Abstract: This work presents ANOVA and Tukey’s statistic tests that were conducted in Knoop microhardness results of boron carbide sintered samples. Three samples, A, B, and C, of different processing conditions were tested and statistical analysis showed that microhardness results are strongly influenced by porosity and chemical composition, mainly due to the presence of C(2H) and WB2.5 contaminant phases. Those phases promoted higher densification in A and B samples and it was found that A ≈ B > C is the relation between the microhardness results of the samples, while A ≈ B < C is the porosity ratio of the samples. Furthermore, this work aims to apply a statistical tool to evaluate the microhardness results performed on advanced ceramics and, using these results, to control parameters in the sintering process, showing that a deeper statistical analysis is necessary for the interpretation and validation of the results merit.

Abstract: A novel freezing unit was developed for use in ceramic processing by the freeze casting technique. This step is crucial, since the macrostructure promoted by this technique is formed during freezing. Several authors present basic information about the apparatus used in the freezing step, but there are no studies that describe a complete unit as we do in this work and there is no commercial equipment for this purpose. The components of the freezing unit were selected according to function, suitability to project, cost and market availability. Advanced ceramic samples of ZnFe2O4, MnFe2O4, CoFe2O4, NiFe2O4, SiO2, Al2O3 and metallic Cu were produced using the freezing unit and the results of typical macrostructure and porosity analysis validated the chosen setup.

Abstract This study processed and characterized the biphasic ceramics Na2Ti3O7/Na2Ti6O13 that were obtained from semi-crystalline nanoparticles synthesized using sonochemical methods. Structural characterization techniques, such as X-ray diffraction and Raman spectroscopy, were used to identify the crystalline phases present. The Rietveld refinement revealed, among other structural parameters, the presence of two crystalline phases in compositions of 55.90% and 44.10% for sodium hexatitanate and trititanate, respectively. Via Raman spectroscopy, the presence of the main vibrational modes that correspond to the phases present in biphasic ceramics was confirmed. Finally, by using complex impedance spectroscopy, a decrease in the electrical resistance of both the grain (106 Ω-104 Ω) and its boundary (108 Ω -105 Ω) under increasing temperature was identified.

1-furoyl-3,3-diethylthiourea was used as a novel neutral carrier in ion selective electrode for copperII detection and determination. The Cu2+ selective plasticized polyvinyl chloride (PVC) membrane electrode exhibited reversible potential responses with Nernstian slope of 29.34± 0.6 mV/decade for Cu2+ ions in the concentration range from 1.0x10-7 to 1.0x10-2 mol/dm³ with a practical detection limit (PDL) of 3.84x10-7 and lower limit of linear response (LLLR) of 6.15x10-7 mol/dm³ and alife-time of 20 days. The response time, pH effect and other characteristics of the electrodes were also studied.

An optimized methodology for improving regeneration of maize plants by direct organogenesis was evaluated. Our objective was to obtain genetically homogeneous plants through in vitro methods to regenera-te clumps of multiple shoots from shoot tips at high frequency. Cultures were initiated from shoot tips of experimental lines of maize on a Murashige & Skoog (MS) medium supplemented with 2 mg/l benziladenine. Two experimental forage maize lines were used, in which two frequencies of subcultu-res were evaluated, namely line L. 850 (every 15 or 30 days) and line L.769 (every 30 days). It was observed that the highest rate of regeneration in line L.850 was reached in the second subculture (1.8 plants) with subculture every 30 days, and in the fifth subculture (1.8 plants) with subculture every 15 days. In line L.769, the highest frequency of regeneration was reached in the fourth subculture (1.7 plants). Regeneration rates were low compared with somatic embryogenesis, but no somaclonal variations were detected in field plant phe-notypes; a marked uniformity was detected within lines.

Se evaluó una metodología de cultivo in vitro tendiente a mejorar la regeneración de plantas de maíz por organogénesis directa, con el objetivo de lograr múltiples vástagos genéticamente homogéneos. La misma consiste en la utilización del meristema apical como explanto y el agregado de 2 mg/l de benziladenina (BA) al medio de cultivo Murashige y Skoog (MS). Se utilizaron dos líneas experimentales de maíces forrajeros. En éstos se evaluaron dos frecuencias de subcultivos (cada 15 ó 30 días) en la línea L.850 y 1 frecuencia (cada 30 días) para la línea L.769. La línea L.850 alcanzó su máxima tasa de regeneración en el segundo repique (1,8 plantas) con subcultivos cada 30 días, y en el quinto subcultivo (1,8 plantas) con sub-cultivos cada 15 días. La línea L.769 alcanzó la máxima tasa de regeneración en el cuarto subcultivo (1,7 plantas). Los valores mencionados son bajos comparados con embriogénesis somática, pero no se detectaron variaciones somaclonales en los fenotipos de las plantas a campo; se observó una acentuada uniformidad dentro de las líneas.

A study was made of wood fiber directions and the resulting surface roughness of radiata pine during a planing process employing acoustic emission control. There have been some studies of the planing process for radiata pine in situations where surface quality problems arise when machining conditions are not well controlled. It is known from previous studies that acoustic emission signals (RMS) are a good monitoring element of the surface roughness under different cutting conditions. The variations in acoustic signals are related to the roughness and to chip formation. The purpose of this study was to establish the most suitable machining conditions for planing radiata pine to achieve the required surface roughness and to determine its relationship to the acoustic emission signals so that surface quality can be easily controlled.

Se estudia la rugosidad superficial resultante del proceso de cepillado de Pinus radiata D. Don. con diferentes ángulos de fibra y su monitoreo con emisión acústica. Algunos estudios se han realizado sobre el proceso de cepillado en pino radiata, donde los problemas de calidad superficial durante el corte no han sido bien controlados. Es conocido que las señales de emisión acústica (RMS) son una buena herramienta en el monitoreo de la rugosidad superficial con diferentes condiciones de corte. Estudios previos permiten afirmar que cambios en las condiciones de corte afectan las señales de emisión acústica, estas variaciones están relacionadas con la rugosidad superficial y la formación de viruta. El propósito de este estudio es investigar cuáles son las condiciones de cepillado de madera de pino radiata que permitan lograr una rugosidad superficial correcta y al mismo tiempo determinar su relación con la emisión acústica (EA) en términos que la calidad de la superficie pueda ser fácilmente controlada.