| 1. |
- Hedlund, Jonas, et al.
(författare)
-
Controlling the preferred orientation in silicalite-1 films synthesized by seeding
- 1999
-
Ingår i: Microporous and Mesoporous Materials. - 1387-1811 .- 1873-3093. ; 28:1, s. 185-194
-
Tidskriftsartikel (refereegranskat)abstract
- Single crystal silicon (100) wafers were seeded with colloidal silicalite-1 crystals and hydrothermally treated in a precursor solution to grow thin silicalite-1 films. A total of 28 experiments in eight series were investigated with SEM and XRD to evaluate the preferred orientation of the crystals constituting the films. The investigated parameters in the film formation process were seed crystal size, amount of adsorbed seed crystals and film thickness after hydrothermal treatment of the seeded substrates. In thin films, most of the crystalline material is oriented with the b-axis perpendicular to the substrate surface. In thick films, most of the crystalline material is oriented with the a-axis perpendicular to the substrate surface. The change in preferred orientation with film thickness is faster when small seeds are used. The amount of adsorbed seeds has a larger influence on the preferred orientation when large seeds are used. A mechanism explaining these trends is proposed. The choice of size and coverage of seeds can be used to control the preferred orientation of the crystals in a film of given thickness within certain limitations.
|
|
| 2. |
|
|
| 3. |
- Mintova, Svetlana, et al.
(författare)
-
Continuous films of zeolite ZSM-5 on modified gold surfaces
- 1997
-
Ingår i: Chemical Communications. - 1359-7345 .- 1364-548X. ; :1, s. 15-16
-
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.
|
|
| 4. |
|
|
| 5. |
|
|
| 6. |
- Mintova, Svetlana, et al.
(författare)
-
Preparation of zeolite Y-vegetal fiber composite materials
- 1996
-
Ingår i: Journal of porous materials. - 1380-2224 .- 1573-4854. ; 3:3, s. 143-150
-
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.
|
|
| 7. |
- Mintova, Svetlana, et al.
(författare)
-
Preparation of ZSM-5 films from template free precursors
- 1997
-
Ingår i: Journal of Materials Chemistry. - 0959-9428 .- 1364-5501. ; 7:12, s. 2341-2342
-
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.
|
|
| 8. |
- Mintova, Svetlana, et al.
(författare)
-
ZSM-5 films prepared from template free precursors
- 1998
-
Ingår i: Journal of Materials Chemistry. - 0959-9428 .- 1364-5501. ; 8:10, s. 2217-2221
-
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.
|
|
| 9. |
- Valtchev, Valentin, et al.
(författare)
-
Preparation and characterization of hollow fibers of silicalite-1
- 1996
-
Ingår i: Zeolites. - 0144-2449. ; 17:5-6, s. 408-415
-
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.
|
|
