Study of the Thermal Nitridation of Nanocrystalline Ti(OH)₄ by X-ray and in Situ Neutron Powder Diffraction

Abstract

In situ neutron diffraction measurements of nanocrystalline titanium oxynitrides were performed, as a function of temperature and time, to explore the nitrogen/oxygen substitution mechanism occurring during their synthesis by reaction of gaseous ammonia with nanocrystalline Ti(OH)(4). These neutron diffraction experiments are supported by chemical analysis and X-ray diffraction, allowing the description of the structural variations and ordering process between the Ti(O/N)(2) anatase and the Ti(O/N) rock-salt phases. Our results show that the formation of the Ti(O/N) rock-salt phase goes along with the creation of vacancies on the Ti sites and that the N/O substitution proceeds but without N/O ordering.

Formation and Decomposition of Metastable α′′‐Fe16N2 from in situ Powder Neutron Diffraction and Thermal Analysis

“…[26] In this in situ neutron diffraction experiment we used a high temperature resistive furnace (HTF) due to its expected larger temperature homogeneity over the sample. A configuration similar to those previously described was chosen, [88][89][90][91] but the gas supply was modified to requirements of using preheated gas. The measurement cell consists of a silica glass tube (480 mm length, 12 mm outer diameter, 1 mm wall thickness) closed at the bottom and connected to the gas supply head part of D20.…”

“…Further description can be found in references. [25,[88][89][90][91] Temperature control is realized with a thermocouple type K [92] inserted into the reaction tube and positioned off-beam close above the sample. The reactions were performed in a well defined gas flow of argon controlled with a mass flow controller (MF1, MKS Instruments Germany).…”

Durability of Composite Materials under Severe Temperature Conditions: Influence of Moisture Content and Prediction of Thermo-Mechanical Properties During a Fire

“…With the heat Equation (1) mentioned above, we explain the thermal behavior through thickness of laminated composite materials exposed to a constant unidirectional heat flux. The first term of the right member of Equation (1) represents the induced effect on temperature T(x, t) by heat conduction through the thickness of the solid material k x (x, t) and the gases k g (x, t), as well as that due to the influence of the transverse thermal conductivity transformation by increasing the temperature. The second term corresponds to the convection of the volatile species: The internal convection of the thermal energy due to the transport of decomposition gases .…”

“…The properties of that material are often drastically modified and new properties can then be studied. These properties could change when a material is subjected to severe environmental conditions of low or high temperatures [1,2], often coupled to a second stress such as an intense magnetic field, a light irradiation [3,4], a mechanical stress [5,6], or a high pressure [7,8]. Under these extreme conditions, the studied material undergoes important physical and/or chemical modifications, often leading to the appearance of phase transitions [9,10] or metastable states.…”

Chemical Reactions followed by in situ Neutron Powder Diffraction

“…[119] These experiments, supported by chemical analysis and XRD, allowed the description of the structural variations and ordering process between the Ti(O/N) 2 In the following, in situ NPD has been performed on the nanocrystalline deuterated oxyhydroxide TiO(OD) 2 similarly under gaseous ammonia, to study the hydrogen-deuterium exchange mechanism. Data were collected at D20 and the analysis of the kinetics was directly based on the contrast variation of the incoherent neutron cross section of hydrogen and deuterium.…”