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The sonochemical reduction of MnO4(-) to MnO2 in aqueous solutions was investigated as a function of alcohol concentration under Ar. The rate of MnO4(-) reduction initially decreased with increasing alcohol concentration, and then increased when the alcohol concentration was increased further. The concentrations at which the reduction rates were minimum depended on the hydrophobic properties of the added alcohols under ultrasonic irradiation. At low concentrations, the alcohols acted as OH radical scavengers; at high concentrations, they acted as reductant precursors: Rab, formed by abstraction reactions of the alcohols with sonochemically formed OH radicals or H atoms, and Rpy, formed by alcohol pyrolysis under ultrasonic irradiation. The results suggest that the reactivity order of the sonochemically formed reducing species with MnO4(-) at pH 7-9 is the sum of H2O2 and H>Rpy>Rab. The peak wavelengths of MnO2 colloidal solutions formed at high 1-butanol concentrations shifted to shorter wavelengths, suggesting the formation of small particles at high 1-butanol concentrations. The rates of sonochemical reduction of MnO2 to Mn(2+) in the presence of 1-butanol were slower than that in the absence of 1-butanol, because the sonochemical formation of H2O2 and H, which act as reductants, was suppressed by 1-butanol in aqueous solutions.

The environment-induced cracking (EIC) of as cold-rolled Ni 3 (Si,Ti) and Ni 3 (Si,Ti) with 2Mo has been investigated as functions of applied stress, chloride ion concentration, test temperature, and pH by using a constant load method in NaCl solutions. The EIC susceptibility of both intermetallic compounds increased with increasing Cl − ion concentration and test temperature; and increased with decreasing pH. Both intermetallic compounds had the same transgranular fracture appearance and the relationship between log t f (time to failure) and log l ss (steady state elongation rate) became the identical straight line irrespective of applied stress, Cl − ion concentration, test temperature, and pH, which means that l ss becomes a relevant parameter for predicting t f . The EIC susceptibility of Ni 3 (Si,Ti) with 2Mo was lower than that of Ni 3 (Si,Ti), which showed the beneficial effect of Mo. From the results obtained, EIC of both intermetallic compounds was presumed to take place by hydrogen embrittlement (HE).

The hydrogen embrittlement behavior of sensitized types 304, 316 and 310 in boiling saturated magnesium chloride solutions was explained in more details in terms of an inhibiting effect of chloride ions, martensite transformation, Cr depletion, HELP, and the degree of corrosiveness through the comparison with those for the solution annealed steels. Furthermore, a transgranular HE (TG-HE) cracking mode that was not observed for the solution annealed steels was discussed as well as IG-HE. Then a TG-HE mechanism for sensitized austenitic stainless steels was proposed, while the IG-HE mechanism for solution annealed austenitic stainless steels was discussed in details and was applied to IG-HE of sensitized austenitic stainless steels. It was also pointed out that the occurrence of both TG-HE and IG-HE was explained with an identical concept.

The pitting corrosion behavior of high-purity aluminum covered with barrier-type anodic films, which are formed in neutral borate and phosphate electrolytes, has been examined in 0.5 mol dm−3 NaCl solution at an applied potential of −0.6 V versus Ag/AgCl, which is slightly nobler than the pitting potential of −0.64 V in the same solution. The pitting current density, i p, increased with time after an incubation time, t i. The double logarithmic plot of i p and polarization time, t, reveal two straight lines, which are separated at the time, τ. The slope becomes larger after τ for the specimens anodized in the phosphate electrolyte, while it becomes smaller for those in the borate electrolyte. Both the t i and τ increase with the thickness of the anodic films, and at the similar film thickness, they are much larger for the anodic films formed in the phosphate electrolyte than for those in the borate electrolyte. The corrosion process can be divided into three stages: the incubation period up to t i, the pit nucleation period before τ, and the pit growth period after τ. We have discussed the different pitting corrosion behavior of the aluminum specimens covered with the anodic films formed in the borate and phosphate electrolytes in terms of ion selectivity of the anodic films.

Two-phase Ni3Al3V intermetallic alloys with and without carbon addition, composed of geometrically closed-packed (GCP) structures of Ni 3 Al ( L 1 2 ) and Ni 3 V ( D 0 22 ), were investigated for dry sliding wear against a G5 disc (WC carbides with a hardness of 1350 HV) at 298 K and 573 K by using a pin-on-disc type configuration. The dry sliding wear of a commercial Inconel 718 was also studied under the same experimental conditions for comparison. The wear mass loss measured for the Ni3Al3V intermetallic alloys increased with increasing sliding distance. In the dry wear test at 298 K, the 0.1 C intermetallic alloy showed the lowest wear mass loss, followed by the 0 C alloy and then the 0.5 C alloy. At 573 K, the 0.5 C alloy showed the smallest wear mass loss, followed by the 0.1 C alloy and then the 0 C alloy. All three intermetallic alloys showed better wear resistance compared to Inconel 718 at both test temperatures. The good wear resistance of the Ni 3 Al/Ni 3 V two-phase intermetallic alloys was attributed to the combination of the positive temperature dependence of the flow strength and the strong friction-induced work hardening during the dry sliding wear process.

The effects of applied stress and test temperature on the environment-induced cracking (EIC) behavior of carbon steel in 5 kmol/m3 NH4NO3 solution were investigated by using constant load method. The three parameters (time to failure (tf), steady state elongation rate (lss) and transition time to time to failure ratio (tss/tf)) were obtained from a corrosion elongation curve. The relationships between applied stress and the three parameters were divided into three regions; the stress-dominated, the EIC-dominated and the corrosion-dominated regions. Under an applied stress of 225 MPa (in the EIC-dominated region), the test temperature dependences of the three parameters were investigated. Although tf decreased with increasing test temperature above 323 K, it became constant independent of test temperature under 323 K. Whenever the EIC takes place, the relationship between log tf and log lss become a good straight line with a slope of -1.1 irrespective applied stress and test temperature, which means that lss becomes a parameter for predicting tf. In addition, the fracture appearance in the EIC-dominated region was intergranular. From the results obtained, the intergranular cracking of carbon steel was discussed in terms of film formation, dissolution and hydrogen permeation.

The corrosion behavior of specimens consisting of two regions of a Ni 3 (Si,Ti) single-phase of L1 2 structure and two phases of L1 2 and fcc Ni was examined in 0.5 kmol/m 3 HCl, H 2 SO 4 and HNO 3 . Ni 3 (Si,Ti) with Cr showed the highest corrosion resistance. The single L1 2 phase region was preferentially dissolved for all specimens in all solutions. This fact was interpreted in terms of lower corrosion resistance of the region due to the presence of active Al or due to the absence of protective Cr and Mo. Ni 3 (Si,Ti) with Al and Ni 3 (Si,Ti) with Cr showed intergranular corrosion in less corrosive HNO 3 .

The pitting corrosion of Ni3(Si,Ti) with 2 at% Mo consisting of a single intermetallic compound Ni3(Si,Ti) phase of L12 structure and a two phase mixture of L12 and fcc nickel solid solution was investigated as functions of test temperature and chloride concentration in sodium chloride solutions by using a potential step method and compared with that of intermetallic compound, Ni3(Si,Ti). The pitting potential obtained for the Ni3(Si,Ti) with 2 at% Mo decreased with increasing chloride concentration and test temperature. A critical chloride concentration below which no pitting corrosion took place was found to exist and to decrease with increasing test temperature. The specific pitting potential at the critical chloride concentration also decreased with increasing test temperature. The pitting potential of Ni3(Si,Ti) with 2 at% Mo was higher than pure nickel, but lower than that of Ni3(Si,Ti). A critical chloride concentration was found to be lower than that of Ni3(Si,Ti), whereas the specific pitting potentials at the critical chloride concentration was found to be higher than that of Ni3(Si,Ti). Pitting corrosion occurred in the two phase mixture region.

The pitting corrosion of intermetallic compound Ni3(Si,Ti) was investigated as functions of test temperature and chloride concentration in sodium chloride solutions by using a potential step method. In addition, the pitting corrosion of solution-annealed austenitic stainless steel type 304 and pure nickel was also studied under the same experimental condition for comparison. The pitting potential obtained for the intermetallic compound decreased with increasing chloride concentration and test temperature. A critical chloride concentration below which no pitting corrosion took place was found to exist and to decrease with increasing test temperature. The specific pitting potential at the critical chloride concentration also decreased with increasing test temperature. In addition, the pitting potential at various constant chloride concentrations above the critical chloride concentration decreased with increasing test temperature. The pitting potential of Ni3(Si,Ti) was higher than pure nickel, but lower than that of type 304.

The corrosion behavior of the intermetallic compounds homogenized, Ni3(Si,Ti) (L12: single phase) and Ni3(Si,Ti) + 2Mo (L12 and (L12 + Niss) mixture region), has been investigated using an immersion test, electrochemical method and surface analytical method (SEM; scanning electron microscope and EPMA: electron probe microanalysis) in 0.5 kmol/m3 H2SO4 and 0.5 kmol/m3 HCl solutions at 303 K. In addition, the corrosion behavior of a solution annealed austenitic stainless steel type 304 was studied under the same experimental conditions as a reference. It was found that the intergranular attack was observed for Ni3(Si,Ti) at an initial stage of the immersion test, but not Ni3(Si,Ti) + 2Mo, while Ni3(Si,Ti) + 2Mo had the preferential dissolution of L12 with a lower Mo concentration compared to (L12 + Niss) mixture region. From the immersion test and polarization curves, Ni3(Si,Ti) + 2Mo showed the lowest corrosion resistance in both solutions and Ni3(Si,Ti) had the highest corrosion resistance in the HCl solution, but not in the H2SO4 solution. For instance, it was found that unlike type 304 stainless steel, these intermetallic compounds were difficult to form a stable passive film in the H2SO4 solution. The results obtained were explained in terms of boron segregation at grain boundaries, Mo enrichment and film stability (or strength).

N,S-codoped TiO 2 photocatalysts were successfully immobilized on the surface of plasma-nitrided pure Ti substrate by anodic oxidation in a sulfuric acid electrolyte and their photocatalytic activities were evaluated. The anodic TiO 2 photocatalysts effectively bleached methylene blue (MB) aqueous solution under visible light illumination. X-ray photoelectron spectroscopy (XPS) analysis clarified the presence of nitrogen and sulfur, and auger electron spectroscopy (AES) analysis revealed that sulfur was distributed over the anodic oxide. It is estimated that N,S-codoping in the anodic TiO 2 narrows the band gap of pristine TiO 2 and improves the photocatalytic activity under visible light illumination.

The environment-induced cracking (EIC) of a commercial Al–Cu alloy has been investigated as functions of applied stress, chloride ion concentration and test temperature in distilled water and sodium chloride solutions by using a constant load method. The effect of chloride ion on EIC is complex. The EIC susceptibility increased, unchanged and then decreased with increasing the chloride ion concentration. However, whenever EIC takes place with and without chloride ion, the fracture appearance and the value of t ss (transition time to deviation from linear elongation)/ t f (time to failure) are the same, and further the relationship between log t f and log l ss (steady state elongation rate) becomes the identical straight line irrespective of applied stress, chloride ion concentration and test temperature. The latter means that l ss becomes a relevant parameter for predicting t f. It has been concluded that EIC of Al–Cu alloy takes place by hydrogen embrittlement (HE) associated with the fracture of hydride, and a HE mechanism is qualitatively proposed to explain the results obtained.

本論文はすでに報告された自然浸漬下，定荷重法で得られた結果に基づいて，オーステナイトステンレス鋼と純チタンの水素脆性感受性評価と機構に関する新たな観点を述べる．さらに，材料の破壊がSCCで起こるのかあるいはHEで起こるのかを判定する定荷重法の基準についても述べる．

We have already proposed a mechanism for intergranular hydrogen embrittlement (IG-HE) for solution annealed austenitic stainless steels (types 304, 316 and 310) in HCl solutions and in boiling saturated magnesium chloride solutions. The proposed IG-HE mechanism was based on martensite transformation, hydrogen-enhanced local plasticity (HELP), grain boundary sliding (GBS). Recently, it was reported that the fracture susceptibility and fracture mode for sensitized steels in boiling saturated magnesium chloride solution under an open-circuit condition were significantly different from those observed for solution annealed steels. In the present paper, the hydrogen embrittlement behavior of sensitized types 304, 316 and 310 in boiling saturated magnesium chloride solutions was explained in more details in terms of an inhibiting effect of chloride ions, martensite transformation, Cr depletion, HELP, the degree of corrosiveness through the comparison with those for the solution annealed steels. Furthermore, a transgranular HE (TG-HE) cracking mode that was not observed for the solution annealed steels was discussed as well as IG-HE. Then a TG-HE mechanism for sensitized austenitic stainless steels was proposed, while the IG-HE mechanism for solution annealed austenitic stainless steels which was discussed in details was applied to IG-HE of sensitized austenitic stainless steels. It was also pointed out that the occurrence of both TG-HE and IG-HE was explained with an identical concept.

The objective of this paper is to propose a new intergranular hydrogen embrittlement mechanism of solution annealed austenitic stainless steels (types 304, 316 and 310) on the basis of the results already reported. An intergranular hydrogen embrittlement (IG-HE) took place for type 316 at potentials less noble than the open-circuit potential in a HCl solution, and for types 304 and 316 at a lower test temperature under an open-circuit condition in saturated boiling magnesium chloride solutions by using a constant load method, while type 310 suffered only a transgranular stress corrosion cracking (TG-SCC) in both solutions under the same experimental conditions, but not IG-HE. In addition, TG-SCC occurred for types 304 and 316 under an open-circuit condition in the HCl solution irrespective of test temperature and in saturated boiling magnesium chloride solutions at higher test temperatures. Thus, the occurrence of IG-HE depended upon the material and test temperature. The new IG-HE mechanism was developed that explains the results obtained in terms of martensite transformation, hydrogen-enhanced local plasticity (HELP), grain boundary sliding (GBS) and so on.

A novel one-pot synthesis method to prepare gold nanorods was developed by using sonochemical reduction of gold ions in aqueous solution. The size of the sonochemically formed gold nanorods was less than 50 nm, and their average aspect ratio decreased with increasing pH of the solution. The aspect ratio measured was 3.0 at pH 3.5, 2.2 at pH 5.0, and 2.1 at pH 6.5. At pH 7.7, irregular shaped gold nanoparticles were formed. At pH 9.8, most of the particles formed had a spherical shape with a smaller particle size than those formed in the lower pH solutions. Based on the obtained results, it was clear that the size and shape of the sonochemically formed gold nanoparticles are dramatically dependent on the pH value of the solution.

Chemical effects of ultrasound have been actively researched in the field of the synthesis of various metal nanoparticles and nanostructured materials. It is very important to understand the reduction mechanism of metal ions, because the reduction processes can be often applied to the synthesis of various materials. In this study, the sonochemical reduction of MnO4- to MnO2 in water under Ar atmosphere was investigated to discuss the reduction mechanism. It has been reported that H, OH, H2 and H2O2 are formed from the sonolysis of water. To understand the roles of H2O2 on the reduction, the reaction of MnO4- with H2O2 without ultrasonic irradiation was investigated. The obtained results suggested the progress of the following reaction: 2MnO4-+3H2O2-->2MnO2+3O2+2OH-+2H2O. In addition, the rates of the sonochemical reduction of MnO4- were investigated in the presence of 1-propanol, where 1-propanol acted as an OH radical scavenger so that the amounts of the sonochemically formed H2O2 molecules were able to be controlled. The results clearly indicated that the sonochemically formed H2O2 molecules as well as H2 molecules and H atoms play an important role for MnO4- reduction. This mechanism was also supported by the analysis of pH changes during ultrasonic irradiation: the pH value increased as the sonochemical reduction of MnO4- proceeded.

Production of fatty acid ethyl ester (FAEE) from oleic acid (FFA) with short-chain alcohols (ethanol, propanol, and butanol) under ultrasonic irradiation was investigated in this work. Batch esterification of oleic acid was carried out to study the effect of: test temperatures of 10–60 °C, molar ratios of alcohol to oleic acid of 1:1–10:1, quantity of catalysts of 0.5–10% (wt of sulfuric acid/wt of oleic acid) and irradiation times of 10 h. The optimum condition for the esterification process was molar ratio of alcohol to oleic acid at 3:1 with 5 wt% of H2SO4 at 60 °C with an irradiation time of 2 h.

Titanium dioxide (TiO2) photocatalyst was fabricated by anodic oxidation on pure titanium in an electrolyte of a sulfuric acid, and effect of ultrasonic irradiation during anodic oxidation was explored. It was found that ultrasonic irradiation increased crystallinity of the anodic oxide. The hydrophilicity of the as-anodized oxide was improved by applying ultrasonic irradiation, and it is similar to that of the annealed oxide without applying ultrasonic irradiation. In contrast, the photoactivity of the as-anodized oxide was not altered by applying ultrasonic irradiation.

最初に，この論文では破断時間を予測できるパラメーターが3試験法（定荷重法，定歪み法，SSRT）において存在するかどうかを述べる．次に，定荷重法における割れ感受性評価の基準を明らかにする．最後に，オーステナイトステンレス鋼および純チタンにおいて得られた結果に基づいて，応力腐食割れと水素脆性の新たな機構が統一的な概念と観点から提案される．

Stress corrosion cracking (SCC) and hydrogen embrittlement (HE) of sensitized stainless steels of types 304, 310 and 316 were investigated as a function of applied stress at different test temperatures in boiling saturated magnesium chloride (MgCl2) solutions under a constant applied stress condition. The stress dependence of fracture appearance and three parameters of time to failure ( t f ) , steady-state elongation rate ( l ss ) and transition time to time to failure ratio ( t ss t f - 1 ) suggests that types 304 and 310 suffered SCC, while type 316 suffered only HE. It was also found that the applied stress dependence of three parameters for the sensitized types 304 and 310 was almost similar to that of the solution-annealed stainless steels, whereas that of type 316 showed a clear difference between sensitized and solution-annealed specimens. The relationships between the logarithms of the time to failure and the steady-state elongation rate became a straight line for all stainless steels. However, its slope depended upon the fracture mode: −2.0 for SCC and −1.5 for HE. This showed that the steady-state elongation rate was a good parameter for predicting the time to failure for the stainless steels in the MgCl2 solutions. The results obtained were explained in terms of martensite transformation, hydrogen entry site, and sensitization.

The hydrogen-induced cracking (HIC) of the commercial pure titanium (Ti) has been investigated as functions of applied stress and test temperature in sulphuric acid and hydrochloric acid solutions by using a constant load method. From the results obtained, HIC was hydrogen embrittlement (HE) related to the fracture of hydride. We have also found that the steady state elongation rate obtained from corrosion elongation curve becomes a relevant parameter for predicting time to failure and a criterion to assess whether HIC takes place or not. A parameter, tsstf−1 was also found to become an indicator to assess whether HE takes place or not. Furthermore, it was deduced that HIC was qualitatively explained in terms of hydride formation and a localized deformation, which was basically based on a hydride formation-rupture event at crack tips.

Stress corrosion cracking (SCC) and hydrogen embrittlement (HE) of the sensitized stainless steels of type 304, 310 and 316 were investigated as a function of test temperature in boiling saturated magnesium chloride (MgCl2) solutions under a constant applied stress condition. The test temperature dependence of fracture appearance and three parameters of time to failure (tf), steady-state elongation rate (lss) and transition time to time to failure ratio (tss/tf) suggests that type 304 suffered SCC and HE, while type 316 suffered only HE and type 310 SCC. It was also found that the test temperature dependence of three parameters for the sensitized type 304 and 310 was almost similar to that of the solution annealed stainless steels, whereas that of type 316 showed a clear difference between sensitized and solution annealed specimens. The relationships between the logarithms of the time to failure and the steady-state elongation rate became a straight line for all stainless steels. However, its slope depended upon the fracture mode; −2.0 for SCC and −1.5 for HE. This showed that the steady-state elongation rate was the parameter for predicting the time to failure for the stainless steels in the MgCl2 solutions. The results obtained were explained in terms of martensite transformation, hydrogen entry site, sensitization, and so on.

The stress corrosion cracking (SCC) of a commercial Cu–30% Zn alloy has been investigated as a function of applied stress in Mattsson solutions with pH 7.0 and 10.0 at 313 K by using a constant load method. It was found that the elongation behavior at pH 10.0 showed clearly the step wise fashion, while that at pH 7.0 did slightly, almost over the whole applied stress. The steady state elongation rate obtained from corrosion elongation curve became a relevant parameter for predicting time to failure. Furthermore, from the results obtained, it is deduced that a unified SCC mechanism is qualitatively proposed to explain both of transgranular SCC (TGSCC) at pH 10.0 and intergranular SCC (IGSCC) at pH 7.0, where the unified SCC mechanism is basically based on a film rupture-formation event at crack tips.

Methanolysis of triolein was investigated at room temperature by 40 kHz ultrasonic irradiation to make biodiesel fuel as methyl esters. It was found that the yield of methyl esters strongly depended on the amount of KOH and the molar ratio of methanol to triolein (M/T) and was highest at the M/T molar ratio of 6/1, KOH concentration of 1 wt% and irradiation time of 30 min. In addition, the effects of sonication on the methanolysis of triolein were discussed in comparison to the effects of stirring experiments. The optimum condition under stirring experiments showed that the molar ratio of M/T, KOH concentration and reaction time were 6/1, 1.5 wt% and 4 h, respectively. These results clearly indicated that the ultrasonic irradiation method would be a promising one compared to the conventional stirring method. The high yield under the ultrasonic irradiation condition would be due to high speed mixing and mass transfer between the methanol and triolein as well as the formation of a microemulsion resulting from the ultrasonic cavitation phenomenon.

The test temperature dependence of the transesterification of triolein with methanol and a base catalyst (NaOH and KOH) was investigated using a molar ratio of methanol to triolein of 6:1, a catalyst concentration of 1% and a temperature range of 3–50 °C under a low-frequency ultrasonic irradiation condition (40 kHz). It was found that the methyl ester concentration at an irradiation time of 5 min increased with increasing temperature, where it tended to level off at temperatures higher than 20 °C. Furthermore, apparent activation energy was estimated from the relationship between the rate and the reciprocal of temperature.

The change in the mechanism of stress corrosion cracking with test temperature for Type 304, 310 and 316 austenitic stainless steels was investigated in boiling saturated magnesium chloride solutions using a constant load method. Three parameters (time to failure; t f , steady-state elongation rate; l ss and transition time at which a linear increase in elongation starts to deviate; t ss ) obtained from the corrosion elongation curve showed clearly three regions; stress-dominated, stress corrosion cracking-dominated and corrosion-dominated regions. In the stress corrosion cracking-dominated region the fracture mode of type 304 and 316 steels was transgranular at higher temperatures of 416 and 428 K, respectively, but was intergranular at a lower temperature of 408 K. Type 310 steel showed no intergranular fracture but only transgranular fracture. The relationship between log l ss and log t f for three steels became good straight lines irrespective of applied stress. The slope depended upon fracture mode; −2 for transgranular mode and −1 for intergranular mode. On the basis of the results obtained, it was estimated that intergranular cracking was resulted from hydrogen embrittlement due to strain-induced formation of martensite along the grain boundaries, while transgranular cracking took place by propagating cracks nucleated at slip steps by dissolution.

The entry and transport of hydrogen in phosphorus (P)-, sulphur (S)- and their mixture (P + S)-implanted nickel specimens with a fluence range of 1 × 1015 to 1 × 1017/cm2 have been investigated using an electrochemical permeation technique and etching treatment (0.2% HF solution). From the hydrogen permeation transients obtained, the effective hydrogen concentration (CH), apparent hydrogen diffusion coefficient (Dlag) and breakthrough time (tlag) were estimated by using the time lag method in addition to the steady state permeation current density (P∞). It was found that at a fluence of less than 1 × 1016/cm2 almost all hydrogen permeation transients of the implanted nickel specimens were affected by the defects (vacancy, compressive stress and so on) generated during ion implantation process. At a high fluence of 1 × 1017/cm2 the hydrogen permeation transient had a specific behavior because of the formation of amorphous phase for P, the structure change from fcc-structure to bcc-structure for S and both of them for the mixture (P and S). However, a synergistic effect of P and S was not observed on the hydrogen permeation transient. The behavior of these parameters depending on fluence and implanting element was discussed in terms of an amount of hydrogen entry site, the degree of defects, the properties of amorphous phase and structure and so on.

The stress corrosion cracking (SCC) of the commercial austenitic stainless steels, type 304 and type 316 has been extensively investigated as functions of applied stress, sensitizing temperature, sensitizing time and the environmental factors such as pH, anion concentration, anion species (chloride ions and sulfate ions), test temperature, applied potential and inhibitor concentrations of chromate and molybdate by using a constant load method. We have found that the steady state elongation rate obtained from corrosion elongation curve becomes a relevant parameter for predicting time to failure and also for criterion on assessment of whether SCC takes place or not. The value of t ss / t f is also found to become an indicator for assessment of whether SCC takes place or not. Furthermore, from the results obtained, it is deduced that a unified SCC mechanism is qualitatively proposed to explain both of transgranular SCC (TGSCC) and intergranular SCC (IGSCC), where the unified SCC mechanism is basically based on a film rupture- formation event at crack tips.

Accepted manuscript version. The final publication is available at Springer via http://doi.org/10.1186/s40712-015-0046-7. Background The environment-induced cracking (EIC) of as-annealed Ni3(Si,Ti) and Ni3(Si,Ti) with 2Mo has been researched as functions of applied stress, chloride ion concentration, test temperature, and pH. Methods The investigation of EIC was carried out by applying a constant method in NaCl solutions. Results The EIC susceptibility of both intermetallic compounds increased with increasing test temperature and Cl− ion concentration and increased with decreasing pH. The fracture surface morphologies of Ni3(Si,Ti) was intergranular while Ni3(Si,Ti) with 2Mo was a mixture of intergranular and transgranular, and the relationship between log t f (time to failure) and log l ss (steady-state elongation rate) became the identical straight line irrespective of applied stress, chloride ion concentration, test temperature, and pH, which means that l ss becomes a relevant parameter for predicting t f. The EIC susceptibility of Ni3(Si,Ti) with 2Mo was lower than that of Ni3(Si,Ti), which showed the advantageous effect of Mo. Conclusions From the results acquired, EIC of both the compounds was indicated to take place by hydrogen embrittlement (HE).

The stress corrosion cracking (SCC) of the austenitic stainless steels of types 304, 310 and 316 was investigated as a function of test temperature in boiling saturated magnesium chloride solution (MgCl 2 ) using a constant load method. Both of types 304 and 316 exhibited similar corrosion elongation curves, while the corrosion elongation curve of type 310 was different from those of types 304 and 316, in terms of the three parameters such as time to failure ( t f ), steady-state elongation rate ( l ss ) and transition time to time to failure ratio ( t ss / t f ) obtained from the corrosion elongation curves for these stainless steels. The relationship between the time to failure and a reciprocal of test temperature fell in two straight lines on a semi-logarithmic scale as well as the relationship between the steady-state elongation rate and a reciprocal of test temperature. These regions were considered to correspond to a SCC-dominated region and a hydrogen embrittlement (HE)-dominated region from the value of ( t ss / t f ) and the fracture appearance. The relationship between the steady state elongation rates versus time to failure on a logarithmic scale became a straight line, whereas the slopes of the line for the stainless steels were different with the different fracture mechanism such as SCC and HE. It was found that the linearity of the relationship can be used to predict the time to failure for the stainless steels in the corrosive environment. In addition, type 310 did not suffer from HE, which means that type 310 showed only SCC. This would be explained by whether or not a formation of α ′-martensite takes place.

The stress corrosion cracking ( SCC ) of a commercial austenitic stainless steel type 316 was investigated as functions of applied stress, sensitizing temperature ( 800 K to 1300 K for 86.4 ks ) and sensitizing time ( 0.36 ks to 1.08 Ms at 923 K ) in 0.82 kmol/m sulphuric acid ( H2SO4 ) solution at 353 K by using a constant load method. The three parameters ( lss, steady state elongation rate, tss, transition time, tf , time to failure ) were obtained from corrosion elongation curves as shown in Fig. 1 and were divided into three regions against applied stress irrespective of sensitizing temperature and sensitizing time, which corresponded to the stressdominated, SCCdominated and corrosiondominated regions, respectively. Fig. 2 shows an example of the relationships between applied stress and tf for the specimens sensitized with various sensitizing times, where the relationships between applied stress and lss correspond to those in Fig. 2. The value of tss/tf was constant independent of applied stress in the SCC-dominated region, whereas it was dependent of sensitizing temperature and sensitizing time. Furthermore, the maximum applied stress and the minimum applied stress in the SCCdominated region depended upon sensitizing temperature and sensitizing time. Fig. 3 shows a representative example of the relationships between lss and tf at the sensitizing temperatures of 923 K and 1123 K for 86.4 ks. In the SCCdominated region, the logarithm of lss was a linear function of the logarithm of tf, showing that lss became a relevant parameter for prediction of tf, although the slope depended upon sensitizing temperature and sensitizing time. The slope was smaller for the sensitized specimens than for the solution annealed specimens. At a sensitizing time of more than 360 ks, the SCC susceptibility was found to reduce because of Cr healing. In addition, sulphate ions were found to become much more aggressive to SCC than chloride ions for the specimens sensitized at a sensitizing temperature of 923 K with a sensitizing time of more than 86.4 ks. From the results obtained, the effect of sensitization on SCC, the role of sulphate ions and an intergranular mechanism were discussed in comparison to the results obtained in 0.82 kmol/m HCl solution. Fig. 1 Corrosion elongation curves at various constant applied stresses for the specimens sensitized at 923 K for 86.4 ks.

超音波化学反応は有害有機物質の分解•無害化に有効であることが報告されているが，有害有機物質の無害化においては何らかの副生成物の生成が示唆される．しかし，超音波分解生成物の詳細な同定やそれらが実際に生物に対し無害であるかどうかについての研究報告はほとんどないのが現状である．そこで本研究では，水処理過程で発生するクロロアセトンの毒性とその超音波分解過程での毒性を酵母の増殖速度及び増殖挙動における代謝熱量から解析する熱量測定法で評価した．熱量測定法では，一般的に微生物の評価に用いられるコロニー計数法と比較すると，微生物の増殖動態を定量的かつ定性的に評価できることが示唆された．

The corrosion behavior of carbon steel with and without shelter at four test sites (four cities) in the south of Vietnam was investigated in terms of the environmental factors such as average relative humidity, rainfall, sulphur dioxide and chloride depositions, and various exposure periods. The mass losses of the specimens with shelter at four test sites were related to SO2 concentration at each site. Without shelter, the mass loss at HoChiMinh was lower than that with shelter, whereas those of the other sites were higher without shelter than with shelter. Although the corrosion behavior at HoChiMinh was difficult to explain based on the environmental factors, it was estimated from a protective corrosion products caused by a synergistic effect among SO2 concentration, rain and sunlight.

The atmospheric corrosion of marble was evaluated in terms of SO 2 concentration as air pollution and climatic factors such as rainfall, relative humidity, temperature and so on under the field exposure. Marble of calcite type (CaCO 3 ) was exposed to outdoor atmospheric environment with and without a rain shelter at four test sites in the southern part of Vietnam for 3-month, 1- and 2-year periods from July 2001 to September 2003. The thickness loss of marble was investigated gravimetrically. X-ray diffraction and X-ray fluorescent methods were applied to study corrosion products on marble. The corrosion product of marble was only gypsum (CaSO 4 · 2H 2 O) and was washed out by rain under the unsheltered exposure condition. It was found that the most substantial factors influencing the corrosion of marble were rainfall, SO 2 concentration in the air and relative humidity. Based on the results obtained, we estimated the dose–response functions for the atmospheric corrosion of marble in the southern part of Vietnam.

The sonochemical decolorization and decomposition of azo dyes, such as C. I. Reactive Red 22 and methyl orange, were performed from the viewpoints of wastewater treatment and to determine the reaction kinetics. A low concentration of the azo dye solution was irradiated with a 200 kHz and 1.25 W/cm2 ultrasound in a homogeneous aqueous solution. The azo dye solutions were readily decolorized by the irradiation. The sonochemical decolorization was also depressed by the addition of the t-butyl alcohol radical scavenger. These results indicated that azo dye molecules were mainly decomposed by OH radicals formed from the water sonolysis. In this paper, we propose a new kinetics model taking into account the heterogeneous reaction kinetics similar to a Langmuir-Hinshelwood mechanism or an Eley-Rideal mechanism. The proposed kinetics model is based on the local reaction site at the interface region of the cavitation bubbles, where azo dye molecules are quickly decomposed because an extremely high concentration of OH radicals exists in this region. To confirm the proposed kinetics model, the effects of the initial concentration of azo dyes, irradiated atmosphere and pH on the decomposition rates were investigated. The obtained results were in good agreement with the proposed kinetics model.

This paper was concerned with evaluating the effect of dry deposition on deterioration of marble. Two types of marble were exposed to atmospheric environment with a rain shelter at four exposure sites in the south of Vietnam for 3-month, 1-year and 2-year periods from July 2001 to September 2003. X-ray diffraction (XRD) and X-ray fluorescent (XRF) methods were applied to study the products of marble deterioration. Ion chromatography was used to analyze dry depositions on marble. The main product of marble deterioration was gypsum (CaSO4·2H2O). The amount of sulfate ions deposited on marble was found to be proportional to SO2 concentration in the air, relative humidity and duration of the exposure. In addition, sulfation of marble caused by SO2 at a relative humidity lower than 70% is almost half of that at relative humidity higher than 70%. Moreover, marble consisting of calcite (CaCO3) was more sensitive to SO2 than marble consisting of dolomite (CaCO3 and MgCO3). A good relation between the amount of sulfate ions deposited on marble and SO2 concentration in the air suggested that marble could serve as an indicator for atmospheric pollution by SO2.

Metal nanoparticles with a narrow size distribution could be prepared by sonolysis of aqueous solutions of metal cations in the presence of surfactants such as sodium dodecyl sulfate, polyethylene glycol monostearate, etc. The role of the surfactans is not only to stabilize formed particles, but also to produce reductive radicals in pyrolysis or hydrogen abstraction of OH radicals from surfactants. Particles with a smaller size could be obtained in a faster reduction rate with dilute metal cations concentration. Pt(IV) is consecutively reduced in two steps to Pt(0)via Pt(II). By comparing the sonolytical reduction withγ-ray radiolysis, two kinds of organic reducing radicals are proposed to contribute to the reduction. One (Rab) is an intermediate radical which is produced by hydrogen abstraction of OH radical from surfactant and effective only on the reduction of Pt(II) to Pt(0). The other (Rpy) is also an intermediate radical which is produced by thermal decomposition of surfactant at the interface between the cavity and bulk solution and effective on the reduction of Pt(IV) to Pt(II).

The stress corrosion cracking (SCC) behavior of the commercial austenitic stainless steels, Type 304 and Type 316 (UNS S30400 and UNS S31600), has been investigated in acidic solutions to ...

The stress corrosion cracking (SCC) of the commercial austenitic stainless steels type 304 and 316 was investigated as functions of strain rate, test temperature and pH in acidic chloride solutions using a slow strain rate technique. From the comparison between the parameters such as time to failure (tf), maximum stress (σm) and strain at tf (ef) obtained in inert and corrosive environments, the relationships between tfCl(corrosive)/tfW(inert), σmCl/σmW and efCl/efW versus strain rate were divided into three regions for type 304 and 316 specimens: the strain rate-dominated, SCC-dominated and corrosion-dominated regions, respectively. Furthermore, it was found that the relationship between tfCl/tfW and σmCl/σmW in the SCC-dominated region became a good straight line for the type 304 and 316 specimens irrespective of strain rate, test temperature and pH. This suggests that σmCl/σmW became the parameter for predicting tf. The results obtained were compared with those obtained from the constant load method and are discussed in terms of the formation of slip steps, dissolution current and film formation rate.

By using a constant load method and inductive coupled plasma (ICP) spectrometer, the metal dissolution and maximum stress (σmair) of type 430 ferritic stainless, and type 304 and type 316 austenitic stainless steels during stress corrosion cracking (SCC) process were investigated under a constant applied stress condition in 0.82 kmol/m3 hydrochloric acid (HCl) and 0.82 kmol/m3 acidic chloride (pH 1.0) solutions. The σmair of the specimens interrupted at various elongations up to failure under the same constant applied stress condition was measured at room temperature and air atmosphere by using an Instron type tensile machine. The metal dissolution behaviour of the stainless steels changed at the transition time (tss) in the corrosion elongation curve; that is, the dissolution rate before tss was larger than that after tss. The σmair decreased gradually with increasing elongation, but showed a rapid small reduction at tss and then decreased with elongation with a sudden reduction around fracture. The results obtained were discussed in terms of the amount of metal ions per the number of cracks, selective dissolution, reduction in cross sectional area and so on.

The stress corrosion cracking (SCC) of a commercial austenitic stainless steel type 304 was investigated as functions of chloride concentration, chromate concentration and test temperature under a constant applied stress condition in 0.82 kmol/m3 sulphuric acid solution by using a constant load method. From the dependence of the three parameters ( l ss , steady state elongation rate; tss, transition time; tf, time to failure) obtained from corrosion elongation curve on chloride/chromate concentrations and test temperature, a parameter for predicting time to failure and critical values of chromate concentration and test temperature, below which little SCC takes place, were estimated. In addition, a transgranular SCC mechanism was qualitatively inferred and then the effect of chromate and chloride on SCC behavior was discussed.

Hydrogen permeation caused by corrosion under a cyclic wet (2 h)–dry (10 h) SO 2 condition was investigated for a high strength steel of MCM 430 by using an electrochemical technique in addition to the corrosion behavior obtained from weight loss measurement and the determination of corrosion products by using X-ray diffraction method. The hydrogen content converted from hydrogen permeation current density was observed in both wet and dry periods. The origin of proton was estimated to be from (1) the hydrolysis of ferrous ions, (2) the oxidation of ferrous ions and ferrous hydroxide, and (3) hydrolysis of SO 2 and formation of FeSO 4 , but not from the dissociation of H 2 O. With respect to the determination of the corrosion products consisting of inner (adherent) and outer (not adherent) layers, the outer layer is composed of α-FeOOH, amorphous phase and γ-FeOOH, where α-FeOOH increases with the increase in the wet–dry cycle, and amorphous phase shows the reverse trend. The corrosion product in the inner layer is mainly Fe 3 O 4 with them. On the basis of the results obtained, the role of the dry or wet period, the effect of SO 2 and the corrosion process during the cyclic wet–dry periods were discussed.

The stress corrosion cracking (SCC) of a commercial austenitic stainless steel type 316 was investigated as a function of sensitizing time (3.6 ks to 1.08 Ms at a sensitizing temperature of 923 K) and test temperature (333–373 K) in 0.82 kmol/m3 hydrochloric acid (HCl) solution by using a constant load method. From the applied stress dependence of the three parameters ( l ss , steady state elongation rate, tss, transition time, tf, time to failure), the relationships between applied stress and the three parameters were divided into three regions that are dominated by either stress, SCC or corrosion. In the SCC-dominated region, the log l ss was a linear function of the logtf regardless of applied stress and test temperature for each sensitized specimens, showing that l ss became a useful parameter for prediction of tf. Furthermore, the results obtained indicated that the degree of sensitization increased with increasing sensitizing time, reached a maximum at a sensitizing time of around 360 ks and then began to decrease at 1.08 Ms by Cr healing. On the basis of the results obtained, the effect of sensitizing time on SCC and the IGSCC mechanism were discussed.

The stress corrosion cracking (SCC) of a commercial austenitic stainless steel type 316 was investigated as a function of sensitizing temperature (800–1300 K) and test temperature (333–373 K) in 0.82 kmol/m 3 sulphuric acid solution by using a constant load method, to compare with that already obtained in 0.82 kmol/m 3 hydrochloric acid solution. The three parameters ( l ss , steady state elongation rate, t ss , transition time, t f , time to failure) were obtained from corrosion elongation curve and were divided into three regions of applied stress, irrespective of sensitizing temperature, which are dominated by either stress, SCC or corrosion. In the SCC-dominated region, the logarithm of l ss was a linear function of the logarithm of t f regardless of applied stress and test temperature for each sensitized specimens, showing that l ss became a useful parameter for prediction of t f , although the slope depended upon sensitizing temperature. The maximum applied stress, the minimum applied stress and the value of t ss / t f in the SCC-dominated region depended upon sensitizing temperature. Specifically, at a sensitizing temperature of around 950 K the maximum applied stress was smaller at a test temperature of 353 K, but larger at a test temperature of 333 K than that of the solution annealed specimens. In addition, sulphate ions were found to become more aggressive than chloride ions for the SCC susceptibility of the specimens with the most severe sensitization. On the basis of the results obtained, the effect of sensitization on SCC, the role of sulphate ions and an intergranular mechanism were discussed in comparison to the results of the sensitized specimens obtained in 0.82 kmol/m 3 HCl solution.

The stress corrosion cracking (SCC) of a commercial austenitic stainless steel type 316 was investigated as a function of sensitizing temperature (750–1300 K) and test temperature (333–373 K) in 0.82 kmol/m 3 hydrochloric acid (HCl) solution by using a constant load method. From the applied stress dependence of three parameters ( i ss : steady state elongation rate, t ss : time interval of SCC-dominated failure, t f : time to failure), the relationships between applied stress and the three parameters were divided into three regions that are dominated by either stress, SCC or corrosion. In the SCC-dominated region, the logarithm of i ss was a linear function of the logarithm of t f irrespective of applied stress and test temperature, although its slope depended upon sensitizing temperature. This result showed that the i ss became a useful parameter for prediction of t f as well as the case of the solution annealed specimens. Furthermore, at the most severe sensitization with a sensitizing temperature of around 1000 K, the slope of the linear function of log i ss vs. log t f showed a minimum, the value of t ss / t f was a maximum and the fracture appearance was an intergranular mode. On the basis of the results obtained, the effect of sensitization on SCC was discussed in comparison to the results for the solution annealed type 316 and a qualitative intergranular SCC (IGSCC) mechanism was inferred.

The stress corrosion cracking (SCC) of a commercial austenitic stainless steel, Type 304 (UNS S30400), has been investigated as a function of sensitizing temperature (800 K to 1,300 K) and...

Stress corrosion cracking (SCC) of a commercial austenitic stainless steel Type 304 (UNS S30400) was investigated as a function of inhibitor concentration (chromate and molybdate), applied...