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Yu, Hai Jiao, Yu Ya Wang, Jun Xue, and Zun Wang. "An Advanced Metal Deposition Technique-Kinetic Metallization." Materials Science Forum 817 (April 2015): 510–15. http://dx.doi.org/10.4028/www.scientific.net/msf.817.510.
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Kinetic metallization (KM) is a sonic cold spray metal deposition technique, which offers promise as a way to produce coatings with a wild range of thickness. It is a solid-state process, from which the obtained coating is oxide free, high compactness (the porosity ratio may less than 0.1%), and has a strong bonding with the matrix. KM now is extensively applied in many fields, such as part/structure dimensional repair, solar battery manufacture, corrosion resistance and protection, wear resistance, oxidation resistance, and polymer spray. The present work presented the elements and advantages of KM, related it with high velocity oxy-fuel (HVOF) and common cold spray (CS), and reviewed the progress of KM over the two decades. Finally, the further development of the KM was discussed.
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Koivuluoto, Heli, Andrea Milanti, Giovanni Bolelli, Jyrki Latokartano, Francesco Marra, Giovanni Pulci, Jorma Vihinen, Luca Lusvarghi, and Petri Vuoristo. "Structures and Properties of Laser-Assisted Cold-Sprayed Aluminum Coatings." Materials Science Forum 879 (November 2016): 984–89. http://dx.doi.org/10.4028/www.scientific.net/msf.879.984.
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In the cold spray process, solid particles impact on a surface with high kinetic energy, deform plastically and form a coating. This enables the formation of pure and dense coating structures. Even more, coating performance and deposition efficiency can be improved by assisting the process with a laser. Laser-assisted cold spraying (LACS) has shown its potential to improve coating properties compared with traditional cold spraying. In this study, coating quality improvement was obtained by using a co-axial laser spray (COLA) process which offers a new, cost-effective laser-assisted cold spray technique, for high-quality deposition and repair. In the COLA process, the sprayed surface is laser heated while particles hit the surface. This assists the better bonding between particles and substrate and leads to the formation of tight coating structures. This study focuses on the evaluation of the microstructural characteristics and mechanical properties (e.g., hardness and bond strength) of LACS metallic coatings.
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Lee, Jae Chul, Doo Man Chun, Sung Hoon Ahn, and Caroline S. Lee. "Material Properties of Thick Aluminum Coating Made by Cold Gas Dynamic Spray Deposition." Key Engineering Materials 345-346 (August 2007): 1097–100. http://dx.doi.org/10.4028/www.scientific.net/kem.345-346.1097.
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Cold gas dynamic spray is a relatively new coating process by which coatings can be produced without significant heating during the process. Cold gas dynamic spray is conducted by powder sprayed using supersonic gas jet, and generally called the kinetic spray or cold spray. Its low process temperature can minimize the thermal stress and also reduce the deformation of the substrate. In this study, thick or macro scale deposition was studied while most researches on cold-spray have focused on micro scale coating. Measured material properties of macro scale deposition layer showed that elastic modulus and hardness were lower and electrical resistivity was higher than those of reference substrate material. The main causes of changed material properties were investigated by FE-SEM (Field Emission Scanning Electron Microscope) and EDS (Energy Dispersive X-ray Spectrometer) data. In this result, porous micro structure generated by imperfect plastic deformation might cause decrease in elastic modulus and hardness of the deposition layer by cold spray, and oxidized Al particles increased the electrical resistivity.
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W. J., W. J. "Effects of Metal Particles on Cold Spray Deposition onto Ti-6Al-4V Alloy via Abaqus/Explicit." Journal of Engineering Sciences 7, no. 2 (2020): E19—E25. http://dx.doi.org/10.21272/jes.2020.7(2).e4.
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Titanium alloy is the main structural material of the aerospace system component. About 75 % of titanium and titanium alloys in the world are used in the aerospace industry. Hence, it is of great significance to study the surface deposition characteristics by cold spraying technology, taking Ti-6Al-4V alloy as an example, smoothed particle hydrodynamics (SPH) method in Abaqus/Explicit was used to spray aluminum, Ti-6Al-4V, copper, tungsten alloy (W alloy) and titanium particles onto Ti-6Al-4V substrate. The simulation results show that the deposition effect is good over 600 m/s, and higher energy is obtained for Ti-6Al-4V particles with the same properties as the matrix. For aluminum, Ti-6Al-4V, copper, W alloy, and titanium particles with different properties, under the same initial speed condition, the greater the density of the material, the deeper the foundation pit. W Alloy has the largest initial kinetic energy, the deepest foundation pit, and better surface bonding performance. The aluminum particle has the smallest initial kinetic energy, the shallowest foundation pit. However, the deposition effect of multiple aluminum particles has not improved. The collision process’s kinetic energy is transformed into internal energy, frictional dissipation, and viscous dissipation. Besides, the internal energy is mainly plastic dissipation and strain energy. Therefore, it is recommended to use Ti-6Al-4V, copper, nickel, W alloy, and titanium particles for different occasions, such as Ti-6Al-4V substrate surface restorative and protective coatings. Pure aluminum particles are not recommended.
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Oyinbo, Sunday Temitope, and Tien-Chien Jen. "Feasibility of numerical simulation methods on the Cold Gas Dynamic Spray (CGDS) Deposition process for ductile materials." Manufacturing Review 7 (2020): 24. http://dx.doi.org/10.1051/mfreview/2020023.
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The techniques of cold gas dynamic spray (CGDS) coating involve the deposition of solid, high speed micron to nano particles onto a substrate. In contrast to a thermal spray, CGDS does not melt particles to retain their physico-chemical properties. There have been many advantages in developing microscopic analysis of deformation mechanisms with numerical simulation methods. Therefore, this study focuses on four cardinal numerical methods of analysis which are: Lagrangian, Smoothed Particles Hydrodynamics (SPH), Arbitrary Lagrangian-Eulerian (ALE), and Coupled Eulerian-Lagrangian (CEL) to examine the Cold Gas Dynamic Spray (CGDS) deposition system by simulating and analyzing the contact/impact problem at deformation zone using ductile materials. The details of these four numerical approaches are explained with some aspects of analysis procedure, model description, material model, boundary conditions, contact algorithm and mesh refinement. It can be observed that the material of the particle greatly influences the deposition and the deformation than the material of the substrate. Concerning the particle, a higher-density material such as Cu has a higher initial kinetic energy, which leads to a larger contact area, a longer contact time and, therefore, better bonding between the particle and the substrate. All the numerical methods studied, however, can be used to analyze the contact/impact problem at deformation zone during cold gas dynamic spray process.
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Tului, Mario, Cecilia Bartuli, Alessia Bezzon, Angelo Luigi Marino, Francesco Marra, Susanna Matera, and Giovanni Pulci. "Amorphous Steel Coatings Deposited by Cold-Gas Spraying." Metals 9, no. 6 (June 12, 2019): 678. http://dx.doi.org/10.3390/met9060678.
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Cold-gas spray (CGS) deposition of amorphous steel coatings starting from a commercial feedstock powder containing boron, tungsten, and silicon was investigated. Microstructural characterization, carried out by X-ray diffraction (XRD), transmission electron microscopy, and backscattered electron diffraction (EBSD) analysis, confirmed the amorphous nature of deposited coatings. The amorphization phenomenon is related to high-strain/strain-rate deformation with shear instability caused by very high particle kinetic energy, with a mechanism that resembles the severe plastic deformation process. The CGS coatings were heat-treated at temperatures ranging from 650 to 850 °C to induce partial recrystallization. The effect of nanocrystal nucleation and growth on the hardness of the coatings was investigated, and the hardness of heat-treated samples was found to increase with respect to as-sprayed coatings, outperforming conventional high-velocity oxy-fuel (HVOF) deposits. Hardness was found to decrease after prolonged (<90 min) or higher temperature (>750 °C) exposures.
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Spencer, Kevin, Daniel Fabijanic, and Ming Xing Zhang. "Cold Spray of Al-MMC Coatings on Magnesium Alloys for Improved Corrosion and Wear Resistance." Materials Science Forum 618-619 (April 2009): 377–80. http://dx.doi.org/10.4028/www.scientific.net/msf.618-619.377.
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Cold spray coatings are considered promising for surface protection of Mg alloys from wear and corrosion since the process temperature is low enough to avoid oxidation of the Mg or any adverse affects on artificial ageing heat treatments. A special version of cold spray known as Kinetic Metallization has been used to produce pure Al and Al alloy metal matrix composite (MMC) coatings on AZ91 Mg alloy substrates in the present work. This surface treatment produces dense coatings with high adhesive and cohesive strength, which have substantially higher hardness and wear resistance than the AZ91 substrate material. The influence of coating composition and subsequent heat treatment on wear and corrosion performance have been investigated, using pin-on-disc wear tests, salt spray testing and electrochemical polarisation techniques. The heat treatment of the cold spray coatings is compatible with the solutionising and T6 ageing heat treatment of AZ91Mg. The results show that cold spray deposition of MMC coatings is a simple and effective technique for improving the surface properties of Mg alloys, both in the as-cast and in the heat treated condition
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Koivuluoto, Heli, Jussi Larjo, Danilo Marini, Giovanni Pulci, and Francesco Marra. "Cold-Sprayed Al6061 Coatings: Online Spray Monitoring and Influence of Process Parameters on Coating Properties." Coatings 10, no. 4 (April 3, 2020): 348. http://dx.doi.org/10.3390/coatings10040348.
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Process optimization and quality control are important issues in cold spraying and coating development. Because the cold spray processing is based on high kinetic energy by high particle velocities, online spray monitoring of particle inflight properties can be used as an assisting process tool. Particle velocities, their positions in the spray jet, and particle size measurements give valuable information about spraying conditions. This, in turn, improves reproducibility and reliability of coating production. This study focuses on cold spraying of Al6061 material and the connections between particle inflight properties and coating characteristics such as structures and mechanical properties. Furthermore, novel 2D velocity scan maps done with the HW CS2 online spray monitoring system are presented as an advantageous powder and spray condition controlling tool. Cold spray processing conditions were similar using different process parameters, confirmed with the online spray monitoring prior to coating production. Higher particle velocities led to higher particle deformation and thus, higher coating quality, denser structures, and improved adhesions. Also, deposition efficiency increased significantly by using higher particle velocities.
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Bala, Niraj, Harpreet Singh, and S. Prakash. "An Overview of Cold Spray Technique." Materials Science Forum 561-565 (October 2007): 2419–22. http://dx.doi.org/10.4028/www.scientific.net/msf.561-565.2419.
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The Cold spray or cold gas dynamic spraying is the new progressive step in the direction of development of high kinetic energy coating processes. The cold spray is a method for coating substrates under atmospheric conditions. In this process micron sized solid particles are accelerated and transported to substrates by means of supersonic free jets. Upon impacting the substrates, particles stick to the surface and form coatings which possess very low porosity. The paper outlines the principles involved in cold spray method and the equipment used for the technique. The cold spray method is related to classical thermal spray methods but it has some interesting additional features, which has been discussed in the paper. A fundamental feature of cold spray method i.e. concept of critical velocity along with the plausible mechanism theory responsible for the deposition of coating has been discussed briefly. Successful applications of cold spray process and its environment friendly aspect has been elaborated. It is reported that well founded cold spray technology will be able to compete for a good market share of VPS/PVD coatings in various fields like power, electronic/electrical, biotechnology, turbines and other industries. The cold spray process is still primarily in the research and development stage and only now becoming commercially available, and has been accepted as a new and novel thermal spray technique mainly in developed countries. The technology has great potential for future research especially with reference to its application to real industrial solution.
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Krumdieck, S. "Kinetic model of low pressure film deposition from single precursor vapor in a well-mixed, cold-wall reactor." Acta Materialia 49, no. 4 (February 2001): 583–88. http://dx.doi.org/10.1016/s1359-6454(00)00356-6.
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Ogawa, Kazuhiro, and Takahiro Niki. "Repairing of Degraded Hot Section Parts of Gas Turbines by Cold Spraying." Key Engineering Materials 417-418 (October 2009): 545–48. http://dx.doi.org/10.4028/www.scientific.net/kem.417-418.545.
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Hot section parts of combined cycle gas turbines are susceptible to degradation due to high temperature creep, crack formation by thermal stress, and high temperature oxidation, etc. Thus, regularly repairing or replacing the hot section parts such as gas turbine blades is inevitable. For this purpose, revolutionary and advanced repair technologies for gas turbines have been developed to enhance reliability of the repaired parts and reduce the maintenance cost of the gas turbines. The cold spraying process, which has been studied as not only a new coating technology but also as a process for obtaining a thick deposition layer, is proposed as a potential repairing solution. The process results in little or no oxidation of the spray materials, so the surfaces stay clean, which in turn enables superior bonding. Since the operating temperature is relatively low, the particles do not melt and the shrinkage on cooling is very low. In this study, the cold spraying conditions were optimized by taking into account the particle kinetic energy and the rebound energy for application in repairing gas turbine blades. A high quality cold-sprayed layer is that which has lowest porosity; thus the spraying parameters were optimized to achieve low-porosity layer, which was verified by scanning electron microscopy (SEM).
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Zasimov, Pavel V., Sergey V. Ryazantsev, Daniil A. Tyurin, and Vladimir I. Feldman. "C2H2···CO complex and its radiation-induced transformations: a building block for cold synthetic astrochemistry." Monthly Notices of the Royal Astronomical Society 506, no. 3 (July 2, 2021): 3499–510. http://dx.doi.org/10.1093/mnras/stab1820.
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ABSTRACT In this work, we have examined the radiation-induced synthetic chemistry occurring in an astrochemically important C2H2–CO system at the molecular level using a matrix isolation approach. The 1:1 C2H2···CO intermolecular complex of linear structure was obtained in the solid low-temperature (5 K) noble gas matrices by deposition of the C2H2/CO/Ng (Ng = Ar, Kr, Xe) gaseous mixtures and characterized by Fourier-transform infrared spectroscopy. It was found that the X-ray radiolysis of the C2H2···CO complex resulted in formation of C3O (tricarbon monoxide), HCCCHO (propynal), c-H2C3O (cyclopropenone), H2CCCO (propadienone), and HC3O (oxoprorynyl radical). This means that the studied complex may be considered as the simplest building block (or minimal size of intermolecular reactor) for cold astrochemistry occurring in mixed interstellar ices. Remarkably, the discovered transformations of the complex actually represent synthetic routes leading to various C3 species, whereas the acetylenic C–H bond cleavage yielding ethynyl radical appears to be a minor process. Prolonged irradiation results in dehydrogenation, while the C3 skeleton is retained. The interpretation of the C2H2···CO radiolysis mechanism (possible reactions pathways) is provided based on the analysis of kinetic curves and matrix effect. Astrochemical implications of the results are discussed.
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Berasategui, Matias, Damien Amedro, Luc Vereecken, Jos Lelieveld, and John N. Crowley. "Reaction between CH<sub>3</sub>C(O)OOH (peracetic acid) and OH in the gas phase: a combined experimental and theoretical study of the kinetics and mechanism." Atmospheric Chemistry and Physics 20, no. 21 (November 13, 2020): 13541–55. http://dx.doi.org/10.5194/acp-20-13541-2020.
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Abstract. Peracetic acid (CH3C(O)OOH) is one of the most abundant organic peroxides in the atmosphere; yet the kinetics of its reaction with OH, believed to be the major sink, have only been studied once experimentally. In this work we combine a pulsed-laser photolysis kinetic study of the title reaction with theoretical calculations of the rate coefficient and mechanism. We demonstrate that the rate coefficient is orders of magnitude lower than previously determined, with an experimentally derived upper limit of 4×10-14 cm3 molec.−1 s−1. The relatively low rate coefficient is in good agreement with the theoretical result of 3×10-14 cm3 molec.−1 s−1 at 298 K, increasing to ∼6×10-14 cm3 molec.−1 s−1 in the cold upper troposphere but with associated uncertainty of a factor of 2. The reaction proceeds mainly via abstraction of the peroxidic hydrogen via a relatively weakly bonded and short-lived prereaction complex, in which H abstraction occurs only slowly due to a high barrier and low tunnelling probabilities. Our results imply that the lifetime of CH3C(O)OOH with respect to OH-initiated degradation in the atmosphere is of the order of 1 year (not days as previously believed) and that its major sink in the free and upper troposphere is likely to be photolysis, with deposition important in the boundary layer.
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Ubertosi, F., M. Gitti, E. Torresi, F. Brighenti, and P. Grandi. "A Chandra study of Abell 795 – a sloshing cluster with an FR0 radio galaxy at its centre." Monthly Notices of the Royal Astronomical Society 503, no. 3 (March 22, 2021): 4627–45. http://dx.doi.org/10.1093/mnras/stab819.
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ABSTRACT We present the first X-ray dedicated study of the galaxy cluster Abell 795 (A795) and of the Fanaroff–Riley type 0 (FR0) hosted in its brightest cluster galaxy. Using an archival 30 ks Chandra observation, we study the dynamical state and cooling properties of the intracluster medium (ICM), and we investigate whether the growth of the radio galaxy is prevented by the surrounding environment. We discover that A795 is a weakly cool-core cluster, with an observed mass deposition rate ${\lessapprox} 14$ M⊙ yr−1 in the cooling region (central ∼66 kpc). In the inner ∼30 kpc, we identify two putative X-ray cavities, and we unveil the presence of two prominent cold fronts at ∼60 and ∼178 kpc from the centre, located along a cold ICM spiral feature. The central galaxy, which is offset by 17.7 kpc from the X-ray peak, is surrounded by a multitemperature gas with an average density of ne = 2.14 × 10−2 cm−3. We find extended radio emission at 74–227 MHz centred on the cluster, exceeding the expected flux from the radio galaxy extrapolated at low frequency. We propose that sloshing is responsible for the ICM spiral morphology and the formation of the cold fronts, and that the environment alone cannot explain the compactness of the FR0. We argue that the power of the cavities and the sloshing kinetic energy can reduce and offset cooling. Considering the spectral and morphological properties of the extended radio emission, we classify it as a candidate radio mini-halo.
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Iannarelli, Riccardo, and Michel J. Rossi. "Heterogeneous kinetics of H<sub>2</sub>O, HNO<sub>3</sub> and HCl on HNO<sub>3</sub> hydrates (<i>α</i>-NAT, <i>β</i>-NAT, NAD) in the range 175–200 K." Atmospheric Chemistry and Physics 16, no. 18 (September 23, 2016): 11937–60. http://dx.doi.org/10.5194/acp-16-11937-2016.
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Abstract. Experiments on the title compounds have been performed using a multidiagnostic stirred-flow reactor (SFR) in which the gas phase as well as the condensed phase has been simultaneously investigated under stratospheric temperatures in the range 175–200 K. Wall interactions of the title compounds have been taken into account using Langmuir adsorption isotherms in order to close the mass balance between deposited and desorbed (recovered) compounds. Thin solid films at 1 µm typical thickness have been used as a proxy for atmospheric ice particles and have been deposited on a Si window of the cryostat, with the optical element being the only cold point in the deposition chamber. Fourier transform infrared (FTIR) absorption spectroscopy in transmission as well as partial and total pressure measurement using residual gas mass spectrometry (MS) and sensitive pressure gauges have been employed in order to monitor growth and evaporation processes as a function of temperature using both pulsed and continuous gas admission and monitoring under SFR conditions. Thin solid H2O ice films were used as the starting point throughout, with the initial spontaneous formation of α-NAT (nitric acid trihydrate) followed by the gradual transformation of α- to β-NAT at T > 185 K. Nitric acid dihydrate (NAD) was spontaneously formed at somewhat larger partial pressures of HNO3 deposited on pure H2O ice. In contrast to published reports, the formation of α-NAT proceeded without prior formation of an amorphous HNO3 ∕ H2O layer and always resulted in β-NAT. For α- and β-NAT, the temperature-dependent accommodation coefficient α(H2O) and α(HNO3), the evaporation flux Jev(H2O) and Jev(HNO3) and the resulting saturation vapor pressure Peq(H2O) and Peq(HNO3) were measured and compared to binary phase diagrams of HNO3 ∕ H2O in order to afford a thermochemical check of the kinetic parameters. The resulting kinetic and thermodynamic parameters of activation energies for evaporation (Eev) and standard heats of evaporation ΔHev0 of H2O and HNO3 for α- and β-NAT, respectively, led to an estimate for the relative standard enthalpy difference between α- and β-NAT of −6.0 ± 20 kJ mol−1 in favor of β-NAT, as expected, despite a significantly larger value of Eev for HNO3 in α-NAT. This in turn implies a substantial activation energy for HNO3 accommodation in α- compared to β-NAT where Eacc(HNO3) is essentially zero. The kinetic (α(HCl), Jev(HCl)) and thermodynamic (Peq(HCl)) parameters of HCl-doped α- and β-NAT have been determined under the assumption that HCl adsorption did not significantly affect α(H2O) and α(HNO3) as well as the evaporation flux Jev(H2O). Jev(HCl) and Peq(HCl) on both α- and β-NAT are larger than the corresponding values for HNO3 across the investigated temperature range but significantly smaller than the values for pure H2O ice at T < 200 K.
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Zhang, Chengzhu, and Jerry Y. Harrington. "The Effects of Surface Kinetics on Crystal Growth and Homogeneous Freezing in Parcel Simulations of Cirrus." Journal of the Atmospheric Sciences 72, no. 8 (August 1, 2015): 2929–46. http://dx.doi.org/10.1175/jas-d-14-0285.1.
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Abstract The uptake of water vapor excess by ice crystals is a key process regulating the supersaturation in cold clouds. Both the ice crystal number concentration and depositional growth rate control the vapor uptake rate and are sensitive to the deposition coefficient . The deposition coefficient depends on temperature and supersaturation; however, cloud models either ignore or assume a constant . In this study, the effects of on crystal growth and homogeneous freezing of haze solution drops in simulated cirrus are examined. A Lagrangian parcel model is used with a new ice growth model that predicts the deposition coefficients along two crystal growth axes. Parcel model results indicate that predicting can be critical for predicting ice nucleation and supersaturation at different stages of cloud development. At cloud base, model results show that surface kinetics constrain the homogeneous freezing rate primarily through the growth impact of small particle sizes in comparison to the mean free path. The deposition coefficient has little effect on homogeneous freezing rates, because the high cloud-base supersaturation produces near unity. Above the cloud-base nucleation zone, decreasing supersaturation causes to decrease to values as low as 0.001. These low values of lead to higher steady-state supersaturation. Also, the low values of produce substantial impacts on particle shape evolution and particle size, both of which are dependent on updraft strength.
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Mehdi, Ghazanfar, Sara Bonuso, and Maria Grazia De Giorgi. "Effects of Nanosecond Repetitively Pulsed Discharges Timing for Aeroengines Ignition at Low Temperature Conditions by Needle-Ring Plasma Actuator." Energies 14, no. 18 (September 14, 2021): 5814. http://dx.doi.org/10.3390/en14185814.
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These days, various national and international research organizations are working on the development of low NOx combustors. The present work describes the experimental and numerical characterization of flow dynamics and combustion characteristics in a rectangular burner. A ring-needle type plasma actuator was developed and driven by a high voltage nanosecond pulsed generator under atmospheric conditions. Smoke flow visualizations and Proper Orthogonal Decomposition (POD) were carried out to identify the relevant flow structures. Electrical characterization of the non-reactive flow was carried out to predict the electrical power and the optimum value of the reduced electric field (EN), which is useful for the implementation of a numerical model for the study of plasma-assisted ignition. A detailed plasma kinetic mechanism integrated with all excited species was considered and validated with experimental studies. Numerical modeling of plasma ignition has been performed by coupling ZDPlasKin with CHEMKIN. Energy and power consumption for methane/air plasma actuation is higher than the air plasma actuation. This could be due to the excitation and ionization of methane that required more energy deposition and power. The mole fraction of O atoms and ozone was higher in the air than the methane/air actuation. However, O atoms were produced in a very short time interval of 10−7 to 10−6 s; in contrast, the concentration of ozone was gradually increased with the time interval and the peak was observed around 10−1 s. Plasma discharges on the methane/air mixture also produced radicals that played a key role to enhance the combustion process. It was noticed that the concentration of H species was high among all radicals with a concentration of nearly 10−1. The concentration peak of CH3 and OH was almost the same in the order of 10−2. Finally, the mixture ignition characteristics under different low inlet temperatures were analyzed for both air and methane/air plasma actuation in the presence of different plasma discharges pulses numbers. Results showed that it is possible to reach flame ignition at inlet temperature lower than the minimum required in the absence of plasma actuation, which means ignition is possible in cold flow, which could be essential to address the re-ignition problems of aeroengines at high altitudes. At Ti = 700 K, the ignition was reached only with plasma discharges; ignition time was in the order of 0.01 s for plasma discharges on methane/air, lower than in case of plasma in air, which permitted ignition at 0.018 s. Besides this, in the methane/air case, 12 pulses were required to achieve successful ignition; however, in air, 19 pulses were needed to ignite.
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Okuno, H., M. Trinquecoste, A. Derré, M. Monthioux, and P. Delhaès. "Catalytic effects on carbon/carbon composites fabricated by a film boiling chemical vapor infiltration process." Journal of Materials Research 17, no. 8 (August 2002): 1904–13. http://dx.doi.org/10.1557/jmr.2002.0283.
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Chemical vapor infiltration (CVI) has been widely studied under several conditions to obtain C/C composites. A “film boiling technique” (so-called Kalamazoo), by the use of liquid precursor, based on thermal gradient CVI has been recently developed as one of the very effective techniques to increase the carbon yield and the densification rate. A small cold wall type laboratory reactor has been realized to analyze the kinetics of reactions and the deposited pyrocarbon matrix. In this study, ferrocene, as the source of catalyst, is mixed to the liquid precursor to induce a catalytic effect on the film boiling technique since the transition metals are known to increase the carbon deposition rate. In addition to an important increase of the densification rate, it is revealed that the deposition mechanism and microtextures are completely modified by the presence of catalyst, with the presence of multiwall nanotubes within the matrix. A model has been adapted from Allendorff and Hunt's work to interpret this peculiar deposition mechanism.
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Walker, Sharon L., Jane E. Hill, Jeremy A. Redman, and Menachem Elimelech. "Influence of Growth Phase on Adhesion Kinetics of Escherichia coli D21g." Applied and Environmental Microbiology 71, no. 6 (June 2005): 3093–99. http://dx.doi.org/10.1128/aem.71.6.3093-3099.2005.
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ABSTRACT The influence of bacterial growth stage and the evolution of surface macromolecules on cell adhesion have been examined by using a mutant of Escherichia coli K-12. To better understand the adhesion kinetics of bacteria in the mid-exponential and stationary growth phases under flow conditions, deposition experiments were conducted in a well-controlled radial stagnation point flow (RSPF) system. Complementary cell characterization techniques were conducted in combination with the RSPF experiments to evaluate the hydrophobicity, electrophoretic mobility, size, and titratable surface charge of the cells in the two growth phases considered. It was observed that cells in stationary phase were notably more adhesive than those in mid-exponential phase. This behavior is attributed to the high degree of local charge heterogeneity on the outer membranes of stationary-phase cells, which results in decreased electrostatic repulsion between the cells and a quartz surface. The mid-exponential-phase cells, on the other hand, have a more uniform charge distribution on the outer membrane, resulting in greater electrostatic repulsion and, subsequently, less adhesion. Our results suggest that the macromolecules responsible for this phenomenon are outer membrane-bound proteins and lipopolysaccharide-associated functional groups.
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Pouraliakbar, Hesam, Gholamreza Khalaj, Lidija Gomidželović, Mohamad-Javad Khalaj, and Mohsen Nazerfakhari. "Duplex ceramic coating produced by low temperature thermo-reactive deposition and diffusion on the cold work tool steel substrate: Thermodynamics, kinetics and modeling." Ceramics International 41, no. 8 (September 2015): 9350–60. http://dx.doi.org/10.1016/j.ceramint.2015.03.306.
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Tamminen, Tarja, Atte Mikkelson, Matti Siika-aho, Kristiina Kruus, Jaakko Pere, Fernando José Borges Gomes, and Jorge Luiz Colodette. "Deposition of xylan isolated from Pennisetum purpureum on fibres of Eucalyptus globulus and characterisation of the composition of the surface xylans by immunolabelling and enzymatic peeling." Holzforschung 72, no. 11 (November 27, 2018): 915–22. http://dx.doi.org/10.1515/hf-2018-0002.
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AbstractAdsorption of xylan on pulp is a potential method to improve its properties, especially refinability for high quality printing and writing (P&W) paper grades. In this study, elephant grass [Pennisetum purpureum(Schumach.)] xylan was used for this purpose. The xylan was extracted using cold caustic extraction (CCE) fromP. purpureumbrown pulp, produced by the Soda-AQ process (kappa 20). Xylan resorption was accomplished during the oxygen delignification phase of eucalypt [Eucalyptus globulus(Labill.)] pulp to avoid problems induced by the colour of the lignin-contaminated deposited xylan. Immunolabelling and enzymatic peeling methodologies were compared for the analysis of the spatial distribution of xylan in the fibre wall. The labelling appeared unevenly as faint and brighter patches on fibre surfaces. Increased labelling of xylan was detected on the samples with precipitatedP. purpureumxylan. The enzymatic peeling method using a total hydrolysis enzyme mixture yielded a composition gradient as a function of time, showing clear xylose (Xyl) enrichment in the very beginning of the reaction, reflecting hydrolysis of fibre surfaces. Pure xylanase and endoglucanase hydrolyses yielded different product patterns and kinetics compared to total hydrolysis, but interpretation of those results in terms of xylan localisation was not straightforward.
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Newman, S. L., and L. K. Mikus. "Deposition of C3b and iC3b onto particulate activators of the human complement system. Quantitation with monoclonal antibodies to human C3." Journal of Experimental Medicine 161, no. 6 (June 1, 1985): 1414–31. http://dx.doi.org/10.1084/jem.161.6.1414.
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Monoclonal antibodies were used to determine the number and molecular form of C3 bound to particulate activators of the complement (C) system by human serum. Sheep erythrocytes (E) coated with IgM (EIgM) and IgG (EIgG) were used to study activation of the classical pathway (CP). Yeast (Y), rabbit erythrocytes (ER), and five species of bacteria (Escherichia coli, Staphylococcus aureus, Streptococcus pneumoniae type 3, Streptococcus pyogenes, and Hemophilus influenzae type b) were used to study activation of the alternative pathway (AP). The deposition of C3b onto EIgM and EIgG incubated in C7-deficient human serum was dependent on the serum concentration. At all serum concentrations tested, there was complete conversion of C3b to iC3b. Kinetic analysis of C3b deposition and conversion to iC3b indicated that these events occurred almost simultaneously; the reaction was completed by 15 min. The deposition of C3 onto the AP activators ER and Y was also dependent on serum concentration, and ER, but not Y, required the presence of Mg-EGTA and thus the activation of only the AP. C3b deposition and conversion to iC3b on Y was complete in 15 min, with 82% of bound C3 converted to iC3b. For ER, maximum C3 deposition required 30 min in both the presence and absence of Mg-EGTA. However, after 1 h of incubation, 74% of bound C2 was iC3b in the absence of Mg-EGTA, compared with only 52% in the presence of Mg-EGTA. Thus, even on AP activators, a large portion of C3b may be converted to iC3b, and this conversion is probably controlled by elements on the particle's surface. Studies with the five species of bacteria yielded similar results. Approximately 3-5 X 10(4) molecules of C3 were bound per microorganism, with opsonization being completed in 30 min. Remarkably, only 16-28% of bound C3 was in the form of iC3b, even after 2 h of incubation. The presence or absence of Mg-EGTA, or the addition of purified CR1 to the reaction mixture, did not significantly effect the ratio of C3b to iC3b. Finally, SDS-PAGE and autoradiography of particle-bound 125I-C3 fragments confirmed that there was no conversion of iC3b to C3d,g or C3d. The data obtained about the opsonization of bacteria suggest that the predominant form of C3 that is encountered by inflammatory phagocytes may be C3b.
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Krok-Borkowicz, Małgorzata, Katarzyna Reczyńska, Łucja Rumian, Elżbieta Menaszek, Maciej Orzelski, Piotr Malisz, Piotr Silmanowicz, Piotr Dobrzyński, and Elżbieta Pamuła. "Surface-Modified Poly(l-lactide-co-glycolide) Scaffolds for the Treatment of Osteochondral Critical Size Defects—In Vivo Studies on Rabbits." International Journal of Molecular Sciences 21, no. 20 (October 13, 2020): 7541. http://dx.doi.org/10.3390/ijms21207541.
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Poly(l-lactide-co-glycolide) (PLGA) porous scaffolds were modified with collagen type I (PLGA/coll) or hydroxyapatite (PLGA/HAp) and implanted in rabbits osteochondral defects to check their biocompatibility and bone tissue regeneration potential. The scaffolds were fabricated using solvent casting/particulate leaching method. Their total porosity was 85% and the pore size was in the range of 250–320 µm. The physico-chemical properties of the scaffolds were evaluated using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffractometry (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), sessile drop, and compression tests. Three types of the scaffolds (unmodified PLGA, PLGA/coll, and PLGA/HAp) were implanted into the defects created in New Zealand rabbit femoral trochlears; empty defect acted as control. Samples were extracted after 1, 4, 12, and 26 weeks from the implantation, evaluated using micro-computed tomography (µCT), and stained by Masson–Goldner and hematoxylin-eosin. The results showed that the proposed method is suitable for fabrication of highly porous PLGA scaffolds. Effective deposition of both coll and HAp was confirmed on all surfaces of the pores through the entire scaffold volume. In the in vivo model, PLGA and PLGA/HAp scaffolds enhanced tissue ingrowth as shown by histological and morphometric analyses. Bone formation was the highest for PLGA/HAp scaffolds as evidenced by µCT. Neo-tissue formation in the defect site was well correlated with degradation kinetics of the scaffold material. Interestingly, around PLGA/coll extensive inflammation and inhibited tissue healing were detected, presumably due to immunological response of the host towards collagen of bovine origin. To summarize, PLGA scaffolds modified with HAp are the most promising materials for bone tissue regeneration.
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Starikovskii, A. Yu, N. B. Anikin, I. N. Kosarev, E. I. Mintoussov, S. M. Starikovskaia, and V. P. Zhukov. "Plasma-assisted combustion." Pure and Applied Chemistry 78, no. 6 (January 1, 2006): 1265–98. http://dx.doi.org/10.1351/pac200678061265.
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This paper presents an overview of experimental and numerical investigations of the nonequilibrium cold plasma generated under high overvoltage and further usage of this plasma for plasma-assisted combustion.Here, two different types of the discharge are considered: a streamer under high pressure and the so-called fast ionization wave (FIW) at low pressure.The comprehensive experimental investigation of the processes of alkane slow oxidation in mixtures with oxygen and air under nanosecond uniform discharge has been performed. The kinetics of alkane oxidation has been measured from methane to decane in stoichiometric and lean mixtures with oxygen and air at room temperature under the action of high-voltage nanosecond uniform discharge.The efficiency of nanosecond discharges as active particles generator for plasma-assisted combustion and ignition has been investigated. The study of nanosecond barrier discharge influence on a flame propagation and flame blow-off velocity has been carried out. With energy input negligible in comparison with the burner's chemical power, a double flame blow-off velocity increase has been obtained. A signicant shift of the ignition delay time in comparison with the autoignition has been registered for all mixtures.Detonation initiating by high-voltage gas discharge has been demonstrated. The energy deposition in the discharge ranged from 70 mJ to 12 J. The ignition delay time, the velocity of the flame front propagation, and the electrical characteristics of the discharge have been measured during the experiments. Under the conditions of the experiment, three modes of the flame front propagation have been observed, i.e., deflagration, transient detonation, and Chapman-Jouguet detonation. The efficiency of the pulsed nanosecond discharge to deflagration-to-detonation transition (DDT) control has been shown to be very high.
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Varble, Adam. "Erroneous Attribution of Deep Convective Invigoration to Aerosol Concentration." Journal of the Atmospheric Sciences 75, no. 4 (April 1, 2018): 1351–68. http://dx.doi.org/10.1175/jas-d-17-0217.1.
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Abstract Contiguous time–height cloud objects at the Department of Energy Atmospheric Radiation Measurement Southern Great Plains (SGP) site are matched with surface condensation nuclei (CN) concentrations and retrieved thermodynamic and kinematic vertical profiles for warm-cloud-base, cold-cloud-top systems in convectively unstable environments. Statistical analyses show that previously published conclusions that increasing CN concentrations cause a decrease in minimum cloud-top temperature (CTT) at the SGP site through the aerosol convective invigoration effect are unfounded. The CN–CTT relationship is statistically insignificant, while correlations between convective available potential energy (CAPE), level of neutral buoyancy (LNB), and CN concentration account for most of the change in the CN–CTT positive correlation. Removal of clouds with minimum CTTs > −36°C from the analysis eliminates the CN–CTT correlation. Composited dirty conditions at the SGP have ~1°C-warmer low levels and ~1°C-cooler upper levels than clean conditions. This correlation between aerosol concentrations and thermodynamic profiles may be caused by an increase in regional rainfall preceding deep convective conditions as CN concentration decreases. Increased rainfall can be expected to increase wet deposition of aerosols, cool low-level temperatures, and warm upper-level temperatures. The masking of a potential aerosol effect by such small thermodynamic changes implies that the strategy of analyzing subsets of aerosol data by binned meteorological factor values is not a valid method for discerning an aerosol effect in some situations. These findings highlight the need for more careful, detailed, and strategic observations to confidently isolate and quantify an aerosol deep convective invigoration effect.
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Y., Gerasymchuk,, Adamenko, O., Lavrishchev, A., and Novoselytskiy, Y. "Determination parameters of the precipitating electrode of the electrotechnical means for cleaning air of livestock buildings from harmful gases and bacterial contamination." Mehanization and electrification of agricultural, no. 9(108) (2019): 141–48. http://dx.doi.org/10.37204/0131-2189-2019-9-17.
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Purpose. Get dependence to determine the mass of the chemical adsorbent which is contained on the rotating precipitating electrode of the electrotechnical means, taking into account the kinetics of the process of air purification of livestock buildings from harmful gases and bacterial contamination with the complex use of electrophysical and chemical methods of decontamination and air purification. Methods. Analysis of the influence of chemical adsorbent and crown discharge field on the efficiency of air purification of livestock buildings from harmful gases and bacterial contamination. Experimental researches for determination of basic parameters of a precipitating electrode of an electrotechnical means. Results. Scheme of the electrotechnical means with the complex using of electrophysical and chemical methods of purification and disinfection of recirculation air of ventilation emissions from ammonia, carbon dioxide, hydrogen sulfide and bacterial contamination. Polynomial dependence for determining the mass of a chemical adsorbent which is contained on a rotating depositing electrode. Conclusions. Complex using of the electrotechnical means for air purification from harmful gases and bacterial contamination of the recirculation air flow and the utilization heat of ventilation emissions with the implementation anti-icing protection heat exchange surface of the recuperative heat utilizers allows to reduce the level of air exchange and significantly reduce energy costs to provide regulatory airspace of livestock buildings in the cold season. On the disks of precipitating electrodes of an electrotechnical mean for cleaning and disinfection of recirculation air of ventilation emissions, it is necessary to fix a polymer mesh with an area of cellules of 16 mm2, and the frequency rotation of the discs to support within the range from 0.25 s-1 to 1 s-1. Keywords: microclimate, heat utilizer, recuperate, air purification, corona discharge, precipitating electrode.
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Broome, Catherine M., Alexander Röth, David J. Kuter, Marie Scully, Roy Smith, Jennifer Wang, Caroline Reuter, and William Hobbs. "Inhibition of the Classical Pathway of Complement with Sutimlimab in Chronic Immune Thrombocytopenic Purpura Patients without Adequate Response to Two or More Prior Therapies." Blood 134, Supplement_1 (November 13, 2019): 898. http://dx.doi.org/10.1182/blood-2019-122210.
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Introduction Immune thrombocytopenia (ITP) is characterized by platelet (plt) destruction and impaired plt production related to multiple humoral and cell-mediated processes. The heterogeneity of ITP pathogenesis is highlighted by clinical experience that shows up to 20% of patients with ITP have an inadequate response to current therapy and remain at risk of life-threatening bleeds and substantially impaired quality of life. Evidence of activation of the classical complement pathway (CP) by plt autoantibodies has long been recognized in ITP. In vitro studies showed sera from approximately 50% of patients with ITP activated the CP and/or fixed complement on plt surfaces. Inhibition of the CP in vitro with TNT003, a monoclonal C1s antibody, decreases deposition of C3b and C5b-9 on plts when exposed to ITP patient sera. Sutimlimab (formerly BIVV009) is a humanized, monoclonal antibody that selectively inhibits C1s, the proximal mediator of the CP, and has shown clinical activity in other CP-mediated disorders, such as cold agglutinin disease. We hypothesized that a primary mechanism of thrombocytopenia in a subset of patients with ITP is CP dependent, and that CP inhibition with sutimlimab should improve thrombocytopenia. Methods Adult patients with chronic (>1 year of duration), severe ITP with inadequate response to ≥2 prior therapies (plt count [ct] ≤30 × 109/L at screening) were enrolled in an open-label Phase 1 trial. Patients could receive concomitant ITP medication if on a stable dose for the prior month and were unable to sustain plt cts ≥30 × 109/L in the absence of bleeds. Patients received sutimlimab on Day 0, 7, and then biweekly for up to 21 weeks (Part A) followed by a scheduled washout to evaluate relapse and re-treatment response in a re-treatment/continuation arm (Part B) for an additional year. Results All results are presented as of a data cutoff of 14 December 2018. Seven patients received at least 1 dose of sutimlimab. At screening for Part A, mean (range) age was 44.9 (28-65) years and 85.7% (n=6) of patients were female. The mean (range) baseline plt ct for Part A was 27.9 × 109/L (8-57). The mean (range) plt ct 24 hours post-initial dose of sutimlimab was 81.3 × 109/L (1-209). The mean (range) plt ct on Day 7 was 206.3 × 109/L (25-435). Mean plt ct was maintained at >50 × 109/L throughout Part A. Response defined as a plt ct >50 × 109/L measured on 2 separate occasions more than 7 days apart was achieved by 57% (n=4) of patients by Day 14 (Figure). One additional patient achieved a stable plt ct 20-50 × 109/L. The mean (range) C4 level increased from 27.6 (15-45) mg/dL at baseline to 37.3 (26-50) mg/dL at Day 7 after the initial sutimlimab treatment. Four patients completed the protocol washout/re-treatment at the end of Part A and entered Part B. In all of these patients, sutimlimab washout resulted in reoccurrence of thrombocytopenia. Mean (range) time in washout was 4.1 (3-7) weeks. These 4 patients were re-treated in Part B. The mean (range) baseline plt ct at re-treatment was 16.0 × 109/L (5-26). Re-treatment efficacy was observed in patients in Part B. Safety data is available from Part A as of the 14 December 2018 data cutoff. Six patients experienced a total of 30 treatment-emergent adverse events. No patients discontinued Part A early due to an adverse event. Two patients experienced a total of 3 treatment-emergent serious adverse events (SAE), of which 1 SAE of migraine was assessed as possibly related to sutimlimab. There were no thrombotic events. The benefit-risk remained positive for continued investigational use of sutimlimab in ITP. Conclusions In a preliminary analysis of interim data, sutimlimab resulted in a rapid (<24 hours), sustained increase in plt ct in patients with chronic ITP who had inadequate responses to ≥2 currently available therapies at trial entry. Washout kinetics demonstrated that thrombocytopenia reoccurs when sutimlimab is discontinued, and that thrombocytopenia resolution occurs upon re-treatment. This is the first clinical evidence that the CP plays a role in thrombocytopenia in a subset of patients with ITP. These responses suggest at least 1 additional pathophysiologic explanation for the clinical heterogeneity of ITP, and provide a strong rationale for continued evaluation of CP inhibition in ITP treatment. Disclosures Broome: Sanofi Genzyme: Honoraria, Research Funding; Cellphire: Research Funding; Rigel: Research Funding; Incyte: Research Funding; Alexion: Honoraria, Research Funding. Röth:Bioverativ: Consultancy, Honoraria; Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Alexion: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Apellis: Consultancy, Membership on an entity's Board of Directors or advisory committees; Roche: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding. Kuter:Daiichi Sankyo: Consultancy, Honoraria; Caremark: Consultancy, Honoraria; Actelion (Syntimmune): Consultancy, Honoraria, Research Funding; Zafgen: Consultancy, Honoraria; Kyowa-Kirin: Consultancy, Honoraria; Novartis: Consultancy, Honoraria; Novartis: Consultancy, Honoraria; Platelet Disorder Support Association: Consultancy, Honoraria; Takeda (Bioverativ): Consultancy, Honoraria, Research Funding; Platelet Disorder Support Association: Consultancy, Honoraria; Kyowa-Kirin: Consultancy, Honoraria; Dova: Consultancy, Honoraria; Protalex: Consultancy, Honoraria, Research Funding; Dova: Consultancy, Honoraria; Shinogi: Consultancy, Honoraria; Zafgen: Consultancy, Honoraria; Sanofi: Consultancy, Honoraria; Up-to-Date: Consultancy, Honoraria, Patents & Royalties: 3 Up-to-Date chapters; Principia: Consultancy, Honoraria, Research Funding; Merck Sharp Dohme: Consultancy, Honoraria; Merck Sharp Dohme: Consultancy, Honoraria; Protalix: Consultancy, Honoraria; Shinogi: Consultancy, Honoraria; Genzyme: Consultancy, Honoraria; Caremark: Consultancy, Honoraria; Protalex: Consultancy, Honoraria, Research Funding; Up-to-Date: Consultancy, Honoraria, Patents & Royalties: 3 Up-to-Date chapters; Shire: Consultancy, Honoraria; UCB: Consultancy, Honoraria; UCB: Consultancy, Honoraria; Principia: Consultancy, Honoraria, Research Funding; Momenta: Consultancy, Honoraria; Momenta: Consultancy, Honoraria; Pfizer: Consultancy, Honoraria; Pfizer: Consultancy, Honoraria; Kezar: Research Funding; Kezar: Research Funding; Bristol Myers Squibb (BMS): Consultancy, Honoraria, Research Funding; Actelion (Syntimmune): Consultancy, Honoraria, Research Funding; Agios: Consultancy, Honoraria, Research Funding; Argenx: Consultancy, Honoraria, Research Funding; Rigel: Consultancy, Honoraria, Research Funding; Rigel: Consultancy, Honoraria, Research Funding; Protalix: Consultancy, Honoraria; Genzyme: Consultancy, Honoraria; Agios: Consultancy, Honoraria, Research Funding; Alnylam: Consultancy, Honoraria, Research Funding; Bristol Myers Squibb (BMS): Consultancy, Honoraria, Research Funding; Daiichi Sankyo: Consultancy, Honoraria; Alnylam: Consultancy, Honoraria, Research Funding; Sanofi: Consultancy, Honoraria; Takeda (Bioverativ): Consultancy, Honoraria, Research Funding; Amgen: Consultancy, Honoraria, Research Funding; Amgen: Consultancy, Honoraria, Research Funding; Argenx: Consultancy, Honoraria, Research Funding; Shire: Consultancy, Honoraria. Scully:Shire/Takeda: Consultancy; Shire: Research Funding; Ablynx/Sanofi: Consultancy; Novartis: Consultancy; Alexion: Consultancy. Smith:Alnylam: Honoraria; Bioverativ: Honoraria. Wang:Sanofi: Employment. Reuter:Pediatric Infectious Disease Society: Other: Social Media Committee, Vaccine Advocacy Committee; Sanofi: Employment. Hobbs:Sanofi-Genzyme: Employment.
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Xie, Jing, Daniel Nélias, Hélène Walter-Le Berre, Kazuhiro Ogawa, and Yuji Ichikawa. "Simulation of the Cold Spray Particle Deposition Process." Journal of Tribology 137, no. 4 (October 1, 2015). http://dx.doi.org/10.1115/1.4030257.
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Cold spray is a rapidly developing coating technology for depositing materials in the solid state. In this work, the cold spray particle deposition process was simulated by modeling high-velocity impacts of spherical particles onto a flat substrate under various conditions. For the first time, we proposed the coupled Eulerian–Lagrangian (CEL) numerical approach as a means of solving the high-strain rate deformation problem. Using this approach, we observed a compressive stress region at the interface between the particles and the substrate induced by large plastic strains in the materials. Due to the high contact pressure (about 1 GPa) and the short contact time (about 40 ns), the high-strain rate (106 s-1) plastic deformation region was only a few micrometers deep and was localized mainly at the bottom of the particle and substrate surface. The ability of the CEL method to model the cold spray deposition process was assessed through a systematic parametric study including impact velocity, initial particle temperature, friction coefficient, and materials combination. The higher the impact velocity, the higher the initial kinetic energy, leading to more substantial plastic deformations and significant temperature increases in the substrate. The initial particle temperature has a greater influence on the equivalent plastic strain than on the temperature increase in the substrate. Friction has a limited effect on the temperature distribution and increase in the substrate, and the equivalent plastic strain increases only slightly as the friction coefficient rises. Four combinations of particle/substrate materials (Cu/Cu, Al/Al, Cu/Al, and Al/Cu) were considered in our study. Obviously, the particle's material had a greater influence on the deposition process and on the deformation than the substrate material. Concerning the particle's material, a higher-density material, such as Cu, has a higher initial kinetic energy, which has the advantage of increasing the contact area and contact time, resulting in better bonding between particles and substrate. Compared to other numerical methods (Lagrangian, arbitrary Lagrangian–Eulerian (ALE), and smooth particle hydrodynamics (SPH)), the CEL approach is globally more accurate and more robust in high-strain rate deformation regimes.
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Heilmann, Ralf K., and Robert M. Suter. "Kinetic Roughening of Quenched Xenon Films." MRS Proceedings 407 (1995). http://dx.doi.org/10.1557/proc-407-239.
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ABSTRACTWe investigate the growth of quenched Xe films formed by deposition onto a cold (15-35K) substrate via in situ measurements of x-ray reflectivity and diffraction. Surface roughness, film density, and crystallinity are determined as a function of Xe film thickness, substrate temperature and Xe flux in order to test for dynamic scaling behavior. Deposition of polycrystalline films with random crystallite orientations is achieved through heating of a grafoil sheet that is enclosed in the sample cell and has previously been covered with bulk Xe. At 16K the films are sufficiently quenched to be stable over several days, while at 25K annealing takes place. Differing atomic mobilities at different temperatures lead to contrasting scaling behavior. The substrate remains unchanged under repeated film deposition and desorption and therefore allows a systematic comparison of different films.
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Smith, Richard W., Feng Ying, and David J. Srolovitz. "Growth and Texture of Polycrystalline Thin Films." MRS Proceedings 403 (1995). http://dx.doi.org/10.1557/proc-403-39.
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AbstractTwo dimensional non-equilibrium molecular dynamics simulations are performed to study microstructural evolution during the growth of polycrystalline thin films. Attention is focused on the interaction between grain boundaries and voids which form during deposition, and on the development of a preferred, crystallographic texture during film growth. In an intermediate temperature regime, where the film is cold enough to allow void formation but hot enough to allow grain boundary motion, boundaries move such as to attach themselves to voids as the voids form from depressions in the film surface. At lower temperatures, the boundaries have insufficient mobility to migrate toward the voids. At higher temperatures, films grow in the absence of voids. At low deposition kinetic energies, there is no tendency for polycrystalline films to develop a preferred texture. At moderate or high energy deposition kinetic energies, however, as in the case of magnetron sputtering, significant texture formation can result due to preferential (re)sputtering of atoms from the surface of grains with low-binding-energy exposed surfaces. Such preferential (re)sputtering provides a height advantage for grains possessing high-binding-energy exposed surfaces. The taller grains are seen to widen as deposition continues, resulting in the development of a preferred crystallographic orientation.
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"Kinetic Spraying of Brittle Materials: From Layer Formation to Applications in Aerosol Deposition and Cold Gas Spraying." Journal of Thermal Spray Technology 30, no. 3 (February 2021): 471–79. http://dx.doi.org/10.1007/s11666-021-01177-z.
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Bae, Y. W., W. Y. Lee, T. M. Besmann, P. J. Blau, K. L. More, and D. N. Braski. "Self-Lubricating, TiN-MoS2 Composite Coatings Produced by Simultaneous Deposition from Ti((CH3) 2N)4/NH3/MoF6/H2S GAS Mixtures." MRS Proceedings 363 (1994). http://dx.doi.org/10.1557/proc-363-231.
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AbstractComposite coatings consisting of discrete phases of TiN and MoS2 were codeposited on graphite substrates from Ti((CH3)2N)4/NH3/MoF6/H2S gas mixtures in a cold-wall reactor at 1073 K and 1.3 kPa. Chemical composition and microstructure of the coatings were characterized by Auger electron spectroscopy, X-ray diffraction, and transmission electron microscopy. Kinetic friction coefficients of the coatings were determined by a computer-controlled friction microprobe and values less than 0.2 were obtained with a type-440C stainless-steel counterface under ambient condition.
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Morgan, R. H., C. J. Sutcliffe, J. Pattison, M. Murphy, C. Gallagher, A. Papworth, P. Fox, and W. O'Neill. "Cold Gas Dynamic Manufacturing – A new approach to Near-Net Shape Metal Component Fabrication." MRS Proceedings 758 (2002). http://dx.doi.org/10.1557/proc-758-ll2.6.
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ABSTRACTCold Gas Dynamic Manufacturing (CGDM) is a high-rate, direct deposition process capable of combining many dissimilar materials in the production of a single component. The process is based on Cold Gas Dynamic Spraying (CGDS) – a surface coating technology in which small, un-heated particles are accelerated to high velocities (typically above 500 m/s) in a supersonic gas jet and directed towards a substrate material. The process does not use a heat source (as with similar plasma and HVOF spray technologies), but rather employs the high kinetic energy of the particles to effect bonding through plastic deformation upon impact with the substrate or previously deposited layer. As a consequence it lends itself to the processing of temperature sensitive material systems such as oxidising, phase-sensitive or nano-structured materials. To achieve metallic bonding incident particles require velocities greater than a certain material-specific threshold value, such that thin surface films are ruptured, generating a direct interface. This bonding mechanism has been compared to explosive welding.This paper discusses the further development of the CGDS technique from surface coating technology into the basis for a novel Additive Fabrication process. The description of the apparatus is presented in addition to the basic processing conditions for the deposition of aluminium material. Particular attention is paid to the morphology of the deposited material, the microstructure and the interfacial boundary between splats.
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Bartzke, Gerhard, Lennart Siemann, Robert Büssing, Paride Nardone, Katinka Koll, Dierk Hebbeln, and Katrin Huhn. "Investigating the Prevailing Hydrodynamics Around a Cold-Water Coral Colony Using a Physical and a Numerical Approach." Frontiers in Marine Science 8 (September 27, 2021). http://dx.doi.org/10.3389/fmars.2021.663304.
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Framework-forming cold-water corals provide a refuge for numerous organisms and, consequently, the ecosystems formed by these corals can be considered as impressive deep-sea biodiversity hotspots. If suitable environmental conditions for coral growth persist over sufficiently long periods of time in equilibrium with continuous sediment input, substantial accumulations of coral mound deposits consisting of coral fragments and baffled sediments can form. Although this conceptual approach is widely accepted, little is known about the prevailing hydrodynamics in their close proximity, which potentially affect sedimentation patterns. In order to refine the current understanding about the hydrodynamic mechanisms in the direct vicinity of a model cold-water coral colony, a twofold approach of a laboratory flume experiment and a numerical model was set up. In both approaches the flow dynamics around a simplified cold-water coral colony used as current obstacle were investigated. The flow measurements of the flume provided a dataset that served as the basis for validation of the numerical model. The numerical model revealed data from the vicinity of the simplified cold-water coral, such as the pressure field, velocity field, or the turbulent kinetic energy (TKE) in high resolution. Features of the flow like the turbulent wake and streamlines were also processed to provide a more complete picture of the flow that passes the simplified cold-water coral colony. The results show that a cold-water coral colony strongly affects the flow field and eventually the sediment dynamics. The observed decrease in flow velocities around the cold water-coral hints to a decrease in the sediment carrying potential of the flowing water with consequences for sediment deposition.
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Perna, Alessia Serena, Antonello Astarita, Domenico Borrelli, Antonio Caraviello, Francesco Delloro, Roberta Della Gatta, Patrizio Lomonaco, Ilaria Papa, Raffaele Sansone, and Antonio Viscusi. "Fused Filament Fabrication of ONYX-Based Composites Coated with Aluminum Powders: a Preliminary Analysis on Feasibility and Characterization." ESAFORM 2021, March 30, 2021. http://dx.doi.org/10.25518/esaform21.4017.
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Polymer-based AM methods are the most mature additive technologies for their versatility and variety of products obtainable. The addition of fibre reinforcement can also confer to the manufactures produced good mechanical properties. Unfortunately, several applications are still precluded because polymers cannot guarantee appropriate electrical conductivity, erosion resistance and operating temperature. Aiming to overcome these issues, the metallization of the surfaces emerges as a possible solution. Unfortunately, thermoplastic polymers exhibit thermosensitive behaviour and run the risk of being damaged when traditional metallization techniques, which require the melting of metal powders which will act as a protective coating. For this reason, studies have focused on Cold Gas Dynamic Spray, an additive manufacturing technology, which exploits kinetic energy to favour the adhesion of metal particles rather than the increase in temperature. In this work, a first attempt is made to verify the feasibility of cold spray coatings on 3D printed composite substrates, produced by means of Fused Filament Fabrication (FFF) technique. FFF technology allows the deposition of two different types of filaments by using a double extruder. These composite fibres within 3D printed parts manage to give the object a resistance comparable to that of a metal part with lower production cost and a high degree of automation. These structures, made of ONYX, a Nylon matrix in which short carbon fibres are dispersed, and reinforced with long carbon fibres, are designed to better fit the CS deposition. Aluminium coatings have been produced and a characterization campaign has been carried on.
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Bruneau, Denis M., Patrick Sebastian, Jean-Yves Lecompte, Antoine Collignan, and Vincent Rochery. "Sizing of an Innovative and Improved Meat Smoking System." International Journal of Food Engineering 1, no. 4 (July 19, 2005). http://dx.doi.org/10.2202/1556-3758.1001.
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There has been recent interest in developing small-scale smoking technologies that respect French sanitary recommendations concerning benzo(a)pyrene deposition on food. The conceptual and embodiment phases of design, and the sizing of a smoker in which this deposition phenomenon is limited are reviewed in this paper. The conceptual phase of design has lead to a process based on the operations of smoking, heating and drying units, using cooled smoke, radiant plates and supplying flows of this cooled smoke directly to the product. For marketing reasons, the power supply is exclusively derived from the combustion of small logs and the smoke comes from sawdust pyrolysis, this smoke being cooled by flowing through a heat exchanger using ice as a cold source. The embodiment phase of design has lead to a versatile system in terms of smoking, heating and drying functionalities. The sizing of this system is based on knowing the drying kinetic of the product in a traditional smoke house (boucan); it was performed by estimating heat and mass transfer phenomena occurring between the product and its surroundings. It leads to a kiln having a thermodynamic efficiency close to 13%.
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Della Gatta, Roberta, Antonello Astarita, Domenico Borrelli, Antonio Caraviello, Francesco Delloro, Patrizio Lomonaco, Ilaria Papa, Alessia Serena Perna, Raffaele Sansone, and Antonio Viscusi. "Manufacturing Of Aluminum Coating On 3D-Printed Onyx With Cold Spray Technology." ESAFORM 2021, March 29, 2021. http://dx.doi.org/10.25518/esaform21.858.
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Composite materials are widely used as main parts and structural components in different fields, especially for automotive and military applications. Although these materials supply different advantages comparing to the metals, their implementation in engineering applications is limited due to low electrical and thermal properties and low resistance to erosion. To enhance these above-mentioned properties, the metallization of composite materials by creating a thin metal film on their surface can be achieved. Among different coating deposition techniques, Cold Spray appears to be the most suitable one for the metallization of temperature-sensitive materials such as polymers and composites with a thermoplastic matrix. This process relies on kinetic energy for the formation of the coating rather than on thermal energy and consequent erosion and degradation of the polymer-based composite can be avoided. In the last years, a new method to produce composite materials, as known as Fused Filament Fabrication (FFF), has been developed for industrial applications. This technique consists of a 3D printing process that involves the thermal extrusion of thermoplastic polymer and fibers in the form of filaments from a heated mobile nozzle. The implementation of this new technique is leading to the manufacturing of customized composite materials for the cold spray application. In the presented experimental campaign, Onyx material is used as a substrate. This material is made of Nylon, a thermoplastic matrix, and chopped carbon fibers randomly dispersed in it. Aluminum powders were cold sprayed on the Onyx substrate with a low-pressure cold spray (LPCS) system. This study aims to investigate the possibility of the metalizing 3D-printed composite material by cold spray technology. For this purpose, optical and microscopical analyses are carried out. Based on the results, the feasibility of the process and the influence of the morphology of the substrate are discussed, and optimal spraying conditions are proposed.
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Wolpert, Charline, Thomas Emmler, Maria Villa Vidaller, Andreas Elsenberg, Kentaro Shinoda, Mauricio Schieda, Frank Gärtner, Jun Akedo, and Thomas Klassen. "Aerosol-Deposited BiVO4 Photoelectrodes for Hydrogen Generation." Journal of Thermal Spray Technology, November 8, 2020. http://dx.doi.org/10.1007/s11666-020-01104-8.
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Abstract Hydrogen generation from renewable energy sources will play a key role in the concerted endeavor to constrain climate change. One environmentally friendly route, powered by sunlight, is the photoelectrochemical water splitting cell (PEC). This technology employs electrodes coated with thin films of semiconductor materials to capture light and generate charge carriers that directly drive the water splitting reaction. Bismuth vanadate is a promising metal oxide semiconductor, as it absorbs visible light, and is abundant, non-toxic and cost-effective. The present study investigates the formation of bismuth vanadate thin films by the aerosol deposition (AD) method. Operating with layer formation at room temperature, AD offers advantages over other routes for the fabrication of photoactive thin film coatings, as no binders or sintering processes need to be applied. Furthermore, compared to traditional cold spraying, micrometer-sized particles can be used, resulting in coatings with thicknesses below 1 µm. Additionally, the lower kinetic energy of the feedstock powder particles enables the use of delicate substrates, such as FTO-coated glass, expanding the range of possible PEC device configurations. The process parameters explored in this study had considerable influence on the resulting coating microstructure, which in turn showed a significant impact on the photoelectrochemical performance.
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Barletta, M. "Al 2 O 3 Graded Coatings on Aluminum Alloy Deposited by the Fluidized Bed (FB) Technique: Film Formation and Mechanical Performance." Journal of Engineering Materials and Technology 132, no. 3 (June 15, 2010). http://dx.doi.org/10.1115/1.4001263.
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Al 2 O 3 coatings have been deposited onto an Al alloy by the fluidized bed (FB) technique using alumina powder. Film formation through a cold deposition process and its growth kinetics have been investigated by varying the deposition time. This allowed us to establish how the morphology, microstructure, hardness, scratch resistance, and adhesion strength of the Al2O3 films were progressively imprinted. The FB process led to the deposition of a good-looking and well-adhered graded Al2O3 coating, which was found to be progressively richer in Al2O3 on moving from the interface with the Al alloy toward the outermost layers. The resulting Al2O3 coatings have been shown to produce a consistent improvement of the overall mechanical and tribological performance of the Al alloy, thus leading to the build-up of an overlying hard and tough protective layer.
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Kermani, Ahmad, Kristian E. Johnsgard, Sailish Suthar, Ki-Bum Kim, and Chung Lam. "Rapid Thermal Chemical Vapor Deposition of Polycrystalline Silicon From Dichlorosilane." MRS Proceedings 182 (1990). http://dx.doi.org/10.1557/proc-182-21.
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AbstractRapid Thermal Chemical Vapor Deposition (RTCVD) of undoped and insitu doped polycrystalline silicon films has been accomplished in a cold-wall reactor. Dichlorosilane was used for the silicon source and AsH3 gas was used as the dopant source. Thedeposition kinetics of poly-silicon films on silicon dioxide over a range of deposition temperatures, pressures and carrier gas chemistries was studied. Both blanket and selective deposition modes were examined. The poly-silicon films were examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) for morphology and grain size analysis. Using X-ray diffraction technique, preferred grain orientation dependency of poly-silicon films on growth conditions was investigated. Dopant incorporation, dopant activation and oxygen content of polysilicon films were measured by secondary ion mass spectrometry (SIMS), four point probe, and spreading resistance profiling (SRP) techniques.This paper is to report the results of material characterization of polysilicon films deposited by RTCVD, and to address the applications and advantages of ‘Integrated Processing’ technology involving deposition of polysilicon.
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Parretta, A., G. Giunta, E. Cappelli, V. Adoncecchi, and V. Vittori. "Influence of Substrate and Process Parameters on The Properties of CVD-SiC." MRS Proceedings 168 (1989). http://dx.doi.org/10.1557/proc-168-227.
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AbstractThe microstructure and mechanical properties (adhesion, hardness) of beta-SiC coatings, prepared in a cold wall reactor, were studied by examining different substrates and deposition process conditions. Hard (3500 HK), fine grained beta-SiC coatings were deposited onto graphite at relatively high deposition terperatures (1473–1673 K) using SiC14,C3H8,H2 gas mixtures. The thermal decomposition of methyltrichlorosilane (MTS) in hydrogen and argon allowed the production of beta-SiC coatings onto a variety of substrate materials in the temperature range 1173–1373 K. The growth mechanisms of SiC deposited from MTS/H2/Ar system onto graphite and polycrystalline alfa-SiC substrates were studied. At low (40 kPa) and atmospheric pressure, the growth kinetics is limited by surface reactions. Also, a strong dependence of the microstructure and crystallographic orientation on the deposition parameters was observed. Hard metals (WC/Co) were succesfully coated with beta-SiC using the MTS/H2/Ar system. Problems of chemical compatibility between the substrate and the beta-SiC coating were minimized by deposition of an intermediate layer of TiN.
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Kuehn, R. T., X. Xu, D. J. Holcombe, V. Misra, J. J. Wortman, J. R. Hauser, Q. F. Wang, and D. M. Maher. "Gate Quality Oxides Prepared by Rapid Thermal Chemical Vapor Deposition." MRS Proceedings 334 (1993). http://dx.doi.org/10.1557/proc-334-531.
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AbstractAs the feature size of MOSFET devices shrink, issues such as thermal budget associated with controlling channel doping profiles and oxide growth kinetics raise concerns about using thermally grown furnace oxides for deep-submicron device applications. To address these concerns, we have developed a new RTCVD oxide process using a gas system of silane and nitrous oxide. The RTCVD oxides are deposited in a lamp-heated, cold wall, RTP system. Deposition rates ranging from 55 Å/min. to 624 Å/min. can be achieved at 800°C with silane nitrous oxide flow rate ratio of 2% and total pressure ranging from 3 to 10 Torr. The results indicate that this RTCVD process can be used to deposit both thin gate and thick isolation insulators for single wafer processing. Deposition rates of the RTCVD oxides exhibit a nonlinear dependence on the total deposition pressure. Electrical characterization of the as-deposited RTCVD oxides shows a mid-gap interface trap density of < 5×1010 eV−1 cm−2 and an average breakdown field of 13MV/cm. AES, RBS and TEM analyses have been used to study surface cleaning effects on the silicon-silicon dioxide interface quality and to determine the chemical composition of the RTCVD oxides. The results show that RTCVD oxides with stoichiometric composition and atomic flat silicon-silicon dioxide interface can be achieved using silane nitrous oxide flow rate ratio of <2%. I-V characteristics and transconductance degradation under hot carrier stress for MOSFET's using as-deposited RTCVD gate oxides have been found to be comparable to those of MOSFET's using thermal gate oxides.
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Siwila, Stephen, and Isobel C. Brink. "Modelling of Escherichia coli removal by a low-cost combined drinking water treatment system." Water Supply, May 7, 2020. http://dx.doi.org/10.2166/ws.2020.084.
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Abstract This work presents mathematical modelling of Escherichia coli (E.coli) removal by a multi-barrier point-of-use drinking water system. The modelled system is a combination of three treatment stages: filtration by geotextile fabric followed by filtration and disinfection by silver-coated ceramic granular media (SCCGM) then granular activated carbon (GAC) filtration. The presented models accounted for removal mechanisms by each treatment stage. E.coli was modelled as a microbial particle. E.coli inactivation by SCCGM was modelled using the Chick's, Chick-Watson, Collins-Selleck and complete mix system bacterial inactivation kinetic models, which were considered adequately representative for describing the removal. Geotextile removal was modelled using colloidal filtration theory (CFT) for hydrosol deposition in fibrous media. The filtration removal contributions by the SCCGM and GAC were modelled using CFT for removal of colloidal particles by granular media. The model results showed that inactivation by silver in the SCCGM was the main bacterial removal mechanism. Geotextile and GAC also depicted appreciable removals. The theoretical modelling approach used is important for design and optimization of the multi-barrier system and can support future research in terms of material combinations, system costs, etc. Collector diameter, particle size, filtration velocity and contact time were identified as critical parameters for E.coli removal efficiency.
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Balazs, Dawn, Dakang Shen, Stefanie Lischer, Kathrin Grieder, Giuseppino Fortunato, Mohammad Mokbul Hossain, Enrico Körner, Peter WIck, Dieter Haas, and Manfred Heuberger. "Multifunctional Nanocomposite Plasma Coatings: Enabling New Biomaterials Applications." MRS Proceedings 1056 (2007). http://dx.doi.org/10.1557/proc-1056-hh04-06.
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ABSTRACTDue to the increasing prevalence of resistance of bacteria to antibiotics and antiseptic methods, new strategies to prevent colonization of biomaterials are needed. Due to its high antimicrobial activity and relatively low toxicity to human cells, we are evaluating silver (Ag) releasing plasma polymers as a strategy to prevent bacterial colonization. Such Ag/plasma polymer nanocomposite materials, consisting of nano-scaled metal clusters embedded within a plasma-polymer matrix can be deposited using a mixed, plasma polymerization /sputtering process. For example, Ag containing plasma polymer nanocomposites are deposited employing an Ag cathode, an appropriate monomer to yield the desired material properties of the matrix (biocompatibility) and an asymmetric reactor design. The focus of this paper is a new development at Empa: a multi-functional Ag/amino-hydrocarbon (Ag/a-C:H:N) nanocomposite that can enhance cell growth and simultaneously prevent bacterial colonization at surfaces. Ag/a-C:H:N coatings containing 4.0% Ag have been demonstrated to reduce bacterial adhesion of E. coli by up to 95%, as compared to an external polyester fabric control in a static assay. Likewise, these coatings demonstrated a bacterial toxic effect both at the surface and in the surrounding media due to the release of Ag ions. XPS characterization of various nanocomposites has shown that the Ag quantity and matrix characteristics of the films can be tailored to specific requirements by altering deposition parameters such as power input, pressure and gas feed ratio. Although the surface chemistry has been characterized, open questions remain to the amount and the kinetics of the release of Ag and the subsequent effect on bacteria and cells. Since Ag release profiles will ultimately determine the antimicrobial efficacy of the coatings, as well as duration of the effect, these dosing issues must be quantified and clarified. Ag release kinetics of the various Ag/a-C:H:N as measured by atomic absorption spectroscopy has been evaluated and the relationships to biological assays, including bacterial and cellular adhesion are clarified. A range of Ag/a-C:H:N coatings having various Ag content are tested in two biological assays, bacterial toxicity and cytoxicity. Bacterial growth tests using the pathogen, P. aeruginosa wild type (PAO1), were performed according to the method of Tiller et al. The method is based on the bacterial deposition from aerosols, thus, it mimics bacterial exposure through airways such as intubation tubes. Secondly, cytotoxicity assays of the nanocomposites has been performed using a murine fibroblast cell line 3T3 testing protocol, and the proliferation of the cultures was measured taking the DNA amount per well as an index (Bruinink 2001). We will answer questions regarding what is the fundamental Ag content and Ag release profile under static bacterial testing environments which allow a maximum bacterial-toxic effect with a minimum amount of Ag.