• Advances in materials Research
• /
• v.4 no.1
• /
• pp.45-60
• /
• 2015

This paper aimed to investigate the effect of MWCNTs on properties of slag Geopolymeric mortar. Geopolymeric matrices containing different MWCNTs concentrations (0.0, 0.1, 0.2, 0.3 and 0.4 % by weight of the used binder) were synthesized. The Geopolymer mortar composed of aluminosilicate slag to sand (1:2), while the alumino silicate source binder composed of 50% air cooled slag and 50%water cooled slag both passing a sieve of $90{\mu}m$, while the sand passing a sieve of 1 ml. The materials prepared at water/binder ratios in a range of 0.34-0.39% depending on the added MWCNT, whereas the Gelenium Ace-30 superplasticizer used in the ratio of 1.4-2.2% from the total dry weight for better dispersion of MWCNT under sonication for 15 min. Alkaline activation of the Geopolymer mortar was carried by using of 6% NaOH. Curing was performed under temperature of $40^{\circ}C$ and 100% R.H. Results showed that the addition of MWCNTs enhanced the resulting amorphous geopolymer structure with marked decrease in the drying shrinkage as well as water absorption specially when using 0.1% MWCNT, while further increase in MWCNTs results in agglomeration in MWCNT within the matrix and so hinder the propagation of Geopolymerization reaction and negatively affect the formed geopolymer structure.

• Advances in nano research
• /
• v.4 no.3
• /
• pp.181-195
• /
• 2016

Addition of nano-$SiO_2$ (NS) to geopolymer composites has been studied through measurement of compressive strengths, FTIR and XRD analysis. Alumino-silicate materials are coarse aggregate included waste concrete and demolished walls with its cementing binder, cement kiln dust (CKD) used and can possess a pronouncing activation for the geopolymer reaction resulting from the high alkali contents within. Materials prepared at water/binder ratios in a range of 0.30: 0.40 under curing of $40^{\circ}C$ and 100% Relative Humidity (R.H.), while the used activator is sodium hydroxide in the ratio of 2 wt. %. First, CKD is added in the ratio from 10 up to 50 wt., %, and the demolished walls was varied depending on the used CKD content, while using constant ratio of waste concrete (40 wt., %). Second step, depending on the optimum CKD ratio resulted from the first one (40 wt. %), so the control geopolymer mix composed of cement kiln dust, demolished walls and waste concrete in the ratio (40:20:40, wt %). Nano-silica partially replaced waste concrete by 1 up to 8%. Results indicated that, compressive strengths of geopolymer mixes incorporating nano-silica were obviously higher than those control one, especially at early ages and specially with 3%NS.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.3 no.4
• /
• pp.374-381
• /
• 2015

This study is investigating the fire resistant finishing materials composed of fly ash and glass forming light weight aggregate has the high temperature thermal stability. High temperatures such as a fire, cementitious materials beget dehydration and micro crack of cement matrix. From the test result, developed fire resistant finishing materials showed good stability in high temperatures. These high temperature stability is caused by the ceramic binding and low thermal conductivity of glass forming light weight aggregate. Also, alkali activation reaction of fly ash and meta kaolin not showing the decomposition of calcium hydrates. Thus, this result indicates that it is possible to fire resistant finishing light weight mortars.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2008.06a
• /
• pp.47-47
• /
• 2008

P-type transparent semiconductor $SrCu_2O_2$ thin films have been prepared by RF sputtering using low-alkali glass for LCD and quartz as substrates. Single phase of $SrCu_2O_2$ powder was obtained by heating a stoichiometric mixture of CuO and $SrCO_3$ at 1223K for 96h under N2 gas flow, and target was fabricated at 1243K for 24h. Room temperature conductivity of the sintered body was about 0.02S/cm, and the activation energy in the temperature range of $-50^{\circ}C$~RT and RT~$150^{\circ}C$ were 0.18eV, 0.07eV, respectively. Effects of deposition pressure and post-annealing temperature on the electrical and optical properties of the obtained thin film have been investigated.

• Bulletin of the Korean Chemical Society
• /
• v.16 no.3
• /
• pp.265-269
• /
• 1995

Complexation of ortho-xylyl-17-crown-5 (X17C5) with alkali metal ions in acetonitrile was studied by 7Li and 23Na NMR spectroscopy. The complex formation constants of X17C5 with LiI, LiSCN, NaI, and NaSCN were determined by investigating the changes in the chemical shifts as a function of the concentration ratio of X17C5 to metal ion. It was found that X17C5 forms 1:1 complex with Li+ and Na+ ions and the log Kf's for the complexation with LiI, LiSCN, NaI, and NaSCN were determined to be 2.88, 2.43, 2.53, and 2.30, respectively. In particular, the kinetics of complexation of X17C5 with Na+ was investigated by the method of 23Na NMR lineshape analysis. Activation energies were determined from Arrhenius plot of the resultant rate constant data to be 25.4 kJ/mol for NaI and 15.1 kJ/mol for NaSCN. Other kinetic parameters were also calculated by employing the Eyring equation. The decomplexation rates measured were 1.82 × 104 M-1s-1 for NaI and 1.50 × 104 M-1s-1 for NaSCN. It is concluded that the decomplexation mechanism is predominantly a bimolecular cation exchange for both cases.

• Resources Recycling
• /
• v.23 no.6
• /
• pp.3-11
• /
• 2014

Bottom ash from coal fired power plants is not widely used due to a broad range of particle sizes and a high carbon content for producing geopolymers. The effect of mechanical activation on compressive strength of bottom ash- based geopolymers was examined by rod and planetary-ball milling to encourage full-fledged recycling of bottom ash, the main component of pond ash. The amount of amorphous component in the milled ash samples did not change significantly after the mechanical activation. It is presumably because needle-shaped mullite crystals, which is a major crystalline phase and grown in a glassy matrix, possess high strength and toughness, and therefore, they could endure external shocks and remain almost intact. Milling operation, however, decreased the particle size and improved the homogeneity of ash, thereby leading to increase reactivity of milled ash with alkali activators. Rod milling produced a relatively narrow particle size distribution of the milled ash particles; however, it was less effective in reducing the particle size. Nevertheless, it was interesting to observe that rod milling had equal effect on improving the compressive strength of geopolymers up to about 37%, as that of planetary ball milling. Rod milling is believed to be suitable process for enhancing the reactivity of bottom ash for large-scale recycling of bottom ash and producing geopolymers.

• Journal of the Korea Concrete Institute
• /
• v.18 no.2 s.92
• /
• pp.267-274
• /
• 2006

Greenhouse gas reduction will be highlighted as the most pending question in the cement industry in future because the production of Portland cement not only consumes limestone, clay, coal, and electricity, but also release waste gases such as $CO_2,\;SO_3$, and NOX, which can contribute to the greenhouse effect and acid rain. To meet the increase of cement demand and simultaneously comply with the Kyoto Protocol, cement that gives less $CO_2$ discharge should be urgently developed. This study aims to manufacture non-sintering cement(NSC) by adding phosphogypsum(PG) and waste lime(WL) to granulated blast furnace slag(GBFS) as sulfate and alkali activators. This study also Investigates the hydration reaction of NSC through analysis of scanning electron microscopy(SEM), X-ray diffraction(XRD), differential thermal analysis(DTA), and pH. Results obtained from analysis of the hydrate have shown that the glassy films of GBFS are destroyed by the activation of alkali and sulfate, ions eluted from the inside of GBFS react with PG and produce ettringite, and consequently the remaining component in GBFS slowly produced C-5-H(I) gel. Here, PG is considered not only to play the role of simple activator, but also to work as a binder reacting with GBFS.

• Journal of the Korean Ceramic Society
• /
• v.47 no.3
• /
• pp.223-231
• /
• 2010

The serious issue of tall building is to ensure the fire-resistance of high strength concrete. The fire resistant finishing method is necessarily essential in order to satisfy the fire resistance time of 3 h required by the law. The fire resistant finishing method is installed by applying a fire resistant material as a method of shotcrete or a fire resistant board to high strength concrete surface. This method can reduce the temperature increase of the reinforcement embedded in high strength concrete at high temperature due to the installation thickness control. This study is interested in identifying the effectiveness of inorganic alumino-silicate compounds including the inorganic admixture such as fly ash and meta-kaolin as the fire resistant finishing materials through the analysis of fire resistance and components properties at high temperature. The study results show that the fire resistant finishing material composed of fly ash and meta-kaolin has the thermal stability of the slight decrease of compressive strength at high temperature. These thermal stability is caused by the ceramic binding capacity induced by alkali activation reaction by the reason of the thermal analysis result not showing the decomposition of calcium hydrate. Inorganic compounds composed of fly ash and meta-kaolin is evaluated to be very effective as the fire resistance material for finishing to protect the concrete substrate by the reason of those simplicity in both application and manufacture. The additional study about the adhesion in the interface with concrete substrate is necessary for the purpose of the practical application.

• Journal of the Korea Convergence Society
• /
• v.8 no.11
• /
• pp.307-312
• /
• 2017

In the industry, galvanizing using the principle of sacrificial anode is used Zn-Ni alloy plating was developed as one of the measures to increase the corrosion resistance rather than pure zinc plating. The alloy plating layer has a corrosion resistance of 4-5 times that of the pure zinc plating layer, so that it is applied to automotive parts requiring high corrosion resistance even though the plating cost is high. The amount of Zn-Ni alloy plating solution is a sulfuric acid bath, a chlorinated bath, an alkali bath, and an ammonia bath. Here, the influence of the electrolytic conditions on the composition of the alloy plating in the chloride bath was investigated. The results are explained by the cathode overvoltage and the diffusion coefficient. In general, as the overvoltage of the cathode increases, the concentration polarization becomes more important than the activation polarization. The concentration polarization is determined by element diffusion in the diffusion layer. That is, as the overvoltage of the cathode increases, the Zn content having a large diffusion coefficient increases.

• The Journal of the Petrological Society of Korea
• /
• v.10 no.3
• /
• pp.233-245
• /
• 2001

With the advent of super-conducting magnet, NMR spectroscopy becomes a very important tool in geology as well as in chemistry. $^{29}Si$ and $^{27}Al$ which are the main components of minerals and contain structural informations, are useful major targets for the NMR study in geology, but some other elements including alkali cations such as $^{23}Na$ are also one of them. NMR can be applied to many different fields. For example, it can be applied to study smaller range of structure (in molecular level) than XRD and TEM. NMR provides us with structural informations such as order-disorder in Al and Si distribution, oxygen coordination number, and distribution of other cations. Another important information that we can obtain from NMR is not only the static structural informations, but also the molecular dynamics. This dynamic informations of molecules also enable us to figure out the frequency of molecular motion and activation energy. Structure of amorphous minerals and chemistry and structure of natural organic materials are also studied by NMR.