• Bulletin of the Korean Chemical Society
• /
• v.34 no.5
• /
• pp.1391-1396
• /
• 2013

The photocontrolled reduction of silver nitrate to silver (Ag) nanoparticles on honeycomb-patterned poly(N-vinylcarbazole) (PVK)-cellulose triacetate (CTA) composite thin films was studied. The composites were prepared via the oxidative polymerization of N-vinylcarbazole with ferric chloride using different CTA concentrations. A honeycomb-patterned film was fabricated by casting the composite solution under humid conditions. Ag particles with a homogeneous distribution were produced by the composite film in a moderate CTA concentration, whereas aggregated Ag was obtained from the pure PVK film.

• Tribology and Lubricants
• /
• v.39 no.6
• /
• pp.244-249
• /
• 2023

This paper presents a comprehensive analysis of the impact of surface roughness on the friction and wear properties of SUS 321, an austenitic stainless steel variant produced using the laser powder bed fusion (LPBF) technique, which is a prevalent additive manufacturing method. After the LPBF fabrication, the specimens go a heat treatment process aimed at alleviating residual stress. Subsequently, they are polished extensively to achieve a refined and smooth surface. To deliberately introduce controlled variations in surface roughness, an etching process is employed. This multi-step method encompassed primary etching in a 3M hydrochloric acid solution, followed by secondary etching in a 35 wt% ferric chloride solution, with varying durations applied to different specimens. A comprehensive evaluation of the surface characteristics ensued, employing precise techniques such as surface roughness measurements and meticulous assessments of water droplet contact angles. Following the surface treatment procedures, a series of friction tests are performed to explore the tribological behavior of the etched specimens. This in-depth investigation reached its peak by revealing valuable insights. It clarified a strong correlation between intentionally altered surface roughness, achieved through etching processes, and the resulting tribological performance of LPBF-fabricated SUS 321 stainless steel. This significantly advances our grasp of material behavior in tribological applications.

• Corrosion Science and Technology
• /
• v.2 no.1
• /
• pp.18-25
• /
• 2003

Effects of the precipitation of $\sigma$ phase on the metastable pitting as a precursor of stable pitting corrosion and also on the progress of stale pitting of the 25Cr-7Ni-3Mo-0.25N duplex stainless steel were investigated in chloride solution. Electrochemical potential and current noises of the alloy were measured in 10 % ferric chloride solution ($FeCl_3$) with zero resistance ammeter (ZRA), and then analyzed by power spectral density (PSD) and by corrosion admittance ($A_c$) spectrum. With aging at $850^{\circ}C$, the passive film of the alloy was found to get significantly unstable as represented by power spectral density (PSD) and a transition from metastable pitting state to stable one was observed. In the corrosion admittance spectrum, the number of negative $A_c$ corresponding to the state of localized corrosion increased with aging, suggesting that the precipitation of $\sigma$ phase considerably degraded the passive film by depleting Cr and Mo around it at $\alpha/\sigma$ or $\gamma/\sigma$ phase boundaries, thereby leading to the initiation of the pitting corrosion. However, the Cr and Mo at $\alpha/\sigma$ or $\gamma/\sigma$ phase boundaries which were once depleted due to the precipitation of the $\sigma$ phase were partly replenished by the diffusion of Cr and Mo from the surrounding matrix with aging time longer. The initiation of pitting seems to be associated with the precipitation density of the $\sigma$ phase with an effective size needed to induce the sufficient depletion of Cr and Mo around it.

• Journal of Korean Society of Environmental Engineers
• /
• v.38 no.4
• /
• pp.169-176
• /
• 2016

This research explored the feasibility of preparing and utilizing preformed polymeric solution of Fe(III) as coagulants for water treatment. The differentiation and quantification of hydrolytic Fe(III) species in coagulant was done by utilizing spectrophotometric method based on the interaction of Fe(III) with Ferron as a complexing agent. The properties of the synthesized polymeric iron chloride (PICl) showed that the quantity of polymeric Fe(III) produced at r = 1.5 was 20% of the total iron in solution, as showing maximum contents. Coagulation experiments were conducted under the condition of various coagulant doses and pH for each coagulant prepared. From the comparison of the characterization of coagulation for $FeCl_3$ (r = 0.0) and PICl (r = 0.5, 1.0, 1.5) coagulants, PICl (r = 0.5, 1.0, 1.5) coagulants was found to be more effective than other coagulant for the removal of organic matters. The experimental results for the coagulation tests at various pH ranges showed that the PICl was least affected by the coagulation pH and PICl was very effective for the removal of turbidity and organic materials over wide pH range (pH 4-9) tested.

• Resources Recycling
• /
• v.17 no.5
• /
• pp.37-43
• /
• 2008

Stripping experiments of iron from the loaded Alamine336 by sulfurous, chloric and sulfuric acid solutions have been performed by varying the concentration of acid and stripping conditions. The stripping percentage of iron decreased with the increase of HCl and $H_{2}SO_4$ concentration, while that increased with the increase of $H_{2}SO_3$ concentration up to 3 M. Stripping temperature had adverse effect on the stripping percentage of iron in the stripping by $H_{2}SO_3$ solution, while the stripping percentage of iron by HCl solution increased with the increase of temperature. Stripping isotherm of iron by 0.1 M HCl and 0.1 M $H_{2}SO_4$ solution indicated that three and four stripping stages could result in a solution containing 0.05 M iron at an O/A ratio of 1/10 from the loaded Alamine336 phase where iron concentration was 0.5 M.

• Korean journal of food and cookery science
• /
• v.30 no.3
• /
• pp.351-359
• /
• 2014

The application of persimmon for making new products was investigated by analyzing the degree of astringency removal, softness of fruit, and sensory properties of Daebong persimmons (Diospyros kaki L) treated with three different astringency removal methods of steeping in water, steeping in 1% salt solution, and vacuum packing at $40^{\circ}C$. The weight of persimmon fruit increased with increasing steeping time, but decreased with increasing vacuum packing time. The fruit steeped in $40^{\circ}C$ salt solution (1%, w/w) was not detected with soluble tannin and not developed color with ferric chloride after steeping for 9 h. A total of 12 h of steeping time was required for removing soluble tannin using other methods. The lightness (L) in color and hardness in texture decreased when storage time increased, regardless of astringency removal methods. In overall, the preference was shown with the highest score in persimmon steeped in salt solution for 9 h and 12 h that were vacuum packed at $40^{\circ}C$. In conclusion, the astringency removal condition of Daebong persimmon was good after being steeped on 1% salt solution for 9 h at $40^{\circ}C$.

• Journal of Korean Society of Water and Wastewater
• /
• v.35 no.4
• /
• pp.285-292
• /
• 2021

Osmotic power is to produce electric power by using the chemical potential of two flows with the difference of salinity. Water permeates through a semipermeable membrane from a low concentration feed solution to a high concentration draw solution due to osmotic pressure. In a pressure retarded osmosis (PRO) process, river water and wastewater are commonly used as low salinity feed solution, whereas seawater and brine from the SWRO plant are employed as draw solution. During the PRO process using wastewater effluent as feed solution, PRO membrane fouling is usually caused by the convective or diffusive transport of PRO which is the most critical step of PRO membrane in order to prevent membrane fouling. The main objective of this study is to assess the PRO membrane fouling reduction by pretreatment to remove organic matter using coagulation-UF membrane process. The experimental results obtained from the pretreatment test showed that the optimum ferric chloride and PAC dosage for removal of organic matter applied for the coagulation and adsorption process was 50 mg/L as FeCl₃ (optimum pH 5.5). Coagulation-UF pretreatment process was higher removal efficiency of organic matter, as also resulting in the substantial improvement of water flux of PRO membrane.

• Bulletin of the Korean Chemical Society
• /
• v.33 no.10
• /
• pp.3225-3232
• /
• 2012

The purposes of this research were to synthesize amoxicillin-carrying magnetic nanoparticles. Magnetic nanoparticles were prepared by a chemical precipitation of ferric and ferrous chloride salts in the presence of a strong basic solution. PLGA and PLGA-PEG copolymers were prepared by ring opening polymerization of lactide (LA) and glycolide (GA) (mole ratio of LA: GA 3:1) with or without polyethylene glycol (PEG). Amoxicillin loaded magnetic PLGA and PLGA-PEG nanoparticles were prepared by an emulsion-evaporation process (o/w). Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) photomicrographs showed that the magnetic nanoparticles have the mean diameter within the range of 65-260 nm also they were almost spherical in shape. Magnetic nanoparticles prepared with PLGA showed more efficient entrapment (90%) as compared with PLGA-PEG (48-52%) nanoparticles. In-vitro release of amoxicillin from magnetic PLGA nanoparticles showed that 78% of drug was released over 24 hours. The amount of amoxicillin released from PLGA-PEG s was higher than PLGA.

• Advances in nano research
• /
• v.2 no.4
• /
• pp.187-198
• /
• 2014

Magnetite nanoparticles (MNPs) of different sizes were synthesized by solvothermal process maintaining their stoichiometric composition and unique structural phase. Utilizing hydrated ferric (III) chloride as unique iron precursor, it was possible to synthesize sub-micrometric magnetite clusters of sizes in between 208 and 381 nm in controlled manner by controlling the concentration of sodium acetate in the reaction mixture. The sub-micrometer size nanoclusters consist of nanometric primary particles of 19 - 26.3 nm average size. The concentration of sodium acetate in reaction solution seen to control the final size of primary MNPs, and hence the size of sub-micrometric magnetite nanoclusters. All the samples revealed their superparamagnetic behavior with saturation magnetization ($M_s$) values in between 74.3 and 77.4 emu/g. $M_s$. The coercivity of the nanoclusters depends both on the size of the primary particles and impurity present in them. The mechanisms of formation and size control of the MNPs have been discussed.

• Resources Recycling
• /
• v.2 no.4
• /
• pp.27-32
• /
• 1993

A process has been studied to recover gallium from steelmaking dust which had several hundreds ppm of gallium. Aqueous solution containing 38 mg/l gallium was obtained by leaching of dust with 2.25 mol/l sulfuric acid. The leach liquor contained iron and zinc about 1,000 times greater than gallium. Gallium was then concentrated by ion exchanger of chelating resin with functional group of amino carboxylic acid after reduction of ferric ion to ferrous ion and pH adjustment. Gallium was concentrated to be 13 g/l in the resulting eluate by double ion exchanges. The liquor was further treated to remove impurities by solvent extraction technique empolying TOMAC as extractant. The galluim with 99% purity was finally obtainable.