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Silicon heterojunction solar cells represent a key technology to approach very high conversion efficiencies. Thus, effective passivation of the interface of the crystalline silicon substrate, to reduce surface recombination losses, is essential. This is realized by controlled deposition of high quality intrinsic hydrogenated amorphous silicon (a-Si:H(i)) layers. To improve the effective minority charge carrier lifetime, epitaxial growth of the a-Si:H(i) film close to the c-Si surface must be prevented. Furthermore, stability against degradation of the passivation quality induced by application of the doped layer needs to be ensured. In the past, a severe deteriorating effect was observed after deposition of the p-doped layer. To prevent this, an innovative approach was developed by several research groups which consists of the formation of dual a-Si:H(i) layers. This describes the concept of splitting the conventional single a-Si:H(i) layer into a layer stack, each featuring different characteristics. It consist of a buffer layer at the c-Si surface with low hydrogen dilution during the deposition process, to prevent epitaxy at the a-Si:H/c-Si interface, and a high H2 dilution processed capping layer to improve the passivation quality with an increased film density, featuring less micro voids. To date, all dual a-Si:H(i) film developments found in literature are conducted on static deposition tools. To increase the throughput and lift this method on an industrial scale, here, dual a-Si:H(i) layers were processed on an inline Plasma Enhanced Chemical Vapor Deposition tool. A successful process integration of this innovative approach could be established on the MAiA platform from Meyer Burger Germany, and moreover, excellent passivation qualities could be reached with the developed dual a-Si:H(i) layers. Furthermore, a significant mitigating effect of the p-doped induced passivation degradation was achieved, which constitutes a crucial step in the investigations of stable a-Si:H(i) layers for SHJ devices. [ABSTRACT FROM AUTHOR]

A heterogeneous base catalyst, Na-CaO, was prepared by wet impregnation of NaOH solution on CaO solid support originated from chicken eggshells waste. Material characterization using TGA, FTIR, XRD, SEM, EDAX and BET surface area has confirmed the formation of Na-CaO. The catalyst was applied in chalcone syntheses between acetophenone and vanillin at several reaction conditions, such as various weight of catalyst, temperature, type of solvents and reaction time. The highest yield of product (97%) was obtained from the reaction in ethanol, with 0.3 g of catalyst at 60 °C for 1 hour. This research provides a new route of chalcone syntheses by green environmentally catalyst support of chicken eggshells waste. [ABSTRACT FROM AUTHOR]

Porous activated carbon (PAC) was synthesized using hard template method from petroleum sludge waste categorized as toxic waste, using mesoporous MCM-41 as silica template. This sludge waste consists of very high carbon content due to the processing and separation's by-product of crude oil and natural gas from the flowing fluids released from the reservoir. The properties of sludge waste was characterized by FTIR to identify the functional group, XRD to determine the crystal structure, SEM-EDX and CS analyzer to perform elemental analysis, as well as determination of moisture content and ash content. The properties of PAC were studied by analyzing the pore size and volume using BET method, and elemental analysis using SEM-EDX and CS analyzer. The elemental analysis results showed that sludge waste consists of 47.10% carbon, indicated it is potential to be converted into activated carbon. The functional group analysis results indicated that sludge waste consists of some functional groups such as hydroxyl, alkene, alkane, and others. The crystal structure analysis results exhibited no crystalline pattern was found, means it could be still in carbon chain form or other amorph compound. The sludge waste has potential to be a good carbon precursor but a template to synthesize porous activated carbon is required. The pore size and volume distribution of PAC in this research is designated to follow the hexagonal arrays possessed by mesoporous MCM-41. The ongoing work shows that this synthesis method is efficient to produce PAC. [ABSTRACT FROM AUTHOR]

Scaling of calcium carbonate (CaCO3) is commonly found in piping systems in oil, gas, desalination and other chemical processes. The scale may create technical problems, leading to the reduction of heat transfer, increase of energy consumption and unscheduled equipment shutdown. This paper presents crystallization scaling experiments and evaluation of the effect of Cu2+ additives on the induction time and calcium carbonate transformation. The crystals precursors were prepared using equimolar of CaCl2 and Na2CO3 resulted in concentrations of 3000 ppm Ca2+ in the solution. The Cu2+ in amounts of 0, 1 and 10 ppm was separately added in the solution. The flow rates (20, 35, and 60 mL/min) and elevated temperatures (27, 35 and 45°C) were selected in the study. The induction time for crystallization of CaCO3 was observed by measuring the solution conductivity over time, while the phase transformation of calcium carbonate was examined by XRD method and SEM/EDX. It was found that the conductivity remained steady for a certain period reflecting to the induction time of crystal formation, and then decreased sharply afterwards,. The induction time was increased from 34 and 48 minutes in the presence of Cu additives (1 and 10 ppm), depending on the flow rates and temperature observed. In all the experiments, the Cu2+ addition leads to the reduction of mass of crystals. Apparently, the presence of Cu2+ could inhibit the CaCO3 crystallization. In the absence of Cu2+ and at elevated temperature, the crystals obtained were a mixture of vaterite and calcite. In the presence of Cu2+ and at elevated temperature, the crystals formed were aragonite and calcite. Here, the presence of Cu2+ additives might have controlled the crystal transformation of CaCO3. [ABSTRACT FROM AUTHOR]

Based on the principal concepts of physical mesomechanics that take into account reversible structural-phase transformations in the rotational-wave flows at the interfaces, a new modification of the multilevel discrete-continuous method of excitable cellular automata (ECA) has been developed. The new modification explicitly takes into account the porosity and the nanocrystalline structure. Also, algorithms for calculating the local moments of forces and the angular velocities of microrotations arising in a structurally heterogeneous medium have been implemented. The model has been complemented by the dissipation conditions expressed for mechanical energy flows. On the basis of the method of excitable cellular automata' some numerical experiments on thermal loading of three-layered compositions with the intermediate layers of different structures have been carried out. It is shown that nanostructuring of the intermediate sublayer and the introduction of nanoporosity gives rise to a positive effect on the relaxation ability of thermal barrier coatings. [ABSTRACT FROM AUTHOR]

Ion beam irradiation of a-Si/Fe/c-Si trilayers with 350-MeV Au ions and of Fe/a-Si bilayers with 250-keV Xe ions were carried out in order to measure the interface mixing rates and microstructure, phase formation, and magnetic polarization in the regimes of electronic and nuclear stopping. For Fe/a-Si and nuclear stopping, an enhancement of the interface mixing rate of 1.75±0.15 was observed relative to Fe/c-Si. For electronic stopping, the enhancement is 3.21 ±0.34. A plausible explanation of this enhancement lies in the much smaller thermal conductivity in a-Si relative to c-Si, which prolongates the relaxation phase of the ion-induced thermal spikes. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

We present 3D-nonequilibrium molecular dynamics results for the velocity dependence of the frictional force at smooth sliding interfaces for Ta and Al single crystals. For Ta/Al we consider Al(100)/Ta(100) and Al(111)/Ta(110) interfaces sliding along [001] and [110]fcc /[001]bcc respectively. These are compared with Al(111)/Al(100) interfaces at the same loads, corresponding to a pressure of 15 GPa. Both interfacial pairs show similar behavior in the velocity dependence of the frictional force: a low velocity regime with an increasing frictional force followed by a strain induced transformation regime at velocities above approximately 1/10 the transverse sound speed, followed by a fluidized interface at high velocities. For both interfacial pairs, the high velocity dependence of the frictional force exhibits power law behavior, Ft ∝ v-β with β=3/4. We discuss the structural changes that influence dissipation in each of these regimes. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

This research focuses on analyzing shock wave propagation in <100>, <110>, and <111> oriented single crystalline Al, <0001> oriented single crystalline Fe2O3, and an interface of {100} surface of Al with {0001} surface of Fe2O3. For this purpose, an interatomic potential is developed to describe atomic interactions in the Fe+Al+Fe2O3+Al2O3 material system. The analyses in single crystalline systems focus on the relationships between the shock wave velocity (US) and the particle velocity (UP) as a function of the single crystalline orientation. Calculations also focus on the formation and propagation of defects. The interfacial shock wave propagation analyses focus on the change in atomic structure near the interface as a function of UP. Calculations show that there is a threshold UP value above which the atomic structure on both sides of the interface undergoes significant changes which are accompanied by enhanced increase in temperature and pressure relative to what is seen in both phases when they are deformed alone. This observation suggests a possibility that this threshold may represent the onset of a shock-induced reactive structural change. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

The subject of consideration is the pseudospin-electron model (PEM) which appears in the description of locally anharmonic crystalline and molecular systems with strong electron correlations. A review of the main results concerning thermodynamics, energy spectrum and dynamics of the model is given. Thermodynamically stable states and phase transitions in the system are investigated in the regimes of constant chemical potential or the fixed electron concentration both within the framework of the generalized random phase approximation and the dynamical mean field scheme. A comparison is performed with thermodynamics of the Falicov-Kimball model. An attention is called to the possibility of applying of the PEM to the description of high-Tc superconductors as well as to the H-bonded systems with the transition metal ions. © 2003 American Institute of Physics [ABSTRACT FROM AUTHOR]

The alleged in-plane polar structure in two-dimensional (2D) smectic-C liquid crystalline phases of Langmuir monolayers was directly confirmed by the optical second harmonic generation (SHG) spectroscopy for the first time. The SH signal associated with the in-plane polar structure was found to be comparable with that coming from the out-of-plane polar distribution of molecular orientation inherent at the air-water interface, This result indicates that there exits a strong preference for the heads and tails of the molecules to spontaneously associate one another over the otherwise isotropic water surface as a resuk of the 2D liquid crystalline order. When the monolayer underwent a first order phase transition from SmC to a solid-like phase under compression, both of the in-plane and out-of-plane components of SH signals were considerably reduced despite an increase in density, implying the rather subtle nature of the centro-symmetry breaking in the SmC phase. [ABSTRACT FROM AUTHOR]