Intergrowth Of Crystals Research Articles

Subduction related population of diamonds in Yakutian placers, northeastern Siberian platform

The 35 paired diamond intergrowths of rounded colorless transparent and gray opaque crystals from the placers of northeastern Siberian Platform were investigated. Mineral inclusions (KFsp, Coe, E-Grt, Po) detected in studied samples belong to eclogitic paragenesis. The majority of studied samples have uniform ranges of nitrogen content (1126–1982 at. ppm) and carbon isotope composition (− 16.8 to − 23.2 ‰). These characteristics pointing towards subducted material are possible sources for their genesis. Two samples consist of a gray opaque crystal with the subduction-related characteristics (δ13C ca. − 21‰ and N ca. 1300 at. ppm) and a transparent crystal with low nitrogen content (412 and 29 at. ppm) and a heavy carbon isotopic composition (δ13C − 4.2 and − 4.6‰) common for primary mantle range. The higher degree of nitrogen aggregation in the crystals with mantle-like characteristics testifies their longer storage in the mantle conditions. These samples reflect multistage diamond growth history and directly indicate the mixing of mantle and subduction carbon sources at the basement of subcontinental lithospheric mantle of northeastern Siberian Platform.

Synthesis of thin SAPO-34 zeolite membranes in concentrated gel

Synthesis of thin zeolite membranes in the sub-micron range is desirable but a great challenge. Despite the successful synthesis of ultrathin Silicalite-1 and CHA membranes, the pursuit of SAPO-34 membranes thinner than 1 μm remains difficult. Herein, thin SAPO-34 membranes were prepared in concentrated gel by conventional hydrothermal synthesis. Concentrated membrane gel (TEAOH/Al2O3 = 4 and H2O/Al2O3 = 10) enhanced nucleation and facilitated the formation of small SAPO-34 crystals and therefore thin membranes. High TEAOH/Al2O3 ratio and special mixing sequence resulted into a homogeneous membrane gel with low viscosity which is beneficial for membrane synthesis with high reproducibility. Al(OH)3 as Al source led to formation of cubic SAPO-34 crystals which facilitated crystal intergrowth and reduced defects. These membranes (∼1.2 μm thick) exhibited high CO2 permeance of 3.9 × 10−6 mol/(m2 s Pa) and CO2–CH4 selectivity of 152 for equimolar CO2–CH4 mixture at room temperature and 0.14 MPa pressure drop. Further optimization of aging treatment or limiting the excessive membrane growth by a two-step hydrothermal synthesis + dry gel conversion method, the membrane thickness was successfully reduced to ∼0.9 μm, which increased the CO2 permeance to ∼5.0 × 10−6 mol/(m2 s Pa) without sacrificing CO2–CH4 selectivity.

Influence of boehmite intermediate layer as covalent linker on synthesis of LTA zeolite coatings

The incorporation of nanostructured materials, such as LTA-type zeolite on the silicon wafers, opens a very interesting door to the use of these materials within silicon based microfabrication technologies. This work studies the deposition and intergrowth of defect-free LTA-type zeolite layer onto 3-inch Silicon wafers with a layer of SiO2 subjected to pretreatment. The main disadvantage associated with zeolite layer synthesis are crack the formation of cracks and difficulty of obtaining a uniform layer. By modifying the supports with boehmite, a substantial improvement was observed in terms of layer continuity and crystal intergrowth in comparrison to coatings prepared on cationic polymer, poly (diallyldimethylammonium chloride). An LTA- type zeolite layer was synthesized in a range of 350 to 1300 nm via hydrothermal ex-situ method at 363 K for 12 h. Tetramethylammonium hydroxide (TMAOH) was used as a template, and aluminum isopropoxide and colloidal silica were used as Al and Si sources, respectively.

Preshearing is an in situ setting modification method for inorganic bone cements

AbstractThe flow behaviour and injectability of calcium phosphate cements are outcomes of the complex interplay between time‐dependent processes of dissolution, nucleation and crystal growth. Their dependence on shear strains, frequencies and rates has been revealed by rheological investigation of the setting processes of a brushite cement under torsional flow. Various oscillatory torsional strain amplitudes and frequencies were seen to promote dissolution or delay crystal intergrowth compared to quiescently set cement samples. Oscillatory torsional strain amplitudes higher than the linear viscoelastic strain limit resulted in a pronounced lag in crystal intergrowth. Dissolution was enhanced and setting was promoted with increasing frequency and strain amplitude within the linear viscoelastic strain range. Changing the preshearing mode to steady torsion increased energy spent to microstructural deformation, counteracting the beneficial vibratory effect on cement setting kinetics, and produced a net retardation by the disruption of the crystal network structure. Such deformation history can be created in the cement suspension prior to injection during clinical practice by precise adjustment of the preshearing modes and parameters to enable the orthopaedic surgeon tailor the setting time, flow behaviour and injectability of calcium phosphate cements in situ without altering the cement chemistry, hence bioactivity.

Synthesis the composites Si3N4-TiN by hot pressing

The Si3N4-TiN composites were obtained by hot pressing at 1600–1800 °C in a nitrogen atmosphere from mixtures of powders of silicon nitride and metallic titanium. The influence of particle morphology, Ti content in the initial charge and synthesis conditions on the microstructure, phase composition, mechanical strength of the samples of ceramic composites Si3N4-TiN was studied. It was established that in the process of sintering, complete nitriding of titanium occurs with the formation of a non-stoichiometric nitride of composition TiN0.9. Samples of composites Si3N4-TiN, obtained from a mixture containing 5-30 % Ti, have a density of 3.02-3.41 g/cm3, water absorption 0.01-0.14 %, open porosity 0.03-0.44 % and flexural strength from 250 to 584 MPa. It is shown that ceramics Si3N4-TiN with a sintering additive of calcium aluminates is characterized by a dense intergrowth of silicon nitride crystals, which provides an increase in the strength of the samples.

Activation of B as a sintering aid and its improved microstructure modification by using Ni-B coated Ti core-shell powder

Ni and B in the Ni-B coated Ti (Ti@Ni-B) core-shell powders fabricated by electroless plating are present in the form of intergrowth of crystals consisting of amorphous Ni-B alloy and Ni3B compounds, which therefore modified the reaction path and liquid formation process. In-situ sintering microstructure evolution indicated that the activation of B as a sintering aid started with the way that Ni and B from coated amorphous Ni-B reacted to form low-melting Ni3B compounds prior to the formation of Ti2Ni between Ni and Ti. Both low-melting-point compounds were melted to form liquid and significantly increased the amount of liquid by which the sintering densification was enhanced. Another positive role of using Ti@Ni-B powders was the in-situ formation of TiB on each Ti particle by which a high number density of low-energy-barrier heterogeneous nucleation sites and pinning points were produced. This resulted in finer grain and better equiaxed crystallization. The enhanced sintering densification contributed to the improved tensile strength while a combination of the equiaxed α-Ti grains, low oxygen increment and reduced porosity were responsible for the increased tensile ductility by 60%.

Vapor-Phase Synthesis of ZIF-8 MOF Thick Film by Conversion of ZnO Nanorod Array.

ZIF-8 metal organic framework "micrometer-thick" films were constructed from ZnO precursor by a vapor-phase synthesis. The ZnO-to-ZIF-8 crystal transformation proceeded in the presence of 2-methylimidazole (Hmim) vapor. Continuous coatings of intergrown ZIF-8 crystals require control of a nucleation density. The dependence of ZnO crystal plane on the ZnO-to-ZIF-8 crystal transformation was investigated using four bulk ZnO single crystals: a-plane (11-20), c-plane (0001), m-plane (10-10), and r-plane (10-11). It was revealed that the m-plane (10-10) of ZnO is more effectively transformed into ZIF-8. In this work, highly oriented ZnO nanorod array film was used to provide the transport pathway of Hmim molecules and volume expansion space of ZnO-to-ZIF-8 crystal transformation for nucleation and crystal intergrowth. The high conversion of ZnO nanorod array into ZIF-8 in a short time could be achieved because (1) such mass transfer is easy due to the uniform internanorod distance being maintained during reaction and (2) the surface of the nanorod array is dominated by the highly reactive m-plane (10-10).

Zeolite synthesis in basic media using expanded perlite and its application in Rhodamine B adsorption

In this work, expanded perlite was employed as a Si and Al source in zeolite synthesis. The products obtained were mixtures of three zeolitic topologies identified by X-ray diffraction and scanning electron microscopy. The zeolite OFF presented elongated prism morphology and the zeolites GIS and ERI appeared as crystal intergrowths. The products and the expanded perlite were used in a Rhodamine B adsorption study . The zeolitic mixture turned out to be a better adsorber than the expanded perlite, obtaining an efficiency of 90% up to 2 min and an equilibrium efficiency of 72% after 5 min.

Orchestrating fluoride effect, secondary growth and microwave irradiation in the synthesis of EU-1/ZSM-48 intergrowth crystals for the conversion of dimethyl ether to olefins

A great decrease in the crystallization time of EU-1 zeolite to 10 h was achieved by coupling between the microwave-assisted hydrothermal synthesis and the addition of fluoride as crystallization promoter in the presence of 10% EU-1 seeds in alkaline media. Interesting characterization results were obtained by observing an octahedral coordination of Al incorporated with the fluoride presented in the synthesis in the form of AlO4F2. This finding was confirmed by analyzing the spectra of FTIR and 27Al MAS NMR which showed additional peak attributed to AlO4F2. The short crystallization time offered a significant decrease of EU-1 particle size to ∼500 nm as observed on FE-SEM. A pure phase of EU-1 was synthesized in the range of 25–100 Si/Al ratio. An intergrowth phase of EU-1 and ZSM-48 was observed on XRD when 200 Si/Al ratio gel was prepared. Excellent catalytic performance of DME conversion to olefins was achieved over the co-crystalline EU-1 and ZSM-48 sample. The sample showed exceptional stability for 360 min on stream compared with other samples and the highest olefins selectivity which reached to 78%.

Visual observation of gas hydrates nucleation and growth at a water – organic liquid interface

Visual observation of nucleation sites of methane and methane-ethane-propane hydrates and their further growth in water – organic liquid – gas systems with/without surfactants was carried out. Sapphire Rocking Cell RCS6 with transparent sapphire cells was used. The experiments were conducted at the supercooling ΔTsub = 20.2 °C. Decane, toluene and crude oils were used as organics. Gas hydrate nucleation occurred on water – metal – gas and water – sapphire – organic liquid three-phase contact lines. At the initial stage of growth hydrate crystals rapidly covered the water – gas or water – organics interfaces (depending on the nucleation site). Further hydrate phase accrete on cell walls (sapphire surface) and into the organics volume. At this stage, growth was accompanied by water «drawing out» from under initial hydrate film formed at water – organic interface. Apparently, it takes place due to water capillary inflow in the reaction zone. It was shown that the hydrate crystal morphology depends on the organic phase composition. In the case of water-in-decane emulsion relay hydrate crystallization was observed in the whole sample, originating most likely due to the hydrate crystal intergrowth through decane. Contacts of such crystals with adjacent water droplets result in rapid hydrate crystallization on this droplet.

Effect of fine-grained components on concrete properties and structure formation

The paper investigates the influence of fine-grained components on the synthesis of new formations and structure of cellular concrete. Grain size composition was defined with the aid of a laser diffraction analyzer of particles ANALYSETTE 22 NanoTecplus. The composition of the obtained hydrated phases was studied using electron microscopy and X-ray phase analysis. The introduction of silica and aluminosilicate components with the specific surface area >350 m2/kg enabled to directly influence the mechanism of the hydrated phases formation. Complex hydrated calcium aluminosilicates of the frame structure of zeolite type and non-permanent composition were identified in the hydration products. The formation of the total set of properties is attributed to the morphological features of the hydrated phases, the nature of connections between the crystalline hydrates, and their location in the material structure. X-ray phase analysis showed that ultra-micro-dispersed components have the stimulating impact on the processes of silicate formation. With the increase in the amount of hydrated new formations and decrease in the liquid phase volume the conditions for building of strong crystal intergrowth contacts were created.

Microwave assisted synthesis of MTT-TON intergrowth crystals for the catalytic conversion of naphtha to olefins

We present herein, the microwave assisted synthesis of SSZ-54, an intergrowth of MTT and TON frameworks using novel dual templates and the ability of the synthesized zeolites in the cracking of hexane to produce propylene was examined. SSZ-54 zeolite was successfully synthesized in a shorter time of 12 h via microwave heating as compared to 6–9 days by conventional oven. To tackle the inherent diffusion resistance in one-dimensional zeolite, we further reduced mass transfer limitation in the synthesized SSZ-54 zeolite by employing desilication and subsequent dealumination using a mixture of NaOH and TEAOH (for desilication) and nitric acid (for dealumination). N2 sorption of modified SSZ-54 samples presented improved mesopore volume, about 30% increment, with zero loss in micropore volume when compared to the parent sample. Furthermore, modified SSZ-54 zeolite showed enhanced catalytic activity and improved resistance to deactivation during hexane conversion. Parent and hierarchical zeolites displayed appreciable conversion for 10 h time on stream, with desilicated and dealuminated sample (DSA-50) showing the highest conversion of ca. 90% during the first 1 h and ca.60% selectivity to light olefins.

Synthesis of stable UiO-66 membranes for pervaporation separation of methanol/methyl tert-butyl ether mixtures by secondary growth

Stable UiO-66 membranes were successfully prepared on macroporous alumina tubes by secondary growth and were for the first time applied in the separation of methanol/methyl tert-butyl ether (MTBE) mixtures by pervaporation. Two key factors affecting the growth of the UiO-66 membranes were investigated. It has been found that acetic acid promotes the crystallization of UiO-66 crystals and water favors the intergrowth of UiO-66 crystals, leading to the formation of high-performance UiO-66 membranes. Under the optimized synthesis conditions, a continuous and dense UiO-66 membrane could be obtained, showing a separation factor of nearly 600 and a flux of 1.21kgm−2h−1 for 5wt% methanol/MTBE mixtures at 40°C. The effects of operation parameters on PV performance of the UiO-66 membranes were also studied in detail. The results reveal that increasing feed temperature or methanol in feed would enhance permeation flux but reduce separation factor, the permeability of components and membrane selectivity. It is worth mentioning that the UiO-66 membranes show excellent operating stability. This work demonstrates that the UiO-66 membranes have great potential for separation of methanol/MTBE mixtures via pervaporation.

Making of Nanopore NaA Zeolite Membranes for Saline Wastewater Treatment

Zeolite membranes have been studied extensively for more than fifteen years, mainly focusing on gas separation and liquid pervaporation processes. Recently, molecular dynamic simulation has shown that zeolite membranes are theoretically suitable for ion removal from aqueous solutions. This work proposes to use zeolite membranes for desalination of saline recycled wastewater for the possibility of avoiding the costly treatment needed for saline wastewater by Conventional approaches. NaA zeolite membrane indicates that it may be possible to simultaneously separate ions and dissolved organic compounds from water by pervaporation (PV) processes. NaA zeolite membranes composed of a continuous intergrowth of NaA zeolite crystals have been prepared hydro thermally on the surface of porous tubular supports. In this research, synthesis of zeolite NaA membrane was investigated. SEM and XRD analysis have been used to confirm zeolite NaA membrane formation. Membrane performance has been evaluated using an experimental pervaporation setup. Effects of operation condition (temperature, rate and pressure) on the membrane structure and performance have been investigated for NaA zeolite membranes grown onto seeded mullite supports.

Crystal chemistry of tourmalines from the Erongo Mountains, Namibia, studied by Raman spectroscopy

Black tourmalines (general formula XY 3 Z 6 T 6 O 18 (BO 3 ) 3 V 3 W) of various morphologies from miarolitic cavities in pegmatites of the Erongo granite are analysed by Raman spectroscopy and in part by electron microprobe, in order to identify the tourmaline species and to study the compositional zoning within a specimen. The samples studied are large euhedral single crystals, intergrowths of small crystals, longitudinally zoned specimens possessing a single-crystal main body and monopolar overgrowth, and a transversely zoned specimen consisting of small crystals covering the single-crystal main body. The results show that the most abundant tourmaline species are schorl deficient in W-site OH ( W OH) and Y Al-rich schorl that additionally contains minor amounts of Y Mg and/or Y Li. In addition, X Na-rich foitite with a composition close to the midpoint of the schorl–foitite join was found in the narrow border area separating the single-crystal part and the small-crystal aggregate in tourmaline with longitudinal zoning. Near-end-member foitite was only found as the last stage of crystallization on the top edge of small secondary-grown crystals in the tourmaline sample with transverse zoning. This study also demonstrates the potential of Raman spectroscopy as a non-destructive easy-to-handle method to track major chemical changes in tourmalines, which might potentially be used to document the evolution of the tourmaline host environment.

New Mineral Names*,†

This New Mineral Names has entries for 10 new minerals, including bulgakite, dyrnaesite-(La), eleonorite, gatewayite, joanneumite, mendeleevite-(Nd), morrisonite, nolzeite, packratite, vanarsite and a new data on nalivkinite. # Bulgakite* and New Data on Nalivkinite {#article-title-2} A.A. Agakhanov, L.A. Pautov, E. Sokolova, Y.A. Abdu and V.Y. Karpenko (2016) Two astrophyllite-supergroup minerals: bulgakite, a new mineral from the Darai-Pioz alkaline massif, Tajikistan and revision of the crystal structure and chemical formula of nalivkinite. Canadian Mineralogist, 54(1), 33–48. Bulgakite, (IMA 2014-041), ideally ![Formula][1] , is a new astrophyllite-supergroup mineral. It occurs in the moraine of the Darai-Pioz glacier (39°30′N 70°40′E) in the upper Darai-Pioz alkaline massif in the upper reaches of the Darai-Pioz river, in the area of the joint Turkestan, Zeravshan, and Alay Ranges, Tajikistan. The Darai-Pioz massif is a multiphase intrusion and occupies the core of a large synclinal fold of Carboniferous (Pennsylvanian series) slates. Rocks of the massif have been intruded by fine-grained dikes of biotite tourmaline granites and veins of calcite carbonatites and fenites. Bulgakite was found in a naturally tumbled amphibole–quartz–feldspar boulder of spotty texture, as individual crystals and intergrowths in small cavities (up to 0.5 cm) and as intergrowths (up to 1 cm) of platy crystals and aggregates of poorly crystallized grains. Associated minerals are alkali amphibole, quartz, microcline, bafertisite, aegirine, calcybeborosilite-(Y) , thorite, fluorite, and later crystallized brannockite and sogdianite. Bulgakite is brownish orange with a pale brown streak and a vitreous luster. Cleavage is perfect parallel to {001} and moderate parallel to {010}. The indentation hardness of bulgakite is VHN50 = … [1]: /embed/mml-math-1.gif

Strategy to design zeolite catalysts in the presence of biomass

LTA, GIS, *BEA and MFI zeolites have been successfully prepared using sugar cane bagasse as a hard templating agent as well as after alkaline hydrolysis of those biomass residues. Depending on the zeolite topology chosen, different effects could be highlighted: susceptibility to crystal intergrowths (LTA), formation of macroporous micron-sized assemblies (GIS), or significant impact on MFI crystal morphologies.The LTA zeolite series was used in ammonia ionic exchange experiments. A definite enhancement in the total NH4+-adsorption capacity could be evidenced for a biomass hydrolysate structured sample.In the case of MFI zeolites, different catalytic activities and stabilities were achieved in the methanol conversion into hydrocarbons. Likewise, drastic changes were observed in the selectivities, ranging from an expected methanol-to-olefins (MTO) behaviour for highly siliceous zeolites, to a close to 90% selectivity toward C5+ gasoline fraction (MTG) for counterparts with low Si/Al-ratios.

Gold and platinum group minerals in placers of the South Urals: Composition, microinclusions of ore minerals and primary sources

Gold and platinum group minerals from the gold placers of the South Urals are studied in order to identify the metal sources. In placers from the Main Uralian fault zone (MUF), the primary gold contains Ag (up to 29wt.%), Cu (up to 2wt.%) and Hg (up to 4wt.%) and its fineness ranges from 538 to 997‰. Tetra-auricupride and cupriferous gold (up to 20wt.% Cu) are common for the Nizhny Karabash placer of the MUF zone. In the eastern part of the South Urals, the placer gold is mainly characterized by high fineness of 900–1000‰ and low Cu contents (max 1.38wt.%). Most of the placer gold grains consist of the primary domains, which are rimmed by secondary high-fineness gold with diffuse and clear boundaries. The secondary gold also develops along the shear dislocations of primary gold. Gold contains microinclusions of geerite, balkanite, chalcopyrite, Se-bearing galena, sphalerite, pyrite, pyrrhotite, arsenopyrite and hematite.Twenty four (including five unnamed) platinum group minerals (PGMs) were found in 28 placers; those from the Kialim and Maly Iremel placers of the Miass placer zone were studied in details. In the Kialim placer, ruthenium is most abundant PGM, which hosts microinclusions of isoferroplatinum, ferroan platinum, laurite, cupriferous gold, a mineral similar in composition to tolovkite, heazlewoodite and unnamed RhSbS phase. The osmium contains microinclusions of erlichmanite and laurite. The iridium grains hosts various sulfides and arsenides of platinum group elements (PGEs). The inclusion-free PGMs form Ru compositional trend in contrast to Os–Ru trend of the Ir-depleted inclusion-hosted PGMs. The isoferroplatinum from the Maly Iremel placer hosts laurite, rhodarsenite, bowieite, a mineral similar in composition to miassite and unnamed sulfide of Pt (Pt1.11S2.00) and antimonide of Pd ((Pd2.41Rh0.43Fe0.17)3.01(Sb0.91Te0.09)1.00). Ruthenium is a host to isoferroplatinum, PGE sulfides and arsenides, and heazlewoodite. Osmium contains microinclusions of ferroan platinum; iridium is a host to a mineral similar in composition to hongshiite. Three types of PGM intergrowths were identified in the Maly Iremel samples: (1) the intergrowths of platy grains of ruthenium with isoferroplatinum and a mineral similar in composition to tulameenite; (2) the open-latticework intergrowths of platy crystals of ruthenium with interstitial aggregates made up of gold, isoferroplatinum and a mineral similar in composition to xingzhongite and (3) the intergrowths of osmium and irarsite and iridarsenite, which are developed along cleavage of the osmium grains. Nickel sulfides associated with some PGMs contain Ru (11.32wt.%) and Rh (2.21wt.%) in millerite and Ir (31.00wt.%), Ru (5.81wt.%) and Rh (2.87wt.%) in vaesite.The primary metal sources were determined on the basis of the mineral assemblages and composition of minerals, taking into account the nearby mineral deposits and directions of rivers. The rodingite-associated gold, gold-bearing massive sulfide and chromite deposits are major sources of gold and PGMs in placers of the Miass placer zone confined to the MUF structure of the South Urals. In the southern part of this structure, gold was mainly originated from orogenic gold–sulfide deposits associated with volcanic/volcaniclastic rocks and listvenite-associated gold deposits. The placer PGMs were derived from the adjacent ultramafic massifs of ophiolitic origin. The distance between the placers and primary deposits varies from 2 to 5km (up to 20km in the extended valley of the Miass River). Usage of ore microinclusions and associated PGMs in study of placer gold is far more advanced than an ordinary consideration of gold composition alone. This approach allowed us to identify the concrete sources for individual placers and to predict some mineralogical findings in already known primary occurrences.

POROUS STRUCTURE OF ROAD CONCRETE

Having a great number of concrete structure classifications it is recommended to specify the following three principal types: microstructure – cement stone structure; mesostructure – structure of cement-sand mortar in concrete; macrostucture – two-component system that consists of mortar and coarse aggregate. Every mentioned-above structure has its own specific features which are related to the conditions of their formation. Thus, microstructure of cement stone can be characterized by such structural components as crystal intergrowth, tobermorite gel, incompletely hydrated cement grains and porous space. The most important technological factors that influence on formation of cement stone microstructure are chemical and mineralogical cement composition, its grinding fineness, water-cement ratio and curing condition. Specific cement stone microstructure is formed due to interrelation of these factors. Cement stone is a capillary-porous body that consists of various solid phases represented predominantly by sub-microcrystals of colloidal dispersion. The sub-microcrystals are able adsorptively, osmotically and structurally to withhold (to bind) some amount of moisture. Protection of road concrete as a capillary-porous body is considered as one of the topical issues. The problem is solved with the help of primary and secondary protection methods. Methods of primary protection are used at the stage of designing, preparation and placing of concrete. Methods of secondary protection are applied at the operational stage of road concrete pavement. The paper considers structures of concrete solid phase and characteristics of its porous space. Causes of pore initiation, their shapes, dimensions and arrangement in the concrete are presented in the paper. The highest hazard for road concrete lies in penetration of aggressive liquid in it and moisture transfer in the cured concrete. Water permeability of concrete characterizes its filtration factor which depends on curing time and conditions and operational conditions as well.

Fabrication of b-oriented MFI Film via Langmuir-Blodgett Technique

A compact and highly b-oriented MFI-type zeolite monolayer was fabricated by assembling anisotropic zeolite micro-crystals extending over the centimeter scale by Langmuir–Blodgett (LB) method. The LB monolayer was subsequently employed as a seed layer for the secondary growth of highly b-oriented and defect-free MFI zeolite films. Firstly, LB technique was used to assemble a highly b-oriented MFI type zeolite monolayer on stainless steel substrates and platinum electrodes at an optimum target pressure of 20 mN/m constantly. Secondly, the precursor pretreatment method for preparing highly b-oriented MFI films was proved to be achievable. The crystal intergrowth and orientation of the MFI films were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The experimental results confirmed that the precursor pretreatment method was an effective route to suppress the undesired a-oriented twin growth during the secondary growth step. Finally, the highly b-oriented MFI-type zeolite film modified platinum electrodes were further tested as the working electrodes in an aqueous solution including [Fe(CN)6] with a diameter of 0.72 nm. Cyclic voltammetry experimental results demonstrated that the b-oriented MFI films fabricated by the Langmuir-Blodgett method were defect-free.