• Journal of the Korean Ceramic Society
• /
• v.32 no.10
• /
• pp.1194-1202
• /
• 1995

The influences of TiC additions to the α-SiC on microstructural, mechanical, and electrical properties were investigated. Electrical discharge machinability of SiC-TiC composites was also studied. Samples were prepared by adding 30, 45, 60 wt.% TiC particles as a second phase to a SiC matrix. Sintering of SiC-TiC composites was done by hot pressing under a vacuum atmospehre from 1000 to 2000℃ with a pressure of 32 MPa and held for 90 minutes at 2000℃. Samples obtained by hot pressing were fully dense with the relative densities over 99% except 60wt.% TiC samples. Flexural strength and fracture toughness of the samples were increased with the TiC content. In case of SiC samples containing 45 wt.% TiC, the fracture toughness showed 90% increase compared to that of monolithic SiC sample. The crack propagation and crack deflection were observed with a SEM for etched samples after Vicker's indentation. The electrical resistivities of SiC-TiC composites were measured utilizing the four-point probe. The electrical dischage machining of composites was also conducted to evaluate the machinability.

• Journal of the Korean Ceramic Society
• /
• v.45 no.9
• /
• pp.544-548
• /
• 2008

The formation of $TiB_2-SiC$ ceramics from $TiB_2$-Polycarbosilane (PCS) mixtures was investigated. The powder mixture of $TiB_2$ with PCS was pressed at $300^{\circ}C$ with 200 MPa and sintered at $1700{\sim}2000^{\circ}C$ for 1 h in a flowing Ar atmosphere. The sintered density of $TiB_2$ with PCS is 93.7% after sintering at $2000^{\circ}C$ for 1 h, which is slightly smaller than that of the specimen without PCS. The microstructure of $TiB_2$ with PCS consists of small and uniform $TiB_2$ particles with well dispersed SiC particles derived from PCS. It is believed that the addition of PCS was effective to suppress the grain growth of $TiB_2$.

• Journal of the Korean Ceramic Society
• /
• v.37 no.12
• /
• pp.1165-1171
• /
• 2000

Ti-C-Ni 혼합분말을 이용하여 SHS 공정에 의해 TiC-Ni 복합체를 제조하였으며, 리칭(leaching) 공정을 통하여 Ni을 제거함으로써 TiC 분말을 얻었다. TiC 분말의 특성분석을 위하여 XRD, SEM, TEM, AES 등을 사용하였다. 리칭 공정에 의해 얻어진 TiC 분말은 구형을 유지하고 있으며, 평균 입자크기는 0.4$\mu\textrm{m}$였다. 구형 TiC 분말을 다시 Ni 분말과 혼합하여 소결한 후 특성을 분석하였다. 140$0^{\circ}C$에서 소결하였을 때 TiC 입자는 구형에서 각진 형태로 변화하였다. 기계적 특성결과 상용 TiC 분말을 사용하였을 때보다 SHS 공정에 의해 제조된 TiC 분말을 사용하여 소결하였을 경우 파괴 인성값이 약 20% 증가하였다.

• Proceedings of the KIEE Conference
• /
• 2006.07b
• /
• pp.1027-1028
• /
• 2006

In this paper, design of current and speed controller for DC motor drive system using Embedded Target for TI C2000DSP in Matlab/Simulink is introduced. Current and speed controller is designed and implemented using program simply and easily, and speed control response of DC motor can be advanced. Current and speed control of DC motor is carried in eZdsp F2812 control board using Embeded Target for TI C2000DSP in Matlab/Simulink. Speed feedback is processed through A/D converter using tacho generator as speed sensor, and current feedback is processed through A/D converter using hall sensor as current sensor. Controller is designed to PI current controller and PI speed controller. Current and speed response is verified through simulations and experiments.

• Proceedings of the Korean Institute of Surface Engineering Conference
• /
• 2000.05a
• /
• pp.11-12
• /
• 2000

• Proceedings of the Korean Powder Metallurgy Institute Conference
• /
• 2000.04a
• /
• pp.12-12
• /
• 2000

• Proceedings of the KIPE Conference
• /
• 2007.07a
• /
• pp.400-402
• /
• 2007

This paper presents a vector control implementation for PMSM using Real Time Workshop and Embedded Target for TI C2000 DSP in MATLAB/SIMULINK. Speed, current and vector controllers are easily designed and implemented by using the MATLAB/SIMULINK program. Feedback of motor speed is processed through C28x QEP(Quadrature Encoder Pulse) block from encoder pulse. 3-Phase currents ares processed through C28x ADC block from current sensors. And gating signal of PWM inverter is generated through SVPWM and PWM block. Real-time program is drawn using SIMULINK and then converted program code for speed control of PMSM is downloaded into the TI eZdsp 2812 board. Experiments were carried out to examine validity of the proposed vector control implementation.

• Korean Journal of Materials Research
• /
• v.2 no.3
• /
• pp.207-212
• /
• 1992

The defect structure of calcium titanates with CaO excess or $TiO_2$ excess was studied by measuring electrical conductivities as a funcition of oxygen partial pressure at $85O^{\circ}C$ to $1050^{\circ}C$. Execess CaO may divide itself equally between A and B sites, resulting in $Ca_{Ti}$" and Vo", while excess $TiO_2$ form $V_{Ca}$" and Vo". The equilibrium electrical conductivity data indicate that the solubilities of CaO and $TiO_2$ in $CaTiO_3$ are 5000ppm and 2000ppm, respectively. Oxygen vacancies contributed to the ionic conduction which flatten the conductivity minima and did not make any defect association with oppositely charged defects.ely charged defects.

• Proceedings of the Korean Ceranic Society Conference
• /
• 2000.04a
• /
• pp.70.1-70.1
• /
• 2000

• Journal of the Korean Ceramic Society
• /
• v.37 no.11
• /
• pp.1114-1118
• /
• 2000

Ti 및 C 입자로 이루어진 다공질 성형체에 용융 Si의 침윤 및 반응으로 새로운 Ti$_3$SiC$_2$합성공정이 개발되었다. 용융 Si 침윤에 의한 Ti$_3$SiC$_2$합성공정에서는 이제까지 연구된 합성방법 보다 넓은 조성 범위에서 Ti$_3$SiC$_2$의 합성이 이루어졌다. 용융 Si을 활성 매질로 사용한 Ti$_3$SiC$_2$의 합성에서는 성형체 조성, 원료 입자 크기 및 침윤되는 용융 Si의 양에 따라 합성되는 상 및 각 합성상의 양이 다르게 나타났다. Ti:Si:C=3:1:6 조성을 제외한 모든 조성의 시편에서 Ti$_3$SiC$_2$상이 합성되었으며, 일부 조성을 제외한 모든 조성의 시편에서 Ti$_3$SiC$_2$, TiC 및 SiC가 함께 합성되었다. 작은 Ti 입자로 이루어진 성형체를 사용하여 합성한 시편에서 Ti$_3$SiC$_2$상의 합성이 용이하게 이루어졌으며, 성형체 조성 및 침윤되는 Si의 양이 화학양론적으로 Ti$_3$SiC$_2$에 근접한 조성을 갖는 시편에서 Ti$_3$SiC$_2$를 높은 수율로 합성할 수 있었다.