气凝胶的性质和生产

1、Material Synthetic ChemistryPPT PresentationGroup 290 1 2 3 4 50 1 2 3 4 40 1 2 3 4 30 1 2 3 4 0 1 2 3 4 A Heavyweight Guest will A Heavyweight Guest will Attend the PPT Competition Attend the PPT Competition ACADEMIC NEWS AND GOSSIPWORLD EXCLUSIVESTHEUSTC NEWSThe ppt competition of the class “mater

2、ial synthetic chemistry” is held in 5204，building 5，USTC today. Students from different majors are ready to give wonderful reports. A heavyweight guest will also attend this competition. Who will it be？ Lets wait and see!2010.12.29AerogelWhats the lightest solid material in the world？Aerogel a manuf

3、actured material with the lowest bulk density of any known porous solid. derived from a gel in which the liquid component of the gel has been replaced with a gas. It is nicknamed frozen smoke,solid smoke, solid air or blue smoke IIntroductionin the 1968,A French called Teichner found a better synthe

4、tic process, namely sol-gel method using TMOS,replacing the sodium silicate used by Kistler with an alkoxysilane.HistoryHistoryThe first aerogel has been created in 1931 by Steven Kistler, due to a bet made with Charles Learned over who would be able to replace the liquid state into a jelly-like sub

5、stance with gas, without reducing its originalVolumeAerogel: More than 99% gasLess than 1% solid in volume The density can be as low as 0.003g/cm3Types1.Silica Aerogelmost commonstrongly absorbs infrared radiation remarkable thermal insulative properties 2.Carbon Aerogelhigh porosity ，high surface a

6、rea 3.Aliumina Aerogelused as catalysts ，doped with another metal Propertieslow densityhigh strengthhigh surface area low dielectric constant high thermal and acoustical resistivitylow refractive indexsemi-elasticbrittlePerformanceProduction of AerogelMain Method :Sol-GelReaction Mechanism （ For Sil

7、icon Alkoxide）Reaction Mechanism（For Water Soluble Silicates (Na2SiO3)）Supercritical dryingSupercritical dryingsurface tension at the solid-liquid interface cause the collapse of the gel bodya “supercritical” fluid in which every molecule can move about freely and the surface tension ceasesSupercrit

8、ical drying Ambient pressure dryingDrawbacks： High cost Energy-intensive Poor process continuity High riskpursue for other economic methodsReduce the surface tension of solventImprove the uniformity of the pore of gelModify surface chemicallyAmbient pressure dryingAmbient Pressure Drying Surface Che

9、mical ModificationCharacterization（Pore structure） Characterization（Optical Properties）The intrinsic absorbance is low in the visible region.Weak absorbances begin to appear in the near infrared, cuts off transmission around 2700-3200 nmThe Si-O-Si fundamental vibration 1100 cm-1O-H stretching vibra

10、tions 3500 cm-1Characterization（Thermal Properties）Carbon is an effective absorber of infrared radiationtrap space dust particles aboard the Stardust spacecraft0 1 2 3 4 鸣谢鸣谢University of Science and Technology of China Shanghai Institute of Ceramics，Chinese Academy of ScienceShanghai Institute of Optics and Fine Mechan