Citrate Nitrate Auto Combustion Research Articles

Unusual features of ferromagnetic/antiferromagnetic nanocomposites

Nanocomposites based on the general formula ((1–x) CFO + (x) LCFO) were successfully synthesized using citrate-nitrate autocombustion technique. Properties of the nanocomposites were characterized by X-ray diffraction and transmission electron microscope. Magnetic properties revealed a colossal compositional change in the coercivity for the nanocomposites despite its small value for the two parents. The saturation magnetization and remanence magnetization were found to decrease linearly with the antiferromagnetic phase (AFM) content rose. The dielectric constant was found to increase with increasing (AFM) content. Potential applications of the nanocomposites in magnetic random access memories (MRAMS) and spintronics are recommended.

Effect of addition of erbium stabilized bismuth oxide on the conductivity of lanthanum doped ceria solid electrolyte for IT-SOFCs

Nanosized powders of compositions, Bi0.8Er0.2O1.5 (ESB) and Ce0.85La0.15O1.925 (CLO) have been prepared using citrate–nitrate auto combustion method. ESB added CLO (ECLO) samples have been prepared by mixing nanosized CLO powder with 0.5, 1, 2 and 3wt.% of ESB. X-ray diffraction patterns confirm that all the samples are single phase having cubic fluorite structure similar to CeO2. Density of Ce0.85La0.15O1.925 increases with increasing ESB content. All the samples have been sintered at 1350°C. All the ECLO samples have density more than 97% of the theoretical value. Field emission scanning electron microscope images show dense microstructure with distinct grains and grain boundaries. Impedance measurements have been made in the temperature range 200–700°C in air. Addition of ESB increases the conductivity of the bulk as well as of grain boundaries. Ce0.85La0.15O1.925 with 0.5wt.% of ESB exhibits the maximum conductivity 1.41×10−2Scm−1 at 600°C of all the compositions. This value is one order of magnitude higher than the conductivity of Ce0.85La0.15O1.925 (1.99×10−3Scm−1).

Sintering and electrical properties of Ce0.75Sm0.2Li0.05O1.95

Ceria-based electrolytes have been widely investigated in intermediate-temperature solid oxide fuel cell (SOFC), which might be operated at 500–600 °C. Samarium doped (20 mol%) ceria (20SDC) one of the most promising material in this class of compounds. In this work we report effect of lattice substitution of 5 mol % Li on Sm in (20SDC). It was prepared by citrate–nitrate auto combustion synthesis having a powder of average particle size ∼50 nm. The sintered density of more than 98% of the theoretical density at 950 °C has been achieved. Increased ionic conductivity (lattice) at 500 °C has also been achieved in Ce0.75Sm0.2Li0.05O1.95 compare to that of Ce0.8Sm0.2O1.95. Corresponding activation energy of conduction ∼0.7 eV has been calculated in the temperature range of 200–600 °C. In reducing atmosphere the electrical conductivity has not been altered much. Thus Ce0.75Sm0.2Li0.05O1.95 has been found to be quite promising in terms of reducing the processing temperature as well as operating temperature of SOFC.

Fascinating properties of multifunctional nanocomposites manganite/magnetite

Multifunctional nanocomposites La0.6Sr0.4MnO3/Fe3O4 (LSMO/Fe3O4) were prepared with different weight ratios and characterized using X-ray diffraction (XRD), high resolution transmission microscope (HRTEM) and vibrating sample magnetometer (VSM). The parent nanomaterials (LSMO and Fe3O4) were prepared by citrate–nitrate auto combustion method and coprecipitation method respectively. Thermal dc magnetization curves were measured from room temperature up to 800K for the nanocomposites. Vibrating sample magnetometer measurements reveal the enhancement of ferromagnetic properties with increasing magnetite ratio. Dielectric properties were reported and discussed for all investigated nanocomposites. The results recommend the use of such nanocomposites in memory devices and spintronics applications.

Low temperature synthesis of Ba(Zr0.2Ti0.8)O3–0.5(Ba0.7Ca0.3)TiO3 nanopowders by solution based auto combustion method

Ba(Zr0.2Ti0.8)O3–0.5(Ba0.7Ca0.3)TiO3 (BZT–BCT) nanopowders were synthesized by citrate–nitrate auto combustion method using TiO2 as a source of titanium. The formation mechanism, phase evolution and particle size were investigated using thermal analysis, Fourier transform infra-red spectroscopy, X-ray diffraction, Raman spectroscopy and transmission electron microscope. The molar ratio of metal, citric acid and ethylene diamine tetraacetic acid was kept at 1:1.5:0.1 and pH ~ 9, to get a uniform and complete combustion. Perovskite BZT–BCT was formed in the as-burnt state (280 °C), though calcination at 700 °C is required to remove a small amount of impurities, which is significantly lower than the solid state reaction method. The particle size of BZT–BCT powder was in the range of 40–70 nm.

Structural characterization and magnetic properties of smart CuCd ferrite/LaSrCo manganite nanocomposites

Smart nanocomposites Cu0.7Cd0.3Fe2O4/La0.67Sr0.33Mn0.98Co0.02O3 in different weight ratios were prepared and characterized by different techniques. The parent compounds were prepared by the citrate–nitrate autocombustion method. Phase formation and crystal structure were investigated by X-ray diffraction. Morphological properties of the nanoparticles were studied using high resolution transmission electron microscopy. Thermal dc magnetization curves were measured from 200 to800K for the nanocomposites and showed a characteristic peak near the blocking temperature of LaSrCo manganite shifted toward higher temperature with increasing CuCd ferrite percentage. Such behavior was explained in light of granular model of exchange bias. Vibrating sample magnetometer measurements reveal an enhancement in the ferromagnetic properties with increasing ferrite ratio. The prominent anisotropic shift in the M-H hysteresis loop was discussed as a consequence of interfacial magnetic interactions between LaSrCo manganite and CuCd ferrite grains. Correlation between the measured magnetic parameters and ferrite/manganite ratio is reported and discussed.

Magnetic and electrical properties of Co1−x Cax Fe2O4 nanoparticles synthesized by the auto combustion method

Nano-sized particles of Co1−x Cax Fe2O4 (x=0.0, 0.01, 0.03, 0.05, 0.07 and 0.09) have been prepared by using the citrate-nitrate auto combustion method. X-Ray diffraction analysis has ensured the formation of the desired ferrites and has been used also to determine some of their structural properties. The particle size of only three samples has been checked out by using both transmission electron microscope (TEM) and particle size analyzer (PSA). Magnetic measurements have been performed by using vibrating sample magnetometer (VSM) at room temperature. The reduction of saturation magnetization of the nano-structured samples in comparison to bulk samples in literature and the effect of Ca addition on saturation magnetization and coercivity of all the samples are discussed. The AC conductivity and dielectric properties of these spinel ferrite nanoparticles have been investigated too as function of frequency at room temperature by using a broadband dielectric spectrometer. The AC conductivity of all the samples has been found to increase with increasing Ca substitution. This behavior is interpreted according to a suggested cationic distribution in agreement with literature and in consistency with the dielectric and loss factor results.

Synthesis of Fluorite-Type Nanopowders by Citrate-Nitrate Auto-Combustion Process: A Systematic Approach

Citrate-nitrate autocombustion process is a promising synthesis route in the field of nanomaterials. This route involves many controlling parameters which ultimately affect properties of the products. In the present research work, the effect of concentration of fuel to that of metal nitrates has been studied in a systematic manner. The nature of exothermic reaction was analyzed with DSC-TGA and the powder properties were characterized by XRD, TEM and BET measurement. The properties of the powders have been explained with respect to fuel content, vigorousness of the exothermic reaction, combustion temperature and duration. The most vigorous reaction was found to occur for the composition with FER of 0.50 with the production of the smallest crystallite size of 9 nm.

A review on nano-TiO2 sol–gel type syntheses and its applications

Nanomaterials, defined as particles ranging from 1 to 100 nm diameter, have become widely utilized because of their unique physicochemical properties. Among those nanoparticles, titanium dioxide (TiO2) is frequently used in the production of paints, paper, plastics, welding rod-coating material, cosmetics, etc. TiO2 is the most commonly used semiconductor photocatalyst. Among the different nanomaterials, it is the most studied. Activated by UV-A irradiation, its photocatalytic properties have been utilized in various applications. A wealth of information on TiO2 photocatalytic in activation of bacteria has been acquired over the last 20 years. Hence, in this review article we have described synthesis methods mainly sol–gel type method like sol–gel method, ultrasonic-assisted sol–gel method, microemulsion method, colloidal synthesis, and also other method are discussed like solvo-thermal method, thermal plasma process, supersonically expanded plasma jet method, induction plasma torch, reactive plasma processing, plasma electrolytic oxidation, hydrolysis method, thermohydrolysis method, coprecipitation method, citrate–nitrate autocombustion method, etc. Also applications of TiO2 like medical applications, environmental application, sensor application, photocatalytic applications, and also its health impact for long-term exposure are discussed.

Citrate–nitrate synthesis of nano-structured titanium dioxide ceramics for gas sensors

Nano-structured TiO 2-based ceramics were synthesized using a citrate–nitrate auto combustion method. Phase purity, particle size, and surface area of TiO 2 nano-powder were studied as a function of citrate-to-nitrate ratio (C/N = 0.1–0.5), water addition during synthesis (0 and 10 vol%), and yttrium as a metal ion dopant (0 and 10 wt.%). The powder X-ray diffraction data showed that all synthesized TiO 2-based powder was primarily anatase phase. BET surface area analysis showed an increase in specific average surface area up to 48 m 2/g with increasing C/N ratio and the addition of water during synthesis. Powder XRD, BET, and TEM measurements confirmed particle size ranged from 10 to 50 nm depending on synthesis parameters. C/N ratio of 0.5 and addition of water during synthesis resulted in the smallest particle size. Sintered compacts made from this nano-powder showed an increase in bulk conductivity with increasing temperature inside a tube furnace open to the air. Addition of yttrium increased conductivity by 3 times over that of pure TiO 2. Higher conductivity was attributed to higher energy of electrons to overcome conduction barriers and higher carrier concentrations caused by both temperature effects and yttrium addition. Thick film sensors made from the synthesized TiO 2 nano-powder with higher surface area showed an improved response to carbon monoxide at 600 °C. Yttrium doping in TiO 2 also increased response to CO compared with pure TiO 2.

Aluminum-doped TiO 2 nano-powders for gas sensors

Nano-powders of pure and Al-doped TiO 2 ceramics were synthesized using a citrate–nitrate auto combustion method. Powders were then used to make thick film gas sensors to measure selectivity and sensitivity in CO and O 2 environment. Titanyl nitrate solution was prepared using commercial TiO 2 powder, hydrofluoric acid (HF) and concentrated nitric acid (HNO 3). An optimized ratio of citrate to nitrate was used to produce TiO 2 nanoparticles. Powder X-ray diffraction data showed that synthesized TiO 2 nano-powders, pure as well as Al-doped, had stable anatase phase up to 800 °C. X-ray fluorescence confirmed the Al concentrations in synthesized nano-powders. BET surface area analysis showed a decrease at 5 wt.% Al addition, followed by an increase at 7.5 wt.% in specific average surface area. Particle size analysis showed particles below 100 nm for both pure and doped TiO 2 even after calcination at 800 °C. The resistance of Al-doped TiO 2 samples was found to be lower than that of pure TiO 2 in O 2 and CO environment. Al-doped TiO 2 gas sensors were more selective and sensitive to CO and O 2 at an operating temperature of 600 °C than pure TiO 2 powders.

Cathode Performance of Nanostructured La1 − aSraCo1 − bFebO3 − x on a Ce0.8Sm0.2O2 Electrolyte Prepared by Citrate-Nitrate Autocombustion

Nanostructured (–0.5; –0.2) and powders were successfully prepared by citrate-nitrate autocombustion synthesis and were characterized by scanning electron microscopy and X-ray diffraction analysis. Electrochemical impedance spectroscopy measurements on symmetric cells were performed to evaluate the applicability of as a cathode material for intermediate temperature solid oxide fuel cells based on Sm doped-ceria electrolytes. Our results demonstrated that strontium has a positive effect while iron shows a slightly negative effect on the interfacial resistance. The effect of the electrode sintering temperature was investigated by varying the temperature from 850 to , and the best sintering temperature was found to be . The best characteristics as cathode at intermediate operating temperatures were found for the composition with and the minimum iron doping, ; at , an area specific resistance of was measured.

Influence of La2O3, SrO, and ZnO Addition on PZT

Effect of ZnO, SrO, and La2O3 additions on properties of lead zirconate titanate (PZT) nanopowder were investigated. Our objective was to densify PZT near 900°C to reduce lead loss and increase processing compatibility of these materials with IC fabrication technique for micro‐electro‐mechanical systems (MEMS). PZT nanopowders were synthesized using citrate nitrate autocombustion method. ZnO was used as sintering aid, which promoted liquid phase sintering. With only 2 wt% ZnO addition, 93% theoretical density was achieved after sintering at 900°C for 1 h. SrO and La2O3 were used as A‐site dopants in PZT to improve dielectric properties. Different amounts of SrO, La2O3, and a combination of both were added in 2 wt% ZnO‐doped PZT. Between 93% and 95% of theoretical densities were obtained in all cases after sintering at 900°C for 1 h. X‐ray diffraction analysis revealed that increase in SrO content increased tetragonal phase formation. However, addition of La2O3 stabilized both tetragonal and rhombohedral phases. Increase in SrO content increased the dielectric constant of PZT with a maximum dielectric constant of 1800 for 1 wt% SrO and 2 wt% ZnO sample. It was observed that an increase in La2O3 up to 2 wt% increased dielectric constant, and the highest dielectric constant obtained was 1500. Combination of both SrO and La2O3 addition showed even higher dielectric constant than their individual contribution. Highest dielectric constant of 2100 was measured for 2 wt% La2O3, 1 wt% SrO and 2 wt% ZnO‐doped PZT which was sintered at 900°C for 1 h. This is one of the highest dielectric constant reported for PZT ceramics that was sintered below 1000°C.

Electrode Performance of Nanostructured La1-aSraCo1-bFebO3-x on a Ce0.8Sm0.2O2 Electrolyte Prepared by Citrate-Nitrate Auto-Combustion

not Available.

Nanostructured alumina doped TiO2 ceramics for gas sensors

ABSTRACTNanostructured TiO2 based ceramics were synthesized using citrate-nitrate auto combustion method with different concentrations of aluminum oxide as dopant. The powder x-ray diffraction data showed that synthesized TiO2 powders, pure as well as alumina doped TiO2 had anatase phase. Dopant concentration was varied between 0 and 15 wt%. Particle size analysis showed that the particle size was in the range of 50 to 80nm for nanosized TiO2 calcined between 600 and 800°C. Average particle size of doped powders was generally less than pure TiO2. BET specific average surface area was between 10 and 25 m2/g. Doping upto 10wt% alumina is not effective in retarding anatase crystallite growth. The resistance of Al doped TiO2 sample is found to be lower than that of pure TiO2. Al2O3 doped TiO2 sensor was found to be selective to CO sensing at an operating temperature of 600 °C.