壳聚糖金属配位控制氧化降解及反应动力学研究--(Ⅰ)壳聚糖金属配位控制氧化降解

将壳聚糖首先转化为壳聚糖金属(Cu(Ⅱ)、Mn(Ⅱ)、Co(Ⅱ)、Zn(Ⅱ))配合物,再以H2O2对壳聚糖金属配合物进行氧化降解制取低聚壳聚糖.降解过程中黏度的变化及降解产物分子量分布表明,金属盐种类对反应影响存在以下趋势Cu2+＞Co2+＞Mn2+＞Zn2+,且随氧化剂用量增加、反应温度升高、pH值升高、O2含量降低,壳聚糖降解速度均会相应增加;产物分子量分布表明在相同降解条件下,壳聚糖配合物的降解速度明显高于壳聚糖,且所得降解产物分子量分布较壳聚糖直接降解窄.脱金属处理后的降解产物不含金属离子.     

低分子量范围内壳聚糖分子量的调控及其线性关系研究

通过固定H_2O2用量为壳聚糖(CS)摩尔单元量的2倍,60℃下氧化降解制备了分子量小于15000的低分子量CS。在低分子量范围内,根据Mark-Houwink方程测定了降解后CS的黏均分子量,并研究了通过控制降解反应时间来调控CS的分子量,结果表明降解反应3h后,CS的黏均分子量变化不大,可降低至5000;在0.5~2.0h之间,CS的黏均分子量与反应时间有着较好的线性关系,线性拟合方程为y=4422.8x+15854,R2=0.9973。该线性方程的建立为低分子量范围内CS分子量的调控制备提供了理论指导。     

壳聚糖金属配位控制氧化降解及反应动力学研究——（Ⅱ）反应动力学

将壳聚糖转化为壳聚糖金属配合物，配位键的形成使得壳聚糖分子链上产生有利于分子链断裂的弱势结构。假定配合物中金属离子在壳聚糖高分子链上均匀分布，金属离子与壳聚糖糖元的摩尔比为1：N，从而将壳聚糖配合物分子看作单体为N个糖元和1个金属离子组成的结合高分子。假定金属离子引入所产生的各弱点性质相同，结合高分子降解应符合无规降解的原理，运用无规降解的动力学方程处理该高分子，其结果吻合性好。对反应速率常数的研究进一步证实壳聚糖铜配合物不仅分子结构有利于壳聚糖降解，其对H2O2分解还存在催化作用，而壳聚糖锰配合物仅在分子结构上有利于壳聚糖降解，不能催化H2O2分解。     

超声波辅助降解壳聚糖的研究

讨论了一种在超声波条件下用H2O2降解壳聚糖的方法,研究表明,在超声波条件下,H2O2降解壳聚糖的反应能在较低温度进行,降解反应速度提高近3倍,且产物白度令人满意。     

海水介质中壳聚糖对碳钢的缓蚀性能

为开发新型绿色海水缓蚀剂,首先采用氧化法对原料壳聚糖进行降解,得到不同分子量的产品,用端基法测量分子量,然后采用失重法和极化曲线法对不同浓度海水体系中原料和降解产品对Q235碳钢的缓蚀性能进行评价,最后用椭圆偏振法分析水溶性壳聚糖及降解产品的缓蚀机理.结果表明,为得到分子量为1000左右的产品,加入15mL 30%H2 O2是较经济的剂量;壳聚糖浓度为400mg/L时缓蚀效率最高,且分子量越小缓蚀效率越高;壳聚糖为阴极控制型缓蚀剂,通过静电作用平铺在碳钢表面发生多层吸附.     

壳聚糖金属配位控制氧化降解及反应动力学研--(Ⅱ) 反应动力学

将壳聚糖转化为壳聚糖金属配合物,配位键的形成使得壳聚糖分子链上产生有利于分子链断裂的弱势结构.假定配合物中金属离子在壳聚糖高分子链上均匀分布,金属离子与壳聚糖糖元的摩尔比为1∶N,从而将壳聚糖配合物分子看作单体为N个糖元和1个金属离子组成的结合高分子.假定金属离子引入所产生的各弱点性质相同,结合高分子降解应符合无规降解的原理,运用无规降解的动力学方程处理该高分子,其结果吻合性好.对反应速率常数的研究进一步证实壳聚糖铜配合物不仅分子结构有利于壳聚糖降解,其对H2O2分解还存在催化作用,而壳聚糖锰配合物仅在分子结构上有利于壳聚糖降解,不能催化H2O2分解.     

酸性离子液体水溶液中壳聚糖的氧化降解EI北大核心CSCD

筛选出对壳聚糖溶解具有良好性能的磺酸型离子液体[MIMBS]HSO4,以该离子液体水溶液为反应介质,在均相体系中进行了壳聚糖的氧化降解反应。考察了离子液体用量、H2O2与壳聚糖单元摩尔比、反应温度和反应时间对该氧化降解反应的影响。利用黏度法测定壳聚糖的相对分子质量,采用X射线衍射和红外光谱对原料和再生壳聚糖的结构进行表征。X射线衍射分析结果表明,溶解过程中壳聚糖的晶体结构遭到破坏,结晶度下降。随着离子液体溶液浓度的增加、H2O2用量的增大、反应温度的升高以及反应时间的延长,氧化降解反应进行得更加彻底。在最佳反应条件(8%离子液体水溶液、底物摩尔比5、反应温度80℃、反应时间3 h)下,再生壳聚糖的收率为74%,其黏均相对分子质量为21.2×103。     

辐射降解法制备低聚水溶性壳聚糖之一:辐射降解方法研究

以食品级大分子壳聚糖为原料,在几种不同的状态下,利用辐射降解的方法,对制备低聚壳聚糖的条件进行了研究。结果表明,在溶液状态下,采用较小的辐照剂量,就可以得到分子量＜10000的低聚水溶性壳聚糖。     

聚乳酸的合成与性能研究

以乳酸单体为原料,采用直接缩聚法合成了具有较高粘均分子质量的聚乳酸,用红外光谱、H—NMR等方法初步表征了聚乳酸的结构。研究了聚乳酸的亲水性和降解性。结果表明,聚乳酸的水接触角和吸水率分别为79．30和2．8％,说明聚乳酸具有一定的亲水性。聚乳酸在降解过程中表现为体型降解特点。粘均分子量和降解温度对聚乳酸的降解规律影响不大,但低分子量聚乳酸及聚乳酸在较高降解温度下的降解程度和初期降解速率明显大于高分子量聚乳酸及较低降解温度。本文还研究了聚乳酸粘均分子量在降解过程中的变化情况。     

壳聚糖接枝丙烯酸负载钯纳米纤维催化剂的制备及催化氢化

制备了壳聚糖接枝丙烯酸负载纳米钯催化剂并对其催化氢化性能进行了研究。首先对分子量为30万的商品壳聚糖进行降解,得到了黏均分子量为10万的壳聚糖,用后者制备壳聚糖接枝丙烯酸共聚物并负载氯化钯,最后通过电纺丝技术得到了纳米纤维状催化剂。对制备的催化剂进行了透射电镜（TEM）,X射线光电子能谱（XPS）和红外光谱（IR）的表...     

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 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.     

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.     

Early ironwork in Biscay: Survey,excavation, experimentation and materials characterization. An integral study of the mountainside ironworks (ferrerías de monte or “haizeolak”)

ABSTRACT

The production of iron in Biscay (Basque Country, Spain) has been a hallmark of this territory of the North of the Iberian Peninsula throughout its history. The Archaeology team of the Basque Country Mining Museum has spent 13 years, so far, studying the origins of this activity through the evidences left at the old pre-hydraulic iron production workshops known as mountainside ironworks (ferrerías de monte) or haizeolak. It has catalogued 170 archaeometallurgical sites of this type in Biscay, and the archeological excavation of some of them has led to the knowledge of the different stages of the production process that took place in these workshops. The team has also experimentally reproduced the work carried out in a mountainside ironworks from the High Middle Ages, and it has currently started the characterization process of this type of activity through the study of the collected materials.     

Mechanism Study on the Wear of CrAlTiN Coated High-Speed Steel Twist Drills Under Dry Cutting Conditions

As demands about environment protection are growing up, dry cutting technology is getting more and more concerns from all over the world. Main works performed here are study on dry cutting performances and wear mechanisms of M2high-speed steel (HSS) twist drills with CrAlTiN multicomponent coatings, which was deposited using magnetron sputter ion plating system, in drilling 45 and 30CrMnSiA steel, and their comparisons to those in drilling the same steel but using monolayer CrN and commercial TiN coated drills. Drilling performances of drills are evaluated mainly through the measurements of width on outer corner flank land and the cutting forces. Results show that performances of CrAlTiN coated drills are better than those of monolayer CrN and TiN coated drills. In drilling 45 and 30CrMnSiA steel, the average tool life of the CrAlTiN coated drills are 17.2 and 11.8 times higher than those of the uncoated drills. Observing wear of the drill with scanning electronic microscope, results show that there is no crack or spallation of the CrAlTiN coatings in wear zones. Main mechanism of the wear here is adhesion.     

Study on Bond Ability of Arc-Spraying Coatings with Different Surface Pretreatment on Cast-Iron

Arc spraying coatings are widely used in various applications, but uncommon in cast iron substrate. Different surface pretreatment technology is tested on substrates of gray cast iron. Surface roughness and residual stress were measured by TR200 and X-ray diffraction analyzer. Influence of different surface pretreatment methods ( dry blasting and fusebond) on roughness and residual stress was analyzed. The arc-sprayed coatings of wire 3Cr13 (φ2mm) on gray cast iron substrate is studied. The microstructure and interface of bonding layer were observed by SEM. The bond strength was taken by tensile test. Results show that bond strength with grit blasting is higher than fuse-bond; it is feasible to make wire 3Cr13 coating with arc spraying on cast iron substrate roughened by grit blasting.     

Structural Characteristics of TiO2 Ceramic Coating by Micro-Plasma Oxidation

TiO2 ceramic coatings with thickness of 20 μm were formed on the surface of pure titanium by micro-plasma oxidation. Their micro-structures were investigated by by using X-ray diffraction and their surface images were detected by using scan electronic microscope. There were three kinds of TiO2 coatings, pure anatase type TiO2 phase, mixed phases consisted of rutile type TiO2 phase and anatase type TiO2 phase, pure rutile type TiO2 phase. The coating surface with the pure anatase type TiO2 phase is rough, while the coating surface with the pure rutile type TiO2phase is smooth. The upper coating surface with the mixed type TiO2 phases is anatase type TiO2 structure and the subsurface of the TiO2 coating is rutile type TiO2structure.     

Evaluation of fatigue life of steel using steel grain size

The insightful discussion of the relationship between the construction of metallographic and fatigue life and proposition of mathematical relationships describing this relationship was conducted in the paper. This paper presents a method for estimating the fatigue life, based on the construction of the microstructural material taking into account the grain size and the participation of ferrite and pearlite phase.