Changes In Crystalline Structure Research Articles

The Optical and Crystallite Characterization of Bilayer TiO2 Films Coated on Different ITO layers

Abstract Titanium dioxide(TiO2) is a well-known material which is non-toxic with efficient photoactivity, high stability, low-cost and corrosion-resistant. Up to today’s technology, TiO2 films are coated for various applications in the scientific area. In this study, bilayer TiO2 films were coated on indium tin oxide(ITO) layers that have different characteristic properties. The devices designed as homemade of Direct Current Magnetron Sputtering (DCMS) and Spray Pyrolysis Deposition (SPD) coating methods were used to coat the first and second layers of bilayer TiO2 films, respectively. The optical and crystalline characterizations of bilayer TiO2 films were analyzed by UV-VIS spectroscopy and XRD techniques. The XPS spectrum showed that O2 molecules simply oxidize from Ti3+ to Ti4+ after SPD coating method. The characterization results of TiO2 films showed change in optical band gap value and crystalline structure of TiO2 bilayer.

Fabrication of gallic acid loaded Hydroxypropyl methylcellulose nanofibers by electrospinning technique as active packaging material

The objective of this study was to encapsulate gallic acid in Hydroxypropyl methylcellulose (HPMC)/ polyethylene oxide (PEO) blend nanofiber by using electrospinning and examine the usage of nanofibers as active packaging materials. Gallic acid loaded nanofibers showed homogenous morphology. Gallic acid was loaded into nanofibers efficiently and nanofibers showed strong antioxidant activity. As the gallic acid amount increased, the TGA curves had shifted one stage to two stage degradation and degradation temperature (Td) of gallic acid decreased from 275 °C to 250 °C due to the crystalline structure change. Interaction between gallic acid and HPMC/PEO nanofiber demonstrated that gallic acid successfully embedded into the nanofibers. Gallic acid loaded nanofibers decreased the oxidation of walnut during storage. Overall, electrospinning technique was proved to be an efficient method to encapsulate bioactive compounds and gallic acid loaded nanofibers showed promissory results that can be suggested as great potential to active packaging material.

Effect of steam explosion on the structural modification of rice straw for enhanced biodegradation and biogas production

The goal of this study was to develop an operational steam explosion pretreatment for effective modification of rice straw chemical structure in order to improve its biodegradability and methane yield. The parameters of pressure (5 bar to 15 bar), moisture (0% to 70%), and time (1 min to 15 min) were studied in steam explosion pretreatment. The steam explosion efficiency was investigated according to the changes in crystallinity structure and chemical composition on rice straw, as well as the methane yield from straw. Steam explosion changed the structure linkages between the lignin and carbohydrate, which was indicated by a reduction in the peak intensities in the bonds from 1648 cm-1 to 1516 cm-1. After pretreatment, the crystallinity index of the rice straw in the 10 bar-10 min cycle with no moisture and 15 bar-10 min cycle with 70% moisture increased from 22.9% to 28.3% and 28.6%, respectively. Steam explosion efficiently decreased the lignin. The highest reduction in the amount of lignin was observed with the 10 bar-10 min cycle, which reached from 18.6% to 13.0%. The methane yield increased with the cycles 10 bar-10 min and 15 bar-15 min with 35% moisture, and 15 bar-10 min with 70% moisture by 113%, 104%, and 147% compared to that of the untreated straw, respectively. Moreover, the highest biodegradation percent of the rice straw was obtained in these cycles.

Controlled mercerization of bacterial cellulose provides tunability of modulus and ductility over two orders of magnitude

Effects of mercerization process on plant-based cellulose is well studied in the literature whereas the effects of mercerization on mechanical properties of bacterial cellulose is not investigated. In this work bacterial cellulose (BC) was mercerized in NaOH solution with different molar concentrations of 0, 1.50, 1.75, 2.00, 2.13, 2.25, 5.00, 7.00 and 10.00 M. The BC samples shrunk substantially with increasing NaOH concentration. At the same concentration, NaOH treatment resulted in significantly larger shrinkage than KOH treatment. Mercerization of BC samples in 7 M NaOH resulted in an order of magnitude increase in elongation from 5.4 ± 1.6% to 50.8 ± 5.7% along with about 30-fold reduction in Young's modulus. Mercerized samples in 4 M NaOH had maximum toughness among all groups at a value of 64.0 ± 15.8 MJ m−3. Changes in BC crystalline structure from cellulose I to cellulose II were characterized and confirmed semiquantitatively by using X-ray diffraction (XRD) and Raman spectroscopy. Results of this work demonstrated mercerization as a method to tune the mechanical properties of BC precisely. Mercerized BC as a biocompatible material with tunable mechanical properties shows potential to be utilized in tissue engineering and regenerative medicine in the future.

Enhanced Comprehension of the Continuous Fusion Bonding Process of Multi-Material Structures

In comparison to monolithic composite structures, tailored multi-material structures offer high potential considering lightweight design approaches in combination with cost efficient manufacturing processes. Roll forming enables flexible large scale production of hybrid structures, due to the continuous manufacturing process as well as high degree of automation. The multi-material structures consist of steel sheets which are selectively reinforced by unidirectional carbon fibre reinforced thermoplastics (CFR-TP). In view of minimizing process steps and decreasing cycle times, both materials are joined by fusion bonding. Therefore, CFR-TP is heated above melting temperature of thermoplastic matrix and joined to the steel surface under defined pressure and time. However, joining of both materials within a continuous process is still challenging due to a lack in terms of process comprehension. Consequently, multi-material specimens were manufactured depending on various process parameters as temperature of either material or processing speed and tested mechanically by floating roller peel test for the evaluation of the adhesion between both materials. Furthermore, viscosity of matrix was determined and investigations of CFR-TP interface were performed by Fourier transform infrared spectroscopy. The results show the requirement of a defined CFR-TP temperature and the change in crystalline structure of the matrix in dependency of the processing.

Toward an understanding of the increase in enzymatic hydrolysis by mechanical refining

BackgroundMechanical refining is a low-capital and well-established technology used in pulp and paper industry to improve fiber bonding for product strength. Refining can also be applied in a biorefinery context to overcome the recalcitrance of pretreated biomass by opening up the biomass structure and modifying substrate properties (e.g., morphology, particle size, porosity, crystallinity), which increases enzyme accessibility to substrate and improves carbohydrate conversion. Although several characterization methods have been used to identify the changes in substrate properties, there is no systematic approach to evaluate the extent of fiber cell wall disruption and what physical properties can explain the improvement in enzymatic digestibility when pretreated lignocellulosic biomass is mechanically refined. This is because the fiber cell wall is complex across multiple scales, including the molecular scale, nano- and meso-scale (microfibril), and microscale (tissue level). A combination of advanced characterization tools is used in this study to better understand the effect of mechanical refining on the meso-scale microfibril assembly and the relationship between those meso-scale modifications and enzymatic hydrolysis.ResultsEnzymatic conversion of autohydrolysis sugarcane bagasse was improved from 69.6 to 77.2% (11% relative increase) after applying mechanical refining and an increase in enzymatic digestibility is observed with an increase in refining intensity. Based on a combination of advanced characterizations employed in this study, it was found that the refining action caused fiber size reduction, internal delamination, and increase in pores and swellability.ConclusionsA higher level of delamination and higher increase in porosity, analyzed by TEM and DSC, were clearly demonstrated, which explain the faster digestibility rate during the first 72 h of enzymatic hydrolysis for disc-refined samples when compared to the PFI-refined samples. In addition, an increased inter-fibrillar distance between cellulose microfibrils at the nano–meso-scale was also revealed by SFG analysis, while no evidence was found for a change in crystalline structure by XRD and solid-state NMR analysis.

Sustainable treatment of harmful dyeing industry pollutants using SrZnTiO3/g-C3N4 heterostructure with a light source-dependent charge transfer mechanism

Herein, we build on the results of previous works describing the use of advanced photocatalytic processes for effective industrial wastewater treatment and investigate SrZnTiO3/g-C3N4 heterostructure (SZTO/CN)-catalyzed removal of rhodamine B (RhB) and indigo carmine (IC), probing the effects of the light source (UV and visible) on charge transfer (Z-scheme and non-Z-scheme) in the above heterostructure. Both RhB (cationic dye) and IC (anionic dye) could be efficiently removed by SZTO/CN, which also exhibited elevated photocurrent responses. In particular, the efficiencies of IC and RhB removal over a SZTO/CN sample with a CN/(SZTO + CN) mass ratio of 0.8 after 3-h visible-light irradiation equaled 93.1 and 82.2%, respectively, while the respective values for STO were obtained as 9.7 and 21.8%. Dye degradation under UV light irradiation (e.g., within 30 min for IC) was much faster than under visible light irradiation (e.g., within 180 min for IC), and optimal CN/(SZTO + CN) ratios were individually determined for both irradiation types. Notably, the best performing catalyst maintained over 95% of its initial photocatalytic performance after five consecutive IC decomposition runs, and the X-ray diffraction patterns of cycled and non-cycled catalysts indicated that cycling did not induce any notable crystalline structure changes. The reactive species involved in photocatalytic degradation were identified as O2•–, h+, and OH• for both light source types, which, together with the results of band energy structure analysis and hydroxyl radical population measurements allowed us to propose two light source-dependent photocatalytic dye removal mechanisms. Thus, it was concluded that the developed SZTO/CN heterostructure can be sustainably applied to the treatment of dye-contaminated wastewater.

Clarification of performance degradation of 20 Ah LIB pouch cell after use in electric bus

Herein, performance degradation of pouch type of 20 A h lithium ion battery from electric bus is clarified after a classification using the resistance value from A to D grade. The obtained cells are carefully disassembled to produce cathode, anode, and separator. Scanning electron microscopy and energy dispersive spectroscopy analysis reveal that morphological change of electrode mostly occur in the anodes surface in D-grade cells, while cathodes of all the grades mostly remain similar. Although the change of crystalline structure of all electrodes is negligible, a growth of solid-electrolyte interphase film mostly happen in the D-grade anodes, which is confirmed by X-ray photoelectron spectroscopy analysis. Furthermore, the degradation of cycle and rate performance happen in the anode of D-grade cells, whereas the cathodes remain invariant irrespective of grade. Furthermore, the disassembled separators exhibit that the Gurley number of separators is commonly increased in the used cells.

Corrosion resistance and tribological behavior of WS2-Ti coatings by Ti cathode power changes in magnetron co-sputtering

Titanium-doped tungsten disulfide thin films (WS2-Ti) were deposited using a DC magnetron co-sputtering on AISI 304 stainless steel and silicon substrates. Different Ti cathode power densities between 0 and 1.25 W/cm2 were used for coating deposition. Energy-dispersive spectroscopy evidenced an increase in Ti percentage at the expense of W, as well as a sulfur deficiency. Raman spectroscopy was used to identify bands corresponding to W-S for undoped WS2. As the material was doped, changes in crystalline structure caused W-S main bands to separate. Scratch adhesion testing showed that Ti percentage increased along with the critical load (Lc). Furthermore, adhesive failure type changed from plastic to elastic. Finally, corrosion resistance analysis using electrochemical impedance spectroscopy (EIS) showed that, at high Ti concentrations, corrosion resistance was enhanced as Ti facilitates coating densification and generates a protective layer.

High thermal stability and low power dissipation PCM with nanoscale oxygen-doped SS thin film.

To improve thermal stability and reduce power dissipation of phase-change memory (PCM), the oxygen-doped Sn15Sb85 (SS) thin film is proposed by magnetron sputtering in this study. Comparing to undoped Sn15Sb85(SS), the oxygen-doped-SS thin film has superior thermal stability and better data retention. Meanwhile, the electrical conductivity of crystallisation oxygen-doped-SS thin film is also lower than that of SS, which means its less power consuming in PCM. The electrical conductivity ratio between amorphous and crystalline states for oxygen-doped SS reaches up to two orders of magnitude. After oxygen doping, the root-mean-square surface roughness from amorphous (0.29 nm) to crystalline (0.46 nm) state for oxygen-doped-SS thin films becomes smaller. The switching time of amorphisation process for the oxygen-doped-SS thin film (∼2.07 ns) is shorter than Ge2Sb2Te5 (GST) (∼3.05 ns). X-ray diffractometer is recorded to investigate the change of crystalline structure. Thus, the authors infer that oxygen-doped SS is a promising phase-change thin film for PCM.

Effect of sputtering pressure on structural and optical properties of silver oxide thin films; Kramers–Kronig method

Silver oxide nano layers were prepared by RF magnetron sputtering on amorphous SiO2 substrates. O2 pressure in chamber was varied from 1 to 4 and 7 mTorr during growth process. The effects of different O2 pressure on structural, morphological and optical properties of the films were investigated by means of X-ray diffraction, scanning electron microscopy, atomic force microscopy and UV–Vis spectroscopy analyses. Optical reflectance measured in the wavelength of 350–950 nm by spectroscopy. Other optical properties and optical band gaps were calculated using Kramers–Kronig relations. The X-ray diffraction measurements showed change in crystalline structure with increasing O2 pressure. Preferred orientation has been changed to another growth orientation at 4 mTorr O2 pressure. The Atomic force microscope images showed increasing in roughness consistently by increasing oxygen pressure. The thickness of the thin films decreases (from 217 to 180 nm) with increasing O2 pressure. Optical results revealed that the highest optical band gap of 3.1 eV and the highest transmittance of ~ 80% were achieved at lower O2 pressure (1 mTorr).

Sintering behavior, crystalline structure and microwave dielectric properties of Li2(Ni1-xMgx)3TiO6 (0 ≤ x ≤ 1) ceramics

Li2(Ni1-xMgx)3TiO6 (0 ≤ x ≤ 1) ceramics were synthesized via conventional solid-state reaction. The changes of phase compositions, crystalline structures, sintering behaviors and microwave dielectric properties were investigated firstly as the Li2Ni3TiO6 ceramics transformed into Li2Mg3TiO6 ceramics. With the addition of Mg2+ ions, the quality factor (Q × f) was improved greatly from 18,159 GHz to 152,189 GHz due to the expansion of cell volume. The dielectric constant εr had a similar trend with the electronic oxide polarizabilities, which was determined by the energy gap, the cation polarizability, and the molar volume. In addition, the octahedral distortion and bond energy were calculated and the temperature coefficient of resonant frequency (τf) correlated with the bond energy of Ni/Mg-O (ENi/Mg-O) primarily.

Cathepsin K inhibitor causes changes in crystallinity and crystal structure of newly-formed mandibular bone in rats

Cathepsin K inhibitors are new drugs with the potential for the treatment of osteoporosis because they sustain bony remodelling better than bone resorption inhibitors such as bisphosphonates. The treatment of osteoporosis with inhibitors of bony resorption is associated with osteonecrosis of the jaw, as the deterioration in bony quality that they induce is thought to be one of its causes. The quality of bone is delineated by structural and material characteristics (which include the degree and quality of mineralisation, and depends on the content of proteoglycan and the structural integrity of the bony collagen).1,2 Animal and clinical studies have shown that cathepsin K inhibitors improve the mineral density and structural characteristics of bone, but their effect on the rest remains unknown. We therefore hypothesised that these inhibitors will affect the material characteristics of newly-formed mandibular bone. To verify our hypothesis, we used Raman microspectroscopy to examine such bone in rats that were given a cathepsin K inhibitor, and found unusual crystallinity and an increased substitution of carbonate (CO32−) in its crystal structure.

Corn Starch Hydrolysis by Alumina and Silica‐Alumina Oxides Solid Acid Catalysts

Starch is an abundant renewable resource and is the raw material for the production of a wide range of products, many of which are obtained by hydrolysis. While the hydrolysis of starch by enzymes and acids has been extensively investigated, there are scant studies with respect to the use of solid acid catalysts for this purpose. In this work, the features of corn starch hydrolysis by alumina (Al) and mixed silica‐alumina (SiAl) oxides solid catalysts have been explored, as they are widely used due to their low cost and ease of synthesis. To this end, native corn starch (CS) aqueous dispersion (0.02 g g−1) is used as such or added with the Al or SiAl (1 g g−1 starch), and gelatinized/hydrolyzed at 90 °C for 180 min. The effect of hydrolysis time on morphology (optical and SEM microscopy), hydrolysis progression (based on total sugar production), apparent amylose content, and starch crystalline structural changes (FTIR) is monitored. It is found that the acidity of the solid acid catalyst is a key factor that affected all of the above‐mentioned parameters. The higher acidity (355.0 mmol NH3 · g−1) of SiAl produces higher maximum hydrolysis progression (90%) and apparent amylose contents (0.60 g g−1 residual starch) than Al (70% and 0.40 g g−1 residual starch, respectively), which exhibit lower acidity (84.0 mmol NH3 · g−1).

Real time in situ x-ray diffraction study of the crystalline structure modification of Ba0.5Sr0.5TiO3 during the post-annealing

We report about an in situ study of crystalline structural changes during thermal treatment of a Ba0.5Sr0.5TiO3 (BSTO) film grown on MgO. The study covers the complete cycle of heating, annealing and cooling and reveals simultaneous phenomena of phase transitions and strain evolution, which have been characterized by in situ 2D reciprocal space mapping (2D-RSM) using high-resolution synchrotron x-ray diffraction in coplanar and grazing incidence geometries. In this way, temperature induced phase transformation from the BSTO2 to the BSTO1 phase has been monitored and the appearance of a further crystalline phase was detected. Moreover, for both BSTO phases, transitions between in-plane compressive and tensile states have been determined during thermal treatment. Furthermore, a contraction of the out-of-plane lattice components has been observed during the annealing phase while the in-plane lattice components remain leading to the change of the residual in-plane strain towards tensile state. The in situ 2D-RSM findings provide valuable and versatile insights into strain engineering and structure modification upon thermal treatment.

Electrodeposition of Zn-Terephthalate MOF Thin Films

Metal organic flamework (MOF) is a class of inorganic / organic compound whose crystalline structure is made by bridging inorganic ions with organic ligands. Due to its open porous structure, special functionalities are anticipated in applications such as sensors, catalysis and batteries. Variation of MOFs is almost unlimited, not only by choice of building blocks but also by change of composition and crystalline structure. We have recently reported microwave assisted hydrothermal synthesis of MOFs with various layered structures, in which Zn2+ ions are bridged by terephthalic acid (TPA). These Zn-TPA MOFs exhibited proton-selective reversible redox reactions, suggesting their usefulness in membrane-free redox batteries. On the other hand, we have established a method to electrochemically self-assemble ZnO / organic dye hybrid thin films. When there is a favorable chemistry between inorganic and organic constituents, their hybrid nanostructures are spontaneously formed during electrolysis. Self-assembly of Zn-TPA MOFs can therefore be expected by minor addition of TPA into the bath for cathodic electrodeposition of ZnO. Potentiostatic electrolysis at -1.0 V (vs. Ag/AgCl) in O2-saturated aqueous electrolyte containing 5 mM ZnCl2 and TPA up to 500 μM resulted in gradual decrease of cathodic current of oxygen reduction current (Fig. 1). Strong passivation occurs when TPA > 75 μM to reduce the steady-state current down to ca. 0.1 mA cm-2, as compared to the O2 transport limit (ca. 1 mA cm-2 for Zn2+ + O2 + H2O + 2e- → ZnO + H2O2). Minor addition of TPA at 5 μM resulted in appearance of thin flake-like deposits together with tiny grains of ZnO, which then changes into entire coverage of the FTO-glass substrate with the flakes at 200 μM while ZnO grains disappear (Fig. 2). X-ray diffraction (XRD) patterns of the deposits revealed that the flakes are those of Zn-TPA layered MOF in a Zn3(OH)4(TPA)•6H2O composition. The passivation is obviously caused by high electrochemical resistance of the electrodeposited MOF towards O2 reduction, making it difficult to obtain thick MOF films for battery applications. Exploring the conditions to promote continuous electrochemical growth of MOF is under way. Figure 1

Na2CO3-doped CaO-based high-temperature CO2 sorbent and its sorption kinetics

CaO-based sorbents have received much research attention for high-temperature CO2 capture because of their high theoretical sorption capacities. However, harsh conditions are needed to regenerate CaO-based sorbents, and their high CO2 sorption capacities diminish significantly in cyclic sorption procedures owing to thermal sintering effects. To solve these problems, dopant components have been applied to CaO-based sorbents. In this study, a new CaO-based sorbent containing Na2CO3 was synthesized using a precipitation method. The prepared sorbent (Na2CO3-CaO) was characterized using various analytic methods, and its CO2 sorption performance was studied using thermogravimetric analysis. Na2CO3-CaO showed high CO2 affinity above 600 °C, and its sorption/regeneration kinetics were faster than those of the conventional CaO sorbent. To investigate the CO2 sorption mechanism onto Na2CO3-CaO, the change in crystalline structure with respect to temperature was analyzed using in-situ X-ray diffraction; the results revealed that the double salt Na2Ca(CO3)2 was generated from the reaction of CO2 with CaO and Na2CO3. Kinetic models were also developed to describe the CO2 sorption behavior of Na2CO3-CaO. The results of this study advance our understanding of the effect of alkali metal carbonates on CaO-based sorbents.

Stability of porous SiC based materials under relevant conditions of radiation and temperature

Porous SiC samples with different percentage of sintering additives have been manufactured by the so-called sacrificial template method at the Ceit-IK4 Technology Center (San Sebastián, Spain). Material stability under ionizing radiation and high temperature conditions considering electrical conductivity and microstructure has been evaluated at Ciemat (Madrid, Spain). Electrical conductivity was measured as a function of temperature before and after irradiation with 1.8 MeV electrons up to 23 MGy (∼10 −6 dpa), and radiation induced conductivity (RIC) was also examined during irradiation at 550 °C for different dose rates (from 0.5 to 5 kGy/s). Electrical conductivity increase with irradiation dose was observed to occur. Posterior XRD analysis allowed interpret radiation induced modification of the electrical conductivity in terms of changes in the SiC crystalline structure. Although neither RIC nor electrical degradation is seen to be an issue when data is extrapolated to future fusion devices radiation levels, the observed phase transformation at relatively low ionizing dose might affect structural stability of SiC-based materials.

X-Ray analysis of compacted and sintered UHMWPE reactor powders

X-ray diffraction analysis of solid-state compaction/sintering-induced changes in crystalline structure of lab-scale (M332) and commercial UHMWPE (X600) reactor powders has been carried out. The profile fitting programs TOPAS-5 and Peakfit 4.1 have been used to deconvolute the overlapping peaks. The linear FWHM of (110) and (002) X-ray peaks have been taken for calculation of the transverse (D110) and longitudinal (D002) crystallite sizes with the help of Sherrer method. The growth of crystallite sizes in cold compacted powders with sintering has been detected in both directions. Besides, the sintering has resulted in the generation of the planar a-texture, more pronounced in the lab-scale UHMWPE samples. As known, orientation hardening of the sintered reactor powders is an alternative route to UHMWPE high performance fibers distinct from the common gel-technology. It has been found that the highly oriented thin film threads produced from highly textured sintered material demonstrated the extremely high tensile strength up to 3.0 GPa, close to that of gel-fibers (3.5GPa) [1] while X600 less textured powders has shown low compactability and drawability.

Change in Crystalline Structure of Cellulose Caused by Wood Preservation

Сhemical interaction of cellulose with reactive groups of four-coordinate boron-nitrogen compounds is an intercrystalline process proceeding without destruction of cellulose crystalline structure; probably, the modifier molecules react with easier accessible hydroxyl groups of the amorphous cellulose regions. The formation of B-O-C ether bonds between OH groups of modifiers and more reactive hydroxyl groups of amorphous parts of cellulose results in redistribution of hydrogen bonds and, as a consequence, to rectification of cellulose macromolecules. Thus, when cellulose is treated with compositions based on four-coordinate boron-nitrogen compounds, crystalline structure of cellulose is not disrupted, hence this process can be called a "mild" modification. Such modification does not lead to accelerated aging of cellulose materials, rapid loss of strength and increases durability of wooden structures.