Papers by Keyword: Co-Precipitation

Abstract: Zirconia (ZrO₂) is one of the refractory ceramic materials that have applications in several fields. The aim of this study was to synthesis ZrO₂ from natural zircon sand collected from Kereng Pangi, Central Kalimantan with a variation of pH deposition using alkali fusion co-precipitation method. The synthesized ZrO₂ began with the preparation process involved magnetic separation, milling, and leaching with HCl. Furthermore, the alkali fusion process was used KOH solution and heated in an electrical furnace at 700°C for 3 h whereas the co-precipitation process was carried out using a filtrate mixed with the NH₄OH solution to reach a pH variation between 3–11 and then precipitated for 12 h. The precipitates were dried in an oven and then calcined at 800°C for 3 h. The structure of synthesized ZrO₂ was characterized using XRD and the particle sizes were measured using particle size analyzer (PSA). The XRD analysis showed that the identified phase of zirconia powder is tetragonal with a crystal size in nanometer size. Result of PSA measurement revealed that the crystal size decreased in the range pH of 3 - 7, but increased in the range pH of 7 - 11. The biggest powder particle size could be achieved at 260 nm with pH 7 whereas the smallest size was at 143 nm occurred at pH 3.

Abstract: A novel red-emitting K₂SiF₆:Mn⁴⁺ phosphors with different Mn⁴⁺ doping mole fraction were synthesized by co-precipitation method. X-ray diffraction (XRD), scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FT-IR) and fluorescence spectrometer were used to characterize the properties of K₂SiF₆:Mn⁴⁺ phosphors. As-prepared K₂SiF₆:Mn⁴⁺ phosphors have cubic crystal structure. Under excitation at 450 nm, an intense red emission peak around 632 nm corresponding to the ²E_g-⁴A₂ transition of Mn⁴⁺ was observed for 8.37 mol% K₂SiF₆:Mn⁴⁺ phosphors and was used as the optimum doping concentration. The excellent luminescent properties make the phosphor K₂SiF₆:Mn⁴⁺ a candidate for applications in InGaN-YAG:Ce³⁺ type LEDs for high color rendering. “A warm” white light LED with an efficiency of 147 lm/w and a color rendering index of 87.4 at a color temperature of 2864K has been obtained by fabricating YAG:Ce³⁺ with K₂SiF₆:Mn⁴⁺ on an InGaN chip.

Abstract: Brushite cement has advantages such as fast setting, high reactivity and good injectability over apatitic cements. To induce the bioactivity of brushite cements, the goal was to convert it into a bone-like low crystalline carbonate apatite. To achieve this induced transformation, potassium and magnesium were used as dopants which were claimed to be effective in the literature. The cements were immersed for 2 periods of time: 1 day and 6 weeks in Tas-Simulated-Body-Fluid (Tas-SBF) due to its excellent biomimetic properties with its adjusted HCO3- and Cl- ionic rates according to human-blood-plasma. 5% of potassium (to calcium sites) seemed to be more effective over magnesium modification. The aim of this study is to define an optimal composition in terms of transforming brushite into apatite.

Abstract: Superparamagnetic iron oxide nanoparticles (SPION) were synthesized by one pot coprecipitation method at room temperature in the presence of Polyvinylpyrrolidone (PVP). X-ray powder diffraction (XRD), transmission electron microscopy (TEM), and Vibrating Sample Magnetometer (VSM) were used to analysis the physicochemical properties of PVP-SPION. The XRD patterns confirmed that the structure of as-synthesized sample is magnetite with cubic structure system. In TEM results, the image of PVP-SPION displayed that the size of particles was 14.05 nm with narrower size distribution and also the PVP played important role to minimize the agglomeration of SPION. Finally, the high saturation magnetization value of PVP-SPION (53.0 emu/g) indicate the as-synthesized sample has a great potential as a contrast agent for MRI.

Abstract: With the development of new energy vehicles, urgent issues have attracted considerable attention. Some power batteries have entered the scrapping period, with the imperative recycling of used power batteries. Some studies have predicted that by 2020, the amount of power lithium battery scrap will reach 32.2 GWh, corresponding to ~500,000 tons, and by 2023, the scrap will reach 101 GWh, corresponding to ~1.16 million tons. In this study, nickel-cobalt-lithium LiNi_0.7Co_0.3O₂ cathode materials are regenerated from spent lithium-ion battery cathode materials as the raw material, which not only aids in the reduction of pressure on the environment but also leads to the recycling of resources. First, extraction is employed using extracting agent p204 to remove aluminum ions from an acid leaching solution. Extraction conditions for aluminum ions are: include a phase ratio of 1:2,a pH of 3, an extractant concentration of 30%, and a saponification rate of 70%.Next, the precursor was prepared by co-precipitation using sodium hydroxide and ammonia water as the precipitant and complexion agents, respectively; hence, the cathode material can be uniformly mixed at the atomic level. The precursor and lithium hydroxide were subjected to calcination at high temperature using a high-temperature solid-phase method. The Calcination conditions include an air atmosphere ; a calcination temperature of 800° °C ; a calcination time of 15 h, an n (precursor): n (lithium hydroxide) ratio of 1:1.1.The Thermogravimetric analysis revealed that the synthesis temperature should not exceed 850°C. X-ray diffraction analysis, scanning electron microscopy, and energy spectrum analysis of the cathode material revealed a composition comprising Li, Ni, and Co oxides. After analysis, the material obtained is lithium nickel-cobalt-oxide, LiN_i0.7Co_0.3O₂, which is a positive electrode material with good crystallinity and a regular layered structure.

Abstract: This work presents the synthesis and characterization of mixed rare earths hydroxide heterogeneous catalyst. The catalysts were prepared by co-precipitation of mixed rare earths with NaOH at different pH (6, 7 and 12). The prepared catalysts were characterized by X-ray fluorescence (XRF), X-ray diffraction (XRD) and scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM–EDS). The XRF results showed that the catalyst composed of cerium (Ce), neodymium (Nd), lanthanum (La), praseodymium (Pr) and samarium (Sm) being predominant at pH up to 7. Particularly, cerium (Ce) was favorable precipitation at pH 7. This results were confirm by SEM-EDS. The Ce (OH)₃ phase was clearly observed for the mixed rare earth catalyst precipitated at pH 7. The XRF, SEM-EDS and XRD results were consistency.

Abstract: In the present study, Fe₃O₄ nanoparticles type/core layer were synthesized by co-precipitation wet method and coated with a polymer mixture of polyethylene glycol (PEG). It was performed a study about the effect of duration in maceration time on the final size of nanoparticles in in order to get reaching the maximum condition of disintegration of the crystals. The samples were synthesized according to the same procedure and amount of reactants used synthetic sequence for all samples, only varying the time spent by each sample maceration process done after synthesis. The different times for the maceration samples were 3 minutes, 5 minutes, 7 minutes, 10 minutes, 12 minutes, 20 minutes and finally 30 minutes. The nanoparticles were characterized by Nanosight, DR-X, rietvield analysis and hysteresis curves plotter techniques. The results showed that the grain size of the particles stabilizes at maceration times of more than 20 minutes. The samples presented a satisfactory hysteresis curve indicating the presence of superparamagnetic behavior expected in hyperthermia treatment.

Abstract: The YAM coatings on the ZrB₂ composites surface were prepared by co-precipitation technique and with Al (NO₃)₃ and Y(NO₃)₃ solutions acting as precursor. The effect of matrix surface treating conditions, dipping times and calcination temperature was investigated. Phase compostion, coating morphology and interface between matrix and coating were analyzed by XRD and SEM. The results indicated that the YAM coating was formed after calcined at 1250°C in vaccum. The thickness of coating was increased with the dipping times, the smoothest coating was obtained by two dipping times, and matrix surface coarsing was beneficial for improving the adhension between matrix and coating. The ablative teste was evaluated at 2000°C by oxy-acetylene flame, the ablative properties was obviously improved by coating compared with uncoated composites.

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 ⁵D₀→⁷F₂ 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.

Abstract: Sc_0.88Lu_0.05(V_1-xP_x)O₄:Eu³⁺_0.07(0≤x≤0.5) phosphors were synthesized by co-precipitation method. The structure, morphology and luminescence spectra of samples were investigated by XRD, SEM and fluorescence spectrophotometer, respectively. The samples doped with Eu³⁺, Lu³⁺ and PO₄^3- can maintain the body-centered tetragonal structure of ScVO₄ and the morphology essentially remains unchanged with slight agglomeration. The excitation spectrum intensity of Sc_0.88Lu_0.05(V_1-xP_x)O₄:Eu³⁺_0.07 increase within the near UV excitation (360-410nm). The optimum doping concentration of PO₄^3- is 0.2(x value), and the maximum emission intensity of Sc_0.88Lu_0.05(V_0.8P_0.2)O₄:Eu³⁺_0.07 is about 35 % higher than the Sc_0.88Lu_0.05VO₄:Eu³⁺_0.07 under 365 nm excitation. Decay curve of ⁵D₀ state for as-prepared samples fits the single order exponential behavior, the lifetime of ⁵D₀ increase first and then decrease with the increase of PO₄^3- doping concentration. The internal quantum efficiency is up to 66.73% under 365nm excitation, When the temperature rises to 200°C, the emission intensity maintains 79.3% of that in the room temperature. Sc_0.88Lu_0.05(V_0.8P_0.2)O₄:Eu³⁺_0.07 phosphor shows high internal quantum efficiency and thermal stability, which is suitable for the UV-pumped white LED as red phosphor.