Onset Crystallization Temperature Research Articles

Effect of Nb addition and annealing treatment on structural and magnetic properties of Fe–Si–B–P–Cu alloy ribbons

Thermal and magnetic properties of Fe85-xSi2B8P4Cu1Nbx (0 ≤ x ≤ 4) alloy ribbons of different microstructures were systematically investigated. Increase in Nb content raised the first crystallization onset temperature from 646 to 701 K suggesting improved thermal stability. XRD results on the as-spun ribbons also suggested the role of Nb increasing the thermal stability and glass-forming ability by showing fully amorphous patterns for all alloys with Nb addition. However, Nb addition turned out to decrease the saturation magnetic flux density from 1.74 to 1.17 T. To further optimize the properties, annealing treatment was carried out to find the optimized condition as Fe84Si2B8P4Cu1Nb1 processed at 793 K for 10 min resulting in nanocrystalline microstructure with a high saturation magnetic flux density of 2.03 T. Transmission electron microscopy confirmed the formation of nanocrystalline α-Fe phase in the annealed ribbons.

Crystallization of an undercooled Zn-based glass forming alloy

Zn-based metallic glasses (Zn40Mg11Ca31+xYb18-x, x = 0 - 4) are strong glass forming alloys with low glass transition temperatures. While the crystallization onset temperature is also low, the nucleation behavior has not been examined and analyzed quantitatively. For a Zn40Mg11Ca31Yb18 metallic glass alloy, the crystallization behavior was determined based on the application of the Flash differential scanning calorimetry (DSC) with ultrafast heating and cooling rates. The critical cooling rate range was measured for glass formation at 1.6(±0.2) × 104K/s. A temperature-time-transformation (TTT) diagram for the nucleation onset in an undercooled liquid was obtained by applying a series of isothermal exposures by fast heating from the glass state or fast cooling from the liquid state to the target temperatures. A heterogeneous nucleation analysis model was developed to interpret the experimental TTT diagram, which provided a further understanding of the nucleation in Zn-based metallic glasses.

Effects of rare-earth element Y content on the microstructure and properties of quinary Al–Ni–Zr–Co–Y high entropy metallic glasses

A series of quinary (Al1/4Ni1/4Zr1/4Co1/4)100-xYx (x = 16–28 at.%) high entropy metallic glass ribbons were successfully fabricated through the high-speed single roller melt-spinning method. The effects of rare-earth element yttrium content on the microstructure and performances of alloy ribbons were systematically investigated by X-ray diffraction (XRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), heat treatment, transmission electronic microscopy (TEM), atomic force microscopy (AFM) and electrochemical experiments. The microhardness of metallic ribbons was measured by Vickers hardness tester. Results show that the microstructure of the as-quenched alloy ribbons maintain the glassy state and the average microhardness value of each specimen can reach 488 HV0.1 or above. The surface morphologies of the as-spun ribbon samples exhibit the smooth surface with small roughness value of Ra = 0.115–0.150 nm. In the meantime, with the increase of Y content, the glass transition temperature can be detected in the DSC traces when Y content is over 22 at.%, and the crystallization onset temperature shifts to the lower temperature region, suggesting that the thermal stability of amorphous state in Al–Ni–Zr–Co–Y alloy ribbons has been weakened. The (Al1/4Ni1/4Zr1/4Co1/4)84Y16 alloy ribbons own the highest crystallization onset temperature (∼742 K). Adding appropriate yttrium element can enlarge the super-cooled liquid region and improve the glass-forming ability. In 3.5 wt% NaCl solution, the prepared alloy ribbons can maintain smaller corrosion current densities (∼10−8 A cm−2) than traditional Al-based amorphous alloys, 6061 Al alloy and other common structural steels. The X-ray photoelectron spectrometer results indicate that the passive film of equiatomic alloy ribbons is rich in oxides of Al, Zr, Co, and Y elements, which has excellent resistance to chloride ion attack. On the basis of all experimental results, (Al1/4Ni1/4Zr1/4Co1/4)84Y16 alloy ribbons can optimally combine outstanding corrosion resistance, superior thermal stability, and acceptable microhardness. The above research results lay a solid foundation for the composition development of high-performance high entropy metallic glasses.

Thermal behavior of gadolinium-silica gels prepared via sol–gel route combined to γ-irradiation process

Gadolinium-silica (Gd-silica) gels were prepared via sol–gel route combined to γ-irradiation (0–30 kGy), starting from Tetra-Ethyl-Orthosilicate (Si(OCH2CH3)4, TEOS) and gadolinium nitrate Gd(NO3).6H2O used as raw materials. The phase transformation and morphology of the gels derived from both precursors were characterized by XRD and TEM analysis. Differential scanning calorimetry (DSC) under non-isothermal conditions was used to determine the crystallization activation energy (E c) at different γ-doses (0, 8, 15, 25 and 30 kGy), using the methods suggested by Kissinger, Moynihan and Ozawa. XRD analysis of the samples calcined up to 1100°C for 2 h reveals the formation of gadolinium silicate (Gd4.67 (SiO4)3O) apatite crystalline phase with the presence of small traces of gadolinium pyrosilicate (Gd2Si2O7), the average particle sizes about 50 nm. TEM observations show spherical Gd-silicate nanoparticles homogeneously dispersed in silica matrix, the mean diameter size is about 40 nm. From DSC analysis, it was observed that the onset crystallization temperature (T x) and peak crystallization temperature (T c) both increase with increasing γ-dose. According to Kissinger, Moynihan and Ozawa models, the crystallization activation energies for Gd-silicate phase formation were found to be 465.2, 474.5 and 465.7 kJ mol−1, respectively for unirradiated samples and 429.1, 447 and 438 kJ mol−1 when the γ-irradiation reaches 30 kGy respectively. Results revealed that the values of E c decreased when the γ-dose increases and attains the minimum value at the dose of 15 kGy and then increase at higher doses. The crystallization rate factor (K) was also seen to decrease with increasing of γ-dose. Gamma irradiation increases the crystallization peak temperature (T c). The crystallization activation energy (E c) estimated from the three models is in good agreement and much well with those reported for silicate systems. Gamma irradiation decreases the E c and crystallization rate factor (K). These preliminary results can provide useful technical information for a better understanding and control of the crystallization process of this type of nanomaterial.

The kinetic characteristics of mullite crystallization in slag with high SiO2 and Al2O3 content at gasification condition of solid fuel

Mullite crystallization leading to poor slag discharge, is the bottleneck of solid fuel gasification. In order to quantify the crystallization behavior and prevent slag blocking, the crystallization thermodynamics and kinetics of slags in the main crystalline phase region of mullite were studied using FactSage, XRD, SEM-EDS and DSC. Mullite crystallization temperatures ranged from 1189 °C to 1325 °C, and an increase in the cooling rate reduced the mullite onset crystallization temperature as detected by DSC. Kinetic analysis showed that mullite possesses strong nucleation capacity and crystallize tendency, and the minimum activation energy of crystallization of slags was 304.4 kJ/mol. The Si-O-Al structure was regarded as the key short-range ordered structure for mullite crystallization ability, and its concentration was reduced by increasing SiO2/Al2O3. Then the crystallization tendency could be weakened by adjustment of SiO2/Al2O3. Meanwhile, slags with SiO2/Al2O3 = 2.0 or Fe2O3 ≤ 15 wt% showed weak crystallization tendency or glassy slag, which was favorable for slagging operation. The results of this study can provide theoretical guidance for the smooth slagging of ash slag in the main crystalline phase of mullite.

Effect of Minor Mo Addition on Microstructure and Corrosion Resistance of High-Velocity Air Fuel-Sprayed Fe-Based Amorphous Coatings

In this work, Fe64Nb3B17Si6Cr6Ni4 and Fe60Nb3B17Si6Cr6Ni4Mo4 (at. %) coatings were prepared with a high-velocity air fuel spraying method, and the effects of minor Mo addition on the microstructure, glass formation, and corrosion resistance of the coating were studied. It was found that the Mo addition improves the glass-forming ability of the alloy and a fully amorphous structure with a higher compactness was obtained in the Mo-containing coating. The thermal stability of the coating is enhanced by Mo addition and the onset crystallization temperature was increased by 20 K. In addition, the Mo-containing amorphous coating exhibited higher corrosion resistance than the Mo-free coating. The superior corrosion resistance can be attributed to the increased proportion of protective, stable Cr, Nb, and Mo oxides in the passive film and fewer defects of the Mo-containing coating.

Effect of glass crystallization parameters on conductivity of Li1.5+xAl0.5Ge1.5SixP3–xO12 glass-ceramics

Glass-ceramic samples of the Li1.5+ x Al0.5Ge1.5Si x P3- x O12 system ( x = 0-0.1) were obtained by directional crystallization of glasses. The glass transition, onset and peak temperatures of crystallization were determined using differential scanning calorimetry. The phase composition of glass-ceramics was determined by X-ray phase analysis. Electrical conductivity is studied using electrochemical impedance. Based on the data obtained, the homogeneity region of solid solutions was established and the optimal conditions for producing SiO2-doped glass-ceramics were identified. The composition with x = 0.02, crystallized at 750°C with a heating rate of 3 deg/min for 2 h, had the highest lithium-ion conductivity at room temperature (4.55×10-4 S/cm).

Anomaly in the relation between thermal conductivity and crystallinity of silicate glass-ceramics

Thermal conductivity is a key property of oxide glass, especially for building applications such as thermal insulation materials and windows or glazed facades. However, this property is difficult to be predicted since it depends on several factors such as the degree of order/disorder and porosity. Here, we report on the effects of crystallization, crystalline phase, and crystal size on the thermal conductivity of a melt-quenched silicate glass. These effects were studied by heat-treating the glass at the onset crystallization temperature for different durations to vary crystallinity in the samples. The results show a general increase in thermal conductivity with crystallinity and crystal size in the nano-range (<75 nm). The growth of devitrite and combeite phases in the glass has a great impact on the thermal conductivity. Interestingly, an anomaly of thermal conductivity is found, i.e., the thermal conductivity of the sample with a relatively low crystallinity of <15 % is reduced by >20 % compared to that of the pure glass phase. This may be attributed to the grain boundaries between amorphous and crystalline phases, which scatter the phonons and thus reduce the thermal conductivity. These results imply that nano-crystallization in window glass might be a useful way to reduce the heat loss from glazed facades in the building envelope.

Effect of Carbon and Cooling Rate on the Structure of Hypereutectic High Chromium Cast Iron in the Cast State and after Heat Treatment

The article presents experimental data on the changes in the structural parameters and properties of castings from high-chromium cast iron G-X300CrMo27-1 depending on the carbon content, which ranged from 2.8 to 4.5 wt. %. Castings were obtained under cooling conditions with two cooling rates—0.083–0.117 °C/s and 4.67–5 °C/s. Changes in the structure and properties of these castings after destabilizing annealing and subcritical heat treatment were assessed. Changes in carbon concentration and cooling rate in the crystallization interval have a significant effect on the sizes of primary carbides (Cr, Fe)7C3, and on the fraction of eutectic carbides. The microprobe analysis results indicating the effects of cooling rate on the composition of phases in cast iron castings with carbon contents of 4.2 wt. % are presented. The offset value of the crystallization onset temperature and eutectic point with an increase in the cast iron melt cooling rate from 0.083 to 0.83 °C/s is shown. The changes found in the properties of castings with increases in carbon concentration and cooling rate cannot be unambiguously explained by the transformation of the structure of primary and eutectic carbides and changes in the elemental composition of phases. The composition and condition of the matrix has a significant effect on the hardness, bending strength and abrasion resistance of castings. It is suggested that internal stresses arising in primary and eutectic carbides affect the properties of castings in the cast and heat-treated state.

Physicochemical characteristics of new complex niobium-containing alloys

The authors studied the physicochemical characteristics of new complex alloys containing, %: 11 – 30 Nb, 23 – 28 Si, 3 – 10 Al and 3 – 4 Ti. It was shown that complex alloys have the most favorable values of density and crystallization temperatures compared to standard ferroniobium (60 wt. % Nb). Complex alloys with a low concentration of niobium have acceptable crystallization temperatures and optimal density values (5740 – 6560 kg/m3). This allows the pieces of ferroalloy to be completely in the liquid steel when it is released into the ladle, and to be constantly in motion, which increases absorption of the leading components. When the niobium concentration increases to 30 %, phase composition of the alloy changes: a decrease in the proportion of the low-temperature FeSi phase with low density values and an increase in the proportion of the high-density ternary compound NbFeSi2 with a crystallization temperature of ~1713 °C. An increase in Nb concentration from 11 to 17 % leads to a decrease in the crystallization temperature, and a further increase to 30 % Nb, on the contrary, is accompanied by an increase in the liquidus and solidus temperatures to 1700 and 1610 °C, respectively, which is consistent with liquidus line in phase diagram of the Fe – Nb system with a minimum in Nb concentration range ~18 %. The best characteristics, both from the point of view of obtaining ferroalloys and use for alloying steel, belong to an alloy containing, wt. %: 17.1 Nb, 24.6 Si, 7.6 Al and 3 Ti. This alloy is characterized by the temperature of crystallization onset (1550 °C) below the liquid steel bath temperature and belongs to the category of low-melting alloys. It has optimal density values – 6390 kg/m3, which has a positive effect on the performance characteristics of niobium ferroalloys.

EFFECT OF CERIUM OXIDE AND BASICITY OF SLAGS ON THEIR VISCOSITY AND CRYSTALLIZATION START TEMPERATURE

The study of the influence of the content of cerium oxide and the basicity of the slag on the viscosity and temperature of the onset of crystallization of the CaO–SiO2–Ce2O3 system containing 15% Al2O3 and 8% MgO was carried out using the simplex-lattice method of experiment planning, which makes it possible to obtain mathematical models describing the dependence of the property on the composition as a continuous function. Using the experimental data, we built mathematical models that describe the relationship between the temperature of a given viscosity and the composition of the oxide system. Then, by combining the obtained composition-temperature diagrams of a given viscosity on the isothermal section of the composition-viscosity diagram, a set of viscosity isolines was obtained. Generalization of the results of mathematical modeling and graphical display on the isothermal section of the composition-viscosity diagram made it possible to obtain new data on the viscosity of the CaO–SiO2–Ce2O3 oxide system containing 15% Al2O3 and 8% MgO, in the range of basicity 2–5 and the content of 0–15% Ce2O3. Experimental data show that the slags of the studied oxide system, which do not contain cerium oxide, are characterized by an increased crystallization temperature and viscosity in the studied range of basicity. The presence of cerium oxide in the slags of the studied oxide system provides a rather low viscosity and crystallization start temperature in the temperature range of 1500–1550°C. An increase in the content of cerium oxide in slags with a basicity of 2–3 from 1 to 15% is accompanied by a decrease in the crystallization onset temperature from 1490 to 1410°C. Increasing the basicity to 5.0 leads to an increase in the temperature of the onset of crystallization to 1520°C. At a temperature of 1500°C, the viscosity of slags with a basicity of 2.0–3.0, containing 7–15% Ce2O3, varies within 0.2–0.3 Pa · s. An increase in slag basicity to 3.0–5.0 at a fixed Ce2O3 content of 7–15% is accompanied by an increase in slag viscosity up to 1.0 Pa · s and reaches 2.0 Pa · s with a decrease in Ce2O3 to 1–6%. An increase in temperature to 1550°C and a fixed basicity of 3–5 is accompanied by a significant decrease in viscosity, which does not exceed 0.35 Pa · s at a Ce2O3 content of 1–15%.

The Intra-Ply Shear Behaviour of Non-Isothermal Thermoplastic Composite Laminates

During the thermoforming of fibre-reinforced thermoplastic (FRTP) organosheets, the desire to minimise tool temperatures leads to non-isothermal temperature profiles through the laminate thickness. The aim of this study was to understand the influence of these non-isothermal conditions on FRTP intra-ply shearing. Novel non-isothermal bias extension tests were conducted, revealing that an average between the isothermal shear curves of both laminate faces approximately represented the respective non-isothermal condition. However, these findings were irrespective of FRTP thickness, and only applied to laminates that wholly remained above the crystallisation onset temperature. Upon the onset of crystallisation in a single ply, the non-isothermal shear resistance skewed heavily towards that (within 5%) of the crystallised ply and inhomogeneous shear angles were observed. Non-isothermal thermoforming validated these findings with the presence of wrinkles on non-isothermal hemispheres in which a single ply had reached crystallisation. This reaffirms the importance of accurate thermal monitoring during FRTP processing.

Influence of CeO2 on glass formation, structural and thermal properties of sodium niobium phosphate glass

Cerium is a well-known surrogate to trivalent and tetravalent actinides and has been investigated to explore the structural and thermal characteristics of simulated radwaste-loaded material systems. The solubility and distribution of CeO2 into a sodium niobium phosphate glass have been explored with the objective of developing a host matrix for radioactive waste immobilization. Niobium phosphate glasses of (100-x) (40Na2O–20Nb2O5–40P2O5)-xCeO2 (x = 0, 1, 3, 5, 8, and 10 mol%) compositions are prepared by melt-quenching method and are characterized by X-ray diffractometry (XRD), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy and scanning electron microscopy (SEM). This study summarises the influence of cerium ion incorporation on the structure, thermal stability, and formation of crystalline phases of the niobium phosphate glass. The various glass stability parameters, such as Hruby (KH), Weinberg (KW), and Lu–Liu (KLL) parameters are estimated to assess the stability of the glass melt against devitrification in the supercooled region. The spectroscopic analysis ascertains the presence of metaphosphate and pyrophosphate networks as primary structural building units in the glass. However, the Raman analysis demonstrates the influence of CeO2 on the network linkages arising from the corner-sharing of NbO6 octahedrons and Nb–O–P bonding in the glass. The CeO2 loading is optimized up to 8 mol% into the base 40Na2O–20Nb2O5–40P2O5 glass matrix without precipitation of any crystalline phase. The glasses are heat treated to obtain glass-ceramics embedded with the crystalline phases, namely, monazite CePO4, NbOPO4, NaNbO3, and niobium phosphate bronze Na6Nb8(PO4)5O15. The microanalysis of these glass ceramics shows that the CeO2 is more aggregated inside the niobium phosphate bronze framework than in the bulk at a higher temperature. It is also observed that the surface crystallization process is a prevalent mechanism for the crystallization of glasses on heating at crystallization onset temperature.

Thermomechanical Properties of High Oleic Palm Oil Assessed Using Differential Scanning Calorimetry, Texture Analysis, Microscopy, and Shear Rheology.

Standard Palm Oil (SPO) is widely used as a food ingredient partially due to its unique thermophysical properties. However, the American Heart Association recommends a saturated fat consumption of <5% of the caloric intake per day. The OxG Palm hybrid yields oil known as "palm oil with a higher content of oleic acid" (HOPO), with <35% SFA and >50% oleic acid. Characterizing novel high oleic oils is the starting point to find processes that can functionalize them such as oleogelation. This study compared the thermophysical properties of HOPO to SPO using Differential Scanning Calorimetry, shear rheology, polarized light microscopy, and texture analysis to characterize the differences between these oils. HOPO had a lower onset crystallization temperature (Δ7 °C) and its rheological behavior followed similar trends to SPO; however, large viscosity offsets were observed and were correlated to differences in crystallization temperatures. The maximum peak force of SPO was an order of magnitude higher than that of HOPO. Overall similar trends between the oils were observed, but differences in firmness, crystal morphology, and viscosity were not linearly correlated with the offset in crystallization temperature. This study quantified differences between these oils that will better enable industry to use HOPO in specific applications.

Exploring the impact of Bi2O3 addition on the thermal properties and crystallization behavior of lead borosilicate glasses

Novel heavy-metal oxide glasses with different compositions, specifically (80-x)PbO– xBi2O3–10B2O3–10SiO2, where x ranges from 0 to 60 mol%, were synthesized using a conventional melt-quenching technique. The amorphous nature of these glasses was confirmed through X-ray diffraction analysis. Additionally, infrared spectra were obtained for the prepared samples to explore their structural characteristics. Differential thermal analysis was performed to investigate the characteristic temperatures of the glasses, including the glass transition temperature, melting temperature, onset crystallization temperature, and peak crystallization temperature. The addition of Bi2O3 shifts the characteristic temperatures to higher values and affects the crystallization process and phases formed. Parameters like ΔT, KH, and KSP are used to evaluate and quantify glass stability. Dilatometric measurements demonstrated that substituting PbO with Bi2O3 in the glass composition resulted in an increase in glass transition temperature and dilatometric softening temperature, as well as a decrease in the coefficient of thermal expansion. Furthermore, we determined the density and calculated the molar volume of the samples. These findings deepen our understanding of the thermal behavior, glass stability, and structure-property relationships in lead borosilicate glasses with Bi2O3, facilitating the development and customization of glass compositions with desired thermal and physical characteristics for specific applications.

Effects of Dietary Supplements of DHA-enriched Micro Algae Diet on Physical and Technological Properties of Dairy Cow Milk Fat

This study examined the effect of dietary supplementation of DHA-enriched micro algae diet on physical and technological properties of dairy milk fat in terms of the dynamic crystallization and melting behaviour. Two dairy cows were subjected to feeding regime of DHA-enriched micro algae diet and control diet. The experiment was carried out during 21-d to determine the normal (control) and DHA-enriched micro algae diet modified milk fat that were taken for further analysis. The melting and crystallization behaviour of the milk fat from the cows fed control and DHA-enriched micro algae diets was studied using differential scanning calorimetry (DSC), Q1000 (TA Instruments, New Castle, DE, United States). DHA-enriched micro algae supplementation strongly affected the melting and crystallization properties of milk fat. Generally, the onset temperature (°C) of milk fat crystallization was significantly lower in DHA-enriched milk fat as compared to the control. The quantity of heat released by fat crystallization expressed as J/g (peak area) was significantly lower in enriched milk fat. DHA-enriched milk fat also had a lower peak maximum temperature as compared to control in all samples investigated. All melting curves displayed two peaks (lower melting and higher melting peaks) and for melting peaks, DHA-enriched milk fat melted at significantly lower temperature as compared to the control indicating an increase in the degree of unsaturation of milk fat. Melting offset temperature was significantly lower for DHA-enriched milk fat as compared to the control. It can be concluded that from the results of this study, micro algae supplementation significantly altered the milk fat composition and positively affected melting and crystallization behaviour of milk fat.

Critical behavior of the fluctuation heat capacity near the glass transition of metallic glasses

The high-frequency shear modulus of five Zr-, Pd-, Cu-based conventional and two high-entropy bulk metallic glasses was measured in a wide temperature range up to the beginning of crystallization. Using these data and general thermodynamic relations, the “fluctuation” heat capacity ΔCf determined by local structural fluctuations in the defect regions is introduced and calculated. It is found that ΔCf temperature dependence for all metallic glasses has a large peak located slightly below or above the glass transition temperature but clearly lower than the crystallization onset temperature. The form of this peak resembles the characteristic λ-peak typical for order–disorder phase transitions. It is suggested that this ΔCf-peak reflects certain underlying critical phenomenon. The critical temperature T0 (peak temperature) and corresponding critical index α are determined. Averaged over all seven metallic glasses under investigation in the initial and relaxed states, the critical index <α>=0.26. The results obtained indicate that the fluctuations of thermal energy near the glass transition bear the marks of a continuous phase transition. However, the derived critical index is between those corresponding to a second-order phase transition (α≈0.1) and a critical transition characterized by a tricritical point (α≈0.5).

Effect of calcium pimelate on crystallization kinetics of polyphenylene sulfide

AbstractThe use of nucleating agents (NAs) to accelerate semicrystalline polymers crystallization is a widely recognized technique during processing. However, the commercially available NA for poly(phenylene sulfide) (PPS) has been rather limited. In this work, it is found that calcium pimelate (CaPim), a commercial nucleating agent for isotactic polypropylene, could also accelerate the crystallization process of PPS. The influence of CaPim addition on the crystallization behaviors of PPS was investigated under non‐isothermal and isothermal condition. Upon the addition of 0.3 wt% CaPim, the crystallization peak temperature and the onset crystallization temperature increases by 5.3 and 8.4°C at 10°C/min cooling rate, and the half‐time of crystallization reduces 51% at crystallization temperature of 272°C. Polarized optical observation revealed a substantial enhancement in nucleation due to the presence of CaPim. Avrami equation analysis suggested that the nucleating agent significantly increased the crystallization rate constant without affecting the growth dimension. Moreover, Lauritzen–Hoffman theory analysis indicateed that the addition of CaPim lowers the nucleation energy barrier, contributing to its high‐nucleation efficiency. These findings demonstrate that calcium pimelate holds promise as an effective nucleating agent for PPS.

The Effects of Emulsifier Addition on the Functionalization of a High-Oleic Palm Oil-Based Oleogel.

Alternatives to oils with high saturated fatty acid content are often liquid oils (high in unsaturated fatty acids) that have a modified structure created either through additives or processing. Emulsifiers are additives that can be used as structuring agents of liquid fats; this process results in products such as oleogels, which can broaden the applications of these oils. This study assessed and compared the effects of mono- and diglycerides at 3%, 5%, 7% and 10% w/w on the mechanical and thermal properties of high-oleic palm oil (HOPO) oleogels. HOPO was heated to 75 °C and mixed with mono- or diglycerides at those four concentrations. The thermomechanical properties of the melted oleogels were assessed using differential scanning calorimetry (DSC). The melted oleogels were cooled to final temperatures of 5 °C, 10 °C and 15 °C under identical cooling rates, after which a puncture test (via a texture analyzer) was used to assess their textures. Finally, polarized light microscopy was used to assess the mechanical changes induced through emulsifier addition. The results showed that the use of mono- and diglycerides significantly modified the thermal and mechanical properties of the oleogels. The addition of saturated monoglycerides promoted a higher-temperature nucleation stage that did not previously occur in HOPO. The onset crystallization temperature increased with the addition of diglycerides, promoting crystallization at higher temperatures of the high-melting fraction of HOPO. The hardness of the oleogel generally increased with emulsifier addition and a reduction of the temperature. The effect of the temperature on the hardness was significantly greater in the diglyceride oleogel than in the monoglyceride oleogel. This study shows that the addition of mono- and diglycerides allows companies to customize their formulations to achieve desired results that may not previously have been possible, thereby facilitating novel uses for these oils within the industry.

Study of Structure and Phase Transformations in Rejuvenated Rapidly Quenched TiNiCu Alloys

Alloys of the quasibinary TiNi-TiCu system manufactured by melt quenching in the form of thin 20–50 μm ribbons have proven to show good potential as materials for the fabrication of micromechanical devices. At high cooling rates (about 106 K/s), this method allows producing high-copper (more than 20 at.%) amorphous alloys which exhibit an excellent shape-memory effect after crystallization. Their properties are known to largely depend on the crystallization conditions and the structure of the initial amorphous material acting as a precursor for the formation of crystal phases. It has been shown recently that the rejuvenation procedure (cryogenic thermocycling) of metallic glasses is one of the most promising methods of improving their properties. In this study, we investigated for the first time the effect of cryogenic thermocycling of rapidly quenched amorphous TiNiCu on the initial state, as well as on structure formation and the phase transformation patterns of subsequent crystallization conducted using various methods. The effect was analyzed utilizing the methods of scanning and transmission electron microscopy, X-ray diffraction analysis, and differential scanning calorimetry. The results show that rejuvenation treatment slightly reduces the glass transition and crystallization onset temperatures and moderately changes the sizes of structural features (grains, martensite plates), the quantity of the martensite phase, and the characteristic temperatures and enthalpy of the martensitic transformation.