Hao WANG
,
Xiaoping SONG
,
Xiangdong YAO
,
Haifeng ZHANG
,
Zhuangqi HU
材料科学技术（英文）
The crystallization behavior and crystallization kinetics of (Cu60Zr30Ti10)99Sn1 bulk metallic glass was studied by X-ray diffractometry and differential scanning calorimetry. It was found that a two-stage crystallization took place during continuous heating of the bulk metallic glass. Both the glass transition temperature Tg and the crystallization peak temperatures Tp displayed a strong dependence on the heating rate. The activation energy was determined by the Kissinger analysis method. In the first-stage of the crystallization, the transformation of the bulk metallic glass to the phase one occurred with an activation energy of 386 kJ/mol; in the second-stage, the formation of the phase two took place at an activation energy of 381 kJ/mol.
关键词:
Bulk metallic glasses
,
null
,
null
Wenhui JIANG
,
Xiangdong YAO
,
Hengrong GUAN
,
Zhuangqi HU
材料科学技术（英文）
The carbide behavior of a directionally solidified Co-base superalloy DZ40M has been investigated after creep at 700 and 900℃. During the high temperature creep, a great amount of secondary carbide, M23C6 precipitated in alloy matrix. At 700℃, the M23C6 precipitation occurred in slip bands, indicating that it was stress-induced, while at 900℃, M23C6 formed surrounding the primary carbides, which is a characteristic of thermally aged alloy. The M23C6 particles pinned up dislocations and subgrain boundaries, strengthening the alloy matrix effectively. The creep crack initiation of DZ40M alloy was exclusively related to the primary carbides. The fracture of the primary carbide and the crack at the interface between them and matrix resulted in the crack formation. Furthermore, it was found that at 900℃, the surface of specimens was oxidized severely and the preferentially oxidized primary carbides acted as crack initiation sites.
关键词:
Applied Physics a-Materials Science & Processing
Amorphous aluminate YAlO3 (YAO) thin films on n-type silicon wafers as gate dielectric layers of metal - oxide semiconductor devices are prepared by pulsed laser deposition. As a comparison, amorphous aluminate LaAlO3 (LAO) thin films are also prepared. The structural and electrical characterization shows that the as-prepared YAO films remain amorphous until 900 degrees C and the dielectric constant is similar to 14. The measured leakage current of less than 10(-3) A/cm(2) at a bias of V-G = 1.0 V for similar to 40-nm-thick YAO and LAO films obeys the Fowler Nordheim tunneling mechanism. It is revealed that the electrical property can be significantly affected by the oxygen pressure during deposition and post rapid thermal annealing, which may change the fixed negative charge density at the gate interface.
关键词:
hafnium oxide;si;stability;silicon;transition;dioxide;devices;hfo2
