Structural changes in fly ash geopolymers activated with different sodium hydroxide and silicate concentrations are investigated using attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy over a period of 200 days. A strong correlation is found between the concentration of silicate monomer in the activating solution and the position of the main Si−O−T stretching band in the FTIR spectrum, which gives an indication of the relative changes in the gel Si/Al ratio. The FTIR spectra of geopolymer samples with activating solution concentrations of up to 1.2 M SiO2 indicate that an Al-rich gel forms before the final gel composition is reached. The time required for the system to reach a steady gel composition depends on the silicate activating solution concentration and speciation. Geopolymers activated with solutions containing predominantly high-order silicate species rapidly reach a steady gel composition without first forming an Al-rich gel. A minimum silicate monomer concentration...

Attenuated Total Reflectance Fourier Transform Infrared Analysis of Fly Ash Geopolymer Gel Aging

Nucleation and growth history of zeolite LTA synthesized from kaolinite by two different methods

In this study, one-part “just add water” geopolymer binders are synthesized through the alkali-thermal activation of the red mud which is relatively rich in both alumina and calcium. Calcination of the red mud with sodium hydroxide pellets at 800°C leads to decomposition of the original silicate and aluminosilicate phases present in the red mud, which promotes the formation of new compounds with hydraulic character, including a partially ordered peralkaline aluminosilicate phase and the calcium-rich phases C3A and α-C2S. The hydration of the “one-part geopolymer” leads to the formation of zeolites and a disordered binder gel as the main reaction products, and the consequent development of compressive strengths of up to 10 MPa after 7 d of curing. These results demonstrate that red mud is an effective precursor to produce one-part geopolymer binders, via thermal and alkali-activation processes.

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One‐Part Geopolymers Based on Thermally Treated Red Mud/NaOH Blends

Using a new quartz-made reactor, large amounts of fullerene-like (IF) MoS2 nanoparticles were synthesized by reacting MoO3 vapor with H2S in a reducing atmosphere. The nanoparticles were found to be of high crystalline order; with an average size of 70 nm and consist of more than 30 closed shells. Extensive tribological testing of the nanoparticles in two types of synthetic oils- poly-alpha olefins (PAO)- was carried out and compared to that of bulk (2H platelets) MoS2 and IF-WS2. These tests indicated that under high pressure and relatively low humidity, the IF-MoS2 exhibited a friction coefficient as low as 0.03 and the smallest wear rate of the measured systems. However, its performance was found to be lower in comparison to IF-WS2 after 2500 cycles, due probably to its inferior chemical stability. This study indicates that the tribological performance of the IF nanoparticles depends strongly on their crystalline order and size.

Fullerene-like MoS 2 Nanoparticles and Their Tribological Behavior

Effect of synthesis parameters on the compressive strength of low-calcium ferronickel slag inorganic polymers.

Hydrosodalites of general composition Na 6+x (SiAlO 4 ) 6 (OH) x .nH 2 O have been prepared from kaolinite and aqueous NaOH solution by hydrothermal synthesis under various conditions and subsequent NaOH extraction with water and/or thermal dehydration

The hydrosodalite system Na6+x[SiAlO4]6(OH)x.cntdot.nH2O: formation, phase composition, and de- and rehydration studied by 1H, 23Na, and 29Si MAS-NMR spectroscopy in tandem with thermal analysis, x-ray diffraction, and IR spectroscopy

Two-dimensional compounds (like graphite or MoS2) are capable of bending their layers and forming a closed cage structure, which is denoted the inorganic-fullerene-like (IF) phase in the case of inorganic materials. Simultaneous thermal analysis (TG-DTA) of a number of nanomaterials (IF-MoS2, IF-NbS2, and IF-WS2) and their bulk counterparts was carried out in inert and oxidizing environments at various heating rates. Oxidation occurred at 295 °C for the smallest particle size (100 nm) but the oxidation temperature increased to 440 °C for the largest particle size (3 μm). At low heating rates, the oxidation occurred through sulfates and lower oxides, while at high heating rates mostly one-step oxidation to the highest oxide was observed. The stability in N2 atmosphere depended on the criterion of stability chosen: Choosing the onset temperatures of the decomposition step (between 1200 °C and 1390 °C), the stability decreased in the order WS2
				≈ MoS2 > NbS2; and the bulk material reacted mostly at higher temperatures compared to the IF-phase. Choosing the extent of decomposition as a measure of stability, no specific trend could be found. Surprisingly, a single IF-WS2 sample was found to be most stable by both methods.This study shows that IF nanoparticles are comparably (though somewhat less) stable against oxidation as well as decomposition than the bulk material exhibiting the usual plate-like structure.

How stable are inorganic fullerene-like particles? Thermal analysis (STA) of inorganic fullerene-like NbS2, MoS2, and WS2 in oxidizing and inert atmospheres in comparison with the bulk material

Orientational disorder of the hydrogen dihydroxide anion, (O2H3-) in sodium hydroxosodalite dihydrate (Na8[Al6Si6O24](OH)2.cntdot.2H2O): single-crystal x-ray and powder neutron diffraction and MAS NMR and FT IR spectroscopy

Synthesis and Structural Characterization of Sodalites with Acetate and Formate Guest Anions, [Na4(CH3COO)]2[Al3Si3O12]2 and [Na4(HCOO)]2[Al3Si3O12]2, and their Intracage Oxidation Product [Na5(CO3)][Na3.box.][Al3Si3O12]2

In monoclinic β-HBO2, endless [B3O3(OH)(H2O)(O2/2)] zigzag chains are linked via an extensive system of hydrogen bonds with stronger major [H⋯O between 1.67 (1) and 1.77 (1) A] and weaker minor components [H⋯O between 2.48 (1) and 2.63 (1) A]. The unique three-dimensional tetrahedral [BO2/2O2/2(H)] network structure of cubic γ-­HBO2 is stabilized by very short asymmetric hydrogen bonds [H⋯O2 1.48 (1) A] with a donor–acceptor distance of 2.485 (1) A and possesses small empty cages with a free diameter of ca 3.2 A.

Juergen Felsche

Papers

The hydrosodalite system Na6+x[SiAlO4]6(OH)x.cntdot.nH2O: formation, phase composition, and de- and rehydration studied by 1H, 23Na, and 29Si MAS-NMR spectroscopy in tandem with thermal analysis, x-ray diffraction, and IR spectroscopy

How stable are inorganic fullerene-like particles? Thermal analysis (STA) of inorganic fullerene-like NbS2, MoS2, and WS2 in oxidizing and inert atmospheres in comparison with the bulk material

Orientational disorder of the hydrogen dihydroxide anion, (O2H3-) in sodium hydroxosodalite dihydrate (Na8[Al6Si6O24](OH)2.cntdot.2H2O): single-crystal x-ray and powder neutron diffraction and MAS NMR and FT IR spectroscopy

Synthesis and Structural Characterization of Sodalites with Acetate and Formate Guest Anions, [Na4(CH3COO)]2[Al3Si3O12]2 and [Na4(HCOO)]2[Al3Si3O12]2, and their Intracage Oxidation Product [Na5(CO3)][Na3.box.][Al3Si3O12]2

The monoclinic and cubic phases of metaboric acid (precise redeterminations)