Two-dimensional (2D) nanosheets, which possess atomic or molecular thicknesses and infinite lateral lengths, have received increasing attention due to their intriguing physicochemical properties distinct from those of their bulk counterparts. In particular, the discovery of graphene has opened new possibilities for exploring the fascinating properties of 2D nanosheets of other layered and non-layered compounds. 2D inorganic nanosheets (ceramic nanosheets) are important targets in this regard due to their diversity in chemical composition, structure and functionality beyond graphene. Here, we review recent advances in the synthesis, assembly and properties of 2D oxide nanosheets, highlighting emerging functionalities in electronic applications.

With the rapid development of electronic device performances, it is crucial to provide an efficient heat removal in electronic devices. For thermal management, ceramic particle/polymer composite materials with high thermal conductivities are of interest. Recently, hexagonal boron nitride (hBN) particles and related composite materials have been intensely studied due to the excellent properties of hBN particles. The shape and orientation of the hBN particles affect the properties of the composite materials because hBN is a plate-like particle and has an anisotropic thermal conductivity. This article provides an overview of powder technologies of hBN particles, such as exfoliation, granulation, and composition with nanofibers, for high thermal conductivities of composite materials. Furthermore, I discuss the fabrication processes and thermal properties of hBN/polymer composite materials potentially applicable in thermal interface materials.

The two types of c-axis-aligned polycrystals of lanthanum silicate oxyapatite (LSO) doped with K₂O and Al₂O₃ were prepared by the templated grain growth method with different template/matrix mass ratios of 11.1/88.9 and 5.9/94.1. The template particles, K₂O- and F-doped plate-like LSO crystals with developed {001} faces, and the matrix powder, mainly Al₂O₃-doped LSO, were those used in a previous study with the template/matrix mass ratio of 20.0/80.0. Considering the ionic conductivity and orientation degree of the three types of textured polycrystals, the intermediate mixing ratio of 11.1/88.9 was found to be optimal among the three, with the texture fraction of {0 0 l}_apatite being 0.74. Thus, the random grain oriented polycrystal was prepared with the same bulk chemical composition as the control sample. As the temperature increased from 773 to 823 K, the bulk oxide-ion conductivity (σ_b) of the textured polycrystal increased from 1.04 × 10⁻³ to 1.71 × 10⁻³ S cm⁻¹ and the activation energy of conduction (E_a) was 0.61 eV. The σ_b value of the random grain oriented polycrystal increased steadily from 3.80 × 10⁻⁵ to 5.26 × 10⁻⁴ S cm⁻¹ with increasing temperature from 773 to 973 K (E_a = 0.92 eV). Comparing the σ_b values at the same temperatures, the former was 27.5 (773 K) and 21.2 (823 K) times higher than the latter. The chemical formula of the doped LSO in the textured polycrystal was determined from the average composition to be (La_9.59K_0.09□_0.32)(Si_5.50Al_0.38□_0.12)O₂₆, where □ denotes vacancies in La and/or Si sites. The major chemical composition of the coexisting interstitial material was estimated to be 29.8 mol % La₂O₃, 44.9 mol % SiO₂, and 25.3 mol % Al₂O₃. The mole fractions were determined by the lever rule to be 0.9824 for doped LSO and 0.0176 for interstitial material.

The solvothermal method was used to prepare 0.125 mol % Li₃BO₃-coated graphite powder as an anode material for an all-solid-state lithium battery. Scanning electron microscopy observations and electron probe microanalysis revealed the Li₃BO₃ was distributed uniformly on the graphite surface as fine particles and a film. The average crush strength of the coated graphite powder particles was higher than that of the uncoated graphite powder particles, and the standard deviation was lower. An all-solid-state lithium battery with the coated graphite powder showed a slightly higher capacity retention rate than that containing uncoated graphite powder.

After a long time of exploration, the solid-state reaction method is further modified. In the granulation process, 10 % isopropanol is added into ethanol to increase the viscosity. More than that, the green body of the ceramic is placed into the isostatic press and pressed at 200 MPa for 3 min again after being kept in the muffle furnace at 120 °C for 1 h. The modified solid-state reaction method further improves the sintering property of the Na₂WO₄ ceramic, which increases the dielectric property of the ceramic sample greatly. Besides, the granulation problem, the bubble problem and the problem in demoulding process are solved. The substitution of ethanol and isopropanol for polyvinyl ethanol (PVA) completely avoids the residue of PVA in the ceramic sample and increases the fluidity of the ceramic particles in the granulation process. As a result, the Na₂WO₄ ceramic can be sintered well at 560 °C with a relative permittivity of 5.82, Q × f value of 131300 GHz and a temperature coefficient of resonant frequency (TCF) value of −56.2 ppm/°C in this work. The modified solid-state reaction method is a good substitute for the conventional solid-state method.

Quantitative valence analysis of iron included in synthesized glasses has been carried out by using high-resolution X-ray fluorescence (XRF) analyzer which attached the high-resolution curved-double analyzing crystals of Si(220). The measurement results of the standard materials of Fe²⁺ (FeTiO₃) and Fe³⁺ (Fe₂O₃) have been carefully compared for the peak analysis of provided high-resolution Fe-K_α profiles. The chemical valences (Fe²⁺ and Fe³⁺) of iron component included in the glasses have been quantitatively analyzed on the basis of multiple peak analysis of Fe-K_α (both Fe-K_α1 and Fe-K_α2). The Fe²⁺/Fe³⁺ ratio has been calculated for the glasses which were synthesized under the different oxidation–reduction conditions. Additionally, the quantitative valence analysis of sulfur has been also carried out by using high-resolution XRF analyzer which attached the analyzing crystals of Ge(111) in order to clarify the relationships with iron component. Chemical valences (S²⁻ and S⁶⁺) of sulfur component were congruent with the chemical valence of iron component. Quantitative valence analysis by high-resolution XRF analysis has large advantages for the sample preparations, the surface analysis and the automated analysis.