The nanometer particles of TiO_2 and TiO_2/SiO_2 oxides wereprepared by sol-gel supercritical fluid drying method. The propertiesof TiO_2 and TiO_2/SiO_2 were characterized by means of BET(Brunner-Emmett- Teller metho...The nanometer particles of TiO_2 and TiO_2/SiO_2 oxides wereprepared by sol-gel supercritical fluid drying method. The propertiesof TiO_2 and TiO_2/SiO_2 were characterized by means of BET(Brunner-Emmett- Teller method), TEM (transmission electronmicroscopy), SEM (scanning electron microscopy), XRD (X-ray diffrac-tion) and FTIR (Fourier transform-infrared) techniques. The effectsof different preparation route, prehydrolysis and non-prehydrolysis,on the properties of TiO_2/SiO_2 oxide were also examined.展开更多
Selective separation of silica from a siliceous-calcareous phosphate ore that had been sieved into different size fractions is investigated by a combination of chemical analysis,zeta potential measurement and FTIR and...Selective separation of silica from a siliceous-calcareous phosphate ore that had been sieved into different size fractions is investigated by a combination of chemical analysis,zeta potential measurement and FTIR and XPS techniques.Scrubbing is a better choice than flotation for removing silica from the coarse fractions.The P_2O_5 grade of the coarse fractions is increased to about 30%by scrubbing and the product yields are higher than those obtained by flotation.The silica in the fine fraction is separated by reverse flotation.An alkyl amine salt(DAH)is an effective collector and the P_2O_5 grade of the fine fraction can be increased by 7%to beyond 30%under acidic conditions.The higher zeta potential obtained using DAH suggests that it is more strongly absorbed onto the ore particles than the other cationic collectors. FTIR and XPS results confirm physical absorption of the cationic collector onto the ore surface.They also indicate that calcite is dissolved at low pH values,which increases the Si concentration on the ore surface.展开更多
This paper reports the surface morphology and I-V curves of porous silicon (PS) samples and related devices. The observed fabrics on the PS surface were found to affect the electrical property of PS devices. When th...This paper reports the surface morphology and I-V curves of porous silicon (PS) samples and related devices. The observed fabrics on the PS surface were found to affect the electrical property of PS devices. When the devices were operated under different external bias (10 V or 3 V) for 10 min, their observed obvious differences in electrical properties may be due to the different control mechanisms in the A1/PS interface and PS matrix morphology.展开更多
The atomic and electronic structures of T1 and In on Si(111) surfaces are investigated using the firstprinciples total energy calculations. Total energy optimizations show that the energetically favored structure is...The atomic and electronic structures of T1 and In on Si(111) surfaces are investigated using the firstprinciples total energy calculations. Total energy optimizations show that the energetically favored structure is 1/3 ML T1 adsorbed at the T4 sites on Si(111) surfaces. The adsorption energy difference of one T1 adatom between (√3 × √3) and (1 × 1) is less than that of each In adatom. The DOS indicates that TI 6p and Si 3p electrons play a very important role in the formation of the surface states. It is concluded that the bonding of TI adatoms on Si(111) surfaces is mainly polar covalent, which is weaker than that of In on Si(111). So T1 atom is more easy to be migrated than In atom in the same external electric field and the structures of T1 on Si(111) is prone to switch between (√3 × √3) and (1 × 1).展开更多
Flotation performance of a de-slimed(-150+53μm)Jordanian siliceous phosphate was evaluated in a batch laboratory flotation column 100 cm high and 5 cm inside diameter.The collector used during anionic flotation wa...Flotation performance of a de-slimed(-150+53μm)Jordanian siliceous phosphate was evaluated in a batch laboratory flotation column 100 cm high and 5 cm inside diameter.The collector used during anionic flotation was sodium oleate while an amine acetate(AEROMINE 3100C)was used for cationic flotation.Flotation comparison at different collector dosage,superficial gas velocity,and frother concentration showed that the maximum difference in performance between cationic and anionic flotation was obtained with these flotation parameters:30×10^(-6)(mg/L)frother concentration,250 g/t collector concentration,and 3.4 cm/s superficial gas velocity.At these operating conditions amine (cationic)flotation gave 7%higher flotation recovery,a 6%cleaner concentrate grade,and was 6%more efficient at removing silica.展开更多
Four-, six-, and eight-membered ring silica nanotubes at temperatures from 300 K to 1600 K are relaxed by classical molecular dynamics simulations with three potential models. The simulation results indicate that the ...Four-, six-, and eight-membered ring silica nanotubes at temperatures from 300 K to 1600 K are relaxed by classical molecular dynamics simulations with three potential models. The simulation results indicate that the stability of the end rings of the three silica nanotubes gradually decreases with increase in temperature. The validity of the vibrational features of silica nanotubes is shown by the vibrational density of states. Infrared spectra on the silica nanotubes under different temperatures are investigated. A detailed assignment of each spectral peak to the corresponding vibrational mode of the three nanotubes has been addressed. The results are in good agreement with the other theoretical and experimental展开更多
Silica materials are located in various regions of Libya in large quantities and different mining conditions, so the purpose of this study is silica materials in the south-west of the Libyan region Edree in terms of q...Silica materials are located in various regions of Libya in large quantities and different mining conditions, so the purpose of this study is silica materials in the south-west of the Libyan region Edree in terms of quality and the possibility of using in various engineering industries, particularly construction. The results show that the sands of silica presented in Edree area are of a high degree of purity, as the percentage of silicon (SIO2) reached 99.5%, the percentage of impurities was negligible and represented in some chemical elements in different proportions, such as calcium 0.224%, sodium 0.004%, iron 0.0006%, zinc 0.0003%, boron 0.0003%, potassium 0.0001%, manganese 0.0001% and magnesium 0.0001%, making these materials very suitable in the manufacture of all types of glass, crystal and semi-crystalline high-quality without needing any important treatment, as well as its suitability as a refinement in manufacture of templates metal castings in addition to the possibility of use in the manufacture of cement, building materials and as a filler in paint and brick making and sand and concrete elements can also be used in electronic industries. A geological material of silica present in the form of a sequence of layers of clay and thin layers of sand stone and a large stock of high-quality near the surface, making mining operations of the type of surface and reduces the cost of extraction.展开更多
In the present article, we study the electrical resistivity ρ, the thermoelectric power (TEP) α, thermal conductivity σ, Knight-Shifts and temperature coefficient of the Knight-Shifts of the liquid Si and Ge usin...In the present article, we study the electrical resistivity ρ, the thermoelectric power (TEP) α, thermal conductivity σ, Knight-Shifts and temperature coefficient of the Knight-Shifts of the liquid Si and Ge using the well known model potential for the first time. The structure factor used in the present work is derived from the Percus-Yevick (PY) theory. Various local field correction functions are used to study the screening influence. The present results of resistivity are found in qualitative agreement with available experimental and theoretical whenever exists.展开更多
Froth flotation is a widely used process of particle separation exploiting differences in surface properties. It is important to point out that overall flotation performance(grade and recovery) is a consequence of the...Froth flotation is a widely used process of particle separation exploiting differences in surface properties. It is important to point out that overall flotation performance(grade and recovery) is a consequence of the quality and quantity of the solid particles collected from the pulp phase, transported into the froth phase, and surviving as bubble-particle aggregates into the overflow. This work will focus on studying these phenomena and will incorporate the effects of particle hydrophobicities in the 3-phase system. Solids are classed as either hydrophilic non-sulphide gangue(e.g. silica, talc), hydrophilic sulphide(e.g. pyrite), or hydrophobic sulphide(e.g. sphalerite). Talc is a surface-active species of gangue that has been shown to behave differently from silica(frother adsorbs on the surface of talc particles). Both are common components of ores and will be studied in detail. The focus of this work is to investigate the role of solids on pulp hydrodynamics, froth bubble coalescence intensity, water overflow rate with solids present, and in particular, the interactions between solids, frother and gas on the gas dispersion parameters. The results show that in the pulp zone there is no effect of solids on bubble size and gas holdup; in the froth zone, although hydrophilic particles solely do not effect on the water overflow rate, hydrophobic particles produce higher intensity of rates on water overflow and bubble coalescence, and many be attributed to the water reattachment.展开更多
The authors' work concerns the study of sedimentary environments, the geometry and the characteristics of the silicon-clastic deposits within the basin of EI Ma Labiod at the Algero-Tunisian confines. The sedimentolo...The authors' work concerns the study of sedimentary environments, the geometry and the characteristics of the silicon-clastic deposits within the basin of EI Ma Labiod at the Algero-Tunisian confines. The sedimentological analysis has proved a Miocene age of the sediments with varied environments: marine, fluvial-deltaic and lake. The geological aspect of the sediment, in particular sandy, is of the movable type or very slightly consolidated. The size of the industrial sand layers can be very diverse, however to feed from the industrial consumers having a certain perenniality, our prospection was directed towards layers with very important reserves. It is about a sedimentary basin with dimensions exceeding very largely the conditions of operating for such projects, which are at least one to two million tons. With the exception of a thin quaternary soil horizon, the basin is almost of an exploitation with open sky. The mineralogical determination has revealed siliceous to extra-siliceous sands, which are absolutely usable in the industry of glass, foundry and also in other functions like the abrasives of sanding and the clothing industry of the sandpapers. Concerning the economic aspect, the materials are very close and this is why the area has known the installation of a glassmaking factory and a cement factory using at the same time the Maastrichtian limestone, the sandy material and the clays of the Western zone of the basin.展开更多
In this paper,the effects of Ar ion bombardment during the electron beam evaporation deposition of the amorphous Si film were investigated.It was found that the bombardment increases the light absorption by two to ele...In this paper,the effects of Ar ion bombardment during the electron beam evaporation deposition of the amorphous Si film were investigated.It was found that the bombardment increases the light absorption by two to eleven times and increases the conductance of the film by 3 000 times.This has never been reported before of amorphous Si with electron beam evaporation deposition.展开更多
Different methods have been investigated for the synthesis of magnetic nanoparticles. Control of the particle size, dispersion, purity and stability have been always regarded an issue. In this study magnetite (Fe304...Different methods have been investigated for the synthesis of magnetic nanoparticles. Control of the particle size, dispersion, purity and stability have been always regarded an issue. In this study magnetite (Fe304) superparamagnetic nanoparticles with a size range about 20 nm have been successfully synthesized using chemical co-precipitation method from the solution of ferrous/ferric mixed salt-solution in alkaline media in oxygen-free environment. The sol-gel method has been chose to encapsulate magnetic nanoparticles into silica matrix. The phase structures, morphologies, surface area, functional classes and magnetic properties have been characterized by X-ray diffraction, SEM and AFM, BET, FT-IR and VSM. The results showed that the resultant films, consisting of encapsulated magnetite have crack free and smooth surface with a roughness value 1.5 rim.展开更多
In a previous study, structure of silica gels prepared in a high magnetic field was investigated. While a direct application of such anisotropic silica gels is for an optical anisotropic medium possessing chemical res...In a previous study, structure of silica gels prepared in a high magnetic field was investigated. While a direct application of such anisotropic silica gels is for an optical anisotropic medium possessing chemical resistance, we show here their possibility of medium in materials processing. In this direction, for example, silica hydrogels have so far been used as media of crystal growth. In this paper, as opposed to the soft-wet state, dried silica gels have been investigated. We have found that lead (II) nanocrystallites were formed induced by electron irradiation to lead (ll)-doped dried Hydrogels made from a sodium metasilicate solution doped with silica gels prepared in a high magnetic field such as B = 10 T. lead (II) acetate were prepared. The dried specimens were irradiated by electrons in a transmission electron microscope environment. Electron diffraction patterns indicated the crystallinity of lead (II) nanocrystallites depending on B. An advantage of this processing technique is that the crystallinity can be controlled through the strength of magnetic field B applied during gel preparation. Specific skills are not required to control the strength of magnetic field.展开更多
To protect carbon/carbon (C/C) composites from oxidation, a SiC coating modified with SiO2 was prepared by a complex technology. The inner SiC coating with thickness varying from 150 to 300 μm was initially coated by...To protect carbon/carbon (C/C) composites from oxidation, a SiC coating modified with SiO2 was prepared by a complex technology. The inner SiC coating with thickness varying from 150 to 300 μm was initially coated by chemical vapor reaction (CVR): a simple and cheap technique to prepare the SiC coating via siliconizing the substrate that was exposed to the mixed vapor (Si and SiO2) at high temperatures (1 923?2 273 K). Then the as-prepared coating was processed by a dipping and drying procedure with tetraethoxysilane as source materials to form SiO2 to fill the cracks and holes. Oxidation tests show that, after oxidation in air at 1 623 K for 10 h and thermal cycling between 1 623 K and room temperature 5 times, the mass loss of the CVR coated sample is up to 18.21%, while the sample coated with modified coating is only 5.96%, exhibiting an obvious improvement of oxidation and thermal shock resistance of the coating. The mass loss of the modified sample is mainly contributed to the reaction of C/C substrate with oxygen diffusing through the penetrating cracks formed in thermal shock tests.展开更多
Based on chromatographic theory, the moment method and the time-domain fitting analysis were applied to measure and evaluate the adsorption equilibrium constant and mass transfer properties (axial dispersion coefficie...Based on chromatographic theory, the moment method and the time-domain fitting analysis were applied to measure and evaluate the adsorption equilibrium constant and mass transfer properties (axial dispersion coefficient and effective intra-particle diffusivity) for toluene and p-dichlorobenzene on silica gel adsorbent in the subcritical and supercritical CO2. An apparatus based on supercritical fluid chromatography was established and the experiments were performed at temperatures of 298.15-318.15 K and pressures of 7.5-17.8 MPa. The two methods have been compared. The results show that for the systems studied here the moment method can give reasonable values for both adsorption equilibrium constant and mass transfer properties, but the time-domain analysis only can obtain the adsorption equilibrium constant. The dependence of adsorption equilibrium constant and mass transfer properties on temperature and pressure was investigated.展开更多
Effects of silylation on surface properties and catalytic performance of Zn-IM5 for butane aromatization were studied in this paper. Collidine-IR and NH3-TPD analyses revealed that the silylation treatment not only de...Effects of silylation on surface properties and catalytic performance of Zn-IM5 for butane aromatization were studied in this paper. Collidine-IR and NH3-TPD analyses revealed that the silylation treatment not only decreased the quantity of both strong and weak acid sites but also led to a slightly reduced intensity of weak acidity. Silylation of the catalyst promoted the selectivity of BTX by narrowing the channel and cutting the acidity. The effect of temperature of silylation and amount of Si loading were evaluated. The best condition has specified a temperature of 50 ℃ and a SiO_2 loading of 4.0%.展开更多
The effect of cement on physiochemical properties of three types of soils i.e garden soil, agricultural soil and roadside soil was investigated. The ordinary Portland cement was used. The amount of cement added to soi...The effect of cement on physiochemical properties of three types of soils i.e garden soil, agricultural soil and roadside soil was investigated. The ordinary Portland cement was used. The amount of cement added to soil samples, as dry mass percentage was 20%. The results of analysis showed that the addition of cement is capable of bringing about changes in physiochemical properties of soil. The electrical conductivity and organic matter content in three soils get decreased by the addition of cement. While the pH, bulk density and water holding capacity of soils after the addition of cement gets increased. The soil found most suitable to be treated with cement was roadside soil. It was concluded that cement can be used to change the physiochemical properties of soil and this technique has great utility in improving the quality of problematic soils.展开更多
基金Supported by PetroChina Company Limited (990801-21-2).
文摘The nanometer particles of TiO_2 and TiO_2/SiO_2 oxides wereprepared by sol-gel supercritical fluid drying method. The propertiesof TiO_2 and TiO_2/SiO_2 were characterized by means of BET(Brunner-Emmett- Teller method), TEM (transmission electronmicroscopy), SEM (scanning electron microscopy), XRD (X-ray diffrac-tion) and FTIR (Fourier transform-infrared) techniques. The effectsof different preparation route, prehydrolysis and non-prehydrolysis,on the properties of TiO_2/SiO_2 oxide were also examined.
基金the National Key Technology R&D Program of China forthe support of this work(No.2007BAE58B01).
文摘Selective separation of silica from a siliceous-calcareous phosphate ore that had been sieved into different size fractions is investigated by a combination of chemical analysis,zeta potential measurement and FTIR and XPS techniques.Scrubbing is a better choice than flotation for removing silica from the coarse fractions.The P_2O_5 grade of the coarse fractions is increased to about 30%by scrubbing and the product yields are higher than those obtained by flotation.The silica in the fine fraction is separated by reverse flotation.An alkyl amine salt(DAH)is an effective collector and the P_2O_5 grade of the fine fraction can be increased by 7%to beyond 30%under acidic conditions.The higher zeta potential obtained using DAH suggests that it is more strongly absorbed onto the ore particles than the other cationic collectors. FTIR and XPS results confirm physical absorption of the cationic collector onto the ore surface.They also indicate that calcite is dissolved at low pH values,which increases the Si concentration on the ore surface.
基金Project supported by the Natural Science Foundation of China (No.60225010) and the Key Project of Chinese Ministry of Education
文摘This paper reports the surface morphology and I-V curves of porous silicon (PS) samples and related devices. The observed fabrics on the PS surface were found to affect the electrical property of PS devices. When the devices were operated under different external bias (10 V or 3 V) for 10 min, their observed obvious differences in electrical properties may be due to the different control mechanisms in the A1/PS interface and PS matrix morphology.
基金Supported by National Natural Science Foundation of China under Grant No.60476047Program for Science & Technology Innovation Talents in Universities of Henan Province under Grant No.2008HASTIT030
文摘The atomic and electronic structures of T1 and In on Si(111) surfaces are investigated using the firstprinciples total energy calculations. Total energy optimizations show that the energetically favored structure is 1/3 ML T1 adsorbed at the T4 sites on Si(111) surfaces. The adsorption energy difference of one T1 adatom between (√3 × √3) and (1 × 1) is less than that of each In adatom. The DOS indicates that TI 6p and Si 3p electrons play a very important role in the formation of the surface states. It is concluded that the bonding of TI adatoms on Si(111) surfaces is mainly polar covalent, which is weaker than that of In on Si(111). So T1 atom is more easy to be migrated than In atom in the same external electric field and the structures of T1 on Si(111) is prone to switch between (√3 × √3) and (1 × 1).
基金done during the first author's Fulbright fellowship at the Center for Advanced Separation (CAST)/Virginia Technical Institute and State University-USA. Salah would like to thank all the people who work at CAST for their friendship and support during his stay in Blacksburg, VA.
文摘Flotation performance of a de-slimed(-150+53μm)Jordanian siliceous phosphate was evaluated in a batch laboratory flotation column 100 cm high and 5 cm inside diameter.The collector used during anionic flotation was sodium oleate while an amine acetate(AEROMINE 3100C)was used for cationic flotation.Flotation comparison at different collector dosage,superficial gas velocity,and frother concentration showed that the maximum difference in performance between cationic and anionic flotation was obtained with these flotation parameters:30×10^(-6)(mg/L)frother concentration,250 g/t collector concentration,and 3.4 cm/s superficial gas velocity.At these operating conditions amine (cationic)flotation gave 7%higher flotation recovery,a 6%cleaner concentrate grade,and was 6%more efficient at removing silica.
文摘Four-, six-, and eight-membered ring silica nanotubes at temperatures from 300 K to 1600 K are relaxed by classical molecular dynamics simulations with three potential models. The simulation results indicate that the stability of the end rings of the three silica nanotubes gradually decreases with increase in temperature. The validity of the vibrational features of silica nanotubes is shown by the vibrational density of states. Infrared spectra on the silica nanotubes under different temperatures are investigated. A detailed assignment of each spectral peak to the corresponding vibrational mode of the three nanotubes has been addressed. The results are in good agreement with the other theoretical and experimental
文摘Silica materials are located in various regions of Libya in large quantities and different mining conditions, so the purpose of this study is silica materials in the south-west of the Libyan region Edree in terms of quality and the possibility of using in various engineering industries, particularly construction. The results show that the sands of silica presented in Edree area are of a high degree of purity, as the percentage of silicon (SIO2) reached 99.5%, the percentage of impurities was negligible and represented in some chemical elements in different proportions, such as calcium 0.224%, sodium 0.004%, iron 0.0006%, zinc 0.0003%, boron 0.0003%, potassium 0.0001%, manganese 0.0001% and magnesium 0.0001%, making these materials very suitable in the manufacture of all types of glass, crystal and semi-crystalline high-quality without needing any important treatment, as well as its suitability as a refinement in manufacture of templates metal castings in addition to the possibility of use in the manufacture of cement, building materials and as a filler in paint and brick making and sand and concrete elements can also be used in electronic industries. A geological material of silica present in the form of a sequence of layers of clay and thin layers of sand stone and a large stock of high-quality near the surface, making mining operations of the type of surface and reduces the cost of extraction.
文摘In the present article, we study the electrical resistivity ρ, the thermoelectric power (TEP) α, thermal conductivity σ, Knight-Shifts and temperature coefficient of the Knight-Shifts of the liquid Si and Ge using the well known model potential for the first time. The structure factor used in the present work is derived from the Percus-Yevick (PY) theory. Various local field correction functions are used to study the screening influence. The present results of resistivity are found in qualitative agreement with available experimental and theoretical whenever exists.
基金financially supported by the Chair in Mineral Processing at McGill University, under the Collaborative Research and Development program of NSERC (Natural Sciences and Engineering Research Council of Canada) with industrial sponsorship from Vale, Teck Cominco, Xstrata Process Support, Agnico-Eagle, Shell Canada, Barrick Gold, COREM, SGS Lakefield Research and Flottec
文摘Froth flotation is a widely used process of particle separation exploiting differences in surface properties. It is important to point out that overall flotation performance(grade and recovery) is a consequence of the quality and quantity of the solid particles collected from the pulp phase, transported into the froth phase, and surviving as bubble-particle aggregates into the overflow. This work will focus on studying these phenomena and will incorporate the effects of particle hydrophobicities in the 3-phase system. Solids are classed as either hydrophilic non-sulphide gangue(e.g. silica, talc), hydrophilic sulphide(e.g. pyrite), or hydrophobic sulphide(e.g. sphalerite). Talc is a surface-active species of gangue that has been shown to behave differently from silica(frother adsorbs on the surface of talc particles). Both are common components of ores and will be studied in detail. The focus of this work is to investigate the role of solids on pulp hydrodynamics, froth bubble coalescence intensity, water overflow rate with solids present, and in particular, the interactions between solids, frother and gas on the gas dispersion parameters. The results show that in the pulp zone there is no effect of solids on bubble size and gas holdup; in the froth zone, although hydrophilic particles solely do not effect on the water overflow rate, hydrophobic particles produce higher intensity of rates on water overflow and bubble coalescence, and many be attributed to the water reattachment.
文摘The authors' work concerns the study of sedimentary environments, the geometry and the characteristics of the silicon-clastic deposits within the basin of EI Ma Labiod at the Algero-Tunisian confines. The sedimentological analysis has proved a Miocene age of the sediments with varied environments: marine, fluvial-deltaic and lake. The geological aspect of the sediment, in particular sandy, is of the movable type or very slightly consolidated. The size of the industrial sand layers can be very diverse, however to feed from the industrial consumers having a certain perenniality, our prospection was directed towards layers with very important reserves. It is about a sedimentary basin with dimensions exceeding very largely the conditions of operating for such projects, which are at least one to two million tons. With the exception of a thin quaternary soil horizon, the basin is almost of an exploitation with open sky. The mineralogical determination has revealed siliceous to extra-siliceous sands, which are absolutely usable in the industry of glass, foundry and also in other functions like the abrasives of sanding and the clothing industry of the sandpapers. Concerning the economic aspect, the materials are very close and this is why the area has known the installation of a glassmaking factory and a cement factory using at the same time the Maastrichtian limestone, the sandy material and the clays of the Western zone of the basin.
基金Supported by National Key Basic Research Plan of China (G200068302) ,Beijing Education Committee funding (KM200310005009) ,Beijing Municipal Science & Technology commission fun-ding(D0404003040221)
文摘In this paper,the effects of Ar ion bombardment during the electron beam evaporation deposition of the amorphous Si film were investigated.It was found that the bombardment increases the light absorption by two to eleven times and increases the conductance of the film by 3 000 times.This has never been reported before of amorphous Si with electron beam evaporation deposition.
文摘Different methods have been investigated for the synthesis of magnetic nanoparticles. Control of the particle size, dispersion, purity and stability have been always regarded an issue. In this study magnetite (Fe304) superparamagnetic nanoparticles with a size range about 20 nm have been successfully synthesized using chemical co-precipitation method from the solution of ferrous/ferric mixed salt-solution in alkaline media in oxygen-free environment. The sol-gel method has been chose to encapsulate magnetic nanoparticles into silica matrix. The phase structures, morphologies, surface area, functional classes and magnetic properties have been characterized by X-ray diffraction, SEM and AFM, BET, FT-IR and VSM. The results showed that the resultant films, consisting of encapsulated magnetite have crack free and smooth surface with a roughness value 1.5 rim.
文摘In a previous study, structure of silica gels prepared in a high magnetic field was investigated. While a direct application of such anisotropic silica gels is for an optical anisotropic medium possessing chemical resistance, we show here their possibility of medium in materials processing. In this direction, for example, silica hydrogels have so far been used as media of crystal growth. In this paper, as opposed to the soft-wet state, dried silica gels have been investigated. We have found that lead (II) nanocrystallites were formed induced by electron irradiation to lead (ll)-doped dried Hydrogels made from a sodium metasilicate solution doped with silica gels prepared in a high magnetic field such as B = 10 T. lead (II) acetate were prepared. The dried specimens were irradiated by electrons in a transmission electron microscope environment. Electron diffraction patterns indicated the crystallinity of lead (II) nanocrystallites depending on B. An advantage of this processing technique is that the crystallinity can be controlled through the strength of magnetic field B applied during gel preparation. Specific skills are not required to control the strength of magnetic field.
基金Project(2006CB600901) supported by the National Basic Research Program of ChinaProject(50802115) supported by the National Natural Science Foundation of China
文摘To protect carbon/carbon (C/C) composites from oxidation, a SiC coating modified with SiO2 was prepared by a complex technology. The inner SiC coating with thickness varying from 150 to 300 μm was initially coated by chemical vapor reaction (CVR): a simple and cheap technique to prepare the SiC coating via siliconizing the substrate that was exposed to the mixed vapor (Si and SiO2) at high temperatures (1 923?2 273 K). Then the as-prepared coating was processed by a dipping and drying procedure with tetraethoxysilane as source materials to form SiO2 to fill the cracks and holes. Oxidation tests show that, after oxidation in air at 1 623 K for 10 h and thermal cycling between 1 623 K and room temperature 5 times, the mass loss of the CVR coated sample is up to 18.21%, while the sample coated with modified coating is only 5.96%, exhibiting an obvious improvement of oxidation and thermal shock resistance of the coating. The mass loss of the modified sample is mainly contributed to the reaction of C/C substrate with oxygen diffusing through the penetrating cracks formed in thermal shock tests.
基金Supported by research grant 02KJB530002 from Jiangsu Provincial Committee of Education.
文摘Based on chromatographic theory, the moment method and the time-domain fitting analysis were applied to measure and evaluate the adsorption equilibrium constant and mass transfer properties (axial dispersion coefficient and effective intra-particle diffusivity) for toluene and p-dichlorobenzene on silica gel adsorbent in the subcritical and supercritical CO2. An apparatus based on supercritical fluid chromatography was established and the experiments were performed at temperatures of 298.15-318.15 K and pressures of 7.5-17.8 MPa. The two methods have been compared. The results show that for the systems studied here the moment method can give reasonable values for both adsorption equilibrium constant and mass transfer properties, but the time-domain analysis only can obtain the adsorption equilibrium constant. The dependence of adsorption equilibrium constant and mass transfer properties on temperature and pressure was investigated.
基金financially supported by the Opening Project of the State Key Laboratory of Catalytic Material and Reaction Engineering of Sinopec Research Institute of Petroleum Processing. (No. 33600000-14-ZC0607-0010)
文摘Effects of silylation on surface properties and catalytic performance of Zn-IM5 for butane aromatization were studied in this paper. Collidine-IR and NH3-TPD analyses revealed that the silylation treatment not only decreased the quantity of both strong and weak acid sites but also led to a slightly reduced intensity of weak acidity. Silylation of the catalyst promoted the selectivity of BTX by narrowing the channel and cutting the acidity. The effect of temperature of silylation and amount of Si loading were evaluated. The best condition has specified a temperature of 50 ℃ and a SiO_2 loading of 4.0%.
文摘The effect of cement on physiochemical properties of three types of soils i.e garden soil, agricultural soil and roadside soil was investigated. The ordinary Portland cement was used. The amount of cement added to soil samples, as dry mass percentage was 20%. The results of analysis showed that the addition of cement is capable of bringing about changes in physiochemical properties of soil. The electrical conductivity and organic matter content in three soils get decreased by the addition of cement. While the pH, bulk density and water holding capacity of soils after the addition of cement gets increased. The soil found most suitable to be treated with cement was roadside soil. It was concluded that cement can be used to change the physiochemical properties of soil and this technique has great utility in improving the quality of problematic soils.