Search Results (48)

The effects of gamma radiation on the performance of two corrosion-resistant coatings applied to stainless-steel 304L (SS304L) surfaces are presented. Specifically, the ability of the coatings to mitigate corrosion of SS304L surfaces as a function of the dose received (0–1300 Mrad) and dose rate (176 compared to 1054 rad/s) is evaluated using electrochemical methods, spectroscopy, and microscopy. Coating A, an organic/inorganic hybrid coating consisting of a two-part silica ceramic component and a polymer linker was evaluated in comparison to Coating B, which utilized Coating A as a topcoat for a commercial, off-the-shelf, Zn-rich primer. Post irradiation, Coating A demonstrated some corrosion protection following exposure to low levels of gamma radiation, but coating degradation occurred with an increased exposure dose and resulted in isolated regions of corrosion initiation. For Coating B, greater corrosion resistance was observed compared to Coating A due to the sacrificial nature of the Zn at elevated doses of gamma radiation. No effect of the dose rate (for the single dose examined) was observed for either coating. It is proposed for Coating B that as the polymer coating thermally degrades above 250 °C (bond scission of the polymer occurs), the remaining Zinc layer adhered to the SS304L post-irradiation enables enhanced corrosion resistance as compared to Coating A, which displays solely polymer degradation. The results presented herein establish an understanding of coating behavior with radiation exposure, specifically the relationship between corrosion coating performance and radiation dose, and can inform ageing and lifetime management for various applications. Full article

Sensor miniaturization offers significant advantages, including enhanced SoC integration efficiency, reduced cost, and lightweight design. While the roll-to-roll printed electronics fabrication process is advantageous for the mass production of sensors compared to the traditional MEMS technology, producing sensors that require air gap-based 3D structures remains challenging. This study proposes an integration of roll-to-roll gravure printing with a transferring and bonding method for touch sensor fabrication. Unlike previously reported methods for sacrificial layer removal, this approach prevents stiction issues, thus enabling sensor miniaturization and providing the flexibility to select materials that minimize sensitivity degradation during scaling. For the lower part of the sensor, Ag and BaSO₄ were roll-to-roll gravure-printed on a flexible PET substrate to form the bottom electrode and dielectric layer, followed by BaSO₄ spin coating on the sensor’s anchor area to form a spacer. For the upper part, a water-soluble PVP sacrificial layer was roll-to-roll gravure-printed on another flexible PET substrate, followed by spin coating Ag and SU-8 to form the top electrode and the structural layer, respectively. The sacrificial layer of the upper part was removed with water to delaminate the top electrode and structural layer from the substrate, then transferred and bonded onto the spacer of the lower part. Touch sensors of three different sizes were fabricated, and their performances were comparatively analyzed along with that of an epoxy resin-based sensor, demonstrating that our sensor attained miniaturization while achieving relatively high sensitivity. Full article

As a promising member of the carbon nitride family, nitrogen-rich g-C₃N₅ has attracted significant attention because of its excellent light absorption performance. Nevertheless, its practical application in photocatalytic CO₂ reduction is hindered by severe photogenerated charge recombination and limited CO₂ adsorption capacity. Constructing a heterojunction has emerged as an effective strategy to mitigate charge recombination, thereby enhancing the photocatalytic performance of the catalyst. Herein, a series of CdS/g-C₃N₅-X heterojunction catalysts were prepared via an in situ hydrothermal approach. The obtained heterojunction catalysts exhibited a novel coral reef-like morphology which facilitated the exposure of additional active sites, thereby enhancing the adsorption and activation of CO₂. Moreover, studies have shown that CdS can be anchored to the surface of g-C₃N₅ through C-S bonds, forming a built-in electric field at the interface, which accelerated the separation and transfer of photogenerated charges. Consequently, the resulting heterojunction materials demonstrated high efficiency in photocatalytic CO₂ reduction with H₂O as a sacrificial agent. In particular, CdS/g-C₃N₅-0.2 exhibited the maximum photocatalytic performance up to 22.9 μmol·g⁻¹·h⁻¹, which was 6 times and 3 times that of unmodified g-C₃N₅ and CdS, respectively. The results indicated that the increased active sites and enhanced charge separation of the Cd/g-C₃N₅-0.2 catalyst were the primary reasons for its improved photocatalytic CO₂ reduction performance. This work provides a novel heterojunction-based photocatalyst for efficient CO₂ photocatalytic reduction, offering insights into the preparation of high-performance photocatalysts for sustainable energy applications. Full article

There is much promise for creating metal organic framework (MOF) films on metal substrates in fields including sensing and electrical conduction. For these applications, direct production of MOF films with strong bonding on metal substrates is extremely desirable. In this study, a simple one-step method without the need for additives or pre-modification is used to directly create zeolitic imidazolate framework-8 (ZIF-8) films with strong bonding on zinc substrate. The formation mechanisms of ZIF-8 film are analyzed. The strong bonding ZIF-8 film can be attributed to an in-situ grown ZnO interlayer between the ZIF-8 and substrate. The growth process shows the formation time of zinc oxide on the substrate, which is subsequently covered by ZIF-8 crystals. The ZnO interlayer results from a combination of decomposition products of the solvent and the zinc ions. Furthermore, the ZnO interlayer serves as a sacrificial precursor for the in-situ nucleation and continuous growth of ZIF-8 film. It serves as an anchoring site between ZIF-8 film and substrate, resulting in strong adhesion. This paper describes a simple and straightforward production process that is expected to provide a theoretical basis for the laboratory preparation of ZIF films. Full article

Hydrogels, known for their outstanding water absorption, flexibility, and biocompatibility, have been widely utilized in various fields. Nevertheless, their application is still limited by their relatively low mechanical performance. This study has successfully developed a dual-network hydrogel with exceptional mechanical properties by embedding amino-functionalized polysiloxane (APSi) networks into a polyvinyl alcohol (PVA) matrix. This hydrogel effectively dissipates energy through dense sacrificial bonds between the networks, allowing for precise control over its tensile strength (ranging from 0.07 to 1.46 MPa) and toughness (from 0.06 to 2.17 MJ/m³) by adjusting the degree of crosslinking in the polysiloxane network. Additionally, the hydrogel exhibits excellent conductivity (10.97 S/cm) and strain sensitivity (GF = 1.43), indicating its potential for use in wearable strain sensors. Moreover, at the end of its life (EOL), the sensor waste can be repurposed as an adsorbent material for metal ions in water treatment, achieving the recycling of hydrogel materials and maximizing resource utilization. Full article

The conversion of nitrogen (N₂) and water (H₂O) into NH₃ by photocatalysis under ambient conditions has been considered an environmentally friendly strategy. However, developing effective catalysts for N₂ fixation is still challenging. Herein, we report a bimetallic JH Fe, Co/TiO₂ derived from NH₂-MIL-125(Ti) by the fast Joule heating (FJH) method for visible–light–driven catalytic N₂ fixation. It was found that the photocatalytic N₂ reduction efficiency of bimetallic FC@TiO₂-JH was improved, enabling an NH₃ yield rate of 110.14 µmol g⁻¹ h⁻¹ without any sacrificial agents. Furthermore, the rate was higher than those of Fe@TiO₂-JH and Co@TiO₂-JH, suggesting that the synergistic effect between Fe and Co broke the electronic equilibrium and increased the center of its d-band, enhancing electronic feedback to the antibonding π* orbitals of N₂ while weakening the bonding energy of N≡N. Meanwhile, the rate was about 2.75 times higher than that of FC@TiO₂-TF, which was calcined in a tube furnace. It is assumed that FJH might lead to the formation of lattice defects, leading to localized charge deficiency, enhanced carrier separation, and transport. Thus, doping of Fe and Co synergistically interacted with the defects produced from FJH, facilitating the photocatalytic reduction process. As detected, it had a greater ability to separate hole–electron pairs and transferred electrons to adsorbed N₂ at faster rates. Our work demonstrates a prospective strategy for designing bimetallic catalysts derived from NH₂-MIL-125(Ti) for N₂ fixation. Full article

Hydrogels endure various dynamic stresses, demanding robust mechanical properties. Despite significant advancements, matching hydrogels’ strength to biological tissues and plastics is often challenging without applying potentially harmful crosslinkers. Using hydrogen bonds as sacrificial bonds offers a promising strategy to produce tough, versatile hydrogels for biomedical and industrial applications. Poly(methacrylic acid) (PMA)/gelatin hydrogels were synthesized by thermally induced free-radical polymerization and crosslinked only by physical bonds, without adding any chemical crosslinker. The addition of gelatin increased the formation of hydrophobic domains in the structure of the hydrogels, which acted as permanent crosslinking points. The increase in PMA and gelatin contents generally led to a lower equilibrium water content (WC), higher thermal stability and better mechanical properties. The values of tensile strength and toughness reached up to 1.44 ± 0.17 MPa and 4.91 ± 0.51 MJ m⁻³, respectively, while the compressive modulus and strength reached up to 0.75 ± 0.06 MPa and 24.81 ± 5.85 MPa, respectively, with the WC being higher than 50 wt.%. The obtained values for compressive mechanical properties are comparable with super-strong hydrogels reported in the literature. In addition, hydrogels exhibited excellent fatigue resistance and biocompatibility, as well as great shape memory properties, which make them prominent candidates for a wide range of biomedical applications. Full article

Shape-shifting polymers are widely used in various fields such as intelligent switches, soft robots and sensors, which require both multiple stimulus-response functions and qualified mechanical strength. In this study, a novel near-infrared-light (NIR)-responsible shape-shifting hydrogel system was designed and fabricated through embedding vinylsilane-modified carbon nanotubes (CNTs) into particle double-network (P-DN) hydrogels by micellar copolymerisation. The dispersed brittle Poly(sodium 2-acrylamido-2-methylpropane-1-sulfonate) (PNaAMPS) network of the microgels can serve as sacrificial bonds to toughen the hydrogels, and the CNTs endow it with NIR photothermal conversion ability. The results show that the CNTs embedded in the P-DN hydrogels present excellent mechanical strength, i.e., a fracture strength of 312 kPa and a fracture strain of 357%. Moreover, an asymmetric bilayer hydrogel, where the active layer contains CNTs, can achieve 0°–110° bending deformation within 10 min under NIR irradiation and can realise complex deformation movement. This study provides a theoretical and experimental basis for the design and manufacture of photoresponsive soft actuators. Full article

Load-bearing biological tissues, such as cartilage and muscles, exhibit several crucial properties, including high elasticity, strength, and recoverability. These characteristics enable these tissues to endure significant mechanical stresses and swiftly recover after deformation, contributing to their exceptional durability and functionality. In contrast, while hydrogels are highly biocompatible and hold promise as synthetic biomaterials, their inherent network structure often limits their ability to simultaneously possess a diverse range of superior mechanical properties. As a result, the applications of hydrogels are significantly constrained. This article delves into the design mechanisms and mechanical properties of various tough hydrogels and investigates their applications in tissue engineering, flexible electronics, and other fields. The objective is to provide insights into the fabrication and application of hydrogels with combined high strength, stretchability, toughness, and fast recovery as well as their future development directions and challenges. Full article

In this work, density functional theory (DFT) calculations were employed to study the photocatalytic reduction of CO₂ into CO using a series of Pt(II) square planar complexes with the general formula [Pt(5-R-dpb)Cl] (dpb = 1,3-di(2-pyridyl)benzene anion, R = H, N,N-dimethylaniline,T thiophene, diazaborinine). The CO₂-into-CO conversion process is thought to proceed via two main steps, namely the photocatalytic/reduction step and the main catalytic step. The simulated absorption spectra exhibit strong bands in the range 280–460 nm of the UV-Vis region. Reductive quenching of the T₁ state of the complexes under study is expected to be favorable since the calculated excited state redox potentials for the reaction with sacrificial electron donors are highly positive. The redox potentials reveal that the reductive quenching of the T₁ state, important to the overall process, could be modulated by suitable changes in the N^C^N pincer ligands. The CO₂ fixation and activation by the three coordinated Pt(II) catalytically active species are predicted to be favorable, with the Pt–CO₂ bond dissociation energies D₀ in the range of −36.9–−10.3 kcal/mol. The nature of the Pt–CO₂ bond of the Pt(II) square planar intermediates is complex, with covalent, hyperconjugative and H-bonding interactions prevailing over the repulsive electrostatic interactions. The main catalytic cycle is estimated to be a favorable exergonic process. Full article

Lignin-containing nanocellulose fibers (LCNF) have been considered as a valuable enhancer for polyacrylic acid (PAA)-based hydrogels that can form rigid porous network structures and provide abundant polar groups. However, the PAA–LCNF hydrogel is dominated by a single-network (SN) structure, which shows certain limitations when encountering external environments with high loads and large deformations. In this paper, sodium alginate (SA) was introduced into the PAA–LCNF hydrogel network to prepare a double-network (DN) hydrogel structure of the SA-Ca²⁺ and PAA–LCNF through a two-step process. The covalent network of PAA–LCNF acts as the resilient framework of the hydrogel, while the calcium bridging networks of SA, along with the robust hydrogen bonding network within the system, function as sacrificial bonds that dissipate energy and facilitate stress transfer. The resulting hydrogel has porous morphologies. Results show that SA can effectively improve the mechanical properties of DN hydrogels and endow them with excellent thermal stability and electrical conductivity. Compared with pure PAA–LCNF hydrogel, the elongation at break of DN hydrogel increased from 3466% to 5607%. The good electrical conductivity makes it possible to use the flexible sensors based on DN hydrogel to measure electrophysiological signals. Our results can provide a reference for developing multifunctional hydrogels that can withstand ultra large deformation. Full article

At present, it is known that when there is clay in concrete, polycarboxylates (PCE) will preferably adsorb in the clay, so that PCE cannot be fully combined with cement particles, which reduces the workability of the cement slurry. In this paper, a new type of maltitol–ammonium salt cationic (KN-lm) sacrificial agent (SA) has been successfully developed via a simple method, which makes PCE easier to bond with cement particles in the cement slurry containing clay. The effect of KN-lm on the fluidity of clay-containing cement paste is studied, and the experimental results show that KN-lm, as an efficient SA of cement slurry, makes PCE more compatible with clay-containing cement slurry, and increases the initial fluidity of cement slurry by about 19%. Further investigations of TOC, XRD, and zeta potential measurements reveal that a KN-lm ion is only preferably adsorbed into clay compared to PCE through electrostatic adsorption but without having any crystal structure change, thus resulting in good dispersion of cement particles. The addition of KN-lm plays an important role in hindering the hydration expansion of the clay by preferential electrostatic adsorption, which means PCE cannot easily insert into the interlayer of the clay. Full article

New heterojunction materials (HJs) were synthesized in-situ by molecularly bonding the monomers of a triazine-based covalent organic framework (bulk COF) on the template of exfoliated carbon nitride (g-C₃N₄). The photocatalysts reduced carbon dioxide to carbon monoxide in aqueous dispersions under UV irradiation. The g-C₃N₄ showed production of 6.50 $\mathsf{\mu }$mol CO g⁻¹ h⁻¹ and the bulk COF of 2.77 $\mathsf{\mu }$mol CO g⁻¹ h⁻¹. The CO yield was evaluated in sustainability photoreduction cycles and their CO₂ uptake capacity and isosteric heat of adsorption were estimated. All the heterojunction photocatalysts obtained ameliorated CO production rates compared to the bulk COF. Finally, the influence of the Pt co-catalyst on the photocatalytic activities was determined without the addition of any sacrificial agent, and the COF:g-C₃N₄ heterojunction with the ratio of 1:10 was proven to be a photocatalytic system with an optimum and selective, CO yield of 7.56 $\mathsf{\mu }$mol g⁻¹ h⁻¹. Full article

Designing and preparing chloroprene rubber (CR) with robust mechanical and excellent flame retardancy performance are challenging. In this work, a biomimetic design for high mechanical and flame-retardant CR by synchronous introducing of sacrificial bond (disulfide) crosslinked networks into the chemically crosslinked network is developed based on two new types of vulcanization reactions. Under the catalysis of $\mathrm{M}\mathrm{g}{\left(\mathrm{O}\mathrm{H}\right)}_2$, the dynamic bond cross-linked network is formed by the reaction between the amino group of cystamine dihydrochloride (CA) and the allylic chlorine group of CR, while the covalently crosslinked network is synchronously formed by two types of nucleophilic substitution reactions in series between $\mathrm{M}\mathrm{g}{\left(\mathrm{O}\mathrm{H}\right)}_2$ and CR. The disulfide bonds serve as sacrificial bonds that preferentially rupture prior to the covalent network, dissipating energy and facilitating rubber chain orientation, so a CA-0.5 sample (CR/CA(0.5 wt%)/$\mathrm{M}\mathrm{g}{\left(\mathrm{O}\mathrm{H}\right)}_2$ (10 wt%) with dual crosslinked networks exhibits excellent mechanical performance, and the tensile strength and elongation at the break of CA-0.5 are 1.41 times and 1.17 times greater than those of the CR-0 sample with covalently crosslinked networks, respectively. Moreover, the addition of $\mathrm{M}\mathrm{g}{\left(\mathrm{O}\mathrm{H}\right)}_2$ significantly improves the flame retardancy of CR. Full article

A series of silylated 2-aminopyrimidines Me_(4−n)Si(NHpyr)_n (Me = methyl, NHpyr = pyrimid-2-ylamino, n = 1, 2, 3, 4), i.e., compounds 1, 2, 3, and 4, respectively, was prepared from a series of the respective chlorosilanes Me_(4−n)SiCl_n and 2-aminopyrimidine. Triethylamine was used as a sacrificial base. Compounds 1, 2, 3, and 4 are solid at room temperature. They were analyzed using ¹H, ¹³C, ²⁹Si NMR, and Raman spectroscopy, and their molecular structures were confirmed by single-crystal X-ray diffraction analyses. All structures exhibit intramolecular van der Waals contacts between the silicon atom and one nitrogen atom of the pyrimidine moiety. Thus, their Si coordination spheres can be interpreted as [4+n] coordinated capped tetrahedra. Intermolecular hydrogen bonds (N–H···N bridges between the Si-bound amino groups and the non-Si-capping pyrimidine N atoms) are a constant contributor to the solid-state structures of these compounds. Furthermore, compounds 2 and 4 exhibit N–H···N bridges which involve 50% of their Si-capping N atoms as hydrogen bridge acceptors. Consequently, 50% of the non-Si-capping pyrimidine N atoms are stabilized by C–H···N contacts. As a result of a particularly dense network of intermolecular hydrogen bridges, the melting point of Si(NHpyr)₄ (compound 4) is higher than 300 °C. Full article