boot - USB drive for macOSX made with dd doesn't work and now can't be used for anything

I bought a new USB drive and I tried to burn to it the mac os x 10.13.02 using dd:

Unmounted the drive

sudo umount /dev/sdb1

Burned the iso:

dd if="myfile.iso" of="/dev/sdb1"

After this I tried to restart and boot from flash, but it didn't work and the USB is corrupted - I can't access the files

When I try to mount it I get:

mz@mz-32:~$ sudo mount /dev/sdb1
[sudo] password for mz: 
mount: /dev/sdb1: can't find in /etc/fstab.