• Resources Recycling
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• v.31 no.2
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• pp.63-69
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• 2022

In this study, mechanical grinding using a planetary ball mill was performed under various conditions to evaluate its effect on the crystal structure of vanadium titanium magnetite (VTM) ore from the Kwain Mine in South Korea. The crystal structure of the activated product was also evaluated. Magnetite and ilmenite were identified as the main types of VTM ore used in the Kwain Mine, and the main types of gangue minerals were iron-based silicate minerals. According to the mechanical activation results, the crystallinity and crystal size decreased as the size of the grinding media (balls) decreased, and the amorphization of the sample/ball filling was significant as the amount of the sample was reduced. In addition, as the grinding speed and time increased, the crystal structure significantly changed, proving that these two parameters had a greater effect on the crystal structure than the ball size and sample/ball filling ratio.

• Journal of the Korean Ceramic Society
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• v.41 no.12 s.271
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• pp.889-892
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• 2004

Acicular type aragonite precipitated calcium carbonate was synthesized by carbonation reaction of $Ca(OH)_2$ slurry and $CO_2$ gas. As increasing the initial concentration of $Mg^{2+}$ ion, calcite crystal phase substantially decreased while that of aragonite crystal phase increased. According to XRD and EDS analysis, it was found that the addition of $MgCl_2$ induced the $Mg^{2+}$ ion to substitute in $Ca^{2+}$ ion site of calcite lattice then the unstabled calcite structure be resolved, consequently the growth of calcite structure is interrupted while the growth of aragonite structure is expedited.

• Korean Chemical Engineering Research
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• v.55 no.3
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• pp.279-286
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• 2017

This review paper evaluates different kinds of synthesis methods for calcite precipitated calcium carbonates by using different materials. The various processing routes of calcite with different compositions are reported and the possible optimum conditions required to synthesize a desired particle sizes of calcite are predicted. This paper mainly focuses on that the calcite morphology and size of the particles by carbonation process using loop reactors. In this regard, we have investigated various parameters such as $CO_2$ flow rate, Ca $(OH)_2$ concentration, temperature, pH effect, reaction time and loop reactor mechanism with orifice diameter. The research results illustrate the formation of well-defined and pure calcite crystals with controlled crystal growth and particle size, without additives or organic solvents. The crystal growth and particle size can be controlled, and smaller sizes are obtained by decreasing the Ca $(OH)_2$ concentration and increasing the $CO_2$ flow rate at lower temperatures with suitable pH. The crystal structure of obtained calcite was characterized by using X-ray diffraction method and the morphology by scanning electron microscope (SEM). The result of x-ray diffraction recognized that the calcite phase of calcium carbonate was the dominating crystalline structure.

• Journal of the Korean Society of Food Science and Nutrition
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• v.27 no.3
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• pp.413-418
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• 1998

There are several types of salts that classifed into raw salts(Chunil salt, Saeng salt), purified salts (NaCl reagent grade, Hanju salt) and processed salts(Gueun salt, Saeng kum, Bamboo salt) in Korea. Their major element is NaCl but raw salt from sea water contains other minerals such as K, Mg and S. Mineral contents of the various kinds of salt analyzed with ICP-AES and AAS were different, especially on the contents of K, Mg and Ca. Chunil salt was abundant in Ca(1,037ppm), K(3,707ppm), Mg(10,266ppm) and S(7,459ppm), and salt water from the Chunil salt contained small amounts of Pb, Al, Cr and Hg. Processed salts contained high levels of Ca, K, Mg and Fe. Especially, high levels of K, P, Fe and Ge were detected in bamboo salt. Purified salts showed regular crystal form and raw salts exhibited irregular crystal form under the SEM. The processed salts were not crystal form, but fused and irregular round form.

• Korean Journal of Materials Research
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• v.12 no.5
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• pp.334-340
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• 2002

$TiO_2$-coated fly ash was synthesized by dropping method of coating agent in order to get $TiO_2$ coating layer with high photocatalytic activity on the surface of coal fly ash. The properties of the $TiO_2$ coating layer such as morphology, crystal structure, crystal size and photocatalytic activity were compared with those of the $TiO_2$-coated fly ash prepared by the traditional method of precipitation. $TiCl_4$ aqueous solution was used as a titanium stock solution and $NH_4HCO_3$ was used as a precipitant. The $TiO_2$ coating layer obtained by dropping method of coating agent was more uniform than that coated by precipitation. However, the crystal of $TiO_2$ coated by dropping method of coating agent was easy to grow by heat treatment because of the small primary particle size and bulky morphology, and its photocatalytic activity was consequently lower than that of the $TiO_2$ coated by precipitation. The $TiO_2$ coating layer obtained by both methods had a crystal structure of anatase, and the temperature of phase transformation into rutile was 90$0^{\circ}C$. The minimum crystal size of $TiO_2$ for the highest photocatalytic activity was found to be about 10nm.

• Korean Journal of Materials Research
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• v.13 no.5
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• pp.285-291
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• 2003

The nanosized silver and gold particles are prepared by ERC method in which metal vapors with high temperature is rapidly quenched by coolants such as liquid nitrogen or liquid argon. In order to monitor the crystal structural changes on the internal and the surface of the nanosized noble metal particles, lattice parameter, internal strain and Debye-Waller factor are investigated, and the calculation of X-ray diffraction scattering intensity is performed. The lattice parameters of silver and gold particles agree with those of bulk materials, and crystal internal strain of the metal particles is not changed by rapid cooling. The Debye-Waller factor of gold particles is increased with decreasing particle size because of the surface softening phenomenon of nanosized particles, but the crystal structural change on the surface of the particles is not detected from the comparison the calculated X-ray diffraction profile with the experimental profile on gold particles with the particle size of 4 nm.

• Korean Journal of Heritage: History & Science
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• v.45 no.4
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• pp.114-125
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• 2012

The purpose of this study is to analysis chromaticity, granulometry, main chemical composition and mineral crystal structure of wall soils excavated from Poongnatoseong Earthen Castle using color reader, XRD, particla size analyzer. The analysed soils of Poongnatoseong Earthen Castle were yellowish brown and isabella. All samples were sands or sands including silty soil(SW~SC) and showed similar granulometry, chemical composition and mineral crystal structure, which were characteristics of construction materials suitable for modern road or airstrip. As resulting in comparison with 4 factors from chromaticity, granulometry, main chemical composition and mineral crystal structure, we decided that the control soils(PNS) near by Poongnatoseong Earthen Castle were not to be used for the castle wall construction We presumed that there was a huge soil distribution area for the wall construction around Poongnatoseong Earthen Castle. For further study, we will make a comparison analysis all kinds of soil characteristics. And then we can understand correctly about wall soils producing area, construction method, repair method and time of Poongnatoseong Earthen Castle.

• Resources Recycling
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• v.26 no.6
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• pp.10-19
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• 2017

It is studied the effect of crystal structure of domestic High-Ca limestones using absorbent for desulfurization on the grinding characteristics and dissolution rates in wet flue gas desulfurization process of domestic coal fired power plant. It compared the crystal structure, grinding work index and dissolution rates with 4 Limestones from Jecheon-Danyang with different crystal structure, and we found that grinding work index differ in crystal size and crystal structure of limestones : The lower the value of the grinding work index is, the higher the dissolution rates of limestones. Confirmed that we have important indicators of grinding characteristics for crystal structure with CaO content of limestones.

• Korean Journal of Materials Research
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• v.13 no.10
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• pp.691-696
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• 2003

To improve the photocatalyticactivity of $TiO_2$-coated coal fly ash, tungsten hydroxide was doped by impregnation method and was oxidized by heat treatment in temperature ranges of $WO^{\circ}C$ for 2 hrs. The changes of crystal structure and crystal size of $TiO_2$and $WO_3$on coal fly ash were investigated by X-ray diffraction analysis. The crystal structure of titanium dioxide showed only anatase type and $TiO_2$-$WO_3$ compounds appeared in the heat treatment temperature ranges of $500∼600^{\circ}C$. By adding $V_3$in $TiO_2$coated on fly ash, the growth of crystal size of anatase was restrained and the anatase phase was stabilized in temperature ranges of TEX>$500∼<800^{\circ}C$. And $WO_3$acted as a trap site of electrons excited from anatase by irradiating UV. The maximum removal efficiency of NO gas for $TiO_2$/$WO_3$-coated coal fly ash was 84% and appeared when the ammonium tungstate of $1.3${\times}$10^{-3}$ M was doped and then heated at $600^{\circ}C$ for 2 hrs.

• Bulletin of the Korean Chemical Society
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• v.29 no.10
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• pp.1969-1972
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• 2008

In this study, horse spleen apoferritins were induced to form biominerals using up to 3000 Fe atoms per protein molecule. The morphology and crystallinity of the nanometer-sized biominerals formed in the ferritins were then analyzed using field emission-energy filtering-transmission electron microscopy (FE-TEM). The ferritins were found to have reconstitution yields of 60-70% in the experiments. The mean core size of the ferritins varied somewhat with protein concentrations, indicating that crystal growth in ferritins could be controlled via protein concentrations. The core mineral size increased with the amount of Fe used. Lattice fringes of the core, associated with good crystallinity, were found in all samples. The lattice fringe images of a single domain ferrihydrite mineral appeared frequently in the (011) planes (d-spacing of 0.246 nm) under [100] zone axis in all samples of this study. In addition, the lattice image occasionally revealed fringes corresponding to the (100) planes (d = 0.254 nm) from the [001] zone axis, indicating the characteristic pattern of hexagonal crystal lattice. Diffraction patterns in the minerals identified as ferrihydrite were fitted well into the space group of $P3_{1c}$.