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1.
在乳液聚合中,传统的小分子表面活性剂发挥着非常关键的作用,但是它们容易在漆膜中发生迁移,最终降低涂膜的耐水性;而高分子表面活性剂的使用,可以较好的避免表面活性剂的解析及其在膜中的迁移.其中,聚氨酯类的高分子表面活性剂由于具有良好的表面活性、优异的耐寒性、弹性、高光泽以及其软硬度可随温度变化,耐有机溶剂性好等优点, 已经成为研究的热点.本文综述了近几年来,聚氨酯表面活性剂的种类、合成以及应用的进展,并对其进行了讨论.  相似文献   

2.
中国纤维素乙醇技术的研究进展   总被引:1,自引:0,他引:1  
杨斌  Charles E.Wyman 《化学进展》2007,19(7):1072-1075
中国面临着严重的能源短缺和环境污染问题,中国政府正在局部几个省份内政策性鼓励燃料乙醇生产和使用.尽管当前主要是用玉米和谷物作为生产乙醇的原料,然而中国具有大量潜在的低成本的纤维素生物质原料,可以极大地扩大乙醇的产量,降低原料成本.近20年来,由于技术的革命性进步,已使得纤维素乙醇的生产成本从4美元/加仑以上,降低至约1.2-1.5美元/加仑.其中,每吨生物质约44美元.因此,目前乙醇掺汽油具有十分强的市场竞争力.已有几个公司正在建造首批商业纤维素乙醇工厂,虽然这些刚起步的小型设施在合理利用和管理上风险较小,但规模经济需要较大型工厂.尽管配送生物质原料的成本会随需求的增加而增加,但在乙醇生产基础上的生物精炼技术的发展,尤其是化工产品和动力的协同生产,将会使全过程的经济可行性大大提高.进一步深入的基础研究,将解决低成本下实现纤维素的完全利用,以确保在无政策性补贴的前提下,真正使纤维素乙醇成为具有市场竞争力的低成本纯液体燃料.  相似文献   

3.
林肃浩  张弘  任飞 《化学教育》2007,28(7):52-53
燃放烟花爆竹是一个历史悠久的民间习俗,在它带来的安全隐患被人们广泛关注的同时,其燃放过程造成的空气污染也不客忽视.本研究通过实验室模拟,测定了燃放一枚鞭炮产生的二氧化硫气体量,并通过收集、分析杭州市区近几年来春节期间空气状况的数据,验证了燃放烟花爆竹造成空气污染的设想,并提出了科学燃放烟花爆竹的方法.  相似文献   

4.
铜是人体必需的微量元素之一,人体内铜的含量为100~150mg。铜在人体中具有造血,促进骨骼、血管和皮肤健康的生理功能,是人体中超氧化物歧化酶(SOD)的重要成分。因此建立高灵敏度测定水、食物、药物中铜的方法十分重要。催化动力学光度法测定痕量铜的研究报道较多〔1-3〕,但利用KIO4氧化结晶紫(CV)作为测定铜的方法则未见报道。笔者发现在pH5.0的HAc-NaAc缓冲体系中,痕量铜对KIO4氧化CV的褪色反应有明显的催化作用,探讨了反应的最佳条件,建立了催化动力学光度法测定铜的新方法,研究了动力学参数。该法可应用于水、食物、中草药中痕…  相似文献   

5.
镧对Mg-Si合金中Mg2Si相变质的影响   总被引:1,自引:0,他引:1  
研究了Mg-5Si合金中La的添加对初生Mg2Si相变质的影响。结果表明,适量的La能够有效地变质初生Mg2Si相。基于本文的研究,在添加约0.5%La时,获得了最佳的变质效果,此时,初生Mg2Si相的尺寸减小到25μm以下,其形态从粗大的树枝形状变为多面体形状。然而,当La增加到0.8%或者更高时,初生Mg2Si相又生长为粗大的树枝形态。而且,在凝固过程中发现形成了一些LaSi2化合物,这些化合物的数量随着La的增加而呈现逐渐增加的趋势。  相似文献   

6.
刘宏娟  杜伟  刘德华 《化学进展》2007,19(7):1185-1189
生物柴油作为可再生的清洁能源,已在美国、欧盟等多个国家和地区推行使用.在生物柴油的生产过程中,最高可得到约10%的副产物甘油,副产物甘油的去向将成为生物柴油大规模产业化发展所面临的严峻问题.1,3-丙二醇是一种重要的化工原料,作为合成新型聚酯PTT的原料,1,3-丙二醇已引起人们的广泛关注.以生物柴油副产物甘油为原料耦合生产1,3-丙二醇,不仅解决了生物柴油副产物甘油的出路问题,同时降低了1,3-丙二醇的生产成本.本文详细介绍了生物柴油及1,3-丙二醇生产技术及联产工艺的研究进展,并对其应用前景进行了展望.  相似文献   

7.
赵桂兰 《化学教育》2007,28(5):21-23
1教材分析上海科学技术出版社出版的高一化学新教材的第二章以“开发海水中的化学资源”为题,分“以食盐为原料的化工产品”、“海水中的氯”、“从海水中提取的重要元素”3节介绍卤素及其化合物的知识。本章知识安排强调化学与生活、化学与化工生产的联系。从学生身边的、熟悉  相似文献   

8.
夏金梅  林凤鸣  元英进 《化学进展》2007,19(7):1159-1163
纤维素生产乙醇的关键问题之一是水解产生的抑制性物质对乙醇发酵具有明显的抑制效应,因而引起了国内外研究者的广泛关注.研究发现,在抑制剂存在下,酵母在基因表达水平,蛋白水平和代谢物水平都有相应的耐受响应,且这些响应错综复杂.从系统角度运用组学的方法研究这一体系将有助于全面深入了解酵母的耐受机制.本文综述了系统研究的思路和方法在酵母对抑制剂耐受方面的研究状况;对主要研究手段和成果进行了回顾;并对酵母发酵乙醇系统分析的前景进行了展望.  相似文献   

9.
聚合物纳米复合电介质   总被引:1,自引:0,他引:1  
黄兴溢  江平开  金天雄  柯清泉 《化学进展》2007,19(11):1776-1782
聚合物纳米复合材料能够发挥纳米材料在电、磁、光等方面的优越性,也具有聚合物的易成型等方面的优点,正成为电介质领域研究的热点.本文综述了聚合物纳米复合材料在介电性能方面的研究概况,主要涉及了电导、介电强度与空间电荷、介电常数、介电损耗以及局部放电等方面的研究.最后展望了今后的研究方向.  相似文献   

10.
近年生物柴油产业的发展——特色、困境和对策   总被引:3,自引:0,他引:3  
闵恩泽  姚志龙 《化学进展》2007,19(7):1050-1059
本文介绍了美国、欧盟、印度生物柴油产业发展的特点、发展生物柴油的新兴原料和生物柴油生产技术的最新进展.分析了造成现在生物柴油产业发展面临困境的原因在于原料植物油的价格高涨.通过对生物柴油产业链的分析,提出生物柴油产业摆脱所面临困境的对策是:从植物育种和栽培开始,到收割、储存和榨油加工的每一步都要降低成本,力求取得低成本的原料油;开发投资少、成本低的清洁生物柴油生产工艺;关键是要从生物柴油(脂肪酸甲酯)和甘油来生产高附加值的化工产品,大幅度提高利润.  相似文献   

11.
Vanadium dioxide (VO2) films were synthesized on mica substrates by a polymer-assisted deposition method, followed by rapid annealing with different annealing temperatures. The crystalline structure and morphology of the films were investigated by XRD and FE-SEM, and their phase transition properties were studied by in situ FT-IR. The results indicated that the annealing temperature affected the crystalline structure and morphology of the films remarkably, which then resulted in varied phase transition properties. In particular, the films annealed at higher temperature showed more polycrystalline structure, increased particle size and reduced phase transition intensity. But the films exhibited the similar hysteresis temperature width with increasing annealing temperature.  相似文献   

12.
嵌段共聚物薄膜淬火形貌与初始化时嵌段共聚物熔体的状态相关,淬火得到的有序形貌有时存在缺陷,而退火则可以消除这些缺陷形成更规整的层状结构,且退火得到的嵌段共聚物分子的均方回转半径等都小于淬火得到的.与淬火比较,退火使高分子链充分松弛,增加了薄膜中有利于提高材料物理力学性能的桥键含量.不同于受限自由表面间的对称二嵌段共聚物首先在表面区域形成有序结构,三嵌段共聚物则在薄膜内部先形成有序的层状结构.  相似文献   

13.
Amorphous SiO2 thin films were prepared on glass and silicon substrates by cost effective sol-gel method. Tetra ethyl ortho silicate (TEOS) was used as the precursor material, ethanol as solvent and concentrated HCl as a catalyst. The films were characterized at different annealing temperatures. The optical transmittance was slightly increased with increase of annealing temperature. The refractive index was found to be 1.484 at 550 nm. The formation of SiO2 film was analyzed from FT-IR spectra. The MOS capacitors were designed using silicon (100) substrates. The current-voltage (I-V), capacitance-voltage (C-V) and dissipation-voltage (D-V) measurements were taken for all the annealed films deposited on Si (100). The variation of current density, resistivity and dielectric constant of SiO2 films with different annealing temperatures was investigated and discussed for its usage in applications like MOS capacitor. The results revealed the decrease of dielectric constant and increase of resistivity of SiO2 films with increasing annealing temperature.  相似文献   

14.
Ag films were deposited on glass substrates using the successive layer adsorption and reaction (SILAR) method and characterized with XRD and AFM. The I‐V curves of the thicker Ag films obeyed ohmic law because of the formation of the continuous films. After annealing at 300°C in N2, the conductance increased due to the removal of imperfections. Compared with the thicker film, the thinner Ag films showed nonlinear I‐V curves. After annealing, these films were inconductible. This may be ascribed to the destruction of the junction, that existed between the Ag islands. The absorption spectra of the films proved the formation of the Ag islands after annealing. With the thickness of the films further decreasing, the Ag films became insulated.  相似文献   

15.
Liquid crystal (LC) alignment layers were prepared by fabricating solution-processed HfZnO films, annealing them, and treating them with ion beam (IB) irradiation, and the effect of annealing temperature upon the resulting film properties was studied. Homogeneous LC alignment was achieved on IB-irradiated HfZnO films. Topographical changes were observed from field-emission scanning electron microscopy as annealing temperature increased. X-ray photoelectron spectroscopy analysis showed that IB irradiation resulted in oxidation of HfZnO surfaces, which caused the LCs to be oriented more uniformly. The best electro-optical characteristics observed corresponded to the annealing temperature of 200°C. The low optimal annealing temperature for fabricating the HfZnO films suggested that this material has remarkable potential for LCD applications.  相似文献   

16.
Surface-patterned ZnO thin films were fabricated by direct imprinting on ZnO sol and subsequent annealing process. The polymer-based ZnO sols were deposited on various substrates for the nanoimprint lithography and converted to surface-patterned ZnO gel films during the thermal curing nanoimprint process. Finally, crystalline ZnO films were obtained by subsequent annealing of the patterned ZnO gel films. The optical characterization indicates that the surface patterning of ZnO thin films can lead to an enhanced transmittance. Large-scale ZnO thin films with different patterns can be fabricated by various easy-made ordered templates using this combination of sol–gel and nanoimprint lithography techniques.  相似文献   

17.
The adsorption of cellulose acetate (CA), cellulose acetate propionate (CAP) and cellulose acetate butyrate (CAB) from solutions prepared in acetone onto silicon wafers led to ultrathin films, which were characterized by ellipsometry, atomic force microscopy (AFM) and contact angle measurements. The polysaccharides films were characterized in the air just after their formation and after annealing at temperatures higher than their glass transition temperature or melt temperature. The films thickness close to 2 nm and surface roughness did not vary significantly upon annealing. AFM images revealed the presence of small clumps dispersed on a homogeneous layer, which covered completely the Si wafers. Such topographic details were also observed after annealing. However, upon annealing the films surfaces changed from hydrophilic to hydrophobic, evidencing molecular re-orientation at the solid–air interface. The adhesion of bovine serum albumin (BSA) and lipase onto the cellulose esters films was quantified in order to evaluate the possibility of applying such films as selective support for biomolecules.  相似文献   

18.
Titanium dioxide thin films have been synthesized by sol–gel spin coating technique on glass and silicon substrates with and without surfactant polyethylene glycol (PEG). XRD and SEM results confirm the presence of nano-crystalline (anatase) phase at an annealing temperature of 300 °C. The influence of surfactant and annealing temperature on optical properties of TiO2 thin films has been studied. Optical constants and film thickness were estimated by Swanepoel's (envelope) method and by ellipsometric measurements in the visible spectral range. The optical transmittance and reflectance were found to decrease with an increase in PEG percentage. Refractive index of the films decreased and film thickness increased with the increase in percentage of surfactant. The refractive index of the un-doped TiO2 films was estimated at different annealing temperatures and it has increased with the increasing annealing temperature. The optical band gap of pure TiO2 films was estimated by Tauc's method at different annealing temperature.  相似文献   

19.
Copper sulphide CuS was deposited on three substrates; glass, Indium Tin Oxide (ITO) and Ti by using spray pyrolysis deposition (SPD). After depositing CuS thin films on the substrates at 200 °C, they were annealed at 50, 100, 150, and 200 °C for 1 hour. Structural measurements revealed covellite CuS and chalcocite Cu2S phases for thin films before and after annealing at 200 °C with changes in intensities, and only covellite CuS phase for thin films after annealing at 50, 100, and 150 °C. Morphological characteristics show hexagonal-cubic crystals for the CuS thin film deposited on glass substrate and plates structures for films deposited on ITO and Ti substrates before annealing, these crystals became bigger in size and there were be oxidation and some agglomerations in some regions with formation of plates for CuS on glass substrate after annealing at 200 °C. For Hall Effect measurements, thin films sheet resistivity and mobility increased after annealing while the carrier concentration decreased. Generally, the thin film deposited on ITO substrate had the lowest resistivity and the highest carrier concentration before and after annealing. The thin film deposited on Ti substrate had the highest mobility before and after annealing, which makes it the best thin film for device performance. The objective of this research is to show the improvement of thin films electrical properties especially the mobility after annealing those thin films.  相似文献   

20.
Yttrium-doped ZnO gel was spin-coated on the SiO2/Si substrate. The as-prepared ZnO:Y (YZO) thin films then underwent a rapid thermal annealing (RTA) process conducted at various temperatures. The structural and photoluminescence characteristics of the YZO films were discussed thereafter. Our results indicated that the grain size of YZO thin films being treated with various annealing temperatures became smaller as compared to the ones without being doped with yttrium. Furthermore, unlike other ZnO films, the grains of YZO thin films appeared to separate from one another rather than aggregating together as both types of the films were annealed under the same environment. The photoluminescence characteristic measured showed that the UV emission was the only radiation obtained. However, the UV emission intensity of YZO thin film was much stronger than that of the ZnO thin film after annealing them with the same condition. It was also found that the intensity increased with an increase in the annealing temperature, which was caused by the exciton generated and the texture surface of the YZO thin film.  相似文献   

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