Stearic Acid Gel Research Articles

Effect of sintering temperature and micro structural analysis on sol-gel derived silver bismuth titanate ceramics

The silver bismuth titanate – Ag0.5Bi0.5TiO3 (ABT) ceramics with various grain sizes were synthesized by stearic acid gel method. The density measurement was calculated based on pycnometer method. The relative density of ABT pellet was calculated as 64.91%. The microstructure analysis establishes the relationship between the sintering temperature and grain size. Moreover, the micrographs show the pores and oriented particles of nano meter to micrometer size. The effect of sintering temperature on grain growth behavior of sol-gel derived porous silver bismuth titanate sample was discussed in detail.

FeAl2O4 Nanopowders; Structural Analysis and Band Gap Energy

AbstractNanoscale FeAl2O4 was successfully synthesized via sol–gel method. The sol constituents containing iron and aluminum cations were formed homogenously in stearic acid gel (formation of organic precursor). The pure structural analysis and the size of the spinels were confirmed by X-ray diffraction (XRD). It was observed that the size of the nanoscale materials obtained at around 30–40nm. The micrographs of FeAl2O4 evidenced the homogenous and nanosize formation of spinel. The semiconducting behavior of this mixed metal oxide was observed at 3.14eV based on the band gap energy (Eg). The final nanoscale materials exhibited a superparamagnetic behavior with a saturation magnetization of 9.8 emu/g at applied field of 10 kOe.

Synthesis and Characterization of Li2Ni8O10 Nanoparticles Using Stearic Acid Gel Method

Synthesis and Characterization of Li2Ni8O10 Nanoparticles Using Stearic Acid Gel Method

Dielectric Properties of W-Type BaCa<sub>2</sub>Fe<sub>16</sub>O<sub>27</sub> Hexaferrite Prepared Using a Stearic Acid Gel Route

W-type hexagonal ferrite with composition BaCa2Fe16O27 was prepared using a stearic acid gel method. The precipitate of barium calcium hexaferrite was calcinated at 650°C, 750°C, 850°C and 950°C in a furnace for 4 hours and then slowly cooled to room temperature. The dielectric constants (real Є and imaginary Є), conductivity (σ) and dielectric loss (tan δ) have been measured at room temperature as a function of frequency (102-106 Hz). The dielectric behavior of prepared hexaferrite samples can be explained by the mechanism of polarization and the electrical conduction mechanism is explained by using the electronic hopping model of Heike Johnson.

Synthesis, characterisation and optical properties of MnTiO3 nanopowders

Pure manganese titanate (MnTiO3) nanopowders have been synthesised by stearic acid gel method. Structural investigations by X-ray diffraction and scanning electron microscopy confirm that the synthesised material is MnTiO3 with rhombohedral crystal structure. Transmission electron microscopy showed that the particle sizes are in the range of 22–30 nm. The formation of MnTiO3 is further supported by the FT-IR and energy dispersive X-ray spectra. An optical band gap of 3.18 eV is determined for MnTiO3 nanopowders from the UV–vis absorption spectrum. A broad emission band with maximum intensity at around 487 nm is observed in the photoluminescence spectra of MnTiO3 nanopowders at room temperature depicting the blue emission, which can be attributed to the 4T2 (4G) → 6A1 transition in the material.

Synthesis, Characterization and Photocatalytic Properties of MnTiO3-Zeolite-Y Nanocomposites

MnTiO3-Zeolite-Y nanocomposites were synthesized with 5-10-20% (w/w) of MnTiO3 by stearic acid gel method. Then, the gels were calcined at 900 °C for 4 hours and the resulted spectra were investigated at 20% (w/w) concentration. Also, the presence of rhombohedral phase of MnTiO3 in Zeolite-Y matrix was confirmed by XRD, SEM, EDX and BET. The VSM results showed the antiferromagnetic properties for the 20% nanocomposite. The photocatalytic activity of the nanocomposites was finally evaluated by degradation of methylene blue and calcon reagents in aqueous solution.

Preparation of SrTi 0.1Fe 0.9O 3− δ and its photocatalysis activity for degradation of methyl orange in water

Magnetic perovskite-type SrTi 0.1Fe 0.9O 3− δ was synthesized by stearic acid gel combustion method. The obtained powders were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FT-IR), vibrating sample magnetometer (VSM) and UV-Visible absorption spectrum techniques. Mean valence of Fe ion and the concentration of oxygen vacancies in SrTi 0.1Fe 0.9O 3− δ were measured by iodometric method. The magnetic properties of the SrTi 0.1Fe 0.9O 3− δ were measured, and the SrTi 0.1Fe 0.9O 3− δ was also evaluated for its photocatalytic activity towards the degradation of methyl orange (MO) under the sunlight irradiation. The experimental results show that the SrTi 0.1Fe 0.9O 3− δ is the photocatalyst possessing of magnetic property and visible-light activity, i.e., bifunctional photocatalyst. The SrTi 0.1Fe 0.9O 3− δ is applicable to the magnetic separation process and also shows excellent photocatalytic activity for the degradation of MO. The optimal conditions for photocatalytic degradation were methyl orange concentration of 20 mg L −1 at pH 6.0 with the SrTi 0.1Fe 0.9O 3− δ concentration of 7.29 mg L −1 for 3 h. In addition, the SrTi 0.1Fe 0.9O 3 is reusable and maintain relatively high activity. This study could point out a potential way to develop new and more active magnetic perovskite-type photocatalysts.

ChemInform Abstract: Synthesis of Substituted M- and W-Type Barium Ferrite Nanostructured Powders by Stearic Acid Gel Method.

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Magnetic properties and heat capacity of CoTiO3 nanopowders prepared by stearic acid gel method

Pure cobalt titanate nanopowders were successfully prepared in wet-chemistry synthesis method, using cobalt acetate and tetra-n-butyl titanate as Co and Ti sources and stearic acid as complexing reagent. The gel was calcined at different temperatures in air ranging from 500°C to 650°C. Results of thermal analysis are given; including both differential thermal gravimetry (DTG) and thermogravimetric. X-ray diffraction was used to characterise the crystallisation process, the particle size and morphology of the calcined powders. The results indicated that cobalt nanopowders with a particle size of about 35 nm could be obtained after calcinations of the dried gel at 600°C for 2 h. In the temperature range between 80°C and 500°C, the empirical equation (C P (JK−1 mol−1) = −136.311 + 0.141 T − 3.551 × 107/T 2) for the C P of CoTiO3 was determined from differential scanning calorimetry. The synthesised CoTiO3 indicate a superparamagnetic behaviour, as evidenced by using vibrating sample magnetometer at room temperature.

Combustion Synthesis of La 0.8Sr 0.2MnO 3 and Its Effect on HMX Thermal Decomposition

Perovskite-type La 0.8Sr 0.2MnO 3 was prepared by stearic acid gel combustion method. The obtained powders were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scaning electron micrograph (SEM) and X-ray photoelectron spectroscopy (XPS) techniques. The catalytic activity of La 0.8Sr 0.2MnO 3 was investigated on thermal decomposition of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) by thermal gravity-differential scanning calorimetry (TG-DSC) techniques. The experimental results show that La 0.8Sr 0.2MnO 3 is an effective catalyst for HMX thermal decomposition. The surface-adsorbed species such as H 2O, OH − and adsorbed oxygen (O ad) could result in an advance in the onset temperature of HMX thermal decomposition. The mixture system of Mn 3+ and Mn 4+ ions and lattice oxygen could play key roles for the increase of the decomposition heat of HMX because these exothermic reactions could be catalyzed by La 0.8Sr 0.2MnO 3 between CO and NO x (from the thermal decomposition of HMX) and the oxidation reaction of CO. According to the previous researches and our results, perovskite-type La 0.8Sr 0.2MnO 3 may be used as a novel catalyst or modifier for nitrate ester plasticized polyether (NEPE) propellant.

Combustion synthesis and effect of LaMnO 3 and La 0.8Sr 0.2MnO 3 on RDX thermal decomposition

Perovskite-type LaMnO 3 and La 0.8Sr 0.2MnO 3 with high specific surface areas were prepared by stearic acid gel combustion method. The obtained powders were characterized by XRD, FT-IR, SEM and XPS techniques. Their catalytic activities were investigated on thermal decomposition of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) by TG-DSC techniques. The experimental results show that LaMnO 3 is a more effective catalyst than La 0.8Sr 0.2MnO 3 for the sublimation and melting process of RDX because of its higher concentration ratio of surface-adsorbed species. And the catalytic activity of La 0.8Sr 0.2MnO 3 is higher than that of LaMnO 3 for thermal decomposition of liquid RDX. This could be attributed to its higher concentration ratios of surface oxygen and Mn 4+/Mn 3+. In conclusion, the concentration ratios of surface oxygen and Mn 4+/Mn 3+ could play key roles for RDX thermal decomposition. This study points out a potential way to develop new and more active perovskite-type catalysts for the RDX thermal decomposition.

Combustion synthesis and effect of LaMnO 3 and LaOCl powder mixture on HMX thermal decomposition

LaOCl powder mixture and perovskite-type LaMnO 3 were prepared by stearic acid gel combustion method. The obtained powders were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) and X-ray photoelectron spectroscopy (XPS) techniques. LaOCl powder mixture was a mixture of LaOCl and significant amounts of amorphous materials. When heated at 973.15 K, the mixture was found to be converted into single-phase perovskite-type LaMnO 3. The catalytic activities of LaOCl powder mixture and LaMnO 3 were investigated for octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) thermal decomposition by thermal gravity (TG) and thermogravimetry-evolved gas analysis (TG–EGA) techniques. The experimental results show that both the mixture and LaMnO 3 have catalytic activities for the thermal decomposition of HMX, and LaOCl powder mixture has much higher catalytic activity than LaMnO 3 on the early stages of HMX thermal decomposition. That could be attributed to the higher surface adsorption oxygen (O ad) and hydroxyl as well as its high specific surface area. LaMnO 3 can obviously reduce activation energy of HMX thermal decomposition than LaOCl powder mixture. This may be due to its catalytic activity on the oxidation reaction of CO and the reaction between CO and NO during HMX thermal decomposition.

Stearic acid gel derived MgTiO3 nanoparticles: A low temperature intermediate phase of Mg2TiO4

Abstract Stearic acid gel is employed to study the phase evolution of MgTiO 3 nanoparticles by thermal gravimetric analysis, X-ray diffraction, and Fourier transform infrared. During the preparation of stearic acid gel, tetrabutyl titanate easily absorbed moisture to hydrolyze into Ti(OH) 4 firstly, and then reacts with stearic acid and magnesium stearate to form magnesium–titanium oxide network polymer gel, meanwhile n-butanol is generated. When stearic acid gel is calcined in air, a series of oxidation and combustion reactions occur, meanwhile apparent heat is given off. The results show that a metastable intermediate phase Mg 2 TiO 4 is generated at 450 °C and nearly disappeared at 550 °C. Simultaneously, a new solid phase of MgTiO 3 appears. The metastable intermediate phase Mg 2 TiO 4 is successfully identified in the current work.

Structural and Magnetic Properties of BaMg<sub>2</sub>Fe<sub>10</sub>O<sub>19</sub> Hexaferrite Particles

BaMg2Fe10O19 hexaferrite particles were synthesized by using a Stearic acid gel method. The prepared Ba-Mg hexaferrite particles were calcinated at Microwave frequency (2.45 GHz, power 900W, 5 min.) as well as at 650°C, 750°C, 850°C and 950°C. Decomposition behavior and the phase associated therein are investigated by means of thermal analysis (DTA, TGA, DSC) and XRD, respectively. The X-ray diffractograms of prepared samples calcinated at 650°C, 750°C, 850°C and 950°C show the presence of M and α- Fe2O3 Phases, whereas the sample heated in a microwave oven shows only single M-phase. Surface morphology of nonporous particles has been examined by using SEM. The samples prepared by conventional heat treatment produces agglomerated clusters of various size particles whereas, the sample heated in a microwave oven shows separate particles with size ranging from 80-240nm. There is significant change in crystallite size of the resultant Ba-Mg hexaferrite particles prepared at microwave frequency. It was observed that heat treatment condition plays a very crucial role in controlling morphology of prepared Ba-Mg hexaferrite particles. Room temperature magnetic measurements were carried out using VSM. Magnetic study reveals that prepared BaMg2Fe10O19 particles possess single magnetic domains.

Low-temperature synthesis of ZnTiO 3 nanopowders

ZnTiO 3 was successfully synthesized by a stearic acid gel method. The as-prepared nanopowders were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), scanning electron microscopy (SEM), Fourier transform infrared spectrometry, UV/vis diffuse reflectance spectra and thermal gravimetric analysis, respectively. The results show that the calcination process of stearic acid gel consists of a series of oxidation and combustion reactions in air, accompanied by exothermal effects. ZnO (zincite) was the dominant phase between 350 and 500 °C. When the calcined temperature is higher than 500 °C, ZnTiO 3 can be formed and becomes the dominant phase at 600 °C. SEM and TEM images of ZnTiO 3 powders prepared at 600 °C show that most ZnTiO 3 nanopowders were agglomerated. The Fourier transform infrared spectra and UV/vis diffuse reflectance spectra can well confirm the observed XRD results.

Synthesis and characterization of Ba 0.5Sr 0.5TiO 3 nanoparticles

Ba 0.5Sr 0.5TiO 3 nanoparticles were successfully prepared by calcined stearic acid gel in air. The as-prepared nanoparticles were characterized by X-ray diffraction, transmission electron microscope, Fourier transform infrared spectrometry, UV/vis diffuse reflectance spectra and thermal gravimetric analysis, respectively. The results show that the calcined process of stearic acid gel consists of a series of oxidation and combustion reactions in air. The formation of Ba 0.5Sr 0.5TiO 3 phase starts at around 500 °C and continues up to 700 °C in our current experiments. BaCO 3 can coexist with Ba 0.5Sr 0.5TiO 3 phase at low calcination temperature, and then decreases quickly with increasing the calcination temperature. TEM images of Ba 0.5Sr 0.5TiO 3 nanoparticles prepared at 600 °C show that the size of most Ba 0.5Sr 0.5TiO 3 nanoparticles is around 50–80 nm. The nanoparticles are almost ellipse in shape and link together to form necks among nanoparticles.

Synthesis of BaTi 2O 5 powders by stearic acid gel method

BaTi 2O 5 was successfully synthesized by a stearic acid gel method. The as-prepared samples were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), scanning electron microscopy (SEM), Fourier transform infrared spectrometry, UV/vis diffuse reflectance spectra and thermal gravimetric analysis, respectively. The present results show that the calcined process of stearic acid gel consists of a series of oxidation and combustion reactions in air. The formation of BaTi 2O 5 phase starts at around 600 °C and continues up to 1100 °C in our designed experiments. Some contaminated phases such as BaTiO 3, BaCO 3 and TiO 2 can coexist with BaTi 2O 5 phase at low calcined temperature, and then dramatically decrease with increasing the calcination temperature. SEM and TEM images of BaTi 2O 5 powders prepared at 900 °C show that BaTi 2O 5 powders are around 200 nm in size, and irregular in shape with slight agglomeration. Fourier transform infrared spectra and UV/vis diffuse reflectance spectra can well confirm the observed XRD results.

Photodegradation of rhodamine B under visible light by bimetal codoped TiO 2 nanocrystals

In the search for efficient photocatalysts working under visible light, we have investigated the effect of metal ions (Bi/Co, Fe/Co) codoping on the photocatalytic activity of TiO 2 prepared by stearic acid gel method. UV–vis spectra revealed that doped Co enhanced the absorbency of TiO 2 under visible light, and Bi/Co codoped TiO 2 showed higher absorbance than Fe/Co codoped TiO 2. The photoreaction based on the prepared samples for photodegradation of 20 mg/l rhodamine B solution was examined. The results showed that Fe(0.1%)/Co(0.4%) codoped TiO 2 had the highest photoactivity among all as-prepared samples under visible light, though less absorbency of visible light, indicating that the photoactivity not only benefits from absorbency but also relates to the cooperative effect of the two dopants.

Structural characterization of NiTiO 3 nanopowders prepared by stearic acid gel method

Pure nickel titanate nanopowders were successfully prepared in wet-chemistry synthesis method, using nickel stearate and tetra-n-butyl titanate as Ni, Ti sources and stearic acid as complexing reagent. The gel was calcined at different temperatures in air ranging from 500 to 750 °C. Results of thermal analysis are given, including both DTG and TG. Fourier transform infrared spectrometry (FTIR), X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used to characterize the crystallization process, the particle size and morphology of the calcined powders. The results indicated that nickel titanate nanopowders with particle size between 30 and 65 nm could be obtained after calcinations of the dried gel at 750 °C for 2 h.

Temperature Dependent Structural Studies and Magnetic Properties of BaCa2Fe16O27 Hexaferrites Prepared by Stearic Acid Gel Route in Presence of SDS Surfactant

The preparation of BaCa2Fe16O27 hexaferrite powders by a stearic acid gel method with SDS surfactant has been investigated at various sintering temperatures. The samples were characterized by X‐ray diffraction, scanning electron microscopy (SEM), TGA, FTIR and vibrating sample magnetometer (VSM). The effect of sintering temperature on properties of BaCa2Fe16O27 hexaferrites was studied. In presence of sodium dodecyl sulfate (SDS) surfactant, the magnetic parameters, like saturation magnetization, coercivity and remanent magnetization, have been calculated from hysteresis loop.