Optimal Conditions for Preparing Ultra-Fine CeO_2 Powders in A Submerged Circulative Impinging Stream Reactor

Cerium carbonate powders were produced in a submerged circulation impinging stream reactor （SCISR） from Ce（NO3）3· 6H2O. NH4HCO3 was used as a precipitant in the reaction. Cerium carbonate powders were roasted to produce ultra-fine cerium dioxide （CeO2） powders. The optimal conditions of such production process were obtained by orthogonal and one-factor experiments. The results showed that ultra-fine and narrowly distributed cerium carbonate powders were produced under the optimal flowing conditions. The concentrations of Ce（NO3）3 and NH4HCO3 solutions were 02,5 and 0.3 mol · L^-1, respectively. The concentration of PEG4000 added in these two solutions was 4 g · L^-1. The stirring ratio, reaction temperature, feeding time, solution pH, reaction time and digestion time were 900 r · min^- 1,80 ℃, 20 min, 5 - 6, 5 min and 1 h, respectively. The final product, CeO2 powders, was obtained by roasting the produced cerium carbonate in air for 3 h at 500 ℃. The finally produced CeO2 powders were torispherical particles with a narrow size distribution of 0.8 -2.5 μm. The crystal structure of CeO2 powders belonged to cubic crystal system and its space point 5 group was OH^5-FM3M. Under optimal conditions, powders produced by SCISR were finer and more narrowly distributed than that by Stirred Tank Reactor （STR）.

DYNAMIC RHEOLOGICAL BEHAVIOR OF POLYPROPYLENE FILLED WITH ULTRA-FINE POWDERED RUBBER PARTICLES

Dynamic rheological characteristics of polypropylene (PP) filled with ultra-fine full-vulcanized powdered rubber (UFPR) composed of styrene-butadiene copolymer were studied through dynamic rheological measurements on an Advanced Rheometric Expansion System (ARES). A specific viscoelastic phenomenon, i.e. 'the second plateau', appeared at low frequencies, and exhibits a certain dependence on the amount of rubber particles and the dispersion state in the matrix. This phenomenon is attributed to the formation of aggregation structure of rubber particles. The analyses of Cole-Cole diagrams of the dynamic viscoelastic functions suggest that the heterogeneity of the composites is enhanced on increasing both particle content and temperature.

Hydrogen Reduction:A Novel Method of Synthesizing Ultra-fine Chromic Oxide Powder

The ultra-fine chromic oxide powder was prepared by a novel gas-solid reduction reaction.Na2CrO4 was firstly reduced with hydrogen at 400-600 ℃.The obtained reduction products,mainly the mixture of NaCrO2 and sodium hydroxide（NaOH）,were converted into chromic oxide through hydrolysis followed by calcination.The obtained chromic oxide product was characterized by powder X-ray diffraction（XRD） and SEM.The results show that the hydrolysis process of sodium chromite is the key step and lower reduction temperature helps intensify the hydrolysis process.

Strengthening of HT250 by modified ultra-fine ceramic powders

In this study, three kinds of modified ultra-fine ceramic powders marked A, B and C, which were prepared by each of three different modifiers mixing with a commercial SiC, were added to HT250 cast iron, respectively, and the effects of the modified ultra-fine ceramic powders on microstructure, mechanical properties and wear resistance were studied. Metallographic examination, tensile test, scanning electron microscopy, and three-dimensional surface topography were applied to analyze and compare the samples containing modified powder with the original samples. The results showed that the most obvious modification effect among the powders was seen in the sample containing powder A, with the graphite and eutectic cells being refined, the tensile strength being increased by 36.9%, and the wear resistance being improved by 45.5% and 47.2% under loads of 150 N and 300 N, respectively. The improvements of mechanical properties and wear resistance in the HT250 cast iron with the modified ultra-fine ceramic powders were attributed to the synergistic effect of the grain refinement with the powder acting as a hard particle phase and the lubrication by the graphite.

CALCULATION AND EXPERIMENTAL INVESTIGATION OF ELECTRIC FIELDS INDUCED BY ELECTRODES IN ELECTROSTATIC CHARGED POWDER SPRAYING TECHNIQUE

Electric fields induced by ring and pin electrodes in electrostatic charged powder sprayingtechnique are analysed. The fundamental formulae to deseribe these fields have been built up. Theseformulae could be used to design electrostatic charged podwer spraying system. The chargingeffectiveness of ring and pin electrode is experimentally investigated and compared each other. Theperformance of ring electrode is better than that of pin electrode.

Preparation of Well Dispersed and Ultra-Fine Ce(Zr)O_2 Mixed Oxide by Mechanochemical Processing

Ultra-fine CeO_2-ZrO_2 mixed oxide was successfully synthesized by wet-solid phase mechanochemical processing, Ce_2(CO_3)_3·8H_2O, ZrOCl_2·xH_2O and ammonia were used as reactants. It is found that the crystalline Ce_2(CO_3)_3·8H_2O and ZrOCl_2·xH_2O are changed to amorphous cerium and zirconium hydroxide precursor after milling with ammonia, and Ce_(0.15)Zr_(0.85)O_2 mixed oxide with pure tetragonal phase structure and medium particle size(D_(50))less than 1μm is formed by calcining precursor over 673 K. The XRD patterns indicate that the crystal unite size increases with rising calcining temperature due to crystal growth. However, the particle size and BET surface area of the Ce(Zr)O_2 mixed oxide decreases with rising calcining temperature, which may be attributed to the contract of particles and the vanish of holes inside grains.

A Novel near Net-Shape Technique for P/M Parts with Large H/D Ratio

In order to overcome the shortcomings of conventional hot pressing, a novel near net-shape technique, called radial hot pressing, for P/M parts with large height-to-diameter (H/D) ratio was introduced. Effects of processing parameters on the microstructures and density of P/M TiAl base alloy valves were studied. Results show that the radial hot pressing is an effective technique for manufacturing valves with a H/D ratio of about 10:1, and the perfect joint interface between the Mo sheet and the parts is helpful for subsequent HIPing.

逍遥散方质量控制技术研究进展

逍遥散方为治疗妇科诸疾、郁证的代表方,由柴胡、当归、茯苓、白芍、白术、甘草、生姜、薄荷8味饮片组成,具有疏肝解郁、养血健脾的功效。文章就近10年来逍遥散方在制备工艺、鉴别技术、含有量测定等方面出现的新方法、新技术进行归纳总结,以期为该方制剂的质量控制及进一步开发应用提供科学依据。

蒙药三子散多指标成分的含量测定

目的基于多指标成分含量测定结合灰色关联度分析(GRA)和逼近理想解排序法(TOPSIS)对蒙药三子散进行整体质量评价。方法采用高效液相色谱(HPLC)法测定15批三子散样品中诃子次酸、没食子酸、石榴皮鞣素、安石榴苷、jasminoside B、咖啡酸、柯里拉京、京尼平苷、诃子鞣酸、1,2,3,4,6-O-没食子酰葡萄糖、诃子林鞣酸、鞣花酸的含量,并对12种活性成分含量建立GRA和TOPSIS质量评价模型。结果12种指标成分在各自质量浓度范围内与峰面积呈良好的线性关系,r均不小于0.9995,平均回收率为96.72%~104.07%,RSD为1.4%~2.6%。GRA和TOPSIS分析结果基本一致,根据TOPSIS分析所得Ci值和GRA分析所得ri值可知,样品S1、S3、S4、S6、S10、S12、S14、S15排名前8。结论GRA-TOPSIS法排除了人为因素的干扰,提高了多指标决策分析的科学性与准确性,精确地反映了各评价方案之间的差距,可对三子散进行整体质量评价及优质资源筛选。

固体分散体制备技术及质量控制研究进展

【目的】从固体分散体(solid dispersions,SDs)制备技术和质量控制角度出发,揭示SDs技术在药物制剂领域的发展现状与挑战,旨在为SDs技术的进一步推广应用提供参考。【研究现状】总结熔融法、溶剂法、溶剂-熔融法、机械分散法等SDs制备技术,其中熔融法又包括传统熔融法、热熔挤出法、熔融凝聚、KinetiSol~?Dispersing、3D打印技术等,溶剂法又包括喷雾干燥、冷冻干燥、流化床干燥、超临界流体法、共沉淀法和静电纺丝法等;目前SDs制备技术存在需要使用有毒溶剂,可能导致药物热降解以及扩展性较差的问题。并归纳总结溶出度、药物和聚合物之间的相互作用、固态等SDs质量控制因素,重点强调一直被研究人员忽视的SDs粉体学性质。【展望】认为今后的研究重点应在开发或引入更多高效、无毒、稳定和扩展性好的SDs制备技术方面,并且要不断完善SDs的质量控制体系。

Preparation of Reactive Powder Concrete Using Fly Ash and Steel Slag Powder

To decrease the cement and SF content of RPC by using ultra-fine fly ash （UFFA） and steel slag powder （SS）, the effect of these mineral admixtures on compressive strength of RPC were investigated. The experimental results indicate that the utilization of UFFA and SS in RPC is feasible and has prominent mechanical performance. The microstructure analysis （SEM and TG-DTG-DSC） demonstrated that the excellent mechanical properties of RPC containing SS and UFFA were mainly attributed to the sequential hydration filling effect of the compound system.

Synthesis and Characterization of Nano-sized Boron Powder Prepared by Plasma Torch

Hydrogen thermal plasma jet was employed to prepare nano-sized boron powder with hydrogen reduction of BCI3. The maximum yield of nano-sized boron powders was about 50% with the operational conditions of H2/BCl3 of 4.5：1, total feed of 4.9 m3/h, and plasma power of 25 kW. The samples were analyzed by X-ray diffraction （XRD）, field emission scanning electron microscopy （FE-SEM）, and inductively coupled plasma - mass spectrometry （ICP-MS）, inductively coupled plasma - atomic emission spectrometry （ICP-AES）, inductive combustion infrared absorption （ICIA） and infrared thermal conductivity of oxygen and nitrogen analyzer （ITCA）. The results show that the boron powders have different crystal structures with higher dispersion and purity. The average diameter is about 50 nm, and the purity is 90.29% or so. This new technology can use simple process to produce high quality boron powders, and is feasible for industrial production.

Indium tin oxide nanosized composite powder prepared using waste ITO target

Indium tin oxide （ITO） nano-particles were prepared directly using waste ITO target, which had been coated by magnetron controlled sputtering. The waste ITO target was cleaned with de-ionized water, and then dissolved in acid, filtrated, neutralized, manipulated through azeotropic distillation and finally dried, and in this way the precursor of indium tin hydroxide was obtained. The nanosized rio composite powder was prepared after the precursor heat-treated at 500℃ for 2 h. TEM images show a narrow distribution of particle size is 5-20 nm and the particle size can be controlled. Its granule has a spherical shape and the dispersion of the particle is well. X-ray diffraction （XRD） patterns indicate the only cubic In2O3 phase in the ITO powder hot-treated at 500℃. The purity of ITO composite powder is 99.9907%. The content of radium within filtrate was detected by using the EDTA titration of determination of indium in the ITO powder and ITO target. Appropriate amount of SnCl4.5H2O was dissolved in the filtrate, and then ITO powder containing 10 wt.% SnO2 was successfully prepared by heat-treating.

Preparation of Ultrafine Tungsten Powder by Sol-Gel Method

Sol-gel method was employed for the preparation of nanoscale tungsten powder. The effects of different preparation conditions on particle size were discussed and the optimum preparation condition was found. The products were characterized by X-ray diffraction, scan electron microscopy and so on. The results show that the intermediate is monoclinic WO3, its particle shape is approximately spherical, and the particle size distribution is narrow. The average particle size is about 60 nm. After deoxidization, WO3 turns into cubic tungsten powder with small particle size （average particle size about 120 nm） and narrow size distribution.

Positron Annihilation Study on TiC Powders

By means of the positron annihilation technique (PAT), superfine TiC powders obtained by ball-milling process were characterized. The results showed that there was a clear correlation between the change in TiC powders and that in the PAT parameters. In the high energy ball-milling process, TiC powders were severely deformed, which caused large increase in the amount of defects and severe distortion of lattice. On the other hand, the extreme refinement of grain size of powders resulted in the increase of grain boundary area and enhancement of system free energy. The spacing between deformed domains in 96 h milled samples is somewhat smaller than those in 48 h milled samples, indicating the size of Type II defects in 96 h milled samples is somewhat smaller than that in 48 h milled samples.

Crystal Structure of Ba_xSr_1-xTiO₃Fine Powder

Various compositions of the system BaxSr1-xTiO3 (BST) have been elaborated both as fine powders and ceramic monoliths, using the co-precipitation route within a warmed supersaturated solution of oxalic acid. The appropriate stoichiometry was determined from the mixtures of precisely titrated aqueous solutions of cations chlorides (SrCl2, BaCl2, and TiCl4). The reason of this process was to apply low sintering temperature in production of BST samples with ultra-fine powders. These powders primarily calcined at (850°C) for (5 hr) were used to elaborate ceramics after pellets sintering at (1200°C) during (8 hrs). Indeed, XRD patterns were confirmed that the samples are a pure phase and a perovskite cubic structural type at (x = 0, 0.5, 0.6). Whereas, (x = 0.7, 0.8, 0.9, 1) showed a tetragonal phase. There is agreement between the FTIR and XRD analysis, by the relation of the wave vector (K) and lattice constant. It was deduced a stimulated relation between (x) and (K). The results of TEM, they were clear that the lowest particle sizes investigated of BST powders nearly (36 - 50 nm).

铝基可磨耗封严涂层制备及性能评价研究进展

随着航空航天技术的发展,人们对发动机效率的要求越来越高。减小涡轮机叶片尖端与机匣之间的缝隙,有利于发动机效率的提升。叶片尖端与发动机涡轮机机匣之间喷涂可磨耗封严涂层,不仅可封严气路、提高发动机效率,又可以减少对叶片的磨损以保护叶片。对于可磨耗封严涂层而言,可磨耗性是其最重要、最本质的特性。综述了国内外铝基封严涂层的粉末制备、喷涂及可磨耗性能评价的研究现状,分析了粉体形式、喷涂参数对涂层组织的影响,以及涂层表面洛氏硬度、叶尖的进给速率/单道进给量、摩擦线速度等对涂层的可磨耗性能的影响,同时还对海洋环境下铝基封严涂层的腐蚀机理进行研究,指出了机器学习、仿真技术在可磨耗涂层性能预测及性能表征等方面的作用。最后,总结了近年来铝基可磨耗封严涂层的研究进展,并对未来的研究方向进行了展望。

水泥粉喷桩在软土路基加固中的质量控制措施分析

在经济的牵引下,路桥项目增多,项目建设期间,一旦遭遇软土地基,就会变得相对棘手。而目前软基处理中,最可靠和广泛的应用技术就是水泥粉喷桩加固(简称粉喷桩),通过研究发现,该技术原理简单,主要作用机理是凭借化学反应科学得到施工后的沉降,借助这种附加力量,形成地基。该地基属于复合地基,功效较强,可承载上部主体荷载。正是因为水泥粉喷桩有这样的特殊性,在软土路基加固中经常被运用,而且效果理想。但水泥粉喷桩施工注意事项多,想要达到理想效果,还需质量控制措施加以支撑,提高路面的稳定性,保障优质路面施工。

铣削工艺参数对镍基粉末高温合金650℃低周疲劳寿命的影响

研究了不同铣削工艺对疲劳损伤的影响规律。对采用4种工艺加工的试样进行了650℃高温空气环境下的低周疲劳试验。分别采用粗糙度表征方法、背向散射电子衍射技术和纳米压痕测试以获得试样的表面粗糙度、残余应力和加工硬化。测试结果表明,采用电火花线切割方法加工的试样疲劳寿命最高(平均80360循环),有最低的表面粗糙度(0.226)和残余应力;而钝刀具加工的试样疲劳寿命最低(平均43978循环),相较于电火花线切割试样的疲劳寿命下降了45%。扫描电镜表征结果表明,疲劳裂纹主要由粗大的非再结晶晶粒和加工缺陷引发。铣削加工方法和参数对疲劳损伤程度和疲劳寿命有重要影响。

Preparation and properties of Nd:YAG ultra-fine powders

Ultra-fine Nd：YAG powders with different doping concentrations were synthesized by sol-gel combustion method. The pure Nd：YAG could be prepared at the low temperature of 900℃. Ethanol could improve the dispersity of powders, and the average size of the ultra-fine powders was around 250 nm. The reflection spectrum showed that there were several apparent characteristic absorption peaks and the intensity of these peaks enhanced with the increasing concentration of Nd^3＋. The luminescence spectrum, which was excited by 808 nm wavelength, exhibited several obvious emission bands in the range of 900-1150 nm. The emission intensity of Nd：YAG powders increased until the Nd content was above 3 mol.% due to the fluorescent quenching effect.