Evaporation of Cr2O3 in Atmospheres Containing H2O

Stainless steels in atmospheres containing H2O form a Cr2O3 scale in the early stage of oxidation. However, the Cr2O3 scale gradually degrades with time. In order to determine the effect of H2O on the deterioration of a Cr2O3 scale, evaporation behavior of Cr2O3 in N2-O2-H2O atmospheres was investigated. The rate of mass loss in a N2-O2-H2O atmosphere was found to be one order of magnitude higher than the rates in N2-O2 and N2-H2O atmospheres, indicating that deterioration of the Cr2O3 scale is likely to occur in mixed atmospheres of oxygen and water vapor. Volatilization of Cr2O3 is probably based on the following reactions: 1/2 Cr2O3(s)+ 3/4 O2(g)+ H2O(g)= CrO2(OH)2(g). However, it was also speculated that the reaction, Cr2O3(s)+ 3/2 O2(g)= 2 CrO3(g), affects the evaporation of Cr2O3 at temperatures higher than 1323 K. The evaporation rate of Cr2O3 is roughly comparable to the growth rate of the Cr2O3 scale. Therefore, a Cr2O3 scale can be degraded by the evaporation of Cr2O3

Comparative study of closeness-changing based on the cultural view of self in Japan and United States

The purpose of this study is to investigate both effects of the cultural differences and the cultural view of self on closeness changing for the close-partners (e. g., friends, family, romantic partner) in the specific situations. On the basis of Markus & Kitayama (1991), we assumed that the interpretation of the situations, which changes closeness, would be affected by the cultural view of self. We hypothesized that in the situations, which sampled in Japan, the Japanese subjects would report greater change in closeness level than the Americans, and the subjects who had the interdependent view of self would show greater change in closeness level than the individuals having the independent view. The results shows that the Japanese's change level of closeness were higher in the situations that imply an attitude of sympathies, the expectation of the social role, and suggesting his/her weak points, than the American's. On the other hand, the American subjects change their closeness highly in the situations that impact upon individual's independence, the pride and the self-confidence, than the Japanese subjects. In addition, the cultural differences but not cultural view of self explained this difference. Implications of these results are discussed

Biologic markers in prostatic intraepithelial neoplasia: immunohistochemical and cytogenetic analyses

Objective:We evaluated the biological properties of High-grade prostatic intraepithelial neoplasia (PIN) by immunohistochemistry and fluorescence in situ hybridization (FISH) analysis in relation to normal tissue and carcinoma lesions. Materials and Methods:Immunohistochemical staining and FISH were performed on23formalin-fixed radical prostatectomy specimens taken from patients with PIN. Assays were performed using MIB-1, chromogranin A (CGA) and an anti-androgen receptor antibody (AR). A centromere probe for chromosome8was used to test for aneuploidy. Results:The MIB-1index of cancerous specimens (16.2±10.5%) was significantly higher than that of benign (1.9±1.6%, p<0.0001) or PIN (4.0±4.5%, p<0.0001) specimens. The percentage of CGA positive cells was significantly lower in normal tissue (1.2±1.8%) than in PIN (3.5±2.9%, p=0.012) or carcinoma (5.4±4.9%, p=0.005) lesions. Positive staining for AR was consistently observed in the nuclei of both benign and malignant epithelial cells, but positive cytoplasmic staining was also seen in PIN epithelial cells. No significant difference in FISH detected anomalies were found between PIN and carcinoma specimens. Conclusions:Our studies concerning proliferative activity, NE differentiation and chromosomal anomalies of prostatic specimens support the hypothesis that PIN is a biologically intermediate stage in the pathogenesis of prostatic carcinoma. The cellular distribution of AR was altered in PIN cells, but the role of AR in PIN is not yet clear

Classification of Oxidation Behavior of Disilicides

This study focuses on classification of structures of oxide scales formed on disilicides. The oxide scales formed on disilicides can be grouped into 3 types, (a) silica scale, (b) mixed oxide (silica+metal oxide) scale, and (c) double layered (silica/metal oxide) scale. Disilicide that forms an oxide scale of the type (a) generally show excellent oxidation resistance. As such disilicides, there are FeSi2, CoSi2, MoSi2, WSi2, etc. In FeSi2 and CoSi2, a protective silica scale must be formed due to the selective oxidation of Si, whereas in MoSi2 and WSi2 evaporation of metal oxide plays an important role for the formation of a silica scale. Oxidation of TaSi2 and NbSi2 belonged to the type (b), and only CrSi2 the type (c).Proceedings of the International Workshop on Designing of Interfacial Structures in Advanced Materials and their Joints, May, 18-20, 2006, held in Osaka, Japa

Effect of SiC Addition on Oxidation Behavior of ZrB2 at 1273 K and 1473 K

The oxidation behavior of ZrB2-SiC composites with different contents of SiC addition was investigated at 1273 and 1473 K in air for 12 h in this study. The SiC addition contents ranged from 0 to 30 wt%. The results showed that when ZrB2-SiC composites were oxidized at 1273 K in air, a two-oxide layer-structure forms: a continuous glassy layer and a ZrO2 layer contained unoxidized SiC. When SiC content is 5 and 10 wt%, the glassy layer is mainly composed by B2O3. When SiC content is 20 and 30 wt%, a borosilicate glass could be formed on the top layer, which could improve the oxidation resistance of ZrB2. When ZrB2-SiC composites were oxidized at 1473 K in air, the oxide layer was composed of ZrO2 and SiO2 and unreacted SiC. Additionally, when SiC addition content was higher than 10 wt%, a continuous borosilicate glass layer could be formed on the top of the oxide layer at 1473 K. With the increase of SiC content in ZrB2, the oxide layer thickness decreased at both 1273 and 1473 K

Improvement of Oxidation Resistance of NbSi2 by Addition of Boron

NbSi2 is a promising candidate as a coating material for Nb-base alloys. However, it shows complicated oxidation behavior, depending on oxidation temperature. In the present study, in order to clarify the oxidation resistance of NbSi2, oxidation tests of sintered NbSi2 were carried out at temperatures ranging from 773 to 1673 K in air. Moreover, the effect of addition of boron on oxidation resistance of NbSi2 was clarified. NbSi2 showed accelerated oxidation at temperatures of 1073 K and above. The accelerated oxidation was caused by formation of a porous oxide layer, which may be due to the phase transformation from amorphous to crystalline SiO2. The addition of boron to NbSi2 leads to the formation of a protective borosilicate layer, resulting in great improvement of the oxidation resistance. Consequently, NbSi2 added with boron shows excellent oxidation resistance up to at least 1673 K

Structure and oxidation resistance of plasma sprayed Ni-Si coatings on carbon steel

Ni-Si coatings consisting of mainly NiSi2 and NiSi were deposited on a carbon steel by air plasma spraying. Isothermal oxidation tests of the carbon steel substrates with the Ni-Si coatings at 500-800 ℃ have been carried out. The result indicated that a protective SiO2-based oxide scale was formed on the surface of the coatings after oxidation. On the other hand, during oxidation, phase transformation occurred among the NiSi2, NiSi and Ni2Si phases constructing the Ni-Si coatings. This was caused by the extraction of silicon from the silicides and the reformation of silicides at the silcide/Si-blocks interface. Above 700 ℃, the outward diffusion of iron and carbon became very fast and consequently decarburization happened at the coating/substrates interface, which induced the formation of pores in the substrates near the interface. In addition, grain boundary oxidation of Cr in the steel substrate was observed above 700 ℃

Synthesis of Mo–Si–B in situ composites by mechanical alloying

In this study, the synthesis of Mo-Si-B multi-phase alloys, so-called in-situ composites, was attempted with the combination of mechanical alloying (MA) and spark plasma sintering (SPS) processes. MA was conducted with mixed powders of Mo, Si and B using a planetary ball mill under various milling conditions. MAed powders were characterized by X-ray diffractometry (XRD) and scanning electron microscopy (SEM). The results obtained by XRD indicated that Mo-Si-B alloyed powders were successfully produced when elemental powders were milled at a higher milling energy. Vacuum heat treatments after the MA process promoted the formation of Mo-Si-B intermetallic phase in MAed powders. On the other hand, the MAed powders were successfully consolidated by a SPS technique, and as a result, sound compacts of Mo5SiB2-based composites were synthesized

Oxidation of β-SiAlONs prepared by a combination of combustion synthesis and spark plasma sintering

The oxidation of β-Si_[6-z]AlzOzN_[8-z]s (z = 1, 2, and 3) prepared by a combination of combustion synthesis (CS) and spark plasma sintering (SPS) was investigated. The oxidation experiments were conducted at temperatures of 1000℃, 1200℃, and 1400℃ in air for 100 h (360 ks). Their oxidation kinetics follows a parabolic rate law, and the deviation from that increases with a decrease in the z value. The results of XRD and EPMA showed that the oxide formed on β-SiAlONs (z = 1 and 2) consists of silica and mullite, and on β-SiAlON (z = 3) of only mullite