Lower power loss and higher flux replacements for traditional ferrite based inductors are required with the continuous shrinking of inductor footprint. One candidate replacement strategy is based on the amorphous CoFeBSi soft-magnetic systems in their metallic glasses forms. This is enabled by significant advancements by the power semiconductor industry of faster and efficient power switches, as the requirements for smaller and more efficient magnetic components becomes more imminent, at these higher frequencies. 2 One of the main difficulties in the miniaturization of power conversion circuits is the reduction in size of energy storage and transfer devices, i.e. inductors and transform- ers. 3 These essential components normally occupy a significant fraction of volume ( ∼ 30%) of the power converters. Inductors and transformers typically use a magnetic core to store the energy. A key roadblock in advancing the passive component technology is the low flux density provided
A relatively new technology which is widely used in Japan and in a smaller scale in North America uses amorphous cores, as illustrated in Figure 4. Using amorphous metal core, no-load losses can be reduced by additional 70 to 80 % compared to the best silicon steel reaching levels of 0.065 W/kg (Irrek, Topalis, Targosz, Rialhe, & Endesa 2008). Amorphousalloys do not have a crystal structure unlike ordinary alloys and amorphous metal cores are suitable for power networks with highfrequency harmonics, which occur due to dramatic increase in the use of power electronics and lead to increased transformer core losses, especially in distribution transformers that use conventional steel core materials. It has low loss performance under higher frequencies (Targosz & Topalis, 2008). Comparison of amorphous versus conventional cores is given in the Table 3.
Fabrication of nanocrystalline soft magnetic materials has been accomplished by standard rapid solidification tech- niques (e.g. melt spinning) followed by isothermal anneal- ing above the primary crystallization temperature of the al- loy. In general, the formation of nanocrystalline soft mag- nets by melt spinning is limited to compositions near deep eutectics where an amorphous precursor can be formed. Early transition metal (i.e. Zr, Hf, Nb), and metalloid elements (i.e. B, Si, P) have been employed to produce the deep eutectics in ferromagnetic transition metal systems. After melt spin- ning, optimal crystallization of the as-spun ribbons produces a two-phase microstructure with FCC, BCC and/or intermetal- lic nanocrystallites surrounded by a residual amorphous ma- trix. This two-phase microstructure is important because each phase improves the highfrequency properties of the material. Specifically, the nanocrystallites provide high magnetization that allows for reduced sizes of the inductors and the residual amorphous phase provides high resistivity that dampens the eddy currents.
those glassy alloy bipolar plates was lower than that with carbon graphite bipolar plates. This may be because it was diﬃcult to mount such a thin bipolar plate on the carbon frame without gas leak and also without the increase in the contact resistance. In this work, metallic glass coated bipolar plates were produced in a bulk form and it was easy to mount those bipolar plates in a single fuel cell. At any rate, we have succeeded to produce the metallic glassy alloy-coated bipolar plates having high corrosion resistance and the single cell employing those metallic glassy alloy-coated bipolar plates shows good I-V performance as well as that with carbon graphite bipolar plates.
It has been recently demonstrated that some of bulk amorphousalloys, e.g., Zr- and Cu-base alloys, can be continuously fabricated in sheet form by twin-roll strip casting which can produce ﬂat rolled products directly from melt in a single step. 13–16) As compared to Zr- and Cu- base alloys, Fe-base alloys generally have high liquidus temper- ature ( 550 K and 380 K higher than those of Zr- and Cu- base alloys, respectively) and the diﬀerence between liquidus temperature and glass transition temperature (T g ) is large
relationship among magnetostriction, crystal structure and magnetic anisotropy for Fe-Ga single crystal and polycrystal- line alloys. 1–3) It is known that the A2 single crystal in Fe-Ga binary system has weak magnetic anisotropies, 2) and exhibits the positive high magnetostriction of 3=2 <100> 350
simultaneously onto the surface of carbonyl iron powder, yielding a concentration of phosphorous between 2.0- 6.0wt.%; as per US Patent 5963771 claims the possibility of fabrication of intricate parts with various combination of magnetic properties. Further, it is said that the parts suitable for utilization in alternating magnetic fields at different frequencies may be easily fabricated by controlling the concentration of P in ternary Fe-Ni-P composites . Coating of iron powder particles with phosphorous or phosphate and then over-coating the phosphorus coated iron with the thermoplastic or thermosetting insulating organic material, molding of coated particles under pressure and heat to cause organic material to melt and allow the bonding between the coated iron powder particles, and applying a strong magnetic field across the material along a preferred direction of magnetic flux flow during compaction molding; results in orientation of the iron grains in the direction of the magnetic field i.e. the molded composite soft magnetic material with grain alignment, US patent no.5898253 dated April 27, 1999 and US patent no.5693250 dated December 2, 1997 . Coating of the particles of soft magnetic metal sendust (85Fe-10Si-5Al) with a non-magnetic metal oxide (e.g., .alpha-alumina) in a mechano-fusion manner, or heating the particles to form a diffusion layer of .alpha.-alumina thereon, coating the coated particles with a high resistance soft magnetic substance (e.g. ferrite), and sintering the double coated particles under pressure as by hot pressing or plasma activated sintering results in the production of soft magnetic material. It exhibits high saturation induction, magnetic permeability, and electric resistivity. The non-magnetic metal oxide intervening between the soft magnetic metal and the high
can be calculated from slopes of the plot of ln½ lnð1 xÞ against ln (covering heating rates of 5, 7.5, 10, 20, and 40 min/K), where the x is the relative crystallinity of the ﬁrst fully crystallization reaction, one example is shown in Fig. 3(a). It is found that n 0 exhibits a decreasing trend with increasing temperature (Fig. 3(b)), from the initial over 4 to nearly 2. The means that the nano-crystalline particles would grow from the initial clean amorphous matrix (with minimum nuclei) in a 3D manner at lower temperatures and would grow in a more rapid and disordered 2D or even 1D way at higher temperatures.
To date, much of the research on improving strength and ductility by reducing SFE has focused on binary and ternary Cu-based alloys and multi-component Mg-based alloys. The main reason for this attention is the well-established ability of some alloying elements to form solid solutions in Cu and Mg and significantly lower the stacking fault energy. While some impressive results have been obtained, the strength of most of the alloys is still relatively low. Cu–10wt%Zn with a grain size of 110 nm retains elongation to failure of greater than 6%, but the yield strength is improved to only ~600 MPa . An alternative, and possibly more desirable system, would be one that, like the Cu-based alloys, can form an fcc solid solution over a wide range of compositions and has low SFE but also retains high intrinsic strength.
Less expensive and capable of higher flux densities are so called thin SiFe alloys (0.1mm to 0.27mm thickness). They have around 3% silicon content and thus a lower electrical resistivity. However, the small lamination thickness still keeps the eddy current losses low at the cost of larger core assembly efforts and thus production costs, compared to thicker non-oriented SiFe laminations. The vast majority of industrial machines are manufactured with standard non-oriented SiFe laminations, having silicon contents of 0.5% to 3%. Sheet thicknesses of 0.5mm or thicker keep the manufacturing costs low and give, in most cases, a good compromise between efficiency and costs for general industrial machines. Non-oriented SiFe is usually not annealed for industrial electrical machines due to the low performance increase with regard to the annealing costs and increased manufacturing time .
Conductors are a class of material that do not experience an increase in the amount of charge carriers when they are exposed to light. Semiconductors can display two different types of photoactivity: photoconductivity and the photovoltaic effect. Photoconductivity is when the amount of charge carriers (electrons and holes) increases when the semiconductor is exposed to light, but the charge carriers can move in both directions and be collected at either electrode, which results in no power being generated. The photovoltaic effect is similar to photoconductivity but the charge carriers can not move in both directions, which results in the electrons being collected at one electrode and the holes being collected at the other, and power is generated. The latter is the effect necessary for a working solar cell. The simplest design for a Schottky cell is a semiconductor layer sandwiched between glass (usually ITO or FTO) and a metal electrode that has a different work function than the glass. This difference promotes charge separation at the interfaces. This is called a Schottky device since there is no p-n junction and the carriers are separated at the interfaces between the semiconductor and the contacts. The active layer in our design is CNx which is responsible for producing the photoinduced charge. If the charge separation is successful, the excited electron will be extracted at the metal electrode which acts as the cathode, and the hole will be extracted at the ITO/FTO glass, which is the anode. It is important for CNx to have an absorption spectra that has its maximum in the UV-VIS range to be applicable in a solar cell. In addition, CNx must have only one type of photogenerated charge carrier, either electrons or holes, to produce the photocurrent. If both types are created recombination will occur and the cell will not show promising photovoltaic properties. We expected CNx to be an n-type semiconductor as described above. Therefore, the photocurrent would be generated by the flux of photogenerated holes, which act as the minority carrier in this case. Finally, the charge carrier mobility must be high within the CNx film to prevent recombination before the carriers can be collected at the electrodes.
Mechanical alloying (MA) is another alternative method to rapid cooling to produce amorphousalloys. Since MA is a solid state process, high cooling rates are not required and the alloy composition can be easily altered .To understand the thermal stability of these Al based alloys, GFA is essential. The simplest and most widely used criteria for GFA are ∆T  and the fragility index m originally introduced by Angell [9, 10]. Fragility index m is also studied by the T g
Despite the extremely low growth temperatures, we observed polycrystalline growth for all undoped GaN layers by in situ RHEED during and after the growth. This was also confirmed by ex situ XRD studies, showing diffraction peaks normally associated with polycrystalline GaN with a strong preferential c-axis orientation along the growth direction. Pol- ycrystalline growth was observed for the layers grown under both Ga-rich and N-rich conditions. However, even a small amount (beam equivalent pressure, BEP above 10 8 Torr) of Sb suppressed the crystallinity and the layers became amor- phous as can be seen by in situ RHEED and ex situ XRD. Such behavior is very similar to the influence of As and Bi flux on the growth of GaN layers, that we have observed pre- viously in epitaxy of GaN 1x As x and GaN 1x Bi x alloys by
(1) The lattice parameter “a” for x = 0.00 is 2.856 Å which is consistent with a bcc Fe structure  and the value of “a” increases slightly with increasing Mn content (as shown in Table 1). Increasing lattice parameter and hence the unit cell volume with Mn content is due to the volume expansion effect, as Mn has the larger ionic ra- dius (0.89 Å) compared to Fe (0.74 Å) . Linear in- creasing of the lattice parameter of these alloys with Mn content suggests a simple dilution process. Annealing Table 1. Lattice parameters, crystallite size and volume of x = 0.00, 0.10, 0.20 and 0.30 at different temperature.
increases rapidly with decreasing temperature. Roig et al. 1) have also reported similar behavior in an amorphous Fe–Ni– P alloy. They suggest that it is inappropriate to regard the very large temperature variation of the characteristic time as a simple activated process. The steep increase of the time- scaling factor with decreasing temperature means slowing down of the crystallization process. This is characteristic of relaxation phenomena in the amorphous state. Several empirical expressions so far have been proposed to describe the temperature dependence of relaxation processes in amorphous state. Among them we used the Williams- Landel-Ferry (WLF) formula 6) to describe the temperature dependence of the scaling factor because the WLF formula involves only two parameters as shown in the equation,
Bulk Metallic Glasses (BMGs) have been drawing increasing attention in recent years due to their scientific and engineering significance. A great deal of effort in this area has been devoted to developing BMGs in different alloy systems. BMGs based on certain late transition metals (e.g., Fe, Co, Ni, Cu) have many potential advantages over those based on early transition metals. These advantages include even higher strength and elastic modulii, and lower materials cost, to name but a few that are highly preferable for a broad application of BMGs as engineering materials. Nevertheless, these ordinary-late- transition-metal-based BMGs generally have quite limited glass-forming ability (GFA). In particular, for the Ni-based and Cu-based alloys reported prior to this research, the maximum casting thickness allowed to retain their amorphous structures is only ~2 mm (or lower) and ~5 mm (or lower), respectively.
structural units (molecules), in which the atomic diﬀusion is not so signiﬁcant. In the crystallization of the metallic glasses, however, atomic diﬀusion plays a signiﬁcant role as it was shown in the present study. This characterizes the glass transition and crystallization in metallic glasses. Conse- quently, the thermal stability of the metallic glasses may depend on making the crystallization diﬃcult by reducing the mobile atoms or making a signiﬁcant diﬀerence between amorphous and crystallized structures.