Estudo de propriedades físicas de nanomateriais produzidos por síntese mecânica: [tese]

Tese (doutorado) - Universidade Federal de Santa Catarina, Centro de Ciências Físicas e Matemáticas. Programa de Pós-graduação em Física

Interaction and compatibility studies of efavirenz with pharmaceutical excipients

Although excipients have traditionally been thought of as being inert, experience has shown that there can be interactions between excipients and drugs. Thus, knowledge of potential physical and chemical interactions can be very useful. The compatibility of efavirenz with the excipients: sodium lauryl sulfate, spray dried lactose, hydroxypropylcellulose, magnesium stearate, microcrystalline cellulose and croscarmellose sodium was studied. X-ray powder diffraction (XRPD), Fourier Transform Infrared Spectroscopy (FT-IR), Raman spectroscopy (RS) and Differential scanning calorimetry (DSC) were used as screening techniques. DSC curves of binary mixtures were quite different from the efavirenz raw material, suggesting a strong interaction, including possible chemical reactions between efavirenz and excipients at increased temperatures. However, FT-IR, XRPD and RS showed that no chemical reaction occurred between efavirenz and excipients at room temperature. Efavirenz can exist in more than one crystalline form, which may have implications for its behavior during production, and also for its in vivo performance. XRPD, DSC, Scanning Electron Microscopy (SEM) and Intrinsic Dissolution Rate (IDR) were used for the solid-state characterization of efavirenz and showed that the raw material used corresponded to Form I and maintained its crystal structure during the study. Intrinsic dissolution studies indicated that bioavailability problems may arise because of the poor solubility of efavirenz

Structure, microstructure and magnetic investigation of the hexagonal d-FeSe nanophase produced by mechanochemical synthesis

We present a systematic structural, microstructural and magnetic characterization of the hexagonal d-FeSe nanophase produced by a simple one-step mechanochemical synthesis route, by using conventional X-ray powder diffraction (XRPD), Rietveld refinement, transmission electron microscopy (TEM) and magnetometry techniques. We observed the simultaneous formation of tetragonal b-FeSe and d-FeSe after 3 h of milling (with minor amounts of unreacted iron), followed by complete b-FeSe / d-FeSe phase transition as milling time increases to 6 h (no unreacted iron). The average crystallite size of the dFeSe phase of about 16 nm after 3 h milling time decreases by about 31% up to the final milling time (24 h). TEM images and electron diffraction patterns confirm the nanometric size of the crystalline domains in the irregularly-shaped agglomerated particles. Two ferromagnetic phases with distinct coercivity spectra were assumed here by considering an assembly of randomly-oriented weakly-anisotropic ferromagnetic particles, mixed at a 4 to 6 volume ratio with other randomly-oriented ferromagnetic grains. Four years after synthesis, the aged samples milled for less than 9 h revealed a certain amount of the b-FeSe phase that slightly affects the d-FeSe (micro)structure but causes some variations (decreasing) in magnetic parameters. Milling times as long as 12 h were shown to be necessary to guarantee the d-FeSe nanophase stability and to retain its magnetic properties over time

Structural, microstructural and magnetic characterization of the β-CoTe nanophase synthesized by a novel mechanochemical method

This work reports an unprecedented mechanochemistry synthesis of β-CoTe and its systematic characterization through X-ray powder diffraction (XRPD), transmission electron microscopy (TEM), and magnetometry techniques. The mechanical alloying produced the desired material within 6 h along with minor impurities, showing good stabilization for higher milling times (15 h) and long-term storage. XRPD characterization employed the Rietveld profile fitting analysis with fundamental parameters analysis in a direct convolution approach, giving the material's structure and microstructure information. For the spherical shape, the diameter mass average of the crystallites furnished values around 13 nm with 1.1% of microstrain. The double-Voigt procedure also modeled a triaxial ellipsoid shape for the crystallite size and obtained a surface-weighted average value for its volume around 150 nm3. TEM images confirmed the nanometric size visually and showed the crystallites to aggregate in large particles hundreds of nanometers in size. Measuring hundreds of supposed crystallite sizes, we could achieve a numerical distribution of their sizes with an average of 16 nm. The magnetization analysis performed both experimentally and via numerical simulations showed that β-CoTe is predominantly superparamagnetic with a magnetic domain size compatible with the double-Voigt one

Direct decomposition of methane over Ni catalyst supported in magnesium aluminate.

In this paper, the results obtained in the methane decomposition reaction promoted by a Ni catalyst supported on MgAl2O4 spinel are presented. The textural properties of the catalyst were investigated by X-ray diffraction (XRD), N2 adsorption/desorption isotherms (BET and BJH methods), thermogravimetric (TGA) and temperature-programmed reduction (TPR) analysis. The influence of the operating conditions employed on the methane decomposition was studied. According to the results, it was found that a N2:CH4 molar ratio of 7:1 and catalyst reduction temperature of 700 ◦C/1 h were the best conditions for methane decomposition. In addition, in the methane decomposition over Ni/MgAl2O4, multiwall carbon nanotubes were formed

Grinding effect on levofloxacin hemihydrate

The grinding techniques were used in different pharmacotechnical process. the control of the effect of grinding in solid state properties of drugs is very important, mainly in hydrated drugs. Levofloxacin hemihydrate (LVF) is a good example of this type of compounds and a broad spectrum antibiotic of the fluoroquinolone drug class. the samples of LVF with and without grinding were studied using different characterization techniques such as thermogravimetry, differential scanning calorimetry, fourier-transformed infrared, X-ray powder diffraction, and hot stage microscopy. the purpose of the present study was to evaluate the effects of grinding in the dehydration and rehydration processes in levofloxacin hemihydrate. After heating, the samples lost water molecules and the rehydration process was modified depending on defects due to the grinding. At room temperature, the complete transformation to the hemihydrate form was detected only for the sample without grinding. On the other hand, the milled sample showed two phases, hydrate and anhydrate forms. Therefore, the defects in the crystalline structure would cause the irreversible transformation.Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Univ Fed Santa Catarina, PGFAR, BR-88040970 Florianopolis, SC, BrazilNatl Univ Cordoba, Fac Math Astron & Phys FAMAF, Cordoba, ArgentinaUniv Fed Santa Catarina, BR-88040970 Florianopolis, SC, BrazilUniversidade Federal de São Paulo, Inst Ciencia & Tecnol, São Paulo, BrazilUniversidade Federal de São Paulo, Inst Ciencia & Tecnol, São Paulo, BrazilWeb of Scienc

Single crystal structure, solid state characterization and dissolution rate of terbinafine hydrochloride

Terbinafine hydrochloride (TH), a poorly water soluble antifungal agent, was characterized by solid state techniques including differential scanning calorimetry, thermogravimetry, X-ray powder diffraction, optical and electron microscopies, Fourier transform infrared, Raman and solid-state nuclear magnetic resonance spectroscopies and intrinsic dissolution rate (IDR). A colorless single crystal of TH was grown from an ethanol:water solution and its crystalline structure was determined through X-ray single crystal diffraction. Also, a new crystal habit of TH was obtained through the slow solvent evaporation technique revealing a needle-like shape. A comparison between the IDR results for the TH raw material and TH needle-like crystal revealed lower values for the new crystal habit, which can be attributed to the preferential orientation of the crystals in the compressed disks.Fil: Kuminek, Gislaine. Universidade Federal de Santa Catarina; BrasilFil: Rauber, Gabriela Schneider. Universidade Federal de Santa Catarina; BrasilFil: Riekes, Manoela Klüppel. Universidade Federal de Santa Catarina; BrasilFil: Campos, Carlos Eduardo Maduro de. Universidade Federal de Santa Catarina; BrasilFil: Monti, Gustavo Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; ArgentinaFil: Bortoluzzi, Adailton João. Universidade Federal de Santa Catarina; BrasilFil: Cuffini, Silvia Lucia. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidade Federal de Santa Catarina; BrasilFil: Cardoso, Simone Goncalves. Universidade Federal de Santa Catarina; Brasi