Construction of a thermal demagnetization oven, and investigations on the Matahina ignimbrite

10.26686/wgtn.16992073.v1 ◽

2021 ◽

Author(s):

◽

Raymond Allan Hoare

Keyword(s):

Magnetic Properties ◽

Thermal Demagnetization ◽

Ancillary Equipment

<p>A non-magnetic oven, and its ancillary equipment have been constructed and used to study magnetic properties of the Matahina ignimbrite, for which the following results have been established: 1. The directions of magnetization do not alter on heating in the oven. 2. The ignimbrite may be divided into sheets on the basis of magnetic properties. 3. Geological faulting has been revealed by divergent magnetization directions. 4. The T.R.M. acquired in the present earth's field is much greater than the N.R.M. This is possibly due to changes in minerals in the rock, either in the field since the rock was deposited, or on heating in the laboratory.</p>

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Tracing of traffic-related pollution using magnetic properties of topsoils in Daejeon, Korea

Environmental Earth Sciences ◽

10.1007/s12665-020-09223-9 ◽

2020 ◽

Vol 79 (20) ◽

Author(s):

Seungwoo Lee ◽

Seoyeon Kim ◽

Hyeji Kim ◽

Youlee Seo ◽

Yeoncheol Ha ◽

...

Keyword(s):

Magnetic Properties ◽

Magnetic Susceptibility ◽

Remanent Magnetization ◽

Coarse Grained ◽

Morphological Observation ◽

Exhaust Emission ◽

Thermal Demagnetization ◽

Main Street ◽

Traffic Related Pollution ◽

The Difference

Abstract The present study was designed to explore the possibility of roadside pollution screening using magnetic properties of topsoil samples in Daejeon, South Korea. Low-field magnetic susceptibility, frequency dependence of magnetic susceptibility, susceptibility of anhysteretic remanent magnetization, isothermal remanent magnetization (IRM) acquisition and demagnetization, back-field IRM treatment, and thermal demagnetization of composite IRM were determined for roadside topsoil samples. Magnetic susceptibility measured on 238 samples from the upper 5 cm of the topsoils ranged from 8.6 to 82.5 × 10–5 SI with a mean of 28.3 ± 10.8 × 10–5 SI. The proximal zone, 55 m wide area situated on either side of the main street, exhibited an enhancement of magnetic susceptibility. In areas distant from the main street, low magnetic susceptibility (< 50 × 10–5 SI) was observed. The topsoil samples exhibited significant susceptibility contrasts, suggesting that two dimensional magnetic mapping was effective in identifying traffic-related pollution. A few magnetic hotspots with intensities of magnetic susceptibility near or over 50 × 10–5 SI might reflect the difference in topographic elevation and surface morphology. Among various IRM-related parameters, remanence of coercivity was most significant statistically. In most samples, IRM component analysis provided dual coercivity components. Thermal demagnetization of composite IRM and morphological observation of magnetic separates suggest angular magnetite produced by vehicle non-exhaust emissions spherical magnetite derived from exhaust emission to be the dominant contributors to the magnetic signal. It is likely that lower- and higher-coercivity components represent the presence of coarse-grained angular magnetite and fine-grained spherical magnetite, respectively.

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Magnetic properties of natural goethite-III. Magnetic behaviour and properties of minerals originating from goethite dehydration during thermal demagnetization

Geophysical Journal International ◽

10.1111/j.1365-246x.1990.tb01765.x ◽

1990 ◽

Vol 103 (1) ◽

pp. 233-250 ◽

Cited By ~ 59

Author(s):

M. J. Dekkers

Keyword(s):

Magnetic Properties ◽

Magnetic Behaviour ◽

Thermal Demagnetization

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Oxide microstructures and the magnetic properties of Leg 37 basalts

Canadian Journal of Earth Sciences ◽

10.1139/e77-066 ◽

1977 ◽

Vol 14 (4) ◽

pp. 656-663 ◽

Cited By ~ 18

Author(s):

M. L. Wayman ◽

M. E. Evans

Keyword(s):

Magnetic Properties ◽

Electron Microscope ◽

Optical Microscopy ◽

Remanent Magnetization ◽

Single Domain ◽

Microstructural Investigation ◽

Thermal Demagnetization ◽

Oceanic Basalts

Samples from DSDP Leg 37 holes 332B, 334, and 335 have been subjected to magnetic and microstructural investigation. A strong, stable remanent magnetization is observed, with the high Koenigsberger ratios that are characteristic of oceanic basalts. The remanence is generally carried by dendritic s ingle-domain and (or) pseudo-single-domain oxide grains, which are homogeneous. However, thermal demagnetization in air leads to the formation of magnetite–ilmenile intergrowths not detectable by optical microscopy but clearly visible in the electron microscope. Such ultra-fine phase splitting has often been invoked as an explanation of magnetic changes observed during laboratory heating.

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AEM analysis of crystallization in Ti-based amorphous alloys

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100075142 ◽

1983 ◽

Vol 41 ◽

pp. 270-271

Author(s):

A.R. Pelton ◽

A.F. Marshall ◽

Y.S. Lee

Keyword(s):

Magnetic Properties ◽

Amorphous Alloys ◽

Amorphous Materials ◽

Isothermal Annealing ◽

Amorphous Matrix ◽

Nucleation And Growth ◽

Current Interest ◽

Amorphous Films ◽

Electrical And Magnetic Properties

Amorphous materials are of current interest due to their desirable mechanical, electrical and magnetic properties. Furthermore, crystallizing amorphous alloys provides an avenue for discerning sequential and competitive phases thus allowing access to otherwise inaccessible crystalline structures. Previous studies have shown the benefits of using AEM to determine crystal structures and compositions of partially crystallized alloys. The present paper will discuss the AEM characterization of crystallized Cu-Ti and Ni-Ti amorphous films.Cu60Ti40: The amorphous alloy Cu60Ti40, when continuously heated, forms a simple intermediate, macrocrystalline phase which then transforms to the ordered, equilibrium Cu3Ti2 phase. However, contrary to what one would expect from kinetic considerations, isothermal annealing below the isochronal crystallization temperature results in direct nucleation and growth of Cu3Ti2 from the amorphous matrix.

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Microstructure in soft magnetic E3 (S1, Al) (Sendust) alloys

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100105916 ◽

1988 ◽

Vol 46 ◽

pp. 770-771

Author(s):

June D. Kim

Keyword(s):

Electron Microscopy ◽

Magnetic Properties ◽

Ternary Phase Diagram ◽

Vertical Tube ◽

Vacuum Induction Melting ◽

Induction Melting ◽

Soft Magnetic ◽

Quenching Temperature ◽

Thin Foils ◽

Vertical Tube Furnace

Iron-base alloys containing 8-11 wt.% Si, 4-8 wt.% Al, known as “Sendust” alloys, show excellent soft magnetic properties. These magnetic properties are strongly dependent on heat treatment conditions, especially on the quenching temperature following annealing. But little has been known about the microstructure and the Fe-Si-Al ternary phase diagram has not been established. In the present investigation, transmission electron microscopy (TEM) has been used to study the microstructure in a Sendust alloy as a function of temperature.An Fe-9.34 wt.% Si-5.34 wt.% Al (approximately Fe3Si0.6Al0.4) alloy was prepared by vacuum induction melting, and homogenized at 1,200°C for 5 hrs. Specimens were heat-treated in a vertical tube furnace in air, and the temperature was controlled to an accuracy of ±2°C. Thin foils for TEM observation were prepared by jet polishing using a mixture of perchloric acid 15% and acetic acid 85% at 10V and ∼13°C. Electron microscopy was performed using a Philips EM 301 microscope.

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