Amorphous Part Research Articles

In Situ X-Ray Photoelectron Spectroscopy for All-Solid-State Batteries: Analysis of Lithiation and Delithiation Reactions of Silicon Thin-Film Electrode

Si is an attractive anode material for next-generation lithium batteries including all-solid-state batteries because it has a high theoretical capacity density (4200 mAh g-1). However, Si suffers from the irreversible capacity loss related to the severe volume expansion/shrinkage during the lithiation/delithiation processes. In liquid-type batteries, the main cause of the capacity loss is the continuous formation/decomposition of the solid electrolyte interphase (SEI) on the Si anodes [1]. However, the capacity loss of the Si anode is also regarded as a serious issue even in all-solid-state batteries without using electrolyte solution. Thus, a fundamental understanding of the lithiation/delithiation reactions of the Si anode is important to solve the problem. X-ray photoelectron spectroscopy (XPS) enables us to analyze the elemental composition, oxidation states, and electronic structure of the sample surface. In situelectrochemical XPS, which can measure the same position of a sample under the operational condition for batteries, allows a stepwise analysis of the reactions without interference from variation and inhomogeneity of samples [2]. Here, lithiation/delithiation reactions of an amorphous Si electrode in a thin-film cell is investigated by using an XPS apparatus equipped with an applying voltage system [3]. The amorphous Si with a thickness of about 100 nm is formed on the Li6.6La3Zr1.6Ta0. 4O12 (LLZT) sheet by radio-frequency magnetron sputtering, and the Cu is further coated on the sputtered Si layer by DC sputtering. During the Cu deposition, a stainless-steel stencil mask is used to yield an uncoated amorphous Si part with a diameter of about 2 mm as an analytical region for the XPS measurements. The Li metal layer is thermally deposited on the other side of LLZT. After the thin-film cell with the final structure of [Cu/Si(100 nm)/LLZT(500 µm)/Li metal(1.3 µm)] is connected to the sample holder in an Ar-filled glove box, it is transferred to the XPS apparatus by using a vacuum suitcase to prevent from exposing to open air. The cell is cycled between 0.01 and 1.2 V at 0.02C (1.245 µA) in UHV chamber of the XPS apparatus. The Si surface is observed by XPS before/after the lithiation/delithiation processes. The galvanostatic potential profiles show that the capacity for the first lithiation and delithiation processes is 3160 and 2977 mAh g-1, respectively. A broad Li 1s peak appears after the first lithiation process, confirming the Li insertion to the Si electrode. According to the peak fitting, the Li 1s peak is composed of lithium-silicide (LixSi), Li2O, and Li2CO3. The Li2O and Li2CO3 are possibly formed by the reaction of the lithium-silicide surface with a trace amount of residual gas from the vacuum chamber and LLZT. The Li2O and Li2CO3 contribute to the irreversible capacity loss because these components remain even after the subsequent delithiation process. In the Si 2p region, peaks originated from bulk Si (Si0) at 99.1 eV and Si suboxide (SiOx) at 101.9 eV are shifted to lower binding energy side. These peak shifts indicate the formation of lithium-silicide (LixSi) and lithium-silicate (Li4SiO4) due to the insertion of Li ions to each layer. Based on the calculation using the peak intensities and known physical parameters, it is proposed that the Si electrode has a surface structure of [Li2O (2.5 nm)/Li4SiO4 (0.9 nm)/LixSi] at this state. In addition, the composition of the LixSi is estimated to be Li3.27Si from the charge integration and the thickness of each layer. After the subsequent delithiation process, the Li4SiO4 peak remains in the same position. In contrast to the immobility of the Li4SiO4 peak, the LixSi peak is shifted back to the higher binding energy side, but it does not completely return to the original position of the Si0 peak. The composition of the lithium-silicide phase at this state is estimated to be Li0.14Si. Therefore, Li trapped in Li0.14Si and formation of Li4SiO4, Li2O, and Li2CO3 contribute to the irreversible capacity loss of the Si electrode.

Browning, Starch Gelatinization, Water Sorption, Glass Transition, and Caking Properties of Freeze-dried Maca ( Lepidium meyenii Walpers) Powders.

The browning, gelatinization of starch, water sorption, glass transition, and caking properties of freeze-dried maca ( Lepidium meyenii Walpers) powders were investigated and compared with a commercial maca powder. The freeze-dried maca powders had lower optical density (browning) and higher enthalpy change for starch gelatinization than the commercial maca. This resulted from a difference in thermal history. The equilibrium water contents of the freeze-dried maca powders were higher than those of commercial maca at each water activity ( a w ) because of differences in amorphous part. The glass transition temperature ( T g ) was evaluated by differential scanning calorimetry. There was a negligible difference in the anhydrous T g (79.5–80.2 ºC) among the samples. The T g -depression of freeze-dried maca powders induced by water sorption was more gradual than that of the commercial maca due to a difference in water insoluble material content. From the results, critical water activity ( a wc ) was determined as the a w at which T g becomes 25 ºC. There was negligible caking below a w = 0.328. At higher a w , the degree of caking remarkably increased with a large variation depending on the samples. The degree of caking could be described uniformly as a function of a w / a wc . From these results, we propose an empirical approach to predict the caking of maca powders.

Polyoxometalate-based complex/graphene for high-rate lithium-ion batteries

The design and synthesis of new high-performance anode materials is greatly essential for the development of lithium ion batteries (LIBs). Herein, we propose an amorphous engineering strategy that the porous polyoxometalate-based complex {[Co4(L)2(HCOO)2(OH)2][SiO4(W3O9)4]}·6DMF·5H2O (Co-SiW) (L = Armand and Tarascon (2008) [4]arene-based methyl imidazole ligand) is anchored on the layered graphene oxide (GO) by ball-milling. The resulting composite materials, Co-SiW-B, [email protected], [email protected], [email protected] and [email protected], were prepared with different contents of GO. The amorphous parts of Co-SiW were produced with the increased contents of GO during the preparation of the [email protected] system. The amorphous part of Co-SiW in [email protected] exposes abundant active sites, which makes lithium ions easily contact with them. Remarkably, the stability and electrical conductivity of [email protected] are markedly improved. The optimal [email protected] features remarkable rate capability and satisfied lithium-ion storage capacity, which are comparable or even better than those known polyoxometalate-based anodes for LIBs. This amorphous engineering strategy affords a feasible route for the development of highly efficient alternative anode materials for LIBs.

Combining Theory and Experiment to Get Insight into the Amorphous Phase of Luminescent Mechanochromic Copper Iodide Clusters.

In the field of stimuli-responsive luminescent materials, mechanochromic compounds exhibiting reversible emission color changes activated by mechanical stimulation present appealing perspectives in sensor applications. The mechanochromic luminescence properties of the molecular cubane copper iodide cluster [Cu4I4[PPh2(C6H4-CH2OH)]4] (1) are reported in this study. This compound can form upon melting an amorphous phase, giving an unprecedented opportunity to investigate the mechanochromism phenomenon. Because the mechanically induced crystalline-to-amorphous transition is only partial, the completely amorphous phase represents the ultimate state of the mechanically altered phase. Furthermore, the studied compound could form two different crystalline polymorphs, namely, [Cu4I4[PPh2(C6H4-CH2OH)]4]·C2H3N (1·CH3CN) and [Cu4I4[PPh2(C6H4-CH2OH)]4]·3C4H8O (1·THF), allowing the establishment of straightforward structure-property relationships. Photophysical and structural characterizations of 1 in different states were performed, and the experimental data were supported by theoretical investigations. Solid-state NMR analysis permitted quantification of the amorphous part in the mechanically altered phase. IR and Raman analysis enabled identification of the spectroscopic signatures of each state. Density functional theory calculations led to assignment of both the NMR characteristics and the vibrational bands. Rationalization of the photoluminescence properties was also conducted, with simulation of the phosphorescence spectra allowing an accurate interpretation of the thermochromic luminescence properties of this family of compounds. The combined study of crystalline polymorphism and the amorphous state allowed us to get deeper into the mechanochromism mechanism that implies changes of the [Cu4I4] cluster core geometry. Through the combination of multistimuli-responsive properties, copper iodide clusters constitute an appealing class of compounds toward original functional materials.

Tuning the Piezoresistive Behavior of Poly(Vinylidene Fluoride)/Carbon Nanotube Composites Using Poly(Methyl Methacrylate).

In conductive polymer composites (CPCs), which can be used as both strain sensors and materials with self-diagnosis capabilities for structural health monitoring, the piezoresistive sensitivity can be tuned by changing the electrical filler network structure, mainly influenced by the conductive filler content. Typically, the electrical resistance increases exponentially with strain, and the piezoresistive sensitivity and linearity cannot be improved simultaneously. In this work, we report a facile method to tune the piezoresistive behavior of melt-mixed poly(vinylidene fluoride) (PVDF)/carbon nanotube (CNT, 0.75-2.0 wt %) composites using blending with poly(methyl methacrylate) (PMMA, 5-30 wt %). PVDF and PMMA are completely miscible in the melt state regardless of the proportion. For PVDF-rich blends, the crystallization of PVDF induces separation of the PVDF crystal region from the miscible PVDF/PMMA amorphous blend part during the cooling process. Addition of PMMA tuned the piezoresistive strain behavior and improved the electrical conductivity and toughness at the same time. The PVDF/PMMA/CNT composites show higher sensitivity at low strains than their PVDF/CNT counterparts with comparable initial resistivity. For example, ΔR/R0 at 5% strain is 18.6% for the PVDF(80)/PMMA(20) blend containing 0.75 wt % CNT versus 11.0% for PVDF containing 1 wt % CNT, both having a volume resistivity of around 104 Ω·cm. The PVDF/PMMA/CNT blend composites also show a less steep exponential increase in the sensing response at higher strains, indicating better linearity. These differences are due to the altered microstructure of the composites and the more homogeneous distribution of CNTs between the smaller and less numerous PVDF crystallites when PMMA is added. The concept of modifying the composite microstructure by adding another commercially available miscible polymer offers a simple and effective way to tune the piezoresistive behavior and improve mechanical properties of CPC sensor materials.

Hybrid materials from tri-aryl amine organogelators and poly[vinyl chloride] networks

Hybrid thermoreversible gels have been prepared from polyvinyl chloride (PVC) and tri-aryl tri-amines organogelators (TATA-C11) in bromobenzene. A thermodynamic investigation by DSC has shown that the TATA-C11 formation and melting temperatures are not altered by the presence of PVC chains, nor are the formation and melting enthalpies. Scanning electron microscopy observations have revealed as each network are clearly distinguished, so that the hybrid gel is simply a combination at the micron level of both original gels. X-ray diffraction experiments have shown that the TATA-C11 structure in bromobenzene differs from its solid state, and is rather reminiscent of a hexatic phase, possibly due to the occurrence of a molecular compound. The structure of the TATA-C11 moiety does not change in the hybrid gel. Finally, the rheological properties have been studied. It is observed that the modulus of the hybrid gel greatly exceeds the Voigt's upper limit (larger than a simple additivity of the moduli). This effect is examined in the light of a possible de-solvation of the amorphous part of the PVC fibrils (de-plasticization).

Study on the Effect of Bleaching Treatment on the Mechanical Properties of Kenaf Fibers

Automotive industries are trying to reduce the weight of cars by replacing parts that are made of steel and aluminum with lighter material but equally strong. It is an emerging trend in these industries to utilize polypropylene reinforced with natural fiber as the alternative lightweight material. PP-natural fiber composite is projected to have market growth with compound annual growth rate (CAGR) of 9.5% within 2018-2025. Blending PP with natural fiber is a challenging process considering these two materials are not compatible enough to produce composite with desired mechanical properties. Prior treatment to the fiber is required to improve its compatibility with PP with cautionary that it does not degrading the mechanical strength of the fiber. The aim of this work was to study the effect of chemical treatment on Kenaf fiber to the tensile strength of the fiber. Kenaf fiber was bleached with NaClO solution at various concentration (1-10% v/w), temperature (25-55°C), and duration (1-6 hours). The effect of bleaching treatment to the chemical structure and the tensile strength of the fiber was analyzed using FTIR and UTM respectively. This study showed that the fiber with highest tensile strength was the one that treated with NaClO solution with concentration 1% v/w, at 25°C for 1 hour. This treatment removed impurities for the surface and reduced some amorphous part of the fiber. However further increasing NaClO concentration, mixing temperature and duration will damage the cellulose chain in Kenaf fiber which will decrease the mechanical strength of the fiber.

Preparation of oxycellulose from medical cotton and gauze using tempo oxidizer

Today there is a steady increase in the use of renewable biological resources for chemical processing. Obtaining hemostatic materials based on oxycellulose, which can be adsorbed in living tissues, is an urgent scientific and practical task.Medical hygroscopic non-sterile cotton wool made of long-fiber cotton fiber of industrial production and non-sterile gauze bandage were used for the experiments. Oxidation of medical cotton wool and gauze fibers was performed with TEMPO solutions with consumption from 0.5% to 10% by weight of absolutely dry raw materials, with the addition of 0.12 g of NaBr and from 5 to 10 cm3 of sodium hypochlorite solution with a concentration of active chlorine of 76 g/dm3, temperature from 20 to 60 oC and the duration of the process from 2 to 48 hours. The chemical composition of medical cotton wool and gauze have an α-cellulose content of more than 98%, as well as a low content of non-cellulose impurities and can be used for the oxidation process.The influence of technological parameters - temperature, duration of oxidation process, consumption of TEMPO and sodium hypochlorite on the quality of oxycellulose from fibers of medical cotton wool and gauze is established. The increase in the consumption of the oxidazer TEMPO and the duration of the oxidation process leads to an increase in the content of carboxyl groups to 4.5% and 5.0% in the obtained samples of oxycellulose from cotton wool and gauze, respectively. Increasing the consumption of sodium hypochlorite helps to increase the content of carboxyl groups in the obtained samples of oxycellulose, but also reduces the yield of oxycellulose due to its destruction.Increasing the temperature of the oxidation process from 20 oC to 40 oC promotes an increase in the number of carboxyl groups, and when the temperature rises to 60 oC there is a partial destruction of cellulose fibers. The yield of oxycellulose decreases with increasing oxidant consumption and increasing process temperature. The highest yield of oxycellulose was observed in medical gauze, because it is more tightly bound fibers, which prevents the process of its destruction.The change of the amount of amorphous and crystalline parts of cellulose of cotton fibers in the oxidation process was determined by the X - ray diffraction method. The oxidation process helps to reduce the content of amorphous parts of cellulose of cotton fibers due to its destruction under the action of oxidants. Medical gauze and cotton wool, oxycellulose from gauze and cotton wool had values of the crystallinity index of 86.5%, 85.7%, 90.0% and 90.9%, respectively.It is recommended to carry out the process of oxidation of cotton pulp to obtain oxycellulose from medical cotton wool and gauze with the maximum content of carboxyl groups at a consumption of TEMPO from 5% to 10% by weight a.s.s., temperature 20 °C for 24 - 48 hours.

Effect of solid fat content on the viscoelasticity of margarine and impact on the rheological properties of cookie dough and fracture property of cookie at various temperature and water activity conditions

Effect of solid fat content (SFC) on the storage modulus (G′) and loss modulus (G″) of margarines was investigated. The G′ and G″ increased linearly with SFC in a double-logarithmic plot, independent of the types of margarine. There was a minor effect of dehydration on the G′ of margarine. Secondly, effect of the margarines on the G′ and yield stress of cookie dough was investigated. They could be corresponded to the G′ of each margarine in a double-logarithmic plot, independent of the types of margarine. These results will be useful to predict the die cutting and kneading properties of cookie dough. Finally, effect of the margarines on the texture properties of cookie was investigated at various temperature and water activity (aw) conditions. It was expected that the cookie samples having aw = 0.328 and aw = 0.753 were glassy state and rubbery state, respectively. Fracture stress of the cookie samples decreased with increasing temperature, and this behavior could be described as a linear relationship between log fracture stress and log G′ of dehydrated margarines. From the result, it was found that the fracture stress increased gradually (glassy cookie) and remarkably (rubbery cookie) with the G′ of dehydrated margarines. The reason why there was a major effect of margarine on the texture of rubbery cookie will be that amorphous hydrophilic part of the cookie was enough soft to be affected by the margarine.

Influence of Controlled Cooling on Crystallinity of Poly (L-Lactic Acid) Scaffolds after Hydrolytic Degradation.

The use of hybrid manufacturing to produce bimodal scaffolds has represented a great advancement in tissue engineering. These scaffolds provide a favorable environment in which cells can adhere and produce new tissue. However, there are several areas of opportunity to manufacture structures that provide enough strength and rigidity, while also improving chemical integrity. As an advancement in the manufacturing process of scaffolds, a cooling system was introduced in a fused deposition modeling (FDM) machine to vary the temperature on the printing bed. Two groups of polylactic acid (PLA) scaffolds were then printed at two different bed temperatures. The rate of degradation was evaluated during eight weeks in Hank’s Balanced Salt Solution (HBSS) in a controlled environment (37 °C–120 rpm) to assess crystallinity. Results showed the influence of the cooling system on the degradation rate of printed scaffolds after the immersion period. This phenomenon was attributable to the mechanism associated with alkaline hydrolysis, where a higher degree of crystallinity obtained in one group induced greater rates of mass loss. The overall crystallinity was observed, through differential scanning calorimetry (DSC), thermo gravimetric analysis (TGA), and Fourier transformed infrared spectroscopy (FTIR) analysis, to increase with time because of the erosion of some amorphous parts after immersion.

Extraordinary lithium storage capacity and lithiation mechanism of partially amorphous molybdenum sulfide on chemically exfoliated graphene

Molybdenum sulfides have been researched actively for application in electrochemical energy storages and conversions. For molybdenum sulfides, modifications in stoichiometry and crystal structure can lead to enhancements in their electro-chemical properties. However, even though performance of crystalline molybdenum disulfide-based lithium ion battery (LIB) anodes have been investigated extensively, amorphous molybdenum sulfide-based anodes still need to be researched. Herein we report specific capacity as high as 1872 mAh/g observed from non-stoichiometric partially amorphous molybdenum sulfide formed on chemically exfoliated graphene (MoSx-rGO) as a LIB anode. According to our analysis, amorphous part consisting [Mo3S13]2- building blocks contains an excess amount of sulfur as bridging, shared, or terminal S22−, which contribute significantly in enhancing the capacity of the anode. In depth electrochemical investigations and analysis suggest that MoSx-rGO undergoes a different lithiation mechanism from crystalline MoS2, and consequently exhibits such high capacity with excellent stability at least up to 200 cycles and a decreased c-rate dependence.

Synchrotron micro-XRD study, the way toward a deeper characterizing the early prehistoric Iranian glass cylinders from Late Bronze Age (1280 BC)

In this article, the chemical and mineralogical composition of a unique glass cylinder obtained from the temple of Chogha-Zanbil and classified as the earliest glass discovered in Iran (2nd millennium BC) has been studied. This was achieved through the use of Fourier transform infrared spectroscopy, environmental scanning electron microscope and synchrotron X-ray micro-diffraction to characterize the presence of microstructures and the distribution of elements within their matrices. In order to accurately determine the characteristic crystalline phase constituents, micro-X-ray diffraction experiments were carried out at the CELLS-ALBA Synchrotron. Results reveal that the glass samples are comprised of silica glass and contain calcite, quartz and gehlenite as the major phases. The presence of argentojarosite as the Ag-bearing mineral within the amorphous part of glasses highlights the first use of Ag (Late Bronze Age) in Iran. The novelty of the results includes the identification of specific minerals (i.e., silver-containing minerals) used in the production of glass cylinders to obtain better luster and produce iridescence effects.

The Crystallinity of Arenga pinnata “Ijuk” Fiber Cellulose through KMnO4 Addition on NaClO Bleaching Process

AbstractArenga pinnata “ijuk” fiber is one of the lignocellulosic sources that is abundant in Indonesia. At present, this fiber is only for brush, shiever, mat, and rope. Delignified “ijuk” fiber is a potential source of cheap crystalline cellulose, a material that can be used for composite. This paper presents chemical treatment of A. pinnata “ijuk” fiber to get cellulose with high crystallinity. The fiber is treated by alkalization with 2% sodium hydroxide (NaOH) for 1 h, 0.01 n KMnO4 as NaClO activator for 10 min and bleaching with 5% NaClO at varying time of treatment 3, 5, 7 h, respectively. For comparison, the fiber is treated with 2% sodium hydroxide (NaOH) for 1 h and then with 5% NaClO without KMnO4 for 3 h (N3). Addition of KMnO4 as NaClO activator will control ClO gas released and then the bleaching process becomes more effective because the ClO gas will bleach the fiber, not releasing fast to the air. Furthermore, NaClO leads an oxidative fragmentation from the remaining lignin and then the lignin dissolves out from the fiber. The result shows that the highest crystallinity of the cellulose is the fiber which is treated by alkalization with 2% sodium hydroxide (NaOH) for 1 h, 0.01 n KMnO4 for 10 min, and oxidation with 5% NaClO for 5 h (KN5). Fourier transform infrared confirms the removal of some lignocellulosic components such as lignin, wax, and hemicelluloses; X‐ray diffraction reveals an increase of crystalline parts in the fiber via cellulose through crystallinity index value. Field emission scanning electron microscopy displays dimension and surface morphology of fiber. So the treatment can remove some amorphous part of the lignocellulose namely, lignin and hemicellulose to obtain cellulose with high crystallinity.

Synthesis of Hierarchical Zeolites with Morphology Control: Plain and Hollow Spherical Beads of Silicalite-1 Nanosheets.

Binderless pure silica zeolites (zeosils) spheres and hollow spheres with a diameter of 20 µm composed of silicalite-1 nanosheets particles were prepared by pseudomorphic transformation of spherical silica beads using different temperatures (110, 130, and 150 °C) and treatment times (1–5 days) in order to adapt the local dissolution rate of silica to the crystallization rate of silicalite-1 nanosheets allowing to preserve the initial morphology of the silica beads. Fully crystalline beads of 20 µm were obtained at 110 °C for 5 days, whereas hollow spheres similar in size were synthesized at higher temperatures. The crystallization process seems to begin at the outer surface of the amorphous silica beads and spreads with the time in the interior of the beads leading to a dissolution of the inner amorphous part of the beads to create zeosil hollow spheres for the highest treatment temperatures (130 and 150 °C). The dissolution rate of the inner amorphous part of the beads increases by increasing the hydrothermal treatment temperature from 130 to 150 °C. The silicalite-1 beads synthesized at 110 °C for 5 days showed to be promising for rapid molecular decontamination by adsorbing n-hexane in larger amount than the silicalite-1 conventional big crystals in powder forms.

An Effect of Water Presence on Surface Exfoliation of Polypropylene Film Initiated by Photodegradation

A polypropylene (PP) film photodegradation test was performed in water at 60 °C with a specific photocatalyst under visible light irradiation to identify its fragmentation mechanism. The photodegradation degree reached a maximum at the 144 h photodegradation time and showed the decreases at the 288 h. The surface being uneven was observed at the 288 h in the SEM photograph. These results showed that the surface exfoliation was provoked by the test. The spherulite structure contributed to the surface microcrack location and growth. The microcrack allowed entrance of water into the inner amorphous part. The water caused an internal stress by expanding itself due to radiant heat from the visible light irradiation and induced a microcraze in the interlamellar amorphous region. The microcraze developed into an internal microcrack, and surface microcracks finally coalesced together, producing a planar exfoliation. The major long side length of the exfoliation part was below 100 μm at both the 144 h and 288 h. The weight change ratio and rate of the photodegraded PP film showed multi-stages with the increase of photodegradation time. The increment of positive rate was small, showing that the exfoliation caused suppression of the autoxidation rate. The negative rate was due to the exfoliation behavior and was nonlinear to the photodegradation time.

Phragmites australis as a new cellulose source: Extraction, characterization and adsorption of methylene blue

The aim of this study was to investigate potential use of Phragmites australis in the production of cellulose microfibrils with chemical extraction process. Characterization of the natural P. australis and extracted fibrils were examined by FT-IR, XRD, FE-SEM, TGA, zeta potential and particle size distribution analyses indicating that amorphous polymer parts have been successfully moved away from the plant structure and cellulose content of P. australis was increased from 39.92% ± 0.78% to 91.45 ± 0.49%. Extracted cellulose samples showed microfibrillar structure based on FESEM images. The usability of cellulose microfibrils extracted from P. australis as an adsorbent was investigated in dye removal studies due to its abundant, eco-friendly and low-cost properties. Therefore, Methylene blue (MB) removal capacity of cellulose microfibrils from aqueous solution was tested and the effects of adsorption process parameters were evaluated in a controlled batch system. Maximum adsorption capacity (qmmax) was found to be 54.9 mg/g and the microfibrils allowed MB removal over a wide pH range. Experimental data fit the both Langmuir and Freundlich isotherm models indicating multilayer adsorption. The adsorption process was better described with pseudo second-order kinetic model. In conclusion, P. australis is a good candidate in high purity cellulose microfibrils production as a natural material. Cellulose microfibrils are a potential alternative source which can be used as an adsorbent for wastewater treatment especially for cationic dye removal. Moreover, it can be used for production of cellulose microfibrils in various industrial applications.

An in-depth study of molecular and supramolecular structures of bamboo cellulose upon heat treatment

In this study, two methods including a common method using high concentration of alkali solution and a mild extraction method at ambient conditions were used to extract cellulose from bamboo. The results showed that two methods affected the initial state of the cellulose. Celluloses obtained by the former was a hybrid of cellulose I and II while the latter was pure cellulose I. However, their heat treatment results indicated that the heat treatment (≤200 °C) would not change the aggregation structure of bamboo cellulose, but it will cause the change of intramolecular and intermolecular hydrogen bonds, and the break of glycosidic bonds in the amorphous region and part of the crystalline region of cellulose. Accordingly, the crystallinity of bamboo cellulose will decrease slightly after heat treatment. Finally, the macroscopic morphology change of bamboo cellulose caused by heat treatment was the thermal expansion in the width direction instead of distort.

Influence of uniaxial orientation of fluorinated polymer/phosphonate‐modified needle‐like nanofiller composite by drawing

AbstractThe orientation effect of sepiolite natural clay, a needle‐shaped nanoparticle, in a polymer matrix was investigated. Uniaxial drawing was performed on polymer‐based nanocomposites containing organo‐modified sepiolite, achieving uniform dispersion in the crystalline polymer by modifying the surface with organic molecular chains. Fluorinated polymer was used as the matrix, and sepiolite was modified using fluorinated chains. High‐temperature drawing was conducted to increase the density of amorphous chains in the fluoropolymer. Observations confirmed the orientation of the nanofiller in the drawing direction. When the filler content was intentionally increased, it was as if it were a nanosized mille‐feuille. As a result of 5× drawing, a 20% improvement in crystallinity was calculated. Small‐angle X‐ray scattering (SAXS) analysis showed a 32 Å increase in long‐period values. When high‐drawing was conducted, some amorphous parts transformed into crystals, and the difference in electron densities between the two regions widened, increasing the long‐period value while decreasing the SAXS intensity. The crystallization temperature increased by 1.8°C, and the Young's modulus calculated from the strain‐stress curve showed a nearly 4× increase. The mechanical strength doubled when the neat fluoropolymer was drawn five times. This provides a clear understanding of the enhancement behavior of the structural and physical properties of a uniform dispersible polymer/needle nanoparticle nanocomposite using uniaxially oriented nanofillers.

Brickwork Chemical Corrosion Features

The use of multilayer enclosing structures in modern construction poses a new task of studying the mutual influence of all materials of multilayer structures on the durability of the structure as a whole. Masonry is the oldest and most representative multi-component envelopes. This work is devoted to the study of the processes of chemical destruction, taking into account the mutual influence of building ceramics (clay bricks) and cement-sand mortar. The article deals with the main process of destruction of materials, based on the destruction of the amorphous part of the brick under the influence of calcium hydroxide, penetrating into the brick of cement-sand mortar, where it is produced in the process of dehydration of calcium silicates and aluminosilicates (leaching reaction). We consider the side processes of the first type, taking into account the presence in the amorphous phase of brick oxides of alkali and alkali-earth metals.

Effect of microbial exopolysaccharide on wheat bran sourdough: Rheological, thermal and microstructural characteristics

Rheological, thermal and microstructural properties of wheat bran sourdough (WBS) containing different levels of microbial exopolysaccharide (EPS) extracted from Lactobacillus plantarum were investigated. All sourdough samples showed pseudoplastic behavior and the highest apparent viscosity was achieved at 1.5% EPS. The values of consistency coefficient of 1 and 2.5% EPS were significantly lower than for the dough without EPS. Increasing EPS in WBS produced a decrease in the storage, loss, and complex moduli of the sourdough, except that made with 1.5% EPS. This can be attributed to the microbial EPS structure and its ability to bind with water. It can be concluded, due to high hygroscopicity of EPS, WBS containing EPS had a lower access to water and other dough constituents. Thermal and microstructural results showed that EPS strongly modified starch gelatinization by prohibiting water access to amorphous parts of the granules and stabilized crystalline regions of starch causing an increase of end set temperature.