Preparation of TiC powders by carbothermal reduction method in vacuum

The preparation of fine TiC powders by carbothermal reduction of TiO2 in vacuum was investigated by XRD,SEM,XRF and laser particle sizer.Thermodynamic analysis indicates that it is easy to prepare TiC in vacuum and the formation sequence of products are Ti4O7（Magneli phase）,Ti3O5,Ti2O3,TiCxO1-x and TiC with the increase of reaction temperature.Experimental results demonstrate that TiC powders with single phase are obtained with molar ratio of TiO2 to C ranging from 1：3.2 to 1：6 at 1 550 ℃ for 4 h when the system pressure is 50 Pa,and TiC1.0 is gained when the molar ratio of TiO2 to C is 1：4 and 1：5.In addition,fine TiC1.0 powders（D50 equals 3.04 μm） with single phase and low impurities are obtained when the molar ratio of TiO2 to C is 1：4.SEM observation shows that uniform shape,low agglomeration,and loose structure are observed on the surface of block product.

Improvement of silty clay by vacuum preloading incorporated with electroosmotic method

A laboratory test was performed to assess the effectiveness of vacuum preloading incorporated with electroosmotic (EOM) treatment on silty clay (combined method) for reclamation projects like new disposal ponds, where the horizontal electrode configurations beneath the soil layer were possible and the drainage pipes and the prefabricated vertical drains (PVDs) system could be easily installed in advance before the sludge dragged from sea bed or river bed was filled into the site. Three groups of tests were conducted on the silty clay from Qinhuai River in Nanjing, China. The model is able to apply vacuum pressure at the bottom of the soil layer and a direct current electric field simultaneously. It is also possible to measure the pore pressures at different depths of soil column, and the changes in settlement and volume with the elapsed time. In this study, the vacuum preloading method, vacuum preloading applied at the bottom (VAB method), was applied and the cathodes were installed beneath the soil layer. The results obtained indicate substantial reduction in water content, and increases in dry density and undrained shear strength in comparison with those obtained by the vacuum preloading only, particularly at the positions close to the anode. The combined method utilizes the vertical drainage flow created by the electroosmosis integrating the horizontal drainage flow created mostly by the vacuum pressure. The total drainage flow can be calculated as a result of the vertical drainage flow by electroosmosis only and the horizontal drainage flow by the vacuum preloading only. The way of placement of the cathode and the anode in the combined method also overcomes the disadvantage of EOM method itself, i.e. the appearance of cracks between the anode and the surrounding soil. Moreover, it is observed that the vacuum preloading plays a primary role in earlier stage in deduction of free pore water; meanwhile, the electroosmotic method is more efficient in later stage for absorbing water in the diffused double layers of soil.

Structure and Performance of Fe-N_x-C Catalyst for Oxygen Reduction Reaction Prepared by Vacuum Casting Method and the Second Pyrolysis

Affordable non-precious metal（NPM） catalysts played a vital role in the wide application of polymer electrolyte membrane fuel cells（PEMFC）. In current work, a facile vacuum casting reacting method based on vacuum casting was introduced to prepare Fe-N_x-C oxygen reduction reaction（ORR） catalysts with high efficient in acid medium. The catalysts were prepared with ammonium ferrous sulfate hexahydrate（AFS） and 1,10-phenanthroline monohydrate utilizing homemade mesoporous silica template. The heat treatment and its influence on structure and performance were systematically evaluated to achieve superior ORR performance and some clues were found. And 850 ℃ was found to be the best temperature for the first and second pyrolysis. The linear sweep voltammetry（LSV） results showed that there were only 18 mV slightly negative shifts of half-wave potential（E_（1/2）） of the optimal catalyst（749 mV） compared with the commercial Pt/C（20 μg·Pt·cm^-2）. Besides, I850 R also showed better electrochemical stability and methanol-tolerance than that of Pt/C. All evidences proved that our vacuum casting reacting strategy and heat treatment process were prospective for the future R＆D of high performance Fe-N_x-C ORR catalysts.

Constant Stress Accelerated Life Tests for Vacuum Fluorescent Display Based on Least Square Method

To estimate the life of vacuum fluorescent display （VFD） more accurately and reduce test time and cost, four constant stress accelerated life tests （CSALTs） were conducted on an accelerated life test model. In the model, statistical analysis of test data is achieved by applying lognormal function to describe the life distribution, and least square method （LSM） to calculate the mean value and the standard deviation of logarithm. As a result, the accelerated life equation was obtained, and then a self-developed software was developed to predict the VFD life. The data analysis results demonstrate that the VFD life submits to lognormal distribution, that the accelerated model meets the linear Arrhenius equation, and that the precise accelerated parameter makes it possible to acquire the life information of VFD within one month.

Vacuum Filling Simulation with Combined Lagranian and VOF Method

Jetting succeeded by accumulation is the characteristic of the vacuum filling,which is different from the conventional pressure-driven flow.In order to simulate this kind of flow,a three-dimensional theoretical model in terms of incompressible and viscous flow is established,and an iterative method combined with finite element method(FEM)is proposed to solve the flow problem.The Lagranian-VOF method is constructed to trace the jetting and accumulated flow fronts.Based on the proposed model and algorithm,a simulation program is developed to predict the velocity,pressure,temperature,and advancement progress.To validate the model and algorithm,a visual experimental equipment for vacuum filling is designed and construted.The vacuum filling experiments with different viscous materials and negative pressures were conducted and compared with the corresponding simulations.The results show the flow front shape closely depends on the fluid viscosity and less relates to the vacuum pressure.

预处理方式对冻干草莓片品质的影响

以草莓为原料制备冻干草莓片,研究鲜切冻藏、亚冻结切片和完全解冻切片3种不同预处理方式对冻干草莓片品质的影响。分析了冷冻草莓原料水分间的迁移情况、花色苷含量,并评价了冻干草莓片的感官品质和质构特性。结果表明:在3种预处理方式中鲜切冻藏(-25℃)和亚冻结切片(-5~-8℃)草莓原料品质较好,水分迁移较小,花色苷含量无显著变化,且两者的冻干草莓片硬度、弹性、形变率等质构特性较好,感官品质与新鲜草莓的冻干成品接近。因此,在草莓冻干加工中宜选用鲜切冻藏或亚冻结切片草莓为加工原料。

不同干燥方式对柠檬片品质的影响

该研究旨在探究不同干燥方式对贮藏期柠檬片品质的影响。分别采用真空冷冻干燥(vacuum freeze drying,VFD)、热风干燥(hot air drying,HAD)、微波干燥(microwave drying,MD)3种方式加工制备柠檬片,并研究了3种干燥方式对柠檬片色泽、基础品质、营养物质和风味的影响。结果表明,柠檬片经过真空冷冻干燥、热风干燥、微波干燥不同干燥处理后品质与风味不同。冻干组柠檬片具有较小的收缩率(11.65%),较高的复水比(5.14)、亮度值(48.6)和V_(C)含量(3.13 mg/g DW),电子鼻各传感器的响应值较高,即其色泽、品质、风味都优于热风干燥与微波干燥方式。因此,使用冻干工艺可以保证品质。

铀矿实物地质资料保护技术探究——以铀矿岩心保护为例

岩心是铀矿资源勘查和开发中重要的数据来源,其对于研究矿床成因、预测矿床分布、评价矿产资源量和开采等具有重要意义。文章深入探究了岩心的保护技术,分析了目前常见的保护方法——石蜡封护法、树脂浇筑法以及真空包覆法的优缺点及对铀矿岩心的适用性。研究结果表明,石蜡封护法、树脂浇筑法和真空包覆法均可用于铀矿岩心保护,应根据实际需要选择最适合的方法,真空包覆法在铀矿实物地质资料保护中的实用性更强,应加强这一方法的应用研究。

时域间断伽辽金-粒子模拟方法研究进展

时域间断伽辽金-粒子模拟(discontinuous Galerkin time-domain particle-in-cell,DGTD-PIC)方法采用非结构网格能准确描述复杂结构,采用高阶基函数进一步提高了计算的精度,同时避免了求解大型逆矩阵,在等离子体和高功率电磁学相关数值模拟方面具有广泛的用途。近年来国内外报道了大量DGTD-PIC方面的研究工作,该方法在核心关键技术方面已取得了许多突破性进展。为促进DGTD-PIC方法的发展及应用,本文对该方法在修正势的DGTD电磁场计算方法、复频移完全匹配层边界、非结构网格中带电粒子定位与电荷和电流分配等关键技术方面所取得的研究成果进行了详细介绍。

侧向排汽凝汽器设计与研发

介绍了侧向排汽凝汽器的设计要点及关键技术,包括汽轮机与凝汽器的整体布置方案、凝汽器管束布置、凝汽器数值传热和真空力平衡方式等。侧向排汽机组布置紧凑,减少了土建成本,具有良好的社会及经济效益,通过对其设计与研发的介绍,为侧向排汽机组的推广提供了技术支持。

真空微波干燥对草莓脯品质的影响

为了研究真空环境下不同微波干燥条件对草莓脯质地和营养品质的影响,本文以热风干燥为对照,对3种真空微波处理条件(2.5 w/g-1.5 h、3.5 w/g-1 h、4.5 w/g-0.5 h)获得的草莓脯的水分迁移特性、质构特性、微观结构、色泽及花色苷和酚类物质进行了测定。结果显示,真空微波干燥将草莓脯干燥至含水量20%±2%所需时间显著低于热风,微波功率越大,干燥时间越短。另外,干燥后获得的草莓脯中水分主要呈现结合水与不易流动水2种状态。真空微波干燥获得草莓脯的弛豫时间T2随微波功率增加而增大,说明水分自由度增加;横截面显微观察发现,真空微波干燥使细胞壁发生破裂,微波功率越大,裂隙形成部位越靠近髓芯,裂隙越大,孔隙率越小,而热风干燥的样品细胞完整性、孔隙率高于微波干燥。另外,真空微波干燥的草莓脯硬度、粘力、a^(*)值均低于热风干燥的样品,但L^(*)值、总糖、花青素以及酚类物质的含量均较高。综上所述,真空微波干燥具有更高的干燥效率,并能更好保留草莓脯中花色苷等营养物质。

不同干燥方式对毛竹笋全粉中氨基酸含量和蛋白质结构的影响

为探究不同干燥方式对竹笋全粉氨基酸含量及蛋白质结构的影响,该实验采用喷雾干燥(spray drying,SD)、热风干燥(hot air drying,HAD)、微波干燥(microwave drying,MD)、低温真空干燥(low-temperature vacuum drying,LVD)4种方式制备毛竹笋全粉(Phyllostachys pubescens shoot powder,PPSP),分析了4种干燥方式的PPSP氨基酸组成及含量,并基于拉曼光谱酰胺Ⅰ带比较了4组样品蛋白质二级结构变化。结果表明,LVD制备的PPSP总氨基酸含量最高,为29.19 g/100 g,其次为SD,HAD制备的PPSP总氨基酸含量最低。LVD组的PPSP中必需氨基酸含量最高,为10.43 g/100 g,占总氨基酸含量的35.73%。LVD和SD制备的PPSP中呈味氨基酸含量分别为17.58 g/100 g、15.81 g/100 g,显著高于HAD和MD组的呈味氨基酸含量。LVD样品中氨基酸组成最接近于标准模式谱。通过主成分分析提取出2个主成分,累计方差贡献率达89.45%,综合评分结果为:LVD>SD>MD>HAD,聚类热图将4种干燥方式分为3类。干燥后的PPSP蛋白质中β-折叠结构最高,占总二级结构的74.66%~83.35%,HAD样中β-折叠、α-螺旋结构含量明显高于其他样品。该研究可为毛竹笋干燥及竹笋全粉的开发利用提供理论参考。

Formulating Highway Paving Asphalts from the Vacuum Residue of a Paraffinic Crude

Many specifications of paving asphalts are closely related to their colloidal stability, which is, however, determined by their exact chemical compositions. The Yumen vacuum residue (YVR), the bottoms of a paraffinic crude oil is unfit for the production of highway paving asphalts directly, Neither are the de-oiled asphalts of the YVR. In this research a blending method and an optimal process of solvent de-asphalts are adopted to investigate the feasibility of formulating highway-paving asphalts from YVR. Results show that highway paving asphalts are formulated by blending solvent de-oiled asphalts with one or more of the materials including YVR, decanted oil from FCC process, and furfural extracts from lubricating base stocks. Further investigations indicate that adding oil decanted from FCC process to the solvent de-asphalting process can increase the de-asphalted oil production, improve the de-oiled asphalts quality, and thus optimize the refinery processes. The methodology of this research can be extended even to refineries processing non-paraffinic crude oils.

光子晶体结构生色真丝织物的制备及应用研究

为实现真丝织物的结构生色,文章分别利用真空辅助过滤法和手绘法在白色真丝织物上构筑光子晶体结构。进一步探究真空辅助过滤法中微球组装液体积浓度对结构色的影响规律,分析微球在真丝织物上形成光子晶体运动机制,讨论真丝织物上光子晶体结构色的虹彩效应,并探究手绘法在真丝织物光子晶体结构生色中的应用效果。结果表明:真空辅助过滤法中聚(苯乙烯-甲基丙烯酸),即P(St-MAA)微球组装液的体积浓度为2.4 L/m^(2)时,真丝织物的两面能同时获得光子晶体结构色,此时正反面结构色的反射率峰值在18%左右;在真空辅助过滤法中,P(St-MAA)微球在真丝织物上形成光子晶体结构的过程遵循“先反后正”堆积原则,即织物反面先形成光子晶体,随后微球进一步透过织物堆积在正面。此外,该光子晶体结构生色真丝织物的虹彩效应不明显,与常规染料或颜料着色效果接近;手绘法可以获得图案化的光子晶体生色结构,较适合于个性化加工。该研究为光子晶体结构生色在真丝织物着色中的应用提供参考。

基于十字中心定位算法的MEMS真空封装光学检漏方法

典型的光学检漏方法需要对整幅干涉图甚至多幅干涉图进行图像处理,过程相对复杂。本文结合MEMS器件封装结构的对称特性以及变形分布特征,提出了一种简单、快捷的十字中心定位算法。通过确定干涉图案中心点坐标,获取中心线光强分布,进而拟合得到样品中心线形貌。进一步利用封装结构中心点随真空度变化的相对位移,计算得到漏气率。本文以圆形封装结构为例,证明了该方法的可行性。

整流罩紧固环故障件分析及专家判定法判定筛选

在硬度不合格故障件排查中,用视觉外观对比、体式显微镜对比、表面能谱和金相组织分析,对整流罩紧固环真空退火和未真空退火零件进行了对比分析,合格件显亮色,有金属光泽,故障件金属光泽暗淡。采用专家判定法,通过视觉外观差异检查判断,对整流罩紧固环待装配零件进行了筛选,从故障批零件中筛选出了硬度偏高不合格零件,筛选后整流罩紧固环滚压粘接100%合格,满足了产品加工需求。

ZIF-8改性细菌纤维素膜的制备及对盐酸四环素吸附性能研究

使用生物基有机材料细菌纤维素(BC)作为载体,沸石咪唑骨架-8(ZIF-8)为客体材料,采用一步真空抽滤法,制备BC/ZIF-8复合纤维膜。通过FT-IR、XRD、SEM、EDS、BET等对制备的复合纤维膜进行了结构表征,考察了接触时间、温度、离子浓度,底物的初始浓度对复合纤维膜吸附盐酸四环素(TC)的影响。结果表明改性后的复合纤维膜较初始BC膜具有更丰富的孔结构,氮气吸附-脱附曲线测得比表面积从6.2415 m^(2)/g增加到265.8820 m^(2)/g。吸附实验表明,离子浓度对吸附影响较小,吸附过程符合准二级动力学模型和Langmuir等温吸附模型,TC主要以单层吸附的形式吸附到在BC/ZIF-8复合纤维膜上,理论最大吸附量为438.59 mg/g。

蒸汽诱导法辅助相转化法制备疏水PDMS-PVDF微孔膜及其结构性能研究

采用蒸汽诱导法辅助浸没沉淀相转换法制备了硅橡胶-聚偏氟乙烯(PDMS-PVDF)疏水微孔膜并用于真空膜蒸馏NaCl水溶液,通过衰减全反射傅里叶变换红外光谱仪、X射线衍射仪、扫描电子显微镜、接触角测试仪对微孔膜的形貌结构和表面接触角进行表征和测试,研究了相对湿度对微孔膜结构和性能的影响。结果表明:随着相对湿度的增加,微孔膜表面接触角逐渐增加,孔隙率提高,平均孔径为(31±2)nm;截留率均达到99.9%以上,渗透通量先增加后降低;相对湿度为70%时制备的微孔膜渗透通量可达5.2kg/(m^(2)·h)。

基于遗传算法的南瓜联合干燥工艺优化

[目的]优化南瓜热风—真空联合干燥最佳工艺参数。[方法]对南瓜进行热风干燥、真空干燥及热风—真空联合干燥试验,以单位能耗、复水比及色差为评价指标,对比其干燥特性,以BP神经网络模型结合遗传算法,基于熵权结合加权评分法对南瓜热风—真空联合干燥进行多目标综合优化。[结果]同等条件下,热风干燥效率最高;当干燥温度为55℃,含水率转换点为30%时,联合干燥时间比真空干燥缩短了52.63%;真空干燥单位能耗最低;热风干燥的复水性能最差;真空干燥的色泽最好;结合BP神经网络模型的遗传算法得到最优干燥参数为热风干燥温度65℃,转换点含水率50%,真空干燥温度56.0509℃,此时单位能耗、复水比和色差值与验证实验值的平均相对误差分别为2.5%,5.53%,4.84%,均<6%。[结论]南瓜热风—真空联合干燥兼具热风干燥和真空干燥的优点,且结合BP神经网络遗传算法模型可以优化其工艺参数。

利用真空衰减法测试预包装食品的密封性

目的 预包装食品的密封性关系到食品质量与安全。本文针对预包装食品目前普遍采用水检气泡法时灵敏度不足的问题,采用真空衰减法检测食品包装的密封性。方法 分别利用2种不同检测技术对市面上55款预包装食品样品进行密封性检测,并根据包装类型、封合方式、包装规格等不同分类方式将测试数据进行综合比较分析。结果 水检气泡法测试成本低,可明显地指示出泄漏位置,但方法灵敏度较低,且无法准确定量;真空衰减法可在不破坏原有包装的情况下,大幅度提高检测灵敏度,并得到定量数据,但无法准确指示泄漏点位。结论 真空衰减法可以作为水检气泡法的有效补充方法在实际工作中使用。