Zinc ferrite synthesis

Shock-synthesis experiments were carried out over a range of peak shock pressures and a range of mean-bulk temperatures. The shock conditions are summarized in Fig. 8.1, in which a marker is indicated at each pressure-temperature pair at which an experiment has been conducted with the Sandia shock-recovery system. In each case the driving explosive is indicated, as the initial incident pressure depends upon explosive. It should be observed that pressures were varied from 7.5 to 27 GPa with the use of different fixtures and different driving explosives. Mean-bulk temperatures were varied from 50 to 700 °C with the use of powder compact densities of from 35% to 65% of solid density. In furnace-synthesis experiments, reaction is incipient at about 550 °C. The melt temperatures of zinc oxide and hematite are 1800 and 1.565 °C, respectively. Under high pressure conditions, it is expected that the melt temperatures will substantially Increase. Thus, the shock conditions are not expected to result in reactant melting phenomena, but overlap the furnace synthesis conditions. 

Four different material probes were used to characterize the shock-treated and shock-synthesized products. Of these, magnetization provided the most sensitive measure of yield, while x-ray diffraction provided the most explicit structural data. Mossbauer spectroscopy provided direct critical atomic level data, whereas transmission electron microscopy provided key information on shock-modified, but unreacted reactant mixtures. The results of determinations of product yield and identification of product are summarized in Fig. 8.2. What is shown in the figure is the location of pressure, mean-bulk temperature locations at which synthesis experiments were carried out. Beside each point are the measures of product yield as determined from the three probes. The yields vary from 1% to 75 % depending on the shock conditions. From a structural point of view a surprising result is that the product composition is apparently not changed with various shock conditions. The same product is apparently obtained under all conditions only the yield is changed. 

In spite of careful analysis of the products with the various sophisticated probes, differences in the composition are reported. All measurements indicate a zinc-deficient zinc ferrite, but the indicated zinc concentration varies from 0.2 to 0.9. The EDS measurements are based on direct zinc concentration measurements. Determinations based on magnetization and Mdssbauer spectra are obtained on zinc ferrite synthesized in more conventional processes. 

One of the most interesting results of the zinc ferrite synthesis is the observation that the yield of the product is dependent on the early pressure history. This behavior is shown in Fig. 8.3, which plots the yield versus temperature for baratol explosive loading and for Composition B explosive loading. The difference between these loadings is that the initial pressure pulse amplitude is significantly greater with Composition B. Apparently, the early pressure history has an important conditioning effect for subsequent reactions. 

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In this chapter synthesis of zinc ferrites, intermetallic compounds, and metal-oxides. 

Fig. 8.1. Shock-induced solid state chemical synthesis of a zinc ferrite has been studied over a wide range of temperature and pressure. The figure shows the location of conditions for which the reaction has been studied.

This chapter presents detailed and thorough studies of chemical synthesis in three quite different chemical systems zinc ferrite, intermetallic, and metal oxide. In addition to different reaction types (oxide-oxide, metal-metal, and metal oxide), the systems have quite different heats of reaction. The oxide-oxide system has no heat of reaction, while the intermetallic has a significant, but modest, heat of reaction. The metal oxide system has a very large heat of reaction. The various observations appear to be consistent with the proposed conceptual models involving configuration, activation, mixing, and heating required to describe the mechanisms of shock-induced solid state chemistry. 

Baranchikiv AE, Ivanov VK, Oleinikov NN, Tretyakov DYu (2004) Microstructural evaluation of Fe203 and ZnFe204 during sonochemical synthesis of zinc ferrite. Inorg Mater 40(10) 1091-1094... 

For the synthesis of zinc ferrite (ZnFe204) of stoichiometric composition CFD and HPS samples were mixed in an appropriate ratio. From the chemical analysis the Fe/Zn molar ratio of the mixture was 2.18. To override the problem of the coohng effect of volatiles on the plasma (mentioned above), prior to mixing HPS sample was preheated at 300 °C to reduce its volatile (H2O) content. Conditions of the plasma treatments can be seen in Table 3. In order to improve heat transport between the hot gases... 

I. Mohai, J. Szepvolgyi, I. Bertoti, M. Mohai, J. Gubicza, T. Ungar, Thermal plasma synthesis of zinc ferrite nanopowders, Solid State Ionics 141-142 (2001) 163-168. 

Shlyakhtin, O.A., Topochemical processes in the freeze drying synthesis of nickel-zinc ferrites, Ph.D. Thesis, Moscow State University, Moscow, 1985. 

These results demonstrate tliat shock-wave synthesis is a novel metliod to prepare nanosized materials with some unique physical and chemical properties. In the light of the experimental results, nanosized zinc ferrite and nickel ferrite synthesized by shock-wave treatment may Iiave potential applications as magnetic materials and photocatalysts. 

Ma and co-workers [26] reported the synthesis of graphene/zinc ferrite/PANI composites, which are photocatalytic inorganic antibacterial agents that show great potential and are prepared via in situ polymerisation and characterised using modern... 

Makovec, D., Drofenik, M., Zthdarsic, A. Hydrothermal synthesis of manganese zinc ferrite powders from oxides. J. Am. Ceram. Soc. 82(5), 1113-1120 (1999)... 

Ueda, M., Shimada, S., Inagaki, M. Synthesis of crystaUine zinc ferrite near room temperature. J. Mater. Chem. 3, 1199-1201 (1993)... 

Grasset, F., Labhsetwar, N., Li, D., Park, D.C., Saito, N., Haneda, H., Cador, O., Roisnel, T., Momet, S., Duguet, E., Portier, J., Etoumeau, J. Synthesis and magnetic characterization of zinc ferrite nanoparticles with different environments powder, colloidal solution, and zinc ferrite-silica core-shell nanoparticles. Langmuir 18, 8209-8212 (2002)... 

Brown P, Hope-Weeks LI (2009) The synthesis and characterization of zinc ferrite aerogels prepared by epoxide addition. J Sol-Gel Sci Technol 51 238-243. 

Shlyakhtin OA., Vinokurov A.L., Baranov A.N., Tretyakov Y.D. Direct synthesis of Bi-2212 by thermal decomposition of salt precursors. J. Supacond. 1998 11 507-514 SUeo E.E., Rotelo R., Jacobo S.E. Nickel zinc ferrites prepared by the citrate precursor method. Physica B 2002 320 257-260... 

A Dias, VTL Buono. Hydrothermal synthesis and sintering of nickel and manganese-zinc ferrites. J Mater Res 1997 12 3278. 

Grasset F., Labhsetwar N., Li D., Park D C., Saito N., Haneda H., Cador O., Roisnel T., Mornet S., Duguet E., Portier J., Etoumeau J., Synthesis and Magnetic Characterization of Zinc Ferrite Nanoparticles with Different Environments Powder, Colloidal Solution and Zinc Ferrite-Silica Core-Shell Nanoparticles. Langmuir, 2002. 18 (21) p. 8209-8216. 

Yener DO, Giesche H (2001) Synthesis or pure and manganese-, nickel- and zinc-doped ferrite particles in water-in-oil microemulsions. J Am Ceram Soc 84 1987-1995... 

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