Solid lipid microparticles were tested as microencapsulation systems for protecting β-carotene from degradation. Blends of long-chain (C18) solid lipids (70% stearic acid) and sunflower oil (30%) were used to produce lipid microparticles encapsulating the carotenoid. Polysorbate 80 (4%) was employed to stabilize the stearic acid microparticles. The concentration of β-carotene was monitored using spectrophotometry, the particle size distribution was measured by laser diffraction, the crystal structure was determined by wide angle X-ray diffraction (WAXD), and the thermal behaviour was characterized by differential scanning calorimetry (DSC) over a period of seven months. All of the systems had an average particle size smaller than 5 µm. To avoid β-carotene oxidation, α-tocopherol was added to the formulations and its action as an oxygen trap was crucial for the antioxidant effect. For stearic-acid microparticles with a-tocopherol, more than 90% of the initial amount of β-carotene was preserved after seven months under refrigerated storage (7-10°C) in the dark. Significant microstructural alterations were detected using WAXD and DSC only in the stearic acid microparticles without alpha-tocopherol. These results seemed promising and suggested that the blends of long-chain solid lipids and liquid lipids were suitable for the production of stable solid lipid microparticles.

Estudou-se o efeito da adição de monoglicerídeo nas propriedades microestruturais, mecânicas e de barreira de filmes de amido de inhame, em diferentes umidades relativas (UR), comparando-as com as de filmes de amido- glicerol. Uma extrusora mono-rosca foi usado para produzir o complexo amido-monoglicerídeo, antes de produzir o filme, e o processo foi efetivo para inibir a separação de fases que geralmente ocorre nesse tipo de filmes. A adição de monoglicerídeo, que é um composto hidrofóbico, reduziu a hidrofilicidade, a transparência e a permeabilidade ao vapor de água dos filmes. O valor desta, para os filmes de amido-glicerol (1,7 x 10-10 g Pa-1 s-1 m-1) foi maior que para os de amido (1,2 x 10-10 g Pa-1 s-1 m-1) e para os de amido-monoglicerídeo (1,0 x 10-10 g Pa-1 s-1 m-1). Os filmes com glicerol tiveram maior cristalinidade relativa (B e V H), com um ligeiro aumento em altas UR, enquanto que nos filmes com monoglicerídeo a cristalinidade foi constante. Os filmes de amido-monoglicerídeo apresentaram piores propriedades mecânicas que os filmes de amido-glicerol, mas foram mais estáveis sob diferentes umidades relativas.

The effect of monoglyceride on microstructural, barrier and mechanical properties of casted yam starch films were investigated in different relative humidities (RH) and compared with glycerol-starch films. A single screw extruder was used to produce the starch - monoglyceride complex before film production and this process was effective to inhibit the phase separation in films. The addition of the hydrophobic compound reduced hydrophobicity, transparency and water vapor permeability of films. This later value for starch-glycerol film (1.7 x 10-10 g Pa-1 s-1 m-1) was higher than starch (1.2 x 10-10 g Pa-1 s-1 m-1) and monoglyceride-starch films (1.0 x 10-10 g Pa-1 s-1 m-1). Films containing glycerol had higher relative crystallinity (B and V H) with a slight increase at higher RH values, while for monoglyceride films, the crystallinity was constant. Monoglyceride-starch films presented poor mechanical properties when compared to glycerol- starch ones but they presented a stable behavior under different relative humidities.

The aim of this work was to study the effect of austenitic grain size (GS) reduction on the structural parameters of the epsilonhcp - martensite in stainless shape memory alloy (SMA). Rietveld refinement data showed an expansion in c-axis and a reduction in a and b-axis with thermo-mechanical cycles for all samples analyzed. Samples with 75 < GS (µm) < 129 were analyzed. It was also observed an increase of the unit cell volume in this phase with GS reduction. The smallest grain size sample (GS = 75 µm) presented a c/a ratio of 1.649, and approximately 90% of total shape memory recovery.

The temperature induced phase transition in MnAs is analyzed in this work using X ray Rietveld refinement. The results show the presence of the hexagonal phase (P6(3)/mmc) at room temperature and the first-order structural-magnetic transition to the orthorhombic phase (Pnma) around 318 K was followed in detail. The MnAs magnetic characterization allowed to obtain the transition temperature and a maximum value of 47 J/(kg.K) for the measured magnetocaloric effect for a magnetic field variation of 5 T.

Gd5(Ge1-xSi x), x < 4 based alloys are potential candidates for magnetic refrigeration in the range ~20 - ~290 K. However, one of the greatest obstacles for the use of that technology in large scale is the utilization of high pure Gd metal (99.99 wt. (%)) to produce the GdGeSi alloys, since the impurity elements decrease the intensity of the magnetocaloric effect (EMC)¹. In this work, we prove that annealing of the Gd5Ge2Si2 can promote remarkable values for the EMC in comparison to those obtained for the alloy with high pure Gd. Also, the as cast alloy and the annealed alloy are not monophasic, but have at least two crystalline phases in their microstructure. Results for X-ray analysis, optical and electronic microscopy and magnetization measurements are reported.