scroll identifier for mobile
main-content

## Weitere Artikel dieser Ausgabe durch Wischen aufrufen

01.04.2015 | Research Paper | Ausgabe 4/2015

# Segregation phenomena in Nd–Fe–B nanoparticles

Zeitschrift:
Journal of Nanoparticle Research > Ausgabe 4/2015
Autoren:
F. Schmidt, D. Pohl, L. Schultz, B. Rellinghaus

## Abstract

We report on the phase stability and phase formation of Nd–Fe–B nanoparticles from the gas phase in the size range from 10 to 25 nm. Particular attention is paid to the question, if the intermetallic $$\hbox {Nd}_{2}\hbox {Fe}_{14}\hbox {B}$$ phase also forms in free particles with a few nanometers in size that grow without contact to any solid or liquid matrix in a low pressure Ar atmosphere. The paper also addresses the possible influence of segregation phenomena that go along with the phase formation and the effect of (rapid) thermal annealing on the structure and phase stability of the particles. Aberration-corrected transmission electron microscopy in combination with spectroscopic methods was used to determine the local atomic structure and the chemical composition of the particles. Unheated particles are found to be mainly amorphous, while the rapidly optically annealed particles are crystalline. In both cases, we observe an enrichment of Nd in the shell of the particles and a Fe enrichment in the core. This segregation of Nd toward the particles' surface is more pronounced in heated particles, which form a clear core-shell structure with a Fe core surrounded by a $$\hbox {Nd}_{2}\hbox {O}_{3}$$ shell. This finding is attributed to the comparably small surface energy and the higher affinity of Nd to oxygen as compared to Fe. A simple model is introduced and used in order to estimate these surface energies. These estimations support the experimentally observed segregation phenomena. It is further found that B prefers the vicinity of Fe over that of Nd atoms, which as a consequence leads to a B enrichment in the Fe-rich parts of the particles. Magnetic measurements show a soft magnetic behavior for both, unheated and heated Nd–Fe–B nanoparticles.

### Springer Professional "Wirtschaft+Technik"

Online-Abonnement

Mit Springer Professional "Wirtschaft+Technik" erhalten Sie Zugriff auf:

• über 69.000 Bücher
• über 500 Zeitschriften

aus folgenden Fachgebieten:

• Automobil + Motoren
• Bauwesen + Immobilien
• Elektrotechnik + Elektronik
• Energie + Umwelt
• Finance + Banking
• Management + Führung
• Marketing + Vertrieb
• Maschinenbau + Werkstoffe

Testen Sie jetzt 30 Tage kostenlos.

### Springer Professional "Technik"

Online-Abonnement

Mit Springer Professional "Technik" erhalten Sie Zugriff auf:

• über 50.000 Bücher
• über 380 Zeitschriften

aus folgenden Fachgebieten:

• Automobil + Motoren
• Bauwesen + Immobilien
• Elektrotechnik + Elektronik
• Energie + Umwelt
• Maschinenbau + Werkstoffe​​​​​​​​​​​​​​

Testen Sie jetzt 30 Tage kostenlos.

Literatur
Über diesen Artikel

Zur Ausgabe