Complex Crystalline Structures Research Articles

Structural and thermal characterization of novel Ni(II)(L-threoninato)2(H2O)2 crystal

This study focuses on the synthesis and characterization of the novel Ni(II)(L-threoninato)2(H2O)2 crystal, a bivalent transition metal complex based on Ni(II) ions, based on crystalline structure and thermal properties. Through crystallographic analysis, we reveal that Ni(II)(L-threoninato)2(H2O)2 complex adopts an orthorhombic system with the C2221 space group. To gain insights into its thermal behavior, thermogravimetric analysis, and differential scanning calorimetry techniques were employed to estimate kinetic parameters related to its thermal degradation. Model-free analysis, employing Friedman, Ozawa-Flynn-Wall, and Kissinger-Akahira-Sunose methods, along with model-based analysis, were utilized to evaluate the activation energy and the logarithm of the pre-exponential factor. Furthermore, we elucidated the complex's crystalline structure thermal behavior using Powder X-ray Diffraction measurements as a function of temperature, at air and under vacuum. No phase transitions were detected at low temperatures only at high temperatures due to loss of water molecules. The measurements showed the crystal goes to a partially crystalline anhydrous phase with a certain long-range order in the [001] direction. Through Rietveld refinement the behavior of the lattice parameters and thermal expansion coefficients were obtained. This comprehensive study provides valuable knowledge about the Ni(II)(L-threoninato)2(H2O)2 crystals and lays the foundation for further exploration of similar complexes.

Screening of Low-Pressure Steam Heating Pretreatment Parameters For Enhanced Delignification of Pineapple Wastes


 
 
 
 Pineapple waste is classified as lignocellulosic biomass that can potentially be used in the production of biofuel (bioethanol) to replace the current resources of fossil fuels. Carbohydrate compositions of pineapple waste (cellulose and hemicellulose) are excellent properties to be exploited as fermentable sugars that can be converted into bioethanol through the fermentation process. In producing fermentable sugars from pineapple wastes, a pretreatment process is required to breakdown the complex crystalline structure of lignocellulose. However, this process is challenging due to the recalcitrant structure of lignocellulosic material. With this regard, extensive researches have been done to improve the efficiency of the pretreatment method for maximum removal of lignin from the lignocellulosic biomass. In this study, low-pressure steam heating pretreatment was introduced to examine the delignification effectiveness of pineapple wastes. In this study, screening of three parameters using low-pressure steam heating pretreatment (biomass loading, pressure, and residence time) were carried out using one-factor-at-a-time (OFAT) analysis. From the results obtained, the best condition for low-pressure steam heating pretreatment was found to be at biomass loading of 5 %w/v, 80 kPa pressure, and 30 minutes residence time. A total of 46.89 % lignin had successfully been removed from pineapple wastes by using this pretreatment condition. The proposed pretreatment in this present study was proven to be a practical approach for biomass delignification.
 
 
 

Modulation of the Complex Spherical Packings through Rationally Doping a Discrete Homopolymer into a Discrete Block Copolymer: A Quantitative Study

The Frank–Kasper phase and quasicrystalline phase are an intriguing class of complex crystalline structures, which so far are sporadically observed only in a limited number of block copolymers. Incorporation of a homopolymer into a block copolymer has recently been demonstrated as an effective and robust approach to regulate the formation and evolution of these complex spherical phases. The experimental explorations, however, suffer from inherent chain length distribution of the blending stocks. In this study, we quantitatively assessed the phase behaviors of the block copolymer/homopolymer binary blends using discrete species with a precise chemical structure and uniform chain length, ruling out all interferences associated with chemical heterogeneities. Diverse spherical packings, including σ, A15, C15, and C14 phases, were captured by rationally tuning the chain length and loading content of the homopolymer. The short chains swell the spherical core and drive a transition toward the lattices with a lower interfacial curvature (i.e., σ → A15 → HEX), whereas the long chains localize in the center of the core and prompt the formation of the Frank–Kasper phases with the increasing particle volume asymmetry (C15 and C14). The experimental observation validates the recent theoretical advances, demonstrating that the blending strategy is a robust approach for structural engineering.

Combined Micromagnetic Simulation and Machine Learning Approach to Analysis of Polycrystalline Bilayer With Exchange Bias

Exchange bias (EB) is a complex interface phenomenon often used in multiple applications ranging from magnetic field sensors to spintronics and neuromorphic computing for inducing a unidirectional anisotropy in a ferromagnetic layer exchange coupled to an antiferromagnetic layer. Despite the significant progress in understanding mechanisms behind the EB, predicting and optimizing hysteresis properties of the pinned layer in real-life systems with complex crystalline and magnetic structure is still a challenge. In this work we use a combined machine learning (ML) and micromagnetic simulation approach for building a unified predictive model giving macroscopic hysteresis properties of the pinned layer for a given set of magnetic and structural parameters. The approximator can be considered as an unknown function, which can be used for finding local or global extrema for coercivity or EB field. We believe that a similar approach can be applied to other computer models or high-quality experimental data for advanced analysis of functional dependencies of hysteresis properties as well as evaluation of computer model used for simulation. A ML model of a bilayer with EB could be helpful for decreasing the computation time, optimizing layers materials and parameters, and minimizing the number of test samples.

Assessment of Local Observation of Atomic Ordering in Alloys via the Radial Distribution Function: A Computational and Experimental Approach

As a powerful analytical technique, atom probe tomography (APT) has the capacity to acquire the spatial distribution of millions of atoms from a complex sample. However, extracting information at the Ångstrom-scale on atomic ordering remains a challenge due to the limits of the APT experiment and data analysis algorithms. The development of new computational tools enable visualization of the data and aid understanding of the physical phenomena such as disorder of complex crystalline structures. Here, we report progress towards this goal using two steps. We describe a computational approach to evaluate atomic ordering in the crystal structure by generating radial distribution functions (RDF). Atomic ordering is rendered as the Fractional Cumulative Radial Distribution Function (FCRDF) which allows for greater visibility of local compositions at short range in the structure. Further, we accommodate in the analysis additional parameters such as uncertainty in the atomic coordinates and the atomic abundance to ascertain short-range ordering in APT data sets. We applied the FCRDF analysis to synthetic and experimental APT data sets for Ni3Al. The ability to observe a signal of atomic ordering consistent with the known L12 crystal structure is heavily dependent on spatial uncertainty, irrespective of abundance. Detection of atomic ordering is subject to an upper limit of spatial uncertainty of atoms described with Gaussian distributions with a standard deviation of 1.3 Å. The FCRDF analysis was also applied to the APT data set for a six-component alloy, Al1.3CoCrCuFeNi. In this case, we are currently able to visualize elemental segregation at the nanoscale, though unambiguous identification of atomic ordering at the Ångstrom (nearest-neighbor) scale remains a goal.

Chemical pre-treatments on oil palm empty fruit bunches: Impacts on characteristics and methane potential

Production of biogas from lignocellulosic biomass by anaerobic digestion (AD) has attracted much interest. Oil palm empty fruit bunches (OPEFB), one of lignocellulosic biomass, is highly abundant in Indonesia and has potential as feedstock for bioenergy production such as biogas or methane. Yet, pre-treatments are needed to improve biogas production due to its complex crystalline structures. Chemical pre-treatments with acid or alkaline solution were reported to increase cellulose or highly reduce the lignin content of OPEFB. This study aimed to evaluate the effect of acid and alkaline pre-treatments on the characteristics of OPEFB and methane potential. The acid pre-treatment experimental design was used factor of H2SO4 concentration (1, 1.3, and 1.6 (%v/v)) and NaOH concentration (1.8, 2.8, and 3.8 (%w/v)). Methane potential evaluation was carried out using the biochemical methane potential (BMP) test with the Automatic Methane Potential Test System (AMPTS) II under mesophilic condition (37°C), operated for 28 days. The results showed that both dilute acid and alkaline pre-treatment positively impact altering the characteristics of OPEFB, hence the specific methane potential. Alkaline pre-treatment with NaOH 3.8 (%w/v) gave the highest average SMP value of 0.161 ± 0.005 m3 CH4/kgVSadded.

Physical characterization of the milk chocolate using whey powder

In this study it was found that the complex microstructure of chocolate was modified by the addition of whey into original milk chocolate. A decreasing particle size diameter of the dispersed cocoa fat particles with increasing whey content followed by dynamic light scattering measurements was confirmed. Changes of the chocolate fat crystallinity through disrupting the highly ordered cocoa fat dense crystal aggregates to the less developed ones deformed by the inclusion of whey particles into the complex chocolate mass were simultaneously confirmed. These morphology changes affected the thermal and rheological behaviour of the studied samples by decreasing the melting peak temperature as well as Casson's plastic viscosity with increasing whey content. Furthermore, a gradual decrease of the hardness, thus reflecting the plasticising effect of the whey particles on the complex crystalline structure of the chocolate, was observed. The latter fact was also confirmed by the decreased acoustic emissions during chocolate breakage, thus indicating the change of the fracture process from brittle to more ductile.

Highly Tunable Piezoresistive Behavior of Carbon Nanotube-Containing Conductive Polymer Blend Composites Prepared from Two Polymers Exhibiting Crystallization-Induced Phase Separation

Conductive polymer composites (CPCs) are suitable as piezoresistive-sensing materials. When using CPCs for strain sensing, it is still a big challenge to simultaneously improve the piezoresistive sensitivity and linearity along with the electrical conductivity and mechanical properties. Here, highly tunable piezoresistive behavior is reported for multiwalled carbon nanotube (CNT)-filled CPCs based on blends of two semicrystalline polymers poly(vinylidene fluoride) (PVDF) and poly(butylene succinate) (PBS), which are miscible in the melt. When cooling the homogeneous mixture of the blend components, successive crystallization of PVDF and PBS occurs, creating complex crystalline structures in a mixed amorphous phase. The morphology of the blend matrix, the crystallinity of the blend components, and the dispersion and location of the CNTs in the blend depend on the CNT content and the blend composition. Compared with PVDF/CNT composites, the substitution of 10 to 50 wt % PVDF by PBS in the composites shifts the electrical percolation concentration Φc from 0.79 wt % to filler contents as low as 0.50 wt % while improving the stretchability. The piezoresistive behavior is highly tunable by changing the PVDF/PBS ratio. The ternary composites with matrix compositions of PVDF (90 wt %)/PBS (10 wt %) and PVDF (50 wt %)/PBS (50 wt %) show either higher piezoresistive sensitivity or linearity, respectively, caused by the differences in the microstructure of the CPCs. For example, the crystallinity of PBS in the ternary composites increased from 19.8% to 52.0% as the PBS content increased from 10 wt % to 50 wt %, which is connected with altered CNT distribution and conductive network structure and substantial improvement of the linearity of the electrical response to strains up to >20%. Our findings highly contribute to the understanding of the piezoresistive properties of CPCs based on two semicrystalline polymers and are important for future studies to tune the piezoresistive behavior to achieve simultaneously improved sensitivity and linearity.

Quantum-mechanical model of thermally stimulated depolarization in layered dielectrics at low temperatures

Built the quantum-mechanical scheme for investigating the spectrum of thermally stimulated currents of depolarization (TCDP), which allows to study the processes of relaxation of hetero-and homo-charge in hydrogen bonded crystals (HBC) with complex crystalline structure (layered silicates, crystal-hydrates), taking into account the distribution of relaxers (protons) over the energy levels of the quasi-discrete spectrum in potential image of the crystal lattice, and allows us to calculate the parameters of low-temperature relaxers by the Klinger method in the quadratic approximation over the external electric field. However, the calculation of the excess proton concentration operator was carried out in the quasi-classical approximation on the basis of the Fokker-Planck operator equation, which is solved together with the Poisson operator equation. By method of density matrix in the quadratic approximation in the external field calculated thermally stimulated depolarization currents on the basis of which the investigated size effects in the nanometer size layers associated with the shift of the maximum current of thermo-depolarization to low temperatures while reducing the thickness of the crystal layer.

Effect of moist and dry-heat treatment processes on the structure, physicochemical properties, and in vitro digestibility of wheat starch-lauric acid complexes

Herein, we investigated the impact of moist (steaming and boiling) and dry (baking and microwaving)-heat treatment processes on the structure and physicochemical properties of wheat starch (WS) supplemented with lauric acid (LA). Elemental composition analysis revealed the interplay between WS and LA. Scanning electron microscopy (SEM) and iodine staining revealed that lamellar crystalline structure of WS-LA complexes was improved after moist-heat treatment (relative to samples without any heat treatments); the finding which is at variance to dry-heat treatment process. Additionally, high resistance to thermal decomposition and a lower 1022/995 cm−1 absorbance ratio were observed in moist-heat treated WS-LA compared with dry-heat samples. Moreover, the V-type diffraction peak intensity and resistance to in vitro enzymatic hydrolysis of samples treated with moist-heat were increased to a greater extent than the dry-heat treated counterparts. In sum, this study would facilitate the application of functional starch-lipid complexes in food necessitated heat treatments.

Four-fold multifunctional properties in self-organized layered ferrite

Four different functional properties at room temperature were found in Ba12Fe28Ti15O84 quaternary ferrite ceramics: a thermoelectric character with a prominent Seebeck coefficient of -400 μV/K, a strong ferrimagnetic character and weak magnetoresistivity, non-linear dielectric character (tunability) and ferro/piezoelectric response. The complex crystalline structure with a naturally occurring self-organized layered structure was mapped by High Resolution Transmission Electron Microscopy. A n-type conduction was found for optimized samples, consistent with the negative Seebeck coefficient. The presence of magnetic domains with a lateral size ranging from few hundreds of nanometers, up to few microns, extended over several grains indicates a strong intergranular magnetic interaction. Local ferroelectric switching as revealed by piezoresponse force microscopy showed a relatively weak effective piezoelectric coefficient with a remnant value of 0.5 p.m./V and a clockwise cycling direction, which was attributed to an effective negative piezoelectric coefficient. The switching behavior was described as originating from the material’s nanoscale layered complexity, with a strong anisotropy of its dielectric and ferro/piezoelectric local properties.

Supplementation of O2-containing gas nanobubble water to enhance methane production from anaerobic digestion of cellulose

Nanobubble water (NBW) contains 106–108 gas bubbles per milliliter with diameter <1 µm. These fine bubbles possess high mass transfer efficiency and hydrophobic property beneficial for agricultural and biomedical application. Nowadays, much attention has been paid to the secure and sustainable management of lignocellulosic wastes. Cellulose is regarded as one kind of slowly biodegradable organic components owing to its complex crystalline structure. This study investigated the effect of O2-containing gas NBW on anaerobic digestion (AD) of cellulose for methane production. Results show that the cumulative methane yields from the reactors with Air-NBW (193 NmL/g-VSreduced), N2-NBW (196 NmL/g-VSreduced) and O2-NBW (233 NmL/g-VSreduced) addition were increased by 8–30% in comparison to the control (with the same amount of deionized water addition) (179 NmL/g-VSreduced). Under NBW addition, the reductions in cellulose content and cellulose crystallinity were respectively enhanced by 8–14% and 9–21% during AD, in which cellulase activity was elevated by 10–38%. The O2-NBW reactor was found to have the highest electron transport system activity, increasing by 1.7 times compared to the control, most probably due to the collapse of O2-nanobubbles and release of O2 resulting in micro-oxygen environment under the test condition. Besides, microbial community analysis suggests that the direct interspecies electron transfer could be quickly established with the addition of NBW. Results from this study also shed light on the mechanisms involved in the bioconversion of cellulose to methane via AD supplemented with NBW.

α-Ag2S: A Ductile Thermoelectric Material with High ZT.

Using first-principles calculation and Boltzmann electron/phonon transport theory, we present an accurate theoretical prediction of thermoelectric properties of the α-Ag2S crystal, a ductile inorganic semiconductor reported experimentally [Nat. Mater. 2018,17, 421]. The semiconductor α-Ag2S has ultralow thermal conductivity associated with high anisotropy, which can be attributed to the complex crystalline structure and weak bonding. The optimal values of the Seebeck coefficient are 0.27 × 10–3 V/K for n-type and 0.21 × 10–3 V/K for p-type α-Ag2S, respectively, which are comparable to those of many promising thermoelectric materials. As a consequence, a maximum ZT value of 0.97/1.12 can be realized for p-type/n-type α-Ag2S at room temperature. More interestingly, the value of ZT can be further enhanced to 1.65 at room temperature by applying 5% compressive strain. Moreover, we find that the electronic thermal conductivity is a major factor limiting the ZT, which is several times the lattice thermal conductivity for n-type α-Ag2S. Our work demonstrates the great advantage of the α-Ag2S crystal as a ductile thermoelectric material and sparks new routes to improve its figure of merit.

Review on applications of synchrotron‐based X‐ray techniques in materials characterization

Synchrotron radiation (SR), as a result of its high‐intensity, brilliant, monochromatic, and collimated beams, is becoming one of the most crucial components of research in various fields of materials science such as nanomaterials, biomaterials, and energy materials. SR‐based characterization methods can be employed to analyze different systems such as powders, thin films, and bulk forms having complex crystalline or amorphous structures. In this review, peculiarities of SR are briefly explained. Moreover, various techniques carried out utilizing this instrument for material characterization such as X‐ray powder diffraction, grazing‐incidence X‐ray diffraction, small/wide‐angle X‐ray scattering, X‐ray absorption spectroscopy, different techniques of X‐ray imaging, X‐ray photoelectron spectroscopy, and X‐ray microprobes/nanoprobes are presented. As a result, by shedding light on the advantages of SR and its superiority to the equivalent laboratory experiments, researchers are recommended to exploit the capabilities of this invaluable tool in their materials characterization.

Enhanced biological properties of taurine metal complexes via binding active sites

A simple preparation of Taurine metal complexes (TauMC) were carried out by general precipitation technique using binary solvent (DMF-Water) in 1:1 ratio. Taurine-metal complex formation were confirmed by the shift in the absorption peaks of UV–Visible spectrum. The role of Taurine played as a vital ligand to form the series of metal complexes with transition metal ions (Mn, Cu, Zn) were clearly observed as the M-O stretching vibration in FT-IR spectroscopy. Thermal stability and crystalline structure of these taurine metal complexes were well characterized by TGA and XRD studies. Co-ordination complex ratio of metal to ligand (1:2) were absolutely determined via XPS analysis. Especially, among the prepared taurine based series of transition metal complexes, Taurine-Cu complex (TauCC) emerged out as binding active sites than ligand which significantly enhanced its biological properties.

QUANTIFICAÇÃO DE MULLITA PROVENIENTE DE RESÍDUOS DE CAULIM DA REGIÃO AMAZÔNICA: USO DO MÉTODO DE RIETVELD

QUANTIFICATION OF MULLITE FROM KAOLIN WASTES FROM THE AMAZON REGION: USE OF THE RIETVELD METHOD. Mullite is used to obtain a refractory material, there are several factors that influence the synthesis process of mullite: the preparation of the mixture, the precipitation and the reaction of SiO2 and Al2O3. For the synthesis of mullite, samples of kaolin processing residues were used as precursor material, because it presents SiO2 and Al2O3 in its composition. This work aimed to identify, by X-ray diffraction, and quantify the mineral phases present in samples of kaolin processing residues from the Amazon region calcined at 1300, 1400 and 1500 ºC, using the Rietveld method. The method allowed the refinement of the complex crystalline structures and was applied to the data supply for quantitative analyses with satisfactory results of good accuracy. The results of the quantification of crystalline and non-crystalline phases (with internal standard) in the samples calcined at 1500 ºC presented approximate values of mullite (62%), cristobalite (32%) and non-crystalline phases (6%), for both samples, indicating that the refinement model applied is optimal. These results obtained from the quantification of the phases by the method of Rietveld are presenting coherent and satisfactory values, in comparison with the theoretical ones by the phase diagram Al2O3 and SiO2

Structural Characterization of Controlled Decrystallization of Cassava Starch

AbstractNative starch granule has a complex crystalline structure. Controlled decrystallization cassava starch (CDCS) was prepared by the alcohol–alkali method. Polarized microscopy, scanning electron microscopy (SEM), X‐ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR) analysis of the CDCS are carried out to investigate its structural information. The results show that the relative crystallinity (RC) of the processed cassava starches can be reduced from 25.56% to 17.90% by adjusting the concentration of sodium hydroxide while keeping the integrity of the starch granule. During the decrystallization process, as the sodium hydroxide concentration is increased from 0.25 to 1.25 mol L−1, the polarized light of the starch granules disappear from the inside to the outside, and the X‐ray diffraction peaks of native cassava starch (NCS) disappear sequentially from 17.16°, 23.04°, 15.08°, to 17.83°. On the other hand, the FTIR peaks of the NCS centered at 1645 cm−1 is shifted to about 1600 cm−1, and the intensity of the peaks at 3424, 2929, 1645, and 1017 cm−1 become weaker with decrystallization process. This study provides valuable data and a theoretical basis to understand the mechanism of the controlled decrystallization of cassava starch.

Apparent auxetic to non-auxetic crossover driven by Co2+ redistribution in CoFe2O4 thin films

Oxide spinels of general formula AB2O4 (A = Mg2+, Fe2+; B = Al3+, Cr3+, etc.) constitute one of the most abundant crystalline structures in mineralogy. In this structure, cations distribute among octahedral and tetrahedral sites, according to their size and the crystal-field stabilization energy. The cationic arrangement determines the mechanical, magnetic, and transport properties of the spinel and can be influenced by external parameters like temperature, pressure, or epitaxial stress in the case of thin films. Here, we report a progressive change in the sign of the Poisson ratio, ν, in thin films of CoFe2O4, defining a smooth crossover from auxetic (ν &amp;lt; 0) to non-auxetic (ν &amp;gt; 0) behavior in response to epitaxial stress and temperature. Microstructural and magnetization studies, as well as ab initio calculations, demonstrate that such unusual elastic response is actually due to a progressive redistribution of Co2+ among the octahedral and tetrahedral sites of the spinel structure. The results presented in this work clarify a long standing controversy about the magnetic and elastic properties of Co-ferrites and are of general applicability for understanding the stress-relaxation mechanism in complex crystalline structures.

Synthesis and Crystalline Structure of Zinc Complexes with Antihypertensive Drug Lisinopril

The structural investigation of Zn2+ complexes with the ligand lisinopril (LIS), an inhibitor of angiotensin-converting enzyme (ACE), was performed. The main objective is to compare if Zn-LIS coordination in vitro is similar to that observed in vivo. Two zinc complexes were obtained from different synthetic routes. The synthesis of LISZn1 used stirring, while for LISZn2 involved solvothermal conditions, which favoured the full deprotonation of lisinopril ligand. In this sense, the different synthetic routes resulted in the formation of complexes with notorious chemical and structural differences. The crystal structure of LISZn2 showed that the ligand is coordinated to Zn2+ ion by oxygen and nitrogen atoms which is different from that observed in vivo. In vitro, the coordination of lisinopril occurs only by an oxygen atom of the central carboxylate group. LISZn2 forms a one-dimensional (1D) coordination polymer and presents disorder atoms in its unit cell.

Statistical Analysis of Metal Particles Forming during Reduction of Oxides with Low Iron Content

Metallurgical Industry slowly moves towards wider utilization of complex ore minerals. Reduction behavior of complex crystalline structures can hardly be interpreted applying kinetic modeling adopted for pure oxides. The quantitative mathematical analysis of the metal particles forming during solid state reduction of a complex mineral has been suggested. The analysis with 95% reliability showed that during solid phase reduction of dunite at 1300 °C for 60 min about 360 particles with an average size about 0.62 mm formed from the total area S = 20880 mm. Such an approach could be useful for development of sophisticated kinetic models applied for reduction of a low-grade complex ore.