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류영복,이만식 대한금속·재료학회 2018 대한금속·재료학회지 Vol.56 No.1
An inorganic binder is a good way to mitigate the environmental issues of organic binders containing phenol, formaldehyde, etc. One of the most representative materials in the field of inorganic moulding sand binders is a group of binder systems based on alkali silicate compounds, however, many aspects need to be improved, such as flowability, usable time and moisture resistance. In order to develop and improve inorganic binders, it is necessary to understand the characteristics of raw materials and utilize them appropriately. In this study, FT-IR analysis and thermal properties of aqueous sodium silicate solution were investigated. The FT-IR analysis results indicated, that asymmetric vibrations had higher wavenumber than their symmetric vibrations and also the stretching vibrations appeared at higher energies than the deformation vibrations. FT-IR analysis of Na2SiO3 showed that the asymmetric stretching vibration absorption band of Si-O(Na) was indicated at around 1030 cm-1, and the absorption bands due to hydrated unit molecules were observed in the sodium silicate solution. As a result of TGA analysis of the dried sample, the weight loss of about 16% which was confirmed to be due to pyrolysis of the silanol group up to 500 oC, and an XRD analysis of the dried sample after heat treatment was confirmed that quartz crystals were formed at 900 oC or higher.
Consolidation of Quartz Powder by the Geopolymer Technique
Ikeda, Ko,Nakamura, Yoshinori The Korean Ceramic Society 2000 The Korean journal of ceramics Vol.6 No.2
The geopolymer technique may be a future-oriented technology for saving energies and resources. This technique requires 3 fundamental elements so-called filler, hardener and geopolymer liquor being generally an alkaline silicate solution. Quartz powder, water quenched granulated blast furnace slag and sodium silicate solution prepared from $Na_2O\cdot2SiO_2$were chosen for these three elements. After mixing these starting materials in appropriate proportions, monoliths were prepared by casting at room temperature. Strength tests showed the following results for 28d age speciment: 7.9-12.7 MPa in flexural strength and 20.2-32.8 MPa in compressive strength, depending on geopolymer liquor/solid ratio, P/S and fineness of the quartz powders used.
Control of the size and morphology of nano-size silica particles using a sodium silicate solution
위상욱,이상훈,Seung-Jae Lim,최성철 한양대학교 세라믹연구소 2009 Journal of Ceramic Processing Research Vol.10 No.4
In general nano-sized silica powders are synthesized using the Stber method. A system of chemical reactions has been developed which permits the controlled growth of spherical silica particles of a uniform size by the hydrolysis of alkyl silicates and subsequent condensation of silicic acid in alcoholic solutions. In this study nano silica powders were synthesized using a low cost sodium silicate instead of high cost alkoxide or organo-metallic compound. Cetyltrimethylammonium bromide (CTABr) was used as an additive to control the particle shape and produce a large surface area. The particle shape and specific surface area were controlled with various molar ratios of CTABr, ethyl acetate, DI water and water glass. The nano silica powders were characterized using BET(Brunauer, Emmett & Teller, specific surface area, powder pore size and distribution), and a scanning electron microscope.
실리카 나노입자의 분산도가 주형의 항절강도에 미치는 영향
김판성,배민아,백재호,제정호,이만식 대한금속·재료학회 2022 대한금속·재료학회지 Vol.60 No.6
Sodium silicate solutions are used as an eco-friendly binder in the casting process. However, the strength of sand molds using the sodium silicate solutions is reduced because of their low humidity resistance. In this study, silica nanoparticles were added to a sodium silicate solution with a constant SiO2/Na2O ratio to improve the humidity resistance of the inorganic binder. The effects of the dissolution times and particle size of the silica on the flexural strength of the molds was also investigated. The physiochemical properties of the inorganic binders were characterized by viscometer, Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA) and scanning electron microscope (SEM). Sand molds for the flexural strength test were prepared by mixing artificial sand and inorganic binders. The addition of silica nanoparticles reduced the viscosity and water evaporation rate of the inorganic binders and improved the humidity resistance of the molds due to an increase in the SiO2/Na2O ratio. The flexural strength of the molds increased as the size of the silica nanoparticles increased, due to formation of discrete silica aggregates with high surface area. However, as the dissolution times of the silica nanoparticles increased, the strength of the molds decreased due to an enhanced Q2/Q3 ratio. Therefore, we suggest that the addition of silica nanoparticles will improve the humidity resistance of molds, and that varying the particle size and dissolution time of the silica nanoparticles affects the strength of the molds.