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The effects of Nb addition on the hard magnetic properties and microstructure evolution in [Nd.sub.8][Fe.sub.78-x][Co.sub.8] [B.sub.6][Nb.sub.x] and [Nd.sub.12][Fe.sub.82-x][B.sub.6][Nb.sub.x] nanocrystalline alloys are presented. Low Nd containing alloys consist of [alpha]-Fe and [Nd.sub.2][Fe.sub.14]B phases. The [Nd.sub.12][Fe.sub.80.5][B.sub.6][Nb.sub.1.5] alloy probably contains NbFeB phase besides the [alpha]-Fe and [Nd.sub.2][Fe.sub.14]B phases. It is found that Nb atoms tend to enrich at grain boundary region, resulting in refined microstructure and significantly improved coercivity over a range of conventional Nd-Fe-B alloys. Index Terms--Electron microscopy, nanocrystalline, Nb, permanent magnets.

3d-rich alloys and their melt-spun materials with nominal compositions of Sm[([Co.sub.bal][Fe.sub.x] [Zr.sub.0.05][Cu.sub.0.08][Ga.sub.y][B.sub.z]).sub.12] (x = 0.1-0.41, y = 0-0.01, z = 0.01-0.02)were synthesized and characterized in the temperature range of 10-1473 K and at fields up to 5 T. The main phase of the as-cast alloys was formed in a [Th.sub.2][Ni.sub.17] type structure, exhibiting a strong uniaxial anisotropy. As a result, encouraging hard magnetic properties with [T.sub.c] = 995-1086 K, [H.sub.a] = 40-115 kOe, [M.sub.s] = 10-12.8 kG at 300 K, and [H.sub.a] = 60-180 kOe, [M.sub.s] 10.4-13.6 kG at l0 K were observed in the as-cast alloys. The melt-spun materials are nano-structured in nature and magnetically hard, even in the as-spun state. The following hard magnetic properties were observed: [H.sub.ci] = 7-10 kOe, 4[pi][M.sub.s] = 9.4-11.7 kG, at 300 K, and [H.sub.ci] = 17-27 kOe, 4[pi][M.sub.s] = 9.6-12.1 kG, at 10 K. The highest [(BH).sub.max] ~ 9.8 MGOe at 300 K was obtained from the Sm[(Co.sub.bal][Fe.sub.0.31][Zr.sub.0.05][Cu.sub.0.08] [B.sub.0.02]).sub.12] ribbon material. A Henkel plot analysis indicates the existence of a strong exchange-coupling interaction between the magnetically hard and soft phases in these ribbon materials. The effects of adding Ga, B, and Fe on the magnetic properties will be discussed. Index Terms--3d-rich magnetic alloy, exchange coupling, hard magnetic property, melt-spun.

We have investigated the microstructures of melt-spun Sm(Co0.58Fe0.31Cu0.04Zr0.05B0.02)z (z=7.5 and 12) ribbons by transmission electron microscopy (TEM) and three dimensional atom probe (3DAP) to correlate them with the hard magnetic properties. The ribbon with z=7.5 has a high coercivity (iHc∼12 kOe) while the ribbon with z=12 possesses a low coercivity (iHc∼4.9 kOe). The high iHc ribbon comprises of nanocrystals (∼10 nm) having 1:7H (TbCu7) type structure as main phase. However, in the low iHc ribbon, the microstructure consists of both 1:7H and 2:17H (Th2Ni17) phases with crystal size ranging from 50 to 80 nm. The low coercivity ribbon also contains (CoFeZr)23B6 (M23B6 type) soft magnetic phase. The low coercivity obtained in the melt-spun ribbon with z=12 is due to: (i) the formation of Th2Ni17 type low anisotropy phase, (ii) the presence of boron-rich soft magnetic phase, and (iii) larger crystal size. Realization of high coercivity in the ribbon with z=7.5 is due to the formation of 1:7H, a high anisotropy phase, as well as reduced grain size. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

OBJECTIVE: MiR-155-5p has various biological cellular functions in diverse pathology, including cardiovascular disease. Nevertheless, the role of miR-155-5p in atherosclerosis is still not well known. PATIENTS AND METHODS: The levels of miR-155-5p and AKT Serine/Threonine Kinase 1 (AKT1) in plasma samples from patients with atherosclerotic CAD were detected using quantitative Real-time PCR (qRT-PCR). Cell counting kit-8 (CCK-8) assay was used to analyze the proliferation of vascular smooth muscle cells (VSMCs) and human umbilical vein endothelial cells (HUVECs) in vitro. The migration of VSMCs and HUVECs was detected using wound healing assay. The invasion of VSMCs and HUVECs using was determined using the transwell invasion assay. The expression of AKT1 was measured using immunofluorescence staining analysis. RESULTS: MiR-155-5p was down-regulated in patients with atherosclerotic CAD. Up-regulation of miR-155-5p inhibited the proliferation, migration and invasion of VSMCs and HUVECs. Bioinformatics analysis and luciferase reporter assay indicated that AKT1 was the direct target of miR-155-5p and miR-155-5p bound to the 3'-untranslated region (3'-UTR) of AKT1. The expression of AKT1 was reduced in cell that was transfected with miR-155-5p. Up-regulation of AKT1 rescued the suppressive effect of miR- 155-5p on the growth, migration and invasion of VSMCs and HUVECs. Down-expression of AKT1 partially neutralized the impacts of miR-155-5p on the growth, invasion and migration of VSMCs and HUVECs. Finally, we found that AKT1 was over-regulated in plasma samples of patients with atherosclerotic CAD and its level was negative with the level of miR-155-5p. CONCLUSIONS: Our study demonstrates that miR-155-5p suppresses the proliferation, migration and invasion of VSMCs and HUVECs through regulating AKT1, which provides the new insights into the precise role of miR-155-5p in atherosclerosis. [ABSTRACT FROM AUTHOR]

Presents a study that evaluated the effect of grain size and grain-size distribution on the intrinsic coercivity and the hysteresis loop of sintered iron-neodymium-boron magnets. Methodology; Influence of a bimodal grain size distribution on the hysteresis loop; Analysis of the scanning electron micrograph of the hard magnet.

Discusses the preparation of the anisotropic and isotropic Sm2Co17-type permanent magnets by using the conventional sintering technique. Characterization of the cellular structure within the Sm2(Fe,Co)17 grains; Application of the singular point detection technique on the anisotropic samples; Measurement of the saturation magnetization.

Corrosion rates for sintered NdFeB magnets are compared with NdFeB magnets prepared from melt spun material (hot pressed and die upset). Corrosion rates were determined by standard electrochemical methods in 0.9 M [Na.sub.2][SO.sub.4], at pH 2.4 and 4.4. Autoclave tests correlated quite well with corrosion rates measured electrochemically in the more aggressive pH electrolyte. The more aggressive pH 2.4 electrolyte is more representative of the conditions occurring in the autoclave tests. The hot pressed and die upset magnets exhibit significantly lower corrosion rates than sintered magnets. The reduction in corrosion rate is probably due to smaller grain size and diminished amounts of Nd-rich material. Index Terms--Corrosion, die upset, hot pressing, potentiodynamic polarization, sintered.

The phase transformations and magnetic properties of rare earth lean and boron rich [([Nd.sub.0.95][La.sub.0.05]).sub.x][Fe.sub.bal.][M.sub.2][B.sub.10.5], where x = 9.5 or 11 and M = Cr, Ti, Nb, V, Mo, Zr, Hf, Ta, Mn or W, melt spun ribbons have been investigated. Two magnetic phases, namely [Alpha]-Fe and [R.sub.2][Fe.sub.14]B, were found in ribbons studied. A third magnetic phase, the [R.sub.2][Fe.sub.23][B.sub.3], was also detected in [([Nd.sub.0.95][La.sub.0.05]).sub.9.5][Fe.sub.78][M.sub.2][B.sub.10.5] (M = Mo and Mn). Remanence ([B.sub.r]) and coercivity ([sub.i][H.sub.c]) values in the range of 8.0 to 9.1 kG and 9.5 to 18.9 kOe, respectively, have been achieved in nanocomposites with merely two magnetic phases. Among compositions studied, the Ti and W-substitutions were found to be most effective in increasing the [B.sub.r] and [sub.i][H.sub.c], respectively. For a fixed refractory metal substitution, namely, M = Cr, Ti or Nb, an increase in the total rare earth concentration resulted in nanocomposites of small grain sizes and a high volume fraction of the [R.sub.2][Fe.sub.14]B phase. The combination of fine grain size and high volume fraction of [R.sub.2][Fe.sub.14]B phase led to an increase in the and maximum energy product, [(BH).sub.max], of nanocomposites studied. A Br of 9.1 kG, [sub.i][H.sub.c], of 16.7 kOe and [(BH).sub.max] of 16.8 MGOe have been obtained on [([Nd.sub.0.95][La.sub.0.05]).sub.11][Fe.sub.76.5][Ti.sub.2][B.sub.10.5]. Index terms--Nanocomposites, [Alpha]-Fe/[Nd.sub.2][Fe.sub.14]B, exchange coupling, refractory metals.

Structure and magnetic properties of both melt-spun and hot deformed bulk Sm–Co type nanocomposite magnets have been investigated with various metal additions, including Zr, Cu, and Nb. The Zr and Nb additions play important roles in constraining grain growth, resulting in an increase of coercivity Hc. The Cu addition significantly improves the squareness of BH loops as well as the energy product (BH)max. A typical hot deformed bulk anisotropic nanocomposite SmCo type magnet with Mr(hard)/Mr(easy)∼0.4, Hc∼9 kOe and (BH)max of 13.2 MG Oe was obtained. [ABSTRACT FROM AUTHOR]

Melt-spun alloys of Pr3(Fe0.7Co0.3)27.5Ti1.5, Pr3(Fe0.6Co0.4)27.5Ti1.5, and Pr3(Fe0.5Ga0.1Co0.4)27.5Ti1.5 prepared at linear wheel speeds of 20, 30, and 40 m/s were found to contain nanocrystalline, a mixture of nanocrystalline and amorphous, and mostly amorphous phases, respectively. Grain sizes of <10 nm were observed for the crystalline phases. Annealed alloys showed an increase in grain size to 15–20 nm. The Curie temperature (TC) values observed in melt-spun alloys were lower than those observed in fully crystalline alloys. A reduction of ∼55 °C in TC was observed for the Pr3(Fe0.7Co0.3)27.5Ti1.5 composition compared to ∼15 °C for Pr3(Fe0.6Co0.4)27.5Ti1.5. For the Ga substituted alloy with Co=0.4, a large difference of ∼50 °C in TC was noted. MS values of 41 and 35 emu/g were observed in alloys with Co=0.4 and Ga=0.1, and Co=0.4, respectively, at room temperature. Ga substitution increased the anisotropy field value, HA, but lowered the intrinsic coercivity value, Hci. In the alloys with Co=0.4 and Ga=0.1, and Co=0.4, spin reorientation transitions (TSR) were observed at 220 and 140 K respectively. The low values of Hci observed in melt-spun ribbons are attributed to large amounts of a soft α-Fe phase. [ABSTRACT FROM AUTHOR]

Fully dense anisotropic nanocomposite Sm(Co0.58Fe0.31Zr0.05Cu0.04B0.02)z (z=7.5-12) magnets have been synthesized via rapid hot pressing and hot deformation processes. The highest (BH)max ∼10.6 MGOe was observed for a magnet with z=10. X-ray diffraction and M-H measurements indicated that the easy magnetization direction of magnets prefers to be in the hot pressing direction. Transmission electron microscopy investigation confirmed that plastic deformation is an important route for forming magnetic anisotropy in the Sm-Co-type nanocomposite magnets. Some stripe and/or platelike patterns have been observed inside the nanograins (50-200 nm), which may present as twins, and stacking faults. The (0001) twins have been observed in the 2:17R phase. [ABSTRACT FROM AUTHOR]

Alloys with nominal compositions of Sm(Co[SUB1-x]Zr[SUBx])[SUBy] (x=0.03- 0.05, y=12- 15) were synthesized by arc melting and characterized in the temperature range of 10-1473 K and with a magnetic field up to 5 T. Near-single-phase materials with Th[SUB2]Ni[SUB17] structure were formed in the as-cast alloys with x = 0.05. Similar to Ti, Zr also stabilizes the Th[SUB2]Ni[SUB17] structure. Hard magnetic properties with T[SUBc]∼ 1142- 1179 K, M[SUBs] ∼ 110- 123 emu/g, and H[SUBa]∼ 63- 86 kOe at 300 K have been observed. An alloy with a nominal composition of Sm(Co[SUB0.75]Fe[SUB0.1]Zr[SUB0.05]Cu[SUB0.08]Ga[SUB0.01]B[SUB0.01])[SUB1 2] (as also prepared by melt spinning. The melt spun materials were nanostructured in nature and magnetically hard in the as-spun states. H[SUBci] ∼ 10 kOe, B[SUBs] ∼ 9.5 kG, and H[SUBci] ∼ 27 kOe, B[SUBs] ∼ 9.8 kG were obtained at 300 and 10 K, respectively. The effects of the heat treatment conditions on magnetic properties of both alloys and ribbon will be also discussed. [ABSTRACT FROM AUTHOR]

There has been continued technological and research interest in Nd[sub 2]Fe[sub 14]B-based compounds due to their excellent intrinsic magnetic properties [(BH)[sup *, sub max]∼64 MGOe,H[sub a]∼73 kOe]. It is found that Ti and Zr substitution in Nd[sub 2]Fe[sub l4]B leaves its magnetic properties largely unaffected. We have carried out neutron diffraction studies on Zr and Ti substituted 2:14:1 compounds. Three specimens of melt spun alloys of compositions (Nd[sub 0.75]Pr[sub 0.25])[sub 12]Fe[sub 80]B[sub 8], (Nd[sub 0.75]Pr[sub 0.25])[sub 8.4]Fe[sub 79.7]Ti[sub 4.7]B[sub 7.2] and (Nd[sub 0.75]Pr[sub 0.25])[sub 9.2]Fe[sub 79.2]Ti[sub 2]Zr[sub 2.2]B[sub 7.4] were studied. Rietveld refinements reveal that the 4f site is equally occupied by Nd and Pr while the 4g site is occupied only by Nd. In the Ti-containing sample, the lattice expands and Ti is found on the j[sub l], j[sub 2] sites normally occupied by Fe, (4% and 8%, respectively). This accounts for about 30% of the added Ti. In the third sample, the lattice contracts, which could occur only if Zr replaces the larger rare-earth atoms. However, due to the possibility of four different species occupying the 4f site (i.e., Nd, Pr, Ti, and Zr), it is not possible to determine their relative concentrations from neutron diffraction data alone. The balance of Ti and Zr in this sample must be locked in the grain boundaries. Despite peak broadening associated with the fine grain structure, robust refinements were achieved. [ABSTRACT FROM AUTHOR]

The effect of Zr substitution for rare earth on the microstructure and hard magnetic properties of melt-spun composition of (Nd[sub 0.75]Pr[sub 0.25])[sub 12.5-χ]Zr[sub χ]Fe[sub 82]B[sub 5.5] (x = 0-3) has been investigated. It has been found that the coercivity decreases monotonically with the increasing Zr content, from 12.0 kOe at χ = 0 to 10.1 kOe with χ = 3. Unlike the coercivity, the remanence first increased with Zr substitution, from 8.65 up to 8.93 kG at χ = 2, and then decreased with further Zr substitution. The energy product behaved similarly, increasing from 15.7 MGOe to a maximum of 16.5 MGOe at χ = 2. X-ray diffraction (XRD), transmission electron microscope (TEM), and thermogravimetric analyzer studies have shown that all the samples were primarily composed of the single R[sub 2]Fe[sub 14]B phase. No additional phase was observed with Zr substitution. The lattice constants and the Curie temperature of the 2:14:1 phase were found to decrease monotonically with increasing Zr content, suggesting that all the Zr is situated into the 2:14:1 matrix, occupying the rare earth sites. TEM and XRD studies also revealed a significant grain size reduction with Zr substitution. The average grain size was reduced from approximately 40 nm in Zr-free samples to about 20 nm in samples with χ = 2. The observed change in magnetic properties with Zr substitution is explained by the grain size reduction. [ABSTRACT FROM AUTHOR]

The magnetic properties and phase evolution of boron enriched Nd[sub χ]Fe[sub bal].TiCB[sub 10.5] (χ = 9, 9.5, 10, and 11) melt spun ribbons have been investigated. For χ = 9, 9.5, and 10, the main phases in the ribbons are Nd[sub 2]Fesub 14]B, Fe[sub 3]B, and a dilute α-Fe. For χ = 11, the Fe[sub 3]B phase is suppressed and only Nd[sub 2]Fe[sub 14]B and α-Fe were detected. An increase of rare earth content, from χ = 9 to χ = 10, was found to improve not only the intrinsic coercivity (iH[sub c]) but also the remanence (B[sub r]). The improvement in B[sub r] may be ascribed to the grain refinement as evidenced by transmission electron microscopy. A B [sub r] = 9.2 kG, [sub i]H[sub c] = 12.1 kOe, and (BH)[sub max] = 16.2 MGOe were obtained on Nd10Fe[sub bal].TiCB[sub 10.5] alloy ribbons quenched at 20 m/s followed with a 675 °C annealing for 10 min. Meanwhile, with an increase in the annealing temperature, the coercivity of the above alloy ribbons could be reduced to 9.8 kOe without sacrificing its B, and (BH)[sub max]. [ABSTRACT FROM AUTHOR]

Polycrystalline Ga-substituted Pr[sub 3](Fe[sub 1-x]Co[sub x])[sub 27.5]Ti[sub 1.5] (x=0.3,0.4) magnets have been studied for high temperature permanent magnets. Using x-ray diffraction, in addition to the majority 3:29 phase, the presence of the minority 2:17, 1:12 and α-Fe phases was observed. An increase in T[sub C] was observed with increasing Co content. A T[sub C] as high as 572 °C was observed for x=0.4. Magnetic measurements at room temperature showed an increase in the anisotropy field H[sub A] with increasing Co and Ga concentration, while the coercivity decreased. Scanning electron microscopy and energy dispersive x-ray analysis measurements indicated the 3:29 phase as the majority phase. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Alloys with the composition RCo[sub 7-x]Zr[sub x] (R=Y, Gd, Nd, or Ho, x=0–0.8) were synthesized and characterized in the temperature range from 10 to 1273 K and in fields up to 5 T. As with the R=Sm, Pr, or Er systems studied earlier in our laboratory, the effects of Zr doping on the stability of TbCu[sub 7] structure phase and changes in the magnetocrystalline anisotropy H[sub A] are observed in the systems in which the rare earth is Y, Gd, Nd, or Ho. Nearly single phase TbCu[sub 7] structure materials were formed in the as-cast alloys when x=0.1 and 0.2. In the case of R=Y or Gd, a large increase in H[sub A] (which is mainly contributed by Co sublattice) by Zr doping was observed. For R=Y, H[sub A] increases from 18 kOe for x=0 to 74 kOe for x=0.2 at 300 K and from 20 kOe for x=0 to 82 kOe for x=0.2 at 10 K. For R=Gd, H[sub A] increases from 35 kOe for x=0 to 140 kOe for x=0.2 at 300 K and to 182 kOe for x=0.2 at 10 K. In the case of R=Ho and Nd, the R-sublattice favors a planar anisotropy at room temperature, presumably due to the negative second order Stevens’ coefficient. For R=Ho, the anisotropy changes from planar for x=0 to axial with H[sub A]∼60–70 kOe at 300 K when x=0.1 and 0.2. For R=Nd, H[sub A] is dominated by R sublattice which results in a planar anisotropy. Other magnetic properties such as magnetization, Curie temperature, and spin reorientation temperature for these alloys are presented. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Discusses a study which stated that the combination of chemical composition and microstructure of cast alloy has been found to be critical to the performance of NdFeB sintered magnets. Reason for developing a two-step method; Result of the reduction in the amount of neodymium-rich grain boundary phase; Area in which NdFeB-type permanent magnets are used.

Investigates the effects of average grain size on the magnetic properties and corrosion resistance of neodymium-iron--boron sintered magnets. Details on the experiment; Relationships of the bulk corrosion rate and the magnetic properties of finished magnets; Optical micrography of magnets made from precursor alloy powders.

Presents a study that investigated the temperature-dependent magnetic properties of nine NdFeB sintered magnets with various cobalt (Co)-niobium, Co-vanadium, or Co-molybdenum additions which were measured up to 175°celsius using both closed-loop and open-circuit methods. Factors that affect the irreversible loss of induction; Details on the intrinsic coercivity; Discussion on magnet composition found to exhibit an outstanding thermal stability.

Presents information on a study which examined the spin-reorientation phenomena in rare earth alloys systems over a given temperature range using susceptibility measurement. Analysis of the rare earth alloy systems; Methodology of the study; Results and discussion.

Investigates microstructures of cast neodymium-iron-boron ingots. Cause of segregation of dendritic iron; Correlation of the magnetic properties of final magnets and the microstructures; Reason for the absence of dendritic iron.

Focuses on spin-reorientation phenomenon in praseodymium (Pr)-cobalt (Co) compound. Use of Hamiltonian consisting of the crystal-field term and exchange interaction; Result of the competition between the off-axial anisotropy of Pr sublattice and the axial anisotropy of Co sublattice; Magnetocrystalline superposition constants of the compound.

Presents a study which investigated the structural and magnetic properties of praseodymium[sub2]cobalt[sub7-x]iron[subx]boron[sub3]. Experimental details; Results and discussion; Conclusion.

Presents an overview of a study on the spin-reorientation transitions in pseudobinary compounds as determined by alternating current susceptibility measurements. Spin-orientation temperature; Causes of the decrease in temperature; Analysis of magnetic anisotropy phase diagrams.

Presents a study which examined the effect of crystal alignment on the remanence of sintered neodymium-iron-boron magnets. Comparison of remanence with the theoretical calculation based on the Stoner-Wohlfarth model; Experimental details; Results and discussion.

Presents information on a study which investigated the structural and magnetic properties of Nd[sub2]Co[7-x]Fe[subx]B[sub3] for x=0 to 7. Thermomagnetic analyses performed; Maintenance of the hexagonal symmetry; Illustration of the x-ray diffraction pattern of the compound.

Presents a study which examined the microstructure and magnetic properties of yttrium titanium iron[sub11-x]cobalt[subx] and gadolinium titanium iron[sub11-x]cobalt[subx] systems. Experimental details; Results and discussion; Conclusion.

Presents a study that examined spin deterioration phenomenon in neodymium[sub0.5] erbium[sub1.5] iron[sub14-x] aluminum and cobalt[subx] boron as determined by alternating current susceptibility measurements. Details of the experiment; Results and discussion; Conclusion.

Presents information on a study which examined the microstructure of conventionally case Sm(Co[subhal]Fe[sub0.28Cu[subv]Zr[sub0.022] alloys, by optical microscopy and scanning electron microscope with energy dispersed analytical x-ray in the as-cast state. Composition of the alloy series; Optical micrographs of cast ingots; Description of the samarium- and copper-rich grain boundary phase found in alloys.

Presents a study which fabricated Sm[sub2]Fe[sub17] nitride magnets with low melting point metal binders, zinc, tin or indium, using a powder metallurgical process. Materials and methods used; Results and discussion.

We report a continuous wave (CW) and passive Q-switching operation of a Nd:YAG ceramic laser at 1112 nm by using a concave-plane cavity, which has not been found in the previous literature but of great potential. A maximum output power of 1.36 W was obtained at the pumped power of 11.30 W, corresponding to an optical-to-optical efficiency of 12.0% and a slope efficiency of 15.1%. We inserted the Cr4+:YAG saturable absorber with initial transmission of 80.0% into the cavity and the maximum average output power of 713 mW was realized at the pumped power of 11.20 W, the minimum pulse width is 8 ns with the pulse repetition rate of 10.8 KHz, corresponding to the signal pulse energy and the maximum peak power of 66 μJ and 8.25 kW, respectively. These unique strengths of Nd:YAG ceramic laser at 1112 nm thereby open up new opportunities in light source to integrated optical processing. [ABSTRACT FROM AUTHOR]