Interlayer Content Research Articles

Self-assembled rectorite films with remarkable mechanical performance: preparation, structural characterization, and properties

Cohesive flexible rectorite clay films with good mechanical performance were prepared by a simple casting method through the self-assembly of exfoliated natural clay from aqueous dispersions. The multi-layered microstructure of the films consisted of continuous layers of aligned clay platelets parallel to the casting surface. Layers overlap randomly in the lateral direction (plane) and join vertically in an irregular manner by edge-to-face cross-linkages (bridging) to form coherent multi-layered nanostructured films with platelet-void microstructure. The films with the highest mechanical properties had thicknesses below 30 µm. Overall films from rectorite clay with monovalent interlayer content exhibited a higher experimental tensile strength ranging up to 44 MPa and Young’s modulus up to 56 GPa. The corresponding experimental values for films with divalent interlayer cations were 23 MPa for strength and 25 GPa for modulus. The highest experimental values for strength and modulus for neat Na–Ca–rectorite films were 25 MPa and 50 GPa respectively. These two mechanical property values of the best rectorite-based clay films compare favorably with values featured by polymer films typically used for packaging applications.

Grain size control on organo-clay complexation and REE fractionation in the Paleozoic strata of the Permian Basin (West Texas, U.S.A.)

As a major component of mudstone, clay minerals are known to conserve organic matter (OM) as well as a range of trace elements through the mechanisms of adsorption, encapsulation, and/or intercalation. The associations of the clay minerals on one hand and trace elements and OM on the other hand impact the diagenetic evolution of such rocks and is of substantial importance for their characterization and assessment. Subsurface core samples collected from Late Paleozoic mudstone within the Permian Basin of Texas were separated into four grain size fractions (>2 µm, 2 to 1 µm, 1 to 0.6 µm, and <0.6 µm) to determine the clay mineralogy, OM abundances, and rock geochemistry using a suite of diffraction, spectroscopic, and chemical analysis. All separates were largely consisted of illite-smectite (I-S), illite-tobelite-smectite (I-T-S), mica/illite and chlorite coupled with some minor quartz and feldspar. The smectite component of I-S was shown to increase with decreasing grain size fractions. Additionally, t he rise in the content of smectite interlayers correlated with an increase in the total organic carbon (TOC) content towards the finest grain size separates in all samples. This suggested that a significant portion of the TOC content resided in the fraction below 2 µm and that smectite interlayers promoted the preservation of OM. Rare earth elements (REE) concentrations were found to be the highest in the finest grain size separates and align with an increased content of smectite interlayers, denoting a plausible interaction between the two. Further on, REE and TOC concentrations display a significant positive correlation in all size fractions and increase with respect to smectite interlayer content. This three-component relation suggests the REE adsorption to illite-smectite was likely promoted by OM. Understanding the close relation between the clay minerals, OM, and trace element content is indicative of polyvalent cationic bridging, ligand exchange, and organo-metallic complexation, which eventually l eads to the enrichment of OM and fractionation of REE in mudstone.

Raw Materials Used in Traditional Pottery from Northern Morocco: Possible Alternative Material for a Sustainable Future in the Fran Ali Area

AbstractThe colluvium and saprolite deposits in the Fran Ali area (Oued Laou, northern Morocco) constitute the main source of raw materials used in traditional pottery. These materials are becoming scarce, however, so alternative materials with the same characteristics are needed; this would ensure the sustainability of pottery activities in the area. The objective of the present study was to examine ten representative samples of clayey materials extracted from the Fran Ali area, i.e. the Ikhadimene, Dar Haddoune, Ihadounene, Aqqbat Ajjoua, and Isalahene sites. The geological materials consist mainly of grayish to brownish phyllites, thin layers of yellowish clay, thicker intervals of reddish-yellow soils ranging in depth from 1 to 4 m, and reddish colluvium soils. The physical properties of these materials were determined using semi-wet sieving and Atterberg limit tests, while chemical, mineralogical, and thermal properties were obtained from the methylene blue test (MBT), the calcimetry test, X-ray fluorescence spectrometry (XRF), X-ray diffraction (XRD), and thermogravimetric and differential thermal (TGA/DTGA) analysis. The results suggest that the soils contain 21–35% clay, 28–34% silt, and 37–52% sand. They are moderately plastic, with methylene blue adsorption capacities ranging from 3 to 7% and minimal CaCO3 carbonate contents (1–4%). Samples are dominated by SiO2 (51–57%), Al2O3 (17–21%), and Fe2O3 (8–10%). Mineralogically, they are composed of illite (19–27%), chlorite (0–22%), kaolinite (5–9%), and quartz (29–32%). Thermal analysis showed a relatively large mass loss of ~10%. The samples are deemed to be moderately plastic. The results indicate that this raw material is acceptable for pottery fabrication, given the small proportion of irregular interlayer content and its average geotechnical properties. In addition, extraction of the colluvium material is not sustainable because of the relative scarcity of the material. Given the mineralogical similarity between the weathered layers (colluvium) and their parent rock (shales), the present results suggest that the latter is a suitable alternative to the former.

Experimental study on the influence of associated pyrite content on coal spontaneous combustion

ABSTRACT In order to study the influence of associated pyrite interlayer content in coal seam on coal spontaneous combustion, the infrared spectrum of anthracite in Shanxi Yangquan mining area with different content of pyrite was tested by Fourier infrared spectrometer, and the variation law of the influence of the content of associated pyrite on coal surface functional groups was studied. In this paper, the TG, DTG, DSC curves and heat release curves of associated pyrite coal samples during programmed temperature rise were studied by synchronous thermal analyzer experiment. The results show that such features can be found in the spectrum of six coal samples that the aliphatic hydrocarbon content is always higher than that of the AP-0 coal sample. When associated pyrite content is 60%, the content of aromatic hydrocarbons in the AP-0 coal sample is the smallest, and the change of hydroxyl content is the largest. The more vigorous the coal surface functional groups are, the slower the oxidation reaction with oxygen occurs. The higher the content of pyrite associated with the formation of this coal sample, the smaller the relevant weight change during the oxidation reaction. The lower the ignition temperature of coal sample is, the more hematite (Fe2O3) is left in the coal residue, and the lower the maximum heat flow rate, the lower the heat release.

Metal-alike polymer composites: The effect of inter-layer content on the pseudo-ductile behaviour of carbon fibre/epoxy resin materials

With interfacially engineered pseudo-ductile carbon fibre reinforced polymer composites, a higher energy absorption capacity and metal-like stress-strain response can be achieved during failure. Due to incorporated inter-layer additives deposited with fused filament fabrication, locally weakened zones can be printed on the surface of the reinforcing material, which provides better energy absorption capability during the composite laminates’ damage process by the alteration of crack propagation. The reason for this phenomenon is that cracks near the inter-layered zones require more energy to propagate, which delays the onset of final failure in the form of local damage. The modified layers are then infiltrated with an amine-cured epoxy by vacuum assisted infusion. The change in pseudo-ductile behaviour as a function of the interfacial additive content was investigated, along with the change in mechanical properties.The stress-strain relationship was determined by various tests, quasi-static and dynamic, from unmodified composites (0% interlayer used) up to 100% interlayer content (i.e. polymer film) between the matrix and the reinforcement. We have investigated a method to repair the specimens after the bending tests via melting the thermoplastic interlayer. The results show that with the use of interlayer material, the critical stress intensity factor increased, and ductile behaviour improved thanks to the altered crack propagation.

Investigation on the influences of interlayer contents on stability and usability of energy storage caverns in bedded rock salt

to balance the intermittent of renewable power, large-scale energy storage in underground salt caverns can be utilized. And the construction and safety evaluations for these caverns become necessary. Aimed at the bedded salt rocks for energy storage, this study focuses on the effect of different interlayer content on the stability and usability of the underground energy storage caverns in bedded salt of China. Salt caverns with five different interlayer content of 0–30% are established for stability and usability comparison. The numerical simulations show that the caverns with high interlayer content have better stability performance than that of the cavern with lower or no interlayer content. A usability evaluation is also discussed by evaluating the effective volume of caverns with different interlayer content. Even though the caverns with high interlayer contents have less volume shrinkage, they have smaller available volume because the collapsed sediments of the interlayer expanded in the cavern bottom. Finally, a method to increase the effective cavern volume is discussed. That is to enlarge the bottom cavern in caverns with high interlayer content.

Comprehensive weighted matter-element extension method for the safety evaluation of underground gas storage.

This study focuses on a safety evaluation method for underground gas storage. Gas storage is usually constructed underground in complex environments, and the service life of such facilities is limited. To ensure the secure and long-term operation of gas storage facilities, safety evaluation has become the focus of management. The present paper provides an effective method for safety evaluation. An index system was established as the foundation of the analysis for this evaluation, and the matter-element extension method was applied to obtain a quantitative evaluation result. For the weight values of each index in the matter-element extension method, this paper presents a comprehensive weight computation method based on vague sets and entropy. By application of this method, the safety level of a gas storage facility in the Jintan salt mines (in Jiangsu, China) was calculated, and the evaluation result was 4.6433, which meant the safety level was V and the underground gas storage was slightly at risk. It indicated that the influence on the overall safety and tightness of this gas storage could be ignored in the operation process, but the frequency of regular monitoring should be increased. The defective indexes were also obtained, such as salt rock cohesion, the roof thickness, the volume contraction ratio, the interlayer content, the height of the casing shoe and the adjacent cavity pressure difference, which need to be monitored and modified. This paper evaluated the safety of the underground gas storage from a unique perspective. It is expected that the results of this research will contribute to the maintenance and operational decisions, and provide a reference for management in the energy industry.

Utilizing phosphate mine tailings to produce ceramisite

There are a large volume of phosphate tailings is produced in China each year. If the tailings are inappropriately disposed of, it may cause serious social problem. This paper presents a study to use phosphate mine tailings to make ceramisite materials, which can be used as building material. In the process, the phosphate tailings were mixed with soft interlayer and black shale materials. The effects of mass ratio among phosphate mine tailings, soft interlayer content and black shale and calcination parameters, such as preheating temperature, preheating time, sintering temperature and sintering time, on the properties of the ceramisite were investigated through single factor experimental testing. Based on the results of experimental tests, the calcination process was optimized. The single factor experimental study shows that the phosphorus content, water absorption rate and particle strength exhibit different correlations under the influence of the material ratio and calcination process. Further optimization tests were carried out and the results demonstrate the significance of influence factors following order: sintering temperature>preheating temperature>sintering time>preheating time. The calcination parameters were also obtained through optimization tests. Preheating temperature and time are 350°C and 9.6min respectively, and sintering temperature and time are 943°C and 60min respectively. Under those optimizing process, the available phosphorus content was determined to be 9.17%.

Bilayered vanadium oxide as the host material for reversible beyond lithium ion intercalation

Bilayered vanadium oxide has emerged as a high-performance cathode material for beyond lithium ion (BLI) battery systems including Na-ion batteries, Mg-ion batteries, and pseudocapacitors. The major structural feature of bilayered V2O5 that makes it attractive for such applications is its large interlayer spacing of ~10-13 Å. This spacing can be controlled via the interlayer content, which can consist of varying amounts of structural water and/or inorganic ions, resulting in numerous chemical compositions. Further, bilayered V2O5 can be synthesized via a number of different methods, resulting in morphologies that include xerogel, aerogel, thin films, and 1-D nanostructures. The interlayer spacing, content, and material morphology can all affect the electrochemical performance of this materials family, and in this review, we discuss the role of each of these factors in the reversible cycling of charge-carrying ions beyond lithium. The different bilayered V2O5 synthesis methods and resulting compositions are reviewed, and important structure-property-performance insights into the reversible insertion/ extraction of larger/multivalent ions into the bilayered V2O5 structure are highlighted.

Electronic structure and phase composition of dielectric interlayers in multilayer amorphous nanostructure [(CoFeB)60C40/SiO2]200

The multilayer amorphous nanostructure [(CoFeB)60C40/SiO2]200 of alternating composite and dielectric layers was obtained by ion-beam sputtering on a rotating pyroceramic substrate of two targets, one of which was a Co40Fe40B20 metal alloy plate with graphite inserts. The dielectric interlayers of SiO2 were sputtered from a quartz plate (second target). The thicknesses of bilayers of the multilayered nanostructure (MNS) (6 nm), consisting of metal–carbon composite layers (CoFeB)60C40 approximately 4 nm in thickness and a silicon oxide dielectric interlayers with a thickness of approximately 2 nm, were determined by small-angle diffraction. The results of experimental layer-by-layer study without destroying the MNS by ultrasoft X-ray spectroscopy (USXES) showed a significant deviation of the stoichiometric composition of the dielectric interlayers from stoichiometry sputtered quartz towards decreasing oxygen concentration with the formation of SiO1.3 suboxide. As a result of simulation of the Si L2,3 spectra of silicon using reference spectra of known phases, the concentration of the silicon suboxide phase in the amorphous dielectric interlayers reaches about half of the interlayer content, the second half of which is accounted for SiO2 dioxide. A “shielding” effect of carbon in the metal layers is manifested in the absence of silicide formation at the interfaces of the multilayer structure under study and should help to increase the anisotropy of their electromagnetic properties.

Water Nanoconfined in Clays: The Structure of Na Vermiculite Revisited by Ab Initio Simulations

The results of Car–Parrinello molecular dynamics simulations of vermiculite clay at the hydration level found in the natural mineral (4 H2O per Na+) are reported. The structure and the vibrational spectrum of the aluminosilicate layer is well reproduced by the simulations. As for the structure of the Na+ cations and of water molecules adsorbed in the interlayer, the ones proposed in X-ray diffraction experimental papers are not in full agreement with the results of neutron diffraction experiments found in literature, yielding only the density profile perpendicular to the aluminosilicate layers, but including hydrogens. Our calculations result in a structure of the interlayer content, which is in agreement with the neutron-diffraction density profile, and yet compatible with X-ray diffraction data. Some features of the adsorbed water resulting from the simulation are an example of incomplete cation hydration and can be of general interest.

ELLINGSENITE, Na5Ca6Si18O38(OH)13{middle dot}6H2O, A NEW MARTINITE-RELATED MINERAL SPECIES FROM PHONOLITE OF THE ARIS ALKALINE COMPLEX, NAMIBIA

Ellingsenite, Na 5 Ca 6 Si 18 O 38 (OH) 13 ·6H 2 O, is a new calcium silicate hydrate (CSH) [triclinic, P 1, a 9.55(3), b 9.395(8), c 16.329(3) A, α 100.2(1), β 94.9(2), γ 117.8(2)°, V 1251(8) A 3 , Z = 1 (from powder-diffraction data) or a 9.576(11), b 9.577(11), c 16.438(19) A, α 85.85(2), β 75.23(2), γ 60.142(14)°, V 1262(3) A 3 , Z = 1 (from single-crystal diffraction data)], chemically and structurally related to minerals of the gyrolite–reyerite group. The mineral is found in a hydrothermally altered phonolite of the Aris alkaline complex, in Namibia, as snow-white spherules (up to 3 mm in diameter) of well-shaped rhomb-like crystals associated with aegirine, albite, manganoneptunite, microcline, natrolite and polylithionite. The mineral is transparent, colorless in separate crystals, white in aggregates, with a vitreous (separate crystals) to silky (aggregates) luster and a white streak. Cleavage is perfect on {001}, and the fracture is smooth. The Mohs hardness is 4. In transmitted light, the mineral is colorless; dispersion is not observed. Ellingsenite is biaxial (–): α 1.520(2), β 1.534(2), γ 1.536 (589 nm), 2 V meas 5°. Optical orientation: X = c . D calc = 2.38 g cm −3 , D meas = 2.32(5) g cm −3 . The mean chemical composition determined by electron microprobe is: Na 2 O 9.26, K 2 O 0.23, CaO 17.35, SiO 2 60.35, H 2 O 12.5 (Penfield method), for a total of 99.69 wt.%. The empirical formula calculated on the basis of 57 atoms of oxygen is (Na 4.95 K 0.09 ) ∑5.04 (Ca 5.57 Na 0.43 ) ∑6.00 Si 18.10 O 38 (OH) 13 ·6H 2 O. The simplified formula is Na 5 Ca 6 Si 18 O 38 (OH) 13 ·6H 2 O. The mineral does not effervesce in 1:1 HCl at room temperature. The strongest X-ray powder-diffraction lines [ d in A(I) hkl ] are: 15.50(100)001, 4.22(16)201, 3.159(30)005, 3.023(33)321, 2.791(24)214, and 1.827(27)511. The crystal-structure model of ellingsenite ( R 1 = 0.247) obtained from a crystal of poor quality displays layers of octahedra and tetrahedra of the T 2 OT 2 type with the composition {Na 1.90 Ca 5.10 [Si 8 O 20 ] X 2 }, where X = O, OH, with the interlayer content unresolved. Ellingsenite can be considered as a derivative of martinite, obtained from the latter by intercalation of some additional species (most probably, Na hydrosilicate) in between the adjacent layers of octahedra and tetrahedra. The principal absorption bands in the infrared spectrum include 3460, 1600, 1360 and 1025 cm −1 (shoulder at 1140 cm −1 ) plus four bands in the region of 780–380 cm −1 . The mineral is named in honor of Dr. Hans Vidar Ellingsen (born 1930), a well-known Norwegian mineral collector, who found this mineral during his expedition to the Aris complex.

The Role of H3O+ in the Crystal Structure of Illite

AbstractIn spite of decades of research on the subject, the crystal structure of illite is still poorly understood. The purpose of this study was to address this problem by investigating the nature of the interlayer content in illite IMt-2 from Silver Hill, Montana, using analytical transmission electron microscopy (ATEM), thermogravimetry (TG), and X-ray powder diffraction (XRPD) analyses. The ATEM data, together with literature and TG results, yielded the formula K0.70a0.01(H2O)0.42 (Al1.53Fe2+0.06Fe3+0.19Mg0.28)Σ−2.06(Si3.44Al0.56)O10(OH)2 or, assuming the presence of H3O+, K0.69Na0.01(H3O)+0.28(Al1.47Fe2+0.06Fe3+0.19Mg0.28)Σ−1.99(Si3.40Al0.60)O10(OH)2. The first formula indicates surplus interlayer and octahedral species, whereas the second shows no excess. The XRPD data were refined by Rietveld techniques, down to an Rp factor of 10.48–13.8%. The mineral composition consists largely of illite-2M1, illite-1M, and minor quartz. Although the refinement accuracy is limited by the intrinsic poor quality diffraction of the illites, the partially refined model is consistent with the chemical composition; in particular, attempts to introduce octahedral cations in excess of 2 were fruitless. All the results support the simple structural model, by which the illite structure strictly corresponds to a dioctahedral mica with H3O+ replacing K. As a consequence, the crystalchemical formula of illites should be calculated on the basis of six tetrahedral plus octahedral cations.

Red micas from basal ignimbrites of Mt. Vulture (Italy): interlayer content appraisal by a multi-methodic approach

The crystal chemistry of red phlogopites from Mt. Vulture (Italy) ignimbrites has been studied by electron microprobe, secondary ion mass spectrometry (SIMS), single crystal structural investigation and Fourier transform infrared (FTIR) spectroscopy. The analysed phlogopite has Fe/(Fe + Mg) ∼ 0.35, TiO2 (wt%): 2.8–5.0 and H2O (wt%): 1.24–3.37. Infrared spectra revealed the presence of bands due to the NH4+ and H2O stretching and bending vibrations. The samples belong to the 1M polytype. The bimodal behaviour of several structural parameters allows red micas to be clustered into two distinct groups: K+ ↔ NH4+, H2O and M3+-vacancy substitutions dominate in the first group; M3+,4+-oxy, in the second group. It has to be pointed out that quantitative analysis of hydrogen (via SIMS) together with the characterization of the local environment of the anionic site (via FTIR) are fundamental in assessing the correct structural formula and the substitution mechanisms in micas.

Consistent Modeling of the XRD Patterns of Mixed-Layer Phyllosilicates

AbstractThe Markovian model of mixed-layering that has been used until now for the modeling of X-ray diffraction (XRD) patterns of 2:1 phyllosilicates describes the mixed-layer crystals as stacks of ‘layer units’ (LUs) that associate a 2:1 layer with an interlayer content. This model is not consistent when it is applied to a mixed-layer mineral (MLM) involving electrically charged layers, i.e. most of the mixed-layer phyllosilicates with 2:1 layers. Two consistent models can be proposed for these MLMs, which, instead of LUs, stack ‘interlayer units’ (IUs), composed of an interlayer content sandwiched between two half-layers. The IU-NPL model (interlayer units, non-polar layers) imposes non-polarity on the 2:1 layers resulting from the stack of these IUs, which implies restrictions on the succession of the IUs. In the other consistent model, the IU-PL one (interlayer units, polar layers), these restrictions are not imposed. These two models reproduce the Non-Polar 2:1 Layer Model and the Polar 2:1 Layer Model described by Altaner and Ylagan for illite-smectite mixed layering, and the second model corresponds to the stacks of O0.5 T I′ T O0.5 units described by Olives et al.The present work points out the similarities and discrepancies of the calculated XRD patterns by using computer programs designed for the three models of mixed-layering (LU, IU-NPL and IU-PL) and for two-and three-component MLMs. Illustrations are provided for some I-S and I-S-V MLMs.The IU-PL model leads to XRD patterns similar to those of the LU model. It is in agreement with lattice-energy calculations, expandability measurement, HRTEM imaging and NMR spectroscopy.

THE CRYSTAL STRUCTURE OF DELINDEITE, Ba2 )3(Ti,Fe)[Ti2(O,OH)4Si4O14](H2O,OH)2}, A MEMBER OF THE MERO-PLESIOTYPE BAFERTISITE SERIES

By using a crystal from a new locality, the structure of delindeite has been refined to R = 0.054 for 703 unique reflections with I > 2σ ( I ). This titanosilicate [ideally Ba 2 {(Na,K,□) 3 (Ti,Fe)[Ti 2 (O,OH) 4 Si 4 O 14 ](H 2 O,OH) 2 }, space group A 2/ m , a 5.327(2), b 6.856(2), c 21.51(3) A, β 93.80(4)°, Z = 2, D calc. = 3.815 g/cm 3 , belongs to a large group of bafertisite-like structures characterized by an ideally octahedral ( O ) sheet sandwiched between two heteropolyhedral ( H ) sheets; these sheets are formed by Ti-octahedra and disilicate groups [Si 2 O 7 ]. The O sheet in delindeite comprises a large (Na,K) polyhedron together with octahedral Na and Ti sites; the alkali polyhedra are partially vacant. The large Ba cation is localized in the interlayer. Evidence of the leaching of alkalis, related atomic disorder, and the position of delindeite within the bafertisite polysomatic series are discussed. On the whole, this series is considered of mero-plesiotype. In fact, the heterophyllosilicate HOH layer, to a first approximation, represents the common module in this series, whereas the interlayer content is variable (merotypism), and may modify its structure in different members (plesiotypism).

Interlayer and Si content of phengite in HP–LT carpholite‐bearing metapelites

AbstractPhengite occurring along with carpholite±lawsonite and/or chloritoid in HP–LT domains shows not only variable Si–(Mg+Fe) contents, but also variable interlayer contents (IC). To determine whether these chemical variations are coherently related to variation in P–T conditions on a regional scale, c. 100 rock samples were sampled in metapelites metamorphosed at conditions varying from 350 °C, 8 to 12 kbar to 450–500 °C, 18 to 20 kbar (Schistes Lustrés complex, franco‐italian Western Alps). Based on microstructural and habit criteria, four types of phengite were differentiated that are related either to the rock mineralogy (carpholite vs chloritoid bearing samples) or correspond to various generations of phengite occurring in the same rock sample or thin section. Microprobe analyses reveal that each type of phengite is characterized by a specific composition and that phengite associated with carpholite has a lower interlayer content than phengite associated with chloritoid. The successive generations of retrograde phengite overgrowing carpholite point to a large decrease of interlayer content (c. 0.9–0.7 pfu) and (Fe+Mg) content (c. 0.25–0 pfu) with decreasing P–T conditions. This change is best accounted for by a gradual increase of the pyrophyllite component. In contrast, phengite from higher‐temperature, chloritoid‐bearing rock samples shows an almost constant interlayer content (c. 0.9–0.95 pfu) but a larger decrease of (Fe+Mg) content (c. 0.6–0.1 pfu). Hence, (1) the composition of the different phengite generations occurring (metastably) in the same rock sample may be used to retrieve points in P–T loops and (2) the pyrophyllitic substitution in phengite is large at low‐temperature conditions and cannot be ignored. Thermobarometric estimates based on the Si‐content alone will therefore result in pressure over‐estimates. We propose a tentative location of the phengite Si and IC isopleths in P–T space which could allow a direct determination of the P–T conditions in carpholite‐bearing rocks. Especially in some carpholite‐bearing rocks, new thermodynamic models accounting for tschermak and pyrophyllitic substitution are also required prior to making reliable thermobarometric estimates in HP‐LT metapelites.

Thermal expansivity of particulate composites: Interlayer versus molecular model

We continue the comparison of the results of an interlayer model, based on the theory of elastic continua, and a molecular model, derived from a theory of mixtures, previously presented in terms of bulk moduli K. We now derive expressions for the dependence of the thermal expansivityαc on the volume fractionφf of the filler, at low and elevated values ofφf. Correspondencies between the characteristic parameters, viz. adhesion and repulsion ratios on the one hand, and interlayer content and thermal properties of matrix, filler, and layer, on the other, are examined. Since in the molecular theory bothα andK are derived from an equation of state, the identical set of parameters determines both functions and suggests correlations between them.

Blockpolymers of styrene and isoprene with variable interphase: Morphology and dynamic viscoelastic behaviour

A method is described to prepare poly[isoprene-b-(isoprene-co-styrene)-b-styrene] threeblock polymers with variable interphase thickness by anionic polymerization. At constant overall molecular weight the total interlayer content multiply exceeds that of normal blockpolymers. At high copolymer content three-phase systems are obtained. The morphology is examined by electron microscopy under various staining conditions. The dynamic viscoelastic behaviour, determined with torsion pendulum experiment, has been simulated for lamellar two-and three-phase systems with different contents of copolymer material. A new interpretation of theT g depression of the hard phase is given in terms of a cooperative softening of the pure hard phase and surface interlayer material.

A Mixed-Layer Clay Mineral Associated with an Evaporite

AbstractClay partings in the ore beds in a New Mexico evaporite section include a range of mixed-layer clay mineral sequences of the corrensite type. Specimens range from nearly regular alternations to sequences which depart from regularity to moderate degrees. The ore bodies consist of halite, polyhalite, sylvite, magnesite, dolomite, carnallite, and iron oxides.Observed x-ray diffraction effects from representative specimens are compared with synthesized effects for montmorillonite- or vermiculite-chlorite layer sequences.It is concluded that the segregation of the abundant Mg interlayer content into specific, regularly spaced interlayers represents the equilibrium relationship between a montmorillonite-chlorite or vermiculite-chlorite mixed assemblage and a mildly acid, Mg2+-, Na+- and K+-rich environment.