材料期刊网

PRODUCTION OF ULTRA-FINEα-AL2O3 PO WDERSFROM AMMONIUM A LUMINUM CARBONATE HY DROXIDE

F. Zhang1) , X. D. Sun1) , J. You2) , Z. Zhang2) , L. X. Ding3)and Y. M. Wang3)1) School of Materials and Metallurgy , Northeastern University , Shenyang 110006 , China2) Liaoning Analyzing and Testing Research Center , Shenyang 110015 , China3) Department of Materials , School of Mechanical Engineering , Shenyang University , Shenyang 110044 , China

金属学报(英文版)

Synthesis of a m m oniu m alu min u m carbonate hydroxide ( A A C H) w as investigated usinga m m oniu m alu min u m sulfate and a m moniu m hydro carbonate as the starting m aterials . Itw as found that A A C Hcan be synthesized by adding a m m oniu m alu m inu m sulfate solution torapidly stirred a m moniu m hydro - carbonate solution at a tem perature of 30 ℃. A A C Hcantransfor m to α Al2 O3 co m pletely by calcining at 1100 ℃ for 1 hour , and the obtained po w ders , with a particle size of 100 n m , can be sintered to 98 99 % relative density at 1500 ℃for 2 hours .

关键词: a m moniu m alu m inu m carbonate hydroxide , null , null , null

Calculations of the spin-lattice coupling coefficients F-ij and Z(ij) for MgO : Co2+ crystal

Communications in Theoretical Physics

According to a uniform and simple method of calculating spin-lattice coupling coefficients and the perturbation formulas of gi factors and hyperfine structure constants Ai based on the cluster approach for 3d(7) ions in Cubic, tetragonal and trigonal octahedral crystal fields, the spin-lattice coupling coefficients F-ij (F-11, F-12, F-44), Z(ij) (Z(11), Z(12), Z(44)) and also g factor and hyperfine constant A for MgO:Co2+ are calculated by using the parameters obtained from the optical spectra without adjustable parameters. The calculated results show good agreement with the observed values. The difficulty in explaining the coefficients F-ij and Z(ij) is therefore removed.

关键词: spin-lattice coupling coefficients;electronic paramagnetic resonance;crystal- and ligand-field theory;Co2+;MgO crystal;superposition model;explanation;symmetry;ions;co2+;g11;g44

掺杂Gd的Co2 Z型铁氧体的微结构和高频性能

郭世海 , 冯则坤 , 王新林 , 何华辉

功能材料与器件学报 doi:10.3969/j.issn.1007-4252.2010.02.002

采用普通陶瓷工艺制备了Gd掺杂的Co2Z型平面六角铁氧体3(Ba0.5Sr0.5)·2Co0·0.05Gd2O3·10.8Fe203,对其微结构和高频性能进行了研究.结果表明,少量掺杂Gd的Co2z型铁氧体仍具有单相的Z型平面六角结构,其磁导率实部μ'明显提高,可达到13,而截止频率仍大于1GHz,具有较好的高频性能.随着烧结温度的提高,材料的磁导率实部μ'增大,但截止频率下降.少量Gd的掺杂对Co2Z型铁氧体的复介电常数值没有明显影响,但材料的铁电共振峰向高频区移动.

关键词: 六角晶系铁氧体 , Co2Z型铁氧体 , 磁性能 , 稀土

PIP工艺制备2D C/SiC复合材料Z-向穿刺工艺

王其坤 , 胡海峰 , 陈朝辉 , 张玉娣 , 罗征

稀有金属材料与工程

针对2D C/SiC复合材料存在碳布层间缺乏纤维增强,层间结合较差的问题,提出通过Z-向穿刺工艺提高碳布层间结合,克服材料使用时可靠性不高的问题,并比较了穿刺工艺对复合材料微观结构和力学性能的影响.结果表明,通过Z-向穿刺工艺制得试样2D C/SiC-Z_(pin)的弯曲强度、弯曲模量和剪切强度分别为247.8 MPa、37.8 GPa和32.1 MPa,而未穿刺试样2D C/SiC的弯曲强度、弯曲模量和剪切强度分别只有219.3 MPa、34.4 GPa和23.3 MPa,由此可见,采用Z-向穿刺工艺能明显提高复合材料的力学性能.微观结构分析认为,试样力学性能提高的根本原因在于采用Z-向穿刺纤维加强了碳布层间结合,使材料具有较好的整体性,克服了复合材料层间结合较弱对力学性能带来的不利影响.

关键词: 2D , C/SiC , Z-向穿刺 , 微观结构 , 力学性能

新型超硬材料z-BC2N的弹性、硬度与热导率研究

王军朋 , 李凤 , 敖靖 , 焦丽娜 , 李春梅 , 陈志谦

无机材料学报 doi:10.15541/jim20140463

采用第一性原理计算研究了超硬材料z-BC2N的弹性各向异性性质、应力-应变关系、硬度及最小热导率性质.计算得到的晶体力学行为判据 B/G 为 0.87, 泊松比为 0.084, 普适弹性各向异性指数为 0.09992.[100]晶向上最大拉伸强度达到180 GPa,(100)[010]应变方向上最大剪切强度达到160 GPa,维氏硬度值为77.07 GPa.基于Cahill模型得到的最小热导率为6.811 W/(m·K).结果表明: z-BC2N是脆性材料且力学稳定性良好,有非常高的拉伸强度、剪切强度, 体弹模量为各向同性, 杨氏模量各向异性程度不大.z-BC2N 的最小热导率低于金刚石的最小热导率.

关键词: 超硬材料 , 弹性性质 , 各向异性 , 热导率

Fatigue behaviors of Z2CND18.12N stainless steel under thermal-mechanical cycling

Liubing WANG

金属学报(英文版)

Tests under mechanical strain control were performed to investigate the TMF behavior of Z2CND18.12N within the temperature range between 150-550℃. Different strain amplitudes and phase-angles were applied. Total strain controlled low cycle fatigue test was also performed at the peak temperature of TMF cycling. The results show that the cyclic stress response of the material displayed an initial hardening regime followed by a saturation period and then cyclic softening till failure. The TMF cycling leads to the development of significant amounts of mean stress. Some life prediction models were employed to predict the TMF life of Z2CND18.12N, and the results indicate that the energy-based models provide good prediction on the thermal-mechanical fatigue behaviors of this material. An optical microscopic observation shows that the surface crack initiations and crack propagations are typically transgranular mode.

关键词: Thermomechanical fatigue

La2-2xSr2xCu2yO3±z的微乳液法合成及表征

于锦 , 王军楠

稀土 doi:10.3969/j.issn.1004-0277.2005.06.024

采用微乳液法,以La2O3、Sr(NO3)2、CuO为原料,制备理论配比为La2-2xSr2xCu2yO3±z的超微粒子.通过X-衍射、扫描电镜和交流阻抗技术对粉体进行表征.在x=0.07和x=0.10时,经600℃下灼烧后,分别得到La1.86Sr0.14CuO4.08和(La0.9Sr0.1)2CuO4固熔体,它们的晶粒尺寸都小于60nm;在600℃下的电导率分别为6.5×10-3 S·cm-1和5.7×10-3 S·cm-1.

关键词: 微乳液法 , La2-2xSr2xCu2yO3±z , 电导率 , 晶粒尺寸

共沉淀法制备Co2-Z型铁氧体形成动力学过程研究

王琦 , 官建国 , 刘飚 , 张清杰

硅酸盐通报 doi:10.3969/j.issn.1001-1625.2004.03.004

用化学共沉淀法制备得到了Z型六角铁氧体,并研究了它的动力学过程;详细讨论了煅烧制度,如煅烧温度、升温速率和却冷方式对最终产物晶体结构的影响.研究表明:Co2-Z型六角铁氧体的生成序为:Ba-M→Ba-M + Co2-Y→Co2-Z;在1200℃下煅烧4h,可获得以Co2-Z为主晶相的铁氧体材料;升温速率及冷却速率对晶体的形成与结构有影响,快速升温影响最为明显.

关键词: 共沉淀 , Co2-Z型六角铁氧体 , 动力学

2D-C/SiC复合材料低温动态Z向压缩性能

叶龙海 , 邓琼 , 汤忠斌

复合材料学报

采用Hopkinson压杆试验装置,对2D-C/SiC复合材料进行了低温条件下的Z向动态压缩性能试验研究,低温条件通过控制酒精和液氮的配比系数得到,通过改变波形整形器几何尺寸的方法来实现恒应变率加载,以得到准确、可信的试验结果.试验结果表明:由于复合材料内部含有大量初始微缺陷,2D-C/SiC复合材料在低温动态加载条件下呈现伪塑性行为,其破坏时并未表现出典型的脆性破坏,而是在应力达到压缩强度时出现了显著的应变软化现象,在经历了较大的变形后才最终破坏.随着温度的降低,复合材料的动态Z向压缩强度增加,但失效应变减小.2D-C/SiC复合材料在低温环境下,其内部纤维和基体之间界面结合力增强,同时强的界面结合力可以导致高的压缩强度.

关键词: 陶瓷基复合材料 , Hopkinson压杆试验装置 , 低温 , 动态Z向压缩力学性能 , 界面强度

Ir4+掺杂Co2Z平面六角软磁铁氧体的磁性能

郭世海 , 冯则坤 , 王新林 , 何华辉

功能材料

采用普通陶瓷工艺制备了Ir4+掺杂的Co2Z型平面六角铁氧体,研究了少量Ir4+掺杂对Co2Z型铁氧体材料结构和磁性能的影响.结果表明,少量掺杂Ir4+的Co2Z型铁氧体仍具有单相的Z型平面六角结构,其磁导率实部μ′明显提高.随着烧结温度的提高,材料的磁导率实部μ′增大,但截止频率下降.在1275℃烧结的掺杂Ir4+铁氧体样品,其μ′达到16.5,截止频率仍＞1GHz,具有较好的高频性能.

关键词: 六角晶系铁氧体 , Co2Z型铁氧体 , 磁性能 , 高频