Since ultraviolet(UV)light,as well as blue light,which is part of visible light,is harmful to skin,samarium-cerium compounds containing Sm_(2)O_(2)S were synthesized by co-precipitation method.This kind of compounds b...Since ultraviolet(UV)light,as well as blue light,which is part of visible light,is harmful to skin,samarium-cerium compounds containing Sm_(2)O_(2)S were synthesized by co-precipitation method.This kind of compounds blocks not only UV light,but also blue light.The minimum values of average transmittance(360-450 nm)and band gap of samarium-cerium compounds were 8.90%and 2.76 eV,respectively,which were less than 13.96%and 3.01 eV of CeO_(2).Elemental analysis(EA),X-ray diffraction(XRD),Fourier transformation infrared(FTIR),and Raman spectra determined that the samples contained Ce_(4)O_(7),Sm_(2)O_(2)S,Sm_(2)O_(3),and Sm_(2)O_(2)SO_(4).The microstructure of samples was analyzed by scanning and transmission electron microscopies(SEM and TEM).X-ray photoelectron spectrum(XPS)showed that cerium had Ce^(3+)and Ce^(4+) valence states,and oxygen was divided into lattice oxygen and oxygen vacancy,which was the direct cause of the decrease of average transmittance and band gap.展开更多
To preserve the environment for civilization,we should remove the pollutants like toxic dyes by friendly and cost efficacious method.In this study,the effect of surfactants or mixed surfactants on physicochemical,opti...To preserve the environment for civilization,we should remove the pollutants like toxic dyes by friendly and cost efficacious method.In this study,the effect of surfactants or mixed surfactants on physicochemical,optical and adsorption properties of ternary mixed oxide CeO_(2)-ZrO_(2)-Al_(2) O_3(CZA) are investigated.The ternary mixed oxide CZA was prepared by surfactants or mixed surfactants assisted ultrasonic coprecipitation method.The physicochemical and optical properties are estimated by different techniques like XRD,TEM,EDX,FTIR,S_(BET) and UV-Vis/DR.The CZA_T and CZA_C have hybrid shapes and high surface area.The adsorption properties of ternary mixed oxides adsorbents were characterized by sono-removing anionic dyes such as Congo red(CR) and Remazol red RB-133(RR).The different factors like contact time,different dye concentrations and temperatures also studied.The kinetics and isotherms applications showed that,the adsorption process was followed pseudo second order kinetics and the Freundlich isotherm model.Also,the adsorption is spontaneous and endothermic process through the thermodynamic study.Finally,the results showed that the ternary mixed oxide nano-adsorbent(CeO_(2)-ZrO_(2)-Al_(2) O_3) is promising and functional materials for anionic dye sweep from wastewater.展开更多
Oxidative coupling of methane(OCM) was conducted over LaAlO3X catalysts that were prepared by a coprecipitation method using different co-precipitation pH values(X = 6–10). The aim is to investigate the effect of p H...Oxidative coupling of methane(OCM) was conducted over LaAlO3X catalysts that were prepared by a coprecipitation method using different co-precipitation pH values(X = 6–10). The aim is to investigate the effect of p H values on the catalytic activity of La AlO3 catalysts in this reaction. The results showed that the co-precipitation pH value affected greatly on the formation of chemical species of precipitate precursors in the co-precipitation step, leading to different phases of the finally obtained LaAlO3 catalysts.When the co-precipitation pH value increased up to 8, the lanthanum-related phases such as La2 O3 and La(OH)3 were gradually formed as by-products, preventing the formation of LaAlO3 perovskite crystalline structure and facilitating the formation of oxygen vacancies on catalyst surface. However, at pH value of9 or higher, the lanthanum content in the precipitate precursor was increased greatly. Not LaAlO3 perovskite but lanthanum-related phases were developed as main phases, reducing their catalytic activities in this reaction. Among LaAlO3 catalysts, the one prepared at pH = 8 showed the highest C2 yield due to its well-developed oxygen vacancies and electrophilic lattice oxygen. Therefore, the co-precipitation pH value strongly affected the LaAlO3 catalyst activity in OCM reaction. A precious pH control should be required to prepare various perovskite catalysts for the OCM.展开更多
The synthesis of precursor of green phosphors, LaPO4:Ce, Tb, by means of co-precipitation with cocurrent flow feed was studied. The effects of the reaction temperature, the kind and concentration of the acid in the bo...The synthesis of precursor of green phosphors, LaPO4:Ce, Tb, by means of co-precipitation with cocurrent flow feed was studied. The effects of the reaction temperature, the kind and concentration of the acid in the bottom water, and the charging rate on the physical properties, such as particle size, were investigated. It is found that the particle size of the powder is controllable by adjusting acidity in bottom water and charging rate. The powder with diameter size of 3 to 5 μm was obtained. Its XRD and SEM were analyzed. XRD patterns of the as-prepared green phosphor powders display the typical peaks of CePO4. SEM shows that the morphology of powders is ball-shaped.展开更多
SnO2 doped with Y were prepared by co-precipitation method and tested in lithium-ion cells. The structure and morphology of the materials were characterized by X-ray diffraction (XRD) and transmission electron microsc...SnO2 doped with Y were prepared by co-precipitation method and tested in lithium-ion cells. The structure and morphology of the materials were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). XRD patterns presented that the all the as-prepared materials had tetragonal rutile structure but a second phase (Y2O3) was observed when Y content reached 4%. TEM micrograph indicated that Y doped SnO2 had a small particle size ranging from 20 to 25 nm. The electrochemical properties for an anode active material in lithium-ion batteries were investigated at room temperature, including the observed capacity involved in the first-discharge and the reversible capacity values during subsequent charge-discharge cycles. The as-prepared Y-doped SnO2 exhibited promising electrochemical properties as anodes for lithium-ion batteries.展开更多
Tetraethylenepentamine(C8H23N5,TEPA) has been used as a novel precipitant to synthesize yttrium aluminum garnet(Y3Al5O12,YAG) precursor from a mixed solution of aluminum and yttrium nitrates via a normal-strike co-pre...Tetraethylenepentamine(C8H23N5,TEPA) has been used as a novel precipitant to synthesize yttrium aluminum garnet(Y3Al5O12,YAG) precursor from a mixed solution of aluminum and yttrium nitrates via a normal-strike co-precipitation method without controlling the pH value during precipitation process.The original precursor was analyzed by thermogravimetry/differential scanning calorimetry(TG/DSC).The evolution of phase composition and micro-structure of the as-synthesized YAG powders were characterized by X-ray diffraction(XRD),Fourier transform infrared(FT-IR) spectroscopy and transmission electron microscopy(TEM).Compositionally pure YAG nanostructured powders were directly obtained by calcination of the precursor at 900 ℃ without the formation of any intermediate phases.The average particle size determined from TEM micrograph for the powder obtained at 1000 ℃ was approximately 50 nm.展开更多
LiNi0.8Co0.1Mn0.1O2 was prepared by a chloride co-precipitation method and characterized by thermogravimetric analysis, X-ray diffractometry with Rietveld refinement,electron scanning microscopy and electrochemical me...LiNi0.8Co0.1Mn0.1O2 was prepared by a chloride co-precipitation method and characterized by thermogravimetric analysis, X-ray diffractometry with Rietveld refinement,electron scanning microscopy and electrochemical measurements.Effects of lithium ion content and sintering temperature on physical and electrochemical performance of LiNi0.8Co0.1Mn0.1O2 were also investigated. The results show that the sample synthesized at 750℃with 105%lithium content has fine particle sizes around 200 nm and homogenous sizes distribution.The initial discharge capacity for the powder is 184 mA·h/g between 2.7 and 4.3 V at 0.1C and room temperature.展开更多
LiNi_(0.8)Co_(0.15)Al_(0.05)O_2(NCA) material is successfully synthesized with a modified co-precipitation method,in which NH_3·H_2O and EDTA are used as two chelating agents. The obtained LiNi_(0.8)Co_(0.15)Al_(...LiNi_(0.8)Co_(0.15)Al_(0.05)O_2(NCA) material is successfully synthesized with a modified co-precipitation method,in which NH_3·H_2O and EDTA are used as two chelating agents. The obtained LiNi_(0.8)Co_(0.15)Al_(0.05)O_2 material has well-defined layered structure and uniform element distribution, which reveals an enhanced electrochemical performance with a capacity retention of 97.9% after 100 cycles at 0.2 C, and reduced thermal runaway from the isothermal calorimetry test. In situ X-ray diffraction(XRD) was employed to capture the structural changes during the charge–discharge process. The reversible evolutions of lattice parameters(a, b, c, and V) further verify the structural stability.展开更多
The M3-3x(PO4)2∶2xCe, xTb(M=Mg, Ca, Sr, Ba) phosphors were prepared by coprecipitation in this paper. Their phase structures, morphologies and luminescent properties were investigated by X-ray diffractometer, field e...The M3-3x(PO4)2∶2xCe, xTb(M=Mg, Ca, Sr, Ba) phosphors were prepared by coprecipitation in this paper. Their phase structures, morphologies and luminescent properties were investigated by X-ray diffractometer, field emission scanning electron microscopy and fluorospectrophotometer. The results indicate that the Ce3+ and Tb3+ enteres the host lattice because the XRD patterns of alkaline earth phosphate show no impurity phase, the SEM shows the spherical particles with an average size about 1 μm. The emission and excitation spectra are similar to rare earth phosphate. Concentration quenching of the Sr3(PO4)2∶Ce, Tb emission intensity was not observed even when the Tb3+ increases to 0.05, while the maximum emission intensity appears when x=0.04 in M3-3x(PO4)2∶2xCe, xTb(M=Ca, Ba) emission spectrum.展开更多
The long afterglow fluorescent material of M1-3xAl2O4:Eu2+ x/Dy3+2x(M2+= Sr2+, Ca2+ and Ba2+) phosphors are successfully synthesized by calcining precursor obtained via co-precipitation method at 1300oC for 4 h with r...The long afterglow fluorescent material of M1-3xAl2O4:Eu2+ x/Dy3+2x(M2+= Sr2+, Ca2+ and Ba2+) phosphors are successfully synthesized by calcining precursor obtained via co-precipitation method at 1300oC for 4 h with reducing atmosphere (20% H2 and 80% N2). The phase evolution, morphology and afterglow fluorescent properties are systematically studied by the various instruments of XRD, FE-SEM, PLE/PL spectroscopy and fluorescence decay analysis. The PL spectra shows that the Sr1-3xAl2O4:Eu2+x/Dy3+ 2x phosphors display vivid green emission at s519 nm (4f65d1!4f7 transition of Eu2+) with monitoring of the maximum excitation wavelength at s334 nm (8S7=2!6IJ transition of Eu2+), among which the optimal concentration of Eu2+ and Dy3+ is 15 at.% and 30 at.%, respectively. The color coordinates and temperature of Sr1-3xAl2O4:Eu2+ x/Dy3+ 2x phosphors are approximately at (s0.27, s0.57) and s6700 K, respectively. On the above basis, the M0:55Al2O4:Eu2+ 0:15/Dy3+ 0:3 (M2+= Ca2+ and Ba2+) phosphors is obtained by the same method. The PL spectra of these phosphors shows the strongest blue emission at s440 nm and cyan emission at s499 nm under s334 nm wavelength excitation, respectively, which are blue shifted comparing to Sr1??3xAl2O4:Eu2+ x/Dy3+ 2x phosphors. The color coordinates and temperatures of M0:55Al2O4:Eu2+ 0:15/Dy3+ 0:3 (M2+= Ca2+ and Ba2+) phosphors are approximately at (s0.18, s0.09), s2000 K and (s0.18, s0.42), s11600 K, respectively. In this work, long afterglow materials of green, blue and cyan aluminates phosphors with excellent properties have been prepared, in order to obtain wide application in the field of night automatic lighting and display.展开更多
In this work, the Mg1-x Znx Fe2 O4 Nanoferrites (where x = 0.0, 0.2, 0.4, 0.6 and 0.8) was synthesized using co-precipitation method. The investigation of structural and optical properties was carried out for the synt...In this work, the Mg1-x Znx Fe2 O4 Nanoferrites (where x = 0.0, 0.2, 0.4, 0.6 and 0.8) was synthesized using co-precipitation method. The investigation of structural and optical properties was carried out for the synthesized samples using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and Ultraviolet visible spectrophotometer (UV-Vis). XRD revealed that the structure of these nanoparticles is spinel with space group Fd3m and crystallite size lies in the range 21.0 - 42.8 nm. Lattice parameter was found to increases with Zn concentration and this may be due to the larger ionic radius of the Zn2+?ion. FTIR spectroscopy confirmed the formation of spinel ferrite and showed the characteristics absorption bands around 612, 1146, 1404, 1649 and 3245 cm-1. The energy band gap was calculated for samples with different ratio and was found to be 4.77, 4.82, 4.86, 4.87 and 4.95 eV. The substitution was resulted in slight increased in the lattice constant and that sequentially may lead to the slightly decreased in the energy gap.展开更多
YAG phosphor doped with Yb (3+) for transparent ceramics was prepared by the co-precipitation method with urea used as precipitant. DTA-TG,XRD,SEM and IR spectrum analyzers were used to investigate the structure and m...YAG phosphor doped with Yb (3+) for transparent ceramics was prepared by the co-precipitation method with urea used as precipitant. DTA-TG,XRD,SEM and IR spectrum analyzers were used to investigate the structure and morphology of the precursor and the sintered poly-crystal. The results indicates that the weight loss is about 40% as the powder calcined at 1200 ℃,and well-crystallized YAG powder is obtained with particle size in the range of 100～150 nm. The SEM analysis of the fracture surface of the sintered body shows that the grain size is about 1～2 μm and the pore volume is very low. The ceramics body with favorite optical properties is obtained by sintering at 1700 ℃.展开更多
The precursors of La0.7Sr0.3-xCaxCo0.9Fe0.1O3-δ(LSCCF, x=0.05, 0.10, 0.15, 0.20) as the cathode materials for intermediate temperature solid oxide fuel cell (ITSOFC) were prepared by reverse titration co-precipitatio...The precursors of La0.7Sr0.3-xCaxCo0.9Fe0.1O3-δ(LSCCF, x=0.05, 0.10, 0.15, 0.20) as the cathode materials for intermediate temperature solid oxide fuel cell (ITSOFC) were prepared by reverse titration co-precipitation method with metal-nitrates as starting materials and mixed alkali (NaOH and Na2CO3) as a precipitating agent. The formation process of LSCCF from the precursors was monitored by TG-DSC, and the crystal structure and particles morphology of the precursors which were calcined at 600, 800, 1000 ℃ for 3 h were characterized using XRD, SEM technologies. Compared with the solid state reaction of constituent oxides, when the pH value of the precipitating solution was in the range of 9.1～9.5, the LSCCF powders from the precursors caclined at 800 ℃ for 3 h had high purity, homogeneous and single perovskite phase. The electrical conductivity of the LSCCF samples sintered at 1200 ℃ for 3 h, which was measured as a function of temperatures from 100 to 800 ℃ by DC four-probe method in air, decreased with x from 0.05 to 0.20. The value of electrical conductivity was almost equal because of Ca2+, Sr2+ co-dopant resulting in the "mix effect" while x=0.10 or 0.15. The electrical conductivity of all doped samples was higher than 100 S·cm-1 at intermediate temperatures from 500 to 800 ℃, and there was good compatibility between the LSCCF cathode and Ce0.8Sm0.2O2 electrolyte.展开更多
We investigated the impure phase problem and summarized its two formation mechanisms of YAG powders synthesized via the co-precipitation method.The ions loss problem caused by high concentration reaction solution in t...We investigated the impure phase problem and summarized its two formation mechanisms of YAG powders synthesized via the co-precipitation method.The ions loss problem caused by high concentration reaction solution in the titration process was emphatically studied,and the corresponding thermodynamic explanation was carried out.In addition,influence of powder crystallinity and its new qualitative and quantitative standards were studied.One reason of impure phase is the local nonuniform mixture of Y and Al elements in precursor,which easily causes intermediate phases during calcination and difficulty of high pure powders at low temperatures.The other reason is the precipitation dissolution during titration and then the Y^(3+)/Al^(3+) loss,caused by high concentration of reaction solution.The powder crystallinity can be promoted by increasing calcination temperature or holding time of precursor.Besides the routine XRD method,the TEM-EDX method should be also introduced to directly determine the quality of crystallinity.展开更多
Co-precipitation was used to prepare cerium oxide nano-particles. The effects of aging temperature and concentration of cobalt ion on the optical property, morphology, and particle size were investigated. The cerium o...Co-precipitation was used to prepare cerium oxide nano-particles. The effects of aging temperature and concentration of cobalt ion on the optical property, morphology, and particle size were investigated. The cerium oxide was prepared by adding ammonia solution into a mixed solution of cerium nitrate with cobalt nitrate solutions to obtain a large amount of precipitates and then aged further. Subsequently, the precipitates were kept in an oven for calcination keeping the temperature at 400?C for lasting 24 h. The average size of cerium oxide particles was obtained from the (111) peak in the X-ray diffraction pattern using the Scherrer equation. The crystal sizes obtained were found to be in the range of 11.82 - 13.47 nm. The results showed that the particle size decreased with an increase in the Co ion concentration and decreased with an increase in temperature. The SEM pictures show that the morphology for cerium oxide is granular and/or columnar. It can be seen from UV/Vis absorption spectrum that the maximum absorption peaks were in the range of 334 - 390 nm, depending on the operating conditions. The corresponding energy gaps were observed in the range of 3.18 - 3.71 eV. Subsequently, the Brus equation for the energy gap was discussed. Finally, particle size was correlated with the aging temperature and Co ion concentration.展开更多
The micron-sized Sr 2(P2O7):Ce,Tb green phosphors were prepared by being annealed at different temperatures with its precursors synthesized by co-precipitates of(NH4) 2HPO4 at ambient temperature. The phase structure,...The micron-sized Sr 2(P2O7):Ce,Tb green phosphors were prepared by being annealed at different temperatures with its precursors synthesized by co-precipitates of(NH4) 2HPO4 at ambient temperature. The phase structure, grain size, surface morphology, and luminescent properties of phosphors were investigated by X-ray diffraction, scanning electron microscope, transmission electron microscope, and fluorescence spectrum. The results show that the product of precursor annealed at 1,100 °C is Sr 2(P 2O7):Ce,Tb, which belongs to orthorhombic phase. The powder is spherical and the size distribution is in micron grade. The sample with the molar ratio of Sr/Tb/Ce of 100.0:0.4:0.6 shows the best fluorescence effect annealed at 1,100 °C for 3 h. The phosphors produce green fluorescence by being excitated with ultraviolet radiation of 254 nm wavelength, and the main emission peak is at 547 nm. The Sr 2(P2O7):Ce,Tb phosphors synthesized by co-precipitation method of precursors at ambient temperature is a kind of efficient green-emitting phosphors.展开更多
Co-precipitation is an important issue in chemical analysis, where it is often undesirable, but in some cases, it can be exploited. The Zn0.5Mn0.5−xLi2xFe2O4 nanomaterials (x = 0.0, 0.1, 0.2, 0.3 and 0.4) wa...Co-precipitation is an important issue in chemical analysis, where it is often undesirable, but in some cases, it can be exploited. The Zn0.5Mn0.5−xLi2xFe2O4 nanomaterials (x = 0.0, 0.1, 0.2, 0.3 and 0.4) was afforded by utilizing co-precipitation method. The structural and optical characteristics were analyzed for the samples employing X-ray diffraction (XRD), Fourier transforms infrared spectroscopy (FTIR) and Ultraviolet-visible spectrophotometer (UV-Vis). XRD revealed that the structure of certain nanoparticles is a cubic spinel with space group (Fd-3m) and crystallite size in the scale 124 - 150 nm. Lattice parameter was determined to increments with Li+1 and that may occur due to the larger ionic radius of the Li1+ ion. FTIR spectroscopy confirmed the form of spinel ferrite and explicated the properties of absorption bands approximately 593, 1111, 1385, 1640, 2922 and 3430. The energy band gap was estimated for all samples with diverse ratios and was observed in the range of 2.58 - 2.52 eV.展开更多
The uniform layered LiNi1/3Co1/3Mn1/3O2 cathode material for lithium ion batteries was prepared by using (Ni1/3Co1/3Mn1/3)C2O4 as precursor synthesized via oxalate co-precipitation method in air. The effects of calcin...The uniform layered LiNi1/3Co1/3Mn1/3O2 cathode material for lithium ion batteries was prepared by using (Ni1/3Co1/3Mn1/3)C2O4 as precursor synthesized via oxalate co-precipitation method in air. The effects of calcination temperature and time on the structure and electrochemical properties of the LiNi1/3Co1/3Mn1/3O2 were systemically studied. XRD results revealed that the optimal calcination conditions to prepare the layered LiNi1/3Co1/3Mn1/3O2 were 950°C for 15 h. Electrochemical measurement showed that the sample prepared under the such conditions has the highest initial discharge capacity of 160.8 mAh/g and the smallest irreversible capacity loss of 13.5% as well as stable cycling performance at a constant current density of 30 mA/g between 2.5 and 4.3 V versus Li at room temperature.展开更多
Mn-Zn ferrites (Mn1-xZnxFe2O4) with different compositions were prepared by the coprecipitation method, and the influences of such synthesis conditions as pH value, composition and volume ratio (R) of the mixed soluti...Mn-Zn ferrites (Mn1-xZnxFe2O4) with different compositions were prepared by the coprecipitation method, and the influences of such synthesis conditions as pH value, composition and volume ratio (R) of the mixed solution and NH4HCO3 solution on their microstructures and magnetic properties were discussed. The samples were characterized by X-ray diffraction (XRD) and magnetization measurement instrument. Lattice parameters and average crystalline size of the synthesized materials were calculated from the corresponding XRD patterns with the related software Jade.5. For samples of different pH values, only one phase was found when pH values were 7.0, 8.0 and 9.0. The sample with pH value of 7.0 exhibited the highest saturation magnetic induction, the lowest coercive force, and crystallized best. For samples of different R values with pH value of 7.0, only one phase was observed in all samples, and the sample with R value of 2.3 exhibited the highest saturation magnetic induction and the lowest coercive force. The composition has mainly afected the magnetic properties, and the saturation magnetic induction increases with the increase of the content of Zn (x), but decreases when x is beyond 0.6. The trend of coercive force is on the contrary. However, no magnetism is exhibited when the x value is up to 0.8.展开更多
基金financially supported by the Major State Basic Research Development Program of China(973 Program)(No.2012CBA01205)the National Natural Science Foundation of China(No.51274060)。
文摘Since ultraviolet(UV)light,as well as blue light,which is part of visible light,is harmful to skin,samarium-cerium compounds containing Sm_(2)O_(2)S were synthesized by co-precipitation method.This kind of compounds blocks not only UV light,but also blue light.The minimum values of average transmittance(360-450 nm)and band gap of samarium-cerium compounds were 8.90%and 2.76 eV,respectively,which were less than 13.96%and 3.01 eV of CeO_(2).Elemental analysis(EA),X-ray diffraction(XRD),Fourier transformation infrared(FTIR),and Raman spectra determined that the samples contained Ce_(4)O_(7),Sm_(2)O_(2)S,Sm_(2)O_(3),and Sm_(2)O_(2)SO_(4).The microstructure of samples was analyzed by scanning and transmission electron microscopies(SEM and TEM).X-ray photoelectron spectrum(XPS)showed that cerium had Ce^(3+)and Ce^(4+) valence states,and oxygen was divided into lattice oxygen and oxygen vacancy,which was the direct cause of the decrease of average transmittance and band gap.
文摘To preserve the environment for civilization,we should remove the pollutants like toxic dyes by friendly and cost efficacious method.In this study,the effect of surfactants or mixed surfactants on physicochemical,optical and adsorption properties of ternary mixed oxide CeO_(2)-ZrO_(2)-Al_(2) O_3(CZA) are investigated.The ternary mixed oxide CZA was prepared by surfactants or mixed surfactants assisted ultrasonic coprecipitation method.The physicochemical and optical properties are estimated by different techniques like XRD,TEM,EDX,FTIR,S_(BET) and UV-Vis/DR.The CZA_T and CZA_C have hybrid shapes and high surface area.The adsorption properties of ternary mixed oxides adsorbents were characterized by sono-removing anionic dyes such as Congo red(CR) and Remazol red RB-133(RR).The different factors like contact time,different dye concentrations and temperatures also studied.The kinetics and isotherms applications showed that,the adsorption process was followed pseudo second order kinetics and the Freundlich isotherm model.Also,the adsorption is spontaneous and endothermic process through the thermodynamic study.Finally,the results showed that the ternary mixed oxide nano-adsorbent(CeO_(2)-ZrO_(2)-Al_(2) O_3) is promising and functional materials for anionic dye sweep from wastewater.
基金supported by C1 Gas Refinery Program through the National Research Foundation of Korea(NRF)funded by the Ministry of Science,ICT&Future Planning(2015M3D3A1A01064908)
文摘Oxidative coupling of methane(OCM) was conducted over LaAlO3X catalysts that were prepared by a coprecipitation method using different co-precipitation pH values(X = 6–10). The aim is to investigate the effect of p H values on the catalytic activity of La AlO3 catalysts in this reaction. The results showed that the co-precipitation pH value affected greatly on the formation of chemical species of precipitate precursors in the co-precipitation step, leading to different phases of the finally obtained LaAlO3 catalysts.When the co-precipitation pH value increased up to 8, the lanthanum-related phases such as La2 O3 and La(OH)3 were gradually formed as by-products, preventing the formation of LaAlO3 perovskite crystalline structure and facilitating the formation of oxygen vacancies on catalyst surface. However, at pH value of9 or higher, the lanthanum content in the precipitate precursor was increased greatly. Not LaAlO3 perovskite but lanthanum-related phases were developed as main phases, reducing their catalytic activities in this reaction. Among LaAlO3 catalysts, the one prepared at pH = 8 showed the highest C2 yield due to its well-developed oxygen vacancies and electrophilic lattice oxygen. Therefore, the co-precipitation pH value strongly affected the LaAlO3 catalyst activity in OCM reaction. A precious pH control should be required to prepare various perovskite catalysts for the OCM.
基金Rare Earth Special Project supported by National Development and Reform Commission
文摘The synthesis of precursor of green phosphors, LaPO4:Ce, Tb, by means of co-precipitation with cocurrent flow feed was studied. The effects of the reaction temperature, the kind and concentration of the acid in the bottom water, and the charging rate on the physical properties, such as particle size, were investigated. It is found that the particle size of the powder is controllable by adjusting acidity in bottom water and charging rate. The powder with diameter size of 3 to 5 μm was obtained. Its XRD and SEM were analyzed. XRD patterns of the as-prepared green phosphor powders display the typical peaks of CePO4. SEM shows that the morphology of powders is ball-shaped.
基金NSFC (20471055)Henan Outstanding Youth Science Fund (0612002700)
文摘SnO2 doped with Y were prepared by co-precipitation method and tested in lithium-ion cells. The structure and morphology of the materials were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). XRD patterns presented that the all the as-prepared materials had tetragonal rutile structure but a second phase (Y2O3) was observed when Y content reached 4%. TEM micrograph indicated that Y doped SnO2 had a small particle size ranging from 20 to 25 nm. The electrochemical properties for an anode active material in lithium-ion batteries were investigated at room temperature, including the observed capacity involved in the first-discharge and the reversible capacity values during subsequent charge-discharge cycles. The as-prepared Y-doped SnO2 exhibited promising electrochemical properties as anodes for lithium-ion batteries.
文摘Tetraethylenepentamine(C8H23N5,TEPA) has been used as a novel precipitant to synthesize yttrium aluminum garnet(Y3Al5O12,YAG) precursor from a mixed solution of aluminum and yttrium nitrates via a normal-strike co-precipitation method without controlling the pH value during precipitation process.The original precursor was analyzed by thermogravimetry/differential scanning calorimetry(TG/DSC).The evolution of phase composition and micro-structure of the as-synthesized YAG powders were characterized by X-ray diffraction(XRD),Fourier transform infrared(FT-IR) spectroscopy and transmission electron microscopy(TEM).Compositionally pure YAG nanostructured powders were directly obtained by calcination of the precursor at 900 ℃ without the formation of any intermediate phases.The average particle size determined from TEM micrograph for the powder obtained at 1000 ℃ was approximately 50 nm.
基金Project(2007CB613607)supported by National Basic Research Program of China
文摘LiNi0.8Co0.1Mn0.1O2 was prepared by a chloride co-precipitation method and characterized by thermogravimetric analysis, X-ray diffractometry with Rietveld refinement,electron scanning microscopy and electrochemical measurements.Effects of lithium ion content and sintering temperature on physical and electrochemical performance of LiNi0.8Co0.1Mn0.1O2 were also investigated. The results show that the sample synthesized at 750℃with 105%lithium content has fine particle sizes around 200 nm and homogenous sizes distribution.The initial discharge capacity for the powder is 184 mA·h/g between 2.7 and 4.3 V at 0.1C and room temperature.
基金partially supported by the National Key Research and Development Program of China (2016YFB0100203)the National Natural Science Foundation of China (21673116,21633003)+1 种基金the Natural Science Foundation of Jiangsu Province of China (BK20160068)PAPD of Jiangsu Higher Education Institutions
文摘LiNi_(0.8)Co_(0.15)Al_(0.05)O_2(NCA) material is successfully synthesized with a modified co-precipitation method,in which NH_3·H_2O and EDTA are used as two chelating agents. The obtained LiNi_(0.8)Co_(0.15)Al_(0.05)O_2 material has well-defined layered structure and uniform element distribution, which reveals an enhanced electrochemical performance with a capacity retention of 97.9% after 100 cycles at 0.2 C, and reduced thermal runaway from the isothermal calorimetry test. In situ X-ray diffraction(XRD) was employed to capture the structural changes during the charge–discharge process. The reversible evolutions of lattice parameters(a, b, c, and V) further verify the structural stability.
基金Heilongjiang Province Education Office (10553013)the Open Laboratory of HUST
文摘The M3-3x(PO4)2∶2xCe, xTb(M=Mg, Ca, Sr, Ba) phosphors were prepared by coprecipitation in this paper. Their phase structures, morphologies and luminescent properties were investigated by X-ray diffractometer, field emission scanning electron microscopy and fluorospectrophotometer. The results indicate that the Ce3+ and Tb3+ enteres the host lattice because the XRD patterns of alkaline earth phosphate show no impurity phase, the SEM shows the spherical particles with an average size about 1 μm. The emission and excitation spectra are similar to rare earth phosphate. Concentration quenching of the Sr3(PO4)2∶Ce, Tb emission intensity was not observed even when the Tb3+ increases to 0.05, while the maximum emission intensity appears when x=0.04 in M3-3x(PO4)2∶2xCe, xTb(M=Ca, Ba) emission spectrum.
基金the National Natural Science Foundation of China (No. 51602126)the National Key Research and Development Plan of China (No. 2016YFB0303505)+1 种基金China and University of Jinan Postdoctoral Science Foundation (No. 2017M622118 and XBH1716)the 111 Project of International Corporation on Advanced Cement-based Materials (D17001).
文摘The long afterglow fluorescent material of M1-3xAl2O4:Eu2+ x/Dy3+2x(M2+= Sr2+, Ca2+ and Ba2+) phosphors are successfully synthesized by calcining precursor obtained via co-precipitation method at 1300oC for 4 h with reducing atmosphere (20% H2 and 80% N2). The phase evolution, morphology and afterglow fluorescent properties are systematically studied by the various instruments of XRD, FE-SEM, PLE/PL spectroscopy and fluorescence decay analysis. The PL spectra shows that the Sr1-3xAl2O4:Eu2+x/Dy3+ 2x phosphors display vivid green emission at s519 nm (4f65d1!4f7 transition of Eu2+) with monitoring of the maximum excitation wavelength at s334 nm (8S7=2!6IJ transition of Eu2+), among which the optimal concentration of Eu2+ and Dy3+ is 15 at.% and 30 at.%, respectively. The color coordinates and temperature of Sr1-3xAl2O4:Eu2+ x/Dy3+ 2x phosphors are approximately at (s0.27, s0.57) and s6700 K, respectively. On the above basis, the M0:55Al2O4:Eu2+ 0:15/Dy3+ 0:3 (M2+= Ca2+ and Ba2+) phosphors is obtained by the same method. The PL spectra of these phosphors shows the strongest blue emission at s440 nm and cyan emission at s499 nm under s334 nm wavelength excitation, respectively, which are blue shifted comparing to Sr1??3xAl2O4:Eu2+ x/Dy3+ 2x phosphors. The color coordinates and temperatures of M0:55Al2O4:Eu2+ 0:15/Dy3+ 0:3 (M2+= Ca2+ and Ba2+) phosphors are approximately at (s0.18, s0.09), s2000 K and (s0.18, s0.42), s11600 K, respectively. In this work, long afterglow materials of green, blue and cyan aluminates phosphors with excellent properties have been prepared, in order to obtain wide application in the field of night automatic lighting and display.
文摘In this work, the Mg1-x Znx Fe2 O4 Nanoferrites (where x = 0.0, 0.2, 0.4, 0.6 and 0.8) was synthesized using co-precipitation method. The investigation of structural and optical properties was carried out for the synthesized samples using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and Ultraviolet visible spectrophotometer (UV-Vis). XRD revealed that the structure of these nanoparticles is spinel with space group Fd3m and crystallite size lies in the range 21.0 - 42.8 nm. Lattice parameter was found to increases with Zn concentration and this may be due to the larger ionic radius of the Zn2+?ion. FTIR spectroscopy confirmed the formation of spinel ferrite and showed the characteristics absorption bands around 612, 1146, 1404, 1649 and 3245 cm-1. The energy band gap was calculated for samples with different ratio and was found to be 4.77, 4.82, 4.86, 4.87 and 4.95 eV. The substitution was resulted in slight increased in the lattice constant and that sequentially may lead to the slightly decreased in the energy gap.
文摘YAG phosphor doped with Yb (3+) for transparent ceramics was prepared by the co-precipitation method with urea used as precipitant. DTA-TG,XRD,SEM and IR spectrum analyzers were used to investigate the structure and morphology of the precursor and the sintered poly-crystal. The results indicates that the weight loss is about 40% as the powder calcined at 1200 ℃,and well-crystallized YAG powder is obtained with particle size in the range of 100～150 nm. The SEM analysis of the fracture surface of the sintered body shows that the grain size is about 1～2 μm and the pore volume is very low. The ceramics body with favorite optical properties is obtained by sintering at 1700 ℃.
基金the National High-Tech Development Plan (2006AA05Z417)the Natural Science Foundation of Lia-oning Province (20062145)the Education department of Liaoning Province (05L073)
文摘The precursors of La0.7Sr0.3-xCaxCo0.9Fe0.1O3-δ(LSCCF, x=0.05, 0.10, 0.15, 0.20) as the cathode materials for intermediate temperature solid oxide fuel cell (ITSOFC) were prepared by reverse titration co-precipitation method with metal-nitrates as starting materials and mixed alkali (NaOH and Na2CO3) as a precipitating agent. The formation process of LSCCF from the precursors was monitored by TG-DSC, and the crystal structure and particles morphology of the precursors which were calcined at 600, 800, 1000 ℃ for 3 h were characterized using XRD, SEM technologies. Compared with the solid state reaction of constituent oxides, when the pH value of the precipitating solution was in the range of 9.1～9.5, the LSCCF powders from the precursors caclined at 800 ℃ for 3 h had high purity, homogeneous and single perovskite phase. The electrical conductivity of the LSCCF samples sintered at 1200 ℃ for 3 h, which was measured as a function of temperatures from 100 to 800 ℃ by DC four-probe method in air, decreased with x from 0.05 to 0.20. The value of electrical conductivity was almost equal because of Ca2+, Sr2+ co-dopant resulting in the "mix effect" while x=0.10 or 0.15. The electrical conductivity of all doped samples was higher than 100 S·cm-1 at intermediate temperatures from 500 to 800 ℃, and there was good compatibility between the LSCCF cathode and Ce0.8Sm0.2O2 electrolyte.
基金Funded by the Science Fund of Educational Department of Henan Province of China (No. 19A430002)。
文摘We investigated the impure phase problem and summarized its two formation mechanisms of YAG powders synthesized via the co-precipitation method.The ions loss problem caused by high concentration reaction solution in the titration process was emphatically studied,and the corresponding thermodynamic explanation was carried out.In addition,influence of powder crystallinity and its new qualitative and quantitative standards were studied.One reason of impure phase is the local nonuniform mixture of Y and Al elements in precursor,which easily causes intermediate phases during calcination and difficulty of high pure powders at low temperatures.The other reason is the precipitation dissolution during titration and then the Y^(3+)/Al^(3+) loss,caused by high concentration of reaction solution.The powder crystallinity can be promoted by increasing calcination temperature or holding time of precursor.Besides the routine XRD method,the TEM-EDX method should be also introduced to directly determine the quality of crystallinity.
文摘Co-precipitation was used to prepare cerium oxide nano-particles. The effects of aging temperature and concentration of cobalt ion on the optical property, morphology, and particle size were investigated. The cerium oxide was prepared by adding ammonia solution into a mixed solution of cerium nitrate with cobalt nitrate solutions to obtain a large amount of precipitates and then aged further. Subsequently, the precipitates were kept in an oven for calcination keeping the temperature at 400?C for lasting 24 h. The average size of cerium oxide particles was obtained from the (111) peak in the X-ray diffraction pattern using the Scherrer equation. The crystal sizes obtained were found to be in the range of 11.82 - 13.47 nm. The results showed that the particle size decreased with an increase in the Co ion concentration and decreased with an increase in temperature. The SEM pictures show that the morphology for cerium oxide is granular and/or columnar. It can be seen from UV/Vis absorption spectrum that the maximum absorption peaks were in the range of 334 - 390 nm, depending on the operating conditions. The corresponding energy gaps were observed in the range of 3.18 - 3.71 eV. Subsequently, the Brus equation for the energy gap was discussed. Finally, particle size was correlated with the aging temperature and Co ion concentration.
基金financially supported by the National Natural Science Foundation of China(No.21273060)the Program for New Century Excellent Talents in Heilongjiang Provincial University(No.1251-NCET-014)
文摘The micron-sized Sr 2(P2O7):Ce,Tb green phosphors were prepared by being annealed at different temperatures with its precursors synthesized by co-precipitates of(NH4) 2HPO4 at ambient temperature. The phase structure, grain size, surface morphology, and luminescent properties of phosphors were investigated by X-ray diffraction, scanning electron microscope, transmission electron microscope, and fluorescence spectrum. The results show that the product of precursor annealed at 1,100 °C is Sr 2(P 2O7):Ce,Tb, which belongs to orthorhombic phase. The powder is spherical and the size distribution is in micron grade. The sample with the molar ratio of Sr/Tb/Ce of 100.0:0.4:0.6 shows the best fluorescence effect annealed at 1,100 °C for 3 h. The phosphors produce green fluorescence by being excitated with ultraviolet radiation of 254 nm wavelength, and the main emission peak is at 547 nm. The Sr 2(P2O7):Ce,Tb phosphors synthesized by co-precipitation method of precursors at ambient temperature is a kind of efficient green-emitting phosphors.
文摘Co-precipitation is an important issue in chemical analysis, where it is often undesirable, but in some cases, it can be exploited. The Zn0.5Mn0.5−xLi2xFe2O4 nanomaterials (x = 0.0, 0.1, 0.2, 0.3 and 0.4) was afforded by utilizing co-precipitation method. The structural and optical characteristics were analyzed for the samples employing X-ray diffraction (XRD), Fourier transforms infrared spectroscopy (FTIR) and Ultraviolet-visible spectrophotometer (UV-Vis). XRD revealed that the structure of certain nanoparticles is a cubic spinel with space group (Fd-3m) and crystallite size in the scale 124 - 150 nm. Lattice parameter was determined to increments with Li+1 and that may occur due to the larger ionic radius of the Li1+ ion. FTIR spectroscopy confirmed the form of spinel ferrite and explicated the properties of absorption bands approximately 593, 1111, 1385, 1640, 2922 and 3430. The energy band gap was estimated for all samples with diverse ratios and was observed in the range of 2.58 - 2.52 eV.
基金financially supported by the Natural Science Foundation of Guangxi Province, China (No. GKZ0832256)
文摘The uniform layered LiNi1/3Co1/3Mn1/3O2 cathode material for lithium ion batteries was prepared by using (Ni1/3Co1/3Mn1/3)C2O4 as precursor synthesized via oxalate co-precipitation method in air. The effects of calcination temperature and time on the structure and electrochemical properties of the LiNi1/3Co1/3Mn1/3O2 were systemically studied. XRD results revealed that the optimal calcination conditions to prepare the layered LiNi1/3Co1/3Mn1/3O2 were 950°C for 15 h. Electrochemical measurement showed that the sample prepared under the such conditions has the highest initial discharge capacity of 160.8 mAh/g and the smallest irreversible capacity loss of 13.5% as well as stable cycling performance at a constant current density of 30 mA/g between 2.5 and 4.3 V versus Li at room temperature.
基金Funded by the Basic Key Project in Shanghai City (06JC14033)the Key Discipline Construction Fund in Shanghai City (P1304)
文摘Mn-Zn ferrites (Mn1-xZnxFe2O4) with different compositions were prepared by the coprecipitation method, and the influences of such synthesis conditions as pH value, composition and volume ratio (R) of the mixed solution and NH4HCO3 solution on their microstructures and magnetic properties were discussed. The samples were characterized by X-ray diffraction (XRD) and magnetization measurement instrument. Lattice parameters and average crystalline size of the synthesized materials were calculated from the corresponding XRD patterns with the related software Jade.5. For samples of different pH values, only one phase was found when pH values were 7.0, 8.0 and 9.0. The sample with pH value of 7.0 exhibited the highest saturation magnetic induction, the lowest coercive force, and crystallized best. For samples of different R values with pH value of 7.0, only one phase was observed in all samples, and the sample with R value of 2.3 exhibited the highest saturation magnetic induction and the lowest coercive force. The composition has mainly afected the magnetic properties, and the saturation magnetic induction increases with the increase of the content of Zn (x), but decreases when x is beyond 0.6. The trend of coercive force is on the contrary. However, no magnetism is exhibited when the x value is up to 0.8.
