抗水性AlN粉体的电动特性研究

通过测量粉体在水溶液中的Zeta电位和颗粒尺寸,研究了引入不同的分散剂时抗水性AlN粉体的电动特性．结果表明,溶液的pH值和引入不同的分散剂均会导致抗水性AlN粒体的表面荷电状况及其在水溶液中的分散状况发生变化．NH4PA是一种适合抗水性AlN粉体水基流延用的有效分散剂,在碱性条件下添加该分散剂有利于抗水性AlN粉体在水溶液中的稳定分散．     

共沉淀法制备Nd:YAG纳米粉体与机理探讨

以碳酸氢铵为沉淀剂采用共沉淀法和添加分散剂的方式．获得具有高烧结活性的碳酸盐前驱体,这种前驱体在较低的温度下烧结即可转变成相。同时借助DTA-TG、IR、XRD和TEM等测试手段对前驱体和YAG粉体进行表征。结果表明：在分散剂存在的情况下,此800℃左右煅烧2h前驱物直接转变为纯的YAG相,而无其它的杂质相,所得的YAG粉体的颗粒尺寸约20nm．是单分散的形貌近似球形的。此外不同温度下粉体的荧光性质表明,随着烧结温度的提高发光强度有所增加。     

己二酸直接沉淀法合成超细二氧化钛粉体

以TiCl4和己二酸为原料，在适当的PH值下，合成Ti2O2（OH）2C6H8O4·1．5H2O前体，经洗涤，干燥，煅烧，得到超细二氧化钛粉体。讨论了煅烧温度，煅烧时间，分散剂和干燥方法等因素对二氧化钛粉体粒度的影响。通过对所得粉体的形貌，颗粒尺寸分析，得出制备超细二氧化钛工艺条件为：添加聚乙二醇作分散剂，微波干燥前体，在500℃下煅烧0．5h，得平均粒径为30nm且粒度分布均匀的粉体。     

分散剂聚合度对纳米氧化铝粉体特性的影响

以不同聚合度的聚乙二醇(PEG)为分散剂,采用沉淀法制备氢氧化铝胶体,胶体经 800~1100℃高温煅烧得到纳米氧化铝粉体。对粉体进行了颗粒分布、XRD谱、HRTEM形貌及电子衍射等分析。结果表明分散剂(PEG)的聚合度对纳米氧化铝的粒度分布有着重要的影响。当用 PEG2000 作分散剂时制备出的粉体颗粒细而均匀,平均粒径为 25nm,无明显团聚与颗粒长大现象;经 1000℃/2h煅烧已完全转化为α Al2O3。文章对不同聚合度的分散剂的分散机理进行了讨论。     

纳米TiN粉体在无水乙醇中的分散研究

应用超声、球磨等分散方法,分别以非离子型表面活性剂吐温-80、聚乙二醇1000、聚乙二醇1500及硅烷偶联剂A-1230为分散剂对纳米TiN粉末在无水乙醇中的分散性能进行了研究。分析了分散剂类型、分散剂用量、体系pH值、超声时间、球磨时间、球磨转速等因素对粉体分散效果的影响。采用分散相的沉降高度和沉降速率表征分散稳定性,试验结果表明硅烷偶联剂A-1230是纳米TiN粉体在无水乙醇中较为理想的分散剂,pH值和分散剂的用量存在一个最佳值,超声分散与球磨分散相结合是合适的分散工艺。当pH值为4、A-1230添加量为粉体质量的23%时,经10min超声处理、4h球磨后所得纳米浆料的分散效果最好,稳定时间可达6个月。对分散后的纳米TiN颗粒进行了TEM、SEM观察,纳米TiN均匀分散在无水乙醇中,颗粒平均粒径在20nm以下,纳米TiN在无水乙醇中的分散遵循空间位阻稳定机制和静电稳定机制。     

液相中分散剂分散超微颗粒研究进展

介绍了液相中分散剂分散超微颗粒的机理;评述了分散剂种类、分散剂用量等因素对分散性能的影响和研究现状;综述了反映分散剂分散超微颗粒效果的表征方法和实验手段的研究进展.     

纳米ZrO2悬浮体的表面化学特性

本文通过测定纳米ＺｒＯ２悬浮液粉体的Ｚｅｔａ电位和颗粒大小,探讨了引入不同的分散剂如聚甲基丙烯酸氨,聚乙烯亚胺及柠檬酸氨对ＺｒＯ２粉体表面带电状况及颗粒分散状况的影响。结果表明,３Ｙ－ＴＸＰ粉体的等电点在ＰＨ＝６附近,没有分散剂的条件下,在碱性介质中ＺｒＯ２粉体容易与溶液中的水分子形成氢键,使ＺｒＬＯ２粉体的等电点会发生明显的偏移。     

机械研磨法制备白炭黑-TiO_2复合粉体及颜料性能研究

通过湿法机械研磨白炭黑进行解聚与分散以及白炭黑与Ti O2共混研磨制备白炭黑-Ti O2复合粉体,对制备过程中的各种因素进行优化,对白炭黑-Ti O2复合粉体的结构、粉体颜料性能以及紫外光作用下的光学性能进行表征。结果表明:影响白炭黑与Ti O2研磨复合的因素及优化条件是,白炭黑中位粒径为2.288μm,球料质量比为5∶1,浆体中粉体颗粒的质量分数为18%,研磨时间为60 min,分散剂质量分数为6%;白炭黑-Ti O2复合颗粒以Ti O2在白炭黑团聚体表面包覆为特征;白炭黑-Ti O2复合粉体与钛白粉颜料性能相似,并因白炭黑与Ti O2的协同作用而具有紫外线屏蔽功能。     

纳米TiO2的原位包覆及分散性研究

采用水热合成法制备纳米TiO2粉体，以自制的1100分散剂对粉体进行原位包覆和后包覆，考察了分散剂用量、pH值对包覆体系分散性的影响，利用XRD和TEM进行结构表征和形貌观测，并采用分光光度法对纳米TiO2粉体水分散体系稳定性进行了检测，在此基础上制备了纳米TiO2／有机复合涂膜．研究表明：原位包覆制备的纳米TiO2中，锐铁矿相的质量分数为100％，分散较均匀，纳米TiO2粉体的平均粒径约为20nm；分散剂用量为8．0％、pH值为3和10时，其水溶液分散稳定性较高；后包覆制备的纳米TiO2粉体由锐钛矿相（73％）和金红石相（27％）构成，纳米TiO2粒子处于团聚状态，无明显颗粒形态；涂膜经自然光照射24h后，对大肠杆菌的杀灭率为99．8％；良好的分散工艺和有效的分散剂可充分发挥纳米TiO2的光催化功能．     

利用TiOSO4液相反应制备透明锐钛矿相二氧化钛溶胶

以TiOSO4水溶液为前驱体,NH3·H2O为沉淀剂,聚乙二醇400(PEG400)为分散剂,在60～80℃下均相沉淀与结晶,制备出透明锐钛矿相二氧化钛溶胶.利用XRD和TEM表征了粉体的晶体结构和形貌.研究了制备过程中溶液中H /Ti摩尔比、表面活性剂、晶化温度和时间对TiO2溶胶颗粒尺寸的影响.结果表明:当溶液中H /Ti摩尔比为5,晶化温度为70℃,分散剂质量分数为2.5%时,得到的二氧化钛晶粒尺寸在10～20nm之间.聚乙二醇400的加入有效抑制了晶化过程中晶粒的长大.     

Experimental methods for measuring the optimum amount of dispersant for seven Sumitomo alumina powders

Seven Sumitomo alumina powders of different surface areas and particle size distributions were studied with a view to determining the optimum amount of dispersant (Darvan 821A) required to stabilise aqueous suspensions prepared from the powders. Three different techniques were used; sedimentation, particle sizing and acoustophoresis. Acoustophoresis proved to be the most accurate and quickest way of establishing the optimum amount. It was also shown that the optimum amount of dispersant (0.59mg/m2/) required to stabilise the different sized alumina powders was independent of thepowder surface area/size. Sedimentation results demonstrated that the larger particles acted like hard spheres with thin double layers and gave a smaller relative sediment height than the small particles under the same conditions, i.e. volume fraction and electrolyte strength. This was because the small particles acted as soft spheres with thick double layers that resulted in the particles keeping far apart from one another and hence giving a larger sediment volume.     

氟化石墨粒度测试分散条件优化

采用激光粒度分析仪,对氟化石墨样品的粒度及粒度分布进行测试研究,获得测试样品最佳分散条件。结果表明:采用质量分数为5%的乳化剂OP-10的水溶液作为氟化石墨的分散剂,超声振荡分散时间为3 min,悬浮液质量浓度为46.67～53.33 mg/L,可使样品粒度分布重现性好,由此表明悬浮体系具有良好的稳定状态。     

低温燃烧合成法制备纳米NiFe_2O_4

以九水硝酸铁、六水硝酸镍、水溶性肼类燃料为原料,添加金属离子络合剂、分散剂等为辅助剂,利用溶液燃烧合成法制备了纳米NiFe2O4粉体。利用XRD、TEM、SEM等测试方法对产物进行了表征,并研究了不同燃料、络合剂用量、分散剂用量、煅烧温度对粉体粒径和形貌的影响。实验结果表明,在以水溶性肼为燃料、络合剂2g、分散剂2g、煅烧温度800℃、煅烧时间2h时,可获得粒径均匀的纳米NiFe2O4粉体。所得产物的粒径范围为40～80nm,结构膨松,分散性良好。     

Comparative study of synthesis and characterization of YAG:Yb3+ nanoparticles using different precipitator by co-precipitation method

Irregular club-shape nanoparticles of Yb3+ doped Y3Al5O12 were synthesized by the co-precipitation method using different precipitator, such as ammonium hydrogen carbonate, hexamethylene tetramine and urea. The reaction mechanism of different precipitator and the effect on the particle size and dispersion of Y3Al5O12:Yb3+ powders were investigated, and the influence of ammonium sulfate as the dispersant in the reaction system was also discussed. The results show that the large and agglomerated Y3Al5O12:Yb3+ powders were obtained from urea compared to that uniform particle size and dispersion one from ammonium hydrogen carbonate and hexamethylene tetramine. Moreover, ammonium sulfate is beneficial to enhance the dispersion of the particles for ammonium hydrogen carbonate and to form the club-shape morphology of Y3Al5O12:Yb3+ crystals for hexamethylene tetramine. The photoluminescence property investigation shows that the near-infrared emission intensity of the powders increased with the calcining temperature as well as the particle size and dispersion of as-prepared particles for all the precipitators.     

Dispersion stabilization of yttria-stabilized zirconia slurry for spray coating by PVB polymeric adsorption

In this study, the dispersion stabilization characteristics of the poly(vinyl butyral) (PVB) adsorbed yttria-stabilized zirconia (YSZ) was investigated. The addition of PVB showed remarkable dispersion effect to the YSZ slurry prepared with isopropyl alcohol (IPA) and toluene as a bi-solvent system, PVB as a dispersant medium and YSZ powders. The agglomerated YSZ particle size decreased with PVB addition until 3 wt% and PVB added more than 3 wt% acted as a binder. The smallest particle size was obtained at 3 wt% PVB and the more PVB addition causes reflocculation of YSZ particles. The relative amount of adsorbed PVB onto the YSZ surface increased with increasing PVB contents. It turns out that the YSZ slurry dispersion stabilization was improved by the interaction between the hydroxyl group of YSZ surface and O-H group in PVB which is newly formed Zr-O-C bonding.     

三异辛醇氧基铝水解法制备超细γ-Al_2O_3粉体

以自制三异辛醇氧基铝为原料,采用醇盐水解法制备γ-Al2O3粉体,利用X射线衍射、扫描电镜以及激光粒度分析等手段,着重探讨pH值、分散剂添加量两个工艺条件对最终产物的相组成、结晶形貌以及粉体粒度的影响。结果表明,制备的样品均为立方相γ-Al2O3,无其它杂质相,结晶纯度较高;pH值和分散剂添加量的调整对产物的相组成影响不大,但对结晶强度却有一定的影响;采用醇盐水解法制备的γ-Al2O3超细粉体粒度分布均匀,粒度为1～15μm,pH和分散剂添加量过大或过小均会导致粉体粒度增大。     

A Novel Process for Particle Size Enlargement

ABSTRACT

We present a droplet formation process as a novel route for the particle size enlargement of fine powders. The aqueous slurry process provides significant control over final particle size distribution, shape, porosity, and strength. The slurry process is suitable for the agglomeration of a wide range of materials, including ceramics and metals. In particular, mixtures of materials can be combined to form homogeneous particles. The process is of relevance to a number of areas, including milling, die compaction, heterogeneous catalysis, and solid phase synthesis.     

超细粉体粒度分析的分散条件比较

测试超细粉体粒度时 ,通过选择不同的沉降介质、分散剂或超声波分散时间做比较实验 ,找出合适的分散条件 ,使得悬浮液中团聚的粉末充分分散 ,以便测得较真实的粒度及粒度分布值。     

纳米Y-TZP形成稳定浆料的流变性质

本文研究了纳米Y－TZP超细粉体分别添加聚丙烯酸钠（NaPAA）及聚丙烯酸铵（NH₄PAA）所制备的浆料的稳定性.综合考虑Zeta电位和分散剂的解离条件,pH8～12为浆料的稳定范围.通过对浆料流变性质的测定,给出固含量与其相应的最佳分散剂用量关系,并比较了NaPAA与NH₄PAA在稳定高固含量浆料中的分散作用.结果表明,使用NH₄PAA可获得较NaPAA低的粘度,且由于它不引入杂质而有更大的优越性.对不同纳米尺寸的Y－TZP,如果吸附等量的分散剂,颗粒越大粘度越低.在一定范围内达到相同的粘度,颗粒越小,所需分散剂用量越多.     

Size effect in Ni-coated TiC particles for metal matrix composites

Nickel (Ni) particles have been coated on the surface of titanium carbide (TiC) particles to enhance the dispersion of TiC particles into a molten metal and to achieve an improvement in the mechanical and thermal properties of the metal matrix. The adhesion of Ni particles on the surface of TiC particles is induced by the attractive force between the TiC with a negative charge and the Ni cation in an aqueous solution. The powders prepared with the relatively large particle sizes of 1, 4, and 40 microm show both TiC and Ni phases, whereas that prepared with a particle size of 0.02 microm shows complex phases of Ni, TiC, and TiO2 (titanium dioxide). The TiO2 phase is caused by the oxidation reaction between the TiC and oxygen. The 1 microm powder shows that the Ni is located only around the TiC without any self-aggregation and the TiC and Ni particles are isolated in the 4 and 40 microm powders, as confirmed in TEM images. The particle size is the essential factor in fabricating highly efficient Ni-coated TiC particles for metal matrix composites.