Advanced Materials Research Vols. 55-57

Abstract: This research fabricated ceramics with formula (1-x)PZT - xBLT, when x = 0, 0.03, 0.05, 0.07, 0.10, 0.15 and 0.20 by a solid-state reaction method and sintered at a temperature of 1150 oC for 4 h with a heating/cooling rate of 5 oCmin-1. Phase analysis using XRD indicated the existence of PZT-based solid solutions with corresponding lattice distortion. SEM micrographs of ceramic surfaces showed a typical grain structure for PZT-rich phase, while a plate-like structure in BLT-rich phase was observed. PZT-rich ceramics possessed relatively high densities due to their more equiaxed grains with high packing capability compared with the ceramics with an addition of BLT. An addition of BLT generally decreased grain size of the ceramics. Mechanical properties such as hardness and fracture toughness could be enhanced significantly with small addition of complex structure BLT.

Abstract: Lead zirconate titanate/tungsten oxide (PZT/WO3) ceramics were prepared from the powders synthesized by a modified triol sol-gel processing method. In this study, the starting materials used for synthesis of PZT-sol were zirconium (IV) propoxide, titanium (IV) isopropxide, lead (II) acetate trihydrate and 1,1,1,- tris (hydroxymethyl) ethane. To prepare PZT/xWO3 powders (where x = 0, 0.5, 1 and 3 wt%), nano-sized WO3 was ultrasonically dispersed and mixed with the PZT sol, dried and calcined at 600°C for 4 h. X-ray diffraction results indicated that fully crystallized powders were obtained. Phase characterization suggested that at high WO3 concentration, the reaction between PZT and WO3 occurred during the calcination process. To prepare PZT/xWO3 ceramics, the powders were pressed and sintered at 1100°C for 6 h. Phase characterization by XRD indicated that the content of WO3 significantly affected tetragonal-to-rhombohedral phase transition. Microstructure of thermally etched samples showed that increasing the content of WO3 decreased grain size of the ceramics.

Abstract: The influence of annealing temperature on the optical and electrical properties, nanostructure and surface morphology of ITO thin films prepared by ion-assisted electron beam evaporation on the glass substrates has been studied. The resistivity and transmittance spectra were measured by a four-point probe method and spectrophotometer, respectively. The nanostructure and surface morphology were examined by X-ray diffractometer and atomic force microscopy. The results show that the ITO thin films with a thickness of 200 nm is amorphous. The crystallite size and optical band gap of ITO thin films increased after annealing in vacuum at different temperatures from 200 to 350 oC. At 350 oC, high quality crystalline thin films with a crystallite size of about 30 nm were obtained. The average optical transmittance was 84% in the visible range (400-700 nm) and the resistivity of 1.34 × 10-4 W-cm was obtained at a temperature of 350 oC.

Abstract: The dielectric properties of the 0-3 lead zirconate titanate (PZT)-portland cement (PC) composite with carbon addition were investigated. Lead zirconate titanate (PZT), Portland cement (PC) composite and carbon powder were fabricated using 50% of PZT, and varying addition of carbon 1, 2 % by volume. The dielectric properties were measured under room temperature at different frequency from 1kHz-20kHz. Carbon addition was found to slightly increase the dielectric constant of PZT-PC composite at room temperature. The results also show that both the carbon powder addition and frequency affected the dielectric constant and dielectric loss tangent of 0-3 all PZT-PC composites.

Abstract: Lead zirconate titanate (PZT)-Portland cement (PC) composites were produced and successfully poled at different poling field and time. The effect of polarization on the microstructure and piezoelectric properties were then investigated. It was found that, at a fixed poling field up to 2 kV/mm, the piezoelectric coefficient (d33) was found to increase with poling time. The optimum poling time was found at 45 minutes where d33 value is 42 pC/N. The optimum and most practical poling field found for the composite was at 2 kV/mm. Lower poling field would give the composite lower piezoelectricity and poling field that is too high would result to breakdown of samples. Therefore, from these results, a poling field of 2 kV/mm at 45 minutes would be the ideal polarization condition used in poling PZT-PC composites.

Abstract: Monte Carlo simulation was used to observe the dynamic magnetic behavior of dilute Ising ultra-thin-film. The hysteresis properties were investigated as varying the non-magnetic concentration, field frequency and field amplitude where the Metropolis algorithm was used. From the results, at fixed temperature and field amplitude, the hysteresis loop increases in size with increasing frequency at low frequency region but reduces at high frequency region due to the increase of the phase-lag between magnetization and external field signals. With the inclusion of non-magnetic sites, the phase-lag shifts to higher frequency as a result of weaker magnetic interaction. In addition, the scaling relation among the hysteresis area, the field parameters and non-magnetic concentration was proposed to provide general information of how the dilution affects hysteresis properties of dilute magnetic in ultra-thin-film structure.

Abstract: Aramid/Al2O3/epoxy resin laminated composites were fabricated using ultrasonic mixing and casting technique. This novo material could be exhibited to the ideal mechanical properties such as high tensile strength, hardness, flexural strength and lightweight which may be used to replace metal parts in vehicles. Moreover, Al2O3 powder was mixed to epoxy resin to improve the scratch resistance. To improve the bending force and interaction between Al2O3 powder phase and epoxy resin phase, the ultrasonic mixing was used for fabricating these laminate composites. The physicals and mechanical properties such as density, hardness, impact test, wear resistance and tensile strength of the composites samples were investigated. It was found that the amounts of percent by volume of the Al2O3 have affected the properties of the laminated composites. Furthermore, microstructures of specimens were also investigated by scanning electron microscope (SEM). From the results, SEM images showed good distribution and adhesion between reinforced phase and epoxy resin matrix phase.

Abstract: Typical fabric sound absorbing materials have excellent absorbing property in high frequency, but in low frequency the absorbing performance is bad. In this study the flame retarded hollow 3D crimp PET fiber and low melting point PET fiber were used to manufacture sound absorption sandwich board (SASB). By changing the skin material of sandwich structure that the low frequency of sound absorbed will improve. The SASB was combined with two skin materials and one core material. The skin materials were manufactured into the nonwoven fabrics by needle punched and thermal compressing process. The skin materials have two different thickness (0.02 mm and 0.5mm).The core material was combined five layers of loose nonwoven fabrics and bonding by thermal compressing at the same gauge (15 mm). The sound absorbing properties of core material and sandwich board were analyzed. The sound absorbing property was evaluated using two microphone impedance tube according to ASTM E1050-98. When the skin material thickness is 0.02 mm, both of the high frequency and low frequency sound absorption was optimized. When the skin material thickness is 0.5mm, the sound absorbing property is similar to typical fabric material. The high frequency sound absorption is excellent, but the low frequency sound absorption is bad.

Abstract: The treatment for wound is a common issue in nursing procedure. Especially in serious wound, the treatment for wound usually spends many costs and time. Generally, wound dressing is used to protect the wound from bacterial infection in the intervening period between hospitalization and grafting. The pectin and chitosan are natural polymers that have biocompatibility and biodegradability, and pectin and chitosan can be easy obtainment and low cost. Tencel is a regenerated fiber. The Tencel fibers are biodegradable and hydrophilic, and have stable capability of dimension. Therefore, if the pectin and chitosan can be properly developed and combine with the tencel fabric for dressing use, the cost and time for wound treatment could be effective reduction. The absorbent cotton fibers were blended with the tencel fibers to create the cotton/Tencel nonwoven substance using nonwoven manufacturing technique. Chitosan will be electrospun on the Tencel nonwoven substance to create chitosan/Tencel composite nonwoven fabric. Furthermore, the surface structure of chitosan/Tencel composite nonwoven was observed by using scanning electron microscopy (SEM) to examine spinning ability of chitosan. Additionally, the pectin solution was blended with calcium chloride solution. Then pectin blended solution was coated on the optimal chitosan/Tencel composite nonwoven fabric by using mesh printing technique to prepare composite dressing. The result shown the Tencel/chitosan/pectin composite dressing has good capabilities of water absorbency and evaporative water loss. This study showed that a novel process for medical dressing was useful, and the composite dressing had an advantage property on wound healing and protection.

Abstract: Honeycomb structures are widely used in various engineering fields, including construction, the auto industry, packaging, the aerospace industry, medicine, and sports. The hexagon cells generate excellent structures and reduce material waste. Honeycomb structures have very good mechanical properties and are low cost. Nonwoven fabric is widely used in many applications because the manufacturing process for nonwoven fabric is easy and fast. In this study, Polylactic Acid (PLA) nonwoven fabric and Thermoplastic Polyurethane (TPU) honeycomb air cushion (TPU-HAC) materials were combined in a sandwich structure for impact protection. The PLA fibers and low-melting-point PLA fibers were used as raw materials to create PLA nonwoven fabric. The PLA fibers and low-melting-point PLA fibers were mixed at weight ratios of (10%, 20%, 30%, 40%, 50%). The mixed fibers were processed using needle punching and thermal bonding to create PLA nonwoven fabric. Additionally, the TPU-HACs were layered to generate various thicknesses (2/8/10 mm, 4/6/10 mm, 6/4/10 mm, 8/2/10 mm). The layered TPU-HAC materials was clamped between two PLA nonwoven fabrics to form a sandwich structure. Impact resistance was assessed using a falling- weight impact-resistance machine. Experimental findings indicate that impact resistance of the sandwich structure of the TPU-HAC materials improved when thin TPU-HAC material was placed on the thick TPU-HAC material. This study demonstrates that the sandwich structure of TPU-HAC materials as excellent impact absorption.