Effect of pre‐processing annealing and ram speed on mechanical properties for low carbon steel processed by constrained groove pressing

Constrained groove pressing (CGP) has emerged for producing ultra‐fine‐grained materials with distinguished properties. Low carbon steel sheets were subjected to severe plastic deformation by constrained groove pressing process. The effect of pre‐processing annealing temperature, ram speed and number of passes on microstructure, mechanical properties and wear behaviour of the sheets were investigated. The 3 mm thick sheets were deformed by a constrained groove pressing die at ram speeds: 5 mm/min, 10 mm min^?1 and 20 mm min^?1. Furthermore, the as received sheets were annealed at 600 °C and 900 °C, then deformed at ram speed 20 mm min^?1. The annealing temperature 900 °C led to slightly coarser grains, lower strength and larger ductility compared to those obtained after annealing at 600 °C. With lowering the ram speed to 5 mm min^?1, the number of passes could be increased to 10 passes while increasing ram speed from 5 mm min^?1 to 20 mm min^?1 improved the mechanical properties; after 3 constrained groove pressing passes, the ultimate tensile strength increased from 420 MPa to 490 MPa, the hardness from 174 HV 1 to 190 HV 1 and the elongation from 7.6 % to 9.5 %. Finer grains were also obtained by increasing ram speed. Wear resistance was greatly enhanced by constrained groove pressing and by the increase in ram speed.     

High‐Mobility Helical Tellurium Field‐Effect Transistors Enabled by Transfer‐Free,Low‐Temperature Direct Growth

The transfer‐free direct growth of high‐performance materials and devices can enable transformative new technologies. Here, room‐temperature field‐effect hole mobilities as high as 707 cm² V^?1 s^?1 are reported, achieved using transfer‐free, low‐temperature (≤120 °C) direct growth of helical tellurium (Te) nanostructure devices on SiO₂/Si. The Te nanostructures exhibit significantly higher device performance than other low‐temperature grown semiconductors, and it is demonstrated that through careful control of the growth process, high‐performance Te can be grown on other technologically relevant substrates including flexible plastics like polyethylene terephthalate and graphene in addition to amorphous oxides like SiO₂/Si and HfO₂. The morphology of the Te films can be tailored by the growth temperature, and different carrier scattering mechanisms are identified for films with different morphologies. The transfer‐free direct growth of high‐mobility Te devices can enable major technological breakthroughs, as the low‐temperature growth and fabrication is compatible with the severe thermal budget constraints of emerging applications. For example, vertical integration of novel devices atop a silicon complementary metal oxide semiconductor platform (thermal budget <450 °C) has been theoretically shown to provide a 10× systems level performance improvement, while flexible and wearable electronics (thermal budget <200 °C) can revolutionize defense and medical applications.     

Flow‐Through Microbial Capture by Antibody‐Coated Microsieves

A new flow‐through method for rapid capture and detection of microorganisms is developed using optically‐flat microengineered membranes. Selective and efficient capture of Salmonella is demonstrated with antibodies coated on membranes (microsieves) having a pore size much larger than the microorganism itself. The silicon‐nitride membranes are first photochemically coated with 1,2‐epoxy‐9‐decene yielding stable Si–C and N–C linkages. The resultant epoxide‐terminated microsieves are subsequently biofunctionalized with anti‐Salmonella antibodies. The capture efficiency of antibody‐coated microsieves with different pore sizes (2.0–5.0 μm) is studied with Salmonella enterica enterica serotype Typhimurium suspensions (10⁷ cfu mL^–1). The antibody‐coated microsieves capture 52% (2 μm microsieves), 30% (3.5 μm microsieves), and 12% (5 μm microsieves) of Salmonella from the suspension. The influence of flow rate (0.8–16 μL min^–1 mm^–2) on the capture efficiency of antibody‐coated 3.5 μm microsieves is investigated. The capture efficiency increases from ≈30% to ≈70% when the flow‐rate decreases from 16 to 0.8 μL min^–1 mm^–2. Antibody‐coated 3.5 μm microsieves can capture Salmonella rapidly and directly from fresh milk suspension (capture 35% at concentration of 80 cfu mL^–1). The use of antibody‐coated microsieves as microbial selective capture devices is thus shown to be highly promising for the direct capture of microorganisms.     

Influence of the condensation surface temperature on the microstructure and intrinsic stress in evaporated chromium films

Chromium was evaporated onto die cast zinc at a pressure of better than 10^?3 Pa (10^?5 Torr). The deposition rate was varied between 0.1 μm min^?1 and 0.6 μm min^?1.The films were found to have a b.c.c. structure and to consist of needle-like crystallites, with fine needles for low deposition rates and coarse needles for high deposition rates. A rapid growth of the crystallites occured for a deposition rate of 0.2?0.3 μm min^?1.During deposition the films were found to crack because of intrinsic stresses developed in the films. There was a strong dependence of the mean distance between cracks on the deposition rate with a maximum at about 0.25 μm min^?1 for a substrate temperature of 323 K (50°C). The relation of the root mean square microstrain to the deposition rate is the inverse of the relation between the mean distance between cracks and deposition rate.A model is proposed that separates the experimentally obtained root mean square strain into two parts, one due to distortions at the grain boundaries and one due to defects in the crystallites. The results given by the model for the two strain components explain the obtained Vickers hardness dependence upon deposition rate.     

Graphene‐Encapsulated FeS2 in Carbon Fibers as High Reversible Anodes for Na+/K+ Batteries in a Wide Temperature Range

Developing low cost, long life, and high capacity rechargeable batteries is a critical factor towards developing next‐generation energy storage devices for practical applications. Therefore, a simple method to prepare graphene‐coated FeS₂ embedded in carbon nanofibers is employed; the double protection from graphene coating and carbon fibers ensures high reversibility of FeS₂ during sodiation/desodiation and improved conductivity, resulting in high rate capacity and long‐term life for Na⁺ (305.5 mAh g^?1 at 3 A g^?1 after 2450 cycles) and K⁺ (120 mAh g^?1 at 1 A g^?1 after 680 cycles) storage at room temperature. Benefitting from the enhanced conductivity and protection on graphene‐encapsulated FeS₂ nanoparticles, the composites exhibit excellent electrochemical performance under low temperature (0 and ?20 °C), and temperature tolerance with stable capacity as sodium‐ion half‐cells. The Na‐ion full‐cells based on the above composites and Na₃V₂(PO₄)₃ can afford reversible capacity of 95 mAh g^?1 at room temperature. Furthermore, the full‐cells deliver promising discharge capacity (50 mAh g^?1 at 0 °C, 43 mAh g^?1 at ?20 °C) and high energy density at low temperatures. Density functional theory calculations imply that graphene coating can effectively decrease the Na⁺ diffusion barrier between FeS₂ and graphene heterointerface and promote the reversibility of Na⁺ storage in FeS₂, resulting in advanced Na⁺ storage properties.     

Efficient and Stable Solid‐State Dye‐Sensitized Solar Cells Based on a High‐Molar‐Extinction‐Coefficient Sensitizer

The high‐molar‐extinction‐coefficient heteroleptic ruthenium dye, cis‐Ru (4,4′‐bis(5‐octylthieno[3,2‐b] thiophen‐2‐yl)‐2,2′‐bipyridine) (4,4′‐dicarboxyl‐2,2′‐bipyridine) (NCS)₂, exhibits an AM 1.5 solar (100 mW cm^?2)‐to‐electric power‐conversion efficiency of 4.6% in a solid‐state dye‐sensitized solar cell (SSDSC) with 2,2′, 7,7′‐tetrakis‐(N,N‐di‐p‐methoxyphenylamine)9,9′‐spirobifluorene (spiro‐MeOTAD) as the organic hole‐transporting material. These SSDSC devices exhibit good durability during accelerated tests under visible‐light soaking for 1000 h at 60 °C. This demonstration elucidates a class of photovoltaic devices with potential for stable and low‐cost power generation. The electron recombination dynamics and charge collection that take place at the dye‐sensitized heterojunction are studied by means of impedance and transient photovoltage decay techniques.     

The Control of Solidification of Ni‐Based Superalloy Single‐Crystal Blade by Mold Design Modification using Inner Radiation Baffle

This work is focused on an investigation of the directional solidification process of CMSX‐4 single‐crystal blades in the mold modified by application of inner radiation baffle (IRB). Micro‐ and macrostructure examination is carried out along the height of single‐crystal blades which are manufactured using standard and modified mold, at the withdrawal rates of 3 and 5 mm min^?1. It is established that application of modified mold allows better control over liquidus isotherm and leads to increase in temperature gradient, as compared to the manufacturing of blades using standard mold. The average value of temperature gradient in airfoil increases from 14 up to approx. 30 K cm^?1 and from 16 up to approx. 40 K cm^?1, for withdrawal rate of 5 and 3 mm min^?1, respectively. The curvature of liquidus isotherm diminishes and attains near‐flat profile along the airfoil for both values of withdrawal rate. The application of proposed technique results in reduction of primary dendrites arm spacing (PDAS) particularly in the inner and middle part of the blade. PDAS reaches average value of approx. 360 μm for withdrawal rate of 5 mm min^?1 and is lower as compared to the standard mold casting withdrawn at the rate of 3 (433 μm) and 5 mm min^?1 (468 μm).

     

A High‐Performing Direct Carbon Fuel Cell with a 3D Architectured Anode Operated Below 600 °C

Direct carbon fuel cells (DCFCs) are highly efficient power generators fueled by abundant and cheap solid carbons. However, the limited triple‐phase boundaries (TPBs) in the fuel electrode, due to the lack of direct contact among carbon, electrode, and electrolyte, inhibit the performance and result in poor fuel utilization. To address the challenges of low carbon oxidation activity and low carbon utilization, a highly efficient, 3D solid‐state architected anode is developed to enhance the performance of DCFCs below 600 °C. The cell with the 3D textile anode framework, Gd:CeO₂–Li/Na₂CO₃ composite electrolyte, and Sm_0.5Sr_0.5CoO₃ cathode demonstrates excellent performance with maximum power densities of 143, 196, and 325 mW cm^?2 at 500, 550, and 600 °C, respectively. At 500 °C, the cells can be operated steadily with a rated power density of ≈0.13 W cm^?2 at a constant current density of 0.15 A cm^?2 with a carbon utilization over 85.5%. These results, for the first time, demonstrate the feasibility of directly electrochemical oxidation of solid carbon at 500–600 °C, representing a promising strategy in developing high‐performing fuel cells and other electrochemical systems via the integration of 3D architected electrodes.     

High‐frequency response analysis via algebraic substructuring

High‐frequency response analysis (Hi‐FRA) of large‐scale dynamical systems is critical to predict the resonant behavior of modern micro‐devices and systems operated over MHz or GHz frequency range. Algebraic substructuring (AS) is a powerful technique to extract a large number of natural frequencies. In this work, we extend the AS technique for FRA between two specified cutoff frequencies ω_min and ω_max. The technique is referred to as ASFRA. ASFRA can be efficiently applied to Hi‐FRA, as demonstrated by two examples of microelectromechanical sensors operated at 1–2 and 200–250 MHz ranges. To some extent ASFRA generalizes the underlying numerical algorithm and functionality of commercially viable automated multi‐level substructuring (AMLS) technique. AMLS is designed for FRA up to a specific frequency ω_max, starting from the lowest, and is inefficient for Hi‐FRA. Copyright © 2008 John Wiley & Sons, Ltd.     

ZIF‐8/ZIF‐67‐Derived Co‐Nx‐Embedded 1D Porous Carbon Nanofibers with Graphitic Carbon‐Encased Co Nanoparticles as an Efficient Bifunctional Electrocatalyst

Herein, an approach is reported for fabrication of Co‐N_x‐embedded 1D porous carbon nanofibers (CNFs) with graphitic carbon‐encased Co nanoparticles originated from metal–organic frameworks (MOFs), which is further explored as a bifunctional electrocatalyst for both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Electrochemical results reveal that the electrocatalyst prepared by pyrolysis at 1000 °C (CoNC‐CNF‐1000) exhibits excellent catalytic activity toward ORR that favors the four‐electron ORR process and outstanding long‐term stability with 86% current retention after 40 000 s. Meanwhile, it also shows superior electrocatalytic activity toward OER, reaching a lower potential of 1.68 V at 10 mA cm^?2 and a potential gap of 0.88 V between the OER potential (at 10 mA cm^?2) and the ORR half‐wave potential. The ORR and OER performance of CoNC‐CNF‐1000 have outperformed commercial Pt/C and most nonprecious‐metal catalysts reported to date. The remarkable ORR and OER catalytic performance can be mainly attributable to the unique 1D structure, such as higher graphitization degree beneficial for electronic mobility, hierarchical porosity facilitating the mass transport, and highly dispersed CoN_xC active sites functionalized carbon framework. This strategy will shed light on the development of other MOF‐based carbon nanofibers for energy storage and electrochemical devices.     

Room‐Temperature Liquid Metal Confined in MXene Paper as a Flexible,Freestanding, and Binder‐Free Anode for Next‐Generation Lithium‐Ion Batteries

Exploring flexible lithium‐ion batteries is required with the ever‐increasing demand for wearable and portable electronic devices. Selecting a flexible conductive substrate accompanying with closely coupled active materials is the key point. Here, a lightweight, flexible, and freestanding MXene/liquid metal paper is fabricated by confining 3 °C GaInSnZn liquid metal in the matrix of MXene paper without any binder or conductive additive. When used as anode for lithium‐ion cells, it can deliver a high discharge capacity of 638.79 mAh g^?1 at 20 mA g^?1. It also exhibits satisfactory rate capacities, with discharge capacities of 507.42, 483.33, 480.22, 452.30, and 404.47 mAh g^?1 at 50, 100, 200, 500, and 1000 mA g^?1, respectively. The cycling performance is obviously improved by slightly reducing the charge–discharge voltage range. The composite paper also has better electrochemical performance than liquid metal coated Cu foil. This study proposes a novel flexible anode by a clever combination of MXene paper and low‐melting point liquid metal, paving the way for next‐generation lithium‐ion batteries.     

Sub‐Micron Anisotropic InP‐based III–V Semiconductor Material Deep Etching for On‐Chip Laser Photonics Devices

Two InP‐based III–V semiconductor etching recipes are presented for fabrication of on‐chip laser photonic devices. Using inductively coupled plasma system with a methane free gas chemistry of chlorine and nitrogen at a high substrate temperature of 250 °C, high aspect ratio, anisotropic InP‐based nano‐structures are etched. Scanning electron microscopy images show vertical sidewall profile of 90° ± 3°, with aspect ratio as high as 10. Atomic Force microscopy measures a smooth sidewall roughness root‐mean‐square of 2.60 nm over a 3 × 3 μm scan area. The smallest feature size etched in this work is a nano‐ring with inner diameter of 240 nm. The etching recipe and critical factors such as chamber pressure and the carrier plate effect are discussed. The second recipe is of low temperature (?10 °C) using Cl₂ and BCl₃ chemistry. This recipe is useful for etching large areas of III–V to reveal the underlying substrate. The availability of these two recipes has created a flexible III–V etching platform for fabrication of on‐chip laser photonic devices. As an application example, anisotropic InP‐based waveguides of 3 μm width are fabricated using the Cl₂ and N₂ etch recipe and waveguide loss of 4.5 dB mm^?1 is obtained.

     

Stability of Mixtoxantrone Hydrochloride in Solution

Abstract

A stability-indicating reversed-phase high performance liquid chromatographic method was developed for the detection of mitoxantrone HC1 and its degradation products under accelerated degradation conditions. The degradation kinetics of mitoxantrone HC1 in aqueous solution over a pH range of 1.18 to 7.20 and its stability in propylene glycol-or polyethylene glycol 400-based solutions were investigated. The observed rate constants were shown to follow apparent first-order kinetics in all cases. The pH-rate profile shows that maximum stability of mitoxantrone HC1 was obtained at pH 4.01. No general acid or base catalysis from acetate or phosphate buffer species was observed. The catalysis rate constants on the protonated mitoxantrone imposed by hydrogen ion water and hydroxy ion were determined to be 3.72 × 10 min^?1 5.64 × 10-min^?1 and 1.108 × 10^?2min^?1, respectively. The degradation rate constants of mitoxantrone affected by different ionic strength systems. Irradiation with 254 nm UV light at 25±0.5°C was found when canpared with the light-protected controls. Incorporation of nonaqueous propylene glycol or polyethylene glycol in the pH 4.01 mitoxantrone solution shows an increase in its stability at 502±0.5°C.     

Influence of B and Ti on hot ductility of high Al and high Al,Nb containing TWIP steels

Abstract

The addition of ～0·002%B and ～0·04%Ti as microalloying additions to improve the poor hot ductility and high risk of cracking on continuous casting of high Al containing twinning induced plasticity (TWIP) steels has been examined. Tensile specimens were either cast in situ or heated to 1250°C before cooling at 60 K min^?1 to test temperatures in the range 700–1100°C and strained to failure at 3×10^?3 s^?1. For tensile specimens reheated to 1250°C, the presence of B with sufficient Ti to combine with all the N improved ductility over the temperature range of 700–950°C, the reduction in area (RA) values being >40%. For the higher strength more complex high Al, TWIP steels having Nb present, there was no improvement in ductility with a similar B and Ti addition, when the average cooling rate after melting to the test temperature was 60 K min^?1. Reducing the cooling rate to 12 K min^?1 resulted in the RA values being close to the minimum required to avoid transverse cracking throughout the temperature range 800–1000°C. Using these additions of B and Ti, transverse cracking was found not to be a problem when continuously casting these high Al containing TWIP steels.     

Solution Combustion Synthesis: Low‐Temperature Processing for p‐Type Cu:NiO Thin Films for Transparent Electronics

Low‐temperature solution processing opens a new window for the fabrication of oxide semiconductors due to its simple, low cost, and large‐area uniformity. Herein, by using solution combustion synthesis (SCS), p‐type Cu‐doped NiO (Cu:NiO) thin films are fabricated at a temperature lower than 150 °C. The light doping of Cu substitutes the Ni site and disperses the valence band of the NiO matrix, leading to an enhanced p‐type conductivity. Their integration into thin‐film transistors (TFTs) demonstrates typical p‐type semiconducting behavior. The optimized Cu_5%NiO TFT exhibits outstanding electrical performance with a hole mobility of 1.5 cm² V^?1 s^?1, a large on/off current ratio of ≈10⁴, and clear switching characteristics under dynamic measurements. The employment of a high‐k ZrO₂ gate dielectric enables a low operating voltage (≤2 V) of the TFTs, which is critical for portable and battery‐driven devices. The construction of a light‐emitting‐diode driving circuit demonstrates the high current control capability of the resultant TFTs. The achievement of the low‐temperature‐processed Cu:NiO thin films via SCS not only provides a feasible approach for low‐cost flexible p‐type oxide electronics but also represents a significant step toward the development of complementary metal–oxide semiconductor circuits.     

Scalable Design of Two‐Dimensional Oxide Nanosheets for Construction of Ultrathin Multilayer Nanocapacitor

Large size of capacitors is the main hurdle in miniaturization of current electronic devices. Herein, a scalable solution‐based layer‐by‐layer engineering of metallic and high‐κ dielectric nanosheets into multilayer nanosheet capacitors (MNCs) with overall thickness of ≈20 nm is presented. The MNCs are built through neat tiling of 2D metallic Ru_0.95O₂^0.2? and high‐κ dielectric Ca₂NaNb₄O₁₃^? nanosheets via the Langmuir–Blodgett (LB) approach at room temperature which is verified by cross‐sectional high‐resolution transmission electron microscopy (HRTEM). The resultant MNCs demonstrate a high capacitance of 40–52 µF cm^?2 and low leakage currents down to 10^?5–10^?6 A cm^?2. Such MNCs also possess complimentary in situ robust dielectric properties under high‐temperature measurements up to 250 °C. Based on capacitance normalized by the thickness, the developed MNC outperforms state‐of‐the‐art multilayer ceramic capacitors (MLCC, ≈22 µF cm^?2/5 × 10⁴ nm) present in the market. The strategy is effective due to the advantages of facile, economical, and ambient temperature solution assembly.     

Influence of process parameters on superplasticity of friction stir processed nugget in high strength Al – Cu – Li alloy

Abstract

A parametric study was carried out to evaluate the influence of friction stir processing (FSP) parameters (tool rotation speed and feed rate) on the superplasticity of the weld nugget. Dynamically recrystallised AA 2095 thin sheets with a fine grain size of 2 μm were welded using four feed rates and three rotational speeds. High temperature tensile testing was employed to understand the significance of the FSP parameters and to optimise the parameters for maximum elongation. The tool rotation speed was found to be the most decisive parameter for controlling superplastic behaviour. A strain rate sensitivity of 0·68 was measured for the highest rotational speed at the optimum superplastic forming (SPF) temperature of 495°C. A maximum percentage 'elongation to failure' of 550% was achieved for the sheets subjected to FSP at 1000 rev min^?1 and 4·2 mm s^?1, compared with 475% obtained for the base metal at the optimum SPF temperature and strain rate of 495°C and 10^?3s^?1, respectively.     

Development of a Dew-Point Generator for Gases Other than Air and Nitrogen and Pressures up to 6?MPa

A new primary humidity standard is currently being developed at VSL that, in addition to ordinary operation with air and nitrogen at atmospheric pressure, can be operated also with special carrier gases such as natural gas and SF₆ and at pressures up to 6?MPa. In this paper, the design and construction of this new primary dew-point generator and the preliminary tests performed on the generator are reported. The results of the first efficiency tests, performed for the dew-point temperature range from ?50?°C to 20°C, for pressures up to 0.7MPa and for carrier gas flow rates up to 4L·?min^?1, showed satisfactory generator performance when used in the single-pass mode, i.e., with no recirculation of the carrier gas.     

Ultrahigh Thermal Conductive yet Superflexible Graphene Films

Electrical devices generate heat at work. The heat should be transferred away immediately by a thermal manager to keep proper functions, especially for high‐frequency apparatuses. Besides high thermal conductivity (K ), the thermal manager material requires good foldability for the next generation flexible electronics. Unfortunately, metals have satisfactory ductility but inferior K (≤429 W m^?1 K^?1), and highly thermal‐conductive nonmetallic materials are generally brittle. Therefore, fabricating a foldable macroscopic material with a prominent K is still under challenge. This study solves the problem by folding atomic thin graphene into microfolds. The debris‐free giant graphene sheets endow graphene film (GF) with a high K of 1940 ± 113 W m^?1 K^?1. Simultaneously, the microfolds render GF superflexible with a high fracture elongation up to 16%, enabling it more than 6000 cycles of ultimate folding. The large‐area multifunctional GFs can be easily integrated into high‐power flexible devices for highly efficient thermal management.     

Chiral Octahydro‐Binaphthol Compound‐Based Thermally Activated Delayed Fluorescence Materials for Circularly Polarized Electroluminescence with Superior EQE of 32.6% and Extremely Low Efficiency Roll‐Off

Circularly polarized organic light‐emitting diodes (CP‐OLEDs) are particularly favorable for the direct generation of CP light, and they demonstrate a promising application in 3D display. However, up to now, such CP devices have suffered from low brightness, insufficient efficiency, and serious efficiency roll‐off. In this study, a pair of octahydro‐binaphthol ( OBN )‐based chiral emitting enantiomers, (R/S)‐OBN‐Cz , are developed by ingeniously merging a chiral source and a luminophore skeleton. These chirality–acceptor–donor (C–A–D)‐type and rod‐like compounds concurrently generate thermally activated delayed fluorescence with a small ΔE_ST of 0.037 eV, as well as a high photoluminescence quantum yield of 92% and intense circularly polarized photoluminescence with dissymmetry factors (|g_PL|) of ≈2.0 × 10^?3 in thin films. The CP‐OLEDs based on (R/S)‐OBN‐Cz enantiomers not only display obvious circularly polarized electroluminescence signals with a |g_EL| of ≈2.0 × 10^?3, but also exhibit superior efficiencies with maximum external quantum efficiency (EQE_max) up to 32.6% and extremely low efficiency roll‐off with an EQE of 30.6% at 5000 cd m^?2, which are the best performances among the reported CP devices to date.