• Journal of Powder Materials
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• 제20권3호
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• pp.180-185
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• 2013

The iron oxides nanoparticles and iron oxide with other compounds are of importance in fields including biomedicine, clinical and bio-sensing applications, corrosion resistance, and magnetic properties of materials, catalyst, and geochemical processes etc. In this work we describe the preparation and investigation of the properties of coated magnetic nanoparticles consisting of the iron oxide core and organic modification of the residue. These fine iron oxide nanoparticles were prepared in air environment by the co-precipitation method using of $Fe^{2+}$: $Fe^{3+}$ where chemical precipitation was achieved by adding ammonia aqueous solution with vigorous stirring. During the synthesis of nanoparticles with a narrow size distribution, the techniques of separation and powdering of nanoparticles into rather monodisperse fractions are observed. This is done using controlled precipitation of particles from surfactant stabilized solutions in the form organic components. It is desirable to maintain the particle size within pH range, temperature, solution ratio wherein the particle growth is held at a minimum. The iron oxide nanoparticles can be well dispersed in an aqueous solution were prepared by the mentioned co-precipitation method. Besides the iron oxide nanowires were prepared by using similar method. These iron oxide nanoparticles and nanowires have controlled average size and the obtained products were investigated by X-ray diffraction, FESEM and other methods.

• Current Applied Physics
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• 제18권11호
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• pp.1403-1409
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• 2018

In the present study, the $SrMoO_4:Eu^{3+}$ phosphors has been synthesized through hydro-thermal co-precipitation method, and single factor and orthogonal experiment method was adopted to find optimal synthesis condition. It is interesting to note that hydro-thermal temperature is a prominent effect on the luminescent intensity of $SrMoO_4:Eu^{3+}$ red phosphor, followed by co-precipitation temperature, calcining time, and the doping amount of $Eu^{3+}$. The optimal synthesis conditions were obtained: hydro-thermal temperature is $145^{\circ}C$, co-precipitation temperature is $35^{\circ}C$, the calcining time is 2.5 h, and the doping amount of activator $Eu^{3+}$ is 25%. Subsequently, the crystalline particle size, phase composition and morphology of the synthesized phosphors were evaluated by X-ray powder diffraction (XRD) and scanning electron microscopy (SEM). The results show that these phosphors possess a scheelite-type tetragonal structure, and the particle size is about $0.2{\mu}m$. Spectroscopic investigations of the synthesized phosphors are carried out with the help of photo-luminescence excitation and emission analysis. The studies reveal that $SrMoO_4:Eu^{3+}$ phosphor efficiently convert radiation of 394 nm-592 and 616 nm for red light, and the luminescence intensity of $SrMoO_4:Eu^{3+}$ phosphors is improved. $SrMoO_4:Eu^{3+}$ phosphors may be a potential application for enhancing the efficiency of white LEDs.

• Journal of the Korea Academia-Industrial cooperation Society
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• 제10권4호
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• pp.852-856
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• 2009

Poly(ethyleneglycol methacrylate-co-benzyl methacrylate) (P(PEGMA-co-BMA)) microgel was prepared by precipitation copolymerization of PEGMA and benzyl methacrylate in poly(acrylic acid)/ethanol solution. The microgels with various sizes were obtained by changing the concentration of poly(acrylic acid), monomer and nature of solvents. The particle size of P(PECMA-co-BMA) microgels was decreased with increasing the concentration of poly(acrylic acid) and increased with that of monomer. By increasing solubility parameter of solvents, the particle size was inecreased. The size of P(PEGMA-co-BMA) microgels was controlled by experimental conditions from $0.1{\mu}m$ to $0.35{\mu}m$.

• Journal of the Korean Ceramic Society
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• 제35권6호
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• pp.559-568
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• 1998

Studies of preparation condition and characteristics of AUC(ammonium uranyl carbonate) were carried out to optimize AUC process with different reactor sizes and precipitation methos. As results four types of precipitates with different chemical compositions and morphologies were obtained from the reaction of {{{{ {(NH }_{4 }) { }_{2 } {CO }_{3 } }} with {{{{ {UO }_{2 }( {NO }_{3 }) { }_{2 } }} solution. A phase diagram has been made and crystal structure and chemical composition of each phase have been characterized by using SEM X-ray IR and thermal analysis. It was found that ammonium uranyl carbonate {{{{ {(NH }_{4 }) { }_{4 } {UO }_{2 } {(CO }_{3 }) { }_{3 } }} with monoclinic crystal morphology could be syn-thesized when the mole ratio of in {{{{ {(NH }_{4 }) { }_{2 } {CO }_{3 }/ {UO }_{2 } {(NO }_{3 }) { }_{2 } }} in the solution was higher than 5 Also a mechanism and a precipitating condition on rounding of the AUC particle were examined in the course of the AUC pre-cipitation. The rounding of the AUC particle was possible only by external circulation using pump not by internal circulation using agitator.

• Journal of the Korean Chemical Society
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• 제56권4호
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• pp.431-439
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• 2012

Dissipative particle dynamics (DPD) was carried out to study the nucleation and crystal growth process of $CeO_2$ nanoparticles in different alcohol aqueous solutions. The results showed that the nucleation and crystal growth process of $CeO_2$ can be classified into three stages: nuclei growth, crystal stabilization and crystal aggregation except the initial induction stage, which could be reproduced by collecting simulation results after different simulation time. Properly selecting the sizes of $CeO_2$ and water bead was crucial in the simulation system. The influence of alcohol type and content in solutions, and precipitation temperature on the particle dimension were investigated in detail and compared with the experimental results. The consistency between simulation results and experimental data verify that the simulation can reproduce the macroscopic particle aggregation process. The effect of solvent on the nucleation and crystal growth of $CeO_2$ nanoparticles are different at three stages and can not be simply described by Derjaguin-Landau-Verwey-Overbeek (DLVO) theory or nucleation thermodynamics theory. Our work demonstrated that DPD methods can be applied to study nanoparticle forming process.

• Computers and Concrete
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• 제15권6호
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• pp.989-999
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• 2015

An advanced continuum-based multi-physical single particle model was recently introduce for the hydration of tricalcium silicate ($C_3S$). In this model, the dissolution and the precipitation events are modeled as two different yet simultaneous chemical reactions. Product precipitation involves a nucleation and growth mechanism wherein nucleation is assumed to happen only at the surface of the unreacted core and product growth is characterized via a two-step densification mechanism having rapid growth of a low density initial product followed by slow densification. Although this modeling strategy has been shown to nicely mimic all stages of $C_3S$ hydration - dissolution, dormancy (induction), the onset of rapid hydration, the transition to slow hydration and prolonged reaction - the major criticism is that many adjustable parameters are required. If formulated correctly, however, the model parameters are shown here to be statistically independent and significant.

• Macromolecular Research
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• 제17권5호
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• pp.339-345
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• 2009

The core/shell type structure of the highly crosslinked poly(glycidylmetharylate-co-divinylbenzene) microspheres prepared in the precipitation polymerization in acetonitrile was thoroughly verified by means of swelling, $^1H$ NMR, XPS, TEM and TGA measurements. In the XPS measurement, the higher the GMA content, the higher the oxygen content was observed, implying that the higher content of GMA is observed in the particle surface. The further verification of the core/shell structure of the poly(GMA-co-DVB) particles was carried out using $^1H$ NMR and TEM techniques, resulting in the poly(GMA-co-DVB) particles with the GMA rich-phase and DVB rich-phase. In overall, the poly(GMA-co-DVB) microspheres consist of a highly crosslinked DVB rich-phase in the core and slightly or non-crosslinked GMA rich-phase in the shell part due to the different reaction ratios between two monomers and self-crosslinking density of DVB.

• Clean Technology
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• 제10권4호
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• pp.215-220
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• 2004

Micronized acetaminophen was precipitated from ethanol solution using supercritical $CO_2$ as antisolvent. A coaxial nozzle was used to introduce the supercritical $CO_2$ and the acetaminophen/ethanol solution. The effects of pressure, temperature, $CO_2$ flow rate and solvent flow rate were studied in the constant pressure and temperature condition. The particle size and morphology were influenced by the variations of precipitation condition. The particle size and morphology were analyzed with scanning electron microscopy.

• Journal of Korean Society of Water and Wastewater
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• 제30권4호
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• pp.409-415
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• 2016

Magnetite particles were synthesized by co-precipitation of water-soluble 밀 스케일-derived precursor by various concentrations of (0.5, 0.67, 1, 2 N) NaOH and (0.6, 0.8, 1.2, 2.4 N) $NH_4OH$. It is theoretically known that as the concentration of the alkaline additive used in iron oxide synthesis increases, the particle size distribution of that iron oxide decreases. This trend was observed in both kind of alkaline additive used, NaOH and $NH_4OH$. In addition, the magnetite synthesized in NaOH showed a relatively smaller particle size distribution than magnetite synthesized in $NH_4OH$. Crystalline phase of the synthesized magnetite were determined by X-ray diffraction spectroscopy(XRD). The particles were then used as an adsorbent for phosphate(P) removal. Phosphorus adsorption was found to be more efficient in NaOH-based synthesized magnetite than the $NH_4OH$-based magnetite.

• Journal of Powder Materials
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• 제23권2호
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• pp.136-142
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• 2016

As precursors of cathode materials for lithium ion batteries, $Ni_{1/3}Co_{1/3}Mn_{1/3}(OH)_2$ powders are prepared in a continuously stirred tank reactor via a co-precipitation reaction between aqueous metal sulfates and NaOH in the presence of $NH_4OH$ in air or nitrogen ambient. Calcination of the precursors with $Li_2CO_3$ for 8 h at $1,000^{\circ}C$ in air produces dense spherical cathode materials. The precursors and final powders are characterized by X-ray diffraction (XRD), scanning electron microscopy, particle size analysis, tap density measurement, and thermal gravimetric analysis. The precursor powders obtained in air or nitrogen ambient show XRD patterns identified as $Ni_{1/3}Co_{1/3}Mn_{1/3}(OH)_2$. Regardless of the atmosphere, the final powders exhibit the XRD patterns of $LiNi_{1/3}Co_{1/3}Mn_{1/3}O_2$ (NCM). The precursor powders obtained in air have larger particle size and lower tap density than those obtained in nitrogen ambient. NCM powders show similar tendencies in terms of particle size and tap density. Electrochemical characterization is performed after fabricating a coin cell using NCM as the cathode and Li metal as the anode. The NCM powders from the precursors obtained in air and those from the precursors obtained in nitrogen have similar initial charge/discharge capacities and cycle life. In conclusion, the powders co-precipitated in air can be utilized as precursor materials, replacing those synthesized in the presence of nitrogen injection, which is the usual industrial practice.