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121.
122.
硅灰石合成多孔二氧化硅 ——工艺条件与产物性质研究 总被引:4,自引:1,他引:4
在一系列硅灰石酸处理实验基础上,研究了产物性质与反应速度、反应时间、中和最终pH值等工艺条件的关系。结果表明,工艺条件不同,物理性质也大不相同。 相似文献
123.
P.V. Sivapullaiah J.P. Prashanth A. Sridharan B.V. Narayana 《Geotechnical and Geological Engineering》1998,16(3):239-250
The use of fly ash in geotechnical engineering depends greatly on its pozzolanic reactivity. Though many factors influence the reactivity of fly ash it is well recognized that reactive silica and lime content play a major role. A new, accurate and reliable method for the determination of reactive silica content of fly ash has been established. The reactive silica content, obtained as acid soluble silica in about 2 to 3 N hydrochloric acid, is found to correlate well with unconfined compressive strength of fly ashes. The reactive silica content of fly ash is also important in the stabilization of soils using fly ash. © Rapid Science Ltd. 1998 相似文献
124.
Sedimentary records of eutrophication in the Changjiang Estuary upwelling area over last 100 a 总被引:3,自引:1,他引:2
FENG Xuwen JING Xianglong YU Xiaoguo LI Hongliang CHEN Jianfang QIAN Jiangchu 《海洋学报(英文版)》2008,27(6):49-61
The upwelling area in the Changjiang Estuary was selected to collect the core, where the red tide occurred frequently and hypoxic existed. The total organic carbon (TOC), total nitrogen (TN), biogenic silica (BSi) and stable organic carbon isotopic ratios(δ13 Corg) were determined on the 210pb-dated sediment core. The concentrations of TOC, TN, BSi as well as their sedimentation fluxes have in- creased to some extent since the 1970s. TOC and TN fluxes increased about 45%, 36% respectively. The average δ13 Coorg value in the core was -23.67 ×10^-3 which remained nearly constant before the 20 century. The δ13 Corg values increased after the 1900s, two marked increases were observed from the 1950s and the 1970s. A simple δ13 Cors model was used to estimate the contribution of terrigenous and marine organic matter inputs for the sediment, which indicated the increase in accumulation since the 1970s has been almost exclusively marine. The increasing of marine organic matter accumulation (TOC, TN and BSi) was corresponding with the increasing of fertilizer consumption and the NO3-N budgets from the Changjiang River. The riverine runoff of fertilizers and nutrients stimulated the algae blooming. Enhanced primary production resulted in an enrichment of organic matter in the sediment. These data support the hypothesis that anthropogenic nutrient loading has been a significant factor on the eutrophication in the Changjiang Estuary. 相似文献
125.
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
126.
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
127.
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
128.
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
129.
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
130.
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