Increase In Phase Transition Temperature Research Articles

Characterization of whey protein isolate and pectin composite film catalyzed by small laccase from Streptomyces coelicolor

Abstract In this current study, whey protein isolate (WPI)/pectin biowaste composite film properties was investigated with addition of Streptomyces coelicolor-derived small laccase (SLAC). It was found that different SLAC concentrations has insignificant effect on the film color while best film transparency obtained with 4 U/100 mL SLAC. Optimum mechanical properties were obtained with 6 U/100 mL SLAC indicating best crosslinking effect on the WPI-pectin film. Lowest moisture content (MC), water vapor transmittance (WVP) and oxygen transmittance ( O 2 P) of the film obtained with 6 U/100 mL SLAC, while 4 U/100 mL SLAC resulted in lowest carbon dioxide transmittance (CO2P). Maximum increase in phase transition temperature and absorption peak shift according to DSC and FTIR results, respectively, indicated largest improvement in heat resistance and chemical bond strength of the film with 6 U/100 mL SLAC addition. The XRD results showed that the addition of SLAC was insignificant towards the film crystallinity. The work presents the development of new degradable composite film that can be derived from biowaste compounds for utilization in food processing application.

Large Negative Thermal Expansion and Magnetoelastic Coupling in Metamagnetic Tetragonal (Mn, T)2Sb (T = Cr, V) Alloys

Metamagnetic phase transition of Mn2-xCrxSb (x = 0.07, 0.09, and 0.11) and Mn2-yVySb (y = 0.1, 0.15) alloys had been studied. More Cr and V substitutions lead into increased phase transition temperature, which is confirmed by differential scanning calorimetry (DSC) measurement. The maximized saturation magnetostriction (λs//) of − 1350 ppm and − 610 ppm under 7 T have been realized in Mn1.93Cr0.07Sb alloy and Mn1.9V0.1Sb alloy, respectively, and gradually decreased with more substitution. Giant negative thermal expansion (NTE) is triggered by metamagnetism. The highest linear coefficient of − 42.4 ppm/K is obtained in Mn1.93Cr0.07Sb alloy, but almost zero expansion is obtained in Mn1.85V0.15Sb alloy. The coincident highest ΔSmax associated with the maximized λs// in both Mn2-xCrxSb (x = 0.07, 0.09, and 0.11) and Mn2-yVySb (y = 0.1, 0.15) systems suggests that the strong magnetoelastic coupling is also beneficial to enhance the magnetic entropy change.

Quenching induced enhancement of coupling between the molecule reorientation and grain boundary relaxation in polycrystalline C60

Dielectric spectroscopy was performed on polycrystalline C60 powder at selected frequencies from 111 Hz to 2 MHz as the temperature rose from 100 K to 473 K. About 3 K increase of the first-order phase transition temperature caused by quenching was observed, but disappeared in the second heating cycle. The apparent activation energy of dipole relaxation in low temperature range increases to 387 ± 4 meV which is 19 meV higher than that of pristine C60. Meanwhile, a novel grain boundary (GB) relaxation was also found in the quenched C60. It is suggested that quenching increase the GB viscosity, which facilitates the coupling between the GB motion and C60 orientation jump.

Microstructure and phase transition kinetics of Mg–Ni–Zn alloy phase change thermal storage materials

Metal and alloy heat storage materials are popular in energy storage fields due to their excellent thermal conductivity and high latent heat value. In this research, by changing the ratio to optimize Mg–Ni–Zn alloys, we study the microstructure and thermal properties of alloys with different composition ratios, and the relationship between alloy composition and properties was deeply analyzed. Besides, we also study the thermal analysis kinetics of the alloys. The results show that the Mg–Ni–Zn heat storage alloy mainly contains α-Mg, Mg2Ni, Mg7Zn3, MgZn2 and its eutectic structure. The increase of Zn content is beneficial to the increase of phase transition temperature and phase transition latent heat value, among which the maximum latent heat value of Mg–13%Ni–37%Zn alloy can reach 165 J g−1. In this research, a new type of ternary alloy heat storage material Mg–16%Ni–24%Zn alloy is proposed, and the activation energy of Mg–16%Ni–24%Zn alloy is 1014.99 kJ mol−1 by Coats-Redfern integral equation and extrapolation method. The mechanism function is the Mampel Power rule, and the integral form is G(α)=α32, which is a reference for subsequent researchers.

Crystal structure effect on the phase transition of (Ca0.28Ba0.72)x(Sr0.61Ba0.39)1−xNb2O6 ceramics

(Ca0.28Ba0.72)x(Sr0.61Ba0.39)1−xNb2O6 ceramics have been prepared by a solid-state reaction method. With the increase of x, the nature of the phase transition varies from the diffuse to the normal, and the phase transition temperature increases. The structural origins of these variations were studied by Rietveld refinement and Raman spectroscopy. The results indicate that the change of the phase transition type is related to the site-occupancy factors of cations at A sites and the increased phase transition temperature is because of the enhanced structural deformation of oxygen octahedral. This enhanced ferroelectricity makes the system have potential applications for high-temperature environments.

실리콘 기판 상 바나듐 이산화물 및 알루미늄 질화물 이종 구조 박막에서의 근적외선 레이저 펄스 기반 가역적인 전류 스위칭

In this paper, we demonstrated a reversible current switching in a two-terminal device based on a vanadium dioxide(VO₂) and aluminium nitride(AlN) heterostructure thin film grown on a silicon(Si) substrate using near-infrared laser pulses. The fabricated VO₂/AlN device has a phase transition temperature ∼10K higher than conventional VO₂ devices grown on sapphire substrates. Current switching operation of up to 50mA was possible at various pulse repetition rates in the device with smaller dimensions owing to the increased phase transition temperature, and the average switching contrast was calculated as ∼9634. In particular, the average rising time of the switched current was measured to be ∼36ms, and the falling time was less than 10ms, which is a significantly improved result. Due to the high phase transition temperature and fast switching response, the fabricated device is expected to be beneficially applied to laser-assisted current switching.

Manufacturing of nanoliposomal extract from Sargassum boveanum algae and investigating its release behavior and antioxidant activity.

In this paper, the fabrication of algal extract‐loaded nanoliposomes was optimized based on the central composite response surface design. Different concentrations of phenolic compounds (500, 1,000, and 1,500 ppm) of algal extract and lecithin (0.5, 1.25, and 2% w/w) were applied for preparation of nanoliposomes at process temperatures of 30, 50, and 70°C. Dependent variables were zeta potential, entrapment efficiency, size, and particle size distribution. The particle size of the loaded nanoliposomes ranged from 86.6 to 118.7 nm and zeta potential from −37.3 to −50.7 mV. The optimal conditions were as follows: 0.5% lecithin, 30°C process temperature, and 1,313 ppm of the phenolic compounds extracted from algae. Under these conditions, the experimental entrapment efficiency of the phenolic compounds was 45.5 ± 1.2%. FTIR analysis has verified the encapsulation of algal extract in nanoliposomes. Algal extract phenolic compounds also increased phase transition temperature (Tc) of nanoliposomes (1.6°C to 6.3°C). Moreover, the thermo‐oxidative protection of nanoliposomes for the algal extract has been proved by examining the DSC thermograms. It has been demonstrated that the formulated nanoliposomes have a good stability during storage conditions, and they are able to control the release of phenolic compounds at different pH values. During the encapsulation process, the antioxidant activity of the algal extract has been maintained to an acceptable level. Consequently, algal extract‐loaded nanoliposomes can be used as a natural antioxidant in lipid‐based foods.

Enhanced Ferromagnetism in Cylindrically Confined MnAs Nanocrystals Embedded in Wurtzite GaAs Nanowire Shells.

Nearly a 30% increase in the ferromagnetic phase transition temperature has been achieved in strained MnAs nanocrystals embedded in a wurtzite GaAs matrix. Wurtzite GaAs exerts tensile stress on hexagonal MnAs nanocrystals, preventing a hexagonal to orthorhombic structural phase transition, which in bulk MnAs is combined with the magnetic one. This effect results in a remarkable shift of the magneto-structural phase transition temperature from 313 K in the bulk MnAs to above 400 K in the tensely strained MnAs nanocrystals. This finding is corroborated by the state of the art transmission electron microscopy, sensitive magnetometry, and the first-principles calculations. The effect relies on defining a nanotube geometry of molecular beam epitaxy grown core-multishell wurtzite (Ga,In)As/(Ga,Al)As/(Ga,Mn)As/GaAs nanowires, where the MnAs nanocrystals are formed during the thermal-treatment-induced phase separation of wurtzite (Ga,Mn)As into the GaAs-MnAs granular system. Such a unique combination of two types of hexagonal lattices provides a possibility of attaining quasi-hydrostatic tensile strain in MnAs (impossible otherwise), leading to the substantial ferromagnetic phase transition temperature increase in this compound.

Electrostatic expansion of polyelectrolyte microgels: Effect of solvent quality and added salt

We report dynamic light scattering data for a PNIPAM based microgel copolymerised with 2% ionic groups. The hydrodynamic radius is measured as a function of temperature (which varies the solvent quality) and added salt concentration (cS) from salt-free conditions up to cS = 0.1 M. Incorporation of the ionic co-monomer leads to an increase of the volume phase transition temperature with respect to a non-ionic microgel from T≃306 K to T≃317 K in salt-free water. The hydrodynamic radius varies as RH∝cS-0.05 in good solvent (T≃278–298 K) and RH∝cS-0.15 in poor solvent (T≃313–319 K). Deep into the poor solvent regime the microgel is collapsed for all salt concentrations and RH∝cS0. Data are fitted to the Flory-Rehner model modified to account for the osmotic pressure of the counterions through the Donnan model. We find that the Flory-Rehner-Donnan (FRD) model does not fully account for the experimental observations, particularly at low ionic strengths, possibly due to the influence of electrostatic excluded volume. The disagreements between theory and experiments are greatly reduced if a cross-linking density three times lower than that expected from synthesis is assumed. The scaling theory exponents for the variation of gel size with temperature and added salt are not in agreement with the experimental results presented.

Aqueous solution behavior of thermoresponsive polyzwitterionic microgels based on poly(N-vinylcaprolactam) synthesized via RAFT precipitation polymerization

A new route to synthesize stimuli-responsive poly(N-vinylcaprolactam) (PNVCL) microgels decorated with zwitterionic poly(sulfobetaine) (PSB) chains was developed, using reversible addition–fragmentation chain transfer (RAFT) precipitation polymerization. The polyzwitterionic PSB macro-RAFTs of controlled molecular weight were synthesized by RAFT polymerization of sulfobetaine (SB). Using this method, macro-RAFTs with good control over the molecular weight could be achieved. The PSB macro-RAFTs, having different molecular weights (1000, 5000, 10,000 g/mol) and concentrations (1, 2, 2.5 mol%), were used along with different amount of the cross-linker N,N'-methylenebisacrylamide (BIS) (1.5 and 2.5 mol%) in the precipitation polymerization of PNVCL microgels to obtain varying amounts of surface-grafted polyzwitterionic chains of controlled length and variable cross-linking degrees. The successful incorporation of PSB macro-RAFTs into PNVCL microgels was characterized by FTIR and 1H NMR studies. Increasing the PSB concentration and BIS content in the PNVCL microgels resulted in a linear increase in electrophoretic mobility (µe) and volume phase transition temperature (VPTT). However, increasing the molecular chain length of the zwitterionic macro-RAFT resulted in a shift of VPTT towards lower temperatures. This kind of stimuli-responsive, polyzwitterion decorated PNVCL microgels can be a potential material for biomedical applications.

Nonvolatile manipulation of the magnetocaloric effect in Ni43Co7Mn39Sn11/(011)PMN-PT composite by electric fields

The nonvolatile electric field control of the magnetocaloric effect (MCE) can be achieved in the Ni-Co-Mn-Sn/(011)0.7Pb(Mg1/3Nb2/3)O3–0.3PbTiO3 composite with the application of asymmetric bipolar electric fields. By controlling the electric fields, different nonvolatile strain states can be obtained and transmit to Ni-Co-Mn-Sn ribbon, which leads to an increase of phase transition temperature. As a result, the effective magnetic refrigeration temperature region can be extended by applying the asymmetric bipolar electric fields. This nonvolatile control of the MCE would have promising applications in designing more efficient magnetocaloric devices.

Control of continuous α-Al2O3 fibers by self-seeding and SiO2-Sol doping

Abstract The effects of self-seeding and SiO2-sol doping on the sol–gel preparation of α-Al2O3 fibers are investigated. Self-seeding induces heterogeneous nucleation of α-Al2O3 from the precursor gels at a low temperature of 800 °C. Using transmission electron microscopy and X-ray diffraction analysis, the primary crystallite size (dp) of α-Al2O3 in the seeded fibers is determined as ∼30 nm, which is much smaller than the size (∼50 nm) in the unseeded fibers. Moreover, self-seeding increases the γ-to-α transformation kinetics and lowers the transformation temperature by 175 °C. Heating at 1500 °C could sinter the self-seeded α-Al2O3 fibers nearly to full density with a grain size of ∼1 μm. By doping with SiO2 sols, this final grain size can be decreased with suppression of the grain boundary migration, at the expense of increased phase transition temperature. Therefore, dense α-Al2O3 fibers of submicron grains could be achieved by the combination of self-seeding and SiO2-sol doping.

Non-equilibrium Phase Transitions in 2D Small-World Networks: Competing Dynamics

Abstract This article offers a detailed analysis of the Ising model in 2D small-world networks with competing Glauber and Kawasaki dynamics. The non-equilibrium stationary state phase transitions are obtained in these networks. The phase transitions are discussed, and the phase diagrams are obtained via Monte Carlo simulations and finite-size analyzing. We find that as the addition of links increases the phase transition temperature increases and the transition competing probability of tricritical point decreases. For the competition of the two dynamics, ferromagnetic to anti-ferromagnetic phase transitions and the critical endpoints are found in the small-world networks.

Effect of Zr Doping on the Magnetic and Phase Transition Properties of VO2 Powder

In this work, V1−xZrxO2 powder (x = 0, 0.01, 0.02, 0.04) was synthesized by two step hydrothermal method. The micro-topography, magnetic and phase transition properties have been investigated using various measurement techniques. All prepared V1−xZrxO2 powder samples exhibit monoclinic structure at room temperature. With the Zr4+ ions doping concentration increased, the shapes of VO2 particles change from spherical to rectangular slice. Besides, the saturation magnetic moment of the samples decrease with the increase of doped Zr4+ ions concentration, while their phase transition temperature increase gradually with Zr ions doping at a rate of around 2 °C/at% on average. We investigated the Zr doping effects on V-V dimers and confirmed the role of V-V dimers in phase transition. We speculate that more V-V dimers form with Zr doping by magnetic measurements, which result in the monoclinic phase of Zr-doped VO2 sample is more stable than rutile phase. Therefore the phase transition temperature is elevated by Zr doping in our experiment. We further consider that the VO2 phase transition should be ascribed to Peierls transition caused by the changing of V-V dimers.

Phase Transition and Side-Chain Crystallization of Poly(methyl vinyl ether-alt-maleic anhydride)-g-Alkyl Alcohol Comb-like Polymers

A series of poly(methyl vinyl ether-alt-maleic anhydride)-g-alkyl alcohol (PVEM -Cn) comb-like polymers were synthesized by a simple esterification reaction between poly(methyl vinyl ether-alt-maleic anhydride) and n-alkyl alcohol with n = 14–26. Thermal property, side-chain crystallization, and phase transition behavior of PVEM-Cn comb-like polymers were investigated by 1H NMR,DSC, variable-temperature X-ray scattering and FTIR, as well as solid-state 13C CP/MAS NMR. Obvious side-chain crystallization behavior from the pended side chains onto the PVEM backbone is well confirmed. With the side-chain length increasing from 14 to 26, phase transition temperature and melting enthalpy both increase from 30.1 to 79.4 °C and from 17.1 to 55.0 kJ/mol, respectively, and the crystallizable carbon atoms (Nc) also vary from Nc = 5.6 to 17.7 accordingly. Regular trans conformation state first transforming into irregular trans conformational disordered one and then to gauche state is well demonstrated, and the chain p...

Tacticity effect on the upper critical solution temperature behavior of Poly(N-isopropylacrylamide) in an imidazolium ionic liquid

Isotactic poly (N-isopropylacrylamides) (PNIPAMs) with a wide range of tacticity exhibit upper critical solution temperature (USCT) type phase transition in an ionic liquid, 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([BMIM][TFSI]). The phase transition temperature becomes higher with increasing isotacticity, since more amide groups are aligned along the same side of backbones to form stronger intramolecular hydrogen bonding. Phase diagrams of highly isotactic PNIPAMs show prominent UCST peaks at low concentrations, similar with the typical polymer solution, which implies the dissolution of isotactic PNIPAMs is dominated by the entropy-driven effect. The increase in phase transition temperature with molecular weight is also from the entropic reason. The phenomena above reveal that the phase transition behavior of PNIPAMs in ionic liquids is highly influenced by tacticity effect.

Effect of B doping on phase transition and magnetic properties of Mn50Ni40In10-xBx: Experimental and theoretical investigation

A series of Mn50Ni40In10-xBx (x = 0 - 4) alloys was synthesized and the effect of B-doping on the structure, phase transition and magnetic properties in them has been investigated theoretically and experimentally. It is found that increasing boron content leads to the contraction of cell volume and increase of the martensitic transformation temperature. The doping of B also enhances antiparallel coupling between Mn spin moments in martensitic Mn50Ni40In10-xBx and lowers the Curie temperature of the austenite. Electronic structure calculations were carried out based on Mn50Ni37.5In12.5 and Mn50Ni37.5In6.25B6.25 supercells, which were close to the experimental compositions. The extra Ni atoms substituting for In/B prefer entering Mn (A) site and push Mn to the D site. In austenite ferromagnetic coupling between Mn moments on B, D sites is preferable, while in martensite the coupling between them becomes antiferromagnetic, which leads to a decrease of the total spin moment compared with the austenite. The total energy difference between the cubic austenite and tetragonal martensite increases with the substitution of boron, implying the increase of phase transition temperature. This can be explained from their DOS structures. These results agree well with experimental results and make reasonable explanation for them.

Structural Phase Transition: Interfacial‐Field‐Induced Increase of the Structural Phase Transition Temperature in Organic–Inorganic Perovskite Crystals Coated with ZnO Nanoshell (Adv. Mater. Interfaces 14/2018)

Structural Phase Transition: Interfacial‐Field‐Induced Increase of the Structural Phase Transition Temperature in Organic–Inorganic Perovskite Crystals Coated with ZnO Nanoshell (Adv. Mater. Interfaces 14/2018)

Interfacial‐Field‐Induced Increase of the Structural Phase Transition Temperature in Organic–Inorganic Perovskite Crystals Coated with ZnO Nanoshell

AbstractThe hybrid organic–inorganic perovskites are known to exhibit a complex crystalline structure, which allows for the structural phase transitions among the orthorhombic, tetragonal, and cubic phases that occur at different temperatures. This behavior of the organic–inorganic perovskites can significantly alter their optoelectronic properties. Here, using photoluminescence spectroscopy, it is shown that the structural orthorhombic‐to‐tetragonal phase transition temperature in MAPbI3 perovskite crystal can be increased from 135 to 160 K upon coating with ZnO nanoshell. The phenomenon is attributed to the interfacial‐field‐induced atomic rearrangement in the near‐surface area. The findings shed light on the great importance of the interfacial electric field effect on the structural and optical properties of the organic–inorganic perovskites, which hold great promise for their potential applications in the structural‐phase‐controlled optoelectronic and photovoltaic devices.

Thermal Emittance of $$\hbox {La}_{0.7}\hbox {Ca}_{0.3-x}\hbox {K}_x\hbox {MnO}_3$$ La 0.7 Ca 0.3 - x K x MnO 3 Coatings on Aluminum Substrate

A novel thermal control coating was presented based on the thermochromism of manganite. The pigment of K-doped manganite nanoparticles was dispersed into polymer matrix to prepare the coating with curing below 200 $$^{\circ }$$ C. The nanoparticles size mainly distributes around 100–200 nm, and it shows a comparable stoichiometric ratio. The phase transition of the nanoparticles was observed from ferromagnetic metallic to paramagnetic insulator state. With increasing K doping level, the phase transition temperature increases, achieving controllable adjustment. Coating surface with and without pore defect was obtained by different polymer matrix. A sharp emittance variation was observed with increasing temperature in K-doped coating. The variation magnitude of emittance is up to 0.46, which is attractive to space thermal control. It is suggested that the pigment content of 50 wt% is sufficient to realize a large emittance variation.