Co-precipitation Temperature Research Articles

Effects of Precursor Co-Precipitation Temperature on the Properties of LiNi1/3Co1/3Mn1/3O2 Powders

Effects of Precursor Co-Precipitation Temperature on the Properties of LiNi1/3Co1/3Mn1/3O2 Powders

Novel Formulation of Chlorhexidine Spheres and Sustained Release with Multilayered Encapsulation.

This work demonstrates the synthesis of new chlorhexidine polymorphs with controlled morphology and symmetry, which were used as a template for layer-by-layer (LbL) encapsulation. LbL self-assembly of oppositely charged polyelectrolytes onto the drug surface was used in the current work, as an efficient method to produce a carrier with high drug content, improved drug solubility and sustained release. Coprecipitation of the chlorhexidine polymorphs was performed using chlorhexidine diacetate and calcium chloride solutions. Porous interconnected chlorhexidine spheres were produced by tuning the concentration of calcium chloride. The size of these drug colloids could be further controlled from 5.6 μm to over 20 μm (diameter) by adjusting the coprecipitation temperature. The chlorhexidine content in the spheres was determined to be as high as 90%. These particles were further stabilized by depositing 3.5 bilayers of poly(allylamine hydrochloride) (PAH) and polystyrenesulfonate (PSS) on the surface. In vitro release kinetics of chlorhexidine capsules showed that the multilayer shells could prolong the release, which was further demonstrated by characterizing the remaining chlorhexidine capsules with SEM and confocal microscopy. The new chlorhexidine polymorph and LbL coating has created novel chlorhexidine formulations. Further modification to the chlorhexidine polymorph structure is possible to achieve both sustained and stimuli responsive release, which will enhance its clinical performance in medicine and dentistry.

Influences of carbonate co-precipitation temperature and stirring time on the microstructure and electrochemical properties of Li1.2[Mn0.52Ni0.2Co0.08]O2 positive electrode for lithium ion battery

The 0.6Li2MnO3·0.4Li [Ni0.5Co0.2Mn0.3]O2 (Li1.2[Mn0.52Ni0.2Co0.08]O2) nanoparticles have been synthesized using a co-precipitation method. The conventional chelating agent NH3·H2O was replaced by environmentally friendly sodium lactate, and then the influences of carbonate co-precipitation temperature and stirring time on the microstructure and electrochemical properties of Li1.2[Mn0.52Ni0.2Co0.08]O2-positive electrode are discussed systematically. The crystal structure, particle morphology and electrochemical properties of the as-prepared samples are studied by XRD, SEM and charge–discharge tests. The optimal material (Li1.2[Mn0.52Ni0.2Co0.08]O2-60°C/16h) had a spherical particle shape and a well-ordered layered structure, as well as high tap-density and a low cation-mixing degree. In addition, the sample delivers the best electrochemical properties with a capacity retention of 96.58% (189.1mAh g−1) after 100cycles at 0.5C rate and the highest discharge capacity of 175.2mAh g−1 at 1C rate.

Performance Study f V2O5/TiO2 Mixed Metal Oxide Nanocatalysts in Selective Catalytic Reduction of Nox Prepared by Co-Precipitation Method

In this work, the selective catalytic reduction of NO with NH3 in the presence of oxygen over a series of Vanadia-Titania was investigated. Catalysts prepared by Co-precipitation method with oxalic acid. Response surface methodology involving central composite design was employed to model and optimize the catalyst preparation parameters of (V loading, calcination temperature, and Co-precipitation temperature) in Selective catalytic reduction of NO at 300°C. Results show that RSM model is able to predict NO conversion data with an acceptable level of accuracy (R2=0.995). The optimum conditions for V loading, Calcinations Temperature, and Co- precipitation temperature were 0.000654 mole, 441°C and 83°C, respectively.

Synthesis of Improved Catalytic Materials for High-Temperature Water-gas Shift Reaction

In this investigation, we report the preparation and characterization of Co-, Cuand Mn-substituted iron oxide catalytic materials supported on activated carbon. Co-precipitation method and low temperature treatment were used for their synthesis. The influence of chemical composition, stoichiometry, particle size and dispersity on their catalytic activity was studied. Samples were characterized in all stages of their co-precipitation, heating and spend samples after catalytic tests. The obtained results from room and low temperature Mossbauer spectroscopy were combined with analysis of powder X-ray diffraction patterns (XRD). They revealed the preparation of nano-sized iron oxide materials supported on activated carbon. Relaxation phenomena were registered also for the supported phases. The catalytic performance in the water-gas shift reaction was studied. The activity order was as follows: Cu0.5Fe2.5O4 > Co0.5Fe2.5O4 > Mn0.5Fe2.5O4. Catalytic tests demonstrated very promising results and potential application of studied samples due to their cost-effective composition.

Magnetic Properties of Fe 3 O 4 Nanoparticles Synthesized by Coprecipitation Method

In this paper, we elucidate several specific magnetic properties of Fe 3O4nanoparticles synthesized by coprecipitation method. The characterizations by X-ray diffraction technique (XRD) and scanning electron microscopy (SEM) showed the particles to be of spinel structure and spherical shapes whose diameter could be controlled in the range from 14 to 22 nm simply by adjusting the precursor salts concentration and coprecipitation temperature. Magnetic properties of the Fe 3O4 nanoparticles measured by using vibration sample magnetometer (VSM) indicated the saturation magnetization and blocking temperature to increase with the particles size. Fe 3O4 nanoparticles with crystal size smaller than 22 nm exhibits superparamagnetic behavior at room temperatures. Characteristic magnetic parameters of the particles including saturation magnetization, effective anisotropy constant, and magnetocrystalline anisotropy constant have been determined. The observed decrease of saturation magnetization was explained on the base of core-shell model. A simple analysis indicated that the shell thickness decreases with an increase in particle size.

Synthesis of Lix[Ni0.225Co0.125Mn0.65]O2 as a positive electrode for lithium-ion batteries by optimizing its synthesis conditions via a hydroxide co-precipitation method

Lix[Ni0.225Co0.125Mn0.65]O2 cathode material for a lithium-ion battery was synthesized from metal hydroxide Ni0.225Co0.125Mn0.65(OH)2. The co-precipitated metal hydroxide was greatly influenced by synthesis conditions of pH, concentration of chelating agent, stirring speed, and co-precipitation temperature. The conditions were optimized by observing the spherical and uniform particles, as examined by scanning electron microscopy. The optimized pH, ammonia concentration stirring speed and co-precipitation temperature were determined to be 11–12, 0.36M, 1000rpm and 50°C, respectively. The final products, Lix[Ni0.225Co0.125Mn0.65]O2 had a well-ordered hexagonal super lattice layered structure as established by Rietveld refinement of X-ray diffraction pattern. As a result, the Lix[Ni0.225Co0.125Mn0.65]O2 compound may be considered as a excellent candidate for cathode material of Lithium secondary battery in terms of cycle life, both safety and energy density, lower cost and low environmental impact.

Synthesis of spherical Li1.167Ni0.2Co0.1Mn0.533O2 as cathode material for lithium-ion battery via co-precipitation

xLi2MnO3·(1−x)LiNi0.4Co0.2Mn0.4O2(x=0.5) powders were synthesized from co-precipitated spherical metal carbonate, Ni0.2Co0.1Mn0.533(CO3)x. It has been found that the preparation of metal carbonate was significantly dependent on synthetic conditions, including the co-precipitation temperature, kind of precipitator, and stirring speed. The results of SEM showed that the shape of precursor powders was sphere-like. And the final product, Li1.167Ni0.2Co0.1Mn0.533O2, was also significantly uniform due to the homogeneity of the metal carbonate precursor, Ni0.2Co0.1Mn0.533(CO3)x,. Li1.167Ni0.2Co0.1Mn0.533O2 has α-NaFeO2 layered structure, as confirmed by XRD analysis. The average particle size was about 10μm in diameter and the particle size distribution was relatively narrow. The results of XRD and chemical analysis showed that the synthesized Li1.167Ni0.2Co0.1Mn0.533O2 had lower cation mixing and good layered structure, and the chemical composition is almost Li1.198Ni0.193Co0.103Mn0.537O2. Electrochemical properties during charge and discharge were discussed. In the voltage range of 2.0–4.8V, the discharge capacity of Li1.167Ni0.2Co0.1Mn0.533O2 was 340mAh/g.

Synthetic optimization of spherical Li[Ni1/3Mn1/3Co1/3]O2 prepared by a carbonate co-precipitation method

Abstract A carbonate co-precipitation method was employed to prepare spherical Li[Ni 1/3 Co 1/3 Mn 1/3 ]O 2 cathode material. The precursor, [Ni 1/3 Co 1/3 Mn 1/3 ]CO 3 , was prepared using ammonia as chelating agent under CO 2 atmosphere. The spherical Li[Ni 1/3 Co 1/3 Mn 1/3 ]O 2 was prepared by mixing the precalcined [Ni 1/3 Co 1/3 Mn 1/3 ]CO 3 with LiOH followed by high temperature calcination. The preparation conditions such as ammonia concentration, co-precipitation temperature, calcination temperature and Li/[Ni 1/3 Co 1/3 Mn 1/3 ] ratio were varied to optimize the physical and electrochemical properties of the prepared Li[Ni 1/3 Co 1/3 Mn 1/3 ]O 2 . The structural, morphological, and electrochemical properties of the prepared LiNi 1/3 Co 1/3 Mn 1/3 O 2 were characterized by XRD, SEM, and galvanostatic charge–discharge cycling. The optimized material has a spherical particle shape and a well ordered layered structure, and it also has an initial discharge capacity of 162.7 mAh g − 1 in a voltage range of 2.8–4.3 V and a capacity retention of 94.8% after a hundred cycles. The optimized ammonia concentration, co-precipitation temperature, calcination temperature, and Li/[Ni 1/3 Co 1/3 Mn 1/3 ] ratio are 0.3 mol L − 1 , 60 °C, 850 °C, and 1.10, respectively.

Effect of coprecipitation temperature on the properties and activity of fibroblast growth factor-2 apatite composite layer

Fibroblast growth factor-2 (FGF-2) apatite composite layers were formed on anodically oxidized titanium (Ti) rods at temperatures lower than the previously used 37 °C to reduce the risk of the inactivation of FGF-2 in calcium phosphate solution. A two-step procedure was used to coprecipitate FGF-2 apatite composite layers on Ti rods. Continuous and homogeneous carbonate-containing low-crystalline apatite layers incorporating FGF-2 were formed on the surface of the Ti. The amounts of apatite and FGF-2 coprecipitated on the Ti rod surface decreased with decreasing coprecipitation temperature. When the coprecipitation temperatures were 15 and 20 °C, the amounts of FGF-2 precipitated on the Ti rods were 0.19 ± 0.03 and 0.20 ± 0.03 μg/cm 2, respectively. A cell proliferation assay for evaluating the mitogenic activity of FGF-2 immobilized in the layer showed that when FGF-2 was coprecipitated at 15 and 20 °C, the number of NIH3T3 cells cultured with FGF-2 extract was significantly larger than that at 4, 10, 25 and 30 °C. To obtain the largest amount of active FGF-2 on a Ti surface, a temperature of 15 or 20 °C should be used for coprecipitating FGF-2.

Influence of the co-precipitation temperature on phase evolution in yttrium-aluminium oxide materials

Yttrium-aluminium garnet (YAG) powders were synthesized using a reverse-strike precipitation, by adding an aqueous solution of yttrium and aluminium chlorides to dilute ammonia while monitoring the pH to a constant value of 9. After precipitation, the gelly product was washed with dilute ammonia and absolute ethanol for avoiding hard agglomeration during drying. Precipitation and washing procedures were performed at three different temperatures, namely at 5, 25 and 60 °C. After drying, the powders were characterized by DTA/TG simultaneous analysis and then calcined at different temperatures and times. Phase evolution was investigated by X-ray analysis; the evolution of crystallites formation and growth as a function of the temperature was followed by TEM observations. In this paper, a relevant influence of the co-precipitation temperature on the phases appearance, crystallisation path and final homogeneity of these powders was demonstrated. Pure YAG was yielded starting from powder synthesized at low temperature, whereas the precipitation performed at 60 °C leaded to monoclinic Y 4Al 2O 9 appearance near YAG.

Study on preparation of manganese–zinc ferrites using spent Zn–Mn batteries

Studies on preparing manganese–zinc ferrites by coprecipitation method using spent Zn–Mn batteries have been carried out to determine the influential factors on preparing process, including coprecipitation pH value, coprecipitation temperature and calcining temperature, etc. Results show that the suitable preparing conditions are: coprecipitation pH value, 7–7.5; copecipitation temperature, 50 °C and calcining temperature, 1100–1150 °C. It also finds that Fe powder is the suitable material to remove Hg existing in spent Zn–Mn batteries completely.

Synthesis and characterization of CoFe2O4 magnetic nanoparticles prepared by temperature-controlled coprecipitation method

Magnetic nanoparticles of cobalt ferrite (CoFe 2 O 4 ) have been synthesized in a homogeneous aqueous solution without any template and subsequent heat treatment. The average particle size could be varied in the range of 2–14 nm by controlling coprecipitation temperature of Co 2+ and Fe 3+ ions in alkaline solution although the size distribution is pretty wide. As the precipitation temperature increased in the range of 20–80°C, the average particle size also increased. However, there is a considerable change in XRD crystallinity and the average size of the nanoparticles at the precipitation temperature between 40°C and 60°C. While the nanoparticles prepared at the temperature below 40°C show superparamagnetic relaxation at room temperature with blocking temperatures between 75 and 200 K, the samples prepared at the temperature higher than 60°C consist of both superparamagnetic and ferrimagnetic nanoparticles that result in magnetic coercivity at room temperature. Mössbauer spectra of the samples also confirmed their magnetic properties and wide size distribution in each sample. The analysis of the spectra gave a rough estimation of the ratio of superparamagnetic and ferromagnetic nanoparticles in each sample at various temperatures.

無機酸塩を原料とするゾルゲル法によるペロブスカイト型ＬａＦｅＯ３超微粒子粉体の調整

erovskite-type LaFe03 powders were prepared by drop coprecipitation method. An aqueous solution of La(NO3)3 and Fe(NO3)3 was dropped slowly (0.4 ml⋅ min-1) into an water-ethanolammonia solution at 40°C. The resultant gel was calcined at temperatures down to 630 °C for 2 h. The sizes of LaFe03 polycrystals were found to be as low as 13-20 nm by XRD and TEM. Their BET surface areas were measured to be 20-49 m2- g-1. In consequence of the experiment with change of coprecipitation temperature, stirring speed, dropping speed or calcination conditions of temperatures and time, the most effective factor to determine the size of ultra-fine particle were found to be the calcination temperature. In addition, the maximum surface area was obtained by short calcination time and ultrasonic stirring as secondary effects. The minimum crystallite size of LaFeO3 was obtained around the crystallization temperature (630 °C).

Separation of thallium-201 from Tl, Pb and Bi cyclotron target materials

Radiochemical methods of thallium-201 separation from proton-irradiated thallium, lead and bismuth targets have been developed. The procedures are based on the processes of coprecipitation, ion-exchange chromatography and high temperature gas chemistry. The purity of thallium samples complies with requirements of nuclear medicine for thallium-201 product.