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.

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）.

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.

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.

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.

Microstructure and properties of liquid-phase sintered tungsten heavy alloys by using ultra-fine tungsten powders

The microstructure and properties of liquid-phase sintered 93W-4.9Ni-2.1Fe tungsten heavy alloys using ultra-fine tungsten powders (medium particle size of 700 nm) and original tungsten powders (medium particle size of 3 μm) were investigated respectively. Commercial tungsten powders (original tungsten powders) were mechanically milled in a high-energy attritor mill for 35 h. Ultra-fine tungsten powders and commercial Ni, Fe powders were consolidated into green compacts by using CIP method and liquid-phase sintering at 1 465 ℃ for 30 min in the dissociated ammonia atmosphere. Liquid-phase sintered tungsten heavy alloys using ultra-fine tungsten powders exhibit full densification (above 99% in relative density) and higher strength and elongation compared with conventional liquid-phase sintered alloys using original tungsten powders due to lower sintering temperature at 1 465 ℃ and short sintering time. The mechanical properties of sintered tungsten heavy alloy are found to be mainly dependent on the particles size of raw tungsten powders and liquid-phase sintering temperature.

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.

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).

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.

Preparation of Ultra-nano Talcum in Sand Mill and Its Application in the Polypropylene

The grinding of ultra-fine talcum powder and its application in a polypropylene （PP） matrix were investigated. Ultra-fine talcum powder was prepared by adjusting the grinding parameters of the physical milling process. The talcum powder exhibited polymodal distribution. The layered morphology of talcum particles in a horizontal sand mill was rarely damaged or destroyed. PP-talcum nanocomposites were prepared by melt blending using a twin-screw extruder. Nano talcum can be seen as a single particle, although it is not very apparent. The bending strength of talcum-filled PP was gradually increased by approximately 28%. The impact strength linearly decreased as the filler weight ratio increased. The overall maximum improvement in mechanical properties was recorded when the filler ratios increased from 15 wt% to 20 wt%.

超细粉末压片-X射线荧光光谱法测定磷矿石中12种组分

粉末压片法是一种理想的绿色环保制样方法，简单快速，但是粒度效应对测定结果的影响很大，限制了这种方法在很多领域的应用。为了解决粒度效应对粉末直接压片法的影响，实验利用超高速行星式超细碎样机，将磷矿石标准物质粉碎至微米级，采用粉末直接压片制样，利用波长色散x射线荧光光谱仪对磷矿石中12种组分（氟、五氧化二磷、二氧化硅、三氧化二铝、全三氧化二铁、氧化锰、二氧化钛、氧化锶、氧化钙、氧化锰、氧化钾、氧化钠）进行了测定。结果表明，将样品粉碎至微米级，能够有效地克服样品的粒度效应，获得了比较满意的结果；特别是将氟的测定范围提高到了10．68％，对轻组分氧化钾和氧化钠的测定结果也很好。采用多种磷矿石标准物质和人工配制标准物质制作校准曲线，各组分的均方根为0．0011～0．53。校准曲线采用经验系数和康普顿散射线内标法校正组分间的吸收增强效应，方法的检出限为3-282μg/g。对两个磷矿石国家标准样品进行精密度考察，各组分测定结果的相对标准偏差（RSD，n=10）为0．17％～5．2％。对采用标准物质配制的混合标准样品进行准确度考察，测定值与参考值一致。

热分解法制备纳米α-Fe_2O_3

用醇盐液热分解结合超临界干燥制备纳米α Fe2 O3粉 ,并用透射电镜和X射线衍射对其表征进行分析。结果显示 ,采用该法 ,可直接制得纳米级红色、分散均匀的α Fe2 O3粉。

柠檬酸盐法合成γ-LiAlO_2超微粉

以ＬｉＮＯ３，Ａｌ（ＮＯ３）３·９Ｈ２Ｏ和柠檬酸为原料合成γＬｉＡｌＯ３超微粉。对合成的材料进行了ＴＧ，ＤＴＡ，ＸＲＤ和ＴＥＭ等表征。结果表明，焙烧温度在５５０℃以上试样基本恒重，５６２℃有一相变峰，生成纯相γＬｉＡｌＯ２超微粉。６００和９００℃焙烧试验表明，粒径在４０～７０ｎｍ范围内随温度的升高而增大。经６５０℃焙烧１，２４和１４８ｈ，产物γＬｉＡｌＯ２超微粉无相变，粒径几乎没有变化，保持在４０～５０ｎｍ范围。

Q235钢固相反应型Al_2O_3-TiB_2复相陶瓷涂层制备及性能研究

利用机械合金化(MA)制备了超细粉体,并采用固相反应法在Q235钢表面制备了Al2O3-TiB2复相陶瓷涂层,用X射线、激光粒度仪、扫描电镜(SEM)、差热分析仪(DTA)研究了粉体和涂层的物相组成、粒度分布及截面形貌,并测试了涂层的耐磨、耐蚀性能。结果表明,MA后骨料粉体的粒度可达纳米级;700℃热固化后涂层有Al2O3、TiB2和MgAl2O4等新相生成;封孔处理后涂层相对耐磨性最多提高3.21倍;涂层耐蚀性能最多提高9.52倍,封孔后的涂层耐蚀性能最多提高15.48倍。

凝胶-共还原法制备超细Mo-Cu粉末及其烧结性能

以(NH4)6Mo7O24·4H2O和CuO为前驱体,采用有机物辅助的凝胶工艺制得干凝胶。干凝胶经煅烧、还原后,获得Cu含量为20%(质量分数)的Mo-Cu复合粉末。该Mo-Cu粉末模压成形后,在H2中于1050～1150℃烧结,制得Mo-Cu复合材料。通过X射线衍射,透射电镜等对干凝胶煅烧后产物及其还原后粉体的相组成、形貌和粒度等进行了表征;通过扫描电镜观测了不同温度烧结所得Mo-Cu复合材料烧结体的显微结构,并对其密度、电导率和强度等物理力学性能进行了测定。结果表明:通过凝胶-共还原法可以制备分散均匀、平均粒度为200nm的Mo-Cu超细粉末;该Mo-Cu粉末烧结活性高,其成形压坯在1150℃下于H2气氛中烧结90min后相对密度可达99.65%,且烧结体的晶粒细小均匀,具有良好的物理力学性能。

肉桂油β-环糊精包合物与肉桂超细微粉药剂学性质的对比研究

目的 为了探索制剂新技术在含挥发油的中药制剂中的应用,我们研究了肉桂油β-环糊精包合物与肉桂超细微粉的药剂学性质。方法 以主要活性成分桂皮醛为对照品,用紫外分光光度法进行含量测定,37℃下以去离子水为溶出介质进行体外溶出实验,60℃下放置10d进行稳定性实验,对肉桂油β-环糊精包合物和肉桂超细微粉的有效成分含量、溶出性能、稳定性进行研究,并以肉桂普通粉进行对比。结论45min时,各样品中桂皮醛的累计溶出均达到90％左右。肉桂油β-环糊精包合物稳定性最好,在60℃下放置10 d,肉桂醛含量仍有94％得以保存,而在肉桂超细微粉和普通粉中分别只有70％和82％。结果表明β-环糊精包合物是制备肉桂油制剂较好的技术选择。

超细Mo-30Cu复合粉末的烧结行为

采用溶胶-喷雾干燥-煅烧-氧还原方法制备了晶粒尺寸为17-30 nm的超细Mo-30Cu复合粉末,在制备过程中经历了一系列的相转变,由喷雾干燥复合盐前驱体Cu_(7.6)O_8(NO_3)+(NH_4)_2(Mo_4O_(13))+(NH_4)_6(Mo_7O_(24))(H_2O)_4+ Cu_4Mo_5O_(17)+CuMoO_4在450℃煅烧后转变为CuMoO_4+MoO_3复合氧化物,在300℃低温还原转变为MoO_2+ Cu_2O+Cu三相,再在700℃高温还原完全转变为Mo+Cu两相复合粉末.该粉末在1050-1200℃烧结时从亚稳态Mo(Cu)固溶体逐渐转变为Mo和Cu相,在1050℃烧结后得到致密度为99.7%的细晶合金,合金的最大抗拉强度可达755 MPa,最大延伸率可达15.8%.

Co-Mn-Ni系NTC热敏电阻超微细粉体的液相法制备

讨论了液相法制备Co-Mn-Ni三元系NTC热敏电阻超微细粉体的一些主要方法,如共沉淀法,均匀沉淀法,溶胶–凝胶法等的基本原理与优缺点,并对一些具体制备方法进行了比较。

低温燃烧法制备La_(0.8)Sr_(0.2)MnO_(3-δ)超细粉体

采用低温燃烧法制备La0.8Sr0．2MnO3-δ（LSM）超细粉体，研究了PH值、柠檬酸用量n（H2O）/n（M^2＋）和加热温度等主要工艺条件对凝胶生成的影响。采用XRD、粒度分析和BET等方法对粉体的相组成、粒度分布状态及比表面积进行了分析和表征，并比较了低温燃烧法与固相反应法和共沉淀法制备LSM粉体的性能差别，结果表明低温燃烧法制备的纳米粉（20～30nm）纯度高，比表面积超过了11m^2／g。

紫芝超细粉挥发油成分GC-MS分析

将紫芝Ganoderma sinense(“闽紫96”,HMAS 77207,阔叶树枝桠材或边材栽培)超微粉碎加工成500目的子实体超细粉。激光粒度分析表明:紫芝超细粉的表面积到834．18m^2/kg,中位径(D50)为12．68μm。气质联用分析结果表明:从紫芝超细粉挥发油中分离到35种成分,出峰时间为7．872～30．239min,确定了其中32个成分,占相对含量的88．642％;绝大多数成分为脂肪族化合物(67．216％),主要成分(20．67％)为2,6-二叔丁基一苯酚为芳香族化合物,还检出2种杂环族化合物。