F. H.(Sam) Froes
,
C. Suryanarayana
,
and D. Mukhopadhyay (Institute for Materials and Advanced Processes (IMAP)
,
University of Idaho
,
Moscow
,
ID 83844-3026
,
USA)C-G. Li(BlM
,
P.O. Box 81
,
Beijing
,
100095
,
P.R. CHINA)K. Brand(On leave from Institut fur Werkstoffwissenshaft
,
Technische Universitst Dresden
,
07062 Dresden
,
Germany
,
at IMAP)
金属学报(英文版)
Mechanical alloying (MA), a solid-state powder processing method, is a "far from equilibrium" synthesis technique which allows development of novel crystal structures and microstructures, leading to enhanced physical and mechanical properties. The ability to synthesize a variety of alloy phases including supersaturated solid solutions, nanocrystalline structures, amorphous phases and intermetallic compounds themselves is discussed. No extension of solubility using MA has been observed in the intermetallics studied. Nanostructured grains were observed in all compositions. Long time milling generally resulted in amorphous phase formation in large part because of the increase in grain boundary energy/mole with reduced grain size; good agreement with the Miedema model for amorphization was obtained in the Al-Fe system. Generally an anneal was required to form the intermetallic after MA; however,intermetallics with a large negative enthalpy of formation were detected in the MA condition. A study of the hot isostatic pressing of γ-TiAl powders produced by MA demonstrated that full density can be achieved at least 400℃ below the normal temperature required for conventional powder, that is 725℃ or below. Nanometered sized grains (≤100nm)were observed after HIP'ing up to 850℃.
关键词:
: Intermetallics
,
null
,
null
王庆
,
巴德纯
,
王晓冬
,
靳雨菲
钢铁研究学报
介绍了RH-KTB炉外精炼真空抽气系统的工作原理和故障特点.该系统的故障诊断应能从大量数据中快速提取征兆并及时诊断,且有一定的自学习能力.为此,采用一种以实例为基础的归纳学习算法即ID3算法进行故障诊断.ID3算法有一定的自学习、自组织能力,适用于复杂系统的智能诊断.通过讨论分析了ID3算法的特点和作用.
关键词:
决策树
,
真空
,
智能
,
故障诊断
范晓娟
,
孙学峰
,
赵霞
,
李晓光
低温物理学报
doi:10.3969/j.issn.1000-3258.2000.01.010
本文考虑高温超导体YBa2Cu3Oy的结构特征,以S表示超导层, N表示非超导层,建立一个简单的SN双层高温超导体模型,用双层高温超导体模型构造成一个Josephson 隧道结SNINS.我们从理论上用格林函数方法计算了c 向结电流随层间耦合强度和s+id 中s 波分量的变化规律.结果发现随层间耦合的加强,结电流随温度的变化规律趋向于传统的AB理论.在一定的层间耦合强度下,随s 波分量的减少,结电流逐渐减小,定性符合实验上确定的高温超导体d波对称性占主要地位的结论.对于YBCO体系, 当层间耦合强度t⊥/Tc=1.9, s波分量ε=0.2时, 计算结果与实验符合很好.
关键词:
Qian LI
,
Qin LIN
,
Lijun JIANG
,
Guozhi ZHOU
,
Feng ZHAN
,
Qiang ZHENG
材料科学技术（英文）
A high activity and large capacity of hydrogen storage alloy Mg2Ni by hydriding combustion synthesis was investigated by means of pressure composition isotherms, X-ray diffraction and scanning electron microscopy. The results showed that the maximum hydrogen absorption capacity of Mg2Ni is 3.25 mass fraction at 523 K, just after synthesis without any activation. The relationships between the equilibrium plateau pressure and the temperature for Mg2Ni were lgp (0.1 MPa)=-3026/T+5.814 (523 K≤T ≤623 K) for hydriding and lgp (0.1 MPa)=-3613/T+6.715 (523 K≤T ≤623 K) for dehydriding. The kinetic equation is [-ln(1-α)]3/2 = kt and the apparent activation energy for the nucleation and growth-controlled hydrogen absorption and desorption were determined to be 64.3±2.31 kJ/(mol·H2) and 59.9±2.99 kJ/(mol·H2) respectively.
关键词:
Hydriding combustion
,
null
,
null
,
null
郭建兵
,
朱红
,
何敏
,
秦舒浩
高分子材料科学与工程
采用熔融共混方法制备了苯乙烯-马来酸酐共聚物(SMA)增容的PA6/ARS共混物,结合吴守恒的临界基体层厚度(IDc)理论,考察了基体层厚度与界面粘接对PA6/ABS共混物脆一韧转变的影响.结果表明,温度低于8℃,当ID减小时,冲击强度先缓慢增加,当ID＜ID.时,共混物缺口冲击强度急剧增加;测试温度处于13℃～23℃时,PA6/ABS共混物要表现出超韧行为,必须同时满足形态(ID＜IDc)及界面粘接的要求;测试温度大于28℃时,共混物只需满足基体层厚度判据.PA6/ABS共混物的脆一韧转变既可在较小的基体层厚度、较低的温度下获得,也可在较大的基体层厚度、较高的温度下获得.
关键词:
尼龙6
,
丙烯腈-丁二烯-苯乙烯共聚物
,
脆-韧转变
,
基体层厚度
,
界面粘接
冯林
,
蒋百灵
,
杨超
,
郝娟
,
张彤晖
稀有金属
将靶材与真空腔之间的伏安特性引入正-反欧姆过渡区间,采用脉冲控制模式研究不同靶电流密度对镀层均匀性和膜/基结合强度的影响规律.实验发现,当靶面放电区电流密度(Id)由0.083 A/cm2增加至0.175 A/cm2时,靶电压随靶电流密度的增大呈线性增大关系,与之对应的镀层厚度差由7.984 μm增大至14.011 μm;但当Id由0.175 A/cm2增大至0.25 A/cm2时,靶电压随靶电流密度的增大呈线性减小关系,与之对应的镀层厚度差则由14.011 μm减小至10.077μm;而薄膜厚度减小率由97.38％ (Id=0.083 A/cm2)降低为89.491％ (Id=0.25 A/cm2);另外,在反欧姆区,膜/基结合强度随Id的增大而快速增大.以上结果表明:反欧姆环境下有利于改善镀层的均匀性和提高膜/基结合强度.
关键词:
磁控溅射离子镀
,
伏安特性
,
反欧姆区
,
离化率
汪英
,
杨洋
,
贾振兴
,
秦家强
高分子材料科学与工程
采用化学亚胺化和热亚胺化相结合的方法制得了一系列聚酰亚胺（PI）薄膜。在化学亚胺化阶段,通过控制脱水剂的量将前驱体转化为具有预定酰亚胺化程度（pre-ID）的酰胺酸-酰亚胺共聚物。原位生成的刚性酰亚胺结构诱导分子链规整排列,得到具有不同的聚集态结构和性能的PI薄膜。X射线衍射（XRD）和差示扫描量热（DSC）测试结果表明,随着pre-ID的增加,最终PI薄膜的结晶度逐渐增加。PI薄膜的力学性能也随着pre-ID的增加呈现出增强趋势,与样品PI-0相比,PI-100的拉伸强度、拉伸模量和断裂伸长率分别增加了23.2%、7.6%和158.6%。
关键词:
聚酰亚胺
,
酰亚胺化程度
,
结晶度
,
力学性能
Journal of Materials Research
This paper describes a new method to synthesize AlN nanowires by the nitridation of Ti(3)Si(0.9)Al(0.1)C(2) solid solution. Single-crystalline AlN nanowires with the hexagonal wurtzite structure can be easily prepared using this method. In particular, the resulting AlN nanowires display a new growth orientation of < 10 (1) over bar1 > besides < 1000 > and < 0001 >. This work indicates that M(N+1)AX(N) compounds are promising raw reactants to synthesize one-dimensional (ID) nanostructures of nitrides and oxides.
关键词:
oxidation resistance;ti3sic2;aluminum;diffusion;phase;si
曾国勋
,
张海燕
,
陈易明
,
熊旋
航空材料学报
doi:10.3969/j.issn.1005-5053.2012.6.014
采用不同温度热处理纳米多壁碳管,研究纳米多壁碳管结构变化对相应复合材料的微波特性的影响.采用拉曼光谱分析表征纳米多壁碳管热处理前后的结构变化;测试纳米多壁碳管/石蜡复合材料在0.5 ～ 6GH介电谱.结果显示,热处理温度≤1000℃,纳米多壁碳管的ID/IG值基本不变,相应复合材料的复介电常数大致相等且吸波性能基本相同;热处理温度＞ 1000℃,ID/IG值明显减小,内部结构发生重排,纳米多壁碳管平均晶粒尺寸增大,相应的纳米多壁碳管复合材料的复介电常数无论实部还是虚部均明显下降,微波吸收峰向高频移动.通过热处理控制纳米多壁碳管的ID/IG值和平均晶粒尺寸,可以调整纳米多壁碳管复合材料的微波介电谱,达到调整纳米多壁碳管复合材料的微波吸收特性的目的.
关键词:
纳米多壁碳管
,
结构
,
介电谱
,
拉曼谱
