Hydrolysis of aluminium metal, synthesis of nano alumina and sol-gel processing of monoliths

High purity alumina is usually prepared using various intermediate aluminium compounds such as aluminium nitrate, aluminium alkoxides etc., as precursors. In fact the above mentioned intermediate aluminium compounds themselves are produced from aluminium metal. The present investigation is concerned with examining the feasibility of using aluminium hydroxides prepared by hydrolyzing aluminium metal, for sol gel processing. The study assumes added significance in view of the claims of Alcoa that it is possible to produce high purity aluminium metal in large quantities economically. During the present investigation sols were prepared by using various hydroxides, ie., bayerite, gibbsite and boehmite. Sol gel transition was observed only in the case of boehmite sol and this was gelated by either forced gelation method to prepare powder or controlled gelation method to prepare monoliths. Transparent Xerogels (boehmite) could be prepared by controlled gelation method but the presence of a thin layer of bayerite often resulted in translucency. Crack free monoliths could be prepared by heating the xerogels at a low heating rate(< 1 degrees C/min). It was found that sol gel processed boehmite transformed to alpha alumina at a relatively lower temperature (similar to 1080 degrees C ) than the as prepared boehmite which transformed at about 1200 degrees C

Hydrolysis of aluminium metal and sol-gel processing of nano alumina

Aluminium metal has been hydrolysed at 100 degreesC to synthesize boehmite. Gelatinous and dry boehmite were used to prepare stable sol. In the case of gelatinous boehmite, sol was prepared by peptizing and in the case of dry boehmite an ultrasonic bath was used to prepare the sol. Gelation was carried out by heating on a hot plate, which resulted in sol-gel processed powder. For sol-gel processed boehmite the theta --> alpha transformation occurred at 1078 degreesC and for the as prepared boehmite the same occurred at 1206 degreesC. Sol-gel processed powder could be transformed to alpha alumina completely, when calcined at 1000 degreesC for 1 h. (C) 200

A New Record of Seagrass Halophila beccarii Ascherson in Bangladesh

During a study of the species diversity and distribution of seagrasses from the Andaman and Nicobar Islands, Halophila beccarii was recorded for the first time. This report updates the list of seagrasses for these islands from nine to ten species. Halophila beccarii was observed in an intertidal area of muddy substratum in Haddo Bay. The occurrence of this species is significant because of its new distributional record and because it is reported as a “vulnerable species” in the IUCN Red List. The morphometric characters, biomass of the species and its habitat are described in Haddo Bay

Influence of Alkali-Treated Fibers on the Mechanical Properties and Machinability of Roselle and Sisal Fiber Hybrid Polyester Composite

In this work, the alkali-treated roselle and sisal fibers were used as reinforcement fillers for thermosetting matrix with aim of obtaining better mechanical properties and machinability of natural fiber hybrid polyester composite. However, their mechanical properties and machinability were compared with untreated fiber composites. The roselle and the sisal fibers were subjected to a 10% sodium hydroxide solution treatment at different duration of 2, 4, 6, and 8 h. Besides, the fractured surfaces of composite specimen were investigated using scanning electron microscopy. Drill hole profiles were analyzed using profile projector and machine vision inspection system. An improvement in strength and stiffness combined with high toughness was achieved by treating the fibers using 10% NaOH solution. POLYM. COMPOS., 31:723–731, 2010. ª 2009 Society of Plastics Engineer

A first record of <em>Gomeza bicornis </em>Gray 1831 (Decapod: Corystidae) in India, from seagrass habitat of Andaman Islands

1866-1869Gomeza bicornis is recorded for the first time from Andaman Islands at three different locations by core sample, during seagrass survey. It belongs to the family Corystidae which has 3 genera and 9 species, dwell in sandy substratum and burrows in seagrass habitat