This study is based on the livelihood used by street children for survival in Bamako, Mali. Two bus stations were selected for this study: Sogoniko bus station and Medina bus station. Most buses leave from these stations to the vicinity of the country. Data was collected through individual interviews (one by one), focus group discussions and interviews. A sample of one hundred and twenty street children aged between 8 and 17 years were selected for this study. Thirty people were also selected to give their opinions on street children. The results indicate that most of street children survive by selling small objects and through begging, 32.5% and 22.50% respectively. Our survey indicates that there are different factors pushing them to the streets, and as a way of survival on the streets, there is need to be organized, hence, they are organize themselves into groups for protection against violence and aggressions.
A mixture of cubic silicon powder, hexagonal boron nitride powder and graphite powder was mechanically alloyed for 30 hrs in argon. The as-milled 2Si-B-3C-N composite powder was heated up to 1900 °C in nitrogen, with a heating rate of 25 °C/min and under a pressure of 80 MPa. XRD and HRTEM results show that the as-milled 2Si-B-3C-N composite powder has a well amorphous structure. Under the current hot-pressing circumstances, the amorphous ceramic starts to crystallize at a temperature between 1800 °C and 1900 °C. Once the temperature is higher than crystallization temperature, crystallites appear in the amorphous matrix with a great nucleation rate, but a small growth rate. Hot pressed at 1900 °C for 0 mins or 10 mins, the prepared 2Si-B-3C-N bulk ceramic has an average grain size of 8.7 nanometers and 22.3 nanometers, respectively. After an intensive literature search, we believe the present work is the first one to make clear that it is possible to use the mechanical alloying route to prepare amorphous Si-B-C-N ceramic with such a high crystallization temperature.
Yttria stabilized tetragonal zirconia (Y0.08Zr0.94O2, YSZ) nanopowders were successfully synthesized by microwave solvothermal method (MSM). The synthesizing temperature, holding time and mineralizer concentration were optimized. The crystallization and particle distribution of as-prepared YSZ nanopowders were identified by DSC/TG, XRD, FESEM, TEM, FTIR, DLS, and BET. The dispersion of YSZ nanopowders dried by different methods and modified by polyethyleneimine (PEI) was analyzed and discussed. The results show that the PEI modified samples have the best dispersion, and the dispersion of freeze-dried samples is better than that of traditional dried ones. The particle size of the PEI modified samples calculated from the surface area determined by BET is 15.7 nm, which is consistent with that determined by TEM (16.5 nm), but slightly smaller than that calculated by the Scherrer formula according to XRD (22.3 nm). This may be attributed to the different testing principles in these methods.
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