Besides the morphological aspects, the TEM images allowed the observation of a variation in the average particle width (d) and length (L), thus enabling determination of the aspect ratio (L/d) of the yielded nanocellulose products. Significant differences were noticed for the average particle length. It was clearly observed that the average diameter (d) of CNCCr(NO3)3 was comparable to that of CNCH2SO4, the length (L) of the former product seems to be much longer than the latter product, and this gave rise to the presumably higher aspect ratio (L/d). The use of MCC as starting material hydrolyzed in the H2SO4 system led to the formation of CNCH2SO4 having an average fiber width of approximately 9.9 ± 3.2 nm with an average length of 34.8 ± 14.2 nm providing an aspect ratio of 3.5. Meanwhile, the inorganic salt-treated CNCCr(NO3)3 displayed a mean width of 29.1 ± 7.8 nm, a length of 455.7 ± 38.1 nm and an aspect ratio of 15.7. Briefly, CNCCr(NO3)3 rendered stronger reinforcing effect (i.e., higher tensile strength and modulus) than that of CNCH2SO4 contributed by its high aspect ratio, making it become an ideal reinforcing agent for polymer matrix . In addition, CNCCr(NO3)3 with higher aspect ratio might exhibit higher optical transmittance when it is used for preparing nano-paper or reinforcement for polymer composites .