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The use of Raman spectroscopy in probing the deformation mechanisms of cellulose fibres (regenerated and natural), and two natural cellulose composite systems (wood and paper) is described. It is shown that during tensile deformation the 1095 cm−1 Raman band, corresponding to the stretching of the cellulose ring structure, shifts towards a lower wavenumber due to molecular deformation. By analysing a number of fibres with different microstructures this shift is shown to be invaluable in understanding the micromechanisms of deformation in these materials. Moreover, the rate of Raman band shift is shown to be invariant with stress for all fibre types, consistent with a fibre microstructure based on a modified series aggregate model. In the composite systems, such as wood and paper, it is shown that the stress-induced Raman band shift in the cellulose gives an important insight into their local deformation micromechanics. [ABSTRACT FROM AUTHOR]

Pt/Al2O3 catalyst powder was successfully incorporated in a microstructured paper-like matrix composed of a ceramic fiber network, by use of a simple papermaking technique. As-prepared composite, denoted paper-structured catalyst, was applied to the reduction of nitrogen oxide (NO X) in the presence of propene, for exhaust gas purification. The paper-structured catalyst demonstrated higher NO X reduction efficiency and more rapid thermal responsiveness than a conventional Pt-loaded honeycomb catalyst, indicating that the paper-like structure with interconnected pore spaces contributes to effective transport of heat and reactants to the catalyst surfaces. Furthermore, the paper-structured catalyst with the appearance of flexible paperboard has a high degree of utility. The efficiency of utilization of Pt catalyst was improved by using hierarchically assembled paper-structured catalysts with preferential location of Pt catalyst in the upper part. The paper-structured catalyst composite with paper-like utility and porous microstructure is thought to be a promising catalytic material for efficient NO X gas purification. [ABSTRACT FROM AUTHOR]

A novel microstructured catalyst that consists of Cu/ZnO catalyst powders and ceramic fibers was successfully prepared using pulp fibers as a tentative matrix by a papermaking technique. As-prepared material, called a paper-structured catalyst, possessed porous microstructure with layered ceramic fiber networks (average pore size ca. 20 μm, porosity ca. 50%). In the process of methanol autothermal reforming (ATR) to produce hydrogen, paper-structured catalysts demonstrated both high methanol conversion and low concentration of undesirable carbon monoxide as compared with catalyst powders and pellets. The catalytic performance of paper-structured catalysts depended on the use of pulp fibers, which were added in the paper-forming process and finally removed by thermal treatment before ATR performance tests. Confocal laser scanning microscopy and mercury intrusion analysis suggested that the tentative pulp fiber matrix played a significant role in regulating the fiber-network microstructure inside paper composites. Various metallic filters with different average pore sizes, used as supports for Cu/ZnO catalysts, were subjected to ATR performance tests for elucidating the pore effects. The tests indicated that the pore sizes of catalyst support had critical effects on the catalytic efficiency: the maximum hydrogen production was achieved by metallic filters with an average pore size of 20 μm. These results suggested that the paper-specific microstructures contributed to form a suitable catalytic reaction environment, possibly by promoting efficient diffusion of heat and reactants. The paper-structured catalyst with a regular pore microstructure is expected to be a promising catalytic material to provide both practical utility and high efficiency in the catalytic gas-reforming process. [ABSTRACT FROM AUTHOR]

This study clarifies the absorption behavior of micro-droplets of water on treated paper to support the design of functional microstructures, such as electronics and micro-fluid channels, on paper. The period of time between when a micro-droplet of water ejected from an ink-jet head lands on the paper's surface and its complete disappearance by absorption was defined as the micro-sizing degree (MSD), and an MSD measurement method was established. The MSD was evaluated using microscopic high-speed video images of the side view recorded every millisecond. Several grades of commercially available ink-jet paper media and laboratory sheets having different levels of water repellency prepared from a pulp and a sizing agent were examined. The MSD of commercial ink-jet papers, which are known to absorb water very quickly, was 3-6 ms. Weakly sized laboratory sheets exhibited a lower MSD of 2-3 ms. The absorption behavior was analyzed in terms of the capillary pressure with and without the Laplace pressure; the theoretical and experimental results agreed moderately well. The results indicated that the Laplace pressure cannot be neglected in the analysis. The MSD of a wet surface where a preceding micro-droplet had already landed was higher than that on a dry or partially wet surface, presumably because water remains inside pores for an unexpectedly long time. [ABSTRACT FROM AUTHOR]

The editorial comments on the multi-scale predictive modelling of the composite materials' behavior. Transition of composite materials from nano to micron to meter-size is examined keeping in view the accuracy of computation and fabrication methods. The article probes the physical behavior of complex material systems under stress in terms of size, time and environment.

Ni-based wrought superalloys are a type of superalloy produced through casting-forging processes, and usually their high-temperature performance is strongly influenced by microstructure and deformation mechanism. The typical microstructure of Ni-based wrought superalloys after heat treatments comprises equiaxed grains, numerous annealed twins, carbides within the grain interior and/or at grain boundaries, and spherical γ′ precipitates (typically comprises around 20% of their volume). The common deformation mechanisms in Ni-based wrought superalloys mainly include anti-phase boundary formed by paired dislocations shearing γ′ phase, stacking fault formed by single dislocation shearing γ′ phase, dislocation bypassing γ′ phase (precipitation-strengthened) and dislocation entanglement, dislocation networks (solid solution strengthened). In this paper, the microstructure and deformation mechanism of tensile and creep in Ni-based wrought superalloys for Advanced ultra-supercritical (A-USC) power plants are reviewed, for the two prominent areas of current research, Ni–Fe-based wrought superalloys exhibit superior processability and cost-effectiveness compared to Ni–Co-based wrought superalloys, thereby offering a more advantageous solution. [ABSTRACT FROM AUTHOR]

Selective electron beam melting (SEBM) has been recently employed for additive manufacturing (AM) Al alloys but showing comparatively low hardness and strength. In this work, SEBM technique was employed to additive manufacture an in-situ TiB2 particle reinforced AlSi10Mg composite. With optimized processing parameters, the SEBM TiB2/AlSi10Mg composite showed good surface quality and a high relative density. The as-printed composite exhibited a refined equiaxed grain structure with an average size of 27.7 µm. The eutectic Si phase was mostly spherical and uniformly distributed in the Al matrix, while the nano-sized TiB2 particles were partly agglomerated. The resultant microstructure was associated with the combined effect of the rapid solidification and annealing-like process during SEBM. Additionally, TiB2 particles facilitated grain refinement by enhancing the heterogeneous nucleation and retarding grain growth. The SEBM TiB2/AlSi10Mg composite presented a yield strength (YS) and ultimate tensile strength (UTS) of 103.6 MPa and 165.4 MPa, respectively, with an appreciable elongation of 15% at as-printed state. After a T6-like treatment, the YS and UTS of the composite were further improved to 225 MPa and 316 MPa, respectively, and an elongation of 12% was maintained. This paper shows the potency of SEBM in AM metal matrix composites (MMCs) with both agreeable strength and ductility. [ABSTRACT FROM AUTHOR]

The mechanism of microstructure evolution during rapid solidification and the proactive regulation of phase constitution to optimize the micromechanical properties of multicomponent alloys have been the focus of research in recent years. In this paper, the evolution of microstructural growth kinetics and the formation of amorphous phase in CoCrFeNiZr0.5 alloy were achieved by melt spinning technique and electrostatic levitation coupled melt quenching. According to the theory of transient nucleation, the nucleation incubation time of Laves, FCC, Fe23Zr6 and BCC phases with undercooling during rapid solidification of the alloy was calculated. And based on this, the mechanism of phase transition in the process of regular eutectic → anomalous eutectic → nanocrystalline → amorphous composite → complete amorphous structure was discussed and explained. The growth behavior of primary and eutectic phases solidified at different undercoolings was investigated. Combined with melt quenching, the alloy melts were quenched in the superheated state, liquidus, undercooled state and recalescence process. Multiple microstructures, including amorphous structure, amorphous plus nano-eutectic, gradient nano-eutectic and composite structure of primary Laves phase, along with primary eutectic plus secondary quenched eutectic structures were obtained, respectively. Moreover, the shear band and free volume theory were applied to explain the deformation behavior and the discrepant mechanical performance between amorphous composites and amorphous structures. The formation of quenched nano-eutectic and amorphous structure not only improves the hardness of the alloy, but also enhances the fracture toughness. [ABSTRACT FROM AUTHOR]

The effects of supersonic particle bombardment (SFPB) on the microstructure, microhardness and wear property of Ti6Al4V alloy prepared by laser metal deposition (LMD) were investigated in this paper. The electrochemical corrosion behaviors of the LMDed Ti6Al4V alloy samples before and after SFPB treatment in 3.5% NaCl solution were measured. The results showed that a gradient severe deformation layer of ~ 350 μm thickness was formed with refined equiaxed grains oriented in various directions on the surface of LMDed Ti6Al4V alloy after SFPB treatment. The microhardness of the deformation layer was significantly increased due to the plastic deformation, grain refinement, dislocations and deformation twins increment. After SFPB treatment, the LMDed Ti6Al4V exhibited higher wear resistance which is about 55.6% decrease in wear loss than that of the untreated sample. Moreover, the corrosion resistance and corrosion rate of the SFPB-treated samples in 3.5% NaCl solution improved due to the finer hexagonal grains and high density of grain boundary in the severe deformation layer. [ABSTRACT FROM AUTHOR]

Due to its excellent performance of lightweight and high strength, Al/Mg bimetal has high application value in the aerospace field. However, the poor bonding quality of the Al/Mg bimetallic interface is still an urgent problem to be solved. Therefore, this paper proposes to use Ni foil as the interlayer to control the interface structure and improve bonding strength. The results show that the Ni interlayer has a positive influence on Al/Mg interface structure regulation. The interface is composed of Al3Ni, Al3Ni2 and Mg2Ni phases, and no Al–Mg brittle intermetallic compounds (IMCs) are formed. Meanwhile, the Mg2Ni phase is distributed as islands on the interface at 490 °C, effectively preventing crack propagation. The average shear strength of the interface reaches a maximum of 69.5 MPa. Besides, the interface fracture mechanism was deeply analyzed. The Al/Ni interface has excellent bonding performance, and the fractures occur at the Mg/Ni interface. The fracture mode from intergranular and cleavage mixed fracture at 490 °C to brittle cleavage fracture at 505 °C. [ABSTRACT FROM AUTHOR]

A new type of inorganic fiber-fly ash continuous fiber was innovatively developed in this study to alleviate the problems of low comprehensive utilization rate and lacking of high-value utilization means of industrial solid waste fly ash. The melt flow temperature and macro-mechanical properties of different samples were studied. The results showed that with the increase in acidity coefficient index (MK), the melt flow temperature decreased first and then increased, and the lowest value was 1340 °C when MK was 3.1. Meanwhile, with the gradual increase in MK, the tensile strength and elastic modulus of monofilament increased first and then decreased. When the MK was 3.8, the tensile strength and elastic modulus of fiber monofilament reached 2064 MPa and 16.7 GPa, respectively. According to the results of XRD, TG-DSC, FTIR and SEM microstructure analysis methods, it is found that the macro-mechanical properties of fibers are closely related to the chemical composition and phase structure evolution of raw materials. After melting at high temperature, the samples with high MK form a dense three-dimensional glassy network structure, which leads to the higher mechanical strength of the fibers. However, in the samples with lower MK, the vitreous network structure is loose, which reduces the mechanical properties of the fiber. Finally, the MK range (2.5–3.8) for preparing high-performance fly ash fiber was proposed in this paper. In this range, the synthesized fly ash continuous fiber has low melting temperature and excellent mechanical properties, which has a potential of industrial application. [ABSTRACT FROM AUTHOR]

In this paper, perfect interface model of Al/AlCu alloy and defect interface model of Al/AlCu alloy after cracks were introduced at different positions of the interface were established by using cohesive zone modeling method. Classical molecular dynamics simulation was used to study the deformation behavior and microstructure evolution of Al/AlCu alloy interface model at a strain rate of 0.05 Å/ps and the temperature of 300 K. The simulation results show that perfect interface exhibits a uniform plastic deformation stage due to structural relaxation after yielding, while there is no structural relaxation during the deformation of defect interface and the tensile strength is much lower than that of perfect interface as well. In the process of deformation, stacking faults formed in perfect interface and cracks are generated and expanded in Al matrix, while there was no stacking faults forming along with the expansion and cracking at the position of introduced cracks in defect interface. Massive dislocation nucleation leads to the reduction in stress at the perfect and defect interfaces after yielding. The extension of Shockley partial dislocation and the nucleation of Stair-rod dislocation are the main mechanisms of interface deformation. Densities of Shockley partial dislocation and Stair-rod dislocation decrease with increasing strain before crack propagation. This study enriches the analysis of microstructure evolution of Al/AlCu alloy interface and similar interfaces during deformation. [ABSTRACT FROM AUTHOR]

With the aim to understand the effect of thermal condition on phase separation in polymer-modified bitumen (PMB), this paper numerically investigates four PMB binders under five thermal conditions between 140 and 180 °C. Based on a phase-field model previously developed by the authors for PMB phase separation, the updated model presented in this paper uses temperature-dependent parameters in order to approach the concerned temperature range, including mobility coefficients, interaction and dilution parameters. The model is implemented in a finite element software package and calibrated with the experimental observations of the four PMBs. The experimental results are well reproduced by the model, and it is thus believed that the calibrated parameters can represent the four PMBs. The simulation results indicate that the model proposed in this paper is capable of capturing the stability differences among the four PMBs and their distinct microstructures at different temperatures. Due to the transition of some PMBs from the thermodynamically stable state at 180 °C to the unstable state at 140 °C, a homogenization process may occur during the cooling applied numerically. After the transition, the PMBs start to separate into two phases and gradually form the binary structures controlled by the temperature. It is indicated that the cooling rate slightly affects the final pattern of the PMB binary microstructure, although the process can be more complicated in reality due to the potential dynamic reasons. [ABSTRACT FROM AUTHOR]

This paper presents the experimental investigation of the effect of Nb2O5 content on the phase composition, microstructure, and physical and mechanical performance of the zirconia-toughened alumina (ZTA) ceramics, aimed to optimize the additional amount of Nb2O5, refine the ceramic grains, and improve the densification, hardness and fracture toughness. ZTA ceramics with various Nb2O5 contents were prepared using the spark plasma sintering method. The addition of trace amounts of Nb2O5 did not produce a new Nb-rich phase; the Nb atoms were dissolved in the ZrO2 grains. The addition of trace amounts of Nb2O5 led to grain refinement and an increase in density, but the addition of excessive Nb2O5 resulted in grain growth and a decrease in relative density. Furthermore, the addition of Nb2O5 promoted uniformity of the microstructure. The sample with 0.25 wt.% Nb2O5 had the maximum Vickers hardness and indentation fracture toughness, which were 1228.40 HV and 9.17 MPa √m, respectively. Mechanical properties of the composite mainly depended on the grain size, which was influenced to some extent by the relative density. [ABSTRACT FROM AUTHOR]

In this paper, semi-solid compression of 2A14 aluminum alloy was conducted on the Gleeble1500D thermophysical simulation experimental compressor to investigate the rheological behavior of 2A14 alloy at high solid fraction in the semi-solid state. The main objective of the study was to establish the constitutive equation suitable for serving the simulation and practical thixoforging forming process of the 2A14 alloy. Another purpose is to investigate the effect of heat deformation parameters on the microstructure of 2A14 alloy. The apparent viscosity of semi-solid 2A14 alloy with high solid fraction as a function of equivalent shear rate was obtained. The constitutive equation for 2A14 aluminum alloy at true strain below 0.2 was established. Increasing the compression temperature or strain rate is beneficial to the deformation and grain refinement in the hard deformation zone, but at the same time, it will also intensify the aggregation of micro-voids in the transition zone into micro-cracks and the formation of macro-cracks. The macroscopic compression instability at true strains above 0.2 was discussed, mainly attributed to the dilatant shear bands generated in the strain localization region inherent in the compression deformation and the higher thermal crack sensitivity of the 2A14 alloy. [ABSTRACT FROM AUTHOR]

The conventional approach to achieve desired effective thermal conductivity (ETC) of porous thermal interface materials (TIM) is processing-microstructure-properties forward analysis, which contains various trial-and-error cycles and is hence inefficient for materials development. Establishing the linkage from ETC to microstructure is essential; however, the recently developed methods including microstructure characterization and reconstruction are suffering from limited accuracy and computational efficiency. To address these problem, in this paper, generative artificial intelligence (AI) model was first implemented to design microstructure of porous TIM with desired ETC. Here, we introduced a representative porous TIM, sintered silver, and a typical kind of generative AI model, conditional generative adversarial network (CGAN), as an example for illustration. The CGAN model can efficiently generate sharp and crisp microstructures of sintered Ag with excellent morphology realism. Besides visual inspection, the ETC values of generated microstructures were evaluated by convolution neural network (CNN) model. It was found that the CGAN model also exhibits satisfactory performance in physical meaning, since the determination coefficient R2 between target ETC and CNN predicted ETC values is 0.985. These results confirm the effectiveness of generative AI model capable of synthesizing microstructure of porous TIM with desired ETC, and not limited to porous TIM, the approaches present here can also be generalized and applicable to design microstructure of other porous media and composites. [ABSTRACT FROM AUTHOR]

Dynamic recrystallization mechanism and microstructure evolution of a novel quasi-continuous network reinforced TiAl matrix composites, TiAl/B4C composites were studied in this paper. The isothermal compression experiments, the scanning electron microscopy, and the electron back-scattered diffraction were carried out. Besides the discontinuous dynamic recrystallization (DDRX), the continuous dynamic recrystallization occurred in γ-phase grains during the loading, characterized by crystal orientation accumulation. Additionally, a large number of 89 ± 3° grain boundaries associated with DDRX also appeared during the loading. With the temperature increasing or/and the strain rate decreasing, the volume fraction of recrystallized grains increased significantly, the < 010 > crystal direction of γ-phase grains within the matrix unit of present composites was gradually parallel to compression direction, and the texture changed from scatter to concentration. The variety of texture was mainly related to different dynamic recrystallization mechanisms in various conditions. [ABSTRACT FROM AUTHOR]

This study provides original experimental data on the microstructural mechanisms of the hygroexpansion of a material made up of lignocellulosic fibres. A paperboard made up of several layers was chosen and subjected to relative humidity variations during X-ray microtomography scanning. The 3D images of the evolving media were analysed using a digital image correlation technique to measure the displacement field within the studied material. This technique allowed the hygroexpansion of the studied material and of each layer of this latter to be analysed in the in-plane and out-of-plane directions. Results show that the hygroexpansion is highly anisotropic. The microstructural hygroexpansive mechanisms for the pore and fibre phases could also be revealed. They have been shown to depend strongly on the fibre content of the fibrous layers. This analysis provides also useful information concerning the size of the Representative Elementary Volume (REV) for the hygroexpansion phenomenon of dense lignocellulosic fibrous networks. In view of the obtained results, the relevancy of common theoretical models used to predict the hygroexpansion of materials such as papers and boards is also discussed. [ABSTRACT FROM AUTHOR]

TiAl alloy becomes a promising high-temperature structural material due to excellent mechanical properties at elevated temperature. However, the inherent brittleness makes it difficult to be processed by traditional technologies. Therefore, an innovative twin-wire plasma arc additive manufacturing (TW-PAAM) process is developed to fabricate TiAl alloy. Substrate heating is indispensable during additively manufactured TiAl alloy, which can alleviate its crack tendency. In this paper, crack-free TiAl alloy samples are fabricated using TW-PAAM, and the effect of substrate temperature (560, 620 and 680 °C) on as-deposited TiAl alloy is investigated in detail. With the increase in substrate temperature, microstructural lamellar spacing and colony size exhibit the tendency of increase. Also, α2 phase content, recrystallization degree and high Schmid factor frequency present the decrease tendency. These variations of microstructure characteristics further lead to the decrease in both microhardness and tensile properties of the deposit. These findings provide a valuable reference for optimizing microstructures and mechanical properties of additively manufactured TiAl alloys. [ABSTRACT FROM AUTHOR]

In this paper, we present the analysis of an interpenetrating metal ceramic composite structure. We introduce a new generation algorithm for the modeling of interpenetrating composite microstructures with connected, spherical cavities embedded into an open-porous foam structure. The method uses a geometric ansatz and is designed to create structures of special topology, as the investigated metal ceramic composite structures consisting of a connected AlSi10Mg phase showing spherical shapes embedded into an Al2O3 preform. Based on the introduced enhanced random sequential absorption approach, the generated microstructures yield numerical insights into the material that are not accessible by experimental techniques. The generated microstructures are compared to structures reconstructed from experimental CT scan data considering microstructural features and mechanical behavior. We show that the proposed method is able to generate statistically equivalent microstructures by using only a small number of statistical descriptors. The numerical formulation is validated using compression tests including plastic yielding in the aluminum and damage progression in the ceramic phase. Both the composite material and the pure ceramic preform are considered in this analysis, and good agreement is found between reconstructed and generated microstructures. Furthermore, the observations reveal the importance of the local geometrical sphere arrangement with respect to the mechanical behavior. A validation with experimental results is presented and it is shown that the model predicts microstructural properties and gives meaningful insights into the structural and material interplay. Finally, we discuss the potential of the method for the investigation of failure mechanisms. [ABSTRACT FROM AUTHOR]

Microstructures play an important role in the research on shape memory alloys (SMA). By using mathematical modeling tools to study microstructures, it is possible to predict the behaviors of these materials under applied fields. In the current paper, a thermo-mechanical model is proposed to simulate the microstructure of a SMA rod with both fixed and impact boundary conditions via Legendre wavelets collocation method. Because of the good performance of Legendre wavelets basis, this method shows excellent properties in both precision and stability. A detailed numerical algorithm is given, and the backward differentiation formula is employed to perform all the simulations in the current paper. Computational simulations are carried out to study the stress-induced phase transformation. The dynamics of microstructure evolution, presented at different temperatures, is well captured by our developed technique. [ABSTRACT FROM AUTHOR]

The effects of rare-earth (RE) inoculants are excellent, but RE is rare and expensive. Consequently, it is necessary to choose other elements to reduce the use of RE. In this paper, research was done to investigate the effects of different content La–O–S complex inoculant on the microstructure and mechanical characteristics of ductile iron (DI) through SEM, EDS, XRD, etc. Studies have shown that the as-cast structures of the samples are graphite nodules, ferrites, and a few pearlites. The graphite core consists of oxides (Al2O3, SiO2, Fe2O3), sulfides (La2S3, LaS), and XO·SiO2·Al2O3 silicate (X: Ca, Ba, Sr). The amount of graphite nodules increases firstly and then slightly decreases, ferrite increases gradually, and pearlite decreases by degrees with the increase in S or O content, which makes the Brinell hardness and tensile strength of the sample decrease, and the elongation of the sample slightly decreases after increasing. When both O and S are 0.3%, mechanical characteristics of the samples are best, Brinell hardness is 163.3 BHW, tensile strength is 513 MPa, and elongation is 16.1%. [ABSTRACT FROM AUTHOR]

The ability to measure elongated structures such as platelets and colonies, is an important step in the microstructural analysis of many materials. Widely used techniques and standards require extensive manual interaction making them slow, laborious, difficult to repeat and prone to human error. Automated approaches have been proposed but often fail when analysing complex microstructures. This paper addresses these challenges by proposing a new, automated image analysis technique, to reliably assess platelet microstructure. Tools from Mathematical Morphology are designed to probe the image and map the response onto a new feature-length orientation space (FLOS). This enables automated measurement of key microstructural features such as platelet width, orientation, globular volume fraction, and colony size. The method has a wide field of view, low dependency on input parameters, and does not require prior thresholding, common in other automated analysis techniques. Multiple datasets of complex Titanium alloys were used to evaluate the new techniques which are shown to match measurements from expert materials scientists using recognized standards, while drastically reducing measurement time and ensuring repeatability. The per-pixel measurement style of the technique also allows for the generation of useful colourmaps, that aid further analysis and provide evidence to increase user confidence in the quantitative measurements. [ABSTRACT FROM AUTHOR]

In this paper, the effects of Nb contents (0.05 ~ 0.50wt%) and hot rolling temperatures (1000 ~ 1200 °C) on microstructure and mechanical properties of high-silicon electrical steel were studied. The results show that adding a small amount of Nb can significantly improve the plasticity of high-silicon electrical steel. Compared with the specimens without Nb, the three-point bending load–deflection curves of the alloys with Nb contents of 0.05 ~ 0.50wt% after warm rolling showed obvious plastic stage. The average fracture deflection increases from 4.5 to 9.9 mm with the Nb content increasing from 0.05 to 0.50wt%. When the hot rolling temperature is 1000 °C, the Nb-containing high-silicon electrical steel has a layered microstructure along the thickness direction. The surface layer is equiaxed grains with dynamic recrystallization, while the center of the thickness is a long strip structure with dynamic recovery. The mechanism of Nb microalloying to improve plasticity includes three aspects: Firstly, the layered structure hinders the propagation of cracks and delays the progress of fracture; secondly, a large number of fine Nb precipitates will hinder the grain growth and refine the grains; thirdly, the formation of the Nb-precipitated phase destroys the ordered rearrangement between adjacent Fe and Si atoms in the matrix, inhibits the ordered transformation and reduces the ordered degree of high-silicon electrical steel. When the hot rolling temperature is increased to 1100 °C or above, the layered structure disappears, the grain coarsens obviously, and the plasticity of the warm-rolled specimens is significantly reduced. [ABSTRACT FROM AUTHOR]

The effect of Ru on microstructures, coating texture changes, mechanical properties improvement, and cutting performance enhancement in CVD TiN-TiCN-Al2O3 coated cemented carbide was investigated in this paper. The results show that with the increasing amount of Ru, the mean grain size of the matrix decreases from 1.28 to 0.95 μm. The microstructural refinement of the matrix creates more nucleation sites for coating growth, which further reduces the grain size of the coating. Moreover, the Ru, diffusing from the matrix into the coating, changes the growth direction of partial grains. The coated cemented carbide with 1.5wt% Ru shows the largest hardness of 17.8GPa, which results from the combined influence of the reduction in coating grain size and the decrease in the concentration of TiCN coating {111} texture. In the process of turning 17-4PH stainless steel, due to the improved hardness and plastic deformation resistance of the composite coating, as well as enhanced (104) texture of Al2O3 coating, the flank wear of the coated tool with 0.5wt% Ru is 31.25% lower than that without Ru, which exhibits the best cutting performance. [ABSTRACT FROM AUTHOR]

Al–Zn–Mg–Cu alloys can be fabricated by a series of thermo-mechanical processing methods (e.g., hot rolling, forging and extrusion), which is able to serve in aeronautic, automobile, and marine industries because of its excellent physical properties. However, reaching the balance between high strength and favorable ductility to present its high performance is still in progress, during which temperature and strain rate are two very important external variables. More importantly, the core lies in sophisticated microstructure evolution paths involved in hot deformation, which consists of different microstructure mechanisms and behaviors and can be expressed as various mechanical responses. Therefore, a fundamental review of microstructure mechanisms and behaviors, microstructure evolution and relevant mechanical responses of Al–Zn–Mg–Cu alloys during high-temperature deformation is of great significance. In present paper, first, various experimental methods have been introduced. Second, general trends of mechanical properties changing with temperature and strain rate have been summarized. Third, major microstructure mechanisms and behaviors have been discussed. Then, a schematic illustration originating from dislocations' movement has been depicted, which succeeding microstructure evolution and mechanical responses (including superplasticity) have been reviewed accordingly. Finally, further suggestions of hot deformation of Al–Zn–Mg–Cu alloys have been given. [ABSTRACT FROM AUTHOR]

This paper aims to unveil effects of α colony and α plate parameters on tensile properties and impact toughness of Ti-55531 alloy with multilevel lamellar microstructures. Microstructures with different α colony and α plate sizes were prepared using varied heat treatments and analyzed by X-ray diffraction, scanning electron microscopy, electron back-scattered diffraction, transmission electron microscopy. Relationships of microstructure and strength, plasticity and impact toughness were discussed. Results indicate that tensile strength increases, while plasticity and impact toughness of the alloy decline with decreasing effective sizes (width/length ratio) of α colony (dc) and α plate (dα) and increasing of volume fraction of α phase. Both dc and dα follow the Hall–Petch principle with strength, and dc was determined to be the critical controlling parameter of strength owing to higher interfacial strengthening effect induced by α colony. However, plasticity is primarily related to dα. Moreover, impact toughness for both dc and dα follows the linear relation, but the coefficient of dα is higher. Furthermore, impact toughness is more dependent on plasticity than strength. Larger α plates lead to more mechanical twins during impacting and result in higher plasticity and impact toughness. Therefore, the impact toughness should depend more on the size of α plates. In order to unveil the influence of α plate size on impact deformation and microcrack initiation behavior of Ti-55531 alloy, the microstructural deformation and crack nucleation characteristics in the impact crack nucleation region were detected by TEM in detail; then, the schematic illustration for microstructural deformation and crack nucleation characteristics was made according to experiment results. [ABSTRACT FROM AUTHOR]

Nickel-based superalloys such as Hastelloy X (HX) are widely used in gas turbine engines for their exceptional oxidation resistance and high-temperature strength. The addition of ceramic reinforcement further enhances these superalloys' mechanical performance and high-temperature properties. For this reason, this paper investigates the microstructure and mechanical property of laser powder bed fusion (LPBF) additively manufactured HX–1 wt% WC (tungsten carbide) composite specimens. The results demonstrate that the LPBF-fabricated composite was observed to have several pores and microcracks, whilst only pores were detected in the as-fabricated pure HX. Compared to the fabricated pure HX, the tensile yield strength of such HX composite parts was increased by 13% without undue sacrifices to ductility, suggesting that the very limited number of microcracks were not sufficient to degrade the mechanical performance. The significantly increased dislocations were considered to be the primary contributor for the mechanical performance enhancement in the LPBF-fabricated composite material. The findings offer a promising pathway to employ LPBF process to fabricate advanced microcrack-free composites with high-strength through a careful selection of ceramic reinforcement materials. [ABSTRACT FROM AUTHOR]

In this paper, we demonstrated that commercially available triblock copolymers such as polystyrene- b-polybutadiene- b-polystyrene (SBS) and polystyrene- b-polyisoprene- b-polystyrene (SIS), used as thermoplastic elastomers, exhibit autonomic self-healing behavior at room temperature without any chemical reaction even after cutting into two separate pieces. The healing efficiency is improved by immediate recombination after cutting, and is attributed to the destruction of the microstructure, i.e., polystyrene domains, leading to marked molecular mobility. Furthermore, quenched samples with obscure phase-separation exhibit good healing behavior. Finally, SBS has better healing efficiency than SIS because the solubility parameter of polybutadiene is closer to that of polystyrene than that of polyisoprene; to some extent, the solubility parameter is responsible for enhanced molecular motion owing to the mutual dissolution of both components. [ABSTRACT FROM AUTHOR]

Investigation of the microscopic properties of cement concrete requires well-prepared samples with a flat and undamaged surface. The epoxy impregnation in concrete sample can prevent damage to the microstructure during polishing process for obtaining the flat surface. However, further exploration about the effect of epoxy impregnation on characterizing the properties of concrete has not been found. In this paper, the vacuum impregnation method is adopted to prepare the epoxy impregnated concrete and paste samples. The aspects of microscopic properties of impregnated and non-impregnated samples are evaluated and compared in terms of the surface elevation, the indentation modulus, and the thickness of the interfacial transition zone between the aggregate and the paste matrix (ITZagg-paste) as well as that between the residual C3S clinker and the hydration product (ITZC3S-HP). The techniques of optical microscope, backscattered electron microscope, scanning probe microscope (SPM) modulus mapping, and the instrumented indentation are adopted to measure the above microproperties. The results show that the epoxy impregnation is favoured in the microscope image analysis, nanoindentation measurement, and characterizing the ITZC3S-HP by SPM modulus mapping. It is not recommended for characterizing the thickness of ITZagg-paste by SPM modulus mapping and for measuring the micromechanical properties at the paste scale by microindentation. [ABSTRACT FROM AUTHOR]

New Rheocasting (NRC) is a recently developed semisolid processing route. There are two versions of this route. In one, molten alloy is poured directly into a mould and through careful temperature control during cooling a spheroidal semisolid microstructure is achieved, before the material in the mould is upended into a shot sleeve and hence forced into a die. Alternatively, the molten alloy is poured onto a cooling slope and thence into a mould before processing. The aim of the work described in this paper, and its companion, was to develop the understanding of the microstructural development during the initial stages of this process, i.e. in the mould before processing and with the cooling slope/mould combination. In the previous paper, an analogue system based on aqueous ammonium chloride has been used to visualise what happens when an alloy is poured into a tilted mould with a chill wall, which acts to mimic the mould and the cooling slope in the NRC process. In this companion paper, the results for pouring A356 aluminium alloy directly into a mould, and also via a cooling slope into a mould, are presented. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to produce acoustic thermoset open-cell foam with both attractive acoustical and mechanical properties using a simple and versatile process. The manufacturing process is based on particulate leaching and is fully controlled to provide predictable foam microstructure. Microscopic and X-ray microtomographic analyses were used to validate the interconnectivity of the porosity as well as the degree of purity of the produced materials. It was shown that the porosity and the thickness depend on the compaction pressure, which is the determinant processing parameter. An optimization model based on the well-known JCAPL model was used to predict the physical properties of the foams microstructure. The acoustical and mechanical properties are shown to be dependent on particle size and compaction pressure. The thermoset foams can be used as effective absorbing acoustic materials with broadband absorption capabilities, combined with compressive modulus as high as 88 MPa. [ABSTRACT FROM AUTHOR]

This paper describes the effect of temperature (85 °C) and relative humidity (RH) (85%) on structure and material properties of an environmental-friendly Sn–3.0Ag–0.5Cu, in wt.% (SAC305) material. A detail microstructure characterization was performed by scanning electron microscope with EDS analysis, X-ray diffraction, electron backscattered diffraction and transmission electron microscope techniques. From this structural analysis, it is evident that in the as-cast alloy, submicron-sized acicular and spherical-shaped ε-Ag3Sn and very fine η-Cu6Sn5 intermetallic compound (IMC) particles are homogeneously distributed in fine β-Sn matrix grains. However, after exposing SAC305 alloy to 85 °C and 85% RH for 60 days, the coarsening of its microstructure was observed changing significantly the morphology (size and shape) of the IMCs as well as of the Sn matrix. The Sn matrix grains size (in diameter) in as-cast alloy ranges within 20–30 µm, while after heat treatment an increase in size of 35–45 µm was observed. Furthermore, the ε-Ag3Sn IMC particles appeared with coarse structure. Therefore, the mechanical properties of SAC305 material turned inferior that confirmed by electrical resistivity and mechanical properties measurements. The electrical resistivity and microhardness values were reduced by about 11.2% and 22%, respectively, with respect to the corresponding values of the reference alloy (as-cast alloy). However, the heat-treatment method enhanced the damping properties of SAC305 material. [ABSTRACT FROM AUTHOR]

Layered double hydroxides (LDHs) are 2D ionic lamellar nanomaterials, which attract increasing interest for applications in different fields. This paper shows that their morphology is strongly affected by the microstructure of the substrate on which they grow. Zn–Al LDHs were grown in the same conditions on Al substrates with different microstructural features obtained from cold-rolled sheets by annealing at 265 °C for increasing soaking time up to 1 h. LDH morphology was then investigated through scanning electron microscopy observations. The homogeneous distribution of petals on the substrate surface mainly depends on grain size distribution. A bimodal grain size distribution in the substrate leads to the formation of petal clusters and a not complete covering of the surface. In the case of grains of large size the nucleation sites are the dislocations forming the walls of the cells, while owing to their low density, the dislocations inside the grains are not a relevant factor in determining the LDH morphology. [ABSTRACT FROM AUTHOR]

Natural fibers are particularly interesting from a materials point of view since their morphology has been tailored to enable a wide range of macroscopic level functions and mechanical properties. In this paper, we focus on mussel byssal threads which possess a morphology specifically designed to provide a hysteretic yet resilient large strain deformation behavior. X-ray diffraction studies have shown that numerous natural fibers have a multi-domain architecture composed of folded modules which are linked together in series along a macromolecular chain. This microstructure leads to a strong rate and temperature dependent mechanical behavior and one which exhibits a stretch-induced softening of the mechanical response as a result of the underlying morphology evolving with imposed stretched. This paper addresses the development of a constitutive model for the stress–strain behavior of the distal portion of mussel byssal threads based on the underlying protein network structure and its morphology evolving with imposed stretched. The model will be shown to capture the major features of the stress–strain behavior, including the highly nonlinear stress–strain behavior, and its dependence on strain rate and stretch-induced softening. [ABSTRACT FROM AUTHOR]

The variation of arrangement of micro-structural entities (i.e. inclusions) influences local properties of composites. Thus, there is a need to classify and quantify different micro-structural arrangements. In other words, it is necessary to identify descriptors that characterize the spatial dispersion of inclusions in random composites. On the other hand, Delaunay triangulation associated with an arbitrary set of points in a plane is unique which makes it a good candidate for generating such descriptors. This paper presents a framework for establishing a methodology for characterizing microstructure morphology in random composites and correlating that to local stress field. More specifically, in this paper we address three main issues: correlating microstructure morphology to local stress fields, effect of clustering of inclusions on statistical descriptors identified in the paper, and effect of number of realizations of statistical volume elements (SVEs) on statistical descriptors. [ABSTRACT FROM AUTHOR]

Equal Channel Angular Extrusion (ECAE), developed and patented in Russia by Segal in 1977, has become in the last few years a very popular tool for studying the evolution of microstructure and properties under severe plastic deformation. It is believed that the strain-stress characteristics are uniform in a cross-section of the billet and this uniformity of the stress-strain distribution ensures the uniformity of microstructure and mechanical properties in ECAE processed billet. However, some experimental data such as the fracture of the extruded billet, which is initiated at the inner surface of the sample, has caused doubts about uniformity of stress-strain distribution. This non-uniformity has been proved recently by Finite Element Simulation.This paper reviewed our results from over six years of work using a unique machine for ECAE with computer controlled back-pressure and velocity of the backward punch. Theoretically back-pressure has been introduced in the earlier papers of Segal. However, practically back-pressure has not been widely used or often used in a primitive form of the consequent extruded sample and its role has not been understood. [ABSTRACT FROM AUTHOR]

This paper presents a systematic study for the production of poly(vinylidene fluoride-hexafluoropropylene) [P(VDF-HFP)], porous films using solvent evaporation (SE) and non-solvent-induced phase separation (NIPS) techniques. Parameters such as volume fraction of the copolymer solution, film thickness, time exposure to air, non-solvent, and temperature of the coagulation bath were investigated on the morphology, crystallization, and mechanical properties of the samples. Films with different porous morphologies including homogeneous pore sizes, macrovoids, and spherulites were obtained depending on the processing conditions, which in turn affect the wettability and mechanical properties of the material. Knowing that the phase content of the films also depends on the processing conditions, this paper shows that P(VDF-HFP) films with tailored porous morphology, electroactive phase content, hydrophobicity, crystallinity, and mechanical properties can be achieved for a specific application using the adequate SE and NIPS techniques conditions. [ABSTRACT FROM AUTHOR]

Zn-(< 1 wt%)Mn alloy is a promising base alloy for developing biodegradable Zn-Mn-based alloys with high strength and high ductility. In this paper, the influence of solution heat treatment on microstructure and hardness of as-cast Zn-0.34Mn and Zn-0.76Mn alloys has been investigated. The temperature of 380 °C is a good choice for the solution heat treatment. ζ-MnZn13 phase is completely dissolved in Zn matrix after 20 h for Zn-0.34Mn alloy and after 30 h for Zn-0.76Mn alloy. Unexpectedly, temporary precipitation of ζ-MnZn13 is observed within grains of Zn-0.76Mn alloy at 5 h, which reaches the peak at 10 h and then decreases until it finally disappears. During the solution heat treatment, hardness of the Zn-Mn alloys decreases with time. Zn-0.76Mn alloy is always about 4-8 HV harder than Zn-0.34Mn alloy. The temporarily formed ζ-MnZn13 particles are rod-like or lath shaped. The orientation relationship between a representative lath-shaped ζ-MnZn13 precipitate and Zn matrix can be described as [101]ζ~//[2-1-10]m and (-131)ζ ~ 5.4° from (0002)m, which is firstly reported as far as our knowledge. The ζ-MnZn13 lath has the long axis parallel to [03-32]m and the habit plane parallel to (-111)ζ//(0-113)m. Simulation of lattice matching reveals that every two ζ-MnZn13 lattice sites match with one Zn lattice site along the direction of the long axis, which explains why the precipitate grows along this direction. No serious segregation of Mn is detected within Zn grains in the as-cast Zn-0.76Mn alloy. The reason why ζ-MnZn13 precipitates temporarily form during the solution heat treatment requires further investigation. [ABSTRACT FROM AUTHOR]

Study of microstructure evolution in the form of grain growth in polycrystalline materials has been an important goal for material scientists as it drastically affects physical and mechanical properties. Specifically, nanocrystalline materials, which are known for their superior mechanical properties, are highly susceptible to grain growth even at low temperatures and stresses. Various experiments and simulations carried out on nanocrystalline materials indicate that the microstructure evolution in these materials takes place due to grain boundary migration and grain rotation. Therefore, migration of grain boundaries and grain rotation-induced grain coalescence contribute in increasing the average grain size in the microstructure. In order to simulate microstructure evolution in polycrystalline materials, the multi-order parameter phase-field model is a popular approach and is widely used for studying evolution purely due to the grain boundary migration. In this work, we present a multi-order parameter phase-field model capable of capturing microstructure evolution due to grain boundary migration and grain rotation-induced grain coalescence. The model couples constitutive equation of viscous sliding-induced grain rotation and the classical phase-field model for curvature-driven grain boundary migration. This paper covers various topological and statistical aspects of the microstructure evolved in the presence of both these growth mechanisms in great detail. [ABSTRACT FROM AUTHOR]

In the natural composites, the reinforcement particles are subtly organized into complex structures in matrix, and its various microstructures endow the biomaterials with a variety of excellent mechanical behaviors. Among the various reinforcement building blocks used in biomaterials, short fibers are the most ubiquitous reinforcement elements. Unfortunately, because of the limitation of fabrication technique, replication of these fiber-reinforced biological composites can be extremely difficult in practice. In this paper, we developed a fiber assembly 3D printing process, which can manipulate the orientation of fibers during 3D printing procedure. Benefiting from this technology, the reinforcement particles were manipulated remotely and the arrangement of reinforcement particles with higher degree of freedom was achieved. Subsequently, based on the herringbone-modified helicoidal architecture of mantis shrimp, the bio-inspired composites with various microstructures were reconstructed by 3D magnetic printing. In addition, the influence of microstructure type and parameters of bio-inspired composites on the properties of composites was studied systematically, and the quantitative relationship between microstructure and properties of the composites was established. The results show that the impact resistance and compression resistance of the composites can be significantly improved by the simple internal microstructures design, and the regression model established in this article can be used for accurate prediction of composites properties and the reliability is higher. In a word, this study opens a new route for the design of composites with unusual features. [ABSTRACT FROM AUTHOR]

Sodium-ion batteries (SIBs) have drawn more attention to serve as one of the promising energy storage devices owing to the abundance of sodium resources and similar characters with lithium element. Hard carbon materials derived from biomass or biomass waste have been considered to act as candidate anode materials for SIBs. In this paper, we have successfully prepared curly hard carbon materials using pistachio shells as biomass template via a two-step approach including hydrothermal treatment and following a pyrolysis process at various temperatures. Physical properties of pistachio shell-derived hard carbons (PSHCs) including microstructure, morphology and pore size distribution are evaluated by X-ray diffraction, Raman spectrum and N2 sorption analysis. The PSHCs carbonized at 1000 °C (PSHC-1000) with average micropores of 0.7398 nm and larger interlayer space of the (002) crystal plane deliver the highest reversible capacity of 317 mAh g−1 at 0.1C, also show the excellent long-term cycling and rate performances. Electrochemical impedance spectroscopy technology is introduced to study the kinetics parameters during the first sodiation process of PSHC-1000 electrode, and also to compare the resistance of the charge transfer process for all the PSHCs. Results exhibit PSHC-1000 electrode with the symmetry factor of 0.1352 has the smallest charge transfer resistance, leading to more easily transportation of electrons and ions. This work can provide a simple and green route for preparation of hard carbon materials derived from biomass waste with unique morphology and microstructure which can exhibit an excellent electrochemical performance. [ABSTRACT FROM AUTHOR]

A strong strain hardening ability in ultra-high strength spring steel 60Si2CrVAT was achieved by the design of multiphase microstructures using a quenching-partitioning-tempering process. The microstructure consisted of ~ 70% martensite/bainite and ~ 30% retained austenite, which was obtained at an optimized partitioning temperature of 380 °C. The corresponding yield strength ratio and the product of strength and elongation were 0.81 and 34,828 MPa%, respectively. Interestingly, this sample exhibited a double-stage strain hardening characteristic with a concave-down shape, which was distinct from that of the other samples. The excellent performance of the ultra-high strength spring steel was mainly due to the interactions between the multiple phases and the stability of the retained austenite during cold deformation. This paper provides a new way of obtaining a strong strain hardening ability in ultra-high strength steels, which is expected to be applicable to the cold coiling process. [ABSTRACT FROM AUTHOR]

The long-term thermal performance of vacuum insulation panels (VIP) is brought by the capacity of their barrier envelope to maintain the core material under vacuum. This study is focused on the detailed modelling of gas transfer through the defects of aluminium-coated polymer films used for VIPs’ envelopes. The 3D simulations were performed with monolayer and multilayer metal-coated polymer films. They have been carried out in dynamic conditions with the SYRTHES® software developed by EDF R&D. The results show that the water vapour and air permeations through a monolayer film slightly depend on the polymer substrate thickness, diffusivity and solubility, but primarily, on the defects geometry and arrangement. Regarding multilayer films, the permeation can be deduced from the ideal laminate theory. We are now able to provide and operate a numerical model, which can calculate the permeance of monolayer or multilayer metallized polymer films as a function of the coating quality and the geometry of the layers. Even if calculated permeances are ten times higher than measurements, this study improves our understanding of gas transports through VIPs’ barrier envelope and allows to manage more efficiently the relations between the films microstructures and their overall permeability. This paper is split into 6 parts: physical phenomena, methodology and modelling tools, simulation results, experiments and model validation and then, discussion and conclusion. [ABSTRACT FROM AUTHOR]

In the present paper, the effects of plastic deformation on the corrosion resistance of strip cast TRIP (transformation-induced plasticity)-aided stainless steel (19Cr-DSS) and conventional lean duplex stainless steel (LDX2101) were studied by observations of deformed microstructure and electrochemical experiments. The electrochemical results indicate that the corrosion susceptibility of experimental steels in 3.5% NaCl solution is increased with increasing deformation amounts. The Mott-Schottky analysis revealed that the passive films formed on both 19Cr-DSS and LDX2101 exhibit the n-type and p-type semiconducting behaviors regardless of strains. With the increase in true strain, the acceptor and donor densities are both continuously increased. The total density of acceptor and donor in 19Cr-DSS is increased more rapidly with increasing strain than that of LDX2101, indicating that the corrosion resistance of 19Cr-DSS is more sensitive to plastic deformation compared to that of LDX2101. For the TRIP-aided 19Cr-DSS, the deterioration of corrosion resistance after plastic deformation may have been caused by the decrease in low-Σ CSL boundaries especially the twin (Σ3) boundaries, the increase in dislocations, and the formation of strain-induced martensite during plastic deformation. [ABSTRACT FROM AUTHOR]

In the present paper, we report a detailed study on the sodium (Na) doping-induced modifications in the copper oxide (CuO) nanostructure and its properties. A facile and sustainable sol-gel synthesis approach was employed for the preparation of high-quality pristine CuO- and Na-doped CuO nanostructures(1.0, 3.0, 5.0 and 7.0 mol% doping levels, CuO/Na) with controlled shape and composition. Due to the remarkable difference in the ionic radii of Cu2+ (0.73 Å) and Na+ (1.02 Å), Na+ substitution in place of Cu2+ generates strain/distortions in CuO lattice. The XRD analysis reveal the structural alteration from monoclinic to cubic symmetry with increase in doping level and also reveal the phase purity up to 3% doping level, and beyond this (i.e., for 5 and 7% doping level) small amount of impurity phase corresponding to Na2O was observed. The FTIR results further confirmed the presence of the Na-Cu-O stretching vibrations at higher Na-doped samples. Morphology of the samples indicates that the Na-doped CuO nanostructures exhibit less agglomeration compared to pristine CuO nanoparticles. The presence of Na in CuO lattice were found to greatly enhances optical and electrical properties owing to the formation of defects like copper vacancies and oxygen vacancies at the grain boundaries of the nanoparticles with increased doping of Na. [ABSTRACT FROM AUTHOR]

In this paper, the core/shell Ni-P@Ni-Co composite with micro-/nanostructure, coating Ni-Co on the precursor Ni-P microspheres, has been synthesized successfully via facile two-step hydrothermal method. The chemical composition and microstructure of as-prepared samples were characterized by XRD, EDS, BET, XPS, SEM, and TEM. The results show that the core/shell composite Ni-P@Ni-Co, with a more rough surface and larger specific surface area (74.2 m g) than bare Ni-P, exhibits good charge storage performance (the specific capacitance reaches up to 1221.1 F g at the current density of 1 A g, 1.8 times of Ni-P under the same conditions), and good cycling performance (the retention of specific capacitance is 95.8% after 5000 cycles at 2 A g current density). To further evaluate the practical application property of Ni-P@Ni-Co, an asymmetric supercapacitor (Ni-P@Ni-Co//AC) was assembled, with the Ni-P@Ni-Co and activated carbon (AC) as the positive and negative electrodes, respectively. The electrochemical results reveal that Ni-P@Ni-Co//AC delivers a high energy density of 28.9 Wh kg at a power density of 0.4 kW kg, along with a specific capacitance retention rate of 89.1% and nearly 100% Coulomb efficiency at a current density of 1 A g after 5000 cycles. [ABSTRACT FROM AUTHOR]

The elytra can protect the body and hind wings of the beetle by absorbing the impact energy and resisting damage from outside loading. In this paper, we firstly observed the microstructures of hollow column and pole canal in the ladybird beetle elytra and revealed the relationship between them. A bionic energy-absorbing structure inspired by ladybird beetle elytra was proposed, and a micron-scale finite element model was built. The mechanical characteristics of bionic structures with and without poles under axial impact loading were investigated by numerical simulations. It could be obtained that the poles could absorb the impact energy by its deformation. Then the parameter studies including the different impact velocities, the different column diameters, and the different thickness of cuticle were carried out. This parameter study shows that geometric variations and impact velocity have a significant influence on mechanical properties. [ABSTRACT FROM AUTHOR]

The aluminum alloy AA5083 is a technologically important structural alloy as it is lightweight, with outstanding weldability and formability, moderate corrosion resistance and strength, making it suitable for a wide range of marine and transportation applications. In the present study, AA5083/nano-γAlO composite metal foam was fabricated using a friction stir processing route (FSP). More precisely, the paper presents a first attempt to use grooves for the integration of the foaming and stabilizing agent on the metal foam precursor by FSP. The implementation of grooves allows to control the amount of foaming, integrates the stabilizing particles within the precursor and permits the production of localized metal foams. Unlike the commonly used manufacturing processes, only one plate is required for the production of the precursor sample in the proposed process. Therefore, this process can be easily implemented in the industrial sector. Furthermore, γ-AlO nanostructured reinforcement, which is characterized by increased interfacial energy, was utilized as a stabilizing agent. The precursor specimens were manufactured by mixing blowing agent powder (0.4% w/w TiH) and stabilization agent nanopowder (2% w/w γ-AlO) into the 5083 aluminum alloy matrix using FSP. The effects of the number of FSP passes and the foaming conditions (holding temperature and time) on the pore density, morphology and distribution were investigated. The microstructure and porosity evolution of the so-obtained metal foam was also examined and analyzed. Results indicate that, following the foaming procedure, a porosity of 60% and an equivalent pore diameter ranging from 0.2 to 3.3 mm can be achieved. Moreover, the microstructure was found to be closely related to microhardness distribution perpendicular to the traversing direction of the FSP tool for both precursor and foamed specimens. [ABSTRACT FROM AUTHOR]

A solid-state bonding technique using fine-grained silver (Ag) foils is presented. The Ag foils are manufactured using many runs of cold rolling and subsequent annealing processes to achieve the favorable microstructure. X-ray diffraction and pole figure measurement are performed to examine the crystal structure and grain orientations. Si chips are bonded to bare Cu substrates using the Ag foil as the bonding medium at 300 °C in 0.1 torr vacuum assisted by 6.9 MPa static pressure, which is much lower than that used in conventional thermal compression bonding. Cross sections prepared by focus ion beam show clear bonding interfaces with only a few voids smaller than 100 nm. The bonded structures do not crack after cooling down to room temperature, indicating that the ductile Ag layer is able to manage the strain induced by the large coefficient of thermal expansion mismatch between Si and Cu. The average shear strength of as-bonded samples is 29 MPa. High-temperature storage tests are conducted, and slight increase in strength can be observed after 300 °C aging. Fracture analyses show that the breakage occurs within the Ag foil rather than on the bonding interface. Transmission electron microscopy and energy-dispersive spectroscopy (TEM/EDX) are conducted for Ag/Cu interface after 200-h aging, and the result shows that slight diffusion proceeds during the aging. Since Ag has the highest electrical and thermal conductivities among metals, therefore the bonded structures reported in this paper probably represent the best possible design for high-temperature and high-power electronic packaging applications. [ABSTRACT FROM AUTHOR]