Search

The reflection of gas-powder impinging on the substrate surface was an important factor to affect the forming quality and efficiency for laser additive remanufacturing. Due to the various substrate shapes, the changes of the powder flow field were different after the powder impinging on he substrates. Gas-solid two-phase flow was taken as the theoretical basis, coupled simulation of EDEM and FLUENT software was used to study the gas-powder flow field distribution characteristics under three kinds of substrate changes, namely, regular substrate boundary, thin-wall substrate thickness and globoidal substrate curvature, and experimental verification was carried out. Results how that the turbulence of the gas field in the contact areas with the substrate increases as the nozzle s far away from the boundary, and the low-speed areas as well as the negative pressure range decreases. Meanwhile, the number of effective particles decrease exponentially. The gas field developes to he both sides obviously and the concentration of the machining centers decreases gradually with the increase of the thin-walled substrate width. And the powder flow rate in the effective ranges increases first and then remains. With the increase of the absolute curvature of substrates, the radial concentration of the convex substrate increases, and the focus range decreases, and the powder flow has a better convergence than that of concave substrates. [ABSTRACT FROM AUTHOR]

A thin thermally insulating vapor layer beneath a levitating Leidenfrost droplet adversely affects the heat transfer from the underlying hot substrate during cooling applications. In this work, we present a theoretical model to determine the total heat transfer to a Leidenfrost droplet on microtextured substrates, taking into account the curved shape of the liquid-vapor interface. The profile of the vapor gap and vapor flow field beneath a Leidenfrost droplet on a microtextured surface is shown to be dependent on the substrate morphology. The shape of the liquid-vapor interface beneath the Leidenfrost droplet, in turn, influences the rate of evaporation on a microtextured substrate. We determine the variation of the minimum and maximum vapor gap over micro-pillared surfaces with different substrate permeability for various droplet volumes and wall superheat. The heat transferred to the droplet is via conduction across the vapor gap beneath the droplet and convection from the ambient air around the droplet. We determine the total evaporation time of a Leidenfrost droplet over a micro-textured substrate using the curved interface model and the conventional flat vapor gap interface model and compare with that obtained from experiments. The overprediction of the average rate of evaporation of a Leidenfrost droplet by the flat interface model ranges from ∼59 % for tall and sparse pillars (marked by high substrate permeability) to ∼ 29 % for short pillars (with low substrate permeability). We show that the average rate of evaporation of the LF droplet obtained using the curved interface model agrees reasonably (within 9%–23 %) with that observed in the experiments. [ABSTRACT FROM AUTHOR]

We use a combined theoretical and experimental approach to investigate the quasi-static peeling behaviors of heterogeneous films from corrugated substrates. The heterogeneity is involved in films through two different methods, i.e., local stiffening and kirigami patterning, and the substrate surface is assumed to adopt a sinusoidal profile. Our results show that the spatial variation in film's bending stiffness, caused by the elastic heterogeneity with period form, can significantly enhance the peak peel force and give rise to asymmetric adhesion performance. The substrate's roughness can further amplify such adhesion enhancement and asymmetry by affecting the local peel angle at the peel front. The adhesion performance depends sensitively on the relative position between the heterogeneous films and corrugated substrates, and our results show that a combination of film heterogeneity and substrate undulation can enhance the adhesive strength by more than 100 times, compared with the case of homogeneous film and flat substrate. This study provides a theoretical framework to reveal multiple peeling mechanisms in the problem and can guide the design of film-substrate systems with tunable and anisotropic adhesion. • Strong and asymmetric adhesion is essential for natural and engineering systems, and various strategies have been proposed. • We modify the apparent adhesion through elastic heterogeneity, kirigami pattern, and substrate morphology. • Peak peel force can be dramatically improved due to the energy dissipation originating from heterogeneity. • Heterogeneity and kirigami in films lead to distinct responses when the films undergo forward and backward peeling. • Our study reveals multiple peeling mechanisms and can guide the design of tunable and anisotropic adhesion. [ABSTRACT FROM AUTHOR]

SiC coating was prepared on the graphite substrate and the effects of substrate morphology on the thermal radiation properties of SiC coating were investigated. As the surface roughness of the graphite substrate decreasing from 2.95 to 0.68 μm, the total emissivity of SiC coating increased 28.33% at 1000 °C and 36.21% at 1600 °C, respectively. At the same time, the spectral emissivity of SiC coating on the graphite substrate all presented the obvious characteristic thermal radiation of SiC. Those results meant that the thermal radiation properties of the coating were both dominated by the substrate and coating. A simple coating model had been established to explain the effect of the substrate morphology on the heat flow between the substrate and coating. The rough substrate morphology enhanced the energy dissipation at interface and weakened the thermal radiation properties of coating finally. [ABSTRACT FROM AUTHOR]

The influence of substrate morphology on the Rashba band splitting at the Dirac point of graphene, has been theoretically investigated. More specifically, the possibility for this splitting to be caused by spin–orbit coupling (with the heavy metal substrate) was of a special interest to study. The model system consisted of a 4H-SiC (0 0 0 1)/graphene interface, with an intercalated metal layer (Ag and Au, respectively). These intercalating metal layers were built with two different types of morphologies; either flat or buckled (with different buckling positions). The results show that depending on the position of the buckled metal atom, the size of the bandgap and band splitting (at the Dirac point of graphene) will either increase (or decrease). Moreover, the enlargement of the buckling size was also shown to affect the electronic properties of graphene (i.e., by increasing the bandgap). The sizes of the bandgaps and band splitting for the different intercalating metals (Ag and Au), were also found to be different. Spin-projected band structures was also implemented in the present study, with the purpose to show the spin-texture of graphene. It was thereby shown that the spins pined to the x and y spin components for most of the cases.

Abstract The cold spray process and laser-induced projectile impact test (LIPIT) are used to deposit Ti powder particles on sintered polycrystalline Al 2 O 3. Whereas LIPIT allows real-time observations of single particle impact and measurement of particle impact velocity, cold spray rapidly and simultaneously deposits particles with a wide range of deposition velocities and sizes. By use of these two techniques, the effect of particle velocity and substrate morphology on adhesion strength of single splats is investigated. The critical velocity for deposition is identified to be approximately 580 m/s for the Ti/Al 2 O 3 system when using LIPIT and particles of 10 μm. Above the critical velocity, flattening ratio (FR) is also evaluated and observed to be linearly dependent on the particle impact velocity. Splat adhesion testing is performed on LIPIT-deposited as well as on cold spray-deposited powder particles to measure adhesion strength. This analysis shows that adhesion strength is highly affected by local substrate surface morphology, where particles bond more weakly to relatively smooth portions of the substrate. Therefore, mechanical bonding plays a significant role in adhesion. Also, adhesion strength decreases with an increase in FR and therefore velocity. This decrease can be associated with fracture of the ceramic substrate and rebound forces. Highlights • Ti splats are deposited on sintered polycrystalline Al 2 O 3 by cold spray and LIPIT. • LIPIT revealed that Ti splats begin to bond to Al 2 O 3 at approximately 580 m/s. • Flattening ratio can be used to estimate an effective velocity for single splats. • Adhesion strength is inversely proportional to flattening ratio for cold spray splats. • Areas on the substrate with smaller Al 2 O 3 grains lead to higher adhesion strength. [ABSTRACT FROM AUTHOR]

Amine-coated biodegradable materials based on synthetic polymers have a great potential for tissue remodeling and regeneration because of their excellent processability and bioactivity. In the present study, we have investigated the influence of various chemical compositions of amine plasma polymer (PP) coatings and the influence of the substrate morphology, represented by polystyrene culture dishes and polycaprolactone nanofibers (PCL NFs), on the behavior of vascular smooth muscle cells (VSMCs). Although all amine-PP coatings improved the initial adhesion of VSMCs, 7-day long cultivation revealed a clear preference for the coating containing about 15 at.% of nitrogen (CPA-33). The CPA-33 coating demonstrated the ideal combination of good water stability, a sufficient amine group content, and favorable surface wettability and morphology. The nanostructured morphology of amine-PP-coated PCL NFs successfully slowed the proliferation rate of VSMCs, which is essential in preventing restenosis of vascular replacements in vivo. At the same time, CPA-33-coated PCL NFs supported the continuous proliferation of VSMCs during 7-day long cultivation, with no significant increase in cytokine secretion by RAW 264.7 macrophages. The CPA-33 coating deposited on biodegradable PCL NFs therefore seems to be a promising material for manufacturing small-diameter vascular grafts, which are still lacking on the current market.

This paper has investigated the impact of the substrate temperature and Ar ion assisted deposition on the surface structure formation mechanism and the film properties during the amorphous TiO 2 thin film deposition process with the molecular dynamics simulation method. The results show that the reduction of the surface roughness happen when the energy of Ar ions assisted is increased or the substrate temperature rises, and also the film density on surface is changed with the increasing of Ar ions energy and substrate temperature. It is also found that the Volmer-Weber (island) growth mode of films is promoted by the lower Ar ion energy and higher substrate temperature when the substrate has an island structure. The assisted Ar ion has power of making a flat surface and increasing the local temperature. Besides, it will influence the growth mode with the change of surface atom mobility. With a high assisted Ar ion energy the Volmer-Weber (island) growth mode is inhibited, which will be conducive to the formation of more smooth film surface. [ABSTRACT FROM AUTHOR]

This paper presents the influence of ageing on the morphological and optical properties of TPD (N, N’ - Bis (3 - methylphenil) - N, N’ diphenylbenzidine) thin films. Understanding of the nucleation mechanism and growth dynamics of molecular thin films is pivotal for controlling their morphology and the film interfacial properties, while the influence of ageing is essential for the potential commercial utilization. Initially, thin films were prepared using a combinatorial physical vapour deposition (CPVD) method, following a cosine-like distribution profile of thickness along monocrystal silica substrate. Morphology of thin films was investigated by using optical (OM) and atomic force microscopy (AFM). The link between optical properties and the resulting thin film morphology was made by spatially correlated morphological (AFM and OM) and optical (absorption and photoluminescence) measurements. The changes in the absorption and photoluminescence spectra are strongly connected to the ageing-induced changes in the microstructure of thin films. Regardless of morphological and differences in the film thickness (two orders of magnitude), all films show amorphous arrangement just after the deposition. Ageing of these films in regular atmosphere conditions results in morphological and changes in optical properties induced by the crystallization. The crystallization of initially amorphous samples was also confirmed by the differentional scanning calorimetry (DSC) measurements. All results indicate the limited possibility of using TPD films in organic electroluminescent devices.

ABSTRACT A mechanistic model of enzymatic hydrolysis taking into account the morphology of the cellulosic particles and its evolution with time was developed. The individual behavior of the main enzymes involved in the reaction (cellobiohydrolases, endoglucanases, and β-glucosidases), as well as synergy effects, were also included. A large panel of experimental tests was done to fit and validate the model. This database included different enzymes mixtures and operating conditions and allowed to determine and compare with accuracy the adsorption and kinetic parameters of the different enzymes. Model predictions on short hydrolysis times were very satisfactory. On longer times, a deactivation constant was added to represent the hydrolysis slowdown. The model also allowed to predict the impact of enzymes ratios and initial substrate parameters (chain length distribution, polymerization degree) on hydrolysis, and to follow the evolution of these parameters with time. This model revealed general trends on the impact of cellulose morphology on hydrolysis. It is a useful tool to better understand the mechanisms involved in enzymatic hydrolysis of cellulose and to determine optimal cellulolytic cocktails for process design. Biotechnol. Bioeng. 2016;113: 1011-1023. © 2015 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

ABSTRACT We develop a novel and general modeling framework for enzymatic hydrolysis of cellulose and hemicellulose simultaneously. Our mechanistic model, for the first time, takes into consideration explicitly the time evolution of morphologies of intertwining cellulose and hemicelluloses within substrate during enzymatic hydrolysis. This morphology evolution is driven by hydrolytic chain fragmentation and solubilization, which is, in return, profoundly affected by the substrate morphology. We represent the substrate morphology as a randomly distributed smallest accessible compartments (SACs) which are described by geometric functions to track total volume and exposed surface substrate materials, including both cellulose and hemicelluloses. Our morphology-plus-kinetics approach then couple the time-dependent morphology with chain fragmentation and solubilization resulted from enzymatic reactions between various bonds in cellulose and hemicelluloses and a mixture (i.e., endo-, exo-, and oligomer- acting) of cellulases and hemicellulases. In addition, we propose an advanced and generalized site concentration formalism that considers different polysaccharide chain types and different monomer unit types on chains. The resulting ODE system has a substantially reduced size compared to conventional chain concentration formalism. We present numerical simulation results under real enzymatic hydrolysis experimental conditions from literature. The comparisons between the simulation results and the experiment measurements demonstrate effectiveness and wide applicability of the proposed mechanistic model. Biotechnol. Bioeng. 2014;111: 1767-1781. © 2014 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Reefs may be formed in the middle parts of sedimentary basins and grow on tectonically uplifted substrate blocks. In this paper, the strata of the Central European reef system of the Upper Permian Zechstein Limestone (Ca1) formation located in West Poland are evaluated. The formation has produced natural gas since the early nineties of the past century. The reefs grew on an uplifted horst built of Carboniferous rocks, known as the Wolsztyn Ridge. As individual sub-blocks originally showed diversified altitudes, four zones suspected to represent initial sedimentation conditions are distinguished: (1) basin zone , located close to the margins of the WR; (2) lower reef zone; (3) transitional zone and (4) the upper reef zone. Clear diagenetic differences between particular zones are observed. The basin zone strata are characterized by a strongly recrystallized mosaic of dolomite but show a limited extent of anhydrite cementation. The lower reef zone rocks, covered by thick Zechstein evaporites have been dolomitized and anhydritized most intensively, probably by means of the downward seepage of heavy brines, as suggested by the stable isotope data. It is assumed that the process was focused on the calm-water facies due to their low primary porosity and permeability. This mechanism was also probably responsible for the dolomitization of Ca1 strata in the remaining zones, where lower δ18O values in dolomite reflect some temperature increase on the final isotopic signature of rocks. Transitional zone carbonates appear to be almost purely calcitic with only a minor dolomite admixture. They contain various types of calcite cement, including marine and meteoric-phreatic phases, reflecting an intermediate position of the substrate and optimal reef growth conditions. Marine phases are also commonly recognized in the upper reef zone. Owing to a significant elevation of the substrate in this zone, the corresponding strata might have experienced some impact of karstification, presumably taking place well before the deposition of the Zechstein evaporites. It is concluded that the morphology of the substrate in tectonically-influenced areas strongly controls the reef diagenesis, and thus can affect the distribution of hydrocarbon accumulations. • The morphology of the substrate influences reef diagenesis and should be considered in hydrocarbon exploration. • The downward seepage of brines can cause dolomitization and anhydritization of reef rocks developed on uneven substrates. • Brine seepage-related dolomitization may be intensified in mud-supported facies of small thickness, overlain by evaporites. • The carbonate build-ups of the highest topographic position may become karstified and penecontemporaneously dolomitized. • Porous reefs formed at intermediate altitudes are areas of intensive calcite cementation in marine and meteoric conditions. [ABSTRACT FROM AUTHOR]

Membrane with molecular selectivity, low fouling propensity and low pressure application is beneficial for effective separation. Designing a multipurpose tight ultrafiltration (M-TUF) membrane is challenging, yet requires for facile separation. Our design towards M-TUF membrane is based on the porous base substrate with rough morphology and weak electrostatic effect towards relatively smaller size ions and greater sieving and charge effect of selective layer towards relatively bigger sized molecules. Layer-by-layer (LbL) assembly of polyelectrolytes on a rough cationic poly(vinylidene fluoride) (PVDF-NMe 3) substrate leads to the formation of TUF membranes. The molecular weight cutoff (MWCO) sharply reduces from about 4 × 105 g mol−1 (base substrate) to about 4 × 103 g mol−1 and 2 × 103 g mol−1 respectively after fourth and fifth layers of LbL assembly. The membranes (fifth and seventh layers) obtained under optimized conditions show low pressure-driven (0.68 bar) selective removal of Rose Bengal (RB, rejection∼99.5% and 99.9%) and Reactive black (RB-5, rejection∼96.8% and 99.2%) from feeds containing dye and monovalent (NaCl rejection<10%) or dye and divalent (MgCl 2 rejection <30%) salts with steady permeate flux. Representative salt (MgCl 2) to RB selectivity values for the two membranes are 164 and 720 respectively. Membranes obtained after third and fifth layers of LbL assembly show water permeance in the range of 71–105 Lm−2h−1bar−1 and flux recovery ratio of 81–85% for the separation of oil-in-water emulsions. The preparation process is extended using copolymer polyelectrolyte for the quick LbL assembly to obtain low fouling membrane. This work provides an insight to obtain TUF membrane for low pressure-driven molecular separation. [Display omitted] • LbL assembly of polyelectrolytes was performed to obtain tight UF membranes. • Morphology of base substrate influenced the water wetting and antifouling property. • The membranes showed separation of dyes and salts with high selectivity. • The membranes showed steady performance during dye separation. • The membranes showed antifouling property during oil-in-water emulsion separation. [ABSTRACT FROM AUTHOR]

The authors present the blue-shift of Raman 2D and G peak of a single layer graphene film, which is fabricated via chemical vapor deposition, on the relatively even Cu foil domain with nearly uniform thickness. This can be interpreted that rather mechanically compressive strain is exerted between graphene and the even Cu domain compared to the uneven. We observe that relaxing compressive strain to minimize the perturbation from Cu surface to the graphene film by virtue of the uneven Cu domain has a critical role in forming a suspended graphene. Furthermore, mechanical strain influence derived from the underlying substrate morphology can be suggested as one of the crucial elements in evaluating high quality graphene film considering suspended shape. [ABSTRACT FROM AUTHOR]

Abstract: In this work, we analyze the effect of rough ZnO front electrodes developed in-house favoring high current versus “smoother” substrates favoring good V oc and FF on the properties of microcrystalline silicon () cells. Complete p-i-n solar cells with intrinsic layer thicknesses varying from 1 to were deposited using very high frequency plasma-enhanced chemical vapor deposition. The better scattering capabilities of rough substrates induce a significantly higher cell current in comparison to the smooth one for all the thicknesses. This allows a current output of more than 27mAcm−2 for cells thicker than . As a result, there is no full compensation of poor light scattering by thickness increase up to in solar cells. Concerning the electrical characteristics, good quality cells are obtained for all thicknesses on smooth substrates, whereas the thick cells on rough substrates exhibit poorer electrical characteristics. Cells grown on smooth substrates show excellent stability under light soaking and atmospheric storage for all the thicknesses. However, a high increase of the saturation current is evidenced after atmospheric storage for cells grown on rough substrates and thus a degradation of their electrical characteristics is observed. [Copyright &y& Elsevier]

Amine-coated biodegradable materials based on synthetic polymers have a great potential for tissue remodeling and regeneration because of their excellent processability and bioactivity. In the present study, we have investigated the influence of various chemical compositions of amine plasma polymer (PP) coatings and the influence of the substrate morphology, represented by polystyrene culture dishes and polycaprolactone nanofibers (PCL NFs), on the behavior of vascular smooth muscle cells (VSMCs). Although all amine-PP coatings improved the initial adhesion of VSMCs, 7-day long cultivation revealed a clear preference for the coating containing about 15 at.% of nitrogen (CPA-33). The CPA-33 coating demonstrated the ideal combination of good water stability, a sufficient amine group content, and favorable surface wettability and morphology. The nanostructured morphology of amine-PP-coated PCL NFs successfully slowed the proliferation rate of VSMCs, which is essential in preventing restenosis of vascular replacements in vivo. At the same time, CPA-33-coated PCL NFs supported the continuous proliferation of VSMCs during 7-day long cultivation, with no significant increase in cytokine secretion by RAW 264.7 macrophages. The CPA-33 coating deposited on biodegradable PCL NFs therefore seems to be a promising material for manufacturing small-diameter vascular grafts, which are still lacking on the current market. [ABSTRACT FROM AUTHOR]

• We examined the role of morphology of intercalation metal layers on Rashba spin–orbit parameter at Dirac Point (DP) of graphene. • Ag and Au metal layers have been considered with different morphologies on SiC substrate. • Results approved that any changes on morphology of metal layers had significant impact on both band splitting and band gap at DP. • Results showed the size of band gap and band splitting were related to the size of hybridization between pz orbitals of graphene and d-orbitals of Au and Ag. • Spin-texture of SiC/metal/Graphene revealed how spin direction of electron pined to x and y spin components. The influence of substrate morphology on the Rashba band splitting at the Dirac point of graphene, has been theoretically investigated. More specifically, the possibility for this splitting to be caused by spin–orbit coupling (with the heavy metal substrate) was of a special interest to study. The model system consisted of a 4H-SiC (0 0 0 1)/graphene interface, with an intercalated metal layer (Ag and Au, respectively). These intercalating metal layers were built with two different types of morphologies; either flat or buckled (with different buckling positions). The results show that depending on the position of the buckled metal atom, the size of the bandgap and band splitting (at the Dirac point of graphene) will either increase (or decrease). Moreover, the enlargement of the buckling size was also shown to affect the electronic properties of graphene (i.e., by increasing the bandgap). The sizes of the bandgaps and band splitting for the different intercalating metals (Ag and Au), were also found to be different. Spin-projected band structures was also implemented in the present study, with the purpose to show the spin-texture of graphene. It was thereby shown that the spins pined to the x and y spin components for most of the cases. [ABSTRACT FROM AUTHOR]