Thermal Cycling Treatment Research Articles

Modulating Ligand‐Exchange Dynamics on Metal‐Organic Polyhedra for Reversible Sorting and Hybridization of Miktoarm Star Polymers

AbstractThe precise synthesis of miktoarm star polymers (MSPs) remains one of the great challenges in synthetic chemistry due to the difficulty in locating appropriate structural templates and polymer grafting/growing strategies with high selectivity and efficiency. Herein, ≈2 nm metal‐organic polyhedra (MOPs), constructed from the coordination of isophthalic acid (IPA) and Cu2+, are applied as templates for the precise synthesis of 24‐arm MSPs for their unique logarithmic ligand‐exchange dynamics. Six different polymers are prepared with IPA as an end group and they further coordinated with Cu2+ to afford the corresponding 24‐arm star homo‐polymers. MSPs can be obtained by mixing targeted homo‐arm star polymers in solutions upon thermal annealing. The compositions of MSPs can be facilely and precisely tuned by the recipe of the star polymer mixtures used. Interestingly, the obtained MSPs can be sorted into homo‐arm star polymers through a typical solvent extraction procedure. The hybridization and sorting process can be reversibly conducted through the cycle of thermal annealing and solvent treatment. The complex coordination framework not only opens new avenues for the facile and precise synthesis of MSPs and MOPs with hybrid functionalities, but also provides the capability to design sustainable polymer systems.

Study on the Behavior of Low-Voltage Cable Insulation Subjected to Thermal Cycle Treatment

Abstract The paper presents a study on the effects of thermal aging on a low-voltage cable. Cable samples with a length of 50 cm were subjected to thermal cycling from +140 °C to −20 °C in a climate chamber with controlled temperature. This treatment compares the short-term failure or the emergency overload of some cables under real operating conditions at low temperatures. The effect of the temperature cycle is investigated through electrical measurements such as dielectric spectroscopy, voltage response measurements, and mechanical measurements such as Shore D hardness investigation. The results revealed that the thermal cycles of accelerated aging caused the plasticizer to diffuse into the jacket and then be released into the environment. At the same time, the thermal shocks produced microcracks in the cable jacket, accelerating the removal of the plasticizer.

Thermal Cycling Induced Aging on Polypropylene/Elastomer Blends for DC Cable Insulation

This paper reports on the ageing phenomenon of the polypropylene (PP) /elastomer blends that are used as DC cable insulation. The elastomers employed are propylene-based elastomer (PBE) and ethylene-octene copolymer elastomer (EOC), which are blended into the PP to form the test samples. The samples go through thermal cycling treatment with temperatures from -30 to 150 °C, after which the trap distribution and the DC breakdown strength are measured. Structural changes in the samples are estimated through Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM) and differential scanning calorimetry (DSC) measurements. The test results indicate that, with the growth of the thermal cycling number, the trap center decreases whereas the trap density increases, and the DC breakdown strength tends to be reduced. The appearance of oxidation product, loose structure and decreased crystallinity with the thermal cycling ageing should be responsible for the encouragement in charge transport and the reduction in the breakdown strength. The degradation of PP/EOC is more obvious than that of PP/PBE due to its worse compatibility, the PP/PBE exhibits better resistance to the thermal cycling ageing.

БҰРҚАҚТЫ РЕЖИМДЕГІ ПАЙДАЛАНЫЛҒАН ҰҢҒЫМАЛАРДЫҢ ЖҰМЫСЫН ТАЛДАУ

Abstract. Despite the intensive development of low-viscosity oil, which is quite easily extracted from world deposits, the content of high-viscosity oil and bitumen processed in a small direction is continuously developing at a high pace on the world stage. Due to the increased demand for hydrocarbon raw materials, the economy leads to the widespread use of thermal methods of efficient extraction of high-viscosity oil. For a long time it was believed that thermal methods have no prospects due to high energy consumption. In the late 50s-early 60s of the last century, the views of oilmen on the impact of the reservoir by thermal methods began to change for the better. In addition, according to the indicators of cyclic steam and thermal treatment of formations, for every 2-3 tons of water vapor injected into the bottom-hole zone of the formation, it is additionally possible to obtain 1 ton of oil. Due to the lag in the development of the Karazhanbas field by objects of thermal impact, wells after their commissioning work for a long time in the natural mode, i.e. the areas of the deposit were operated in the depletion mode. Such development of the deposit was not provided for by the current technological scheme for the development of the Karazhanbas field by thermal methods and is due to the need to implement the plan for oil production in conditions of chronic lag in the development of fields for active thermal effects on formations. Considering that this lag has already been maintained for quite a long time, it is relevant to conduct an analysis of the operation of wells in the natural mode. The significant field material of the operation of producing wells in the natural mode is summarized. Keywords: development, operation, well, oil, steam-thermal effect, analysis, complications, waterlogging, formation.

The migration and transformation mechanisms of heavy metals during molten salt cyclic thermal treatment of MSWI fly ash

Molten salt thermal treatment has been demonstrated to be effective in dissolving heavy metals in municipal solid waste incineration (MSWI) fly ash. However, the complex thermochemical reactions of various heavy metals during the process remain unclear. This study investigated the migration and transformation mechanisms of typical heavy metals during molten salt (NaCl-CaCl2) cyclic thermal treatment of fly ash at 600–750 °C, as well as the leaching characteristics and recovery methods of heavy metals in the reacted products. Molten chlorides could be recycled to extract heavy metals from fly ash, which reduced the leaching toxicity of heavy metals in the reacted slags. Over 64.3% of Cd, Cu and Pb in fly ash were transferred to molten salt while the migration rate of Zn was restrained to only 32.3% during the cyclic process at 750 °C. Regarding Cd, Cu, and Pb in molten salt, the chlorination and dissolution of their oxides were significant, while the combination of their chlorides with free O2– to form oxides precipitation was weak. However, the above reaction characteristics of Zn were the opposite. Furthermore, Zn2+ could be stabilized into hardystonite (Ca2ZnSi2O7) in molten salt by reacting with Si2O76- generated from the combination of O2– and SiO2. Besides, increasing the reaction temperature facilitated the chlorination and dissolution of heavy metals. For recovery, heavy metals could be concentrated on the insoluble matters of molten salt, with a maximum concentration of approximately 5 times that in fly ash.

Long term properties of cement-based material incorporated with n-octadecane/diatomite composite SSPCM

The energy-saving concrete was developed by incorporating n-octadecane and diatomite composite shape-stabilized phase change materials (OC/D SSPCMs) into cement concrete. OC/D SSPCMs were prepared by vacuum impregnation of barrel diatomite. The results show that the melting point and enthalpy of OC/D SSPCMs are 25.02 °C and 60.26 J/g, and OC/D SSPCMs have good dispersion and compatibility in cement paste. As a structure-function integrated material, energy-saving concrete with compressive strength of 33.5 MPa has a broad application prospect. Self-designed room test results reveal that energy-saving concrete can reduce the indoor temperature by 4.5 °C. Long-term thermal/mechanical properties, volume deformation and microstructure after thermal cycling treatment were investigated. The results indicate that phase transformation behavior has a huge negative effect on the compressive strength and deformation tendency of energy-saving concrete, being mainly attributed to the significant volume evolution with the temperature of PCM and PCM encapsulation leakage.

Thermochemical heat storage utilization of MSWI fly ash after carbonation enhancement with ammonia water regulation: Carbon sequestration efficiency, heavy metal immobilization, and heat storage characteristics analysis

Accelerated carbonation is an effective method of treating municipal solid waste incineration fly ash (FA). However, the efficiency of CO2 sequestration is limited and the usage of products is uncertain. This study proposed a method for enhancing carbonation by ammonia water (NH4OH) regulation and thermochemical heat storage of its products. The influences of NH4OH on CO2 sequestration and heavy metals immobilization were investigated. The results demonstrated that the carbon sequestration efficiency improved from 65.2% to 98.3%, with the NH4OH addition increasing (0–20%). NH4OH promoted the conversion of calcium chloride (CaCl2) and calcium sulfate (CaSO4), which were not originally involved in the carbonation reaction, to calcium carbonate (CaCO3). Excess NH4OH increased the release of heavy metals into the liquid phase due to the chelation of heavy metals by ammonia ions (NH4+) and the effect of high pH. The appropriate amount of NH4OH (8%) offered a high-efficient immobilization of heavy metals. The energy density of FA samples increased from 226.6 kJ/kg to 1207.8 kJ/kg with the NH4OH addition increasing, positively correlating with the content of CaCO3. After the thermal cycle treatment, the non-ammonia carbonated FA had a serious sintering phenomenon with chlorellestadite (Ca5(P,Si,S)3O12(Cl,OH,F)), which was produced from the reaction between CaSO4 and other compounds; while the carbonated FA with NH4OH addition (8%) showed good thermal cycle stability with fine particles and single component (calcium oxide). Therefore, the carbonation treatment in this study is a novel and highly-efficient method, with the final products providing an alternative material for thermochemical heat storage.

Exploration of Effect of Thermal Cycling Treatment on Mechanical and Tribological Performance of Polyimide Composites

Polyimide (PI) and PI composites reinforced with glass fiber (GF), and aramid fiber (AF) were fabricated with hot-pressing technology. Then polyimide and its composites were treated with a thermal cycling (TC) condition from –50 °C to 150 °C with 300 cycles continuously. Compared with the samples without TC treatment, the fracture morphologies, mechanics, and tribological properties of the samples were studied. The results showed that, based on the fractographic morphologies, the phenomenon of fiber stripping could be obviously observed in the PI composite materials after TC treatment. Compared with before TC treatment, the friction coefficients (FC) and wear rates (WR) of PI and PI composites showed different variations, respectively. In conclusion, TC treatment had a great influence on the morphologies of the worn surface and the composition of transfer film. As the shear force increased, the elemental analysis demonstrated that GF was extruded into the groove.

Experimental study on the nonlinear flow characteristics of fractured granite after high-temperature cycling

To understand the influence of temperature on the flow characteristics of fractured granite, high-temperature cyclic thermal treatment and flow tests on the fractured rock sample with different joint roughness coefficients and intact rock samples were conducted. The larger confining pressure and larger joint roughness coefficient will increase the resistance of fluid flow and affect the flow characteristics of the fluid. With the temperature increasing, the aperture of the fractures, the number of micro-fractures, and micropores increase which forms a large number of new connected hydraulic channels in the matrix. Forchheimer's law and Izbash equation can well describe the nonlinear flow characteristics, and the fitting coefficients are greater than 0.99. As the increasing temperature, the slope of the curve between the volumetric flow rate and pressure gradient gradually decreases, and the coefficients in Forchheimer's law and the Izbash equation decrease. The transmissivity decrease with the increasing Reynolds number and the change range of that increase with the increasing temperature. When the temperature is at the lower level (T = 200 ~ 600 °C), the contribution of split fracture to the permeability is greater than that of the matrix. When the temperature continuously increases to 800 °C, the contribution of the matrix to the permeability gradually rises and then exceeds that of split fracture. The results indicate that 400 °C is the critical temperature, after which the flow characteristics of fractured granite after high-temperature cycling change more obviously.

Effects of Accelerated Aging on Thermal, Mechanical and Shape Memory Properties of Cyanate-Based Shape Memory Polymer: III Vacuum Thermal Cycling.

Shape memory polymers (SMPs) with intelligent deformability have shown great potential in the field of aerospace, and the research on their adaptability to space environments has far-reaching significance. Chemically cross-linked cyanate-based SMPs (SMCR) with excellent resistance to vacuum thermal cycling were obtained by adding polyethylene glycol (PEG) with linear polymer chains to the cyanate cross-linked network. The low reactivity of PEG overcame the shortcomings of high brittleness and poor deformability while endowing cyanate resin with excellent shape memory properties. The SMCR with a glass transition temperature of 205.8 °C exhibited good stability after vacuum thermal cycling. The SMCR maintained a stable morphology and chemical composition after repeated high-low temperature cycle treatments. The SMCR matrix was purified by vacuum thermal cycling, which resulted in an increase in its initial thermal decomposition temperature by 10-17 °C. The continuous vacuum high and low temperature relaxation of the vacuum thermal cycling increased the cross-linking degree of the SMCR, which improved the mechanical properties and thermodynamic properties of SMCR: the tensile strength of SMCR was increased by about 14.5%, the average elastic modulus was greater than 1.83 GPa, and the glass transition temperature increased by 5-10 °C. Furthermore, the shape memory properties of SMCR after vacuum thermal cycling treatment were well maintained due to the stable triazine ring formed by the cross-linking of cyanate resin. This revealed that our developed SMCR had good resistance to vacuum thermal cycling and thus may be a good candidate for aerospace engineering.

A criterion of the critical threshold of the maximum shear stress in bulk metallic glasses with cryogenic thermal cycling by statistics in nanoindentation

The shear transformation zones of metallic glasses have been widely studied by nanoindentation. In this work, the mathematic relationship between the relevant parameters is analyzed emphatically. Bulk metallic glasses were given different activation volumes by the cryogenic thermal cycling treatment. Nanoindentation experiments were carried out in a load-controlled loading mode. The critical threshold of the maximum shear stress, (τmax)C, was obtained by the noise-reduction procedures and the statistical analysis. And the activation volume, V*, was obtained from the nonlinear slope by introducing a first-order polynomial. Based on the mean-filed theory, a criterion is successfully established, (τmax)C=V*−λ, where λ=0.30±0.10. According to lots of previous studies on (τmax)C and V* of metallic glasses, three applicable conditions of the criterion are extracted.

Study of the tribological performance of pre- and post-heat treatment of AISI D2 steel with AlCrN coating under wet conditions

ABSTRACT This study examined the impact of a combination of hardened and tempered surface change technologies and AlCrN coating on the tribological characteristics of AISID2 steel. The duplex surface change, such as the combination of a heat treatment at 600°C for 1 hr and a PVD (sputtering), archives the superior wear resistance and mechanical properties. AlCrN coating has been implemented in AISID2 steel after a hardened and tempered treatment. This process was carried out as part of an appropriate thermal treatment cycle in accordance with ASM Vol.2. Subsequently, the AlCrN coating synthesised by PVD (sputtering) improves the adhesion between the coatings and the AISID2 steel. The wear properties according to ASTMG99 have been tested with a typical load of 10N, 20N and 30N for a sliding distance of 6000 m with a constant velocity of 1.256 ms−1 in wet conditions. Tests revealed that the AlCrN coating deposited on the hardened and tempered steel was more resistant to wear than the AlCrN coating applied to the unhardened steel. Therefore, it should be possible to implement the results of this study for forming operations with low COF and a low amount of resulting wear such as drawing and rolling in dies.

Microstructure and Mechanical Properties of an Ultrahigh-strength Titanium alloy Ti-4.5Al-5Mo-5V-6Cr-1Nb Prepared Using Laser Directed Energy Deposition and Forging: A Comparative Study

The application of titanium alloys in aerospace put forward the requirement for higher strength. Additive manufacturing is a promising method for the efficient and economical processing of titanium alloys. However, research on the additive manufacturing of ultrahigh-strength titanium alloys is still limited. The mechanisms of microsegregation for high alloying elements and poor plasticity are still not clear. In this study, an ultrahigh-strength titanium alloy Ti–4.5Al–5Mo–5V–6Cr–1Nb (TB18) was prepared using two methods: laser direct energy deposition (LDED) and forging. The LDEDed alloy contains three zones with similar grain morphologies but different microstructure. The microsegregation of the alloy is limited due to the rapid solidification and almost eliminated after the thermal cycle and solution treatment. With stress relief treatment, the LDEDed alloy exhibits anisotropic mechanical properties. After solution and aging treatments, its ultimate strength is enhanced; however, its plasticity is relatively lower than that of the wrought alloy with equally high strength. The excellent balance of the strength and plasticity of the wrought alloy can be ascribed to the formation of αWGB and multiscale α laths, which provides enlightenment for optimizing the properties of the LDEDed alloy.

Study of regularities of structural-phase transformations during thermocyclic treatment of tool steels

Movement of carbon atoms to dislocations reduces the specific volume of the martensite phase, which, in turn, affects the general level of volumetric changes that occur as a result of phase transformations during quenching. The measurements carried out on samples of steel ShX15 showed that the minimum increase in geometric dimensions is observed. Intermediate tempering and re-quenching do not change this pattern. At the same temperature, for this steel grade, the minimum degree of martensite tetragonality was recorded. This study has shown that to obtain a high level of final properties of tool steel, the most optimal is to obtain a substructure with a high level of defectiveness of the crystal structure of steel. It was found that the use of thermal cycling treatment contributes to an increase in the level of defectiveness of the crystal structure. It was also found that the use of aqueous solutions of polymers as a quenching medium makes it possible to obtain a cooling rate less than in oil quenching, which helps to reduce the level of quenching stresses.

Quantification of Chemical Composition Distribution of Polyolefin Materials for Improved Accuracy and Speed

Crystallization-based separation techniques are widely used for chemical composition distribution (CCD, also often referred as short chain branching distribution SCBD) measurement in the polyolefin industry, in which CCD is among the most critical structural parameters to define their properties and applications. The desire to improve the sample throughput rate by shortening the analysis time in the current CCD techniques would normally sacrifice measurement accuracy due to the cocrystallization phenomena, in which the polymer chains with similar molecular architectures will cocrystallize or coelute enigmatically in the CCD analysis. Herein, we reported the investigation by exploring various separation packing materials on the cocrystallization phenomena. In comparison with the commercially available Crystallization Elution Fractionation (CEF) technique, an improved technique for CCD measurement (iCCD) was developed using the columns packed with gold-coated nickel substrate or spherical gold particles with or without the dynamic cooling process. With iCCD, it was observed with equivalent cocrystallization degree to the industrial gold standard benchmark Wild-TREF method but with over 70+ times improved sample throughput rate (62 vs 4500 min). The experimental CCD chromatogram for a polyolefin blend similarly assembled to the mathematically constructed result further demonstrated the minimized cocrystallization and measurement accuracy in the iCCD method. In addition, the superior mechanical properties of gold-coated nickel particles enabled the long-term robustness and enhanced measurement precision of the iCCD technique during the repeated thermal treatment cycles and pressure variations.

High thermal stability of ultra-high temperature surface acoustic wave devices with multilayer composite electrodes

The main challenge to maintain high-temperature performance of surface acoustic wave (SAW) devices is to improve the high-temperature resistance of the interdigital transducers (IDT). This work reports on the development of the Pt-Rh alloy-based multilayered composite IDTs for high-temperature applications. Composite electrode-based wire-type resistors with different structures were prepared by magnetron sputtering, and their resistances and surface morphologies at temperatures up to 1600 °C were investigated. The proposed composite electrode has a structure of ZrO2 /Pt-Rh (10%) /Al2O3 /Pt-Rh (10%) /Al2O3 with a 40 nm ZrO2 protective layer at the top of the electrode. It has a 300 nm thickness Pt-Rh (10%) film, a 10 nm Al2O3 layer in the middle of Pt-Rh (10%) layer, and a 20 nm Al2O3 layer between the electrode and the substrate. The results showed that the composite electrodes could withstand a maximum operating temperature up to 1600℃ in air. The electrodes maintained excellent stability even after five cyclic thermal treatments at temperatures up to 1200 ℃ for one hour, and good stability after two cyclic thermal treatments up to 1400 ℃ for 1 h. The SAW devices based on AlN single-crystal piezoelectric film using the composite electrodes showed good stability at 1200 ℃ for 1 h.

Experimental investigation on damage and seepage of red sandstone subjected to cyclic thermal and cold treatment

For geothermal mining projects in cold regions, the problems of surrounding rock and water damage caused by thermal-cold shocks have become the main factors affecting engineering stability and construction safety. In addition, the permeability and damage characteristics of the rock mass after the thermal-cold cyclic shock action are not yet known. Therefore, in this study, seepage tests of red sandstone during complete stress-strain after thermal-cold cyclic shock were carried out to analysis the change in permeability of red sandstone during progressive fracturing. Meanwhile, the permeability model considering damage was further constructed by using the damage constitutive relationship based on statistical damage theory. And found that peak stress and elastic modulus were found to decrease with temperature and cycles, and both initial and maximum permeability increase with temperature and cycles during its gradual fracture. Moreover, the theoretical curve calculated by the permeability model is not much different from the experimental curve, which can effectively characterize the relationship between permeability and damage. The research results can provide reference value for the damage assessment, repair and reinforcement of the wellbore surrounding rock structure after thermal-cold shock cycle in the geothermal engineering of cold regions.

Thermal stress influence on the long-term performance of fast-charging paraffin-based thermal storage

• Fast-charging cycle leads to a higher thermal stress and hysteresis losses. • 10,000 cycle assessment reveals the deterioration on thermal performances. • The storage efficiency decreases 12.7% after 10,000 fast charging cycles. • Isothermal phase transition provides a better power rate and duration. The present study evaluates the impact of charging speeds on the long-term performance of paraffin-based thermal energy storage (TES) up to 10,000 actual thermal cycles. Paraffin and form-stable phase change material (FSPCM) is used as the reference materials. The FSPCM is made of paraffin (80 wt%) and high-density polyethylene (HDPE, 20 wt%). The thermal cycling treatment is applied to the samples using slow (1 °C/min), normal (5 °C/min) and fast-charging cycles (10 °C/min). Performance assessment is conducted using an active thermal storage model. According to the assessment, thermal stress and hysteresis effect occur severely after 10,000 fast-charging cycles. It disrupts the heat transfer process, reducing the power and charging rate. Scanning electron microscope (SEM) shows the void formation for paraffin which correspond to a lower efficiency (62.5%) than FSPCM (66.6%). The presence of HDPE reduces the impact of the fast-charging effect on paraffin. The SEM micrograph for FSPCM indicates that a chemi-crystallization leads to phase-separation between paraffin and HDPE. It helps to maintain the charging and discharging duration after 10,000 fast-charging cycles. Furthermore, the decrement of melting enthalpy of FSPCM (5.5%) is much lower than paraffin (12.7%). Hence, FPSCM maintains the storage capacity after 10,000 fast-charging cycles at a sufficient level. The multi-step transition and power curve during the charging/discharging cycle are discussed in detail within the article. Further improvement can be taken to minimize the performance degradation of fast-charging paraffin-based TES by compositing paraffin to withstand thermal stress or modifying the system operation after a certain fast-charging cycle.

Mechanical Properties and Sand Erosion Damage Mechanism of TiN/Ti Multilayer Coatings after Thermal Cycling Treatment

Mechanical Properties and Sand Erosion Damage Mechanism of TiN/Ti Multilayer Coatings after Thermal Cycling Treatment

Rejuvenation and Malleability Enhancement of Zr-Based Metallic Glass by Sub-Tg Annealing and Cryogenic Thermal Cycle Treatment

Rejuvenation and Malleability Enhancement of Zr-Based Metallic Glass by Sub-Tg Annealing and Cryogenic Thermal Cycle Treatment