Closed Field Unbalanced Magnetron Sputtering Research Articles

Amorphous Zr-based thin films fabricated by magnetron sputtering for potential application in hydrogen purification

Amorphous hydrogen separation membranes are under development because of their resistance to hydrogen embrittlement, improved mechanical properties, resistance to corrosion and most importantly lower intrinsic cost. The Closed Field Unbalanced Magnetron Sputter Ion Plating (CFUBMSIP) is a versatile technique for deposition of high quality thin-films of almost any composition, while enabling the control of film size, thickness and shape. In this work, it was demonstrated that thin-films (∼3–6μm) of amorphous Zr40.5Ni59.5, Zr54Cu46 and Zr30Cu57.5Y12.5 could be deposited onto glass substrates by the CFUBMSIP technique. XRD measurements only showed one broad peak for each alloy, with a peak centred between 36° and 42° 2θ, indicating that the films were amorphous. Surface analysis by SEM and confocal microscopy suggest deposition of continuous films. The thermal stability of the films appears to be mainly governed by the alloying elements and their compositions. However, the measured activation energies indicated that the nucleation and growth mechanism in the magnetron sputtered films may be different from that reported for melt-spun amorphous alloys with similar compositions.

Influence of CrCN Coatings Steel Ball Deposited by Closed Field Unbalanced Magnetron Sputtering on the Performance of Bearing

The CrCN coatings was deposited on the substrate of GCr15 steel ball by closed field unbalanced magnetron sputter ion plating. The performances of vibration, temperature rise, rotational speed, load carrying ability and wear resistance of CrCN coatings steel ball bearing and uncoated steel ball bearing were tested by a bearing tester, and also comparatively analyzed. Results show that, compared to the uncoated bearing, the CrCN coatings steel ball bearing, in the case of rotational speeds higher than 5 000 rpm, have lower vibration values, especially above 6 000 rpm, the vibration values were significantly reduced, and the coated bearing has vibration stability performance. And the coated bearing has also slower temperature rise performance, excellent high-speed performance, good load carrying capacity characteristics and wear resistance performance etc.

Influence of duty cycle on microstructure, tribological and corrosion behaviors of a-C/a-C:Ti multilayer films

a-C/a-C:Ti multilayer films were deposited on medical Ti6Al4V alloy using a closed field unbalanced magnetron sputtering system with various substrate bias duty cycle. The tribological and corrosion behaviors of the multilayer films in Hank's solution were evaluated by a ball-on-disk tribometer and an electrochemical workshop. The duty cycle has a significant effect on the bonding structure, and mechanical and tribological properties of the films. The polarization resistance of the films on Ti alloy is approximately ten times more than that of Ti6Al4V which indicates that higher corrosion resistance can be achieved in Hank's solution at 37°C. However, the polarization resistance and corrosion current do not change so much with the variation of duty cycle, implying that its influence on corrosion behavior of these a-C/a-C:Ti multilayer films is not so obvious.

Electrical and Optical Properties of Fluorine Doped Tin Oxide Thin Films Prepared by Magnetron Sputtering

Fluorine doped tin oxide (FTO) coatings have been prepared using the mid-frequency pulsed DC closed field unbalanced magnetron sputtering technique in an Ar/O2 atmosphere using blends of tin oxide and tin fluoride powder formed into targets. FTO coatings were deposited with a thickness of 400 nm on glass substrates. No post-deposition annealing treatments were carried out. The effects of the chemical composition on the structural (phase, grain size), optical (transmission, optical band-gap) and electrical (resistivity, charge carrier, mobility) properties of the thin films were investigated. Depositing FTO by magnetron sputtering is an environmentally friendly technique and the use of loosely packed blended powder targets gives an efficient means of screening candidate compositions, which also provides a low cost operation. The best film characteristics were achieved using a mass ratio of 12% SnF2 to 88% SnO2 in the target. The thin film produced was polycrystalline with a tetragonal crystal structure. The optimized conditions resulted in a thin film with average visible transmittance of 83% and optical band-gap of 3.80 eV, resistivity of 6.71 × 10−3 Ω·cm, a carrier concentration (Nd) of 1.46 × 1020 cm−3 and a mobility of 15 cm2/Vs.

Tailoring the mechanical and tribological properties of sputtered boron carbide films via the B1 − xCx composition

Boron carbide films are very attractive due to their high hardness and interesting tribological properties. In the present work, the compositional effect of boron carbide B1−xCx (0<x<1) films is systematically studied to tailor mechanical, tribological and corrosion properties of the films. The B1−xCx layers were deposited on Si (100) and M2 high speed steel substrates using a pilot-scale closed-field unbalanced magnetron sputtering system equipped with one graphite and two boron targets. Different compositions were obtained by tuning the electrical power applied to the graphite target. The hardness of the B1−xCx films decreases from 28 to 20GPa as the carbon content [C] rises from 19 to 56at.%, but thereafter it increases again up to ~25GPa when [C] reaches 76at.%. The hardness variation is explained by changes in the film microstructure, namely formation of either a nanocrystalline boron carbide in the case of boron-rich films, or boron carbide nanocrystals dispersed in an amorphous boron carbide/a-C matrix in the case of carbon-rich films as deduced from the combined XPS, micro-Raman and XRD measurements. The friction coefficient of the B1−xCx films reduces from 0.66 to 0.13, and the wear rate against alumina ball drops from 6.4×10−5mm3/Nm to 1.3×10−7mm3/Nm with increasing the [C]. Raman analyses indicate that improvement of the tribological properties of the B1−xCx films is primarily caused by the presence of the amorphous carbon phase that leads to the formation of a graphitic tribolayer acting as a solid lubricant during the wear process. Deposition of the B0.81C0.19 film with high hardness (28GPa) improves the corrosion resistance of the M2 steel substrate by four orders of magnitude, documented by the decrease of the corrosion current from 3×10−6A/cm2 to 8×10−10A/cm2. We demonstrate that adjustment of the x-portion in the B1−xCx system allows one to tailor the tribo-mechanical properties over a large range from high hardness/high friction to high hardness/low friction structures.

The effect of process parameters on the structure, photocatalytic and self-cleaning properties of TiO2 and Ag-TiO2 coatings deposited using reactive magnetron sputtering

This article reports on the morphology, structure, wettability, photocatalytic and mechanical properties of TiO2 and Ag-TiO2 thin films, with the latter also displaying antimicrobial activity. The coatings were deposited using reactive closed field unbalanced magnetron sputtering. It was possible, by varying the process parameters, to tailor the structure and composition of the coatings. TiO2 coatings which were deposited from a single titanium target (thickness ~1μm) were relatively dense with low crystallinity and a mixed anatase and rutile structure. The addition of silver resulted in the formation of submicron sized silver particles dispersed throughout the coating. TiO2 coatings deposited from two titanium targets (thickness ~2μm) had a mixed anatase and rutile structure with a less dense topography. Ag-TiO2 coatings deposited using this process showed a uniform dispersion of silver throughout the coating. All coatings presented excellent adhesion to the substrate and high photocatalytic activity under fluorescent light. Annealing at 600°C had a detrimental effect on the photocatalytic activity as well as the mechanical properties of the coatings. The coatings deposited from a single Ti target were evaluated for their antimicrobial potential against E. coli. No reduction in the number of bacteria was observed using TiO2. Ag-TiO2 coatings, however, showed antimicrobial properties in the dark as well as light conditions, as a result of the innate antimicrobial potential of silver.

Structural, mechanical and tribological properties of WS2-Ti composite coating with and without hard under layer of TiN

The present work reports on the structural, mechanical and tribological properties of WS2 and WS2-Ti composite coating with and without hard under layer of TiN. Pulsed DC closed field unbalanced magnetron sputtering was employed for deposition of the films. The films were characterised with energy dispersive X-ray microanalysis (EDX), grazing incidence X-ray diffraction (GIXRD), field emission scanning electron microscopy (FESEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), scratch adhesion test, nanoindentation test and pin-on-disc tribological test. The GIXRD spectrum for WS2 film showed prominent orientation of (002) basal plane parallel to the substrate which was also supported by its morphology showing a fine granular structure. Addition of around 13at.% Ti to the WS2 matrix induced turbostratic stacking of the 10 L (L=0, 1, 2,…) planes, however, the (002) orientation was retained. The film’s hardness, adhesion to the substrate, as well as the tribological properties improved with Ti addition. Addition of a hard under layer of TiN resulted in a denser top WS2-Ti layer because of enhanced nucleation promoted by structural defects of the hard under layer. The tribological performance of the top WS2-Ti layer also improved on TiN under layer addition because of the enhanced load bearing capacity of the top layer.

Investigation of the friction and wear properties of Ti/TiB2/MoS2 graded-composite coatings deposited by CFUBMS under air and vacuum conditions

MoS2 coatings are effectively used in vacuum and in water vapor-free environments because of increased friction coefficient and decreased service life under atmospheric conditions. A lot of different alloy elements (e.g., Ti, Nb, Cr) and compounds (e.g., TiN, TiB2) are used to enhance the friction and wear properties of MoS2 coatings. In this study Ti/TiB2/MoS2 graded-composite coatings (GCC) were deposited by closed-field unbalanced magnetron sputtering (CFUBMS). The structural properties of the coatings were analyzed by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). The hardness of the coatings was measured with the use a microhardness tester. The tribological properties of the coatings were determined under air and vacuum conditions. Ti/TiB2/MoS2 (GCC) have MoS2 (002) and TiB2 (100) reflections. The coatings exhibited a dense and non-columnar structure. Tribological properties of the coatings under air and vacuum conditions significantly affected the hardness, thickness and stoichiometric ratio of elements in the structure.

Fretting wear and fretting fatigue behaviors of diamond-like carbon and graphite-like carbon films deposited on Ti-6Al-4V alloy

To investigate their effect on the fretting wear (FW) and fretting fatigue (FF) resistance of a Ti6Al4V alloy, the diamond-like carbon (DLC) and graphite-like carbon (GLC) films were deposited on a Ti6Al4V alloy substrate using closed field unbalanced magnetron sputtering. The basic film properties, such as surface morphology, micro-structure, micro-hardness, bonding strength, and toughness were investigated by atomic force microscopy, X-ray photoelecton spectroscopy, nano-hardness testing, scratch testing and by a home-made repeated press-press test system, respectively. The FW and FF resistance was studied using home-made devices. The results show that DLC and GLC films can reduce the friction factor while the FW and FF resistance of the titanium alloy were improved significantly. However, the FW and FF resistance of the DLC film on the titanium alloy was better than that of the GLC film. This was attributed to the excellent properties of bonding strength and toughness of the DLC film. Moreover, the effect of bonding strength and toughness is more important than that of friction factor in improving the FW and FF resistance.

Microstructure and cutting performance of CrTiAlN coating for high-speed dry milling

Using a closed field unbalanced magnetron sputtering system, the cemented carbide end mills were coated with a CrTiAlN hard coating, which consisted of a Cr adhesive layer, a CrN interlayer and a CrTiAlN top layer. The microstructure and mechanical properties of the coating were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), micro indentation and scratch test. The cutting performance of the coated end mills were conducted by high-speed dry milling hardened steel (P20, HRC 45). The results indicates that the coating is composed of (Cr, Ti, Al)N columnar grains with nanolayers. The coating exhibits good adhesion to cemented carbide substrate and high microhardness of around 30 GPa. The coated end mills show significant improvement on tool life and much lower cutting force as compared to the uncoated ones. And the related mechanisms were discussed.

Mo doped DLC nanocomposite coatings with improved mechanical and blood compatibility properties

Abstract Mo (molybdenum) doped diamond like carbon (Mo-DLC) coatings with improved mechanical and blood compatibility properties were deposited by closed field unbalanced magnetron sputtering. The undoped and Mo-doped DLC coatings were analyzed by various characterization techniques such as Raman spectra, Atomic force microscopy, and temperature-dependent frictional wear testing. The results showed that the Mo-DLC coating with low Mo concentration was a effective protective coating with reduced residual stress and increased cohesive strength, and kept good wear resistance at the ambient temperature of 500 °C. The blood compatibility of Mo-DLC coatings was investigated by platelet adhesion. The results showed that the amount of thrombus on the Mo-DLC nanocomposite coatings was much less than that of thrombus on pyrolytic carbon films. The Mo-DLC nanocomposite coatings would be a new kind of promising materials applied to artificial heart valve and endovascula stent.

Small grain size zirconium-based coatings deposited by magnetron sputtering at low temperatures

Hard, partly amorphous, ZrTiB(N) coatings were deposited by Physical Vapour Deposition (PVD) onto (111) silicon wafers at low substrate temperatures of 85 and 110°C using Closed Field Unbalanced Magnetron Sputtering. A segmented rectangular sputter target composed of three pieces (Zr/TiB2/Zr) was used as the source of evaporation of coating components. Two different substrate biases (i.e. floating potential and −50V) and N2 reactive-gas flow rates of 2, 4 and 6sccm were employed as the main deposition parameter variables.The chemical composition, structure, morphology and mechanical properties were investigated using a variety of analytical techniques such as Glow-Discharge Optical Emission Spectroscopy, cross-sectional Scanning Electron Microscopy (SEM), Glancing Angle X-ray Diffraction (GAXRD) and nanoindentation. With other parameters fixed, coating properties were found to be dependent on the substrate negative bias and nitrogen flow rate. Linear scan profiles and SEM imaging revealed that all coatings were smooth, dense and featureless (in fracture cross section) with no apparent columnar morphology or macro-defects. GAXRD structural analysis revealed that mostly metallic phases were formed for coatings containing no nitrogen, whereas a solid solution (Zr,Ti)N single phase nitride was found in most of the reactively deposited coatings — exhibiting a very small grain size due to nitrogen and boron grain refinement effects.Hardness values from as low as 8.6GPa up to a maximum of 25.9GPa are related mainly to solid solution strengthening effects. The measured elastic moduli correlated with the trends in hardness behaviour; values in the range of 120–200GPa were observed depending on the selected deposition parameters. Also, high H/E values (>0.1) were achieved with several of the coatings.

Synthesis, characterisation and wear performance of W–Al coatings

W, W–15 at-%Al, W–30 at-%Al and W–45 at-%Al coatings were synthesised by using a reactive four-target DC closed field unbalanced magnetron-sputtering ion plating system. Structure, morphology, composition, hardness and adhesion were studied by using an X-ray diffractometer, an energy dispersive spectrometer, a scanning electron microscope, a scanning transmission electron microscope and nanohardness and scratching testers. Wear performance was evaluated by using a pin-on-disk wear tester. The sputtering deposition of this binary system led to the formation of single-layer W–Al coatings as a result of complete dissolution of the Al atoms into the W lattice during the depositing process. The W–15 at-%Al coating showed improved wear resistance as compared with the W coating.

Investigation of single-layer and multilayer coatings for aluminum bipolar plate in polymer electrolyte membrane fuel cell

Aluminum bipolar plates offer good mechanical performance and availability for mass production while allow up to 65% lighter than stainless steel. To improve the corrosion resistance and surface electrical conductivity of aluminum bipolar plates, several coatings, including TiN, CrN, C, C/TiN and C/CrN, are deposited on aluminum alloy 5052 (AA-5052) by close field unbalanced magnetron sputter ion plating. Scanning electron microscope (SEM) results show that the coatings containing carbon layer are denser than TiN and CrN. Although the potentiodynamic test results show improved corrosion resistance by all the coatings, the potentiostatic test results reveal different stability of these coatings in PEMFC environments. Comparing the SEM images of these coatings after potentiostatic test, C/CrN multilayer coating exhibits the best stability. C/CrN multilayer coated AA-5052 has the lowest metal ion concentration after potentiostatic test, being 11.12 ppm and 1.29 ppm in PEMFC cathodic and anodic environments, respectively. Furthermore, the interfacial contact resistance (ICR) of the bare AA-5052 is decreased from 61.58 mΩ-cm2 to 4.08 mΩ-cm2 by C/CrN multilayer coating at the compaction force of 150 N-cm−2. Therefore, C/CrN multilayer coating is a good choice for surface modification of aluminum bipolar plate.

Improved adaptability of PEEK by Nb doped graphite-like carbon composite coatings for bio-tribological applications

Polyaryl-ether-ether-ketone (PEEK), an alternative to metal alloys in prosthesis implants, suffers from insufficient elasticity and biocompatibility, and generates wear particulates initiating the destructive osteolysis process. In this study coating the implant with Nb containing graphite-like carbon (GLC) film is performed using the closed field unbalanced magnetron sputtering system, the as-deposited Nb/GLC film is uniform and smooth. The mechanical assessment shows that Nb/GLC film has the strongly adhesive strength and good matching compliance to the flexible PEEK substrates. Especially, the use of GLC film not only effectively reduced the wear-generated debris in simulated body fluids but also exhibited excellently low friction character, as well as the lowest wear of the counterpart. Furthermore, Nb/GLC matrix greatly improved the biocompatibility and osteogenesis of PEEK by the indication of the excellent adherent attachment, proliferation and differentiation of L-929 fibroblast-like cell.

The effect of nitrogen flow rate on TiBN coatings deposited on cold work tool steel

TiBN coatings have high hardness and high adhesion. Due to these excellent properties there has been increasing interest in TiBN coatings. In this study, TiBN coatings were deposited on AISI D2 cold work tool steel and silicon wafers by closed field unbalanced magnetron sputtering (CFUBMS). The structural, mechanical and adhesion properties of these coatings were analysed by X-ray diffraction, scanning electron microscopy, microhardness test, indentation test and scratch tests. TiBN coatings produced by magnetron sputtering exhibited a dense and columnar structure. These results indicate that TiB2, TiN and h-BN exist in crystalline forms at all coatings. The highest hardness was obtained at the lowest nitrogen flow rate. Very few cracks were observed at the edge of the indentation marks at the highest nitrogen flow rate. The highest critical load obtained with scratch test was identified as 102 N.

The Influences of Process Parameters on Properties of CrNx Coatings Deposited by Closed Field Unbalanced Magnetron Sputtering

CrNx coatings were prepared by closed filed unbalanced magnetron sputtering (CFUMS), and the effects of N2 flux ratio and bias voltage on CrN coatings were investigated. Results showed that the phase in coatings was the coexistence of CrN, Cr2N and Cr, and CrN(111) always showed an intensive preferred orientation in both cases, but CrN(200) enhanced with the rise of bias voltage. The hardness of coatings decreased with an increasing N2 flux ratio, while improved with an increasing bias voltage. The grain edges were polished off and the boundaries became blurred when higher bias voltage was applied. All in all, the surface morphologies of CrN coatings became flatter and denser with both increasing N2 content and bias voltage, respectively.

Impact fatigue behavior of ZrN/Zr-N/Zr coatings on H13 steel by CFUBMSIP

ZrN/Zr-N/Zr coatings were deposited on H13 steel by close field unbalanced magnetron sputtering ion plating (CFUBMSIP) technique. The effect of two main parameters such as OEM and bias voltage for the CFUBMSIP process on the microstructure, mechanical properties and impact fatigue behavior of the coatings was investigated. The results indicate that with OEM increasing from 55% to 65% the surface particles size of the coatings increases while it remains almost similar when the bias voltage changes from 60 to 75 V. An aggregation of the particles occurs on the coatings surface with further increasing the OEM and bias voltage to 75% and 90 V, respectively. The coatings show a columnar grain structure and are mainly composed of two phases of ZrN and Zr. The coating hardness decreases with OEM value increasing and both the coating hardness and modulus go up with bias voltage. The coating deposited under OEM of 65% and bias voltage of 75 V shows the best impact fatigue property.

Microstructure, Mechanical, and Scratch Resistance Properties of TiAlCrNbN-Graded Composite Coating Deposited on AISI H13 Steel Substrate with Pulsed DC Closed Field Unbalanced Magnetron Sputtering Method

Structure and adhesion properties of TiAlCrNbN coatings were investigated. These coatings were deposited onto AISI H13 steel substrate using pulsed dc closed field unbalanced magnetron sputtering at different deposition parameters including duty cycle, bias voltage, and working pressure. The coatings have been characterized by X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy. The TiAlCrNbN-graded composite coatings have a dense and columnar structure. The X-ray diffraction patterns of coatings exhibited predominantly c-TiAlCrN, h-NbN, and h-TiAlN reflections. Scratch resistance test showed that the highest adhesion strength was attained as 68 N at 2.5 μs duty time, 100 V bias voltages, and 3 × 10−3 Torr deposition parameters. The lowest adhesion strength was obtained as 55 N at 0.5 μs duty time, 50V bias voltage, and 2 × 10−3 Torr deposition parameters.

Smooth Particle Hydrodynamics Simulation of Micro-Cup-Extrusion Using a Graphit-ic Coating

Microextrusion is becoming increasingly important for the manufacturing of microcomponents. However, this reduction in scale to a microlevel means that the influence of friction and the need for suitable lubrication are greatly increased. This study therefore looks at the use of a low-friction and highly wear resistant Graphit-ic coating on the mold-forming section of a microextrusion mold, this coating being applied by a closed-field unbalanced magnetron sputter ion plating technique. A microcup of CuZn33 brass alloy was then extruded, with a wall thickness of 0.45 mm, outside diameter of 2.9 mm, and an internal diameter of 2 mm. The experimental results in which extrusion uses the mold coating with Graphit-ic film are compared against the experimental results in which extrusion uses the mold uncoating with Graphit-ic film. This showed that the load was decreased a lot and the self-lubricating solid coating facilitates a smooth extrusion process. As the extrusion rate was quite high, smoothed particle hydrodynamics method simulations of the extrusion process were conducted, these being then compared with the experimental results. These result showed that the SPH simulation can be applied to show the deformation of materials and predict the load trend.