• Title/Summary/Keyword: Hydrate

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Pressureless Sintering and Microstructure of Pure Tungsten Powders Prepared by Ultrasonic Spray Pyrolysis (초음파 분무 열분해법으로 제조한 텅스텐 분말의 상압소결과 미세조직)

  • Heo, Youn Ji;Lee, Eui Seon;Oh, Sung-Tag;Byun, Jongmin
    • Journal of Powder Materials
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    • v.29 no.3
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    • pp.247-251
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    • 2022
  • This study demonstrates the effect of the compaction pressure on the microstructure and properties of pressureless-sintered W bodies. W powders are synthesized by ultrasonic spray pyrolysis and hydrogen reduction using ammonium metatungstate hydrate as a precursor. Microstructural investigation reveals that a spherical powder in the form of agglomerated nanosized W particles is successfully synthesized. The W powder synthesized by ultrasonic spray pyrolysis exhibits a relative density of approximately 94% regardless of the compaction pressure, whereas the commercial powder exhibits a relative density of 64% under the same sintering conditions. This change in the relative density of the sintered compact can be explained by the difference in the sizes of the raw powder and the densities of the compacted green body. The grain size increases as the compaction pressure increases, and the sintered compact uniaxially pressed to 50 MPa and then isostatically pressed to 300 MPa exhibits a size of 0.71 m. The Vickers hardness of the sintered W exhibits a high value of 4.7 GPa, mainly due to grain refinement.

Development of Bottom Ash Replacement Cement Using Diethanol Isopropanolamine (Diethanol Isopropanolamine을 활용한 바텀애시 치환 시멘트 개발)

  • Hyunuk Kang;Ahyeon Lim;Juhyuk Moon
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.12 no.1
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    • pp.72-81
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    • 2024
  • In this study, DEIPA was used for enhancing cementitious performance of bottom ash replaced cement. By applying the partial or no-known crystal structure method to X-ray diffraction data, the amounts of amorphous bottom ash and calcium silicate hydrate(C-S-H) could be separated and quantified. In the sample without DEIPA, the bottom ash hardly reacted, resulting in low compressive strength. However, the addition of DEIPA not only altered the hydration behavior of the cement but also enhanced the pozzolanic reaction between bottom ash and calcium hydroxide, leading to the generation of additional C-S-H. This resulted in high compressive strength not only in the early stages but also in the later stages. Therefore, with the addition of DEIPA during the pulverization of the bottom ash, the reactivity of the bottom ash was significantly improved. Hence, there is potential in the development of bottom ash replacement cement.

Strength and Hydration Properties of Cement Paste as a Function of Reactive Nanomaterials Replacement Rate (반응성 나노소재 대체율에 따른 시멘트 페이스트의 강도 및 수화특성)

  • Chul-Woo Beak;Sung-Woo Choi;Deuk-Hyun Ryu
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.12 no.1
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    • pp.33-39
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    • 2024
  • In this study, the basic properties of cement paste with varying replacement ratio of micro-silica and fumed silica were analyzed to determine the suitability of nanomaterials for use as concrete admixtures. Referring to the ultra-high strength mix, the fluidity of cement paste was evaluated according to the nanomaterial replacement rate and the compressive strength characteristics were compared and analyzed. The related properties of the reactive nanomaterials to the cement hydrate were analyzed using SEM and EDS to observe the microstructure and identify the components of the hydration product. The reactive nanomaterials used in this study had tap densities between 0.061 and 0.264 g/cm3, which were lower than SF. Micro silica exhibited excellent compressive strength properties with increasing replacement ratio, but fumed silica, unlike micro white, obtained excellent compressive strength at replacement ratio of 0.01~0.1 %. The same trend was observed in the hydration characterization.

An experimental investigation on dispersion and geotechnical properties of dispersive clay soil stabilized with Metakaolin and Zeolite

  • Ahmadreza Soltanian;Amirali Zad;Maryam Yazdib;Amin Tohidic
    • Geomechanics and Engineering
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    • v.36 no.6
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    • pp.589-599
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    • 2024
  • Dispersion occurs when clay soil disperses under specific conditions and is rapidly washed away. While there are numerous methods for rectifying it, they are neither cost nor time-effective. The current study used metakaolin and zeolite to improve heavily dispersive clay soil either separately or in combination at 0%, 2%, 4%, 6%, and 8% of the soil weight. After 7 days of curing, the samples were tested to determine the extent of change in the dispersion potential, as well as the improvement of the geotechnical properties of the soil. The results indicated that the addition of 2% zeolite with 6% to 8% metakaolin decreased the dispersion potential considerably. Double hydrometry test findings revealed that the dispersion potential decreased by almost 70% and entered the non-dispersive group; the crumb test also revealed this. Atterberg limits testing indicated a decrease in the plasticity index which reduced the flexibility of the samples. The greatest decrease in PI (67.5%) was achieved with the addition of 8% zeolite plus 8% metakaolin to the soil. The results of density tests revealed that a decrease in the optimal moisture content increased the maximum dry density of soil. This increase in density was a response to the high reactivity of metakaolin with calcium hydroxide and the formation of calcium hydroxide hydrate gel. This eventually caused an increase in the unconfined compressive strength, the greatest increase in strength of about 1.8-fold was observed with a combination of 2% zeolite and 6% metakaolin compared to the unmodified sample.

Studies for CO2 Sequestration Using Cement Paste and Formation of Carbonate Minerals (시멘트 풀을 이용한 CO2 포집과 탄산염광물의 생성에 관한 연구)

  • Choi, Younghun;Hwang, Jinyeon;Lee, Hyomin;Oh, Jiho;Lee, Jinhyun
    • Journal of the Mineralogical Society of Korea
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    • v.27 no.1
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    • pp.17-30
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    • 2014
  • Waste cement generated from recycling processes of waste concrete is a potential raw material for mineral carbonation. For the $CO_2$ sequestration utilizing waste cement, this study was conducted to obtain basic information on the aqueous carbonation methods and the characteristics of carbonate mineral formation. Cement paste was made with W:C= 6:4 and stored for 28 days in water bath. Leaching tests using two additives (NaCl and $MgCl_2$) and two aqueous carbonation experiments (direct and indirect aqueous carbonation) were conducted. The maximum leaching of $Ca^{2+}$ ion was occurred at 1.0 M NaCl and 0.5 M $MgCl_2$ solution rather than higher tested concentration. The concentration of extracted $Ca^{2+}$ ion in $MgCl_2$ solution was more than 10 times greater than in NaCl solution. Portlandite ($Ca(OH)_2$) was completely changed to carbonate minerals in the fine cement paste (< 0.15 mm) within one hour and the carbonation of CSH (calcium silicate hydrate) was also progressed by direct aqueous carbonation method. The both additives, however, were not highly effective in direct aqueous carbonation method. 100% pure calcite minerals were formed by indirect carbonation method with NaCl and $MgCl_2$ additives. pH control using alkaline solution was important for the carbonation in the leaching solution produced from $MgCl_2$ additive and carbonation rate was slow due to the effect of $Mg^{2+}$ ions in solution. The type and crystallinity of calcium carbonate mineral were affected by aqueous carbonation method and additive type.

Effects of Magnesium and Sulfate Ions on the Sulfate Attack Resistance of Alkali-activated Materials (알칼리 활성화 결합재 모르타르의 황산염 침식 저항성에 미치는 마그네슘 및 황산 이온의 영향)

  • Park, Kwang-Min;Cho, Young-Keun;Shin, Dong-Cheol
    • Journal of the Korea Concrete Institute
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    • v.29 no.4
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    • pp.415-424
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    • 2017
  • The purpose of this study is to investigate the effect of sulfate (${SO_4}^{2-}$) and magnesium ($Mg^{2+}$) ions on sulfate resistance of Alkali-activated materials using Fly ash and Ground granulated blast furnace slag (GGBFS). In this research, 30%, 50% and 100% of GGBFS was replaced by sodium silicate modules ($Ms(SiO_2/Na_2O)$, molar ratio, 1.0, 1.5 and 2.0). In order to investigate the effects of $Mg^{2+}$ and ${SO_4}^{2-}$, compression strength, weight change, lengh expansion of the samples were measured in 10% sodium sulfate ($Na_2SO_4$), 10%, 5% and 2.5% magnesium sulfate ($MgSO_4$), 10% magnesium nitrate ($Mg(NO_3)_2$), 10% [magnesium chloride ($MgCl_2$) + sodium sulfate ($Na_2SO_4$)] and 10% [magnesium nitrate $(Mg(NO_3)_2$ + sodium sulfate ($Na_2SO_4$)] solution, respectively and X-ray diffraction analysis was conducted after each experiment. As a result, when $Mg^{2+}$ and ${SO_4}^{2-}$ coexist, degradation of compressive strength and expansion of the sample were caused by sulfate erosion. It was found that the reaction of $Mg^{2+}$ with Calcium Silicate Hydrate (C-S-H) occurred and $Ca^{2+}$ was produced. Then the Gypsum ($CaSO_4{\cdot}2H_2O$) was formed due to reaction between $Ca^{2+}$ and ${SO_4}^{2-}$, and also Magnesium hydroxide ($Mg(OH)_2$, Brucite) was produced by the reaction between $Mg^{2+}$ and $OH^-$.

Preparations of Universal, Functionalized Long-Chain Alkylthiol Linkers for Self-assembled Monolayers (자기조립단분자막을 위한 보편적이고 기능화된 긴 사슬 알킬티올 연결자의 제조)

  • Yoo, Dong-Jin;Lee, Kyong-Sub;Kim, Ae-Rhan;Nahm, Kee-Suk
    • Korean Chemical Engineering Research
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    • v.49 no.3
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    • pp.330-337
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    • 2011
  • In this research, the preparation processes for making a series of $\omega$-mercapto alkylamine 1 and $\omega$-mercapto alkanoic acid 2 useful for studying of the self-assembled monolayer(SAM) are described. The preparation methods of the first goal materials, $\omega$-mercapto alkylamines 1 were carried out as follows: First, $\omega$-phthalimide alkanol 3 was synthesized from commercially available potassium phthalimide derivatives and $\omega$-bromoalkanol in DMF at $80{^{\circ}C}$ via substitution reaction. After refluxing $\omega$-phthalimide alkanol 3 with hydrazine hydrate in ethanol followed by treating with c-HCl, $\omega$-aminoalkanol 4 was obtained in 76-98% yield, accompanied with side-product 5. Bromination of hydroxyl moiety of $\omega$-aminoalkanol 4 using aqueous hydrobromic acid furnished $\omega$-bromoamine 6 in 34-97% yields. Substitution reaction 6 with thiourea in 95% ethanol gave $\omega$-aminoalkanthiuronium 7, which was treated with aqueous strong base and aqueous strong sulfuric acid gave desired products, $\omega$-mercapto alkylamines 1 through overall 5 steps. The second target material, $\omega$-mercapto alkanoic acid 2 was prepared via 2 steps. $\omega$-bromo alkanoic acid was reacted with thiourea to give $\omega$-thiourea alkanoic acid 7 in 69-85%, which was treated with aqueous strong base and strong acid to furnish $\omega$-mercapto alkanoic acid 2 in 50-98%. The fabricated long-chain alkylthiol(LCAT) can be used as linkers to immobilize protein, enzyme and various kinds of biomolecules on the surface of metallic materials(Au, Pt, Ti) by SAM, and can be useful chemical tools for the application study on the surface modification of metallic materials.

A Study on Change in Cement Mortar Characteristics under Carbonation Based on Tests for Hydration and Porosity (수화물 및 공극률 관측 실험을 통한 시멘트모르타르의 탄산화 특성 변화에 대한 연구)

  • Kwon, Seung-Jun;Song, Ha-Won;Park, Sang-Soon
    • Journal of the Korea Concrete Institute
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    • v.19 no.5
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    • pp.613-621
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    • 2007
  • Due to the increasing significance of durability, much researches on carbonation, one of the major deterioration phenomena are carried out. However, conventional researches based on fully hardened concrete are focused on prediction of carbonation depth and they sometimes cause errors. In contrast with steel members, behaviors in early-aged concrete such as porosity and hydrates (calcium hydroxide) are very important and may be changed under carbonation process. Because transportation of deteriorating factors is mainly dependent on porosity and saturation, it is desirable to consider these changes in behaviors in early-aged concrete under carbonation for reasonable analysis of durability in long term exposure or combined deterioration. As for porosity, unless the decrease in $CO_2$ diffusion due to change in porosity is considered, the results from the prediction is overestimated. The carbonation depth and characteristics of pore water are mainly determined by amount of calcium hydroxide, and bound chloride content in carbonated concrete is also affected. So Analysis based on test for hydration and porosity is recently carried out for evaluation of carbonation characteristics. In this study, changes in porosity and hydrate $(Ca(OH)_2)$ under carbonation process are performed through the tests. Mercury Intrusion Porosimetry (MIP) for changed porosity, Thermogravimetric Analysis (TGA) for amount of $(Ca(OH)_2)$ are carried out respectively and analysis technique for porosity and hydrates under carbonation is developed utilizing modeling for behavior in early-aged concrete such as multi component hydration heat model (MCHHM) and micro pore structure formation model (MPSFM). The results from developed technique is in reasonable agreement with experimental data, respectively and they are evaluated to be used for analysis of chloride behavior in carbonated concrete.

Corrosion Characteristics by CCPP Control in Simulated Distribution System (CCPP 조절에 따른 모의 상수관로의 부식특성에 관한 연구)

  • Kim, Do-Hwan;Lee, Jae-In;Lee, Ji-Hyung;Han, Dong-Yueb;Kim, Dong-Youn;Hong, Soon-Heon
    • Journal of Korean Society of Environmental Engineers
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    • v.27 no.12
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    • pp.1249-1256
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    • 2005
  • This study was performed to investigate the efficiency of the corrosion prevention in the simulated distribution system using CCPP(Calcium Carbonate Precipitation Potential) as the anti-corrosive index by adjusting pH, total dissolved solids, alkalinity and calcium hardness in the water treatment pilot process. The materials of the simulated distribution system(SDS) were equiped with same materials of real field water distribution system. CCPP concentrations controlled by $Ca(OH)_2$, $CO_2$ gas and $Na_2CO_3$ in the simulated distribution system and uncontrolled by the chemicals in the general water distribution system were average 0.61 mg/L and -7.77 mg/L. The concentrations of heavy metals like Fe, Zn, Cu ions in effluent water of the simulated distribution system controlled with water quality were decreased rather than the general water distribution system uncontrolled with water quality. In simulated distribution system(SDS), corrosion prevention film formed by CCPP control was observed that scale was come into forming six months later and it was formed into density as time goes on. We were analyzed XRD(X-ray diffraction) for investigating component of crystal compounds and structure for galvanized steel pipe(15 mm). Finding on analysis, scale was compounded to $Zn_4CO_3(OH)_6{\cdot}H_2O$ (Zinc Carbonate Hydroxide Hydrate) after ten months late, and it was compounded on $CaCO_3$(Calcium Carbonate) and $ZnCO_3$(Smithsonite) after nineteen months later.

Comparison of Volatile Compounds from Thymus Magnus Nakai by Three Different Extraction Methods (추출방법에 따른 섬백리향의 휘발성 향기성분 비교)

  • Lee, Sa Eun;Kim, Songmun;Lim, Won Churl;Kang, Ki Choon;Pyo, Hyeong Bae
    • Journal of the Society of Cosmetic Scientists of Korea
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    • v.40 no.2
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    • pp.171-178
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    • 2014
  • The purpose of this study was to analyse the volatile components of Thymus magnus Nakai extracted by different extraction methods and reproduce scent close to original plant based on the results. For this purpose, the essential oil of T. magnus was extracted by supercritical fluid extraction (SFE), water and steam distillation (WSD) and simultaneous steam distillation and extraction (SDE) methods. The compositions of the essential oil were analyzed by gas chromatography-mass spectrometry (GC-MS). Consequently, linalool (0.1%) and trans-sabinene hydrate (0.9%) contents in the essential oil extracted by SFE method of $40^{\circ}C$ - 400 bar condition were relatively higher than compositions of the essential oil extracted by different conditions. The contents of borneol (3.82%), terpinen-4-ol (0.3%) and caryophyllene oxide (2.2%) were relatively higher at $50^{\circ}C$ - 400 bar and the contents of ${\beta}$-bisabolene (5.88%), 1-octen-3-ol (0.31%), caryophyllene (2.91%), p-cymene (2.04%) and ${\gamma}$-terpinene (0.52%) were extracted relatively higher at $50^{\circ}C$ - 300 bar. The compositions of the essential oil extracted by SFE method of $50^{\circ}C$ - 200 bar condition contained relatively higher contents of thymol (77.63%) and carvacrol (5.65%). The contents of ${\alpha}$-bisabolol (0.17%), caryophyllene (6.46%), cis-${\alpha}$-bisabolene (1.52%) and ${\beta}$-bisabolene (20.65%) in the essential oil extracted by WSD method were relatively higher than compositions of the essential oil extracted by SFE method, and by SDE method we couldn't obtained essential oil. The results of this study could be utilized to reproduce scent close to original scent of T. magnus.