Boonchoat Paosawatyanyong

Improvement of Hydrophobic Properties of the Electrospun PVA Fabrics by SF6 Plasma Treatment

Electrospun fabrics, prepared from 5, 7 and 10%w/v were Poly(vinyl alcohol) (PVA) solutions successfully prepared. The electrospinning condition was 15 kV, distance 15 cm, flow rate of 1 ml/hr and spinning time of 5 hours. Physical properties of electrospun PVA fabrics were analysed by SEM, FE-SEM and contact angle measurement.The contact angle of the electrospun PVA fabrics was 54.5°, characterizing the hydrophilicity of the fabrics. Hydrophobic properties of the electrospun PVA fabrics were improved by plasma treatment using radio frequency inductively coupled plasma (RF-ICP). RF-ICP plasma treatment of the electrospun PVA fabrics were carried out sulphurhexafluorene (SF6) gas with pressure of 0.5 Torr, RF power of 30W and treating time of 30, 60, 90 and 120 seconds. Effects of the PVA solution concentration and plasma treating time on hydrophobicity of the electrospun PVA fabrics were determined by contact angle that result of contact angle of treated fabrics increased when treated time increased and they decreased when concentration of fabrics increased.

Electrical Characteristics of DLC Deposited by RF Inductively Coupled Plasma Process

A Radio Frequency Inductively Couple Plasma Reactor (RFICP) was designed and set up for DLC deposition onto aluminum substrates using CH4-H2 admixture precursor gas. Plasma parameters of the discharge during the deposition process were measured using Langmuir probe technique. The structure and morphology of the DLC films were characterized by SEM and Raman spectroscopy. SEM images show granule morphology which yield smaller grain size with increasing of RF power. It was found that the structure and composition of DLC films are controlled by changes in the RF power. Raman spectrum of DLC films show two typpical modes of the graphite lattice labelled as ‘G’ and ‘D’ modes. The G peak position shift to higher wave number and the ratio of the peak intensity ID/IG increases with increasing RF power. DLC samples yield good ohmic characteristics with decreasing resistivity in films grown at higher RF power. Both electrical and structural characteristics indicated that the films contain more graphitic content of sp2 hybridization with increasing RF power in the plasma process.

DLC-Film Schottky Barrier Diodes

A microwave plasma reactor (MPR) is constructed as a facility for the plasma assisted chemical vapor deposition (PACVD) process. The reactor is a mode-adjustable resonance cavity of cylindrical shape. A 2.45 GHz microwave generator is used to ignite the plasma inside the lengthadjustable cavity. The diamond-like carbon (DLC) thin film depositions onto the silicon substrates are carried out using H2–CH4 discharge. The Schottky barrier diodes (SBD) are then formed on to the DLC films. The responses of DLC-SBD to DC and time varying signals have been studied as a function of frequency. The frequency dependent response results are compared to the computer models, which includes as input parameters the bulk series resistance, the capacitance associated with the bulk material between the space-charge layer and the ohmic contact, the space-charge layer capacitance, and the diode dynamic resistance.

Electrical Characterization of Diamond-Like Carbon Films Synthesized by Plasma Enhanced CVD Technique

Diamond-like carbon (DLC) films have been deposited on silicon substrates using microwave plasma enhanced chemical vapor deposition (PE-CVD) process of CH4 in H2 gas mixture. The well-faceted good quality DLC film with distinct diamond Raman spectroscopic characteristics are found at low CH4 concentration. Schottky barrier diode (SBD) structures are fabricated onto the grown DLC films using Ti/Au and Al as ohmic and rectifying contacts, respectively. The responses of DLC-SBD to DC and time varying signals have been studied. The frequency dependent response results are compared to models, which includes as input parameters the depletion and bulk regions resistances and capacitances trap effects, and SBD parameters of which extracted from the DC I-V characteristics. It is found that the frequency dependent properties of DLC-SBD can be associated with deep trap states inside the DLC material rather than with only the SBD geometrical structure.

More fun and curiosity with magnetic guns in the classroom

The magnetic gun was chosen as a hands-on activity for our high school students. When conducting this activity in the classroom, we found some interesting points were raised following difficulties encountered by the students. Some students proposed that during the collision, the magnet changed its pole then it pushed the last ball out of the apparatus, but some suggested that all the balls were attracted by magnetic forces, therefore the last ball could not shoot out. With a question to raise their curiosity, ‘How do magnetic guns work?’, our students explored notions of magnetic force, work, and conservation of energy and momentum through their own design of magnetic guns. This article describes a method for measuring the changes of kinetic energy and describes factors that students should consider for making magnetic guns more powerful and for having fun with the activity of building them.

Effect of Hydrogen in rf Plasma Nitriding on Al-6wt%Cu Alloy

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%H2+75%N2, 50%H2+50%N2, 75%H2+25%N2, and 100%N2) 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%H2 with 75% nitrogen, 50%H2 with 50%N2, 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.

Synthesis of Conducting Polymer Films by Plasma Polymerization Process

A microwave (MW) plasma reactor for the synthesis of polythiophene (PTh) thin films as well as in situ doping during polymerization process has been designed and assembled. Plasma polymerization parameters were studied. A good MW power was found to be in the range of 150-250W. PTh films were characterized by various spectrophotometric methods. IR analyses showed absorption frequencies of important functional groups. PTh films exhibited UV-Vis spectra indicative of increased conjugative systems as the MW power increased although at 300 and 380W partial fragmentation was evident. Surface analysis by SEM revealed a uniformly deposited film morphology. EDS results were also suggestive of partial fragmentation of the films at high MW powers. Preliminary conductive measurements revealed that the undoped films exhibit higher conductivity (3 to 9×10-5 s.cm-1) than PTh typically prepared from electrochemical methods.

Surface Hardening of Aluminium-Copper Alloy 2011 by RF Plasma Nitriding Process

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.

Etching Effect of SF6 Plasma on Cotton Fiber

The plasma treatment of cotton was performed by the inductively coupled 13.56 MHz RF plasma reactor. The samples were treated with sulfur hexafluoride (SF6) plasma under different power, pressure and exposure time conditions. The morphology change, the weight loss and the reduction in tensile strength of cotton fabrics were strongly related to the etching effect of the SF6 plasma. The exposure time plays an important role in the change of mechanical strength of the fabric while the operating pressure imparts less prominent effects. Prolonged plasma process beyond 5 min or at high plasma operating pressure above 0.5 torr revealed significant damage to the cotton fiber. However, dramatic surface morphology change was not observed on cotton fiber having less than 2% weight loss after plasma treatment.

College Students’ Intuitive Understanding and Problem‐Solving of Energy and Momentum

This study addresses students’ intuitive understanding of energy and momentum and their problem solving ability. The subjects of this research were students who had experiences with conservation of energy and momentum. Nine undergraduate students completed event‐based Interviews with three related events which composed of Event I: Simple collisions, Event II: Newton’s cradle and Event III: Gauss gun. Their intuitive understanding was explored through three well‐defined items involving Event I and II. The interviews revealed that most students explained the two events by utilizing their intuitive understanding rather than scientific conceptions. Then problem‐solving thinking was identified through ill‐defined problems involving Event III. From the Gauss gun setting, students were asked to explain how Gauss gun works, how to build the highest power Gauss gun and interpret the graph of mass and distance of steel ball after collisions. Research findings showed that students who have fairly good command of bas...