Shift Of Transition Temperature Research Articles

Nanoindentation Test of Ion-Irradiated Materials: Issues, Modeling and Challenges

Exposure of metals to neutron irradiation results in an increase in the yield strength and a significant loss of ductility. Irradiation hardening is also closely related to the fracture toughness temperature shift or the ductile-to-brittle transition temperature (DBTT) shift in alloys with a body-centered cubic (bcc) crystal structure. Ion irradiation is an indispensable tool in the study of the radiation effects of materials for nuclear energy systems. Due to the shallow damage depth in ion-irradiated materials, the nanoindentation test is the most commonly used method for characterizing the changes in mechanical properties after ion irradiation. Issues that affect the analysis of irradiation hardening may arise due to changes in the surface morphology and mechanical properties, as well as the inherent complexities in nanoscale indentation. These issues, including changes in surface roughness, carbon contamination, the pile-up effect, and the indentation size effect, with corresponding measures, were reviewed. Modeling using the crystal plasticity finite element method of the nanoindentation of ion-irradiated materials was also reviewed. The challenges in extending the nanoindentation test to high temperatures and to multiscale simulation were addressed.

Effect of isothermal aging on Poly(N-isopropylacrylamide): Correlation between chemical structure and phase transition temperature property

Poly(N-isopropylacrylamide) (PNIPAm) is a stimuli-responsive polymer with wide applications as a scaffold in biomedical applications. This study presents the PNIPAm's thermoresponsive behavior during storage and its stability in potential pharmaceutical formulations as a drug delivery excipient. Therefore, the turbidity curves of linear PNIPAm aqueous solutions are investigated before and after its thermal oxidation under air at 120°C and 130°C. First, PNIPAm aqueous phase separation diagram is determined for unaged polymer and then compared to thermally aged samples at two distinct points (1 and 10%(w/w)). After isothermal aging, the transition temperature has increased with a shift up to 4°C. The correlation between PNIPAm's chemical structure and phase transition temperature properties is illustrated in terms of chemical modifications, macromolecular changes as well as the polar/non-polar groups balance. It is observed that the water affinity and glass transition temperature (Tg) have increased at the macromolecular level. In addition, chains scissions are highlighted and seem to explain the shift of transition temperature. Chemical changes have revealed the presence of supplementary polar groups induced by aging. This multiscale study suggests a possible mechanism for the partial thermal oxidation based on all the observations.

Super soft poly(N-isopropylacrylamide) microgels using functionalized starch nanoparticles as crosslinker

A set of poly(N-isopropylacrylamide) p(NIPAM) microgels was successfully prepared through precipitation polymerization (PP) using acryloyl starch nanoparticles (ASNPs) as crosslinkers. Functionalized starch nanoparticles used in microgel preparation, with a degree of substitution (DS) of 0.78 (ASNP12) or 1.37 (ASNP24) were found to have different properties. Dynamic light scattering (DLS) revealed that microgels prepared with ASNP12 exhibit a higher swelling capacity compared to the microgels designed with ASNP24, which was also observed by atomic force microscopy (AFM), showing super soft microgels flattened into disk shape on the substrate. This may be related to softer and surface smoothed microgels. Turbidity analysis revealed a slight shift of the so-called volume phase transition temperature (VPTT) towards higher values for microgels synthesized with ASNP24, indicating its contribution as a hydrophilic comonomer. Considering their high swelling capacity, these bio-based crosslinked microgels are potential materials for adsorptive processes. They can also be considered as candidates for biomedical applications due to the presence of a biopolymer in their structure.

Impact of neutron irradiation on the tensile properties of advanced EUROFER97-type steels

Tensile properties (strength and ductility) of three different experimental EUROFER97 variants and two standard EUROFER97 products were investigated before and after neutron irradiation performed in the temperature range 275–300 °C up to ∼3 dpa, i.e a damage dose comparable to the end-of-life of ITER operation. The grades with the chemical compositions within and outside the specifications of EUROFER97 steel followed alternative thermo-mechanical treatments (TMT) as compared to the reference EUROFER97. Mechanical properties were assessed with hardness and tensile tests, while fracture surface was investigated by scanning electron microscopy. Post irradiation examination was conducted to evaluate the hardening behavior, change in ductility and fracture surface after irradiation. Furthermore, Ductile-to-Brittle Transition Temperature (DBTT) shift due to neutron irradiation was estimated based on the correlation formerly established for EUROFER97 at the studied irradiation temperature.

Enhancing performance: insights into the augmentation potential of acrylonitrile butadiene styrene/boron nitride composites

Abstract This work aims to investigate the morphological, mechanical and thermal characteristics of boron nitride (BN)-reinforced acrylonitrile-butadiene styrene (ABS) composites. ABS and ABS/BN composites with a maximum BN loading up to 8 wt% were developed using two-roll mill followed by compression molding. Scanning electron microscopy (SEM) images presented interlinking of BN flakes in the dimple texture of ABS. A modest decrease in tensile properties was observed for the composites. The tensile strength and impact strength for the ABS/BN8 specimen were lowered by 4.7 and 81.7 %, respectively. On the other hand, hardness increased by 3.39 % for ABS/BN8 composite. The interaction effect of BN in the ABS matrix on the thermal properties was assessed using thermo-gravimetric analysis (TGA). An enhancement in the thermal-stability was observed for BN incorporated ABS. There is a modest shift in glass transition (T g) temperature to a higher value for the ABS/BN composites.

Facile purification of glass fiber powder by sedimentation for enhanced epoxy resin composites

Glass fiber powder contains two distinct forms: crumb-shaped and rod-shaped glass fiber powder particles. The shape and size of the particles in glass fiber powder have a great influence on its application. In order to separate rod-shaped glass fiber, the effects of different dispersants, such as SHMP, NaOL, and Na2SiO3 on them were investigated by settling experiments. Zeta potential, X-ray photoelectron spectroscopy (XPS), optical microscope, and other methods were used to analyze the adsorption behavior and settling mechanism. Three-point bending experiment and dynamic mechanical analysis (DMA) were used to evaluate the performance of epoxy resin composites reinforced with the raw glass fiber powder and the rod-shaped glass fiber powder. The results show that SHMP can effectively separate crumb-shaped glass fiber powder and rod-shaped glass fiber powder, leading to a notable increase in sedimentation recovery difference, up to Δ=51.08%. A preferential sedimentation separation mechanism is proposed to elucidate the settling mechanism. When the content of glass fiber powder and rod-shaped glass fiber is 5%, the glass transition temperature shifts significantly towards higher values, leading to the optimum comprehensive mechanical properties of the composites. Compared with the original epoxy resin, the flexural strength increased by 10.38% to 95.18 MPa and by 20.11% to 103.57 MPa. Similarly, the storage modulus increased by 14.14% to 2083 MPa and by 21.64% to 2220 MPa.

In-situ polymerization of polythiophene/silicon carbide nanocomposites for gas sensing and optoelectronic devices

Silicon carbide (SiC)-reinforced polythiophene (PTh) nanocomposites were synthesized by oxidative in-situ polymerization. The successful inclusion of SiC nanoparticles into the PTh was confirmed by the characteristic peak of Si–C bond around 865 cm−1 in the Fourier transform infrared (FT-IR) spectra. The X-ray diffraction (XRD) patterns demonstrate that the amorphous nature of PTh reduces with the addition of SiC. The intensity of UV–Vis absorbance increased proportionally with filler loading, indicating improved optical properties for PThSiC7 (polythiophene/silicon carbide 7 wt%) nanocomposite compared to pristine PTh. Field emission scanning electron microscopy (FE-SEM) images illustrate the changes in surface morphology of PTh with the addition of SiC and uniform dispersion was observed in PThSiC7. The formation of spherical-shaped moieties was confirmed using transmission electron microscopy (TEM). The shifts in degradation and glass transition temperatures towards higher values were attributed to the enhanced thermal properties of the nanocomposites. Temperature-dependent studies on the electrical and dielectric properties of the samples underscored the excellent conductivity exhibited by PThSiC7 (7 × 10−3 S/cm) with a low activation energy of 0.058 eV. In response to the growing demand for gas sensors, samples were tested to sense ammonia gas, demonstrating that PThSiC nanocomposites were more sensitive than PTh. The controllable optical properties, thermal stability, electrical characteristics, and gas sensing performance of the PThSiC nanocomposites suggest their potential as a promising material for the development of advanced energy storage systems, sensors, and optoelectronic devices.

Dielectric and Magnetoelectric Properties of TGS-Magnetite Composite.

In our studies, we combined two powdered materials, i.e., ferroelectric triglycine sulfate (TGS) and ferrimagnetic magnetite Fe3O4, to obtain a magnetoelectric composite. The ferroelectric (E) part, i.e., TGS, was a hybrid organic-inorganic crystal, which we obtained as a pure single crystal from an aqueous solution using a static water evaporation method. The magnetic (M) part of the composite was commercially available magnetite. The samples used for the dielectric and magnetoelectric measurements were cold-pressed and made in the form of a circular tablet. The measuring electrodes were made of silver-based conductive paste and were attached to the sample. We measured the temperature dependencies of selected electrical parameters (e.g., dielectric permittivity, electrical capacity, and loss angle tangent). We used the dynamic lock-in method to check whether magnetoelectric coupling existed between the E and M phases. In this paper, we present the dielectric properties of pure monocrystalline TGS as a reference sample and compare the results for TGS powder, TGS + carbon powder, and TGS + Fe3O4 powder. The magnetoelectric coupling presumably appeared for the composite TGS + 10 wt. % Fe3O4, as evidenced by the shift in the phase transition temperature in the TGS. Moreover, the theoretical interpretation of the effect is proposed.

Intertwined crystal structure, magnetic, and charge transport properties in mixed valent A-site ordered manganite NdBaMn2O6

In the present work, we report a correlation between crystal structure, magnetic, and electrical properties in an exotic magnetic compound, NdBaMn2O6 having ∼92% ordering between Nd and Ba, investigated using temperature-dependent synchrotron x-ray diffraction (XRD), dc magnetization and transport measurements. Temperature-dependent XRD data reveals that the compound undergoes various complex crystallographic phase transitions from high-temperature (T > 320 K) P4/mmm phase to intermediate (320 K – 280 K) Cmmm phase to a mixed (Cmmm and P21am) phase (280 K – 220 K) and to low-temperature P21am phase (T < 220 K). It is found that these crystallographic phase compositions play a crucial role in controlling its magnetic and transport properties. Temperature-dependent dc magnetization data show a sharp drop at the onset of mixed phase (Cmmm + P21am) at 280 K followed by a broad hump at ∼ 220 K where mixed phase to P21am transition occurs, thus indicating a correlation between the structural and magnetic properties. The dc magnetization in the mixed phase region is calculated by considering a superposition of the magnetic moments of Cmmm and P21am phases weighted by the fraction of each phase, which exactly follows the experimental magnetization data. Temperature variation of resistivity data shows a jump at ∼260 K, a temperature corresponding to 50–50% phase composition of Cmmm and P21am phases. The compound shows insulating behavior over a whole temperature range as confirmed from the resistivity data. Further, application of magnetic field causes a shift of magnetic and transport transition temperatures which may be due to the magnetic field induced structural transition in the system.

54 K Spin Transition Temperature Shift in a Fe6L4 Octahedral Cage Induced by Optimal Fitted Multiple Guests.

Spin-crossover (SCO) coordination cages are at the forefront of research for their potential in crafting next-generation molecular devices. However, due to the scarcity of SCO hosts and their own limited cavities, the interplay between the SCO host and the multiple guests binding has remained elusive. In this contribution, we present a family of pseudo-octahedral coordination cages (M6L4, M = ZnII, CoII, FeII, and NiII) assembled from a tritopic tridentate ligand L with metal ions. The utilization of FeII ion leads to the successful creation of the Fe6L4-type SCO cage. Host-guest studies of these M6L4 cages reveal their capacity to encapsulate four adamantine-based guests. Notably, the spin transition temperature T1/2 of Fe6L4 is dependent on the multiple guests encapsulated. The inclusion of adamantine yields an unprecedented T1/2 shift of 54 K, a record shift in guest-mediated SCO coordination cages to date. This drastic shift is ascribed to the synergistic effect of multiple guests coupled with their optimal fit within the host. Through a straightforward thermodynamic cycle, the binding affinities of the high-spin (HS) and low-spin (LS) states are separated from their apparent binding constant. This result indicates that the LS state has a stronger binding affinity for the multiple guests than the HS state. Exploring the SCO thermodynamics of host-guest complexes allows us to examine the optimal fit of multiple guests to the host cavity. This study reveals that the T1/2 of the SCO host can be manipulated by the encapsulation of multiple guests, and the SCO cage is an ideal candidate for determining the multiple guest fit.

Experimental study on coupled caloric effect driven by dual fields in metamagnetic alloy ErCo2

This study presents an experimental investigation of the coupled caloric effect driven by dual-fields in metamagnetic alloy ErCo2 with strong magneto-structural coupling. Magnetic measurements were conducted under different pressures, revealing that the application of hydrostatic pressure stabilizes a small volume of paramagnetism (PM) phase, resulting in a shift of the phase transition temperature towards the low-temperature region. This shift is opposite to the temperature associated with the magnetic field-driven phase transition. As pressure increases, the metamagnetic transition in ErCo2 is suppressed, and the hysteresis disappears. However, the produced cross-coupling caloric effect compensates the decrease in entropy change caused by the disappearance of the metamagnetic transition. As a result, a reversible giant magnetocaloric effect of 46.2 J/(kg·K) without hysteresis is achieved at a pressure of 0.910 GPa. Moreover, we propose that the temperature span of ErCo2 can be significantly widened by optimizing the thermodynamic pathway of the magnetic and pressure fields, overcoming the defect of a narrow temperature range.

The Role of Diamonds Dispersed in Ferronematic Liquid Crystals on Structural Properties

A study of the role of diamond nanoparticles on 5CB liquid crystal composites with Fe3O4 nanoparticles is presented. Composite ferronematic systems based on the nematic liquid crystal 5CB doped with Fe3O4 magnetic nanoparticles and additionally bound to diamond nanoparticles (DNPs), of a volume concentration of 3.2 mg/mL, 1.6 mg/mL and 0.32 mg/mL, were investigated using both magneto-optical effect and surface acoustic waves (SAWs) to study the role of diamond nanoparticles on the structural properties of ferronematic liquid crystals. The responses of light transmission and SAW attenuation to an external magnetic field were investigated experimentally under a linearly increasing and decreasing magnetic field, respectively. Investigations of the phase transition temperature shift of individual composites were also performed. The experimental results highlighted a decrease in the threshold field in the ferronematic LC composites compared to the pure 5CB as well as its further decrease after mixing Fe3O4 with diamond powder. Concerning the transition temperature, its increase with an increase in the volume fraction of both kinds of nanoparticles was registered. The role of diamond nanoparticles in the structural changes and the large residual light transition and/or attenuation (memory effect) were also observed. The presented results confirmed the potential of diamond nanoparticles in nematic composites to modify their properties which could lead to final applications.

Sustainable Materials with Improved Biodegradability and Toughness from Blends of Poly(Lactic Acid), Pineapple Stem Starch and Modified Natural Rubber.

Poly(lactic acid) (PLA), derived from renewable resources, plays a significant role in the global biodegradable plastic market. However, its widespread adoption faces challenges, including high brittleness, hydrophobicity, limited biodegradability, and higher costs compared to traditional petroleum-based plastics. This study addresses these challenges by incorporating thermoplastic pineapple stem starch (TPSS) and modified natural rubber (MNR) into PLA blends. TPSS, derived from pineapple stem waste, is employed to enhance hydrophilicity, biodegradability, and reduce costs. While the addition of TPSS (10 to 40 wt.%) marginally lowered mechanical properties due to poor interfacial interaction with PLA, the inclusion of MNR (1 to 10 wt.%) in the PLA/20TPSS blend significantly improved stretchability and impact strength, resulting in suitable modulus (1.3 to 1.7 GPa) and mechanical strength (32 to 52 MPa) for diverse applications. The presence of 7 wt.% MNR increased impact strength by 90% compared to neat PLA. The ternary blend exhibited a heterogeneous morphology with enhanced interfacial adhesion, confirmed by microfibrils and a rough texture on the fracture surface. Additionally, a downward shift in PLA's glass transition temperature (Tg) by 5-6 °C indicated improved compatibility between components. Remarkably, the PLA ternary blends demonstrated superior water resistance and proper biodegradability compared to binary blends. These findings highlight the potential of bio-based plastics, such as PLA blends with TPSS and MNR, to contribute to sustainable economic models and reduce environmental impact for using in plastic packaging applications.

Grain size effect on the transport properties of polycrystalline Bi(000l) films grown in MgO(001) and glass

The crystal growth and transport properties of the polycrystalline Bi(0001) films grown on MgO(001) and glass substrates were compared. The morphology and electron transport properties with different thickness have been analyzed. The stress-induced bandgap leads to the shift of transition temperature from semimetal to semiconductor transition. Compared with MgO(001) substrates, Bi(0001) thin films on glass substrates have the higher semimetal-semiconductor transition temperature. Furthermore, the electron transport performance is improved, which is attributed to the strain-free van-der-Waals epitaxial preferred orientation grown on the glass substrate. The strain effect on the transport performance is greater than that on in-plane grain boundaries.

Utilizing a blend of expandable graphite and calcium/zinc stearate as a heat stabilizer environmentally friendly for polyvinyl chloride

AbstractPolyvinyl chloride (PVC) is one of the most important commercial plastics but it is thermally unstable at processing temperatures. Therefore, heat stabilizers are widely used to safeguard by improving resistance of PVC products at high temperature. But most of them are a highly toxic that can cause severe health issues in humans and harmful to the environment. In the present study mixed of calcium/zinc stearate heat stabilizer and green Expandable graphite (EG) is prepared via hydrothermal treatment using additives of nontoxic, environmental protection. The characteristics of the thermal stability of poly vinyl chloride can be investigated by Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) will be used to examine structure of the heat stabilizers, A universal testing equipment will be used to determine the mechanical properties and thermal gravimetric analysis (TGA). From TGA results the weight loss was 43.49% at 342°C for sample with Ca/Zn‐ stearate, while wt loss is 55.87% at 260°C for sample with EG which increase thermal stability. Differential scanning calorimetry affirmed the enhancement of PVC's thermal stability, showing a shift in the glass transition temperature an increase of 67°C. Mechanical tests indicated that samples with EG exhibited higher tensile strength and elongation at break, emphasizing the positive impact on PVC's mechanical properties. The burning test highlighted thermal stability of EG‐containing samples, retaining color and structure even after exposure to 180°C heat. This innovative approach not only enhances thermal stability but also aligns with eco‐friendly principles, making it a promising solution for improving PVC properties.Highlights Ca/Zn‐ stearate, expandable graphite developed by a safe hydrothermal process. Comprehensive analysis indicates improved thermal stability. Safe stabilization of eco‐friendly calcium/zinc, expandable graphite. Effective solution: Eco‐friendly, improved PVC properties. Expandable graphite improved mechanical properties of PVC.

Magnetostriction and Magnetocaloric Properties of the Mn&lt;sub&gt;1 – &lt;i&gt;x&lt;/i&gt;&lt;/sub&gt;Fe&lt;sub&gt;&lt;i&gt;x&lt;/i&gt;&lt;/sub&gt;As System

Abstract—The results of studying the temperature dependence of the magnetocaloric effect (ΔТad), thermal expansion and magnetostriction in the Mn1 – хFexAs (х = 0.003, 0.006) system in magnetic fields up to 8 T are presented. It is shown that an increase in the iron concentration in the Mn1 – xFexAs system leads to a shift in the phase transition temperature towards low temperatures by 15 K. In a field of 8 T, the value ΔTad = 8.3 K for the Mn0.997Fe0.003As sample at the initial temperature T0 = 318 K, and ΔTad = 7.7 K for Mn0.994Fe0.006As at T0 = 307 K. The data on thermal expansion and magnetostriction show that the magnetostriction decreases with increasing iron concentration, which also leads to a decrease in the magnetocaloric effect.

Coil-Helix Block Copolymers Can Exhibit Divergent Thermodynamics in the Disordered Phase.

Chiral building blocks have the ability to self-assemble and transfer chirality to larger hierarchical length scales, which can be leveraged for the development of novel nanomaterials. Chiral block copolymers, where one block is made completely chiral, are prime candidates for studying this phenomenon, but fundamental questions regarding the self-assembly are still unanswered. For one, experimental studies using different chemistries have shown unexplained diverging shifts in the order-disorder transition temperature. In this study, particle-based molecular simulations of chiral block copolymers in the disordered melt were performed to uncover the thermodynamic behavior of these systems. A wide range of helical models were selected, and several free energy calculations were performed. Specifically, we aimed to understand (1) the thermodynamic impact of changing the conformation of one block in chemically identical block copolymers and (2) the effect of the conformation on the Flory-Huggins interaction parameter, χ, when chemical disparity was introduced. We found that the effective block repulsion exhibits diverging behavior, depending on the specific conformational details of the helical block. Commonly used conformational metrics for flexible or stiff block copolymers do not capture the effective block repulsion because helical blocks are semiflexible and aspherical. Instead, pitch can quantitatively capture the effective block repulsion. Quite remarkably, the shift in χ for chemically dissimilar block copolymers can switch sign with small changes in the pitch of the helix.

Enhanced electrocaloric effect in Sr-doped Ba0.85Ca0.15Zr0.1Ti0.9O3 lead-free thin films near room temperature

Ferroelectric thin films with giant room-temperature electrocaloric effect (ECE) could be very useful in design of solid-state refrigeration devices. Here, lead-free Ba0.85Ca0.15-xSrxZr0.1Ti0.9O3 (BCZT-xSr, 0.01 ≤ x ≤ 0.10) thin films are successfully prepared on the substrates (Pt/Ti/SiO2/Si) via sol-gel route, and the effect of the Sr substitution on the structure, electric properties and ECE of the films were investigated. The dielectric analyses show that the rhombohedral-tetragonal phase transition temperature (TR-T) move to a higher temperature and the tetragonal-cubic phase transition temperature (Tm) shift to a lower temperature with increasing Sr content, and finally the TR-T peaks merge into the Tm peaks at room temperature. The BCZT-0.05Sr film presents a giant ECE with ΔT = 27.1 K and ΔS = 30.6 J K−1 kg−1 at 800 kV cm-1 near room temperature (301 K). The giant ΔT benefits from a multiphase coexisting region with successive R-T and T-C phase transition character near room temperature. These results indicate that the lead-free Sr-doped BCZT thin film is an attractive material for application in ECE refrigeration devices.

Improved miscibility and toughness of biological poly(3-hydroxybutyrate-co-4-hydroxybutyrate)/poly(lactic acid) blends via melt-blending-induced thermal degradation

Polymer blending has been a facile method to resolve the brittle issue of poly(lactic acid) (PLA). Yet, miscibility becomes the primary concern that would affect the synergy effect of polymer blending. This study aimed to improve the miscibility of poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P34HB) and PLA by lowering their molecular weights via a melt-blending-induced thermal degradation during mechanical mixing to form m-P34HB/PLA blends. The molecular weight of the P34HB was significantly reduced after blending, thereby improving the miscibility of the blends, as evidenced by the shift of glass transition temperatures. Also, simulation based on Flory-Huggins theory demonstrated increased miscibility with decreasing molecular weight of the polymers. Moreover, the thermal gravimetric analysis revealed that the PLA provided a higher shielding effect to the P34HB in the blends prepared by melt-blending than those by solution-blending, that the addition of PLA could retard the chain scission of P34HB and delay its degradation. The addition of m-P34HB at 20 wt% in the blend contributed to a 60-fold enhancement in the elongation at break and an increment of 4.6 folds in the Izod impact strength. The enzymatic degradation using proteinase K revealed the preferential to degrade the PLA in the blends and followed the surface erosion mechanism.

Tracing titanomagnetite alteration with magnetic measurements at cryogenic temperatures

SUMMARY Titanomagnetite containing up to 0.6–0.7 Ti atoms per formula unit is a primary magnetic mineral phase in submarine basalts and in some terrestrial volcanic rocks. On a geological timescale, it often undergoes alteration, forming new magnetic phases that may acquire (thermo)chemical remanent magnetization. The initial stage of this natural process can be modelled by prolonged laboratory annealing at moderately elevated temperatures. In this study, our goal is to characterize the alteration products resulting from annealing a submarine basalt containing homogeneous titanomagnetite Fe3−xTixO4 (x ≈ 0.46) at temperatures of 355, 500 and 550 °C for up to 375 hr, by examining their magnetic properties over a wide range of temperatures. The effect of extended annealing is most apparent in the low-temperature magnetic properties. In the fresh sample, a magnetic transition is observed at 58 K. Below the transition temperature, the field-cooled (FC) and zero-field-cooled (ZFC) saturation isothermal remanent magnetization (SIRM) curves are separated by a tell-tale triangular-shaped area, characteristic for titanomagnetites of intermediate composition. The room-temperature SIRM (RT-SIRM) cycle to 1.8 K in zero field has a characteristic concave-up shape and is nearly reversible. For the annealed samples, the magnetic transition temperature shifts to lower temperatures, and the shape of the curves above the transition changes from concave-up to concave-down. The shape of the RT-SIRM cycles also progressively changes with increasing annealing time. The SIRM loss after the cycle increases up to ∼30 per cent for the samples annealed for 375 hr at 355 °C, and for 110 hr at 500 and 550 °C. The Curie temperatures of the newly formed magnetic phases exceed the Curie temperature of the fresh sample (205 °C) by up to 350 °C. While this effect is most commonly attributed to extensive single-phase oxidation (maghemitization), the behaviour observed at cryogenic temperatures appears incompatible with the known properties of highly oxidized titanomaghemites. Therefore, we propose that, at least in the initial stage of the ‘dry’, that is, not involving hydrothermalism, alteration of titanomagnetite, temperature- and time-controlled cation reordering is the primary mechanism driving changes in both low- and high-temperature magnetic properties.