Search

Search Results

• Study of Rotating and Jet Plasma Treatments on Surface Wettability of Glass

  67-79

  Miklós Berczeli

  Zoltán Weltsch

  Views:

  87

  This work investigates the wettability properties of a glass surfaces by using atmospheric pressure cold plasma systems. Treatments were performed by using a rotating-head unit and a jet-type torch during the plazma treatments. The nozzle-to-surface distance (8–15 mm) and the feed rate (50–400 mm/s) were modifying. The untreated glass showed limited wetting, with average water and ethylene glycol contact angles (WCA and EGCA) of 64.7° ± 1.8° and 45.2° ± 1.5°, respectively. After plasma treatment, both systems showed clear improvements, although their efficiency profiles were different. Using the rotating plasma head at 8 mm and 100 mm/s speeds, the WCA decreased to 9.3° ± 0.8°, indicating almost complete wetting. Jet plasma achieved similar results (WCA = 14.1° ± 1.2°), but slightly less uniformly. Changes in wettability were closely related to the exposure time determined by the feed rate: slower movement increased activation, while overexposure occasionally resulted in small thermally induced surface marks that were visible under an optical microscope. As the results showed the rotating plasma reached more homogeneous activation, while the jet system provided stronger local effects at a lower energy input. Based on these results the atmospheric plasma is effective in increasing the surface energy. Rotating systems appear to be advantageous for large, flat areas, while jet plasma is better suited for localized surface modification aimed at improving adhesion or coating performance.

• Improvement of High Strength Automotive Steels Wettability Properties Using CO2 Laser Surface Treatment

  422-427

  Ferenc Tajti

  Miklós Berczeli

  Zoltán Weltsh

  Views:

  262

  As a result of stricter environmental and safety standards, vehicle manufacturers have to reduce the weight of the vehicles, because 10% weight loss cause 8-10% reduction of fuel consumption. To reduce car’s weight and increase safety, vehicle manufacturers use high-strength steels. Further weight reduction can be achieved by using corresponding bonding technology (soldering, sticking) and optimizing these technologies can increase the strength of the joints. According to literature research, the improvement of interface properties has a large effect on bonding technologies. In order to improve interface properties, we can use multiple surface treatments. In our research we investigate the effects of CO2 laser surface treatment on high strength steels, because CO2 lasers are often used in the vehicle industry. In order to detect the effect of surface treatment, we investigate the wettability of the treated and untreated steels. In our research we measure the surface tension of treated and untreated steels. Our main goal is to improve wettability properties thus the bonding technology. In our research we used DP 600 high strength steel sheet with the thickness of 1 mm. We cut the steel sheet to 25mm wide and 55mm long workpieces. Before the surface treatment, the workpieces had to be cleaned and degreased using methanol. We searched for parameters that do not cause any visible changes on the surfaces. Among the parameters of the treatment we were able to change the output power of the laser. We used contact angle measurement to examine the wettability.

• Properties of Cellulose Sheets Modified with Potassium-Humate and Copper (II)-Sulfate

  276-285

  Annamária Tóth

  Katalin Halász

  Views:

  213

  Throughout our research we have made potassium-humate from brown coal of Dudar. With potassiumhumate and copper(II)-sulfate we made test sheets of linter cellulose fibers. The surface energy, surface wettability, CIE Lab color-coordinates changing, bending resistance and tensile strength of the produced test sheets has been examined. There was no big difference in the different samples during surface energy and wettability testing. Examination of mechanical properties suggests that potassium-humate content increases bending resistance of the test sheets. The bending resistance of samples increased by 32%, 100% and 336% compared to the control test sheets while adding potassium-humate.