Papers by Keyword: Chlorine

Abstract: In order to understand the influence of the Cl/Si ratio on the morphology of the low-temperature chloro-carbon epitaxial growth, HCl was added during the SiCl4/CH3Cl growth at 1300°C. Use of higher Cl/Si ratio allowed only modest improvements of the growth rate without morphology degradation, which did not go far beyond what has been achieved previously by optimizing the value of the input C/Si ratio. On the other hand, when the epitaxial growth process operated at too low or too high values of the input C/Si ratio, i.e., outside of the window of good epilayer morphology, any additional increase of the Cl/Si ratio caused improvement of the epilayer morphology. It was established that this improvement was due to a change of the effective C/Si ratio towards its intermediate values, which corresponded to more favorable growth conditions.

Abstract: Using first-principles calculations, we investigated the migration mechanisms of Cl in cubic SiC. The analysis of the formation energies of several defect configurations (isolated interstitials and complex defects), either reported in the literature or calculated in the present study, revealed that three migration mechanisms are possible: Interstitialcy and two different vacancy-mediated mechanisms (both concerted exchange and second-neighbor hop). Our calculations showed that vacancy-mediated diffusion is more energetically favorable than an intersticialcy one and the values of the diffusivity, for both n-type and p-type SiC were also estimated.

Abstract: Disinfection is essential for medical wastewater treatment. Concerns about environmental safety, pathogenic microorganisms need to be killed by qualified disinfectant without secondary pollution from medical wastewater treatment. Traditional chlorination is a main technique among current disinfection technologies. However, due to the hazardous byproducts, it is likely to be replaced by new technologies such as ultraviolet ray. In addition, membrane disinfection and electrochemical disinfection are emerging techniques with prosperous market.

Abstract: An annealing study, in the 100-1400 C temperature range ,was carried out on Cl-implanted n- or p-type 4H-SiC epilayers. The electrical characterization of the epilayers shows the rise of several deep levels and the role of Cl, on both carrier concentration and defects' microscopic structure, is discussed in the light of theoretical results obtained by density functional calculations performed on a 64-atom cubic SiC supercell.

Abstract: Relationship between the chemical reactivity and the orientation of SiC substrates was investigated. Thermal etching of 4H-SiC in the mixed gas of oxygen and chlorine was carried out as the chemical reaction. The etching rate did not change monotonously with the increase of the off angle in 4H-SiC (000-1) C substrate. By the use of such tendency in the thermal etching, the three dimensional structure with the specific pyramidal plane was able to be obtained.

Abstract: The sub-trenches in 4H-SiC Si- and C-faces could be disappeared by the thermal treatment in chlorine ambience at 900-1000oC. The surface morphologies of the thermally treated trench-sidewalls were unchanged. It is considered that the sub-trench is selectively removed because thermally Cl2 etching rate of the (0001) Si- and (000-1) C-face are different to the (11-20) and (1-100).

Abstract: The co-pyrolysis process of coal and waste plastics was studied. Changing and transferring property of chlorine in the process was investigated. There was synergistic effect between coal and waste plastics when chlorine was released, which resulted in increase of chlorine in tar and decrease in coke. The effect of waste plastics’ amount on chlorine releasing property varied with the amount of waste plastics in the sample and the time of constant temperature at the same final co-pyrolysis temperature (such as 950 oC). Using the distributional function of chlorine, the distribution of chlorine in coke, tar and gas was studied. The results indicated that the distribution of chlorine in the co-pyrolysis process could be controlled to a certian extent by controlling the percentage of waste plastics and the time of constant temperature. The amount of chlorine redistributed in coke decreases with the increase of constant temperature time and increased with the increase of the percentage of waste plastics. On the contrary, the chlorine in tar increased with the increase of the constant temperature time and the percentage of waste plastics. And the chlorine redistributed in gas increased with the increase of the constant temperature time, but it decreased when the percentage of waste plastics increased. Additionally, the mathematical model of chlorine changing and transferring rule was established.

Abstract: Microcontents of Cl- and SO42- in boric acid were determined by photoelectricity turbidimetry with acid as medium. The effects of stabilizer, acidity of solution, content of precipitant, heating time and temperature as well as measuring time on the turbidity of the solution were studied. After above experiment parameters were optimized, in the measurements to determine SO42- in boric acid, the stabilizer was glycerine-ethanol (1:4), the precipitant was acidic BaCl2. The solution was shaked and heated, as a result, the adding sequence of reagents had no effects on results. The detection limit was 0.10mg/L, relative standard deviation (RSD) was less than 3%, recovery rate was 98.85%~103.00%, and measuring time last over 40min. SO^42- concentration in the range of 0.33 mg/L ~0.83mg/L showed a linear relationship with turbidity. In the determination of chlorine, the stabilizer was glycerine, measuring time held in 40min, detection limit was 0.03mg/L, RSD was less than 4%, and recovery rate was 102.2%~106.5%. Cl^- concentration in the range of 0.10 mg/L ~0.25mg/L showed a linear relationship with turbidity. Photoelectricity turbidimetry improve the precision and accuracy of the measurements. The method of turbidimetry to determine Cl^- and SO^42- in boric acid is simple, reliable, innocuous and applicable in practice.

Abstract: The recent progress of co-pyrolysis of waste plastics contained chlorine or PVC with biomass was introduced. Different type raw materials of plastics and biomass, the experiments and facilities were presented. The characteristics of co-pyrolysis, the mechanism of reactions and kinetics studies were summarized, also. The development and prospect of this environmentally friendly wastes reclamation were proposed.

Abstract: This study compared the differential absorbance spectroscopy of the raw water oxidized with chlorine and chlorine dioxide to explore the reactions between oxidants and natural organic matter in disinfection by-products (DBPs) formation. The correlations between the differential absorbance at 272 nm (ΔA₂₇₂) and 254 nm (ΔA₂₅₄) and DBPs formation in chlorinated water were also examined, respectively. The intensity of the differential absorbance increased with increasing doses for both chlorine and chlorine dioxide. The sites in natural organic matter oxidized with chlorine and chlorine dioxidate are different. Unlike the well defined band at 272 nm and 254 nm in differential spectra of water oxidized with chlorine, a well defined band at 220 nm was found in water oxidized with chlorine dioxide. The behavior of -ΔA₂₇₂ during chlorination process was determined to be strongly correlated with DBPs concentrations quantified by linear equations with R² values > 0.95. A weak correlation (R² value 254, indicating the formation of DBPs independent of destruction in UV-absorbing sites.