Danièle Laub

Introduction to Materials

Natural materials such as organic matter, mineral matter, and living matter, along with artificial materials produced industrially, make up all of the materials found on the Earth. They all have a chemical composition and particular structure that give them specific properties or functions in relation to their surroundings or their formation conditions.

Artifacts in Transmission Electron Microscopy

An artifact is damage caused by a preparation technique and can easily be confused with the sample’s microstructure. Artifacts can be due to mechanical, chemical, ionic, or physical action. During TEM observation, especially in a TEM/STEM, other artifacts may be produced due to irradiation under the electron beam.

Combustion synthesis of cadmium sulphide nanomaterials for efficient visible light driven hydrogen production from water

AbstractAnion-doped cadmium sulphide nanomaterials have been synthesized by using combustion method at normal atmospheric conditions. Oxidant/fuel ratios have been optimized in order to obtain CdS with best characteristics. Formation of CdS and size of crystallite were identified by X-ray diffraction and confirmed by transmission electron microscopy. X-ray photoelectron spectroscopy confirmed the presence of C and N in the CdS matrix. The observed enhanced photocatalytic activity of the CdS nanomaterials for the hydrogen production from water (2120 μmol/h) can be attributed to high crystallinity, low band gap and less exciton recombination due to the C and N doping.n Graphical AbstractA single pot synthesis of C and N doped cadmium sulfide (CdS) nanomaterials has been achieved by using combustion synthesis. Oxidant/fuel (O/F) ratio has been optimized in order to obtain CdS with desirable characteristics for hydrogen production under visible light irradiation. Photocatalytic activity of the CdS was evaluated by the hydrogen production from water containing Na2S and Na2SO3 as sacrificial reagents. Typical results indicated a high rate of H2 evolution (2120 μmol/h) for CdS sample with oxidant/fuel ratio 2, which may be attributed to the high crystallinity, low band gap and less exciton recombination.

Mechanical Preparation Techniques

Crushing is used to very quickly produce a fine powder from a bulk material or fine particle using mechanical crushing.

Thinning Preparation Techniques

This technique is used to produce a thin slice (measuring 3 mm in diameter and between 50- and 100-μm thick) without strain hardening, by thinning until a perforation is made in the center. The resulting hole has electron-transparent thin edges.

Preliminary Preparation Techniques

This technique is used to make slices of bulk samples in order to reduce their dimensions and then prepare them using other preparation or finishing techniques (final thinning for transmission electron microscopy). In most cases, this means obtaining a slice with parallel faces of the right thickness (a foil or disk 1- to 0.1-mm thick).

Contrast Enhancement and Labeling Techniques

This technique is used to enhance contrast in a sample. It is particularly useful for highlighting very faint surface relief. The method consists of depositing heavy-metal (high Z) particles on or around a sample’s relief. The contrast of a sample is enhanced by shadowing resulting from a metallic deposit.

Methodology: General Introduction

This book is aimed at the entire scientific community (solid state physics, chemistry, earth sciences, and live sciences), to those who use transmission electron microscopy (TEM) to analyze structure in relation to the properties and specific functions of materials. This work is essentially dedicated to the recommended methodology for beginning the preparation of a sample for the TEM. In particular it stresses the approach to take in selecting the best technique by taking into account the material problem presented, the type of material, its structure, and its properties. It proposes the tools for the most appropriate preparation of samples for observing the true structure of the material.

Techniques: General Introduction

The second volume of the “Sample Preparation Handbook for Transmission Electron Microscopy” contains descriptions of 14 preliminary and/or complementary sample preparation techniques and 21 thin slice preparation techniques for the transmission electron microscope (TEM).

Selection of Preparation Techniques Based on Material Problems and TEM Analyses

The best choice of preparation technique is the one that produces a suitable thin slice of the material to be investigated. The technique must also be suitable for the different TEM analyses and should contain a minimum of artifacts.