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Selective growth of either monolayer or bilayer graphene is of great importance. We developed a method to readily tune large area graphene growth from complete monolayer to complete bilayer. In an ambient pressure chemical vapor deposition process, we used the sample temperature at which to start the H2 flow as the control parameter and realized the change from monolayer to bilayer growth of graphene on Cu foil. When the H2 starting temperature was above 700°C, continuous monolayer graphene films were obtained. When the H2 starting temperature was below 350°C, continuous bilayer films were obtained. Detailed characterization of the samples treated under various conditions revealed that heating without the H2 flow caused Cu oxidation. The more the Cu substrate oxidized, the less graphene bilayer could form.

We report preparation of large area quasi-one-dimensional (1D) monolayer graphene superlattices on a prototypical high-index surface Cu(410)-O and characterization by Raman spectroscopy, Auger electron spectroscopy, low-energy electron diffraction, scanning tunneling microscopy, and scanning tunneling spectroscopy. The periodically stepped substrate gives a 1D modulation to graphene, forming a superlattice of the same superperiodicity. Consequently, the moire pattern is also quasi-1D, with a different periodicity. Scanning tunneling spectroscopy measurements revealed new Dirac points formed at the superlattice Brillouin zone boundary as predicted by theories. [ABSTRACT FROM AUTHOR]

The article presents a study which examines the sorption mechanisms of chlorinated volatile organic compounds in organic-cation-modified clays (organoclays). The study assesses the physicochemical properties of three chlorinated methanes such as dichloromethane, trichloromethane, and tetrachloromethane, while the sorption properties of organoclay was evaluated using X-ray diffraction.

Although regionalization policies have been proven as good strategies for municipal solid waste (MSW) management in previous studies, the optimal allocation of the waste stream is significantly affected by several influential factors, thus further investigation of the impacts of these factors on regional MSW management strategies is necessary. This study demonstrated the impacts of waste-to-electricity transformation coefficient (WETC) of incinerators and the fluctuation of unit tipping fees on the regional MSW flow/allocation of the Taipei metropolitan area from practical and economic perspectives. Real-world data and linear programming were used to obtain the least-cost alternatives under different scenarios. Analytical results indicated some treatment facilities had geographic superiority and their priorities changed when actual WETCs of incinerators were considered. Treatment facilities located at weighted centers were identified. The allocation of MSW among incinerators and landfills is affected by fluctuation of unit tipping fees within a certain range. Treatment facilities sensitive to the changes in unit tipping fees were also identified. Regression equations were also established that can estimate the cost items of MSW management scenarios with different unit tipping fees. The results of this study are very useful for daily basis regulation of MSW administration. [ABSTRACT FROM AUTHOR]

Municipal solid waste (MSW) management is a major concern for highly urbanized societies. Among proposed MSW management systems, regionalization programs generally have received considerable attention. This study analyzes real-world operational data to assess different MSW management policies, especially regionalization strategies, and their impact on MSW management systems in the Taipei metropolitan area. Linear programming is also used to identify the minimum costs sustained by each policy. The linear programming results show that regionalization programs are more economical and also improve incinerator operation efficiency. Sensitivity analysis indicates that the minimum treatment requirement of incinerators is a very sensitive influence on the MSW flows distributed through the entire region. The MSW of several "sensitive" administrative districts will be allocated to different treatment facilities according to different management strategies. A list of preferential sequences of MSW treatment and disposal facilities can also be identified by the model presented in this study. The results of this study may provide a useful tool for aiding decision-making related to real-world MSW management problems. [ABSTRACT FROM AUTHOR]