高固含量氧化锆水系料浆的制备

选用经1450℃保温4h预烧处理的氧化钇稳定氧化锆粉为原料,以丙烯酰胺为单体,N,N-亚甲基双丙烯酰胺为交联剂,由稀盐酸和氢氧化钠溶液调节pH,制成高固含量的氧化锆水系料浆。研究分散剂种类(聚丙烯酸铵、六偏磷酸钠、聚乙烯醇或柠檬酸铵)、聚丙烯酸铵的添加量(质量分数,0.5%~2.5%)、pH(0.5~13)和球磨时间(分别为0.5、1、1.5、2h)对料浆沉降高度、Zeta电位和黏度的影响。结果表明:添加0.55%(w)的聚丙烯酸铵分散剂,在pH=12时,球磨1h后获得了固相体积分数高达54%,黏度为344mPa·s的稳定的氧化锆水系料浆。     

氧化锆料浆性能对其喷雾造粒粉料性质的影响

本文研究了料浆含固量和粘度对其喷雾造粒粉料性质影响。结果表明：氧化锆料浆含固量是喷雾造粒（ＳＤ．）粉料填充密度的主要控制因素，高含固量料浆能得到高填充密度喷雾造粒粉料，且其颗粒显微结构相对致密；随着ＺｒＯ２料浆含固量、粘度增加，喷雾造粒粉料平均粒径增大，粗颗粒含量增多，细颗粒含量减少。     

Cr2O3料浆固含量对其喷雾造粒料性能的影响

以Cr2O3料浆为对象,研究三聚磷酸钠、六偏磷酸钠和柠檬酸等减水剂对料浆ζ电位、粘度和固含量的影响,并采用SEM等方法观察分析了料浆固含量对Cr2O3喷雾造粒料松装密度、粒径分布和颗粒形状的影响.结果表明由三聚磷酸钠和水玻璃复合的减水剂对Cr2O3料浆的分散效果最好;在保证喷雾造粒要求的粘度下,加入0.2%复合减水剂可将Cr2O3料浆的固含量由不添加时的58%(w,下同)提高到79%;Cr2O3料浆固含量为75%的喷雾造粒料松装和摇实密度大,粒径分布合理,空心、破损和梨形颗粒少.     

堆积法制造青瓷用胎体陶瓷粉料体制备及表征

针对堆积法制造龙泉青瓷,采用水基料浆与流态化喷雾造粒相结合制备青瓷胎体陶瓷粉料,研究了水基料浆的分散稳定机制及其喷雾造粒行为,分析了固相含量对料浆流变性能、造粒粉粒径分布及成型性能的影响机制。研究表明:水基料浆具有宾汉型流体特性,固相含量为40%的料浆具有较低粘度和剪切应力,而固相含量为50%的料浆的稳定性和分散性更好;喷雾造粒后,固相含量为50%料浆喷雾造粒颗粒呈规则球形,粒径分布较宽,具有较好的填充性能和成型性能。     

部分稳定氧化锆陶瓷的凝胶注模成型工艺

用流变学的方法研究了不同条件,如:固相含量、分散剂加入量、烧结助剂、增塑剂等对碱性部分稳定氧化锆(partially stabilized zirconia,PSZ)悬浮体的流变性的影响.结果表明:分散剂含量对悬浮液的流变性能有明显影响,当PSZ固相体积含量为55%时,分散剂加入量(占固相含量的质量分数)应为0.4%.当固相体积含量为50%～56%时,氧化锆碱性料浆呈现剪切变稀行为,具有较低的黏度(在剪切速率为10 s-1时,低于50mPa·s).氧化锆陶瓷碱性料浆(pH>7)在低的剪切速率(<100s-1)时,表现为剪切变稀.凝胶注模法生产的PSZ陶瓷坯体的内部结构是均匀的.     

水基SiC料浆的分散稳定机制及喷雾造粒

以去离子水为液体介质,引入有机添加剂,配制水基SiC悬浮料浆,研究了水基料浆的分散稳定机制及其喷雾造粒行为,分析了有机添加剂和固相含量对料浆流变性能、造粒粉粒径分布及成型性能的影响机制.结果表明:当料浆pH≥10时,水基碳化硅料浆的分散性和稳定性较好,料浆具有剪切稀化的非Newton体特性:当加入0.2%(质量分数,下同)四甲基氢氧化铵、2.0%聚乙烯醇和1.0%聚乙二醇时,料浆黏度较小:固相含量为50%水基料浆喷雾造粒后,造粒粉的流动性、填充性能及成型性能明显提高,但球状造粒粉需要在一定成型压力下才能完全破碎.     

影响氧化铝水基料浆流变学特性的关键因素

用流变学的方法在RV-20型流变仪上研究不同条件,如:固含量、分散剂加入量、烧结助剂、增塑剂等对碱性氧化铝悬浮体的流变性的影响.结果表明:氧化铝陶瓷碱性料浆(pH＞7)在低的剪切速率(＜100 s-1)时,表现为剪切变稀.在水基料浆中添加MgO时,会发生强烈的水合反应,导致料浆失去流动性.增塑剂甘油的加入导致料浆粘度升高的幅度是有限的,不会对料浆固含量和浇铸工艺造成显著不利的影响.加入水溶性丙烯酸乳液后,在低的剪切速率下,料浆仍然呈现剪切变稀行为,随着乳液含量的增加,料浆的静态粘度逐渐增大.分散剂聚丙烯酸氨的加入量对料浆的稳定性具有显著的影响.在分散剂的加入量为固相质量的0.8%左右时,分散剂在陶瓷颗粒表面形成饱和吸附,此时料浆的稳定性达到了最佳状态.     

Al2O3料浆流变性能的研究

研究了pH值、分散剂柠檬酸铵添加量、固相含量对Al2O3料浆流变性能的影响.结果表明:当pH为9-10时,当分散剂柠檬酸铵添加量为2wt%时,所制备的Al2O3料浆粘度最低,该料浆流动性能最佳.同时,料浆粘度会随料浆固相含量增加而增加.     

颗粒级配法制备高固相含量低黏度氧化铝料浆

以平均粒径分别为0.97 μm(CQ)和2.18 μm(HNXY)的2种Al2O3粉体为原料采用级配混合的方法,分别添加离子型分散剂柠檬酸铵或高聚物型分散剂聚丙烯酸,制备了适合胶态成型的高固相含量、低黏度的料浆.讨论了胶态成型中粒度分布,以及分散剂的种类和各自不同的用量对悬浮体流变学特性的影响.当粉体CQ和HNXY的级配质量比为1:2时,其混合粉体粒度分布最接近于Dinger模型理论分布,此时可以得到黏度最低的料浆,当固相含量为65%(体积分数)时,料浆的黏度仍然在1 Pa·s以下;与分散剂柠檬酸铵相比,在相同的周相含量和级配比例下,采用聚丙烯酸的科浆流动性更好.     

以聚硅氧烷乳液/聚丙烯酸铵为复合分散剂制备高性能氮化硅料浆

以聚硅氧烷乳液(S-17)/聚丙烯酸铵[poly(acrylic acid)ammonium,PAA-NH4]为复合分散剂制备了高浓度且稳定的Si3N4凝胶注模料浆,用电泳仪分析了料浆中颗粒表面zeta电位,用转子黏度计测量了料浆的黏度,用沉降法表征了Si3N4粉体的分散稳定性,用黏度法获得颗粒对聚硅氧烷分子的吸附等温线.研究了PAA-NH4分散剂和聚硅氧烷表面活性剂对高固相含量、低黏度料浆的稳定性影响机制.结果表明:单独使用PAA-NH4不能达到较好的稳定效果,采用聚硅氧烷乳液/PAA-NH4复合分散剂,聚硅氧烷乳液用量为0.4%(质量分数,下同),PAA-NH4为0.8%时,可制备固相体积含量为50%,黏度低于1.0 Pa·s,稳定性较高的料浆.该料浆适于凝胶注模操作.根据静电作用原理,结合颗粒对聚硅氧烷分子的吸附特性,提出通过降低液相表面张力来降低料浆黏度及提高稳定性,探讨了高固相含量料浆分散的理论机理.     

分散剂对ZrO2料浆及陶瓷性能的影响

分散剂是流延料浆中的关键组元.本文选用了3种分散剂(三乙醇胺、磷酸三丁酯、松油醇),通过对分散剂用量、pH值对ZrO2料浆性能的影响、素坯及烧结体密度、气孔率和收缩率等方面的研究,分析比较了分散剂对料浆及陶瓷性能的作用.实验结果表明:pH在10～12.5内,三乙醇胺对ZrO2粉体的分散用量少、料浆稳定,适于制备气孔少,致密度高的ZrO2固体电解质薄片.     

Aqueous processing of Ce0.8Sm0.2O1.9 green tapes

An aqueous tape casting of Ce_0.8Sm_0.2O_1.9 (SDC) ceramics was developed using poly(acrylic acid) (PAA) as dispersant, poly(vinyl alcohol) (PVA) as binder, poly(ethylene glycol) (PEG) as plasticizer, and deionized water as solvent. Surface properties of SDC powder with and without PAA dispersant were characterized by electrokinetic measurements. The rheology of the SDC slurries was evaluated with a rotary viscometer. The zeta potential measurement showed that the isoelectric point (IEP) for SDC powders in the absence of dispersant corresponds to a pH value of 3.66. The experimental results showed that the pH value greatly affects the rheology of the slurry. The optimum content to get a stable dispersed slurry is 2 wt% PAA in pH value range of 9–10. In presence of 2 wt% PAA dispersant, 55 wt% SDC powders exhibited shear thinning behavior, indicating that SDC slurry was homogenous and well stabilized. Homogeneous, smooth, and defect-free green tapes were successfully obtained by an appropriate slurry formula.     

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.     

3D printing of zirconia via digital light processing: optimization of slurry and debinding process

Digital light processing (DLP) is regarded as one of the most promising 3D printing technologies to process ceramics, however the precise composition of the slurry and the optimisation of the debinding process are still challenges that need to be overcome. In this work, both the dispersion and rheological behaviour of the zirconia slurry were studied using rheometery and UV-vis spectroscopy, and optimising the dispersant concentration was found to have significant benefits. Zirconia green parts were fabricated with zirconia slurry based on DLP technology, which exhibited good dimensional resolution under an exposure energy dose of 15 mJ cm^-2. In addition, the debinding process was studied using TGA and an optimised approach was designed and developed. Dye penetration and SEM results showed that debinding under argon, rather than flowing air, could lead to crack-free parts at heating rates of either 0.2 or 0.5 °C min^-1, though the former yielded slightly better results overall.     

Aqueous tape casting and crystallization kinetics of Ce0.8La0.2O1.9 powder

An aqueous tape casting of Ce_0.8La_0.2O_1.9 (LDC) ceramics was developed using PAA as dispersant, PVA as binder, PEG as plasticizer, and deionized water as solvent. Surface properties of LDC powder with and without PAA dispersant were characterized by electrokinetic measurements. The rheology of the LDC slurries was evaluated with a rotary viscometer. The zeta potential measurement showed that the isoelectric point for LDC powders in the absence of dispersant corresponds to a pH value of 4.02. The experimental results showed the pH value greatly affects the rheology of the slurry. The optimum content to get a stable dispersed slurry is 1.5 wt% PAA at pH value of 9–10. In presence of 1.5 wt% PAA dispersant, 5 wt% PVA binder, 5 wt% PEG plasticizer, and 55 wt% LDC powders exhibited shear thinning behavior, indicating that LDC slurry was homogenous and well stabilized. With an appropriate formulation homogeneous, smooth, and defect-free green tapes were successfully obtained. Moreover, the crystallization kinetics of LDC powders prepared by coprecipitation process also has been investigated in this study. The activation energy of crystallization was calculated on the basis of differential scanning calorimetry (DSC) at different heating rates. From non-isothermal DSC data presented values in the range of 343.3–379.1 kJ/mol and 2.282–2.030 for the activation energy of crystallization and the Avrami exponent, respectively, at specific temperatures ranging from 280 to 285 °C.     

Aqueous tape casting and crystallization behavior of gadolinium-doped ceria

An aqueous tape casting of gadolinia-doped ceria (GDC) ceramics was developed using Poly(acrylic acid) PAA as dispersant, Poly(vinyl alcohol) PVA as binder, Poly(ethylene glycol) PEG as plasticizer, and deionized water as solvent. Surface properties of GDC powder with and without PAA dispersant were characterized by electrokinetic measurements. The zeta potential measurement revealed that the isoelectric point for GDC powders in the absence of dispersant corresponds to a pH value of 4.06. The experimental results showed that pH value greatly affects the rheology of the slurry. Homogeneous, smooth, and defect-free green tapes were successfully obtained by using an appropriate slurry formula. Moreover, the crystallization kinetics of GDC powders prepared by coprecipitation process also has been investigated in this study. The activation energy of crystallization was calculated by differential scanning calorimetry (DSC) at different heating rates. Analysis of non-isothermal DSC data presented values of 105.3 kJ/mol and 1.171 for the activation energy of crystallization presented and the Avrami exponent, respectively.     

Alumina/zirconia ceramic membranes fabricated by temperature induced forming technique

It is well known that the fabrication technique of porous ceramic composites has a significant effect on their microstructure and properties. In the present study, alumina/zirconia ceramic composites doped with magnesia were fabricated by temperature induced forming technique using tri-ammonium citrate and polyacrylic acid (PAA) as dispersant and gelling agents, respectively. The zirconia content was up to 20 wt% and added at the expense of alumina while the magnesia content was up to 2 wt% over the total mass. The optimum amount of ammonium citrate tribasic needed for dispersing the ceramic slurry was determined by measuring zeta potential of slurries. The prepared green alumina/zirconia composites were subjected for solid state sintering at 1550 °C for 1 h. The densification parameters, phase composition, average pore diameter, microstructure and cold crushing strength of sintered alumina/zirconia ceramics were investigated by the suitable techniques. The results revealed that the addition of tri-ammonium citrate to ceramic slurries enhanced the zeta potential which reached ?28.3 mV by adding 1 wt.-%. The bulk density was decreased while the apparent porosity was increased with the increase of zirconia content. The apparent porosities of sintered porous composites were in the range of 38.8–48.5%. The average pore diameter for the composite containing 15% zirconia was 1.79 μm and pore volume was 0.11 ml/g. The obtained microstructure exhibited zirconia grains located on the grain boundaries of Al₂O₃ matrix. The existence of zirconia in addition to magnesia hindered the growth and deformation of the matrix. The cold crushing strength of porous composites was decreased from 16.0 to 8.5 to MPa by increasing the zirconia content from 5 to 20 wt.-%.     

淮化Texaco气化炉备选煤种所用水煤浆分散剂的遴选

研究了多种水煤浆分散剂对安徽淮化Texaco气化炉备选煤种成浆性能的影响。结果表明,萘系分散剂对煤种成浆浓度高、流动性好;木质素类分散剂对煤的成浆浓度较低,流动性较差。相较于分散剂而言,煤质是影响水煤浆成浆性能的最关键的因素。北宿煤的制浆浓度大部分都在65.0%以上,是制备气化用浆性能较好的煤种。满足实际生产能力的要求下,HH分散剂对华亭煤最高制浆浓度达60.5%,ZH分散剂对北宿煤最高制浆浓度达67.0%,对于不同的煤种,不可盲目追求性价比较高、广谱性强的分散剂。     

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。     

Dispersion and properties of zirconia suspensions for stereolithography

Stereolithography is an attractive technique for the fabrication of complex-shaped ceramic components with high dimensional accuracy. One of the challenges in this technology is the development of high solid loading, low viscosity photosensitive ceramic suspension. In this study, the dispersion of zirconia in photocurable resin and the slurry properties were intensively investigated. Rheological measurements showed that DISPERBYK-103 proved to be an effective dispersant. 42 vol% ZrO₂ suspension was successfully prepared using 3.5 wt% DISPERBYK-103 as the dispersant, with a suitable viscosity (4.88 Pa·s) below the maximum allowable viscosity value (5 Pa·s) for stereolithography applications. The adsorption behavior of DISPERBYK-103 on the surface of zirconia powders was characterized by TG and FT-IR, confirming the dispersion effect of dispersant. Contact angle measurements were also conducted to show that the adsorption of DISPERBYK-103 could help to improve the wettability between powder and photocurable resin. Results showed that DISPERBYK-103 was effective for the preparation of suitable slurries for the development of ZrO₂ ceramics through stereolithography.