Here are some rhythmic figures which combine sixteenth notes and eighth notes within one beat. These figures are very common, so you will need to know them well. Practice each one carefully and be sure to tap your foot and count.
Once you have learnt these rhythms on a single note, try using them with the minor pentatonic scale as shown here. The more familiar you are with these rhythms, the easier you will find it to play parts containing 16th notes as well as improvising with them.
As soon as you start to feel comfortable with 16th note rhythms, try using them to create riffs. Here are some examples using the notes of the A minor pentatonic scale.
This one combines three note power chords with 4th intervals.
Here is another one with a more complex rhythm. Count carefully with this one.