壳聚糖分子对共沉淀法合成羟基磷灰石/壳聚糖粉体材料晶体形貌的影响

采用沸腾水浴共沉淀法,以尿素为pH调节剂制备羟基磷灰石/壳聚糖(HA/CS)复合粉体材料,通过XRD、FTIR和SEM对晶体组成、形貌进行表征,考察了壳聚糖平均分子量、添加量及反应物浓度对HA/CS晶体形貌的影响.结果表明,沸腾水浴共沉淀法可在较短时间内制备HA/CS复合粉体,改变反应物浓度可使晶体形貌由针状与球状同时存在转变为几乎全部是球状晶体,而CS平均分子量和添加量的影响较小.     

微波诱导燃烧法合成MgO-Y2O3纳米粉体

以硝酸钇、硝酸镁、乙酸镁为原料,采用微波诱导燃烧法合成了体积比50:50的MgO-Y2O3纳米粉体,并研究了粉体的烧结性能.采用DSC-TGA、XRD、SEM、BET、IR等手段对粉体进行了分析表征.研究表明,在500 W微波功率下合成的粉体,经过600℃煅烧2h,结晶性良好,呈现均匀球状,粒度尺寸在30 ～50nm之间,比表面积为35.6m2/g.粉体经过200 MPa压力下等静压成型后,在1300℃温度下保温2h,样品相对密度可达95;.     

超细磁性钴粉的制备及磁性能

在室温条件下,水溶液中以聚乙烯吡咯烷酮K30(PVP)作为分散剂,水合联氨为还原剂,制备超细磁性钴粉。用扫描电子显微镜(SEM)、X射线衍射仪(XRD)、能谱仪(EDS)和振动样品磁强计(VSM)对其进行表征。结果显示:超细磁性钴粉为蠕虫状微球,粒径约为0.8μm,晶型为面心立方(FCC)和六方密堆积(HCP)结构,饱和磁化强度为25.6 emu·g~(-1),矫顽力为499.2 Oe(1 Oe=79.577 5 A·m~(-1),测试温度为298.15 K)。     

Radiation effects in high-disperse metal media and their application in powder metallurgy

Experimental and theoretical results showing up effects of metal powder radiation processing, such as powder grinding, chemical refinement, and changes in powder particle surface state, are discussed. It is shown that preliminary irradiation of metal powders leads to profound structural alterations at all further stages of their processing by conventional methods of powder metallurgy and eventually effects the properties of the resulting product.     

煅烧制度对Lu2Ti2O7粉体生长形貌的影响

采用熔盐法制备Lu2Ti2O7粉体,研究了不同煅烧工艺对粉体形貌的影响,确定了适用于Lu2Ti2O7粉体合成的工艺条件,并在利用XRD、SEM等方法分析表征样品的基础上,提出了初步的粉体形貌生长转变机制。实验结果表明:形核速率和生长速率对粉体的颗粒尺寸和形状影响很大,过快的形核速率和生长速率有利于多面棱柱状晶粒的生长,反之则有利于八面体形状的晶粒生长。     

Ultrasound-assisted microfeeding of fine powders

Ultrasonic microfeeding of powders is a new and promising method for use in solid freeforming and pharmaceutical dosing. In this work, computer-controlled microfeeding systems using ultrasonic vibration of a capillary were built. A wide range of controlled, stable rates of flow and switching control were achieved in the acoustic vibration system and uniform powder doses were obtained in the ultrasonic system. Experimental results show that nozzle diameter, transmission fluid depth, waveform, voltage amplitude, frequency and oscillation duration all influence the dose mass. Among these factors, nozzle diameter, voltage amplitude and oscillation duration can be best used to control the dose mass. An artificial neural network （ANN） technique was applied to predict the dose mass. Based on these research results, four types of microfeeding were proposed.     

燃烧剂对燃烧法合成CeO_2纳米粉体的影响

通过燃料-硝酸盐低温燃烧法合成了纳米二氧化铈粉体.考察了新型燃烧剂甘油和甘露醇对二氧化铈纳米粉体的影响,通过TG-DTA对凝胶的分解特性进行了分析,并利用XRD、氮气吸脱附和SEM对粉体的性能进行了表征.结果表明:使用甘露醇制备的CeO2晶粒较小(10.1 nm),比表面积较大(87.1 m2·g-1).     

过氧化合物法PLZT纳米粉体的制备和表征

掺镧的锆钛酸铅固溶体（Pb1-x,Lax）(Zry,Ti-y)1-x/4O3（简称PLZT）是一种有重要用途、性能优良的电光陶瓷材料[1]。为避免局部组成变化引起散射和保证良好的电光性能,材料的组成和均匀性非常重要。用传统的固相法制备PLZT粉体耗能大,生成的粉体颗粒大,组成均匀性差,不能满足现代高科技应用的要求。近年来研究的溶胶．凝胶[2]、柠檬酸法[3]、EDTA凝胶法[4]等湿化学法有许多优点,受到人们的关注,但这些方法需用较贵原料。而在众多的湿化学法中,以共沉淀法最为经济,并且它比传统的固相法好,能够制得均匀性好的纳米粉体。但该…     

On appearance of “cold” layer in explosive consolidation of powders

Abstract. Numerical modeling of explosive consolidation of powders under two-dimensional conditions has been performed. Various regimes of flow depending on detonation velocity have been considered. The appearance of “cold” layer during explosive consolidation of powders has been studied by calculations. Received 12 July 1999 / Accepted 27 April 2000     

多金属氧酸盐纳米粉体室温固相合成、表征及催化性能

多金属氧酸盐纳米粉体室温固相合成、表征及催化性能;多金属氧酸盐;纳米粉体;固相合成;催化性能