An infrared method has been developed for estimating kaolinite in sediments. Hydroxyl stretching bands of kaolinite in sediments can be recorded by using a differential technique which eliminates the overlapping owing to other mineralic constituents present. By adding known amounts of an appropriate standard to the sample and by measuring intensities of the OH bands before and after the addition it is possible to calculate the proportion of kaolinite in the test sample. The choice of the added standard is made from characteristic features of the hydroxyl stretching bands.

Raman and Fourier-transformed infrared spectra of natural trioctahedral chlorites of polytype IIb were obtained for a series of samples characterized by distinct Fe/(Fe + Mg) and Si/Al ratios ranging, respectively, from 0.04 to 0.94 and from 5.18 to 1.86. All samples were characterized by X-ray powder diffraction, and quantitative electron microprobe analysis. In the 3683-3610-cm−1 spectral range, the wave number of the OH-stretching band from the 2:1 layer (band I) decreased with an increase of iron content at constant Al(IV) content. The more intense bands II and III at about 3600 cm−1 and 3500 cm−1, were assigned to hydroxyl groups involved in hydrogen bonds: (SiSi)O... HO, with the hydrogen bonds being roughly perpendicular to the basal plane, and (SiAl)O... HO, respectively. At higher tetrahedral Al and octahedral Fe contents, spectra exhibited OH-bands II and III, respectively, at a lower frequency. Band III intensity increased and band II was enlarged for chlorites displaying higher Al(IV) contents.

In the 1300–1350-cm−1 spectral range, most infrared spectra displayed intense bands at 1090, 1050, 990, and 960 cm−1, which were assigned to T-O stretching of symmetry species Al and E1. The second type of bands observed both in Raman and infrared spectra were at about 650–800 cm−1; they were assigned to OH vibrations and were strongly dependent on the composition of the interlayer octahedral sheet, especially on the Fe content.

Sulfate adsorption on kaolinite was followed at 0.7 μeq/ml to 99 μeq/ml solution concentrations at 30°C and at pH 6.0, and the amount of OH~ ions released and the change in surface charge were determined. Sulfate was adsorbed at positive and neutral sites by displacing OH2 and OH− groups, respectively. Adsorption of sulfate occurred predominantly at positive sites at low (0.7 μeq/ml to 0.9 /μeq/ml) solution concentrations, whereas at higher solution concentrations, the proportion of the sulfate adsorbed at the neutral sites increased, varying from 51% at 4.9 μeq/ml to 68% at 99 μeq/ml. The form of sulfate bonding was apparently governed by the level of the positive charge on the clay surface. Higher positive charge at low and intermediate levels of sulfate saturation resulted in the adsorption of sulfate as a divalent anion by forming a 6-member ring with surface Al. With a decrease in positive charge at higher levels of adsorption, the sulfate ion formed both monodentate and bidentate complexes.

A corrensite from Taro Valley, Italy, was studied by infrared analysis at different temperatures in the natural state and after exchange with seven different cations. The vibrational bands in the OH-stretching region can be divided into three main absorption regions: 3690-3640, 3580-3560, and 3500-3000 cm−1. The influence of the cation hydration water was observed in the third region only, whereas the intensity, frequency, and shape of the residual bands were not related to the nature of the exchangeable cations. The bands of region I were unaffected by heating the sample to 500°C; however, those in regions II and III were destroyed. Deuteration was not observed for any of the three OH-stretching regions. The dichroic behavior of the OH-stretching bands in the three regions were relatively affected by the exchangeable cations. Generally, the bands in region I exhibited a more dichroic behavior than those in regions II and III.

From the IR data corrensite appears to consist of: (1) a trioctahedral silicate layer with an OH-stretching band at about 3685 cm−1, (2) a hydroxide layer with OH-stretching bands at about 3570 and 3420 cm−1, and (3) a distinct interlayer space that is not interstratified with the hydroxide layers.

In alkaline media and at 70°C dilute suspensions of ferrihydrite transformed to goethite between pH 11.2 and 14 and to a mixture of goethite and hematite above and below this pH range. Increasing the temperature of the transformation or the concentration of the suspension reduced the pH range in which goethite alone formed. The morphology of goethite was chiefly a function of the pH of the system. Acicular crystals formed at all pHs and exclusively above pH 12.2. Epitaxial twinned crystals predominated at pHs below 11, and twins free from hematite formed at higher pHs. Increasing the suspension concentration, ionic strength, or temperature extended the pH range over which twinned crystals formed. Electron micrographs showed that twins formed mainly during the initial stage of the transformation, whereas acicular crystals formed over a longer period. Thus, the twins appeared to nucleate in the ferrihydrite; nucleation of acicular particles took place in solution.

Sepiolite from Vallecas-Vicálvaro, Spain, contains 1.3% fluorine. Laser microprobe mass spectrometry of this sepiolite suggests the presence of fragments of (SiO2)nOMgF and (SiO2)nOMgOH, which are typical of the sepiolite structure. During thermal dehydroxylation, the fluorine in this sepiolite is removed simultaneously with OH groups at about 750°C. Nuclear magnetic resonance spectroscopy (NMR) of 19F indicates that the fluorine is located in the interior of the sepiolite structure, probably substituting for OH groups, and is homogeneously distributed. In the Vallecas-Vicálvaro sepiolite, about one of every four OH groups bound to Mg2+ is substituted by fluorine. The kinetics of extraction of Mg2+ and F- ions by acid treatment (1 N HCl) shows a more rapid extraction of Mg2+, with a monotonous decrease of the Mg/F ratio as the extent of extraction increases. These results support the internal location of the fluorine, as suggested by the NMR data.

Four hydrates with d(001) = 8.4, 8.6, and 10 Å (two types) were synthesized by intercalating kaolinite with dimethylsulfoxide and treating the intercalated clay with fluoride ions. X-ray powder diffraction, infrared spectroscopy, differential scanning calorimetry, thermal gravimetric analysis, and kinetics of dehydration experiments have led to the identification of two types of interlayer water. One type of water (hole water) is situated in the ditrigonal holes of the silica tetrahedral surface; the second type (associated water) forms a discontinuous layer of mobile water. The 8.4-Å and 8.6-Å hydrates have only hole water, whereas the two synthetic 10-Å hydrates and halloysite(10Å) contain both hole and associated water. The hole water is probably hydrogen bonded to the basal oxygens of the silica tetrahedra or, in the 8-Å hydrates when fluorine exchanges for inner-surface hydroxyls, the water molecules may reorient and form stronger hydrogen bonds to the fluorine. Associated water forms water-water hydrogen bonds approximately equal in strength to liquid water but is less strongly bonded to the clay surfaces than hole water. At room temperature the hole and associated water in the 10-Å hydrates do not form an ice-like structure.

Hydrated kaolinite (d(001) = 10 Å) can be synthesized by mild heating of a kaolinite-organic suspension, allowing time for the clay to be intercalated by the organic solvent, and then dissolving a fluoride salt in the liquid. After mild heating of the suspension, the salt and organic solvent are removed by repeated water washings. The kaolinite retains interlayer water in the form of a 10-Å kaolinite hydrate. The influence of the intercalating agent, type of salt, concentration of salt, and the time of treatment on the synthesis of 10-Å hydrate was examined for several kaolinites. The most effective salt is NH4F; much smaller yields were obtained using KF and RbF. Not all organic molecules gave high yields of the hydrate; dimethyl sulfoxide, formamide, and hydrazine worked well but N-methyl formamide did not. The reaction between clay and salt resulted in the replacement of some hydroxyls by fluoride. This replacement was rapid; after 1 min of fluoride treatment a substantial yield of hydrate was obtained. The intercalation step separated the layers and also disordered the kaolinite, facilitating the F for OH replacement at or near crystallite edges. This replacement weakens the interlayer bonding at the edges and thereby reduces the possibility of layer collapse and attendant dehydration.

The dehydroxylation of a series of the kaolinite clay minerals, kaolinite, halloysite and dickite, has been investigated by Fourier transform in situ infrared emission spectroscopy over a temperature range of 100 to 800°C at both 50 and 5° intervals. Excellent correspondence was obtained between the high temperature emission spectra and FTIR absorption spectra of the quenched clay mineral phases. The major advantage of the technique lies in the ability to obtain vibrational spectroscopic information in situ at the elevated temperature. Dehydroxylation at a number of temperatures was determined by the loss of intensity of hydroxyl bands as indicated by intensity changes of the 3550 cm−1 to 3750 cm−1 emission spectra. As with all clay minerals, kaolinite clay mineral dehydroxylation is structure dependent. No clay phase changes occur until after dehydroxylation takes place. The kaolinite clay mineral loses the inner sheet and inner hydroxyl groups simultaneously, whereas dickite and halloysites are shown to lose the outer hydroxyls, as evidenced by the intensity loss of the ~3684 cm−1 peak, before the inner hydroxyl groups as determined by the intensity loss of the 3620 cm−1 peak. Evidence for a high temperature stable hydroxyl band at 3730 cm−1 for dickite and halloysite was obtained. This band is attributed to the formation of a silanol group formed during the dehydroxylation process. It is proposed that the dehydroxylation process for kaolinite takes place homogenously and involves 2 mechanisms. The dehydroxylation of dickite and halloysite takes place in steps, with the first hydroxyl loss taking place homogenously and the second inhomogenously.

The hydroxyl deformation modes of kaolins have been studied by Fourier transform (FT) Raman spectroscopy. Kaolinites showed well-resolved bands at 959, 938 and 915 cm−1 and an additional band at 923 cm−1. For dickites, well-resolved bands were observed at 955, 936.5, 915 and 903 cm−1. Halloysites showed less-resolved Raman bands at 950, 938, 923, 913 and 895 cm−1. The first 3 bands were assigned to the librational modes of the 3 inner-surface hydroxyl groups, and the 915-cm−1 band was assigned to the libration of the inner hydroxyl group. The band in the 905 to 895 cm−1 range was attributed to “free― or non-hydrogen-bonded inner-surface hydroxyl groups. The 915-cm−1 band contributed ~65% of the total spectral profile and was a sharp band with a bandwidth of 11.8 cm−1 for dickite, 14.0 cm−1 for kaolinites and 17.6 cm−1 for halloysites. Such small bandwidths suggest that the rotation of the inner hydroxyl group is severely restricted. For the inner-surface hydroxyl groups, it is proposed that the hydroxyl deformation modes are not coupled and that the 3 inner-surface deformation modes are attributable to the three OH2-4 hydroxyls of the kaolinite structure. For intercalates of kaolinite and halloysite with urea, a new intense band at ~903 cm−1 was observed with concomitant loss in intensity of the bands at 959, 938 and 923 cm−1 bands. This band was assigned to the non-hydrogen-bonded hydroxyl libration of the kaolinite-urea intercalate. Infrared reflectance (IR) spectroscopy confirms these band assignments.

The configuration of hydroxyl groups around the octahedral cations of 2:1 phyllosilicate minerals has long been an important question in clay science. In the present study, 27Al multiple quantum (MQ) magic angle spinning nuclear magnetic resonance (MAS NMR) was applied to the local structural analysis of octahedral Al positions in a purified Na-montmorillonite. Three octahedral Al sites ([6]Ala, [6]Alb, and [6]Alc) are distinguished by 27Al 5QMAS NMR, whereas these sites are not differentiated by 27Al MAS and 3QMAS NMR. The isotropic chemical shift (δcs) and the quadrupolar product (PQ) were estimated to be 5.8 ppm and 2.6 MHz for [6]Ala, 6.2 ppm and 3.0 MHz for [6]Alb, and 6.7 ppm and 3.7 MHz for [6]Alc, respectively. The three Al sites originated from geometric isomers with cis and trans structures, which have mutually different configurations of the OH groups around the central Al3+ ions. From the view point of symmetry for the OH groups, [6]Ala and [6]Alb in the upfield region were assigned to cis sites, and [6]Alc in the downfield region was assigned to a trans site. The occurrence of multiple Al sites implies that Na-montmorillonite used in the present study has cis-vacant structure in the octahedral sheet. This is a reasonable insight, supported by the chemical composition and the differential thermal analysis data of the Na-montmorillonite.

We present results of a VLBI experiment at a wavelength of 18 cm, which simulates the ground-space interferometer with space link to RadioAstron. An array of five antennas was used, four of them are located in the Russian Federation, plus the the 32-m radio telescope in Medicine (Italy). The 22-m radio telescope in Pushchino (Moscow Region) acted in place of the space arm. It has an effective area of 100 square meters. The three other Russian 32-m antennas are operated by the Institute of Applied Astronomy RAS; they are located at Badary, Svetloe and Zelenchukskaya (interferometer network “Quasar”). The maximum base-line, Badary-Svetloe, was about 4402 km, providing an angular resolution of about 0.009 arc seconds at a wavelength of 18 cm. The duration of the experiment was 10 hours on 02/03 February 2011. The program of observations included quasars 3C273, 3C279, 3C286 and the maser source - W3(OH). W3(OH) was observed only by the Russian telescopes and was investigated at the frequency of the 1665 MHz main line. The data were recorded on the MK5 recorder (32-m radio telescopes) and the RDR system (RadioAstron Digital Recorder) in Pushchino. The low SEFD (system equivalence of flux density) of Pushchino emulated the RadioAstron antenna. Correlation was performed with the universal software correlator of the AstroSpace Center of Lebedev Physical Institute. The correlator output format is compatible with that used by the AIPS package, which was used for data analysis. After analyzing the correlated data we obtained relative coordinates of the maser components. The main results are tabulated and presented in the figures. The data quality is sufficient for astrophysical analysis and comparison with previous observations of maser source W3(OH) on VLBI networks EVN and VLBA.