Experimental Considerations and Limitations in the Application of Ultra High Temperature (2100°C) X-Ray Diffraction

In-situ, high temperature X-ray diffraction (XRD) is an extremely useful tool for studying, monitoring or investigating crystal structure modifications as well as phase transformations in crystalline material during thermal treatments in controlled atmospheres. This technique has been used to investigate the thermal behavior of materials such as carbonate minerals, ceramic fibers, coating pigments, etc. The advantages of such a technique over the conventional practice, where samples are heat treated in a separate oven and then analyzed by XRD include: consistency of sample placement; preservation of high temperature structures to facilitate observation of metastable phases that are unstable upon exposure to outside atmosphere or during cooling; real time monitoring of reactions that occur, and products that are formed at a desired temperature or environment; and need for multiple samples or analysis.

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A Low-High Temperature Camera for In-Situ X-Ray Diffraction Studies of Catalysts

Advances in X-ray Analysis ◽

10.1154/s0376030800017183 ◽

1983 ◽

Vol 27 ◽

pp. 285-291

Author(s):

J. Pielaszek ◽

J.B. Cohen

Keyword(s):

High Temperature ◽

Porous Silica ◽

X Ray Diffraction ◽

X Ray ◽

Controlled Atmospheres ◽

Research Areas ◽

High Temperature Xrd ◽

Different Temperatures ◽

Porous Silica Glass

X-Ray diffraction studies of substances under controlled atmospheres and at different temperatures are of great importance in many research areas. This is especially true in the area of catalysis, where the correlation of structural and catalytic properties is needed. The camera described here was made for this purpose although any sample in the powdered form can be studied as well. Many catalysts are in the form of highly dispersed metal deposited on a granulated support. The content of metal may vary from a few tenths to several percent. In a camera used by Janko and Borodzinski a small amount of catalyst was spread out on a porous silica glass sample holder which then was placed in a high temperature XRD camera with flowing gas of controlled composition.

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In situ high-temperature X-ray diffraction studies of reduction of K2CrO4 and the formation of KxCrOy compounds

Powder Diffraction ◽

10.1017/s0885715617000690 ◽

2017 ◽

Vol 32 (3) ◽

pp. 168-174 ◽

Cited By ~ 3

Author(s):

Shu-ting Liang ◽

Hong-ling Zhang ◽

Min-ting Luo ◽

Yu-lan Bai ◽

Hong-bin Xu ◽

...

Keyword(s):

Fourier Transform ◽

High Temperature ◽

Hydrogen Reduction ◽

Potassium Chromate ◽

Crystalline Material ◽

Reduction Mechanism ◽

X Ray Diffraction ◽

X Ray ◽

First Time

In this work, the reduction mechanism of potassium chromate (K2CrO4) was investigated via in situ high-temperature X-ray diffraction coupled with Fourier transform infrared spectroscopy. During the hydrogen reduction of K2CrO4, the formation of K3CrO4, KCrO2, and KxCrO2 were detected for the first time. The study discovered that K2CrO4 was firstly reduced to K3CrO4 and an amorphous Cr(III) intermediate product at low temperature (400–500 °C). Moreover, the K3CrO4 was the only crystalline material at this stage. As the temperature increased, a stabilized amorphous CrOOH was formed. At a high temperature (550–700 °C), KCrO2 was generated. Interestingly, a portion of KCrO2 was spontaneously decomposed during the hydrogen reduction, accompanying by the formation of K0.7CrO2. Finally, the results clearly illustrated the reduction mechanism of K2CrO4: K2CrO4 → K3CrO4 → amorphous intermediate → KCrO2.

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