Specific Surface Area Calculation At least three data points in the Vg relative pressure range 0.05 to 0.30 …… Y=mX+ m+I V(P/P1-1 Total surface area= Weight of adsorbate 0-10-203 Total surface area SSA(Specific surface area Weight of sample http://nano.materials.drexel.edu Single Point BET / Single-point method offers the advantage of simplicity and speed, often with little loss in accuracy V=v 1-P/P 1.e 1/slope A relative pressure of 0. 3 gives good general agreement with the multi-point method Correction of single point"error"at P/po=0.3 by multiplying the single point BET value by CIC-2 decreases the difference Sample Multi-poin Uncorrected Uncorrected Corrected Corrected BET single-point difference differenc m2l 4.923 4.241 13.9 4.948 0.51 3.664 14.5 4.275 0.26 6.867 8.011 -0.56 5.957 5.194 12.8 +1.73 1515 http://nano.materials.drexel.edu Specific Surface Area Calculation Specific Surface Area Calculation P V C P V C C V P P P m o m o a ( 1) 1 ( ) ⎟ + ⎠ ⎞ ⎜ ⎝ − ⎛ = − Y =mX+i m i Vm + = 1 P/Po 1 V[(Po/P)-1] 0-1 0-2 0-3 At least three data points in the relative pressure range 0.05 to 0.30 Weight of adsorbate Totalsurface area Vm NavAcs = Weight of sample Totalsurface area SSA (Specific surface area) = http://nano.materials.drexel.edu Single Point BET Single Point BET ¾Single-point method offers the advantage of simplicity and speed, often with little loss in accuracy. ( ) o Vm =Va 1− P P i.e. Vm = 1/slope ¾A relative pressure of 0.3 gives good general agreement with the multi-point method. ¾ Correction of single point “error” at P/P0 = 0.3 by multiplying the single point BET value by C/C-2 decreases the difference. 5.957 8.056 4.286 4.923 Multi-point BET (m2/g) 5.194 6.867 3.664 4.241 Uncorrected single-point (m2/g) -12.8 -14.8 -14.5 -13.9 Uncorrected difference (%) 4 3 2 1 Sample No. 6.060 +1.73 8.011 -0.56 4.275 -0.26 4.948 0.51 Corrected difference (%) Corrected single – point (m2/g)