The effect of mechanochemical treatments of sepiolite with CsCl on the calcination products

Calcination of sepiolite and of two sepiolite/CsCl mixtures, unground and air-ground was investigated by thermo-XRD-analysis. At 200 °C sepiolite, neat, mixed or air-ground with CsCl lost interparticle and zeolitic water. The framework of sepiolite persisted during the dehydration but became defected, mainly in the air-ground mixture, less in the unground mixture and little in the neat clay. At 500 °C, with the loss of bound water, the neat clay was folded and transformed into sepiolite anhydride. In sepiolite/CsCl mixtures the dehydrated variety persisted but the degree of crystal-imperfection increased in the air-ground mixture more than in the unground mixture. At 700 °C the neat clay remained crystallized, but the CsCl mixtures became amorphous. Some crystalline dehydrated sepiolite or sepiolite anhydride persisted in the unground and air-ground CsCl mixtures, respectively. At 850 °C, the neat clay crystallized into protoenstatite with some enstatite and clinoenstatite. The amorphous fraction of sepiolite in the unground sepiolite/CsCl mixtures crystallized into pollucite and forsterite and the crystalline fraction was transformed into enstatite, protoenstatite, and clinoenstatite. In the air-ground mixture, the amorphous phase was transformed into pollucite with some forsterite and the crystalline fraction into enstatite.     

Thermo-XRD-analysis of montmorillonite treated with 1,4-diaminoanthraquinone

Charcoals formed during the thermo-XRD-analysis of montmorillonite (MONT) complexes with the dye 1,4-diaminoanthraquinone (DAAQ) were investigated by using curve-fitting calculations. Five saturated dye solutions were prepared (i) in distilled water and (ii–v) in 0.1, 0.5, 1.0, and 2.0 molar HCl. Two series of dye-clay complexes were prepared by using clay suspensions of 0.6 %and of 0.006 % labeled first and second series, respectively. Five dye-clay complexes were prepared of each series by adding 25 mL of dye solution to 25 mL of clay suspension. There is no free dye in complexes of the first series, but those of the second series, which were synthesized with a high ratio between dye and clay, contain non-adsorbed dye even after five washings. Complexes of the first series are loaded with very small amounts of molecular and protonated DAAQ (5–24 mmol DAAQ per 100 g clay), and their spacings are 1.25–1.54 nm suggesting the presence of tactoids with protonated or molecular DAAQ lying parallel to the clay layers. No carbon analyses were performed to the second series complexes. In addition to tactoids with spacing of 1.32 nm, they contain tactoids with spacings of 1.81–1.96 nm, suggesting that intercalated DAAQ are lying perpendicular to the clay layers. Three types of intercalated charcoal are identified in both series during the thermal analysis, one type with a low thermal stability and two types with high thermal stabilities. Charcoals of the second series complexes preserve the geometry of the original complexes up to high temperatures.     

Spectroscopy of two coincident charged particles emitted following bound pion absorption in 12C, 59Co and 197Au

Energy spectra and angular distributions of two coincident charged particles emitted following stopped negative pion absorption in ¹²C, ⁵⁹Co and ¹⁹⁷Au were measured. Most of the data can be understood within the framework of a pair absorption model including final-state interactions. Ground-state transitions in the missing mass spectra of ⁴H and ⁴He deduced from the αα and tα spectra of ¹²C, respectively, show that reactions involving a large part of the nucleus also occur.     

New constructions for De Bruijn tori

A De Bruijn torus is a periodicd-dimensionalk-ary array such that eachn ₁ × ... ×n _d k-ary array appears exactly once with the same period. We describe two new methods of constructing such arrays. The first is a type of product that constructs ak ₁ k ₂ -ary torus from ak ₁ -ary torus and ak ₂ -ary torus. The second uses a decomposition of ad-dimensional torus to produce ad+1 dimensional torus. Both constructions will produce two dimensionalk-ary tori for which the period is not a power ofk. In particular, for and for all natural numbers (n ₁ , n ₂ ), we construct 2-dimensionalk-ary De Bruijn tori with order n ₁ , n ₂ and period where .Dedicated to the memory of Tony BrewsterPartially supported by NSF grant DMS-9201467Partially supported by a grant from the Reidler Foundation     

Studying the Polarization Characteristics of Thermal Microwave Emission from a Cloudy Atmosphere

We present the results of spectral studies of thermal microwave emission from a cloudy atmosphere at 37 and 85 GHz. The experimental data are interpreted on the basis of modeling of microwave radiation transfer in the mixed-type clouds containing ice crystals of different shapes and supercooled water drops. All orders of scattering are taken into account. It is shown that polarization radiometric measurements allow one to separately determine ice-water and liquid-water contents of the clouds and also to diagnose the cloud microstructure (crystal shapes and characteristic sizes).     

Thermal analysis of tetraethylammonium and benzyltrimethylammonium montmorillonites

Na-montmorillonite was loaded with tetraethylammonium cations (TEA) or with benzyltrimethylammonium cations (BTMA) by replacing 77 and 81% of the exchangeable Na with TEA or BTMA, labeled TEA-MONT and BTMA-MONT, respectively. TEA- and BTMA-MONT were heated in air up to 900?°C. Thermally treated organoclays are used in our laboratory as sorbents of organic compounds from water. The two organoclays were studied by TG and DTG in air and under nitrogen. Carbon content in each of the heated sample was determined. They were diffracted by X-ray, and fitting calculations of d(001) peaks were performed on each diffractogram. TG and thermo-C analysis showed that at 150 and 250?°C both organoclays lost water but not intercalated ammonium cations. DTG peak of the first oxidation step of the organic cation with the formation of low-temperature stable charcoal (LTSC) appeared at 364 and 313?°C for TEA- and BTMA-MONT, respectively. The charcoal was gradually oxidized by air with further rise in temperature. DTG peak of the second oxidation step with the formation of high-temperature stable charcoal (HTSC) appeared at 397 and 380?°C for TEA- and BTMA-MONT, respectively. DTG peak of the final oxidation step of the organic matter appeared at 694 and 705?°C for TEA- and BTMA-MONT, respectively, after the dehydroxylation of the clay. Thermo-XRD analysis detected TEA-MONT tactoids with spacing 1.40 and 1.46?nm up to 300?°C. At 300 and 360?°C, LTSC-MONT tactoids were detected with spacing of 1.29?nm. At higher temperatures, HTSC-MONT-?? and -?? tactoids were detected with spacings of 1.28 and 1.13?nm, respectively. BTMA-MONT tactoids with spacings 1.46 and 1.53?nm were detected up to 250?°C. At 300 and 360?°C, LTSC-MONT tactoids were detected with a spacing of 1.38?nm. At higher temperatures, HTSC-MONT-?? and -?? tactoids were detected with spacings of 1.28 and 1.17?nm, respectively. At 650?°C, both clays were collapsed. HTSC-??-MONT differs from HTSC-??-MONT by having carbon atoms keying into the ditrigonal holes of the clay-O-planes. At 900?°C, the clay fraction is amorphous. Trace amounts of spinel and cristobalite are obtained from thermal recrystallization of amorphous meta-MONT.