Mechanical and thermal properties of hot pressed neodymium-substituted britholite Ca9Nd(PO4)5(SiO4)F2

Neodymium-substituted britholite, a phosphate–silicate apatite Ca₉Nd(PO₄)₅(SiO₄)F₂, is considered as a potential host matrix for specific immobilization of radionuclides. Complementary investigations have been carried out to complete the database concerning this compound. The aim was to establish mechanical and thermal properties of dense britholite. Hot pressing was used to nearly fully densify the material. Low values of mechanical properties were found: 0.75 MPa m^1/2 for the fracture toughness and 95 MPa for the flexural strength. The Young's modulus and the Poisson's ratio were 108 GPa and 0.30, respectively. The specific and the thermal conductivity at 298 K were Cp=0.75 J g⁻¹ K⁻¹ and λ=1.15 W m⁻¹ K⁻¹. The average coefficient of thermal expansion in the 20–1000 °C temperature range was α=21×10⁻⁶ K⁻¹.     

Evaluation of stress corrosion cracking and hydrogen embrittlement in an API grade steel

Stress corrosion cracking (SCC) and hydrogen embrittlement (HE) of pipeline steels in contact with soil was investigated. Different soils were prepared in order to determine their physical, chemical and bacteriological characteristics. Slow strain rate testing was carried out by using aqueous extracts from soil samples and NS4 standard solution. Stress vs. strain curves of API 5L grade X46 steel were obtained at different electrode potentials (E_corr, 100 mV below E_corr and 300 mV below E_corr) with 9 × 10⁻⁶ s⁻¹ and 9 × 10⁻⁷ s⁻¹ strain rate. In addition, the hydrogen permeation tests were carried out in order to evaluate the susceptibility of hydrogen penetrates into theses steels. The results demonstrated the incidence of cracking and their dependence on the potential imposed. In that case, cracking occurred by stress corrosion cracking (SCC) and the hydrogen embrittlement (HE) had an important contribution to cracking initiation and propagation. Cracking morphology was similar to the SCC reported on field condition where transgranular cracking were detected in a pipeline collapsed by land creeping. It was important to point out that even under cathodic potentials the material showed the incidence of secondary cracking and a significant reduction of ductility.     

Thermal and Mechanical Properties Optimization of ABO4 Type EuNbO4 By the B-Site Substitution of Ta

Ferroelastic ABO₄ type RETaO₄ and RENbO₄ ceramics (where RE stands for rare earth) are being investigated as promising thermal barrier coatings (TBCs), and the mechanical properties of RETaO₄ have been found to be better than those of RENbO₄. In this work, B-site substitution of tantalum (Ta) is used to optimize the thermal and mechanical properties of EuNbO₄ fabricated through a solid-state reaction (SSR). The crystal structure is clarified by means of X-ray diffraction (XRD) and Raman spectroscopy; and the surface microstructure is surveyed via scanning electronic microscope (SEM). The Young’s modulus and the thermal expansion coefficient (TEC) of EuNbO₄ are effectively increased; with respective maximum values of 169 GPa and 11.2 × 10⁻⁶ K⁻¹ (at 1200 °C). The thermal conductivity is reduced to 1.52 W·K⁻¹·m⁻¹ (at 700 °C), and the thermal radiation resistance is improved. The relationship between the phonon thermal diffusivity and temperature was established in order to determine the intrinsic phonon thermal conductivity by eliminating the thermal radiation effects. The results indicate that the thermal and mechanical properties of EuNbO₄ can be effectually optimized via the B-site substitution of Ta, and that this proposed material can be applied as a high-temperature structural ceramic in future.     

Effects of proton irradiation on the microstructure and mechanical properties of Amosic-3 silicon carbide minicomposites

One dimensional Amosic-3 silicon carbide fiber reinforced silicon carbide matrix composites (SiC_f/SiC minicomposites) prepared by chemical vapor infiltration were irradiated with 2.8 MeV proton ions. The ion fluences were 1.0 × 10¹⁷ and 1.5 × 10¹⁷ cm⁻² at room temperature and 300 °C, respectively. The microstructure and mechanical properties were investigated before and after proton irradiation. Raman spectra showed no evident change in Amosic-3 fibers regardless of irradiation temperature, which is confirmed by high resolution transmission electron microscopy observation. Pyrolytic carbon interphase showed slightly expansion after 300 °C irradiation, however, no microstructure changes were observed in SiC matrix. Moreover, it can be deduced that no irradiation induced changes in mechanical properties were observed after present proton irradiation.     

Proton conductive membranes based on silicotungstic acid/silica and polybenzimidazole

Membranes formed by polybenzimidazole and silicotungstic acid supported on silica have been prepared. The membranes were characterized in order to evaluate their proton conduction, mechanical stability and structural characteristics. Silica produced a beneficial effect on proton conduction of the membranes. The membranes with 50 wt.% of SiWA–SiO₂/PBI was mechanically stable and gave proton conductivity of 1.2×10⁻³ S cm⁻¹ at 160°C and 100% relative humidity. All the materials prepared had amorphous structure.     

Accelerating Industrial-Level NO3− Electroreduction to Ammonia on Cu Grain Boundary Sites via Heteroatom Doping Strategy

Although the electrocatalytic nitrate reduction reaction (NO₃⁻RR) is an attractive NH₃ synthesis route, it suffers from low yield due to the lack of efficient catalysts. Here, this work reports a novel grain boundary (GB)-rich Sn-Cu catalyst, derived from in situ electroreduction of Sn-doped CuO nanoflower, for effectively electrochemical converting NO₃⁻ to NH₃. The optimized Sn_1%-Cu electrode achieves a high NH₃ yield rate of 1.98 mmol h⁻¹ cm⁻² with an industrial-level current density of −425 mA cm⁻² at −0.55 V versus a reversible hydrogen electrode (RHE) and a maximum Faradaic efficiency of 98.2% at −0.51 V versus RHE, outperforming the pure Cu electrode. In situ Raman and attenuated total reflection Fourier transform infrared spectroscopies reveal the reaction pathway of NO₃⁻RR to NH₃ by monitoring the adsorption property of reaction intermediates. Density functional theory calculations clarify that the high-density GB active sites and the competitive hydrogen evolution reaction (HER) suppression induced by Sn doping synergistically promote highly active and selective NH₃ synthesis from NO₃⁻RR. This work paves an avenue for efficient NH₃ synthesis over Cu catalyst by in situ reconstruction of GB sites with heteroatom doping.     

Mechanical and thermal properties of RE4Hf3O12 (RE=Ho,Er, Tm) ceramics with defect fluorite structure

The thermal and environmental barrier coatings (T/EBC) are technologically important for advanced propulsion engine system. In this study, RE₄Hf₃O₁₂ (RE=Ho, Er, Tm) with defect fluorite structure was investigated for potential use as top TBC layer. Dense pellets were fabricated via a hot pressing method and the mechanical and thermal properties were characterized. RE₄Hf₃O₁₂ (RE=Ho, Er, Tm) possessed a high Vickers hardness of 11 GPa. The material retained high elastic modulus at elevated temperatures up to 1773 K, which made it attractive for high temperature application. The coefficient of thermal expansion (CTE) of RE₄Hf₃O₁₂ (RE = Ho, Er, Tm) laid in the range between 7 × 10⁻⁶ K⁻¹ to 10 × 10⁻⁶ K⁻¹ from 473 K to 1673 K. In addition, the rare earth hafnates exhibited lower thermal conductivity which rendered it a good candidate material for thermal barrier applications.     

Construction of Bimetallic Heterojunction Based on Porous Engineering for High Performance Flexible Asymmetric Supercapacitors

It remains a great challenge to design and manufacture battery-type supercapacitors with satisfactory flexibility, appropriate mechanical property, and high energy density under high power density. Herein, a concept of porous engineering is proposed to simply prepare two-layered bimetallic heterojunction with porous structures. This concept is successfully applied in fabrication of flexible electrode based on CuO-Co(OH)₂ lamella on Cu-plated carbon cloth (named as CPCC@CuO@Co(OH)₂). The unique structure brings the electrode a high specific capacity of 3620 mF cm⁻² at 2 mA cm⁻² and appropriate mechanical properties with Young's modulus of 302.0 MPa. Density functional theory calculations show that porous heterojunction provides a higher intensity of electron state density near the Fermi level (E–E_f = 0 eV), leading to a highly conductive CPCC@CuO@Co(OH)₂ electrode with both efficient charge transport and rapid ion diffusion. Notably, the supercapacitor assembled from CPCC@CuO@Co(OH)₂//CC@AC shows high energy density of 127.7 W h kg⁻¹ at 750.0 W kg⁻¹, remarkable cycling performance (95.53% capacity maintaining after 10 000 cycles), and desired mechanical flexibility. The methodology and results in this work will accelerate the transformative developments of flexible energy storage devices in practical applications.     

Enhanced Crystallinity,Dielectric, and Energy Harvesting Performances of Surface‐Treated Barium Titanate Hollow Nanospheres/PVDF Nanocomposites

Enhancement of the energy harvesting performance and dielectric constants of poly(vinylidene fluoride) (PVDF)‐based capacitors is realized by incorporating 16 wt% of surface‐treated BaTiO₃ hollow nanospheres (HNSs) in comparison with the pristine PVDF. The fabricated BaTiO₃ HNSs with particle sizes of ≈20 nm and BET surface area of 297 m² g⁻¹ are treated by three different surface modifiers. The changes in crystallinity of the PVDF containing the surface‐treated BaTiO₃ HNSs are induced by both enlarged surface areas and increased surface functionality of the HNSs. Effects of such surface functionalities on the crystalline, dielectric, and energy harvesting performances of the nanocomposites are systematically investigated to identify the optimal surface modifier to enhance the energy density of the nanocomposites. Consequently, these changes in crystallinity lead to higher dielectric constants (ε′ ≈ 109.6) and energy density (U_e ≈ 21.7 J cm⁻³) with highly retained breakdown strength (E = 3.81 × 10³ kV cm⁻¹) compared to pristine PVDF (ε′ ≈ 11.6 and U_e ≈ 2.16 J cm⁻³ at 3.98 × 10³ kV cm⁻¹), indicating their potential as high energy density capacitors.     

Hierarchically 3D structured milled lamellar MoS2/nano-silicon@carbon hybrid with medium capacity and long cycling sustainability as anodes for lithium-ion batteries

A hierarchically 3D structured milled lamellar MoS₂/nano-silicon@carbon hybrid with medium capacity and long-term lifespan is designed by a green and scalable approach using ball milling process and spray-drying/pyrolysis routes. The microspheres consist of low-content nano-silicon (20 wt%), milled lamellar MoS₂ sheets and porous carbon skeletons. A mixture of silicon nanoparticles and MoS₂ flakes serves as an inner core, while porous carbon pyrolyzed from petroleum pitch acts as a protective shell. The particular architecture affords robust mechanical support, abundant buffering space and enhanced electrical conductivity, thus effectively accommodating drastic volume variation during repetitive Li⁺ intercalation/extraction. The Si/MoS₂@C hybrid delivers a high initial discharge specific capacity of 1257.8 mA h g⁻¹ and exhibits a reversible capacity of 767.52 mA h g⁻¹ at a current density 100 mA g^-1 after 250 cycles. Most impressively, the electrode depicts a superior long-cycling durability with a discharge capacity of 537.6 mA h g⁻¹ even after 1200 cycles at a current density of 500 mA g^-1. Meanwhile, the hybrid also shows excellent rate performance such as 388.1 mA h g⁻¹ even at a large current density of 3000 mA g^-1.     

Removal of oil from stable oil-water emulsion by induced air flotation technique

The present study investigates the application of induced air flotation technique on oil removal performance of a separator column (d = 10 cm; H = 150 cm). A preparation method to produce a very stable synthetic emulsion was developed. The stability rate constants K_st were determined under different conditions, and K_st for very stable emulsion was 0.000907 h ⁻¹. Several parameters affecting the performance of the separator were investigated. The experimental data were also analyzed in terms of a first-order kinetic rate model. A removal rate constant, K_r, was obtained. The maximum oil removal obtained from stable emulsion contained 4% by weight sodium chloride was 78.1%, and the corresponding K_r value was 9.18 h⁻¹.     

A Solid‐State Fibriform Supercapacitor Boosted by Host–Guest Hybridization between the Carbon Nanotube Scaffold and MXene Nanosheets

Fiber‐shaped supercapacitors with improved specific capacitance and high rate capability are a promising candidate as power supply for smart textiles. However, the synergistic interaction between conductive filaments and active nanomaterials remains a crucial challenge, especially when hydrothermal or electrochemical deposition is used to produce a core (fiber)–shell (active materials) fibrous structure. On the other hand, although 2D pseudocapacitive materials, e.g., Ti₃C₂T _x (MXene), have demonstrated high volumetric capacitance, high electrical conductivity, and hydrophilic characteristics, MXene‐based electrodes normally suffer from poor rate capability owing to the sheet restacking especially when the loading level is high and solid‐state gel is used as electrolyte. Herein, by hosting MXene nanosheets (Ti₃C₂T _x ) in the corridor of a scrolled carbon nanotube (CNT) scaffold, a MXene/CNT fiber with helical structure is successfully fabricated. These features offer open spaces for rapid ion diffusion and guarantee fast electron transport. The solid‐state supercapacitor based on such hybrid fibers with gel electrolyte coating exhibits a volumetric capacitance of 22.7 F cm⁻³ at 0.1 A cm⁻³ with capacitance retention of 84% at current density of 1.0 A cm⁻³ (19.1 F cm⁻³), improved volumetric energy density of 2.55 mWh cm⁻³ at the power density of 45.9 mW cm⁻³, and excellent mechanical robustness.     

Mechanical properties of Al2O3/Ni laminated composites

Al₂O₃/Ni laminated composites were prepared by aqueous tape casting and hot pressing with intent to study mechanical properties including the fracture strength and toughness. The residual stress was evaluated and proved. The relations of mechanical properties with the thermal residual stress, the ductility of metal layers and the layer thickness ratio were studied, respectively. It was found that the toughness and work of fracture of Al₂O₃/Ni laminar reached to 12.56 MPa m^1/2 and 12 450 J m^− 2, which are 3.6 and 478.8 times that of pure Al₂O₃.     

A facile preparation of graphene/reduced graphene oxide/Ni(OH)2 two dimension nanocomposites for high performance supercapacitors

A Ni(OH)₂ composite with good electrochemical performances was prepared by a facile method. Ni(OH)₂ was homogeneously grown on the hydrophilic graphene/graphene oxide (G/GO) nanosheets, which can be prepared in large scale in my lab. Then G/GO/Ni(OH)₂ was reduced by L-Ascorbic acid to obtain G/RGO/Ni(OH)₂. Caused by the synergy effects among the components, the G/RGO/Ni(OH)₂ electrode showed good electrochemical properties. The G/RGO/Ni(OH)₂ electrode possessed a specific capacitance as high as 1510 F g⁻¹ at 2 A g⁻¹ and even 890 F g⁻¹ at 40 A g⁻¹. An asymmetric supercapacitor device consisting of G/RGO/Ni(OH)₂ and reduced graphene oxide (RGO) was installed and displayed a high energy density of 44.9 W h kg⁻¹ at the power energy density of 400.1 W kg⁻¹. It was verified that the G/GO nanosheets are ideal supporting material in supercapacitor.     

Fabrication of microwave exfoliated graphite oxide reinforced thermoplastic polyurethane nanocomposites: Effects of filler on morphology,mechanical, thermal and conductive properties

Different formulations of microwave-exfoliated graphite oxide (MEGO) based thermoplastic polyurethane (TPU) nanocomposites were successfully prepared via melt blending followed by injection molding. The spectroscopic study indicated that a strong interfacial interaction had developed between the MEGO and the TPU matrix. The microscopic observations showed that the MEGO layers were homogeneously dispersed throughout the TPU matrix. Thermal analysis indicated that the glass transition temperatures (T_g) of the nanocomposites increased with increasing MEGO content and their thermal stability improved in comparison with pure TPU matrix. The mechanical properties of nanocomposites improved substantially by the incorporation of MEGO into the TPU matrix. Electrical conductivity test indicated that a conductivity of 10⁻⁴ S cm⁻¹ was achieved in the nanocomposite containing only 4.0 wt.% of MEGO.     

Thiol-Branched Solid Polymer Electrolyte Featuring High Strength,Toughness, and Lithium Ionic Conductivity for Lithium-Metal Batteries

Lithium-metal batteries (LMBs) with high energy densities are highly desirable for energy storage, but generally suffer from dendrite growth and side reactions in liquid electrolytes; thus the need for solid electrolytes with high mechanical strength, ionic conductivity, and compatible interface arises. Herein, a thiol-branched solid polymer electrolyte (SPE) is introduced featuring high Li⁺ conductivity (2.26 × 10⁻⁴ S cm⁻¹ at room temperature) and good mechanical strength (9.4 MPa)/toughness (≈500%), thus unblocking the tradeoff between ionic conductivity and mechanical robustness in polymer electrolytes. The SPE (denoted as M-S-PEGDA) is fabricated by covalently cross-linking metal–organic frameworks (MOFs), tetrakis (3-mercaptopropionic acid) pentaerythritol (PETMP), and poly(ethylene glycol) diacrylate (PEGDA) via multiple C S C bonds. The SPE also exhibits a high electrochemical window (>5.4 V), low interfacial impedance (<550 Ω), and impressive Li⁺ transference number (t_Li+ = 0.44). As a result, Li||Li symmetrical cells with the thiol-branched SPE displayed a high stability in a >1300 h cycling test. Moreover, a Li|M-S-PEGDA|LiFePO₄ full cell demonstrates discharge capacity of 143.7 mAh g⁻¹ and maintains 85.6% after 500 cycles at 0.5 C, displaying one of the most outstanding performances for SPEs to date.     

Highly Flexible K-Intercalated MnO2/Carbon Membrane for High-Performance Aqueous Zinc-Ion Battery Cathode

The layered MnO₂ is intensively investigated as one of the most promising cathode materials for aqueous zinc-ion batteries (AZIBs), but its commercialization is severely impeded by the challenging issues of the inferior intrinsic electronic conductivity and undesirable structural stability during the charge–discharge cycles. Herein, the lab-prepared flexible carbon membrane with highly electrical conductivity is first used as the matrix to generate ultrathin δ-MnO₂ with an enlarged interlayer spacing induced by the K⁺-intercalation to potentially alleviate the structural damage caused by H⁺/Zn²⁺ co-intercalation, resulting in a high reversible capacity of 190 mAh g⁻¹ at 3 A g⁻¹ over 1000 cycles. The in situ/ex-situ characterizations and electrochemical analysis confirm that the enlarged interlayer spacing can provide free space for the reversible deintercalation/intercalation of H⁺/Zn²⁺ in the structure of δ-MnO₂, and H⁺/Zn²⁺ co-intercalation mechanism contributes to the enhanced charge storage in the layered K⁺-intercalated δ-MnO₂. This work provides a plausible way to construct a flexible carbon membrane-based cathode for high-performance AZIBs.     

Low temperature phase barium borate: A new optical limiter in continuous wave and nano pulsed regime

Low temperature phase barium borate was synthesized by hydrothermal method. XRD analysis confirms the formation of γ-BBO or hydrated barium polyborate (Ba₃B₆O₉(OH)₆) which crystallizes in monoclinic system in the P2/c space group. The molecular structure analysis shows the presence of dominant BO₄ unit and the hydrated nature of material. γ-BBO exhibits sharp absorption edge at 202 nm and highly transparency in the UV–Visible–NIR region. The peak at 347 nm in the emission spectrum is due to the presence of self-trapped exciton. The third order nonlinear optical properties and limiting behavior of low temperature barium borate in both pulsed and continuous wave regime were studied. The effective 2PA absorption coefficient of γ-BBO under ns pulse excitation is estimated to be 0.38 × 10⁻¹⁰ m/W. The nonlinear absorption coefficient, refractive index and optical susceptibility of the material in cw regime were found to be in the order of 10⁻⁵ m W⁻¹, 10⁻¹² m² W⁻¹, 10⁻⁶ esu respectively. In both regimes, low temperature phase barium borate exhibits better optical limiting properties than high temperature phase β-BBO.     

Role of iodate ions in chemical mechanical and electrochemical mechanical planarization of Ta investigated using time-resolved impedance spectroscopy

Chemical mechanical planarization (CMP) is currently used in the processing of Cu/Ta interconnect structures. Electrochemical mechanical planarization (ECMP) is an emerging extension of CMP that can potentially allow low down-pressure planarization of newer interconnect structures containing easily breakable porous dielectrics. In both CMP and ECMP of Ta, it is necessary to chemically (or electrochemically) form a “soft” surface film that can be easily removed by minimum mechanical abrasion. Alkaline KIO₃ solutions appear to serve this purpose in CMP of Ta and, as we show in this work, may also be utilized in ECMP of Ta. Using time-resolved impedance spectroscopy we study here the relevant surface reactions of IO₃⁻ that lead to a structurally weak surface film of soluble hextantalate [(Ta₆O₁₉)⁸⁻] embedded in (native or electro-generated) Ta₂O₅ on Ta. Catalytic reduction of IO₃⁻ on Ta₂O₅ enhances the local pH at the oxidized surface and promotes the conversion of Ta₂O₅ to (Ta₆O₁₉)⁸⁻. The chemical role of iodate ions in material removal through these reactions is similar to that of hydrogen peroxide in CMP of Ta in alkaline media.     

Electrochemical and structural aspects of lithium insertion into the new layered compound CdIn2S2Se2

Electrochemical lithium insertion in pure and (PTFE-and/or C-) mixed CdIn₂S₂Se₂ has been investigated by galvanostatic discharge experiments in the (−) Li/organic electrolyte/CdIn₂S₂Se₂ (+) cell, also considering the behaviour in quasi-equilibrium open-circuit conditions, and by cyclic voltammetry. Structural changes induced by lithium insertion have been observed by powder X-ray diffraction measurements. The reversibility of the process is poor in the whole range explored, but differences in behaviour are noticed. During a galvanostatic discharge of the cell up to about 0.7 F.mol⁻¹ no structural change takes place and the lithium diffusion process is slow, as shown by the very low value of the chemical diffusion coefficient (around 10⁻¹² cm².s⁻¹, at 30 °C) determined according to a current-pulse relaxation technique. During a deeper discharge up to 5.35 F.mol⁻¹ two plateaux — a short and an extended one — are noted in the experimental curve, while pseudocrystalline phases are formed. As a consequence of these structural rearrangements, the time needed to reach open-circuit quasi-equilibrium conditions after a galvanostatic discharge is high, particularly in the region of the first plateau. Analyses of the results evidence that CdIn₂S₂Se₂ is a very interesting new compound, more significant for its fundamental properties than in view of its application as cathode material in aprotic solvent lithium cells.