Air Gas Atmosphere Research Articles

Modification of hydroxyapatite surface properties by electron irradiation

In the present work, the modification of wetting properties of EB irradiated HA ceramics are studied under air and N2 gas atmospheres. We show a noticeable increase of the hydrophily of electron irradiated HA ceramics in an air gas atmosphere and a lesser increase when the samples are irradiated in an N2 atmosphere, such a phenomenon is correlated to a modification of grain morphology obtained under the 2 atm. With a progressive water saturation of the ceramics, the wetting angles increase progressively until they reach plateau values different from each set of samples (irradiated under air, irradiated under N2 atmosphere and pristine). Profilometry, SEM/EDX, XRD and Raman spectrometry analysis do not show differences between irradiated and pristine samples which indicates that the EB irradiation modifies the surface chemical elements related to the surface wetting properties and not those analysed by the above techniques.

Surface Modification of Pure Titanium by Plasma Exposure and Its Bonding to Resin

The purpose of this study was to investigate the effects on shear bond strength to resin after pure titanium (Ti) was exposed to plasma under different kinds of gas atmosphere. Polished Ti samples were treated using a plasma exposure apparatus in gas atmospheres of air, CO2, and C3F8. Surface analysis of Ti exposed to plasma was achieved through surface free energy and XPS measurements. The Ti sample was bonded with adhesive resin (4-META, MAC-10, HEMA, MDP, VBATDT) to a stainless steel piece. After which, shearing adhesion test was done. It was observed that plasma exposure in a specific gas atmosphere in regulated the bonding strength of titanium surface to resin. Based on the results of this study, we concluded that plasma exposure was a useful surface treatment method for dental practices.

無容器凝固によるY123およびNd123の直接成長の雰囲気依存性

Containerless solidification of YBa2Cu3O7−δ(Y123) and NdBa2Cu3O7−δ(Nd123), which are representative of stoichiometric compounds and compounds with solid solution, respectively, was performed in order to investigate the effects of the oxygen pressure on the direct growth behavior of Y123 and Nd123 from the undercooled melt. In the case of Nd123 samples, the dendritic morphology of the Nd123 phase indicates that the Nd123 phase solidified directly from the undercooled melt, which was independent of the oxygen partial pressure. On the other hand, the Y4Ba3O9(Y430) phase, the metastable high temperature phase, solidified as a primary phase at Ar and air gas atmosphere in the Y123 samples. Containerless solidification in oxygen gas flow allowed the direct growth of the Y123 phase, suppressing the primary solidification of the Y430 phase. The mechanism for the direct growth of the Y123 phase is mainly associated with the instability of the Y430 phase at oxygen gas atmosphere. Moreover, the difference in the direct growth behavior in the Y123 and Nd123 systems is understood by the difference in the high temperature phase: the Y430 phase for the Y123 system and the Nd2BaO4 phase for the Nd123 system.