成型压力对氧化铝瓷球性能的影响

研究了成型压力对瓷球烧结、密度及耐磨性的影响。结果表明：在本研究系统内随着压力的增加,瓷球的烧结温度下降,烧成温度范围拓宽。采用150MPa成型的瓷球的密度最大且耐磨性最好。     

Effect of Temperature on the Slurry Characteristics and Green Bodies of Alumina

The importance of temperature in colloidal processing was examined by investigating its effect on the characteristics of a ceramic slurry and on the subsequent processing before firing. An aqueous alumina slurry was used as a model system in the present study. The viscosity of the slurry was found to vary significantly with temperature, and the structure of the resultant green bodies made by centrifugation varied correspondingly. The importance of temperature in the production of ceramics is discussed in light of these results.     

Modeling of the Pressure Distribution in Three-Dimensional Porous Green Bodies during Binder Removal

A model is developed to describe flow in porous media from the thermal decomposition of binder in three-dimensional bodies with anisotropic permeability. The model is able to describe the pressure within the body as a function of position, time, and temperature during the heating cycle. The results from numerical solution of the un-steady-state partial differential equation are compared to those obtained from an analytical solution to the steady-state equation. Under many conditions that are representative of binder removal, the analytical solution provides a reasonable representation of the numerical solution. A criterion is also developed to determine when the analytical solution is valid. Scaling relationships for the buildup of pressure in terms of the dimensions of the body, the rate of reaction, and the permeability are also derived.     

Effect of Moisture on the Structure and Fracture Strength of Ceramic Green Bodies

To study independently the effects of moisture on the structure and the mechanical strength of the binder in green bodies, specimens of the system alumina/PVA were formed with spray-dried granules of various moisture contents. The structure and fracture strength of these specimens then were examined after their moisture contents had been adjusted to specified values. As moisture content increased in the granules during compaction, the density and strength of the green body also increased. The accompanying change in the fracture mode, from intergranular to transgranular, showed that the strength of the green bodies was affected more significantly by bonding between granules than by bonding between powder particles.     

复合乳液成膜过程中蒙脱土的结构研究

对丙烯酸酯／蒙脱土复合乳液干燥成膜过程中蒙脱土结构的变化进行了研究。利用冷冻干燥技术对不同成膜阶段的复合乳液进行了处理。TEM、XRD和SEM研究表明：蒙脱土的结构在复合乳液的成膜过程中有着显的变化，其在复合乳液中的层间距要大于成膜后的样品，成膜之后蒙脱土的结构特征很大程度上取决于复合乳液中水分干燥的方式。     

成形压力对氧化铝瓷球性能的影响

本文以不同的压力等静压成形瓷球，研究了成形压力对瓷球烧结温度、密度及耐磨性的影响。结果表明：在本研究系统内随着压力的增加瓷球的烧结温度下降，烧成温度范围拓宽。采用150MPa成形的瓷球密度最大且耐磨性最好。     

晶粒大小及孔结构对氧化铝陶瓷耐磨性的影响

利用扫描电子显微镜研究了氧化铝陶瓷中Al2O3晶体的大小、均匀程度和孔结构对氧化铝陶瓷耐磨性的影响,指出了采取有效措施控制Al2O3晶体长大和使微孔小而均匀是提高氧化铝陶瓷耐磨性的主要途径。     

阳极氧化工艺对氧化铝纳米孔膜形成过程及结构的影响

采用高纯度的铝片为阳极，以铂网为阴极，在3％～5％草酸溶液中，电压在30～70V，温度控制在17～25℃范围内进行恒压阳极氧化制备氧化铝膜，并采用环境扫描电镜观察纳米孔形貌，金相显微镜测量氧化膜厚度。研究了电解电压、电解液浓度、温度等条件对氧化铝多孔膜结构的影响。结果表明：氧化膜形成速度、纳米孔孔径、胞径、孔壁厚度、氧化膜厚度受电解电压影响显著，随着电解液浓度和温度的增大，氧化膜生长速度加快，纳米孔孔径、孔壁厚度等都随之增大，在相同时间内生成的氧化膜厚度增大。     

Effect of Liquid Content on the Abnormal Grain Growth of Alumina

Alumina specimens with small amounts of CaO and TiO₂ were prepared and their microstructural evolution during sintering was investigated. Because of the appearance of a liquid phase during sintering, a duplex microstructure of a few abnormal grains and fine matrix grains was obtained when the CaO + TiO₂ content was small (≤0.04 wt%). When the CaO + TiO₂ content was relatively high (≥0.1 wt%), many grains grew and impinged upon each other. As a result, a rather uniform and homogeneous microstructure was observed.     

密炼机的混炼时间对天然橡胶结构与性能的影响

研究了密炼机的混炼时间对天然橡胶结构与性能的影响。结果表明,随混炼时间延长,排胶温度升高且有加快的趋势,混炼胶的门尼黏度先变大后减小。混炼时间适度延长有利于炭黑的分散,但达到一定程度后影响变小。选择合适的混炼时间既能有利于炭黑的分散,又能保证较高的平均分子量,此时硫化胶综合物理机械性能最好。     

钛铁矿精矿替代氧化铈制备绿玻的研究

通过实验,研究了钛铁矿精矿替代车用绿色浮法玻璃着色剂后的各种性能,确定了Na2O-CaO-SiO2系统玻璃使用钛铁矿为着色剂时的用量比例.研究结果表明,钛铁矿作为车用绿色玻璃的着色剂可大大降低玻璃原料成本.利用钛铁矿替代氧化铈及部分红粉后可以得到与氧化铈作为着色剂时光学性能相同的玻璃样品.     

Effect of Calcination Conditions on Crystalline Structure and Pore Size Distribution for a Mesoporous Alumina

In this article, a mesoporous commercial alumina was calcined in the temperature range of 600°C–1200°C. The effect of several parameters such as calcination temperature, calcination time, heating rate, and calcination steps on phase transformation and crystal size was experimentally investigated. The characterization of the commercial mesoporous alumina and samples calcined at 1000°C, 1040°C, 1070°C, 1100°C, and 1200°C by single-step and multi-step calcination was performed using XRD and N₂ adsorption/desorption techniques. For the commercial mesoporous alumina, TG/DTA analysis was also performed. Experimental results showed that mostly pure α-Al₂O₃ was obtained at 1100°C.     

Green TPUs from Prepolymer Mixtures Designed by Controlling the Chemical Structure of Flexible Segments

This study concerns green thermoplastic polyurethanes (TPU) obtained by controlling the chemical structure of flexible segments. Two types of bio-based polyether polyols—poly(trimethylene glycol)s—with average molecular weights ca. 1000 and 2700 Da were used (PO3G1000 and PO3G2700, respectively). TPUs were prepared via a two-step method. Hard segments consisted of 4,4′-diphenylmethane diisocyanates and the bio-based 1,4-butanodiol (used as a chain extender and used to control the [NCO]/[OH] molar ratio). The impacts of the structure of flexible segments, the amount of each type of prepolymer, and the [NCO]/[OH] molar ratio on the chemical structure and selected properties of the TPUs were verified. By regulating the number of flexible segments of a given type, different selected properties of TPU materials were obtained. Thermal analysis confirmed the high thermal stability of the prepared materials and revealed that TPUs based on a higher amount of prepolymer synthesized from PO3G2700 have a tendency for cold crystallization. An increase in the amount of PO3G1000 at the flexible segments caused an increase in the tensile strength and decrease in the elongation at break. Melt flow index results demonstrated that the increase in the amount of prepolymer based on PO3G1000 resulted in TPUs favorable in terms of machining.     

煅烧温度对高岭土结构及其氧化铝浸出率的影响

对内蒙煤系高岭土的煅烧进行了研究。考察了煅烧温度对内蒙煤系高岭土结构及其氧化铝浸出率的影响。研究发现内蒙煤系高岭土在70 0～90 0℃煅烧,可以保持活性较高的偏高岭土结构,其中75 0℃左右煅烧后进行酸处理,可以获得高的氧化铝浸出率。     

Abnormal Grain Growth in Alumina with Anorthite Liquid and the Effect of MgO Addition

Abnormal grain growth (AGG) in alumina with anorthite liquid has been observed with varying anorthite and MgO contents, at 1620°C. When only anorthite is added to form a liquid matrix, the grain–liquid interfaces have either flat or hill-and-valley shapes indicating atomically flat (singular) structures. The large grains grow at accelerated rates to produce AGG structures with large grains elongated along their basal planes. This is consistent with the slow growth at low driving forces and accelerated growth above a critical driving force predicted by the two-dimensional nucleation theory of surface steps. With increasing temperature, the AGG rate increases. The number density of the abnormally large grains increases with increasing anorthite content. The addition of MgO causes some grain–liquid interfaces to become curved and hence atomically rough. The grains also become nearly equiaxed. With increasing MgO content the number density of the abnormally large grains increases until the grain growth resembles normal growth. This result is qualitatively consistent with the decreasing surface step free energy associated with partial interface roughening transition.     

Effect of Residual Strain on the Electronic Structure of Alumina and Magnesia

The reflectance spectra of polycrystalline Al₂O₃ and singlecrystal MgO, with different surface treatments were measured using vacuum ultraviolet (VUV) spectroscopy to determine the effect of residual stresses and strains. The bulk stresses were estimated using the R-line flourescence of trace Cr³⁺ in Al₂O₃. No grain-size dependence was observed for the residual thermal expansion anisotropy stresses in polycrystalline Al₂O₃. The effects of mechanical-polishing-induced damage in Al₂O₃ shifted the band-to-band and exciton transitions to higher energies, compared with those of chemically polished Al₂O₃. There was little difference in peak positions between cleaved and chemically polished surfaces of MgO. However, mechanically polished MgO surfaces exhibited band-to-band and exciton-peak shifts to higher energies. The VUV technique of determining the exciton-peak and band-gap shifts was used with knowledge of the band-gap strain coefficient to estimate the magnitudes of residual surface stresses in the 1-μm surface layer probed. The polishing-damage-induced residual surface stress is 2.2 GPa for Al₂O₃ and 1.1 GPa for MgO. These values are based on band-gap strain coefficients of 700 meV/(lin% strain) derived for Al₂O₃ and 400 meV/(lin% strain) estimated for MgO.     

多组分组合作用下Al2O3掺杂对阿利特结构及活性的影响

采用X射线衍射结合Rietveld方法、热释光及微量热分析,研究了在Na、K等熟料阿利特中常见固溶组分作用下,Al2O3掺杂对阿利特结构、缺陷及水化活性的影响。结果表明:约1/3Al取代Ca,2/3Al取代Si;少量Al2O3即可将阿利特稳定为M3型,且M3晶格常数随Al2O3含量增加呈线性变化,直至达到Al2O3固溶极限1%(质量分数),符合Vegard固溶体定律;Al2O3进入阿利特,形成杂质缺陷,使其热释光性及水化反应动力学特征随之发生显著变化,且缺陷类型对水化的影响比浓度的影响更为显著;阿利特原始热释光强度与其水化反应活性大小一致,这与阿利特中以俘获电子形式亚稳储藏的能量有关。     

低温液体泵出口压力不上升故障的处理

介绍了低温液体泵的构造、工作原理以及在空分设备中的主要作用,分析其故障产生的原因,并提出排除故障的措施。     

有机添加剂对ZrO2流延生坯性能的影响

有机添加剂是流延料浆的关键组元,它们对料浆和流延生坯的性能有很大的影响.文章用流延法制备了YSZ电解质薄膜,并对生坯的力学性能进行了研究,分析了各有机添加剂对生坯力学性能的影响,最终提出了提高生坯及烧结体质量的方法.     

Effect of Aqueous Film‐Forming Foams on the Evaporation Rate of Hydrocarbon Fuels

A class of firefighting foams, known as aqueous film‐forming foam (AFFF), has the ability to form a film by spreading on the free surface of some hydrocarbon fuels. To find out whether this film could reduce the evaporation losses of volatile hydrocarbons, the evaporation rates of fuels covered with a film of AFFF were measured by weighing the fuel at different time intervals. The results proved that the addition of aqueous surfactant solutions on the fuels is not always synonymous to the reduction of evaporation rates, but sometimes it might also cause an increase. However, it was found that polyethylene glycol could modify AFFF in a way that it can form a protective permanent film on the surface of a fuel such as kerosene, thereby leading to a reduction of evaporation losses.