Shape-selective catalysts for the disproportionation of toluene were prepared by the modification of the cylinder-shaped ZSM-5 zeolite extrudates with chemical liquid deposition with TEOS （tetraethyl orthosilicate）....Shape-selective catalysts for the disproportionation of toluene were prepared by the modification of the cylinder-shaped ZSM-5 zeolite extrudates with chemical liquid deposition with TEOS （tetraethyl orthosilicate）.Various parameters for preparing catalysts were changed to investigate the suitable conditions.The resulting cata-lysts were tested in a pressured fixed bed reactor and characterized by SEM （scanning electron microscopy）.The conversion of toluene and para-xylene selectivity were influenced remarkably by the n（SiO2）/n（Al2O3） ratio of ZSM-5 zeolite,the type and amount of deposition agent,acid and solvent used,and the time and cycle of deposition treatment.TEOS was proved to be a more efficient agent than the conventional polysiloxanes when the deposition amount was low.The catalyst prepared at the suitable conditions exhibited a high para-xylene selectivity of 91.1% with considerable high conversion of 25.6%.SEM analyses confirmed the formation of a layer of amorphous silica on the external surface of ZSM-5 zeolie crystals,which was responsible for the highly enhanced shape-selectivity.展开更多
The world is currently facing the challenges of global warming and climate change. Numerous efforts have been taken to mitigate CO2 emission, among which is the use of solid sorbents for CO2 capture. In this work, Li4...The world is currently facing the challenges of global warming and climate change. Numerous efforts have been taken to mitigate CO2 emission, among which is the use of solid sorbents for CO2 capture. In this work, Li4SiO4 was synthesised via a sol-gel method using lithium nitrate （LiNO3） and tetraethylorthosilicate （SiC8H20O4） as precursors. A parametric study of Li：Si molar ratio （1-5）, calcination temperature （600-800℃） and calcination time （1-8 h） were conducted during sorbent synthesis. Calcination temperature （700-800℃） and carbonation temperature （500-700℃） during CO2 sorption activity were also varied to confirm the optimum operating temperature. Sorbent with the highest CO2 sorption capacity was finally introduced to several cyclic tests to study the durability of the sorbent through 10 cycles of CO2 sorption-desorption test. The results showed that the calcination temperature of 800℃ and carbonation temperature of 700℃ were the best operating temperatures, with CO2 sorption capacity of 7.95 mmol CO2·（g sorbent）^-1 （93% of the theoretical yield）. Throughout the ten cyclic processes, CO2 sorption capacity of the sorbent had dropped approximately 16.2% from the first to the tenth cycle, which was a reasonable decline. Thus, it was concluded that Li4SiO4 is a potential CO2 solid sorbent for high temperature CO2 capture activity.展开更多
The piezoelectric quartz crystal (PQC) impedance analyzer was used to monitor in situ the generation of monodisperse silica particles during the hydrolysis of tetraethyl orthosilicate (TEOS) and their adsorption o...The piezoelectric quartz crystal (PQC) impedance analyzer was used to monitor in situ the generation of monodisperse silica particles during the hydrolysis of tetraethyl orthosilicate (TEOS) and their adsorption onto an Au electrode in alcohol solutions containing water (6-15 mol/L) and ammonia (0 2-2 0 mol/L). The equivalent circuit parameters, the resonance frequencies and the half peak width values of the conductance spectra of the PQC resonance were obtained. The resonant frequency decreased notably while the motional resistance changed very slightly (within 1 Ω) during the hydrolysis reaction, suggesting that the mass effect do^minated the adsorption of generated monodisperse silica particles on the gold electrode in this system. Changes in f 0 indicated that the ammonia concentration affected the hydrolytic reaction obviously, and the influence of water concentration on the reaction was small while the water was significantly excessive. Kinetics of monodisperse silica particle adsorption occurring at the electrode|solution interface was analyzed using a first order reaction scheme. In addition, the electrolyte induced precipitation of the monodisperse silica particles was monitored and discussed. The mean size, the number of adsorbed particles per area and the converge of monodisperse silica particles were obtained from scanning electron microscope (SEM) observations.展开更多
A novel lithium orthosilicate based adsorbent doping with halloysite nanotubes(HNTs) was synthesized with Kaolin clay and SiO_2 by an impregnation-precipitation method.The samples were characterized by X-ray diffracti...A novel lithium orthosilicate based adsorbent doping with halloysite nanotubes(HNTs) was synthesized with Kaolin clay and SiO_2 by an impregnation-precipitation method.The samples were characterized by X-ray diffraction and scanning electron microscopy,nitrogen adsorption-desorption isotherm analysis and thermo-gravimetry,respectively.The results indicate that the reactivity of Li_4SiO_4 for CO_2 absorption can be enhanced by doping alumina.Different aluminum sources result in different degrees of the CO_2 adsorption performance.It is also found that the CO_2 capture amount of the adsorbent doping with Halloysite nanotubes is 15.25 wt.%at 560 ℃,which is better than that of the adsorbent doping with γ-Al_2O_3(i.e.,10.88 wt.%).展开更多
Core-shell structured SiO2/poly（N-isopropylacrylamide） （SiO2/PNIPAM） microspheres were successfully fabricated through hydrolysis and condensation reaction of tertraethyl orthosilicate （TEOS） on the surface of P...Core-shell structured SiO2/poly（N-isopropylacrylamide） （SiO2/PNIPAM） microspheres were successfully fabricated through hydrolysis and condensation reaction of tertraethyl orthosilicate （TEOS） on the surface of PNIPAM template at 50 ~C. The PNIPAM template can be easily removed by water at room temperature so that SiO2 hollow microspheres were finally obtained. The transmission electron microscope and scanning electron microscope observations indicated that SiO2 hollow microspheres with an average diameter of 150 nm can be formed only if there are enough concentration of PNIPAM and TEOS, and the hy- drolysis time of TEOS. FTIR analysis showed that part of PNIPAM remained on the wall of SiO2 because of the strong interaction between PNIPAM and silica. This work provides a clean and efficient way to prepare hollow microspheres.展开更多
The synthesis and luminescence properties of Zn2 SiO4: Mn phosphor layers on spherical silica spheres, i.e.,a kind of core-shell complex phosphor, Zn2SiO4: Mn@ SiO2 were described.Firstly, monodisperse silica spheres ...The synthesis and luminescence properties of Zn2 SiO4: Mn phosphor layers on spherical silica spheres, i.e.,a kind of core-shell complex phosphor, Zn2SiO4: Mn@ SiO2 were described.Firstly, monodisperse silica spheres were obtained via the Stober method by the hydrolysis of tetraethoxysilane(TEOS) Si ( OC2H5 ) 4 under base condition ( using NH4 OH as the catalyst).Secondly, the silica spheres were coated with a Zn2 SiO4: Mn phosphor layer by a Pechini solgel process.X-ray diffraction ( XRD), scanning electron microscope ( SEM), energy-dispersive X-ray spectrum ( EDS )and photoluminescence (PL) were employed to characterize the resulting complex phosphor.The results confirm that1000 ℃ annealed sample consists of crystalline Zn2SiO4: Mn shells and amorphous SiO2 cores.The phosphor show the green emission of Mn2+ at 521 nm corresponding 4T1 (4G) - 6 A1 (6S) transition, and the possible luminescence mechanism is proposed.展开更多
Sol-gel method was utilized to synthesize two different series of red silicate phosphors : MgSiO3 and Mg2SiO4 powder samples doped with Mn2+, conducted the investigation of red long-lasting phosphor: MgSiO3 : Eu2 + , ...Sol-gel method was utilized to synthesize two different series of red silicate phosphors : MgSiO3 and Mg2SiO4 powder samples doped with Mn2+, conducted the investigation of red long-lasting phosphor: MgSiO3 : Eu2 + , Dy3+, Mn2+ . TGA curves of the gel precursor for two series depicted that the loss of residual organic groups and NO3 groups occurs below 450℃. According to the XRD patterns, the major diffraction peaks of the MgSiO3 and Mg2SiO4 series are consistent with a proto-enstatite structure (JCPDS No.11-0273) and a forsterite structure (JCPDS No.85-1364) respectively. With the excitation at 415 nm, the red emission band of Mn2+ ions is peaked at 661 nm for MgSiO3:1%(atom fraction) Mn2+ or 644 nm for MgiSiO4: 1 %(atom fraction) Mn2+ . Compared with Mg2SiO4:Mn2+ samples, MgSiO3:Mn2+ samples exhibit higher luminescence intensity and higher quenching concentration. In addition, the two series co-doped with Eu2+ , Dy3+ , Mn2+ were also prepared. Photo-luminescence and afterglow properties of the two co-doped series were analyzed, which show that MgSiO3: Eu2 + , Dy3+ , Mn2+ is more suitable for a red long-lasting phosphor.展开更多
Li4SiO4 ceramic pebble is considered as a candidate tritium breeding material of Chinese Helium Cooled Solid Breeder Test Blanket Module （CH HCSB TBM） for the International Thermonuclear Experimental Reactor （ITER...Li4SiO4 ceramic pebble is considered as a candidate tritium breeding material of Chinese Helium Cooled Solid Breeder Test Blanket Module （CH HCSB TBM） for the International Thermonuclear Experimental Reactor （ITER）. In this paper, LiaSiO4 ceramic pebbles deposited with catalytic metals, including Pt, Pd, Ru and Ir, were prepared by wet impregnation method. The metal particles on Li4SiO4 pebble exhibit a good promotion of hydrogen isotope exchange reactions in H2-D20 gas system, with conversion equilibrium temperature reduction of 200-300 ~C. The out-of-pile tritium release experiments were performed using 1.0 wt% Pt/Li4SiO4 and Li4SiO4 pebbles irradiated in a thermal neutron reactor. The thermal desorption spectroscopy shows that Pt was effective to increase the tritium release rate at lower temperatures, and the ratio of tritium molecule （HT） to tritiated water （HTO） of 1.0 wt% Pt/LiaSiO4 was much more than that of Li4SiO4, which released mainly as HTO. Thus, catalytic metals deposited on LiaSiO4 pebble may help to accelerate the recovery of bred tritium particularly in low temperature region, and increase the tritium molecule form released from the tritium breedin~ materials.展开更多
Li2Fe0.9Mn0.1SiO4/C composites were synthesized by using X-ray diffractometry （XRD）, scanning electron microscopy （SEM） glucose as carbon source. The samples were characterized by and electrochemical measurements....Li2Fe0.9Mn0.1SiO4/C composites were synthesized by using X-ray diffractometry （XRD）, scanning electron microscopy （SEM） glucose as carbon source. The samples were characterized by and electrochemical measurements. All Li2Fe0.9Mn0.1SiO4/C composites are of the similar crystal structure. With increasing the carbon content in the range of 5%-20% （mass fraction）, the diffraction peaks in XRD patterns broaden and the particle sizes and the tap density of samples decrease. The Li2Fe0.9Mn0.1SiO4/C composites with carbon content of 14.12% show excellent electrochemical performances with an initial discharge capacity of 154.7 mA.h/g at C/16 rate, and the capacity retention remains 92.2% after 30 cycles.展开更多
A homogeneous crack-free nano- or meso-porous silica films on silicon was fabricated by colloidal silica sol derived by hydrolyzing tetraethyl orthosilicate (TEOS) catalyzing with (C4H9)4N+OH- in water medium. The sol...A homogeneous crack-free nano- or meso-porous silica films on silicon was fabricated by colloidal silica sol derived by hydrolyzing tetraethyl orthosilicate (TEOS) catalyzing with (C4H9)4N+OH- in water medium. The solution with ratio of H2O/TEOS15, R4N+ and glycerol as templates, combining with the hydrolyzed intermediate, controlled the silica aggregating; the templated silica film with heterostructure was developed into homogeneous nano-porous then meso-porous silica films after being annealed from 750 C to 850 C; the formation mechanism of the porous silica films was discussed; morphologies of the silica films were characterized. The refractive indexes of the porous silica films were 1.2561.458, the thermal conductivity < 0.7 W/m/K. The fabricating procedure and the sequence had not been reported before.展开更多
Background: The silica leaching activity of some of the mystifying non-pathogenic BKH1 bacteria present in the cluster of hot springs (temperatures range 35°C - 80°C) at Bakreshwar (West Bengal, India, 23...Background: The silica leaching activity of some of the mystifying non-pathogenic BKH1 bacteria present in the cluster of hot springs (temperatures range 35°C - 80°C) at Bakreshwar (West Bengal, India, 23°52'48"N;87°22'40"N) has provided some significant advancements in the field of nanotechnology. The present investigation was designed to synthesis the silica particles using bioremediase protein at different pH conditions. Methods: A secretary bacterial protein bioremediase (UniProt Knowledgebase Accession Number P86277) isolated from a thermophilic non-pathogenic bacterium BKH1 (GenBank Accession No. FJ177512) has been used to synthesis the silica particles at different pH conditions (pH at 3.0, 5.0, 8.0, 10.0, and 12.0 respectively). The silica particles were synthesized by the action of bioremediase protein on Tetra-ethyl-orthosilicate (TEOS) under ambient condition. Morphological and compositional studies of the biosynthesized silica particles were characterized by Field emission scanning electron microscope (FE-SEM) equipped with Energy dispersive X-ray analyser (EDX). Results: The Fourier transformed infra-red (FTIR) spectroscopic analysis confirmed the nature as well as occurrence of several functional groups surrounded on the silica particles. The amorphous nature of the prepared silica particles was confirmed by X-ray diffractometer (XRD) study. The Zeta potential (ζ) study revealed the stability of silica particles in neutral pH environment. The Brunauer-Emmett-Teller (BET) surface area measurement confirmed the porosity variation in all biosynthesized silica particles prepared at different pH conditions. Raman spectra analytically depend on their respective specific surface (BET) area. Thermogravimetry tool was used to monitor the effects of the thermal treatment on the surface properties of all the samples. Conclusions: The method for the synthesis of silica particles at different pH condition using the protein bioremediase has a special implication as it is an environmentally benign, cost-effective and facile technique which may have conceivable application in chromatographic packing. In addition, controlling of size as well as porosity of the silica particles can be achievable by pH as an only variable.展开更多
It is urgent to develop excellent solid CO<sub>2</sub> sorbents with higher sorption capacity, simpler synthetic process, better thermal stability and lower costs of synthesis in CO<sub>2</sub>...It is urgent to develop excellent solid CO<sub>2</sub> sorbents with higher sorption capacity, simpler synthetic process, better thermal stability and lower costs of synthesis in CO<sub>2</sub> capture and storage technologies. In this work, a number of Li<sub>4</sub>SiO<sub>4</sub>-based sorbents synthesized by lithium carbonate with three different kinds of fly ashes in various molar ratios were developed. The results indicate that the Li<sub>2</sub>CO<sub>3</sub>:SiO<sub>2</sub> mole ratio used in the sorbents synthesis significantly affects the CO<sub>2</sub> absorption properties. The sorption capacity increased with the excess of Li<sub>2</sub>CO<sub>3</sub> first and then decreased when the excessive quantity was beyond a certain amount. The experiments found that FA-Li<sub>4</sub>SiO<sub>4</sub>_0.6, CFA-Li<sub>4</sub>SiO<sub>4</sub>_0.4, HCl/CFA-Li<sub>4</sub>SiO<sub>4</sub>_0.3 presented the best sorption ability among these fly ash derived Li<sub><span style="font-family:Verdana;">4</span></sub><span style="font-family:Verdana;">SiO</span><sub><span style="font-family:Verdana;">4</span></sub><span style="font-family:Verdana;"> samples, and the corresponding weight gain was 28.2 wt%, 25.1 wt% and 32.5 wt%, respectively. The three sorbents with the optimal molar ratio were characterized using various morphological </span><span style="font-family:Verdana;">characterization techniques and evaluated by thermogravimetric analysis </span><span style="font-family:Verdana;">for their capacity to chemisorb CO<sub>2</sub> at 450<sup></sup></span><span><span><span style="font-family:;" "=""><span style="font-family:Verdana;"><span style="font-family:Verdana, Helvetica, Arial;white-space:normal;background-color:#FFFFFF;">°</span></span><span style="font-family:Verdana;"></span><span style="font-family:Verdana;">C</span><span style="font-family:Verdana;"> - 650<sup></sup></span><span style="font-family:Verdana;"><span style="font-family:Verdana, Helvetica, Arial;white-space:normal;background-color:#FFFFFF;">°</span></span><span style="font-family:Verdana;"></span><span style="font-family:Verdana;">C</span><span style="font-family:Verdana;">, diluted CO<sub>2</sub> (10%, 20%) and in presence of water vapor (12%). The adsorption curve of FA- Li<sub>4</sub>SiO<sub>4</sub>_0.6 at different temperatures was simulated with the Jander-Zhang model to explore the influence of carbon dioxide diffusion on adsorption reaction. Further experiments showed that the adsorbent had a good sorption capacity in a lower partial pressure of CO<sub>2</sub> and the presence of steam enhanced the mobility of Li<sup>+</sup>. What’s more, FA-Li<sub>4</sub>SiO<sub>4</sub>_0.6, CFA-Li<sub>4</sub>SiO<sub>4</sub>_0.4 and HCl/CFA-Li<sub>4</sub>SiO<sub>4</sub>_0.3 particles showed satisfactory sorption capacity in fixed-bed reactor and excellent cyclic sorption stability during 10 sorption/ desorption cycles.</span></span></span></span>展开更多
The photoluminescence properties of Eu2+-activated α’-Sr2SiO4 and α’-Ba2SiO4 with a high Eu2+ concentration were investigated. In the case of Sr2-xEuxSiO4, emission was shifted from 585 to 611 nm with increasing t...The photoluminescence properties of Eu2+-activated α’-Sr2SiO4 and α’-Ba2SiO4 with a high Eu2+ concentration were investigated. In the case of Sr2-xEuxSiO4, emission was shifted from 585 to 611 nm with increasing the total Eu2+ concentration (x) from 0.1 to 0.8. This trend was similar to that in Ba2-xEuxSiO4, where the emission was shifted from 513 to 545 nm. The large redshifts in both the excitation and emission spectra were discussed in terms of the Eu2+ occupancies on two kinds of M sites and their local structural changes (M: Sr and Ba).展开更多
The aim of this study is to fabricate a multifunctional biohybrid composite utilizing double walled carbon nanotubes(DWCNTs)as a carrier for loading of the colistin sulfate(CLS)through the application of the sol-gel t...The aim of this study is to fabricate a multifunctional biohybrid composite utilizing double walled carbon nanotubes(DWCNTs)as a carrier for loading of the colistin sulfate(CLS)through the application of the sol-gel technique.The resulting composite was analyzed by Fourier transform infrared spectroscopy(FTIR),thermogravimetric analysis(TGA),scanning electron microscope(SEM),X-ray diffraction patterns(XRD),and particle size distribution analysis utilizing dynamic light scattering technique(DLS).Furthermore,an assessment of in vitro bone bioactivity was conducted under physiological levels of Ca2+and PO4+(SBF)at 37°C and pH 7.4 over a period of 7 days.Additionally,the in vitro cytotoxicity against mice bone marrow cells was evaluated using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide(MTT)assay.The outcomes indicated that the composite possessed a particle size of 365 nm in diameter with a PDI of 0.21(the pure CLS and untreated DWCNTs were 290 and 459 nm in diameter,respectively),improved biocompatibility,and promoted the formation of a Ca-phosphate apatite layer on the surface with a Ca/P ratio of approximately 1.78.The findings collectively validated the significant contribution of the CLS peptide in DWCNTs-based composite for the purposes of bone tissue engineering.展开更多
Transparent paper with good hydrophobicity and flexibility was expected to act as an alternative substrate in fabrication of flexible electronics.However,conventional paper made of cellulose fibers was opaque and hydr...Transparent paper with good hydrophobicity and flexibility was expected to act as an alternative substrate in fabrication of flexible electronics.However,conventional paper made of cellulose fibers was opaque and hydrophilic without undergoing special processing.Herein,cellulose fiber paper was treated by impregnating with hydrolyzed tetraethyl orthosilicate(TEOS)followed by coating with hydrophobic polydimethylsiloxane(PDMS)to prepare hydrophobic transparent pa-per.The results showed that silica nanoparticles produced by the TEOS hydrolysis improved the paper transparency to some extent,increased the paper thermal stability,but still remained the hydrophilicity of paper.After the paper was further coated with the PDMS and the PDMS was consolidated,the paper became clearly transparent and hydrophobic.The processed paper had a transmittance of more than 90%at 550 nm.The water contact angle of the paper reached about 110°.This work provided a new approach for the fabrication of hydrophobic transparent paper with conventional cellulose fiber paper.展开更多
Polycarbosilane(PCS)has been widely used to fabricate silicon carbide(SiC)fibers via pyrolysis.In this paper,for improving the morphology of SiC fibers,tetraethyl orthosilicate(TEOS,m=1 g,3 g and 5 g,respectively)was ...Polycarbosilane(PCS)has been widely used to fabricate silicon carbide(SiC)fibers via pyrolysis.In this paper,for improving the morphology of SiC fibers,tetraethyl orthosilicate(TEOS,m=1 g,3 g and 5 g,respectively)was added into the PCS precursor solution(containing 1.5 g PCS).The continuous fibers have been prepared by electrospinning,and then the SiC fibers were synthesized by calcination at 1300℃,1400℃and 1600℃for 4 h respectively with a heating rate of 10℃/min in flowing nitrogen(N_(2)).The morphologies of the fibers were investigated by the scanning electron microscope(SEM)and it could be seen that the crystallinity of the SiC fibers was lower,the length of the SiC fibers was increased,and the diameter was uniform with the increase of the addition amount of TEOS.展开更多
基金Supported by the Key Natural Science Foundation for Universities of Jiangsu Province（06KJA53012） the National Natural Science Foundation of China（20776069 20976084）
文摘Shape-selective catalysts for the disproportionation of toluene were prepared by the modification of the cylinder-shaped ZSM-5 zeolite extrudates with chemical liquid deposition with TEOS （tetraethyl orthosilicate）.Various parameters for preparing catalysts were changed to investigate the suitable conditions.The resulting cata-lysts were tested in a pressured fixed bed reactor and characterized by SEM （scanning electron microscopy）.The conversion of toluene and para-xylene selectivity were influenced remarkably by the n（SiO2）/n（Al2O3） ratio of ZSM-5 zeolite,the type and amount of deposition agent,acid and solvent used,and the time and cycle of deposition treatment.TEOS was proved to be a more efficient agent than the conventional polysiloxanes when the deposition amount was low.The catalyst prepared at the suitable conditions exhibited a high para-xylene selectivity of 91.1% with considerable high conversion of 25.6%.SEM analyses confirmed the formation of a layer of amorphous silica on the external surface of ZSM-5 zeolie crystals,which was responsible for the highly enhanced shape-selectivity.
基金fully sponsored by the Ministry of Education of Malaysia and Universiti Sains Malaysia through LRGS-USM Nano MITe Grant (203/PJKIMIA/6720009)
文摘The world is currently facing the challenges of global warming and climate change. Numerous efforts have been taken to mitigate CO2 emission, among which is the use of solid sorbents for CO2 capture. In this work, Li4SiO4 was synthesised via a sol-gel method using lithium nitrate （LiNO3） and tetraethylorthosilicate （SiC8H20O4） as precursors. A parametric study of Li：Si molar ratio （1-5）, calcination temperature （600-800℃） and calcination time （1-8 h） were conducted during sorbent synthesis. Calcination temperature （700-800℃） and carbonation temperature （500-700℃） during CO2 sorption activity were also varied to confirm the optimum operating temperature. Sorbent with the highest CO2 sorption capacity was finally introduced to several cyclic tests to study the durability of the sorbent through 10 cycles of CO2 sorption-desorption test. The results showed that the calcination temperature of 800℃ and carbonation temperature of 700℃ were the best operating temperatures, with CO2 sorption capacity of 7.95 mmol CO2·（g sorbent）^-1 （93% of the theoretical yield）. Throughout the ten cyclic processes, CO2 sorption capacity of the sorbent had dropped approximately 16.2% from the first to the tenth cycle, which was a reasonable decline. Thus, it was concluded that Li4SiO4 is a potential CO2 solid sorbent for high temperature CO2 capture activity.
文摘The piezoelectric quartz crystal (PQC) impedance analyzer was used to monitor in situ the generation of monodisperse silica particles during the hydrolysis of tetraethyl orthosilicate (TEOS) and their adsorption onto an Au electrode in alcohol solutions containing water (6-15 mol/L) and ammonia (0 2-2 0 mol/L). The equivalent circuit parameters, the resonance frequencies and the half peak width values of the conductance spectra of the PQC resonance were obtained. The resonant frequency decreased notably while the motional resistance changed very slightly (within 1 Ω) during the hydrolysis reaction, suggesting that the mass effect do^minated the adsorption of generated monodisperse silica particles on the gold electrode in this system. Changes in f 0 indicated that the ammonia concentration affected the hydrolytic reaction obviously, and the influence of water concentration on the reaction was small while the water was significantly excessive. Kinetics of monodisperse silica particle adsorption occurring at the electrode|solution interface was analyzed using a first order reaction scheme. In addition, the electrolyte induced precipitation of the monodisperse silica particles was monitored and discussed. The mean size, the number of adsorbed particles per area and the converge of monodisperse silica particles were obtained from scanning electron microscope (SEM) observations.
文摘A novel lithium orthosilicate based adsorbent doping with halloysite nanotubes(HNTs) was synthesized with Kaolin clay and SiO_2 by an impregnation-precipitation method.The samples were characterized by X-ray diffraction and scanning electron microscopy,nitrogen adsorption-desorption isotherm analysis and thermo-gravimetry,respectively.The results indicate that the reactivity of Li_4SiO_4 for CO_2 absorption can be enhanced by doping alumina.Different aluminum sources result in different degrees of the CO_2 adsorption performance.It is also found that the CO_2 capture amount of the adsorbent doping with Halloysite nanotubes is 15.25 wt.%at 560 ℃,which is better than that of the adsorbent doping with γ-Al_2O_3(i.e.,10.88 wt.%).
文摘Core-shell structured SiO2/poly（N-isopropylacrylamide） （SiO2/PNIPAM） microspheres were successfully fabricated through hydrolysis and condensation reaction of tertraethyl orthosilicate （TEOS） on the surface of PNIPAM template at 50 ~C. The PNIPAM template can be easily removed by water at room temperature so that SiO2 hollow microspheres were finally obtained. The transmission electron microscope and scanning electron microscope observations indicated that SiO2 hollow microspheres with an average diameter of 150 nm can be formed only if there are enough concentration of PNIPAM and TEOS, and the hy- drolysis time of TEOS. FTIR analysis showed that part of PNIPAM remained on the wall of SiO2 because of the strong interaction between PNIPAM and silica. This work provides a clean and efficient way to prepare hollow microspheres.
文摘The synthesis and luminescence properties of Zn2 SiO4: Mn phosphor layers on spherical silica spheres, i.e.,a kind of core-shell complex phosphor, Zn2SiO4: Mn@ SiO2 were described.Firstly, monodisperse silica spheres were obtained via the Stober method by the hydrolysis of tetraethoxysilane(TEOS) Si ( OC2H5 ) 4 under base condition ( using NH4 OH as the catalyst).Secondly, the silica spheres were coated with a Zn2 SiO4: Mn phosphor layer by a Pechini solgel process.X-ray diffraction ( XRD), scanning electron microscope ( SEM), energy-dispersive X-ray spectrum ( EDS )and photoluminescence (PL) were employed to characterize the resulting complex phosphor.The results confirm that1000 ℃ annealed sample consists of crystalline Zn2SiO4: Mn shells and amorphous SiO2 cores.The phosphor show the green emission of Mn2+ at 521 nm corresponding 4T1 (4G) - 6 A1 (6S) transition, and the possible luminescence mechanism is proposed.
基金Project is supported by National High Technology Research and Development Program of China (863 Program) (2002 AA 324060)National Natural Science Foundation of China (10404028)
文摘Sol-gel method was utilized to synthesize two different series of red silicate phosphors : MgSiO3 and Mg2SiO4 powder samples doped with Mn2+, conducted the investigation of red long-lasting phosphor: MgSiO3 : Eu2 + , Dy3+, Mn2+ . TGA curves of the gel precursor for two series depicted that the loss of residual organic groups and NO3 groups occurs below 450℃. According to the XRD patterns, the major diffraction peaks of the MgSiO3 and Mg2SiO4 series are consistent with a proto-enstatite structure (JCPDS No.11-0273) and a forsterite structure (JCPDS No.85-1364) respectively. With the excitation at 415 nm, the red emission band of Mn2+ ions is peaked at 661 nm for MgSiO3:1%(atom fraction) Mn2+ or 644 nm for MgiSiO4: 1 %(atom fraction) Mn2+ . Compared with Mg2SiO4:Mn2+ samples, MgSiO3:Mn2+ samples exhibit higher luminescence intensity and higher quenching concentration. In addition, the two series co-doped with Eu2+ , Dy3+ , Mn2+ were also prepared. Photo-luminescence and afterglow properties of the two co-doped series were analyzed, which show that MgSiO3: Eu2 + , Dy3+ , Mn2+ is more suitable for a red long-lasting phosphor.
基金supported by the Development Fund of China Academy of Engineering Physics (No.2010B0301035)the National Magnetic Confinement Fusion Science Program (No. 2010GB112004)
文摘Li4SiO4 ceramic pebble is considered as a candidate tritium breeding material of Chinese Helium Cooled Solid Breeder Test Blanket Module （CH HCSB TBM） for the International Thermonuclear Experimental Reactor （ITER）. In this paper, LiaSiO4 ceramic pebbles deposited with catalytic metals, including Pt, Pd, Ru and Ir, were prepared by wet impregnation method. The metal particles on Li4SiO4 pebble exhibit a good promotion of hydrogen isotope exchange reactions in H2-D20 gas system, with conversion equilibrium temperature reduction of 200-300 ~C. The out-of-pile tritium release experiments were performed using 1.0 wt% Pt/Li4SiO4 and Li4SiO4 pebbles irradiated in a thermal neutron reactor. The thermal desorption spectroscopy shows that Pt was effective to increase the tritium release rate at lower temperatures, and the ratio of tritium molecule （HT） to tritiated water （HTO） of 1.0 wt% Pt/LiaSiO4 was much more than that of Li4SiO4, which released mainly as HTO. Thus, catalytic metals deposited on LiaSiO4 pebble may help to accelerate the recovery of bred tritium particularly in low temperature region, and increase the tritium molecule form released from the tritium breedin~ materials.
基金Project(50302016) supported by the National Natural Science Foundation of China
文摘Li2Fe0.9Mn0.1SiO4/C composites were synthesized by using X-ray diffractometry （XRD）, scanning electron microscopy （SEM） glucose as carbon source. The samples were characterized by and electrochemical measurements. All Li2Fe0.9Mn0.1SiO4/C composites are of the similar crystal structure. With increasing the carbon content in the range of 5%-20% （mass fraction）, the diffraction peaks in XRD patterns broaden and the particle sizes and the tap density of samples decrease. The Li2Fe0.9Mn0.1SiO4/C composites with carbon content of 14.12% show excellent electrochemical performances with an initial discharge capacity of 154.7 mA.h/g at C/16 rate, and the capacity retention remains 92.2% after 30 cycles.
文摘A homogeneous crack-free nano- or meso-porous silica films on silicon was fabricated by colloidal silica sol derived by hydrolyzing tetraethyl orthosilicate (TEOS) catalyzing with (C4H9)4N+OH- in water medium. The solution with ratio of H2O/TEOS15, R4N+ and glycerol as templates, combining with the hydrolyzed intermediate, controlled the silica aggregating; the templated silica film with heterostructure was developed into homogeneous nano-porous then meso-porous silica films after being annealed from 750 C to 850 C; the formation mechanism of the porous silica films was discussed; morphologies of the silica films were characterized. The refractive indexes of the porous silica films were 1.2561.458, the thermal conductivity < 0.7 W/m/K. The fabricating procedure and the sequence had not been reported before.
文摘Background: The silica leaching activity of some of the mystifying non-pathogenic BKH1 bacteria present in the cluster of hot springs (temperatures range 35°C - 80°C) at Bakreshwar (West Bengal, India, 23°52'48"N;87°22'40"N) has provided some significant advancements in the field of nanotechnology. The present investigation was designed to synthesis the silica particles using bioremediase protein at different pH conditions. Methods: A secretary bacterial protein bioremediase (UniProt Knowledgebase Accession Number P86277) isolated from a thermophilic non-pathogenic bacterium BKH1 (GenBank Accession No. FJ177512) has been used to synthesis the silica particles at different pH conditions (pH at 3.0, 5.0, 8.0, 10.0, and 12.0 respectively). The silica particles were synthesized by the action of bioremediase protein on Tetra-ethyl-orthosilicate (TEOS) under ambient condition. Morphological and compositional studies of the biosynthesized silica particles were characterized by Field emission scanning electron microscope (FE-SEM) equipped with Energy dispersive X-ray analyser (EDX). Results: The Fourier transformed infra-red (FTIR) spectroscopic analysis confirmed the nature as well as occurrence of several functional groups surrounded on the silica particles. The amorphous nature of the prepared silica particles was confirmed by X-ray diffractometer (XRD) study. The Zeta potential (ζ) study revealed the stability of silica particles in neutral pH environment. The Brunauer-Emmett-Teller (BET) surface area measurement confirmed the porosity variation in all biosynthesized silica particles prepared at different pH conditions. Raman spectra analytically depend on their respective specific surface (BET) area. Thermogravimetry tool was used to monitor the effects of the thermal treatment on the surface properties of all the samples. Conclusions: The method for the synthesis of silica particles at different pH condition using the protein bioremediase has a special implication as it is an environmentally benign, cost-effective and facile technique which may have conceivable application in chromatographic packing. In addition, controlling of size as well as porosity of the silica particles can be achievable by pH as an only variable.
文摘It is urgent to develop excellent solid CO<sub>2</sub> sorbents with higher sorption capacity, simpler synthetic process, better thermal stability and lower costs of synthesis in CO<sub>2</sub> capture and storage technologies. In this work, a number of Li<sub>4</sub>SiO<sub>4</sub>-based sorbents synthesized by lithium carbonate with three different kinds of fly ashes in various molar ratios were developed. The results indicate that the Li<sub>2</sub>CO<sub>3</sub>:SiO<sub>2</sub> mole ratio used in the sorbents synthesis significantly affects the CO<sub>2</sub> absorption properties. The sorption capacity increased with the excess of Li<sub>2</sub>CO<sub>3</sub> first and then decreased when the excessive quantity was beyond a certain amount. The experiments found that FA-Li<sub>4</sub>SiO<sub>4</sub>_0.6, CFA-Li<sub>4</sub>SiO<sub>4</sub>_0.4, HCl/CFA-Li<sub>4</sub>SiO<sub>4</sub>_0.3 presented the best sorption ability among these fly ash derived Li<sub><span style="font-family:Verdana;">4</span></sub><span style="font-family:Verdana;">SiO</span><sub><span style="font-family:Verdana;">4</span></sub><span style="font-family:Verdana;"> samples, and the corresponding weight gain was 28.2 wt%, 25.1 wt% and 32.5 wt%, respectively. The three sorbents with the optimal molar ratio were characterized using various morphological </span><span style="font-family:Verdana;">characterization techniques and evaluated by thermogravimetric analysis </span><span style="font-family:Verdana;">for their capacity to chemisorb CO<sub>2</sub> at 450<sup></sup></span><span><span><span style="font-family:;" "=""><span style="font-family:Verdana;"><span style="font-family:Verdana, Helvetica, Arial;white-space:normal;background-color:#FFFFFF;">°</span></span><span style="font-family:Verdana;"></span><span style="font-family:Verdana;">C</span><span style="font-family:Verdana;"> - 650<sup></sup></span><span style="font-family:Verdana;"><span style="font-family:Verdana, Helvetica, Arial;white-space:normal;background-color:#FFFFFF;">°</span></span><span style="font-family:Verdana;"></span><span style="font-family:Verdana;">C</span><span style="font-family:Verdana;">, diluted CO<sub>2</sub> (10%, 20%) and in presence of water vapor (12%). The adsorption curve of FA- Li<sub>4</sub>SiO<sub>4</sub>_0.6 at different temperatures was simulated with the Jander-Zhang model to explore the influence of carbon dioxide diffusion on adsorption reaction. Further experiments showed that the adsorbent had a good sorption capacity in a lower partial pressure of CO<sub>2</sub> and the presence of steam enhanced the mobility of Li<sup>+</sup>. What’s more, FA-Li<sub>4</sub>SiO<sub>4</sub>_0.6, CFA-Li<sub>4</sub>SiO<sub>4</sub>_0.4 and HCl/CFA-Li<sub>4</sub>SiO<sub>4</sub>_0.3 particles showed satisfactory sorption capacity in fixed-bed reactor and excellent cyclic sorption stability during 10 sorption/ desorption cycles.</span></span></span></span>
文摘The photoluminescence properties of Eu2+-activated α’-Sr2SiO4 and α’-Ba2SiO4 with a high Eu2+ concentration were investigated. In the case of Sr2-xEuxSiO4, emission was shifted from 585 to 611 nm with increasing the total Eu2+ concentration (x) from 0.1 to 0.8. This trend was similar to that in Ba2-xEuxSiO4, where the emission was shifted from 513 to 545 nm. The large redshifts in both the excitation and emission spectra were discussed in terms of the Eu2+ occupancies on two kinds of M sites and their local structural changes (M: Sr and Ba).
基金supported by the National Research Centre,Egypt,according to the project No.13020207.
文摘The aim of this study is to fabricate a multifunctional biohybrid composite utilizing double walled carbon nanotubes(DWCNTs)as a carrier for loading of the colistin sulfate(CLS)through the application of the sol-gel technique.The resulting composite was analyzed by Fourier transform infrared spectroscopy(FTIR),thermogravimetric analysis(TGA),scanning electron microscope(SEM),X-ray diffraction patterns(XRD),and particle size distribution analysis utilizing dynamic light scattering technique(DLS).Furthermore,an assessment of in vitro bone bioactivity was conducted under physiological levels of Ca2+and PO4+(SBF)at 37°C and pH 7.4 over a period of 7 days.Additionally,the in vitro cytotoxicity against mice bone marrow cells was evaluated using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide(MTT)assay.The outcomes indicated that the composite possessed a particle size of 365 nm in diameter with a PDI of 0.21(the pure CLS and untreated DWCNTs were 290 and 459 nm in diameter,respectively),improved biocompatibility,and promoted the formation of a Ca-phosphate apatite layer on the surface with a Ca/P ratio of approximately 1.78.The findings collectively validated the significant contribution of the CLS peptide in DWCNTs-based composite for the purposes of bone tissue engineering.
基金The authors are grateful for the financial support from National Natural Science Foundation of China(Nos.31270625 and 21506105)Major Program of Natural Science Foundation of Shandong Province(No.ZR2018ZC0842).
文摘Transparent paper with good hydrophobicity and flexibility was expected to act as an alternative substrate in fabrication of flexible electronics.However,conventional paper made of cellulose fibers was opaque and hydrophilic without undergoing special processing.Herein,cellulose fiber paper was treated by impregnating with hydrolyzed tetraethyl orthosilicate(TEOS)followed by coating with hydrophobic polydimethylsiloxane(PDMS)to prepare hydrophobic transparent pa-per.The results showed that silica nanoparticles produced by the TEOS hydrolysis improved the paper transparency to some extent,increased the paper thermal stability,but still remained the hydrophilicity of paper.After the paper was further coated with the PDMS and the PDMS was consolidated,the paper became clearly transparent and hydrophobic.The processed paper had a transmittance of more than 90%at 550 nm.The water contact angle of the paper reached about 110°.This work provided a new approach for the fabrication of hydrophobic transparent paper with conventional cellulose fiber paper.
基金This work was financially supported by the Fundamental Research Funds for the Central Universities(No.DUT12LAB03)the National Natural Science Foundation of China(No.51104028)the Specialized Research Fund for the Doctoral Program of Higher Education(20110041120031).
文摘Polycarbosilane(PCS)has been widely used to fabricate silicon carbide(SiC)fibers via pyrolysis.In this paper,for improving the morphology of SiC fibers,tetraethyl orthosilicate(TEOS,m=1 g,3 g and 5 g,respectively)was added into the PCS precursor solution(containing 1.5 g PCS).The continuous fibers have been prepared by electrospinning,and then the SiC fibers were synthesized by calcination at 1300℃,1400℃and 1600℃for 4 h respectively with a heating rate of 10℃/min in flowing nitrogen(N_(2)).The morphologies of the fibers were investigated by the scanning electron microscope(SEM)and it could be seen that the crystallinity of the SiC fibers was lower,the length of the SiC fibers was increased,and the diameter was uniform with the increase of the addition amount of TEOS.
