微纤化程度对MFC气凝胶的性质和包装性能的影响

目的 深入研究制备过程中微纤化程度对微纤化纤维素（MFC）气凝胶的性质及导热、保温、缓释等性能的影响。根据相应性能数据将该气凝胶应用于包装领域,解决精油在包装内释放速率过快而造成精油浓度过高和短时间内消耗完毕的问题。方法 采用TEMPO(2,2,6,6-四甲基哌啶-1-氧自由基)/NaBr/NaClO氧化体系预处理针叶木漂白硫酸盐浆,通过改变高压均质次数和低温真空冷冻干工艺制备不同微纤化程度的MFC气凝胶,利用FT-IR、XRD、SEM和BET等技术分析气凝胶的结构性质,运用应力-应变测试、导热系数测试、TGA测试和GC-MS分析等方法分别对气凝胶的压缩、保温、耐热和缓释性能进行研究。结果 随着微纤化程度的增加,MFC气凝胶的结晶度逐渐增加,气凝胶的比表面积呈现先减小后增加的趋势,范围为17.643～35.171m2/g;气凝胶的压缩强度呈现增加趋势,增幅为15.35%;均质次数为10的气凝胶的耐热性最好,均质次数为8的气凝胶次之。结论 均质次数的增加引起MFC微纤化程度提高,不同微纤化程度的MFC气凝胶具有不同的内部结构性质,以及压缩、保温、耐热和精油负载缓释性能。     

静电纺缓释抗菌纳米纤维的制备及抗菌性能研究

目的 解决天然抗菌剂精油封装到聚合物中的受控释放问题。方法 选用聚乙烯醇和纳米纤维素为主体材料，采用百里香精油为活性物质，通过静电纺丝技术制备纳米纤维。结果 采用质量比为3∶4的纳米纤维素水凝胶(质量分数1%)和聚乙烯醇水溶液(质量分数6%)，并加入质量分数为4%~10%的百里香精油制备纺丝液，在纺丝电压为16 kV、纺丝速率为0.8 mL/h、纺丝距离为11 cm、针头直径为0.7 mm的条件下制备了直径为100~150 nm的纳米纤维，并成功将百里香精油包埋在纳米纤维中。结论 所制备的纳米纤维可以达到百里香精油缓慢释放的效果，对大肠杆菌、金黄葡萄球菌、黑曲霉和橘青霉均有抑制作用。     

改性剂对二氧化硅气凝胶性能的影响

本文以正硅酸乙酯(TEOS)为前驱体,通过酸碱两步溶胶-凝胶法,常压干燥制备疏水性SiO2气凝胶。研究了两种改性剂(三甲基氯硅烷、六甲基二硅氮烷)对二氧化硅气凝胶结构和性能的影响。对制备的气凝胶样品进行表面微观形态分析、热重差热分析、傅里叶红外分析以及比表面积分析。结果表明,通过改性制备的样品具有较好的性能,使用六甲基二硅氮烷改性得到的SiO2气凝胶密度为0.204g/cm3,接触角为128°,BET比表面积为973m2/g,平均孔径7.57nm;使用三甲基氯硅烷改性得到的SiO2气凝胶密度为0.115g/cm3,疏水性优良,接触角为158°,BET比表面积为1067m2/g,平均孔径13.40nm。综合考虑各种因素,采用TMCS进行改性制备得到的SiO2气凝胶综合性能更加优异。     

常压制备低孔径高比表面积疏水SiO2气凝胶

以正硅酸乙酯为先驱体,丙三醇为干燥控制化学添加剂(DCCA),通过酸碱两步溶胶-凝胶法制备了二氧化硅气凝胶,同时利用六甲基二硅氮烷(HMDZ)和正己烷的混合液对湿凝胶进行表面疏水改性。测试分析了所制备气凝胶的密度、疏水性、比表面积和形貌。结果表明,经过表面改性的SiO2气凝胶具有良好疏水性,与水的接触角约为139.4°,比表面积为952m2/g,平均孔径为5～10nm,孔隙率达94.2%,且其密度仅为0.127g/cm3。     

碳气凝胶在电化学领域中的应用研究进展

碳气凝胶是一种新型的非晶态纳米材料,具有比表面积高(600~1 100m2/g)、孔隙率高(80%~98%)和物理化学性能稳定等优点,特别适合作为催化剂及其载体。并且碳气凝胶具有极低的热导率和良好的导电性能,这使得碳气凝胶在耐高温材料和电化学领域中表现出极大的应用前景。近年来,碳气凝胶作为电化学能源材料得到了蓬勃的发展。本文针对现状主要介绍了碳气凝胶的制备工艺,并全面综述了碳气凝胶在燃料电池、锂离子电池和电化学超级电容器等电化学领域中的主要应用研究进展。     

掺杂TiO2对硅气凝胶高温绝热性能的影响

以TiO2作为红外遮光剂,采用溶胶凝胶工艺,研究了遮光剂添加量、超声功率和时间、pH值等对硅气凝胶性能的影响,从而制备出具有高温绝热性能的硅气凝胶。利用扫描电子显微镜(SEM),BJH比表面积及孔结构测定,红外线光谱分析仪(FT-IR)等手段对所得样品进行表征。结果表明:当TiO2掺量为5%时,表观密度为0.122g/cm3,比表面积497.23m2/g,平均孔径24.8nm,孔隙率高达95%。     

超临界干燥制备PSNB气凝胶及其超疏水性能研究

以聚硼硅氮烷为原料,二乙烯苯为交联剂,通过硅氢加成反应结合超临界干燥工艺制备聚硼硅氮烷气凝胶。利用红外光谱、扫描电镜、比表面积与孔径分析仪对所制备气凝胶的形成及微观结构进行了分析,并通过接触角仪对样品的疏水性能进行了研究。结果表明:聚硼硅氮烷和二乙烯苯通过硅氢加成反应制得聚硼硅氮烷气凝胶;所制备的气凝胶的比表面积为307~458cm~2/g,孔体积为1.20~2.17cm~3/g,孔径分布为2.0~100nm,是一种具有三维网状结构的介孔材料,并具有超疏水性能,且当起始溶剂体积分数为85%时,气凝胶疏水性能最佳,接触角为151.5°。     

常压干燥法制备TiO2气凝胶

以钛酸丁酯为原料, 以甲酰胺为干燥控制化学添加剂控制凝胶网络结构, 采用溶胶－凝胶法制得TiO₂醇凝胶; 结合正硅酸乙酯母液浸泡和低表面张力溶剂替换及常压干燥等后处理步骤, 实现了TiO₂气凝胶的常压干燥法制备. 采用XRD、BET、TEM、SEM、EDS及FT-IR等测试手段对样品进行表征. 结果表明：所制备的TiO₂气凝胶为无定形结构, 表观密度为0.375g/cm³, 比表面积达523m²/g, 平均孔径约9.9nm; 经850℃空气气氛下煅烧4h后, TiO₂气凝胶转变为锐钛矿型结构, 平均孔径增大到16.3nm, 比表面积仍达208m²/g. 本研究提出的制备方法简单, 所制备的气凝胶比表面积高、热稳定好.     

纤维素纳米纤丝复合气凝胶的制备与性能研究

以高长径比的纤维素纳米纤丝(CNF)与片层结构的氧化石墨(GO)为原料，采用乙二胺还原和液氮梯度冷冻干燥制备纤维素纳米纤丝/石墨烯(CNF/rGO)复合气凝胶，并通过红外光谱、X射线衍射、X射线光电子能谱、扫描电镜、比表面积(BET)、电化学测试仪等对其进行性能表征。结果表明，所制备的CNF/rGO复合气凝胶具有完整的三维网络结构，当CNF和GO质量比为10∶1时，复合气凝胶的平均孔径为13nm,比表面积为110.2m²/g,在电流密度为1A/g下获得的质量比电容约为156F/g。     

百里香精油/多孔淀粉微胶囊的制备及性能研究

目的制备一款环境友好可降解且具有缓释效果的植物精油微球囊。方法采用不同酶水解条件制得多孔淀粉(PS),通过植物精油吸附率对其吸附性能进行评价;探究羧甲基壳聚糖(CMCS)和海藻酸钠(SA)的浓度对百里香精油(TEO)主要成分的缓释效果,以确定微胶囊最佳的制备条件。采用GC-MS分析在室温(温度为(30±1)℃,相对湿度为(50±3)%)密闭体系下微胶囊主要成分的释放规律。结果当CMCS和SA的质量分数分别为1.2%和2.4%时,制得的CMCS-SA-PS/TOE微胶囊具有优异的缓释效果。在封闭体系中,14 d麝香草酚的累计释放率为19.18%。结论CMCS和SA包覆的微胶囊具有良好的缓释性能,可以延长TEO的主要成分麝香草酚在室温下的释放时间。     

Insertion of triangulated surfaces into a meccano tetrahedral discretization by means of mesh refinement and optimization procedures

In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method.     

From Industry 4.0 to Research 4.0. Development of High Performance Fibers in the Light of Digitization

We associate a variety of innovations with the term ＂Industry 4.0＂. The pioneer of many 4.0 modifications forms the basisfor the trend towards the integrated di...     

The Research of Anti-Wear Properties of Organomolybdenum Compounds in the Engine Oils

A four-ball tester was used to evaluate the anti-wear performance of three kinds of organomolybdemun compounds in the engine oils, i. e., molybdenum dialkyldithiophosphate (MoDDP), molybdenum dialkyldithiocarbamate ( MoDTC), and sulphur and phosphorus freeorganomolybdeum (Molybdate). The results indicate that a low concentration of MoDDP doesn' t improve the anti-wear properties of the commercial engine oils, but a high concentration of MoDDP can obviously improve the anti-wear properties and the load-carrying capacity of the engine oils. MoDTC doesn' t improve the antiwear properties of the engine oils, but worsens the anti-wear properties of the oils. Signifi can timprove ment of frictional and wear characteristics is obtained with Molybdate added in the commercial engine oils and the formulated oils.     

Roman iron and steel: A review

ABSTRACT

The production of ferrous metal increased during the Roman Late Republican period, Principate and Empire. The direct bloomery process was used to extract the metal from its ores using slag-tapping and slag-pit furnaces. The fuel was charcoal and an air blast was introduced by bellows-operated tuyères. Iron formed as a bloom, often as a spongy mass of metal, which contained impurities from the smelting process, including unreacted ore, fuel, slag and fragments from the furnace walls, while the metal was often inhomogeneous with varied carbon contents. Blooms were either smithed directly into bars or ingots or they were broken up, which also allowed the removal of gross impurities and a selection of pieces with similar properties to be made. These could then be forge-welded together and formed into characteristically shaped ingots. Making steel in the furnace seems to have been achieved: it depended on the ore and the furnace and conditions within it. Surface carburization was also carried out. Iron and steel were used extensively in construction and for tools and weapons. Fire welding was often used to add pieces of steel to make the edges of tools and weapons, which could be heat-treated by quenching to harden them.     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

Flow calorimeter for enthalpy increment measurements on condensed gases

A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa.     

Synthesis of Alumina-Zirconia Nanocomposites by Solgel Process

Al₂O₃-ZrO₂ nanocomposites were developed starting with the solgel process. Composite alumina-zirconia nanopowders were synthesized from metallorganic precursors (Aluminium secondary butoxide and zirconium Iso propoxide) using the solgel process. The parameters affecting the synthesis—solvent, concentration of precursor, R/H ratio (i.e., dilution of water in solvent)—were varied as also the temperature and pH. BET and TEM were used to measure nanosize. Diffuse reflectance spectroscopy and also qualitative optical absorption led to identical particle size estimate. The variation of process parameters was used to study the effect and interdependence of process parameters. Artificial Neural Networks was used to rigorously analyze the process. Although this led to confirmation of interdependence of parameters, the presence of a single overwhelming solvent variable was also established. Then the optimal process was used to synthesize more nanopowder. To produce bulk nanocomposite the nanopowders were sintered by varying the temperature and time period. The sintered lithoids were probed with a vickers hardness tester to measure elastic modulus, hardness, and fracture toughness. The results showed high elastic modulus, modest hardness, and very high fracture toughness.     

Certification Becomes Important for the I Quality; and Safety Supervision of the Chinese Liquor Sector

The end of 2007, over 200 unit products of more than 80 Chinese firms have passed the quality grade certification for liquor products. These products involve distilled spirits, beer, wine, yellow wine, fruit syrup wine and others, and cover over 80% of the national top-branded liquor products.……     

Deposition and Coating Properties on CVD Tungsten

Surface characterization and microstructure studies are performed on chemical vapor deposited (CVD) tungsten coating. There is about 2 μm thickness diffusion layer of tungsten in the molybdenum substrate. The thermal shock test shows tungsten coating has good adhesion with molybdenum substrate, but the elements of oxygen and carbon in the tungsten coating have the bad affection to the adhesion. The result of high-temperature diffusion experiment is the diffusion rate from molybdenum substrate to tungsten coating is faster.