TiC/TiN/Al2O3复合陶瓷的研究进展

文章综述了TiC/TiN/Al2O3复合陶瓷的研究进展,介绍了复合陶瓷的制备工艺、组织与性能,探讨了材料成分对组织和力学性能的影响,总结了复合陶瓷的增韧机制及在刀具上的应用情况,指出纳米复合陶瓷是进一步改善强韧性的主要发展方向,为氧化铝陶瓷的广泛应用丰富了科学内涵.     

Near-infrared to visible up-conversion emissions of Er^3＋ doped Al2O3 powders derived from the sol-gel method

The Er3 doped Al2O3 powders were prepared by the sol-gel method using the aluminium isopropoxide [Al(OC3H7)3]-derived Al2O3 sols with addition of the erbium nitrate [Er(NO3)3.5H2O]. The different phase structure, including three crystalline types of (Al,Er)2O3 phases, γ, θ, α, and two Er-Al-O phases, ErAlO3 and Al10Er6O24, was obtained with the 1 mol% Er3 doped Al2O3 powders at the different sintering temperatures of 600―1200℃. The green and red up-conversion emissions centered at about 523, 545 and 660 nm, corresponding respectively to the 2H11/2, 4S3/2→4I15/2 and 4F9/2→4I15/2 transitions of Er3 , were detected by a 978 nm semiconductor laser diodes excitation. The phase structure and OH content had evident influence on the up-conversion emissions intensity. The maximum intensities of both the green and red emissions were obtained respectively for the Er3 doped Al2O3 powders sintered at 1200 ℃, which was composed mainly of α-(Al,Er)2O3, less of ErAlO3 and Al10Er6O24 phases, and with the least OH content. The two-photon absorption up-conversion process was involved in the green and red up-conversion emissions of the Er3 doped Al2O3 powders.     

Fe2O3/Al2O3二元超细复合材料的制备

用溶胶-凝胶法(Sol-Gel)结合超临界干燥技术(SCFD)制备Fe2O3／Al2O3二元超细复合材料，并用XRD，TEM进行检测。研究结果表明，采用该法，可制得红色、分散性好、粒径小于1μm的Fe2O3／Al2O3二元超细复合材料。     

Al2O3-Cr2O3固溶体烧结动力学研究

以纳米η-Al2O3与工业铬绿为原料,采用固相烧结的方法制备Al2O3-Cr2O3固溶体.以聚乙烯醇为结合剂,经过冷等静压成型后,分别以埋碳和空气两种气氛在1400～1600℃常压烧结.研究不同气氛、不同温度下试样的性能、显微结构和烧结动力学.在烧结过程中,随温度升高,两种不同气氛的Al2O3-Cr2O3固溶体晶粒生长指数减小,晶粒生长活化能下降.埋碳气氛下Al2O3-Cr2O3固溶体平均晶粒生长指数为1.763,晶粒生长主要受晶界的曲率和一小部分体积扩散控制;空气气氛下Al2O3-Cr2O3固溶体平均晶粒生长指数为3.454,晶粒生长主要受离子随机越过晶界和体积扩散控制.对比晶粒生长活化能发现,空气气氛更有利于Al2O3-Cr2O3固溶体晶粒的生长发育,但当温度过高时应考虑CrO3的挥发对晶粒生长的影响.     

电解负载法制备Pt/Al2O3/Al催化剂

以铝板阳极氧化生成的多孔质氧化膜为载体，采用电解负载法将铂负载在载体上，制得挥发性有机物催化燃烧的催化剂。从催化剂的负载量和催化活性出发，对电解负载的实验条件进行了探讨。研究结果表明，低浓度、低电流密度及较短的电解负载时间是较适宜的催化剂制备条件。实验还表明，利用电解负载法负载的催化组分在催化剂中分布均匀。     

高Al2O3炉渣脱硫能力的研究

针对目前高炉的冶炼条件,分析高炉炉渣中Al2O3的来源以及对炉渣脱硫的危害。从热力学和动力学角度分析了Al2O3对炉渣脱硫能力的影响。通过实验研究了Al2O3含量以及MgO／Al2O3对炉渣脱硫能力的影响。实验结果表明Al2O3含量过高不利于高炉渣的脱硫。Mg0／Al2O3适当提高可以增强Al2O3含量较高时炉渣的脱硫能力。     

内氧化工艺对Al2O3/Cu复合材料中Al2O3颗粒分布的影响

采用压块加入法和分别加入法两种内氧化工艺，将ＣｕＯ和Ａｌ粉末加入到Ａｒ气保护的铜液中制备Ａｌ２Ｏ３／Ｃｕ复合材料，在光学显微镜、扫描电镜及Ｘ射线衍射仪上观察分析了Ａｌ２Ｏ３颗粒的数量，分布及材料的相组成。结果表明，压块加入法生成的Ａｌ２Ｏ３颗于枝晶状分布，最体保温时间为３０－４５ｍｉｎ。分别加入法生成的Ａｌ２Ｏ３颗粒呈弥散状分布，最佳保温时间为４５－６０ｍｉｎ。     

特殊液相沉淀法制备纳米Al2O3粉体

采用特殊液相沉淀法制备氧化铝前驱体，经不同温度焙烧，通过TEM表征，给出了焙烧温度与粉体粒径的曲线。可以看出，在500℃至1100℃范围内，随焙烧烧温度的升高，粉体粒径有增大的趋势，但不明显；当温度继续升高，粉体粒径明显增大，当温度升至1250℃时平均粒径达到50nm。XRD检测表明，经1250℃焙烧，可得到℃相纳米氧化铝粉体。对反应过程中沉淀产物的过滤性进行比较，发现Al2（SO4）3为反应物较AlCl3为反应物的过滤性好。     

Ni/Al2O3、Co /Al2O3和Ni-Co /Al2O3催化剂催化乙醇水蒸气重整制氢的性能

利用浸渍法制备Ni/Al2O3、Co/Al2O3、Ni-Co/Al2O3催化剂,考察催化剂对乙醇水蒸气重整反应的催化性能,对催化剂进行x射线衍射(XRD)表征.实验结果表明,Ni/Al2O3催化剂具有较好的低温活性,Co/Al2O3催化剂具有较高的氢气选择性和较低的甲烷选择性,而Ni-Co/Al2O3催化剂表现出良好的催化性能,有较高的低温活性,较高的氢气、二氧化碳选择性,较低的一氧化碳、甲烷选择性,450 ℃时乙醇转化率达到100%, 氢气选择性为79.8%,二氧化碳选择性为91.9%.     

Chemical quenching and inhibition of positronium in Cr<Subscript>2</Subscript>O<Subscript>3</Subscript>/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> catalysts

The pore structure of Cr2O3/Al2O3 catalysts and the surface chemical properties of these pores were characterized by positron lifetime and coincidence Doppler broadening (CDB) measurements. Four lifetime components could be resolved from the positron lifetime spectrum, with two long lifetime components and two short lifetime components. The two long lifetimes τ4 and τ3 are attributed to ortho-positronium (o-Ps) annihilation in large pores and microvoids, respectively. With increasing Cr2O3 content, both τ4 and its intensity I4 show sharp decrease, while τ3 and its intensity I3 keep nearly unchanged. The Doppler broadening S parameters also show sharp decrease with increasing Cr2O3 content. Detailed analysis of the CDB spectrum reveals that the parapositronium (p-Ps) intensity also decreases with increasing Cr2O3 content. This indicates that the change of o-Ps lifetime τ4 is due to the chemical quenching by Cr2O3 but not spin-conversion of positronium. The decrease of o-Ps intensity I4 indicates that Cr2O3 also inhibits positronium formation.     

Character and fabrication of Al/Al<Subscript>2</Subscript>O<Subscript>3</Subscript>/Al tunnel junctions for qubit application

The superconductive Josephson junction is the key device for superconducting quantum computation. We have fabricated Al/Al2O3/Al tunnel junctions using a double angle evaporation method based on a suspended shadow mask. The Al2O3 junction barrier has been formed by introducing pure oxygen into the chamber during the fabrication process. We have adjusted exposure conditions by changing either the oxygen pressure or the oxidizing time during the formation of tunnel barriers to control the critical current density Jc and the junction specific resistance Rc. Measurements of the leakage in Al/Al2O3/Al tunnel junctions show that the devices are suitable for qubit applications.     

Nonlinear optical properties of Eu<Subscript>2</Subscript>O<Subscript>3</Subscript> doped 5ZnO-20Nb<Subscript>2</Subscript>O<Subscript>5</Subscript>-75TeO<Subscript>2</Subscript> glasses

The third-order optical nonlinearities, including third-order nonlinear susceptibility X^(3), nonlinear refractive index (n2) and temporal response, were measured with forward DFWM using Nd:YAG mode-locked pulse laser. The results show that Eu203 doped 5ZnO-20Nb2O5-75TeO2 glasses have large n2 and ultra-fast temporal response. Raman spectra show that Eu2O3 dopant induces the changes in the local structure of glasses. The higher the dopant concentration, the larger the nonlinear refractive n2 and the faster the temporal response. The enhancement on the third-order optical nonlinearities can be attributed to the deformation of the electronic clouds in [TeO4] enhanced by Eu2O3 dopant.     

Synthesis of highly ordered SnO2／Fe2O3 composite nanowire arrays by electrophoretic deposition method

Highly ordered SnO2/Fe2O3 composite nanowire arrays have been synthesized by electrophoretic deposition method. The morphology and chemical composition of SnO2/Fe2O3 composite nanowire arrays are characterized by SEM, TEM, EDX, XPS, and XRD. The results show that the SnO2/Fe2O3 composite nanowires are about 180 nm in width and tens of microns in length, and they are composed of small nanoparticles of tetraganal SnO2 and rhombohedral α-Fe203 with diameters of 10-15nm. The SnO2/Fe2O3 composite nanowires are formed by a series of chemical reactions.     

纳米ZTM／Al2O3复相陶瓷材料抗热震损伤性能

简要分析了表述复相陶瓷材料的抗热震损伤的一些机理。并且利用典型的湿化学法制备了两种ZTM／Al2O3复相陶瓷材料;晶间型和纳米／纳米型;分别对高温和低温深冷条件下,两种不同结构材料的抗热震损伤性能进行了研究。结果表明:对ZTM／Al2O3复相陶瓷材料,高温热冲击下,纳米／纳米型材料的残余强度的衰减变化大于晶间型材料;晶间型材料的抗热冲击性能优于纳米／纳米型材料。低温深冷条件下,晶间型材料由于ZrO2马氏体相变的失效和残余微量玻璃相的脆化,表现出与普通耐火材料相似的残余强度衰变趋势,而纳米／纳米型材料却呈现与高温热冲击条件下相似的变化趋势。     

Preparation and luminescence properties of YeO3：Er^3＋/TiO2 with high specific surface area

The three composites Y2O3 :Er3+ , Y2O3 :Er3+ /Yb 3+ andY2O3 :Er3+ /TiO2 were prepared using coprecipitation and sol-gel techniques. Their morphology, specific surface area, porosity, UV-vis. absorption spectra and fluorescence spectra were measured using SEM, TEM, surface analysis, UV-vis. absorption and photoluminescence spectrophotometry. SEM and TEM showed that samples prepared using coprecipitation were dispersed, while Y2O3 :Er3+ /TiO2 particles possessed a mesoporous surface and average diameter of ab...     

Polysaccharide separation mechanism in polysulfone-Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> magnetic composite membranes

Polysulfone (PSF)-Fe3O4 composite membranes were prepared by the phase-inversion process and their polysaccharide separation mechanism was explored using chondroitin sulfate (CS) and dextran. The mechanism was analyzed from constraints on the magnetic field and geometric deformation. It was found that variations in dextran rejection from 58% to 46% were mainly influenced by the geometric deformation of the composite membrane, while the magnetic field had a significant influence on variations in CS rejection from 82% to 35%. The results indicate that it is possible to continuously separate different types of polysaccharide with a composite membrane by adjusting the external magnetic field.     

Adsorption and catalytic combustion of ARB on CuO-Fe<Subscript>2</Subscript>O<Subscript>3</Subscript>

CuO-Fe2O3 composite material with strong magnetism and a large surface area is prepared by the co-precipitate method. Its adsorption properties towards Acid Red B (ARB) and the regeneration by catalytic combastion of organic compounds have been studied. The results show that the prepared CuO-Fe2O3 composite is an excellent adsorbent for ARB adsorption at acid condition. The presence of Cl^- has no effect on ARB adsorption. But the SO4^2- can inhibit ARB adsorption. After being recovered by the magnetic separation method, the adsorbent can be regenerated by catalytic oxidation of absorbate at 300℃ in air atmosphere. The combustion reactions of ARB in the presence or absence of CuO-Fe2O3 are studied by in situ diffuse refieclion FTIR. The results indicate that, in the presence of CuO-Fe2O3, the degradation temperature is significantly lowered by the catalysis of CuO-Fe2O3, and ARB can be oxidized completely without volatile organic compound by-product; in comparison, in the absence of CuO-Fe2O3, the temperature needed for oxidation of ARB is higher and the reaction is incomplete with some N-containing harmful compounds produced. The reusability of CuO-Fe2O3 is also studied in successive seven adsorption-regeneration cycles.     

Al2O3/WC-10Co/ZrO2/Ni金属陶瓷的微波烧结

以纳米WC-10Co复合粉末、YSZ纳米粉末、Al2O3亚微粉末与工业Ni粉为原料,采用微波烧结＋热等静压处理制备性能优良的Al2O3/WC-10Co/ZrO2/Ni金属陶瓷,研究微波烧结、微波烧结＋热等静压处理对Al2O3/WC-10Co/ZrO2/Ni金属陶瓷的组织结构和力学性能的影响。研究结果表明：WC-10Co（10%,质量分数）,YSZ（30%）,Al2O3（55%）与Ni（5%）复合粉末高能球磨后,经过微波烧结＋热等静压处理,可以得到平均晶粒度小于1.5μm的整体性能较好的亚微Al2O3/WC-10Co/ZrO2/Ni金属陶瓷,其相对密度为98.4%,洛氏硬度为HRA 94.0;微波烧结＋热等静压可以有效地消除微波烧结造成Al2O3/WC-10Co/ZrO2/Ni金属陶瓷中的孔隙,提高复合材料的密实度和力学性能,而且金属陶瓷的晶粒基本没有异常长大。