Coat Layer Research Articles

Construction of Uniform LiF Coating Layers for Stable High-Voltage LiCoO2 Cathodes in Lithium-Ion Batteries.

Stabilizing LiCoO2 (LCO) at 4.5 V rather than the common 4.2 V is important for the high specific capacity. In this study, we developed a simple and efficient way to improve the stability of LiCoO2 at high voltages. After a simple sol-gel method, we introduced trifluoroacetic acid (TA) to the surface of LCO via an afterwards calcination. Meanwhile, the TA reacted with residual lithium on the surface of LCO, further leading to the formation of uniform LiF nanoshells. The LiF nanoshells could effectively restrict the interfacial side reaction, hinder the transition metal dissolution and thus achieve a stable cathode-electrolyte interface at high working-voltages. As a result, the LCO@LiF demonstrated a much superior cycling stability with a capacity retention ratio of 83.54% after 100 cycles compared with the bare ones (43.3% for capacity retention), as well as high rate performances. Notably, LiF coating layers endow LCO with excellent high-temperature performances and outstanding full-cell performances. This work provides a simple and effective way to prepare stable LCO materials working at a high voltage.

Control of Meniscus Formation Using an Electrohydrodynamics Module in Roll-to-Roll Systems for the Stable Coating of Functional Layers.

In fabricating functional layers, including thin-film transistors and conductive electrodes, using roll-to-roll (R2R) processing on polymer-based PET film, the instability of the slot-die coating meniscus under a high-speed web impedes functional layer formation with the desired thickness and width. The thickness profiles of the functional layers significantly impact the performance of the final products. In this study, we introduce an electrohydrodynamic (EHD)-based voltage application module to a slot-die coater to ensure the uniformity of the cross-machine direction (CMD) thickness profile within the functional layer and enable a stable, high-speed R2R process. The module can effectively control the spreadability of the meniscus by utilizing variations in the surface tension of the ink. The effectiveness of the EHD module was experimentally verified by applying a high voltage to a slot-die coater while keeping other process variables constant. As the applied voltage increases, the CMD thickness deviation reduces by 64.5%, and the production rate significantly increases (up to 300%), owing to the formation of a stable coated layer. The introduction of the EHD-based application module to the slot-die coater effectively controlled the spreadability of the meniscus, producing large-area functional layers.

Ceramic metal oxide coatings formation by hybrid plasma electrolytic treatment: Interaction scenarios of ceramic NPs with oxide layers

Understanding the formation of protective ceramic metal oxide (CMO) coatings (layers) on the surface of light alloys remains a pressing task in light of products operating in extreme conditions. Plasma electrolytic oxidation (PEO) of light alloy surfaces has recently been modified by introducing various ceramic nanoparticles (NPs) into the electrolyte to perform hybrid plasma electrolytic treatment (HPET). In this work, the general and distinctive features of the interaction mechanisms of TiC, SiO2 and ZrO2 nanoparticles (NPs) with the CMO coating formed by HPET of Al–Si and Mg-based alloys were summarized and theoretically substantiated. The interaction of charged ceramic NPs accelerated by an electric field with the oxide layer is determined by transformation of the NPs kinetic energy into heating and plastic deformation, into phase transformations, as well as into the creation of new surface defects. One of the controlling factors is the ratio of the particle and the oxide layer hardnesses. In the case of SiO2 in Al–Si alloys, the formed coating is harder than the ceramic NPs while in other cases, the NPs are harder than the CMO coating, which determines the different scenarios for the interaction of NPs with the coating under HPET. In summary 7 different scenarios for the interaction of ceramic NPs added to the electrolyte with the СМO layer during its formation put forward, which depending on the ratio of the hardness of the CMO layer and the added particles, temperature/pressure conditions of the phase transformations in the NP (including its melting), the particles size distribution and the base PEO process parameters.

An In Situ Near‐Surface Reconstruction Strategy Endowing Lithium‐Rich Oxides with Li/O Dual Vacancies and Spinel‐Carbon Dual Coating Layers Toward High Energy Density Cathode

AbstractLi‐rich cathode materials (LRMs) are regarded as the key cathode candidates for next‐generation lithium‐ion batteries(LIBs) because of their high specific capacity and environmental friendliness. However, LRMs encounter poor cyclability and low initial coulombic efficiency (ICE) hindering their practical application. Herein, a general near‐surface in situ reconstruction strategy is proposed of constructing the Li/O dual vacancies and spinel‐carbon dual coating layers on the surface of LRMs concurrently to improve Li+ storage performance. The as‐prepared LRMs exhibit a greatly strengthened specific capacity of 283 mAh g−1 with an enhanced ICE of 94% and long‐term cyclability of 91% retention after 200 cycles compared with the pristine LRMs (212 mAh g−1 with an ICE of 65%, 76% retention after 200 cycles). Furthermore, it is theoretically revealed that O vacancies (Ov) prefer to occur at the interface of the C2/m and Rm phases to mitigate lattice stress, rather the O sites in individual C2/m or Rm phase with more coordinated atoms. Besides, Li ions exhibit lower migration energy from C2/m phase to Rm phase with the Ov located at the lattice interface. Therefore, this strategy opens a new avenue in the design perspective of the LRMs’ near‐surface for high‐energy‐density LIBs.

Preparation and high-temperature performance of Sc2O3–Y2O3 co-stabilized ZrO2 thermal barrier coatings

As a promising material for the advanced thermal barrier coatings (TBCs), scandium oxide (Sc2O3) and yttrium oxide (Y2O3) co-stabilized zirconia (ScYSZ) has been given increasing attention during the past decade. In this study, three types of TBCs including YSZ, ScYSZ and ScYSZ-YSZ double ceramic layer (DCL) coatings were deposited by a wide-velocity range high-energy plasma spraying technology. The thermal physical property, phase stability and thermal cycling performance of TBCs were comparatively studied. The results suggested that the thermal conductivity from 200 °C to 1000 °C of ScYSZ coating was reduced by approximately 30 % compared to the YSZ coating. After exposure at 1400 °C for 1000 h, the ScYSZ coating still kept the initial tetragonal phase structure, while the tetragonal phase was completely disappeared in the YSZ coating after 300 h at 1400 °C. Notably, the ScYSZ-YSZ DCL coating demonstrated the highest thermal cycling life within the temperature range of 1320∼1370 °C, exhibiting a remarkable 43 % increase over the single ScYSZ coating and doubling that of the single YSZ coating. The outcomes of this study hold significant promise for practical applications in the realm of high-performance TBCs.

Influence of Oxide Coating Layers on the Stability of Gold Catalysts for Furfural Oxidative Esterification to Methyl Furoate

The use of gold nanoparticles (Au NPs) as catalysts has gained widespread attention in various reactions due to their high activity and selectivity under mild reaction conditions. However, one major challenge in utilizing these catalysts is their tendency to aggregate, leading to catalyst deactivation and hindering their amplification and industrial application. To overcome this issue, herein, we used a method by coating the surface of Au NPs with a thin layer of SiO2, which resulted in the formation of a superior catalyst denoted as Au@SiO2/ZA. Characterization studies revealed that the SiO2 layer is coated on the surface of Au NPs and effectively prevents the aggregation and growth of the gold particles during the reaction process, which makes the catalyst display excellent stability in furfural (FF) oxidative esterification to methyl furoate (MF). Moreover, the stabilization strategy is not limited to SiO2 alone. It can also be extended to other oxides such as ZrO2, CeO2, and TiO2. We believe this work will provide a good reference for the design and development of an efficient and stable gold catalyst for the oxidative esterification reaction.

Exploring the relationship between seed weight and seed coat characteristics in the adlay (Coix lacryma-jobi L.) cultivar WATANI-2 through N, P and K treatment compositions

Adlay plant (Coix lacryma-jobi) grown in many Asian countries, as a source of carbohydrates. The cultivation of adlay faces challenges such as long growth periods, low yields, and hard seeds. Efforts to enhance productivity are crucial, specifically by applying Nitrogen, Phosphorus, and Potassium fertilizers at the appropriate and balanced doses that have not yet been established. Therefore, this study aimed to investigate the relationship between seed weight and seed coat characteristics under optimal N, P, and K fertilizer doses. The exploration process was conducted at the Research Station and Plant Production Technology Laboratory, Faculty of Agriculture, Padjadjaran University, from April 2019 to November 2020. Features of the location included an altitude of 750 – 800 m above sea level, a climate type C3 (Oldeman), an average temperature of 23.8oC, and a soil classified as Inceptisols with a pH of 5.83. The experimental design incorporated several treatments at minimum, optimum, and maximum dosage levels, namely N (90kg/ha, 180 kg/ha, and 270 kg/ha), P (37.5kg/ha, 75 kg/ha, and 150 kg/ha), and K (60 kg/ha, 120 kg/ha and 240 kg/ha) fertilizers, each was repeated twice. Fertilizer application was administered at the beginning of growth and the late vegetative phase, while P was given during the late vegetative phase and before seed formation. Subsequently, a regression analysis was performed to determine the relationship of the weight of 100 seeds with thickness and hardness, generating the equation: Y = 13.755 + 0.061 X1 + 0.012 X2, where X1 = seed hardness and X2 = seed coat thickness. Observations were carried out on the weight, thickness, and hardness of adlay seeds, both macroscopically by measuring length and width or diameter and microscopically through the evaluation of coat and silica layer thickness). The results showed a significant relationship between seed weight, thickness, and hardness, yielding 5.56 t/ha with an 80% land efficiency.

Blocking Effects of Foliar Conditioners on Cadmium, Arsenic, and Lead Accumulation in Wheat Grain in Compound-contaminated Farmland

Heavy metal contamination of soil has become a hot issue of social concern due to its impact on the safety of agricultural products in recent years. Wheat is one of the most dominant staple food crops worldwide and has become a major source of toxic metals in human diets. Foliar application was considered to be a more efficient and economical method of heavy metal remediation. Field experiments were carried out in Cd-, As-, and Pb-contaminated farmland soils. The effects of foliar conditioners on the accumulation of Cd, As, and Pb in wheat grains were investigated after being sprayed with Zn (0.2% ZnSO4), Mg (0.4% MgSO4), and Mn (0.2% MnSO4) separately and in combination. Thus, the effective foliar conditioners were selected to block the accumulation of Cd, As, and Pb in wheat grains grown in combined heavy metal-contaminated farmland in north China. The results showed that, compared with that in the control, the Cd, As, and Pb contents in wheat grains of the Zn+Mg+Mn foliar treatment were significantly decreased by 18.96%, 23.87%, and 51.31%, respectively, and TFgrain/straw decreased by 14.62%, 27.73%, and 47.70%, respectively. Thus, spraying the compound foliar conditioner of Zn+Mg+Mn could effectively reduce heavy metal accumulation in wheat grains through inhibition translocation of those metals from stem leaves to grain. In addition, the results indicated that Cd and As were mainly distributed at the central endosperm (34.08%-37.08%), whereas Pb was primarily distributed at the pericarp and seed coat (27.78%) of the wheat grain. Compared with that in the control, spraying the compound foliar conditioner of Zn+Mg+Mn extremely decreased Cd and As accumulation in the aleurone layer of the wheat grain by 81.10% and 82.24%, respectively. Except for the pericarp, seed coat, and central endosperm layers, the Pb content in each grain layer was dramatically decreased by 42.85% to 91.15%. There was only a significant negative correlation between heavy metal content and Zn content in the aleurone layer (P2) of wheat flour. In summary, the accumulation of Cd, As, and Pb in wheat grains, especially in the aleurone layer, could be effectively reduced by foliar conditioner application at the jointing, booting, and early filling stages of wheat, separately. Furthermore, besides the foliar treatment, removing wheat bran to reduce Cd contamination in wheat grains is highly recommended to ensure the safe production of wheat.

Investigating cationic and zwitterionic successive multiple ionic-polymer layer coatings for protein separation by capillary electrophoresis

Successive multiple ionic-polymer layers (SMILs) have long since proved their worth in capillary electrophoresis as they ensure stable electroosmotic flow (EOF) and relatively high separation efficiency. Recently, we demonstrated that plotting the plate height (H) against the solute migration velocity (u) enabled a reliable quantitative evaluation of the coating performances in terms of separation efficiency. In this work, various physicochemical and chemical parameters of the SMIL coating were studied and optimized in order to decrease the slope of the ascending part of the H vs u curve, which is known to be controlled by the homogeneity in charge of the coating surface and by the possible residual solute adsorption onto the coating surface. SMILs based on poly(diallyldimethylammonium chloride) (PDADMAC) and poly(sodium styrene sulfonate) (PSS) were formed and the effect of each polyelectrolyte molar mass and of the number of polyelectrolyte layers (up to 21 layers) was studied. The use of polyethylene imine as an anchoring first layer was considered. More polyelectrolyte couples based on PDADMAC, polybrene, PSS, poly(vinyl sulfate), and poly(acrylic acid) were tested. Finally, zwitterionic polymers based on the poly(α-l-lysine) scaffold were synthesized and used as the last layer of SMILs, illustrating their ability to finetune the EOF, while maintaining good separation efficiency.

Polyelectrolyte Platforms with Copper Nanoparticles as a Multifunctional System Aimed at Healing Process Support

(1) Purpose: The aim of the study was to develop a nanocomposite with copper nanoparticles constituting a bacteriostatic surface to maintain human lung cell function. (2) Methods: A polyelectrolyte layer coating that incorporated copper nanoparticles was designed. As a bacteriostatic factor, copper nanoparticles were applied as a colloidal solution of copper nanoparticles (ColloidCuNPs) and a solution of copper nanoparticles (CuNPs). The influence of the polyelectrolytes on selected Gram (+) and Gram (−) strains was examined. The function and morphology of the human adenocarcinoma A549 cell line, comprising human epithelial lung cells cultured in the presence of nanocomposite layer coatings, were evaluated. We applied fluorescence and scanning electron microscopies, as well as flow cytometry, for these studies. Furthermore, the layer coating material was characterized by atomic force microscopy (AFM) and energy dispersive X-ray analysis (EDX). (3) Results: It was observed that the polyelectrolytes polyethyleneimine (PEI) and poly-L-lysine (PLL) did not induce proliferation of the E. coli strain. However, they did induce the proliferation of the S. aureus strain. Due to the effectiveness of the CuNPs against the E. coli strain, CuNPs were selected for further research. The designed coatings of proper NPs shared the sustained function of human lung cells within 10 days of culture. The AFM and EDX characterization confirmed the presence of copper in the layer coating nanomaterial. The presence of CuNPs in polyethyleneimine-based nanocomposite deepened the bacteriostatic effect on E. coli compared with PEI alone. Meanwhile, incorporating CuNPs in PLL allowed A549 cell maintenance but did not exert a bacteriostatic influence on the examined strain. (4) Conclusions: The platform based on polyelectrolytes, incorporated with copper nanoparticles, that ensures the growth and appropriate morphology of the human lung epithelial cells, might be considered an element of a system for medical devices used to maintain the function of human lung cells.

In Situ Construction of a Polymer Coating Layer on the LiNi0.8Co0.1Mn0.1O2 Cathode for High-Performance Lithium-Ion Batteries.

Lithium-ion batteries (LIBs) are known for their high energy density but exhibit poor cyclic stability and safety risks due to side reactions between the electrode and electrolyte. To address these issues, a novel approach involving construction of a polymer coating layer (PCL) via in situ self-polymerization using 2,2,3,4,4,4-hexafluorobutyl methacrylate (HFBM) as an electrolyte additive on the cathode is proposed. The PCL endows the electrolyte with a high onset oxidation potential (4.78 V) and lithium-ion transference number (0.52). The uniform and robust in situ constructed PCL can effectively inhibit the severe irreversible side reactions and suppress harmful reactions, thus providing a protective barrier against degradation. The resulting Li||LiNi0.8Co0.1Mn0.1O2 batteries exhibit an improved discharge capacity retention of 80% at 1C over 100 cycles. These results demonstrate that the in situ self-polymerization strategy holds promising potential for enhancing LIB performance and long-term stability, especially when high-voltage cathode materials are used.

Application of an Antibacterial Coating Layer via Amine-Terminated Hyperbranched Zirconium-Polysiloxane for Stainless Steel Orthodontic Brackets.

The massive growth of various microorganisms on the orthodontic bracket can form plaques and cause diseases. A novel amine-terminated hyperbranched zirconium-polysiloxane (HPZP) antimicrobial coating was developed for an orthodontic stainless steel tank (SST). After synthesizing HPZP and HPZP-Ag coatings, their structures were characterized by nuclear magnetic resonance spectroscopy, scanning electron microscopy, thickness measurement, contact angle detection, mechanical stability testing, and corrosion testing. The cell toxicity of the two coatings to human gingival fibroblasts (hGFs) and human oral keratinocytes (hOKs) was detected by cell counting kit eight assays, and SST, HPZP@SST, and HPZP-Ag@SST were cocultured with Staphylococcus aureus, Escherichia coli, and Streptococcus mutans for 24 hr to detect the antibacterial properties of the coatings, respectively. The results show that the coatings are about 10 μm, and the water contact angle of HPZP coating is significantly higher than that of HPZP-Ag coating (P < 0.01). Both coatings can be uniformly and densely distributed on SST and have good mechanical stability and corrosion resistance. The cell counting test showed that HPZP coating and HPZP-Ag coating were less toxic to cells compared with SST, and the toxicity of HPZP-Ag coating was greater than that of HPZP coating, with the cell survival rate greater than 80% after 72 hr cocultured with hGFs and hOKs. The antibacterial test showed that the number of bacteria on the surface of different materials was ranked from small to large: HPZP@SST < HPZP-Ag@SST < SST and 800 μg/mL HPZP@SST showed a better bactericidal ability than 400 μg/mL after cocultured with S. aureus, E. coli, and S. mutans, respectively (all P < 0.05). The results showed that HPZP coating had a better effect than HPZP-Ag coating, with effective antibacterial and biocompatible properties, which had the potential to be applied in orthodontic process management.

Influence of the Composition of Asphalt Granular Concrete Mixture on the Deformation of the Coating Layer During the Construction of the Road Pavement

Statement of the problem. The introduction of cement into the composition of the bitumen emulsion at the stage of preparation affects not only the strength of the layer, but also the properties of the asphalt granular concrete mixture, which must be taken into account when developing technological processes for compaction. Under the action of the compacting load, taking into account the content of cement in the binder material, the deformability and rigidity of the compacted layer change. The change in the rigidity of the layer affects the choice of parameters of compacting machines. Therefore, whiledeveloping a pavement technology using asphalt-granular concrete mixes using combined binders, it is necessary to establish the effect of cement content on the deformability and rigidity of the compacted layer. Results. The results on the influence of the cement content in the combined binder in the asphalt-granular concrete mix on the deformability of the layer under the action of the compacting load are presented. Dependences were obtained to determine the residual deformation and rigidity of the mix layer under the action of a load, taking into account the layer thickness and cement content. Conclusions. The use of a combined binder (bitumen emulsion and cement), depending on the cement content, leads to a decrease in the deformability of the layer of asphalt granular concrete mixture up to 40 %, regardless of the size of the granulate fractions and the thickness of the layer during laying, as well as an increase in the rigidity of the layer from 1.8 to 2.1 times, which must be taken into account when choosing the parameters of the rollers in the compaction process.

Friction Behavior of Anodic Oxide Layer Coating on 2017A T4 Aluminum Alloy under Severe Friction Solicitation: The Effect of Anodizing Parameters

This article aims to highlight the wear mechanisms and friction behavior of the 2017A T4 anodized aluminum alloy used for automotive and aerospace applications. The effect of the processing parameters on the durability of the anodized layer under high friction is studied. Scratch tests were carried out to study the level of the friction coefficient with the increase in the thickness of the oxide layer formed on the Al 2017 A (AU4G) substrate. The results of the scratch tests show that the variation in the anodization duration, which influences the thickness of the oxide layer, induces an increase in the coefficient of friction. Besides, the variations in friction coefficient with sliding distance are influenced by the changes in wear morphology and degree of oxidation. Treated surfaces with a thickness of 50 μm have the lowest friction coefficients and wear rates. Their improved wear resistance may be related to the increased bond strength compared to other anodized surfaces. The tribological damage was characterized by the detachment of debris, which increases with the increase of the duration of anodization. Upon sliding, its detachment leads to delamination of the underlying anodic aluminum oxides and subsequent abrasion of the aluminum substrate.

UV-Induced Spectral and Morphological Changes in Bacterial Spores for Inactivation Assessment.

The ability to detect and inactivate spore-forming bacteria is of significance within, for example, industrial, healthcare, and defense sectors. Not only are stringent protocols necessary for the inactivation of spores but robust procedures are also required to detect viable spores after an inactivation assay to evaluate the procedure's success. UV radiation is a standard procedure to inactivate spores. However, there is limited understanding regarding its impact on spores' spectral and morphological characteristics. A further insight into these UV-induced changes can significantly improve the design of spore decontamination procedures and verification assays. This work investigates the spectral and morphological changes to Bacillus thuringiensis spores after UV exposure. Using absorbance and fluorescence spectroscopy, we observe an exponential decay in the spectral intensity of amino acids and protein structures, as well as a logistic increase in dimerized DPA with increased UV exposure on bulk spore suspensions. Additionally, using micro-Raman spectroscopy, we observe DPA release and protein degradation with increased UV exposure. More specifically, the protein backbone's 1600-1700 cm-1 amide I band decays slower than other amino acid-based structures. Last, using electron microscopy and light scattering measurements, we observe shriveling of the spore bodies with increased UV radiation, alongside the leaking of core content and disruption of proteinaceous coat and exosporium layers. Overall, this work utilized spectroscopy and electron microscopy techniques to gain new understanding of UV-induced spore inactivation relating to spore degradation and CaDPA release. The study also identified spectroscopic indicators that can be used to determine spore viability after inactivation. These findings have practical applications in the development of new spore decontamination and inactivation validation methods.

Coating stress analysis under temperature increase for diamond and silicon CVD coatings

The CVD–coated parts are found in a wide range of applications and must meet high quality requirements. The stress state due to temperature changes on diamond and silicon dioxide coated parts is studied. For single–layer coatings, the stress state under tensile load is analysed. In addition, the strength of the diamond–coated part under bending stress is also investigated.

Fluoride-Incorporated Apatite Coating on Collagen Sponge as a Carrier for Basic Fibroblast Growth Factor.

Coating layers consisting of a crystalline apatite matrix with immobilized basic fibroblast growth factor (bFGF) can release bFGF, thereby enhancing bone regeneration depending on their bFGF content. We hypothesized that the incorporation of fluoride ions into apatite crystals would enable the tailored release of bFGF from the coating layer depending on the layer's fluoride content. In the present study, coating layers consisting of fluoride-incorporated apatite (FAp) crystals with immobilized bFGF were coated on a porous collagen sponge by a precursor-assisted biomimetic process using supersaturated calcium phosphate solutions with various fluoride concentrations. The fluoride content in the coating layer increased with the increasing fluoride concentration of the supersaturated solution. The increased fluoride content in the coating layer reduced its solubility and suppressed the burst release of bFGF from the coated sponge into a physiological salt solution. The bFGF release was caused by the partial dissolution of the coating layer and, thus, accompanied by the fluoride release. The concentrations of released bFGF and fluoride were controlled within the estimated effective ranges in enhancing bone regeneration. These findings provide useful design guidelines for the construction of a mineralized, bFGF-releasing collagen scaffold that would be beneficial for bone tissue engineering, although further in vitro and in vivo studies are warranted.

Corrosion-resistant behavior and structural optimization of Ti/Cr, Ti/Cu, Cr/Cu, Ti/Cr/Cu multimetallic layer coatings in simulated seawater

This article is based on the sacrificial anode cathodic protection principle and the optimization method of multilayer structure. According to the standard electrode potential of metals, starting from the corrosion-resistant passive film formed by the metal itself, Ti/Cr, Ti/Cu, Cr/Cu, and Ti/Cr/Cu coatings were prepared on a 316L stainless steel substrate using magnetron sputtering technology. The corrosion performance of the coatings was studied to explore the interaction patterns between them. The results showed that in artificial seawater, the Cr/Cu, Ti/Cu, and Ti/Cr metal bilayer film coatings exhibited an increasing impedance arc radius and widening phase angle plateau in the electrochemical impedance spectroscopy. In the polarization curve, the self-corrosion current, the self-corrosion potential and polarization resistance are all better than the substrate. In the static immersion test, the weight loss rate of the metal multi-layer film gradually decreased, with all samples showing a lower weight loss rate in the second week compared to the first week, ranging from 27% to 52%. By further designing the microstructure of the coating to mitigate the contradiction between hardness and toughness, and reduce the generation of pores, the corrosion performance of the new Ti/Cr/Cu coating is significantly improved. The coating can repair surface defects of the material, fill in micro and nano gaps, and enhance the cathodic protection effect of sacrificial anodes.

Characterization of surface properties of TiC ceramic coating developed on AISI 1020 steel

The aim of this research was to develop the TiC ceramic coating on the AISI 1020 steel substrate by a tungsten inert gas cladding (TIG) process and to comprehensively assess the surface properties of deposited TiC coatings. Various TIG currents were employed to deposit the TiC coating. The study included a detailed investigation of the two pivotal aspects: wear rate and microhardness. Additionally, a comprehensive examination of the microstructure and the presence of different phases in the coating layers was done. TiC ceramics were found to be dispersed remarkably and uniformly over the whole coating region, as revealed by scanning electron microscopy (SEM) examinations. Additionally, it was noted that neither the coating area nor the interfacial areas included any harmful flaws like voids or cracks. The results of this experiment clearly showed that the processing current and the subsequent wear resistance and microhardness were directly correlated. In particular, it was shown that wear resistance and microhardness both showed a noticeable increase when the processing current decreased. The coating developed at lower proceeding current 80 A found the most remarkable results, achieving a peak microhardness of 2846 HV0.1 and an impressively low wear rate of only 10.96 × 10−8 g/Nm. These extraordinary results can be directly attributable to the hard TiC phase's significant presence inside the coatings layer. Due to its improved wear behaviour and microhardness as compared to untreated mild steel, pure TiC-coated AISI 1020 steel finds a suitable material for application in wear-resistance components where hardness is considered as a crucial factor. The TiC coating has achieved an exceptionally high friction coefficient, making it particularly valuable for applications within the automobile industry.

Failure behaviors of EB-PVD thermal barrier coatings under isothermal oxidation and thermal cycling conditions

The thermal growth oxide (TGO) layer formed by oxidation of the bond coat (BC) layer is an important factor affecting the durability of thermal barrier coatings (TBCs). In this study, a series of isothermal oxidation and thermal cycling experiments were performed on samples containing TBCs at different temperatures. The initiation, propagation and connection process of cracks in the cross-section of the samples were studied, and the oxidation failure mechanism of the samples was analyzed. The results demonstrate that the diffusion of the Al element in NiCoCrAlYHf coating to the top coat (TC) layer promotes the formation and rapid thickening of TGO at TC/BC interface. With the consumption of Al, two sublayers of mixed oxide layer and Al2O3 layer are gradually formed in the TGO layer. The TC/TGO interface is the main initiation location of interface crack. In addition, the types and initiation locations of cracks caused by isothermal oxidation are different from those caused by thermal cycling. Under isothermal oxidation, the TC layer near the TC/TGO interface and the TC/TGO interface are prone to induce horizontal cracks, which finally lead to the delamination and spalling of TBCs. Under the thermal cycling, vertical cracks occur in the TC layer, extend towards the TC/TGO interface, and merge with the interface cracks, eventually resulting in the delamination failure of the TBCs.