Low Elastic Modulus Research Articles

Improving the performance of crumb rubber concrete using waste ultrafine glass powder

Due to its superior toughness and environmental benefits over traditional concrete, crumb rubber (CR) concrete (CRC) gained considerable attention in both research and practical engineering fields. However, the static mechanical characteristics of CRC exhibit a certain level of decline as CR demonstrates a lower elastic modulus and less effective bonding capabilities with mortar when compared to natural aggregates. Consequently, this study explores the potential of substituting cement with ultra-fine waste glass powder (WGP) to enhance the mechanical characteristics and microstructure of CRC. The impact of varying WGP substitution rates on workability, wet packing density (WPD) in the fresh phase is examined. Moreover, analyses on compressive strength, flexural-tensile strength, ductility index, dynamic elastic modulus, damping ratio, and impermeability post-hardening are presented. The use of scanning electron microscopy (SEM), X-ray diffraction (X-RD), and mercury intrusion piezometry (MIP) provided insights into the influence of WGP on the micromorphology, mineral composition, and pore structure characteristics. The results revealed that WGP introduction enhanced the fresh properties of CRC, notably in terms of workability and WPD. The slump and slump-flow increased to 270 mm and 630 mm for WGP dosing increased to 30 %. A gradual enhancement in strength, dynamic elastic modulus, and impermeability was observed with increased WGP content, alongside a significant improvement in toughness. The compressive and flexural strengths of 30 % WGP were mentioned to be about 11 % and 62 %, respectively, and the permeability coefficient was reduced to 0.78 × 10−12 m2/s. The damping ratio initially decreases, then rises to a peak of 1.6 % at a WGP content of 30 %. Integration of WGP resulted in a progressive decrease in interfacial frictional zone width, average pore diameter, and porosity, while the fraction of harmless pores increased, likely aiding the strength and dynamic elastic modulus.

In vitro bioprinted 3D model enhancing osteoblast-to-osteocyte differentiation

In vitrobone models are pivotal for understanding tissue behavior and cellular responses, particularly in unravelling certain pathologies' mechanisms and assessing the impact of new therapeutic interventions. A desirablein vitrobone model should incorporate primary human cells within a 3D environment that mimics the mechanical properties characteristics of osteoid and faithfully replicate all stages of osteogenic differentiation from osteoblasts to osteocytes. However, to date, no bio-printed model using primary osteoblasts has demonstrated the expression of osteocytic protein markers. This study aimed to develop bio-printedin vitromodel that accurately captures the differentiation process of human primary osteoblasts into osteocytes. Given the considerable impact of hydrogel stiffness and relaxation behavior on osteoblast activity, we employed three distinct cross-linking solutions to fabricate hydrogels. These hydrogels were designed to exhibit either similar elastic behavior with different elastic moduli, or similar elastic moduli with varying relaxation behavior. These hydrogels, composed of gelatin (5% w/v), alginate (1%w/v) and fibrinogen (2%w/v), were designed to be compatible with micro-extrusion bioprinting and proliferative. The modulation of their biomechanical properties, including stiffness and viscoelastic behavior, was achieved by applying various concentrations of cross-linkers targeting both gelatin covalent bonding (transglutaminase) and alginate chains' ionic cross-linking (calcium). Among the conditions tested, the hydrogel with a low elastic modulus of 8 kPa and a viscoelastic behavior over time exhibited promising outcomes regarding osteoblast-to-osteocyte differentiation. The cessation of cell proliferation coincided with a significant increase in alkaline phosphatase activity, the development of dendrites, and the expression of the osteocyte marker PHEX. Within this hydrogel, cells actively influenced their environment, as evidenced by hydrogel contraction and the secretion of collagen I. This bio-printed model, demonstrating primary human osteoblasts expressing an osteocyte-specific protein, marks a significant achievement. We envision its substantial utility in advancing research on bone pathologies, including osteoporosis and bone tumors.

MECHANICAL CHARACTERIZATION OF HOMOGENIZED TI-12MO-13NB AND TI-10MO-20NB ALLOYS

Beta titanium alloys have been developed for biomedical applications due to their outstanding mechanical properties, including low elastic modulus, high strength, excellent fatigue resistance, good ductility, and exceptional corrosion resistance. To enhance safety, the metastable beta titanium alloys Ti-12Mo-13Nb and Ti-10Mo-20Nb have been introduced as alternatives to the traditional Ti-6Al-6V alloy. The Ti-6Al-6V alloy contains vanadium, which is biotoxic and can lead to cell death, and aluminum, which may contribute to neural cell degeneration and accelerate the progression of Alzheimer’s disease. The objective of this work is to explore and present the properties and microstructure of the Ti-12Mo-13Nb and Ti-10Mo-20Nb alloys. Microstructural characterization of these alloys was performed using techniques such as X-ray diffraction and optical microscopy. The mechanical characterization was realized by Vickers hardness and the Young’s modulus was obtained by the nanoidentation technique. Both alloys presented elastic modulus (~90 GPa) lower than the widely used Ti-6Al-4V alloy (135 GPa). The results of the microstructural characterization showed only the presence of the β-Ti phase in the alloys.

The Effect of DLC Surface Coatings on Microabrasive Wear of Ti-22Nb-6Zr Obtained by Powder Metallurgy

Titanium alloys have a high cost of production and exhibit low resistance to abrasive wear. The objective of this work was to carry out diamond-like carbon (DLC) coating, with dissimilar thicknesses, on Ti-22Nb-6Zr titanium alloys produced by powder metallurgy, and to evaluate its microabrasive wear resistance. The samples were compacted, cold pressed, and sintered, producing substrates for coating. The DLC coatings were carried out by PECVD (plasma-enhanced chemical vapor deposition). Free sphere microabrasive wear tests were performed using alumina (Al2O3) abrasive suspension. The DLC-coated samples were characterized by scanning electron microscopy (SEM), Vickers microhardness, coatings adhesion tests, confocal laser microscopy, atomic force microscopy (AFM), and Raman spectroscopy. The coatings did not show peeling-off or delamination in adhesion tests. The PECVD deposition was effective, producing sp2 and sp3 mixed carbon compounds characteristic of diamond-like carbon. The coatings provided good structural quality, homogeneity in surface roughness, excellent coating-to-substrate adhesion, and good tribological performance in microabrasive wear tests. The low wear coefficients obtained in this work demonstrate the excellent potential of DLC coatings to improve the tribological behavior of biocompatible titanium alloy parts (Ti-22Nb-6Zr) produced with a low modulus of elasticity (closer to the bone) and with near net shape, given by powder metallurgy processing.

Medium-entropy Zr–Nb–Ti alloys with low magnetic susceptibility, high yield strength, and low elastic modulus through spinodal decomposition for bone-implant applications

Medium-entropy Zr–Nb–Ti (ZNT) alloys are being extensively investigated as load-bearing implant materials because of their exceptional biocompatibility and corrosion resistance, and low magnetic susceptibility. Nevertheless, enhancing their yield strength while simultaneously decreasing their elastic modulus presents a formidable obstacle, significantly constraining their broader utilization as metallic biomaterials. In this study, three medium-entropy ZNT alloys, i.e., Zr45Nb45Ti10, Zr42.5Nb42.5Ti15, and Zr40Nb40Ti20 (denoted ZNT10, ZNT15, and ZNT20, respectively), were designed based on the miscibility gap in the ZNT phase diagram and prepared by annealing of cold-rolled ingots. Their microstructures, mechanical properties, wear resistance, corrosion resistance, magnetic susceptibility, and biocompatibility were systematically studied. Spinodal decomposition occurred in the cold-rolled ZNT10 and ZNTi15 after annealing at 650°C for 2 h and resulted in nanoscale Zr-rich β1 and (Nb, Ti)-rich β2 phases, which significantly improved their yield strength and reduced their elastic modulus. The wear resistance of the alloys decreased with an increase in Ti content. Dense ZrO2, Nb2O5, and TiO2 oxide layers were formed during the polarization process in Hanks’ solution, which enhanced the corrosion resistance of the alloys. These ZNT alloys exhibited significantly lower magnetic susceptibility than medical Ti alloys. The ZNT alloys showed a cell viability of more than 94 % toward MG-63 cells after culturing for 3 d. Overall, the spinodal ZNT15 showed the best combination of mechanical properties, wear resistance, corrosion resistance, low magnetic susceptibility, and sufficient biocompatibility among the three alloys. Statement of SignificanceThis work reports on medium-entropy Zr–Nb–Ti (ZNT) alloys with heterostructure. Spinodal decomposition significantly improved their mechanical strength and reduced the elastic modulus of the alloys. The wear resistance of the ZNT alloys decreased with an increase in Ti content. Dense ZrO2, Nb2O5, and TiO2 oxide layers were formed during the polarization process in Hanks’ solution, which enhanced the corrosion resistance of the alloys. The ZNT alloys exhibited significantly lower magnetic susceptibility than medical Ti alloys. The ZNT alloys showed a cell viability of more than 94% toward MG-63 cells after culturing for 3 d. The results demonstrate that spinodal ZNT alloys have enormous potential as bone-implant materials due to their outstanding overall mechanical properties, high corrosion resistance, wear resistance, low magnetic susceptibility, and sufficient biocompatibility.

Oxide-Metal Hybrid Glass Nanomembranes with Exceptional Thermal Stability.

Contrary to oxide or polymeric glasses, metallic glasses are infamously known for their relatively limited thermal stability, which is often characterized by their narrow supercooled liquid regions. Nonetheless, we successfully fabricated metallic-glass based nanomembranes with an ultrahigh thermal ability by a polymer surface buckling enabled exfoliation technique. These nanomembranes exhibit a distinctive nanostructure with nanosized metallic-glasses encapsulated within an interconnected nanoamorphous-oxide network. Due to a pronounced nanoconfinement effect, crystallization is significantly suppressed. Consequently, these oxidized metallic-glass nanomembranes initiate a glass transition at 324 K at a heating rate of 10 K/min. Remarkably, they also showcase an expansive supercooled liquid region of 448 K, surpassing various metallic and oxide glasses reported. Furthermore, these nanomembranes not only exhibit a low elastic modulus but also achieve superplasticity even at room temperature. This unique blend of thermomechanical properties positions our metallic-glass based nanomembranes as an ideal candidate for nanofabrication processing, such as nanoimprinting, for the creation of next-generation nanodevices.

Stress-Dilatancy Behavior of Highly Elastic Rubber-Added Cohesionless Materials.

Dilatancy is commonly defined as the ratio of the rates of plastic volumetric strain to plastic deviatoric strain, denoted as Dp. Owing to the high modulus of elasticity, the elastic volumetric and deviatoric strain rates under shear stress in conventional cohesionless materials are negligible. Therefore, using the ratio of the rates of total volumetric to deviatoric strain (Dt) as an approximation is common in studying stress-dilatancy behavior and calibrating dilatancy model parameters. This approach is also common in the study of rubber-added cohesionless materials (RCM). However, RCM with a common range of rubber content exhibit a significantly lower modulus of elasticity compared to conventional cohesionless materials. Further research is needed to evaluate the potential impact of elastic strain rates in RCM on stress-dilatancy analysis. Therefore, comparisons were conducted on the stress-dilatancy responses of a series of tests on RCM, where dilatancy is calculated by Dp and Dt, respectively. Furthermore, a modified method for calibrating the parameters of a state-dependent dilatancy model considering Dp is presented. It turns out that Dp is better suited and more precise for dilatancy analysis on highly elastic RCM. Additionally, the dilatancy model can more precisely capture the test results of RCM with parameters calibrated by the proposed method.

New low elastic modulus equimassic βeta Ti-Nb-Zr-(Ta-Mo) multiprincipal alloys

The increasing life expectancy, evolving patient demographics, and advancements in implant technologies underscore the need for better biomaterials, particularly alloys with superior mechanical and chemical biocompatibility for biomedical applications like orthopedic implants. β-Ti alloys are promising due to their mechanical properties, including an elasticity modulus (E) of 44–80 GPa, and chemical/biological attributes such as corrosion resistance and osseointegration. This work developed equimassic multicomponent high (HEA) and medium entropy (MEA) β-Ti alloys within the ternary Ti-33Nb-33Zr, quaternary Ti-25Nb-25Zr-25Ta, and quinary Ti-20Nb-20Zr-20Ta-20Mo weight percent systems to achieve an optimized elastic modulus. The study analyzed β-Ti alloys with different β-stabilizing elements, leading to varying entropy levels, and established a relationship between microstructure and properties for enhanced implant efficacy. For the high entropy quinary alloy, increasing the number of alloying elements decreases lattice parameters, increasing the elastic modulus and Vickers microhardness (HV), from 247 HV for the ternary alloy to 453 HV for the quinary alloy. This corresponds to an increase in the entropy degree from 1.041 R to 1.523 R. While a higher entropy degree hinders a low elastic modulus, medium entropy β-Ti alloys such as the quaternary β-Ti-25Nb-25Zr-25Ta alloy achieve an elastic modulus as low as 73 GPa.

Evaluation of the Applicability of Waste Rubber in Insulation Panels with Regard to Its Grain Size and Panel Thickness.

This paper explores the effect of waste rubber grain size on the porosity, modulus of elasticity, thermal properties, and soundproofing performance of polymer composites with different thicknesses (10, 15, and 20 mm). All properties were tested in accordance with European standards, with the exception of porosity, which was measured using Archimedes' principle. The findings indicate that with a consistent amount of polyurethane glue, finer rubber grains result in composites with higher porosity, leading to a lower modulus of elasticity but enhanced thermal and sound insulation. In contrast, coarser rubber grains produced composites with lower porosity and a higher modulus of elasticity, though with slightly reduced thermal insulation and significantly worse soundproofing. A combination of fine and coarse rubber grains provided a balanced performance, offering both good thermal and sound insulation while maintaining a high modulus of elasticity. Among the thicknesses tested, 15 mm was identified as optimal, combining a relatively high modulus of elasticity, low thermal conductivity, and better airborne sound insulation index. Future research will focus on applying this composite in concrete building products that meet noise protection and energy efficiency standards.

Effect of ultrasound on the physicochemical, mechanical and adhesive properties of micro-arc oxidized coatings on Ti13Nb13Zr bio-alloy

Implant surgeries are increasingly challenging due to their rising number. Achieving the desired biomaterial surface properties to ensure a strong bond with human tissue is a significant issue. This study investigates the influence of ultrasound (US) during the micro-arc oxidation (MAO) process on Ti13Zr13Nb bio-alloy, an area not previously explored, to enhance titanium alloy coatings’ properties for biomedical applications. Porous calcium-phosphate-based coatings were successfully deposited on Ti13Zr13Nb using MAO and ultrasound micro-arc oxidation (UMAO). Various properties such as morphology, chemical composition, topography, wettability, surface free energy, thickness, adhesion to the substrate, as well as mechanical and corrosion characteristics were thoroughly analyzed. Cytocompatibility was assessed using human osteoblasts. Using US during the MAO process increased coating roughness (up to ~ 17%), core height (up to 22%), isotropy (up to 17%), thickness (up to ~ 46%), and hardness (up to ~ 18%), depending on MAO parameters and US mode. Optimal coating performance was achieved at 136 mA, 600 s, and a sinusoidal US setting, resulting in the highest isotropy (~ 79%) and rutile quantity (2.6%), the lowest elastic modulus (~ 57 GPa), and the contact angle of ~ 70°, all of which could have contributed to enhancing osteoblast viability in vitro. This study, for the first time, underscores the importance of using the US during the MAO in tailoring the Ti13Zr13Nb for specific biomedical applications.

Shear performance of glued and screwed timber-steel composite connections for composite timber-steel beams

Mid- to high-rise mass timber buildings gained popularity in the last decade. Yet, engineered wood products (EWPs) used to erect these buildings have structural limitations. EWPs present brittle failure modes, particularly in bending, shear and tension, and have a low modulus of elasticity resulting in shorted spans and deeper beams relative to those in the steel and reinforced concrete counterparts. Timber-steel hybrid beams represent a potential sustainable solution to overcome these limitations by taking advantages of the high strength, stiffness and ductility of steel, and the high capacity to weight ratio of timber. However, for this solution to be structurally performant, it is essential to create effective composite action between the two materials. This study therefore compares the structural efficiency of various bonding techniques between the steel and the timber materials. Two sets of assembly solutions, representing four connection types, were proposed and experimentally investigated: (1) connecting an embedded steel plate into the timber elements by using either polyurethane (PUR) structural adhesive with two manufacturing variations or 14 G×75 mm heavy duty screws, and (2) connecting a steel plate on the surface of the timber element using either PUR structural adhesive with self-tapping M4×40 mm screws or only self-tapping screws. Softwood Laminated Veneer Lumbers (LVL) and Grade 350 steel plates were used in the experimental tests. All bonding techniques were tested in shear. The shear capacity, the slip stiffness and the failure mode were evaluated. Additionally, the efficiency of the proposed manufacturing solutions was quantified by analytically evaluate the effective bending stiffness of a timber-steel composite beam manufactured with different bonding techniques being investigated. Results indicated that the glued connections allowed a significantly more efficient composite action, with failure occurring in the timber instead of at the composite interface and near-full composite action was reached, than the screwed connections. To achieve high composite action with the screwed solutions, a large number of screws was needed which may incur high manufacturing costs.

Deformation and optical aberration prediction in ultra-precision Single Point Diamond Turning of optical components

Aluminum is the material of choice for the majority of aerospace components, and, in the past few years, its application has been extended also to the mirrors of space telescopes because of the improved thermal behavior and the possibility to build the entire telescope with the same material. However, the low elastic modulus of such material, combined with the extremely tight tolerances of optical applications, make the production of these components very challenging and, usually, based on a trial-and-error approach. This paper presents a structured methodology for the prediction of the results of manufacturing in Single Point Diamond Turning of optical components, both in terms of absolute deformation as well as optical aberrations (via Zernike polynomials). All the most significant parameters acting on the workpiece have been simulated and combined. The proposed approach has been experimental validated on an actual aluminum mirror, proving its good accuracy (<5 % rms error). While some improvement can be performed to better match the experimental data in terms of Zernike coefficients, especially for non-symmetric aberrations, this paper forms the basis for an off-machine optimization of the SPDT process, drastically reducing the trial-and-error efforts.

Reduction in Floor Impact Noise Using Resilient Pads Composed of Machining Scraps.

Floor impact noise is a significant social concern to secure a quiescent living space for multi-story building residents in South Korea. The floating floor, consisting of a concrete structure on resilient pads, is a specifically designed system to minimize noise transmission. This floating structure employs polymeric pads as the resilient materials. In this study, we investigated the utilization of helically shaped machining scraps as a resilient material for an alternative approach to floor noise reduction. The dynamic elastic modulus and loss factor of the scrap pads were measured using the vibration test method. The scrap pads exhibited a low dynamic elastic modulus and a high loss factor compared to the polymeric pads. Heavyweight impact sound experiments in an actual building were conducted to evaluate the noise reduction performance. The proposed pads showed excellent performance on the reduction in the structure-borne vibration of the concrete slab and resulting sound generation. The analytical model was used to simulate the response of the floating floor structure, enabling a parametric study to examine the effects of the resilient layer viscoelastic properties. Both experimental and analytical evidence confirmed that the proposed scrap pads contribute to the development of sustainable solutions for the minimization of floor impact noise.

Ductility assessment of GFRP reinforced concrete beams with a wedge-based mechanical model accounting for discrete fibers and confinement

Glass fiber-reinforced polymer (GFRP) bars for internal reinforcement for concrete have gained attention due to their non-corrosive properties, high resistance, and electromagnetic transparency. On the other hand, the brittle behavior and low modulus of elasticity of FRP bars limit their application and diffusion in the civil construction market. From this perspective, this work investigates the influence of three components on the increase of ductility of GFRP beams: i) discrete alkali-resistant glass fibers added to the concrete; ii) confinement of the concrete with GFRP stirrups; and iii) use of longitudinal reinforcement on the compression zone. An experimental program including four over-reinforced beams with different reinforcement configurations was conducted. The beams were tested in four-point bending configuration and the use of fibers, stirrups and compression reinforcement contributed to substantially increasing the beam ductility index. Finally, a concrete wedge model was developed to obtain equivalent stress-strain relationships for the concrete in compression. The model was successfully validated against experiments and proved to be a useful tool for rationally evaluating GFRP RC beams’ ductility.

Ti-Ta-Cu Biocompatible Alloy System Development via Selective Laser Melting for Prosthetic Applications

This study investigated the development of Ti-Ta-Cu alloys via selective laser melting (SLM) for potential prosthetic applications. Ti-Ta-Cu alloys with 10, 15, and 20 wt.% Ta were fabricated using in situ alloying of elemental powders. We examined the effects of Ta content and SLM processing parameters on microstructure, phase composition, mechanical properties, and corrosion resistance. X-ray diffraction analysis revealed an increase in β-phase content with increasing Ta concentration. Microstructural analysis showed a dendritic structure in Ta-rich areas, with remelting strategies improving chemical homogeneity and Ta dissolution. The Ti-20Ta-5Cu alloy exhibited the best balance of strength and ductility, with an ultimate tensile strength of 1011 MPa and elongation of 5.7%. All compositions demonstrated lower elastic moduli (103–109 GPa) compared to traditional titanium alloys. Microhardness values were highest for Ti-15Ta-5Cu, ranging from 359 to 410 HV0.5 depending on SLM parameters. Corrosion testing in Hank’s solution showed improved pitting resistance for Ti-15Ta-5Cu and Ti-20Ta-5Cu compared to Ti-10Ta-5Cu. The study demonstrates the feasibility of producing Ti-Ta-Cu alloys with tailored properties via SLM, offering potential for customized prosthetic applications with improved biomechanical compatibility and functionality.

Evolution of TiAlSi thin film coatings under varying target power in DC magnetron sputtering

This study, for the first time, presents the growth, nucleation, and characteristics of TiAlSi thin films sputtered from a partially sintered Ti30Al16Si10 (at. %) composite target under controlled conditions of target power. The TiAlSi thin films were grown on soda-lime glass substrates through Direct Current (DC) sputtering at varying levels of the target power: 73.2 W, 151.2 W, and 269.5 W. The other deposition parameters: the deposition temperature, time, argon mass flow rate, substrate rotation, and deposition pressure, were kept constant at 23 °C, 150 min, 25 sccm, 5 rpm, and 10−3 mbar, respectively. The pre-sputter power, argon flow rate, and time were also kept constant at 73.2 W, 20 sccm, and 5 min, respectively. The physical properties, microstructure, crystal structure, topography, and mechanical properties of the thin film coatings were analysed. The thickness and rate of deposition of the TiAlSi thin films increased with an increase in the target power (73.2 W – 269.5 W) from 414.6 nm and 0.046 nm/s to 1358.8 nm and 0.151 nm/s, respectively. The chemical composition of all the thin films remained constant, with the formation of a uniform TiAlSi alloy with no segregation of elements. However, a thin (wetting) interlayer consisting of Si and O elements was observed between the TiAlSi layer and the glass substrate. Further, the structure sizes and roughness values of the TiAlSi thin films increased with an increase in the target power, with a maximum of 75.4 nm for the size and 4.78 nm for the RMS roughness of thin films deposited at the maximum target power (269.5 W). Lastly, mechanical analysis of the TiAlSi thin films depicted an increase in the hardness as the target power increased, with the highest hardness at maximum power (269.5 W) obtained as 4.76 GPa. Despite having the lowest elastic modulus (50.5 GPa), the coating deposited at the highest power exhibited the highest plasticity index (H/E) and plastic deformation factor (H3/E2) of 0.094 and 0.042 GPa, respectively, which indicated the high resistance to abrasive wear, cracking, and deformation, compared to thin films deposited at the lowest target power (H/E = 0.066 and H3/E2 = 0.015 GPa). This study demonstrates that target power is a significant factor in determining the growth of TiAlSi thin films during the sputtering process and can be used for better control of their physical, structural, and mechanical properties.

Lamellar liquid crystals in commercial polyether‐modified polydimetilsiloxanes for coating applications: Structure, rheology and cross‐linking

AbstractWe have constructed the phase diagrams in water of two commercial additives for coatings consisting of polyether‐modified polydimethylsiloxanes. These aqueous systems form a liquid crystal mesophase (LC) at copolymer concentrations higher than 60 wt%. At low copolymer concentrations, this LC coexists with a diluted aqueous phase. Small angle x‐ray scattering (SAXS) measurements and polarized optical microscope observations indicate that the structure of the mesophase is lamellar, with an interlayer spacing that increases linearly with the concentration of water in the system. The lamellar liquid crystals display temperature‐dependent viscoelastic behavior, with the copolymer with longer spacing showing a much lower elastic modulus. Since one of the copolymer has terminal acryl groups, its lamellar phase can be crosslinked to produce gelled liquid crystals. Other cross‐linked self‐assembled structures, such as bicontinuous microemulsions, are envisaged.

Influences of size effect and workpiece temperature during cryogenic micro milling of soft viscoelastic polymer: an experimental assessment

Application of tool-based micromachining in soft polymer has been limited due to high adhesion and low elastic modulus of this material at room temperature. This study aims to evaluate the machinability of a typical viscoelastic soft polymer and understand the effect of material and process parameters on machining performances. In this study, a micro-milling process using cryogenic-assisted cooling is proposed and the importance of temperature control toward glass transition zone was particularly addressed. To identify insight of machinability in micro domain, this article also determines minimum uncut chip thickness (MUCT) and size effects by considering the variations of cutting force and surface integrity with the ratio of h/re (uncut chip thickness (h) to cutting edge radius (re)). The experimental results reveal that consideration of size effect during micromilling of soft viscoelastic polymer helps in reduction of machined surface roughness (Sa) value. Based on the cutting force pattern, it is evaluated that higher machining stability can be achieved during cryogenic machining by reduction of specific cutting force value. Moreover, temperature range around glass transition zone yields more promising experimental outcomes, outperforming other cooling zones.

Effect of micromechanical properties of commercial grade electrolytic copper foils on lithium-ion batteries

As the carrier and electrical conduction component of positive and negative electrode materials, current collector plays an important role in lithium-ion batteries(LIBs). With the industrial application of silicon-doped anode materials with higher gram capacity, the huge volume change of silicon-doped anode materials puts forward higher requirements for the mechanical properties of copper foils(CFs). It is of great significance to study the effect of micromechanical properties on LIBs for the application screening of CFs. In this article, the effects of micromechanical properties of conventional tensile strength(CTS), high tensile strength(HTS) and ultra-high tensile strength(UHTS) commercial grade electrolytic CFs on LIBs were studied. The tensile strength of CTS, HTS and UHTS was 316.88 MPa, 464.74 MPa and 673.43 MPa, respectively; the elongation were 6.49 %, 5.38 % and 4.47 %, respectively. The surface morphology and XRD tests show that the microstructure such as grain size and dislocation density are the key factors affecting the mechanical properties of CFs. And under the same conditions, the main factors affecting bonding strength of electrode are microstrain and residual stress of CFs rather than surface roughness. The larger the microstrain and residual stress of CFs, the worse the interface bonding strength between CFs and coating materials, and the larger the corresponding interface charge transfer impedance, which is well confirmed by DCR and EIS. The charge-discharge test results show that the mutual stress between CFs and coating materials also have a great influence. The lower elastic modulus and microscopic stress of CFs can better eliminate the expansion pressure and contraction tension of coating materials, thereby reducing the resistance and overpotential in the process of lithium-ion diffusion, and achieving higher capacity under high rate system. The retention rates of three CFs after 500 cycles at 25℃ and 45℃ were 25-CTS(92.64 %), 25-HTS(90.63 %) 25-UHTS(89.11 %), and 45-CTS(82.17 %), 45-HTS(82.14 %), 45-UHTS(80.77 %), respectively, which indicates that the difference in mechanical properties of CFs have an important influence on long-term application of LIBs. The primary cause of the variation in electrochemical performance, aside from copper foil’s conductivity, is the phase interface shift brought on by the microstress of the material; and the overpotential caused by the phase interface force cannot be ignored.

Synthesis and Characterization of Ti-13Ta-6Sn Foams Produced Using Mechanical Alloying, the Space Holder Method and Plasma-Assisted Sintering

Highly porous titanium foams are great candidates for replacing bone structures with a low elastic modulus owing to their ability to avoid the stress shielding effect. However, the production of highly porous foams (&gt;70 vol.%) with well-distributed, stable, and predictable porous architectures using powder compaction and space holders is challenging. In this study, pure titanium powder and mechanically alloyed Ti-13Ta-6Sn were mixed with 50, 70, and 80 vol.% KCl powders as a space holder, cold-compacted, and sintered in a plasma-assisted sintering reactor to produce highly porous foams. The space holder was completely removed using heat and plasma species collisions prior to sintering. A Ti-13Ta-6Sn alloy powder with α, β, and metastable FCC-γ phases was synthesized. The characteristics of the alloyed powder, mixing step, and the resulting sintered samples were compared to those of CP-Ti. After sintering, the alloy exhibited α and β phases and a reduced elastic modulus. Foams with an elastic modulus in the range of the cortical and trabecular bones were obtained. The results showed the effects of the space holder volume fractions on the volume fraction, size, distribution, interconnectivity, and shape of the pores. The Ti-13Ta-6Sn foams exhibited a uniform open-celled porous architecture, lower elastic modulus, higher yield strength, and higher passivation resistance than CP-Ti. Ti-13Ta-6Sn exhibited a nontoxic effect for the mouse fibroblast cell line.