Coatings

14 pages, 40606 KiB

Open AccessArticle

Characterization and In Vitro Studies of Low Reflective Magnetite (Fe₃O₄) Thin Film on Stainless Steel 420A Developed by Chemical Method

by Reghuraj Aruvathottil Rajan, Kaiprappady Kunchu Saju and Ritwik Aravindakshan

Coatings 2021, 11(9), 1145; https://doi.org/10.3390/coatings11091145 - 21 Sep 2021

Cited by 4 | Viewed by 2773

Abstract

Stainless steel has been the most demanded material for surgical utensil manufacture due to superior mechanical properties, sufficient wear, and corrosion resistance. Surgical grade 420A stainless steel is extensively used for producing sophisticated surgical instruments. Since these instruments are used under bright light [...] Read more.

Stainless steel has been the most demanded material for surgical utensil manufacture due to superior mechanical properties, sufficient wear, and corrosion resistance. Surgical grade 420A stainless steel is extensively used for producing sophisticated surgical instruments. Since these instruments are used under bright light conditions prevalent in operation theatres, the reflection from the material is significant which causes considerable strain to the eye of the surgeon. Surgical instruments with lower reflectance will be more efficient under these conditions. A low reflective thin -film coating has often been suggested to alleviate this inadmissible difficulty. This paper reports the development of an optimum parametric low reflective magnetite coating on the surface of SS 420A with a black color using chemical hot alkaline conversion coating technique and its bioactivity studies. Coating process parameters such as coating time, bath temperature, and chemical composition of bath are optimized using Taguchi optimization techniques. X-ray photoelectron spectroscopy (XPS) analysis was used to identify the composition of elements and the chemical condition of the developed coating. Surface morphological studies were accomplished with a scanning electron microscope (SEM). When coupled with an energy-dispersive X-ray analysis (EDAX), compositional information can also be collected simultaneously. Invitro cytotoxicity tests, corrosion behavior, the effect of sterilization temperature on adhesion property, and average percentage reflectance (R) of the developed coating have also been evaluated. These results suggest adopting the procedure for producing low reflective conversion coatings on minimally invasive surgical instruments produced from medical grade 420A stainless steel. Full article

(This article belongs to the Special Issue Surface Modification Technology of Biomedical Metals)

► Show Figures

Figure 1

20 pages, 9112 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Rare Earth Elements Enhanced the Oxidation Resistance of Mo-Si-Based Alloys for High Temperature Application: A Review

by Laihao Yu, Yingyi Zhang, Tao Fu, Jie Wang, Kunkun Cui and Fuqiang Shen

Coatings 2021, 11(9), 1144; https://doi.org/10.3390/coatings11091144 - 21 Sep 2021

Cited by 31 | Viewed by 4061

Abstract

Traditional refractory materials such as nickel-based superalloys have been gradually unable to meet the performance requirements of advanced materials. The Mo-Si-based alloy, as a new type of high temperature structural material, has entered the vision of researchers due to its charming high temperature [...] Read more.

Traditional refractory materials such as nickel-based superalloys have been gradually unable to meet the performance requirements of advanced materials. The Mo-Si-based alloy, as a new type of high temperature structural material, has entered the vision of researchers due to its charming high temperature performance characteristics. However, its easy oxidation and even “pesting oxidation” at medium temperatures limit its further applications. In order to solve this problem, researchers have conducted large numbers of experiments and made breakthrough achievements. Based on these research results, the effects of rare earth elements like La, Hf, Ce and Y on the microstructure and oxidation behavior of Mo-Si-based alloys were systematically reviewed in the current work. Meanwhile, this paper also provided an analysis about the strengthening mechanism of rare earth elements on the oxidation behavior for Mo-Si-based alloys after discussing the oxidation process. It is shown that adding rare earth elements, on the one hand, can optimize the microstructure of the alloy, thus promoting the rapid formation of protective SiO₂ scale. On the other hand, it can act as a diffusion barrier by producing stable rare earth oxides or additional protective films, which significantly enhances the oxidation resistance of the alloy. Furthermore, the research focus about the oxidation protection of Mo-Si-based alloys in the future was prospected to expand the application field. Full article

(This article belongs to the Special Issue Strengthening, Corrosion and Protection of High Temperature Structural Materials)

► Show Figures

Figure 1

11 pages, 2581 KiB

Open AccessArticle

Preparation and Application of Polyurethane Coating Material Based on Epoxycyclohexane-Tetrahydrofuran in Paper Conservation

by Juan Liu, Shan-Shan Jin, Ying-Ping Qi, Yong-Feng Shen and Hua Li

Coatings 2021, 11(9), 1143; https://doi.org/10.3390/coatings11091143 - 20 Sep 2021

Cited by 4 | Viewed by 3023

Abstract

Paper cultural heritages are valuable historical records and also abound in cultural resources. Due to its organic property, paper is susceptible to aging, destruction by environmental pollution and human factors. At present, many countries in the world are facing the problem of paper [...] Read more.

Paper cultural heritages are valuable historical records and also abound in cultural resources. Due to its organic property, paper is susceptible to aging, destruction by environmental pollution and human factors. At present, many countries in the world are facing the problem of paper conservation. Coating reinforcement is one of the methods for paper conservation, in which the choice of reinforcing resin is key. A transparent polyurethane, based on epoxycyclohexane (CHO)-tetrahydrofuran (THF) copolyether, was adopted in this study. The ring-opening polymerization for generating the CHO-THF copolyether took place by the reactants CHO and THF, in the catalysis of boron trifluoride diethyl etherate, initiation of glycerol. Characterizations of the synthetic copolyether were conducted by infrared (IR) spectroscopy and proton nuclear magnetic resonance (¹HNMR) spectroscopy. The transparent polyurethane was then produced by the CHO-THF copolyether and hexamethylene diisocyanate (HDI) trimer. The influences of different concentrations of polyurethane solution upon the paper tensile strength, elongation, folding endurance, tearing strength, gloss, and brightness were studied. These findings suggest that 10% polyurethane solution is optimal, not only for greatly improving the paper performance, but also for keeping with the principle of “repair as old”. The applied results demonstrate that the polyurethane based on the CHO-THF copolyether has the characteristics of copolyether along with polyurethane, displaying good mechanical properties in paper reinforcement. Full article

► Show Figures

Figure 1

14 pages, 2316 KiB

Open AccessArticle

Coupling Effect of Salt Freeze-Thaw Cycles and Carbonation on the Mechanical Performance of Quick Hardening Sulphoaluminate Cement-Based Reactive Powder Concrete with Basalt Fibers

by Guoping Huang, Hui Wang and Feiting Shi

Coatings 2021, 11(9), 1142; https://doi.org/10.3390/coatings11091142 - 20 Sep 2021

Cited by 20 | Viewed by 2839

Abstract

The effect of salt freeze-thaw cycles coupled with carbonation on the mechanical performance of quick hardening sulphoaluminate cement-based reactive powder concrete combined with basalt fibers was investigated. The ratios of basalt fibers in sulphoaluminate cement-based reactive powder concrete (SAC-RPC) were 1%, 2%, 3% [...] Read more.

The effect of salt freeze-thaw cycles coupled with carbonation on the mechanical performance of quick hardening sulphoaluminate cement-based reactive powder concrete combined with basalt fibers was investigated. The ratios of basalt fibers in sulphoaluminate cement-based reactive powder concrete (SAC-RPC) were 1%, 2%, 3% and 4% by the volume of concrete. The mechanical strengths (compressive strength, flexural strength and bonding strength) of SAC-RPC were investigated after curing for 5 h, 1 d, 14 d and 28 d, respectively. Meanwhile, the mechanical strengths of resultant concrete were detected, when different NaCl freeze-thaw cycles and carbonation were adopted. Results showed that the addition of basalt fibers could effectively improve the mechanical strengths, especially the flexural strength of SAC-RPC. The dosage of 3.0% was the threshold value affected mechanical strengths. The flexural, compressive and bonding strengths of SAC-RPC were higher than 8.53 MPa, 34 MPa and 3.21 MPa, respectively. The mass loss and mechanical strengths loss of SAC-RPC increased in the form of quadratic function with the increasing number of NaCl freeze-thaw cycles and varied in the form of quadratic decreasing function. Meanwhile, the effect of carbonation on the mechanical strengths of SAC-RPC can be ignored. Additionally, the coupling effect of salt freeze-thaw cycles and carbonation could accelerate the attenuation of concrete strength. The mechanical strengths loss demonstrated a decreased quadratic function with the increasing volume of basalt fibers. Full article

(This article belongs to the Special Issue Interface and Surface Modification for Durable Concretes)

► Show Figures

Figure 1

12 pages, 9618 KiB

Open AccessArticle

Effect of Thermal Management Approaches on Geometry and Productivity of Thin-Walled Structures of ER 5356 Built by Wire + Arc Additive Manufacturing

by Leandro João da Silva, Henrique Nardon Ferraresi, Douglas Bezerra Araújo, Ruham Pablo Reis and Américo Scotti

Coatings 2021, 11(9), 1141; https://doi.org/10.3390/coatings11091141 - 20 Sep 2021

Cited by 13 | Viewed by 3448

Abstract

The present paper aimed at assessing the effect of two thermal management approaches on geometry and productivity of thin-walled structures built by Wire + Arc Additive Manufacturing (WAAM). Thin-walls of ER 5356 (Al5Mg) with different lengths and the same number of layers were [...] Read more.

The present paper aimed at assessing the effect of two thermal management approaches on geometry and productivity of thin-walled structures built by Wire + Arc Additive Manufacturing (WAAM). Thin-walls of ER 5356 (Al5Mg) with different lengths and the same number of layers were deposited via the gas metal arc (GMA) process with the aid of an active cooling technique (near-immersion active cooling—NIAC) under a fixed set of deposition parameters. Then, the same experiment was performed with natural cooling (NC) in air. To characterize the thermal management approaches, the interpass temperature (i.e., the temperature at which subsequent layers are deposited) were monitored by a trailing/leading infrared pyrometer during the deposition time. Finally, thin walls with a fixed length were deposited using the NC and NIAC approaches with equivalent interpass temperatures. As expected, the shorter the wall length the more intense the deposition concentration, heat accumulation, and, thus, geometric deviation. This behavior was more evident and premature for the NC strategy due to its lower heat sinking effectiveness. The main finding was that, regardless of the thermal management technique applied, if the same interpass temperature is selected and maintained, the geometry of the part being built tends to be stable and very similar. However, the total deposition time is somewhat shorter with the NIAC technique due its greater heat sinking advantage. Thus, the NIAC technique facilitates the non-stop manufacturing of small parts and details via WAAM. Full article

(This article belongs to the Special Issue Progress in Coatings Deposition by Advanced Welding and Welding-Related Processes)

► Show Figures

Figure 1

14 pages, 3410 KiB

Open AccessArticle

Preparation of ZnO/Bi₂O₃ Composites as Heterogeneous Thin Film Materials with High Photoelectric Performance on FTO Base

by Yuhan Nie, Yadong Xie, Ying Zheng, Yao Luo, Jianguo Zhang, Zao Yi, Fusheng Zheng, Li Liu, Xifang Chen, Pinggen Cai and Pinghui Wu

Coatings 2021, 11(9), 1140; https://doi.org/10.3390/coatings11091140 - 20 Sep 2021

Cited by 15 | Viewed by 3962

Abstract

In recent years, ZnO nanomaterials have achieved great performance in solar energy applications. How to synthesize a ZnO nanocomposite structure with high photoelectric conversion efficiency has become an urgent problem to solved. In this paper, a narrow band gap bismuth trioxide (Bi₂ [...] Read more.

In recent years, ZnO nanomaterials have achieved great performance in solar energy applications. How to synthesize a ZnO nanocomposite structure with high photoelectric conversion efficiency has become an urgent problem to solved. In this paper, a narrow band gap bismuth trioxide (Bi₂O₃) coated on a ZnO nanoarray by magnetron sputtering was used to prepare a composite heterojunction ZnO/Bi₂O₃. Studies have found that ZnO/Bi₂O₃ exhibits excellent photoelectric conversion performance. By preparing a composite heterostructure of ZnO/Bi₂O₃, it can effectively compensate for the insufficient absorption of ZnO in the visible light range and inhibit the recombination of carriers within the material. The influence of Bi₂O₃ thickness on the microstructure and electronic structure of the ZnO/Bi₂O₃ composite structure was explored and analyzed. The energy gap width of the composite heterostructure decreases with the increase in the Bi₂O₃ thickness on the surface of the ZnO nanorod array. At the same time, the conductive glass composite film structure is simple to prepare and is very environmentally friendly. The ZnO/Bi₂O₃ composite heterogeneous material prepared this time is suitable for solar cells, photodetectors, photocatalysis and other fields. Full article

(This article belongs to the Section Surface Engineering for Energy Harvesting, Conversion, and Storage)

► Show Figures

Figure 1

17 pages, 9494 KiB

Open AccessArticle

Effect of Ni Addition on the Corrosion Resistance of NiTi Alloy Coatings on AISI 316L Substrate Prepared by Laser Cladding

by Yuqiang Feng, Zexu Du and Zhengfei Hu

Coatings 2021, 11(9), 1139; https://doi.org/10.3390/coatings11091139 - 19 Sep 2021

Cited by 13 | Viewed by 3631

Abstract

In this paper, an equiatomic NiTi (55NiTi) alloy powder was mixed with pure Ni powder to prepare laser cladding coatings on a 316L stainless steel substrate to study the effect of Ni addition on the microstructure and corrosion resistance of the coatings. The [...] Read more.

In this paper, an equiatomic NiTi (55NiTi) alloy powder was mixed with pure Ni powder to prepare laser cladding coatings on a 316L stainless steel substrate to study the effect of Ni addition on the microstructure and corrosion resistance of the coatings. The microstructure and phase composition of the coatings were analyzed using a scanning electron microscope (SEM) with configured energy-dispersive spectrometer (EDS) and X-ray diffractometer (XRD). OCP (open-circuit potential), PD (potentiodynamic polarization) and EIS (electrochemical impedance spectroscopy) experiments were conducted by a Gamry electrochemical workstation, and corresponding eroded morphologies were observed to evaluate the coating’s anti-corrosion performance. The addition of Ni led to fine and uniform dendrites and dense microstructure under the metallurgical microscope, which were beneficial for the formation of the passive film mainly consisting of titanium dioxide (TiO₂). The results show that the pitting potential of the 55NiTi + 5Ni coating was 0.11 V nobler than that of the 55NiTi coating, and the corrosion current density was less than half that of the 55NiTi coating. The corrosion initiated preferentially at the interfaces of dendrites and inter-dendritic areas, then spread first to dendrites rather than in the inter-dendritic areas. Full article

(This article belongs to the Section Corrosion, Wear and Erosion)

► Show Figures

Figure 1

16 pages, 9012 KiB

Open AccessArticle

Analysis of the Possibility of Using New Types of Protective Coatings and Abrasion-Resistant Linings under the Operating Conditions of the Spiral Classifier at KGHM Polska Miedź S.A. Ore Concentration Plant

by Marcin Czekajło, Krzysztof Zakowski, Stefan Krakowiak and Sławomir Kierepa

Coatings 2021, 11(9), 1138; https://doi.org/10.3390/coatings11091138 - 19 Sep 2021

Cited by 2 | Viewed by 2948

Abstract

A study was carried out to select the appropriate coatings for corrosion protection of the spiral classifier working at KGHM Polska Miedź S.A. Ore Concentration Plant. The abrasion resistance of selected protective coatings and wear-resistant linings was investigated using a DT-523 rotary abrasion [...] Read more.

A study was carried out to select the appropriate coatings for corrosion protection of the spiral classifier working at KGHM Polska Miedź S.A. Ore Concentration Plant. The abrasion resistance of selected protective coatings and wear-resistant linings was investigated using a DT-523 rotary abrasion tester with Taber CS-10 rubber abrasive discs. The average weight loss of the coatings after a cycle of 2000 revolutions was determined. Tests of protective coatings using the electrochemical impedance spectroscopy (EIS) technique were carried out to determine the suitability of coatings in the highly saline environment of the aqueous suspension of ground copper ore. During the measurements, changes in resistance, polarising current and capacitance were determined as a function of time for the tested coatings. The linings selected on the basis of laboratory tests were also tested under industrial conditions. Their degrees of wear were characterised. The results obtained indicated the highest abrasion resistance of materials from the polyolefin group (polyethylenes), where the average weight loss did not exceed 5 g/dm². In the case of protective coatings, the highest durability was demonstrated by coatings with additives of ceramic aggregates, phenol-epoxy, and an elastomeric coating based on polyurea, whose average weight loss during the test cycle did not exceed 19 g/dm². EIS measurements showed that the tested coatings were resistant to the aggressive environment of the feedstock. Tests under cathodic polarisation conditions of the samples at a potential below the protection potential showed that they were resistant to a highly saline environment and were also resistant to its alkalinisation resulting from the application of cathodic protection, which will be used to protect the classifier together with protective coatings. Tests carried out under industrial conditions using wear-resistant linings made of plastics have made it possible to analyse the mechanism and degree of wear of the various materials during the operation of the classifier. Measurements of lining wear were made in relation to baseline volumes. Polyurethane, a polymer lining based on MDI and PTMG, and those made of ultra-high-molecular-weight polyethylene with anti-stick additives showed the lowest wear rates. Full article

(This article belongs to the Special Issue Industrial Coatings: Applications and Developments)

► Show Figures

Figure 1

11 pages, 3431 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Three-Dimensional Carbon-Coated LiFePO₄ Cathode with Improved Li-Ion Battery Performance

by Can Wang, Xunlong Yuan, Huiyun Tan, Shuofeng Jian, Ziting Ma, Junjie Zhao, Xuewen Wang, Dapeng Chen and Yifan Dong

Coatings 2021, 11(9), 1137; https://doi.org/10.3390/coatings11091137 - 18 Sep 2021

Cited by 17 | Viewed by 5145

Abstract

LiFePO₄ (LFPO)has great potential as the cathode material for lithium-ion batteries; it has a high theoretical capacity (170 m·A·h·g⁻¹), high safety, low toxicity and good economic benefits. However, low conductivity and a low diffusion rate inhibit its future development. To [...] Read more.

LiFePO₄ (LFPO)has great potential as the cathode material for lithium-ion batteries; it has a high theoretical capacity (170 m·A·h·g⁻¹), high safety, low toxicity and good economic benefits. However, low conductivity and a low diffusion rate inhibit its future development. To overcome these weaknesses, three-dimensional carbon-coated LiFePO₄ that incorporates a high capacity, superior conductivity and low volume expansion enables faster electron transport channels. The use of Cetyltrimethyl Ammonium Bromid (CTAB) modification only requires a simple water bath and sintering, without the need to add a carbon source in the LFPO synthesis process. In this way, the electrode shows excellent reversible capacity, as high as 159.8 m·A·h·g⁻¹ at 2 C, superior rate capability with 97.3 m·A·h·g⁻¹ at 5 C and good cycling ability, preserving ~84.2% capacity after 500 cycles. By increasing the ion transport rate and enhancing the structural stability of LFPO nanoparticles, the LFPO-positive electrode achieves excellent initial capacity and cycle life through cost-effective and easy-to-implement carbon coating. This simple three-dimensional carbon-coated LiFePO₄ provides a new and simple idea for obtaining comprehensive and high-performance electrode materials in the field of lithium cathode materials. Full article

(This article belongs to the Special Issue Surface Coating in Advanced Energy Storage Devices)

► Show Figures

Figure 1

15 pages, 50187 KiB

Open AccessArticle

Corrosion Resistance of a Plasma-Oxidized Ti6Al4V Alloy for Dental Applications

by N. Velazquez-Torres, J. Porcayo-Calderon, H. Martinez-Valencia, R. Lopes-Cecenes, I. Rosales-Cadena, E. Sarmiento-Bustos, C. I. Rocabruno-Valdés and J. G. Gonzalez-Rodriguez

Coatings 2021, 11(9), 1136; https://doi.org/10.3390/coatings11091136 - 18 Sep 2021

Cited by 6 | Viewed by 2608

Abstract

A Ti6Al4V alloy was plasma-oxidized at 600 °C during 1, 2, 3, 5 and 8 h and corroded in an artificial saliva solution. Electrochemical evaluation was performed by using potentiodynamic polarization curves, linear polarization resistance (LPR), and electrochemical impedance spectroscopy (EIS) measurements during [...] Read more.

A Ti6Al4V alloy was plasma-oxidized at 600 °C during 1, 2, 3, 5 and 8 h and corroded in an artificial saliva solution. Electrochemical evaluation was performed by using potentiodynamic polarization curves, linear polarization resistance (LPR), and electrochemical impedance spectroscopy (EIS) measurements during 100 h. Corroded specimens were characterized by using Raman spectroscopy and scanning electronic microscopy (SEM). All tests indicated that the highest corrosion resistance was obtained for specimen oxidized during 3 h since the noblest free corrosion potential, lowest passive and corrosion current density values, as well as the highest polarization resistance values were obtained under these circumstances. EIS measurements indicated that the highest impedance and phase angle values obtained for this specimen exhibited a high capacitive behavior typical of a very compact passive film. Full article

(This article belongs to the Section Corrosion, Wear and Erosion)

► Show Figures

Figure 1

9 pages, 1600 KiB

Open AccessArticle

Comparative Study on the Separate Extraction of Interface and Bulk Trap Densities in Indium Gallium Zinc Oxide Thin-Film Transistors Using Capacitance–Voltage and Current–Voltage Characteristics

by Dong-Ho Lee, Dae-Hwan Kim, Hwan-Seok Jeong, Seong-Hyun Hwang, Sunhee Lee, Myeong-Ho Kim, Jun Hyung Lim and Hyuck-In Kwon

Coatings 2021, 11(9), 1135; https://doi.org/10.3390/coatings11091135 - 18 Sep 2021

Cited by 2 | Viewed by 4432

Abstract

The interface and bulk trap densities were separately extracted from self-aligned top-gate (SA-TG) coplanar indium gallium zinc oxide (IGZO) thin-film transistors (TFTs) using the low-frequency capacitance–voltage (C–V) characteristics and space-charge-limited current (SCLC) under the flat-band condition. In the method [...] Read more.

The interface and bulk trap densities were separately extracted from self-aligned top-gate (SA-TG) coplanar indium gallium zinc oxide (IGZO) thin-film transistors (TFTs) using the low-frequency capacitance–voltage (C–V) characteristics and space-charge-limited current (SCLC) under the flat-band condition. In the method based on the C–V curve, the energy distribution of the interface trap density was extracted using the low-frequency C–V characteristics, and that of the bulk trap density was obtained by subtracting the density of interface trap states from the total subgap density of states (DOS) at each energy level. In the SCLC-based method, the energy distribution of the bulk trap density was extracted using the SCLC under the flat-band condition at high drain-to-source voltages, and that of the interface trap density was obtained by subtracting the density of bulk trap components from the total subgap DOS at each energy level. In our experiments, the two characterization techniques provided very similar interface and bulk trap densities and showed that approximately 60% of the subgap states originate from the IGZO/SiO₂ interface at the conduction band edge in the fabricated IGZO TFTs, although the two characterization techniques are based on different measurement data. The results of this study confirm the validity of the characterization techniques proposed to separately extract the interface and bulk trap densities in IGZO TFTs. Furthermore, these results show that it is important to reduce the density of interface trap states to improve the electrical performance and stability of fabricated SA-TG coplanar IGZO TFTs. Full article

(This article belongs to the Special Issue New Advances in Thin-Film Transistor)

► Show Figures

Figure 1

12 pages, 3858 KiB

Open AccessFeature PaperArticle

Improved Corrosion Protection of Acrylic Waterborne Coating by Doping with Microencapsulated Corrosion Inhibitors

by Jacob Ress, Ulises Martin and David M. Bastidas

Coatings 2021, 11(9), 1134; https://doi.org/10.3390/coatings11091134 - 17 Sep 2021

Cited by 11 | Viewed by 3305

Abstract

Herein, a waterborne acrylic coating doped with pH sensitive colophony microcapsules containing corrosion inhibitors was studied on carbon steel plates. The changes in the physical properties of the coatings were studied. The microcapsule coating specimens maintained more noble E_corr values compared to [...] Read more.

Herein, a waterborne acrylic coating doped with pH sensitive colophony microcapsules containing corrosion inhibitors was studied on carbon steel plates. The changes in the physical properties of the coatings were studied. The microcapsule coating specimens maintained more noble E_corr values compared to the control in deionized water and simulated concrete pore solutions with −513 and −531 mV_SCE, respectively. Additionally, the microcapsule polarization results for both pH 12.6 and 6.2 electrolyte solutions showed lower i_corr values of 1.20 × 10⁻⁶ and 3.24 × 10⁻⁶ A·cm⁻², respectively, compared to the control sample (1.15 × 10⁻⁵ and 4.21 × 10⁻⁵ A·cm⁻²). Therefore, the microcapsule coating provided more protection from chloride attack on the substrate as well as the deleterious effects of low pH on carbon steel. The electrochemical impedance spectroscopy analysis corroborated the DC polarization results, showing increased corrosion resistance for the microcapsule coated specimens compared to the control. Moreover, the R_pore and R_ct are much higher than the control, indicating the protection of the inhibitors. The C_eff,dl also shows lower values for the microcapsule coating than the control, showing a more protective and less doped double layer. Full article

(This article belongs to the Special Issue New Trends in Surface Protection Coatings, Films and Corrosion Inhibition)

► Show Figures

Figure 1

9 pages, 1820 KiB

Open AccessArticle

Effect of Nitrogen Flow Ratio on Degradation Behaviors and Failure of Magnetron Sputter Deposited Tantalum Nitride

by Zhigang Li, Yubao Zhang, Yi Wang, Jinfeng Li and Hongtao Zhao

Coatings 2021, 11(9), 1133; https://doi.org/10.3390/coatings11091133 - 17 Sep 2021

Cited by 13 | Viewed by 2881

Abstract

A series of Tantalum Nitride (TaN) films under a reactive direct current magnetron sputtering method with a controlled total gas flow rate were prepared on aluminum oxide substrates. To find the nitrogen flow rate, which produced the minimum sheet resistance, TaN films deposited [...] Read more.

A series of Tantalum Nitride (TaN) films under a reactive direct current magnetron sputtering method with a controlled total gas flow rate were prepared on aluminum oxide substrates. To find the nitrogen flow rate, which produced the minimum sheet resistance, TaN films deposited under a nitrogen gas flow ratio of 2.5%, 5%, 10%, 15%, 20%, 25% were characterized in terms of their structural and electrical properties. The optimum total gas flow rate was 60 sccm, revealing the lowest deviation of sheet resistance. Next, the durability and reliability at high temperatures, after heating and cooling cycles and exposure to the induced current, were tested. When the nitrogen flow ratio reaches 2.5%, it gets the maximum for the adhesion force, roughness, and deposition rate of the TaN film, and maximum values are 75.4 N, 1.1 nm, and 3.67 nm/min, respectively, and the sheet resistance of the TaN film reaches a minimum of 20.32 Ω/sq. The degradation behaviors and failure of TaN films were investigated by measuring the sheet resistance variation. To further explain the degradation of TaN films, additional analysis of their crystallinity was conducted. The results showed that TaN-based thin film resistors have high durability and reliability, and are suitable for embedded passive resistors. Full article

(This article belongs to the Special Issue State-of-the-Art on Coatings Research in Asia)

► Show Figures

Figure 1

16 pages, 6585 KiB

Open AccessFeature PaperArticle

Mathematical Simulation and Experimental Verification of Carburizing Quenching Process Based on Multi-Field Coupling

by Jiangang Wang, Shuai Yang, Jianhui Li, Dongying Ju, Xusheng Li, Fangbo He, Hui Li and Yong Chen

Coatings 2021, 11(9), 1132; https://doi.org/10.3390/coatings11091132 - 17 Sep 2021

Cited by 7 | Viewed by 2829

Abstract

Based on the multi-field coupling effect of temperature, diffusion, and phase change, the finite element model of carburizing and quenching was established. The 20CrMnTiH steel helical gear as the research object, prediction accuracy of carburizing, and quenching model of complex helical gear was [...] Read more.

Based on the multi-field coupling effect of temperature, diffusion, and phase change, the finite element model of carburizing and quenching was established. The 20CrMnTiH steel helical gear as the research object, prediction accuracy of carburizing, and quenching model of complex helical gear was studied. The material properties database of experimental steel was established by JMatPro, and the material thermophysical parameters needed in the calculation process were obtained. The carburizing and quenching process of transmission helical gear was numerically simulated by thermodynamic three-dimensional coupling analysis method combined with actual heat treatment process. The microstructure morphology, macro hardness, and deformation were characterized. The experimental results show that the microstructure of the hardened surface layer was acicular martensite and a small amount of residual austenite. The highest hardness appears at the surface layer of 778.8 HV, the effective hardened layer depth was 0.9 mm, and the maximum deformation of the gear was 0.055 mm. By comparing the experimental measurement results with the simulation results, they were in good agreement, which verifies the accuracy of the finite element model. This indicates that the model has good prediction ability in carburizing and quenching process. Full article

(This article belongs to the Special Issue Surface Modification and Functionalization for Advanced Materials)

► Show Figures

Graphical abstract

9 pages, 1470 KiB

Open AccessArticle

The Influence of CBD Parameters on the Energy Gap of ZnS Narcissus-Like Nanostructured Thin Films

by Mohammed Hussein Khalil, Raghad Y. Mohammed and Mohammed Aziz Ibrahem

Coatings 2021, 11(9), 1131; https://doi.org/10.3390/coatings11091131 - 17 Sep 2021

Cited by 11 | Viewed by 2671

Abstract

Recently, the efficient preparation techniques of zinc sulfide (ZnS) nanostructured films have drawn great attention due to their potential applications in optoelectronics. In this study, the low-cost and high-yield chemical bath deposition (CBD) technique was used to deposit ZnS nanostructured thin films. The [...] Read more.

Recently, the efficient preparation techniques of zinc sulfide (ZnS) nanostructured films have drawn great attention due to their potential applications in optoelectronics. In this study, the low-cost and high-yield chemical bath deposition (CBD) technique was used to deposit ZnS nanostructured thin films. The effect of various deposition parameters such as time, pH, precursor concentration, and temperature on the morphology and energy bandgap (Eg) of the prepared thin films were investigated. The characterization of the prepared thin films revealed the formation of polycrystalline ZnS with Narcissus-like nanostructures. Moreover, the optical characterization showed inverse proportionality between both the transmission and Eg of the nanostructured thin films and the variation of the deposition parameters. A range of different Eg values between 3.92 eV with 20% transmission and 4.06 eV with 80% transmission was obtained. Tuning the Eg values and transmission of the prepared nanostructured films by manipulating the deposition parameters of such an efficient technique could lead to applications in optoelectronics such as solar cells and detectors. Full article

(This article belongs to the Special Issue Advances in Epitaxial Thin Films: Materials and Applications)

► Show Figures

Figure 1

17 pages, 5251 KiB

Open AccessArticle

Core/Shell Glycine-Polyvinyl Alcohol/Polycaprolactone Nanofibrous Membrane Intended for Guided Bone Regeneration: Development and Characterization

by Marwa Alazzawi, Nabeel Kadim Abid Alsahib and Hilal Turkoglu Sasmazel

Coatings 2021, 11(9), 1130; https://doi.org/10.3390/coatings11091130 - 17 Sep 2021

Cited by 11 | Viewed by 3417

Abstract

Glycine (Gly), which is the simplest amino acid, induces the inflammation response and enhances bone mass density, and particularly its β polymorph has superior mechanical and piezoelectric properties. Therefore, electrospinning of Gly with any polymer, including polyvinyl alcohol (PVA), has a great potential [...] Read more.

Glycine (Gly), which is the simplest amino acid, induces the inflammation response and enhances bone mass density, and particularly its β polymorph has superior mechanical and piezoelectric properties. Therefore, electrospinning of Gly with any polymer, including polyvinyl alcohol (PVA), has a great potential in biomedical applications, such as guided bone regeneration (GBR) application. However, their application is limited due to a fast degradation rate and undesirable mechanical and physical properties. Therefore, encapsulation of Gly and PVA fiber within a poly(ε-caprolactone) (PCL) shell provides a slower degradation rate and improves the mechanical, chemical, and physical properties. A membrane intended for GBR application is a barrier membrane used to guide alveolar bone regeneration by preventing fast-proliferating cells from growing into the bone defect site. In the present work, a core/shell nanofibrous membrane, composed of PCL as shell and PVA:Gly as core, was developed utilizing the coaxial electrospinning technique and characterized morphologically, mechanically, physically, chemically, and thermally. Moreover, the characterization results of the core/shell membrane were compared to monolithic electrospun PCL, PVA, and PVA:Gly fibrous membranes. The results showed that the core-shell membrane appears to be a good candidate for GBR application with a nano-scale fiber of 412 ± 82 nm and microscale pore size of 6.803 ± 0.035 μm. Moreover, the wettability of 47.4 ± 2.2° contact angle (C.A) and mechanical properties of 135 ± 3.05 MPa average modulus of elasticity, 4.57 ± 0.04 MPa average ultimate tensile stress (UTS), and 39.43% ± 0.58% average elongation at break are desirable and suitable for GBR application. Furthermore, the X-ray diffraction (XRD) and transmission electron microscopy (TEM) results exhibited the formation of β-Gly. Full article

(This article belongs to the Special Issue Advanced Coatings for Manufacturing Prosthetic Tubular Devices)

► Show Figures

Graphical abstract

19 pages, 1280 KiB

Open AccessArticle

Nanomechanical Concepts in Magnetically Guided Systems to Investigate the Magnetic Dipole Effect on Ferromagnetic Flow Past a Vertical Cone Surface

by Auwalu Hamisu Usman, Zahir Shah, Poom Kumam, Waris Khan and Usa Wannasingha Humphries

Coatings 2021, 11(9), 1129; https://doi.org/10.3390/coatings11091129 - 16 Sep 2021

Cited by 9 | Viewed by 2545

Abstract

Because of the floating magnetic nanomaterial, ferrofluids have magneto-viscous properties, enabling controllable temperature changes as well as nano-structured fluid characteristics. The study’s purpose is to evolve and solve a theoretical model of bioconvection nanofluid flow with a magnetic dipole effect in the presence [...] Read more.

Because of the floating magnetic nanomaterial, ferrofluids have magneto-viscous properties, enabling controllable temperature changes as well as nano-structured fluid characteristics. The study’s purpose is to evolve and solve a theoretical model of bioconvection nanofluid flow with a magnetic dipole effect in the presence of Curie temperature and using the Forchheimer-extended Darcy law subjected to a vertical cone surface. The model also includes the nonlinear thermal radiation, heat suction/injection, viscous dissipation, and chemical reaction effects. The developed model problem is transformed into nonlinear ordinary differentials, which have been solved using the homotopy analysis technique. In this problem, the behavior of function profiles are graphically depicted and explained for a variety of key parameters. For a given set of parameters, tables representthe expected numerical values and behaviors of physical quantities. The nanofluid velocity decreases as the ferrohydrodynamic, local inertia, and porosity parameters increase and decrease when the bioconvection Rayleigh number increases. Many key parameters improved the thermal boundary layer and temperature. The concentration is low when the chemical reaction parameter and Schmidt number rises. Furthermore, as the bioconvection constant, Peclet and Lewis numbers rise, so does the density of motile microorganisms. Full article

(This article belongs to the Special Issue Current Perspective on the Study of Liquid-Fluid Interfaces: From Fundamentals to Innovative Applications)

► Show Figures

Figure 1

9 pages, 3166 KiB

Open AccessArticle

Yttria-Coated Tungsten Fibers for Use in Tungsten Fiber-Reinforced Composites: A Comparative Study on PVD vs. CVD Routes

by Saravanan Palaniyappan, Maik Trautmann, Yiran Mao, Johann Riesch, Parikshith Gowda, Nick Rudolph, Jan Willem Coenen, Rudolf Neu and Guntram Wagner

Coatings 2021, 11(9), 1128; https://doi.org/10.3390/coatings11091128 - 16 Sep 2021

Cited by 4 | Viewed by 3530

Abstract

Tungsten fiber-reinforced tungsten (W_f/W) composites are being developed to improve the intrinsic brittleness of tungsten. In these composites, engineered fiber/matrix interfaces are crucial in order to realize toughening mechanisms. For such a purpose, yttria (Y₂O₃), being one [...] Read more.

Tungsten fiber-reinforced tungsten (W_f/W) composites are being developed to improve the intrinsic brittleness of tungsten. In these composites, engineered fiber/matrix interfaces are crucial in order to realize toughening mechanisms. For such a purpose, yttria (Y₂O₃), being one of the suitable interface materials, could be realized through different coating techniques. In this study, the deposition of thin films of yttria on a 150 µm tungsten wire by physical and chemical vapor deposition (PVD and CVD) techniques is comparatively investigated. Although fabrication of yttria is feasible through both CVD and PVD routes, certain coating conditions such as temperature, growth rate, oxidation of W_f, etc., decide the qualitative nature of a coating to a particular extent. In the case of PVD, the oxidation of W_f is highly reduced compared to the WO₃ formation in high-temperature CVD coating processes. Yttria-coated tungsten fibers are examined comprehensively to characterize their microstructure, phase, and chemical composition using SEM, XRD, and Raman spectroscopy techniques, respectively. Full article

► Show Figures

Figure 1

11 pages, 3289 KiB

Open AccessArticle

Ecofriendly Ultrasonic Rust Removal: An Empirical Optimization Based on Response Surface Methodology

by Lijie Zhang, Bing He, Shengnan Wang, Guangcun Wang and Xiaoming Yuan

Coatings 2021, 11(9), 1127; https://doi.org/10.3390/coatings11091127 - 16 Sep 2021

Cited by 1 | Viewed by 5469

Abstract

This study shows that the hard-to-remove rust layer on the guide sleeve surface of a used cylinder can be removed using a specially developed, environmentally friendly formula for cleaning rust. Furthermore, we studied the rust removal technology that is based on ultrasonic cavitation [...] Read more.

This study shows that the hard-to-remove rust layer on the guide sleeve surface of a used cylinder can be removed using a specially developed, environmentally friendly formula for cleaning rust. Furthermore, we studied the rust removal technology that is based on ultrasonic cavitation and chemical etching. The surface morphology and structural components of the rust layer were observed using an electron microscope and an X-ray powder diffractometer. These tools were used to explore the mechanism of combined rust removal. Using response surface methodology (RSM) and central composite design (CCD), with the rust removal rate as our index of evaluation, data were analyzed to establish a response surface model that can determine the effect of cleaning temperature and ultrasonic power interaction on the rate of rust removal. Results showed that the main components of the rust layer on a 45 steel guide sleeve were α-FeOOH, γ-FeOOH, and Fe₃O₄. The rust was unevenly distributed with a loose structure, which was easily corroded by chemical reagents and peeled off under ultrasonic cavitation. With the increase in the cleaning temperature, the chemical reaction effect was intensified, and the cleaning ability was enhanced. With the increase in ultrasonic power, the cavitation effect was aggravated, the ultrasonic agitation was enhanced, and the rust removal rate was improved. According to response surface analysis and the application scope of the rust remover, we determined that the optimal cleaning temperature is 55 °C, and that the optimal ultrasonic power is 2880 W. The descaling rate under these parameters is 0.15 g·min⁻¹·m⁻². Full article

(This article belongs to the Special Issue Strengthening, Corrosion and Protection of High Temperature Structural Materials)

► Show Figures

Figure 1

14 pages, 5224 KiB

Open AccessArticle

The Influence of Nanostructured Alumina Coating on Bonding and Optical Properties of Translucent Zirconia Ceramics: In Vitro Evaluation

by Tine Malgaj, Tadej Mirt, Andraž Kocjan and Peter Jevnikar

Coatings 2021, 11(9), 1126; https://doi.org/10.3390/coatings11091126 - 16 Sep 2021

Cited by 3 | Viewed by 2836

Abstract

Thin, non-retentive, monolithic restorations fabricated from novel translucent zirconia ceramics are widely used in contemporary dentistry. Because of the chemical inertness of zirconia, debonding of such restorations remains the main clinical complication. Limited evidence on the bonding performance of novel translucent zirconia exists; [...] Read more.

Thin, non-retentive, monolithic restorations fabricated from novel translucent zirconia ceramics are widely used in contemporary dentistry. Because of the chemical inertness of zirconia, debonding of such restorations remains the main clinical complication. Limited evidence on the bonding performance of novel translucent zirconia exists; therefore, the present study aimed to evaluate, in vitro, the shear-bond strength (SBS) of translucent zirconia modified with a nanostructured alumina coating (NAC). The SBS of resin cement to translucent zirconia, materials containing 3, 4 or 5 mol.% of yttria modified with NAC, was measured and related to airborne-particle abraded (APA) zirconia surfaces. Half of each of the specimen groups (n = 20) were subjected to 37,500 thermocycles in water. In addition, to evaluate the effect of NAC on thin translucent zirconia discs (n = 10), the translucency parameter (TP) was measured and compared with APA. The results were statistically analyzed using a t-test and one-way ANOVA. NAC provided higher resin-zirconia SBS compared to APA, not affecting the zirconia optical properties. APA, on the other hand, lowered TP for all types of zirconia. NAC did not impair the mechanical or optical properties of translucent zirconia materials and should be regarded as a zirconia pretreatment alternative to APA. Full article

(This article belongs to the Special Issue Dentistry and Dental Biomaterials)

► Show Figures

Figure 1

9 pages, 2074 KiB

Open AccessFeature PaperArticle

Exchange Bias Effect in LaFeO₃: La_0.7Ca_0.3MnO₃ Composite Thin Films

by Feng Wang, Wei Fu, Chengming Jiang, Junxiao Li and Jijie Huang

Coatings 2021, 11(9), 1125; https://doi.org/10.3390/coatings11091125 - 16 Sep 2021

Cited by 2 | Viewed by 2282

Abstract

Composite thin films arouse great interests owing to the multifunctionalities and heterointerface induced physical property tailoring. The exchange bias effect aroused from the ferromagnetic (FM)–antiferromagnetic (AFM) heterointerface is applicable in various applications such as magnetic storage. In this work, (LaFeO₃)_x [...] Read more.

Composite thin films arouse great interests owing to the multifunctionalities and heterointerface induced physical property tailoring. The exchange bias effect aroused from the ferromagnetic (FM)–antiferromagnetic (AFM) heterointerface is applicable in various applications such as magnetic storage. In this work, (LaFeO₃)_x:(La_0.7Ca_0.3MnO₃)_1−x composite thin films have been deposited via pulsed laser deposition (PLD) and the exchange bias effect was investigated. In such system, LaFeO₃ (LFO) is an antiferromagnet while La_0.7Ca_0.3MnO₃ (LCMO) is a ferromagnet, which results in the exchange bias interfacial coupling at the FM/AFM interface. The composition variation of the two phases could lead to the exchange bias field (H_EB) tuning in the composite system. This work demonstrates a new composite thin film system with FM-AFM interfacial exchange coupling, which could be applied in various spintronic applications. Full article

(This article belongs to the Special Issue Nanocomposite Thin Film and Multilayers)

► Show Figures

Figure 1

14 pages, 2185 KiB

Open AccessArticle

Self-Aligned Thin-Film Patterning by Area-Selective Etching of Polymers

by Chao Zhang, Markku Leskelä and Mikko Ritala

Coatings 2021, 11(9), 1124; https://doi.org/10.3390/coatings11091124 - 16 Sep 2021

Cited by 4 | Viewed by 5142

Abstract

Patterning of thin films with lithography techniques for making semiconductor devices has been facing increasing difficulties with feature sizes shrinking to the sub-10 nm range, and alternatives have been actively sought from area-selective thin film deposition processes. Here, an entirely new method is [...] Read more.

Patterning of thin films with lithography techniques for making semiconductor devices has been facing increasing difficulties with feature sizes shrinking to the sub-10 nm range, and alternatives have been actively sought from area-selective thin film deposition processes. Here, an entirely new method is introduced to self-aligned thin-film patterning: area-selective gas-phase etching of polymers. The etching reactions are selective to the materials underneath the polymers. Either O₂ or H₂ can be used as an etchant gas. After diffusing through the polymer film to the catalytic surfaces, the etchant gas molecules are dissociated into their respective atoms, which then readily react with the polymer, etching it away. On noncatalytic surfaces, the polymer film remains. For example, polyimide and poly(methyl methacrylate) (PMMA) were selectively oxidatively removed at 300 °C from Pt and Ru, while on SiO₂ they stayed. CeO₂ also showed a clear catalytic effect for the oxidative removal of PMMA. In H₂, the most active surfaces catalysing the hydrogenolysis of PMMA were Cu and Ti. The area-selective etching of polyimide from Pt was followed by area-selective atomic layer deposition of iridium using the patterned polymer as a growth-inhibiting layer on SiO₂, eventually resulting in dual side-by-side self-aligned formation of metal-on-metal and insulator (polymer)-on-insulator. This demonstrates that when innovatively combined with area-selective thin film deposition and, for example, lift-off patterning processes, self-aligned etching processes will open entirely new possibilities for the fabrication of the most advanced and challenging semiconductor devices. Full article

(This article belongs to the Topic Inorganic Thin Film Materials)

► Show Figures

Figure 1

9 pages, 1977 KiB

Open AccessArticle

Structural Color Control of CoFeB-Coated Nanoporous Thin Films

by Xiaomin Zhu, Cuicui Zhao, Weiwei Zhang, Bo Zhang, Mengtao Sun, Xinhua Chen, Vladimir I. Belotelov and Yujun Song

Coatings 2021, 11(9), 1123; https://doi.org/10.3390/coatings11091123 - 16 Sep 2021

Cited by 7 | Viewed by 2551

Abstract

Unlike color dyes, structural colors only slightly fade during long-term usage. Here, structural colors were controllably achieved by constructing CoFeB photonic crystal layers on the surface of a nanoporous aluminum oxide (AAO) substrate by magnetron sputtering deposition. The resulting material showed a wide [...] Read more.

Unlike color dyes, structural colors only slightly fade during long-term usage. Here, structural colors were controllably achieved by constructing CoFeB photonic crystal layers on the surface of a nanoporous aluminum oxide (AAO) substrate by magnetron sputtering deposition. The resulting material showed a wide visible spectral response and achieved structural color control with a high resolution, high color purity, and saturation. The angle-dependent color changes of CoFeB@AAO films were further investigated by changing the incident light angle. The simulation results of the model are consistent with the experiments, which is significant in practical applications. This strategy may have great potential applications for solid structure color coatings, anti-counterfeiting and security, information storage, and electromagnetic sensors. Full article

(This article belongs to the Special Issue Advances in Nanostructured Thin Films and Coatings)

► Show Figures

Figure 1

12 pages, 9882 KiB

Open AccessArticle

Acceleration of Plasma Nitriding at 550 °C with Rare Earth on the Surface of 38CrMoAl Steel

by Dongjing Liu, Yuan You, Mufu Yan, Hongtao Chen, Rui Li, Lin Hong and Tingjie Han

Coatings 2021, 11(9), 1122; https://doi.org/10.3390/coatings11091122 - 16 Sep 2021

Cited by 8 | Viewed by 2591

Abstract

In order to explore the effect of the addition of rare earth (RE) to a steel microstructure and the consequent performance of a nitrided layer, plasma nitriding was carried out on 38CrMoAl steel in an atmosphere of NH₃ at 550 °C for [...] Read more.

In order to explore the effect of the addition of rare earth (RE) to a steel microstructure and the consequent performance of a nitrided layer, plasma nitriding was carried out on 38CrMoAl steel in an atmosphere of NH₃ at 550 °C for 4, 8, and 12 h. The modified layers were characterized using an optical microscope (OM), a microhardness tester, X-ray diffraction (XRD), a scanning electron microscope (SEM), a transmission electron microscope (TEM), and an electrochemical workstation. After 12 h of nitriding without RE, the modified layer thickness was 355.90 μm, the weight gain was 3.75 mg/cm², and the surface hardness was 882.5 HV_0.05. After 12 h of RE nitriding, the thickness of the modified layer was 390.8 μm, the weight gain was 3.87 mg/cm², and the surface hardness was 1027 HV_0.05. Compared with nitriding without RE, the ε-Fe_2-3N diffraction peak was enhanced in the RE nitriding layer. After 12 h of RE nitriding, La, LaFeO₃, and a trace amount of Fe₂O₃ appeared. The corrosion rate of the modified layer was at its lowest (15.089 × 10⁻² mm/a), as was the current density (1.282 × 10⁻⁵ A/cm²); therefore, the corrosion resistance improved. Full article

(This article belongs to the Special Issue Surface Engineering of C/N/O Functionalized Materials)

► Show Figures

Figure 1

1 pages, 151 KiB

Open AccessErratum

Erratum: Yaragani et al. Structural, Magnetic and Gas Sensing Activity of Pure and Cr Doped In₂O₃ Thin Films Grown by Pulsed Laser Deposition. Coatings 2021, 11, 588

by Veeraswamy Yaragani, Hari Prasad Kamatam, Karuppiah Deva Arun Kumar, Paolo Mele, Arulanandam Jegatha Christy, Kugalur Venkidusamy Gunavathy, Sultan Alomairy and Mohammed Sultan Al-Buriahi

Coatings 2021, 11(9), 1121; https://doi.org/10.3390/coatings11091121 - 16 Sep 2021

Cited by 2 | Viewed by 2422

Abstract

The authors wish to make the following changes to their published paper [...] Full article

(This article belongs to the Special Issue Functional Oxide Thin Films and Nanostructures: Growth, Properties, and Applications)

19 pages, 11467 KiB

Open AccessFeature PaperArticle

Effects of Surface Pretreatment of Titanium Substrates on Properties of Electrophoretically Deposited Biopolymer Chitosan/Eudragit E 100 Coatings

by Łukasz Pawłowski, Michał Bartmański, Aleksandra Mielewczyk-Gryń and Andrzej Zieliński

Coatings 2021, 11(9), 1120; https://doi.org/10.3390/coatings11091120 - 15 Sep 2021

Cited by 13 | Viewed by 3375

Abstract

The preparation of the metal surface before coating application is fundamental in determining the properties of the coatings, particularly the roughness, adhesion, and corrosion resistance. In this work, chitosan/Eudragit E 100 (chit/EE100) were fabricated by electrophoretic deposition (EPD) and both their microstructure and [...] Read more.

The preparation of the metal surface before coating application is fundamental in determining the properties of the coatings, particularly the roughness, adhesion, and corrosion resistance. In this work, chitosan/Eudragit E 100 (chit/EE100) were fabricated by electrophoretic deposition (EPD) and both their microstructure and properties were investigated. The present research is aimed at characterizing the effects of the surface pretreatment of titanium substrate, applied deposition voltage, and time on physical, mechanical, and electrochemical properties of coatings. The coating’s microstructure, topography, thickness, wettability, adhesion, and corrosion behavior were examined. The applied process parameters influenced the morphology of the coatings, which affected their properties. Coatings with the best properties, i.e., uniformity, proper thickness and roughness, hydrophilicity, highest adhesion to the substrate, and corrosion resistance, were obtained after deposition of chit/EE100 coating on nanotubular oxide layers produced by previous electrochemical oxidation. Full article

(This article belongs to the Special Issue Recent Developments of Electrodeposition Coatings II)

► Show Figures

Figure 1

15 pages, 6699 KiB

Open AccessArticle

A Facile Nitriding Approach for Improved Impact Wear of Martensitic Cold-Work Steel Using H₂/N₂ Mixture Gas in an AC Pulsed Atmospheric Plasma Jet

by Jhao-Yu Guo, Yu-Lin Kuo and Hsien-Po Wang

Coatings 2021, 11(9), 1119; https://doi.org/10.3390/coatings11091119 - 15 Sep 2021

Cited by 8 | Viewed by 3272

Abstract

In this study, we propose a rapid plasma-assisted nitriding process using H₂/N₂ mixture gas in an atmospheric pressure plasma jet (APPJ) system to treat the surface of SKD11 cold-working steel in order to increase its surface hardness. The generated NH [...] Read more.

In this study, we propose a rapid plasma-assisted nitriding process using H₂/N₂ mixture gas in an atmospheric pressure plasma jet (APPJ) system to treat the surface of SKD11 cold-working steel in order to increase its surface hardness. The generated NH radicals in the plasma region are used to implement an ion-bombardment for nitriding the tempered martensite structure of SKD11 within 18 min to form the functional nitride layer with an increased microhardness around 1095 HV_0.3. Higher ratios of H/E and H³/E² were obtained for the values of 4.514 × 10⁻² and 2.244 × 10⁻², referring to a higher deformation resistance as compared with the pristine sample. After multi-cycling impact tests, smaller and shallower impact craters with less surface oxidation on plasma-treated SKD11 were distinctly proven to have the higher impact wear resistance. Therefore, the atmospheric pressure plasma nitriding process can enable a rapid thermochemical nitriding process to form a protective layer with unique advantages that increase the deformation-resistance and impact-resistance, improving the lifetime of SKD11 tool steel as die materials. Full article

(This article belongs to the Special Issue Advances in Functional Thin Films: Fabrication, Properties, and Applications)

► Show Figures

Figure 1

25 pages, 42494 KiB

Open AccessArticle

Improved Adsorption of the Antimicrobial Agent Poly (Hexamethylene) Biguanide on Ti-Al-V Alloys by NaOH Treatment and Impact of Mass Coverage and Contamination on Cytocompatibility

by Paula Zwicker, Norman Geist, Elisabeth Göbler, Martin Kulke, Thomas Schmidt, Melanie Hornschuh, Ulrich Lembke, Cornelia Prinz, Mihaela Delcea, Axel Kramer and Gerald Müller

Coatings 2021, 11(9), 1118; https://doi.org/10.3390/coatings11091118 - 15 Sep 2021

Cited by 1 | Viewed by 2714

Abstract

Unlike the native surface of the implant material (Ti6Al4V), oxidation with H₂O₂ leads to increased binding of the effective antimicrobial agent poly(hexamethylene) biguanide [PHMB]. However, treating with NaOH instead results in an even higher PHMB mass coverage. After oxidation with [...] Read more.

Unlike the native surface of the implant material (Ti6Al4V), oxidation with H₂O₂ leads to increased binding of the effective antimicrobial agent poly(hexamethylene) biguanide [PHMB]. However, treating with NaOH instead results in an even higher PHMB mass coverage. After oxidation with H₂O₂, strong differences in the PHMB adsorption capability between polished and corundum-blasted surfaces appear, indicating a roughness dependence. After NaOH treatment, no such effect was observed. The wetting properties of specimens treated with either H₂O₂ or NaOH prior to PHMB exposure clearly varied. To unravel the nature of this interaction, widespread in silico and in vitro experiments were performed. Methods: By X-ray photoelectron spectroscopy, scanning electron microscopy, water contact angle measurements and MD simulations, we characterized the interplay between the polycationic antimicrobial agent and the implant surface. A theoretical model for PHMB micelles is tested for its wetting properties and compared to carbon contaminated TiO₂. In addition, quantitation of anionic functional group equivalents, the binding properties of PHMB with blocked amino end-group, and the ability to bind chlorhexidine digluconate (CHG) were investigated. Ultimately, the capability of osteoblasts to build calcium apatite, and the activity of alkaline phosphatase on PHMB coated specimens, were determined. Results: Simulated water contact angles on carbon contaminated TiO₂ surfaces and PHMB micelle models reveal little influence of PHMB on the wetting properties and point out the major influence of remaining and recovering contamination from ambient air. Testing PHMB adsorption beyond the critical micelle concentration and subsequent staining reveals an island-like pattern with H₂O₂ as compared to an evenly modified surface with NaOH. Both CHG and PHMB, with blocked amino end groups, were adsorbed on the treated surfaces, thus negating the significant influence of PHMB’s terminal groups. The ability of osteoblasts to produce calcium apatite and alkaline phosphatase is not negatively impaired for PHMB mass coverages up to 8 μg/specimen. Conclusion: Differences in PHMB adsorption are triggered by the number of anionic groups and carbon contaminants, both of which depend on the specimen pre-treatment. With more PHMB covering, the implant surface is protected against the capture of new contamination from the ambient air, thus building a robust antimicrobial and biocompatible surface coating. Full article

(This article belongs to the Special Issue Surface Modification of Medical Implants)

► Show Figures

Graphical abstract

1 pages, 134 KiB

Open AccessExpression of Concern

Expression of Concern: Hamza et al. A Potential Role of Apelin-13 against Hepatic Injury and Metabolic Disorders in Preeclampsia Induced by L-NAME. Coatings 2021, 11, 391

by Coatings Editorial Office

Coatings 2021, 11(9), 1117; https://doi.org/10.3390/coatings11091117 - 15 Sep 2021

Viewed by 1542

Abstract

Following acceptance of the Special Issue article by the Guest Editor, El-Sayed Abd El-Aziz, concerns were raised regarding the integrity of the peer review process [...] Full article

(This article belongs to the Special Issue Biomedical Application of Natural Plant Extracts)

1 pages, 138 KiB

Open AccessExpression of Concern

Expression of Concern: Hamza et al. Therapeutic and Ameliorative Effects of Active Compounds of Combretum molle in the Treatment and Relief from Wounds in a Diabetes Mellitus Experimental Model. Coatings 2021, 11, 324

by Coatings Editorial Office

Coatings 2021, 11(9), 1116; https://doi.org/10.3390/coatings11091116 - 15 Sep 2021

Cited by 6 | Viewed by 1914

Abstract

Following acceptance of the Special Issue article by the Guest Editor, El-Sayed Abd El-Aziz, concerns were raised regarding the integrity of the peer review process [...] Full article

(This article belongs to the Special Issue Biomedical Application of Natural Plant Extracts)

Journal Menu

Journal Browser

Coatings, Volume 11, Issue 9 (September 2021) – 134 articles

Further Information

Guidelines

MDPI Initiatives

Follow MDPI