Search results for "hydrothermal synthesis"
showing 10 items of 62 documents
Selective oxidation of ethane: Developing an orthorhombic phase in Mo–V–X (X=Nb, Sb, Te) mixed oxides
2009
Abstract Mo–V–X (X = Nb, Sb and/or Te) mixed oxides have been prepared by hydrothermal synthesis and heat-treated in N2 at 450 °C or 600 °C for 2 h. The calcination temperature and the presence or absence of Nb determines the nature of crystalline phases in the catalyst. Nb-containing catalysts heat-treated at 450 °C are mostly amorphous solids, while Nb-free catalysts heat-treated at 450 °C and samples treated at 600 °C clearly contain crystalline phases. TPR-H2 experiments show higher H2-consumption on catalysts with amorphous phases. Catalytic results in the oxidative dehydrogenation of ethane indicate that the selective production of the olefin is strongly related to the development of …
Characterization of MCM-48 Materials
2000
Mesoporous molecular sieves of MCM-48 type were prepared by conventional hydrothermal and novel room temperature syntheses. Scanning electron microscopy (SEM) studies have shown that nonagglomerate...
Synthesis and crystal structure of α-NH4(VO2)(HPO4)
1992
Abstract Hydrothermal synthesis starting from β-NH 4 (VO 2 )(HPO 4 ) leads to α-NH 4 (VO 2 )(HPO 4 ): orthorhombic, space group Pb 2 1 a ; Z = 4; a = 6.830(1) A, b = 9.233(2) A, c = 8.817(2) A; R = 0.037 for 3371 reflections. NH + 4 cations connect isolated chains of trans -corner sharing VO 5 square pyramids running along the a -axis. The a -phase transforms irreversibly into the β-form by heating near 200°C. Comparison is made between the two phases.
Synthèses optimisées et caractérisations avancées de nanotubes de titanate et de leurs fonctionnalisations : vers l'élaboration de nanovecteurs de mo…
2017
The aim of this PhD thesis is to develop new nanohybrids based on titanate nanotubes (TiONts) in order to use them as nanocarrier of a therapeutic molecule: a stilbene phenol, 4'-hydroxy-4-(3-aminopropoxy)-trans-stilbene (HAPtS), which is a transresveratrol derivative.TiONts are synthesized by a hydrothermal treatment from a precursor of rutile titanium dioxide. Two methods of hydrothermal synthesis have been studied (the static and dynamic ones): the second approach uses an original hydrothermal device which provides a vigorous mechanical stirring during the hydrothermal process with controllable stirring time par hour. A parametric study was carried out to evaluate the effect of reaction …
Protonic ceramic fuel cell : elaboration and characterization. Investigation of the BaZr0.8Y0.2O3-d electrolyte by electrochemical impedance spectros…
2021
One of the current global challenges is to find novel, clean and efficient techniques for the energy production. The use of electrochemical cells and hydrogen is one of the solutions. These cells convert the excess energy produced by conventional systems into hydrogen by steam electrolysis. The hydrogen can be stored and transformed into electricity when needed in the fuel cell mode. Among the different electrochemical cells, protonic ceramic electrochemical cells have attracted much attention due to their high efficiency at intermediate temperature (400 – 600 °C). In addition, these systems offer the advantage of not diluting the fuel in electrolysis mode. This thesis work focuses on the e…
Influence of the pH on the ZnO nanoparticle growth in supercritical water: Experimental and simulation approaches
2014
Abstract In order to improve the knowledge on the nucleation and the growth mechanisms of metal oxides nanoparticles produced in supercritical water domain, ZnO was used as a “model” material. A continuous process of hydrothermal synthesis was employed to synthesize ZnO nanopowders ( T = 410 °C and P = 305 bar) from Zn(NO 3 ) 2 and KOH solutions with different values of [KOH]/[Zn(II)] ratio from 0 to 8 in order to investigate the pH effect on the growth of ZnO nanocrystallite in terms of size and morphology. The samples were characterized by X-Ray Diffraction and Transmission Electronic Microscopy. ZnO crystal was considered as a cylindrical crystallite with a diameter D and height H . Es…
Continuous hydrothermal synthesis of inorganic nanopowders in supercritical water: towards a better control of the process
2009
International audience; A hydrothermal synthesis process working in supercritical conditions (T > 374 °C, P > 22 MPa) and in a continuous mode has been developed for inorganic nanopowder synthesis. This paper presents a review of the past 5 years of research conducted on this process. Numerous materials (oxides: ZrO2, TiO2, Fe2O3..., ferrites: Fe2CoO4..., or BaZrO3) were obtained with specific features. Some technical issues have been solved, that are presented here. Heat transfer was studied, leading to a more efficient design of the reactor. Future developments have been examined through process engineering, in which our group is engaged, especially through CFD modelling.
Direct Synthesis of Aluminosilicate IWR Zeolite from a Strong Interaction between Zeolite Framework and Organic Template.
2019
A large amount of zeolite structures are still not synthetically available or not available in the form of aluminosilicate currently. Despite significant progress in the development of predictive concepts for zeolite synthesis, accessing some of these new materials is still challenging. One example is the IWR structure as well. Despite successful synthesis of Ge-based IWR zeolites, direct synthesis of aluminosilicate IWR zeolite is still not successful. In this report we show how a suitable organic structure directing agent (OSDA), through modeling of an OSDA/zeolite cage interaction, could access directly the aluminum-containing IWR structure (denoted as COE-6), which might allow access to…
A systematic study of the optical properties of mononuclear hybrid organo-inorganic lanthanoid complexes
2020
A series of hybrid organo-inorganic mononuclear lanthanoid complexes, [n-NBu4]3[LnH(PW11O39)(phen)2]·H2O, denoted as LM4-1-Ln (Ln = DyIII, TbIII, EuIII, NdIII, ErIII, HoIII and GdIII), were synthesized via hydrothermal synthesis and were structurally characterized by X-ray diffraction. The optical properties of all complexes have been investigated in the solid state. The temperature-dependent emission spectra of LM4-1-Dy, LM4-1-Tb and LM4-1-Eu complexes show intense lanthanoid emissions in the visible region, while LM4-1-Nd shows near-infrared (NIR) luminescence. The EuIII complex shows typical strong red emissions from the 5D0 → 7F0,1,2,3,4 transitions, with the CIE colour coordinates (0.6…