Strong Aqueous Gels of Cellulose Nanofibers and Nanowhiskers Isolated from Softwood Flour

TAPPI Journal ◽  
2011 ◽  
Vol 10 (2) ◽  
pp. 7-14 ◽  
Author(s):  
GUAN GONG ◽  
AJI P. MATHEW ◽  
KRISTIINA OKSMAN
Keyword(s):  
Acid Hydrolysis ◽  
Aqueous Suspension ◽  
Cellulose Nanofibers ◽  
Low Frequency ◽  
Aqueous Gels ◽  
Frequency Independent ◽  
Solids Content ◽  
Mechanical Fibrillation ◽  
20 Nm ◽  
Long Fibers

Two nanocelluloses (cellulose nanofibers [CNF] and nanowhiskers [CNW]) were extracted from softwood flour using chemical refining followed either by mechanical fibrillation or acid hydrolysis. The CNF slurry formed an opaque gel that exhibited highly coiled and entangled long fibers with widths between 10 and 20 nm when studied using atomic force microscopy (AFM). The aqueous suspension of the CNW formed a transparent gel with unique morphology of rigid and uniform, whiskerlike structures with widths as low as 1.5–3 nm and lengths in micrometer levels. The viscoelastic properties of these hydrogels with solids content of 0.2 wt% were measured using dynamic rheology experiments. The elastic modulus (G') and viscous modulus (G'') were frequency independent in the low-frequency region. Furthermore, G' was almost 10-fold higher than G'', showing a typical elastic gel behavior. The lower crystallinity obtained from X-ray analysis indicated that the unique structure of CNW from wood could be attributed to the native cellulose being partly dissolved and regenerated during acid hydrolysis.

Isolation of Nanocellulose from Pomelo Fruit Fibers by Chemical Treatments

2013 ◽  
Vol 747 ◽  
pp. 363-366 ◽  
Author(s):  
Niti Yongvanich ◽  
Pattama Visuttpitukul
Keyword(s):  
Electron Microscopy ◽  
Acid Hydrolysis ◽  
Alkali Treatment ◽  
Aqueous Suspension ◽  
Cellulose Nanofibers ◽  
Compact Structure ◽  
X Ray ◽  
Chemical Treatments ◽  
Transmission Electron ◽  
20 Nm

This study aims to isolate cellulose nanofibers from locally abundant pomelo fruit. Only the inner, soft peels were selected for investigation. The peels were subjected to alkali treatment (NaOH) with different concentrations and soaking times. Acid hydrolysis was also carried out to obtain an aqueous suspension of nanocellulose. The treated cellulose fibers were characterized by various methods. The effect of alkali treatment was initially confirmed by Fourier Transformed Infrared (FTIR) Spectra which displayed disappearance of several peaks belonging to non-cellulosic materials. The sharpening of the absorption at around 914 cm-1 is attributed the β-glycosidic linkages between the sugar units in cellulose. Alkali treatment also helped eliminate the non-cellulosic constituents via reduction in the 1240 and 1750 cm-1 peak. Thermogravimetric (TG) analysis revealed an improved onset of degradation likely caused by an increase in crystallinity evidenced by X-ray diffractometry (XRD) through the presence of two well-defined reflections characteristic of cellulose. The morphological and structural characterization by Scanning electron microscopy (SEM) still revealed a compact structure even after alkali treatment. However, acid hydrolysis was successful in individualizing cellulose nanofibers as observed by transmission electron microscopy (TEM). The diameter of these nanofibers was in the 10 - 20 nm range with various lengths.

Mode Switching of the Natural Low-Frequency Oscillations of the Tobacco Mosaic Virus when the Temperature of Its Aqueous Suspension Changes

JETP Letters ◽  
2021 ◽  
Vol 113 (11) ◽  
pp. 733-737
Author(s):  
A. F. Bunkin ◽  
M. A. Davydov ◽  
A. N. Fedorov ◽  
M. V. Arkhipenko ◽  
V. B. Oshurko ◽  
...  
Keyword(s):  
Tobacco Mosaic Virus ◽  
Mosaic Virus ◽  
Aqueous Suspension ◽  
Low Frequency ◽  
Mode Switching ◽  
Low Frequency Oscillations

Low-Frequency Stimulated Raman Scattering on Acoustic Vibrations of Dielectric Nanospheres in Aqueous Suspension

2018 ◽  
Vol 45 (6) ◽  
pp. 187-189 ◽  
Author(s):  
A. F. Bunkin ◽  
M. A. Davydov ◽  
V. N. Lednev ◽  
S. M. Pershin ◽  
E. A. Trifonova ◽  
...  
Keyword(s):  
Raman Scattering ◽  
Stimulated Raman Scattering ◽  
Aqueous Suspension ◽  
Low Frequency ◽  
Acoustic Vibrations ◽  
Stimulated Raman

scholarly journals Cellulose Nanofibers Preparation from Cassava Peels via Mechanical Disruption

Fibers ◽  
2019 ◽  
Vol 7 (5) ◽  
pp. 44
Author(s):  
Sonny Widiarto ◽  
Edi Pramono ◽  
Suharso ◽  
Achmad Rochliadi ◽  
I Made Arcana
Keyword(s):  
Physical Properties ◽  
Acid Hydrolysis ◽  
Alkali Treatment ◽  
Cellulose Nanofibers ◽  
Chemical Properties ◽  
Bleaching Process ◽  
Mechanical Disruption ◽  
Similar Chemical ◽  
Cassava Peels

In this study, cellulose and cellulose nanofibers (CNF) were extracted and prepared from cassava peels (CPs). The method of the cellulose extraction was performed by alkali treatment followed by a bleaching process. The CNF were prepared by mechanical disruption procedure (homogenization and ultrasonication), and the results were compared with a common acid hydrolysis procedure. The resulting cellulose and CNF from both procedures were then analyzed using FTIR, SEM, TEM, XRD, and TGA. The results show that cellulose and CNF were successfully prepared from both procedures. The physical properties of the produced CNF were different; however, they had similar chemical properties.

scholarly journals Effect of Unbleached Rice Straw Cellulose Nanofibers on the Properties of Polysulfone Membranes

Polymers ◽  
2019 ◽  
Vol 11 (6) ◽  
pp. 938 ◽  
Author(s):  
Mohammad Hassan ◽  
Ragab E. Abou Zeid ◽  
Wafaa S. Abou-Elseoud ◽  
Enas Hassan ◽  
Linn Berglund ◽  
...  
Keyword(s):  
Rice Straw ◽  
Lower Cost ◽  
Lignin Content ◽  
Aqueous Suspension ◽  
Cellulose Nanofibers ◽  
Water Flux ◽  
Current Work ◽  
Medium Size ◽  
Maximum Improvement ◽  
Sulfite Pulp

In addition to their lower cost and more environmentally friendly nature, cellulose nanofibers isolated from unbleached pulps offer different surface properties and functionality than those isolated from bleached pulps. At the same time, nanofibers isolated from unbleached pulps keep interesting properties such as hydrophilicity and mechanical strength, close to those isolated from bleached pulps. In the current work, rice straw nanofibers (RSNF) isolated from unbleached neutral sulfite pulp (lignin content 14%) were used with polysulfone (PSF) polymer to make membrane via phase inversion. The effect of RSNF on microstructure, porosity, hydrophilicity, mechanical properties, water flux, and fouling of PSF membranes was studied. In addition, the prepared membranes were tested to remove lime nanoparticles, an example of medium-size nanoparticles. The results showed that using RSNF at loadings from 0.5 to 2 wt.% can significantly increase hydrophilicity, porosity, water flux, and antifouling properties of PSF. RSNF also brought about an increase in rejection of lime nanoparticles (up to 98% rejection) from their aqueous suspension, and at the same time, with increasing flux across the membranes. Tensile strength of the membranes improved by ~29% with addition of RSNF and the maximum improvement was obtained on using 0.5% of RSNF, while Young’s modulus improved by ~40% at the same RSNF loading. As compared to previous published results on using cellulose nanofibers isolated from bleached pulps, the obtained results in the current work showed potential application of nanofibers isolated from unbleached pulps for improving important properties of PSF membranes, such as hydrophilicity, water flux, rejection, and antifouling properties.

DIELECTRIC PROPERTIES OF DRY, GEOLOGIC MATERIALS

Geophysics ◽  
1970 ◽  
Vol 35 (4) ◽  
pp. 624-645 ◽  
Author(s):  
M. Saint‐Amant ◽  
David W. Strangway
Keyword(s):  
Dielectric Properties ◽  
Loss Tangent ◽  
Relaxation Times ◽  
Low Frequency ◽  
Frequency Dispersion ◽  
Relaxation Peak ◽  
Debye Relaxation ◽  
Thermally Activated ◽  
Geologic Materials ◽  
Frequency Independent

A detailed investigation of the dielectric properties of powdered and solid dry rocks in the frequency range of 50 hz to 2 mhz has revealed the following general characteristics: 1) All dry rocks, powdered and solid, show an increase in both the dielectric constant and the loss tangent as frequency decreases and as temperature increases. This dispersion is believed to be due to polarization associated with charge buildup at grain boundaries or at grain imperfections. 2) Dry powdered rocks often show a thermally‐activated relaxation peak with a typical Debye‐relaxation character. This is due to the presence of pyroxene and biotite and may be associated with other minerals. The relaxation peak is not seen in solid rocks, where it is hidden by the low‐frequency dispersion. 3) At high frequencies, the loss tangent approaches a constant value which is frequency independent. This behavior is observed in many dielectrics and may be the result of a distribution of relaxation times.

Extraction of Bamboo Nanofibers Using Acid Hydrolysis for Functional Chemicals of Ecological Dyeing and Finishing

2012 ◽  
Vol 441 ◽  
pp. 759-763 ◽  
Author(s):  
Yong Zhang ◽  
Guo Xin Xue ◽  
Xiu Mei Zhang ◽  
Yan Jun Tang
Keyword(s):  
Acid Hydrolysis ◽  
Cellulose Nanofibers ◽  
Average Diameter ◽  
Degree Of Polymerization ◽  
X Ray Diffraction ◽  
Surface Charges ◽  
Aggregation State ◽  
Transmission Electron ◽  
Different Types ◽  
Bamboo Fibers

In this work a study on the feasibility of extracting cellulose nanofibers from bamboo fibers, by means of three different procedures was carried out. These processes included the using of three different types of acids (H2SO4, HCl, and a mixture of H2SO4/HCl). The raw bamboo fibers were mercerized with NaOH solutions. They were then submitted to the three different acid hydrolysis processes. The final bamboo nanofibers were morphologically characterized by transmission electron microscopy (TEM) and their surface charges in suspensions were estimated by Zeta-potential. Their degree of polymerization (DP) was characterized by viscometry and the crystallinity was tested by X-ray diffraction (XRD). All bamboo nanofibers presented a rod-like shape, an average diameter (D) of 6-10 nm and length (L) of 100-180 nm, with an aspect ratio (L/D) of around 16-18. The aggregation state increases with the amount of HCl introduced into the extraction, due to the decrease of surface charges. However, this release presented nanofibers with litter better degree of polymerization than those whose acid hydrolysis was carried out using only H2SO4.

Field and/or resistivity mapping in MT-VLF and implications for data processing

Geophysics ◽  
1994 ◽  
Vol 59 (11) ◽  
pp. 1695-1712 ◽  
Author(s):  
Roger Guerin ◽  
Alain Tabbagh ◽  
Pierre Andrieux
Keyword(s):  
High Frequency ◽  
Low Frequency ◽  
Test Site ◽  
Horizontal Polarization ◽  
Resistivity Measurements ◽  
Magnetic Components ◽  
Frequency Independent ◽  
Prismatic Bodies ◽  
Lateral Variations ◽  
A Current

The ratio of the horizontal electric and magnetic components of the electromagnetic field generated by a radio transmitter in the very low frequency (VLF) range is used in MT-VLF resistivity mapping to determine the apparent resistivity of the ground. A theoretical calculation of the responses of simple 2-D and 3-D prismatic bodies shows that the measurable lateral variations in both fields are independent, uncoupled, and correspond to frequency‐independent, static variations. It is advantageous therefore to process and map the fields separately. Processing methods used in gravimetry and magnetics are especially appropriate in correcting the apparent anisotropy related to the horizontal polarization of the primary field and in integrating (upward continuation) the high‐frequency spatial variations. The different processes tested on a synthetic case and on data obtained at the Centre de Recherches Géophysiques (CRG) test site showed how to eliminate shallow features and a current channeling conductor to favor the anomaly of a fault. A third example with a hydrogeological application shows the advantages of this method over Wenner direct‐current resistivity measurements.

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