Comparative Kinetic Study Research Articles

Comparative Single-Molecule Kinetic Study for the Effect of Base Methylation on a Model DNA-Protein Interaction.

We studied how the interaction between HindIII endonuclease and dsDNA is affected by the single-base modification of the latter by a single-molecule kinetic assay. For a comparative study of chemical modifications, we measured the binding and unbinding rates of the HindIII-DNA complex for normal dsDNA, methylated DNA, and hydroxymethylated DNA. We found that methylation of DNA at the recognition site results in a large increase in the unbinding rate due to the steric effect, which is consistent with the standard free energy change in the transition state. On the contrary, methylation minimally affects the binding rate, as simultaneous increases in the activation energy and the pre-exponential factor compensate for each other.

Online Headspace-Solid Phase Microextraction-Gas Chromatography-Mass Spectrometry-based untargeted volatile metabolomics for studying emerging complex biopesticides: A proof of concept

This work introduces a novel online Headspace-Solid Phase Microextraction-Gas Chromatography-Mass Spectrometry-based untargeted metabolomics approach, suggested as an alternative tool to study the environmental fate of volatile xenometabolites in emerging complex biopesticides, e.g. the Myrica gale methanolic extract herbicide containing several unknown metabolites. A “living” microcosm sample was designed for non-destructive analysis by a 35-min HS-SPME automated extraction and a 36-min GC-MS run. A 38-day kinetics study was then applied on two groups of soil samples: control and spiked. Statistical tools were used for the comparative kinetics study. The Principal Component Analysis revealed and explained the evolution and the dissipation of the herbicide volatile xenometabolome over time. The time-series Heatmap and Multivariate Empirical Bayes Analysis of Variance allowed the prioritization of 101 relevant compounds including 22 degradation by-products. Out of them, 96 xenometabolites were putatively identified. They included 63 compounds that are identified as herbicide components for the first time. The Orthogonal Projections to Latent Structures Discriminant Analysis and its Cross-Validation test were used to assess the total dissipation of the herbicide volatile residues and method detection limit. The reproducibility of the method was also assessed. The highest inter-samples (n = 3) Peak Area RSD was 7.75 %. The highest inter-samples (n = 3) and inter-days (n = 8) Retention Time SD were 0.43 sec and 3.44 sec, respectively. The work presents a green, non-laborious and high-throughput approach. It required a small number of environmental samples (6 microcosms) that were analyzed 8 times and were not destroyed during the study.

A comparative kinetic study of C8–C10 linear alkylbenzenes pyrolysis in a single-pulse shock tube

This work presents a comparative study on the pyrolysis of C8–C10 linear alkylbenzenes including ethylbenzene, n-propylbenzene and n-butylbenzene. Experiments were performed with highly diluted mixtures in argon containing respectively the three fuels under nearly identical conditions in a single-pulse shock tube, at a nominal pressure of 20 bar and over a temperature range of 950–1700 K. Post-shock gas mixtures were sampled and analyzed with the gas chromatographic technique so that species concentration evolutions as function of temperature were obtained for the pyrolysis of each fuel. A kinetic model was developed to interpret the similarities and differences regarding the fuel decomposition and species formation behaviors observed in the experiments. The fuel conversion of n-propylbenzene and n-butylbenzene proceeds along a similar curve, which is much faster than that of ethylbenzene. All three fuels are consumed mainly through the bond fission producing benzyl radical. The simultaneously formed C1–C3 alkyl radicals in separate cases significantly impact the fuel reactivity and the formation of small C1–C4 and monocyclic aromatic hydrocarbons. Specifically, in n-propylbenzene pyrolysis, the decomposition of ethyl radicals produces a considerable amount of hydrogen atoms, which enhances the reactivity of the reaction system and meanwhile results in relatively high production of benzene during the fuel consumption. The formation of other monocyclic aromatic hydrocarbon intermediates, such as toluene and styrene, is also influenced by fuel-related pathways. Concerning PAH formation, the kinetic schemes in the pyrolysis of linear C8–C10 alkylbenzenes are very similar, which are dominated by the reactions of benzyl and other resonantly-stabilized radicals produced from benzyl decomposition. The major PAH formation reactions are barely influenced by the fuel chemistry. The only notable fuel-specific pathway is the indene formation from 1-phenyl-2-propenyl in n-propylbenzene and n-butylbenzene pyrolysis at relatively low temperatures. Styrene is an abundant product and its reaction with phenyl is found to be an important channel of phenanthrene formation.

MODULATORY EFFECT OF POLYMER TYPE AND CONCENTRATION ON DRUG RELEASE FROM SUSTAINED RELEASE MATRIX TABLETS OF RANOLAZINE: A COMPARATIVE RELEASE KINETIC STUDY

Objective: Ranolazine (RZ), antianginal drug indicated for the treatment of chronic stable angina pectoris, was formulated into sustained-release matrix tablets and optimized to improve patient compliance and achieve controlled release over a certain period.
 Methods: Different formulations were prepared by wet- and melt-granulation techniques. Excipients at different ratios as Eudragit® L100-55, Methocel™ E5, Avicel® PH-101, and carnauba wax powder were used to develop a ternary polymeric matrix system for the controlled delivery of RZ. The prepared formulations were subjected to granulometric and characteristic studies. Comparative dissolution and release kinetic studies of the selected formulation and the reference product, Ranexa® extended-release film-coated tablets, Gilead Sciences, Inc., USA, were further carried out to ensure product similarity.
 Results: The optimum pH-dependent to pH-independent polymers ratio was 1:1.3 (w/w). Extragranular carnauba wax in a concentration of 32.50 mg/tablet (2.50 gm% w/w) was the key excipient in controlling drug release kinetics by forming waxy matrix granules which prevent rapid dissolution. Modulation of the microenvironmental pH using a potent alkalinizing agent was very effective for controlling drug release patterns in different dissolution media from pH 1.2–6.8.
 Conclusion: The release of RZ from the matrix tablets was controlled for a period of 24 h, and thereby expected to provide patient compliance with minimal side effects.

Zirconia assisted crystallization of ferroelectric BaBi2Nb2O9 based glass-ceramics: Kinetics, optical and dielectrical properties

Crystallization of ferroelectric BaBi2Nb2O9 (BBN) based glass-ceramics (GCs) doped with different amounts of zirconia (ZrO2) as nucleating agent are carried out via the synthesis of base glasses through melt quenching technique followed by temperature controlled crystallization. For the first time, transparent BBN based GCs have been synthesized with ZrO2 promoting bulk nucleation and facilitating evolution of BBN nanocrystals, which was otherwise difficult in the undoped glass. Non-isothermal DSC studies and several trial heat-treatments facilitated in determining the crystallization temperature of 630 °C, at which controlled rate of crystallization was feasible and crystallite size could be controlled in nanometric scale. Comparative crystallization kinetics studies along with XRD and TEM analyses elucidated the role of ZrO2 as nucleating agent in crystallization of the BBN GCs. The refractive index (RI) of the GCs has been increased compared to the corresponding base glasses and found in the range of 1.833–1.854. When ceramized for 30 h, the dielectric constant of the undoped GC has been found to be 131.3 which have been increased enormously to 301 for the 5 mol% ZrO2 doped GC. A maximum polarization of 2.4 μC/cm2 and recoverable energy storage density of 0.014 J/cm3 has been obtained at 150 °C for the 5 mol% ZrO2 doped 30 h heat-treated GC.

Separation efficiency kinetics of capillary flow micro-pillar array columns for liquid chromatography.

We report on a comparative study of the basic separation kinetics of commercial packed bed columns and a micro-pillar array column (μPAC) working in the 1-10μL/min flow rate range, i.e., operating in the area of capillary flow LC. This is done using a basic test mixture of 8 alkylphenones under both isocratic and gradient separation conditions. Care was taken the μPAC and the packed bed columns have similar volumes (around 10μL) and hence also similar t0-times when compared at the same flow rate. In addition, the isocratic mobile phase composition and gradient programs were selected such to have similar elution windows (in absolute times) for all 4 column types. It was found that the μPAC produces significantly more theoretical plates (up to 3 times) in the 1-4μL/min range, while, the packed bed columns perform better at the higher flow rates because of the relatively large inter-pillar distance in the μPAC. Under gradient conditions, the μPAC produces a clearly higher peak capacity than any of the three packed bed columns over the entire range of investigated flow rates, albeit that this is also partly to be owed to the steeper gradient that needed to be used in the μPAC in order to maintain a similar elution window on all columns.

Comparative kinetic studies and pH-rate profiling of aniracetam degradation using validated stability-indicating RP-HPLC method

Aniracetam is a cognitive enhancer drug that is susceptible to chemical degradation at room temperature. A validated stability-indicating RP-HPLC has been developed and used for studying the kinetics of aniracetam degradation processes and pH-rate profiling. Chromatographic separation of aniracetam and its degradation products was achieved on a C18 column (250 × 4.6 mm) with particle size 5 μm. The stationary phase surface silanol activity and hydrophobicity was evaluated by Galushko method then the mobile phase was optimized for the separation of intact drug from degradation products. Water-acetonitrile-methanol (50:25:25 v/v/v) was used as a mobile phase in isocratic mode with flow rate 1 mL/min. Aniracetam and its degradation products were monitored at 210 nm. Determination was carried out in the concentration range of 0.4–20 µg/mL with a detection limit of 0.21 µg/mL. A new behavior of aniracetam stability was concluded based on structural elucidation of degradation products by infra-red and mass spectrometry. Degradation kinetic parameters including the order of reaction, the rate constant, and half-life have been calculated. The study of the pH-rate profile was evaluated in the range of 3–10 pH units and it was found that aniracetam is stable in uncatalyzed degradation compared to the acid or base-catalyzed reaction. Good recoveries were obtained for aniracetam capsules and the proposed method validity was assessed by standard addition technique. Moreover, the results obtained were statistically compared with those obtained by the manufacturer method and therefore the proposed RP-HPLC method could be successfully used in quality control laboratories for the determination of aniracetam and detection of degradation products.

Kinetic Study of Nonthermal Plasma Activated Catalytic CO2 Hydrogenation over Ni Supported on Silica Catalyst

Nonthermal plasma (NTP) is a promising alternative to conventional thermal activation for promoting efficient heterogeneous catalysis under ambient conditions. However, full understanding of the hybrid NTP catalyst system is challenging due to its complexity. Herein, using the catalytic CO2 hydrogenation over the Ni@SiO2 catalyst as the model system, we carried out comparative kinetic studies of the catalysis under both thermal and NTP conditions to assess the reaction dynamics and kinetics, aimed at understanding the interactions between NTP and catalyst surface. Specifically, the performance of process parameters was evaluated by varying temperature, total flow rate, partial pressure of H2, and dielectric barrier discharge (DBD) power. Kinetic studies showed that, under the NTP conditions, the catalysis exhibited non-Arrhenius behavior likely due to the complex interactions between NTP and Ni catalyst, showing a linear correlation between the natural logarithmic turnover frequency (TOF) and the reciprocal DBD power (instead of the bulk reactor temperature measured). Additionally, under the conditions used, the activation energy of the catalysis under the NTP conditions was independent of the total feed flow rate (at ∼29 kJ mol–1, being significantly lower than that of thermal catalysis (∼80 kJ mol–1). Kinetic studies suggested that the dissociated H species due to NTP discharge in the gas phase are ready to interact with Ni surfaces, thus reducing the activation barrier required to enable the surface reactions.

Kinetics of the Trans Effect in Ruthenium Complexes Provide Insight into the Factors That Control Activity and Stability in CO2 Electroreduction

Comparative kinetic studies of a series of new ruthenium complexes provide a platform for understanding how strong trans effect ligands and redox-active ligands work together to enable rapid electrochemical CO2 reduction at moderate overpotential. After synthesizing isomeric pairs of ruthenium complexes featuring 2'-picolinyl-methyl-benzimidazol-2-ylidene (Mebim-pic) as a strong trans effect ligand and 2,2':6',2″-terpyridine (tpy) as a redox-active ligand, chemical and electrochemical kinetic studies examined how complex geometry and charge affect the individual steps and overall catalysis of CO2 reduction. The relative trans effect of picoline vs the N-heterocyclic carbene (NHC) was quantified through a kinetic analysis of reductively triggered chloride dissociation, revealing that chloride loss is 1000 times faster in the isomer with the NHC trans to chloride. The kinetics of CO dissociation from a site trans to the NHC were examined in a systematic study of isostructural carbonyl complexes across four different overall charges. The rate constants for CO loss span 12 orders of magnitude and are fastest upon two-electron reduction, leading to a hypothesis that redox-active ligands play a key role in promoting reductive CO dissociation during catalysis. Analogous studies of complexes featuring the picoline ligand trans to the carbonyl reveal the importance of the trans effect of the CO ligand itself, with picoline ligand dissociation observed upon reduction. The complexes with NHC trans to the active site proved to be active electrocatalysts capable of selective CO2 electroreduction to CO. In acidic solutions under a N2 atmosphere, on the other hand, H2 evolution proceeds via an intermediate that positions a hydride ligand trans to picoline. The mechanistic insight and quantitative kinetic parameters that arise from these studies help establish general principles for molecular electrocatalyst design.

A comparative study of thermal kinetics and combustion performance of Al/CuO, Al/Fe2O3 and Al/MnO2 nanothermites

The performance of energetic materials is mainly reflected in two aspects, thermal performance and combustion performance. To figure out the differences in reaction performance, in this paper, thermal and combustion properties of Al/CuO, Al/Fe2O3 and Al/MnO2 nanothermites were studied respectively by thermal analysis and fast heating wire experiments. According to the thermal analysis, the exothermic peak temperature points of Al/MnO2, Al/CuO, Al/Fe2O3 nanothermites were 552.1 °C, 563.1 °C and 565.3 °C, respectively, while the sequence of activation energy calculated from low to high was Al/Fe2O3, Al/CuO, Al/MnO2 nanothermites. By the way, the values of Al/CuO and Al/Fe2O3 nanothermites showed little difference in temperature and activation energy. The ignition energy characterized by direct current had little difference among them, and the sequence from low to high was Al/MnO2, Al/Fe2O3, Al/CuO nanothermites, corresponding to 1.169 A, 1.214 A and 1.221 A, respectively. As for burning rate, Al/CuO burnt the fastest clearly while the Al/Fe2O3 burnt the longest. In terms of combustion performance, Al/CuO and Al/MnO2 were basically the same, with little splash of sparks, and the concentrations of combustion energy were better. The combustion phenomenon of Al/Fe2O3 nanothermite was quite unique with a large number of scattered sparks and poor energy concentration. Finally, the intrinsic reasons for above different phenomena of these three nanothermites were analyzed and discussed.

Kinetic properties of infrared and visible luminescence induced by electron beam in CsI:Tl crystal

Presented are the results of comparative study of the decay kinetics for luminescence in the visible (350 ÷ 700 nm) and infrared (1000 ÷ 1900 nm) spectral regions, which is excited in CsI:Tl crystals by a pulsed electron beam (Еm = 250 keV, t1/2 = 15 ns, j= 8 mJ/cm2). The infrared luminescence is assumed to be caused by radiative transition from the excited 62P3/2 state into the ground 62P1/2 state of Tl0 center. The decay kinetics of this luminescence at temperatures within 77 ÷ 450 К range is found to have two pronounced stages. One of them is exponential with a time constant characteristic for the given temperature and independent of Tl concentration within 0.018 ÷ 0.43 mass% range. The other stage has the same decay kinetics as that of the visible luminescence measured under the same conditions. In terms Tl0-Vk recombination giving rise to Tl-perturbed excitons, the visible luminescence arise due to disintegration of [(Tl0)*,Vk] complexes, where Tl0 center has the populated ψ sub-level of the 62P3/2 excited state. The exponential nature and rather long duration of the visible luminescence decay (τ = 700 ns) at room temperature are determined by the lifetime of Tl0 center in the excited metastable state.

Simple Single-Legged DNA Walkers at Diffusion-Limited Nanointerfaces of Gold Nanoparticles Driven by a DNA Circuit Mechanism.

We designed and prepared a single-legged DNA walker that relies on the creation of a simple diffusion-limited nanointerface on a gold nanoparticle (DNA/PEG(+)-GNP) track co-modified with fluorescence-labeled hairpin DNA and poly(ethylene glycol) (PEG) containing a positively charged amino group at one end. The movement of our single-legged DNA walker is driven by an enzyme-free DNA circuit mechanism through cascading toehold mediated DNA displacement reactions (TMDRs) using fuel hairpin DNAs. The acceleration of TMDRs was observed for the DNA/PEG(+)-GNP track through electrostatic interaction between the positively charged track and negatively charged DNAs, resulting in the acceleration of the DNA circuit and amplification of the fluorescence signal. Furthermore, the DNA/PEG(+)-GNP track allowed autonomous and persistent movement of a walker DNA strand on the same GNP track, because the intraparticle DNA circuit occurred preferentially by preventing diffusion of the negatively charged free walker DNA strand from near the positively charged tracks into solution through electrostatic interaction. Based on comparative study of kinetics of TMDRs and DNA walking behaviors, it is to be noted that the DNA/PEG(+)-GNP track showed the fastest DNA circuit reaction (walking rate) and the largest number of steps taken by the walker DNA strand compared to other GNP tracks with varying nanointerfaces that differ in terms of their type of charges (no and negative charges), density of positive charges, and number of hairpin DNAs per GNP track. These facts reveal that the positive charges on the GNP track play an important role in the acceleration of the DNA circuit, as well as the successful walking motion of the single-legged DNA strand. By using the fluorescence signal amplification functions, our single-legged DNA walker could be applied directly and successfully to enzyme-free miRNA-detection systems. The miRNA-detection system provided higher discrimination of other mismatched miRNAs and higher sensitivity (the lowest LOD: 4.0 pM) when compared to other miRNA-detection systems based on other GNP tracks without positive charges. Unlike existing single-legged DNA walkers, our single-legged DNA walkers do not require complex processes, such as immobilization of the walker DNA strand on the tracks and precise adjustment of the sequence of walker DNA. Therefore, our strategy, based on the creation of diffusion-limited nanointerfaces, has enormous potential for the applications of single-legged DNA walkers to biosensors, bioimaging, and computing.

Intraparticle diffusion of Cr(VI) through biomass and magnetite coated biomass: A comparative kinetic and diffusion study

In this study, NaOH treated pine (NTP) and magnetite-pine composite (NTP-NC) were prepared and applied for Cr(VI) adsorption at varying temperatures and the impact of the inorganic-organic nanocomposite combination on the kinetics, diffusion, equilibrium and Cr(VI) uptake mechanism was determined. FE-SEM-EDX analysis of NTP-NC showed that the composite was homogeneous containing Fe, O and C and the iron oxide was well dispersed over the composite. XPS analysis of NTP-NC revealed a shift in the 1s O to higher binding energy suggesting the incorporation of Fe3O4 on oxygenated groups of lignin. Kinetic modelling showed pseudo-second and pseudo nth order model best fitted the experimental data for both adsorbents. Intraparticle diffusion modelling revealed that initial adsorption behaviour was classified as strong initial adsorption for NTP and approaching complete initial adsorption for NTP-NC. Intraparticle diffusion coefficient, Di, where in the range of 10−5 to 10−13 cm2/s indicating that intraparticle diffusion occurred in a chemisorption controlled process. This was confirmed by the good fit of the chemisorption-diffusion model with the experimental data. Film diffusion was found to be active in the mechanism of Cr(VI) uptake by NTP but pore diffusion was active for NTP-NC. Activation energies, Ea, entropies, ΔS# and enthalpies, ΔH# of activation for the kinetic and diffusion processes where calculated from the various rate constants. Pseudo-first order Ea and ΔH# had the highest values for NTP while pseudo-second order had the highest values for NTP-NC for adsorption kinetics while intraparticle diffusion and chemisorption-diffusion gave the highest Ea and ΔH# for NTP and NTP-NC for the diffusion processes.

Synthesis and Comparative Kinetic Study of Reaction-Based Copper(II) Probes to Visualize Aromatic Substituent Effects on Reactivity

Recently, researchers have paid extensive attention to colorimetric/fluorimetric probe development and its applications in biological and industrial samples. The actual development of such probe molecules, however, often requires an iterative process to achieve certain goals such as selectivity and sensitivity toward a target analyte. In spite of growing interest in the development of practical molecular probes, there has not been much effort to implement the synthesis of detector molecules and the examination of their structure–reactivity relationship in undergraduate laboratories. A straightforward synthesis of copper probe molecules, which are systematically varied with aromatic substituents, is described to compare the reactivity toward copper(II) ion. The comparative kinetic study can readily visualize how the number and position of aromatic substituents affect the reactivity. This experiment is appropriate to demonstrate how mechanistic understanding will provide significant insight into rational design of practical colorimetric/fluorimetric probe molecules.

Spectral and Kinetic Studies of Photochromic Systems Based on Graphene and Graphene Oxide Nanostructures

A comparative spectral and kinetic study of the reactions of thiol-substituted molecules of diarylethene and spirooxazine with graphene nanoparticles and graphene oxide nanoplates has been performed. Differences in the photochromic transformations of compounds that are in contact with the surface of carbon nanoparticles in relation to the structure of the compounds and the nature of the nanoparticles are revealed, which indicates the chemical and physical interaction of the molecules of photochromic compounds with the surface groups of carbon nanostructures.

Research Synthesis of La3+ Doped TiO2 Nanoparticles by Hydrothermal Method, Study on Photocatalytic Activity of Decomposition of Methylene Blue under Ultraviolet Irradiation

In this study, with the aim of improving the photocatalytic efficiency of TiO2, we studied the synthesis of La3+ doped TiO2 (with doped rates 1%, 2.5%, 5% mol/mol compared to Ti4+) by hydrothermal method. The hydrothermal condition was set at 180 °C for 12 hours. Material characteristics were investigated by XRD, SEM and solid UV-Vis methods. The results show that, all prepared materials have a crystal particle size of about nano-meters, small and smooth (4.5¸6.5 nm). La3+ doped TiO2 samples had a shift towards longer wavelengths (l» 400¸500 nm) compared to non-doped TiO2 sample (l£ 380 nm). The band gap energy (Eg) of La3+ doped TiO2 samples was reduced to 3.04¸3.10 eV . The yield of MB degradation of La3+ doped TiO2 at 5% mol/mol reached the highest ~93% after 60 minutes under ultraviolet irradiation.
 Keywords
 Anatase TiO2, photocatalysis, La3+ doped TiO2, hydrothermal method, ultraviolet irradiation. 
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Comparative behavior study of steel corrosion inhibition kinetics by three phosphate inhibitors with mass loss measurements

Kinetic study of steel corrosion inhibition using three inhibitors based on phosphate (sodium phosphate Na3PO4, potassium monohydrogenphosphate K2HPO4 and, sodium monofluorophosphate Na2PO3F) was investigated in synthetic mediums of concrete pores solutions contaminated with chlorides at different times up to 60 days by gravimetric measurements. The evolution of inhibition efficiencies for these three inhibitors showed a slightly decrease over time and tend to stabilize between 30 and 45 days. The pH at initial time and final time was also recorded; it reveals that pH decreases slowly comparing with initial time, also comparing with pH of Blank solutions. The effect of temperature was studied for these three inhibitors in order to determine the influence of this parameter on the corrosion inhibition kinetics; it shows that increasing of temperature reduces inhibitors effectiveness. Moreover, thermodynamic studies indicate that adsorption of inhibitor molecules is spontaneous and leads to physical adsorption through Langmuir isotherm model.

Template-free hydrothermal synthesis of hexa ferrite nanoparticles and its adsorption capability for different organic dyes: Comparative adsorption studies, isotherms and kinetic studies

The comparison of adsorption of hazardous dyes such as Evans blue, Congo red and Rhodamine B is studied using novel calcium hexaferrite (CaAl5Fe7O19) nanoparticles, which are synthesized through the solution combustion method. During the synthesis process, the calcium hexaferrite nanoparticles are doped with 15.5% of aluminum nitrate. The synthesized doped-ferrite nanoparticles are characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD). The comparative adsorption studies of three different hazardous environmental chemical pollutants such as Evans blue, Congo red and Rhodamine B dye were investigated by batch adsorption experiments with varying influencing parameters such as dosage effect, dye concentration, pH and contact time. It is found that the maximum adsorption for Evans blue (90.85%) at the wavelength of 608 nm, Congo red (58.17%) at 418 nm, and Rhodamine B (65.6%) is at 627 nm. Freundlich and Langmuir’s adsorption are compared and the results obtained matches well with the Freundlich isotherm model. Such novel materials have the potential for applications in environmental remediation.

Comparative Kinetic Study on Heavy Oil Oxidation in the Presence of Nickel Tallate and Cobalt Tallate

A remarkable feature of heavy oil oxidation during the in situ combustion process is the difficulty in maintaining combustion front to flow throughout the reservoir. Recent developments suggest the...

Comparative Study of the Continuous and Batch Thermal Processing of MgB2 Wires

The last stage of the manufacturing process requires complex reactive diffusion formation process of MgB <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> in the presence of SiC nanoparticles. Continuous thermal processing was adopted to produce long length MgB <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> in situ wires with a homogeneous mixture of micron-sized Mg, nanosized B, as well as SiC dopant powders. This process has enabled the formation of MgB <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> superconducting compound in a relatively short time. Traditional superconductor batch processing requires the wire batch to be heat treated in dedicated large furnaces. Additionally, such a batch process requires controllable slow heating-up, dwelling, and cooling down procedures to ensure uniformity of the superconducting properties along the wire length. Such a prolonged reactive diffusion process does require lower dwelling temperature and can potentially prevent full utilization of the doping materials, resulting in less effective pinning centers formation. On the other hand, continuous wire thermal processing enables rapid formation of the doped MgB <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> with full utilization of the dopant. Also, in the continuous process, the moving thermal front brings complex dynamics to Mg-B, C-B, Mg-Si interaction during MgB <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> formation processes. The manuscript presents a comparative study of the reactive diffusion kinetics, the microstructural formation of the doped MgB <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> compound, and their J <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> (B, T) characteristics.