Innovative ozone sensors for environmental monitoring working at low temperature

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Investigations of BaFe0.5Nb0.5O3 nano powders prepared by a low temperature aqueous synthesis and resulting ceramics

A facile method to prepare nanoscaled BaFe0.5Nb0.5O3 via synthesis in boiling NaOH solution is described herein. The nano-crystalline powder has a high specific surface area of 55 m2 g−1 and a crystallite size of 15 nm. The as-prepared powder does not show any significant crystallite growth up to 700 °C. The activation energy of the crystallite growth process was calculated as 590 kJ mol−1. Dense ceramics can be obtained either after sintering at 1200 °C for 1 h or after two-step sintering at 1000 °C for 10 h. The average grain sizes of ceramic bodies can be tuned between 0.23 μm and 12 μm. The thermal expansion coefficient was determined as 11.4(3)⋅10−6 K−1. The optical band gap varies between 2.90(5) and 2.63(3) eV. Magnetic measurements gave a Néel temperature of 20 K. Depending on the sintering regime, the ceramic samples reach permittivity values between 2800 and 137000 at RT and 1 kHz

Nanocomposites of polymer and inorganic nanoparticles for optical and magnetic applications

This article provides an up-to-date review on nanocomposites composed of inorganic nanoparticles and the polymer matrix for optical and magnetic applications. Optical or magnetic characteristics can change upon the decrease of particle sizes to very small dimensions, which are, in general, of major interest in the area of nanocomposite materials. The use of inorganic nanoparticles into the polymer matrix can provide high-performance novel materials that find applications in many industrial fields. With this respect, frequently considered features are optical properties such as light absorption (UV and color), and the extent of light scattering or, in the case of metal particles, photoluminescence, dichroism, and so on, and magnetic properties such as superparamagnetism, electromagnetic wave absorption, and electromagnetic interference shielding. A general introduction, definition, and historical development of polymer–inorganic nanocomposites as well as a comprehensive review of synthetic techniques for polymer–inorganic nanocomposites will be given. Future possibilities for the development of nanocomposites for optical and magnetic applications are also introduced. It is expected that the use of new functional inorganic nano-fillers will lead to new polymer–inorganic nanocomposites with unique combinations of material properties. By careful selection of synthetic techniques and understanding/exploiting the unique physics of the polymeric nanocomposites in such materials, novel functional polymer–inorganic nanocomposites can be designed and fabricated for new interesting applications such as optoelectronic and magneto-optic applications

Biomedical waste management by using nanophotocatalysts: The need for new options

Biomedical waste management is getting significant consideration among treatment technologies, since insufficient management can cause danger to medicinal service specialists, patients, and their environmental conditions. The improvement of waste administration protocols, plans, and policies are surveyed, despite setting up training programs on legitimate waste administration for all healthcare service staff. Most biomedical waste substances do not degrade in the environment, and may also not be thoroughly removed through treatment processes. Therefore, the long-lasting persistence of biomedical waste can effectively have adverse impact on wildlife and human beings, as well. Hence, photocatalysis is gaining increasing attention for eradication of pollutants and for improving the safety and clearness of the environment due to its great potential as a green and eco-friendly process. In this regard, nanostructured photocatalysts, in contrast to their regular counterparts, exhibit significant attributes such as non-toxicity, low cost and higher absorption efficiency in a wider range of the solar spectrum, making them the best candidate to employ for photodegradation. Due to these unique properties of nanophotocatalysts for biomedical waste management, we aim to critically evaluate various aspects of these materials in the present review and highlight their importance in healthcare service settings

Síntese e caracterização de cerâmicos magnetoeléctricos/multiferróicos

Mestrado em Engenharia de MateriaisMateriais magnetoelétricos e multiferróicos que exibem simultaneamente propriedades ferroelétricas e ferromagnéticas, têm suscitado um crescente interesse na comunidade científica para o desenvolvimento de materiais multifuncionais. Neste trabalho pretendeu-se fabricar materiais cerâmicos multiferroicos e realizar um estudo do acoplamento entre propriedades magnéticas e as propriedades piezoelétricas/ferroelétricas dos compósitos. Assim, foram realizados estudos sobre a síntese das hexaferrites (BaFe12O19, SrFe12O19, Ba3Co2Fe24O41 e Sr3Co2Fe24O41), com diferentes temperaturas de reacção e diferentes métodos de preparação: reação de estado sólido, co-precipitação, sol-gel e combustão de citratos. De seguida, foram preparados compósitos de hexaferrites e piezoelétricos, nomeadamente BaTiO3 e K0.5Na0.5NbO3 (KNN), foram realizadas as prensagens: uniaxial e isostática a frio. A densidade relativa obtida após a sinterização foi 85% da densidade teórica nos compósitos com BaTiO3 e 81% nos compósitos com KNN. Foram efetuadas medições magnéticas, nomeadamente por microscópia de força magnética e magnetometria por vibração de amostra, e medições piezoelétricas, por microscópia de força piezoelétrica. Em alguns compósitos foi detetada a inter-difusão de átomos do bário e estrôncio produzindo várias fases secundárias diminuindo o efeito piezoelétrico. As medições magnéticas mostraram que os compósitos com ferrites duras (BaFe12O19 e SrFe12O19) formaram um ciclo de histerese com maior área do que os compósitos com ferrites macias (Ba3Co2Fe24O41 e Sr3Co2Fe24O41). Alguns compósitos demonstram acoplamento magnetoelétrico significativo.Magnetoelectric and multiferroic materials that exhibit both ferroelectric and ferromagnetic properties, have raised great interest in the scientific community for the development of multifunctional materials. In this work we intended to fabricate multiferroic ceramics and to study the coupling between magnetic properties and piezoeletric/ferroelectric properties of composite materials. Synthesis of hexaferrites (BaFe12O19, SrFe12O19, Ba3Co2Fe24O41 and Sr3Co2Fe24O41), was undertaken with different reacting temperatures and different preparation methods: solid state reaction, coprecipitation, sol-gel and citrate. Also we performed analysis by XRD and determined the phases of each material. We prepared composites of hexaferrites and piezoelectric phases (BaTiO3, KNN) with uniaxial pressing and cold isotactic pressing. BaTiO3 composites have shown a relative density of 85% compared with the theoretical density and the KNN composites had a maximum density of 81%. We performed magnetic (MFM and VSM), and piezoelectric (PFM) measurements, and it was verified that in some composites we observed diffusion of atoms between barium and strontium sources producing new phases lowering the piezoelectric effect. In the magnetic analysis it also was verified that the hard ferrites formed hysteresis loops with greater area than the soft ferrites. It was found that some composites demonstrate capable magnetoelectric coupling

Structure, Microstructure and Magneto-Dielectric Properties of Barium Titanate-Ferrite Based Composites

Magneto-dielectric composites materials are those which perform both magnetic and dielectric properties in one single component. Due to the coupling between the ferroelectric and ferromagnetic, the magnetization can be controlled by an applied electric field, while the electric polarization can be controlled by applying a magnetic field. The phase connectivity and phase morphology plays an important role in the modifying the magneto-dielectric properties of the composites. Synthesis method is great tool to explore the microstructure and magneto-dielectric properties of the composites. In present work three synthesis methods were adopted to prepare magneto-dielectric composites. They are combustion derived solid-state mixing, combustion derived in-situ synthesis method. BaTiO3 selected for the ferroelectric phase which is having moderate properties of permittivity, loss, piezoelectric constant. CoFe2O4, ZnFe2O4 and Co0.5Zn0.5Fe2O4 are selected for ferrite phase, which are hard, soft and non-magnetic in nature respectively. Ferrite weight percentage was used in magneto-dielectric composites at 20%, 30%, 40%. Structure, microstructure and magneto-dielectric properties of composites were studied and analyzed. Dielectric, magnetic and magneto-dielctric properties of composites varied significantly by varying synthesis method. Traces hexagonal BaTiO3 has been detected when tetragonal BaTiO3 sintered along with ferrites. Plate like morphology of BaTiO3 was evolved along with nearly spherical morphology of BaTiO3 in solid-state derived composites, but no evidence of plate like BaTiO3 in in-situ composites. Cobalt ferrite based composite shows negative magneto-capacitance response in both solid state and in-situ synthesis, which not in other ferrite systems of solid-state and in-situ derived composites. Along with the solid-state and in-situ synthesis methods, ex-situ synthesis method was also adopted to explore in present magneto dielectric composites. Typical 30 wt% ferrite (CoFe2O4, ZnFe2O4 and Co0.5Zn0.5Fe2O4) composites were made in this method. Microstructural study shows large no of plate like BaTiO3 exists in ferrite@BT composites than BT@ferrite composites. Cobalt and zinc ferrite based ex-situ composites show both positive and negative magneto capacitances in 7BT@3(CF/ZF) and 3(CF/ZF)@7BT composites respectively. Cobalt zinc ferrite based ex-situ composite show the positive magneto-capacitance in both 7BT@3CZF and 3CZF@7BT. Magneto-capacitance responses are dependent on both magnetostriction and magnetoresistance. Magneto-capacitance values of about -1.48%, -1.08%, 19.9% and -2.1% were observed in 7BT$3CZF, 7BT#3CZF, 7BT@3CZF and 3CZF@7BT composites respectively. Similarly 9.91%, 19.76% and 19.9% were observe in 7BT@3CF, 7BT@3ZF and 7BT@3CZF composites respectively

Advances in Functional Inorganic Materials Prepared by Wet Chemical Methods

Functional inorganic materials are an indispensable part of innovative technologies that are essential to the development of many fields of industry. The use of new materials, nanostructures, or multicomponent composites with specific chemical or physical properties promotes technological progress in electronics, optoelectronics, catalysis, biomedicine, and many other areas that are concerned with many aspects of human life. Due to the broad and diverse range of potential applications of functional inorganic materials, the development of superior synthesis pathways, reliable characterization, and a deep understanding of the structure–property relationships in materials are rightfully considered to be fundamentally important scientific issues. Only synergetic efforts of scientists dealing with the synthesis, functionalization and characterization of materials will lead to the development of future technologies