共查询到20条相似文献,搜索用时 31 毫秒
1.
Robert R. Nellums Brandon C. Terry Bryce C. Tappan Steven F. Son Lori J. Groven 《Propellants, Explosives, Pyrotechnics》2013,38(5):605-610
Sensitive nanoenergetic powders, such as nanothermites, have traditionally been processed by ultrasonic mixing of very low solids loaded suspensions in organic solvents, which has restricted their use and application due to high solvent content and associated handling issues. In this work, we report on the performance and mixing quality of nanothermite mixtures prepared in a LabRAM resonant mixer at high solids loadings as compared to ultrasonic mixing. Specifically, the aluminum‐bismuth(III) oxide (Al/Bi2O3) system processed in the polar solvent N,N‐dimethylformamide (DMF) was investigated. It was found that the performance and overall quality of mixing was strongly correlated to the volumetric solids loading during processing; increasing volumetric solids loading decreases separation of particles, leading to more particle interaction and more intimate mixing. The measured performance of this system processed at 30 vol‐% was similar to traditionally ultrasonicated mixtures. Increasing the solids loading above 30 vol‐% yielded diminishing returns in performance and may introduce additional safety concerns since dry powders are very sensitive to electrostatic discharge. This mixing approach uses significantly less solvent than traditional ultrasonic mixing, results in a higher density final material, and is amenable to scaling. In addition, solvent wetted nanothermite mixed at 30 vol‐% solids loading can be mixed and deposited from a single applicator and was observed to be over five orders of magnitude less sensitive to electrostatic discharge than dry powders. This relative insensitivity enables the safe deposition of high density nanothermite ink onto devices. 相似文献
2.
Sudipta Halder P.K. Ghosh M.S. Goyat S. Ray 《Journal of Adhesion Science and Technology》2013,27(2):111-124
Dispersion of nanoparticles and its effect on the tensile properties were investigated by preparing nanocomposites via mechanical mixing (MM) and optimized ultrasonic dual mode mixing (UDMM) routes. The MM of SiO2 nanoparticles in epoxy resin was employed using glass rod stirring and the UDMM was employed by ultrasonic vibration along with magnetic stirring to produce SiO2-epoxy nanocomposite. Taguchi method was used for optimization of the process parameters of UDMM route considering the tensile strength of the base epoxy. Field emission scanning electron microscopy (FE-SEM) micrographs revealed an improved dispersion quality of SiO2 nanoparticles especially for the UDMM route. Consequently, quality of dispersion affects tensile strength (max 49.2%) along with ductility and absorbed failure energy at low nanoparticle content. Moreover, elastic modulus increases with increasing content of nanoparticle, e.g. in one case 62.55% for 20?wt.% of SiO2 nanoparticles. 相似文献
3.
固液混合技术是广泛应用于工农业生产中固体分散、溶解和浸出、结晶和沉淀、固体催化反应以及粉剂农药混合等领域的一种重要操作技术。固液两相混合的均匀性对产品的生产或应用有着重要的影响。因此本文综述了固液两相混合技术的研究现状。首先介绍了固体颗粒在液相中的分散机理,讨论了常见的两大类固液两相混合方法,即化学分散法与物理分散法。其中化学分散法包括添加表面活性剂与偶联剂以及进行电化学改性;物理分散法包括使用搅拌釜、撞击流混合器、射流混合器、静态混合器、动态混合器进行的机械混合以及超声分散和通过静电分散进行的预分散。同时介绍了部分具有代表性的固液两相分散混合均匀性的检测方法,如探针、图像分析处理、超声衰减、动态光散射、电阻层析成像等。最后在分析现有问题的基础上对固液两相混合技术未来在多元化、智能化方向上的发展进行了展望。 相似文献
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Zhikai Liu Mei Yang Zhengya Dong Chaoqun Yao Guangwen Chen 《American Institute of Chemical Engineers》2023,69(7):e18080
A facile and robust ultrasonic micromixer was developed to intensify antisolvent precipitation via ultrasonic cavitation. The gas supersaturation created from solvent–antisolvent mixing was found to be a novel driving force which facilitated the generation of cavitation bubbles (CBs). Instead of being attached on the channel wall, numerous CBs translated across the microchannel at a speed up to 1.7 m/s, inducing intense transverse flow over the cross-section. The unique cavitation behavior enabled rapid mixing (mixing time 15–45 ms at 30 W) of solvent–antisolvent over wide Reynolds number range (70–500) and flow rate ratio (5:1–2:3), providing better operability for antisolvent precipitation. The effects of ultrasonic power, total flow rate, flow rate ratio, and solvent on cavitation behavior and mixing performance were quantitatively studied. Finally, the potential of the ultrasonic micromixer as a new tool for antisolvent precipitation was demonstrated by synthesizing size-controllable and monodisperse polymeric nanoparticles in a high-throughput and reproducible manner. 相似文献
6.
Kai Zheng Kuriakose Kunnath Rajesh N. Davé 《American Institute of Chemical Engineers》2022,68(4):e17603
The effects of processing intensity, time, and particle surface energy on mixing of binary cohesive powder blends in high-intensity vibration system were investigated via discrete element method simulations. The mixedness was quantified by the coefficient of variation, Cv; lower being better. The mixing rate, which is the speed at which homogeneity was achieved, was inversely proportional to the mixing Bond number, defined as the ratio of particle cohesion to the shear force resulting from the mixing intensity. Results show that both increasing processing intensity and reducing surface energy led to a faster mixing rate. However, the mixedness improved initially as mixing action (the product of mixing rate and mixing time) increased, but later deteriorated upon its further increase. Thus, both mixing rate and mixing intensity need to be tuned for optimum mixing performance depending on the cohesion level of particles; too high or too low mixing action should be avoided. 相似文献
7.
Ultrasonic mixing and closed microwave irradiation-assisted transesterification of soybean oil 总被引:1,自引:0,他引:1
The present study employed ultrasonic mixing and closed microwave irradiation to assist transesterification of soybean oil. The purpose was to obtain the optimal ultrasonic mixing and closed microwave irradiation procedure. The optimal reaction conditions including amount of catalyst used, reaction temperature and methanol/oil molar ratio were also investigated to achieve the highest possible conversion rate of biodiesel. Results showed that the optimal procedure involved 1-min ultrasonic mixing and 2-min closed microwave irradiation. The optimal reaction conditions that can reach 97.7% of conversion rate were amount of catalyst used, 1.0 wt%; reaction temperature, 333 K; and methanol/oil molar ratio, 6:1. 相似文献
8.
This paper investigates the accelerated mixing of hot and cold liquid layers in storage tanks of different physical dimensions by the application of high-frequency, high-intensity pulsed ultrasound. In pulsed operation, the ultrasonic field is switched on for a few seconds and then switched off. This cycle is repeated several times. Pulsed mixing of hot and cold water due to ultrasonics was measured in this study. Acoustic streaming and cavitation phenomena associated with the ultrasonic field can induce enhanced mixing in the storage containers leading to de-stratification of liquid. The experimental results indicate that dual frequency operation, which combines one high-frequency mode with one low-frequency mode, is optimal in enhancing mixing compared to other frequencies. Mixing efficiency increases with cavitation intensity and the introduction of acoustic streaming augments it further. The experimental result indicates that as the height of the cylinder increases, the mixing time also increases. The ultrasonic mixing times obtained for different frequencies indicate that as the frequency increases, the time required to reach the steady state temperature also increases, due to decrease in cavitation intensity. 相似文献
9.
针对焦炉煤气杂质堵塞煤气掺混器孔道,造成焦炉煤气回炉煤气压力升高的问题,安装了超声波防垢除垢装置,并对其在线除垢能力进行了考察。结果表明,安装超声波防垢除垢装置后,高炉煤气、焦炉煤气及掺混后的煤气热值不变,基本保持稳定;在机、焦侧直行温度平均值无明显变化的前提下,焦炉煤气机、焦侧掺混压力由安装前5.3kPa、3.0 kPa下降到安装后2.5kPa、2.4kPa,说明安装该装置达到了在线智能除垢的目的。 相似文献
10.
Magnetic nanofluid actuation by rotating magnetic fields was proposed as a high‐performance tool for liquid mixing with enhanced micromixing features. A comparative study was conducted to evaluate the mixing index in T‐type mixers of magnetic and nonmagnetic fluids subject to static (SMF), oscillating (OMF), and rotating (RMF) magnetic fields. RMF excitation unveiled superior mixing indices with strong dependences to magnetic field frequency and content of magnetic nanoparticles. The impact of magnetic field types on micromixing was further examined at low and moderate Re numbers using the Villermaux–Dushman reaction and IEM micromixing model. The IEM‐inferred micromixing times were remarkably shorter by nearly four orders of magnitude in comparison with OMF and SMF excitations, and without magnetic field. The proposed mixing strategy is foreseen to complement innovative microfluidic devices with valuable mixing tools and methods for the diagnosis of the coupling between transport and intrinsic kinetics. © 2016 American Institute of Chemical Engineers AIChE J, 63: 337–346, 2017 相似文献
11.
Mixing-sensitive chemical reactions conducted under controlled conditions can be used to qualitatively and quantitatively assess mixing in aqueous systems. These reactions are typically competitive reactions where the distribution of products is used to quantify mixing. This technique is valuable for studying both mixing and local energy dissipation in dispersed systems where the opacity of the suspension prevents the use of other techniques. However, correct interpretation of the test results requires that adsorption of reactants and product dyes on the dispersed phase be known. The adsorption of the reactants and product dyes formed in the mixing-sensitive azo coupling between mixtures of 1- and 2- naphthol and diazotized sulfanilic acid was measured in aqueous suspensions of nylon, polyethylene, fibreglass and kraft pulp fibres. The polyethylene fibre did not adsorb the reactants or product dyes. The nylon, fibreglass and kraft fibres adsorbed both reactants and product dyes, with adsorption described by Langmuir isotherms. Accounting for the adsorption of dye on the dispersed phase allowed correct interpretation of mixing in the aqueous phase of the dispersions. This technique is evaluated for mixing assessment in suspensions of nylon fibre and fully bleached kraft (FBK) pulp in a medium-intensity mixer. 相似文献
12.
林宏伟;刘颖;吴大鸣 《中国塑料》2009,23(10):83-86
采用从国外引进的超声波检测系统以及实验室自行设计的超声波检测辅助装置,对碳酸钙填充的聚丙烯(PP)以及丙烯腈-丁二烯-苯乙烯共聚物(ABS)体系进行超声波检测,发现超声波声速随着碳酸钙含量的增加呈下降趋势;在注塑机喷嘴处进行超声波在线检测,从超声波声速波动情况以及制品的力学性能两方面,评价了不同注塑螺杆的混炼能力。 相似文献
13.
以氯化血红素(1)为原料,经过加成和取代反应制得血卟啉(2)。然后在超声波激励下,以血卟啉(2)作为原料,浓硫酸作为催化剂,甲醇既作溶剂又作反应剂,合成了[2,7,12,18-四甲基-3,8-(-1-羟基乙基)-13,17-二甲氧基羰基乙基]-卟啉(血卟啉二甲酯,3),两步反应总产率达到74.8%。探讨了反应时间、催化剂用量以及超声功率对血卟啉二甲酯(3)合成的影响,并且将超声波激励法与加热搅拌法进行了比较。实验结果表明,同加热搅拌法相比,超声激励法反应时间更短,产率更高,副产物更少。产物结构通过1 H NMR、MS和IR测试技术进行了表征。 相似文献
14.
在VC403纺丝机上应用犁钉螺杆生产PP长丝。生产实践表明:犁钉螺杆以分流三维混合为特征,加大了槽深,强化了剪切、混合。与常规螺杆相比,生产过程稳定,工艺易于控制,产品物理性能指标提高,不匀率降低,相同工艺条件下,产量约增加30%;同样产量下,螺杆转速、加热温度降低,减少了能耗。 相似文献
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16.
Debmalya Mukherjee Nirvik Sen Krishna Kumar Singh Shilpi Saha Anuradha Mayya Kalsanka Trivikram Shenoy 《American Institute of Chemical Engineers》2023,69(3):e17966
Estimation of mixing time is an essential aspect in characterization of stirred tanks. In this work, we report a novel, non-invasive technique to estimate mixing time in an unbaffled stirred tank using a contact type ultrasonic sensor. Variation in speed of sound in stirred tank is measured by ultrasound and is used to determine the mixing time of solutions. A sensing time of 16.6 ms (~60 Hz) is achieved which leads to an estimation of the mixing process dynamics under forced vortex conditions. The method is validated against colorimetric technique using a dye. The technique is thereafter used to determine mixing time under different operating (impeller speed) and geometrical (impeller design, vessel diameter, and off-bottom clearance) conditions. Though the results presented are specific to unbaffled stirred tank, the method reported is general and can be used in any kind of stirred tank. 相似文献
17.
Effect of Ultrasonication on Droplet Size in Biodiesel Mixtures 总被引:1,自引:0,他引:1
Peng Wu Ying Yang José A. Colucci Eric A. Grulke 《Journal of the American Oil Chemists' Society》2007,84(9):877-884
Biodiesel fuels have become more attractive recently because of their environmental benefits and cost competitiveness compared
to diesel fuel. Many processing improvements have been proposed to increase the conversion rates and the yields of vegetable
oil in order to lower production costs and improve biodiesel product quality. In conventional biodiesel production chemistries,
alkaline transesterifications of alcohol/oil dispersions should occur primarily near the interface. Ultrasonic mixing has
already been shown to increase overall conversion rates for alcohol/vegetable oil mixtures. Our data show that ultrasonic
mixing produced smaller droplet sizes than conventional agitation, leading to more interfacial area for the reaction to occur.
Droplet size distributions have been measured for conventional impeller and ultrasonic mixing systems using methanol/soybean
oil as a model system. The dispersions were stabilized by surfactant in order to obtain droplet size distribution for mixture
samples. Ultrasonic mixing produced dispersions with average droplet sizes 42% smaller than those generated using standard
impellers. 相似文献
18.
三硝基间苯三酚(TNPG)是重要的医药中间体,通常以间苯三酚(PG)为原料,在间歇反应釜中经硝化合成。该工艺存在反应时间长、能耗高、安全性差等问题,亟需开展新型连续合成工艺研究。在超声微反应器中开展了PG混酸硝化过程研究,通过引入超声解决微通道中高黏流体混合差和固体产物易造成通道堵塞的难题,实现TNPG连续合成并大幅缩短了反应时间。此外,基于对原料和产物的质谱等分析,初步探讨了反应路径和行为特征。在优化工艺条件下(PG浓度:1.0 mol/L;硝酸与PG摩尔比:4;反应温度:40℃;停留时间6~10 min),TNPG收率可达80%,固体纯度大于98%。 相似文献
19.
三硝基间苯三酚(TNPG)是重要的医药中间体,通常以间苯三酚(PG)为原料,在间歇反应釜中经硝化合成。该工艺存在反应时间长、能耗高、安全性差等问题,亟需开展新型连续合成工艺研究。在超声微反应器中开展了PG混酸硝化过程研究,通过引入超声解决微通道中高黏流体混合差和固体产物易造成通道堵塞的难题,实现TNPG连续合成并大幅缩短了反应时间。此外,基于对原料和产物的质谱等分析,初步探讨了反应路径和行为特征。在优化工艺条件下(PG浓度:1.0 mol/L;硝酸与PG摩尔比:4;反应温度:40℃;停留时间6~10 min),TNPG收率可达80%,固体纯度大于98%。 相似文献
20.
李晓翠;彭炯;陈晋南 《中国塑料》2010,24(2):109-112
用正交设计法设计了9组不同排布的销钉单螺杆。采用混合熵作为评价销钉单螺杆混炼段混合性能的指标,数值研究了不同销钉结构的单螺杆混炼段内聚丙烯熔体的等温流动过程,考察了一个导程内销钉排数、每排销钉个数和销钉高度对销钉单螺杆混炼段混合性能的影响。结果表明,在所设计的正交试验中,沿螺杆挤出方向各截面的混合熵逐渐增大,出口处该值达到最大;在销钉螺杆混炼段一个导程内安装5排,每排5个高度为12 mm的销钉时,其混合性能较优。 相似文献