Search

In this work, Cu-1.5 wt%Y (Cu-Y) and Cu-0.75 wt%Y-0.75 wt%La (Cu-Y-La) were prepared by mechanical alloying combined with spark plasm sintering and hot rolling, followed with annealing at different temperatures. The effects of the introduction of La and annealing temperatures on the microstructures, mechanical properties, electrical conductivity and thermal stability of Cu-Y alloys were investigated. Both Cu-Y and Cu-Y-La obtain the heterogeneous mixed grain structures composed of coarse grains and fine grains, and oxide nanoparticles are uniformly dispersed in Cu matrix. With the introduction of La, the grains and oxide nanoparticles are refined, and LaYO 3 nanoparticles with the coherent interfacial structure can be observed in Cu-Y-La. After annealing at 500 ℃, both Cu-Y and Cu-Y-La obtain the most excellent comprehensive tensile properties and highest electrical conductivity (63 %IACS for Cu-Y and 62 %IACS for Cu-Y-La). Benefited from effectively enhanced grain boundary strengthening and particle strengthening mechanisms induced by the combination effect of La and Y, Cu-Y-La shows higher strength than that of Cu-Y (after annealing at 500 ℃, 244 MPa of yield strength for Cu-Y and 300 MPa for Cu-Y-La). Meanwhile, benefited from improved dynamics stability of the Cu matrix induced by significantly refined precipitates and the formation of LaYO 3 nanoparticles with the coherent interfacial structure after introducing La, the better softening resistance is achieved by Cu-Y-La in comparsion with Cu-Y, and almost 100 ℃ improvement of the softening temperature is achieved (966 ℃ for Cu-Y-La and 870 ℃ for Cu-Y). • A novel system of Cu-Y-La alloy for the field of ITER is designed and prepared. • Effects of heat treatment on microstructure and properties of Cu alloys reinforced by rare earth elements are studied. • The significant improvement of mechanical property of Cu-Y alloy is achieved through the combination effect of Y and La. • The softening resistance of Cu-Y alloy is successfully improved through the combination effect of Y and La. [ABSTRACT FROM AUTHOR]

In this work, (Mg 1/3 Nb 2/3)4+ cationic substitution in lead-free polycrystalline Na 0.5 Bi 0.5 TiO 3 (NBT) has been adopted to synthesize by the conventional solid-state reaction method. The cationic substitution was introduced into NBT through compositional modification, which significantly restricted grain growth and promoted a ferroelectric to relaxor ferroelectric phase transition. The substitution of (Mg 1/3 Nb 2/3)4+ influenced the crystal structure, ferroelectric, dielectric properties, and micromorphology, which had been investigated systematically. The enhancement of relaxor nature is found with this substitution and further verified by dielectric curve, polarization (P) - electric field (E) hysteresis loop, and current (I)- electric field (E) curve. The recoverable energy density was determined to be 1.09 J/cm3 and 1.24 J/cm3 at 101 kV/cm and 114 kV/cm in the 10 mol% and 20 mol% of (Mg 1/3 Nb 2/3)4+ substituted systems, respectively. Furthermore, over the 35 ˚C to 490 ˚C temperature range, the 30 mol% (Mg 1/3 Nb 2/3)4+ substituted composition showed superior thermal stability in the permittivity. Therefore, this study concluded that these cationic substituted NBT compositions are appropriate materials for applications involving higher-temperature and energy storage in electronic devices. • Recoverable energy storage density (W rec) ≈ 1.24 J/cm3 obtained in the 20 mol% with the efficiency of 54 %. • The introduction of (Mg 1/3 Nb 2/3)4+decreases the grain size and improve BDS to improve W rec. • Thermal stability increases in the 35- 490 ˚C temperature range, in the 30 mol% (Mg 1/3 Nb 2/3)4+composition. [ABSTRACT FROM AUTHOR]

A series of CaY 1.97−y Al 4 SiO 12 : 0.03Dy3+, yGd3+ white phosphors were prepared by high temperature solid phase method. The structure and phase purity of representative samples were characterized by Rietveld refinement and Fourier transform infrared spectrum. In CaY 1.97 Al 4 SiO 12 : 0.03Dy3+ phosphors, the sample has two characteristic peaks at 485 nm (4F 9/2 →6H 15/2) and 574 nm (4F 9/2 →6H 13/2) excited at 350 nm. In CaY 1.97−y Al 4 SiO 12 : 0.03Dy3+, yGd3+ phosphors, the luminescence intensity of CaY 1.97 Al 4 SiO 12 : 0.03Dy3+ samples were significantly improved by partially substituting Y3+ in the host with Gd3+, showing strong white luminescence. The reasons for enhanced luminescence after partial substitution of Gd3+ are discussed in detail from the perspective of phosphor structure and crystal field effect around Dy3+. In addition, with the substitution of Gd3+, the sample showed low thermal quenching, which was illustrated by combining the calculation of Debye temperature and activation energy. Finally, the chromaticity coordinates of CaY 1.97−y Al 4 SiO 12 : 0.03Dy3+, yGd3+ phosphors were all located in the white region, and combined with the 310 nm chip package, white phosphors with high color rendering index were obtained. Therefore, CaY 1.93 Al 4 SiO 12 : 0.03Dy3+, 0.04Gd3+ phosphors can be used as high-quality materials in the field of w-LED. [ABSTRACT FROM AUTHOR]

Investigation of powder-based additive manufacturing (AM) of metallic alloys is quickly increasing due to reduced defects, low cost, and high efficiency. Recent developments in the printing of defect-free sections promise fundamental motion beyond conventional technologies and also enable the production of complex parts by adding material layer upon layer. Fabricated parts by additive manufacturing have notable mechanical properties owing to the experienced thermal gradient and high cooling rate compared with conventional processes. Thermal stability, determining the material's ability to keep its properties and sustain at desired temperatures over prolonged service time, is becoming the next limiting factor for AM-built metallic alloys. The development of thermally stable materials will provide a wider temperature range for structural applications, particularly in the automotive and aerospace industries. In this review, the previous studies have been purposefully collected to survey the high-temperature mechanical properties and thermal stability of metallic alloys fabricated with AM. We explored and discussed the thermal stability of five categories of metallic alloys (aluminum alloys, ferrous alloys, titanium alloys, superalloys, and high entropy alloys) fabricated by various methods of additive manufacturing technology. We emphasized their phase transformation, microstructure development during solidification, and various strengthening mechanisms activated at high and low temperatures, all of which affecting on high-temperature mechanical properties. The main goal of this article is to develop an ample comprehension of the mechanical properties and thermal stability of the metallic alloys AM-built under various conditions. [ABSTRACT FROM AUTHOR]

Metallic glasses can exhibit a wide range of local atomic arrangements which are determined by their processing history, and which control their mechanical properties. While recent studies show that thermally stable thin film metallic glasses with high strength and plasticity can be synthesized using physical vapor deposition, they often differ in terms of their structure and mechanical performance from bulk metallic glasses. In that aspect, two different fabrication methods – physical vapor deposition and arc melting – were utilized to fabricate compositionally similar Zr-based glasses in thin-film and bulk form. The as-fabricated samples were characterized in terms of oxygen concentration, element composition, and atomic structure. The mechanical response of the thin film metallic glass (TFMG) and the bulk metallic glass (BMG) was examined using in situ micropillar compression in a scanning electron microscope over a temperature range of room temperature to 500 °C. While the two glasses show overall similar failure characteristics, the TFMG exhibits higher strength together than the BMG without sacrificing plasticity at all testing temperatures. At elevated temperatures, the deformation mechanism changes to homogenous deformation above glass transition temperature (T g). The higher strength and thermal stability of the TFMG is associated with a much higher oxygen concentration in the thin film compared to the BMG. The enhanced mechanical performance of the TFMG compared to the BMG highlights the potential of oxygen in the thermal stability characteristics and deformation capacity of Zr-based thin film metallic glasses. • Investigated mechanical response & thermal stability of thin film & bulk Zr-based metallic glasses via in-situ micro-pillar compression. • Oxygen concentration, degree of crystallization and free volume content were correlated to mechanical properties at various temperatures. • Higher oxygen in TFMG contributes to superior mechanical properties, thermal stability while maintaining plasticity across all temperatures. [ABSTRACT FROM AUTHOR]

This paper investigated the structure, microwave dielectric properties and thermal properties of xZn 0.15 Nb 0.3 Ti 0.55 O 2 @VTMS/polyolefin composites in the range of x = 83–91 wt%. Zn 0.15 Nb 0.3 Ti 0.55 O 2 (ZNT) powder underwent conventional sintering process before being laminated with 1,2-PB/EPDM/SBS through hot-press process after being modified by Vinyltrimethoxysilane (VTMS). In this study, we analyzed the surface character, microstructure, microwave dielectric properties and thermal performances of the composite material. The findings indicate that a core-shell structure was formed to enhance the compatibility between ceramic particles and polyolefin matrix. Furthermore, the modified ceramic formed an interfacial layer with resin matrix that limited the movement of resin chain segments and improved the thermal stability of the composites. However, further increase of ceramic content more ceramic agglomerates and pores introduced more ceramic agglomerates and pores resulting in reduced cross-linking density of the resin. Consequently, a high-D k composite was obtained when x = 89 wt% at 10 GHz: D k = 16.79, D f = 0.0023 and τ ε = −120 ppm/℃, which is promising for microwave applications. • Zn 0.15 Nb 0.3 Ti 0.55 O 2 was coated by VTMS and laminated with polyolefin (1,2-PB/EPDM/SBS) by hot-press process. • The composite exhibits a high D k of 16.79, small D f of 0.0023 and low τ ε of − 120 ppm/℃. • Ceramic fillers hinder the movement of resin chain segments and improved the thermal stability of the composites. • Introducing ceramic fillers reduces cross-link density of the composite. [ABSTRACT FROM AUTHOR]

Composites with a high ceramic content (60 vol% TiC) and residual porosity below 1.9% were fabricated through liquid infiltration at 1515 °C under argon atmosphere. Scanning electron microscopy revealed a homogeneous distribution of the matrix phases and composite reinforcement, with slight superficial smoothing of the TiC particles due to a dissolution-precipitation process. System thermodynamics predict the partial dissolution of TiC particles and their precipitation during cooling, as well as the formation of insignificant quantities of Ti 3 O 5 and Ti 2 O 3 oxides. Nevertheless, only the phases corresponding to Ni and TiC were detected through x-ray diffraction. The microstructure, hardness values, modulus of elasticity, and flexural strength indicated strong adhesion between the ceramic and the metal. Good adhesion also favored the heat flow between the components, obtaining an effective thermal conductivity of 44–48.9 W/mK at a room temperature range of up to 700 °C. The incorporation of TiC particles lineally reduced the coefficient of thermal expansion (CTE) of the composite. Thermal cycling tests carried out from 25 to 450 °C showed that the composite exhibited an insignificant hysteresis cycle and a small residual plastic deformation, indicating high thermal stability. Thanks to its excellent dimensional stability, the composite is a potential candidate for applications in advanced engineering. Image 1 • A dissolution-precipitation process improves integration of TiC into the Ni matrix. • A thermodynamic study confirms the viability of TiC dissolution in the matrix. • Thermal deformation is restricted by TiC phase and the strong interface bond. • Good adhesion in the TiC/Ni interface promotes moderate resistance to thermal flow. • Small residual plastic deformation indicates high thermal dimensional stability. [ABSTRACT FROM AUTHOR]

In this study, α-Cu 2 Se single crystal with space group C 2/ c was prepared by the Bi-flux method according to the stoichiometric ratio of Cu 2 Se (1+ x) Bi 3 (x = 0, 0.01, 0.02, 0.03). All samples involve hole conduction and carrier concentration increases with the increase of Se content. The valence of Bi atom is +3 in the sample, and the solubility limit of Bi atom is approximately 0.012% in Cu 2 Se. The crystal cell volume of all samples is larger than that of standard α -Cu 2 Se for the larger ion radius of Bi3+ than Cu+. In addition, the crystal cell volume of the samples decreases with the increase of Se content because of more Cu vacancies caused by excessive Se. The transmission electron microscopy image and the corresponding area electron diffraction pattern show that the prepared samples have a complete crystal structure. Eventually, the single crystal α -Cu 2 Se 1.01 sample obtains the highest power factor of 1.53 × 10−3 W m−1 K−2 at 690 K. Thermogravimetric-differential thermal analysis shows that no weight loss occurred below the melting point. After three continuous thermal cycles, the value of power factor drops down to ∼0.04 × 10−3 W m−1 K−2 at 660 K. In comparison with polycrystalline sample prepared by hot pressing, the thermal stability is improved obviously. • Single crystalline α -Cu 2 Se samples were prepared by Bi-flux method. • The carrier concentration of the material is modulated by hole. • Power factor was enhanced significantly compared with polycrystalline α -Cu 2 Se. • The samples prepared by Bi-flux method possess good thermal stability. [ABSTRACT FROM AUTHOR]

Abstract In 2 Se 3 nanostructures have attracted much attention due to their potential applications in diverse areas, such as solar energy conversion, thermoelectric power generation, phase change random access memories, photodetectors, and optoelectronics in the visible region. In the present work, we have fabricated various In 2 Se 3 nanostructures on SiO 2 /Si substrate using a simple and single-step physical vapor deposition (PVD) method, without using metal seed layer on the substrates. Morphology, structure and phase of the as-grown In 2 Se 3 nanostructures have been carried out using scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy, respectively. In addition, we have also explored thermal properties of In 2 Se 3 nanostructures on SiO 2 /Si substrate using temperature and power dependent Raman spectroscopy. Further, the thermal conductivity of nanoparticles, nanospheres, and rod like flowers at room temperature were found to be ∼37.6, ∼39.5, and ∼15.6 W/m-K, respectively. This work suggests an effective way to form various novel nanostructures, opening up a new scenario to understand the vibrational properties and electron-phonon interactions of In 2 Se 3 nanostructures. Graphical abstract Image 1 Highlights • A simple and single step PVD method was used to grow various In 2 Se 3 nanostructures. • Temperature and power-dependent Raman study was done on various In 2 Se 3 nanostructures. • Thermal conductivity of various In 2 Se 3 nanostructures was evaluated. • p-p and e-p interactions have been analyzed with Raman measurements. [ABSTRACT FROM AUTHOR]

Abstract In this investigation, aluminum matrix composites with different graphite contents (6%, 12% and 18% volume fraction) are prepared using hot-press and powder metallurgy method. The distribution of graphite particles in the matrix is investigated by optical microscope. Density of the composite samples are examined and it is seen that increasing the graphite content decreases the densification due to graphite content and particle size. Results reveal that thermal conductivity of Al-18%G composite sample increased to 252 W/m.K. Similarly, results show that by compositing coefficient of thermal expansion (CTE) in 50–250 °C range decreased to 19.6 ppm/K. Finally, thermal stability of Al-18%G sample is evaluated by exposing to 1, 20, 50 and 100 thermal cycles. Due to difference between CTE of matrix and graphite, cracks propagate through the reinforcement/matrix interface and results in sample failure. Calculated CTE values are highly consistent with theoretical results of geometrical, Maxwell and Maxwell-Eiken models. Highlights • No crack, porosity or Al-carbide was found at the interface of the Al-G composites. • Density of composite samples was very close to theoretical value. • Samples microhardness reduced by 19 HV by increasing the graphite content to 18%. • A model was suggested based on graphite geometrical and physical properties. • By rising the graphite content to 18%, thermal conductivity increased to 252 W/m.K. [ABSTRACT FROM AUTHOR]

Abstract Hot-deformed Nd-Fe-B magnets co-doped with and without Tb-Fe addition are prepared to study the effect of Tb-Fe particles on the magnetic properties and thermal stability. With the addition of 2 wt. % Tb-Fe particles, the coercivity increases by 28.7%, while the remanence decreases by only 3.6%. It is observed that Tb atoms are diffused from the Tb-Fe particles to neighboring Nd-Fe-B melt-spun ribbons, in which Nd atoms in 2:14:1 grains are partially substituted by Tb atoms. The formation of local high-anisotropy (Nd, Tb) 2 Fe 14 B regions promotes the locally magnetically hardening, suppressing the nucleation of reversed magnetic domains at the low-anisotropy surface magnetic "defects". This can be employed to explain the coercivity enhancement of diffusion-processed hot-deformed magnets. In addition, the thermal stability of the magnet is improved due to the higher Curie temperature of (Nd, Tb) 2 Fe 14 B grain. Highlights • The coercivity enhancement is achieved while the remanence loss is small. • Thermal stability is improved in the diffusion of Tb-Fe particles. • Small remanence loss is attained. [ABSTRACT FROM AUTHOR]

This paper compares the evolution patterns of microstructure, mechanical properties and heat exposure response behavior of alloys with low (0.15 wt%) and high Ti (0.75 wt%) content prepared by conventional casting processes. The results show that the alloy with high Ti content has slightly finer grains and no improvement in the thermal stability of the θ' precipitates compared to the low Ti content alloy. Moreover, after exposing the as-aged alloy to 300 ℃ for 100 h, the high Ti content alloy exhibits higher tensile strength at room temperature, attributing to the reinforcement effect of Al 3 Ti nanoparticles. The results of geometric phase analysis and transmission electron microscope images reveal that the compressive strain field occurring on the Al 3 Ti/matrix interface can validly block the movement of dislocations, thus hardening the alloy. Finally, the classical nucleation theory was referred to explain the difference on the thermal exposure response behavior of two alloys with various Ti contents at 300 ℃. With increasing thermal exposure time, the stiffening role of the Al 3 Ti nanoparticles gradually overcomes the softening behavior caused by the destabilization of coarsened θ' and becomes the dominant factor governing the mechanical properties of the alloy. The theoretical analysis is consistent with the microstructure and the thermal exposure hardness response behavior. • The formation of Al 3 Ti at 300 °C enables the Al-Cu alloy to exhibit superior mechanical properties at room temperature. • The remarkable compression strain at the Al 3 Ti/α-Al interface increases the critical dislocation shear stress. • The stiffening role of the Al 3 Ti nanoparticles gradually overcomes the softening behavior during thermal exposure. [ABSTRACT FROM AUTHOR]

Bulk nanostructured n-type PbTe (0.2 wt% PbI 2 ; 0.3 wt% Ni) and p-type Ge 0.96 Bi 0.04 Te were prepared by grinding the synthesized materials in a planetary ball mill followed by compaction by spark plasma sintering. Hardness, Young's modulus and stiffness of the synthesized and nanostructured thermoelectric materials were investigated by nanoindentation. Nanostructured thermoelectric materials have significantly higher mechanical properties than synthesized materials, and grinding time have small effect on the hardness, Young's modulus and stiffness. The efficiency of nanostructured thermoelectric materials in the entire range of operating temperatures is 10–14% higher than that of the materials obtained by hot pressing. The maximum values of dimensionless thermoelectric figure of merit for nanostructured thermoelectric materials on the basis of PbTe and GeTe are equal to 1.34 and 1.43, respectively. The increase in the efficiency is explained by the scattering of phonons by inhomogeneities of the nanocrystalline structure. Thermal treatment at a temperature of 750 K for 72 h reduced dimensionless thermoelectric figure of merit by not more than 2% and 3% for GeTe and PbTe nanostructured thermoelectric materials, respectively. Repeated differential scanning calorimetry showed that nanostructured thermoelectric materials are thermally stable up to 850 K. The grinding time does not affect the thermal stability of materials. According to thermogravimetry sublimation of thermoelectric materials begins above 850 K. To ensure long-term use of thermoelectric materials on the basis of PbTe and GeTe in the temperature range of 850–900 K it is necessary to use protective Si 3 N 4 or SiO 2 coatings. • Nanostructured thermoelectric materials were developed for range of 600–900 K. • The mechanical properties of nanostructured thermoelectric materials were studied. • Complex investigation of thermal and electrical properties was carried out. • Mechanisms of electrical and thermal conductivities were determined. • Thermal stability of developed materials was determined in the range of 300–900 K. [ABSTRACT FROM AUTHOR]

In order to improve the diffusion characteristics of heavy rare earth in the grain boundary, effects of the diffusion process as well as the ratio of Tb and Cu (R Tb/Cu) during the layered deposition process on the magnetic properties of Tb-Cu diffused Nd-Fe-B magnets were systematically investigated. The coercivity of the diffused magnet with R Tb/Cu = 4:1 was enhanced most, which increased from 10.86 kOe to 21.80 kOe. Cu greatly improved the composition homogenization of diffused magnets. For the present designed diffused magnet, the highest utilization efficiency of Tb reached 43.96 kOe/wt%. Moreover, the reduced demagnetization risk of sintered Nd-Fe-B magnets was verified by using finite element method based on the experimentally obtained temperature characteristics of the magnet. • A layered deposition process was applied to improve the utilization of HRE. • Cu greatly improved the composition homogenization of diffused magnets. • The reduced demagnetization risk was verified by using finite element method. [ABSTRACT FROM AUTHOR]

Thermal stability of coercivity and domain structure in sintered Nd–Fe–B magnets with various grain sizes has been studied. Microstructure analysis shows that the improved thermal stability arises from the grain morphology beneficial to a small effective demagnetization factor N eff . In-situ magnetic domain evolution during thermal demagnetization indicates that lower surface stray field in fine-grained magnets suppresses the reversion of domain in high temperature condition, which results from temperature-dependent competition between the local demagnetizing field and effective anisotropy field of surface grains. [ABSTRACT FROM AUTHOR]

Submicron Cu particles mixed with Cu complex are used successfully to fabricate highly conductive Cu films for printed electronics. This study investigates the effects of Cu particle size on microstructure, conductivity and on the long-term stability of printed Cu films. In particular, the oxidation behaviors of printed Cu films at high temperatures are studied from the evolutions in microstructure and chemical composition. The submicron Cu particles are sintered efficiently due to the help of in-situ formed Cu nanoparticles from the decomposition of the Cu complex. Low resistivity of 5.8 μΩ cm is easily achieved. At temperatures of 140 °C and 180 °C, the printed Cu films prepared from 800 nm Cu particles are more stable than that from those 350 nm particles, which can be attributed to larger Cu particles possessing higher oxidation resistance. At 220 °C, the result becomes opposite because the loose structure with many large voids in the printed Cu films from large particles provides sufficient space for oxygen and accelerate the break of pathways between adjacent particles by the formation of Cu oxides layers. This indicates the long-term stability of printed Cu films is attributed to not only the intrinsic oxidation of Cu to Cu 2 O but also the degradation of microstructures. At all events, the printed Cu films from submicron Cu particles with Cu complex exhibit excellent oxidation resistance and are superior to those from Cu nanoparticles. This presents significant potential and favorable prospects for the fabrication of highly reliable and cost-effective printed electronics. [ABSTRACT FROM AUTHOR]

We present a detailed study of post-deposition annealing effects on contact resistance of Au, Ti, Hf and Ni electrodes on Mg 2 Si thin films. Thin-film Mg 2 Si and metal contacts were deposited using magnetron sputtering. Various post-annealing temperatures were studied to determine the thermal stability of each contact metal. The specific contact resistivity (SCR) was determined using the Cross Bridge Kelvin Resistor (CBKR) method. Ni contacts exhibit the best thermal stability, maintaining stability up to 400 °C, with a SCR of approximately 10 −2 Ω-cm 2 after annealing. The increased SCR after high temperature annealing is correlated with the formation of a Mg-Si-Ni mixture identified by cross-sectional scanning transmission electron microscopy (STEM) characterization, X-ray diffraction characterization (XRD) and other elemental analyses. The formation of this Mg-Si-Ni mixture is attributed to Ni diffusion and its reaction with the Mg 2 Si film. [ABSTRACT FROM AUTHOR]

Thermal barrier coatings (TBCs) were applied to gas turbines to function at higher gas temperatures. Extensive effort has been invested in identifying new materials with even better performance compared to yttria-stabilized zirconia (YSZ) being the industry standard up-to-date. La 2 Zr 2 O 7 (LZ) with the pyrochlore structure has received attention and been identified as a new candidate material for TBCs. In this study, two different coatings produced with commercial and high-energy ball milled LZ powders were investigated. Coatings were annealed for 50 h, 100 h, 200 h and 500 h at 1150 °C. Microstructures of the coatings were examined with Scanning Electron Microscopy and thermal conductivities were investigated with laser flash measurements. Mercury porosimetry was used as well to identify pore size changes that might occur with annealing process. X-Ray diffraction analysis was used to determine any possible phase changes. The results showed a sintering effect leading to an increase in thermal conductivity, and after 500 h heat treatment time, phase decomposition occurred on LZ based coatings. [ABSTRACT FROM AUTHOR]

The trade-off between printability and performance of Al–Ni–Sc alloy fabricated by additive manufacturing (AM) herein is demonstrated. By designing eutectic solidification, a crack-free microstructure was obtained. Extremely high cooling rate during rapid solidification promoted the formation of spherical Al 3 Ni nano-particles. Further by adding Sc, coherent L1 2 Al 3 Sc nano-particles were formed, which served as nucleation sites of α-Al to transform columnar grains into equiaxed grains and provided further strengthening. Superior mechanical properties with tensile strength of 445 MPa and yield strength of 320 MPa at ambient temperature were obtained. And this Al–Ni–Sc alloy can still exhibit excellent tensile strength of 259 MPa and yield strength of 248 MPa at 250 ℃. After thermal exposure at 200–400 °C, Al–Ni–Sc alloy consistently showed higher microhardness than the corresponding Al–Ni alloy and both alloys retained hardness at 300 °C for 50 h. The Al 3 Sc nano-precipitates provided additional hardness increments and compensated the microhardness decrease owing to the coarsening of Al 3 Ni nano-particles during high-temperature exposure. The coarsening process studied on Al–Ni alloy can be divided into two stages, rapid coarsening stage at first 0.5 h due to solute supersaturation and coarsening slowing stage due to the decreased coarsening drive. Following the classical coarsening mechanism–LSW model and Arrhenius equation, the corresponding diffusion activation energy of the second stage was calculated to be 23.03 KJ/mol, much lower than Ni self-diffusion in Al. This phenomenon was attributed to the formation of numerous defects and grain boundaries during AM as fast diffusion channels of atoms. The finding of this work provides guidance for considering discrepancy of Al alloys produced by AM and cast. [Display omitted] • The trade-off between printability and performance by Sc adding to Al-Ni eutectic alloy. • Coherent L1 2 Al 3 Sc particles served as nucleation sites to promote columnar to equiaxed transition. • Two nano-sized spherical Al 3 Ni and Al 3 Sc particles contributed to excellent mechanical properties • The strengthening of Al 3 Sc precipitates compensated the coarsening of Al 3 Ni particles during thermal exposure. [ABSTRACT FROM AUTHOR]

The superior mechanical properties and thermal stability of Ti-Al-Si-N coatings have attracted extensive research interests in academia as well as industry. In this study, Ti 0.52 Al 0.48 N, Ti 0.53 Al 0.38 Si 0.09 N, Ti 0.43 Al 0.48 Si 0.09 N, and Ti 0.48 Al 0.38 Si 0.14 N coatings are developed by arc-evaporation. This compositional variation allows to study the impact of Al and Si on structure, thermal stability, and oxidation behavior. Incorporation of Si into Ti-Al-N leads to a nanocomposite structure with an amorphous-like SiN x boundary-phase – encapsulating small crystalline Ti-Al-N grains – and promotes wurtzite-type AlN formation. This causes a significant change in the mechanical and thermal properties of the originally single-phase face-centered cubic structured Ti 0.52 Al 0.48 N. The Si-containing coatings experience an initial increase in hardness from 29.1 ± 1.0 GPa for Ti 0.52 Al 0.48 N to 33.1 ± 1.2 GPa for Ti 0.53 Al 0.38 Si 0.09 N, and then a decrease to 26.4 ± 0.8 GPa for Ti 0.43 Al 0.48 Si 0.09 N and 28.1 ± 0.8 GPa for Ti 0.48 Al 0.38 Si 0.14 N. Alloying with Si improves the thermal stability of Ti-Al-N by retarding the decomposition towards its thermodynamically stable constituents TiN and AlN. Moreover, the oxidation resistance of Ti-Al-N can be largely improved by the Si-addition due to the retarded anatase-to-rutile TiO 2 transformation as well as the formation of a protective oxide scale at the nitride-to-oxide interface. Cross-sectional scanning electron microscopy studies reveal that the oxide scales of the Si-containing coatings exhibit a lamellar structure comprising Al-rich, TiSi-rich, and/or Ti-rich oxide layers. Higher Si and, especially, higher Al content is favorable to the formation of an Al-rich layer, which can act as a diffusion barrier for oxygen. Especially, all Si-containing coatings present an abnormal oxidation behavior, where the consumed nitride layer thickness is not continuously increasing with oxidation temperature. • Both thermal stability and oxidation resistance are enhanced after Si-alloying. • The effect of Si on the oxidation behavior of Ti-Al-Si-N is multifold. • The Si/Ti ratio of 0.21 retards the anatase-to-rutile transformation most. • Si-alloying leads to an abnornal oxidation behavior of Ti-Al-N coatings. [ABSTRACT FROM AUTHOR]

The present study (part B) is a direct continuation of the leading study (part A), in which we had introduced extruded aluminum (Al) + 8.8 and 14.7 vol% aluminum nitride (AlN) metal matrix composites (MMC) manufactured at a cost-effective industrial scale and targeted for structural load-bearing applications with an expected service at elevated temperatures. In the leading study the processing, microstructure of nitrided and extruded Al-AlN MMC and the thermal stability of the extruded Al-AlN MMC as reflected in changes to their tensile mechanical properties induced by annealing up to 600 °C were elaborated. In the present ensuing study we discussed in details the mechanical, thermal and creep properties, active strengthening mechanisms, and microstructure-property relations of Al-AlN MMC annealed at 500 °C for 24 h, which were examined in a broad temperature range of 22–500 °C. In addition to increased Young's modulus Al-AlN MMC showed high tensile strengths determined at 300 °C, which were superior to any conventional Al alloy, accompanied with reasonably high ductility. At the same time Al-AlN MMC preserved excellent creep performance, which was superior to the heat resistant reference alloys, reduced coefficient of thermal expansion and reasonable thermal conductivity. The results confirmed that reported thermally stable Al-AlN MMC may be considered a promising material with an appealing set of the properties directed for load-bearing structural applications with an expected service at elevated temperatures. • in-situ Al-AlN MMC fabricated by cost-effective approach realized at a large scale. • The mechanical, thermal and creep properties of Al-AlN MMC determined at 22–500 °C. • Active strengthening mechanisms and microstructure-property relations discussed. • An attractive set of the properties at 300 °C superior to conventional Al alloys. • A promising material for structural applications with service at high temperatures. [ABSTRACT FROM AUTHOR]

Bi 4 Ti 3 O 12 (BIT), a typical layered-structure ferroelectric with a high Curie temperature (T C), is a promising material for high-temperature sensors. Herein, W/Cr co-substitution at the B-site of BIT ceramics (BITWC100 x) is carried out to investigate the phase structure, domain structure, and electrical properties. The W/Cr addition apparently reduces the concentration of oxygen vacancies, effectively improving the ferroelectric and piezoelectric properties as well as the resistivity of the BIT ceramics. The BITWC2 ceramic exhibits a high piezoelectric coefficient (d 33 = 31.1 pC/N), a moderate T C (651 °C), a large remnant polarization (P r = 12.2 μC cm−1), and a prominent direct current resistivity (5.49 ×106 Ω·cm at 500 °C). Moreover, the BITWC2 ceramic possesses a large d 33 of 26.6 pC/N at an annealing temperature of 600 °C, indicating the excellent thermal stability of the piezoelectric coefficient. Overall, the BITWC100 x ceramics can be used in piezoelectric devices at temperatures up to 500 °C. • BITWC100 x ceramics with a high T C and excellent electricity properties can be used in high-temperature piezoelectric devices. • The information of domain structure is obtained by PFM. • The refinement of the domain size contributes to enhancement of piezoelectric properties of BITWC100 x ceramics. [ABSTRACT FROM AUTHOR]

The wide applications of Cu-10Ta (at%) composite are limited due to the high cost of Ta element (24 wt%). In the present research, Cu-0.6Ta-0.6Cr and Cu-0.6Ta alloys with low Ta content were fabricated by mechanical alloying and spark plasma sintering. The results indicate that the thermal stability and tensile strength of Cu-0.6Ta-0.6Cr alloy are significantly increased by the addition of Cr. The microstructure characterizations reveal that the performance enhancement of Cu-0.6Ta-0.6Cr alloy is ascribed to the transformation of nanoparticles in the matrix from Ta to more stable Cr 2 Ta Laves and the refinement effects of these nanoparticles from 19.4 nm to 14.1 nm. This work provides a potential for the wide applications of Cu-Ta alloy with low Ta by alloying with Cr at elevated temperatures. • The addition of Cr transforms the nanoparticles from Ta to Cr 2 Ta Laves. • The grains and nanoparticles in Cu-Ta-Cr alloy have extremely high growth resistance. • The thermal stability of the Cu-Ta-Cr alloy is highly improved by adding Cr. • The tensile strength of Cu-Ta-Cr alloy is greatly increased by adding Cr. [ABSTRACT FROM AUTHOR]

Highlights: [•] Organic compound containing antipyrine and thiadiazole moieties has been synthesized. [•] The frequency dependence of AC conductivity is found to follow Jonscher’s universal power law. [•] The dielectric relaxation behavior is explained in terms of electric modulus formalism. [•] Thermal properties of the compound have been reported. [ABSTRACT FROM AUTHOR]

• A novel high entropy ceramic with hybrid mixing of Si and metal atoms was proposed. • Hf 0.25 Zr 0.25 Ce 0.25 Y 0.125 Si 0.125 O 2-δ was synthesized and its single phase was confirmed. • This Si-stabilized fluorite oxide has high thermal stability, good mechanical, and thermal properties, promising for aerospace applications. We design and synthesise a new high-entropy ceramic Hf 0.25 Zr 0.25 Ce 0.25 Y 0.125 Si 0.125 O 2-δ through a hybrid mixing of non-metal and metal atoms. First-principles calculations predict the thermal stability of the single-crystal phase at high temperatures. XRD and EDS mapping confirm a single cubic fluorite phase with a uniform elemental distribution. In-situ high-temperature XRD shows that the phase is stable with no phase separation or secondary phases. The measured mechanical and thermal properties are comparable with reported high-entropy fluorite oxides. Our results add to the compositional space of high-entropy ceramics for a wide range of applications from thermal insulators to electronics. [ABSTRACT FROM AUTHOR]

• Stability for MGs under simulated space conditions was investigated. • The dynamics of MGs under simulated space conditions were found to be different from those in laboratory-based works. • MGs with lower fragility were determined to be preferable for space applications for their greater thermal stability. Metallic glasses (MGs), due to their exceptional properties resulting from the amorphous structures, may be potential candidates for space applications. However, the effect of space conditions on the stability of MGs is not clear, which should be taken into account for practical use. The present work assessed the thermal stabilities of MGs in the simulated space thermal fields under vacuum condition, with a specific focus on the cryogenic thermal cycling with a high ratio of the non-isothermal to isothermal durations and the cryogenic treatment for a long-duration. The dynamics and thermal properties of MGs under the simulated space conditions were found to be different than those in laboratory-based conditions. MGs with lower fragility values were also determined to show greater thermal stability. On this basis, rules for the selection of MGs to ensure thermal stability during future space applications were proposed. [ABSTRACT FROM AUTHOR]

• Thermally-stable high-performance nanocrystalline MMP Nd-Ce-Fe-B magnet is fabricated by grain boundary engineering. • H cj and thermal stability are obviously improved with simultaneously enhanced (BH) max. • Microstructure evolution is revealed, and the Dy diffusion model is proposed. • The underlying mechanisms for enhanced magnetic properties and thermal stability are systematically analyzed. Low coercivity and poor thermal stability are still the main challenges for practical application of low-cost Nd-Ce-Fe-B magnet. To solve these challenging problems, a strategy to simultaneously improve the coercivity and thermal stability of Nd-Ce-Fe-B magnet through combining the nanocrystalline multi-main-phase (MMP) structure and grain boundary engineering is demonstrated. In this study, nanocrystalline MMP Nd-Ce-Fe-B magnet was grain boundary engineered by co-adding DyF 3 and Cu powders. The results show that the intrinsic coercivity H cj is significantly improved, and meanwhile optimum maximum energy product (BH) max is achieved at 2 wt% DyF 3 -Cu. Moreover, the superior reversible temperature coefficients of H cj (β) and B r (α) are both achieved, implying the improved thermal stability for the DyF 3 -Cu added magnet. Microstructural and compositional characterizations indicate that the modified RE-rich phase, the inhibited abnormal grain growth near the flake boundary, and the diffused Dy towards main phase grains are the main reasons for simultaneously enhanced magnetic properties and thermal stability. Thus, combining the nanocrystalline MMP structure and grain boundary engineering will be a promising approach for preparing thermally-stable high-performance Nd-Ce-Fe-B magnet. [ABSTRACT FROM AUTHOR]

• Simultaneously appearing CaTiO 3 and TiO 2 phases in CaCu 2.8 Ti 4 O 12 ceramics were prepared by a polymer pyrolysis route. • Mg2+ substitution at the Cu sites of Cu-deficient CaCu 2.8- x Mg x Ti 4 O 12 (x = 0–0.10) causes increased R gb values. • tanδ = 0.011, ε′ = 11,603 and ∆ε′ ≤ ± 15% (−60 to 180 °C) were attained for x = 0.05. • This ceramic has a potential applications in a high-temperature X8R capacitors. • The highest α = 53.02 with E b = 9548.1 V cm−1 was achieved. Mg2+ substitution at the Cu sites of Cu-deficient CaCu 2.8- x Mg x Ti 4 O 12 (x = 0.00, 0.05, and 0.10) ceramics was accomplished using a polymer pyrolysis technique. The nonlinear and dielectric properties of all ceramics under various sintering temperatures were investigated. Very low tanδ ∼ 0.011–0.030 and giant ε ′ ∼ 4406–13,521 were obtained in these ceramics. Surprisingly, excellent thermal stability, where ε ′ remained within± 15% and is adequate for X8R capacitors, is obtained in CaCu 2.75 Mg 0.05 Ti 4 O 12 and CaCu 2.7 Mg 0.1 Ti 4 O 12 ceramics sintered at 1100 °C for 8 h. Additionally, the nonlinear J-E properties were improved compared to an unmodified sample. Interestingly, a nonlinear coefficient (α) of ∼ 58.05 in the CaCu 2.75 Mg 0.05 Ti 4 O 12 ceramic sintered at 1100 °C for 8 h is acceptable for varistor applications. Improvement of nonlinear and dielectric properties arise from the electrical interface responses altered by Mg2+ substitution. The ceramics were characterized using XRD, TEM and FE-SEM techniques to investigate their crystal structure and microstructure. EDXS results confirmed the coexistence of TiO 2 and CaTiO 3 phases in all ceramics. It was suggested that the enhancement of grain boundary resistance (R gb) with simultaneously improved electrical and nonlinear J-E behaviors caused by the alternation of electrical interface responses at GBs. XPS measurements of these ceramics presented Cu3+/Cu2+/Cu+ ratios that indicate the semiconducting properties of grains. [ABSTRACT FROM AUTHOR]

• The Sr 3- x Ca x La(VO 4) 3 : Sm3+ and Sr 2 CaLa(VO 4) 3 : y Sm3+ were synthesized by citric-assisted sol-combustion method. • SCLVO: Sm3+ has a hexagonal structure with space group R-3 m (166). • The replacement of Sr2+ by Ca2+ improves the emission intensity of Sr 3 La(VO 4) 3 : Sm3+ phosphor. • Phase structure, luminescent behaviors and thermal stability were systematically studied. Sr 3- x Ca x La(VO 4) 3 : Sm3+ (x = 0, 0.5, 1.0, 1.5, 2.0, 2.5) and novel Sr 2 CaLa(VO 4) 3 : y Sm3+ (SCLVO: y Sm3+, y = 0.01, 0.03, 0.05, 0.07, 0.09) phosphors were synthesized by the citric acid-assisted sol-combustion method. The crystal structure, morphology, concentration-dependent emission spectrum, decay time, and thermal stability of phosphors were studied. These synthesized phosphors have a hexagonal structure with a space group of R-3 m (166). High-purity Sr 3- x Ca x La(VO 4) 3 : Sm3+ phosphors were obtained when x < 2.5. The change in particle shape and unit cell parameters of the Sr 3- x Ca x La(VO 4) 3 : Sm3+ phosphors led to reduced luminescence performance when the Ca2+ concentration was x > 1. The optimal doping concentration of Sm3+ in the SCLVO host is 3 mol%. Under the excitation of 402 nm near-ultraviolet (NUV) light, all phosphors in this series emit orange–red light at 603 nm, which is attributed to the 4G 5/2 →6H 7/2 transition of Sm3+. The SCLVO: 0.03Sm3+ phosphor exhibits a double exponential decay time of 0.872 ms, excellent thermal stability with an activation energy E a of 0.232 eV, a chromaticity coordinate of (0.5817, 0.4136), and a high color purity of 98.48%. These experimental results demonstrate the potential application of phosphor SCLVO: 0.03Sm3+ in the red component of white light-emitting diodes (WLEDs). [ABSTRACT FROM AUTHOR]

TiAlVN coatings gain extensive attention due to the self-lubrication effect with elevated temperatures. However, the poor oxidation resistance of TiAlVN limits their industrial application. In order to improve the oxidation resistance of TiAlVN, the TiAlSiN insertion layer is introduced into TiAlVN to synthesize nano-multilayered Ti 0.40 Al 0.50 V 0.10 N/Ti 0.56 Al 0.34 Si 0.10 N (ML_1) and Ti 0.40 Al 0.50 V 0.10 N/Ti 0.46 Al 0.45 Si 0.09 N (ML_2). Ab initio calculations combined with experiments prove that Si-doping reduces the solid solubility of Al in the cubic structure, while V-addition increases its solubility. The hardness of Ti 0.40 Al 0.50 V 0.10 N and Ti 0.56 Al 0.34 Si 0.10 N with cubic structure are 29.2 ± 0.9 and 36.5 ± 0.9 GPa, while Ti 0.46 Al 0.45 Si 0.09 N with mixed cubic and hexagonal structure exhibits low hardness of 29.1 ± 0.9 GPa. The coherently interfacial strengthen enhances the hardness to 33.6 ± 1.0 GPa of ML_1 and 35.2 ± 1.1 GPa of ML_2. Additionally, the Si-containing insertion layers improve the thermal stability of TiAlVN coating, where the onset temperature of w-AlN formation during annealing is increased by ~ 200–300 °C. After annealing at 1200 °C, Ti 0.40 Al 0.50 V 0.10 N, Ti 0.56 Al 0.34 Si 0.10 N and Ti 0.46 Al 0.45 Si 0.09 N possess the hardness values of 26.2 ± 1.5, 38.8 ± 0.8 and 29.5 ± 1.0 GPa, while ML_1 and ML_2 still manifest superior hardness values of 35.4 ± 1.1 and 35.1 ± 1.1 GPa. Furthermore, the oxidation resistance of our multilayers lies between that of TiAlVN and TiAlSiN. After oxidation at 700 °C for 10 h, Ti 0.56 Al 0.34 Si 0.10 N, Ti 0.46 Al 0.45 Si 0.09 N, ML_1 and ML_2 present oxide layers of ~0.1, ~0.1, ~2.3 and ~1.7 µm, respectively, while Ti 0.40 Al 0.50 V 0.10 N coatings has been completely oxidized. • Individual V- and Si-addition increases and reduces the solubility of Al in c-TiN. • TiAlVN reveals preferential spinodal decomposition than TiAlSiN by ab initio. • TiAlVN/TiAlSiN multilayers exhibit coherent interfaces. • TiAlSiN insertion layer improves the thermal properties of TiAlVN coating. [ABSTRACT FROM AUTHOR]

A series of Dy3+ activated Ba(YLu) 2 Si 3 O 10 samples were prepared by high temperature solid-phase method. The purity of the phase was determined and the structural changes were analyzed. Under excitation at 350 nm, the BaY 2 Si 3 O 10 : Dy3+ phosphor shows two stronger luminescence peaks at 486 nm and 572 nm and weaker emission peak at 668 nm. In addition, with the continuous replacement of Y3+ in the matrix by Lu3+ ions, the chromaticity coordinates of samples in the system can be adjusted from the cold white region to the warm white region, and the luminescence performance of phosphors can be effectively improved. It was observed that the thermal stability of the phosphor was gradually enhanced with Lu3+ concentration increases, and the emission intensity of the BaLu 2 Si 3 O 10 : 0.04Dy3+ phosphor at 453 K could still maintain 83.78% of that at room temperature, which was discussed in conjunction with the Debye temperature and the rigid structure model to provide a reference for the improvement of the thermal stability performance. In addition, the increase of the concentration of Lu3+ ions doping will shorten the lifetime of phosphors due to the non-radiative energy transfer caused by the shortening of the ion distance in the lattice. • Ba(YLu) 2 Si 3 O 10 : Dy3+ phosphors with weak thermal quenching were synthesized. • The emission intensity of phosphor increased by 23.23% with increasing Lu3+ content from 0 to 2. • The chromaticity coordinates of samples can be effectively adjusted from the cold white region to the warm white region. • The emission intensity of the BaLu 2 Si 3 O 10 : 0.04Dy3+ could still maintain 83.78%. [ABSTRACT FROM AUTHOR]

Highlights: [•] Bi x (Se20Te80)100−x (0⩽ x ⩽12) glasses was synthesized by the melt quench technique. [•] The glass density and compactness increases with increasing the Bi content. [•] DSC results under non-isothermal conditions were reported and discussed. [•] The dependence of Eg and Ec was discussed in terms of the chemical bond approach. [•] The thermal stability decreases with increasing the Bi content. [ABSTRACT FROM AUTHOR]

• Design and development of newly Zr 33 Hf 8 Ti 6 Cu 32 Ni 10 Co 5 Al 6 HEBMG according to Cu 47 Zr 47 Al 6 prototype BMG. • Improving thermal stability for the HEBMG compared to the BMG. • Significant improvement in plastic strain of the HEBMG compared to the BMG. • Study and correlation of fragility parameter, structural relaxation enthalpy, and the free volume with plastic strain. In this study, new non-equiatomic high entropy bulk metallic glass (HEBMG) Zr 33 Hf 8 Ti 6 Cu 32 Ni 10 Co 5 Al 6 was developed according to the Cu 47 Zr 47 Al 6 prototype BMG. Kinetic studies were performed with non-isothermal DSC for the BMG and the HEBMG, and their thermal properties were compared. Calculation of activation energies by different methods indicated that E g is higher for the HEBMG than the BMG, while E p is lower for the HEBMG than the BMG, and E x is similar for both alloys. The values of structural relaxation enthalpy for the BMG and the HEBMG were 4.95 J/g and 8.19 J/g, respectively. Free volume was calculated at room temperature and T g. By doing so, the direct correlation between fragility, structural relaxation enthalpy, diffusion, and free volume was shown. Using a compression test at room temperature, a 58% improvement in plastic strain was obtained for HEBMG, which confirmed the calculations. [ABSTRACT FROM AUTHOR]

Abstract: The thermal expansion and stability of predominantly single-phase Ti2SC powders in argon and air was investigated by Rietveld analysis of synchrotron X–ray diffraction spectra. When the sample was heated in an Ar atmosphere, it started to dissociate into TiS2 (see footnote 1) at ≈400°C. At 8.5 (5)×10−6 °C−1 and 8.8 (2)×10−6 °C−1 the thermal expansion coefficients along the a and c-directions, respectively, are quite similar. The volumetric thermal expansion is 25.2 (5)×10−6 °C−1. When Ti2SC was heated in air, it started to oxidize, at 400°C, first to anatase, which converts, at higher temperatures, to rutile. The sulfur and carbon atoms presumably diffuse outward and escape as gases. [Copyright &y& Elsevier]

• Er3+-doped gallate-based glasses are prepared by containerless solidification. • The prepared glasses exhibit superior thermal properties as well as excellent down-conversion luminescence properties. • Non-isothermal kinetic analyses are adopted to further assess the thermal stability of the selected glass. • We think the glasses might be the potential promising optical materials for fiber amplifier and laser. 55Ga 2 O 3 -(35-x)La 2 O 3 -10Ta 2 O 5 -xEr 2 O 3 transparent and bulk glasses were successfully synthesized by a containerless processing method. The effects of Er3+ concentration on thermal stability and optical properties were studied in detail. The prepared glasses exhibited high glass-transition temperature (T g > 798 °C) and goodo resistance to crystallization (ΔT > 134 °C) by differential thermal analysis (DTA). Moreover, the detailed crystallization kinetics of 33La 2 O 3 -55Ga 2 O 3 -10Ta 2 O 5 -2Er 2 O 3 glass was investigated, and the activation energy (E) and the frequency factor (v) of crystallization were gained by means of Kissinger method. The refractive indices were higher than 1.94 as well as the Abbe numbers were greater than 31. The transmittance spectra showed a wide transparent window ranging from 280 nm to 7.5 µm and the prepared glasses performed high infrared transmittance of nearly 80.5%. Two intense emissions centered at 1535 nm and 2700 nm could be observed when the glasses were excited by a 980 nm laser, corresponding to the Er3+ ions: 4I 13/2 →4I 15/2 , 4I 11/2 →4I 13/2 transitions, respectively. By fitting the decay curves, the highest lifetime of 4I 13/2 level could be evaluated to be 7.49 ms. Finally, a reasonable luminescence mechanism of down-conversion was proposed systematically. [ABSTRACT FROM AUTHOR]

• TiSiN/TiAlN multilayers exhibit the epitaxial growth with coherent interfaces. • TiSiN/TiAlN multilayers release effectively the stress of TiSiN coatings. • TiSiN/TiAlN exhibit a wide temperature range of age-hardening up to 1200 °C. • TiSiN/TiAlN multilayers reveal better oxidation resistance. ga1 Multilayer architecture to optimize the properties of TiAlN coating attracts extensive interests in industrial applications. Here, the structure, mechanical and thermal properties of Ti 1−x Si x N/TiAlN (x = 0.13, 0.17 and 0.22) multilayers consisting of ~6.0 nm Ti 1−x Si x N and ~4.0 nm TiAlN sublayers as well as TiAlN monolithic coating are investigated. Ti 1−x Si x N/TiAlN multilayers with an epitaxial growth between Ti 1−x Si x N and TiAlN sublayers exhibit a similar hardness value of ~37.6 GPa, corresponding to ~30.9 GPa of TiAlN. Annealing of TiAlN coating induces an age-hardening related to spinodal decomposition, and thus conduces to a peak hardness of ~32.8 GPa at 800 °C. The coherent strain between Ti 1−x Si x N and TiAlN sublayers of Ti 1−x Si x N/TiAlN multilayers retards the thermal decomposition of TiAlN and thus broadens the temperature range of age-hardening. Therefore, the hardness of Ti 1−x Si x N/TiAlN multilayers still stay 41.1 ± 1.4 GPa even after annealing at 1200 °C, which corresponds to a low hardness of ~22.1 GPa of TiAlN coating. Furthermore, after oxidation of 10 h at 850 °C, Ti 1−x Si x N/TiAlN multilayers exhibit oxide scales of ~2.65 µm for x = 0.13, ~2.1 µm for x = 0.17 and ~1.9 µm for x = 0.22, respectively, whereas TiAlN and Ti 1−x Si x N coatings have been completely oxidized. [ABSTRACT FROM AUTHOR]

• The effect of Mn additions on the structural and magnetic properties of AlCoCrFeNi was studied. • The arc-melted alloys consisted of a mixture of B2 and bcc phases, the relative amount of which was dependent on Mn content. • Gas atomised powders were single phase with the B2 structure. • Mn additions increased saturation magnetisation but lowered the magnetic transition temperature and the thermal stability. ga1 Alloys of AlCoCrFeMn x Ni (x = 0.0, 0.04, 0.08, 0.12 and 0.16) have been synthesized through arc–melting and gas atomisation (x = 0.0 and 0.16) to investigate the effect of Mn additions to AlCoCrFeNi. Here, the structure, magnetic properties and the thermal stability of the alloys is presented. Electron microscopy confirmed the elemental composition and revealed the microstructure to consist of two spinodally decomposed phases. Rietveld analysis of standard powder X-ray diffraction showed the arc-melted samples consisted of two phases, a B2 phase and a bcc phase while the gas atomised powders consisted of a single-phased B2 structure. Magnetic measurements revealed an increase in the saturation magnetisation at room temperature by 68% for AlCoCrFeMnNi compared to AlCoCrFeNi. The thermal stability of the alloys was investigated using magnetometry, differential scanning calorimetry and in–situ X-ray diffraction, which showed that an increase in Mn content adversely effected the thermal stability of the alloy. [ABSTRACT FROM AUTHOR]

Co 61 Ta 6 B 33 , Co 59 Ta 8 B 33 , Co 57 Ta 10 B 33 and Co 53 Ta 10 B 37 bulk metallic glasses (BMGs) exhibit a good combination of the ultra-high fracture strength in the range of about 5.4–6.2 GPa, Vickers hardness of 1459–1653 HV0.2 and plastic strain of 0.3–3.2%, depending on composition. Glass forming-ability and physical properties of Co–Ta–B BMGs are discussed in relationship to the Ta and B content and atomic structure. Crystallization upon isochronal and isothermal annealing is studied using differential scanning calorimetry and X-ray diffraction. A novel crystalline phase with ~Ta 2 Co 15 B 8 or ~TaCo 7 B 4 formula is shown to form upon glass annealing. The incubation time for isothermal crystallization in the supercooled liquid state near T g is supposed to be sufficient for thermoplastic forming of Co–Ta–B BMGs. ga1 • Co–Ta–B BMGs with ultrahigh strength and ductility in compression tests. • High glass transition temperature and large supercooled liquid region. • Incubation time for crystallization sufficient for thermoplastic forming. • Novel boride with ~Ta 2 Co 15 B 8 or ~TaCo 7 B 4 unit formula found. [ABSTRACT FROM AUTHOR]

In this manuscript the crystal structure of Li 3 UF 7 from powder X-ray and neutron diffraction studies is reported. The existence of Li 3 UF 7 has been debated for a long time, as it is often missed in a number of phase diagram studies. This study adopted a judicious composition of LiF and UF 4 , and an optimum cooling rate to prepare Li 3 UF 7. The Li 3 UF 7 phase could be obtained by cooling the molten LiF-UF 4 with large excess of LiF at a rate of 5 K/min while slower cooling tends to form LiUF 5. The crystal structures of Li 3 UF 7 and LiUF 5 in the temperature range of 300–10 K have been obtained from the powder neutron diffraction studies. At 300 K, Li 3 UF 7 has an orthorhombic lattice with unit cell parameters: a = 8.698(2) Å, b = 8.692(2) Å, c = 12.803(1) Å, V = 968.0(4) Å3; Z = 8 (Space group: C cca), and is isostructural to orthorhombic Li 3 ThF 7. On cooling, the orthorhombic distortion of Li 3 UF 7 increases but does not reveal any structural transition down to 10 K. The crystal structure of Li 3 UF 7 is built from the defective (Li-deficient) layers of edge shared octahedral LiF 6 and layers corner connected UF 9 polyhedra. Analogous studies on LiUF 5 have also been carried out, which has a tetragonal (Space Group: I 4 1 /a) lattice with unit cell parameters: a = 14.8882(8) Å, c = 6.5438(7) Å, V = 1450.5(2) Å3; Z = 16. The structure of LiUF 5 is built from the three-dimensional sub -lattice formed by U 4 F 30 units and the empty tunnels of the sublattice are occupied by Li 4 F 16 clusters formed by four edge shared LiF 6 octahedra. Also, the details of crystal chemistry of the compounds in LiF-UF 4 systems and their thermal stabilities are discussed. The complexity in the crystal chemistry in LiF-UF 4 system is manifested in multiple close by thermal events in the DTA runs which has also been discussed in the manuscript. ga1 • Synthesis and crystal structure of metastable Li 3 UF 7 in LiF-UF 4 are reported. • Conditions for formation of different phases in LiF-UF 4 system are delineated. • Crystal structures of Li 3 UF 7 and LiUF 5 down to 5 K are studied by LT-PND. • Anisotropic thermal expansion in Li 3 UF 7 is observed in between 5 and 300 K. • LiF-UF 4 phase diagram and comparative crystal chemistry phases in it are discussed. [ABSTRACT FROM AUTHOR]

Greenhouse plant cultivation (GPC) has attracted great attention in recent years, and the search for novel high efficiency far-red emitting phosphor is a crucial task. With this aim in view, in the present paper Ca 14 Al 10 Zn 6 O 35 :Mn4+ (CAZO:Mn4+) was investigated as a prototype phosphor. By simply incorporating excessive amount of Al, CA 10.25 ZO:Mn4+ can meet two criteria simultaneously: it has relatively high quantum efficiency (QE) and good thermal stability, which tackle the goal of "killing two birds with one stone". The internal QE (IQE) could further enhance from 83.9% to 90.0% due to the increased occupancy capability of Mn4+ in [AlO 6 ] octahedron, which is evidenced by solid-state 27Al nuclear magnetic resonance (NMR) and energy dispersive spectra (EDS) measurements. In addition, the Mn4+ concentration-dependent excitation and emission spectra also demonstrate that the optimal doping concentration of Mn4+ in CA 10.25 ZO host increases from 0.15 to 0.17 mol. Moreover, compared with CA 9.85 ZO:0.15Mn4+, the thermal stability of CA 10.25 ZO:0.15Mn4+ improves from 55% to 58% at 150 °C and 38%–45% at 200 °C, respectively. The as-fabricated plant growth LED devices shows better potential to be applied in GPC. This design strategy shown here provides an alternative pathway to further improve the luminescence properties of phosphors. Image 1 • Various amounts of Al doped Ca 14 Al x Zn 6 O 35 :0.15Mn4+ phosphors were synthesized. • The internal quantum efficiency of CAZO:Mn4+ was significantly improved up to 90.0%. • Better thermal stability of CAZO:Mn4+ was realized at 150 and 200 °C. • The potential apply of CAZO:Mn4+ in greenhouse plant cultivation was demonstrated. [ABSTRACT FROM AUTHOR]

In this study, we present that anisotropic MnBi bulk magnets can be obtained using spark-plasma-sintering technique (SPS). Grain misalignment was suppressed by either external field or addition of appropriate polymer binder. Various microstructures were effectively achieved during SPS processing, and lead to distinct magnetic performance. Microstructure analysis reveals that the coercive field of the SPS-compacted magnets declines strongly with increasing grain size. Bi-rich residue clearly plays a role in magnetic decoupling to enhance the coercive field, whereas the exchange coupling mediated by excess Mn reduces it dramatically. In addition, the amount and distribution of Mn and Bi residue has a profound influence on the thermal magnetic stability of sintered MnBi magnets. We suggest that fast consolidation methods like SPS technique enable to tailor the microstructure of bulk magnetic products to meet specific application requirements. • Fabricated anisotropic bulk magnets by spark-plasma-sintering technique. • The coercivity of MnBi magnets is associated with their Mn and Bi residue levels. • The thermal magnetic properties are strongly influenced by the corresponding microstructure. [ABSTRACT FROM AUTHOR]

The variations of structure and thermal properties in iron phosphate glasses and boron-doped iron phosphate glasses due to MoO 3 addition up to 50 mol% were investigated and compared in detail. The results show that MoO 3 depolymerizes the phosphate networks resulting in a higher connectivity of the networks through [MoO 4 units and the formation of Mo–O–P bonds diversifies the cross-linking of the glass networks, leading to the conversion of long phosphate chains to pyrophosphate units and/or orthophosphate units. These structure variations cause the decrease of glass transition temperature, thermal stability and glass formation ability of iron phosphate glasses. Moreover, the MoO 3 loading, thermal stability and glass formation ability of iron phosphate glasses were improved by boron. The reasons on the improved properties are also explained and analyzed. The obtained conclusions provide researchers with the role of Mo in structure and properties of phosphate glasses for Mo containing nuclear waste immobilization. • Mo depolymerizes phosphate networks resulting in high connectivity of the networks. • Formation of Mo–O–P bonds diversifies cross-linking of the phosphate glass network. • MoO 3 loading and thermal stability of iron phosphate glasses were improved by boron. • Boron prohibits the formation of Mo-containing cluster in iron phosphate glasses. • Mo decreases thermal stability and glass formation ability of iron phosphate glasses. [ABSTRACT FROM AUTHOR]

A series of red emitting phosphors Mg 3 Y 2-x Ge 3 O 12 :xSm3+ (0≤x ≤ 0.06) were successfully synthesized. Samples Mg 3 Y 2-x Ge 3 O 12 :Sm3+ exhibited a cubic structure pertaining to the I a-3d (230) space group and the particle sizes range from 1 μm to 5 μm. The optical properties displayed that the optimum doping concentration of Sm3+ is 4%. The phosphor Mg 3 Y 1.96 Ge 3 O 12 :0.04Sm3+ not only exhibited a broad band gap of 5.54 eV but also showed a high color purity of 97.6%. In addition, the strongest emission intensity located at 566 nm belonged to the 4G 5/2 → 6H 5/2 transition when excited at 405 nm. Thermal quenching test revealed that the sample Mg 3 Y 1.96 Ge 3 O 12 :0.04Sm3+ are excellent powders with splendid thermal stability, in which only 3.6% of the PL intensity is quenched at 473 K in comparison with that of 298 K. As a result, the W-LEDs based on Mg 3 Y 1.96 Ge 3 O 12 :0.04Sm3+ yielded a high R a of 91.1, a low CCT of 4881 K, and CIE coordinates of (0.3476, 0.3466) in a 20 mA driven current. This research work provided important guidance for the synthesis of Sm3+ doped red component with excellent luminesce properties and high thermal stability characteristics used in W-LEDs. • The phosphor Mg 3 Y 1.96 Ge 3 O 12 :0.04Sm3+ not only exhibited a broad band gap of 5.54 eV but also showed a high color purity of 97.6%. • The sample Mg 3 Y 1.96 Ge 3 O 12 :0.04Sm3+ are excellent powders with splendid thermal stability. • The W-LEDs based on Mg 3 Y 1.96 Ge 3 O 12 :0.04Sm3+ exhibited an excellent electroluminesce performance in a 20 mA driven current. [ABSTRACT FROM AUTHOR]

0.8Na 0.5 Bi 0.5 TiO 3 -(0.2- x)K 0.5 Bi 0.5 TiO 3 - x Bi(Zn 0.5 Ti 0.5)O 3 (NBT-KBT-BZT, x = 0–0.05 with interval of 0.01) lead-free piezoceramics were prepared and investigated. The addition of BZT has not led to deviation of rhombohedral-tetragonal morphotropic phase boundary, but apparently composition-dependent electrical property and monotonously improved thermal stability. The x = 0.02 has the optimal electrical property with remnant polarization, bipolar total strain, piezoelectric constant of 26.5 μC/cm2, 0.30%, 121 pC/N respectively, while the depolarization temperature is increased from 93 °C for x = 0–135 °C for x = 0.05 based on dielectric measurement. Detailed investigation reveals that the domain structure transforms from labyrinthian domain for x = 0 to coexistence of nanodomain and labyrinthian domain for x = 0.02, end up with large amount of nanodomain (x = 0.04). Such domain evolution should be responsible for the composition dependent electrical property and improved thermal stability. Our work confirms that domain engineering is an alternative method to develop high performance piezoelectric materials. • NBT-KBT-BZT lead-free piezoceramics have been prepared. • The piezoceramics show composition-dependent property and improved thermal stability. • Domain transforms from labyrinthian domain, coexisted nanodomain and labyrinthian domain, to nanodomain. [ABSTRACT FROM AUTHOR]

AgPb9(VO4)6I and AgBa9(VO4)6I were synthesized as a potential waste form to immobilize radioactive iodine. The thermal and mechanical properties such as the Young’s modulus and thermal conductivity were measured. The crystal systems of AgBa9(VO4)6I and AgPb9(VO4)6I are rhombohedral and monoclinic, respectively. They are stable up to 950 K under Ar atmosphere. The thermal conductivity of the samples is less than 1.0 W m-1 K-1, which is lower than that of borosilicate glasses used for high-level nuclear waste forms. [Copyright &y& Elsevier]