水溶性环氧树脂为凝胶体系的SiC凝胶浇注成型

研究了以水溶性环氧树脂为凝胶体系的SiC凝胶浇注成型,考察了水溶性环氧树脂对SiC浆料枯度和固化过程流变特性的影响.通过与丙烯酰胺体系的比较表明:水溶性环氧树脂导致浆料粘度增加,但可以制备固含量接近54%(体积含量,下同)的SiC浆料,粘度为1.25Pa·s(100s-1);以环氧树脂体系固化后的坯体强度较高,可以制备大尺寸或精细结构的SiC坯体;以橡胶模具浇注的SiC坯体结构完整、不失真.     

PEG对双组分AM-MBAM-YSZ凝胶打印浆料性能的影响

通过在水基AM-MBAM-YSZ浆料中加入水溶性高分子PEG,并将可反应单体与引发剂分离,制备了固相含量为52vol%,室温下可稳定储存数天、混合后固化可控的双组份打印浆料.浆料粘度为11.2 Pa·s(剪切速率100 s-1),屈服应力为510.7 Pa,浆料打印的线条尺寸均匀、边缘平整,坯体表面无剥离,烧结后显微结构均匀致密.打印线条烧结后的相对密度为99.3%,圆柱试样烧结后的相对密度为95.6%.     

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.     

苯乙烯-马来酸酐共聚物表面改性SiC浆料的流变性研究

通过自由基聚合反应,合成了含有苯乙烯-马来酸酐共聚物的改性剂.通过表面改性将上述改性剂接枝在粉体表面,研究了不同因素对改性SiC浆料流变特性的影响.结果表明,表面改性使SiC浆料的粘度显著降低,且浆料呈现出近似Newton流体行为.通过控制影响改性SiC浆料流变性的因素,在改性剂中WD-20与SMA配比为1:1,改性剂用量为1、wt%,pH=9,加入分散剂TMAH的量为0.6wt%的条件下,成功地制备出了固相含量为58vol%,粘度低于1Pa·s的SiC陶瓷浆料.     

氧化锆陶瓷注凝成型浆料流变性研究

陶瓷浆料流变性能是注凝成型工艺的关键,注凝成型要求浆料固含量高,粘度低.本文主要研究了固相含量、浆料pH值、分散剂、交联剂、单体等在制备低粘度高固含量氧化锆陶瓷浆料时,对浆料流变性的影响.实验结果表明:控制浆料的pH值为10左右,加入0.3wt％聚丙烯酸铵作为分散剂、1 wt％ AM作为单体,单体和交联剂比例为20∶1时,可制得粘度为2.12 Pa·s、流动性好适宜于复杂形状制品注模的陶瓷浆料.     

苯乙烯-马来酸酐共聚物表面改性SiC浆料的流变性研究

利通过自由基聚合反应,合成了含有苯乙烯-马来酸酐共聚物的改性剂。通过表面改性将上述改性剂接枝在粉体表面,研究了不同因素对改性SiC浆料流变特性的影响。结果表明,表面改性使SiC浆料的粘度显著降低,且浆料呈现出近似Newton流体行为。通过控制影响改性SiC浆料流变性的因素,在改性剂中WD-20与SMA配比为1∶1,改性剂用量质量分数为1%,pH=9,加入分散剂TMAH的质量分数为0.6%的条件下,成功地制备出了固相体积分数为58%,粘度低于1Pa·s的SiC陶瓷浆料。     

几种因素对刚玉-尖晶石复合浆料粘度的影响

研究了分散剂 (包括AN - 2 0 0 0、聚丙烯酸铵、三聚磷酸钠以及质量比为 1 1的三聚磷酸钠和六偏磷酸钠 )、浆料固相体积含量及助烧剂电熔镁砂细粉对刚玉 -尖晶石浆料粘度的影响。研究结果显示 :AN - 2 0 0 0对该复合浆料具有最佳的分散效果 ;添加 0 .5 %的AN - 2 0 0 0可制得固相体积含量为 5 7%的刚玉 -尖晶石浆料 ,该浆料在剪切速率为 5 0s- 1时粘度为 0 .37Pa·s ;为制备高固相体积分数的刚玉 -尖晶石浆料 ,电熔镁砂的添加量以小于 0 .7%为宜     

氧化锆水悬浮液的分散

通过考察多元共聚物分散剂对氧化锆zeta电位和浆料流变性的影响,研究了氧化锆浓悬浮液的分散性.结果表明: 多元共聚物分散剂的加入增加了氧化锆zeta电位的绝对值,等电点移至2.4以下.随分数剂加入量的增加,悬浮液的流变性出现复杂的情况:低剪切速率下(100s-1以下),悬浮液粘度略微增加;高剪切速率下(100s-1以上),悬浮液的粘度明显降低;4种分散剂中,二元共聚物分散的氧化锆浆料流动性最好,加入质量分数为0.14%,pH值为9.6左右.并制备了体积分数54%的氧化锆浆料,粘度为0.91Pa·s(100s-1).     

氧化锆、不锈钢复合粉体浆料流变性的研究

初步探索金属-陶瓷复合粉体浆料的粘度与浆料的pH值、分散剂含量、固体含量之间的关系,制备出高固体含量(体积分数为40%)、低粘度(0.32Pa·s)的氧化锆、不锈钢复合粉体浆料.     

PZT压电陶瓷浆料注凝成型中的分散和聚合反应

为得到凝胶注模成型所需的高固相低粘度的锆钛酸铅压电陶瓷浆料,进行沉降试验和流变性实验,研究了分散剂柠檬酸三铵、浆料pH值和固相含量对浆料粘度的影响,实验结果表明其分散剂最佳用量为陶瓷粉体质量分数1.5%～2.0%、浆料最佳pH值为10.0左右。此时,可制备粘度小于1Pa·s,体积分数为50%适于凝胶注模的稳定锆钛酸铅浆料。研究了聚合反应的影响因素,结果表明浆料pH对聚合反应有一定的影响。     

硅藻土光固化成型浆料和多孔陶瓷的制备

本文成功开发了用于光固化成型的树脂基硅藻土浆料,系统探讨了分散剂种类、含量及固含量对硅藻土浆料流变特性的影响,并对其作用机理进行了分析,获得了用于光固化成型的高固含量、低黏度的硅藻土浆料,并采用3D陶瓷光固化设备制备了结构复杂的硅藻土多孔陶瓷。结果表明,BYK2009为硅藻土浆料的最佳分散剂,且当分散剂相对粉体质量为3%时,浆料黏度最低。成功制备出粉体体积分数为40%的硅藻土浆料,在剪切速率为30 s^-1时,硅藻土浆料黏度为17.30 Pa·s。在900 ℃烧结时得到显气孔率为51.30%、抗弯强度为(46.28±2.63) MPa的硅藻土多孔陶瓷。本研究为光固化成型具有复杂多级孔结构的硅藻土载体提供了参考。     

不同工艺条件下PS/ScCO2均相体流变特性研究

通过建立含有类似锥板流变仪结构的实验平台对不同的温度、压力、剪切速率以及CO2质量分数等工艺条件下聚苯乙烯(PS)/超临界CO2(ScCO2)均相体的流变性能展开研究。结果表明:压力的升高会增加均相体的黏度,压力由7.5 MPa升高到10.5 MPa时,CO2质量分数为0.5%的均相体黏度增加了140 Pa s,约为原来的4.6%;增加温度则会降低均相体黏度,而且随着温度的升高,黏度的下降趋势在逐渐减小,温度从443.15 K逐渐增加到473.15 K时,CO2质量分数为0.5%的均相体黏度的减少值分别为778,482,327 Pa s;当均相体中CO2质量分数逐渐增加时,其黏度变化呈线性下降,CO2质量分数每升高0.1%,均相体黏度下降约为52 Pa s;加大剪切速率可以大幅度降低均相体的黏度,当CO2质量分数为0.5%的均相体在剪切速率从(120/π)/s增加到(240/π)/s时其黏度下降趋势最大,值为40%。     

Observation of Particle Motion in High‐Concentration Ceramic Slurries Under Low Shear Rate

The dispersed state of particles in high‐concentration slurries has a significant effect on the development of the particle packing structure of the powder compact. We observed individual particle motion directly in highly concentrated ceramic slurries under slow flow through confocal laser scanning fluorescent microscopy using transparent slurries. In particular, we focused on particle motion soon after the application of a constant low shear rate. Measurements of the shear stresses indicated that the stress of a 30 vol% slurry gradually increased from 0.018 Pa over time, whereas the stress of a 40 vol% slurry soon reached 0.03 Pa and remained constant. For direct observation, shear stress was applied to the slurry, which was set between two glass plates, by moving one unilateral glass plate at 0.8 μm/s, to create a shear rate of 0.01 s^?1. The motion of the particles could be observed continuously. In the early stage, particles in the 30 vol% slurry near the moving plate were united as one body and did not alternate positions. Then, a speed incline developed gradually over time. For the 40 vol% case, the particles moved at the same time and together. Increases in the shear stress were caused by increased interaction when the particles were close together.     

生物质水煤浆流变特性研究

以福建无烟煤、水葫芦、添加剂等制备生物质水煤浆,研究了其流变特性。结果表明：添加3％～3．5％的水葫芦及1％的分散剂制得的生物质水煤浆粘度在0．8～1．2Pa·s之间,且稳定性较好。生物质含量提高,生物质水煤浆的粘度逐渐上升;分散剂含量为1％时,能够制得流变性较佳的生物质水煤浆;搅拌强度的增加能够使生物质水煤浆的粘度降低;当温度低于60℃时生物质水煤浆的粘度随温度升高而下降;当温度高于60℃时,生物质水煤浆的粘度随温度升高而上升。     

Thickness control and interface quality as functions of slurry formulation and casting speed in side-by-side tape casting

A novel method of co-casting called side-by-side tape casting was developed aiming to form thin functionally graded films with varying properties within a single plane. The standard organic-based recipe was optimized to co-cast slurries into thick graded tapes. Performed numerical simulations identified the stable flow beneath the blade with a shear rate profile independent of slurry viscosity as long as the slurry load in the casting tank was low. Thickness and interface shape could be well predicted if the rheological behaviour of slurries is known and the processing parameters are well-controlled. A well-defined steep interface was obtained by co-casting slurries with similar viscosities above 4000 mPas at a speed of 40 cm/min. The elastic properties of green tapes were proven to be defined by the binder concentration in the recipe formulation. The interfaces in graded tapes were shown to withstand high stresses identifying a good adhesion between side-by-side cast materials.     

水基纳米SiC复合料浆的流变性能和稳定性

引言 纳米复相碳化硅陶瓷是在多相复合碳化硅陶瓷基础上发展起来的-种新型碳化硅陶瓷材料,通过引人第二或第三纳米增强相来同时实现细晶结构、梯度残余应力场、裂纹桥联、自增韧等增强增韧机理,从而获得多强韧化机理协同强化碳化硅陶瓷,已成为碳化硅陶瓷的研究方向之一[1-4].其中,纳米增强相在碳化硅基体(包括料浆、复合粉体、陶瓷)中的分布是制备纳米复相碳化硅陶瓷的关键和前提之一[5].     

RHEOLOGICAL BEHAVIOR OF LOW-RANK COAL-WATER SLURRIES

The rheological behavior of low-rank coal-water slurries was studied using a Brookfleld Rheolog viscometer. A Sarpy Creek subbituminous coal from Montana, with particle sizes ranging from 0.044 mm to 0.223 mm, was used. The solids concentration in the slurry varied from 15 to 65 weight % and the temperature was maintained constant at 82°F. The rheological behavior of the slurry made from as received coal was compared with that of the slurry made from hot water dried coal

Coal-water slurries, made from both as received and hot water dried coal exhibited pseudoplastic behavior. The shear stress was found to be related to the shear rate by the power law model. As expected, the apparent viscosity was found to increase sharply with solids loading. It was also observed that the apparent viscosities of the slurries made from hot water dried coal were lower than those made from as received coal.     

RHEOLOGICAL BEHAVIOR OF LOW-RANK COAL-WATER SLURRIES

The rheological behavior of low-rank coal-water slurries was studied using a Brookfleld Rheolog viscometer. A Sarpy Creek subbituminous coal from Montana, with particle sizes ranging from 0.044 mm to 0.223 mm, was used. The solids concentration in the slurry varied from 15 to 65 weight % and the temperature was maintained constant at 82°F. The rheological behavior of the slurry made from as received coal was compared with that of the slurry made from hot water dried coal

Coal-water slurries, made from both as received and hot water dried coal exhibited pseudoplastic behavior. The shear stress was found to be related to the shear rate by the power law model. As expected, the apparent viscosity was found to increase sharply with solids loading. It was also observed that the apparent viscosities of the slurries made from hot water dried coal were lower than those made from as received coal.     

前驱物裂解法低温制备碳化硅陶瓷膜

将碳化硅(SiC)粉体和一定量聚碳硅烷(polycarbosilane,PCS)、蒸馏水、聚丙烯酰胺(polyacrylamide,PAM)、聚丙烯酸(polypropylene acid,PAA)混合球磨以制备水性SiC浆料并测定了SiC粒子的动电位及粘度;将浆料均匀涂在SiC支撑体上,在1100℃真空条件下烧成,制备了SiC陶瓷膜并测定陶瓷膜的孔径分布及纯水通量及观察其形貌.研究结果表明:涂膜所用的浆料在pH值为11左右时,SiC粒子动电位最大达到-40 mV,浆料表观粘度最小为20 mPa·s,制备的陶瓷膜孔径大小集中在1μm左右,纯水通量达40 m3/(m2·h).     

Effect of SiC powder on the properties of SiC slurry for stereolithography

Silicon carbide (SiC) is a kind of structural ceramics with excellent properties and it is widely used in industrial fields. Stereolithography (SL) is a potential additive manufacturing technique to fabricate fine complex SiC components, the resin-based SiC slurry with superior rheological and photo-polymerization properties is important for SL. In this paper, we investigated the influence of SiC powder on the properties of the SiC slurries for SL. The physical characteristics of SiC powder such as particle size, size distribution and appearance were tested and observed, and their influence on the dispersion, sedimentation and photo-polymerization property of the SiC slurry were investigated and discussed in detail based on their correlative theory, we finally prepared SiC slurry with superior rheological and photo-polymerization properties, and fabricated the fine complex SiC green body with low defects, high accuracy and high bending strength successfully. The SiC slurry with the solid content of 40 vol% was fabricated by the SiC powder with the median diameter D₅₀ ≈ 10.0 μm and a narrow particle size distribution, it is Bingham fluid with good fluidity and the viscosity of it is 464.40 mPa s under the shear rate of 51.08 s^?1, the cured SiC parts with Z – axis dimension change of 0.75% was finally fabricated, the three points bending strength of it is 50.18 MPa. Our research work provides some fundamental understanding of the SL technique for fabricating fine complex SiC components, explored a suitable way to fabricate high quality SiC green parts through SL, and offers some valuable references for preparing SiC slurry with superior rheological and photo-polymerization properties.