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The addition of zirconia to alumina can improve the chemical properties, mechanical stability, acidity and surface area of alumina. The aim of this work is to evaluate the influence of 0.005 moles of zirconia addition to the structure and morphology of alumina powders by combustion reaction. The compositions were called AP (alpha-Al2O3) and AZ (Zr0.005Al1.995O3) and were prepared by using a silica container with direct heating on a hot plate at 480oC until selfignition. The powders were characterized by X-ray diffraction and nitrogen adsorption by BET analysis. The composition AZ showed high surface area (47 m2/g) and small crystallite size (60 nm). The alpha-alumina AP showed a wide agglomerates distribution with small agglomerates size when compared with AZ composition.

Ultrafine magnetic nickel ferrite particles have a significant potential for use in many applications such as magnetic recording media, ferrofluids, microwaves, catalysis and radar-absorbing coatings [1, 2]. Nickel ferrite powders with a nominal NiFe2O4 composition were synthesized by combustion reaction and an evaluation was made of the effect of two different conditions of synthesis on the nanostructural and magnetic characteristics of the resulting powders. Two synthesization routes were studied. The first, NFB, involved the preparation of the powder using a Pyrex beaker heated directly on a hot plate at 480°C until self-ignition occurred. By the second route, NFC, the powder was obtained under the same synthesization condition as the NFB route, but a vitreous silica basin was used. The resulting powders were characterized by X-ray diffraction (XRD), nitrogen adsorption by BET and scanning electron microscopy (SEM). The first route, NFB, proved more favorable to obtain powders with high surface area and, hence, smaller crystalline sizes (5.70 nm) and a superparamagnetic behavior. The NFC route confirmed the feasibility of obtaining powders with a crystalline size of 18.00 nm and a magnetic behavior. Saturation magnetization was 33.18 emu/g and the coercivity field was 25.63 Oe for powders obtained by the NFC route.

The continued growth in demand for cement has raised concerns in the industry about environmental and sustainability issues. In addition, the worldwide generation of large quantities of solid waste threatens human health and on environmental quality. This paper proposes to assess the feasibility of using a residual powder derived from organic waste of vegetable or animal origin for replacing part of Portland cement during concrete production. Specifically, the powder is derived from a living being such as the remains of food (meat, vegetables, fruits and eggshells), paper, wood, bones and seeds. Its scientific contribution is a conscious change due to development of an alternative material to contribute with more sustainable processes in the construction industry. Three types of mixtures for cement content were studied: aggregate/cement (A/C) ratios of 15, 10 and 6. Concrete samples were then made by replacing the cement with organic waste powder in percentages of 5%, 10%, 15%, and 20%. These mixtures were evaluated for their physical and mechanical properties. The results showed that the reference concrete had higher compressive strength than the concrete with low cement content (A/C ratio of 15:1). However, samples made with 5% of powder and an A/C ratio of 10:1 presented values at least 2.1% greater than compressive strength of the reference concrete. Mixtures rich in cement (A/C ratio of 6:1) and the powder replacements of up to 10% showed in the best mechanical behavior in 13% in relation to the reference concrete. Therefore, waste powder can be used as filling material to replace part of the cement, resulting in denser and more resistant concrete, as well as less specific absorption and voids.

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