A synthetic octahedral-site-vacancy-free annite sample and its progressive oxidation, induced by heating in air, were studied by powder X-ray diffraction (pXRD), Mössbauer spectroscopy, nuclear reaction analysis (NRA), Raman spectroscopy, X-ray fluorescence (XRF) spectroscopy, gas chromatography (GC), thermogravimetric analysis (TGA), differential thermal analysis (DTA), scanning electron microscopy (SEM), and size-fraction separation methods. For a set heating time and as temperature is increased, the sample first evolves along an annite-oxyannite join, until all H is lost via the oxybiotite reaction (Fe2+ + OH− ⇌ Fe3+ + O2− + H↑). It then evolves along an oxyannite-ferrioxyannite join, where ideal ferrioxyannite, KFe3+8/3□1/3AlSi3O12, is defined as the product resulting from complete oxidation of ideal oxyannite, KFe3+2Fe2+AlSi3O12, via the vacancy mechanism (3 Fe2+ ⇌ 2 Fe3+ + [6]□ + Fe↑). A pillaring collapse transition is observed as a collapse of c near the point where ${\text{Fe}}^{2+}\text{/Fe}=\raisebox{1ex}{$1$}\!\left/ \!\raisebox{-1ex}{$3$}\right.$ and all OH groups are predicted and observed to be lost. Quantitative analyses of H, using NRA, GC, and Raman spectroscopy, corroborate this interpretation and, in combination with accurate ferric/ferrous ratios from Mössbauer spectroscopy and lattice parameter determinations, allow a clear distinction to be made between vacancy-free and vacancy-bearing annite. The amount of Fe in ancillary Fe oxide phases produced by the vacancy mechanism is measured by Mössbauer spectroscopy to be 11.3(5)% of total Fe, in agreement with both the theoretical prediction of 1/9 = 11.1% and the observed TGA weight gain. The initiation of Fe oxide formation near the point of completion of the oxybiotite reaction (${\text{Fe}}^{2+}\text{/Fe}=\raisebox{1ex}{$1$}\!\left/ \!\raisebox{-1ex}{$3$}\right.$) is corroborated by pXRD, TGA, Raman spectroscopy, and appearance of an Fe oxide hyperfine field sextet in the Mössbauer spectra. The region of Fe oxide formation is shown to coincide with a region of octahedral site vacancy formation, using a new Mössbauer spectral signature of vacancies that consists of a component at 2.2 mm/s in the [6]Fe3+ quadrupole splitting distribution (QSD). The crystal chemical behaviors of annite-oxyannite and of oxyannite-ferrioxyannite are best contrasted and compared to the behaviors of other layer-silicate series in terms of b vs. [D] (average octahedral cation to O bond length). This also leads to a diagnostic test for the presence of octahedral site vacancies in hydrothermally synthesized annite, based on a graph of b vs. Fe2+/Fe. The implications of the observed sequence of thermal oxidation reactions for the thermodynamic relevance of the oxybiotite and vacancy reactions in hydrothermal syntheses are examined and it is concluded that the oxybiotite reaction is the relevant reaction in the single-phase stability field of annite, at high hydrogen fugacity and using ideal starting cation stoichiometry. The vacancy reaction is only relevant in a multi-phase field, at lower hydrogen fugacity, that includes an Fe oxide equilibrium phase (magnetite) that can effectively compete for Fe, or when using non-ideal starting cation stoichiometries.

Intercalation of amino acids into 10.0-Å hydrated kaolinite was studied by powder X-ray diffraction (XRD), differential thermal analysis-thermal gravimetry (DTA-TG), and infrared (IR) spectroscopy. Intercalation was found to be dependent on the chain-length, pH, and the concentration of the amino acid zwitterion. Near the isoelectric point, fully intercalated phases were obtained in solutions of concentration >0.5–1 M for glycine (Gly), 2–3 M for β-alanine (β-Ala), and 12 M for both γ-aminobutyric acid (γ-Aba) and δ-aminovaleric acid (δ-Ava). ∊-aminocaproic acid (∊-Aca) with a long chain (C = 6) was only partially intercalated. Intercalated amino acid formed a mono-molecular arrangement with the alkyl chain tilting toward the layer at an angle related to H2O content. The compositions of the intercalates of the Gly and β-Ala are Al2Si2O5(OH)4·(Gly)0.67·0.24H2O and Al2Si2O5(OH)4·(β-Ala)0.63·0.25H2O, respectively, based on TG data. From IR data, Gly and β-Ala molecules are found intercalated as zwitterions and these molecules form hydrogen bonds with both the Al-OH and Si-O surfaces of kaolinite. Washing the intercalate with water produced a hydrated kaolinite, which may form a second amino-acid intercalate of high order. Thus, hydrated kaolinite intercalates or deintercalates amino acids depending on concentration and conditions.

Acoustic and electroacoustic measurements of particle-size distribution (PSD) and zeta potential (ζ potential), respectively, were used to obtain in situ measures of the effects of suspension concentration and pH on interactions between mixed-charge clays and clay minerals from a highly weathered sediment. Measurements were obtained in concentrated suspensions as a function of weight fraction and as a function of pH during titrations. Standard dispersion and centrifugation methods were used to obtain a comparative measure of PSD. Thermogravimetric analysis and X-ray diffraction patterns were used to obtain semi-quantitative and descriptive analyses, respectively, of the sediment, which is composed of Fe oxide minerals, kaolinite, gibbsite, quartz, crandallite, chlorite and traces of other clay minerals. Acoustic measurements showed that the PSD of the clay fraction varied with suspension concentration, and electroacoustic measurements showed the ‘bulk’ ζ potential increased in absolute value as the suspension concentration decreased. Titration results were also sensitive to suspension concentration. Acoustic measurements indicated that the suspensions became unstable at ∼pH 7.5–8.0, as the attenuation spectra changed character near this pH and the calculated PSD shifted to a larger particle size. This pH value is near the points of zero charge of goethite and gibbsite, as verified by titrations on mineral standards. The results confirm the central role oxide minerals play in regulating clay mineral interactions in highly weathered sediments, and indicate that the average ζ potential of a suspension may be a poor indicator of controls on suspension stability.

The fluoride ion is crystal chemically very similar to the hydroxyl ion, substituting for hydroxyl in many minerals in which hydrogen bonding is not important. Fluoride substitutions are particularly common in 2:1 layer silicates, such as micas, illites and smectites. The brick and tile industries, which use naturally occurring clays as their primary raw materials, have devoted considerable effort to understanding fluorine evolution during firing of the raw materials due to increasingly stringent fluorine emission regulations. In order to understand fluorine evolution from ceramic raw materials, we have studied a number of phyllosilicate materials used in making bricks. X-ray powder diffraction and fluorine analyses were combined with heating experiments and thermogravimetric analysis to evaluate the chemical and structural changes taking place on heating. Fluorine remained in 2:1 layer silicates to higher temperatures than did hydroxyl, but it behaved identically to hydroxyl in the kaolinite studied. In all cases, fluorine evolution coincided with structural breakdown of the clay host. These results show that fluorine evolution will consistently occur during firing of clay raw materials, and the problems of fluorine emission cannot be readily solved by simple variations of firing temperatures or times.

Brushite (CaHPO4.2H2O) is an important calcium phosphate encountered in bone tissue engineering and bone cement formulation. There are many studies on the synthesis and characterization of brushite, but full-scale substitution and replacement of Ca by Sr in brushite as a key element in medical and environmental applications has not yet been explored systematically. Therefore, this study aims to evaluate the effects of substitution of Ca by Sr on the microstructural and thermal properties of brushite, including the chemical phases present, crystallization, structural water and phase stability. The chemical phases were determined by means of powder X-ray diffraction. The thermal properties were studied by thermogravimetric analysis. Crystallization and surface morphology were analysed using scanning electron microscopy. Various properties were dependent on the incorporated Sr ions. The replacement percentage of Sr may be divided into two major stages: the first from 0% to 50%; and the second from 50% up to 100%. The (CaxSr1–x)HPO4.nH2O shows that micro-scale crystals of platy brushite formed in the first stage of Sr replacement, from 0% up to 50%. As Sr might inhibit the formation of crystals, crystal nucleation rates were reduced as the Sr percentage increased. An amorphous product formed as a result of 50% Sr replacement. The second stage of Sr replacement with Sr contents >50% yielded a new crystal morphology corresponding mainly to SrHPO4.nH2O. The complete replacement of Ca by Sr transforms the brushite with platy microcrystals into SrHPO4 nanosheets.

To study thermal desulfurization of pyrite (FeS2), we conducted in situ neutron diffraction experiments in the temperature range 298–1073 K. On heating, pyrite remained stable up to 773 K, at which it started to decompose into pyrrhotite (Fe1−xS) and S2 gas. Rietveld analysis of the neutron data from 298 to 773 K allowed determination of the thermal expansion coefficient of pyrite (space group Pa$\bar 3$) to be αV = 3.7456 × 10−5 K−1, which largely results from the expansion of the Fe–S bond. With further increase in temperature to 1073 K, all the pyrite transformed to pyrrhotite (Fe1−xS) at 873 K. Unit-cell parameters of Fe1−xS (space group P63/mmc) increase on heating and decrease on cooling. However, the rates in cell expansion are larger than those in contraction. This hysteresis behavior can be attributed to continuous desulfurization of pyrrhotite (i.e., x in Fe1−xS decreases) with increasing temperature until the stoichiometric troilite (FeS) was formed at 1073 K. On cooling, troilite underwent a magnetic transition to an orthorhombic structure (space group Pnma) between 473 and 573 K. In addition, using differential thermal analysis (DTA) and thermogravimetric analysis (TGA) implemented with a differential scanning calorimeter, we performed kinetic measurements of pyrite decomposition. Detailed peak profile and Arrhenius (k = A exp(−Ea/RT)) analyses yielded an activation energy Ea of 302.3 ± 28.6 kJ/mol (based on DTA data) or 302.5 ± 26.4 kJ/mol (based on TGA data) and a ln(A) of 35.3 ± 0.1.

A clayey soil from southern Tunisia has been studied in order to assess its possible use as an anti-pollution barrier. The soil has been characterized from both geotechnical and physicochemical points of view. The physicochemical characterization was carried out using X-ray diffraction, thermogravimetric and differential thermal analyses, specific surface area and cation exchange capacity measurements. Hydration tests were carried out using oedometers to determine the swelling behaviour of compacted specimens under different stress conditions. The large swelling pressure (420 kPa) is in agreement with the mainly smectitic character of the soil highlighted by the physicochemical tests. The changes in the fabric of the soil and in its porosity after the hydration tests were investigated using the same physicochemical methods, and related to the macroscopic hydro-mechanical properties. X-ray diffraction and mercury intrusion measurements show that there are changes in the interlayer spacing, particle size and inter-aggregate pore distribution. Comparing the properties of the soil with the Belgian guidelines for the construction of anti-pollution barriers showed that the material was suitable for that use.

The thermal regeneration of sulfamethoxazole (SMX)-loaded Y and ZSM-5 zeolites was studied using a combined in situ high-temperature synchrotron X-ray powder diffraction and thermal degradation study. The evolution of the structural features was monitored in real time in the 30–575°C temperature range by full-profile Rietveld analysis. SMX thermal degradation pathways into high-silica zeolite antibiotic adducts, as well as the release of evolved species are similar to those for pure SMX. The adsorption/desorption process occurs without any significant loss of zeolite crystallinity, though slight deformations to the channel apertures are observed. Regenerated zeolites regain almost perfectly ‘bare’ (i.e. unloaded) material unit-cell parameters and only a slight memory effect, in terms of structural deformations induced by the process, is registered in the channel geometry. Interestingly, these changes do not affect the adsorption properties of the regenerated samples, which are able to re-adsorb comparable amounts of antibiotic molecules as in the first adsorption cycle.

Apophyllite, analcite, chabazite, prehnite and stilbite are described from pectolite-, chlorite-, calcite- and quartz-bearing veins and joint coatings in the late Carboniferous quartz dolerite of the Whin Sill of the northern Pennines. These veins represent the final hydrothermal stages in the sill's emplacement and are not related to the widespread lead-zinc-barium-fluorite mineralization of the northern Pennine orefield. Thermogravimetric studies of apophyllites from the two Whin Sill occurrences reveal that at one locality the minreal is fluorapophyllite, at the other hydroxyapophyllite.

Novel 1–1.5 μm BiOCl0.5Br0.5 composite microspheres were prepared by coprecipitation method, then calcined at different temperatures. The BiOCl0.5Br0.5 samples before and after calcination were characterized by powder x-ray diffraction, thermogravimetric analysis, N2-physical adsorption, scanning electron microscopy, Fourier transformed infrared spectroscopy, and UV-Vis diffuse reflectance spectroscopy. The photocatalytic activity of the samples was evaluated by photocatalytic degradation of Rhodamine B under visible light irradiation. The results showed that the thermostability of BiOCl0.5Br0.5 composite microspheres is lower than BiOCl and higher than BiOBr. Heat treatment at low 500 °C could obviously improve the crystallinity of BiOCl0.5Br0.5 microspheres, resulting in a significant increase in activity. BiOCl0.5Br0.5 microspheres calcined at 450 °C displayed the highest activity and stability. At elevated temperature calcination (600–800 °C), phase transition occurred over BiOCl0.5Br0.5. Br element was gradually lost and new phase of Bi24O31Br10 appeared. High temperature calcination did not change the morphology of BiOCl0.5Br0.5, but the surface area and surface OH groups decreased, which resulted in a large decrease in activity.

A hyperbranched epoxy resin has been synthesized by using epichlorohydrin, bisphenol-A, and hyperbranched polyether polyol by a low-temperature polycondensation technique in the presence of a base. The reaction parameters of this polycondensation reaction were optimized, and 5 N aqueous sodium hydroxide solution, (54 ± 1) °C reaction temperature and 3 h reaction time were found to be the best. The degree of branching of the resin was found to be 0.57 as determined from 13C nuclear magnetic resonance spectroscopy (Fig. 3). This hyperbranched epoxy resin was cured with poly(amido amine) hardener at 120 °C for a specified period of time. The resin exhibits very good crosscut adhesive strength (100%). The cured films showed moderate impact strength (60 cm), good scratch resistance (5.5 kg), good gloss (82 at 60°), thermostability up to 270 °C, and good chemical resistance in various chemical media. All these results indicate its suitability to be used as an advanced surface coating material.

The oxidation behavior of Cu50Zr50 and Cu46Zr46Al8 glasses during continuous heating up to 1073 K has been investigated, with special emphasis on the oxidation resistance in the supercooled liquid (SCL) state. For Cu50Zr50, the oxide layer mostly consists of monoclinic ZrO2 (m-ZrO2), while for Cu46Zr46Al8, the oxide layer consists of two different layers: an outer layer consisting of tetragonal ZrO2 (t-ZrO2) + Al2O3 + metallic Cu (oxidation product from the SCL state of the glass matrix) and inner layer comprised of m-ZrO2 + metallic Cu islands (oxidation product from the crystallized matrix). Cu-enriched regions consisting of Cu51Zr14 (in Cu50Zr50) or AlCu2Zr + Cu70Zr15Al15 + Cu51Zr14 (in Cu46Zr46Al8) are present below the oxide layer. The present study shows that the addition of Al (8 at.%) in Cu50Zr50 results in a significant deterioration of the oxidation resistance in the SCL state since the solutionizing of Al in t-ZrO2 leads to a higher oxygen ion vacancy concentration, thus providing a higher activity of oxygen ions.

Electrochemical oxidation of graphite in mixed solutions of H2SO4–H3BO3 with various mass ratios was investigated. The potential correction to concentration in the formation of graphite intercalation compound II stage in the system graphite–H2SO4–H3BO3 was determined and compared with other systems. Boric acid was shown not to be co-intercalated with sulfuric acid into graphite matrix, but to be distributed on the surface of expandable graphite (EXP). The amount of boric acid on EXP depends on concentration of H3BO3 in electrolyte and it ranges from 3.7 to 11.0 wt%. Content of boric oxide formed after thermoshocking is equal to 3–9 wt% in exfoliated graphite (EG). Modification resulted in reducing specific surface area of EG. As the pores in modified EG were blocked by boric oxide, the temperature of oxidation of the EG and graphite foil increased by 200 °C.

NiMn2−xMgxO4 (0 ≤ x ≤ 0.4) ceramics have been studied by powder x-ray diffraction (XRD), infrared (IR) spectroscopy, and thermogravimetric analysis. NiMn2−xMgxO4 ceramics are all single-phase with spinel structure. XRD and IR spectroscopy results indicate that Mg2+ ions occupy A- and B-site of spinel lattice, which inhibits the formation of cation vacancies. Moreover, Mg2+ substitution enhances the tolerance of the oxidation in air. As a result, Mg substitution leads to a significant increase in ρ25, temperature coefficient of resistivity B25/85, and activation energy, which improves the aging property of NiMn2−xMgxO4 negative temperature coefficient thermistors.