Precipitates in hot pressed Nd-Fe-B magnets

1989 ◽  
Vol 47 ◽  
pp. 572-573
Author(s):  
Tsung-Yao Chu
Keyword(s):  
Elevated Temperature ◽  
High Performance ◽  
Melt Spinning ◽  
Permanent Magnets ◽  
Ion Beam ◽  
Boundary Phase ◽  
Full Density ◽  
Mechanical Grinding ◽  
Thin Sections ◽  
Argon Ion

High-performance permanent magnets based on the Nd-Fe-B ternary system can be prepared by melt-spinning of the molten alloy and subsequent pressing to full density at elevated temperature. The starting composition is always slightly rich in Nd compared to stoichiometric Nd2Fe14B in order to ensure the formation of the Nd-rich grain boundary phase. The excess Nd additions also serve to keep elemental Fe particles from precipitating but, instead, lead to unexpected precipitation within the Nd2Fe14B grains. The current research seeks to fully characterize the structure of the precipitates.Electron transparent specimens for TEM examination were prepared by mechanical grinding of thin sections cut from the hot pressed Nd0.135Fe0.815B0.05 magnets, followed by argon ion beam milling at 6 kV. Most of the samples were studied in a JEOL 1200EX STEM equipped with EDS, operating at 120 kV. A few samples were examined at higher resolution in a JEOL 200 CX TEM operated at 200 kV, employing a side entry goniometer stage and a LaB6 cathode.

Phase transformations in rapidly solidified Nd33Fe77 alloy

1992 ◽  
Vol 50 (1) ◽  
pp. 56-57
Author(s):  
A. Zaluska ◽  
L.X. Liao ◽  
X. Chen ◽  
Z. Altounian ◽  
J.O. Ström-Olsen
Keyword(s):  
Phase Transformations ◽  
High Performance ◽  
Melt Spinning ◽  
Permanent Magnets ◽  
New Materials ◽  
Amorphous Precursor ◽  
Eutectic Melting ◽  
Subsequent Transformation ◽  
Fe Alloys ◽  
Rapidly Solidified

Nd-Fe alloys are important for high performance permanent magnets (usually in combination with B, C or N) and a knowledge of the metastable and stable phases of the system is necessary for the development of these new materials. An effective way to investigate such phases is by crystallizing an amorphous precursor.Amorphous ribbons of the binary alloy Nd33Fe77 were produced by melt-spinning. The phase transformations induced by heat treatment of the as-quenched ribbons is complex involving first the production of metastable phases followed by subsequent transformation into stable phases and finally eutectic melting.

Intergranular phase in Nd-Fe-B permanent magnets

1990 ◽  
Vol 48 (4) ◽  
pp. 994-995
Author(s):  
Tsung-Yao Chu ◽  
L. K. Rabenburg
Keyword(s):  
Melt Spinning ◽  
Permanent Magnets ◽  
Ternary Phase Diagram ◽  
Ion Beam ◽  
Scanning Transmission Electron Microscope ◽  
Exact Nature ◽  
Intergranular Phase ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Means Of Transmission

Even though the significance of the intergranular phase in the Nd-Fe-B magnets in terms of sintering aid and domain wall pinping has now been recognized, its exact nature has not yet been conclusively determined. This is so because the Nd-rich intergranular phase has been reported to stabilize in a variety of structures instead of the equilibrium hexagonal α-Nd structure as the ternary phase diagram suggests. This study is directed toward obtaining detailed crystal structure of the intergranular phase by means of transmission electron microscopy.Magnet ribbons with a starting composition of Nd13.5Fe80B6.5 were prepared by melt-spinning; the ribbons were subsequently hot pressed into fully dense magnets. Electron transparent samples, prepared from the hot-pressed magnets by mechanical grinding and ion beam milling, were examined in a JEOL 1200EX scanning transmission electron microscope.

High performance Sm2+δ Fe15Ga2C2 permanent magnets made by melt spinning and hot pressing

1998 ◽  
Vol 83 (10) ◽  
pp. 5549-5551 ◽  
Author(s):  
J. van Lier ◽  
M. Kubis ◽  
W. Grünberger ◽  
L. Schultz ◽  
H. Kronmüller
Keyword(s):  
Hot Pressing ◽  
High Performance ◽  
Melt Spinning ◽  
Permanent Magnets

Oblique Ion Etching for Copper at Elevated Temperature

2010 ◽  
Vol 670 ◽  
pp. 131-134 ◽  
Author(s):  
Tomoaki Hino ◽  
T. Kobayashi ◽  
Y. Yamauchi ◽  
Y. Nobuta ◽  
M. Nishikawa
Keyword(s):  
Elevated Temperature ◽  
Smooth Surface ◽  
Ion Irradiation ◽  
Incident Angle ◽  
Ion Beam ◽  
Polycrystalline Copper ◽  
Ion Etching ◽  
Atomic Force ◽  
Before And After ◽  
Argon Ion

In order to smooth the uneven surface of polycrystalline copper, argon ion etching at the elevated temperature was conducted. The polycrystalline copper was obliquely irradiated by argon ion beam with ion energy of 1 keV and an incident angle of 70°. The substrate temperatures during argon ion irradiation were room temperature (RT), 473 K and 573 K. Before and after the irradiation, the surface morphology was observed using an atomic force microscope (AFM). After the irradiation at 473 K and 573 K, the surface was significantly smoothed compared with that at RT. In addition, the fluence required to obtain the smooth surface can be very low, compared with the case at RT. The present study shows that the oblique ion etching at elevated temperature is quite useful to obtain the smooth surface.

EM of rapidly solidified permanent magnets

1992 ◽  
Vol 50 (1) ◽  
pp. 198-199
Author(s):  
Raja K. Mishra
Keyword(s):  
Melt Spinning ◽  
Permanent Magnets ◽  
Dark Field Image ◽  
Dark Field ◽  
Maximum Energy ◽  
Quench Rate ◽  
Maximum Energy Product ◽  
Energy Product ◽  
Annular Dark Field ◽  
Rapidly Solidified

The discovery of a new class of permanent magnets based on Nd2Fe14B phase in the last decade has led to intense research and development efforts aimed at commercial exploitation of the new alloy. The material can be prepared either by rapid solidification or by powder metallurgy techniques and the resulting microstructures are very different. This paper details the microstructure of Nd-Fe-B magnets produced by melt-spinning.In melt spinning, quench rate can be varied easily by changing the rate of rotation of the quench wheel. There is an optimum quench rate when the material shows maximum magnetic hardening. For faster or slower quench rates, both coercivity and maximum energy product of the material fall off. These results can be directly related to the changes in the microstructure of the melt-spun ribbon as a function of quench rate. Figure 1 shows the microstructure of (a) an overquenched and (b) an optimally quenched ribbon. In Fig. 1(a), the material is nearly amorphous, with small nuclei of Nd2Fe14B grains visible and in Fig. 1(b) the microstructure consists of equiaxed Nd2Fe14B grains surrounded by a thin noncrystalline Nd-rich phase. Fig. 1(c) shows an annular dark field image of the intergranular phase. Nd enrichment in this phase is shown in the EDX spectra in Fig. 2.

Ultrastructural Features of Normal and Diseased Hair Revealed by Ion Beam Etching and Freeze Fracture

1975 ◽  
Vol 33 ◽  
pp. 358-359
Author(s):  
M. Spector ◽  
A. C. Brown
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Ectodermal Dysplasia ◽  
Ion Beam ◽  
Freeze Fracture ◽  
Ion Current ◽  
Ion Beam Etching ◽  
Pili Torti ◽  
Argon Ion ◽  
Scanning Electron

Ion beam etching and freeze fracture techniques were utilized in conjunction with scanning electron microscopy to study the ultrastructure of normal and diseased human hair. Topographical differences in the cuticular scale of normal and diseased hair were demonstrated in previous scanning electron microscope studies. In the present study, ion beam etching and freeze fracture techniques were utilized to reveal subsurface ultrastructural features of the cuticle and cortex.Samples of normal and diseased hair including monilethrix, pili torti, pili annulati, and hidrotic ectodermal dysplasia were cut from areas near the base of the hair. In preparation for ion beam etching, untreated hairs were mounted on conducting tape on a conducting silicon substrate. The hairs were ion beam etched by an 18 ky argon ion beam (5μA ion current) from an ETEC ion beam etching device. The ion beam was oriented perpendicular to the substrate. The specimen remained stationary in the beam for exposures of 6 to 8 minutes.

A TEM study of the interface between organic matrix and aragonite in a biological hard tissue, nacre

1992 ◽  
Vol 50 (2) ◽  
pp. 1024-1025
Author(s):  
Jun Liu ◽  
Katie E. Gunnison ◽  
Mehmet Sarikaya ◽  
Ilhan A. Aksay
Keyword(s):  
Mechanical Properties ◽  
Ion Beam ◽  
Laminated Composite ◽  
Organic Matrix ◽  
Pearl Oyster ◽  
Interfacial Structure ◽  
Interfacial Region ◽  
Thin Sections ◽  
Organic Layers ◽  
Transmission Electron

The interfacial structure between the organic and inorganic phases in biological hard tissues plays an important role in controlling the growth and the mechanical properties of these materials. The objective of this work was to investigate these interfaces in nacre by transmission electron microscopy. The nacreous section of several different seashells -- abalone, pearl oyster, and nautilus -- were studied. Nacre is a laminated composite material consisting of CaCO3 platelets (constituting > 90 vol.% of the overall composite) separated by a thin organic matrix. Nacre is of interest to biomimetics because of its highly ordered structure and a good combination of mechanical properties. In this study, electron transparent thin sections were prepared by a low-temperature ion-beam milling procedure and by ultramicrotomy. To reveal structures in the organic layers as well as in the interfacial region, samples were further subjected to chemical fixation and labeling, or chemical etching. All experiments were performed with a Philips 430T TEM/STEM at 300 keV with a liquid Nitrogen sample holder.

The microstructure of a TiB2/Ti-47 Al composite material

1989 ◽  
Vol 47 ◽  
pp. 674-675
Author(s):  
O. Popoola ◽  
A.H. Heuer ◽  
P. Pirouz
Keyword(s):  
Composite Material ◽  
Ion Beam ◽  
Chemical Properties ◽  
Intermetallic Alloys ◽  
Transmission Electron ◽  
Diamond Polishing ◽  
Al Composite ◽  
The Matrix ◽  
Argon Ion ◽  
And Chemical Properties

The addition of fibres or particles (TiB2, SiC etc.) into TiAl intermetallic alloys could increase their toughness without compromising their good high temperature mechanical and chemical properties. This paper briefly discribes the microstructure developed by a TiAl/TiB2 composite material fabricated with the XD™ process and forged at 960°C.The specimens for transmission electron microscopy (TEM) were prepared in the usual way (i.e. diamond polishing and argon ion beam thinning) and examined on a JEOL 4000EX for microstucture and on a Philips 400T equipped with a SiLi detector for microanalyses.The matrix was predominantly γ (TiAl with L10 structure) and α2(TisAl with DO 19 structure) phases with various morphologies shown in figure 1.

Low Energy Ar Ion Milling of FIB TEM Specimens from 14 nm and Future FinFET Technologies

2018 ◽  
Author(s):  
C.S. Bonifacio ◽  
P. Nowakowski ◽  
M.J. Campin ◽  
M.L. Ray ◽  
P.E. Fischione
Keyword(s):  
Field Effect Transistor ◽  
Focused Ion Beam ◽  
Ion Beam ◽  
Specimen Preparation ◽  
Ion Milling ◽  
Transmission Electron ◽  
High Resolution Tem ◽  
Effect Transistor ◽  
20 Nm ◽  
Argon Ion

Abstract Transmission electron microscopy (TEM) specimens are typically prepared using the focused ion beam (FIB) due to its site specificity, and fast and accurate thinning capabilities. However, TEM and high-resolution TEM (HRTEM) analysis may be limited due to the resulting FIB-induced artifacts. This work identifies FIB artifacts and presents the use of argon ion milling for the removal of FIB-induced damage for reproducible TEM specimen preparation of current and future fin field effect transistor (FinFET) technologies. Subsequently, high-quality and electron-transparent TEM specimens of less than 20 nm are obtained.

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