3. Results and discussion3.1. Visua

3. Results and discussion
3.1. Visual examination
The aqueous suspensions of the original wood fibers, chemicalpurified
cellulose fibers, and cellulose nanofibers after 30 min of
ultrasonic treatment with an output power of 400, 800, 1000, and
1200 W,respectively, were placed motionlessly at least 30 minafter
they were prepared, and then the photos in Fig. 2 were taken.
Raw wood fibers and chemical-purified cellulose fibers were precipitated
at the bottom of the glass bottle; brown wood fibers
became white after chemical purification, indicating that a significant
amount of lignin was removed. After ultrasonic treatment,
a substantial increase in the dispersion of the nanofiber suspensions
was observed when the ultrasonic output power increased
from 400 to 1200 W. Although the cellulose nanofibers were not
homogenously dispersed in water at 400 W, there was a noticeable
improvement when the output power increased to 800 W. After
an output power of 1000 or 1200W was conducted, a more colloidal
structure was obtained. Then the cellulose nanofibers were
sufficiently dispersed and converted to highly viscous suspensions.
This finding indicated that there was an improvement in the degree
of nanofibrillation of the cellulose fibers, and more surface area
on the nanofibers was exposed as the ultrasonic output power
increased.