• Title/Summary/Keyword: structural silica

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Effect of Boron Content on Atomic Structure of Boron-bearing Multicomponent Oxide Glasses: A View from Solid-state NMR (비정질 소듐 보레이트와 붕소를 함유한 다성분계 규산염 용융체의 붕소의 함량에 따른 원자 구조에 대한 고상 핵자기 공명 분광분석 연구)

  • Lee, A Chim;Lee, Sung Keun
    • Journal of the Mineralogical Society of Korea
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    • v.29 no.3
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    • pp.155-165
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    • 2016
  • Understanding the effect of boron content on atomic structures of boron-bearing multicomponent silicate melts is essential to reveal the atomistic origins of diverse geochemical processes involving silica-rich magmas, such as explosive volcanic eruption. The detailed atomic environments around B and Al in boron-bearing complex aluminosilicate glasses yield atomistic insights into reactivity of nuclear waste glasses in contact with aqueous solutions. We report experimental results on the effect of boron content on the atomic structures of sodium borate glasses and boron-bearing multicomponent silicate melts [malinkoite ($NaBSiO_4$)-nepheline ($NaAlSiO_4$) pseudo-binary glasses] using the high-resolution solid-state NMR ($^{11}B$ and $^{27}Al$). The $^{11}B$ MAS NMR spectra of sodium borate glasses show that three-coodrinated boron ($^{[3]}B$) increases with increasing $B_2O_3$ content. While the spectra imply that the fraction of non-ring species decreases with decreasing boron content, peak position of the species is expected to vary with Na content. Therefore, the quantitative estimation of the fractions of the ring/non-ring species remains to be explored. The $^{11}B$ MAS NMR spectra of the glasses in the malinkoite-nepheline join show that four-coordinated boron ($^{[4]}B$) increases as $X_{Ma}$ [$=NaBSiO_4/(NaBSiO_4+NaAlSiO_4)$] increases while $^{[3]}B$ decreases. $^{27}Al$ MAS NMR spectra of the multicomponent glasses confirm that four-coordinated aluminum ($^{[4]}Al$) is dominant. It is also observed that a drastic decrease in the peak widths (full-width at half-maximum, FWHM) of $^{[4]}Al$ with an addition of boron ($X_{Ma}=0.25$) in nepheline glasses. This indicates a decrease in structural and topological disorder around $^{[4]}Al$ in the glasses with increasing boron content. The quantitative atomic environments around boron of both binary and multicomponent glasses were estimated from the simulation results of $^{11}B$ MAS NMR spectra, revealing complex-nonlinear variation of boron topology with varying composition. The current results can be potentially used to account for the structural origins of the change in macroscopic properties of boron-bearing oxide melts with varying boron content.

Strength Development of Sulfur-Polymer-Based Concrete Surface Protecting Agents Depending on Curing Condition and Hazard Assessment of Sulfur Polymers (유황폴리머를 활용한 콘크리트 표면보호재의 양생조건에 따른 강도 평가 및 유황폴리머의 유해성 평가)

  • Lee, Byung-Jae;Lee, Eue-Sung;Kim, Seung-Gu;Kim, Yun-Yong
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.19 no.1
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    • pp.139-146
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    • 2015
  • The amount of by-product from sulphur increases in domestic industrial facilities. However, the amount of its consumption is limited so that the amount of unused sulphur continues to increase. Therefore, in this study, the use sulfur polymer as the concrete surface protecting material was conducted. The compressive strength showed that as the substitution ratio of filler increased up to 40%, the compressive strength also increased. A high compressive strength was shown at the curing temperature of $40^{\circ}C$ (SS, FA) and $60^{\circ}C$ (OPC) according to the type of filler. The difference of compressive strength between air dry curing and water curing was insignificant so that there was no significant influence of moisture during curing process. The evaluation result of bond strength showed that the highest bond strength was shown at the air-dry condition of $40^{\circ}C$ regardless of type of filler. Bonding didn't occur properly during water curing in comparison to air dry curing. Also, in case of the specimen cured at $60^{\circ}C$, discoloration and hair cracks appeared due to the influence of temperature, and the highest bond strength was shown at the substitution ratio of 20% (SS, FA) and 30% (OPC) according to the type of filler. The releasing test result of harmful substance showed that no harmful substance was released, so there is no harmfulness in the surface protecting material using sulfur polymer. As a conclusion drawn in this study, it is most appropriate to substitute silica by approximately 20%, mix and cure at the air-dry condition of $40^{\circ}C$ in order to use sulfur polymer as the surface protecting material.

Performance Evaluation of Hydrocyclone Filter for Treatment of Micro Particles in Storm Runoff (Hydrocyclone Filter 장치를 이용한 강우유출수내 미세입자 제거특성 분석)

  • Lee, Jun-Ho;Bang, Ki-Woong;Hong, Sung-Chul
    • Journal of Korean Society of Environmental Engineers
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    • v.31 no.11
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    • pp.1007-1018
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    • 2009
  • Hydrocyclone is widely used in industry, because of its simplicity in design, high capacity, low maintenance and operational cost. The separation action of a hydrocyclone treating particulate slurry is a consequence of the swirling flow that produces a centrifugal force on the fluid and suspended particles. In spite of hydrocyclone have many advantage, the application for treatment of urban stormwater case study were rare. We conducted a laboratory scale study on treatable potential of micro particles using hydrocyclone filter (HCF) that was a combined modified hydrocyclone with perlite filter cartridge. Since it was not easy to use actual storm water in the scaled-down hydraulic model investigations, it was necessary to reproduce ranges of particles sizes with synthetic materials. The synthesized storm runoff was made with water and addition of particles; ion exchange resin, road sediment, commercial area manhole sediment, and silica gel particles. Experimental studies have been carried out about the particle separation performance of HCF-open system and HCF-closed system. The principal structural differences of these HCFs are underflow zone structure and vortex finder. HCF was made of acryl resin with 120 mm of diameter hydrocyclone and 250 mm of diameter filter chamber and overall height of 800 mm. To determine the removal efficiency for various influent concentrations of suspended solids (SS) and chemical oxygen demand (COD), tests were performed with different operational conditions. The operated maximum of surface loading rate was about 700 $m^3/m^2$/day for HCF-open system, and 1,200 $m^3/m^2$/day for HCF-closed system. It was found that particle removal efficiency for the HCF-closed system is better than the HCF-open system under same surface loading rate. Results showed that SS removal efficiency with the HCF-closed system improved by about 8~20% compared with HCF-open system. The average removal efficiency difference for HCF-closed system between measurement and CFD particle tracking simulation was about 4%.

A review on the design requirement of temperature in high-level nuclear waste disposal system: based on bentonite buffer (고준위폐기물처분시스템 설계 제한온도 설정에 관한 기술현황 분석: 벤토나이트 완충재를 중심으로)

  • Kim, Jin-Seop;Cho, Won-Jin;Park, Seunghun;Kim, Geon-Young;Baik, Min-Hoon
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.21 no.5
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    • pp.587-609
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    • 2019
  • Short-and long-term stabilities of bentonite, favored material as buffer in geological repositories for high-level waste were reviewed in this paper in addition to alternative design concepts of buffer to mitigate the thermal load from decay heat of SF (Spent Fuel) and further increase the disposal efficiency. It is generally reported that the irreversible changes in structure, hydraulic behavior, and swelling capacity are produced due to temperature increase and vapor flow between $150{\sim}250^{\circ}C$. Provided that the maximum temperature of bentonite is less than $150^{\circ}C$, however, the effects of temperature on the material, structural, and mineralogical stability seems to be minor. The maximum temperature in disposal system will constrain and determine the amount of waste to be disposed per unit area and be regarded as an important design parameter influencing the availability of disposal site. Thus, it is necessary to identify the effects of high temperature on the performance of buffer and allow for the thermal constraint greater than $100^{\circ}C$. In addition, the development of high-performance EBS (Engineered Barrier System) such as composite bentonite buffer mixed with graphite or silica and multi-layered buffer (i.e., highly thermal-conductive layer or insulating layer) should be taken into account to enhance the disposal efficiency in parallel with the development of multilayer repository. This will contribute to increase of reliability and securing the acceptance of the people with regard to a high-level waste disposal.

Occurrence and Chemical Composition of Dolomite from Komdok Pb-Zn Deposit (검덕 연-아연 광상의 돌로마이트 산상과 화학조성)

  • Yoo, Bong Chul
    • Korean Journal of Mineralogy and Petrology
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    • v.34 no.2
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    • pp.107-120
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    • 2021
  • The Komdok Pb-Zn deposit, which is the largest Pb-Zn deposit in Korea, is located at the Hyesan-Riwon metallogenic zone in Jiao Liao Ji belt included Paleoproterozoic Macheolryeong group. The geology of this deposit consists of Paleoproterozoic metasedimentary rocks, Jurassic Mantapsan intrusive rocks and Cenozoic basalt. The Komdok deposit which is a SEDEX type deposit occurs as layer ore and vein ore in the Paleoproterozoic metasedimentary rocks. Based on mineral petrography and paragenesis, dolomites from this deposit are classified four types (1. dolomite (D0) as hostrock, 2. early dolomite (D1) associated with tremolite, actinolite, diopside, sphalerite and galena from amphibolite facies, 3. late dolomite (D2) associated with talc, calcite, quartz, sphalerite and galena from amphibolite facies, 4. dolomite (D3) associated with white mica, chlorite, sphalerite and galena from quartz vein). The structural formulars of dolomites are determined to be Ca1.00-1.20Mg0.80-0.99Fe0.00-0.01Zn0.00-0.02(CO3)2(D0), Ca1.00-1.02M0.97-0.99Fe0.00-0.01Zn0.00-0.02(CO3)2(D1), Ca0.99-1.03Mg0.93-0.98Fe0.01-0.05Mn0.00-0.01As0.00-0.01(CO3)2(D2) and Ca0.95-1.04Mg0.59-0.68Fe0.30-0.36Mn0.00-0.01 (CO3)2(D3), respectively. It means that dolomites from Komdok deposit have higher content of trace elements (FeO, MnO, HfO2, ZnO, PbO, Sb2O5 and As2O5) compared to the theoretical composition of dolomite. These trace elements (FeO, MnO, ZnO, Sb2O5 and As2O5) show increase and decrease trend according to paragenetic sequence, but HfO2 and PbO elements no show increase and decrease trend according to paragenetic sequence. Dolomites correspond to Ferroan dolomite (D0, D1 and D2), and Ferroan dolomite and ankerite (D3), respectively. Therefore, 1) dolomite (D0) as hostrock was formed by subsequent diagenesis after sedimentation of Paleoproterozoic (2012~1700 Ma) silica-bearing dolomite in the marine evaporative environment. 2) Early dolomite (D1) was formed by hydrothermal metasomatism origined metamorphism (amphibolite facies) associated with intrusion (1890~1680 Ma) of Paleoproterozoic Riwon complex. 3) Late dolomte (D2) was formed from residual fluid by a decrease of temperature and pressure. and dolomite (D3) in quartz vein was formed by intrusion (213~181 Ma) of Jurassic Mantapsan intrusive rocks.