SPS法制备高密度烧结铜的工艺研究

采用平均颗粒度为3 μm的铜粉,利用放电等离子烧结(简称SPS)分别在700,750和800 ℃进行快速烧结,并系统研究了烧结体的密度和微观组织.结果表明,采用在升温阶段施加＜15 Mpa的压力作为初始压力,在保温和冷却阶段的烧结压力＞45 Mpa的烧结工艺,可以获得相对密度＞98%的致密铜烧结体.铜烧结体的密度随着烧结温度的提高而升高,其中800 ℃时铜烧结体的相对密度＞99.5%,而采用从烧结开始就施加30 Mpa初始压力的烧结工艺制备的烧结铜,其相对密度＜98%.烧结温度为700 ℃时,微观组织的晶粒度可以细化到10～15 μm.     

导电墨水用纳米铜的制备及表征

以CuO为铜源,水合联氨为还原剂,首次制备出适合导电墨水用的高浓度、高纯度纳米铜颗粒混合溶液。试验结果表明:该方法可获得质量分数在11%以上的纳米铜固体颗粒,平均颗粒尺寸约为98nm;制备工艺简单,不需要水洗或复杂的电渗析处理。方法有较大的工业应用前景。     

纳米钨粉的烧结工艺

采用催化-凝胶法制备的平均粒径60nm的纳米钨粉为原料,经钢模压制成生坯,用高温膨胀仪测定了纳米钨粉坯体的烧结收缩动力学曲线;然后分别测定了不同烧结温度和烧结时间下烧结体晶粒尺寸和相对密度的变化.结果表明,纳米钨粉的坯体在200℃开始收缩,1300℃基本停止收缩.从1000℃到1200℃,其相对密度提高了24%,是致密化过程最快的阶段.在1200℃×120min的烧结工艺下得到烧结体相对密度为95%,晶粒尺寸为5μm的钨材.     

超细Cu粉在导电浆料中的烧结性能研究

为了得到Cu导电浆料所需的纳米金属粉,通过直流电弧等离子法制备纳米Cu粉,利用X射线衍射(XRD)、FESEM等测试手段对Cu粉的晶体结构、形貌进行表征。以丙烯酸树脂、乙基纤维素和松油醇为有机载体,采用超细Cu粉(质量分数70%)为导电相配制了导电浆料,研究了不同烧结温度(450~600℃)及烧结时间(15~60 min)下Cu导电浆料的导电特性及形貌变化。结果表明,烧结工艺对导电膜层的导电性能影响较大,随着烧结温度的升高和保温时间的延长,浆料层的导电能力增强,方阻逐渐减小;600℃烧结60min时,浆料方阻最小,可达到14.8 mΩ/□。     

纳米粉末硬质合金烧结机理研究

本文研究了三种组分相同的（８４（重量）％Ｗ、１５（重量）％Ｃｏ、（重量）％ＶＣ，但晶粒度（纳米、亚微米、微米）不同的ＷＣ－Ｃｏ粉末。三种粉末均采用两种方法在盯同条件下烧结：常规真空烧结法和膨胀仪烧结法。测定了常规烧结制品的各种机械与物理性能，膨胀仪烧结试样的烧结机理。通过分析研究了不同温度下的收缩速率，研究发现粉末的初始晶粒度影响致密化的起始烧结温度、致密化速率、最终硬度和断裂韧性。     

纳米WC-Co复合粉末的制备工艺及其烧结特性

综述了纳米WC－Co复合粉末制备工艺的国内外研究进展，总结了纳米WC－Co硬质合金复合粉末的烧结特性，并对目前国内外的研究现状进行了分析，指出了研究中所存在的问题和研究趋势。     

烧结温度对高速压制制备弥散强化铜材料导电率的影响

弥散强化铜材料具有高强度和高导电性的特性,孔洞是影响导电率的重要因素.本文采用高速压制成形技术,对Al₂O₃质量分数为0.9%的弥散强化铜粉压制成形,研究了压制速度对生坯的影响.当压制速度为9.4 m·s^-1时得到密度为8.46 g·cm^-3的生坯.研究了烧结温度对烧结所得Al₂O₃弥散强化铜试样导电率的影响.当生坯密度相同时,烧结温度越高,所得试样的导电率也越高.断口与金相分析表明:烧结温度为950℃时,烧结不充分,颗粒边界以及孔洞多而明显,孔洞形状不规则;烧结温度为1080℃时,颗粒边界消失,孔洞圆化,韧窝出现,烧结坯的电导率为71.3%IACS.     

纳米铜粉的制备研究

本文研究了化学还原法制各纳米铜粉的方法。本实验以次磷酸钠为制备纳米铜粉的还原剂。实验得出其较佳工艺条件： pH值在1．5—2．0之间，温度60℃左右，高速搅拌，反应时间15—20min，硫酸铜溶液中的Cu^ 2被还原为紫红色粉末。对所得产品进行XRD谱图分析，证实紫红色粉末为铜粉，但其在空气中不稳定，极易被氧化为Cu2O。通过扫描电镜图片观察，所得铜粉一次粒径约为十个纳米，但团聚体为数百个纳米的颗粒。     

纳米晶W-25Cu复合粉末烧结行为的研究

研究了机械合金化工艺制备纳米晶W-25Cu复合粉末的烧结致密化和晶粒长大行为,并考察了一种新型晶粒长大抑制剂对抑制W晶粒长大的作用,探讨了其作用机理。结果表明,烧结致密化和晶粒长大强烈依赖于烧结温度和时间。经1200℃烧结30min后,烧结相对密度和W晶粒尺寸为97.7%和310nm。新型晶粒长大抑制剂抑制W晶粒长大效果明显。     

含油轴承专用烧结铜粉的研究

根据含油轴承的特殊工况,研制出适用于高强度、低噪音的含油轴承专用烧结铜粉;并测试了粉末的松装密度、流动性及粒度组成等基本物理性能;对影响粉末性能的因素进行了详尽的分析,并获得了最佳的工艺参数。研究结果表明,烧结铜粉具有严格的粒度分布,良好的流动性、压制性和较低的烧结尺寸变化率,适合粉末冶金机械零件的制造。     

Charging composition and structure optimisation in the sintering process (Part I)

In this paper, an optimisation system for charging composition and structure in the sintering process was established in order to reduce the sinter cost in the ironmaking process. The system comprised four modules: sinter metallurgical performance testing and analysis, sintering burdening design and optimisation, sintering matching calculation, and sinter component and property prediction. The data for the first module came from actual production values of a steelworks and from testing in the laboratory. Based on material balance theory, the second module used a linear programming method to optimise sinter cost, quality and quantity. The third module was built to predict the sintering production data. The fourth module can be used to predict some composition and properties of the sinter based on a Back-Propagation neural network. The system integrated all of these modules using Visual Basic and MATLAB. As the result, the optimum charging composition and structure of sinter which satisfies all constraint conditions can be obtained. Compared with traditional production testing and hand calculation in the sintering process the system can reduce the sinter cost and greatly decrease the production risk. Industrial application proves that the system is very useful and efficient in reducing sinter cost while ensuring output quantity and quality.     

Preparation of porous titanium materials by powder sintering process and use of space holder technique

It is shown that an adapted powder sintering process can successfully prepare a 24.0%-35.5% porous titanium composite using 20μm Ti powder and rice husk particles ranging in size between 250μm and600μm.The phase constituents of the porous Ti composite samples were determined by X-ray diffraction(XRD)pattern sintered at 1250°C.The generation of silicon in the form of a TiSi_2 solid solution,injected into the substrate,illustrates the solid solution strengthening effect.The average grain size of the tested sample and the grain boundary area increase along with the silicon content.This indicates that silicon is dispersed within the green compact of Ti.As the distance from a hole becomes greater,the nanohardness increases until it reaches a maximum hardness of 3.5GPa at approximately 1.5mm.This may be due to the solid solution strengthening of SiO_2.However,nanohardness is 3.3GPa at a distance of approximately 0.5mm from a hole′s edge.The compressive strength is measured to be in the range of 440-938 MPa.The strain reaches 14.8%-16.6% under compression testing.A large number of cleavage steps appear following a fracture.The observed fracture is a brittle fracture.Porous Ti composites with about 36% porosity have promising potential biomaterial applications,specifically related to bone implants and biological bearings.     

烧结过程协同处理垃圾焚烧飞灰的可行性探讨

中国生活垃圾焚烧飞灰产量逐年增长,其中含有二噁英、重金属和氯,对环境危害巨大,属典型的难处理危险废弃物,烧结工序拥有成熟的高温冶金技术和设备,具备处理垃圾焚烧飞灰的潜力。根据飞灰和烧结过程的主要特点,结合飞灰处理过程中存在的难点,探讨了添加飞灰对烧结过程的影响,飞灰中二噁英、重金属在烧结工序中的代谢过程,确定了烧结过程协同处理垃圾焚烧飞灰的可行性,为国内外飞灰处理企业和钢铁流程协同处置固体废弃物提供一定的参考。     

金纳米颗粒烧结的分子动力学模拟

采用分子动力学模拟方法研究了不同尺寸Au纳米颗粒在烧结过程中晶型转变及烧结颈长大机制.研究发现纳米颗粒的烧结颈生长主要分为两个阶段：初始烧结颈的快速形成阶段和烧结颈的稳定长大阶段.不同尺寸纳米颗粒烧结过程中烧结颈长大的主要机制不同：当颗粒尺寸为4 nm时,原子迁移主要受晶界（或位错）滑移、表面扩散和黏性流动控制;当尺寸在6nm左右时,原子迁移主要受晶界扩散、表面扩散和黏性流动控制;当颗粒尺寸为9 nm时,原子迁移主要受晶界扩散和表面扩散控制.烧结过程中Au颗粒的fcc结构会向无定形结构转变.此外,小尺寸的纳米颗粒在烧结过程中由于位错或晶界滑移、原子的黏性流动等因素会形成hcp结构.     

Dehydrating and sintering of Philippine nickel laterite

Abstract

Dehydrating of nickel laterite is necessary when high magnesium laterite ores are treated by pyrometallurgical means. In this work, the Philippine nickel laterite was dehydrated and sintered simultaneously in a laboratory scale sintering apparatus. The original nickel laterite was characterised using thermogravimetric (TG) analysis, differential thermal analysis (DTA) and X‐ray diffraction (XRD) experiments. The measurements indicate that chlorite (Fe,Mg,Al)₃(Si,Al)₂O₅(OH)₄ and serpentine Mg₂₁Si₂O₂₈(OH)₃₄H₂O are the primary phases, while FeO(OH) and (Fe,Mg,)₃Si₄O₁₀(OH)₂ are the minor phases in Philippine nickel laterite. The laterite contains free water, water of crystallisation and hydroxyl group; these can be removed in that order during the heating. The temperature range for the removal of free water is 25–140°C, for water of crystallisation it is 200–480°C, and for hydroxyl group it is 500–800°C. Sintering experiments with various coal additions show that sintering time, sintering product ratio, mass loss and the temperatures of off‐gas and burden increase with increasing coal addition. The sintered samples were analysed using XRD, scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS). The results demonstrate that olivine (Mg,Fe)₂SiO₄ and spinel MgFe₂O₄ are the main bonding phases during the sintering.

La déshydratation de la latérite de nickel est nécessaire lorsque des minerais de latérite à haute teneur en magnésium sont traités par méthodes pyrométallurgiques. Dans ce travail, on a déshydraté et fritté simultanément la latérite de nickel des Philippines dans un appareil de frittage à l’échelle du laboratoire. On a caractérisé la latérite de nickel originale en utilisant des expériences de thermogravimétrie (TG), d’analyses thermiques différentielles (DTA) et de diffraction des rayons X. Les mesures indiquent que le chlorite (Fe,Mg,Al)₃(Si,Al)₂O₅(OH)₄ et la serpentine Mg₂₁Si₂O₂₈(OH)₃₄H₂O sont les phases primaires alors que FeO(OH) et (Fe,Mg)₃Si₄O₁₀(OH)₂sont les phases mineures de la latérite de nickel des Philippines. La latérite contient de l’eau libre, de l’eau de cristallisation et le groupe hydroxyle; on peut les enlever dans cet ordre lors du chauffage. La gamme de température pour l’enlèvement de l’eau libre est de ～25 à 140°C, elle est de ～200 à 480°C pour l’eau de cristallisation et de ～500 à 800°C pour le groupe hydroxyle. Les expériences de frittage, avec additions variées de charbon, montrent que le temps de frittage, le ratio du produit de frittage, la perte de masse et les températures du gaz de dégagement et du lit de fusion, augmentent avec une augmentation d’addition de charbon. On a analysé les échantillons frittés en utilisant la XRD, la microscopie à balayage d’électrons (SEM) et la spectroscopie à dispersion d’énergie (EDS). Les résultats démontrent que l’olivine (Mg,Fe)₂SiO₄ et le spinelle MgFe₂O₄ sont les principales phases de liaison lors du frittage.     

关于烧结废气脱硫技术发展现状的分析

针对钢铁联合企业各工序排放二氧化硫的特点,指出烧结是主要污染源之一．介绍了当前几种烧结废气脱硫技术的机理和工艺流程,同时分析了烧结脱硫技术的特点和发展趋势．     

Preliminary study to determine the sintering stress from microstructural analysis of green parts

Solid-state sintering theory predicts shrinkage kinetics assuming the two-sphere model. Spheres are of equal diameter, undeformed and smooth. The actual condition of powder particles in cold compacted green parts deviates very much from this model: particles have a broad size distribution and an irregular surface profile, they are not spherical and plastically deformed. Therefore the sintering stress cannot be directly correlated to the particle radius, as made in the two-sphere model. The actual neck curvature radius should be therefore determined. In this work, a first attempt to determine sintering stress experimentally is presented. Iron green parts produced by cold isostatic pressing were pre-sintered in order to provide a minimum consolidation avoiding densification. By means of image analysis, the microstructure was investigated to characterise the particle and the pore morphology, and in particular their profiles. A geometrical model of the pore morphology was proposed, from which the radii of curvature in correspondence of the neck regions may be calculated.     

Solid state sintering and consolidation of Al powders and Al matrix composites

As an attempt to depart from conventional transient liquid phase sintering practice, solid state vacuum sintering was studied in loose powder and in hot quasi-isostatically forged samples composed of commercial inert gas atomized (CIGA) or high purity Al powder. The high purity Al powder was generated by a gas atomization reaction synthesis (GARS) technique that results in spherical powder with a far thinner surface oxide. After vacuum sintering at 525 °C for up to 100 h, SEM results showed that the GARS Al powder achieved significantly advanced sintering stages, compared to the CIGA Al powder. Tensile results from the forged samples also showed that although its ultimate tensile strength is lower, 95 vs. 147 MPa, the ductility of the GARS pure Al sample is higher than the CIGA Al sample. Forging also consolidated a model powder-based composite system composed of an Al matrix reinforced with quasi-crystalline Al–Cu–Fe powders, where the same powder synthesis methods were compared. Auger surface analysis detected evidence of increased matrix/reinforcement interfacial bonding in the composite sample made from GARS powder by alloy interdiffusion layer measurements, consistent with earlier tensile property measurements. The overall results indicated the significant potential of using Al powders produced with a thin, high purity surface oxide for simplifying current Al powder consolidation processing methods.     

Effects of sintering process and heat treatments on microstructures and mechanical properties of VANADIS 4 tool steel added with TiC powders

Abstract

In this study, commercial VANADIS 4 (V-4) tool steel powders were classified by sifting, which was previously the matrix, and fine TiC powder was used as an additive to produce a new material with high hardness and wear resistance, via powder metallurgy and a sintering process. Experimental results showed that the transverse rupture strength of the original V-4 steel powder was 678·5 MPa and was enhanced to 868·6 MPa below 25 μm, after the addition of 35 wt-%TiC powders through sintering at 1400°C. In addition, the hardness increased to 86·2 HRA, transverse rupture strength reached 1059·3 MPa and porosity decreased to 1·2% of the V-4 steel powders (below 25 μm) added with 35 wt-%TiC after sintered at 1400°C and annealed at 850°C, followed by quenching at 1030°C and tempering at 200°C.     

High strength aluminium alloys prepared by nanocrystallisation of amorphous powders using spark plasma sintering

Al based nanocrystalline alloys with high fracture strength are fabricated using consolidation and controlled crystallisation strategy of amorphous powder precursors. The sintered product exhibits high specific strength of 3.18?×?10⁵?Nm?kg^??1. The compacted microstructure and ultrafine grains caused by sufficient densification and crystallisation of Al based amorphous powders are responsible for considerable properties of the sample. Furthermore, the densification process and mechanical behaviour of the sintered Al based nanocrystalline alloy are investigated in detail. The Al based nanocrystalline alloys prepared by synergetic process of powder consolidation and crystallisation of amorphous can exhibit much improved mechanical properties compared with conventional Al alloys, which can have potential engineering applications.