The Pristine Mayenite Ca₁₂Al₁₄O₃₃ (C12A7) Cement was simply synthesized by using solid-state reaction. The C12A7 and Graphene Oxide (GO) composites (C12A7_GO-x) with various contents of the GO suspension loading (x = 0 wt%, 1 wt%, 2 wt%, 3 wt%, and 4 wt%) were directly prepared by mixing the C12A7 and GO. X-ray diffraction results of pristine C12A7 and all C12A7_GO composites indicated a pure phase corresponding to the standard of C12A7 cement. Raman spectroscopy confirmed the existence of GO in all C12A7_GO samples. Scanning Electron Microscopy (SEM) showed the micrometer grain sizes and the occurrence of grain boundary interfaces for GO incorporation in all C12A7_GO samples. UV–Vis spectroscopy revealed the absorption value of all C12A7_GO samples and red shift near longer wavelengths when increasing the GO concentrations. The dielectric constant of C12A7_GO composites can be explained by the high density of free electron charges for the interfacial polarization on the GO surface. The maximum specific capacitance of C12A7_GO-4 electrode of 21.514 at a current density of 0.2 A g⁻¹ can be attributed to the increase in the electrochemically active surface area for the formation of the electrical double layer capacitors behavior and the effects of high surface area GO connections. Also, the mechanical properties exhibited an increase in Vickers indenter hardness (HV) values with increasing GO contents. The highest HV value was 117.8 HV/2 kg at the C12A7_GO-4 sample. These results showed that the composite materials of the pristine C12A7 cement with GO were highly efficient. All in all, the GO material contained a high potential for enhancing low-cost cement materials in multifunctional properties such as optical, dielectric, electrochemical, and mechanical properties.

Mixed-trivalent Fe ³⁺ /Cr ³⁺ content CuFe _{1− x} Cr _x O ₂ ( x = 0.25, 0.5, and 0.75) compounds were synthesized to investigate the effects of spin entropy, and lattice strain on their electronic, thermoelectric and optical properties. The XPS results showed the existence of mixed Cu ¹⁺ /Cu ²⁺ , Fe ³⁺ /Fe ⁴⁺ and Cr ²⁺ /Cr ³⁺ ion states in the structures. The mixed Fe ³⁺ /Cr ³⁺ ions caused a strong correlation to occur between the spin and the orbitals of the carriers in the octahedral layer of the sample, affecting the carrier degeneracy Seebeck coefficient behaviour, and the Cu ²⁺ and Fe ⁴⁺ ions caused an effect of enhancing the electric conductivity. These effects meant that CuFe _0.75 Cr _0.25 O ₂ had the highest electrical conductivity, an enhanced Seebeck coefficient compared to that of CuFeO ₂ -based compounds, and the highest thermopower value. The lowest thermal conductivity was that of CuFe _0.5 Cr _0.5 O ₂ , which was a result of the mismatched atomic radii of the mixed trivalent Fe ³⁺ (0.645 Å)/Cr ³⁺ (0.615 Å), which caused the lattice strain to occur in the structure and thus affected the point defect scattering of the phonon thermal conductivity. The lowest total thermal conductivity was that of CuFe _0.5 Cr _0.5 O ₂ , because it had the maximum lattice strain. Overall, the effect of the mixed trivalent elements caused CuFe _0.75 Cr _0.25 O ₂ to have the highest value of the dimensionless figure of merit ZT , with a value that was four times that of CuFeO ₂ -based compounds and six times that of CuCrO ₂ -based compounds. With regard to optical properties, the lattice strain causes the indirect optical gap to increase with increasing x content, but has no effect on the direct optical gap. These results verified that the mixed-trivalent Fe ³⁺ /Cr ³⁺ content of CuFe _{1− x} Cr _x O ₂ ( x = 0.25, 0.5, and 0.75) affected the electronic, thermoelectric and optical properties of the structure by causing spin entropy and lattice strain to occur.

This paper presents the influence of the graphene oxide (GO) sheet contents at conditions of 0, 0.01, 0.03, 0.05, and 0.1 wt% on the mechanical and thermal properties of GO/CAST 11 LW mortar (GMT) composites for heat insulating brick. The GMT composites were prepared by a simple mixing method. The structure of GMT composites was investigated by X-ray diffraction (XRD) and Raman spectroscopy (Raman) techniques. The small grain sizes of GMT composites were confirmed by transmission electron microscopy (TEM). The mechanical properties of GMT composites are increased with increasing GO contents. A lot of functional groups in GO such as carboxylic acid reacted with a calcium silicate hydrate, CaH₂O₄Si (CSH), calcium hydroxide, Ca(OH)₂ (CH) and Ettringite, and Ca₆[Al(OH)₆]₂(SO₄)₃·26H₂O (CA) phases in the mortar, which can be considered good mechanical properties in the GMT composites. The heat insulation values of GMT composites were improved by the interaction with the CSH, CH, and CA phases in the cement mortar on the surface of GO. The highest compressive and tensile strengths and low heat transfer rate of about 0.465 W/min were observed at 0.05 of GO (GMT_0.05) composites in the curing age of 7 days. Thus, a new pathway of GMT composites can be prepared by a simple mixing method to significantly improve the mechanical and thermal properties of mortar GMT composites.