以表面负载季铵盐阳离子型苯/丙乳胶粒为模板制备ZrO_2空心微球

以C9油与甲基丙烯酰氧乙基三甲基氯化胺的共聚物P(C9-DMC)为乳化剂制备苯/丙阳离子乳胶粒,并以其为模板,利用直接包覆法制备了由17 nm左右微晶体堆成的ZrO2空心微球。所制得的样品采用FT-IR、XRD、TEM和SEM等进行了表征。     

Preparation of submicrometer-sized titania hollow spheres by templating sulfonated polystyrene latex particles

Submicrometer-sized titania hollow spheres with tunable shell thickness and smooth surfaces have been successfully synthesized by employing sulfonated polystyrene (PS) latex particles as a template in sol-gel method. The structure of the particles was characterized by scanning electron microscopy and transmission electron microscopy. The shell thickness was readily tuned by altering the concentration of titanium tetrabutoxide (TBOT) in ethanol solutions. The surface roughness as well as the shell thickness has the tendency to increase with the increase in the concentration of TBOT. The diameter of the hollow spheres was on the average of 20-26% smaller than the diameter of template PS latex particles. Some titania fragments were also observed for the sample with the highest TBOT concentration.     

Granular gases in mechanical engineering: on the origin of heterogeneous ultrasonic shot peening

The behavior of an ultrasonic shot peening process is observed and analyzed by using a model of inelastic hard spheres in a gravitational field that are fluidized by a vibrating bottom wall (sonotrode) in a cylindrical chamber. A marked heterogeneous distribution of impacts appears when the collision between the shot and the side wall becomes inelastic with constant dissipation. This effect is one order of magnitude larger than the simple heterogeneity arising from boundary collision on the cylinder. Variable restitution coefficients bring the simulation closer to the general observation and allow the investigation of peening regimes with changing shot density. We compute within this model other physical quantities (impact velocities, impact angle, temperature and density profile) that are influenced by the number N of spheres.     

填充HDPE复合材料基体结晶形态的控制因素

本文以HDPE/玻璃微珠和HDPE/CaCO₃体系为研究模型,通过扫描电镜、红外光谱、偏光显微、小角激光散射和材料力学性能实验等方法考察了这两种体系的界面粘结性、填料含量、粒径及试样成型冷却速率等与其材料性能及基体结晶形态变化间的关系。实验结果表明;在复合材料试样成型过程中,因基体树脂冷却收缩而产生的界面应力可干扰基体中球晶的生长环境,应变诱导填料颗粒周围基体树脂的结晶,促使其表面伸展链晶体结构的形成,并由此而明显改变了复合材料的耐热性;复合材料的界面粘结性是产生这种应变诱导作用,并控制异相结晶的关键。     

Drag on two co-axial rigid spheres moving normal to a plane: Newtonian and Carreau fluids

The boundary effect and the presence of a nearby entity on the drag of a rigid entity is investigated by considering the movement of two identical, rigid, coaxial spheres normal to a plane in both a Newtonian and a Carreau fluid at a low to medium large Reynolds number. The parameters key to the phenomenon under consideration, including the nature of the fluid, the separation distance between two spheres, the distance between the near sphere and the plane, and the Reynolds number, on the drag coefficient are discussed. We show that the influence of a boundary on the drag coefficient is more important than that of the nature of a fluid and that of the separation distance between two spheres. The variation of the drag coefficient as a function of Reynolds number for a Carreau fluid is similar to that for a Newtonian fluid. Due to the shear-thinning nature of the former the drag coefficient in the former is smaller than that in the latter. The influence of the index parameter of a Carreau fluid becomes appreciable only if the Carreau number is sufficiently large. Correlations between the drag coefficient and the key parameters of a system are developed for the case when the Reynolds number is smaller than l.     

球形氧化锆的湿法制备过程研究

以氯氧化锆和碳酸氢铵为原料，采用连续反应沉淀法制备了微米级球形氧化锆前驱体，此前驱体在500℃下于空气气氛中煅烧2h得到球形氧化锆粉体。探讨了锆盐溶液浓度、加料速度、pH、反应时间对粉体颗粒粒径大小及其分布的影响。经SEN，XRD，TG—DSC和激光粒度测试仪分析，结果表明在最佳工艺条件下制备的氧化锆前驱体颗粒呈球形，分散性好，粒径分布在8—18μm。     

改性磷石膏球作缓凝剂对水泥性能的影响

研究了工业化生产的改性磷石膏球对水泥标准稠度用水量、凝结时间、胶砂流动度、胶砂强度及水泥与减水剂相容性的影响,并与原状磷石膏和天然石膏进行对比,结合X-射线衍射、综合热分析等微观测试,分析了改性磷石膏球对水泥水化产物相、水化程度的影响.结果表明:采用改性磷石膏球配制的水泥,其初凝、终凝时间与掺配原状磷石膏水泥相比分别缩短217 min、227 min,1d、3d强度显著高于原状磷石膏配制的水泥,28d强度高于天然石膏配制的水泥,且标准稠度用水量、胶砂流动度、与减水剂的相容性等指标优于天然石膏配制的水泥.改性磷石膏球对水泥早期水化无不良延缓作用,且能提高水泥后期水化程度.综合对比上述三种石膏对水泥性能影响的各项指标,认为改性磷石膏球可以完全替代天然石膏作水泥缓凝剂.     

Particle-Substrate Collisions, Particle Rebound and Removal

Recent progress in particle capture and rebound and its effect on the adhesion force is reviewed in this paper. Particles rebound when the incident velocity is greater than a characteristic critical velocity. Lower impaction velocity particles experience elastic and plastic deformation. Recent models for particle rebound and capture are discussed and evaluated in terms of their restrictive assumptions and results. Recent experimental data of particle rebound and capture is also discussed, as is the hydrodynamic removal of captured particles. The removal of particles occurs when the applied hydrodynamic removal force overcomes the adhesion force. The effect of adhesion-induced deformation on the removal of particles is introduced and discussed.     

Adaptive Linear Dynamic Matrix Control applied to an integrating process

Dynamic Matrix Control (DMC) has proven to be a powerful tool for optimal regulation of chemical processes under constrained conditions. It is based on a linear convolution model derived from step-response measurements. A model predictive control algorithm optimises closed-loop performance for a nominal operating point. However, as the process moves away from this point, control usually becomes sub-optimal due to process non-linearity. As seen in this work, the DMC algorithm can be made adaptive, to establish a new local model, by recursive estimation of the local step response parameters from normal plant variations. However, when used for control of plants containing integrating process units, steady-state offsets occur for sustained changes. Thus, a novel Adaptive Linear Dynamic Matrix Control (ALDMC) algorithm has been developed and used to control a 2-input/2-output system with an integrating behaviour. Comparisons of model control and plant control with and without these features demonstrated the importance of integral compensation for integrating processes, and model adaptation in the case of plant/model mismatch. Some cross-compensation of integration by the adaptive feature was also noted. An holistic technique is demonstrated which simultaneously recognises residual integration disturbances and matrix parameter variations, whereas previous techniques which recognise only one of these will fail in the presence of the other.     

Nano-sized carbon hollow spheres for abatement of ethylene

In this paper, the ethylene adsorption capacities of the nano-sized carbon hollow spheres (CNB) and active carbon (AC), the Pd (PdCl₂) impregnated CNB or AC (Pd/CNB, Pd/AC) and heat treatment under various conditions, were studied at different ethylene concentrations from 64 to 1060 ppm. The results indicated that AC had a good ethylene adsorption capacity at high ethylene concentration. Pd impregnation decreased the ethylene adsorption capacity of AC. Heat treatment and H₂ activation could increase the ethylene adsorption capacity, but also lowered than AC itself. CNB had lower ethylene adsorption capacity than AC, but heat treatment and H₂ activation could increase its ethylene adsorption capacity markedly. With activating condition from heat treatment in N₂ at 300 °C to activation in H₂/N₂ at 100 °C, to activation in H₂ at 200 °C, and to activation in H₂ at 300 °C, the ethylene adsorption capacity of Pd/CNB was increased regularly. At low ethylene concentration, viz., 64 ppm, the ethylene adsorption quantities (q _a) by Pd/CNB activated in H₂ at 200 or 300 °C were higher than any other adsorbents. So, activated in H₂ atmosphere at higher than 100 °C, Pd/CNB is particularly advantaged for adsorbing low concentration of ethylene. Amongst all the adsorbents used, Pd/CNB activated in H₂ atmosphere at 300 °C for 2 h has the highest ethylene adsorption capacity at lower concentration than 125 ppm. In addition, all the CNB, Pd/CNB, AC, and Pd/AC samples can be easily regenerated in airflow for more than 3 h.