Science China Materials最新文献

MAX phases are a member of ternary carbide and nitride, with a layered crystal structure and a mixed nature of chemical bonds (covalent-ionic-metallic) that promote MAX phases embracing both ceramic and metal characteristics. As a result, MAX phase ceramics emerge with remarkable properties unique from other traditional ceramics. In this review, we focus on alternate processing approaches for MAX phases that are cost-effective and energy-saving. The MAX phase purity, formation of other unwanted phases, microstructure, and properties are influenced by many parameters during processing. Therefore, we highlight the effect of numerous factors, which alternately diminish the efficiency and performance of materials. Here, the impact of several parameters, such as starting materials, stoichiometric composition, temperature, pressure, particle size, porosity, microstructure, mechanical alloying, mechanical activation, ion irradiation, and doping, are summarized to reveal their influence on the synthesis and properties of MAX phases. The potential applications of MAX phases are considered for their development on a commercial scale toward the industry.

The creation of Cu⁰/Cu⁺ interface over Cu-based catalysts is known to facilitate the production of multi-carbon (C₂₊) products during CO₂ reduction reaction (CO₂ RR). However, the Cu⁺ moieties exhibit high susceptibility towards reduction into Cu⁰ at a high current density. Thus, a comprehensive understanding and rational shaping strategy for the construction and stabilization of Cu⁰/Cu⁺ interface in Cu-based catalysts is imperative. Herein, we proposed a controllable “nanoparticle assembly” strategy to obtain hollow spherical assemblies (HSA) composed of numerous Cu₂O nanoparticles (HSA-Cu₂O). The HSA-Cu₂O catalysts significantly enhance the selectivity of C₂₊ products, resulting in an impressive overall Faraday efficiency (FE) of 79.2% ± 0.7% at a partial current density of 317.1 mA cm⁻². The HSA-Cu₂O catalysts undergo in-situ electrochemically reconstruction during CO₂RR, achieving Cu⁰/Cu⁺ interfacial sites with a high density. The Auger electron spectra, in-situ Raman, and morphological evolution studies have confirmed that the combination of the Cu⁰/Cu⁺ interface and hollow sphere architecture facilitated the concentration of *CO intermediates, thereby promoting C–C dimerization to boost C₂₊ selectivity in CO₂RR.

Removing CO₂ impurities from C₂H₂/CO₂ mixtures is an essential process for producing high-purity C₂H₂ under high humidity. High-stability and low-cost metal-organic frameworks (MOFs) have great potential in C₂H₂/CO₂ industrial separation. However, due to the complementary adsorption of H₂O and CO₂, water vapor has a negative impact on the implementation of C₂H₂ purification. Herein, we propose a synergistic strategy of pore surface functionalization and polydimethylsiloxane (PDMS) deposition to avoid the influence of water vapor while improving C₂H₂/CO₂ separation performance. A commercially available metal-organic framework (ALP-MOF-1) was used as a template to functionalize its pore surface with CH₃, Br, and F. The optimized material ALP-MOF-1(F) exhibits the highest C₂H₂ uptake (117.78 cm³/g at 298 K and 10⁶ Pa) and C₂H₂/CO₂ uptake ratio (3.1) among ALP-MOF systems. Computational simulations show that the well-matched pore space and the significant electronegativity and polarizability of the fluorine groups on the pore surface jointly enhance the framework-C₂H₂ interaction. Furthermore, the deposition of PDMS on ALP-MOF-1 and ALP-MOF-1(F) significantly improves their C₂H₂/CO₂ separation stability under 80% humidity conditions.

The development of hydrogels capable of emitting multicolor fluorescence presents a promising avenue for addressing concerns related to information leakage and distortion of sensitive data. The integration of multifactor-induced tunable fluorescence with a unique upper critical solution temperature (UCST) behavior in hydrogels significantly contributes to the development of multi-dimensional and multi-level information storage materials that can dynamically display information as well as offer a high level of security and protection for information. However, the fusion of these advantageous properties into hydrogels intended for information storage and display remains a considerable challenge. In this context, we introduce a novel three-dimensional (3D) fluorescent code-producing hydrogel array fabricated via vat photopolymerization (VP) 3D printing, a technique offers a sustainable and efficient approach. This array unites the desired properties, capable of sequentially revealing concealed information through two distinct steps: (i) a heat-induced phase transition, and (ii) multicolor fluorescence triggered by ultraviolet (UV)/temperature exposure under specific conditions (i.e., certain UV irradiation duration, heating time, and wavelength). The reversible transparency and reprogrammable fluorescence emission properties of these hydrogels are expected to significantly enhance the processes of information encryption and anti-counterfeiting. This advancement could potentially revolutionize the field of information security.

CdSe quantum-dot (QD) film, as the core function layer, plays a key role in various optoelectronic devices. The thickness uniformity of QD films is one of the key factors to determine the overall photoelectric performance. Therefore, it is important to obtain the thickness distribution of large-area QD films. However, it is difficult for traditional methods to quickly get the information related to its thickness distribution without introducing additional damage. In this paper, a non-contact and non-destructive inspection method for in-situ detecting the thickness uniformity of CdSe QD film is proposed. The principle behind this in-situ inspection method is that the photoluminescence quenching phenomenon of the QD film would occur under a high electric field, and the degree of photoluminescence quenching is related to the thickness of the quantum dot films. Photoluminescence images of the same QD film without and with an electric field are recorded by a charge-coupled device camera, respectively. By transforming the brightness distribution of these two images, we can intuitively see the thickness information of the thin film array of QD. The proposed method provides a meaningful inspection for the manufacture of QD based light-emitting display.

We report a simple, effective, and universal lattice reconstruction approach to improve the quality of perovskite films by using nonpolar solvents with high Gutmann donor numbers (DNs). We find that high-DN nonpolar solvents, for instance, ethyl acetate, can interact with perovskite precursors. Such a solvent can make the perovskite lattice more ordered and “harder” and promote the formation of heterostructures with low-dimensional perovskite impurities and residual solvent molecules. As a result, the lattice-reconstructed perovskite films exhibit reduced defect densities and suppressed ion migration. The resultant mixed-halide blue perovskite light-emitting diodes (PeLEDs) show greatly enhanced tolerance to high driving current densities and voltages, demonstrating high brightness, outstanding color stability and low efficiency roll-off. Our work provides a deep understanding of the interactions between nonpolar solvents and perovskites and offers useful guidelines for further development of high-power PeLEDs.

The synthetic path of a catalyst determines its morphology, species, and performance, and in-situ monitoring the catalyst formation process is fascinating and challenging. Herein, a newly developed synchrotron radiation small-angle X-ray scattering/X-ray diffraction/X-ray absorption fine structure (SAXS/XRD/XAFS) combined technique was used to in-situ monitor the isothermal-isobaric synthesis process of CO₂-assisted (BiO)₂CO₃ (BOC) photocatalyst, and the atomic near-neighbor structure, crystalline structure and nanoscale particle size evolution with reaction time were simultaneously captured. The results show that both polyvinyl pyrrolidone and CO₂ formed uniformly-distributed nano-sized scatterers in the Bi-based precursor solution, presenting short-range ordered structures to a certain extent. The as-prepared BOC catalytic particles underwent the evolution process of initial Bi(OH)₃ precipitate, early-stage formed KBiO₂ molecules, intermediate amorphous (BiO)₄CO₃(OH)₂ nanoparticles, and finally crystallized flower-like BOC particles self-assembled by nanosheets. The flower-like BOC particles, Bi/BOC composite, and Bi nanospheres were further prepared with different synthesis paths. Flower-like BOC particles showed the best photocatalytic degradation performance of RhB. Scavenger experiment and theoretical calculation revealed the photocatalytic mechanisms of BOC. This work has implications for path-dependent synthesis of other catalysts.