• Korean Chemical Engineering Research
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• v.53 no.1
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• pp.103-110
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• 2015

In this work, the performance of various promoters was investigated used in $CO_2$ separation from the gases emitted from steel-making process using gas hydrate technology. The studied promoters are tetrahydrofuran (THF), propylene oxide and 1,4-dioxane, which are all expected to form a structure II hydrate, and the target gases include $CO_2/N_2$ mixed gases ($CO_2/N_2$ = 20/80 and 40/60) and Blast Furnace Gas (BFG). The phase equilibrium points were measured when each promoter was added with various concentrations. For fast acquisition of abundant data, the "continuous" Quartz crystal microbalance (QCM) method was employed. In addition, the crystal structure of each gas hydrate was analyzed by Powder X-ray diffraction (PXRD).

• Journal of Sericultural and Entomological Science
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• v.45 no.2
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• pp.121-125
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• 2003

Dissolution of Antheraea pernyi silk fiber was carried out in a zinc nitrate 6 hydrate (Zn(NO$_3$)$_2$ㆍ6$H_2O$) solution with various dissolving conditions. The solubility was significantly dependent on the concentration of zinc nitrate, dissolving temperature and time. Regenerated A. pernyi silk fibroin powder was obtained through dialysis process to remove chaotropic salt. FTIR and X-ray diffractometer showed that the conformation of regenerated A. pernyi silk powder was sheet structure.

• Journal of Integrative Natural Science
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• v.1 no.2
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• pp.76-78
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• 2008

A series of the long-chain iron(II) alkylsulfonate hydrates were synthesized via self-assembly of surfactant alkyl chains in aqueous medium. Reaction of iron(II) salts with n-alkylsulfonate yields lamellar $Fe(CnH2n+1SO3)2{\cdot}4H_2O$. These compounds show a layered structure, as determined by XRD, consisting of alternating organic alkylsulfonate layers and inorganic iron(II) hydrate layers, with interlayer distances of upto 3.2 nm. This lamellar structure may be attributed to the amphiphilic nature of the surfactants, mediating the coordination and H-bionding interactions, and the hydrophobic alkyl chains. An alkyl chain packing of present system are differ from those of similar Cu(II) series, which are attributed from the size of hydrated metal(II) ions.

• Korean Journal of Materials Research
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• v.14 no.11
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• pp.790-794
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• 2004

Ultra-fine Copper particles for a conductive paste in electric-electronic field were prepared using wet-reduction process with hydrazine hydrate ($N_{2}H_4{\cdot}H_{2}O$) as a reductor. The effect of reaction conditions such as the amount of dispersion ($Na_{4}O_{7}P_2{\cdot}10H_{2}O$) and reductor ($N_{2}H_4{\cdot}H_{2}O$) on the particle size and shape for the prepared Cu powders was investigated. The quantity of dispersion and reductor varied from 0 to 0.0025 M and from 5 to 40 ml at a reaction temperature of $70^{\circ}C$, respectively. The particle size, shape, and structure for the obtained Cu particles were characterized by means of XRD, SEM, TEM, EDS and TGA. The aggregation of Cu particles was reduced with relatively increasing of the amount of dispersion at fixed other reaction conditions. The smaller Cu particle with size of approximately 300nm was obtained from 0.032 M $CuSO_4$ with adding of 0.0025 M $Na_{4}O7P_2{\cdot}10H_{2}O$ and 40ml $N_{2}H_4{\cdot}H_{2}O$ at a reaction temperature of $70^{\circ}C$.

• Journal of the Korean Ceramic Society
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• v.28 no.9
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• pp.721-729
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• 1991

SnO2-TiO2(Pt or Pd), as raw material for hydrocarbon gas sensors, was prepared by a coprecipitation method. The SnO2-TiO2-based thick film gas sensors were made by screen printing technique. The titanium dioxide synthesized was shown to be anatase structure from XRD peaks and was transformed to rutile structure between 700$^{\circ}C$ and 1000$^{\circ}C$. Titanium dioxide in SnO2-TiO2 thick films devices plays a very important role in the enhancement of the sensitivity to CH4 and C4H10. In the case of SnO2-TiO2(Pt) sensors, titanium dioxide that was rutile structure enhanced the sensitivity of the thick film to CH4. Platinum added to the raw powder at coprecipitation (as chloroplatinic acid VI hydrate) improved the gas sensitivity to hydrocarbon gases. Therefore, it is expected that the SnO2-TiO2(Pt) thick film sensors fabricated in this experiment could be put into practical use as LPG (primary component : C4H10 and C3H8) and LNG (primary component : CH4) sensors.

• Clean Technology
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• v.19 no.4
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• pp.476-480
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• 2013

The growth behavior of $CH_4$ and $SF_6$ mixture gas hydrate has been investigated by a combined approach of Raman spectroscopy and molecular modeling. Raman spectroscopy results presented that when $CH_4$ is used only, $CH_4$ guest molecule is inserted first into the large cavity of the host structure built by $H_2O$ molecules and then into the small cavity to stabilize the whole gas hydrate structure. In the other hand, when $SF_6$ is mixed together, $SF_6$ is favored over (or competing with) $CH_4$ in being inserted into the large cavity and the small cavity still prefers $CH_4$ insertion. The calculations of binding energies clearly supported this. While $SF_6$ has a binding energy of -26.9 kcal/mol a little lower than -24.2 kcal/mol of $CH_4$ in the large cavity, $SF_6$ and $CH_4$ has 1.2 kcal/mol and -22.0 kcal/mol, respectively, in the small cavity. It indicates that the sizable $SF_6$ is not preferred in the small cavity but has a relative energetic advantage over $CH_4$ in the large cavity.

• Korean Chemical Engineering Research
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• v.49 no.3
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• pp.367-371
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• 2011

TBAB (tetra-n-butyl ammonium bromide) forms a semi-clathrate with water under atmospheric pressure conditions and recently has attracted great attention due to its usage as a thermodynamic promoter in gas storage and separation process using gas hydrate formation. In this study, we measured the three-phase (hydrate (H) - liquid water ($L_{w}$)-vapor (V)) equilibria of the ternary $CH_{4}$+TBAB+water and $CO_{2}$+TBAB+water mixtures at the TBAB concentrations of 5 and 32 wt% to investigate promoting characteristics of TBAB. The greater promotion effect of TBAB was observed at 32 wt% than at 5 wt%. This result was in good agreement with that from pure TBAB semi-clathrate phase diagram under atmospheric pressure conditions. Through $^{13}C$ NMR analysis of the $CH_{4}$+TBAB semi-clathrate, it was found that $CH_{4}$ molecules are enclathrated in the cages of the double semi-clathrate and the position of resonance peak from encaged $CH_{4}$ molocules in the double semi-clathrate is the same as that from encaged $CH_{4}$ molocules in the pure $CH_{4}$ hydrate of structure I.

• International Journal of Concrete Structures and Materials
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• v.5 no.1
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• pp.3-10
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• 2011

Theoretical models for prediction of the mechanical properties of cement mortar are developed based on the morphology and interactions of cement hydration products, capillary pores and microcracks. The models account for intermolecular interactions involving the nano-scale calcium silicate hydrate (C-S-H) constituents of hydration products, and consider the effects of capillary pores as well as the microcracks within the hydrated cement paste and at the interfacial transition zone (ITZ). Cement mortar was modeled as a three-phase material composed of hydrated cement paste, fine aggregates and ITZ. The Hashin's bound model was used to predict the elastic modulus of mortar as a three-phase composite. Theoretical evaluation of fracture toughness indicated that the frictional pullout of fine aggregates makes major contribution to the fracture energy of cement mortar. Linear fracture mechanics principles were used to model the tensile strength of mortar. The predictions of theoretical models compared reasonably with empirical values.

• Advances in Computational Design
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• v.3 no.2
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• pp.147-163
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• 2018

Cementitious composites are multiphase heterogeneous materials with distinct dissimilarity in strength under compression and tension (high under compression and very low under tension). At macro scale, the phenomenon can be well-explained as the material contains physical heterogeneity and pores. But, it is interesting to note that this dissimilarity initiates at molecular level where there is no heterogeneity. In this regard, molecular dynamics based computational investigations are carried out on cement clinkers and calcium silicate hydrate (C-S-H) under tension and compression to trace out the origin of dissimilarity. In the study, effect of strain rate, size of computational volume and presence of un-structured atoms on the obtained response is also investigated. It is identified that certain type of molecular interactions and the molecular structural parameters are responsible for causing the dissimilarity in behavior. Hence, the judiciously modified or tailored molecular structure would not only be able to reduce the extent of dissimilarity, it would also be capable of incorporating the desired properties in heterogeneous composites. The findings of this study would facilitate to take step to scientifically alter the structure of cementitious composites to attain the desired mechanical properties.

• Journal of the Korea Institute of Building Construction
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• v.18 no.3
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• pp.305-312
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• 2018

This study is about the development of a non-sintered binder (NSB) which does not require a sintering process by using the industrial by-products Phosphogypsum (PG), Waste Lime (WL) and Granulated Blast Furnace Slag (GBFS). In this report, through SEM analysis of the NSB paste hardening body, micropore analysis of paste using the mercury press-in method and microstructure observation were executed to consider the influence of the formation of the pore structure and the distribution of pore volume on strength, and the following conclusions were reached. 1) Pore structure of NSB paste of early age is influenced by hydrate generation amount by GBFS and activator. 2) Through observing the internal microstructure of NSB binder paste, it was found that the strength expression at early age due to hydration reaction was achieved with a large amount of ettringite serving as the frame with C-S-H gel generated at the same time. It was confirmed that C-S-H gel wrapped around ettringite, and as time passed, the amount generated continually increased, and C-S-H gel tightly filled the pores of hardened paste, forming a dense network-type web structure. 3) For NSB-type cement, the degree of formation of gel pores below $10{\mu}m$ had a greater influence on strength improvement than simple pore reduction by charging capillary pores, and the pore size that had the greatest effect on strength was micropores with diameter below $10{\mu}m$.