M.S.Nizami
,
M.Z.Iqbal
材料科学技术（英文）
An industrial mineral wollastonite (CaSiO3) was produced under solid state conditions from rice husk silica and limestone. Reaction was carried out at 900 degreesC to 1300 degreesC for 1 h. The product batches were subjected to XRD and chemical analysis techniques specific for wollastonite. Mole fractions of different product batches were calculated on the basis of accumulated data to study the kinetics. Specific rate constants and reaction rate were also found out. Various probable models of mechanism for reaction were considered and testified with the laid down criterion for suggesting the suitable one. The resulting data were treated with Arrhenius equation as well and activation energy was calculated-therefrom. In addition to finding it's value from the slope of Arrhenius curve, an alternate method was also applied for this purpose. Both of the values were observed to be comparable. The activation energy required for performed reaction was found to be almost one third of that reported for synthesizing CaSiO3 by using quartz. This referred to the economical preparation of wollastonite by using rice husk as a source of silica instead of quartz.
关键词:
M.S.Nizami
,
M.K.Farooq
,
K.Hussain
,
M.Z.Iqbal
材料科学技术（英文）
Wollastonite, a mineral of wide industrial applications was synthesised from rice husk ash silica and limestone. A number of raw batches consisting of these starting materials, in 1:1 molar ratio, were heat treated to produce it through solid state reaction from 900℃ to 1300℃. The conducted reaction was monitored by XRD step by step. Amount of Wollastonite formed at every temperature was also studied to some extent. Analyses of the obtained data indicated that the target mineral formation was quite effective and almost proportional to a rise in temperature up to 1200℃. The results from both, XRD and chemical analysis were found in fair agreement with one another.
关键词:
Materials Letters
Secondary M,C precipitation was investigated in K40S cobalt-base alloy after 100 h aging at 950 degreesC. The results showed that it was closely related to the tungsten-rich zones inherited from the as-cast condition and the degeneration of the primary M7C3 carbide. A direct element reaction, 6M + C --> M6C, in which C comes from the decomposition of the M7C3 carbides, is suggested as the mechanism of secondary M6C precipitation in K40S alloy. (C) 2001 Elsevier Science B.V. All rights reserved.
关键词:
M6C precipitation;aging;M7C3 carbide;superalloy
WU Jianxin JIANG Bohong XU Zuyao (T.Y.Hsu) Shanghai Jiaotong University
,
Shanghai
,
China Associate Professor
,
Dept.of Materials Science and Engineering
,
Shanghai Jiaotong University
,
Shanghai
,
China
金属学报(英文版)
The effect of grain size and ordering of the parent phase on the critical points of thermoelastic martensitic transformation in Cu-25.62 Zn-3.97 Al-0.0018 B(wt-%)shape memory alloy has been investigated.Based on the thermodynamics of phase transformation,a linear rela- tionship between the starting temperature of martensitic transformation and the reciprocal of the square root of grain size is obtained,i.e.M_s temperature rises with increasing grain size. It shows a good agreement with the results of electric resistance measurement.Applying the Landau's theory,a quantitative relationship between M_s and the ordering parameter of the parent phase is set up,which is well confirmed by the results of X-ray diffraction and electric resistance measurement.The activation energy of the ordering process in the parent phase of the alloy is calculated to be 46 kJ/mol.
关键词:
Cu-Zu-Al
,
null
,
null
,
null
,
null
Ruijie ZHANG
,
Zhi HE
,
Zhongwei CHEN
,
Wanqi JIE
材料科学技术（英文）
A method to predict the solid-liquid interface stability during unidirectional solidification is developed by coupling M-S model with CALPHAD method. The method was applied to Al-0.38 Zn and Al-0.34 Si-0.14 Mg (wt pct) alloys, and the predicted results were compared with some former experimental data of the two alloys. The good agreement between the calculation results and the experimental data demonstrates the superiority of the present method to the classical one based on constant parameter assumptions.
关键词:
Interface stability
,
null
,
null
汪艳宁
,
张智超
,
苑宏英
,
靖大为
膜科学与技术
doi:10.16159/j.cnki.issn1007-8924.2016.06.003
以反映管道压降的系统模拟软件为工具,以特定基准系统参数及2 m/s管道流速为基础,分析了各种径流方向组合的反渗透系统运行工况,提出了全壳产水量与全壳错流比两个分别表征各壳元件污染速度与清污力度的运行指标,证明了各壳元件产水量失衡是其污染失衡的主要原因,明确了目前工程中常用的2 m/s流速管道系统中底层膜壳污染最重.
关键词:
反渗透系统
,
管道压降
,
径流方向
,
污染分布
赵德文
,
郭长武
,
刘相华
,
王国栋
,
徐辉
,
戴建明
钢铁
开展了在空气和氮气两种气氛下，采用Gleeble-1500热模拟机与普通电炉两种加热方式、不同加热温度、加热时间对D2、M2、S5钢脱碳层深度影响的试验研究。依据试验结果，结合现场实际制定了较为合理的生产工艺并在现场成功应用，使上述模具扁钢脱碳层指标达到了美国ASTM-A681技术标准。
关键词:
脱碳层深度
,
模具扁钢
,
ASTM-A681
Journal of Materials Research
MAX-phase carbides (M is an early transition metal, A is an A-group element) exhibit an interesting bonding characteristic of alternative stacking of strong M-C bonds and relatively weak M-A bonds in one direction. In the present first-principles total energy calculations, we establish the relationship between mechanical properties and electronic structure for ternary M(2)AC (M = Ti, V, Cr. A = Al, Si, P, S) carbides. By systematically tuning elements on the M and A sites, pronounced enhancements of bulk modulus, elastic stiffness, and ideal shear strength are achieved in V-containing V(2)AC (A = Al, Si, P, and S) carbides. It is suggested that tailoring on the A site is more efficient than on the M site in strengthening the mechanical properties of studied serial carbides. The results highlight a general trend for tailor-made mechanical properties of ternary M(2)AC carbides by control of chemical bonding.
关键词:
strength;solids;shear;dislocations;ti3sic2
邹东利
,
郭亚昆
,
帅茂兵
,
肖大武
中国有色金属学报(英文版)
doi:10.1016/S1003-6326(17)60122-5
通过激光共聚焦、背散射衍射、透射电子显微镜和显微压痕相结合的技术研究贫铀在钢弹50 m/s撞击下显微组织的演变过程.结果表明,贫铀在钢弹撞击下会形成球冠状弹坑,弹坑直径和深度分别为5.45和1.01 mm.从弹坑边沿到基体内部,变形组织可划分为4个区域:孪晶碎化区、高密度孪晶区、低密度孪晶区和基体组织区.贫铀在动态变形过程中的主要塑性变形方式是孪生.除孪生外,位错滑移在协调塑性变形时也发挥着重要作用.最后,提出贫铀在高速撞击条件下显微组织的演变过程.
关键词:
贫铀
,
钢弹
,
动态变形
,
显微组织演变
,
孪生
Zhenya Zhang
材料科学技术（英文）
This study investigated the microstructures and mechanical properties of ZK60 alloy prepared by a simplified rapid solidification powder metallurgy (RS P/M) processing system (S-RS P/M), which consists of warm press in dry air and hot extrusion. Microstructure characterizations showed that S-RS P/M alloy consisted of magnesium matrix and oxide stringers of ~1 μm in width. TEM (transmission electron microscopy) observations illustrated nano-size magnesia particles (10{30 nm) constituted oxide stringer in detail. Due to a relatively higher volume of nano-size magnesia particle produced during S-RS P/M process, 0.2% yield strength of S-RS P/M ZK60 alloy was found to be as high as 382 MPa, which is 10% higher than that of RS P/M alloy. The improvement in mechanical properties is mainly attributed to the combination effects of Orowan mechanism and coe±cient of thermal expansion (CTE) mismatch because of the approximately same average grain size.
关键词:
Microstructure
