纳米二氧化锆悬浮液分散稳定性研究

纳米二氧化锆悬浮液分散稳定性是一个十分重要的问题。通过测定纳米二氧化锆悬浮液的ξ电位和吸光度，探讨了不同pH、不同表面活性剂种类和浓度对纳米氧化锆水相体系分散性的影响，并分析其作用机理。发现在阴离子和非离子复配表面活性剂中分散稳定性最好，体系ξ电位绝对值较高。氧化锆水相体系的等电点（IEP）在pH=6附近，在pH为2-3附近具有较大的正电位，在pH为9-11附近具有较大的负电位。     

分离粗分散悬浮液的新方法及设备

<正> 聚乙烯、聚氯乙烯和聚苯乙烯等悬浮液的固粒粗而均匀,过滤速度快,滤饼不可压,一般使用自动卸料离心机分离。该机结构较复杂,造价高,运行的可靠性较低。粗分散悬浮液分离技术在原理上的新发展方向是一种借助旋流气体的流动过滤,在此,一种固定的圆筒滤板代替了离心机的多孔转鼓的作用,悬浮液以液膜形式被往里送     

氧化铝-氧化锆复合材料的分散、流变性以及泥浆的带式浇注

用Darvan（达范聚偏[二]氰乙烯短纤维）C作为分散剂在最佳的pH值条件下单独地将氧化铝和氧化锆进行分散。基于沉淀、流变能力、屈服应力、电极沉积和Z电位，发现按质量计2％的分散剂和10．5pH值是最佳的条件。在分散最佳的条件下制备了按质量计含固体物32％的含水带式浇注泥浆。获得了40μm厚和56％的生料密度的氧化铝一氧化锆的复合带形材料。     

氧化铝粉体在水悬浮液中的分散特性研究

采用Zeta电位表征Al_2O_3粉在悬浮液中的分散特性,研究了超声波分散时间、不同粒度Al_2O_3粉以及分散剂六偏磷酸钠的浓度和Al_2O_3粉体悬浮液pH值对Al_2O_3粉体Zeta电位的影响.研究结果表明:Zeta电位绝对值随超声波作用时间发生明显变化,在一定条件下存在一个最佳分散时间为4～6 min;悬浮液中Al_2O_3粉体颗粒的粒度对悬浮液的Zeta电位有重要影响;在Al_2O_3粉体悬浮液中添加分散剂六偏磷酸钠,Zeta电位随其浓度发生变化,存在一个最佳浓度0.5%;在不同pH值下,Al_2O_3粉体悬浮液的Zeta电位不同,在碱性条件下,粉体的分散性较好,且碱性越强,分散性越好.     

氧化铁-水悬浮液的流变性研究

应用DV-Ⅲ+型可编程流变仪测定了三氧化二铁-水悬浮液的流变特性。考察因素包括颗粒浓度、pH值以及分散剂用量。结果表明,悬浮液在测定范围内表现出宾汉流体的特征。表观粘度随颗粒浓度的增大显著增加,其模型可用本文提出的三阶多项式模型表示。悬浮液的表观粘度受pH值的影响,pH在等电点处时,溶液的流动性最差;pH低于等电点时的粘度比pH高于等电点时要明显降低。这些现象可用颗粒的空间结构化理论及凝聚原理予以解释。改善悬浮液流动性的分散剂添加量存在最佳点。     

高分散高稳定α-Al2O3和纳米SiC单相及混合水悬浮液的制备

采用胶体电空间稳定机制改善陶瓷的分散,以聚电解质ＰＭＡＡ－ＮＨ４为分散剂制备出分散、高稳定单相α－Ａｌ２Ｏ３,单相ＳｉＣ（α－Ａｌ２Ｏ３和纳米ＳｉＣ）水悬浮液。此法可获得较理想的结果。     

凹凸棒石粘土-NH4PAA-水悬浮液流变性研究

研究了聚丙烯酸铵(NH4PAA)用量、离子强度等对凹凸棒石粘土的流变性影响。研究表明，在凹凸棒石粘土悬浮液中添加NH4PAA分散剂可使粘土流变性获得很大的改善。pH为8．5时，添加量为4．5％NH4PAA分散剂，可以制备分散良好的凹凸棒石粘土悬浮液，而且pH提高，分散剂最佳添加量减少。电解质NaCl使凹凸棒石粘土的流变性下降。但NaCl浓度从0．5mol／L变化到1．0mol／L时悬浮液的流变性基本不变。     

螯合分散法制备超细纳米四方氧化锆粉体

本文利用形成纳米ZrO2粉体的前驱体的化学结构特征设计合成一种能与之发生螯合作用的新型分散剂(简称为D1),能够有效地减小颗粒尺寸,提高分散效果.采用螯合分散剂制备纳米氧化锆的最佳工艺条件为ZrOCl2·8H2O浓度1.0 mol/L,D1分散剂用量1%(ω),沉淀pH值10.0,陈化时间12 h,锻烧温度750℃,锻烧时间1 h.以稀土元素Y作晶型稳定剂,成功制备粒径超细(5～8 nm),均匀分散的四方纳米ZrO2粉体(3Y-TZP).螯合分散剂同十六烷基三甲基氯化铵,TritonX-100等常用分散剂相比,对纳米ZrO2的分散性能和颗粒尺寸的改善效果最为显著,明显优于其它几种分散剂.结果表明根据纳米粉体的化学结构设计特定的分散剂是解决纳米颗粒团聚问题的重要途径.     

碳酸钙悬浮液混凝处理后的流变性

应用LVDV-Ⅲ+型可编程流变仪测定了微米级碳酸钙悬浮液混凝处理后的流变特性,考察因素包括悬浮液固相质量浓度、pH值、混凝剂种类及添加量、搅拌速度.结果表明,混聚后碳酸钙悬浮液在测定范围内流变曲线符合Herschel-Bulkley模型.表观粘度随颗粒浓度的增大而增大,其中屈服应力随体系浓度的增大而增大,刚性系数随体系...     

纳米二氧化硅水悬浮液的稳定性研究

本文采用胶体“电空间稳定机制”,以聚羧酸盐为分散剂,研究了纳米S iO2粉体在水中的分散行为和表面化学特性,讨论了pH值、分散剂种类及用量对体系的悬浮稳定性及流动特性的影响。在最佳pH值和分散剂加入量条件下制备了高固含量、稳定性和分散性好的纳米S iO2浆料。     

Electrokinetic Properties of Colloidal Zirconia Powders in Aqueous Suspension

Pure zirconia, yttria, and three yttria-doped zirconia powders of submicrometer size have been dispersed in various aqueous solutions. The zeta potential (zeta) of the zirconia powders is determined primarily via streaming-current (SC) detection and is confirmed using electrophoretic spectroscopy techniques. The results reveal that the isoelectric point (IEP) of these zirconia powders is in the pH range of 5.6-7.2 and zeta is controlled primarily by the yttrium content of the zirconia powders and the type of electrolyte. In addition, the yttria content strongly affects the potential and SC in zirconia suspensions only at high solids contents (>1 vol%). The electrokinetic data reveal that the surface of the yttria-doped tetragonal zirconia powder (TZP) can be modified via the adsorption of ionic molecules or polymeric species in the suspension. The adsorption of an anionic polymer can stabilize zirconia particles in a solution that is almost neutral or weakly basic (in the IEP range of pure ZrO₂). The interaction of the zirconia and yttria particles with the electrolytes in an aqueous suspension will be discussed to reveal the roles of hydrated oxide formation and zirconia surface interaction with polymeric dispersants.     

水溶性高分子对氧化锆悬浮体分散性和流变性的影响

在氧化锆陶瓷的凝胶注模成型制备中,为了消除空气中坯体表面脱粉现象,试图在常用的丙烯酰胺体系的基础上增加了一种新的水溶性聚合物组分,形成一种新型的聚合物-单体共存的凝胶注模成型体系。这种体系在某种条件下要优于原有单一丙烯酰胺体系。着重研究了添加聚乙二醇对氧化锆悬浮体的分散特性、固化特性及其流变行为的影响。结果表明,通过添加1.5wt%水溶性聚合物聚乙二醇发现可以消除坯体的表面脱粉,同时大大地改善了氧化锆浓悬浮体的分散性和流动性。     

纳米钛酸钡粉体的分散及水基悬浮体制备

通过测定超重力法制备的纳米钛酸钡悬浮体的Zeta电位和团粒尺寸分布,确定了纳米BaTiO3在水中稳定分散的基本条件,制备了不同体积分数的悬浮体并研究了其流变学特性. 该纳米BaTiO3在水中的等电点约为pH 2.8,加入分散剂PAA-NH4后,颗粒零电点向更低pH值移动;当分散剂用量为干粉量的1.2%(w)时,悬浮体中平均团粒尺寸最小,分散效果最佳. FT-IR分析证明颗粒表面上PAA-NH4的吸附为物理化学吸附. 制备了体积分数高达45%的纳米BaTiO3悬浮体,其流变特性表现为剪切变薄行为,流延成型的BaTiO3陶瓷生坯片具有较高的相对密度(55.4%).     

Effects of Solids Loading and Dispersion Schedule on the State of Aqueous Alumina/Zirconia Dispersions

The effects of solids loading and dispersion order on the state of aqueous slips of either zirconia or alumina, and binary slips of these two powders, have been examined. Since these powders can acquire surface charge when they are dispersed in aqueous media, changes in the ionic composition of the slip can occur as a result of the addition of solids. At higher solids loading, a substantial fraction of the ionic activity within the slip may be attributed to the solid itself. As the solids loading within unary powder suspensions is increased, it is possible to drive the suspension pH toward the point of zero-charge for the powder, resulting in diminished electrostatic stabilization and possible powder agglomeration. An analytical model was constructed to account for the observed results. This embodied a simple surface site complexation model which was augmented to include material and charge balance constraints on ionized surface sites as well as solvated ions. For binary powder dispersions of alumina and zirconia, it was found that the order of dispersing the two components could have a pronounced effect on the overall suspension behavior. The variability in results is attributed to the solubility of the alumina in the basic processing media.     

Ultrasonic Dispersion of TiO2 Nanoparticles in Aqueous Suspension

Aggregation and dispersion behavior of nanometer and submicrometer scale TiO₂ particles in aqueous suspension were investigated using three kinds of mechanical dispersion methods: ultrasonic irradiation, milling with 5-mm-diameter balls, and milling with 50 μm beads. Polyacrylic acids with molecular weights ranging from 1200 to 30 000 g/mol were used as a dispersant, and the molecular weight for each dispersion condition was optimized. Viscosities and aggregate sizes of the submicrometer powder suspensions were not appreciably changed in the ultrasonic irradiation and 5-mm-ball milling trials. In contrast, in the trials in which nanoparticle suspension was used, ultrasonic irradiation produced better results than 5-mm-ball milling. Use of ultrasonication enabled dispersion of aggregates to primary particle sizes, which was determined based on the specific surface area of the starting TiO₂ powders, even for relatively high solid content suspensions of up to 15 vol%. Fifty-micrometer-bead milling was also able to disperse aggregates to the same sizes as the ultrasonic irradiation method, but 50-μm-bead milling can be used only in relatively low solid content suspensions. It was concluded that the ultrasonic dispersion method was a useful way to prepare concentrated and highly dispersed nanoparticle suspensions.     

Electrospinning Zirconia Fiber From a Suspension

A zirconia suspension containing 5–10 nm size zirconia particles was modified by adding different amounts of polymer solution to enable electrospinning of zirconia fibers from a range of compositions. The electrospun fibers were heat treated at 600° and 1200°C, and analysis of size distribution reveals that zirconia fibers down to about 200 nm in diameter can be prepared in this way, in contrast to other spinning processes, which are able to produce zirconia fibers having diameters ≥3000 nm.     

Deposition of Nanostructured Fluorine‐Doped Hydroxyapatite Coating from Aqueous Dispersion by Suspension Plasma Spray

In this study, we prepared an aqueous dispersion of fluorine‐doped hydroxyapatite (FHA) nanoparticles by a wet chemical method. For the first time, the as‐prepared aqueous dispersion of FHA nanoparticles was directly used as suspension for depositing nanostructured FHA coating on stainless steel substrate by suspension plasma spray (SPS) method. Field‐emission scanning electron microscopy images confirm that the coating was nanostructured. X‐ray Diffraction pattern, Fourier‐transform infrared spectroscopy, and Raman spectra show that the as‐sprayed coating was FHA phases. The experimental result confirmed that OH^? and F^? ions have been well kept in FHA crystal lattice and structural integrity has been maintained during SPS process by using an aqueous dispersion of FHA nanoparticles. The potentiodynamic polarization and electrochemical impedance spectroscopy results prove that the nanostructured FHA coating can greatly enhance the anticorrosion performance of stainless steel in phosphate‐buffered saline solution.     

Colloidal Stability for Concentrated Zirconia Aqueous Suspensions

This work started as part of an investigation into the mechanisms by which fine zirconia aqueous dispersions can be processed for ceramic materials engineering. Aqueous dispersions of TZ3Y fine zirconia particles obtained by dispersion of dry powder in acidic solutions (pH 3) have been subjected to compression through osmotic experiments. The results show a behavior that is unusual when compared with the classical behavior of colloidal dispersions. Indeed, the 50 nm particles are well dispersed and protected from aggregation by electrical double layers, with a high zeta potential (60–80 mV). Yet, during osmotic compression, the dispersion goes from a liquid state to a gel state at a rather low volume fraction, φ=0.2, whereas the liquid–solid transition for repelling particles is expected to occur only at φ=0.5. This early transition to a state in which the dispersion does not flow may be a severe drawback in some uses of these dispersions, and thus it is important to understand its causes. A possible cause of this early aggregation is the presence of a population of very small particles, which are seen in osmotic stress experiments and in light scattering. We propose that aggregation could result from the compression of this population, through either of the following mechanisms: (a) An increase in pressure causes the small particles to aggregate with each other and with the larger ones or (b) An increase in pressure induces a depletion flocculation phenomenon, in which the large particles are pushed together by the smaller ones.     

Synthesis of Zirconia Colloids from Aqueous Salt Solutions

We monitor the synthesis of ZrO₂ colloids from dissolved ZrOCl₂·8H₂O using quasi-elastic light scattering and cryo-transmission electron microscopy (cryo-TEM). We investigate the effects of both precursor salt concentration and pH on the final size distribution. We find that the initial pH plays the most important role in the final particle size and yield. These trends and cryo-TEM observations help elucidate the roles of nucleation, aggregation, and recrystallization.     

Injection of Aqueous Slurry for Making Zirconia Fiber

Zirconia aqueous slurry was prepared with fine zirconia powder.Injection process for making zirconia fiber was demonstrated,including preparation of aqueous slurry,injection of slurry,fiber setting in acetone,and fiber firing.The principle of the process was discussed.The effects of solid loading in the zirconia slurry,addition of dispersant in the slurry,and ball milling time on the rheological properties of the slurry,especially yield stress,were illustrated.The role of acetone as curing agent was discussed.Zirconia poly-crystalline fber with at 1 530 ℃ for 5 h.Microstructure of the sintered zirconia fiber was investigated.