Privious Issue

Volume 46 Number 4 (2015.12)

Special Feature

Nanomaterials and Processing

Part I. Special Feature

2. Nitrogen-functionalized Graphene Quantum Dots with Tunable Optical Properties(3,270kB)

pages 1-9
Hiroyuki Tetsuka, Akihiro Nagoya and Ryoji Asahi

Nitrogen-functionalized graphene quantum dots extracted from graphene sheets glow with various bright colors, which are dependent on their surface functional groups, under single-wavelength excitation. These quantum dots are potentially applicable as color conversion materials for white light-emitting diodes through efficient incorporation into a flexible and transparent cellulose nanofiber@clay host.

3. A Facile and Scalable Synthetic Method for Si-based and Silicide-based Nanomaterials towards Energy-related Applications (1,740kB)

pages 11-19
Hiroshi Itahara, Song-Yul Oh and Haruo Imagawa

We have developed a novel synthetic method to fabricate nanomaterials composed of Si or silicide (Si-based intermetallic compounds). The method is based on the solid-state exfoliation reaction, during which Ca is extracted from layered CaSi₂ with simultaneous exfoliation of the layered structure. We have successfully prepared various functional nanomaterials such as Ca_xSi₂/nickel silicide nanocomposites, which exhibit excellent performance as Li ion battery anodes.

4. Enhancement of Pressure-free Bonding with Cu Nanoparticles Using Ni Affinity Layers and Ni Alloy Nanoparticles(4,427kB)

pages 21-32
Toshitaka Ishizaki and Ryota Watanabe

Robust bonding strength was achieved at 250℃ without pressure by a combination of three approaches: the use of readily decomposable capping layers on Cu nanoparticles in an inert atmosphere, Ni affinity layers onto bonding interfaces employed to improve adhesion to sintered Cu, and the sintering-assist effects of Ni alloy nanoparticles on Cu nanoparticles.

5. Fabrication of Colloidal Nanoparticles by High Efficiency Laser Ablation(1,540kB)

pages 33-40
Teppei Nishi, Noritomo Suzuki, Naoko Takahashi, Hidehiko Sugiyama, Kazuhisa Yano and Hirozumi Azuma

Laser ablation for colloidal nanoparticle generation are reported. Ag nanoparticles were fabricated by laser ablation of a Ag powder target precipitated in a piriform flask filled with pure water. Pd nanoparticles were also fabricated by laser ablation at the air-liquid interface using a Pd powder target agitated in pure water.

6. Modeling the Surge Voltage Generation Mechanism of an Electromagnetic Clutch and a Proposed Structure for Surge Voltage Suppression (1,761kB)

pages 41-52
Junya Muramatsu, Takashi Kojima, Hiroya Tanaka, Yoshiyuki Hattori, Hiroshi Okada, Hiroki Keino, Takashi Nakanishi and Keisuke Fujisaki

In this paper, we clarify the surge voltage generation mechanism of an electromagnetic clutch, and propose a new clutch structure for surge voltage suppression.　First, we constructed a 2D FEM model of the electromagnetic clutch and carried out electromagnetic simulations. Next, we proposed a new electromagnetic clutch structure for surge voltage suppression based on the above 2D FEM simulations. Finally, we demonstrated that the proposed structure could suppress the surge voltage by more than 50% compared with that of a conventional structure.
7. Reliability Design for Neutron Induced Single-event Burnout of IGBT (2,294kB)

pages 53-61
Tomoyuki Shoji, Shuichi Nishida, Toyokazu Ohnishi, Touma Fujikawa, Noboru Nose, Kimimori Hamada and Masayasu Ishiko

Single-event burnout (SEB) caused by cosmic ray neutrons leads to catastrophic failures in insulated gate bipolar transistors (IGBTs). It was found that the SEB failure rate increases as a function of the applied collector voltage, and the SEB threshold voltage can be controlled by device optimum design.