Dheerawan Boonyawan

A heavy ion implanting facility at the Chiang Mai University

Abstract Nitrogen ion implantation is widely used to improve the wear and corrosion resistance of metals and alloys. Different kinds of ions, including metal and heavier ions can be used for this purpose. The proposed ion implanter as a 0°- and a 45°-beam line. The 0°-beam line has been installed and tested by using an RF source with an ion energy of about 140 keV. The nitrogen beam current is about 200 μA at the target position. The beam can be magnetically swept to cover a 10 cm × 10 cm target area. Preliminary tests with an ion dose of about 10 17 ions/cm 2 improved the hardness of stainless steel and aluminium samples. The 45°-beam line and the analyzing magnet are under construction. When this will be completed, the present RF ion source will be replaced by a Danfysik 910 ion source which can be used for producing metal and heavier ions.

The Healing Effect of Low-Temperature Atmospheric-Pressure Plasma in Pressure Ulcer A Randomized Controlled Trial

Pressure ulcers are difficult to treat. Recent reports of low-temperature atmospheric-pressure plasma (LTAPP) indicated its safe and effectiveness in chronic wound care management. It has been shown both in vitro and vivo studies that LTAPP not only helps facilitate wound healing but also has antimicrobial efficacy due to its composition of ion and electron, free radicals, and ultraviolet ray. We studied the beneficial effect of LTAPP specifically on pressure ulcers. In a prospective randomized study, 50 patients with pressure ulcers were divided into 2 groups: Control group received standard wound care and the study group was treated with LTAPP once every week for 8 consecutive weeks in addition to standard wound care. We found that the group treated with LTAPP had significantly better PUSH (Pressure Ulcer Scale for Healing) scores and exudate amount after 1 week of treatment. There was also a reduction in bacterial load after 1 treatment regardless of the species of bacteria identified.

Epoxy resin surface functionalization using atmospheric pressure plasma jet treatment

Atmospheric pressure plasma jet (APPJ) of N2 has been applied to promote adhesion between the epoxy resin post and composite core material due to the chemical active functional groups created. The APPJ was proved to be able to improve adhesive ability of the epoxy resin through the polar groups such as carbonyl group on its surface revealed by decreasing contact angle. The jet was generated from N2/Ar and N2/He gas mixture with ratio as low as 0.40–0.44 vol %, respectively. The optical emission spectrometry showed that the active species which could react with the substrate surface are nitrogen molecules and nitrogen molecules ion. The radial distribution functions (RDFs) calculations indicated that the most probable position of nitrogen active species reacting on the epoxy surface is at hydroxyl group with hydrogen bonding distance less than 35 nm.

Diamond-Like Carbon Formed by Plasma Immersion Ion Implantation and Deposition Technique on 304 Stainless Steel

Diamond-like carbon (DLC) films were deposited on stainless steel disc substrates by plasma immersion ion implantation and deposition (PIII&D) technique. Ar, CH4 and C2H2 gas were used as the working gases and discharged by radio frequency at 13.56 MHz. During the implantation and deposition process the plasma discharge was monitored by optical emission spectroscopy in order to analyze the state of the chemical species presented in the plasma. Ion implantation (Vbias = -20 kV and –10 kV) process served to produce a graded interface between the DLC films and the substrate material. Deposition (Vbias = -5 kV) process using a gas mixture of C2H2/Ar with a ratio of 1:1. The structure information of the DLC films was evaluated by Raman spectroscopy and Fourier transform infrared spectroscopy (FTIR). The composition of the DLC films and the thickness was measured by Rutherford backscattering spectrometry (RBS). The tribological properties were analyzed using a pin-on-disk tribometer and a microhardness tester, respectively. It was found that the DLC film was 0.8 μm thick with a hardness of 2.54 GPa and had good friction properties. Raman spectra appeared as G-band and D-band centered at 1550 cm-1 and 1418 cm-1, respectively. FTIR analysis observed the sp3 C=H2 asymmetric and sp2 C=C bond at 2928.73 cm-1 and 1667.10 cm-1 peak.

Ion beam modification of materials program at Chiang Mai University

Chiang Mai University has been equipped with a 150 kV heavy ion implantation facility consisting of both non-analyzed and analyzed implanters. With this facility, a program of nitrogen ion implantation in commercial steels for surface modification is carried out. Here 90 keV 28 N + 2 ions are selectively implanted into samples of 304 stainless steel, 316 stainless steel and white steel (soft/low carbon) to fluences of 4 × 10 17 cm −2 . Some of the implanted samples are annealed at 220°C in air. Tests for hardness, wear resistance and corrosion resistance of the implanted steels are performed to determine improvements in the mechanical and chemical properties. The experimental results are reported and further discussed.

Cold Atmospheric Plasma Sources—An Upcoming Innovation in Plasma Medicine

In terms of physics and chemistry, plasma is a completely or partially ionized gas with ions, electrons, and uncharged particles such as atoms, molecules, and radicals, regarded as the fourth state of matter.

Optimization of Diamond-Like Carbon Thin Film on Copper Substrate for Carbon Nanotubes Synthesis by ACVD Technique

In this research, demonstrate plasma treatment on copper substrate by Radio Frequency Plasma (RF) using a mixture of 70%C2H2 + 30%H2 as the working gases. The plasma exposure time were varied from 10, 20 and 30 min under the electrical power of 50 Watts for synthesizing the diamond-like carbon (DLC) thin film on copper substrate. Thereafter, the substrates were used for synthesizing the carbon nanotubes (CNTs) via alcohol chemical vapor deposition technique (ACVD). It could be found that the plasma treatment for 10 min exhibited the small contact angle less than those of substrates treated with 20, 30 min and untreated sample which relate to the hydrophilic and affect to improve the adhesion and distribution of catalyst on substrate. The roughness of DLC film showed the different high and low level like hillock. After that, the 10 min treatment time sample was used for synthesizing the CNTs and the results found that the obtained CNTs showed good distribution on substrate.

Effect of cold argon plasma on eggs of the blow fly, Lucilia cuprina (Diptera: Calliphoridae)

Non-thermal plasma has been used in many medical applications, including treatment of living cells, blood coagulation, wound healing, and sterilization. The process uses an environmentally friendly gas (e.g., argon, helium, oxygen, nitrogen, or hydrogen) to destroy bacteria cells with no serious adverse effect on humans or animals. However, information on the effect of argon plasma on blow fly eggs is lacking. In this study, we explored the ability of cold argon plasma to destroy the eggs of the Australian sheep blow fly, Lucilia cuprina (Wiedemann, 1830); its larvae are a myiasis-producing agent in both human and animals. We tested the effect of cold argon plasma exposure for 1, 2, 3 and 5min on L. cuprina eggs. Since the temperature of cold Ar plasma is around 30°C, to clarify the effect of temperature on the fly eggs, hot air from an electric dryer was tested for comparison. Cold argon plasma exposure in eggs significantly reduced the survival rates of second instar larvae at all exposures tested; the effects were time dependent, with a stronger effect at longer exposure (32% survival rate after a 1-min treatment; 20%, 2min; 20%, 3min; and 6%, 5min), compared to the control (86%). No significant differences were observed in larval survival rates from eggs treated with hot air (80-84%, after 1- to 5-min treatments) versus the control (86%). These results were supported by observing the treated eggshells under a scanning electron microscope (SEM), we found noticeable aberrations only in the plasma treated groups. The emission spectrum of the argon gas discharge revealed emission lines of hydroxyl radicals at 309.1nm; these may cause the deterioration of the treated L. cuprina eggs. Our results have shown the possibility of using cold argon plasma in medical applications, in particular treating myiasis wounds.

Mechanical Properties Study of Plasma Treated Epoxy-Base Post in Dual-Material Systems

Improvement of adhesion between epoxy based post and composite resin core materials by low temperature plasma is an on-going dental material development. To systematically investigate the effects of surface change on the material’s chemical and mechanical properties, three series of two component materials, epoxy/urethane dimethacrylate (UDMA), epoxy/polyethylene (PE), and epoxy/poly(methylmethacrylate) (PMMA), were compared with dental epoxy based post/composite resin core. Each dual-materials system was modeled at an atomistic level. A molecular dynamics (MD) method with COMPASS force field was employed to simulate the most probable functionalization and the materials physical properties changes. Material surface modification was modeled and optimized using quantum calculations based on experimental characterization. To validate calculation results, the effect of plasma treatment on the mechanical properties of the dental post materials were examined by tensile pull out test.

Immobilization of Silk Fibroin as Scaffold for Cell Culture by Plasma Grafting Polymerization

According to the low efficiency of cell attachment and proliferation on commercial polystyrene (PS) dish, scaffold with porous structure on the polystyrene dish is required to improve the cell attachment and proliferation efficiency on the dish. The scaffold with porous structure was fabricated from a solution of powdered silk fibroin by plasma grafting polymerization technique. Argon plasma was utilized by a 13.56 MHz capacitively coupled discharge (CCP) reactor at working pressure of 100 mTorr. Rf power, plasma treatment time, and the cycle of grafting on the dish were varied. The proper treatment time and rf power set to 10 minutes and 100 W, respectively. The experimental results showed the uniformly and highly distributed of porosity of fibroin scaffold on the PS dish surface. The Ar-treated dish had lower UV-Vis absorbance than the untreated dish indicating the efficiency of grafting between fibroin structure and treated PS surface is better than the untreated surface. The absorbance spectra of phanyalanine at 280 nm affirmed the success of the fibroin amino acid grafting to PS aromatic structure.