Methylammonium paradodecatungstate, (CH3NH3)10[H2W12O42] ⋅ nH2O, was prepared by the reaction of WO3 or H2WO4 in aqueous methylamine, followed by drying. The [H2W12O42]10− anion consists of two HW3O13 groups containing three edge‐sharing WO6 octahedra and two W3O14 groups having two edge‐sharing connections. On drying the produced material at 70 °C, some lattice water was released, but this did not affect the [H2W12O42]10− structure, although there was a decrease in the unit cell volume. By adding water, the loss of lattice water and structural changes were reversed. The existence of paradodecatungstate anions was confirmed by single‐crystal and powder X‐ray diffraction, Fourier transform infrared, Raman, 183W nuclear magnetic resonance, and ultraviolet‐visible spectroscopy. When the methylammonium paradodecatungstate was heated to more than 150 °C, CH3NH2 and H2O were released, and amorphous WO3 was observed as an intermediate product and monoclinic WO3 as the final product. These results reveal the structure of methylammonium tungstate, which was first reported in 1909 and now is used as an important negative staining reagent for virus observation, is methylammonium paradodecatungstate.

The solid‐state thermal structure transformation of methylammonium vanadate, (CH 3 NH 3 )VO 3 , from −150 °C to 350 °C is reported. Variable‐temperature X‐ray single‐crystal structure analysis at 23, 0, −50, −100, and −150 °C reveal (CH 3 NH 3 )VO 3 comprises of methylammonium cations and “snake‐like” ([VO 3 ] − ) n anion chains propagating along the c ‐direction in the Pna 2 1 space group. In between −150 and −100 °C, we observe a reversible structural transformation due to the re‐orientation of the methylammonium cations in the crystal packing, which is also confirmed by the reversible profiles observed in differential scanning calorimetry. The methylammonium vanadate is stable until at ca. 100 °C and further heating releases methylamine and water and V 2 O 5 is formed at ca. 275 °C . Furthermore, we show that the methylammonium vanadate can be used as a negative staining reagent for visualizing SARS‐CoV‐2, allowing us to discern the spike proteins from the body of the virus using transmission electron microscopy.

Lightweight geopolymer concrete was synthesized using fly ash as an aluminosilicate source with the addition of a pore-forming agent. The synthesis of a geopolymer was conducted by employing various volume ratios of geopolymer paste to the foaming agent: 1:0.50, 1:0.67, 1:0.75, 1:1.00, 1:1.33, 1:1.50, and 1:2.00, while the ratios of aluminum powder weight percentage to the fly ash weight varied between 0.01 - 0.15 %wt. The results showed that the higher foaming agent content, the lower the compressive strength and density of the geopolymer. The ratio of the geopolymer paste to the foaming agent, 1:1.33 was found to produce the strongest light weight geopolymer whose compressive strength and density were 33 MPa and 1760 kg/m3, respectively. With the addition of 0.01%wt aluminum powder, the geopolymer specimen showed the highest compressive strength of 42 MPa and density of 1830 kg/m3, respectively. X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM) and FT-IR were utilized to study the effects of foaming agent and aluminum powder addition onto the microstructure, surface morphology, and functional groups of the geopolymer. Both types of synthesized geopolymers have the potential to be developed in terms of compressive strength and density in the future.

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Abstract. Geopolymer as a water absorbent material has been synthesized from fly ash. This research aims to determine the ability of geopolymer to save water content with variations of NaOH molar ratio. In this research, the synthesis of geopolymer was conducted by setting NaOH molar ratio at 3, 4, 5, 6 and 7 M. The resulting material characterization was done by using XRD, FTIR and SEM in order to characterize the geopolymer structures. Water absorption capacity was measured by immersing the geopolymer specimens in water for 24 hours. The results show that the optimum molar ratio of NaOH was 3 M, which water absorption capacity was 11.10%wt.