Microcrystalline Parameters Research Articles

Impact of Graphitization Degree on the Electrochemical and Thermal Properties of Coal.

Coal-based cryptocrystalline graphite is an intermediate phase formed during the transformation of highly metamorphic anthracite into crystalline graphite. In order to explore the relationship between the graphitization degree of coal-based cryptocrystalline graphite and its physical properties from macromolecular structure to provide a theoretical basis for industrial application, samples were tested by X-ray diffraction, electrochemistry, and thermal conductivity and compared with standard graphite (SG) and artificial thermal simulation graphitized samples. The results show that with the increase of graphitization degree and the growth of microcrystalline structure, the electrical impedance of cryptocrystalline graphite decreases, the conductivity increases, the specific capacity of initial discharge increases, and the thermal conductivity increases, which gradually approach the electrical and thermal properties of crystalline graphite. The linear equations between impedance and La and Lc are y = -0.42x + 70.44 and y = -1.87x + 70.62, and the correlation coefficients are 0.93 and 0.88. The linear equations between thermal conductivity and the horizontal extension length (La) and vertical stacking thickness (Lc) are y = 0.09x + 1.36 and y = 0.4x + 0.76, the correlation coefficients are 0.82 and 0.84., and the reduction of microcrystalline parameters d002 and the increase of La and Lc lead to a direct improvement of physical properties. Artificial thermal simulation samples also show the same regularity, but their physical properties are lower than those of natural evolution samples. Short-term high-temperature simulation is different from long-term magma heat and pressure, and the growth of graphite microcrystals is more complete under long-term geological conditions, resulting in better physical properties.

Microcrystalline Characterization and Morphological Structure of Tectonic Anthracite Using XRD, Liquid Nitrogen Adsorption, Mercury Porosimetry, and Micro-CT

Tectonic deformation acts as an indispensable factor affecting the crystalline structure, but its relationship with the evolution mechanism of the morphological structure is seldom considered. In this work, the characterization of microcrystalline and morphological structures in tectonic coal was comprehensively explored using X-ray diffraction (XRD), pore structure analyzers (liquid nitrogen and mercury intrusion methods), and micro-computed tomography (micro-CT). The XRD results indicate that a transformation of the chemical composition was observed in the coal body after continuous tectonic deformation. Meanwhile, the variation in microcrystalline parameters, such as the interlayer spacing (d), stacking height (L), effective stacking layer number (N), aromaticity (f), and graphitization degree (g), reveal that the microcrystalline structure of tectonic coal has experienced a positive evolution with graphitization and aromatization. Pore morphological analyses demonstrate that pore volume distributions of micropores, mesopores, and macropores were totally enhanced by tectonism while the pore shape potentially changes slightly. Simultaneously, the incremental noneffective pores of tectonic coal may promote gas accumulation and storage in the pore space. Fracture morphological analyses utilizing micro-CT lay emphasis on the orderly distributed cleats with a uniform scale in original coal, whereas the reconstruction of microstructures in tectonic coal illustrates a scattered distribution with good connectivity. In addition, the evolution of the macromolecular structure has an influence on the growth of nanoscale pores since the lattice defects may generate from the interlayer of the aromatic ring or the internal space. This research is of an enlightening significance for understanding the influence of tectonic stress on the chemical structure evolution of coals and its relationship with the nanoscale morphological structure development in tectonic coal.

Evolution of structural and surface chemistry during pyrolysis of Zhundong coal in an entrained-flow bed reactor

In this study, a typical Zhundong coal sample was examined, and a series of step-wise pyrolysis experiments, where the temperature was gradually elevated in small increments, were carried out by using an entrained-flow bed reactor. In addition, chars from pyrolysis were investigated by X-ray diffraction and Raman spectroscopy with the aim of revealing the microcrystalline parameters and degree of crystallinity, defects, and disorder. Then, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy were employed to observe the changes in the chemical surface properties of Zhundong coal before and after pyrolysis. The XRD and Raman spectra indicate that the transition from small aromatic ring systems to large aromatic ring systems in coal with the increase in pyrolysis temperature results in the increase in the lateral size of the basic lattice unit of carbon. Furthermore, condensation and the combination of aromatic rings cause the stacking height of the basic lattice units to first decrease and then increase. When the pyrolysis temperature is lower than 1000 °C, the content of graphite decreases, and the inter-layer spacing of the lattice changes slightly with an increase in temperature. As the pyrolysis temperature continues to rise, the content of graphite increases, the inter-layer spacing of the lattice decreases sharply, reaching a minimum of 0.347 nm at 1500 °C, which represents the degree of increase in the graphitisation of coal char and the transformation of the microcrystalline structure of coal char to that of graphite. FT-IR and XPS analyses show that exchangeable sodium is primarily connected with oxygen functional groups in coal char, and the oxygen functional groups are easily decomposed during coal pyrolysis. Meanwhile, the content of CH/CC/CC groups increases with increasing pyrolysis temperature, while that of CO decreases. As a result, there are more hydrocarbon groups on the surface of the coal char, whereas less oxygen functional groups are exposed to the coal char surface.

Whole-Pattern Fitting and Positron Annihilation Studies of Magnetic PVA/α-Fe2O3 Nanocomposites

A low-temperature solution combustion method was used to synthesize α-Fe2O3 nanoparticles. Magnetic polyvinyl alcohol (PVA)/α-Fe2O3/NaCl nanocomposites were prepared by solvent cast method. The Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) results are in confirmation with X-ray diffraction (XRD) results indicating the formation of nanocomposites. The microcrystalline parameters, crystallite size (<N>), lattice strain (g in %), stacking faults (α d ), and twin faults (β) of prepared polymer nanocomposites were evaluated by whole-pattern fitting technique. The refinement was carried out using the computed microstructural parameters in which the twin faults and stacking faults did not vary much and statistical deviation was less than 5 %. Positron annihilation lifetime spectroscopy (PALS) was used for microstructural characterization. PALS results show that the ortho-positronium (o-Ps) lifetime (τ3) increases gradually as a function of nanoparticle concentration and about 219 ps increase observed from1.50 to1.71 ns at 3 wt%. This indicates the increase of free volume hole size (V f ) from 54.47 to 72.18 Å3. The o-Ps intensities (I 3) decrease indicating the inhibition of o-Ps formation upon incorporation of nanoparticles into PVA. The increase in I 2 values suggests the increased annihilation at the interface region. Positron lifetime parameters, viz., o-Ps lifetime, and its intensities indicate the effect of quenching and inhibition upon incorporation of metal oxide nanoparticles and inorganic salt into PVA.

Polyurethane/Soya Protein Isolate Green Composites: Spectral, Microstructural, Thermal, Swelling, and Biodegradation Behaviors

ABSTRACTA series of polyurethane (PU) green composites were synthesized with varying amounts, viz. 0, 2, 4, 8, and 12 wt% of soya protein isolate (SPI). Formation of the urethane linkage in the prepared green composites is revealed by infrared spectroscopy. The glass transition temperature (Tg) of the fabricated PU/SPI composites has been evaluated by differential scanning calorimeter. Thermal stability and degradation analysis of the PU/SPI composites have been performed using a thermogravimetric analyzer (TGA). TGA thermograms clearly revealed that the fabricated composites were thermally stable upto 181°C and show a three‐step of thermal degradation. The water uptake behaviors of PU/SPI systems have been studied at different chemical environments such as distilled water, salt solution, acidic and alkaline solutions. The microcrystalline parameters such as crystallite size (〈N〉) and surface weighted crystal size (Ds) have been evaluated from wide‐angle X‐ray scattering profiles using two different asymmetric distribution functions. PU/SPI green composites were subjected to biodegradation in the presence of Aspergillus niger. The structure–property response of the PU/SPI green composites has been established on the basis of these parameters.

Evaluation of Mechanical, Thermal, and Morphological Behaviors of Polyurethane/Mahua Seed Cake Green Composite

ABSTRACTTo know the possibility of using Indian butter tree seed waste (mahua seed cake [MSC]) as a filler in the production of value‐added product such as polyurethane (PU) green composites, a series of PU composites have been fabricated with varying amounts, namely, 0, 2.5, 5.0, 7.5, and 10 wt%, of MSC, and their effects on the physicomechanical properties such as density, surface hardness, tensile strength, tensile modulus, and percentage elongation at break have been studied. It was found that the tensile strength of the green composites increased from 5.61 to 9.5 MPa and tensile modulus increased from 4.75 to 6.07 MPa with an increase in filler content from 2.5 to 7.5 wt%. The fabricated PU/MSC composites were characterized for structural behavior by Fourier transform infrared spectroscopy and for morphological behaviors by scanning electron microscopy. The chemical resistance of the green composites in different chemical environments has been investigated. The thermal stability and thermal degradation behaviors of composites were performed using thermogravimetric analysis. The microcrystalline parameters such as crystallite size (&lt;N&gt;) and lattice strain (g, %) have been computed using wide‐angle X‐ray scattering data. Based on these parameters, the structure–property relationship of the PU/MSC green composites has been established.

Modification in physical properties of organo clay filled polyurethane nanocomposites

Polyurethane (PU) have been prepared by using polyether polyol (jagropol oil) and 1,6-hexamethylene diisocyanate (HMDI) as a cross-linker. The organically modified montmorillonite clay (o-MMT) is well dispersed into urethane matrix by in-situ polymerization method. A series of PU/o-MMT nanocomposites have been prepared by varying amounts viz., 1, 3, 5 and 6 wt % of nanoclay. The mechanical properties such as tensile strength, percentage elongation at break and tensile modulus of the composites were experimentally determined. The swelling behavior of the composites has been studied in different organic solvents. It was noticed that the swelling data of the composites significantly depends on the solubility parameters of the solvents. Microcrystalline parameters such as, lattice strain (g in %), average number of unit cells (〈N〉) in direction perpendicular to Bragg plane, surface weighted crystal size (Ds) and interplanar distance (dhkl), were calculated from X-ray patterns. These parameters were computed using Exponential asymmetric column length distribution functions. Morphological features of cryofractured PU/o-MMT composites were also analyzed using scanning electron microscopy (SEM).

1-D Paracrystalline Model to Simulate a Bragg Reflection: Computation of Crystallite Size and Lattice Strain

A simple and elegant method to simulate single order reflection profile based on 1-D paracrystal- line model has been proposed here. For variety of polymer films this approach has been applied to compute microcrystalline parameters like crystallite size and lattice strain. Other metallic oxide compounds are also analysed using this approach. Employing this model, X-ray diffraction pat- terns from various polymer samples have been analysed and corresponding microstructure pa- rameters have been reported in this article.

Structure–Property Relationship of Biobased Polyurethanes Obtained from Mixture of Naturally Occurring Vegetable Oils

ABSTRACTA series of castor oil (CO)‐based polyurethanes (PUs) were prepared by reacting CO with toluene diisocyanate (TDI) in the presence of coconut oil (CCO). The effects of CCO content viz., 5, 10, 20, and 30 wt% on the physico‐mechanical properties and chemical structure of PUs have been evaluated. The mechanical properties of the PUs indicate that the incorporation of CCO improves the tensile behaviors. The swelling behaviors of the PUs have been studied in organic solvents. The microcrystalline parameters, such as crystal size (&lt;N&gt;) and lattice disorder (g), of PUs have been estimated using wide‐angle X‐ray scattering studies. The results of tensile behaviors were corroborated with the microcrystalline parameters of the PUs. For a holistic view of the parameters involved in these systems, we have carried out the multivarient analysis that gives a better perspective of the result. © 2013 Wiley Periodicals, Inc. Adv Polym Technol 2014, 33, 21390; View this article online at wileyonlinelibrary.com. DOI 10.1002/adv.21390

The Influence of ginger spent loading on mechanical, thermal and microstructural behaviours of polyurethane green composites

Polyurethane green composites with varying amounts viz., 0, 2.5, 5, 7.5 and 10 wt% of finely powdered ginger spent have been fabricated. The fabricated polyurethane/ginger spent green composites have been performed for mechanical properties such as surface hardness and tensile behaviours. The swelling behavior of the composites has been studied in different organic solvents. Improvement in tensile behaviors of the polyurethane/ginger spent composites were noticed up to 7.5 wt% of ginger spent content. Thermogravimetric analysis of the green composites has been carried out in order to determine the thermal stability and their mode of thermal degradation behaviour. The thermogravimetric analysis curves of polyurethane/ginger spent composites indicated three-step thermal degradation processes, suffers no weight loss up to 193℃ and completely degrades at around 540℃. Thermal degradation kinetic parameters such as energy of activation (Ea) have been calculated for the green composites using two mathematical models namely Coats–Redfern and Broido’s models. The microcrystalline parameters such as crystal size (&lt;N&gt;) and lattice strain have been computed using wide-angle X-ray scattering data. The structure-property relationship of the polyurethane/ginger spent composites has been established on the basis of these parameters.

Investigation on microstructural behavior of styroflex/polyaniline blends by WAXS

AbstractStyroflex/polyaniline (STF/PAni) blends were prepared by two routes namely by in situ and thermo mechanical processing method with various PAni compositions, namely, 0, 15, 30, and 45 wt %. The influence of volume fraction of PAni in the blends and synthetic routes of the STF/PAni blends on the volume resistivity and microcrystalline parameters have been investigated. The microcrystalline parameters such as the nanocrystal size (&lt;N&gt;), lattice disorder (g), interplanar distance (dhkl), width of the crystallite size distribution, surface weighted crystal size (Ds), and crystallite area were evaluated from the wide angle X‐ray scattering profiles. The different asymmetric column length distribution functions namely, exponential, reinhold, and lognormal distribution methods were employed to probe the microcrystalline behavior of the STF/PAni blends and the results are compared. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Changes in microstructural parameters of NB4D2 silk fibres due to electron irradiation: X-ray line profile analysis

The present study is concerned with changes of microcrystalline parameters in NB4D2 (Bombyx mori) silk fibres, due to electron irradiation. The irradiation process was performed in air at room temperature using 8 MeV electron beam at different dose rates: 0, 25, 50 and 75 kGy, respectively. X-ray recording of these irradiated samples and the line profile analysis were carried out. The crystal imperfection parameters such as crystallite size 〈N〉, lattice strain (g in %) and surface weighted crystallite size (D s) were computed and compared with other physical parameters in order to asertain the changes that have crept into these irradiated fibres. Exponential, lognormal and Reinhold functions for the column length distributions have been used for the determination of these parameters.

Microcrystalline and kinetic parameters of glass-PEEK hybrid composites

The cowoven hybrid fiber fabric consisting of E-glass and poly(ether ether ketone) fiber was compression-molded to obtain the hybrid composites. The effect of heat aging at different temperatures (400°C and 500°C) for different time intervals (1, 2, and 5 min) on the microcrystalline properties of the composites has been investigated and it was observed that heat aging for short time enhances the structure property relationships as reflected in the changes in crystal size and volume. The microcrystalline parameters such as the nanocrystal size (&lt;N&gt;), lattice disorder (g), interplanar distance (dhkl), width of the crystallite size distribution, and surface-weighted crystal size (Ds) were evaluated using wide angle X-ray scattering profiles. The different asymmetric column length distribution functions namely, exponential and Reinhold distribution methods were employed to probe the microcrystalline behavior of the composites and the results were compared. The kinetics of thermal degradation (using Flynn—Wall—Ozawa) revealed that, the activation energy decreased with increase in mass loss up to 15% and remains constant thereafter.

Comparative study of natural and man-made polymers using whole powder pattern fitting technique

Natural polymers like chitosan, hemp and man-made polymers like poly(ethylene oxide)(PEO) and hydroxypropyl methylcellulose (HPMC) were investigated using wide angle X-ray scattering (WAXS) method. The merits and demerits of natural and man-made polymers were quantified in terms of microcrystalline parameters, determined by whole powder pattern fitting technique, which is an extension of single order method developed by us.

Structure-Property Relationship of Castor Oil Based Chain Extended Polyurethane/Starch Biocomposites

Polyurethane (PU)/starch biocomposites have been prepared with different weight fractions of starch (viz., from 0 to 40 wt %). The fabricated PU/starch composites were characterized by mechanical properties and thermal (DSC and TGA) behaviors. Microcrystalline parameters were calculated using X-ray profile. Water uptake and its effect on mechanical properties have been evaluated.

Effect of zeolite particulate filler on the properties of polyurethane composites

Polymer-Zeolites composites have been prepared, using castor oil based polyurethane (PU) as a host and AlPO4-5 as particulate filler. The prepared PU/zeolite composites have been characterized for mechanical properties such as tensile strength and tensile modulus. These PU composites exhibited an improved mechanical performance compared to the unfilled PU. Thermo gravimetric analyzer (TGA) curve shows that all the chain-extended PUs are stable up to 250 °C and maximum weight loss occurs at 490 °C. The thermal stability of composites increases with increase in zeolite content. Microcrystalline parameters and micro voids of composites have been measured by using wide-angle X-ray scattering (WAXS) and Positron Annihilation Lifetime (PALS) methods respectively. The microcrystalline parameters and micro-voids from PALS indicate the interaction of the filler with the matrix is stronger beyond 5% of the filler which reflect the mechanical performance as well. Surface morphology of composites has been studied using Scanning Electron Microscopy (SEM). The photomicrograph of SEM indicates a uniform distribution of zeolite filler in the PU matrix.

Polyaniline‐multiwalled carbon nanotube composites: Characterization by WAXS and TGA

AbstractPolyaniline/carboxylated multi‐walled carbon nanotube (PAni/c‐MWNT) nanocomposites have been synthesized by micellar aided emulsion polymerization with various c‐MWNTs compositions, viz., 0.5, 1, 5, and 10 wt %. The microcrystalline parameters such as the nanocrystal size (〈N〉), lattice strain (g), interplanar distance (dhkl), width of the crystallite size distribution, surface weighted crystal size (Ds), and volume of the ordered regions were calculated from the X‐ray data by using two mathematical models, namely the Exponential distribution and Reinhold distribution methods. The effects of heat ageing on the microcrystalline parameters of the PAni/c‐MWNT nanocomposites were also studied and the results are correlated. The thermal stability and electrical resistivity of the PAni/c‐MWNT nanocomposites were examined with thermogravimetric analysis (TGA) and a conventional two‐probe method. The TGA data indicate that the thermal stability of the nanocomposites improved after the incorporation of c‐MWNTs. The influence of temperature on the resistivity of the nanocomposites was also measured. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci 2008

Physico-mechanical and WAXS studies of PU/PS semi interpenetrating polymer networks

The polyethylene glycol (PEG) based polyurethane (PU) and its semi interpenetrating polymer networks (SIPNs) with polystyrene (PS) were prepared. The FTIR, physico-mechanical properties like density, tensile strength, percentage elongation at break and surface hardness of the IPNs were measured. Wide angle X-ray studies (WAXS) were made to know the microcrystalline parameters such as crystal size (〈 N〉), lattice disorder ( g), surface ( D s) and volume ( D v) weighted crystal size of SIPNs. The different asymmetric column length distribution functions were employed using Exponential, Lognormal and Reinhold methods and the results are compared.

Microcrystalline parameters of polyurethane/polymethyl methacrylate semi interpenetrating polymer networks by WAXS

A series of polyurethane (PU) and polymethyl methacrylate (PMMA) semi interpenetrating polymer networks (SIPNs) in the weight percent ratios of 90/10, 70/30, 60/40 and 50/50 were synthesized. The obtained SIPNs were characterized for physico-mechanical properties. Wide angle X-ray scattering studies (WAXS) were made to know microcrystalline parameters such as crystal size (〈 N〉), lattice disorder ( g), surface ( D s ) and volume ( D v ) weighted crystal size of SIPNs. These parameters were expressed using exponential, lognormal and Reinhold asymmetric column length distribution functions and results are compared.

Crystallite size and shape in Twaron fibers heat treated at different temperatures using WAXS

AbstractWe have determined the crystallite size of Twaron fibers heat treated at various temperatures by analyzing the wide angle X‐ray scattering (WAXS) data employing a profile analysis technique developed by us. This study indicates that the differential change of size with temperature is less than 1% of the mean value along both (110) and (200) directions. Hence, these fibers are thermally stable and thermal aging is negligible. We have also observed that the lattice strain variation with temperature is negligible. These studies demonstrate the thermal stability of fibers in terms of the changes in the microcrystalline parameters. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4910–2916, 2006