Watcharee Rattanasakulthong

Magnetic properties of NdFeB-coated rubberwood composites

Magnetic properties of composites prepared by coating lacquer containing neodymium iron boron (Nd-Fe-B) powders on rubberwood were characterized by vibrating sample magnetometry (VSM), magnetic moment measurements, and attraction tests with an iron-core solenoid. The Nd-Fe-B powders were recycled from electronic wastes by the ball-milling technique. Varying the milling time from 20 to 300 min, the magnetic squareness and the coercive field of the Nd-Fe-B powders were at the minimum when the powders were milled for 130 min. It followed that the coercive field of the magnetic wood composites was increased with the milling time increasing from 130 to 300 min. For the magnetic wood composites using Nd-Fe-B obtained from the same milling time, the magnetic squareness and the coercive field were rather insensitive to the variation of Nd-Fe-B concentration in coating lacquer from 0.43 to 1.00 g/cm3. By contrast, the magnetization and magnetic moment were increased with the Nd-Fe-B concentration increasing. Furthermore, the electrical current in the solenoid required for the attraction of the magnetic wood composites was exponentially reduced with the increase in the amount of Nd-Fe-B used in the coating.

Dependence of Hysteresis Loops on Thickness of Thin Nickel Films Prepared by RF Sputtering

Nickel films of varying thicknesses between 70 and 300 nm were deposited on glass substrates by RF sputtering and their broad (111) FCC peaks were identified by X-ray diffraction. The surface roughness and sub-micron grains were revealed by scanning electron microscopy. According to vibrating sample magnetometry, the films showed hysteresis loops with comparable coercive field and saturation field for the in-plane and perpendicular magnetizations. The increase in thickness substantially increased the magnetization and the squareness of the Ni films. The thickness can be classified into 2 regimes by the variation of squareness. The films are thinner than 200 nm showed the in-plane anisotropy whereas the perpendicular anisotropy was developed in the case of the thickness above 200 nm.

Characterization of Cobalt Films on X-Ray Lithographic Micropillars

Arrays of SU-8 photoresist pillars (10 μm ×10 μm × 50 μm) on copper substrates were fabricated by X-ray lithography. The photoresist-coated substrates were irradiated by X-ray from a synchrotron source through patterned silver dots on a graphite mask. After the resist development, the chemically stable and mechanically hardened SU-8 pillars exhibited smooth vertical sidewalls and cross section with up to 10 % dimensional errors from the designated pattern. Cobalt of thickness ranging from 50 to 80 nm was then deposited on these patterned substrates by RF sputtering. These cobalt films on SU-8 pillars showed a lower in-plane magnetization than that of continuous cobalt films because of their smaller grain size. The measurement with out-of-plane magnetic field gave rise to a higher magnetization and this anisotropic behavior was observed only in cobalt-coated pillars.

Effect of Dealloying Conditions on Nanoporous Surface of Cu-Zn Alloy

This research aims to develop a porous layer surface using two steps: the radio frequency (R.F.) sputtering and dealloying. The glass substrate was firstly coated with Cu-Zn using the R.F. sputtering method. Then nano-porous layer surface is produced by dealloying-corrosion to dissolve unwanted element (Zn) from the base metal (Cu). The characterization techniques are scanning electron microscope (FE-SEM) for topographical analysis, X-ray fluorescent (XRF) for chemical analysis, and potentiostat for electrochemical measurement. It was found that the coated specimens obtained by R.F. sputtering are uniformly distributed by Cu-Zn alloys on the substrate’s surface. In addition, after dealloying, it was found that the diameter of the ligament size and pore size are in the nano-scale over the substrate’s surface.

Raman spectrometry of carbon nanotubes using an Al-catalyst supported layer on nickel film deposited on silicon substrate

Carbon nanotubes (CNTs) were grown on Ni catalyst with Al catalyst supported layer prepared on silicon substrate at different temperatures by TCVD. TEM images clearly showed the multi-wall structure of carbon nanotubes (MWCNTs) and SEM images revealed that the average diameters of MWCNTs were 116, 121, 142 and 162 nm for the growing temperatures of 600, 700, 800 and 900°C, respectively. The increase of tube diameter was due to the difference of Ni particle size and distribution after pretreatment. Raman spectrum revealed the two peaks of the D and G band at 1282- 1290 and 1588-1598 cm-1, respectively. The tubes grown at 800°C showed a shoulder peak of G band at 1598 cm-1. The minimum of defect induced disorder (ID/IG) of 1.19 was found at 800°C whereas the maximum disorder of 1.70 was observed at 600°C. All results confirm that the tube growth at 800°C shows the minimum imperfective disorder and the tube diameter can be manipulated by the Ni particle size and distribution.

Effect of Sputtering Power on Morphological, Structural and Optical Properties of Al-Doped Zinc Oxide Film

Transparent conductive Al-doped zinc oxide (ZnO:Al) films with different sputtering power were prepared on glass substrate using an RF sputtering technique. Two main peaks of the hexagonal wurtzite structure in the (002) and (004) direction were observed in every deposited ZnO:Al film. Intensities of these peaks were increased with the increasing sputtering power. Moreover, the surface roughness tended to increase with increasing sputtering power whereas the electrical resistance decreased with increasing sputtering power. The ZnO:Al film deposited at 150 and 200 W showed maximum optical transmittance of over 80% in the visible wavelength range. All results confirmed that the sputtering power directly affected film thickness because the higher sputtering power gave rise to a higher deposition rate; the surface morphology of the deposited films was dependent on the sputtering power and the optical properties were indirectly affected by the power of the deposition process.

Morphological and Magnetic Properties of Co100-xCux Film Prepared by RF-Sputtering

Granular Co100-xCux films with different compositions of x = 19, 40, 54, 65 and 76 were deposited on glass substrates using sputter deposition. Co (HCP) and Cu (FCC) phases were observed in all deposited Co-Cu films. Film thickness was increased with increasing Cu-composition. The minimum and maximum values of electrical resistance measured using a four-point probe were observed on the Co24Cu76 and Co46Cu54 films, respectively, which confirmed that the electrical property of the films is a function of the film thickness and composition. The morphological and magnetic properties of all deposited films were clearly dependent on film composition. The AFM result confirmed the dependence of surface morphology and magnetic properties on the film composition because of the difference in the deposition rate between Co and Cu atoms during the sputtering process. The VSM results showed that all films had a ferromagnetic phase when the magnetic field was applied perpendicular to the film plane. All results confirmed that the desired morphological, electrical and magnetic properties of Co-Cu granular film can be achieved by manipulating its chemical composition.

Effects of Under-layers on Surface Morphology of Sputtered Co Film

The structure, electrical resistance and surface morphology of 85 nm Co films sputtered on Cr, Co, Cu Ag and Al under-layers were studied. The average thickness and electrical resistance of the Co films were significantly altered, depending on the under-layer thickness and material. The Co film on various under-layers consisted of a Co (HCP) phase in the (101) direction. The surface morphology of the Co film was strongly dependent on the surface roughness and morphology of the under-layers. The Co film showed a maximum surface roughness of 1.69 nm and a minimum roughness of 0.720 nm over a scan area of 1 μm2 on the Ag and Cr under-layers, respectively. The grain size and distribution of the Co films were affected by the grain size and distribution of the under-layer film. The average grain size of the Co films ranged from 13.3 nm on a Co under-layer to 26.2 nm on a Cu under-layer. AFM results indicated that a small grain size on the surface area of the under-layer film gave rise to a bigger grain size of the Co film, whereas a big grain size of the under-layer film produced a smaller grain size of the Co film. The under-layer thickness and material had a secondary effect on the surface morphology of Co films, because both the thickness and material were surface morphology dependent. All results confirmed that the morphology of an under-layer film plays an important role in the surface roughness of a Co film. It can be concluded that the surface roughness and morphology of a Co film can be modified by the under-layer roughness and material.