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1.
本文以单晶硅粉作为硅源,氨水作为催化剂,制备了二氧化硅纳米粒子。研究了单晶硅粉制备二氧化硅纳米粒子时反应条件对反应产率和粒径的影响,并通过单因素实验法和正交设计法获得了最佳实验条件。通过激光粒度分析仪、电感耦合等离子体-质谱(ICP-MS)、扫描电子显微镜(SEM)等方法对纳米二氧化硅粒子的纯度、形貌、粒径进行了表征,得到了高纯、单分散的二氧化硅纳米粒子。  相似文献   

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本文介绍了目前国内超细二氧化硅的生产、使用的品种及超细二氧化硅在各个行业的应用。  相似文献   

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大颗粒、高浓度硅溶胶的制备新方法   总被引:8,自引:0,他引:8  
以水玻璃为原料,采用滴加工艺制备一定粒径大小的二氧化硅作为母核;采用在催化剂和分散剂共同作用下水解硅粉的方法使母核二氧化硅颗粒进一步增长,得到了高均匀分布的平均粒径在100nm以上、浓度可达50%的二氧化硅溶胶。并对新方法下pH值、温度以及母核SiO2的浓度、粒径大小对二氧化硅平均粒径及其均匀性的影响进行了分析。研究结果对制备大颗粒、高浓度的硅溶胶具有积极意义。  相似文献   

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对于含有游离二氧化硅、单质硅及碳化硅的耐火材料及原料,分别测定其中二氧化硅、单质硅及碳化硅量的方法都比较繁杂.而含碳化硅制品中总硅含量较高(以SiO2计其质量分数常大于100%),因此,没有可套用的标准且测定误差较大,结果不可靠.根据碳化硅不溶于氢氟酸-硝酸及单质硅不溶于氢氟酸的原理,制定了氢氟酸挥散重量法连续测定游离二氧化硅、单质硅、碳化硅的方法.本方法比分别测定该3个项目的方法可提高功效近3倍,其准确度也有所提高.  相似文献   

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硅石、萤石中二氧化硅的测定   总被引:1,自引:0,他引:1  
一、前言“氢氟酸——氟硅酸钾直接滴定法测定玻璃中的二氧化硅”,首次用氢氟酸在常温常压下快速、完全地分解了钠钙硅铝硼玻璃试样并成功地在共存元素不分离的情况下直接水解滴定氟硅酸钾,准、快、省、简地测定了中碱、无碱、平板等玻璃中的二氧化硅。目前尚未见有类似的方法报导,为硅酸盐中高含量二氧化硅的测定开辟了新的途径。文献证明:CaF_2、MgF_2、BF~-_4、NaF、KF等氟化物非常稳定,并不干扰氟硅酸钾的水解滴定;氟铝酸钾的水解是微弱  相似文献   

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前言二氧化硅乳胶是一种新型的液态扩散源,它已广泛应用于集成电路和半导体器件的生产上。例如,纯二氧化硅乳胶经氧化致密可作屏蔽层,掺砷二氧化硅乳胶可作模拟集成电路的埋层扩散源,掺磷二氧化硅乳胶可作为衬底扩散源,掺硼二氧化硅乳胶则可作为PNP管发射区的扩散源等等。使用这些新型液态扩散源,可使工业流程缩短,成品合格率提高。我们参照国外有关资料研制成功的此类二氧化硅乳  相似文献   

7.
朱慧仙  王力 《广东化工》2008,35(2):19-22
酸性硅溶胶是二氧化硅微粒在水中均匀扩散形成的胶体溶液,pH为2~4,具有许多优良性质和特点,作为一种精细化工产品,被广泛应用于化工、材料、纺织、造纸、电子等工业。文章介绍了酸性硅溶胶的制备工艺、结构及特性,分析了pH、电解质盐浓度和二氧化硅粒径对其稳定性的影响,并对酸性硅溶胶的研究前景进行了展望。  相似文献   

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王文利 《中国玻璃》2005,30(1):17-29
硅质原料主要包括——工业砂和砾石、水晶(结晶硅石的一种形式)、特种二氧化硅产品和硅藻土等4类。特种二氧化硅产品中的多数岩石是质密石英岩。硅藻土组中包括硅藻土和其它细粒、多孔硅质材料,如硅质软土。本报告重点介绍工业砂与砾石的有关情况,另外再简略介绍水晶及特种二氧化硅产品。  相似文献   

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二氧化硅气凝胶由于其特殊的网络结构使其具有密度小、隔热性好、孔隙率高、比表面积大、传声速率低等优良性能。从1931年开始,经过广大研究者几十年的深入研究,二氧化硅气凝胶有了更广阔的发展。本文介绍了以不同原料制备二氧化硅气凝胶的方法,论述了二氧化硅气凝胶的干燥技术,概述了二氧化硅气凝胶的改性措施,分析了二氧化硅气凝胶的应用前景。  相似文献   

10.
本发明提出了一种制备高强度、低密度二氧化硅气凝胶的新方法,属于无机多孔材料技术领域。制备的具体步骤如下:将正硅酸甲酯或者正硅酸乙酯在pH为1.5—4.5条件下于50~80℃水解2—6h;之后滴加氨水,并注入到模具中,使之在空气中成为湿凝胶单体;将所得的湿凝胶放在高压罐中,在一定配比的老化液中于80~150℃下老化3—10d;最后进行干燥,即可得到强度高并且密度低的二氧化硅气凝胶定型材料。本发明的优点在于:操作简便,工艺简单,在提高了传统二氧化硅气凝胶材料强度的同时,保证了其密度低的优点,促进了二氧化硅气凝胶在定型绝热制品领域的应用。  相似文献   

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Despite its industrial importance, the subject of freeze-thaw (F/T) stability of latex coatings has not been studied extensively. There is also a lack of fundamental understanding about the process and the mechanisms through which a coating becomes destabilized. High pressure (2100 bar) freezing fixes the state of water-suspended particles of polymer binder and inorganic pigments without the growth of ice crystals during freezing that produce artifacts in direct imaging scanning electron microscopy (SEM) of fracture surfaces of frozen coatings. We show that by incorporating copolymerizable functional monomers, it is possible to achieve F/T stability in polymer latexes and in low-VOC paints, as judged by the microstructures revealed by the cryogenic SEM technique. Particle coalescence as well as pigment segregation in F/T unstable systems are visualized. In order to achieve F/T stability in paints, latex particles must not flocculate and should provide protection to inorganic pigment and extender particles. Because of the unique capabilities of the cryogenic SEM, we are able to separate the effects of freezing and thawing, and study the influence of the rate of freezing and thawing on F/T stability. Destabilization can be caused by either freezing or thawing. A slow freezing process is more detrimental to F/T stability than a fast freezing process; the latter actually preserves suspension stability during freezing. Presented at the 82nd Annual Meeting of the Federation of Societies for Coatings Technology, October 27–29, 2004 in Chicago, IL. Tied for first place in The John A. Gordon Best Paper Competition.  相似文献   

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In 2002–2004, we examined the flight responses of 49 species of native and exotic bark and ambrosia beetles (Coleoptera: Scolytidae and Platypodidae) to traps baited with ethanol and/or (−)-α-pinene in the southeastern US. Eight field trials were conducted in mature pine stands in Alabama, Florida, Georgia, North Carolina, and South Carolina. Funnel traps baited with ethanol lures (release rate, about 0.6 g/day at 25–28°C) were attractive to ten species of ambrosia beetles (Ambrosiodmus tachygraphus, Anisandrus sayi, Dryoxylon onoharaensum, Monarthrum mali, Xyleborinus saxesenii, Xyleborus affinis, Xyleborus ferrugineus, Xylosandrus compactus, Xylosandrus crassiusculus, and Xylosandrus germanus) and two species of bark beetles (Cryptocarenus heveae and Hypothenemus sp.). Traps baited with (−)-α-pinene lures (release rate, 2–6 g/day at 25–28°C) were attractive to five bark beetle species (Dendroctonus terebrans, Hylastes porculus, Hylastes salebrosus, Hylastes tenuis, and Ips grandicollis) and one platypodid ambrosia beetle species (Myoplatypus flavicornis). Ethanol enhanced responses of some species (Xyleborus pubescens, H. porculus, H. salebrosus, H. tenuis, and Pityophthorus cariniceps) to traps baited with (−)-α-pinene in some locations. (−)-α-Pinene interrupted the response of some ambrosia beetle species to traps baited with ethanol, but only the response of D. onoharaensum was interrupted consistently at most locations. Of 23 species of ambrosia beetles captured in our field trials, nine were exotic and accounted for 70–97% of total catches of ambrosia beetles. Our results provide support for the continued use of separate traps baited with ethanol alone and ethanol with (−)-α-pinene to detect and monitor common bark and ambrosia beetles from the southeastern region of the US.  相似文献   

14.
Glycidyl carbamate chemistry combines the excellent properties of polyurethanes with the crosslinking chemistry of epoxy resins. Glycidyl carbamate functional oligomers were synthesized by the reaction of polyfunctional isocyanate oligomers and glycidol. The oligomers were formulated into coatings with several amine functional crosslinkers at varying stoichiometric ratios and cured at different temperatures. Properties such as solvent resistance, hardness, and impact resistance were dependent on the composition and cure conditions. Most coatings had an excellent combination of properties. Studies were carried out to determine the kinetics of the curing reaction of the glycidyl carbamate functional oligomers with multifunctional and model amines. Detailed kinetic analysis of the curing reactions was also undertaken. The results indicated that the glycidyl carbamate functional group is more reactive than a glycidyl ether group. Presented at the 82nd Annual Meeting of the Federation of Societies for Coatings Technology, on October 27–29, 2004, in Chicago, IL.  相似文献   

15.
A highly moisture-proof polysilsesquioxane coating was obtained from a new bis-silylated precursor, which was synthesized from 3-aminopropyltriethoxysilane (APTES) and m-xylylene diisocyanate (m-XDI) in tetrahydrofuran (THF) and verified by 1H MAS NMR. For direct comparison purposes, an SiO2 coating was also prepared by the Stöber method using tetraethoxysilane (TEOS) as the reactant. Interestingly, the coating obtained from the polysilsesquioxane sol exhibited a much higher moisture resistance capability than its counterpart, which was attributed to its more compact feature between nanoparticles as characterized by N2 absorption experiment and transmission electron microscopy (TEM). Furthermore, its high transparency of about 92% showed potential for application in the protection of optical crystals.  相似文献   

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Vismiones and ferruginins, representatives of a new class of lypophilic anthranoids from the genusVismia were found to inhibit feeding in larvae of species ofSpodoptera, Heliothis, and inLocusta migratoria.  相似文献   

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