Micaceous iron oxide （MIO） with a hexagonal flaky shape was prepared by hydrothermal method. The ferric hydroxide used as precursor was obtained by an acidic leaching solution of pyrite cinders reacting with ammonia...Micaceous iron oxide （MIO） with a hexagonal flaky shape was prepared by hydrothermal method. The ferric hydroxide used as precursor was obtained by an acidic leaching solution of pyrite cinders reacting with ammonia solution. The optimal experimental conditions for preparing micaceous iron oxide were investigated by orthogonal experiments. Micaceous iron oxide can be successfully prepared when optimal parameters of total iron concentration of 2.0 mol/L, pH value of 8, n（Fe2＋）/n（Fe3＋） of 0.1, mass of seed crystal of 1 g, reaction temperature of 260 ℃ and reaction time of 30 min are applied. X-ray diffractometry （XRD）, scanning electron microscopy （SEM）, transmission electron microscopy （TEM） and selected area electron diffractometry （SAEM） were adopted to characterize the hydrothermal products prepared under optimal conditions. The results indicate that highly crystallized α-Fe2O3 hexagonal flakes, about 1.0-1.5 μm in diameter and 0.1 μm in thickness, are prepared. Furthermore, the quality of micaceous iron oxide prepared can meet the required characteristics of micaceous iron oxide pigments for paints （ISO 10601--2007）.展开更多
MnZn ferrite nanoscale particles were synthesized by hydrothermal method. The effects of amount of addition La3+ on the products were discussed. The product was characterized by X-ray diffraction （XRD） and transmiss...MnZn ferrite nanoscale particles were synthesized by hydrothermal method. The effects of amount of addition La3+ on the products were discussed. The product was characterized by X-ray diffraction （XRD） and transmission electron microscope （TEM）. The results show that the sample with 0.2% La3+（mass fraction） or without La3+ has only spinel phase, but the sample with mass fraction of La3+ exceeding 0.4% posses second phase besides the spinel one; and the nano-MnZn ferrites change from cube to hexagon when the mass fractions of La3+ is up to （1.2%.） TEM image of the sample with 1.2% La3+ indicates that the homogeneous hexagonal crystal is obtained and the particles are larger than those of undoped; the addition of La3+ has great influence on the crystallization of hydrothermal process and can change the shape of particles and improve their growth. The saturation magnetization of the sample with 1.2% La3+ (2.64 A·m2·kg-1) is lower than that of undoped (17.54 (A·m2·kg-1)) and it behaves superparamagnetically.展开更多
ZnO is a highly significant II-VI semiconductor known for its excellent optoelectronic properties,making it widely applicable and promising for use in light-emitting devices,solar cells,lasers,and photodetectors.The m...ZnO is a highly significant II-VI semiconductor known for its excellent optoelectronic properties,making it widely applicable and promising for use in light-emitting devices,solar cells,lasers,and photodetectors.The methods for preparing ZnO are diverse,and among them,the hydrothermal method is favored for its simplicity,ease of operation,and low cost,making it an optimal choice for ZnO single-crystal growth.Most studies investigating the effects of different hydrothermal experimental parameters on the morphology and performance of ZnO nano-materials typically focus on only 2—3 variable parameters,with few examining the impact of all possible experimental parameter changes on ZnO nano-mate-rials.The principles of the hydrothermal method and its advantages in nano-material preparation were briefly introduced in this article.The detailed discussion on the influence of various experimental parameters on the preparation of ZnO nano-materials was provided,which including reaction materials,Zn^(2+)/OH^(-)ratio,reaction time and temperature,additives,experimental equipment,and annealing conditions.The review co-vers how different experimental parameters affect the morphology and performance of the materials,as well as how different rare earth doping elements influence the performance of ZnO nano-materials.It is hoped that this work will contribute to future research on the hydrothermal synthesis of nano-materials.展开更多
Mesoporous cerium-zirconium mixed oxides were prepared by hydrothermal method using cetyl trimethyl ammonium bromide (CTAB) as template. The effects of amount of template, pH value of solution and hydrothermal tempera...Mesoporous cerium-zirconium mixed oxides were prepared by hydrothermal method using cetyl trimethyl ammonium bromide (CTAB) as template. The effects of amount of template, pH value of solution and hydrothermal temperature on mesostructure of samples were systematically investigated. The final products were characterized by XRD, TEM, FT-IR, and BET. The results indicate that all the cerium-zirconium mixed oxides present a meso-structure. At molar ratio of n(CTAB)/n((Ce)+(Zr))= 0.15, pH value of 9, and hydrothermal temperature of 120 ℃, the samples obtained possess a specific surface area of 207.9 m2/g with pore diameter of 3.70 nm and pore volume of 0.19 cm3/g.展开更多
Sulfur-doped iron-cobalt tannate nanorods(S-FeCoTA)derived from metal-organic frameworks(MOFs)as electrocatalysts were synthesized via a one-step hydrothermal method.The optimized S-FeCoTA was interlaced by loose nano...Sulfur-doped iron-cobalt tannate nanorods(S-FeCoTA)derived from metal-organic frameworks(MOFs)as electrocatalysts were synthesized via a one-step hydrothermal method.The optimized S-FeCoTA was interlaced by loose nanorods,which had many voids.The S-FeCoTA catalysts exhibited excellent electrochemical oxygen evolution reaction(OER)performance with a low overpotential of 273 mV at 10 mA·cm^(-2)and a small Tafel slope of 36 mV·dec^(-1)in 1 mol·L^(-1)KOH.The potential remained at 1.48 V(vs RHE)at 10 mA·cm^(-2)under continuous testing for 15 h,implying that S-FeCoTA had good stability.The Faraday efficiency of S-FeCoTA was 94%.The outstanding OER activity of S-FeCoTA is attributed to the synergistic effects among S,Fe,and Co,thus promoting electron transfer,reducing the reaction kinetic barrier,and enhancing the OER performance.展开更多
A reduced graphene oxide/Ni(OH)2 composite with excellent supercapacitive performance was synthesized by a facile hydrothermal route without organic solvents or templates used.XRD and SEM results reveal that the nicke...A reduced graphene oxide/Ni(OH)2 composite with excellent supercapacitive performance was synthesized by a facile hydrothermal route without organic solvents or templates used.XRD and SEM results reveal that the nickel hydroxide,which crystallizes into hexagonal β-Ni(OH)2 nanoflakes with a diameter less than 200 nm and a thickness of about 10 nm,is well combined with the reduced graphene oxide sheets.Electrochemical performance of the synthesized composite as an electrode material was investigated by cyclic voltammetry,electrochemical impedance spectroscopy and galvanostatic charge/discharge measurements.Its specific capacitance is determined to be 1672 F/g at a scan rate of 2 mV/s,and 696 F/g at a high scan rate of 50 mV/s.After 2000 cycles at a current density of 10 A/g,the composite exhibits a specific capacitance of 969 F/g,retaining about 86% of its initial capacitance.The composite delivers a high energy density of 83.6 W·h/kg at a power density of 1.0 kW/kg.The excellent supercapacitive performance along with the easy synthesis method allows the synthesized composite to be promising for supercapacitor applications.展开更多
Properties of hydroxyapatite （HA, Ca10（PO4）6（OH）2）, including bioactivity, biocompatibility, solubility and adsorption could be tailored over wide ranges by the control of particle composition, particle size and...Properties of hydroxyapatite （HA, Ca10（PO4）6（OH）2）, including bioactivity, biocompatibility, solubility and adsorption could be tailored over wide ranges by the control of particle composition, particle size and morphology. In order to satisfy various applications, well-crystallized pure HA nanoparticles were synthesized at moderate temperatures by hydrotherrnal synthesis, and HA nanoparticles with different lengths were obtained by adding organic additives. X-ray diffractometry （XRD） and Fourier transform infrared （FTIR） spectrometry were used to characterize these nanoparticles, and the morphologies of the HA particles were observed by transmission electron microscopy （TEM）. The results demonstrate that shorter rod-like HA particles can be prepared by adding cetyltrimethylammonium bromide （CTAB）, as the additive of CTAB can block the HA crystal growth along with c-axis. And whisker HA particles are obtained by adding ethylenediamine tetraacetic acid （EDTA）, since EDTA may have effect on the dissolution-repreeipitation process of HA.展开更多
Hollow-structured Cu_(0.3)Co_(2.7)O_(4) microspheres have been synthesized by a simple one-pot template-free hydrothermal method with copper sulfate,cobalt acetate and ammonia as raw materials.The products were charac...Hollow-structured Cu_(0.3)Co_(2.7)O_(4) microspheres have been synthesized by a simple one-pot template-free hydrothermal method with copper sulfate,cobalt acetate and ammonia as raw materials.The products were characterized by powder X-ray diffraction,energy dispersive X-ray analysis,selected area electron diffraction,high-resolution transmission electron microscopy,scanning electron microscopy and BET measurements.The research results show that the hollow Cu_(0.3)Co_(2.7)O_(4) microspheres consist of single-crystalline nanocubes with the diameter of about 20 nm.The formation mechanism of hollow Cu_(0.3)Co_(2.7)O_(4) microspheres is suggested as Ostwald ripening in a solid-solution-solid process,and Cu_(0.3)Co_(2.7)O_(4) microspheres are mesoporous containing two pore sizes of 3.3 and 5.9 nm.The as-prepared Cu_(0.3)Co_(2.7)O_(4) sensors have optimal gas responses to 50×10^(−6) mg/m^(3) C_(2)H_(5)OH at 190℃.展开更多
Silver-tin oxide powders were synthesized by the hydrothermal method with Ag(NH_3)_2^+ solution and Na_2SnO_3 solution as raw materials and Na_2SO_3 as reductant. The precipitation conditions of Na2SnO3 solution and t...Silver-tin oxide powders were synthesized by the hydrothermal method with Ag(NH_3)_2^+ solution and Na_2SnO_3 solution as raw materials and Na_2SO_3 as reductant. The precipitation conditions of Na2SnO3 solution and the reduction conditions of Ag(NH_3)_2^+ were also investigated. The powders prepared were characterized by differential thermal analysis (DTA), X-ray diffraction analysis (XRD), scanning electron microscope (SEM) and energy spectrum analysis. The results show that pH value of the solution is a key parameter in the formation of Sn(OH)_4 precipitate and the reduction reaction of Ag(NH_3)_2^+ can release H+ ions, which results in synchronous precipitation of Sn(OH)_6~2- as Sn(OH)_4. The reduction of Ag(NH_3)_2^+ and precipitation of Na_2SnO_3 occur simultaneously and the coprecipitation of silver and tin oxide is reached by the hydrothermal method. The silver-tin oxide composite powders have mainly flake shape of about 0.3 μm in thickness and there exists homogeneous distribution of tin oxide and silver in the powder synthesized.展开更多
A simple hydrothermal process followed by heat treatment was applied to the preparation of spinel Li1.05Mn1.95O4. In this process, electrolytic manganese dioxide(EMD) and LiOH·H2O were used as starting materials....A simple hydrothermal process followed by heat treatment was applied to the preparation of spinel Li1.05Mn1.95O4. In this process, electrolytic manganese dioxide(EMD) and LiOH·H2O were used as starting materials. The physiochemical properties of the synthesized samples were investigated by thermogravimetry-differential scanning calorimetry(TG-DSC), X-ray diffractometry(XRD), and scanning electronic microscopy(SEM). The results show that the hydrothermally synthesized precursor is an essential amorphous. The precursor can be easily transferred to spinel powders with a homogeneous structure and a regularly-shaped morphology by heat treatment. Li1.05Mn1.95O4 powder obtained by heat treating the precursor at 430 °C for 12 h and then calcining at 800 °C for 12 h shows an excellent cycling performance with an initial charge capacity of 118.2 mA·h·g-1 obtained at 0.5C rate and 93.8% of its original value retained after 100 cycles.展开更多
Wurtzite strcture gallium nitride, GaN,a direct bandgap semiconductor (3.4 eV at room temperature),is an ideal material for fabrication of blue/green light emit ti ng diodes, laser diodes,and high power integrated cir...Wurtzite strcture gallium nitride, GaN,a direct bandgap semiconductor (3.4 eV at room temperature),is an ideal material for fabrication of blue/green light emit ti ng diodes, laser diodes,and high power integrated circuits.Recent progress in th in film crystal technique has realized the output of blue semiconductor lasers w i th a lifetime of over 10000 hours under continuous wave operation at room tempe r ature.So far GaN and its ternary indium and aluminum alloys are grown almost uni v ersally on foreign substrates with varying lattice mismatches.The mismatch undou btedly results in a significant dislocation density in the grown films.Hence it is necessary to grow single crystal GaN to be used as substrates for improvement of laser diodes.On the other hand,low dimensional GaN materials such as nanocry stalline powder,nanocrystal assembled bulk(nanophase) and nano wires are very u seful in both fundamental mesoscopic research and future development of GaN nano devices.Here we report our main recent progresses on the crystal growth of GaN a nd the preparation of its low dimensional materials.展开更多
Na0.44MnO2 nanorods have been prepared by a hydrothermal method.The experimental parameters have been systematically investigated and optimized.The results show that Na0.44MnO2 nanorods obtained via the hydrothermal t...Na0.44MnO2 nanorods have been prepared by a hydrothermal method.The experimental parameters have been systematically investigated and optimized.The results show that Na0.44MnO2 nanorods obtained via the hydrothermal treatment at 200℃for 16 h show the best electrochemical properties,which deliver the high initial discharge capacity of 110.7 mA·h/g at 50 mA/g in potential window 2.0-4.0 V.To further improve their electrochemical properties,a ball milling process with graphene has been carried out to obtain Na0.44MnO2/graphene composite.The initial discharge capacity of Na0.44MnO2/graphene composite is 106.9 mA·h/g at a current density of 50 mA/g.After 100 cycles,the residual discharge capacity is 91.8 mA·h/g and the capacity retention rate is 85.9%,which is much higher than that of pristine Na0.44MnO2 nanorods(74.7%)at the same condition.What is more,when the current density reaches 500 and 1000 mA/g,the corresponding discharge capacities of Na0.44MnO2/graphene composite are about 89 and 78 mA·h/g,respectively,indicating outstanding rate capability.展开更多
Ag/ZnO nanosheet composites were prepared by zinc nitrate, sodium hydroxide and silver nitrate via a simple hydrothermal method. The crystal structure, morphology, optical property and photocatalytic performance were ...Ag/ZnO nanosheet composites were prepared by zinc nitrate, sodium hydroxide and silver nitrate via a simple hydrothermal method. The crystal structure, morphology, optical property and photocatalytic performance were studied by means of XRD, SEM, HRTEM, XPS, and PL methods. It is found that both the pure ZnO and composite Ag/ZnO samples have the same morphology of nanosheet. The interaction of spherical Ag particles with ZnO matrix in the Ag/ZnO sample leads to an increase in photocatalytic efficiency for the possible increase of concentration of surface hydroxyl and the photo-induced electrons and holes. The addition of Ag can reduce the recombination rate of photo-generated carriers and the sample with addition of 3 at% Ag to ZnO exhibits the best photocatalytic activity with the degradation rate up to 95% within 15 min.展开更多
Ultrasonic treatment and hydrothermal method were applied in the traditional homogeneous precipitation for nano-TiO_2 preparation, which was used as carrier material for the production of honeycomb selective catalytic...Ultrasonic treatment and hydrothermal method were applied in the traditional homogeneous precipitation for nano-TiO_2 preparation, which was used as carrier material for the production of honeycomb selective catalytic reduction(SCR) catalyst. The influence rules of the two improved methods on characterization of TiO_2 samples, denitration activity and mechanical strength of honeycomb SCR catalyst samples were mainly focused on. The results indicate that the specific surface area, particle size and uniformity of TiO_2 samples are significantly improved by both of the ultrasonic and hydrothermal treatments compared with the traditional homogeneous precipitation. Also, the denitration activities of catalyst samples are enhanced by the two improved methods(the NO_x reduction ratio increases from 88.89% to 95.45% by ultrasonic homogeneous precipitation process, and to 94.12% by hydrothermal homogeneous precipitation process). On the other hand, because of good spherical shape and high particle distribution of TiO_2 sample from hydrothermal homogeneous precipitation process, the corresponding honeycomb catalyst samples get the best mechanical strength, which is even higher than that of the reference sample from commercial nano-TiO_2. So, it is concluded that the hydrothermal homogeneous precipitation can be a feasible and effective preparation method of TiO_2 carrier for the honeycomb SCR catalyst production.展开更多
Graphene under high temperature was prepared and loaded on Ni foam.Then,cobalt tetroxide precursor was grown on Ni foam in situ by the hydrothermal method.Finally,the sample was burned at high temperature to obtain Co...Graphene under high temperature was prepared and loaded on Ni foam.Then,cobalt tetroxide precursor was grown on Ni foam in situ by the hydrothermal method.Finally,the sample was burned at high temperature to obtain Co_(3)O_(4)+graphene@Ni.The hydrothermal method used in this paper is easy to operate,with low-risk factors and environmental protection.The prepared Co_(3)O_(4)+graphene@Ni electrode exhibits superior electrochemical performance than Co_(3)O_(4)@Ni electrode.At a current density of 1 A/g,the specific capacitance of the Co_(3)O_(4)+graphene@Ni electrode calculated by a charge-discharge test is 935 F/g,which is much larger than that of Co_(3)O_(4)@Ni electrode of 340 F/g.展开更多
基金Project(2008A090300016) supported by Major Science & Technology Special Program of Guangdong Province,China
文摘Micaceous iron oxide （MIO） with a hexagonal flaky shape was prepared by hydrothermal method. The ferric hydroxide used as precursor was obtained by an acidic leaching solution of pyrite cinders reacting with ammonia solution. The optimal experimental conditions for preparing micaceous iron oxide were investigated by orthogonal experiments. Micaceous iron oxide can be successfully prepared when optimal parameters of total iron concentration of 2.0 mol/L, pH value of 8, n（Fe2＋）/n（Fe3＋） of 0.1, mass of seed crystal of 1 g, reaction temperature of 260 ℃ and reaction time of 30 min are applied. X-ray diffractometry （XRD）, scanning electron microscopy （SEM）, transmission electron microscopy （TEM） and selected area electron diffractometry （SAEM） were adopted to characterize the hydrothermal products prepared under optimal conditions. The results indicate that highly crystallized α-Fe2O3 hexagonal flakes, about 1.0-1.5 μm in diameter and 0.1 μm in thickness, are prepared. Furthermore, the quality of micaceous iron oxide prepared can meet the required characteristics of micaceous iron oxide pigments for paints （ISO 10601--2007）.
文摘MnZn ferrite nanoscale particles were synthesized by hydrothermal method. The effects of amount of addition La3+ on the products were discussed. The product was characterized by X-ray diffraction （XRD） and transmission electron microscope （TEM）. The results show that the sample with 0.2% La3+（mass fraction） or without La3+ has only spinel phase, but the sample with mass fraction of La3+ exceeding 0.4% posses second phase besides the spinel one; and the nano-MnZn ferrites change from cube to hexagon when the mass fractions of La3+ is up to （1.2%.） TEM image of the sample with 1.2% La3+ indicates that the homogeneous hexagonal crystal is obtained and the particles are larger than those of undoped; the addition of La3+ has great influence on the crystallization of hydrothermal process and can change the shape of particles and improve their growth. The saturation magnetization of the sample with 1.2% La3+ (2.64 A·m2·kg-1) is lower than that of undoped (17.54 (A·m2·kg-1)) and it behaves superparamagnetically.
文摘ZnO is a highly significant II-VI semiconductor known for its excellent optoelectronic properties,making it widely applicable and promising for use in light-emitting devices,solar cells,lasers,and photodetectors.The methods for preparing ZnO are diverse,and among them,the hydrothermal method is favored for its simplicity,ease of operation,and low cost,making it an optimal choice for ZnO single-crystal growth.Most studies investigating the effects of different hydrothermal experimental parameters on the morphology and performance of ZnO nano-materials typically focus on only 2—3 variable parameters,with few examining the impact of all possible experimental parameter changes on ZnO nano-mate-rials.The principles of the hydrothermal method and its advantages in nano-material preparation were briefly introduced in this article.The detailed discussion on the influence of various experimental parameters on the preparation of ZnO nano-materials was provided,which including reaction materials,Zn^(2+)/OH^(-)ratio,reaction time and temperature,additives,experimental equipment,and annealing conditions.The review co-vers how different experimental parameters affect the morphology and performance of the materials,as well as how different rare earth doping elements influence the performance of ZnO nano-materials.It is hoped that this work will contribute to future research on the hydrothermal synthesis of nano-materials.
基金Project(CHCL0501) supported by Hubei Provincial Open Fund of Key Laboratory of Catalytic Material Science and Technology
文摘Mesoporous cerium-zirconium mixed oxides were prepared by hydrothermal method using cetyl trimethyl ammonium bromide (CTAB) as template. The effects of amount of template, pH value of solution and hydrothermal temperature on mesostructure of samples were systematically investigated. The final products were characterized by XRD, TEM, FT-IR, and BET. The results indicate that all the cerium-zirconium mixed oxides present a meso-structure. At molar ratio of n(CTAB)/n((Ce)+(Zr))= 0.15, pH value of 9, and hydrothermal temperature of 120 ℃, the samples obtained possess a specific surface area of 207.9 m2/g with pore diameter of 3.70 nm and pore volume of 0.19 cm3/g.
文摘Sulfur-doped iron-cobalt tannate nanorods(S-FeCoTA)derived from metal-organic frameworks(MOFs)as electrocatalysts were synthesized via a one-step hydrothermal method.The optimized S-FeCoTA was interlaced by loose nanorods,which had many voids.The S-FeCoTA catalysts exhibited excellent electrochemical oxygen evolution reaction(OER)performance with a low overpotential of 273 mV at 10 mA·cm^(-2)and a small Tafel slope of 36 mV·dec^(-1)in 1 mol·L^(-1)KOH.The potential remained at 1.48 V(vs RHE)at 10 mA·cm^(-2)under continuous testing for 15 h,implying that S-FeCoTA had good stability.The Faraday efficiency of S-FeCoTA was 94%.The outstanding OER activity of S-FeCoTA is attributed to the synergistic effects among S,Fe,and Co,thus promoting electron transfer,reducing the reaction kinetic barrier,and enhancing the OER performance.
基金Project(KJ2012A045) supported by the Natural Science Foundation of Education Commission of Anhui Province,China
文摘A reduced graphene oxide/Ni(OH)2 composite with excellent supercapacitive performance was synthesized by a facile hydrothermal route without organic solvents or templates used.XRD and SEM results reveal that the nickel hydroxide,which crystallizes into hexagonal β-Ni(OH)2 nanoflakes with a diameter less than 200 nm and a thickness of about 10 nm,is well combined with the reduced graphene oxide sheets.Electrochemical performance of the synthesized composite as an electrode material was investigated by cyclic voltammetry,electrochemical impedance spectroscopy and galvanostatic charge/discharge measurements.Its specific capacitance is determined to be 1672 F/g at a scan rate of 2 mV/s,and 696 F/g at a high scan rate of 50 mV/s.After 2000 cycles at a current density of 10 A/g,the composite exhibits a specific capacitance of 969 F/g,retaining about 86% of its initial capacitance.The composite delivers a high energy density of 83.6 W·h/kg at a power density of 1.0 kW/kg.The excellent supercapacitive performance along with the easy synthesis method allows the synthesized composite to be promising for supercapacitor applications.
基金Project(20070410304) supported by Postdoctoral Foundation of ChinaProject(07JJ3105) supported by Hunan Provincial Natural Science Foundation of China
文摘Properties of hydroxyapatite （HA, Ca10（PO4）6（OH）2）, including bioactivity, biocompatibility, solubility and adsorption could be tailored over wide ranges by the control of particle composition, particle size and morphology. In order to satisfy various applications, well-crystallized pure HA nanoparticles were synthesized at moderate temperatures by hydrotherrnal synthesis, and HA nanoparticles with different lengths were obtained by adding organic additives. X-ray diffractometry （XRD） and Fourier transform infrared （FTIR） spectrometry were used to characterize these nanoparticles, and the morphologies of the HA particles were observed by transmission electron microscopy （TEM）. The results demonstrate that shorter rod-like HA particles can be prepared by adding cetyltrimethylammonium bromide （CTAB）, as the additive of CTAB can block the HA crystal growth along with c-axis. And whisker HA particles are obtained by adding ethylenediamine tetraacetic acid （EDTA）, since EDTA may have effect on the dissolution-repreeipitation process of HA.
基金Project(51202066)supported by the National Natural Science Foundation of ChinaProject(NCET-13-0784)supported by the Program for New Century Excellent Talents in University of China。
文摘Hollow-structured Cu_(0.3)Co_(2.7)O_(4) microspheres have been synthesized by a simple one-pot template-free hydrothermal method with copper sulfate,cobalt acetate and ammonia as raw materials.The products were characterized by powder X-ray diffraction,energy dispersive X-ray analysis,selected area electron diffraction,high-resolution transmission electron microscopy,scanning electron microscopy and BET measurements.The research results show that the hollow Cu_(0.3)Co_(2.7)O_(4) microspheres consist of single-crystalline nanocubes with the diameter of about 20 nm.The formation mechanism of hollow Cu_(0.3)Co_(2.7)O_(4) microspheres is suggested as Ostwald ripening in a solid-solution-solid process,and Cu_(0.3)Co_(2.7)O_(4) microspheres are mesoporous containing two pore sizes of 3.3 and 5.9 nm.The as-prepared Cu_(0.3)Co_(2.7)O_(4) sensors have optimal gas responses to 50×10^(−6) mg/m^(3) C_(2)H_(5)OH at 190℃.
基金Project(2001BA901A09)supported by the Key Program of Science and Technology Action of West China Development
文摘Silver-tin oxide powders were synthesized by the hydrothermal method with Ag(NH_3)_2^+ solution and Na_2SnO_3 solution as raw materials and Na_2SO_3 as reductant. The precipitation conditions of Na2SnO3 solution and the reduction conditions of Ag(NH_3)_2^+ were also investigated. The powders prepared were characterized by differential thermal analysis (DTA), X-ray diffraction analysis (XRD), scanning electron microscope (SEM) and energy spectrum analysis. The results show that pH value of the solution is a key parameter in the formation of Sn(OH)_4 precipitate and the reduction reaction of Ag(NH_3)_2^+ can release H+ ions, which results in synchronous precipitation of Sn(OH)_6~2- as Sn(OH)_4. The reduction of Ag(NH_3)_2^+ and precipitation of Na_2SnO_3 occur simultaneously and the coprecipitation of silver and tin oxide is reached by the hydrothermal method. The silver-tin oxide composite powders have mainly flake shape of about 0.3 μm in thickness and there exists homogeneous distribution of tin oxide and silver in the powder synthesized.
基金Project(50174058)supported by the National Natural Science Foundation of ChinaProject(2011A025)supported by the Glorious Laurel Scholar Program of Guangxi Zhuang Autonomous Region,China
文摘A simple hydrothermal process followed by heat treatment was applied to the preparation of spinel Li1.05Mn1.95O4. In this process, electrolytic manganese dioxide(EMD) and LiOH·H2O were used as starting materials. The physiochemical properties of the synthesized samples were investigated by thermogravimetry-differential scanning calorimetry(TG-DSC), X-ray diffractometry(XRD), and scanning electronic microscopy(SEM). The results show that the hydrothermally synthesized precursor is an essential amorphous. The precursor can be easily transferred to spinel powders with a homogeneous structure and a regularly-shaped morphology by heat treatment. Li1.05Mn1.95O4 powder obtained by heat treating the precursor at 430 °C for 12 h and then calcining at 800 °C for 12 h shows an excellent cycling performance with an initial charge capacity of 118.2 mA·h·g-1 obtained at 0.5C rate and 93.8% of its original value retained after 100 cycles.
文摘Wurtzite strcture gallium nitride, GaN,a direct bandgap semiconductor (3.4 eV at room temperature),is an ideal material for fabrication of blue/green light emit ti ng diodes, laser diodes,and high power integrated circuits.Recent progress in th in film crystal technique has realized the output of blue semiconductor lasers w i th a lifetime of over 10000 hours under continuous wave operation at room tempe r ature.So far GaN and its ternary indium and aluminum alloys are grown almost uni v ersally on foreign substrates with varying lattice mismatches.The mismatch undou btedly results in a significant dislocation density in the grown films.Hence it is necessary to grow single crystal GaN to be used as substrates for improvement of laser diodes.On the other hand,low dimensional GaN materials such as nanocry stalline powder,nanocrystal assembled bulk(nanophase) and nano wires are very u seful in both fundamental mesoscopic research and future development of GaN nano devices.Here we report our main recent progresses on the crystal growth of GaN a nd the preparation of its low dimensional materials.
基金Project(51672234)supported by the National Natural Science Foundation of ChinaProject(1337304)supported by the Program for Innovative Research Cultivation Team in University,Ministry of Education,China
文摘Na0.44MnO2 nanorods have been prepared by a hydrothermal method.The experimental parameters have been systematically investigated and optimized.The results show that Na0.44MnO2 nanorods obtained via the hydrothermal treatment at 200℃for 16 h show the best electrochemical properties,which deliver the high initial discharge capacity of 110.7 mA·h/g at 50 mA/g in potential window 2.0-4.0 V.To further improve their electrochemical properties,a ball milling process with graphene has been carried out to obtain Na0.44MnO2/graphene composite.The initial discharge capacity of Na0.44MnO2/graphene composite is 106.9 mA·h/g at a current density of 50 mA/g.After 100 cycles,the residual discharge capacity is 91.8 mA·h/g and the capacity retention rate is 85.9%,which is much higher than that of pristine Na0.44MnO2 nanorods(74.7%)at the same condition.What is more,when the current density reaches 500 and 1000 mA/g,the corresponding discharge capacities of Na0.44MnO2/graphene composite are about 89 and 78 mA·h/g,respectively,indicating outstanding rate capability.
基金Project(21373273)supported by the National Natural Science Foundation of ChinaProject(2019CG033)supported by the Deepening Reform Project of Innovation and Entrepreneurship Education of Central South University,China+1 种基金Project(2019JG067)supported by the Graduate Education and Teaching Reform Research Project of Central South University,ChinaProject(201810533278)supported by the National College Students’ Innovative Experiment Project of Central South University,China
文摘Ag/ZnO nanosheet composites were prepared by zinc nitrate, sodium hydroxide and silver nitrate via a simple hydrothermal method. The crystal structure, morphology, optical property and photocatalytic performance were studied by means of XRD, SEM, HRTEM, XPS, and PL methods. It is found that both the pure ZnO and composite Ag/ZnO samples have the same morphology of nanosheet. The interaction of spherical Ag particles with ZnO matrix in the Ag/ZnO sample leads to an increase in photocatalytic efficiency for the possible increase of concentration of surface hydroxyl and the photo-induced electrons and holes. The addition of Ag can reduce the recombination rate of photo-generated carriers and the sample with addition of 3 at% Ag to ZnO exhibits the best photocatalytic activity with the degradation rate up to 95% within 15 min.
基金Project(201031)supported by the Environmental Protection Scientific Research of Jiangsu Province,ChinaProject(BE2010184)supported by the Technology Support Program of Jiangsu Province-Industrial Parts,China
文摘Ultrasonic treatment and hydrothermal method were applied in the traditional homogeneous precipitation for nano-TiO_2 preparation, which was used as carrier material for the production of honeycomb selective catalytic reduction(SCR) catalyst. The influence rules of the two improved methods on characterization of TiO_2 samples, denitration activity and mechanical strength of honeycomb SCR catalyst samples were mainly focused on. The results indicate that the specific surface area, particle size and uniformity of TiO_2 samples are significantly improved by both of the ultrasonic and hydrothermal treatments compared with the traditional homogeneous precipitation. Also, the denitration activities of catalyst samples are enhanced by the two improved methods(the NO_x reduction ratio increases from 88.89% to 95.45% by ultrasonic homogeneous precipitation process, and to 94.12% by hydrothermal homogeneous precipitation process). On the other hand, because of good spherical shape and high particle distribution of TiO_2 sample from hydrothermal homogeneous precipitation process, the corresponding honeycomb catalyst samples get the best mechanical strength, which is even higher than that of the reference sample from commercial nano-TiO_2. So, it is concluded that the hydrothermal homogeneous precipitation can be a feasible and effective preparation method of TiO_2 carrier for the honeycomb SCR catalyst production.
基金Project(21502014)supported by the National Natural Science Foundation of ChinaProjects(20180550736,2019-ZD 0117)supported by the Natural Science Foundation of Liaoning Province,China+1 种基金Projects(JDL 2019004,JDL 2017027)supported by the Research Foundation of Educational Committee of Liaoning Province,ChinaProject(191008-K)supported by Guangxi Key Laboratory of Information Materials(Guilin University of Electronic Technology),China。
文摘Graphene under high temperature was prepared and loaded on Ni foam.Then,cobalt tetroxide precursor was grown on Ni foam in situ by the hydrothermal method.Finally,the sample was burned at high temperature to obtain Co_(3)O_(4)+graphene@Ni.The hydrothermal method used in this paper is easy to operate,with low-risk factors and environmental protection.The prepared Co_(3)O_(4)+graphene@Ni electrode exhibits superior electrochemical performance than Co_(3)O_(4)@Ni electrode.At a current density of 1 A/g,the specific capacitance of the Co_(3)O_(4)+graphene@Ni electrode calculated by a charge-discharge test is 935 F/g,which is much larger than that of Co_(3)O_(4)@Ni electrode of 340 F/g.
