Tensile Adhesion Research Articles

Characterization Studies of Slurry-Sprayed Mullite–Nickel Coatings on ASTM 1018 Steel

Slurry spray technique (SST) is a simplistic deposition technique which could easily be contrived to the choice of material for appropriate functionality. With the continual technological progress and manufacturing efficiency, the appropriacy of SST needs to be expanded to meet the growing demand for surface engineering. Functionally graded mullite–nickel $$(\hbox {3Al}_{2}\hbox {O}_{3}\cdot \hbox {2SiO}_{2}\hbox {-Ni})$$ -based environmental barrier coatings were slurry sprayed on ASTM 1018 steel. This study reports the findings pertaining to the fundamental mechanical, thermal, corrosion and microstructural investigations performed to evaluate and ascertain the utility of the coatings produced by SST. Sound and resilient coatings with density in the range 1238– $$5320\hbox { kg/m}^{3}$$ and coating thickness in the range of 99– $$380\,\upmu \hbox {m}$$ were attained at distinct processing parameters. Within the experimental design space, a maximum adhesion strength value of 18.15 MPa was measured during tensile adhesion test. The developed coatings with microhardness up to $$204.2\hbox { HV}_{0.1}$$ , exhibit the surface roughness value ranged from 3.27 to $$7.98\,\upmu \hbox {m}$$ (Ra) and the porosity with an overall mean value of 9.9% by volume. During the thermal cycling testing, the majority of the specimens did survive up to 30 thermal cycles, which encapsulate acceptable thermal shock resistance of the coatings. The corrosion studies of the mullite–nickel coatings performed by immersion test in $$0.5\hbox {M Na}_{2}\hbox {SO}_{4}$$ proclaimed a decent corrosion rate of 5.217 mpy. The microstructural studies supported by SEM/EDS and XRD demonstrate as-sprayed splat morphology and the continuous interface and suggest a good adherence of the coatings fabricated wielding SST.

Nghiên cứu chế tạo nhựa epoxy biến tính bằng thiokol lỏng dùng để sản xuất keo dán trong ngành hàng không admin

This study related to polysulfide modified epoxy resins and developing an adhesive from this modified resin. The composition comprises the copolymerization product of epoxy resin with polysulfide and polyester acrylate. Some mechanical properties of obtained adhesive has been enhanced such as tensile strength, chemical resistance and adhesion. The tested results have shown that the working life of the obtained adhesive is 125 mins, the tensile strength is 115 kgf/cm2, watter and oil resistances are good level. Such adhesive can be useful in a wide variety of application such as electrical and aviation adhesives.

Experimental and modelling study on nonlinear time-dependent behaviour of thin spray-on liner

Thin spray-on liners (TSLs) are fast-setting multi component polymeric materials applied on rock or coal surface with a thickness of 2–5 mm that have fairly high tensile strength, adhesion, and elongation capabilities. Compared to conventional surface support elements, TSLs with polymer content exhibit different material responses over time. As a matter of fact, the creep behaviour of TSLs under a constant load has a significance for the evaluation of the long term performances of TSLs. This paper investigates the nonlinear creep behavior of a polymer based TSL for different curing times. Experimental studies were completed to show the nonlinear time-dependent response of the liner under various constant load and curing time conditions. Dogbone shape test specimens were sustained under constant loads up to 2 months of testing time for different test sets. New equations were proposed for rupture time prediction (creep rupture envelopes) which may aid support design engineers to estimate the effective permanent support time and maximum allowable strain amount of the TSL. Test results were used to construct nonlinear viscoplastic models and viscoelastic models consisting of one independent spring and multi Kelvin–Voight elements. A good agreement was obtained between model predictions and experimental values. Generated constitutive models might aid to further numerical studies in TSL literature.

Development of bilayer films based on shellac and esterified cellulose nanocrystals for buccal drug delivery

Bilayer films were fabricated based on natural-based and biocompatible polymers such as esterified cellulose nanocrystals (ECNCs) and shellac, aiming for use in buccal drug delivery. Baicalin was used as the model drug. The swelling properties, drug loading and mechanical properties of films were evaluated and further characterized for mucoadhesion and in vitro drug release properties. The film (F2) containing ECNCs 45%, shellac 25% and polyethylene glycol 30% shows the best properties for the development of the film formulation. The swelling capacity of films was in the range of 36.5 ± 4.1–279.2 ± 14.1%. In vitro drug release shows that anomalous transport behavior indicates that transport includes drug diffusion and polymer relaxation. For film F2, the tensile strength and adhesion strength reaches to the maximum value of 21.57 ± 0.83 MPa and 0.073 ± 0.004 N, respectively. The interfacial interactions between drug and film components were confirmed by FTIR and XRD.

The effect of fluorination of aramid fibers on vinyl ester composites

Composite materials are associated with low densities and high mechanical performance, thus favoring protection of personnel, military vehicles and aircrafts. Polyaramid fibers like Kevlar®, are well‐known for their ballistic performance, but their chemically inert and smooth surface hinders interaction with polymeric resins. The objective of this work is to surface treat aramid fibers with fluoride to improve fiber reactivity and interfacial adhesion with a thermoset matrix. The Kevlar®/vinyl ester composites were prepared by compression molding and characterized. Composites with treated fibers had lower void content and higher glass transition temperature, stiffness, storage and loss module. Nevertheless, they showed lower tensile strength, impact strength, damping, and adhesion factors. The treated fiber composites also presented higher adhesion between fibers and matrix, resulting in less chain segment movement and higher energy dissipation. POLYM. COMPOS., 2018. © 2018 Society of Plastics Engineers

Elucidation of cold-spray deposition mechanism by auger electron spectroscopic evaluation of bonding interface oxide film

The relationship between the cold spray deposition mechanism, microstructure, and strength of the resulting film must be understood for this innovative process to be practical. Previous studies have suggested that the coating mechanism is reliant on breaking the natural oxide film such that metallic bonding occurs through direct contact between the metal surfaces. In this study, the proposed model was experimentally verified by a small tensile adhesion test and auger electron spectroscopy analysis of the bonding interface. Since shear deformation does not occur at the tip (south pole) of the incoming particle, the oxide film is not broken, such that the bonding strength is weak. In contrast, at the outer edge of the particle, metallic bonding occurs, attaining a level of strength that exceeds that of the base material due to the huge plastic deformation. This phenomenon is known as the “south-pole problem,” and can lead to a decrease in the overall adhesion strength despite the local adhesion being strong. However, detailed observations revealed, in parts of the deposits, particles that had adhered across their entire surface. This suggests that, provided the collision state can be controlled, it is possible to overcome the south-pole problem and improve the adhesion strength.

Biologic and mechanical aspects of tendon fibrosis after injury and repair

ABSTRACTTendon injuries of the hand that require surgical repair often heal with excess scarring and adhesions to adjacent tissues. This can compromise the natural gliding mechanics of the flexor tendons in particular, which operate within a fibro-osseous tunnel system similar to a set of pulleys. Even combining the finest suture repair techniques with optimal hand therapy protocols cannot ensure predictable restoration of hand function in these cases. To date, the majority of research regarding tendon injuries has revolved around the mechanical aspects of the surgical repair (i.e. suture techniques) and postoperative rehabilitation. The central principles of treatment gleaned from this literature include using a combination of core and epitendinous sutures during repair and initiating motion early on in hand therapy to improve tensile strength and limit adhesion formation. However, it is likely that the best clinical solution will utilize optimal biological modulation of the healing response in addition to these core strategies and, recently, the research in this area has expanded considerably. While there are no proven additive biological agents that can be used in clinical practice currently, in this review, we analyze the recent literature surrounding cytokine modulation, gene and cell-based therapies, and tissue engineering, which may ultimately lead to improved clinical outcomes following tendon injury in the future.

Fabrication of functionally graded Fe-TiC wear resistant coating on CK45 steel substrate by plasma spray and evaluation of mechanical properties

The main challenge in production of metal matrix composite coatings is the existence of thermal residual stress in coating – substrate interface which results in delamination of the coating eventually. The aim of this paper is to enhance the tensile bond adhesion of the coating by fabricating functionally graded coating. In this regard, raw materials including titanium carbide and iron powders were milled with different compositions. From the substrate to the surface, the weight fraction of TiC particulates increased from 25% to 100%, while the weight fraction of Fe particulates decreased in mentioned direction. Moreover to make a comparison between mechanical properties of the graded coating with those of duplex and single layer coatings, a coating system comprising NiCrAlY bond coat and 100 wt% TiC top coat and a single layer titanium carbide coating were prepared as well. X-Ray diffraction method was used to identify obtained phases from each composition. In addition, microstructural properties of the coatings were investigated by scanning electron microscope. Mechanical properties such as adhesion, hardness and wear resistance were evaluated by tensile bond test, Vicker's method and pin- on- disc method, respectively. The results revealed that the FGC sample has higher coating adhesion in comparison with other coating. Moreover the wear test results showed that the FGC sample faced with less weight loss which means higher wear resistance.

Lamination of Chitin-Cellulose Film and Thermoplastic Starch

In this study, chitin-cellulose films (CC) and nanocomposite (NC) films were successfully laminated to thermoplastic starch (TPS). These were prepared using adhesive, controlled heated compression, and heated compression with adhesive. Lamination was investigated by utilizing direct tensile adhesion strength test to acquire the adhesion strength between the two layers. The highest adhesion strength of 0.502±0.036 MPa resulted for CC/TPS. Combination of failure at the interface and substrate was observed for most CC/TPS laminates. FTIR spectra indicated presence of -NH groups from chitin and -OH groups from starch and cellulose that could improve interfacial adhesion by hydrogen bonding. Scanning Electron Micrographs (SEM) showed a rough surface of chitin-cellulose films, and the clear continuity of CC film with TPS. An increase in modulus from from 0.342 ± 0.020 MPa for TPS to 1.059 ± 0.162 for CC/TPS and 0.939 ± 0.143 MPa for NC/TPS.

Adhesion and mechanical properties of nanocrystalline hydroxyapatite coating obtained by conversion of atomic layer-deposited calcium carbonate on titanium substrate.

The purpose of this study was to evaluate the mechanical properties of nanocrystalline hydroxyapatite coating by tensile adhesion testing and scratch testing. The coating was manufactured on titanium substrate by converting atomic layer-deposited (ALD) calcium carbonate thin film in dilute phosphate solution. The tensile adhesion testing was performed with hydraulic testing device in accordance with ISO 4624 and ISO 16276-1. Scratch testing was done according to SFS-EN 13523-12 with spherical 10 µm scratching tip. Characterization of the samples was done with light and electron microscopy after which they were stained with alizarin red and the failure modes and loadings were analyzed. The highest obtained tensile adhesion value was 6.71 MPa produced with 4000 ALD cycles, converted to hydroxyapatite in alkaline solution, and annealed for 30 min in 700 °C. The annealing improved the adhesion values by approximately 0.8 MPa, but examining the samples with electron microscopy showed intact coating in both annealed and non-annealed samples. Samples produced with 4000 cycles performed better in testing than 2000 cycle samples, and better adhesion was also achieved with alkaline conversion solution compared to neutral solution.

Dielectric breakdown of alumina thin films produced by pulsed direct current magnetron sputtering

Alumina films (~2 μm thick) were deposited with a mixed Cu/Al interlayer onto copper. Direct current (DC)/Pulsed DC (PDC) magnetron sputtering techniques were independently compared for reactive alumina sputtering. In DC sputtered films, elemental aluminium of 9.2 at.% and nano-crystallites were present within the x-ray amorphous matrix, resulting from target arcing. Defects lead to premature dielectric breakdown/increased current leakage. PDC sputtering improved film quality by removing crystallites, metallic clusters and through thickness cracking. Time dependent dielectric breakdown (TDDB) measurements were carried out using conductive atomic force microscopy identified an improvement in dielectric strength (166 to 310 V μm−1) when switching from DC to PDC deposition power. TDDB suggested that at high applied field the dominant pre-breakdown conduction mechanism was Fowler-Nordheim tunnelling in DC films. Tensile pull-off adhesion ranged from 56 to 72 MPa and was highest following incorporation of an Cu/Al blended interfacial layer. Scratch testing indicated various cracking/buckling failures.

Effects of blackening parameters on the formation and adhesion of oxide on AISI 4140 steel

PurposeThe purpose of this study is to investigate the aesthetic blackening coating formed by a hydrothermal process, focusing on the formation of magnetite and the oxide adhesion for improving the corrosion resistance of the steel.Design/methodology/approachThe aesthetic black coating was applied on AISI 4140 steel using a hydrothermal process with a non-toxic solution consisted of ferrous sulphate hydrate (FeSO4·7H2O), sodium hydroxide (NaOH) and hydrazine hydrate (N2H4·H2O). Upon process parameters temperature and time, the morphology of the coatings and oxidation kinetics were investigated by using scanning electron microscopy and X-ray diffraction (XRD) analysis. Furthermore, the samples with coatings were subjected to the adhesion test using a tensile testing machine equipped with a charge-coupled device (CCD) camera.FindingsFrom the formation parameters due to temperature and time for the conversion coatings, it was found that the oxidation kinetics had special characteristics which were in accordance with a linear rate law and Arrhenius relation. For the samples blackened, the XRD analysis results revealed that the magnetite was successfully formed on the surface of the steel. On the other hand, increasing the blackening temperature worsened the scale adhesion as observed by the lower strain provoking the first spallation and the higher sensitivity of the oxide to spall out with the imposed strain.Originality/valueThe effects of parameters of the formation of conversion coatings were investigated to understand the kinetics of the coatings. Furthermore, a tensile adhesion test using a CCD camera was applied to evaluate the adhesion between the native oxide formed by conversion coating.

Microstructure and Adhesion Strength of Ni3Ti Coating Prepared by Mechanical Alloying and HVOF

In the present work we report the development of Ni3Ti intermetallic compound by high energy ball milling of Ni and Ti powders. The ball milled powders were taken at various intervals (4, 6, 8, 10, and 11 h) to analyze the formation of Ni x Ti x intermetallic compounds. The ball milled powders were analyzed using scanning electron microscopy and X-ray diffraction. The layered shaped powder particles of Ni3Ti phase were formed after 11 h of ball milling, which was confirmed by X-ray peaks. Further High-Velocity Oxy-Fuel (HVOF) process was used to coat Ni3Ti and Ni3Ti + (Cr3C2 + 20NiCr) on MDN 420 steel. Both the coated materials displayed excellent cohesion with minimal porosity less than 2%. The tensile adhesion strength test was carried out on these coatings to check the bond strength. Out of the two the Ni3Ti coating showed excellent bond strength of 41.04 MPa compared to that of Ni3Ti + (Cr3C2 + 20NiCr) coating.

Application of a new immobilized impinging jet stream reactor for photocatalytic degradation of phenol: Reactor evaluation and kinetic modelling

A new photocatalytic reactor was designed using impinging jet stream on a TiO2 coated disc. The characterizations of the TiO2 film were carried out by transmission electron microscope, atomic-force microscope, BET and tensile adhesion tests. The influences of the liquid flow rate, coating disc diameter, nozzle-to-disc distance, and initial concentration on phenol removal were investigated. Complete decomposition of a 30 mg L−1 phenol solution was obtained within almost 210 min; additionally, the removal of COD and TOC after 240 min of reaction time were 84% and 79%, respectively. Hydrodynamic model, Langmuir-Hinshelwood kinetics and mass transfer phenomenon were combined to predict the degradation of phenol. The reactor has a higher effectiveness compared to other conventional reactors based on photonic efficiency, electrical energy per order and photocatalytic space-time yield. The performance of the new reactor was also compared with a spinning disc reactor (SDR) in the same operational and structural condition and the results indicated that the new reactor has a higher removal efficiency than the SDR with a rotational speed lower than 150 rpm.

Effect of Thermo-Treatment on the Physical and Mechanical, Color, Fungal Durability of Wood of Tectona Grandis and Gmelina Arborea from Forest Plantations

This study evaluated the effect of thermo-treatment (THT) at 4 temperatures on the density, shrinking, mass loss, moisture absorption, color, durability in terms of resistance to decay, flexural strength, tensile adhesion of glue line and the infrared spectrum of the wood of Tectona grandis and Gmelina arborea. Sapwood, heartwood and radial and tangential grain patterns were studied. The results showed that the THT temperature decreases the density, the percentage of moisture absorption, the modulus of elasticity and modulus of rupture in the flexure test and the tensile adhesion of glue line. The percentage of shrinking and durability presented irregular behavior relative to the THT temperature. The percentage of mass loss increased with increasing THT temperature in both species. The total color change (∆E*) of thermo-treated wood (THTwood) also increased with increasing THT temperature. Sapwood of T. grandis and G. arborea, having clearer shades, showed a more noticeable color change compared to hardwood; however, no significant differences were obtained between some of the THT temperatures.DOI: http://dx.doi.org/10.5755/j01.ms.24.1.17545

Tensile Adhesion Strength of Biomass Ash Deposits: Effect of the Temperature Gradient and Ash Chemistry

Replacing coal with biomass in power plants is a viable option for reducing net CO2 emissions and combating climate change. However, biomass combustion in boilers may exacerbate problems related to ash deposition and corrosion, demanding effective deposit removal. The tensile adhesion strength of model biomass ash deposits, containing mixtures of KCl, K2SO4, CaO, CaSO4, and K2Si4O9, has been investigated in this study. The deposits were prepared on superheater steel tubes and sintered in an oven. The superheater steel tube was cooled by air, incorporating a temperature gradient across the deposits. After sintering, the deposits were removed using an electrically controlled arm and the corresponding tensile adhesion strength was measured. The influence of the flue gas temperature (500–700 °C), steel surface temperature (500–650 °C), and deposit composition were investigated. The results revealed that increasing the flue gas temperature as well as the steel surface temperature led to a sharp increase in the...

Microstructural, mechanical and thermal shock properties of triple-layer TBCs with different thicknesses of bond coat and ceramic top coat deposited onto polyimide matrix composite

In this study, a triple-layer thermal barrier coating (TBC) of Cu-6Sn/NiCrAlY/YSZ was deposited onto a carbon-fiber reinforced polyimide matrix composite. Effects of different thicknesses of YSZ ceramic top coat and NiCrAlY intermediate layer on microstructural, mechanical and thermal shock properties of the coated samples were examined. The results revealed that the TBC systems with up to 300µm top coat thicknesses have clean and adhesive coating/substrate interfaces whereas cracks exist along coating/substrate interface of the TBC system with 400µm thick YSZ. Tensile adhesion test (TAT) indicated that adhesion strength values of the coated samples are inversely proportional to the ceramic top coat thickness. Contrarily, thermal shock resistance of the coated samples enhanced with increase in thickness of the ceramic coating. Investigation of the TBCs with different thicknesses of NiCrAlY and 300µm thick YSZ layers revealed that the TBC system with 100µm thick NiCrAlY layer exhibited the best adhesion strength and thermal shock resistance. It was inferred that thermal mismatch stresses and oxidation of the bond coats were the main factors causing failure in the thermal shock test.

Influence of dovetail microstructures on adhesive tensile strength and morphology of thermally sprayed metal coatings

An approach for a reduction of weight and fuel consumption of passenger cars consists in a replacement of grey cast iron by aluminium alloys as base material of combustion engine blocks. Regarding the insufficient chemical resistance of these alloys to the fuels with its additives, material compounds with thermally sprayed coatings are used as cylinder linings. For machining and in service a high connection strength between the substrate and the coating is demanded. This can be gained by a predefined microstructuring of the substrate surface to attain a local form fit with the coating. But, the microstructured surface also influences the local morphology of the layer. Another possibility to improve the connection strength is the application of a primer between the substrate and the coating.For basic investigations, spiral dovetail microstructures with different pitches (200 µm – 500 µm) are machined by face turning using tools with CVD diamond tippings. The substrates consist of the aluminium alloy EN AW-5754 and their microstructured surfaces are coated with a nickel-aluminium layer. The coating with a thickness of about 200 µm is produced by high-velocity arc spraying. The material is usually used as a primer between the substrate and an iron-based coating. The substrate microstructures and the morphology of the coatings are analysed by SEM and 3D laser scanning microscopy. To determine the adhesive tensile strength of the coating tensile adhesion strength tests are performed.The results show that a higher number of structure elements per length increase the tensile adhesion strength, the hardness and the oxide proportion of the coating. Furthermore, tensile adhesion strength tests reveal failure mechanisms of the compound of substrate and coating depending on the substrate microstructure.

Thermal spray metallisation of carbon fibre reinforced polymer composites: Effect of top surface modification on coating adhesion and mechanical properties

Thermal Spray (TS) processes are used to enhance the surface properties of Polymer Matrix Composites. However, poor adhesion and mechanical degradation are usually experienced. The main objective of this work is to investigate the effect of the modification of the top surface of Carbon Fibre Reinforced Polymer (CFRP) substrate on the TS deposition of metallic coatings. CFRP composite panels were manufactured with different upper layers: (I) pure epoxy overflow layer, (II) pure copper powder filler layer, (III) mixture copper and stainless steel powder filler layer, and (IV) aluminium mesh layer. The top layers of the CFRP substrates were manufactured during the forming process. Arc Spray, one of the TS processes, was used to deposit zinc coating onto the manufactured CFRP panels. The substrates were sandblasted before the TS process to enhance the adhesion of the deposited zinc to the substrate. The quality of the coatings including adhesion and mechanical properties was investigated using tensile adhesion and bending test, respectively. The porosity, microstructure, morphology and surface fracture of the metallised CFRP coupons were characterized using optical and electronical microscopy techniques. The results obtained revealed that pure epoxy top layer did not resist to sandblasting prior to TS process, contrary to the substrates with fillers and mesh top layer. Moreover, the aluminium based mesh layer improved the adhesion strength by about 50%. Bending test results indicated that coating on CFRP composites decreased their mechanical properties. However, the use of a metallic mesh layer reduced the degradation effect of spraying.

Microstructure, Tensile Adhesion Strength and Thermal Shock Resistance of TBCs with Different Flame-Sprayed Bond Coat Materials Onto BMI Polyimide Matrix Composite

In this study, thermal barrier coatings (TBCs) composed of different bond coats (Zn, Al, Cu-8Al and Cu-6Sn) with mullite top coats were flame-sprayed and air-plasma-sprayed, respectively, onto bismaleimide matrix composites. These polyimide matrix composites are of interest to replace PMR-15, due to concerns about the toxicity of the MDA monomer from which PMR-15 is made. The results showed that pores and cracks appeared at the bond coat/substrate interface for the Al-bonded TBC because of its high thermal conductivity and diffusivity resulting in transferring of high heat flux and temperature to the polymeric substrate during top coat deposition. The other TBC systems due to the lower conductivity and diffusivity of bonding layers could decrease the adverse thermal effect on the polymer substrate during top coat deposition and exhibited adhesive bond coat/substrate interfaces. The tensile adhesion test showed that the adhesion strength of the coatings to the substrate is inversely proportional to the level of residual stress in the coatings. However, the adhesion strength of Al bond-coated sample decreased strongly after mullite top coat deposition due to thermal damage at the bond coat/substrate interface. TBC system with the Cu-6Sn bond coat exhibited the best thermal shock resistance, while Al-bonded TBC showed the lowest. It was inferred that thermal mismatch stresses and oxidation of the bond coats were the main factors causing failure in the thermal shock test.