纳米W-Cu粉末的热机械化学法制备及其烧结性能研究

通过均相沉淀获得Cu2WO4(OH)2/CuWO4·2H2O共沉淀物,并对煅烧该沉淀物所得的W、Cu氧化物进行球磨,然后H2还原,得到了含Cu量为30%的W-Cu复合粉末。对该复合粉末的性能进行了表征,并对其烧结体的密度、微结构和力学性能等进行了测试分析。结果表明,热机械化学法制备的W-Cu复合粉末粒度为纳米级,烧结活性高,其压坯在H2气氛中固相烧结可达到96%的相对密度,液相烧结则可达到高于99%的相对密度,烧结体具有细小均匀的微结构和良好的力学性能。     

纳米晶W-Cu复合粉末烧结行为

研究了机械合金化制备的纳米晶W-xCu(x=15,20,25)复合粉末的烧结行为.结果表明,纳米晶W-Cu复合粉末烧结致密化强烈地依赖于烧结温度与烧结时间.当烧结温度从1 150℃提高到1 200℃时,烧结30min后的烧结体相对密度由91%～94%增加到97%～98%;当烧结温度超过1 300℃时,烧结体发生快速致密化,5 min内相对密度即可达到98%左右.研究还发现,W-Cu合金中W晶粒尺寸也强烈地依赖于烧结温度,即烧结温度愈高,W晶粒长大愈显著.当压坯在1 200～1 250℃烧结30 min后,所得到的晶粒度约为300～500 nm,其中经1 200℃烧结时的晶粒尺寸约为300～350 nm.另外,Cu含量增加有利于烧结致密化,并降低W晶粒长大的趋势.     

纳米W-Cu粉末的均相沉淀法制备及其烧结性能

采用湿化学工艺--蒸氨均相沉淀法,制备了纳米CuWO4·2H2O/Cu2WO4(OH)2均相沉淀物,然后煅烧、还原,得到含Cu 30%的W-Cu复合粉.将该复合粉压坯在H2气氛中于不同温度下烧结后,对烧结体的微结构和物理、力学性能等进行了测试分析.实验结果表明:蒸氨均相沉淀法制备的W-Cu复合粉体具有纳米粒度和均匀的化学组成,其烧结活性高,在较低温度下烧结即可达很高的致密化程度.由上述W-Cu粉体所制备的烧结体具有良好的物理、力学性能.     

Mo-30％Cu复合材料加Ni活化烧结工艺研究

采用添加过渡金属元素活化烧结的方法,对Ni活化烧结Mo-30％Cu复合材料进行研究,并对其烧结机制进行了研究分析.结果表明,Ni的加入加速了Mo-30％Cu的烧结进程,提高了致密性.其主要原因是Mo的过剩空位的形成导致致密性的提高.     

放电等离子烧结温度对超细晶W-40Cu复合材料的影响

采用高能球磨法制备了W-40Cu超细晶复合粉体,继而进行了放电等离子烧结(SPS),获得了致密的超细晶W-40Cu块体复合材料,着重研究了烧结温度对复合材料组织和性能的影响.结果表明,随着烧结温度升高,材料的致密度、硬度和电导率也随之升高;在950℃烧结5 min的W-40Cu复合材料,W颗粒尺寸约300～500 nm,相对致密度达98％,显微硬度HV为287,电导率为17.9 MS/m.     

残余应力对W-Cu复合材料导热性能的影响

用熔渗法制备的W-Cu复合材料在小批量生产时，发现熔渗结束后样品的热导率数据分散不稳定，受熔渗时摆放位置的影响很大。将熔渗结束后的样品退火，采取不同的方式冷却。用X射线衍射法测量其残余应力，用热脉冲法测量其热导率，研究了残余应力对材料导热性能的影响。结果表明：随冷却速度的加快，残余应力值增大，热导率降低。钨和铜的热膨胀系数相差较大，从高温冷到室温时两相收缩程度不一样，冷却速度过快时，在界面处产生残余应力，使材料的热导率降低。分析了残余应力对材料导热性能的影响及机制。     

机械合金化对W-20Cu复合材料的显微组织与性能的影响

采用机械合金化结合粉末冶金技术制备W-20Cu（vo1％）复合材料。利用扫描电镜和金相显微镜对不同球磨时间的W-20Cu复合材料显微组织进行表征，并对材料的各项物理性能进行测试。结果表明，随着球磨时间的延长，W-20Cu烧结体的组织越来越均匀，Cu相分布也越来越均匀。W-20Cu烧结体密度、收缩率、硬度、抗弯强度随球磨时间的延长而增大；球磨20h的W-20Cu复合粉烧结体热导率达到峰值（130．61Wm^-1K^-1），继续球磨，热导率减小。综合考虑所有研究结果，通过机械合金化所制备的W-Cu复合粉体可以获得具有优异综合物理性能的W-20Cu复合材料。     

碳含量对VC增强铁基复合材料加硼活化烧结的影响

在Fe-V-C-B系统中，分别添加不同含量的碳进行原位反应真空烧结，用XRD、SEM分析检测物相和组织结构。结果表明：在满足合成VC所需碳量的条件下，额外的碳会参与Fe3（C，B）的合成，从而与Fe产生共晶液相，提高了产品的致密度，同时增强相形状趋于球形，分布也趋于均匀。     

电镀制备WC@W-Cu复合材料与性能研究

W-Cu复合材料因具有低膨胀系数、高强度及导电导热性能而广泛用作电子封装、电极、电触头和炮弹的罩壳等材料。W-Cu复合材料传统制备方法在致密化、微观组织的均匀性等方面难以兼顾,导致材料的导电导热性能不足,难以满足现代电子工业的要求。以W粉及W粉表面碳化得到的WC@W粉为原料,采用复合电镀技术成功制备了W-Cu和WC@W-Cu复合材料。结果表明,W-Cu复合材料表面粗糙,微观组织存在孔洞,而WC@W-Cu复合材料晶粒细化,微观结构组织均匀、致密。WC@W-Cu复合材料的W含量为43.6wt.%,硬度达205HV,相对密度为99.3%,电导率可达54.6MS/m。采用WC@W纳米粉,电镀制备出的WC@W-Cu复合材料不仅增加了W含量,明显提高了硬度,而且在相对密度和导电性方面也优于W-Cu复合材料。     

TiB2—TiC和TiB2—SiC陶瓷复合材料的活化烧结

TiC、TiB2和SiC都具有许多非常重要的性能，其中包括强耐磨性、高熔点、高硬度和良好的化学稳定性．加入第二相能够提高碳化物陶瓷的强度和韧性．往SiC基体内添加TiB2或者TiC粒子就能够大大提高SiC制品的断裂韧性，SiC含量高的材料用于生产耐磨和耐蚀制品，而TiC和TiB2含量高的材料则在电子技术方面具有广阔的前景．俄罗斯莫斯科罗蒙诺夫精微化学工艺研究所（MNTXY）的彼得洛夫和．列文斯基指出，目前这些复合材料尚未得到广泛的工业普及，原因是由担本混合物（热压坯料）制取致富产品的成本高和韧性低．在烧结这些材料时，扩散一…     

放电等离子烧结法制备Cu/金刚石复合材料的性能与显微组织

由于具备较高的热导率,铜/金刚石复合材料已成为应用于电子封装领域的新一代热管理材料。采用放电等离子烧结工艺（SPS）成功制备含不同金刚石体积分数的Cu/金刚石复合材料,研究复合材料的相对密度、微观结构均匀性和热导率（TC）随金刚石体积分数（50%、60%和70%）和烧结温度的变化规律。结果表明：随着金刚石体积分数的降低,复合材料的相对密度、微观结构均匀性和热导率均升高;随着烧结温度的提高,复合材料的相对密度和热导率不断提高。复合材料的热导率受到金刚石体积分数、微观结构均匀性和复合材料相对密度的综合影响。     

用掺碳活化烧结技术制取碳化硼材料

研究了 3种烧结活化剂 (葡萄糖、酚醛树脂和硬脂酸 )和不同的掺碳量对碳化硼烧结的影响。发现活化剂葡萄糖优于其它两种活化剂 ,以葡萄糖为活化剂 ,掺碳 3%,在 2 2 70℃氢气中常压烧结 1h获得的碳化硼材料密度为 2 .0 6 g/cm3 (相对密度 82 %) ,这一密度高于文献中报道的采用相同粒度粉末制得的结果。     

基于机械搅拌和烧结工艺制备的GNPs/Al复合材料特性研究

采用机械搅拌和烧结工艺制备了GNPs/Al复合材料,实现了无损伤GNPs的完全铺展及在铝基体中均匀弥散分布。研究了GNPs对复合材料粉末冷压-烧结致密化行为的作用机制,阐明了GNPs对复合材料强度和塑性的作用机理,探讨了烧结时间对GNPs/Al复合材料力学性能的影响规律。结果表明,GNPs含量低于0.5%,烧结态GNPs/Al复合材料相对密度达到98%以上。烧结态Al-0.5wt.%GNPs屈服强度达到204MPa,相对于纯铝提高了18.6%。以Al-0.5wt.%GNPs为例,烧结6h后,复合材料硬度为61.5HV,屈服强度为173MPa,压缩应变40%时未发生明显破坏。     

Tungsten-copper composite production by activated sintering and infiltration

Activated sintering of tungsten has been used to have infiltrable skeletons. For this purpose the effects of sintering temperature and activator amount were studied and appropriate production parameters were obtained. The results showed that by activated sintering, moderate sintering temperature such as 1400 °C can be used instead of conventional temperatures i.e. > 2000 °C. Activated sintering has the ability to produce fully open and interconnected porosities with desirable density that is ideal for infiltration. This method of production for infiltrated W-Cu composites has not been reported elsewhere.     

Spark plasma sintering on mechanically activated W-Cu powders

Mechanically activated W-Cu powders were sintered by a spark plasma sintering system (SPS) in order to develop a new process and improve the properties of the alloy. Properties such as density and hardness were measured. The microstructures of the sintered W-Cu alloy samples were observed by SEM (scanning electron microscope). The results show that spark plasma sintering can obviously lower the sintering temperature and increase the density of the alloy. This process can also improve the hardness of the alloy. SPS is an effective method to obtain W-Cu powders with high density and superior physical properties.     

Effect of thermal annealing on microstructure and mechanical properties of a gradient structured tantalum prepared by plasma activated sintering

Fully dense bulk tantalum compacts of two different nitrogen contents with gradient structure within an individual particle were successfully synthesized by means of plasma activated sintering (PAS). Annealing of the compacts induces disappearing of the gradient structure due to the promoted diffusion of nitrogen in Ta matrix accompanied by enhancement of the strength. For the compact with low nitrogen content of 0.09 wt.%, a drop in ductility was observed. While for the compact with nitrogen content of 0.215 wt.%, improved strength was obtained without sacrificing its ductility.     

Corrosion of MCrAlY: Pt composites prepared by spark plasma sintering

Cyclic oxidation tests of sintered MCrAlY:Pt composites were carried out at temperatures of 1223 and 1273?K. Composite tablets were previously produced by spark plasma sintering. To assess an effect of platinum dispersed, microstructural characterisation was performed on the tablets before and after the cyclic oxidation treatment. Scanning electron microscopy analysis of the oxide layer showed that the presence of typical α-Al₂O₃ and NiAl₂O₄ spinel had structure columnar and equiaxial in both samples. Fine sintered microstructure and addition of Pt into the MCrAlY matrix enhanced the resistance of the material to cyclic oxidation.     

Effect of particle size on the microstructure and thermal conductivity of Al/diamond composites prepared by spark plasma sintering

Spark plasma sintering (SPS) was used to fabricate Al/diamond composites. The influence of diamond particle size on the microstructure and thermal conductivity (TC) of composites was investigated by combining experimental results with model prediction. The results show that both composites with 40 μm particles and 70 μm particles exhibit high density and good TC, and the composite with 70 μm particles indicates an excellent TC of 325 W·m⁻¹·K⁻¹. Their TCs lay between the theoretical estimated bounds. In contrast, the composite with 100 μm particles demonstrates low density as well as poor TC due to its high porosity and weak interfacial bonding. Its TC is even considerably less than the lower bound of the predicted value. Using larger diamond particles can further enhance thermal conductive performance only based on the premise that highly dense composites of strong interfacial bonding can be obtained.     

Microstructure and properties of ultra-fine tungsten heavy alloys prepared by mechanical alloying and electric current activated sintering

The microstructure and properties of the 93W-4Ni-2Co-1Fe(mass fraction,%) tungsten heavy alloys prepared by mechanical alloying and electric current activated sintering from mixed elemental powders were investigated.After 15 h milling,the average W grain size in the powders is decreased to 120 nm.For the powders milled for 15 h,the density,hardness and transverse rupture strength of the alloys sintered only by an intensive pulse electric current are the maximum.When the total sintering time keeps constant,t...     

Hydrogen storage performance of Mg-based composites prepared by spark plasma sintering

The hydrogen storage capacities, hydrogen absorption mechanism and hydride stability of Mg-based composites prepared by spark plasma sintering (SPS) were investigated in this paper. The results showed that the composites had a double-phase microstructure of Mg phase and V-based solid solution, with nanocrystalline magnesium existing at their sintering interface. With the addition of the V-based solid solution in 20% volume fraction, the composite exhibited a maximum reversible hydrogen storage capacity of 4.2 wt.% at 573 K, compared with that of pure Mg of almost zero. DSC results indicated that the hydride decomposition temperature of MgH₂ decreased sharply from 708 K in pure Mg to 636 K and to 591 K as the volume of V-based solid solution increased from 20 vol.% to 50 vol.%. With the addition of V-based solid solution, the hydrogen absorption kinetics of pure Mg was greatly improved at 573 K, and its hydrogen absorption mechanism changed from surface reaction control to diffusion control in the composite. Based on these experimental results, a model was put forward to describe the hydrogen absorption/desorption mechanism in these composites.