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乳化交联法制备壳聚糖微球粘连原因分析 总被引:1,自引:0,他引:1
乳化交联法是制备壳聚糖微球常用的工艺,但在制备过程中,常出现微球产物粘连的现象。分析了搅拌速度、油水体积比、表面活性剂添加量和交联剂用量等影响微球粘连的因素,优化出了分散性好,粒度均匀的壳聚糖微球制备工艺参数。结果表明,搅拌速度〉350r/min,油水体积比〉2.5,表面活性剂span80用量为水相的20%时,可获得分散性好的壳聚糖微球,微球的粒径可以控制在1~5μm之间。 相似文献
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用微机械加工技术和微电子平面工艺制备了微型Clark型氧电极。外型尺寸为15×2×07mm3,敏感面积为1×05mm2。在敏感区固定葡萄糖氧化酶(GOD),构成了微型葡萄糖传感器。传感器的主要性能:灵敏度22nA/(mmol/L);响应时间<1min,线性范围01~10mmol/L,变动系数97%,稳定响应在二十天以上。 相似文献
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聚乳酸-乙醇酸的合成及在药物缓释微球中的应用 总被引:17,自引:1,他引:17
采用熔融聚合法直接合成生物降解材料聚乳酸-乙醇酸(PLGA).并以其为载体制备基因重组人干扰素聚乳酸-乙醇酸微球(IFN-α-PLGA-MS)。通过正交试验对干扰素微球的制备工艺进行了优选,同时对微球的性质进行了考察。结果以D,L-乳酸、乙醇酸为原料,氮化亚锡(SnCll)为催化剂,在165℃、70Pa下熔融聚合10h.PLGA特性粘数[η]最高可达0.2382dL/g,干扰素微球的形态圆整.平均粒径为10.71μm。药物确已被包裹在微球中,微球载药量和包封率分别为8.06%、36.97%,且获得了较满意的干扰素微球制备工艺。 相似文献
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分别以Ni包裹氧化铝微球、氧化铝包裹Ni微球以及氧化铝/Ni共沉淀复合微球粉体为烧结原料,通过热压烧结法制备了Ni质量含量在0%~30%的氧化铝基金属陶瓷。利用SEM,TEM,XRD对烧结Al2O3/Ni金属陶瓷的微结构及前躯体、热还原粉体和金属陶瓷的晶相进行了分析,通过阿基米德法测量了金属陶瓷的相对密度,并分别利用三点弯曲法和单边切口横梁法对材料的抗弯强度和断裂韧性进行了评估。结果显示:3种粉体制备的金属陶瓷分别形成了晶间型、晶内型及晶间/晶内混合型结构,且在烧结过程中,Ni相在某种程度上降低了材料的致密化速率,也抑制了氧化铝晶粒的长大.同时,Ni掺杂方式的不同导致了氧化铝基质的断裂模式及力学性能的变化。 相似文献
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采用分散聚合法,在Fe3O4磁流体存在下,通过PVA分子单体共聚制备磁性高分子微球。用透射电镜和X射线对磁流体的形貌、粒径进行表征和衍射分析,同时借助于显微拍照和红外光谱,对磁性微球的微观形貌和化学成分进行了研究。通过对比磁性微球的磁响应性及粒径,研究了反应温度、搅拌速度、聚乙烯醇用量、盐酸用量等操作因素对磁性微球性质的影响。结果表明,在70℃操作温度、750r/min的搅拌速度,5ml9%PVA和0.5ml37%盐酸条件下能制备出粒径在8~44μm之间、具有良好磁响应性、表面富含羟基和羧基等官能团的磁性聚乙烯醇微球。 相似文献
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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. 相似文献
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The end of over unit products of more than Chinese firms have passed the quality grade certification for liquor products. These products involve distilled spirits beer wine yellow wine fruit syrup wine others cover over % of the national top-branded liquor products.…… 《中国标准化(英文版)》2008,25(1):30
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.…… 相似文献
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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. 相似文献
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N.A. Odintsova N.V. Ageenko K.V. Kiselev N.M. Sanina E.Y. Kostetsky 《International Journal of Refrigeration》2006,29(3):387
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. 相似文献
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David R. Smith F. R. Fickett 《Journal of research of the National Institute of Standards and Technology》1995,100(2):119-171
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. 相似文献
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Fco. Javier Franco Pérez Marc Gener Moret 《Materials and Manufacturing Processes》2017,32(7-8):876-884
ABSTRACTThe 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. 相似文献
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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. 相似文献
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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. 相似文献
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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. 相似文献
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R. Owsiński S. Kamiński M. Szymaniec A. Niesłony T. Łagoda 《Materialwissenschaft und Werkstofftechnik》2015,46(10):1059-1067
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. 相似文献