Mineralogical composition for the bulk samples powder were determined using X-ray diffraction (Philips X-ray diffraction equipment model PW/171) with monochromator, Cu k -á radiation (1.542 =גÅ) at 40 kV and 35 mA at X-ray diffraction lab, Physics Department, Assiut Faculty of Science, Egypt. The patterns were recorded from 4 to 90°2è. In addition, reflection peaks were between 4 and 902Ѳ, of 0.06◦/min speed. Corresponding spacing (d,Å) and the relative intensities (I/I°) were also obtained [Moore and Reynolds,1997].
Table 3 shows the magnetic and surface area characteristic of bentonite and bentonite-Fe3O4 composites. Magnetic measurements of bentonite and bentonite-Fe3O4 composites at 293 K. Bentonite particles show no value of saturation magnetization. The process of coating Fe3O4 which has a higher value of saturation magnetization onto bentonite surface caused composites having magnetic properties. The saturation magnetization increased with an increase of Fe3O4 content. Study of silica coated magnetite particles (Fe3O4/SiO2) indicated that saturation magnetization is lower than Fe3O4 . The surface area of composite decreased with increasing content of Fe3O4, because most of the pores in the bentonite blocking with Fe3O4. Futhermore, BET surface
Co–Cd ferrite is a mixed spinel, in which A-sites are occupied by Cd2+ and Fe3+ ions and B-sites are occupied by Co2+ and Fe3+ ions in the cubic spinel lattice . Narendra et al. reported on cadmium substituted CoFe2O4 nanoparticles exhibits the super paramagnetic behavior . Also, S.V. P. Vattikuti et al. reported on cadmium substituted CoFe2O4 nanoparticles and concluded that the synthesized materials are promising candidate to use in development of actuators and high-density data storage device applications
As magnetite is well-researched, multiple factors influence the formation of iron oxide magnetosomes have been identified. The most important factors are the presence of oxygen, and substrates in the form of nitrogen oxides (Bazylinski 2004). MORE
ABSTRACT. Curie’s law, first proposed by a French physicist, Pierre Curie, states that the magnetization of paramagnetic materials varies directly with the applied magnetic field and inversely with the absolute temperature of the substance. This paper presents prerequisite definitions and a detailed explanation of Curie’s law along with a brief historical account.
Romanenko et al. identified a correlation between large LAM values and the “hot” regions of cavities [10, 11]. The temperature increase from local heating increases the fraction of normally conducting electrons, so any potential sources for the heating need to be minimized. A proposed explanation for the local heating is that dislocations vibrate with passing phonons and disperse them, thus slow down thermal conduction . Dislocations can also affect cavity performance if they pin magnetic flux centers, resulting in irreversibility of magnetization curves . These adverse effects of dislocations necessitate a heat treatment for recovery or recrystallization after deep drawing.
Generically, cast iron are a class of iron-carbon alloys with carbon contents above 2.14 wt%; in practice, however, most cast irons contain between 3.0 and 4.5 wt% carbon and, in addition, other alloying elements. The most common types of cast iron are gray, nodular, white, malleable and compact graphite. The silicon and carbon content in Gray Cast Iron vary between 1.0 and 3.0 wt% and 2.5 and 4.0 wt%, respectively. In Gary Cast Iron, the graphite exists in from of flakes (similar to corn flakes). It is easily seen in figure 2(a) that those graphite flakes are surrounded by a matrix of α-ferrite and pearlite. Because of these flakes when surface of this cast iron is fractured it takes the
In stark contrast, MCM-41 and UVM-7 show much different magnetic properties after successful incorporation into the silica pores. Notably, the χMT term for both silicas is higher than expected for magnetically isolated Ni8 molecules (such as those in UVM-11) which supports the presence of repeating Ni8 units forming [Ni8]x aggregates. χMT also reaches a maximum at a range of 3-10 K, in contrast to the Tmax = 3 K of the SMM alone where Tmax generally increases with increasing loading amount. This behavior can be rationalized due to magnetic anisotropy and/or antiferromagnetic interactions between aggregates. A proposed mechanism consists of Ni8 SMMs filling the silica pores and consequent aggregation which is mediated by deprotonated silanol groups present on the pores (Fig. 4). In turn [Ni8]x aggregates, joined by Ni-O-Ni bonds interact in a ferromagnetic manner which allows for the Ni8 monomers to undergo magnetic exchange interactions. This mechanism holds up to a point, a 100% loading amount results in packing which imposes a steric strain on the filamentous [Ni8]x and pushes the Ni-O-Ni angle towards a higher value, prompting antiferromagnetic interactions leading to a decrease in magnetic susceptibility.
The M-type hard ferrites with hexagonal crystal structure can be generally represented as (MO.6Fe2O3), where M is divalent metal including Sr, Ba, and Pb or a mixture of these . The direction of magnetization in these materials cannot be changed easily to another axis so that they are referred to as hard . Barium hexaferrite (BaFe12O19) as a famous M-type hard ferrite with a magnetoplumbite structure has relatively high Curie temperature, coercive force and magnetic anisotropy field, along with high chemical stability and corrosion resistivity .
The design of new stainless steel alloys with novel physical properties is vital to the petroleum industry in order to develop technologies which will perform more efficiently at high temperatures and pressures. While stainless steels with the addition of nickel have mechanical and thermal properties which are desirable at high temperatures and pressures, the high cost of nickel is prohibitive towards development of new devices which can be used in harsh conditions, so discovering stainless steel alloys with similar properties with little to no nickel content with be ideal. Ferritic alloys (Fe-Cr) already have some applications in high temperatures in the presence of sulfur, but they generally have poor tensile properties. The addition of
The immersion effect at 6 and 12 month using various ratios of EAFS as illustrated in FTIR spectra Figures (5, 6). The patterns of 6 months [Fig. (5)] show an increased in broadness of T-O-Si band at about 975 cm-1 with EAF slag increase up to 50 % in addition to low wave number shift which depicts vitreous component increase. The increased intensity of the Si–O–(Si, Al) asymmetric band in addition to the shift to higher wave number (from 690 to 779 cm-1) with increased contents of EAFS up to 50 % (A3), suggests aluminosilicate framework modification as compared with solely GGBFS based geopolymers as a consequence of cation substitution in the non-framework sites [Bernal, et al. (2012)]. However, a sharp increase in asymmetric stretching vibration at about 1110 cm-1 corresponding to ettringite [Mollah et al. (1998); Hanna et al. (1995)], upon using 75 % EAFS reflecting the decreased content of the amorphous geopolymer resulting from the increased iron content resulting in lower stability against sulfate attack as reflected from ettringite formation, the increased intensity of carbonate bands at 1430 cm-1 (ν C–O ), and 867 cm-1(δ C–O ) with EAFS as a result of the carbonates in the used raw material which inactive under alkaline activation [Bernal, et al. (2012)].
A simplified brick geometries with two different types of defect arrangements were considered throughout the modelling study, these are: (i) straight sub-surface slot and (ii) inclined sub-surface defect that has zigzag type profile mainly generated to mimic a real crack, but not necessarily identical. The key-way slots and the methane holes in the graphite brick models have been deliberately omitted to reduce the number of elements on the models and the time required obtaining the solutions. As in the graphite model discussed in section 6, the brick geometry was discretised but in this case into twenty sub-domains each having the thickness approximately 4.63mm. The discretisation of the brick geometry is mainly made to allow a control over the mesh density within each sub-domains independently, such that regions closer to the coils contains more denser mesh compared to those away from the coils. But, initial study of the mesh density in this particular models show that having denser mesh around the coil region show negligible effects in the solution except from increasing the computational cost. For this reason the mesh density was kept constant throughout the brick geometry as shown in figure 8.1 (a) and (b). The slots in the models were created using Transition Boundary Condition (TBD) available within the Magnetic-Feld (MF) solver in COMSOL Multiphysics.
X-ray powder diffraction patterns of good quality were obtained for the samples using CuKα radiation of wavelength 1.5406A0 at room temperature. The obtained X-ray diffraction patterns confirmed the formation of a single phase cubic spinel structure for the ferrite samples with a crystallite size ranging from 25-34nm as reported earlier . The X-ray diffraction patterns were fitted using a Rietveld refinement procedure as shown in Fig 2 [17,18]. The fitted patterns were observed for eight peaks indexed by miller indices (220), (311), (222), (400), (422), (511) and (440), evident from the normal XRD patterns as reported earlier . From the Fig 2 it is observed that sharpness in the peak is increased with an observed decrease in the width of the peak, which is the indication of the increase in particle size of the ferrite with the increase in Indium content. From the Fig 2 it is evident that observed patterns were exactly coinciding with the calculated values and the difference is very negligible. In comparison with the normal XRD patterns Rietveld patterns have shown some extra peaks of (331), (531), (422), (620), (533) and (622) which correspond to the second order impurity phase. The intensities of the impurity peaks reflect that the percentage of the impurity is negligible. From the Rietveld refinement patterns of the samples it is clear that the ferrites belong to the space group Fd3m with lattice parameter values ranging from 8.3106A0 to 8.3648A0. The values are in
(1) Previous experimental results indicate that the amount of η-Ni3Al0.5Nb0.5 phase can significantly affect the DFCGR property of AA alloy. The η-Ni3Al0.5Nb0.5 phase mainly plays a role of pinning grain boundary and retarding the intergranular diffusion of oxygen. Thus, the crack growth at grain boundaries can be retarded, and the notch sensitivity of the alloy can be avoided. Therefore, more the η-Ni3Al0.5Nb0.5 phase, the fatigue crack growth rate of the alloy can be reduced favourably. Figure 1 shows that the amount and morphology of η-Ni3Al0.5Nb0.5 phase precipitated from AA alloy with different grain sizes are different under the same thermal treatments. With decreasing grain size, both the grain boundary area of the alloy and the amount of η-Ni3Al0.5Nb0.5 phase increase, and the ability of grain boundary pinning and grain boundary oxygen diffusion retarding are significantly enhanced, thus the fatigue crack growth rate will reduce