查看更多>>摘要：Approximately 30 to 40 years ago the group of Stan Vep.rek of the University of Zurich described the fabrication of silicon thin films by formation and decomposition of silicon hydride. In their paper they described how pieces of silicon exposed to a low-pressure hydrogen plasma could promote the formation of a volatile silicon hydride. The hydride was then transported to a hot substrate which caused its thermal decomposition and the formation of the silicon film. Hollow cathodes under appropriate experimental conditions can produce a semi-resonant high-density plasma. In a previous study we used such a high-density hydrogen plasma to etch pieces of quartz but under extreme conditions, we observed that rather than etching there was deposition of a thin film of the metal used for the electrode of the hollow cathode. In this paper we describe the etching of the metal (Mo or Ta) lining of a water-cooled cylindrical hollow cathode by a high-density hydrogen plasma. The metal hydride vapour generate in the plasma by chemical sputtering was directed, by the gas flow, to the quartz substrates which were maintained at various temperatures in excess of 573 K. Here the metal hydride was thermal decomposed, and a thin film of the metal was formed. To improve the experimental reproducibility a special substrate heater was constructed such that four quartz substrates could be simultaneously exposed to the metal hydride vapour, but with each substrate at a different temperature: each approximately 30.3 K greater than the neighbouring one. In this way, depositions under identical plasma conditions could be carried out at the same time, but at four different temperatures. We report the deposition rate as a function of the substrate temperature, the hydrogen gas flow and the RF or P-DC plasma power applied to the hollow cathode.
查看更多>>摘要：Biopolymer and carbon-based materials have found widespread applications, spanning across different industries, including the medical, energy storage, wind energy, and aerospace sectors. The increasing popularity of both types of materials in industry has created a driving force for the enhancement of their properties to meet the current and future requirements. Active-screen plasma (ASP) has attracted much attention as a versatile and powerful surface engineering solution to meet these growing demands, owing to its treatment uniformity, remote plasma nature, capability for treating both electrically conductive and insulating materials, ability to functionalise surfaces, and the unique combined function of surface activation and deposition (CFAD). Through the introduction of moieties, modification of chemical bonding, change of morphology, and improvement in wettability on the treated surfaces, recent studies have demonstrated the ability for ASP treatments to enhance the biocompatibility of biopolymers. Moreover, ASP has also been tested (and 'bespoke' ASP techniques developed) for advanced carbon-based materials for tailored applications with promising property/performance enhancements, including a) enhanced wettability and interfacial shear strength for carbon fibres in polymer matrix composites, b) improved catalyst layer growth on carbon paper, c) improved electrical conductivity and capacitive performance for carbon nanofibers, and d) enhanced electric and electrochemical properties for graphene oxide.This review evaluates the recent achievements and findings of ASP treatments performed on biopolymers and carbon-based materials from the Surface Engineering group in the University of Birmingham. The current status of ASP surface multi-functionalisation is communicated, along with the future research focus for materials with poor electrical conductivity and/or vulnerability to degradation.
查看更多>>摘要：The influence of Ag content on the morphology, structure, hardness (H) and reduced Young's modulus (E), thermal stability, and oxidation resistance of TiAlSiN(Ag) coatings is investigated. The coatings were produced by DC reactive magnetron sputtering, with increasing Ag contents from 0 up to 15.9 at.%. All coatings exhibit a fcc type structure. The coating with 1.5 at.% Ag content displays the highest H and E values as a result of the coating densification and the grain refinement caused by the co-deposition of immiscible phases. Further Ag concentration degrades the H and E values of the coatings due to the incorporation of a softer Ag phase in the structure. Annealing at 800 C in protective atmosphere for 2 h enhances the coatings crystallinity, with small increments in the H and E values. The dynamic thermal gravimetric oxidation curves reveal that Ag additions do not affect the starting point of oxidation of the coatings (~990 C). However, it enhances their oxidation resistance. The improved oxidation resistance of the coatings with Ag incorporation is caused by the diffusion of Ag through the oxide scale to the surface, which modifies the composition of the Ti-Al-O layer, producing a more protective Al rich layer.
Bussell, B. C.Gibson, P. N.Lawton, J.Couture, P....
19页
查看更多>>摘要：Aluminium-doped ZnO (AZO) thin films were deposited by remote plasma sputtering of a ZnO:Al2O3 98:2 wt% ceramic target in a pulsed DC configuration. The target power was kept constant at 445 W and the RF plasma power was varied between 0.5 and 2.5 kW. The as-deposited AZO thin films exhibited an optimum resistivity of 6.35 x 10(-4) omega.cm and optical transmittance of 92% at a RF plasma power of 1.5 kW. The thin film microstructure, chemical composition, and residual stress were investigated using SEM, RBS, XPS and XRD. Accurate determination of the chemical composition and correct interpretation of GIXRD data for AZO thin films are a particular focus of this work. The AZO layer thickness was 500-700 nm and Al content in the range of 2.3-3.0 at.%, determined by RBS. The AZO thin films exhibited a strong (002) preferential orientation and grain sizes between 70 and 110 nm. The (103) peak intensity enhancement in GIXRD is proven to be a result of the strong (002) preferential orientation and GIXRD geometrical configuration rather than a change in the crystallite orientation at the surface. XPS depth profiles show preferential sputtering of O and Al using a 500 eV Ar+ beam, which can be reduced, but not eradicated using an 8 keV Ar-150(+) beam. The preferential sputtering can be successfully modelled using the simulation software TRIDYN. A plasma power of 1.5 kW corresponds to a highly ionised plasma and various microstructural and compositional factors have all contributed to the optimum low resistivity occurring at this plasma power. The grain size exhibits a maximum in the 1.25-1.5 kW range and there is improved (002) orientation, minimising grain boundary scattering. The highest carrier concentration and mobility was observed at the plasma power of 1.5 kW which may be associated with the maximum in the aluminium doping concentration (3.0 at.%). The lowest residual stress is also observed at 1.5 kW.
Uglov, V. V.Abadias, G.Zlotski, S. V.Saladukhin, I. A....
8页
查看更多>>摘要：The work is dedicated to the study of the phase stability and surface erosion of a novel Zr-based multilayer system consisting of a combination of ceramic (ZrN) and metallic glass (Zr-Cu) nanoscale layers after He irradiation (40 keV and doses up to 1.1 x 1018 cm(-2)). Periodic ZrN/Zr(1-x)Cux multilayers with elementary layer thicknesses of 5 nm/5 nm and 5 nm/10 nm and Cu content x = 0.45, 0.53, 0.61 and 0.74 were grown by magnetron sputter-deposition from Zr and Cu targets at the substrate temperature of 300 C. X-ray diffraction and X-ray reflectivity analysis reveal that multilayered films consist of alternating nanocrystalline (nc) ZrN and amorphous (a) ZrCu layers with relatively sharp interfaces. The stability of the phase composition of nc-ZrN/a-Zr1-xCux multilayer films to irradiation with helium ions up to fluence of 1.1 x 1018 cm- 2 has been established. For x = 0.74, crystallization of the metallic glass layer was observed. The surface integrity of the multilayer films remained unaltered up to an ion fluence of 5 x 1017 cm(-2). At higher ion fluence, surface erosion of the nc-ZrN/a-Zr(1-x)Cu(x )films occurs by the flacking mechanism. In this case, an increase in the thickness of the amorphous Zr(1-x)Cux layer and in Cu content leads to improved radiation resistance as the critical fluence for delamination increases from 5 x 1017 cm(-2) upto 8 x 1017 cm(-2).
查看更多>>摘要：The functional performance of coatings can be transformed using coatings to form an engineered surface system where resistance to wear and friction are improved relative to the uncoated substrate. Understanding the failure mechanisms of coatings in tribological contacts is difficult to achieve. This paper shows results from real time in situ measurements of tribological behaviour of coated surfaces. Two different test systems have been used. These are a microtribometer fitted inside an SEM which provides sequences of high resolution images of the deformation processes occurring in coatings, and a ball on disc tribometer fitted with imaging and profilometric systems giving real-time information on the tribological response of coatings. DLC and TiN coatings on tool steel substrates were tested in the experiments reported here. Delamination failure of the DLC coatings was observed with both test system. A new rotating scratch test is also described that can provide real-time in situ information on the response of the coatings to repeated abrasion. The in situ results are supported by post-test surface examination.
Martinez-Martinez, D.Tiss, B.Glanzmann, L. N.Wolthuizen, D. J....
11页
查看更多>>摘要：Deposition of thin films is an appropriate methodology to enhance the performance of a material by modification of its surface, while keeping the properties of the bulk largely unaffected. However, a practical implementation becomes less straightforward when dealing with sensitive or complex substrates, for instance, those which cannot be subjected to harsh treatments, such as cleaning and etching, or extreme deposition conditions, like high temperatures, and ion impingement et cetera. This paper concentrates on deposition processing of complex substrates. In particular, it discusses the deposition of two types of protective coatings (diamond-like carbon (DLC) films against friction and wear, and TiO2 films against UV light) on three types of thermoplastic and cellular elastomers (rubber, nylon and cork). It is demonstrated that a successful protection of thermoplastic elastomers against wear with DLC films can be attained, after a thorough adaptation of the procedure to the characteristics of the specific substrate. In addition, the paper reports the very first depositions on a cellular elastomer like cork by vapor deposition methods, including Atomic Layer Deposition (ALD).
查看更多>>摘要：In this article, a CrCoNbB thin film metallic glass (TFMG) is fabricated by DC power magnetron sputtering. Its microstructure, surface properties, mechanical properties and thermal stability are characterized. Results are compared with sputter-deposited chromium (Cr) coating which is an industrial popular choice of hard coating by physical vapor deposition (PVD). We obtained a fully amorphous Cr48Co31Nb7B14 TFMG with glass transition (Tg) and crystallization (Tx) temperatures at 530 ? and 615 ?, respectively. Nanoindentation revealed that Cr(48)Co(31)Nb(7)B(14)TFMG has significantly lower surface roughness and higher hardness than Cr. Also, in nano scratch test with normal load applied between 0.5 mN ~ 9 mN, Cr48Co31Nb7B14 TFMG has a lower coefficient of friction (CoF) than Cr. Annealing the TFMG above Tg at 550 C for 60 min showed no sign of crystallization, implying excellent thermal stability. Contact angle analysis also revealed that the TFMG has very low surface free energy (SFE), specifically a low polar component. We also discovered that spreading of molten low-density polyethylene (LDPE) on Cr48Co31Nb7B14 TFMG is weaker than on Cr film as a consequence of its low SFE. In summary, Cr48Co31Nb7B14 TFMG has advantages such as high hardness and thermal stability, low roughness, friction and surface energy compared to PVD Cr coating. Low adhesion to molten LDPE also suggests its potential in applications such as injection mold coating where lower friction and higher wear resistance is preferred.
查看更多>>摘要：Herein, the deposition of titanium films on complex bowl-shaped workpieces was conducted using direct-current magnetron sputtering (DCMS) and high-power impulse magnetron sputtering (HiPIMS) methods, and the differences in the properties of the film deposited using these methods were investigated. Metallic titanium films were deposited on the inner (concave) and outer (convex) surfaces of a bowl-shaped workpiece. The deposition rate, crystal structure, microhardness, and cross-sectional morphology of the titanium films at different deposition angles with respect to the normal vector of the target surface were characterized. Results showed that HiPIMS films exhibited better uniformity in terms of the crystal texture, microhardness, and microstructure than that of DCMS films, for both concave and convex surfaces. The differences between the properties of the HiPIMS and DCMS deposited films can be attributed to the significantly reduced self-shadowing effect in the oblique incidence deposition provided by HiPIMS. The enhanced energetic bombardment of depositing species on the substrate in the ionization-rich HiPIMS plasma facilitates the deposition films with uniform crystal structures and properties. However, a distinct difference in the film deposition rates was observed for the different shapes of the substrates in both deposition techniques. The films deposited on concave surfaces showed better uniformity than that of the films deposited on convex surfaces. This phenomenon can be explained by considering both the effect of the substrate-to-target distance, line of sight and the electric field near the substrate. The results presented in this manuscript are therefore crucial for the coating design of objects with complex shapes when depositing pure metals using DCMS and/or HiPIMS for decorative, tribological, and tool applications.
Kiryukhantsev-Korneev, Ph. V.Sytchenko, A. D.Sviridova, T. A.Sidorenko, D. A....
13页
查看更多>>摘要：The Mo-Si-B, Mo-Zr-Si-B, and Mo-Hf-Si-B coatings were deposited by magnetron sputtering of the MoSi2-MoB, MoSi2-MoB-ZrB2 and MoSi2-MoB-HfB2 targets. The composition and structure of coatings were investigated by glow discharge optical emission spectroscopy, scanning electron microscopy, X-ray diffraction, transmission electron microscopy, X-ray photoelectron and Raman spectroscopy. Mechanical properties were measured by nanoindentation method. The short-time oxidation resistance of coatings was evaluated at temperatures of 1100, 1300, and 1500 degrees C. The results showed that all coatings deposited onto alumina substrates were characterized by a dense columnar structure. Mo-Si-B coatings contained phases of hexagonal h-MoSi2 and amorphous a-MoB. With the addition of Zr and Hf, an increase in the lattice parameter and a decrease in the grain size of h-MoSi2 by 50 and 25%, respectively, were observed. The base Mo-Si-B coating had a high hardness of 30 GPa. The introduction of Zr and Hf led to a decrease in hardness by 24 and 20%, respectively. The Mo-Si-B coating was characterized by a minimal oxidation depth (<10 nm) at 1100 degrees C and 1300 degrees C, but a network of cracks that penetrated to the substrate was formed. Cracks on the surface of the Mo-Zr-Si-B and Mo-Hf-Si-B coatings were not observed; the formation of oxide layers, 0.3-2.0 mu m thick, was revealed. The oxidation resistance of coatings at temperature of 1500 degrees C increased in direction Mo-Si-B -> Mo-Hf-Si-B -> Mo-Zr-Si-B. The best results for the MoZr-Si-B coating were associated with a smaller grain size, higher thermal stability, and the formation of a protective layer based on SiO2 with the inclusion of ZrO2 crystallites.
NSTL
Elsevier