Scanning Electron Microscopy Methods Research Articles

Synergistic effect of PTB emulsion, CaCO3 whisker and Nano-SiO2 on the properties of cement-based materials

With the rapid development of the civil engineering industry, performance requirements for building materials are also increasing rapidly. It is particularly critical to improve the performance of cement-based materials using admixtures. In this study, the synergistic effect of PTB (COMPAKTUNA.PRO) emulsion, calcium carbonate whisker (CaCO3 whisker) and nano-silica (nano-SiO2) on material properties was analyzed. Macroscopic properties such as rheology, compressive strength, flexural strength, durability, bond strength, and permeable pressure were tested. Microstructures were analyzed using the porosity, hydration heat, X-ray diffraction, and scanning electron microscopy methods. The results revealed that the PTB emulsion, CaCO3 whiskers, and nano-SiO2 increased the plastic viscosity and yield stress of the cement. When the nano-SiO2 content was high, the fluidity of the slurry decreased significantly. Overall, PTB emulsion, CaCO3 whisker and nano-SiO2 can improve the strength, durability, bond strength, and permeability of composite materials. PTB emulsions can prolong the hydration process, resulting in low early strength and reduced compressive strength. However, they play a key role in terms of improving durability, bond strength, and permeability pressure. CaCO3 whiskers yield slight improvements in various properties. Nano-SiO2 can promote the hydration rate and hydration effect, thereby improving the strength, compactness, and properties of composite materials. Performance can be optimized by leveraging these synergistic effects and each material has its own unique advantages and limitations. In engineering applications, critical properties should be considered when selecting appropriate admixture contents. This study aimed to improve various properties and to develop materials that are suitable for the complex environment of underground engineering.

Microstructure and Properties of AISI 316L Steel Processed by Selective Laser Melting Technology (SLM) and Hot Isostatic Pressing Technology (HIP)

The aim of our study was to determine changes in the microstructure and mechanical properties of AISI 316L steel processed by additive SLM technology which will be induced by additional processing using HIP technology and solution annealing. The specimens for this experiment were made in the form of bars with a diameter of 5 mm for tensile testing. The specimens were additively manufactured in the vertical direction with respect to the position of the build plate using standard process parameters. The HIP processing of the specimens was performed at a temperature of 1150 °C and pressure of 150 MPa. Some of the specimens were heat treated using solution annealing at 1150 °C after the SLM and HIP processes. The analyses performed consisted of metallographic analysis of the microstructure using light and scanning electron microscopy methods, which were further complemented by basic mechanical property tests, namely tensile testing and HV1 hardness measurements. The tensile test showed that the solution annealing of the printed specimens reduced the ultimate strength from 545±6.2 MPa to 508±0.0 MPa and increased the ductility from 44±5.4 % to 56±0.4 %. The HIP process reduced the ultimate strength to 522±2.7 MPa and the further annealed specimens to 514±1.8 MPa. The ductility of the specimens after HIP treatment was higher than that of the additively manufactured specimens, corresponding to 52±0.3 %. After solution annealing, it reached values like those of the specimens annealed after 3D printing. The metallographic analysis carried out showed a positive effect of the HIP process on the porosity achieved after 3d printing, whose volume was reduced as a result.

3D spatial fracture behavior of sandstone containing a surface flaw under uniaxial compression

Surface defects are prevalent in natural rock masses, and the newborn cracks that initiate from these defects and significantly affect structural stability usually extend in a three-dimensional (3D) manner. Hence, in this research, a series of uniaxial compression tests were conducted on sandstone specimens containing a surface flaw to examine the effect of nondimensional flaw depth (0, 0.3, 0.5 and 0.75) on the fracture behavior. The crack propagation process was monitored by digital image correlation (DIC) technique, and postmortem microscopic fracture morphology was measured using scanning electron microscope (SEM) method. In addition, the fracture energy evolution and stress intensity factors (SIFs) along the semi-elliptical flaw perimeter were discussed in detail to theoretically interpret the experimental phenomena. The results indicate that the strength decreased by 2.70%, 10.90% and 11.91% for nondimensional surface flaw depths of 0.3, 0.5 and 0.75, respectively, and elastic modulus exhibited a reduction of 3.71%, 10.69% and 3.21%, respectively. Full-field deformation contours demonstrate that crack paths in the front surface of the specimen were totally different from those in the back surface, but the failure pattern tended to be similar to that of specimens containing a penetrated flaw with the increasing flaw depth. The micro appearance of a typical fracture further reveals the complicated stress state (mixed I-II-III mode) under uniaxial compression. For a larger flaw depth, the proportion of releasable elastic strain energy in total input strain energy was improved, while the percentage of dissipated energy was reduced. Based on fracture mechanics, SIFs along the flaw periphery uncover the magnitude of KI, KII and KIII and further the type of initiation crack type. Finally, parametric analysis was carried out to investigate the effects of flaw length and specimen thickness. The difference in crack pattern from surface and penetrated flaw was also discussed in detail.

Histo-morphological Characterization of the Tongue and Oropharyngeal Cavity of the Shining Sunbird (Cinnyris habessinicus).

Sunbirds, as specialized nectarivores, have developed multiple lingual and oropharyngeal peculiarities imposed by this dietary specialization that particularly extract floral nectar. We have described the functional morphology of the tongues and palates of the shining sunbird, Cinnyris habessinicus, using gross anatomical, histological, and scanning electron microscopic methods. The tongue was bifurcated with fringed lamella and extended posteriorly, forming a broad trough at the lingual body and terminating in two fleshy, alae linguae. The lingual apex and body are nonpapillate and nonglandular, and its root had a muscular pad followed by a conspicuous laryngeal mound bordered by three prominent rows of conical papillae. The lingual root had clusters of mucoid glands with rich acidic mucins, and the laryngeal region had complex papillary distribution at the back margins. Both the lingual body and root had well-developed skeletal elements, musculature, and connective tissues. Furthermore, the palate was membranous and made up of four main ridges with a central choanal slit guarded by choanal papillae. Overall, the presented results showed structural and anatomical features that are the results of the nectarivory dietary niche.

UV aging behavior evolution characterization of HALS-modified asphalt based on micro-morphological features

Abstract To clarify the effect of Hindered amine light stabilizer (HALS) on ultraviolet (UV) aging behavior of asphalt binder, the evolution history and characteristics of the UV induced micro-structure of modified asphalt were characterized. Scanning Electron Microscope (SEM) and Atomic Force Microscope (AFM) were used to analyze the microscopic morphology evolution of light stabilizer-modified asphalt during UV aging. By defining the micro-structure of asphalt in aging joints induced by UV, the identification and classification of typical micro-structure are proposed. On this basis, an evaluation method based on the morphology evolution process of modified asphalt aging was proposed to quantitatively analyze the effect of HALS on the UV aging of asphalt binder. The results show that the control effect of HALS on the UV aging behavior of asphalt can be verified by SEM and AFM detection methods. At the same time, the aging interval of the asphalt modified by hindered amine was divided by the method, and it was verified that the HALS could significantly prolong the service life of the asphalt binder. The micro-morphology of asphalt binder undergoes the process of crack generation and propagation during UV aging. The micro-morphological changes of UV aged asphalt were interfered effectively by HALS, which could alleviate and control the development of UV induced micro-cracks, and promote the fusion of micro-cracks. This study provides an effective evaluation method for detecting UV aging microscopic evolution of HALS.

Encapsulation Of β-Carotene And Curcumin In Liposome From Soybean Lecithin And L-α-Phosphatidylcholine Using SC-CO2 With The Assistance Of Ultrasonication

The newest method to maintain better bioavailability of antioxidant compounds in the human digestive process is encapsulation using liposomes. The liposomes used were lecithin from soybean seeds and L-α-Phosphatidylcholine. Furthermore, curcumin and β-carotene were encapsulated in soy lecithin liposomes using SC-CO2 with 100% ethanol, aquadest 50% v/v ethanol and 100% aquadest at 50°C, 60°C, and 70°C and pressure 15 MPa, 20 MPa and 25 MPa by ultrasonication for 60 minutes. This research was conducted to obtain liposomes from curcumin and β-carotene encapsulation, analyse the effect of lecithin from soybean seeds on the formation of encapsulation in liposomes, analyse the effect of operating conditions on the encapsulation process on the size of curcumin and β-carotene in liposomes and determine the size characteristics of liposomes. This was analysed using a UV-Vis Spectrophotometer and Particle Size Analyzer (PSA) with the Dynamic Light Scattering method and also using the Scanning Electron Microscope (SEM) method. The results of the PSA test showed that the increase in operating temperature and pressure resulted in an increase in liposome particle size. UV-Vis analysis proved that the content of curcumin and β-carotene in liposomes from L-α-Phosphatidylcholine had better results. It was found that using SC-CO2+Sonicator had higher concentrations of curcumin and β-carotene with the condition that the higher the temperature, the higher the curcumin content. The use of liposomes has increased the stability of encapsulated suspensions and prevented flocculation. SEM analysis proved that the encapsulation of curcumin with L-α-Phosphatidylcholine has the smallest particle size distribution of 2 micro meters so that it can be categorized as multilamellar vesicles (MLV).

Preparation of Cationic Composite Hydrogel Improved by Activated Carbon and Its Use in Removal of Anionic Dye

Water-insoluble p(AETAC)/AC composite hydrogels containing quaternary ammonium were prepared by free-radical polymerisation method with [2-(Acryloyloxy)ethyl]trimethylammonium chloride (AETAC) and activated carbon (AC). The composite hydrogel was characterized by Fourier Transform Infrared Spectroscopy (FT-IR), Thermogravimetric analysis (TGA), X-Ray Diffraction (XRD), and Scanning Electron Microscopy (SEM) methods. In addition, the swelling behavior of p(AETAC)/AC composite hydrogels containing 50 mg, 75 mg, 100 mg, and 150 mg AC in deionized water was investigated. The swelling capacity of the p(AETAC)/AC75 composite hydrogel containing 75 mg AC in various waters was determined. Initial dye concentration, contact time, pH of dye solution, amount of adsorbent, and temperature parameters affecting MO adsorption of p(AETAC)/AC75 composite hydrogel were investigated. The obtained adsorption data agree with the Langmuir isotherm model and the PFO kinetic model. It was determined that the maximum adsorption ability of p(AETAC)/AC75 composite hydrogel according to Langmuir isotherm was 909.09 mg/g. ΔH° and ΔS° values for the adsorption of MO dye-stuff of p(AETAC)/AC75 composite hydrogel were calculated as 22.25 ± 1.43 and 85.40 ± 4.60, respectively. In addition, the value of ΔG° less than zero at four different temperatures indicates that the dye adsorption is spontaneous. According to all the data obtained, p(AETAC)/AC75 composite hydrogel can be considered a promising candidate for the removal of anionic dyestuffs from water.

(Digital Presentation) The Utilization of Platinum Catalysts Deposited on Carbon Support Synthesized from Coffee Grounds in a Polymer Electrolyte Membrane Fuel Cell

Exploring alternative sources for platinum catalyst carbon support material is vital for the further development of polymer electrolyte membrane fuel cells (PEMFC).1 The support material and the method of depositing Pt nanoparticles are crucial for defining the catalytic properties of the catalyst. In this study, carbon support material, derived from coffee grounds was used in the preparation of Pt catalysts for PEMFC application. The carbon material was synthesized using ZnCl2 activated pyrolysis method2 and the Pt nanoparticles were deposited onto carbon support by two methods: using ethylene glycol3 or hydrogen4 as a reducing agent.The physical properties of the support material, as well as catalysts were analysed through thermogravimetric analysis (TGA), dynamic light scattering, X-ray diffraction (XRD), N2 sorption analysis and high-resolution scanning electron microscopy (HR-SEM) methods. The electrochemical activity, as well as the electrochemically active surface area (ECSA) of the catalysts were determined in a completed PEMFC. The properties and performance of catalysts synthesised were compared with the catalyst which was deposited onto commercial carbon (Ketjenblack, EC-300J).TGA displayed that carbon derived from coffee grounds contained 6.9 % of impurities by mass in the form of metal oxides and that the coffee carbon Pt catalyst contained 60 wt% of Pt. The Pt crystallite size was determined through XRD and it was 1.4 nm. HR-SEM analysis displayed that the average particle size of Pt nanoparticles on the coffee carbon catalyst was 4.7±2.5 nm. Results from N2 sorption analysis showed that all materials were micro-mesoporous, with coffee ground carbon having a specific surface area of 590 m2 g-1. The coffee carbon Pt catalyst produced smaller results of 370 m2 g-1 compared to the carbon support, due to the Pt nanoparticles depositing in the micropores, however still had a larger specific surface area than the commercial carbon catalyst with a specific surface area of 300 m2 g-1.Catalysts deposited on coffee ground carbon produced comparable electrochemical results to catalysts deposited on commercially available carbon. The coffee carbon catalyst produced a higher ECSA of 64 mPt 2 gPt -1, compared to the commercial carbon catalyst with an ECSA of 51 mPt 2 gPt -1. The current density of the Pt catalyst deposited onto coffee carbon was 0.68 A cm-2 at 670 mV, whilst in the same conditions commercial carbon peaked at 0.70 A cm-2. Both coffee and commercial carbon Pt catalysts produced similar power density maximums with the coffee Pt catalyst producing 0.56 W cm-2 and the commercial Pt catalyst producing 0.60 W cm-2.Physical and electrochemical characterizations displayed that higher ECSA values were strongly correlated to smaller Pt crystallite size. Other techniques to increase fuel cell performance were also experimented with, such as covering the gas diffusion layer with catalyst instead of Nafion membrane and adding additional Nafion layers, with both methods producing promising results.This study displays that there is a lot of potential in improving the catalytic performance of Pt catalysts by depositing on support materials derived from alternative sources. The methods of boosting PEMFC performance could be further investigated for catalysts deposited on different carbon supports. Acknowledgements This work was supported by the EU through the European Regional Development Fund TK141 “Advanced materials and high-technology devices for energy recuperation systems” (2014-2020.4.01.15-0011), Personal Research Grant PRG676 and by private limited company AuVe Tech LLTKT20148 “Production of Polymer Electrolyte Membrane Fuel Cells”. The SEM measurements were conducted using the NAMUR+ core facility funded by the Estonian Research Council (TT 13). References S. Shahgaldi and J. Hamelin, Carbon, 94, 705-728 (2015). M. Härmas, PhD thesis, University of Tartu, Tartu, Estonia (2020). Y. Shao, S. Zhang, R. Kou, X. Wang, C. Wang, S. Dai, V. Viswanathan, J. Liu, Y. Wang, Y. Lin, J. Power Sources 195, 1805-1811 (2010). Y. Zheng, Z. Dou, Y. Fang, M. Li, X. Wu, J. Zeng, Z. Hou, S. Liao, J. Power Sources, 306, 448-453 (2015).

Piezodynamic Eradication of Both Gram-Positive and Gram-Negative Bacteria by Using a Nanoparticle Embedded Polymeric Membrane.

Nowadays, bacterial infection is regarded as a serious threat to humankind, which needs to be taken care of. The emergence of antibiotic resistance and multidrug resistance (MDR) is rendering this situation more troublesome. However, several alternative treatment regimens have aided such diseases quite well in the recent past, among which dynamic antibacterial therapies combat this situation quite well. Among various dynamic therapies, piezodynamic therapy is a very recent avenue, in which mechanical stimuli have been exploited to treat bacterial infections. Herein, piezo-active bismuth ferrite-loaded poly(vinylidene fluoride-co-hexafluoropropylene) polymer has been utilized to eradicate gram-positive bacteria (E. faecalis) and gram-negative bacteria (E. coli). The sample has been designed in a free-standing membrane form, which, under soft ultrasound (~10 kHz), generates reactive radicals to ablate bacteria. Initially, the structure and morphology of the membrane have been substantiated by using X-ray diffraction and scanning electron microscopy methods; besides, Fourier transform infrared spectrum of the sample depicts a tremendously high value of polarizability and further confirms the piezo-activity of the membrane. More than 99% of E. coli and E. faecalis have been successfully eradicated within 30 min of ultrasound. Moreover, the solid-state structure and hydrophobic nature of the membrane help us to reuse it in a cyclic manner, which is possibly reported herein for the very first time. This novel membrane could be deployed in healthcare systems and pigment industries and could be exploited as a self-cleaning material.

SMALL ANGLE X-RAY SCATTERING UNIT FOR ANALYSIS OF SECONDARY NANOPHASES AND PORES IN BAINITE STEEL

The work presents the results of studies aimed at analyzing the morphology and dimensional distribution of cementites and pores/microcracks in bainite steel used as tubing couplings during fluid transportation. For the first time, the method of small-angle X-ray scattering (SAXS) has demonstrated the possibility of analyzing not only secondary phases (particles, precipitates), but also shows the potential to expand the limits of applicability of this method for analyzing the morphology and dimensional distribution of pores/microcracks that originated both during casting and heat treatment and during subsequent operation of the tubing. The SAXS approach was adapted, taking into account the shape of cementites/pores, the relationship and ordering of cementites/pores in three-dimensional space, the factor of scale and absorption, analyzed volume and background radiation when processing scattering curves. The analysis of the scattering curves obtained on the transmission revealed cylindrical cementites with a diameter of 26 nm and a length of 180 nm, as well as manganese sulfides of an elliptical shape. Analysis of scattering curves measured in reflection mode has been shown to detect cylindrical nanopores/microcracks 36 nm in diameter and 170 nm in length, as well as spherical macropores 700 nm in diameter. To validate the obtained data, microstructure studies were carried out by scanning and transmission electron microscopy methods, which showed a convincing convergence of results between them. Nature and causes of identified pores in bainite steel are discussed.

Structure and Properties of Amorphous Quasi-High-Entropy Fe-Co-Ni-Cr-(Mo,V)-B Alloys with Various Boron Content

This study focuses on the effect of replacing molybdenum with vanadium in rapidly quenched quasi-high-entropy alloys of the Fe-Co-Ni-Cr-(Mo,V)-B system. The paper analyzes the effect of the chemical composition of alloys with different boron content levels on structure formation, characteristic temperatures of alloys, and mechanical properties. An analysis of the relationship between the structure of alloys and their properties is performed. X-ray diffraction and scanning electron microscopy methods were used in the work to establish the structural dependencies. Characteristic temperatures were determined by differential scanning calorimetry. It is suggested that the addition of vanadium to the alloys of this system leads to the formation of vanadium nitrides in the structure, due to the binding of dissolved nitrogen. Furthermore, it is found that replacing molybdenum with vanadium leads to an increase in the thermal stability of the amorphous phase.

Olive Leaves-Derived Hierarchical Porous Carbon as Cathode Material for Anti-Self-Discharge Zinc-Ion Hybrid Capacitor.

As a promising low-cost and high-safety energy storage candidate, zinc-ion hybrid capacitors (ZIHCs) have received extensive attention. For maximizing the advantages of ZIHC with high energy density and high power density, the structural engineering of the porous carbon materials is the crucial and effective strategy. Herein, an oxygen-enriched hierarchical porous carbon has been fabricated from the pyrolysis of olive leaves combing the chemical activation. The abundant interfacial active sites and short ions/electrons transfer length endow the hierarchical porous carbon cathode with high ions adsorption capacity and fast kinetic behaviors. Meanwhile, the oxygen-rich functional groups can provide extra pseudocapacitance and improve the wettability and conductivity of porous carbon. Benefiting from these advantages, an anti-self-discharge ZIHC device with a high energy-power feature has been assembled. The electrochemical process is studied by ex situ X-ray diffraction (XRD) and scanning electron microscope (SEM) methods. Finally, an excellent energy density of 136.3W h kg-1 , and high power output of 20kW kg-1 , as well as long cycle life with 91% capacity retention over 20 000 cycles at 10 A g-1 are realized by as-assembled ZIHC.

Differences and Similarities between Colorectal Cancer Cells and Colorectal Cancer Stem Cells: Molecular Insights and Implications.

Malignant tumors are formed by diverse groups of cancer cells. Cancer stem cells (CSCs) are a subpopulation of heterogeneous cells identified in tumors that have the ability to self-renew and differentiate. Colorectal cancer (CRC), the third most frequent malignant tumor, is progressively being supported by evidence suggesting that CSCs are crucial in cancer development. We aim to identify molecular differences between CRC cells and CRC CSCs, as well as the effects of those differences on cell behavior in terms of migration, EMT, pluripotency, morphology, cell cycle/control, and epigenetic characteristics. The HT-29 cell line (human colorectal adenocarcinoma) and HT-29 CSCs (HT-29 CD133+/CD44+ cells) were cultured for 72 h. The levels of E-cadherin, KLF4, p53, p21, p16, cyclin D2, HDAC9, and P300 protein expression were determined using immunohistochemistry staining. The migration of cells was assessed by employing the scratch assay technique. Additionally, the scanning electron microscopy method was used to examine the morphological features of the cells, and their peripheral/central elemental ratios were compared with the help of EDS. Furthermore, a Muse cell cycle kit was utilized to determine the cell cycle analysis. The HT-29 CSC group exhibited high levels of expression for E-cadherin, p53, p21, p16, cyclin D2, HDAC9, and P300, whereas KLF4 was found to be high in the HT-29. The two groups did not exhibit any statistically significant differences in the percentages of cell cycle phases. The identification of specific CSC characteristics will allow for earlier cancer detection and the development of more effective precision oncology options.

A simple way to predict the flip–chip gap

Using laser scanning confocal microscopy measurement, a concise method for extracting the indium bump shape in microelectronics was first established. The extracted bump shape was then used as the input for finite element analysis. The modeled one-bump deformation was used to predict the final flip–chip gap after bonding. Dovetailed with the results of cross-sectional scanning electron microscopy, this simple and non-destructive method for predicting a flip–chip gap of the order of 10 microns or less was eventually validated.

The Catalytic Effect of Vanadium on Sorption Properties of MgH2-Based Nanocomposites Obtained Using Low Milling Time.

The effects of catalysis using vanadium as an additive (2 and 5 wt.%) in a high-energy ball mill on composite desorption properties were examined. The influence of microstructure on the dehydration temperature and hydrogen desorption kinetics was monitored. Morphological and microstructural studies of the synthesized sample were performed by X-ray diffraction (XRD), laser particle size distribution (PSD), and scanning electron microscopy (SEM) methods, while differential scanning calorimetry (DSC) determined thermal properties. To further access amorph species in the milling blend, the absorption spectra were obtained by FTIR-ATR analysis (Fourier transform infrared spectroscopy attenuated total reflection). The results show lower apparent activation energy (Eapp) and H2 desorption temperature are obtained for milling bland with 5 wt.% added vanadium. The best explanation of hydrogen desorption reaction shows the Avrami-Erofeev model for parameter n = 4. Since the obtained value of apparent activation energy is close to the Mg-H bond-breaking energy, one can conclude that breaking this bond would be the rate-limiting step of the process.

Biosynthesis, in-vitro antioxidant and cytotoxic potential of silver nanoparticles of Abutilon hirtum (Lamp) Sweet

The world's leading cause of cancer-related death with most aggressive tumor is hepatocellular carcinoma. Silver nanoparticles have grown in relevance as molecular imaging agents and anticancer activities due to their benefits and versatility. An aqueous extract of Abutilon hirtum was employed in this investigation to produce silver nanoparticles, which showed showed a quick reduction of silver ions, and analysed using UV, Attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), Energy-dispersive X-rayanalysis (EDAX), and Scanning electron microscope (SEM) methods. The UV analysis showed 450 nm as the peak of the Plasmon resonance. The scanning electron microscope and x-ray diffraction study determined that the synthesised nanoparticles were spherical in shape with average size range of 15–30 nm. The ATR-FTIR data revealed the functional groups of silver nanoparticles and the biosynthesized nanoparticles were tested for their in-vitro antioxidant and cytotoxic potential against HepG2 cell lines. The synthesized compounds showed significant antioxidant activity in both 2,2-diphenyl-1-picrylhydrazyl (DPPH) and Ferric reducing ability of plasma (FRAP) assays and showed promising cytotoxic activity against HpG2 cell lines by the MTT assay method.

Preparation and Electrocatalytic Activity of Bimetallic Ni-Cu Micro- and Nanoparticles

Bimetallic Ni/Cu core–shell and Cu-Ni heterostructural micro- and nanoparticles were prepared using two simple successive reduction procedures. Monometallic Ni and Cu particles were synthesized for comparison. The phase constitutions and morphological features of the particles were studied by means of X-ray diffraction, energy-dispersive X-ray spectroscopy, and scanning electron microscopy methods. All the prepared mono- and bimetallic particles were applied as electrocatalysts in the electrohydrogenation of p-nitrophenol (p-NPh). An additional electrochemical reduction of copper cations during the hydrogen saturation of Cu-containing particles was established. The prepared Ni/Cu particles exhibited the highest electrocatalytic activity with an increase in the hydrogenation rate of p-NPh by more than three times compared to its electrochemical reduction on the nonactivated cathode, and p-NPh conversion yielded the maximum values. The main product of p-NPh electrocatalytic hydrogenation over Ni-Cu particles is p-aminophenol, which is an intermediate in the synthesis of many drugs. p-Aminophenol formation is confirmed by UV-Vis spectra.

Studies of the Solvent-Free Knoevenagel Condensation over Commercial NiO compared with NiO Drived from Hydrotalcites

In this study, we compared the effect of the commercial NiO, synthesis NiAl-HT and NiO-HT drived from hydrotalcite in Knoevenagel condensation reaction. The NiAl-HT sample was synthesized by the coprecipitation method with a molar ratio M2+/M3+ = 2 at constant basic pH. X-ray Diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR) were utilized to identify crystalline phases present in NiAl-HT, NiO-HT and commercial NiO. The chemical composition of the obtained solids was determined by Atomic Absorption Spectroscopy (AAS). Other techniques, such as Thermogravimetric Thermal Analyzer (TGA), Scanning Electron Microscopy (SEM) and Brunauere Emmette Teller Method (BET) were also used. As well as the BET showed the increase of the specific surface for the solid NiO-HT. The performance of the catalysts were studied in Knoevenagel condensation of benzaldehyde with ethyl acetoacetate without solvent to synthesis of organic compounds such as intermediates of dihydropyridines derivatives. The influence of different parameters, such as catalyst amount, reaction temperature and reaction time were optimized for studied the activity, the selectivity and the stability of the solids. Catalytic activity was in its lowest in the presence of NiAl-HT (26% of benzaldehyde conversion) whereas the benzaldehyde conversion increased to 77% in case of NiO-HT which can be explained by the presence of the basic sites of the NiO-HT oxides, a high surface area and a small crystallite size. Therefore, the lower increase in benzaldehyde conversion was noticed using commercial NiO (84%), perhaps owing to its high purity. A reaction mechanism is proposed by using density functional method (DFT). Copyright © 2023 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0)

Particleboard Creation from Agricultural Waste Residue of Seed Hemp.

In this research, agricultural residue of seed hemp variety "Adzelvieši" was used to create hemp particleboard samples. Hemp was grown in three experimental fields where it was observed that after seed harvesting, 3.5 tonnes of hemp stems per hectare remained. The plants were processed with milling, cutting, and sieving equipment. Moisture content and particle size distribution were observed throughout raw material processing. Hemp boards were produced using the cold pressing method with 10% urea formaldehyde resin as the binder. The boards were made as 20 mm thick single-layer parts with a density range of 220 ± 30 kg/m3 and porosity of 86%. Board structural analysis was performed using optical microscopy and scanning electron microscopy methods. Mechanical strength was determined by performing bending strength, internal bond strength, and screw withdrawal tests. The thermal conductivity reached 0.047 ± 0.008 W/(mK). The results were compared with industrially produced hemp shive boards and materials in the developmental or production stage. The feasibility for the experimental production cycle proposed in the study is discussed.

Evaluation of Effective Composite Biosorbents Based on Wood Sawdust and Natural Clay for Heavy Metals Removal from Water.

Bentonitic clay and wood sawdust are natural materials widely available in nature at low cost with high heavy metals sorption properties that, in this work, were combined to achieve an effective composite biosorbent with high sorption properties and enhanced mechanical stability. Pine, aspen, and birch wood sawdust, as well as different bentonite clays and different sawdust modification methods (H3PO4 or HCl) were used for preparing new composite biosorbents. A mixture of wood sawdust and bentonite in a ratio of 2:1 was used. All materials were characterized by using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscope (SEM) methods and tested for Cu and Ni ions removal from water. The adsorption process for all composite biosorbents was well described from a pseudo-second order kinetic model (R2 > 0.9999) with a very high initial adsorption rate of Cu and Ni ions and a maximum uptake recorded within 2 h. The results have shown that the adsorption capacity depends mainly on the kind of wood and the acid treatment of the wood that enhances the adsorption capacity. At a concentration of 50 mg/L, the biosorbent prepared using birch wood sawdust showed the worst performance, removing barely 30% of Cu and Ni ions, while aspen wood sawdust improved the adsorption of Cu (88.6%) and Ni (52.4%) ions. Finally, composite biosorbent with pine wood sawdust showed the best adsorption be haviour with an efficiency removal of 98.2 and 96.3% of Cu and Ni ions, respectively, making it a good candidate as an inexpensive and effective biosorbent for the removal of heavy metals.