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

Performance augmentation of machining centers by improving the overall equipment effectiveness in subsystems

Abstract The demand for increase in performance of the manufacturing units is increasing day by day. This project work aims at improving the Overall Equipment Effectiveness (OEE) of a Hardinge 600 II series Vertical Machining Centre (VMC) machine by modification of its subsystems. The problems related to higher power consumption and decreases in the units produced per unit hour were taken for analysis. By analyzing the earlier conditions it was found that the productivity of the VMC machine was found to be limited because of low OEE. The installation of an accumulator in the hydraulic system of work holding device and a simplification of the chip removal mechanism was proposed on the VMC subsystem. Also these changes were only possible to be done effectively by removing the existing conveyer belt and introducing tray disposal system. After the suggested changes were made the machine was again investigated to check for any possible increase in the OEE. An increase of 40% in OEE was achieved after implementation of the suggested changes. The improvement in OEE could be followed in similar machines such as HMC machines, FMS setups and other machines through proper steps for better productivity of the manufacturing facility.</jats:p

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

ABSTRACTHigh 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(&lt; 1 °C/min). It was found that sol gel processed boehmite transformed to alpha alumina at a relatively lower temperature (∼ 1080 °C ) than the as prepared boehmite which transformed at about 1200 °C.</jats:p

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