Effect Of Post-processing Treatments Research Articles

Effect of post-processing treatments on surface roughness and mechanical properties of laser powder bed fusion of Ti–6Al–4V

This study focuses on enhancing the surface characteristics of Ti–6Al–4V alloy fabricated through laser powder bed fusion (LPBF), a prominent additive manufacturing technique. The primary objective is to assess the impact of post-processing surface treatments on the surface roughness, microstructure, and mechanical properties of LPBF Ti–6Al–4V. As-built specimens with fully dense structures underwent sandblasting (SB), chemical etching (CE), and a combination of sandblasting and chemical etching (SB + CE). The investigation reveals significant variation in the surface morphology of as-built samples, primarily influenced by factors such as spattered particles, powder adhesion, and the stair-step effect. In the as-built condition, the down-skin exhibited the highest particle adhesion, covering 11.9 % of the surface. Sandblasting proved particularly effective in removing adhered particles, reducing surface roughness to 5.1 μm from an initial value of 17.8 μm for the down-skin surface. Furthermore, combining sandblasting and chemical etching was more effective than chemical etching alone in achieving uniform surface profiles. Tensile testing indicated that while the ultimate tensile strength remained unchanged, the strain at break significantly improved from 4.8 % to 11.5 %, representing a noticeable increase in ductility in post-processed samples compared to as-built conditions. These findings underscore the influence of post-processing treatments in mitigating surface roughness and enhancing ductility without compromising mechanical strength.

Effect of Post-Processing Treatment on Fatigue Performance of Ti6Al4V Alloy Manufactured by Laser Powder Bed Fusion

Fatigue properties of parts are of particular concern for safety-critical structures. It is well-known that discontinuities in shape or non-uniformities in materials are frequently a potential nucleus of fatigue failure. This is especially crucial for the Ti6Al4V alloy, which presents high susceptibility to the notch effect. This study investigates how post-processing treatments affect the mechanical performance of Ti6Al4V samples manufactured by laser powder bed fusion technology. All the fatigue samples were subjected to a HIP cycle and post-processed by machining and using combinations of alternative mechanical and electrochemical surface treatments. The relationship between surface properties such as roughness, topography and residual stresses with fatigue performance was assessed. Compressive residual stresses were introduced in all surface-treated samples, and after tribofinishing, roughness was reduced to 0.31 ± 0.10 µm, which was found to be the most critical factor. Fractures occurred on the surface as HIP removed critical internal defects. The irregularities found in the form of cavities or pits were stress concentrators that initiated cracks. It was concluded that machined surfaces presented a fatigue behavior comparable to wrought material, offering a fatigue limit superior to 450 MPa. Additionally, alternative surface treatments showed a fatigue behavior equivalent to the casting material.

Fabrication and photoresponsive characteristics of ZnO film for ultraviolet ZnO/porous Si photodetector: The effect of post-processing treatment

This article demonstrates a well-designed fabrication process of ultraviolet (UV) ZnO/porous Si photodetector as a function of post-processing temperature. The structural and optical features of the deposited ZnO layers were thoroughly elucidated through which a robust correlation between the post-processing temperature and the addressed characteristics were established. Particularly, a decrease in the attained energy bandgap from 3.3 eV to 3.22 eV was obtained upon increasing the treatment temperature from 600 °C to 800 °C; the morphological analysis revealed the occurrence of average nanoparticle diameters of 69 nm and 64 nm, respectively. Continuously, the fabricated devices also demonstrated a well-established relation with the applied post-processing temperature wherein relatively high photoresponsivity and specific detectivity were attained at high temperature. Specifically, the photoresponsivity and specific detectivity values were observed to be 5.6 (μA/mW) and 1.8×1011 Jones at 25mW/cm2 illumination power using treatment temperature of 800 °C, respectively. In the meanwhile, the response time of the proposed device was estimated to be ∼300ms.

Rapid Scalable Processing of Tin Oxide Transport Layers for Perovskite Solar Cells.

The development of scalable deposition methods for perovskite solar cell materials is critical to enable the commercialization of this nascent technology. Herein, we investigate the use and processing of nanoparticle SnO2 films as electron transport layers in perovskite solar cells and develop deposition methods for ultrasonic spray coating and slot-die coating, leading to photovoltaic device efficiencies over 19%. The effects of postprocessing treatments (thermal annealing, UV ozone, and O2 plasma) are then probed using structural and spectroscopic techniques to characterize the nature of the np-SnO2/perovskite interface. We show that a brief “hot air flow” method can be used to replace extended thermal annealing, confirming that this approach is compatible with high-throughput processing. Our results highlight the importance of interface management to minimize nonradiative losses and provide a deeper understanding of the processing requirements for large-area deposition of nanoparticle metal oxides.

Tough and Low Friction Polyvinyl Alcohol Hydrogels Loaded with Anti-inflammatories for Cartilage Replacement

The development of new materials that mimic cartilage and its function is an unmet need that will allow replacing the damaged parts of the joints, instead of the whole joint. Polyvinyl alcohol (PVA) hydrogels have raised special interest for this application due to their biocompatibility, high swelling capacity and chemical stability. In this work, the effect of post-processing treatments (annealing, high hydrostatic pressure (HHP) and gamma-radiation) on the performance of PVA gels obtained by cast-drying was investigated and, their ability to be used as delivery vehicles of the anti-inflammatories diclofenac or ketorolac was evaluated. HHP damaged the hydrogels, breaking some bonds in the polymeric matrix, and therefore led to poor mechanical and tribological properties. The remaining treatments, in general, improved the performance of the materials, increasing their crystallinity. Annealing at 150 °C generated the best mechanical and tribological results: higher resistance to compressive and tensile loads, lower friction coefficients and ability to support higher loads in sliding movement. This material was loaded with the anti-inflammatories, both without and with vitamin E (Vit.E) or Vit.E + cetalkonium chloride (CKC). Vit.E + CKC helped to control the release of the drugs which occurred in 24 h. The material did not induce irritability or cytotoxicity and, therefore, shows high potential to be used in cartilage replacement with a therapeutic effect in the immediate postoperative period.

Influence of the heat treatment on the microstructure and machinability of titanium aluminides produced by electron beam melting

Additive manufacturing (AM) has been emerging as a promising fabrication technology for polymers and metal products. This technology is able to fabricate complex shape components with high geometrical freedom and allows to reduce the overall waste material, as the powder can be recycled several times, and time from drawing to production can be consistently reduced. In the case of materials for aerospace applications, like TiAl alloys, conventional machining is needed to obtain the required surface finish. The machinability is strongly dependent on the specific alloys and on the production technology used, leading to different microstructures, that can be tuned undergoing the alloys to several treatments after the AM process. The paper focus on the effect of post processing treatment on hardness, structural properties and machinability of Ti48Al2Nb2Cr obtained by electron beam melting process. Untreated and heat treated alloys were considered. Turning tests were carried out under dry conditions by using cemented carbides cutting tools coated with TiCN-Al2O3-TiN. The structure, microstructure and hardness of the material were studied and related to machinability, that was evaluated in terms of tool life and surface integrity, focusing on both surface and sub-surface alterations. Tool wear, cutting forces, chip morphology and surface roughness were also analyzed. Adhesion prevailed on abrasion as main wear phenomenon, leading to cutting edge breaking. Results indicated a higher machinability of the alloys that underwent post processing treatment because of the different microstructure and crystalline phases induced. Indeed, α2 and β phases present in heat treated material enhanced the formation of built up edge, acting as protective layer and then slowing down the degradation phenomena. Also the lower porosity leaded to a lower diffusion phenomenon, positively affecting the tool life.

Effects of post-processing treatments on sensory quality and Shiga toxigenic Escherichia coli reductions in dry-fermented sausages

The effects of post-processing treatments on sensory quality and reduction of Shiga toxigenic Escherichia coli (STEC) in three formulations of two types of dry-fermented sausage (DFS; salami and morr) were evaluated. Tested interventions provided only marginal changes in sensory preference and characteristics. Total STEC reductions in heat treated DFS (32°C, 6days or 43°C, 24h) were from 3.5 to >5.5 log from production start. Storing of sausages (20°C, 1month) gave >1 log additional STEC reduction. Freezing and thawing of sausages in combination with storage (4°C, 1month) gave an additional 0.7 to 3.0 log reduction in STEC. Overall >5.5 log STEC reductions were obtained after storage and freezing/thawing of DFS with increased levels of glucose and salt. This study suggests that combined formulation optimisation and post-process strategies should be applicable for implementation in DFS production to obtain DFS with enhanced microbial safety and high sensory acceptance and quality.

The effect of post-processing treatments on inflection points in current–voltage curves of roll-to-roll processed polymer photovoltaics

Inflection point behaviour is often observed in the current–voltage ( IV) curve of polymer solar cells. This phenomenon is examined in the context of flexible roll-to-roll (R2R) processed polymer solar cells in a large series of devices with a layer structure of: PET–ITO–ZnO–P3HT:PCBM–PEDOT:PSS–Ag. The devices were manufactured using a combination of slot-die coating and screen printing; they were then encapsulated by lamination using a polymer based barrier material. All manufacturing steps were carried out in ambient air. The freshly prepared devices showed a consistent inflection point in the IV curve and a corresponding poor performance or lack of photovoltaic behaviour. Upon exposure to 1000 Wm −2 illumination at ca. 85 °C and repeated IV scans (photo-annealing) the inflection point gradually disappeared, and performance drastically increased over time. The characteristics and stability of this “photo-annealing” behaviour was further investigated by studying the effects of several key factors: temperature, illumination and atmosphere. The results consistently showed that the inflection point is a dynamic phenomenon which can be removed under specific conditions. Subsequently, chemical characterization of device interfaces was carried out in order to identify possible chemical processes that are related to photo-annealing. A possible mechanism based on ZnO photoconductivity, photooxidation and redistribution of oxygen inside the cell is proposed, and it is anticipated that the findings are applicable to various other device structures based on semi-conducting oxides. The findings may have influences on the possibilities and scale-up of polymer solar technologies.

Effect of Post-Processing Treatments on Improvement of the Taste of Silicone Rubber for Beverage Use

Effect of Post-Processing Treatments on Improvement of the Taste of Silicone Rubber for Beverage Use

Effects of post-processing treatment on sorption isotherm of an effectively hydrophilic zeolite β

The effects of post-processing treatments on infiltration and defiltration of liquids in acid-leached zeolite β were investigated. The infiltration pressure, which reflects the effective degree of hydrophobicity of the nanopore surface, and the defiltration pressure, which dominates the system hysteresis, can be controlled in broad ranges by adjusting anion species and liquid composition, and/or performing hydrothermal or silicon addition treatment. These experimental results have important relevance to developing liquid spring and active control techniques.