Zhaoxia Hou

Fine-grained Yb:Y₂O₃ laser ceramics with excellent transmittance and thermal conductivity were fabricated from commercial powders. The process involved aqueous colloidal forming, additive-free air pre-sintering at 1400 °C, and hot isostatic pressing at 1550 °C. Suspensions were prepared with a deionization process to alleviate the hydrolysis issue, which optimizes the microstructure uniformity and enhances the green compacts’ density after consolidation. The microstructure, in-line transmittance, microhardness, and fracture toughness of the Yb³⁺-doped Y₂O₃ ceramics with different concentrations were measured. The 5.0 at% Yb³⁺-doped Y₂O₃ ceramic yielded a superior transmittance of 80.1% at 1100 nm and 83.0% in the mid-infrared region. The average grain size was 752 nm. The sample exhibited a thermal conductivity of 9.94 W·m⁻¹·K⁻¹ while achieving a 1076 nm laser output with a 42 mW peak power and 4.3% slope efficiency.

All‐solid‐state stretchable supercapacitors (SSSCs) have attracted widespread attention in the wearable and medical fields because of their nontoxic, safe, and environmentally friendly characteristics. In this paper, a dual network hydrogel polymer was synthesized by a one‐pot method, which was constructed from sodium alginate (SA) and zwitterion copolymer of acrylamide (AM) and sulfobetaine methacrylate (SBMA). The dual network hydrogel polymerSA_m/P(AM‐co‐SBMA (SAS_m for short) were immersed in 1 M H₂SO₄ electrolyte to obtain gel polymer electrolytes (GPEs). Stretchable electrodes were synthesized on the matrix of SAS_m gels. Non‐integrated all‐solid‐state stretchable supercapacitors (non‐integrated SSSCs), integrated all‐solid‐state supercapacitors (SSCs) and integrated SSSCs were all assembled into the ‘sandwich’ structure. The elongation of the integrated SSSC is the best and reaches 280 %, and its areal capacitance is 1.96 mF/cm² under a current destiny of 50 μA/cm², and the capacitance still remains 95 % of the initial value after 10000 charge and discharge cycles, and its energy density is 5.8×10⁻² μWh/cm² at a power density of 2.9×10⁻² mW/cm². This integrated SSSC has excellent cycling stability while maintaining good tensile properties.

The free‐standing electrodes are important for high‐performance supercapacitors. Polyaniline/graphene (PANI/rGO) composites are extensively researched. However, the structural design of free‐standing PANI/rGO electrodes needs further discussion. Herein, free‐standing PANI/rGO with 3D double‐crosslinked network structures is prepared by rGO modification, freeze drying, in situ polymerization, and gel die‐casting technology. The uniform precipitation of the ammonium persulfate on the surface of modified graphene (P‐rGO) sheets is profit to build a 3D double‐crosslinked network structure with PANI. Besides, the synergistic effect of aniline and p‐phenylenediamine helps to construct crosslinked PANI on the surface and deep in the pores of P‐rGO. The PANI/P‐rGO aerogels with a 3D porous double‐crosslinked structure are pressed into free‐standing electrodes by gel die casting and assembled into symmetrical supercapacitors. The electrodes show good cycling stability, which is much higher than that of P‐rGO or pure PANI.

Improved optical and mechanical properties are required for future infrared windows working in harsher mechanical and thermal environments than today. Ameliorating the homogeneity of the phase domain and reducing the size of the phase domain are effective approaches for enhancing the optical transmittance and mechanical hardness of a nanocomposite. In this work, we reported that the Gd₂O₃-MgO nanopowders were prepared by two different processes. The core–shell nanopowders synthesized by urea precipitation have a much lower agglomeration than the nanopowders prepared by sol–gel. Excellent transmittance (70.0%–84.1%) at 3–6 μm mid-infrared wave range and a high Vickers hardness value (10.3 ± 0.6 GPa) were maintained using the nanopowders synthesized by urea precipitation mainly due to its homogenous phase domain distribution.

An easy approach is described for the preparation of ZrO₂-coated Y₂O₃ nanopowder from a solution of zirconium nitrate with commercial Y₂O₃ nanopowder. The evolution process of the ZrO₂ coating layer upon calcination, such as the phase and microstructure of the particles’ surface, was studied. Calcination of the powder at 700 °C resulted in ZrO₂-coated Y₂O₃ nanopowder. The rheological properties of the suspensions of ZrO₂-coated Y₂O₃ powders were studied. A well-dispersed suspension with a solid loading of 35.0 vol% using ZrO₂-coated Y₂O₃ nanopowder was obtained. The consolidated green body obtained by the centrifugal casting method showed improved homogeneity with a relative density of 50.2%. Transparent ceramic with high transparency and an average grain size of 1.7 µm was obtained by presintering at 1500 °C for 16 h in air, followed by post-HIP at 1550 °C for 2 h under 200 MPa pressure. The in-line transmittance at the wavelength of 1100 nm (1.0 mm thick) reached 81.4%, close to the theoretical transmittance of Y₂O₃ crystal.

Graphite oxide was prepared via the modified Hummers’ method and graphene via chemical reduction. Deoxygenation efficiency of graphene oxide was compared among single reductants including sodium borohydride, hydrohalic acids, hydrazine hydrate, and vitamin C. Two‐step reduction of graphene oxide was primarily studied. The reduced graphene oxide was characterized by XRD, TG, SEM, XPS, and Raman spectroscopy. Square resistance was measured as well. Results showed that films with single‐step N₂H₄ reduction have the best transmittance and electrical conductivity with square resistance of ~5746 Ω/sq at 70% transmittance. This provided an experimental basis of using graphene for electronic device applications.