共查询到17条相似文献,搜索用时 390 毫秒
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溶液结晶技术在许多领域有着广泛的应用,其中结晶成核是溶液结晶的关键环节。以无水α-葡萄糖为研究对象,采用双频复合超声(25 k Hz+40 k Hz)强化糖液结晶成核,研究了溶液浓度、超声功率和作用时间对成核速率的影响,对单频和双频作用的晶核形态进行了对比,并采用碘化钾溶液中碘的释放量研究超声空化产额。研究结果表明:在同等条件下,双频复合超声降低了溶液成核的初始浓度,提高了成核速率,同时得到粒度均匀的晶核;双频复合超声的空化产额远高于单频25 k Hz超声和单频40 k Hz超声的空化产额,双频复合超声具有协同作用。双频复合超声强化溶液成核是一种快速、高效、节能的方法。 相似文献
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大功率超声作用于溶液时会产生空化效应,并影响溶液的物理化学性质,如电导率、液体粘度及液体表面张力等。文章对不同功率的超声作用于弱电解质溶液时其电导率的变化进行了实验研究,发现溶液电导率与超声波强度有关。当强度增大到有空化产生时,电导率开始减小;继续增大强度,溶液电导率减小到一定程度后有小幅回升现象出现。且液体内空化效应的出现将导致液体的电导率减小,空化达到一定强度时,空化效应引起的局部瞬态高温高压、冲击波和微射流导致的新导电粒子,会使电导率小幅回升。 相似文献
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《制冷与空调(北京)》2021,(10)
根据溴化锂溶液的物性参数方程,利用试验数据和超声作用于均相液体中空化气泡运动的动力学模型,推导出溴化锂溶液超声空化气泡运动方程。利用MATLAB对溴化锂溶液超声空化气泡的运动特性进行数值模拟,对过冷沸腾和饱和沸腾条件下溴化锂溶液沸腾气泡的运动变化特性进行研究,得到超声空化效应对气泡运动特性变化影响的模拟结果。为溴化锂溶液传热性能和吸收式制冷机组制冷效率的提高提供一定的理论依据。 相似文献
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利用TiOSO4液相反应制备透明锐钛矿相二氧化钛溶胶 总被引:1,自引:0,他引:1
以TiOSO4水溶液为前驱体,NH3·H2O为沉淀剂,聚乙二醇400(PEG400)为分散剂,在60~80℃下均相沉淀与结晶,制备出透明锐钛矿相二氧化钛溶胶.利用XRD和TEM表征了粉体的晶体结构和形貌.研究了制备过程中溶液中H /Ti摩尔比、表面活性剂、晶化温度和时间对TiO2溶胶颗粒尺寸的影响.结果表明:当溶液中H /Ti摩尔比为5,晶化温度为70℃,分散剂质量分数为2.5%时,得到的二氧化钛晶粒尺寸在10~20nm之间.聚乙二醇400的加入有效抑制了晶化过程中晶粒的长大. 相似文献
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Study on Enhancement in Gibbsite Precipitation of Bayer Process under 33 kHz Ultrasound 总被引:1,自引:0,他引:1
JihuaZHAO QiyuanCHEN 《材料科学技术学报》2003,19(6):607-610
The enhancement of gibbsite precipitation in Bayer process by 33 kHz ultrasound has been studied. From orthomethod experiment, the optimized operating parameters of treatment under 33 kHz ultrasonic cleaner have obtained.Compared with crystallization of Al(OH)3 without treatment of ultrasound, the precipitation time is reduced by 15 h when the precipitation ratio is 45%. From the results of grain size distribution and SEM photographs of gibbsite, it is found that secondary nucleation and agglomeration could be enhanced under 33 kHz ultrasound. The products are same from comparison of X-ray powder diffraction, but the Raman spectrum of sodium aluminate solution under 33 kHz ultrasound is different from that without ultrasound. 相似文献
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声场效应对溶液蒸发过程实验表明,声场促进溶液的蒸发,不同的声场作用参数和不同的温度,影响效果不同,溶液蒸发效率提高2%-6%,平均效率提高达4%以上。对水.乙醇以及苯.乙醇二组分溶液的超声蒸发动力学过程进行了分析,表明蒸发速率随时间的关系表现出线性的关系,两组分之间的体积百分比越接近,蒸发速率随时间越容易表现出线性的变化关系。通过液气两相平衡、成核和挥发等过程的分析.认为声场强化溶液蒸发的作用机理是声场具有“空化效应”。声场降低溶液的表面张力,从而降低了成核势垒.促进了液体内部的能量交换。增加了汽化成核几率,使溶液蒸发过程得以强化。 相似文献
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根据超声空化泡在相间特殊运动时周围流体流动特性,以相间传质渗透理论为依据,结合流体动力学原理,在充分研究相界面上气泡行为的基础上,根据界面上超声空化气泡生长过程的动力学行为,导出了相界面上超声空化气泡聚并和滑移促进的传质模型。在此基础上,建立了相界面上气泡滑移、聚并及脱离界面逸出这三种气泡行为共同促进的传质模型,该模型可用于描述超声空化界面等相界面上的传质行为,为超声波强化传质过程提供了理论依据。 相似文献
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The formation of nano-sized crystals of gadolinium carbonate via reaction crystallization was studied in a semi-batch crystallizer using gadolinium chloride and ammonium hydrogen carbonate as the reactants. The gadolinium carbonate crystals were formed by the aggregation of primary particles sized about 5 nm. Thereby, the crystallization parameters acting directly on the aggregation of the primary particles, such as the reactant concentrations, non-stoichiometry of the reactants, solution pH, acoustic energy, and agitation speed, were mechanistically investigated. As such, increasing the reactant concentrations enhanced the crystal size due to higher nucleation of the primary particles for the aggregation. Non-stoichiometric reactant concentrations resulted in a significant reduction of the crystal size, due to the adsorption of the excess species on the primary particles. Similarly, the surface charge of the primary particles depended on the solution pH. Thus, the crystal size was reduced when the pH deviated from the neutral point. The acoustic cavitation of the ultrasound was much more effective than the turbulent fluid motion of the agitation in inhibiting the primary particle aggregation. Thus, the crystal size was remarkably reduced, even at a low acoustic energy of 6 watts. 相似文献
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Umemura S Kawabata K Sasaki K 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2005,52(10):1690-1698
The ultrasonic power absorbed by a microbubble in its continuous wave response is estimated through numerically solving a version of the Rayleigh-Plesset equation. At an ultrasonic frequency of 3 MHz, a resonant microbubble, approximately 1.1 microm in radius, showed an absorption cross section of about 0.005 mm2 in its low power response. This estimation predicts that the tissue ultrasonic absorption will be doubled when such microbubbles are delivered to the tissue at a concentration of about eight bubbles/mm3 in tissue. An exteriorized murine kidney was exposed to focused ultrasound at 3.2 MHz in degassed saline, and the tissue temperature change was measured. With an intravenous bolus administration of a microbubble agent, the ultrasonically induced temperature elevation was multiplied by up to five times. The enhancement in temperature elevation gradually decreased as the microbubble agent was eliminated from the body. The experimental results agreed with the prediction in the order of magnitude. This effect may have a potential use to enhance the throughput as well as the selectivity of focused ultrasound treatment. 相似文献