Abstract: Silicene and germanene are the silicon and germanium counterparts of graphene, respectively. Recent experimental works have reported the growth of silicene on (1 1 1)Ag surfaces with different atomic configurations, depending on the growth temperature and surface coverage. We first theoretically study the structural and electronic properties of silicene on (1 1 1) Ag surfaces, focusing on the (4 x 4) silicene/Ag structure. Due to symmetry breaking in the silicene layer (nonequivalent number of top and bottom Si atoms), the corrugated silicene layer, with the Ag substrate removed, is predicted to be semiconducting, with a computed energy bandgap of about 0.3 eV. However, the hybridization between the Si 3p orbitals and the Ag 5s orbital in the silicene/(1 1 1)Ag slab model leads to an overall metallic system, with a distribution of local electronic density of states, which is related to the slightly disordered structure of the silicene layer on the (1 1 1)Ag surface. We next study the interaction of silicene and germanene with different hexagonal non-metallic substrates, namely ZnS and ZnSe. On reconstructed (0 0 0 1)ZnS or ZnSe surfaces, which should be more energetically stable for very thin layers, silicene and germanene are found to be semiconducting. Remarkably, the nature and magnitude of their energy bandgap can be controlled by an out-of-plane electric field, an important finding for the potential use of these materials in nanoelectronic devices. (C) 2013 Elsevier B. V. All rights reserved.

Abstract: The Covid era has made us aware of the need for resilient, self-sufficient, and local production. We are likely willing to pay an extra price for that quality. Ammonia (NH3) synthesis accounts for 2 % of global energy production and is an important point of attention for the development of green energy technologies. Therefore, we propose a thermally integrated process for H2 production and NH3 synthesis using plasma technology, and we evaluate its techno-economic performance and CO2 footprint by life cycle assessment (LCA). The key is to integrate energy-wise a high-temperature plasma (HTP) process, with a (low-temperature) non-thermal plasma (NTP) process and to envision their joint economic potential. This particularly means raising the temperature of the NTP process, which is typically below 100 ◦ C, taking advantage of the heat released from the HTP process. For that purpose, we proposed the integrated process and conducted chemical kinetics simulations in the NTP section to determine the thermodynamically feasible operating window of this novel combined plasma process. The results suggest that an NH3 yield of 2.2 mol% can be attained at 302 ◦ C at an energy yield of 1.1 g NH3/kWh. Cost calculations show that the economic performance is far from commercial, mainly because of the too low energy yield of the NTP process. However, when we base our costs on the best literature value and plausible future scenarios for the NTP energy yield, we reach a cost prediction below 452 $/tonne NH3, which is competitive with conventional small-scale Haber-Bosch NH3 synthesis for distributed production. In addition, we demonstrate that biogas can be used as feed, thus allowing the proposed integrated reactor concept to be part of a biogas-to-ammonia circular concept. Moreover, by LCA we demonstrate the environmental benefits of the pro­posed plant, which could cut by half the carbon emissions when supplied by photovoltaic electricity, and even invert the carbon balance when supplied by wind power due to the avoided emissions of the carbon black credits.

Abstract: The deviation effect of spinor mode from the single-mode for a spin-1 Bose gas of trapped atoms is studied beyond the mean field theory. Based on the effective Hamiltonian with nondegenerated level of the collective spin states, the splitting level of the system energy due to the deviation effect has been calculated. For the large condensates of (87)Rb and (23)Na with atom number N > 10(5), the splitting fraction of the energy, arising from the magnetization exhibited by the trapped Bose gas, is found to have a typical order of (10(-4) similar to 10(-8)), decreasing as N(-2) for (87)Rb and increasing as -N(-2) for 23 Na, respectively.

Abstract: The adsorption of CO2 on surfaces of graphene and carbon nanotubes (CNTs), decorated with Fe atoms, are investigated using the self-consistent-charge density-functional tight-binding (SCC-DFTB) method, neglecting the heat effects. Fe ad-atoms are more stable when they are dispersed on hollow sites. They introduce a large density of states at the Fermi level (N-F); where keeping such density low would help in gas sensing. Furthermore, the Fe ad-atom can weaken the C=O double bonds of the chemisorbed CO2 molecule, paving the way for oxygen atoms to drain more charges from Fe. Consequently, chemisorption of CO2 molecules reduces both N-F and the conductance while it enhances the sensitivity with the increasing gas dose. Conducting armchair CNTs (ac-CNTs) have higher sensitivity than graphene and semiconducting zigzag CNTs (zz-CNT5). Comparative study of sensitivity of ac-CNT-Fe composite towards various gases (e.g., O-2, N-2, H-2, H2O, CO and CO2) has shown high sensitivity and selectivity towards CO, CO2 and H2O gases. (C) 2016 Elsevier B.V. All rights reserved.

Abstract: We studied the transport of copper droplets through an inductively coupled plasma, connected to the sampling cone of a mass spectrometer, by means of a computational model. The sample droplets are followed until they become evaporated. They are inserted as liquid particles from the central inlet and the effects of injection position (i.e. “on” and “off” axis), droplet diameter, as well as mass loading flow rate are investigated. It is shown that more “on-axis” injection of the droplets leads to a more straight path line, so that the droplets move less in the radial direction and are evaporated more on the central axis, enabling a better sample transfer efficiency to the sampler cone. Furthermore, there are optimum ranges of diameters and flow rates, which guarantee the proper position of evaporation along the torch, i.e. not too early, so that the sample can get lost in the torch, and not too late, which reduces the chance of becoming ionized before reaching the sampler.

Abstract: In order to minimize the dead volume in large cells for laser ablation inductively coupled plasma mass spectrometry, and improve the aerosol entrainment characteristics, the gas inlet nozzle has been set in rotation. This allowed a wider volume to be swept than with the traditional static inlet nozzle approach. Therefore, sensitivity combined with site-to-site repeatability was improved by a factor of two, together with minimization of aerosol loss within the cell and signal dispersion.