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The formation of aluminum borates (Al 18 B 4 O 33 and Al 4 B 2 O 9) from alumina and boron oxide occurs between 600 and 800°C. These materials have refractory properties and corrosion resistance. The objective of this work is to develop materials from the Al 2 O 3-B 2 O 3 system, employing alumina and boric acid as starting powders, to study the critical processing variables and describe the developed microstructure and properties. Three formulations (13, 19.5 and 26 wt% B 2 O 3) were studied. In order to confirm the formation of borates, the differential thermal analysis and thermogravimetric analysis were carried out. Afterwards, uniaxially pressed disc-shaped specimens were fired at four temperatures above the formation temperature. The textural properties of the ceramics were evaluated by the immersion method, this permit to evaluate the sintering processes. Then the degree of borate formation was confirmed by X-ray diffraction. Finally, the developed microstructures were characterized by scanning electron microscopy, and the diametral compression behavior was evaluated. A series of porous (≈50%) refractory materials from the Al 2 O 3-B 2 O 3 system were developed. The processing strategy resulted in materials with Al 18 B 4 O 33 as the main crystalline phase. Needle grains with diameters between 0.2 and 1 µm and an aspect ratio over 20:1 were obtained. Thus, based on the information gathered from our research, aluminum borate ceramic materials can be designed for structural, insulating or filtering applications employing only alumina and boric acid as boron oxide source.

The protective properties of dodecanethiol layers against copper corrosion in a Borax buffer containing chloride anions are investigated by using electrochemical techniques complemented with scanning tunneling microscopy. Results show that copper is protected against corrosion provided that the copper electrode does not reach the potential region of Cu(II) oxide formation and the concentration of chloride ions in the environment remains low. These findings should be taken into account for the use of alkanethiol layers for the corrosion protection of copper.

The Vaca Muerta Formation (Tithonian-early Valanginian) is the main source rock in the Neuquén Basin and the most important unconventional shale resource in South America. In the present study, organic geochemistry, electron microscopy and basin and petroleum system modelling (BPSM) were combined to evaluate source rock properties and related processes along a transect from the early oil (east) to the dry gas (west) window. The unit is characterized by high present-day (1%-8% average) and original (2%-16% average) total organic carbon contents, which increase to-

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In this article we assess and compare the complex mechanical behavior of two complex microstructure ceramics material formed within the reaction sintering framework Two comparable pairs of materials with respectively similar microstructures were obtained by reaction sintering from boric acid and alumina. Two single phase porous ceramics were compared with two composite (1:1) porous ceramic. The first and second phases were aluminum borate needles (Al 18 B 4 O 33) and alumina (Al 2 O 3). The four with comparable grain size and analogous apparent porosities: in diameter (≈ 0.7 µm) and in volume fraction (≈ 45%). The mechanical behavior was studied by means of the diametral compression test at low displacement rate and explained in terms of the texture, microstructure features evaluated by mercury intrusion porosimetry and scanning electron microscopy. Single Al 18 B 4 O 33 phase porous materials presented higher mechanical strengths than the composite materials. Within the respective microstructural configurations the whisker thickness did not affect significantly the mechanical behavior and parameters. A well-defined fragile behavior was observed and described in the composite material. On the other hand the single Al 18 B 4 O 33 needle porous material presented a distinctive behavior with local discontinuities without loss of integrity in the diametral stress behavior, and achieved strength up to 50% higher than the corresponding composite.

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