水性聚氨酯对聚乙烯醇-海藻酸钠水凝胶结构与性能的影响

以聚乙烯醇(PVA),海藻酸钠(SA)和水性聚氨酯(WPU)为原料,采用冷冻解冻法制备含水性聚氨酯的聚乙烯醇-海藻酸钠水凝胶,并探究WPU的用量对聚乙烯醇-海藻酸钠水凝胶结构与性能的影响。通过各种实验方法对WPU的合成进程,凝胶的形成,以及凝胶的微观结构,凝胶的溶胀性能、凝胶分数、愈合性能及力学性能进行观察和表征。结果表明,随着WPU含量的增多,凝胶内部微孔体积增大,且数量增多;当凝胶中WPU含量为25wt%时,凝胶拥有较好的微孔结构并获得1000%的吸水溶胀率;WPU的用量对复合水凝胶的凝胶分数、自愈合性能和力学性能也存在较大的影响。     

可注射海藻酸钙水凝胶的制备研究

海藻酸钙水凝胶因其良好的生物相容性广泛应用于组织工程支架材料的研究。以海藻酸钠(SA),碳酸钙,葡萄糖酸内酯(GDL)为原料,通过原位相转变制备可注射凝胶,用于软骨组织微创修复材料的研究。测定了单一变量条件下不同海藻酸钠浓度、f值(钙离子与羧基的摩尔比)及n值(葡萄糖酸内酯与钙离子的摩尔比)对海藻酸凝胶力学强度、溶胀率、浸提液pH值等的影响,从而获得各组分最适的配比;另外,通过原位接种软骨细胞,研究了软骨细胞在凝胶中的生长行为。综合海藻酸钙凝胶性能,最终确定海藻酸钠浓度为2.5%、f=0.5及n=0.6为最佳配比;细胞培养结果表明软骨细胞在凝胶中具有较高的活性且维持了其软骨细胞形态,证实了研究制得的海藻酸钙水凝胶是一种优良的可注射软骨组织工程支架材料。     

海藻酸钠-碳材料复合凝胶吸附水中污染物的研究进展

海藻酸钠的亲水性和其凝胶的三维网状结构赋予海藻酸钠水凝胶良好的吸附性能,成为处理水中污染物的理想吸附材料。碳材料如石墨烯、碳纳米管等因其具有较高的比表面积,常用于污染物的吸附,与海藻酸钠复合可进一步改善和丰富海藻酸钠凝胶的性能。针对海藻酸钠-碳材料复合凝胶吸附水中污染物的研究现状,以氧化石墨烯、碳纳米管和活性炭这3种碳材料为主线,简单总结了海藻酸钠-碳材料复合凝胶吸附水中污染物的研究进展,并提出需要解决的若干问题。     

聚丙烯酸水凝胶自修复性能及溶胀行为的研究

采用胶束共聚法将丙烯酸(AA)与少量甲基丙烯酸十八酯(OMA)共聚,制备具有自修复功能的聚丙烯酸(PAA)水凝胶。采用红外光谱表征PAA水凝胶的结构,采用拉力实验表征PAA水凝胶的自修复功能和测试其拉伸强度,并分别研究PAA水凝胶在水中和氯化钠溶液中的溶胀行为。结果表明,PAA具有良好的自修复性能,修复后PAA水凝胶能保持修复前80%以上的拉伸强度,并且修复后的水凝胶断裂伸长率接近于修复前的水凝胶。PAA水凝胶的自修复功能归功于羧基间形成的氢键网络和OMA与表面活性剂形成的疏水缔合网络的联合作用。PAA水凝胶在水中的溶胀主要受水分子在凝胶中渗透扩散过程控制,而在氯化钠溶液中的溶胀主要受聚合物链段的松弛过程影响。     

基于金属离子交联的自修复聚丙烯酸水凝胶EI北大核心CSCD

自修复水凝胶在被破坏后,断裂部分能够自发愈合回复到初始状态,其具有重要的应用价值。文中利用Fe^(3+)与聚丙烯酸分子链中羧基之间的相互作用,构筑具有自修复性能的水凝胶。聚合过程中,在丙烯酸单体中加入Fe Cl_3和过硫酸钾,在室温条件下引发丙烯酸聚合,反应6 h后制得水凝胶。Fe^(3+)在体系中同时起到交联剂和引发剂的作用。该方法制备时原料简单、反应条件温和,特别适合于规模化生产。所制备的水凝胶自修复速度快,12 min内即可完全修复,修复后水凝胶力学性能基本能回复到修复以前的状态。而且水凝胶透明性好,适合于制备光学性能优异的水凝胶材料。     

新型水凝胶高效吸附废水中Cd(II)的研究

以廉价的海藻酸钠、丙烯酸和三乙烯四胺作为原料,设计并制备出具有双网络互穿结构的海藻酸钠/聚丙烯酸水凝胶。通过对水凝胶的物理化学性能表征,发现该凝胶具有三维网络结构和较好的稳定性能。以Cd(II)离子作为研究对象,以水凝胶作为重金属吸附剂进行吸附实验,结果表明该水凝胶能在pH值大于2.5时具有较高的吸附率;吸附实验中由于水凝胶的三维网络结构,Cd(II)离子能在其内部进行有效扩散,在离子质量浓度为120 mg/L,水凝胶质量浓度为1g/L的条件下,整个吸附过程在60 min内达到吸附平衡;离子质量浓度低于120 mg/L时,大量暴露的活性位点使水凝胶的吸附效率达到95%以上。在选择性吸附实验中,水凝胶对Cd(II)的吸附效率最高,分配系数Kd达到84.62 L/g。海藻酸钠/聚丙烯酸水凝胶是一种具有处理重金属废水潜力的吸附材料。     

基于金属离子交联的自修复聚丙烯酸水凝胶

自修复水凝胶在被破坏后,断裂部分能够自发愈合回复到初始状态,其具有重要的应用价值。文中利用Fe~(3+)与聚丙烯酸分子链中羧基之间的相互作用,构筑具有自修复性能的水凝胶。聚合过程中,在丙烯酸单体中加入Fe Cl_3和过硫酸钾,在室温条件下引发丙烯酸聚合,反应6 h后制得水凝胶。Fe~(3+)在体系中同时起到交联剂和引发剂的作用。该方法制备时原料简单、反应条件温和,特别适合于规模化生产。所制备的水凝胶自修复速度快,12 min内即可完全修复,修复后水凝胶力学性能基本能回复到修复以前的状态。而且水凝胶透明性好,适合于制备光学性能优异的水凝胶材料。     

全物理交联三重互穿网络水凝胶的制备与性能

为提升水凝胶的综合力学力学性能,设计并研究了一种全物理交联三重互穿网络水凝胶。以自由基乳液聚合法,获得疏水缔合交联的聚丙烯酰胺网络,水凝胶一步成型,依次通过冷冻-融化循环、浸没FeCl_3溶液分别形成微晶交联的聚乙烯醇网络及离子交联的海藻酸钠网络。获得P(AM-SMA)/PVA/SA三重互穿网络(HMITN)水凝胶。通过傅里叶变换红外对水凝胶结构进行了表征;通过电子万能试验机对水凝胶的力学性能进行了研究。结果表明,HMITN水凝胶具有良好的强度、韧性、抗疲劳及自恢复性能,强度0.45 MPa,断裂能2.48 MJ/m~3,在200%应变下进行5次循环拉伸后仍然保持20.3%的韧性,室温下自恢复260 min后,韧性可恢复66.7%。     

动态杂化双网络水凝胶的构建与性能

针对自修复凝胶中高效自修复功能和优异力学性能难以同步兼顾的关键问题,文中以苯硼酸修饰的透明质酸(PBA-HA)为凝胶基质、聚乙烯醇(PVA)为交联剂,通过硼酯键形成第一重交联,之后通过冻融形成PVA结晶区形成第二重交联,制备了动态硼酯键、氢键协同作用的双重网络水凝胶。结果表明,所制备的PBA-HA/PVA水凝胶不仅具有较强的力学性能,而且展现出优异的室温自修复性能。该凝胶材料创造性地将高效自修复和提高力学强度的2个关键职能协同分配到该材料的不同交联网络上,充分发挥动态共价键和反复冻融形成的微晶区的各自功能和协同效应,有望解决凝胶材料的自修复功能与力学性能无法同步兼容的问题。     

聚乙二醇共价交联海藻酸钠凝胶制备及其药物缓释性能

为了增强海藻酸钠凝胶的稳定性以及对药物的缓释效果,将海藻酸钠用聚乙二醇(PEG200)交联,在水溶液中用对甲苯磺酸催化、经过酯化反应合成了共价交联的海藻酸钠凝胶;通过红外光谱、热重分析和X-射线分析对产物进行了表征。与钙离子交联的海藻酸钠凝胶相比,共价交联海藻酸凝胶在仿生体液中结构稳定,在模拟体液中完全降解时间持续到60天。凝胶对牛血清白蛋白的载药率达到11.5%,显示出明显的缓释效应和pH响应性能,具有作为pH控释和缓释药物载体的应用前景。     

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.