Handa, Japan
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Yamada M.,Nagoya University | Sekine K.,Mino Ceramic Co. | Kumazawa T.,Mino Ceramic Co. | Tanabe Y.,Nagoya University
Nippon Seramikkusu Kyokai Gakujutsu Ronbunshi/Journal of the Ceramic Society of Japan | Year: 2010

Ceramics will be widely used for enhancing the efficiency of power generating systems, particularly gas turbines. However, ceramics used in these systems suffer damage owing to impact by foreign objects. In this study, various ceramic plates are impacted by a spherical projectile with an impact velocity of 320 m/s. The volume of the cone cracks formed on the plates decreases with an increase in the fracture toughness of the ceramic material. No cone cracks are formed on the zirconia (3Y-TZP) plate because crack formation is prevented by stress-induced phase transformation outside the impacted region. The volume of the cone crack is higher and the energy consumed by surface formation is smaller in transgranular-fractured ceramics than in intergranular-fractured ones. The fracture process can be controlled by controlling the characteristics of the grain boundaries, as well as by stress-induced phase transformation. © 2010 The Ceramic Society of Japan. All rights reserved.


Sekine K.,Mino Ceramic Co. | Sekine K.,Nagoya University | Kumazawa T.,Mino Ceramic Co. | Tanabe Y.,Nagoya University
International Journal of Applied Ceramic Technology | Year: 2015

Impact damage of laminated B4C ceramic samples was investigated using four types of aluminum sheets - without holes and with 25 4-, 8-, and 25-mm-diameter holes - at joining ratios of 100, 94, 76, and 45%. Four 1-mm-thick B4C ceramics plates were laminated using three aluminum sheets of the same type and joined at 700°C in vacuum. In impact damage tests using spherical SUJ-2 projectile with a diameter of 4 mm with a velocity of approximately 300 ms-1, bulk B4C showed a large conical crack and significant fractures; the conical crack in the laminated samples was smaller than that of the bulk B4C. However, the conical cracks of the laminated B4C with the joining ratio 45 to 96% were of the same size, irrespective of the joining ratios. The total load and induced pressure area on the rear side of laminated samples were smaller than that observed for bulk B4C, and total load and induced pressure area were similar for laminated samples with high and low joining ratios. The maximum pressure on the rear face of laminated B4C samples was higher than that observed for bulk B4C and increased with decreasing joining ratio of laminate interlayer. © 2014 The American Ceramic Society.


Sekine K.,Stereo Fabric Research Association | Kumazawa T.,Mino Ceramic Co. | Tian W.-B.,Stereo Fabric Research Association | Hyuga H.,Japan National Institute of Advanced Industrial Science and Technology | Kita H.,Japan National Institute of Advanced Industrial Science and Technology
Nippon Seramikkusu Kyokai Gakujutsu Ronbunshi/Journal of the Ceramic Society of Japan | Year: 2012

Low-temperature joining of boron carbide (B 4C) ceramics using an Al sheet was investigated in the temperature range of 6001200° for 2 h in vacuum (10 -210 -4 Pa). Successful joining and high bending strength close to that of the B 4C base were achieved in the samples joined at 7001100°. Different techniques including scanning electron microscopy (SEM), electron probe microanalysis (EPMA) and transmission electron microscopy (TEM) were used to characterize the high-strength B 4C joints. SEM observations suggested the dense interlayer and the crack-free interface as well as the penetration of Al into the surface microcracks of B 4C base. Further TEM examinations revealed that B 4C and Al joined directly. EPMA analysis demonstrated the existence of several reaction products within interlayer, including AlB 2 and Al 3BC, which resulted in the development of high-strength composite interlayer. © 2012 The Ceramic Society of Japan.


Sekine K.,Stereo Fabric Research Association | Kumazawa T.,Mino Ceramic Co. | Tian W.B.,Stereo Fabric Research Association | Hyuga H.,Japan National Institute of Advanced Industrial Science and Technology | Kita H.,Japan National Institute of Advanced Industrial Science and Technology
Nippon Seramikkusu Kyokai Gakujutsu Ronbunshi/Journal of the Ceramic Society of Japan | Year: 2012

The influence of the joining time and temperature on the flexural strength of B 4C ceramics joined using an Al sheet was investigated. The B 4C ceramics were joined over a temperature range 600-1400°C for 2-72 h in vacuum (101210 14 Pa) and in an Ar atmosphere. A joining interlayer with a dense structure was found in the B 4C joint formed at 1000°C after 2 h in vacuum, and mainly Al was present in this joining interlayer. On the other hand, some voids existed in the joining interlayer in the B 4C joint formed after 72 h. In addition, Al was not present in this interlayer owing to its reaction with B 4C as well as the evaporation of Al. Four-point bending tests of the B 4C joints formed at 1000°C in vacuum for periods ranging from 2 to 72 h were performed at room temperature. The average four-point bending strengths of the B 4C joints formed after 2 h at 700-1100°C were close to that of the B 4C base material, and the B 4C ceramics were considered to have successfully bonded. However, the joint strength decreased with an increase in the joining time, and the B 4C ceramics did not bond at temperatures over 1200°C in vacuum. On the other hand, the B 4C ceramics did bond at 1200-1400°C in Ar. © 2012 The Ceramic Society of Japan.


A bonded, boron carbide-containing ceramic body includes ceramic members. These ceramic members each contain boron carbide at 2 mass% or higher, and are integrated together via a bonding layer bonded with a bonding material containing at least one metal selected from the group consisting of aluminum, copper, gold and zirconium or integrated together via a bonding layer formed from one of aluminum metal and an aluminum compound and a titanium compound as bonding materials, wherein a bonded part has a strength of 100 MPa or higher. According to this technology, the boron carbide-containing ceramic members can be bonded together with a high strength of 100 MPa or more by a simple process, and further, the bonding is feasible with excellent chemical resistance at the bonded part as needed.


A bonded, boron carbide-containing ceramic body includes ceramic members. These ceramic members each contain boron carbide at 2 mass % or higher, and are integrated together via a bonding layer bonded with a bonding material containing at least one metal selected from the group consisting of aluminum, copper, gold and zirconium or integrated together via a bonding layer formed from one of aluminum metal and an aluminum compound and a titanium compound as bonding materials, wherein a bonded part has a strength of 100 MPa or higher. According to this technology, the boron carbide-containing ceramic members can be bonded together with a high strength of 100 MPa or more by a simple process, and further, the bonding is feasible with excellent chemical resistance at the bonded part as needed.


Patent
Mino Ceramic Co. | Date: 2013-02-27

A shock absorbing member 50 having a ceramic bonded body 15 having: a plurality of first sheet-like members 5 each having a ceramic containing 60 mass % or more of boron carbide and each having a thickness of 0.1 to 50 mm; and a bonding layer arranged between the first sheet-like members 5 adjacent to each other, the bonding layer bonding surfaces to be bonded facing each other of the first sheet-like members adjacent to each other, wherein the bonding layer has a bonding material containing at least one metal selected from the group consisting of aluminum, copper, silver, and gold.


Patent
Mino Ceramic CO. | Date: 2010-03-24

An obj ect of the present invention is to provide an economical production technology for obtaining a dense boron carbide ceramic product without impairment to excellent mechanical properties, which boron carbide ceramics are inherently equipped with, by conducting heating under normal pressure without application of pressure and without needing addition of a large amount of a sintering additive to a rawmaterial or needing any special additive or treatment. The present invention provides a production process in which, upon heating a boron carbide green body under normal pressure without application of pressure after pressing a boron carbide powder material to obtain the boron carbide green body, the boron carbide green body is heated with one of a powder, green body or sintered body, which contains at least one of aluminum and silicon, being disposed in a furnace.


Patent
Mino Ceramic CO. | Date: 2015-01-07

A shock absorbing member 50 having a ceramic bonded body 15 having: a plurality of first sheet-like members 5 each having a ceramic containing 60 mass% or more of boron carbide and each having a thickness of 0.1 to 50 mm; and a bonding layer arranged between the first sheet-like members 5 adjacent to each other, the bonding layer bonding surfaces to be bonded facing each other of the first sheet-like members adjacent to each other, wherein the bonding layer has a bonding material containing at least one metal selected from the group consisting of aluminum, copper, silver, and gold.


Miyazaki H.,Japan National Institute of Advanced Industrial Science and Technology | Zhou Y.,Japan National Institute of Advanced Industrial Science and Technology | Hyuga H.,Japan National Institute of Advanced Industrial Science and Technology | Yoshizawa Y.-i.,Japan National Institute of Advanced Industrial Science and Technology | Kumazawa T.,Mino Ceramic CO.
Journal of the European Ceramic Society | Year: 2010

97.4% of theoretical density was obtained for boron carbide (B4C) ceramics by heating up to 2226 °C in an Ar atmosphere containing gaseous Al and Si species without external pressure. Impurities and secondary phases in the sintered B4C samples were examined by X-ray fluorescence and X-ray diffraction analyses respectively, which revealed that both Al and Si elements infiltrated into the green compacts and reacted with B4C to form SiC, Al4C3 and Al4SiC4 during the sintering. Triple junctions observed in the polished surfaces of the densified samples were filled by the secondary phases, indicating formation of liquid phase during heating. Dilatometric measurements at a constant heating rate in the Ar gas with the metallic gas species demonstrated that the shrinkage started at around 1700 °C, which was the liquid-phase formation temperature for the system reported in the previous studies. It was supposed that the liquid phase might be responsible for the densification. © 2009 Elsevier Ltd. All rights reserved.

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