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To Overcome Never Ending Corrosion Problems
Masao OKUBO
2002 Volume 51 Issue 11 Pages
1181-1189
Published: November 15, 2002
Released on J-STAGE: June 03, 2009
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Hiroshi IMAGAWA
2002 Volume 51 Issue 11 Pages
1190-1196
Published: November 15, 2002
Released on J-STAGE: June 03, 2009
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Yutaka TSURU, Yuji TAMAE, Youko NAGAI, Tomomi NAKAHATA, Katsu MATSUI
2002 Volume 51 Issue 11 Pages
1197-1202
Published: November 15, 2002
Released on J-STAGE: June 03, 2009
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The galvanic cell current between a steel plate and a platinum wire cathode immersed in oxygenated lime water containing sodium chloride and various amino acids as inhibitors was measured, permitting continuous monitoring and evaluation of corrosive effects of the solution pH and of the efficacy of the corrosion inhibitors.
A relation of log[Cl
-]=0.41log[OH
-]-0.17 was found in a criterion concentration between Cl
- and OH
- for the onset of pitting corrosion on the steel surface. It was also found that the amino acids functioned as corrosion inhibitors. Especially, the composite additive consisting of DL-glycine and DL-aspartic acid, or of DL-serin and DL-aspartic acid effectively adsorbed on the steel surface and greatly suppressed the pitting corrosion of the steel.
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Hiroaki FUJII, Toshihiro KUBO, Hiroaki SHIMIZU, Yukio KATANO, Toshio S ...
2002 Volume 51 Issue 11 Pages
1203-1209
Published: November 15, 2002
Released on J-STAGE: June 03, 2009
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It is important to evaluate the corrosion extent of buried pipes for maintaining them. But it requires much time and much cost to get corrosion data for evaluating the corrosion extent of buried pipes. So we have tried to evaluate the corrosion extent simply by using corrosion resistance based on A.C. impedance measurment method in solution containing many soluble compo-nents extracted from soil.
We have investigated the relationship between every corrosion resistance and analysis value of water extracted from soil, weight loss by the corrosion and corrosion rate of buried ductile iron pipes and have established the simple prediction method of the depth of external corrosion by the corrosion resistance and soil quality judged visually on the spot.
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Akinobu NISHIKAWA, Hidemasa NONAKA
2002 Volume 51 Issue 11 Pages
1210-1217
Published: November 15, 2002
Released on J-STAGE: June 03, 2009
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Cathodic protection is being applied to buried heat supply pipelines in district heating and cooling systems. However, there is possibility of corrosion due to the inner jumping current occurring at insulating joints.
In this study, a corrosion protection method which makes the bare pipe behave as if it were coated on its inner surface with resin or a resin tube was developed and evaluated. This method utilizes the behavior that the passivity of corrosion-resistant material restrains the outflow of current from its surface. As a result of various experiments, it has been found to be most effective to use a pipe made of titanium with insulating joints at both ends for reducing the inner-jumping current.
This corrosion protection method has already been adopted at worksites and confirmed in its effect.
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Atsushi NONAKA, Hidemasa NONAKA
2002 Volume 51 Issue 11 Pages
1218-1222
Published: November 15, 2002
Released on J-STAGE: June 03, 2009
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In order to evaluate the corrosion of copper which is used as an absorber vessel material in the absorption refrigeration cycle, electrochemical measurements of copper in the condition of a thin-solution layer, which is 1mm in thickness, of concentrated aqueous solution of lithium bromide in argon atmosphere were made.
As a result, values of corrosion rate in the condition of a thin-solution layer were 3 to 6 times larger than in the immersed condition regardless of whether there was an inhibitor or not. This difference seems to be due to the following reason. As the argon gas phase above the solution contained a little air (oxygen), the oxygen concentration was higher in the condition of a thin-solution layer than in the immersed condition. Therefore, the values of free corrosion potential in the condition of a thin-solution layer became more noble than in the immersed condition, and cathodic diffusion limit current density in the condition of a thin-solution layer increased, compared with that in the immersed condition.
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Hitoshi UCHIDA, Masato YAMASHITA, Satoshi HANAKI, Hiroyuki KAGAWA
2002 Volume 51 Issue 11 Pages
1223-1228
Published: November 15, 2002
Released on J-STAGE: June 03, 2009
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Titanium nitride (TiN) films were prepared onto stainless steels by nitrogen ion irradiation during titanium vapor deposition, i.e., ion mixing and vapor deposition (IVD) technique. The influence of preparation conditions on surface morphology, preferred orientation and microstructure of TiN films were investigated. The TiN films with preferred orientation of {111} or {100} plane were characterized by the respective appearance of triangular or grainy crystals, which were strongly dependent of preparation conditions. The area ratio of pinhole defects in the TiN films evaluated by electrochemical measurement successfully decreased with the orientation of plane preferring {100}. On the contrary, they increased with the orientation of plane preferring {111}. Here, the correlation between preferred orientation and pinhole defect of TiN films was discussed with the optimum preparation conditions for the corrosion-protective dry coating films.
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Soshu KIRIHARA, Yoshinari MIYAMOTO
2002 Volume 51 Issue 11 Pages
1229-1234
Published: November 15, 2002
Released on J-STAGE: June 03, 2009
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Keiji HOUJOU, Kiyohito HIRAI, Kotoji ANDO, Min-Cheol CHU, Sinya MATUSI ...
2002 Volume 51 Issue 11 Pages
1235-1241
Published: November 15, 2002
Released on J-STAGE: June 03, 2009
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High temperature oxidation behavior of Si
3N
4-based ceramics was investigated systematically. The test has been made at 13000C in dry air environment up to 2000 hours. The Si
3N
4 specimens tested were as follows. a) S-1: Si
3N
4 added 8mass% Y
2O
3. b) S-2: Si
3N
4/SiC added 8mass% Y
2O
3. c) S-3: Si
3N
4 added 5mass% Y
2O
3 and 3mass% Al
2O
3. d) S-4: Si
3N
4/SiC added 5mass% Y
2O
3 and 3mass% Al
2O
3. The main conclusions are as follows. 1) Oxidized layer thickness of S-3 and S-4 were much thicker than those of S-1 and S-2. 2) Relationship between the oxidation time and oxidized layer thickness obeyed the parabolic law in all specimens. 3) The Y concentration under the oxidized layer was reduced considerably. The zone was defined as diffused layer. The thickness of diffused layer was very large in S-3 and S-4 samples. 4) Crystalline phases in the oxidized layer were mainly SiO
2 and Y
2Si
2O
7. 5) Effect of SiC composition on the oxidation behavior was slight.
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Noriyuki MIYAZAKI, Toru IKEDA, Toshihiro KOMURA
2002 Volume 51 Issue 11 Pages
1242-1247
Published: November 15, 2002
Released on J-STAGE: June 03, 2009
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Al
2O
3/YAG eutectic composite has been developed for a structural material used in ultra high temperature environments more than 1500°C such as in a gas turbine. Creep behavior is one of the important material properties in ultra high temperature materials. In the present study, we propose image-based finite element analysis for estimating the steady state creep behavior of the Al
2O
3/YAG eutectic composite. In the image-based finite element analysis, micro-structure of the material taken by a SEM is modeled into a finite element mesh using a software for image processing. Then finite element creep analysis is carried out to obtain the steady state creep behavior of the Al
2O
3/YAG eutectic composite by using steady state creep constitutive equations for both Al
2O
3 single crystal and YAG single crystal. The results of steady state creep behavior obtained from the image-based finite element analysis are compared with the experimental results. It is found that the steady state creep behavior of the Al
2O
3/YAG eutectic composite is accurately estimated by the image-based finite element analysis. Furthermore, we examine the effect of volume fractions of the constituents on the steady state creep behavior of the Al
2O
3/YAG eutectic composite.
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Takashi YAMASAKI, Hiroyuki MIYAMOTO, Takuro MIMAKI
2002 Volume 51 Issue 11 Pages
1248-1252
Published: November 15, 2002
Released on J-STAGE: June 03, 2009
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Stress corrosion crack (SCC) propagation tests have been carried out in 1kmol/m
3 sodium nitrite aqueous solution to investigate SCC propagation behaviour of ultra-fine grained (UFG) copper produced by equal-channel angular pressing (ECAP) technique. SCC propagation tests have been performed on Compact Tension (CT) specimens under constant load. Phenomenon of SCC propagation was estimated from the crack propagation rate (
da/dt) and the stress intensity factor (
KI). Relationship between the
da/dt and the
KI in UFG copper could be divided into region I and II. The
da/dt increased with the
KI in region I. The
da/dt was independent of the
KI and showed constant value in region II. SCC in UFG copper had propagated along grain boundary. On the other hand, the transgranular SCC propagation was observed in polycrystalline copper. The anodic dissolution mechanism should be considered for the SCC of UFG and polycrystalline coppers. The SCC propagation in UFG copper could be understood from the film rupture and dissolution if the grain boundary sliding is considered as a dominant slip event.
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Jin-Quan XU, Yoshiharu MUTOH
2002 Volume 51 Issue 11 Pages
1253-1258
Published: November 15, 2002
Released on J-STAGE: June 03, 2009
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Frictional contact interface edge appears in the fretting pair of a mechanical structure, and reduces its fatigue life. Due to the frictional force on the contact interface, the singular behavior at the edge is different from that of a bonded wedge, and is also different from that obtained by Hertz theory for elastic contact problems. In this paper, the singular stress field at a frictional contact interface edge is deduced theoretically. Based on the eigenequation which determines the singular order, the optimum geometry of the contact pad is discussed. Numerical analysis by using the boundary element method is also carried out to verify the theoretical results. It is found that the singularity depends not only on the material combination and the geometry shape of the frictional interface edge, but also on the coefficient of friction. Moreover, the singularity can be even stronger than 1/√
r.
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Hisao MATSUNAGA, Yukitaka MURAKAMI
2002 Volume 51 Issue 11 Pages
1259-1266
Published: November 15, 2002
Released on J-STAGE: June 03, 2009
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Nobuyuki TAKEUCHI, Yuji YAMASAKI, Shingo ISHIDA
2002 Volume 51 Issue 11 Pages
1267-1270
Published: November 15, 2002
Released on J-STAGE: June 03, 2009
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Effects of sintering additives on mechanical and electrical properties of Gd-doped barium titanate ceramics have been studied by measuring their electrical resistivity, bending strength, and ESR spectra. The bulk density of the sample prepared by sintering at 1100°C with small amounts of BaB
2O
4 doped as sintering aids was as high as 90% of the theoretical value. Semiconducting BaTiO
3 was obtained by sintering the BaB
2O
4-doped samples at 1100°C. The electrical resistivity of the 3mol% BaB
2O
4-doped sample sintered at 1100°C was the lowest in all samples and its PTCR jump was more than 4 orders of magnitude. In addition, the bending strength of the sample was the highest in all samples and the value was close to that of the sample sintered at 1380°C without sintering additives. The line width of the ESR signal of Gd
3+ observed in the sample sintered at 1100°C with BaB
2O
4 was almost equal to that in the sample sintered at 1380°C without sintering additives. The result showed that in the samples doped with BaB
2O
4 as a sintering aids, Gd
3+ ions were dissolved uniformly in BaTiO
3 grains at a sintering temperature of 100°C.
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Yukuo SHINOZAKI, Kazuo SHIMADA
2002 Volume 51 Issue 11 Pages
1271-1277
Published: November 15, 2002
Released on J-STAGE: June 03, 2009
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Incombustible radio wave (RW) absorbers are developed by using inorganic carbon fiber-reinforced superlightweight polymer-modified mortars in place of conventional organic materials. The RW absorbers have a satisfactory RW absorbing performance for higher frequencies abve 30MHz. The RW absorbers can also be applied to microwave absorbers which are required to be more incombustible and to be able to absorb microwaves above 1GHz. The development of such materials makes it possible to design a highly fire-resistant anechoic chamber that has not been considered impossible to make until now.
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Nobuaki OTSUKI, Takahiro NISHIDA, Hiroshi MINAGAWA, Wanchai YODSUDJAI
2002 Volume 51 Issue 11 Pages
1278-1283
Published: November 15, 2002
Released on J-STAGE: June 03, 2009
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The purpose of this study is to investigate the durability of reinforced concrete member on land repaired by electrodeposition. In this study, there are two series of tests. In the first series, the reinforced concrete specimen after electrodeposition has been exposed outdoor for 2 years. Then, the durability of specimen after electrodeposition is investigated by measurement of the ratio of crack closure and the apparent coefficient of water permeability. Also, in the second series, the existing reinforced concrete member after electrodeposition has been left there for 2 years. Then, the durability of existing member after electrodeposition is investigated by measurement of ratio of crack closure, half-cell potential, polarization resistance, and carbonation depth. As a result, it can be derived that the repair effect of the electrodeposition method is maintained after the reinforced concrete repaired by electrodeposition has been exposed for 2 years.
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II: Impact Problems and Numerical Simulation
Toshio IMAKI, Sunao TOKURA
2002 Volume 51 Issue 11 Pages
1284-1289
Published: November 15, 2002
Released on J-STAGE: June 03, 2009
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