Fast Deposition Rate Research Articles

Colloid-associated plutonium transport in the vadose zone sediments at Lop Nor

A framework to describe the characteristics of pore water in unsaturated media was established in order to study transport of colloid-associated 239Pu (i.e., colloidal Pu) through the vadose sediments. Effluent concentrations and recoveries of Pu were found to decrease with increasing ionic strength. However, they would remain approximately constant at a critical value of 0.0289 M (Na+) though ionic strengths were further increased. Fast deposition rate coefficient (kfast) was thus experimentally determined. To our knowledge, this relationship between the mobility of colloidal Pu and the critical ionic strength was the first time observed. On the other hand, significant detachment of colloidal Pu once retained in the sediments was not observed during the subsequent chemical and physical perturbations. But slow release and transport could persist as long as flow continued. The threshold infiltration intensity (0.166 cm/min) revealed a nonmonotonic dependence of the cumulative amount of detached colloidal Pu on the intensity.

AZ31 마그네슘 합금의 플라즈마 전해 산화에서 Sodium Aluminate 농도가 산화막 특성에 미치는 영향

Abstract Magnesium alloy have good physical properties such as good castability, good vibration absorption,high strength/weight ratios. Despite the desirable properties, the poor resistance of Mg alloy impedes their use inmany various applications. Therefore, magnesium alloy require surface treatment to improve hardness, corrosionand wear resistance. Plasma Electrolytic Oxidation (PEO) is one the surface treatment methods to form oxidelayer on Mg alloy in alkali electrolyte. In comparison with Anodizing, there is environmental process having higherhardness and faster deposition rate. In this study, the characteristies of oxide film were examined after coating theAZ31 Mg alloy through the PEO process. We changed concentration of sodium aluminate into K 2 ZrF 6 , KF baseelectrolyte. The morphologies of the coating layer were characterized by using scanning electron microscopy(SEM). Corrosion resistance also investigated by potentiodynamic polarization analysis. As a result, propertiy ofoxide layer were changed by concentration of sodium aluminate. Increasing with concentration of sodium alumi-nate in electrolyte, the oxidation layer was denser and the pore size was smaller on the surface.(Received July 27, 2012; Revised August 13, 2012; Accepted August 20, 2012)Key words: PEO, Plasma electrolytic oxidation, MAO, Micro arc oxidation, AZ31, Magnesium alloy

상온 진공 분말 분사 공정을 이용한 다층 박막 소재의 제조 및 전기적 특성

Room temperature powder spray in vacuum process, so called Aerosol deposition (AD) is a room temperature (RT) process to fabricate thick and dense ceramic films, based on collision of solid ceramic particles. This technique can provide crack-free dense thin and thick films with thicknesses ranging from sub micrometer to several hundred micrometers with very fast deposition rates at RT. In addition, this technique is using solid particles to form the ceramic films at RT, thus there is few limitation of the substrate and easy to control the compositions of the films. In this article, we review the progress made in synthesis of piezoelectric thin/thick films, multi-layer structures, NTC thermistor thin/thick films, oxide electrode thin films for actuators or sensor applications by AD at Korea Institute of Materials Science (KIMS) during the last 4 years.

Segmented Electrode Plasma Source with Anti-Phase Discharge

A new plasma source concept, consisting of segmented electrodes and an economical 13.56 MHz power generator, has been developed for the plasma-enhanced chemical vapor deposition (PECVD) of microcrystalline silicon thin films on large-area substrates. Using a plurality of rectangular column-type electrodes fed with RF (13.56 MHz) at various relative phases, a two-stage plasma, which consists of an upper and lower plasma, was generated. In the case of supplying the anti-phase RF, we could control the ion incident energy on a substrate to be lower, so as to keep the high crystallinity and high deposition rate during the film growth. The agreement between the observed light emission profiles from Ar or Ar/H2 plasma and the numerically calculated ones was good, confirming the accuracy of the simulation model, and we performed the thin-film growth of microcrystal silicon with this new plasma source and H2/SiH4 gas. Consequently, we could achieve a fast deposition rate of more than 1.5 nm/s with good crystallinity over 60%.

Growth Mechanism of CdS NanoFilms Prepared by Chemical Bath Deposition

Deposition of CdS nanofilms was performed using the chemical bath deposition method, as a function of the concentration ratio of [S] to [Cd] (S/Cd) and of deposition temperature. As the S/Cd ratio and deposition temperature increased, the deposition rate of the films increased, and the transmittance was improved. With increasing S/Cd ratio, the crystallinity of the CdS nanofilms decreased due to the formation of small grains therein. Atomic force microscopy revealed that the surface morphology of the films became smooth with increasing S/Cd ratio and deposition temperature. The evolution of the grain formation showed that the slow deposition rate of the films leads to a small number of grains at the initial stage of the deposition, followed by fast grain growth, resulting in a rough surface. On the other hand, a fast deposition rate initially causes the formation of many grains on the entire surface as well as slow grain growth, making the films smooth. It is evident that the deposition rate affects the physical and optical properties of the films due to their different growth mechanisms.

Deposition of zinc oxide thin films by an atmospheric pressure plasma jet

The ZnO thin film deposition process by using an atmospheric pressure (AP) plasma jet is studied. In this process, nebulized ZnCl 2 solution is sprayed into the downstream of the nitrogen plasma jet to perform thin film deposition. X-ray diffraction analysis confirms that this AP jet has the capability to convert ZnCl 2 solution to well-crystallized ZnO thin films with a hexagonal wurtzite structure in a short time. This film exhibits a smooth and mirror-like appearance visually. Scanning electron microscopy and atomic force microscopy show that the deposited film is dense and continuous with a root mean square surface roughness of 8.6 nm. A 1.29 nm/s deposition rate is obtained using this process. Given the fast deposition rate, we believe that both the temperature and the reactivity of the plasma play important roles. A ZnO film on a larger substrate is fabricated, which suggests the process capability in large area and continuous processing applications.

The Oxidation Behavior of TBC with Cold Spray CoNiCrAlY Bond Coat

Cold gas dynamic spray (CGDS) has been considered a potential technique to produce the metallic bond coat for TBC applications, because of its fast deposition rate and low deposition temperature. This article presents the influence of spray processes for bond coat, including air plasma spray, high velocity oxy-fuel, and in particular CGDS, on the oxidation performance of TBCs with a Co-32Ni-21Cr-8Al-0.5Y (wt.%) bond coat and an air plasma sprayed topcoat. Oxidation behavior of the TBCs was evaluated by examining the coating microstructural evolution, TGO growth behavior, and crack propagation during thermal exposure at 1050 °C. The relationship between the TGO growth and crack propagation will be discussed.

Electrodeposition of CoMo and CoMoP alloys from the weakly acidic solutions

INTRODUCTIONThe procedures for the electrodeposition of CoMoalloys have been intensively developed because thesealloys possess premium hardness, high melting point,reasonable resistance to corrosion and wear of thesecoatings [1–5]. Some of them also show catalyticproperties and might be used for hydrogen generation[6–12]. Introduction of 5 to 11 wt % molybdenum intocobalt electrodeposits leads to obtaining of materialswith good lowcoercitivity properties [13–16]. Themagnetic and mechanical properties of CoMo alloysmake them promising for application in the microelectronics, e.g. in microelectromechanical systems(MEMS) applications. The electrochemical forming ofMEMS have many advantages over other physical processes, such as a room temperature operation, lowenergy requirements, fast deposition rates, fairly uniform deposition over complicated shapes, low cost,simple scaleup and easily maintained equipment.MEMS are integrated micro devices or systems combining electrical and mechanical components fabricated using integrated circuit (IC) compatible batchprocessing techniques and range in size from micrometers to millimeters. The properties of the deposit can be“tailored” by controlling solution compositions anddeposition parameters [17]. In this case the depositionprocesses have to be compatible with other MEMS processing operations. The magnetic deposits must havegood adhesion, low stress, corrosion resistance andthermal stability at operating temperatures withoutcontaminating ICs. In addition, the stresses in deposit isimportant factor, because may result cracks or deformations of electroformed MEMS devices.Several types of baths are used for the electrodeposition of Co–Mo films. Co–Mo alloys are depositedfrom citrate and citrate–ammonium electrolytes

CuInSe2 thin films obtained by pulse-plating electrodeposition technique with novel pulse wave

CuInSe2 films were electrodeposited onto indium tin oxide (ITO) substrate in constant current mode using bell-like wave modulated square wave in aqueous solution. The films obtained at different pulse frequencies were characterized by scanning electron microscopy (SEM), X-ray energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). UV-Vis-NIR absorption spectroscopy was used to study the optical properties of these films. The results showed that the chalcopyrite phase CuInSe2 films with a smooth surface and stoichiometric composition could be obtained at appropriate pulse frequency. The crystallinity of CuInSe2 films could be further improved after annealing treatment. Despite this, we also found that the films obtained using the pulse-plating electrodeposition technique had a faster deposition rate and better film adhesion ability than that using the traditional CIS electrodeposition technique, which is significant to the low-cost CIS thin film solar cell production.

New excimer lasers advance coated conductor upscaling

High power excimer lasers designed for use in pulsed laser deposition (PLD) of thin films, including coated conductor layers allow faster deposition rates and eventually faster tape feed rates than before. Throughput increase depends on the individual PLD system design and can be driven mainly by excimer laser repetition rate or by pulse energy. Intelligent beam delivery as well as substrate-target scanning algorithms will leverage the full potential of the latest generation of high power excimer lasers.

Effects of Pulsed Laser Deposition Conditions on the Microstructure of Ca3Co4O9 Thin Films

The influence of deposition conditions on the microstructure of Ca 3 Co 4 O 9 (CCO) thin films fabricated by the pulsed laser deposition technique was investigated. X-ray diffraction revealed that a fast deposition rate resulted in not only low crystallinity but also the existence of the Ca x CoO 2 secondary phase. The Ca x CoO 2 structure was further confirmed by high-resolution transmission electron microscopy. The CCO thin-film growth was deduced to be a kinetically controlled process, and the quality of the thin films strongly depended on the coalescence process. The formation of Ca x CoO 2 was inevitable during the thin-film growth. However, given enough time and supply of oxygen at a lower deposition rate, it was possible to transform the Ca x CoO 2 phase into the desired CCO phase during the coalescence process, while with faster deposition, more Ca x CoO 2 structure was formed, and the secondary phase could hardly transform into the CCO phase.

A comparative study of two advanced spraying techniques for the deposition of biologically active enzyme coatings onto bone-substituting implants

Surface modification of implant materials with biomolecule coatings is of high importance to improve implant fixation in bone tissue. In the current study, we present two techniques for the deposition of biologically active enzyme coatings onto implant materials. The well-established thin film ElectroSpray Deposition (ESD) technique was compared with the SAW-ED technique that combines high-frequency Surface Acoustic Wave atomization with Electrostatic Deposition. By immobilizing the enzyme alkaline phosphatase (ALP) onto implant surfaces, the influence of both SAW-ED and ESD deposition parameters on ALP deposition efficiency and ALP biological activity was investigated. ALP coatings with preserved enzyme activity were deposited by means of both the SAW-ED and ESD technique. The advantages of SAW-ED over ESD include the possibility to spray highly conductive protein solutions, and the 60-times faster deposition rate. Furthermore, significantly higher deposition efficiencies were observed for the SAW-ED technique compared to ESD. Generally, it was shown that protein inactivation is highly dependent on both droplet dehydration and the applied electrical field strength. The current study shows that SAW-ED is a versatile and flexible technique for the fabrication of functionally active biomolecule coatings.

Fast deposition of microcrystalline Si films from SiH 2Cl 2 using a high-density microwave plasma source for Si thin-film solar cells

Fast deposition rate of 27 Å/s for microcrystalline (μc-) Si films was investigated using a high-density and low-temperature microwave plasma source with a spoke antenna of SiH 4–H 2 and SiH 2Cl 2–H 2 mixtures. The film crystallization was promoted efficiently when film was fabricated using SiH 4 with an aid of large amount of hydrogen atom, while the volume fraction of void in the film was relatively the larger of 10–20%. On the other hand, the volume fraction of amorphous silicon phase in the μc-Si films were 20–30% with no significant void fractions in films fabricated from SiH 2Cl 2, although the volume fraction of the crystalline silicon phase was 75–85%. The role of chlorine in the growth of μc-Si films is discussed in terms of the chemistry of the H and Cl terminated growing surface. The preliminary result of p–i–n Si thin-film solar cell is demonstrated using μc-Si:H:Cl films as an intrinsic layer.

Characterization of La-doped YBCO superconducting films deposited by DC magnetron sputtering at various off-axis geometries

La-doped YBCO (Y0.9La0.2Ba1.9Cu3Oy) superconducting films were deposited by an off-axis DC magnetron sputtering method. We investigated the relationship between the film characteristics and the deposition conditions, and drew systematical maps in terms of composition, surface morphology, crystal structure and superconducting properties for the films deposited at various spatial geometries of a substrate and a target. Correspondence between the Cu content and the surface morphology was clearly observed. Cu-rich films had precipitates on the surface. Slightly Cu-poor films exhibited c-axis orientation and a high Tc of 87 K. Among them, the film deposited at a rather fast deposition rate exhibited a flat surface with an average surface roughness Ra less than 1 nm for an area of 10 micron square. Considerably Cu-poor films contained a-axis oriented grains or exhibited very rough surfaces. The cationic ratio of Y:La:Ba did not change significantly.

Influence of pulsed laser deposition rate on the microstructure and thermoelectric properties of Ca 3Co 4O 9 thin films

The effects of deposition rate on the microstructure and thermoelectric (TE) properties of Ca 3Co 4O 9 thin films fabricated by pulsed laser deposition (PLD) technique were investigated. X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HR-TEM) revealed that a fast deposition rate resulted in not only low crystallinity but also the existence of the Ca x CoO 2 secondary phase. Formation of Ca x CoO 2 was inevitable during the thin film growth, and this was discussed from both structural and compositional point of view. With longer deposition interval or with sufficient oxygen at a lower deposition rate, the Ca x CoO 2 phase was able to transit into the desired Ca 3Co 4O 9 phase during the coalescence process. The quality of the thin films was further analyzed by electrical properties measurements. The Ca 3Co 4O 9 thin film fabricated at a slower deposition rate was found to exhibit a low electrical resistivity of 9.4 mΩ cm and high Seebeck coefficient of 240 μV/K at about 700 °C, indicating a good quality film.

Effect of composition of NiO/YSZ anode on the polarization characteristics of SOFC fabricated by atmospheric plasma spraying

Atmospheric plasma spraying is regarded as one of the most promising processing methods for the production of solid oxide fuel cells (SOFCs) because of its fast deposition rate and cost-effective characteristic compared with other film formation processes. Thermally sprayed ceramic deposits are characterized by lamellar structure resulting from the insufficient filling and incomplete wetting of molten liquid on previously formed rough coating surfaces. There are large voids (especially larger than 10 μm), nonbonded interface, and vertical cracks (in particular, in individual ceramic lamella which are in the submicrometer size range). The bonding at the interface between flattened particles is much less than the apparent total interface area. The microstructure of plasma-sprayed coating can be significantly influenced by the feedstock. In this paper, a Ni–Al 2O 3 cermet supported tubular SOFC cell with three different anodes was fabricated by thermal spraying. The effect of the anode microstructure on the performance of SOFC was investigated. The influence of the anode structure on the electrode polarization was examined. The results showed that the maximum output power density strongly depends on the anode microstructure. The length of the triple-phase boundaries (TPBs) can be increased by decreasing the particle size of YSZ and Ni in composite anode.

Electrochemical reaction of lithium with orthorhombic bismuth tungstate thin films fabricated by radio-frequency sputtering

Bi 2WO 6 thin films with fast deposition rate have been fabricated by radio-frequency (R.F.) sputtering deposition, and are used as positive electrodes in rechargeable thin film lithium batteries. An initial discharge capacity of 113 μAh/cm 2-μm is obtainable for Bi 2WO 6 film electrode with good capacity reversibility. A multiple-center reactive mechanism associated with both Bi 3+/Bi 0 and W 6+/W x+ ( x < 6) is investigated by ex situ X-ray diffraction patterns, transmission electron microscopy and selected area electron diffraction techniques, apart from the direct comparison of Bi 2WO 6 electrochemical performance with those of Bi 2O 3 and WO 3 thin films. A possible explanation about smooth capacity loss of Bi 2WO 6 after long-term cycling is suggested from the incomplete reaction of Bi component. The advantages of Bi 2WO 6 thin films over the singer-center Bi 2O 3 or WO 3 thin films are shown in both the aspects of volumetric capacity and cycling life.

Patterning PDMS using a combination of wet and dry etching

PDMS films of 10 µm thickness can be patterned within 30 min by combining dry etching to achieve substantially vertical sidewalls with wet etching to achieve high etch rates and to protect the underlying substrate from attack. Dry etching alone would have taken 5 h, and wet etching alone would produce severe undercutting. In addition, using either technique alone produces undesirable surface morphologies. The mask used during etching is critical to a successful patterning outcome. E-beam evaporated Al was found to work well, adhering strongly to oxygen-plasma-treated PDMS and holding up well during both dry and wet etching. To prevent wrinkling of the PDMS, a fast deposition rate should be used.

Conformal metal oxide coatings on nanotubes by direct low temperature metal-organic pyrolysis in supercritical carbon dioxide

The authors demonstrate that low temperature (&amp;lt;200 °C) thermal decomposition of metal-organic precursors dissolved in supercritical carbon dioxide (scCO2) is an effective method to penetrate into dense three-dimensional networks and deposit conformal metal oxide films with tunable thickness. The results specifically show that thermal decomposition of gallium acetylacetonate in scCO2, leads to conformal coatings of gallium oxide on multiwalled carbon nanotube forests with a fast deposition rate (∼3–4 nm/min), without the need for any cosolvent. Moreover, as-formed metal oxide/nanotube structures can be further conformally coated by metal atomic layer deposition to produce nanotube/oxide/metal nanocomposites.

River bed evolution due to channel expansion: general behaviour and application to a case study (Kugart River, Kyrgyz Republic)

AbstractWe study the effect of spatial variations of river width on bed aggradation and degradation processes, making use of a one‐dimensional numerical model of channel morphodynamics. We refer to a peculiar case, the downstream reach of the Kugart River (Kyrgyzstan). The river has been partly channelized in the recent past with the aim of reducing the flooding risk for the surrounding villages; the consequent reduction of channel width in some reaches was also expected to improve channel conveyance with respect to the high sediment load produced in the upper river basin. The resulting longitudinal sequence of relatively sharp channel expansions and contractions has, however, triggered rapid siltation rates, especially in the narrowest reaches. This motivated the application of a 1‐D numerical model of river morphodynamics.Abrupt channel expansions are found to be the main driving forces for aggrading processes, which may extend for long distances from where they are generated. In order to obtain a thorough understanding of the morphodynamics of channel expansions, we first apply the model to simple test cases. This allows us to characterize the basic features of the problem and the dependence of bed evolution on the upstream Froude number Fr and on the expansion ratio rb, which are the most relevant controlling parameters. We invariably find that deposition occurs in expansion regions with bed aggradation observed both upstream and downstream. The deposition prism progressively increases its height and lengthens both in the upstream and downstream directions. The deposition process is particularly intense, in terms of deposition prism height, in super‐critical conditions. Moreover, it is found that higher values of Fr strongly reduce the time scale of morphological processes and faster deposition rates are further facilitated by abrupt expansions.The present outcomes are relevant for assessing the expected altimetric response of river bed to the implementation of localized channelization works and to local river widening, a practise which is increasingly being employed within river restoration projects, with the aim of enhancing habitat diversity. Copyright © 2008 John Wiley &amp; Sons, Ltd.