Evolution of the Morphology of Zinc Oxide/Silica Particles Made by Spray Combustion

Pure and mixed ZnO–SiO₂ particles were made by flame-spray pyrolysis of zinc acetate and hexamethyldisiloxane or SiO₂ sol dispersed in methanol or water-in-oil emulsion, respectively. The product particles were characterized by nitrogen adsorption, infrared absorption, and X-ray diffraction. The evolution of solid or hollow particle formation along the flame axis was unraveled by transmission electron microscopy after collection by thermophoretic sampling. The effects of silicon precursor and solvent on product particle characteristics were evaluated. The characteristics of the product particles were controlled by the Si precursor and solvent.     

Influence of pH and Ionic Impurities on the Adsorption of Poly(acrylic) Dispersant onto a Zinc Oxide Surface

We have studied the properties of aqueous suspensions of ZnO powders with different purities. Our results suggest that powder purity determines the amount of dispersant necessary to form a stable aqueous suspension as well as the maximum adsorption capacity of the dispersant: the higher the positive surface charge of the as-received ZnO powders, the higher the amount of dispersant adsorbed onto the metal oxide surface. The surface charge of the ZnO particles in suspension is affected by the concentration of zinc as well as sulfate ions, which are the major impurities in the supernatant. The pH of the aqueous ZnO suspensions increases with increasing concentration of poly(acrylic) dispersant until the maximum adsorption capacity is attained. Further additions of dispersant do not increase the pH because of a buffer formation with impurity ions.     

不同分散剂对提高钛白粉生产过程中分散效果的研究

针对钛白粉生产过程中粗品分散问题进行了研究,主要添加分散剂硅酸钠和六偏磷酸钠比较分散的情况。试验表明,当分散剂加入量为钛白粉质量的0.5%时,硅酸钠对几种钛白粉的分散性比较好,矿浆黏度比较低;六偏磷酸钠的分散性比较弱,矿浆黏度下降很少。分析表明是因为分散剂在水中水解成阴离子吸附在颗粒表面,使颗粒表面带电,阻止了颗粒之间的团聚。     

聚电解质分散剂对ZnO悬浮体流变性的影响

本文研究了聚电解质分散剂PMAA－NH_4对ZnO悬浮体流变性的影响。结果表明：pH在9~10.5,分散剂用量为0.2~0.3Wt％时,ZnO悬浮体粘度最低。此条件下,可制得固相量达43vol％（81wt％）、粘度仅为237mPa·S的稳定悬浮体。     

Preparation of Hydroxyapatite Lathlike Particles Using High-Speed Dispersing Equipment

Hydroxyapatite lathlike monocrystalline particles were prepared using high-energy dispersing equipment in combination with a pH shock-wave method. The Ca/P atomic ratios were very close to theoretical, and the acidic group content was very small. The particles were nonporous, with anisotropic crystal growth and average grain size ∼140–1300 nm in length, ∼20–100 nm in width, and ∼10–40 nm in thickness. The high-speed dispersing equipment created the proper hydrodynamic conditions for lathlike particle growth in the [001] direction. The hydroxyapatite particles formed aggregates of 1–5 μm average diameter.     

氨配合法制备活性氧化锌过程研究

以粗氧化锌为原料,用氨水－碳酸氢铵作浸取液,经粗氧化锌溶解,除杂净化,蒸氨结晶,洗涤脱水,干燥,煅烧可制得活性氧化锌,有本文方法制得的活性氧化锌的质量符合HG／T72572－94标准。     

Dispersion and Grinding of Oxide Powders into an Aqueous Slurry

The present paper deals with a comprehensive analysis of the dispersion behavior of oxide powders to determine accurate conditions for mixing and grinding dense slurries without the use of steric dispersing agents. The experimental support of the work was the synthesis of (Zr,Sn)TiO₄ microwave dielectric ceramics by the solid-state reaction of raw materials mixed and ground by attrition milling. Zeta potential measurements were performed on the raw materials versus pH to determine the optimum pH of the slurry, allowing a good dispersion of all the species: the absolute value of the zeta potential of every powder >20 mV, with all potentials having the same sign. During the grinding process, as the surface of the materials increases due to the breakup of the grains, surface reaction occurs with the dispersion liquid, and pH must be continuously adjusted to be maintained at an adequate level. We have correlated these characterizations of the optimal processing conditions with the rheological behavior of the slurries, thus providing an analysis of the flocculated or deflocculated state. When applied to synthesizing (Zr,Sn)TiO₄ microwave dielectric ceramics, these conclusions made it possible to produce reproducible resonators with a k = 37 dielectric constant and characterized by a quality factor, Q × F > 60 000 GHz measured at 3 GHz, the highest value reported for this composition.     

纳米氧化锌的制备与表征

选择不同的微乳液体系及适宜反应条件,制备出粒径不同的纳米氧化锌,并进行了性质表征和比较。     

低纯度氧化锌制备磷酸锌研究

研究了用低纯度氧化锌(96%)通过复合溶剂净化,同时将氧化锌转化为液相改变传统的固-液相反应为液-液反应制备磷酸锌的新工艺,考察了净化和液-液反应的有关的工艺条件,制备得到高纯度磷酸锌。     

用含锌烟尘制备活性氧化锌的工艺研究

以含锌烟尘为原料,用酸法制得了活性氧化锌,产品达部颁标准。考察了硫酸浓度、固液比、温度及时间对浸出率的影响。在优惠条件下,实验浸出率可达９８％左右。三段控温添加锌粉除杂以及氨水与碳酸氢铵复配作为沉淀剂是技术关键。     

Aqueous Processing and Stabilization of Manganese Zinc Ferrite Powders via a Passivation–Dispersion Approach

A dispersion scheme for aqueous processing of manganese zinc ferrite suspensions is presented. The addition of oxalic acid leads to the formation of a uniform negative charge on the surface such that a cationic polyelectrolyte, polyethyleneimine (PEI), adsorbs and provides electrosteric dispersion. At 0.5 w/w (weight percent with respect to the dry powder) oxalic acid addition, there is a relatively uniform negative surface charge (approximately −30 mV) within the suspension pH range investigated (3–10), eliminating the isoelectric point (pH ∼7.6) present for the as-received metal oxide powder. At the addition of 0.5 w/w PEI on an oxalate-treated surface, the surface charge is constant and positive (∼20 mV) through a wide pH range, ∼5–10. The resulting rheological data for passivation–dispersion of relatively high-solids manganese zinc ferrite suspensions (∼80 wt%) demonstrate improved colloid stability with improved rheological properties. The resulting apparent viscosity and Bingham yield point is 0.01 Pa·s (12.0 cP) and 0.24 Pa (2.4 dynes/cm²), respectively. A sulfonated napthalene-based dispersant, typically used in industry, gives an apparent viscosity and Bingham yield point of 0.03 Pa·s (32 cP) and 3.1 Pa (31 dynes/cm²), respectively.     

纳米氧化锌的制备及应用研究进展

综述了纳米氧化锌的不同制备方法,以及在不同的领域中的应用。     

Effect of Bismuth of Oxide Content on the Sintering of Zinc Oxide

Densification and microstructure de velopment in Bi₂O₃-doped ZnO have been studied with a special emphasis on the effect of the Bi₂O₃ content. A small amount of Bi₂O₃ in ZnO (0.1 mol%) retarded densification, but the addition of Bi₂O₃ to more than 0.5 mol% promoted densification by the formation of a liquid phase above the eutectic temperature (∼740°C). The liquid phase increased grain-boundary mobility, which was responsible for the formation of intragrain pores and the decrease in the sintered density. The increase in the Bi₂O₃ content increased the probability of the formation of skeleton structure, which reduced the grain growth rate and the sintered density.     

纳米氧化锌的制备及应用

纳米氧化锌是一种性能优异的新型功能材料,应用前景广阔。本文综述了纳米氧化锌的制备及近年来新的应用领域和研究前沿。     

Electrophoretic Deposition Behavior of Aqueous Nanosized Zinc Oxide Suspensions

The rheological behavior and electrophoretic deposition (EPD) of ZnO nanopowder (nano-ZnO) in aqueous media have been described. A cationic polyelectrolyte (polyethylenimine, PEI) was used to disperse and modify the surfaces of the ZnO nanoparticles. The rheological properties of the ZnO aqueous suspension were investigated by measuring the viscosity versus the pH and amount of dispersant. The EPD processing was conducted via cathodic electrodeposition, using stable suspensions with low viscosity, and the depositional behavior was investigated. Bubble-free nano-ZnO deposits with uniform microstructures were successfully obtained, which was an indication of good sintering behavior.     

Zinc Vanadates in Vanadium Oxide-Doped Zinc Oxide Varistors

Convergent-beam electron diffraction has been used to determine the space groups of β- and γ-Zn₃(VO₄)₂ particles in vanadium oxide-doped zinc oxide varistors. The crystal structure of β-Zn₃(VO₄)₂ has been determined to be monoclinic with space group P 2₁ and lattice parameters of a = 9.80 Å, b = 8.34 Å, c = 10.27 Å, and β= 115.8°, whereas that of γ-Zn₃(VO₄)₂ is monoclinic with space group Cm and a = 10.40 Å, b = 8.59 Å, c = 9.44 Å, and β= 98.8°. Energy-dispersive X-ray microanalysis of these two phases shows significant deviations from their expected stoichiometry. It is apparent that the β-phase is, in fact, the metastable Zn₄V₂O₉ phase, whereas the γ-phase either is a new oxide that consists of zinc, vanadium, and manganese or, more likely, is a zinc vanadate phase with a Zn:V atomic ratio of 1:1 that has the ability to go into solid solution with manganese.     

纳米氧化锌的制备及应用研究

综述了纳米氧化锌的制备及应用。按照固相、气相和液相分类法叙述了纳米氧化锌生产及研究进展。对上述各种氧化锌生产方法的优点和缺点进行了评述。并对纳米氧化锌的几种应用、生产提出了展望。     

乙二胺-水体系中合成氧化锌纳米带

以乙二胺为介质,采用溶剂热法,在乙二胺-水体系中合成出宽度为20~30 nm、长度为500~600 nm的氧化锌纳米带,并进行了表征. 在反应过程中,氧化锌纳米带通过"溶解-结晶"机制形成,溶剂乙二胺的配位是氧化锌纳米带形成的关键因素,通过调整NaOH用量控制溶液碱度,实现了氧化锌纳米带的取向生长.     

活性纳米ZnO的制备

用成本低廉的锌焙砂为原料 ,通过直接沉淀法首先合成前驱物碱式碳酸锌 ,然后烘干分解得到活性纳米ZnO粉体。TG -DTA表明前驱物为碱式碳酸锌 ,XRD估测颗粒尺寸为 90nm ,产品气敏度为 17.8。