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Published By Mdpi Ag

2079-6412
Updated Wednesday, 19 January 2022

Coatings ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 96
Author(s):  
Yung-Lin Chen ◽  
Yi-Cheng Lin ◽  
Wan-Yu Wu

It has always been a huge challenge to prepare the Mo back contact of inorganic compound thin film solar cells (e.g., CIGS, CZTS, Sb2Se3) with good conductivity and adhesion at the same time. High-power impulse magnetron sputtering (HiPIMS) has been proposed as one solution to improve the properties of the thin film. In this study, the HiPIMS technology replaced the traditional DC power sputtering technology to deposit Mo back contact on polyimide (PI) substrates by adjusting the experimental parameters of HiPIMS, including working pressure and pulse DC bias. When the Mo back contact is prepared under a working pressure of 5 mTorr and bias voltage of −20 V, the conductivity of the Mo back contact is 9.9 × 10−6 Ωcm, the residual stress of 720 MPa, and the film still has good adhesion. Under the minimum radius of curvature of 10 mm, the resistivity change rate of Mo back contact does not increase by more than 15% regardless of the 1680 h or 1500 bending cycle tests, and the Mo film still has good adhesion in appearance. Experimental results show that, compared with traditional DC sputtering, HiPIMS coating technology has better conductivity and adhesion at the same time, and is especially suitable for PI substrates.


Coatings ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 94
Author(s):  
Pepen Arifin ◽  
Heri Sutanto ◽  
Sugianto ◽  
Agus Subagio

We report the growth of non-polar GaN and AlGaN films on Si(111) substrates by plasma-assisted metal-organic chemical vapor deposition (PA-MOCVD). Low-temperature growth of GaN or AlN was used as a buffer layer to overcome the lattice mismatch and thermal expansion coefficient between GaN and Si(111) and GaN’s poor wetting on Si(111). As grown, the buffer layer is amorphous, and it crystalizes during annealing to the growth temperature and then serves as a template for the growth of GaN or AlGaN. We used scanning electron microscopy (SEM), atomic force microscopy (AFM), and X-ray diffraction (XRD) characterization to investigate the influence of the buffer layer on crystal structure, orientation, and the morphology of GaN. We found that the GaN buffer layer is superior to the AlN buffer layer. The thickness of the GaN buffer layer played a critical role in the crystal quality and plane orientation and in reducing the cracks during the growth of GaN/Si(111) layers. The optimum GaN buffer layer thickness is around 50 nm, and by using the optimized GaN buffer layer, we investigated the growth of AlGaN with varying Al compositions. The morphology of the AlGaN films is flat and homogenous, with less than 1 nm surface roughness, and has preferred orientation in a-axis.


Coatings ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 92
Author(s):  
Pouya Shojaei ◽  
Riccardo Scazzosi ◽  
Mohamed Trabia ◽  
Brendan O’Toole ◽  
Marco Giglio ◽  
...  

While deposited thin film coatings can help enhance surface characteristics such as hardness and friction, their effective incorporation in product design is restricted by the limited understanding of their mechanical behavior. To address this, an approach combining micro-indentation and meso/micro-scale simulations was proposed. In this approach, micro-indentation testing was conducted on both the coating and the substrate. A meso-scale uniaxial compression finite element model was developed to obtain a material model of the coating. This material model was incorporated within an axisymmetric micro-scale model of the coating to simulate the indentation. The proposed approach was applied to a Ti/SiC metal matrix nanocomposite (MMNC) coating, with a 5% weight of SiC nanoparticles deposited over a Ti-6Al-4V substrate using selective laser melting (SLM). Micro-indentation testing was conducted on both the Ti/SiC MMNC coating and the Ti-6Al-4V substrate. The results of the meso-scale finite element indicated that the MMNC coating can be represented using a bi-linear elastic-plastic material model, which was incorporated within an axisymmetric micro-scale model. Comparison of the experimental and micro-scale model results indicated that the proposed approach was effective in capturing the post-indentation behavior of the Ti/SiC MMNC coating. This methodology can also be used for studying the response of composite coatings with different percentages of reinforcements.


Coatings ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 91
Author(s):  
Aliah Nursyahirah Kamarudin ◽  
Mohd Mustafa Awang Kechik ◽  
Siti Nabilah Abdullah ◽  
Hussein Baqiah ◽  
Soo Kien Chen ◽  
...  

The development of high-temperature superconductor (HTS) YBa2Cu3O7~δ (Y123) bulks in industrial applications were established years ago. It is one of the developments that currently attracts great attention especially in transportation, superconductor cables and wires. This study is focused on the preparation of the Y123 bulk superconductors by the thermal treatment method due to the promising ways to develop high-quality Y123 superconductors with its simplicity, low cost, and relatively low reaction temperature used during the process. Y123 were added with graphene nanoparticles (x = (0.0–1.0) wt.%). Samples were then characterized by X-ray diffraction (XRD) analysis, field-emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDX), and alternating current susceptibility (ACS). It was found that Y123 confirmed that the majority of phases in all the XRD patterns was the orthorhombic crystal structure and the Pmmm space group with secondary phases belonged to Y2Ba1Cu1O5 (Y211). The highest Tc obtained when graphene nanoparticles were added in the Y123 sample was x = 1.0 wt.%, followed by x = 0.5 wt.% with 92.64 and 92.59 K, respectively. From the microstructure analysis, the average grain size significantly decreased to 4.754 µm at x = 0.5 wt.%. The addition of graphene nanoparticles had disturbed the grain growth of Y123, affecting the superconducting properties of the samples. On the other hand, the intergranular critical current density, Jcm, was found to increase with graphene nanoparticle addition and had the highest value at x = 1.0 wt.%, indicating that graphene nanoparticles acted as pinning centers in the Y123 matrix.


Coatings ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 88
Author(s):  
Eka Safitri ◽  
Zatul Omaira ◽  
Nazaruddin Nazaruddin ◽  
Irfan Mustafa ◽  
Sitti Saleha ◽  
...  

Considering the significance of its demand around the world, the accurate determination of fish freshness with a simple and rapid procedure has become an interesting issue for the fishing industry. Hence, we aimed to fabricate a new optical pH sensor based on a polyelectrolyte (PEC) membrane of pectin–chitosan and the active material chromoionophore ETH 5294. A trial-and-error investigation of the polymer compositions revealed that the optimum ratio of pectin to chitosan was 3:7. With an optimum wavelength region (λ) at 610 nm, the constructed sensor was capable of stable responses after 5 min exposure to phosphate-buffered solution. Furthermore, the obtained sensor achieved optimum sensitivity when the PBS concentration was 0.1 M, while the relative standard deviation values ranged from 2.07 to 2.34%, suggesting good reproducibility. Further investigation revealed that the sensor experienced decreased absorbance of 16.67–18.68% after 25 days of storage. Employing the optimum conditions stated previously, the sensor was tested to monitor fish freshness in samples that were stored at 4 °C and ambient temperature. The results suggested that the newly fabricated optical sensor could measure pH changes on fish skin after 25 h storage at room temperature (pH 6.37, 8.91 and 11.02, respectively) and 4 °C (pH 6.8, 7.31 and 7.92, respectively).


Coatings ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 87
Author(s):  
Atef S. Gadalla ◽  
Hamdan A. S. Al-shamiri ◽  
Saad Melhi Alshahrani ◽  
Huda F. Khalil ◽  
Mahmoud M. El Nahas ◽  
...  

In this study, cadmium Sulfide (CdS) thin films were synthesized on quartz substrates using an infrared pulsed laser deposition (IR-PLD) technique under high vacuum (~10−6 Torr) conditions. X-ray diffraction was used to evaluate the structural features. According to X-ray analysis, the deposited CdS films are crystalline and have a favored orientation on a plane (110) of an orthorhombic. The peak intensity and the average crystallite size increases with increasing the film thickness. After annealing at 300 °C, the orthorhombic phase transformed into a predominant hexagonal phase and the same result was obtained by SEM photographs as well. Spectrophotometric measurements of transmittance and reflectance of the CdS films were used to derive optical constants (n, k, and absorption coefficient α). The optical band gap energy was found to be 2.44 eV. The plasma plume formation and expansion during the film deposition have also been discussed. The photocurrent response as a function of the incident photon energy E (eV) at different bias voltages for different samples of thicknesses (85, 180, 220 and 340 nm) have been studied, indicating that the photocurrent increases by increasing both the film thickness and photon energy with a peak in the vicinity of the band edge. Thus, the prepared CdS films are promising for application in optoelectronic field.


Coatings ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 90
Author(s):  
Sherif Fathy El-Gioushy ◽  
Mohamed F. M. Abdelkader ◽  
Mohamed H. Mahmoud ◽  
Hanan M. Abou El Ghit ◽  
Mohammad Fikry ◽  
...  

Guava is a nutritious fruit that has perishable behavior during storage. We aimed to determine the influences of some edible coatings (namely, cactus pear stem (10%), moringa (10%), and henna leaf (3%) extracts incorporated with gum Arabic (10%)), on the guava fruits’ properties when stored under ambient and refrigeration temperatures for 7, 14, and 21 days. The results revealed that the coating with gum Arabic (10%) only, or combined with the natural plant extracts, exhibited a significant reduction in weight loss, decay, and rot ratio. Meanwhile, there were notable increases in marketability. Moreover, among all tested treatments, the application of gum Arabic (10%) + moringa extract (10%) was the superior treatment for most studied parameters, and exhibited for the highest values for maintaining firmness, total soluble solids, total sugars, and total antioxidant activity. Overall, it was suggested that coating guava with 10% gum Arabic combined with other plant extracts could maintain the postharvest storage quality of the cold-storage guava.


Coatings ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 89
Author(s):  
Ran Zhang ◽  
Haoxiang Wang ◽  
Jie Ji ◽  
Hainian Wang

The purpose of this study is to explore the viscoelastic properties, rutting resistance, and fatigue resistance of waste wood-based biochar-modified asphalt. The biochar with 2%, 4%, and 8% mixing amounts and two kinds of particle size, 75–150 μm and <75 μm, were used as modifiers of petroleum asphalt. Meanwhile, in the control group, a graphite modifier with a particle size of 0–75 μm and mixing amount of 4% was used for comparison. Aged asphalts were obtained in the laboratory by the Rolling Thin Film Oven (RTFO) test and the Pressure Aging Vessel (PAV) test. The viscoelastic properties, rutting resistance, and fatigue resistance of biochar-modified asphalt were evaluated by phase angle, critical high temperature, and fatigue cracking index by the Dynamic Shear Rheometer (DSR) test. In addition, the micromorphology of biochar and graphite was compared and observed by using the scanning electron microscope (SEM). The results show that increasing the mixing amount of biochar gave a higher elastic property and significantly better rutting resistance of the modified asphalt at high temperature. Compared with graphite, the biochar has a rougher surface and more pores, which provides its higher specific surface area. Therefore, it is easier to bond with asphalt to form a skeleton network structure, then forming a more stable biochar–asphalt base structure. In this way, compared to graphite-modified asphalt, biochar-modified asphalt showed better resistance to rutting at high temperature, especially for the asphalt modified with biochar of small particle size. The critical high temperature T(G*/sinδ) of 4% Gd, 4% WD, and 4% Wd was 0.31 °C, 1.57 °C, and 2.92 °C higher than that of petroleum bitumen. In addition, the biochar asphalt modified with biochar of small particle size had significantly better fatigue cracking resistance than the asphalt modified with biochar of large particle size. The fatigue cracking indexes for 2% Wd, 4% Wd, and 8% Wd were 29.20%, 7.21%, and 37.19% lower by average than those for 2% WD, 4% WD, and 8% WD at 13–37 °C. Therefore, the waste wood biochar could be used as the modifier for petroleum asphalt. After the overall consideration, the biochar-modified asphalt with 2%–4% mixing amount and particle size less than 75 μm was recommended.


Coatings ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 85
Author(s):  
Kent Davis ◽  
Scott Leavengood ◽  
Jeffrey J. Morrell

Wood exposed in exterior applications degrades and changes color due to weathering and fungal growth. Wood coatings can reduce the effects of weathering by reducing the damaging effects of ultraviolet light, reducing water absorption, and slowing fungal growth on the surface. Coating performance depends on the blend of resins, oils, and pigments and varies considerably among different wood species and conditions. Specific information describing expected service for different wood species and exposure conditions is not commonly available; certain combinations may work well in one climate or on one timber species, but underperform elsewhere. This study compared the performance of three industrial wood coatings on two wood species for two temperate climates under natural weathering conditions. Most of the coatings/species combinations lost their protective properties within 12 to 15 months; however, fungal growth was more prevalent at the wetter site than at the drier site for several combinations. Film-forming coatings often peeled and cracked, while penetrating coatings weathered and changed color relatively uniformly during the study. While no coating was completely effective, the results illustrate the benefits of using coatings that promote the development of natural, uniform-patinaed wood surfaces. The findings also guide coating maintenance programs for mass timber structures exposed to natural weathering conditions.


Coatings ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 81
Author(s):  
Gergana Alexieva ◽  
Konstantin Lovchinov ◽  
Miroslav Petrov ◽  
Rositsa Gergova ◽  
Nikolay Tyutyundzhiev

The detection of hazardous gases at different concentration levels at low and room temperature is still an actual and challenging task. In this paper, Al-doped ZnO thin films are synthesized by the electrochemical deposition method on the gold electrodes of AT-cut quartz resonators, vibrating at 10 MHz. The average roughness, surface morphology and gas sensing properties are investigated. The average roughness of Al-doped ZnO layers strongly depends on the amount of the doping agent Al2(SO4)3 added to the solution. The structural dependence of these films with varying Al concentrations is evident from the scanning electron microscopy images. The sensing properties to ethanol and ammonia analytes were tested in the range of 0–12,800 ppm. In the analysis of the sensitivity to ammonia, a dependence on the concentration of the added Al2(SO4)3 in the electrochemically deposited layers is also observed, as the most sensitive layer is at 3 × 10−5 M. The sensitivity and the detection limit in case of ammonia are, respectively, 0.03 Hz/ppm and 100 ppm for the optimal doping concentration. The sensitivity depends on the active surface area of the layers, with those with a more developed surface being more sensitive. Al-doped ZnO layers showed a good long-term stability and reproducibility towards ammonia and ethanol gases. In the case of ethanol, the sensitivity is an order lower than that for ammonia, as those deposited with Al2(SO4)3 do not practically react to ethanol.


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