Scanning Electron Microscopy Observations Research Articles

Effect of 3D printed skeleton shapes on strength behavior, stress evolution and microstructural response of cement-based tailings backfills

The inherent brittle behavior of cement-based tail backfill (CTB) poses some challenges that can significantly impact the safety and effectiveness of underground mining operations. Due to its propensity for abrupt and catastrophic failure without considerable deformation, CTB can endanger both the structural solidity of mined-out cavities and workers’ security. Hence, implementing appropriate strategies is critical to mitigate the risks associated with the brittle nature of CTB. An experiment investigation was commenced to consider the influence of diverse 3D printed polymer reinforcement geometries - specifically, hexagon, staggered quadrilateral, and rhomboid shapes - on strength behavior, stress evolution, and microstructural response of CTB via peak compression strength test plus scanning electron microscope observations. Lab findings specified a decrease in fill strength upon adding these polymer reinforcements. Specifically, the N-3D-PP-reinforced CTB exhibited a strength of 0.61 MPa. In comparison, the reinforced samples showed lower strengths of 0.39 MPa for the hexagon shape, 0.44 MPa for the staggered quadrilateral shape, and 0.45 MPa for the rhomboid shape. The toughness of CTB incorporating 3D-PP was higher than that of N-3D-PP ones. The optimal shape for an ideal toughness was the rhomboid shape, with a value of 58.06 KJ.m−3. N-3D-PP-reinforced CTB specimens exhibited a semi-brittle behavior, while 3D-PP-reinforced CTBs displayed a more ductile response with high total and dissipative energies. Cracks in N-3D-PP reinforced CTB were tensile, and mainly a combination of tensile and shear in 3D-PP reinforced CTB. Despite enhanced toughness, the presence of pores, the poor interfacial bonding between the CTB matrix and the 3D-PP, the low volume of polymer reinforcement, and the potential disruption of cement particle packing compromised the CTB’s overall strength. This research highlights the potential of 3D-printed reinforcements in transforming the landscape of mining backfill technology. The findings pave the way for the widespread adoption of 3D-printed polymer-reinforced CTB in metalliferous mines, promoting safer, more productive, and, ultimately, more profitable underground mining operations.

Laser Powder Bed Fusion Printing of CoCrFeMnNi High Entropy Alloy: Processing, Microstructure, and Mechanical Properties

AbstractEquiatomic CoCrFeMnNi high entropy alloy (HEA) powder was processed by laser powder bed fusion (LPBF) additive manufacturing (AM). The properties of the spherical pre-alloyed CoCrFeMnNi powder were characterized and its processability using LPBF AM was systematically investigated through the volumetric energy density (VED) based on the surface roughness, defects (micro-cracks and porosity) and densification. After optimization, LPBF processing at a VED of 104 J/mm3 achieved highly dense and crack-free vertical and horizontal test specimens with a porosity fraction lower than 0.01% and micro-pores having a mean size of, respectively, 25.9 μm and 13.4 μm, as determined from X-ray micro-computed tomography (μCT) inspection. Scanning electron microscope (SEM) analysis of the as-built (AB) CoCrFeMnNi processed at a VED of 104 J/mm3 showed a heterogeneous solidification microstructure, consisting of columnar grains with a cellular subgrain structure, and electron backscattered diffraction (EBSD) revealed a crystallographic texture mainly along the < 100 > direction. Post treatment with hot isostatic pressing (HIP) was effective in closing the remnant micro-pores in the bulk volume of the AB CoCrFeMnNi. Also, the cellular sub-grain structure in the AB CoCrFeMnNi completely disappeared after HIP and the resulting microstructure consisted of recrystallized equiaxed grains with annealing twins. The room temperature tensile response was anisotropic for AB CoCrFeMnNi with horizontally built specimens exhibiting higher strength and fracture strains (global and local) compared to vertically built ones; HIP reduced the anisotropy in the tensile properties and led to similar tensile strength with elongation values that were ~ 50% higher than in the AB condition. The HIPed CoCrFeMnNi also displayed higher Charpy impact toughness and absorbed energy at both room and liquid nitrogen temperatures compared to the AB material. Examination of the fracture surfaces after tensile and Charpy impact testing revealed ductile features with characteristic dimpled appearance and pointed to the important role of the remnant micro-pores on failure in the AB CoCrFeMnNi. Tribological assessments pointed to the superior low-stress abrasion resistance of AB and HIPed CoCrFeMnNi compared to 316L stainless steel (SS), which was included in this study to reinforce the analysis. SEM observations revealed that scratching and micro-fracture are the dominant wear mechanisms for the CoCrFeMnNi HEA, whereas ploughing and cutting parallel to the abrasive flow direction are the dominant mechanisms for 316L SS. To the authors’ knowledge, this study is the first to evaluate and report the low-stress abrasion resistance of any high entropy alloy. To understand the corrosion behavior, polarization curves of AB and HIPed CoCrFeMnNi were measured in 3.5 wt% NaCl and 1N H2SO4 solutions, and the results were compared to those of 316L SS. The findings indicate that AB and HIPed CoCrFeMnNi outperform 316L SS in a chloride-containing environment, but not in an acid-containing environment. Additionally, observations of hydrogen permeability revealed that AB CoCrFeMnNi permeates a lower volume of hydrogen atoms (by ~ 5 times) compared to 316L SS, despite its higher (by nearly 3 times) diffusion coefficient. Electrochemical hydrogen permeation data showed that the concentration of atomic hydrogen in the sub-surface of AB and HIPed CoCrFeMnNi was, respectively, about 32 and 26 times lower than in 316L SS. This study provides important material–structure–property data and indicates a promising outlook for LPBF of the CoCrFeMnNi HEA with high-performance.

Biodegradation of Polystyrene by Plastic-Eating Tenebrionidae Larvae

Polystyrene (PS) is an extremely stable polymer with a relatively high molecular weight and a strong hydrophobic character that makes it highly resistant to biodegradation. In this study, PS was subjected to biodegradation tests by Tenebrio Molitor (T. Molitor) and Zophobas Morio (Z. Morio) larvae. Specifically, six different experimental diets were compared: (i) T. Molitor fed with bran; (ii) T. Molitor fed only PS; (iii) T. Molitor fed only PS treated with H2O2; (iv) Z. Morio fed with bran; (v) Z. Morio fed only PS; and (vi) Z. Morio fed only PS treated with H2O2. Therefore, the mass change of the larvae and the survival rate were measured periodically, while the frass collected after 15 and 30 days was analyzed by different analyses, such as spectroscopy (FTIR), spectrometry (molecular weight and polydispersity), thermal analysis (TGA) and microscopy (scanning electron microscopy observations). The obtained results suggest that in the case of T. Molitor larvae, larvae feeding on bran showed the highest survival rate of ~94% at 30 days, while in the case of the Z. Morio larvae, the highest survival rate was exhibited by larvae eating PS-H2O2. Although not strongly pronounced, the Mw and Mn of PS in the frass of both T. Molitor and Z. Morio larvae decreased over 30 days, suggesting PS biodegradation. Finally, the morphological analysis shows that PS samples isolated from the frass of T. Molitor and Z. Morio larvae showed completely different, rough and irregularly carved surface structures, in comparison to PS before biodegradation.

From Antagonism to Enhancement: Triton X-100 Surfactant Affects Phenanthrene Interfacial Biodegradation by Mycobacteria through a Shift in Uptake Mechanisms.

Polycyclic aromatic hydrocarbons (PAHs), as persistent environmental pollutants, often reside in nonaqueous-phase liquids (NAPLs). Mycobacterium sp. WY10, boasting highly hydrophobic surfaces, can adsorb to the oil-water interface, stabilizing the Pickering emulsion and directly accessing PAHs for biodegradation. We investigated the impact of Triton X-100 (TX100) on this interfacial uptake of phenanthrene (PHE) by Mycobacteria, using n-tetradecane (TET) and bis-(2-ethylhexyl) phthalate (DEHP) as NAPLs. Interfacial tension, phase behavior, and emulsion stability studies, alongside confocal laser scanning microscopy and electron microscope observations, unveiled the intricate interplay. In surfactant-free systems, Mycobacteria formed stable W/O Pickering emulsions, directly degrading PHE within the NAPLs because of their intimate contact. Introducing low-dose TX100 disrupted this relationship. Preferentially binding to the cells, the surfactant drastically increased the cell hydrophobicity, triggering desorption from the interface and phase separation. Consequently, PAH degradation plummeted due to hindered NAPL access. Higher TX100 concentrations flipped the script, creating surfactant-stabilized O/W emulsions devoid of interfacial cells. Surprisingly, PAH degradation remained efficient. This paradox can be attributed to NAPL emulsification, driven by the surfactant, which enhanced mass transfer and brought the substrate closer to the cells, despite their absence at the interface. This study sheds light on the complex effect of surfactants on Mycobacteria and PAH uptake, revealing an antagonistic effect at low concentrations that ultimately leads to enhanced degradation through emulsification at higher doses. These findings offer valuable insights into optimizing bioremediation strategies in PAH-contaminated environments.

Cocconeis crisscrossis sp. nov., a new monoraphid diatom (Bacillariophyta) from southern China

A novel monoraphid diatom species, Cocconeis crisscrossis You, Yu, Kociolek & Wang, sp. nov. is examined and described from the Qingyi River and Maolan Nature Reserve of southern China. The morphological description is based on light microscopy and scanning electron microscopy observations and the new species is compared with similar taxa in this genus. The characteristics unique to Cocconeis crisscrossissp. nov. include its central area extending irregularly to both sides, it having closed valvocopulae with heavily silicified fimbriate margins and poles of the valvocopulae have ‘sword-shaped’ siliceous extensions. These features differentiate this new species from others in the genus. This new species was found in alkaline waterbodies, including streams, waterfall and ponds. It was usually found as an epiphyte on the stones; however, it was present on other substrates such as mosses.

Exploring microstructural evolution, nitrogen depth profile, and dry wear performance in 31CrMoV9 steel through combined severe shot peening and plasma nitriding

The present study investigates the influence of severe shot peening (SSP) on the plasma nitriding behavior and sliding wear performance of 31CrMoV9 steel. Initially, the steel was austenitized at 880 °C, followed by oil quenching, and tempering at 520 °C for one hour. These samples were shot peened using high-carbon steel shots, resulting in an enhancement in surface hardness up to 447 HV, gradually converging to the initial martensitic hardness after 140 µm depth. X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) scrutinized the initial and surface treated martensitic samples. Afterward, the plasma nitriding treatments were carried out at temperatures of 400 °C, 450 °C, and 500 °C for 8 hours in a 30% N2 + 70% H2 atmosphere and 300 Pa pressure. Microhardness testing, SEM, XRD, and glow-discharge optical emission spectroscopy (GDOES) evaluated both plasma nitrided (PN) and severe shot peened/plasma nitrided (SSP-PN) samples. Cross-sectional SEM observations revealed compound layer thicknesses of approximately 2.8 µm, 5.0 µm, and 6.3 µm for PN samples at 400 °C, 450 °C, and 500 °C, respectively. SSP-PN samples exhibited a substantial increase — roughly 71%, 44%, and 33% increase, respectively, compared to PN samples. GDOES analysis supported this trend and indicated enhanced nitrogen diffusion depth, particularly evident in SSP-PN samples at consistent temperatures. The XRD results showed the stability of Fe4N, Fe2–3N, and CrN phases at all three nitriding temperatures. Furthermore, the intensity of these phases increases with temperature and is augmented by the application of the SSP. Microhardness measurements indicated hardness escalation: from 775 HV to 980 HV at 400 °C, 932 HV to 1096 HV at 450 °C, and 1011 HV to 1205 HV at 500 °C due to SSP. Finally, the wear performance was investigated between the non-nitrided, SSP, PN, SSP-PN, samples. Initially, SSP led to decreased wear performance up to 500 m, followed by improved behavior up to 1500 m. At 400 °C, the SSP-PN sample exhibited a 12% lower wear rate than PN. At 450 °C and 1500 m, the SSP-PN sample displayed a 24% reduction, while at 500 °C, it showed a 27% reduction compared to PN. SEM observations indicated abrasion as the primary wear mechanism across all samples. The overall results indicated a significant similarity in the nitrogen depth profile, hardness depth, and wear performance between the SSP-PN sample at 450 °C and the PN sample at 500 °C. The fact suggested a potential reduction of approximately 50 °C in the typical plasma nitriding temperature for 31CrMoV9 steel as a result of the SSP process.

Fabrication and electrochemical properties of Mn, N, and S co-doped carbon fiber composite bamboo-based woodceramics electrodes

Prepared in this study, Mn, N and S co-doped woodceramics electrodes (WC@Mn-N/S) were prepared using waste bamboo as the base material, carbon fiber as the reinforcement fiber, KMnO4 and CH4N2S as dopants and activators. Mechanical analysis revealed a 68 % increase in the flexural strength of the matrix material reinforced with carbon fibers. Scanning electron microscopy observation indicated that WC@Mn-N/S retained the original natural pore structure of bamboo. The specific surface area (BET) analysis revealed that WC@Mn-N/S exhibited a specific surface area of 861.7 m2/g, with its pore size structure mainly distributed in the range of 1.3–3.8 nm. Electrochemical performance tests showed that the introduction of Mn, N and S elements endowed the bamboo-based electrode with pseudocapacitance characteristics. Additionally, the synergistic effect between these three elements imparted pseudocapacitance to the electrode material. WC@Mn-N/S performent a specific capacitance of 615 F/g, at 0.2 A/g with excellent capacitance retention (99.4 % after 5000 cycles). In the practical assembled in symmetrical capacitor the material showed high power density 500 W/kg and energy density 57.9 Wh/kg, indicating its excellent electrochemical performance.

Gold nanosheet modified electrode with reduced impedance for electrophysiological recordings

In neurophysiological recording, reducing electrode impedance is crucial for enhancing the signal-to-noise ratio and achieving the desired spatial resolution. This study presents an approach to improve the performance of Au/Cr/glass electrodes by incorporating synthesized gold nanosheets without the need for additional adhesive material. We characterized the performance of the modified electrodes using electrochemical impedance spectroscopy and equivalent circuit analysis. Our findings showed an 81% reduction in mean impedance for the modified electrode, which was 0.85 kΩ at 1 kHz, compared to the unmodified electrode at 4.5 kΩ, an improvement attributed to the higher effective surface area of the modified electrode. Additionally, Scanning electron microscopy observations of PC12 cells cultured on the modified electrodes indicated favorable cell elongation and interaction with the rough surface. Stability studies indicated acceptable performance of the modified electrodes in solution environments. These results suggest that surface modification of electrodes with gold nanosheets could be a promising strategy for enhancing neural interface applications.

Preparation of Polyoxymethylene/Exfoliated Molybdenum Disulfide Nanocomposite through Solid-State Shear Milling

In this paper, the solid-state shear milling (S3M) strategy featuring a very strong three-dimensional shear stress field was adopted to prepare the high-performance polyoxymethylene (POM)/molybdenum disulfide (MoS2) functional nanocomposite. The transmission electron microscope and Raman measurement results confirmed that the bulk MoS2 particle was successfully exfoliated into few-layer MoS2 nanoplatelets by the above simple S3M physical method. The polarized optical microscope (PLM) observation indicated the pan-milled nanoscale MoS2 particles presented a better dispersion performance in the POM matrix. The results of the tribological test indicated that the incorporation of MoS2 could substantially improve the wear resistance performance of POM. Moreover, the pan-milled exfoliated MoS2 nanosheets could further substantially decrease the friction coefficient of POM. Scanning electron microscope observations on the worn scar revealed the tribological mechanism of the POM/MoS2 nanocomposite prepared by solid-state shear milling. The tensile test results showed that the pan-milled POM/MoS2 nanocomposite has much higher elongation at break than the conventionally melt-compounded material. The solid-state shear milling strategy shows a promising prospect in the preparation of functional nanocomposite with excellent comprehensive performance at a large scale.

Effect of high sodium ion level on the interaction of AmB with a cholesterol-rich phospholipid monolayer

Invasive fungal infections are a primary reason for high mortality in immunocompromised people, especially in critically ill patients, such as intensive care unit (ICU) patients, advanced cancer patients, or severe burn patients. Hypernatremia also can increase mortality in severely ill patients. Amphotericin B (AmB) is the gold standard for treating infections, but in severely ill patients, AmB can cause hematotoxicity when administered intravenously due to its interaction with cholesterol on red blood cell membranes. This results in limited doses of AmB and affects the treatment of infections. The proportion of cholesterol molecules in membrane lipids in red blood cells is as high as 50 mol%, and the sodium ions can influence the interaction between AmB and lipids on the membrane. Therefore, in the complex clinical situation of a severely ill patient with a fungal infection and hypernatremia, the interaction between amphotericin B and the red blood cell membranes is worth studying in depth. In this work, the interaction between AmB and the dipalmitoyl phosphatidylcholine (DPPC)/cholesterol mixed monolayer in the presence of high sodium ion levels was studied when the proportion of cholesterol was 50%. The results show that the effect of AmB on reducing the monolayer’s area at a high level of sodium ions is slightly stronger at 30 mN/m. The effect of AmB on reducing the elastic modulus of the DPPC/Chol monolayer is significantly weakened by a high sodium ion level, compared with the level of sodium ions at normal physiological concentration. The higher the sodium ion concentration, the weaker the intermolecular force of the DPPC/Chol/AmB mixed monolayers. The scanning electron microscope (SEM) and atomic force microscopy (AFM) observations suggest that at a high sodium ion level, the presence of AmB significantly reduces the surface roughness of the DPPC/Chol monolayer. AmB may bind to cholesterol molecules, and it isolates cholesterol from the monolayer, resulting in a reduced height of the cholesterol-rich monolayer and an increasingly dispersed monolayer region. The results are beneficial to understanding the mechanism of impact of a high sodium ion level on the relationship between AmB and red blood cell membranes rich in cholesterol and are valuable for understanding the hemolytic toxicity of AmB to red blood cells at a high sodium ion level.

Flaw sensitivity of bacterial cellulose hydrogel under monotonic and cyclic loadings

The presence of flaw in solid materials can lead to stress concentration, resulting in the reduction of rupture stress and stretchability of material. When the flaw is sufficiently smaller than a material-specific length, referred to as flaw sensitivity length, the material exhibits flaw insensitivity. The flaw sensitivity length is a critical material property that reflects how the material is sensitive or insensitive to crack. However, the impact of crack length on the load-bearing process of material remains an open problem. In this work, we characterize the flaw sensitivity of a stretchable material, bacterial cellulose hydrogel, under monotonic and cyclic loadings. Through fracture and fatigue tests, we first determine that the hydrogel exhibits high fracture toughness and fatigue resistance. We next characterize the flaw sensitivity of the hydrogel through two visualized experimental methods. Photoelasticity observation on the stress distribution in samples during loading shows that the samples with cracks below 2 mm exhibit uniform stress distribution during the deformation process, while those with cracks above 2 mm experience stress concentration at crack tip. Scanning electron microscope observation on the microstructure morphology of samples under fixed stretch shows that the samples with cracks below 2 mm exhibit uniform alignment of nanofibers, while those with cracks above 2 mm exhibit more intense alignment and even bundling of nanofibers at crack tip. Similar trends are observed in the samples under cyclic loading, where the transition length is also about 2 mm. Notably, the flaw sensitivity lengths obtained by the visualized methods agree well with that obtained by direct measurement of rupture stress and theoretical estimations under monotonic and cyclic loadings. The methods offer novel way to study the flaw sensitivity of materials, thereby contributing to the exploration of failure mechanisms.

Accelerated Li Penetration and Crack Propagation Due to Mechanical Degradation of Sulfide-Based Solid Electrolyte.

This work presents quantitative investigations into the relationships between lithium dendrite growth in the defects of Li6PS5Cl (LPSCl) solid electrolyte (SE), crack nucleation and propagation in the SE, and the associated mechanical forces driving these dendrites and cracks. Two different growth modes for lithium dendrites are identified by ex situ scanning electron microscopy (SEM) observation: longitudinal cracking inside pores in the SE and lateral penetration along boundaries of the SE particles. These in situ TEM tests reveal that concentrated Li plating in a nano-sized defect on the LPSCl surface will lead to the nucleation and propagation of cracks into the LPSCl under a stress much smaller than the expected mechanical strength of the LPSCl material. This unexpected mechanical degradation is caused by a reduction in the mechanical strength of LPSCl during electrochemical charge/discharge cycling, resulting from a disorder in the crystal structure of LPSCl as revealed by DFT simulations. Due to this mechanical degradation of LPSCl, the threshold force necessary to initiate crack growth is much lower than the previously expected force to drive dendrite growth.

Characteristics and development model of deep-ultra deep reservoirs in the Upper Wuerhe Formation of Permian in the sags of eastern Junggar Basin, China

Taking the deep-ultra deep glutenite reservoirs in the Upper Wuerhe Formation of Permian in Fukang Sag and Dongdaohaizi Sag as the research object and representative of the eastern Junggar Basin, its characteristics and main controlling factors are analyzed using various methods, including core analysis, thin section examination, and scanning electron microscope observation. High-pressure mercury injection and logging imaging were also employed to reveal the reservoir that Fukang and Dongdaohaizi sags harbor deep-ultra deep glutenite reservoirs, with Fukang Sag being a typical low porosity to ultra-low permeability reservoir, while Dongdaohaizi Sag is a low porosity to low permeability reservoir. Reservoir space types vary between the two sags, with Fukang Sag characterized by microfractures and corrosion pores, while a large number of corrosion pores with fewer fractures existing in Dongdaohaizi Sag. Both compaction and cementation exhibit a strong destructive effect on the reservoirs in the eastern Junggar Basin. However, the compaction effect in Fukang Sag is very strong, and the dissolution effect is weak. The large number of fractures generated by overpressure becomes an effective channel for ultra-deep oil and gas migration. The cracks in the Dongdaohaizi Sag are underdeveloped, and a large number of intra-particle corrosion pores generated by the dissolution of feldspar and turbidite improve reservoir properties. In addition, its rich turbidite also plays a compressive and pore retention role. There are two types of reservoir models developed in the Upper Wuerhe Formation of Permian in the eastern Junggar Basin: the deep fracture model represented by the Fukang Sag and the solution pore model rich in turbidite in Dongdaohaizi Sag. These models create favorable conditions for oil and gas accumulation in the deep-ultra deep reservoirs in the depression area.

Lattice variation as a function of concentration and grain size in MgO–NiO solid solution system

The study aimed to understand how changes in crystal's size affect the lattice parameters and crystal structure of Mg1-xNixO solid solution for six X values ranging from x = 0 to x = 1. Mg1-xNixO was synthesized via two different wet-chemical techniques: the sol-gel and the microwave hydrothermal method, both followed by calcination at different temperatures of 673, 873, 1073, 1273 and 1473 K. As annealing caused grain growth, the varied temperature range allowed to examine a wide range of grain sizes. The lattice parameters and x values were determined from XRD (X-ray diffraction) peak positions and intensities respectively. The grain size was evaluated by XRD line profile analysis and supported by SEM (scanning electron microscope) observations. At the temperatures of 673 and 873 K grain size was in the nanometric range and from 1073 K and above grain size was in the micrometric range. A non-monotonic lattice variation versus grain size was found for each concentration. When grain size decreased there was a slight contraction, however for grain size in the nanometric range there was a severe lattice expansion. Both lattice parameter changes were explained by two effects acting together: contraction due to surface stress and expansion due to weakening of the ionic bonding at nanocrystalline particles. In this current research study, the lattice parameter was mapped in two dimensions: concentration and grain size. The findings of this study provided valuable insights into the lattice variation in the MgO–NiO solid solution system.

Development of a microfurnace dedicated to in situ scanning electron microscope observation up to 1300 °C. I. Concept, fabrication, and validation.

The development of a new heating system dedicated to in situ scanning electron microscope (SEM) experimentation at high temperatures is reported. This system, called FurnaSEM, is a compact microfurnace, enabling heat treatments up to 1300 °C. The choice of materials for the microfurnace is explained. The design of the microfurnace is optimized by iterations of numerical simulations, and the thermal characteristics of the microfurnace are calculated numerically. The numerical results obtained are compared with the thermal characteristics of a manufactured microfurnace, measured on a specially developed dedicated test bench. This test bench includes a working chamber simulating a SEM chamber equipped with a thermal camera. The results obtained during various qualification tests enabled us to determine the main technical characteristics of the FurnaSEM microfurnace: temperature profiles on the sample support surface, energy consumption at high temperatures, and the range of achievable thermal cycles.

Development of a microfurnace dedicated to in situ scanning electron microscope observation up to 1300 °C. II. Study of the thermal response of samples.

When conducting in situ experiments at high temperatures in a scanning electron microscope using microfurnaces, controlling the temperature of a sample of a few mm3 placed in the hot zone of the furnace can be a complex task. In most cases, the temperature of the sample is estimated by means of a thermocouple placed in the hot body of the furnace, and the assumption made is that the temperature of the furnace is the temperature of the sample. In this work, a detailed understanding of the thermal response of the sample placed in the hot zone of the furnace is proposed. Temperature differences due to contact resistance between the furnace surface and the sample, the nature of the sample, and the sample geometry are calculated with a numerical model and measured experimentally on a dedicated test bench. Three technical solutions (bonding, sandwiching, and mini-crucible) for limiting temperature differences between the furnace surface and sample are proposed and validated by numerical calculations and experimental measurements.

Effect of Bismuth Doping on Electrodeposition, Physicochemical Properties and Electrocatalytic Activity of Lead Dioxide Electrodes

The bismuth (Bi)-doped PbO2 electrodes were electrodeposited from a nitric plating solution containing Pb (II) and Bi (III) ions by varying the concentrations of Bi (III). Cyclic voltammetry was used to investigate the effect of Bi (III) ions on the kinetics of PbO2 electrodeposition. It is observed that increasing Bi (III) ions in the plating solution reduces the rate of nucleation or formation of PbO2 but does not change the process mechanism. X-ray diffraction confirms that the incorporation of bismuth results in an apparent β (301) texture. Scanning electron microscopic observation reveals that the size of the PbO2-deposit particles gradually decreases by several micrometers as the doping content of Bi (III) increases from 2 to 6mM. Linear scanning voltammograms show that the oxygen overpotential on Bi-PbO2 is much higher than on undoped PbO2 electrodes. Electrochemical degradation of the target pollutant was performed, and HPLC analysis demonstrated that Bi doping significantly improves the electrocatalytic ability of PbO2 electrodes.

Development of a microfurnace dedicated to in situ scanning electron microscope observation up to 1300 °C. III. In situ high temperature experiments.

The FurnaSEM microfurnace was installed in the chamber of a scanning electron microscope to carry out in situ experiments at high temperatures and test its limits. The microfurnace was used in combination with different types of detectors (Everhart-Thornley for the collection of secondary electrons in a high vacuum, gas secondary electron detector for the specific collection of secondary electrons in the presence of gas, and Karmen© detector for the collection of backscattered electrons at high temperature). Experiments carried out on various samples (metal alloys and ceramics) show that the microfurnace operates in both high-vacuum and low-vacuum modes. Temperature ramp rates during temperature cycles applied to the sample range from 1 to 120 °C/min (temperature rise) and 1 to 480 °C/min (controlled and natural cooling). The maximum temperature at which images were recorded up to 25k × magnification was 1340 °C, with a residual air atmosphere of 120Pa. The choice of a flat furnace with the sample placed directly above it has enabled innovative experiments to be carried out, such as low-voltage imaging (using a shorter working distance-up to 10 mm-than is possible with conventional furnaces), 3D imaging (by tilting the stage by up to 10°), and high-temperature backscattered electron imaging (using a dedicated detector).

Selective growth and unveiling semiconductor nanostructured based La,Mo and O elements: Structural, morphological, and optical investigations

La2Mo2O9 ternary compound thin film has been prepared by the chemical spray pyrolysis technique on glass substrates at 460°C. Characterization via X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), energy dispersive X-ray, X-ray photoelectron spectrometry (XPS) and spectrophotometry through reflectance and transmittance measurements were performed. X-ray analysis shows that La2Mo2O9 material crystallizes in cubic structure belonging to the P 213 space group with a preferred orientation of the crystallites along (210) direction parallel to the substrate plane. Raman spectroscopy witnesses the presence of bonds like La-O and Mo-O. SEM observation shows that the prepared film exhibits a uniform grain of regular sizes in the range of 70–120 nm and some chains. EDX spectroscopy highlights the presence of La, Mo and O elements with a slight non-stoichiometry reflecting the oxygen deficiency. XPS measurements reveal the well defined states O 1s, Mo 3d5/2, Mo 3d3/2, La 3d5/2 and La 3d3/2 of oxygen, molybdenum and lanthanum elements. Optical measurements show a high transparency in the visible range. These measurements were used to deduce the optical band gap and Urbach energy.

Rational design, synthesis, and antimicrobial evaluation of novel 1,2,4-trizaole-substituted 1,3,4-oxadiazole derivatives with a dual thioether moiety.

In this paper, a series of novel 1,2,4-trizaole-substituted 1,3,4-oxadiazole derivatives with a dual thioether moiety were constructed. The synthetic compounds were characterized by 1H NMR, 13C NMR, HRMS, and single crystal diffraction. The antimicrobial activities of title compounds against fungi (Pyricutaria oryzae Cav., Phomopsis sp., Botryosphaeria dothidea, cucumber Botrytis cinerea, tobacco Botrytis cinerea, blueberry Botrytis cinerea) and bacteria (Xanthomonas oryzae pv. oryzicola, Xoc; Xanthomonas axonopodis pv. citri, Xac) revealed these compounds possessed excellent antibacterial activity through mycelial growth rate method and turbidity method, respectively. Among them, compounds 7a, 7d, 7g, 7k, 7l, and 7n had the antibacterial inhibition rate of 90.68, 97.86, 93.61, 97.70, 97.26, and 92.34%, respectively. The EC50 values of 7a, 7d, 7g, 7k, 7l, and 7n were 58.31, 48.76, 58.50, 40.11, 38.15, and 46.99μg/mL, separately, superior to that of positive control pesticide thiodiazole copper (104.26μg/mL). The molecular docking simulation of compound 7l and glutathione s-transferase also confirmed its good activity. The in vivo bioassay toward Xac infected citrus leaves was also performed to evaluate the potential of compounds as efficient antibacterial reagent. Further study of antibacterial mechanism was also carried out, including extracellular polysaccharide production, permeability of bacterial membrane, and scanning electron microscope observations. The excellent antibacterial activities of these compounds provided a strong support for its application for preventing and control plant diseases.