• Resources Recycling
• /
• v.6 no.1
• /
• pp.29-34
• /
• 1997

The feasibility of using the industrial inorganic waste materials such as l~mestone sludge. Soundly sand. coal fly 'ash, and chemical glasses as a raw material for cement clinker by melting treatmeut was iovestigated. The slag wh~ch is obtained from thc melts of the mixtnres of waste materials is composed of P-C,S(ZCaO - SIOJ and C,AS(ZCaO . AI,O, . SiO,) phases. The effect of melting tempcrabre, coaling condition and CIS ratio on the fo~mation of P-C,S phasc was examed. In order to obtain thc P-CiS phase which is useful in thc utilhtion as a clinkcr malcrid, it B found that sudl considerations as low melting temperature as possible of the wastc mixhire, quenching the melts and law CIS ratio of the mlxhlre are necessary.

• Korean Journal of Environmental Biology
• /
• v.31 no.4
• /
• pp.302-307
• /
• 2013

Microbial fermented cellulose gel, citrus gel (CG), was successfully fabricated to porous foam by radiation treatment and freeze drying. The chemically induced radiation was used to create highly porous foam and further freeze drying of the CG produced tough foams with interconnected open pores for use in tissue engineering. The microstructure of the CG foam was controlled by varying the irradiation dose and quenching temperature with pore size ranging from several microns to a few hundred microns. Tensile strength and Gurley value of the CG foam were influenced by irradiation dose. These radiation induced CG foams are promising scaffolds for tissue engineering.

• Resources Recycling
• /
• v.4 no.4
• /
• pp.37-58
• /
• 1995

Whole tues were put uto cement kiln inlet where the tempmalures or gas and cemcnt-raw-materials were 1050 and 800- 850.C. respcclrvely. Tl~ck iln consisls of \ulcorner-stage suspension preheatel- and air quenching coolers The amount of wusle tlrcs added in lhc normal encrgy in lhc ce~ncnlk iln was 3, 5, 7% by volume Welght and steel contents of tiles. ulti~~iaalcn d elemental analysis, ash contents. ash hsion temperature. etc, wete detcnutned to inveshgate thc prnpcrlics a1 tires and ilreir ashes. Flucluat~ons of cement kiln placess, cement quality and an pollulton were invesligalerl during lhc burning tins. When the Ieeding ralio ol wasle lires to normal cncrgy was 50'0, there was nn wlde d~ffereilces m the cemmt quctlity and air pollutcon between operation with tiles and withoul tires. Tl~ch cal iccovcry was uhout 50% w~th5 % add~tionI n the nonndl energy. There was a little lxt fluctuation of cement quultty ncld an pollution at olher feeding ralios.

• Korean Journal of Materials Research
• /
• v.22 no.7
• /
• pp.368-373
• /
• 2012

Glasses were prepared with compositions of $(13-x)BaO-80B2_O_3-7Li_2O{\cdot}xSm_2O_3$, BBLSx(x=0.5, 0.4, 0.3) by melting the starting materials of boron oxide(99.9%), lithium oxide(99.9%), barium carbon oxide(99.9%), and samarium oxide(99.9%) and then quenching the melt at $1350^{\circ}C$. This led to good-quality BBLSx(x=0.4, 0.3) and poor-quality BBLSx(x=0.5) glasses. The physical and structural properties of the BBLSx glasses were studied by means x-ray diffraction, scanning electron microscopy(SEM), differential scanning calorimetry(DSC), and dielectric spectroscopy. From the x-ray diffraction and SEM results, the quality of the BBLSx glasses significantly depends on the $Sm_2O_3$ concentration. The x-ray diffraction pattern showed that the crystallites in the BBLSx glasses after heat treatment at $700^{\circ}C$ may be $LiBaB_9O_{15}$. From the DSC results, the glass transition temperatures($T_g$), crystallization temperatures($T_c$), and the maximum temperatures of the crystallized($T_p$) BBLSx glasses all changed with the $Sm_2O_3$ concentration. According to the dielectric spectroscopy results, the values of the real dielectric constant and Tan ${\delta}$ of the BBLSx glasses depended on the $Sm_2O_3$ concentration. The values of the real dielectric constant and Tan ${\delta}$ were also shown to depend on the measuring temperature, possibly due to the ion migration in the bulk of the BBLSx glasses.

• Journal of the Korean Society for Heat Treatment
• /
• v.18 no.4
• /
• pp.247-255
• /
• 2005

Although heat treatment is a process of great technological importance in order to obtain desired mechanical properties such as hardness, the process was required a tedious and expensive experimentation to specify the process parameters. Consequently, the availability of reliable and efficient numerical simulation program would enable easy specification of process parameters to achieve desired microstructure and mechanical properties without defects like crack and distortion. In present work, the developed numerical simulation program could predict distributions of microstructure and thermal stress in steels under different cooling conditions. The computer program is based on the finite difference method for temperature analysis and microstructural changes and the finite element method for thermal stress analysis. Multi-phase decomposition model was used for description of diffusional austenite decompositions in low alloy steels during cooling after austenitization. The model predicts the progress of ferrite, pearlite, and bainite transformations simultaneously during quenching and estimates the amount of martensite also by using Koistinen and Marburger equation. To verify the developed program, the calculated results are compared with experimental ones of casting product. Based on these results, newly designed heat treatment process is proposed and it was proved to be effective for industry.

• Journal of the Korean Applied Science and Technology
• /
• v.31 no.3
• /
• pp.453-465
• /
• 2014

The paper provides a review on bio-oil production technology from biomass by using fast pyrolysis to use heating fuel, power fuel and transport fuel. One of the most promising methods for a small scale conversion of biomass into liquid fuels is fast pyrolysis. In fast pyrolysis, bio-oil is produced by rapidly heating biomass to intermediate temperature ($450{\sim}600^{\circ}C$) in the absence of any external oxygen followed by rapid quenching of the resulting vapor. Bio-oil can be produced in weight yield maximum 75 wt% of the original dry biomass and bio-oils typically contain 60-75% of the initial energy of the biomass. In this study, it is described focusing on the characterization of feedstock, production principle of bio-oil, bio-oil's property and it's application sector.

• Korean Journal of Metals and Materials
• /
• v.48 no.11
• /
• pp.974-980
• /
• 2010

Various types of steel, namely, 0.35C, 0.2C-Cr, and 0.2C-Cr-Mo steels, were quenched and tempered by high-frequency induction heat treatment. The type, size, and spheroidization of the carbides varied depending on the tempering temperatures ($450{\sim}720^{\circ}C$). During the tempering process, the carbide was precipitated in the martensite matrix. The 0.35C, 0.2C-Cr, and 0.2C-Cr-Mo steels contained carbides that were smaller than 120 nm. The carbide was spheroidized as the tempering temperature increased. Owing to the fine microstructure and spheroidization of the carbides, all three steels had a high tensile strength as well as yield ratio and reduction of area. In the case of the 0.2C-Cr steel, the use of Cr as an alloying element facilitated the precipitation of alloyed carbides with an extremely small particle and resulted in an increase in the spheroidization rate of the carbides. As a result, a large reduction of area was achieved (>70%). The 0.2C-Cr-Mo steel had the highest tensile strength because of the high hardenability that can be attributed to the presence of alloying elements (Cr and Mo). Quenching and tempering steels by induction heat treatment resulted in a high strength of over 1 GPa and a large reduction of area (>70%) because of the rapid heating and cooling rates.

• Journal of Korea Foundry Society
• /
• v.39 no.1
• /
• pp.7-13
• /
• 2019

Few studies of large blooms over 700 mm thick among those used for the forging of raw materials have been reported. The cooling rate difference between the surface and the center of a large bloom is large, and the degradation of the mechanical properties is likely in cases involving excessively coarse precipitates resulted from the slow cooling rate of a large bloom after casting. Therefore, a schematic investigation of the growth behaviors of precipitates while varying their locations in blooms is necessary. The dissolution behaviors of precipitates were investigated by simulating a reheating process during which the bloom is heated to a high temperature. The segregation behavior of the as-cast large bloom was also investigated. Reheating specimens were obtained after an isothermal heat treatment at $1150^{\circ}C$ with various holding times to simulate the reheating process, with the samples undergoing a subsequent water quenching step. The precipitates were extracted using an electrolytic extractor and a particle size analysis was conducted with the aid of SEM, EDS, and TEM. In the present work, Al oxide, MnS and Nb carbide were mainly observed.

• Korean Journal of Materials Research
• /
• v.31 no.1
• /
• pp.29-37
• /
• 2021

Martensitic stainless steel is commonly used in the medical implant instrument. The alloy has drawbacks in terms of strength and wear properties when applied to instruments with sharp parts. 440C STS alloy, with improved durability, is an alternative to replace 420 J2 STS. In the present study, the carbide precipitation, and mechanical and corrosion properties of STS 440C alloy are studied as a function of different heat treatments. The STS 440C alloy is first austenitized at different temperatures; this is immediately followed by oil quenching and sub-zero treatment. After sub-zero treatment, the alloy is tempered at low temperatures. The microstructures of the heat treated STS 440C alloy consist of martensite and retained austenite and carbides. Using EDX and SADP with a TEM, the precipitated carbides are identified as a Cr23C6 carbide with a size of 1 to 2 ㎛. The hardness of STS 440C alloy is improved by austenitization at 1,100 ℃ with sub-zero treatment and tempering at 200 ℃. The values of Ecorr and Icorr for STS 440C increase with austenitization temperature. Results can be explained by the dissolution of Cr-carbide and the increase in the retained austenite. Sub-zero treatment followed by tempering shows a little difference in the properties of potentiodynamic polarizations.

• Current Optics and Photonics
• /
• v.6 no.6
• /
• pp.521-549
• /
• 2022

Fiber lasers have made remarkable progress over the past three decades, and they now serve far-reaching applications and have even become indispensable in many technology sectors. As there is an insatiable appetite for improved performance, whether relating to enhanced spatio-temporal stability, spectral and noise characteristics, or ever-higher power and brightness, thermal management in these systems becomes increasingly critical. Active convective cooling, such as through flowing water, while highly effective, has its own set of drawbacks and limitations. To overcome them, other synergistic approaches are being adopted that mitigate the sources of heating at their roots, including the quantum defect, concentration quenching, and impurity absorption. Here, these optical methods for thermal management are briefly reviewed and discussed. Their main philosophy is to carefully select both the lasing and pumping wavelengths to moderate, and sometimes reverse, the amount of heat that is generated inside the laser gain medium. First, the sources of heating in fiber lasers are discussed and placed in the context of modern fiber fabrication methods. Next, common methods to measure the temperature of active fibers during laser operation are outlined. Approaches to reduce the quantum defect, including tandem-pumped and short-wavelength lasers, are then reviewed. Finally, newer approaches that annihilate phonons and actually cool the fiber laser below ambient, including radiation-balanced and excitation-balanced fiber lasers, are examined. These solutions, and others yet undetermined, especially the latter, may prove to be a driving force behind a next generation of ultra-high-power and/or ultra-stable laser systems.