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[Display omitted] • The as-deposited AlCrFeCoNiCu 0.5 films were annealed at 500 °C for up to 72 h. • Four new phases were formed during the 72 h of annealing. • The formation of a new heterogeneous nanocomposite thin film was revealed. • A 30% enhancement of mechanical properties was achieved after 72 h annealing. • The as-annealed thin films exhibited superior thermal stability. High entropy alloy (HEA) films offer excellent mechanical properties due to their random solid solution structure. However, their large grain boundary volume fraction can cause thermal instability, resulting in phase decomposition that affects their high-temperature performance. Nevertheless, it remains an interesting question whether phase decomposition can be used as a processing tool to create new HEA materials. In this study, AlCrFeCoNiCu0.5 HEA thin films were fabricated and annealed at 500 °C for up to 72 h. The 72-hour annealed thin film exhibited a 30 % increase in mechanical properties, exceeding most other HEA thin films. Characterization using X-ray and electron microscopy revealed a decomposition-induced phase transformation, which produced four new phases, including Cu-rich FCC phase, Cr-rich BCC phase, and ordered B2 phase of AlNi and FeCo. The enhanced mechanical properties were due to back stress strengthening and BCC + B2 phase strengthening. The 72-hour annealed thin film also showed excellent thermal stability through a new round of annealing, exhibiting a low variation in microstructure and chemical composition after being annealed at 500 °C for 100 h. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel Sc/Zr/Ti/Er modified Al-Cu alloy was successfully fabricated by wire-arc directed energy deposition technology. • The fine equiaxed grain structure was obtained due to the heterogeneous nucleation caused by the primary Al3X dispersoids. • Homogenization prefabricates more Al3X dispersoids, which promote the transition from θ″ to θ′ precipitate. • Homogenization ripens the existing pores, resulting in a better tensile isotropy. In this study, a novel Sc/Zr/Ti/Er-modified 2219 aluminum alloy was designed and wall-shaped components were then fabricated by wire-arc directed energy deposition (DED). Due to the heterogeneous nucleation promoted by primary Al 3 X dispersoids, the as-deposited alloy exhibits a highly equiaxed fine grain structure. Two heat treatment schedules were conducted to tailor the strength and thermal stability of the alloy. Compared with the classical T6 heat treatment, the additional homogenization step before the T6 heat treatment (HT6) prefabricated more Al 3 X dispersoids, which indirectly promoted the transition from θ″ precipitates to θ′ precipitates, resulting in a slight reduction in strength. However, this homogenization step helps to avoid the aggregation of pores by promoting pores ripening and significantly alleviates the anisotropy of ductility. In addition, the better thermal stability of the HT6 heat treated alloy is due to more Al 3 X dispersoids and finer θ′ precipitates with high coarsening resistance caused by the segregation of Sc and Mn at the θ′/Al interface during thermal exposure. In general, the wire-arc DEDed micro-alloyed 2219 Al alloy exhibits a promising combination of strength and ductility after heat treatment and its mechanical properties are superior to those of the wrought micro-alloyed Al-Cu alloys. [ABSTRACT FROM AUTHOR]

The microstructure design strategy is introduced to improve the mechanical property of a novel γ-Ti-43.5Al-6.5Nb-1.5Cr-0.5C/TiB 2 metal matrix composite (MMC) fabricated by hot isostatic press (HIP). With increasing the content of TiB 2 from 0 to 3 wt%, the average grain size, {001} maximum texture index and average schmid factor of HIP-processed Ti-43.5Al-6.5Nb-1.5Cr-0.5C/TiB 2 parts generally decrease from 27.4 μm, 7.9 and 0.43 to 22.7 μm, 4.1 and 0.38, in addition, the crystallographic texture transforms from the mixture of (001) and (111) orientations to a strong (101) orientation. The phases evolution mechanism in the HIP-processed Ti-43.5Al-6.5Nb-1.5Cr-0.5C/TiB 2 parts can be divided into four steps: first of all, β phase transforms to γ and α phases, then, a small amount of new phases of TiB and TiC emerge by the diffusion of Ti and C atoms, subsequently, the β and α orderly transform to B 2 and α 2 , lastly, the B 2 , α 2 , TiB 2 , TiB and TiC uniformly distribute in the γ matrix. Both the tensile strength and strain of HIP-processed Ti-43.5Al-6.5Nb-1.5Cr-0.5C/TiB 2 components increase from 471.9 MPa and 1.7% to 653.4 MPa 2.1% with the increase of TiB 2 content from 0 to 3 wt%. [ABSTRACT FROM AUTHOR]

Conventional polyimide nanocomposites reinforced with graphene-based nanofillers usually possess excellent properties, such as high thermal decomposition temperature, enhanced tensile strength, tensile modulus, etc. However, the elongation at break of the nanocomposites is reduced. Here, we prepared N-doped graphene quantum dots/colorless polyimide nanocomposite (N-GQDs/CPI) films for the first time by in-situ polymerization, whose elongation at break is about 2 times that of the pure film. Meanwhile, the thermal properties and other mechanical properties of the films are improved. Through analyzing FT-IR, XPS, XRD, TAG SEM, etc. of N-GQDs and the films, we consider that the strengthening mechanism of matrix performance is attributed to N-GQDs' well dispersion, its small size effects and strong interface interaction with the matrix. Furthermore, at the indicative wavelength of 550 nm, the optical transmittance of the film with 1 wt% N-GQDs still maintains 79%, indicating the resulting films have excellent optical transmittance. The hydrophilic properties of the prepared films' surface is reduced, their water surface contact angle are increased from 63 ± 2.7° to 92 ± 1.7° with the content of N-GQDs increasing. This research shows that N-GQDs can enhance the various properties of polyimide and provides a high performance nanocomposite films for potential flexible substrates. [ABSTRACT FROM AUTHOR]

More effective approaches need to be developed for solving the aging and thermal stability problems of crumb rubber modified asphalt (CRMA). This paper focused on microwave and trans-polyoctenamer (TOR). Therefore, various CRMA were prepared by crumb rubber (CR), microwave irradiated CR, TOR and base asphalt. The samples were subjected to thin film oven test (TFOT), pressure aging vessel (PAV) and high temperature storage tests. The effects of microwave and TOR were evaluated by rheological, FTIR and SEM tests. The results showed that microwave activated CR increases the risk of fatigue cracking caused by hardening effect of aging but endows the aged residue with stronger resistance to thermal cracking. These results attribute to the degradation and de-vulcanization effect of microwave on CR (verified by FTIR). TOR activated CRMA displayed a more obvious hardening effect and the improved low temperature creep behavior after aging. TOR improves the compatibility and storage stability of CRMA. Double bonds in TOR participate in chemical reaction and benefit to stability, which are verified by the decreased intensity of peak at 966 cm − 1 . However, microwave treatment on CR has negative effect on stability of CRMA. Thermal stability was further verified by steady flow method. [ABSTRACT FROM AUTHOR]

[Display omitted] • Compact and nanogranular ZrCu/O films were deposited by pulsed laser deposition and annealed to investigate thermal stability. • Nanogranular films crystallize at 300 °C, while the crystallization of compact films occurs >420 °C. • The Young's modulus and hardness increase with annealing temperatures due crystallization process, reaching 180 and 14 GPa for nanogranular films. • The residual stresses of compact films increase with annealing temperature, while for nanogranular ones they reach a maximum at 420 °C, indicating a complete crystallization. • The evolution of structural/mechanical properties is studied, considering film morphology, local chemistry and free volume. Binary ZrCu nanocomposite amorphous films are synthetized by pulsed laser deposition (PLD) under vacuum (2 × 10−3 Pa) and 10 Pa He pressure, leading to fully amorphous compact and nanogranular morphologies, respectively. Then, post-thermal annealing treatments are carried out to explore thermal stability and crystallization phenomena together with the evolution of mechanical properties. Compact films exhibit larger thermal stability with partial crystallization phenomena starting at 420 °C, still to be completed at 550 °C, while nanogranular films exhibit early-stage crystallization at 300 °C and completed at 485 °C. The microstructural differences are related to a distinct evolution of mechanical properties and residual stress, with compact TFMGs showing the highest values of Young's modulus (157 GPa), hardness (12 GPa), strain rate sensitivity (0.096), and local residual stress (+691 MPa) upon annealing at 550 °C, while nanogranular films reach the maximum values of mechanical properties at 485 °C followed by relaxation at higher temperatures due to complete crystallization. We show that PLD in combination with post-thermal annealing can generate different families of amorphous films with varying nanoscale morphologies, resulting in tunable mechanical properties and thermal stability, which can thus be used for designing novel film configurations for different fields of application. [ABSTRACT FROM AUTHOR]

[Display omitted] • The mechanical properties and thermal stability of nanostructured columnar Zr 100-x Cu x thin film metallic glasses were investigated and compared to those of homogeneous films. • Crystallization temperature, hardness and elastic modulus were found to be mostly dependent on composition and local atomic order rather than from film nanostructure. • Viscoplastic behavior show high influence on both film composition and nanostructure, with columnar Zr-rich films showing higher tendency toward serrated flow deformation. • Resistance to cracking is higher for Cu-rich and homogeneous films thanks to the higher density of full icosahedral atomic packing, while interfaces favored crack initiation. Thin film metallic glasses (TFMGs) are a novel class of materials showing a mutual combination of large plastic deformation in tension (>10% strain) and superior yield strength up to ∼ 3.5 GPa, which make them ideal candidates for applications such as flexible electronics. Nevertheless, a clear relationship between the atomic structure and mechanical properties of TFMGs has not yet been achieved. In particular, the role of composition in determining a different local atomic order and the effect of nanostructure on TFMGs properties must be further investigated. In this work, the mechanical properties and thermal stability of several amorphous Zr 100-x Cu x TFMGs with either compact or fine columnar nanostructure were studied. The mediating role of composition in controlling crystallization temperature and hardness is here reported, which was found to increase from 4.6 to 7.7 GPa with increasing Cu content from 26 to 76 at.%. Moreover, plastic behavior and fracture resistance are shown to be highly dependent on both composition and nanostructure, with the Cu-rich and homogeneous film able to withstand elongation up to 2% strain before crack initiation. These results underline how atomic structure changes induced by composition can effectively influence TFMG properties, while demonstrating an approach to tune their behavior for various technological applications. [ABSTRACT FROM AUTHOR]

Highlights: [•] A new strategy was proposed to make PVA/rGO composites by solvothermal reduction. [•] The solvent acted not only as a reducing agent but also as a good stabilizer. [•] The homogeneous dispersion of rGO sheets in the PVA matrix was achieved. [•] The crystallinity of PVA/rGO nanocomposites was investigated. [•] Mechanical properties and thermal stability were greatly improved by adding rGO. [Copyright &y& Elsevier]

The negative thermal expansion (NTE) or nearly zero thermal expansion (NZTE) behaviors have been found in some magnetic metallic compounds with great application prospects. However, it is a big challenge for applications that the responding temperature range is not broad enough or far away from room temperature. Herein, a new method is put forward to design the wide temperature range of NTE and NZTE Behavior by NTE/NZTE multi-phase composite. In this method, the optimized volume fraction of the components achieves a concordant collaboration of multi-phase in the counteraction of NTE and positive thermal expansion (PTE) at several adjacent temperature ranges and thus the temperature range is broadened as expected. By this method, MnCuGeN-based NTE composite (290 K ≤ T ≤ 385 K, ΔT = 95 K) and MnCuZnSiGeN-based NZTE composite (200 K ≤ T ≤ 400 K, ΔT = 200 K) with excellent stability have been successfully designed and prepared. This idea will open an avenue to the multi-phase composite with designable NTE/NZTE properties, which would have important applications in aerospace and other modern industries. [Display omitted] • A novel method is proposed to design multi-phase composite with NTE/NZTE behavior in a broadened temperature range. • The feasibility of the broadening effect for the proposed method is verified by multi-phase composites experimentally. • Multi-phase composite designed by the proposed method shows excellent stability in thermal expansion properties. • The proposed method may open an avenue to the multi-phase composite with designable thermal expansion properties. [ABSTRACT FROM AUTHOR]

Accumulative fold-forging (AFF) as a newly developed severe plastic deformation (SPD) process based on the repetitive fold-forging steps is implemented for the production of the layered UFG (~200 nm) AA8006 alloy and AA8006-B 4 C nanocomposite (~35 nm, 10 vol %) materials from the initial AA8006 alloy foil. The remarkably refined grains and nanoparticles can control metallic materials' mechanical properties, including the strength, strain rate dependency, and thermal stability behavior. In this context, nano-grains' local mechanical response during nanoindentation can vary considerably depending on the testing temperature, and this has yet to be discussed. In this research, after materials characterization of produced nanostructured materials according to the AFF route, the relating depth-sensing thermal stability of them assessed by conducting the nanoindentation testing at different temperatures in the range of 300–523 K. Depth sensing softening behavior is elaborated to identify the low-temperature thermal stability of processed materials. The results enunciated the occurrence of thermal softening by refining the grain structure. However, introducing the reinforcing nanoparticles lead to a pinning action that stabilized the grain boundaries. [Display omitted] • The UFG alloy and NS nanocomposite were produced by the new AFF route. • Formation of nano-grains and nanoparticles dispersion studied. • Depth-sensing thermal property interrogated the more stability of nanocomposite. • The importance of nanoparticles is retarding the coalescence of nano-grains. [ABSTRACT FROM AUTHOR]

Resilient, fire-retardant and mechanically strong polyimide-polyvinylpolymethylsiloxane (PI-PVPMS) composite aerogels have been prepared via stepwise chemical liquid deposition (SCLD). The synthesis is based on the formation of PI-PVPMS crosslinked network structure with (3-aminopropyl)trimethoxysilane (APTMS) as a coupling agent to provide reactive sites on the backbone. We successfully realize the PI in-situ growth on the whole super-flexible PVPMS gel skeleton with this simple method. The effect of APTMS amount and deposition time on the properties of final samples is deeply investigated. The resultant PI-PVPMS composite aerogels show excellent mechanical and thermal properties. They can support at least 10,000 times of their own weight and can recover 20% from a 60% of compressive strain, with an elastic modulus of 32 MPa. For thermal performance, they can maintain their structural integrity after being subjected to the alcohol lamp outer flame of around 650 °C for 30 min. These results together with the simple synthesis process demonstrate the potential for construction materials using PI-PVPMS composite aerogels. Furthermore, the SCLD synthesis method could also be applied to prepare other composite aerogels, especially for those containing complex polymer. Unlabelled Image • We successfully realize the in-situ growth of polyimide on the super-flexible PVPMS gel skeleton. • The PI-PVPMS composite aerogel shows both resilient mechanical property and high thermal stability. • The synthesis method has the potential to realize the large-scale production of PI-PVPMS composite aerogels. [ABSTRACT FROM AUTHOR]

The leading purpose of this work was to broaden the current knowledge about the impacts of various chain configurations of polypropylene (PP), i.e., linear and branched form, on the thermal properties (thermal stability, thermal conductivity, crystallinity, thermal mechanical properties) of PP nanocomposites reinforced by graphene nanoplatelet (GnP) particles. The utilization of GnP with different particle size gave us good information about the impacts of filler's dimension on the thermal properties as well. Regardless of the PP type, EC1500-filled (small size GnP) composites showed higher storage modulus in the dynamic mechanical analysis. With respect to DSC results, incorporation of GnP, particularly GnP with smaller particles, led to a striking increment in crystallization temperature and crystallinity, and nucleating efficiency of GnP in linear PP-based composites was higher. The employment of GnP brought about an improvement in degradation temperature and thermal stability of nanocomposites, and smaller GnP was more effective in this context. However, due to its higher aspect ratio, EC100 GnP (large size GnP) could enhance thermal conductivity more satisfactory, specifically in linear PP-based samples. Unlabelled Image • Polypropylene(PP)/graphene nanoplatelet (GnP) nanocomposites were prepared via solid state mixing followed by melt blending. • Small GnP had better performance in dynamic modulus, while large GnP was more effective in thermal conductivity enhancement. • Long side chains in branched PP affected the formation of GnP network and thermal properties, adversely. [ABSTRACT FROM AUTHOR]