Editor’s Choice Articles

The effect of artificial ageing on spruce (Picea abies), beech (Fagus sylvatica L.), birch (Betula pendula), and sessile oak (Quercus petraea) wood surfaces were investigated using qualitative (total phenolic and total soluble carbohydrate content) chemical examination methods. During ageing (∑240h), the influence of surface chemistry modifications was monitored by contact angle measurements of polar, dispersive (distilled water), and dispersive (diiodomethane) liquids. The results clearly show the relation between the ratio of main chemical components of the wood surface layer and surface wettability during artificial radiation. The identified surface chemistry modifications cause more significant change in the contact angle of polar and dispersive liquid, relative to the change of dispersive liquid contact angle. Chemical changes of the wood surface layer are due to the degradation of the main wood components (cellulose, hemicelluloses, and lignin) which can be properly monitored by total phenolic (TPC) and total soluble carbohydrate content (TSCC) measurements. Full article

Surface modification is an effective way to improve the hemocompatibility of biomaterials. Quercetin has significant anticoagulation and antithrombotic effects, and thus it is a promising candidate agent for the surface modification of blood-contacting materials. In this study, quercetin was successfully encapsulated in tripolyphosphate–chitosan nanoparticles (TCs) based on the ionic gelation of chitosan with tripolyphosphate (TPP) anions. Then, hyaluronan acid (HA)/quercetin-loaded TPP–chitosan nanoparticle (QTCs) films, in addition to HA/TCs films, were prepared separately using an electrostatic layer-by-layer self-assembly technique. The encapsulation of quercetin in the chitosan nanoparticles was confirmed by UV spectra. The quercetin-loaded multilayer coatings were also successfully self-assembled, as confirmed by the UV spectra and contact angle measurements. Platelet adhesion experiments were carried out with platelet-enriched plasma so as to evaluate the blood compatibility of the different samples. There were many platelets on the surfaces of the glass and HA/TC-coated titanium, which were partially activated but not aggregated. Meanwhile, many more platelets were observed on the uncoated titanium surfaces, most of which developed pseudopodia. By contrast, the platelet adhesion and activation were reduced remarkably on the surface of the HA/QTC-coated titanium. These results showed that the multilayer coatings containing quercetin could act as potential biomaterials to improve the anticoagulation performance of blood-contacting materials. Full article

The surface treatment of titanium implants has been applied mainly to increase surface bioactivity and, more recently, to introduce antibacterial properties. To this end, composite coatings have been investigated, particularly those based on hydroxyapatite. The present research was aimed at the development of another coating type, chitosan–nanosilver, deposited on a Ti13Zr13Nb alloy. The research comprised characterization of the coating’s microstructure and morphology, time-dependent nanosilver dissolution in simulated body fluid, and investigation of the nanomechanical properties of surface coatings composed of chitosan and nanosilver, with or without a surface-active substance, deposited at different voltages for 1 min on a nanotubular TiO₂ layer. The microstructure, morphology, topography, and phase composition were examined, and the silver dissolution rate in simulated body fluid, nanoscale mechanical properties, and water contact angle were measured. The voltage value significantly influenced surface roughness. All specimens possessed high biocompatibility. The highest and best adhesion of the coatings was observed in the absence of a surface-active substance. Silver dissolution caused the appearance of silver ions in solution at levels effective against bacteria and below the upper safe limit value. Full article

Increasing demands for environmental accountability and energy efficiency in industrial practice necessitates significant modification(s) of existing technologies and development of new ones to meet the stringent sustainability demands of the future. Generally, development of required new technologies and appropriate modifications of existing ones need to be premised on in-depth appreciation of existing technologies, their limitations, and desired ideal products or processes. In the light of these, published literature mostly in the past 30 years on the sealing process; the second highest energy consuming step in aluminum anodization and a step with significant environmental impacts has been critical reviewed in this systematic review. Emphasis have been placed on the need to reduce both the energy input in the anodization process and environmental implications. The implications of the nano-porous structure of the anodic oxide on mass transport and chemical reactivity of relevant species during the sealing process is highlighted with a focus on exploiting these peculiarities, in improving the quality of sealed products. In addition, perspective is provided on plausible approaches and important factors to be considered in developing sealing procedures that can minimize the energy input and environmental impact of the sealing step, and ensure a more sustainable aluminum anodization process/industry. Full article

This study investigated the characteristics of an indirect-type hybrid X-ray detector with a conjugated polymer poly(3-hexylthiophene) (P3HT) and CdSe quantum dot (QD) blended active layer. To improve detection sensitivity, the optimal blending ratio of P3HT:CdSe QDs, ligand exchange effect, and optimal process condition of the active layer were examined. The detector with a P3HT:CdSe QDs = 1:5 blended active layer showed the highest collected charge density (CCD) and highest sensitivity under X-ray irradiation. The replacement of a trioctylphosphine (TOP) ligand by a pyridine ligand effectively assisted the charge transport and reduced the QD aggregation, increasing the detection sensitivity of the detector by 75% after the ligand exchange. To further improve the sensitivity of the proposed detector, the optimized process conditions of the active layer were studied. The sensitivity of the detector with an active layer of about 80 nm thickness formed by a double-coating method showed the highest CCD of 62.5 nA/cm², and the highest sensitivity of 0.14 mA/Gy∙cm². Due to additional pyridine treatment between the double-coating processes, the surface roughness of the active layer decreased, and the CCD and sensitivity subsequently increased. Full article

In this work, polyester/TiO₂ coatings on wood surfaces were prepared in one step via two deposition methods by using an atmospheric pressure plasma jet technique with the aim to further enhance the stabilization of the wood surfaces against UV-radiation and moisture. The first method, based on the combination of plasma spray powder (PSP) coating and liquid precursor plasma spraying (LPPS) coating techniques, used polyester powder and titanium tetraisopropoxide (TTIP) liquid precursor as feedstock. In the second method, the polyester/TiO₂ coatings were prepared by using a mixed powder of polyester micro-particles and TiO₂ nano-particles as feedstock and applied via plasma spray powder coating technique. The surface topology and morphology of the wood samples were observed by scanning electron microscopy (SEM). The SEM results showed the presence of a rough structure after coating with polyester/TiO₂. The surface chemical compositions of the samples were characterized by X-ray photoelectron spectroscopy and by Fourier transform infrared spectroscopy. The wetting behaviour of the coated wood surfaces was studied by measuring the water contact angle. After coating a hydrophilic wood surface with polyester/TiO₂ prepared via (PSP + LPPS), it showed excellent water repellency; the wood surfaces were transformed from hydrophilic to superhydrophobic, while the polyester/TiO₂ coating prepared via (PSP) was hydrophilic. Protection against UV radiation-induced colour changes was determined by UV tests and photo-assisted analysis using the CIELab colour system. The abrasion test results indicated that the polyester-containing films had good abrasion resistance and good adhesion to the wood substrates. Full article

The electrodeposition technique was used to fabricate graphene and Cr particle-reinforced Ni–Cr–graphene coatings. The Rietveld refinement was utilized to analyze the microstructure of Ni deposits in the coatings. The properties including micro-hardness and corrosion behaviors of the coatings were also tested. Results showed that the addition of graphene particles contributed to the dendrite like structure on the surface of the Ni–Cr–graphene coating. The crystallite size and [200] texture of the Ni deposits in the Ni–Cr–graphene coatings were significantly decreased by the graphene particles. The crystallite size of 149.8 nm in the Ni-25–Cr-0–graphene coating was reduced to 35 nm in the Ni-25–Cr-8–graphene coating due to the addition of 8 g/L graphene to the electrolyte. The microstructure evolution of the Ni–Cr–graphene coatings brought about an enhancement in micro-hardness and corrosion resistance of the coatings. The micro-hardness of the coatings was improved from 260.1 HV_0.2 of the pure Ni coating to 285.9 HV_0.2 of the Ni-25–Cr-0–graphene coating and continually to 461.8 HV_0.2 of the Ni-25–Cr-8–graphene coating. In corrosion solution (3.5 wt.% NaCl), the corrosion current (6.22 μA/cm²) of the Ni-25–Cr-0–graphene coating could be decreased by about an order of magnitude through the addition of graphene particles, which was 0.33 μA/cm² for the Ni-25–Cr-8–graphene coating. Full article

To improve the tribological properties of pure MoS₂ coating, the MoS₂–Zr composite lubricating coatings were prepared on the WC/TiC/Co carbide surface utilizing radio frequency magnetron sputtering method combining with multiple arc ion plating technology. The effects of different Zr target currents on the surface morphologies, roughness, Zr content, adhesive force, thickness, microhardness and tribological behaviors of the composite coatings were systematically investigated. Results showed that the properties of MoS₂ coating can be remarkably enhanced through co-deposition of a certain amount of Zr. As the Zr target current increased, the Zr content, surface roughness, thickness, and micro-hardness gradually increased, while the adhesive force of coatings increased first and then decreased. The friction behaviors and wear modes of the composite coatings both varied obviously with the increase of Zr current. The mechanism was mainly attributed to the different components and mechanical properties of the coatings caused by various Zr current. Full article

In this study, we propose and fabricate a perfect absorber on a planar substrate using alternate silicon dioxide and ultrathin metallic lossy chromium (Cr) films. Furthermore, we transfer the absorber to a curved substrate via an optimization design of symmetric structures. The absorber exhibits a highly efficient absorption and large incident-angular tolerance characteristics in the whole visible region. We investigate each layer contribution to the absorption theoretically, and find that ultrathin (~5 nm) lossy Cr films play a dominant absorptive role. Using the effective interface method, we calculate the phase difference on the lossy Cr front surface. It is close to the destructive interference condition, from which we clarify why the proposed structures can produce a highly efficient absorption. Full article

Optical polyimide (PI) membranes have been increasingly attractive in optoelectronic substrate and optical element material applications. Controlled stress distribution is very important to optical PI membrane-based optics. However, nondestructive absolute stress measurement inside optical PI membranes remains challenging. In this letter, we adopted the stress birefringence method to experimentally investigate the correlation between stress and retardation in uniaxially, biaxially, and circularly stretched PI membranes. The calculated value of the photoelastic coefficient was found to be around 400 nm/Mpa·cm. A theoretical model was established where the retardation angle is the negative arctan of the principal stress ratio in the biaxially stretched membrane. We also found that the average retardation angle is an important parameter for evaluating the uniformity of stretching force in the circularly stretched membrane. This work provides a better understanding of the stress birefringence measurement of membrane materials. Full article

A novel approach toward the production of multifunctional printed technical textiles is reported. Three different metal oxides nanoparticles including titanium dioxide, magnesium oxide, and zinc oxide were prepared and characterized. Both natural wool and synthetic acrylic fibers were pretreated with the prepared metal oxide nanoparticles followed by printing using polylactic acid based paste containing acid or basic dyestuffs. Another route was applied via post-treatment of the targeted fabrics with the metal oxide nanoparticles after running the printing process. The color strength (K/S) and colorfastness properties of pretreated and post-treated printed fabrics were evaluated and compared with untreated printed fabrics. The presence of nanoparticles on a fabric surface during the coating process was found to significantly increase the color strength value of the coated textile substrates. The increased K/S value depended mainly on the nature and concentration of the applied metal oxide, as well as the nature of colorant and fabric. In addition, the applied metal oxide nanoparticles imparted the printed fabrics with good antibacterial activity, high ultraviolet protection, photocatalytic self-cleaning, and improved colorfastness properties. Those results suggest that the applied metal oxide-based nanoparticles could introduce ideal multifunctional prints for garments. Full article

Urinary catheters are common medical devices, whose main function is to drain the bladder. Although they improve patients’ quality of life, catheter placement predisposes the patient to develop a catheter-associated urinary tract infection (CAUTI). The catheter is used by pathogens as a platform for colonization and biofilm formation, leading to bacteriuria and increasing the risk of developing secondary bloodstream infections. In an effort to prevent microbial colonization, several catheter modifications have been made ranging from introduction of antimicrobial compounds to antifouling coatings. In this review, we discuss the effectiveness of different coatings in preventing catheter colonization in vitro and in vivo, the challenges in fighting CAUTIs, and novel approaches targeting host–catheter–microbe interactions. Full article

To reduce the fabrication costs while maximizing the superconducting and pinning properties of YBa₂Cu₃O_7−δ (YBCO) nanocomposite films, the drop-on-demand ink-jet printing technique was used to deposit colloidal YBCO inks onto LaAlO₃ substrates. These inks containing preformed HfO₂ nanocrystals were carefully adjusted, prior to the jettability, as the droplet formation depends on the rheological properties of the inks themselves. After carefully adjusting printing parameters, 450-nm thick pristine YBCO films with a self-field critical current density (J_c) of 2.7 MA cm⁻² at 77 K and 500-nm thick HfO₂-YBCO nanocomposite films with a self-field J_c of 3.1 MA·cm⁻² at 77 K were achieved. The final HfO₂-YBCO nanocomposite films contained dispersed BaHfO₃ particles in a YBCO matrix due to the Ba²⁺ reactivity with the HfO₂ nanocrystals. These nanocomposite films presented a more gradual decrease of J_c with the increased magnetic field. These nanocomposite films also showed higher pinning force densities than the pristine films. This pinning enhancement was related to the favorable size and distribution of the BaHfO₃ particles in the YBCO matrix. Full article

The oxidation and corrosion behavior at elevated temperatures of a SiC_F/SiC(N) composite with two plasma-sprayed environmental barrier coating (EBC) systems were studied. After both processes, the formation of a silica-based thermally grown oxide (TGO) layer was observed. The formation of this TGO caused two principal failure mechanisms of the EBC. Firstly, spallation of the EBC induced by stresses from volume expansion and phase transformation to crystalline SiO₂ was observed. Water vapor corrosion of the TGO with gap formation in the top region of the TGO was found to be a second failure mechanism. After a burner rig test of the Al₂O₃-YAG EBC system, this corrosion process was observed at the TGO surface and in the volume of the Al₂O₃ bond coat. In the case of the second system, Si-Yb₂Si₂O₇/SiC-Yb₂SiO₅, the formation of the TGO could be delayed by introducing an additional intermediate layer based on Yb₂Si₂O₇ filled with SiC particles. The SiC particles in the intermediate layer were oxidized and served as getter to reduce the permeation of oxidants (O₂, H₂O) into the material. In this way, the formation of the TGO and the failure mechanisms caused by their formation and growth could be delayed. Full article

This work reviewed innovative wood surface treatments based on nanotechnology. It is well documented in the literature that the cell walls of wood present significant porosity; this porosity is on a molecular scale. The main reason for the use of nanotechnology in wood science and technology is the unique characteristic of nano-based materials to effectively penetrate deeply into wood substrates, which, in turns, results in the alteration of their surface chemistry. This subsequently causes an improvement in wood properties. Any potential change in the wood properties due to treatment with nanomaterials is based on the higher interfacial area which is developed due to the treatment. This occurs because the number of particles is significantly reduced to the nanoscale. The nanomaterials improve the properties of wood as a raw material and alter its original features to a limited extent. However, their potential impact on both health and the environment should be addressed by applying tools such as life-cycle assessments. This will avoid mistakes being made in which new technologies are released on the market prior to an impact assessment having been carried out. Full article

The formation of an ordered surface texture with micro and nanometer features on Ti/Zr multilayers is studied for better understanding and improvement of cell integration. Nanocomposite in form 30×(Ti/Zr)/Si thin films was deposited by ion sputtering on Si substrate for biocompatibility investigation. Surface texturing by femtosecond laser processing made it possible to form the laser-induced periodic surface structure (LIPSS) in each laser-written line. At fluence slightly above the ablation threshold, beside the formation of low spatial frequency-LIPSS (LSFL) oriented perpendicular to the direction of the laser polarization, the laser-induced surface oxidation was achieved on the irradiated area. Intermixing between the Ti and Zr layers with the formation of alloy in the sub-surface region was attained during the laser processing. The surface of the Ti/Zr multilayer system with changed composition and topography was used to observe the effect of topography on the survival, adhesion and proliferation of the murine mesenchymal stem cells (MSCs). Confocal and SEM microscopy images showed that cell adhesion and their growth improve on these modified surfaces, with tendency of the cell orientation along of LIPSS in laser-written lines. Full article

The article presents selected properties of a titanium metallization coating deposited on aluminum nitride (AlN) ceramics surface by means of the friction surfacing method. Its mechanism is based on the formation of a joint between the surface of an AlN ceramics substrate and a thin Ti coating, involving a kinetic energy of friction, which is directly converted into heat and delivered in a precisely defined quantity to the resulting joint. The largest effects on the final properties of the obtained coating include the high affinity of titanium for oxygen and nitrogen and a relatively high temperature for the deposition process. The titanium metallization coating was characterized in terms of surface stereometric structure, thickness, surface morphology, metallographic microstructural properties, and phase structure. The titanium coating has a thickness ranging from 3 to 7 μm. The phase structure of the coating surface (XPS investigated) is dominated by TiN_xO_y with the presence of TiO_x, TiN, metallic Ti, and AlN. The phase structure deeper below the surface (XRD investigated) is dominated by metallic Ti with additional AlN particles originating from the ceramic substrate due to friction by titanium tools. Full article

In this paper, a new semiempirical probability model, allowing for prediction of the composition of multimaterial cold spray coating in dependence on the initial percentage of blend components, is developed and applied. The proposed modeling approach takes into account the deposition efficiencies and the particle sizes of each component of the spraying powder blend. The experimental validation using several Cu/Cr₂C₃NiCr mixtures with different percentages of copper and cermet powders showed that the simulation results were in a good agreement with the experimental data. It was demonstrated that the deposition efficiency of the Cr₂C₃NiCr cermet powder strongly decreased when its mass percentage in the Cu/Cr₂C₃NiCr mixture increased from 5% to 75%. It was also shown that the dependence of the Cr₂C₃NiCr content in the coating on the initial percentage in the blend was nonlinear and the standard rule of mixtures was not applicable for prediction of copper–cermet coating composition. Full article

Friction stir processing (FSP) has evolved as an important technique in fabrication of metal matrix composites. The surface properties enhancement is obtainable by insertion of desired discontinuous particular reinforcements into base alloy using FSP. Despite having high specific strength, more applications of Al alloys are restricted due to their poor surface properties under various loading conditions. In this study, the main focus is on enhancing the microhardness and wear properties of Al 7075 base alloy by means of uniform dispersion of silicon carbide and graphite (SiC/Gr) nano particles into the base alloy using the FSP technique. The tool rotational speed (w: 500, 1000, 1500 rpm), tool traverse speed (v: 20, 30, 40 mm/min), reinforcement particles hybrid ratio (HR: 60:40, 75:25, 90:10) and volume percentage (vol%: 4%, 8%, 12%) are used as independent parameters. The effect of these parameters on microstructure, micro hardness and wear properties of surface composites are studied in detail. For desired wear rate and microhardness as responses, the aforementioned independent parameters are optimized using response surface methodology (RSM). The significance of factors and their interactions for maximizing hardness and minimizing wear rate and coefficient of friction (COF) were determined. Analysis of variance (ANOVA) for responses has been carried out, and the models were found to be significant in all three responses. The minimum wear rate of 0.01194 mg/m was obtained for parameters w 1500 rpm, v 40 mm/min, HR 60:40, vol% 4 (Run 10). The maximum micro hardness of 300 HV obtained for parameters w 1000 rpm, v 30 mm/min, HR 75:25, vol% 12 (Run 14). The presence and uniform distribution of SiC and Gr into the base alloy was confirmed through field-emission scanning electron microscopy (FESEM) imaging, energy-dispersive X-ray spectroscopy (EDX) and mapping tests. The wear rate and COF decreased significantly due to graphitized mechanically mixed layer developed at the sliding contacts. The microhardness of resultant composites observed to be dependent on effect of the independent parameters on extent of inherent precipitates dissolution and grain size strengthening in the resultant materials. Full article

Vertically aligned carbon nanotube arrays (VACNTs) have many excellent properties and show great potential for various applications. Recently, there has been a desire to grow VACNTs on nonplanar surfaces and synthesize core-sheath-structured VACNT–inorganic hybrids. To achieve this aim, atomic layer deposition (ALD) has been extensively applied, especially due to its atomic-scale thickness controllability and excellent conformality of films on three-dimensional (3D) structures with high aspect ratios. In this paper, the ALD of catalyst thin films for the growth of VACNTs, such as Co₃O₄, Al₂O₃, and Fe₂O₃, was first mentioned. After that, the ALD of thin films for the synthesis of VACNT–inorganic hybrids was also discussed. To highlight the importance of these hybrids, their potential applications in supercapacitors, solar cells, fuel cells, and sensors have also been reviewed. Full article

The paper presents the investigation of a series of silver-incorporated diamond-like carbon (Ag-DLC) coatings with increasing Ag content on Ti50Zr and deposited using high voltage anodic plasma (HVAP). The coatings surface properties were analyzed with scanning electron microscope (SEM), atomic force microscope (AFM), and contact angle determinations. Electrochemical tests were performed in Afnor artificial saliva and evaluated by potentiodynamic polarization and electrochemical impedance spectroscopy. Based on these properties, comparisons of coatings performance were linked with the amount of deposited Ag. Increasing the Ag content led to the increase of the corrosion resistance and to the decrease of the forces exhibited on the surface. The hydrophobic character of the coating with the highest Ag amount could prevent thrombosis, thus suggesting its possible use for medical implants. Full article

Dealing with waste materials, particularly hazardous waste, is a serious problem. Disposal areas keep growing, and the costs incurred are high. Disposing of such waste reduces negative environmental impacts and offers considerable financial savings. This paper focuses on the possibilities of incorporating pollutants found in hazardous wastes as fillers in coatings based on polymers (epoxide and polyurethane). These coatings are intended mainly for concrete and metal bases and offer secondary protection against adverse weather conditions. Important physical and mechanical properties of the newly developed materials were determined; they include surface hardness, impact resistance, tensile properties, and chemical resistance. These properties were also compared to those of the reference filler. At the same time, the influence of aggressive media on the properties of these materials was observed, in particular on flexural characteristics. The microstructures of the developed coatings were tested using a high-resolution optical microscope, before and after exposure to the chemicals. The positive effect of using progressive fillers, such as solidified hazardous waste (a solidification product (SF)), was witnessed by their constructive contribution to the materials’ physical and mechanical properties. The use of solidification products is unambiguously advantageous from technical, ecological, and economical stand points (utilization of hazardous waste as a progressive filler instead of landfilling, improvement of tensile properties, reduction in the price of coating system, and incorporation of the pollutants into the polymer matrix). Full article

The thermoelectric properties of In−Sn−O (ITO) thin films were estimated in relation to microstructures with various zinc concentrations. The zinc-doped ITO (ITO:Zn) thin films were amorphized with increasing zinc concentration. The carrier density (n) of the thin films decreased as the zinc content increased, which could be attributed to a decline in oxygen vacancies. The highest Seebeck coefficient (S, 64.91 μV/K) was obtained with an ITO film containing 15.33 at.% of Zn due to the low n value, which also exhibited the highest power factor (234.03 μW K⁻² m⁻¹). However, the highest thermoelectric figure of merit value (0.0627) was obtained from the film containing 18.26 at.% of Zn because of both low n and the lowest thermal conductivity (κ) (1.085 W m⁻¹·K⁻¹). The total κ decreased as increasing zinc concentration in the thin films. It was confirmed that the decrease of total κ was dominated by electron κ rather than lattice κ. Full article

In this study, we investigated the luminous properties of undoped cesium iodide (CsI) and Na-doped CsI (CsI:Na) films deposited by thermal vacuum evaporation and treated with different substrate temperatures, post-annealing temperatures, and deposition rates. The quality of the deposited films was evaluated by their XRD pattern, SEM cross-section/surface morphologies and UV/X-ray luminescence, the spectra of which were used to derive the luminescence mechanism of the deposited films. The 310 nm luminescence demonstrates that the exciting light arises from the electron–hole recombination through the self-trapped exciton (STE) process, which is characteristic of the host polycrystalline CsI. The broad-band luminescence from ~400 to 450 nm demonstrates the other electron–hole recombination between the new energy states created by doping Na in the forbidden gap of CsI. When we deposited higher quality films at a substrate temperature of 200 °C, the undoped CsI films showed preferred crystal orientation at (200), and the CsI:Na films co-evaporated by 1 wt.% NaI at (310) and had the highest UV/X-ray luminescence. Full article

Au-Pt-Ti/high-k/n-InAlAs metal-oxide-semiconductor (MOS) capacitors with HfO₂-Al₂O₃ laminated dielectric were fabricated. We found that a Schottky emission leakage mechanism dominates the low bias conditions and Fowler–Nordheim tunneling became the main leakage mechanism at high fields with reverse biased condition. The sample with HfO₂ (4 m)/Al₂O₃ (8 nm) laminated dielectric shows a high barrier height ϕ_B of 1.66 eV at 30 °C which was extracted from the Schottky emission mechanism, and this can be explained by fewer In–O and As–O states on the interface, as detected by the X-ray photoelectron spectroscopy test. These effects result in HfO₂ (4 m)/Al₂O₃ (8 nm)/n-InAlAs MOS-capacitors presenting a low leakage current density of below 1.8 × 10⁻⁷ A/cm² from −3 to 0 V at 30 °C. It is demonstrated that the HfO₂/Al₂O₃ laminated dielectric with a thicker Al₂O₃ film of 8 nm is an optimized design to be the high-k dielectric used in Au-Pt-Ti/HfO₂-Al₂O₃/InAlAs MOS capacitor applications. Full article

We present organic, diamagnetic materials based on structurally simple (hetero-)tolane derivatives. They form crystalline thin-film aggregates that are suitable for Faraday rotation (FR) spectroscopy. The resulting new materials are characterized appropriately by common spectroscopic (NMR, UV-Vis), microscopy (POM), and XRD techniques. The spectroscopic studies give extremely high FR activities, thus making these materials promising candidates for future practical applications. Other than a proper explanation, we insist on the complexity of designing efficient FR materials starting from single molecules. Full article

Natural polymers have been widely investigated for the development of eco-friendly materials. Among these bio-polymers, cactus mucilage is attracting increasing interest regardless of the plant species or the plant organ used for extraction. Mucilage, which is a highly branched heteropolysaccharide, has been previously studied for its chemical composition, structural features, and biotechnological applications. This review highlights the mucilage application in the food packaging industry, by developing films and coatings. These cactus-based biomaterials will be discussed for their functional properties and their potential in preserving food quality and extending shelf life. Full article

Mg-rich primer (MRP) containing aluminum tri-polyphosphate functions via a galvanic mechanism to protect AZ91D alloy from corrosion in the 3 wt % NaCl solution. However, its protective performance can be strongly affected by the testing environment. Therefore, it is important to investigate the performance of the primer on magnesium alloys in an acid rain environment. In the present study, the protective performance of MRP with or without aluminum tri-polyphosphate was investigated via open circuit potential (OCP), electrochemical impedance spectroscopy (EIS), scanning electronic microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) in the simulated acid rain. Compared to the primer without aluminum tri-polyphosphate, the MRP containing aluminum tri-polyphosphate pigments exhibited better protective performance in the simulated acid rain condition. In the initial stage, the acidic condition prompted the aluminum tri-polyphosphate pigments to release phosphates and H⁺ to form magnesium phosphates on Mg particles, retarding their consumption rate. The Mg-rich primer with aluminum tri-polyphosphate can provide cathodic protection to AZ91D alloy for about 49 days in the simulated acid rain solution. Simultaneously, the corrosion products of Mg particles, magnesium oxides and phosphates, precipitated on the Mg particles and improved the stability of the primer. In addition, a protective film, consisting of magnesium oxides and phosphates, formed on the AZ91D substrate. Consequently, all these factors contributed to the long cathodic protection and improved corrosion resistance of MRP containing aluminum tri-polyphosphate in the simulated acid rain. Full article

Mn/acetylacetone chelate was synthesized using Mn(CH₃COO)₂·4H₂O as raw material, methanol as the solvent, and acetylacetone as the chelating agent. The ultraviolet (UV)-absorption peak of the synthesized chelate was found around 298 nm. CaMn₇O₁₂ sol was subsequently prepared using the Mn/AcAc chelate as the Mn source and calcium nitrate as the calcium source. The UV test indicates that the CaMn₇O₁₂ sol has the UV-sensitive characteristics. Owing to its photo-sensitivity, micro-patterned CaMn₇O₁₂ ceramic film can be prepared without photoresist, only through dip-coating, drying, UV-irradiation, solvent-washing, and heat treatment. The magnetic test result indicates that the micro-patterned CaMn₇O₁₂ ceramic film has a saturation magnetization of 112.8 emu/cm³, which is close to that of non-patterned CaMn₇O₁₂ ceramic film. Full article

Co-based coating was prepared by plasma cladding on FV520B substrates. Microstructure of the coatings was observed by scanning electron microscope. Finite element simulation as a predictive method to research the stress distributed after thermal cycling. Thermal fatigue resistance of the coating-substrate was evaluated at temperature of 600 °C, 700 °C, 800 °C, and 900 °C. Results indicate that the surface/interface structure has excellent thermal fatigue resistance at 600 °C, and the thermal fatigue crack initiated near the interface and extended along the grain boundary. The difference of expansion coefficient of the coating and substrate is small near 600 °C, and the difference increased when the temperature climbed above 600 °C. The diffuse elements could be found near the interface after the thermal cycle, and the dislocations and precipitated phase were observed. Full article

Micropitting is a typical surface contact fatigue in rolling–sliding contact. The kinematic sliding is of great significance in the initiation and progression of micropitting. A numerical surface fatigue model considering rolling–sliding contact and surface evolution is developed based on mixed-EHL (elastohydrodynamic lubrication) theory, rainflow cycle counting method and Archard’s law. Surface evolution is evaluated using Archard’s wear law based on measured teeth surface topography. Surface damage is determined via the Palmgren–Miner line rule and Goodman diagrams. The effect of rolling speed and surface roughness are discussed in detail. Results show that stress micro-cycles are introduced by rough sliding in the rolling–sliding contact. The mild wear reduces the height of asperities, the maximum pressure and alleviates subsurface stress concentration. For rolling–sliding contact, the faster moving surface dominates the composite height of asperities, then decides the fluctuations of pressure, as well as stress ranges. The combination of surface topography should be considered in the surface design. Full article

The effect of rare earth oxides on the microstructure and corrosion behavior of laser-cladding coating on 316L stainless steel was investigated using hardness measurements, a polarization curve, electrochemical impedance spectroscopy (EIS), a salt spray test, X-ray diffraction, optical microscopy, and scanning electron microscopy (SEM). The results showed that the modification of rare earth oxides on the laser-cladding layer caused minor changes to its composition but refined the grains, leading to an increase in hardness. Electrochemical and salt spray studies indicated that the corrosion resistance of the 316L stainless steel could be improved by laser cladding, especially when rare earth oxides (i.e., CeO₂ and La₂O₃) were added as a modifier. Full article

High-temperature durable mirrors based on a protected silver sputter coating are attractive for secondary reflector applications in concentrated solar thermal power plants. In this paper, silver films are deposited by high-power impulse magnetron sputtering (HiPIMS) and standard direct current (DC) magnetron sputtering, either as exposed discretely deposited films or in-sequence-deposited thin film systems, where the silver is protected and embedded between adhesion and barrier layers. The unprotected silver films and equivalent protected silver thin film systems are compared and characterized as deposited and after 400 °C oven temperature exposure. The reflectance is measured and grazing incident X-ray diffraction (GIXRD) and scanning electron microscopy (SEM) pictures were taken. The HiPIMS silver film, sputtered with a peak current of 200 A and an approximately equivalent average power density to the DC magnetron sputtered silver, exhibits higher reflectance (and conductivity). Increasing the power density further, yields silver films with lower reflectance, correlating to a reduced grain size. In the protected silver film system, the reflectance does not improve, due to the presence of a less reflective top adhesion layer. The protected film system, with the 200 A HiPIMS, is, however, more durable at 400 °C than the DC magnetron sputtered equivalent. Full article

In this study, a low concentration (10 μg·mL⁻¹) of poly(N-vinylpyrrolidone) (PVP)-coated silver nanoparticles (AgNPs) were deposited by spray and exhaustion (30, 70 and 100 °C) methods onto untreated and dielectric barrier discharge (DBD) plasma-treated polyamide 6,6 (PA66) fabric. DBD plasma-treated samples showed higher AgNP deposition than untreated ones for all methods. After five washing cycles, only DBD plasma-treated samples displayed AgNPs on the fabric surface. The best-performing method was exhaustion at 30 °C, which exhibited less agglomeration and the best antibacterial efficacy against S. aureus (4 log reduction). For E. coli, the antimicrobial effect showed good results in all the exhaustion samples (5 log reduction). Considering the spray method, only the DBD plasma-treated samples showed some bacteriostatic activity for both strains, but the AgNP concentration was not enough to have a bactericidal effect. Our results suggest DBD plasma may be a low cost and chemical-free method for the preparation of antibacterial textiles, allowing for the immobilization of a very low—but effective—concentration of AgNPs. Full article

Long-term packaging of miniaturized, flexible implantable medical devices is essential for the next generation of medical devices. Polymer materials that are biocompatible and flexible have attracted extensive interest for the packaging of implantable medical devices, however realizing these devices with long-term hermeticity up to several years remains a great challenge. Here, polyimide (PI) based hermetic encapsulation was greatly improved by atomic layer deposition (ALD) of a nanoscale-thin, biocompatible sandwich stack of HfO₂/Al₂O₃/HfO₂ (ALD-3) between two polyimide layers. A thin copper film covered with a PI/ALD-3/PI barrier maintained excellent electrochemical performance over 1028 days (2.8 years) during acceleration tests at 60 °C in phosphate buffered saline solution (PBS). This stability is equivalent to approximately 14 years at 37 °C. The coatings were monitored in situ through electrochemical impedance spectroscopy (EIS), were inspected by microscope, and were further analyzed using equivalent circuit modeling. The failure mode of ALD Al₂O₃, ALD-3, and PI soaking in PBS is discussed. Encapsulation using ultrathin ALD-3 combined with PI for the packaging of implantable medical devices is robust at the acceleration temperature condition for more than 2.8 years, showing that it has great potential as reliable packaging for long-term implantable devices. Full article

A six-channel fan-shaped integrated narrow-band filter on a silicon substrate was designed on the basis of the Fabray–Perot (FP) theory and was fabricated using e-beam thermal evaporation. The central wavelength was modulated by modifying the FP cavity thickness using the combination mask method. Germanium and zinc sulfide were selected as the high and low refractive index film materials, respectively. Its average peak transmission reached 83.3%, the cut-off transmittance was less than 1%, and the full width at half maximum (FWHM) changed from 55 and 94 nm, and the central wavelength positioning accuracy error was less than 0.35%. Furthermore, transmittance was also calculated inversely, using the thickness of each layer of films, in order to deduce the reason of the decrease in peak transmittance. Thickness deviation of each layer and interface scattering contributed to the decrease of peak transmittance. Compared with the same type of products in the market, our filter showed better properties than that of some published and commercial filter. Full article

Titanium nitride (TiN) coating has been used in various application as it gives excellent performance in many aspects. It has been proven to prolong machining tool life since the mid-1960s. Industrial deposition processes of TiN, including magnetron sputtering, arc ion plating, and chemical vapor depositions, have their individual advantages and limitations. Due to the rising demands of the dry machining technique, the massive amount of heat generated from the friction of cutting tools against the surface of a work piece has become the main issue to overcome. Oxidation of TiN, which occurs around 400 °C, puts a limit on the applications of the coatings. Comparing TiN tool coatings deposited by arc evaporation, the novel high-power impulse magnetron sputtering (HiPIMS) technology provides smoother film surface, denser structure and subsequent corrosion resistance. Therefore, this research aims to investigate the wear behavior of TiN thin film deposited by HiPIMS at high temperature. The influences of the coating properties on the wear resistance of coatings at high temperature are also investigated. The results show that the HiPIMS technique enables a denser epitaxial-grown TiN coating with higher surface hardness and adhesion in contrast with TiN coating deposited using direct current (DC) magnetron sputtering techniques, which provides a higher wear resistance. Full article

The rising rate of individuals with chronic kidney disease (CKD) and ineffective treatment methods for catheter-associated infections in dialysis patients has led to the need for a novel approach to the manufacturing of catheters. The current process requires moulding, which is time consuming, and coated catheters used currently increase the risk of bacterial resistance, toxicity, and added expense. Three-dimensional (3D) printing has gained a lot of attention in recent years and offers the opportunity to rapidly manufacture catheters, matched to patients through imaging and at a lower cost. Fused deposition modelling (FDM) in particular allows thermoplastic polymers to be printed into the desired devices from a model made using computer aided design (CAD). Limitations to FDM include the small range of thermoplastic polymers that are compatible with this form of printing and the high degradation temperature required for drugs to be extruded with the polymer. Hot-melt extrusion (HME) allows the potential for antimicrobial drugs to be added to the polymer to create catheters with antimicrobial activity, therefore being able to overcome the issue of increased rates of infection. This review will cover the area of dialysis and catheter-related infections, current manufacturing processes of catheters and methods to prevent infection, limitations of current processes of catheter manufacture, future directions into the manufacture of catheters, and how drugs can be incorporated into the polymers to help prevent infection. Full article

Residual stress in coatings often affects the service performance of coatings, and the residual stresses in some local areas even lead to premature failure of coatings. In this work, we characterized the residual stress of local micro-areas of a nanocrystalline Cr₂O₃ coating deposited on a Si wafer through micro-Raman spectroscopy, including the depositional edge zone where the electrode was placed, the micro-area containing Cr₂O₃ macroparticles, and other micro-areas vulnerable to cracks. To accurately measure the thickness of the coating, we combined optical interferometry and direct measurement by a profilometer. The results indicate the existence of in-plane tensile residual stress on the Cr₂O₃ coating. In thick coatings, the residual stress is independent of the coating thickness and is stable between 0.55 GPa and 0.75 GPa. As the coating thickness is less than 0.8 μm, the residual stress is directly related to the coating thickness. This in-plane tensile stress is considered as the origin of the observed microcrack, which can partially release the stress. Full article

In this research, silica nano-particles are deposited over the borosilicate glass and silicon wafer substrates by indigenously developed Aerosol impact deposition assembly using SiH₄, oxygen, and helium as precursors. The coating process involves deionization of gases leading towards nucleation sites for silica in the presence of plasma, while tuning the pressure difference between reaction and deposition chamber controls the coating thickness, porosity, and refractive index. The deposited coating layer on the substrate enhanced the transmittance to 99.6% at 600 nm wavelength. The induced porous nature and the graded index of the coated layer as observed from the AFM and SEM resulted in superhydrophilic behavior with a water contact angle of near to 0°. The super-hydrophilicity of the coating contains self-cleaning properties, suggesting an improvement of the performance of solar PV modules as well. Full article

An ecological ammonium thiocyanate (NH₄SCN)-modified geopolymeric coating was facilely prepared for flame-retarding plywood. The effect of NH₄SCN on the flame resistance was preliminarily investigated using cone calorimeter (CC), scanning electron microscope (SEM), X-ray diffraction (XRD), and thermal gravimetry (TG). The results show that 1 wt.% NH₄SCN as dopant is of paramount importance to generate a compact and continuous coating. The formation of a smooth, intact, and uniform-swelling siliceous layer during combustion facilitates enhanced fire resistance, evidenced by the increased fire performance index (FPI), reduced fire growth index (FGI), and 39.7% decreased value of peak heat release rate (pHRR), in comparison to those of the sample without NH₄SCN. Because of the reducibility of O₂-consuming NH₄SCN, the compact shielding-layer containing carbonate and sulfate, as well as the release of NH₃, the NH₄SCN-modified geopolymeric coating exerts an enhancement on the flame-retardant efficiency. Full article

The plasma spray–physical vapor deposition (PS–PVD) process has received considerable attention due to its non-line of sight deposition ability, high deposition rates, and cost efficiency. Compared with electron beam–physical vapor deposition (EB–PVD), PS–PVD can also prepare thermal barrier coatings (TBCs) with columnar microstructures. In this paper, yttria-stabilized zirconia (YSZ) coatings were fabricated by PS–PVD. Results showed that the as-deposited coating presented a typical columnar structure and was mainly composed of metastable tetragonal (t′-ZrO₂) phase. With thermal exposure, the initial t′ phase of YSZ evolved gradually into monoclinic (m-ZrO₂) phase. Significant increase in hardness (H) and the Young’s modulus (E) of the coating was attributed to the sintering effect of the coating during the thermal exposure, dependent on exposure temperature and time. However, the values of H and E decreased in the coatings thermally treated at 1300–1500 °C for 24 h, which is mainly affected by the formation of m-ZrO₂ phase. Full article

In the present paper, the influence of self-mated friction materials on the tribological properties of hydrogenated amorphous silicon films (a-Si:H films) is studied systemically at high temperature. The results are obtained by comparing the tribological properties of a-Si:H films under different friction pair materials and temperatures. The a-Si:H films exhibit super-low friction of 0.07 at a temperature of 600 °C, and ceramic materials are appropriate for anti-friction behaviors of a-Si:H films at high temperature. The results of tribotests and observations of the fundamental friction mechanism show that super-low friction of a-Si:H films and ceramic materials of the friction system are involved in high temperature oxidation; this also applies to the tribochemical reactions of a-Si:H films, steel and iron silicate in open air at elevated temperature in the friction process. Full article

A self-healing coating with UV-shielding property was prepared in this paper. The self-healing property was based on the inclusion between a host (β-CD-TiO₂) and a guest HEMA-Ad). After inclusion of the host and guest, the host–guest complex (HEMA-Ad/β-CD-TiO₂) was polymerized with other reactive monomers (HEMA and BA) to obtain the final coating. The coating had good hydrophobicity (water contact angle >90°, moisture absorption rate <2%) and excellent UV-shielding performance (ultra-violet protect factor >90%), and could be firmly bonded to a soft substrate. In addition, the coating had good self-healing property, which means that cracks in the material can recover many times after being damaged and that the UV-shielding ability can be fully restored with the self-healing process. Full article

It is important to detect the surface and/or subsurface cracks in coatings because the cracks usually indicate the failure of the system. Conventional detection techniques face two main challenges. One is the locating of the shallow cracks or defects in thin coatings. The other is the detection of the vertical cracks. Conventional infrared thermography can efficiently detect the horizontal cracks or defects. However, when locating the shallow cracks, it requires a high sampling frequency which is unrealistic for most of the infrared cameras. In terms of the vertical cracks, it is invalid since the propagation of its detecting signal is parallel to the cracks and does not interact with them. We introduce a new grating thermography method to overcome the two difficulties. In this paper we mainly illustrate its fundamental principle, which is validated by numerical simulations and a simple experiment. Overall, the principle analysis shows that grating thermography is highly effective in detecting cracks in coatings. Full article

Bioactive Plasma Electrolytic Oxidation (PEO) coatings enriched in Ca, P and F were developed on Mg0.6Ca and Mg0.6Ca2Ag alloys with the aim to impede their fast degradation rate. Different characterization techniques (SEM, TEM, EDX, SKPFM, XRD) were used to analyze the surface characteristics and chemical composition of the bulk and/or coated materials. The corrosion behaviour was evaluated using hydrogen evolution measurements in Simulated Body Fluid (SBF) at 37 °C for up to 60 days of immersion. PEO-coated Mg0.6Ca showed a 2–3-fold improved corrosion resistance compared with the bulk alloy, which was more relevant to the initial 4 weeks of the degradation process. In the case of the Mg0.6Ag2Ag alloy, the obtained corrosion rates were very high for both non-coated and PEO-coated specimens, which would compromise their application as resorbable implants. The amount of F⁻ ions released from PEO-coated Mg0.6Ca during 24 h of immersion in 0.9% NaCl was also measured due to the importance of F⁻ in antibacterial processes, yielding 33.7 μg/cm², which is well within the daily recommended limit of F⁻ consumption. Full article

This work investigates environmentally friendly alternatives to toxic and carcinogenic Cr (VI)-based surface treatments for aluminium alloys. It is focused on multifunctional thin or flash plasma electrolytic oxidation (PEO)-layered double hydroxides (LDH) coatings. Three PEO coatings developed under a current-controlled mode based on aluminate, silicate and phosphate were selected from 31 processes (with different combinations of electrolytes, electrical conditions and time) according to corrosive behavior and energy consumption. In situ Zn-Al LDH was optimized in terms of chemical composition and exposure time on the bulk material, then applied to the selected PEO coatings. The structure, morphology and composition of PEO coatings with and without Zn-Al-LDH were characterized using XRD, SEM and EDS. Thicker and more porous PEO coatings revealed higher amounts of LDH flakes on their surfaces. The corrosive behavior of the coatings was studied by electrochemical impedance spectroscopy (EIS). The corrosion resistance was enhanced considerably after the PEO coatings formation in comparison with bulk material. Corrosion resistance was not affected after the LDH treatment, which can be considered as a first step in achieving active protection systems by posterior incorporation of green corrosion inhibitors. Full article

Starch–gellan (80:20) coating formulations were applied to apples and persimmons to analyse their effectiveness controlling the weight loss, respiration rate, fruit firmness, and fungal decay during postharvest. Thyme essential oil (EO) was incorporated (0.25 and 0.5 g per g of polymer) directly or encapsulated in lecithin to enhance antifungal action. Coatings did not reduce weight loss or firmness changes in apples, but they prevented water loss in persimmons. In contrast, no significant effect of the coatings was observed on the respiration rates and the respiration quotient of persimmons, whereas the respiration rates and quotient was increased in apples. On the other hand, the coatings without lecithin reduced the incidence and severity of black spot caused by Alternaria alternata in persimmons, regardless of the content of essential oil. Likewise, these reduced the severity of gray mold caused by Botrytis cinerea in apples. No positive effect of lecithin in coatings was observed on the postharvest quality and decay in either apples or persimmons, nor did EO exert antifungal action despite its proven effectiveness in in vitro tests. Full article

Infiltration of molten calcium–magnesium–alumina–silicates (CMAS) through thermal barrier coatings (TBCs) causes structural degradation of TBC layers. The infiltration kinetics can be altered by careful tailoring of the electron beam physical vapor deposition (EB-PVD) microstructure such as feather arm lengths and inter-columnar gaps, etc. Morphology of the feathery columns and their inherent porosities directly influences the infiltration kinetics of molten CMAS. To understand the influence of columnar morphology on the kinetics of the CAMS flow, a finite element based parametric model was developed for describing a variety of EB-PVD top coat microstructures. A detailed numerical study was performed considering fluid-solid interactions (FSI) between the CMAS and TBC top coat (TC). The CMAS flow characteristics through these microstructures were assessed quantitatively and qualitatively. Finally, correlations between the morphological parameters and CMAS flow kinetics were established. It was shown that the rate of longitudinal and lateral infiltration could be minimized by reducing the gap between columns and increasing the length of the feather arms. The results also show that the microstructures with long feather arms having a lower lateral inclination decrease the CMAS infiltration rate, therefore, reduce the CMAS infiltration depth. The analyses allow the identification of key morphological features that are important for mitigating the CMAS infiltration. Full article

The specific microstructure of aluminum alloys is herein explored to grow spatially-resolved layered double hydroxide (SR-LDH) clusters on their surface. Upon chemical modification of LDHs via intercalation, adsorption and grafting with different functional molecules, novel surface-engineered surfaces were obtained. Crystal structure and phase composition were analyzed by X-ray diffraction (XRD) and surface morphology was observed by scanning electron microscopy (SEM). X-ray photoelectron spectroscopy (XPS) and glow discharge optical emission spectrometry (GDOES) were used to correlate structural changes upon ion-exchange and interfacial modifications with chemical composition and surface profiles of the SR-LDH films, respectively. The protection conferred by these films against localized corrosion was investigated at microscale using the scanning vibrating electrode technique (SVET). LDH-NO₃ phase was obtained by direct growth onto AA2024 surface, as evidenced by (003) and (006) XRD diffraction reflections. After anion exchange of nitrate with 2-mercaptobenzothiazole (MBT) there was a decrease in the SR-LDH thickness inferred from GDOES profiles. The subsequent surface functionalization with HTMS was confirmed by the presence of Si signal in XPS and GDOES analyses, leading to an increase in the water contact angle (c.a 144° ± 3°). SVET measurements of the SR-LDH films revealed exceptional corrosion resistance, whereas the bioluminescent bacteria assay proved the anti-microbial character of the obtained films. Overall the results obtained show an effective corrosion protection of the SR-LDHs when compared to the bare substrate and the potential of these films for biofouling applications as new Cr-free pre-treatments. Full article