Hydrothermal Synthesis and Characterization of Perovskite Oxide AgTaO_3

The perovskite-type AgTaO3 crystals were prepared by mild hydrothermal method and determined by powder X-ray diffraction. Rietveld refinement indicates that AgTaO3 crystallized in an orthorhombic system with the space group Pcmn. The lattice parameters are a=5.5822（1） nm, b=7.8522（2） nm and c=5.5347（1） nm, with α=β=γ= 90.0o. The compound was characterized by scanning electron microscopy（SEM）, X-ray photoelectron spectroscopy （XPS）, high resolution transmission electron microscopy（HR-TEM） and UV-Vis diffuse reflectance spectrometry （UV-Vis DRS）. The photocatalytic activity of AgTaO3 powder was evaluated by the degradation of Congo red under UV-light irradiation. The result shows that the titled compound has a high photocatalytic activity at room temperature and potential application in photocatalysis.

Methane Oxidation to Synthesis Gas Using Lattice Oxygen of La_(1-x)Sr_xMO_(3-λ)(M =Fe,Mn) Perovskite Oxides Instead of Molecular Oxygen

In this paper, the partial oxidation of methane to synthesis gas using lattice oxygen of La1- SrxMO3-λ (M=Fe, x Mn) perovskite oxides instead of molecular oxygen was investigated. The redox circulation between 11% O2/Ar flow and 11% CH4/He flow at 900℃ shows that methane can be oxidized to CO and H2 with a selectivity of over 90.7% using the lattice oxygen of La1- SrxFeO3-λ (x≤0.2) perovskite oxides in an appropriate reaction condition, while the lost lattice x oxygen can be supplemented by air re-oxidation. It is viable for the lattice oxygen of La1- SrxFeO3-λ (x≤0.2) perovskite x oxides instead of molecular oxygen to react with methane to synthesis gas in the redox mode.

Hydrothermal Synthesis and Structure of [CH3NH3]2[(VⅣO)2(VⅤO4)2]:A New Layered Mixed-valence Vanadium Oxide Incorporated with Organic Cations

A new layered mixed valence vanadium oxide, [CH 3NH 3] 2[(V ⅣO) 2(V ⅤO 4) 2], which contains interlamellar organic cations was prepared under hydrothermal conditions and its single crystal structure was determined. It crystallizes in a triclinic system with space group P 1, a =0 625 59(8) nm, b =0 639 84(9) nm, c =0 747 19(10) nm, α =78 718(2)°, β =80 099(2)°, γ =77 100(2). The compound contains mixed valence V 4+ /V 5+ vanadium oxide layers constructed from VO 4 tetrahedra, pairs of edge sharing VO 5 square pyramid and methylamine with protonated organic amines occupying the interlayer space.

Hydrothermal synthesis of vanadium oxide nanotubes by a facile route

Vanadium oxide nanotubes were synthesized by hydrothermal treatment from V2O5·nH2O sols as precursor and dodecylamine as structure-directing template. The morphology and structure of the nanotubes were characterized by SEM, TEM, XRD, TG-DTA and FTIR. The experimental results reveal that the duration of the hydrothermal treatment is of importance for obtaining VOx-NTs which have a layered structure. TG-DTA study indicates that V5+ cations in nanotubes are partially reduced to V4+ cations. The results from FTIR spectra indicate the difference in V-O vibrations between before and after hydrothermal treatment. From the results, it suggests that during hydrothermal treatment, the rearrangement of the vanadium oxide structure leads to the formation of VOx nanotubes from lamellar structure because of the presence of V4+ species.

Hydrothermal Synthesis and Characterization of Double Perovskites RSrMnFeO_6(R=La,Pr,Nd,Sm)

A series of double perovskites RSrMnFeO6（R=La, Pr, Nd, Sm） was synthesized under mild hydrothermal conditions. Crystal growths of the samples were sensitive to alkalinity, temperature, filling fraction, and composition of initial reaction mixture. The desired series of compounds belongs to the class of AA＇BB＇O6 perovskites with a random distribution of Mn and Fe atoms over the B-cation sub-lattice. Their structures show the distorted orthorhombic symmetry with space group Pnma. The shapes and sizes of the crystals were analyzed on a Rigaku JSM-6700F by scanning electron microscopy. Analysis done by XPS, Mossbauer spectroscopy and iodometric titration reveals that Mn and Fe ions have ＋4 and ＋3 oxidation states, respectively.

Hydrothermal Synthesis and Dielectric Characterization of a Double Perovskite Ba_2FeSbO_6

A double perovskite oxide Ba2FeSbO6 was hydrothermally synthesized and structurally characterized by X-ray diffraction. This solid compound shows a single phase and has a trigonal structure with space group R3 ？m and cell parameters of a=0.57261 nm and c=1.40244 nm. The dielectric constant and loss tangent of the solid measured in a frequency range from 100 Hz to 1 MHz at temperatures from 313 K to 513 K reveal a relaxation process of frequency dependence of the real part（ε＇） of dielectric constant and dielectric loss tan？. The frequency dependence of electrical property led to the framework of conductivity and electric modulus formalisms. The scaling behavior of imaginary part of electric modulus suggests that the relaxation describes the single mechanism at various temperatures. The variation tendency of the alternating current impedance indicates the thermally activated conduction process follows Jonsche＇s power law.

Hydrothermal Synthesis, Crystal Structure and Fluorescent Property of a Cd(Ⅱ) Complex Based on Biimidazole and Isonicotinate-N-oxide

A new complex [Cd（H2biim）2（H2O）2]·（ino）2·4H2O （H2biim = 2,2＇-biimidazole, ino = isonicotinate-N-oxide） has been prepared and characterized by single-crystal X-ray diffraction analysis, IR and fluorescence spectra analysis. The crystal is of triclinic system, space group P1 with a = 7.5380（6）, b = 8.0402（7）, c = 13.5094（11） , α = 104.269（1）, β = 93.604（1）, γ = 98.349（1）°, V = 780.93（11） 3, Mr = 765.00, Dc = 1.627 g/cm3, F（000） = 390, μ = 0.776 mm-1 and Z = 1. The final R = 0.0322 and wR = 0.0825 for 7038 observed reflections with I 2σ（I） and R = 0.0341 and wR = 0.0832 for all data. The title complex exhibits an infinite chain-like structure through bridging isonicotinate-N-oxide. Strong interchain hydrogen bonds between isonicotinate-N-oxide and H2biim result in the robust 3-D supramolecular architecture. Moreover, the complex shows strong photoluminescence with emission maximum at λ = 401 nm upon λex = 330 nm.

Hydrothermal Synthesis and Characterization of a Novel Zirconium Oxide and Its Application as an Ion Exchanger

A novel hydrothermal zirconium oxide (ZrO2) ion exchange material was successfully synthesized by hydrothermal technique. The material has been characterized using different tools such as thermal analysis (DTA-TGA), FT-IR and X-ray diffraction studies. The results show that the prepared ZrO2 is pure and with a unique shape and it belongs to the hexagonal system. Chemical resistively of the material for various media such as, water, acids and bases have been assessed. The capacity of ZrO2 ion exchanger for Na+, Cu2+, Ni2+ and Zn2+ ions at natural pH has been determined. The effect of heating treatment for ZrO2 on ion exchange capacity was studied. The sorption/ion exchange behaviour of Cu2+, Ni2+ and Zn2+ ions towards ZrO2 in dif-ferent pH media has been investigated. The distribution coefficients and separation factors were determined. Finally, Freundlich isotherms for Cu2+, Zn2+ and Ni2+ ions on hydrothermal ZrO2 ion exchanger were inves-tigated and the Freundlich isotherm constants were conduced.

Comparison of LaFeO_3,La_(0.8)Sr_(0.2)FeO_3,and La_(0.8)Sr_(0.2)Fe_(0.9)CO_(0.1)O_3 perovskite oxides as oxygen carrier for partial oxidation of methane

Comparison of LaFeO3, La0.8Sr0.2FeO3, and La0.8Sr0.2Fe0.9CO0.1O3 perovskite oxides as oxygen carrier for partial oxidation of methane in the absence of gaseous oxygen was investigated by continuous flow reaction and sequential redox reaction, Methane was oxidized to syngas with high selectivity by oxygen species of perovskite oxides in the absence of gaseous oxygen. The sequential redox reaction revealed that the structural stability and continuous oxygen supply in redox reaction decreased over La0.8Sr0.2Fe0.9Co0. 1O3 oxide, while LaFeO3 and La0.8Sr0.2FeO3 exhibited excellent structural stability and continuous oxygen supply.

High quality Sb-doped SnO2 electrodes with high oxygen evolution potential prepared by in situ hydrothermal synthesis method

High quality Sb-doped SnO2 electrode, with high oxygen evolution potential of 3.0 V, was successfully synthesized on the Ti substrates by in situ hydrothermal synthesis method.

Hydrothermal Synthesis and Structure of a Mixed-valence Polyoxotungstate Decorated by Copper(I) Coordination Group, [Cu(en)_2H_2O]_2[{Cu(en)_2}HPW_(12)O_(40)]·2H_2O

A complex [Cu(en)2H2O]2[{Cu(en)2}HPW12O40]?2H2O (C12H57Cu3N12O44PW12, Mr = 3501.49) has been synthesized under hydrothermal conditions and its crystal structure was determined by X-ray diffraction. It crystallizes in the orthorhombic system, space group Pbca with a = 21.680(4), b = 20.680(4), c = 26.120(5) ?, V = 11711(4) ?3, Dc = 3.972 g/cm3, Z = 8, μ(MoKa) = 24.661 mm?1, F(000) = 12440, the final R = 0.0527 and wR = 0.1416 for 11527 observed reflec- tions with I > 2σ(I). The crystal structure is composed of [{Cu(en)2}HPW12O40]2? anions, discrete [Cu(en)2H2O]+ complex cations and crystal water molecules, which are held together into a three- dimensional network through hydrogen-bonding interactions. The anionic [{Cu(en)2}HPW12O40]2? is formed by the mixed valance {HPWVI11WVO40}3? Keggin unit covalently linked by a {Cu(en)2}+ group.

Hydrothermal Synthesis and Thermal Stability of Natural Mineral Lindgrenite

A natural mineral, lindgrenite Cu3 （ MoO4 ）2 （ OH）2, was synthesized from a mixture of sodium molybdate, copper sulfate, and morpholine in water under autogenous pressure at 170 ℃. The crystal structure of the mineral was determined and the final refinement for 791 observed reflections with Ⅰ 〉 2σ（Ⅰ） gave R1 = 0. 0205 and wR2 = 0. 0496. The thermal stability of the mineral was investigated by using TG-DTA and variable-temperature in situ X-ray diffraction（XRD） techniques. The crystalline Cu3Mo2O9 was obtained when the mineral underwent thermal dehydration at a temperature ranging from 300 to 400 ℃, and the mixture of MoO3 and CuO was formed through decomposition of Cu3Mo2O9 at a temperature ranging from 650 to 700 ℃. Therefore, the structure of the mineral was thermally unstable at above 300 ℃, suggesting that Lindgrenite was likely formed via the hydrothermal route occurring in the nature.

Chemical synthesis of zinc oxide nanorods for enhanced hydrogen gas sensing

Zinc oxide （ZnO） nanorods are prepared using equimolar solution of zinc nitrate （（Zn（NO3）2） and hexamethylenete- tramine （C6HleN4） by the hydrothermal technique at 80 ~C for 12 h. Epitaxial growth is explored by X-ray diffraction （XRD） patterns, revealing that the ZnO nanorods have a hexagonal （wurtzite） structure. Absorption spectra of ZnO are measured by UV-visible spectrometer. The surface morphology is investigated by field emission scanning electron mi- croscopy （FESEM）. The synthesized ZnO nanorods are used for detecting the 150 ~C hydrogen gas with a concentration over 1000 ppm. The obtained results show a reversible response. The influence of operating temperature on hydrogen gas detecting characteristic of ZnO nanorods is also investigated.

Hydrothermal Synthesis and Characterization of a Novel Low Temperature Phase K_4InTi_4O_(11) (OH)·5H_2O

A novel low temperature phase K4InTi4O11 (OH)'5H2O was prepared by thehydrothermal method. The product was characterized by XRD, SEM, TG, DTA and ICP. Theresults indicated that the product crystallizes in a cubic system with a cell parameter a=0.7868 um.Moreover, it ecomposes to an amorphous phase after calcining at 340 ℃.

Microwave-assisted hydrothermal synthesis of copper oxide-based gas-sensitive nanostructures

Hydrothermal methods are widely used in chemical synthesis of target products with specific morphology and nanostructure.Those methods are very efficient for the preparation of well-controlled structures but the reaction time is usually long.The assistance of microwave makes the reaction system heat up faster,more uniformly and reactions are accelerated,it also can be utilized to change the morphology or structure of materials,which improves the physic-chemical properties of synthesized products and influences its gas-sensing performance.Copper oxide(CuO)is widely applied in semiconductor gas sensors because of its good reactivity and stability.This review article briefly introduces the principle,mechanism and recent development of CuO nanostructures obtained by microwave-as sis ted hydrothermal synthesis(MWHS)process.It also discussed the relation between endopathic factors of material and its gas-sensitive performance.The technical challenges and prospective solutions for highperformance CuO-based gas-sensitive materials with unique nanostructure are proposed.It is pointed out that the hierarchical CuO-based nanostructures and their composite materials prepared by MWHS process are efficacious methods to improve the gas-sensitive performance of the materials.On the basis of the morphology,the materials are divided into nanorods,nanoflowers,nanosheets,nanospheres and other nanostructures.The influence of microwave parameters on the properties of synthetic products is analyzed.The influence followed by metal element loading on the structure and properties of CuO-based materials by MWHS process is further discussed.Then this review summarizes the research progress of graphene-CuO and metal oxide-CuO composites prepared by MWHS process in recent years.

Effect of rare earth elements(La,Y,Pr)in multi-element composite perovskite oxide supports for ammonia synthesis

A series of BaCe0_(3)modified with different rare earth elements(La,Y,Pr)were synthesized by coprecipitation and calcination and the effect of rare earth elements for catalytic ammonia synthesis under mild conditions was studied.The ammonia synthesis performance tests show that 2.5%Ru/BaCe_(0.9)La_(0.1)O_(3-δ)catalyst(All the percentages of Ru in this article are in mass fraction)exhibits the highest ammonia synthesis rate(34 mmol/(g·h))at 3 MPa,450℃,and no sign of deactivation after 100 h of reaction.H_(2)-TPR and XPS analyses indicate that the introduction of La increases the amount of oxygen vacancies of the catalyst,which is beneficial to increasing the electron density of Ru surface.HRTEM analysis shows that the Ru particle size is reduced greatly after La is introduced,which facilitates the catalyst generating more Bs-type sites(active sites of Ru species for N=N dissociation).CO_(2)-TPD analysis indicates that BaCe_(0.9)La_(0.1)O_(3-δ)has stronger basicity,which promotes electrons transfer from support to Ru.This work provides an effective method for design and synthesis of Ru-based multi-element composite perovskite oxide catalysts.

A facile one-pot hydrothermal synthesis as an efficient method to modulate the potassium content of cryptomelane and its effects on the redox and catalytic properties

Cryptomelane has been widely applied as catalyst in oxidation reactions due to its excellent redox properties and low cost.Here,a novel one-pot hydrothermal synthesis using a potassium permanganate aqueous solution as precursor and ethanol as reducing agent has successfully been developed to obtain cryptomelane nano-oxides.This synthetic route makes it possible to control the amount of potassium incorporated into the structure of the cryptomelane by selecting the appropriate synthesis temperature and ethanol initial concentration.Taking advantage of this approach,the effect of potassium concentration on the structural stability and reducibility of the cryptomelane,which are poorly discussed in the literature,has been studied.We have observed that samples with low content of potassium(~11%)show high conversions of CO to CO2 especially at low temperatures.The lower activity of the samples with high K contents(~16%)can be ascribed to the beneficial effect of K on the structural stability of cryptomelane in detriment of labile oxygen on cryptomelane surface.

Crystal structure and catalytic performance for direst oxidation of propylene to acrylic acid of MoVTeNbO_(x) prepared by high-pressure hydrothermal synthesis

MoVTeNbO_(x) catalysts were prepared through a high-pressure hydrothermal method,in which the crystalline structure and properties of the catalysts were tuned by varying the system pressure(0-12.0 MPa).Results showed that the system pressure had a significant influence on the structure and catalytic performance of MoVTeNbO_(x).Under 3.0 MPa,MoVTeNbO_(x) prepared possessed the highest content of M1 phase(90.6%)and V5+content(60.7%),exhibiting a uniform short and thick needle-like morphology.Also,it showed excellent selectivity(79.1%)and yield(52.8%)to acrylic acid at the catalytic temperature of 380℃.However,under 4.4 and 11.6 MPa,the characteristic peaks of M1 shifted to a certain extent and the morphology changed from short and thick to slender.As a result,the V5+content of M1(001)plane decreased,resulting in a remarkable decline of the selectivity to acrylic acid.Moreover,DFT simulation results showed that the anti-bond orbital energy of V-O bond is the highest under 3.0 MPa,while further increase of pressure leads to obvious extrusion between atoms in the internal structure of MoVTeNbO_(x).Moreover,it was clear that the lower the anti-bond orbital energy of V-O bond,the lower the selectivity to acrylic acid.

Impermeability Research of Autoclaved Propylene Oxide Sludge Shell-aggregate Concrete

We aimed to reuse the propylene oxide sludge(POS).Propylene oxide sludge shell-aggregate(POSS-A)and propylene oxide sludge gradient shell-aggregate(POSGS-A)whose main hydrated phase is tobermorite were successfully manufactured by the hydrothermal synthesis of POS and silica materials under the condition of autoclaved(180℃,1.0 MPa)curing.Influences of pre-wetting time of coarse aggregate and pressure application mode on the different concretes were investigated.The experimental results show that the concrete with POSS-A as coarse aggregate(POSS-A concrete),the concrete with POS gradient shell-aggregate as coarse aggregate(POSGS-A concrete),sintered aggregate concrete and common concrete,all have excellent impermeability performance whatever the pre-wetting time of coarse aggregate is 0.5 h or 24 h,and the pre-wetting time of coarse aggregate has a negligible influence on the concrete.The influence degree of pressure application mode on the impermeability performance of the sintered aggregate concrete is the greatest among three kinds of concrete,which has a negligible influence on impermeability performance of the other concretes.POSGS-A can be used as a green building light aggregate in hydraulic concrete.

Morphology-controlled preparation of tungsten oxide nanostructures for gas-sensing application

A novel three-dimensional（3D） hierarchical structure and a roughly oriented one-dimensional（1D） nanowire of WO3 are selectively prepared on an alumina substrate by an induced hydrothermal growth method.Each hierarchical structure is constructed hydrothermally through bilateral inductive growth of WO3 nanowire arrays from a nanosheet preformed on the substrate.Only roughly oriented 1D WO3 nanowire can be obtained from a spherical induction layer.The analyses show that as-prepared 1D nanowire and 3D hierarchical structures exhibit monoclinic and hexagonal phases of WO3,respectively.The gas-sensing properties of the nanowires and the hierarchical structure of WO_3,which include the variations of their resistances and response times when exposed to NO2,are investigated at temperatures ranging from room temperature（20 ℃） to 250 ℃ over 0.015 ppm-5 ppm NO2.The hierarchical WO3 behaves as a p-type semiconductor at room temperature,and shows p-to-n response characteristic reversal with the increase of temperature.Meanwhile,unlike the1 D nanowire,the hierarchical WO3 exhibits an excellent response characteristic and very good reversibility and selectivity to NO2 gas at room temperature due to its unique microstructure.Especially,it is found that the hierarchical VO3-based sensor is capable of detecting NO2 at a ppb level with ultrashort response time shorter than 5 s,indicating the potential of this material in developing a highly sensitive gas sensor with a low power consumption.