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Friction stir lap welding (FSLW) was employed to weld dissimilar joints of zirconium and stainless steel for the first time. The microstructure, evolution mechanism of intermetallic compounds (IMCs) and mechanical properties of joint were investigated. Discontinuous dynamic recrystallization (DDRX) and continuous dynamic recrystallization (CDRX) occurred in zirconium, while DDRX occurred in stainless steel during FSLW. The formation sequence of IMCs at the interface was FeZr3, FeZr2, Fe2Zr, and Fe23Zr6. The crack nucleated at the hook zone on the advancing side (HookAS), and IMCs in the Zr/SS mixed zone accelerated crack propagation. The fracture surface exhibited ductile-brittle mixed fracture characteristic.

Friction stir welding (FSW), as a new type of solid-solid welding method, was utilized to join transformation-induced plasticity (TRIP) steel. This method can avoid the solidification structural defects caused by fusion welding technology and improve the welding quality. In this study, the microstructural transformation and deformation behavior of TRIP steel during FSW were evaluated by optical microscopy, electron backscatter diffraction, and room-temperature tensile test. The results show that after FSW, martensite transformation occurred in the stir zone (SZ) and thermomechanically affected zone (TMAZ), and the retained austenite content decreased. The grain refinement and ratio of low-angle boundaries (LABs) increased. In heat-affected zone (HAZ), the retained austenite was thermally spheroidized and decomposed, the grains were coarsened, and the ratio of LABs decreased. No obvious preferred grain orientation was observed in each region of joint, and the texture strength decreased by phase transformation and grain rotation. After the tensile deformation of FSW joint, the retained austenite disappeared, the grains were refined, and the proportion of LABs increased in the base metal (BM) and HAZ. The content of retained austenite in SZ remained unchanged, but decreased in TMAZ. The grains were refined, and the ratio of LABs did not change significantly in SZ and TMAZ. FSW increased the microhardness of SZ and TMAZ by 218 HV and 93 HV, respectively, while the microhardness of HAZ decreased by 4 HV. The yield strength, tensile strength, and elongation of joint were 563 MPa, 942 MPa, and 12.8 %, respectively, reaching 96%, 104%, and 59%of BM, respectively. The tensile fracture exhibited ductile fracture characteristics. In addition, the joint exhibited strain nonuniformity during the tensile deformation, and the order of deformation degree was as follows: HAZ > TMAZ > SZ. Therefore, HAZ became a weak zone of joint mechanical properties. Continuous dynamic recrystallization and discontinuous dynamic recrystallization were the main mechanisms of grain refinement, and the martensite transformation conformed to the Kurdjumov-Sachs orientation relationship.

Although numerous fluorescent probes are designed to detect the pH value in the past decades, developing fluorescent probes for extreme alkalinity (pH > 14) detection in aqueous solution is still a great challenge. In this work, we utilized 1H-imidazo[4,5-f][1, 10] phenanthroline (IP) group as the recognition group of hydroxyl ion and introduced two triethylene glycol monomethyl ether groups to improve its solubility. This IP derivative, BMIP, possessed good solubility (25 mg/mL) in water. It displayed high selectivity toward extreme alkalinity (pH > 14) over other ions and pH (from extreme acidity to pH = 14). From 3 to 6 mol/L OHˉ, the exact concentration of OHˉ could be revealed by BMIP and the whole detection process just needed a short time (≤ 10 s). Meanwhile, it exhibited good anti-interference ability and repeatability during the detection process. Through optical spectra and NMR analysis, its detection mechanism was proved to be deprotonation by hydroxyl ion and then aggregation-induced enhanced emission. Our study presents a new basic group based on which researchers can develop new fluorescent probes that can detect extreme alkalinity (pH > 14) in aqueous solution.

Ce3+-doped silicate phosphors (Mg2-xSiO4:xCe3+, x = 0.001–0.007 mol) for NUV w-LEDs have been synthesized by solid-state reaction method at 1450°C. The as-prepared samples have been characterized by XRD and fluorescence spectrophotometer, respectively. The XRD results show that the aim phase has been synthesized and doping Ce3+ has not resulted in impurity phase. This phosphor material exhibits a strong blue-violet emission (330–520 nm) under the near-ultraviolet radiation excitation. The average colorimetric coordinate of Mg2-xSiO4:xCe3+ (x = 0.0025 mol) is (0.1508, 0.0694), locating in blue-violet region. We have obtained bright blue-violet light via pumping the sample by NUV light (λ ≈ 365 nm), suggesting that this material can be potential as a NUV converting blue-violet phosphor for the NUV w-LEDs.

Color rendering index and color temperature are the key factors for the LEDs application. The two points are closely related to the emission spectrum shape of phosphors. As the key factors for the LEDs application, both the above aspects are closely dependent on the emission spectrum shape of phosphors. In this study, the emission spectrum shape has been adjusted via a home designed route. A combination of structural, morphological, and optical characterization techniques has been used to study the shape evolution mechanism. The structural results show that the Sr2SiO4 phase has not been changed with the sintering temperature increasing, but the emission spectrum shape has changed dramatically, meanwhile, the colorimetric coordinate moves from blue-green to green region. Gaussian fitting method has been used to treat the emission spectrum, and the as-obtained results indicate the emission spectrum contains two single bands, which come from the 4f7(7S7/2)–4f6(7FJ)5d1 transition of Eu2+ on the different Sr sites in the Sr2SiO4 crystal. The intensity of the two single bands is driven by sintering temperature, because of the difference between the energy barrier of the Eu2+ occupying the different Sr sites in the matrix crystal. Moreover, the mechanism of the above phenomenon has also been studied by means of first principles method, and the obtained results agree well with the former deduction.

Integrating the advantages of ultrahigh sensitivity, good breathability, low-cost and large-area fabrication processes, and facile integration with other functional devices is full of challenges for wearable pressure sensors. Here, a novel all-fabric piezoresistive pressure sensor is designed with a bottom interdigitated textile electrode screen-printed using silver paste and a top bridge of AgNW-coated cotton fabric. The entire fabrication process is facile, economical and suitable for large-scale integrated production. Benefiting from the highly porous microstructure, large surface roughness and ultra-low resistance of the conductive fabric, our piezoresistive pressure sensors show excellent detection performance, including an extra-high sensitivity of 2.46 × 104 kPa−1 to 5.65 × 105 kPa−1 over a wide pressure regime (0–30 kPa), a giant on/off ratio of ≈106, a fast response time (6 ms), and a low detection limit (0.76 Pa). Thanks to these merits, the devices not only have the ability to detect various tiny signals of the human body, but also can be widely applied in a human–computer interactive system as a real wearable sensor platform, which was demonstrated by playing the piano and computer games.

Silver nanowire (AgNW) ink has great influence on the performance of the resulting AgNW-based conductive film, especially for the large-scale roll-to-roll processed films. However, AgNW inks made by researchers are almost immature because there is not a clear research procedure for the development of qualified inks. In this work, electric double layer model, Young equation, bubble theory, percolation theory, Rhodes & Orchad equation, Kelvin equation and other theoretical models were introduced successively to describe those processes which additives in inks should adjust. Based on the guidance of these theories, additives were determined successively and an optimized light grey ink with the composition of 0.4% AgNW + 0.2% 2-amino-2-methyl-1-propanol + 0.01% Zonyl FSO-100 + 1.5% diacetone alcohol + 5% 1,4-dioxane + 92.89% isopropyl alcohol was obtained. Except for trace amount of Zonyl FSO-100, other additives could be easily eliminated at low temperature (110 °C), which could retain the original properties of AgNW furthest and greatly lower the dosage of AgNW in inks. Based on this ink, excellent AgNW/PET composite film was prepared. The sheet resistance, transmittance and haze of this film were 29.5 Ω/sq, 88.9% and 1.49% respectively. Finally, touch screens (180 mm × 105 mm) and tablets (10 inches) were prepared from our films and showed good performance. These results demonstrated that excellent AgNW ink could be developed through our research procedure. Our studies not only produce an excellent AgNW ink, but also provide a systematic research procedure and series of theoretical models for many kinds of conductive inks.

Silver nanowire (AgNW) ink has a great influence on the performance of large-scale transparent conductive films (TCFs). However, most researchers didn’t know how to make their self-made AgNWs into qualified inks. For this reason, most TCFs prepared from the self-made AgNWs were only small-scale films and there was a lack of large-scale films. In this study, a systematic and effective development procedure starting from AgNWs to a qualified water-based AgNW ink is reported. Several new additives were exploited step by step to adjust the dynamic processes, which were crucial for the preparation of large-scale uniform films, including the stabilization and distribution of AgNWs, as well as the wetting, spreading, adjustment, and drying of the wet film. Then, an AgNW ink was obtained that showed stability comparable to commercial inks. After this, a large-scale flexible film (0.5 m × 10 m) was prepared using a roll-to-roll printing machine, and then a large-scale touch screen (32 inches) was realized. The performance of this film and that of the touch screen demonstrated that our ink was a qualified ink. The present study not only provides an effective procedure for researchers to make their self-made AgNWs into qualified inks in fundamental research, but also supplies a reference for engineers to develop commercial inks.

Thermally activated delayed fluorescence (TADF) dendrimers have received much attention in solution-processed non-doped organic light-emitting diodes. However, the study of their application as self-host materials in white organic light-emitting diodes (WOLEDs) is quite limited. In this contribution, solution-processed small-molecule WOLEDs were obtained by employing a newly designed blue TADF dendrimer bis(4-(3,6-bis(3,6-di-tert-butylcarbazol-N-yl) carbazole)phenyl)sulfone (G2) with a wide bandgap and a high triplet energy (3.0 eV) as the host and the blue-light-emitting material, combined with an orange iridium complex (bis(2-phenylbenzothiazolato) (acetylacetonate)iridium(III)) (Ir(bt)2(acac)) as the dopant. The devices achieved a maximum external quantum efficiency of 10.1%, a maximum current efficiency of 17.69 cd A−1 and CIE coordinates of (0.32, 0.33). They also exhibited stable electroluminescence spectra and low efficiency roll-off at a relatively high current density. These improved performances benefit from the advantages of the TADF dendrimer used as the host material. More importantly, the fast rate constant of Forster resonance energy transfer (KET > 107 s−1) suppressed intersystem crossing (ISC) on the G2 host from singlet to triplet states, leading to a reduced singlet density and suppressed singlet–triplet annihilation on the G2 host. Therefore, these results indicate that TADF dendrimers have a promising prospect in the application of high-performance solution-processed two complementary color WOLEDs.

Highly dispersed copper nanowire (CuNW) is an essential prerequisite for its practical application in various electronic devices. At present, the dispersion of CuNW is almost realized through the steric hindrance effect of polymers. However, the high post-treatment temperature of polymers makes this dispersion mechanism impractical for many actual applications. Here, after investigating the relationship between the electrostatic dispersion force and influence factors, an electrostatic dispersion mechanism is refined by us. Under the guidance of this mechanism, high dispersion of CuNW and a record low post-treatment temperature (80 °C) are realized simultaneously. The high dispersity endows CuNW with good stability (-45.66 mV) in water-based ink, high uniformity (65.7 ± 2.5 Ω sq-1) in the prepared transparent conducting film (TCF) (23 cm × 23 cm), and industrial film preparation process, which are the issues that hinder the widespread application of CuNW-based TCF at present. The low post-treatment temperature makes the application of CuNW possible on any substrate. In addition, the charge modifier, 2-mercaptoethanol, enables CuNW to resist oxidation well. Finally, flexible optoelectronic devices employing the CuNW film as the electrode are fabricated and show efficiencies comparable to those of optoelectronic devices on indium tin oxide/glass.

In this work, a novel twisted 3-benzoyl-4H-chromen-4-one (BZC) acceptor is reported and a BZC-based thermally activated delayed fluorescence (TADF) emitter, 3-(4-(10H-phenoxazin-10-yl)benzoyl)-4H-chromen-4-one (BZC-PXZ), is developed. The unique structure of BZC endows BZC-PXZ with favorable molecular and stacking structures. First, the small and twisted structure of BZC group not only brings about large dihedral angle (88.78°) between donor and acceptor groups, but also efficiently prevents π∙∙∙π interaction. Second, the three oxygen atoms of BZC group bring about abundant weak intermolecular interactions which can enhance the charge-transporting ability of BZC-PXZ and facilitate the exciton recombination on it. As a result, BZC-PXZ exhibits small singlet-triplet energy splitting (0.02 eV) and high photoluminescence quantum yield (93%) simultaneously. Meanwhile, the BZC-PXZ-based device displays high efficiency (64.6 cd/A, 69.0 lm/W, 21.3%), high exciton utilization efficiency (77.2%) and low roll-off of efficiencies even at ultralow doped concentration of 1%. These results demonstrate that BZC group is a good acceptor for developing high-performance TADF emitters.

Ensuring stable red and blue emission from white organic light-emitting devices (WOLEDs) with complementary colors is a major challenge. Here, a novel exciplex systems were used to solve this problem, where a thermally activated delayed fluorescence (TADF) material 10, 10, 10-(4, 4, 4-Phosphoryltris (benzene-4,1-diyl)) tris (10Hphenoxazine) (TPXZPO) and a common hole transporting material N,N′-dicarbazolyl-3,5-benzene (MCP) were mixed with an electron-transporting material (1,3,5-Triazine-2,4,6-triyl)tris(benzene-3,1-diyl)) tris(diphenylphosphineoxide) (PO-T2T) to form exciplex host for red and blue phosphorescent materials, respectively. Benefitted from the high triplet energy of donor and accepter were select to form exciplex host which ensures that excitons are excellent confined to the EMLs. Matched exciplex host-guest systems and a multichannel reverse intersystem crossing reduces energy loss during energy transfer processes and prevents triplet-triplet annihilation. The use of stepped energy transfer channels and exciplex interlayer switch ensures WOLEDs have greater stability. The devices exhibited a maximum power efficiency, current efficiency, and external quantum efficiency of 69.25 lm/W, 56.69 cd/A and 24.55%, respectively. More importantly, the devices exhibited extremely stable color rendering index ranging from 74 to 76 with luminance ranging from 102 to 104 cd/m2. These results indicate that the exciplex are promising for use in developing high performance complementary color WOLEDs.

In this paper, two novel azobenzene-containing poly(aryl ether)s with different absorption wavelengths were synthesized via Ullmann coupling and Sonogashira coupling, respectively. The obtained polymers were characterized and evaluated by elemental analysis, IR, 1H NMR, UV-vis, DSC and TGA. Rare earth complexes were prepared by using the two novel azobenzene-containing poly(aryl ether)s as macromolecular ligands. The obtained rare earth complexes were characterized by elemental analysis, IR and WAXD. The influence of the absorption wavelength of azobenzene chromophores on the fluorescent properties was investigated. The polymer whose absorption wavelength was far from the excitation wavelengths of the rare earth complexes showed a much larger fluorescence intensity. By exposing the films of the rare earth complexes to two interference laser beams, SRGs can be formed on the films and can also be detected by fluorescence microscopy measurement.

Molybdenum (Mo) doped BiVO4 was fabricated via a simple electrospun method. Morphology, structure, chemical states and optical properties of the obtained catalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance spectroscopy (DRS), N2 adsorption–desorption isotherms (BET) and photoluminescence spectrum (PL), respectively. The photocatalytic properties indicate that doping Mo into BiVO4 can enhance the photocatalytic activity and dark adsorption ability. The photocatalytic test suggests that the 1% Mo-BiVO4 shows the best photocatalytic activity, which is about three times higher than pure BiVO4. Meanwhile, 3% Mo-BiVO4 shows stronger dark adsorption than pure BiVO4 and 1% Mo-BiVO4. The enhancement in photocatalytic property should be ascribed to that BiVO4 with small amount of Mo doping could efficiently separate the photogenerated carries and improve the electronic conductivity. The high concentration doping would lead the crystal structure transformation from monoclinic to tetragonal phase, as well as the formation of MoO3 nanoparticles on the BiVO4 surface, which could also act as recombination centers to decrease the photocatalytic activity.

Silver nanowires without particles are synthesized by a solvothermal method at temperature 150 °C. Silver nanowires are prepared via a reducing agent of glycerol and a capping agent of polyvinylpyrrolidone (M w ≈ 1,300,000). Both of them can improve the purity of the as-prepared silver nanowires. With controllable shapes and sizes, silver nanowires are grown continuously up to 10–20 μm in length with 40–50 nm in diameter. To improve the yield of silver nanowires, the different concentrations of AgNO3 synthesis silver nanowires are discussed. The characterizations of the synthesized silver nanowires are analyzed by UV-visible absorption spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), and atomic force microscope (AFM), and silver nanowires are pumped on the cellulose membrane and heated stress on the PET. Then, the cellulose membrane is dissolved by the steam of acetone to prepare flexible transparent conducting thin film, which is detected 89.9 of transmittance and 58 Ω/□. Additionally, there is a close loop connected by the thin film, a blue LED, a pair of batteries, and a number of wires, to determinate directly the film if conductive or not.

Orange-red phosphors NaY(WO4)2:Eu3+, Sm3+ were successfully synthesised by hydrothermal synthesis method. The photoluminescence (PL) properties were investigated. The PL emission spectrum of Na Y (WO4)2: Eu3+ shows good luminous properties under 398 nm, which mainly located at 596 and 615 nm, with the additional of Sm3+ could broaden and increase emission intensity of Eu3+, which could be suitable for the excitation of UV light emitting diodes (LEDs) (~400 nm). The PL results indicated that Na Y (WO4)2: Eu3+, Sm3+ may be a promising red phosphor candidate for use in white LEDs.