• Korean Journal of Heritage: History & Science
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• v.46 no.3
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• pp.48-67
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• 2013

This study was focused on the recognition of historical values and the establishment of conservation schemes for a Silla stone monument in Bongpyeong-ri, Uljin by combining the humanistic investigation of inscription reinterpretation and the scientific conservational diagnosis of deterioration. According to the investigation of inscription, a total of 13 letters were reconsidered compared to the preceding researches. Thus, the meaning and interpretation of previous inscription was partially changed. This monument is composed of gneissose leucogranite and the most suitable site as provenance of the stone would be the Jukbyeon seashore (2.1km). The site shows similar color, size and composition of minerals, gneissose structure and magnetic susceptibility as the Bongpyeong stone monument. This monument developed a structural crack (crack index 0.4) and a microcrack (crack index 2.0) along the gneissose structure. The horizontal strength is weaker than the vertical strength. Therefore, the cracks should be reinforced and treated. However, consolidating is not urgently needed because the total weathering grade by ultrasonic velocity shows the stage of moderate weathering(3,403m/s, 0.32). Also, the major problems of chemical deterioration are blackening (85.2%) with soil, iron oxide,rubbing mark, and salt crystals (17.3%) from the sea. Therefore, the contaminants and the salt crystals should be removed using pressure spray and pulp paper, while the application of poultice should be examined through clinical tests.

• Journal of Korean Society on Water Environment
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• v.37 no.6
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• pp.442-448
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• 2021

Seawater desalination is a technology through which salt and other constituents are removed from seawater to produce fresh water. While a significant amount of fresh water is produced, the desalination process is limited by the generation of concentrated brine with a higher salinity than seawater; this imposes environmental and economic problems. In this study, characteristics of seawater from three different locations in South Korea were analyzed to evaluate the feasibility of crystallization to seawater desalination. Organic and inorganic substances participating in crystal formation during concentration were identified. Then, prediction and economic feasibility analysis were conducted on the actual water flux and obtainable salt resources (i.e. Na2SO4) using membrane distillation and energy-saving crystallizer based on multi-stage flash (MSF-Cr). The seawater showed a rather low salinity (29.9~34.4 g/L) and different composition ratios depending on the location. At high concentrations, it was possible to observe the participation of dissolved organic matter and various ionic substances in crystalization. When crystallized, materials capable of forming various crystals are expected. However, it seems that different salt concentrations should be considered for each location. When the model developed using the Aspen Plus modular was applied in Korean seawater conditions, relatively high economic feasibility was confirmed in the MSF-Cr. The results of this study will help solve the environmental and economic problems of concentrated brine from seawater desalination.

• The Journal of Korean Academy of Prosthodontics
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• v.43 no.5
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• pp.684-693
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• 2005

Statement of problem: Ti-6Al-7Nb alloy is used instead of Ti-6Al-4V alloy that was known to have toxicity. Purpose: This study was performed to investigate the effect of electrolyte concentration on the surface characteristics of anodized and hydrothermally-treated Ti-6Al-7Nb alloy Materials and methods: Discs of Ti-6Al-7Nb alloy of 20 mm in diameter and 2 mm in thickness were polished sequentially from #300 to 1,000 SiC paper ultrasonically washed with acetone and distilled water for 5 min, and dried in an oven at $50^{\circ}C$ for 24 hours. Anodizing was performed at current density $30mA/cm^2$ up to 300 V in electrolyte solutions containing $\beta-glycerophosphate$ disodium salt hydrate $(\beta-GP)$ and calcium acetate (CA). Hydrothermal treatment was conducted by high pressure steam at $300^{\circ}C$ for 2 hours using a autoclave. All samples were soaked in the Hanks' solution with pH 7.4 at $36.5^{\circ}C$ for 30 days. Results and conclusion: The results obtained were summarized as follows: 1. After hydrothermal treatment, the precipitated HA crystals showed the dense fine needle shape. However, with increasing the concentration of electrolyte they showed the shape of thick and short rod. 2. When the dense fine needle shape crystals was appeared after hydrothermal treatment, the precipitation of HA crystals in Hanks' solution was highly accelerated. 3. The crystal structures of $TiO_2$ in anodic oxide film were composed of strong anatase peak and weak rutile peak as analyzed with thin-film X-ray diffractometery. 4. The Ca/P ratio of the precipitated HA layer was equivalent to that of HA crystal in Hanks' solution.

• Macromolecular Research
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• v.15 no.2
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• pp.95-99
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• 2007

The most recent developments in two areas: (a) synthesis of inorganic particles with control over size and shape by polymer additives, and (b) synthesis of inorganic-polymer hybrid materials by bulk polymerization of blends of monomers with nanosized crystals are reviewed. The precipitations of inorganics, such as zinc oxide or calcium carbonate, in presence and under the control of bishydrophilic block or comb copolymers, are relevant to the field of Biomineralization. The application of surface modified latex particles, used as controlling agents, and the formation of hybrid crystals in which the latex is embedded in otherwise perfect crystals, are discussed. The formation of nano sized spheres of amorphous calcium carbonate, stabilized by surfactant-like polymers, is also discussed. Another method for the preparation of nanosized inorganic functional particles is the controlled pyrolysis of metal salt complexes of poly(acrylic acid), as demonstrated by the syntheses of lithium cobalt oxide and zinc/magnesium oxide. Bulk polymerization of methyl methacrylate blends, with for example, nanosized zinc oxide, revealed that the mechanisms of tree radical polymerization respond to the presence of these particles. The termination by radical-radical interaction and the gel effect are suppressed in favor of degenerative transfer, resulting in a polymer with enhanced thermal stability. The optical properties of the resulting polymer-particle blends are addressed based on the basic discussion of the miscibility of polymers and nanosized particles.

• Journal of the Korean Ceramic Society
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• v.43 no.8 s.291
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• pp.463-468
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• 2006

Hydrothermal deposition of hydroxyapatite coatings on two types of $ZrO_2$ substrates (3 mol% $Y_2O_3$-doped and 13 mol% $CeO_2$-doped tetragonal $ZrO_2s$) was studied using aqueous solutions of $Ca(NO_3)_2\;4H_2O$ and $(NH_4)_2HPO_4$ containing EDTA (ethylene diamine tetra acetic acid) disodium salt as a chelating agent for $Ca^{2+}$ ions. For the precipitation of the coatings, the $EDTA-Ca^{2+}$ chelates were decomposed by oxidation with $H_2O_2$ at $90^{\circ}C$. The deposition behavior, morphology, and orientation of the coatings were investigated while varying the solution pH using scanning electron microscopy and X-ray diffractometry. For the two sub-strates, sparse deposition of the coating was obtained at pH 5.5, whereas a uniform deposition was obtained at pH 7.1, 9.8, and 11.4 with a denser microstructure for the higher pH. The coating consisted of thin needle-like or plate-like crystals ($1-2{\mu}m$ length or diameter) at pH 7.1, but fine rod-like crystals ($1-2{\mu}m$ length, $0.1{\mu}m$ diameter) at pH 9.8 and 11.4. The coatings were $1-3{\mu}m$ thick and showed a preferred orientation of the hydroxyapatite crystals with their c axis (i.e., the elongated direction) perpendicular to the substrate surface especially for pH 9.8 and 11.4.

• Journal of the Korean Society of Food Science and Nutrition
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• v.42 no.10
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• pp.1664-1672
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• 2013

Solar salt is manufactured naturally, and therefore, it contains insoluble substances such as sandy compounds. This study is performed in order to effectively produce clean sea salt by removing the impurities in sea salt through filtration and evaporation in a vacuum condition. Brine was concentrated and crystallized at $90^{\circ}C$ by a rotary vacuum evaporator, which was then recovered as salt crystals by filtration, and then the salt was dehydrated. Manufacturing yields were determined by the amount of water evaporation. Brine was concentrated to 40%, 50% and 60% of the initial volume of brine and manufactured salt were designated as 40S, 50S and 60S, respectively. The salt produced by this process is called ESBS (evaporated salt with brine from salt-farm). The yield of 40S, 50S and 60S were 7.22%, 10.79% and 15.06%, respectively. The NaCl concentration of 40S and 50S were 90.38% and 91.16%, respectively. From a sensory evaluation analysis, the most tasty salt was 40S and the bitter salt was 60S. The average contents of sand compound and insoluble substances in ESBS were 0.001~0.012% and 0.067~0.12%, respectively. The mineral compositions, such as Na, Mg, K, and Ca of 40S and 50S were similar with those of the natural solar salt. In solubility tests, the solubility (g of salt/100 mL $H_2O$/sec) of 40S, 50S, and 60S was 0.69, 0.70, and 0.69, respectively. On the other hand, the solubility of natural solar salt was 0.47. By comparing the water reabsorption rate analysis results, water reabsorption rate of 40S and 50S was about 3 to 5 times lower than that of the solar salt. In the aspects of physical and chemical properties, such as minerals, impurities, solubility and moisture re-absorption rate, salts developed in this study are judged to be better than that of the general solar salt.

• 보존과학연구
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• s.30
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• pp.189-202
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• 2009

Ceramics from Taean shipwreck were studied to investigate the deterioration by soluble salts and desalination pattern according to each ceramic characterization. NaCl crystals were found as a crystal growth on the ceramic microstructure and deteriorated to push off the glaze layer of some Puncheong ware sample. As a result of monitoring the desalination pattern of ceramics for 74days, the earthenware sample with big pores and no glaze removed soluble salts so fast, but Puncheong ware and Whiteware samples removed lots of soluble salts slowly and continuously. Generally, it takes long time to remove soluble salts from porcelains, due to small pores and glaze, but the long-term desalination probably can cause the damage on the surface layer such like glaze. As some soluble salts still remains in the ceramic microstructures after desalination, it is very important to control and keep the relative humidity stable through the proper storage. There are various ceramic deterioration patterns by soluble salts. Therefore, it needs to select the desalination method of ceramics from shipwreck, considering the material characteristics and the production techniques.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.20 no.6
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• pp.283-288
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• 2010

Nanosized NiO powder was prepared by mixing an acid nickel salt and a base nickel salt and their reduction behavior was studied. Ni formate was employed as an acid salt and nickel hydroxide and basic nickel carbonate as base salts. One equivalent acid salt was mixed with 9 equivalent base salt. The mixture of the formate and the carbonate produced ~100 run spherical NiO powder by heat treatment at $750^{\circ}C$/2 h, but the mixture of the formate and the hydroxide gave rise to ~100 nm pseudo spherical NiO powder by heat treatment at $600^{\circ}C$/2 h and grew fast to give pseudo cubic crystals of 100~600 run by heat treatment at $750^{\circ}C$/2 h. Reduction by hydrogen gas proceeded much faster for the one with the hydroxide than that with the carbonate to give porous body with well grown necks. Their behavior was studied by analysis of TG/DSC, XRD, and SEM.

• Korean Journal of Materials Research
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• v.14 no.9
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• pp.607-613
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• 2004

This study was to investigate the surface properties of electrochemically oxidized Ti-6Al-7Nb alloy by anodic spark discharge technique. Anodizing was performed at current density 30 $mA/cm^2$ up to 300 V in electrolyte solutions containing $DL-{\alpha}$-glycerophosphate disodium salt hydrate($DL-{\alpha}$-GP) and calcium acetate (CA). Hydrothermal treatment was done at $300^{\circ}C$ for 2 hrs to produce a thin outermost layer of hydroxyapatite (HA). The bioactivity was evaluated from HA formation on the surfaces in a Hanks' solution with pH 7.4 at $36.5^{\circ}C$ for 30 days. The size of micropores and the thickness of oxide film increased and complicated multilayer by increasing the spark forming voltage. Needle-like HA crystals were observed on anodic oxide film after the hydrothermal treatment at $300^{\circ}C$ for 2 hrs. When increasing $DL-{\alpha}$-GP in electrolyte composition, the precipitated HA crystals showed the shape of thick and shorter rod. However, when increasing CA, the more fine needle shape HA crystals were appeared. The bioactivity in Hanks' solution was accelerated when the oxide films composed with strong anatase peak with presence of rutile peak. The increase of amount of Ca and P was observed in groups having bioactivity in Hanks' solution. The Ca/P ratio of the precipitated HA layer was equivalent to that of HA crystal and it was closer to 1.67 as increasing the immersion time in Hanks' solution.

• Bulletin of the Korean Chemical Society
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• v.25 no.4
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• pp.466-470
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• 2004

The crystals of the new melaminium salt, i.e. melaminium acetate acetic acid solvate monohydrate, $C_3H_7N_6^+ {\cdot}CH_3COO^- {\cdot}CH_3COOH{\cdot}H_2O$, were obtained by the slow evaporation of an aqueous solution at room temperature. Powder infrared and Raman spectra were measured and interpreted. The vibrational spectra in the region of internal vibrations of ions corroborate structural data recently published by Perpetuo and Janczak.$^1$ Some spectral features of this new crystal are referred to corresponding one for melamine crystal as well as other melamine complexes in crystalline form. Hydrogen-bonded network present in the crystal gives notable vibrational effect.