Thin Films and Coatings

Interfacial fracture mechanics is a relatively new field with many issues that have not yet been resolved. One such issue is the ability to accurately predict whether or not a bimaterial interface crack will propagate along the interface, kink into the film or substrate, or not propagate at all. In the present work, a crack driving force criterion is proposed in order to predict the level of applied load required to propagate a pre-existing interface crack in thin-film composites subjected to thermal loading. A primary objective is to predict the critical length of an interface crack at which it kinks into the substrate. The phenomenon of interface cracks kinking into the substrate is frequently observed when the film is under tensile loading and the substrate is brittle. An interface crack that advances into the substrate eventually propagates parallel to the interface at a certain steady-state depth. Ultimately, the portion of the structure that remains above the crack may spall, ...

a b s t r a c t Solar modules are becoming an everyday presence in several countries. So far, the installation of such modules has been performed without esthetic concerns, typical locations being rooftops or solar power plants. Building-integrated photovoltaic (BIPV) systems represent an interesting, alternative approach for increasing the available area for electricity production and potentially for further reducing the cost of solar electricity. In BIPV, the visual impression of a solar module becomes important, including its color. The color of a solar module is determined by the color of the cells in the module, which is given by the antireflection coating (ARC). The ARC is a thin film structure that significantly increases the amount of current produced by and, hence, the efficiency of a solar cell. The deposition of silicon nitride single layer ARCs with a dark blue color is the most common process in the industry today and plasma enhanced chemical vapor deposition (PECVD) is mostly used for this purpose. However, access to efficient, but differently colored solar cells are important for the further development of BIPV. In this paper, the impact of varying the color of an ARC upon the optical characteristics and efficiency of a solar cell is investigated. The overall transmittance and reflectance of a set of differently colored single layer ARCs are compared with multilayered silicon nitride ARCs, all made using PECVD. These are again compared with porous silicon ARCs fabricated using an electrochemical process allowing for the rapid and simple manufacture of ARC structures with many tens of layers. In addition to a comparison of the optical characteristics of such solar cells, the effect of using colored ARCs on solar cell efficiency is quantified using the solar cell modeling tool PC1D. This work shows that the use of multilayer ARC structures can allow solar cells with a range of different colors throughout the visual spectrum to retain very high efficiencies.

Rugate filters are a special kind of graded-index films that may provide advantages in both, optical performance and
mechanical properties ofthe optical coatings. In this work, design and optimization of a high reflection rugate filter
having reflection peak at 540nm has been presented which has been further optimized for side-lobe suppression. A
suitable number of apodization and matching layers, generated through Quintic function, were added to the basic
sinusoidal refractive index profile to achieve high reflectance of around 80% in the rejection window for normal
incidence. Smaller index contrast between successive layers in the present design leads to less residual stress in the thinfilm stack which enhances the adhesion and mechanical strength of the filter. The optimized results show excellent side
lobe suppression achieved around the stopband.

In this study, the novel Ni-Al-Y2O3 nanocomposite coatings were prepared by two steps:
1)  Electrodeposition  of  Ni-Y2O3
nanocomposite  film  on  low  carbon  steel,  2)  Aluminizing  the
electrodeposited Ni-Y2O3
film using pack cementation method at 700 ˚C for 3 h. The effect of Y2O3
content  on oxidation resistance was investigated. Morphology and phase structure of the coatings
were  characterized  by  Scanning  Electron  Microscope  (SEM),  Energy  Dispersive  Spectroscope
(EDS) and X-ray Diffractometer  (XRD).  The cyclic oxidation results at 850 ˚C  for 96 h  show that
the Y
2O3
modified aluminized  coatings had  better oxidation resistance and  the parabolic oxidation
rate constant of the coatings decreased from 0.0328 to 0.0083 mg
2
.cm
-4
.h
-1
with the increase of the
Y2O3
content from 0 to 3.4 wt.%.

Titanium alloys have been extensively used in the aerospace industry because of their outstanding properties, such as high strength-to-weight ratios, high corrosion resistances, and high melting points. However, it is hypothesized that the performance of titanium alloys can be further enhanced to be more resistant to hypervelocity impact by coating them. Earlier experimental investigations showed that coating a Ti-6Al-4V substrate by Ti/SiC Metal Matrix Nanocomposite (MMNC) improved hypervelocity impact resistance of the composite. The coating had 7% SiC by volume. These experiments were simulated using the Smoothed Particle Hydrodynamics (SPH) modeling approach. Johnson-Cook material models were used for the Ti-6Al-4V substrate and the Lexan projectile. Due to the lack of detailed mechanical characterization of the MMNC, a bilinear elastic plastic material model was used to model the coating. In this study, single-parameter sensitivity analyses were conducted to understand the sensitivity of the SPH model based on comparison with the experimental crater volume. The parameters of the bilinear elastic plastic material model were modulus of elasticity, Poisson's ratio, yield strength, tangent modulus, and the failure strain. These parameters were varied by ±5%, and ±10% of their respective base values for a Ti/SiC Metal Matrix Nanocomposite (MMNC) with 35% SiC by volume for which stress-strain curves under various strain rates were available. These values were applied to the full range of tested velocities. Exploiting the parameters from sensitivity analyses, the results show that the accuracy of SPH modeling of MMNC can be enhanced when experimental data is not available. The results also show that bilinear elastic plastic material model can be used for MMNC coating under elevated strain rates. Abstract Titanium alloys have been extensively used in the aerospace industry because of their outstanding properties, such as high strength-to-weight ratios, high corrosion resistances, and high melting points. However, it is hypothesized that the performance of titanium alloys can be further enhanced to be more resistant to hypervelocity impact by coating them. Earlier experimental investigations showed that coating a Ti-6Al-4V substrate by Ti/SiC Metal Matrix Nanocomposite (MMNC) improved hypervelocity impact resistance of the composite. The coating had 7% SiC by volume. These experiments were simulated using the Smoothed Particle Hydrodynamics (SPH) modeling approach. Johnson-Cook material models were used for the Ti-6Al-4V substrate and the Lexan projectile. Due to the lack of detailed mechanical characterization of the MMNC, a bilinear elastic plastic material model was used to model the coating. In this study, single-parameter sensitivity analyses were conducted to understand the sensitivity of the SPH model based on comparison with the experimental crater volume. The parameters of the bilinear elastic plastic material model were modulus of elasticity, Poisson's ratio, yield strength, tangent modulus, and the failure strain. These parameters were varied by ±5%, and ±10% of their respective base values for a Ti/SiC Metal Matrix Nanocomposite (MMNC) with 35% SiC by volume for which stress-strain curves under various strain rates were available. These values were applied to the full range of tested velocities. Exploiting the parameters from sensitivity analyses, the results show that the accuracy of SPH modeling of MMNC can be enhanced when experimental data is not available. The results also show that bilinear elastic plastic material model can be used for MMNC coating under elevated strain rates.

Metallic bipolar plate (BPP) with high corrosion and low contact resistance, durability, strength, low cost,
volume, and weight requirements is one of the critical parts of the PEMFC. This study is dedicated to
understand the effect of the process sequence (manufacturing then coating vs. coating then
manufacturing) on the corrosion resistance of coated metallic bipolar plates. To this goal, three different
PVD coatings (titanium nitride (TiN), chromium nitride (CrN), zirconium nitride (ZrN)), with three
thicknesses, (0.1, 0.5, 1 mm) were applied on BPPs made of 316L stainless steel alloy before and after two
types of manufacturing (i.e., stamping or hydroforming). Corrosion test results indicated that ZrN coating
exhibited the best corrosion protection while the performance of TiN coating was the lowest among the
tested coatings and thicknesses. For most of the cases tested, in which coating was applied before
manufacturing, occurrence of corrosion was found to be more profound than the case where coating was
applied after manufacturing. Increasing the coating thickness was found to improve the corrosion
resistance. It was also revealed that hydroformed BPPs performed slightly better than stamped BPPs in
terms of the corrosion behavior.

Copper Chromium Oxide thin films deposited on glass substrates with different thicknesses from 200-350 nm by reactive dc magnetron sputtering technique. The films were characterized by Glancing Angle XRD (GAXRD) for structural studies, FESEM for surface morphology, four probe method for electrical measurements and UV-vis for optical properties. The results from GAXRD show that all the films have delafossite structure. The crystallite size was increased up to 300 nm film thickness and further decreased. The average transmittance of the films was observed maximum and also maximum band gap at 300 nm. The nature of the films was p-type which was confirmed with Hall coefficient.

The aim of this work is to investigate the stick–slip phenomenon under friction of CrV(x)N (x¼0%, 12%,
27%, and 35%) coatings at room and high temperatures. The effects of vanadium (V) content and the
temperature on the friction and stick–slip parameters for the contact pair: coating-ceramic ball were
analyzed. The amplitude – a difference between the maximal and minimal values of the friction force, the
static force (at the beginning of friction) and the kinetic friction force (average value in the steady state)
were chosen for the description of the stick–slip phenomenon. The surface morphology, the structure
and the mechanical properties of coatings were analyzed by SEM, AFM and XRD techniques. The
hardness and roughness parameters before and after friction were measured. It was shown that
the addition of V up to 27–35% in CrV(x)N coatings increased the hardness and toughness and decreased
the grain size. These parameters are responsible for the improved tribological properties of coatings with
high a content of V. Friction of the CrV(0)N coating rubbed at room temperature is accompanied by
strong sticking. High values of the stick–slip parameters are explained by mechanical “catching” and
adhesion on the contact spots due to high roughness and transfer of Si films on the surface of the coating.
Low values of the stick–slip parameters under friction of CrV(35)N at high temperature (T¼500 1C) are
due to the formation of lubricious V2O5 oxide layer providing easy shearing of tribofilms in the interface
of rubbed surfaces.

The invention consists of three parts made to work together to ensure safe, fast and effective deployment to the end users, which include but are not limited to surgeons and doctors in emergency and operating rooms, occupational hazards equipment goggles, visors and shields, defensive protective armors and high impact vision wear, high performance athletic equipment, and avionics surfaces. The three parts are the anti-fog coating materials composition, their methods of preparation and processing in large, medium or small scale manufacturing, and a single unit delivery device with the coating materials to apply on any existing surface, lens, scope, tools or dials, as a wet or quickly drying coating.

Nickel doped zinc oxide (Ni/ZnO) nanostructures have the potential to improve the performance of electrochemical capacitors. This study investigates the preparation of Ni/ZnO nanomaterials by facile co-precipitation (CPM) and hydrothermal (HTM) methods. The effect of the synthesis methods on the optical, structural, chemical and morphological properties on ZnO products is investigated using ultra violet (UV)-visible spectroscopy, X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), X-ray spectrometry (EDX), room temperature photoluminescence (PL), Fourier transform infrared (FTIR) and Raman spectroscopy. Finally, the electrochemical performance of the synthesized nanorods were examined by fabrication of a supercapacitor using standard three electrode cell configuration and tested with a cyclic voltammogram (CV) and galvanostatic charge-discharge (GCD) measurements. The results shown that the samples synthesized by HTM exhibited improved electrochemical capacitance performance with higher current density. The discharge curves are linear in the total range of potential with constant slopes, showing perfect capacitance. In conclusion, Ni/ZnO nanoparticles synthesized by this method with further optimization have the potential to lead to a high-efficiency supercapacitors.