Porous materials have promise as sound insulation, heat barrier, vibration attenuation, and catalysts. Most industrial solid wastes, such as tailings, coal gangue, and fly ash are rich in silicon. Additionally, a high...Porous materials have promise as sound insulation, heat barrier, vibration attenuation, and catalysts. Most industrial solid wastes, such as tailings, coal gangue, and fly ash are rich in silicon. Additionally, a high silicon content waste is a potential raw material for the syn- thesis of silicon-based, multi-porous materials such as zeolites, mesoporous silica, glass-ceramics, and geopolymer foams. Representative sil- icon-rich industrial solid wastes (SRISWs) are the focus of this mini review of the processing and application of porous silicon materials with respect to the physical and chemical properties of the SRISW. The transformation methods of preparing porous materials from SRISWs are summarized, and their research status in micro-, meso-, and macro-scale porous materials are described. Possible problems in the application of SRISWs and in the preparation of functional porous materials are analyzed, and their development prospects are discussed. This review should provide a typical reference for the recycling and use of industrial solid wastes to develop sustainable “green materials.”展开更多
Wood-based panels containing urea-formaldehyde resin result in the long-term release of formaldehyde and threaten human health.In this study,inorganic aluminosilicate coatings prepared by combining metakaolin,silica f...Wood-based panels containing urea-formaldehyde resin result in the long-term release of formaldehyde and threaten human health.In this study,inorganic aluminosilicate coatings prepared by combining metakaolin,silica fume,NaOH,and H_(2)O were applied to the surfaces of wood-based panels to obstruct formaldehyde release.The Si/Al,Na/Al,and H_(2)O/Na_(2)O molar ratios of the coatings were regulated to investigate their effects on the structure and formaldehyde-resistant barrier properties of coatings.Results showed that the cracks in the coatings gradually disappeared and the formaldehyde resistance rates of the barrier increased as the Si/Al molar ratio was increased from 1.6 to 2.2.This value also increased as the Na/Al molar ratio was increased from 0.9 to 1.2 because of the improvement of the degree of polymerization.As the H_(2)O/Na_(2)O molar ratio was increased from 12 to 15,the thickness of the dry film decreased gradually and led to the reduction in the formaldehyde resistance rate.When the Si/Al,Na/Al,and H_(2)O/Na_(2)O molar ratios were 2.2,1.2,and 12,respectively,the inorganic aluminosilicate coating showed good performance as a formaldehyde-resistant barrier and its formaldehyde resistance rate could reach up to 83.2%.展开更多
SnSb alloy powders for the anode of Li-ion batteries were synthesized by two kinds of reduction precipitation methods: solution titration and rapid mixing. Two kinds of SnSb alloy powders showed different phase compo...SnSb alloy powders for the anode of Li-ion batteries were synthesized by two kinds of reduction precipitation methods: solution titration and rapid mixing. Two kinds of SnSb alloy powders showed different phase compositions and particle morphologies although the same starting materials were used. The SnSb alloy electrode synthesized by titration exhibits high reversible specific capacity and good cycling stability, whereas the rapid-mixing sample shows high irreversible capacity and fast capacity fade. The broad particle size distribution of SnSb powders synthesized by titration is considered to be responsible for the improvement of cycling stability. The initial charge-discharge efficiency exceeding 80% has been obtained for the titration sample. The electrochemical reaction process of two kinds of synthesized SnSb composite electrodes was characterized by cyclic voltammetry and AC impedance techniques.展开更多
Development of an electrocatalyst that is cheap and has good properties to replace conventional noble metals is important for H_(2) applications.In this study,dealloying of an amorphous Ti_(37)Cu_(60)Ru_(3) alloy was ...Development of an electrocatalyst that is cheap and has good properties to replace conventional noble metals is important for H_(2) applications.In this study,dealloying of an amorphous Ti_(37)Cu_(60)Ru_(3) alloy was performed to prepare a freestanding nanostructured hydrogen evolution reaction(HER)catalyst.The effect of dealloying and addition of Ru to TiCu alloys on the microstructure and HER properties under alkaline conditions was investigated.3 at.%Ru addition in Ti_(40)Cu_(60) decreases the overpotential to reach a current density of 10mA cm^(-2) and Tafel slope of the dealloyed samples to 35 and 34mV dec−1.The improvement of electrocatalytic properties was attributed to the formation of a nanostructure and the modification of the electronic structure of the catalyst.First-principles calculations based on density function theory indicate that Ru decreases the Gibbs free energy of water dissociation.This work presents a method to prepare an efficient electrocatalyst via dealloying of amorphous alloys.展开更多
Surface modification of up-conversion luminescence materials (Na[Y0.57Yb0.39Er0.04]F4 modified by amino groups) by grafting and modifying with aldehyde groups was studied by means of Fourier transform infrared spect...Surface modification of up-conversion luminescence materials (Na[Y0.57Yb0.39Er0.04]F4 modified by amino groups) by grafting and modifying with aldehyde groups was studied by means of Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and emission spectrum (EM). The surface modification effect was compared using two different finishhag agents, p-phthalaldehyde and glutaraldehyde. It was found that the surface of up-conversion luminescence materials could be modified by aldehyde groups of the two finishing agents, the systematic dispersibility and the thermostability of the up-conversion luminescence material modified by p-phthalaldehyde were better than those of the material modified by glutaraldehyde, and the luminous intensity of the material modified by p-phthalaldehyde was increased. The AI (the ratio of the suspended segmental quality in the specimen to the total mass of the specimen) of the material modified by p-phthalaldehyde was higher than that of the material modified by glutaraldehyde. It is obviously seen that the embellishment effect of p-phthalaldehyde as a finishing agent was better than that of glutaraldehyde. In addition, the reasons why p-phthalaldehyde is a good finishing agent are also explained.展开更多
Si C nanowires are excellent high-temperature electromagnetic wave (EMW) absorbing materials. However, their polymer matrix composites are difficult to work at temperatures above 300℃, while their ceramic matrix comp...Si C nanowires are excellent high-temperature electromagnetic wave (EMW) absorbing materials. However, their polymer matrix composites are difficult to work at temperatures above 300℃, while their ceramic matrix composites must be prepared above 1000℃ in an inert atmosphere. Thus, for addressing the abovementioned problems, SiC/low-melting-point glass composites were well designed and prepared at 580℃ in an air atmosphere. Based on the X-ray diffraction results, SiC nanowires were not oxidized during air atmosphere sintering because of the low sintering temperature. Additionally, SiC nanowires were uniformly distributed in the glass matrix material. The composites exhibited good mechanical and EMW absorption properties. As the filling ratio of SiC nanowires increased from 5wt%to 20wt%, the Vickers hardness and flexural strength of the composite reached HV 564 and 213 MPa, which were improved by 27.7%and 72.8%, respectively, compared with the low-melting-point glass. Meanwhile, the dielectric loss and EMW absorption ability of SiC nanowires at 8.2–12.4 GHz were also gradually improved. The dielectric loss ability of low-melting-point glass was close to 0. However, when the filling ratio of SiC nanowires was 20wt%, the composite showed a minimum reflection loss (RL) of-20.2 dB and an effective absorption (RL≤-10 dB) bandwidth of2.3 GHz at an absorber layer thickness of 2.3 mm. The synergistic effect of polarization loss and conductivity loss in SiC nanowires was responsible for this improvement.展开更多
Using cetyltrimethylammonium bromide (CTAB) as the template agent, cerium nitrate as the cerium resource, yttrium nitrate as the yttrium resource, and ammonium carbonate as the precipitating agent, mesoporous CeO2 p...Using cetyltrimethylammonium bromide (CTAB) as the template agent, cerium nitrate as the cerium resource, yttrium nitrate as the yttrium resource, and ammonium carbonate as the precipitating agent, mesoporous CeO2 powders doped with different yttrium contents were successfully synthesized using a chemical precipitation method, under an alkalescent condition. Properties of the obtained samples were characterized and analyzed with X-ray diffraction (XRD), energy dispersive analysis of X-rays (EDAX), transmission electron microscopy (TEM), infrared (IR) absorbance, and the BET method. For the prepared samples with 20% (molar ratio) Y-doped content, a BET specific surface area of 106. 6 m^2 · g^- 1, with an average pore size of3~27 nm were obtained. XRD patterns showed that the doped samples were with a cubic fluorite structure. TEM micrographs revealed that the doped samples showed a spherical morphology with a diameter ranging from 20 to 30 nm and a round pore shape. IR results indicated that the Ce-O-Ce vibration intensity decreased as the Y-doped content increased. N2 adsorption-desorption isotherms showed that the samples possessed typical mesopore characteristics. The average pore size of the samples decreased alter mesoporous CeO2 was doped with yttrium, and the average pore size decreased largely as the Y-doped content increased.展开更多
The electrochemical behavior of silicon wafer in alkaline slurry with nano-sized CeO2 abrasive was investigated.The variations of corrosion potential(φcorr)and corrosion current density(Jcorr)of the P-type(100)silico...The electrochemical behavior of silicon wafer in alkaline slurry with nano-sized CeO2 abrasive was investigated.The variations of corrosion potential(φcorr)and corrosion current density(Jcorr)of the P-type(100)silicon wafer with the slurry pH value and the concentration of abrasive CeO2 were studied by polarization curve technologies.The dependence of the polishing rate on the pH and the concentration of CeO2 in slurries during chemical mechanical polishing(CMP)were also studied.It is discovered that there is a large change of φcorr and Jcorr when slurry pH is altered and the Jcorr reaches the maximum(1.306 μA/cm2)at pH 10.5 when the material removal rate(MRR)comes to the fastest value.The Jcorr increases gradually from 0.994 μA/cm2 with 1% CeO2 to 1.304 μA/cm2 with 3% CeO2 and reaches a plateau with the further increase of CeO2 concentration.There is a considerable MRR in the slurry with 3% CeO2 at pH 10.5.The coherence between Jcorr and MRR elucidates that the research on the electrochemical behavior of silicon wafers in the alkaline slurry could offer theoretic guidance on silicon polishing rate and ensure to adjust optimal components of slurry.展开更多
Highly sensitive methods are important for monitoring the concentration of metal ions in industrial wastewater.Here,we developed a new probe for the determination of metal ions by fluorescence quenching.The probe cons...Highly sensitive methods are important for monitoring the concentration of metal ions in industrial wastewater.Here,we developed a new probe for the determination of metal ions by fluorescence quenching.The probe consists of hydroxylated graphene quantum dots(H-GQDs),prepared from GQDs by electrochemical method followed by surface hydroxylation.It is a non-reactive indicator with high sensitivity and detection limits of 0.01μM for Cu2+,0.005μM for Al3+,0.04μM for Fe3+,and 0.02μM for Cr3+.In addition,the low biotoxicity and excellent solubility of H-GQDs make them promising for application in wastewater metal ion detection.展开更多
The surface of an up-conversion luminescence material was modified by overcoating with SiOa, which was synthesized from a hydrolysis progress of telraethoxysilane (TEOS) in alkalescent condition. By analyzing the hy...The surface of an up-conversion luminescence material was modified by overcoating with SiOa, which was synthesized from a hydrolysis progress of telraethoxysilane (TEOS) in alkalescent condition. By analyzing the hydrolyzed mechanism of TEOS, it was found that there was not only physical adsorption but also chemical bonding between the up-conversion material and SiO2. At the same time, some adsorption bands at 1100, 475, 950, and 3500 cm^-1 were found by FI-IR, which were the characteristic bands of Si-OH and Si-O-Si. By analyzing the surface elements of the coated material by XPS, it was found that its surface only included Si, O, and C elements, and not F and Y. In the picture of XRD, there was no additional peak after surface modification, suggesting that the silica shell was amorphous. The small peak at 20 = 23° in the X-ray diffraction pattern of the coated material was caused by the amorphous SiO2 shell, and the TEM image also proved that the surface of the material was successfully modified by overcoating with SiO2. The amount of hydroxyls was then increased on the surface of the material, which made it easy to connect with other active groups.展开更多
The electrochemical behaviors of n-type silicon wafers pH value and solid content of the slurry on the corrosion of silicon in silica-based slurry were investigated, and the influences of the wafers were studied by us...The electrochemical behaviors of n-type silicon wafers pH value and solid content of the slurry on the corrosion of silicon in silica-based slurry were investigated, and the influences of the wafers were studied by using electrochemical DC polarization and AC impedance techniques. The results revealed that these factors affected the corrosion behaviors of silicon wafers to different degrees and had their suitable parameters that made the maximum corrosion rate of the wafers. The corrosion potential of (100) sttrface was lower than that of(111), whereas the current density of (100) was much higher than that of(111).展开更多
LiMn2O4 powder as a cathode materials for rechargeable lithium-ion batteries was prepared by solid-state reaction from LitCO3 and electrolytic MnOz at different sintering periods (2, 6, 18, and 32 h). X-ray diffract...LiMn2O4 powder as a cathode materials for rechargeable lithium-ion batteries was prepared by solid-state reaction from LitCO3 and electrolytic MnOz at different sintering periods (2, 6, 18, and 32 h). X-ray diffraction (XRD) patterns of the prepared samples are identified as the spinel structure with a space group of Fd3 m. The lattice parameters almost remain the same as the sintering periods increase. The sample with a sintering period of 32 h shows good cycling performance at both low and nigh current densities, and also elevated temperature. It is believed that the excellent electrochemical behavior of this sample results from its good crystallinity and large grain size compared with other samples. Different electrochemical measurements were conducted to investigate the electrochemical properties of spinel LiMn204. 2008 University of Science and Technology Beijing. All rights reserved.展开更多
Monodispersed manganese ferrite (MnFe2O4) nanocrystals could be successfully synthesized in large quantities via a facile synthetic technique based on the pyrolysis of organometallic compound precursor, in which oct...Monodispersed manganese ferrite (MnFe2O4) nanocrystals could be successfully synthesized in large quantities via a facile synthetic technique based on the pyrolysis of organometallic compound precursor, in which octadecene was used as solvent, and oleic acid and oleylamine were used as capping ligands. MnFe204 nanocrystals were obtained with size in a tunable range of 4- 15 nm and their morphologies could be tuned from spherical to triangle-shaped by varying the surfactants. The phase structure, morphology, and size of the products were characterized in detail by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Magnetic properties of MnFe2O4 nanocrystals with different morphologies were measured using a superconducting quantum interference device (SQUID). Both monodisperse MnFe204 nanocrystals with spherical and triangle-shapes are superparamagnetic at room temperature while ferromagnetic at 2 K. The pyrolysis method may provide an effective route to synthesize other spinel ferrites or metal oxides nanocrystals.展开更多
Density function theory (DFT) at the B3LYP/6- 311 + + G(2d) (5D, 7F) level of theory was calculated to predict the geometry structures, toted energy and net charges of four kinds of dynamic isomer molecules of...Density function theory (DFT) at the B3LYP/6- 311 + + G(2d) (5D, 7F) level of theory was calculated to predict the geometry structures, toted energy and net charges of four kinds of dynamic isomer molecules of 2-aminino-5 mercapto- 1,3,4-thiodizole ( AA/IT for short). The fact that the atoms in four kinds of dynamie AMT isomer molecules lie in a plane and one kind of AMT is most stable is approved. The results also indicate that the pentogon ring in four kinds of dynamic AMT isomer molecules are aromatics, and the AMTc and Cu corrosion mitigation film produces as a result of the bonds form one by one of the covalent bond of Cu(1) with 7 N atom in AMTc amd the coordinate bond of Cu with 2S atom in ATMc. The resonant vibration frequencies and IR intensity for the four kituds of dynamic isomer of AMT are also calculated and their IR spectra are shown.展开更多
An approach named "pore structure collapsed replication route" has been developed to prepare mesoporous WC materials with a high surface area (105 m2/g) and crystallized framework at a temperature as low as 700 ℃...An approach named "pore structure collapsed replication route" has been developed to prepare mesoporous WC materials with a high surface area (105 m2/g) and crystallized framework at a temperature as low as 700 ℃. The XRD, TEM, EDS, and BET characterizations were conducted to analyze the effects of the synthesis parameters and the template types on the structure of mesoporous WC. The compaction on the templates is the key to form mesoporous structure of WC while the templates help to control the size of crystalline. At a content of 7 wt% for the precursor of WC, the mesoporous WC could be formed with well ordered structure.展开更多
A cryogenic scanning electron microscopy(cryo-SEM) technique was used to explore the shear-thickening behavior of Fe-ZSM5 zeolite pastes and to discover its underlying mechanism. Bare Fe-ZSM5 zeolite samples were fo...A cryogenic scanning electron microscopy(cryo-SEM) technique was used to explore the shear-thickening behavior of Fe-ZSM5 zeolite pastes and to discover its underlying mechanism. Bare Fe-ZSM5 zeolite samples were found to contain agglomerations, which may break the flow of the pastes and cause shear-thickening behaviors. However, the shear-thickening behaviors can be eliminated by the addition of halloysite and various boehmites because of improved particle packing. Furthermore, compared with pure Fe-ZSM5 zeolite samples and its composite samples with halloysite, the samples with boehmite(Pural SB or Disperal) additions exhibited network structures in their cryo-SEM images; these structures could facilitate the storage and release of flow water, smooth paste flow, and avoid shear-thickening. By contrast, another boehmite(Versal 250) formed agglomerations rather than network structures after being added to the Fe-ZSM5 zeolite paste and resulted in shear-thickening behavior. Consequently, the results suggest that these network structures play key roles in eliminating the shear-thickening behavior.展开更多
The meso-macroporous Fe-doped Cu O was prepared by a simple hydrothermal method combined with post-annealing. The samples were characterized by X-ray powder diffraction(XRD), scanning electron microscopy(SEM), Brunaue...The meso-macroporous Fe-doped Cu O was prepared by a simple hydrothermal method combined with post-annealing. The samples were characterized by X-ray powder diffraction(XRD), scanning electron microscopy(SEM), Brunauer-Emmett-Teller N2 adsorption-desorption analyses and UV-vis diffuses reflectance spectroscopy. The Fe-doped Cu O sample shows higher adsorption capacity and photocatalytic activity for xanthate degradation than pure Cu O under visible light irradiation. In addition, the adsorption process is found to fit Langmuir isotherms and pseudo-second-order kinetics. The the first order kinetic Langmuir Hinshelwood model was used to study the reaction kinetics of photocatalytic degradation, and the apparent rate constant( k) was calculated. The value of k for Fe-doped Cu O is 1.5 times that of pure Cu O. The higher photocatalytic activity of Fe-doped Cu O is attributed to higher specific surface area together with stronger visible light absorption.展开更多
Based on the traditional sintering model incorporating the characteristic of microwave sintering, the ionic conductance diffusion mechanism in microwave sintering was studied. A flat-ball model was presented to descri...Based on the traditional sintering model incorporating the characteristic of microwave sintering, the ionic conductance diffusion mechanism in microwave sintering was studied. A flat-ball model was presented to describe the kinetics process in microwave sintering, and was applied to the sintering process of TZP and ZrO2-Al2O3 ceramics. The results indicate that the shrinkage rate of materials in microwave sintering is proportional to t2/3 and r-4/3, respectively, where t is the sintering time and r is the particle radius. Whereas, the shrinkage rate of materials in conventional sintering is proportional to sintering time t2/5. Our model suggests that microwave sintering is faster than conventional sintering, which shows a good agreement with the experimental observation in sintering process of TZP and ZrO2-Al2O3.展开更多
The diffusion mechanism of boron in bcc-Fe has been studied by first-principles calculations. The diffusion coefficients of the interstitial mechanism, the B-monovacancy complex mechanism, and the B-divacancy complex ...The diffusion mechanism of boron in bcc-Fe has been studied by first-principles calculations. The diffusion coefficients of the interstitial mechanism, the B-monovacancy complex mechanism, and the B-divacancy complex mechanism have been calculated. The calculated diffusion coefficient of the interstitial mechanism is DO = 1.05 x l0-7 exp (-0.75 eV/kT) m2. s-1, while the diffusion coefficients of the B-monovacancy and the B-divacancy complex mechanisms are D1 =1.22 x 10-6fl exp (-2.27 eV/kT) mE. s-1 and D2 - 8.36 x 10-6 exp (-4.81 eV/kT) m2. s-l, re- spectively. The results indicate that the dominant diffusion mechanism in bcc-Fe is the interstitial mechanism through an octahedral interstitial site instead of the complex mechanism. The calculated diffusion coefficient is in accordance with the reported experiment results measured in Fe-3%Si-B alloy (bcc structure). Since the non-equilibrium segregation of boron is based on the diffusion of the complexes as suggested by the theory, our calculation reasonably explains why the non-equilibrium segregation of boron is not observed in bcc-Fe in experiments.展开更多
基金National Natural Science Foundation of China(No.51774331)Funds for Nationsl&Local Joint Engineering Research Center of Mineral Salt Deep Utilization(No.SF202103).
文摘Porous materials have promise as sound insulation, heat barrier, vibration attenuation, and catalysts. Most industrial solid wastes, such as tailings, coal gangue, and fly ash are rich in silicon. Additionally, a high silicon content waste is a potential raw material for the syn- thesis of silicon-based, multi-porous materials such as zeolites, mesoporous silica, glass-ceramics, and geopolymer foams. Representative sil- icon-rich industrial solid wastes (SRISWs) are the focus of this mini review of the processing and application of porous silicon materials with respect to the physical and chemical properties of the SRISW. The transformation methods of preparing porous materials from SRISWs are summarized, and their research status in micro-, meso-, and macro-scale porous materials are described. Possible problems in the application of SRISWs and in the preparation of functional porous materials are analyzed, and their development prospects are discussed. This review should provide a typical reference for the recycling and use of industrial solid wastes to develop sustainable “green materials.”
基金financially supported by the National Key Research and Development Program of China(Nos.2016 YFC0700607,2017YFB0304305,and 2016YFC0700901)the Fundamental Research Funds for the Central Universities of China(No.FRF-TP-20-006A3).
文摘Wood-based panels containing urea-formaldehyde resin result in the long-term release of formaldehyde and threaten human health.In this study,inorganic aluminosilicate coatings prepared by combining metakaolin,silica fume,NaOH,and H_(2)O were applied to the surfaces of wood-based panels to obstruct formaldehyde release.The Si/Al,Na/Al,and H_(2)O/Na_(2)O molar ratios of the coatings were regulated to investigate their effects on the structure and formaldehyde-resistant barrier properties of coatings.Results showed that the cracks in the coatings gradually disappeared and the formaldehyde resistance rates of the barrier increased as the Si/Al molar ratio was increased from 1.6 to 2.2.This value also increased as the Na/Al molar ratio was increased from 0.9 to 1.2 because of the improvement of the degree of polymerization.As the H_(2)O/Na_(2)O molar ratio was increased from 12 to 15,the thickness of the dry film decreased gradually and led to the reduction in the formaldehyde resistance rate.When the Si/Al,Na/Al,and H_(2)O/Na_(2)O molar ratios were 2.2,1.2,and 12,respectively,the inorganic aluminosilicate coating showed good performance as a formaldehyde-resistant barrier and its formaldehyde resistance rate could reach up to 83.2%.
基金the National Natural Science Foundation of China (No.50371007)the National High-Tech Research and Development Program of China (863 Program, No.2006AA03Z231).
文摘SnSb alloy powders for the anode of Li-ion batteries were synthesized by two kinds of reduction precipitation methods: solution titration and rapid mixing. Two kinds of SnSb alloy powders showed different phase compositions and particle morphologies although the same starting materials were used. The SnSb alloy electrode synthesized by titration exhibits high reversible specific capacity and good cycling stability, whereas the rapid-mixing sample shows high irreversible capacity and fast capacity fade. The broad particle size distribution of SnSb powders synthesized by titration is considered to be responsible for the improvement of cycling stability. The initial charge-discharge efficiency exceeding 80% has been obtained for the titration sample. The electrochemical reaction process of two kinds of synthesized SnSb composite electrodes was characterized by cyclic voltammetry and AC impedance techniques.
基金National Natural Science Foundation of China,Grant/Award Number:52071217。
文摘Development of an electrocatalyst that is cheap and has good properties to replace conventional noble metals is important for H_(2) applications.In this study,dealloying of an amorphous Ti_(37)Cu_(60)Ru_(3) alloy was performed to prepare a freestanding nanostructured hydrogen evolution reaction(HER)catalyst.The effect of dealloying and addition of Ru to TiCu alloys on the microstructure and HER properties under alkaline conditions was investigated.3 at.%Ru addition in Ti_(40)Cu_(60) decreases the overpotential to reach a current density of 10mA cm^(-2) and Tafel slope of the dealloyed samples to 35 and 34mV dec−1.The improvement of electrocatalytic properties was attributed to the formation of a nanostructure and the modification of the electronic structure of the catalyst.First-principles calculations based on density function theory indicate that Ru decreases the Gibbs free energy of water dissociation.This work presents a method to prepare an efficient electrocatalyst via dealloying of amorphous alloys.
基金This work was financially supported by the National Natural Science Foundation of China (Nos.50372006 and 20273007).
文摘Surface modification of up-conversion luminescence materials (Na[Y0.57Yb0.39Er0.04]F4 modified by amino groups) by grafting and modifying with aldehyde groups was studied by means of Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and emission spectrum (EM). The surface modification effect was compared using two different finishhag agents, p-phthalaldehyde and glutaraldehyde. It was found that the surface of up-conversion luminescence materials could be modified by aldehyde groups of the two finishing agents, the systematic dispersibility and the thermostability of the up-conversion luminescence material modified by p-phthalaldehyde were better than those of the material modified by glutaraldehyde, and the luminous intensity of the material modified by p-phthalaldehyde was increased. The AI (the ratio of the suspended segmental quality in the specimen to the total mass of the specimen) of the material modified by p-phthalaldehyde was higher than that of the material modified by glutaraldehyde. It is obviously seen that the embellishment effect of p-phthalaldehyde as a finishing agent was better than that of glutaraldehyde. In addition, the reasons why p-phthalaldehyde is a good finishing agent are also explained.
基金financially supported by the National Natural Science Foundation of China (Nos.51702011 and 51572018)the Fundamental Research Funds for the Central Universities of China (No.FRF-TP-20-006A3)the Scientific Research Project of Hunan Province Department of Education,China (No.20B323)。
文摘Si C nanowires are excellent high-temperature electromagnetic wave (EMW) absorbing materials. However, their polymer matrix composites are difficult to work at temperatures above 300℃, while their ceramic matrix composites must be prepared above 1000℃ in an inert atmosphere. Thus, for addressing the abovementioned problems, SiC/low-melting-point glass composites were well designed and prepared at 580℃ in an air atmosphere. Based on the X-ray diffraction results, SiC nanowires were not oxidized during air atmosphere sintering because of the low sintering temperature. Additionally, SiC nanowires were uniformly distributed in the glass matrix material. The composites exhibited good mechanical and EMW absorption properties. As the filling ratio of SiC nanowires increased from 5wt%to 20wt%, the Vickers hardness and flexural strength of the composite reached HV 564 and 213 MPa, which were improved by 27.7%and 72.8%, respectively, compared with the low-melting-point glass. Meanwhile, the dielectric loss and EMW absorption ability of SiC nanowires at 8.2–12.4 GHz were also gradually improved. The dielectric loss ability of low-melting-point glass was close to 0. However, when the filling ratio of SiC nanowires was 20wt%, the composite showed a minimum reflection loss (RL) of-20.2 dB and an effective absorption (RL≤-10 dB) bandwidth of2.3 GHz at an absorber layer thickness of 2.3 mm. The synergistic effect of polarization loss and conductivity loss in SiC nanowires was responsible for this improvement.
基金Project supported by the International Cooperation of Science and Technology Ministry PRC (2005DFBA028)the National Natural Science Foundation of China (59925412)
文摘Using cetyltrimethylammonium bromide (CTAB) as the template agent, cerium nitrate as the cerium resource, yttrium nitrate as the yttrium resource, and ammonium carbonate as the precipitating agent, mesoporous CeO2 powders doped with different yttrium contents were successfully synthesized using a chemical precipitation method, under an alkalescent condition. Properties of the obtained samples were characterized and analyzed with X-ray diffraction (XRD), energy dispersive analysis of X-rays (EDAX), transmission electron microscopy (TEM), infrared (IR) absorbance, and the BET method. For the prepared samples with 20% (molar ratio) Y-doped content, a BET specific surface area of 106. 6 m^2 · g^- 1, with an average pore size of3~27 nm were obtained. XRD patterns showed that the doped samples were with a cubic fluorite structure. TEM micrographs revealed that the doped samples showed a spherical morphology with a diameter ranging from 20 to 30 nm and a round pore shape. IR results indicated that the Ce-O-Ce vibration intensity decreased as the Y-doped content increased. N2 adsorption-desorption isotherms showed that the samples possessed typical mesopore characteristics. The average pore size of the samples decreased alter mesoporous CeO2 was doped with yttrium, and the average pore size decreased largely as the Y-doped content increased.
基金Project(2005DFBA028)supported by the International Cooperation of Science and Technology Ministry of ChinaProject(LA07023)supported by the National Undergraduate Innovative Experiment Plan
文摘The electrochemical behavior of silicon wafer in alkaline slurry with nano-sized CeO2 abrasive was investigated.The variations of corrosion potential(φcorr)and corrosion current density(Jcorr)of the P-type(100)silicon wafer with the slurry pH value and the concentration of abrasive CeO2 were studied by polarization curve technologies.The dependence of the polishing rate on the pH and the concentration of CeO2 in slurries during chemical mechanical polishing(CMP)were also studied.It is discovered that there is a large change of φcorr and Jcorr when slurry pH is altered and the Jcorr reaches the maximum(1.306 μA/cm2)at pH 10.5 when the material removal rate(MRR)comes to the fastest value.The Jcorr increases gradually from 0.994 μA/cm2 with 1% CeO2 to 1.304 μA/cm2 with 3% CeO2 and reaches a plateau with the further increase of CeO2 concentration.There is a considerable MRR in the slurry with 3% CeO2 at pH 10.5.The coherence between Jcorr and MRR elucidates that the research on the electrochemical behavior of silicon wafers in the alkaline slurry could offer theoretic guidance on silicon polishing rate and ensure to adjust optimal components of slurry.
基金financially supported by the National Natural Science Foundation of China (No. 21674011)Beijing Municipal Natural Science Foundation (No. 2172040)
文摘Highly sensitive methods are important for monitoring the concentration of metal ions in industrial wastewater.Here,we developed a new probe for the determination of metal ions by fluorescence quenching.The probe consists of hydroxylated graphene quantum dots(H-GQDs),prepared from GQDs by electrochemical method followed by surface hydroxylation.It is a non-reactive indicator with high sensitivity and detection limits of 0.01μM for Cu2+,0.005μM for Al3+,0.04μM for Fe3+,and 0.02μM for Cr3+.In addition,the low biotoxicity and excellent solubility of H-GQDs make them promising for application in wastewater metal ion detection.
基金the National Natural Science Foundation of China (Nos. 50372006, 20273007, and 20407003).
文摘The surface of an up-conversion luminescence material was modified by overcoating with SiOa, which was synthesized from a hydrolysis progress of telraethoxysilane (TEOS) in alkalescent condition. By analyzing the hydrolyzed mechanism of TEOS, it was found that there was not only physical adsorption but also chemical bonding between the up-conversion material and SiO2. At the same time, some adsorption bands at 1100, 475, 950, and 3500 cm^-1 were found by FI-IR, which were the characteristic bands of Si-OH and Si-O-Si. By analyzing the surface elements of the coated material by XPS, it was found that its surface only included Si, O, and C elements, and not F and Y. In the picture of XRD, there was no additional peak after surface modification, suggesting that the silica shell was amorphous. The small peak at 20 = 23° in the X-ray diffraction pattern of the coated material was caused by the amorphous SiO2 shell, and the TEM image also proved that the surface of the material was successfully modified by overcoating with SiO2. The amount of hydroxyls was then increased on the surface of the material, which made it easy to connect with other active groups.
基金This study was financially supported by the National Natural Science Foundation of China (No.59925412)the Natural Science Foundation of Hunan Province of China (No.03JJY3015).
文摘The electrochemical behaviors of n-type silicon wafers pH value and solid content of the slurry on the corrosion of silicon in silica-based slurry were investigated, and the influences of the wafers were studied by using electrochemical DC polarization and AC impedance techniques. The results revealed that these factors affected the corrosion behaviors of silicon wafers to different degrees and had their suitable parameters that made the maximum corrosion rate of the wafers. The corrosion potential of (100) sttrface was lower than that of(111), whereas the current density of (100) was much higher than that of(111).
基金the National Natural Science Foundation of China(No.50272012).
文摘LiMn2O4 powder as a cathode materials for rechargeable lithium-ion batteries was prepared by solid-state reaction from LitCO3 and electrolytic MnOz at different sintering periods (2, 6, 18, and 32 h). X-ray diffraction (XRD) patterns of the prepared samples are identified as the spinel structure with a space group of Fd3 m. The lattice parameters almost remain the same as the sintering periods increase. The sample with a sintering period of 32 h shows good cycling performance at both low and nigh current densities, and also elevated temperature. It is believed that the excellent electrochemical behavior of this sample results from its good crystallinity and large grain size compared with other samples. Different electrochemical measurements were conducted to investigate the electrochemical properties of spinel LiMn204. 2008 University of Science and Technology Beijing. All rights reserved.
基金Project(2010QZZD008) supported by the Prospect Key Projects of Fundamental Research Funds for the Central UniversitiesProject(2007FJ3008) supported by the Hunan Provincial Key Science and Technology Program of China
文摘Monodispersed manganese ferrite (MnFe2O4) nanocrystals could be successfully synthesized in large quantities via a facile synthetic technique based on the pyrolysis of organometallic compound precursor, in which octadecene was used as solvent, and oleic acid and oleylamine were used as capping ligands. MnFe204 nanocrystals were obtained with size in a tunable range of 4- 15 nm and their morphologies could be tuned from spherical to triangle-shaped by varying the surfactants. The phase structure, morphology, and size of the products were characterized in detail by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Magnetic properties of MnFe2O4 nanocrystals with different morphologies were measured using a superconducting quantum interference device (SQUID). Both monodisperse MnFe204 nanocrystals with spherical and triangle-shapes are superparamagnetic at room temperature while ferromagnetic at 2 K. The pyrolysis method may provide an effective route to synthesize other spinel ferrites or metal oxides nanocrystals.
基金Supported by the National Natural Science Foundation ( No.59925412) and Natural Science Foundation of Hunan Province (No.03JJY3015)
文摘Density function theory (DFT) at the B3LYP/6- 311 + + G(2d) (5D, 7F) level of theory was calculated to predict the geometry structures, toted energy and net charges of four kinds of dynamic isomer molecules of 2-aminino-5 mercapto- 1,3,4-thiodizole ( AA/IT for short). The fact that the atoms in four kinds of dynamie AMT isomer molecules lie in a plane and one kind of AMT is most stable is approved. The results also indicate that the pentogon ring in four kinds of dynamic AMT isomer molecules are aromatics, and the AMTc and Cu corrosion mitigation film produces as a result of the bonds form one by one of the covalent bond of Cu(1) with 7 N atom in AMTc amd the coordinate bond of Cu with 2S atom in ATMc. The resonant vibration frequencies and IR intensity for the four kituds of dynamic isomer of AMT are also calculated and their IR spectra are shown.
基金Funded by the National Natural Science Foundation of China (No. 20633090)Shanghai Nano-Science Program (No. 0552nm030)
文摘An approach named "pore structure collapsed replication route" has been developed to prepare mesoporous WC materials with a high surface area (105 m2/g) and crystallized framework at a temperature as low as 700 ℃. The XRD, TEM, EDS, and BET characterizations were conducted to analyze the effects of the synthesis parameters and the template types on the structure of mesoporous WC. The compaction on the templates is the key to form mesoporous structure of WC while the templates help to control the size of crystalline. At a content of 7 wt% for the precursor of WC, the mesoporous WC could be formed with well ordered structure.
基金financially supported by the National Natural Science Foundation of China (No. 51602018)Beijing Natural Science Foundation (No. 2154052)+2 种基金China Postdoctoral Science Foundation Funded Project (No. 2014M560044)the Fundamental Research Funds for the Central Universities (FRF-GF-17-B7)National Key Technologies Research and Development Program of China:Key International Science and Technology Cooperation Projects (2016YFE0111500)
文摘A cryogenic scanning electron microscopy(cryo-SEM) technique was used to explore the shear-thickening behavior of Fe-ZSM5 zeolite pastes and to discover its underlying mechanism. Bare Fe-ZSM5 zeolite samples were found to contain agglomerations, which may break the flow of the pastes and cause shear-thickening behaviors. However, the shear-thickening behaviors can be eliminated by the addition of halloysite and various boehmites because of improved particle packing. Furthermore, compared with pure Fe-ZSM5 zeolite samples and its composite samples with halloysite, the samples with boehmite(Pural SB or Disperal) additions exhibited network structures in their cryo-SEM images; these structures could facilitate the storage and release of flow water, smooth paste flow, and avoid shear-thickening. By contrast, another boehmite(Versal 250) formed agglomerations rather than network structures after being added to the Fe-ZSM5 zeolite paste and resulted in shear-thickening behavior. Consequently, the results suggest that these network structures play key roles in eliminating the shear-thickening behavior.
基金Project(51102285)supported by the National Natural Science Foundation of China
文摘The meso-macroporous Fe-doped Cu O was prepared by a simple hydrothermal method combined with post-annealing. The samples were characterized by X-ray powder diffraction(XRD), scanning electron microscopy(SEM), Brunauer-Emmett-Teller N2 adsorption-desorption analyses and UV-vis diffuses reflectance spectroscopy. The Fe-doped Cu O sample shows higher adsorption capacity and photocatalytic activity for xanthate degradation than pure Cu O under visible light irradiation. In addition, the adsorption process is found to fit Langmuir isotherms and pseudo-second-order kinetics. The the first order kinetic Langmuir Hinshelwood model was used to study the reaction kinetics of photocatalytic degradation, and the apparent rate constant( k) was calculated. The value of k for Fe-doped Cu O is 1.5 times that of pure Cu O. The higher photocatalytic activity of Fe-doped Cu O is attributed to higher specific surface area together with stronger visible light absorption.
基金Supported by the State Key Program of National Natural Science of China (Grant No. 50332010)the National Key Technology Research and Development Program for Resource and Environment of China (Grant Nos. 2006BAB12B03, 2006BAB12B05)
文摘Based on the traditional sintering model incorporating the characteristic of microwave sintering, the ionic conductance diffusion mechanism in microwave sintering was studied. A flat-ball model was presented to describe the kinetics process in microwave sintering, and was applied to the sintering process of TZP and ZrO2-Al2O3 ceramics. The results indicate that the shrinkage rate of materials in microwave sintering is proportional to t2/3 and r-4/3, respectively, where t is the sintering time and r is the particle radius. Whereas, the shrinkage rate of materials in conventional sintering is proportional to sintering time t2/5. Our model suggests that microwave sintering is faster than conventional sintering, which shows a good agreement with the experimental observation in sintering process of TZP and ZrO2-Al2O3.
基金Project supported by the National Natural Science Foundation of China(Grant No.51276016)the National Basic Research Program of China(Grant No.2012CB720406)
文摘The diffusion mechanism of boron in bcc-Fe has been studied by first-principles calculations. The diffusion coefficients of the interstitial mechanism, the B-monovacancy complex mechanism, and the B-divacancy complex mechanism have been calculated. The calculated diffusion coefficient of the interstitial mechanism is DO = 1.05 x l0-7 exp (-0.75 eV/kT) m2. s-1, while the diffusion coefficients of the B-monovacancy and the B-divacancy complex mechanisms are D1 =1.22 x 10-6fl exp (-2.27 eV/kT) mE. s-1 and D2 - 8.36 x 10-6 exp (-4.81 eV/kT) m2. s-l, re- spectively. The results indicate that the dominant diffusion mechanism in bcc-Fe is the interstitial mechanism through an octahedral interstitial site instead of the complex mechanism. The calculated diffusion coefficient is in accordance with the reported experiment results measured in Fe-3%Si-B alloy (bcc structure). Since the non-equilibrium segregation of boron is based on the diffusion of the complexes as suggested by the theory, our calculation reasonably explains why the non-equilibrium segregation of boron is not observed in bcc-Fe in experiments.