超细Al（OH）3的粒度控制研究

采用铝酸钠种子分解法制备超细Al（OH）3.用X射线衍射仪（XRD）表征了样品的晶相组成,用扫描电子显微镜（SEM）观察了样品的形貌,用激光粒度分析仪测定样品的粒度分布.研究了NaOH浓度、NaOH/Al（OH）3摩尔比,分解温度,分解时间、晶种率和搅拌速率等因素对Al（OH）3的粒度的影响.结果表明：NaOH浓度越高,分解温度越低,NaOH/Al（OH）3摩尔比越小,得到的Al（OH）3颗粒的粒度越小.试验条件为：NaOH浓度180 g/L,NaOH/Al（OH）3摩尔比1.15,分解温度40℃,分解时间26 h,晶种率8％,搅拌速率200 rpm时,氢氧化铝颗粒的平均粒度为2.89 μm.     

Influence of Atomizing Gases on the Oxide-Film Morphology and Thickness of Aluminum Powders

Fine powders of aluminum were produced in a pilot-plant, inert-gas atomizerwith a confined-design nozzle, which operated vertically upward. Argonand helium at 1.85 MPa and nitrogen at 1.56 MPa were used as the atomizingagent. The morphology of the powder particles was examined by SEM. Powderswere sieved dry and wet. The Sauter mean diameter of the powders varied from20.70 to 10.25 m depending on the atomizing gas. The distribution ofsizes was bimodal. The mean thickness of oxide on the surface of the powderwas calculated from the total oxygen contents of powder samples (determinedby a Leco analyzer). In addition, ESCA measurements and BET tests werecarried out for surface-oxide thickness and area measurements,respectively. The finest powder produced under helium incorporated thinnersurface-oxide layers than the coarser ones produced under argon andnitrogen. This was due to differences in physical properties (such asdensity, thermal conductivity) and flow properties (such as gasvelocity and relative velocity) of the atomizing gases used, i.e., helium,argon, and nitrogen. The oxide was very irregular in thickness in thecoarse-size range of the Al powders produced under argon and nitrogen. Thiswas presumably because of the high- and low-temperature oxidation ofaluminum droplets during the atomization and subsequent solidification andcooling periods leading to the rough surfaces observed with SEMinvestigation in the present work.     

用计算机图形处理软件定量分析SEM图像

用图形处理软件PHOTOSHOP对SEM图像进行图像定量分析，对高温合金K23σ析出相的体积分数和M8钢样的夹杂物颗粒尺寸进行了定量测定。结果表明，该方法操作方便，有一定的可行性。     

Development of design principles for a creep-limited alloy for turbine blades

Recent advancements in turbine-blade materials engineering are reviewed in light of general superalloy research and the author’s work on a new powder metallurgy IN-792 creep-limited alloy for application in blades of gas-turbine engines. The developed set of principles presented in this paper incorporates all the factors that must be taken into consideration in selecting and designing an alloy for turbine blades.     

湿法冶金制备的Ag—Pd合金粉末的固溶合金化研究

根据Ｘ射线衍射原理，建立湿法冶金固溶合金粉末的定量测定方法，可用于电子浆料合金粉末的检测，相对误差在±０．０１２５。     

Research on graphite powders used for HTR-PM fuel elements

Different batches of natural graphite powders and electrographite powders were characterized by impurity, degree of graphitization, particle size distribution, specific surface area, and shape characteristics. The graphite balls consist of proper mix-ratio of natural graphite, electrographite and phenolic resin were manufactured and characterized by thermal conductivity, anisotropy of thermal expansion, crush strength, and drop strength. Results show that some types of graphite powders possess very high purity, degree of graphitization, and sound size distribution and apparent density, which can serve for matrix graphite of HTR-PM. The graphite balls manufactured with reasonable mix-ratio of graphite powders and process method show very good properties. It is indicated that the properties of graphite balls can meet the design criterion of HTR-PM. We can provide a powerful candidate material for the future manufacture of HTR-PM fuel elements.     

铜金粉的颜色及其影响因素

利用分光光度计对国内外铜金粉的颜色进行了测试，研究了铜金粉的成分、微观状态对颜色的影响。结果表明：铜金粉颜色可以用色彩三要素进行描述，其中铜金粉的色相只与合金成分有关，而与铜金粉片的大小、形状及粒度分布无关；明度和纯度与铜金粉片在油墨层中定向排列状态、片的大小、形状及粒度分布有关，而与成分无关；合金成分的微小波动不会引起铜金粉色相的明显改变。     

Mechanical activation-assisted electro-thermal explosion synthesis of the Ti2AlC phase

This study deals with the synthesis of the Ti₂AlC phase using the Electro-Thermal Explosion under Pressure with Confinement (ETEPC) technique. The effects of the ETEPC technique and the milling process parameters on the TiC_x phase content and the formation mechanism of the Ti₂AlC phase were investigated. The latter is mainly affected by the morphology of the powder mixture and aluminum melted amount. The optimization of the above parameters allowed the achievement of the desired reaction, leading to the formation of the Ti₂AlC phase with a purity of about 97?wt%. The results clearly demonstrate that the ETEPC process enables one to control both time and material synthesis temperature.     

Pore segmentation of cement-based materials from backscattered electron images

A technique to segment pores from a normal backscattered electron (BSE) image of cement-based materials is presented. The upper threshold grey level for porosity is determined from the inflection point of the cumulative brightness histogram of the BSE image. This represents a critical point where a small incremental grey value will cause a sudden increase in thresholded area, a condition termed as overflow. The proposed technique was found to be more consistent and reliable than existing methods. Significantly fewer images are required to achieve a satisfactory level of statistical confidence for quantifying porosity.