• Journal of Powder Materials
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• v.22 no.1
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• pp.39-45
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• 2015

In this study, cobalt nanopowder is fabricated by sonochemical polyol synthesis and magnetic separation method. First, sonochemical polyol synthesis is carried out at $220^{\circ}C$ for up to 120 minutes in diethylene glycol ($C_4H_{10}O_3$). As a result, when sonochemical polyol synthesis is performed for 50 minutes, most of the cobalt precursor ($Co(OH)_2$) is reduced to spherical cobalt nanopowder of approximately 100 nm. In particular, aggregation and growth of cobalt particles are effectively suppressed as compared to common polyol synthesis. Furthermore, in order to obtain finer cobalt nanopowder, magnetic separation method using magnetic property of cobalt is introduced at an early reduction stage of sonochemical polyol synthesis when cobalt and cobalt precursor coexist. Finally, spherical cobalt nanopowder having an average particle size of 22 nm is successfully separated.

• Korean Journal of Materials Research
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• v.21 no.3
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• pp.138-143
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• 2011

Nanosized Pt, Pt-Ru and Pt-$CeO_2$ electrocatalysts supported on acid-treated carbon nanotube (CNT) were synthesized by microwave-assisted heating of polyol process using $H_2Cl_6Pt{\cdot}6H_2O$, $RuCl_3$, $CeCl_3$ precursors, respectively, and were characterized by XRD and TEM. And then the electrochemical activity of methanol oxidation for catalyst/CNT nanocomposite electrodes was investigated. The microwave assisted polyol process produced the nano-sized crystalline catalysts particles on CNT. The size of Pt supported on CNT was 7~12 nm but it decreased to 3~5 nm in which 10wt% sodium acetate was added as a stabilizer during the polyol process. This fine Pt catalyst particles resulted in a higher current density for Pt/CNT electrode. It was also found that 10 nm size of PtRu alloys were formed by polyol process and the onset potential decreased with Ru addition. Cyclic voltammetry analysis revealed that the $Pt_{75}Ru_{25}/CNT$ electrode had the highest electrochemical activity owing to a higher ratio of the forward to reverse anodic peak current. And the chronoamperemetry test showed that $Pt_{75}Ru_{25}$ catalyst had a good catalyst stability. The activity of Pt was also found to be improved with the addition of $CeO_2$.

• Clean Technology
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• v.25 no.1
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• pp.7-13
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• 2019

Recently, attention has been paid to obtaining bio-polyols from renewable resources. Successful use of these natural ingredients successfully produced in the industry for the synthesis of various polyurethanes is a very important task. In this study, a series of dimethylformamide (DMF) based polyurethanes were synthesized from methylene diphenyl diisocyanate (MDI)/1, 4-butanediol and bio-polyol (polytrimethylene ether glycol based on 1, 3-propanediol : B-POL)/polyester polyol (polyadipate diol based on 1,4-butandiol : H-PET). The effect of different ratio of bio-polyol (B-POL)/polyester polyol (H-PET) on the physical properties of polyurethane was investigated. As the B-POL content in B-POL/H-PET mixture increased, the glass transition of soft segment (Tgs) and tensile strength of polyurethane decreased, however, the elongation at break and tear strength increased. On the other hand, artificial leather was produced by wet process using synthesized DMF-based polyurethanes. It was found that there was almost no difference in the effect of the B-POL/H-PET composition on the average size and density (the number of cells per unit volume) of the porous cells formed in artificial leather. These results show that there is no problem in using bio-polyol (B-POL) based polyurethane for artificial leather produced by wet process.

• Bulletin of the Korean Chemical Society
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• v.35 no.11
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• pp.3209-3212
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• 2014

This paper describes a selective synthetic method of fabricating Ag nanowires by using a modified polyol process. To synthesize the Ag nanowire, an ethylene glycolic solution of silver nitrate and an ethylene glycolic solution of polyvinylpyrrolidone solution containing a small amount of organic oxidant, 1,4-benzoquinone, were slowly added to a hot ethylene glycol medium at $160^{\circ}C$ for 8 min using a syringe pump. The reaction mixtures were heated for an additional 45 min and cooled to room temperature. Finally, the silver nanomaterials were isolated from the mixture by centrifugation. The crystal structure of the nanomaterials was investigated by powder X-ray diffraction analyses, and their morphology was investigated by scanning electron microscopy. A small amount of organic oxidant, 1,4-benzoquinone, played a significant role in controlling the morphology during crystal growth. Consequently, Ag nanowires rather than Ag nanoparticles were selectively obtained.

• Journal of Powder Materials
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• v.23 no.4
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• pp.297-302
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• 2016

Ag nanoparticles are extensively studied and utilized due to their excellent catalysis, antibiosis and optical properties. They can be easily synthesized by chemical reduction methods and it is possible to prepare particles of uniform size and high purity. These methods are divided into vapor methods and liquid phase reduction methods. In the present study, Ag particles are prepared and analyzed through two chemical reduction methods using solvents containing a silver nitrate precursor. When Ag ions are reduced using a reductant in the aqueous solution, it is possible to control the Ag particle size by controlling the formic acid ratio. In addition, in the Polyol process, Ag nanoparticles prepared at various temperatures and reaction time conditions have multiple twinned and anisotropic structures, and the particle size variation can be confirmed using field emissions scanning electron microscopy and by analyzing the UV-vis spectrum.

• Applied Chemistry for Engineering
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• v.16 no.1
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• pp.39-44
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• 2005

In this study, polyurethane-acryl emulsion resins were synthesized from HDI (hexamethylene diisocyanate), IPDI (isophorone diisocyanate), Polyol, 2-HEMA (2-hydroxy ethylmethacrylate), n-BA (n-butyl acrylate) and MMA (methylmethacrylate). The effects of polyol types on the properties of polyurethane-acryl emulsion resin, such as degree of strength and water resistance and on the manufacturing process were investigated. In addition, the results were compared with those of acrylic emulsion. The test results showed that polyester type polyol demonstrated stronger tensile strength and higher water resistance with time than did acrylic emulsion and polyether type polyol.

• 한국신재생에너지학회:학술대회논문집
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• 2006.11a
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• pp.443-446
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• 2006

Carbon-supported Platinum (Pt) is the potential electro-catalyst material for anodic and cathodic reactions in fuel cell. Catalytic activity of the metal strongly depends on the particle shape, size and distribution of the metal in the porous supportive network. Conventional preparation techniques based on wet impregnation and chemical reduction of the metal precursors often do not provide adequate control of particle size and shape. We have proposed a novel route for preparing nano sized Pt colloidal particles in solution by oxidation of ethylene glycol. These Pt nano particles were deposited on large surface area carbon support. The process of nano Pt colloid formation involves the oxidation of solvent ethylene glycol to mainly glycolic acid and the presence of its anion glycolate depends on the solution pH. In the process of colloidal Pt formation glycolate actsas stabilizer for the Pt colloidal particle and prevents the agglomeration of colloidal Pt particles. These mono disperse Pt particles in carbon support are found uniformly distributed in nearly spherical shape and the size distribution was narrow for both supported and unsupported metals. The average diameter of the Pt nano particle was controlled in the range off to 3 nm by optimizing reaction parameters. Transmission electron microscopy, CV and RRDE experiments were used to compliment the results.

• Journal of Powder Materials
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• v.19 no.1
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• pp.60-66
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• 2012

In this study, Platinum(Pt) nanoparticles were synthesized by using polyol process which is one of the liquid phase reduction methods. Dihydrogen hexachloroplatinate (IV) hexahydrate $(H_2PtCl_6{\cdot}6H_2O)$, as a precursor, was dissolved in ethylene glycol and silver nitrate ($AgNO_3$) was added as metal salt for shape control of Pt particle. Also, polyvinylpyrrolidone (PVP), as capping agent, was added to reduce the size of particle and to separate the particles. The size of Pt nanoparticles was evaluated particle size analyzer (PSA). The size and morphology of Pt nanoparticles were observed by transmission electron microscopy (TEM) and high resolution TEM (HRTEM). Synthesized Pt nanoparticles were studied with varying time and temperature of polyol process. Pt nanoparticles have been successfully synthesized with controlled sizes in the range 5-10 and 20-40 nm with cube and multiple-cube shapes.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.36 no.2
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• pp.164-169
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• 2023

Nano Pt particles were dispersed on carbon-based supports by a polyol process for a catalyst application in a polymer electrolyte fuel cell. We tried to optimize the effect of pH on the electrostatic forces between the support and the Pt colloids. We investigated the relationship among the surface charges on the carbon support, the solution pH, and the concentration of a glycolate, and the Pt particle size. The produced catalyst with nano Pt particles on the support was evaluated by the long-term cyclic voltammetry (CV) performance test and compared with the results from a commercial catalyst. Our experimental results reveal that the pH-control can modify the particle size distribution and the dispersion of the nano Pt particles. This resulted in a cost-effective method for the synthesis of highly Pt loaded Pt/C catalysts for fuel cells better than a commercial catalyst system.

• KEPCO Journal on Electric Power and Energy
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• v.2 no.2
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• pp.187-192
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• 2016

Chemical utilization of $CO_2$ is recognized as the technology for the reduction of greenhouse gas as well as the use of carbon to resources. Although various chemicals are commercially produced, the innovative development is still necessary to utilize large quantity of $CO_2$. In this report, the current status of technology to preserve -CO-O- linkage into the molecules was introduced, particularly for the synthesis of dimethyl carbonate (DMC) and polyols, which are raw materials of polycarbonate and polyurethane, respectively. RIST developed the novel process for the DMC production via urea methanolysis and the new catalytic system for polyol synthesis. Because of high contents of $CO_2$ in both chemicals, it is expected that they are able to contribute for the reduction of greenhouse gas.