금속 알콕사이드를 원료로하여 분무 건조법에 의해 제조된 코오디어라이트 세라믹의 전기적 특성

박희찬,류봉기,류수착 釜山大學校生産技術硏究所 1995 生産技術硏究所論文集 Vol.49 No.-

코오디어라이트 세라믹 원료 분말이 금속 알콕사이드를 원료로 하여 제조되었다. 가수분해에 의해 제조된 졸을 분무 건조법과 오븐 건조기 건조법으로 건조하였으며 800℃에서 하소 처리한 후 1300℃에서 코오디어라이트 세라믹 소결체를 제조하였다. 분무 건조분말의 소결체의 유전상수 및 유전손실은 1㎒에서 1.1과 0.035의 값을 나타내었고, 건조기 건조분말의 소결체는 1.6 및 0.08의 값을 나타내었다. 분무건조 분말의 소결체의 겉보기 기공율 및 부피비중은 평균 1.3%와 2.448g/㎤ 이였고, 건조기 건조 분말의 소결체의 겉보기 기공율과 부피비중은 평균 3.2%와 2.185g/㎤이였다. Cordierite ceramic precursor powders were prepared from metal alkoxides. Hydrolyzed also were dried by spray dryer and oven dryer, and then they were calcined at 800℃. Calcined cordierite powders were sintered at 1300℃. In the codierite ceramics that were prepared from spray drying powders, dielectric constant and loss factor have 1.1 and 0.035 in 1MHz, respectively. In the codierite ceramics that were prepared from oven drying powders, dielectric constant and loss factor have 1.6 and 0.08 in 1MHz, respectively, Spray dried and sintered cordierite ceramics have apparent porosity of 1.3% and bulk density of 2.448g/㎤. Oven dried and sintered cordierite ceramics have apparent porosity of 3.2% and bulk density of 2.185g/㎤.

Influence of Pore on Dielectric Constant of Colrdierite Ceramics Prepared by Sol-Gel Process

Ryu, Su-Chak The Korean Ceramic Society 1998 The Korean journal of ceramics Vol.4 No.2

Cordierite ceramics with low dielectric constants were obtained through sol-gel techniques using as metal alkoxides. The powders for the sintered cordierite ceramics were prepared by hydrolysis of metal alkoxides with ethanol and distilled water. In the hydrolysis, the mole ratio of HCI/TEOS was controlled by changing the amount of HCI as a catalyst. The sol-gel derived powders were dried, pressed, and fired at $1300^{\circ}C$. The dried powders were calcined at $800{\circ}C$ for 3hours to remove residual organics. The fired bodies with different dielectric constants were obtained by using HCI adjusted to various mole ratios of HCI/TEOS in the process. The variation of the amount of HCI catalyst led to a significant influence on dielectric contant, which was attributed to the formation of pores in the sintered body. Especially, the porosity of the sintered body influenced the dielectric constants.

Development of low-cost non-powered prosthesis using multi-axis system of toe joint and ankle

Su Chak Ryu,JoonHyup Kim,Woo Sob Sim,Seung-Hyeon Kim 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.3

A prosthetic foot for a low-income class was developed. The prosthetic foot was produced through 3D printing, and a walking situation was produced and tested through a compression tester. After the heel strike, the elastic energy stored in the spring in the foot flat motion is released from the swing motion and is 661.89 N, and the muscle power exerted by the human body in the same motion is like 641.2 N. In addition, when heel off is operated, the foot is bent by 1 degree of freedom of the toe, and the angle of operation is stored as elastic energy in the torsion spring, and 880.68 N is emitted when toe off. In addition, the manufactured prosthetic foot showed similar gait response to that of the existing prosthetic foot through comparison according to the load for each gait stage. It has been shown that it works according to the walking mechanism to provide natural walking, and it can be manufactured as a low-cost elastic device.

Development of an elastic storage-release prosthetic foot that mimics the metatarsal bone head and midtarsal joint

Su Chak Ryu,JoonHyub Kim,Woo Sob Sim,김승현 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.4

This study aimed to develop prosthetic foot for the low-income class. Considering that the prosthetic foot was manufactured through 3D printing, we tested whether the material used can be used for such application. Through load-added simulation, a safety factor of at least 6 was measured. The results show that it can be introduced into the prosthetic foot. An ankle multi-axis rotation device, metatarsal head, and toe joint were introduced for comfortable walking of the patient. The muscle power required for walking was simulayed by conducting a load test of the corresponding motion. The prosthetic foot simulated a muscle power of 1263.56 N through the ankle device and 25.7 N·m through the toe joint. Therefore, the actual human body had a value exceeding the muscle power of 1058.90 N and 20.2 N·m, which would help the wearer’s walking.

Regeneration of a Micro-Scratched Tooth Enamel Layer by Nanoscale Hydroxyapatite Solution

Ryu, Su-Chak,Lim, Byoung-Ki,Sun, Fangfang,Koh, Kwang-Nak,Han, Dong-Wook,Lee, Jae-Beom Korean Chemical Society 2009 Bulletin of the Korean Chemical Society Vol.30 No.4

Hydroxyapatite (HAp)-based materials have attracted considerable attention on account of their excellent stability and recrystallization. Nanoscale HAp powders with a mean particle size of 200 nm were used to regenerate the enamel layers of damaged teeth. An artificially scratched tooth was immersed in a nanoscale HAp powder suspension in d.i. water (HAp of 70 wt%) at 37 ${^{\circ}C}$ for a period of 1~3 months. SEM and AFM showed that the scratched surface was ultimately inlaid with HAp after three months and the roughness increased from 2.80 to 5.51. Moreover, the hardness of the neo-generated HAp layer on the crown was similar to that of the innate layer. $Ca^{2+}$ and ${PO_4}^{3-}$ ions from the HAp powders dissolved in d.i. water were precipitated on the tooth to produce cemented pasteson the enamel surface due to its high recrystallizing characteristics, resulting in a hard neo-regenerated HAp layer on the enamel layer. This nanoscale HAp powder solution might be used to heal decayed teeth as well as to develop tooth whitening appliances.

유진놀을 이용한 수산화아파타이트 성형체에 관한 연구

류수착,Ryu, Su-Chak 한국재료학회 2004 한국재료학회지 Vol.14 No.6

The samples were prepared with hydroxyapatite(HAp) powder and eugenol (Eugenol/HAp = 15, 20, 25, 30wt%). The samples were dried at room temperature. The higher mechanical properties was observed in HAp sample with 25wt% Eugenol. The average compressive and bending strength in HAp with 25wt% Eugenol are 542 kgf/$\textrm{mm}^2$ and 366 kgf/$\textrm{mm}^2$ respectively. This strength is higher compare to that of the cortical bone.

수산화아파타이트(HAp)를 이용한 치아 수복제에 관한 연구

류수착,Ryu, Su-Chak 한국세라믹학회 2005 한국세라믹학회지 Vol.42 No.10

Hydroxyapatite powder was injected into the tooth after decayed tooth clinic. The microstructure of tooth was observed after a tooth extraction in the body. The hydroxyapatite powder was stiffened and the junction of hydroxyapatite powder and tooth was observed. The Ca/P atomic ratio of hydroxyapatite-tooth boundary was higher than hydroxyapatite matrix. And microhardness of hydroxyapatite matrix was 92.4 Hv. The junction of hydroxyapatite powder and tooth was due to the $Ca^{2+}$ ion shift of hydroxyapatite or the firm waxy body was due to setting of hydroxyapatite powder.

폴리카복실레이트를 이용한 수산화아파타이트 성형체에 관한 연구

류수착,Ryu, Su-Chak 한국재료학회 2005 한국재료학회지 Vol.15 No.10

The samples were prepared with hydroxyapatite(HAp) powder and Polycaboxylate (P.C/HAp=10, 15, 20, 25, 30, 35 $wt\%$). The hydroxyapatite green body with Polycaboxylate were obtained by compaction and drying at room temperature for 3hrs. The higher mechanical properties were observed in HAp sample with $35 wt\%$ Polycaboxylate. The average compressive ana bending strength in HAp with $35 wt\%$ Polycaboxylate are $302 kgf/cm^2$ and $213 kgf/cm^2$ respectively. This strength is higher compare to that of the cortical bone.

굴 껍질로부터 제조된 calcium phosphate 결정상에 관한 연구

류수착,Ryu, Su Chak 한국재료학회 2003 한국재료학회지 Vol.13 No.4

Calcium phosphate was prepared by chemical reaction formula using Oyster shells and $H_3$$PO_4$solutions. After added to 0.1 M∼0.9$ M H_3$$PO_4$ solution for oyster shell, prepared powders were investigated for heating properties and formation phase with heat treatment temperatures. As the results of XRD analysis of heated powders at $500^{\circ}C$∼$1200^{\circ}C$,$ CaCO_3$ phases were observed at the temperature of below 900 $^{\circ}C$ and in the condition of 0.1 M∼0.9 M $H_3$$PO_4$ solutions. However, $CaCO_3$, $CaPO_3$(OH) and $Ca_3$($PO_4$)$_2$ phases were appeared at the temperature range between $500∼900^{\circ}C$ and in the solution of 0.7 M to 0.9 M $H_3$$PO_4$. $Ca_{ 5}$($PO_4$)$_3$(OH) and CaO phases due to the decarbonation of oyster shells($CaCO_3$) were appeared at above $1000^{\circ}C$ and in the solution of below 0.5 M $H_3$X$PO_4$. However in the case of above 0.7 M $H_3$$H_4$ solutions, $Ca_{5}$ ($PO_4$)$_3$(OH) was decomposed into $Ca_3$($PO_4$)$_2$ at more higher 100$0^{\circ}C$. Thus $Ca_3$(X$Ca_4$)$_2$ phases were appeared at higher than 100$0^{\circ}C$.

습식법에 의한 Al₂O₃-TiO₂ 복합체의 합성 및 특성연구 I. Al₂O₃-TiO₂ 복합체의 기계적 특성(2)

류수착,Ryu, Su-Chak 한국세라믹학회 2002 한국세라믹학회지 Vol.39 No.2

습식법에 의하여 제조된 $Al_2O_3$-1∼11 wt% $TiO_2$계 복합체를 1350$^{\circ}C$, 1450$^{\circ}C$ 에서 2시간 열처리 한 후 이에 대한 기계적 물성변화 및 미세구조를 조사하였다. 그 결과, $TiO_2$ 첨가량이 3 wt%였을 때의 복합체가 bulk density도 높고 기공율도 낮은 치밀한 미세구조를 이루었으며 이 때 young's modulus는 35.5 GPa, 곡강도값은 68.7 MPa로서 다른 $TiO_2$ 첨가량에 비하여 우수한 물성을 나타내었다. $TiO_2$ 첨가량이 증가할 수록 많은 양의 aluminium titanate의 합성으로 인해 열팽창 계수는 낮은 값을 나타내었다. $Al_2O_3$ composites powders with 1∼11 wt% $TiO_2$ were prepared by wet method and sintered at 1350$^{\circ}C$, 1450$^{\circ}C$ for 2h. Mechanical properties and microstructural evolution were investigated in this study. $Al_2O_3$-3 wt% $TiO_2$ composite were high bulk density of 2.37 g/$cm^3$ and low apparent porosity of 6.3%. The composites containing of 3 wt% $TiO_2$ showed moderately high bending strength of 68.9 MPa and the young's modulus of 35.5 MPa. The composites with increasing $TiO_2$ contents exhibit reduced thermal expansion coefficient due to the formation of $Al_2TiO_5$ phase.