内嵌式钨铜粉末爆炸复合结构材料的研究

为满足托克马克核聚变装置内壁材料对W-Cu复合材料的需求,提出了内嵌式粉体爆炸复合方法和技术工艺。先用该方法制备内嵌式W-Cu粉复合材料,其实验粉末分别采用粒径3μm与23μm的纯钨粉和添加10%铜粉的W-Cu混合粉末(质量分数)。然后利用扫描电子显微镜、显微硬度计对内嵌式W-Cu粉复合材料进行表征、分析。结果显示,实验粉末经过爆炸烧结压实后能达到90%以上该密实材料的密度。添加10%铜粉后制备的W-Cu粉复合结构材料结合界面更加规则均匀理想,结合界面附近几乎没有孔隙,粉末压实部分孔隙度更小且孔隙的尺寸更小,均匀致密性更好,但粉末压实层硬度更低。使用粒径3μm的混合粉末与23μm的混合粉末,后者制备的W-Cu粉复合材料,粉末压实部分均匀致密性更好,孔隙度更小且孔隙的尺寸更小,粉末压实层密度更大,但硬度更低。     

爆炸粉末烧结法制取WC/Cu复合材料的研究

采用行星式球磨机球磨WC/Cu粉,并在直接粉末爆炸压制成型的装置中进行爆炸压实,制成WC增强Cu基复合材料。试验结果表明,常规的爆炸粉末压实起到了弥散强化作用,致密度为95%~97%,材料具有一定韧性,并且硬度有较大的提高,达到了WC颗粒增强的作用。可以认为能够通过爆炸压实的方法用WC/Cu粉末制取电极复合材料。     

不同粒度SiCP增强铜基复合材料拉伸性能及断裂机制的研究

以不同粒度SiCP和电解铜粉为原料,采用粉末冶金工艺制备了SiCP增强Cu基复合材料.研究了SiCP和基体铜粉粒度的变化对材料拉伸性能和断裂机制的影响.结果表明,在基体铜粉粒度为44μm时,10μm的SiCP增强复合材料的抗拉强度达到最大值,为265.7MPa,其断裂机制是以Cu-SiC界面处基体撕裂为主,而当SiCP粒度为2μm时,由于分散不均匀、团聚等原因使得材料强度降低.大粒度SiCP(＞10μm)增强复合材料由于界面面积有限和增强颗粒间距过大,使得增强效果有限,其断裂机制是以Cu-SiC界面脱粘和SiCP解理开裂为主.实验证实了在SiCP增强铜基复合材料中基体和增强颗粒粒度存在着最佳配比关系可使复合材料达到最佳增强效果.     

孔隙可调控多孔铜粉的气相去合金制备及性能研究

多孔铜粉具有独特的孔隙结构和大比表面积,是适合于催化生长和化学负载的基元功能材料。但受限于粉末尺寸小、活性高,目前鲜有关于多孔铜粉制备工艺的研究。以球磨后的铜锌合金粉末为前驱体,采用气相去合金的方法成功制备了多孔铜粉。应用SEM、EDS、XRD、TEM等表征手段研究了去合金温度、时间、原始合金成分和球磨变形对粉末性能的影响。实验结果表明,孔隙结构变化是Zn原子去合金驱动力,Cu原子表面扩散和Cu原子体扩散三者互相竞争的结果。表面孔隙粗化过程受Cu原子表面扩散主导,而Cu原子体扩散会引起孔隙结构的收缩。球磨引入的位错通过提供快速扩散通道的方式降低了孔隙粗化过程的扩散激活能,加快了去合金过程的进行。制备的多孔粉末最大表面孔隙率为17%,平均孔隙尺寸为0.6～1.1μm。通过调整工艺参数,可以调控多孔铜粉的表面孔隙。     

熔渗法制备的钨铜复合材料及其显微组织

采用粉末预处理、添加诱导铜粉和还原气氛下熔渗的方法制备了用于电子封装／热沉的钨铜金属基复合材料。对比了不同工艺条件下采用熔渗法制备的钨铜复合材料的显微组织，并讨论了钨粉粒径、添加诱导刺等不同工艺条件对钨铜复合材料组织的影响。实验结果表明，当钨粉粒径为5～9μm，诱导铜粉粒径-500目时，经预烧结与熔渗过程得到的钨铜复合材料具有较高的组织均匀性和相对密度及良好的物理性能。     

铁粉粒径和硅树脂含量对铁基复合磁粉芯软磁性能的影响

将不同粒径铁粉颗粒和适量高温硅树脂进行充分混合,在铁粉颗粒表面上均匀包覆一层硅树脂,采用粉末压实成型工艺将铁粉-硅树脂复合粉末制备成致密的铁基复合磁粉芯。系统研究铁粉粒径和硅树脂包覆量对磁粉芯密度及软磁性能的影响,探索最佳铁粉粒径大小和硅树脂包覆量。研究表明,在相同粒径下,磁粉芯的密度、涡流损耗和磁感应强度均随硅树脂包覆量增加而降低。在相同硅树脂包覆量下,磁粉芯的密度和涡流损耗随粒径增大而增加,磁滞损耗却随着粒径增大而降低。在平均粒径为120μm的铁粉表面上均匀包覆0.5%硅树脂可制备出高密度、低损耗和较高磁感应强度的复合磁粉芯,在大功率条件下,较好软磁性能参数为Ps(B=1T,f=400Hz)=69 W/kg,B4k(H=4000A/m)=0.96T。     

颗粒粒径对碳化钨/高强钢复合材料界面微观组织和元素扩散的影响

利用"冷压成型-真空烧结法"制备了碳化钨/高强钢复合材料.结合光学显微镜、扫描电镜、超高温激光共聚焦显微镜和显微硬度计等分析测试手段对不同碳化钨(WC)颗粒粒径下获得的复合材料以及界面的显微组织和硬度进行了分析.实验结果表明,WC粉末颗粒粒径越小,WC平均晶粒尺寸越小;同时,WC致密度越高,当WC粉末颗粒粒径为100 ...     

电子封装用SiCp/Al复合材料的组织与性能

本文选用粒径为20μm和60μm的SiC混合颗粒,采用挤压铸造方法制备了体积分数为70%的SiCp/LD11(Al-12%Si)复合材料.材料组织致密,颗粒分布均匀.复合材料具有低膨胀、高导热的特性和十分优异的力学性能,并且可以通过退火处理进一步降低其热膨胀系数.采用化学镀方法,在复合材料表面涂覆镍层,以其做为底座的二极管满足器件的可靠性测试要求.     

超细球形铜粉的制备

研究了一种新颖的球形铜粉制备方法,即先用葡萄糖还原法制备球形超细Cu2O粉末,然后用氢气还原Cu2O粉末制备球形铜粉.用葡萄糖还原Cu(Ⅱ)可以制备球形的Cu2O粒子.在240℃下用氢气还原球形Cu2O粉末,得到了分散性良好的球形铜粉,铜粉具有良好的导电性和稳定性.铜粉粒径大小和粒径分布取决于前驱体Cu2O粒子的大小和粒径分布.还原后的粉末粒径略有收缩,平均粒径为1.18μm,振实密度为2.1g/ml.     

Al_2O_3/B_4C的致密化机制

初始晶粒尺寸为0.33μm和7.0μm的Al2O3/14%B4C粉末在不同温度烧结,并模拟计算陶瓷粉末烧结过程。通过对比实验结果和计算结果,找出影响材料致密化的机制,讨论晶粒尺寸对扩散机制的影响,并估算出致密化激活能。在实验烧结温度范围内,界面反应被认为是影响Al2O3/B4C粉末致密化过程的主要因素。Al2O3/14%B4C陶瓷的致密化激活能是1820±60KJ.mol-1,这结果很大程度上支持界面反应致密化机制。     

钨铜梯度材料热震过程中显微组织及热性能

针对目前W-Cu功能梯度材料(FGM)在长期热震循环过程中的稳定性缺乏相应研究的问题,以化学镀W-10wt%Cu复合粉体和Cu粉为原料,通过叠层压制和常压气氛烧结的工艺制备了W-10wt%Cu/W-20wt%Cu/W-30wt%Cu层状梯度材料。在600℃、800℃、1000℃温度下进行热震试验,对试样在不同热震温度、热震次数下的显微组织和热学性能变化进行了研究。试验结果表明,随着热震温度升高,渗出至试样各梯度层表面的Cu逐渐增加。当热震温度达到1000℃时,试样各梯度层表面出现大量Cu聚集成片的现象,同时在W-20wt%Cu/W-30wt%Cu界面处发现了界面裂纹。随着热震次数的提高,在W-10Cu层中,Cu逐渐渗出表面并在内部留下微孔。此外,W-Cu FGM的热导率随热震次数的增加而减小,在1000℃经过200次热震后,室温热导率由200.54 W·(m·K)?1降至159.23 W·(m·K)?1,降低了20.60%。该结果揭示了热震循环中裂纹形成与显微组织变化的耦合失效机制,明确了W-Cu FGM安全服役的范围。      

Preparation and Arc Breakdown Behavior of Nanocrystalline W-Cu Electrical Contact Materials

1. IntroductionBecause of high strength and high conductivity cou-pled with low thermal expansion coefficient, W-Cu alloyshave been widely used in the field of power engineer-ing and plasma technology, such as contact materials formedium and high voltage interrupters as well as weld-ing electrode[1,2]. Usually, W-Cu alloys are produced bypowder metallurgy, but this technology often results inthe segregation of copper phase that will influence elec-trical properties of the contact material. I…     

超细钨铜复合粉末注射成型药型罩研发及测试

W-Cu合金结合了钨的高密度与铜的高动态延伸率,是一种前景广阔的药型罩材料.为获得性能优良的金属射流,提高油气井射孔弹的穿孔指标,对高致密均质W-Cu合金药型罩进行了研发.采用热化学工艺开发了不同含铜率(质量分数为10%,15%,20%,25%)的亚微米级超细W-Cu复合粉末,选W-25Cu型复合粉末并采用注射近净成型工艺技术制备了药型罩,将脱脂件在H_2气氛中烧结,峰值温度为1 200℃.采用SEM观察发现,烧结药型罩微观结构为亚微米级的W粒子均匀地分布在Cu基体中,其实测密度高达14.75 g/cm~3.拉伸试验表明,所开发的药型罩材料具有优良的力学性能,极限抗拉强度达到822.4 MPa,屈服强度达807.5 MPa,延伸率为1.18%.破甲性能测试实验证明,该类药型罩具有极其稳定的侵彻性能.     

Characteristics of W-20Cu nano-crystallite composites fabricated by mechanical alloying

In the present study, the microstructure and properties characteristics of W-20Cu nano-crystallite composites were investigated. Characterization techniques like XRD and SEM have been used to study the crystallite size of W-Cu powder obtained by mechanical alloying. As well as, the effect of milling time on the microstructure and properties of W-20Cu composites was discussed. The results show that with increasing milling time, the crystallite size of W-Cu composite powder decreased and kept steady at last, and the crystallite size of W(Cu) solid solution was 6.6 nm for milling 20 h. The microstructure of W-20Cu composites became homogeneous and tungsten crystallite size became fine. The relative density and bending strength of W-20Cu composites increased. The value of thermal conductivity peaked when milling time was 20 h.     

Physico-mechanical properties and structure of diamond polycrystalline composite materials produced from variously dispersed powders

A nanostructural diamond composite material having grains of average size 0.08 μm and hardness corresponding to the hardness of diamond composite materials with grains of average size 30 μm has been produced using nanotechnologies of powder materials. Temperature dependences of hardness of nanostructural diamond composites of various dispersions have been compared. The thermostability of a diamond composite has been shown to depend not only on the composition of a sintering aid but on the size of diamond powders as well. Our findings have indicated that the material obtained holds promise in finishing products of nonferrous metals and alloys instead of natural diamonds.     

A composite material used as a membrane for ophthalmology applications

New biomaterials for intracorneal ophthalmologic implants were designed, manufactured and characterized. A composite material in the form of a membrane was manufactured in a two-stage process. The first stage of the process depended on preparation of multidimensional (MD-type) fibrous polymer composite. A stable terpolymer polytetraflouroethylene-co-polyvinylene fluoride-co-polypropylene (PTFE–PVDF–PP) was used as a composite matrix, and sodium alginate-based biopolymer (NA) in the form of short fibres and/or powder were used as porogenic constituents. The composite materials were subjected to physicochemical treatment in order to remove a water soluble biopolymer. The treatment led to about 50% of open porosity within the polymer matrix. Depending on the membrane type the mean pore size determined with SEM microphotographs was 15–25 μm. Permeability and durability of the membranes in simulated eye fluid (culture medium enriched with albumin) was tested. The size and shape of the pores before and after the permeability test were compared (SEM), and they depend on the porogen form. Mechanical parameters of the composite materials such as; tensile strength, Young’s modulus, and strain to failure were measured. A membrane derived from fibres and particles showed better mechanical properties than a membrane derived from porogen particles. Microstructure and mechanical properties make the membranes a good candidate for ophthalmological implants.     

大气等离子喷涂NiCrBSi-Mo/Ni涂层中黏结层对NiCrBSi-Mo复合工作层性能的影响

利用大气等离子喷涂系统在叶片钢材料FV520B上依次制备镍基黏结层和NiCrBSi-Mo复合工作层,并对NiCrBSi-Mo粉末的沉积率、涂层孔隙率、结合强度及表面硬度进行测试。结果表明:在NiCrBSi-Mo/Ni涂层中,厚度为180~220μm的黏结层在提高NiCrBSi-Mo粉末沉积率的同时可制备较低孔隙率、较高结合强度和硬度的表层涂层;黏结层厚度的增大导致工作层起始沉积位置的孔隙率增大,且加快了工作层在垂直方向上孔隙率的衰减过程。SEM分析发现,黏结层厚度的增大引起黏结层与工作层结合界面处熔滴沉积堆叠形貌的变化,黏结层中的缺陷对工作层产生"遗传性"的影响;胶结拉伸实验表明,黏结层厚度过大会导致拉伸过程中黏结层与工作层结合面处的断裂;在不同的抛磨面,一定黏结层厚度的试样块在垂直方向上的维氏硬度衰减较为缓慢,NiCrBSi-Mo/Ni涂层不仅保持了涂层表面高的硬度,且增大了涂层的厚度,以修复材料表面的损伤。     

Facile chemical synthesis of W-Ag and W-Cu nanocomposites at low temperature

W-Ag (80.2W-19.8Ag, 70.4W-29.6Ag and 60.5W-39.5Ag) and W-Cu (79.7W-20.3Cu, 70.5W-29.5Cu and 59.8W-40.2Cu) nanocomposites in the size range of 24-30 nm have been synthesized by thermal decomposition of W(CO)6/CH3COOAg and W(CO)6/Cu(acac)2 in diphenyl ether as solvent at 220 degrees C in presence of oleic acid and hexadecyl amine and characterized. FTIR spectra have been used to explain the role of oleic acid and hexadecyl amine in the synthesis of W-Ag and W-Cu composite powders. XRD studies show that the tungsten phase is amorphous, whereas both Ag and Cu crystallize in fcc for as-synthesized W-Ag and W-Cu nanocomposites. These composite powders when annealed at 700 degrees C results in the formation of bcc tungsten and peaks corresponding to fcc silver and copper still persists. The particle size, shape and distribution of these nanocomposites of various compositions have been studied by SAXS, ESEM and TEM and found to be nearly spherical with the average diameters below 30 nm.     

Preparation and properties of Al2O3 dispersed fine-grained W-Cu alloy

In this study, high-performance fine-grained W-Cu sintered blocks with the addition of dispersed Al₂O₃ particles were successfully produced by low temperature liquid-phase sintering, using the raw material of ultrafine W-Cu alloy powder. The ultrafine W-Cu alloy powder was obtained by a two-step reduction process composed of stages of carbothermal reaction and hydrogen deep deoxidation. The fine Al₂O₃ grains with uniform distribution in W-Cu alloy were introduced by spray method, leading to the decrease of W grain size and W-W connectivity. The relative densities of all sintered blocks were>97%, and a higher degree of densification ensures that the alloy has excellent comprehensive properties. With the increase of Al₂O₃ content, W grain size and W-W connectivity of sintered W-Cu samples decrease from 664 nm to 472 nm and 0.2 to 0.14, respectively. The W-Cu alloy with the ultimate tensile strength of 415 MPa and the highest elongation of 7.22% was obtained when the addition amount of Al₂O₃ was 0.5 wt%. At the same time, it also possessed the maximum bending strength of 1028 MPa and microhardness of 312 HV, respectively. In addition, due to the good network structure of Cu and uniform three-phase distribution, the sintered samples had excellent conductivity and compressive strength.