Surface Analysis Research Articles

Analysing the mechanisms of failure in polycarbonate sheets deformed by SPIF

This article presents experimental research conducted on polycarbonate sheets deformed via single-point incremental forming (SPIF). Building upon established frameworks from previous studies, the analysis focuses on evaluating the formability and failure modes, particularly necking and fracture, of polymeric sheets in both conventional and incremental forming processes. The experimental design encompasses an investigation of spindle speed and step down process parameters, utilizing both oil and water as lubricants, to comprehensively assess their effects. The findings provide insights into how these parameters influence formability and affect the failure mode. When using oil as a lubricant, three distinct failure modes were observed during deformation: fracture, twisting, and crazing. An increased twisting was associated with higher step down values, whereas elevated spindle speeds contributed to increase crazing. Additionally, these tests revealed a “post-crazing” failure mode following deformation. Conversely, when water was used as a lubricant, only fracture and twisting were observed in the SPIF specimens. This work introduces, for the first time ever, a complete investigation of these failure modes through scanning electron microscopy analysis of the failure surface. This analysis scrutinizes surface features and interprets them, thus providing a valuable tool for failure analysis.

Crystal structure and Hirshfeld surface analysis of a halogen bond between 2-(allyl-thio)-pyridine and 1,2,4,5-tetra-fluoro-3,6-di-iodo-benzene.

The crystal structure of the title 2:1 mol-ecular complex between 2-(allyl-thio)-pyridine and 1,2,4,5-tetra-fluoro-3,6-di-iodo-benzene, C6F4I2·2C8H9NS, at 100 K has been determined in the monoclinic space group P21/c. The most noteworthy characteristic of the complex is the halogen bond between iodine and the pyridine ring with a short N⋯I contact [2.8628 (12) Å]. The Hirshfeld surface analysis shows that the hydrogen⋯hydrogen contacts dominate the crystal packing with a contribution of 32.1%.

Synthesis, structure and Hirshfeld surface analysis of 2-oxo-2H-chromen-4-yl penta-noate.

In the title compound, C14H14O4, the dihedral angle between the coumarin ring system (r.m.s deviation = 0.016 Å) and the penta-noate ring is 36.26 (8)°. A short intra-molecular C-H⋯O contact of 2.40 Å is observed. Hirshfeld surface analysis reveals that 46.1% of the inter-molecular inter-actions are from H⋯H contacts, 28.6% are from H⋯O/O⋯H contacts and 14.7% are from H⋯C/C⋯H.

Kinetic Isotope Effects and the Mechanism of CO2 Insertion into the Metal-Hydride Bond of fac-(bpy)Re(CO)3H.

The 1,2-insertion reaction of CO2 into metal-hydride bonds of d6-octahedral complexes to give κ1-O-metal-formate products is the key step in various CO2 reduction schemes and as a result has attracted extensive mechanistic investigations. For many octahedral catalysts, CO2 insertion follows an associative mechanism in which CO2 interacts directly with the coordinated hydride ligand instead of the more classical dissociative mechanism that opens an empty coordination site to bind the substrate to the metal prior to a hydride migration step. To better understand the associative mechanism, we conducted a systematic quantum chemical investigation on the reaction between CO2 and fac-(bpy)Re(CO)3H (1-Re-H; bpy = 2,2'-bipyridine) starting with the gas phase and then moving to THF and other solvents with increased dielectric constants. Detailed analyses of the potential energy surfaces (PESs) and intrinsic reaction coordinates (IRCs) reveal that the reaction is enabled in all media by an initial stage of making a 3c-2e bond between the carbon of CO2 and the metal-hydride bond that is most consistent with an organometallic bridging hydride Re-H-CO2 species. Once CO2 is bent and anchored to the metal-hydride bond, the reaction proceeds by a rotation motion via a cyclic transition state TS2 that interchanges Re-H-CO2 and Re-O-CHO coordination. The combined stages provide an asynchronous-concerted pathway for CO2 insertion on the Gibbs free energy surface with TS2 as the highest energy point. Consideration of TS2 as a rate-determining TS gives activation barriers, inverse KIEs, substituent effects, and solvent effects that agree with the experimental data available in this system. An important new insight revealed by the analyses of the results is that the initial stage of the reaction is not a hydride transfer step as has been assumed in some studies. In fact, the loose vibration of the TS that can be identified for the first stage of the reaction in solution (TS1) does not involve the Re-H stretching vibrational mode. Accordingly, the imaginary frequency of TS1 is insensitive to deuteration, and therefore, TS1 leads to no significant KIE.

1D analytic and numerical analysis of thin film heat transfer gauges and infra-red cameras in non-planar applications

The impulse response method is widely used for heat transfer analysis in turbomachinery applications. Traditionally, the 1D method assumes a: linear time invariant, isotropic, semi-infinite block with planar surfaces and does not accurately model the true geometric behaviour. This paper evaluates the error introduced by the planar assumption and outlines the required modifications for accurate freeform surface analysis. Adapted cylindrical basis functions are defined for the impulse response method and used to evaluate the impact of the 1D planar assumption. The analytic solutions for both convex and concave surfaces are presented. A penta-diagonal algorithm, for a modified numerical Crank-Nicolson scheme, is also evaluated for fast stable implementation of curved geometry simulation. The scheme shows comparable performance to the impulse response, whilst removing the requirement for linear time invariance. The new methods are demonstrated in the case of aerothermal analysis for heat transfer in a turbine nozzle guide vane. A 3D ANSYS simulation is used as a benchmark and further highlights the importance of the curvature effects. The methods are extended using curvature mapping for infra-red camera data, enabling direct 3D thermal simulation or the fast calculation of freeform curvature. This paper defines the methodology to analyse heat transfer measurements on non-planar geometry.

Crystal structure and Hirshfeld surface analysis of 2-bromo-ethyl-ammonium bromide - a possible side product upon synthesis of hybrid perovskites.

This study presents the synthesis, characterization and Hirshfeld surface analysis of a small organic ammonium salt, C2H7BrN+·Br-. Small cations like the one in the title compound are considered promising components of hybrid perovskites, crucial for optoelectronic and photovoltaic applications. While the incorporation of this organic cation into various hybrid perovskite structures has been explored, its halide salt counterpart remains largely uninvestigated. The obtained structural results are valuable for the synthesis and phase analysis of hybrid perovskites. The title compound crystallizes in the solvent-free form in the centrosymmetric monoclinic space group P21/c, featuring one organic cation and one bromide anion in its asymmetric unit, with a torsion angle of -64.8 (2)° between the ammonium group and the bromine substituent, positioned in a gauche conformation. The crystal packing is predominantly governed by Br⋯H inter-actions, which constitute 62.6% of the overall close atom contacts.

Current Overview of Corrosion Inhibition of API Steel in Different Environments.

API (American Petroleum Institute) steels are the most employed metal alloys in the oil industry due to their outstanding mechanical properties; however, their protection is considered as an imperative matter because of their corrosion damage vulnerability when exposed to different surroundings that provoke a rate increase in the concomitant redox reactions. This problematic situation becomes more relevant when the generation and/or use of one or various aqueous corrosive environments occur, in addition to process conditions, the result of which is extremely difficult to be controlled. For these reasons, the internal and external protection of exposed metallic systems are considered as a fundamental concern, where internal corrosion is often controlled through the addition of corrosion inhibitors (CIs). The present review analyzes researchers' contributions in the last years to the study and evaluation of CIs for API steel in different corrosive media featuring HCl, H2SO4, H3NSO3H, CO2, H2S, NaCl, and production water under different temperature and flow conditions. Different CIs derived from plant extracts, drugs, nanoparticles, or ionic liquids, mainly destined for acid media, were found. Throughout the review, an exhaustive analysis of inhibition process results is carried out based on gravimetric and/or electrochemical techniques that consider the weight loss of the metallic material and electrical behavior (current density, resistance, capacitance, frequency, impedance, etc.). Likewise, the results of computational analyses and those of surface analysis techniques were taken into account to reinforce the study of CIs.

Surface Enhanced Raman Scattering substrates based on Au-molecularly imprinted nanofibers for phthalate esters detection

Phthalate esters (PAEs), a type of plasticizer extensively used in plastic products, are known as endocrine disruptors that exert various adverse physiological effects on organisms. Surface Enhanced Raman Scattering (SERS) technology offers effective detection of substances at low concentrations. However, its low sensitivity and poor specificity often lead to suboptimal outcomes in PAEs detection. Therefore, integrating molecular imprinting technology, nanomaterials, and SERS detection technology, an Au-molecularly imprinted nanofiber-enhanced substrate film was developed for PAEs detection. The addition of Au nanoparticles enhanced the Raman signal intensity of the SERS film. Molecularly imprinted nanofibers improved the adsorption capacity and specificity recognition of PAEs molecules. The optimal preparation method was investigated based on response surface analysis. Experimental results demonstrated that the lowest detectable concentration of PAEs was 10−8 mol/L. Thus, the Au-molecularly imprinted nanofiber-enhanced SERS substrate film represented a rapid, highly sensitive, and specific approach for PAEs detection.

What makes for digital entrepreneurs? The role of AI-related drivers for nascent digital start-up activities

PurposeApplying the Stimulus–Organism–Response (SOR) model, this study aims to explore how AI-driven stimuli (e.g. ChatGPT adoption in entrepreneurship and perceived AI competencies) stimulate individuals’ cognitive organisms (e.g. digital entrepreneurial opportunity exploration and exploitation), and how these individually, congruently, and incongruently trigger their behavioral responses (e.g. nascent digital start-up activities).Design/methodology/approachUtilizing a sample of 1326 MBA students in Vietnam with a stratified sampling approach, multiple linear regression and polynomial regression with response surface analysis were used to test hypotheses.FindingsThe findings reveal that ChatGPT adoption in entrepreneurship and perceived AI competencies have a positive and significant impact on individuals’ digital entrepreneurial opportunity exploration and exploitation, which in turn, positively affects nascent digital start-up activities. Moreover, the study also reports that digital entrepreneurial opportunity exploration and exploitation can be congruently combined with each other to trigger the effects of nascent digital start-up activities.Practical implicationsSome valuable recommendations based on the findings have been provided for practitioners and policymakers.Originality/valueThe study contributes to the academic landscape by validating the SOR model within the context of AI adoption and entrepreneurship. It emphasizes the sequential processes of stimulus, cognitive responses, and behavioral outcomes, shedding light on nuanced effects in the digital entrepreneurial landscape.

Crystallization experiments of the wheel-and-axle host compound, 1,4-phenylene-bis(di-p-tolylmethanol), from pyridine and methylpyridine mixtures

Abstract1,4-Phenylene-bis(di-p-tolylmethanol) (H), a host compound with the wheel-and-axle design, formed complexes with organic guest solvents pyridine (PYR) and 2-, 3- and 4-methylpyridine (2MP, 3MP and 4MP). The host: guest (H: G) ratios were 1:3, 1:2, 1:2 and 1:1, respectively. Host crystallization experiments from mixed guests demonstrated H to prefer both PYR and 4MP; however, it was established that these difficult-to-separate (by fractional distillations) guest mixtures cannot be purified/separated by means of H through supramolecular chemistry strategies owing to these selectivities for PYR and 4MP being less than optimal. Single crystal X-ray diffraction experiments showed that each guest compound was held in its complex by means of a classical hydrogen bond with H, and that one of the preferred guests, PYR, experienced a significantly shorter contact of this type than the other guests. Hirshfeld surface analyses demonstrated that PYR was also involved in a greater percentage of (guest)N···H(host) interactions compared with the other guest molecules. Thermal analyses, on the other hand, revealed that 4MP (also a favoured guest species) formed the most stable complex of the four in this investigation. These results with H were compared to those obtained when employing a closely related host compound from a previous report, 1,4-bis(diphenylhydroxymethyl)benzene: while both host species preferred the same guests (PYR and 4MP), the extent of the selectivity of that host compound compared with H in the present work was significantly more enhanced. Thus, minor modifications may deleteriously affect the selectivity behaviour of closely related host compounds.

Mechanism study of H2-plasma assisted Si3N4 layered etch

The cyclic two-step process, comprised of energetic H2 plasma followed by HF wet clean or in situ NF3 plasma, demonstrates Si3N4 layer-by-layer removal capability exceeding 10 nm per cycle, surpassing typical atomic layer etch methods by an order of magnitude. In this paper, we investigated the surface reaction mechanisms via first principle density functional theory simulations and surface analysis. The results unveiled that energetic H2 plasma, in the first step, selectively removes nitrogen (N) in preference to silicon (Si), generating ammonia (NHx) and transforming Si3N4 into SiON upon exposure to air, which becomes removable by HF wet clean in the second step. For the second step employing in situ NF3 plasma, it further leverages H-passivated surfaces to enhance NF3 dissociation and provide alternative reaction pathways to yield volatile byproducts such as SiHF3 and SiFx, thereby significantly improving nitride removal efficiency.

Microstructural, texture, and crystallographic analysis of SiC particle incorporation in double-sided friction stir welding of dissimilar aluminium alloys

This paper investigates the impact of incorporating SiC nanoparticles into the welded interface joint of dissimilar aluminium alloys 2024 and 7075. Double-sided friction stir welding (DS-FSW) was performed to investigate the impact of added nanoparticles on the joint's mechanical properties and crack growth rate. Microstructural analysis of the fractured surface was conducted to assess the influence of nanoparticles on crack propagation, while field emission scanning electron microscopy (FESEM) was utilized to examine the grain size distribution across different weld zones. On analyzing the DS-FSW joint with SiC-reinforced particles using electron backscattered diffraction (EBSD), predominant shear texture components such as B/B̅ and C are observed. Additionally, there are deformed textures like Rotating cube (H) {001} <110> and F {111} <112>, along with recrystallization texture elements such as Goss {110} <001>, P {011} <112>, and Cube {001} <101>. Mechanical properties, determined through hardness and tensile tests, were compared between nanocomposite weldments and base metal to assess the improvement in mechanical properties following the inclusion of SiC particles. Crack growth tests were performed using compact test (CT) specimens at a maximum load of 5 kN and a stress ratio of R = 0.1. The addition of SiC nanoparticles to the joint area led to a significant decrease in grain size and an increase in hardness within the stir zone, compared to the base metal and samples without the powder. The tests revealed an approximately 62 % increase in tensile strength and a notable increase in microhardness of the weld zone of the aluminium alloy metal matrix composite (AAMMCs).

Stabilizing Bifurcated Hydrogen Bond in 8-Aminoquinoline Appended Peptides.

The hydrogen bonding interaction between an amide N-H and the amide N of the preceding residue is prevalent in proline-containing proteins and peptides. However, the N-H···N hydrogen bonding interaction is rare in non-prolyl natural peptides due to restricted dihedral angles. Herein, we stabilize this type of interaction in 8-aminoquinoline appended non-prolyl peptides through bifurcated N···H···N hydrogen bond. The 8-aminoquinoline-incorporated model peptides 2a-i were designed, synthesized, and the crystal structures of 2a-c and 2i were solved. Analysis of crystal data reveals that the amide N-H of aminoquinoline is involved in bifurcated hydrogen bonding interaction with the nitrogen of the preceding amino acid residue and the nitrogen in quinoline. Analysis of crystal packing, Hirshfeld surface and fingerprint plots confirms that the intermolecular O···H contacts significantly contribute to stabilizing bifurcated N···H···N hydrogen bonding interaction. Furthermore, NMR experiments and CD spectroscopy were conducted to examine the preferred conformation in solution, and the data corroborate with the crystal structure conformation.

Crystal structure of tris-{N,N-diethyl-N'-[(4-nitro-phen-yl)(oxo)meth-yl]carbamimido-thio-ato}cobalt(III).

The synthesis, crystal structure, and a Hirshfeld surface analysis of tris-{N,N-diethyl-N'-[(4-nitro-phen-yl)(oxo)meth-yl]carbamimido-thio-ato}cobalt(III) conducted at 180 K are presented. The complex consists of three N,N-diethyl-N'-[(4-nitro-benzene)(oxo)meth-yl]carbamimido-thio-ato ligands, threefold sym-metric-ally bonded about the CoIII ion, in approximately octa-hedral coordination, which generates a triple of individually near planar metallacyclic (Co-S-C-N-C-O) rings. The overall geometry of the complex is determined by the mutual orientation of each metallacycle about the crystallographically imposed threefold axis [dihedral angles = 81.70 (2)°] and by the dihedral angles between the various planar groups within each asymmetric unit [metallacycle to benzene ring = 13.83 (7)°; benzene ring to nitro group = 17.494 (8)°]. The complexes stack in anti-parallel columns about the axis of the space group (P), generating solvent-accessible channels along [001]. These channels contain ill-defined, multiply disordered, partial-occupancy solvent. Atom-atom contacts in the crystal packing predominantly (∼96%) involve hydrogen, the most abundant types being H⋯H (36.6%), H⋯O (31.0%), H⋯C (19.2%), H⋯N (4.8%), and H⋯S (4.4%).

Ethylene Adsorption on Alkali-Hydrophobic Zeolite Y

Zeolites HY with different hydrophobicity having Si/Al ratios of 10, 100 and 750 were modified by an ion exchange process with nitrate solutions of alkali cations in the concentration range 0.1 - 100 mM. The modified samples were characterized by ICP-OES, XRD and surface analysis with N2-adsorption. The ethylene adsorptivities of these modified zeolites were measured under degassed and non-degassed conditions. All zeolites showed the enhancement in ethylene adsorptivity upon modification, while the K+ ions modified ones showed the best enhancement. The modified hydrophobic zeolites with Si/Al ratios of 100 and 750 showed no differences in adsorptivity under the degassed and non-degassed conditions. However, for less hydrophobic zeolite (Si/Al = 10), the adsorption under the degassed condition was much higher than the adsorption under the non-degassed condition. These results indicate that the modified hydrophobic zeolites with Si/Al ratios of 100 and 750 are suitable as ethylene scavengers at ambient conditions. HIGHLIGHTS Zeolites Y with different Si/Al ratios were modified by alkali nitrate solutions The ethylene adsorptivities were measured under degassed and non-degassed conditions Zeolites showed better ethylene adsorptivity upon modification with alkali cation K+ ions modified zeolite showed the best enhancement Modified zeolites (100 and 750) suited as ethylene adsorbent at ambient conditions GRAPHICAL ABSTRACT

A Multiscale Statistical Analysis of Rough Surfaces and Applications to Tribology

Mathematical modelling of surface roughness is of significant interest for a variety of modern applications, including, but not limited to, tribology and optics. The most popular approaches to modelling rough surfaces are reviewed and critically examined. By providing counterexamples, it is shown that approaches based solely on the use of the fractal geometry or power spectral density have many drawbacks. It is recommended to avoid these approaches. It is argued that the surfaces that cannot be distinguished from the original rough surfaces can be synthesised by employing the concept of the representative elementary pattern of roughness (REPR), i.e., the smallest interval (or area) of a rough surface that statistically represents the whole surface. The REPR may be extracted from surface measurement data by the use of the “moving window” technique in combination with the Kolmogorov–Smirnov statistic.

Crystal to Hydrogel Transformation in S‐Benzyl‐L‐Cysteine‐Containing Cyclic Dipeptides ‐ Nanostructure Elucidation and Applications

Cyclic dipeptides (CDPs) are crucial building blocks for a range of functional nanomaterials due to their simple chemical structure and high molecular stability. In this investigation, we synthesized a set of S‐benzyl‐L‐cysteine‐based CDPs (designated as P1–P6) and thoroughly examined their self‐assembly behavior in a methanol‐water solvent to elucidate the relationship between their structure and gelation properties. The hydrophobicity of the amino acids within the CDPs was gradually increased. The present study employed a comprehensive array of analytical techniques, including NMR, FT‐IR, AFM, thioflavin‐T, congo‐red CD, X‐ray crystallography, and biophysical calculations like Hirshfield Surface analysis and DFT analysis. These methods revealed that in addition to hydrogen bonding, the hydrophobic nature of the amino acid side chain significantly influences the propensity of CDPs to form hydrogels. Each CDP yielded distinct nanofibrillar networks rich in β‐sheet structures, showcasing unique morphological features. Moreover, we explored the practical application of these CDP‐based hydrogels in water purification by utilizing them to remove harmful organic dyes from contaminated water. This application underscores the potential of CDPs in addressing environmental challenges, offering a promising avenue for the future development of these materials in water treatment technologies.

Electrospun nanofiber composite based on bimetallic metal–organic framework/halloysite nanotubes/deep eutectic solvents/molecularly imprinted polymers for thin film microextraction of sulfonamides in milk, eggs and chicken meat by HPLC analysis

Herein, electrospun nanofibers based on bimetallic metal–organic framework@ functionalized halloysite/deep eutectic solvents/molecularly imprinted polymers was synthesized as new solid phase extractant for thin film microextraction of sulfacetamide, sulfamethoxazole, sulfamethazine and silversulfadiazine by HPLC-UV analysis. After synthesizing new phase through electrospinning nanofibers and thin film fabrication, we effectively leverage the synergistic properties of these materials within the composite structure. The resultant thin film nanocomposite, which integrates molecularly imprinted nanofibers, highlights the presence of inorganic nanotubes called halloysite, functionalized with a deep eutectic solvent and bimetallic metal–organic frameworks. Characterization of synthesized thin films were successfully characterized for structural, morphological, and surface analysis using infrared spectroscopy (FTIR), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX) and scanning electron microscopy (SEM). In this study, a syringe design was employed for the microextraction of sulfonamides (SAs) using thin film microextraction, which is carried out in two stages: adsorption and desorption, both within the syringe. The effects of several experimental conditions on desorption stage, including desorption parameters including pH, desorption solvent type, and ultrasonication time were studied by the single factor at a time. A Box-Behnken design (BBD) was applied to optimize the significant variables to obtain the optimum extraction conditions. The detection limit of the method was 0.003 µg/L and also the limit of quantification method was in the range of 0.01 µg/L. These results demonstrate the presented thin film microextraction method can serve as a good candidate for the microextraction and determination of sulfonamides in food samples like milk, eggs and chicken meat.

Microwave-Mediated ammonia synthesis over Co2Mo3N catalysts at low pressures

The Haber-Bosch process for ammonia (NH3) synthesis is a major contributor to greenhouse gas emissions and is responsible for > 2 % of the world’s energy consumption each year encouraging the need for alternative renewable-based options. This study investigates an earth-abundant ternary metal nitride (i.e., Co2Mo3N) catalyst to develop a renewable-based NH3 synthesis approach, utilizing an energy-efficient microwave-assisted route. Using a combination of spectroscopic and catalytic measurements coupled with surface analysis techniques, Co2Mo3N was evaluated as a stable and efficient NH3 synthesis catalyst. Results presented here demonstrate NH3 synthesis on Co2Mo3N at ∼420 ℃ and ambient pressure yield ∼0.7 mmolNH3.gcat-1.h−1 and up to ∼12 mmolNH3.gcat-1.h−1 at 28 bar under microwave irradiation. Co2Mo3N displayed an activation energy of ∼72 kJ.mol−1 and yielded NH3 following first-order kinetics with respect to both H2 and N2. These studies illustrate the potential of using this catalyst for a sustainable, cost-effective, and environmentally friendly approach to producing NH3.

Inhibition of acid rock drainage with iron-silicate or phosphate film: in rainy and submerged environments.

Iron phosphate-based coating and iron silicate-based coating were used to inhibit the oxidation of sulfide minerals in rainy and submerged environments. The inhibiting effectiveness of coating agents on the oxidation of iron sulfide minerals was investigated using pyrite and rock samples resulting from acid drainage. The film formed with both surface-coating agents was identified by pyrite surface analysis. It was also confirmed that the formation of coatings varies depending on the crystallographic orientation. The inhibitory effects under rainy and submerged conditions were investigated using column experiments. Submerged conditions accelerated deterioration compared to that under rainy conditions. Iron phosphate coating had a significantly better oxidation-inhibitory effect (84.86-98.70%) than iron silicate coating (56.80-92.36%), and at a concentration of 300mM, H+ elution was inhibited by more than 90% throughout the experiment. Furthermore, methods for effective film formation were investigated in terms of producing Fe3+; (1) application of coating agents mixed with oxidant (H2O2), (2) application of coating agent after the use of the oxidant. In a rainy environment, applying iron phosphate-based coating using the sequential method showed oxidation inhibition effects for cycles 1-9, whereas applying the mixed material showed effects for cycles 9-13. The use of a surface-coating agent after applying an oxidant did not inhibit oxidation. The surface coating agent and the oxidizing agent should be applied as a mixture to form a film.