Avrami Exponent Research Articles

Non-Isothermal Analysis of the Crystallization Kinetics of Amorphous Mg72Zn27Pt1 and Mg72Zn27Ag1 Alloys.

In this study, thin ribbons of amorphous Mg72Zn27Pt1 and Mg72Zn27Ag1 alloys with potential use in biomedicine were analyzed in terms of the crystallization mechanism. Non-isothermal annealing in differential scanning calorimetry (DSC) with five heating rates and X-ray diffraction (XRD) during heating were performed. Characteristic temperatures were determined, and the relative crystalline volume fraction was estimated. The activation energies were calculated using the Kissinger method and the Avrami exponent using the Jeziorny-Avrami model. The addition of platinum and silver shifts the onset of crystallization towards higher temperatures, but Pt has a greater impact. In each case, Eg > Ex > Ep (activation energy of the glass transition, the onset of crystallization, and the peak, respectively), which indicates a greater energy barrier during glass transition than crystallization. The highest activation energy was observed for Mg72Zn27Pt1 due to the difference in the size of the atoms of all alloy components. The crystallization in Mg72Zn27Ag1 occurs faster than in Mg72Zn27Pt1, and the alloy with Pt has higher (temporary) thermal stability. The Avrami exponent (n) values oscillate in the range of 1.7-2.6, which can be interpreted as one- and two-dimensional crystal growth with a constant/decreasing nucleation rate during the process. Moreover, the lower the heating rate, the higher the nucleation rate. The values of n for Mg72Zn27Pt1 indicate a greater number of nuclei and grains than for Mg72Zn27Ag1. The XRD tests indicate the presence of α-Mg and Mg12Zn13 for both Mg72Zn27Pt1 and Mg72Zn27Ag1, but the contribution of the Mg12Zn13 phase is greater for Mg72Zn27Ag1.

Microstructure, deformation behavior, and dynamic recrystallization kinetics of FeNiMnCu-based high entropy alloys prepared by mechanical alloying and spark plasma sintering

In the present research, FeNiMnCuX (X: Co, Cr, Mo, Ti, W) high entropy alloys (HEAs) were successfully fabricated by mechanical alloying (MA) and spark plasma sintering (SPS). SPS transformed the base and Co-containing alloys into FCC structures, Cr- containing alloys changed into a mix of FCC and BCC structures, while other alloys formed a combination of FCC/BCC structure and an intermetallic compound. The base alloy and alloys with Co, and Cr additions exhibited plastic deformation in cold compression tests, whereas other alloys exhibited brittle behavior. During hot compression tests, dynamic recrystallization occurred with a peak in flow stress followed by a gradual decrease to a steady state stress in alloys with Co, Mo, Ti and W additions. The highest peak stresses were observed at 800 °C for Ti- and W- containing alloys. The dynamic recrystallization and fractional softening kinetics are explained by the Avrami kinetic model. An Avrami exponent around 1 was obtained based on the kinetics of dynamic recrystallization for the alloys doped with Co, Mo, Ti, and W.

Non-isothermal crystallization kinetics and memory switching properties of Tl-Se-Ge-Sb chalcogenide semiconductor alloy for thermally stable phase change memory applications

Quaternary (Tl20Se70Ge10)0.85Sb0.15 chalcogenide glass was synthesized using melt-quenching and thermal evaporation techniques for bulk and thin film samples, and its amorphous character was confirmed by XRD. Based on different models of non-isothermal crystallization kinetics, the average values of the glass transition and the crystallization activation energies are 121.33 and 82.94 kJ mol−1, respectively. The crystallization mechanism in the examined composition is 2D nucleation growth, according to Avrami exponent Thermal parameters of the studied quaternary glass, like fragility fluctuation free volume reduced glass transition temperature thermal stability and glass formation ability were investigated and indicated that the (Tl20Se70Ge10)0.85Sb0.15 ChG exhibits a good ability of glass formation and thermal stability. The obtained results of the dc electrical conductivity are found to increase with temperature and decrease with film thickness. The electrical conduction activation energy (0.583 ± 0.004 eV) is thickness independent and the predominant conduction mechanism is the hopping of charge carriers in the band tail localized states. The () curves of (Tl20Se70Ge10)0.85Sb0.15 chalcogenide glass film samples were analyzed and shown to be appropriate for a memory switch. The mean value of the threshold voltage decreases exponentially as temperature increases, whereas it increases linearly as film thickness increases. The values of threshold voltage and threshold resistance activation energies are 0.282 ± 0.003 and 0.521 ± 0.004 eV, respectively. The obtained switching characteristics data were discussed in view of the electrothermal model motivated by current channel Joule heating. These findings highlight the suitability of the investigated composition for various optoelectronic applications, such as memory switching devices, optical data storage, phase-change memories and optical fibres sensing devices.

Crystallization kinetics and nanoindentation studies of Cu46Zr40Ti8.5Al5.5 glassy alloy

Crystallization kinetics of Cu46Zr40Ti8.5Al5.5 metallic glass is investigated in non-isothermal and isothermal conditions. In non-isothermal condition, the crystallization activation energy is determined using Kissinger's method. Further, activation energy of reported Cu-Zr-Al metallic glasses are compared with Cu46Zr40Ti8.5Al5.5 alloy to understand the effect of Ti addition on crystallization kinetics. Detailed investigation on activation energy through the crystallization process is studied. To understand the influence of nucleation and growth mechanism during the crystallization steps, samples are heated in isothermal conditions at various annealing temperatures in supercooled liquid region to determine the local Avrami's exponent using Johnson-Mehl-Avrami equation. Additionally, small scale mechanical response is noted on metallic glass sample to determine the influence of structure on hardness and elastic modulus. Nanoindentation results showed hardness value of 5.39 ± 0.09 GPa and Young's modulus of 92.81± 0.52 GPa.

Effect of Al doping on the kinetics of reverse martensitic transformation in Ni-Mn-In Heusler alloys

In this work, the effects of Al on the microstructure and kinetics of reverse martensitic transformation in Ni50Mn34In16-xAlx (x = 0, 0.5, 1, and 1.5 (% at)) Heusler alloy was studied. The structural and phase transformation behavior of the samples was evaluated by XRD, FE-SEM, and DSC techniques. In order to evaluate the transformation kinetics parameters in the non-isothermal state upon the heating rates of 5, 10, and 15 K/min, the Johnson-Mehl-Avrami-Kolmogorov (JMAK) and isoconversional methods were utilized. The results indicated that the reverse martensitic transformation temperatures and activation energy shifted to higher values due to doping the Al content up to 1 at.%. Conversely, the substitution of In by 1.5 at.% Al leads to a decrease in the transformation temperatures and activation energy. Furthermore, due to the lack of dependence on the activation energy and Avrami exponent on the degree of transformation, the reverse martensitic transformation is single-stage for all samples.

A kinetic approach for valorisation of hydrodesulphurisation catalyst residue into mullite

Mullite (3Al2O3·2SiO2) is a silicoaluminate widely used for the production of ceramics, and it is usually synthesised from different raw materials with solid-state reactions. In this work, petrochemical industry catalyst waste (Ni–Mo waste) composed principally of alumina and silica has been envisaged as a suitable precursor to prepare mullite via thermal treatment. The kinetics of mullite crystallisation from the catalyst waste were studied with differential thermal analysis (DTA). The starting Ni–Mo waste was an amorphous material, and the crystallisation process takes place at temperatures between 1200 and 1300 °C. The activation energies calculated with isothermal and nonisothermal methods were 1059 and 743 kJ mol-1, respectively. The Avrami exponent (n) obtained with the Ligero method and the parameter m calculated with the Matusita method indicated two-dimensional crystal growth, probably through a diffusion-controlled bulk crystallisation mechanism from a constant number of nuclei. The frequency factor calculated by the isothermal treatment was 8 x 1033 s-1.

Tuning Non-Isothermal Crystallization Kinetics between Fe20Co20Ni20Cr20(P0.45B0.2C0.35)20 High-Entropy Metallic Glass and the Predecessor Fe75Cr5P9B4C7 Metallic Glass

In the present work, comparisons of non-isothermal crystallization kinetics between Fe20Co20Ni20Cr20(P0.45B0.2C0.35)20 high-entropy metallic glass (HEMG) and the predecessor Fe75Cr5P9B4C7 metallic glass (MG) were performed with X-ray diffraction and differential scanning calorimetry approaches. The HEMG possesses a harsher crystallization process compared with the predecessor MG, deriving from a higher triggering energy for all the characteristic transitions and local activation energy along with a smaller local Avrami exponent and a growth with pre-existing nuclei. Meanwhile, the glass transition is the easiest process, but the nucleation of the second crystallization case is the hardest transition for the HEMG. However, the predecessor MG possesses distinctly different crystallization features of a moderate difficulty for the glass transition, the harshest process for the growth transition of the second crystallization case, and a crystallization of growth with a diverse nucleation rate. These results conclusively prove that the non-isothermal crystallization kinetics can be significantly changed after the present high-entropy alloying with the substitution of similar solvent elements Co, Ni, and Cr with Fe in Fe75Cr5P9B4C7 MG. Moreover, the two alloys possess a strong glassy formation melt with high thermal stability and diverse crystallized products after non-isothermal crystallization.

Promoting Effect of Microwave Field on Gas Phase Diffusion Limited Magnetite Reduction in Carbon Monoxide

To investigate the effect of microwave irradiation on the rate of magnetite reduction while increasing the gas phase diffusion rate limit, the microstructure and kinetics of CO reduction of magnetite powder were studied. The investigation was conducted through microwave irradiation and conventional heating at 900~1100 °C. Under the two heating methods, the iron crystal is selectively reduced and gradually expanded along the direction normal to the length of the ore powder, forming a strip of iron crystal that penetrates the powder and expands outward across the width. The microwave field can effectively improve the sintering of minerals. The changes in Avrami exponents m and k in the reduction process were determined by combining the Johnson–Mehl–Avrami (JMA) model with the lnln method. The microwave field did not change the limiting step. Microwave irradiation proves to be the most effective means to enhance both the initial reduction rate and the rate during the primary iron crystal precipitation phase. The morphology of the iron crystal takes on a dense punctate shape, influenced by the rate of diffusion control.

Machinability of martensitic and austempered ductile irons with dual matrix structure

The main goal of present paper is to highlight the influence of type of hard phase at different volume fraction onto the cutting force of dual matrix structure ductile iron (DMS-DI) in order to achieve the DMS-DI articles having the suitable machining performance for the DMS-DI market development. DMS-DI specimens were prepared by casting, followed by partially austenitising at temperatures of 870 °C for various times and then quenching into water or molten salt with the temperature 350 °C. The machinability of the workpieces was investigated by adopting, cutting index (relative cutting force with respect to AISI 1110 steel) as a general criterion. Fitting the data to the Johnson-Avrami model revealed the ferrite-to-austenite phase transformation kinetics with two consecutive distinguishable stages with Avrami exponents of 3.5 and 2. In both series of DMS-MDI (martensitic DMS) and DMS-ADI (ausferritic DMS) samples, with increasing percentage of hard phase (Vf), the hardness value was increased, while, surprisingly the cutting index was improved by enhancing of Vf to ≈37%, and then worsened. The dependence of the cutting force on the cutting depth was linear for steel AISI 1110, DMS-MDI and DMS-ADI. The slope of the line and its y-intercept depend on the base materials, type of hard phase, the feeding rate and the spindle turning speed. The hardness value of the DMS-MDI was higher than the DMS-ADI, despite this, for Vf≈37%, the cutting index of the former was up to 20% and 60% better than the DMS-ADI and regular austempered ductile iron, respectively.

Nanocrystallization of Cu46Zr33.5Hf13.5Al7 Metallic Glass

The recently discovered Cu46Zr33.5Hf13.5Al7 (at.%) bulk metallic glass (BMG) presents the highest glass-forming ability (GFA) among all known copper-based alloys, with a record-breaking critical casting thickness (or diameter) of 28.5 mm. At present, much remains to be explored about this new BMG that holds exceptional promise for engineering applications. Here, we report our study on the crystallization behavior of this new BMG, using isochronal and isothermal differential scanning calorimetry (DSC), X-ray diffraction (XRD), and transmission electron microscopy (TEM). With the calorimetric data, we determine the apparent activation energy of crystallization, the Avrami exponent, and the lower branch of the isothermal time–temperature–transformation (TTT) diagram. With XRD and TEM, we identify primary and secondary crystal phases utilizing samples crystallized to different degrees within the calorimeter. We also estimate the number density, nucleation rate, and growth rate of the primary crystals through TEM image analysis. Our results reveal that the crystallization in this BMG has a high activation energy of ≈360 kJ/mole and that the primary crystallization of this BMG produces a high number density (≈1021 m−3 at 475 °C) of slowly growing (growth rate < 0.5 nm/s at 475 °C) Cu10(Zr,Hf)7 nanocrystals dispersed in the glassy matrix, while the second crystallization event further produces a new phase, Cu(Zr,Hf)2. The results help us to understand the GFA and thermal stability of this new BMG and provide important guidance for its future engineering applications, including its usage as a precursor to glass–crystal composite or bulk nanocrystalline structures.

The aging characteristics of resistance rivet welded aluminum/steel joints

The aging characteristics of Al/UHSS resistance rivet welding (RRW) joints are investigated for the first time in this paper. Microstructure studies have shown that the aging treatment does not change the phase composition of the Al/steel mixed nugget still remaining the ferrite structure, while the precipitation, growth and dissolution occur for the microstructure of Al alloy varying with the distance from the rivet. Mechanical tests revealed that for interfacial fracture (IF) and button pullout fracture (BPF) joints, the maximum peak load increased by 13% and 26% with the prolonged aging time, respectively. The improvement in the joint strength after aging can be attributed to the relaxation of the residual stress for IF joint and the age hardening of Al sheet for BPF joint. In addition, interestingly, the accelerated artificial aging is discovered firstly in Al/steel RRW joint. The phenomenon can be attributed to the higher solid solubility of Mg and Si in softening zone of Al sheet, resulting in faster and more precipitation during the aging treatment. The precipitation kinetics indicated that the average Avrami exponent was 1.25, proving the one-dimensional linear growth of fresh nuclei of the hardening phase β''. The block shear model analysis suggested that the Canadian Standards Association, giving the calculating/test values ratio ranged from 0.88 to 1.08, could provide a more reasonable calculation, which showed that the shear failure was mainly determined by the yield of the gross shear plane, and the tension plane failed because of tensile rupture during the lap-shear test.

A study on the crystallization and melting of PLA nanocomposites with cellulose nanocrystals by DSC

AbstractPoly(lactic acid) (PLA)/cellulose nanocrystal (CNC) nanocomposites with 1 or 3 phr of CNC were prepared by melt mixing and compression molding then their % crystallinities as well as crystallization and melting behavior during the first heating/cooling/second heating process were investigated by differential scanning calorimetry (DSC). Isothermal crystallization at 80–130°C for 5 min was performed during the cooling process to see how the isothermal crystallization affects % crystallinity at 25°C. The % crystallinity at 25°C as well as the crystallization rate of the nanocomposite increased with CNC content and showed a maximum at the isothermal crystallization temperature of 105°C regardless of CNC content. The bimodal DSC melting peaks observed during the second heating process were considered due to the crystals with many defects (α′) and the crystals with more perfect structure (α), respectively. Isothermal crystallization kinetic analysis by Avrami equation showed that the Avrami exponents of the nanocomposites were about 1, meaning a rod‐ or disc‐shaped crystal growth mechanism. Improving the mechanical properties of the PLA/CNC nanocomposite would be possible because the % crystallinity at 25°C could be effectively increased by changing CNC content and cooling history.Highlights PLA/CNC nanocomposites. Crystallization and melting behavior analysis of the nanocomposites by DSC. Isothermal crystallization at 80–130°C for 5 min during cooling by DSC. Crystallization degree was maximum for the isothermal crystallization at 105°C. Isothermal crystallization kinetic analysis by Avrami equation.

Separation of overlapping phases for Se88Te10Ag2 glass

Results of crystallization kinetics for Se88Te10Ag2 glass using differential scanning calorimetry under non-isothermal condition are described and discussed. The glass has a single glass transition and two crystalline phases that overlap. The Gaussian fit model was used to separate the overlapping crystalline phases. By applying the Matusita et al. approach to analyses the data, it was possible to determine the activation energy (Ec) and Avrami exponent (n) for the two phases. The average Ec values for the first and the second phases are 126.16 and 113.99 kJ mol−1, respectively. It was shown that the activation energy strongly depended on the heating rate. Using the Kissinger–Akahira–Sunose method, the variable activation energies with crystalline fraction are calculated. This variation demonstrates how the transition from the amorphous to the crystalline phase is a complicated process requiring several nucleation and growth mechanisms. It was discussed if the Johnson–Mehl–Avrami model to describe the crystallization for the composition under investigation. The results show SB(M, N) that model is more appropriate to represent the crystallization process for the examined composition. While the results agree with JMA models at low heating rates. Through the use of scanning electron microscopy and X-ray diffraction, the crystalline phases for the two stages were identified.

Modelling crystallization: When the normal growth velocity depends on the supersaturation

The crystallization proceeds by the advance of the crystal faces into the disordered phase at the expense of the material excess, the supersaturation. Using a conservation constraint for the transformation ratio α∈[0,1] as complementing the rescaled supersaturation to 1 and a kinetic law for the normal growth velocity as function of the supersaturation raised to power g, the growth order, we derive an equation for the rate of transformation dα/dt. We integrate it for the six combinations of the three spatial dimensions D = 1, 2, 3 and the two canonical values of g = 1, 2 towards obtaining expressions for αDg. The same equation, with g = 1 and D = n (n is the so called Avrami exponent) is obtained when taking only the linear in α term from the Taylor's expansion around α = 0 of the model equation of Johnson-Mehl-Avrami-Kolmogorov (JMAK). We verify our model by fitting datasets of α21 and α31 (from α = 0 to αupper = 0.999) with JMAK to obtain from the fit n = 1.725, 2.43, resp. We show further how the values of n depend on the value of αupper to which the fit is performed starting always from 0. Towards building a validation protocol, we start with validating α21 with published results.

Nanocrystallization process in Mn-modified finemet-type alloy

In this paper, we studied the effect of heat treatment on the structural features and crystallization kinetics process of rapidly quenched Finemet-type ribbon for composition with 10% of iron substitution by manganese in initial state. After ribbon annealing at 580 °C for 30 min, and also at 600 °C for 10 and 30 min, the Fe(Si), Fe3B and Fe23B6 phases were identified. The crystallization activation energy, Ea, was found 585 kJ/mol (6.06 eV/at), and the Avrami exponent, n, was determined to be 3.13. In contrast to classical Finemet, where the crystallization process is a typical diffusion-controlled three-dimensional growth at a constant nucleation rate, in the modified alloy with 10% manganese, the growth of small particles predominates with an increase in the nucleation rate. During heat treatment the surface roughness and average peak height were increased from 3.0 to 24.2 nm and from 4.5 to 75.2 nm, respectively.

Kinetika Kristalisasi Campuran Minyak Sawit Bebas Asam Lemak Trans untuk Produksi Margarin

Non-trans-fat (NTF) margarine was produced by substituting partially-hydrogenated palm oil in margarine oil blend with fully-hydrogenated palm oil. Three types of NTF oil blends were used in this study. To obtain an NTF oil blend with similar physical properties to the reference oil blend, which contain partially-hydrogenated oil, the melting properties and crystallization kinetics were evaluated. The iodine value of raw material oil was measured, and the oil was mixed to form the margarine oil blends. Fatty acid composition (FAC) and solid fat content (SFC) of the oil blends were examined. Melting properties of the oil blends were determined based on SFC analysis, while crystallization kinetics were determined using Avrami model. The results showed that there was no trans fatty acids detected in the NTF oil blends. The rate of crystallization constant (k) of the Avrami index of reference oil and NTF-1 oil blend were 0.1413 ± 0.0047 and 0.1369 ± 0.0016 min-n, respectively, whilst their Avrami exponent (n) were 0.93 ± 0.02 and 0.94 ± 0.01, respectively. There was no significant difference on these Avrami indexes, and therefore NTF-1 oil blend could be selected as an alternative oil blend for margarine production.

Kinetics of Austenite Decomposition in 54SiCr6 Steel during Continuous Slow Cooling Conditions

In this study, dilatometry and metallography were used to investigate the effect of silicon and copper alloying on the decomposition kinetics of 54SiCr6 steel during continuous slow cooling. It is different from the published literature for using the approach of the local activation energy of the austenite decomposition Ef and the local Avrami exponent n of the volume fraction of the transformed phase f to study the kinetics of austenite-pearlitic transformation in cooled 54SiCr steel at slow cooling rates. The Johnson–Mehl–Avrami equation was used to determine the dependence of the local activation energy for austenite decomposition Ef and the local Avrami exponent n on the volume fraction of the transformed phase f. The mechanism of the austenite decomposition was analysed based on the calculated values of n. Both the local and average activation energies were used to evaluate the alloying effect, and the results were compared with those obtained from other methods. The type of microstructure formed as a result of cooling at rates of 0.5 K/s, 0.3 K/s, 0.1 K/s and 0.05 K/s was determined. The effects of changes in the cooling rate and the content of silicon (1.5–2.5 wt.%) and copper (0.12–1.47 wt.%) on the dimension of nucleation and growth kinetics of the transformed phase were studied. It was revealed that the pearlite microstructure was formed predominantly in 54SiCr6 steel as a result of continuous cooling at slow cooling rates. It was also found that alloying this steel with copper led to a significant decrease in the value of Ef, as well as to a change in the mechanism of the kinetics of the austenite-pearlite transformation, which was realised in predominantly two- and three-dimensional nucleation and growth at a constant nucleation rate. At the same time, alloying this steel with silicon led only to a slight change in Ef. The results of the study of 54SiCr steel presented the dependence of the activation energy of transformation and the local Avrami exponent on the volume fraction of the transformed phase at a given cooling rate at different copper and silicon contents. In addition, the study provides insight into the mechanism of kinetics in cooled 54SiCr steel as a function of the cooling rate.

Thermal stability and crystallisation behavior of newly developed Cu–Zr–Ag–Ti–Ni multicomponent bulk metallic glass

A comprehensive understanding of the thermal stability of multicomponent bulk metallic glasses (MBMGs) is imperative for their possible technological applications. In this study, new MBMGs, Cu39Zr42Ag9Ti10 and Cu32Zr39Ag8Ti9Ni12, were developed employing a multilayer perceptron neural network, intelligently expanding the binary Cu50Zr50 BMG. X-ray diffraction (XRD) and transmission electron microscopy (TEM) analyses were used to confirm the amorphous nature of the as-cast alloys. The crystallisation kinetics of the alloys were investigated using differential scanning calorimetry (DSC) under isochronal conditions at different heating rates coupled with microstructural analyses tools. The thermal attributes suggest that glass transition and crystallisation are more sluggish in the case of Cu32Zr39Ag8Ti9Ni12 compared to Cu39Zr42Ag9Ti10. The local activation energies (Eα) and the Avrami exponent (nα) indicate a diffusion-controlled crystallisation mechanism for both alloys. The nucleation rate of the crystalline phase(s) is relatively lower for Cu32Zr39Ag8Ti9Ni12, indicating sluggish crystallisation. Moreover, the rate of change of nα becomes much slower for Cu32Zr39Ag8Ti9Ni12 MBMG during the later stages of crystallisation owing to higher undercooling and, thus, a higher required driving force for the growth of nucleated phases. The free volume of Cu32Zr39Ag8Ti9Ni12 remains smaller at both room and elevated temperatures, pointing towards its better glass forming ability. XRD and TEM analyses of the crystallised alloys suggested progressively increasing precipitation of the topologically disordered Cu10Zr7 phase from Cu42Zr48Ag10 to Cu32Zr39Ag8Ti9Ni12 MBMG, potentially aiding in its increased thermal stability.

Viscosity of the supercooled liquid and crystallization kinetic analysis in the Fe74B20Nb2Hf2Si2 amorphous alloy

The non-isothermal thermal behavior of Fe74B20Nb2Hf2Si2 bulk metallic glass (BMG) was studied utilizing various thermal analytical methods. The obtained results showed that the viscosity behavior of this alloy in the supercooled region was strong due to the high kinetic fragility parameter (D* = 49.5) and low fragility parameter (m = 20.2). Also, the apparent activation energy (Ep) values for crystallization process were calculated in the range of 188.7–394.6 kJ/mol using the Gao-Wang method. Additionally, the Avrami's exponent (n) values increased from 2 to 4 with the progress of the crystallization process. The two-parameter Šesták-Berggren (SB) model was used to demonstrate the autocatalytic behavior of crystallization. Furthermore, the kinetic analysis revealed that all crystallization stages were controlled by the interface. The phase analysis showed that the Fe23B6, α-Fe, Fe2(Hf, Nb), and Fe2B phases were formed during the crystallization process. As obtained by the microstructural characterization, it was founded that the low dimensional growth (m = 2) is due to the complex structure of the main phase of Fe23B6 in the first crystallization stage. Moreover, the high dimensional growth (m = 3) during the second and third crystallization stages attributed to the Fe2B phase as the heterogeneous nucleation, as well as a significant increase in the volume fraction of the α-Fe phase, and the preferential orientation of the various crystalline phases. Hence, the values of Avrami's exponent (n) in the second and third crystallization stages were calculated equal to 3 and 4, respectively.

Effect of rice protein on the gelatinization and retrogradation properties of rice starch

In this study, rice starch (RS) was mixed with varying amounts of rice protein (RP; 0 % to 16 %) to explore the effects of protein on the gelatinization and retrogradation of starch during storage. The increased RP addition decreased the viscosity and gelatinization enthalpy of the mixtures but caused an upward trend in the gelatinization temperature, indicating that protein hampers the process of starch gelatinization. Furthermore, RP addition reduced gel hardness, decreased retrogradation enthalpy and crystallization rate constant, but increased Avrami exponent upon RS retrogradation. RP addition also facilitated the mobility of water molecules, weakened the conversion from bound water to free water in the gels, and moderately increased the uniformity and thickness of gel shape. In summary, RP had a dose-dependent effect on the gelatinization and retrogradation behavior of RS, although the anti-retrogradation concentration effect strongly weakened at protein levels exceeding 12 %. It is noteworthy, that excessive RP addition resulted in disulfide bond formation, which increased gel strength and network structure but reduced the ability of RP to facilitate water molecule mobility and restrict water migration, ultimately reducing its anti-retrogradation capability. This phenomenon can be partially attributed to spontaneous protein-protein interaction caused by excessive protein addition, replacing the starch-protein interaction.