检索结果-南通市图书馆

Effect of alkali-activation on aluminosilicate-based cementitious materials

在线全文

学校读者我要写书评

暂无评论

Journal of University of Science and Technology Beijing 2008年第6期15卷 796-801页

作者： Xiaoguang Yang wen ni Xufang Zhang Yali Wang School of Civil and Environmental Engineering University of Science and Technology Beijing Beijing 100083 China Central Research Institute of Building and Construction Co. Ltd. MCC Group Beijing 100088 China

High-performance aluminosilicate-based cementitious materials were produced with fly ash from a coal power plant as one of the major raw materials. The structures of fly ash containing aluminosilicate-based cementitious materials were compared before and after treatment by the methods of nuclear magnetic resonance （NMR） and scanning electron microscopy （SEM）. During the 28 d curing time, the compressive strength of water glass and fly ash samples increased from 9.08 MPa to 26.75 MPa. The results show that most of the stiff shells are destroyed after mechanical grinding and chemical activation. Magic angle spinning （MAS） NMR of 27Al shows that the wide peak becomes narrow and the main peak shifts to the direction of low field, indicating the decrease of polymerization degree, the enhancing of activity, the decrease of six-coordination structure, and the increase of small and symmet- rical four-coordination polyhedron structure within the aluminum-oxygen polyhedron network. Comparisons between MAS NMR of 29Si with different treatments suggest that QO disappears, the quantity of Q2 increases, and the quantity of Q4 decreases. The polymerization degree of silicon-oxygen is reduced, and the potential activity of fly ash is increased.

关键词： fly ash modification alkali activation water glass

Cementing properties of steel slag activated by sodium silicates and sodium hydroxide

在线全文

学校读者我要写书评

暂无评论

Journal of University of Science and Technology Beijing 2005年第5期12卷 464-468页

作者： wen ni En Wang Jianping Li Han Sun Civil and Environmental Engineering School University of Science and Technology Beijing Beijing 100083 China

Steel slag which is mainly composed of γ-Ca2SiO4 and other silicates or alumino-silicates is activated by sodium sificates and sodium hydroxide. The powders of such steel slag are usually inert to hydrate and subsequently have very low ability of cementing. But when sodium silicates and sodium hydroxide are used as activators the steel slag shows very good properties of cementing. When activated with NaOH solution the hardened slurry of the steel slag has a compressive strength of 11.13 MPa after being cured for 28 days. When activated with Na2SiO3 solution the samples after being cured for 28 days have an average compres- sive strength of 40.23 MPa. While the steel slag slurry which is only mixed with water has a compressive of 0.88 MPa after being cured for 28 days.

关键词： steel slag sodium silicate sodium hydroxide cement binding material

High Purity Mullite-Corundum Thermal Insulating Firebricks

在线全文

学校读者我要写书评

暂无评论

International Journal of Minerals,Metallurgy and Materials 1999年第4期13卷 237-241页

作者： wen ni Fengmei Liu(Resource Engineering School, University’ of Sctence and Technology Beijing Beijing. 100083, China) Resource Engineering School University of Science and Technology Beijing Beijing 100083 China

Laboratory and industrial experiments were carried out to study the possibility of producing high purity purity mullite-corundumthermal insulating firebricks. The results show that by using industrial alumina. natuual powder power, coal gangues and a small amountof additives. high purity mullite-corundum thermal insulating firebrieks can be produced The service. temperature of these brick can beup to 1780 with low. thermal conductivity' and good thermal shock resistance

关键词： mullite corundum thermal insulating firebricks

Two Improvements on Numerical Simulation of 2-DOF Vortex-Induced Vibration with Low Mass Ratio

在线全文

学校读者我要写书评

暂无评论

China Ocean Engineering 2017年第6期31卷 764-772页

作者： KANG Zhuang ni wen-chi ZHANG Xu SUN Li-ping Deepwater Engineering Research Center Harbin Engineering University Harbin 150001 China

Till now, there have been lots of researches on numerical simulation of vortex-induced vibration. Acceptable results have been obtained for fixed cylinders with low Reynolds number. However, for responses of 2-DOF vortex-induced vibration with low mass ratio, the accuracy is not satisfactory, especially for the maximum amplitudes. In Jauvtis and Williamson＇s work, the maximum amplitude of the cylinder with low mass ratio m＊=2.6 can reach as large as 1.5D to be called as the ＂super-upper branch＂, but from current literatures, few simulation results can achieve such value, even fail to capture the upper branch. Besides, it is found that the amplitude decays too fast in the lower branch with the RANS-based turbulence model. The reason is likely to be the defects of the turbulence model itself in the prediction of unsteady separated flows as well as the unreasonable setting of the numerical simulation parameters. Aiming at above issues, a modified turbulence model is proposed in this paper, and the effect of the acceleration of flow field on the response of vortex-induced vibration is studied based on OpenFOAM. By analyzing the responses of amplitude, phase and trajectory, frequency and vortex mode, it is proved that the vortex-induced vibration can be predicted accurately with the modified turbulence model under appropriate flow field acceleration.

关键词： 2-DOF vortex-induced vibration numerical simulation modified turbulence model acceleration

Recovery of iron from copper slag by deep reduction and magnetic beneficiation

在线全文

学校读者我要写书评

暂无评论

International Journal of Minerals,Metallurgy and Materials 2013年第11期20卷 1035-1041页

作者： Ke-qing Li Shuo Ping Hong-yu Wang wen ni Key Laboratory of the Ministry of Education of China for High-Efcient Mining and Safety of Metal Mines University of Science and Technology Beijing School of Civil and Environmental Engineering University of Science and Technology Beijing

Aiming at recovering iron from high-iron-content copper slag, this article introduced a combination technol- ogy of deep reduction and magnetic beneficiation, investigated the iron recovery efficiency and optimized the technical conditions. When coke powder with 86wt% fixed carbon was used as a reductant, iron was successfully extracted from the copper slag. Under the optimized condition of the coke powder content of 14wt%, the calcium-to-silicon mass ratio （Ca/Si） of 0.2, the roasting temperature of 1300℃, the roasting time of 3 h, the grinding time of 20 min, and the magnetic field intensity of 61 kA-m-1, the iron recovery rate of the copper slag can reach 91.82%, and the extracted iron powder has an iron grade of 96.21%. With the characteristics of high iron grade and low impurity content, the extracted iron powder can be used as high-quality raw materials of weathering steel.

关键词： copper slag waste utilization ore reduction magnetic separation beneficiation

Hydration mechanism of a cementitious material prepared with Si-Mn slag

在线全文

学校读者我要写书评

暂无评论

International Journal of Minerals,Metallurgy and Materials 2011年第2期18卷 234-239页

作者： Xu-fang Zhang wen ni Jun-yu Wu Li-ping Zhu Key Laboratory of the Minstry of Education of China for High-Efficient Mining and Safety of Metal Mines Ministry of Education University of Science and Technology Beijing Beijing 100083 China North China University of Water Resources and Electric Power Zhengzhou 450011 China Beijing Dongfangjianyu Institute of Concrete Science and Technology Beijing 100190 China

A cementitious material was prepared by mixing 80wt% Si-Mn slag powder, 10wt% lime, and 10wt% anhydrite. The compressive strength of mortar samples reaches 51.48 MPa after 28 d curing. The analyses of X-ray diffraction （XRD） and scanning electron microscopy （SEM） show that much ettringite is formed in the sample cured for 3 d, and C-S-H gel increases rapidly during subsequent curing. Nuclear magnetic resonance （NMR） analysis of 29Si and 27Al and infrared spectroscopy （IR） analysis show that aluminum decomposition from tetrahedral network of the slag glass and its subsequent migration and re-combination play an important role in the process of hydration and strength development of the samples.

关键词： slag cement mechanical properties nuclear magnetic resonance (NMR) hydration

Preparation of natural brucite nanofibers by the dispersion method

在线全文

学校读者我要写书评

暂无评论

Journal of University of Science and Technology Beijing 2008年第4期15卷 489-494页

作者： Li Xu wen ni wenping Li Xingde Liu Hailong Yang Xiaoguang Yang State Key Laboratory of the Ministry of Education of China for High-Efficient Mining ＆ Safety of Metal Mines University of Science and Technology Beijing Beijing 100083 China China Electric Power Research Institute Beijing 102401 China Kemeos Aluminate Technologies Ltd. Beijing 100027 China

The preparation of natural brucite nanofibers through dispersion by the wet process is described. The test results indicate that brucite fibers can be well dispersed by using sodium dioctyl sulfosuccinate （OT） as the dispersant at a dispersant/fiber mass ratio of 0.15：1, dispersing for 30 min at a water/solid mass ratio of 20：1. The prepared nanofibers were characterized with X-ray diffraction （XRD）, scanning electron microscope （SEM）, and transmission electron microscope （TEM）. It is shown that the prepared single brucite nanofiber is around 30 nm in diameter and the talus of the nonsingle brucite nanofibers is about 50-150 nm in diameter. Natural brucite mineral fibers were treated by the dispersion method to obtain nanomaterials. These fibers have significant advantages over artificial nanofibers both in yield and in cost.

关键词： brucite nanofiber sodium dioctyl sulfosuccinate (OT) ultrasonic dispersion method

Mechanism of low thermal conductivity of xonotlite-silica aerogel nanoporous super insulation material

在线全文

学校读者我要写书评

暂无评论

Journal of University of Science and Technology Beijing 2008年第5期15卷 649-653页

作者： Hailong Yang wen ni Deping Chen Guoqiang Xu Tao Liang Li Xu Civil and Environmental Engineering School University of Science and Technology Beijing Beijing 100083 China

In an effort to incorporate the low thermal conductivity of the silica aerogel and the superior structure strength of the xonotlite,a composite material of these two was produced. It was synthesized under vacuum condition and dried by supercritical drying technique. The thermal conductivity of the new material,which is at 298K with the gas pressure ranging from 1.01×10^5 to 1×10^-2 Pa,was measured using the transient hot-strip method. The mechanism of the low thermal conductivity was studied. The results indicate that the low thermal conductivity mainly results from the significant decrease of gaseous thermal conductivity of the new material due to the restriction of the motion of gas molecules in its fine structures. The formation of the fine structures is because the new material takes the pore structure of the silica aerogel which consists of mainly nanometer-sized pores.

关键词： silica aerogel xonotlite nanometer-sized pore super insulation thermal conductivity

Producing Calcium-Bearing Mullite Thermal-Insulating Refractories by Kyanite

在线全文

学校读者我要写书评

暂无评论

International Journal of Minerals,Metallurgy and Materials 1999年第1期13卷 50-53页

作者： wen ni (Resources Engineering School, University of Science and Technology Beijing, Beijing 100083, China) Resources Engineering School University of Science and Technology Beijing Beijing 100083 China

To improve the physical properties, a series of experiments have been camed out to produce calcium-bearing mullite thermal-insulating refractories by using kyanite as major raw materials. The experiments were carried out by a foaming technique and using white cement as a combing agent. The results show that the calcium-bearing mullite refractory has much better physical properhes than traditional clay refractory and high-alumina refractory.

关键词： mullite thermal-insulating refractory kyanite