Comparison between the Requirements of Flowability and Moldability and the Shape Retention of PIM Compacts during Debinding Process

To successfully employ powder injection molding (PIM) as a manufacturing technique, the function of the component, design of the part, material and process should be optimized for overall processing ability of the PIM process. A comparison between the requirements of flowability and moldability and the compacts shape retention has been made in this work. There is often a contradiction between the requirements of flowability and the compacts shape retention. Many works have been done to attain good molding conditions. However, they fail to take into account the effect of some factors that satisfies good molding conditions on the compacts shape retention during debinding. This paper studies the effect of the powder-binder mixture characteristics and the molding conditions on the flowability and moldability and the shape retention of PIM compacts during debinding process so as to attain the benefits of each.     

大尺寸ZrO2注射成型坯体热脱脂缺陷成因探究

采用蜡基ZrO2粉末喂料注射成型获得大尺寸ZrO2陶瓷粉末注射产品（坯体）,并根据喂料热分析曲线的变化特点,系统研究了大尺寸ZrO2坯体的热脱脂过程及规律。通过对热脱脂前后坯体的重量损失、尺寸收缩、外观缺陷和微观组织形貌的分析评估,着重探讨了大尺寸ZrO2坯体热脱脂过程中存在的主要缺陷和成因。研究表明,流蜡、鼓泡和开裂等热脱脂缺陷主要发生在低温脱脂阶段,其主要原因是液态石蜡扩散及分解过程的失衡。为此,结合“失重率控制”的思路和喂料的热失重规律,对热脱脂工艺进行了优化,在不延长总脱脂时间的前提下,显著提高了大尺寸ZrO2坯体的脱脂合格率。     

Influence of the Compacts Homogeneity on the Incidence of Cracks during Thermal Debinding in Ceramic Injection Molding

During thermal debinding in ceramic injection molding, the inhomogeneity of green body is a key origin of cracks. In this study, the impact of low molecular weight binders on the homogeneity of the green body was investigated. Incidence of cracks during thermal debinding indicated that the volume ratio of wax to stearic acid should be out of high viscosity and incompletely wetting region. In these two formulation regions,typical inhomogeneous microstructures were observed. By mercury intrusion method, it was shown that pore size distribution of the debinded compacts was determined by thermal degradation of low molecular weight binders. A particle-rich region model was established to predict the nucleation of cracks caused by solid loading fluctuation. The criterion of cracks nucleation was that local capillary force from solid loading fluctuation was larger than the suction force from the surroundings.     

粉末注射成形溶剂脱脂研究进展

简述了粉末注射成形溶剂脱脂的基本过程,介绍了目前使用的一些溶剂脱脂方法及其研究进展,讨论了粉末注射成形溶剂脱脂工艺的发展趋势.     

溶剂脱脂型MIM粘结剂的研究

对溶剂脱脂的原理及其影响因素进行了阐述，介绍了溶剂脱脂型粘结剂的研究发展情况。认为水溶性粘结剂是一类环境友好的粘结剂，具有良好的应用前景，从分子量和溶度参数两个影响因素出发，简述了溶剂脱脂型粘结剂的设计方法。     

粉末近净成形溶剂脱脂技术

溶剂脱脂技术在粉末注射成形和粉末挤压成形工业生产中广泛应用。本文阐述了溶剂脱脂的基本过程,介绍了目前常见的一些溶剂脱脂方法及其研究进展,讨论了溶剂脱脂理论的研究现状,指出了当前溶剂脱脂技术发展要解决的主要问题。     

高岭土在真空下的热分解行为

以含高岭石、一水硬铝石、黄铁矿的高岭土为原料,经过压块烘干后,在真空(15~50 Pa)、不同加热温度下,采用同步热分析仪(DSC-TGA)、X射线衍射(XRD)等分析手段对高岭土在真空下的热分解进行研究。DSC-TGA的结果与高岭石、一水硬铝石、黄铁矿三种矿物常压下的热力学计算出的分解温度相符。实验产物的XRD结果表明:在真空条件(15~50 Pa)下,一水硬铝石AlO(OH)在100~200℃之间脱水,300℃时脱水完全;黄铁矿FeS2在500~600℃分解,分解产物为FeS和S2,在700℃时,黄铁矿FeS2分解完全;高岭石Al2Si2O5(OH)4在实验煅烧过程中,在200~300℃之间脱水,生成非晶态的偏高岭石,比该矿在常压的脱水温度提前200℃左右。继而转变成A-lSi尖晶石,最后形成莫来石与方石英。实验结果与热力学计算符合,充分说明真空条件对高岭土中各种矿物分解产生气体的反应有较大的促进作用。在本实验三种矿物分解产生气体的过程中,先进行的反应对后一反应的发生影响不明显。     

钛合金粉末注射成形热脱脂工艺的研究

采用粉末注射成形方法制备了钛合金坯体,然后利用溶剂脱脂方法脱除坯体中可溶性粘结剂.在热脱脂速率为2.0℃/min、最高脱脂温度600℃、保温时间为1h和真空脱脂气氛条件下脱除坯体中剩余粘结剂,坯体中残余碳氧含量分别0.092%(质量分数)和0.28%,低于国外报道的PIM钛合金脱脂坯中残余碳氧含量.XRD结果表明,脱脂坯中只存在α相,没有TiC,Ti3Al,TiO和TiN等杂质相存在.N2气氛下脱脂,脱脂坯中残余碳含量较低,但氧含量较高.     

Effects of Polymer Decomposition Behavior on Thermal Debinding Process in Metal Injection Molding

The thermal degradation mechanism of several polymers was studied for the metal injection molding (MIM) process. The depolymerization type polymers (polybutyl-methacrylate (PBMA) and polyacetal (POM)) had fast thermal degradation speed. On the other hand, the thermal degradation of the random type polymers (polypropylene (PP) and ethylene-vinyl acetate (EVA)) was influenced by the type of debinding atmosphere (air and nitrogen). In the thermal debinding process, it was clear that the thermal degradation speed of the feedstocks that contained more than 35.3 vol.% of depolymerization type polymers was faster than that of the feedstocks which contained more than 8.5 vol.% of random type polymers. For the feedstocks that contained more than 35.3 vol.% of POM and PBMA, the sintered test pieces had less than 30 ppm of carbon and the sintering relative density of the sintered parts was in the range of 95.5 to 96.5%. The debinding ratio of the test pieces decreased with an increase in the PP content. However, the thermal degradation gases of POM and PBMA (without any PP) caused some cracks and holes when a heating rate greater than 30°C hr^-1 was used to heat the specimen to the 270-300°C temperature range.     

硫硒化镉纳米棒的溶剂热法合成及其光致发光性能的研究

以溶剂热法合成了CdSxSe1-x（0〈x〈1）纳米棒,以XRD、TEM、HRTEM、SAED等方法对样品进行表征。该法制备的CdSxSe1-x（0〈x〈1）纳米棒半径为15—20nm,长为300—400nm,为六方纤锌矿结构。PL光谱结果表明,通过对三元化合物组分的调节可实现对CdSxSe1-x（0〈x〈1）纳米棒光致发光性能的调控。     

Design, Development, and Biopharmaceutical Properties of Buccoadhesive Compacts of Pentazocine

Buccoadhesive compacts (BCs) of pentazocine (PZ) were prepared by the direct compression method using polymers like carbopol 974P (CP 974P) and hydroxypropyl methylcellulose (HPMC K4M) in ratios of 1:0 (batch B₁), 1:1 (B₂), 1:2 (B₃), 1:4 (B₄), and 0:1 (B₅). The compacts were evaluated for thickness uniformity, weight variation, drug content uniformity, and swelling index. Swelling was increased with an increase in HMPC K4M content in the compacts. An in vitro assembly was developed to measure and compare the bioadhesive strength of compacts. The maximum bioadhesive strength was observed in compacts formulated with a combination of CP 974P and HPMC K4M. The compacts were evaluated in vitro for 24 hr in pH 6.6 phosphate buffer using a standardized dissolution apparatus. The data were evaluated by a simple power equation (M_t/M_∞ = Ktⁿ); it was observed that all the compacts followed non-Fickian release kinetics. Some of the buccoadhesive compacts were evaluated in vivo in rabbits. The compacts gave controlled blood level profiles with a twofold to threefold increase in area-under-the-curve (AUC) values in comparison to oral administration of aqueous drug solution.     

Design,Development, and Biopharmaceutical Properties of Buccoadhesive Compacts of Pentazocine

Buccoadhesive compacts (BCs) of pentazocine (PZ) were prepared by the direct compression method using polymers like carbopol 974P (CP 974P) and hydroxypropyl methylcellulose (HPMC K4M) in ratios of 1:0 (batch B₁), 1:1 (B₂), 1:2 (B₃), 1:4 (B₄), and 0:1 (B₅). The compacts were evaluated for thickness uniformity, weight variation, drug content uniformity, and swelling index. Swelling was increased with an increase in HMPC K4M content in the compacts. An in vitro assembly was developed to measure and compare the bioadhesive strength of compacts. The maximum bioadhesive strength was observed in compacts formulated with a combination of CP 974P and HPMC K4M. The compacts were evaluated in vitro for 24 hr in pH 6.6 phosphate buffer using a standardized dissolution apparatus. The data were evaluated by a simple power equation (M_t/M_∞ = Ktⁿ); it was observed that all the compacts followed non-Fickian release kinetics. Some of the buccoadhesive compacts were evaluated in vivo in rabbits. The compacts gave controlled blood level profiles with a twofold to threefold increase in area-under-the-curve (AUC) values in comparison to oral administration of aqueous drug solution.     

液体真空蒸发冻结过程的动力学研究

简要介绍了液体物料真空蒸发冻结过程中出现的暴沸、过冷、冻结等实验现象.针对溶液由液相表面蒸发为汽相、由冻干室向冷阱室流动迁移、在冷凝器上凝结的全过程,从质量与能量守恒原理、热力学原理和气体动力学原理出发,建立了完整的数学模型,并以纯水为例进行了模拟计算.同时利用专门组建的实验装置,对纯水的真空蒸发冻结过程开展了实验观测研究,得到整个过程的质量、温度、压力-时间曲线.通过对比理论模拟计算和实验测试的结果,说明了所建立的动力学模型的正确性.     

Analysis of Zinc 65 Contamination After Vacuum Thermal Process

Radioactive contamination with a gamma energy emission consistent with ⁶⁵Zn was detected in a glovebox following a vacuum thermal process. The contaminated components were removed from the glovebox and subjected to examination. Selected analytical techniques were used to determine the nature of the precursor material, i.e., oxide or metallic, the relative transferability of the deposit and its nature. The deposit was determined to be borne from natural zinc and was further determined to be deposited as a metallic material from vapor.     

真空热还原氧化镁的理论分析与实验研究

通过对C、Si和Al热还原MgO的热力学计算,分析了不同条件下热还原吉布斯自由能和反应初始温度的变化.计算结果表明:在常压下C、Si和Al还原MgO时,反应初始温度分别高达1900,2200和1600℃;通过添加CaO造渣和使用真空,不但能提高MgO的还原率,而且使标准自由能降低;在系统压力为10 Pa时,碳热还原所需的初始温度为1100℃,加入CaO造渣的硅热还原、铝热还原所需的初始温度分别为800和690℃.在采用焦炭真空热还原MgO的验证试验中,发现在1500℃下还原120min,MgO的还原率高达84.59％.     

Vacuum Insulation Panels – Exciting Thermal Properties and Most Challenging Applications

Vacuum insulation panels (VIPs) have a thermal resistance that is about a factor of 10 higher than that of equally thick conventional polystyrene boards. VIPs nowadays mostly consist of a load-bearing kernel of fumed silica. The kernel is evacuated to below 1 mbar and sealed in a high- barrier laminate, which consists of several layers of Al-coated polyethylene (PE) or polyethylene terephthalate (PET). The laminate is optimized for extremely low leakage rates for air and moisture and thus for a long service life, which is required especially for building applications. The evacuated kernel has a thermal conductivity of about 4 × 10⁻³ W · m⁻¹ · K⁻¹ at room temperature, which results mainly from solid thermal conduction along the tenuous silica backbone. A U-value of 0.2 W · m⁻² · K⁻¹ results from a thickness of 2 cm. Thus slim, yet highly insulating fa?ade constructions can be realized. As the kernel has nano-size pores, the gaseous thermal conductivity becomes noticeable only for pressures above 10 mbar. Only above 100 mbar the thermal conductivity doubles to about 8 × 10⁻³ W · m⁻¹ · K⁻¹, such a pressure could occur after several decades of usage in a middle European climate. These investigations revealed that the pressure increase is due to water vapor permeating the laminate itself, and to N₂ and O₂, which tend to penetrate the VIP via the sealed edges. An extremely important innovation is the integration of a thermo-sensor into the VIP to nondestructively measure the thermal performance in situ. A successful “self-trial” was the integration of about 100 hand-made VIPs into the new ZAE-building in Würzburg. Afterwards, several other buildings were super-insulated using VIPs within a large joint R&D project initiated and coordinated by ZAE Bayern and funded by the Bavarian Ministry of Economics in Munich. These VIPs were manufactured commercially and integrated into floorings, the gable fa?ade of an old building under protection, the roof and the facades of a terraced house as well as into an ultra-low-energy “passive house” and the slim balustrade of a hospital. The thermal reliability of these constructions was monitored using an infrared camera.Invited paper presented at the Seventh European Conference on Thermophysical Properties, September 5-8, 2005, Bratislava, Slovak Republic.     

NTC热敏电阻材料的制备、性能优化及相关机理的研究进展

总结了NTC热敏电阻材料的类型和常用的制备方法.综述了材料基体中主要元素和掺杂元素对材料性能的影响以及降低烧结温度的方法.最后介绍了NTC热敏材料的导电机理和发展前景.     

基于正则化稀疏滤波的轴承声信号故障诊断方法

基于声信号的故障诊断由于其所具有的非接触、易安装等优点开始逐渐在机械故障诊断领域中得到广泛应用,但声信号的信噪比低导致其诊断准确率较差,因此急需有效的智能方法以实现噪声背景下的信号特征提取。稀疏滤波算法是一种基于无监督学习的智能特征提取算法,它能够优化特征分布的稀疏性从而得到好的特征表达。为了实现轴承声信号的特征提取和故障诊断,采用稀疏滤波算法从声信号频谱中提取特征,通过对其目标函数添加L2 范数约束以减少过拟合现象,然后采用Softmax 回归函数作为分类器,实现对不同轴承故障类型的精准识别。最后通过一组特殊设计的轴承故障诊断实验验证了所提方法的有效性。     

Characterization of Failure Mechanisms of Duplex and Graded Thermal Barrier Coatings Exposed to Thermal Shock Test

The beginning of failure of a (ZrO2-7%Y2O3)/(Ni-22%Co-17%Cr-12.5%Al-0.6%Y) duplex andgraded coating systems on lnconel 617 and IN738LC in burner rig tests has been characterized.The test conditions are 40 s heating up to 75O℃ substrate temperature followed by 80 s aircooling. Failure is considered at the appearance of the first bright spot during heating period.Stresses due to thermal expansion mismatch strains on cooling are the probable cause of life-limiting in this conditions of testing.     

热真空试验设备控温热沉设计分析

为满足某型号航天产品的热真空试验要求,设计了专用的控温热沉,由热沉、加热器及配套的控温系统等组成。本文简述了某型号专用控温热沉的设计,并对该结构进行了仿真分析验证,分析结果表明,产品发热量为200W时,空间温度最高可高于+120℃,热沉本体低温可低于-180℃,具备温控条件。温控系统采用PID自适应调节,使用结果表明,能将空间温度度在(-180～+120)℃可控,控温精度可达±0.5℃,满足试验要求。