This invention comprises a method of increasing the magnetostrictiveresponse of rareearthiron (RFe) magnetostrictivealloyrods by a thermal-magnetic treatment. The rod is heated to a temperature above its Curie temperature, viz. from 400 rod is at that temperature, a magnetic field is directionally applied and maintained while the rod is cooled, at least below its Curie temperature.
Rods of magnetrostructive alloys of iron with rareearth elements are formed by flowing a body of rareearth- ironalloy in a crucible enclosed in a chamber maintained under an inert gas atmosphere, forcing such molten rare-earth-ironalloy into a hollow mold tube of refractory material positioned with its lower end portion within the molten body by means of a pressure differential between the chamber and mold tube and
It is generally accepted that a higher concentration than lx lO % m ^ of erbium in silicon is not achievable ( in fact erbium has been shown to be optically inactive at these concentrations). Thus, as the maximum possible concentration is limited, the only other variable which can be altered is the emission cross-section which would have to increase by at least two orders of magnitude above its normal value. All studies o f erbium in different hosts conclude that the erbium spectrum and cross- section are virtually independent of the host material. Therefore, the only possibility of significantly changing the emission cross-section - without altering the spectrum - is by increasing the degree of mixing between the / levels and states of different parity. Since the host material has been seen to have virtually no influence upon the energy levels of the rareearth, the only other possibility of increased mixing is by the inclusion o f co-dopants. The m odelling conducted during this project has successfully demonstrated that a co-dopant such as fluorine, will enhance the cross- section by a factor of two without any significant change in the spectrum. However, the fact that the model employed was very approximate leaves open the possibility that much larger em ission cross-sections may be feasible with other co-dopants. Furthermore, it would appear that the phenomenon of mixed valence may eventually be em ployed to achieve direct electrical activation o f the erbium w ithin its semiconductor host.
is shown in Fig. 1. The magnet wastes are dissolved in acid solution such as sulfuric acid at ﬁrst. Iron is precipitated to be removed by charging much alkali solution. A rareearth element isolated by using solvent extraction is precipitated as oxalates to be recovered. The oxalate is oxidized into an oxide to be a raw material of molten salt electrolysis. Rareearth metals are regenerated by using the molten salt electrolysis. Rareearth metals with trace oxygen (major impurity of magnet waste) are regenerated in the recycling process. Separation of rareearth elements is also possible. However, much waste water is generated because not only rareearth metals but also iron is dissolved by using acid solution. Furthermore, energy consumption is huge because molten salt electrolysis requires much electricity. Location for recycling operation is also limited to a country bearing a smelting facility for rareearth metals.
The facet cleavage is due to the development of slip bands during the cycling loading, acting as stress concentration sites; thus, once the damage takes place, the crack could quickly propagate. Cleavage was observed in a large grain with a size of about 200 μm, the average grain size of the alloy being 45 ± 2 μm. Coarse grains, in fact, can easily form longer initial cracks, due to a large number of dislocations and defects, resulting in a higher probability of localised damage under cyclic loading compared to fine grains.
properties to disordered A2 Fe–Ga alloys, and will therefore act as impurities in the A2 matrix, such as rare-earth inclu- sions in Terfenol-D, decreasing the magnetostrictive perfor- mance of the materials. If element 共 M 兲 substitution or the addition method, in addition to quenching, can be used to hinder the formation of second phase material such as D0 3
throughout the specimen, resulting in lower ﬂow stress in the homogenized specimen. However, the ﬂow stress in the as- cast specimen was higher even before the strain softening accompanying DRX (Fig. 2); consequently, the diﬀerence in texture variation cannot fully explain the higher ﬂow stress in the as-cast specimen. Thus, Al segregation around the second-phase particles has a crucial inﬂuence on the DRX in the Mg-Al-Ca-RE alloy.
basal slip operation, while the isotropic strain by Zn atoms is larger than those by the rare-earth elements. Strain-rate changing tests revealed that the activation volumes estimated for Mg alloys with Y and Dy are much smaller than that of Zn-added alloy, which implies larger interaction between a dislocation and a solute atom. The elastic interaction based on isotropic or anisotropic distortion strains by solute atoms are evaluated, and it is concluded that these strains are insuﬃcient to explain the strengthening eﬀect by Y and Dy addition quantitatively.
Considering the above discussion, we can draw a conclusion that, when the AZ31B samples are treated by rareearth bath, reactions 1-7 will take place, which results in the formation of rareearth cerium film, As the coating formation proceeds, the substrate surface is gradually covered with cerium oxide and magnesium hydroxide, but the film is unevenly distributed on AZ31B attributed to the electrochemical corrosion. The coating retards the corrosion of AZ31B somewhat. However, when the samples pretreated by rareearth bath are immersed in stannate bath again, some aggressive ions can penetrate the cerium coating and cause the dissolution of AZ31B, which brings some Mg 2+ ions into solution, consequently, reactions 8 and 9 will occur and form an indissoluble magnesium stannate layer on cerium coating, which further inhibits the dissolution of AZ31B magnesium alloy. Due to the sequential cooperation between rareearth cerium and stannate, a multilayer film composed of cerium oxide, magnesium stannate compounds and magnesium hydroxide forms on AZ31B surface, which shows much higher corrosive resistance than the film coated by single curium or stannate.
treatment is one of the most promising methods to solve the corrosion problem of Mg and its alloys. The protection layer can be conversion coatings or coatings prepared through anodizing, vapor phase deposition, spinning organic coatings and electro-less plating etc. [4-13]. Among these methods, coatings prepared by chemical conversion treatment have attracted much attention for its low cost, uniform deposition structure, and simplicity in operation. The conventionally used conversion coatings are usually based on chromium compounds that have been proven to be highly toxic carcinogens. Therefore, it is imperative to develop new environment-friendly conversion treatments for Mg alloys. The rareearth based conversion coatings [14-16] are considered to be one of the best candidate for replacing the hexavalent chromium compounds for its low toxicity [17,18]. In previous works, the addition of rareearth La and Ce were widely adopted to improve the corrosion resistance capability of Mg alloys, Al alloys and Zn alloys [19-21]. But there are few reports about the application of other rareearth elements such as Y, Gd and Nd in preparation of chemical conversion coatings. Besides, there are large amount of micro-cracks in the rareearth element-based conversion coatings, and which seriously decrease the corrosion resistance capability of the coatings [22,23]. Chol etc.  improved the corrosion resistance of the AZ31 magnesium alloy by simple stannite post-treatment, and Sol-gel technique [25-28] was also used to seal the micro-cracks of the conversion coating, which have a positive effect on the interlayer.
to cool the magnet and control the temperature inside the sample space. To take measurements, a magnetic field is applied to the sample as it is slowly moved through the coils in a series of 32 steps. The magnetic response of the sample generates a current in the pick-up coils which in turn is detected by the SQUID. The SQUID is shielded from the magnetic fields so as to detect only the current from the pick-up coils. After the sample has been moved through the specified range (typically 4 cm), the measured signal is fitted and then converted into a magnetic moment value in electromagnetic units (emu). A schematic diagram of the SQUID is shown in Figure 2.3. Two different SQUID magnetometers were used to take the measurements presented in this thesis - a Quantum Design MPMS-5S and MPMS-XL. The MPMS-5S can be used to take magnetisation measurements over a temperature range of 1.8 − 400 K and applied magnetic field range of up to ±5 T. The MPMS-XL is able to reach ±7 T.
(12) Where D, S, Y, D*and S* are the constants, which depend upon the crystal structure of compounds. The numerical values of these constants for these materials are 0.0308, 0.089, 0.094, 0.894 and 19934.75 respectively. In above expressions the valence electron Plasmon energy is to be calculated using the relation (1) in our previous publication 13 . A detailed discussion of electronic properties of rareearth compounds has been given elsewhere 1,2,7-9,11,20 and will not be presented here.
The oxide facies BIF is composed of quartz as the main gangue mineral associated with various iron oxides, prin- cipally martite, goethite and magnetite (Figures 4(a) and 5(a)). Minor phases present include monazite, apatite, rare pyrite and pyrrhotite. This BIF facies has an almost homogeneous mineral composition, with little textural va- riations that permit their differentiation into various sub- types, including granular and massive, specularite (slaty), granular, massive and weakly banded BIF (Figure 5). The granular and massive type is composed of quartz bands and two ferruginous layers: one with magnetite grains in a brown massive martite matrix, and a second gray to brown massive bands. Both layers display very little quartz. The massive bands are composed of rhythmical gray massive bands and white to yellowish stained silica bands; the granular bands show white silica layers and brown granular ferruginous bands, while the specularite bands type display some white silica and grey shiny slen- der grains of specular hematite rich bands. A poor align- ment of xenomorphic martite, goethite and relict magnet- ite grains is discernable in the weakly banded sub-type BIF. In this facies, iron oxides are disseminated in a lar- gely siliceous matrix that makes up over 60% of the rock. Weathering in both the oxides and silica layers on this facies is similar.
Rareearth elements (REEs) have become vital and indispensable components of many high-tech products, de- vices and technologies. China’s production of rareearth minerals has provided more than 90% of the world’s supply since 2001 (Su, 2009; Chen, 2011)  . However, what is left in China is million tons of tailings be- cause rareearth ore deposits have relatively low REEs concentrations ranging from 10 to a few hundred parts
and then rinse with water. IMT iSolution DT V12.0 image analyser was used to examine the microstructure. Average grain sizes of the investigated alloys were measured quantitatively by using the linear intercept method based on ASTM standard E112-12 with approximately 500 intersections which required for obtaining better % relative accuracy. The microstructure was characterized by optical microscopy (a Nikon optical microscope) and scanning electron microscopy SEM (JEOL JSM-6380LA) equipped with an EDS detector. The phase compositions of the investigated alloys were analyzed using SEM equipped with energy dispersive X-ray spectroscopy (EDS) system. X-ray diffraction (XRD) was carried out to confirm the phase identification by EDS using PANalytical X-pert 3 X-ray diffractometer and the data was characterized by
usually inferior to wrought alloy due to the defects. The ingots were hot extrusion to remove the cast-defects and enhance mechanical property. Consequently, the Mg-8Al- xRE alloys used in present study were in as-extruded alloys. After hot extrusion, as shown in Figs. 1(c) and (d), all the precipitates were crushed to form homogeneously distribut- ed ﬁne particles with size less than 10 mm. All the as- extruded specimens exhibit a uniform equiaxed grain structure with the mean grain size of about 20 mm. The morphology of the Mg-8Al alloy is an -Mg matrix with irregular -phase precipitates distributed inside grains and also along grain boundaries as shown in Fig. 1(c). Fig- ure 1(d) represents the Mg-8Al-2RE alloy, which containing the rod-like Al 11 RE 3 intermetallic phase and homogene-