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高固相含量氮化硅水基浓悬浮体制备的研究 总被引:1,自引:0,他引:1
运用一种特定的氮化硅粉料,研究了基悬浮特性很差的限制性因素,并通过酸洗和后续热氧化处理使其悬浮特性有了显著的提高。对改性后的氮化硅粉料,采用NH4PA高分子分散剂,研究了分散剂的用量和浆料的pH对含烧结助剂的氮化硅悬浮体流变特性的影响。并在含烧结助剂的情况下,分别以TMAH和NH4PA为分散剂,制备出了低粘度的50vol%的氮化硅浓悬浮体。 相似文献
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以蒸馏水为研磨介质,采用行星式球磨机对平均粒径约为10μm的SiC粉料进行了球磨,对球磨粉料进行酸洗除铁及水洗,制备出平均粒径为351.5nm的SiC超细粉料,详细分析了粉料制备过程中的物理化学变化与机理.结果发现:粗分散体系长时间球磨所得超细粉体溶液形成胶体分散系,体系固相含量增加,颗粒平均最小间距减小,颗粒间的范氏引力倍增,易形成团聚体;超细粉料胶体溶液在酸洗过程中产生了硬团聚,主要是由于Fe2+氧化水化成为Fe(OH)3胶桥,将超细粉料钳住所致;另外,测试溶液接近SiC等电点时亦会导致颗粒团聚.酸洗去除胶桥、调解溶液pH值可有效消除团聚. 相似文献
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碳化硅陶瓷是一种高性能的陶瓷,具有高强度、高硬度、耐高温、耐化学腐蚀、高热导率、低热膨胀以及低密度等性能,广泛应用于各个工业领域以及航空航天领域.从纳米复相陶瓷制备过程中的分散方法以及碳化硅基陶瓷的烧结方法与烧结助剂等方面详细论述了目前有关碳化硅基纳米复相陶瓷的研究进展. 相似文献
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TiCl4水解条件对相转变的影响 总被引:8,自引:0,他引:8
以TiCl4为原料控制反应温度为70℃可以制备出金红石相氧化钛粉体。沉淀物不经分离通过改变体系的pH值可以部分或全部转变成锐钛矿相氧化钛粉体,这种锐钛矿相粉体经700℃燃烧2h,可以全部转变成金红石相粉体。对氧化钛制备过程中的相转变进行了结构方面的解释。 相似文献
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用非均匀成核法和液相共沉淀法相结合的方法制得ZrO2(3Y)包裹Al2O3纳米复合粉体,经干压成型,常压烧结制备ZTA复相陶瓷.通过XRD、TEM对粉料的物相组成和显微形貌进行表征,研究了包裹粉体中煅烧温度和ZrO2含量对烧结体的烧结性能和力学性能的影响.结果表明:随着前驱体粉料煅烧温度的升高,包裹后的Al2O3-ZrO2(3Y)复合陶瓷粉体比表面积降低,粒径变大;ZrO2含量为20wt.%的Al2O3-ZrO2(3Y)复合陶瓷粉体,经过1000℃锻烧后,干压成型制备的烧结样品的抗弯强度和断裂韧性分别高达454.9MPa和11.6MPa·m1/2,SEM观察结果表明烧结体结构致密. 相似文献
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以α-SiC、B_4C、TiO_2为原料,用AlN、Y_2O_3作为烧结助剂,采用热压烧结工艺制备出SiC-TiB_2复相陶瓷样品。采用等温氧化增重法,研究原位合成的SiC-TiB_2复相陶瓷在600℃、800℃、1000℃和1200℃下的抗氧化性能。采用扫描电镜(SEM)对所制备的复相陶瓷的表面形貌进行分析,同时采用X射线衍射仪(XRD)对烧结体样品及其氧化产物的物相成分进行分析。实验结果表明,当烧结助剂的含量为15%(体积分数)时,烧结体样品气孔较少,且颗粒尺寸的均匀性较好,赋予复相陶瓷较好的致密度(相对密度达98.3%)、抗弯强度(551 MPa)和硬度(90.1HRA)。SiC-TiB_2复相陶瓷在空气中中温氧化时,其氧化行为表现为氧化增重随时间的变化服从抛物线规律。在研究的温度范围内,该复相陶瓷的氧化机理为:TiB_2优先被氧化成TiO_2和B_2O_3,然后是SiC在较高温度下被氧化成SiO_2和CO_2。 相似文献
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We demonstrate the room temperature crystallization of colloidal silica particles dispersed in a mixture of ethanol and water at the air–liquid interface of the colloidal suspension spread on a glass substrate. By combining this approach with the dip-drawing technique, a room temperature floating self-assembly method has been developed. Applying this method, a three-dimensional silica colloidal crystal film of several square centimeters in area has been fabricated within 10 min without special facilities or heating of the suspension. SEM images and the normal incidence transmission spectrum of the sample show that the colloidal crystal film fabricated by this method had very high crystalline quality. 相似文献
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Udit Choudhury Dhruv P. Singh Tian Qiu Peer Fischer 《Advanced materials (Deerfield Beach, Fla.)》2019,31(12)
The rheological properties of a colloidal suspension are a function of the concentration of the colloids and their interactions. While suspensions of passive colloids are well studied and have been shown to form crystals, gels, and glasses, examples of energy‐consuming “active” colloidal suspensions are still largely unexplored. Active suspensions of biological matter, such as motile bacteria or dense mixtures of active actin–motor–protein mixtures have, respectively, reveals superfluid‐like and gel‐like states. Attractive inanimate systems for active matter are chemically self‐propelled particles. It has so far been challenging to use these swimming particles at high enough densities to affect the bulk material properties of the suspension. Here, it is shown that light‐triggered asymmetric titanium dioxide that self‐propel, can be obtained in large quantities, and self‐organize to make a gram‐scale active medium. The suspension shows an activity‐dependent tenfold reversible change in its bulk viscosity. 相似文献
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用凝胶注模成型制备压电陶瓷体及其电学性能研究 总被引:6,自引:0,他引:6
对PZT陶瓷浆料胶体化学特性进行了研究,成功制备了高固相含量低粘度的PZT陶瓷浆料.对含不同分散剂凝胶注模成型PZT样品电学性能的研究及其与普通干压法制备样品的比较表明,成型过程中的各种有机添加剂如单体和交联剂等不会对PZT的性能造成影响,而某些无机成份如选择不当的分散剂,则会起到一种掺杂剂的作用,从而影响成型后样品的各种电学性能.本文结果说明,对于电子陶瓷材料,在应用凝胶注模这种成型方法时,必须考虑各种添加剂可能对样品性能造成的影响 相似文献
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A novel five-step method for fabricating mesoporous SiO2 glass was described in this paper, which consists of: (1) formation of colloidal suspension of Zn(OH)2, (2) synthesis of silica sol, (3) mixture of Zn(OH)2 colloidal suspension and silica sol to form nano-ZnO embedded precursor glass, (4) annealing of the precursor glass, and (5) treating nano-ZnO embedded glass with HCl to obtain the mesoporous glass. The mesostructure of the glass was investigated by X-ray diffraction (XRD), field emission scanning electron microscope (SEM), and BET surface area analysis. The average pore size distribution is in the range of 3.7 nm, and the surface area is as high as 496.5 m2/g. 相似文献
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A. A. Potanin V. E. Chernomaz V. M. Tarakanov N. B. Ur'ev 《Journal of Engineering Physics and Thermophysics》1991,60(1):26-33
A relation is obtained to describe the effect of the volume content of particles on the effective viscosity of a concentrated monodisperse suspension of spherical particles in a medium which can be regarded as a power-law fluid. It is shown that this effect becomes weaker as the nonlinearity of the medium increases. The analysis is performed on the basis of the proposition that the deciding role is played by the lubricant action of thin interlayers of the medium between the surfaces of the particles. These results are used to calculate the viscosity of a bidisperse suspension containing a highly dispersed colloidal fraction and a coarsely dispersed fraction (filler). The viscosity is calculated as a function of the ratio of the two fractions. The calculated results are compared with experimental data for model systems.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 60, No. 1, pp. 32–41, January, 1991. 相似文献
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A mathematical 2D model for a consolidation process of a highly concentrated, flocculated suspension is developed. The suspension is treated as a mixture of a fluid and solid particles by an Eulerian two-phase fluid model. The suspension is characterized by constitutive relations correlating the stresses, interaction forces, and inter-particle forces to concentration and velocity gradients. This results in three empirical material functions: a permeability, a non-Newtonian viscosity and a non-reversible particle interaction pressure. Parameters in the models are fitted to experimental data. A simulation program using finite difference methods both in time and space is applied to one and two dimensional test cases. The effect of different viscosity models as well as the effect of shear on consolidation rate is studied. The results show that a shear thinning viscosity model yields a higher consolidation rate compared to a model that only depends on the volume fraction. It is also concluded that the size of the viscosity influences the time scale of the process and that the expected effect of shear on the process is not weil reproduced with any of the models. 相似文献
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A solgel process was developed, through which silica films possessing both high antireflection and super water repellence were obtained. In this process, methyl-modified SiO2 sols synthesized by colloidal suspension of SiO2 particles and hexamethyldisilazane (HMDS) were used to deposit spinning-coating films on optical glass substrates. On the resultant films the contact angle for water increased with the increasing amount of HMDS in the reaction mixture. The biggest contact angle was 165 degrees, and the lowest reflectivity on one-sided film reached 0.03%. The antireflections were high all the while. One advantage of this process is that neither a roughened surface nor fluoroalkyltrialkoxylsilane (FAS) is needed to obtained super water repellence. 相似文献
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V. N. Manoharan A. Imhof J. D. Thorne D. J. Pine 《Advanced materials (Deerfield Beach, Fla.)》2001,13(6):447-450
Macroporous titania, which undergoes transition to the rutile phase by calcination without collapse of the pore structure, is obtained by polymerizing a titania sol suspended around “colloidal crystals” of oil droplets. The deformable template counteracts cracking of the titania phase. The Figure shows a scanning electron micrograph of a rutile sample with 200 nm pores obtained by the method described. 相似文献
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《Drug development and industrial pharmacy》2013,39(18):2705-2716
AbstractChange-can mixing and handling technology has changed dramatically during the past few years. Today, change-can mixing systems are available with up to three different mixers to handle formulations having viscosities up to several million centipoise. These systems incorporate low and high shear and low and high speed mixers that are independently driven and controlled. This permits processors to fine-tune the equipment for single or multiple tasks including emulsification, particle size reduction, dispersion and suspension.Because of the high viscosity mixing capability of modern change-can mixers, a Follower Plate Discharge System has been specially designed. This discharge system pushes the viscous mixture out of the can into product cartridges, moulds or hoppers of packaging machinery. The development of new mixing and discharging systems and their integration open fresh opportunities to streamline processing operations and substantially lower production costs. 相似文献