Function Of Heating Time Research Articles

Structural evolution of pea-derived albumins during pH and heat treatment studied with light and X-ray scattering

Pea albumins are found in the side stream during the isolation of pea proteins. They are soluble at acidic pH and have functional properties which differ from their globulin counterparts. In this study, we have investigated the aggregation and structural changes occurring to pea albumins under different environmental conditions, using a combination of size-exclusion chromatography coupled with multi-angle laser light scattering (SEC-MALS) and small-angle X-ray scattering (SAXS). Albumins were extracted from a dry fractionated pea protein concentrate by precipitating the globulin fraction at acidic pH. The albumins were then studied at different pH (3, 4, 4.5, 7, 7.5, and 8) values. The effect of heating at 90 °C for 1, 3, and 5 min on their structural changes was investigated using SAXS. In addition, size exclusion of the albumins showed 4 distinct populations, depending on pH and heating conditions, with two large aggregates peaks (∼250 kDa): a dimer peak (∼24 kDa) containing predominantly pea albumin 2 (PA2), and a monomer peak of a molar mass of about 12 kDa (PA1). X-ray scattering intensities as a function of q were modeled as polydisperse spheres, and their aggregation was followed as a function of heating time. Albumins was most stable at pH 3, showing no aggregation during heat treatment. While albumins at pH 7.5 and 8 showed aggregation after heating, solutions at pH 4, 4.5, and 7 already contained aggregates even before heating. This work provides new knowledge on the overall structural development of albumins under different environmental conditions, improving our ability to employ these as future ingredients in foods.

First evidence of metallisation circle in a Chromium doped UO2 pellet submitted to a thermal gradient

In order to better understand the formation of metallic fission product precipitates at the centre of power ramped UO2 fuel, we performed a separate effects experiment. An annular pellet made of chromia doped UO2 with an initially uniform distribution of chromium oxide precipitates, was subjected to a temperature gradient. The chromia precipitates became metallic in the hottest part of the pellet but stayed in an oxide phase in the coldest part. The border between oxide and metallic precipitate, named metallisation circle, moved from the pellet inner surface towards mid-pellet as a function of heating time. After one hour of heating, stationary state under thermal gradient was reached. The position of the metallisation circle in stationary conditions allowed an assessment of the oxygen potential profile inside the pellet.

In-situ investigation of the decomposition process in cold-rolled Nb53Ti47 alloy

The multi-layer composite development primarily aims to develop and test the components of the next generation of hadron colliders (e.g., Large Hadron Collider - LHC) consisting of superconducting raw materials. Multilayer sheet is very similar to the commonly used NbTi wire products, a 2D version of the commercial wire. These composites consist of layers such as NbTi superconductor, Nb diffusion barrier (between NbTi and Cu) and Cu stabilizer. In β-NbTi superconducting alloys, α-Ti precipitates are primary flux pinning centers that maintain stable superconductivity. A multi-step series of heat treatments and cold-forming processes can develop the flux pinning centers. Practically, this process means three heat treatments of constant period and temperature and drawing or rolling between the heat treatments.The study aimed to describe the behavior of the cold-rolled (ε = 3.35) Nb53Ti47w% alloys during isothermal heating at 673 K as a function of heating time. The processes during the aging were investigated by the in-situ XRD method in the heating chamber. The X-ray diffraction patterns were evaluated by Rietveld refinement. The thermally activated spinodal decomposition and precipitation processes were described based on the phases identified at the individual heat treatment steps and their lattice parameters. The in-situ study also revealed an increase in α-Ti precipitation with time and decomposition that co-occurs. This is the basic study that prepares the applicability of the alloy.

Differential effects of clay mineralogy on thermal maturation of sedimentary n-alkanes

Clay minerals serve as important catalysts for the degradation of a range of biomolecules during diagenesis, yet their effects are seldom considered when interpreting organic molecular and isotopic data in the context of paleoenvironmental reconstruction. We investigated the thermal maturation of immature sedimentary organic matter in the presence of two clay minerals (kaolinite and montmorillonite) using a series of laboratory-based anhydrous pyrolysis experiments. Organic matter was extracted from a modern terrestrial sediment, mixed with each clay mineral, and heated at 100–300 °C for up to 30 days – in this way, initial organic matter was identical in each system. Abundances, molecular distributions, and paired compound-specific stable isotopic compositions (δDn-alkane and δ13Cn-alkane) of n-alkanes were measured as a function of heating time. For both kaolinite and montmorillonite amended experiments, the shifts in molecular distributions are highly controlled by significant secondary production of n-alkanes from molecularly large lipid precursors, as evidenced by significant increases in the total amount of n-alkanes accompanying increased thermal maturation. Significant decreases in carbon preference index (CPI) are observed before minor decreases in average chain length (ACL), leading to behavior in CPI-ACL space that is fundamentally different from identical systems free of clay minerals. Furthermore, distinct distributions of secondary n-alkanes between the clay mineral systems indicate differential mechanisms and sites of precursor degradation. In the presence of clay minerals, δ13Cn-alkane of immature bituminous organics initially decreases with increasing thermal maturation, opposite most data reported from experimental alteration of relatively mature sedimentary matter. This shift is similarly driven by secondary production of n-alkanes, arising from kinetic fractionation associated with preferential cleavage of 12C12C bonds from parent molecules – the kinetics of this process vary per clay mineralogy but are controlled by the same process. Conversely, we see an enrichment in δDn-alkane with increasing maturation, indicating control of the two isotopic systems by separate mechanisms. Moreover, kaolinite and montmorillonite exhibit differential control on δDn-alkane, leading to separate domains in dual isotopic space. Overall, the changes in δ13Cn-alkane and δDn-alkane are relatively small over the timescales studied, even at temperatures as high as 300 °C (less than ∼0.6–1‰ for δ13Cn-alkane and ∼8–15‰ for δDn-alkane). Considering these factors on a geological timescale, variations in clay mineralogy through a buried sedimentary sequence may impart matrix effects on molecular and isotopic signatures that can bias interpretation of paleoenvironmental conditions.

CALCULATING FIRE RESISTANCE OF NON-STANDARD CROSS-SECTIONS OF ELEMENTSOF REINFORCED CONCRETE STRUCTURES USING THE ANSYS SOFTWARE COMPLEX

The article considers mainelements of cast-in-placereinforced concrete structures: slabs, beams and columns.Theirbehavior under temperature conditionsof a standard fire has been studied. As an example structures of the International Medical Center in Moscow, Western District, the territory of the Innovation Center "Skolkovo"were considered. The software Ansys Workbenchwas usedfor calculation of structures. According to the results of the thermo technical calculation, graphs of temperature distribution over the section height of the elements as a function of heating time are plotted and an assessment of fire resistance based on the criterion of loss of heat-insulating properties is proposed.

Fracture -healing properties of asphalt mixtures and microwave heating thermo-sensitivity analysis of their constituent materials

The self-healing ability of asphalt mixture can be enhanced by increasing the temperature to improve the flow capacity of the asphalt binder. However, more than 90% of the raw materials that constitute asphalt mixtures are aggregates, and the asphalt binder content does not exceed 10%. In this study, microwave heating was used to evaluate the thermo-sensitivity of asphalt mixture components, including aggregates, asphalt mastics, fine aggregate matrices, and mixtures. The semicircular bending fracture–healing–fracture test was used to analyze the healing properties of asphalt mixtures after microwave and oven heating, and the fracture energy ratios of the two fracture processes before and after healing were defined as the healing index (HI). Finally, an asphalt mixture healing model was established according to the capillary flow theory. The results show that when microwave heating was used to heat the asphalt mixture, the temperature increased linearly as a function of heating time. This process relied heavily on the aggregate to absorb the microwaves and raise the temperature. Additionally, as the aggregate size increased, the heating rate increased. There was no significant variation in temperature between 70# and the SBS asphalt mastic at the same heating conditions. The HImax values for microwave and oven heating in this study were approximately 40% and 56%, respectively. The HI increased as the heating time period increased, but the growth rate first increased and then decreased. In evaluations with AC-13 and AC-20 mixtures. AC-13 exhibited superior healing properties. The healing model yielded a good fit with the test results (R2 > 0.96).

Kinetic Control of Long‐Range Cationic Ordering in the Synthesis of Layered Ni‐Rich Oxides

AbstractDeciphering the sophisticated interplay between thermodynamics and kinetics of high‐temperature lithiation reaction is fundamentally significant for designing and preparing cathode materials. Here, the formation pathway of Ni‐rich layered ordered LiNi0.6Co0.2Mn0.2O2 (O‐LNCM622O) is carefully characterized using in situ synchrotron radiation diffraction. A fast nonequilibrium phase transition from the reactants to a metastable disordered Li1−x(Ni0.6Co0.2Mn0.2)1+xO2 (D‐LNCM622O, 0 < x < 0.95) takes place while lithium/oxygen is incorporated during heating before the generation of the equilibrium phase (O‐LNCM622O). The time evolution of the lattice parameters for layered nonstoichiometric D‐LNCM622O is well‐fitted to a model of first‐order disorder‐to‐order transition. The long‐range cation disordering parameter, Li/TM (TM = Ni, Co, Mn) ion exchange, decreases exponentially and finally reaches a steady‐state as a function of heating time at selected temperatures. The dominant kinetic pathways revealed here will be instrumental in achieving high‐performance cathode materials. Importantly, the O‐LNCM622O tends to form the D‐LNCM622O with Li/O loss above 850 °C. In situ XRD results exhibit that the long‐range cationic (dis)ordering in the Ni‐rich cathodes could affect the structural evolution during cycling and thus their electrochemical properties. These insights may open a new avenue for the kinetic control of the synthesis of advanced electrode materials.

Identification of the Olfactory Profile of Rapeseed Oil as a Function of Heating Time and Ratio of Volume and Surface Area of Contact with Oxygen Using an Electronic Nose.

The process of deep fat frying is the most common technological procedure applied to rapeseed oil. During heat treatment, oil loses its nutritional properties and its original consumer quality is lowered, which is often impossible to determine by organoleptic assessment. Therefore, the aim of the study was to correlate markers of the loss of the nutritional properties by rapeseed oil related to the frying time and the surface area of contact with oxygen with changes in the profile of volatile compounds. The investigations involved the process of 6-, 12-, and 18-h heating of oil with a surface-to-volume ratio (s/v ratio) of 0.378 cm−1, 0.189 cm−1, and 0.126 cm−1. Samples were analysed to determine changes in the content of polar compounds, colour, fatty acid composition, iodine value, and total chromanol content. The results were correlated with the emission of volatile compounds determined using gas chromatography and an electronic nose. The results clearly show a positive correlation between the qualitative degradation of the oil induced by prolonged heating and the response of the electronic nose to these changes. The three volumes, the maximum reaction of the metal oxide semiconductor chemoresistors, and the content of polar compounds increased along the extended frying time.

Investigation of the thermal parameters of an aluminum heater with nanoporous alumina

An important task faced in the industry of permanently installed heating systems addressed by a large number of manufacturers is power saving. Heating systems may have variegated designs, yet there are basic design requirements, i.e., high operational reliability, resource saving, environmental resistivity and stability of electric parameters. The key component of any heating unit is the heater. Flat resistive heaters have found wide application in heating units aimed at sustaining healthy indoor microclimate, maintaining preset process parameters on industrial premises, as well as in anti-icing systems, agriculture and general industry. We studied the thermal parameters of flat aluminum heating units containing carbon fiber ribbon heaters. To ensure the required insulation of the heater from the metallic base plate, the aluminum surface had a 20 mm thick porous aluminum oxide layer. The ends of the carbon fiber were metalized with a layer of copper for further soldering upon integration into the electric heating unit assembly. The electrical resistance of the heater with a carbon fiber was 60 Ohm. The propagation of heat flows inside a plate of aluminum with nanoporous aluminum oxide was studied using thermal imaging measurements. Temperatures on the surface of the aluminum heater cover and on the opposite heat emitting side were shown as a function of heating time. The experimental results suggest that the heat generated by the linear carbon fiber heater distributes rapidly in the entire bulk of the aluminum heater plate. This indicates a high heat conductivity of the heater aluminum base plate whose parameters provide for the required thermal parameters of the heating unit.

The Impact of Local Heating Time of the Compressed Column on its Stability

The present paper considers the influence of activity time of a local heat source on the stability of a supporting system (column) subjected to the Euler’s external load. Constant heat having impact on the entire circumference of the column on a chosen length was adopted as the boundary heat flux. The formulation and solution of the initial-boundary problem of heat transport in the column was presented by means of the Finite Element Method (FEM). The stiffness of particular segments of the column, onto which it was divided, was determined on the basis of the obtained temporary temperature distributions. The boundary problem of stability of the system was formulated and solved with the inclusion of material changes, resulting from the influence of high temperature. The paper presents the results of numerical simulations, defining the change of a critical load parameter of the system as the function of heating time with the inclusion of stiffness of the supported structure and various positions of the heat flux influence

Thermal degradation kinetics of carotenoids: Acrocomia aculeata oil in the context of nutraceutical food and bioprocess technology

In the present study, the kinetics of β-carotene and β-cryptoxanthin degradation were investigated in edible oil mechanically extracted from the mesocarp of macauba fruit. The crop has a similar productive potential to African palm (Elaeis guineensis), which is among the highest oil-yielding plants in the world. The heating process was conducted under a nitrogen atmosphere, without light exposure. Heat treatments were assumed isothermal and performed at five temperatures, ranging from 110 to 150 °C. HPLC analyses were carried out in addition to spectrophotometric determinations to monitor the carotenoid variations over the heating time. The initial composition of the oil was also highlighted for tocols, peroxide, and trace metal contents. Thermodynamic parameters were obtained from the expression of rate constant derived from transition state theory. The results indicated that the first-order kinetic model is appropriate for describing the oxidative degradation of the compounds in the macauba oil. The carotenoid concentrations decreased for all the treatments as a function of heating time, becoming faster at higher temperatures. A definite influence of temperature on the reaction rates of β-carotene and β-cryptoxanthin was determined, based on the Arrhenius model. The apparent activation energy estimated for β-cryptoxanthin (87 kJ mol−1) was higher as compared to β-carotene (80 kJ mol−1) and the sum of β-carotene + β-cryptoxanthin (84 kJ mol−1). Correlated combinations of kref and Ea indicate that the kinetic parameters estimated for overall carotenoids might predict the retention of the individual compounds with relative accuracy in the context of industrial-scale processes.

Thermal degradation in edible oils by surface enhanced Raman spectroscopy calibrated with iodine values

We present a facile surface enhanced Raman scattering (SERS) based methodology to study the thermal degradation of edible oils using a special gold sputtered SERS tattoo. The methodology is calibrated with Iodine values, which is an industrial standard. This analytical study aims to compare the safety of 7 edible oils rich in monounsaturated (MU), polyunsaturated (PU), and saturated (S) fatty acids (FA) against high temperature re-cooking as done in most restaurants, and street food joints. The changes in the SERS signal intensity (I) ratio of the saturated (@1440 cm-1), and unsaturated (@ 1265 cm−1) FA, I1265/I1440, was studied as a function of heating time, and temperature (T), around the ‘smoke point’. The SERS marker for thermal degradation, I1265/I1440, measuring the normalized unsaturated FA content in the oils decreased consistently, and significantly for the PUFA, and MUFA oils when heated above the ‘smoke point’, following the changes in the industrial standard ‘Iodine value’. Olive (MUFA), and Coconut (SFA) oil showed marginal, and no decrease, respectively, of the SERS marker over the temperature range studied. Based on the SERS marker, a parameter ζ, -the decrease of (I1265/I1440) value of the heated oil with respect to the as-purchased value, is defined that can compare the degradation of the edible oils under different thermal stressing. The Arrhenius fit of the SERS marker yielded similar activation energy of the thermal degradation to that obtained independently from Iodine value, and demonstrates the correctness of the presented methodology.

Experimental and numerical thermo-mechanical analysis of the influence of thermoplastic slabs installation on the assessment of their fire hazard

This work aims at determining the influence of orientation and dimensions of structural samples on the measurement of their burning properties and therefore on the assessment of fire hazard. Poly (methylmethacrylate) (PMMA) slabs are tested thanks to a new experimental setup specially designed to study the combustion of large samples exposed to medium to high radiative heat fluxes. The experimental results evidence a relation between the heat release rate (HRR) and structural phenomena such as mechanical instability, slump, collapse and material flow. The understanding of the dimensions-behavior relationship is completed by finite element simulations of the conducted experiments. The thermo-mechanical simulations consist in the sequence of a transient thermal computation up to a given heating time followed by an eigen buckling calculation, all encapsulated in a parametric study of that heating time. The evolution of the buckling critical load factor as a function of heating time allows predicting for samples of different sizes the time needed to buckle. These simulations corroborate the experimental results, namely that buckling occurs sooner for thin or large samples, which elucidates the discrepancies between the fire response assessed in vertical and horizontal sample orientations.

A Numerical simulation of delamination caused by internal gas pressure for mid-density CFRP

Interlaminar debonding (delamination) is a major problem for carbon fiber-reinforced plastic (CFRP) when it is used in thermal protection systems subjected to rapid heating, such as in a re-entry situation. In this study, the possibility of avoiding delamination by controlling material porosity was investigated experimentally and numerically. CFRP specimens having various initial porosities (mid-density CFRP) were prepared and rapid heating tests (∼6 MW/m2) were performed, and the specimens were examined to determine whether delamination had occurred. To predict the delamination, heat transfer and pyrolysis gas-induced internal gas pressure growth were simulated numerically as a function of heating time. The parameters regarding temperature-dependent chemical reaction rate, orthotropic coefficients for gas permeability, and flatwise tensile strength were determined by individual experiments using the CFRP specimens. The coupled analysis of thermal transfer and pyrolysis gas flow following Darcy’s law was conducted by finite-difference form, employing the experimentally obtained parameters. When the gas pressure exceeds the flatwise tensile strength of CFRP, delamination is assumed to occur. The numerical results show good agreement with the experimental results, and it is concluded that delamination can be eliminated by using mid-density CFRP.

Major cause of strength improvement of a ramie/PA composite with low fiber contents

Abstract The tensile strength of injection-molded semi-crystalline resin (polyamide) matrix composites was improved to higher than the values predicted from the rule of mixture merely by adding 1.0–5.0 wt% of ramie fibers to the resin. This improvement was attributed to faster crystallization on the ramie fiber surface: so-called ‘transcrystalline’. The resin strength became equivalent to the composite strength after isothermal heat treatment. To elucidate this phenomenon, we observed transcrystallization on the fiber surface in a single fiber composite specimen as a function of heating time. Results show that, despite the short heating time, the transcrystalline layer occurs earlier than spherulites. However, with longer heating time, spherulite radius reached a level equivalent to the transcrystalline layer thickness, eventually exceeding it. Although the heat treatment applied for the low-fiber-content composites or the neat resin improves their strength, premature crystallization on the fiber surface can efficiently enhance the composites’ tensile strength without heat treatment.

Wax transfer printing to enable robust barrier definition in devices based on non-standard porous materials

Wax printing has become a common method of fabricating channels in cellulose-based microfluidic devices. However, a limitation of wax printing is that it is restricted to relatively thin, smooth substrates that are compatible with processing by a commercial wax printer. In the current report, we describe a simple patterning method that extends the utility of wax printers for creating hydrophobic barriers on non-standard porous substrates via a process called wax transfer printing. We demonstrate the use of multiple wax transfer cycles to create well-defined, robust, and reproducible barriers in a thick cellulose substrate that is not compatible with feeding through a wax printer. We characterize the method for (i) wax spreading within the substrate as a function of heating time, (ii) the ability to create functional barriers in a substrate, and (iii) reproducibility in line width.

Effect of the pH and NaCl on the microstructure and rheology of mixtures of whey protein isolate and casein micelles upon heating

Thermal gelation of aqueous solutions of micellar casein (MC), whey protein isolate (WPI) and mixtures was investigated as a function of the total protein concentration and the composition at different pH between 5.8 and 6.6. The sol-gel state diagram was determined visually and the mechanical properties of the gels were studied by oscillatory shear rheology. The evolution of the shear moduli was measured as a function of heating time at different temperatures. Strong synergy between the two types of milk proteins was observed during gelation of mixtures. MC gels are formed above a critical temperature that increases with increasing concentration. The MC gels are reinforced by co-aggregation of denatured whey proteins. Hybrid gels display stronger elastic moduli and less syneresis than pure MC gels. The microstructure of the gels was assessed using confocal laser scanning microscopy and showed that hybrid gels were more homogeneous than pure MC gels. The structure of rapidly formed MC gels was not modified by subsequent co-aggregation with denatured WPI. The effect of electrostatic interactions was probed by comparing gelation of salt free solutions with that at 0.1 M NaCl. Addition of salt led to an increase of the minimal gel concentration of MC.

Evaluation of long-heating kinetic process of edible oils using ATR-FTIR and chemometrics tools.

Long thermal oxidative kinetic and stability of four different edible oils (colza, corn, frying, sunflower) from various brands were surveyed with the use of attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) combined with multivariate curve resolution-alternative least square (MCR-ALS). Sampling from the heated oils (at 170°C) was performed each 3h during a 36-h period. Changes in the ATR-FTIR spectra of the oil samples in the range of 4000-550cm-1 were followed as a function of heating time. MCR-ALS was utilized to resolve the concentration and spectral profiles of three detected kinetic components. Three variations in resolved concentration profiles were related to the thermal-deduction of triacylglycerol of unsaturated acid, appearance of hydroperoxides form of triacylglycerols and generation of secondary oxidation products. The kinetic profiles of these species were dependent on the type of oil. The proposed method can define a new way to monitor the oils' quality.

Kinetics of Gas Emission from Heated Moulding Sands Together with the On-line Assessment of H2 and O2 Fractions - New Investigation Method

Abstract The new investigation method of the kinetics of the gas emission from moulding sands used for moulds and cores is presented in this paper. The gas evolution rate is presented not only as a function of heating time but also as a function of instantaneous temperatures. In relation to the time and heating temperature the oxygen and hydrogen contents in evolving gases was also measured. This method was developed in the Laboratory of Foundry Moulds Technology, Faculty of Foundry Engineering, AGH. Gas amounts which are emitted from the moulding sand at the given temperature recalculated to the time unit (kinetics) are obtained in investigations. Results of investigations of moulding sand with furan resin are presented - as an example - in the paper.

Preparation and characterization of zein thermo-modified starch films

A new method of preparing films from zein thermo-modified starch was presented. According to data of micro-visco-amylography and rheometer, dry heating with zein significantly decreased the pasting properties of waxy corn starch and distarch phosphate, the values of G′ and G″ of starches dry heated with zein decreased, while the loss tangent increased as a function of heating time. Scanning electron microscopy images showed that the surfaces of starch granules became rough after dry heating with zein, suggesting interactions between zein and the granule surface. In films made from mixtures, the starch/zein compatibility was improved through dry heating. Compared with films cast from mixtures of separately heat-treated starch and zein, films made from the starch/zein mixtures heated together possessed higher water contact angle and tensile strength. Simple dry heating with zein could thus be used as a promising modification method for improving the functionality of edible films from starches.