Dvelopment of EPR Low Temperature in Situ Device and its Application on Catalyst Characterization

The EPR low temperature in situ device from 77K to 300K had been developed. A good heat-insulating material-polytetrafluoroethylene film with slotting was used to wrap up the quartz casing in cavity so as to reduce heat exchanging betwen quartz casing and out side, and N₂ flew continuously from chink between quartz casing and cavity through microwave tube out off the end of cavity, in order to avoid the water congealing outside quartz casing in cavity and make microwave electric magnetic fields entered efficaciously sample tube with satisfied electric magnetic field boundary conditions so that EPR low temperature in situ experiment could be conducted. The EPR low temperature in situ device was made of quartz tube, Dewar bottle of wide mouth and good head-exchanging copper spiral tube. Changing flow velocity of cooled N₂ gas blowing to the sample tube could regulate the experimental temperature. The device effectively overomed the limitation of the present general EPR low temperature experimental device-finger-model quartz Dewar bottle experimental device at 77 K and helium closed cyclic cryocooler: liquid N₂ bubbling, expensive making material and complicated making technology, etc. The ideal experimental results were obtained by applying the above developed device to detect the VMgO catalyst active sites.