Tokyo Metropolitan Industrial Technology Research Institute

This study was designed to investigate the effect of silicon (Si) ion implantation on the strength of zirconia bonding to resin cement.

Si ions were implanted in a sintered zirconia plate at an acceleration energy of 50 or 100 keV. The implantation dose was divided into four subgroups of 1 × 10¹³, 1 × 10¹⁴, 1 × 10¹⁵, or 1 × 10¹⁶ ions/cm². A total of nine groups were set up, including a control group. Stainless steel rods were bonded to the zirconia plates using resin cement and subjected to tensile bond strength testing. Other plates were subjected to surface roughness measurement and elemental analyses.

In the tensile bond strength test, some groups exhibited significantly higher values than the control group. The surface roughness measured using a confocal laser scanning microscope showed no significant differences in any group compared with the control group. The elemental analyses showed that X-ray photoelectron spectroscopy was able to detect Si ions that could not be detected by energy-dispersive X-ray spectroscopy.

Despite the limitations of this study, it proved possible to implant Si ions into zirconia materials. It was also suggested that the strength of zirconia bonding to resin cement could be improved by irradiation.

Surface electronic states in aqueous solutions affect many properties of materials used in aqueous solutions, for example, the reactivity of photocatalysts. Therefore, evaluation of the surface electronic states is a coveted objective for developing such materials. Although several methods to evaluate surface electronic states in aqueous solutions have been developed, those methods entail difficulties; electrochemical impedance spectroscopy (EIS) requires electrode fabrication, and photoelectron spectroscopy requires synchrotron radiation. Herein, we present the first successful application of photoemission yield spectroscopy in air (PYSA) as a method to evaluate the surface electronic states of particles in aqueous solution. This method is simple and easily accessible in a laboratory. PYSA can measure the valence band maximum (E _v) of materials under ambient pressure. Specifically with PYSA, the surface E _v of hematite (α-Fe₂O₃) and molybdenite (MoS₂) particles dispersed in aqueous solutions was evaluated. This study assessed the effects of pH and solutes in aqueous solution on the surface E _v. When the pH of the dispersion changed, the surface E _v of hematite and molybdenite shifted linearly with the pH. The correlation between the pH and E _v evaluated using PYSA was similar to that evaluated using EIS. In addition to the pH, we investigated the effects of solute adsorption on the surface E _v of hematite. As a solute, phenol and phenol derivatives of five types were used: p-methoxyphenol, p-cresol, p-chlorophenol, p-acetylphenol, and p-nitrophenol. The surface E _v shifted when the solutes were adsorbed onto hematite. The shift direction was related to the electron-donating and accepting properties of p-substituted functional group of phenol and its derivatives.

The combination of laser ablation and inductively coupled plasma mass spectrometry (LA-ICP-MS) is a powerful tool for direct analysis of solid samples. However, quantitative analyses by LA-ICP-MS require matrix-matched standard materials, which are not always available. In this study, we have developed a method that enables quantitative analyses of powder samples using LA-ICP-MS. The sample powder is dispersed in a polyvinyl alcohol (PVA) paste, which is a hydrophilic resin, and a film sample is obtained by a screen-printing technique. Analyte concentrations can be determined by a standard-addition method using an analyte-spiked film prepared by mixing standard solutions into the PVA paste. Because of its hydrophilicity, it is possible to increase the ratio of analytes (standard solutions) to the resin. Despite samples being diluted with the resin, this method has enough sensitivity to detect elements at concentrations < 0.1 μg/g. Several types of ceramic powder (SiC, ZrO₂, and TiO₂) were analyzed using this method, and all the analytes, the concentrations of which differed by five orders of magnitude (from < 1 μg/g to > 1 wt%), were accurately quantified. This method, in which reliable matrix-matched standard materials are easily tailored for each sample, can be potentially important in quantitative analyses using LA-ICP-MS.