In situX-ray diffraction environments for high-pressure reactions

New sample environments and techniques specifically designed forin situpowder X-ray diffraction studies up to 1000 bar (1 bar = 105 Pa) gas pressure are reported and discussed. The cells can be utilized for multiple purposes in a range of research fields. Specifically, investigations of gas–solid reactions and sample handling under inert conditions are undertaken here. Sample containers allowing the introduction of gas from one or both ends are considered, enabling the possibility of flow-through studies. Various containment materials are evaluated,e.g.capillaries of single-crystal sapphire (Al2O3), quartz glass (SiO2), stainless steel (S316) and glassy carbon (Sigradur K), and burst pressures are calculated and tested for the different tube materials. In these studies, high hydrogen pressure is generated with a metal hydride hydrogen compressor mounted in a closed system, which allows reuse of the hydrogen gas. The advantages and design considerations of thein situcells are discussed and their usage is illustrated by a case study.

Versatile in situ powder X-ray diffraction cells for solid-gas investigations

Two multipurpose sample cells of quartz (SiO₂) or sapphire (Al₂O₃) capillaries, developed for the study of solid–gas reactions in dosing or flow mode, are presented. They allow fast change of pressure up to 100 or 300 bar (1 bar = 100 000 Pa) and can also handle solid–liquid–gas studies.

This paper describes new sample cells and techniques for in situ powder X-ray diffraction specifically designed for gas absorption studies up to ca 300 bar (1 bar = 100 000 Pa) gas pressure. The cells are for multipurpose use, in particular the study of solid–gas reactions in dosing or flow mode, but can also handle samples involved in solid–liquid–gas studies. The sample can be loaded into a single-crystal sapphire (Al₂O₃) capillary, or a quartz (SiO₂) capillary closed at one end. The advantages of a sapphire single-crystal cell with regard to rapid pressure cycling are discussed, and burst pressures are calculated and measured to be ∼300 bar. An alternative and simpler cell based on a thin-walled silicate or quartz glass capillary, connected to a gas source via a VCR fitting, enables studies up to ∼100 bar. Advantages of the two cell types are compared and their applications are illustrated by case studies.

In situ neutron powder diffraction and structure determination in controlled humidities

A controlled-humidity sample environment has been constructed, allowing bulk powder samples undergoing humidity-induced phase transitions and reactions to be studied via in situ neutron diffraction. Associated developments in data collection and analysis permit this to be achieved without the use of D(2)O.