Jonghee Hwang

A study on the fabrication of soda-lime glass by using refused coal ore and its properties

Glass was fabricated by using refused coal ore obtained from Dogye coal mine in Samchuk. We additionally used soda ash and calcium carbonate as raw materials to make a glass with the chemical composition of soda-lime glass. And the properties of glass were measured when limestone was used as natural raw materials instead of calcium carbonate as chemical raw materials. Transparent glass was fabricated by melting raw materials at for 1 hr in an electrical furnace. The various kinds of glass samples were fabricated according to the kinds of refused coal ore and glass cullet. The optical properties of transmittance and color chromaticity were measured by UV/VIS/NIR spectrometer and the thermal properties of thermal expansion coefficient and softening point were measured. Transparent glass with the transmittance of over 70% in visible range was fabricated by using normal refused coal ore and black colored glass with the transmittance of 0~35% was fabricated by using shel1 type refused coal ore. Therefore, it is concluded that refused coal ore can be used for raw materials to manufacture secondary glass products such as a glass tile and foamed glass panel for construction material.

Characterization of Residual Stress and Pore Distribution in Sealed Area of Large PDP Panel

Residual stress of front and rear glass substrates and remained pore in sealed areas of AC-PDP panel were measured to see the trend of the characteristics of sealed area as the panel size of PDP increased. For this, we compared these characteristics of 6″, 42″ and 80″ panels, between the corner side & straight line, the vertical & horizontal sides, and the around area of ventilation port & area far from that each. Residual stress was measured by the automatic stress meter and the remained pore was analyzed by non destructive X-ray detector and optical microscope. As a result, we showed the trend of sealed area characteristics according to the magnification of PDP panel.

Fabrication and characterization of glass with E-glass fiber composition by using silica-alumina refused coal ore

The glass of E-glass fiber composition was fabricated by using refused coal ore which is obtained as by-product from Dogye coal mine in Samcheok. We used silica-alumina refused coal ore which has low carbon content relatively, and the amount of refused coal ore has been changed from 0 to 35 % in batch composition. E-glass was fabricated by the melting of mixed batch materials at 1550oC for 2 hrs with different refused coal ore composition of 0~35 %. We obtained a transparent and clear glass with high visible light transmittance value of 81~84%, thermal expansion coefficient of 5.39~5.61 × 10?6/oC and softening point of 851~860oC. The glass fiber samples were also obtained through fiberizing equipment at 1150oC, and tested chemical resistance and tensile strength to evaluate the mechanical property as a reinforced glass fiber of composite material. As the result, we identified the properties of E-glass fiber by using refused coal ore are plenty good enough compare to that of normal Eglass without refused coal ore, and confirmed the possibility of refused coal ore as for the raw material of E-glass fiber.

Optical Properties of Soda-lime Color Glass Fabricated by Using Refused Coal Ore

Glass was fabricated using refused coal ore obtained from the Dogye coal mine in Samcheok. We additionally used soda ash and calcium carbonate to make a glass with the chemical composition of soda-lime glass, and we also used white, brown, and green glass cullet to make various kinds of colored glass. Transparent glass was fabricated by melting batch materials including refused coal ore at for 1 hr in an electrical furnace. The light transmittance and color chromaticity were measured by a UV/VIS/NIR spectrometer. Transparent glass with a light transmittance of over 80% was fabricated using normal refused coal ore and white glass cullet. Various kinds of colored glass with a light transmittance of 30-80% were fabricated using refused coal ore and brown or green glass cullet. The light transmittance of the mixed color glass samples, fabricated using normal refused coal ore and brown glass cullet and green glass cullet, indicated 30-47%, a relatively low value, in the condition of a cullet ratio of 20-50%. The characteristics of the color chromaticity of the glass samples were indicated in a chromaticity diagram by x-coordinates, y-coordinates, Y (lightness). The values of x-coordinates and y-coordinates were moved with a regular directional property according to the kind and amount of glass cullet. Therefore, we concluded that refused coal ore can be used for raw materials of color glass products like art glass and glass tile.

One-stage rotational osteotomy for congenital radioulnar synostosis

We report the results of a one-stage rotational osteotomy of the proximal third of the ulna and distal third of the radius with segmental bone resection for treating congenital radioulnar synostosis. We retrospectively reviewed 25 patients (28 forearms) treated by operation. Patients were divided into two groups according to the method of internal fixation at the osteotomy sites. In Group 1 the ulnar osteotomy was stabilized with an intramedullary pin and in Group 2 no fixation was used. The average forearm position improved from 47° pronation before surgery, to 27° supination after surgery. There were no statistically significant differences between the two groups in surgical outcomes. One-stage rotational osteotomy of the proximal third of the ulna and distal third of the radius with segmental bone resection is a simple and safe treatment for patients with congenital radioulnar synostosis. Internal fixation at the osteotomy site seems to be unnecessary. Level of Evidence: Level 4

Fabrication and characterization of boron free E-glass fiber compositions

E-glass fiber is the most widely used glass fiber for reinforced composite materials of aircrafts, automobiles and leisure equipments. But recently researches are being progressed to reduce boric oxide from 8 % to 0 (zero), as is called ‘Boron free E-glass’, because of increasing material cost, environmental problem, and improving chemical resistance and mechanical properties of E-glass fiber. In this study, we fabricated the bulk glass and fiber glass of ‘Boron free E-glass (BF) compositions’, and characterized thermal properties and optical properties. ‘Boron free E-glass (BF)’ was obtained by the melting of mixed batch materials at 1550oC for 2 hrs with different Al2O3 compositions 5~10 %. We obtained transparent clear glass with high visible light transmittance value of 81~86 %, and low thermal expansion coefficient of 4.2~4.9 × 10?6/oC and softening point of 907~928oC. For the chemical resistance test of ‘BF’ fiber samples, we identified that the higher alumina contents gives the better corrosion resistance of glass fiber.

A study on the fabrication of foamed glass by using refused coal ore and its physical properties

Foamed glass was fabricated by using glass powder and foaming agents. For the glass powder, we used sodalime glass which`s manufactured by using refused coal ore obtained as by-product from Dogye coal mine in Samcheok. And for the foaming agents, we used Calcium carbonate, Calcium phosphate and powder of shale type refused coal ore itself which has high content of carbon materials. We additionally used liquid binder for forming, and mixed together. And we formed rectangular shape and treated for 20 min in an electrical furnace. The various kinds of foam glass samples were fabricated according to the kinds of foaming agents. The physical properties of samples, as specific gravity and compressive strength, were measured. Pore structure of each samples were investigated too. Foam glass with specific gravity of 0.4~0.7 and compressive strength of 30~72 kg/. Especially we get satisfying foam glass sample with low specific gravity of 0.47 and high compressive strength of 72 kg/ by the use of liquid calcium phosphate as foaming agent. It also had small and even shape of pore structure. Therefore, it is concluded that refused coal ore can be used for raw materials to manufacture secondary glass products such as a foamed glass panel for construction and industrial materials.

A facile single-step synthesis of polyvinylpyrrolidone−silver nanocomposites using a conventional spray dryer

We have developed a facile single-step synthesis of silver nanocomposite using a conventional spray dryer. We investigated the synthetic conditions by controlling the concentrations of the chemical reactants. Further, we confirmed the effect of the molecular weight of polyvinylpyrrolidones, and revealed that the molecular weight significantly affected the properties of the resultant silver nanocomposites. The long-term stability of the silver nanocomposites was tested, and little change was observed, even after storage for three months. Most of all, the simple commercial implementation, in combination with large-scale synthesis, possesses a variety of advantages, compared to conventional complicated and costly dry-process synthesis methods. Thus, our method presents opportunities for further investigation, for both lab-scale studies and large-scale industrial applications.

Comparison between mixed and spatially separated remote phosphor fabricated via a screen-printing process

Abstract. We developed a fabrication method for remote phosphor by a screen-printing process, using green phosphor, red phosphor, and thermally stable glass frit. The glass frit was introduced for long-term stability. The optical properties of the remote phosphor were observed via an integrating sphere; the photoluminescence spectrum dramatically changed on incorporating a minor amount of the red phosphor. These unique optical properties were elucidated using four factors: phosphor ratio, scattering induced by packing density, light intensity per unit volume, and reabsorption. The thermal stability of the remote phosphor was investigated at 500°C, demonstrating its outstanding thermal properties.

Effects of forming and cooling temperature on the opaque properties of translucent opal glass for the glass diffuser of LED lighting

Translucent opal glass was fabricated in order to substitute polycarbonate diffuser of LED lighting for the purpose of improving the durability problem. Calcium phosphate was used for the opacifier of opal glass and melted at 1550 o C for 2 hrs in electric furnace. Because opal glass was made by phase separation and growth of opacifier grains during cooling procedure after forming of melted glass, we identified the effect of opaque properties by the change of forming and cooling temperature, as R.T. (room temperature), 850 o C, 1100 o C and 1200 o C. As the results, it had excellent optical properties for the diffuser of LED lighting in the fabricated sample of forming and cooling at 1200 o C, with no dazzling from direct light by high haze value over 82 % and low parallel transmittance value under 10 %. For the thermal properties, it had expressed thermal expansion coefficient of 6.352 × 10 −6 / o C and softening point of 839 o C.