工艺参数对凝胶注模成型ZrO_2料浆性能的影响

以亚微米级ZrO2粉体为原料,采用丙烯酰胺(AM)/N,N-亚甲基双丙烯酰胺(MBAM)凝胶体系,通过凝胶注模成型工艺制备低粘度、高固相含量的ZrO2料浆。探讨了分散剂用量、料浆pH值、固相含量及研磨时间等工艺参数对ZrO2料浆性能的影响。用Zeta电位仪、粘度计和流变仪分别对料浆的Zeta电位、粘度值和流变学特性曲线进行测定。结果表明,A型分散剂(聚丙烯酸盐)用量为ZrO2体积的2%~2.5%时,对超细ZrO2粉体分散效果最佳,其料浆pH值以10~11为宜,研磨时间控制在12~15h,料浆固相体积分数可达50%~54%。     

海藻酸钠稳定Al2O3—ZrSiO4注浆料的研究

本文以海藻酸钠(SA)为分散剂制备Al_2O_3—ZrSiO_4料浆.通过对悬浮体PH值、SA加入量与粘度和Zeta电位关系的研究,确定了最佳工艺条件,制得浇注性能良好,固相浓度为68wt%的浆料,并通过注浆成型获得性能良好结构均匀的氧化铝—莫来石—氧化锆复合烧结体.     

SiC浆料的流变性能研究

为制备结构均匀的多孔SiC陶瓷的料浆,本文比较了不同质量分数(40%~60%)的SiC浆料的剪切应力和黏度随剪切速率的变化.结果表明:浆料的等电点在3.6左右,Zeta电位值随着pH值的增加而减小,碱性环境下分散效果更好;用Casson方程拟合浆料的剪切应力,相关系数在0.98以上,随着固相含量的增加,拟合的极限粘度和屈服应力增加;当剪切速率达到100 s-1时,固相含量为40%~55%浆料的粘度都在1 Pa·s以下,固相含量为60% 的浆料粘度大概是2.1 Pa·s.     

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％.     

注浆成形制备氮化硅陶瓷

研究了分散剂加入量、固含量、球磨时间、料浆pH值等因素对以氧化铝、氧化钇为烧结助剂的氮化硅料浆的粘度及注浆生坯密度的影响情况，并作了分析讨论。制备出生坯密度高达2．25g/cm^3的生坯。     

凝胶注模成型制备SiAlON-SiC材料料浆的流变特性

以Al粉、Si粉、SiO2 微粉和粗细两种粒度的SiC为原料 ,利用凝胶注模成型技术制备了SiAlON与SiC的质量比为 1∶3的SiAlON -SiC材料 ,研究了其料浆的 pH值、固相体积分数以及分散剂加入量、环境温度等因素对料浆流变特性的影响。结果表明 :当原料料浆的球磨时间在 80min左右 ,pH值为 8.5 ,固相体积分数为 54 % ,分散剂加入量为 0 .6 % (质量分数)时 ,该料浆的流变特性最佳     

ZrB_2-SiC复相陶瓷的注浆成形与无压烧结

研究了ZrB2-SiC复相陶瓷的注浆成形技术,着重讨论了pH值和固相体积含量对料浆粘度的影响;分析了注浆成形后,生坯断面的显微结构以及相对应的烧结体的显微结构。结果表明:ZrB2原始粉料的研磨处理有利于复相陶瓷制品的烧结致密化。当pH值为11时,可制得固相体积含量为50%,粘度为660mPa.s的ZrB2-SiC浆料。     

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.     

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.     

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.     

High solid loading,low viscosity photosensitive Al2O3 slurry for stereolithography based additive manufacturing

Photosensitive Al₂O₃-resin slurries with high solid loading, low viscosity used for stereolithography based additive manufacturing were prepared in this paper. The dispersion behavior and rheological behavior of the Al₂O₃-resin slurries were studied by rheology observation and sedimentation tests. The dispersant type, concentration and solid loading had significant effects on the rheological behavior and stability of the photosensitive Al₂O₃-resin slurries. A long term stability and homogeneity slurry was obtained when the dispersant and concentration were KOS110 and 5?wt%, respectively. The Al₂O₃ slurry prepared with a high solid loading up to 60?vol%, low viscosity of 15.4?Pa?s at 200?s^?1 was chosen for stereolithography based additive manufacturing.     

Preparation of dense 0.9Al2O3−0.1TiO2 ceramics with highly improved microwave dielectric properties by a noncontaminated DCC method

In this paper, dense 0.9Al₂O₃ ??0.1TiO₂ ceramics with highly improved microwave dielectric properties were prepared by a noncontaminated direct coagulation casting (DCC) method. The suspension was destabilized and coagulated by consumption of the dispersant without introducing impurity ions. The effect of dispersant content, pH value and solid loading on the rheological properties of 0.9Al₂O₃ ??0.1TiO₂ suspension was investigated. It was found that 0.9Al₂O₃ ??0.1TiO₂ suspension with a high solid loading of 50?vol% and low viscosity of 0.7?Pa?s could be prepared by adding 0.5?wt% TMAOH at the pH in the range of 10–12. The suspension was coagulated by adding 2?vol% GDA when it was treated at 60 ~ 80?°C for 40 ~ 60?min. Compared with dry pressing method, more homogeneous and denser microstructure could be obtained in 0.9A1₂O₃ ??0.1TiO₂ ceramics prepared by DCC via dispersant reaction which were sintered at 1550?°C for 3?h and annealed at 1100?°C for 5?h. The Al₂TiO₅ second phase in 0.9A1₂O₃ ??0.1TiO₂ ceramics prepared by DCC via dispersant reaction could be eliminated more easily by annealing treatment. After annealing treatment, only Al₂O₃ and TiO₂ phases could be detected. Therefore, higher density and much better microwave dielectric properties with ρ?=? 3.81?±?0.02?g/cm³, ε_r =?12.17?±?0.02, Q ×?f =?25,637?±?749?GHz, τ_f =?13.12?±?1.62?ppm/°C were obtained by DCC via dispersant reaction, and the Q ×?f value almost improved by 25%. Without introducing impurity ions, it provides a new insight into preparing complex shaped function ceramics with high properties.     

Alumina/MWCNTs composites by aqueous slip casting and pressureless sintering

Slip casting of stabilized aqueous suspensions followed by pressureless sintering was used for preparation of dense Al₂O₃/MWCNTs composites. The suspensions were stabilized by commercial polyelectrolyte dispersant Darvan C–N. In order to increase the stability, the pH value of the suspension was adjusted to ∼10. At this pH the highest ζ-potential values of the alumina powder and of the MWCNTs functionalised in boiling nitric acid were achieved. Two different agents, namely ammonium hydroxide and sodium hydroxide, were used for the pH adjustment. Their influence on the viscosity of suspensions and on consolidation and densification behaviour of the Al₂O₃/MWCNT composites was evaluated. The effect of ammonium hydroxide was more pronounced, as confirmed by lower viscosity of the suspension, higher sintered density, and fine-grained microstructure of the sintered composites. The Al₂O₃/t-MWCNTs composites with 0.1 wt% of the MWCNTs, with 99.9% relative density, the mean size of alumina grains ∼1 μm, and homogeneously distributed carbon nanotubes were prepared by the pressureless sintering at 1500 °C.     

纳米Cu分散稳定性能影响因素及作用机理研究

鉴于粉体分散对纳米流体强化传热具有重要意义,通过测定纳米Cu-水悬浮液的Zeta电位和吸光度,探讨了不同pH值、不同分散剂种类及质量分数对纳米Cu-水悬浮液分散稳定性的影响,并分析其作用机理。结果表明:Zeta电位绝对值与吸光度有良好的对应关系,Zeta电位绝对值越高,吸光度越大,则体系分散稳定性越好;pH值、分散剂种类及加入量是影响纳米Cu-水悬浮液分散稳定性的主要因素。pH值为9.5左右时,体系Zeta电位绝对值和吸光度较高,相应分散稳定性较好。CTAB和SDBS能显著提高水溶液中Cu表面Zeta电位绝对值,增大了颗粒间静电排斥力,改善了悬浮液稳定性,而TX-10通过空间位阻在颗粒表面形成良好的水化膜,提高了Cu在水溶液中的分散稳定性。在质量分数为0.1%的纳米Cu-水悬浮液中,TX-10,CTAB,SDBS 3种分散剂加入质量分数分别为0.43%,0.05%,0.07%时,均能得到分散稳定的悬浮液体系。     

ZrO2(3Y)包裹Al2O3纳米复合粉体的制备

以pH值缓冲溶液为沉淀剂,用非均匀成核和液相共沉淀相结合的方法合成出了ZrO₂（3Y）包裹Al₂O₃纳米复合粉体.用XRD、TEM对所制备粉体进行了表征.研究表明：加入分散剂使Al₂O₃悬浮液的等电点向酸性区移动,Zeta电位绝对值增大,其中pH值为9.56对应的Zeta电位绝对值最大,悬浮液最稳定.Al₂O₃悬浮液pH值为9.5,ZrOCl₂和YCl₃混合溶液浓度为0.2 mol•L^-1时前驱体的收得率最高.600℃煅烧后得到的粉体中只有α-Al₂O₃、t-ZrO₂两种物相,在Al₂O₃颗粒表面附着10 nm左右的ZrO₂（3Y）颗粒.     

Effects of sintering additives on dispersion properties of Al2O3 slurry containing polyacrylic acid dispersant

The effects of sintering aid adsorption on the dispersion properties of aluminum oxide slurries were investigated. We considered Al₂O₃ slurry without additives and Al₂O₃ slurry with a Mg additive with 0.1 mass% in oxide equivalent as a sintering aid. In this study, we evaluated the adsorption isotherm of polyacrylic acid (PAA) onto Al₂O₃ and the dispersion degree of Al₂O₃ slurries in sedimentation tests under gravity. The adsorption isotherm featured a characteristic adsorption isothermal line with a maximum value when Mg additive was present in Al₂O₃. In addition, the packing fractions did not correspond to the apparent viscosity. However, in slurry that was allowed to settle for several days, both of them agreed.Therefore, the disagreement between the packing fraction and the apparent viscosity immediately after preparation arose from changes of the dispersion state, such as the decrease of the distance between particles with time.     

YAG ceramic processed by slip casting via aqueous slurries

Stable YAG (Y₃Al₅O₁₂) aqueous slurry with ammonium polyacrylate (NH₄PAA) polyelectrolytes as dispersant was prepared by ball mill method. The effects of polyelectrolyte concentration and pH value on the stability of the suspension is described here, and the stability maps are constructed at different pH value and polymer concentration. The rheological behavior of YAG slips of different solid loading (60–70%) has been studied by measuring their viscosity and shear stress as a function of shear rate and pH of the slurry. An optimal amount of dispersant and pH value for the suspension was found. YAG suspension displays a maximum in zeta potential values and a minimum viscosity in pH range of 9–11. Slips behaved as near Newtonian at the pH value up to a solid loading of 60 wt% and as non-Newtonian with thixotropic behaviors above this solid loading value. The density and the green as well as sintered microstructure of the cast products bear a direct relationship to the state of this slips induced by the alternation in the pH and the concentration of the dispersant as well as solid loading.     

Effect of Al2O3 nanoparticles on the electrochemical characteristics of P(VDF-HFP)-based polymer electrolyte

Alumina (Al₂O₃) nanoparticles have been used as fillers in the preparation of poly(vinylidenefluoride-co-hexafluorpropylene) (P(VDF-HFP))-based porous polymer electrolyte. The degree of crystallization of polymer film filled with Al₂O₃ nanoparticles decreases with increase of the mass fraction of Al₂O₃ nanoparticles and the amorphous phases of polymer film expand accordingly. The Al₂O₃ nanoparticles play the role of solid plasticizer for polymer matrix. Nevertheless that excessive Al₂O₃ nanoparticles existing in polymer matrix leads to micro-phase separation between polymer matrix and fillers. As a result, both ionic conductivity and lithium ions transference number reduces whereas the activation energy for ions transport increases. When the polymer film is filled with 10% of the mass fraction of Al₂O₃ nanoparticles, polymer electrolyte possesses the ionic conductivity up to 1.95 × 10⁻³ S cm⁻¹ and the lithium ions transference number to 0.73 while the activation energy for ions transport of them falls to 5.6 kJ mol⁻¹. Effect of Al₂O₃ on the electrochemical properties of polymer electrolyte has been investigated in this paper. Analysis of FTIR spectra shows that there is the interaction between Al₂O₃ nanoparticles and polymer chains.     

Tape casting of aqueous Al2O3 slurries

The well-dispersed aqueous Al₂O₃ slurries suitable for tape casting were prepared, the effects of the concentration of dispersant, of the pH value, of solid content etc. on the properties of slurries were investigated, and the results indicated that the rheological of slurries was effected greatly by pH value and organic additives. After cutting, laminating and binder removal, the laminated Al₂O₃ green bodies were sintered by hot-press in a vacuum furnace. SEM micrographs showed that the microstructure of the aqueous green-body and samples were different from that of non-aqueous, and the mechanical properties of aqueous Al₂O₃ samples were much high than that of non-aqueous Al₂O₃.     

Effect of Polyacrylic Acid Addition on Rheology of SiC‐Al2O3‐ZrO2(3Y) Mixed Suspensions

A suspension with good rheology and high stability is crucial for slip casting and gelcasting technology. However, a mixed suspension from two or more different powders usually has bad rheology because of the easy agglomeration of mixed powders caused by the attractive force between the powders with heterocharges. We studied the surface modification of the each single‐component powders (SiC, Al₂O₃, ZrO₂(3Y) powders) and the SiC‐Al₂O₃‐ZrO₂(3Y) mixed powders to increase the repulsive force by adjusting the pH value and adding polyacrylic acid (PAA) as dispersant. The PAA addition effects on the SiC‐Al₂O₃‐ZrO₂(3Y) mixture were investigated in terms of zeta potential, pH range for heterocharge region, dispersion of the mixed powders and rheology of the mixed slurry based on the study of each unary suspensions. The results show that before surface modification the SiC‐Al₂O₃‐ZrO₂(3Y) mixed powders were agglomerated severely because they were in the heterocharge region with a broad pH range from 3.5 to 8.25, while after surface modification (pH = 10.5, PAA = 0.8wt%) the heterocharge region was narrowed with a relatively narrower pH range from 2.6 to 3.7. The mixed powders with homocharges were dispersed well because of the great electrostatic repulsive force and steric hindrance offered by PAA and the mixed suspensions had favorable rheology.