Argon Gas Plasma Research Articles

Change of PET film surface by low-temperature plasma.

PET films stretched under different conditions were treated by radio frequency low-temperature plasma with various gases, and the surface topographical change was investigated by wettability and the introduction of functional groups. The results indicated that undrawn and biaxially drawn films treated with plasma were etched irregularly and randomly, but regular etching structure (seashore structure) which was made at right angle to the stretching direction was observed on uniaxially drawn films treated with plasma. This tendency was especially conspicuous, in oxygen and argon gas plasma treatment, but the degree of etching of the surface treated with nitrogen-containing gas plasma such as nitrogen and ammonia was small because nitrogen atoms were incorporated into PET surface during plasma treatment, Untreated PET films exhibited different wettability according to stretching conditions, but once they underwent the low-temperature plasma treatment, they showed nearly equal wettability irrespective of stretching conditions. The results showed that the oxygen gas plasma improved surface wettability exceedingly among the gasses used in this study, and it gave the greatest critical surface tension. Hydrophilic functional groups may have been introduced into PET surface treated with oxygen gas plasma, judging from the ratio of dispersion force and polar force calculated from expanded Fowkes equation.

Optimisation of instrumental parameters for the precise measurement of isotope ratios with inductively coupled plasma mass spectrometry

The effect of several instrumental operating parameters (IOPs) on the precise and accurate measurement of isotope ratios was investigated. The IOPs of interest were: dwell time (DT) and cycle time (CT) of the software control parameters, the r.f. power level, the analyte solution flow-rate and the argon gas plasma, auxiliary and nebuliser flow-rates. Two measurement criteria were evaluated for each isotope pair (a,b) in relation to these independent variables: the precision (RSD) of the isotope ratio measurements and the deviation (Δ) of the measured isotope ratio (MRa/b) from a reference value (MR0a/b). The isotope pairs of interest were: 6Li : 7Li, 57Fe : 54Fe, 58Fe : 54Fe, 65Cu: 63Cu, 67Zn : 68Zn and 70Zn : 68Zn.It was shown that the best precision (lowest RSD) and most stable measurements (lowest Δ) were generally obtained over a relatively wide range of r.f. powers, while the range of r.f. power corresponding to the maximum ion-beam intensity was much narrower. The optimum r.f. power for the best results was Li, 1170; Fe, 1240; Cu, 1250; and Zn, 1290 W. Argon gas flow-rates corresponding to the optimum values for %RSD and %Δ were: plasma flow-rate 15 for Li and 12 l min–1 for the other elements, auxiliary flow-rate 1.7 for Li and 1.8–1.9 l min–1 for the other elements, and nebuliser pressure 42 lb in–2 for all elements. The analyte solution flow-rate giving the best results was investigated for Cu only (best value 0.91 ml min–1).Employing the optimum settings of the IOPs, the long-term stability (5 h of continuous operation) of the measurements was investigated. It was shown that the ion-beam intensities were stable to better than 8%. In contrast, values of isotope ratios (MRa/b) always stayed within the expected measurement precision [RSD<1% for all except Li (<1.5%)].It was concluded that inductively coupled plasma mass spectrometry (ICP-MS) permitted the precise and accurate measurement of stable isotope ratios for routine application in the studies of trace-element metabolism in man employing the concept of stable isotope tracers.

プラズマジェットの衝突力の測定 平行平板構造のロードセルを用いた試作装置による測定

The new measuring apparatus of plasma jet force using the load-cell on the parallel beams structure has been developed and applied to the measurement of argon gas plasma jet force.The load-cell of parallel beams structure is easily manufactured and has excellent sensitivity of measurement. The experimental results of the plasma jet force measurement are described and discussed.It has been indicated that the plasma jet force depends on arc current, arc voltage, working gas flow rate, gas supplying method, and stand-off condition. The plasma jet force is closely related with the input power and is proportion to the square root of input power.

A microstructural study of local melting of grey cast iron by a static plasma arc

The microstructural changes produced by plasma arc local-melting method in the fusion region or deposited metal, fusion boundary region and heat-affected zone (HAZ) of flake graphite cast iron were investigated. Cylindrical base metal specimens were locally melted at fixed time intervals under a stationary plasma torch using argon plasma gas and Ar + 10% H2 shielding gas. The welds were produced autogenously and with filler metals. The cooling rate in the fusion region was recorded. Evaluation of the fusion boundary area included metallurgical analysis, microhardness and electron probe microanalysis. In the absence of filler metal, the structure of fusion region where completely melted was ledeburite. In the centre of the fusion region the structure appears to be that of hypoeutectic white cast iron, and in the fusion boundary of this region the structure appears to be fined ledeburite. In the fusion boundary region where supercooled phenomena can occur, fine martensite precipitates appear along the fusion line for small heat input and secondary graphite is seen for large heat input. The HAZ is composed of white martensitic, dark martensitic and martensitic-fine pearlitic layers for small heat input, and of finely laminated pearlitic and finely laminated pearlitic-ferritic layers for large heat input. Using filler metal, the structure of the deposited metal is found to be that of a nickel austenitic matrix precipitating tiny graphite nodules or slim graphite for nickel and Ni-Fe filler metals, but to be a pearlitic matrix for iron filler metal. In the fusion boundary region, nickel-martensite, eutectic or slim graphite and fine nickel-martensite are precipitated from the nickel system filler metal, and the columnar structure of ferrite and pearlite is obtained from iron filler metal. The HAZ is composed of thin ledeburitic, martensitic, martensitic-fine pearlitic and finely laminated pearlitic layers for the nickel filler metal, of ledeburitic and finely laminated pearlitic layers for the Ni-Fe filler metal, and of thick ledeburitic, eutectic graphite-crystallized and finely laminated pearlitic layers for iron filler metal. The hardness of the ledeburitic layer and the nickel-martensitic portion is very high where the liquid existed. The diffusion of nickel from the deposited metal into the HAZ can occur at least until the fused base metal of HAZ.

Metallurgical reaction and deposit fusion boundary microstructure under a stationary plasma arc

Alloy element loss, decarburization in melted region and microstructural change of a deposit fusion boundary under a stationary plasma arc have been investigated by a first-order kinetic and interfacial microstructure. The cylindrical specimens of iron-based alloys, Fe-C, Ni-C, and Co-C alloys were locally melted by a plasma arc using argon plasma gas and Ar+H2 shielding gas, and the rates of alloy element loss and decarburization in the melted region were measured. Moreover, the fusion boundaries experienced when nickel, iron, Ni-Fe filler metals were deposited on iron, Fe-C, nickel and cobalt base metals, were evaluated metallographically. The initial rate of alloy element loss decreases as follows: Fe-Al>Fe-Mn>Fe-Cr>SGI-Mg>Fe-Ni. The loss reaction mechanism is metallic evaporation and the rate seems to be limited by transport in the gas boundary layer. The magnitude of decarburization is as follows: Ni-C>Fe-C> Co-C. The decarburization rate in Fe-C alloy is assumed to be governed by a process involving mass transfer in the gas phase and the molten metal. However, at low carbon concentrations, the rate appears to be limited by transfer in liquid metal. Fusion boundary deposited with nickel filler metal on iron is regular, but with carbon added to iron, an infiltration of deposit metal into adjacent base metal occurs. The fusion boundary with iron deposited on nickel is irregular where thin Ni-Fe solid solution is formed. In a deposited fusion boundary of cobalt with iron, nickel, and Ni-Fe filler metals, FeCo compound formation occurs, with cobalt dissolving into the nickel deposit metal resulting in a tongue-like structure produced by nickel penetration and a fine columnar substructure formation produced by Ni-Fe diffusion.

The plasma scalpel: a new thermal knife.

A new thermal knife, the plasma scalpel, capable of simultaneous division of tissue and coagulation of blood vessels, is described. A high temperature argon gas plasma (unrelated to blood plasma) is created by passing the gas through a direct current arc, ionizing the gas and elevating its temperature to 3000 degrees C. A small plasma cutting jet is formed by a nozzle at the tip of the handpiece. Liver resections and muscle transections performed in a canine model, and full thickness burn excisions in a pig skin model showed effective division of tissue and significantly less blood loss when compared to the steel scalpel. Wound healing studies of histologic comparisons and wound breaking strength were performed for steel, plasma, laser, and electrosurgical scalped incisions in the skin of mice and rats. All thermal knife wounds showed localized tissue damage at the edges of the incision, but the events of healing began at the same time. Compared to the steel scalpel, there was a three to six day delay in the onset of healing, but healing occurred in the normal fashion and all thermal knife wounds reached the same healed breaking strength as the steel scalpel wounds. Clinically, the plasma scalped has been used for 138 procedures in 96 patients. The majority of cases have been transection of muscle, hepatic resection or debridement, or soft tissue debridement. Muscle transection data for the plasma scalped compared to the electrosurgical scalpel has shown virtually no blood loss with a shorter time to hemostasis for the plasma scalpel. The plasma scalpel has proved to be an effective thermal knife, capable of simultaneous division and coagulation. Further development work and proof of its efficacy in the clinical setting are necessary to establish the plasma scalpel and adequately demonstrate its proper role in surgery.

Ionization instability and stable region in potassium seeded argon gas plasma MHD generation

In nonequilibrium MHD generation with alkali metal seeded noble gas plasma, stable regions free from ionization instability are investigated in terms of seed fraction magnetic field strength and current density by using linear perturbation theory with allowance for the ionization of noble gas atoms. Regardless of fluctuations, a Faraday-type MHD generator with finely segmented electrodes operating with a seed fraction of 10-3 gives, in general, higher power density than a smaller seed fraction of 10-5, and the power density can attain the target power density 50 MW/m3 even at a low gas temperature of 1500K and a high pressure of 20 atm.