| 1. |
- Mintova, Svetlana, et al.
(författare)
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Continuous films of zeolite ZSM-5 on modified gold surfaces
- 1997
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Ingår i: Chemical Communications. - 1359-7345 .- 1364-548X. ; :1, s. 15-16
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Tidskriftsartikel (refereegranskat)abstract
- Thin continuous films of zeolite ZSM-5 on gold surfaces are prepared by a novel method including silanization, charge modification and seeding of the surface prior to the hydrothermal crystallization of the zeolite.
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| 2. |
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| 3. |
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| 4. |
- Mintova, Svetlana, et al.
(författare)
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Preparation of zeolite Y-vegetal fiber composite materials
- 1996
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Ingår i: Journal of porous materials. - 1380-2224 .- 1573-4854. ; 3:3, s. 143-150
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Tidskriftsartikel (refereegranskat)abstract
- Zeolite Y crystallization on chemi thermo mechanical pulp (CTMP) fluff, linen and cotton substrates using two different approaches for the deposition was studied. In the first approach a seed-film method was applied. This method involves surface charge modification of the substrates, adsorption of a monolayer of colloidal zeolite Y crystals onto the surfaces and subsequent growth of these colloidal zeolite crystals into a continuous zeolite film. Application of this method resulted in continuous films of zeolite Y on all substrates investigated. The second approach involved direct synthesis on substrates subjected to chemical or mechanical pretreatment in order to modify their surface properties. Chemical treatment was found to improve the crystallization on cotton and linen fibers but not so for the CTMP. Mechanical pretreatment enhanced the zeolite crystallization on the linen fibers but not on the other substrates. The zeolite Y-vegetal fiber composites were characterized by SEM, XRD, and thermal analysis.
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| 5. |
- Mintova, Svetlana, et al.
(författare)
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Preparation of ZSM-5 films from template free precursors
- 1997
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Ingår i: Journal of Materials Chemistry. - 0959-9428 .- 1364-5501. ; 7:12, s. 2341-2342
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Tidskriftsartikel (refereegranskat)abstract
- Thin films of zeolite ZSM-5 on quartz substrates have been prepared in the absence of organic templates by growth of adsorbed seed crystals attached to a polymer-modified substrate surface.
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| 6. |
- Mintova, Svetlana, et al.
(författare)
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ZSM-5 films prepared from template free precursors
- 1998
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Ingår i: Journal of Materials Chemistry. - 0959-9428 .- 1364-5501. ; 8:10, s. 2217-2221
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Tidskriftsartikel (refereegranskat)abstract
- Thin continuous films of zeolite ZSM-5 were synthesized on quartz substrates. The substrates were first surface modified and covered by a monolayer of colloidal silicalite-1 seed crystals. These crystals were grown into continuous films with thicknesses in the range 230-3500 nm by hydrothermal treatment in a synthesis gel free from organic templates. The preferential orientation of the crystals constituting the film was initially one with thec-axis close to parallel to the substrate surface. During the course of crystallization this orientation changed to one with most of the crystals having the c-axes directed approximately 35° from perpendicular to the substrate surface. A mechanism explaining this behavior is proposed. The final thickness of the film was controlled by the synthesis time but also by the addition of seed crystals to the synthesis gel. Films prepared according to this method may be of great value for the development of zeolite based membranes.
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| 7. |
- Su, Jie, et al.
(författare)
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Structure analysis of zeolites by rotation electron diffraction (RED)
- 2014
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Ingår i: Microporous and Mesoporous Materials. - : Elsevier BV. - 1387-1811 .- 1873-3093. ; 189, s. 115-125
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Tidskriftsartikel (refereegranskat)abstract
- Single crystal X-ray diffraction and powder X-ray diffraction (PXRD) are powerful methods for determination of unknown crystal structures including zeolites. However, these techniques have some limitations. For instance, single crystal X-ray diffraction requires large enough crystals which are often difficult to synthesize. For powder X-ray diffraction, peak indexing and intensity extraction become difficult if there exist peak broadening caused by small crystal sizes and peak overlap due to large unit cell and high symmetry. This becomes even more complicated for samples that contain more than one phase. We developed a new rotation electron diffraction (RED) method that can overcome these limitations. Almost complete three-dimensional electron diffraction datasets can be collected from micron- or nano-sized single crystals in a transmission electron microscope by combining electron beam tilt and goniometer tilt. Here, we demonstrate the power and limitations of the RED method for ab initio structure determination of four sub-micron sized zeolites, including a calcined silicalite-1, an EUO-type germanosilicate, an FER-type aluminogermanosilicate and an AST-type aluminogermanosilicate. The latter three zeolites were found in multiphasic samples. We show how the tilt range, tilt step and resolution affect the unit cell determination, structure solution and structure refinement. The EUO-, FER- and AST-type zeolites were found in two multiphasic samples in the Al-Ge-Si system, which were also characterized by PXRD and N-2 sorption.
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| 8. |
- Tosheva, Lubomira, et al.
(författare)
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Amorphous very high surface area silica macrostructures
- 2000
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Ingår i: Journal of Materials Chemistry. - : Royal Society of Chemistry (RSC). - 0959-9428 .- 1364-5501. ; 10:10, s. 2330-2337
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Tidskriftsartikel (refereegranskat)abstract
- A procedure for the preparation of amorphous silica spherical macroparticles using strongly basic anion exchange gel resins as shape directing macro-templates is presented. Resin beads were hydrothermally treated with either clear homogeneous TPA–silicate solutions containing tetraethoxysilane, tetrapropylammonium hydroxide and distilled water or with sodium silicate solutions. As a result of the ion exchange of silica species into the resin structure, resin–silicate composites were formed. After separation and drying of the resin–silicate composites, the resin was removed by combustion leaving solid spherical silica particles with surface areas exceeding 1000rm2rgm1. Two types of gel resins having different active groups and degrees of cross-linking were employed and the products obtained were characterised by SEM, Raman spectroscopy and nitrogen adsorption measurements. The type of the resin as well as the type of silicate solution used were of great importance for the pore structure of the final materials.
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| 9. |
- Tosheva, Lubomira, et al.
(författare)
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Silicalite-1 containing microspheres prepared using shape-directing macro-templates
- 2000
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Ingår i: Microporous and Mesoporous Materials. - 1387-1811 .- 1873-3093. ; 35-36, s. 621-629
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Tidskriftsartikel (refereegranskat)abstract
- Silicalite-1 microspheres were prepared by a novel method based on the use of anion exchange resins as shape-directing macro-templates. In a first step, spherical beads of the ion exchange resin were hydrothermally treated in a silicalite-1 synthesis solution. This resulted in the crystallization of silicalite-1 in the pores of the resin and the formation of a silicalite-1/resin composite material. The organic ion exchange resin was then removed by calcination leaving self-bonded spherical particles of silicalite-1. The influence of the type of ion exchange resin, the treatment time as well as the weight ratio between synthesis solution and resin on the properties of the resultant materials were investigated. The silicalite-1 containing microspheres were characterized by XRD, Raman spectroscopy, SEM, nitrogen adsorption and microhardness measurements.
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| 10. |
- Tosheva, Lubomira, et al.
(författare)
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Silicalite-1 macrostructures – preparation and structural features
- 2000
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Ingår i: Microporous and Mesoporous Materials. - 1387-1811 .- 1873-3093. ; 39:1-2, s. 91-101
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Tidskriftsartikel (refereegranskat)abstract
- Zeolite macrostructures in the form of silicalite-1 spheres were prepared using anion exchange resin beads as shape directing macrotemplates. The resin was removed after the synthesis by combustion leaving solid spherical particles identical in shape and size to the original resin beads. The formation of the silicalite-1 spheres was studied by Raman spectroscopy, X-ray diffraction, scanning electron microscopy and nitrogen adsorption measurements. Samples prepared for different times of treatment and at two different temperatures, 100°C and 165°C, were investigated. The spheres obtained for short treatment times consist of amorphous silica, which after longer hydrothermal treatment in the presence of TPA cations is partially or entirely transformed into an MFI structure. A single treatment at 100°C resulted in hard silicalite-1 spheres of low crystallinity, whereas fully crystalline spheres could be obtained by a treatment at the higher temperature. However, the spheres prepared at 165°C have inferior mechanical properties and can even loose their shape at certain conditions. A better control of both hardness and crystallinity was achieved by using a two-step synthesis procedure, where a treatment at 100°C was followed by a treatment at 165°C.
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| 11. |
- Tosheva, Lubomira, et al.
(författare)
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Zeolite beta spheres
- 2001
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Ingår i: Microporous and Mesoporous Materials. - 1387-1811 .- 1873-3093. ; 48:1-3, s. 31-37
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Tidskriftsartikel (refereegranskat)abstract
- Zeolite beta was crystallized from clear homogeneous solutions within the pores of anion exchange resin beads. The organic macrotemplate was then removed by combustion leaving stable macrospheres of zeolite beta. The zeolite beta crystallization within the resin beads was investigated by X-ray diffraction, Raman spectroscopy, SEM and nitrogen adsorption measurements. Crystallization within the macrotemplates was compared with the crystallization from bulk solution. The influence of the resin beads on the crystallization process was investigated by increasing the amount of ion exchanger present during synthesis and also by preparing bulk samples in the absence of macrotemplates.
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| 12. |
- Valtchev, Valentin, et al.
(författare)
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Preparation and characterization of hollow fibers of silicalite-1
- 1996
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Ingår i: Zeolites. - 0144-2449. ; 17:5-6, s. 408-415
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Tidskriftsartikel (refereegranskat)abstract
- Hollow fibers consisting solely of silicalite-1 were prepared by a novel method consisting of four basic steps. Carbon fibers were first surface modified to facilitate adsorption of colloidal seed crystals of silicalite-1. Such particles were then adsorbed as a monolayer on the fiber surface and induced to grow into a continuous film of intergrown crystals of silicalite-1. Finally, the carbon fiber used as a template was removed by calcination in air, yielding hollow fibers of silicalite-1. Hollow fibers were prepared in two experimental series employing different synthesis conditions resulting in two different modes of growth. The first experimental series was performed with a clear homogeneous TPAOH/silica solution crystallizing at 100°C, and the second series with a NaOH-TPABr/silica gel crystallizing at 150°C. Materials produced in the first series showed a smooth and homogeneous surface and a relatively uniform fiber wall with a final thickness of 1.1 μm. In these materials the film was formed by crystals growing outward from the surface of the carbon fiber. Materials produced in the second series were less uniform with a final thickness of the fiber wall of about 3.2 μm. The crystal growth in these materials appeared to take place both in an inward and outward direction starting from the seed crystals adsorbed on the carbon fiber. The hollow fibers prepared were characterized by SEM, XRD, FT i.r., and nitrogen adsorption measurements.
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| 13. |
- Zheng, Haoquan, et al.
(författare)
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Nanosized inorganic porous materials : fabrication, modification and application
- 2016
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7488 .- 2050-7496. ; 4:43, s. 16756-16770
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Forskningsöversikt (refereegranskat)abstract
- Owing to their nature nanosized inorganic porous materials exhibit novel properties, different from those of bulk solids. This review highlights recent developments in the synthesis and unconventional applications of nanosized inorganic porous materials including zeolites, microporous carbons and mesoporous materials. The factors controlling the formation of nanosized inorganic porous materials are reviewed. The preparation, functionalisation, and advanced applications of nanosized inorganic porous materials in free and fixed forms are summarized. A comprehensive analysis of the emerging applications of microporous nanosized inorganic porous materials in the fields of catalysts, biomedical applications and energy-related applications is presented. Finally, the future needs and perspectives of nanosized inorganic porous solids are addressed.
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