Structural evolution during nucleation of Si-rich LTA nanocrystals from colloidal solution

Singh, Puyam S.; Aswal, Vinod K.; Chaudhri, Sanjay G.; Schwieger, Wilhelm

doi:10.1016/j.micromeso.2017.10.006

Cited by 11 publications

(8 citation statements)

References 14 publications

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“…In figure 2A synthesized zeolite seed and crystal layer were 1.57 and 1.19, respectively. These values were according with the reported range of LTA-zeolite compositions [1,2]. These results indicate that after calcination, the Si/Al ratio of zeolite crystals is lower than zeolite seeds, because the aluminum concentration increases at zeolite film, due to the possible aluminum migration from the boehmite layer to the zeolite film during calcination [16].…”

Section: Synthesis Of Lta-zeolite Seedssupporting

confidence: 86%

“…For example, LTA zeolite, synthesized by using template (tetramethylammonium), has a Si/Al ratio about 2. In contrast, template-free synthesis leads to Si/Al =1 [1,2]. As a result of the increase of Si/Al ratio, thermal and chemical stability of the product will be remarkably improved.…”

Section: Synthesis Of Lta-zeolite Seedsmentioning

confidence: 99%

“…When a zeolite framework contains an equal number of aluminum and silicon atoms, molar ratio equals 1, each oxygen atom is linked to one aluminum and one silicon atom; therefore, the cavities contain the maximum density of exchangeable cations resulting in a high adsorption capacity [1,2]. At some places of the framework, Silicon (Si 4+ ) by aluminum (Al 3+ ) replacement provides a charge unbalance.…”

Section: Introductionmentioning

confidence: 99%

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

Rodríguez-Castro

Urbiztondo-Castro

Pina-Iritia

2020

Rev.Fac.Ing.Univ.Antioquia

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La incorporación de materiales nanoestructurados como la zeolita tipo LTA en las obleas de silicio, abre una puerta muy interesante para el uso de estos materiales dentro de las tecnologías de microfabricación basadas en silicio. En este trabajo, se estudió la deposición y el entrecruzamiento de la capa de zeolita tipo LTA libre de defectos en obleas de silicio de 3 pulgadas con una capa de SiO2 sometida a pretratamiento. La principal desventaja asociada con la síntesis de la capa de zeolita es la formación de grietas y la obtención de una capa uniforme. Al modificar los soportes con boehmita, se observó una mejora sustancial en términos de continuidad de capa y crecimiento de cristales en comparación con los recubrimientos preparados en polímero catiónico, poli (cloruro de dialildimetilamonio). Se sintetizó una capa de zeolita de tipo LTA entre un rango de 350 y 1300 nm mediante un método hidrotermal ex situ, a 363 K durante 12 h. Se usó hidróxido de tetrametilamonio (TMAOH) como molde y se usaron isopropóxido de aluminio y sílice coloidal como fuentes de Al y Si, respectivamente.

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Section: Synthesis Of Lta-zeolite Seedssupporting

confidence: 86%

Section: Synthesis Of Lta-zeolite Seedsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

Rodríguez-Castro

Urbiztondo-Castro

Pina-Iritia

2020

Rev.Fac.Ing.Univ.Antioquia

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“…1B) constructed from the interconnection of sod and d4R composite building units (CBUs). Zeolite A prepared in the absence of organics is enriched in aluminum (Si/Al = 1) (44) with few exceptions (9,(45)(46)(47)(48). The silicon content can be increased using tetramethylammonium (TMA + ) as an organic SDA (48-50), In the upper scheme, the length of the smallest step is less than L crit and is not moving.…”

Section: Significancementioning

confidence: 99%

In situ imaging of two-dimensional surface growth reveals the prevalence and role of defects in zeolite crystallization

Choudhary

Jain

Rimer

2020

Proc. Natl. Acad. Sci. U.S.A.

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Zeolite crystallization predominantly occurs by nonclassical pathways involving the attachment of complex (alumino)silicate precursors to crystal surfaces, yet recurrent images of fully crystalline materials with layered surfaces are evidence of classical growth by molecule attachment. Here we use in situ atomic force microscopy to monitor three distinct mechanisms of two-dimensional (2D) growth of zeolite A where we show that layer nucleation from surface defects is the most common pathway. Direct observation of defects was made possible by the identification of conditions promoting layered growth, which correlates to the use of sodium as an inorganic structure-directing agent, whereas its replacement with an organic results in a nonclassical mode of growth that obscures 2D layers and markedly slows the rate of crystallization. In situ measurements of layered growth reveal that undissolved silica nanoparticles in the synthesis medium can incorporate into advancing steps on crystal surfaces to generate defects (i.e., amorphous silica occlusions) that largely go undetected in literature. Nanoparticle occlusion in natural and synthetic crystals is a topic of wide-ranging interest owing to its relevance in fields spanning from biomineralization to the rational design of functional nanocomposites. In this study, we provide unprecedented insight into zeolite surface growth by molecule addition through time-resolved microscopy that directly captures the occlusion of silica nanoparticles and highlights the prevalent role of defects in zeolite crystallization.

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“…Zeolite Linde Type A (Zeolite LTA or Zeolite A) [Na 12 [(AlO 2 ) 12 (SiO 2 ) 12 ] • 27 H 2 O [1] can be synthesised using a variety of sources including different types of alumina and silica materials [2][3][4][5][6][7][8][9][10][11][12][13]. Many nucleation and crystal-growth mechanisms have been proposed for this type of zeolite [14][15][16][17][18], and many literature data have documented microcrystals zeolite A growth on various substrates to form highly oriented monolayers or multilayers composed of micro crystalline building blocks [19][20][21].…”

Section: Introductionmentioning

confidence: 99%

Effect of H2O Activity on Zeolite Formation

Belviso

Cavalcante

2020

Materials

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In an effort to understand the effects of H2O activity on zeolite formation, we have synthesized LTA zeolite using a combination of freezing processes and varying drying temperatures. Sodium aluminate and sodium silicate were used to form LTA zeolite, according to the IZA (International Zeolite Association) protocol. The synthesis steps were modified by adding the precursor frozen process by a rapid liquid nitrogen (−196 °C) treatment or slow conventional freezer treatment (−20 °C). The samples were subsequently sonicated and then dried at 80 °C or 40 °C. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were performed on the samples immediately after the drying process as well as after 2 weeks and 1 month of aging the solid products. The results indicated that LTA zeolite does not form. The silica-alumina precursor after both freezing processes and after being dried at 80 °C showed the presence of sodalite displaying stable behavior over time. Both sets of samples dried at 40 °C and did not show the presence of zeolite immediately after the drying process. However, after 2 weeks, the liquid nitrogen–frozen precursor was characterized by the presence of EMT whereas zeolites never formed in the −20 °C samples. These results suggest that freezing processes differently control the H2O activity during the drying and aging processes in the solid state. Thus, although the precursor chemical composition is the same, the type of zeolite formed is different.

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Structural evolution during nucleation of Si-rich LTA nanocrystals from colloidal solution

Cited by 11 publications

References 14 publications

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

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

In situ imaging of two-dimensional surface growth reveals the prevalence and role of defects in zeolite crystallization

Effect of H2O Activity on Zeolite Formation

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