Thermal Cycling Treatment Research Articles

Persistently reversible pH-/thermo-responsive chitosan/poly (N-isopropyl acrylamide) hydrogel through clickable crosslinked interpenetrating network

Hydrogels with multi-stimuli responsiveness were variously developed to enable advanced applications. Although the durability under swelling/shrinking reversibility and repeatability are also needed, the plausible fabrication processes were still under investigation. The present work proposes a simple approach to achieve persistently reversible multi-responsive hydrogels by crosslinking the two responsive interpenetrating networks (IPNs), so-called crosslinked network IPN (CN-IPNs). The combination of two responsive hydrogels, i.e., pH-responsive chitosan (CS) crosslinked with diacid, and thermo-responsive poly(N-isopropylacrylamide) (PNIPAM) crosslinked with divinyl, is a good model for CN-IPNs. The further crosslinking of both networks via thiol-ene Click results in CS/PNIPAM in the form of CN-IPNs hydrogel. The hydrogel obtained expresses the persistently reversible pH-/thermo-responsiveness as evidenced from the maintaining appearances and the dimensional stability including the mechanical strength even after several pH and thermal treatment cycles. The CN-IPNs fabrication is ease and practical for stimuli-responsive polymers which the persistent swelling/shrinkage reversibility brings in the long-lasting performances for the advanced bio-related applications, especially artificial muscles, etc.

Role of Cyclic Thermal Shocks on the Physical and Mechanical Responses of White Marble

Marble is a common rock used in many buildings for structural or ornamental purposes and is widely distributed in underground engineering projects. The rocks are exposed to high temperatures when a tunnel fire occurs, and they will be rapidly cooled during the rescue process, which has a great impact on the rock performance and the underground engineering stability. Therefore, the role of cyclic thermal shocks on the physical and mechanical properties of marble specimens was systematically investigated. Different cyclic thermal shock treatments (T = 25, 200, 400, 600, 800 °C; N = 1, 3, 5, 7, 9) were applied to marble specimens and the changes in mass, volume, density and P-wave velocity were recorded in turn. Then, the thermal conductivity, optical microscopy and uniaxial compression tests were carried out. The results showed that both the cyclic thermal shock numbers (N) and the temperature level (T) weaken the rock properties. When the temperature of a thermal shock exceeds 600 °C, the mass loss coefficient and porosity of the marble will increase significantly. The most noticeable change in P-wave velocity occurs between 200 and 400 °C, with a 52.98% attenuation. After three thermal shocks, the cyclic thermal shock numbers have little influence on the uniaxial compressive strength and Young’s modulus of marble specimens. Shear failure is the principal failure mode in marble specimens that have experienced severe thermal damage (high N or T). The optical microscopic pictures are beneficial for illustrating the thermal cracking mechanism of marble specimens after cyclic thermal shocks.

Efficient rejuvenation of heterogeneous {[(Fe0.5Co0.5)0.75B0.2Si0.05]96Nb4}99.9Cu0.1 bulk metallic glass upon cryogenic cycling treatment

The effects of cryogenic thermal cycling on deformation behaviour and structural variation of {[(Fe0.5Co0.5)0.75B0.2Si0.05]96Nb4}99.9Cu0.1 bulk metallic glass (BMG) were studied and compared with Cu-free [(Fe0.5Co0.5)0.75B0.2Si0.05]96Nb4 BMG. After thermal-cycled treatment between 393 K and cryogenic temperature, the {[(Fe0.5Co0.5)0.75B0.2Si0.05]96Nb4}99.9Cu0.1 BMG obtained a plastic strain of 7.4% combined with a high yield strength of 4350 MPa. The excellent soft magnetic properties were maintained after CTC treatment. The minor addition of Cu element results in an initial nano-sized heterogeneity in the matrix, which facilitates the rejuvenation process during thermal cycling, and brings to a low optimal thermal temperature of 393 K, making the {[(Fe0.5Co0.5)0.75B0.2Si0.05]96Nb4}99.9Cu0.1 BMG more attractive in industrial application. During thermal cycling, the formation of more soft regions leads to the increase of structural heterogeneities, which is beneficial to the initiation of shear transition zones and the formation of multiple shear bands, and thus results in the enhancement of plasticity. This study links the subtle variation of specific structure with macroscopic mechanical properties, and provides a new insight of composition selection for cryogenic thermal cycling treatment.

The thermal cycling method induces structural defects to enhance the mechanical properties of FeGa alloys

The substantial improvement of mechanical properties in magnetostrictive alloys always accompanies the sacrifice of magnetic properties, limiting the potential applications in the fields involving precision drives and intelligent sensing, etc. In this paper, we proposed a novel thermal cycling method to enhance the mechanical properties of FeGa alloys without affecting the magnetic properties as much as possible. Specifically, the hardness raised from 4.90 GPa to 5.43 GPa, and the elastic modulus increased by 28.16% after 30-times thermal cycling treatments, accompanied by the initial permeability of specimens slightly dropping from 52.47 × 10−3 Oe g/emu to 50.16 × 10−3 Oe g/emu. The significant improvement in the mechanical properties of FeGa alloys was mainly attributed to the appearance of stacking faults and twins, which were caused by a sharp decrease in the stress between adjacent lattices. Meanwhile, the weakening of magnetic properties in FeGa alloys was associated with obstacles in magnetic domains. The proposed thermal cycling method would provide a substantial basis for developing novel FeGa alloys with more desirable physical properties.

Increasing the rating performance of paraffin up to 5000 cycles for active latent heat storage by adding high-density polyethylene to form shape-stabilized phase change material

The unstable phase transition of pure paraffin limits its application, particularly for active latent heat storage (ALHS). In passive latent heat storage, the addition of high-density polyethylene (HDPE) can decrease paraffin's leakage rate, which is associated with unstable phase transition and increase its durability after a large thermal number. This study aims to discover the possibility to use HDPE as a shape-stabilizer to increase the paraffin's performance for the ALHS system. Pure paraffin and composite paraffin/HDPE (80:20 wt%) are prepared as the reference material. The evaluation is focused on thermal properties, stability and performance during charging and discharging under different thermal cycles. Thermal cycle treatment uses temperature as a working boundary where the sample is heated from 30°C to 150°C, then cooled back to 30°C and repeated until 5000 cycles. Three different cycle references are chosen (1, 1000 and 5000 cycles) for each evaluation. The melting temperature of paraffin is decreased from 61.6°C to 59.8°C after 5000 cycles where Paraffin/HDPE slightly decreased from 60.4°C to 60.1°C. The heat fusion is decreased by 8.7% and 2.9% for paraffin and Paraffin/HDPE, respectively. The isothermal phase change is observed for paraffin/HDPE even after 5000 cycles with a higher rating performance by 30% faster to complete one cycle than pure paraffin. The other thermal performance is discussed in detail within the article, including the phase transition model during charging and discharging for the sample.

Hydrophobic and corrosion resistance properties of the electrochemically etched Zr-based bulk metallic glasses after annealing and cryogenic thermal cycling treatment

The effects of annealing and cryogenic thermal cycling treated on hydrophobic properties of Zr-based bulk metallic glasses surfaces fabricated by electrochemical etching were studied. The cryogenic thermal cycling on leads to poor corrosion performance for heat-treated metallic samples, while the annealing treatment induces the improved corrosion performance. Under the same electrochemical etching process, the etched sample surface is covered by dense coral-like micro-nano composite structures after cryogenic thermal cycling treatment for 30 cycles, and achieves superhydrophobic. However, there almost no nanoscale structures appear on the sample surface heat-treated at 702 K which results in the poor hydrophobic properties. Superhydrophobic film can generate a corrosion protection due to the existence of micro-nano composite structures in the samples.

A novel cyclic thermal treatment for enhanced globularisation kinetics in Ti-6Al-4V alloy: Experimental, constitutive and FE based analyses

Secondary hot-working on dual phase titanium alloys are essential for microstructural modification to tailor mechanical properties, which is typically challenging due to a narrow available processing window, especially during industrial scale manufacturing. Poor workability, strain induced porosity and adiabatic temperature rise in α + β phase region (i.e., sub-transus) are some of the main challenges faced. Cyclic thermal treatment (CTT) is an emerging technology showing potentials for microstructure modification (i.e., globularisation) in Ti‐6Al‐4V with significantly reduced mechanical work in the α + β region. This study summarises the results of CTT investigations conducted on a wrought Ti‐6Al‐4V alloy subjected to various thermo-mechanical conditions to develop different initial microstructures. Samples with uniform strain distributions were extracted from pre-forged samples and subsequently subjected to CTT using both conventional electric furnace (i.e., for slow heating and cooling rates), and induction heating (i.e., for faster heating and cooling rates). CTT of the samples forged at sub-transus temperature in conventional furnace led to maximum (i.e. ~100%) globularisation and significant coarsening of α grains, resulting in an equiaxed bimodal microstructure. On the other hand, CTT with induction heating method has resulted in a maximum of 80% globularisation fraction in samples forged to 60% reduction, and ~35% globularisation fraction in those forged to 20% reduction. The globularisation mechanisms during CTT of the sub-transus forged samples was dominated by the boundary splitting and thermal grooving. A Johnson-Mehl-Avarmi-Kolmogorov (JMAK) based model has been developed to predict the evolution of globularisation and grain growth during CTT. The developed JMAK model was then successfully incorporated into DEFORM® software as post-processing user subroutines. The predicted microstructure evolution by Finite Element (FE) simulations shown a good convergence towards the experimentally measured data following CTT.

Functionalized Poly(phenylene ether) with high thermal stability as flexible dielectrics and substrates for organic field-effect transistors

Extensive research efforts are devoted into seeking the thermally and mechanically durable dielectric materials for flexible electronics. In this work, a series of sulfonylated poly (phenylene ether)s (PPEs) were synthesized and served as gate dielectrics in the flexible OFET devices with crosslinked poly (2-allyl-6-methylphenol- co -2,6-dimethylphenol) (APPE) as substrate. The chemical structure, thermal, morphology, and dielectric properties were investigated, and the corresponding OFET devices were accordingly fabricated and characterized. We found that the discrepancy in sulfone content of PPE-xS renders the difference in thermal stability, surface polarity and dielectric constants. Among them, PPE-9kS with the highest sulfone content of 63% shows the best dielectric properties in the flexible OFET devices with hole mobility ( μ p ) of 0.45 cm 2 V −1 s −1 , outperforming its parent polymer without sulfone group (PPE-9k) with μ p of 0.14 cm 2 V −1 s −1 . Besides, the flexible device with PPE-9kS as dielectric exhibits highly retained device performance after cyclic bending or thermal treatment, which indicates the decent mechanical and thermal durability. The present study documents a practical methodology to fabricate a high-performance flexible OFET with excellent thermal and mechanical stability. In this research, flexible organic field effect transistor based on poly( p -phenylene ether) (PPE) was developed. A series of sulfonylated PPEs were synthesized and served as high dielectric constant gate dielectrics. The flexible device with PPE-9kS as dielectric exhibits highly retained device performance after cyclic bending or thermal treatment. • Flexible field effect transistor based on poly (phenylene ether) is developed. • Gate insulator with high dielectric constant enhances the device performance. • Thermally stable poly (phenylene ether) prevents the device from thermal failure.

Strength and Surface Properties of a 3D-Printed Denture Base Polymer.

This in vitro study evaluated the flexural strength, impact strength, hardness, and surface roughness of 3D-printed denture base resin subjected to thermal cycling treatment. According to ISO 20795-1:2013 standards, 120 acrylic resin specimens (40/flexural strength test, 40/impact strength, and 40/surface roughness and hardness test, n = 10) were fabricated and distributed into two groups: heat-polymerized; (Major.Base.20) as control and 3D-printed (NextDent) as experimental group. Half of the specimens of each group were subjected to 10,000 thermal cycles of 5 to 55°C simulating 1 year of clinical use. Flexural strength (MPa), impact strength (KJ/m2 ), hardness (VHN), and surface roughness (μm) were measured using universal testing machine, Charpy's impact tester, Vickers hardness tester, and profilometer, respectively. Data were analyzed by ANOVA and Tukey honestly significant difference (HSD) test (α = 0.05). The values of flexural strength (MPa) were 86.63 ± 1.0 and 69.15 ± 0.88; impact strength (KJ/m2 )-6.32 ± 0.50 and 2.44 ± 0.31; hardness (VHN)-41.63 ± 2.03 and 34.62 ± 2.1; and surface roughness (μm)-0.18 ± 0.01 and 0.12 ± 0.02 for heat-polymerized and 3D-printed denture base materials, respectively. Significant differences in all tested properties were recorded between heat-polymerized and 3D-printed denture base materials (P < 0.001). Thermal cycling significantly lowered the flexural strength (63.93 ± 1.54 MPa), impact strength (2.40 ± 0.35 KJ/m2 ), and hardness (30.17 ± 1.38 VHN) of 3D-printed resin in comparison to thermal cycled heat-polymerized resin, but surface roughness showed non-significant difference (p = 0.262). 3D-printed resin had inferior flexural strength, impact strength, and hardness values than heat-polymerized resin, but showed superior surface roughness. Temperature changes (thermal cycling) significantly reduced the hardness and flexural strength and increased surface roughness, but did not affect the impact strength.

Alternative Thermal Cycling Treatment to Produce Abnormal Grain Growth in FeMnAlNi Alloys: Study of Composition Variations and Effects on the Relative Phase Stabilities

An alternative method to obtain abnormal grain growth in Fe–Mn–Al–Ni system is presented. A crucible is used to control the cooling speed of the samples from 1200 °C enabling the nucleation of the equilibrium fcc phase. This fcc structure leads to an abnormal grain growth after heating to 1200 °C, temperature at which the bcc phase is stable. In this way, crystals with a mean diameter of 18 mm are obtained after 4 thermal cycles which take approximately 2 h. Additionally, precise composition measurements using neutron activation allowed the detection of a decrease in Mn content after each thermal cycle. Using electrical resistivity measurements, the effect of the variation of Mn content on the relative phase stability between the bcc austenite and the fcc martensite has been observed and is discussed here.

Investigation of properties change in the reacted molten salts after molten chlorides cyclic thermal treatment of toxic MSWI fly ash

To realize the thermal detoxification of municipal solid waste incineration (MSWI) fly ash in a relatively mild environment, molten salts thermal treatment technology was proposed in our previous research, which showed good effects. To investigate the properties of molten salts (NaCl-CaCl2) during cycling reusing, the change of the main components and the physical properties of the used molten salts were estimated. Results showed that the salts in fly ash would dissolve into molten salts. During this process, the concentration of K+, SO42- kept increasing while Cl- was decreased. The changing trend of Na+ and Ca2+ was dependent on the ratio of Ca/Na in raw fly ash. Ca(OH)2 in fly ash would react with CaCl2 to form CaClOH. Moreover, the introduction of the salt components on the thermal properties of molten salts were also studied. The melting point hardly changed by NaCl, CaSO4, and SiO2. Nevertheless, it was lowered to 431 °C with 15% CaCO3 addition, while increased to 523 °C with 20% KCl. Besides, there were no significant influences on the viscosity, stability, and thermal diffusivity of molten salts. KCl had the greatest influence on the specific heat capacity of molten salt, with an increase of about 20%.

Thermal stability and plasmonic photothermal conversion of surface-modified solar nanofluids: Comparing prolonged and cyclic thermal treatments

In this work, the thermal stability of plasmonic nanofluids upon continuous and cyclic heating and cooling for different durations and temperatures was investigated for volumetric-absorption solar applications. Gold nanoparticles (AuNPs) capped with citrate (CIT) were compared to polymer-protected AuNPs coated using physical/chemical adsorption with natural bovine serum albumin (BSA) or synthetic polyethylene glycol (PEG) and polyvinylpyrrolidone (PVP) polymers. Evaluation of post-test stability and identification of possible failure modes were realized using complementary characterization techniques. Furthermore, simulations were used to gain insight on the effects of nanofluid stability on the optical and thermal performance of direct-absorption solar collectors (DASCs). All nanofluid types retained their dispersion stability after long-term aging for 3 + years. For the first time, to our knowledge, the heating mode (whether cyclic or continuous), not just the heating temperature and duration, was found to play a critical role in determining the effects on dispersion stability, physicochemical coating transformations, optical properties, and wettability of nanofluids. This emphasized the importance of testing solar nanofluids using thermal stability tests that mimicked the cumulative failure modes induced by diurnal solar cycling. The impact of prolonged and cyclic heating was found to vary from excessive aggregation, weakened polymer-Au linkage, and reduced polymer–solvent affinity, depending on the AuNP coating. Overall, PVP was found most suitable as a soft protectant shell for plasmonic nanoparticles in solar photothermal applications. This work represents an important step towards the commercial use of photothermally efficient yet colloidally stable solar nanofluids capable of retaining their superior properties in field deployments.

Study on the Reliability of Sn–Bi Composite Solder Pastes with Thermosetting Epoxy under Thermal Cycling and Humidity Treatment

In this study, a Sn–Bi composite solder paste with thermosetting epoxy (TSEP Sn–Bi) was prepared by mixing Sn–Bi solder powder, flux, and epoxy system. The melting characteristics of the Sn–Bi solder alloy and the curing reaction of the epoxy system were measured by differential scanning calorimeter (DSC). A reflow profile was optimized based on the Sn–Bi reflow profile, and the Organic Solderability Preservative (OSP) Cu pad mounted 0603 chip resistor was chosen to reflow soldering and to prepare samples of the corresponding joint. The high temperature and humidity reliability of the solder joints at 85 °C/85% RH (Relative Humidity) for 1000 h and the thermal cycle reliability of the solder joints from −40 °C to 125 °C for 1000 cycles were investigated. Compared to the Sn–Bi solder joint, the TSEP Sn–Bi solder joints had increased reliability. The microstructure observation shows that the epoxy resin curing process did not affect the transformation of the microstructure. The shear force of the TSEP Sn–Bi solder joints after 1000 cycles of thermal cycling test was 1.23–1.35 times higher than the Sn–Bi solder joint and after 1000 h of temperature and humidity tests was 1.14–1.27 times higher than the Sn–Bi solder joint. The fracture analysis indicated that the cured cover layer could still have a mechanical reinforcement to the TSEP Sn–Bi solder joints after these reliability tests.

Diffusion crushing of graphite in integrated cast iron processing

Purpose. It is necessary to investigate the possibility of crushing graphite inclusions in cast irons. The aim of the work was to study structural changes in graphite under explosive action followed by thermal cycling treatment of gray cast iron. Methods. Gray cast irons were subjected to explosive action (pressure is 90 GPa, the deformation rate is 100 s-1, the time is 10-6...10-7 s). Then the cast irons were subjected to thermal cycling: 950 °C, holding for 20 min, cooling with a furnace; 5 cycles. Metalographic ("Neophot-21"), micro-X-ray spectral ("Nanolab-7"), X-ray diffraction (DRON-2.0) research methods were used. Results. The features of diffusion crushing of graphite in cast irons with different types of metal matrix (ferritic, austenitic) and graphite shape (lamellar, spherical) have been studied. The features of structural changes in the cast iron matrix under explosive action, which determine the conditions for the transformation of graphite during subsequent thermal cycling, are discussed. It is shown that this process of diffusional crushing of graphite can be accompanied by local melting, which leads to the formation of regularly distributed dispersed particles of graphite. Scientific novelty. From the point of view of physical mesomechanics of plastic deformation, the processes of structural changes in the metal matrix of cast irons are considered. It is shown that nonequilibrium defect substructures of the cast iron matrix obtained during the explosion determine the features of diffusion crushing of graphite inclusions during subsequent thermal cycling. The conditions for diffusion crushing of graphite with reflow and in the solid-phase state have been established. Practical significance. It has been established that the complex processing of “explosive loading + thermal cycling” promotes crushing of coarse graphite inclusions, which is favorable for the mechanical and operational properties of cast irons. The use of the results obtained will make it possible to develop technologies for complex processing with regulated parameters of graphite inclusions, which will lead to an expansion of the field of application of gray cast irons. Keywords: cast iron; shock wave treatment; graphite; thermal cycling; stress relaxation

Comparison of Mechanical Properties of Chairside CAD/CAM Restorations Fabricated Using a Standardization Method

The aim of this in vitro study was to investigate the fracture resistance, fracture failure pattern, and fractography of four types of chairside computer-aided design/computer-aided manufacturing (CAD/CAM) restoration materials in teeth and titanium abutments fabricated using a standardization method. An artificial mandibular left first premolar prepared for all-ceramic crown restoration was scanned. Forty extracted mandibular molars and cylindrical titanium specimens were milled into a standardized shape. A total of eighty CAD/CAM restoration blocks were milled into a crown and twenty pieces of each lithium disilicate (LS), polymer-infiltrated-ceramic-network (PICN), resin nano ceramic (RNC), and zirconia-reinforced lithium silicate (ZLS) materials were used. Crowns were bonded to abutments, and all specimens underwent thermal cycling treatment for 10,000 cycles. Fracture resistance was measured using a universal testing machine and fracture failure patterns were analyzed using optical microscopy and scanning electron microscopy. Statistical differences were analyzed using appropriate ANOVA, Tukey HSD post hoc tests, and independent sample t-tests (α = 0.05). The results indicated that, in both teeth abutments and titanium abutments, the fracture resistances showed significantly the highest values in LS and the second highest in ZLS (p < 0.05). The fracture resistances based on teeth abutments and titanium abutments were significantly different in all the CAD/CAM restoration materials (p < 0.05). There are statistically significant correlations between the types of materials and the types of abutments (p < 0.05). Each of the different materials showed different fracture failure patterns, and there was no noticeable difference in fractographic analysis. Lithium disilicates and zirconia-reinforced lithium silicates exhibited statistically high fracture resistance, indicating their suitability as restoration materials for natural teeth or implant abutments. There were no distinct differences in the fracture pattern based on the restoration and abutment materials showed that the fracture initiated at the groove where the ball indenter was toughed and propagated toward the axial wall.

Influence of Thermal Cycling Modes on VK8 Hard Alloy Mechanical and Tribological Properties

Hard alloys are popular materials widely used in the toolmaking industry. The refractory carbides included in their composition make carbide tools very hard (80 to 92 HRA) and heat-resistant (from 800 to 1000°С), so they can be used at cutting speeds several times higher than those used for high-speed steels. However, hard alloys differ from the latter in their lower strength (from 1000 to 1500 MPa) and the absence of impact strength; this is an urgent problem that needs to be solved. We study the influence of thermal cycling modes on the mechanical and tribological properties of VK8 (WC–8Co) hard alloy used in the manufacture of cutters and cutting inserts for metal working on metal-cutting machines. As the object of study, we select 5 × 5 × 35 mm rods made of VK8 (WC–8Co) alloy manufactured by powder metallurgy at the Dimitrovgrad Tool Plant. The following criteria are selected for evaluating the heat-treatment mode: Vickers hardness, flexural strength, and mass wear resistance (compared to the wear of as-received samples that were not heat treated). Plates in the initial state and after heat treatment (HT) are subjected to abrasion tests. Wear results are evaluated by the change in the mass of plates. Regularities of the influence of various time and temperature conditions of HT on the tribological properties of products made of VK-group tungsten hard alloys are determined. An increase in the number of thermal cycling cycles improves mechanical properties of the VK8 hard alloy such as strength and hardness. When repeating the cycle five times, an increase in abrasive wear resistance over the initial non-heat-treated sample is obtained. The elemental composition of the VK8 hard alloy changes insignificantly after thermal cycling; only a slight increase in oxygen is observed on the surface of the plates. The grain size after thermal cycling increases in comparison with the initial VK8 hard alloy. It is found that VK8 hard alloy thermal cyclic treatment leads to a change in the phase composition. X-ray phase analysis shows the presence of a large amount of α-Co with an hcp-type lattice on the surface of a hard alloy and a solid solution of WC in α-Co. A change in the cobalt modification ratio causes a decrease in microstresses. An analysis of the carbide phase structure state shows that the size of crystallites and microstresses changes after thermal cycling. The lattice constant of the cobalt cubic solid solution decreases, which may indicate a decrease in the amount of tungsten carbide and carbon dissolved in it. Statistical processing of the experimental results includes a calculation of the average value of the mechanical property, its dispersion, and standard deviation in the selected confidence interval.

The Influence of Thermocyclic Treatment on the Structure and Mechanical Properties of Pseudo-Alpha Titanium Alloys for Steam Turbine Blades

The influence of thermal cycling treatment of pseudo-α-titanium alloys OT4 and VT20 on their structural and substructural characteristics, as well as their mechanical properties is considered. A significant change in structural characteristics is established. This contributes to an increase in the strength properties of alloys with satisfactory ductility and high-temperature strength.

Some observations on the replication of precious metal artefacts in experimental archaeology

The aim of this study is to verify processes of thermochemical bonding and the removal of the resultant thermal oxidation and surface segregation values according to descriptions in ancient recipes through experimental replication. Etruscan and Hellenistic jewellery could require dozens of cycles of thermochemical bonding throughout the fabrication process. Yet even simple artefacts, such as those produced in Troy, Ur and Mari in the third millennium BCE, required several cycles. The repetition of thermal bonding is known to have a deleterious effect on previous bonds in the case of brazing joins with lower melting temperature alloys. On the contrary, copper salt bonding mixtures may be used repeatedly by an accomplished goldsmith on the same artefact. Two copper salt bonding recipes, one reported by Pliny, the other by Dioscorides, are replicated and used. Experiments in surface treatment are based on two recipes in Leiden Papyrus X. Repeated cycles of thermal ramps and surface treatments modify surface metal values. The results of the experimentation are evaluated as contributions to interpreting archaeological data.

Fatigue Resistance of Welded Titanium Joints

The paper presents the results of studies of the structural state, changes in mechanical characteristics during static and cyclic loading of welded joints from technically pure titanium during thermal cycling. Based on the change in the relative deflection of the sample, a quantitative assessment of the fatigue damage accumulation at the stage of cyclic deformation up to the moment of opening and propagation of the main crack depending on the number of cycles of thermal cycling treatment is provided.

Non-Monotonic Evolution of Carrier Density and Mobility under Thermal Cycling Treatments in Dirac Semimetal Cd3As2 MicrobeltsSupported by the National Key Research and Development Program of China (Grant No. 2016YFA0401003), and the National Natural Science Foundation of China (Grant Nos. 11804340, 11774353, U19A2093, and U1732274), and the CAS/SAFEA International Partnership Program for Creative Research Teams of China.

Tunable carrier density plays a key role in the investigation of novel transport properties in three-dimensional topological semimetals. We demonstrate that the carrier density, as well as the mobility, of Dirac semimetal Cd3As2 nanoplates can be effectively tuned via in situ thermal treatment at 350 K for one hour, resulting in non-monotonic evolution by virtue of the thermal cycling treatments. The upward shift of Fermi level relative to the Dirac nodes blurs the surface Fermi-arc states, accompanied by an anomalous phase shift in the oscillations of bulk states, due to a change in the topology of the electrons. Meanwhile, the oscillation peaks of bulk longitudinal magnetoresistivity shift at high fields, due to their coupling to the oscillations of the surface Fermi-arc states. Our work provides a thermal control mechanism for the manipulation of quantum states in Dirac semimetal Cd3As2 at high temperatures, via their carrier density.