共查询到20条相似文献,搜索用时 109 毫秒
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磁流变液凭其灵活、可控、稳定的特点成为应用最广的智能材料,磁流变液的稳定性对磁流变液功能的实现具有非常重要的意义。对磁流变液在机械传动、精密加工、医学、土木工程等领域的应用及其原理进行综述,总结对比了多种磁流变液沉降稳定性的检测方法。重点介绍磁流变液沉降稳定性的影响因素,通过总结不同类型添加剂的作用机理,从沉降率的角度对比分析了添加剂对磁流变液沉降稳定性的影响。同时指出改变磁性颗粒的结构、形成低密度复合材料主要是通过增大磁性颗粒与基载液之间的摩擦力和减小磁性颗粒和基载液之间的密度差来改善磁流变液的沉降性能。最后对磁流变液的发展趋势进行预测。 相似文献
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LIU Qi TANG Long ZHANG Ping 《材料导报》2004,18(Z3):76-77
研究了基液和添加剂对磁流变体的温度稳定性、润滑减磨性及磁流变性能的影响规律.实验结果表明,采用合理的基液和添加剂复合工艺制备的磁流变体材料,最低使用温度达-40℃,5000Gs磁场下剪切应力值达56kPa,且具有良好的润滑性能和抗沉降团聚稳定性能. 相似文献
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《Drug development and industrial pharmacy》2013,39(11):1357-1364
Purpose: In this study, micron-sized crystalline drug particles of irbesartan (IBS) were prepared to improve its stability and dissolution rate.Method: The approach to crystalline particles was based on the liquid precipitation process by which the amorphous particles were prepared. Pharmaceutical acceptable additives were used as the crystallization agent to convert the amorphous drug into crystalline particles. High pressure homogenization (HPH) process has been employed to reduce the size of the crystalline particles, and the micron-sized particles were obtained by the freeze-drying process.Results: Different additives show different influences on the polymorphic form of IBS. Polyvinylpyrrolidone (PVP) and hydroxypropyl methylcellulose (HPMC) were effective in stabilizing amorphous particles instead of converting amorphous drug into crystalline particles, while poloxamer407 (F127) and tween80 (T80) could convert the amorphous drug into crystalline particles. T80 was also effective in controlling the particle size than that of F127. After HPH, crystalline particles with an average of 0.8 μm were obtained. The freeze-dried micron-sized crystalline particles exhibited significantly enhanced in vitro dissolution rate when compared to the raw drug. SEM, FT-IR, XRD, DSC and dissolution rate studies indicated that the micron-sized particles were stable during 6 months storage.Conclusion: The preparation of micron-sized crystalline drug particles is an effective way to improve the stability and dissolution rate of irbesartan. 相似文献
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加料方式对超细氧化亚铜粉体分散性与粒度稳定性的影响 总被引:3,自引:0,他引:3
在不加任何添加剂和高反应物浓度的条件下, 用CuSO4、NaOH、葡萄糖为原料制备了Cu2O球形粉体. 利用扫描电镜和smileview软件对Cu2O粉体进行了表征分析, 主要考察了加料方式对Cu2O颗料的分散性与粒度稳定性的影响, 并根据Lamer模型初步探讨了其影响机理. 结果表明, 当采用先将NaOH溶液与CuSO4溶液分步缓慢混合制备Cu(OH)2作为铜源, 再加入葡萄糖还原Cu(OH)2制备Cu2O的加料方式时, Cu2O颗粒按“爆发成核, 缓慢生长”的模式形成, 制得的Cu2O粉体分散性高, 粒度稳定性好. 分散性高是由于缓慢的晶核生长有利于通过搅拌作用使初始晶核间的软团聚体再分散, 避免软团聚体进一步通过化学键合发展成为硬团聚. 粒度稳定性好的原因是将NaOH溶液分步缓慢加入到CuSO4溶液中制备的前驱体Cu(OH)2热稳定性好, 较好地保持了前驱体升温过程中铜源组分的单一性, 避免了还原过程中出现二次成核现象. 相似文献
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Summary The effect of Suction-Injection-Combination (SIC) on the linear stability of Rayleigh-Bénard Marangoni convection in a horizontal layer of an Boussinesq fluid with suspended particles confined between an upper free adiabatic boundary and a lower rigid isothermal/adiabatic boundary is considered. The Rayleigh-Ritz technique is used to obtain the eigenvalues. The influence of various parameters on the onset of convection has been analysed. It is found that the effect of Prandtl number on the stability of the system is dependent on the SIC being pro-gravity or anti-gravity. A similar Pe-sensitivity is found in respect of the critical wave number. It is observed that the fluid layer with suspended particles heated from below is more stable compared to the classical fluid layer without suspended particles. The problem has possible applications in microgravity situations. 相似文献
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Jung Y Son YH Lee JK Phuoc TX Soong Y Chyu MK 《ACS applied materials & interfaces》2011,3(9):3515-3522
Two different types of clay nanoparticle hybrid, iron oxide nanoparticle clay hybrid (ICH) and Al(2)O(3)-SiO(2) nanoparticle clay hybrid (ASCH), were synthesized and their effects on the rheological properties of aqueous bentonite fluids in steady state and dynamic state were explored. When ICH particles were added, bentonite particles in the fluid cross-link to form relatively well-oriented porous structure. This is attributed to the development of positively charged edge surfaces in ICH that leads to strengthening of the gel structure of the bentonite susensions. The role of ASCH particles on the interparticle association of the bentonite fluids is different from that of ICH and sensitive to pH. As pH of ASCH-added bentonite suspensions increased, the viscosity, yield stress, storage modulus, and flow stress decreased. In contrast, at low pH, the clay suspensions containing ASCH additives were coagulated and their rheological properties become close to those of ICH added bentonite fluids. A correlation between the net surface charge of the hybrid additives and the rheological properties of the fluids indicates that the embedded nanoparticles within the interlayer space control the variable charge of the edge surfaces of the platelets and determine the particles association behavior of the clay fluids. 相似文献
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Y. Zimmels 《Particulate Science and Technology》1994,12(1):21-44
The stability of an assembly of particles which are suspended in a flow field of a gas, under the action of force fields, is considered. It is shown that the stability of the particle dispersion depends on the composite energy density due to the flow and the force fields. The stability can be maintained by balancing the change occurring in the flow and force fields, so that the total energy density after the change remains fixed. This capability is well established in Magnetically Stabilized Fluidized Beds (MSFBs), where the magnetic field can be used to lower the energy of the system against the rise in the kinetic energy of the fluidizing gas. A general criterion for stability is formulated in terms of the balance between energy densities that can be assigned to the dispersion as a composite entity. The sedimentation behavior of particles fluidized by gas discloses the factors that affect the intensity of instability of these systems. Simulation of batch sedimentation of concentrated, i.e. low voidage, polydisperse particle mixtures shows that the evolution of voidage disturbances is enhanced at higher particle concentrations and narrower size distributions. Under these conditions, relaxation time of the system becomes too high so that the evolution of the disturbance cannot be suppressed. This behaviour is the result of fluid particle interaction and the high sensitivity of the system to relatively small voidage perturbation. The application of polarization fields can eliminate this high sensitivity and render the system more stable. The extra stability is achieved by formation of ordered, pearl chain structures of the polarized particles. These structures render the system higher permeability levels to the flow of gas, thus allowing higher velocities at the same pressure drop. Alternatively, the formation of pearl chains changes the fluid particles interactions, decreasing the fluid drag and increasing the sedimentation velocity of the particles. 相似文献
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Tian Zuzhi Chen Fei Wu Xiangfan Wang Jian 《Materials and Manufacturing Processes》2016,31(15):2030-2036
We report the preparation of a high-performance magnetorheological (MR) fluid by using silane coupling agent and bentonite as additives at appropriate contents determined by a series of experiments. We also adopted a new preparation process that was optimized through an orthogonal experimental design. The effects of process parameters on the sedimentation stability of the MR fluid were determined. Sedimentation ratio, apparent viscosity, and yield stress were measured to evaluate the performance of the MR fluid prepared by the optimized process. Results indicated that the MR fluid exhibited enhanced sedimentation stability when the silane coupling agent and bentonite mass fractions were 2.88% and 3.60%, respectively. Moreover, the effect of the second stirring process on sedimentation stability was found to be more important than the first. The optimal preparation parameters determined for the high-performance MR fluid are as follows: first and second stirring temperature of 20°C, first stirring time of 5 min, second stirring time of 5 h, and first and second stirring rotation speed of 2000 rpm. 相似文献