Solution combustion synthesis of Ni-Y_2O_3 nanocomposite powder

Ni-Y2O3 nanocomposite powder with uniform distribution of fine oxide particles in the metal matrix was successfully fabricated via solution combustion process followed by hydrogen reduction. The combustion behavior was investigated by DTA-TG analysis. The influence of urea to nickel nitrate（U/Ni） ratio on the combustion behavior and morphology evolution of the combusted powder was investigated. The morphological characteristics and phase transformation of the combusted powder and the reduced powder were characterized by FESEM, TEM and XRD. The HRTEM image of Ni-Y2O3 nanocomposite powder indicated that Y2O3 particles with average particle size of about 10 nm dispersed uniformly in the nickel matrix.

Preparation of V-doped TiO_2 Photocatalysts by the Solution Combustion Method and Their Visible Light Photocatalysis Activities

A series of nanocrystalline V-doped （0.0-3.0 at.%） TiO2 catalysts have been successfully prepared by the one-step solution combustion method using urea as a fuel. The obtained powders were characterized by XRD, SEM, Raman, XPS and UV-Vis DRS. The effects of V doping concentration on the phase structure and photocatalytic properties were investigated. XRD, Raman, and XPS show that V doping diffuses into TiO2 crystal lattice mainly in the form of V5＋ and causes a phase transition from anatase to mille. V doping can widen the light absorption range of TiO2, with the absorption threshold wavelength shifting from 425 to 625 nm. The photocatalytic activity of V-doped TiO2 powders were evaluated by the photocatalytic degradation of methyl orange （MO） under visible light irradiation. It is found that V doping enhances the photoeatalyilc activity under visible light irradiation and the optimal degradation rate of MO is about 95.8% with 1.0 at% V-doped TiO2.

One-Step Synthesis of Nanocrytalline Perovskite LaMnO_3 Powders via Microwave-Induced Solution Combustion Route

Perovskite LaMnO3 powders with an average crystallite size of 12.5 nm were rapidly synthesized via a microwave-induced autocombustion reaction using glycine as a fuel and nitrate as an oxidant. After self-propagating combustion, the desired nanocrystalline perovskite LaMnO3 was obtained and no further calcination was carried out. The possible processes of combustion reaction were discussed according to the principle of propellant chemistry. The autocombustion and thermal decomposition of the precursor were investigated using the TG-DTA and FT-IR techniques. The influences of glycine-nitrate molar ratio and heat-treatment temperature on the perovskite phase formation and crystallite size of as-burnt powder were studied by XRD. The morphology and size of the as-burnt powder before and after milling were characterized and compared by TEM.

Effect of Preparation Conditions on Visible Photocatalytic Activity of Titania Synthesized by Solution Combustion Method

Titania catalysts were synthesized by a solution combustion method （SCM）. Photodegradation of 4-chlorophenol （4-CP） using the synthesized catalysts was studied under both visible light （λ≥420nm） and sunlight irradiation. The effect of preparation conditions on photocatalytic activities of the synthesized catalysts was investigated. The optimal photocatalytic activity of the catalyst （denoted as A1 ） was obtained under the following synthesis conditions： ignition temperature of 350~C, fuel ratio （ φ） of 1 and calcination time of lh. The degradation and mineralization ratio of 4-CP were 78.2% and 53.7% respectively under visible light irradiation for 3h using catalyst A1. And the catalyst A1 also showed high photocatalytic activity under sunlight irradiation.

Structural and Optical Properties of Cu2+ + Ce3+ Co-Doped ZnO by Solution Combustion Method

In this work, ZnO, Ce3+ doped ZnO (ZnO/Ce3+) and Cu2+ + Ce3+ co-doped ZnO (ZnO/Cu2+ + Ce3+ ) solid solutions powders were synthesized by a solution combustion method maintaining the Ce3+ ion concentration constant in 3%Wt while the Cu2+ ion concentration was varied in 1, 2, 3, 10 and 20%Wt. After its synthesis, all the samples were annealed at 900?C by 24 h. The ZnO, ZnO/Ce3+ and ZnO/Cu2+ + Ce3+ powders were structurally characterized using X-ray diffraction (XRD) technique, and the XRD patterns showed that for pure ZnO, Cu2+ undoped ZnO/Ce3+ and ZnO/Ce3+ doped with the Cu2+ ion, the three samples exhibited the hexagonal wurtzite ZnO crystalline structure. However, the morphology and particle size of both samples were observed by means of a scanning electron microscopy (SEM);from SEM image, it is observed that the crystallites of both samples are agglomerated forming bigger amorphous particles with an approximate average size of 1 μm. In addition, the photoluminescence of the ZnO, Ce3+ doped ZnO and Cu2+ + Ce3+ doped ZnO samples was measurement under an illumination of 209 nm wavelength (UV region): for the ZnO/Ce3+ sample, your emission spectrum is in the visible region from blue color until red color;the UV band of the ZnO is suppressed. The multicolor emission visible is attributed to the Ce3+ ion photoluminescence, while for the ZnO/Cu2+ + Ce3+, its emission PL spectrum is quenching by the Cu2+ ion, present in the ZnO crystalline.

Solution combustion synthesis of Fe-Ni-Y_2O_3 nanocomposites for magnetic application

Fe-Ni-Y2O3 nanocomposites with uniform distribution of fine oxide particles in the gamma Fe Ni matrix were successfully fabricated via solution combustion followed by hydrogen reduction. The morphological characteristics and phase transformation of the combusted powder and the Fe-Ni-Y2O3 nanocomposites were characterized by XRD, FESEM and TEM.Porous Fe-Ni-Y2O3 nanocomposites with crystallite size below 100 nm were obtained after reduction. The morphology, phases and magnetic property of Fe-Ni-Y2O3 nanocomposites reduced at different temperatures were investigated. The Fe-Ni-Y2O3 nanocomposite reduced at 900 °C has the maximum saturation magnetization and the minimum coercivity values of 167.41 A/(m2·kg)and 3.11 k A/m, respectively.

One-step solution combustion synthesis of micro-nano-scale porous Cu/CeO_(2)with enhanced photocatalytic properties

The Cu/CeO_(2)nanoporous composite material was prepared via a one-step and energy-saving method of solution combustion synthesis(SCS).The phase composition,surface morphology and optical characteristics of Cu/CeO_(2)were studied.The results show that the SCS products are composed of cubic fluorite CeO_(2)and Cu.Due to the generation and escape of gas during the synthetic reaction,the SCS CeO_(2)shows porous structure,in which the mesopores(diameter 10-17 nm)nest in the wall of large pores(diameter80-300 nm).X-ray photoelectron spectroscopy(XPS)outcomes indicate that the oxygen vacancy concentration of CeO_(2)increases(18.97%-30.93%)with the increase of Cu concentration.The decoration of Cu greatly enhances the catalytic activity of CeO_(2)nanomaterials.30 wt%Cu/CeO_(2)composite material shows the best photocatalytic activities for the degradation of methyl orange(MO)(95.99%),which is about 4.3times that of CeO_(2)at the same time(120 min).UV-vis diffuse reflectance spectroscopy(DRS)results show that the semiconductor band gap is reduced with the addition of metallic Cu,which leads to the enhancement of photocatalytic activity.The free radical trapping experiments demonstrate that·O_(2)-and h+are the main active species in the photocatalytic degradation of MO.Based on the above results,a hypothesized mechanism for enhanced photocatalysis of Cu/CeO_(2)nanomaterials was proposed:the porous structure provides more reactive sites and channels for mass transfer,and the presence of metallic Cu improves the oxygen vacancy concentration of CeO_(2)and then promotes charge-carrier separation,which helps enhance the photocatalytic performance of Cu/CeO_(2).

A modified solution combustion method to superfine Gd_2O_3:Eu^(3+) phosphor:preparation,phase transformation and optical properties

Cubic and monoclinic Gd2O3:Eu3+ phosphors in the range of nano-scale and submicron-scale were prepared by a modified solution combustion method.Coexistence of cubic and monoclinic phases was found in the highest luminescent sample synthesized at 600 oC.In relation to commercial sample,the relative luminescence intensity was 49.8%.The shape of emission spectrum of the sample thus changed and the charge-transfer-state band of excitation spectrum slightly shift toward higher energies.With increasing the anneal...

Catalytic activity of porous manganese oxides for benzene oxidation improved via citric acid solution combustion synthesis

Various manganese oxides(MnOx) prepared via citric acid solution combustion synthesis were applied for catalytic oxidation of benzene. The results showed the ratios of citric acid/manganese nitrate in synthesizing process positively affected the physicochemical properties of MnOx, e.g., BET(Brunauer-Emmett-Teller) surface area, porous structure, reducibility and so on, which were in close relationship with their catalytic performance. Of all the catalysts, the sample prepared at a citric acid/manganese nitrate ratio of 2:1(C2M1) displayed the best catalytic activity with T(90)(the temperature when 90% of benzene was catalytically oxidized) of 212 ℃. Further investigation showed that C2M1 was Mn2O3 with abundant nano-pores, the largest surface area and the proper ratio of surface Mn^4+/Mn^3+, resulting in preferable low-temperature reducibility and abundant surface active adsorbed oxygen species. The analysis results of the in-situ Fourier transform infrared spectroscopy(in-situ FTIR) revealed that the benzene was successively oxidized to phenolate, o-benzoquinone, small molecules(such as maleates, acetates, and vinyl), and finally transformed to CO2 and H2O.

Solution combustion synthesis and luminescence properties of (Y,Gd)Al_3(BO_3)_4:Eu^(3+) phosphors

Ultrafine Y0.95–xGdxEu0.05Al3(BO3)4 phosphors with different Gd3+ concentrations were prepared by a solution combustion method, and characterized with X-ray diffraction (XRD), scanning electron microscopy (SEM). Results showed that the pure phase of YAl3(BO3)4 was obtained at 1000 oC and the prepared particle size varied with calcining temperatures. Photoluminescence spectra indicated that the dominant emission peak was observed at 612 nm due to the 5D0→7F2 transition of Eu3+. The luminescence intensity of ...

Characterization and photoluminescence of Lu_2O_3-Eu^(3+) nano-phosphor prepared by modified solution combustion method

Nanoscale Lu2O3：Eu3＋ phosphor was prepared by a modified solution combustion method using urea and acrylamide monomer.The particle sizes and photoluminescent properties of nano-phosphor were closely related to the molar ratio of urea-to-RE nitrates and acrylamide monomer-to-RE nitrates.The as-prepared samples with the sizes of 9.6-11.6 nm were characterized by X-ray diffraction,scanning electron microscopy,transmission electron microscopy and energy dispersive spectrometer.Lu2O3：Eu3＋ nano-phosphor that depicted high photoluminescence in the size around 10 nm was reported.Compared with the sample prepared by solid state reaction,the photoluminescence of sample was increased sufficiently to be 45.1%.The emission spectra of the samples presented the typical emission from 5D0 level to 7FJ（J=0,1,2,3,4） level of the Eu3＋ ion.

Solution-combustion Synthesized Nano-pellet α-Al_(2)O_(3) and Catalytic Oxidation of Cyclohexane by Its Supported Cobalt Acetate

Nano-pelletα-Al_(2)O_(3) was prepared using aluminum nitrate as precursor and urea as fuel by a fast method of solution combustion synthesis.The formation of the nano material was dependent on the molar ratio of fuel/oxidant,calcination temperature,and foreign metallic ions.The prerequisite conditions of the formation were a suitable fuel/oxidant molar ratio larger than two and calcination temperature higher than 673 K.Foreign ions,Ce^(4+) or Co^(2+),hindered this formation via promoting the generation of stable penta-coordinated Al^(3+) ions due to strong interaction with alumina,were revealed by ^(27)Al NMR spectra.Such Al^(3+) ions were recognized as a critical intermediate state for the phase transformation of alumina and their presence deterred the transformation.The nano-pellet morphology of the product demonstrated a specific surface area of 69 m^(2)/g,of which the external surface area occupied 59 m^(2)/g.It was found that the supported cobalt acetate on such nano-pellets existed as nanoparticles attached to the external surface,evidenced by the TEM characterization.The prepared catalyst could efficiently catalyze the selective oxidation of cyclohexane under the reaction condition of pressure under 0.8 MPa,temperature at 373 K,and time for 4 hours.The conversion of the reaction achieved up to 7.9%;while the cyclohexanone selectivity was 42.7%and the cyclohexanone and cyclohexanol selectivity was 91.6%.This catalytic performance recommends the supported cobalt acetate on the inert nano-pellet a-Al_(2)O_(3) as a promising catalyst for the selective oxidation of cyclohexane.

THE WEAK DETONATION SOLUTIONS TO THE SIMPLEST COMBUSTION MODEL

In the present paper the authors prove that all the generalised entropy,solutions of the CJ-model, which for the given Riemann initial data are a oneparameter family u(eta) characterised by weak detonation discontinuity point eta, are just the limits of the admissible solutions u(ek) Of the selfsimilar combustion model. In fact, the authors prove that for any possible eta, there exists a constant B>0 s.t.

EXISTENCE OF GENERALIZED SOLUTIONS TO A HYPERBOLIC MODEL OF COMBUSTION

In this paper we obtain the existence of the generalized solutions to the Cauchy problem for a model of combustion provided that the function f is of nonconvexity and initial values lie in the bounded, measurable class.

Comparison of Perovskite Systems Based on AFeO_(3)(A=Ce,La,Y)in CO_(2) Hydrogenation to CO

CO_(2) is the most cost-eff ective and abundant carbon resource,while the reverse water-gas reaction(rWGS)is one of the most eff ective methods of CO_(2) utilization.This work presents a comparative study of rWGS activity for perovskite systems based on AFeO_(3)(where A=Ce,La,Y).These systems were synthesized by solution combustion synthesis(SCS)with diff erent ratios of fuel(glycine)and oxidizer(φ),diff erent amounts of NH 4 NO_(3),and the addition of alumina or silica as supports.Various techniques,including X-ray diff raction analysis,thermogravimetric analysis,Fourier transform infrared spectroscopy(FTIR),scanning electron microscopy,energy-dispersive X-ray spectroscopy,N 2-physisorption,H_(2) temper-ature-programmed reduction,temperature-programmed desorption of H_(2) and CO_(2),Raman spectroscopy,and in situ FTIR,were used to relate the physicochemical properties with the catalytic performance of the obtained composites.Each specifi c perovskite-containing system(either bulk or supported)has its own optimalφand NH_(4) NO_(3) amount to achieve the highest yield and dispersion of the perovskite phase.Among all synthesized systems,bulk SCS-derived La-Fe-O systems showed the highest resistance to reducing environments and the easiest hydrogen desorption,outperforming La-Fe-O produced by solgel combustion(SGC).CO_(2) conversion into CO at 600°C for bulk ferrite systems,depending on the A-cation type and preparation method,follows the order La(SGC)<Y<Ce<La(SCS).The diff erences in properties between La-Fe-O obtained by the SCS and SGC methods can be attributed to diff erent ratios of oxygen and lanthanum vacancy contributions,hydroxyl coverage,morphology,and free iron oxide presence.In situ FTIR data revealed that CO_(2) hydrogenation occurs through formates generated under reaction conditions on the bulk system based on La-Fe-O,obtained by the SCS method.γ-Al_(2)O_(3) improves the dispersion of CeFeO_(3) and LaFeO_(3) phases,the specifi c surface area,and the quantity of adsorbed H_(2) and CO_(2).This led to a signifi cant increase in CO_(2) conversion for supported CeFeO_(3) but not for the La-based system compared to bulk and SiO_(2)-supported perovskite catalysts.However,adding alumina increased the activity per mass for both Ce-and La-based perovskite systems,reducing the amount of rare-earth components in the catalyst and thereby lowering the cost without substantially compromising stability.

Synthesis,Characterization and Impedance Analysis of Calcium-Doped Zinc Oxide Nanoparticles

The calcium-doped ZnO nanoparticles,Zn1-xCaxO(x=0,0.025,0.05,0.075)were prepared by the solution combustion meth­od.The synthesized nanoparticles were characterized by various techniques such as XRD,FTIR,Raman,FESEM-EDX,PL,Impedance,and UV-Vis.The Rietveld refinement of the X-ray diffractogram yields the crystalline structure and lattice parameters.Also,the XRD analysis shows that the substitution of Ca into ZnO does not alter the Wurtzite structure of ZnO.The crystallite size of the samples,calculated using the Scherer equation,was found to be between 46 nm and 92 nm.FTIR spectra detect the ZnO-re­lated vibration modes of the samples.The FESEM morphological images suggest the spherical shape of the synthesized nanopar­ticles.The EDAX spectra identify the presence of Zn,Ca,and O atoms in the samples.The Raman active modes of the ZnO phase were identified by Raman spectral analysis.The analysis of Photoluminescence(PL)spectra gives information about the UV emis­sion and other visible bands corresponding to violet,blue,and green emission representing different intrinsic defects in synthesized nanoparticles.Using UV-vis spectroscopy,the optical transparency and band gap values were examined.The energy band gap ob­tained by Tauc’s plot was decreased with the increase in Ca doping.Impedance analysis shows that the grain conductivity increased with the increase in dopant concentration.Contrarily,the total conductivity decreased with the increasing doping concentration due to increased grain boundary resistance.The proposed work demonstrates the changes in microstructure,electrical conductivity,and optical bandgap energy with Ca-doping.These synthesized Ca-doped ZnO nanoparticles could be promising materials for photo­catalytic applications.

Effects of doping route on microstructure and mechanical properties of W−1.0wt.%La2O3 alloys

A comparative study was conducted by using solution combustion synthesis with three different doping routes(liquid-liquid(WL10), liquid-solid(WLNO) and solid-solid(WLO)) to produce nanoscale powders and further fabricate the ultrafine-grained W-1.0 wt.%La2O3 alloys by pressureless sintering. Compared with pure tungsten, W-1.0 wt.%La2O3 alloys exhibit ultrafine grains and excellent mechanical properties. After sintering, the average grain size of the WLO sample is larger than that of WL10 and WLNO samples;the microhardness values of WL10 and WLNO samples are similar but larger than the value of WLO sample. The optimized La2O3 particles are obtained in the WL10 sample after sintering at 1500 ℃ with the minimum mean size by comparing with WLNO and WLO samples, which are uniformly distributed either at grain boundaries or in the grain interior with the sizes of(57±29.7) and(27±13.1) nm, respectively. This study exhibits ultrafine microstructure and outperforming mechanical properties of the W-1.0 wt.%La2O3 alloy via the liquid-liquid doping route, as compared with conventionally-manufactured tungsten materials.

One-step synthesis of dimethyl ether from syngas on ordered mesoporous copper incorporated alumina

Ordered mesoporous copper incorporated Al;O;（Cu/Al;O;） with high Cu dispersion were prepared by a facile solution combustion synthesis method using aluminum nitrate and copper nitrate as oxidants and urea as fuel. It is a facile and green route to synthesize catalysts for dimethyl ether directly from syngas. Cu/Al;O;catalysts were characterized by XRD, N;adsorption–desorption, SEM-EDS, and H;-TPR.The results indicate that the catalysts obtain an ordered mesoporous structure and copper is homogenously dispersed. The mesoporous Cu/Al;O;catalysts were utilized as bifunctional catalysts in syngas to dimethyl ether reaction（STD）. The copper content affects the catalytic performance in STD reaction. The CO conversion and DME selectivity of Cu/Al;O;with 15% copper molar ratio achieve 52.9% and 66.1%,respectively. Moreover, the mesoporous Cu/Al;O;catalysts show excellent stability in STD reaction.

Facile synthesis of porous LiNiVO_4 powder as high-voltage cathode material for lithium-ion batteries

Porous LiNiVO4 powder was synthesized via solution combustion synthesis method using lithium nitrate, nickel nitrate,ammonium metavanadate and citric acid as raw materials. Thermogravimetry (TG) and differential scanning calorimetry (DSC),X-ray diffraction (XRD), Fourier-transform infrared (FT-IR) spectroscopy and transmission electron microscopy (TEM) were used toevaluate the structures and morphologies of samples. The results show that the calcination temperature has significant effect on thecrystallinity and morphologies. Pure LiNiVO4 flaky nanoparticles with a mean particle size around 20 nm can be readily prepared bycalcining the precursor in air at 500 °C for 2 h. As a cathode material for lithium-ion batteries, the porous LiNiVO4 powder exhibits agood structural reversibility.

Low-temperature thermocatalytic particulate carbon decomposition via urea solution-combustion derived CeO2 nanostructures

A facile,one-pot,urea solution combustion route was utilized to synthesize highly catalytic CeO2 nanostructures.CeO2 prepared under varying thermal conditions was characterized by electron microscopy,energy dispersive X-ray spectroscopy,X-ray diffraction,X-ray photoelectron spectroscopy,infrared and Raman techniques.As the synthesis temperature is raised from 400 to 1000℃,the crystallite size and dspacing of nanoparticles are observed to reduce while cell parameters remain in the same range.Particle size exhibits an accession from~20 to~50 nm along the process.Initial CeO2 nanoparticles are detected as a composite structure of CeO2 and graphitic carbon nitride(g-C3 N4)produced by the pyrolysis of urea.Concerning the solid carbon particulate oxidation capacity,an outstanding performance is exhibited by CeO2 synthesized at 800℃where the oxidation onset temperature is reduced by 27%compared with the others.The superior performance is attributed to the carbon nitride-generated unique CeO2 nanomorphology consolidating ample reactive sites and facilitated oxygen delivery for a highly efficient thermocatalytic process.Concerning atmospheric pollution mitigation,synthesis of these CeO2 nanostructures represents a cost effective and convenient abatement technique for carbon particulates in comparison to cost-intensive,environmentally detrimental and noble-metal based techniques.