Xianting SUN
,
Lianzeng YAO
,
Chimei MO
,
Gang SHI
,
Weili CAI
,
Yimin ZHANG
,
Lide ZHANG
材料科学技术（英文）
Alumina aerogels with high porosity of nanometer size were prepared from Al, n-butanol and ethyl acetoacetate by the sol-gel route and the Na supercritical extraction drying technique. Optical experiment results showed that for alumina aerogels after annealing at 500 degrees C for 4 h one intense blue emission band appeared in the wavelength range of 400 to 800 nm, and the optical absorption edge moved from 8.0 eV of coarse grain Al2O3 to 3 similar to 5 eV and with increasing the annealing temperature, this luminescence band presented blue shifts. The reasons of these new optical properties are discussed in detail.
关键词:
Weili CAI
,
Chimei MO
,
Lan ZHANG
,
Yuanhong LI and Lianzeng YAO)(Dept. of Materials Science and Engineering
,
University of Science and Technology of China
,
Hefei 230026
,
China)
材料科学技术（英文）
Porous Al2O3 host/NiO nanocomposites have been prepared by pyrolysis of Ni2(OH)2CO3 inthe nanostructured Al2O3 hosts. Diffuse reflection spectra in the wavelength range of 200 to800 nm were measured. Results show that (1) in each spectrum exist several absorption bandsof nano-NiO. With increasing the pyrolysis temperature from 550 to 1000℃, the numbers ofabsorption bands of NiO increase from 2 to 6 (P1-P6), (2) comparing with optical absorptionbands of single crystal NiO, for porous nanocomposites the P1, P2 and P4 present "blue shift"and the P3, P5 and P6 exhibit "red shift"; (3) when the pyrolysis temperature, Tp, is 550℃, theabsorption bands become so weak that only two bands (P1 and P6) can be observed and inverselywhen Tp=1000℃ all six absorption bands of NiO are strong, (4) for porous Al2O3/NiOnanocomposites prepared by pyrolysis at 1000℃ the PF+ caused by the F+ centers in theAl2O3 host moves towards the short wavelength at first with increasing the doping amount ofNiO from 5 to 50 wt pct and then shifts to the long wavelength with further increasing NiO. Inthis paper, the above phenomena and mechanism of the absorption bands of NiO are discussedin detail.
关键词:
Ye ZHANG
,
Lide ZHANG
,
Chimei MO
,
Yuanhong LI
,
Lianzeng YAO
,
Weili CAI
材料科学技术（英文）
The synthesis of dispersions of MMA (methylmethacrylate) with different concentrations of oleic acid coated nano-TiO2 particles was performed by hydrolysis of TiCl4 in the mixture solutions of MMA, oleic acid and H2O with various concentrations. When MMA :oleic acid : H2O : TiCl4 1.00 : 0.064 : 0.01 : 0.032 (by mol fraction), the dispersion of MMA with oleic acid coated nano-TiO2 particles was very stable. Optical absorption result showed that the absorption band was located in the ultraviolet range from 200 to 400 nm. This dispersion was added to a kind of automobile surface lustering agent (type II), and then this lustering agent with nano-TiO2 was coated on the surface of automobile surface paint. When the doping amount of the dispersion in the lustering agent=10 vol. pet, the state of paint (color and glossiness) did not present any change after irradiation of an ultraviolet lamp with the power of 1000 watt for two days. The sample with surface paint and lustering agent doped by 10 percent dispersion after suffering from irradiation of the sunlight for half a year (from May to November) kept the original state. However, for the samples with automobile paint and lustering agent without doping of nano-TiO2, the color and glossiness lost easily after irradiation of an ultraviolet lamp. These results prove that nano-TiO2 is a kind of high-efficient additive of paint for protection against ultraviolet irradiation.
关键词:
Yushuang LIU
,
Chimei MO
,
Weili CAI
材料科学技术（英文）
The change of the temperature coefficient of resistivity (cr) with the particle size, d(p), and the grain size, d(c), in the nanostructured Ag bulk samples was investigated. d(p) and d(c) were controlled by heating the nano-Ag powders over the temperature range from 393 to 453 K. The electrical resistance measurements of the nanostructured Ag bulk samples obtained by compacting the Ag powders after heat treatments showed a change in the sign of alpha with d(p) and d(c). When d(p) and d(c) are smaller or equal to 18 and 11 nm below room temperature or 20 and 12 nm above room temperature, respectively, the sign of the temperature coefficient of resistivity changes from positive to negative. The negative alpha arises mainly from the high resistivity induced by the particle interfaces with very lowly ordered or even disordered structure, a large volume fraction of interfaces and impurities existing in the interfaces, and the quantum size effect appearing in the nano-Ag grains.
关键词:
陈松
,
胡昌义
,
郭俊梅
,
杨家明
稀有金属材料与工程
研究了Ir/Re喷管制备过程中的Ir/Mo互扩散问题.在电子探针测量的基础上,根据扩散理论和Ir-Mo相图数据,建立并推导Ir/Mo扩散模型和解.计算得到Ir3Mo相中的互扩散系数为:D=9.0×10-9exp(-1.46 eV/kT)(cm2/s),Ir基固溶体中的互扩散系数为:D=5.0×10-10exp(-1.1eV/kT)(cm2/s).确定喷管中Ir/Mo互扩散的特点,给出估算Ir3Mo相层厚的方法.确定Re在Ir3Mo相中的扩散主要是受Ir控制.
关键词:
Ir
,
Mo
,
Re
,
扩散
李云凯
,
王勇
,
李树奎
,
韩文波
复合材料学报
doi:10.3321/j.issn:1000-3851.2003.06.009
利用有限元分析方法,对PSZ/Mo功能梯度材料进行了优化设计,确定了最佳形状因子、层数和每一层的厚度.在此基础上,用热压烧结方法制备了六层结构的PSZ/Mo功能梯度材料.利用自制的FGM热性能测试仪,对制备的试样进行了热震性能实验,通过该实验条件下应力场和温度场的有限元计算,阐述了PSZ/Mo功能梯度材料优良抗热震性的原因.
关键词:
优化设计
,
有限元
,
PSZ/Mo功能梯度材料
LIANG Guoxian WANG Erde HUO Wencan Harbin Institute of Technology
,
Harbin
,
China Post Box 435
,
Harbin Institute of Technology
,
Harbin 150006
,
China
金属学报(英文版)
Ni_(100-x)Mo_x(x=20,30,38)alloys have been synthesized by mechanical alloying.The structure evolution of powders in mechanical alloying process has been monitored by X-ray diffraction,scanning electron microscopy and transmission electron microscopy analyses.The results show that the Ni_(62)Mo_(38)sample becomes partially amorphous after high energy ball milling,while the Ni_(80)Mo_(20)and Ni_(70)Mo_(30)become non-equilibrium nanocrystals.
关键词:
mechanical alloying
,
null
,
null
,
null
李雪
,
卢公昊
,
王淼
,
高田润
材料与冶金学报
doi:10.14186/j.cnki.1671-6620.2015.02.011
利用Al-Si混合粉末包覆金属Mo,并在Ar气氛围中,900℃进行高温扩散反应,在金属Mo表面制备Mo(Si,Al)2化合物层.在空气中12 00℃的条件下进行的高温氧化试验表明,化合物Mo(Si,Al)2具有优异的抗氧化性,样品外表面生成了致密的氧化铝层,从而阻止样品内部被进一步氧化.另外,氧化试验后在基体Mo和Mo (Si,Al)2层界面处还观察到Mo5(Si,Al)3层和Mo3 Al8层.
关键词:
金属Mo
,
Mo(Si,Al)2
,
粉末包覆法
,
高温抗氧化性
