We present a novel method, by using an ion implantation and subsequent heat treatment, to prepare Fe nanocrystalline in SiO2. The formation process of Fe granules was monitored by means of conversion electron Mössbauer spectroscopy and the size of which was determined by transmission electron microscopy. The magnetic coercivity of 100 and 70 Oe have been observed at room temperature and 80 K, respectively. A decrease of the coercivity at 80 K is probably caused by the appearance of a multidomain structure in the granules due to reducing the critical radius of single domain.

N-type strain-compensated Ge/Si0.15Ge0.85 multiple quantum wells (MQWs) were grown on a Si0.1Ge0.9 virtual substrate using ultrahigh vacuum chemical vapor deposition on a n+-Si(001) substrate. Under low forward bias voltage ranging from 0.6 to 1.2 V, narrow direct-bandgap electroluminescence (EL) peak from MQWs light emitting diode was observed at room temperature. The quantum confinement effect of the direct-bandgap transitions and the temperature dependent EL peak redshift are in good agreement with the calculated results.

An arc ultrasonic test system consisting of ultrasonic frequency excitation source, isolation coupling device, plasma arc welding power and signal acquisition system was created, successfully obtaining ultrasonic vibration in AC arc. The mechanism of arc ultrasonic on microstructures of joint of SiC p /6061Al matrix composites in plasma arc 'in situ' welding with flux cored wire (alloy composition: Al-15Ti-3Si) as filler metal was investigated. Comparing the weld microstructures without arc ultrasonic and with arc ultrasonic (excitation frequencies: 20, 30, 40, 50, 60 and 70 kHz respectively), it can be found that newborn Al 3 Ti phase obviously refined owing to ultrasound, and gradually became coarse with the increasing frequency. When the frequencies were 30, 50 and 60 kHz, Al 3 Ti was crushed to granular or block, and uniformly distributed in the weld. When the frequencies were 20, 40 and 70 kHz, Al 3 Ti was partially crushed and distributed at the original location along the vertical in the weld. The analysis showed that arc ultrasonic impacted the morphology and distribution of Al 3 Ti mainly through cavitations and acoustic streaming, also subjected to 'resonant wave group' phenomenon of arc ultrasonic.