Single-Step Granulation Method with Microwaves: Preliminary Studies and Pilot Scale Results

Abstract

Common pharmaceutical excipients and compounds were dried either by a simple convection method or by a combined convection and microwave method in a static bed or by a combined microwave and vacuum method in a mixed bed. A simple placebo granulation was dried by an exclusive vacuum method and by a combined microwave and vacuum method in a mixed bed. The results were compared.     

Single-Step Granulation: Development of a Vacuum-Based IR Drying Method (Pilot Scale Results)

A simple placebo granulation was dried either by an exclusive vacuum method or by combined microwave, strip-gas, infrared, and vacuum methods in a 50-liter pilot scale single-step granulator (Zanchetta Roto P). The results were compared.     

硅基热电堆真空传感器的耦合场分析

利用商业化的1．2μm标准CMOS生产流水线,配合无掩模体硅各向异性腐蚀工艺,制造了一种热电堆型真空传感器,器件敏感部分尺寸为124um×100μm,由5层薄膜组成,最大厚度为3．2μm．采用一种简化方式对传感器建立有限元模型．新模型一方面忽略了气体对流和热辐射的传热作用,另一方面将各层介质和热电堆结构层分别进行了合并．模型具有简单的断面结构,网格划分容易,收敛速度快．运用ANSYS软件对模型进行了电一热、热一电耦合场分析,直接得到了1．5v加热电压驱动时不同压强下的热电堆输出电压,并与0．1～200Pa之间的测试结果进行比较,结果表明,采用简化建模方式的计算结果与测试结果之间的偏差小于6％．     

Convection induced by vibrating rod in fine-powder bed

In this study, vibration-induced convection was studied experimentally using a fine powder with a mass median particle diameter of 8 μm. A cylindrical rod arranged vertically in a powder container was vibrated horizontally with simple harmonic motion at a frequency of 300 Hz using a piezoelectric vibrator. For a vibration amplitude of 10 μm, particles around the cylindrical rod were consolidated to a certain extent due to gravity; however, for a vibration amplitude of 70 μm or more, a pair of convection rolls formed on both sides of the vibrating rod. The strength of the convection was quantified from the particle velocity distribution in the convection rolls, and the relationship between the convection strength and vibration amplitude was elucidated. In addition, the air-pressure distribution in the powder bed was measured showing that the convection strength correlates with the characteristic positive pressure, i.e., the average value of positive pressure measurements. Elliptical motion and circular motion as well as simple harmonic motion were applied to the cylindrical rod by adding two harmonic motions in directions orthogonally crossing each other with a phase difference of π/2 rad. The convection of the particles varied according to the Lissajous trajectory of the cylindrical rod. Even for simple harmonic motion, heaps of a pair of convection cells overlapped each other. In the case of elliptical motion, the overlapping portion of the heaps became larger. In the case of circular motion, the two heaps were integrated into one circular heap, and there were no effects of the circumferential angle on the particle velocity and the characteristic positive pressure.     

一种新型的平板式太阳能制冷吸附器复合体设计

在成功研究太阳能固体吸附式制冷循环的基础上,结合平板式太阳能热水器集热芯片的制造技术,提出了一种新型的吸附器设计方法,并成功地实现了新型吸附器复合体的制造。实验表明,新制作的吸附器复合体结构合理,操作简便,能够有效地实现太阳能固体吸附制冷过程中供热与制冷联合循环的新思路,为太阳能固体吸附制冷技术吸附床的有效设计做了一次全新的尝试。     

浸渍阴极的真空预处理技术

本文总结了用于真空微波电子器件的浸渍阴极的蒸发规律,通过分析提出了浸渍阴极预处理工艺,建立了超高真空装置.在超高真空环境下,将浸渍阴极灯丝加热,使阴极温度升高到1100～1200℃,保持1～200h(温度和时间依不同微波管型而定).预处理工艺解决了浸渍阴极发射与蒸发的矛盾,现已建立数十台、几十个工位的浸渍阴极预处理设备...     

The dynamics of wet granular matter under a vertical vibration bed

This study investigates the dynamic properties of convection rolls in a 2D wet vibrated granular bed. A particle tracking method with the help of image-processing technology was used to measure the velocity fields, convection flow rate, and the granular temperatures in the wet vibrated granular bed. This study examines the dynamic behaviors of wet granular materials subjected to external vertical vibration. Different liquid contents, viscosities, and surface tensions were added to glass beads forming cohesive granular materials in the vibrated granular bed. This study presents a systematic investigation of the effects of the addition of liquid content, viscosity, and surface tension on dynamic properties of wet particulates. Results show that the convection flow rate and granular temperature decrease monotonically as the added liquid content and liquid viscosity increase. However, the effects of surface tension on the convection flow rate are more significant at the smaller liquid content than that at a higher liquid content. The convection flow rate also decreases in a power decay as the modified Bond number increases.     

Mechanical properties and area retention of leather dried with biaxial stretching under vacuum

The conversion of animal hides to leather involves many complicated chemical and mechanical operations. Drying is one of the mechanical operations, and plays a key role in determining the physical properties of leather. It is where leather acquires its final texture, consistency, and flexibility. We have investigated a drying method using a combination of vacuum and biaxial stretching. Total area loss often accompanies drying of leather; however, by adding a stretching action during vacuum drying one may significantly increase the area retention and dimensional stability. Moreover, this method is particularly advantageous to heat-vulnerable organic tanned leathers because vacuum drying offers fast moisture removal at a low temperature. We investigated this dual functional drying method and observed how drying variables affected the mechanical properties and area retention of chrome-free leather. We used a central composite experimental design to formulate the relationship between drying variables and resultant leather properties into second-order polynomial equations. Results showed that the stretching applied in a drying operation significantly affects mechanical properties, area retention, and thickness of leather. Moreover, studies showed that biaxial stretching increased the tensile strength but had less effect on fracture energy. A significant area increase of 16% can be achieved by using this combined drying (vacuum plus stretching) method compared to the regular vacuum dried leather without stretching.     

Effect of microwaves on synthesis of MoS2 and WS2

The present work was aimed on utilizing the solid state microwave synthetic method for the growth of molybdenum disulphide (MoS₂) and tungsten disulphide (WS₂) in powder as well as in the form of thin films. It was observed that the microwave exposure of simple powder mixture of Mo (or W) and S could not lead to the formation of MoS₂ (or WS₂).Therefore the work was pursued by the study of the possibility to use this technique to grow thin films. Either Mo or W in the form of thin foils or Mo layers deposited by sputtering onto glass substrates was used as metal source. These metal samples were introduced with some sulphur into a Pyrex tube and sealed under vacuum. After microwave oven exposure the formation of polycrystalline 2H-WS₂ with well-defined grains was confirmed by X-ray diffraction and scanning electron microscopy, respectively. Mo foil as well as Mo layers deposited on glass showed formation of MoS₂ under the limit of our experimental conditions that is to say homogeneous thin films can be achieved only as small surface films.     

陶瓷材料的微波—等离子体分步烧结

提出微波加热和微波等离子加热分步烧结方法。在这一方法中,把微波加热和微波等离子和热有机地结合到一个微波应用器内,等离子的激励无需在负压下进行;烧结分两步完成。先用微波直接将烧结件加热到一定温度,再用微波等离子体继续加热到烧结度。     

多孔物料微波冷风对流干燥Re自模区研究

针对多孔物料在微波冷风时而干燥过程中出现流速变化对干燥速率无影响区间或称为Ｒｅ自模化区这一现象，采用集总参数分析法，从理论上对多孔物料的微波对流干燥过程进行量化分析，找出Ｒｅ自模化区的范围。结合实验结果，对这一现象的成因作出解释，从而获得一些有益的结论。     

The effects of hydroxide gel drying on the characteristics of co-precipitated zirconia-hafnia powders

Mixed zirconia-hafnia (Hf_0.25Zr_0.75O₂) powders of fine particle size and narrow particle-size distribution can be prepared via co-precipitation routes using mixed zirconium and hafnium salts as the starting materials. The characteristics of the resultant zirconia-hafnia powders are dependent strongly on the dehydration route by which the co-precipitated hydroxide gels are dried. Zirconium-hafnium hydroxide gels are formed when zirconium and hafnium oxynitrates are co-precipitated in an ammonia solution of pH 10.5. The co-precipitated hydrous gels were dried by three very different routes including organic solvent dehydration, microwave drying, and conventional infrared heating lamp drying. The dried hydroxides were then calcined at various temperatures in the temperature range 550–1150 °C, followed by ball milling to remove large soft-particle agglomerates. The resultant zirconia-hafnia powders were characterized for crystallite size, particle size, particle-size distribution, particle morphology, and the degree of powder agglomeration, using experimental techniques such as X-ray diffraction, BET surface area, differential thermal analysis, thermo-gravimetric analysis, sedigraph, scanning and transmission electron microscopy. Hard particle aggregates, which cannot be effectively eliminated using ball milling, occur in the zirconia-hafnia powders processed via either the microwave drying or conventional infrared heating lamp drying routes. In contrast, the organic solvent dehydration route resulted in an almost aggregate-free powder of fine crystallite and particle sizes. Therefore, the zirconia-hafnia powder processed via the organic solvent dehydration route exhibited high sinterability on sintering at 1300 °C.     

Influence of gravity state upon bubble flow in the deep penetration molten pool of vacuum electron beam welding

The governing equations of two-dimensional bubble flow model for gas–liquid two-phase system in deep penetration molten pool of vacuum electron beam welding were developed according to the laws of mass and momentum conservation. The separation models of gas and liquid convections in bubble flow were formed by regarding the gas phase in molten pool as a particle phase, and the vacuolar fraction, velocity slip, pressure gradient and other factors were introduced into the models. The influences of the gravity state upon the convection of bubble flow and the distribution of cavity-type defects in molten pool of AZ91D magnesium alloy were studied by the method of numerical simulation based on the mathematical models. The results showed that the gravity is an important factor to drive the convection of the bubble flow in the deep penetration molten pool during vacuum electron beam welding. The gravity has an impact on the gas distribution in molten pool, thus affects the distribution of cavity-type defects in weld. Because of the gravity contributing to driving the convection of bubble flow, it is conducive to the escape of gas phase in molten pool and reducing the air rate. A larger convection velocity of gas phase is helpful to the escape of gas phase, thus reduce the tendency of cavity-type defects.     

乙醇共沉淀法制备纳米CoSb3化合物前驱体的研究

探索了乙醇共沉淀法制备纳米CoSb3化合物前驱体。采用无水乙醇作为溶剂，以SbCl3和COCl2．6H2O为起始原料，NaOH作沉淀剂，得到了蓝色的沉淀。所得沉淀的混合溶液分别经过直接干燥和多次洗涤后干燥，得到了两种不同的前驱体粉体。研究了两种前驱体粉体的相组成和微结构，以及它们之间的差异。     

Development of microwave-assisted drying methods for sample preparation for dried spot micro-X-ray fluorescence analysis

Although dried spot micro X-ray fluorescence (MXRF) is an effective analytical technique for trace elemental analysis, the sample preparation procedures currently used suffer from a number of drawbacks. These drawbacks include relatively long preparation times, lack of control of the sample preparation environment, and possibility of loss of volatile analytes during the drying process. Microwave-assisted drying offers several advantages for dried spot preparation, including control of the environment and minimized volatility because of the differences between microwave heating and conventional heating. A microwave-assisted drying technique has been evaluated for use in preparing dried spots for trace analysis. Two apparatus designs for microwave drying were constructed and tested using multielement standard solutions, a standard reference material, and a "real-world" semiconductor cleaning solution. Following microwave-assisted drying of these aqueous samples, the residues were redissolved and analyzed by ICPMS. Effective recovery was obtained using the microwave drying methods, demonstrating that the microwave drying apparatus and methods described here may be more efficient alternatives for dried spot sample preparation.     

A comparison of bismuth nanoforms obtained in vacuum and air by microwave heating of bismuth powder

The synthesis of bismuth nanotubes in the conditions of microwave (MW) heating is reported as a lower-cost and simple technique in comparison with the traditional methods. The nanotubes were prepared by heating the Bi powder (a) in air for 15, 30, 60, and 90 min and (b) in vacuum for 5, 10, and 15 min in a domestic MW-oven (2.45 GHz, 1300 W). The products were characterized by TEM and AFM. A mechanism of formation for bismuth nanotubes in different conditions (air and vacuum) is presented.     

Evaluation of Microwave Drying for Pharmaceutical Granulations

Abstract

The experiments were designed to compare the granule characteristics following the microwave drying and conventional tray drying. The formulations were designed to study the effect of microwave radiation under different conditions. This later criterion was studied by using granules prepared with different granulating fluids. The granules were prepared by using sulfathiazole as a model drug, lactose as a diluent, and starch as a disintegrating agent. The granulating fluids were 5% solution of PVP in 100% water, 50% water 50% ethanol, and 100% ethanol, respectively. The granules were dried in a microwave oven and in a conventional tray oven at 40±2° C. The loose and bulk densities were measured in a 100 ml glass cylinder. The granule morphology was examined using a scanning electron microscope. Dissolution rates of the granules were monitored using a rotating paddle dissolution apparatus. The loose and tapped bulk densities, the percentage compressibility, hardness, and the time required for 100% dissolution of the granules dried in the microwave oven and in the conventional tray oven were not significantly different (p>0.05). The scanning electron micrographs of the granules also showed no evidence of morphological changes or thermal damage to the granule surface or interior. In conclusion, the microwave radiation has no significant effect on the granules' characteristics.     

Microwave enhanced stabilization of heavy metal sludge

A microwave process can be utilized to stabilize the copper ions in heavy metal sludge. The effects of microwave processing on stabilization of heavy metal sludge were studied as a function of additive, power, process time, reaction atmosphere, cooling gas, organic substance, and temperature. Copper leach resistance increased with addition of aluminum metal powder, with increased microwave power, increased processing time, and using a gaseous environment of nitrogen for processing and air for cooling [N2/air]. The organic in the sludge affected stabilization, whether or not the organic smoldered. During heating in conventional ovens, exothermic oxidation of the organic resulted in sludge temperatures of about 500 degrees C for oven control temperatures of 200-500 degrees C. After microwave heating dried the sludge, the sludge temperature rose to 500 degrees C. The reaction between copper ions and metal aluminum in the dried sludge should be regarded as a solid phase reaction. Adding aluminum metal powder and reaction temperature were the key parameters in stabilizing copper in the heavy metal sludge, whether heated by microwave radiation or conventional oven. The mass balance indicates insignificant volatization of the copper during heating.     

The flow behavior of granular material due to horizontal shaking

This paper studied the convection phenomena that occurred in a granular bed under horizontal vibration. High-speed photography was employed to measure the movements of particles. The fields of the instantaneous velocities and the long-term velocities were plotted. Two symmetric convection rolls were observed. The granular temperature distributions were also measured and analyzed. The controlling parameters included the acceleration amplitude and the wall condition. The convection strength was found to increase linearly with the total granular temperature in the bed.     

In situ Investigation of Microwave Impacts on Ethylene Glycol Aqueous Solutions

Recently, the in-situ IMPACT of MICROWAVES on the behavior of aqueous solutions have been reported. The results, including surface tension and in situ bubble formation, indicated a nonthermal effect of microwave on solutions. To clarify the role of fluid properties on such effects, this study applied microwave to ethylene glycol (EG) aqueous solutions at different concentrations. The surface tension, bubble size and convection were monitored during and after microwave irradiation. It was found that surface tension reduction was maximized in the medium EG content, 20 to 60 vol.%. The size of bubble formed during microwave was reduced by the addition of EG. The convection was also reduced by EG. The obtained data indicated that the dielectric constant and intermolecular bonds were the main underlining principles for microwave effects. The new insights can be used to provide practical ways to manipulate microwave effects on aqueous solutions.