Closure Mechanism Research Articles

Fatigue crack tip corrosion processes and oxide induced closure

This paper reviews the corrosion and hydrolysis reactions that occur inside a fatigue crack at ambient temperatures and pressures in humid air and aqueous solutions. This study examines the individual reaction steps, intermediate phases formed, and the time required for the metal ions to transition into hard oxide phases. This study also finds that when a fatigue crack closes at ambient temperatures, the corrosion products inside the crack should consist of thin (≈2 nm) hard oxide films on the fracture surfaces and viscous layers of water with metal ions in various states of the transition from aqueous ions to stable end-product phases, but with insufficient strengths to resist load transfer at the crack tip. This analysis assumes that metal ion complexes form at the crack tip and transition toward the end-product phases in the wake of the crack in a manner analogous to that reported for plane surfaces exposed to humid air and aqueous solutions. It is concluded that the contribution of the viscous layers to an oxide induced crack closure (OICC) mechanism should be negligible. The impact of this finding on the interpretation of R-ratio effects on fatigue crack threshold and oxide thickness measurements is discussed. The OICC mechanism should be possible at high temperatures and in the near threshold fatigue crack growth region where hard oxides can grow to sizes relevant to the cyclic crack opening displacement (COD).

Molecular characteristics of isoprene synthase and its control effects on isoprene emissions from tropical trees.

The isoprene emission rate from plants is simulated by a function of light intensity and leaf temperature, and the G-93 formula is the most extensively applied algorithm for this purpose. Isoprene is biosynthesized by the enzyme isoprene synthase (IspS), and instantly emitted from the leaf. Enzyme kinetics of IspS and substrate availability are important factors involved in the short-term leaf-level control of isoprene emissions. It is thus assumed that the parameters of G-93 may correlate with the kinetics of IspSs, however, at present there is no data available on the relationship between these two parameters. In this investigation, six IspS genes from tropical trees were cloned, their properties characterized, and the relationship between the enzyme kinetics of IspSs and the parameters of G-93 examined. There was a negative correlation between the enzyme kinetics of IspS Km and parameter CT1 of G93, which is used to define the temperature dependency of isoprene emissions. However, performance constant of IspS (kcat/Km) only showed slight positive correlation with CT1.suggesting that the enzyme kinetics of IspS has limited significance in controlling the temperature response of isoprene emissions. The molecular structure of IspS was further elucidated using a molecular dynamics simulation with a focus on the active site in the 6 α-helices bundle. The simulation of the enzyme-substrate complex of IspS from B. variegata predicted a new metal binding domain in helix F (E383) and catalytic motif FXRDRLXE in the A-C loop that could involve the deprotonation of dimethylallyl diphosphate (DMADP) to form a carbocation. Notably, after the binding of a metal ion and DMADP, the active-site closure mechanism was found to involve conformational alterations in the helix H-α1 and transition from a loose to tight enclosure of the 6 α-helices bundles to tune the active pocket size. The characteristics identified for the IspSs from tropical trees could help to explain regional isoprene emissions in tropical areas.

Molecular dynamics simulation of nanocrack closure mechanism and interface behaviors of polycrystalline austenitic steel

Void-type defects in heavy forgings deteriorate their mechanical properties and service life. In this work, the evolutions of a pre-crack closure and the healing and mechanical properties of FeCrNi polycrystalline samples are assessed under different loading conditions using molecular dynamics simulation. The stress–strain curves show that the sample with interface exhibits higher Young’s modulus and yield strength than those with cracks, despite the loading conditions. These results imply that samples under compression loading have a higher ability to resist plasticity, while the shear stress facilitates plastic flow. Crack closure and healing occur under compression stress by dislocation-dominant plastic deformation, while the crack length shrinks and the crack tips expand along grain boundaries (GBs) and the interface because of its higher stress under shear loading. Dislocation activities, including dislocation emission, slip, and interactions with cracks, grain boundaries, and dislocations, contribute to the plasticity of the specimen under compressive loading. In addition to dislocation activities, grain boundary slip, grain rotation, and twinning are potential plastic-deformation mechanisms under shear loading.

Comparison of Cast, Wrought, and LPBF Processed IN718 Concerning Crack Growth Threshold and Fatigue Crack Growth Behavior

Abstract This study focuses on the influence of microstructure and ductility on the short crack behavior and the fatigue crack growth (FCG) threshold. For this, an additively manufactured batch of the nickel-based alloy IN718, made via Laser Powder Bed Fusion (LPBF) process, is compared to both conventionally wrought and cast IN718 material. An initial characterization revealed significant differences in grain structure, from regular fine grained wrought material to large grains of several millimeters in diameter in the cast variant and a chessboard-like grain structure typical for LPBF. The ductility parameters of IN718-LPBF and wrought IN718 are comparable at room temperature, but at 650 °C the LPBF-variant shows macroscopic brittle fracture. The fatigue crack behavior both in the short and long crack regime is investigated in air at 650 °C. To produce minimal crack growth increments of about 1 μm, a compressive precracking and subsequent threshold test procedure with stepwise load increase has been adapted for high temperature testing. To assess the short crack behavior, cyclic R-curves have been generated taking the influence of three different stress ratios (R = −1, 0, and 0.5) into account. As expected, increasing crack closure mechanisms at higher stress ratios lead to higher stress intensity amplitudes ΔKI necessary to initiate crack growth. The crack growth resistance of the LPBF-processed variant is higher compared to wrought IN718. In the long crack regime, the wrought alloy yields higher crack growth rates compared to LPBF and cast IN718. An expected R-ratio dependency is observed for all material states.

Theoretical study on the mechanism and kinetics of the oxidation of allyl radical with atomic and molecular oxygen

The C3H5O and C3H5O2 potential energy surfaces accessed by the oxidation reactions of allyl radical with atomic and molecular oxygen have been mapped out at the CCSD(T)-F12b/cc-pVTZ-F12//ωB97XD/6-311G(d,p) level of electronic structure theory to unravel the reaction mechanism. Temperature- and pressure-dependent reaction rate constants have been evaluated using variable reaction coordinate transition state and RRKM-Master Equation theoretical kinetics methods. The C3H5 + O reaction is found to be fast in the 300-2500 K temperature interval, with the total rate constant of 1.8-1.0 × 10−10 cm3 molecules s−1 independent of pressure in the considered 30 Torr – 100 atm range. Acrolein + H formed by a simple O addition/H elimination mechanism via the CH2CHCH2O association complex are predicted to be the major reaction products with the branching ratio decreasing from 61% at 300 K to 44% at 2500 K. Other substantial bimolecular products include C2H3 + formaldehyde (32%-26%) formed through the C-C bond β-scission in CH2CHCH2O and two minor products C2H4 + formyl radical HCO and allene + OH, where the latter, formed via direct H abstraction by O from the central carbon atom of allyl, becomes significant only at high temperatures above ∼1500 K. The C3H5 + O2 reaction studied in the 200-2500 K temperature range shows a peculiar kinetic behavior characteristic for a bimolecular reaction with a low entrance barrier, shallow association well, and high ensuing isomerization and decomposition barriers to bimolecular products. This behavior is described in terms of three distinct temperature regimes: the low-temperature one with slightly negative dependence of the rate constant, the intermediate one where the rate constant sharply drops, and the high-temperature regime with an Arrhenius-like rate constant. The rate constant is relatively high (10−13-10−12 cm3 molecule−1 s−1) in the low-temperature regime when the reaction produces the peroxy association complex CH2CHCH2OO, but slow at higher temperatures when it leads to bimolecular products. Under combustion relevant conditions, the C3H5 + O2 rate constant is by 5 to 3 orders of magnitude lower than that for C3H5 + O, but since O2 concentrations in flames could be as much as 3 orders of magnitude larger than O concentrations, C3H5 + O2 cannot be ruled out as a significant allyl radical sink. Above 1500 K, the C3H5 + O2 reaction can form vinoxy radical + formaldehyde (40%-15%) via the five- or four-membered ring closure and opening mechanism starting from the initial peroxy intermediate, acrolein + OH (41%-49%) via the H shift from the attacked carbon to the terminal oxygen followed by the immediate O-O bond cleavage, and allene + OH (18-25%) via the H migration from the central CH group to the terminal O atom accompanied or followed by the C-O bond rupture. Modified Arrhenius expressions fitting the computed rate constants for both reactions have been generated and proposed for kinetic models.

OP01.06: Readjustable sling in stress urinary incontinence and hypomobile urethra: understanding the mechanisms of closure by transperineal ultrasound

OP01.06: Readjustable sling in stress urinary incontinence and hypomobile urethra: understanding the mechanisms of closure by transperineal ultrasound

The hydromechanical behavior of opalinus clay fractures: Combining roughness measurements with computer simulations

The role of surface roughness of fractures in Opalinus Clay and in rocks in general is relevant in understanding the hydromechanical behavior of fractures. Two different fracture surfaces of shear fractures in the Opalinus Clay were investigated. The fracture surfaces were characterized based on their roughness power spectrum. It was found that slickensides fracture surfaces are near fractal-like up to the longest scale with a fractal dimension Df ∼ 2.1 and in the absence of a roll-off region at long wavelengths. In contrast, the glassy fracture surfaces show a roll-off region, which is characteristic of a flat surface with rather small and local topographic height variations. The glassy fracture surface is near fractal like with Df ∼ 2.0. The measured roughness power spectra were used to create fracture models to study the behavior of different fracture closure mechanism: 1) increasing congruence (matedness), 2) closure by compression and 3) closure by swelling. It turned out that the relationship between permeability and mean aperture depends on the fracture closure mechanism. Concerning closure by compression, the root mean square (rms) value of the aperture (aper) distribution aperrms influences the contact formation behavior, which in turn controls the hydromechanical properties. The lower aperrms is, the lower the fracture compliance. Apart from aperrms, the simulations show that in clay rocks, plastic deformation plays an important role in the closure of fractures by compression. In agreement with the experiments, the simulations predict that the permeability falls below 10% of the initial value at a compressive stress of 5 MPa. The simulations predict that fracture closure by swelling is rather ineffective for confining pressures exceeding ∼1 MPa.

Extracellular malate induces stomatal closure via direct activation of guard-cell anion channel SLAC1 and stimulation of Ca2+ signalling.

Plants secrete malate from guard cells to apoplast under stress conditions and exogenous malate induces stomatal closure. Malate is considered an extracellular chemical signal of stomatal closure. However, the molecular mechanism of malate-induced stomatal closure is not fully elucidated. We investigated responses of stomatal aperture, ion channels, and cytosolic Ca2+ to malate. A treatment with malate induced stomatal closure in Arabidopsis thaliana wild-type plants, but not in the mutants deficient in the slow (S-type) anion channel gene SLOW ANION CHANNEL-ASSOCIATED 1 (SLAC1). The treatment with malate increased S-type anion currents in guard-cell protoplasts of wild-type plants but not in the slac1 mutant. In addition, extracellular rather than intracellular application of malate increased the S-type currents of constitutively active mutants of SLAC1, which have kinase-independent activities, in a heterologous expression system using Xenopus oocytes. The treatment with malate transiently increased cytosolic Ca2+ concentration in the wild-type Arabidopsis guard cells and the malate-induced stomatal closure was inhibited by the Ca2+ channel blocker and the Ca2+ chelator. These results indicate that extracellular malate directly activates SLAC1 and simultaneously stimulates Ca2+ signalling in guard cells, resulting in steady and solid activation of SLAC1 for stomatal closure.

Verifying Efficacy of Self-Inhalation Training for Velopharyngeal Dysfunction

Velopharyngeal closure in healthy adults during different tasksObjective: Velopharyngeal dysfunction causes not only resonance problems (so-called “hypernasality”) but also dysphagia, particularly in the elderly. In our previous study, we developed a new inhaling training method to objectively improve velopharyngeal function using the measurement of peak inspiratory flow (PIF) rate, which was effective in all patients. In this study, we clarify the degree of velopharyngeal closure to determine the efficacy of our training to improve the closure mechanism. Methods: Three healthy volunteers performed tasks in a magnetic resonance imaging (MRI) gantry in the supine position. To confirm velopharyngeal function, volunteers were first asked to distinguish the difference in the velum position between the production of a nonnasal (sustained phonation /shi:/) and a nasal (sustained phonation /n:/) sound. They were then asked to inhale forcefully through the mouth from an empty 500-mL plastic bottle. For comparison, volunteers performed exhaling forcefully, then inhaling and exhaling softly, through a straw. Each task was performed for 30 s, and the MRI images were obtained in sagittal sections. Results: Inhaling forcefully from an empty plastic bottle created the strongest velopharyngeal closure between the posterior surface of the velum (soft palate) and the posterior pharyngeal wall in all volunteers. Conclusion: The results of our MRI study supported our training method. Using inhalation through a PIF meter or from a plastic bottle to create resistance strengthens particularly the levator veli palatini muscle for velopharyngeal closure, which may be useful in patients with other acquired velopharyngeal dysfunctions including physiological aging. Also, anyone anywhere can train with plastic bottles.

The SARS-CoV nsp12 Polymerase Active Site Is Tuned for Large-Genome Replication.

ABSTRACTPositive-strand RNA viruses replicate their genomes using virally encoded RNA-dependent RNA polymerases (RdRP) with a common active-site structure and closure mechanism upon which replication speed and fidelity can evolve to optimize virus fitness. Coronaviruses (CoV) form large multicomponent RNA replication-transcription complexes containing a core RNA synthesis machine made of the nsp12 RdRP protein with one nsp7 and two nsp8 proteins as essential subunits required for activity. We show that assembly of this complex can be accelerated 5-fold by preincubation of nsp12 with nsp8 and further optimized with the use of a novel nsp8L7 heterodimer fusion protein construct. Using rapid kinetics methods, we measure elongation rates of up to 260 nucleotides (nt)/s for the core replicase, a rate that is unusually fast for a viral polymerase. To address the origin of this fast rate, we examined the roles of two CoV-specific residues in the RdRP active site: Ala547, which replaces a conserved glutamate above the bound NTP, and Ser759, which mutates the palm domain GDD sequence to SDD. Our data show that Ala547 allows for a doubling of replication rate, but this comes at a fidelity cost that is mitigated by using a SDD sequence in the palm domain. Our biochemical data suggest that fixation of mutations in polymerase motifs F and C played a key role in nidovirus evolution by tuning replication rate and fidelity to accommodate their large genomes.IMPORTANCE Replicating large genomes represents a challenge for RNA viruses because fast RNA synthesis is needed to escape innate immunity defenses, but faster polymerases are inherently low-fidelity enzymes. Nonetheless, the coronaviruses replicate their ≈30-kb genomes using the core polymerase structure and mechanism common to all positive-strand RNA viruses. The classic explanation for their success is that the large-genome nidoviruses have acquired an exonuclease-based repair system that compensates for the high polymerase mutation rate. In this work, we establish that the nidoviral polymerases themselves also play a key role in maintaining genome integrity via mutations at two key active-site residues that enable very fast replication rates while maintaining typical mutation rates. Our findings further demonstrate the evolutionary plasticity of the core polymerase platform by showing how it has adapted during the expansion from short-genome picornaviruses to long-genome nidoviruses.

An anatomical pathway for restoration of bladder neck closure by a midurethral sling, according to the integral theory.

A firm pubourethral ligament (PUL) is required to prevent the reflex posterior pelvic muscle forces forcibly opening out the posterior urethral wall on effort. A weak or loose PUL elongates on effort and this allows the posterior pelvic muscles to stretch open the posterior urethral wall causing urine loss, "stress urinary incontinence."Such forcible opening out of the urethra exponentially reduces the urethral resistance to flow inversely by the fourth power of the radius (i.e., 16 times). For example, if the radius doubles in size, the bladder pressure required for urine to flow out decreases by a factor of 16, from say, 160to 10 cm H2 O. A midurethral sling reinforces PUL to prevent the urethra opening out, thereby restoring both the distal urethral and bladder neck closure mechanisms.

Intersectional Experiences: Experiences of Commonwealth Female Migrant Architects in the UK

This paper presents the emergent findings of a larger research project on the lived experiences and career outcomes of female migrant architects from the Commonwealth in the UK architectural profession. I will employ a postcolonial feminist analysis, and the paper will, in particular, focus on considering the key challenges related to occupational closure hurdles. In the UK, architecture is a regulated profession. The geographic origin of qualifications is often used as a part of a professional project and closure mechanism, which can be used as a basis for exclusion. Adopting an intersectional framework merging with postcolonial feminist theory with the literature on professionalisation and professional closure, this paper addresses the question: how does the geographic origin of their architectural qualification influence the experiences of female migrant architects from the Commonwealth living and working in the UK? With a commitment to feminist research design, I am carrying out fifty semi-structured interviews with female migrant architects from Commonwealth countries. One of the key findings indicates that the re-qualification and re-certification requirements for labour market participation in the UK can create significant challenges for them. Some of the requalified migrant architects' lived experiences indicate that instead of successfully crossing occupational closure hurdles in terms of re-qualification, intersections of race, gender and migrant status significantly impact their experience at work. This research intends to contribute to the literature on professionalisation and closure of architecture by examining the intersections of migration, race and gender – an intersection hitherto underexamined in the context of architecture.

Dataset for Estimated Closures of Scallop (Pecten maximus) Production Areas Due to Phycotoxin Contamination along the French Coasts of the Eastern English Channel

Commercial bans due to harmful algal blooms (HABs), which are natural events, question the sustainability of human activities in marine and coastal areas. A risk assessment of these bans is important to support decision-making to better manage and mitigate their impacts. However, data are sparse and difficult to collect. The dataset presented in this paper includes “estimated closures of scallop fishing areas” due to HAB toxicity along the French coasts of the English Channel. The closure data were simulated for each scallop (Pecten maximus) fishing area through an algorithm applied to the in situ dataset from the French monitoring network REPHYTOX. The methodology of the production of closure data consists of comparing phycotoxin concentration in scallop to regulatory thresholds of phycotoxins, and then, simulating the number and duration of closures based on the monitoring strategies and closure mechanisms as defined in the regulations. These data only cover closures related to regulatory threshold exceedances of phycotoxins in shellfish. Closures induced by the lack of sampling or other reasons (e.g., failures in toxin analysis) are not included in the dataset because of the lack of information. Data are produced during the scallop fishing season. Facing the non-existence of such a closure database due to the lack of centralized management of local closure decrees, this dataset can be used to analyse the management strategies to deal with HABs and to highlight the governance challenges related to these strategies. It is also useful to study the link between the ecological and the socioeconomic dimensions of HABs, and to describe how toxin concentrations in shellfish translate into socioeconomic impacts and management challenges. This methodology can be applied to other species, other areas and other economic activities.

A hybrid approach of modified bootstrap and physics-based methods for probabilistic fatigue life prediction considering overload effects

A hybrid approach is proposed by combining the modified bootstrap and physics-based methods, which aims to achieve a reasonable and accurate probabilistic fatigue life prediction under arbitrary overload conditions based on constant amplitude fatigue data. The fatigue crack growth model and equivalent initial flaw size (EIFS) are employed to calculate the fatigue life. The crack closure mechanism is used to account for the loading interaction effects. Furthermore, the uncertainties of EIFS, coefficient of the fatigue model and overload intervals are considered. Fatigue data are collected by performing testing of aluminum alloy 7075-T6 under constant amplitude loading with/without overloads. The bootstrap method is modified by generating the expanding samples, which is utilized to quantify the dispersion of fatigue data. The resampling is conducted based on the expanding samples, instead of the original data directly obtained from the experiment. Eventually, the fatigue lives with different failure probabilities and confidence levels are calculated. In addition, other testing data sets of Al–Li alloy 2060 are also employed to verify the effectiveness and accuracy. Good agreements are observed.

Gap-Scale Disturbance Patterns and Processes in a Montane Pinus palustris Woodland

Gap-scale disturbances drive successional and structural development patterns in most forest ecosystems. Although fire-maintained Pinus palustris woodlands are less light limited than closed canopy forests, gap-scale disturbance processes may still influence successional and developmental pathways. We quantified biophysical characteristics of 50 canopy gaps in a montane Pinus palustris woodland to analyze gap-scale disturbance patterns and processes. We found most gaps (64%) were caused by the death of a single tree. Snag-formed gaps were most common (38%) followed by snapped stems (32%). We hypothesized that insect-induced mortality, perhaps in combination with drought periods, resulted in the high frequency of snag- and snapped stem-formed gaps. We did not find significant differences in gap size or shape based on gap formation or closure mechanisms. Most gaps (74%) were projected to close by lateral crown expansion of gap perimeter trees. We hypothesized most gaps projected to close via subcanopy recruitment would be captured by a P. palustris stem. The majority of gaps were small and gap frequency declined with increased gap size. We found gaps were significantly clustered through the woodland at distances of 8–36 m from gap edge to gap edge but were randomly distributed beyond 36 m.

Malate induces stomatal closure via a receptor-like kinase GHR1- and reactive oxygen species-dependent pathway in Arabidopsis thaliana.

A primary metabolite malate is secreted from guard cells in response to the phytohormone abscisic acid (ABA) and elevated CO2. The secreted malate subsequently facilitates stomatal closure in plants. Here, we investigated the molecular mechanism of malate-induced stomatal closure using inhibitors and ABA signaling component mutants of Arabidopsis thaliana. Malate-induced stomatal closure was impaired by a protein kinase inhibitor, K252a, and also by the disruption of a receptor-like kinase GHR1, which mediates activation of calcium ion (Ca2+) channel by reactive oxygen species (ROS) in guard cells. Malate induced ROS production in guard cells while the malate-induced stomatal closure was impaired by a peroxidase inhibitor, salicylhydroxamic acid, but not by the disruption of Nicotinamide adenine dinucleotide (phosphate) (NAD(P)H) oxidases, RBOHD and RBOHF. The malate-induced stomatal closure was impaired by Ca2+ channel blockers, verapamil, and niflumic acid. These results demonstrate that the malate signaling is mediated by GHR1 and ROS in Arabidopsis guard cells.

A Novel Concept for Unidirectional Communication With an Active Implant Based on Deliberately Produced Human Body Signals.

A new patient-friendly and discrete approach to build a unidirectional communication path with active implants based on deliberately produced human body signals is presented. The application for which this approach is intended is an artificial urinary sphincter implant, the closure mechanism of which is wirelessly actuated in the event of micturition need. Conventional implant communication methods can be associated with limitations regarding technological implementation and usability, and are used by medical professionals only. In order to enable patients to discretely and directly communicate with their implant without the need for an external handheld device, the feasibility of a communication approach based on manually applied 'knocking' signals on abdominal tissue is examined in the presented work. A gelatin-based phantom model is used to mimic vibro-acoustic properties of human soft tissue in vitro. A piezoelectric element and an electret microphone are applied as sensors for signal detection at the implantation site and are investigated with respect to their suitability for the intended application. Clinical Relevance- The presented implant communication method can contribute to urinary incontinence therapy by enabling patients to discretely and user-friendly actuate their artificial sphincter implant and can provide a basis for future research into new implant communication technologies.

Cryo-EM structures of recombinant human sodium-potassium pump determined in three different states

Sodium-Potassium Pump (Na+/K+-ATPase, NKA) is an ion pump that generates an electrochemical gradient of sodium and potassium ions across the plasma membrane by hydrolyzing ATP. During each Post-Albers cycle, NKA exchanges three cytoplasmic sodium ions for two extracellular potassium ions through alternating changes between the E1 and E2 states. Hitherto, several steps remained unknown during the complete working cycle of NKA. Here, we report cryo-electron microscopy (cryo-EM) structures of recombinant human NKA (hNKA) in three distinct states at 2.7–3.2 Å resolution, representing the E1·3Na and E1·3Na·ATP states with cytosolic gates open and the basic E2·[2K] state, respectively. This work provides the insights into the cytoplasmic Na+ entrance pathway and the mechanism of cytoplasmic gate closure coupled with ATP hydrolysis, filling crucial gaps in the structural elucidation of the Post-Albers cycle of NKA.

Cavity dynamics of water entry for a head-ventilated cylinder

This paper describes the flow field and impact load characteristics of a ventilated cylinder upon vertical and angled water entry. A high-speed camera is used to record the evolution of the cavity, and a pressure sensor placed on the head of the cylinder records the impact load. The results show that head ventilation produces an initial cavity before the cylinder enters the water. This changes the evolution of the cavity, reduces the volume of the cavity, and modifies the cavity closure mechanism. As the ventilation rate increases, the impact load decreases rapidly at first and then stabilizes at a certain level. The angle of attack also changes the flow field and impact load characteristics. In the case of angled water entry, an obvious asymmetric cavity is formed, and then cavity separation occurs. An increase in the angle of attack or the ventilation rate strengthens the cavity separation. The impact load decreases with increasing angle of attack at low ventilation rates but is independent of the angle of attack at high ventilation rates.

Distinguishing of carbons and oxidation behaviour (Part 1): Exploring model-free kinetics and RAMAN spectroscopy as a synergistic approach for evaluating carbon-bonded-refractories

• Exploring the synergy of model free kinetics and Raman for industrial routine application on product performance. • Using carbon as a sensor to monitor and track oxidation within carbon bonded refractories. • Investigating microstructural changes using high temperature Raman to support oxidation reaction mechanism. • Utilising cluster analysis feature of the WiTec Raman software to distinguish carbons and the effects of aggregates on carbon signals. A rapid synergetic profiling approach to determining oxidation behaviour and distinguishing of carbons within a refractory composite was explored for steel end user application. The efficacy for both Raman spectroscopy and model free kinetics were studied and proved successful for adoption as routine techniques. With the model free approach, the complex reaction steps were profiled as a multi-step reaction with series of activation energy ranging from 230 KJ/Mol to 150 KJ/Mol. The complex oxidation behaviour was supported by high temperature Raman spectroscopy which corroborated the pore closure mechanism that plays a critical role in modulating reaction intensity. Raman tracked oxidation via its effect on the crystallite sizes of resin (∼ 5.5 nm to 8.5 nm) and intensity peak ratio of D to G peak within some limitations that are discussed in the study. Lastly, an empirical prediction of isothermal experiment from non-isothermal kinetics was validated and considered useful for determining the life of carbon especially in cases where under performance was suspected due to improper preheating by the end-user.