纳米WC/Co复合粉微观结构研究

本文以喷雾转化法制备的WC-6%Co复合粉为研究对象,通过研磨、分散等手段,结合扫描电子显微镜、X射线衍射仪、离子束抛光、激光粒度分布及Co浸蚀等方法,详细分析了其形貌、内部结构、粒度等参数,得出了复合粉团粒松散空心球体结构下的一次颗粒表现为预合金化的团聚状态,该团聚体形状、大小差异较大,且不易被破碎,对一次颗粒的剖面分析清晰地揭示出复合粉的预合金化,团聚体内部有大量的孔隙存在。由于预合金化的作用,约质量分数为1%的Co因WC阻隔不能与酸发生反应。复合粉经过研磨后的分布数据显示,虽然有少量的粗颗粒聚集现象,但测量数据基本稳定,粒度分布D50值为2μm左右,为复合粉的相关研究提供依据。     

微粉粒度测量中形貌因素的影响

从理论上分析了用电阻法(库尔特)颗粒计数器和激光粒度仪测量相同的非圆球颗粒样品时,测试结果不一致的必然性,并进行了对比实验.实验结果显示:对圆球形颗粒,两者的测试结果一致(在合理的误差范围内);但是对非圆球形颗粒,二者有明显的差异.激光粒度仪测量的结果比电阻法颗粒计数器测量的结果分布宽,所得d50的值大;同时样品的平均圆度越小,则所述的差异越大.实验结果说明:用不同原理的仪器测量磨料微粉的粒度时,必然存在测量上的差异,并且差异的大小随微粉颗粒形状的变化而变化.因此,不同原理仪器之间的测量差异不能用一个固定的数值来修正;另一方面,这种差异可以用来表征颗粒偏离圆形的程度.     

激光粒度分析中颗粒折射率的确定方法

随着粉末冶金技术的发展,金属颗粒粒度分析越来越受到关注,激光法是粒度分析中较常用的方法。比较了Mie散射理论与Fraunhofer衍射理论模型选择对颗粒粒度测试的影响。对于粒度较大颗粒,可以不考虑颗粒的折射率,使用Fraunhofer理论。而对于亚微米小颗粒,应选择Mie理论,需要提供颗粒与分散介质的折射率。并讨论了待测颗粒折射率实部与虚部的确定方法。     

静态图像分析法在亚微WC粉末粒度分析中的应用

原料WC粉末粒度是影响WC-Co硬质合金微观结构和性能的关键因素,目前仍没有一个完全精确的方法用于测量亚微WC粉末粒度。本研究采用静态图像分析法得到亚微WC粉末颗粒尺寸,并针对WC06和WC08两种粉末粒度进行表征分析,测得平均颗粒尺寸分别为0.40μm和0.42μm,表明两者一次颗粒粒径相差不大,WC06和WC08是传统粒度测试方法下分类的产物。同时将该结果与常规粒度测试方法（费氏粒度法、比表面积法和激光衍射法）以及常用静态图像分析技术（扫描电镜法、电子背散射衍射法）进行对比分析。结果表明,静态图像分析法能在很大程度上消除团聚的二次颗粒的影响,能迅速完成图像处理,并对粉末颗粒粒度进行定量表征。     

WC粉粒度特征与硬质合金WC晶粒粒度关系的定量研究

本文研究了粒度接近的5个批次原料WC粉及对应合金的特性。利用扫描电镜分析原料WC粉的整体特征及WC颗粒聚集体构成特征,用激光粒度分析仪分析了各批次原料WC粉的粒度分布,用定量金相软件分析了合金成品WC晶粒粒度分布。结果表明,粒度接近的各批次的原料WC粉颗粒粒度分布不尽相同。在相同的球磨时间下,WC粉末粒度分布相同的批次,合金WC晶粒粒度分布曲线不尽相同,原料WC粉末中单晶WC颗粒的粒度对合金WC晶粒粒度分布有直接影响。评价WC的质量应从Fsss粒度、粒度分布、电镜形貌和球磨实验合金的晶粒分布进行综合分析。     

EBSD技术在WC粉末晶粒度测量上的应用

WC粉末是一个复杂的体系,传统的粒度测试方法如筛分法、透气法、激光法、电子显微镜等,都是以粉末的"颗粒度"为检测对象,而难以对其"颗粒度"进行真实的统计。本文在多次实验的基础上,成功的将电子背散射衍射(EBSD)技术应用于WC粉末的晶粒尺寸统计。本实验选取四种不同Fsss粒度的WC样品,应用EBSD技术对其晶粒度大小和晶粒取向进行分析的同时,还与其他粒度测试方法(激光粒度法、X衍射法和SEM截线法)进行对比分析。实验结果表明:利用EBSD技术对粉末进行分析检测,可以通过对WC晶粒取向差分析从多晶颗粒和团粒中分辨出WC晶粒,从而对WC的晶粒度进行真实的统计。     

碳化钨粉分级对粉末特性与合金性能的影响

对市售16μmWC进行风力分级,得到了粗中细三种粒级的粉末,分析了原粉、分级粉的供应态和研磨态费氏粒度、粒度分布等特性,比较了用4种粉末制备的WC-10%Co的合金特性。结果表明:分级粉的均匀性都有改善;粗粉费氏粒度是细粉的2倍,研磨态粒度则相差很小;粉末的碳含量是随分级粉粒度变小而增高。4种粉末制备的合金的密度、硬度、磁力、钴磁差别不大,分级粉的抗弯强度则随着粒度变细而提高,Fsss供/Fsss研的值越小,合金强度越高,比值为3.1的细粉制备的合金的抗弯强度比其值为6.2的粗粉合金的抗弯强度提高29%,且金相组织中的WC和Co相最为均匀。     

微粉磨料粒度不同检测方法对比

采用d50、d3粒径分辨率及颗粒形状等参数,对电阻法、沉降管法、激光衍射法、图像法四种微粉粒度检测方法进行了对比试验。结果表明,图像法不但能对微粉颗粒形状进行检测,而且对d50粒径分辨率、d3粒径对粗大颗粒的分辨率最高;该方法可对微粉磨料粗大颗粒、粒径特征值、颗粒形状三要素进行有效检测,是控制微粉磨料产品质量稳定的有效检测方法。     

粉料粒度分布对黄壤土基铸造涂料性能的影响

检测了以黄壤土粉、矿渣粉为主要材料的耐火粉料在不同研磨时间下的粒度分布,并研究了不同粒度分布对黄壤土基铸造涂料的悬浮性、粘度、触变性和涂刷性的影响.试验结果表明,研磨2h后的粉料粒度可以满足涂料的使用要求.     

应用于钼靶材的大粒度钼粉制备技术

研究了在两阶段氢气还原法生产钼粉的过程中还原温度、料层厚度等已达到设备极限的情况下,通过提高一段还原氢气露点以继续提高钼粉粒度的可行性。结果表明,露点从-20℃提高到20℃后,钼粉颗粒的微观形貌仍基本呈近球形,且团聚程度更低,小颗粒更少;激光粒度分布与费氏粒度结果均显示钼粉的粒度有明显提高。     

Characterization of nanometer tungsten powders

Three types of tungsten powders were prepared by hydrogen reduction of three precursor powders at low temperature,which were used as samples,and were then characterized by Brunauer-Emmer-Teller (BET) method,scanning electron microscopy (SEM),transmission electronic microscopy (TEM),small angle X-ray scattering (SAXS),and field-emission scanning electron microscopy (FESEM) respectively.The results showed that although BET and SEM could not characterize the particle size of nanometer powders,they were important means of assistance to exclude non-nanometer powders.TEM and FESEM could directly measure the particle size of nanometer powders,but this needs a lot of time,to count the average particle size and particle size distribution.SAXS could not describe the state of agglomeration.By the combination of FESEM and SAXS,the particle size,particle size distribution,and particle shape of nanorneter powders could be preciscly characterized.     

Preparation and particle size characterization of Cu nanopartides prepared by anodic arc plasma

Copper nanoparticles were successfully prepared in large scale by means of anodic arc discharging plasma method in inert atmosphere. The particle size, specific surface area, crystal structure, and morphology of the samples were characterized by X-ray diffraction （XRD）, BET equation, transmission electron microscopy （TEM）, and the corresponding selected area electron diffraction （SAED）. The experimental results indicate that the crystal structure of the samples is fcc structure the same as that of the bulk materials. The specific surface area is 11 m^2/g, the particle size distribution is 30 to 90 nm, and the average particle size is about 67 nm obtained from TEM and confirmed from XRD and BET results. The nanoparticles with uniform size, high purity, narrow size distribution and spherical shape can be prepared by this convenient and effective method.     

Preparation and particle size characterization of Cu nanoparticles prepared by anodic arc plasma

1. Introduction Metal nanoparticles exhibit novel physical and chemical properties owing to the small size effect, surface effect, quantum size effect, and quanta tun-nel effect [1-4]. In recent years, the research and de-velopment for metal nanoparticles have attracted significant interest and is still the subject of intense investigation owing to their intriguing properties and various potential applications [5-7]. Because the properties depend strongly on the details of particle size, speci…     

真空感应熔炼气雾化法制备高强度PH13-8Mo钢粉末的特性表征

采用真空感应熔炼气雾化(VIGA)法制备出球形高强度PH13-8Mo钢粉末,通过不同目数的筛网对粉末进行筛分,得到120~212μm,53~120μm,15~53μm和<15μm不同粒度区间的高强度PH13-8Mo钢粉末。利用氧氮分析仪、扫描电镜(SEM)、激光粒度分布仪和智能粉体特性测试仪等分析手段研究了不同粒径区间的PH13-8Mo钢粉末的氧含量、表面形貌、表面及内部微观组织、流动性和松装密度。结果表明:随着粉末粒度区间减小,PH13-8Mo钢粉末的比表面积从0.017 m^2/g显著增大到0.243 m^2/g,粉末中的O含量从0.017%增大到0.033%;当PH13-8Mo钢粉末粒径的范围为15~53μm区间时,粉末中的O含量相对较低,冷却速率较大,卫星球颗粒少,表面和内部组织主要由胞状晶和微晶组成,且该粒度范围的PH13-8Mo钢粉末的松装密度和流动性指数高。     

Preparation and characterization of Ni nanopowders prepared by anodic arc plasma

Ni nanopowders were successfully prepared in large quantities by anodic arc discharged plasma method with homemade experimental apparatus in inert gas. The particle size, microstructure and morphology of the particles were characterized via X-ray diffractometry (XRD), transmission electron microscopy (TEM) and the corresponding selected area electron diffractometry(SAED). The specific surface area and pore parameters were investigated by nitrogen sorption isotherms at 77 K with Brunauer-Emmett-Teller(BET) equation and Barrett-Joyner-Halenda (BJH) method. The chemical compositions were determined by X-ray energy dispersive spectrometry(XEDS) and element analysis. The experimental results indicate that this method is convenient and effective, and the nanopowders with uniform size, higher purity, weakly agglomerated and spherical chain shape are gotten. The crystal structure of the samples is FCC structure as the bulk materials, the particle size distribution ranges from 20 to 70 nm, and the average particle size is about 46 nm obtained by TEM and confirmed by XRD and BET results. The specific surface area is 14.23 m^2/g, specific pore volume is 0.09 cm^3/g and average pore diameter is 23 nm.     

阳极弧等离子体制备镍纳米粉的性能表征

采用阳极弧放电等离子体方法成功制备了高纯镍纳米粉末;利用X射线衍射（XRD）、透射电子显微镜（TEM）和选区电子衍射（SAED）、BET吸附法测试手段对试样的成分、形貌、晶体结构、比表面积、粒度及其分布进行性能表征,并采用元素分析仪测定C,H,N含量,采用X射线能量色散分析谱仪（EDS）测定试样所含的元素及其相对含量,用红外吸收光谱（FT-1R）对结构组成进行定性分析.实验结果表明：本法所制备的镍纳米粉末的晶体结构与相应的块体材料基本相同,为fcc结构的晶态,平均粒径为47 nm,粒度范围分布在20 nm～70 nm,呈规则的球形链状分布,比表面积为14.23 m2/g,试样纯度高且具有很强吸附性.     

Shape memory TiNi powders produced by plasma rotating electrode process for additive manufacturing

This study aimed to produce spherical TiNi powders suitable for additive manufacturing by plasma rotating electrode process (PREP). Scanning electron microscopy, X-ray diffractometry and differential scanning calorimetry were used to investigate the surface and inner micro-morphology, phase constituent and martensitic transformation temperature of the surface and inner of the atomized TiNi powders with different particle sizes. The results show that the powder surface becomes smoother and the grain becomes finer gradually with decreasing particle size. All the powders exhibit a main B2-TiNi phase, while large powders with the particle size ≥178 μm contain additional minor Ti₂Ni and Ni₃Ti secondary phases. These secondary phases are a result of the eutectoid decomposition during cooling. Particles with different particle sizes have experienced different cooling rates during atomization. Various cooling rates cause different martensitic transformation temperatures and routes of the TiNi powders; in particular, the transformation temperature decreases with decreasing particle size.     

Internal Mechanism Analysis of Modeling on Particles Size Distribution Characteristics of Impact Attrition Beryllium Powders

基于铍(Be)冲击制粉颗粒的形貌特征,建立了一个描述Be粉颗粒尺寸分布的物理模型,该模型仅含一个物理意义明确的参数。模型中考虑了2种重要的内在影响机制:具有不同初始动能的颗粒在完成冲击后的存在状态应该遵从Maxwell-Boltzmann分布,即大颗粒具有高的能量,状态不稳定,在冲击过程中容易碎成小颗粒,这一影响可以用颗粒尺寸的负指数函数来描述;获得低表面能的倾向又使得颗粒尽可能具有大的体积,这一影响可以用颗粒尺寸的立方函数来描述。实际的颗粒尺寸分布是这2种影响竞争的结果。计算结果与实验数据符合得很好。     

Surface properties of modified nanosized silica and their influence on human serum albumin immobilization

Silica powders with different surface functional groups were synthesized using the sol-gel method. The introduction of functional groups on the surface of silica was confirmed by IR spectroscopy. Surface physical parameters of silica particles (specific surface area, pore size, pore shape and volume) were obtained using BET. We have studied the adsorption capacity of human serum albumin on synthesized powders. Using atomic-force microscopy, we determined the size of silica particles with adsorbed protein. The influence of silica particle surface properties on the amount of adsorbed protein is speculated.     

不同粒径Ti粉的高速压制行为和烧结性能

以平均粒径为150,75,48和38μm的4种Ti粉为原料(依次定义为A,B,C和D粉末),采用高速压制技术进行成形,考察粉末粒径对压坯密度、最大压制力和脱模力的影响,进一步研究粉末的高速压制特性和压坯的烧结性能.结果表明,高速压制的压坯密度与粉末粒径和松装密度有关.冲击能量较小时,压坯密度主要取决于松装密度,而冲击能量较高时,则主要取决于粉末粒径.在冲击能量≤761 J下成形时,具有最大松装密度的B粉末所获得的压坯密度最高;进一步增大冲击能量,平均粒径最大的A粉末所获得的压坯密度最高.粉末粒径对压坯密度和最大压制力具有相似的影响,并且4种粉末的最大压制力和压坯密度之间的关系均符合黄培云压制方程;但粉末粒径对脱模力无明显影响.试样的烧结密度随粒径的细化而增加,同时伴随着不同程度的晶粒长大.4种压坯经1250℃真空烧结后,最终均获得了近全致密的试样.