巻号一覧
54 巻, 4 号
April
選択された号の論文の13件中1～13を表示しています
- |<
- <
- 1
- >
- >|
研究
研究
-
Yukio Makino, Masashi Sakaguchi, Jun Terada, Katsuya Akamatsu2007 年 54 巻 4 号 p. 219-225
発行日: 2007年
公開日: 2007/07/13
ジャーナル オープンアクセスSPS consolidation of two ultrafine α-alumina powders (TM-alumina with 100nm and AA-alumina with 230nm) was examined under the two pressurizing conditions of 30MPa and 100MPa. It was found that densification behavior under 30MPa was influenced by the grain size of raw powder alumina and the influence of grain size on the densification was remarkably suppressed under 100MPa. It was also indicated that the grain growth was fairly suppressed in the consolidation of TM-alumina powder even when the powder was consolidated at a higher temperature than 1300°C. Further, the growth of crystallite was suppressed by increasing the applied pressure from 30MPa to 100MPa. Under the condition of 100MPa, nano-structural aluminas with less than 300nm and about 500nm were synthesized by consolidating TM-alumina at 1150°C and AA-alumina at 1200°C, respectively, indicating that SPS method has high capabilities of synthesizing nano-structured ceramics.抄録全体を表示PDF形式でダウンロード (1140K) -
Jiro Abe, Masafumi Kobune, Tetsuo Yazawa, Hiroshi Nishioka2007 年 54 巻 4 号 p. 226-231
発行日: 2007年
公開日: 2007/07/13
ジャーナル オープンアクセスHigh-density ceramics with compositions of (Bi0.5-xNa0.5TiO3)0.94(BaTiO3)0.06 (BNBT-6), where x=0−0.03, were fabricated to develop potentially useful lead-free piezoelectric materials with high mechanical quality factors, Qm. Effects of Bi-deficiency on the physical properties of the fabricated ceramics were investigated. Microstructures of the samples with a Bi-deficiency of x≥0.015 showed no appreciable grain boundaries. This is due to the liquid-phase sintering that occurs for a Bi-deficiency concentration of x≥0.015. The mechanical quality factors for the radial vibration mode and the thickness vibration mode exhibited a maxima at x=0.022 and 0.024 with values of 674 and 128, respectively. The temperature coefficients of resonant and antiresonant frequencies (TCF) of the BNBT-6 samples with x=0.019−0.030 were almost constant with TCFfr1=−400 ppm/°C for the fundamental resonant frequency and TCFfa1=−320 ppm/°C for the fundamental antiresonant frequency, respectively. This method of creating a deficiency of a very small quantity of Bi in the BNBT-6 composition produces substantial improvement in Qm characteristics without deterioration of other piezoelectric parameters.抄録全体を表示PDF形式でダウンロード (802K) -
中根 純一, 神島 謙二, 柿崎 浩一, 平塚 信之2007 年 54 巻 4 号 p. 232-235
発行日: 2007年
公開日: 2007/07/13
ジャーナル オープンアクセスZ-type hexagonal ferrite samples with Ba3Co2-2xLixFe24+xO41 (x=0∼1.0) were prepared from stoichiometric mixtures of BaCO3, CoO, Li2Co3 and α-Fe2O3, by calcinning at 1250°C and then sintering at 1275°C. The single phase of the Z-type was confirmed for the crystal structure of these samples with x=0∼0.5 by X-ray diffraction analysis. The sample with x=0 showed μ' of 8 at 50MHz. The maximum μ' was 24.5 at x=0.3. The Snoek's product of μ' × fr was 9GHz at x=0 and then increased to 15GHz at x=0.1∼0.3. The bulk density took a maximum at x=0.3, and the coercivity had a minimum at x=0.3. Therfore, high frequency properties of Co2Z ferrite are specifically improved by the Li+−Fe3+ ions substitution with x=0.3.抄録全体を表示PDF形式でダウンロード (466K)
研究速報
-
Shoichi Nasu, Shinji Nagata, Sorin Kihara, Katsumi Takahiro, Tatsuo Sh ...2007 年 54 巻 4 号 p. 236-240
発行日: 2007年
公開日: 2007/07/13
ジャーナル オープンアクセスWe examined compatibility of lithium oxide (Li2O, tritium breeding materials) single crystals with nickel (Ni) foils by Rutherford backscattering spectroscopy (RBS) with He ions and protons. After heating the samples at 673 K for 3600 s without electric fields, or after applying the electric field of 200 V mm−1 between the Ni contacted surface (positive) and the free back surface (negative) of Li2O crystals at 673 K for 3900 s, any reactions were not observed between the Ni foils and the Li2O crystals. On the other hand, after applying the electric field of 300 V mm−1 at 353 K for 600 s, heavy reactions were observed. That is, lithium and oxygen atoms migrated into the Ni foil, and Ni atoms diffused into the Li2O crystals. In addition, we examined the effect of the reverse electric field on reactions, and found a heavier reaction for the attractive force of lithium ions.抄録全体を表示PDF形式でダウンロード (438K)
特集：硬質材料の製造・性能・評価技術の新たな展開
総報
-
松原 秀彰2007 年 54 巻 4 号 p. 242
発行日: 2007年
公開日: 2007/07/13
ジャーナル オープンアクセスPDF形式でダウンロード (99K)
受賞記念講演
-
棚瀬 照義2007 年 54 巻 4 号 p. 243-250
発行日: 2007年
公開日: 2007/07/13
ジャーナル オープンアクセスWC-Co cemented carbide with grain size less than 1μm is a very important tool material because it has high hardness and strength, and easily yields mirror finish and a sharp edge. On manufacturing the alloy, grain growth control is necessary. This report introduces effects of duplex addition of VC and Cr3C2 as a grain growth inhibitor.
For investigating basic characteristics, submicro-grained WC-12mass%Co alloys with various amount of VC and Cr3C2 and with medium carbon content were used as a specimen which were heated up in vacuum to certain temperatures and immediately cooled. Some of them were fully sintered at 1380°C for 1 hr. They were examined by density measurement, TG-DTA, SEM, HRTEM, etc. Coarse-grained alloys were also used for analyzing binder composition by EPMA. Mechanical properties were measured using two series of submicro-grained specimens as above. One has fixed Cr3C2 content and varied VC content. The other is vice versa. They were vacuum-sintered at 1380°C for 1hr and HIP treated.
Major results are as follows. (1) Similar to the alloy mono-doped with VC, duplex addition of VC and Cr3C2 (a) lowered liquidus temperature, (b) retarded densification from solid stage of sintering and abruptly increased density later, (c) remarkably controlled grain growth from solid stage, (d) formed micro-facets on WC grains composed of WC(1010) and WC(0001), and segregation of V mainly on WC(0001), and (e) decreased W content in the binder phase.
(2) In the alloy series with fixed Cr3C2 content, grain size decreased with increasing VC addition to 0.5mass% and then was saturated, resulting in the corresponding change in hardness and fracture toughness. Bending strength and compressive strength had a peak at 0.2mass% and 0.5mass% addition of VC, respectively.
(3) In the alloy series with fixed VC content, change in grain size was similar to that of the other alloy series though the critical value was 0.6mass%Cr3C2, and hardness and fracture toughness showed the same tendency as above. Bending strength was almost constant, and compressive strength increased up to 0.6mass%Cr3C2, then was saturated in the scope of this experiment. These changes in strength could be understood by considering the change in grain size, the fracture mechanism and the (V,W)C phase which precipitates in the binder phase over 0.5mass% addition of VC.抄録全体を表示PDF形式でダウンロード (1793K) -
大久保 貴広, 酒井 秀樹, 阿部 正彦, 西山 勝廣2007 年 54 巻 4 号 p. 251-259
発行日: 2007年
公開日: 2007/07/13
ジャーナル オープンアクセスFine particles of TiB2, ZrB2, and HfB2 were prepared by metallothermic reduction (MTR) of their oxides with Mg. As a result, we found that theory of function-building fine particle preparation was able to be applied to synthesize nano-atomized fine particles of borides. ZrB2 can also be obtained directly from mixture of ZrSiO4, B2O3, and Mg by MTR method. This sample has no borides such as silicon boride except for ZrB2. Therefore, this result shows the possibility to obtain ZrB2 easily from natural source. On the other hand, B doped TiO2 samples were prepared by the calcination of TiB2 in the air condition and MTR method. As a result, we could effectively dope B atoms to TiO2 samples by this method. These samples also show the photocatalytic activity for the oxidation of 2-propanol even under the visible-light irradiation.抄録全体を表示PDF形式でダウンロード (1013K)
研究
-
阪上 楠彦, 河野 信一, 山本 勉2007 年 54 巻 4 号 p. 260-263
発行日: 2007年
公開日: 2007/07/13
ジャーナル オープンアクセスIt is very important to acquire knowledge on bending fatigue characteristics of cemented carbides tools for cold forging, because the tools are generally applied under strong repeated stress at their use. In this study, the effects of grain size of WC and Co content on the bending fatigue characteristics were mainly investigated for fine and coarse-grained WC-0.5∼1.0mass%Cr3C2-10∼22mass%Co alloys and the relation between transverse-rupture strength and fatigue limit was discussed.
The results obtained were as follows: (1) The bending fatigue limit of fine-grained WC alloys was higher than that of coarse-grained WC alloys and that of low Co alloys was higher than that of high Co alloys in each WC grain size. This tendency was similar to the case of transverse-rupture strength. (2) The fracture origin observed in low cycle range was mostly aggregated WC, while that in high cycle range above 105 cycles showed tendency to change Co pool or its segregation. (3) There was a very strong correlation between transverse-rupture strength and bending fatigue limit, and 45∼55% of the transverse-rupture strength was equivalent to the bending fatigue limit. This relation enables to estimate the fatigue limit of cemented carbides.抄録全体を表示PDF形式でダウンロード (769K) -
竹田 容大, 河野 信一, 山本 勉2007 年 54 巻 4 号 p. 264-268
発行日: 2007年
公開日: 2007/07/13
ジャーナル オープンアクセスHeterogeneous pores were often observed on lapped surface of cemented carbides with high Co content manufactured under some conditions. Therefore, the conditions and mechanism of the pore formation were mainly investigated and considered.
The results obtained were as follows: The amount and size of the pores increased with the increase of sintering temperature, cobalt content and particle size of WC. And these pores were distributed heterogeneously along certain curves on the lapped surface. Comparing the pore distribution with domain boundary of Co binder phase, the pores were confirmed to distribute at the domain boundary of cobalt phase. Especially, larger pores were generated near triple point of the domain boundary. Consequently, these heterogeneous pores were considered to be caused by solidification and shrinkage of Co binder phase during cooling.抄録全体を表示PDF形式でダウンロード (1121K) -
小林 慶三, 松本 章宏, 西尾 敏幸, 安井 幸栄2007 年 54 巻 4 号 p. 269-273
発行日: 2007年
公開日: 2007/07/13
ジャーナル オープンアクセス75vol%WC-FeAl (Fe-40at%Al) mixture has been prepared by milling of WC, Fe, Al and graphite powders for 3.6ks using a planetary ball milling. The reaction between Fe and Al in the mixture during heating has been examined by DTA. The mixture has shown an exothermic reaction starting at 1163K after Al was melted.
The obtained mixture has been consolidated using pulsed-current sintering at 1223-1423K. The sintered compact at 1223K has had Fe peaks in the X-ray diffraction pattern and had magnetization. The exothermic reaction at 1163K in the DTA curve has been a combustion synthesis of various Fe-Al intermetallic compounds from molten Al and Fe. The 75vol%WC-FeAl sintered compact has been densified according to a sintering temperature with solid phase diffusion and increased FeAl content in the binder phase. The 75vol%WC-FeAl sample sintered at 1423K has had non-magnetization and Vickers hardness of 1470Hv.抄録全体を表示PDF形式でダウンロード (740K) -
砂田 聡, 細田 幸宏, 山本 勉, 真島 一彦2007 年 54 巻 4 号 p. 274-280
発行日: 2007年
公開日: 2007/07/13
ジャーナル オープンアクセスThough WC-Co cemented carbides are widely used for a variety of machining, cutting, drilling and other applications because of their high strength, high hardness and excellent wear resistance, there exist corrosion issues during practical use. However, little work is currently available in the published literature on this subject. In this study, the corrosion behaviors of three cemented carbide specimens, i.e., WC-Co (Sample A), WC-Cr3C2-Co (Sample B) and WC-βt-Co (Sample C) in which βt indicates (Ti, W, Ta, Nb) C, are investigated by the electrochemical methods such as the polarization test and the electrochemical impedance spectroscopy, hereafter shortened as EIS, as well as the immersion test under constant potential in comparison with that of SUS304 stainless steel. The similar active, passive and over passive state regions to SUS304 stainless steel during the polarization test, and the preferential dissolution of Co were observed for all of the three specimens mentioned above. Both Cr3C2 and βt improved the corrosion resistance of WC-Co alloy, in which the effect of the former was better than that of the latter. EIS test showed that all of the three samples showed the similar capacitance semicircle in the first quadrant. The induction semicircle followed the capacitance semicircle mentioned above for the sample A and sample C while the other capacitance semicircle followed for the sample B.抄録全体を表示PDF形式でダウンロード (1042K) -
杉山 重彰, 小平 雄一郎, 泰松 斉2007 年 54 巻 4 号 p. 281-286
発行日: 2007年
公開日: 2007/07/13
ジャーナル オープンアクセスDense WC-W2C composite ceramics were prepared by reactive resistance-heated hot-pressing of WC-W powder mixtures. Product W2C phase in the ceramics was increased with W content in the mixtures, and a single W2C phase ceramic was obtained at 31.1 mol%C. Increasing W2C phase improved sinterability, decreased hardness, Young's modulus and fracture toughness, and increased Poisson's ratio. A slightly W2C-containing ceramic, W-48.7 mol% C, has almost the same mechanical properties as WC, Young's modulus 673 GPa, Vickers hardness 25.3 GPa, fracture toughness 5.8 MPa m1/2, and Poisson's ratio 0.22, and is superior in sinterability to WC.抄録全体を表示PDF形式でダウンロード (805K) -
藤 祐輔, 嶋田 志郎, 清野 肇2007 年 54 巻 4 号 p. 287-293
発行日: 2007年
公開日: 2007/07/13
ジャーナル オープンアクセスMonolithic (TiBC, TiBN, SiNx) and double layered films (TiBC-SiNx, TiBN-SiNx) were deposited on Si wafers or WC-Co substrates at about 800°C from a hexamethyldisiloxane, titanium tetra-ethoxide or tri-ethoxy borate solution and their mixed solution by thermal plasma chemical vapor deposition. The films were characterized by thin film X-raydiffractmetry (XRD), X-ray photoelectron spectroscopy, scanning electron microscopy, EDS analysis and the cutting tests. XRD indicated that TiBC and TiBN phases were crystalline, but SiNx was amorphous. Thickness of under-layered TiBC or TiBN and over-layered SiNx in the double layered films was 0.5 and 2-4μm, respectively. The cutting tests for the double layered film deposited on WC-Co showed that the double layered TiBC-SiNx and TiBN-SiNx films possessed the good wear resistance comparable to or higher than the commercial TiN film deposited on WC-Co prepared by thermal CVD, in terms of crater and flank wear resistances.抄録全体を表示PDF形式でダウンロード (1419K)
- |<
- <
- 1
- >
- >|