PAA-NH_4对氧化铝悬浮液沉降性能的研究

采用PAA-NH4作为分散剂制备了超细氧化铝悬浮液,通过沉降实验观察了PAA-NH4的添加量、pH值对α-A12O3低固含量悬浮液的沉降性能的影响,并用Zeta电位仪测定了不同pH值条件下稀固相含量悬浮液的Zeta电位;同时对烧结坯体进行了微观分析.结果表明:分散剂PM-NH4的最佳用量为1.0%左右,最佳pH值为9;对添加PAA-NH4前后的稀悬浮液Zeta电位进行了测定,发现等电势点左移,Zeta电位的绝对值变化显著.添加PAA-Nh4后,pH值的变化对悬浮液的沉降性能和Zeta电位影响很大.     

氧化锌悬浮液的分散行为及其影响因素研究

本文详细研究了氧化锌悬浮液的分散行为及固含量、p H值和聚丙烯酸(PAA)添加量对分散行为的影响。实验结果表明:固含量、p H值和PAA添加量对氧化锌悬浮液的分散行为有显著的影响。粘度法及Zeta电位测试法所反映的悬浮液分散性随p H值和分散剂添加量的变化规律基本一致。当p H=9~10、分散剂添加量为0.40wt%~0.60 wt%时,粘度最低、Zeta电位绝对值最大、分散效果最好。分散剂添加量存在最佳范围,其最佳范围不随固含量的变化而改变,颗粒的粒径分布窄、平均粒径小。     

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。     

TiB2泡沫陶瓷浆料的制备

通过沉降实验、Zeta电位的测定及粘度和流变性能测量的方法研究了制备高固相含量TiB2泡沫陶瓷浆料的工艺条件;通过挂挂浆量的测定及烧结体的扫描照片分析研究了浸渍工艺的条件。研究表明：浆料最佳pH值为9,分散剂的引入有效提高了悬浮粒子的Zeta电位,改善浆料的分散性,最佳的分散剂含量为0.3wt%,最佳固相含量为77wt%。     

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.     

分散剂用量和pH值对纳米氧化锆水基浆料稳定性的影响

在氧化锆陶瓷制作过程中采用凝胶注模成型工艺时,为了获得高分散性、低粘度的浆料,试图使用聚丙烯酸铵(PAA-NH4)作为分散剂,主要研究了氧化锆悬浮体的3个指标:Zeta电位、流变学行为、沉降度,在不同p H值和分散剂用量下的变化规律,并分析其影响机理。试验结果表明:PAA-NH4的加入能够明显提高氧化锆浆料的Zeta电位,用氨水调节悬浮体p H为11的情况下,当添加3.0 wt%的分散剂聚丙烯酸铵PAA-NH4时,Zeta电位为负值,达到最小,粘度和沉降高度也均达到最小值,此时,ZrO2水基浆料的分散性、稳定性和流变学行为达到最佳。     

PAA-PEO对ZrO2-H2O悬浮液流变性能的影响

利用一种新型的分散剂—梳型共聚物poly（acrylic acid）-pofy（ethyfene oxide）（PAA—PEO）,研究了pH、分散剂的添加量及固含量对ZrO2-H2O悬浮液的流变性能的影响。结果表明：在pH为3、PAA-PEO的添加量为0．3wt％,ZrO2-H2O悬浮液的粘度最低;固含量在31vol％以下时,浆料都保持稳定状态;随着固含量的增加,浆料的粘度也增加,当固含量达到33vol％时,浆料呈现出明显的剪切变稀行为。     

pH对α-Al2O3-H2O-聚丙烯酸悬浮液稳定性的影响

研究了pH对α-Al2O3-H2O-聚丙烯酸悬浮液稳定性的影响。研究结果表明：对于给定的PAA添加量的浆料．其稳定性随着pH的提高有明显地提高；提高浆料的pH值，PAA最佳添加量减少；固含量分数在54％左右的浆料．在不同的pH值，加入最佳PAA添加量时，其浆料粘度显著不同；以PAA为分散剂制备高固相体积分数的α-Al2O3浆料的最佳pH值为8．5。     

TiC—Ni粉体水系共悬浮

通过测定粉体Zeta电位、酸碱性和对分散剂PAA的吸附,探讨了TiC-Ni水系浆料的共悬浮。TiC粉体是酸性,等电点在PH值2.5处,并在PH值为9.5处出现Zeta电位最大值。TiC的Zeta电位随PAA浓度的增加而增加,并且对应于TiC对PAA的饱和吸附,Zeta电位增加到最大值,达到饱和吸附后,继续增加PAA的浓度反而导致Zeta电位的减小。Ni粉体呈碱性,通过理论分析,其等电点应在碱性区。当PAA的加入量为0.3wt％、pH值为6.5时单组分TiC浆料稳定,TiC-Ni浆料相对失稳;当PAA的加入量为0.2wt％、pH值为8.5时,TiC-Ni浆料稳定,并且沉降后的组分均一。     

注浆成型Yb∶YAG激光陶瓷浆料的流变性能研究

通过Zeta电位的测定、沉降实验及粘度测试优化了制备较高固含量陶瓷浆料的工艺条件,分析了pH值及分散剂加入量对Yb∶YAG浆料流变性能的影响并进行了注浆成型实验,得到具有连通气孔、密度达1.789 g/cm3的较致密坯体.结果表明:形成稳定浆料合适的pH值为11.83,分散剂的加入显著改善了浆料的流动性,合适的分散剂含量为陶瓷粉料质量的1.0wt％,固相含量为55wt％.     

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%).     

Dispersion properties of alumina powders in silica sol

The dispersion of alumina powders in silica sol has been investigated by zeta potential, sedimentation, and rheological measurements. Zeta potential of alumina in silica sol changes significantly in comparison with that of alumina in deionized water. This is caused by the absorption of silica colloidal particles with negative charge on the surface of alumina particles. Sol-dispersed alumina slurry shows a minimum in sedimentation volume and viscosity around pH 10. The viscosity depends strongly on the silica sol concentration and reaches a minimum in 10–15 wt.% silica sols. It is proposed that the dispersion and stabilization of alumina particles in silica sol are attributed to the electrostatic and steric effects of the colloidal particles absorption. Effects of pH, solids content and silica sol concentration on the rheological behavior of sol-dispersed alumina slurries are discussed in detail.     

Electrokinetic and Rheological Properties of Aqueous TiN Suspensions with Ammonium Salt of Poly(methacrylic acid)

The study illustrates how rheology and electrokinetics can be utilized in the investigation and optimization of the properties of ceramic suspensions. Zeta potential studies show that the isoelectric point of TiN particulates is at pH=4, and for the pH range used, PMAA–NH₄ addition results in a more negative zeta potential value. The rheological behavior of titanium nitride in the presence of PMAA–NH₄ is strongly dependent on pH and three rheological types have been defined.     

Mullite coatings on ceramic substrates: Stabilisation of Al2O3–SiO2 suspensions for spray drying of composite granules suitable for reactive plasma spraying

The present work deals with the preparation of stable alumina + silica suspensions with high solid loading for the production of spray-dried composite powders. These composite powders are to be used for reactive plasma spraying whereby the formation of mullite and the coating on a ceramic substrate are achieved in a single step process. Electrostatic stabilisation of alumina and silica suspensions has been studied as a function of pH. Silica suspensions are most stable at basic pH whereas alumina suspensions are stable at acidic pH. The addition of ammonium polymethacrylate (APMA) makes it possible to stabilise alumina and prepare a stable 50 wt% alumina + silica suspension at pH 10. The optimum amounts of dispersant and binder have been determined by zeta potential, viscosity and sedimentation measurements. Spray drying of the suspension yields composite powders whose morphology, size distribution and flowability have been characterized before realizing reactive plasma spraying tests.     

Interaction and dispersion stability of alumina suspension with PAA in N,N′-dimethylformamide

The alumina suspension in N,N′-dimethylformamide (DMF) was studied in the presence of a polyacrylic acid (PAA) dispersant. The sedimentation measurements of the suspensions show that PAA can impart favorable dispersion stability to alumina in DMF over a wide apparent pH (pH_a) range. The adsorption of PAA on alumina and the zeta potential of the suspension are pH_a dependent. FTIR-ATR spectroscopic studies reveal that the different interaction mechanisms between PAA and alumina work as a function of pH_a. But the observable difference of dispersion between pH_a values of 2.6–12.7 is small according to the sedimentation experiments. This can be explained by a combination of the static effect of PAA dispersant and different sizes of steric barrier resulting from the configurational variation of PAA with changing pH_a values.     

陶瓷添加剂ISOBAM对氧化铝浆料流变性能的影响

ISOBAM(异丁烯-马来酸酐共聚物)是一种新型的陶瓷添加剂,主要用作凝胶注模成型中浆料的分散剂和凝胶剂。以α-Al₂O₃为对象,分别研究了pH值、ISOBAM添加量和球磨时间对Al₂O₃浆料流变性质的影响及Al₂O₃浆料的凝胶机理。结果表明,ISOBAM对氧化铝浆料有明显的分散作用,其主要分散机理是ISOBAM通过羧基的氢键作用吸附在氧化铝颗粒表面,增加了颗粒表面负电荷密度,提高了颗粒Zeta电位绝对值。其中,添加0.2%质量分数的ISOBAM的浆料可以快速凝胶化,原因是浆料的pH值接近等电点,ISOBAM分子和氧化铝能够通过氢键作用而形成凝胶网络。     

分散剂用量对碳化硅浆料流变性能的影响

使用四甲基氢氧化铵(TMAH)作为分散剂,研究了分散剂用量对SiC浆料流变性能的影响,并分析了其原因。结果表明：TMAH能够显著提高SiC粉体的zeta电位,降低浆料粘度,从而显著优化浆料的流变性能。在pH为10左右,加入质量分数为0．3％和o．6％NTMAH后zeta电位分别提高了11.7mV和21mV。实验中,在不同体积分数SiC浆料中,加入0．6%TMAH时能够达到最优性能,浆料粘度都达到最低。过量的分散剂则会增加浆料中的离子浓度而导致双电层厚度减小,从而恶化浆料的流变性。     

Elucidation of Viscosity Reduction Mechanism of Nano Alumina Suspensions with Fructose Addition by DSC

Control of the rheological properties of the nanoparticle suspensions is challenging. In this study influence of the solids content and the fructose addition on the viscosity of nano alumina suspensions have been investigated by low temperature differential scanning calorimetry (LT‐DSC), rheometry, and zeta potential measurements. Analysis of the water melting events in LT‐DSC revealed useful information for explaining the rheological behavior of the nanoparticle suspensions. It was shown that the bound water layer has a negligible effect on the viscosity of micrometer‐size particle suspension while it increases the effective solid content of alumina nanoparticle suspensions significantly leading to high viscosities. The presence of fructose modifies the bound water layer, decreases the effective solids content, hence resulting in viscosity reduction. Fructose addition lowers the pH of the suspension, but has a negligible effect on the zeta potential. The origin of the bound water, and electrostatic and steric effects of the fructose addition on the viscosity are discussed.     

分散剂聚乙二醇对Si3N4纳米粉末分散性的影响

纳米相颗粒弥散在陶瓷基体中构成的陶瓷刀具材料具有优异的力学性能,制备这类复合材料的体的均匀混合.基于此,研究了制备Si3N4基陶瓷刀具材料所用纳米Si3N4粉末分散性与悬浮液pH值、分散剂聚乙二醇(polyethylene glycol,PEG)分子量及用量之间的关系.为得到分散良好、抗团聚的纳米Si3N4悬浮液,用PEG作为分散剂,测定了电位与pH值关系,进行了沉降实验.结果表明:所采用Si3N4纳米粉末等电位点在pH=5.5附近,最佳分散条件为PEG相对分子量为4 000,分散剂质量含量为0.5%及分散介质pH值在9.5～10之间.