Metal ion induced room temperature phase transformation and stimulated infrared spectroscopy on TiO2-based surfaces

2008 ◽  
Vol 255 (3) ◽  
pp. 718-721 ◽  
Author(s):  
James L. Gole ◽  
S.M. Prokes ◽  
Mark G. White
Keyword(s):  
Phase Transformation ◽  
Infrared Spectroscopy ◽  
Metal Ion ◽  
Room Temperature ◽  
Temperature Phase

scholarly journals Structure and Properties of Ln2MoO6 Oxymolybdates (Ln = La, Pr, Nd) Doped with Magnesium

Crystals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 611
Author(s):  
Ekaterina Orlova ◽  
Elena Kharitonova ◽  
Timofei Sorokin ◽  
Alexander Antipin ◽  
Nataliya Novikova ◽  
...  
Keyword(s):  
Rare Earth ◽  
Infrared Spectroscopy ◽  
Room Temperature ◽  
High Temperature Phase ◽  
Temperature Phase ◽  
Spectroscopy Data ◽  
Structure And Properties ◽  
Hygroscopic Properties ◽  
Thermogravimetric Studies ◽  
Mg Doped

The literature data and the results obtained by the authors on the study of the structure and properties of a series of polycrystalline and single-crystal samples of pure and Mg-doped oxymolybdates Ln2MoO6 (Ln = La, Pr, Nd) are analyzed. Presumably, the high-temperature phase I41/acd of Nd2MoO6 single crystals is retained at room temperature. The reason for the loss of the center of symmetry in the structures of La2MoO6 and Pr2MoO6 and the transition to the space group I4¯c2 is the displacement of oxygen atoms along the twofold diagonal axes. In all structures, Mg cations are localized near the positions of the Mo atoms, and the splitting of the positions of the atoms of rare-earth elements is found. Thermogravimetric studies, as well as infrared spectroscopy data for hydrated samples of Ln2MoO6 (Ln = La, Pr, Nd), pure and with an impurity of Mg, confirm their hygroscopic properties.

Structural phase transformation and microwave dielectric studies of SmNb1−x(Si1/2Mo1/2)xO4 compounds with fergusonite structure

2015 ◽  
Vol 17 (19) ◽  
pp. 12623-12633 ◽  
Author(s):  
S. D. Ramarao ◽  
V. R. K. Murthy
Keyword(s):  
Phase Transition ◽  
Phase Transformation ◽  
Room Temperature ◽  
Structural Phase ◽  
High Temperature Phase ◽  
Temperature Phase ◽  
Dielectric Studies ◽  
Scheelite Structure ◽  
Structural Phase Transformation ◽  
Microwave Dielectric

Temperature variation powder XRD measurements reveal that SmNbO4 undergoes a phase transition around 800 °C. SmNbO4 possesses a monoclinic fergusonite structure at ambient temperature and a tetragonal scheelite structure above the transition temperature. We report the stabilization of this high temperature phase at room temperature.

Phase transformation in nanocrystalline Sm2Co17permanent magnet material

2009 ◽  
Vol 42 (4) ◽  
pp. 691-696 ◽  
Author(s):  
Xiaoyan Song ◽  
Nianduan Lu ◽  
Wenwu Xu ◽  
Zhexu Zhang ◽  
Jiuxing Zhang
Keyword(s):  
Crystal Structure ◽  
Phase Transformation ◽  
Room Temperature ◽  
Permanent Magnets ◽  
Temperature Phase ◽  
The Relationship ◽  
Magnetization Behavior ◽  
Annealing Experiments

Single-phase ultrafine nanocrystalline Sm2Co17, a candidate material for permanent magnets, was prepared by a novel simple route based on a home-built `oxygen-free'in situfabrication system. The as-prepared nanocrystalline Sm2Co17has the stable hexagonal Th2Ni17-type (2:17 H) crystal structure at room temperature, which is distinctly different from the conventional polycrystalline Sm2Co17having the rhombohedral Th2Zn17-type (2:17 R) crystal structure at room temperature. Phase transformations in the nanocrystalline Sm2Co17alloy were investigated systematically by a series of annealing experiments. It was found that, along with the nanograin growth in the heat-treatment process, the crystal structure of the room-temperature phase transforms from 2:17 H to 2:17 R. The magnetization behavior of Sm2Co17alloys in different structural states was characterized. The relationship between the magnetic performance and the structure characteristics was analyzed. Understanding the phase transformation of Sm2Co17nanocrystals facilitates the development of nanocrystalline Sm2Co17-type magnets for high-temperature applications.

Microstructure and Crystallography of β Phase Formed through Electric Current Pulse (ECP) Treatment in Cold-Rolled Cu-40%Zn Alloy

2018 ◽  
Vol 941 ◽  
pp. 1117-1122
Author(s):  
Mei Shuai Liu ◽  
Yu Dong Zhang ◽  
Xin Li Wang ◽  
Benoit Beausir ◽  
Mao Lin Liu ◽  
...  
Keyword(s):  
Phase Transformation ◽  
High Temperature ◽  
Room Temperature ◽  
Alpha Phase ◽  
High Temperature Phase ◽  
Temperature Phase ◽  
Metallic Materials ◽  
Product Phase ◽  
Cold Rolled ◽  
Zn Alloy

Most of the studies on phase transformation in metallic materials have focused on transformations during cooling processes due to the easiness of the conservation of the product phase. However, for phase transformation happening during heating processes, the experimental investigations have been indirect if the product high temperature phase could not be preserved to the convenient observation temperature, for example the room temperature. The high density Electric Current Pulse (ECP) treatment allows the phase transformation during heating process and the preservation of the high temperature phase to the room temperature, offering possibilities for direct experimental examinations. Thus, in the present work, a cold-rolled Cu–40%Zn alloy was ECP treated and the microstructure of the product phase and the transformation orientation relationship were investigated. Results show that during the ECP treatment, the high temperature beta phase with BCC structure formed in the parent alpha phase with FCC structure. Especially, two kinds of orientation relationships could be detected between the parent alpha phase and the product beta precipitates. The one is the Kurdjumov-Sachs orientation relationship (K-S OR), and the other is the Nishiyama-Wasserman (N-W). In addition, the amount of beta precipitates obeying the K-S OR is more than that of precipitates obeying the N-W OR. The results of this work provide new fundamental information on phase transformation of metallic materials.

High Temperature Phase Transformation in a Cold-Rolled Fe-Mn-Si Alloy

2013 ◽  
Vol 803 ◽  
pp. 243-246
Author(s):  
Z.C. Zhou ◽  
D.K. Yang ◽  
J. Du ◽  
Y.J. Yan ◽  
S.Y. Gu ◽  
...  
Keyword(s):  
Phase Transformation ◽  
High Temperature ◽  
Internal Friction ◽  
Cold Rolling ◽  
Forced Vibration ◽  
Room Temperature ◽  
High Temperature Phase ◽  
Temperature Phase ◽  
Internal Friction Peak ◽  
Cold Rolled

The internal friction of a cold-rolled Fe-Mn-Si alloy has been investigated using a multifunctional internal friction apparatus though forced vibration method from room temperature to 950 °C. It has been shown that an internal friction peak is found on the IF-T curves during first heating at around 640 °C for the cold-rolled Fe-Mn-Si alloy. The internal friction peak is confirmed to be crystallizing peak of amorphous. The amorphous is resulted from the cold-rolling of the Fe-Mn-Si alloy.

Active Nanostructures at Interfaces for Photocatalytic Reactors and Low-power Consumption Sensors

2010 ◽  
Vol 1257 ◽  
Author(s):  
James L Gole ◽  
Serdar Ozdemir ◽  
Sharka M Prokes ◽  
David M Dixon
Keyword(s):  
Power Consumption ◽  
Low Power ◽  
Metal Ions ◽  
Metal Ion ◽  
Room Temperature ◽  
Transition Metal Ions ◽  
Low Power Consumption ◽  
Temperature Phase ◽  
Photocatalytic Reactors ◽  
Nanostructured Metal Oxides

AbstractActive nanostructures which provide unique transformations are being introduced to phase matched porous silicon (PS) nano/micropores to form a platform for low power consumption highly selective sensors and microreactors. TiO2-xNx photocatalysts have been formed in seconds at room temperature at the nanoscale via the direct nitration of anatase TiO2 nanocolloids. Tunability throughout the visible depends upon the degree of agglomeration and the ability to seed these nanoparticles with metal ions. Co metal ion seeding leads to the efficient room temperature phase transformation, of anatase to rutile TiO2, where normally much higher temperatures are required. Seeding of a properly nitridated TiO2 nanocolloid with transition metal ions (Co, Ni) allows for the enhancement of the infrared spectra of the TiO2-xNx nitridated titania surface in excess of 10-fold, providing a means to analyze for minor contaminants and intermediates. Evidence for nitrogen fixation is found in Fe treated systems. The TiO2-xNx systems act as visible light absorbing photocatalyts. These photocatalysts and additional nanostructured metal oxides can be placed on the surface of PS-based sensor and microreactor configurations to greatly improve the interface response.

Electron Microscope study of commensurate-incommensurate phase transition in BaZnGeO4

1990 ◽  
Vol 48 (4) ◽  
pp. 172-173
Author(s):  
Naoki Yamamoto ◽  
Makoto Kikuchi ◽  
Tooru Atake ◽  
Akihiro Hamano ◽  
Yasutoshi Saito
Keyword(s):  
Phase Transition ◽  
Electron Microscope Study ◽  
Room Temperature ◽  
Hexagonal Lattice ◽  
Ferroelectric Materials ◽  
Temperature Phase ◽  
X Ray Diffraction ◽  
X Ray ◽  
Periodic Arrays ◽  
Modulation Wave Vector

BaZnGeO4 undergoes many phase transitions from I to V phase. The highest temperature phase I has a BaAl2O4 type structure with a hexagonal lattice. Recent X-ray diffraction study showed that the incommensurate (IC) lattice modulation appears along the c axis in the III and IV phases with a period of about 4c, and a commensurate (C) phase with a modulated period of 4c exists between the III and IV phases in the narrow temperature region (—58°C to —47°C on cooling), called the III' phase. The modulations in the IC phases are considered displacive type, but the detailed structures have not been studied. It is also not clear whether the modulation changes into periodic arrays of discommensurations (DC’s) near the III-III' and IV-V phase transition temperature as found in the ferroelectric materials such as Rb2ZnCl4.At room temperature (III phase) satellite reflections were seen around the fundamental reflections in a diffraction pattern (Fig.1) and they aligned along a certain direction deviated from the c* direction, which indicates that the modulation wave vector q tilts from the c* axis. The tilt angle is about 2 degree at room temperature and depends on temperature.

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