Maria Gabriela Araujo Ranieri
@unifei.edu.br
Federal University of Itajuba
Institute of Production Engineering and Management
EDUCATION
Graduation in Interior Design.
Master and doctorate in mechanical engineering in the field of materials.
RESEARCH INTERESTS
Ceramic materials; wastes; alternative materials; composite materials; civil engineering; friendly materials.
Scopus Publications
Scholar Citations
Scholar h-index
Scholar i10-index
Scopus Publications
Fernanda Rodrigues Santos Valle, Paulo Cesar Gonçalves, Maria Gabriela A. Ranieri, Mirian de Lourdes Noronha Motta Melo, and Valquíria Claret dos Santos
FapUNIFESP (SciELO)
abstract: The utilization of wastes from demolition in civil construction in self compacting concrete (SCM) has the potential to reduce both the environmental impact and financial cost. In this context, this article aims to verify the behavior of the incorporation of recycled aggregates of civil construction in the mix designs of self-compacting mortar (SCM) in replacing cement, presenting as an interesting alternative to natural raw materials. This study used the EMMA® software to optimize the choice of percentages of fine recycled aggregates when replacing cement. The proportions chosen were 0%, 5%, 15%, and 25%, through the analysis of the granular packing curve of the respective mix designs. The proportion of 0% has in its composition cement, metakaolin, sand, superplasticizer (SP) and water. The parameters obtained, through tests in the fresh state of the mini-slump and mini-funnel V, certified the samples as SCM. The compressive strength and flexural tensile strength tests in the hardened state demonstrated a reduction in mechanical properties of the material with cement replacement. It is concluded that the waste used brick and ceramic can be added in replacement to the cement in SCM without significant loss of properties in the fresh and hardened state.
Maria Auxiliadora de Barros Martins, Lucas Ramon Roque da Silva, Maria Gabriela A. Ranieri, Regina Mambeli Barros, Valquíria Claret dos Santos, Paulo César Gonçalves, Márcia Regina Baldissera Rodrigues, Rosa Cristina Cecche Lintz, Luísa Andréa Gachet, Carlos Barreira Martinez,et al.
MDPI AG
The reuse of waste in civil construction brings environmental and economic benefits. However, for these to be used in concrete, it is necessary a previous evaluation of their physical and chemical characteristics. Thus, this study aimed to characterize and analyze the waste foundry exhaust sand (WFES) for use in self-compacting concrete (SCC). Foundry exhaust sand originates from the manufacturing process of sand molds and during demolding of metal parts. It is a fine sand rich in silica in the form of quartz collected by baghouse filter. Characterization of WFES was conducted through laser granulometry, scanning electron microscopy (SEM) in the energy dispersive spectroscopy (EDS) mode, X-ray diffraction (XRD), X-ray fluorescence (XRF), Fourier transform infrared spectroscopy (FTIR), thermogravimetry (TG) and derivative thermogravimetry (DTG) techniques. The waste was classified as non-hazardous and non-inert, with physical and chemical properties suitable for use in SCC composition, as fine aggregate or mineral addition. Five mixtures of SCC were developed, in order to determine the waste influence in both fresh and hardened concrete. The properties in the fresh state were reached. There was an increase in compressive strength and sulfate resistance, a decrease in water absorption of self-compacting concrete by incorporating WFES as 30% replacement.
M.G.A. Ranieri, P.P. Ortega, H. Moreno, M.A. Ramirez, E.C. Aguiar, and A.Z. Simões
Elsevier BV
Abstract This study examines resistive switching behavior and magnetoelectric coupling in La0.5Pr0.5FeO3 thin films obtained through the polymeric precursor method at a temperature of 500 °C for 2 h. The real and imaginary part of dielectric constant (e′ and e″) as a function of temperature demonstrate significant values with increasing temperature and can be caused by the ferroelectric ordering in the present system. The magnetic and dielectric measurements suggest a coupling between magnetic and electric dipoles at room temperature. The magnetization versus temperature curves under zero-field cooling (ZFC) and field cooling (FC) conditions suggest antiferromagnetic to ferromagnetic transition. The maximum magnetoelectric coupling value is ∼0.06 for H ∼1.7 T. By varying the applied electric field, we noted the resistive memory phenomenon from current-voltage (I–V) characteristics being reversibly switched between two stable resistance states. Such behavior can be ascribed to the electron hopping from Fe2+ to Fe3+ levels with oxygen vacancies present in the lattice, as evidenced using XPS analysis. These state-of-art analyses motivated us to study the introduction of praseodymium (Pr) in La3+ sites, considering that LaFeO3 shows paramagnetic behavior at room temperature. La0.5Pr0.5FeO3 thin films exhibited slightly ferromagnetic behavior associated with coupling between cations at the octahedral and tetrahedral sites with the coexistence of resistive switching and magnetoelectric coupling behavior.
Patricia Capellato, Daniela Sachs, Lucas V. B. Vasconcelos, Miriam M. Melo, Gilbert Silva, Maria G. A. Ranieri, Cecilia A. de C. Zavaglia, Roberto Z. Nakazato, and Ana P. R. Alves Claro
MDPI AG
The current metallic biomaterial still presents failures associated with the bulk alloy and the interface of material/human body. In previous studies, titanium alloy with tantalum showed the elastic modulus decrease in comparison with that of commercially pure (cp) titanium. In this study, surface modification on Ti-30Ta alloy was investigated. Titanium and tantalum were melted, homogenized, cold-worked by a rotary swaging process and solubilized. The anodization process was performed in electrolyte contained glycerol + NH4F 0.25% at 30 V using seven different durations—4 h, 5 h, 6 h, 7 h, 8 h, 9 h, and 10 h and annealed at 530 °C for 1 h. The surface topography was characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM) measurements, X-ray diffraction analysis (XRD), and contact angle. From the results, we conclude the time of anodization process influences the shape and morphology of the anodized layer. The 5 h-anodization process produced a smooth and porous surface. The 4-, 6-, 7-, 8-, 9-, and 10-h conditions showed nanotubes morphology. All surfaces are hydrophilic (<90°). Likewise, all the investigated conditions present anatase phase. So, this surface modification presents potential for biomedical application. However, more work needs to be done to better understand the influence of time on the anodization process.
M. G. A. Ranieri, M. Cilense, E. C. Aguiar, A. Z. Simões, M. A. Ponce, and E. Longo
Springer Science and Business Media LLC
Samarium substituted lanthanum orthoferrite La0:5Sm0:5FeO3 thin film has been prepared by soft chemical method. A single perovskite phase with orthorhombic crystallographic structure was attained. Magnetic and ferroelectric orderings of the film is observed at room temperature (RT). The magnetization of the sample measured at room temperature increases non-linearly with the increase of magnetic field, which suggests the presence of dipole–dipole/exchange interaction in the sample. The resistivity measured in the temperature range 25–375 °C showed that the film is a semiconducting material with low resistivity. The Cole–Cole model reveals different grain boundaries electrical resistance caused by the equilibrium concentration of oxygen vacancies in orthoferrite and that the addition of samarium results in loss of oxygen during sintering. The ferroelectric behaviour of La0:5Sm0:5FeO3 at RT is also confirmed by its capacitance–voltage (C–V) characteristic suggesting a weak ferroelectric behaviour at room temperature. The variation of dielectric constant as a function of frequency predicts the presence of spontaneous polarization in the sample. The semiconductor electrical behavior of the La0:5Sm0:5FeO3 is mainly composed of tunneling current.
M. G. Ranieri, R. A. C. Amoresi, M. A. Ramirez, J. A. Cortes, L. S. R. Rocha, C. C. Silva, and A. Z. Simões
Springer Science and Business Media LLC
Thin films of BiFeO3 (BFO), LaFeO3 (LFO), and LFO/BFO heterostructures were successfully obtained on Pt/TiO2/SiO2/Si(100) substrates by chemical solution deposition. The films were characterized by structural, morphological and magneto-electrical techniques. The polycrystalline films obtained with good crystalline phases of BFO and LFO. The heterostructures films LFO/BFO showed no diffusion between the phases, and without the presence of secondary phases. The bottom layer of LFO was able to promote the grain growth, reducing oxygen vacancies, and influenced the tension between the new interfaces of the subsequent layer of BFO, thereby altering the physical and chemical properties obtained in the heterostructure. These show the coexistence of ferroelectricity and magnetism in the material. Measurements of capacitance and electrical polarization as a function of the magnetic field have been made and have indicated the magnetic–electric coupling at room temperature with high dielectric constant. Such materials may be of great significance in basic as well as applied research.
M.G.A. Ranieri, M. Cilense, E.C. Aguiar, C.C. Silva, A.Z. Simões, and E. Longo
Elsevier BV
Abstract Perovskite structured oxides are important functional materials often used for the development of modern devices. To extend their applicability, these materials need to be scalably and efficiently grown in the form of thin films. In this work, perovskite structured thin films of nanograined LaFeO3 (LFO) were chemically grown using polymeric precursors on Pt substrates. The thin films were characterized by X-ray diffraction, field-emission scanning electron microscopy, atomic force microscopy, and transmission electron microscopy. The electrical properties of the films were also measured. The homogeneous LFO thin films synthesized at a sintering temperature of 500 °C in 2 h contained grains with lateral dimensions of about 68 nm and 356 nm in thickness. The dielectric permittivity and dielectric loss measurements of the sample indicated only a slight dispersion in the frequency because of the lower two-dimensional stress in the plane of the film. The nanograined LFO semiconductor thin films showed a room temperature magnetic coercive field, which rendered them magnetically soft. The electrical characterization of the films, including temperature-dependent conductivity and thermopower confirmed p-type conduction and the mobility activation energy was measured to be 0.96 eV. A strong magnetization with a remnant magnetization of ~60 emu/g was observed in the LFO films, indicating the uncompensated spin magnets moments of the Fe3+ ions.
M.G.A. Ranieri, E.C. Aguiar, M. Cilense, B.D. Stojanovic, A.Z. Simões, and J.A. Varela
Elsevier BV
Highlights: • Bi{sub 4}Ti{sub 3}O{sub 12} thick films were obtained by SSR and PPM methods. • Both systems crystallize in an orthorhombic structure. • Textured characteristics were evidenced. • Grain morphology affects the P–E loops. - Abstract: Bismuth titanate powders (Bi{sub 4}Ti{sub 3}O{sub 12}-BIT) were fabricated by solid state reaction (SSR) and polymeric precursor method (PPM). From these powders, Bi{sub 4}Ti{sub 3}O{sub 12} pellets were obtained by tape-casting using plate-like templates particles prepared by a molten salt method. The BIT phase crystallizes in an orthorhombic structure type with space group Fmmm. Agglomeration of the particles, which affects the densification of the ceramic, electrical conduction and leakage current at high electric fields, was monitored by transmission electronic microscopy (TEM) analyses. FEG-SEM indicated that different shape of grains of BIT ceramics was influenced by the processing route. Both SSR and PPM methods lead to unsaturated P–E loops of BIT ceramics originating from the highly c-axis orientation and high conductivity which was affected by charge carriers flowing normally to the grain boundary of the crystal lattice.
L. F. Goncalves, J. A. Cortés, M. G. A. Ranieri, F. B. Destro, M. A. Ramirez, and A. Z. Simões
Springer Science and Business Media LLC
Abstract
Bi3NbO7 (BNO) thin films were deposited on Pt/TiO2/SiO2/Si (100) substrates at room temperature from the polymeric precursor method. X-ray powder diffraction and transmission electron microscopy were used to investigate the formation characteristics and stability range of the tetragonal modification of a fluorite-type solid solution. The results showed that this tetragonal, commensurately modulated phase forms through the intermediate formation of the incommensurately modulated cubic fluorite phase followed by the incommensurate-commensurate transformation. The 200 nm thick BNO films exhibit crystalline structure, a dielectric constant of 170, capacitance density of 200 nF/cm2, dielectric loss of 0.4 % at 1 MHz, and a leakage current density of approximately 1 × 10−7 A/cm2 at 5 V. They show breakdown strength of about 0.25 MV/cm. The leakage mechanism of BNO film in high field conduction is well explained by the Schottky and Poole–Frenkel emission models. The 200 nm thick BNO film is suitable for embedded decoupling capacitor applications directly on a printed circuit board.
L. V. Costa, M. G. Ranieri, M. Cilense, E. Longo, and A. Z. Simões
AIP Publishing
Magnetoelectric coupling was observed at room temperature in calcium modified bismuth ferrite BiFeO3 (BFO) thin films deposited on Pt/TiO2/SiO2/Si (100) substrates by the chemical solution deposition. Undoped and Ca-doped BiFeO3 films were coherently grown at a temperature of 500 °C for 2 h. The highest doped BFO film has a tetragonal structure with P4mm space group, while BFO has a rhombohedral structure with space group R3c, which can be treated as a special triclinic structure. Room temperature magnetic coercive field indicates that the undoped film is magnetically soft with maximum magnetoelectric coefficient in the longitudinal direction was about 12 V/cm. Adding Ca2+ ions to BFO in high concentration decreases the remnant polarization and stabilizes the charged domain walls which interact with oxygen vacancies reducing coercive field.
G. Biasotto, M.G.A. Ranieri, C.R Foschini, A.Z. Simões, E. Longo, and M.A. Zaghete
Elsevier BV
Abstract Good quality zinc oxide ZnO films were deposited on alumina substrates by the polymeric precursor method (PPM) using zinc acetate as the precursor. X-ray diffraction (XRD) was used to confirm the crystallinity of the zinc oxide films which were free of impurities and SEM study revealed the uniform deposition of fine grains with a thickness of 120 nm. ZnO films were used for CO gas detection at different times by recording the change in the film conductance. The faster response of ZnO sensors to CO gas is believed to be due to high porous sensing films which show higher surface-to-volume ratio. The O 2 ′, O″, O ′ species concentration emerging from the [ZnO 5 ·VO•]+1/2O 2 → [ZnO 6 ] chemisorptions reaction affects the ZnO gas sensor response owing to the fact that the oxygen ion acts as a trap for electrons from the bulk of films.
F.B. Destro, F. Moura, C.R. Foschini, M.G. Ranieri, E. Longo, and A.Z. Simões
Elsevier BV
Abstract This paper focuses on the electrical properties of Bi 0.95 Nd 0.05 FeO 3 thin films (BNFO05) deposited on Pt/TiO 2 /SiO 2 /Si (100) substrates by the soft chemical method. A BNFO05 single phase was simultaneously grown at a temperature of 500 °C for 2 h. Room temperature magnetic coercive field indicates that the film is magnetically soft. The remanent polarization ( P r ) and the coercive field ( E c ) measured were 51 μC/cm 2 and 65.0 kV/cm, respectively, and were superior to the values found in the literature. XPS results show that the oxidation state of Fe is purely 3+, which is beneficial for producing a BNFO05 film with low leakage current. The polarization of the Au/BNFO05 on Pt/TiO 2 /SiO 2 /Si (100) capacitors with a thickness of 230 nm exhibited no degradation after 1×10 8 switching cycles at a frequency of 1 MHz. Experimental results demonstrated that the soft chemical method is a promising technique for growing films with excellent electrical properties, and can be used in various integrated device applications.
M.G.A. Ranieri, E.C. Aguiar, M. Cilense, A.Z. Simões, and J.A Varela
Elsevier BV
Abstract Bismuth titanate templates (Bi 4 Ti 3 O 12 ) were synthesized by the molten salt method in Na 2 SO 4 and K 2 SO 4 fluxes, using an amorphous Bi 4 Ti 3 O 12 precursor and a mechanically mixed Bi 2 O 3 +TiO 2 mixture as the starting materials. The templates were characterized by means of X-Ray Diffraction, FT-IR, FT-Raman, FEG-SEM and TEM. The templates are free of secondary phases and present orthorhombic structure with orientation in the c -plane. FT-IR suggests no traces of sulfate groups revealing that the molten salt synthesis was beneficial for elimination of inorganic species and for the arrangement of individual nanocrystals into ordered lattices. FEG-SEM analyses of BIT templates revealed that most of the grains were homogeneous with a length of 3.1 µm and a width of 0.3 µm and had plate-like morphology. TEM investigations show that the c -axis of the perovskite units is parallel to the thickness direction of the grains and no liquid-phase was formed during BIT phase formation.