Papers by Author: F.Y.C. Boey

Abstract: Boron carbide is one of the hardest materials known. The research on the synthesis of nano-sized boron carbide is of great importance. RF plasma synthesis of B4C nanoparticle was carried out by powder feeder using micro-sized commercial boron carbide powder as the stating material. Different plasma energy and powder feeder probe position was used to find out the optimum condition to achieve nanoparticles. Powders were collected from Chamber 1, 2 and 3. fine particles can be achieved, but the decomposition and oxidation of B4C powder during the high temperature plasma spray was detected. Boron oxide was found in the sprayed powder, and the powder was purified by washing and heat treatment. XRD, SEM and TEM was used to for characterization of the particles.

Abstract: A piezoelectric microactuator for minimally invasive surgery procedures was developed using the piezoelectric tube actuator. The tube was fabricated by electrophoretic deposition of a doped PZT powders on the graphite rod substrate and co-sintering. The obtained tube shows maximum strain 0.045% in 31 mode and coercive field 1.5 kV/mm under static condition. Under dynamic condition, bending and longitudinal vibration modes can be identified from impedance spectrum and simulation. Theoretical analysis indicates that the displacement of the two modes depends on the geometry, material property, driving condition and damping conditions. The developed device uses bending mode to create rotation mechanical motion, and longitudinal mode to produce ultrasonic energy to soften and break up the target into fragments.

Abstract: In the present work, the FGM monomorph actuator was developed and applied in the impedance pump. The actuator was fabricated using electrophoretic deposition (EPD). Two starting materials, pure PZT and doped PZT, were mixed to form four different compositions. The actuator was then fabricated by sequential deposition of the four compositions layer by layer on the substrate and followed by sintering to full density. The actuator shows both piezoelectric property and microstructural gradient across the layers. The actuator is able to achieve a bending displacement of nearly 2 mm at resonant frequency. It has been successfully applied to the impedance pump as the actuating component. The pumping action comes from the periodic compression by the actuator to induce a net flow. Maximum flow was observed at the resonant frequency of the actuator. A flow rate of about 9 ml/min was generated.

Abstract: Rotary and linear ultrasonic motors were developed in the present paper using metal-PZT composite piezoelectric stator transducer configuration. The transducer consists of a concentric PZT tube and a metal tube, which structurally improve the reliability of the stator transducer. The developed transducer can provide a free vibration velocity of 0.9 m/s under 100 Vp-p at the resonant state. The rotary motor and linear motor use the developed transducer as the driving component, which produces the rotational motion to drive the motor. The rotary motor is able to achieve about 700 rpm no-load speed, above 2 mNm torque, maximum 70 mW output power and 50% efficiency under driving voltage of 80 Vp-p. The linear motor produces rotational motion and linear motion simultaneously. The linear speed of 5 mm/s can be achieved under the driving voltage of 50 Vp-p under no-load state. Under the loaded state, maximum 8 N load has been observed to be moved by the motor at a speed of 0.6 m/s. The maximum output power and efficiency of the linear motor are 9 mW and 11%, respectively.