浅谈影响铝土矿中二氧化硅测试质量的因素     

陆杰芬 《南方国土资源》2002,15(2):76-78

文章分析、总结了影响铝土矿中二氧化硅测试质量的因素 ,即操作因素、样品因素、温度及试剂因素 ,提出了提高铝土矿中二氧化硅测试质量的办法  相似文献   

口径20厘米蜂窝熔石英平面镜制造及加工情况简介     

李德培 《天文学报》1994,35(2):215-218,T001

本文叙述了口径２０．７厘米，厚３厘米，采用蜂窝结构的熔石英平面镜坯的制造与磨制情况。给出了最后面形的干涉图及阴影图。  相似文献   

Measurements of Atmospheric Formaldehyde (HCHO) and Acetaldehyde (CH3CHO) during POPCORN 1994 Using 2.4-DNPH Coated Silica Cartridges     

L. Benning  A. Wahner 《Journal of Atmospheric Chemistry》1998,31(1-2):105-117

The 2.4-dinitrophenylhydrazine coated silica cartridge technique (DSC) was used for the measurements of HCHO and CH3CHO during the POPCORN campaign in August 1994. A total number of 505 measurements was carried out using an automatic sampling system. The sampling time for each measurement was 30 minutes. During the first two weeks of the campaign samples were taken every 3 hours and during the last two weeks every 30 minutes. No significant diurnal variation of HCHO and CH3CHO was observed. The average mixing ratios of HCHO and CH3CHO were 1.8 ±1.0 ppb and 1.4 ±1.3 ppb. The results for HCHO are in a good agreement with simultaneous measurements by differential optical absorption spectroscopy (DOAS). The absence of a strong diurnal variation of the HCHO mixing ratio can be explained by production and destruction processes during day and night. The measured mixing ratios of HCHO and CH3CHO, especially the mixing ratios during night, are a strong indication that during the POPCORN campaign the maize was a local source of HCHO and CH3CHO.  相似文献   

The preparation of silica from the olivine process and its possible use as a catalyst support     

D. J. Lieftink  J. W. Geus 《Journal of Geochemical Exploration》1998,62(1-3)

The production of silica from the dissolution of olivine in sulphuric acid has been studied. Variations in grainsize of the olivine result in different specific surface areas of the silica. The microporosity of the silica supports an aggregative growth model responsible for the increasing particle size. The silica is used in the preparation of a nickel catalyst. The performance of the produced catalyst is equal to a nickel catalyst based on commercially available silica  相似文献   

硅微粉增韧环氧树脂的研究   总被引：4，自引：0，他引：4  

余志伟 《华东地质学院学报》1998,21(2):137-142

增韧硅微粉是为增韧环氧树脂而研制开发的一种电工级专用填料。本文着重论述了硅微粉增韧的配方、工艺条件和增韧处理过程;通过对填充增韧硅微粉的环氧树脂固化物的冲击试验,证明了增韧硅微粉对环氧树脂具有明显的增韧效果;初步探讨了增韧硅微粉对环氧树脂增韧的机理。  相似文献   

Opaline concretions in Weichselian Late-glacial lake marl from Flanders, northern Belgium     

Luc Denys  Patrick Kiden  Cyriel Verbruggen 《Journal of Paleolimnology》1998,20(1):91-98

Macroscopic opal-A concretions were observed in lake marl deposited in a small Flemish lake (Belgium) during the Allerød biozone of the Weichselian Late-glacial (ca. 12–11 ka BP). The silica from these concretions was derived within the profile, by the leaching of siliceous microfossils – mainly diatom frustules. Formation of the concretions probably resulted from pH- and/or evaporation related precipitation of the silica at a lower stratigraphic level, presumably corresponding more or less to a former low position of the groundwater table. The presence of these concretions is probably related to alternatingly wet and dry local conditions during the middle and later part of the Allerød.  相似文献   

The Rate-equation for Biogenic Silica Dissolution in Seawater – New Hypotheses     

Victor?W.?TruesdaleEmail author  Jim?E.?Greenwood  Andrew?Rendell 《Aquatic Geochemistry》2005,11(3):319-343

This paper investigates the kinetics of biogenic silica dissolution in seawater, through batch dissolution, where the reaction is observed as the increase in dissolved silicic acid concentration with time. It utilises new data from dissolution of the marine diatom Cyclotella cryptica, and the freshwater diatom C. meneghiniana, as well as literature results. The sum of exponentials form: , is hypothesised as the most general rate equation, with the single exponential form occurring in a minority of cases. The consistency of this behaviour with a near-exponential decay of surface area with time, an appropriate mathematical integration, and surface heterogeneity, is discussed. (Serious errors in some existing integrations are identified.) The rate of dissolution at constant surface area is shown to decrease non-linearly as the ambient concentration of silicic acid increases. A fractional order with respect to silicic acid in the back reaction, close to 0.5, leads to a mechanism in which an intermediate is formed from the surface and an, as yet, unidentified molecule, probably water. Good preliminary fits are found between the model and literature results found using entirely different methods. A parallel treatment of hydrogen ion dependency is suggested. The likely distortion of full reaction curves from exponential behaviour imposed by the back reaction, is considered in detail.  相似文献   

The role of shoreland development and commercial cranberry farming in a lake in Wisconsin,USA     

Paul J.?GarrisonEmail author  Sharon A.?Fitzgerald 《Journal of Paleolimnology》2005,33(2):169-188

Musky Bay in Lac Courte Oreilles, Wisconsin, USA, is currently eutrophic. This large, shallow bay of an oligotrophic lake possesses the densest aquatic plant growth and a floating algal mat. Paleoecological reconstructions encompassing the last 130 years, were based on multiproxy analyses of sediment cores from three coring sites, two within the bay and one in the lake itself. These data were compared to historical records of the construction and expansion of two commercial cranberry bogs and shoreline residential homes to identify temporal and causal relations of eutrophication. The proxies investigated included: minor and trace elements; biogenic silica; and the diatom community. Post-depositional diagenesis of organic carbon, nitrogen, and phosphorus in the upper 30 cm of the core obscured records of historical ambient nutrient concentrations in the bay obviating their usefulness for this purpose. In contrast, calcium, magnesium, and potassium concentration profiles appeared to reflect runoff of soil amendments applied to the cranberry bogs and aerial fertilizer spraying over the eastern bog adjacent to Musky Bay. The increase in aluminum content since about 1930 coincided with the historical trend in shoreland development and construction of the original commercial cranberry farm. The biogenic silica profile recorded a steady increase of nutrients to Musky Bay over the last several decades. Stratigraphic changes in the diatom community indicated that nutrient input began to increase in the 1940s and accelerated in the mid-1990s with the onset of a noxious floating algal mat. The diatom community indicates the bay has possessed a significant macrophyte community for at least the last 200 years, but increased nutrient input was manifested by a change in the composition, and an increase in the density of the epiphytic diatom community. Cranberry farming appeared to be the major source of nutrients because the diatom community changes occurred prior to the significant increase in residential housing.  相似文献   

Norwegian Sea intermediate water in the Faroe-Shetland Channel     

Martin  J. H. A. 《ICES Journal of Marine Science》1993,50(2):195-201

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水溶液中有机染料分子在甲基（苯乙基）键合硅胶上的吸附     

胡中华  马延军 《海洋湖沼通报》1994,(4):24-29

本文研究了０．２Ｍ ＮａＣｌ水溶液中亚甲兰,亮绿,中性红,品红和孔雀石绿在甲基（苯乙基）键合硅胶上的吸附速率曲线和等温线,结果表明,５种有机染料分子在键合硅胶上的平衡时间小于１ｈ,其吸附等温线符合改进ＢＥＴ方程,而且推测其吸附过程是一个开始在键合硅胶表面发生单分子层吸附,然后在微孔“凝聚”的过程。  相似文献