•Na2Li2Ti6O12 has been successfully synthesized via a molten salt route.•Calcination temperature is an important effect on the component and microstructure of the product.•Pure phase Na2Li2Ti6O12 ...could be obtained at 700°C for 2h.
The sodium lithium titanium oxide with composition Na2Li2Ti6O14 has been synthesized by a molten salt synthesis method using sodium chloride and potassium chloride mixture as a flux medium. Synthetic variables on the synthesis, such as sintering temperature, sintering time and the amount of lithium carbonate, were intensively investigated. Powder X-ray diffraction and scanning electron microscopy images of the reaction products indicates that pure phase sodium lithium titanium oxide has been obtained at 700°C, and impure phase sodium hexatitanate with whiskers produced at higher temperature due to lithium evaporative losses. The results of cyclic voltammetry and discharge–charge tests demonstrate that the synthesized products prepared at various temperatures exhibited electrochemical diversities due to the difference of the components. And the sample obtained at 700°C revealed highly reversible insertion and extraction of Li+ and displayed a single potential plateau at around 1.3V. The product obtained at 700°C for 2h exhibits good cycling properties and retains the specific capacity of 62mAhg−1 after 500 cycles.
When exposed to high magnetic fields, certain materials manifest an exotic superconducting (SC) phase that has attracted considerable attention. A proposed explanation for the origin of the ...high-field SC phase is the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state. This state is characterized by inhomogeneous superconductivity, where the Cooper pairs have finite center-of-mass momenta. Recently, the high-field SC phase was observed in FeSe, and it was deemed to originate from the FFLO state. Here, we synthesize FeSe single crystals with different levels of disorder. The level of disorder is expressed by the ratio of the mean free path to the coherence length and ranges between 35 and 1.2. The upper critical field Bc2 was obtained by both resistivity and magnetic torque measurements over a wide range of temperatures, which went as low as ∼ 0.5 K, and magnetic fields, which went up to ∼ 38 T along the c axis and in the ab plane. In the high-field region parallel to the ab plane, an unusual SC phase was confirmed in all the crystals, and the phase was found to be robust against disorder. This result suggests that the high-field SC phase in FeSe is not a conventional FFLO state.
The back-streaming neutrons (back-n) is a white neutron experimental facility at the China spallation neutron source (CSNS). The time structure of the primary proton beam makes it fully applicable to ...use the time-of-flight (TOF) method for neutron energy measuring. We implemented the electronics of TOF measurement on the general-purpose readout electronics designed for all the seven detectors in back-n. The electronics are based on the peripheral component interconnect express eXtensions for instrumentation (PXIe) platform, which is composed of field digitizer modules (FDM), trigger and clock modules (TCM), and signal conditioning modules. The T0 signal synchronous to the CSNS accelerator represents the neutron emission from the target. It is the start of the time stamp. The TCM receives, synchronizes, and distributes the T0 signal to each FDM based on the PXIe backplane bus. Meanwhile, the detector signals, after being conditioned, are fed into FDMs for waveform digitizing. The first sample point of the signal waveform is the stop of the time stamp. According to the time stamp and the time of the signal over the threshold, the total TOF can be obtained. The time-to-digital converter (TDC) based on field-programmable gate array (FPGA) is implemented on the TCM to accurately acquire the time interval between the asynchronous T0 signal and the global synchronous clock phase. There is also an FPGA-based TDC on the FDM to accurately acquire the time interval between the T0 signal arriving at the FDM and the first sample point of the signal waveform. The over-threshold time of signal is obtained offline. This method for TOF measurement is efficient and not needed for additional modules. Test results showed that the accuracy of TOF is subnanosecond and can meet the requirement for back-n at the CSNS.
The evolution of microstructure and mechanical properties of Zr0.5Be alloy were investigated by varying the annealing temperature. X-ray diffraction results show that the examined Zr alloy is ...composed of α phase and Be2Zr compound after annealing at temperatures between 600 and 850°C. The optical and transmission electron microscopy results reveal that the recrystallization volume fraction of the α phase gradually increases with increase in annealing temperature. The mechanical properties of the alloy were also investigated by varying the annealing temperature. It was observed that both the tensile strength and micro-hardness of Zr0.5Be alloy gradually decrease with increase in annealing temperature, while the elongation-to-failure increases at higher annealing temperatures. The decrease in dislocation density, the increase in recrystallization volume fraction of the α phase, and distribution of compounds were largely responsible for the decreased tensile strength and micro-hardness and improved ductility of the examined alloys. This work provides a better understanding of the mechanical properties of Zr alloys and helps pave the path for their further development.
Sc addition and rolling were performed to optimize the mechanical properties of Al alloys with high Zn concentrations. The addition of 0.5 Sc reduced the grain size of the Al–35Zn alloys during ...solidification, heat treatment, and rolling. Nanosized, rod-shaped Zn particles dynamically precipitated from the Al lattice during hot rolling and consequently coarsened during further cold rolling. Following 50% hot rolling and 80% cold rolling, Al–35Zn–0.5Sc alloy demonstrated the highest strength, i.e., an ultimate tensile strength (UTS) of 482MPa. Moreover, following 90% hot rolling, Al–35Zn–0.5Sc alloy demonstrated balanced mechanical properties including high strength and reasonable ductility (UTS and tensile elongation of 430MPa and 10%, respectively). This work provided an effective strategy to fabricate Al alloys with high Zn concentrations and excellent mechanical properties.
The precipitation kinetics during non-isothermal annealing of an Al-Mn alloy (AA3003) rolled over a large strain range (ε = 0–2) has been investigated. Precipitation strengthening can overtake ...recovery softening when prestrained alloy was annealed below 573 K. The precipitate size distributions were similar in undeformed and prestrained alloys annealed at low temperature (673 K). We developed a coupled deformation-recovery-precipitation model for nucleation kinetics of heterogeneous precipitation. Strain-induced dislocations significantly promote nucleation at small and moderate strains while nucleation rate on sub-boundaries of higher misorientation increases by orders of magnitude with strain, and becomes dominant at large strains.
•The precipitation kinetics of an Al-Mn alloy pre-strained ε = 0–2 has been studied.•The tensile strength of pre-strained alloy was increased by annealing below 573 K.•We developed a coupled deformation-recovery-precipitation kinetics model.•The heterogeneous nucleation kinetics at different sites were modeled.
The alloying effect of Zr on β (body-centred cubic)-phase stability was investigated in α (hexagonal close packed)-type Ti–Al alloys. According to calculations and experiments, adding Zr ...significantly modified the β-phase stability, because Zr was identified as a β-stabilising element in these Ti–Zr–Al alloys under the solution treatment. However, the water-quenched β-phase did not continue to be preserved after aging. In addition, stress-induced α″ (orthorhombic)-phase martensite transformation would occur during deformation.
Abstract
Multiwavelength simultaneous observations are essential to the constraints on the origin of fast radio bursts (FRBs). However, it is a significant observational challenge due to the nature ...of FRBs as transients with a radio millisecond duration, which occur randomly in the sky regardless of time and position. Here, we report the search for short-time fast optical bursts in the Ground-based Wide Angle Camera (GWAC) archived data associated with FRB 20181130B, which were detected by the Five-hundred-meter Aperture Spherical radio Telescope and recently reported. No new credible sources were detected in all single GWAC images with an exposure time of 10 s, including images with coverage of the expected arrival time in optical wavelength by taking the high dispersion measurements into account. Our results provide a limiting magnitude of 15.43 ± 0.04 mag in the
R
band, corresponding to a flux density of 1.66 Jy or 8.35 mag in AB system by assuming that the duration of the optical band is similar to that of the radio band of about 10 ms. This limiting magnitude makes the spectral index of
α
< 0.367 from optical to radio wavelength. The possible existence of longer-duration optical emission was also investigated with upper limits of 0.33 Jy (10.10 mag), 1.74 mJy (15.80 mag), and 0.16 mJy (18.39 mag) for the durations of 50 ms, 10 s, and 6060 s, respectively. This undetected scenario could be partially attributed to the shallow detection capability, as well as the high inferred distance of FRB 20181130B and the low fluence in radio wavelength. The future detectability of optical flashes associated with nearby and bright FRBs are also discussed in this paper.
This paper presents an optical fiber-based readout system that is intended to provide a general purpose multi-channel readout solution for various Micro-Pattern Gas Detectors (MPGDs). The proposed ...readout system is composed of several front-end cards (FECs) and a data collection module (DCM). The FEC exploits the capability of an existing 64-channel generic TPC readout ASIC chip, named AGET, to implement 256 channels readout. AGET offers FEC a large flexibility in gain range (4 options from 120 fC to 10 pC), peaking time (16 options from 50 ns to 1 us) and sampling freqency (100 MHz max.). The DCM contains multiple 1 Gbps optical fiber serial link interfaces that allow the system scaling up to 1536 channels with 6 FECs and 1 DCM. Further scaling up is possible through cascading of multiple DCMs, by configuring one DCM as a master while other DCMs in slave mode. This design offers a rapid readout solution for different application senario. Tests indicate that the nonlinearity of each channel is less than 1%, and the equivalent input noise charge is typically around 0.7 fC in RMS (root mean square), with a noise slope of about 0.01 fC/pF. The system level trigger rate limit is about 700 Hz in all channel readout mode. When in hit channel readout mode, supposing that typically 10 percent of channels are fired, trigger rate can go up to about 7 kHz. This system has been tested with Micromegas detector and GEM detector, confirming its capability in MPGD readout. Details of hardware and FPGA firmware design, as well as system performances, are described in the paper.
A series of novel composite microfibers composed of β-cyclodextrin (β-CDs) functionalized POM (polyoxymethylene) were prepared using electrospining technology with a mixture of hexafluoroisopropanol ...(HFIP) and N,N-dimethylformamide (DMF) as solvent. The concentration of β-CDs with respect to the POM was varied from 0 to 50 wt.%. The effect of β-CDs content on the morphology of POM/β-CD composite microfiber was investigated. The results showed that the introduction of β-CDs reduced the surface roughness and porosity of the microfibers, and the morphology of the fibers was changed. The increase of β-CDs content from 10% to 50% has led to increased average diameter of POM/β-CD composite fiber from 2.1 μm to 6.4 μm. The mechanical properties of the blend fiber mats were further investigated. In addition, silver nanoparticles were introduced to the POM/β-CD composite microfiber matrices during electrospinning. The POM/β-CD composite fiber allows CDs to form host–guest complexes with various small molecules and macromolecules. The TEM, SEM, XRD, and XPS were utilized to characterize the prepared samples. The data suggest that Ag nanoparticles were homogeneously distributed within the POM/β-CD fibers, and no aggregation was observed. The catalytic activity of Ag nanoparticles was tracked by ultraviolet-visible (UV-vis) spectroscopy which showed excellent catalytic degradation performance of organic dyes in the presence of NaBH4. The Ag/POM/β-CD mats are promising for use in waste treatment, molecular recognition, catalysis, and so on.
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