• Korean Journal of Materials Research
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• v.29 no.1
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• pp.23-29
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• 2019

Three-dimensional(3D) printing is a process for producing complex-shaped 3D objects by repeatedly stacking thin layers according to digital information designed in 3D structures. 3D printing can be classified based on the method and material of additive manufacturing process. Among the various 3D printing methods, digital light processing is an additive manufacturing technique which can fabricate complex 3D structures with high accuracy. Recently, there have been many efforts to use ceramic material for an additive manufacturing process. Generally, ceramic material shows low processability due to its high hardness and strength. The introduction of additive manufacturing techniques into the fabrication of ceramics will improve the low processability and enable the fabrication of complex shapes and parts. In this study, we synthesize silica composite material that can be applied to digital light processing. The rheological and photopolymeric properties of the synthesized silica composite are investigated in detail. 3D objects are also successfully produced using the silica composite and digital light processing.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.21 no.8
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• pp.79-86
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• 2022

With the recent increase in the demand for electric vehicles, it is necessary to identify the high current safety of automobile parts. Among the automobile parts, the EPDM parts required colored parts from the existing black; therefore, it was necessary to change the basic filler from carbon black to silica. The rubber used in automobile parts is flexible and exhibits basic characteristics of high strength and elongation. However, as the filler is changed to silica, its physical properties, such as tensile strength and elongation, are lower than those of the existing carbon black base. Therefore, it is necessary to evaluate the mechanical properties with the addition of the EPDM compound using silica as a base without degrading the physical properties of EPDM. In this study, an experiment based on the additive content was performed using the mixture experimental planning method to analyze the mechanical properties according to the additive type and mixing ratio of silica-based EPDM. The mixing ratio of the four additives was set using a simplex lattice design, and the tensile strength, elongation, modulus 300%, and permanent compression reduction rate were analyzed for mechanical characteristics, and rheometer experiments were performed for vulcanization characteristics. Through statistical analysis of the measured data, the main effects and interactions of the EPDM-blended rubber additives were analyzed. These results can be used to derive a mixing ratio of additives that satisfies the required characteristics of the EPDM compound.

• Proceedings of the Korean Society of Rheology Conference
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• 2001.09a
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• pp.159.4-159
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• 2001

• Journal of the Microelectronics and Packaging Society
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• v.25 no.4
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• pp.143-148
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• 2018

Sodium silicate based silica aerogels are lower in cost than silica alkoxide based silica aerogels, but the demand is decreasing as their physical properties are lowered. In this research, acetonitrile as a drying control chemical additive (DCCA) is added in the sol state to improve the pore-structural properties of sodium silicate based silica aerogel by preventing the agglomeration of particles and cross-linked bond. The sodium silicate based silica aerogel by ambient pressure drying were prepared by sol-gel process. Acetonitrile/$Na_2SiO_3$ molar ratio of 0, 0.05, 0.1, 0.15, and 0.2 was added to the sol state. The physical properties of the final product were analyzed using Fourier transform infrared, contact angle measurement, Brunauer-Emmett-Teller and Barrett-Joyner-Halenda measurements and field emission scanning electron microscopy. It was confirmed that the sample with adding 0.15 molar ratio of acetonitrile and sodium silicate showed a high specific surface area ($577m^2/g$), a high pore volume (3.29 cc/g), and a high porosity (93%) comparable to the pore-structural properties of silica alkoxide based silica aerogels.

• Elastomers and Composites
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• v.56 no.2
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• pp.72-78
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• 2021

A phase-change material (PCM) is a material that has the ability to delay heat transfer by absorbing heat from its environment or releasing heat to its environment while its phase changes from solid to liquid or liquid to solid at a specific temperature. As it is applied, it can contribute to environmental conservation such as energy savings and carbon dioxide emission reduction. In order for a PCM to store and release heat, the volume change during its phase transition should be large, and thus a phase transition space is required. When a PCM is used as a polymer additive, it is confined within the polymer, and there is no phase transition space; thus, its ability to absorb and release heat is significantly reduced. Therefore, in this study, porous silica was used to provide EVA/PCM compounds with sufficient space for their phase transition, and to improve the compatibility between the EVA and PCM, modified silica is used: surface-modified 5 wt% silica with 3-methacryloxypropyltrimethoxysilane. The compound was prepared and compared with the silica compound. The presence or absence of the modified silica surface modification was confirmed using Fourier-transform infrared spectroscopy and thermogravimetric analysis, the heat capacity of the compound was evaluated based on a differential scanning calorimetry analysis, and its mechanical strength and morphology were determined using scanning electron microscopy.

• Advances in concrete construction
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• v.4 no.3
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• pp.195-206
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• 2016

Today, application of additives to replace cement in order to improve concrete mixes is widely promoted. Micro-silica is among the best pozzolanic additives which can desirably contribute to the concrete characteristics provided it is used properly. In this paper, the effects of AP2RC and P1RB micro-silica gels on strength characteristics of normal concrete are investigated. Obtained results indicated that the application of these additives not only provided proper workability during construction, but also led to increased tensile, compressive and flexural strength values for the concrete during early ages as well as ultimate ones with the resulting reduction in the porosity lowering permeability of the micro-silica concrete. Furthermore, evaluation of microbial contamination of the mentioned gels showed the resultant contamination level to be within the permitted range.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.6
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• pp.493-500
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• 2006

This paper concerns the measurement of thermal conductivity of grouting materials for ground loop heat exchanger. A thermal conductivity meter, QTM-500 based on modified transient hot wire method was used to measure the thermal conductivity of neat bentonite and mixtures of bentonite and various additives. Relative to the total mixture mass, as the percent additive was increased the mixture thermal conductivity increased. For the bentonite-silica sand mixtures, the higher density of the sand particles resulted in much higher mixture thermal conductivity. The quartzite and silica sands produced the largest increases in mixture thermal conductivity, while common masonry and limestone sands produced lower thermal conductivity increases.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2008.11a
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• pp.67-71
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• 2008

Blast Furnace slag a pigiron waste that is produced more than 800 thousand tons per year, and micronized double quenching blast furnace slag improves flexibility of concrete, and even shows improvement effect of long-term intensity. However, the concrete that used micronized double quenching blast furnace slag is restricted in its use because of many problems to assure early intensity. Even micronized blast furnace slag can assure its early intensity of concrete when maximizing, and is considered that can be applied in high strength of blast furnace slag as an alternation material for Silica-fume that depends on overall import. Hereby this paper is revised activity index and fluidity of mortar that used Nano Slag that is produced by rotten Nano crush equipment to propose its size, and possible utility of Nano Slag that was produced by blast furnace slag made in Korea as an alternation material, with the conclusion as following. 1. To measure micronized Nano slag, it is judged that it should be in progress with BET method that is based on micronized Silica-fume for concrete. 2. As a result, the test based on KS L ISO 679 is shown to satisfy the basic additive size of KS F 2563 and of KS F 2567, and to determine new combination of stipulations. 3. The strength development of Nano Slag was shown excellent in the daily initial installment of 1, 3, 7 days against the basic additive. This is judged that contains CaO controlling initial strength against Silica-fume, and contributes to higher fineness than the basic blast furnace slag 1 type.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.29 no.2
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• pp.54-60
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• 2019

Recently, various composite materials for additive manufacturing are interested to expand the application field of 3D printing. 3D printing technique was mainly developed using polymer, and ceramic materials for 3D printing are still in the early stage of research due to the requirement of high solid content and post treatment process. In this study, silica particles with various diameters were surface treated with silane coupling agent, and synthesized as silica composite with photopolymer to apply DLP 3D printing process. DLP is an additive manufacturing technology, which has high accuracy and applicability of various composite materials. The rheological behavior of silica composite was analyzed with various solid contents. After DLP 3D printing was performed using silica composites, the printing accuracy of the 3D printed specimen was less than about 3 % to compare with digital data and he bending strength was 34.3 MPa at the solid content of 80 wt%.

• Polymer(Korea)
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• v.34 no.5
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• pp.430-433
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• 2010

The gasket materials of for the lithium ion battery requires chemical resistance to electrolyte, electrical insulating, compression set, anti-contamination and low temperature property. To check the special characteristics of fillers which are applied to rubber for gasket, compound of EPDM, NBR and FKM (fluoro elastomer) were made by adjusting weights of carbon black and silica additive. Using these compounds, we had done tests of long-term stability against electrolyte, compression set and low-temperature property with considering operating condition of the lithium ion battery. From this test, we investigated the physical and chemical characteristics of rubber with using of carbon black and silica additive in each.