Dispersing graphene into ceramics is an effective way to increase the emissivity of ceramics. In this study, a series of high-emissivity ZrO₂/graphene composite ceramic blocks with different graphene content are successfully synthesized through combustion synthesis and spark plasma sintering (SPS), in which Mg powder, ZrO₂ powder and CO₂ gas are used as raw materials. Infrared performance studies show that, at room temperature, the emissivity of SPSed ZrO₂/graphene over 3–8 µm band is up to 0.927. The peak wavelength of ZrO₂/graphene at 470 °C is the same as that of moxibustion, which is ∼3.98 µm. The optimal composition is a ZrO₂/graphene ceramic sample with a content of Mg = 14.3 wt % in raw powder. At 470 °C, its spectral integral intensity could reach 88.0 % of that of moxibustion. And the ZrO₂/graphene composite ceramic block shows better oxidation resistance compared with powder. After 15 h heat treatment (470 °C), the integral emissivity of bulk is basically unchanged, and it is 1.50 times than that of the powder. Using the ZrO₂/graphene ceramic as emission source in the moxibustion instrument developed by us can achieve the therapeutic effect.

Macroporous ceramics are potentially applicable in a wide range of industrial applications. The porous structure of macroporous ceramics is designed depending on the application of macroporous ceramics. This paper reviews gradient macroporous ceramics fabricated via powder-based direct foaming to produce a relatively dense surface and a highly porous body. The fabrication process and the characterization of such ceramics are also considered. In terms of fabrication, an overview of the direct-foaming and foaming conditions to obtain a uniform porous structure is described. With regard to characterization, the unique structure of porous ceramics and effect of the denser surface on the bending strength are summarized through the results of microstructural observation and three-point bending strength measurements. The presence of the surface layer enables an improvement in the bending strength while maintaining high porosity. The fabrication processes reviewed herein are highly promising for reducing the weight of porous ceramics while enhancing their mechanical strength.

Inorganic/organic superlattices represented by TiS₂/organic superlattice have received extensive interest due to exceptional thermoelectric properties. Superlattices with alternating inorganic layers and organic layers provide a new strategy to access the phonon-blocking but electron-transmitting structure for the improvement of thermoelectric performance. In this review, taking the TiS₂/organic superlattices as an example, the synthesis strategies and various structures of the superlattices are introduced, followed by a statement of the unique mechanisms inside inorganic/organic superlattices that would facilitate the optimization of the thermoelectric performances. Combining good thermoelectric performance with excellent mechanical flexibility, the inorganic/organic superlattices can remarkably enhance the thermoelectric performance, and provide inspiriting for other superlattices.

C/C composite has been considering to be used as structural components in the field of nuclear energy. However, the material will be subjected to rapid oxidation in the air. This paper presents the microstructure evolutions of a type of high density C/C composites at 550 °C in the air. Synchrotron radiation X-ray micro-computed tomography (SR-µCT, resolution: 0.65 µm) was used to characterize the microstructure in different oxidation stages. The results showed that the material was oxidized nearly homogeneous. The large pores played great rule in the oxidation behavior. The pores in the material started to extend quickly in initial stage and the number of pores and porosity were rapidly increased. Then the oxidation rate decreased as defective graphite in the composition exhausted. In addition, it also can be seen that SR-µCT is a perspective tool for microstructural characterization, especially structure evolution in 3D in the materials.

Amorphous calcium carbonate (ACC) is a precursor of crystalline calcium carbonate; hence, its structural information at the atomic level is very important for controlling the morphology of crystalline calcium carbonate. In this study, we attempted to elucidate the process of Sr extraction from aqueous solution by using ACC for the purpose of removal of radioactive Sr from the contaminated water leaked after the Fukushima Daiichi nuclear accident. The pair distribution functions, g(r) obtained by X-ray and neutron diffraction (ND) measurements show that ACC has a structure partially similar to that of monohydrocalcite, suggesting that ACC is transferred to the crystalline calcium carbonate starting from its crystal nucleus. Rietveld analysis of the ND data showed that the ACC that removed Sr was crystallized to calcite. However, the Sr–O coordination analyzed using extended X-ray absorption fine structure (EXAFS) implies that the local environment of O around Sr is similar to that in crystalline calcium carbonate aragonite.

Single crystals of new rubidium sodium niobium fluoride, RbNaNbF₇, were prepared by a hydrothermal reaction using HF solution. This fluoride crystallized in the orthorhombic space group Cmcm (#63) with a = 6.7031(6), b = 10.9813(11) and c = 8.2969(8) Å (Z = 4) and the final R factors (all reflections) are R = 0.0364 and wR₂ = 0.0847. The crystal structure is formed by isolated polyhedra NbF₇ with quasi pentagonal bi-pyramid geometry, and Na atom also forms NaF₇ quasi pentagonal bi-pyramid polyhedron. Rb atom is coordinated by 8 fluorine atoms to form RbF₈ tetragonal prism polyhedron. The position of one fluorine atom splits statistically, which coordinates Nb and Na ions. The tantalum analogue, RbNaTaF₇ was the same crystal structure. This new rubidium sodium niobium fluoride exhibited photoluminescence properties by doping Mn⁴⁺ ion, which are similar to those of red phosphors. The emission intensity of RbNaNbF₇:Mn⁴⁺ spectrum was inferior to those of KNaMF₇:Mn⁴⁺ (M; Nb, Ta) on excitation at 455 nm.

Bi₄V₂O₁₁ (BiVO) is an Aurivillius-type layered compound that exhibits a red color, and has been attracting attention for its non-toxicity. In this study, we have synthesized a variety of metal oxide-doped Bi₄V₂O₁₁, and aimed to evaluate the effect of the doped metal element on the color tone of the pigments. Bi₂O₃ and V₂O₅ were weighed to 2:1 in mole fraction and mixed in a dry-ball mill with zirconia media for 10 min. Next, transition metal oxides (MnO₂, α-Fe₂O₃, CoO, NiO, CuO, TiO₂, ZrO₂, and HfO₂) were added to the Bi₂O₃–V₂O₅ mixture, and they were mixed, and calcined at 800 °C in the air for 10 h. The obtained powders were pulverized to obtain sample pigments, BiVO and BiXVO (X = Mn, Fe, Co, Ni, Cu, Ti, Zr, and Hf). The BiVO pigment had a brownish-red color. The BiFeVO, BiNiVO, BiTiVO, BiZrVO, and BiHfVO pigments demonstrated orangish-red colors. The BiCuVO pigment displayed a dark and dull yellow, and the BiMnVO and BiCoVO pigments showed black achromatic colors, which were verified by UV–Vis spectroscopy.

MgZr₄(PO₄)₆ is an Mg²⁺ ion conductor with an isotropic three-dimensional network structure. In this study, we have examined the effect of pH adjustment on the synthesis of fine MgZr₄(PO₄)₆ powders by a sol–gel method from Mg(NO₃)₂·6H₂O, ZrCl₂O·8H₂O, and NH₄H₂PO₄. X-ray diffraction and transmission electron microscopy analyses revealed that controlling the pH at ∼10.1 during the sol–gel process was favorable for obtaining fine MgZr₄(PO₄)₆ powder, and it was also beneficial for obtaining almost single-phase sintered MgZr₄(PO₄)₆. Spark plasma sintering of the pH-controlled powder at 1200 °C for 10 min resulted in 94.1 % dense MgZr₄(PO₄)₆, which had an electrical conductivity of 8.38 × 10⁻⁴ S cm⁻¹ at 800 °C.