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Direct management and assessment of metal film properties applied to polymer microneedle (MN) biosensors remains difficult due to constraints inherent to their morphology. By simplifying the three-dimensional structure of MNs and adjusting the deposition time, different thicknesses of Au films were deposited on the UV-cured polymer planar and MN substrates. Several properties relevant to the biosensing of the Au films grown on the polymer surfaces were investigated. The results demonstrate the successful deposition of pure and stable Au nanoparticles onto the surface of UV-curable polymer materials. Initially, Au islands formed within the first minute of deposition; however, as the sputtering time extended, these islands transformed into Au nanoparticle films and disappeared. The hydrophilicity of the surface remains unchanged, while the surface resistance of the thin film decreases with increasing thickness, and the adhesion to the substrate decreases as the thickness increases. In short, a sputtering time of 5–6 min results in Au films with a thickness of 100–200 nm, which exhibit exceptional comprehensive biosensing performance. Additionally, MNs made of Au/UV-curable polymers and produced using magnetron sputtering maintain their original shape, enhance their mechanical characteristics, and gain new functionalities. The Au/UV-curable polymer MNs exhibited remarkable electrode performance despite being soaked in a 37 °C PBS solution for 14 days. These discoveries have important implications in terms of decreasing the dependence on valuable metals in MN biosensors, lowering production expenses, and providing guidance for the choice and design of materials for UV-curable polymer MN metallization films. [ABSTRACT FROM AUTHOR]

Abstract The Na 0.47 Bi 0.47 Ba 0.06 Ti 1- x Fe x O 3-Δ lead-free piezoelectric ceramics (BNBT-100 x Fe, x = 0, 0.01, 0.02, 0.03) were synthesized by using the solid-state reaction technique. X-ray powder diffraction patterns demonstrate that the doping Fe 2 O 3 has totally diffused into the crystal lattice of the ceramics and form a pure perovskite structure. Enhanced piezoelectric property is obtained at x = 0.01, which is reflected on the enhanced remnant polarization (P r) and a giant piezoelectric constant (d 33) up to 168 pC/N. The increasing ferroelectric-to-relaxor phase transition temperature (T F-R) on dielectric permittivity curves suggest the enhanced ferroelectric characteristics with increasing the Fe3+ content. By using the complex ac impedance analysis, the grain, grain boundary and electrode effects are all detected at the appreciate composition. The resistivity behavior of the samples is sensitive to the doping Fe3+ concentration, and additionally, the oxygen vacancies play an important role in this characteristic. [ABSTRACT FROM AUTHOR]

A series of (Bi 0.5 Na 0.4 K 0.1 )Ti 0.98 Nb 0.02 O 3 - x Li lead-free ceramics were fabricated using the solid-state reaction technique. The effects of Li/Nb cations on the structural and electrical properties of the ceramics were investigated. All the sintered ceramics exhibited pure perovskite structure and the average grain size increased slightly with increasing the Li content. Shape of the P - E loops illustrated the relaxor characteristic of all the samples. A giant strain of 0.4% was obtained at 60 kV/cm at x = 0.01 and the corresponding normalized strain was up to 683 pm/V, moreover, the strain exhibits excellent fatigue-resistance behavior. The giant strain can be attributed to the ferroelectric-relaxor phase transition under external driving electric field. These results indicate the sintered Li/Nb co-doped lead-free ceramics can be promising candidate for actuator applications. [ABSTRACT FROM AUTHOR]

A series of Nb-doped (BiNaK)TiO lead-free piezoelectric ceramics were fabricated by a conventional solid-state reaction method. The X-ray diffraction patterns reveal a pure perovskite structure for all the samples. A giant strain of 0.34% is achieved at 2 mol% Nb-doping concentration, and the corresponding normalized strain $$d_{33}^*$$ reaches 625 pm V, which is one of the best results of the BNT-based ceramics. Complex ac impedance data indicate that only the bulk effect contributes to the resistivity. The compositionally induced disruption of long-range ferroelectric order and relaxor transition contributed to the pinched polarization loops as well as the large electric field-induced strain. The results indicate that appropriate Nb-dopant content can remarkably enhance the strain level of (BiNaK)TiO ceramics, making it a promising candidate for actuator applications. [ABSTRACT FROM AUTHOR]

Abstract: The microstructure evolution and mechanical properties of hypereutectic Al–20%Si alloy with Er addition were investigated in the article. The as-cast samples were characterized by optical microscopy (OM), scanning electron microscopy (SEM) and electron probe microanalysis (EPMA). Microstructural analyses demonstrated that primary Si was significantly refined from coarse polygonal, platelet-like and star-like shape to fine blocky shape, and eutectic Si structure was modified from coarse platelet-like/needle-like structure to fine coral-like fibrous structure as the addition contents of Er is 0.5%. However, the primary and eutectic Si phases became coarser when the level of rare earth Er was up to 0.8%. The mechanical properties were investigated by tensile test with various concentration of Er. It was found that the ultimate tensile strength (UTS) and elongation (El) increased by 72.5% and 72%, respectively, due to decreasing of the size and changing of morphology on primary and eutectic Si crystals, and the change of mechanical properties corresponds to the evolution of microstructure. In addition, the modification mechanism of Er on Al–20%Si alloy was also discussed. [Copyright &y& Elsevier]

Highlights: [•] Aluminum ammonium sulfate (NH4Al(SO4)2) power can decomposed out γ-Al2O3 particles in high temperature Al–20%Si alloy melt. [•] In situ γ-Al2O3 particles can refine primary and eutectic Si phases of Al–20%Si alloy. [•] The refinement mechanisms are attributed to heterogeneous nucleation and restrict growth. [ABSTRACT FROM AUTHOR]

Abstract: It is well known that the mechanical properties of hypereutectic Al–Si alloys are influenced by the size, morphology and distribution of primary and eutectic Si crystals. In the present work, the microstructure evolution and mechanical properties of hypereutectic Al–20%Si alloy with rare earth cerium (Ce) additions (0, 0.3, 0.5, 0.8 and 1.0wt.%) were investigated. The as-cast samples were characterized by optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD) and electron probe microanalysis (EPMA) with wavelength dispersive spectroscopic (WDS). The microstructural observation showed that primary Si crystals were significantly refined from coarse polygonal and star-like shape to fine blocky shape with smooth edges and corners, and eutectic Si phases were modified from coarse platelet-like/needle-like structure to fine fibrous structure and discrete particles with increasing the addition contents of rare earth Ce. The mechanical properties were investigated by tensile test with various concentration of Ce. It was found that the ultimate tensile strength (UTS) and elongation (El) increased by 68.2% and 53.1%, respectively, due to decreasing of the size and changing of morphology on primary and eutectic Si crystals. [Copyright &y& Elsevier]

Abstract: Nickel nanoparticles with various grain sizes were successfully prepared by anodic arc discharge plasma method. The samples prepared by this method were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and the corresponding selected-area electron diffraction (SAED) to determine the crystal structure, lattice parameter, morphology and particle size. The experiment results indicate that the crystal structure of the samples is FCC structure as same as the bulk materials. The lattice parameters for Ni nanoparticles are always larger than the equilibrium values of the perfect single crystal lattice respectively, the lattice parameter increase significantly with the decrease of the grain size, the lattice expansion was found, and the expansion quantity of the lattice parameter is in direct proportion to the reciprocal of grain size. The values of the unit cell volume increase remarkably with the decrease of the grain size. The lattice expansion is the result of the interfacial energy and surface tension mutual attraction of Ni nanoparticles, this phenomenon can be explained according to the thermodynamic theory. [Copyright &y& Elsevier]

Abstract: To investigate the phase transformation behaviors of combustion synthesis of MgB2, a mixture of Mg, B was used for a combustion front quenching test, and the microstructural evolution in the quenched sample was observed by scanning electron microscopy (SEM) and electron probe microanalyzer (EPMA). The temperature–time profile of the combustion was measured, and the phase constituents of the different zones of the quenched sample were inspected by X-ray diffraction (XRD). Based on these experimental results, the transformation behaviors in the SHS-synthesized superconductor MgB2 was analyzed, and a solid phase diffusion and dissolution–precipitation mechanism was proposed. [Copyright &y& Elsevier]

Abstract: Sphere-shape nickel nanopowders were successfully prepared at high rate (up to 1.3 g/min) by anodic arc discharge plasma method. The morphology, crystalline structure, particle size and specific surface area of the samples were characterized via X-ray diffraction (XRD), transmission electron microscopy (TEM) and the corresponding selected area electron diffraction (SAED), and Brunauer–Emmett–Teller (BET) surface area analysis. The influences of the technology parameters on the yield rate and particle size of Ni nanopowders were studied, and the referential process parameters were obtained. The experimental results indicate that the crystal structure of the samples is FCC structure as same as that of the bulk materials. The specific surface area is 14.23 m2/g, with the particle size distribution ranging from 20 to 70 nm, the average particle size about 47 nm obtained from TEM and confirmed from XRD and BET results. This technique is a convenient and effective method to prepare high quality nanopowders with uniform size, higher purity, narrow size distribution and spherical shape. The yield rate and particle size increase with the increase of the arc current or gas pressure when other factors are fixed. [Copyright &y& Elsevier]

0.8(Bi 0.5 Na 0.5 )TiO 3 −0.2(Bi 0.5 K 0.5 )(Hf x Ti 1−x )O 3 (abbreviated as BNT-BKH x T 1−x ) lead-free ceramics are prepared using a solid state reaction method and their dielectric, field-induced strain and energy storage properties have been systemically investigated. It was found that the largest strain induced by an external electric field occurs for x=0.02. For the x=0.02 sample, S 33 =0.41%, S max /E max =683 pm/V. However, the energy storage density is optimized at the x=0.03 sample, for which W 1 =0.51 J/cm 3 . Those results may originate from the field-induced transition between a relaxor-ferroelectric mixture phase and a ferroelectric phase. [ABSTRACT FROM AUTHOR]

It is well known that the mechanical properties of hypoeutectic Al–Si alloys are influenced by the size, morphology and distribution of primary α-Al and eutectic Si crystals. In the present study, the effect of in-situ γ-Al 2 O 3 particles and heat treatment on the size and morphology of the primary α-Al dendrites and eutectic Si phases in A356 alloy has been investigated. The as-cast and solution treatment samples were characterized by scanning electron microscopy (SEM). Microstructural analyses demonstrated that primary α-Al was significantly refined by in-situ γ-Al 2 O 3 particles. The secondary dendrite arm space (SDAS) of unrefined α-Al is about 25 μm. The SDAS decreases to 11 μm when the content of in-situ γ-Al 2 O 3 particles is 0.6%. In addition, the eutectic Si structure was modified from coarse needle-like/platelet-like structure to short plate-like structure and some discrete particles. The mechanical properties were investigated by tensile test with various concentrations of γ-Al 2 O 3 particles. It was found that the ultimate tensile strength (UTS) and elongation (El) increased by 41% and 137%, respectively, due to decreasing SDAS of primary α-Al dendrites and modifying eutectic Si crystals. Moreover, the change of mechanical properties corresponds to the evolution of microstructure. [ABSTRACT FROM AUTHOR]

The Al-5Ti-0.62C master alloy was prepared through a method of thermal explosion in molten aluminum. The process of remelting and refining of commercially pure aluminum was conducted, and precipitation samples with different heat-treatment times were obtained. Scanning electron microscopy (SEM), X-ray diffraction (XRD), optical microscopy (OM), and other techniques were used to analyze the microstructure of the precipitates at the bottom of the samples so as to explore the fading mechanism of Al-Ti-C alloy refinement. The results showed that an obvious precipitation phenomenon of titanium compounds existed in the remelted Al-5Ti-0.62C master alloy and that there were both TiC compounds and TiAl3 compounds in the precipitates; in the refined pure aluminum samples, the precipitates were mainly TiC compounds. Precipitation of titanium compounds in aluminum melting is the main cause of fading in the refinement effect of an Al-Ti-C master alloy. [ABSTRACT FROM AUTHOR]

• A novel modifier of AlCoCrFeNiTi high-entropy alloy (HEA) is prepared. • The HEA can effectively modify the eutectic silicon structure of Al-7Si alloy. • The HEA can significantly refine the α-Al grains of Al-7Si alloy. • The mechanical properties of alloy with 0.2 wt%HEA are significantly improved. In this work, the AlCoCrFeNiTi high-entropy alloy (HEA) was prepared as an inoculant to refine the α-Al and silicon phases in Al-7Si alloy. The modification mechanism and the existing form of HEA in Al-7Si alloy were studied. The results show that Fe-rich intermetallics including Al, Si, Co, Fe and Ni, precipitated when the 0.2% AlCoCrFeNiTi HEA was added into Al-7Si alloy. In addition, the elements of Ti and Cr uniformly distributed within Al-7Si alloy. The morphology of the eutectic silicon changed from long needle structure to short rod and granular structure. Moreover, the size of α-Al grains significantly decreased in Al-7Si-0.2HEA alloy. The mechanical properties of Al-7Si alloy significantly improved. [ABSTRACT FROM AUTHOR]

The effects of three different substrate materials (glassy carbon, gold, and nickel electrodes) on the electrocrystallization behavior of nanocrystalline nickel in an industrial electrolyte with complex compositions were studied by cyclic voltammetry (CV), single potential step chronoamperometry. The CV results indicated that the initial deposition potentials of nickel shift to the positive direction in the order glassy carbon < gold < nickel electrodes, while the nickel deposition overpotential decreased at the same time. Chronoamperometry results indicated that from the glassy carbon to gold and nickel electrodes, the adhesion of nickel nanoparticles on the electrodes increased, nucleation relaxation time became shorter, and the number of nuclei decreased. As the deposition potential is negatively shifted and the deposition time is prolonged, the I-t curves for the nickel and gold electrodes are more stable and reliable than those from the glassy carbon electrodes. The chronoamperometric study combined with SEM revealed that the nucleation mechanism of nickel on different substrates changed from three-dimensional progressive to instantaneous, but the time of the transition is different. When the deposition time is 100 s, the nanocrystalline nickel deposited on the nickel and gold electrodes has good integrity and uniformity. This was also confirmed in studies using atomic force microscopy and transmission electron microscopy. Moreover, the results of transmission electron microscopy (TEM) show that there are many twins in the nanocrystalline nickel layer deposited on the gold electrode at −0.95 V, 100 s. The electrocrystallization process of nickel is complicated by the complex ionic components in the industrial electrolyte of the nickel sulfide soluble anode/mixed acid system. • Different substrates do not change the electrocrystallization mechanism of nickel. • Glassy carbon electrode is not suitable for prolonged high-potential nickel deposition. • Electrocrystallization of nickel is complicated by the complex electrolyte composition. [ABSTRACT FROM AUTHOR]

It is well known that the mechanical properties of hypoeutectic Al–7%Si alloys are influenced by the size, morphology, and distribution of primary α-Al and eutectic Si crystals. In the present work, a novel Al–Ti–C–Ce master alloy was prepared by the pure molten aluminum thermal explosion reaction, and its effects on the microstructure and mechanical properties of hypoeutectic Al–7%Si alloy were investigated. The results show that the Al–Ti–C–Ce master alloy containing α-Al, granular TiC, lump-like TiAl3, and block-like Ti2Al20Ce has excellent refining and modification properties for hypoeutectic Al–7%Si alloy. When 1.5 wt.% Al–Ti–C–Ce master alloy is added, the coarse dendritic α-Al in hypoeutectic Al–7%Si alloy is refined into equiaxed grains. The secondary dendritic arm spacing (SDAS) was also reduced, and the coarse needle-flake eutectic Si phase was transformed into a fibrous and granular phase. It was found that the ultimate tensile strength and elongation increased by 59% and 56%, respectively, due to the decrease in the SDAS of primary α-Al dendrites and the modification of eutectic Si crystals. Moreover, the change of mechanical properties corresponds to the evolution of microstructure. [ABSTRACT FROM AUTHOR]

The effect of the addition of yttrium (Y) and Al–5Ti–1B modifiers mixing melt (3M) on the microstructure and mechanical properties of hypereutectic Al–20Si alloy was studied in the present work. The as-cast specimens were examined by scanning electron microscope equipped with energy spectrometer, electron probe microanalysis and X-ray diffraction. The results demonstrated that the morphology of primary Si could be refined from coarse irregular star-like/plate-like structures into fine blocks with the addition of 0.6 wt% Y and 1.0 wt% Al–5Ti–1B at 650 °C. The average grain size of primary Si was reduced from 82 to 29 µm, and the aspect ratio was decreased from 1.81 to 1.47. Similarly, the eutectic Si structure was modified from coarse needlelike/flake-like structures into fine coral fibrous structures and partial granular structures, with the mean roundness of eutectic Si decreased from 7.8 to 2.32. In addition, the coarse α-Al dendrites were significantly refined into the uniform equiaxed dendrites. With the refinement and homogenization of Si phases, the optimal modified alloy obtained the optimal ultimate tensile strength (UTS) and elongation (EL). The UTS was enhanced from 94 to 154 MPa, and the EL was increased from initial 1.12 to 1.79%. Furthermore, the refinement and modification mechanism of the addition of yttrium and Al–5Ti–1B modifiers mixing melt on Al–20Si alloy were also discussed. [ABSTRACT FROM AUTHOR]

Abstract The new type of Al-Ti-C-La master alloy was prepared by commercial pure Al, Ti powder, graphite powder, Al powder and La 2 O 3 powder by aluminum melt in-situ reaction method. The microstructure and the effect on commercial pure aluminum of Al-Ti-C-La master alloy have been studied by means of X-ray diffraction (XDR), scanning electron microscopy (SEM) equipped with energy-dispersive spectrometry (EDS). The synthesis thermodynamics and kinetics of Al-Ti-C-La master alloy were analyzed. The experiment shows that Al-Ti-C-La master alloy is composed of Al, Al 3 Ti, TiC and Ti 2 Al 20 La. The refining performance of the prepared Al-Ti-C-La master alloy is obviously better than that of Al-Ti-C master alloy when the addition of rare earth oxide La 2 O 3 is 10 wt% and the preparation temperature is 930 °C. The analysis of thermodynamic calculation and the process of kinetics demonstrate that, in the preparation process of Al-Ti-C-La master alloy, firstly, Al reacts with Ti to produce Al 3 Ti, C reacts with Ti and Al 3 Ti to form TiC based on the aluminothermy reaction. Rare earth oxide La 2 O 3 and C powder react with Ti powder and O 2 in the air occur to generate CO, TiC, [La] atoms and LaC 2. [La] atoms adsorb on the surface of Al 3 Ti to form the new rare earth compounds Ti 2 Al 20 La. Highlights • Al-Ti-C-La master alloy was prepared while structure of the master alloy was studied. • Thermodynamics was calculated in the preparation process of Al-Ti-C-La master. • A kinetic model of the synthesis reaction of Al-Ti-C-La master alloy was established. • The refinement mechanism of Al-Ti-C-RE master alloy was analyzed. • Adding La 2 O 3 contributes to the refining performance of Al-Ti-C-La master alloy. [ABSTRACT FROM AUTHOR]

In the present work, the effect of Sm addition (0.2, 0.4, 0.6, and 0.8 wt%) on the microstructure evolution and tensile properties of as-cast hypereutectic Al-20%Si alloy were investigated. The scanning electron microscopy, X-ray diffraction (XRD), and electron probe microanalysis with wavelength dispersive spectroscopy (WDS) were used to quantitatively characterize the samples. The results indicated that the primary Si phases were significantly refined from coarse polygonal and star-like shape to fine block with smooth edges and corners when the addition of Sm increased from 0 to 0.6%. Furthermore, eutectic Si phases were fully modified from coarse platelet-like/needle-like structure to fine fibrous structure and discrete particles with the addition of 0.6%Sm. However, the primary and eutectic Si phases became coarser when the level of rare earth Sm reached 0.8%. The analysis of XRD and WDS shows that Sm mainly exists in the form of Al2Si2Sm compounds. In addition, the tensile properties of as-cast Al-20%Si alloy with different concentrations of Sm were investigated by tensile test. It was found that the ultimate tensile strength (UTS) and elongation (EL) gradually enhanced with the increasing concentration of Sm from 0 to 0.6% due to decrease of the size and the change of morphology on Si phases. Compared with unmodified Al-20%Si alloy, the UTS and EL values of Al-20%Si alloy with 0.6%Sm were increased by 48.5 and 68.8%, respectively. [ABSTRACT FROM AUTHOR]

The effects of Y additions (0.2, 0.4, 0.6, 0.8 and 1.0 wt%) on the microstructure and mechanical properties of hypereutectic Al-20Si alloy have been studied in the present work. The as-cast specimens were examined by scanning electron microscope (SEM) equipped with energy spectrometer (EDS), electron probe micro-analysis (EPMA) and X-ray diffraction (XRD). The results demonstrated that the morphology of primary Si could be refined from coarse irregular star-like and plate-like shape to fine block-like when the addition contents of Y increased to 0.8%. The average size of primary Si reduced by 62.9% from 89 µm to 33 µm and the aspect ratio decreased by 38.6% from 2.07 to 1.27. In addition, the eutectic Si structure was modified from coarse needle / flake to fine coral fibrous structure and partial particles. With the refinement and homogenization of Si phases, the optimal elongation (El) increased by 22.5% from 1.13% to 1.36% when the Y content was 0.6%. However, the ultimate tensile strength (UTS) enhanced by 47.9% from 94 MPa to 139 MPa when the addition content of Y was up to 0.8%. Moreover, the refinement and modification mechanism of Y on Al-20Si alloy was also discussed. [ABSTRACT FROM AUTHOR]

It is well known that the mechanical properties of hypoeutectic Al-Si alloys are influenced by the size, morphology and distribution of primary α-Al dendrites, eutectic Si crystals and other intermetallics. In the present work, the effect of Mg addition on the size and morphology of the primary α-Al dendrites and eutectic Si phases in Al-7%Si alloy has been investigated. The microstructure of as-cast samples with different Mg content was characterized by scanning electron microscopy. Microstructural analyses demonstrated that primary α-Al was significantly refined from coarse dendrites to fine equiaxed grain with increasing the amounts of Mg. In addition, the eutectic Si structure was modified from coarse needle-like/platelet-like structure to a fine coral-like fibrous structure. The mechanical properties were investigated by tensile test with various concentrations of Mg. It was found that the ultimate tensile strength improved by 61% with an increase in Mg content. However, the ductility initially increased by 80% with an increase in Mg content from 0.5 to 1.5%, then it decreased with further increasing Mg content up to 2.0 and 2.5%. It is due to precipitation of coarse Chinese script MgSi phase that leads to the increase in strength and the decrease in ductility. [ABSTRACT FROM AUTHOR]

This paper presents the experimental investigation on the thermal properties and electrical conductivity of the new microencapsulated phase change material by entrapping of stearic acid (SA) into PANI (polyaniline) shell through self-assembly method. Experimental results reveal that PANI nuclei grew on the surface of SA, and then copied its original morphological structure and finally exhibited peony flower-like morphology. The two components have good compatibility and have no chemical reaction both in the process of fabrication and subsequent use, while hydrogen bondings between the imino groups and carboxyl groups exist. The maximum mass fraction of stearic acid loaded in SA/PANI is determined as high as 62.1 wt% without seepage of melted SA from capsules. Due to the secondary doping with carboxyl group, the composite phase change material embedded with SA exhibits improved electrical conductivity from 0.3968 S cm −1 to 0.7042 S cm −1 when compared to PANI. The phase change temperatures and latent heats of SA/PANI are measured to be 55.6 °C and 113.02 J/g for melting and, 50.8 °C and 112.58 J/g for freezing, respectively. TG analysis test revealed that the prepared SA/PANI composite PCM has high thermal durability in working temperature range. Moreover, the results of DSC, FT-IR, TG, conductivity investigation and thermal cycling test are all show that the thermal reliability and electrical conductivity of the SA/APNI have imperceptible changes. In total, the additional electrical conductivity, high heat storage potential and good thermal reliability and stability facilitated SA/PANI to be considered as a viable candidate for thermal energy storage, antistatic thermo-regulating textiles and other applications. [ABSTRACT FROM AUTHOR]

Spark plasma sintering (SPS) is an important method of preparation of Ni-Al alloy high performance aircraft material. This paper adopted grey cluster analysis to estimate the Ni-AI alloy aircraft material with different chemical compositions. The cluster properties were judged according to the summary of three grey degrees. The evaluating results can be used for guiding experiment technology and future application in actual production. [ABSTRACT FROM AUTHOR]

Abstract: The particle size, specific surface area, crystal structure and morphology of Ni nanoparticles prepared by an anodic arc discharge plasma method were characterized via X-ray diffraction (XRD), transmission electron microscopy (TEM) and the corresponding selected area electron diffraction (SAED), X-ray energy dispersive spectrometry (XEDS), the Brunauer–Emmett–Teller (BET) equation, and the Barrett–Joyner–Halenda (BJH) method. The experimental results indicate that the crystal structure of the samples is face centered cubic (FCC) the same as that of the bulk materials, the specific surface area is 14.23m2/g, with the particle size distribution ranging from 20 to 70nm, the cumulative volume of the pores is 0.09cm3/g, the average pore diameter is 23nm, and the average particle size about 47nm. The grain size D XRD is smaller than the particle size D TEM and D BET due to agglomeration. The nanoparticles prepared by this method achieved uniform size, low impurity contamination, narrow size distribution and spherical shape. [Copyright &y& Elsevier]

In the present work, AlSiTiCrNiCu high entropy alloy (HEA) has been used in as-cast Al-5wt%Cu alloy to investigate the effect of HEA addition level (0.3 wt% and 0.6 wt%) on the microstructure and mechanical performance. The results revealed that the addition of HEA has a distinct influence on the size and morphology of primary α-Al and second phases in the cast Al-5wt%Cu alloy. When 0.3 wt% and 0.6 wt% HEA was added to Al-5wt.%Cu alloy, the primary α-Al dendrites was obviously refined and the mean size of α-Al grains was significantly reduced from 372.5 μm to 183.4 μm and 156.3 μm, respectively. Meanwhile, the size and morphology of θ-Al 2 Cu phases distributing inter-dendritic zone occurred to obvious change with increase of HEA addition concentration. In addition, the θ-Al 2 Cu phases disappeared and eutectic Al 3 CuNi phases precipitated after adding the HEA in Al-5wt%Cu alloy. Compared with θ-Al 2 Cu phases, the width was decreased and the continuity of Al 3 CuNi was improved when HEA was added to Al-5wt%Cu alloy. Moreover, it was found by TEM that some novel nano-particles precipitated from Al-5wt%Cu alloy with the addition of HEA in solidification, which uniformly distributed in the α-Al matrix. The yield strength, ultimate tensile strength and elongation of Al-5wt%Cu alloy with 0.6 wt.% HEA addition were significantly increased by 19.7%, 20.1% and 92.3%, respectively. The improvement of mechanical properties was attributed to change of morphology and decreasing size of α-Al and Al 3 CuNi phases. In addition, a new plate-like structure precipitated which morphology is similar to θ phase and multi-elements nano-particles formed, which strengthened the Al-5wt%Cu alloy. • HEA addition can effectively refine the α-Al grains of Al-5wt.%Cu alloy from dendrites to equiaxed grains. • The addition of HEA can precipitate nano-sized AlCuNi phases and AlSiTiCrNiCu particles precipitate in Al-5wt.%Cu alloy. • The improvement of strength is mainly attribute to the Orowan strengthening and solid solution strength. [ABSTRACT FROM AUTHOR]

The effects of Sc addition on the primary α-Al phases and novel nano-AlCu phases were investigated in Al-5%Cu alloys without and with 0.8%Sc. The microstructural evolution was characterized by scanning electron microscopy (SEM) and transmission electron microscope (TEM) with energy dispersive X-ray spectroscopy (EDS). In the study, the novel ribbon nano-AlCu phases were found in as-cast Al-5%Cu alloy and the average length is about 200–300 nm. When 0.8%Sc was added into the Al-5%Cu alloy, the α-Al phases were obviously refined from coarse dendrites to fine equiaxed grains and the average grains size decreased to 29.8 μm. Moreover, the number of nano-AlCu phases significantly increases, but the length and width obviously decrease. In addition, the nano-AlCu phases have a good lattice matching relationship with α-Al phases, which can act as a precursor refining α-Al grains. • Sc can not only refine the α-Al grains, but also can change the morphology of θ-Al 2 Cu phases. • A novel nano-AlCu phase is found in Al-5%Cu alloys and the nano-Al 3 Sc particles can form in Al-5%Cu-0.8%Sc alloy. • The formation of nano-Al 3 Sc can restrict the growth of nano-AlCu phase and act as the precursors refining α-Al. [ABSTRACT FROM AUTHOR]

Grain refinement is one of the effective methods to improve the yield strength and toughness of Al-Cu alloys. The effects of Sc addition (0.2%, 0.4%, 0.6%, 0.8% and 1.0 wt%) on the microstructural evolution and mechanical properties of as-cast Al-5%Cu alloys were studied. The as-cast samples were characterized by optical microscope (OM), transmission electron microscopy (TEM), scanning electron microscope (SEM) and electron probe microanalysis (EPMA). The results revealed the primary α-Al occurred to obvious change from developed dendrites to fine equiaxed grains with the increasing Sc content in Al-5%Cu alloy. When the addition concentration of Sc reaches 0.8%, the developed α-Al dendrites were significantly refined and the average size of α-Al decreased from 218.3 μm to 29.6 μm. Moreover, the morphology and size of θ-Al 2 Cu phases of Al-5%Cu alloy caused noticeable changes with the increase of Sc concentration. Mechanical properties test illustrated that the ultimate tensile strength (UTS), yield strength (YS) and elongation (El) increased by 61.59%, 66.82% and 57.20%, respectively, which could be attributed to microstructure refinement and fine Al 3 Sc particle precipitate. • Sc can significantly refine the α-Al phase from coarse dendrites to uniform fine equiaxed grains in Al-5%Cu alloy. • The addition of Sc change the morphology of θ-Al 2 Cu from discontinuous to continuous tissues. • The YS and UTS was improved by 61.59% and 66.82% and the El was enhanced by 57.20% when the addition of Sc reached 0.8%. [ABSTRACT FROM AUTHOR]