Spinel ferrites particles

Mollard, P. Germi, P. Rousset, A. (1977) Surface effects of saturation magnetization of fine spinel ferrite particles. Physica 86-88 B-rC 1393-1394... 

Determine the spray dried particle diameter resulting from the Rayleigh breakup of a jet 1 nun in diameter operating on a 0.001 molar doped iron nitrate solution of Ni—Al-Ga spinel ferrite (i.e., MFe204 M = Nio.5-Alo 3—Gao.2). Assume that the dr3dng conditions are sufficient to evaporate the water but not thermally decompose the hydrated metal nitrates. 

When the particle size is reduced to the nanolevel, contributions from disordering, vacancies, lowering of symmetry at surface, and so on also contribute to considerably modifying the trends seen in bulk. It has been generally observed that the accepted site preferences of cations established in bulk spinel ferrites need not necessarily hold in their nanosized counterparts. For example, the presence of Zn at the octahedral B site is nearly never realized in bulk spinel ferrites, whereas there are several reports wherein Zn is present at the B site in nanosized samples [10]. 

In the present study, spinel ferrites nanocrystals with different structures were prepared from an aqueous solution containing metal nitrates, poly (vinyl pyrrolidon), and deionized water using a relatively low temperature thermal treatment method, followed by grinding and calcinations. No other chemicals were added to the solution. This method is environmentally friendly in that it neither uses nor produces toxic substances, and it offers the advantages of simplicity, low cost, and low reaction temperatures. The textural and morphological characteristics of the spinel ferrites nanocrystals we prepared were studied with various techniques to determine the influence of calcination temperature on the crystallization, morphology, and particle size distribution of the nanocrystals and to explore other parameters of interest. 

As with pfa low in CaO, fine, spherical particles consisting largely of glass predominate, but the glasses are higher in CaO and the assemblages of crystalline phases are different. In a study of 26 ashes from the western USA. McCarthy el al. (M84) found that quartz, lime, periclase, anhydrite and a ferrite spinel were ubiquitous or nearly so. Other crystalline phases present in some cases or in minor amounts included C3A, merwinite, alkali sulphates, melilites, mullite, sodalite and possibly others. Due to the presence of... 

In addition to the above reported synthesis of ferrites our search has revealed that aluminates [119], nickelates [120], and manganates [121], have also been prepared by the sonochemical method. Nanosized nickel aluminate spinel particles have been synthesized [119] with the aid of ultrasound radiation by a precursor approach. Sonicating an aqueous solution of nickel nitrate, aluminum nitrate, and urea yields a precursor which, on heating at 950 °C for 14 h yields nanosized N1A1204 particles with a size of ca. 13 nm and with a surface area of about 108 m g-i. 

A magnetic material which is easy to magnetise (and demagnetise) is known as a soft material, and permanent magnets are referred to as hard magnets. The boundary in coercive field value for these two cases is somewhere between 1 kA/m (soft if // < 1 kA/m) and 10 kA/m (hard for k 10 kA/m). In ferrites, Mn-Zn spinels have the lowest values (//< 16 A/m) and BaFe 120,9 particles the highest 420 kA/m, Mee... 

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