Gel Aluminous Grit로 제조한 정밀연삭용 Vitrified 숫돌에 관한 연구

최성민,박유근,이관주,정윤중 明知大學校 産業技術硏究所 1998 産業技術硏究所論文集 Vol.17 No.-

The ultra fine grained vitrified grinding wheel manufactured with the gel state Al₂(SO₄)₃·14-18H₂O. At this, the seeds were added to inhibit the participation of the Al₂O₃to the composition of bonds by the reaction between grit and bond. The grit structure was cellular, but the particles were ultrafine of sub-micron order. Among the various frit used as bonds, R₁series were the most appropriate at wetting and firing. The value of M.O.R was the highest, at the specimen of 70 w/o bond contents and the 50 w/o seed contents in grit. The similar tendencies were detected with the other bonds and firing conditions. The firing could be possible at the same conditions of the commonlyfired vitrified grinding wheel at 1300℃.

Cusil/SiC 접합의 계면 현상

오세철,윤호욱,최성민,정윤중 明知大學校 産業技術硏究所 1997 産業技術硏究所論文集 Vol.16 No.-

To detect the interfacial phenomena on Ceramic/metal. SiC and Cusil were joined in N₂ or Ar gas atmosphere at various reaction temperature and the cross section were observed. Ag, which was separated from Cusil infiltrated into SiC side and separated it to Si and C. As a matrix, Ag transfered free Si to Cusil side and helped to form (Cu, Si) eutectic phase in Cusil side. the (Cu, Si) eutectic phase was transfered and precipitated into CuxSiy silicide in SiC side. The remaining SiC, not separated, was growing by the process of Ostwald ripenning in Ag matrix. (Cu, Si) eutectic phase had a dendrite type crystal phase in Ag molten matrix at N₂ gas atmosphere. This phenomena were appeared explicitly with the increased reaction temperature from 850, 900 to 950℃. But at the Ar gas atmosphere, the shapes of (Cu, Si) eutectic phase were aggromerated, and the transfer phenomenon to ceramic side was less compare to N₂ gas atmosphere.

Study on CaO-SiO₂-Gypsum/Slag계의 관한 연구

이희수,박정현,정윤중 연세대학교 산업기술연구소 1979 논문집 Vol.11 No.1

At the CaO-SiO₂basic system, The slags that outputed from steel industry and phosphate by-products gypsum that produced from fertilizer industry were added with schematically according to the changes of gypsum/slag content ratio. With the fixed condition of hydration 180℃, 6h₁s., The physical properties, the composition system, the mineralogical compositions were compared and detected. In this research, the experimental results were as follows. The added slag was well hydrated and compressive strength was 21 ×10³psi when the slag was added 10%. The hydrogarnet and gehlenite, when the the slag was added, the hydroxyl ellestadite and anhydrite, when the gypsum was added, were the influence factor for the hydration.

Si₃N₄-SiC계 복합체의 기계적 성질

정은주,최성민,오세철,정윤중 明知大學校 産業技術硏究所 1995 産業技術硏究所論文集 Vol.14 No.-

Silicon nitride composites reinforced with 0∼40 vol% silicon carbide particle were prepared by hot pressing under 30 MPa for 60 min in flowing nitrogen atmosphere. The range of sintering temperature was between 1750 to 1850℃ The effects of silicon carbide particle dispersoids on fracture toughness and fIexural strength of silicon nitride based composites were investigated Fully densed silicon carbide reinforced silicon nitride composites were obtained up to 20 vol% particle at 1850℃. Flexural strengths were less than that of Si₃N₄ monolith, and showed a maximum value(911 MPa) at 20 vol%. Hardness increased with silicon carbide particle content up to 40 vol%, and showed a maximum value (18.9 GPa) at 40 vol%. Fracture toughness had the tendecy to increase with silicon carbide particle content up to 20 vol%, and showed a maximum value (6.9 MPam1/2) at 10 vol%. Fracture toughness was improved by crack branching crack deletion and crack bridging mechanism.

TiO₂-CaSO₄와 TiO₂-CaCO₃계의 고상반응기구 : TiO₂의 반응성 및 상형성 Reactivity of TiO₂and Phase Forming

김홍대,한인섭,유태석,정윤중 明知大學校 産業技術硏究所 1986 産業技術硏究所論文集 Vol.5 No.-

For to detect the mechanism of the product phase and the assignment of the two reactant on the solid state reaction of TiO₂ with the CaSO₄ and CaCO₃ respectively at the reaction temperature 900℃ - 1400℃, the refractive microscope, scanning electron microscope, and electron dispersive spectroscope analysis were examined. For the reaction of TiO₂ with CaSO₄ the product phase which earned is CaTiO₃perovskite and from the first, the intermediate product of TiO₂· CaO·SO₂ was formed. However, the main product phase is Ca₃Ti₂O7, which is coexisted in the product layer, at the reaction of TiO₂ with CaCO₃·TiO₂ was diffused into CaSO₄ and CaCO₃ reactant side is both two reaction. Specially, in the case of CaCO₃, the transfer of TiO₂ is rapid through the pore, which was formed with vaporization of CO₂ gas.

석회-석영계의 수열 반응속도

鄭允中 명지대학교 1983 明大論文集 Vol.14 No.-

석회와 석영계의 수열반응속도와 반응의 율속단계를 규명하기 위하여 CaO/SiO_2의 몰비를 0.8되게한 CaO-SiO_2계와 slag첨가량을 CaO/SiO_2와 동일한 양으로 취급한 CaO-SiO_2-slag계의 두계를 비교하였다. disc 3개를 중적시켜 80,152 및 181℃의 각 온도에서 2,6,10,14 및 24시간 반응시켜 미반응 CaO와 미반응 SiO_2로부터 반응율을 계산하고 반응의 율속단계를 규명하여 다음과 같은 결과를 얻었다. 1. 석회의 반응율은 석영에 비해 5배정도 크다. 2. 온도와 반응층의 깊이에 대한 의존성은 석영이 석회보다 현저하다. 3. CaO-SiO_2계는 반응온도 8℃와 152℃에서 반응시간 10시간을 기준하여 그 이후부터는 확산이 율속인 단계로 전환하지만, 181℃에서는 반응시작부터 확산이율속이다. 한편 CaO-SiO_2-slag계는 반응온도 80℃에서 반응시작부터 계면반응이 율속이나, 152℃와 181℃에서는 10시간을 기준하여 그 이후부터 확산이 율속인 단계로 전환한다. For the study of kinetics and the reaction controlled stages on the hydrothermal reaction between Lime and Silica, the two systems which is CaO-SiO_2 (mole ratio of CaO/SiO_2 is 0.8)and CaO-SiO_2-slag(same weight percentage of CaO/SiO_2 and slag are mixed) system were compared. At reaction temperature 80,152 and 181℃, the piled up discs were reacted for 2,6,10,14 and 24 hours respectively. After hydrothermal treatments, the free Lime and free silica were detected by quantitative anlaysis for the reaction conversion. The results are followed. 1) The reaction conversion of lime is large 5 times as silica. 2) Temperature and reacting depth dependence of silica is considerably large as lime. 3) The reaction controlled steps are changed from phase boundary to diffusion in the process of 10 hours at reaction temperature 80 and 152℃ for CaO-SiO_2 system and at 152 and 181℃ for CaO-SiO_2-slag system.

폐자원을 이용한 경량골재의 개발에 관한 연구

최성민,박유근,정윤중 明知大學校 産業技術硏究所 1998 産業技術硏究所論文集 Vol.17 No.-

The method of manufacture for the light-weight aggregate from waste resources is developed at this study. The physical properties such as specific gravity, water absorption and are measured in study. Waste resources seems problem as raw material to make the aggregate with other by certain mixture. The sintering temperature is about 1300℃ and the adequate heating time is about 20 minutes.

MgO, Al₂O₃doping에 의한 CaO-SiO₂계의 상변화 기구

정윤중 明知大學校 産業技術硏究所 1985 産業技術硏究所論文集 Vol.4 No.-

For to detect the mechanism of the reaction product phases and their formations according to the reactions temperature and reaction time variation on the system (CaO-10% Al₂O₃ - doped with χ% MgO) - SiO₂ (here χ varies with 3,5 and 10 by weight %), the x-ray diffraction, scanning electron microscope and polarizing microscope were analyzed. The main product phase were C₂S, CS and glass phase, and a little amount of C₃S and C₃S₂ phase were finded out when the doping contents of MgO were 3 and 5% respectively. These tendancy were increased with the reaction temperature at the same doping content. Especially, the CS phase was formed needle shape crystal, and precipitated MgO was formed inside the glass phase. However, when MgO was doped with 10%, MgO-Al₂O₃ spinel and anorthite crystal were formed inside the CAM and the product layer. In that condition, the product thichness of CS was reduced compared to 3 and 5% doped with MgO. But C₂s phase was increased with its elevated temperature.

CaO-SiO_2 반응의 속도와 기구

鄭允中 명지대학교 1985 明大論文集 Vol.16 No.-

CaO와 SiO_2의 몰비를 1로하고 여기에 광화제로 Li_2CO_3와 K_2CO_3를 각각 3%(무게비)씩 첨가시켜 생성물의 phase를 관찰하고 반응의 율속 단계를 규명하기 위해 β?? αCS전이 온도를 중심으로 반응온도와 반응 시간을 변화시켰다. 반응 속도는 주 생성물에 의해 지배되며 광화제를 첨가하지 않은 계에서는 1300℃이상, Li_2CO_3가 첨가된 계에서는 1200℃이상 그리고 K_2CO_3가 첨가된 계에서는 1100℃ 이상에서 반응 시간 30분을 전후하여 율속 변화된다. 이때 α-CS phase는 유리상과 혼존하며 α- CS phase가 주 결정상으로 반응을 율속하는 반응온도는 광하제를 첨가하지 않은 계, 광화제 Li_2CO_3 첨가계 및 K_2CO_3 첨가계의 순으로 낮아진다. The reaction temperature and processing time was varied above and below the transitoin temperature of β?? α-CS for to find out the product phase and for to detect the rate-controlled steps as compare the system of C/S=1 (mole ratio) to the system which was added with mineralizer Li_2CO_3 and K_2CO_3, respectively. The reaction rate is controlled by the main product phase. The rate-controlled steps are changed before and after processing time 30 min. at over 1300℃ as a system with no addition, 1200℃ as a system with Li_2CO_3 addition and 1100℃ as a system with K_2CO_3 addition. Almost of all α-CS is the main rate-controlled phase, the reaction temperature is decreased as an order of the system with no addition, Li_2CO_3 addition and K_2CO_3 addition.

BaO-Al₂O₃-SiO₂계 유리의 결정화

이희수,조동현,정윤중 연세대학교 산업기술연구소 1981 논문집 Vol.13 No.1

In the study of dielectric properties and structure for the BaO-Al₂O₃-SiO₂ system glass ceramics, the following results were obtained: 1. The parent glass batch for 36BaO-24TiO₂-36SiO₂-6Al₂O₃for mula melted when it at was heated at the 1520℃ for 2hrs. 2. The two crystals, Barium titanate and Barium celsian, existed together in the glass ceramics of this system. It was observed that the Barium titanate controls the crystallizatton. As the crystallinity of Barium tiatate was increased, the dieliectric constant was increased in the glass of this system. The variation of dielctric loss factor was slightly increased. 3. The conditions which have the large value of the crystallinity of Barium titanate and the uniform distribution of the crystal are the heating temperature of 650˚C and the soaking time of 3hrs for nucleation and 1150℃ and 5hrs for crystallization. The crystallinity was 35wt% and the dielectric constantwas 400.