Synchrotron Radiation Wide-angle X-ray Research Articles

Cellulose Nanowhiskers from Moso Bamboo Residues: Extraction and Characterization

To take full advantage of moso bamboo processing waste, bamboo cellulose nanowhiskers were isolated from bamboo residues using sulfuric acid hydrolysis. Changes in bamboo cellulose at different stages of processing, as well as the roles of acid concentrations (55 wt% and 65 wt%) and hydrolysis times (1 h to 5 h) on the characteristics of nanowhiskers were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetry-Fourier transform infrared spectroscopy analysis (TGA-FTIR), synchrotron radiation wide angle X-ray scattering (WAXS), composition analysis, and Brunauer-Emmett Teller (BET) analysis. Both rod-like and network-like nanowhiskers were observed. Alkaline pretreatment removed impurities and part of the hemicellulose. Cellulose content increased to nearly 85%, and specific surface area improved as well after bleaching. Nanowhiskers had an average length of 455 nm, diameter of 12 nm, and an aspect ratio of about 37. Cellulose I was the dominant composition in bamboo cellulose; the transformation of cellulose Iα to cellulose Iβ was observed. Nanowhiskers presented greater crystallinity and crystallite size than those of cellulose without hydrolysis, but lower thermal stability. These bionanowhiskers might be used as reinforcements in nanocomposites.

Study on the Crystal Structure of Cellulose in Bamboo with Synchrotron Radiation Wide Angle X-Ray Scattering

The crystal structure of cellulose will directly affect the properties of bamboo fiber -reinforced composite, but the unit cell of native cellulose in bamboo has never been investigated. The most accepted model for the structure of native cellulose is Meyer-Misch model which provides a reference to understand the unit cell of native cellulose in bamboo. The native cellulose consists of two different crystal structures (Ⅰ(α) and Ⅰ(β)) which exist in different plants with different proportions. Because of this situation, the crystal structure of bamboo cellulose should have a unique model. The moso bamboo (Phyllostachys edulis (Carr. ) H. de Lehaie)was selected. The crystal structure of cellulose of bamboo was investigated with two dimensional synchrotron radiation wide angle X-ray scattering (SR-WAXS). The values of the interplanar spacings of each peak were obtained from SR-WAXS patterns, and then crystal structure parameters were calculated according to monoclinic crystal system. The results show that the fibre axis of a bamboo cellulose unit cell with a monoclinic unit cell of a=8.35 Å, b (fiber axis)=10.38 Å, c=8.02 Å, β=84.99°. This model has a two antiparallel arrangement for the chains in unit cell, with four glucose residues. Thus, the model may be used to provide a theoretical basis for high value-added bamboo fiber -reinforced composite.

Enhanced driving force and charge separation efficiency in disordered SnNbxOy: Boosting photocatalytic activity toward water reduction

In this work, the disordered SnNbxOy with controlled structural distortion was developed in order to uncover the underlying origination for highly enhanced photocatalytic activity of the disordered materials. Synchrotron radiation wide-angle X-ray scattering (SR-WAXS) and transmission electron microscopy (TEM) results indicated that the as-prepared catalysts show disordered features with controlled short range ordering limits. In combination with optical diffuse reflectance spectra, valence band X-ray photoelectron spectroscopy (VB-XPS) and density functional theory (DFT) prediction, the disordered structure engineering can induce continuous band gap broadening and downward valence band edge, predicting enhanced oxidation driving force. Moreover, transient absorption spectroscopy (TAS), electron spin resonance (EPR) spectra suggested that the highly enhanced photocatalytic activity mainly originates from defect-assisted charge separation, which implies that abundant defective centers may serve as trap centers for efficient charge separation and improve charge transfer rate to suppress the charge recombination process. Photocatalytic test demonstrated that the optimal photocatalytic activity toward H2 evolution of the disordered catalyst shows ∼11.7 times improvement with respect to that of the crystalline counterpart.

Higher-order-structure Formation in Liquid Crystal Epoxy Thermosets Investigated by Synchrotron Radiation–Wide-angle X-ray Diffraction

We report the investigation of the mesophase transformations of a liquid crystalline molecule with terminal epoxy groups from the initial stages of curing with a diamine compound. The ordered arrangement of molecules within the smectic layers in the thermoset formed at the end of the curing process was characterized by synchrotron radiation–wide-angle X-ray diffraction (SR-WAXD). Data from this experiment helps us understand the phase transitions from the nematic to smectic phases of curing liquid crystalline epoxies.

Hybrid Silk Fibers Dry-Spun from Regenerated Silk Fibroin/Graphene Oxide Aqueous Solutions.

Regenerated silk fibroin (RSF)/graphene oxide (GO) hybrid silk fibers were dry-spun from a mixed dope of GO suspension and RSF aqueous solution. It was observed that the presence of GO greatly affect the viscosity of RSF solution. The RSF/GO hybrid fibers showed from FTIR result lower β-sheet content compared to that of pure RSF fibers. The result of synchrotron radiation wide-angle X-ray diffraction showed that the addition of GO confined the crystallization of silk fibroin (SF) leading to the decrease of crystallinity, smaller crystallite size, and new formation of interphase zones in the artificial silks. Synchrotron radiation small-angle X-ray scattering also proved that GO sheets in the hybrid silks and blended solutions were coated with a certain thickness of interphase zones due to the complex interaction between the two components. A low addition of GO, together with the mesophase zones formed between GO and RSF, enhanced the mechanical properties of hybrid fibers. The highest breaking stress of the hybrid fibers reached 435.5 ± 71.6 MPa, 23% improvement in comparison to that of degummed silk and 72% larger than that of pure RSF silk fiber. The hybrid RSF/GO materials with good biocompatibility and enhanced mechanical properties may have potential applications in tissue engineering, bioelectronic devices, or energy storage.

Cellulose nanofibrils extracted from the byproduct of cotton plant

Cotton stalk bark, as the byproduct of cotton plant, was usually discarded and/or combusted, leading to waste of resources and environment pollution. How to efficiently utilize this kind of cellulosic materials is of significative to energy saving and environment protection. Herein, we report on the extraction of cellulose nanofibrils (CNF) from the cotton stalk bark for the first time by a combination of TEMPO-oxidation and mechanical disintegration method. The obtained CNF showed a yield more than 20wt%. The morphologies, crystalline structures and thermal properties of CNF were extensively investigated by the transmission electron microscopy, scanning electron microscopy, synchrotron radiation wide-angle X-ray scattering, Fourier transform infrared spectra and differential scanning calorimetry, respectively. The results showed that the final extracted CNF have similar polymorphs with their starting materials and a significantly increased crystallinity. This work will provide a new way to utilize the cotton stalk barks.

Reinforced and Ultraviolet Resistant Silks from Silkworms Fed with Titanium Dioxide Nanoparticles

As the perfect combination of strength and luster, silkworm silks have been widely used in many fields but still need improvements. This paper demonstrates an in vivo uptake of titanium dioxide (TiO2) nanoparticles by silkworms, leading to the direct production of intrinsically modified silk. The nanoparticles can be easily incorporated into the silk gland of silkworm by using this method due to the interactions between TiO2 and silk fibroin molecules. Infrared spectra indicate that TiO2 nanoparticles confine the conformation transition of silk fibroin from random coil/α-helix to β-sheet. Results of synchrotron radiation wide-angle X-ray diffraction and small-angle X-ray scattering suggest that modified silks have lower crystallinity, higher mesophase content, and higher Herman’s orientation functions of crystalline region and mesophase region than control group. The breaking strength and elongation at break of the modified silk can be improved up to 548 ± 33 MPa and 16.7 ± 0.8%, respectively, by adding 1...

Strain-induced crystallization of polyimide fibers containing 2-(4-aminophenyl)-5-aminobenzimidazole moiety

Structural evolution induced by cyclization reaction and heat-drawing of polyimide (PI) fibers containing the 2-(4-aminophenyl)-5-aminobenzimidazole moiety was studied by means of synchrotron radiation wide-angle X-ray diffraction (WAXD) and small-angle X-ray scattering (SAXS). WAXD results indicate that the drawing process induces an increase in the crystallinity and crystal orientation of PI fibers, leading to improvement of the mechanical properties. SAXS results reveal that lamellar structures formed upon heat-drawing. A mechanism for strain-induced phase transitions has been proposed to correlate the structural information with WAXD/SAXS patterns. Dynamic mechanical analysis (DMA) of the obtained fibers shows an obvious α relaxation process above room temperature, which is found to be crystallinity dependent, the intensity of tan δ decreases significantly after heat-drawing. The stretched fiber exhibits a negative value of the linear coefficient of thermal expansion (CTE), while the unstretched PI fiber exhibits a positive value. Moreover, heat-drawing increases the thermal stability of the prepared fibers. These improvements may be related to the aggregation structure of the high performance fibers.

Fundamental insights into barium sulfate precipitation by time-resolved in situ synchrotron radiation wide-angle X-ray scattering (WAXS)

The particle formation of barium sulfate is examined in situ for reaction times from tens of milliseconds up to several seconds. Precipitation of the crystalline solid is performed in a tubular reactor of adjustable length equipped with a free jet cell. The transient development of the mass concentration of precipitated solid is determined using synchrotron radiation wide-angle X-ray scattering (WAXS). Precipitated suspensions are stabilized by off-line experiments to measure particle sizes without agglomeration and aggregation. The experimental data are compared to the results of population balance simulation calculations. Nucleation and growth kinetics are derived by theoretical approaches from the literature. It is found that barium sulfate particles grow by aggregation of previously formed particles.

Nutrient and Wind Effects on Dragline Properties: Perspectives from WAXS & SAXS

Spider dragline silk is one of the strongest nature fibers and some of their features are even better than those of the best synthetic fibers. Understanding the mechanisms inducing silk variability may have implications for biomimetics and the synthesis of environmentally responsive materials. Dragline silk contains both elasticity (amorphous) and crystalline regions. Our previous studies had demonstrated that spiders might vary the protein composition and thus physical properties of silks when experiencing food with different nutrient level. In this study we fed Nephila pilipes with high, low and no protein foods and collected their dragline silks for synchrotron Radiation (SR) wide-angle X-ray scattering (WAXS) and small-angle X-ray scattering (SAXS) examinations. The WAXS data showed a significant difference in crystalline fractions of dragline silks produced by N. pilipes experiencing different food treatments. In addition, the orientation of crystallines also varied considerably among silks produced by spiders in three treatment groups. The SAXS data, obtained with the beam incident along and perpendicular to the fiber axis revealed a mesostructure comprising nano crystallites (beta sheets) stack spirally along the spider fibril axis. Such results indicate that spiders experiencing different nutrient stress level might produce dragline silks of different physical properties due to variations in crystalline density, orientation and the meso-phase structures in nano scale. Furthermore, varying environmental wind strength leads to changes in tensile mechanics of spider dragline silk hence produced. Exposing the spider Cyclosa mulmeinensis to controlled stress from constant airflow, we found correlated changes in (i) amino acid composition, (ii) tensile mechanics and (iii) crystallinity, of the dragline silk; which results suggest that protein variation and/or post secretion crystalline variations are associated with the mechanical properties of the spider silks.

Role of Ca2+ on structures and properties of regenerated silk fibroin aqueous solutions and fibres

It has been known that the concentration of Ca2+ gradually increased along the silk gland of silkworm and it played an important role in the spinning process of silk fibre in vivo. In this work, Raman spectrometer, synchrotron radiation wide angle X-ray diffraction facility and material testing instrument were used to investigate the effect of Ca2+ on the structures and properties of regenerated silk fibroin (RSF) in its aqueous solutions and dry spun fibres. It was found that as the concentration of Ca2+ increased in the RSF aqueous solutions and fibres, the conformational transition to β-sheet was promoted, and the resultant post-treated RSF fibre showed higher crystallinity, higher crystalline orientation as well as better mechanical properties. Therefore, it could be concluded that the addition of Ca2+ had improved the structures of RSF aqueous solutions and the resultant fibres, and it might be a feasible approach to obtaining high performance RSF fibres.

Chemical structure and interlayer distance correlation of graphite oxide in the heating process as revealed by in situ Fourier transform infrared spectroscopy and wide-angle X-ray diffraction techniques.

The thermal reduction behavior of graphite oxide (GO) film in an air atmosphere during a continuous heating process was monitored in situ using temperature-dependent infrared (IR) spectroscopy and synchrotron radiation wide-angle X-ray diffraction (WAXD) techniques. The results show that most of the water adsorbed by the GO sheets is removed by heating them to 130 °C. The dehydration process leads to a slight decrease of the interplane distance of the GO sheets. The IR data suggest that the thermal reduction occurs starting at 160 °C. The synchronous change of the of hydroxyl and carbonyl stretching mode (ν(-OH) and ν(C=C)) bands of GO between 160 and 210 °C suggest that the recovery of conjugated structure is mainly due to the reduction of -OH groups in this temperature region, in which the d spacing has not been affected. When the temperature reaches 210 °C, the rapid reduction of C=O groups together with the removal of the residual -OH and ether (C-O-C) groups leads to the sudden collapse of the GO sheets. Based on these findings, we present a schematic of the thermal stability of GO film in a continuous heating process, in which the thermal-induced chemical and crystallographic structural changes of the GO film have been correlated.

A novel way to monitor the sequential destruction of parent-daughter crystals in isotactic polypropylene under uniaxial tension

The cross-hatched structural evolution of isotactic polypropylene (iPP) during uniaxial tensile deformation was investigated with in situ synchrotron radiation wide angle X-ray scattering. An effective way was developed to study parent and daughter lamellae separately with in situ environment. iPP sample was preoriented to generate a bimodal orientation of lamellae for distinguishing the parent and daughter lamellae, which will orient in orthogonal directions under flow-induced crystallization. The dumbbell samples were prepared along different angles with respect to preorientation direction to achieve multisided stretching. The structural evolution of parent and daughter lamellae was followed by recording the scattering from (110) crystallographic plane. It was observed that the parent lamellae were destroyed earlier than daughter ones, no matter which the tensile direction was. Mesophase was observed at very small strain of 0.3, immediately after the damage of cross-hatched structure, which may be attributed to the destruction of parent lamellae. Deformation induced mesophase was proved to be the small crystal cluster which was transformed from parent and daughter lamellae.

Cellulose nanofibrils generated from jute fibers with tunable polymorphs and crystallinity

Cellulose nanofibrils (CNF), as a kind of renewable, sustainable and biodegradable natural-based nanomaterial, have shown great potential application in numerous fields due to their fascinating properties. Some properties of CNF-based materials are closely related to their cellulose polymorph and crystallinity index. In this work, we present a facile method for the generation of CNF with tunable polymorphs and crystallinity via the alkali treatment of jute fibers under various conditions followed by (TEMPO)-mediated oxidation and mechanical disintegration. The changes of the cellulose polymorphs and crystallinity induced by alkali treatment on the jute fibers and consequently obtained CNF were well investigated by synchrotron radiation wide-angle X-ray scattering (SR-WAXS), Fourier transform infrared spectra (FTIR) and differential scanning calorimetry (DSC), respectively. Moreover, the morphology of the as-prepared CNF was also examined by transmission electron microscopy (TEM). It has been found that the CNF showed an identical cellulose polymorph to their source material, but a much higher crystallinity index, which revealed the feasibility of CNF generated from jute fibers with tunable polymorphs and crystallinity indexes.

The changes of crystalline structure of cellulose during dissolution in 1-butyl-3-methylimidazolium chloride

The morphology and crystalline structure changes of cellulose during dissolution in 1-butyl-3-methylimidazolium chloride [(BMIM)Cl] were investigated by optical microscopy and synchrotron radiation wide-angle X-ray diffraction (WAXD). Neither swelling nor dissolution of cellulose was observed under the melting point of [BMIM]Cl. While the temperature was elevated to 70 °C, the swelling phenomenon of cellulose happened with the interplanar spacing of (\( 1\bar{1}0 \)) and (020) planes increased slightly. With the temperature further going up to 80 °C, cellulose was dissolved gradually with the crystallinity (Wc,x) and crystalline index (CrI) of cellulose decreased rapidly, which indicated the crystalline structure of cellulose was destroyed completely and transformed into amorphous structure.

Stretch-Induced Crystal–Crystal Transition of Polybutene-1: An in Situ Synchrotron Radiation Wide-Angle X-ray Scattering Study

Deformation induced crystal–crystal transition of polybutene-1 (PB-1) from forms II to I at different temperatures is studied with in situ synchrotron radiation wide-angle X-ray scattering (WAXS). Analyses on the evolution of crystallinity and orientations of forms II and I during tensile deformation show that stretch accelerates the transformation from forms II to I, which is interpreted based on either a direct crystal–crystal transition or an indirect approach via an intermediate state of melt, namely a melting recrystallization process. A three-stage mechanical deformation including linear deformation, stress plateau, and strain hardening is observed in the engineering stress–strain curves, which corresponds to a process of incubation, nucleation, and gelation of form I crystals. It establishes a nice correlation between phase transition and mechanical behavior in this study.

In-situ monitoring the inhibiting effect of polyphosphinocarboxylic acid on CaCO 3 scale formation by synchrotron X-ray diffraction

The formation of calcium carbonate mineral scale is a persistent and expensive problem in oil and gas production. The aim of this paper is to further the understanding of scale formation and inhibition by in-situ probing of crystal growth by synchrotron radiation wide angle X-ray scattering (WAXS) in the absence and presence of polyphosphinocarboxylic acid (PPCA) scale inhibitor. This technique offers an exciting prospect for the study of scaling. It has been shown that the nucleation and growth of various calcareous polymorphs and their individual crystal planes can be followed in real-time and from this the following conclusions are reached: • The process of scale depositing on the surface can be divided into an unstable phase and a stable phase. • PPCA lengthens the induction time of the surface deposition process. • PPCA suppresses calcite formation and results in vaterite-dominated scale. • PPCA causes a change of lattice parameter for both calcite and vaterite crystals. The c-axis of unit cell increases and the a-axis and b-axis of unit cell decrease.

Using in situ synchrotron radiation wide angle X-ray scattering (WAXS) to study CaCO3 scale formation at ambient and elevated temperature

The formation of calcium carbonate mineral scale is a persistent and expensive problem in oil and gas production, water piping systems, power generator, and batch precipitation. The aim of this paper is to further the understanding of scale formation and inhibition by in situ probing of crystal growth by synchrotron radiation wide angle X-ray scattering (WAXS) at ambient and elevated temperature. This novel technique enables in situ study of mineral scale formation and inhibition and as such, information on the nucleation and growth processes are accessible. This technique studies bulk precipitation and surface deposition in the same system and will be of great benefit to the understanding of an industrial scaling system. It offers an exciting prospect for the study of scaling. It has been shown that the nucleation and growth of various calcareous polymorphs and their individual crystal planes can be followed in real-time and from this the following conclusions are reached. The process of scale deposition on the surface can be divided into an unstable phase and a stable phase. The initial phase of crystallization of calcium carbonate is characterized by instability with individual planes from various vaterite and aragonite polymorphs emerging and subsequently disappearing under the hydrodynamic conditions. After the initial unstable phase, various calcium carbonate crystal planes adhere on the surface and then grow on the surface. At 25 degrees C, the main plane of surface deposit is calcite and a strong (104) peak is detected. The other calcite planes (102), (006), (110) (113) and (202) are hardly detectable under this condition. At 80 degrees C, the main planes in the surface deposit are the (104), (113) and (110) planes of calcite. Stable planes of vaterite and aragonite are also observed. This paper will discuss how surface scale evolves--exploring the power of the synchrotron in situ methodology.

Polarized Light Scattering and Synchrotron Radiation Wide-Angle X-ray Diffraction Studies on Smectic Liquid Crystal Formation of Main-Chain Polyester

Polarized Light Scattering and Synchrotron Radiation Wide-Angle X-ray Diffraction Studies on Smectic Liquid Crystal Formation of Main-Chain Polyester

The use of synchrotron X-ray scattering coupled with in situ mechanical testing for studying deformation and structural change in isotactic polypropylene

The mechanical behaviour of semi-crystalline polymers is greatly influenced by the properties of the crystalline and the amorphous phases. As a result this topic has been the subject of extensive research. However, to date, a comprehensive relationship between the structure and mechanical properties for semi-crystalline polymers has yet to be established. This present study concerns the commissioning of a novel method for in situ data collection during the deformation of polymers. This involves the combination of three different techniques into a single experiment, namely tensile testing, synchrotron radiation wide angle X-ray scattering, and optical microscopy. For this current investigation, three isotactic polypropylene samples have been studied, produced using different thermal treatments. This enables the influence of thermal treatment on the mechanical properties and crystallographic structure to be assessed. The results indicate that tensile properties are influenced by thermal treatment via the relative fraction of β-phase material in the sample. As the temperature increases at which thermal treatment takes place, iPP ductility decreases due to the greater rigidity of the increasing α-phase content. Differences in crystal strain between the different iPP crystal phases are also observed although the reasons for such differences remain unclear.