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.

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).

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.

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.

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.

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.

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.

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.

Effect of La_(2)O_(3) addition on the synthesis of tungsten nanopowder via combustion-based method

In this study, the influences of La_(2)O_(3) added on the phase, morphology and reduction process of tungsten oxide prepared by solution combustion synthesis(SCS) were investigated for the first time. And tungsten nanopowders with different La_(2)O_(3) doping amount(0.5~5.0 wt%) were successfully prepared by SCS and followed hydrogen reduction. The results showed that with the increase of La_(2)O_(3) addition,the product synthesized by SCS changed from needle-like W_(18) O_(49) to irregularly granulated H0.53 WO3 and the complete reduction temperature also increased form 700°C to 850°C. The densification behavior of as-prepared W nanopowders revealed that the densification inhibitory effect of La_(2)O_(3) was enhanced as the La_2O_3 addition increased. Nevertheless, due to the optimal size and distribution of La_(2)O_(3) particles,the sample with 2.0 wt% La_(2)O_(3) addition has a smallest grain size of 0.47 μm and a highest microhardness value of 739.3 Hv0.2, which are the best compared with the literature.

Catalytic Removal of PM by Li-Co Delafossite Catalysts

By using solution combustion synthesis method, several Li-Co delafossite catalysts were prepared via a highly exothermic and self-sustaining reaction. The prepared catalysts were characterized by XRD, SEM and the catalytic activities of the catalysts were evaluated by small sample experiment. It is shown that under loose contact conditions this catalyst can catalyze soot combustion at 360 ℃, and the best prepared catalyst Li Co0.9O2 can ignite soot combustion below 300 ℃. In the incompletely synthesized catalysts the Co cations shift to higher electrovalence, so the number of the surface adsorbed oxygen（O-） of the prepared delafossite catalysts increase and Li Co0.9O2 has the optimum catalytic activity.

Ce-substituted Lithium Ferrite:Preparation and Electrical Relaxation Studies

Ce-substituted lithium ferrite, Li0.5CexFe2.5-x04 （x = 0, 0.05 and 0.1 ） compositions were synthesized from metal nitrates and citric acid by the solution combustion process by keeping the oxidizer to fuel ratio at unity. The thermal decomposition process was investigated by thermogravimetry-differential thermal analysis, which showed a stable phase formation above 600 ℃. The phase composition and molecular bonding of Li0.5CexFe2.5_x04 were characterized by X-ray powder diffraction analysis and Fourier transform infrared spectroscopy, respectively. An extensive study of electrical relaxation process has been represented with impedance and modulus as a function of frequency at different temperatures. The activation energy obtained from both the formalisms was found to be equal within the error. The dc conductivity and hopping frequency were thermally activated and their activation energies were found to be in the range of 0.69-0.64 eV for x = 0.05. The scaling of modulus and impedance were used to understand the electrical relaxation behaviour of the compositions and they suggest the time temperature superposition principle.

Fabrication and ultraviolet-shielding properties of silica-coated titania-doped ceria nanoparticles

A series of well-dispersed titania-doped ceria nanoparticles Ce1–xTixO2 were rapidly prepared by a novel salt-assisted solution combustion process using correspondent metal nitrates as oxidizers and ethyl glycol as fuel, and then coated with amorphous silica by seeded polymerization using tetraethyl orthoslicate （TEOS）. The as-prepared samples were characterized by transmission electron microscopy （TEM）, X-ray diffraction （XRD）, Fourier-transform infrared spectroscopy （FTIR）, and ultraviolet-visible light （UV-Vis） diffuse reflectance spectroscopy. The results indicated that compared with the as-prepared pure ceria nanoparticles, the red-shift phenomenon occurred for Ti-doped ceria nanoparticles with Ti incorporation. Meanwhile, the absorption intensity in the UV light region slightly decreased and transmission rate in visible light region was somewhat enhanced. In comparison with the silica-coated CeO2 nanopowders, the silica-coated Ce0.95Ti0.05O2 nanopowders displayed the same absorption intensity in the UV light region, broader UV absorption band and higher transmission rate in visible light region.

MgO-based adsorbents for CO2 adsorption:Influence of structural and textural properties on the CO_2 adsorption performance

A series of MgO-based adsorbents were prepared through solution–combustion synthesis and ball-milling process.The prepared MgO-based powders were characterized using X-ray diffraction,scanning electron microscopy,N_2 physisorption measurements,and employed as potential adsorbents for CO_2 adsorption.The influence of structural and textural properties of these adsorbents over the CO_2 adsorption behaviour was also investigated.The results showed that MgO-based products prepared by solution–combustion and ball-milling processes,were highly porous,fluffy,nanocrystalline structures in nature,which are unique physico-chemical properties that significantly contribute to enhance their CO_2 adsorption.It was found that the MgO synthesized by solution combustion process,using a molar ratio of urea to magnesium nitrate（2：1）,and treated by ball-milling during 2.5 hr（MgO-BM2.5h）,exhibited the maximum CO_2 adsorption capacity of 1.611 mmol/g at 25℃ and 1 atm,mainly via chemisorption.The CO_2 adsorption behaviour on the MgO-based adsorbents was correlated to their improved specific surface area,total pore volume,pore size distribution and crystallinity.The reusability of synthesized MgO-BM2.5h was confirmed by five consecutive CO_2adsorption–desorption times,without any significant loss of performance,that supports the potential of MgO-based adsorbent.The results confirmed that the special features of MgO prepared by solution–combustion and treated by ball-milling during 2.5 hr are favorable to be used as effective MgO-based adsorbent in post-combustion CO_2 capture technologies.