Erease usb disk:
diskutil eraseDisk MS-DOS "WINDOWS10" MBR disk#
Open the Windows 10 ISO, it mount as a volume named CCCOMA_X64FRE_XX_DV9, use the following command to copy its contents to the USB drive:
cp -rp /Volumes/CCCOMA_X64FRE_EN-US_DV9/* /Volumes/WINDOWS10/