Ferrite, 1.28

On heating the dried precursor up to 600 C/3h, well-crystallized y-Fe203 was obtained as an intermediate. At 650 C, the first signs of the ferrite were observed. Pure phase SrFei20i9 was obtained at 900 C/3h. The particle size (78 nm after calcination at 900 C) was much larger than expected in microemulsion synthesis. 

O Connor et al [308] used two reverse microemulsions containing AOT and isooctane, as also an aqueous solution of FeS04/MS04(M = Mn or Co) or NH4OH, and mixed them to obtain ferrites and other related phases. The average particle size was 10 nm. 

In a two-microemulsion (W/O) method used by Pillai and Shah [311], the basic system was CTAB/n-octane/n-butanol. The two microemulsions contained as the water phase aqueous solutions of Co(N03)2 + Fe(N03)3 or ammonia solution (10 % higher concentration than the stoichiometric requirement). The two microemulsions were mixed under stirring to obtain a (Co,Fe) hydroxide. The product was centrifuged, washed with a 1 1 mix of methanol and chloroform, then pure methanol, and calcined at 600 C/5h to convert the hydroxide to phase-pure CoFe204. The agglomerate size was less than 50 nm. 

Alkali aluminate crystals clearly entrap alite and some belite, thus the aluminate crystals form later than some of the silicates, but this is not a new conclusion. Alkali aluminate rarely includes crystals of ferrite and appears to interrupt the continuity of ferrite, suggesting that the alkali aluminate crystallized first. 

Ono (1995) stated that dendritic non-cubic G3A crystallized first, in accord with a phase diagram, when laboratory reagents were burned under conditions of rapid heating and cooling. Ordinary clinker, containing an excess of G3S, crystallized in the following sequence G3S, G2S (small amount), G AF, C3A-GgA2F. 

Reducing conditions and their microscopical effects have received much attention recently and, because the effects largely involve iron and ferrite, the subject is discussed here. 

With regard to the observation of brown -centered clinkers, Pennell (1986) stated, We have observed that brown-cored clinker results from burning in a CO2 

Ichikawa, Imai, and Komukai (1992) showed that oxidation in ferrite produced a color change from yellowish brown to blackish gray during substitution of magnesium for aluminum and ferric iron. Increases in silica/magnesia ratio in ferrite were said to reduce oxygen vacancies and therefore prevent color change. 

---

Two types of materials are studied in the CIAPES programme ferritic steel and stainless steel. A database for vessels monitored by acoustic emission has been builded to collect the results of all the tests carried out in laboratory and in situ. 

Fig. 2 Single slice of porosity in ferritic weld (a) original image, (b) image recontruction without noise, (c) image reconstruction with noise.

Simulations of the adaptive reconstruction have been performed for a single slice of a porosity in ferritic weld as shown in Fig. 2a [11]. The image matrix has the dimensions 230x120 pixels. The number of beams in each projection is M=131. The total number of projections K was chosen to be 50. For the projections the usual CT setup was used restricted to angels between 0° and 180° with the uniform step size of about 3.7°. The diagonal form of the quadratic criteria F(a,a) and f(a,a) were used for the reconstruction algorithms (5) and (6). 

This correction function was calculated for different kinds of excitation coils, like circular coils without ferrite core, spiral coils, double-D coils and a sheet inducer. For this purpose the eddy current density was determined for frequencies between 10 and 1000 Hz and for depths between 0 and 30 mm. 

The sensitivity to defects and other control parameters can be improved by optimizing the choice of the probe. It appears, after study of different types of probes (ferritic, wild steel, insulator) with different geometries (dish, conical,. ..), necessary to underline that the success of a feasibility research, largely depends on a suitable definition of measure collectors, so that they are adapted to the considered problem. 

By increasing the probe diameter, we bring down tlie impedance point along the impedance curve with the same way as the electrical frequency or conductivity. We will describe only one type of probes, namely, the probe with ferritic circular section that we could qualify as punctual with an optimal sensibility. In order to satisfy these conditions, tests will be made to confirm these results by ... 

As a conclusion to this experiment and in order to optimize the sensibility of tire probe it is necessary that the coil shall be on the edge of the ferrite. The results obtained confirm the probe stability. 

Figure 3 Ferritic probe with a cross section.

Figure 4 Ferritic probe with a conic section.

Figure 7 Normalized impedance diagram (ferritic conic probe).

Figure 3 Picture of the inspected part (plasma-sprayed chromium cast iron on ferritic steel). The surface presents several cracks I to 15 pm wide.

BE-7500 A novel creep resistant tin strengthened 9 12 CR ferritic steel for advanced steam Dower olant. Mr.G. Shrimpton AEA Technology... 

Waveguides are coimnonly used to transmit microwaves from the source to the resonator and subsequently to the receiver. For not-too-high-frequency radiation (<10 GHz) low-loss MW transmission can also be achieved usmg strip-lines and coaxial cables. At the output of a klystron an isolator is often used to prevent back-reflected microwaves to perturb the on-resonant klystron mode. An isolator is a microwave-ferrite device that pemiits the transmission of microwaves in one direction and strongly attenuates their propagation in the other direction. The prmciple of this device involves the Faraday effect, that is, the rotation of the polarization... 

Feltin N and Pileni M P 1997 New teohnique for synthesizing iron ferrite magnetio nanosized partioles Langmuir "[Z 3927... 

Magnesias Magnesia-spin el Magnesil Magnesio ferrite Magnesite... 

---