纳米纤维素修饰的碳纳米纤维制备及其疏水性研究

为拓展碳纳米纤维在环境清洁领域的应用，提高碳纳米纤维的水接触角，改善膜表面的疏水性能，获得疏水性较好的碳纳米纤维薄膜，利用静电纺丝法将纳米纤维素(CNFs)与碳纳米纤维前驱体复合，获得具有低表面能和良好疏水性能的纳米碳纤维/纳米纤维素复合纤维膜。通过对纳米纤维素含量进行调控，经预氧化和碳化处理后得到一系列具有规则三维空间网络结构的复合纤维膜，并探究不同纳米纤维素含量对复合纤维膜疏水性能的影响。结果表明：纳米纤维素修饰复合纤维膜随着碳化程度的提高其表面能呈现逐渐降低的趋势，其对水的接触角也逐渐增大，疏水效果得到较大幅度提升。随着纳米纤维素含量继续增加，复合纤维膜的水接触角呈上升趋势，未添加前接触角为36.13°,当纳米纤维素添加质量为20%时，水接触角最大为132.14°,提高了366%。     

聚丙烯腈纳米纤维膜连续预氧化碳化过程中的结构性能演变

对静电纺丝制备的聚丙烯腈（PAN）纳米纤维膜进行连续预氧化碳化处理,借助差示扫描量热仪、红外光谱、扫描电镜、元素分析、拉曼光谱、体密度、力学性能等表征和测试方法,综合分析了纳米纤维膜在预氧化碳化过程中的结构性能演变。研究结果表明,相较于微米级的PAN聚合体,纳米纤维具有更低的环化活化能,当氧化纳米纤维的氧含量为8.3%时,得到的碳纳米纤维膜综合性能较佳,其密度、碳收率和拉伸强度分别为1.799 g/cm³,59.8%和29.6MPa。     

静电纺丝法制备壳聚糖/聚乙烯醇基复合碳纳米纤维及其电化学性能

本工作观察并研究了不同碳化温度下制备的静电纺丝壳聚糖/聚乙烯醇基复合碳纳米纤维膜用作超级电容器电极材料时的电化学性能。通过SEM、XRD、Raman等技术对不同碳化温度得到的碳纳米纤维膜进行结构表征,利用循环伏安法(CV)和恒电流充电/放电(GCD)等电化学技术对不同碳化温度得到的碳纳米纤维膜进行电化学性能测试。结果表明,碳化温度为700℃时所制备的复合碳纳米纤维具有较好的电化学性能,在电流密度为1 A/g时放电比电容高达215 F/g,且循环4 000次后容量保持率几乎高达100%,表现出较高的放电比电容和较好的循环稳定性。     

木质素磺酸盐-丙烯腈共聚物及其碳纳米纤维的制备

通过酯化反应和自由基共聚反应制得木质素磺酸盐-丙烯腈共聚物(P(LS-AN)),采用静电纺丝技术将其制成纳米纤维,再经预氧化和碳化处理,制得碳纳米纤维。采用红外光谱仪(FTIR)、差示扫描量热/热重同步分析仪(DSC/TG)、扫描电子显微镜(SEM)和拉曼光谱仪(Raman)对P(LS-AN)、电纺纤维及其碳纳米纤维的结构进行表征。结果表明,P(LS-AN)纳米纤维具有良好的热稳定性,在较高升温速率(10℃/min)下对其进行预氧化和碳化处理,所制得的碳纳米纤维单丝间未产生粘连。在碳化过程中,LS的苯酚结构有利于促进有序碳结构的形成,使得碳纳米纤维的结构更为完善。     

PAN基碳化纤维的电性能及应用

采用连续预氧化碳化法,在700～1300℃制备了聚丙烯腈(PAN)基碳化纤维。使用元素分析仪、X射线衍射仪和高精度电阻仪检测了碳化纤维的化学成分、物相结构和体电阻率;使用绝缘电阻仪测试了碳化纤维/树脂复合涂层的表面电阻率。研究结果表明,随着碳化温度的升高,纤维的碳元素含量增大,同时纤维中形成大量类石墨结构,增强了纤维的导电性,碳化纤维的电阻率由1.12Ω.cm急剧下降至1.95×10-3Ω.cm;在树脂中添加短切碳化纤维制备的防静电复合涂层的表面电阻率可在104～107Ω之间调整。     

低温碳化过程PAN氧化纤维骨架结构转变

为实现PAN纤维在低温碳化过程的结构调控,利用核磁共振碳谱(13C-NMR)研究了PAN预氧化纤维在500-800℃的低温碳化过程中骨架结构的演变.结果表明:在低温碳化过程中,随着碳化温度的升高,预氧化纤维骨架结构中饱和的CH、CH2和C=0结构逐渐消失,共轭-HC=C<和>C=N-逐渐减小,共轭>C=C<逐渐增加,纤...     

PAN原丝在预氧化及碳化石墨化过程中微观结构的变化研究

利用拉曼光谱和X射线衍射对聚丙烯腈原丝在预氧化以及碳化石墨化阶段的微观结构进行研究,分析了纤维的石墨结构有序性、晶态结构在不同处理阶段的变化规律。结果表明,240℃开始出现明显的拉曼特征峰;在碳化过程中,逐渐形成碳基平面,G峰峰强不断增强,有序性提高;石墨化过程中,D、G峰的半高宽(FWHM)和R值迅速减小,并出现G′峰,有序性进一步提高。在碳化石墨化阶段,随着处理温度的提高,产生乱层石墨结构,晶面间距d002减小,微晶尺寸La、Lc增加,C—C原子键距不断增大并接近SP2杂化碳原子间距。     

增塑熔纺聚丙烯腈预氧丝的低温碳化过程

本文研究了增塑熔纺聚丙烯腈原丝在氧化为预氧化纤维后,进一步进行低温碳化,并探索了纤维在不同温度下(600~1000℃)和升温速率下的演变过程。本文采用差示扫描量热法(DSC),热失重分析(TGA),扫描电镜(SEM)和拉曼光谱(Raman)等手段对纤维的性能进行表征。结果表明,在合适的升温速率下纤维具有较小的放热焓和较强的热稳定性及较高的碳收率。随着热处理温度的升高,纤维表面的杂质减小,同时断面变得越来越致密,但是当温度超过800℃后,纤维的表面会产生较多的微孔。     

由液化物树脂制备多孔碳纳米纤维及其表征

以壳粉为原料,在碱性条件下制备液化物树脂(LPF),经静电纺丝、固化、碳化得到多孔碳纳米纤维(PCNF)。探讨了聚乙烯醇(PVA)用量对纺丝液特性及纤维形貌的影响。同时,采用傅里叶变换红外光谱(FTIR)、热重分析仪(TG)、扫描电子显微镜(SEM)、X射线衍射仪(XRD)、全自动比表面积及孔隙分析仪(BET)等方法对不同碳化温度下的样品进行表征。结果表明:少量PVA可以明显提高LPF的纺丝性,且随PVA用量的增加,纤维的形貌更规整、直径更小;随着碳化温度的升高,LPF/PVA纤维逐渐裂解,多数官能团消失,基体为多苯稠环结构;同时,层间距d_((002))逐渐减小,平面尺寸L_c和L_c/d_((002))增加,纤维内部的类石墨结构逐渐向更规整、有序的石墨微晶结构转变;当碳化温度为800℃时,LPF/PVA的含碳量达55%以上,随着PVA用量的增加,纤维的比表面积明显增大且多以微孔为主,当PVA用量为8%时,得到比表面积为590m~2/g的多孔碳纳米纤维。     

聚合物共混制备纳米和多孔碳纤维及性能研究

聚丙烯腈(PAN)和聚甲基丙烯酸甲酯(PMMA)共混膜的结构和尺寸可由两组分比例和分子量调整。以PAN为碳前驱体,PMMA为热分解聚合物,并控制m(PAN)/m(PMMA)为30/70和70/30,通过湿法纺丝制备了PAN/PMMA共混纤维。以m(PAN)/m(PMMA)为30/70和70/30的共混纤维为原丝经碳化后获得了纳米碳纤维(CNFs)和多孔碳纤维(PCFs)。利用扫描电镜观察了所得CNFs和PCFs的形貌,发现单根CNFs的直径为50～150nm,PCFs中孔的直径为0.1～1μm。由CNFs和PCFs的拉曼光谱分析了不同碳化温度对CNFs和PCFs石墨化程度的影响,结果表明随碳化温度升高,石墨化程度也增加,同时电导率也随之提高。     

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.     

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.     

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.     

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.     

Refrigerators Enter a New Era of Health Preservation Frestech initiates the establishment of China's first standard for household sterilization refrigerators

On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.……     

Analysis of marine hydrobiont lipid extracts as possible cryoprotective agents

We studied a combined effect of the cryoprotectants both of lipid and carbohydrate origin at the presence of DMSO or without it on cell viability and the RNA synthesis in the embryonic mollusc and echinoderm cell cultures obtained at different developmental stages. Cryoprotective properties of exogenous lipids correlated with their thermotropic behavior. Lipid extracts from marine hydrobiontes, which thermal transitions are characterized by relatively small part of calorimetric thermogram area lying at temperatures above 0 °C (6–18%), were found to possess a considerable cryoprotective activity. The results are discussed in relation to the prediction of the cryoprotective activity of lipid extracts for marine animal cells. In addition, it was found that marine invertebrate cells can be cryopreserved without DMSO at the presence of trehalose and lipid extracts of some marine hydrobiontes.     

Low-Temperature Properties of Silver

Pure silver is used extensively in the preparation of high-temperature superconductor wires, tapes, films, and other configurations in which the silver not only shields the superconducting material from the surrounding materials, but also provides a degree of flexibility and strain relief, as well as stabilization and low-resistance electrical contact. Silver is relatively expensive, but at this stage of superconductor development, its unique combination of properties seems to offer the only reasonable means of achieving usable lengths of conductor. In this role, the low-temperature physical (electrical, thermal, magnetic, optical) and mechanical properties of the silver all become important. Here we present a collection of properties data extracted from the cryogenic literature and, to the extent possible, selected for reliability.