Without this object, it's hard to tell. See the FAQ: How to do a minimal reproducible example reprex for beginners. The form of the code is ok.
dat <- data.frame(TMT_1 = mtcars[,1] / mtcars[,1],
TMT_2 = mtcars[,1] / mtcars[,2],
TMT_3 = mtcars[,1] / mtcars[,3],
TMT_4 = mtcars[,1] / mtcars[,4],
TMT_5 = mtcars[,1] / mtcars[,5],
TMT_6 = mtcars[,1] / mtcars[,6],
TMT_7 = mtcars[,1] / mtcars[,7],
TMT_8 = mtcars[,1] / mtcars[,8],
TMT_9 = mtcars[,1] / mtcars[,9])
head(dat,2)
#> TMT_1 TMT_2 TMT_3 TMT_4 TMT_5 TMT_6 TMT_7 TMT_8 TMT_9
#> 1 1 3.5 0.13125 0.1909091 5.384615 8.015267 1.275820 Inf 21
#> 2 1 3.5 0.13125 0.1909091 5.384615 7.304348 1.233843 Inf 21
Created on 2022-12-15 by the reprex package (v2.0.1)