scholarly journals Mean Magnetic Moment of Polydisperse Superparamagnetic Nanoparticles: Correlation Between Grain Size and Magnetic Moment Distributions

2007 ◽  
Vol 7 (3) ◽  
pp. 1043-1051 ◽  
Author(s):  
J. S. Blázquez ◽  
V. Franco ◽  
C. F. Conde ◽  
A. Conde
Keyword(s):  
Grain Size ◽  
Magnetic Moment ◽  
Superparamagnetic Nanoparticles

Definition of Amorphous Tapes Magnetic Condition Using Temperature Dependence of the Saturation Magnetic Moment

2014 ◽  
Vol 215 ◽  
pp. 268-271
Author(s):  
Vladimir S. Pechnikov
Keyword(s):  
Temperature Dependence ◽  
Magnetic Moment ◽  
Superparamagnetic Nanoparticles ◽  
Ferromagnetic Phase ◽  
Initial Condition ◽  
Saturation Magnetic Moment ◽  
Magnetic Elements ◽  
Phase Temperature ◽  
Definition Of ◽  
Quantitative Definition

In article results of research of the saturation magnetic moment temperature dependence of ferromagnetic amorphous tapes on an iron and cobalt basis, and also one not ferromagnetic amorphous tape are described. It is shown that in an initial condition not all atoms of magnetic elements are in a ferromagnetic phase. Temperature dependence of the saturation moment of a ferromagnetic phase of amorphous tapes is well described by Brillouin's function. Possibility of quantitative definition of part of the magnetic atoms forming not ferromagnetic phase of a tape is proved. It is shown that the tape on the iron basis, containing about 20% of chrome, not ferromagnetic in an initial condition, consists of the superparamagnetic nanoparticles including about 10 atoms of iron.

Effect of Chemical Reaction Temperature on Magnetic Properties of Cu2+ Substituted NiZn Ferrites

2013 ◽  
Vol 547 ◽  
pp. 181-193 ◽  
Author(s):  
Neelam S. Shinde ◽  
Sujata. S. Khot ◽  
R.M. More ◽  
Shrikant C. Watawe
Keyword(s):  
Grain Size ◽  
Magnetic Properties ◽  
Structural Analysis ◽  
Reaction Temperature ◽  
Magnetic Moment ◽  
Magnetic Losses ◽  
X Ray Diffraction ◽  
Precursor Method ◽  
Oxalate Precursor ◽  
X Ray

Ni-Cu-Zn ferrites with general formula Ni0.5Cux/2Zn0.5-x/2Fe2O4 (with x = 0.3, 0.4, 0.5 and 0.6) have been synthesized using oxalate precursor method with different precursor reaction temperatures in the range 100C to 700C. The structural analysis has been carried out using X-ray diffraction studies which reveal the formation of ferrites structure. The lattice parameters obtained using the most intense 311 peak are found to be in the range 8.37 to 8.42 Å for all the samples. The saturation magnetization is found to be in the range 20 to 51 emu/g, while the magnetic moment is found to be in the range 0.63 to 1.5 µB. The magnetic losses were found to be maximum for the samples obtained at precursor reaction temperature of 350C. The grain size is found to be in the range 0.4 to 2.0 µm. There is variation in the magnetic properties for different precursor temperatures indicating the effect of reaction history on the various parameters studied.

The Influence of Grain-Boundary Structural Disorder on the Magnetic Properties of Nanocrystalline Nickel

1993 ◽  
Vol 318 ◽  
Author(s):  
Barbara Szpunar ◽  
Uwe Erb ◽  
Karl T. Aust ◽  
Gino Palumbo ◽  
Laurent J. Lewis
Keyword(s):  
Grain Size ◽  
Magnetic Properties ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Magnetic Moment ◽  
Recent Observation ◽  
Extreme Case ◽  
Structural Disorder ◽  
Nanocrystalline Nickel ◽  
Electrodeposited Nickel

ABSTRACTThe influence of grain boundaries on the magnetic properties of nanocrystalline nickel, in particular the ∑ = 3 and ∑ = 5 special grain boundaries and the extreme case of a purely amorphous sample, has been investigated. Our calculations reveal that the magnetic moment is rather insensitive to the structural disorder varying by at most 15 %. These results correlate extremely well with the recent observation in electrodeposited nickel that the magnetic moment depends very little on grain size, down to about 10 nm.

Effect of Shock Loading on the Microstructure of Uniloy 326

1974 ◽  
Vol 32 ◽  
pp. 504-505
Author(s):  
K. P. Staudhammer ◽  
L. E. Murr
Keyword(s):  
Grain Size ◽  
Shock Loading ◽  
Current Investigation ◽  
Two Phase ◽  
05 C ◽  
Shock Deformation ◽  
Heat Treated

The effect of shock loading on a variety of steels has been reviewed recently by Leslie. It is generally observed that significant changes in microstructure and microhardness are produced by explosive shock deformation. While the effect of shock loading on austenitic, ferritic, martensitic, and pearlitic structures has been investigated, there have been no systematic studies of the shock-loading of microduplex structures.In the current investigation, the shock-loading response of millrolled and heat-treated Uniloy 326 (thickness 60 mil) having a residual grain size of 1 to 2μ before shock loading was studied. Uniloy 326 is a two phase (microduplex) alloy consisting of 30% austenite (γ) in a ferrite (α) matrix; with the composition.3% Ti, 1% Mn, .6% Si,.05% C, 6% Ni, 26% Cr, balance Fe.

Aspects of microanalysis in a transmission electron microscope

1978 ◽  
Vol 36 (1) ◽  
pp. 510-511
Author(s):  
R. Sinclair ◽  
B.E. Jacobson
Keyword(s):  
Grain Size ◽  
Electron Beam ◽  
Electron Microscope ◽  
Chemical Analysis ◽  
Transmission Electron Microscope ◽  
Vapor Deposition ◽  
Critical Currents ◽  
X Ray ◽  
Fine Grain ◽  
Transmission Electron

INTRODUCTIONThe prospect of performing chemical analysis of thin specimens at any desired level of resolution is particularly appealing to the materials scientist. Commercial TEM-based systems are now available which virtually provide this capability. The purpose of this contribution is to illustrate its application to problems which would have been intractable until recently, pointing out some current limitations.X-RAY ANALYSISIn an attempt to fabricate superconducting materials with high critical currents and temperature, thin Nb3Sn films have been prepared by electron beam vapor deposition [1]. Fine-grain size material is desirable which may be achieved by codeposition with small amounts of Al2O3 . Figure 1 shows the STEM microstructure, with large (∽ 200 Å dia) voids present at the grain boundaries. Higher quality TEM micrographs (e.g. fig. 2) reveal the presence of small voids within the grains which are absent in pure Nb3Sn prepared under identical conditions. The X-ray spectrum from large (∽ lμ dia) or small (∽100 Ǻ dia) areas within the grains indicates only small amounts of A1 (fig.3).

Novel magneto-optical recording materials: Bi-substituted garnet films

1991 ◽  
Vol 49 ◽  
pp. 776-777
Author(s):  
Takao Suzuki ◽  
Hossein Nuri
Keyword(s):  
Grain Size ◽  
Amorphous Film ◽  
Nitrogen Atmosphere ◽  
Optical Recording ◽  
Garnet Film ◽  
Media Noise ◽  
Garnet Films ◽  
Order Of Magnitude ◽  
A New Technique ◽  
A Current

For future high density magneto-optical recording materials, a Bi-substituted garnet film ((BiDy)3(FeGa)5O12) is an attractive candidate since it has strong magneto-optic effect at short wavelengths less than 600 nm. The signal in read back performance at 500 nm using a garnet film can be an order of magnitude higher than a current rare earth-transition metal amorphous film. However, the granularity and surface roughness of such crystalline garnet films are the key to control for minimizing media noise.We have demonstrated a new technique to fabricate a garnet film which has much smaller grain size and smoother surfaces than those annealed in a conventional oven. This method employs a high ramp-up rate annealing (Γ = 50 ~ 100 C/s) in nitrogen atmosphere. Fig.1 shows a typical microstruture of a Bi-susbtituted garnet film deposited by r.f. sputtering and then subsequently crystallized by a rapid thermal annealing technique at Γ = 50 C/s at 650 °C for 2 min. The structure is a single phase of garnet, and a grain size is about 300A.

Structure of second phases in TiAl alloys containing Cr and B

1991 ◽  
Vol 49 ◽  
pp. 576-577
Author(s):  
Ernest L. Hall ◽  
Shyh-Chin Huang
Keyword(s):  
Grain Size ◽  
Second Phase ◽  
Structure And Properties ◽  
Tial Alloys ◽  
Second Phases ◽  
Interstitial Elements

Addition of interstitial elements to γ-TiAl alloys is currently being explored as a method for improving the properties of these alloys. Previous work in which a number of interstitial elements were studied showed that boron was particularly effective in refining the grain size in castings, and led to enhanced strength while maintaining reasonable ductility. Other investigators have shown that B in γ-TiAl alloys tends to promote the formation of TiB2 as a second phase. In this study, the microstructure of Bcontaining TiAl alloys was examined in detail in order to describe the mechanism by which B alters the structure and properties of these alloys.

Interfacial studies in Nb3Sn superconductors

1991 ◽  
Vol 49 ◽  
pp. 590-591
Author(s):  
Ernest L. Hall ◽  
Lee E. Rumaner ◽  
Mark G. Benz
Keyword(s):  
Grain Size ◽  
Grain Boundaries ◽  
Flux Pinning ◽  
Size Control ◽  
High Magnetic Fields ◽  
Type Ii ◽  
Reaction Interface ◽  
Liquid Diffusion ◽  
Type Ii Superconductor ◽  
Grain Size Control

The intermetallic compound Nb3Sn is a type-II superconductor of interest because it has high values of critical current density Jc in high magnetic fields. One method of forming this compound involves diffusion of Sn into Nb foil containing small amounts of Zr and O. In order to maintain high values of Jc, it is important to keep the grain size in the Nb3Sn as small as possible, since the grain boundaries act as flux-pinning sites. It has been known for many years that Zr and O were essential to grain size control in this process. In previous work, we have shown that (a) the Sn is transported to the Nb3Sn/Nb interface by liquid diffusion along grain boundaries; (b) the Zr and O form small ZrO2 particles in the Nb3Sn grains; and (c) many very small Nb3Sn grains nucleate from a single Nb grain at the reaction interface. In this paper we report the results of detailed studies of the Nb3Sn/Nb3Sn, Nb3Sn/Nb, and Nb3Sn/ZrO2 interfaces.

The crystallization of thin-film ceramics

1992 ◽  
Vol 50 (1) ◽  
pp. 338-339
Author(s):  
J.M. Schwartz ◽  
L.F. Francis ◽  
L.D. Schmidt ◽  
P.S. Schabes-Retchkiman
Keyword(s):  
Thin Films ◽  
Grain Size ◽  
Sol Gel ◽  
Processing Route ◽  
Small Areas ◽  
Ceramic Thin Films ◽  
Complex Shapes ◽  
Sol Gel Process ◽  
Ceramic Precursors ◽  
Crystalline Ceramic

Ceramic thin films and coatings are of interest for electrical, optical, magnetic and thermal barrier applications. Critical for improved properties in thin films is the development of specific microstructures during processing. To this end, the sol-gel method is advantageous as a versatile processing route. The sol-gel process involves depositing a solution containing metalorganic or colloidal ceramic precursors onto a substrate and heating the deposited layer to form a crystalline or non-crystalline ceramic coating. This route has several advantages, including the ability to create tailored microstructures and properties, to coat large or small areas, simple or complex shapes, and to more easily prepare multicomponent ceramics. Sol-gel derived coatings are amorphous in the as-deposited state and develop their crystalline structure and microstructure during heat-treatment. We are particularly interested in studying the amorphous to crystalline transformation, because many key features of the microstructure such as grain size and grain size distribution may be linked to this transformation.

A TEM study of the influence of microstructure on the superplastic behavior of a U-5.8 wt.% Nb alloy

1986 ◽  
Vol 44 ◽  
pp. 568-569
Author(s):  
G. Mackiewicz Ludtka
Keyword(s):  
Grain Size ◽  
Heating Rate ◽  
Phase Field ◽  
Single Phase ◽  
Superplastic Behavior ◽  
Two Phase ◽  
Single Phase Field

Historically, metals exhibit superplasticity only while forming in a two-phase field because a two-phase microstructure helps ensure a fine, stable grain size. In the U-5.8 Nb alloy, superplastici ty exists for up to 2 h in the single phase field (γ1) at 670°C. This is above the equilibrium monotectoid temperature of 647°C. Utilizing dilatometry, the superplastic (SP) U-5.8 Nb alloy requires superheating to 658°C to initiate the α+γ2 → γ1 transformation at a heating rate of 1.5°C/s. Hence, the U-5.8 Nb alloy exhibits an anomolous superplastic behavior.

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