In this study, experimental investigations were carried out to estimate the mechanical and microstructural properties of polypropylene (PP) and steel fiber reinforced geopolymer mortar. Two ...industrial by-products are used as binders to produce the geopolymer composites, i.e., fly ash (FA) and ground granulated blast furnace slag (GGBFS). Different percentages of PP and steel fibers are used in geopolymer mortars to find the mechanical properties such as compressive, splitting tensile and flexural strengths were investigated to understand the strength behavior. However, the compressive elastic modulus values were estimated through the proposed equation based on the compressive strength of the fiber reinforced geopolymer composite samples. Moreover, to understand the geopolymeic reaction, microstructural studies, i.e., scanning electron microscopy (SEM), were conducted. The experimental results revealed that the addition of PP fibers up to 2.0% (volume fraction) enhanced the flexural properties of geopolymer mortar samples. The compressive strength of the steel fiber-reinforced geopolymer composite reached a maximum of 2.5% volume fraction, being a 13.26% improvement over the control mix. The flexural toughness index of the PP and steel fiber reinforced composites improved with increasing the fraction. However, steel fiber reinforced geopolymer samples are shown better flexural toughness compared to PP fibers. The SEM analysis of the geopolymer control mix achieved a good degree of geopolymerization and both the fibers yielded a considerable interfacial bonding with the geopolymer paste.
Abstract Polyetheretherketone (PEEK) possesses a similar elastic modulus as bones but yet suffers from bio-inertness and poor osteogenesis. In this work, tantalum ions are implanted energetically ...into PEEK by plasma immersion ion implantation (PIII) to form Ta2 O5 nanoparticles in the near surface. Nanoindentation reveals that the surface elastic modulus of the Ta ion implanted PEEK is closer to that of human cortical bones. In vitro cell adhesion, alkaline phosphatase activity, collagen secretion, extracellular matrix mineralization, and real-time PCR analyses disclose enhanced adhesion, proliferation, and osteogenic differentiation of rat bone mesenchymal stem cells (bMSCs) on the Ta-PIII modified PEEK. In vivo evaluation of the cortico-cancellous rat femur model by means of micro-CT, sequential fluorescent labeling, and histological analysis after 8 weeks confirms significantly improved osteointegration. The bone-like elastic modulus and modified surface topography of the Ta-PIII modified PEEK synergistically induce osteogenic differentiation of bMSCs and the surface-modified materials have large potential in dental and orthopedic implants.
•Waste rubber fiber used for partial replacement of fine aggregate in concrete.•Effect of elevated temperature on the properties of waste rubber fiber concrete is examined.•Strength, modulus of ...elasticity, water permeability and chloride diffusion were studied.•Inclusion of rubber fiber causes higher reduction in properties of concrete on exposure to elevated temperature.•Temperature higher than 150°C leads to decomposition of rubber fiber in concrete.
Accumulation of the waste tire is a major problem as degradation of these tires is extensively difficult. The results of experimental studies available for rubberized concrete provide a strong recommendation for the use of this waste where strength is not a major concern. The effect of partial replacement of fine aggregate by waste rubber fiber on the properties of concrete subjected to elevated temperature has been evaluated in this paper. A systematic experimental investigation has been carried out to evaluate the effect of elevated temperature on compressive strength, mass loss, static modulus of elasticity, dynamic modulus of elasticity, water permeability and chloride-ion permeability of control mix (no replacement of fine aggregate by rubber fiber) and waste rubber fiber concrete. Two types of cooling, normal cooling and fast cooling have been considered for the effect on compressive strength. Six levels of temperature with three exposure durations have been considered in this study for all the specimens. Microstructure analysis of waste rubber fiber concrete has also been carried out to investigate the effect of elevated temperature on crack pattern and bonding of rubber fiber and cement matrix.
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•Hydrate formed on soft and stiff solid surfaces shows distinct adhesion strengths.•Adhesion strength of hydrate on soft substrates is greatly dictated by the shear loading ...rate.•Adhesion strength of hydrate on stiff substrates is greatly affected by the elastic modulus of the substrates.
Hydrate formation and accumulation pose significant challenges in oil and gas pipelines, leading to flow assurance issues and safety hazards. It is crucial to understand hydrate adhesion to prevent the accretion of hydrate in petro-pipelines. In this study, the adhesion strength (AS) of tetrahydrofuran (THF) hydrate on various solid surfaces with different elastic moduli subjected to shear loading rates ranging from 10 to 10000 μm/s is comprehensively investigated by shear force experimental measurements and finite element (FE) simulations. The results reveal that the hydrate AS is primarily influenced by the elastic modulus of the substrates, and the shear-induced detachment properties are strongly dependent on the shear loading rate. Specifically, when the hydrate is synthesized on a soft polydimethylsiloxane (PDMS) substrate, the AS exhibits minimal changes at low and high shear loading rates. However, under intermediate shear loading rates, the AS rapidly increases by approximately 500 %. In contrast, when the hydrate is formed on stiff polytetrafluoroethylene (PTFE) and polyethylene (PE) substrates, the AS is increased by approximately 200 % and 230 %, respectively as shear loading rate increases. Interestingly, for the hydrate on a stiff hydrophobic coated glass slide (CG) substrate, the AS anomalously decreases with increasing shear loading rates. These findings provide valuable insights into the effects of substrate properties and shear loading rate on hydrate adhesion. The results are of significance for the design of optimal coatings that ensure flow assurance of oil and gas in pressure-variant petro-pipelines.
This paper aims to investigate the effect of hydrogen-induced mechanical degradation of low carbon steel at macro-, micro- and nano-levels in the hydrogen-rich acidic environments. From the test ...results of specimens, a relationship in hydrogen concentration and corrosion propagation was observed that led to the significant reductions of bulk elastic modulus after 28 days of exposure to the hydrogen-rich acidic environments. Through microstructural analysis, the deformation of larger grains, cracks, and blisters caused by hydrogen penetration was found as the possible cause for this reduction. Moreover, by performing nanoindentation on the areas of interest of various specimens at planned time periods, the influence of hydrogen on the nano-elastic and nano-hardness properties of grains was determined. The 3D surface profiles of the nano-elastic modulus and nano-hardness of various specimens are presented in this paper.
•The hydrogen embrittlement (HE) behavior of low carbon steel was investigated.•Hydrogen-rich acidic corrosive environments were used, and their effects analyzed.•Hydrogen assisted cracking, blister, and grain boundary deterioration were detected.•Nanoelastic and nanomechanical properties changes due to HE were investigated.•Nanoelastic modulus reduced to 45% in some of the grains due to HE.
Lutetium disilicate (Lu2Si2O7) is considered a promising material for environmental barrier coatings because of its remarkable high-temperature stability and low thermal conductivity. In this study, ...nanostructured Lu2Si2O7 coating was prepared successfully using as-prepared feedstocks via atmospheric plasma spraying. The nanomechanical performance of the coating was studied. The results showed that the coating exhibited a bimodal nanomechanical performance attributed to the bimodal distribution of its microstructure; i.e., in the coating, the melted lamella exhibited higher elastic modulus and nanohardness, whereas the unmelted and semi-melted parts processed low elastic modulus and nanohardness. The elastic modulus and nanohardness of the coating were 143.438 ± 25.449 GPa and 9.239 ± 3.514 GPa, respectively. Furthermore, the elastic and plastic works were 9.018–14.752 nJ and 12.792–25.793 nJ, respectively. The average value of the microhardness dissipation parameter of the coating was 0.615, demonstrated that the remarkable wear resistance of the coating.
The first-principle calculations were selected to investigate the structure, elastic modulus, electronic properties and thermodynamic properties of three W3Si cubic structures (Pm-3m, Fm-3m and ...Pm-3n). The influence of pressure on the stability and elastic modulus of W3Si is further studied. Two novel W3Si phases: Pm-3m and Fm-3m are firstly found. The order of thermodynamic stability is Pm-3n > Fm-3m > Pm-3m. The bulk modulus and shear modulus of Pm-3n structure are up to 306.8 GPa and 157.1 GPa, respectively. In particular, the elastic modulus of Pm-3n structure is bigger than the Pm-3m and Fm-3n structures at the range of whole pressure. Compared to Pm-3m and Fm-3m structures, the high elastic modulus of Pm-3n structure is attributed to the role of the W–W and W–Si bonds. The high-temperature thermodynamic properties of W3Si are attributed to the vibration of Si atom. Finally, the order of Debye temperature is Pm-3n > Fm-3m > Pm-3m.
The contact angle that a liquid drop makes on a soft substrate does not obey the classical Young's relation, since the solid is deformed elastically by the action of the capillary forces. The finite ...elasticity of the solid also renders the contact angles differently from those predicted by Neumann's law, which applies when the drop is floating on another liquid. Here, we derive an elastocapillary model for contact angles on a soft solid by coupling a mean-field model for the molecular interactions to elasticity. We demonstrate that the limit of a vanishing elastic modulus yields Neumann's law or a variation thereof, depending on the force transmission in the solid surface layer. The change in contact angle from the rigid limit to the soft limit appears when the length scale defined by the ratio of surface tension to elastic modulus γ/E reaches the range of molecular interactions.
•Lactoferrin-whey protein aggregates formed at pH 6.7 are smaller and more homogeneous.•Lactoferrin interacts with whey proteins differently during heating at pH 6.7 and 5.8.•Incorporation of ...lactoferrin increased the strength of whey protein gel.•Lactoferrin improved the water holding capacity of whey protein gel at pH 6.7.
In this paper, the influence of lactoferrin (LF) on the structural development of whey protein isolate (WPI) gels during heating was investigated. The results demonstrated that the presence of sufficient LF could improve the strength and elasticity of WPI gels. When 30% LF was added, the elastic modulus of WPI gels increased from 254 ± 31 and 413 ± 58 Pa to 3222 ± 105 and 2730 ± 131 Pa at pH 6.7 and 5.8, respectively. The addition of LF improved the water holding capacity (WHC) of WPI gels at pH 6.7, while no improvement was observed at pH 5.8. LF interacted with whey proteins differently at pH 6.7 and 5.8 during heating. The LF/whey proteins complexes formed at pH 6.7 had smaller sizes and narrower size distributions than those formed at pH 5.8.
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