Post-thermal Treatment Research Articles

Soda-lime glass as biocompatible material to fabricate capillary-model devices by laser technologies

Microfluidic devices have been widely developed in the last decades because of the huge number of fields where they can be applied. Among all the different fabrication techniques available, laser direct writing stands out since it is a fast, accurate, versatile and non-contact method. It is particularly well-suited when working with glass, a robust and cost-efficient material. These laser advantages allow the direct fabrication of not only high quality single microchannel devices but also complex and bifurcated structures. This work establishes a roadmap for manufacturing capillary-model devices with good biocompability in soda-lime glass substrates with pulsed lasers operating in the nanosecond, picosecond and femtosecond temporal range. We determine the optimal laser parameters required for fabricating channels with a diameter:depth rate of 2:1, keeping a semi-circular section. The presence of tin doping (∼2%) in the soda-lime glass is shown to enable the fabrication with nanosecond pulses, and to improve the quality of the channels, reducing the cracking at the sides, when picosecond or femtosecond pulses were used. On the other hand, two regimes of surface roughness are found: a low roughness regime for channels fabricated with nanosecond lasers and a high roughness regime for those fabricated with pico and femtosecond lasers. Human umbilical vein endothelial cells (HUVEC) are employed for cell culturing for evaluating the biocompatibility of the channels. Structures manufactured with the nanosecond laser resulted more suitable in terms of cell adhesion than those fabricated with the picosecond and femtosecond lasers, due to the different surface roughness regimes obtained. In order to increase the biocompatibility of the channels fabricated with pico and femtosecond lasers and to improve the cell growth, a controlled post-thermal treatment is carried out for smoothing the surface.

Individual and synergistic effects of thermal and mechanical surface post-treatments on wear and corrosion behavior of laser powder bed fusion AlSi10Mg

Materials fabricated by laser powder bed fusion (LPBF) are generally characterized with internal defects, inhomogeneous microstructure and rough surface with multiple forms of irregularities in their as-built state. Post-treatments are needed to resolve the issues associated with these imperfections. In this study, the individual and synergistic effects of different post-treatments including heat treatment, shot peening and ultrasonic nanocrystalline surface modification on microstructure, surface morphology, roughness, mechanical, corrosion and tribological properties of LPBF AlSi10Mg specimens have been investigated. Two different sets of parameters were considered for the surface treatments, both with mechanical energy source. Apart from surface characteristics, various properties including microhardness and residual stresses as well as wear and corrosion behavior of post-processed specimens were analyzed and compared with those of the as-built condition. The results indicated that hybrid post-treatments have the highest positive effects on wear and corrosion resistance as their kinetic energy affected multiple physical aspects; these include the microstructure leading to surface grain refinement paired with deep compressive residual stress field and improved surface morphology offering a more regular surface.

Controlling of lattice strains for crack-free and strong ferroelectric barium titanate films by post-thermal treatment

In this study, we experimentally demonstrate fabrication of ultra-smooth and crystalline barium titanate (BTO) films on magnesium oxide (MgO) substrates by engineering lattice strain and crystal structure via thermal treatment. We observe that oxygen-depleted deposition allows growth of highly strained BTO films on MgO substrates with crack-free surface. In addition, post-thermal treatment relaxes strain, resulting in an enhancement of ferroelectricity. Surface roughening of the BTO films caused by recrystallization during post-thermal treatment is controlled by chemical–mechanical polishing (CMP) to retain their initial ultra-smooth surfaces. From Raman spectroscopy, reciprocal space map (RSM), and capacitance–voltage (C–V) curve measurements, we confirm that the ferroelectricity of BTO films strongly depend on the relaxation of lattice strain and the phase transition from a-axis to c-axis oriented crystal structure.

Synthesis of Vitamin B3 through a Heterogeneous Photocatalytic Approach Using Metal-Free Carbon Nitride-Based Catalysts.

Vitamin B3 (nicotinic acid, VB3) was synthesized through the photocatalytic oxidation of 3-pyridinemethanol (3PM) under visible-light-emitting diode (LED) irradiation using metal-free graphitic carbon nitride (GCN) - based materials. A bulk (GCN) material was prepared by a simple thermal treatment using dicyandiamide as the precursor. A post-thermal treatment under static air and nitrogen flow was employed to obtain the GCN-T and GCN-T-N materials, respectively. The conditions adopted during the post-treatment revealed differences in the resulting materials’ morphological, electronic, and optical properties. The post-treated photocatalysts revealed an enhanced efficiency in the oxidation of 3PM into VB3, with the GCN-T-N photocatalyst being the best-performing material. The defective surface, reduced crystallinity, and superior photoabsorption of GCN-T-N account for this material’s improved performance in the production of VB3. Nevertheless, the presence of nitrogen vacancies in the carbon nitride structure and, consequently, the creation of mid-gap states also accounts to its highly oxidative ability. The immobilization of GCN-T-N in sodium alginate hydrogel was revealed as a promising strategy to produce VB3, avoiding the need for the photocatalyst separation step. Concerning the mechanism of synthesis of VB3 through the photocatalytic oxidation of 3PM, it was possible to identify the presence of 3-pyridinecarboxaldehyde (3PC) as the intermediary product.

Chemical and mechanical post-processing of Alloy 718 built via electron beam-powder bed fusion: Surface texture and corrosion behavior

Alloy 718 specimens manufactured via electron beam-powder bed fusion (EB-PBF) were subjected to post-processing techniques, such as thermal post-treatment and surface finishing. Hot isostatic pressing followed by solution-aging heat treatment (HIP-HT) was used as the thermal post-treatment. Surface finishing techniques, such as turning (TU), shot peening (SP), chemically accelerated vibratory finishing (CAVF), and electro-polishing (EP), were applied on the as-built and HIP-HT specimens. The surface texture of all the specimens was characterized, with the HIP-HT specimen having the highest area arithmetical mean height (Sa) value of 52 ± 1.8 µm and the TU specimen having the lowest at 1.1 ± 0.1 µm. The corrosion performance, typically associated with surface texture, was not always tied to the overused Sa value. CAVF had the highest polarization resistance of 75.8 kΩ.cm2 among the studied methods, followed by TU with polarization resistance of 43.8 kΩ.cm2, showing that the two techniques have a great potential for improving the surface characteristics of the EB-PBF-built Alloy 718 parts.

Dopamine-Supported Metallization of Polyolefins─A Contribution to Transfer to an Eco-friendly and Efficient Technological Process.

Metallization is a common method to produce functional or decorative coatings on plastic surfaces. State-of-the-art technologies require energy-intensive process steps and the use of organic solvents or hazardous substances to achieve sufficient adhesion between the polymer and the metal layer. The present study introduces a facile bio-inspired "green" approach to improve this technology: the use of dopamine, a small-molecule mimic of the main structural component of adhesive mussel proteins, as an adhesion promoter. To understand dopamine adhesion and identify conditions for successful metallization, polyethylene surfaces were dip-coated with dopamine and metallized with nickel by electroless metallization; essential parameters such as temperature, pH value, concentration of dopamine and buffer, and the deposition time were systematically varied. Effects of adding oxidants to the dopamine bath, cross-linking, thermal and UV post-treatment of the polydopamine film, and plasma pretreatment of the substrate were investigated. The properties of the polydopamine layer and the quality of the metal film were studied by physico-chemical, optical, and mechanical techniques. It was shown that simple dip-coating of the substrate with dopamine under optimal conditions is sufficient to support metal layers with a good optical quality. Technologically relevant metal layer quality and adhesion were obtained with annealed and UV-treated polydopamine films and enhanced by plasma pretreatment of the substrate. The study shows that dopamine provides a new interfacial design for plastic metallization that can reduce energy consumption, use of hazardous substances, and reject rate during manufacturing. The results are essential findings for further technological developments of a universal platform to promote adhesion between plastics and metal or potentially also other material classes, enabling economic material development and more eco-friendly applications.

Silver nanowire synthesis analyzing NaCl, CuCl2, and NaBr as halide salt with additional thermal, acid, and solvent post-treatments for transparent and flexible electrode applications

Silver nanowire synthesis analyzing NaCl, CuCl2, and NaBr as halide salt with additional thermal, acid, and solvent post-treatments for transparent and flexible electrode applications

The quality control assessment of cyanate ester blend (EX-1515) resin based composites concerning hydrolysis

Cyanate ester resins are essential matrix materials for advanced composites demanding excellent mechanical properties and dimensional stability under varying hygrothermal and radiative environments. However, a critical processing complication arises due to moisture sensitivity during cure which compromizes mechanical and thermal properties. Therefore, a reliable evaluation technique is necessary to ensure the successful use of cyanate ester-based composites. In this report, quality control (QC) signatures of a cyanate ester blend (EX-1515) are evaluated in comparison to those of an unmodified single-component cyanate ester resin (RS3C). Varying degrees of EX-1515 hydrolysis, i.e., carbamate formation, were investigated via FTIR and correlated to decreases in glass transition temperature by DSC and changes in the thermal decomposition profile by TGA. Also flatwise tension (FWT) strengths were observed to decrease with increasing hydrolysis. These results on as-cured EX-1515 were analogous to what was previously reported on RS3C. However, with elevated thermal post-treatments, their thermomechanical properties displayed an opposite trend; While hydrolyzed RS3C exhibited even further progressive reductions in Tg with a post-cure, EX-1515 showed significant increases, likely due to a new polymerization reaction involving carbamates and additional chemical moieties in the blend formulation. Interestingly, the post-cure Tg increase did not translate to any improvement in mechanical properties. On the contrary, the strength showed a dramatic reduction due to thermal degradation of the hydrolysis by-products resulting in increased porosity. The QC signatures of EX-1515 proved to be more complex than RS3C. Therefore, it is necessary to consider multiple QC signatures with carefully chosen thermal treatments rather than relying on a single point Tg measurement without the full thermal history information of the cyanate ester material.

Interfacially coupled thin sheet-like NiO/NiMoO4 nanocomposites synthesized by a simple reflux method for excellent electrochemical performance.

Herein, hierarchical sheet-like assemblies of interfacially coupled NiO/NiMoO4 (NNMO) nanocomposites are prepared by a simple and cost-effective one-step aqueous reflux method followed by post-thermal treatment. The reaction time is optimized for a high precursor yield and the homogeneity of the final product. The fabricated electrodes with varying amounts of active material and conducting carbon show better electrochemical activity for 50 : 50 weight ratio combinations as extrinsic pseudocapacitors. The optimized NNMO-3 electrode (obtained from the Ni-Mo hydroxide precursor during the 10 h reaction time) exhibits superior performance among all the tested nanocomposite electrodes like a high specific capacity of 649.8 C g-1 (1624.5 F g-1) and 73.5% retention of capacity after 2200 cycles at a specific current of 1.0 A g-1 along with satisfactory rate capability (42.5% retention after a ten-times increment in specific current), which may be attributed to the abundant electroactive sites due to the high bulk as well as electrochemically active surface area, mesoporous structure, and synergistic coupling between the optimum compositions of NiO and NiMoO4 within the sheet-like networks. Moreover, an aqueous asymmetric supercapacitor is assembled by employing NNMO-3 and activated carbon as the positive and negative electrodes, respectively, and exhibits a maximum specific capacity of 216.2 C g-1 (144.1 F g-1), specific energy of 45.0 W h kg-1 at a specific power of 750.0 W kg-1, promising rate capability of 58.5%, and good cycling stability with 86.2% capacitive retention after 2500 charge-discharge cycles. Based on the overall performance, we can infer that the NNMO-3 nanocomposite may be a promising electrode material for high-performance supercapacitor applications.

Hybrid thermal, mechanical and chemical surface post-treatments for improved fatigue behavior of laser powder bed fusion AlSi10Mg notched samples

Complex geometries can be produced by laser powder bed fusion (LPBF) techniques in a layer-by-layer manner. These parts exhibit inhomogeneous microstructure and poor surface quality in their as-built state. Performing post-treatments to modify these imperfections can play a substantial role in enhancing the performance of LPBF parts. However, the effects of post treatments on local geometrical irregularities are not still well documented. In this study, four different post-treatments including heat treatment, mechanical and chemical surface treatments as well as their combination were considered. Their effect was studied on microstructure, surface, and mechanical properties of LPBF V-notched AlSi10Mg samples. The as-built samples were subjected to two different shot peening processes (using different Almen intensity, shot diameter, and shot hardness), chemical polishing and electro-chemical polishing, in individual and combined configurations. Comprehensive microstructural characterization was carried out and the surface state of the samples was studied in detail in terms of surface morphology and roughness. In addition, mechanical properties including microhardness and residual stresses were measured and finally the fatigue behaviors of the samples were analyzed and compared at a constant stress level. All post treatments led to improved fatigue life. The combination of the aforementioned post-treatments led to a remarkable fatigue life improvement up to 414 times higher compared to the as-built state.

Effect of post coating processing on the morphological and mechanical properties of plasma Spray-reinforced hydroxyapatite coating

The biocompatible Hydroxyapatite (H.A.) coating helps titanium alloy recover and insulates implants from the body's environment. FDA recommends plasma spray to cover H.A. on body implants. H.A.'s poor mechanical properties limit its use in weight-bearing orthopaedic applications like hip and knee joints. This study examines the influence of H.A. reinforcement on plasma-sprayed coatings' microstructure and mechanical characteristics. The influence of thermal post-treatments on as-deposited (pure H.A. & reinforced H.A.) coatings was also examined. SEM images of as-deposited (pure H.A. & reinforced H.A.) coatings were taken before and after thermal processing (S.E.M.). The use of reinforcement improves as-sprayed coatings' microhardness and bond strength. After two hours at 700 °C in air, both substrates had ultrafine particles that may connect to bone and promote bone development.

Carbonitrides-Modified Silver Phosphotungstate Photocatalysts Constructed by Thermal Post-Treatment of Self-Assembled Polyoxometalate Hybrids for Efficient Visible-Light Photocatalytic Activity

Carbonitrides-Modified Silver Phosphotungstate Photocatalysts Constructed by Thermal Post-Treatment of Self-Assembled Polyoxometalate Hybrids for Efficient Visible-Light Photocatalytic Activity

Solution–processed Cu2O/ZnO/TiO2/Pt nanowire photocathode for efficient photoelectrochemical water splitting

State–of–the–art Cu2O photocathodes are mostly fabricated by means of electrodeposition and have been reported to be flooded with the copper vacancies (VCu), into which the photoexcited electrons are rapidly trapped and thereby hardly injected into the electrolyte for photoelectrochemical water splitting. To address this issue, an alternative approach consisting of simple wet chemistry combined with post–thermal treatment is employed in the present contribution to grow the Cu2O nanowires (NWs) on the Cu foil, which provides the Cu ions to fill VCu. An important result of the depletion of VCu is the space charge layer extending deep into the Cu2O NWs, wherein the photoexcited charge carriers are rectified by the surface band bending for efficient separation. The charge separation is further reinforced by using ZnO to first extract the photogenerated electrons from Cu2O, TiO2 to further glean the electrons from ZnO, and the Pt co–catalyst to facilitate their injection into the electrolyte. These materials are deposited sequentially on the Cu2O NWs by means of chemical bath deposition, which is put forward in the present contribution as a cost–effective and readily scalable alternative to the conventional atomic layer deposition technique. The synergistic effect leads to a photocurrent density of the Cu2O/ZnO/TiO2/Pt NWs of −8.2 mA cm−2, well outperforming that of the pristine Cu2O NWs by more than 2.5–fold and, moreover, being comparable to that of the electrodeposited counterparts reported in the literature.

Posttreatment of powder aerosol deposited oxide ceramic films by high power LED

AbstractThe powder aerosol deposition (PAD) method is becoming increasingly important as an energetically advantageous coating method compared to classic ceramic technologies. However, due to the process‐related lattice deformation, ceramic coatings often exhibit reduced functional properties in the as‐deposited state. A thermal posttreatment at temperatures well below the sintering temperature can significantly reduce the lattice deformation and the stress within the film to restore the functional film properties close to sintered bulk samples. In this work, the optothermal posttreatment of PAD films using three different high‐power light emitting diodes (HP‐LED) with different wavelengths within the visible light spectrum is investigated as an alternative to time‐consuming furnace or energy‐intensive laser processes on the example of thermoelectric CuFe0.98Sn0.02O2 films. We demonstrate that the space‐saving LED‐based posttreatment not only restores the film properties but also significantly reduces the required processing time to a few seconds.

Thermal post-treatment of digestate in order to increase biogas production with simultaneous pasteurization

Biogas production by anaerobic digestion (AD) of organic wastes is important for the transition to fossil free fuels in both the transport sector, industries and shipping. The aim of this study was to target the residual organic matter in the outgoing residue from the AD process, so called digestate, with different thermal treatment methods in order to improve digestate degradability and biogas potential upon post-digestion. The thermal treatment was performed at 55 °C in 24 h, 70 °C in 1 h and by thermal hydrolysis process (THP; 165 °C, 8 bar in 0.33 h), and were carefully selected to offer a simultaneous possibility for pasteurization of the digestate according to the regulations in Sweden. Digestates from ten full-scale biogas plants were collected, with different substrate profiles including wastewater treatment plant (WWTP), food waste digestion, agriculture digestion and manure digestion. The results showed that all thermal treatment methods caused increased dissolved organic carbon concentration (DOC). Four of the thermal treated digestates with the highest increase in DOC were subsequently tested for the bio-methane potential. Thermal treatments at 70 °C and THP, respectively, resulted in the highest increase in bio-methane potentials, with an increase of 15–39% for one WWTP, 38 – 40% for digestate from an agriculture digestion plant and 20 – 22% for digestate from a co-digestion plant treating food waste. Interestingly, the bio-methane potential from digestate treated with the energy-intense THP method, did not show any significant difference compared to thermal treatment at 70 °C for 1 h. The outcomes of this study suggest that placing a pasteurization unit between a main digester and a post digester, when applying two-step digestion allows for a combined pasteurization and increased biogas production.

A short review on thermal treatments of Titanium & Nickel based alloys processed by selective laser melting

Selective laser melting (SLM) has been considered as a well-researched technology used to produce near net shape metallic components with superior mechanical and physiochemical characteristics. Recently SLM has recently been used for the production of components made by high-performance alloys such as Titanium and Nickel. However, the microstructural and physical anisotropy along with the defects have negative impact on the performance and behavior of SLM-produced alloys. Therefore, to improve the material characteristics, extra attention must be paid to the source(s), identification, and removal of these deviations. Thermal heat treatments are often considered as an effective approach to deal with aforementioned issues. stress-relieving, quenching/hardening, annealing/recrystallization, and thermo-mechanical heat treatments are among prominent procedures adopted for the post processing of SLM fabricated metallic components and hence considered in this article. Since these procedures have substantial impact on the microstructure and mechanical behavior therefore an assessment of their influence and resulting changes is significantly important. Therefore, this short review provides the said knowledge on thermal treatments used to improve the SLM fabricated titanium and nickel-based alloys. This review can significantly help in designing and selecting appropriate post processing thermal treatments keeping in mind the expected outcome.

Characterization and Optimization of AZO Nanoparticles as Coatings for Flexible Substrates toward High IR Reflectivity.

Energy consumption by air-conditioning is expansive and leads to the emission of millions of tons of CO2 every year. A promising approach to circumvent this problem is the reflection of solar radiation: Rooms that would not heat up by irradiation will not need to be cooled down. Especially, transparent conductive metal oxides exhibit high infrared (IR) reflectivity and are commonly applied as low-emissivity coatings (low-e coatings). Indium tin oxide (ITO) coatings are the state-of-the-art application, though indium is a rare and expensive resource. This work demonstrates that aluminum-doped zinc oxide (AZO) can be a suitable alternative to ITO for IR-reflection applications. AZO synthesized here exhibits better emissivity to be used as roofing membrane coatings for buildings in comparison to commercially available ITO coatings. AZO particles forming the reflective coating are generated via solvothermal synthesis routes and obtain high conductivity and IR reflectivity without the need of any further post-thermal treatment. Different synthesis parameters were studied, and their effects on both conductive and optical properties of the AZO nanoparticles were evaluated. To this end, a series of characterization methods, especially 27Al-nuclear magnetic resonance spectroscopy (27Al-NMR) analysis, have been conducted for a deeper insight into the particles' structure to understand the differences in conductivity and optical properties. The optimized AZO nanoparticles were coated on flexible transparent textile-based roofing membranes and tested as low-e coatings. The membranes demonstrated higher thermal reflectance compared with commercial ITO materials with an emissivity value lowered by 16%.

Maximizing Polyacrylonitrile Nanofiber Piezoelectric Properties through the Optimization of Electrospinning and Post-thermal Treatment Processes

While high-performance piezoelectric polymeric nanofibers such as polyvinylidene fluoride and its derivatives have been extensively studied to various applications, limited works examined other fun...

In-situ biogas upgrading in an anaerobic trickling filter bed reactor treating a thermal post-treated digestate

Digestate, residual organic matter produced as byproducts during the anaerobic digestion process, needs to be utilized because of its potential greenhouse gas emissions. An alternative solution is to valorize digestate for biogas production. The current study investigates feasibility of simultaneous thermal post-treatment of digestate and in-situ biogas upgrading in the trickling filter bed (TFB) reactor. Thermal post-treatment improved the solubilization of food waste-based digestate for biogas production. It was reported that the TFB reactor are efficient to facilitate gas-liquid mass transfer during production of methane (CH4) from carbon dioxide (CO2) and hydrogen (H2). The exogenous H2 injection in in-situ biogas upgrading decreased CO2 content from 51.35% to 16.72% and upgrade CH4 content from 48.65% to 81% in the output gas. The reactor CH4 production rate reached 0.89 L/LR•d and the H2 utilization efficiency of 98% was accomplished. Furthermore, the results showed that chemical oxygen demand removal efficiency of digestate reached to a maximum of 64% in 10 days hydraulic retention time. The microbial analysis indicated hydrogenotrophic Methanobacterium ferruginis was highly abundant in the liquid and biofilm phase, while acetoclastic Methanosarcina flavescens localized in the biofilm phase. The findings from this work showed that digestate can be simultaneously exploited for improving effluent quality and biogas upgrading.

Effect of organic solvent on the cold sintering processing of SrFe12O19 platelet-based permanent magnets

In this work we have investigated the effect of the solvent during the processing of SrFe12O19 platelet-based permanent magnets by cold sintering process (CSP) plus a post-thermal treatment. Several organic solvents: glacial acetic acid, oleic acid and oleylamine have been analyzed, optimizing the CSP temperatures at 190−270 °C, under pressures of 375−670 MPa and 6−50 wt% of solvent. Modifications in the morphological and structural properties are identified depending on the solvent, which impacts on the magnetic response. Independently of the solvent, the mechanical integrity of ferrite magnets obtained by CSP is improved by a post-annealing at 1100 °C for 2 h, resulting in relative densities around 92 % with an average grain size of 1 μm and a fraction of SrFe12O19 phase >91 %. HC ≥ 2.1 kOe and MS of 73 emu/g are obtained in the final sintered ceramic magnets, exhibiting the highest HC value of 2.8 kOe for the magnet sintered using glacial acetic acid.