Course Of Annealing Research Articles

Crystallization and performance evolution of PHBV nanocomposites through annealing: The role of surface modification of CNCs

To address the brittleness challenge of polyhydroxybutyrate-co-valerate (PHBV) rooting from its slow nucleation rate, cellulose nanocrystals (CNCs) were employed as bio-based nano nucleation and reinforcement agents. CNCs were further functionalized through succinylation using aliphatic dodecyl succinic anhydride (DDSA), for improved compatibility and dispersion within PHBV. Nanocomposites of PHBV incorporating pristine or DDSA-modified CNC (mCNC) were prepared through solution mixing followed by melt injection molding. The study focused on investigating how CNCs and mCNCs affect the crystallization behavior, thermal, rheological, and mechanical properties of PHBV nanocomposites over time, in the course of annealing or conditioning. Thermal results revealed that the incorporation of neat CNCs generally improving stability due to restricted polymer chain mobility and hydrogen bonding, while DDSA-modified CNCs show varied effects depending on the concentration, sometimes diminishing stability due to increased chain mobility. Polarized optical microscopy revealed the superior nucleation efficiency of mCNC, especially at low contents, leading to smaller and numerous spherulites over conditioning. Rheological analysis indicated a dilution effect of the hairy mCNCs, decreasing both dynamic modulus and complex viscosity. Mechanical properties, assessed through tensile testing and dynamic mechanical analysis after 15 days of conditioning, demonstrated the evolving effect of CNCs on aging-induced embrittlement and thermo-mechanical performance of PHBV during storage. The results revealed that incorporating 1 wt% mCNCs effectively toughened PHBV, increasing Young's modulus, and decreasing Tg without scarifying elongation at break compared to neat PHBV. The findings position mCNCs as a promising nucleation agent which retains PHBV nanocomposites toughness after aging.

Controllable synthesis and PL propertiesof ZnO flower-like nanostructures by chemical bath method

Zinc oxide (ZnO) flower-like nanosheets and nanorods were synthesized on a glass substrate with an Al layer by a simple chemical bath method, and their morphology was controlled by adjusting the pH of the solution without the assistance of an additional surfactant. For the 3D nanostructures of the annealed nanosheets, the blue light emission at about 410 nm disappeared, which may be due to the defect of zinc vacancy. The emission of the yellow band at about 550 nm was enhanced, which could have originated from the interstitial oxygen. These results indicate that the concentrations or types of the dominant defects could be changed because of the diffusion of Al substrates during the course of annealing. The as-prepared flower-like nanostructures of nanorods exhibited a high UV emission peak (at about 380 nm). After the samples were annealed, the green emission (at about 500 nm) was also enhanced abnormally, except for the UV emission (at 380 nm), indicating that the crystalline quality could not be improved by annealing for complex nanostructures, except for the top of the structures. Our results present a simple, reproducible, and cost-competitive method to synthesize ZnO three-dimensional flower-like structures and would provide useful information for the fabrication of optoelectronic devices at room temperature.

The Temperature Dependences of Mechanical Properties, Deformation Hardening, and Fracture of FeMnNiCoCr Heterophase Alloy

It is established that the temperature dependence of the mechanical properties and deformation behavior of a heterophase multicomponent Cantor alloy (FeMnNiCoCr) and the mechanisms of its fracture under uniaxial static tension in the temperature range 77–300 K are determined by the mechanism of formation and distribution of dispersed phases in it. The heterogeneous formation of chromium-enriched σ‑phases and phases with an fcc crystal lattice,mainly at grain boundaries in the course of annealing of homogenized samples (when particles are inhomogeneously distributed over the structure) and at deformation defects in the course of annealing of preliminarily strained samples (when particles are distributed uniformly over the structure), takes place in the Cantor alloy as a result of annealing. It is found that the grain-boundary phases slightly affect the temperature dependence of yield stress σ0.2, the deformation behavior of the heterophase alloy and its mechanism, but contribute to a decrease in the plasticity and to the formation of brittle secondary cracks on fracture surfaces under low-temperature deformation. The complex effect of the dispersion and the grain boundary hardenings in samples with a uniform distribution of particles that are formed in the course of aging of pre-strained samples leads to a substantial increase in the strength properties of the Cantor alloy in the entire temperature range while maintaining high plasticity and a strong temperature dependence of σ0.2.

Action Planning for Improvement of Design and Operating Parameters of Ball-Bearing Steel Tube Annealing

Annealing process was reviewed for hot rolled 100Cr6 steel tubes in a chamber furnace with subhearth burners. Based on the obtained results of thermotechnical testing at the chamber furnace it was detected that the current annealing curve conceptually do not allow production of satisfactory quality tube in the course of annealing. As a result an adjusted curve corresponding to the annealing requirements for 100Cr6 steel and chamber furnace capabilities was proposed. Causes were determined for poor quality tube annealing and detailed review was carried out for chamber furnace capabilities in terms of required heat treatment duration ensuring sufficiently high quality of annealed tubes. List of actions allowing significant improvement of chamber furnace performance and annealed tube quality was considered. Chamber furnace renovation option was proposed where the total heat treatment time of tubes may be reduced significantly through heat transfer process intensification in the furnace working space, uniformity of tube heating in the batch, annealing quality and therefore furnace performance may be improved.

DEGRADATION PROCESSES IN THE AI-TI-SI SYSTEM UNDER THERMAL SHOCK

In recent years, much attention of developers of integrated microcircuits is given to designing novel types of microprocessors, development, and mastery of technologies of both multilayer 3D integrated circuits and making devices based on complex semiconductors. The aim of the present work is to study thermal processes in the Al-Ti-Si multilayer system up to the development of degradation processes. The degradation issues in aluminum metallization with titanium sublayer deposited onto silicon surface are considered. The evolution of processes of irreversible destruction of film conductor under passage through it of single square-wave current pulses with energy up to 300 mJ and duration of 50…1000 μs was analyzed. It was found that, under the action of a single square-wave current pulse with a duration of no more than 80 μs and energy of 85 mJ, the priority process of structural damage is the melting of the metal film. Increasing pulse duration (τ > 80 μs) changes the priority of thermal degradation, and contact melting becomes the main mechanism of structure damage. It was also found that isothermal annealing leads to improving system heat-conducting properties and increasing critical current densities. This is related to the improvement of adhesion properties of the structure as well as with phase transformations in the Al-Ti-Si system in the course of annealing. The results of the article can be used in further studies of the properties of the AI-TI-SI system, as well as in the creation of semiconductor structures taking into account properties such as high electrical conductivity, good processability, the absence of chemical components in the Al-Si system, chemical stability, and a tendency to electromigration, the possibility of short circuit, high diffusion mobility, low melting point, the inability to attach the wire by soldering.

Effect of Bentonite Modification with Glycerol on Adsorbent Structure and Physicochemical Characteristics

The effect of targeted, glycerol-aided modification of natural clay mineral bentonite was studied in terms of changes in the structure and general properties of the adsorbent material. The modification was performed using natural bentonite with a high content of montmorillonite. The bentonite micro- and mesoporosity can be increased by introducing certain struts—pillars into the interlayer structure of aluminosilicates. The data on structural features and physicochemical properties of granular formed samples of adsorbents based on the original bentonite clay were compared to those of glycerol-modified ones. Specific surface area, porosity, volume, and pore size distribution values of the samples studied were measured using the sorption method and gas capillary condensation techniques. The structure of the samples was determined was determined with X-ray phase analysis, and their elemental composition was found with an energy dispersive spectrometer. It was proved that bentonite was modified by pyrolytic carbon resulting from decomposition of glycerol in an oxygen-free medium, in the course of annealing of pellets. The modified bentonite adsorbent had a 4-fold higher specific surface area value compared to the starting material with retention of the basic elemental composition.

Annealing of defects after irradiation of YBCO single crystals with fast electrons

The effect of annealing on the conductivity of optimally doped YBa2Cu3O7−δ single crystals irradiated with fast electrons is investigated. The variation of width of the superconducting transition with increase of the irradiation dose and in the course of annealing is associated with the evolution of the sample inhomogeneity. A recovery of the critical temperature Tc after annealing to some intermediate value between those in the initial and irradiated states is observed. This recovery of Tc is accompanied by a substantial narrowing of the superconducting transition whose width nicely matches that in the non-irradiated state. The observed transition narrowing is attributed to an improvement of the sample homogeneity in consequence of the diffusion-induced growth and eventual coalescence of superconducting domains. In addition, the complete recovery of the normal conductivity after annealing points to a reversible change of parameters of the charge carriers scattering on phonons and defects.

Effect of short-range atomic order on macroscopic magnetic properties of equiatomic FePd alloy

ABSTRACTX-ray diffraction, magnetic measurements, and Mössbauer spectroscopy were employed to comparatively analyse the relation of the basic characteristics of highly anisotropic materials– coercive force Hc and Curie temperature TC to the peculiarities of short-range atomic order that forms upon annealing of disordered samples of equaiatomic FePd alloys produced by different techniques (casting, melt-spinning, severe deformation). It is shown that for all samples, independently of methods of their preparation, the ordered states with the maximal values of coercivity are inhomogeneous in the composition of short-ordered regions, type of atomic ordering, and degree of tetragonality. The Curie temperature depends on the temperature and duration of annealing for ordering similarly to the conventional course of coercivity, which is peculiar to these alloys. The behaviour of these macroscopic characteristics (Hc and TC) in the course of annealing is shown to correlate with changes in the local atomic configurations revealed in the Mössbauer spectroscopy experiments.

High performance UV photodetectors using Nd3+ and Er3+ single- and co-doped DNA thin films

Even though lanthanide ion (Ln3+)-doped DNA nanostructures have been utilized in various applications, they are rarely employed for photovoltage generating devices because of difficulties in designing DNA-based devices that generate voltages under light illumination. Here, we constructed DNA lattices made of synthetic strands and DNA thin films extracted from salmon (SDNA) with single-doping of Nd3+ or Er3+ and co-doping of Nd3+/Er3+ for high performance UV detection. The topological change of the DNA double-crossover (DX) lattices during the course of annealing was estimated from atomic force microscope (AFM) images to find the optimum concentration of Ln3+ ([Ln3+]O). No topological disturbance in DNA DX lattices were observed up to [Ln3+]O, and significant enhancement in the physical properties was obtained at [Ln3+]O. The interactions between Ln3+ and SDNA were examined using spectroscopic methods of UV–visible, Raman, and X-ray photoelectron spectroscopy (XPS). Current and photovoltage measurements for Ln3+-doped SDNA thin films under UV illumination with varying power intensities were conducted. Under UV illumination, the photocurrent and photovoltage of Ln3+-doped SDNA thin films increased with increasing applied external voltages and input power intensities, respectively. In addition, we observed considerable increases in photovoltage responses, i.e., 5-fold increase for Nd3+, 10-fold for Er3+, and 13-fold for Nd3+/ Er3+, compared to the pristine SDNA due to the additional charge carriers generated in Ln3+-doped SDNA thin films. Device performance was measured in terms of photovoltage responsivity and retention characteristics. These phenomena indicate the high stability and substantial endurance characteristics of Ln3+-doped SDNA thin films.

Synthesis and characterization of doxorubicin hydrochloride drug molecule-intercalated DNA nanostructures

In this paper, we demonstrate the feasibility of constructing DNA nanostructures (i.e. DNA rings and double-crossover (DX) DNA lattices) with appropriate doxorubicin hydrochloride (DOX) concentration and reveal significant characteristics for specific applications, especially in the fields of biophysics, biochemistry and medicine. DOX-intercalated DNA rings and DX DNA lattices are fabricated on a given substrate using the substrate-assisted growth method. For both DNA rings and DX DNA lattices, phase transitions from crystalline to amorphous, observed using atomic force microscopy (AFM) occurred above a certain concentration of DOX (at a critical concentration of DOX, 30 μM of [DOX]C) at a fixed DNA concentration. Additionally, the coverage percentage of DNA nanostructures on a given substrate is discussed in order to understand the crystal growth mechanism during the course of annealing. Lastly, we address the significance of optical absorption and photoluminescence characteristics for determining the appropriate DOX binding to DNA molecules and the energy transfer between DOX and DNA, respectively. Both measurements provide evidence of DOX doping and [DOX]C in DNA nanostructures.

Peculiar Kinetics of Coercivity of Sintered Sm(Co0.78Fe0.10Cu0.10Zr0.02)7 Magnet Upon Slow Cooling

The origin of coercivity of the sintered Sm(Co0.78Fe0.10Cu0.10Zr0.02)7 magnets has been studied in the course of step annealing by X-ray diffraction and magnetic measurements. The Cu redistribution in the Sm(Co,Cu)5 boundary phase of the cellular structure modifies the domain-wall energy and increases the coercivity upon step cooling. Interphase stresses are considered to be the main reason for copper redistribution upon slow cooling. It is shown that the coercivity abruptly increases in the course of annealing at a temperature of 500 °C, which is close to the Curie temperature of the Sm(Co,Cu)5 phase. The effect may be caused by an increase in the interphase stresses at the boundary of the coherent 1:5 and 2:17 phases in the course of the annealing at the temperature close to the Curie temperature of the 1:5 phase. The accelerated Cu diffusion into the boundary compensates these stresses. The new scheme of the Cu redistribution over the cell-boundary phase is suggested. Contrary to the known schemes, it assumes that Cu is localized in the 1:5 phase near the interface between the phases, rather than in the center of the 1:5 phase.

Specific structural features of crystalline regions in biodegradable composites of poly-3-hydroxybutyrate with chitosan

Differential scanning calorimetry and X-ray diffraction at wide and small angles were used to examine the biodegradable composites of poly-3-hydroxybutyrate with chitosan, produced by mixing of these polymers in a rotor disperser at 150°C. Samples of individual polymers and composites with 80, 40, and 20 wt % poly- 3-hydroxybutyrate were studied. It was found that the presence of chitosan in the composites leads to a change in the crystallite size of poly-3-hydroxybutyrate and to an increase in the large period in this polymer. Mixing of poly-3-hydroxybutyrate with chitosan affects the structural rearrangement in crystalline regions of poly-3-hydroxybutyrate under a high-temperature treatment. The effect of a high-temperature treatment of the composites via alternation of melting–crystallization cycles in the nonisothermal mode, when a sample is heated and cooled at the same constant rate of 8 deg min–1 in the range from 20 to 200°C and is annealed at a temperature of 150°C, was analyzed. This analysis suggests that, in composites of this kind, the intermolecular interaction between the components is a factor strongly affecting the structure of the crystalline regions and the mechanism of their rearrangement in the course of annealing. The mechanism of this interaction is discussed.

Effect of 0.3% Sc on microstructure, phase composition and hardening of Al-Ca-Si eutectic alloys

The phase composition, microstructure and hardening of aluminum-based experimental alloys containing 0.3% Sc, 0–14% Si and 0–10% Ca (mass fraction) were studied. The experimental study (electron microscopy, thermal analysis and hardness measurements) was combined with Thermo-Calc software simulation for the optimization of the alloy composition. It was determined that the maximum hardening corresponded to the annealing at 300–350 °C, which was due to the precipitation of Al3Sc nanoparticles with their further coarsening. The alloys falling into the phase region (Al)+Al4Ca+Al2Si2Ca have demonstrated a significant hardening effect. The ternary eutectic (Al)+Al4Ca+Al2Si2Ca had a much finer microstructure as compared to the Al–Si eutectic, which suggests a possibility of reaching higher mechanical properties as compared to commercial alloys of the A356 type. Unlike commercial alloys of the A356 type, the model alloy does not require quenching, as hardening particles are formed in the course of annealing of castings.

The combined effect of aging and accumulative roll bonding on the evolution of the microstructure and mechanical characteristics of an Al–0.2 wt % Zr alloy

This work is devoted to the effect of processes initiated by the combined action of aging (A) and accumulative roll bonding (ARB) on the evolution of the microstructure and the mechanical characteristics of an Al–0.2 wt % Zr alloy. Upon solution treatment (ST), followed by aging at temperatures of 350 and 450°C, the specimens were subjected to deformation to a degree of deformation of 80% using ARB. The evolution of the microstructure was examined using atomic force microscopy and the mechanical characteristics of the specimens were determined using tensile tests and Vickers microhardness measurements. The results have shown that, upon ten ARB cycles, the grain size decreased to 0.3, 0.4, and 0.32 μm in the specimens subjected to ST followed by ARB (ST–ARB), ST followed by A at a temperature of 350°C and ARB (350°C–A–ARB), and ST followed by A at a temperature of 450°C and ARB (450°C–A–ARB), respectively. This study has also shown that the combined use of preliminary A and subsequent ARB holds promise in enhancing the mechanical characteristics of the alloy due to precipitates that appear in the course of annealing. Fracture surfaces of the rolled specimens subjected to the tensile tests were examined using scanning electron microscopy. The results of these examinations have shown that in the specimens subjected to ST followed by ARB brittle fracture has been observed at the stage of the final ARB cycles, while in the A–ARB specimens cleavage facets (sites of fracture over the cleavage plane) and river lines have appeared on the fracture surfaces.

Numerical Simulation of Copper Migration in Single Crystal CdTe

With better CdTe material properties and more effective contacts, the compensated Cu doping is crucial for enhancing the performance of CdTe solar cells. Moreover, the metastable behavior of CdTe devices is associated with Cu migration. To understand the formation of Cu acceptors in CdTe and Cu-related metastabilities, we developed a one-dimensional diffusion-reaction simulator to study the kinetics of Cu-related defects in CdTe material. A detailed kinetic model that explicitly describes the evolutions of point defects was developed and applied for the first time. Migration of intrinsic and Cu-related extrinsic defects in single crystal CdTe (sx-CdTe) bulk has been investigated in time-space domain self-consistently with free carrier transport. Cu profiles achieved from simulations match with the experimental profiles quantitatively. The simulation results provide explanations of limited Cu incorporation (also known as the Cu solubility limits) and the development of Cu compensation in course of annealing and cooling processes. Although the one-dimensional simulation has intrinsic limitations when applied to poly-crystalline CdTe solar cells, the results suggest that the approach still has strong potential in better understanding the performance and the metastabilities of poly-crystalline CdTe photovoltaic devices.

Effect of scandium on structure and hardening of Al–Ca eutectic alloys

The phase composition, structure and hardening of alloys in the aluminium corner of the Al–Ca–Sc system were studied in the range up to 10% Ca and up to 1% S≿. The experimental study (optical, scanning and transmission electron microscopy with electron-microprobe analysis, differential thermal analysis and hardness measurements) was combined with Thermo-Calc software simulation for the optimization of the alloy composition. It was shown that only phases of the binary systems (Al4Ca и Al3Sc) might be in equilibrium with the aluminium solid solution. It was shown that the (Al) + Al4Ca eutectic had a much finer structure as compared with the Al–Si eutectic, which suggests a possibility of reaching higher mechanical properties as compared to commercial alloys of the A356 type. The influence of the annealing temperature within the range up to 600 °С on the structure and hardness of the Al–Ca–Sc experimental alloys was studied. It was determined that the maximum hardening corresponded to the annealing at 300 °С, which was due to the precipitation of Al3Sc nanoparticles with their further coarsening. With an example of an Al-7.6% Ca-0.3% Sc model experimental alloy, a principal possibility of manufacturing aluminium casting alloys based on the (Al) + Al4Ca eutectic was demonstrated. Unlike commercial alloys of the A356 type, the model alloy does not require quenching, as hardening particles are formed in the course of annealing of casting.

An investigation on microstructure and mechanical propertiesof a Nb-microalloyed nano/ultrafine grained 201 austenitic stainless steel

The present study was aimed to investigate the mechanical properties of a nano/ultrafine grained Nb-containing 201 austenitic stainless steel. For this purpose, 90% cold rolled sheets with fully martensitic microstructure were isothermally annealed at 900°C for different times of 1 to 1800s, leading to the reversion of strain- induced α′-martensite to austenite and significant grain refinement. Ferritescopy, X-ray diffractometery and optical/electron microscopy techniques along with hardness measurements and tensile tests were used to study the evolution in microstructure and mechanical properties in the course of annealing. It was found that heavy cold-rolling promoted formation of Nb-rich carbonitrides which effectively retarded the growth of fine reverted austenite grains. The obtained results showed that the complete transformation of martensite to austenite took about 60s with the corresponding austenite grain size of about 90nm. This sample had an ultrahigh yield strength of 1170MPa, which was almost four times higher than that of the raw material and outstanding elongation of 37%. Further, the true stress–strain curves of the reversion annealed samples revealed two distinct uniform elongation stages (stage I and stage II), whereas, the onset of stage II was concurrent with pronounced strain hardening. This was related to the sharp increase in the formation of α′-martensite upon tensile straining.

Formation of the microstructure in the course of low-temperature annealing of cryogenically deformed copper

The formation of the microstructure in the course of annealing of cryogenically deformed copper is investigated. It is shown that this material is very unstable, and the primary recrystallization in it is finished already after 1-h annealing at 150°C. The formation of the microstructure and texture in the course of the recrystallization are determined by the selective growth of grains with orientations close to (90;27;45), (80;31;35), and (55;30/60;0).

Effect of annealing on the spectra of nuclear quadrupole resonance in gallium-indium selenides and characteristics of structures based on these materials

The results of studying the effect of low-temperature annealing (at temperatures no higher than 250°C) on the spectra of nuclear quadrupole resonance in layered GaSe and InSe single-crystal semiconductors are reported. The electrical and photoelectric characteristics of the p-GaSe-n-InSe structures have also been studied. It is shown that, as the annealing temperature is lowered to room temperature, the quality of the samples improves due to a decrease in the defect concentration in the crystals and due to ordering in a system of polytypes. The temperature conditions for the heat treatments, at which the main parameters of the heterojunction are improved, are determined. Mechanisms affecting the behavior of the p-GaSe-n-InSe structure during the course of annealing are discussed.

Annealing of ion implanted CdZnO

We have studied the effect of the Cd content on the recovery of ion-induced damage in wurtzite CdxZn1−xO (x ⩽ 0.05) films and compared with that in pure wurtzite ZnO and rock-salt CdO. 200 keV Au+ and 55 keV Ar+ ion implants were performed at room temperature in the dose range of 5 × 1014–6.5 × 1015 cm−2. Rutherford backscattering/channelling spectrometry was used to characterize the damage evolution in the course of annealing (600–900 °C in air). A complex defect annealing behaviour is revealed in CdZnO as a function of annealing temperature, Cd content and ion dose. In particular, defects in the low dose implanted CdZnO films can be effectively removed at 800 °C, while the high dose implantation results in the formation of defects stable at least up to 900 °C. Moreover, annealing of the CdZnO films is accompanied by Cd loss at the surface for temperatures exceeding 800 °C. In contrast, CdO exhibits a typical damage accumulation behaviour for metals and semiconductors with high degree of ionicity, resulting in saturation and extended defect formation at high ion doses. These extended defects in pure ZnO and CdO, formed either directly during implantation or by reconstruction during post-implant annealing, are substantially more stable compared with small defects which can be efficiently removed at 700 °C and 600 °C for ZnO and CdO, respectively.