Increase In Deposition Rate Research Articles

Anthropogenic influence on rates of aeolian dune activity within the northern European Sand Belt and socio-economic feedbacks over the last ~2500 years

In North-Western Europe, Pleistocene sand sheets have been reactivated during phases of Holocene deforestation and agricultural land use. Although there are temporal overlaps between anthropogenic activity and sand sheet reactivation, the root cause and subsequent feedbacks between aeolian activity and societal response remain largely unknown. Here, we seek to establish cause and effect by examining the detailed co-variation in both timing and magnitude of aeolian and anthropogenic activity through the quantification of Holocene dune sediments in combination with archaeological and pollen records. These records indicate a series of complex phases of aeolian activity followed by landscape stabilization, which we attribute primarily to changing patterns of human impact. We find that a steady increase in dune deposition rates in the Medieval Period corresponds to an increase in settlement activity and deforestation (~AD 1000–1500). At their peak, Medieval deposition rates were 3.4 times larger than during the late Pleistocene, the period experiencing the most favourable natural conditions for aeolian sediment transport. Prior to the Medieval Period, relative land-surface stability (represented by a depositional hiatus) persisted from the late Pleistocene until the Roman Iron Age Period (AD 0–400). Deforestation to fuel iron production had minor impact on aeolian activity, as indicated by the lowest recorded deposition rate (0.12 ± 0.02 t/ha/a). Following the Medieval Period peak in deposition rates, aeolian activity diminished rapidly and coincided with the abandonment of nearby human settlement. This sequence of events provides evidence of a direct positive feedback in which Medieval agricultural overexploitation favoured aeolian activity that rendered the landscape practically unworkable for cropping agriculture. Based on our findings and a comprehensive review of Northern European sand belt activity, we interpret a very high sensitivity of aeolian activity to past and present human impact and argue that unsustainable land-use practices have been the cause for widespread settlement abandonment.

Electrodeposition of Zn–Ni–P compositionally modulated multilayer coatings: An attempt to deposit Ni–P and Zn–Ni alloys from a single bath

The effects of bath composition and deposition variables on the electrodeposition of Zn–Ni–P alloys were studied in order to develop a single bath for deposition of Ni–P/Zn–Ni compositionally modulated multilayer coatings (CMMCs). The basis for development of the bath was a large increase in the Ni deposition rate compared to that of Zn at low deposition overpotentials combined with the impossibility of codeposition of Zn with P. EDS analysis demonstrated that the deposits obtained from the Zn–Ni–P bath at low overpotentials were practically all Ni–P, while the alloy deposited at high overpotentials was mainly Zn–Ni with around 3.2wt% P content.

Combined magnetron sputtering and pulsed laser deposition of TiO2 and BFCO thin films

We report the successful demonstration of a hybrid system that combines pulsed laser deposition (PLD) and magnetron sputtering (MS) to deposit high quality thin films. The PLD and MS simultaneously use the same target, leading to an enhanced deposition rate. The performance of this technique is demonstrated through the deposition of titanium dioxide and bismuth-based perovskite oxide Bi2FeCrO6 (BFCO) thin films on Si(100) and LaAlO3 (LAO) (100). These specific oxides were chosen due to their functionalities, such as multiferroic and photovoltaic properties (BFCO) and photocatalysis (TiO2). We compare films deposited by conventional PLD, MS and PLD combined with MS, and show that under all conditions the latter technique offers an increased deposition rate (+50%) and produces films denser (+20%) than those produced by MS or PLD alone, and without the large clusters found in the PLD-deposited films. Under optimized conditions, the hybrid technique produces films that are two times smoother than either technique alone.

Chemical composition and properties of MoAl thin films deposited by sputtering from MoAl compound targets

Molybdenum-based thin films are widely used as back-contact layers in solar cells, as interconnect material or diffusion barriers in microelectronics, or as gate and source/drain lines in thin film transistor liquid crystal displays. Within this work, the sputter behavior of three different molybdenum-aluminum compound targets with Al contents of 24, 37, and 49 at. % manufactured by cold gas spraying as well as the chemical composition, the microstructure, and the properties of the deposited thin films have been investigated. The increase in the Al content in the targets results in an increasing deposition rate of the films. The fine-columnar films are characterized by the formation of a body-centered cubic solid solution resulting in an electrical resistivity increasing from 100 μΩ cm for 10 at. % Al to more than 200 μΩ cm for 30 at. % Al. Monte Carlo simulations of sputtering and gas phase transport indicate that the observed large deviations of the chemical compositions of the films with respect to the target are mainly caused by aluminum losses due to gas phase scattering.

Fabrication of columnar structured lanthanum zirconate films by laser CVD

AbstractColumnar lanthanum zirconate (LZ) films were deposited by laser chemical vapor deposition (LCVD). The effects of deposition conditions, preheat temperature and laser power, on crystal structure, morphology, and deposition rate were investigated. A large region in the terms of preheat temperature and laser power for the formation of cubic pyrochlore‐structured LZ films was mapped under a fixed total pressure of 950 Pa. The morphology of LZ films without laser irradiation showed a dense and glass‐like structure with a flat cauliflower surface. It was changed into a columnar structure with an unflat cauliflower surface by low‐power laser irradiation during deposition process. The transformation occurred once a critical laser power beyond 16 W/cm2. Thus, the effect of laser on the deposition of LZ films was a result of double‐side action including both pyrolytic effect and photolytic effect. Plasma gas around the substrate resulted in significant increases in deposition temperature and deposition rate due to self‐propagating high‐temperature reactions between the precursors and O2. The maximum deposition rate can reach 250 μm/h by LCVD.

Tapered laminate designs for new non-crimp fabric architectures

Non-Crimp Fabric (NCF) materials are now available in a range of areal weights and layer architectures, including 0/45, 0/−45, 45/−45 and 0/90, which correspond to the standard ply orientations employed in traditional UD material lay-ups. The benefit of NCF material is generally associated with increased deposition rate, but this advantage may be offset by reduced design freedoms when a specific form of mechanical coupling behaviour is required, layer terminations must be introduced and/or thermal warping distortion eliminated.This article investigates the extent to which new NCF architectures can be tailored to achieve warp free tapered laminates with mechanical Extension-Shearing Bending-Twisting coupling, by single axis (longitudinal) deposition of all ply angles; thus avoiding ply discontinuities that may be introduce in large component manufacture. Lamination parameter design spaces are used to demonstrate the extent of the feasible solutions both before and after applying a laminate tapering scheme.

Vector Analysis of Ionic Collision on CaCO3 Precipitation Based on Vibration Time History

Vibration effects on the piping system can result from the internal factor of fluid or the external factor of the mechanical equipment operation. As the pipe vibrated, the precipitation process of CaCO3 on the inner pipe could be affected. In the previous research, the effect of vibration on CaCO3 precipitation in piping system was clearly verified. This increased the deposition rate and decreased the induction time. However, the mechanism of vibration control in CaCO3 precipitation process as the presence of vibration has not been recognized yet. In the present research, the mechanism of vibration affecting the CaCO3 precipitation was investigated through vector analysis of ionic collision. The ionic vector force was calculated based on the amount of the activation energy and the vibration force was calculated based on the vibration sensor data. The vector resultant of ionic collision based on the vibration time history was analyzed to prove that vibration brings ionic collision randomly to the planar horizontal direction and its collision model was suspected as the cause of the increasing deposition rate.

Enhancing the oxygen ionic conductivity of (111) oriented Ce0.80Sm0.20O2-δ thin film through strain engineering

Several physicochemical properties can be tailored by tuning the lattice strain of the crystal. Here, we report the effect of lattice strain on oxygen ion conduction of oriented samarium doped ceria (SDC) films deposited over an amorphous quartz substrate. Lattice distortion was induced by varying the deposition rate in electron beam deposition technique (EB-PVD). Texture coefficient calculation and pole figure analysis confirms the (111) orientation in out‐off plane direction. Stress state was monitored using sin2Ψ method in tri-axial direction and the results indicate a reduction in compressive stress with an increase in deposition rate. A difference in the mean free path of adatom influences the surface morphology of SDC films with compressive stress leading to a significant impact on conductivity. Compared to higher compressive stress, thin film containing lower stress along (111) orientation exhibited a two order enhancement in conductivity. The faster ionic conductivity arises from the ease of oxygen ion hopping through the expanded lattice as compared to the highly-stressed crystal structure. Thus, the deposition rate in EB-PVD provides a valuable technique for engineering the strain to realize the potential enhancement in the efficiency of electrolyte for ITSOFC application.

Modeling of retention and re-entrainment of mono- and poly-disperse particles: Effects of hydrodynamics, particle size and interplay of different-sized particles retention

In this paper, numerical simulations of experimental data were performed with kinetic rate coefficients to characterize the retention and re-entrainment dynamics under different hydrodynamic conditions for monodisperse and polydisperse latex particles (3, 10, 16μm and the mixture). The results show that drastic increase in fluid velocity provokes hardly any remarkable decrease in retention in the presence of large energy barriers (>2000kT). Systematical increases in deposition and re-entrainment dynamic rates were observed with fluid velocity and/or particle size. Increased irreversible deposition rate indicates straining and wedging dominate deposition in this study. Excess retention of 3μm particle in the polydisperse particle suspension was observed. The origins are reckoned that deposited larger particles may hinder the re-entrainment of smaller particles near the grain-to-grain contact and can provide additional sites of attachment.

Effect of material of the crucible on operation of magnetron sputtering system with liquid-phase target

The paper presents a high-rate method for metal coating deposition by the means of magnetron sputtering system (MSS) with liquid-phase target. Maximum copper deposition rate at a power density of 55 W/cm2 is 200 nm/s, which is twenty times higher than if an ordinary magnetron is used. The effect of material of the crucible on operation of MSS with liquid-phase target and copper coating deposition rate is studied. It is demonstrated that using the crucible with a lower emissivity allows the several-fold increase in deposition rate.

Deposition rate dependant formation and properties of Sn2S3 and SnS thin films by co-evaporation

We report the effect of deposition rate on the formation and properties of tin sulfide (Sn2S3 and SnS) thin films prepared by co-evaporation technique. The structural, morphological and optical properties of these films have been investigated as the function of deposition rate. X-ray photoelectron spectroscopy analysis confirmed the transformation of Sn2S3 phase to SnS phase with the increase in deposition rate of tin. The structural analysis by XRD and Raman showed the formation of Sn2S3 and SnS phases. The variation in surface morphology and roughness of the as- deposited films have been examined by scanning electron microscopy (SEM) and atomic force microscopy (AFM). UV–Vis–NIR spectrometer was employed to record the transmission spectra of the samples in the wavelength range of 200–3000 nm. Film thickness (d), optical band gap (Eg), refractive index (n) and extinction coefficient (k) of the deposited thin films are estimated from the optical data. Photo conductivity of the as-deposited films has been studied using two probe method. Hall effect measurements show an n-type to p-type conversion in electrical conductivity with increase in deposition rate.

Instabilities of nanofluid flow displacements in porous media

Thanks to a number of advantageous characteristics, nanofluids are widely used in a variety of fluid flow systems. In porous media flows, the presence of nanoparticles can have dramatic effects on the flow dynamics and in particular on viscous fingering instabilities that develop when a less viscous fluid displaces a more viscous one. In the present study, these effects have been investigated both analytically and numerically using linear stability analysis (LSA) and non-linear simulations. The LSA problem was solved analytically using step function approximation, and general conclusions about the effects of nanofluids on the instability were derived from long wave expansion and cutoff wave number analyses. Furthermore, the quasi-steady-state approximation was used to expand the results of the LSA to diffusing initial concentration profiles, and simulations of the full non-linear problem have been carried out using a Hartley-transform based pseudo-spectral method. Results revealed that nanoparticles cannot make an otherwise stable flow unstable but can enhance or attenuate the instability of an originally unstable flow. In particular it was found that increases in the nanoparticles deposition rate or their rate of diffusion have both destabilizing effects. Furthermore, nanoparticles deposition can change the initial monotonically decreasing viscosity distribution to a non-monotonic one and results in the development of vortex dipoles. Analyses of vortex structures along with the viscosity distributions allowed to explain the observed trends and the resulting finger configurations.

Variation of effective damping factor for CoPt-based alloy films with various atomic stacking structures

Ferromagnetic resonance (FMR) was observed for Co82Pt12 films with various process. And relation between effective damping factor (αeff) and compositional modulation (CM) in the atomic layers, and other magnetic properties to investigate the relationship between local variation of the magnetic properties and the αeff. The CM was changed by the substrate temperature Tsub and deposition rate of the Co-Pt alloy film. As a result, it was found that 1) For the Tsub dependence, αeff took maximum value of 0.22 at Tsub = 200 oC. 2) For the rate dependence, aeff linearly increases with 0.12 to 0.35 with increasing deposition rate from 0.3 to 2.0 nm/sec. 3) There was no similar tendency between aeff and CM for the Co-Pt alloy film with Tsub and rate change. Thus the CM is not dominant factor of the aeff for the compositionally modulated Co-Pt alloy film.

The linking of the upper-middle and lower reaches of the Yellow River as a result of fluvial entrenchment

The upper–middle Yellow River flows through the Fenwei graben, a structure resulting from extensional tectonism that was formed and repeatedly extended during the Cenozoic. The drainage system within this graben was formerly isolated from the lower reaches of the Yellow River system by the Xiaoshan mountains, an actively growing ∼ NW–SE trending range. The modern course of the Yellow River takes it through this range along the Sanmen gorge, the formation of which was of great significance in that it initiated through-going drainage between the upper–middle and lower reaches of the system. The timing of this event, which was clearly a critical point in the evolution of the Yellow River, can be established by dating the terraces in the gorge. Intermittent deepening of this gorge by the Yellow River from a high-level planation surface capping the mountain range has resulted in the formation of five terraces. Magnetostratigraphic records from aeolian deposits accumulated on these surfaces provide a geochronological sequence for this geomorphic archive, in which the ages of the planation surface and of terraces T5, T4, T3, T2, and T1 have been determined as ∼3.63 Ma, ∼1.24 Ma, ∼0.86 Ma, ∼0.62 Ma, ∼129 ka, and ∼12 ka, respectively.Under the constraint of this chronological framework, a model for landscape evolution is proposed here. Uplift of the inner Fenwei graben and of the surrounding mountain ranges led to dissection of the 3.63 Ma old planation surface in conjunction with the formation of the Sanmen gorge. Drainage of the lake previously occupying the basin would have promoted incision into the fluvio-lacustrine graben sediments; indeed, gorge formation through the Xiaoshan may have been initiated or intensified by lake overflow. The ages obtained for the planation surface and uppermost terrace suggest that the formation of the Sanmen gorge and the initiation of the through-going eastward drainage of the Yellow River occurred between 3.63 and 1.24 Ma. Before the start of gorge entrenchment, the products of erosion in the modern upper catchment of the Yellow River were unable to reach the sea. The dramatic increase in deposition rates in the Bohai Gulf (at the mouth of the modern Yellow River in the East China Sea), ∼1.0 Ma ago, thus resulted from the initiation of an integral (enlarged) Yellow River catchment drainage through the Sanmen gorge; it does not imply an increase in erosion rates at that time.

Design and optimization of rectangular cold spray nozzle: Radial injection angle, expansion ratio and traverse speed

A cold spray nozzle with radially injected powder was numerically modeled and experimentally validated. The gas flow field and particle trajectories were simulated for various injection angles and expansion ratios. Injection angle was seen to affect particle distribution and injection pressures. The effect of expansion ratio was numerically studied and experimentally verified with stainless steel powders. For this material system, highest deposition efficiency was observed at an overexpanded flow regime. High deposition rate was accompanied by strain rate induced phase change. In addition, the effect of traverse speed (between 1 and 6mm/s) was assessed experimentally. While the speed did not affect bond strength and coating hardness, an optimum speed was found where there was a substantial increase in deposition rate.

Evaluation of cold wire addition effect on heat input and productivity of tandem submerged arc welding for low-carbon microalloyed steels

The addition of a cold wire in conventional tandem submerged arc welding (TSAW), i.e., the CWTSAW process, is proposed to improve the productivity of pipeline manufacturing by increasing welding travel speed and deposition rate, while retaining adequate joint geometry without increasing the welding heat input. In addition to increasing productivity, incorporating a cold wire in the TSAW process improves the fracture toughness by refining the microstructure of the weld heat-affected zone (HAZ). In the present work, the influence of cold-wire addition on the heat input, productivity and properties of an X70 microalloyed steel welded by CWTSAW is investigated. Charpy impact testing and microhardness testing were utilized to investigate the mechanical properties of the HAZ. Scanning electron microscopy (SEM) and tint etching optical microscopy (TEOM) were used to correlate the microstructure alterations with the properties. The low-temperature fracture toughness of the HAZ was improved by 38% when a cold wire was fed at 25.4 cm/min in the conventional TSAW process with a heat input of 22.1 kJ/cm. This improvement was attributed to a reduction in the prior austenite grain (PAG) size and martensite-austenite (M-A) constituent fraction as a result of the reduction in the effective heat input (7.5% reduction) by cold wire addition. The amount of heat input reduction is a function of the cold wire addition rate and the nominal welding heat input. The increase in travel speed and deposition rate of welding by addition of a cold wire at 58 cm/min in the TSAW process with a heat input of 23.2 kJ/cm was 26 and 12%, respectively.

Monte Carlo Modeling of Astrophysically-Relevant Temperature-Programmed Desorption Experiments

AbstractThe formation of molecules in the interstellar medium is significantly driven by grain chemistry, ranging from simple (e.g. H2) to relatively complex (e.g. CH3OH) products. The movement of atoms and molecules on amorphous ice surfaces is not well constrained, and this is a quintessential component of surface chemistry. We show that ice structure created by utilizing an off-lattice Monte Carlo kinetics model is highly dependent on deposition parameters (i.e. angle, rate, and temperature). The model, thus far, successfully predicts the densities of deposition rate- and temperature-dependent laboratory experiments. The simulations indicate, when angle and deposition rate increase, the density decreases. On the other hand, temperature has the opposite effect and will increase the density. We can make ices with desired densities and monitor how molecules, like CO, percolate through H2O ice pores. The strength of this model lies in the ability to replicate TPD-like experiments by monitoring molecules diffusing on and desorbing from user-defined surfaces.

The arc arises: The links between volcanic output, arc evolution and melt composition

Subduction initiation is a key process for global plate tectonics. Individual lithologies developed during subduction initiation and arc inception have been identified in the trench wall of the Izu–Bonin–Mariana (IBM) island arc but a continuous record of this process has not previously been described. Here, we present results from International Ocean Discovery Program Expedition 351 that drilled a single site west of the Kyushu–Palau Ridge (KPR), a chain of extinct stratovolcanoes that represents the proto-IBM island arc, active for ∼25 Ma following subduction initiation. Site U1438 recovered 150 m of oceanic igneous basement and ∼1450 m of overlying sediments. The lower 1300 m of these sediments comprise volcaniclastic gravity-flow deposits shed from the evolving KPR arc front. We separated fresh magmatic minerals from Site U1438 sediments, and analyzed 304 glass (formerly melt) inclusions, hosted by clinopyroxene and plagioclase.Compositions of glass inclusions preserve a temporal magmatic record of the juvenile island arc, complementary to the predominant mid-Miocene to recent activity determined from tephra layers recovered by drilling in the IBM forearc. The glass inclusions record the progressive transition of melt compositions dominated by an early ‘calc-alkalic’, high-Mg andesitic stage to a younger tholeiitic stage over a time period of 11 Ma. High-precision trace element analytical data record a simultaneously increasing influence of a deep subduction component (e.g., increase in Th vs. Nb, light rare earth element enrichment) and a more fertile mantle source (reflected in increased high field strength element abundances). This compositional change is accompanied by increased deposition rates of volcaniclastic sediments reflecting magmatic output and maturity of the arc. We conclude the ‘calc-alkalic’ stage of arc evolution may endure as long as mantle wedge sources are not mostly advected away from the zones of arc magma generation, or the rate of wedge replenishment by corner flow does not overwhelm the rate of magma extraction.

PH effect on zinc recovery from the spent pickling baths of hot dip galvanizing industries

Abstract In this work, the pH effect on the zinc electrowinning present in the spent pickling baths (SPBs) is analysed with the aim of decreasing the energetic cost of the process. Specifically, the effect of increasing the initial pH with and without its control during the whole electrolysis experiment is studied on synthetic solutions with concentration values similar to those present in the spent pickling baths. Finally, real SPBs are treated under pH control and the results obtained are also compared with those acquired with the direct electrolysis of these SPBs in a membrane reactor. The modification of the initial pH on synthetic solutions shows an increase in zinc deposition rate as the initial pH is risen. However, the zinc redissolution phenomenon is present during the whole experiment. On the other hand, when the pH is controlled, the results obtained are much better as zinc redissolution is prevented and the hydrogen evolution reaction rate is decreased. Comparing the behaviour between the reactor under pH control and that in the presence of an anion-exchange membrane, reflects zinc conversion values slightly higher for the membrane reactor due to the zinc precipitation occurring in the reactor under pH control, which is higher as the pH rises. However, the specific energy consumption is considerably higher in the membrane reactor mainly due to the ohmic drop introduced by the membrane.

Using wire shaping techniques and holographic optics to optimize deposition characteristics in wire-based laser cladding.

In laser cladding, the potential benefits of wire feeding are considerable. Typical problems with the use of powder, such as gas entrapment, sub-100% material density and low deposition rate are all avoided with the use of wire. However, the use of a powder-based source material is the industry standard, with wire-based deposition generally regarded as an academic curiosity. This is because, although wire-based methods have been shown to be capable of superior quality results, the wire-based process is more difficult to control. In this work, the potential for wire shaping techniques, combined with existing holographic optical element knowledge, is investigated in order to further improve the processing characteristics. Experiments with pre-placed wire showed the ability of shaped wire to provide uniformity of wire melting compared with standard round wire, giving reduced power density requirements and superior control of clad track dilution. When feeding with flat wire, the resulting clad tracks showed a greater level of quality consistency and became less sensitive to alterations in processing conditions. In addition, a 22% increase in deposition rate was achieved. Stacking of multiple layers demonstrated the ability to create fully dense, three-dimensional structures, with directional metallurgical grain growth and uniform chemical structure.