Electron Microscopy of Modified Aluminum Alkoxide Microstructures on Freeze–Drying
✍ Scribed by Anuj Srivastava; Ashok R. Menon; Jayesh R. Bellare
- Publisher
- Elsevier Science
- Year
- 1997
- Tongue
- English
- Weight
- 713 KB
- Volume
- 191
- Category
- Article
- ISSN
- 0021-9797
No coin nor oath required. For personal study only.
✦ Synopsis
microstructural evolution in gels during freeze-drying. The high vacuum environment of the SEM coupled with intentional heating of the gel sample Direct imaging of microstructures in chelated aluminum alkoxwith a heater or under the electron beam produces conditions very similar ide systems subjected to freeze-drying and freeze-thaw -drying to those prevalent in a freeze-dryer.
is reported using cryo-scanning electron microscopy (SEM) and
The objective of the research reported here was to study the morphology SEM techniques. Aluminum sec-butoxide was chelated with a bof the unchelated and chelated aluminum alkoxide gels freeze-dried in a diketoester in different molar ratios. This system was gelled by cryo-SEM environment and comparing them with the morphology of hydrolysis under intense sonication. The sonogels formed were freeze-thaw-dried gels using SEM. subjected to cryo-SEM. Samples for cryo-SEM were made by freezing the chelated alkoxide samples in liquid nitrogen and EXPERIMENTAL freeze -fracturing them inside the cryo-SEM and monitoring the apparent morphological changes on exposure to the cryo-SEM
The materials used were aluminum sec-butoxide (ASB) (Fluka), isoproenvironment including intentional sample heating. Microstrucpyl alcohol (IPA), and ethyl acetoacetate (EAA) from the b-diketone tures of unchelated, 1:1 chelated and 1:2 chelated ( alkoxide:chelfamily. Three types of gels were prepared for the study. Concentration of ate) sonogels after freezing, thawing, and drying were also imaged ASB for all samples were kept at 0.82 mol/liter of solvent (IPA). Modified by SEM techniques. Heterogeneity introduced by chelation of al-ASB was prepared by ultrasonically agitating ASB with two different molar koxide is proposed as the cause for the formation of flakes in ratios of EAA with IPA. The different molar ratios of ASB:EAA used were freeze -thaw -dried chelated alkoxide gels. Microstructures of 1:1 1:1 and 1:2. The detailed procedure for sample preparation is given else- chelated freeze dried alkoxide were compared with the freezewhere (5) and involved hydrolysis together with the use of ultrasonic processing.
thaw -dried gels. The absence of flakes in the chelated samples Sonication was performed using Brason-450 probe type sonicator at when subjected to in situ freeze-drying indicated reversible na-18.750 kHz at 90 W output at 30ЊC. The sonogelation process resulted in ture of the gels. ᭧ 1997 Academic Press formation of homogeneous gels in these systems within a few minutes