Mechanochemical synthesis of barium titanate

A powder mixture of BaO and TiO2, was mechanochemically treated in a planetary ball mill in an air atmosphere for up to 4 h, using zirconium oxide vial and zirconium oxide balls as the milling medium. Mechanochemical reaction leads to the gradual formation of BaTiO3 phase. Phase evolution during synthesis and changes in powder size and morphology were monitored by XRD, DSC, IR and TEM analysis and it was shown that the formation of BaTiO3 phase was initiated after 60 min. Extended time of milling directed to formation of higher amount of BaTiO3 perovskite phase. Barium titanate with good crystallinity was formed after 240 min sintering without pre-calcination step was performed at 1330 degrees C for 2 It within heating rate 10 degrees C/min. (c) 2005 Elsevier Ltd. All rights reserved.

Mechanochemical synthesis of PZT powders

PZT ceramic powders were successfully prepared from the mixture of PbO, ZrO2 and TiO2 by mechanochemical synthesis in a planetary ball mill, under different milling conditions. Phase evolution during synthesis was monitored by X-ray diffraction analysis. Intensive milling resulted in formation of the nanocrystalline, perovskite PZT powders after 1 h of milling. This is a significant improvement in comparison to milling conditions reported by other authors. Depending on milling parameters the presence of some other phases, such as unreacted ZrO2, was also detected in some samples. The changes in powder size and morphology due to intensive milling, were determined by SEM and TEM, while BET analysis was used to determine specific surface area of the powders. Conclusions about processes taking place during mechanochemical synthesis of PZT powders were made based on the results of characterization. (C) 2002 Elsevier B.V. B.V. All rights reserved.

Ferroelectric properties of mechanically synthesized nanosized barium titanate

Barium titanate ceramics were prepared through mechanochemical synthesis starting from fresh prepared barium oxide and titanium oxide in rutile form. Mixture of oxides was milled in zirconia oxide jar in the planetary ball-mill during 30, 60, 120 and 240 min. Extended time of milling directed to formation of higher amount of barium titanate perovskite phase. Barium titanate with good crystallinity was formed after 240 min. Sintering without pre-calcinations step was performed at 1330 degrees C for 2 hours with heating rate of 10 degrees C/min. The XRD, DSC, IR and TEM analyses were performed. Electric and ferroelectric properties were studied. Very well defined hysteresis loop was obtained.

Structure and Properties of Barium Bismuth Titanate Prepared by Mechanochemical Synthesis

Bi4Ti4O15 [BBT], a member of Aurivillius bismuth-based layer-structure perovskites, was prepared from stoichiometric amounts of BaTiO3 [BT] and Bi4Ti3O12 [BIT] obtained via mechanochemical synthesis. Mechanochemical synthesis was performed in air atmosphere in a planetary ball mill. BBT ceramics were sintered at 1100C for 4 h without pre-calcination step within heating rate 10C/min. The formation of phase and crystal structure of BT, BIT and BBT were approved using X-ray analysis. The morphology of obtained powders and microstructure were exhamined using scanning electron microscopy. The electrical properties of sintered samples were carried out.

Study of Structure and Properties of Bi4Ti3O12 Prepared by Mechanochemical Syntheses

Bi4Ti3O12 powder was synthesized from bismuth oxide and titanium oxide. Mixture of oxides was milled in zirconium oxide jar in the planetary ball-mill during 1, 3 and 6 h. Extended time of milling directed to formation of higher amount of titanates perovskite phase. Bi4Ti3O12 was formed between 1 and 3 h of milling time. The phase formation of Bi4Ti3O12, crystal structure and powder particle size were followed by XRD, Raman spectroscopy and SEM analysis. After milling for various times the powders were compacted by pressing and isothermal sintering. Sample milled for 3 h and subsequently sintered at 1000C for 24 h exhibit a hysteresis loop, confirming that the synthesized material possesses ferroelectric properties. All results affect that the structure Bi4Ti3O12 is strongly dependent on the milling time.

Mechanochemical synthesis of Bi4Ti3O12

Our efforts were directed to the preparation of bismuth titanate - Bi 4e;Ti3O12 (BIT) by mechanically assisted synthesis. The mechanical activation was applied to prepare bismuth titanate, Bi4e;Ti3O12, from bismuth oxide, Bi 2O3, and titanium oxide, TiO2 (in an anatase crystal form). Mechanochemical synthesis was performed in a planetary ball mill in air atmosphere. Bismuth titanate ceramics was obtained by sintering at 1000° C The formation of Bi4e;Ti3O12 in the sintered samples was confirmed by X-ray diffraction analysis. Scanning electron microscopy, SEM, was used to study the particle size and powder morphology. The obtained results indicate that Bi4e;Ti3O12 from the powder synthesized by high-energy ball milling exhibits good sinterability, showing advantage of the mechanochemical process over conventional solid-state reaction.

Determinação do teor de extrato etéreo de grãos de oleaginosas através de diferentes processamentos

The objective of this work was to determine the ether extract content of peanut and canola seeds, with extraction in Soxhlet apparatus and with three types of processing: grinding in ball mill type; maceration in mortar and grind into micro mill after maceration in mortar. Data were analyzed in an entirely randomized design with 3 treatments and 12 replicates, submitted to variance analysis and the means were compared using Tukey test (P<0.05) with routines of the SAS statistical package. The largest percentage of ether extract was obtained in the treatment which the peanuts were subjected to a greater number of extractions (56.43%), and all treatments presented different results(P <0.05). In canola grains, it was observed that the extraction with the method of grinding in ball mill and the method of sequential extraction (macerate + ground in micro mill) were statistically similar (43.52 and 42.35% respectively), and these methods were more efficient (P <0.05) to extract the ether extract than the treatment in which the grains were only macerated. For peanut grains it was concluded that the most efficient method was the sequential one and to the canola grain, it can be used only a grinding mill as samples processing witch will be submitted to ether extract extraction.

Surface study of vitreous carbon obtained from glassy carbon powder

This work presents a surface study of monolithic vitreous (or glassy) carbon - MVC - obtained from vitreous carbon powder. Defective MVC pieces are crushed in a ball mill and size classified by sifting. The MVC powder is mixed with furfuryl-alcohol resin and compacted in a mould using a hydraulic press. Samples with different powder granulometries are produced in this way and carbonized in a furnace under nitrogen atmosphere. Complete carbonization of the powder is achieved in only one day and losses due to breakage of the pieces is less than 5%. These results compare very favorably with respect to traditional MVC production methods where full carbonization may require up to seven days and losses due to breakage can be as high as 70%. After carbonization, samples are sanded and polished. Surface roughness and microstructure are characterized by light microscopy. Porosity is quantified from micrographs using ImageJ software and nanometric height variations are measured by atomic force microscopy. © 2012 Materials Research Society.

Mechanochemical synthesis of yttrium manganite

Yttrium manganite (YMnO3) is a multiferroic material, which means that it exhibits both ferromagnetic and ferroelectric properties, so making it interesting for a variety of technological applications. In this work, single-phase YMnO3 was prepared for the first time by mechanochemical synthesis in a planetary ball mill. The YMnO3 was formed directly from the highly activated constituent oxides, Y 2O3 and Mn2O3, after 60 min of milling time. During prolonged milling, the growth of the particles occurred. The cumulative energy introduced into the system during milling for 60 min was 86 kJ/g. The X-ray powder-diffraction analysis indicates that the as-prepared samples crystallize with an orthorhombic (Pnma) YMnO3 structure. The morphology and chemical composition of the powder were investigated by SEM and FESEM. The magnetic properties of the obtained YMnO3 powders were found to change as a function of the milling time in a manner consistent with the variation in the nanocomposite microstructure. © 2012 Elsevier B.V. All rights reserved.

'Ti''O IND.2'/'Sn''O IND. 2 modificado com 'Ag IND. 2''O', para obtenção de fotocatalisadores

Pós-graduação em Química - IQ

Efeito da hidrólise enzimática seguida da moagem em moinho de bolas sobre as características estruturais e físico-químicas do amido de madioquinha-salsa

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Estudo da modificação ácido-etanólica do amido de mandioca seguida de moagem

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Otimização da produção massal e formulação de Bipolaris euphorbiae visando à obtenção de um bioherbicida

Pós-graduação em Microbiologia Agropecuária - FCAV

Nanocompósito de alumina com inclusão nonométricas de zircônia para infraestruturas de próteses odontológicas livres de metal: avaliação de prosperidades mecânicas e análise microestrutural. -

Pós-graduação em Reabilitação Oral - FOAR

Crop optimization and pre-steps standardization to get a Bipolaris euphorbiae-based bioherbicide

Making bioproducts available to the market requires finding appropriate processes for mass production and formulation of biological agents. This study aimed at evaluating the Bipolaris euphorbiae production in a solid medium (fermentation in solid substrate) and in a biphasic system (growth in a liquid medium followed by growth in a solid medium), as well as determining the processes for collecting and drying conidia, under laboratory conditions. The influence of the incubation period and inoculum quantity were also investigated. The conidia were dried by using an oven (30ºC, 35ºC, 40ºC, 45ºC, 50ºC, 55ºC and 60ºC), and laminar flow, continuous air flow and aseptic chamber at room temperature. Dry conidia were obtained by sieving and grinding in a ball mill, hammer mill or grain grinder. The conidia viability and sporulation efficiency were evaluated in the solid medium and in the biphasic system. For growth period, the best sporulation on solid medium was obtained after 10 days of incubation, reaching 8.3 x 10(7) conidia g-1 of substrate. The biphasic system did not increase the B. euphorbiae sporulation (4.5 x 10(7) conidia g-1 of substrate), after 14 days, and the amount of liquid inoculum used in this system was not an important factor for increasing its production. The continuous air flow and laminar flow preserved the conidial viability (94.6% and 99.1%, respectively), while promoting a great moisture loss (62.6% and 54.0%, respectively). All the grinding processes reduced the conidia germination (86.2%, 10.5% and 12%, respectively), while sieving allowed the collecting of powdered conidia with high viability (94.8%).