The synthesis of magnetic spinel ferrites at the nanoscale is a field of intense study, because the meso- scopic properties enable their novel applications. Spinel nanoparticles have a promising role because of their ...The synthesis of magnetic spinel ferrites at the nanoscale is a field of intense study, because the meso- scopic properties enable their novel applications. Spinel nanoparticles have a promising role because of their extraordinary properties compared with those of micro and macro scale particles. Several colloidal chemical synthetic procedures have been developed to produce monodisperse nanoparticles of spinel let- rites and other materials using sol-gel, co-precipitation, hydrothermal, and microemulsion techniques. To improve the synthesis method and conditions, quality and productivity of these nanoparticles, understanding the effect of extrinsic （pH, temperature, and molecular concentration） and intrinsic parameters （site preferences, latent heat, lattice parameters, electronic configuration, and bonding energy） on the particle size during synthesis is crucial. In this review, we discuss the effect of the intrinsic parameters on particle size of spinel ferrites to provide an insight to control their particle size more precisely.展开更多
To analyze the effect of different lowland rice varieties and different cooking methods on physical and chemical characteristics of cooked rice. A factorial randomized block design with two factors was used and each c...To analyze the effect of different lowland rice varieties and different cooking methods on physical and chemical characteristics of cooked rice. A factorial randomized block design with two factors was used and each combination of the factors was repeated three times. The first factor was rice variety（Ciherang and Ciliwung） and the second factor was the cooking method（stovetop, boiling and steaming, and rice cooker）. Results showed that Ciherang and Ciliwung varieties were classified into slender grain rice type with yellowred color. The amylose content of Ciherang was classified as moderate, while the amylose content of Ciliwung classified as low. The most abundant amino acid contained in Ciherang and Ciliwung varieties was glutamic acid. Statistical analysis showed that cooking method had significant effects on texture, lightness, chroma, hue and moisture content of cooked rice. Rice cooked with liwet method had the lowest texture value, lowest lightness value, highest chroma value, and highest moisture content.展开更多
Linear mRNA vaccines are constrained by exonuclease susceptibility and instability,leading to compromised antigen expression.Circular RNA(circRNA) lacking canonical 5' and 3' untranslated regions demonstrates ...Linear mRNA vaccines are constrained by exonuclease susceptibility and instability,leading to compromised antigen expression.Circular RNA(circRNA) lacking canonical 5' and 3' untranslated regions demonstrates intrinsic exonuclease resistance.Current circularization strategies face three principal limitations:chemical methods produce non-native 2',5'-phosphodiester bonds;ribozyme-mediated approaches are restricted to RNA fragments shorter than 500 nucleotides;the Anabaena Group I intron system retains immunogenic exon sequences.In contrast,the self-splicing Group I intron ribozyme from Tetrahymena enables precisely controlled circularization through autonomous structural rearrangement,yielding exonfree constructs.Through optimized purification protocols,historical scalability challenges are systematically addressed.This Perspective establishes the mechanistic rationale and therapeutic superiority of this engineered RNA circularization platform.展开更多
Ferroelastic rare earth tantalates(RETaO_(4))are widely researched as the next-generation thermal barrier coatings(TBCs),and RETaO_(4)powders are hugely significant for synthesizing their coatings.The current research...Ferroelastic rare earth tantalates(RETaO_(4))are widely researched as the next-generation thermal barrier coatings(TBCs),and RETaO_(4)powders are hugely significant for synthesizing their coatings.The current research used chemical co-precipitation within an automated experimental device to synthesize RETaO_(4)(RE=Nd,Sm,Gd,Ho,Er)powders.The device automatically monitored and controlled the solutions'pH,improving the chemical co-precipitation efficiency.The crystal structure and microstructure of the RETaO_(4)powders can be controlled by changing the annealing temperature,and the materials undergo an m'-m phase transition.The m'-RETaO_(4)powders exhibit nano-size grains,while m-RETaO_(4)powders evince micron-size grains,altered by the annealing temperatures.A simultaneous thermal analysis es-timates the reversive ferroelastic tetragonal-monoclinic phase transition temperatures.Overall,this research focuses on the synthesis,crystal structures,microstructures,and phase transition of the fabricated RETaO_(4)powders.展开更多
Lung cancer has one of the highest rates of incidence and mortality worldwide,mak-ing research on its mechanisms and treatments crucial.Animal models are essential in lung cancer research as they accurately replicate ...Lung cancer has one of the highest rates of incidence and mortality worldwide,mak-ing research on its mechanisms and treatments crucial.Animal models are essential in lung cancer research as they accurately replicate the biological characteristics and treatment outcomes seen in human diseases.Currently,various lung cancer models have been established,including chemical induction models,orthotopic transplan-tation models,ectopic transplantation models,metastasis models,and gene editing mouse models.Additionally,lung cancer grafts can be categorized into two types:tissue-based and cell-based grafts.This paper summarizes the phenotypes,advan-tages,and disadvantages of various induction methods based on their modeling tech-niques.The goal is to enhance the simulation of clinical lung cancer characteristics and to establish a solid foundation for future clinical research.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
A simple chemical method was developed for inducing bioactivity on NiTi alloys (50 at. pct by Ni/Ti). A layer of calcium phosphate was deposited on the surface to improve biocompatibility of the alloy. NiTi alloys wer...A simple chemical method was developed for inducing bioactivity on NiTi alloys (50 at. pct by Ni/Ti). A layer of calcium phosphate was deposited on the surface to improve biocompatibility of the alloy. NiTi alloys were first etched in HNO3 aqueous solution, and then treated with boiling diluted NaOH solution. A rough surface was created and a thin TiO2 layer was formed on the surface. Pre-calcification was then introduced by immersing the treated NiTi alloys in supersaturated Na2HPO4 solution and supersaturated Ca(OH)2 solution in turn before calcification in simulated body fluid (SBF). A dense and uniform bonelike calcium phosphate (Ca-P) bioactive layer was formed on the surfaces of the specimen, which would improve their biocompatibility. Morphology and element analysis on NiTi surfaces during the treatments were investigated in detail by means of environment scanning electron microscopy (ESEM), energy dispersion X-ray spectroscopy (EDXS), and X-ray diffraction (XRD).展开更多
The fine powders of Mn-Zn ferrites with uniform size were prepared via chemical co- precipitation method. X-ray diffraction analysis （XRD）, scanning electron microscopy （SEM）, vibrating sample magnetometer （VSM）...The fine powders of Mn-Zn ferrites with uniform size were prepared via chemical co- precipitation method. X-ray diffraction analysis （XRD）, scanning electron microscopy （SEM）, vibrating sample magnetometer （VSM）, frequency dependence of permeability and metallographical microscope were used to investigate the crystal structure, surface topography and magnetic properties of the powders and the sintering samples. The experimental results demonstrate that the precursor powders have formed a pure phase cubic spinel MnxZn1-xfe2O4 while in the reactor and show definite magnetism, which can solve the difficult issue in washing process effectively. When calcined beneath 450 ℃, the powders have intact crystal form and the crystallite size is less than 20 nm. Comparison tests of sintering temperatures show that 1 300 ℃ is the ideal sintering temperature for Mn-Zn ferrites prepared by using the chemical co-precipitation.展开更多
Two-dimensional(2 D)few-layerVSe_(2),V_(1-x)Fe_(x)Se_(2) nanosheets have been synthesized by a hightemperature organic solution-phase method. The thickness of VSe_(2) nanosheets can be tuned from 12 to 5 layers by dec...Two-dimensional(2 D)few-layerVSe_(2),V_(1-x)Fe_(x)Se_(2) nanosheets have been synthesized by a hightemperature organic solution-phase method. The thickness of VSe_(2) nanosheets can be tuned from 12 to 5 layers by decreasing the precursor concentrations. The few-layer VSe_(2) nanosheets show the room-temperature ferromagnetism. The coercivity and magnetization reach 0.024 T and 0.036 mA·m^(2)·g^(-1) at room temperature. The chargedensity wave behavior is also confirmed in VSe_(2) by the hysteresis loops and zero-field-cooling curve. V_(1-x)Fe_(x)Se_(2) nanosheets can be obtained by doping Fe(acac)3 in the reaction process. The room-temperature coercivity and magnetization of V_(0.8)Fe_(0.2)Se_(2) nanosheets are 5 times higher than those of the pure VSe_(2) nanosheets without destroying the structures. The enhancement of magnetization is due to the coupling interaction of 3 d orbits between V and Fe atoms. Higher Fe concentration is beneficial to improve the coercivity, which is attributed to the formation of the second phase Fe3 Se4. This simple chemical preparation method can be extended to prepare the other 2 D materials.展开更多
Highly pure active γ-Al2O3 nanoparticles were synthesized from aluminum nitrate and ammonium carbonate with a little surfactant by chemical precipitation method. The factors affecting the synthesis process were studi...Highly pure active γ-Al2O3 nanoparticles were synthesized from aluminum nitrate and ammonium carbonate with a little surfactant by chemical precipitation method. The factors affecting the synthesis process were studied. The properties of γ-Al2O3 nanoparticles were characterized by DTA, XRD, BET, TEM, laser granularity analysis and impurity content analysis. The results show that the amorphous precursor AI（OH）3 sols are produced by using 0.1 mol/L Al（NO3）3·9H2O and 0.16 mol/L （NH4）2CO3·H2O reaction solutions, according to the volume ratio 1.33, adding 0.024%（volume fraction） surfactant PEG600, and reacting at 40℃, 1000 r/min stirring rate for 15min. Then, after stabilizing for 24 h, the precursors were extracted and filtrated by vacuum, washed thoroughly with deionized water and dehydrated ethanol, dried in vacuum at 80℃ for 8h, final calcined at 800℃ for 1h in the air, and high purity active γ-Al2O3 nanoparticles can be prepared with cubic in crystal system, OH^7-FD3M in space group, about 9 nm in crystal grain size, about 20 nm in particle size and uniform size distribution, 131.35 m^2/g in BET specific surface area, 7 - 11 nm in pore diameter, and not lower than 99.93% in purity.展开更多
In this paper, the effectiveness, applicability and validity of chemicalephysical combined methods（CPCMs） for treatment of marine clay （MC） slurries were evaluated. The method CPCM1 combineschemical stabilization ...In this paper, the effectiveness, applicability and validity of chemicalephysical combined methods（CPCMs） for treatment of marine clay （MC） slurries were evaluated. The method CPCM1 combineschemical stabilization and vacuum preloading （VP）, while CPCM2 is similar to CPCM1 but includes boththe application of surcharge and use of geo-bags to provide confinement during surcharge preloading.The key advantage of CPCM2 using geo-bags is that the surcharge can be immediately applied on thechemically stabilized slurries. Two types of geo-bags were investigated under simulated land filling anddyke conditions, respectively. The test results show that the shear strength （cu） of treated slurry byCPCM2 is generally much higher than that by CPCM1. Besides, the use of CPCM2 can significantly reducethe treatment time due to the short drainage paths created by geo-bags. Overall, CPCM2 allows fasterconsolidation and higher preloading that help to achieve higher mechanical properties of the stabilizedslurry. There are consistent relationships between cU and water content of slurries treated by CPCM2.Several important observations were also made based on comparisons of experimental data. 2015 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting byElsevier B.V. All rights reserved.展开更多
GB/T 13245-91 1 Theme and Scope This standard specifies the method abstract, reagents, apparatus, specimen, analyzing procedure, result calculation and permissible tolerance used for determination of the total carbon ...GB/T 13245-91 1 Theme and Scope This standard specifies the method abstract, reagents, apparatus, specimen, analyzing procedure, result calculation and permissible tolerance used for determination of the total carbon with combustion gravimetric method.展开更多
Molecular mechanics, molecular dynamics and semi empirical quantum chemical method have been used to study the geometric and electronic structures of six phosphonate ester as rare earth extractants. The results show ...Molecular mechanics, molecular dynamics and semi empirical quantum chemical method have been used to study the geometric and electronic structures of six phosphonate ester as rare earth extractants. The results show that the phosphorus atom exhibits sp 3 hybridization. The structures of the extractants are determined by the repulsion of the hydrocarbon groups. In the extractants that have two 2 ethyl hexyl groups, one 2 ethyl hexyl extends straight, and the other extends twistily. When the number of oxygen atom decreases, the negative charge of the phosphoryl oxygen atom increases, but the negative charge of oxygen atom and the positive charge of hydrogen of the hydroxyl group decreases, and the energies of highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital(LUMO) increase. The energies of the occupied frontier orbitals are close to each other.展开更多
In order to improve the homogeneous distribution of the TiC particles and facilitate the TiC particles to distribute in the tungsten grain interiors,two kinds of TiCdoped tungsten precursors with a core-shell structur...In order to improve the homogeneous distribution of the TiC particles and facilitate the TiC particles to distribute in the tungsten grain interiors,two kinds of TiCdoped tungsten precursors with a core-shell structure were prepared by an improved wet chemical method at different reaction temperature conditions.Consequently,fine platelike precursor(200-400 nm)and flower-like precursor(approximately 1.25μm)are obtained.After reduction and sintering,the microstructures of the samples were characterized by scanning electron microscopy and transmission electron microscopy.In the sample sintered from the platelike precursor,TiC particles with sizes in the range of40-300 nm and an average size of approximately 80 nm were uniformly distributed in the tungsten matrix with a high share in the grain interiors.However,in the sample sintered from the flower-like precursor,the TiC particles with sizes in the range of 50-700 nm are significantly aggregated and non-uniformly distributed in the tungsten matrix.As a result,the sample sintered from the plate-like precursor achieves higher mechanical properties and a much narrower range of bending strength values than that sintered from the flower-like precursor.The average bending strength of the sample sintered from the plate-like precursor is 655 MPa,which is higher than that of the sample sintered from the flower-like precursor(524 MPa).Different reaction mechanisms and dispersing stabilities of the TiC particles at different temperature conditions should be accounted for the differences between the two samples.展开更多
A silver nanostructures prepared by using chemical reduction method. The silver nanoparticles were prepared with diameters of about (20 nm). Numerous techniques had been used to study the optical, structural like the ...A silver nanostructures prepared by using chemical reduction method. The silver nanoparticles were prepared with diameters of about (20 nm). Numerous techniques had been used to study the optical, structural like the UV-Vis absorption spectrometer, Ttransmission Electron Microscopy (TEM), Field-Emission Scanning Electron microscope (FESEM), and X-ray diffraction (XRD). The practical results exhibited the absorption spectrum of the prepared nanoparticles at (357 nm), it was found that there is a relationship between the positions of the optical absorption peak and the size of the silver nanoparticles. The analysis of TEM results showed the presence of nanoparticles in the range (20 nm). The analyzing of XRD results explained the crystal structure for silver nanoparticles. It is found a cubic unit cell have a lattice constants (a = 4.0855 <span style="white-space:nowrap;">Å</span>), with the Miller indices were (111), (002), (002), and (113).展开更多
The alcoholysis mechanism of 1,2-thiazetidine-1,1-dioxide with methanol, in which the relatively stable product is sulfonate ester, has been investigated by quantum chemical method. Our calculations indicate the react...The alcoholysis mechanism of 1,2-thiazetidine-1,1-dioxide with methanol, in which the relatively stable product is sulfonate ester, has been investigated by quantum chemical method. Our calculations indicate the reaction for alcoholysis of 1,2-thiazetidine-1,1-dioxide proceeds via two possible mechanisms: concerted and stepwise. In the stepwise mechanism, two possible reaction pathways can be followed while only one possible reaction pathway can be followed in the concerted mechanism.展开更多
Nanoparticles of Fe<sub>3</sub>O<sub>4</sub> and Fe are chemically synthesized by reduction of Fe(acac)<sub>3</sub> using ascorbic acid in controlled condition. It was observed that...Nanoparticles of Fe<sub>3</sub>O<sub>4</sub> and Fe are chemically synthesized by reduction of Fe(acac)<sub>3</sub> using ascorbic acid in controlled condition. It was observed that addition of water during the chemical synthesis process yields Fe3O4 nanoparticles, whereas if the reaction is carried out in absence of water yields Fe nanoparticles—which get oxidized upon exposure to air atmosphere. Fe<sub>3</sub>O<sub>4</sub> (15 ± 5 nm) and Fe/iron oxide nanoparticles (7 ± 1 nm) were successfully synthesized in the comparative study reported herewith. Mechanism for formation/synthesis of Fe<sub>3</sub>O<sub>4</sub> and Fe/iron oxide nanoparticles is proposed herewith in which added water acts as an oxygen supplier. Physico-chemical characterization done by SEM, TEM, EDAX, and XPS supports the proposed mechanism.展开更多
Chemical reduction method was employed to prepare nano-sized Sn2SbNi alloy composites used as anode material for rechargeable lithium ion batteries.This strategy was adopted to combine the virtues of both active/inact...Chemical reduction method was employed to prepare nano-sized Sn2SbNi alloy composites used as anode material for rechargeable lithium ion batteries.This strategy was adopted to combine the virtues of both active/inactive and active/active alloys to fabricate a Sn2SbNi alloy powder with two active components and one inactive component.The two active components can realize the high capacity feature of electrode and can make the volume change of electrode take place in a stepwise manner due to the different lithiation potentials of two active components,leading to a stable cycling performance.Sn2SbNi alloy provides a reversible specific capacity over 640 mA·h/g with an excellent cyclic ability.The Sn-Sb-Ni alloy composite material shows to be a good candidate anode material for the lithium ion batteries.展开更多
文摘The synthesis of magnetic spinel ferrites at the nanoscale is a field of intense study, because the meso- scopic properties enable their novel applications. Spinel nanoparticles have a promising role because of their extraordinary properties compared with those of micro and macro scale particles. Several colloidal chemical synthetic procedures have been developed to produce monodisperse nanoparticles of spinel let- rites and other materials using sol-gel, co-precipitation, hydrothermal, and microemulsion techniques. To improve the synthesis method and conditions, quality and productivity of these nanoparticles, understanding the effect of extrinsic （pH, temperature, and molecular concentration） and intrinsic parameters （site preferences, latent heat, lattice parameters, electronic configuration, and bonding energy） on the particle size during synthesis is crucial. In this review, we discuss the effect of the intrinsic parameters on particle size of spinel ferrites to provide an insight to control their particle size more precisely.
基金supported by International Rice Research Institute (IRRI)Research Center of Sub-Optimal Land (PUR-PLSO) Universitas Sriwijaya
文摘To analyze the effect of different lowland rice varieties and different cooking methods on physical and chemical characteristics of cooked rice. A factorial randomized block design with two factors was used and each combination of the factors was repeated three times. The first factor was rice variety（Ciherang and Ciliwung） and the second factor was the cooking method（stovetop, boiling and steaming, and rice cooker）. Results showed that Ciherang and Ciliwung varieties were classified into slender grain rice type with yellowred color. The amylose content of Ciherang was classified as moderate, while the amylose content of Ciliwung classified as low. The most abundant amino acid contained in Ciherang and Ciliwung varieties was glutamic acid. Statistical analysis showed that cooking method had significant effects on texture, lightness, chroma, hue and moisture content of cooked rice. Rice cooked with liwet method had the lowest texture value, lowest lightness value, highest chroma value, and highest moisture content.
基金supported by the National Key Research&Development Program of China(Nos.2021YFC2302400,2021YFA1201000,2023YFC2606004)the Fundamental Research Funds for the Central Universities(No.2022CX01013)。
文摘Linear mRNA vaccines are constrained by exonuclease susceptibility and instability,leading to compromised antigen expression.Circular RNA(circRNA) lacking canonical 5' and 3' untranslated regions demonstrates intrinsic exonuclease resistance.Current circularization strategies face three principal limitations:chemical methods produce non-native 2',5'-phosphodiester bonds;ribozyme-mediated approaches are restricted to RNA fragments shorter than 500 nucleotides;the Anabaena Group I intron system retains immunogenic exon sequences.In contrast,the self-splicing Group I intron ribozyme from Tetrahymena enables precisely controlled circularization through autonomous structural rearrangement,yielding exonfree constructs.Through optimized purification protocols,historical scalability challenges are systematically addressed.This Perspective establishes the mechanistic rationale and therapeutic superiority of this engineered RNA circularization platform.
基金the Rare and Precious Metals Material Genetic Engineering Project of Yunnan Province(202102AB080019-1)National Key Research and Development Program of China(2022YFB3708600)the National Natural Science Foundation of China(91960103).
文摘Ferroelastic rare earth tantalates(RETaO_(4))are widely researched as the next-generation thermal barrier coatings(TBCs),and RETaO_(4)powders are hugely significant for synthesizing their coatings.The current research used chemical co-precipitation within an automated experimental device to synthesize RETaO_(4)(RE=Nd,Sm,Gd,Ho,Er)powders.The device automatically monitored and controlled the solutions'pH,improving the chemical co-precipitation efficiency.The crystal structure and microstructure of the RETaO_(4)powders can be controlled by changing the annealing temperature,and the materials undergo an m'-m phase transition.The m'-RETaO_(4)powders exhibit nano-size grains,while m-RETaO_(4)powders evince micron-size grains,altered by the annealing temperatures.A simultaneous thermal analysis es-timates the reversive ferroelastic tetragonal-monoclinic phase transition temperatures.Overall,this research focuses on the synthesis,crystal structures,microstructures,and phase transition of the fabricated RETaO_(4)powders.
基金Sichuan Provincial Administration of Traditional Chinese Medicine,Grant/Award Number:2023MS564National Natural Science Foundation of China,Grant/Award Number:82474436。
文摘Lung cancer has one of the highest rates of incidence and mortality worldwide,mak-ing research on its mechanisms and treatments crucial.Animal models are essential in lung cancer research as they accurately replicate the biological characteristics and treatment outcomes seen in human diseases.Currently,various lung cancer models have been established,including chemical induction models,orthotopic transplan-tation models,ectopic transplantation models,metastasis models,and gene editing mouse models.Additionally,lung cancer grafts can be categorized into two types:tissue-based and cell-based grafts.This paper summarizes the phenotypes,advan-tages,and disadvantages of various induction methods based on their modeling tech-niques.The goal is to enhance the simulation of clinical lung cancer characteristics and to establish a solid foundation for future clinical research.
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This work was supported by the National Natural Science Foundation of China (59971032) by Foundation for University Key Teacher, the Ministry of Education (GG-805-10056-1603).
文摘A simple chemical method was developed for inducing bioactivity on NiTi alloys (50 at. pct by Ni/Ti). A layer of calcium phosphate was deposited on the surface to improve biocompatibility of the alloy. NiTi alloys were first etched in HNO3 aqueous solution, and then treated with boiling diluted NaOH solution. A rough surface was created and a thin TiO2 layer was formed on the surface. Pre-calcification was then introduced by immersing the treated NiTi alloys in supersaturated Na2HPO4 solution and supersaturated Ca(OH)2 solution in turn before calcification in simulated body fluid (SBF). A dense and uniform bonelike calcium phosphate (Ca-P) bioactive layer was formed on the surfaces of the specimen, which would improve their biocompatibility. Morphology and element analysis on NiTi surfaces during the treatments were investigated in detail by means of environment scanning electron microscopy (ESEM), energy dispersion X-ray spectroscopy (EDXS), and X-ray diffraction (XRD).
基金Funded by the National Natural Science Foundation of China(Nos.51162019 and 51462019)
文摘The fine powders of Mn-Zn ferrites with uniform size were prepared via chemical co- precipitation method. X-ray diffraction analysis （XRD）, scanning electron microscopy （SEM）, vibrating sample magnetometer （VSM）, frequency dependence of permeability and metallographical microscope were used to investigate the crystal structure, surface topography and magnetic properties of the powders and the sintering samples. The experimental results demonstrate that the precursor powders have formed a pure phase cubic spinel MnxZn1-xfe2O4 while in the reactor and show definite magnetism, which can solve the difficult issue in washing process effectively. When calcined beneath 450 ℃, the powders have intact crystal form and the crystallite size is less than 20 nm. Comparison tests of sintering temperatures show that 1 300 ℃ is the ideal sintering temperature for Mn-Zn ferrites prepared by using the chemical co-precipitation.
基金financially supported by the National Natural Science Foundation of China(Nos.51971122,51571135 and 51701106)the National Key R&D Program of China(No.2017YFB0405703)。
文摘Two-dimensional(2 D)few-layerVSe_(2),V_(1-x)Fe_(x)Se_(2) nanosheets have been synthesized by a hightemperature organic solution-phase method. The thickness of VSe_(2) nanosheets can be tuned from 12 to 5 layers by decreasing the precursor concentrations. The few-layer VSe_(2) nanosheets show the room-temperature ferromagnetism. The coercivity and magnetization reach 0.024 T and 0.036 mA·m^(2)·g^(-1) at room temperature. The chargedensity wave behavior is also confirmed in VSe_(2) by the hysteresis loops and zero-field-cooling curve. V_(1-x)Fe_(x)Se_(2) nanosheets can be obtained by doping Fe(acac)3 in the reaction process. The room-temperature coercivity and magnetization of V_(0.8)Fe_(0.2)Se_(2) nanosheets are 5 times higher than those of the pure VSe_(2) nanosheets without destroying the structures. The enhancement of magnetization is due to the coupling interaction of 3 d orbits between V and Fe atoms. Higher Fe concentration is beneficial to improve the coercivity, which is attributed to the formation of the second phase Fe3 Se4. This simple chemical preparation method can be extended to prepare the other 2 D materials.
文摘Highly pure active γ-Al2O3 nanoparticles were synthesized from aluminum nitrate and ammonium carbonate with a little surfactant by chemical precipitation method. The factors affecting the synthesis process were studied. The properties of γ-Al2O3 nanoparticles were characterized by DTA, XRD, BET, TEM, laser granularity analysis and impurity content analysis. The results show that the amorphous precursor AI（OH）3 sols are produced by using 0.1 mol/L Al（NO3）3·9H2O and 0.16 mol/L （NH4）2CO3·H2O reaction solutions, according to the volume ratio 1.33, adding 0.024%（volume fraction） surfactant PEG600, and reacting at 40℃, 1000 r/min stirring rate for 15min. Then, after stabilizing for 24 h, the precursors were extracted and filtrated by vacuum, washed thoroughly with deionized water and dehydrated ethanol, dried in vacuum at 80℃ for 8h, final calcined at 800℃ for 1h in the air, and high purity active γ-Al2O3 nanoparticles can be prepared with cubic in crystal system, OH^7-FD3M in space group, about 9 nm in crystal grain size, about 20 nm in particle size and uniform size distribution, 131.35 m^2/g in BET specific surface area, 7 - 11 nm in pore diameter, and not lower than 99.93% in purity.
基金the R&D project, titled " Creating a Marine Clay Matrix with Incineration Bottom Ash (IBA) for Land Reclamation " (Wu et al., 2014), under the Innovation for Environmental Sustainability (IES) Fund from National Environment Agency (NEA) of Singapore (ETO/CF/3/1)
文摘In this paper, the effectiveness, applicability and validity of chemicalephysical combined methods（CPCMs） for treatment of marine clay （MC） slurries were evaluated. The method CPCM1 combineschemical stabilization and vacuum preloading （VP）, while CPCM2 is similar to CPCM1 but includes boththe application of surcharge and use of geo-bags to provide confinement during surcharge preloading.The key advantage of CPCM2 using geo-bags is that the surcharge can be immediately applied on thechemically stabilized slurries. Two types of geo-bags were investigated under simulated land filling anddyke conditions, respectively. The test results show that the shear strength （cu） of treated slurry byCPCM2 is generally much higher than that by CPCM1. Besides, the use of CPCM2 can significantly reducethe treatment time due to the short drainage paths created by geo-bags. Overall, CPCM2 allows fasterconsolidation and higher preloading that help to achieve higher mechanical properties of the stabilizedslurry. There are consistent relationships between cU and water content of slurries treated by CPCM2.Several important observations were also made based on comparisons of experimental data. 2015 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting byElsevier B.V. All rights reserved.
文摘GB/T 13245-91 1 Theme and Scope This standard specifies the method abstract, reagents, apparatus, specimen, analyzing procedure, result calculation and permissible tolerance used for determination of the total carbon with combustion gravimetric method.
文摘Molecular mechanics, molecular dynamics and semi empirical quantum chemical method have been used to study the geometric and electronic structures of six phosphonate ester as rare earth extractants. The results show that the phosphorus atom exhibits sp 3 hybridization. The structures of the extractants are determined by the repulsion of the hydrocarbon groups. In the extractants that have two 2 ethyl hexyl groups, one 2 ethyl hexyl extends straight, and the other extends twistily. When the number of oxygen atom decreases, the negative charge of the phosphoryl oxygen atom increases, but the negative charge of oxygen atom and the positive charge of hydrogen of the hydroxyl group decreases, and the energies of highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital(LUMO) increase. The energies of the occupied frontier orbitals are close to each other.
基金financially supported by the ITER-National Magnetic Confinement Fusion Program(No.2014GB123000)。
文摘In order to improve the homogeneous distribution of the TiC particles and facilitate the TiC particles to distribute in the tungsten grain interiors,two kinds of TiCdoped tungsten precursors with a core-shell structure were prepared by an improved wet chemical method at different reaction temperature conditions.Consequently,fine platelike precursor(200-400 nm)and flower-like precursor(approximately 1.25μm)are obtained.After reduction and sintering,the microstructures of the samples were characterized by scanning electron microscopy and transmission electron microscopy.In the sample sintered from the platelike precursor,TiC particles with sizes in the range of40-300 nm and an average size of approximately 80 nm were uniformly distributed in the tungsten matrix with a high share in the grain interiors.However,in the sample sintered from the flower-like precursor,the TiC particles with sizes in the range of 50-700 nm are significantly aggregated and non-uniformly distributed in the tungsten matrix.As a result,the sample sintered from the plate-like precursor achieves higher mechanical properties and a much narrower range of bending strength values than that sintered from the flower-like precursor.The average bending strength of the sample sintered from the plate-like precursor is 655 MPa,which is higher than that of the sample sintered from the flower-like precursor(524 MPa).Different reaction mechanisms and dispersing stabilities of the TiC particles at different temperature conditions should be accounted for the differences between the two samples.
文摘A silver nanostructures prepared by using chemical reduction method. The silver nanoparticles were prepared with diameters of about (20 nm). Numerous techniques had been used to study the optical, structural like the UV-Vis absorption spectrometer, Ttransmission Electron Microscopy (TEM), Field-Emission Scanning Electron microscope (FESEM), and X-ray diffraction (XRD). The practical results exhibited the absorption spectrum of the prepared nanoparticles at (357 nm), it was found that there is a relationship between the positions of the optical absorption peak and the size of the silver nanoparticles. The analysis of TEM results showed the presence of nanoparticles in the range (20 nm). The analyzing of XRD results explained the crystal structure for silver nanoparticles. It is found a cubic unit cell have a lattice constants (a = 4.0855 <span style="white-space:nowrap;">Å</span>), with the Miller indices were (111), (002), (002), and (113).
文摘The alcoholysis mechanism of 1,2-thiazetidine-1,1-dioxide with methanol, in which the relatively stable product is sulfonate ester, has been investigated by quantum chemical method. Our calculations indicate the reaction for alcoholysis of 1,2-thiazetidine-1,1-dioxide proceeds via two possible mechanisms: concerted and stepwise. In the stepwise mechanism, two possible reaction pathways can be followed while only one possible reaction pathway can be followed in the concerted mechanism.
文摘Nanoparticles of Fe<sub>3</sub>O<sub>4</sub> and Fe are chemically synthesized by reduction of Fe(acac)<sub>3</sub> using ascorbic acid in controlled condition. It was observed that addition of water during the chemical synthesis process yields Fe3O4 nanoparticles, whereas if the reaction is carried out in absence of water yields Fe nanoparticles—which get oxidized upon exposure to air atmosphere. Fe<sub>3</sub>O<sub>4</sub> (15 ± 5 nm) and Fe/iron oxide nanoparticles (7 ± 1 nm) were successfully synthesized in the comparative study reported herewith. Mechanism for formation/synthesis of Fe<sub>3</sub>O<sub>4</sub> and Fe/iron oxide nanoparticles is proposed herewith in which added water acts as an oxygen supplier. Physico-chemical characterization done by SEM, TEM, EDAX, and XPS supports the proposed mechanism.
基金Project(2008cd148)supported by the Social Development Plan of Yunnan Province,ChinaProject(2010)supported by Key Science and Technology Fund of Education Department,China
文摘Chemical reduction method was employed to prepare nano-sized Sn2SbNi alloy composites used as anode material for rechargeable lithium ion batteries.This strategy was adopted to combine the virtues of both active/inactive and active/active alloys to fabricate a Sn2SbNi alloy powder with two active components and one inactive component.The two active components can realize the high capacity feature of electrode and can make the volume change of electrode take place in a stepwise manner due to the different lithiation potentials of two active components,leading to a stable cycling performance.Sn2SbNi alloy provides a reversible specific capacity over 640 mA·h/g with an excellent cyclic ability.The Sn-Sb-Ni alloy composite material shows to be a good candidate anode material for the lithium ion batteries.
