Effect Of Low-temperature Annealing Research Articles

Effect of low-temperature annealing on the superelastic response and electrochemical corrosion behaviour of equi-atomic Ni-Ti alloy

ABSTRACT Nickel–Titanium (Ni–Ti) alloys have exemplary properties such as good thermo-mechanical response and biocompatibility. Hence, they are one of the prime materials of interest in today’s context for the fabrication of advanced biomedical devices. Such properties can be exemplified with certain techniques such as heat-treatment techniques. However, peer-reviewed literature for the same appears to be inadequate to efficiently quantify the effect of such techniques on the overall performance of such materials. Therefore, the present study focuses on analysing the effect of low-temperature heat treatment on the superelastic behaviour and corrosion resistance of titanium-rich Ni–Ti alloys. The superelastic behaviour has been evaluated for different strains. Meanwhile, the Tafel extrapolation method is incorporated to assess the electrochemical corrosion of these materials. It is noticed that the low-temperature heat treatment has marginal effects on the superelastic behaviour of the alloy. The Ni–Ti alloy annealed at 450°C at 6% predetermined strain rate showed the best enhancement in the superelastic behaviour and the corrosion resistance increased upto treatment temperatures of 350°C. Therefore, the most optimum temperature of annealing is found to be 350°C, resulting in about 35.72% improvement in the corrosion resistance of the alloy when compared to their untreated counterparts.

(Invited) Tailoring 2D Materials As Artificial Enzymes for Developing Electrochemical Biosensors

There is a significant need for development of low-cost and portable diagnostics for non-invasive monitoring of biochemical markers. Among various biosensors, electrochemical sensors are at the forefront of point of care diagnostics, due to simple and real-time readout, low cost, high sensitivity, and portability, as evident from the dominance of enzymatic glucose sensors in the healthcare sector.(1) Despite their significant success, one of the main challenges with enzyme-based sensors is the limited (or none) choice of enzymes for analytes beyond glucose and their incompatibility with device engineering processes.(2)Over the past few years, there have been significant advances in flexible sensors, printed electronics, and wireless devices based on graphene and other 2D materials.(2–5) Being atomically thin, with high surface-to-volume ratio, 2D materials are extremely sensitive to surface perturbation, making them suitable for highly sensitive and selective electrochemical sensors. Moreover, their physical, electronic, and electrochemical properties can be modified via doping, defects, and heterostructures to enable new functionalities for biochemical sensing. We have recently made significant progress in developing non-enzymatic electrochemical sensors based on 2D materials and hybrids as ‘artificial enzymes’, with special focus on device scalability and ease of fabrication. In this regard, we have studied the role of substrate in material-analyte interface characteristic,(6) the effect of post-deposition low-temperature annealing of 2D inks on material-analyte interaction, and the importance of defect configuration in tuning the material-analyte band alignment.(7) In this talk, I will present our recent progress and undergoing research in this area.

Improved Hydrogen Embrittlement Resistance of Steel by Shot Peening and Subsequent Low-temperature Annealing

The effect of shot peening and subsequent low-temperature annealing (SP treatment) on hydrogen embrittlement in tempered martensitic steel was investigated comparing the typical hydrogen charging methods, constant current controlled cathodic charging test and combined cyclic corrosion test (CCT). The hydrogen entry behavior was evaluated by hydrogen permeation technique and hydrogen visualization using secondary ion mass spectrometry. The SP treatment improved hydrogen embrittlement resistance in both hydrogen charging methods. On the other hand, the effect of SP treatment on the hydrogen entry was different depending on hydrogen charging method. The hydrogen entry was suppressed by SP treatment in the cathodic charging test because the compressive residual stress reduced hydrogen concentration in the surface layer and the potential increased by the increase of surface roughness and the formation of a surface film. In CCT, although the surface hydrogen concentration decreased due to compressive residual stress, the total hydrogen content did not decrease by SP treatment since the surface film disappeared by corrosion and an increase of surface roughness led to an increase in hydrogen entry sites. The improved hydrogen embrittlement resistance by the SP treatment in the cathodic charging test is a result of hydrogen entry suppression in addition to the effect of compressive residual stress. In CCT, the hydrogen embrittlement resistance was improved by SP treatment due to effect of compressive residual stress, i.e., the suppression of stress concentration as well as the stress-induced hydrogen diffusion in stress concentration area and the reduction of hydrogen concentration in the surface layer.

Effect of low annealing temperature on the structure and chemical order of Ni2MnGa thin films

Low temperature annealing effect on the structure, residual stress and local chemical order of Ni2MnGa alloys thin films were investigated by atomic force microscopy, x-ray diffraction and x-ray stress analyses as well as extended x-ray absorption fine structure. Thin films were prepared by sputtering on GaAs substrates maintained at room temperature and 300 °C during deposition. The samples prepared at 300 °C were subsequently annealed at 150 °C and 300 °C for one and half hour. X-ray diffraction measurements indicated both a development of crystalline texture in which austenite (110) crystalline planes are preferentially aligned parallel to the film plane as well as compressive residual stress, mainly induced by the accommodation of the film on the substrate surface and by heating-cooling in the growth process. Atomic force microscopy analyses reveal a surface morphology dominated by a topography of hillocks and peaked massifs, whose roughness increases by about twenty times with the increase in the crystalline texture induced by annealing at 300 °C of the samples. Interestingly, extended x-ray absorption fine structure analysis performed at Mn K-edge indicate that residual stress is preserved even after significant increase of the structural and chemical ordering induced by the low temperature annealing.

Enhanced Thermal Stability of Elevated-Metal Metal-Oxide Thin-Film Transistors via Low-Temperature Nitrogen Post-Annealing

Effects of low-temperature annealing in nitrogen atmosphere on elevated-metal metal-oxide (EMMO) thin-film transistors (TFTs) are investigated and reported in this article. Compared with the short-circuit behavior of EMMO TFTs after annealing in nitrogen atmosphere at 300 °C, it is found that TFTs received annealing in nitrogen atmosphere at 200 °C prior to that at 300 °C not only remain the transfer characteristics, but also exhibit improved on-state current and subthreshold characteristics. Both the results of X-ray photoelectron spectroscopy (XPS) and persistent photoconductivity (PPC) confirmed the reduction of oxygen vacancies in the a-IGZO after annealing in nitrogen atmosphere at 200 °C, indicating that the passivation of oxygen vacancy with nitrogen is dominant rather than the generation of oxygen vacancy. Furthermore, the thermal stability improvement could not be realized when the annealing in nitrogen atmosphere at 200 °C was performed before the source/drain formation annealing at 400 °C, which emphasizes the importance of annealing procedures during device fabrication.

Effect of Low-Temperature Annealing on Creep Properties of AlSi10Mg Alloy Produced by Additive Manufacturing: Experiments and Modeling

The effects of postprocessing annealing at 225 °C for 2 h on the creep properties of AlSi10Mg alloy were investigated through constant load experiments carried out at 150 °C, 175 °C and 225 °C. In the range of the experimental conditions here considered, the annealing treatment resulted in an increase in minimum creep rate for a given stress. The reduction in creep strength was higher at the lowest temperature, while the effect progressively vanished as temperature increased and/or applied stress decreased. The minimum creep rate dependence on applied stress was modeled using a physically-based model which took into account the ripening of Si particles at high temperature and which had been previously applied to the as-deposited alloy. The model was successfully validated, since it gave an excellent description of the experimental data.

Effects of low‐temperature thermal annealing on interface characteristics in IZO/IGZO dual‐channel thin‐film transistors

Dual-channel thin-film transistors (TFTs) show excellent effective mobility (μ eff ) and reliability, including negative-bias-illumination stability. To enhance the performance of these devices, post-thermal annealing in air is performed for 2 h at the low temperature of 250°C. To investigate the effects of low-temperature thermal annealing, indium–zinc-oxide/gallium–indium–zinc-oxide (IZO/IGZO) dual-channel TFTs with various IZO thicknesses are fabricated and examined. The observed parameters are μ eff, saturation mobility (μ sat ), subthreshold slope (SS), and threshold voltage (V TH ). The interface quality may be improved by low-temperature thermal annealing, which was confirmed by the improvement in μ eff and SS. However, these performance enhancements are intensively observed only in the channels with an IZO thickness below 10 nm. When the IZO thickness becomes 10 nm or more, the improvement in μ eff due to low-temperature thermal annealing hardly occurs. This is because μ eff is greatly influenced by the interface quality due to Coulomb scattering when the IZO thickness is <10 nm. However, for an IZO thickness above 10 nm, as phonon scattering also has a significant effect on μ eff, the improvement in interface quality by thermal annealing is small. This is also supported by low-frequency noise measurements, which are sensitive to interface quality.

Effects of low-temperature annealing on capacitance performances of NiCo-based bimetal-organic framework materials synthesized in various solvents

As electrode materials, MOFs have large specific capacitance but poor stability. Here, a low-temperature annealing strategy is reported to optimize structures and capacitance performances of bimetallic MOFs (NiCo-BPDC) synthesized in various solvents. Annealing at 350 °C or 400 °C hardly changes crystalline and chemical structure of NiCo-BPDC, but expels trapped or coordinated solvent molecules and homogenizes MOFs, which can benefit electrolyte-ion transport and storage. Annealing does enhance significantly rate capability and cycling stability of NiCo-BPDC. Capacitance retention of annealed NiCo-BPDC is above 59% as current density increases to 10 A g−1 from 0.5 A g−1, and exceeds 70% after 3000 GCD cycles at 1 A g−1.

Effects of cold rolling and low-temperature annealing on microstructure and mechanical properties of rapidly solidified Cu–3Ag-0.5Zr alloy

The effects of cold rolling and low-temperature annealing on the microstructure and mechanical properties of Cu–3Ag-0.5Zr alloy prepared by gas atomization and hot isostatic pressing (HIP) were investigated. The HIPed alloy provides a fine and homogeneous microstructure for the subsequent rolling. The high density of dislocations, the large number of ultrafine grains, and the interaction between dislocations and fine precipitates (nano-sized Ag and micro-sized Cu4AgZr) are responsible for the high hardness (193 Hv), excellent tensile strength (654 MPa), but relatively low elongation (5.6%). Low-temperature annealing achieves a desirable combination of high strength and moderate elongation. After annealing at 350 °C for 2 h, the tensile strength, yield strength and elongation are 584 MPa, 534 MPa and 13%, respectively. When annealed for 8 h, the tensile strength and yield strength decrease to 558 MPa and 504 MPa, respectively, while the elongation recovers to 16.5%. The increased elongation is mainly attributed to the recovery of dislocation-accumulation ability and the slight grain growth.

Effect of Magnetic Pulsing and Low-Temperature Vacuum Annealing on the Soft Magnetic Properties of Hitperm Amorphous/Nanocrystalline Alloy

We studied soft magnetic properties of FeCoHfBCu amorphous/nanocrystalline alloy treated by medium-frequency magnetic pulsing (frequency 1500-2000Hz, field intensity 200-250Oe) and vacuum annealing at low temperature. The results of Mössbauer spectroscopy and transmission electron microscope show that the treating of magnetic pulsing with a medium frequency can introduce the nanocrystallization of amorphous FeCoHfBCu, precipitation of nm phase α-Fe(Co). And, with the increasing of pulsed frequency and field itensity, the crystalized volume friction increases from 24.71% to 35.2%. The low-temperature vacuum annealing for 100°C/30min of magnetic pulsed samples further improved the soft magnetic properties of nanocrystalline alloy. As compared with the amorphous state, the magnetic coerelvity decreaced from 103.4A/m to 34.0A/m, the saturated magnetization decreased from 160.47emu/g to 149.32emu/g.

Effect of low-temperature annealing on void-related microstructure in amorphous silicon: A computational study

We present a computational study of void-induced microstructure in amorphous silicon (a-Si) by generating ultra-large models of a-Si with a void-volume fraction of 0.3%, as observed in small-angle X-ray scattering (SAXS) experiments. The relationship between the morphology of voids and the intensity of scattering in SAXS has been studied by computing the latter from the Fourier transform of the reduced pair-correlation function and the atomic-form factor of amorphous silicon. The effect of low-temperature annealing on scattering intensities and the microstructure of voids has been addressed, with particular emphasis on the shape and size of voids, by studying atomic rearrangements on void surfaces and computing the average radius of gyration of the voids from the spatial distribution of surface atoms and the intensity plots in the Guinier approximation. The study suggests that low-temperature annealing can lead to considerable restructuring of void surfaces, which is clearly visible from the three-dimensional shape of the voids but it may not necessarily reflect in one-dimensional scattering-intensity plots.

Microstructure and mechanical properties of heavily cold drawn pearlitic steel wires: Effects of low temperature annealing

Heavily cold drawn pearlitic steel wires prepared with drawing strains (ε) of 4.5, 5.1 and 5.3 were annealed at low temperatures for different durations. Microstructural characteristics and mechanical properties of the annealed wires were investigated and determined. The tensile strength of cold drawn pearlitic steel wires was found to increase, due to low temperature annealing treatment. For example, for the cold drawn wires (ε = 5.3) annealed at 60 °C for 1 h, the tensile strength is enhanced from about 4920 MPa to 5020 MPa. Counterintuitively, the ductility shows little decrease. With the increase of annealing temperature and time, the tensile strength decreases. For the annealed wires, carbon atoms were observed to segregate at subgrain boundaries (SGBs), and particle precipitation can also be observed. Substitutional solid solution atoms, such as Cr, Mn and Si, remain locked in their original positions. Exothermic peaks in differential scanning calorimetry (DSC) curves were found to shift to higher temperatures for the annealed wires.

Effect of Low Temperature Annealing on Microstructure and Mechanical Properties of Ultra-Heavy Cold-DrawnPearlitic Steel Wires

Effect of Low Temperature Annealing on Microstructure and Mechanical Properties of Ultra-Heavy Cold-DrawnPearlitic Steel Wires

The Effect of Low-Temperature Annealing on the Structural and the Magnetic Characteristics of Co-Precipitated Strontium Cobalt Ferrite

This study aims to prepare strontium-substituted cobalt ferrite (Sr0.1Co0.9Fe2O4) nanoparticles by using a simple co-precipitation process followed by annealing at 300°C–600°C for 5 h. The Sr0.1Co0.9Fe2O4 nanoparticles thus obtained have a face-centred cubic (fcc) inverse-spinel crystalline structure with crystallite sizes in the range from 17.26 to 26.97 nm. The saturated magnetization of the nanoparticles increases with increasing annealing temperature. Furthermore, the transition from a multi-domain to a single-domain configuration is investigated from the viewpoint of the dependence of the crystallity on the coercive field.

Enhancement of the corrosion resistance and mechanical properties of nanocrystalline titanium by low-temperature annealing

Annealing deformed metals usually leads to reduced strength. In the case of nanocrystalline materials, the opposite effect was observed after low-temperature annealing. The annihilation of mobile dislocations and a relaxation of grain boundaries are probable reasons for the observed phenomenon. Dislocation density and grain boundaries character affect also on the corrosion resistance. Hence, in this work the effect of low-temperature annealing on both the hardness and corrosion resistance of nanotitanium was investigated. The results indicated that low-temperature annealing is a fast, simple and inexpensive way to further enhance nanotitanium's mechanical and corrosion properties, which are crucial for implantable materials.

(Invited) Full Wafer CMOS-Compatible Integration of Ge with Si By Direct Wafer Bonding

Silicon is the base material for electronic technologies and has emerged as a very attractive platform for photonic integrated circuits (PICs). PICs allow optical systems to be made more compact with higher performance than discrete optical components. Some of the applications of PICs are in the areas of fibre-optic communications, biomedical devices, photovoltaics and imaging. Germanium, due to its low bandgap, maturity and compatibility with Si technology is preferred over III-V compounds as an integrated on-chip detector at near infrared wavelengths. In the integration of Ge with Si a high-quality defect-free, 100% Ge layer is desirable for realising high-performance photodiodes. Low defect density in the Ge layer will lower the dark current by minimising the leakage mechanisms and noise sources. There are two main approaches for Ge/Si integration: epitaxial growth [1] and wafer bonding [2]. Lattice mismatch of ~4.2% between Ge and Si is the main problem of the former technique leading to high density of dislocations and hence increased leakage current, while the bond strength and conductivity of the interface are the main challenges of the latter. Both result in the formation of trap states which are expected to play a critical role in the device performance. Understanding the physics of the interface is key in the design of Ge/Si devices. In this talk, an alternative integration approach of low-temperature CMOS-compatible plasma activated direct wafer bonding, developed in order to accommodate the lattice mismatch, will be discussed. Electronic and optical devices fabricated exploiting this full wafer integration technique will be demonstrated. The focus will be on the physics of the heterojunction interface and its role in the band alignments. In the first part, a proof of concept of Ge/Si integration by using wafer bonding and layer exfoliation (Smart Cut™ process) with low thermal budget will be outlined. Mesa diodes made by transferring a 700nm-thick Ge layer onto Si using this technique will be reported. Fabrication, characterisation, and analysis of the electrical transport across the interfacial oxide present between the Ge and Si wafers will also be discussed. Highly-doped n-type Si and p-type Ge wafers are used to allow the electric field distribution to drop within short distances from the interface enabling us to investigate the influence of bonded interface on carrier transport through the p-n junction. Effects of low-temperature annealing on the device performance and on the conductivity of the interface will be reviewed. The carrier transport mechanism is shown to be dominated by generation-recombination before anneal and direct tunnelling in forward bias and band-to-band tunnelling in reverse bias after annealing which are defined by the role of interface traps. In the next part of the talk, we report on a remarkably-high responsivity photodiodes especially at low incident powers made by integrating low-doped p-Ge with highly-doped n-Si (p −-Ge/n +-Si heterojunction) by direct wafer bonding. The p −-Ge/n +-Si photodiode arrangement was selected to enable collection of electrons into the Si due to the more favourable band-offset. Responsivities in excess of 3.5 A/W at wavelength of 1.55 µm under surface normal illumination is measured for photodiodes with 5.4 µm Ge layer transferred onto Si by wafer bonding followed by chemical mechanical polishing (CMP). Detailed analysis regarding the temperature-dependent carrier transport across the junction and the band alignments at the interface will be presented. The high responsivity of the detectors is shown to be due to light-induced potential barrier lowering at the interface. To our knowledge, this is the first report of light-gated responsivity for vertical illuminated Ge/Si photodiodes. The developed wafer bonding process followed by either layer exfoliation or CMP is a low-temperature wafer-scale process. The unique results discussed in this talk are compatible with surface normal illumination and are capable of being integrated with CMOS electronics and readout circuits in the form of 2D arrays of detectors. One potential future application is a low-cost back-end-of-line compatible dual-band near infrared/visible cameras. [1] Y. Kang, et al., Nature Photonics, pp. 59-63, 2009. [2] H. Kanbe, et al., Japanese Journal of Applied Physics, pp. L644-L646, 2006. The figure shows a schematic illustration of a Ge/Si photodiode made by wafer bonding followed by CMP. The XTEM images confirm the presence of interfacial amorphous layer at the bonded interface. Photoresponse of the detector as a function of input optical power at a wavelength of 1.55 µm is also presented at two different temperatures. Schematic representation of the band diagram at the Ge/Si interface at equilibrium and under illumination is shown indicating the potential barrier lowering due to filling of acceptor-type traps at interface by the photogenerated carriers. Figure 1

Effect of Low-Temperature Heating on the Properties of Graphene Oxide Aerogel

The paper describes the effect of low-temperature annealing in air on the composition and structure of graphene oxide aerogel. It has been found that the concentration of carbon in the aerogel sharply increases, i.e., its carbonization occurs, already at a temperature of 175°C. At the same time, both the outer shape of the aerogel granules and the internal porous structure are preserved.

The investigation of strength and plasticity mechanism of low-temperature annealed ultrafine grained stainless steel

The properties of steel material can be greatly improved when its grain size becomes finer, so grain refinement is the most commonly used to improve the strength, ductility and impact on the toughness of steel at the same time. Compared to ordinary fine-grained steel, the average grain size of ultra-fine grained steel is less than 2 μm and it has different strength and plasticity mechanism. In this paper, effect of low-temperature annealing on the microstructure and properties of ultra-fine grained stainless steel in internal friction was studied by utilizing transmission electron microscope (TEM) and universal tensile testing machine. At the same time, the strength and plasticity mechanism of ultra-fine grained stainless steel was revealed by internal friction experiments. The results show that with the increase of annealing time and annealing temperature, both the tensile strength and yield strength decreases, while the elongation increases continuously. The mechanical properties of tested steel are more sensitive to the temperature. In the internal friction curve of tested steel, the peak of P1 which result from the interaction between solid solution atoms and dislocations increases first and then decreases, while the peak of P2 which result from the interaction between dislocation and carbide precipitates decreases first and then increases. The peak of P3 which result from the structure, area and movement of grain boundary decreases continuously. The strength and plasticity mechanism of tested steel at room temperature is the result of interaction between the grain boundary and dislocation.

Effect of low-temperature annealing on tensile behavior of electrodeposited bulk nanocrystalline Ni–W alloys

Relatively low-temperature thermal treatment of nanocrystalline metals results in grain boundary relaxation and the absence of clear grain growth. However, the manner in which the relaxation affects the tensile properties of bulk nanocrystalline metals is unclear. In this study, the effect of low-temperature annealing on the tensile behavior of nanocrystalline metals was studied using electrodeposited Ni–W alloys as a model system. Tensile tests were conducted using the electrodeposited bulk nanocrystalline Ni–W alloys in the as-deposited state and after annealing at 200–300°C for 24h. After annealing, the yield strength and tensile strength increased by 0.25–0.34 and 0.13–0.18GPa, respectively, while uniform elongation decreased from 4.8% to 2.5%. Good local elongation of 6.0–7.0%, which was comparable with the value in the as-deposited state, was observed after annealing at 200 and 250°C. However, annealing at 300°C induced a degradation of local elongation to 2.6%. The results of this study indicate that reduction of excess boundary defects affects dislocation emission from grain boundaries, leading to increasing yield strength and decreasing uniform elongation, whereas the relaxation has no effect on the local elongation. In addition, discussion of the microstructures of Ni–W alloys also suggest the possibility that the failure mode changes at annealing temperatures near 250–300°C by changing the shape of grain boundaries more linearly, in addition to a reduction of excess boundary defects.

Low Temperature Annealing Improves the Electrochromic and Degradation Behavior of Tungsten Oxide (WOx) Thin Films

This research aims to understand the fundamental aspects of annealing on the electrochromic performance of tungsten oxides, using as-synthesized W18O49 substoichiometric bundled nanowires benchmarked against commercial WO3 nanoparticles. Linking detailed structural analyses with the electrochromic measurement results, we have investigated the electrochromic performance effects of low temperature annealing, up to 350 °C, on tungsten oxide (WOx) thin films, trying to establish the fundamental heat treatment–structure–performance loop. We have found that the annealing treatment at low temperature improved the optical modulation and long-term durability of the WOx thin films, without changing the structure and morphology of the as-synthesized samples. The 350 °C annealing was found to have the best stability improvement for the WO3 nanoparticle films during the electrochromic assessments, with a 4% improvement for Li+ intercalation and a 12% improvement for deintercalation, compared with the untreated WO3 sam...