In this work, an inductively-coupled rf plasma reactor was utilized in the nitriding process for surface hardness improvement of aluminium-copper alloy 2011. Substrate bias at 400V was used in the pre-sputtering step to eliminate the aluminium oxide on the samples. Plasma nitriding was carried out in a N2-H2 admixture at total pressure of 1 torr. The process length was varied from 9 to 36 hours while the input rf power and substrate temperature were varied from 100 to 300 W and kept at 400 oC, respectively. A negative bias voltage up to 400 V was used in the nitriding process. Glancing incident-angle x-ray diffraction (GIXRD) results showed the hexagonal crystal structure of AlN on samples. The roughness increased slightly when the voltage increase up to 400V and was investigated by Scanning Electron Micrograph (SEM). Electron Probe Microscopy Analysis (EPMA) and Energy Dispersive X-ray Analysis (EDX) were used to detect the N atoms in specimens. Significant increases of surface hardness are observed after plasma nitriding.

In this work, plasma nitriding of Al-6wt%Cu alloy was carried out using radio frequency inductively coupled plasma (rf-ICP). The nitrided sample was performed under various percentages of hydrogen gas mixture (25%H 2 +75%N 2 , 50%H 2 +50%N 2 , 75%H 2 +25%N 2 , and 100%N 2 ) with the input rf power of 200 W and working pressure of 0.5 torr. The plasma nitriding process time was set at 6 h. The substrate temperature was kept between 290 o C and 316 o C. The AlN hexagonal (wurtzite) crystal structures were identified by X-ray Diffraction (XRD). Electron probe micro analysis (EPMA) was carried out in order to determine the nitrogen profile. Nitrogen content in all samples was obtained in this experiment. However, only 25%H 2 with 75% nitrogen, 50%H 2 with 50%N 2 , and with 100% nitrogen was able to clearly indicate the crystal structure of AlN. The surface hardness was measured by using nanoindentation with a Berkovich indenter.

This study aims to isolate cellulose nanofibers from locally abundant pomelo fruit. Only the inner, soft peels were selected for investigation. The peels were subjected to alkali treatment (NaOH) with different concentrations and soaking times. Acid hydrolysis was also carried out to obtain an aqueous suspension of nanocellulose. The treated cellulose fibers were characterized by various methods. The effect of alkali treatment was initially confirmed by Fourier Transformed Infrared (FTIR) Spectra which displayed disappearance of several peaks belonging to non-cellulosic materials. The sharpening of the absorption at around 914 cm-1 is attributed the β-glycosidic linkages between the sugar units in cellulose. Alkali treatment also helped eliminate the non-cellulosic constituents via reduction in the 1240 and 1750 cm-1 peak. Thermogravimetric (TG) analysis revealed an improved onset of degradation likely caused by an increase in crystallinity evidenced by X-ray diffractometry (XRD) through the presence of two well-defined reflections characteristic of cellulose. The morphological and structural characterization by Scanning electron microscopy (SEM) still revealed a compact structure even after alkali treatment. However, acid hydrolysis was successful in individualizing cellulose nanofibers as observed by transmission electron microscopy (TEM). The diameter of these nanofibers was in the 10 - 20 nm range with various lengths.

In this work, systematic substitution of ZnO with SnO2 in ZnO-based varistor composition was investigated through analysis of densification, phase formation, microstructure and non-linear properties. The general formula was Zn0.96-xSnxBi0.02Co0.02Oβ with x = 0, 0.01, 0.02 and 0.04. The high rate of densification starting at 800°C is believed to be related to Bi2O3 via liquid-phase sintering. The complex nature of this multi-phasic varistor system was demonstrated through occurrence of different phases at different sintering temperatures. The low-temperature pyrochlore (Bi2Sn2O7) started to dissociate at approximately 1100°C with the spinel (Zn2SnO4) forming afterwards. The grain size variation with composition might be induced by the changes in the availability of Bi2O3 which has been reported to help facilitate abnormal grain growth. All samples sintered at 1200°C, with data extrapolation, possessed breakdown voltages of higher than 1400 V/cm.