Papers by Keyword: Co-Precipitation

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Authors: Feng Rao Lang
Abstract: This paper selects the LiNi0.5Mn0.5O2 with layer structure as the research object, and does the future research about preparation methods and synthesis conditions. LiNi0.5Mn0.5O2 cathode material was successfully synthesized by co-precipitation method. In order to explore the optimal path of LiNi0.5Mn0.5O2 material synthesized by co-precipitation method optimal path, pretreatment, calcining heat, calcining time, cooling way on the material structure. Finally find the better synthesis conditions and improve synthesis technology.
Authors: Xiang Dong Li, Ying Chen, Li Hong Zhou, Feng Xia, Jian Zhong Xiao
Abstract: Mg2CuxFe1O3.5+x mixed metal oxides were found to be active catalysts for the selective oxidation of ammonia. In this paper, Mg2CuxFe1O3.5+x mixed metal oxides were prepared by co-precipitation method and calcined at 600°C for 12 h in an air atmosphere, then ammonia sensors have been made by screen-printed Mg2CuxFe1O3.5+x electrode on the electrolyte (8moleYSZ) surface and sintered at 1126°C for 1h in an air atmosphere. The samples were characterized by XRD and ESEM. The performance of ammonia sensors were tested in different concentration of ammonia. It can be found that Mg2Cu0.25Fe1O3.75 electrode showed a higher response value and good sensitivity to ammonia at 350°C, the value of sensitivity is 226.6mV/decsde. The influences of Cu content on the ammonia response performance of Mg2CuxFe1O3.5+x mixed metal oxides electrodes are discussed.
Authors: Sachin Tyagi, Ramesh Chandra Agarwala, Vijaya Agarwala
Abstract: Nanocrystalline strontium hexaferrite (SrFe12O19) and barium hexaferrite (BaFe12O19) powders were synthesized by co-precipitation method. The ‘as synthesized’ powders were heat treated (HT) at different temperatures ranging from 800 to 1200°C at a heating rate of 30°C /min in nitrogen atmosphere. Decomposition behaviour and the phases associated therein are investigated by thermal analysis (DTA/DTG/TG) and X-ray diffraction (XRD). Formations of ultrafine particles have been confirmed through field emission scanning electron microscop (FESEM). The superparamagnetic behavior of both, barium and strontium hexaferrite is confirmed by vibrating sample magnetometer (VSM). The increase in saturation magnetization from 1.94 to 31.05 emu/gm in case of barium hexaferrite and from 2.44 to 43.38 emu/gm for strontium hexaferrite is observed with HT temperatures. The changes in coercivity and remanence with HT temperatures for both the ferrites are analysed.
Authors: Fan Liu, Jing Bao Lian, Guang Xi Xu, Nian Chu Wu
Abstract: A series of Eu3+ ions activated La2O2SO4 nanophosphors had been prepared successfully by a facial co-precipitation route followed by a subsequent calcination treatment. The commercial Eu2O3, La2O3, HNO3, (NH4)2SO4 and NH3·H2O were used as the raw materials. The structural analyses and luminescence properties of as-prepared products were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM) and photoluminescence (PL) spectra. Pure La2O2SO4 quasi-sphere nanoparticles with an average diameter of 40 nm were successfully prepared by calcining the precursor at 800 °C for 2 h in air. PL results reveal that the strongest red emission peak is centred at 617 nm upon 393 nm light excitation, corresponding to the 5D07F2 transition of Eu3+ ions. Its quenching concentration is 9 mol%, which can be attributed to the exchange interaction among Eu3+ ions and the corresponding decay process shows a double exponential decay behavior, with 0.310 μs for t1 and 1.419 μs for t2.
Authors: Mohammad Ebrahim Zeynali
Abstract: The dehydrogenation of diethylbenzene to divinylbenzene is a catalytic reaction. The catalyst for the dehydrogenation was prepared by co-precipitation of iron and chromium hydroxide from nitrate solution, followed by doping with potassium carbonate and drying. To make available the internal surface area of the catalyst for the reactant, the pores must be of the proper sizes to allow the reactant to diffuse and penetrate inside the catalyst pellets. The prepared catalyst was considered as a model for investigating the role of diffusion in catalyst design. In this study, different mechanisms of diffusion, such as Knudsen and bulk, were investigated for the case of diethylbenzene diffusion into the catalyst and it was concluded that the pore sizes should be in a range that permits transitional diffusion (both Knudsen and bulk diffusion). The catalyst grain size can be controlled and varied by acting on parameters such as the speed and time of mixing, type of alkali, temperature and pH. Particle size distribution experiments were conducted for different types of alkali and speeds of mixing in order to characterize the catalyst. The effects of the grain size, formed during co-precipitation, upon the pore size distribution of the catalyst pellet which affects the effective diffusivity were discussed. The pore size distribution of the model catalyst was obtained and the effective diffusivities were calculated by numerical integration of the Johanson-Stewart equation.
Authors: Yan Dong, Yang Zhou, Xue Lin Han, Wei Jie Gu
Abstract: Mg doped BaAl12O19:Mn2+ phosphor is one of the most efficient green phosphors for PDP. It is difficult to prepare the phosphor both have small particle size (< 3μm) and high luminescence. In the present work, a BaAl12O19:Mn2+ phosphor with small particle size was synthesized by the chemical co-precipitation method. Phase transformation and particle growth process during calcining process were investigated. The nucleation process was also discussed. The results show that, the phase transformation is complicated, the transition phases include BaCO3, γ-Al2O3, BaF2, BaAl2O4 and two phases contain Mn; The BaAl12O19 phase is formed from the reaction between BaAl2O4 phase and γ-Al2O3 phase, no a-Al2O3 phase appears during the entire process; The formation temperature of pure BaAl12O19 phase is 1200°C, which is lower than that in the high-temperature solid state reaction method. High efficiency BaAl12O19:Mn2+ phosphor with small particle size (< 2μm) and hexagonal flaky shape can be prepared by this method.
Authors: Kyung Sik Oh, Sang Hoon Park, Young Keun Jeong
Authors: Li Qun Sun, Zhi Quan Ren
Abstract: The calcined Mg-Fe LDH adsorbent (CLDH) was fabricated by co-precipitation and calcination processes. The adsorbent was characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy. The adsorbent exhibited high adsorption capacity for the removal of acid red G (ARG) dye. The effects of the adsorbent dose, solution pH, contact time, reaction temperature and initial ARG dye concentrations upon the ARG dye adsorption were investigated in detail. The kinetic studies indicated that the adsorption process was fitted well with the pseudo-second-order kinetic model (R2 > 0.99). The equilibrium data were well described by the Freundlich equation. Moreover, after three regeneration cycles, the CLDH still showed high adsorption capacity. The results showed that the CLDH is an efficient adsorbent for the removal of organic pollutants from wastewater.
Authors: Márcia Caldeira Brant, Felipe da Silva Possa, Fernando Soares Lameiras
Abstract: Powders of Ce0.8Gd0.2O1.9 were synthesized by co-precipitation and amorphous citrate routes and their compositions and structures were compared. Co-precipitation process was carried out at room temperature, while amorphous citrate synthesis was performed at 60-70 °C. The powders obtained were calcined at 700 °C for 1 h. X-ray diffraction analyses showed that a single fluorite structure was formed by both synthesis techniques. Pellets from these powders were prepared by compaction at 30 kN/cm2 and sintered at 1593 °C in air. WDS analysis confirmed the homogeneity of the pellets. The sintered pellets obtained by amorphous citrate and by coprecipitation routes showed relative densities over 97 % of the theoretical density. These results indicated that the citrate amorphous route is an interesting and simple technique to prepare gadolinium-doped ceria powders with high sinterability.
Authors: Irwan Nurdin, Idris Yaacob Iskandar, M. Rafie Johan, Bee Chin Ang
Abstract: Maghemite nanoparticle suspensions were synthesized using a co-precipitation method and characterized by a variety of techniques including XRD, TEM, magnetic measurement, DLS, and zeta potential. The stability of the suspension was monitored by measuring the particle size distribution using DLS over a period of two months. The diffraction pattern from XRD measurement confirmed that the particles were maghemite with an average crystallite size of 9.4 nm. TEM observations and analyses showed that the geometry of maghemite nanoparticles were nearly spherical with a mean physical diameter of 9.9 nm. The maghemite nanoparticles showed superparamagnetic behavior with saturation magnetization value of 32.20 emu/g. The mean hydrodynamic diameter of the suspension remained unchanged after two months which indicated no formation of aggregation. The hydrodynamic diameters recorded were 45.1 nm and 48.4 nm, respectively. Additionally, lack of sedimentation indicated that the suspension was stable. The suspension’s zeta potential values were 41.5 mV and 40.4 mV for as synthesized and after two month of storage respectively.
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