新型超细钴粉的制备及添加剂对其性能影响

以自制Co(OH)2为原料,利用高温液相多元醇还原法制备超细钴粉。重点考察了不同表面活性剂对其性能的影响。利用SEM、XRD、BET和激光粒度分析仪,对钴粉进行了表征。结果表明多原醇还原的钴粉为球形,以面心立方晶体为主,钴粉粒度分布较窄,平均粒径小于0.7μm,比表面积为3.46 m2/g,钴含量>99.5%。     

Effect of Polyelectrolyte Dispersants on the Preparation of Silica-Coated Zinc Oxide Particles in Aqueous Media

Sodium silicate was utilized to obtain a SiO₂ coating on ZnO particles to prevent a photocatalytic reaction between ZnO and phenol. During the coating process, pH control is important to avoid dissolution of the ZnO as well as to obtain a good dispersion. Two kinds of polyelectrolyte dispersants were used to control the surface charge of the ZnO particles in aqueous media. As a result, poly(ethylenimine) (PEI) shifted the isoelectric point of ZnO from pH 9 to pH 10, whereas poly(ammonium acrylate) (PAA) made the surface charge of ZnO negative between pH 6 and pH 11. The change in the ZnO surface charge produced by adding polyelectrolyte dispersants makes it possible to obtain uniform silica–coated ZnO particle in aqueous media. UV–irradiation experiments showed that PEI, which can make the surface charge opposite to that of SiO₂, is more effective in obtaining a thick silica coating on ZnO.     

Interactions in the Silicon Carbide–Polyacrylic Acid–Yttrium Ion System

Interactions in the SiC powder–polyacrylic acid (PAA, dispersant)–Y³⁺ ion (sintering additive) system were investigated in the pH range from 2 to 6. The amount of Y³⁺ ions adsorbed on SiC particles increased with an increase of pH because of the electrostatic attraction between the negatively charged SiC surface and Y³⁺ ions. On the other hand, the amount of PAA adsorbed on SiC particles decreased with increasing pH because of the electrostatic repulsion between the negatively charged SiC surface and dissociated PAA. The addition of PAA to the SiC suspension with Y³⁺ ions increased the amount of Y³⁺ ions fixed to SiC particles through the strong interaction between Y³⁺ ions and PAA adsorbed on SiC particles. The above-described interactions in the SiC–PAA–Y³⁺ ions system were closely related to the coagulation of SiC particles and the rheology of SiC suspensions. The coagulation of SiC particles through the adsorbed Y³⁺ ions decreased the specific surface area of SiC powder after calcination in an argon atmosphere. The addition of PAA to the SiC suspensions with Y³⁺ ions kept the SiC particles separate during calcination, i.e., the PAA addition contributed to enhancement of the driving force of sintering (no decrease of specific surface area) and to control of the amount of Y³⁺ ions uniformly fixed to the SiC surface.     

Interaction between Dissolved Ba2+ and PAA-NH4 Dispersant in Aqueous Barium Titanate Suspensions

The interaction between dissolved Ba²⁺ and dissociated ammonium salt of poly(acrylic acid) (PAA-NH₄) in aqueous suspension has been studied. The dissolved Ba²⁺ causes flocculation of dissociated PAA-NH₄, thus degrading its dispersing effectiveness in aqueous BaTiO₃ suspensions. The concentration of PAA-NH₄ required to stabilize aqueous BaTiO₃ suspension increases with increasing Ba²⁺ concentration at a given pH. A stability map, which is determined by a rheological study, is constructed to describe the amount of PAA-NH₄ required to have well-dispersed aqueous BaTiO₃ suspensions as a function of Ba²⁺ concentrations at different pH values.     

纳米氧化锌的分散性研究

研究了单一、二元混合以及三元混合分散剂对纳米ZnO的分散效果,探讨了分散剂用量对纳米ZnO粉体分散性的影响.结果表明:二元混合分散剂分散效果优于单一分散剂;三元混合分散剂分散效果更佳,分散剂的用量为水的质量分数的0.4%时分散效果最好.     

复配分散剂对ZrO2悬浮液稳定性的影响

本实验选用由乳化剂OP(壬基酚聚氧乙烯醚)与CPB(溴代十六烷基吡啶)所组成的复配分散剂对纳米ZrO2 进行分散,制备ZrO2 悬浮液,并讨论了复配分散剂两组分用量比、pH值、悬浮液中的离子强度等对悬浮液稳定性的影响.结果表明:加入复配分散剂得到的ZrO2 悬浮液,具有更好的分散稳定性;当OP与CPB用量比为1∶ 1,复配分散剂用量为ZrO2 含量的6%时,能使ZrO2 粉末具有良好的分散,在pH=1.8时,悬浮液颗粒粒径最小,中位粒径达到178 nm.实验中还发现,添加复配分散剂后悬浮液等电点由原来的pH= 6右移到pH=13附近,另外,增加悬浮液中的离子强度,使Zeta电位值降低,粒径增大,但离子强度大小并不会影响ZrO2 的等电点,其等电点仍保持在13左右.     

A new concept for dispersing agents in aqueous coatings

After a short overview about the development of synthetic dispersing agents for solvent-borne coatings up to the actual state of technique, analogous concepts of polymeric additives for water-borne coatings are introduced. The performance of these polyfunctional dispersants will be critically reviewed and described in comparison to dispersing agents based on new concepts. With these new concepts using mono- and difunctional oleochemical agents or a combination of them it is often possible to reach better performance than with polyfunctional polymers. During our study different physicochemical methods (Zeta potential, adsorption, desorption) and paint application tests including numerous binders and pigments were done. These investigations lead to the discussion of new models for the dispersing of pigments in water-borne coatings and to more knowledge about the design of a dispersant to reach high gloss, optimal rub-out and high color-strength. Furthermore the formulation of solvent- and resin-free water-borne pigment pastes is possible using dispersing agents selected by the new concepts.     

水热法制备Mg/Sn/W复合氧化物催化剂及其性能评价

采用水热法制备了Mg/Sn/W催化剂,利用N_2吸附-脱附、XRD、FTIR、SEM等手段对制备的催化剂进行表征,考察了不同种类的分散剂和分散剂含量对催化剂活性的影响,探究了共沉淀法和水热法制备的催化剂在使用过程中W的流失情况。实验结果表明,以聚乙二醇和三乙醇胺为混合分散剂制备的催化剂拥有更大的比表面积和更小的孔径,提高了催化剂的活性;当混合分散剂的含量为7.5 g/L、钨酸质量浓度为6 g/L时,催化剂的活性最大,环己酮转化率达66.23%,ε-己内酯选择性达89.56%;与共沉淀法制备Mg/Sn/W催化剂相比,水热法制备的Mg/Sn/W催化剂合成ε-己内酯的活性更高,可以有效解决活性组分W的流失问题,也能在一定程度上保持催化剂活性。     

有机分散剂对含碳酸盐铁矿石浮选的影响研究

目的在于确定能够有效分散含碳酸盐铁矿石的分散剂。通过有机分散剂种类及用量条件试验,确定了最佳分散剂为NMS-3,其最佳用量为200 g/t。制定了适合选别东鞍山含碳酸盐混合磁选精矿的一次粗选、两次精选、一次扫选的分散浮选工艺流程。闭路试验获得了品位66.37%、回收率75.00%的铁精矿。该浮选指标良好,且工艺流程简单。论文运用DLVO理论对NMS-3分散机理进行了初步探讨,为含碳酸盐铁矿石的有效利用提供理论基础。     

Effect of Magnesium Ions on the Adsorption of Poly(acrylic acid) onto Alumina

The adsorption isotherms of poly(acrylic acid) (PAA) onto alumina powder have been determined as a function of pH, ionic strength, and magnesium-ion concentration. The adsorption of PAA is strongly enhanced by magnesium ions in alkaline media but less affected under acidic conditions. The adsorption isotherms display a maximum when PAA is fully complexed with magnesium ions in the solution, corresponding to a ratio of 0.25 ± 0.05 [Mg²⁺]/[acrylic acid monomer]. The decrease in adsorbed amount with an increase in PAA concentration at constant magnesium-ion concentration is related to a decrease in the complexation ratio.