Geopolymers or polysialates are inorganic polymeric, ceramiclike materials composed of alumina, silica, and alkali metal oxides that can be made without any thermal treatment. Additions of reinforcing phases vastly improve the mechanical properties and high-temperature stability of the geopolymer. The processing and mechanical properties of both chopped strand mat as well as 2-D woven fabric-reinforced potassium geopolymer composites have been evaluated. Hand lay-up and hydraulic press processing methods were used to produce composite panels. The room-temperature tensile and flexural strength of chopped strand mat composites was 21.0 AE 3.1 and 31.7 AE 4.4 MPa, respectively, while those of basalt weave-reinforced geopolymer composites reached 40.0 AE 5.9 and 45.2 AE 9.3 MPa, respectively. Composite microstructures were examined using optical microscopy as well as scanning electron microscopy (SEM). Mass, volume, and porosity fractions were also determined. The effect of high-temperature treatments at 25°C, 300°C, 600°C, and 800°C were analyzed. Finally, Weibull statistical analysis was performed, which showed an increase in reliability when a reinforcement phase was added to K-geopolymer.

A nanoscale and pure, olivine-structured LiFePO 4 was synthesized at ;300°C using an organic-inorganic steric entrapment method. Normally, when calcined and crystallized in air, this method leads to the synthesis of compounds where the cations are in their highest oxidation state. However, in this study, we found a way to produce compounds having lower oxidation states (e.g., compounds containing Fe 21 ), which may have wider applications in the synthesis of other compounds with complex chemistry that have variable oxidation states and, therefore, potential applications in electronic ceramics. The resulting LiFePO 4 or (Li 2 OÁ2FeOÁP 2 O 5 ) was characterized by thermogravimetric analysis/differential thermal analysis, x-ray diffractometry, scanning electron microscopy, transmission electron microscopy, inductively coupled plasma emission spectroscopy, specific surface area by Brunauer-Emmett-Teller nitrogen absorption, and particle size analysis.

Potassium‐based, geopolymer composites were made with BASF® metakaolin and Mymensingh clay‐derived metakaolin from Bangladesh. Since the natural Mymensingh clay contained 40 wt.% quartz, this same amount of quartz particulates was added to the BASF® metakaolin to make a synthetic analog of the natural calcined clay. By analogy with bone china, bone ash or calcined hydroxyapatite (5CaO•3P2O5 or “HA”) particles, having a Ca: P ratio of 3.3:1, were added to make the three types of geopolymer‐based composites described above. For less refractory particulate additions, dicalcium phosphate (DCP) (2CaO•P2O5 or “DCP”) particles, having a Ca: P ratio of 2:1, were also added to another set of geopolymers. The ambient temperature compressive and flexural strengths were measured for all of the geopolymer composites. The HA or DCP reinforced geopolymer composites were fabricated and heat‐treated to 1150°C/1 h, after which they were converted to their mineralogical analogs. Their mechanical properties of compressive and 3‐point flexural strengths were again measured. Flexural strengths of 22.42 ± 11.0 MPa and 31.97 ± 8.3 MPa were measured in 1 × 1 × 10 cm3 heat‐treated geopolymer bars reinforced with 10 wt.% of DCP and in geopolymer reinforced with 10 wt.% DCP +40 wt.% quartz additions, respectively. Significant improvements to ambient temperature properties were observed due to the self‐healing effect of the flowing amorphous DCP, whose presence was verified by SEM. The geopolymer samples exhibited reduced water absorption (WA) (on a percentage dry weight basis) of within 0.03‐0.5% after being heated at 1100℃/1 h and 1125℃/1 h, as compared with those at room temperature, which varied between 2.56% and 7.89%.

Crystalline pure NaTi2(PO4)3 (NTP) powder was synthesized at 700°C using a simple and low energy, hybrid inorganic–organic, steric entrapment method. Sodium nitrite (NaNO2) and ammonium phosphate dibasic ((NH4)2HPO4) dissolved in water, whereas titanium (IV) isopropoxide (Ti[OCH(CH3)2]4) hydrolyzed in water. Ethylene glycol (HOCH2CH2OH) was used as a polymeric entrapper and hydrolysis of the Ti source was hindered by its dissolution in isopropyl alcohol. The resulting NTP powder was characterized by thermogravimetric analysis/differential thermal analysis, X‐ray diffractometry, scanning electron microscopy, specific surface area by Brunauer–Emmett–Teller nitrogen absorption, and particle size analysis. Furthermore, C, H, N were measured by the classical Pregl‐Dumas method. The thermal expansion behavior in all {hkl} pole directions was also determined by in situ high‐temperature X‐ray diffraction using synchrotron radiation and was found to be in agreement with other published studies.

The thermal expansion of Dy2TiO5 in the hexagonal phase was evaluated and compared with the orthorhombic phase using in situ high‐temperature X‐ray diffraction. The crystal structure, volume changes before and after the transformation process, as well as the mechanism behind the thermal expansion behavior was determined and proposed. It was found that in the hexagonal phase, the thermal expansion was caused by the oxygen anions in the axial positions of the trigonal bipyramidal structure moving toward the central Ti atom. While expanding, the movement of these oxygen anions slows the expansion along the c‐axis resulting in a decrease in α33 with temperature. Furthermore, a structural relationship between the orthorhombic and the hexagonal phases was proposed.