APPLICATION OF CONTROLLED THERMAL EXPANSION IN MICROLAMINATION FOR THE ECONOMICAL PRODUCTION OF BULK MICROCHANNEL SYSTEMS

Diffusion bonding has been widely used within microlamination architectures for the fabrication of micro energy and chemical systems (MECS). MECS are microsystems with the ability to process bulk amounts of fluid within highly parallel microchannel arrays capable of accelerated heat and mass transfer. Thus far, diffusion bonding of microchannel arrays is commonly done in a vacuum hot press system. The use of the hot press greatly restricts the production rate due to vacuum pump-down time and heating-up and cool-down periods. Furthermore, larger substrates are gaining interest in the system design of MECS devices, and it is not apparent that uniaxial pressing within a hydraulic vacuum hot press will provide the bonding pressure uniformity necessary for large substrate bonding. This article presents a novel fabrication approach for high-volume thermal bonding of MECS devices with the use of controlled thermal expansion. A thermal bonding fixture based on the principle of differential thermal expansion was developed with a focus on controlling the bonding pressure magnitude, the pressure timing, and its sensitivity. The application of such a fixture within a conveyorized furnace system could be the key to a continuous thermal bonding approach for the mass production of MECS devices.     

硫化机热工管路双排双抽改造

为解决硫化胶囊泄压慢导致硫化机无法开模以及轮胎过硫的问题,研究过热水硫化工艺硫化机热工管路改造方案。设计了3种改造方案:在硫化机进路增加0 MPa热水排,在硫化机进路增加抽真空,在硫化机进路同时增加0 MPa热水排和抽真空。结果表明:在硫化机进路同时增加0 MPa热水排和抽真空,泄压量明显提升,硫化机开模前硫化胶囊内的压力能够全部排净,改进效果最好;硫化机可以自动开模,单机生产效率提高,轮胎过硫问题得到解决。     

PPy/CS复合电极热压成型条件的优化

以壳聚糖（CS）和聚吡咯（PPy）制备的复合材料为活性基体,在不添加黏结剂的条件下,采用热压成型法制备复合电极。重点考察了不同导电剂对电极力学性能的影响,热压温度、成型压力、热压时间及不同种类活性炭对电极电化学性能的影响规律。结果表明：通过热压法不添加黏结剂能够获得性能优良的复合电极;以活性炭为导电剂的电极溶胀性和亲水性最好,且活性炭的比表面积越大电极的电化学性能越好;电极热压成型的最优条件为：热压温度150℃、成型压力10 MPa、热压时间20 min。     

太阳能电池胶接结构在真空热循环下粘接性能研究

利用模拟空间热循环温度场设备对太阳能电池中石英玻璃盖片 /硅橡胶粘合剂 /硅晶片胶接结构进行了真空热循环试验 ( 12 3～ 4 0 3K ,10 -5Pa)。测试了热循环前后胶接试样的拉伸剪切性能、质损率和表面残余应力 ,观察了拉伸剪切断口形貌。结果表明 ,胶接试样室温拉伸剪切强度随热循环次数的增加而增强后下降 ,相应的断口破坏类型由混合型破坏转变为内聚破坏 ,最后为界面破坏 ,且胶接结构表面残余应力的变化为 :拉应力→零应力→压应力     

Microinjection molding of plastic microfluidic chips including circular microchannels

In this study, a microfluidic chip prototype having circular microchannels was replicated by microinjection molding process, employing a modularized and sectioned micromold system (MSMS). In the viewpoint of microfluidic manipulation, a microchannel with circular cross‐section shows several advantages over a conventional rectangular and/or square microchannel. To achieve a mass production of the microchannels with circular or round cross‐sections, the micromold was designed and fabricated based on the concept of MSMS. It consisted of several micromold modules, each having half‐circular cross‐sectional microstructures on its one‐side surface. The modules were precisely manufactured by a deep X‐ray lithography using a synchrotron radiation and a subsequent nickel electroforming process. Then, the MSMS for a microinjection molding process was constructed by assembling the nickel modules. After the molding of plastic plate with open microchannels of half‐circular cross‐section, a thermal bonding of microinjection‐molded plates was carried out to produce the microfluidic chip prototype including the circular microchannels. Observation of the surface quality, measurement of cross‐sectional profiles, and microfluidic test were carried out, which verified the usefulness of the present fabrication process. POLYM. ENG. SCI., 54:42–50, 2014. © 2013 Society of Plastics Engineers     

铜基正弦波微通道内流动沸腾传热特性试验研究

基于超快激光技术加工铜基正弦波弯曲型微通道,以去离子水为流动工质,在不同质量流量和热通量条件下,对弯曲型微通道内流动沸腾特性进行试验研究。基于温度/压力数据和流动可视化结果,发现通道传热系数随出口干度增大,呈迅速增大后减小并趋于稳定趋势,正弦波微通道相较直微通道具有更好的换热性能,传热系数最大提高127.7%,压降仅增加14.4%。波状通道结构能明显抑制流动沸腾中不稳定现象发生。通过可视化试验发现,随热通量增大,流型经历泡状流-弹状流-环状流的转变,换热主导机制由核态沸腾逐渐过渡到薄液膜蒸发。     

基于黏弹性模型的PMMA微流控芯片模内键合微通道变形研究

针对聚合物微流控芯片模内键合过程中微通道变形的问题,采用黏弹性材料模型对聚甲基丙烯酸甲酯(PMMA)微流控芯片模内键合过程中具有梯形截面的微通道变形进行了仿真分析;研究了在105℃下,芯片微通道在不同键合压力和键合时间下微通道的变形。结果表明:微通道不能保持键合前的尺寸,温升对微通道变形影响很小;微通道顶部与两侧的黏合使得微通道顶部宽度和微通道高度变形远大于底部宽度变形,并随着键合压力的增大而增大;当键合时间超过50 s后,键合时间对微通道变形影响很小,可以采用较长的键合时间来保证键合强度而不影响微通道形貌。     

氧化锆对微通道板用铅硅玻璃结构和性能的影响

通过X射线衍射(XRD)分析、拉曼光谱(Raman)分析、热膨胀系数以及维氏硬度等测试,探究了ZrO₂对微通道板铅硅玻璃的结构和性能等方面的影响。研究表明,引入8%(质量分数,下同)以内的ZrO₂可实现无析晶微通道板用铅硅玻璃的制备。玻璃中桥氧键的振动强度随ZrO₂含量的增加出现先增加后降低的变化趋势,对应热膨胀系数呈先降低后增加的变化趋势。ZrO₂含量为2%时,玻璃中桥氧含量达到最大,对应玻璃的热膨胀系数最小为80.5×10^-7 ℃^-1,此时微通道板耐离子轰击能力比无锆微通道板提高了33%。玻璃的维氏硬度随ZrO₂含量的增加逐渐变大,且ZrO₂含量低于5%时,维氏硬度变化较为明显。ZrO₂含量为8%时,玻璃的维氏硬度最大为5.1 GPa。     

30MN石墨电极压机真空系统故障诊断及处理

压机真空系统的真空度是影响石墨电极压型时生坯质量的关键因素之一,本文根据实际生产中积累的大量案例,对压机真空系统在运行过程中遇到的各类问题进行了描述,分析了故障出现的原因,并提出解决故障的办法.     

VACUUM CONTACT DRYING OF SELECTED BIOTECHNOLOGY PRODUCTS

The paper is mainly concentrated on investigations of the vacuum contact drying of the following biomaterials: (1) beer yeast, (2) whey and its components: proteinaceous liquid, lactose, post-lactose liquid, (3) saturated solution of the citric acid, (4) post-fermentation broth of the fodder antibiotic bacitracin. The investigations of vacuum contact drying process in which dried material adheres closely to a hot surface were performed. In order to make possible the determination of optimal process parameters the measurements were performed for various constant temperatures of the hot surface, total pressures in vacuum chamber and layer thickness of biomaterials.

The effective thermal properties for dry layers of selected biomaterials depending on temperature and total pressure were also experimentally determined.

A mathematical model of the vacuum contact drying for most intensive regime of its performance i.e. boiling one was presented. It will enable the process simulation and estimation of the dryers efficiency depending on process parameters.

In addition, investigations of beer yeast viability depending on the hot surface temperature and the total pressure were performed.     

金属基烤瓷牙冠残余应力产生的原因与控制方法

详细分析了金属基烤瓷牙冠残余应力产生的原因，认为金属与烤瓷热膨胀系数不匹配，制备工艺不合理以及金属与烤瓷结合欠佳等是产生残余应力和导致烤瓷破坏的主要原因，并对如何控制残余应力，关少烤瓷开裂和肃落进行了论述。     

VACUUM CONTACT DRYING OF SELECTED BIOTECHNOLOGY PRODUCTS

ABSTRACT

The paper is mainly concentrated on investigations of the vacuum contact drying of the following biomaterials: (1) beer yeast, (2) whey and its components: proteinaceous liquid, lactose, post-lactose liquid, (3) saturated solution of the citric acid, (4) post-fermentation broth of the fodder antibiotic bacitracin. The investigations of vacuum contact drying process in which dried material adheres closely to a hot surface were performed. In order to make possible the determination of optimal process parameters the measurements were performed for various constant temperatures of the hot surface, total pressures in vacuum chamber and layer thickness of biomaterials.

The effective thermal properties for dry layers of selected biomaterials depending on temperature and total pressure were also experimentally determined.

A mathematical model of the vacuum contact drying for most intensive regime of its performance i.e. boiling one was presented. It will enable the process simulation and estimation of the dryers efficiency depending on process parameters.

In addition, investigations of beer yeast viability depending on the hot surface temperature and the total pressure were performed.     

Sintering Kinetics of a MgAl2O4 Spinel Doped with LiF

The sintering kinetics of a pure magnesium aluminate spinel, MgAl₂O₄, and that doped with LiF were determined through the use of the master sintering curve technique developed by Su and Johnson. ²⁰ Powders with 0%, 0.5%, and 1.0% by mass LiF were densified in a vacuum hot press under a range of unaxial pressures. After the sintering mechanisms in each temperature and pressure regime were determined, an optimized vacuum hot-pressing schedule was formulated for spinel powders doped with 1.0% by mass of LiF. In addition to forming a transient liquid phase, the presence of LiF leads to the formation of oxygen vacancies that promote late-stage sintering in MgAl₂O₄.     

GF/PP复合纱针织物预型件热压成型的压力对复合材料拉伸强度的影响

本文实验研究了热压成型压力对GF/PP复合纱针织物制成的复合材料拉伸强度的影响.研究结果表明,在实验研究的压力范围内随着压力的增大,成型后的复合材料的拉伸强度呈现出先增大后减小的变化趋势.本文从压力的变化对熔融的树脂基体受到的向纤维束内部及纤维束之间渗透的外界推动力和阻力的影响角度分析讨论了产生该变化趋势的原因.     

Origin of improved average power factor and mechanical properties of SnTe with high-dose Bi2Te3 alloying

Chemical bond and defect engineering have profound impact on energy band and crystal structure of materials, which can adjust physicochemical and mechanical properties of materials. Bi_Sn and V_Sn are simultaneously designed in SnTe material system via the (SnTe)_x(Bi₂Te₃) alloying form, which was realized by vacuum melting and spark plasma sintering technology. Both point defects increase band gap and decrease ΔE_L−Σ, which improves obviously Seebeck coefficient of SnTe. The high-efficiency improvement in the middle temperature zone makes average power factor of (SnTe)₂₄(Bi₂Te₃) achieves 1656 μWm^-1K⁻²(323K–773K). Bi_Sn induces strong coupling hybridization between Te-5s and Te-5p, and forms the lower bonding state. The lower bonding state and the larger -IpCOHP increase bond strengthen, which result in the smaller thermal expansion coefficient and the higher hardness. Bonding evolution makes thermal expansion coefficient of SnTe reduce by 27%, and Vickers hardness increase by 44%. Higher average power factor, lower thermal expansion coefficient and higher hardness can improve output power density and service life, which provides strategies for exploiting high-power thermoelectric devices with suitable mechanical properties.     

Cyclic adsorption separation processes: analysis strategy and optimization procedure

An innovative analysis strategy and an optimization procedure have been developed with the purpose of design, evaluation and optimization of small- and large-scale units of cyclic adsorption processes using the classical Skarstrom's cycle: pressure swing adsorption (PSA) and vacuum swing adsorption (VSA).The system of partial differential equations of the dynamic simulator model was solved using a recent numerical technique developed within our group, based on an adaptive multiresolution approach, thus ensuring stability and accuracy. The simulator provides models for the multiple phenomena involved in fixed-bed adsorption: pressure drop, mass transfer resistance and energy balance.An extended parametric analysis is presented for the particular case of oxygen production from air by PSA and VSA: influence of the normalized purge flow rate, the high and low pressure values, dimensionless pressurization time, dimensionless production time, pressure drop and temperature in the bed.     

HRS技术在冶炼烟气制酸装置中的应用与实施

介绍了孟莫克HRS技术在2套800 kt/a铜冶炼烟气制酸装置中的应用与实施。简要介绍了制酸装置概况,详述了HRS系统的工艺流程、主要设备、仪表及自动化,以及项目的实施,包括采购与供货、制作与施工、试车与开车等。每套制酸装置生产低压饱和蒸汽52.1 t/h,产汽率达到0.493 t/t,收到良好的经济和环境效益。     

Preparation of La0.8Sr0.2CoO3-δ sputtering targets using a deformable compaction die

Fabrication of sputtering targets deviates from the customary practices in ceramic processing as their production volumes are often quite low. The use of hot-press, in this context, greatly facilities the fabrication of sputter targets since both the density and the dimensions of the target are controlled during the pressing. In the absence of hot press, however, the fabrication requires extensive preliminary work, but difficult to justify due to limited volume production. In this study, in place of customary rigid die, we propose the use of a deformable die which greatly simplifies the fabrication procedure. In this approach, polytetrafluoroethylene (PTFE) rings are used as compaction die filled with powders, tapped to uniform density. The die is then deformed between parallel platens whereby compacting the powders. The method relies on the fact that the pressing leads to almost no change in the internal diameter of the ring. This approach was illustrated with the fabrication of 2 in. La_0.8Sr_0.2CoO_3-δ (LSC-113) target where the deformable die was dimensioned by preliminary experiments on PTFE rings of small diameter. Sputter targets of sintered density greater than 0.95 and dimensions within the tolerances of the sputter gun were successfully fabricated. It is proposed that the approach may also be applicable to flat products of irregular shape, as high friction in tapped particulate media makes the lateral flow difficult, confining the compaction mainly to axial direction.     

Electron field emission from semiconducting nanowires

In this paper we report on investigations of field emission (FE) properties of semiconducting (SiC, ZnO) one-dimensional (1D) nanostructures – nanowire/nanorod arrays, and fabrication of low-voltage field emission display (FED) devices based on these 1D nanomaterials. SiC nanowires were grown on Ni-coated Si substrates using a thermal metal-organic chemical vapor deposition (MOCVD) technique, and ZnO nanostructures were grown on gold-coated Si substrates by a thermal CVD method. Electron field emission properties of SiC and ZnO nanostructures were examined in plane geometry using a flat phosphor screen. The interrelation between the FE characteristics (emission thresholds, current density, surface uniformity, etc.) and microstructure and surface morphology of the produced 1D nanostructures was established. Diode-type FED devices (flat vacuum lamps) with SiC-nanowire-based cathodes were developed and fabricated. The FEDs are characterized by low threshold and operating electric fields – lower 2 V/μm and 5 V/μm, respectively, high current density and brightness, and stable performance of the nanowire-based cathodes.     

Recent advances in electrochemical biosensing schemes using graphene and graphene-based nanocomposites

The last decade has witnessed tremendous advances in the use of graphene and graphene-based nanocomposites for the fabrication of electrochemical (EC) sensors and biosensors with improved analytical performance. With unique and highly desirable morphology, chemical/thermal stability and EC properties, the graphene-based materials are paving way to the implementation of mediatorless EC detection schemes with direct electron transfer. This approach enables the development of highly performed biosensors with respect to detection sensitivity, precision, specificity, and stability. This review provides a comprehensive overview of the field apart from providing intensive information of the fabrication, properties, characterization and EC applications of graphene and its nanocomposites. Two key challenges, the lack of international regulatory guidelines for nanotoxicity analysis and potential mass production of analytical devices, will also be discussed along with the trends in nanobiotechnology and the requirements in healthcare and industrial applications.