PREPARATION OF NANOMETER ZINC OXIDE BY EVAPORATION METHOD

Nanometer ZnO particles were synthesized by evaporating of zinc powders of averageparticle size of 370μm studied by XRD, TEM and electron diffraction. The particleswere formed by the oxidation of evaporated zinc vapor in the air. It was found that the particles range from 70 to 100nm in average particle size. The effect of experimental parameters was investigated, the increase of the air flow-rates reduced the average particle size, while increasing the evaporation temperature and the amount of metal charged increased the average particle size. TEM of the particles collected showed that the crystal habits of particles have a tetrapod-like of wurtzite structure consists of four needle crystals. It was found by electron diffraction that all particles were single crystal.

STUDY ON NANOMETER ZINC PARTICLES FABRICATED BY GAS EVAPORATION METHOD

Nanometer Zn particles with mean diameters 12-100nm made by evaporating its powders in argon gas were studied mainly by X-ray diffraction and electron microscopy. They are collected at various distances and those factors influencing the mean particle size were studied. The optimal synthetic conditions were obtained, i.e., evaporation temperature is 1200℃; argon flow rate is 0.4m3/h; amount of powder charged is 3g; distance from evaporation source is 10cm. It was found that the size of particles was governed by argon flow rate, evaporation temperature, amount of metal charged and distance from the source. The size increases remarkably with distance in the space where no metal vapor exists. This implies that the crystallites grow by coalescence. Electron micrographs and diffraction patterns are reproduced to show the size, shape and state of oxidations. Nanoparticles with definite crystal habits were sometimes observed among those with irregular ones.

PHOTODEGRADATION OF p-NITROCHLORBENZENE(p-NCB)USING NANOMETER-SIZED ZnO PARTICLES PREPARED BY REACTIVE EVAPORATION METHOD

Photocatalytic degradations of p-nitrochlorbenzene (p-NCB) with distilled water wereinvestigated with ZnO crystals (catalyst) of 70nm in diameter under UV irradiation.The suitable experimental conditions are determined as: ZnO 0.25g, pH 7, p-NCBconcentration 30mg/L. These variables in terms of the degradation rate have beendiscussed, which was defined as the rate of the initial degradation to the final degrada-tion of p-NCB. When all of the experimental degradation rate values are plotted as afunction of irradiation time, all of the points appeared on a single line for wide range ofp-NCB degradations. On the basis of these results, it has been concluded that at lowerZnO catalyst amount, much of the light is transmitted through the slurry in the con-tainer beaker, while at higher catalyst amount, all the incident photons are observedby the slurry. Degradation rates of p-NCB were found to decrease with increasingsolution pH. It has been concluded that the maximum degradation rate values of p-NCB under principally the same experimental conditions mentioned above are 97.4%,98.8% and 95.5% at 100min respectively. The results suggest that the photocatalyticdegradation is initiated by an oxidation of the p-NCB through ZnO surface-adsorbedhydroxyl radicals. Absorption spectra are recorded using spectrophotometer before andafter UV-irradiation in the wavelength range 200-400nm at room temperature. Itis found that the variation of irradiation time over the range 20-100min resulted inchange in the form of the spectrum linear absorption and a higher maximum valuewill be obtained at longer irradiation time.

Synthesis and growth mechanism of SiC/SiO2 nanochains by catalyst-free thermal evaporation method in Ar/CO atmosphere

SiC/SiO2 nanochains were synthesized on a carbon fiber substrate by a catalyst-free thermal evaporation method in the Ar/CO atmosphere.X-ray diffraction(XRD),Fourier-transform infrared spectroscopy(FT-IR),scanning electron microscopy(SEM)and transmission electron microscopy(TEM)revealed that the as-synthesized SiC/SiO2 nanochains are composed of single-crystalline SiC nanowires and amorphous SiO2 beads.The introduction of CO can promote the formation of SiO2,so that the SiC/SiO2 nanochains are subsequently formed during cooling.In addition,the photoluminescence spectrum of SiC/SiO2 nanochains showed a broad emission peak at around 350 nm,which is ascribed to the oxygen discrepancy in the SiO2 beads as well as the SiC/SiO2 interfacial effect.These findings can provide guidance for further study of the vapor growth of 1D SiC-based materials.

STRUCTURE IMPROVEMENT AND TEMPERATURE FIELD SIMULATION OF PREPARING NANOPOWDER BY EVAPORATION-CONDENSATION METHOD

A new apparatus, with a segregable conical water cooling condenser, which is heated by an electric arc using the evaporation-condensation method to prepare carbon-coated nanopowder, has been developed by the authors. Numerical simulation of the temperature field is done by the ANSYS software, and temperature in the reaction vessel is measured with the help of an experiment, to verify the simulation result. Influence of the temperature field in the reaction vessel, on the process of preparing nanopowder is then discussed simply. It is shown that the segregable conical water cooling condenser and carbon-coated surface process can be used to prepare steady carbon-coated metal nanopowder, at a lower cost and higher yield rate than the traditional structure. Simulation of the temperature field in the apparatus shows that the arc heating method can form a temperature field in the apparatus, which is quite favorable for nanopowder formation. Experiments show that the rational parameters using this apparatus, with the arc heating method to prepare carbon-coated nanopowder are electricity 60-100 A and arc length 5-8 mm.

Numerical Simulation and Control of Two-Phase Flow with Evaporation in a Vertical Tube Submitted to a Conjugate Heat Transfer

A better understanding of two-phase flows with evaporation allows leading to an optimal design of evaporators. For that purpose, numerical simulations are very useful. In this paper, a numerical study has been carried out in order to model and simulate the combination of a two-phase flow with evaporation in a vertical tube. The VOF （volume-of-fluid） multiphase flow method and a phase-change model for the mass transfer have been used. For an accurate modeling, the effect of axial conduction has been also taken into account using a conjugate heat transfer model. Since thermal oscillations are undesirable as they can lead to the failure of the tube, flow instabilities have also been analyzed, using FFT （fast Fourier transforms）, in order to comprehend their behavior and influence. A control study of the flow instabilities in the tube is also presented. For that purpose tube inlet temperature has been varied using a gain control parameter.

The Application of Synthetic Fuzzy Assessing Method in Measurement and Control System of Plating Solution Evaporator

The synthetic fuzzy assessing method is usually applied to sensory evaluation. The method has simple and reliable virtue, and it is consistent with objective evaluation results. Using this method, system status of plating solution evaporator is evaluated, and the result is applied to compensate a fuzzy controller. Experimental results have shown the correctness and the validity of the proposed approach.

翅片管蒸发器传热性能的参数灵敏度分析

采用Sobol´全局灵敏度分析方法,计算出了各个影响参数对传热系数的一阶灵敏度和总灵敏度,探索和分析了单个及多个波纹翅片管参数对波纹翅片管蒸发器传热系数影响的程度和规律,并构建了传热系数与各个参数之间关系的响应面。结果:从灵敏度数值及响应面的分析皆显示:翅片间距对传热系数的影响最大,翅片厚度的影响次之,质量流量与工资热流密度对传热系数的影响相差不大,但大于管外径的影响;且翅片间距与其余各个因素之间的交互影响在一定范围内极其剧烈,其中翅片间距与翅片厚度之间的交互影响最大,又以质量流率与工质侧热流密度之间的交互影响次之;再者,垂直于风速方向的管间距与平行于风速方向的管间距的灵敏度数值皆为0,说明两者对传热系数的影响可以忽略不计。

耐高温阻硅垢荧光缓释微球的制备与缓释特征

缓释型阻垢剂常用来延长阻垢剂作用距离和时间,但在地热开采等高温循环水中,常规缓释技术释放速度过快导致效果不佳。为增强高温下的缓释效果,本文以耐热材料聚苯乙烯为壁材,以固相/油相/水相溶剂挥发法制备新型阻垢缓释微球,优选了芯材和乳化剂,探究了制备工艺,并利用荧光技术测试了缓释效率和阻垢效果。结果表明:硅藻土和十六烷基磺酸钠分别适宜用作固相吸附材料和乳化剂;乳化剂浓度为2%,芯材浓度为50 mg/mL,搅拌速度300 r/min为最佳制备条件。制备的微球静态释放时间长达100 h,动态释放时间超过20 h, 20 h阻垢率50%以上。本成果有望为高温循环水提供新型缓释阻垢技术。

包覆低共熔溶剂的聚苯乙烯微胶囊吸附Li^(+)的性能研究

为实现绿色、低成本从海水中提锂的目标,采用同轴共流微流体技术结合溶剂挥发法制备包覆有低共熔溶剂(甲基三辛基氯化铵/癸酸)的聚苯乙烯微胶囊。所制备的微胶囊颗粒呈均一的球形。将该微胶囊用作萃取Li^(+)吸附剂,系统研究了吸附时间、吸附温度、溶液pH、初始锂浓度和固液比对Li^(+)吸附量和萃取率的影响。结果表明在吸附Li^(+)水溶液时,微胶囊对Li^(+)的最大吸附量为32 mg·g^(-1)。碱性条件时微胶囊对模拟海水中的Li^(+)吸附分配比为10.22 L·g^(-1)。

蒸发冷却空调室外计算参数生成方法研究

介绍了现行规范中夏季室外计算参数和设计日的确定方法,并在我国现行规范方法的基础上,根据蒸发冷却技术适应区,选取4个典型城市,形成了以湿球温度为主、干球温度为辅的蒸发冷却空调室外计算参数。提出一种新的设计日确定方法,以台站历史长期观测数据为基准,提取典型城市夏季室外气候日变化特征和趋势,利用逐时系数法获得夏季设计日的数据。结果表明:新方法得到的室外计算干湿球温差降低,蒸发冷却潜力下降,按照现行规范中的方法指导设计会造成设计不足;现行规范中的设计日不能准确反映各地区夏季室外气候的变化趋势,研究提出的逐时系数法得到的设计日数据更符合典型城市的实测数据。

聚丁二酸-共-对苯二甲酸丁二醇酯/氧化镁复合薄膜的制备及性能

以聚丁二酸-共-对苯二甲酸丁二醇酯(PBST)为基体,纳米氧化镁(MgO NPs)为抗菌剂,通过溶剂挥发法制备了PBST/MgO纳米复合薄膜,并探讨了复合薄膜在食品包装中的应用。研究了MgO NPs对纳米复合薄膜的机械性能、水蒸汽透过率(WVP)、氧气透过率(OTR)和紫外阻隔性能的影响。结果表明:MgO NPs的加入改善了PBST基体的力学性能和阻隔性能。与PBST薄膜相比,复合膜的拉伸强度和断裂伸长率分别提高了43.7%和32.2%,水蒸汽透过率和氧气透过率分别降低了28.1%和23.6%,并具有良好的紫外阻隔性能。当MgO NPs质量含量为5%时,复合膜的性能最佳。

含蒸发式稳定器模型燃烧室的液雾两相燃烧数值模拟

带蒸发式稳定器的燃烧室通过向稳定器蒸发管内供油的方式,改善稳定器下游的油雾分布,在低压和低油气比等极限工作条件下提高燃烧室的燃烧性能。然而由于蒸发管内存在燃油雾化、液滴碰壁飞溅以及蒸发等过程,难以直接对蒸发管内的物理过程进行数值模拟得到稳定器下游的油雾场分布。对于燃油蒸发管内部复杂的物理过程,根据蒸发管内部流动特性提出蒸发管雾化简化模型,并在欧拉-拉格朗日框架下,采用PaSR湍流燃烧模型结合动态自适应建表(ISAT)方法,对含蒸发式稳定器模型燃烧室在低压条件下的流动及两相燃烧开展数值模拟,得到的燃烧室横截面燃气温度以及燃烧效率的模拟结果和实验接近,表明提出的简化蒸发管雾化模型能够给出合适的稳定器下游燃油分布以及燃烧场计算。

从酸性高浓度含砷溶液中脱砷研究进展

含砷的有色金属和贵金属硫化矿在冶炼过程中会产生酸性高浓度含砷溶液,其具有砷浓度高、成分复杂、变化大、毒性强和难以存放等特点,如不加处理直接排放,会对环境和人类健康产生很大影响。综述了化学沉淀法、蒸发浓缩法和金属粉末法的脱砷原理及优缺点,以及各脱砷方法的研究进展,为脱砷技术发展提供参考和借鉴。

乳化溶剂蒸发法在递送体系中的应用

将生物活性物质载入递送体系可以改善其水溶性、稳定性和生物利用度,便于在食品、药品和化妆品等领域应用。乳化溶剂蒸发法是一种常见的制备活性物质递送载体的方法,具有使用条件温和,易于操作和放大,溶剂残留较低等优点。本文简要介绍乳化溶剂蒸发法,综述材料的选择和制备过程对所制载体的影响以及该法在制备活性物质递送体系中的应用研究进展,旨在推动乳化溶剂蒸发法的深入研究和实际应用。

外水相组成对醋酸戈舍瑞林PLGA微球理化性质的影响

目的 采用W/O/W和O/W乳化溶剂挥发法制备醋酸戈舍瑞林PLGA微球,考察在外部水相中加入不同浓度的氯化钠和甘露醇对所制备微球理化性质的影响。方法 醋酸戈舍瑞林PLGA微球采用W/O/W和O/W乳化溶剂挥发法制备,以微球的表面形态、内部形态、粒径、载药量、体外累计释放行为、结构和晶型来评价不同浓度的添加剂对两种制备方法所制得微球的影响。结果 采用W/O/W制备的微球增加外水相中氯化钠的浓度,微球载药量增加、粒径减小、突释量降低、微球表面及内部孔洞减少;增加外水相中甘露醇的浓度,微球载药量增加、粒径减小,突释量降低、微球表面孔洞减少,内部孔洞未减少;O/W法制备的微球增加水相中氯化钠和甘露醇的浓度,微球载药量增加、粒径减小、突释量降低、微球表面及内部孔洞减少。结论 通过增加外部水相中添加剂的浓度,有效改善了醋酸戈舍瑞林PLGA微球的结构和性质。

套管式CO_(2)蒸发器的性能模拟与优化计算

为优化设计套管式CO_(2)蒸发器,达到提高换热器效率的目的,采用稳态分布参数法对其建立仿真模型,并对模型精度进行实验验证。分析蒸发器内外部条件、结构参数对换热性能的影响,并分析干涸现象与管长的关系。结果表明:蒸发温度和质量通量对换热性能影响较大,蒸发温度由4℃降至-4℃,制冷量下降4 500 W/(m^(2)·K);质量通量每升高100 kg/(m^(2)·s),换热系数平均升高约1 000 W/(m^(2)·K);在设计工况下,干涸前CO_(2)流体所行进管路长度先下降再升高,且在蒸发温度为0℃达到最低点。在结构参数方面,外管管径为23 mm时,蒸发器换热效果较好。当冷冻水温度从11℃降至10℃时,压降下降3.5 kPa,明显低于其他温度情况下的压降情况。

基于最小二乘法的间冷开式循环水系统水量损失计算

某炼油厂循环水系统每天的计算水损失量与实际水损失量存在一定的偏差。针对该问题,对该套循环水系统水量损失的计算情况进行了校正。通过试验装置的水量损失数据与计算数据对比并利用最小二乘法进行拟合,拟合后的曲线最优区间变化斜率k控制在1.06~1.09且循环水最优区间变化截距b控制在14~19时,实际损失量与计算数值的偏差率可控制在5%以内;当k取值为1.07且b取值为15时,最大偏差率仅为4.77%,验证了该算法的可行性。

吸湿排汗功能织物研究现状及展望

文章针对影响织物吸湿排汗性能的因素,从润湿芯吸和蒸发排汗两个方面进行分析,介绍吸湿排汗过程中水分传递及分布的测试方法,综述织物吸湿排汗过程的理论模型,包括毛细管芯吸模型和蒸发排汗模型。研究发现,针对织物内部水分芯吸传递的理论研究还比较匮乏。最后,结合纺织品的发展现状与趋势,对吸湿排汗织物未来的研究重点、应用前景和绿色化生产进行展望,为织物性能优化与舒适性面料开发提供参考。

差压法测定NEG吸氢性能

通过对定压法进行改进提出了差压法,用于测试非蒸散型吸气剂(NEG)的吸氢性能。该方法在进气室和吸气室之间安装固定流导元件,利用调节微调阀提供可控的进气流量,通过测量吸气室、进气室和参考室的压力计算NEG的吸气性能参数。利用两种NEG比较了差压法和改进的定压法所测吸气性能。结果表明:差压法测得的吸气容量比改进的定压法测得的吸气容量低0.07268 Pa·L;腔室壁面吸附能力使改进定压法的试验结果高于理论结果,而差压法的试验结果不受影响;对改进的定压法进行优化后,其计算结果与差压法的接近。差压法可以获得更准确、更有效的吸气剂性能参数,在差压法中,参考部分和试验部分同时进行测试,可缩短测试时间,减少控制进气带来的误差。