scholarly journals Time-resolved dissolution elucidates the mechanism of zeolite MFI crystallization

2021 ◽  
Vol 7 (25) ◽  
pp. eabg0454
Author(s):  
Krassimir N. Bozhilov ◽  
Thuy Thanh Le ◽  
Zhengxing Qin ◽  
Tanguy Terlier ◽  
Ana Palčić ◽  
...  
Keyword(s):  
Crystal Growth ◽  
Ammonium Fluoride ◽  
Ex Situ ◽  
Zeolite Crystal ◽  
Time Resolved ◽  
Crystal Dissolution ◽  
Detailed Structural Analysis ◽  
Zeolite Formation ◽  
Type Zeolite ◽  
Growth Features

Zeolite crystal growth mechanisms are not fully elucidated owing to their complexity wherein the formation of a particular zeolite can occur by more than one crystallization pathway. Here, we have conducted time-resolved dissolution experiments of MFI-type zeolite crystals in ammonium fluoride medium where detailed structural analysis allowed us to extrapolate and elucidate the possible mechanism of nucleation and crystal growth. A combination of electron and scanning probe microscopy shows that dissolution initiates preferentially at lattice defects and progressively removes defect zones to reveal a mosaic structure of crystalline domains within each zeolite crystal. This mosaic architecture evolves during the growth process, reflecting the changing conditions of zeolite formation that can be retroactively assessed during zeolite crystal dissolution. Moreover, a more general implication of this study is the establishment that dissolution can be used successfully as an ex situ technique to uncover details about crystal growth features inaccessible by other methods.

Nucleation and Crystal Growth Features of EMT-Type Zeolite Synthesized from an Organic-Template-Free System

2012 ◽  
Vol 24 (24) ◽  
pp. 4758-4765 ◽  
Author(s):  
Eng-Poh Ng ◽  
Jean-Michel Goupil ◽  
Aurélie Vicente ◽  
Christian Fernandez ◽  
Richard Retoux ◽  
...  
Keyword(s):  
Crystal Growth ◽  
Organic Template ◽  
Free System ◽  
Type Zeolite ◽  
Template Free ◽  
Growth Features

Sector growth and symmetry of (F,OH) apatite from the Asio mine, Japan

1994 ◽  
Vol 58 (391) ◽  
pp. 307-314 ◽  
Author(s):  
Mizuhiko Akizuki ◽  
Hirotugu Nisidoh ◽  
Yasuhiro Kudoh ◽  
Tomohiro Watanabe ◽  
Kazuo Kurata
Keyword(s):  
Optical Properties ◽  
Crystal Growth ◽  
Electron Diffraction ◽  
Chemical Analysis ◽  
Growth Surface ◽  
Complete Disappearance ◽  
X Ray ◽  
Solid Crystal ◽  
Wet Chemical ◽  
Growth Features

AbstractA study of apatite crystals from the Asio mine, Japan, showed sectoral texture related to the growth of the crystal, and with optically biaxial properties within the sectors. Wet chemical analysis gave a composition Ca5(PO4)3(F0.64,OH0.38,Cl0.01)1.03 for the specimen.Additional diffraction spots were not observed in precession and oscillation X-ray photographs and electron diffraction photographs. Since the internal textures correlate with the surface growth features, it is suggested that the internal textures and the unusual optical properties were produced during nonequilibrium crystal growth. The fluorine/hydroxyl sites in hexagonal apatite are symmetrically equivalent in the solid crystal but, at a growth surface, this equivalence may be lost, resulting in a reduction of crystal symmetry. Heating of the apatite to about 850°C results in the almost complete disappearance of the optical anomalies due to disordering, which may be related to the loss of hydroxyl from the crystal.

scholarly journals Temperature dependence of molybdenum dialkyl dithiocarbamate (MoDTC) tribofilms via time-resolved Raman spectroscopy

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Carlos E. Garcia ◽  
Mao Ueda ◽  
Hugh Spikes ◽  
Janet S. S. Wong
Keyword(s):  
Raman Spectroscopy ◽  
Shear Stress ◽  
Formation Process ◽  
Friction Reduction ◽  
Chemical Mechanism ◽  
Ex Situ ◽  
Oil Degradation ◽  
Molybdenum Disulphide ◽  
Friction Modifier ◽  
Time Resolved

AbstractMolybdenum dialkyl dithiocarbamate (MoDTC) is a friction reducing additive commonly used in lubricants. MoDTC works by forming a low-friction molybdenum disulphide (MoS2) film (tribofilm) on rubbed surfaces. MoDTC-induced MoS2 tribofilms have been studied extensively ex-situ; however, there is no consensus on the chemical mechanism of its formation process. By combining Raman spectroscopy with a tribometer, effects of temperature and shear stress on MoS2 tribofilm formation in steel-steel contacts were examined. Time-resolved Raman spectra of the tribofilm were acquired, together with the instantaneous friction coefficient. The tribofilm is constantly being formed and removed mechanically during rubbing. Increasing shear stress promotes MoS2 formation. The nature of the tribofilm is temperature-dependent, with high-temperature tribofilms giving a higher friction than lower temperature films. Below a critical temperature Tc, a small amount of MoS2 gives significant friction reduction. Above Tc, a patchy film with more MoS2, together with a substantial amount of amorphous carbon attributed to base oil degradation, forms. The composition of this tribofilm evolves during rubbing and a temporal correlation is found between carbon signal intensity and friction. Our results highlight the mechanochemical nature of tribofilm formation process and the role of oil degradation in the effectiveness of friction modifier MoDTC.

MFI-type zeolite nanosheets for gas-phase aromatics chlorination: a strategy to overcome mass transfer limitations

RSC Advances ◽  
2014 ◽  
Vol 4 (52) ◽  
pp. 27242-27249 ◽  
Author(s):  
Marilyne Boltz ◽  
Pit Losch ◽  
Benoit Louis ◽  
Guillaume Rioland ◽  
Lydie Tzanis ◽  
...  
Keyword(s):  
Mass Transfer ◽  
Catalytic Activity ◽  
Gas Phase ◽  
Zeolite Crystal ◽  
Silanol Groups ◽  
Type Zeolite

Mass transfer limitations and catalytic activity were studied for various ZSM-5 zeolite crystal sizes in the chlorination of deactivated arenes. An estimation of the quantity of mild acidic external silanol groups of zeolite nanosheets was made.

scholarly journals Zeolite Crystal Growth Analysis by Dissolution

2019 ◽  
Vol 25 (S2) ◽  
pp. 816-817
Author(s):  
Krassimir N. Bozhilov ◽  
Valentin Valtchev
Keyword(s):  
Crystal Growth ◽  
Growth Analysis ◽  
Zeolite Crystal

Kinetics of Crystal Nucleation and Growth in Thin Films of Amorphous Te Alloys measured by Atomic Force Microscopy

2003 ◽  
Vol 803 ◽  
Author(s):  
J. Kalb ◽  
F. Spaepen ◽  
M. Wuttig
Keyword(s):  
Thin Films ◽  
Atomic Force Microscopy ◽  
Crystal Growth ◽  
Data Storage ◽  
Optical Data Storage ◽  
Crystal Nucleation ◽  
Ex Situ ◽  
Optical Data ◽  
Force Microscopy ◽  
Atomic Force

ABSTRACTBoth the crystal nucleation rate and the crystal growth velocity of sputtered amorphous Ag0.055In0.065Sb0.59Te0.29 and Ge4Sb1Te5 thin films used for optical data storage were determined as a function of temperature. Crystals were directly observed using ex-situ atomic force microscopy, and their change in size after each anneal was measured. Between 140°C and 185°C, these materials exhibited similar crystal growth characteristics, but differed in their crystal nucleation characteristics. These observations provide an explanation for the different re-crystallization mechanisms observed upon laser-induced crystallization of amorphous marks.

Laser-Induced Crystal Growth Measurements By Time-Resolved Optical Reflectivity

1981 ◽  
Author(s):  
G. L. Olson ◽  
S. A. Kokorowski ◽  
J. A. Roth ◽  
R. S. Turley ◽  
L. D. Hess
Keyword(s):  
Crystal Growth ◽  
Time Resolved ◽  
Optical Reflectivity

X-Ray Absorption Spectroscopy as an in-situ Tool in Materials Science

1997 ◽  
Vol 502 ◽  
Author(s):  
T. Ressler ◽  
Joe Wong ◽  
W. Metz
Keyword(s):  
Absorption Spectroscopy ◽  
Materials Science ◽  
Ex Situ ◽  
Structural Studies ◽  
Time Resolved ◽  
X Ray ◽  
Complementary Techniques ◽  
X Ray Absorption ◽  
Established Technique

ABSTRACTIn addition to being an established technique for ex-situ structural studies, x-ray absorption spectroscopy (XAS) has recently been realized to be a powerful tool for in-situ time-resolved investigations in materials science. This paper describes two complementary techniques: quick-scanning EXAFS (QEXAFS) and energy-dispersive XAS (DXAS) which offer time resolution in the seconds and milliseconds range, respectively. Formation of a heterogeneous catalyst from a solid-state reaction of a precursor is presented as an example of a time-resolved XAS application.

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