刚玉-尖晶石-铝酸钙悬浮液流变特性的研究

用NXS－11型旋转粘度计对刚玉－尖晶石－铝酸钙粉体与水组成的悬浮液流变特性进行了研究。试验结果表明：在适当的铝酸钙水泥加入量下,超细粉（＜2μm）／细粉（＜0．088mm）重量比为0．43时,采用聚磷酸盐分散剂并控制其加入量,可使刚玉－尖晶石质浇注料的基质具有最佳的流变特性。     

尖晶石对刚玉尖晶石质浇注料性能的影响

以烧结刚玉、活性氧化铝微粉、铝镁尖晶石、纯铝酸钙水泥为主要原料制备了刚玉尖晶石质浇注料,研究了添加不同粒度的尖晶石对刚玉尖晶石质浇注料流变性能、烧后永久线变化率、抗折强度、抗热震和抗渣侵蚀性等性能的影响.结果 表明,加入的尖晶石粒度越小,越有利于改善浇注料流变性,越有利于提高材料的烧结性能,降低材料的膨胀幅度,提高材料的强度.加入细小的甚至是微米级的尖晶石颗粒分散在基质中,隔离了材料中低融物相,提高了材料的抗渣侵蚀性能和抗热震性能.浇注料在钢包上的使用结果也表明,加入超细颗粒尖晶石有利于提高其使用寿命.     

尖晶石种类对刚玉-尖晶石浇注料性能的影响

采用板状刚玉颗粒（6～3、3～1、≤1 mm）及细粉（0.045 mm）、电熔尖晶石颗粒（≤1 mm）及细粉（0.045 mm）、烧结尖晶石颗粒（≤1 mm）及细粉（0.045 mm）、活性尖晶石微粉(d₅₀=1.82μm)、活性α-Al₂O₃微粉(d₅₀=1.68μm)、Secar 71水泥等原料制备了刚玉-尖晶石浇注料。研究了不同种类尖晶石（电熔尖晶石、烧结尖晶石、烧结尖晶石+活性尖晶石）对浇注料性能的影响。结果表明：1)在刚玉-尖晶石浇注料中引入不同的尖晶石对试样经110℃保温24 h烘干后的抗折强度和耐压强度影响不大,但采用电熔尖晶石能降低加水量,提高流动性,得到优良的施工性能;2)采用电熔尖晶石有利于材料的抗渣侵蚀性能,但在抗渣渗透性及抗热震性方面,烧结尖晶石更占优势;3)加入适量的活性尖晶石微粉可以弥补烧结尖晶石的不足,提高浇注料的可施工性能,但对抗热震性会产生一定负面影响。     

促凝剂对刚玉-尖晶石质喷射浇注料性能的影响

本文研究了促凝剂对添加尖晶石细粉和镁砂细粉的两种刚玉-尖晶石质喷射浇注料性能的影响,结果表明:添加镁砂细粉后,喷射浇注料的流变性能下降;通过四种促凝剂对刚玉-尖晶石质喷射浇注料性能的影响研究,发现加入促凝剂后,含镁砂的喷射浇注料增粘变稠的速度快,施工时附着率高;铝酸钠和氢氧化钠复合的促凝剂与两种有机物复合的促凝剂都能使喷射浇注料快速增粘变稠、凝结硬化,但含Na+促凝剂的引入,提高了材料中Na+的含量,降低了喷射浇注料的高温抗折强度、热震稳定性能、抗渣侵蚀性能和常温物理性能.     

以微孔刚玉-尖晶石骨料替代刚玉骨料制备刚玉-尖晶石浇注料

为提高钢包工作衬用刚玉-尖晶石浇注料的保温性能,以微孔刚玉-尖晶石骨料部分或全部替代同粒级的烧结刚玉骨料,制备了刚玉-尖晶石浇注料,对比研究了不同骨料对浇注料的体积密度、气孔率、力学强度、热导率、抗渣性等的影响。结果表明：采用微孔刚玉-尖晶石骨料部分或全部替代同粒级的烧结刚玉骨料制备的刚玉-尖晶石浇注料,其体积密度和热导率均明显降低,抗渣性能与传统烧结刚玉骨料制备的浇注料相当。将其用于钢包工作衬,有助于钢包减重,提高钢包保温性能。     

尖晶石加入量对刚玉-尖晶石浇注料性能的影响

以板状刚玉、尖晶石、氧化铝微粉和纯铝酸钙水泥为原料,研究了尖晶石加入量(质量分数分别为0、3%、6%、9%、12%、15%、18%)对刚玉-尖晶石浇注料性能的影响。结果表明:随着尖晶石加入质量分数在0～18%范围内的增加,试样的高温抗折强度和抗渣性能均逐渐改善;试样的抗热震性呈先下降后上升趋势,以尖晶石加入质量分数为9%时最差;试样1 550℃3 h处理后的冷态强度呈先上升后下降的趋势,以尖晶石加入质量分数为9%时最大。     

刚玉-尖晶石浇注料基质部分最佳配比研究

以致密电熔刚玉为骨料,研究了刚玉-尖晶石浇注料基质中电熔刚玉、电熔镁砂和烧结尖晶石细粉的配比关系,测试了材料的物理性能和抗渣侵蚀性能。结果表明：在电熔刚玉细粉与电熔镁砂细粉之比为72：28,尖晶石细粉加入量为15％时,材料具有合理的线变化率和良好的抗渣性能。     

白云石微粉对刚玉-尖晶石质浇注料物理性能的影响

以电熔白刚玉、电熔镁铝尖晶石、氧化铝微粉、白云石微粉以及铝酸钙水泥为主要原料,研究了白云石微粉加入量(质量分数分别为0、1.5%和3%)对刚玉-尖晶石质浇注料物理性能的影响。结果表明:加入1.5%白云石微粉对浇注料的线变化率影响不大,并能够明显提高浇注料800～1100℃烧后的冷、热态抗折强度,对1400℃烧后的冷、热态抗折强度影响不大,但1600℃烧后冷、热态抗折强度降低。加入3.0%的白云石微粉使各试验温度烧后浇注料的线变化率增大且不利于浇注料强度的提高。与1400℃烧后相比,1600℃烧后所有试样冷、热态强度均有所降低,而且随白云石微粉加入量的增加降低幅度增大。白云石微粉的加入能够明显提高刚玉-尖晶石质浇注料的强度保持率,但试样热震前后的抗折强度均明显降低。     

烧结尖晶石细粉加入量对刚玉-尖晶石浇注料性能的影响

为了改善刚玉-尖晶石浇注料的高温性能,以质量分数分别为10%的15~8 mm的白刚玉、58%的≤8 mm的白刚玉、5%的≤0.08 mm的白刚玉、14%的≤0.045 mm的白刚玉、9%的α-Al2O3微粉、4%的水泥制备了刚玉-尖晶石浇注料。在固定以5%(w)的≤0.048 mm的烧结尖晶石等量替代≤0.045 mm的白刚玉基础上,研究≤0.038 mm的烧结尖晶石等量替代≤0.045 mm的白刚玉的加入量(质量分数分别为1%、3%、5%和7%)对刚玉-尖晶石浇注料性能的影响。结果表明:烧结尖晶石细粉的添加可以改善材料的高温抗折强度和抗热震性能,并且在≤0.038 mm的烧结尖晶石细粉加入量为5%(w)时,试样的高温抗折强度最高,抗热震性最好。分析认为,刚玉在烧结尖晶石细粉中的固溶作用,对试样的高温性能影响较大。     

Effects of Several Factors on Viscosity of Alumina-spinel Slurries

1IntroductionSpinelismorestablethanaluminainoxidation ,al kali,salt,fusedmetal,slagandcarbonatmosphere .Inrecentyears ,moreattentionhasbeengiventoit .Andithasbeenwidelyusedinthefieldofinsulated materials ,high performanceceramicsandrefractories .Concentratedalumina spinelslurrieswithgoodfluid ityarecrucialtopreparealumina spinelcastables .Whethertheconcentratedslurrycanbeobtainedornothastightrelationshiptoitsrheologicalbehavior .Ingener al ,therheologicalbehavioroftheslurryisaffectedbyanumber…     

Titanium porous scaffolds from precursor powders: rheological optimization of TiH2 slurries

Titanium macroporous scaffolds were prepared from TiH₂ suspensions by reactive sintering, using inverse replication of a sacrificed polymer sponge. This work describes investigation on the rheological behaviour of TiH₂ suspensions with a maximum solid content of 45 vol.% in water. Stabilization of the suspensions was investigated by sedimentation tests and rheology measurements and optimized by using the proper concentration of dispersant and gelling agent.     

The effect of coal properties on the viscosity of coal-water slurries

Studies on coal-water slurries (CWSs) have been conducted for many years to replace fuel oil. In this research project, the effect of coal properties on CWSs have been investigated using two Turkish coals of different ranks and a Siberian bituminous coal. Physical, chemical and surface properties of coal samples were determined. Furthermore, adsorption tests were carried out in order to put forward the effect of additive adsorption on the viscosity of CWSs. Viscosity measurements were realized for CWSs of various solid ratios by weight that were prepared using coal samples having mean particle sizes of 19, 35 and 50 μm.     

Preparation of high solid loading and low viscosity ceramic slurries for photopolymerization-based 3D printing

In this study, high solid loading and low viscosity cordierite slurries are successfully developed for the first time for photopolymerization-based additive manufacturing. The processability of the slurries is mainly determined by their rheological properties and photocuring parameters. The slurry preparation involves the orthogonal optimization of compositions in order to achieve suitable viscosity, stability and homogeneity. The photocuring parameters of the as-prepared slurries, including penetration depth D_p and critical exposure E_c, are also determined experimentally. Results show that viscosity increases with reduction in particle size. A higher solid-volume fraction also results in an exponential growth in viscosity. As for the dispersant amount, a concentration of 5?wt% leads to the lowest viscosity. Particle size also play an important role in the solid loading capacity of the slurries, as results suggest that smaller particles improve performance. In terms of the photocuring behaviors, the addition of 2?wt% photoinitiator generates an optimal curing process. 40?vol% solid loading leads to the thickest curing depth for all slurries with different types of particle sizes. Finally, a cordierite part with a complex hollow structure and a fine resolution is successfully fabricated. The present study offers a material basis for the polymerization-based 3D printing of porous cordierite structures.     

阳离子双子表面活性剂C18-4- C18•2Br的流变性

对阳离子双子表面活性剂四亚甲基-1,2-双(十八烷基二甲基烷基溴化铵)(C18-4-C18.2Br)的流变特性进行了研究,考察了表面活性剂质量分数、水杨酸钠质量分数及温度对表面活性剂溶液黏度和黏弹性的影响。C18-4-C18.2Br溶液的黏度随着质量分数的增加而增加。随着水杨酸钠质量分数的增加,C18-4-C18.2Br溶液的黏度和黏弹性出现先增加后下降的过程。温度对C18-4-C18.2Br溶液的黏度有较大影响,水杨酸钠的加入可明显提高C18-4-C18.2Br溶液的抗温性。TEM结果表明,适量的水杨酸钠能够促进C18-4-C18.2Br胶束从球形向蠕虫状转变,过量的水杨酸钠又会使蠕虫状胶束向囊泡转变。     

Role of molecular structure of monosaccharides on the viscosity of aqueous nanometric alumina suspensions

The effect of molecular structure of d-galactose, d-mannose, d-glucose, 2-deoxy-d-glucose and 3-O-methyl-d-glucose on the viscosity of aqueous alumina nanoparticle suspensions was investigated by rheological measurements. The viscosity was found to be dependant on the molecular structure of these hexopyranoses. The research reveals that the orientation of primary and quaternary hydroxyl groups in a pyranose ring plays a crucial role in dispersing properties of monosaccharides. Moreover, the most important is the mutual orientation of these hydroxyl groups. Monosaccharides with axial and equatorial orientation of hydroxyl groups at first (C₁) and fourth (C₄) carbon atom in pyranose ring decrease the viscosity more than monosaccharides with two axial hydroxyl groups in these positions. Due to the differences in molecular structure of saccharides resulting in different shape of molecules and different compatibility to the water structure, the saccharides differ in ability to disturb water layers around alumina particles.     

Effects of inorganic fillers on the shear viscosity and fire retardant performance of waterborne intumescent coatings

In the present work, the effects of inorganic fillers on the fire retardant performance of waterborne intumescent coatings are investigated by thermogravimetry (TG), capillary rheometer, X-ray diffraction spectroscopy (XRD) and fire retardant test, etc. The TG results indicate that the thermal stability of vinyl acetate-vinyl ester of versatic acid copolymer (hereafter VAc-VeoVa) in VAc-VeoVa/Si–Al powder composite or in VAc-VeoVa/Halloysite nanometer-tube (HNTs) composite is improved mainly due to the release of the crystal water in Si–Al powder or HNTs. Capillary rheometer analysis results demonstrate that the VAc-VeoVa/HNTs composite melt possesses the highest shear viscosity, because of the large specific surface area of HNTs and the strong interaction force between HNTs and VAc-VeoVa. Weight loss difference (ΔT) of filler/ammonium polyphosphate (APP) composites show antagonism effects at 300 °C < T < 650 °C and synergistic effects at T > 650 °C. The fire retardant test results show the coatings using TiO₂/Si–Al powder/HNTs (8/1/1) as multiple fillers obtains an intumescent char layer with intumescent ratio of 28.14 and presents excellent fire retardant performance (3327 s). It is found that the high melt viscosity, resulted from the effect of inorganic filler, immobilizes the relaxation and rotation of polymer chain, restricts the intumescent behavior of the coatings, which leads to the formation of an intumescent char layer with lower intumescent ratio and the shortening of the fire retardant time. Moreover, the antagonism effect between filler and APP reduces the catalytic dehydration efficiency of pentaerythritol (PER) and VAc-VeoVa, which, as a result, also affects the final fire retardant performance of coatings.     

Experimental study on the time change in fluidity and particle dispersion state of alumina slurries with and without sintering aid

The time change of the fluidity and particle dispersion state of alumina slurries with and without a sintering aid were investigated. The apparent viscosity of the slurry was measured at certain intervals. The hydrostatic pressure of the slurry, which represents the particle dispersion state, was also measured. We showed that the pH value, adsorbed amount of dispersant, and Mg ion concentration of the slurry hardly changed with time even though the apparent viscosity of the slurry increased with time. We suggest that the time change in the apparent viscosity, that is, the behaviour in which the apparent viscosity of the slurry increased with time, occurs when the electrostatic repulsion force is insufficient to maintain the particle dispersion state for a long time, such as shortage in the dispersant to its saturated amount.     

A quantitative evalution of the photocatalytic performance of TiO2 slurries

This paper reports the results of a comparison between two TiO₂ photocatalysts that differ for particle size and absorption/scattering optical properties. The catalyst with larger particles and lower surface area performed better in the degradation of phenol than the specimen with smaller particles and larger surface area. Following carefully designed experiments, it is possible to assess the relative role of light absorption/scattering properties and catalyst-related efficiency by means of a basic kinetic model for the rate of photocatalytic reactions. Explicit relationships are derived in the framework of the steady-state approximation for the quantum yield as a function of one a-dimensional number collecting surface kinetic constants for charge carrier reactions at the interface, absorbed light and surface substrate concentrations. The dimensionality change to volume-defined quantities allows derivation of the explicit dependence of the quantum yield on substrate concentration and partition constants, catalyst concentration, and the rate of volumetric light absorption. Following this approach, the rate expression for slurry systems, valid in the absence of back reactions, is directly derived. Some further simplification of the rate equation for the case of low quantum yield regime leads to analytical relationships able to account for the dependence of the rate on catalyst concentration and absorbed light in the case of stirred and unstirred conditions. The reported properly designed experiments allow the estimation of catalyst-specific micro-kinetic constants.