Thermal Annealing Treatment Research Articles

Nano-TiO2 Coating Layers with Improved Anticorrosive Properties by Aerosol Flame Synthesis and Thermophoretic Deposition on Aluminium Surfaces.

TiO2 in the form of nanoparticles is characterized by high photocatalytic activity and high resistance to oxidation, making it an excellent candidate to realize coatings for improving the corrosion resistance of aluminium surfaces. Different coating technologies have been proposed over the years, which often involve the use of toxic compounds and very high temperatures. In this work, an alternative and novel one-step method for the coating of aluminium alloy surfaces with titania nanoparticles is presented. The method is based on the combination of aerosol flame synthesis and direct thermophoretic deposition and allows to produce nanostructured thin coating layers of titania with different features. Specifically, 3.5 nm anatase nanoparticles were synthesized and deposited onto aluminium alloy AA2024 samples. The thickness of the coating was changed by modifying the total deposition time. A thermal annealing treatment was developed to improve the adhesion of nano-titania on the substrates, and the morphology and structures of the coatings were characterized using (ultra violet) UV-vis absorption, scanning electron microscopy, transmission electron microscopy and Raman spectroscopy. The corrosion resistance behavior of the coatings was evaluated by means of electrochemical polarization measurements, coupled with a numerical analysis using COMSOL software. Both the experimental and numerical electrochemical polarization curves showed a significant increase in the corrosion potential of coated substrates with respect to the bare aluminium and a decrease in the current density. The coatings obtained with higher deposition time and greater thickness showed the best performances in terms of the resistance of the aluminium surfaces to corrosion.

Regulating the properties of small molecular acceptors with different end groups

In this work, we designed and synthesized two small molecular acceptors, based on benzotriazole (BTA) as the center core with isopropyl alkyl chain, thienothiophene unit (TT) β-position connected n-hexane alkyl chain as wing, and using different end groups, 2-(3-oxygen generation-2, 3-2H − 1H-indane-1-alkyl)-malononitrile (IC) and 2-(5,6-difluoro-3-oxo-2,3-dihydro-1H-indane-1-alkylene) (2FIC), named BIT-IC and BIT-2FIC, respectively. The device based on PM6: BIT-IC achieved the PCE of 3.63%, which exhibited inferior performance because the device absorption is not complementary with solar spectrum, leading to the low Jsc of the device. However, the absorption band of the acceptor BIT-2FIC with 2FIC end group can reach 944 nm, and the HOMO energy level is lower than BIT-IC, therefore, the device based on PM6: BIT-2FIC can achieve more efficient exciton dissociation and charge transport, after thermal annealing treatment at 90 °C for 10 min, the device based on PM6: BIT-2FIC can achieve the PCE over 14%.

Algorithmically extracted morphology descriptions for predicting device performance

The device performance of thin film electronics is known to be dependent on morphological properties such as the size, shape, and orientation of aggregates and crystalline domains. So far, descriptions of morphology have been semi-quantitative and loosely linked to device performance. However, by using our recently reported quantitative analysis tool m2py, we create morphology labels and, for the first time, extract quantitative morphology information from scanning probe microscopy measurements. In this work, we use the labels and extracted morphology measurements to validate a novel approach of generating quantitative structure–property relationships through the use of machine learning and regression models; we present this generalizable approach by demonstrating it on organic photovoltaics. In our approach, the open-source toolkit, m2py, is used to label and describe a set of organic photovoltaic devices that have received different thermal annealing treatments, thereby altering their morphologies and, subsequently, their performance. Different regressors and types of morphology descriptions are used to examine the efficacy of quantitative morphology descriptors in predicting device performance. Despite the fact that scanning probe measurements only image the thin film surface, we find that the information-rich nature of morphology data enables accurate device performance predictions, even with datasets that would traditionally be considered too small to generate high-quality predictions. The implications of introducing quantitative morphology information for predictive analysis of other devices and materials is also discussed; given the general and material-agnostic nature of m2py, it is anticipated that the predictive capability of these labels will be ubiquitous to all thin film applications.

Optical emission bands of Sm2O3 and their link with crystalline defects and 4fd→4fd electronic transitions at UV-Vis region

The Chemical Bath deposition method has been used to synthesize Samarium Oxide (Sm2O3) in previous research where the morphological, structural, and optical properties were studied after thermal annealing treatment at ~1000 °C in the air atmosphere. The present study continues the research on this interesting inorganic material. The average grain size is located at ranges ~22.10 nm to ~28.20 nm, and the optical absorption shows two bands located at ~277 nm (~4.47 eV) and ~408 nm (~3.03 eV) situated in the UV-Vis region. We apply the photoluminescence (PL) spectroscopic technique to examine the emission bands that overlap with the 4fd→4fd electronic transitions in the context of some optical properties at the UV-Vis region. The emission signals present peaks at ~2.52, ~2.55, ~2.56, ~2.60, ~2.63 and ~2.66 eV. Likewise, the Maxwell-Boltzmann statistical model (MBSM) is employed to correlate the native crystalline defects with the cited electronic transitions and emission bands. Finally, the MBSM theoretical curve wraps the emission signals associated with the 4fd→4fd electronic transitions linked with crystalline native defects confirmed by the calculated density of traps. A brief analysis of the chemical kinetics of crystal growth is proposed here.

Laser-assisted synthesis of carbon coatings with cobalt oxide nanoparticles embedded in gradient of composition and sizes

We report on a new laser-assisted method for the synthesis of composite coatings consisting of cobalt oxide-embedded porous carbon with gradient of composition and sizes. Uniform carbon thin films containing cobalt oxide nanoparticles (CoO NPs) of various concentrations and sizes are obtained by Combinatorial Matrix-Assisted Pulsed Laser Evaporation (C-MAPLE) followed by a post-annealing treatment. Specifically, simultaneous pulsed laser irradiation of two concentric cryogenic targets was applied for gradient thin films assembling on solid substrates. Both targets contained environmentally friendly phloroglucinol/glyoxylic acid organic precursors and a template dissolved in an ethanol-chloroform mixture, whereas one of them enclosed, in addition, cobalt nitrate salt. Due to angular dispersion and crossing of the two vapor plumes during co-deposition process, thin composite polymeric nanocoatings containing Co nitrate salt were obtained. After subsequent thermal annealing treatment of samples at 600 °C, mesoporous carbon films exhibiting CoO NPs gradient distribution were then directly obtained onto the substrates. Carbon matrix formation was supported by EDX analyses and characteristic D, G and 2D bands present in the Raman spectra. Co NPs concentration varied from 3 to 32 wt% on the substrates with a minimum at furthest interaction point of the Co salt containing plume and substrate, while carbon concentration significantly decreased from 91 to 63 wt%. Oxygen amount was relatively constant at about 6 wt% for all coatings. The CoO NPs are homogenously dispersed in the carbon matrix whereas a tendency for aggregation is observed for high loadings. In addition, the CoO NPs size gradient distribution ranged from 3 to 8 nm with the minimum size correlating the minimum concentration.

CNTs-intertwined and N-doped porous carbon wrapped silicon anode for high performance lithium-ion batteries

Silicon is evaluated as a competitive lithium-ion batteries anode material by virtue of its ultrahigh specific capacity and relatively low discharge potential. However, the large volume change during lithiation/delithiation processes, and the low intrinsic electric conductivity have seriously impeded its widespread practical application. Herein, silicon nanoparticles (SiNPs) coated with CNTs-intertwined N-doped porous carbon (NPC) are prepared via a facile solution-phase method, followed by thermal annealing treatment. In this hierarchical structure, the bimetallic ZIF-derived porous carbon can shorten the migration channels of Li+ and electrons. Moreover, the formed Co nanoparticles can not only catalyze the graphitization of carbon, but also propel in-situ growth of CNTs to constitute a 3D interconnected conductive network, thereby improving the electrochemical performance. Benefiting from the unique structure, the as-prepared Si@CoSi2/Co-NPC@CNTs electrode exhibits superior electrochemical performance of 1191 mAh g−1 at 0.5 A g−1 after 200 cycles. Meanwhile, the electrode also shows excellent rate capability of 930 mAh g−1 even at a high current density of 6 A g−1. This work provides a new strategy to design exceptionally high electrical conductivity and structure stability of Si-based anode materials.

Solvent Annealing Enables 15.39% Efficiency All‐Small‐Molecule Solar Cells through Improved Molecule Interconnection and Reduced Non‐Radiative Loss

AbstractPost‐treatment is of great importance to form nanoscale phase‐separated morphology for all‐small‐molecule organic solar cells (ASM‐OSCs), while the reasons for the difference between thermal annealing (TA) and solvent annealing (SVA) remain unclear. In this work, the influences of TA and SVA (with three common solvents of THF, CS2, and CF) are systematically investigated based on BT‐2F:N3 through characterization of photovoltaic performance, molecular stacking, charge transfer, etc. The results indicate that: i) solvents with good solubility induce stronger molecular interaction than that of TA treatment, and thus endowing molecules with better mobility to migrate for crystallization and phase separation, which leads to better J‐aggregation and molecular interconnection. ii) Donor‐selectively dissolved CS2 is better for optimizing the donor domain for its suitable domain size, improved molecular interaction and interconnection, and reduced trap states. iii) CS2 imposes a small impact on N3 acceptors and thus alleviates the increment of non‐radiative recombination. As a result, CS2 SVA with unique multifunctions enables a PCE of 15.39% with simultaneously improved voltage (0.845 V) and fill factor (75.02%), which is much higher than 14.66% of TA treatment. Moreover, 15.39% efficiency is also the highest value in binary ASM‐OSCs.

Simultaneously enhancing strength and ductility of Ti-6Al-4V alloy with the hierarchical structure via a novel thermal annealing treatment

A novel solution and aging (STA) heat treatment was proposed to improve the strength and ductility of Ti-6Al-4V alloy simultaneously. Effects of the novel heat treatment on microstructure and mechanical properties of the Ti-6Al-4V alloy prepared by spark plasma sintering (SPS) were studied in this work. The crystalline structure and microstructure of both the as-fabricated Ti-6Al-4V alloy and the STA Ti-6Al-4V alloy were observed using X-ray diffraction (XRD) technique, optical microscope (OM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM), respectively. The XRD patterns indicated that the two Ti-6Al-4V samples have the similar crystalline structure with α phase and β phase. However, the results of OM images suggested that the microstructure of Ti-6Al-4V alloy was transformed from the Widmanstätten structure to a hierarchical structure which included the basket-weave structure and the Widmanstätten structure after the STA heat treatment. Apart from the above-mentioned microstructure, the hierarchical structure also exhibited specifically some fine dispersed β surrounded by some equiaxed α. Moreover, the results of the room temperature tensile tests revealed that the STA heat treatment could improve the strength and ductility of the Ti-6Al-4V alloy simultaneously. Based on the observation of TEM images, the increment of the elongation of the STA Ti-6Al-4V alloy can be attributed to the effect of annealing twins and equiaxed α, and the total strength increments should be caused by the dispersion strengthening effect of the dispersed β.

Surface activation of poly(methyl methacrylate) for microfluidic device bonding through a H2O plasma treatment linked with a low-temperature annealing

This paper reports on a rapid, lossless process for the bonding of poly(methyl methacrylate) (PMMA) substrates for use in microfluidic devices for blood tests, utilizing H2O plasma, and H2O linked rapid thermal annealing (RTA) treatments. The bonding of PMMA produced with H2O plasma linked with RTA was analyzed, and its effect on the bonding of free radicals was investigated. The PMMA surface treatment was performed at constant RF power and H2O vapor flow but changing plasma treatment times in both processes. The surface modification of the PMMA subjected to the H2O plasma treatment was studied by optical emission spectroscopy, which confirmed that the relative intensity of hydroxyl radicals and oxygen emission peaks. The surface of the PMMA after being subjected to the plasma linked with RTA treatment was also characterized. The free energy increased with the plasma treatment time. The tensile test results revealed that the strength of OH bonds on the PMMA surface increased with a high plasma treatment time of 120 s. After bonding, UV–visible transmission spectrum measurements revealed that the transparency of the microfluidic device increased. We demonstrated the bonding of a microfluidic device with plasma treatment without deformation. This method provides an ideal bonding technique for the manufacture of microfluidic devices with PMMA. This technique has more advantages than other bonding techniques.

Self-organized nanostructures in magnetic CoGa0.8Mn1.2O4 thin films fabricated by pulsed laser deposition

The fabrication of highly-ordered nanostructures by self-organization is one of the greatest challenges in nano science. Herein, we report the formation of a self-organized nanostructure in the CoGa0.8Mn1.2O4 thin film through a thermal annealing treatment. The thin film as-deposited by pulsed laser deposition exhibits a single crystalline phase epitaxially oriented along the [001] direction the SrTiO3 [001] substrate. Post-annealing in air was found to promote crystalline phase separation into tetragonal and cubic phases driven by the Jahn–Teller effect resulting in the formation of the nano-zigzag pattern. The structural and magnetic properties of the nanostructured films strongly depend on the annealing time, which can be attributed to the inter-diffusion of Ga and Mn ions.

Metal-organic framework derived hollow CoFe@C composites by the tunable chemical composition for efficient microwave absorption

Controlling the composition and microstructure of nanomaterials is still a significant challenge in developing high-performance microwave absorption (MA) materials. Herein, metal–organic framework (MOF)-derived hollow CoFe@C nanoboxes are designed and prepared through the facile regulating the mass ratios of ZIF-67/PFC and a thermal annealing treatment. The CoFe@C composite can achieve an excellent MA performance, which have two high reflection loss (RL) values at different thickness. A RL value of −31.0 dB is obtained at 11.84 GHz with a matching thickness of 2.4 mm, and a RL value can reach −44.1 dB (4.08 GHz) at a matching thickness of 5.8 mm, and a correspondingly wide absorbing bandwidth (5.20 GHz, from 9.7 to 14.9 GHz) is simultaneously obtained at a matching thickness of 2.3 mm. The magnetic loss, interfacial polarization and hollow structure are the main reasons for their excellent MA capability. This work provides a research idea for the development of the efficient MOF-based MA materials in practical application.

Two‐Step Thermal Annealing: An Effective Route for 15 % Efficient Quasi‐2D Perovskite Solar Cells

Low-dimensional perovskites (LDP) are nowadays recognized as promising materials for the realization of highly performing photovoltaic cells. However, issues related to film morphology, composition, crystal quality and material homogeneity limit the device performances and reproducibility. In this work, we implement a robust method for the deposition of a LDP mixing methylammonium (MA) and phenylethylammonium (PEA) cations to create the mixed system (PEA)2 MA39 Pb40 I121 by using a two-step thermal annealing treatment (at 60 and 100 °C). Our approach results in LDP films with high crystal quality and enhanced carrier lifetime, which double the power conversion efficiency of reference devices, reaching up to 15 %.

Formation of β-Be3N2 nanocrystallites in Be-implanted GaN

A small Be ion dose of 5 × 1014 cm−2 was implanted in a 2 μm thick GaN epilayer at an energy of 50 keV. The sample was characterized by high-resolution transmission electron microscopy (HRTEM) and Raman spectroscopy techniques after a post-implantation rapid thermal annealing (RTA) treatment. The HRTEM images show the crystallographic (1 1 0) and (0 0 2) planes of β-Be3N2. Two characteristic parallelograms drawn in Fast Fourier transform (FFT) image support the formation of β-Be3N2 nanocrystallites in RTA treated sample. Two Raman peaks at 168 and 199 cm−1 are observed in the Raman spectrum of the sample that are assigned to β-Be3N2 on the basis of group theory and HRTEM data. The Raman peak at 168 cm−1 is found close to the K point in the first Brillouin zone of β-Be3N2 while the peak at 199 cm−1 is assigned as a combination mode of the fundamental Raman modes of β-Be3N2.

Effects of rapid thermal annealing as back contacts activation treatment on CdS/CdTe multi-contacted solar cells

Cd2SnO4/CdS/CdTe/CuxTe/Au structure solar cells were made in samples of 20 × 20 mm2. Multiple metallic back-contacts were deposited on each sample by thermal evaporation. A series of rapid thermal annealing treatments (RTA) were performed on the cells, controlling work pressure (Pw) and temperature (Ta), to activate the interface of CdTe-back contact. Several combinations of pressure (746 mbar ≤ Pw ≤ 1112 mbar) and temperature (180 °C ≤ Ta ≤ 260 °C) were studied. The best results were obtained for the lowest Pw, increasing the average efficiency from 6.9% to 9.8% as Ta increased. All photovoltaic parameters (VOC, JSC, FF, RS, and RSh) were enhanced with the RTA treatments along with the dispersion values. Once the thermal activation's optimal conditions were determined, the highest efficiency was 11.3% with an RTA single treatment. The improvement is attributed to the formation of Cu1·85Te phase. It is shown that this kind of thermal treatment on CuxTe/Au back-contact of the cells can be employed to obtain higher area solar cells.

Irreversible structural changes of recovered hydrogen hydrate transforming from C0 phase to ice XVII

• Neutron diffraction on the recovered high-pressure hydrate C 0 . • Crystalline structure transformation from the recovered C 0 hydrate to ice XVII. • Spurious guest contamination in recovered gas hydrates. • Thermal annealing treatment on the recovered filled ice. The present work, performed by means of ex-situ neutron diffraction measurements and combined with complementary Raman data, reports the first structural characterization of the recovered hydrogen hydrate during the transformation from the C 0 phase to ice XVII. The measurement of the position of the Bragg reflections in the neutron data allows to obtain the behaviour of the lattice parameters for the C 0 filled ice as a function of temperature during hydrogen release. From this analysis, we demonstrate the irreversibility of the structural changes passing from the pristine filled hydrate to the empty one, i.e. ice XVII. Meanwhile, we observe also the release of the spurious nitrogen molecules previously absorbed by the hydrate crystal when recovered at low temperature and ambient pressure. A significant release of guest molecules starts around 60 K, reaching the complete evacuation of the water structure above 100 K.

High performance infrared detectors compatible with CMOS-circuit process* *Project supported by the National Natural Science Foundation of China (Grant Nos. 11933006, 61805060, and 61290304).

A type of Si-based blocked impurity band photoelectric detector with a planar architecture is designed and demonstrated by a modified silicon semiconductor processing technique. In this route, multiple ion implantation is utilized to ensure the uniform distribution of the P elements in silicon, and rapid thermal annealing treatment is used to activate the P atoms and reduce damages caused by ion-implantation. The fabricated prototype device exhibits an excellent photoelectric response performance. With a direct current (DC) bias voltage of –2.3 V, the device detectivity to blackbody irradiation is as high as 5 × 1013cm⋅Hz1/2/W, which corresponds to a device responsivity of nearly 4.6 A/W, showing their potential applications in infrared detection, infrared astrophysics, and extraterrestrial life science. In particular, the developed device preparation process is compatible with that for the CMOS-circuit, which greatly reduces the manufacturing cost.

Green synthesis of palladium mixed with PdO nanoparticles by chemical bath deposition

In this paper, we present preliminary experimental results in the synthesis of Pd mixed with PdO nanoparticles, grown by chemical bath deposition at ~80 °C. These samples were subjected to further thermal annealing treatment at ~1000 °C in air atmosphere. The properties of these compounds were investigated using the scanning electron microscopy (SEM), Fourier-transform infrared (FTIR), X-ray diffraction (XRD), optical absorption and photoluminescence (PL) techniques. The SEM images for the grown sample show small dense and compact crystals. The FTIR spectra shows absorption bands associated with the OH− and CO32− ions. XRD diffractograms identified a face-centred cubic structure for metallic Pd, and traces of PdO in the tetragonal structure. The grain size ranges between ~33.91 nm and 86.92 nm, and ~33.96 nm–86.94 nm, respectively. The bandgap energy (~3.7 eV) showed a shift towards higher energy linked with the quantum confinement effect. PL spectrum displayed eight emission bands at the UV–Vis range (~363–524 nm). The time-resolved (delayed) PL spectra were achieved ~13.0 ns after excitation. PL signals presented two blue emission bands in the Vis region, and they were associated with native crystalline defects. These blue emission bands are explained by the vacancies and interstitial defects, mostly associated with surfaces or grain boundaries. Likewise, emission bands were investigated, applying the Maxwell–Boltzmann theoretical model and contrasting them with the experimentally registered signals. The PL dependence on trap density and the surface recombination velocity is discussed in the light of calculated lifetimes, PdA1 ~2.04 cm3 s−1 and PdA2 ~9.65 cm3 s−1.

F and Al co-doped zinc oxide thin films deposited by ultrasonic spray pyrolysis: Effects of substrate temperature on physical properties

In this study, F and Al co-doped ZnO (FAZO) films were prepared by ultrasonic spray pyrolysis combined with rapid thermal annealing treatment. The influence of substrate temperature (Ts) on the structure, morphology, and electrical and optical properties of the prepared FAZO films was systematically studied. The results showed the hexagonal wurtzite structure of all prepared FAZO films and the gradual changes in the preferred orientation of the films from (100) to (100) and (002) with increasing temperature. With increasing Ts, the diffraction peak of (002) became stronger, the morphology of the thin film changed from a mix of “rice-granular” small particles and “shell-like” large particles to flat and dense morphology, and the root-mean-square variation of the film’s particle size decreased. Furthermore, the resistivity decreased with an increase in Ts, and the film transmittance and optical bandgap increased significantly. The FAZO film prepared at 480 °C had the best photoelectric characteristics, with mobility of 22.9 cm2/(Vs), carrier concentration of 1.75 × 1020 cm–3, resistivity of 1.56 × 10–3 Ωcm, and over 85% average transmittance in the optical range of 400–1400 nm.

A small molecular acceptor based on dithienocyclopentaindenefluorene core for efficient fullerene-free polymer solar cells

In recent years, acceptor–donor–acceptor (A–D–A) type of small molecules have become very promising non-fullerene acceptors (NFAs) to overcome the energy levels and absorption drawbacks of the fullerene-based acceptors in polymer solar cells (PSCs). A non-fullerene small-molecular acceptor named DTIF-IC with dithienocyclopentaindenefluorene (DTIF) as the electron-donating core sealed with 2-(3-oxo-indane-1-ylidene)-malononitrile as the electron-withdrawing groups was developed. The molecule exhibits strong absorption in the range from 550 to 720 nm and relatively high-lying lowest unoccupied molecular orbital (LUMO) energy level (−3.86 eV). Due to its up-shifted LUMO energy levels, high and balanced charge mobility and the homogeneous nanophase separations, the inverted polymer solar cells blending with the donor polymer poly[[2,6-4,8-di(5-ethylhexylthienyl)benzo[1,2-b;3,3-b]dithiophene]-[3-fluoro-2[(2-ethylhexyl)carbonyl]thieno[3,4-b]-thiophenediyl]] (PTB7-Th) and DTIF-IC deliver a best power conversion efficiency (PCE) of 7.84% with relatively high open circuit voltage (Voc) of 0.95 V by thermal annealing treatment, which demonstrated that the DTIF-type small molecule could be the promising electron acceptor for high-performance polymer solar cells with a high Voc.

Enhanced dielectric permittivity and relaxor behavior in thermally annealed P(VDF-TrFE) copolymer films

Modification of relaxor behavior and large enhancement in dielectric permittivity are demonstrated in a P(VDF-TrFE) ferroelectric polymer film by thermal annealing treatment. For coexisting normal ferroelectric and relaxor behavior in P(VDF-TrFE) (molar ratio: 45:55) films, the relative contribution from the relaxor component is increased when annealed at high temperature and subsequently quenched. A relative peak permittivity of ε′ ∼ 100 is obtained for an annealing temperature of T = 90 °C, which is one of the highest reported so far among poly(vinylidene fluoride) copolymer and terpolymer films. Based on x-ray diffraction analysis, we attribute the changes in dielectric properties to a decrease in crystallite domain size and a consequent increase in the crystalline-amorphous interfacial area.