This review is devoted to the analysis of the problems related to fabrication of the Si porous layers. The review was motivated by a great interest to Si-based porous materials from nano- to macro-scale for various applications in electronics, optoelectronics, photonics, chemical sensors, biosensors, etc. The peculiarities of the silicon porosification and the principles of preparing porous layers are considered in the present article. Various methods used for Si porosification such as chemical stain etching, chemical vapor etching, laser-induced etching, metal-assisted etching, spark processing and reactive ion (plasma) etching were analyzed. However, the main attention was focused on electrochemical porosification of Si. The review discusses in detail the influence of parameters such as electrolyte composition and pH, current density, etching time, temperature, wafer doping and orientation, lighting, magnetic field, and ultrasonic agitation on the process of Si porosification. It was shown that the stru...

Silicon Porosification: State of the Art

Pyrolysis of fast-growing aquatic biomass - Lemna minor (commonly known as duckweed) with the emphasis on production, characterization and catalytic application of bio-char is reported in this paper. The yield of bio-char was determined as a function of L. minor pyrolysis temperature and sweep gas flow rate. It was found that the pore development during L. minor pyrolysis was not significant and the changes in the reaction conditions (temperature and sweep gas flow rate) did not alter markedly the textural characteristics and BET surface area of the bio-char produced. Thermogravimetric/differential thermogravimetric (TG/DTG) analyses of L. minor and different bio-char samples in inert (helium) and oxidative (air) media showed substantial differences in their TG/DTG patterns. A comparison of scanning electron micrographs (SEM) of L. minor, bio-char and ash indicated that the basic structural features of L. minor remained intact and were not affected by thermolysis. The inorganic ash content of L. minor derived bio-char is significantly higher than that of typical terrestrial (plant) biomass. The energy dispersive spectroscopic (EDS) analysis of L. minor ash showed that it mostly consisted of silica, and small quantities of Na, K and Ca compounds. The treatment of bio-char with CO2 at 800 °C increased its BET surface area. It was found that CO2-treated bio-char exhibited appreciable initial catalytic activity in biogas reforming.

Production and characterization of Lemna minor bio-char and its catalytic application for biogas reforming

Preparation of a geopolymer from red mud slurry and class F fly ash and its behavior at elevated temperatures

Production and analysis of fuels and chemicals obtained from rice husk pyrolysis with concentrated solar radiation

Extracellular environments can regulate cell behavior because cells can actively sense their mechanical environments. This study evaluated the adhesion, proliferation and morphology of endothelial cells on polydimethylsiloxane (PDMS)/alumina (Al2 O3 ) composites and pure PDMS. The substrates were prepared from pure PDMS and its composites with 2.5, 5, 7.5, and 10 wt % Al2 O3 at a curing temperature of 50°C for 4 h. The substrates were then characterized by mechanical, structural, and morphological analyses. The cell adhesion, proliferation, and morphology of cultured bovine aortic endothelial (BAEC) cells on substrate materials were evaluated by using resazurin assay and 1,1'-dioctadecyl-1,3,3,3',3'-tetramethylindocarbocyanine perchlorate-acetylated LDL (Dil-Ac-LDL) cell staining, respectively. The composites (PDMS/2.5, 5, 7.5, and 10 wt % Al2 O3 ) exhibited higher stiffness than the pure PDMS substrate. The results also revealed that stiffer substrates promoted endothelial cell adhesion and proliferation and also induced spread morphology in the endothelial cells compared with lesser stiff substrates. Statistical analysis showed that the effect of time on cell proliferation depended on stiffness. Therefore, this study concludes that the addition of different Al2 O3 percentages to PDMS elevated substrate stiffness which in turn increased endothelial cell adhesion and proliferation significantly and induced spindle shape morphology in endothelial cells.

Endothelial cell responses in terms of adhesion, proliferation, and morphology to stiffness of polydimethylsiloxane elastomer substrates.

Se presenta un estudio de la evolucion de las caracteristicas de los espectros de FTIR y la respuesta de fotoluminiscencia (PL) en peliculas de silicio poroso (PSL) oxidadas quimicamente y envejecidas en condiciones controladas. Las PSL se obtuvieron por el metodo electroquimico para obtener buena uniformidad en grandes areas. Las mediciones de FTIR en las PSL recien preparadas manifiestan bandas de siliciohidrogeno asociadas con la terminacion en hidrogeno de superficie de silicio poroso justo despues del proceso de porificacion. Al oxidar las peliculas, los distintos modos de vibracion se modifican. Esos modos de vibracion se relacionan con los defectos en el oxido de silicio que recubre la superficie del silicio poroso. Los espectros de PL en muestras recien preparadas presentan un maximo en ~700 nm. El espectro de PL en las PSL oxidadas quimicamente y luego envejecidas, en condicion de vapor de agua saturado, se modifica fuertemente con respecto a las muestras recien obtenidas. Estas variaciones estan asociadas con los cambios en la estructura de las PSL inducidos por los procesos de oxidacion. Los datos de FTIR y el comportamiento de la senal de PL nos permiten relacionar estas senales con los efectos de cuantizacion por pequenas dimensiones e indicar que las transiciones a altas energias las produce algun centro de defecto en la pelicula de oxido de silicio que se forma en su superficie. Las caracteristicas de las PSL reportadas en este trabajo son perfectamente reproducibles en las condiciones que se utilizaron para prepararlas; por ello, las peliculas pueden usarse en distintas aplicaciones.

/pdf/ftir-and-photoluminescence-studies-of-porous-silicon-layers-53pvba2hpg.pdf

FTIR and photoluminescence studies of porous silicon layers oxidized in controlled water vapor conditions

CO$_2$ concentration sensor based on the infrared (IR) absorption is presented, by using a pyroelectric detector the sample absorbed IR radiation is obtained and the CO$_2$ concentration is calculated, system capabilities, sensibility, repeatibility and, time response of developed system are studied, results show that based on a photopyroelectric technique is possible to get an accurate CO$_2$ measurement system.

http://www.scielo.org.mx/pdf/rmf/v62n3/0035-001X-rmf-62-03-00278.pdf

G. Aguila Rodríguez

Papers

FTIR and photoluminescence studies of porous silicon layers oxidized in controlled water vapor conditions

CO2 measurement system based on pyroelectric detector