Nm For Samples Research Articles

Investigation of structural, morphological, optical, and magnetic properties of Sm-doped LaFeO3 nanopowders prepared by sol–gel method

Pure orthorhombic phase of La1−xSmxFeO3 (x = 0, 0.1, 0.2, and 0.3) nanoparticles can be obtained by sol–gel method after calcination at 800 °C for 3 h in air. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, X-ray absorption near edge spectroscopy, ultraviolet-visible spectroscopy, and vibrating sample magnetometry were used to study the crystal structure, morphology, oxidation state, functional group, optical, and magnetic properties of samples. Pure orthorhombic phase of perovskite structure is confirmed by X-ray diffraction results. Decreasing lattice parameters, crystallite sizes, and cell volumes with increasing microstrains indicate structure distortion due to the substitution of Sm ions with small ionic radius on the La sites in the orthorhombic structure. Scanning electron microscopy and transmission electron microscopy images show a homogeneous distribution of almost spherical nanoparticles with decreasing average particle sizes ranging from 56.48 ± 3.22 to 23.21 ± 4.40 nm for samples of high Sm content. Fourier transform infrared spectroscopy spectra confirm the Fe–O stretching mode in octahedral FeO6 unit of a perovskite structure. X-ray photoelectron spectroscopy and X-ray absorption near edge spectroscopy results indicate the oxidation states +3 of La and Fe ions. The optical band gaps are found to decrease from 2.218 to 1.880 eV with increasing Sm content. vibrating sample magnetometry results show the antiferromagnetic behavior of undoped sample and ferromagnetic behavior for doped samples, affecting by structure distortion and particle size reduction. Interestingly, the coercive field is significantly enhanced from 95.07 Oe (x = 0.1) to 13,062.79 Oe (x = 0.3). Curie temperature (T c) is suggested to be above 400 K. The magnetization curves of La1-xSmxFeO3 (x = 0.0, 0.1, 0.2, and 0.3) nanoparticles prepared by the sol-gel method with the inset show the comparing coercive forces (Hc) of the present work and the previous works, La0.7M0.3FeO3 (M = Al and Ga). Sm-doped LaFeO3 nanoparticles can exhibit ferromagnetic behavior with the significant enhancement of Hc from 95.07 to 13,062.79 Oe.

Sonochemically assisted colloidal route to CdSe quantum dot assemblies: an alternative way to further fine-tune the size-dependent properties

Continuous-wave heterogeneous sonochemical method was developed to synthesize 3D assemblies composed by QDs of metastable (cubic) modification of CdSe with sphalerite structural type. 3D QD assemblies were deposited in thin film form and as bulk precipitates. Structure, surface morphology, optical absorption as well as charge carriers’ and phonon confinement effects were studied in details. The average nanocrystal radius, calculated by the Scherrer and Williamson–Hall methods, diminishes from 2.7 nm for samples synthesized by conventional colloidal chemical route to 2.0 nm for samples synthesized by sonochemical route. Upon post-deposition thermal annealing this value increases to 12.0 nm. QD size decrease is followed by increase of the uni-directional lattice strain and dislocation density (as defined by Hirsch), as well as by decrease of the lattice constant value. Previous findings were justified by analysis of X-ray diffraction peaks shape, which were found to be dominated by the particle size-distribution, instead of non-uniform strain. The energy of the fundamental direct \(\Gamma_{8}^{v} \to \Gamma_{6}^{c}\) interband electronic transition, computed from optical absorption data within parabolic approximation for the dispersion relation, shifts from 2.67 eV for sonochemically deposited samples and 2.08 eV for chemically deposited ones, to 1.77 eV upon post-deposition thermal treatment (close to the bulk value of 1.74 eV). The type of “interband” transitions does not change upon dimensionality reduce. Enhanced band gap energy blue shift upon average QD size decrease is followed by oscillator strength increase. Such trends were rationalized in terms of 3D confinement effects on charge carriers’ motion. Experimentally observed band gap energies agree very well with the predictions of the effective mass model of Brus. The next direct interband electronic transition, from the spin–orbit split component of the valence band to the conduction band, has been detected and analyzed. The 1LO bands in the Raman spectra of chemically and sonochemically deposited samples appear at 206 and 204 cm−1, as compared to the bulk value of 210 cm−1. The extent of homogeneous broadening of the corresponding band is larger in sonochemically deposited samples, indicating enhanced frequency of phonon–phonon collisions in smaller QDs. The observed frequency shifts are dominated by phonon-dispersion terms, instead of lattice contraction.

Magnetic microstructure in a stress-annealed Fe73.5Si15.5B7Nb3Cu1 soft magnetic alloy observed using off-axis electron holography and Lorentz microscopy

Fe-Si-B-Nb-Cu alloys are attractive for high frequency applications due to their low coercivity and high saturation magnetization. Here, we study the effect of stress annealing on magnetic microstructure in Fe73.5Si15.5B7Nb3Cu1 using off-axis electron holography and the Fresnel mode of Lorentz transmission electron microscopy. A stress of 50 MPa was applied to selected samples during rapid annealing for 4 s, resulting in uniaxial anisotropy perpendicular to the stress direction. The examination of focused ion beam milled lamellae prepared from each sample revealed a random magnetic domain pattern in the sample that had been rapidly annealed in the absence of stress, whereas a highly regular domain pattern was observed in the stress-annealed sample. We also measured a decrease in domain wall width from ∼ 94 nm in the sample annealed without stress to ∼ 80 nm in the stress-annealed sample.

Structural, Morphological, Optical and Magnetic Properties of Al-Doped CoFe2 O 4 Nanoparticles Prepared by Sol–Gel Auto-Combustion Method

CoFe2−xAlxO4 (x = 0.0,0.5,1.0, and 1.5) ferrite nanoparticles have been synthesized by the sol–gel auto-combustion method. The effect of non-magnetic Al content on their structural, morphological, optical, and magnetic properties was also investigated. X-ray diffraction (XRD) diffraction analysis was applied and indicated that the synthesized nanopowders of samples with x<1.5 and calcined at 800 ∘C have single-phase spinel structure. It has shown also by increasing Al content, the particle size, lattice parameter, unit cell volume, coercivity, anisotropy constant, and magnetization decrease, while the energy band gap increases. The size of particles was measured by TEM being in the range of 65–75 nm (for x = 0.0) and 9–10 nm (for x = 1.0). For sample with x = 1.5, the minimum calcination temperature for obtaining a single-phase spinel structure was 1000 ∘C. By increasing the calcination temperature from 1000 to 1100 ∘C, the mean crystallite size and crystallinity increase, while the lattice parameter, coercivity, anisotropy constant, and magnetization decrease. The average grain size evaluated by SEM analysis was found to be \(\tilde 91\) and 166 nm for samples calcined at 1000 and 1100 ∘C, respectively.

Ultrasound-assisted synthesis of nanosized zero-valent iron for metal cations extraction and wastewater treatment applications

Nanosized zero-valent iron has shown good results in wastewater treatment and activation of physicochemical processes. Its applications in modern industry are complicated by high production costs of nanomaterials produced via existing synthesis routes. Therefore there is a need of cheap and high-productive methods of nanosized zero-valent iron with advanced functional properties. Improvement of oxidative conditions with additions may find its place in extraction of rare-earth metals, where high cost of nanomaterials could be viable. In this paper we studied an effect of ultrasonic irradiation on specific surface area and particle size of nanosized zero-valent iron synthesized by methods of chemical precipitation with high- temperature reduction in hydrogen flow and sodium borohydride reduction. Obtained results showed significant decrease of particle size and differences in particles morphology depending on presence of ultrasonication during synthesis and on chosen method. For ultrasonic-assisted synthesis with 100% amplitude, particle size calculated from specific surface area was 70 nm for sample synthesized by chemical precipitation with high-temperature reduction and 35 nm for borohydide reduction method compared to 63 nm for reference sample without ultrasonication.

Influence of some sol-gel synthesis parameters of mesoporous TiO2 on photocatalytic degradation of pollutants

The titanium dioxide (TiO2) nanopowders were produced by sol-gel technique from tetrabutyl titanate as a precursor by varying some parameters of the sol-gel synthesis like the temperature (500 and 550 ?C) and the duration of the calcination (1.5, 2, and 2.5 h). X-ray powder diffraction (XRPD) results have shown that all synthesized nanopowders are dominantly in anatase phase, with the presence of a small amount of rutile in samples calcined at 550 ?C. According to the results obtained by Williamson-Hall method, the anatase crystallite size was increased with the duration of the calcination (from 24 to 29 nm in samples calcined at lower, and from 30 to 35 nm in samples calcined at higher temperature). The analysis of the shift and linewidth of the most intensive anatase Eg Raman mode confirmed the XRPD results. The analysis of pore structure from nitrogen sorption experimental data described all samples as mesoporous, with mean pore diameters in the range of 5-8 nm. Nanopowder properties have been related to the photocatalytic activity, tested in degradation of the textile dye (C.I. Reactive Orange 16), carbofuran and phenol.

Au nanostructure arrays for plasmonic applications: annealed island films versus nanoimprint lithography.

This paper attempts to compare the main features of random and highly ordered gold nanostructure arrays (NSA) prepared by thermally annealed island film and nanoimprint lithography (NIL) techniques, respectively. Each substrate possesses different morphology in terms of plasmonic enhancement. Both methods allow such important features as spectral tuning of plasmon resonance position depending on size and shape of nanostructures; however, the time and cost is quite different. The respective comparison was performed experimentally and theoretically for a number of samples with different geometrical parameters. Spectral characteristics of fabricated NSA exhibited an expressed plasmon peak in the range from 576 to 809 nm for thermally annealed samples and from 606 to 783 nm for samples prepared by NIL. Modelling of the optical response for nanostructures with typical shapes associated with these techniques (parallelepiped for NIL and semi-ellipsoid for annealed island films) was performed using finite-difference time-domain calculations. Mathematical simulations have indicated the dependence of electric field enhancement on the shape and size of the nanoparticles. As an important point, the distribution of electric field at so-called ‘hot spots’ was considered. Parallelepiped-shaped nanoparticles were shown to yield maximal enhancement values by an order of magnitude greater than their semi-ellipsoid-shaped counterparts; however, both nanoparticle shapes have demonstrated comparable effective electrical field enhancement values. Optimized Au nanostructures with equivalent diameters ranging from 85 to 143 nm and height equal to 35 nm were obtained for both techniques, resulting in the largest electrical field enhancement. The application of island film thermal annealing method for nanochips fabrication can be considered as a possible cost-effective platform for various surface-enhanced spectroscopies; while the NIL-fabricated NSA looks like more effective for sensing of small-size objects.

Effect of Nitriding Current Density on the Surface Properties and Crystallite Size of Pulsed Plasma-Nitrided AISI 316L

In this work, plasma-nitrided AISI 316L stainless steel samples were performed by ion nitriding process under pulsed direct current (DC) discharge at different current densities (1 to 2.5 mA/ cm 2 ). The effect of nitriding current density on the size of crystalline coherently diffracting domains (crystallite size) and strain grade was investigated using X-ray diffraction (XRD) coupled with Williamson-Hall method. Additionally, hardness and wear resistance of the nitriding layer were characterized using a Vickers indenter and pin-on-disk technique respectively. Results showed a decrease in crystallite size from 99 nm for untreated samples to 1.4 nm for samples nitrided at 2.5 mA/cm2 promoted both: an increase in hardness from 226 HV25g to 1245 HV25g, and a considerably decrease in volume loss by wear effect.

Laser-assisted synthesis, and structural and thermal properties of ZnS nanoparticles stabilised in polyvinylpyrrolidone

Zinc sulphide (ZnS) nanoparticles have been synthesised by a green approach involving laser irradiation of an aqueous solution of zinc acetate (Znac2) and sodium sulphide (Na2S·9H2O) or thioacetamide (TAA) in polyvinylpyrrolidone (PVP). The structural and morphological properties of the prepared samples were analysed using a transmission electron microscope, TEM, a high resolution transmission electron microscope, HRTEM, X-ray diffraction, and Raman spectroscopy. The thermal properties were studied using a simultaneous thermal analyser (SDTA). Better dispersed and larger particles were obtained by using sodium sulphide (Na2S) instead of TAA as the sulphur source. X-ray diffraction (XRD) analyses and Raman measurement show that the particles have a cubic structure, which is usually a low temperature phase of ZnS. There were phonon softening and line broadening of the peaks which are attributed to the phonon confinement effect. The average crystallite size of the ZnS nanoparticles estimated from the XRD showed a reduction in size from 13.62 to 10.42nm for samples obtained from Na2S, and 9.13 to 8.16nm for samples obtained from TAA, with an increase in the time of irradiation. The thermal stability of PVP was increased due to the incorporation of the ZnS nanoparticles in the matrices. The absorption spectra showed that the nanoparticles exhibit quantum confinement effects.

Magnetic and thermodynamic properties of nanosized Zn ferrite with normal spinal structure synthesized using a facile method.

Normal spinel zinc ferrite (ZnFe2O4) nanoparticles (NPs) with zero net magnetization were synthesized by a facile coprecipitation method in which two kinds of organic alkali, namely, 1-amino-2-propanol (MIPA) and bis(2-hydroxypropyl)-amine (DIPA), were used. The diameters of the ZnFe2O4 NPs were determined to be about 7 and 9 nm for samples prepared with MIPA and DIPA, respectively, and the normal spinel structure was confirmed by the magnetic property measurement at room temperature and the temperature dependence of the direct current magnetization. These results are different from those reported in the literature, where ZnFe2O4 NPs show a nonzero net magnetization. The heat capacity of the ZnFe2O4 NPs synthesized using DIPA was measured using a physical property measurement system in the temperature range from 2 to 300 K, and the thermodynamic functions were calculated based on the curve fitting of the experimental heat capacity data. The heat capacity of the ZnFe2O4 NPs was compared with that of a nanosized (Zn(0.795)Fe(0.205))[Zn(0.205)Fe(1.795)]O4 material studied in the literature, indicating that the Debye temperature of the present sample is more comparable with that of the bulk ZnFe2O4 reported by Westrum et al.

Optical transition in nanocrystalline Si doped SiO2 thin films formed by cosputtering

Optical transition properties of nanocrystalline silicon (nc-Si) doped SiO2 thin films prepared by cosputtering with SiO2 target and Si-chips followed by high temperature annealing were investigated as a function of ratio of target area (Si/SiO2) in the range of 0 to 0.19. Optical transmission measurements revealed that the indirect band-gap of nc-Si decreased from 4.87 to 2.32 eV with increasing Si/SiO2 from 0.04 to 0.19, whereas no noticeable absorption was observed for the samples with Si/SiO2 = 0.00. Photoluminescence (PL) measurements showed that considerably weak emissions due to oxygen deficient center (ODC) in SiO2 films were observed at 514–539 nm for samples with lower Si/SiO2 of 0.0–0.09, while the strong emissions due to an interfacial layer between the nc-Si core and the SiO2 surface layer were observed at 746–808 nm for samples with higher Si/SiO2 of 0.13–0.19. PL excitation spectrum monitored at 800 nm showed that the PL at 800 nm was excited through nc-Si. On the other hand, cathodoluminesncence peaks were observed at 455 and 465 nm for the samples with 0.04 and 0.13, respectively, in which both peaks were assigned to originate from oxygen vacancies created during electron beam irradiation. The mechanisms of three types of luminescence, due to the ODC in SiO2, band-to-band transition of nc-Si, and the interfacial layer between the nc-Si core and the SiO2 surface layer, are discussed.

Transient absorption in pumped Yb fibers opens a path to photodarkening

We investigated the strong absorption change appearing in ytterbium (Yb)-doped silica simultaneously with Yb3+ excitation and vanishing immediately after pump power switch-off. The transient absorption peaks below 300 nm for all the investigated host glass compositions. It extends at least to 500 nm for samples with aluminum codoping or without any codoping and is therefore supposed to constitute the first step needed to enable photodarkening (PD). Our observations indicate that defect complexes including one Yb3+ ion can be activated stepwise. Firstly, their original absorption spectrum is shifted by the energy of the Yb3+ excitation. Secondly, this transient absorption opens the path to the generation of PD color centers by pump photons or energy transfer from neighboring excited Yb3+ ions. In samples codoped with phosphorous only, we found transient absorption of comparable strength but limited to the wavelength range below 350 nm. Thus, the second step of activation seems to be inhibited, which might be an explanation for the consistently observed low PD effects in this fiber type.

Alginate/chitosan nanoparticles for encapsulation and controlled release of vitamin B2

This work aims at evaluating encapsulation and controlled release of vitamin B2 from alginate/chitosan nanoparticles. Ionotropic polyelectrolyte pre-gelation was used as production method being chitosan and alginate used as main materials. Nanoparticles were characterized in terms of average size, polydispersity index (PDI), zeta potential and vitamin entrapment efficiency. The average size for alginate/chitosan nanoparticles was 119.5±49.9nm for samples without vitamin B2 and 104.0±67.2nm with the encapsulation of vitamin B2, presenting a PDI of 0.454±0.066 and 0.319±0.068, respectively. The nanoparticles showed encapsulation efficiency and loading capacity values of 55.9±5.6% and 2.2±0.6%, respectively. Release profiles were evaluated at different conditions showing that the polymeric relaxation was the most influent phenomenon in vitamin B2 release. In order to study their stability nanoparticles were stored at 4°C being particles sizes and PDI evaluated during 5 months showing the results that vitamin B2-loaded nanoparticles are more stable (in terms of size and PDI) than nanoparticles without vitamin B2.

Plasmonically Enhanced Optical Characteristics From Europium Organometallic Complex

We demonstrated that the plasmonic effect can enhance the photoluminescence of the europium organometallic complex in conventional organic light emitting diodes stack from an anode to emissive layer with solution processing. The aggregated gold nanoparticles (A-Au NPs) were incorporated in poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) layer to increase the luminescent quantum efficiency of the emissive layer. An enhancement of 31% was achieved in the emission intensity at 614 nm for samples with A-Au NPs. The reduced exciton lifetime measured by time-resolved photoluminescence comply with the Purcell effect. These improvements are attributed to the localized surface plasmon of A-Au NPs increasing the electric dipole transition rate from Eu3+ ions.

Effect of Initial Microstructure on Impact Toughness of 1200 MPa-Class High Strength Steel with Ultrafine Elongated Grain Structure

A medium-carbon low-alloy steel was prepared with initial structures of either martensite or bainite. For both initial structures, warm caliber-rolling was conducted at 773 K (500 °C) to obtain ultrafine elongated grain (UFEG) structures with strong 〈110〉//rolling direction (RD) fiber deformation textures. The UFEG structures consisted of spheroidal cementite particles distributed uniformly in a ferrite matrix of a transverse grain size of about 331 and 311 nm in samples with initial martensite and bainite structures, respectively. For both initial structures, the UFEG materials had similar tensile properties, upper shelf energy (145 J), and ductile-to-brittle transition temperatures 98 K (500 °C). Obtaining the martensitic structure requires more rapid cooling than is needed to obtain the bainitic structure and this more rapid cooling promote cracking. As the UFEG structures obtained from initial martensitic and bainitic structures have almost identical properties, but obtaining the bainitic structure does not require a rapid cooling which promotes cracking suggests the use of a bainitic structure in obtaining UFEG structures should be examined further.

Structural, optical, and ferroelectric behavior of Zn1−xLixO (0⩽x⩽0.09) nanostructures

Abstract The present study reports structural, optical and ferroelectric behavior of lithium doped zinc oxide (Zn1−xLixO with x = 0.0, 0.05, 0.07 and 0.09) nanostructures synthesized by hydrothermal method. The XRD pattern indicates the pure phase formation of ZnO without any impurity and the particle size, calculated through XRD data, is found to decreases from 51 to 42 nm for samples with x = 0–0.09, respectively. FESEM images show that the size of Li doped ZnO nanostructures decreases with increasing lithium concentrations. Moreover, Raman and Photoluminescence spectra also confirm the wurtzite phase formation of ZnO. PL spectra show a blue shift in both UV and visible region as a result of doping. A significant enhancement in optical band are found to be 3.39–4.23 eV by Li doping due to increasing carrier concentration that blocks the lowest states in the conduction band and results the increase in band gap. Further, Li incorporation enhances the room temperature ferroelectric behavior and the maximum value of polarization (Pmax) increases from 8.973 to 19.394 μC/cm2 for x = 0–0.09, respectively.

Electrospinning of PCL/natural rubber blends

In this study, a thermoplastic/elastomeric binary blend of non-vulcanized natural rubber (NR) and polycaprolactone (PCL) was electrospun using polymer solutions consisting of varying proportions of PCL and NR. Specifically, an 8 % (w/v) NR/toluene solution was mixed with an 8 % (w/v) PCL/chloroform solution at proportions of 2, 15, 30, and 50 % (v/v). The morphological, thermal, and mechanical properties of the electrospun mats were investigated by scanning electron microscopy (SEM), differential scanning calorimetry, and uniaxial tensile tests. The SEM images demonstrated the production of micrometer- and sub-micrometer-sized fibers with no bead formation. Fibers with diameters ranging from 1.3 μm for samples with 0 % NR to 210 nm for samples containing 50 % NR were observed. Fibers with rough and smooth morphologies were observed, showing that the PCL/NR mats had phase-separated. The blend miscibility was evaluated by thermal analysis, which showed that blending did not improve the thermal stability of the systems. An investigation of the mechanical properties of the electrospun mats showed that adding NRL to the blend increased the tensile modulus, the ultimate elasticity, and the strain. Thus, non-vulcanized NR was successfully incorporated into electrospun mats, which exhibited useful mechanical properties that could be harnessed in biomaterials applications.

Nano Silicon from Nano Silica Using Natural Resource (Rha) for Solar Cell Fabrication

High purity (∼99%) nano silica with an average particle size of ∼100 nm was extracted at pH 3 at 650°C from a natural resource, rice husk, using alkaline extraction followed by acid precipitation method. Using nano silica as a precursor, silicon (Si) nanoparticles have been synthesized by high-temperature magnesiothermic reduction method. The prepared sample was characterized by X-ray diffraction, particle size analyzer, Fourier transform infrared spectroscopy, transmission electron microscopy, X-ray fluorescence analyzer, and UV–Vis spectroscopy. The comprehensive characterization studies indicate the pure phase formation of Si and the variation of particle size from 70 nm to 100 nm for samples synthesized at different sintering temperatures. Moreover, the silicon nanoparticles produced at 850°C have pure phase formation, high purity, and good absorption peaks. The efficiency calculated through IV characteristics is found to be increasing in silicon and ruthenium combination (2.67%), which is better than that achieved from the conventional solar cells. The produced silicon nanoparticles could be applied as an anode material for solar cell fabrication.

Structural, morphological and luminescence properties of nanocrystalline up-converting Y1.89Yb0.1Er0.01O3 phosphor particles synthesized through aerosol route

Abstract Nanocrystalline up-converting Y2O3:Yb3+, Er3+ phosphor particles were processed in a dispersed system-aerosol, generated ultrasonically at 1.3 MHz from common nitrate precursor solution having fixed ytterbium-to-erbium concentration ratio. The appropriate process parameters: residence time 21 s, carrier gas (air) flow rate 1.6 dm3/min, synthesis temperature 900 °C, led to the formation of un-agglomerated spherical nanostructured secondary particles, having mean particle size of approx 450 nm, composed of primary nanoscaled (20 nm) subunits. In order to reach targeting phase crystallinity, the as-prepared particles were additionally annealed at 1100 °C in air for 12, 24 and 48 h, respectively. Particle structure, morphology and purity were analyzed by X-ray powder diffraction (XRPD), scanning electron microscopy (FESEM/SEM), analytical and high resolution transmission electron microscopy (TEM/HRTEM) in combination with energy dispersive X-ray analysis and Fourier Transform Infrared Spectroscopy (FTIR). All samples crystallized in a cubic bixbyte-structure, space group Ia-3. The crystallite size changed with annealing time from 30 nm in as-prepared sample to 135 nm in sample annealed for 48 h, respectively. Emission spectra were assigned to the following trivalent erbium f–f electronic transitions: 2H9/2 → 4I15/2 (blue: 407–420 nm), (2H11/2, 4S3/2) → 4I15/2 (green: 510–590 nm), and 4F9/2 → 4I15/2 (red: 640–720 nm). The significant improvement of the emission decay times were observed after thermal treatment and this effect is correlated further with the structural and morphological particles characteristics. For the annealing time of 12 h a quite high emission decay times were achieved (blue: 0.14 ms, green: 0.32 ms and red: 0.39 ms).

Fibrillar Structure of Methylcellulose Hydrogels

It is well established that aqueous solutions of methylcellulose (MC) can form hydrogels on heating, with the rheological gel point closely correlated to the appearance of optical turbidity. However, the detailed gelation mechanism and the resulting gel structure remain poorly understood. Herein the fibrillar structure of aqueous MC gels was precisely quantified with a powerful combination of (real space) cryogenic transmission electron microscopy (cryo-TEM) and (reciprocal space) small-angle neutron scattering (SANS) techniques. The cryo-TEM images reveal that MC chains with a molecular weight of 300 000 g/mol associate into fibrils upon heating, with a remarkably uniform diameter of 15 ± 2 nm over a range of concentrations. Vitrified gels also exhibit heterogeneity in the fibril density on the length scale of hundreds of nanometers, consistent with the observed optical turbidity of MC hydrogels. The SANS curves of gels exhibit no characteristic peaks or plateaus over a broad range of wavevector, q, from 0.001-0.2 Å(-1). The major feature is a change in slope from I ∼ q(-1.7) in the intermediate q range (0.001 - 0.01 Å(-1)) to I ∼ q(-4) above q ≈ 0.015 Å(-1). The fibrillar nature of the gel structure was confirmed by fitting the SANS data consistently with a model based on the form factor for flexible cylinders with a polydisperse radius. This model was found to capture the scattering features quantitatively for MC gels varying in concentration from 0.09-1.3 wt %. In agreement with the microscopy results, the flexible cylinder model indicated fibril diameters of 14 ± 1 nm for samples at elevated temperatures. This combination of complementary experimental techniques provides a comprehensive nanoscale depiction of fibrillar morphology for MC gels, which correlates very well with macro-scale rheological behavior and optical turbidity previously observed for such systems.