed metallic phases. The sample was completely decomposed at 673 K in H 2, and RuO 2 was formed with minor amounts of Ru 0. When the temperature was increased to 773 K to heat the sample, the ratio of Ru 0 to RuO 2 increased. However, after the addition of CeO 2, only RuO 2 was detected on surface. The catalysts exhibited high activities in Catalytic Wet Air Oxidation (CWAO) of different organic compounds at high concentration such as isopropyl alcohol, phenol, acetic acids and N,N-dimethylformamide, which is attributed to the better dispersion of Ru particles and the addition of CeO 2 further enhanced number of effectively active sites on the cluster-derived catalyst surface.

  15. On the c-Si surface passivation mechanism by the negative-charge-dielectric Al2O3

    Science.gov (United States)

    Hoex, B.; Gielis, J. J. H.; van de Sanden, M. C. M.; Kessels, W. M. M.

    2008-12-01

    Al2O3 is a versatile high-κ dielectric that has excellent surface passivation properties on crystalline Si (c-Si), which are of vital importance for devices such as light emitting diodes and high-efficiency solar cells. We demonstrate both experimentally and by simulations that the surface passivation can be related to a satisfactory low interface defect density in combination with a strong field-effect passivation induced by a negative fixed charge density Qf of up to 1013 cm-2 present in the Al2O3 film at the interface with the underlying Si substrate. The negative polarity of Qf in Al2O3 is especially beneficial for the passivation of p-type c-Si as the bulk minority carriers are shielded from the c-Si surface. As the level of field-effect passivation is shown to scale with Qf2, the high Qf in Al2O3 tolerates a higher interface defect density on c-Si compared to alternative surface passivation schemes.

  16. Microstructure and Mechanical Properties of In-situ Synthesized Al2O3/TiAl Composites

    Institute of Scientific and Technical Information of China (English)

    Ai Taotao

    2008-01-01

    Al2O3 particle-reinforced TiAI composites are successfully reaction-synthesized from the powder mixture of Ti, A1, TiO2, and Nb2O5, using the hot pressing reaction synthesis technique. The microstmcture and mechanical properties of the as-sintered products are investigated. It is found that in the as-sintered products consisting of γ-TiA1, α2-Ti3Al, Al2O3, and NbAl3 phases, the f'me Al2O3 particles tend to disperse on the grain boundaries. With the Nb2O5 content increasing, the grains are remarkably refined and the Al2O3 particles are dispersing more uniformly in the TiAI matrix, forming a partial lamellar structure containing γ and lamellar phases. The hardness of the in-situ composites increases gradually, and the bending strength and the fi-acture toughness of the as-sintered products reach the maxi-

  17. Influence of the Oxidant on the Chemical and Field-Effect Passivation of Si by ALD Al2O3

    NARCIS (Netherlands)

    Dingemans, G.; Terlinden, N. M.; Pierreux, D.; Profijt, H. B.; M. C. M. van de Sanden,; Kessels, W. M. M.

    2011-01-01

    Differences in Si surface passivation by aluminum oxide (Al2O3) films synthesized using H2O and O-3-based thermal atomic layer deposition (ALD) and plasma ALD have been revealed. A low interface defect density of D-it = similar to 1011 eV(-1) cm(-2) was obtained after annealing, independent of the o

  18. Epoxidation of alkenes through oxygen activation over a bifunctional CuO/Al2O3 catalyst.

    Science.gov (United States)

    Scotti, Nicola; Ravasio, Nicoletta; Zaccheria, Federica; Psaro, Rinaldo; Evangelisti, Claudio

    2013-03-07

    The epoxidation of alkenes was carried out over a CuO/Al(2)O(3) catalyst using cumene as an oxygen carrier, through a one-pot reaction, giving high conversion and selectivity with different substrates. Trans-β-methylstyrene gave the corresponding epoxide in 95% yield after 3 h.

  19. Retardation mechanism of ultrathin Al2O3 interlayer on Y2O3 passivated gallium nitride surface.

    Science.gov (United States)

    Quah, Hock Jin; Cheong, Kuan Yew

    2014-05-28

    A systematic investigation was carried out by incorporating an ultrathin aluminum oxide (Al2O3) as an interlayer between yttrium oxide (Y2O3) passivation layer and GaN substrate. The sandwiched samples were then subjected to postdeposition annealing in oxygen ambient from 400 to 800 °C. The Al2O3 interlayer was discovered to play a significant role in slowing down inward diffusion of oxygen through the Y2O3 passivation layer as well as in impeding outward diffusion of Ga(3+) and N(3-) from the decomposed GaN surface. These beneficial effects have suppressed subsequent formation of interfacial layer. A mechanism in association with the function of Al2O3 as an interlayer was suggested and discussed. The mechanism was explicitly described on the basis of the obtained results from X-ray diffraction, X-ray photoelectron spectroscopy, energy-filtered transmission electron microscopy (TEM), high resolution TEM, and electron energy loss spectroscopy line scan. A correlation between the proposed mechanism and metal-oxide-semiconductor characteristics of Y2O3/Al2O3/GaN structure has been proposed.

  20. Photoluminescence Enhancement in Nanotextured Fluorescent SiC Passivated by Atomic Layer Deposited Al2O3 Films

    DEFF Research Database (Denmark)

    Lu, Weifang; Ou, Yiyu; Jokubavicius, Valdas

    2016-01-01

    The influence of thickness of atomic layer deposited Al2O3 films on nano-textured fluorescent 6H-SiC passivation is investigated. The passivation effect on the light emission has been characterized by photoluminescence and time-resolved photoluminescence at room temperature. The results show that...

  1. Effect of Processing on Mechanically Alloyed and Spark Plasma Sintered Al-Al2O3 Nanocomposites

    Directory of Open Access Journals (Sweden)

    Nouari Saheb

    2015-01-01

    Full Text Available Metal matrix nanocomposites are advanced materials developed using ceramic nanoreinforcements and nanocrystalline metal matrices. These composites have outstanding properties and high potential for large number of functional and structural applications. In this work, nanocrystalline aluminium and Al-Al2O3 nanocomposites were synthesised using mechanical alloying and consolidated through spark plasma sintering technique. Scanning electron microscopy, X-ray diffraction, and mapping were used to characterize the powders and sintered samples. Density and hardness of sintered samples were measured using densimeter and hardness tester, respectively. It was found that milling of pure aluminium for 24 h reduced its crystallite size to less than 100 nm. For Al-Al2O3 nanocomposites, milling for 24 h decreased the crystallite size of the aluminium phase and resulted in uniform dispersion of the reinforcement. Sintering of the synthesised powders led to grain growth. Al2O3 contributed to growth inhibition when samples were sintered for 20 minutes and improved the hardness but reduced densification. The Al-10 vol.%  Al2O3 nanocomposite had the highest Vickers hardness value of 1460 MPa.

  2. Electrical performance of multilayer MoS2 transistors on high-κ Al2O3 coated Si substrates

    Directory of Open Access Journals (Sweden)

    Tao Li

    2015-05-01

    Full Text Available The electrical performance of MoS2 can be engineered by introducing high-κ dielectrics, while the interactions between high-κ dielectrics and MoS2 need to be studied. In this study, multilayer MoS2 field-effect transistors (FETs with a back-gated configuration were fabricated on high-κ Al2O3 coated Si substrates. Compared with MoS2 FETs on SiO2, the field-effect mobility (μFE and subthreshold swing (SS were remarkably improved in MoS2/Al2O3/Si. The improved μFE was thought to result from the dielectric screening effect from high-κ Al2O3. When a HfO2 passivation layer was introduced on the top of MoS2/Al2O3/Si, the field-effect mobility was further enhanced, which was thought to be concerned with the decreased contact resistance between the metal and MoS2. Meanwhile, the interface trap density increased from 2.4×1012 eV−1cm−2 to 6.3×1012 eV−1cm−2. The increase of the off-state current and the negative shift of the threshold voltage may be related to the increase of interface traps.

  3. Numerical simulation of stress distribution in Al2 O3-TiC/Q235 diffusion bonded joints

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The distributions of the axial stress and shear stress in Al2O3-TiC/Q235 diffusion bonded joints were studied using finite element method (FEM). The effect of interlayer thickness on the axial stress and shear stress was also investigated. The results indicate that the gradients of the axial stress and shear stress are great near the joint edge. The maximal shear stress produces at the interface of the Al2O3-TiC and Ti interlayer. With the increase of Cu interlayer thickness, the magnitudes of the axial stress and shear stress first decrease and then increase. The distribution of the axial stress changes greatly with a little change in the shear stress. The shear fracture initiates at the interface of the Al2O3-TiC/ Ti interlayer with high shear stress and then propagates to the Al2O3-TiC side, which is consistent with the stress FEM calculating results.

  4. Catalytic oxidation of elemental mercury over the modified catalyst Mn/alpha-Al2O3 at lower temperatures.

    Science.gov (United States)

    Li, Jianfeng; Yan, Naiqiang; Qu, Zan; Qiao, Shaohua; Yang, Shijian; Guo, Yongfu; Liu, Ping; Jia, Jinping

    2010-01-01

    In order to facilitate the removal of elemental mercury (Hg(0)) from coal-fired flue gas, catalytic oxidation of Hg(0) with manganese oxides supported on inert alumina (alpha-Al2O3) was investigated at lower temperatures (373-473 K). To improve the catalytic activity and the sulfur-tolerance of the catalysts at lower temperatures, several metal elements were employed as dopants to modify the catalyst of Mn/alpha-Al2O3. The best performance among the tested elements was achieved with molybdenum (Mo) as the dopant in the catalysts. It can work even better than the noble metal catalyst Pd/alpha-Al2O3. Additionally, the Mo doped catalyst displayed excellent sulfur-tolerance performance at lower temperatures, and the catalytic oxidation efficiency for Mo(0.03)-Mn/alpha-Al2O3 was over 95% in the presence of 500 ppm SO2 versus only about 48% for the unmodified catalyst. The apparent catalytic reaction rate constant increased by approximately 5.5 times at 423 K. In addition, the possible mechanisms involved in Hg(0) oxidation and the reaction with the Mo modified catalyst have been discussed.

  5. Reproducibility of optically stimulated luminescence measurements from single grains of Al2O3: C and annealed quartz

    DEFF Research Database (Denmark)

    Truscott, A.J.; Duller, G.A.T.; Bøtter-Jensen, L.;

    2000-01-01

    of nine-by-nine holes, which are drilled in the sample disc, We report on tests carried out to determine the precision with which the laser beam can be directed at individual grains in these holes. Single grains of aluminium oxide (Al2O3:C) (90-180 mum) and annealed quartz (90-120 mum) were used to test...

  6. Effect of phase interaction on catalytic CO oxidation over the SnO2/Al2O3 model catalyst

    Science.gov (United States)

    Chai, Shujing; Bai, Xueqin; Li, Jing; Liu, Cheng; Ding, Tong; Tian, Ye; Liu, Chang; Xian, Hui; Mi, Wenbo; Li, Xingang

    2017-04-01

    We investigated the catalytic CO oxidation over the SnO2/Al2O3 model catalysts. Our results show that interaction between the Al2O3 and SnO2 phases results in the significantly improved catalytic activity because of the formation of the oxygen vacancies. The oxygen storage capacity of the SnO2/Al2O3 catalyst prepared by the physically mixed method is nearly two times higher than that of the SnO2, which probably results from the change of electron concentration on the interface of the SnO2 and Al2O3 phases. Introducing water vapor to the feeding gas would a little decrease the activity of the catalysts, but the reaction rate could completely recover after removal of water vapor. The kinetics results suggest that the surface Sn4+ cations are effective CO adsorptive sites, and the surface adsorbed oxygen plays an important role upon CO oxidation. The reaction pathways upon the SnO2-based catalysts for CO oxidation follow the Langmuir-Hinshelwood model.

  7. Directed laser processing of compacted powder mixtures Al2O3-TiO2-Y2O3

    Directory of Open Access Journals (Sweden)

    Vlasova M.

    2013-01-01

    Full Text Available The phase formation, microstructure and surface texture of laser treated ternary powder mixtures of Al2O3-TiO2-Y2O3 had been studied. Rapid high temperature heating and subsequent rapid cooling due to the directed movement of the laser beam forms concave ceramic tracks. Phase composition and microstructure of the tracks depends on the Al2O3 content and the TiO2/Y2O3 ratio of the initial mixtures. The main phases observed are Y3Al5O12, Y2Ti2O7, Al2O3 and Al2TiO5. Due to the temperature gradient in the heating zone, complex layered structures are formed. The tracks consist of three main layers: a thin surface layer, a layer of crystallization products of eutectic alloys, and a lower sintered layer. The thickness of the crystallization layer and the shrinkage of the irradiation zone depend on the amount of Y3Al5O12 and Al2O3 crystallized from the melt.

  8. Conductividad iónica en nuevos compositos (PEO10(CF3COONa-X % Al2O3

    Directory of Open Access Journals (Sweden)

    Nori Jurado Meneses

    2013-07-01

    Full Text Available To increase the ionic conductivity of solid polymer electrolyte, (PEO10CF3COONa, we formed new composites by adding alumina particles as a filler. We prepared these composites by dissolving them ina liquid solvent, and characterized them through impedance spectroscopy (IS, using a Pt/electrolyte/Pt electrode configuration. The combination of polyethylene oxide (PEO with sodium trifluoroacetate (CF3COONa produced a reduction in resistance of up to two orders of magnitude in Nyquist plots, and up to three orders of magnitude when we added Al2O3 particles at room temperature. DC conductivity concentration graphs show an increase in the ionic conductivity with low alumina concentrations. The new synthesized ionic conductor composite presented conductivity values of 2.00x10-5 Scm-1 at room temperature and of 7.70x10-4 Scm-1 at a temperature of 383 K. Two sections of the conductivity diagrams also evidenced a temperature induced Arrhenius behavior, indicating a thermally activated process. Higher concentrations of Al2O3 induced a Vogel-Tamman-Fulcher (VTF behavior. Conductivity variations produced by Al2O3 concentration are linked to the number of sites involved in ion transport between Al2O3 ionic electrolyte species through Lewis acid-base interactions.

  9. Towards advanced structural analysis of iron oxide clusters on the surface of γ-Al2O3 using EXAFS

    Science.gov (United States)

    Boubnov, Alexey; Roppertz, Andreas; Kundrat, Matthew D.; Mangold, Stefan; Reznik, Boris; Jacob, Christoph R.; Kureti, Sven; Grunwaldt, Jan-Dierk

    2016-11-01

    Iron oxide centres are structurally investigated in 0.1% Fe/γ-Al2O3, which is known as highly active catalyst, for instance in the oxidation of CO. The sample was characterised by using X-ray absorption spectroscopy (XAS) in terms of X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS), Mössbauer spectroscopy, X-ray diffraction (XRD) and transmission electron microscopy (TEM). These analyses evidenced high dispersion of the iron oxide entities without significant presence of bulk-like aggregates associated with the low Fe content of the catalyst. A library of structural models of Al2O3-supported surface Fe was created as input for EXAFS fitting. Additionally, several model structures of Fe substituting Al ions in bulk γ-Al2O3 were created with optimised geometry based on density-functional theory (DFT) calculations. From EXAFS refinement of the best 8 out of 24 models, it was found that the trivalent Fe ions are coordinated by 4-5 oxygen atoms and are located on octahedral lattice sites of the exposed surfaces of γ-Al2O3. These iron oxide species exist mainly as a mixture of monomeric and binuclear species and due to the low concentration represent suitable model systems as alternative to single crystal systems for structure-function relationships.

  10. Study of Mechanical Characteristics for Polymer Composite Reinforced by Particles of (Al2O3 or (Al

    Directory of Open Access Journals (Sweden)

    Saad M. elIa

    2007-01-01

    Full Text Available A particulate polymer composite material was prepared by reinforcing with the Aluminum Oxide (Al2O3 or Aluminum (Al metallic particles with a particle size of (30 µm to an unsaturated Polyester Resin with a weight fraction of (5%, 10%, 15%, 20%. Tensile test results showed the maximum value of elastic modulus reached (2400MPa. in the case of reinforcing with (Al particles with weight fraction (20% and (1500 MPa. in the case of reinforcing with (Al2O3 particles of the same weight fraction. When the impact and the flexural strength tests were done, the results showed that flexural strength (F.S, maximum shear stress (?max, impact strength (Gc and fracture toughness (Kc were increased with the increase of weight fraction, where the results of the samples of (Al particles were higher than that of (Al2O3 particles reinforced at a weight fraction of (20% at ratios of (45.43%, 45.45%, 25%, 41% respectively. While the hardness of the samples reinforced with (Al2O3 particles was higher than that reinforced with (Al particles with a ratio of (2.82% at a weight fraction of (20%.

  11. Study on thermal expansion behavior of Dy2O3- Al2O3- SiO2 glass

    Institute of Scientific and Technical Information of China (English)

    LIU Yuzhu; GENG Zhiting; ZHUANG Weidong; HE Huaqiang

    2008-01-01

    Employing Dy2O3, Al2O3, and SiO2 as starting materials, several series of Dy2O3-Al2O3-SiO2 sealing glass were prepared. The relationship between their coefficients of thermal expansion and the contents of Dy2O3, Al2O3, and SiO2 were studied respectively. Experimental results showed that Dy2O3 and Al2O3 had a positive effect on the coefficient of thermal expansion of glass, whereas, SiO2 had a negative effect. The coefficient of thermal expansion of glass showed an apparent linear relation to the contents of these three raw materials, from which an estimation model was built, to calculate the coefficient of thermal expansion of sealing glass. Relative errors of the calculating resalts to testing results were no more than 2%, which suggested that the estimation model was reasonable. This study provides a good theory reference for the practical utilizing of this sealing material, through which a proper glass composition for good sealing could be easily found.

  12. Al-Si/Al2O3 in situ composite prepared by displacement reaction of CuO/Al system

    Directory of Open Access Journals (Sweden)

    Zhang Jing

    2010-02-01

    Full Text Available Al2O3 particle-reinforced ZL109 composite was prepared by in situ reaction between CuO and Al. The microstructure was observed by means of OM, SEM and TEM. The Al2O3 particles in sub-micron sizes distribute uniformly in the matrix, and the Cu displaced from the in situ reaction forms net-like alloy phases with other alloy elements. The hardness and the tensile strength of the composites at room temperature have a slight increase as compared to that of the matrix. However, the tensile strength at 350 ℃ has reached 90.23 MPa, or 16.92 MPa higher than that of the matrix. The mechanism of the reaction in the CuO/Al system was studied by using of differential scanning calorimetry(DSC and thermodynamic calculation. The reaction between CuO and Al involves two steps. First, CuO reacts with Al to form Cu2O and Al2O3 at the melting temperature of the matrix alloy, and second, Cu2O reacts with Al to form Cu and Al2O3 at a higher temperature. At ZL109 casting temperature of 750–780 ℃, the second step can also take place because of the effect of exothermic