凝胶注模成型SiAlON-SiC材料的烧结性能

以SiC、Si、SiO2 和Al为原料 ,采用凝胶注模成型工艺制备了SiAlON -SiC材料。研究了SiC的粒度组成、β SiAlON的设计组成 (z值 )及烧成温度等因素对SiAlON -SiC材料的烧结性能的影响。研究表明 :对于凝胶注模成型的SiAlON -SiC来说 ,当其β SiAlON的设计组成 (z值 )为 2 ,烧成温度为 1 5 70℃时 ,试样具有最佳的烧结性能 ;由两种粒度的SiC配成的试样比由单一粒度的SiC或 3种粒度的SiC配成的试样具有更好的烧结性能 ,所得试样具有最佳的体积密度、抗折强度和显气孔率     

影响凝胶注模成型SiAlON-SiC复相材料坯体性能的因素

选用Al粉、Si粉、SiO2 等活性原料与较大颗粒的SiC ,采用凝胶注模成型工艺制备了SiAlON-SiC复相耐火材料的坯体 ,并研究了有机单体、分散剂和引发剂的加入量以及催化剂、胶凝温度等因素对坯体性能的影响。最终 ,在有机单体AM加入量为 1.8% (质量分数 ,下同 ) ,交联剂MBAM加入量为 0 .6‰ ,引发剂过硫酸铵溶液的最佳加入量为 0 .9% (体积分数 ) ,胶凝温度在 6 0℃左右 ,不加催化剂的条件下 ,制备出了抗折强度达到 32MPa ,密度为 2 .5g·cm- 3的均匀致密的SiAlON -SiC复相材料坯体。     

凝胶注模成型制备SiAlON-SiC复相材料

以Al、Si、SiO2和SiC为原料,采用凝胶注模成型及氮气气氛下烧成的方法制备了SiAlON-SiC复相材料。对浆料的流变特性、坯体的性能及制品烧结性能进行了研究。     

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%。     

水基料浆凝胶注模法制备氧化锆陶瓷刀具的研究

本文采用水基料浆凝胶注模法制备出了高质量的氧化锆陶瓷刀具。解决了高固相体积分数水基料浆的配制、注模、凝胶固化和脱模操作等一系列问题。研究结果表明,其尺寸精度和表面质量良好。证实了水基料浆凝胶注模法制备氧化锆陶瓷刀具是一种新的低成本制备技术,值得推广应用。     

凝胶注模成型制备Si3N4-SiC材料

以SiC颗粒(3.36～0.15 mm)、SiC细粉(≤19μm)、改性Si粉(≤26μm)、改性Al粉、α-Si3N4粉为原料制成固相体积分数为75%的悬浮体,采用凝胶注模成型工艺和氮化烧成工艺制备Si3N4-SiC材料,并研究了SiC系悬浮体的流变特性以及氮化烧成后Si3N4-SiC材料的性能和显微结构。结果表明:1)悬浮体在切变速率10～160 s-1范围内表现出剪切变稀的特征,满足凝胶注模成型的要求;其流变特征符合Sisko模型,流变方程为η=4.625 4+2 172.9γ-0.450 3,拟合流变曲线与试验流变曲线基本吻合。2)脱模后湿坯的抗折强度为16 MPa,体积密度为2.57 g.cm-3;干燥后坯体结构致密,SiC大颗粒被Si粉和SiC粉均匀包裹。3)氮化烧成后试样的Si3N4含量、常温抗折强度和高温抗折强度均高于非凝胶注模成型的工业产品;Si3N4晶体发育完整,形成了Si3N4晶体紧密环绕SiC颗粒的均匀结构。     

硅酸锆凝胶注模成型工艺的研究

主要以降低ZrSiO4陶瓷浆料的粘度和提高固相含量为目的,利用正交实验研究了硅酸锆陶瓷凝胶注模成型工艺中固相含量、pH值和分散剂3个因素对料浆粘度的影响,并根据实验结果拟合出回归方程;同时通过电镜分析了坯体微观形貌的差异,制备出固相体积含量55%、粘度0.57Pa·s的硅酸锆陶瓷浆体,所得坯体微观结构均匀、团聚少.     

氧化锆陶瓷的凝胶注模成型研究

研究了氧化锆陶瓷凝胶注模成型工艺中单体、引发剂、固相含量、固化温度对料浆的凝胶固化时间的影响及坯体在干燥、烧成中的影响因素.     

凝胶注模成型制备Sialon陶瓷的研究进展

本文系统阐述了凝胶注模成型制备Sialon陶瓷的研究与进展,根据凝胶来源分成非水基凝胶注模体系和水基凝胶注模体系,介绍它们的工艺过程和原理。最后提出了凝胶注模成型制备Sialon陶瓷目前应当注意的问题,并展望了它的前景。     

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.     

Preparation of alumina by aqueous gelcasting

The alumina ceramic was prepared by aqueous gelcasting. The effects of zeta potentials, solid loading, dispersant content and milling time on the alumina suspension were studied systematically. The dispersant content has remarkable effects on the viscosity of the suspension. The appropriate dispersant concentration for alumina aqueous slurry with the solid loading of 55 vol.% is 0.6 wt.%. It can be seen that all suspensions (50–56 vol.% solid loading) exhibited a shear-thinning behavior and relatively low viscosity, which was suitable for casting. The degree of shear thinning and the viscosity at high shear rates increased with increasing volume fraction of solid. As the milling time prolongs, viscosity of the suspension decreases first, then the plateau appears and the average diameter keeps changeless. When the milling time was shorter than 20 h, the viscosity of slurries decreased gradually as the time of milling increased. After 20 h milling, the viscosity of the slurry tended to be consistent. Therefore, the ball milling time should be equal to or more than 20 h to obtain a stable suspension at equilibrium. The time available for casting the slurry (idle time) can be controlled by the amounts of initiator and catalyst added to the slurry as well as by the processing temperature. Micrograph of the gelcast green body was homogeneous.     

Effect of Sintering Additive on the Properties of Sialon-SiC by Gelcasting

Sintering additivesto gelcasting Sialon‘SiC were decided by the optimizing experiments , The resuhs show that Sialon-SiC can be sintered under 1450℃ and sintering temperature dcreases by 100℃，when 2%～3% TiO2 or Guangxi clay is used as sintering additive.     

Fractions design of irregular particles in suspensions for the fabrication of multiscale ceramic components by gelcasting

A new approach for the preparation of suspensions with a high solid loading and low viscosity by using irregular particles was proposed. These suspensions were prepared for the fabrication of multiscale ceramic components by gelcasting. Based on the Funk-Dinger function and fractal theory, the closest packing theory was applied to optimize the volume fractions of different particles. The maximum solid loading of slurries prepared for gelcasting was 62 vol%, and the viscosity at a shear rate of 100 s^?1 was only 0.29 Pa s. By as-prepared suspensions, a decimeter-scale ceramic part with submillimeter features was fabricated successfully by gelcasting, which verify the feasibility of the proposed method.     

Isobam assisted slurry optimization and gelcasting of transparent YAG ceramics

Gelcasting is a simple near-net shaping method to fabricate large-sized and/or complicated-structural ceramics. In this paper, a transparent yttrium alumina garnet (YAG) ceramic was successfully fabricated by gelcasting with a nontoxic, water soluble copolymer (isobutylene and maleic anhydride, Isobam) as both dispersant and gelling agent. The rheological behaviors of the slurries with different solids loading and Isobam contents were systematically investigated. The optimized slurry of 0.5 wt% Isobam and the solid loading of 68 wt% had the low viscosity and high stability, resulting in better homogeneity of the green body and better optical quality of transparent ceramics. A nearly pore-free structure of the sintered YAG ceramics with average grain size about 10.0 µm was obtained possessing an in-line transmittance of 75.7% at the wavelength of 1064 nm for a sample 2.5 mm thick.     

ZrO_2基陶瓷注凝成型料浆流变性的研究

陶瓷料浆流变性能是注凝成型工艺的关键,料浆流变性要求高固含量,低粘度。实验通过在ZrO2表面包覆A l2O3,形成ZrO2-A l2O3复相陶瓷料浆。根据静电位阻稳定理论,通过调节pH值和分散剂的加入量,可得到满足成型要求的高固含量,低粘度的料浆。结果表明,在pH值为10左右,分散剂加入量为粉料质量的3%时,料浆固相体积分数可以达到40%。同时表明了A l2O3对ZrO2颗粒表面有改性作用,提高了悬浮体的稳定性。     

超细二氧化锆注凝成形料浆流变性研究

研究了ZrO2凝胶注模成形工艺中制备低粘度、高固相含量浓悬浮体的关键技术。分析讨论了pH值、分散剂、研磨时间、固相含量等因素对ZrO2浆料粘度的影响。实验表明：pH值、分散剂用量均会明显地影响悬浮液的分散效果和流变性。在悬浮体系中当pH为10-11，分散剂添加量为1．5％（体积分数）时，研磨时间为20h时分散效果最好，并制备了固相含量达56％（体积分数）的浓悬浮液，粘度为308mPa·s，完全能满足凝胶注模成形的要求。     

凝胶成型Al2O3-(30vol%)MgO·1.35Al2O3泡沫陶瓷的研制

以板状刚玉和富铝尖晶石为主原料,采用泡沫浸浆凝胶工艺制备了Al2O3-(30 vol%)MgO@1.35Al2O3泡沫陶瓷.研究了分散剂AN-2000与pH值对Al2O3-(30vol%)MgO@1.35Al2O3混合浆料流变特性的影响.在pH值=9.5、AN-2000添加量为0.4 mL@m-2的条件下制备的粘度为O.14 Pa@s,固相体积分数为55%的Al2O3-(30vol%)MgO@1.35Al2O3混合浆料,通过有机泡沫浸浆、引发凝胶反应、湿坯干燥、排胶和烧结,制备出了气孔率为89.3%,强度为5.2 MPa的Al2O3-(30vol%)MgO@1.35Al2O3泡沫陶瓷.     

凝胶注模成型制备刚玉-尖晶石耐火材料

以板状刚玉颗粒和富铝尖晶石细粉为主要原料 ,以含丙烯酰胺 (AM)、N ,N’ -亚甲基双丙烯酰胺 (MBAM)和分散剂AN - 2 0 0 0的水溶液为预混液 ,制备出临界粒度为 3mm ,固相体积分数为 80 %的刚玉 -尖晶石混合浆料 ,加入引发剂过硫酸铵(APS)和催化剂N ,N ,N’ ,N’ -四甲基乙二胺(TEMED)快速搅拌混合 15s后注入钢模中 ,于 4 0℃引发凝胶反应 ,脱模后于湿度不低于 5 0 %的环境中干燥 4 8h ,再于 110℃干燥 2 4h ,然后在空气中于5 30℃以上排胶 ,再经 16 0 0℃保温 2h烧成。结果表明 :坯体的干燥强度达 11.6MPa ;烧成后试样的体积密度为 3.0 6g·cm-3 ,显气孔率为 16 .5 % ,耐压强度为 72 .5MPa ;烧成后试样基质中除了极少量的刚玉相外 ,其余的全为尖晶石相 ,在制备过程中没有被污染。     

Fabrication and properties of porous Si3N4 ceramics by aqueous gelcasting using low-toxic DMAA gelling agent

A low-toxic and water-soluble monomer N, N-dimethylacrylamide (DMAA) was employed as a gelling agent in the gelcasting of porous Si₃N₄ ceramics. The process conditions and composition for slurry preparation (with a solid loading of 36?vol%), the consolidation and sintering of green bodies were investigated and optimized. The effects of various factors such as zeta potential, pH value of the premix solution, dispersant dosage and ball milling time on the rheological properties of the slurries were investigated. The results suggest that the best rheological properties (66.5 mPa.s at a shear rate of 96.3?s^?1) of the slurries were obtained when pH value ranged between 9 and 11, dispersant dosage reached 1?wt%, and ball milling time was 6?h. All the as-prepared green bodies showed a homogeneous microstructure and high flexural strength ≥ 26?MPa with a maximum up to 46.3?MPa when the ratio of DMAA to MBAM, initiator dosage, polymerization temperature and time were 14, 1?wt%, 70?°C and 90?min, respectively. The sintered bodies had a homogeneous microstructure, excellent and regulatable properties, a flexural strength of 216.3–327.3?MPa, and a porosity of 39.6–29.1% by varying the sintering temperature from 1710?°C to 1810?°C and the holding time from 1?h to 3?h. The superior comprehensive effect makes DMAA a promising candidate for an environmentally friendly gelling agent in gelcasting of porous Si₃N₄ ceramics.     

The rheological behavior and surface charging of gelcasting alumina suspensions

Aim of this work is to investigate the effect of monomers containing either carboxylate (ammonium acrylate) or acrylamide (hydroxymethylacrylamide) functional groups on the surface charging and rheological behavior of alumina suspensions. The rheological behavior was investigated by changing the concentrations of dispersant (ammonium polyacrylate) and monomers in the suspensions. The zeta potential of alumina suspensions containing each of the different monomers was measured as a function of dispersant additions. The suspension rheological behavior varied significantly depending on the monomer type, which could be explained in terms of repulsive forces, pH changes and additive interactions.