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ZnO nanodevices have been widely used in practice, but one-dimensional ZnO grown in a polar preferred orientation is still partially localized. In this work, copper nitrate, nickel nitrate and silver nitrate were assisted with zinc acetate and hexamethylenetetetramine for the synthesis of ZnO films by conventional chemical bath deposition method. All samples were characterised by X-ray diffraction, field emission scanning electron microscopy, atomic force microscopy, photoluminescence, and UV–visible spectrophotometer. The results show that non-polar (110), (100) and coexisting preferred orientation ZnO films were controllably prepared by controlling the type and concentration of nitrate. On this basis, the growth process and mechanism of ZnO films with different nonpolar preferred orientations were characterized. It was also found that the ZnO films with 5 % Cu(NO 3) 2 ·3 H 2 O had the minimum surface roughness. The PL spectra confirmed the type and number of defects were also related to the preferred orientations. In addition, the non-polar (110) preferred orientation ZnO films had the highest optical transmittance of 82.26 %. This work enriches the method of preparing ZnO films with various nonpolar preferred orientations and provides new ideas for the design of ZnO-based transparent nanodevices. [Display omitted] • The defects and preferred orientation of ZnO film were effectively controlled by changing Cu, Ni and Ag ion concentrations. • Effective control of the preferred orientations of ZnO films. • Effective control of surface morphology and roughness by controlling cation type and concentration. • Analyzed the relationship between preferred orientations and internal defects of ZnO films. [ABSTRACT FROM AUTHOR]

Abstract LiZn 1-x M x NbO 4 (M = Co, Ni) (x = 0–0.06) systems were fabricated by a facile solid-state reaction method. Structure and property relationships of spinel structured LiZn 1-x M x NbO 4 were investigated systematically. Appropriate amount of Co2+ and Ni2+ greatly improved the dielectric loss of LiZnNbO 4 ceramics. While, the dielectric loss deteriorated seriously when the doping content exceeded x = 0.02. The origin of dielectric loss in LiZn 1-x M x NbO 4 ceramics was investigated systematically. Moreover, the theoretical dielectric constant and linear expansion coefficient were calculated on the bases of the crystallographic parameters from XRD refinement. The temperature coefficient of resonant frequency calculated by the P-V theory agreed well with the test values. Due to the small doping content, the change in chemical bonds was negligible. Density became the major factor determining the variation of dielectric constant in LiZnNbO 4 ceramics. At last, excellent microwave dielectric properties were obtained: Ts = 1010 °C, ε r = 15.25, Q f = 107,000 GHz, τ f = −63.3 ppm/°C for LiZn 0.98 Co 0.02 NbO 4 and Ts = 995 °C, ε r = 14.85, Q f = 104,000 GHz, τ f = −61.7 ppm/°C for LiZn 0.98 Ni 0.02 NbO 4. Highlights • Structure and property of spinel structured LiZn 1-x M x NbO 4 are investigated. • The origin of dielectric loss in LiZn 1-x M x NbO 4 ceramics is clarified. • Dielectric constant and linear expansion coefficient are obtained by the P-V theory. • Excellent microwave performance make it a promising candidate for LTCC applications. [ABSTRACT FROM AUTHOR]

The development of gas sensors based on metal oxide semiconductor (MOS) with highly regular morphology, highly stable structures, and easy preparation is greatly desired but remains a challenge. Herein, we first prepared a highly regular array of TiO 2 nanorods on FTO by a modified in situ hydrothermal method. Then a uniform SnO 2 layer grew on the nanorods to form a core-shell nanocomposite by an ion-layer adsorption-reaction process. The TiO 2 /SnO 2 sensors show enhanced gas sensing performance compared with the TiO 2 sensors, including higher sensitivity to ethanol, lower working temperature, and better long-term stability. And the highest ethanol response can be obtained when the growth cycle of the SnO 2 shell was two times. The gas-sensing mechanism of the TiO 2 /SnO 2 nanocomposites was discussed concerning the unique core-shell structure and a heterojunction between TiO 2 and SnO 2. • Core-shell TiO 2 /SnO 2 nanorod arrays were prepared via a facile two-step method. • The TiO 2 /SnO 2 exhibited better ethanol sensing properties compared with pristine TiO 2. • The enhanced ethanol sensitivity mechanism of TiO 2 /SnO 2 was discussed detailed. [ABSTRACT FROM AUTHOR]

Powder metallurgy (PM) Ti–6Al–2Sn–4Zr–2Mo–0.1Si–(0, 2, 4)W (wt%) alloys were fabricated by thermomechanical consolidation of TiH 2 -based powder compacts and subsequent heat treatments. Samples of the as-fabricated alloys were also heated at 650 °C for 200 h. The addition of 2 or 4 wt%W to the base alloy changed its microstructure of parallel α/β lamellar colonies and grain boundary α (α GB) to an interwoven α/β t microstructure consisting of α GB and a network of interpenetrating α plates with β transformed structure (β t) domains comprising variants of fine α laths and β matrix. The partition of the β stabilizing W between β and α phases and the low diffusivity of W atoms limited the growth of α plates/laths, decreasing the thickness of α plates/laths and increasing the volume fraction of β. The increased hardening of the β phase and enhanced α/β interface strengthening associated with the 4 wt%W addition led to a significant increase in the tensile strength of the alloy from 1281 ± 10–1411 ± 12 MPa. However, the high flow stress and the very fine microstructure caused significant strain localization in the weak α GB , resulting in premature fracture of the α GB (intergranular fracture) and the low ductility (1.4%). Here, premature fracture meant the fracture occurred prior to the alloy reaching its ultimate tensile strength. The heating caused the β interlaths in the W-free alloy to partially dissolve and become β particles distributed along the original lines of β interlaths accompanied by the precipitation of α 2 -Ti 3 Al in the α plates. The addition of W inhibited the dissolution of β interlaths and caused the precipitation of a higher volume fraction of α 2 precipitates during heating. The microstructural changes caused by heating resulted in a slight decrease in strength and a significant decrease in ductility for the W-free alloy, but a significant increase of the yield strength of the 2 W and 4 W alloys with some sacrifice of the tensile ductility. The microstructural reasons for the effects on mechanical properties were analyzed with the assistance of detailed characterization of the dislocations in the deformed specimens. • Effects of W alloying on a PM Ti–6Al–2Sn–4Zr–2Mo–0.1Si alloy are investigated. • W refines α plates and enhances formation of β transformed structure domains. • W enhances hardening of the β phase and α/β interface strengthening. • W increases the microstructural stability and prevents the strength reduction from heating. • High W content promotes α 2 precipitation strengthening of the alloy after heating. [ABSTRACT FROM AUTHOR]

The phase composition, crystal structure and microwave dielectric properties of (1-x) (3ZnO-Nb 2 O 5 )-xGeO 2 were investigated systematically. The phase composition and phase transformation of (1-x) (3ZnO-Nb 2 O 5 )-xGeO 2 ceramics were confirmed by XRD refinement, SEM micrographs and EDS analysis. All sintered samples were composed of Zn 3 Nb 2 O 8 and ZnNb 2 O 6 phases. Phase transition between Zn 3 Nb 2 O 8 and ZnNb 2 O 6 was closely related the introduction of GeO 2 . When the doping content was low (x = 0–0.007), the phase transformation from ZnNb 2 O 6 to Zn 3 Nb 2 O 8 occurred, which was discovered for the first time. To clarify the phase transition, the local charge density and band structures were calculated using the CASTEP program. With the substitution of Ge 4+ , part of the electrons transferred from the oxygen atom to the middle of 'niobium-oxygen' and 'zinc-oxygen'. According, the covalency of 'niobium-oxygen' and 'zinc-oxygen' was enhanced. The shrinkage of ZnO 6 octahedron resulted in a decrease in the coordination number of zinc atoms. At last, the relationships between phase transition, crystal structure and the microwave performance were established. The system of 2.73ZnO-0.91Nb 2 O 5 -0.09GeO 2 sintered at 1150 °C for 6 h had excellent microwave dielectric properties: ε r  = 21.3, Q f  = 99,140 GHz, τ f  = −54 ppm/°C, which, to our best knowledge, the best performance with relative lower sintering temperature. [ABSTRACT FROM AUTHOR]

Two samples of an α + β Ti-4Al-4Mo-4Sn-0.5Si (wt%) alloy, one with fine prior β grains and a heterogeneous microstructure and the other with coarse prior β grains and a homogeneous microstructure were prepared by extrusion of compacts of TiH 2 /Al/Mo/Sn/Si powder blend at 1200 and 1300 °C respectively. The heterogeneous microstructure is manifested by softer Mo-rich regions with a full α/β lamellar structure containing a high number density of parallel and nanometer sized FCC δ (TiH) needles in a harder matrix with a microstructure consisting of interweaved α plates and β transformed structure (β t) domains and grain boundary α (GB α) layers. The matrix also contains a small fraction of Sn-rich regions which have the same microstructure as the matrix. The Mo-rich and Sn-rich regions form due to the limited diffusion of Mo and Sn alloying elements. This heterogeneous microstructure sustains a high tensile yield strength of 1199 MPa, a high strain hardening rate, and an excellent tensile ductility of 12.0%. In contrast, the homogeneous microstructure comprising of interweaved α plates and β t domains together with GB α layers sustains a similar high strength, but a clearly lower strain hardening rate and a significantly lower tensile ductility of 3.5%. Non-homogeneous deformation capacity, the release of energy by forming numerous microcracks and the intermittent growth of microcracks of the heterogeneous microstructure suggest that this microstructure has a high plasticity and high resistance to the growth of microcracks. • The α + β titanium alloy fabricated has a heterogeneous microstructure and fine prior β grains. • The heterogeneous microstructure encompasses softer Mo-rich regions in a matrix of α/β t microstructure. • This alloy exhibits a superior combination of high strength (YS: 1199 MPa and excellent ductility (12.0%). • This is attributed to the compatible deformation and high microcrack growth resistance of the microstructure. [ABSTRACT FROM AUTHOR]

• With an addition of 0.2 wt%Si, the Si atoms are equally in α and β phases. • Si solute atoms retard the growth of α phase, causing refinement of the α/β t lamellar structure. • Si atoms enhance solid solution strengthening and Si atoms enhanced α/β t interface strengthening. • Increasing the Si content to 0.5 wt% cause a further increase of the yield strength by 50 MPa. • With a high strength, the tensile ductility deteriorates, due to the premature fracture of grain boundary α layers. Ti-4Al-4Mo-4Sn-xSi (wt%) (x = 0, 0.2, 0.5) alloys were fabricated by hot extrusion of compacts of blends of TiH 2 , AlMo60 master alloy and other required elemental powders followed by heat treatments involving vacuum annealing, solution treatment, air cooling and aging. The microstructure of the alloys consists of α plates, lamellae of α and transformed β structure (β t), β t blocks as well as grain boundary α layers. With the addition of 0.2 wt%Si, the Si atoms exist in equal concentration in both α and β t regions as solute atoms, and they retard the growth of α phase, causing a decrease of the average thickness of α plates and lamellae and slight increase of the volume fraction of β t lamellae and blocks. The solid solution strengthening and enhanced α/β interface hardening brought by the 0.2 wt%Si cause the yield strength of the Ti-4Al-4Mo-4Sn alloy to increase significantly from 1030 to 1130 MPa with a slight decrease of the tensile ductility (7.4% vs 6.8%) and without changing the fracture behavior. With the addition of 0.5 wt%Si, the extra Si causes nanometer sized silicide (Ti 5 Si 3) precipitates to form in both α and β t regions and further microstructural refinement. The additional α/β interface hardening and precipitation hardening cause the yield strength of the alloy to increase further to 1177 MPa, but the tensile ductility deteriorates clearly with the elongation to fracture decreasing to 4.9%. The main reason for this ductility decrease is the premature fracture of grain boundary α layers caused by the higher flow stress which can induce more strain localization at the grain boundary α layers. [ABSTRACT FROM AUTHOR]

Halide perovskite quantum dots have attracted considerable research interest as excellent candidate for photonic and optoelectronic applications due to their unique optoelectronic properties. Stability is prerequisite and therefore is of critical importance. Here we demonstrate highly stable luminescent CsPbBr 3 quantum dots (QDs) can be achieved in different glass matrices via the high temperature melting process and melt-quench method. The microstructure of CsPbBr 3 QDs glass as well as their optical properties are systematically characterized by microscopic techniques and time-resolved spectroscopic techniques. We conclude the surface passivation is the key aspect for the high stability and high luminescence by embedding the quantum dots in the glass matrix. This study provides technical method to form highly stable luminescent solid devices and detailed physical understanding which is critical for the practical applications. • Luminescence in CsPbBr 3 QDs glass were study. • CsPbBr 3 QDs precipitated in 3 kinds of glass matrices. • Exciton recombination is confirmed as the dominant radiative mechanism. • the QDs glass could be flexibly fabricated into various device. [ABSTRACT FROM AUTHOR]

Polyanion Na 3 V 2 (PO 4) 3 belongs to sodium-ion super conductor (NASICON) materials, and its NASICON framework offers a stable sodium capacity. The open three-dimensional (3D) channels can provide the transfer paths for sodium-ions. Besides, the unique 3D structure is helpful to achieve the high reversibility of charge and discharge processes. As the cathode compounds for sodium-ion batteries (SIBs), Na 3 V 2 (PO 4) 3 materials meet requirements of low cost and high safety. Moreover, Na 3 V 2 (PO 4) 3 materials possess a high voltage platform and have been widely concerned in SIBs. It is deemed that Na 3 V 2 (PO 4) 3 is a promising cathode material for SIBs. However, the low electronic conductivity of Na 3 V 2 (PO 4) 3 materials hampers the rate capability. Herein, the recent researches of Na 3 V 2 (PO 4) 3 are roundly reviewed. Firstly, this paper introduced the structural characteristics of Na 3 V 2 (PO 4) 3 materials. And then synthetic methods were narrated, such as sol-gel, spray-drying, hydrothermal, electrospinning, and solid-state reaction methods. Moreover, the modified researches of Na 3 V 2 (PO 4) 3 were summarized, mainly including carbon coating, nanocrystallization, and ionic doping. Finally, we prospected the future development direction of Na 3 V 2 (PO 4) 3 modification methods, and made a few suggestions. • The transfer mechanism of sodium ions in Na 3 V 2 (PO 4) 3 is explained in more detail. • The methods of experimental synthesis of Na 3 V 2 (PO 4) 3 materials are reviewed. • The latest research progress in modification methods of Na 3 V 2 (PO 4) 3 as cathodes materials for sodium ion battery is reviewed. • Several suggestions on the modification of Na 3 V 2 (PO 4) 3 materials are put forward. [ABSTRACT FROM AUTHOR]

Many studies on the protection of C/C composites in oxidizing environments have been carried out. Coating technology has proven to be highly effective in improving the oxidation resistance of C/C composites. Summaries and comparisons of antioxidation coating materials for C/C composites are needed for comprehensive understanding and further researches. In this paper, recent advances in promising single-phase materials as protective coatings for C/C composites were firstly reviewed, with attention to their characteristics and antioxidation mechanisms. Then, several common mixture systems, such as carbide mixtures, boride mixtures and MoSi 2 -based ultrahigh-temperature ceramics (UHTCs), were discussed. In addition, three kinds of nanostructured materials used for doping coatings were described in detail. Finally, some typical problems and future challenges in the development of these coating materials for C/C composites were highlighted. [ABSTRACT FROM AUTHOR]

Tri-layered Zn 3 Nb 2 O 8 –TiO 2 –Zn 3 Nb 2 O 8 ceramic with high temperature stability are initially fabricated. On the basis of X-ray diffraction, Raman spectra and HFSS (High Frequency Structure Simulator) simulation, a reasonable parallel mode is put forward, then the transition layer at the heterogeneous interface is considered to be crucial to the microwave response in this system, and the theoretical feasibility of layer-cofired microwave dielectric ceramics is verified. Contrasting to the random distribution type Zn 3 Nb 2 O 8 –TiO 2 , this structure can substantially reduce the amount of TiO 2 and achieve an eightfold increase in Q f value, which is conducive to produce the new generation microwave passive devices. • Temperature-stable tri-layered Zn 3 Nb 2 O 8 –TiO 2 –Zn 3 Nb 2 O 8 ceramics are initially fabricated. • Compared to the random-type, an eightfold-increasing in Q f value can be achieved using this architecture. • A reasonable parallel mode is put forward to illustrate the microwave response in multi-layered ceramic system. [ABSTRACT FROM AUTHOR]

The quality of perovskite film seriously affects the performance of organic-inorganic hybrid halide perovskite solar cells. In this paper, we demonstrate an anti-solvent treatment by controlling the perovskite recrystallize to enhance the quality of perovskite film and photophysical properties, including crystallinity, high coverage and high absorption. The fabricated carbon-based perovskite solar cells show PCE improvement from 6.82% to 10.81% with less hysteresis, and remained 90% of the original value after 93 days in the air environment. Our work provides a way to prepare simple and stable perovskite devices with high stability and low cost. • The high-stability perovskite solar cells (PSCs) based on carbon electrode was fabricated under humidity air atmosphere. • The crystallization kinetics of perovskite was optimized by anti-solvent CB washing and high-quality films were prepared. • We investigated the effect of different dosage of CB the on PSCs. • The power conversion efficiency (PCE) of champion PSC was 10.81% with optimum dosage CB (100 μ L). [ABSTRACT FROM AUTHOR]

Uniform Lu 2 (C 4 H 4 O 6 ) 3 ·6H 2 O cauliflower-like microspheres have been synthesized via a direct precipitation method at room temperature, without any templates and catalysts. The solvent-dependent morphological evolution and the formation mechanism of the Lu 2 (C 4 H 4 O 6 ) 3 ·6H 2 O cauliflower-like microspheres were investigated in detail. Furthermore, Eu 3+ /Tb 3+ -doped Lu 2 O 3 inherited their parents' morphology were obtained through a direct annealing process. The Lu 2 (C 4 H 4 O 6 ) 3 ·6H 2 O:Eu 3+ , Lu 2 O 3 :Eu 3+ exhibit strong red emission corresponding to the 5 D 0 - 7 F j transition of the Eu 3+ ions. The Lu 2 (C 4 H 4 O 6 ) 3 ·6H 2 O:Tb 3+ , Lu 2 O 3 :Tb 3+ exhibit strong green emission corresponding to the 5 D 4 - 7 F j transition of the Tb 3+ ions under UV light excitation. The samples may have potential applications in the fields, such as light-emitting phosphors, advanced flat panel displays, or biological labeling. [ABSTRACT FROM AUTHOR]

Robust bonding and thermal-stable sinter Ag joining on an Au finished substrate was first time achieved for use in SiC power modules. Five kinds of Ag paste, including different solvents and Ag fillers, and four kinds of Au plating processes (ENIG, ENIGEG, ENEPIG and ENEPIGEG) were used to optimize the initial shear strength of Ag–Au joints. Here, EN means electroless Ni plating, EP means electroless pure palladium plating, IG means immersion gold plating process and EG is the process of electroless gold plating. Micro-scaled Ag flake paste showed the best die shear strength at 33.9 MPa by in-suit formation of Ag nanoparticles, accomplished with a sintering temperature of 250 °C without pressure in air. With the use of Electron backscatter diffraction (EBSD) analysis, the ENEPIG plating process exhibited an Au surface with greater Au (111) grain orientation and larger grain size, which both of that benefits bonding with Ag paste. The thermal-stable sinter Ag joining on ENEPIG was evaluated by aging at 250 °C up to 1000 h. The shear strength had slightly increased to 36.5 MPa after 1000 h. The mechanism of robust bonding and thermal-stable during high temperature aging were systematically analyzed via Scanning Electron Microscope (SEM), Energy dispersive X-ray spectroscopy (EDS), Transmission Electron Microscope (TEM) and X-ray diffraction (XRD), which was attributed to the large Au grains size, the favorable surface condition of the ENEPIG, and the Pd barrier layer which prohibited Ni diffusion into the Au layer during sintering and aging. Image 1 • Shear strength of sinter Ag–Au joints achieved to 33.9 MPa at 250 °C without pressure sintering in air. • In-suit formation of Ag nanoparticles improved the necking growth of sintered Ag. • ENEPIG plating shows a larger ratio of Au (111) grain orientation and bigger Au grains size. • Shear strength of sinter Ag–Au joints increased at 250 °C aging for1000 h. • Robust bonding and thermal-stability were attributed to less grain boundary diffusion and the Pd barrier layer. [ABSTRACT FROM AUTHOR]