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An understanding of the thermodynamics of triple-chain silicate phases can offer insight into their formation in nature. Because the more common Mg triple-chain silicates have not yet been synthesized, this study focused on the Na-analogue to clinojimthompsonite (Na-cjt), which forms readily in a laboratory setting. Synthetic Na-cjt was characterized using electron microscopy and microanalysis, thermogravimetric analysis, infrared spectroscopy, and loss on ignition to determine its water content. The results of these studies indicated a formula for Na-cjt of [Na.sub.3.74][Mg.sub.8.13][Si.sub.12][O.sub.32.00][(OH).sub.4]*1.40 [H.sub.2]O, although there was substantial uncertainty ([+ or -] 13%) associated with the total water (OH + [H.sub.2]O) content. A series of experimental reversals was performed over a temperature range of 350-650[degrees]C and a pressure range of 0.1-1 GPa for the reaction between Na-cjt and a double-chain silicate. In the pressure range of 0.2-0.5 GPa, this reaction has the stoichiometry [Na.sub.3.74] [Mg.sub.8.13][Si.sub.12][O.sub.32.00][(OH).sub.4]*1.40[H.sub.2]O(Na-cjt) = 1.5 [Na.sub.2.49][Mg.sub.5.42][Si.sub.8][O.sub.21.34][(OH).sub.2.66] (Na-Mg amph) + 1.40 [H.sub.2]O. The equilibrium boundary reaches a maximum temperature near 550[degrees]C at 0.4 GPa, continuing to lower temperatures above this pressure. The third-law entropy and enthalpy of formation of both Na-cjt and the associated Na-Mg amphibole were measured using adiabatic and oxide-melt solution calorimetry, respectively. Calculating the equilibrium boundary for the reaction using the calorimetrically determined values does not produce the same boundary found through the experimental reversals. The discrepancy was attributed to water variability in Na-cjt with pressure. This variability and its effect on Na-cjt's thermodynamic values can be expressed by the following equations that, for simplicity, indicate the total water content (OH + [H.sub.2]O) as moles of [H.sub.2]O in Na-cjt over the range of 0.1 to 1.0 GPa: [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII.] where the entropy does not include any contributions from configurational mixing. If one includes configurational entropy contributions from cation and vacancy disorder in the triple-chain silicate and amphibole, one obtains [S.sup.o] and [DELTA][H.sup.o.sub.f] for Na-cjt of 919.2 J/(K*mol) and-18417.6 kJ/mol, respectively, and [S.sup.o] and [DELTA][H.sup.o.sub.f] for Na-Mg amphibole of 650.9 J/(K*mol) and -11 919.7 kJ/mol, respectively. Keywords: Triple-chain silicate, Na-clinojimthompsonite, thermochemistry, calorimetry

A series of experiments with and without sample retreatment was performed on a starting mixture of dolomite plus quartz at 0.5 GPa and 600 [degrees]C in a C[O.sub.2]-[H.sub.2]O fluid with a mole fraction of C[O.sub.2] of 0.2 for durations up to 582 h. The initial reaction of dolomite and quartz led to rapid formation of talc and calcite instead of tremolite and calcite by the intended reaction: 5 dolomite + 8 quartz + [H.sub.2]O = tremolite + 3 calcite + 7 C[O.sub.2]. With continued treatment, the talc+ calcite + quartz assemblage gradually reacts to form increasing amounts of tremolite and diopside with the eventual loss of quartz and nearly complete loss of talc. The detailed structure of the amphibole and the nature of the Mg enrichment were revealed using AEM analysis of individual amphibole crystals. The most abundant defects are triple-chain chain multiplicity faults (CMFs), which appear as isolated lamellae with single periodicity in short-duration experiments and increasingly as groups of lamellae with variable multiplicity and periodicity in longer duration experiments and especially in a long-duration experiment without retreatment. In this latter experiment, a calcian clinojimthompsonite domain extending 15 unit cells along the b axis was observed. The sample after 582 h and five retreatments shows, on average, 3.5% true solid solution with Mg expressed as the Mg-cummingtonite (MC) component after correction for the presence of CMFs. This sample is thought to most closely approach the equilibrium composition for the amphibole. The sample after 250 h with three retreatments has about 10%, whereas that after 582 h without retreatment has 0.6% MC component, the latter having a relatively high density of CMFs. This study affirms the importante that precursor non-amphibole biopyriboles play in the formation of tremolitic amphibole. Keywords: Tremolite, HRTEM, analytical electron microscopy, mineral growth, calcian clinojimthompsonite

The room temperature synthesis approach helps in studying the transformation of the amorphous zeolite A precursors with minimum invasive postsynthesis treatments. The void structures in the solid part of the system and their solid-liquid interfaces are identified as the specific locations where the formation of protozeolite nuclei takes place.

A series of low-Ca (1.8-1.65 atoms Ca per formula unit) actinolites were synthesized in the system CaO-FeO-MgO-Si[O.sub.2]-[H.sub.2]O with bulk compositions of 0, 10, 20, and 30 mol% ferro-actinolite when projected onto the tremolite--ferro-actinolite join for the purpose of determining the cation site occupancies as a function of bulk composition. Syntheses were done by multiple treatments of the oxide-metal mixtures in internally heated gas vessels at 600-800 [degrees]C, 6 kbar, f[o.sub.2] near the Co-CoO buffer, which is sufficiently low to prevent the appearance of [Fe.sup.3+] in this study, and for total durations up to 774 hours. Bulk compositions of the synthesis products were assessed by electron microprobe analysis (EMPA), analytical transmission electron microscopy (AEM), and by using unit-cell dimensions (CD method), whereas the site occupancies were assessed using powder X-ray diffraction (XRD) Rietveld refinements, Fourier-transform infrared (FTIR) spectroscopy, and Mossbauer spectroscopy. Selected-area electron-diffraction (SAED) patterns and high-resolution transmission electron microscopy (HRTEM) images were obtained to study the stRucture and defects of the samples. A maximum of about 2% non-amphibole chain-multiplicity faults (CMFs) were observed in the sample with 10 mol% ferroactinolite component, indicating the strong reduction in CMFs that occurs with only a small addition of ferro-actinolite to tremolitic amphiboles. This study, as with earlier studies, found no significant preferential partitioning of Fe and Mg relative to the bulk Fe content of the sample at the M1 and M3 sites, weak partitioning of Mg relative to Fe into the [M.sub.2] site, and strong partitioning of Fe relative to Mg at the M4 site. No ferric iron was detected. The partitioning of Fe and Mg at the M4 site was modeled by a simple ideal-activity, two-site exchange reaction using the actinolites from this study and those of previous studies with bulk Fe/(Fe + Mg) [less than or equal to] 0.3 and with low Al, Mn, and Na contents using 1 bar and 298K values of [DELTA]G[degrees] = 62 kJ and [DELTA]S[degrees] = 54 J/K. The FFIR data were analyzed for the presence of short-range order of Fe and Mg at the M1 and M3 sites but none was found.

FAU-type zeolite was synthesized at room temperature to study the mechanism of its formation. The processes taking place at the nanometer scale were studied by transmission electron microscopy (TEM) and the crystalline character of the particles observed during the induction period was determined by in situ synchrotron XRD analysis.

The first direct transmission electron microscopic (TEM) observation is carried out on the continuous monocrystal-thick b-oriented pure silica zeolite MFI films produced by in situ crystallization. This TEM investigation provides direct unambiguous new evidence to support the homogeneous nucleation mechanism by which the films form through homogeneous nucleation and crystal growth in the bulk to form equal-sized disk-shape crystals followed by self-assembly of these crystals onto the substrate to produce a two-dimensional close-packed structure.

The formation mechanisms of tremolite in a time series of hydrothermal experiments at 850 [degrees]C and 6.l kbar were studied using transmission electron microscopy (TEM), analytical TEM, and X-ray diffraction. The starting materials were unseeded mixtures of reagent-grade oxides. After the first 8 min of reaction, the synthesis products were diopside, enstatite, clinoenstatite, quartz, and minor C-centered and primitive monoclinic amphibole (13 wt% total). The compositions of the first-formed amphiboles vary considerably, from essentially pure cummingtonite (Ca/Mg = 0) to nearly ideal tremolite (Ca/Mg = 0.4). Three groupings of amphiboles with successively higher Ca/Mg ratios were identified, respectively 0.1. 0.22. and 0.35. Over a period of 97 h, the proportions of Mg-rich amphibole gradually decrease, and the average Ca/Mg ratios of all amphiboles steadily increase from about 0.22 to 0.35. Other changes include: (1) a decrease in the aspect ratio of amphibole crystals with increasing time: (2) a decrease in the number of non-amphibole chain multiplicity faults (CMFs), from early A'(2) values as low as 0.81 to a final value of 0.94; and (3) a distinct change in the rate of amphibole growth after l h of synthesis. These observations suggest that two mechanisms of amphibole formation are dominant: (1) formation of pyroxene modules with subsequent hydration and arrangement into the double-chain amphibole structure and (2) direct nucleation and growth of amphibole from hydrothermal solution. A third mechanism involving formation of talc-like modules, followed by their breakdown into double-chain modules, incorporation of Ca, and ordering into the amphibole structure, may also occur but probably only at the lamellar or unit-cell scale, because these syntheses were performed outside the stability field of talc.

The re-investigation of the synthesis, characterization, and upper-thermal stability of ferro-actinolite is performed in the system CaO-FeO-SiO2-H2O. The results obtained from the different experiments conducted on ferro-actinolites are given.

High-resolution transmission-electron microscopy (HRTEM) and infrared spectroscopy (FTIR) analyses have been done on amphiboles near the join tremolite [[Ca.sub.2][Mg.sub.5][Si.sub.8][O.sub.22][(OH).sub.]2 = TR]-pargasite [Na[Ca.sub.2][Mg.sub.4][Al.sub.3][Si.sub.6][O.sub.22] [(OH).sub.2] = PG] in the ternary system tremolite-pargasite-cummingtonite [[Mg.sub.7][Si.sub.][O.sub.22] [(OH).sub.2] = MC] that were synthesized previously by Sharma and Jenkins (1999). Representative samples across the join were examined in detail by HRTEM to document the presence and concentration of chain multiplicity defects (CMFs). There was relatively little change in the defect density with composition, with the tremolitic sample (TREM 23-13) having the highest defect concentration (6%) and the more PG-rich samples having slightly lower CMF concentrations (4-5%). CMFs with multiplicities of 1,3, 4, 5, and 6 were observed, usually as isolated chains, with the most common being triple-chain slabs. Correction of the bulk composition of the tremolitic amphibole for the presence of these Mg-rich, wide-chain defects reduces the MC content from an apparent value of 8.5 to 4-7.5 mol% MC, depending on which composition is used for the triple-chain defect. The entire amphibole join was examined by FTIR spectroscopy in the OH-stretching region (3000-3800 [cm.sup.-1]) for the purpose of determining the presence of short-range order. A total of 10 component bands were fitted to the spectra across the join. These bands were assigned to specific cation configurations on the basis of earlier studies of the FTIR spectra of chemically simplified amphibole joins pertinent to this study. The extent of short-range order was qualitatively determined by comparing the observed intensities for groups of related bands, corrected for differences in their molar absorptivities, to their calculated intensifies based on random-mixing probabilities. From this exercise, it is observed that the intensities of sodic amphibole configurations are consistently high, tremolite is lowest near the middle of the join, and aluminous amphibole configurations cross over from being higher (at low A1 contents) to being lower (at high A1 contents) than expected near the middle of the join. These differences between observed and predicted band intensities may reflect the presence of deviations in the thermodynamic activities of amphibole components from those predicted on the basis of random-mixing models.

The mesopores formation in zeolite crystals has long been considered to occur through the stochastic hydrolysis and removal of framework atoms. Here, we investigate the NH4F etching of representative small, medium, and large pore zeolites and show that the zeolite dissolution behavior, therefore the mesopore formation probability, is dominated by zeolite architecture at both nano‐ and sub‐nano scales. At the nano‐scale, the hidden mosaics of zeolite structure predetermine the spatio‐temporal dissolution of the framework, hence the size, shape, location, and orientation of the mesopores. At the sub‐nano scale, the intrinsic micropore size and connectivity jointly determine the diffusivity of reactant and dissolved products. As a result, the dissolution propensity varies from removing small framework fragments to consuming nanodomains and up to full digestion of the outmost part of zeolite crystals. The new knowledge will lead to new understanding of zeolite dissolution behavior and new adapted strategies for tailoring hierarchical zeolites. [ABSTRACT FROM AUTHOR]

Background: The atomizers of electronic cigarettes (ECs) contain metals that transfer to the aerosol upon heating and may present health hazards. This study analyzed 4th-generation EC pod atomizer design features and characterized their elemental/metal composition. Methods: Eleven EC pods from six brands/manufacturers were purchased at local shops and online. Pods were dissected and imaged using a Canon EOS Rebel SL2 camera. Elemental analysis and mapping of atomizer components was done using a scanning electron microscope coupled with an energy dispersive x-ray spectrometer. Results: EC pods varied in size and design. The internal atomizer components were similar across brands except for variations occurring mainly in the wicks and filaments of some products. The filaments were either Elinvar (nickel, iron, and chromium) (36.4%), nichrome (36.4%), iron-chromium (18.2%), or nickel (9%). Thick wires present in 55% of the atomizers were mainly nickel and were joined to filaments by brazing. Wire-connector joints were Elinvar. Metal air tubes were made of Elinvar (50%), nickel, zinc, copper, and tin (37.5%), and nickel and copper (12.5%). Most of the wick components were silica, except for two pods (PHIX and Mico), which were mainly ceramic. Connectors contained gold-plated nickel, iron-chromium multiple alloys of nickel, zinc, gold, iron, and copper. Wick chambers were made of Elinvar. Outer casings were either nickel, copper-tin, or nickel-copper alloys. Magnets were nickel with minor iron, copper, and sulfur. Some frequently occurring elements were high in relative abundance in atomizer components. Conclusions: The atomizers of pods are similar to previous generations, with the introduction of ceramic wicks and magnets in the newer generations. The elements in EC atomizers may transfer into aerosols and adversely affect health and accumulate in the environment. [ABSTRACT FROM AUTHOR]

The changes in composition and structure of sodium hydroxide rich aluminosilicate gel yielding zeolite A are studied. The studies have shown the unrivaled sensitivity of hyperpolarized (HP) [super 129]Xe NMR that is capable of identifying presence of small amounts of crystalline zeolite material in amorphous medium with detection limit extending below 1 wt%.

30-80 nm thick yttrium iron garnet (YIG) films are grown by pulsed laser deposition on a 5 nm thick sputtered Pt atop gadolinium gallium garnet substrate (GGG) (110). Upon post-growth rapid thermal annealing, single crystal YIG(110) emerges as if it were epitaxially grown on GGG(110) despite the presence of the intermediate Pt film. The YIG surface shows atomic steps with the root-mean-square roughness of 0.12 nm on flat terraces. Both Pt/YIG and GGG/Pt interfaces are atomically sharp. The resulting YIG(110) films show clear in-plane uniaxial magnetic anisotropy with a well-defined easy axis along (001) and a peak-to-peak ferromagnetic resonance linewidth of 7.5 Oe at 9.32 GHz, similar to YIG epitaxially grown on GGG. Both spin Hall magnetoresistance and longitudinal spin Seebeck effects in the inverted bilayers indicate excellent Pt/YIG interface quality. [ABSTRACT FROM AUTHOR]

The principle aspects and constraints of the dynamics and kinetics of zeolite nucleation in hydrogel systems are analyzed on the basis of a model Na-rich aluminosilicate system. A detailed time-series EMT-type zeolite crystallization study in the model hydrogel system was performed to elucidate the topological and temporal aspects of zeolite nucleation. A comprehensive set of analytical tools and methods was employed to analyze the gel evolution and complement the primary methods of transmission electron microscopy (TEM) and nuclear magnetic resonance (NMR) spectroscopy. TEM tomography reveals that the initial gel particles exhibit a core-shell structure. Zeolite nucleation is topologically limited to this shell structure and the kinetics of nucleation is controlled by the shell integrity. The induction period extends to the moment when the shell is consumed and the bulk solution can react with the core of the gel particles. These new findings, in particular the importance of the gel particle shell in zeolite nucleation, can be used to control the growth process and properties of zeolites formed in hydrogels. [ABSTRACT FROM AUTHOR]

Interest in graphene as a two-dimensional quantum-well material for energy applications and nanoelectronics has increased exponentially in the last few years. The recent advances in large-area single-sheet fabrication of pristine graphene have opened unexplored avenues for expanding from nano- to meso-scale applications. The relatively low level of absorptivity and the short lifetimes of excitons of single-sheet graphene suggest that it needs to be coupled with light sensitizers in order to explore its feasibility for photonic applications, such as solar-energy conversion. Red-emitting CdSe quantum dots are employed for photosensitizing single-sheet graphene with areas of several square centimeters. Pyridine coating of the quantum dots not only enhances their adhesion to the graphene surface, but also provides good electronic coupling between the CdSe and the two-dimensional carbon allotrope. Illumination of the quantum dots led to injection of n-carrier in the graphene phase. Time-resolved spectroscopy reveals three modes of photoinduced electron transfer between the quantum dots and the graphene occurring in the femtosecond and picosecond time-domains. Transient absorption spectra provide evidence for photoinduced hole-shift from the CdSe to the pyridine ligands, thereby polarizing the surface of the quantum dots. That is, photoinduced electrical polarization, which favors the simultaneous electron transfer from the CdSe to the graphene phase. These mechanistic insights into the photoinduced interfacial charge transfer have a promising potential to serve as guidelines for the design and development of composites of graphene and inorganic nanomaterials for solar-energy conversion applications. [ABSTRACT FROM AUTHOR]

During mineralization, the hard outer magnetite-containing shell of the radular teeth of Cryptochiton stelleri undergoes four distinct stages of structural and phase transformations: (i) the formation of a crystalline α-chitin organic matrix that forms the structural framework of the non-mineralized teeth, (ii) the templated synthesis of ferrihydrite crystal aggregates along these organic fibers, (iii) subsequent solid state phase transformation from ferrihydrite to magnetite, and (iv) progressive magnetite crystal growth to form continuous parallel rods within the mature teeth. The underlying α-chitin organic matrix appears to influence magnetite crystal aggregate density and the diameter and curvature of the resulting rods, both of which likely play critical roles in determining the local mechanical properties of the mature radular teeth. [ABSTRACT FROM AUTHOR]

The growth of crystalline copper sulfide using a viral template was investigated using sequential incubation in CuCl2 and Na2S precursors. Non-specific electrostatic attraction between a genetically-modified M13 bacteriophage and copper cations in the CuCl2precursor caused phage agglomeration and bundle formation. Following the addition of Na2S, polydisperse nanocrystals 2-7 nm in size were found along the length of the viral scaffold. The structure of the copper sulfide material was identified as cubic anti-fluorite type Cu1.8S, space group FmN3m. Strong interband absorption was observed within the ultraviolet to visible range with an onset near 800 nm. Furthermore, free carrier absorption, associated with the localized surface plasmon resonance of the copper sulfide nanocrystals, was seen in the near infrared with absorbance maxima at 1060 nm and 3000 nm, respectively. [ABSTRACT FROM AUTHOR]

A series of experiments with and without sample retreatment was performed on a starting mixture of dolomite plus quartz at 0.5 GPa and 600 °C in a CO2-H2O fluid with a mole fraction of CO2 of 0.2 for durations up to 582 h. The initial reaction of dolomite and quartz led to rapid formation of talc and calcite instead of tremolite and calcite by the intended reaction: 5 dolomite + 8 quartz + H2O = tremolite + 3 calcite + 7 CO2. With continued treatment, the talc + calcite + quartz assemblage gradually reacts to form increasing amounts of tremolite and diopside with the eventual loss of quartz and nearly complete loss of talc. The detailed structure of the amphibole and the nature of the Mg enrichment were revealed using AEM analysis of individual amphibole crystals. The most abundant defects are triple-chain chain multiplicity faults (CMFs), which appear as isolated lamellae with single periodicity in short-duration experiments and increasingly as groups of lamellae with variable multiplicity and periodicity in longer duration experiments and especially in a long-duration experiment without retreatment. In this latter experiment, a calcian clinojimthompsonite domain extending 15 unit cells along the b axis was observed. The sample after 582 h and five retreatments shows, on average, 3.5% true solid solution with Mg expressed as the Mg-cummingtonite (MC) component after correction for the presence of CMFs. This sample is thought to most closely approach the equilibrium composition for the amphibole. The sample after 250 h with three retreatments has about 10%, whereas that after 582 h without retreatment has 0.6% MC component, the latter having a relatively high density of CMFs. This study affirms the importance that precursor non-amphibole biopyriboles play in the formation of tremolitic amphibole. [ABSTRACT FROM AUTHOR]

Our experimental simulations of the exhumation path of mantle peridotites show that high-temperature (1400 °C) decompression of lherzolite from 14 to 13 and 12 GPa results in exsolution of interstitial blebs of diopside and Mg2SiO4 (wadsleyite) lamellae from majoritic garnet. At lower pressures (from 8 to 5 GPa, atT = 1400 °C) only enstatite exsolves as blebs at garnet boundaries. Continuous high-temperature decompression from 14 to 7 GPa produces zoned majoritic garnet containing blebs of exsolved pyroxenes inside garnet rims. No intracrystalline precipitation of pyroxene was observed in garnet, although such lamellae are found in some natural garnet peridotites. The explanation appears to be the three orders of magnitude difference in grain size between experimental and natural specimens. Our data suggest that Mg2SiO4 and diopside exsolutions reflect the deepest point of the exhumation path of garnet peridotites, whereas enstatite precipitation may be restricted to garnets with less majoritic component at shallower depths.Terra Nova, 16, 325–330, 2004 [ABSTRACT FROM AUTHOR]

Presents a study that determined the three-dimensional distribution of ilmenite in olivine from Alpe Arami, Switzerland using confocal laser scanning microscopy. Background of confocal laser scanning microscopy; Comparison of the ilmenite distribution determined by wavelength dispersive x-ray spectroscopy and energy dispersive x-ray spectroscopy; Determination of the volumetric abundance of ilmenite.

Presents a transmission electron microscopy study which revealed the microstructure of polysynthetically twinned near end-member grunerite from Rockport, Massachusetts. Structure of amphiboles; Details of electron microprobe analysis; Implication of the clear difference in the microstructures of grunerite from Rockfort and protoferroanthophyllite from Cheyenne.

Two new polymorphs of niobium trisulfide are established by single crystal x-ray diffraction. NbS3-iv crystallizes in the monoclinic space group P21/c with lattice parameters a = 6.7515(5) Å, b = 4.9736(4) Å, c = 18.1315(13) Å, and β = 90.116(2)°. Its structure is based on chains of [NbS6] trigonal prisms containing Nb–Nb pairs with a bond length of 3.0448(8) Å; this pairing causes the chains to corrugate slightly along their axis, a feature also present in triclinic NbS3-i that leads to semiconductor properties. The stacking arrangement of chains is different in these polymorphs, however, with NbS3-i having an ABCDE repeating sequence of chain bilayers and NbS3-iv having an AB repeating sequence. HRTEM studies show the presence of topotactically-oriented intergrown zones and numerous dislocations, which result in mosaic structuring. A second new polymorph, NbS3-v, crystallizes in the monoclinic space group P21/m with lattice parameters a = 4.950(5) Å, b = 3.358(4) Å, c = 9.079(10) Å, β = 97.35(2)°. In contrast to NbS3-iv, NbS3-v maintains fixed a Nb–Nb bond distance of 3.358(4) Å along the chains, and it has an ABCDE repeating sequence of chain bilayers similar to NbS3-i. High resolution scanning transmission electron microscopy (HR-STEM) imaging of an exfoliated NbS3-v nanoribbon shows the continuous [NbS6] chains oriented along the b-axis. These results provide the first firmly established structural data for monoclinic NbS3. In addition, SEM images show the formation of NbS3 rings and cylinders, and a combination of powder x-ray diffraction and Raman spectroscopy provides a way to distinguish between NbS3 polymorphs. [ABSTRACT FROM AUTHOR]

A correction to the article "3D Study of the Morphology and Dynamics of Zeolite Nucleation" that was published in a 2015 is presented.

Many biological materials are known for their remarkable structural complexity as well as their impressive mechanical properties. The ultrahard abrasion‐resistant radular teeth of the chitons are one such example and members of this group of mollusks, studied by David Kisailus and co‐workers on page 2908, have the surprising capacity to erode away the rocky substrates on which they graze for algae. The foreground image depicts the anterior end of the conveyor belt‐like radula that contains the magnetite‐rich teeth and the background image depicts the oriented rod‐like aggregates of magnetic nanoparticles that comprise the material. [ABSTRACT FROM AUTHOR]