Search

A molecular complex Mo2O2(μ-S)2(Et2dtc)2 (dtc = dithiocarbamate) is prepared and loaded onto carbon cloth (CC) through facile solvothermal treatment, followed by subsequent single-source pyrolysis. This results in a highly porous 2H-MoS2/CC composite with a sponge-like stacked lamellar morphology. Due to its high porosity and unique nano/microstructure, the MoS2/CC composite exhibits a specific capacitance of 550.0 F g−1 at 1 A g−1, outperforming some 1T-MoS2 based electrodes. The composite is further assembled into a symmetric all-solid-state supercapacitor, which can be operated stably at a wide potential window and shows a specific capacitance of 127.5 F g−1 at 1 A g−1. In addition, the device delivers a high energy density of 70.8 W h kg−1 at 1 kW kg−1, which still remains 15.0 W h kg−1 at 18.0 kW kg−1. 75% of the performance of the device can be retained after 8000 cycles. Such remarkable electrochemical performance is attributed to its novel nano/microstructures with a large surface area, convenient ion transport pathways, enhanced conductivity, and improved structural stability. Thus, this work demonstrates a highly promising dithiocarbamate-based single-precursor pyrolysis route towards the fabrication of metal sulfides/carbon composites for energy storage applications.

Li-ion batteries attract great attention due to the rapidly increasing and urgent demand for high energy storage devices. MAX phase compounds, layered ternary transition metal carbides and/or nitrides show promise as candidate materials of electrodes for Li-ion batteries. However, the highest specific capacity reported up to now is relatively low (180 mA h g-1), preventing them from use in real applications. Exploring more MAX phase compounds with delaminated two-dimensional structure is an effective solution to increase the specific capacity. Herein, we report the reversible electrochemical intercalation of Li+ into Ti2SnC (MAX phase) nanosheets. Owing to the synergistic effects of intercalation and dimethyl sulfoxide (DMSO)-assisted exfoliation, Ti2SnC nanosheets are successfully obtained via sonication in DMSO. Moreover, when using as an anode of a Li-ion battery, Ti2SnC nanosheets exhibited an increasing specific capacity with cycling due to the exfoliation of Ti2SnC nanosheets via reversible Li-ion intercalation. After 1000 charge-discharge cycles, Ti2SnC nanosheets delivered a high specific capacity of 735 mA h g-1 at a current density of 50 mA g-1, which is far better than other MAX phases, such as Ti2SC, Ti3SiC2 and Nb2SnC. The current work demonstrates the Li-ion storage potential and indicates a novel strategy for further intercalation and delamination of MAX phases.

There have been over 17 million COVID-19 infections worldwide up to July 31, 2020, but the exact transmission route remains a subject for debate. Virus load in different-sized respiratory droplets is the key to address the above question. Investigation on the droplet deposition characteristics during exhalation inside the respiratory tract will facilitate the understanding of their origin and importance in transmitting the respiratory infection. Based on a realistic respiratory model, this study utilized the computational fluid dynamic (CFD) simulation to investigate the deposition of droplets originating from infection sites like pharynx, larynx and trachea under three flow conditions, namely 30 L/min (representing the normal breathing condition), 60 L/min (speaking) and 180 L/min (coughing). The SST k - ω turbulence model integrated in ANSYS Fluent software was utilized to obtain the flow field inside the respiratory tract by solving the continuity and momentum equations, and the Lagrangian approach was used to calculate droplet motion and deposition with the discrete random walk model to account for the turbulence fluctuation effect. Evaporation of droplets was not considered inside the saturated respiratory tract. Droplet diameter, flow rate of the exhaling air, and complexity of the respiratory tract geometry are the most important factors in determining the deposition pattern of respiratory droplets. It is revealed that the largest droplet that originates from the joint of pharynx and larynx and is able to escape out of the respiratory tract is about 20 µm (30 L/min) or 10 µm (60–180 L/min) in diameter; the so-called cut-off sizes for vocal cord and trachea originated droplets are 7 µm (30 L/min), 5 µm (60 L/min) or 3 µm (180 L/min). Larynx and joint of larynx and pharynx are the most important deposition sites due to their complexity in geometry and the existence of the laryngeal jet, whose velocity is up to 102 m/s during coughing and 32 m/s during speaking; the nasal cavity is also effective in trapping relatively small droplets as the airflow has a sudden change in direction before entering the oral cavity. Under the investigated speaking scenario (60 L/min), the escape rate of 1 µm droplets is around 50%, and the maximum escape rates of 5 and 10 µm droplets are respectively 13.1% and 1.3% (originating from the joint of pharynx and larynx). Although large droplets up to several hundred micrometers can be produced inside the oral cavity due to the atomization mechanism, they seldom carry pathogen. Thus, for COVID-19 patents in the early stage of infection who show upper respiratory symptoms, the cut-off size of virus-laden droplets released into the environment is about 20 µm; with the shifting of infection to the lower respiratory tract in the later stage, the cut-off size decreases to 7 µm. Respiratory droplets evaporate immediately after escaping into the indoor environments and shrink to about one third of their initial size, so airborne route is speculated to be important in the transmission of COVID-19. Further investigations considering realistic flow conditions together with droplet sampling experiments on human volunteers are necessary to confirm these cut-off sizes.

A proton therapy facility based on an isochronous superconducting cyclotron is under constructed at the Proton Therapy Facility of the Huazhong University of Science and Technology. Due to the limi...

A new proton therapy facility is under construction in Huazhong University of Science and Technology. Scanning magnets play an important role in this device. They can form an arbitrary two-dimensional radiation shape conformal with the tumor. In the pencil beam scanning system, the magnetic fields are excited by time-varying currents and the maximum repetition is up to 50 Hz. Therefore, the temperature rises of two magnets caused by eddy currents should be considered. In this paper, the coupling analysis of Multiphysics was carried out by COMSOL electromagnetic thermal module to optimize the magnetic pole structure of the scanning magnet. The tapered air gap of the downstream magnet X was designed to match the deflection envelope of the proton beam after the upstream magnet Y. The pole of the magnet SMX was optimized to meet the requirement of the local and integral fields. The module of natural convection and surface heat radiation were used to replace the empirical heat transfer coefficient in the thermal analysis so that the simulation agrees better with reality. The results show that the accuracy of the heat transfer coefficient should be further validated by comparison with the simulation that is more realistic.

Two different structures of MoSi2 coatings were prepared on Niobium based alloys by using a two step process. The as-deposited type(a) MoSi2 coating structure consists of a MoSi2 layer on the surface and a NbSi2 layer underneath, while the type(b) MoSi2 coating consists of an outer MoSi2 layer and an inner unsiliconized Mo layer. The oxidation behaviors of the two different types MoSi2 coatings were examined at 1200 °C for 100 h in air, and the mass gains of type(a) and type(b) MoSi2 coated specimens were 0.64 mg/cm2 and 0.59 mg/cm2 respectively. The excellent oxidation resistance of both type(a) and type(b) MoSi2 coated samples at 1200 °C was due to the formation of a dense and continuous SiO2 scale during oxidation. As the CTE mismatch between the outer MoSi2 coating and the inner layer, cracks distributed within both type(a) and type(b) MoSi2 coating structures.

The study of transient heat conduction in multilayered slabs is widely used in various engineering fields. In this paper, the transient heat conduction in multilayered slabs with general boundary conditions and arbitrary heat generations is analysed. The boundary conditions are general and include various combinations of Dirichlet, Neumann or Robin boundary conditions at either surface. Moreover, arbitrary heat generations in the slabs are taken into account. The solutions are derived by basic methods, including the superposition method, separation variable method and orthogonal expansion method. The simplified double-layered analytical solution is validated by a numerical method and applied to predicting the temporal and spatial distribution of the temperature inside a landfill. It indicates the ability of the proposed analytical solutions for solving the wide range of applied transient heat conduction problems.

Iron-doped ZnTe (Fe2+:ZnTe) crystal can be used as promising gain media for mid-infrared laser. However, there are few studies in the optical properties of Fe2+:ZnTe crystal from mid-infrared to ultraviolet. In this work, large size Fe2+:ZnTe bulk crystal (the concentration of Fe ions is about 1019 cm−3) with a dimension of Φ30 mm × 50 mm was grown by the temperature gradient solution growth (TGSG) method. The luminescence and optical properties of Fe2+:ZnTe from terahertz wave to ultraviolet wave have been studied. The evaluated refractive index of Fe2+:ZnTe crystal is approximately 2.5–3.0 at the frequency range of 0.5–2.0 THz range. And its band gap is estimated to be about 2.24 eV. It is noted that strong absorptions at the wavelength of 2.8–4.7 μm and 705 nm were observed. Based on the experimental results, the energetic positions of Fe2+ center such as 3T1, 5T2, 5E in ZnTe crystal were proposed.

Traditional cathodes for aqueous Zn-ion batteries are afflicted by a limited specific capacity and fearful Zn dendrites. Herein, these troubles are disposed of with a conversion-type Zn-S battery and low-cost deep eutectic solvent (DES). By utilizing the optimized electrolyte, the symmetrical Zn battery can stably cycle over 3920 h, which also confers on the Zn-S battery an ultrahigh specific capacity of ∼846 mA h g

Tellurite glasses of TeO2 BaF2−REF3 (RE = La, Gd, and Y) co-doped with Er3+/Yb3+ were prepared and investigated comparatively for optical fiber temperature sensors. For this purpose, their thermal and optical properties were examined in detail. The J-O theory was adopted to estimate the transition properties based on absorption spectra. The dominant green emissions were observed in both of the downshifting and upconversion luminescence. The optical temperature sensing abilities based on the FIR of Er3+ green emissions were studied under both of the UV (380 nm) and NIR (980 nm) excitations. Results show that these three tellurite glasses, especially for the TBG glass, should be very qualified for the design of optical fiber temperature sensors under different excitation modes.

A MoSi2 coating was prepared on Nb-10Hf-1Ti alloys by a two-step process. The first step was arc ion plating (AIP) of the Mo layer, and the second step was halide-activated pack cementation (HAPC) of Si. The coating is composed of an outer layer of MoSi2 and an inner bond layer. After oxidation testing at 1200 °C for 100 h in a static air atmosphere, the mass gain of the coated specimen was 0.64 mg/cm2. The good oxidation resistance of the MoSi2 coating is attributed to the protective SiO2 scale generated by the oxidation process.

Constructing electronic systems without an external power source is urgently required toward self-powered photodetection. In this work, we proposed a self-driven photodetection system with a MoS2 nanosheets photodetector as light intensity sensor, a vertical contact-separate mode triboelectric nanogenerator (CS-TENG) as power source, and several LEDs as alarm. The MoS2 based planar photodetector was fabricated by conventional photolithography technique and lift-off process. It is highly sensitive for visible light illumination with high current on-off ratio and excellent reproducibility characteristics under light on-off switching. When conjuncting these functional devices, the induced output voltage of the CS-TENG is tuned by the load resistance of the photodetector, which is responded to the light intensity. The mechanism can be ascribed to the impedance matching effect between specific output characteristics of TENG and working status of photodetector. By adding a Zener diode acts as a voltage regulator, the self-driven renders the voltage and current varying from 1.58 to 20.60 V and 0.06–4.78 μA in a range of light intensity from 0 to 3.19 W/m2, respectively. Finally, it is demonstrated that the output of CS-TENG varies with the variable working states of the MoS2 photodetector and then accurately reflects on the lighted number of LEDs.

ZnTe crystal is a promising electro-optical crystal materials applied for THz generation and detection. However, there is still a big challenge to obtain large sized high quality ZnTe crystals. In this work, large sized ZnTe bulk crystals with Φ30 mm × 150 mm were grown by the traveling solvent melting zone (TSMZ) method. With the characterization of the optical and electrical properties of as-grown ZnTe crystals, the band gap (2.22 eV), high IR transmittance (around 60%), high resistivity (3.5 × 103 Ω·cm), low density (1.3 × 105 cm−2) and small sizes (3 μm - 5 μm) of Te inclusions in ZnTe crystals, low etch pit densities (1.5 × 105 cm−2), high peak intensity to FWHM ratio (2.5 × 104) of the LO peak in the Raman spectra were obtained. Furthermore, the THz transmission spectra was measured and the maximum transmittance is more than 40% at the range of 0.3 - 3 THz. Based on these results, high quality and large aspect ratio ZnTe bulk crystals can be obtained by the TSMZ technique. Our work has greatly facilitated the application of ZnTe crystals in THz device.

The electronic structure of GaSe/silicane (GaSe/SiH) van der Waals (vdW) heterostructure in response to a vertical electric field and strain was studied via first-principle calculations. The heterostructure had indirect band gap characteristics in the range [−1.0, −0.4] V/Å and direct band gap features in the range [−0.3, 0.2] V/Å. Furthermore, a type-II to type-I band alignment transition appeared at −0.7 and −0.3 V/Å. Additionally, the GaSe/SiH vdW heterostructure had a type-II band alignment under strain, but an indirect to direct band gap semiconductor transition occurred at −3%. These results indicated that the GaSe/SiH vdW heterostructure may have applications in novel nanoelectronic and optoelectronic devices.

Self-powered sensors, as the essential information notes in low power consumption of Internet of healthcare, exhibit a great potential to monitor the state of human health in real time. In this work, a bamboo-inspired self-powered triboelectric sensor (BSTS) using 3D-printing and freeze-drying fabrication processes is presented. The designed triboelectric layer with hollow and bamboo-joint microstructures has a low equivalent stiffness coefficient and a great deformation limit, contributing significantly to the high sensitivity and wide detection range of BSTS. An electromechanical model was proposed to better understand the influence mechanism of inner structures in the dielectric layer on the sensing performance. The sensitivity of the BSTS can reach 3.627 kPa-1 in the pressure range of 0-8 kPa and still keep 1.264 kPa-1 in the range of 8-80 kPa. Moreover, the BSTS is able to detect tiny pressure as low as 5 Pa and possesses ultra-fast response time of 40 ms. A touch-controlled lighting system and a sitting posture monitoring system based on the BSTS for healthcare application are demonstrated. This strategy paves a way to fabricate the self-powered triboelectric pressure sensor with high sensitivity in all working ranges.

The portable UV photodetector is used to timely remind humans of overexposure to UV radiation. However, the traditional UV photodetector cannot meet the practical demands, and the power supply problem hinders its further development. In this work, we demonstrated a flexible, transparent, and self-powered UV photodetector by coupling of triboelectric and photoelectric effects. The device integrates a flexible ZnO nanoparticle (NP) UV photodetector, a transparent- and flexible-film-based TENG (TFF-TENG), commercial chip resistors, and LEDs on the PET thin film. The TFF-TENG could harvest mechanical energy from finger tapping and sliding motion and power the ZnO NP UV photodetector to realize self-powered detection. The voltage of the constant resistors connected with the UV photodetector in series changes from 0.5 to 19 V under the UV light with power intensities increasing from 0.46 to 21.8 mW/cm2, and the voltage variation is reflected by the number of LEDs directly. The excellent flexibility and transparency of the device could extend its application scenarios; for example, such a portable device could be applied to real-time monitoring of the UV radiation to remind humans of intense UV light.

We propose an injection-locked VCSEL on silicon photonics through a grating coupler to enhance the injection directionality. The measured coupling efficiency of the coupler is -2.5 dB at 1546.8 nm under 10o incidence.

The application of recycled fibers is steadily increasing in various paper products recently. It is necessary to improve the mechanical properties of paper products made from these fibers. An eco-friendly polymeric additive, sodium alginate (SA), was prepared from waste seaweeds and developed as functional additives. The properties of SA were characterized by proton nuclear magnetic resonance, Fourier transform infrared spectroscopy, thermal gravity analysis, gel permeation chromatography, and compared with the commercial SA. Coupled with polyamideamine-epichlorohydrin (PAE), the extracted SA was used to enhance the mechanical properties of paper from recycled fibers. The surface and cross-section morphology of the paper were measured by scanning electron microscopy and discussed. Compared with the single addition of PAE, the SA-PAE binary system significantly improved the mechanical properties of paper sheets.

Surface-microengineering of the active layer in triboelectric tactile sensor enables to effectively reduce the surface stiffness of the non-ideal planar triboelectric film and increase the contact area during the triboelectric process. In this work, a facile and dynamically controllable two-step method based on the unique characteristic of ferrofluid has been proposed to fabricate a high-performance self-powered triboelectric tactile sensor. Through adjusting the distance and rotating angle of magnet, ferrofluid spikes with different lengths and inclination angles ranging from 30° to 90° can be obtained. The adjustable microstructures distributed on the active layer were analyzed theoretically and verified experimentally, indicating the inclined and high microstructures can effectively facilitate the sensing performance. When the inclination angle of the microstructure is 30°, the sensitivity delivers 6.75 kPa−1 with pressure lower than 44 kPa, and keeps excellent linearity with the sensitivity of 3.01 kPa−1 even the detection pressure reaches 250 kPa. Simultaneously, the tactile sensor has a fast response/recovery time of 75 ms and 56 ms, respectively. Finally, it was demonstrated to adopt in the bionics robotic hands for weight perception and attached to various parts of the human body for detecting physiological activities with outstanding repeatability and stability.

Fluorotellurite glass ceramics (GCs) are promising photonic materials owing to their unique characteristic of integration of low cut-off phonon energy of fluorides and the high refractive index of tellurite glasses. Here, appropriate heat treatment to obtain the transparent GC from the parent glass (PG) of TeO2–Al2O3–NaF–CaF2-YbF3-ErF3 was established. The XRD, TEM, and spectroscopy techniques were employed to characterize the structure and properties of the as-prepared samples. The single fluoride phase NaYb2F7 crystallized from the PG was confirmed by XRD. TEM images displayed that in the transparent GC the nanocrystals are uniformly distributed in glassy matrix with an average size of about 6 nm. Under the 980 nm NIR excitation, the transparent GC exhibited bright upconversion luminescence in the visible region with intensity enhancement of ~73% comparing with the PG. The upconversion fluorescence kinetics were studied, along with the upconversion mechanism analyzed in details. Furthermore, the dependence of upconverted fluorescence intensity ratio (FIR) of the 2H11/2 → 4I15/2 emission to 4S3/2 → 4I15/2 emission from Er3+ ions on temperature was studied over a temperature range of 323–548 K. The results have shown that the Er3+:NaYb2F7 imbedded transparent fluorotellurite GC can be favorably employed for temperature sensing.

Long term thermal stability and temperature induced ageing mechanisms of different solar absorber coatings are investigated in this study. These coatings are chromium, chromium nitride and chromium oxynitride based coatings on aluminium substrate. The coatings were annealed at 278 °C for 600 h during the first round test. The second round test was performed at 308 °C for 342 h. An additional test at 400 °C for 200 h is designed for the sake of obtaining more degradation information. Thermal stability, microstructure, composition distribution, element diffusion and oxidation were studied using UV/VIS/NIR spectrophotometer, FTIR spectrometer, scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD) and Auger electron spectroscopy (AES) respectively. The result shows that the main ageing mechanism is diffusion and oxidation of Cr, Al, N and O. And the microstructure defects, such as enlarged grain boundaries, micro cracks and holes, act as a facilitating role during the ageing process because they provide fast diffusion paths for short-circuit diffusion.

The reliability of a substrate curvature-based stress measurement method for CrN thin films on substrate with fluctuant surface was discussed. The stress error led by the ignorance of substrate thermal deformation was studied. Results showed that this error could be as large as several hundred MPa under general deposition conditions. Stress in the CrN thin films with different thicknesses ranging from 110 to 330 nm on stainless steel was studied by this method, in comparison with conventional results on silicon wafer. The thin films’ morphology and structure were investigated and related to the film stress. A significant result of the comparison is that stress evolution in the thin films on steel obviously differs from that on silicon wafer, not only because the two substrates have different coefficients of thermal expansion, which provokes thermal stress, but also the considerable discrepancy in the thin films’ grain coarsening rate and structure that induce different intrinsic stresses.

Purpose The aim of this work was to experimentally demonstrate the feasibility of x-ray acoustic computed tomography (XACT) as a dosimetry tool in a clinical radiotherapy environment. Methods The acoustic waves induced following a single pulse of linear accelerator irradiation in a water tank were detected with an immersion ultrasound transducer. By rotating the collimator and keeping the transducer stationary, acoustic signals at varying angles surrounding the field were detected and reconstructed to form an XACT image. Simulated XACT images were obtained using a previously developed simulation workflow. Profiles extracted from experimental and simulated XACT images were compared to profiles measured with an ion chamber. A variety of radiation field sizes and shapes were investigated. Results XACT images resembling the geometry of the delivered radiation field were obtained for fields ranging from simple squares to more complex shapes. When comparing profiles extracted from simulated and experimental XACT images of a 4 cm × 4 cm field, 97% of points were found to pass a 3%/3 mm gamma test. Agreement between simulated and experimental XACT images worsened when comparing fields with fine details. Profiles extracted from experimental XACT images were compared to profiles obtained through clinical ion chamber measurements, confirming that the intensity of XACT images is related to deposited radiation dose. Seventy-seven percent of the points in a profile extracted from an experimental XACT image of a 4 cm × 4 cm field passed a 7%/4 mm gamma test when compared to an ion chamber measured profile. In a complicated puzzle-piece shaped field, 86% of the points in an XACT extracted profile passed a 7%/4 mm gamma test. Conclusions XACT images with intensity related to the spatial distribution of deposited dose in a water tank were formed for a variety of field sizes and shapes. XACT has the potential to be a useful tool for absolute, relative and in vivo dosimetry.

The fluorotellurite glasses (FTGs) of TeO2–Al2O3–NaF–CaF2–YbF3–ErF3 with varying TeO2 content were prepared. Their densities, refractive indices, and thermal behaviors were characterized and analyzed with respect to the TeO2 content. The network structural nature was studied by the IR and Raman spectral techniques. The absorption and upconversion emission spectral properties of Er3+ in the FTGs were examined. Specifically, the absorption spectra were measured and used for fitting the J-O intensity parameters. The upconversion luminescence (UCL) was examined under the excitation of 980 nm laser. Furthermore, the temperature sensing performances based on the fluorescence intensity ratio (FIR) of Er3+ upconverted green emissions were evaluated for each FTG. The results confirm that the FTGs are potential materials for optical glassy temperature sensors.

In this study, oil recovery performance and carbon dioxide (CO2) storage potential of a CO2 water-alternating-gas (CO2-WAG) injection after continuous CO2 injection process for multilayer formation were experimentally determined under immiscible and miscible conditions. First, a slim-tube apparatus was used to measure the minimum miscibility pressure (MMP) of a CO2–crude oil system (MMP = 22.79 MPa), which was applied as a guide for follow-on investigations. Afterward, the CO2-WAG injection after the continuous CO2 injection for a triple-layer system, horizontally placed and parallel-connected, was conducted to evaluate the capacity of enhanced oil recovery and CO2 storage potential of the multilayer formation at different operating pressures and a reservoir temperature of 98 °C. Results revealed that the oil recovery of the entire system was determined by the recovery of a layer with the highest permeability, which was more than 90% of the entire system recovery provided by the highest permeability layer...

AISI 316 L austenitic stainless steels (316 L SS) were nitrided to enhance their mechanical property and corrosion resistance by a high efficiency low-pressure arc plasma nitriding process at low temperature (~ 400 °C). Arc currents ranging from 55 A to 95 A were applied to generate the arc plasma. The effect of arc current on the microstructure, mechanical property of the nitrided layers was investigated by using XRD, SEM, TEM, Vickers microhardness tester and ball-on-disk tribometer, respectively. The corrosion resistance was also evaluated by potentiodynamic polarization in 3.5% NaCl solution. The results showed that the nitrided layers consisted primarily of the expanded austenite (γN) phase with a trace of a mixture of CrN and Fe3N. The thickness of nitrided layer could reach 15 μm in 1 h at 400 °C in virtue of the high-density and high-energy nitrogen plasma generated from this process, which showed an extremely fast nitriding kinetics. Due to the solution strengthening of the nitrogen super-saturation γN-phase formed on the surfaces of the samples, the surface microhardness and the wear resistance of the nitrided 316 L SS was significantly improved. The worn surfaces revealed that worn behavior of the low current (below 85 A) nitrided samples was remarkably dominated by micro-abrasion and spalling holes, while the 95 A sample was worn in a mode featured by cracks and spalling blocks. Besides, because chromium nitride precipitation was eliminated, the nitrided samples still showed excellent corrosion resistance, which was comparable to untreated 316 L SS.

Tungsten oxide thin films were deposited at room temperature under different negative bias voltages (Vb, 0 to −500 V) by DC reactive magnetron sputtering, and then the as-deposited films were annealed at 500 °C in air atmosphere. The crystal structure, surface morphology, chemical composition and transmittance of the tungsten oxide thin films were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS) and UV–vis spectrophotometer. The XRD analysis reveals that the tungsten oxide films deposited at different negative bias voltages present a partly crystallized amorphous structure. All the films transfer from amorphous to crystalline (monoclinic + hexagonal) after annealing 3 h at 500 °C. Furthermore, the crystallized tungsten oxide films show different preferred orientation. The morphology of the tungsten oxide films deposited at different negative bias voltages is consisted of fine nanoscale grains. The grains grow up and conjunct with each other after annealing. The tungsten oxide films deposited at higher negative bias voltages after annealing show non-uniform special morphology. Substoichiometric tungsten oxide films were formed as evidenced by XPS spectra of W4f and O1s. As a result, semi-transparent films were obtained in the visible range for all films deposited at different negative bias voltages.

In the present study, WB 2 (N) films are fabricated on silicon and YG8 substrates at different N 2 pressures by reactive magnetron sputtering. The influence of N 2 partial pressure ( P N2 ) on the film microstructure and characteristics is studied systematically, including the chemical composition, crystalline structure, residual stress, surface roughness as well as the surface and the cross-section morphology. Meanwhile, nano-indentation and ball-on-disk tribometer are performed to analyze the mechanical and tribological properties of the films. The results show that the addition of nitrogen apparently leads to the change of the structure from (1 0 1) to (0 0 1) orientation then to the amorphous structure with the formation of BN phase. And the addition of nitrogen can greatly refine the grain size and microstructure of the films. Furthermore, the residual stress of the film is also found to change from tensile to compressive stress as a function of P N2 , and the compressive stress increases with P N2 . The WB 2 (N) films with small nitrogen content, which are deposited at P N2 of 0.004 and 0.006 Pa, exhibit better mechanical, tribological and corrosion properties than those of other films. Further increase of nitrogen content accelerates the formation of BN phase and fast decreases the film hardness. In addition, the large N 2 partial pressure gives rise to the target poisoning accompanied by the increase of the target voltage and the decrease of the deposition rate.

It has long been a dream to achieve tumor targeting therapy that can efficiently reduce the toxicity and severe side effects of conventional antitumor chemotherapeutic agents. Taking advantage of the abnormalities of tumor vasculature, we demonstrate here a new powerful tumor vascular-targeting therapeutic technique for solid cancers that applies advanced nanotechnology to cut off the nutrient supply of tumor cells by physically destroying the abnormal tumor blood vessels. Water soluble magnetic Gd@C82 nanocrystals of the chosen sizes are deliberately designed with abilities to penetrate into the leaky tumor blood vessels. By triggering the radiofrequency induced phase transition of gadofullerene nanocrystals while extravasating the tumor blood vessel, the explosive structural change of nanoparticles generates a devastating impact on abnormal tumor blood vessels, resulting in a rapid and extensive ischemia necrosis and shrinkage of the tumors. This unprecedented target-specific physiotherapy is found to work perfectly for advanced and refractory solid tumors.

The paramount parameters to determine the electrical output of triboelectric nanogenerator (TENG) are the surface triboelectric charges and the electrostatic induced transferred charges between triboelectric layer and electrode. However, diffusion of surface charge into the triboelectric layer reduces the surface charge density and thus weakens the electrostatic induction effect. In this work, we present a multifunctional layered TENG (ML-TENG) with an addition of reduced graphene oxide and Ag nanoparticles hybrid layer between a PVDF membrane triboelectric layer and bottom Al electrode to trap and block the interfacial charges. The output performance of ML-TENGs significantly yields 50 μC m−2 in charge density, which is improved by 500% compared with that of a traditional TENG. The surface potential of the PVDF membrane before triboelectrification drops with the insertion of the rGO-AgNPs hybrid layer, demonstrating the larger triboelectric potential difference and a better output performance. The trapping effect of rGO caused by sp2-hybrid structured carbon-atom coupled with the enhanced polarization effect by AgNPs to prevent interfacial charges from diffusing and drifting, providing efficient enhancements in TENG output. The output peak power from the TENG with a rGO-AgNPs hybrid layer reaches approximately 5.4 mW, which is 67.5 times that of a pristine TENG. Finally, the mechanism of the rGO-AgNPs layer working as the charge-trapping-blocking sites has been investigated and elaborated. It is anticipated to offer a new insight to the material science and device structure design for improving the performance of triboelectric devices.

Tellurite glass-ceramics co-doped with Yb3+/Er3+ were fabricated and investigated for optical purpose. The thermal properties of parent glass were analyzed to make appropriate heat treatment schedule for preparing glass-ceramics. The XRD, TEM, FT-IR, and spectroscopy were used to characterize the samples. The Y2Te6O15 was confirmed as precipitation of monocrystalline phase in the glassy matrix. The transparent glass-ceramic was obtained with sphere-liked crystalline particle size about 10 nm by adjusting the crystallization dwell time. Under the 980 nm NIR excitation, the transparent glass-ceramic has exhibited bright upconversion luminescence with an enhancement of ~40% comparing with its parent glass. Results indicate that the Yb3+/Er3+ co-doped tellurite glass-ceramic has good potential for optical and photonic applications such as upconversion luminescent concentrator for solar cells.

To improve the precision in radiation therapy and optimize treatment strategies during the radiotherapy, in vivo radiation dosimetry monitoring which measures the actual dose received in and around target region during treatment becomes necessary. Given the fact that X-ray induced acoustic amplitude is proportionally correlating to X-ray absorption, we propose applying X-ray acoustic computed tomography (XACT) to monitor X-ray dosimetry during radiotherapy. A prototype X-ray acoustic (XA) detection system with single immersion ultrasound transducer, which was positioned by a motor controlled rotation stage, was synchronized with a medical linear accelerator to acquire the XA signal at each rotating position. A porcine gel phantom, which is embedded with equally spaced lard made cylindrical indicators, was shot by different X-ray beams modulated by physical wedge filters (with wedge angles of 15°, 30°, 45° and 60°). The reconstructed 2D XACT images not only showed the positions of the indicators but also displayed the different intensity profiles for each indicator, which had good correlations with the corresponding dose distributions captured in radiochromic film tests. A dose difference as small as 3.6% can be determined. Moreover, a phantom imitating complex scenario of body, which has lard made indicators covered by different materials (bone, muscle and air-gap), was shot by uniform beam. The variances of dose delivered to target regions suffering different attenuations were successfully presented in XACT images. The results of phantom experiments have proved that XACT can be a promising technique in monitoring the 2D dosimetry during radiotherapy with high sensitivity and good accuracy.

Purpose To study, using phantoms made from biological tissues, the feasibility and practical challenges of monitoring the position of the radiation beam and the deposited dose by x-ray acoustic computed tomography (XACT) during external beam radiotherapy delivery. Material and methods A prototype XACT system with a single immersion ultrasound transducer, which was positioned around the target sample driven by a motor-controlled rotation stage, was used to acquire the x-ray acoustic (XA) signals produced by a medical linear accelerator (Linac) to form an XACT image of the irradiated phantom. To investigate the feasibility of XACT in tracking the position of radiation dose, a large piece of veal liver with embedded fat tissue was imaged and beam misalignments were measured. Next, we explored the sensitivity of XACT in monitoring and quantifying the delivered dose, in which a block of porcine gel was embedded with equally spaced lard cylinders and imaged. The doses on the lard cylinders modulated by physical wedges were quantified from the XACT image and were verified by comparison to measurements from radiochromic films as the gold standard. Then, to simulate how XACT can perform in a targeted tissue in the human body, a porcine gel phantom with lard cylinders covered by different materials (bone, muscle, and air gap, respectively) was also imaged. Results The reconstructed XACT images of the phantoms show congruence with the boundaries of the beam field and the interfaces between the different tissue materials. The beam displacement from the target was tracked properly by the reconstructed XACT images. An intensity difference as small as 2.9% in delivered dose region can be measured from XACT images P = 0.02. The intensities of XACT images were highly correlated to the film measurements with an R2 better than 0.986. The expected variances of dose delivered to different target regions as a result of the difference in attenuation were successfully captured by the XACT images. Conclusions This study validated the feasibility of XACT in accurately obtaining relative dose maps of tissue-mimicking phantoms. XACT offers a practical method for verifying the beam position against the target and quantifying the relative dose delivered to the target during external beam radiotherapy.

We report a laser-diode end-pumped high-repetition frequency laser operating at 1.34 μm. Under acousto-optic Q-switched operation frequency of 50, 75, and 100 kHz, we study experimentally the characteristics of the output pulse versus the pump power. At 11.6 W pump power and 100 kHz repetition rate, we obtain an average output power of 2.33 W with a pulse width of 153.6 ns and a peak power of 150 W. We achieve a peak–peak pulse fluctuation of less than 10%.

Nickel hydroxide is widely used as cathode materials in nickel-metal secondary batteries. In this work, Mn-substituted nickel hydroxide samples with a special α/β mixed phase structure were synthesized by chemical co-precipitation method. The physical properties were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC) and field emission scanning electron microscopy (FE-SEM). The results show that the structure of the samples and the amount of intercalated anions and water molecules are highly related to the content of the Mn substituted. Their electrochemical performances were characterized by charge/discharge tests and electrochemical cycle tests. The results demonstrate that the Mn-substituted samples with a α/β mixed phase structure perform a much higher discharge capacity than normal β-nickel hydroxide. The specific discharge capacity reaches 330 mAh·g−1 after 50 cycles of charge/discharge in charging rate of 0.2C under ambient temperature. Meanwhile, the samples show no capacity loss in electrochemical cycles, which indicates that the mixed phase nickel hydroxide maintains high structure stability.

Phase behavior of hydrocarbon fluids is closely related to porous media. However, there are many limitations of current detection techniques. Therefore, it is very urgent to find a suitable method to solve this problem. In this paper, based on the brine and three natural cores from Jilin oilfield, the relations of the interval transit time and fluid saturation of these cores both in brine/air system and kerosene/air system were measured, and the difference of these relations during the process of displacement, imbibition and air drying were compared and analyzed. Results show that the ultrasonic technique is a potential method to invert fluid saturation in porous media.

Lanthanide-based multimodal probes with high sensitivity, simple synthesis strategy, and good biocompatibility promise new applications for clinical diagnosis. However, today's challenge is not only to develop high-performance multimodal probes for more accurate and reliable diagnosis, but also to understand the fate of these probes in vivo. In this context, a novel PEGylated Dy-doped NaGdF4 nanoprobe (PEG-NaGdF4:Dy) was designed and fabricated as a T1/T2-weighted MRI/CT imaging agent. This nanoprobe has a distinct longitudinal relaxivity (r1 = 5.17 mM(-1) s(-1)), relatively high transverse relaxivity (r2 = 10.64 mM(-1) s(-1)), and exhibits strong X-ray attenuation properties (44.70 HU L g(-1)) in vitro. Furthermore, T1/T2-weighted MRI/CT imaging in vivo confirmed that this PEG-NaGdF4:Dy nanoprobe could lead to a significant contrast enhancement effect on liver, spleen and kidney at 24 h post injection. The MTT assay, histological analysis, and biodistribution investigation demonstrated that this multifunctional nanoprobe possessed relatively low cytotoxicity, negligible tissue damage and could be completely excreted out of the body of mice as time prolonged. Therefore, the present PEG-NaGdF4:Dy nanoprobe has the potential for the development of multifunctional T1/T2-weighted MRI/CT imaging to provide more comprehensive and accurate diagnosis information.

The Cr–Mo–N films were deposited on high speed steel (HSS) substrates by a DC reactive magnetron sputtering equipment coupled with two horizontal magnetron sources. The effects of substrate negative bias voltage (Vb), substrate temperature (Ts) and gas flow ratio (R = N2/(N2 + Ar)) on the microstructure, morphology, as well as the mechanical and tribological properties of the Cr–Mo–N films were investigated by virtue of X-ray diffraction (XRD) analysis, X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), nano-indentation test, ball-on-disk tribometer, and Rockwell indenter et al. With increasing Vb to −100 V, the preferred orientation of the films changed from (111) to (200) and their mechanical and tribological properties were improved gradually, too. It was also found that Ts gave a significant effect on mechanical property enhancement. When the Ts reached 300 °C, the film obtained the highest hardness and effective elastic modulus of approximately 30.1 and 420.5 GPa, respectively and its critical load increased to about 54 N. With increasing R, the phase transformation from body-centered-cubic (bcc) Cr and hexagonal CrMoNx multiphase to single face-centered-cubic (fcc) solid solution phase was observed. The correlations between values of hardness (H), effective elastic modulus (E*), H/E*, H3/E*2, elastic recovery (We) and tribological properties of the films were also investigated. The results showed that the elastic recovery played an important role in the tribological behavior.

The gasochromic effect and its potential applications of tungsten oxide (WO3) thin films are introduced. The research progress in gasochromics mechanism of WO3films is reviewed and various mechanism models are summarized and discussed. The double injection model, oxygen vacancy diffusion model and localized water molecules model are extensively used to explain the gasochromic coloration of WO3films. A perspective on the gasochromics mechanism development of WO3films is tended to fabricate WO3film with single crystal and regular structure, which may simply the quantitative characterizations induced by the complicated structure. Elucidating gasochromics mechanism of WO3films not only helps to understand gasochromic coloration phenomenon well but also improves the performance of gasochromic coloration devices. It also accelerates the development of the relative science, such as gas detector, atom/ion transport material, surface catalysis of semiconductor, and so on.

Horizontal drilling and hydraulic fracturing have been proven to significantly increase production from tight oil formations, however, one of the characteristics of these reservoirs is high production declining rate. In the long term, it is necessary to increase the development efficiency of block matrix, many studies have shown that spontaneous imbibition is a potential way. In addition, precisely predicting the behavior of the imbibition recovery under different viscosity ratios is thus critically important. The goals of this paper include theoretically and experimentally investigating the effect of the viscosity on the imbibition recovery. In this paper a novel pore-scale spontaneous imbibition model is established by two steps. At first, the spontaneous imbibition equation in a single capillary tube considering that immobile oil is established based on Hagen Poiseuille formula. Then, pore-scale spontaneous imbibition model based on fractal theory has been derived. In addition, the corresponding spontaneous imbibition tests have been conducted on sandstone natural cores collected from Xinjiang oilfield. The predictions of the imbibition recovery by the proposed model have been validated by comparing them with the experiments conducted. Data of cores H-56 and H-39 are used to comparing the calculated imbibition recovery with the measured imbibition recovery. Under four different oil/water viscosity ratio, 0.5, 1, 5 and 10, the relative errors between calculated data and measured data are less than 7%. And both the theoretical and experimental results show that the viscosity ratio of the mixed oil and brine has a significant effect on the spontaneous imbibition recovery. The predicted and experimental results demonstrate that a higher imbibition recovery corresponds to a lower oil/brine viscosity ratio. In addition, rate of spontaneous imbibition has a significant decline which is the same as the result of the calculation. In general, since the established model has a high precision, it can be used to analyze the effects of different parameters like the contact angle, the interfacial tension and other structural parameters and the results can be useful for understanding the spontaneous imbibition law. What's more, the conclusion can guide the surfactant screening in surfactant-aided imbibition schemes.

The research progress in gasochromics of nano-structured WO3film is reviewed. Various fabrication methods of the nano-structured WO3film are summarized and compared. Recent gasochromic applications of the nano-structured WO3film is introduced. The gasochromic properties were significantly enhanced by applying nanostructures, resulting in faster responses, higher stability and higher optical modulation. A perspective on the development trends in fabrication of nano-structured WO3film and devices is also proposed.

In this study, AlB2-type WB2 films are deposited on YG8 (WC–Co) substrates by DC magnetron sputtering at different substrate bias voltages and temperatures. Their effects on the film microstructure, elemental composition, mechanical and tribological properties are investigated systematically by various analysis methods, including X-ray diffraction (XRD), electron probe X-ray microanalyzer (EPMA), field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM), atomic force microscopy (AFM), nano-indentation, ball-on-disk tribometer and micro scratch tester. The as-deposited films show an under-stoichiometric composition with rich tungsten concentration and have an obvious columnar structure. With the substrate bias voltage increasing (from 0 V to − 150 V), the orientation of the films changes from (0 0 1) to (1 0 1). And films obtained at − 50 V show superior mechanical and tribological properties. By increasing the substrate temperature to 500 °C, the maximum hardness about 40.5 GPa and the best adhesive strength of 60 N are detected. The films with the fine-grain amorphous structure, produced at 300 °C and − 50 V, exhibit the minimum friction coefficient of 0.28. And the minimum wear rate of 2.3 × 10− 7 mm3/mN is obtained for the films deposited at − 50 V and 400 °C. The properties described above are attributed to the variations of microstructure and morphologies in the films. Furthermore, the wear track and debris are also discussed by virtue of FESEM/EDS to explore the self-lubricating behavior of the AlB2-type WB2 film.

The effect of the anchoring group of surface ligands on the magnetic properties, especially relaxometric properties, of PEGylated Fe O nanoparticles is investigated. Systematic experimental results together with in-depth theoretical analysis reveal that the ligand binding affinity can largely vary the saturation magnetization, whereas conjugated anchoring groups can remarkably enhance the transverse relaxivity, which highlights a novel approach for achieving high-performance MRI contrast agents.

Thermal expansion coefficient of AlB 2 -type WB 2 was investigated using in-situ x-ray diffraction (XRD) measurements and quasi-harmonic Debye approximation combined with density functional theory (DFT) calculations. The calculated average volumetric thermal expansion coefficient 24.86 × 10 −6 K −1 agrees with the experimental value 21.52 × 10 −6 K −1 in the temperature range of 298 K to 473 K. Different linear thermal expansion coefficients along the a (6.04 × 10 −6 K −1 ) and c (9.39 × 10 −6 K −1 ) directions have been found experimentally. This anisotropic behavior is attributed to the different bonding characteristics along the two directions. A Lindemann-like melting rule has been found for AlB 2 -type MB 2 ( M = Ti, Zr, V, Nb, Ta, Cr, Mo and Mn), and the melting point of AlB 2 -type WB 2 has been estimated about 2833.80 ± 18.4 K according to this rule. Furthermore, the temperature and pressure dependence of thermal expansion and heat capacity is also studied. To our knowledge, it is the first time to investigate the thermal properties of AlB 2 -type WB 2 .

Tungsten-trioxide (WO3) films were deposited using two types of sputtering systems: a planar magnetron sputtering system and a facing-target sputtering (FTS) system. The structure and gasochromic properties of the resulting films were compared, and film uniformity and gasochromic properties were found to be significantly improved when using FTS because the incidence of high-energy negative oxygen ions on the substrate during sputtering was significantly suppressed. The authors confirmed that the deposition rate of WO3 films increased by hundreds of times with an increase of the sputtering voltage from 500 to 800 V in the FTS system, and a deposition rate above 100 nm/min was easily achieved. The authors clarified that the deposition rate of the WO3 film strongly depends on the sputtering voltage under the condition of a constant sputtering current.Tungsten-trioxide (WO3) films were deposited using two types of sputtering systems: a planar magnetron sputtering system and a facing-target sputtering (FTS) system. The structure and gasochromic properties of the resulting films were compared, and film uniformity and gasochromic properties were found to be significantly improved when using FTS because the incidence of high-energy negative oxygen ions on the substrate during sputtering was significantly suppressed. The authors confirmed that the deposition rate of WO3 films increased by hundreds of times with an increase of the sputtering voltage from 500 to 800 V in the FTS system, and a deposition rate above 100 nm/min was easily achieved. The authors clarified that the deposition rate of the WO3 film strongly depends on the sputtering voltage under the condition of a constant sputtering current.