• Resources Recycling
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• v.31 no.6
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• pp.44-51
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• 2022

In the steelmaking process using an electric arc furnace (EAF), light-burnt dolomite, which is a flux containing MgO, is used to protect refractory materials and improve desulfurization ability. Furthermore, a recarburizing agent is added to reduce energy consumption via slag foaming and to induce the deoxidation effect. Herein, a waste MgO-C based refractory material was used to achieve the aforementioned effects economically. The waste MgO-C refractory materials contain a significant amount of MgO and graphite components; however, most of these materials are currently discarded instead of being recycled. The mass recycling of waste MgO-C refractory materials would be achievable if their applicability as a flux for steelmaking is proven. Therefore, experiments were performed using a target composition range similar to the commercial EAF slag composition. A pre-melted base slag was prepared by mixing SiO₂, Al₂O₃, and FeO in an alumina crucible and heating at 1450℃ for 1 h or more. Subsequently, a mixed flux #2 (a mixture of light-burnt dolomite, waste MgO-C based refractory material, and limestone) was added to the prepared pre-melted base slag and a melting reaction test was performed. Injecting the pre-melted base slag with the flux facilitates the formation of the target EAF slag. These results were compared with that of mixed flux #1 (a mixture of light-burnt dolomite and limestone), which is a conventional steelmaking flux, and the possibility of replacement was evaluated. To obtain a reliable evaluation, characterization techniques like X-ray diffraction (XRD) analysis and X-ray fluorescence (XRF) spectrometry were used, and slag foam height, slag basicity, and Fe recovery were calculated.

• Journal of Korea Foundry Society
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• v.13 no.5
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• pp.476-483
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• 1993

The influence of substrate materials on the degree of basal porosity during spray casting process has been investigated. Different conditions of droplet spreading on the substrate were induced by varying the substrate material. Flat sections of cast iron and aluminum have been spray deposited via spray casting process onto an aluminum substrate, a low carbon steel substrate, and an alumina based refractory substrate. Results for cast iron and aluminum sprayed onto the aluminum substrate showed significant improvements in the surface condition and degree of basal porosity with evidence of substrate deformation that round pits ranging from $5{\mu}m$ to $20{\mu}m$ in diameter are distributed on the surface of aluminum substrate. The lowest level of porosity was developed in alumina based refractory material. Several mechanisms for porosity formation were discussed with droplet impact pressure and droplet spreading. Adopting a spray cutting mechanism for removing the periphery of spray cone, porosity level was remarkably decreased.

• Proceedings of the Materials Research Society of Korea Conference
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• 2008.11a
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• pp.38.1-38.1
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• 2008

• Proceedings of the Materials Research Society of Korea Conference
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• 2001.05a
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• pp.156-156
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• 2001

• Proceedings of the Korean Vacuum Society Conference
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• 2004.02a
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• pp.75-75
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• 2004

• Korean Journal of Crystallography
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• v.8 no.2
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• pp.89-96
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• 1997

In order to apply synthesis technique of the high purity ceramic powder to the traditional ceramic powder, mullite powder which is widly used for refractory materials was synthesized. Boehmite and Hadong kaolin with high alumina content were used as starting materials and gel coating method was tried to produce the mullite powder. As a result, the mullite powder of high quality was successfully obtained at 1350℃. The unreacted silica and cornudum were not observed in the synthesized mullite powder, mullite content was more than 80% when the starting materials were sintered at 1700℃. Their properties showed bulk specific gravity of 2.56, water absorption of 1.9%, and 3-point flexual strength of 169 MPa. It is thought that that their good properties are applicable to refractory materials of high quality.

• Nuclear Engineering and Technology
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• v.54 no.6
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• pp.1954-1961
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• 2022

Lead-based fast reactor (LFR) has become one of the most promising reactors for Generation IV nuclear systems. A developing trend of LFR is high efficiency, along with operation temperatures up to 800 ℃ or even higher. One of key issues in the high-efficiency LFR is corrosion of cladding materials with lead at high temperatures. In this study, corrosion behavior of some refractory metals (Nb, Nb521, and Mo-0.5La) was investigated in static lead at 1000 ℃ for 1000 h. The results showed that Nb and Nb521 exhibited an intense dissolution corrosion with obvious lead penetration after corrosion, and lead penetration extended along the grain boundaries of the specimens. Furthermore, Nb521 showed a better corrosion resistance than that of Nb as a result of the elements of W and Mo included in Nb521. Mo-0.5La showed much better corrosion resistance than that of Nb and Nb521, and no lead penetration could be observed. However, an etched morphology appeared on the surface of Mo-0.5La, indicating the occurrence of corrosion to a certain degree. The results indicate that Mo-0.5La is compatible with lead up to 1000 ℃. While Nb and Nb alloys might be not compatible with lead for high-efficiency LFR at such high temperatures.

• Resources Recycling
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• v.8 no.1
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• pp.23-28
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• 1999

Firing characteristics, transverse rupture strength, and heat capacity were studied of the heat-reservoir refractory materials made of red-firing clay, mill scale, and water glass. The firing shrinkage increased with increase of the clay proportion in samples. The volume of fired bodies showed shrinkage by drying up to $300^{\circ}C$, steady expansion in the 300-$700^{\circ}C$ range due to phase transition of iron oxides. and drastic expansion above $1200^{\circ}C$. Flexural strength decreased from 5.6 Mpa to 2.35 Mpa with the decrease of the ratio of clay to mill scale from 1:1 to 1:3 Heat capacities changed from 1.1 Joul/g$^{\circ}$C to 1.35 Joul/g$^{\circ}$C with the ratio of millscale to clay ratio from 1:1 to 1:3. Mill scale in the specimen appears to exist as liquid phase during firing. Firing the specimens in air leads to the eruption of the molten mill scale to the sample surfaces. Contrarily, firing samples in a refractory sagger with a cover suppressed the eruption of the molten mill scale to the surfaces. The addition of mill scale gave rise to porous sintered bodies which would delay cooling rates of heat-reservoir brick.

• Structural Engineering and Mechanics
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• v.72 no.3
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• pp.339-354
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• 2019

Reusing building materials and concrete of old buildings can be a promising strategy for sustained development. In buildings, the performance of materials under elevated temperatures is of particular interest for determining fire resistance. In this study, the effect of pozzolan and aggregate type on properties of concrete exposed to fire was investigated. In doing so, nanosilica with cement-replacement levels of 0, 2, and 4% as well as silica fume and ultrafine fly ash with cement-replacement levels of 0, 7.5, and 15% were used to study effect of pozzolan type, and recycled refractory brick (RRB) fine aggregate replacing natural fine aggregate by 0 and 100% was utilized to explore effect of aggregate type. A total of 126 cubic concrete specimens were manufactured and then investigated in terms of compressive strength, ultrasonic pulse velocity, and weight loss at $23^{\circ}C$ and immediately after exposure to 400 and $800^{\circ}C$. Results show that replacing 100% of natural fine aggregate with recycled refectory brick fine aggregate in the concretes exposed to heat was desirable, in that it led to a mean compressive strength increase of above 25% at $800^{\circ}C$. In general, among the pozzolans used here, silica fume demonstrated the best performance in terms of retaining the compressive strength of heated concretes. The higher replacement level of silica fume and ultrafine fly ash pozzolans in the mixes containing RRB fine aggregate led to a greater weight loss rate, while the higher replacement level of nanosilica reduced the weight loss rate.

• Asian Pacific Journal of Cancer Prevention
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• v.16 no.6
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• pp.2391-2395
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• 2015

Objective: The aim of this retrospective study was to evaluate the feasibility and efficacy of response to continuous-infusion ifosfamide and doxorubicin combination as second-line chemotherapy for patients with recurrent or refractory osteosarcoma. Materials and Methods: Eighteen recurrent or refractory osteosarcoma patients who were treated with continuous-infusion ifosfamide and doxorubicin combination between May 1999 and April 2011 were included in the analysis. Ifosfamide at $12g/m^2$ was administered by intravenous continuous infusion over 3 days, and doxorubicin $60mg/m^2$ was administered as an intravenous bolus injection on day 1. The combination therapy was repeated every 3 weeks. Treatment was continued until evidence of disease progression or unacceptable toxicity. Results: The patients (ages 7-53 years) received a total of 42 cycles of chemotherapy (median: 2 courses; range: 2-5 courses). The overall response rate was 0% and the disease control rate was 22.3%, with four patients having stable disease. The median time to progression and overall survival time were 2 months (range: 2-5 months) and 9 months (range: 3-29 months), respectively. Major severe toxicities were leucopenia 7 (38.9%), nausea and vomiting 3 (16.7%) and alopecia 9 (50%). There were no treatment-related deaths. Conclusions: In our experience, continuous-infusion ifosfamide and doxorubicin combination therapy at this dosage and schedule was found to be well tolerated and moderate effective, which could be considered as salvage therapy for patients with recurrent or refractory osteosarcoma. Further assessment is necessary to confirm the safety and efficacy of this treatment.