Influence of TiCl_4 treatment on performance of dye-sensitized solar cell assembled with nano-TiO_2 coating deposited by vacuum cold spraying

Titanium tetrachloride (TiCl4) treatment was employed to TiO2 coating deposited on fluoride-doped tin oxide (FTO) conducting glass and indium oxide doped tin oxide (ITO) conducting glass, respectively. The nano-crystalline TiO2 coating was deposited using a composite powder composed of polyethylene glycol (PEG) and 25 nm TiO2 particles by vacuum cold spraying (VCS) process. A commercial N-719 dye was used to adsorb on the surface of TiO2 coating to prepare TiO2 electrode, which was applied to assemble dye-sensitized solar cell (DSC). The cell performance was measured under simulated solar light at an intensity of 100 mW·cm-2. Results show that with an FTO substrate the DSC composed of a VCS TiO2 electrode untreated by TiCl4 gives a short-circuit current density of 13.1 mA·cm-2 and an open circuit voltage of 0.60 V corresponding to an overall conversion efficiency of 4.4%. It is found that after TiCl4 treatment to the VCS TiO2 electrode with an FTO substrate, the short circuit current density of the cell increases by 31%, the open-circuit voltage increases by 60 mV and a higher conversion yield of 6.5% was obtained. However, when an ITO substrate is used to deposit TiO2 coating by VCS, after TiCl4 treatment, the conversion efficiency of the assembled cell reduces slightly due to corrosion of the conducting layer on the ITO glass by TiCl4.

EFFECT OF VACUUM HEAT TREATMENT ON OXIDATION BEHAVIOR OF SPUTTERED NiCrAlY COATING

A bond coat for thermal barrier coating (TBC), NiCrAlY coating, is subjected to vac-uum heat treatment in order to remove internal stress before ceramic top coat is de-posited. The effect of vacuum heat treatment on the oxidation behavior of the sputtered NiCrAlY coating has been investigated. The as-sputtered NiCrAlY coating consists of γ-Ni and b-NiAl phases. After vacuum heat treatment, the sputtered NiCrAlY coating mainly consists of γ'-Ni3Al, β-NiAl, γ-Ni, and trace of α-Al2O3 phases. The isothermal oxidation of sputtered NiCrAlY coating with and without vacuum heat treatment has been performed at 1000℃. It is shown that a-Al2O3 formed during vacuum heat treatment acts as nuclei for the formation of a-Al2O3, and the protective a-Al2O3 scale is formed more rapidly on the vacuum heat treated NiCrAlY coating than that formed on the untreated coating. Also the a-Al2O3 scale has a better adherence to the vacuum heat treated NiCrAlY coating. Therefore the vacuum heat treatment improves the oxidation resistance of sputtered NiCrAlY coating.

Effects of Vacuum Ultraviolet Radiation on Atomic Oxygen Erosion of Polysiloxane/SiO_2 Hybrid Coatings

Polysiloxane/SiO2 hybrid coatings have been prepared on Kapton films by a sol-gel process. The erosion resistance of polysiloxane/Si02 （20 wt pct） coating was evaluated by exposure tests of vacuum ultraviolet radiation （VUV） and atomic oxygen beam （AO） in a ground-based simulation facility. The experimental results indicate that this coating exhibits better AO resistance than pure polysiloxane coating. The erosion yield （Ey） of the polysiloxane/Si02 （20 wt pct） hybrid coating is about 10-27 cm3/atom, being one or two orders of magnitude lower than that of polysiloxane. VUV radiation can affect the erosion process greatly. Under simultaneous AO and VUV exposure, the value of Ey of the polysiloxane/5iO2 （20 wt pct） hybrid coating increases by 3g% compared with that under single AO exposure.

Influence of Interfacial Diffusion on Mechanical Property of Vacuum Fusion Sinter (VFS) WC-Co Composite Coating

The WC-Co composite coatings bonded tightly to steel substrate have been made by vacuum fusion sinter （VFS）. The concentration distribution of some components were measured by the electron probe, and the microstructure and morphology of VFS coatings were observed and analyzed by SEM, X-ray diffractometer and microhardness tester. Diffusion coefficient of every element was calculated by using the experimental results. The influence of the interracial diffusion on the microstructure, Vickers hardness and interracial bond strength of the VFS coatings was studied in detail. The experimental results show that there is a metallurgical bond area between the VFS WC-Co coatings and the steel substrate. The VFS coatings are characterized by the gradient hardness of the interface and the high bond strength to the steel substate, both of which are beneficial to the improvement of the wear resistance and corrosion resistance.

Effect of vacuum heat treatment on microstructure and microhardness of cold sprayed Cu-4Cr-2Nb alloy coating

The effect of vacuum heat treatment on the microstructure and microhardness of cold-sprayed Cu-4%Cr-2%Nb alloy coating was investigated. The heat treatment was conducted under the temperatures from 250 ℃ to 950 ℃ with a step of 100 ℃ for 2 h. It was found that a dense thick Cu-4Cr-2Nb coating could be formed by cold spraying. After heat treatment, a Cr2Nb phase was uniformly distributed in the matrix, which was transferred from the gas-atomized feedstock. A little grain growth of Cr2Nb phase was observed accompanying with the healing-up of the incomplete interfaces between the deposited particles at the elevated temperatures. The coating microhardness increases a little with increasing the temperature to 350 ℃, and then decreases with further increasing temperature up to 950 ℃. This fact can be attributed to the microstructure evolution during the heat treatment.

Interface microstructure and diffusion of vacuum annealed ceramic coating on superalloy GH202

In order to improve the wear resistance and high-temperature oxidation resistance of superalloy GH202, the ultrafine-grain ceramic coating containing nano-size nickel particles was obtained by flow coat method on the surface of GH202. The interface microstructure between ceramic coating and superalloy GH202 substrate during vacuum diffusion was studied. It is shown that Al2O3 oxide layer and (Ti, N) compound exist in the alloy substrate close to interface. During long time diffusion, nano-size nickel powders gradually congregate and grow up, and the confluent interface appears, which shows that the nano-size nickel powders have the effect of restraining the coating from failure.

New developments for vacuum coating of steel strips

Vapor deposited coatings onto strip steel are a promising alternative as functional layers for corrosion protection or high abrasion resistance.Conventional coating systems have some limits regarding environmental compatibility,the range of coating materials and application properties. Physical vapor deposition(PVD) is an environment-friendly technology and enables nearly unlimited material and process variety.Electron beam high-rate evaporation with deposition rates up to some micrometers per second is the most productive PVD technology for low cost coating.The combination of evaporation with powerful plasma is an efficient way to improve the layer properties.The developed plasma sources can be used for special plasma enhanced chemical vapor deposition(PECVD) processes too. The paper gives an overview about the latest developments in these technologies.Furthermore,the paper explains some examples of new layer stacks onto steel strips.While enhanced corrosion protection can be obtained by magnesium,aluminium or copper containing coatings other functional surface properties come more and more in the focus of interest.For instance,decorative gold colored layers,transparent scratch resistant layers,hard coatings and photo catalytic layers were deposited on running steel strips.Functional layers and layer systems for energy saving and sun energy absorption by solar thermal effects and photo voltaics are under development.The coatings are prepared under the conditions of very high deposition rates using our in-line vacuum coater for metallic strips and sheets with the name MAXI.The influence of the process and plasma parameters on the layer properties were investigated and will be demonstrated for some applications.

Influence of vacuum heat treatment on structure and micro-hardness of electroless Ni-P-SiC composite coating

The electroless Ni-P-SiC composite coatings were prepared and the influence of vacuum heat treatment on its structure and properties was analyzed. The Ni-P-SiC composite coatings were characterized by morphology,structure and micro-hardness. The morphology and structure of the Ni-P-SiC composite coatings were studied by scanning electron microscopy(SEM) and X-ray diffractometry(XRD),respectively. A great deal of particles incorporation and uniform distribution were found in Ni-P-SiC composite coatings. XRD results show a broad peak of nickel and low intensity SiC peaks present on as-deposited condition. Micro-hardness of as-deposited Ni-P-SiC composite coatings is improved greatly,and the best micro-hardness is obtained after heat treatment in a high vacuum at 400 ℃ .

Effects of surface roughness of substrate on properties of Ti/TiN/Zr/ZrN multilayer coatings

Ti/TiN/Zr/ZrN multilayer coatings were deposited on Cr_17Ni_2 steel substrates with different surface roughnesses by vacuum cathodic arc deposition method. Microstructure, micro-hardness, adhesion strength and cross-sectional morphology of the obtained multilayer coatings were investigated. The results show that the Vickers hardness of Ti/TiN/Zr/ZrN multilayer coating, with a film thickness of 11.37 μm, is 29.36 GPa. The erosion and salt spray resistance performance of Cr_17Ni_2 steel substrates can be evidently improved by Ti/TiN/Zr/ZrN multilayer coating. The surface roughness of Cr_17Ni_2 steel substrates plays an important role in determining the mechanical and erosion performances of Ti/TiN/Zr/ZrN multilayer coatings. Overall, a low value of the surface roughness of substrates corresponds to an improved performance of erosion and salt spray resistance of multilayer coatings. The optimized performance of Ti/TiN/Zr/ZrN multilayer coatings can be achieved provided that the surface roughness of Cr_17Ni_2 steel substrates is lower than 0.4μm.

Tribological behavior of TiN,AlTiN,and AlTiCrN coatings in atmospheric and vacuum environments

In this study,the tribological characteristics of TiN,AlTiN,and AlTiCrN coatings sliding against a SUS420J1 stainless steel pin were investigated in atmospheric and vacuum environments.The coatings were deposited on SUS440C substrates using the arc-physical vapor deposition technique.The friction and wear behavior of the coatings were evaluated based on the systematic analyses of the friction coefficient data as well as the physical and chemical state of the wear track.The results revealed that the friction coefficients of the SUS440C specimen and AlTiCrN coatings increased,whereas those of the TiN and AlTiN coatings decreased when the environment was changed from atmospheric to vacuum.It was confirmed that the formation of an oxide layer and adsorption of oxides on the surface were dominant factors that influenced the tribological behavior in the atmospheric environment.On the other hand,the compatibility,oxidation inhibition,and droplets of the surface mainly affected the frictional characteristics in the vacuum environment.The results of this work are expected to aid in the selection of proper coating materials for tribological systems operating in a vacuum.

Thermal Performance Study of VPS-W Coatings on CuCrZr Under High Heat Flux

Three tungsten coatings with a thickness of 250 μm, 600μm and 220 μm, respectively, were deposited on a CuCrZr substrate by the vacuum plasma spraying technology. In order to study the thermal performance of the coatings, heat load limit, thermal fatigue lifetime and thermal response tests were performed by means of the electron beam irradiation with a heat flux from 0 MW/m^2 to 10 MW/m^2. Experimental results indicated that tungsten coatings on CuCrZr with a titanium or tungsten/copper interlayer could expel heat flux timely and had good thermal fatigue properties, titanium was a promising compliant layer which provided a reliable way to join tungsten onto the CuCrZr heat sink, even suffering from a heat flux of 10 MW/m^2 or withstanding 54 cycles of fatigue tests under 5 MW/m^2. However, the better quality of tungsten coating itself was necessary because its surface temperature was higher than that of the sample with a tungsten/copper interlayer.

Influence of a TiAlN Coating on the Mechanical Properties of a Heat Resistant Steel at Room Temperature and 650℃

A TiA1N coating was deposited on a heat resistant steel X12CrMoWVNbN10-1-1 by vacuum arc ion plating. The tensile and fatigue properties of the coated steel were investigated at room temperature （RT） and 650 ℃. The results reveal that the TiA1N coating is compact, on which a small number of large particle and pits are present. The Ti/Al atomic ratio in the coating is about 0.94. The average hardness of the coating is 1 868 HV0.1 and the interface bonding force between TiAIN coating and the substrate is about 3 l N. The elastic modulus and the strength of the steel are improved by the deposition of TiAIN coating. The influence of the TiA1N coating on the tensile properties of the steel can be ignored at both RT and 650 ℃. Moreover, there is no obvious decrease of the fatigue limit of substrate when the steel is coated by the coating at the investigated temperature.

Preparation and characterization of PTFE coating in new polymer quartz piezoelectric crystal sensor for testing liquor products

A new method was developed based on the electron beam vacuum dispersion（EBVD） technology to prepare the PTFE polymer coating of the new polymer quartz piezoelectric crystal sensor for testing liquor products. The new method was applied in the new EBVD equipment which we designed. A real-time system monitoring the polymer coating＇s thickness was designed for the new EBVD equipment according to the quartz crystal microbalance（QCM） principle, playing an important role in preparing stable and uniform PTFE polymer coatings of the same thickness. 30 pieces of PTFE polymer coatings on the surface of the quartz crystal basis were prepared with the PTFE polymer ultrafine powder（purity ≥ 99.99%）as the starting material. We obtained 30 pieces of new PTFE polymer sensors. By using scanning electron microscopy（SEM）, the structure of the PTFE polymer coating＇s column clusters was studied. One sample from the 30 pieces of new PTFE polymer sensors was analysed by SEM in four scales, i.e., 400×, 1000×, 10000×, and 25000×. It was shown that under the condition of high bias voltage and low bias current, uniformly PTFE polymer coating could be achieved, which indicates that the new EBVD equipment is suitable for mass production of stable and uniform polymer coating.

Preparation and properties of supersonic atmospheric plasma sprayed TiB2−SiC coating

With the TiB2−SiC powders after spray granulation and vacuum calcination as raw materials,the TiB2−SiC coating was prepared by supersonic atmospheric plasma spraying(SAPS).The effects of spraying power and spraying distance on the properties of the TiB2−SiC coating were investigated and the fabrication processing of SAPS was optimized.The results show that the sprayed powders after calcination have a uniform particle size distribution,good sphericity and enhanced fluidity.The coating prepared by the calcined powders has a dense structure and high deposition efficiency.When the calcined TiB2−SiC powders are used and the spraying power is 95 kW and the spraying distance is 150 mm during supersonic plasma spraying,the obtained TiB2−SiC coating behaves the best comprehensive performance with the porosity,microhardness,bonding strength and resistivity equal to 5.6%,3.57 GPa,18.3 MPa and 10.8 mΩ·cm,respectively.

Mierostrueture and Properties of Coating from Cemented Carbide on Surface of Hl3 Steel

The microstructures and properties of coating from cemented carbide on the substrate of H 13 by vacuum powder sintering were studied. The effect of sintering temperature on the microstructures of coating was discussed. The interface characteristics between coating and H 13 steel substrate, microhardness distribution and wear resistance in the coating were analyzed. The coating from cemented carbide with thickness of 1-3 mm by vacuum powder sintering at temperature ranging from 1280℃to 1300 ℃ was obtained. The experimental results indicated that the coating with microhardness of HV 1600 favorable to wear resistance is strongly bonded with the H 13 steel substrate by mutual diffusion and penetration of Fe,Cr, Mo,V in substrate towards the coating and W, Co,Ni in coating towards the substrate.

Behavior of NiCrAlY coating on the TC6 titanium alloy

A NiCrAlY coating was deposited on the TC6 titanium substrate by arc ion plating （ALP）. The structure and morphologies of the NiCrAlY coating were characterized by X-ray diffraction （XRD） and scanning electron microscopy （SEM）, and the influence of vacuum heat treatment on the element diffusion behavior was studied. The results showed that the y＇-Ni3Al phase was precipitated on the NiCrAlY coating after heat treatment. The Ni3（AI,Ti）, TiNi, and Ti2Ni intermetallic layers appeared at the interface from the outside to the inside at 700℃, and the thickness of the intermetallic layers increased with the increase in temperature. At 700℃ Ti and Ni were the major diffusion elements, and the diffusion of Cr was observed when the heat treatment temperature increased up to 870℃. The violent inward diffusion of Ni at 950℃ resulted in the degradation of the NiCrAlY coating.

Study on the formation of intermetallic phases in the new type of Zn-Mg coatings on steel sheets

Zn-Mg alloy coatings were obtained by physical vapor deposition （PVD） on electroplated steel sheets. Study on the formation of intermetallic phases in the coatings was conducted through the use of X-ray diffraction （XRD） ,scanning electron microscope （SEM） and glow discharge optical emission spectrometry （GDOES）. It is found that MgZn2 is the main Zn-Mg alloy phase formed after heat treatment. The formation of Mg-Zn intermetallic phases is controlled not only by thermodynamics, but also by kinetics. MgZn2 has different morphologies, such as laminar structure,porous structure and floc-like structure,which are mainly determined by the annealing temperature. Obvious diffusion of Mg starts at 350 ℃, and the diffusion of iron increases significantly when the temperature is elevated to 380℃.

Effect of Y_2O_3 on microstructure and oxidation of γ-Ni+γ′-Ni_3Al coatings transformed from electrodeposited Ni-Al films at 1000℃

The electrodeposited Y2O3-dispersedγ-Ni+γ′-Ni3Al coatings on Ni substrates were developed by the conversion of electrodeposited Ni-Al-Y2O3 films with dispersed Al microparticles in Ni matrix into Ni3Al by vacuum annealing at 800℃for 3 h. For comparison,Y2O3-freeγ-Ni+γ′-Ni3Al coatings with a similar Al content were also prepared by vacuum annealing the electrodeposited microparticle-dispersed composite coatings of Ni-Al under the same condition.SEM and TEM characterizations show that the electrodeposited Y2O3-dispersedγ+γ′coatings exhibit finer grains,a more homogeneous distribution ofγ′,and a narrowedγ′phase spacing compared with the electrodeposited Y 2 O3-freeγ+γ′coatings.The oxidation at 1 000℃shows that the addition of Y2O3 significantly improves the oxidation resistance of the electrodepositedγ+γ′coatings.The effect of Y2O3 particles on the microstructure and oxidation behavior of the electrodepositedγ+γ′coatings was discussed in detail.

Effect of bias voltage on microstructure,mechanical and tribological properties of TiAlN coatings

TiAlN multilayer coatings composed of TiAl and TiAlN layers were deposited on ZL109 alloys using filtered cathodic vacuum arc(FCVA)technology.The effect of bias voltage on the microstructure and properties of the coating was systematically studied.The results show that the coating exhibits a multi-phase structure dominated by TiAlN phase.As the bias voltage increases,the orientation of TiAlN changes from(200)plane to(111)plane due to the increase of atomic mobility and lattice distortion.The hardness,elastic modulus and adhesion of the coating show the same trend of change,that is,first increase and then decrease.When the bias voltage is 75 V,the coating exhibits the highest hardness(~30.3 GPa),elastic modulus(~229.1 GPa),adhesion(HF 2)and the lowest wear rate(~4.44×10^(−5)mm^(3)/(N·m)).Compared with bare ZL109 alloy,the mechanical and tribological properties of TiAlN coated alloy surface can effectively be improved.

Research on Ultimate Vacuum and Pumping Capacity of TiZrV Coated Pipe

TiZrV non-evaporable getters have been widely used to improve vacuum properties in the field of accelerators due to the excellent activation temperature[1].The ultimate vacuum and pumping capacity of TiZrV film tubes at different activation temperatures were investigated in the experiment.The results show that the coated pipe is not activated at 180℃.The coated pipe is activated at 220℃and the ultimate vacuum is decreased by about 25%relative to the uncoated pipe,and the coated pipe enables a uniform pressure distribution therein.