In this work, the effect of Fe and Ta content on the microstructure and β phase stability of as-cast designed Ti-xFe-yTa (x = 8, 9, 10 wt% and y = 0, 5, 8, 9, 10 wt%) alloys was investigated. ...Additionally, its influence on the resulting mechanical properties including hardness (H), reduced elastic modulus (Er), elastic recovery and wear resistance of the alloys was evaluated using nanoindentation. Microstructural studies and phase analysis showed that all alloys are comprised of body-centered cubic β and orthorhombic α″ phases, the proportion of which depends on their Fe and Ta contents. Nanoindentation measurements indicated that the reduced elastic modulus of the alloys decreases with increase in the Fe and Ta contents owing to increase in their β phase proportion and its stability. It was also observed that the hardness and elastic recovery of the alloys are in the range of 3.38–5.73 GPa and 0.241–0.298, respectively, which are higher than the corresponding ones for the commonly used CP-Ti biomaterial. Additionally, their H/Er and H3/Er2 ratios are higher than those of CP-Ti suggesting a better wear resistance of the designed Ti-Fe-Ta alloys. It is concluded that among the studied alloys, Ti-10Fe-10Ta with dominant β phase microstructure exhibits a good combination of mechanical properties which make it more desirable than CP-Ti for orthopedic application.
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•Fe and Ta addition affects the β stability and α″ phase content in the alloys.•The reduced elastic modulus of the alloys decreases with Fe and Ta addition.•All alloys show higher hardness, elastic recovery and wear resistance than CP-Ti.•Ti-10Fe-10Ta exhibits the lowest reduced elastic modulus among the studied alloys.•Ti-10Fe-10Ta is more desirable than CP-Ti for biomedical application.
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•The properties of different rejuvenated SBS modified asphalt binders were researched.•The network structure of the aged SBS modified asphalt binder can be restored.•The properties of ...asphalt binder with good network structure can be regulated in a reasonable range.
SBS modified asphalt binder (SBSMA) is widely used because of its excellent pavement performance. Recycling application for aged SBSMA has drawn increasing attention. In this study, aged SBSMA was rejuvenated with different rejuvenation methods, including the use of rejuvenator (RA), original SBSMA, base asphalt (SK-70) and original SBSMA mixed with SK-70. The conventional performance and rheological behavior of different rejuvenated SBSMA were investigated. The microscopic changes were analyzed by using Gel permeation chromatography (GPC), Fourier transform infrared (FTIR) spectroscopy and Fluorescence microscopy (FM). Results revealed that RA and original SBSMA have significant effect on the improvement of the physical-rheological and microstructures of aged SBSMA, but SK-70 did not exhibit good rejuvenation effect. The conventional tests showed that the addition of RA greatly improved the low temperature ductility and elastic recovery rate of aged SBSMA. Moreover, it was proved that RA could increase the creep compliance and improve the stress relaxation ability of aged SBSMA according to physical rheological parameters. This result indicated that RA improved the cracking resistance of aged SBSMA at low temperature. Based on the microscopic test results, it was found that RA not only could regulate the internal components of aged SBSMA, but also restore the network structure of aged SBSMA. Furthermore, the SBS polymer content indices and the softening indices are closely correlated with the performances of the rejuvenated SBSMA. From the analysis, it is necessary to rejuvenate the aged SBSMA by softening base asphalt and restoring the network structure of SBS copolymer.
Capabilities for controlled formation of sophisticated 3D micro/nanostructures in advanced materials have foundational implications across a broad range of fields. Recently developed methods use ...stress release in prestrained elastomeric substrates as a driving force for assembling 3D structures and functional microdevices from 2D precursors. A limitation of this approach is that releasing these structures from their substrate returns them to their original 2D layouts due to the elastic recovery of the constituent materials. Here, a concept in which shape memory polymers serve as a means to achieve freestanding 3D architectures from the same basic approach is introduced, with demonstrated ability to realize lateral dimensions, characteristic feature sizes, and thicknesses as small as ≈500, 10, and 5 µm simultaneously, and the potential to scale to much larger or smaller dimensions. Wireless electronic devices illustrate the capacity to integrate other materials and functional components into these 3D frameworks. Quantitative mechanics modeling and experimental measurements illustrate not only shape fixation but also capabilities that allow for structure recovery and shape programmability, as a form of 4D structural control. These ideas provide opportunities in fields ranging from micro‐electromechanical systems and microrobotics, to smart intravascular stents, tissue scaffolds, and many others.
The use of shape‐memory polymers in mechanically guided formation of 3D structures provides immediate access to freestanding 3D architectures and functional devices across length scales from micrometers to centimeters. The resulting engineering options provide opportunities in fields ranging from micro‐electromechanical systems and microrobotics to smart intravascular stents, tissue scaffolds, and many others.
Since, during different physical activities, garments should have the ability to be extended due to the body movements, it is a necessity for it to have suitable elasticity and recovery in order to ...provide comfort for the wearer. Therefore, the dynamic elastic recovery behavior of the fabric is very important and indicates the resistance of the garment and its immediate response to body movements. In this research, four weft knitted fabrics with different elastic properties have been studied. Besides the analysis of the tensile properties of fabric, the influence of fabric elasticity, strain percentage and the number of loading cycles on the dynamic elastic recovery has been investigated. Moreover, the fatigue and residual percentage and residual strain were calculated. Furthermore, the exerted pressure by the garment on the body, was measured throughout wearing leggings with different sizes. Finally, the relationship between elastic recovery and the amount of exerted pressure was investigated. The results showed that in both course and wale directions, by increasing the applied strain level, the dynamic elastic recovery of fabric decreased. Moreover, it was revealed that the fabric with more elasticity had better elastic recovery. The higher elasticity of the fabric led to higher and lower static and dynamic pressure, respectively. In addition, by increment of dynamic elastic recovery of fabric, lower pressure was applied on the body during walking and running which indicates to the improvement of body movement comfort.
The anisotropy of the grain orientation of aluminium nitride (AlN) ceramics leads to great differences in elastic recovery of grains which makes it difficult to achieve high machining accuracy. In ...this study, the anisotropic elastic recovery behavior of AlN ceramic was investigated by nanoindentation and scratch experiments. The results show that as the main Euler angle the grain increases, the elastic recovery rate of the indentation decreases from 39% to 31%, and the elastic recovery of scratch decreases from 47% to 39%. However, there is a local peak in the elastic recovery rate when the main Euler angle is 75° during scratching. Through the analysis of the Schmid factor, it is found that the ease of activating the sliding system of a grain has a great impact on the elastic recovery rate of scratches. Through further analysis, the elastic recovery rate of grains is mainly affected by the combined action of the base slip system and the prismatic slip system during scratching. The prediction models of the elastic recovery rate during nanoindentation and scratching were established and the prediction results are consistent with the experimental results, indicating the reliability of the prediction model.
•The elastic recovery rate (η) of AlN exhibits distinct anisotropy.•The elastic recovery rate decreases with the main Euler angle of grain increasing.•The η of indentation is influenced by the ratio of hardness to elastic modulus of grain.•The η of scratch is influenced by the synergistic effect of basal and prismatic slip system.•The prediction models of η during nanoindentation and scratching were established.
Multilayers consisting of alternating soft and hard layers offer enhanced toughness compared to all-hard structures. However, shear instability usually exists in physically sputtered multilayers ...because of deformation incompatibility among hard and soft layers. Here, we demonstrate that 2D hybrid organic-inorganic perovskites (HOIP) provide an interesting platform to study the stress-strain behavior of hard and soft layers undulating with molecular scale periodicity. We investigate the phonon vibrations and photoluminescence properties of Ruddlesden-Popper perovskites (RPPs) under compression using a diamond anvil cell. The organic spacer due to C4 alkyl chain in RPP buffers compressive stress by tilting (n = 1 RPP) or step-wise rotational isomerism (n = 2 RPP) during compression, where n is the number of inorganic layers. By examining the pressure threshold of the elastic recovery regime across n = 1-4 RPPs, we obtained molecular insights into the relationship between structure and deformation resistance in hybrid organic-inorganic perovskites.
Nature has engineered delicate synergistic covalent and supramolecular polymers (CSPs) to achieve advanced life functions, such as the thin filaments that assist in muscle contraction. Constructing ...artificial synergistic CSP materials with bioinspired mechanically adaptive features, however, represents a challenging goal. Here, we report an artificial CSP system to illustrate the integration of a covalent polymer (CP) and a supramolecular polymer (SP) in a synergistic fashion, along with the emergence of notable mechanical and dynamic properties which are unattainable when the two polymers are formed individually. The synergistic effect relies on the peculiar network structures of the SP and CPs, which endow the resultant CSPs with overall improved mechanical performance in terms of the stiffness, strength, stretchability, toughness, and elastic recovery. Moreover, the dynamic properties of the SP, including self‐healing, stimuli‐responsiveness, and reprocessing, are also retained in the CSPs, thus leading to their application as programmable and tunable materials.
Greater than the sum of the parts: The combination of a covalent polymer (CP) and a supramolecular polymer (SP) has led to networks (CSPs) in which the properties of the component polymers are not only retained, but improved upon. The CSPs show improved mechanical performance (stiffness, strength, stretchability, toughness, and elastic recovery) as well as improved dynamic properties (self‐healing, stimuli‐responsiveness, and reprocessing).
The removal mechanism of conventional cutting and in-process-heat laser-assisted cutting (In-LAC) of binderless polycrystalline tungsten carbide (WC) material is studied through systematic numerical ...analysis and experimental investigation. The proposed In-LAC model considers the accumulated thermal effect and the laser in-process-heat thermal boundary condition simultaneously. Results of molecular dynamics (MD) analysis are remarkably consistent with the experimental results qualitatively. The high-temperature nanoindentation test reveals the improved machinability of WC at an elevated temperature and provides a theoretical basis for cutting force reduction. A small Young's modulus measured at an elevated temperature presents a large elastic recovery value for the In-LAC model. The critical depth of no observed surface cracks of binderless WC increases from 26.6 nm to 106.3 nm, which can be attributed to in-process laser assistance. Furthermore, the In-LAC method is beneficial to avoid subsurface crystal bending and reduce subsurface damage in the MD model and the taper cutting sample subsurface. The existence of the laser annealing effect during the In-LAC process is directly proven by binderless WC cross-section transmission electron microscopy (TEM). According to the simulation analysis results and diamond turning chip morphology, the optimal laser power for polycrystalline WC ranges from 10 W to 15 W, which facilitates obtaining the surface finish of 4.66 nm in Sa and significantly improving the tool life.
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•An accurate MD model for In-LAC is successfully established.•The binderless WC removal mechanisms of conventional cutting and In-LAC have been revealed.•The NOSC depth of binderless WC was improved from 26.6 nm to 106.3 nm with better subsurface integrity.•The surface finish of 4.66 nm in Sa was achieved, while the diamond tool wear was improved simultaneously.
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Various studies investigate the predictability of the compressibility and compactibility of tablet formulations based on the behaviour of the pure materials. However, these studies ...are limited to a few materials so far probably because of the complexity of the powder compaction process. One approach preventing the excessive increase in complexity is the extension of the investigations from pure materials to binary powder mixtures. The focus of this study is on the predictability of the compressibility and compactibility of binary mixtures consisting of an active pharmaceutical ingredient (API) and the excipient microcrystalline cellulose. Three APIs with markedly different deformation behaviour were used. The API concentration and type are systematically varied. For all three material combinations it is found that the in-die compressibility of the binary mixtures can be precisely predicted based on the characteristic compression parameters of the raw materials using the extended in-die compression function in combination with a volume-based linear mixing rule. Since the tablet porosity (out-of-die) also follows a linear mixing rule, the predictability can be further extended using the method of Katz et al. In contrast, the influence of the API concentration on compactibility or rather on tablet tensile strength is non-linear and strongly dependent on the deformation behaviour of the API, making the predictability more difficult. Neither the approach of Reynolds et al. nor this of Kuentz and Leuenberger are able to predict the compactibility when clear deviations from a linear mixing rule appear.
Abstract
Conductive hydrogels (CHs) are regarded as one of the most promising materials for bioelectronic devices on human‐machine interfaces (HMIs). However, conventional CHs cannot conform well ...with complex skin surfaces, such as hairy or wrinkled skin, due to pre‐formation and insufficient adhesion; they also usually lack antibacterial abilities and require tissue‐harm and time‐consuming preparation (e.g., heating or ultraviolet irradiation), which limits their practical application on HMIs. Herein, an in situ forming CH is proposed by taking advantage of the PEDOT:PSS‐promoted self‐polymerization of zwitterionic 2‐(methacryloyloxy)ethyldimethyl‐(3‐sulfopropyl) (SBMA). The hydrogel is formed spontaneously after injection of the precursor solution onto the desired location without any additional treatments. The as‐prepared hydrogel possesses excellent elasticity (elastic recovery >96%), desirable adhesive strength (≈6.5 kPa), biocompatibility, and intrinsically antibacterial properties. Without apparent heat release (<5 °C) during gelation, the hydrogel can form in situ on skin. Additionally, the obtained hydrogel can establish tight contact with skin, forming highly conformal interfaces on hairy skin surfaces and irregular wounds. Finally, the in situ forming hydrogels are applied as conformal epidermal electrodes to record stable and reliable surface electromyogram signals from hairy skin (with high signal‐to‐noise ratio, SNR ≈ 32 dB) and accelerate diabetic wound healing under electrical stimulation.
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