Applied Technology

Indigenous Innovation on Magnesium Alloy Sheets

Recently, Profs. Han Enhou and Chen Rongshi of the Environmental Corrosion Center, Institute of Metal Research, CAS, together with doctoral graduates Yan Hong and Wu Di, have developed a series of Mg-Zn-RE rolling sheets by addition of Y, Nd, Gd, etc. and optimizing parameters of rolling process, in-pass between each two passes and final annealing treatment, and investigated their microstructure, texture, ductility and formability, anisotropy. The relevant paper was published in Scripta Materilia, DOI and Materials Science and Engineering A, 527(2010), P3317-3322. The results suggest that the newly developed Mg-Zn-RE system is propitious to rolling process; the fully recrystallized fine microstructures with a large amount of homogeneously distributed fine particles in the matrix are obtained after hot rolling. The results of the Erichsen tests at room temperature further show that the new rolling sheets exhibit excellent stretch formability (IE ~8), which is much better than that of AZ31 Mg alloy sheets (IE value usually lower than 4) and a close match for that of 5000 and 6000 series Al alloy. IE ~8 means the Mg-Zn-RE sheet can be formed locally to shape strengthening rib, checkered pattern, mark and so on, and may even be applied to producing the coating of car and airplane by deep drawing and stretching.

Two-step Process for Jatropha curcas Biodiesel Production

Prof. Fang Zhen and his research team of Xishuangbanna Botanical Garden, CAS studied the transesterification of high free fatty acid content oil with methanol to biodiesel catalyzed directly by NaOH and high-concentrated H2SO4 or by two-step process in an ultrasonic reactor at 60°C. Their research result was as the following: If NaOH was used as catalyst, biodiesel yield was only 47.2% with saponification problem. With H2SO4 as catalyst, biodiesel was increased to 92.8%. However, longer reaction time (4h) was needed and the biodiesel was not stable. A two-step, acid-esterification and base-transesterification process was further used for biodiesel production. It was found that after the first-step pretreatment with H2SO4 for 1 h, the acid value of Jatropha oil was reduced from 10.45 to 1.2 mg KOH/g, and subsequently, NaOH was used for the second-step transesterification. Stable and clear yellowish biodiesel was obrained with 96.4% yield after reaction for 0.5 h. The total production time was only 1.5 h that is just half of the previous figure reported. The two-step process with ultrasonic radiation is effective and time-saving for biodiesel production from Jatropha oil.

Urbanization: Increasing Ill Effects on Biodiversity

Prof. Zhang Runzhi’s research group, from the Institute of Zoology, CAS, conducted a 3-year survey of willow trunk-dwelling insects in 25 parks and greenbelts within the 6th ring road of Beijing, the urban area of which expanded in a typical concentric pattern. Change pattern of insect diversity along the urbanization gradient was studied. The environmental factors affecting this spatial pattern were also identified. The results showed a significant influence of urban expansion on insect diversity. It was estimated that within a 30-km limit, species richness and abundance might be reduced by one species and 60% of individuals per 5 km toward urban center. The change pattern of diversity was significantly correlated to landscape variables such as isolation degree and proportion of impervious surface. These results support that urbanization is one of the most important impact factors to the current global biodiversity. To maximize the conservation value of urban forests, efforts should not only be focused on local afforestation, but also be directed to optimize the structure of urban landscape and to increase the connectivity between urban remnants and natural landscape in outskirts. Besides, the proportion of impervious surface in inner urban zones should also be controled. Related results were recently published in the Landscape and Urban Planning and Journal of Insect Conservation.

High Efficiency Solar Cells for More Energy

Recently, a high-efficiency solar cell research team led by Prof. Jia Rui of the Microwave Devices and Integrated Circuits Department, Institute of Microelectronics, CAS successfully developed a new type of semiconductor nano-material, of which the energy gap can be flexibly adjusted based on its size and components. Combining this down-conversion material with mass-produced 125mm×125mm crystal silicon substrate, researchers developed the down-conversion crystal silicon solar cell with high efficiency. Results of relevant tests of packaged cells showed that the light absorption and utilization of this down-conversion crystal silicon solar cell are significantly improved in the wave band of 300-630nm and the scale of its spectral response is increased by 10%, which means that the performance of crystal silicon cells is greatly improved.