共查询到20条相似文献,搜索用时 31 毫秒
1.
Mehdi Jonoobi Jalaluddin Harun Aji P. Mathew Mohd Zobir B. Hussein Kristiina Oksman 《Cellulose (London, England)》2010,17(2):299-307
The aim of this study was to develop cellulose nanofibers with hydrophobic surface characteristics using chemical modification.
Kenaf fibers were modified using acetic anhydride and cellulose nanofibers were isolated from the acetylated kenaf using mechanical
isolation methods. Fourier transform infrared spectroscopy (FTIR) indicated acetylation of the hydroxyl groups of cellulose.
The study of the dispersion demonstrated that acetylated cellulose nanofibers formed stable, well-dispersed suspensions in
both acetone and ethanol. The contact angle measurements showed that the surface characteristics of nanofibers were changed
from hydrophilic to more hydrophobic when acetylated. The microscopy study showed that the acetylation caused a swelling of
the kenaf fiber cell wall and that the diameters of isolated nanofibers were between 5 and 50 nm. X-ray analysis showed that
the acetylation process reduced the crystallinity of the fibers, whereas mechanical isolation increased it. The method used
provides a novel processing route for producing cellulose nanofibers with hydrophobic surfaces. 相似文献
2.
Eliangela de Morais Teixeira Ana Carolina Corrêa Alexandra Manzoli Fabio de Lima Leite Cauê Ribeiro de Oliveira Luiz Henrique Capparelli Mattoso 《Cellulose (London, England)》2010,17(3):595-606
Suspensions of white and colored nanofibers were obtained by the acid hydrolysis of white and naturally colored cotton fibers.
Possible differences among them in morphology and other characteristics were investigated. The original fibers were subjected
to chemical analysis (cellulose, lignin and hemicellulose content), X-ray diffraction (XRD) analysis, and scanning electron
microscopy (SEM). The nanofibers were analyzed with respect to yield, elemental composition (to assess the presence of sulfur),
zeta potential, morphology (by scanning transmission electron microscopy (STEM)) and atomic force microscopy (AFM), crystallinity
(XRD) and thermal stability by thermogravimetric analysis in air under dynamic and isothermal temperature conditions. Morphological
study of several cotton nanofibers showed a length of 85–225 nm and diameter of 6–18 nm. The micrographs also indicated that
there were no significant morphological differences among the nanostructures from different cotton fibers. The main differences
found were the slightly higher yield, sulfonation effectiveness and thermal stability under dynamic temperature conditions
of the white nanofiber. On the other hand, in isothermal conditions at 180 °C, the colored nanofibers showed a better thermal
stability than the white. 相似文献
3.
Xiangqian Shen Mingquan Liu Fuzhan Song Xianfeng Meng 《Journal of Sol-Gel Science and Technology》2010,53(2):448-453
The SrFe12O19/poly (vinyl pyrrolidone) (PVP) composite fiber precursors were prepared by the sol-gel assisted electrospinning with ferric
nitrate, strontium nitrate and PVP as starting reagents. Subsequently, the M-type strontium ferrite (SrFe12O19) nanofibers were derived from calcination of these precursors at 750–1,000 °C.The composite precursors and strontium ferrite
nanofibers were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy
and vibrating sample magnetometer. The structural evolution process of strontium ferrite consists of the thermal decomposition
and M-type strontium ferrite formation. After calcined at 750 °C for 2 h the single M-type strontium ferrite phase is formed
by reactions of iron oxide and strontium oxide produced during the precursor decomposition process. The nanofiber morphology,
diameter, crystallite size and grain morphology are mainly influenced by the calcination temperature and holding time. The
SrFe12O19 nanofibers characterized with diameters of around 100 nm and a necklace-like structure obtained at 900 °C for 2 h, which
is fabricated by nanosized particles about 60 nm with the plate-like morphology elongated in the preferred direction perpendicular
to the c-axis, show the optimized magnetic property with saturation magnetization 59 A m2 kg−1 and coercivity 521 kA m−1. It is found that the single domain critical size for these M-type strontium ferrite nanofibers is around 60 nm. 相似文献
4.
Mingquan Liu Fuzhan Song Xiangqian Shen Yongwei Zhu 《Journal of Sol-Gel Science and Technology》2010,56(1):39-46
The composite nanofibers of xSrSiO3/(100 − x)SrFe12O19 (x = 0–13 wt%) with diameters around 110 nm have been prepared by calcination of the electrospun SrSiO3/SrFe12O19/poly (vinyl pyrrolidone) (PVP) composite fibers at 800–900 °C. The composite nanofibers were characterized by Fourier transform
infrared spectroscopy, X-ray diffraction, scanning electron microscopy and vibrating sample magnetometer. After calcined at
800° the M-type strontium ferrite is formed and the strontium silicate exists as an amorphous state when the calcination temperature
below about 950 °C. The addition of SrSiO3 has an obvious suppression effect on the strontium ferrite grain growth and the ferrite grain size decreases from 66.9 to
33.5 nm corresponding SrSiO3 content from 0 to 9 wt% in the composite. The specific saturation magnetization (Ms) of the xSrSiO3/(100 − x)SrFe12O19 composite nanofibers exhibits a continuous reduction from 58.0 to 45.6 A m2 kg−1 with the increase of SrSiO3 content from 0 to 13 wt%. With addition of SrSiO3 from 0 to 13 wt%, the coercivity of the composite nanofibers obtained at 900 °C initially increases, reaching a maximum value
501.1 kA m−1 at the silicate content 7 wt%, and then shows a reduction tendency with the strontium silicate content increase further up
to 13 wt%. This influence on the coercivity by strontium silicate can be attributed mainly to the ferrite grain growth suppression
and the non-magnetic phase barrier for the domains misalignment. 相似文献
5.
Ana Carolina Corrêa Eliangela de Morais Teixeira Luiz Antonio Pessan Luiz Henrique Capparelli Mattoso 《Cellulose (London, England)》2010,17(6):1183-1192
Curaua nanofibers extracted under different conditions were investigated. The raw fibers were mercerized with NaOH solutions;
they were then submitted to acid hydrolysis using three different types of acids (H2SO4, a mixture of H2SO4/HCl and HCl). The fibers were analyzed by cellulose, lignin and hemicellulose contents; viscometry, X-ray diffraction (XRD)
and thermal stability by thermogravimetric analysis (TG). The 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, crystallinity by XRD and thermal stability by TG. Increasing the NaOH solution concentration
in the mercerization, there was a decrease of hemicellulose and lignin contents and consequently an increase of cellulose
content. XRD patterns presented changes in the crystal structure from cellulose I to cellulose II when the fibers were mercerized
with 17.5% NaOH solution. All curaua nanofibers presented a rod-like shape, an average diameter (D) of 6–10 nm and length
(L) of 80–170 nm, with an aspect ratio (L/D) of around 13–17. The mercerization of fibers with NaOH solutions influenced the
crystallinity index and thermal stability of the resulting nanofibers. The fibers mercerized with NaOH solution 17.5% resulted
in more crystalline nanofibers, but thermally less stable and inferior DP. The aggregation state increases with the amount
of HCl introduced into the extraction, due to the decrease of surface charges (as verified by Zeta Potential analysis). However,
this release presented nanofibers with better thermal stability than those whose acid hydrolysis was carried out using only
H2SO4. 相似文献
6.
Wei Zheng Xiaofeng Lu Wei Wang Zhenyu Li Hongnan Zhang Zhaojie Wang Xiuru Xu Shangyu Li Ce Wang 《Journal of colloid and interface science》2009,338(2):366-370
In this paper, we presented a simple and effective solution route to deposit Pt nanoparticles on electrospun In2O3 nanofibers for H2S gas detection. The morphology and chemical structure of the as-prepared samples were analyzed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectra (XPS). The results showed that large quantities of In2O3 nanofibers with diameters about from 60 to 100 nm were obtained and the surface of them was decorated with Pt nanoparticles (5–10 nm in size). The In2O3 nanofibers decorated by Pt nanoparticles exhibited excellent gas sensing properties to H2S, such as high sensitivity, good selectivity and fast response at relatively low temperature. 相似文献
7.
Soo-Jin Park George G. Chase Kwang-Un Jeong Hak Yong Kim 《Journal of Sol-Gel Science and Technology》2010,54(2):188-194
Flexible mats of titania fibers are prepared by calcination of electrospun polyvinylpyrrolidone fibers containing titanium
isopropoxide precursor. Structural investigation of the calcinated nanofibers by X-ray diffraction (XRD) and electron diffraction
(ED) combined with the morphologies by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) show
the titania fibers, with an average diameter of 180 nm, were comprised of anatase and rutile crystals. The mechanical, chemical
and thermal properties of the titania fiber mats are further investigated by the techniques of Instron mechanical tester,
thermogravimetric analyzer (TGA), and Fourier transform infrared spectroscopy (FT-IR). The titania fiber mat prepared in this
method exhibited a significant flexibility with 461 MPa Young’s modulus. 相似文献
8.
Shidi Tang Yuanfu Deng ShuZhong Zhan 《Journal of Thermal Analysis and Calorimetry》2011,104(2):653-659
A new heterobimetallic nitrilotriacetatoperoxotitanate complex of titanium and lead [Pb(H2O)3]2[Ti2(O2)2O(nta)2]·4H2O (C6H6O6N=H3nta) was isolated in pure crystals directly from the solution containing tetrabutyl orthotitanate, hydrogen peroxoide, lead
acetate, and nitrilotriacetic acid at pH = 2.0–4.0. The isolated complex was characterized by elemental analyses, IR spectrum,
thermal analysis (TG), and single-crystal X-ray diffraction. The single-crystal X-ray structural analysis revealed that the
titanium atom is N,O,O′,O′′-chelated by the nitrilotriacetate and O,O′-chelated by the peroxo group and was coordinated to
the bridging O atom in an overall pentagonal-bipyramidal geometry. The thermal decomposition of this precursor led to the
formation of phase-pure lead titanate (PbTiO3) at ≥450 °C. The morphology, microstructure, and crystalline of the resulting PbTiO3 product have been characterized by BET, transmission electron microscopy, and powder X-ray diffraction. The TEM micrographs
revealed that the size of the as-synthesized crystallines to be 50–100 nm range. The BET measurement revealed that the PbTiO3 powders had a surface area of 5.6 m2/g. 相似文献
9.
Wenshuai Chen Haipeng Yu Yixing Liu Yunfei Hai Mingxin Zhang Peng Chen 《Cellulose (London, England)》2011,18(2):433-442
Cellulose nanofibers (CNFs) were isolated from four kinds of plant cellulose fibers by a chemical-ultrasonic treatment. The
chemical composition, morphology, crystalline behavior, and thermal properties of the nanofibers and their intermediate products
were characterized and compared. The CNFs extracted from wood, bamboo, and wheat straw fibers had uniform diameters of 10–40 nm, whereas the flax fibers were not uniformly nanofibrillated because of their initially high cellulose content. The chemical
composition of each kind of nanofibers was mainly cellulose because hemicelluloses and lignin were significantly removed during
chemical process. The crystallinity of the nanofibers increased as the chemical treatments were applied. The degradation temperature
of each kind of nanofiber reached beyond 330 °C. Based on the properties of the CNFs, we expect that they will be suitable
for use in green nanocomposites, filtration media and optically transparent films. 相似文献
10.
Jinhee Choi Juyun Park Jisoo Kang Margaret W. Frey Jin-Woo Oh Yong-Cheol Kang 《Surface and interface analysis : SIA》2019,51(6):641-648
Copper-tin (CuSn) nanomaterials have been receiving substantial attention due to their excellent thermal, electrical, and optical properties. However, how such properties are affected based on heat treatment temperature and chemical composition of copper and tin is still not very well understood. In this paper, CuSn nanofibers were fabricated by electrospinning a precursor solution of polyacrylonitrile, copper, and tin. Calcination temperatures were selected using thermogravimetric/differential thermal analysis (TG/DTA) and Fourier transform infrared (FT-IR) results. Analytical techniques such as scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and ultraviolet photoelectron spectroscopy (UPS) were employed to investigate the physicochemical properties of the CuSn nanofibers. SEM images and EDS revealed the formation of pores on the nanofibers and high concentrations of tin were in the core, while copper was located on the surface. XRD results confirmed the monoclinic phase of Cu6Sn5 for the CuSn nanofibers because peaks for diffraction angles at 27.6°, 53.4°, and 60.0° were observed. XPS results showed that Cu―C and Sn―C bonds occur at binding energies around 932 and 484 eV, respectively. The work function of the CuSn NF heat treated at 150°C was calculated from the UPS spectra, and the value was 4.19 eV. 相似文献
11.
Sreeraj Gopi Augustine Amalraj Shintu Jude K.T. Benson Preetha Balakrishnan Józef T. Haponiuk 《高分子科学杂志,A辑:纯化学与应用化学》2019,56(4):327-340
Turmeric spent, a by-product of turmeric processing industries, was used as a source to prepare nanofibers (NF). The chemical treatments methods followed by acid hydrolysis accompanied with high pressure homogenization were used to prepare NF. The resulting turmeric nanofibers (TNF) were characterized by Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), X-ray diffraction (XRD) and thermogravimetric analysis (TGA/DTA). The TNF presented needle like structure, high thermal stability, an average width of 38.5?nm, average length of 245.7?nm, and giving an aspect ratio (L/D) of 23.15. The prepared TNF showed pronounced antimicrobial activity against Bacillus cereus, Escherichia Coli, Salmonella typhimurium and Staphylococcus aureus and also registered good antioxidant activity. The results showed that TNF were successfully obtained from turmeric spent and might be potentially applied in different fields, such as pharmaceutical, biological active species, nutraceuticals, components for food industries and bionanocomposites. 相似文献
12.
Tetragonal copper ferrite (CuFe2O4) nanofibers were fabricated by electrospinning method using a solution that contained poly(vinyl pyrrolidone) (PVP) and Cu and Fe nitrates as alternative metal sources. The as-spun and calcined CuFe2O4/PVP composite samples were characterized by TG-DTA, X-ray diffraction, FT-IR, and SEM, respectively. After calcination of the as-spun CuFe2O4/PVP composite nanofibers (fiber size of 89 ± 12 nm in diameter) at 500 °C in air for 2 h, CuFe2O4 nanofibers of 66 ± 13 nm in diameter having well-developed tetragonal structure were successfully obtained. The crystal structure and morphology of the nanofibers were influenced by the calcination temperature. After calcination at 600 and 700 °C, the nature of nanofibers changed which was possibly due to the reorganization of the CuFe2O4 structure at high temperature, and a fiber structure of packed particles or crystallites was prominent. Crystallite size of the nanoparticles contained in nanofibers increases from 7.9 to 23.98 nm with increasing calcination temperature between 500 and 700 °C. Room temperature magnetization results showed a ferromagnetic behavior of the calcined CuFe2O4 samples, having their specific saturation magnetization (Ms) values of 17.73, 20.52, and 23.98 emu/g for the samples calcined at 500, 600, and 700 °C, respectively. 相似文献
13.
Franciele Maria Pelissari Paulo José do Amaral Sobral Florencia Cecilia Menegalli 《Cellulose (London, England)》2014,21(1):417-432
Cellulose nanofibers were isolated from banana peel using a combination of chemical treatments, such as alkaline treatment, bleaching, and acid hydrolysis. The suspensions of chemically treated fibers were then passed through a high-pressure homogenizer 3, 5, and 7 times, to investigate the effect of the number of passages on the properties of the resulting cellulose nanofibers. The cellulose nanofibers isolated in this study had a dry basis yield of 5.1 %. Transmission electron microscopy showed that all treatments effectively isolated banana fibers in the nanometer scale. The micrographs of the process steps used to isolate the nanofibers revealed gradual removal of amorphous components. Increasing number of passages in the homogenizer shortened the cellulose nanofibers while furnishing more stable aqueous suspensions with zeta potential values ranging from ?16.1 to ?44.1 mV. All the samples presented aspect ratio in the range of long nanofibers, hence being potentially applicable as reinforcing agents in composites. X-ray diffraction studies revealed that homogenized nanofiber suspensions were more crystalline than non-homogenized suspensions. Fourier transform infrared spectroscopy confirmed that alkaline treatment and bleaching removed most of the hemicellulose and lignin components present in the banana fibers. Thermal analyses revealed that the developed nanofibers exhibit enhanced thermal properties. In general, the nanoparticles isolated from the banana peel have potential application as reinforcing elements in a variety of polymer composite systems. 相似文献
14.
Carboxymethyl cellulose Sn(IV) phosphate composite nano-rod like cation exchanger with diameter in the range of 20–40 nm,
length in the range of 100–150 μm and particle size in the range of 21–38 nm have been successfully prepared by surfactant
assisted sol–gel method. Scanning electron microscopy, transmission electron microscopy, X-ray powder diffraction, fourier
transform infra red spectroscopy and thermogravimetric analysis-differential thermal analysis studies were carried out to
study the structure and morphology of this composite nano-rod like cation exchanger. Freundlich adsorption isotherm is well
fitted for the adsorption of pyridine on the surface of this composite nano-rod like cation exchanger. The thermodynamic parameters
such as Freundlich constant, thermodynamic equilibrium constant (K
0), standard free energy changes (ΔG
0), standard enthalpy changes (ΔH
0) and standard entropy changes (ΔS
0) have been evaluated. These parameters indicated that the adsorption of pyridine on the surface of composite nano-rod like
cation exchanger was feasible, spontaneous and exothermic in nature which suggests for the potential application of pyridine
removal from water. 相似文献
15.
This paper describes a procedure of preparing sodium tantalite nanofibers for the first time. Sodium tantalite nanofibers
were synthesised by electrospinning a sol–gel precursor solution of poly(vinyl pyrrolidone)/sodium tantalite, followed by
careful sintering of the as-electrospun composite fibers at 550 °C for 3 h. The morphology, microstructure and crystal phase
were investigated by transmission electron microcopy and X-ray diffraction. The optical property was characterized by ultraviolet–visible
(UV–vis) spectrometer. Typical nanofibers were with diameter between 70 and 90 nm and length exceeding 0.1 mm. An unusual
phenomenon, the red-shift of optical absorption band edge happened, indicated the fabricated NaTaO3 nanofibers were potential good candidates for photocatalytic application. The experiment photodegradation of methylene blue
by NaTaO3 nanofibers under UV light irradiation was performed. 相似文献
16.
This study examined the relationship between the functions of plant cells and the characteristics of cellulose microfibril
aggregates in the cell walls. For this purpose, the mature bamboo (Phyllostachys pubescens) culm was separated into fiber and parenchyma cells, and then the morphological and physical properties of the cellulose
microfibril aggregates isolated from both cells were compared. SEM observations revealed that both fiber and parenchyma cells
consist of similar microfibril aggregates approximately 15–20 nm in width. Moreover, X-ray analysis and the tensile tests
of the sheets prepared from the microfibril aggregates showed that the cellulose microfibrils isolated from fiber and parenchyma
cells had almost the same cellulose crystallinity and longitudinal Young’s modulus in the dry state. These results suggest
that all the cellulose microfibrils synthesized in the same individual exhibit the same characteristics in the dry state regardless
of cell function. 相似文献
17.
K.V. Syamala G. Panneerselvam G.G.S. Subramanian M.P. Antony 《Thermochimica Acta》2008,475(1-2):76-79
The lattice thermal expansion characteristics of europium titanate (Eu2TiO5) have been studied by measuring the lattice parameter by high temperature X-ray diffraction technique (HT-XRD) in the temperature range 298–1573 K. Percentage linear thermal expansion and mean linear thermal expansion coefficients were computed from the lattice parameter data. The percentage linear thermal expansion in the temperature range 298–1573 K along a, b and c axes are 1.05, 1.15 and 0.95 respectively. 相似文献
18.
To date, biosynthesis of metal nanoparticles has been intensively studied using bacteria and fungi. We have isolated and identified metal resistant bacterial strains from electroplating industries, they produce silver nanoparticles. The reduction reaction of aqueous silver nitrate with bacterial biomass was carried out for 120 h. Bacteria produced metallic nanoparticles showed a strong absorbance at surface plasmon resonance wavelength around 420 nm. The size and morphology of these nanoparticles were typically imaged using high resolution transmission electron microscopy, the particles size ranges between 4 and 5 nm and are spherical in shape. The crystal structure of the particles was characterized by X-ray diffraction pattern. The full width half maxima from X-ray diffraction measurements indicated that the particles exhibited face-centered cubic phase. 相似文献
19.
Well-dispersed cellulose II nanofibers with high purity of 92 % and uniform width of 15–40 nm were isolated from wood and compared to cellulose I nanofibers. First, ground wood powder was purified by series of chemical treatments. The resulting purified pulp was treated with 17.5 wt% sodium hydroxide (NaOH) solution to mercerize the cellulose. The mercerized pulp was further mechanically nanofibrillated to isolate the nanofibers. X-ray diffraction patterns revealed that the purified pulp had been transformed into the cellulose II crystal structure after treatment with 17.5 wt% NaOH, and the cellulose II polymorph was retained after nanofibrillation. The cellulose II nanofiber sheet exhibited a decrease in Young’s modulus (8.6 GPa) and an increase in fracture strain (13.6 %) compared to the values for a cellulose I nanofiber sheet (11.8 GPa and 7.5 %, respectively), which translated into improved toughness. The cellulose II nanofiber sheet also showed a very low thermal expansion coefficient of 15.9 ppm/K in the range of 20–150 °C. Thermogravimetric analysis indicated that the cellulose II nanofiber sheet had better thermal stability than the cellulose I nanofiber sheet, which was likely due to the stronger hydrogen bonds in cellulose II crystal structure, as well as the higher purity of the cellulose II nanofibers. 相似文献
20.
Rodica Olar Mihaela Badea Dana Marinescu Larisa Calu Cristina Bucur 《Journal of Thermal Analysis and Calorimetry》2011,105(2):571-575
Novel complexes of type [M2LCl4]·nH2O ((1) M:Ni, n = 5; (2) M:Cu, n = 0 and (3) M:Zn, n = 2; L: ligand resulted from 1,2-phenylenediamine, 3,6-diazaoctane-1,8-diamine and formaldehyde template condensation) were
synthesised and characterised. The features of complexes have been assigned from microanalytical, IR and UV–Vis data. The
thermal analyses have evidenced the thermal intervals of stability and also the thermodynamic effects that accompany them.
Processes as water or hydrochloric acid elimination as well as oxidative degradation of the organic ligand were observed.
Complexes display a different thermal behaviour as result of dissimilar chemical interaction of metal ions with chloride anions.
The final product of decomposition was metal(II) oxide as powder X-ray diffraction indicated. 相似文献