Amorphous Composition Research Articles

Corrosion resistance of amorphous AlPO4 coating in salty atmospheres

AbstractThe objective of the present study was to introduce a cost‐effective and environmentally friendly coating to improve the corrosion resistance of the structures located in salt water. The coating solution, based on amorphous aluminum phosphate composition, was synthesized by sol–gel process and applied to AISI 304 stainless steel by dip coating technique. X‐ray diffraction, scanning electron microscopy, and energy dispersive X‐ray spectroscopy analyses were employed to investigate the phase composition and morphology of the coating. Corrosion behavior of the uncoated and coated samples was investigated using standard salt spray test, potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS) in 3.5 wt.% NaCl solution. Salt spray test results for the bare substrate revealed a corrosion rate of six‐time greater than that of the coated surface after 168 hr exposure time. Electrochemical test results declared that the amorphous AlPO4 coating decreased the corrosion current density of the AISI 304 stainless steel by 10 orders of magnitude. Furthermore, according to the corresponding EIS measurements, the coated surface exhibited a superior anti‐corrosion performance than uncoated sample. Overall, the results declared that the amorphous AlPO4 coating could be a good choice for surface protection of stainless steel against electrochemical corrosion in salty environments.

Effect of amorphous complexions on plastic deformation of nanolayered composites

Interface-induced dislocation nucleation and interface sliding are two decisive mechanisms to understand plastic deformation of nanolayered composites. Taking the Cu-Nb system as a prototype, with atomic simulations, we reveal the atomic mechanism of dislocation nucleation and interface sliding after introducing the CuNb amorphous complexions with different compositions. Under tension loading, the initial nucleation sites correspond to the localized shearing region, and the amorphous composition can regulate the ordering degree of crystalline/amorphous interfaces. Under shear loading, the pathway of interface sliding corresponds to the low-energy region of the energetic landscape, and the shear resistance increases with the increase of Cu content owing to the enhancement of the sliding barrier. These findings reveal the influence of the amorphous complexions on plastic deformation, and provide theoretical guidance for the design of nanolayered composites.

A practical analysis for decelerated growth processes to get physically meaningful kinetic parameters from classical nucleation and growth theory despite of overgrowth

We have analyzed the overgrowth problem arising in decelerated growth processes of spherical crystals in the frame of classical nucleation and growth theory developed by Kolmogorov, Johnson and Mehl, and Avrami (KJMA). To do that, simulations of decelerated growth transformations with a constant nucleation rate have been performed, changing the linear growth rate of spherically shaped nuclei from null (instantaneous growth rate) to constant (characteristic of interface controlled growth processes). We propose the determination of the actual kinetic parameters through the analysis of the inflection point of time evolution of transformed fraction. The correlations found between the effective kinetic parameters from direct KJMA analysis and the actual ones make it possible obtaining physically meaningful parameters. The proposed analysis has been applied to the nanocrystallization of amorphous FINEMET-type compositions.

Ab initio study of boron‐rich amorphous boron carbides

AbstractAmorphous boron carbide compositions having high B contents (BxC1−x, 0.50 ≤ x ≤ 0.95) are systematically created by way of ab initio molecular dynamics calculations, and their structural, electrical, and mechanical characteristics are inclusively investigated. The coordination number of both B and C atoms increases progressively with increasing B/C ratio and more close‐packed materials having pentagonal pyramid motifs form. An amorphous diamond‐like local arrangement is found to be dominant up to 65% B content, and beyond this content, a mixed state of amorphous diamond– and B‐like structures is perceived in the models because sp3 hybridization around C atoms is still leading one for all compositions. The pentagonal pyramid motifs around C atoms are anticipated to appear beyond 65% content. The intericosahedral linear C–B–C chains do not form in any model. All amorphous boron carbides are semiconducting materials. The mechanical properties gradually increase with increasing B concentration, and some amorphous compositions are proposed to be hard materials on the basis of their Vickers hardness estimation.

Characterization of Brazilian Buriti oil biomaterial: the influence on the physical, chemical properties and behaviour of Goat Wharton's jelly mesenchymal stem cells.

The Brazilian Buriti oil presents low extraction costs and relevant antioxidant properties. Thus, this work aimed to analyze Buriti oil biomaterial (BB), within its physicochemical properties, biocompatibility and cellular integration, with the purpose to the use as a growth matrix for Goat Wharton's jelly mesenchymal stem cells. Biomaterials were produced from Buriti oil polymer (Mauritia flexuosa), for it's characterization were performed Infrared Region Spectroscopy (FTIR) and Thermogravimetric Analysis (TG and DTG). The biointegration was analyzed by Scanning Electron Microscopy (SEM) and histological techniques. In order to investigate biocompatibility, MTT (3-(4,5-dimetil-2-tiazolil)-2,5-difenil-2H-tetrazólio) test and hemolytic activity tests were performed. The activation capacity of immune system cellswas measured by phagocytic capacity assay and nitric oxide synthesis . The BB presented an amorphous composition, with high thermal stability and high water expansion capacity, a surface with micro and macropores, and good adhesion of Wharton's jelly mesenchymal stem cells (MSCWJ). We verified the absence of cytotoxicity and hemolytic activity, in addition, BB did not stimulate the activation of macrophages. Proving to be a safe material for direct cultivation and also for manufacturing of compounds used for in vivo applications.

Adsorption of dyestuff by nano copper oxide coated alkali metakaoline geopolymer in monolith and powder forms: Kinetics, isotherms and microstructural analysis

To remove contaminants and pollutants from wastewater systems, adsorbents are widely used. Geopolymers offer a convenient alternative as adsorbents in the wastewater treatment system as they are low-cost, environmentally friendly, and safer. A new adsorbent material prepared by coating nano copper oxide on the surface of alkali-activated metakaolin showed a higher ability to remove methylene blue (MB) dye from wastewater, thus making them attractive in dye removal applications. First, nano copper oxide was prepared by sol gel method and metakaolin geopolymer was produced using sodium silicate solution having a Ms value of 1.1 (M). Afterwards, nano copper oxide (MC) was coated on the surface of the geopolymer. The ability of MB dye to bind to both pristine (Mp, MCp) and powder forms (Mpr, MCpr) of the geopolymer was evaluated. X-ray diffraction revealed that the halo found at 27.40°–31.077° (2θvalue) in both samples related to amorphous gel's composition and the major peaks of copper oxide in MCpr were sited at a 2θ value of 35.45° and 38.88°.The dye removal efficiency can be inferred from the increased adsorption capacity of 11.9 mg/g (Mp) and 14.4 mg/g (MCp) for the monolith form and 81.43 mg/g (Mpr) and 87.82 mg/g (MCpr) for the powder form. The adsorption of reused active sites was 73% for Mpr and 83% for MCpr up to the fifth cycle after regeneration by heat treatment at 400 °C. The models that best suited the adsorption data were pseudo-second-order and Freundlich isotherms, which indicated possible chemisorption with intra-particle diffusion. Furthermore, the binding energy is shifted to lower value in XPS spectra due to dye adsorption arising from electrostatic attraction. A higher electron density is formed due to interaction with an equal contribution of silanol Si–O–H and Si–O–Na/Cu(O1s). The adsorbents are effective over a wide pH range and their improved recycling capability increases their applications for a wide range of uses.

Synthesis and characterization of amorphous alloy Co69Nb25b6

. In this paper, amorphous alloy composition Co69Nb25B6 was prepared by high-energy ball milling which allows the formation of phases through solid state reaction. In addition, the effects of a 21:1 powder to ball mass ratio were used and the milling time during high energy milling was crucial for the formation of the amorphous and ferromagnetic phases. The characterization of the Co69Nb25B6 alloy was investigated by X-ray diffraction, scanning electron microscopy and hysteresis loops of alloy were measured with a VSM, and exhibited the typical soft magnetic character.

Deposition rate controls nucleation and growth during amorphous/nanocrystalline competition in sputtered Zr-Cr thin films

Dual-phase Zr-based thin films synthesized by magnetron co-sputtering and showing competitive growth between amorphous and crystalline phases have been reported recently. In such films, the amorphous phase grows as columns, while the crystalline phase grows as separated cone-shaped crystalline regions made of smaller crystallites. In this paper, we investigate this phenomenon and propose a model for the development of the crystalline regions during thin film growth. We evidence using X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), that this competitive self-separation also exists in co-sputtered Zr-Cr thin films with Cr contents of ∼84–86 at%, corresponding to the transition between the amorphous and crystalline compositions, and in the Zr-V system. Then, to assess the sturdiness of this phenomenon, its existence and geometrical characteristics are evaluated when varying the film composition and the deposition rate. The variation of geometrical features, such as the crystalline cone angle, the size and density of crystallites, is discussed. Is it shown that a variation in the deposition rate changes the nucleation and growth kinetics of the crystallites. The surface coverage by the crystalline phase at a given thickness is also calculated for each deposition rate. Moreover, comparison is made between Zr-Cr, Zr-V, Zr-Mo and Zr-W dual-phase thin films to compare their nucleation and growth kinetics.

Quantification of amorphous Si, Al, and Fe in palagonitic Mars analogs by chemical extraction and X-ray spectroscopy

Data collected by orbiters and landers have consistently shown abundant amorphous materials on Mars. Developing analytical techniques that target amorphous materials in terrestrial analogs can help determine the environmental conditions under which the amorphous assemblages on Mars were formed. However, the inherent short-range order, chemical heterogeneity, and nanoscale phase interactions create challenges in characterizing these phases. This study is aimed to overcome these challenges by combining chemical dissolution rate analysis with spectroscopy-based mass balance calculations (MBC) to characterize different pools of amorphous materials in terrestrial analogs. The differences in dissolution rates between rapidly dissolving Si, Al, and Fe amorphous materials and the slowly dissolving crystalline minerals were modeled to predict amorphous composition in five palagonitic samples from Hawaii (Mauna Kea) and four hyaloclastite tuffs from the subglacial volcanoes in southwest Iceland. These samples were selected as potential analogs because of their spectral and compositional resemblance to Mars's surface materials.The amorphous Si, Al, and Fe compositions from both sites varied based on the degree of aqueous alteration, grain size, and location. The amorphous fractions of the unconsolidated palagonitic analogs from Hawaii are composed of alteration products such as opal CT and ferrihydrite with minor amounts of unaltered basaltic glass. In contrast, the amorphous fractions of the cemented Icelandic samples were composed mainly of unaltered glass and mixed Fe(II, III) iron phases. Amorphous compositions of the loose Hawaiian and the consolidated Icelandic palagonites are comparable with the Martian modern and ancient aeolian materials respectively. The amorphous compositions in the Hawaiian sample, HWMK101, closely resemble the amorphous materials in Rocknest, a modern aeolian material from the sand shadow, and the Icelandic samples are comparable to the ancient aeolian materials from the Stimson formation. Our analysis indicates the presence of hydrated secondary alteration products such as ferrihydrite and allophane in Rocknest, and a mixture of reduced iron phases and silicate glass outlined with finer altered opaline silicates in Greenhorn. The chemical extraction analysis combined with MBC can be used to characterize amorphous phases in terrestrial analogs to better constrain the formation and characterization of the abundant amorphous materials on Mars.

Study of Thermal Properties, Molecular Dynamics, and Physical Stability of Etoricoxib Mixtures with Octaacetylmaltose near the Glass Transition.

In this paper, we thoroughly investigated the physical stability of the anti-inflammatory drug etoricoxib, which has been reported earlier to be resistant to recrystallization in its glassy and supercooled states at ambient pressure. Our unique application of the standard refractometry technique showed that the supercooled liquid of the drug was able to recrystallize during isothermal experiments in atmospheric conditions. This enabled us to determine the crystallization onset timescale and nucleation energy barrier of etoricoxib for the first time. As the physical instability of etoricoxib requires working out an efficient method for improving the drug’s resistance to recrystallization to maintain its amorphous form utility in potential pharmaceutical applications, we focused on finding a solution to this problem, and successfully achieved this purpose by preparing binary mixtures of etoricoxib with octaacetylmaltose. Our detailed thermal, refractometry, and molecular dynamics studies of the binary compositions near the glass transition revealed a peculiar behavior of the glass transition temperatures when changing the acetylated disaccharide concentration in the mixtures. Consequently, the anti-plasticization effect on the enhancement of physical stability could be excluded, and a key role for specific interactions in the improved resistance to recrystallization was expected. Invoking our previous results obtained for etoricoxib, the chemically similar drug celecoxib, and octaacetylmaltose, we formulated a hypothesis about the molecular mechanisms that may cause an impediment to crystal nuclei formation in the amorphous mixtures of etoricoxib with octaacetylmaltose. The most plausible scenario may rely on the formation of hydrogen-bonded heterodimers of the drug and excipient molecules, and the related drop in the population of the etoricoxib homodimers, which disables the nucleation. Nevertheless, this hypothesis requires further investigation. Additionally, we tested some widely discussed correlations between molecular mobility and crystallization properties, which turned out to be only partially satisfied for the examined mixtures. Our findings constitute not only a warning against manufacturing the amorphous form of pure etoricoxib, but also evidence for a promising outcome for the pharmaceutical application of the amorphous compositions with octaacetylmaltose.

Facile synthesis of Co-Rh bimetallic catalysts for methane decomposition: Effect of support morphology

In this study, the performance of 10 wt.% Co -1 wt. % Rh/TiO2 catalysts with varying textural properties have been investigated to produce the hydrogen and carbon nanotubes via the methane decomposition process. An improved evaporation-induced self-assembly approach synthesized the mesoporous TiO2 supports, and Co-Rh nanoparticles over the as-synthesized TiO2 supports were created by the co-impregnation method. XRD, BET, TGA, SEM, and TEM studies characterized the fresh and used catalysts. The findings revealed that the texture of TiO2 support has an important influence on catalytic performance. With the increase in calcination temperature, the specific surface area of the catalysts decreases while the anatase content of TiO2 species increases. The catalyst prepared with TiO2 calcined at 600 °C displayed superior catalytic activity and stability due to the better metal dispersion and higher anatase phase content in support. The initial activity depended on the specific surface area, whereas the stability or the hydrogen productivity for the equal deactivation level was related to the anatase composition of the catalyst. The nature of deposited carbon varies due to the phase composition of TiO2. The SEM and TEM images revealed that anatase TiO2 generated smaller multi-walled carbon nanotubes (MWCNTs) with a more consistent diameter distribution than the other catalysts. Catalysts with an amorphous composition increase the formation of CHx carbon species. The apparent activation energies for various Co-Rh catalysts varied between 65 and 85 kJ mol−1. The Co-Rh bimetallic combination had more significant activity than the Ni metal.

Crystallization evolution behavior of amorphous Fe85.7Si7.9B3.6Cr2C0.8 powder produced by a novel atomization process

Fe-Si-B amorphous alloy has the advantages of excellent soft magnetic properties, low magnetic loss, stable DC bias performance and strong corrosion resistance, etc. It is one of the commonly used raw materials for high-end electronic and electrical components. In this study, the thermodynamics and kinetics of the crystallization transition of high magnetic induction amorphous powder Fe85.7Si7.9B3.6Cr2C0.8 produced by a novel atomization process were investigated experimentally under non-isothermal and isothermal conditions based on DSC and XRD. The results show that the high Si contents in the amorphous composition and the eutectic reaction during initial crystallization stage lead to a structural transition between the ordered Fe-Si phases A2(α-Fe(Si)), B2(FeSi) and DO3(Fe3Si), thus resulting in the third exothermic peak of crystallization in the DSC curve of this system. In addition, the first exothermic peak of crystallization corresponding to the eutectic reaction is analyzed in detail in this paper. The crystallization process of the amorphous material is as follows: (a) Amorphous; (b) Amorphous+Fe3B+α-Fe(Si)+Fe3Si+Fe5Si3+FeSi; (c) Amorphous+ Fe3B+Fe2B+α-Fe(Si)+Fe3Si+Fe5Si3+FeSi; (d) Fe2B+α-Fe(Si)+Fe3Si+Fe5Si3+FeSi; (e) Fe2B+α-Fe(Si)+Fe3Si+Fe5Si3. And the undercooled liquid region of the amorphous powder is 52 K, the activation energy of glass transition is 396.73 kJ·mol−1, the activation energy of the first crystallization peak is 292.64 kJ·mol−1, and the fragility value is 27 belongs to strong metallic glass system. It also suggests that the amorphous materials have good thermal stability and glass forming ability (GFA).

Composition engineering of ultra-soft-magnetic Co-based alloys

In the present study, the liquidus temperature, mixing enthalpy, and atomic mismatch factor are used to predict and empirically evaluate the amorphisation capability of Co-Fe-B alloys fabricated by melt spinning. Based on this approach, five out of seven alloys have an amorphous structure, confirming the capability of the proposed model in predicting the alloy compositions with higher amorphisation ability in a ternary alloy system in the absence of any costly elements, such as Nb, Mo and Zr. X-ray diffraction, TEM and Mössbauer results show that the other two alloys exhibit different in-situ crystallisation behaviour. In one case, only the free-side crystallises, whereas the crystallisation occurs through the entire thickness of the ribbon in the other alloy. The lower amorphisation ability exhibited by these alloys in relation to the predictive parameters has been evaluated. Additionally, there is a strong correlation between amorphisation ability and crystallisation behaviour of alloys. Alloys, which crystallise through eutectic mode, are more likely to exhibit high amorphisation capability, whereas crystallisation via the primary mechanism can be the sign of lower amorphisation ability. The output of the alloy design process is five amorphous compositions, among which one is magnetically ultra-soft, Hc = 2.9 A/m; a surface crystalline alloy, with a low coercivity and higher value of anisotropy field compared to amorphous samples; and a nanocrystalline sample with a very high saturation flux density, Bs = 1.57 T. The surface crystallisation can eliminate the need for inducing transverse anisotropy by magnetic annealing. Therefore, optimising the alloy composition through this method can be a universal strategy of composition design for the fabrication of alloys with excellent properties, to be utilised in both high-Bs and low-Hc applications.

Effect of aluminum oxide on the structure and conduction behaviors of silver borate glasses

ABSTRACT. The current study focuses on glass preparation and characterization in the glass system of chemical formula xAl2O3 (35-x) Ag2O.65B2O3 (0≤x≤35 mol%), where Ag2O is replaced with Al2O3. To examine a wide range of both structure and morphology of the prepared glasses, nuclear magnetic resonance (NMR) of 27Al nuclei, X-ray diffraction (XRD) spectroscopy, and transmission electron microscopy (TEM) are used. In Al2O3-rich glass, the well-formed AlO6, AlO5, and AlO4 structural groups are the well-formed units. In samples of (20 and 30 mol % Al2O3), tetrahedral AlO4 and traces from AlO6 units could be detected. At lower concentrations of Al2O3 (10 mol%), the dominant forming unit is only AlO4 groups containing non-bridging oxygen bonds (NBO). The XRD spectra confirm the amorphous nature of the glasses of Al2O3 ˂20 mol% while glasses of higher Al2O3 concentrations contain crystalline Ag2Al2B2O7 formed due to the higher oxygen packaging of the mixed AlO5 and AlO4 compared with that of glasses containing only AlO4 species only. The morphology of crystalline units is confirmed from TEM to differ from that of an amorphous composition. The increase of activation energy and the hardness number of the glasses led to an increase in the durability of the investigated glasses.
 
 KEY WORDS: Aluminum borate glass, NMR, Coordination of aluminum atom, Conductivity, Crystallization process
 Bull. Chem. Soc. Ethiop. 2022, 36(3), 597-606. 
 DOI: https://dx.doi.org/10.4314/bcse.v36i3.9

Novel extraction protocol for evaluating abundances and structural features of amorphous SiO2

Spectral data from satellite and rover missions on Mars identified significant abundances of amorphous phases in most samples analyzed, and SiO2 is the principal amorphous constituent in the Gale crater. Identifying and quantifying these short-range ordered, highly reactive phases is challenging but necessary to gain insight into the evolution of these materials. Terrestrial analogs are frequently employed to allow detailed analyses that cannot be performed on Martian samples. Historically, chemical extraction techniques have been extensively used to characterize amorphous materials in terrestrial soils, but most automated systems are complex, expensive, and limited to analyzing a single sample at one time. This study aims to develop a cost-effective apparatus that will allow latitude in choosing an extractant, process several samples simultaneously, enable rapid sampling over time without interruption and provide the resolution for quantitative differentiation of rapidly dissolving SiO2(a) phases in natural samples. Dissolution rates as a function of time were used as input for kinetic models to estimate the abundances of amorphous phases. When 2 M Na2CO3 is used as the extractant, dissolution rates differ significantly between secondary phases such as opal and primary glass phases. A stronger base, NaOH, is necessary for the complete dissolution of basaltic glass. Palagonitic tuffs from Iceland (proposed analogs of Martian soils) with >90% (w/w) amorphous composition were analyzed with 2 M Na2CO3 in the proposed apparatus, and both primary glass and secondary SiO2 appear to be present. Using the kinetic model of the dissolution, the palagonitic tuff has a composition of approximately 25% (w/w) of a rapidly reacting amorphous phase and 13% (w/w) of the slower reacting glass-like phase. The proposed high-efficiency analytical method can be applied to screen multiple terrestrial analogs and archive dissolution kinetics of many standard amorphous minerals. Although this paper focuses on extracting SiO2(a), the same setup can be applied to study time-based dissolution reactions using other extractants such as ammonium oxalate oxalic acid.

Correlating the amorphous phase structure of vitrified bauxite residue (red mud) to the initial reactivity in binder systems

The initial reactivity in cementitious systems (i.e. alkali-activated and blended cement systems) of three slags produced using bauxite residue (BR) as the main raw material were assessed; these slags ranged from semi-vitrified to fully amorphous. Additions of C, SiO2 and CaO to BR decreased the liquidus, therefore, firing at 1200 °C was performed and slags with different amorphous contents were achieved after quenching. Results demonstrated that the content of amorphous phase (50–98 wt%) and composition of the amorphous phase, and thus the degree of polymerisation, vary significantly, depending on the amount and type of the additions. Some crystalline phases were detected, which, very beneficially, are able to incorporate potentially unwanted elements. The results of simplified heat flow reactivity tests that simulated alkali-activated binders (Na-silicate-solution as activator) and reactivity tests that modelled the situation in blended cements (reactivity assessment according to the RILEM-TC-267-TRM, rapid, relevant and reliable – R3test) coincided and demonstrated a correlation between the structure of the amorphous phase of the slags (i.e. degree of polymerisation) and reaction kinetics. The lower the degree of polymerisation of the amorphous phase, the faster the dissolution of the slag. The content of amorphous phase did not seem to have an influence on this early reactivity of the BR derived slags. As the results of both calorimeter tests demonstrated the same trend, it is likely that the R3reactivity test can also be used for Fe-rich slags and potentially as a tool to determine the reactivity of Fe-rich slags in alkali-activated systems.

Разноразмерная пористость и теплопроводность оксидных слоев, сформированных плазменно-электролитическим оксидированием на силумине АК12Д

Oxide layers formed by plasma-electrolytic oxidation (PEO) are characterized by a sufficiently high porosity, which influences almost the whole complex of service characteristics. However, the known data on the integral porosity of PEO-produced layers are rather contradictory, and the nature of the pore size distribution in these layers remains understudied. As a result of processing the images of the layer cross-section produced in a wide magnification range (scanning electron microscopy – SEM, image-based analysis), the authors obtained the pore size distribution in the range of 10 nm to 10 µm, which is sufficiently well described by a lognormal distribution function (pore geometry was approximated by a spherical shape). Such distribution pattern indicates the nature of pore formation, which can be related to the thermally activated process of gas emission from a liquid melt, the volume and average temperature of which, in their turn, depend on the micro-arc discharge energy. The paper presents the results of identifying the oxide layer phase composition and crystallites sizes by the X-ray crystallography method. Comparing the results of X-ray spectral microanalysis and X-ray crystallography, the amorphous component phase composition was evaluated. Using the stationary method and the method of pulsed laser heating, the authors determined the thermal conductivity of the initial oxide layer and the layer after the removal of its highly-porous outer part. The porosity values obtained experimentally and calculated based on the analysis of SEM-images and the results of determining the phase composition, including amorphous phases, allowed evaluating the oxide layer thermal conductivity with the help of four known analytical models. The results of calculating the thermal conductivity using the Loeb model showed good convergence with the experimental results obtained in this work. The modeling demonstrated that the size of crystallites influence the oxide layer thermal conductivity much less than the porosity and amorphous phase.

Synthesis of tetragonally stabilized lanthanum doped bismuth vanadium oxide nanoparticles and its enhanced visible light induced photocatalytic performance

ABSTRACT In order to enhance the performance of bismuth vanadium oxide (Bi4V2O11) we synthesized La doped Bi4V2O11 in different concentrations (La = 5%, 10%, 15%) by using sol-gel method. The nanoparticles are stabilized in tetragonal phase in the range of 50 nm particle size. With the help of XPS it was confirmed that in La/Bi4V2O11 lattice La is in 3+ oxidation state and replaces Bi3+ in the lattice. SEM and EDX show the amorphous nature and chemical compositions of the nanoparticles. The structural analysis and energy calculations revealed that La3+ ion replaces Bi3+ in Bi4V2O11 lattice without disturbing its host structure. The PL results revealed that photogenerated charges recombination was significantly reduced. The photocatalytic degradation of MB under visible light illumination is performed and the best photocatalytic activity among various compositions of La/Bi4V2O11 is shown by 15% La/Bi4V2O11 nanoparticles. 15% La/Bi4V2O11 photocatalyst show 98% of degradation of MB in 120 mins.

Structural and electrical properties of polyvinyl alcohol (PVA):Methyl cellulose (MC) based solid polymer blend electrolytes inserted with sodium iodide (NaI) salt

This paper studies the structural and electrical properties of solid polymer blend electrolytes based on polyvinyl alcohol (PVA) and methylcellulose (MC) incorporated with sodium iodide (NaI). The polymer electrolyte films were assembled through a solution casting technique. The host matrix, which is doped with different NaI salt concentrations between 10 and 50 wt%, utilizes the most amorphous blend compositions (60 wt% Polyvinyl alcohol and 40 wt% methylcellulose). The structural behaviour of the electrolyte films was examined utilizing X-ray diffraction (XRD) and Fourier transformation infrared (FTIR) techniques. The semi crystalline nature of PVA:MC with inserted NaI was derived from the X-ray diffraction studies, while the XRD analysis suggests that the highest ion conductive sample displays the minimum crystalline nature. The interaction between polymer blends and inserted salt was conceived from the FTIR investigation. Shifting of peaks and variation in the intensity of FTIR bands was detected. To investigate the structural properties and calculate the degree of crystallinity of the films, the (XRD) technique was employed, while electrical impedance spectroscopy (EIS) was utilized for studying the conductivity of the samples. In order to comprehend all of the electrical properties of the ion-conducting systems, the EIS outcome of each electrolyte was matched with Equivalent Electrical Circuits ( EEC) s. Ion transport parameters including mobility, carrier density and diffusion are well assessed for the samples and the dielectric properties were compared with the conductivity measurement. At lower frequencies, the dielectric constant was elevated and dielectric loss was detected. Loss tangent and electric modulus plots were used to study the relaxation nature of the samples. The highest ambient temperature conductivity of PVA loaded 50 wt% of NaI was determined to be 1.53 × 10 −5 S/cm. The loss tangent relaxation peak shifts towards high-frequency side which indicates the decrease of relaxation time and faster ion dynamics.

Superior Gas Barrier Properties of Biodegradable PBST vs. PBAT Copolyesters: A Comparative Study.

As a bio-based counterpart of poly(butylene adipate-co-terephthalate) (PBAT), the well-known commercially available biodegradable aliphatic-aromatic copolyester, poly(butylene succinate-co-terephthalate) (PBST) has comparable physical and mechanical properties, but its gas barrier properties, which are very important for packaging material and mulch film applications, have not yet been reported in literature. In this paper, the O2, CO2 and water vapor barrier properties of PBST vs. PBAT were comparatively studied and reported for the first time. Theoretical calculation of O2 and CO2 permeation coefficients via group contribution method was also conducted. The barrier properties of PBST show clear copolymer composition dependence due to different contribution of BS and BT repeat units and composition-dependent crystallinity. Comparing with PBAT, PBST with close copolymer and three-phase (crystalline, amorphous, rigid amorphous) compositions shows 3.5 times O2 and CO2 and 1.5 times water vapor barrier properties. The slower segment movement and less free volume of PBST, and therefore slower gas diffusion in PBST, accounts for its superior O2 and CO2 barrier, while the better hydrophilicity of PBST counteracts partial contribution of slower segment movement so that the improvement in water vapor barrier is not as high as in O2 and CO2 barrier.