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The combined effects of proton irradiation and forward gate-bias stress on the interface traps of AlGaN/GaN heterostructure have been studied in this article. It is found that the effect of proton irradiation and forward gate-bias on the shift of flat band voltage $V_{\mathrm {FB}}$ is independent. By utilizing the frequency-dependent conductance technique, it is found that the trap density $D_{\mathrm {T}}$ at metal/AlGaN interface decreases after proton irradiation and the $D_{\mathrm {T}}$ at most energy levels increases after the following forward gate-bias. The $D_{\mathrm {T}}$ at AlGaN/GaN interface increases after proton irradiation and then decreases after the following forward gate-bias. The energy level range of metal/AlGaN interface traps reduces significantly under the forward gate-bias for the irradiated devices, however, that of AlGaN/GaN interface traps decreases little. In summary, the combined effect of proton irradiation and forward gate-bias stress on the interface traps is more complex than that on the bulk traps in AlGaN layer.

The effect of gamma ( $\gamma $ )-irradiation on AlGaN-based light-emitting diodes (LEDs) in the short-wavelength ultraviolet (UVC, 210–280 nm) spectral range under electrical stress is characterized by electroluminescence and current–voltage measurement. Different from previous reports that $\gamma $ -irradiation can hardly damage nitride devices, we observe that the optical power decreases and leakage current increases obviously after electrical stress under $\gamma $ -irradiation. To delve into the nature of degradation, variation of defects is studied using temperature-dependent low-frequency noise measurement. After stress, the ~0.78-eV defects attributed to N antisite are generated and lead to device degradation, which is accompanied by a reduction of the intrinsic Ga vacancy with an energy level of ~0.38 eV. The variation of defects after stress in $\gamma $ -irradiated environment is more evident than that in nonirradiated environment, which is well corresponding to the performance degradation behavior. In conclusion, $\gamma $ -irradiation is found to accelerate degradation induced by electrical stress, and the study can help improve irradiation resistance in AlGaN-based UVC LEDs.

In this article, three frequency independent optical paths are designed and analyzed. A two-parabolic-mirror system and a four-parabolic-mirror system are studied and developed over 140–220 GHz to achieve precision complex permittivity measurements of a dielectric substrate. To achieve a wide plane wave zone for the center of the four-parabolic-mirror system, two 80-mm-length corrugated horns are designed and fabricated for the measurement systems. The Gaussicity of the corrugated horn is larger than 97.4%. For the multiple reflection model and direct wave model, two closed-form expressions of loss tangent are derived from the transmission parameters (insertion losses) of the measurement systems. Meanwhile, the resolution and uncertainty of loss tangent can be calculated according to the working frequency, the thickness of the wafer, the real part of the relative permittivity, and the $| {{S_{21}}} |$ measurement uncertainty. The complex permittivity of the Rogers/Duroid series PCB substrates, which are commonly used at microwave frequencies, and silicon wafers are measured in G -band.

Dielectric waveguides have potential as transmission lines in subterahertz (sub-THz) applications due to their low-loss. A new application of a rectangular dielectric waveguide (RDW) for a THz superconducting receiver system for radio astronomy is investigated and demonstrated for the first time. The RDW can be used to transmit sub-THz local oscillator (LO) signals into the cryostat for driving the superconductor insulator superconductor mixer, with very low heat transfer. A series of RDWs with different lengths are fabricated. The measured average attenuation constants of the RDW are 0.034 and 0.069 dB/mm at 3.4 and 300 K measurement environments over 240–300 GHz, respectively. The double-sideband system noise temperature of the receiver system is also measured. With this LO signal feeding system, there is only 0.69 mW thermal transfer power from the 300 to the 3.4 K cold stage. Compared to traditional pumping signal feeding schemes, such as the horn-to-horn structure and beam splitter method, this approach outperforms the traditional schemes in terms of feeding flexibility, insertion loss, and thermal isolation for the cryostat. The proposed RDW can be widely applied to superconducting receivers for radio astronomy in the future.

The development of a millimeter-wave unbalanced frequency tripler based on the nonlinear characteristics of planar Schottky varactors is presented. The entire module is designed by hybrid integration. A frequency multiplier circuit model was established to reflect the influence of diode parameters and the impedance matching on the multiplier in different frequency bands. The effect of junction imbalance on the output power of the frequency multiplier was investigated and the multiplier was improved based on the basic design. The addition of a cut microstrip stub in the improved diode unit reduced the impact of a power imbalance on frequency multiplier performance. The characteristics of the multiplier circuit were analyzed by the full-wave electromagnetic simulation of the three-dimensional structure and the harmonic balance simulation of the circuit. Test results showed that the peak output power of the improved frequency tripler was 12.6 mW at 277 GHz with an input power of 200 mW, an effective 12% improvement over the basic design.

Core-shell porphyrin-based magnetic nanocomposites with multi-functional groups were synthesized and used as effective adsorbents and crystal nuclei for removing Pb(II) from water. The effect of initial Pb(II) concentration (C0), equilibrium time and experimental temperature on the adsorption capacity has been investigated. Under the optimized conditions, the removal rate of Pb(II) can reach 84.3% only within 5 min, more efficient than similar adsorbents. In addition, the maximum adsorption capacity of FST is up to 798.34 mg/g, which is much higher than previously reported results for removing Pb(II) in aqueous solution. Furthermore, the adsorption mechanisms were proposed based on the results of field emission scanning electron microscopy (FE-SEM), ultraviolet-visible spectroscopy (UV–vis) and X-ray diffraction tests. The adsorption processes could be well described by pseudo-second-order kinetic model regardless of C0. However, when C0 was NH, C O and Si O Si in porphyrin. This study provides a facile method for removal of Pb(II) from aqueous solutions and offers theoretical and practical guidance on new adsorbent designs for selective removal of heavy metal ions.

Although there are many primary carbides in the cutting edge of knives made of high-carbon martensitic steel, the effect of primary carbides on the sharpness of knives has not been clarified. In this paper, the evolution of primary carbides during the production process of 8Cr13MoV steel was presented. The effect of size and amount of primary carbides on the sharpness of knives was studied via employing rolling forging and diffusion annealing process, respectively. Results indicated that primary carbides easily fell off from cutting edge during cutting process, which would decrease the wear resistance of knives. The refinement of primary carbides could not only improve the wear resistance of cutting edge, but also weaken the fluctuation of sharpness during the service process of knives. By decreasing the amount of primary carbides, the wear resistance of knives would increase effectively, which improved the cutting performance effectively. Reducing the amount of primary carbides and refining the primary carbides in cutting edge were both effective ways to improve the sharpness of knives.

Equilibrium swelling test was employed to determine the swelling responses of Fluororubber (FKM) and Fluorosilicone Rubber (FVMQ) in different types of solvents, and the one-dimensional solubility parameters of FKM and FVMQ were obtained with a range of 17–25 MPa1/2 and 16–20 MPa1/2 respectively. It was attempted to calculate the three-dimensional solubility parameters (HSP) of FKM and FVMQ by using a professional computer software, and a new type of bio-fuel, represented by biodiesel, was further selected as an object in this work to investigate its swellability. Flory-Huggins interaction parameter (χHSP) between FKM, FVMQ and each solvents used in this work was calculated by HSP values, and the results turned out that the swelling ratio (q) decreased with increasing χHSP value. By mathematical fitting, two functional relationships between q and χHSP for FKM and FVMQ were achieved to predict the swelling properties of rubber in fluids. The increasing use of biodiesel with their effect on rubber materials has become an important topic of industrial research. The second components, including ethanol and ethylene glycol, were added into biodiesel with the purpose of cost reduction, which however might cause a critical increase of rubber swelling. One of the possible applications of χHSP values is the prediction or explanation of swelling behavior. Therein, χHSP values between FKM, FVMQ and biodiesel/additive blends were calculated and found that χHSP firstly decreased and then increased with increase of the additive (ethanol and ethylene glycol) content. Taking advantage of this tendency one can predict the swelling properties of rubber products in the biodiesel blends and provide an important reference for such applications in liquid medium.

The precipitation and growth of primary carbides in 8Cr13MoV steel during electroslag remelting (ESR) were studied. The effects of melting rate and fill ratio of ESR on the reduction of primary carbides were clarified. Primary carbides M7C3 precipitated from liquid steel at the final stage of solidification, which is attributed to an enrichment of carbon and chromium in liquid steel. The carbon content in the residual liquid steel was the determining factor for the formation of primary carbides. The growth of primary carbides was affected mainly by the chromium-concentration and temperature-field gradients. An appropriate melting rate facilitated the nucleation and growth of dendrites, which caused dendrite closure and prevented the further enrichment of carbon atoms. Primary carbides were refined and their amount was reduced when using a lower ESR melting rate. The fill ratio can affect the uniformity of the temperature field in the liquid metal pool and heat transfer from the slag pool to the liquid metal pool, and an optimal fill ratio resulted in a minimum mushy zone and less primary carbides. The volume fraction of primary carbides was reduced by 23 pct when the melting rate decreased from 150 to 133 kg/h and the fill ratio increased from 0.23 to 0.33.

Compared with Gallium Arsenide material, GaN device has better power endurance characteristics, and hence has great potential in the development of high power source. This paper proposes a heterojunction structure of GaN Schottky diode to improve the electron mobility of the device, and the cut-off frequency is over 250 GHz. Furthermore, a 120 GHz doubler is designed based on the proposed device. The simulated result shows that the conversion efficiency reaches 15% when the input power is 1 W.

In this article, we review the terahertz (THz) dielectric transmission lines in recent decade. Moreover, the developed special measurement technologies for measuring the THz dielectric transmission lines are introduced. Final, the various application scenarios of the THz dielectric transmission lines are presented.

The phase transformation behavior of crack-arrest steel during continuous cooling either with or without deformation at high temperatures was investigated. By carefully examining the microstructures of continuous cooled samples, we found that pearlite, quasi-polygonal ferrite (QPF), acicular ferrite (AF), granular bainite (GB), upper bainite, lath-like bainite and martensite/austenite will exist depending on cooling rates and transformation temperatures in both conditions of deformation and without deformation after austenization. The transformation curves of AF and GB moved toward the left in deformation condition in comparison with that of without deformation condition, which indicated that deformation promoted the formation of QPF and AF; meanwhile, deformation inhibited the formation of bainite. Finer bainite and the accompanying M/A could be obtained by reducing the bainite nucleation activation energy as follows: (i) increasing the undercooling by increasing the cooling rate; (ii) increasing the stored energy by deformation of the austenite.

We present a theoretical study on the potential thermoelectric performance of antimony nanoribbons (SNRs). Based on density functional theory and the semiclassical transport model, the thermoelectric figure of merit ZT was calculated for various Sb nanoribbon sizes and different chiralities. The results indicated that the chemical-bond-driven edge reconstruction of nanoribbons (denoted as SNRs-recon) eliminated all of the dangling bonds and passivated all of the boundary antimony atoms with 3-fold coordination. SNRs-recon are the most energy favorable compared to the ribbons with unsaturated edge atoms. Semimetal to semiconductor transition occurred in SNRs-recon. The band gap was width-dependent in armchair SNRs (denoted as ASNRs-recon), whereas it was width-independent in zigzag SNRs (ZSNRs-recon). After nanolization and reconstruction, the TE properties of SNRs were enhanced due to higher Seebeck coefficient and lower thermal conductivity. The thermoelectric properties of n-doped ASNRs-recon and p-doped ZSNRs-recon showed width-dependent odd–even oscillation and eventually resulted in ZT values of 0.75 and 0.60, respectively. Upon increasing the ribbon width, ZT of n-doped ASNRs-recon decreased and approached a constant value of about 0.85. However, n-doped ZSNRs-recon exhibited poor TE performance compared with the others. Importantly, the ZT value could be optimized to as high as 1.91 at 300 K, which was larger than those of Sb-based bulk materials and 100 times that of thin Sb films. These optimizations make the materials promising room-temperature high-performance thermoelectric materials. Furthermore, the proposed new concept of chemical-bond-driven edge reconstruction may be useful for many other related systems.

Host immune response to tissue engineering tissues or organs directly determines the graft survival and the integration with host. Our and other previous studies have successfully regenerated the organs/tissues based on allogeneic native decellularized matrix (aNDM). But the very limited aNDM clinically hinders the artificial organs/tissues application to resolve the native organs/tissues loss with high incidence. However, the xenogeneic NDM will induce host immune rejection leading to the transplantation failure. This study constructed the xenogeneic (porcine) NDM (xNDM) which carried the immunoregulator Rosiglitazone (xNDM-RSG), a synthetic highly selective agonist of peroxisome proliferator-activated receptor-γ (PPARγ), evaluated xNDM's physical and chemical characterization, immunomodulatory properties, and its effect on the tissue regeneration. Results showed that the xNDM-RSG did not affect the proliferation and differentiation of odontogenic stem cells. In addition, the xNDM-RSG could also effectively decrease the expression of IL-1 and TNFα, and increase the expression of IL-10 and TGFβ to enable a favorable immunomodulation and promote the ligament-to-bone regeneration by PPARγ to induce the alternative activated macrophages (M2 macrophages) antagonizing classically activated macrophages (M1 macrophages). Meanwhile the xNDM-RSG obviously reduces the implants absorption and promotes the regenerated ligament-to-bone expressing the key proteins (ALP, OPN, DSP) which are relative to the native dental and bone. This study demonstrated that protein adsorption could aggravate the immune inflammatory reaction, whereas, xNDM-RSG could effectively control the host immune response to accelerate tissue reparation and regeneration by facilitating the macrophage polarization, which highlighted a new strategy for improving the transplantation survival of the artificial organ or tissue based on the xenogeneic decellularized biomaterials.

Magnetic aqueous ammonia (MAA) was prepared as a magnetic extractant for dispersive microextraction of petroleum acids (PAs). The amount of extractant in MAA was custom-made by a simple approach. In the MAA composed of an aqueous ammonia coating and Fe3O4@SiO2 core, the coating is a base extractant that can selectively extract acids, while the magnetic core serves as a support to achieve dispersion as well as rapid magnetic retrieval of the extractant during the extraction processes. This is the first use of reusable, stable and modifiable Fe3O4@SiO2 as a support instead of bare Fe3O4 in a magnetic particle assisted dispersive liquid–liquid microextraction technique. The parameters that affect extraction efficiency were investigated. The sampling step as well as the desorption step can be completed in 2 min. The linear ranges are 5–5000 ng g−1, while the limits of quantification range from 2.5 to 6.2 ng g−1. The recoveries in spiked crude oil samples are in the range of 79.1% to 112.1% with relative standard deviations less than 11.3% (intra-day) and 13.4% (inter-day). Finally, the proposed method was applied to the analysis of PAs in diluted crude oils with different maturities. In comparison to the existing methods for extraction of PAs, the proposed method provides superior performances including high throughput (12-well plate), high degree of sample clean-up, and low consumption of separation material, solvent and time.

The microstructure of as-cast ingot and three-dimensional microstructure of carbides were analyzed by optical microscope and scanning electron microscope. The types of carbides were identified by X-ray diffraction. Directional solidification of electroslag remelting effectively reduced the segregation of alloying elements in as-cast ingot. The growing direction of dendrites in as-cast ingot refined by directional solidification of electroslag remelting was paralleled to crystallographic orientation. The solidification microstructure of austenitic hot-work die steel was composed of austenite and primary carbides (V 8 C 7 -type and Mo 2 C-type) which distributed along grain boundaries. Compared with conventional electroslag remelting, the directional solidification of electroslag remelting process reduced the size of primary carbides and improved dispersed distribution of carbides, but not changed the types and compositions of carbides. The direction of driving force for carbides growth was irregular in conventional electroslag remelting, while that was nearly parallel to crystal in directional solidification of electroslag remelting.

We demonstrate a stretchable optical sensor based on the wavy microfiber. With great sensitivity and stretchability, the proposed sensor is employed for human respiration monitoring and the finger bend, preforming an application potential for human health monitoring and robotics. © 2020 The Author(s)

We propose, investigate, and demonstrate a pure and simple dielectric probe operating in the sub-terahertz range with an example band of interest 190–220 GHz. High-resistivity silicon technology is deployed for this non-TEM mode probe development as it presents a viable low-loss material. A T-shape alignment dowel was used to integrate the silicon probe with the waveguide block. The probe can be used to measure and characterize the low permittivity-based dielectric waveguide transmission line and its building components free from the use of any transition structures and TEM-mode probes. For demonstration, the silicon probe was used to measure a substrate integrated image guide and its components in the range of 190–220 GHz. A substrate integrated image guide (SIIG)-based thru, reflect, and line (TRL) calibration kit was developed, and a two-tier TRL calibration was used to characterize the SIIG.

2D materials exhibit superior properties in electronic and optoelectronic fields. The wide demand for high-performance optoelectronic devices promotes the exploration of diversified 2D materials. Recently, 2D covalent organic frameworks (COFs) have emerged as next-generation layered materials with predesigned π-electronic skeletons and highly ordered topological structures, which are promising for tailoring their optoelectronic properties. However, COFs are usually produced as solid powders due to anisotropic growth, making them unreliable to integrate into devices. Here, by selecting tetraphenylethylene monomers with photoelectric activity, elaborately designed photosensitive 2D-COFs with highly ordered donor-acceptor topologies are in situ synthesized on graphene, ultimately forming COF-graphene heterostructures. Ultrasensitive photodetectors are successfully fabricated with the COFETBC-TAPT -graphene heterostructure and exhibited an excellent overall performance with a photoresponsivity of ≈3.2 × 107 A W-1 at 473 nm and a time response of ≈1.14 ms. Moreover, due to the high surface area and the polarity selectivity of COFs, the photosensing properties of the photodetectors can be reversibly regulated by specific target molecules. The research provides new strategies for building advanced functional devices with programmable material structures and diversified regulation methods, paving the way for a generation of high-performance applications in optoelectronics and many other fields.

A net-like mesoporous carbon nanocomposite (MCN) was hydrothermally prepared by using filter paper as the raw material. The MCN contains magnetic nanoparticles of type Fe3O4 which result from the addition of Fe(NO3)3·9H2O during synthesis. The MCN was characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, Raman spectra, Brunauer-Emmett-Teller methods and vibrating sample magnetometry. The MCN is shown to be a viable material for magnetic solid-phase extraction of trace sulfonamides (SAs) including sulfadiazine, sulfapyridine, sulfamerazine, sulfamethazine, sulfamethizole, sulfamethoxypridazine, sulfachloropyridazine and sulfadimethoxine. Following desorption with acetone containing 0.5% ammonia, the SAs were quantified by UPLC with high-resolution mass spectrometric detection. With sulfamethazine as an example, the adsorption equilibrium configurations and the major interaction mechanism between SAs and the MCN were calculated by using density functional theory. Under the optimal conditions, the calibration plots are linear in the 0.05–10 ng·mL−1 SA concentration ranges. The limits of detection are between 7.2 and 13.6 ng·L−1. The recoveries from spiked samples ranged from 79 to 107%, with relative standard deviations of

Fe2O3 is one of promising negative materials for supercapacitors (SCs), because of its low cost and high theoretical value of specific capacitance. However, the inferior conductivity and insufficient ionic diffusion rate of Fe2O3 will seriously hinder the electrochemical performance of Fe2O3, resulting in limiting its practical application in SCs. Herein, a sea urchin-like 3D Fe2O3 was synthesized via hydrothermal methods. And then, the 2D Ti2C3Tx MXene nanosheets with high conductivity closely self-assemble on the surface of Fe2O3 to provide efficient pathways for the rapid electrons transport. In addition, the sea urchin-like structure of Fe2O3 can facilitate the rapid diffusion of the electrolyte to accelerate faradaic reaction. The optimized Fe2O3/MXene composite as electrode material exhibits a high specific capacitance of 486.3 F g−1 at current density of 1 A g−1, and excellent cycling stability with 95.7% capacity retention after 5000 charge/discharge cycles. Furthermore, an asymmetric supercapacitors (ASCs) device was assembled by using Fe2O3/MXene composite as anode and MnO2 as cathode, showing a high energy density of 32.2 Wh kg−1 at the power density of 900.6 W kg−1, and remarkable long-term durability (95.7 % capacitance retention after 5000 cycles). This work demonstrates an effective approach of integrating the sea urchin-like Fe2O3 with 2D MXene nanosheets to fabricate Fe2O3/MXene composite for high-performance SCs.

A fundamental study on the precipitation behavior of carbides was carried out. Thermo-calc software, scanning electron microscopy, electron probe microanalysis, transmission electron microscopy, X-ray diffractometry and high-temperature confocal laser scanning microscopy were used to study the precipitation and transformation behaviors of carbides. Carbide precipitation was of a specific order. Primary carbides (M7C3) tended to be generated from liquid steel when the solid fraction reached 84 mol.%. Secondary carbides (M7C3) precipitated from austenite and can hardly transformed into M23C6 carbides with decreasing temperature in air. Primary carbides hardly changed once they were generated, whereas secondary carbides were sensitive to heat treatment and thermal deformation. Carbide precipitation had a certain effect on steel-matrix phase transitions. The segregation ability of carbon in liquid steel was 4.6 times greater that of chromium. A new method for controlling primary carbides is proposed.

Highly efficient flame retardants for engineering plastics are needed to reduce the deterioration of the mechanical and other properties of the host polymer. Herein, a novel functionalized polyhedral oligomeric silsesquioxane (F-POSS) containing phosphorus and nitrogen has been synthesized by the reaction between N-phenylaminopropyl-POSS and diphenylphosphinic chloride. Untreated POSS and F-POSS have been respectively mixed with poly(1,4-butylene terephthalate) (PBT) to prepare the nanocomposites via the melt blending method. PBT/F-POSS shows improved mechanical properties, thermal stability and thermo-oxidative resistance in comparison with PBT/POSS. F-POSS exhibits a more significant inhibiting effect on the smoke production of PBT in the early heating stage of smoke density testing without a flame. In cone calorimeter tests, the peak heat release rate (PHRR), peak smoke production rate (PSPR), peak carbon dioxide production (PCO2P) and peak carbon monoxide production (PCOP) of PBT/F-POSS are reduced by 50%, 46%, 45% and 35%, respectively, compared to those of neat PBT. Residue analysis indicates that more C and O elements are left during the expansion and carbonization process in which phosphinic groups of F-POSS can capture the free radicals or decomposed products produced from PBT to form a stable SiOxCyPz network. The multiple protective char layers act as a thermal barrier at the surface of the substrate to reduce the fire, smoke and toxicity hazards. This work provides a facile and simple way to achieve high-performance PBT nanocomposites.

We investigated a dielectric transmission line consisting of three dielectric substrate layers for millimeter-wave (mmW) applications. This line is referred to as a narrowed dielectric microstrip line (N-DML). The effective dielectric constant method is used to analyze the propagation characteristics of the N-DML. The result of the analysis of the normalized phase constant is consistent with the simulation. For demonstration, two J -band N-DML prototypes of different lengths with transitions to rectangular waveguides were designed, fabricated, and measured. Good agreement between the simulated and measured results is observed. In particular, due to its nonmetal structure, the N-DML shows a low average attenuation constant of only 0.52 dB/cm over 220-280 GHz in the experiment. Due to its good performance, ease of fabrication, low loss, and low cost, the N-DML is a suitable candidate for various mmW applications.

In this work, a micro-solid phase extraction (micro-SPE) method was developed for the analysis of petroleum acids in crude oils. Plastic vessels were found to be unsuitable as the micro-SPE vessel, because of the plasticizer interferences and the serious adhesion of oil samples on vessel surfaces. To reduce or eliminate these influences, a glass pipette was selected as the micro-SPE vessel. With the glass pipette micro-SPE format, amino-functionalized silica was chosen as the sorbent for extraction of petroleum acids based on mix-mode hydrogen bonding/ion-exchange interactions. The conditions of the micro-SPE were carefully optimized. Under the optimized conditions, no evaporation was needed, which can save time and reduce losses of analytes. By coupling with gas chromatography-mass spectrometry (GC-MS), the proposed micro-SPE method for analysis of petroleum acids was proved to be easily operated, fast (the micro-SPE can be accomplished within 5 min), solvent-saving (3 mL of solvent), reproducible and sensitive (the limits of detection range from 2 ng g−1 to 6 ng g−1).

The effects of holding time during both austenitizing and spheroidizing on microstructure and mechanical properties of high-carbon martensitic stainless steel 8Cr13MoV were experimentally studied. The results showed that the amount of carbides and the proportion of fine carbides decrease first and then increase with the increase in austenitizing time (t 1) in the case of short spheroidizing time (t 2), whereas the amount of the lamellar carbides increases. In the case of long t 2, both the amount of carbides and the proportion of fine carbides decrease, and the amount of the lamellar carbides did not increase. The hardness of the steel decreases first and then increases with the increase of t 1. Under the conditions of different t 1, the change in the size of carbides and hardness of the steel show a same trend with the variation of t 2. The size of spheroidized carbides increases, whereas the hardness of the steel decreases with increasing t 2. The longer the holding time of austenitizing, the higher is the spheroidizing rate at the earlier stage. However, the spheroidizing rate shows an opposite trend with t 1 at the later stage of spheroidizing. The effect of cooling rate on microstructure is similar with t 2. With increasing cooling rate, the dimension of carbides became smaller, and the amount of lamellar carbides increased. The elongation of the sample fracture exhibits no corresponding relationship with holding time, whereas it is closely related to the precipitation of secondary carbides caused by the alloying elements segregation.

A wideband THz H-plane dielectric horn antenna based on silicon (Si) technology is proposed in this paper. The antenna can be integrated with the planar structure circuit and the dielectric ridge waveguide. To fabricate the proposed antenna, the deep reactive ion etching high-resistivity Si fabrication process is used. The size of the proposed antenna is $3.13 \times 4 \times 0.1$ mm3. The operating frequency of the antenna ranges from 750 to 1000 GHz, which corresponds to a fractional impedance bandwidth of 28.6%. The antenna has a narrow beamwidth in the H-plane and a high gain. To test this antenna, the characterization of the metal waveguide diagonal horn for measurement is analyzed. Then the non-contact measurement method is applied to measure the designed dielectric horn. The simulated radiation efficiency of the antenna is higher than 80% while the measured gain of the antenna is larger than 8 dBi. Measured H-plane radiation patterns from the proposed antenna are presented and show reasonable agreement with the simulated results.

The effect of oxide inclusions modification during electroslag remelting (ESR) process on nitrides and primary carbides in as-cast and annealed 8Cr17MoV tool steel was investigated. Impact toughness testing and fractography were performed. Primary carbides M7C3 were found to be dominant precipitates in as-cast ingot, besides a very small fraction of M23C6-type carbides. Al2O3 and MgO·Al2O3 inclusions promoted the formation of (Ti,V)N and primary carbides through serving as preferred nucleation sites, whereas heterogeneous nucleation of (Ti,V)N and primary carbides was avoided by modifying Al2O3 and MgO·Al2O3 inclusions to calcium aluminates. Oxide inclusions modification only refined the dimensions and distribution of carbides, but did not change the types and compositions of carbides. The improvement in the dimensions and distribution of carbides increased significantly the impact toughness of annealed steel. Large secondary carbides precipitated near retained primary carbides in annealed steel, which lowered greatly the impact toughness of 8Cr17MoV steel. Suppressing the formation of large primary carbides in as-cast ingot was favorable to preventing large secondary carbides formation after annealing, which improved greatly the impact energies of annealed steel accordingly.

Carbides in annealed steel H13 without magnesium and with a micro-addition of magnesium (0.0010%) are studied. Trace amounts of magnesium strengthen carbide segregation and reduce their size. Carbides phases M7C3, M6 C, and M(C, N) are detected in steel H13, and this agrees with results of thermodynamic calculations.

A heterometallic MOF [GdCu2(pydc)3(phen)4I(H2O)] (pydc = pyridine-2,6-dicarboxylate, phen = 1,10-phenanthroline) (1, CCDC 1429233) has been synthesized hydrothermally. In compound 1, the metalloligand [Gd(pydc)3] assembly with [Cu(phen)2] units to construct a hexanuclear cluster via Cu–O bonds and π⋯π interaction. The clusters are further stacked into a 3D supramolecular framework with cavities. The cyclic voltammogram shows an irreversible peak for CuII → CuI reduction and a quasi-reversible peak for the couple CuII/CuIII. Its optical and thermal properties have been investigated as well.

Millions of tons of paper and its derivatives are annually wasted without being recycled and reused. To promote the comprehensive utilization of resources and eco-friendly preparation, waste filter paper, printer paper, and napkins were chosen as carbon sources to one-step synthesize three types of three dimensional (3D) net-like magnetic mesoporous carbon (MMC) by an eco-friendly and low-cost method. These mesoporous (3.90–7.68 nm) composites have a high specific surface area (287–423 m2 g−1), well-developed porosity (0.24–0.74 cm3 g−1) and abundant oxygen-containing functional groups. Compared to the other two composites, the adsorbent derived from filter paper showed the highest adsorption capacity towards methylene blue (MB) (qmax = 332.03 mg g−1) and rhodamine B (RhB) (qmax = 389.59 mg g−1) with a high adsorption rate (

A low-loss dielectric microstrip line (DML) integrated circuit based on silicon (Si) technology is proposed for THz applications in this paper. Using the DML, a coupler and a crossover are designed. In the proposed technology, all THz passive components are made of high-resistivity silicon on insulator (SOI) wafer. To fabricate the proposed transmission line and its components, we developed a high-precision fabrication process for the SOI wafer. A non-contact measurement technology is used to test the fabricated samples. The measured loss per wavelength of DML ranges from 0.0082 to 0.042 dB/λ over 750–925 GHz. The measured isolation of the crossover is 25.45 ± 5.54 dB, and the measured coupler factor of the coupler is –13.22 ± 3.23 dB.

The effect of electroslag remelting (ESR) on carbides in 8Cr13MoV martensitic stainless steel was experimentally studied. Phases precipitated from liquid steel during solidification were calculated using the Thermo-Calc software. The carbon segregation was analyzed by original position analysis (OPA), and the carbides were analyzed by optical microscopy (OM), scanning electron microscopy (SEM), energy- dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD). The results indicated that more uniform carbon distribution and less segregation were obtained in the case of samples subjected to the ESR process. After ESR, the amount of netty carbides decreased significantly, and the chromium and vanadium contents in the grain-boundary carbides was reduced. The total area and average size of carbides were obviously smaller after the ESR process. In the sample subjected to ESR, the morphology of carbides changed from lamellar and angular to globular or lump, whereas the types of carbides did not change; both M23C6 and M7C3 were present before and after the ESR process.

The microstructure and hardness of high-carbon martensitic stainless steel (HMSS) were investigated using thermal expansion analyzer, Thermo-calc, scanning electron microscope, x-ray diffraction, and Ultra-high temperature confocal microscope. The results indicate that the experimental steel should be austenitized in the temperature range of 1025-1075 °C, which can give a maximum hardness of 62 HRc with the microstructure consisting of martensite, retained austenite, and some undissolved carbides. With increasing austenitizing temperature, the amount of retained austenite increases, while the volume fraction of carbides increases first and then decreases. The starting temperature and finish temperature of martensite formation decrease with increasing cooling rates. Air-quenched samples can obtain less retained austenite, more compact microstructure, and higher hardness, compared with that of oil-quenched samples. For HMSS, the martensitic transformation takes place at some isolated areas with a slow nucleation rate.

Hydrogels are becoming widely used in biomaterial applications. The available methods for the preparation of these materials are continually growing. The gelation time (GT) of silk protein fibroin is difficult to control by physical methods. The cross-linkers used in available chemical techniques are likely to impact the biocompatibility of the resultant materials. In this paper, we demonstrate that the addition of sodium N-lauroyl sarcosinate (an amino-acid-based surfactant) accelerates the formation of hydrogels from fibroin. GT, turbidity variations, changes of viscoelasticity during the gelation process, and the mechanical properties of the products are measured. The secondary structure was probed by Fourier transform infrared spectroscopy, X-ray diffraction and the morphologies of the products were investigated by scanning electron microscopy. Transformations in the β-sheet content were monitored by the fluorescence of Thioflavine T and circular dichroism measurements. The relationship between the surface tension of sodium N-lauroyl sarcosinate and the GT was also explained. To investigate cell compatibility, fibroblast cells were seeded onto the surface of the hydrogels. The results indicate that the sodium N-lauroyl sarcosinate/fibroin GT can be controlled. This blend-hydrogel demonstrates excellent cell compatibility, good compression strength, and outstanding compression-recovery characteristics. Sodium N-lauroyl sarcosinate/silk fibroin hydrogels containing β-sheets have considerable potential as replacement materials in addressing the tissue defects involved with repair surgery.

Various methods were developed to prepare hydrogels including photo-cross-linking, chemical cross-linking, enzymatic cross-linking, pH or temperature-induced gelation, ionic interaction, and hydrophobic interactions. Whereas silk fibroin gelation time was difficult to control by physical methods, the cross-linkers used in chemical technique were likely to reduce the cell biocompatibility. Sodium N-Lauroyl Sarcosinate (SNS), an amino acid-based surfactant, came into accelerate silk fibroin to form silk hydrogel. To monitor the gelation process and determine the gelation time, turbidity changes during gelation were measured by Synergy HT. Cylindrical gels have been measured with universal material experiment machine and KES for mechanical properties. Fibroblast (L929) cells were seeded on the surface of hydrogels to investigate the cell compatibility. The results show that the SNS/SF gelation time ranges from 20 min to 120 min, which is affected by environment temperature, the final concentrations of SF and SNS. Compared with pure silk fibroin hydrogels, the compression strength of SNS/SF gel is much stronger. SNS/SF gel has excellent compression-recovery performance in KES test as well. A logarithmic stable cell growth appears on the surface of SNS/SF hydrogels, which indicates that SNS/SF hydrogels have excellent cell compatibility. Therefore, the SNS/SF hydrogels have great potential in tissue repair for surgery.

Silk fibroin hydrogel is an ideal model as biomaterial matrix due to its excellent biocompatibility and used in the field of medical polymer materials. Nevertheless, native fibroin hydrogels show poor transparency and resilience. To settle these drawbacks, an interpenetrating network (IPN) of hydrogels are synthesized with changing ratios of silk fibroin/N-Vinyl-2-pyrrolidonemixtures that crosslink by H2O2 and horseradish peroxidase. Interpenetrating polymer network structure can shorten the gel time and the pure fibroin solution gel time for more than a week. This is mainly due to conformation from the random coil to the β-sheet structure changes of fibroin. Moreover, the light transmittance of IPN hydrogel can be as high as more than 97% and maintain a level of 90% within a week. The hydrogel, which mainly consists of random coil, the apertures inside can be up to 200 μm. Elastic modulus increases during the process of gelation. The gel has nearly 95% resilience under the compression of 70% eventually, which is much higher than native fibroin gel. The results suggest that the present IPN hydrogels have excellent mechanical properties and excellent transparency., This work was supported by The National Key Research and Development Program of China (Grant No. 2017YFC1103602), National Natural Science Foundation of China (Grant No. 51373114, 51741301), PAPD and Nature Science Foundation of Jiangsu, China (Grant No. BK20171239, BK20151242)., info:eu-repo/semantics/publishedVersion

In the current study, monolithic ordered mesoporous silica (MOMS) was successfully prepared by a modified Stober method using natural pomelo peel and cetyltrimethylammonium bromide (CTAB) as dual templates. A mesostructured CTAB/silica composite was deposited on the carbohydrate-based surface of the sponge-like pomelo peel. After removing the templates by calcination and acid treatment, MOMS with a continuous skeleton, interconnecting macropores and ultra-high surface area (1120 m2 g−1) was obtained. MOMS materials with various and controllable sizes and shapes could be prepared simultaneously in a one-pot synthesis. Small pieces of MOMS (millimeter size) were then applied as the adsorbent to enrich peptides. Owing to the ordered mesoporous structure, the as-prepared MOMS was demonstrated to be an excellent adsorbent for effective enrichment of endogenous peptides from human plasma.

We design two novel d10 metal complexes [Zn(3-qlc)2]n (Zn1), [Cd(3-qlc)2]n (Cd1) (3-Hqlc = quinoline-3-carboxylic acid), which display similar 2D layer structures, and further form 3D 6-connected primitive cubic (pcu) network topology via π⋯π stacking interactions with the point symbol {412·63}. Complexes Zn1 and Cd1 exhibit tunable luminescence and photovoltaic properties as a new type of multifunctional materials. Zn1 and Cd1 show tunable luminescence from blue to green by varying the temperature in the solid state. What's more, both of them exhibit excellent aggregation-induced emission (AIE) properties in DMSO/water mixtures. Encouraged by the UV-visible absorption in an ethanol solution result, Zn1 and Cd1 can be considered as co-sensitizers in combination with N719 to investigate their effect on enhancing the dye-sensitized solar cells (DSSCs) performance. Zn1 and Cd1 could overcome the deficiency in the ruthenium complex N719 absorption in the ultraviolet and blue-violet region, offsetting competitive visible light absorption of I3− and reducing the charge recombination of injected electrons. After being co-sensitized with Zn1 and Cd1, the devices co-sensitized by Zn1/N719 and Cd1/N719 yield an overall efficiency of 7.75% and 7.70%, which are 44.59% and 43.66% higher than that of the device sensitized only by N719 (5.36%).

In view of the requirements for mechanical properties and service life above 650 °C, a high-Mn austenitic hot work die steel, instead of traditional martensitic hot work die steel such as H13, was developed in the present study. The effect of heat treatment on the microstructure and mechanical properties of the newly developed work die steel was studied. The results show that the microstructure of the high-Mn as-cast electroslag remelting (ESR) ingot is composed of γ-Fe, V(C,N), and Mo2C. V(C,N) is an irregular multilateral strip or slice shape with severe angles. Most eutectic Mo2C carbides are lamellar fish-skeleton-like, except for a few that are rod-shaped. With increasing solid solution time and temperature, the increased hardness caused by solid solution strengthening exceeds the effect of decreased hardness caused by grain size growth, but this trend is reversed later. As a result, the hardness of specimens after various solid solution heat treatments increases first and then decreases. The optimal combination of hardness and austenitic grain size can be obtained by soaking for 2 h at 1170 °C. The maximum Rockwell hardness (HRC) is 47.24 HRC, and the corresponding austenite average grain size is 58.4 μm. When the solid solution time is 3 h at 1230 °C, bimodality presented in the histogram of the austenite grain size as a result of further progress in secondary recrystallization. Compared with the single-stage aging, the maximum impact energy of the specimen after two-stage aging heat treatment was reached at 16.2 J and increased by 29.6%, while the hardness decreased by 1–2 HRC. After two-stage aging heat treatment, the hardness of steel reached the requirements of superior grade H13, and the maximum impact energy was 19.6% higher than that of superior grade H13, as specified in NADCA#207-2003.

The evolution of the carbides and mechanical properties of 7Cr17MoV stainless steel used as cutlery material during cold rolling was investigated in this study. The results demonstrate that the microstructure of the rolled steel is composed of pearlite and spheroidal carbides. After cold rolling, the aggregation of carbides was no longer evident, and the carbides appeared to be small in size and uniformly distributed, whereas carbides in hot-rolled strips are clearly aggregated. Decreasing the thickness of the cold-rolled strips decreased the size of the carbide particles while increasing their number, which improved the particle distribution. A large number of fine, even nano-scaled carbides were observed in the material. The carbide phase, which primarily consisted of M23C6, did not change during cold rolling and annealing. The tensile strength and yield strength first decreased and then increased, and the elongation increased as the thickness of the cold-rolled strips decreased. Dimples and inclusion p...

In this paper, microscopic method, transmission technique and attenuated total reflection method of infrared spectroscopy and differential scanning calorimetry were investigated for analyzing the component of inner and outer layer of sheath-core polymer fiber. Results showed that transmission technique and attenuated total reflection method of infrared spectroscopy was a quick and accurate method for identification of sheath-core fiber of fiber.