Papers by Keyword: Growth Conditions

Abstract: We investigated the run-to-run fluctuation in growth conditions of physical vapor transport growth of 4H-SiC boules through observations of surface morphology on the (000-1) facet of the boules. The boules, which were grown under the same macroscopic growth conditions, exhibited slightly different surface morphologies. This indicates that some microscopic growth parameters that influence the surface morphology fluctuate between growth runs. We have considered the C/Si ratio of the vapor sublimed from the source material as a major parameter and discussed the associated variations in the physical and surface properties of the grown crystals.

Abstract: The growth and photosynthesis of Eichhornia crassipes affected by mixed rare earth elements (REEs) were measured under indoor mesocosm. The results showed that appropriate concentration range of mixed REEs could promote Eichhornia crassipes absorbing nitrogen and phosphorus effectively, and improve the efficiency of light energy utilization and transformation which made photosynthesis improved, and thus it could promote plant growth, and improve contents of protein and chlorophyll; fatherly, with increase of Eichhornia crassipes breeding density, dissolved oxygen (DO) reduced but chemical oxygen demand (COD) raised (a maximum value of 16.170 mg/L) in water, which eventually led to water quality worsen. The research results demonstrate that suitable contents of mixed REEs can promote aquatic plants such as Eichhornia crassipes growing, thereby contributing a positive catalytic effect to the development process of eutrophication.

Abstract: The growth conditions of a Geobacillus sp. were investigated by single-factor experiments. The strain was strictly aerobic bacterium, and could grow on hydrocarbons as the sole carbon source. The optimum carbon and nitrogen sources were 3.0% sucrose and 0.20% KNO3, respectively. The range of temperature, salinity and pH for the bacterial growth was 35-70 °C, 0-10% NaCl and 5.5-9.5, and good growth was obtained at 35-65 °C, 0.5-8% NaCl and 6.0-9.0, respectively. Particularly, the optimum temperature for the bacterial growth was between 50 °C and 60 °C. The strain had wide adaptability to the extreme conditions, and may be potentially applied to microbial enhanced oil recovery and oil-waste bioremediation technology.

Abstract: Graphene layers were created on both C and Si faces of semi-insulating, on-axis, 4H- and 6H-SiC substrates. The process was performed under high vacuum (<10-4 mbar) in a commercial chemical vapor deposition SiC reactor. A method for H2 etching the on-axis substrates was developed to produce surface steps with heights of 0.5 nm on the Si-face and 1.0 to 1.5 nm on the C-face for each polytype. A process was developed to form graphene on the substrates immediately after H2 etching and Raman spectroscopy of these samples confirmed the formation of graphene. The morphology of the graphene is described. For both faces, the underlying substrate morphology was significantly modified during graphene formation; surface steps were up to 15 nm high and the uni-form step morphology was sometimes lost. Mobilities and sheet carrier concentrations derived from Hall Effect measurements on large area (16 mm square) and small area (2 and 10 m square) samples are presented and shown to compare favorably to recent reports.

Abstract: GNFs with fish-bone structure were first produced by a simple method. To optimize the growth conditions, different hydrogen treatment of the catalyst, different growth time and growth temperature, as well as different gas flow rate were employed. The effects of these growth conditions on the morphology and yield of GNFs were studied in details. It is found that fish-bone GNFs with high yield and high purity can be produced under the optimized conditions.

Abstract: Beta gallium oxide (β-Ga2O3) crystals were grown on β-Ga2O3 ceramics heated by electric current under vacuum at various ambient temperatures. From cathodoluminescence at room temperature, emission peaks at 2.9 and 3.5 eV were clearly observed. With increasing ambient temperature, the relative intensity of ultraviolet emission (3.5 eV) to blue emission (2.9 eV) showed a peak at 400oC. These results suggest that the ambient temperature during the electric current heating of β-Ga2O3 ceramics in vacuum is one of the most effective factors for the ultraviolet emissive β-Ga2O3 crystal.