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Hafnium (Hf) has attracted considerable attention as a component of biomedical titanium (Ti) alloys with low Young's moduli and/or shape-memory functionalities, because its cytotoxicity is as low as that of Ti. The drawback of metals is that their bone-bonding ability is generally low. It is known that apatite formation in the body is a prerequisite for bone-bonding. Although several chemical treatments have been proposed for preparing Ti for bone-bonding, there have been no similar investigations for Hf. In the present study, NaOH- and heat-treatments were applied to pure Hf and Ti-Hf alloys and their bone-bonding ability was assessed in vitro with the use of simulated body fluid (SBF). After NaOH- and heat-treatments, anatase formed on alloys with low Hf content (20-40% (atom%) Hf); mixtures of sodium titanate and hafnium titanate formed on alloys with similar Ti and Hf content (60% Hf); and hafnium oxide formed on alloys with high Hf content (80% Hf and pure Hf). Precipitates of apatite were observed on all the metals in SBF, except for the alloy with 60% Hf. We speculated that the hafnium titanate formed on this alloy had a low apatite-forming ability owing to its high negative surface charge, which inhibited P adsorption. The apatite-forming abilities of the Ti-Hf alloys strongly depended on their Hf content. The present results indicate that Hf-based materials have good potential for bone-bonding. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 2519-2523, 2018.

The effects of small additions of oxide-forming elements (In, Fe, Sn, or Zn) on high-temperature oxidation behaviors and surface oxide colors in experimental Pd-free, Au-Pt-based metal-ceramic alloys for dental applications were investigated by means of spectrophotometric colorimetry, thin-film X-ray diffraction, and field-emission electron probe microanalysis. Three mirror-polished plate samples sized 10 × 10 × 0.5 mm3 from each alloy were subjected to the oxide-forming heat treatments at 950 °C for 10 min in air and then submitted to the above-mentioned investigations. The sole addition of Fe or Sn to the parent Au-10 at.% Pt alloy (AP10) formed very thin external oxide layers of Fe2O3 or SnO2, respectively. Chromaticity indices for these oxidized surfaces largely varied with concentrations of Fe or Sn due to light interference phenomena. On the other hand, the sole addition of In to the parent AP10 alloy developed In2O3 precipitates by the internal oxidation mechanism. Their surface colors did not change significantly regardless of In concentrations. It was highlighted that the combinative addition of 2 at.% In and Fe or Sn to the AP10 alloy well developed In2O3 precipitates in the Au-Pt alloy substrate by the internal oxidation mechanism. Owing to this significant effect of In inclusion, all of the oxidized ternary AP10-In and quaternary (AP10-In2)-Fe/Sn alloys showed similar surface oxide colors with a * coordinates (red-green direction) of nearly +4 and b * coordinates (yellow-blue direction) of nearly +11, which were pale yellow-brown subjectively. Results of this study are expected to be useful in designing esthetic and novel Pd-free, Au-Pt-based metal-ceramic alloys for dental applications.

Silicon carbide(SiC) is used as a raw material contained in the refractory that is in contact with molten iron or slag during steel-making processes. In present work, the interfacial reactions between the SiC ceramic substrate and the blast furnace slag were investigated and the thermodynamic study on the reaction products was carried out. The results showed that the Ti component contained in the slag became TiC, and gathered at the whole interface between the SiC substrate and the slag after experiments.

The effect of the oxygen concentration in the molten iron on the formation of the FeO-MgO phase at the interface between the MgAl2O4 spinel substrate and the molten iron was investigated at 1833 K on the basis of thermodynamics. The results showed that the FeO-MgO phase was formed at the interface between the molten iron and the substrate, if the oxygen concentration in the molten iron was larger than 0.04 mass% for the 50mol%Al2O3-50mol%MgO substrate and 0.08 mass% for the 61mol%Al2O3-39mol%MgO substrate, respectively. For both the substrates, with increasing the oxygen concentration in the molten iron, the activity coefficient of FeO in the spinel substrate increased, and when this value reached above 1.5, a part of MgO was discharged from the spinel and reacted with Fe and oxygen in the molten iron to form the FeO-MgO phase.

The wettability of molten aluminum-silicon alloys with silicon contents of 0, 6, 10, and 20 mass pct on graphite substrates by changing the placing sequence of aluminum and silicon and the surface tension of those alloys were investigated at 1273 K (1000 °C) using the sessile drop method under vacuum. The results showed that the wetting was not affected by changing the placing sequence of the Al-Si alloys on the graphite substrates. The wettability was not improved significantly upon increasing the Si content from 0 to 10 mass pct, whereas a notable decrease of 22 deg in the contact angle was observed when increasing the Si content from 10 to 20 mass pct. This was attributed to the transformation of the interfacial reaction product from Al4C3 into SiC, provided the addition of Si to Al was sufficient. It was verified that the liquid Al can wet the SiC substrate very well in nature, which might explain why the occurrence of SiC would improve the wettability of the Al-20 mass pct Si alloy on the graphite substrate. The results also showed that the surface tension values of the molten Al-Si alloys decreased monotonously with an increase in Si content, being 875, 801, 770, and 744 mN/m for molten Al, Al-6 mass pct Si, Al-10 mass pct Si, and Al-20 mass pct Si alloys, respectively.

It is general to use plural analysis methods to elucidate the structure and the composition of micro-sized materials. However, the following problems will arise during the use of these analysis methods: (1) It may be diffi cult to pinpoint the analysis area in some analysis methods, such as the X-ray diffraction (XRD) analysis. (2) Since an electron beam and X-rays are irradiated many times onto the same area, the sample surface gets damage such as carbon contamination. (3) It takes a long time to analyze. Therefore, electron probe micro-analyzer (EPMA) that can be used to elucidate the compound state of the micro-sized material by only once measurement has been discussed here. Generally, the EPMA can not only obtain the information of simple substances or elements, but also know the variation of the spectrum as changing the bonding state (Kinouchi, 2001; The Surface Science Society of Japan, 1998). However, since the spectrum cannot change regularly for each element in different bonding states, data such as peak shift, peak intensity ratio and half-value width must be one by one analyzed. As it is very diffi cult to prove the change of the characteristic X-ray spectrum theoretically from the viewpoint of the instrumental analysis according to many previous studies, a number of the analysis techniques of the characteristic X-ray have been established based on the experimental data (Abe et al., 2001; Honma et al., 1974; Murakami et al., 1991; Nishimura, 2007; Ohtsuka, 1982; Soejima, 1987; Uchikawa & Numata, 1973; Watanabe et al., 1970). In this study, EPMA that is suitable for micro area analysis was used and we tried to distinguish the kind of compound of the Si series material. At the same time, it was also discussed

A study of the effects of heat treatments of plasma sprayed SUS316L stainless steel coatings was performed. The stainless steel coatings were treated at the conditions of 1273 K and 1373 K for 45 minutes in flowing argon. The effectiveness of the heat treatment was determined using an electron probe microanalyzer (EPMA). The results indicated that the heat treatments were able to significantly affect the composition and the microstructure. After the heat treatment, the interconnected micro-pores were found to appear in the large-scale rod-like oxide in the coating and the content of chromium and manganese in the oxides became higher than that in the as-sprayed coating. The heat-treatment became more effective with increasing temperature.

The wetting behavior of the Cu-Ti alloys with titanium content of 4, 6, and 10 mass pct on the graphite substrate was investigated at 1373 K (1100 °C), using the sessile drop method in three kinds of placement states, which were from top to bottom settled as pre-alloyed Cu-Ti/C, Ti/Cu/C, and Cu/Ti/C, respectively. The results showed that a TiC layer was formed at the interface between Cu-Ti alloy and graphite substrate in all cases. The wettability improved with increasing titanium content from 4 to 10 mass pct. And with the same Ti content, the best wettability was obtained in the placement state of Cu/Ti/C, followed by Ti/Cu/C and pre-alloyed Cu-Ti/C. The different wetting behaviors of three kinds of placement states can be attributed to the contact area between the generated Cu-Ti liquid phase and the graphite substrate during the heating process, as well as the actual content of molten Ti in the generated Cu-Ti liquid phase.

A study on the effect of SUS316L stainless steel surface conditions on the wetting behavior of molten multi-component oxides ceramic was performed and aimed to contribute to the further understanding of the application of oxides ceramic in penetration treatment of stainless steel coatings and the deposition of stainless steel cermet coatings. The results show that at 1273 K, different surface pre-treatments (polishing and heating) had an important effect on the wetting behavior. The molten multi-component oxides showed good wettability on both stainless steel substrates, however, the wetting process on the polished substrate was significantly slower than that on the heated substrates. The mechanism of the interfacial reactions was discussed based on the microscopic and thermodynamic analysis, the substrates reacted with oxygen generated from the decomposition of the molten multi-component oxides and oxygen contained in the argon atmosphere, and the oxide film caused the molten multi-component oxides ceramic to spread on the substrates surfaces. For the polished substrate, more time was required for the surface oxidation to reach the surface composition of Heated-S, which resulted in relatively slow spreading and wetting rates. Moreover, the variance of the surface roughness drove the final contact angles to slightly different values following the sequence Polished-S > Heated-S.

A study of the penetration treatment of plasma sprayed SUS316L stainless steel coatings by molten MnO–SiO 2 oxides with near-eutectic composition was performed. The penetration treatment was introduced at 1353 K for 5, 20, and 45 min, and the effectiveness of the penetration and the underlying mechanisms of interfacial reactions are discussed on the basis of structural observation (EPMA), high-temperature wetting measurements and further supported by a thermodynamic calculation and analysis. The results indicated that at 1353 K, the MnO–SiO 2 oxides could infiltrate into the stainless steel coating within a depth of approximately 100 μm within 5 min due to the very good wettability of the stainless steel coating by molten MnO–SiO 2 oxides. The oxide could further penetrate to the coating/substrate interface when the treatment was extended to 20 min. During the penetration into the coating, a reaction between the MnO–SiO 2 oxides and adjacent stainless steel particles occurred, which produced MnCr 2 O 4 crystalline particles characterized by a spinel structure. As a result, a variation of the MnO–SiO 2 oxides composition was observed.

Hafnium (Hf) has attracted considerable attention as a component of biomedical titanium (Ti) alloys with low Young's moduli and/or shape-memory functionalities, because its cytotoxicity is as low as that of Ti. The drawback of metals is that their bone-bonding ability is generally low. It is known that apatite formation in the body is a prerequisite for bone-bonding. Although several chemical treatments have been proposed for preparing Ti for bone-bonding, there have been no similar investigations for Hf. In the present study, NaOH- and heat-treatments were applied to pure Hf and Ti-Hf alloys and their bone-bonding ability was assessed in vitro with the use of simulated body fluid (SBF). After NaOH- and heat-treatments, anatase formed on alloys with low Hf content (20-40% (atom%) Hf); mixtures of sodium titanate and hafnium titanate formed on alloys with similar Ti and Hf content (60% Hf); and hafnium oxide formed on alloys with high Hf content (80% Hf and pure Hf). Precipitates of apatite were observed on all the metals in SBF, except for the alloy with 60% Hf. We speculated that the hafnium titanate formed on this alloy had a low apatite-forming ability owing to its high negative surface charge, which inhibited P adsorption. The apatite-forming abilities of the Ti-Hf alloys strongly depended on their Hf content. The present results indicate that Hf-based materials have good potential for bone-bonding. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 2519-2523, 2018.

A study of the effects of penetration treatments on plasma sprayed SUS316L stainless steel coatings was performed. The stainless steel coatings were sealed using multi-component oxides introduced at the conditions of 1273 K for 20 min, 1273 K for 45 min and 1373 K for 45 min. The effectiveness of the penetration was determined using an electron probe microanalyzer (EPMA). The results indicated that the molten multi-component oxides could seal the open pores near the stainless steel coating surface quickly and effortlessly due to the good wettability. The molten multi-component oxides could pass through the oxide path connected to the inter micro-pores smoothly and infiltrated into the stainless steel coating when the period of impregnation was prolonged to 45 min. The penetration became more effective with increasing temperature because of the reactions between the molten multi-component oxides and the original oxides that occurred in the stainless steel coating around the inter pores. The results of a salt spray test indicated that the penetration treatment could significantly improve the corrosion resistance of the stainless steel coating.

The wetting behavior of molten Cu-Ti alloys with titanium content of 10mass%, 20mass% and 30mass% on the Yttria Partially-Stabilized Zirconia (Y-PSZ) substrates was investigated at 1273K using the sessile drop method. The wettability improved with increasing the titanium content of the alloy. The stabilized contact angles of Cu-10mass%Ti, Cu-20mass%Ti and Cu-30mass%Ti alloys on the Y-PSZ substrate were measured to be 69°, 47°and 30°, respectively. The surface tension of the molten Cu-Ti alloys and the work of adhesion of alloy/substrate interface increased with increasing the titanium content. A larger work of adhesion attributes to firmer bonding between the molten Cu-Ti alloy and the Y-PSZ substrate, and can greatly improve the wettability.

The wettability between molten impregnating materials and thermal spray coatings is an important factor in post-treatment process of porous coatings. Here, we present the study of wetting behavior of stainless steel substrates by multi-component oxides, using the sessile drop method. The multi-component oxides was mainly composed by SiO2 and Al2O3 and also with a little K2O, Na2O etc. At 1273K and 1353K, we found that the contact angles stabilized at around 45° and 75° respectively. The micro-observation confirmed that the evaporation of alkali metal oxides become a leading position in molten multi-component oxides evaporation at 1353K. As a result, the rupture of NaO and KO bonds will occur and lattice network structure of multi-component oxides reconstruct at excessively high temperature, leading the molten oxides to a higher viscosity and poorer wettability. As the basic researches, this paper also provide a theoretical basis for the deeply study on the post penetration treatment.

The study was conducted to compare the optical parameters of VM7(®) M-shade base dentin ceramics (VITA, Germany) for all ceramic restorations to the chemical composition across the 3D-MASTER(®) shade system., Dental materials, 27(2), pp.165-172; 2011

The wettability between porous MgAl 2 O 4 substrates and molten iron was investigated by the sessile drop method at 1833 K as a basic study in order to elucidate the interactions between molten iron and a refractory material. For the study, MgAl 2 O 4 substrates with 2, 8, 13, 27, and 39% porosity were prepared. The contact angle increased with the substrate porosity. In substrates with 2%, 8%, and 13% porosity, the contact angles were independent of time. In contrast, for substrates with 27% and 39% porosity, the contact angle decreased rapidly during the first hour and then gradually reached a steady value. The decrease in contact angle with time was attributed to the interfacial free energy. The work of adhesion was 1.27 J·m -2 , and it was suggested that the interfacial bond consists of not only a physical bond but also a chemical bond.

The sealing of pores by a veined oxide in a thermal sprayed alumina coating with some kinds of metal particle was investigated by heating in air. Also, the oxide grew from the metallic substrate into an artificial pore in the alumina block was observed after heating in air. The sealing of pores arose by the spinel oxide in the alumina coating containing Ni, Co or NiCrAlY particles after heating at 1173K for 100h in air. The oxide grew from Ni substrate into the artificial pore in alumina block after heating at 1273K for 100h in air. The oxide formed from the Ni substrate in the pore consisted of NiO (core) and NiAl2O4 spinel oxides. Also, the NiAl2O4 spinel formed from the top of the grown oxide on the surface of the pore. The spinel oxide preferentially forms on the surface of the pore and the primary oxide of the metal occupies the remaining space in the pore.

The main concern of classical homogeneous nucleation theory has been a thermodynamic description of initial stage of nucleation from embryo to nucleus with a little larger size over the critical one, thus, the change of parent phase in the system has been assumed to be negligible because of the largeness in volume and mass comparing that of nuclei. As a result, the nucleation curve (free energy change versus nucleus size) passes through well-known single maximum point corresponding to the critical size of the nucleus. In the present study, thermodynamics of the classical homogeneous nucleation was re-visited and developed a modified equation for multi-component solution and gas system with multi-component nuclei by taking into account the change of the free energy of parent phase. Using this equation, the calculation of nucleation curve beyond the size of critical nucleus became possible. A calculation of A–B binary solution system revealed a new minimum point in the nucleation curve, in addition to the maximum point. This minimum point indicates the theoretical possibility to stabilize a large amount of nano-nuclei in equilibrium with the supersaturated parent phase. In addition, Kelvin equation was proved at the extremum on the nucleation curve. Many scientists have misunderstood that Kelvin equation corresponds to the maximum state because they have unnoticed the presence of the minimum and its stability. At the minimum state, the nuclei should be more stable than those at the maximum state. Thus, Kelvin equation should correspond to the minimum state rather than the maximum state.

A new method to obtain experimentally the interfacial free energy between molten iron and graphite has been proposed. A high purity iron was melted on a graphite substrate, and the dissolution of carbon from the substrate to molten iron occurred. The interfacial free energy was measured from the morphological evaluation of the molten iron-graphite interface. This method is different from the conventional method using Young's equation in the point that the surface free energy value of graphite is not required. Moreover, it is possible to measure simultaneously, the graphite surface free energy. This method was confirmed to be useful for measuring the interfacial free energy, because the values obtained in the experiments almost agreed to each other.

The contact angle between molten magnesium and graphite was measured at 973K in order to obtain basic data for magnesium-base composite manufacturing. Two kinds of sessile drop methods were used for the purpose: the conventional method in which solid magnesium was put on graphite prior to heating and another method in which molten magnesium was dropped on graphite by a metal dropping device. In the conventional sessile drop method, though it was difficult to melt magnesium due to the surface oxidation, pure magnesium droplet could be finally gotten after trial and error. It was possible to easily get pure magnesium droplet in the sessile drop method using a dropping device, and magnesium evaporated rapidly. The contact angle between molten magnesium and graphite was estimated to be about 125 deg from the results obtained by the two methods. It was guessed that molten magnesium and graphite were bonded at the interface by the weak intermolecular force, because the work of adhesion was calculated to be 7 kJ/mol.

The measurements of contact angle between molten aluminum and MgAl2O4 spinel substrate and surface tension of molten aluminum, and the direct observation of aluminum surface were conducted. An oxide layer, which was formed in the whole surface of molten aluminum during elevating temperature, disappeared almost within about 2 ks at 1273 K. It is guessed that the layer consists of spinel oxide. An increase of surface tension and a decrease of contact angle were caused by elimination of the oxide layer. The marangoni flow, which probably resulted from the difference of surface tension, was observed from upper to lower part of aluminum surface.

A basic research study for improvement of the galvanizing process has been conducted. The contact angle and surface tension of the molten zinc/oxide ceramic systems were measured at 873 and 973 K by the sessile drop method. The measurement became possible by using sponge titanium as deoxidizer under vacuum. It was found that zinc didn't react or wet zirconia and alumina significantly. The surface tension of molten zinc decreased slightly with increasing temperature. On the basis of the work of adhesion, it was presumed that the dispersion force was predominant for the bond at zinc/zirconia and zinc/alumina interface.

A basic research study for improvement of plasma-sprayed zirconia coatings has been conducted. The contact angle and surface tension of the molten manganese/zirconia-yttria ceramic system were measured at 1573 K by the sessile drop method, suggesting that molten manganese would spontaneously infiltrate open pores in zirconia coatings. Structure and elementary composition development of zirconia ceramics caused by reaction with manganese were examined by using scanning electron microscopy (SEM), an electron probe microanalyzer (EPMA), and an X-ray diffractometer (XRD). Manganese not only stabilized cubic zirconia but also contributed to the growth and volume increase of zirconia particles. In this article, the mechanism of making zirconia coatings dense with manganese is discussed based on the results of experiments.

溶融マンガンによる多孔質セラミックのぬれを測定し、多孔質表面のぬれを表すために熱力学的に導き出されたCassie-Baxterの式が高温融体にも適用できるかどうか調べた。セラミック表面は複雑な性状であるが、彼らの式をおおよそ満足することがわかった。

In order to clarify the mechanism of change in molten pool geometry by plasma arc heating, the effects of oxygen contents of Fe-O melts on the geometry and flow behavior of molten pool were investigated. Also, the temperature coefficients of surface tension of Fe-O melts were examined in a temperature range from 1823 to 2023 K. The depth of molten pool increased and the width of it decreased with increasing oxygen contents. Outward flow was observed at the surface of molten pool in the case of a low oxygen level and inward flow was observed in the case of a high oxygen level

The interfacial properties between liquid Fe-O alloy and alumina substrates with different purities, 99.9% and 96% Al 2 O 3 , were measured by the sessile drop method. The interfaces of samples were examined by SEM and EPMA after the experiment. It was found that the surface tension decreased with increasing oxygen concentration in the iron for both substrates. The contact angle of 99.9% Al 2 O 3 abruptly increased with increasing oxygen concentration at lower oxygen concentrations. These phenomena were attributed to the dissociation of Al 2 O 3

To clarify the mechanism of TiO2 reduction by Fe-C melt, effects of carbon and sulfur contents in liquid iron and temperature on the reduction rate of solid TiO2 were examined at temperatures of 1 350 to 1 550°C under argon atmosphere.The reduction rate of solid TiO2 was proportional to the activity of carbon in liquid iron, while it decreased by the addition of a small amount of sulfur to the liquid iron. An apparent activation energy for TiO2 reduction by carbon was calculated to be about 400 kJ mol-1.It was concluded from these experimental results that the overall rate of TiO2 reduction was controlled by the rate of chemical reaction step at the solid TiO2-liquid iron interface. The decrease in reduction rate of TiO2 by the addition of sulfur to the liquid iron was attributed to the decrease in effective reaction area by the adsorption of sulfur to the interface.

Objective The study was conducted to observe the spectral reflectance curves, and evaluate the color coordinates (CIELAB) of VM7 ® dentin ceramics (VITA, Germany) across the whole 3D-MASTER ® shade system. Methods Three disc samples, 13 mm in diameter and 1.4 mm in thickness, were produced for each shade by firing following the manufacturer's instructions. Each fired disc was ground to a thickness of 1.0 mm and both faces were polished. Spectral reflectance data in the visible spectrum under the standard illuminant D65 were collected at 1 nm intervals by using a computer-controlled spectrophotometer. Color coordinates, L *, a *, b *, C *, h , in the three-dimensional CIELAB color space were obtained. Results (1) Spectral reflectance in the short-wavelength range systematically decreased with increasing chroma number (M1, M2, and M3) when compared within the same value (lightness) group (1M, 2M, 3M, 4M, and 5M). (2) Spectral reflectance decreased systematically across the whole visible spectrum with increasing value group when compared within the same chroma group. (3) A negative relationship was recognized between lightness ( L *) and chromaticity index a * (red–green direction). That is, a * coordinate increases from approximately 1 for the 1M1 sample to approximately 13 for the 5M3 sample, the corresponding lightness systematically decreased from 87 to 69. (4) With increasing a * coordinate, hue angle ( h ) significantly decreased from 85° for the 1M1 sample to 69° for the 5M3 sample. (5) Lightness apparently increased with increasing hue angle ( h ) throughout the whole range of the 3D-MASTER ® shade system. (6) A strong positive relationship between chroma ( C *) and chromaticity index b * (yellow–blue direction) was found, demonstrating that the chroma of the present ceramic is mainly controlled by the b * coordinate. Significance Systematic variations in spectral reflectance and color coordinates of VM7 ® dentin were observed throughout the 3D-MASTER ® shade system and were suggested to be caused by the fine structure of the sample which can interfere with shorter wavelengths in the visible spectrum.