Search Results (52)

Additive manufacturing, or 3D printing, is a process where a part is produced layer by layer, and represents a promising approach for designing components close to their final shape. Titanium alloys produced by additive manufacturing find application in various industries. This overview examines the features of the formation of the microstructure and properties in Ti alloys synthesized with the use of powder and wire laser additive technologies, as well as solid-phase methods of additive manufacturing such as friction stir additive manufacturing. Their main drawbacks and advantages are discussed, as applied to Ti alloys. The main approaches to solving the problem of increasing the strength properties of the synthesized Ti workpieces are considered. The authors of this overview propose a new area of research in the field of the application of additive technologies for producing ultrafine-grained Ti semi-products and parts with enhanced performance characteristics. Research in this area opens up prospects for designing heavily loaded complex-profile products for the aerospace, oil and gas, and biomedical industries. Full article

The aim of this study is to produce a biodegradable food packaging material that reduces environmental pollution and protects food safety. The effects of total solids content, substrate ratio, polyphenol content, and magnetic stirring time on bovine bone gelatin/sodium carboxymethylcellulose nanoemulsion (BBG/SCMC–NE) were investigated using particle size, PDI, turbidity, rheological properties, and zeta potential as evaluation indexes. The micro, structural, antioxidant, encapsulation, and release properties were characterized after deriving its optimal preparation process. The results showed that the nanoemulsion was optimally prepared with a total solids content of 2%, a substrate ratio of 9:1, a polyphenol content of 0.2%, and a magnetic stirring time of 60 min. SEM showed that the nanoemulsion showed a dense and uniform reticulated structure. FTIR and XRD results showed that covalent cross-linking of proteins and polysaccharides altered the structure of gelatin molecular chains to a more compact form but did not change its semi-crystalline structure. DSC showed that the 9:1 BBG/SCMC–NE had a higher thermal denaturation temperature and greater thermal stability, and its DPPH scavenging rate could reach 79.25% and encapsulation rate up to 90.88%, with excellent slow-release performance. The results of the study provide basic guidance for the preparation of stable active food packaging with excellent properties. Full article

Nowadays it is common to see the production of complex and critical automotive and aeronautical components reduced in weight for energy efficiency using light alloys with improved microstructural and mechanical properties. The casting processes involved in this trend are strong; in this study, an optimized design of a vertical serpentine channel and a novel design of a horizontal serpentine channel to produce semi-solid slurry (S2S) with thixotropic behavior by self-stirring for rheocasting of A380 and A356 alloys are tested. Simultaneously, chilling during solidification, flow development, and shearing on the alloys to improve the performance of solid fractions and self-stirring at high shear rate are applied. The effects of these conditions on the modification of the morphology transition of the α(Al) phase from dendrite to equiaxed grain are discussed. The results suggest the ability of the mentioned processes to promote the morphological transition of the primary solid due to the produced equiaxed grains of α(Al) phase having sizes between 25–50 µm from A380 alloy processed by vertical self-stirring. On the other hand, the treatment of the A356 alloy using the new horizontal serpentine channel produces equiaxed grains with an average size of 39 µm. Unexpected Si crystals, trapped in the α(Al) phase using both methods with both alloys, are detected. The applied operation parameters were aided by gravity-pouring close to the liquidus temperature, and the obtained microstructural results show the ability for S2S to form alongside thixotropic behavior and non-dendritic solidification by mean of self-stirring in the serpentine channels, suggesting the potential for further experiments under die-casting conditions. Full article

Advanced processing techniques are required to produce functionally graded metal matrix composites due to the metallurgical conditions required during production. In this study, we developed a novel approach for this task by using a combination of two different methods to produce functionally graded 7075 Al/SiC_p (5–20 wt.%) composites. The first process was direct semisolid stirring, which was used to prevent particle agglomeration, brittle reaction products, floating or settling of the reinforcements, and poor wettability. The second process was sequential squeeze casting, which enabled liquid diffusion between the two composite layers that were used to produce a functionally graded aluminum matrix composite. Thus, a method was developed to eliminate the problems encountered in the production of particle-reinforced metal matrix composite materials using liquid stirring methods and to produce composite materials with the desired functionally graded structure. The resulting functionally graded material was subjected to spectrometer analyses, density measurements, and metallographic examinations to determine the characteristics of its layers and interfacial zones, as well as to assess the formation of the graded structure. The results indicate the potential of using this new combined manufacturing method, which is efficient and controllable, to produce functionally graded metal matrix composites. Full article

Imiquimod (IMQ) has been successfully formulated to date mainly as semi-solid lipophilic formulations for topical application. In this study, we investigated the solubility of IMQ in solvents suitable for developing innovative formulations in the form of powder obtained, for instance, by spray drying; thus, water, ethanol, methanol, acetone, acetonitrile, and dimethyl sulfoxide were tested at different temperatures. Temperature variations, stirring intensity, and the contact time between IMQ and the solvent greatly affected the evaluation of IMQ equilibrium solubility. The attainment of the solid–liquid equilibrium requires 13 days starting from solid IMQ and 2 days from a cooled-down supersaturated IMQ solution. A correlation between IMQ solubility and the solubility parameters of solvents was not found. IMQ solutions in water, ethanol, methanol, acetonitrile, and dimethyl sulfoxide were neither ideal nor regular. The Scatchard–Hildebrand equation does not apply to IMQ solutions because of association phenomena due to intermolecular hydrogen bonds and/or π-stacking, as supported by the hyperchromic effect that was very pronounced in highly polar solvents, such as water, with the increase in temperature. Finally, IMQ solubility values measured in acetone cannot be considered reliable due to the reaction with the solvent, leading to the formation of new molecules. Full article

Allantoin possesses numerous beneficial properties for the skin, like anti-irritant effects, wound healing, skin hydration, and epithelization. In this paper, we investigated a suitable preparation method for an allantoin hydrogel using the Semi-Solid Control Diagram (SSCD) method and characterized its rheological and consistency behavior. To accomplish this, xanthan gum (XG) was selected as a model gelling agent. Briefly, four hydrogels were prepared, two without allantoin (coded M01 and M02) and two with allantoin (M1 and M2). Similarly, the formulations were either prepared through magnetic stirring (M01 and M1) or homogenization in a mortar (M02 and M2). The prepared hydrogels were evaluated using the SSCD for specific parameters and indexes. The Good Quality Index (GQI) shows a higher value for the formulation, M1 = 6.27, compared to M2 = 5.45. This result is also underlined by the value of M01 = 6.45, which is higher than M02 = 6.38. Considering the consistency, the formulation M01 possessed the highest spreadability, followed by M02 and then the allantoin hydrogels M1 and M2. The rheological behavior had a thixotropic pseudoplastic flow for all the formulations. The use of SSCD pictographs outlined the rheological properties that need improvement, the method that is suitable to prepare the allantoin hydrogels, and the influence of the allantoin suspended in the XG hydrogel. Full article

This study aims to enhance energy recovery from sugarcane leaf (SCL) through two-stage anaerobic digestion (TSAD) for hydrogen and methane production. The influence of hydraulic retention time (HRT) on this process was investigated. Optimal conditions established through batch experiments (5% total solids (TS) (w/v) and rice straw compost inoculum) were applied in semi-continuous stirred tank reactors (CSTR-H₂ and CSTR-CH₄). Remarkably, the highest production rates were achieved with HRTs of 5 days for CSTR-H₂ (60.1 mL-H₂/L·d) and 25 days for CSTR-CH₄ (238.6 mL-CH₄/L·d). Microbiological analysis by 16s rRNA sequencing identified Bacillus as predominant in CSTR-H₂ followed by Lactobacillus and Clostridium. Utilizing SCL for TSAD could reduce greenhouse gas (GHG) emissions by 2.88 Mt-CO₂ eq/year, compared to open-field burning, and mitigate emissions from fossil-fuel-based power plants by 228 kt-CO₂ eq/year. This research underscores the potential of TSAD for efficient energy recovery and significant GHG emission reductions. Full article

A cycloaliphatic tetracarboxylic dianhydride, octahydro-2,3,6,7-anthracenetetracarboxylic dianhydride (OHADA) was synthesized to obtain novel colorless polyimides (PIs). Herein, approaches for decolorizing an OHADA prototype and simplifying the entire process are described, and a plausible steric structure for OHADA is proposed. The polyaddition of OHADA and 2,2′-bis(trifluoromethyl)benzidine (TFMB) was unsuccessful; specifically, the reaction mixture remained inhomogeneous even after prolonged stirring. However, the modified one-pot process was applicable to the OHADA/TFMB system. The isolated PI powder form, as well as those for the other OHADA-based PIs, was highly soluble in numerous solvents and afforded a homogeneous and stable solution with a high solid content (20–30 wt%). Solution casting produced a colorless and ductile PI film with a very high glass transition temperature (T_g~300 °C). Furthermore, the OHADA/TFMB system exhibited remarkable thermal stability compared with those of the other related TFMB-derived semi-cycloaliphatic PIs. However, contrary to our expectations, this PI film did not exhibit a low linear coefficient of thermal expansion (CTE). This PI film also possessed excellent thermoplasticity, probably reflecting its peculiar steric structure. The use of an amide-containing diamine significantly enhanced the T_g (355 °C) and somewhat reduced the CTE (41.5 ppm K⁻¹) while maintaining high optical transparency and excellent solubility. Full article

Coarse primary and eutectic Mg₂Si phases were generally precipitated in Mg-Al-Si alloys during solidification at a low cooling rate, which tends to deteriorate the strength and ductility of magnesium alloys due to stress concentration. Different volume fractions of TiB₂ nanoparticles (1%, 3%, and 5%) were added to an Mg-4Al-1.5Si alloy to refine the coarse Mg₂Si phases based on a heterogeneous nucleation mechanism. The nanoparticles were incorporated and dispersed in the molten Mg alloys and by using semi-solid stirring followed by ultrasonic treatment (SSUT), and TiB₂/Mg-4Al-1.5Si composites were obtained. The effect of TiB₂ content on the microstructure and mechanical properties of the composites was studied. The results showed that the average size of primary Mg₂Si phases and α-Mg grains decreased as the TiB₂ content raised, the dendritic primary Mg₂Si phases were refined into polygonal shapes with smaller sizes, and the refined primary Mg₂Si phases were uniformly distributed in the alloys after adding 1 vol.% or 3 vol.% TiB₂ nanoparticles. As the TiB₂ content increased, the morphology of the eutectic Mg₂Si phases was modified from coarse Chinese characters to short rod or fine dot shapes. Vickers hardness and yield strength of the composites reached a maximum (153 HV and 90.9 MPa, respectively) when TiB₂ content was 5 vol.%, while the most superior ultimate tensile strength (142.4 MPa) and elongation (9.2%) were obtained when TiB₂ content was 3 vol.%, which were improved by 173.2%, 31.5%, 69.8%, and 187.5%, respectively compared with the Mg-4Al-1.5Si alloys. Full article

Poultry waste is rich in organic matter, which allows its treatment by the process of anaerobic digestion (AD) to reinforce economic and environmental green strategies. The aim of this study is to assess the technical feasibility of poultry waste AD in semi-continuous mode and to intensify methane production by co-digestion with physico-chemical sludge, i.e., the product of the primary treatment of wastewater after the slaughtering process. First, the AD of poultry droppings is conducted in a continuous stirred anaerobic digester (CSAD) at 37 °C. A volume of 0.791 and 0.623 Nm³·Nm⁻³ reactor·days⁻¹ of biogas and methane, respectively, were produced during the entire process stabilization period. Biochemical characterization of the substrate and the final digestate show high reduction rates of the biochemical fractions, which corroborates with methane yield. In addition, the co-digestion of poultry droppings with two different ratios of physico-chemical sludge (20% and 40% added sludge considering the amount of volatile solids) shows an increase in methane production versus droppings alone, with a higher increase of 54% with a sludge ratio of 40%. Altogether, these promising results were obtained in stable processes, highlighting the pertinence of our study. Full article

In this study, CNTs-reinforced Al-Cu-Mg-Si nanocomposites were successfully fabricated by high-energy ball milling (HEBM) combined with semi-solid stir casting. Then, the composites were subjected to hot extrusion. The Microstructure and Phase analysis of the CNT/Al-Cu-Mg-Si composites were characterized by an Optical microscope, Scanning Electron Microscope (SEM), and XRD. Additionally, density, hardness, and wear were measured. The results revealed that the addition of CNTs effectively inhibited the growth of α-Al grains, and the grains were dramatically refined. Additionally, the dynamic recrystallization degree of the composite extruded rod gradually increased from 1.3% to 68.4%, with the content of CNTs from 0 wt% to 3.0 wt%. The hardness values of the composite increased with an increase in CNTs. Moreover, the friction factor and wear rate of the composites first decreased and then increased as the content of CNTs increased. When 1.5CNTs were added, the friction coefficient (COF) and wear rate of composites reached the minimum of 0.3577 and 3.42 mg/km, which were reduced by 30.09% and 73.03% compared with Al-Cu-Mg-Si alloy, respectively. Full article

Hydrate-based technology has yet to find its way to commercial applications due to several issues, including formation conditions and slow kinetics. Several solid particles were introduced to speed up hydrate formation. However, these solid compounds have given contradictory results. This study investigated the effect of high thermal conductive metallic nanofluids of silver (Ag) and copper (Cu) on CH₄ and CO₂ hydrates. The solid particles were suspended in a 0.03 wt% SDS aqueous solution, and the results were compared with the 0.03 wt% SDS and deionized water samples. A stirred tank batch reactor was used to conduct the thermodynamic and kinetic experiments. The thermodynamic study revealed that 0.1 wt% of solid particles do not shift the equilibrium curve significantly. The kinetic evaluation, including induction time, the initial rate of gas consumption, half-completion time, t₅₀ and semi-completion time, t₉₅, gas uptake, and storage capacity, have been studied. The results show that the Ag and Cu promote CH₄ hydrates while they inhibit or do not significantly influence the CO₂ hydrates formation. A predictive correlation was introduced to get the apparent rate constant of hydrate formation in the presence of metal-based fluid at the concentrations range of 0.005–0.1 wt%. Full article

The thixo process has the benefit of producing a semi-solid material in which fine primary α-Al grains are uniformly distributed. However, it also has the disadvantage of a costly raw material billet. In this study, a semi-solid slurry was prepared from the rheo process by cooling and electromagnetic stirring, and then a billet for the thixo process was manufactured through an upsetting process with semi-solid slurry. Then, the billet was reheated (thixo process) to make a semi-solid state, and then a final sample was manufactured through a forming process. In both A356 and A6061 materials, the equivalent diameter of the primary α-Al grains became smaller and the roundness became close to one throughout rheo, upsetting, thixo, and forming processes. Due to the refinement and spheroidizing effect of the primary α-Al grains, the tensile strength was improved by each process, and the elongation was slightly decreased. However, after T6 heat treatment, the tensile strength of A356 was decreased, but the elongation was greatly improved. In the case of A6061, on the other hand, the tensile strength was significantly improved, and its elongation decreased after T6 heat treatment. Full article

Ni-CNTs/AZ91 magnesium matrix composites were fabricated by ultrasound treatment combined with a semi-solid stirred method for the first time. The agglomerated spherical Ni-CNTs transferred from spherical shape to clear tubular shape after pre-dispersion treatment. For the Ni-CNTs/AZ91 magnesium matrix composite prepared by semi-solid stirring followed by ultrasonic treatment, Ni-CNTs were evenly distributed in the magnesium matrix or wrapped on the β (Mg₁₇Al₁₂) phase. Mg₂Ni were formed at the interface of the magnesium matrix and CNTs by in-situ reaction, which significantly improved the interface bonding strength of CNTs and the Mg matrix. The tensile strength and elongation of 1.0wt.% Ni-CNTs/AZ91 magnesium matrix composites were improved by 36% and 86%, respectively, compared with those of AZ91 matrix alloy. After Ni-CNTs were added to AZ91 matrix alloy, more dimples were observed at the fracture surface. The fracture behavior of Ni-CNTs/AZ91 composite was transformed from a cleavage fracture of AZ91 matrix alloy to a quasi-cleavage fracture. Meanwhile, the CNTs dispersed near the fracture showed a “pull-out” state, which would effectively bear and transfer loads. The strengthening mechanism of CNTs was also discussed. Full article

Advanced metallurgical processing techniques are required to produce aluminum matrix composites due to the tendency of the reinforcement particles to agglomerate. In this study, graphene nano-platelet reinforcement particles were effectively incorporated into an automotive A319 aluminum alloy matrix using a liquid metallurgical route. Due to its low density, it is a highly difficult task to produce an aluminum matrix composite reinforced with graphene. Hence, this study explored a novel approach to prevent particle floating to the melt surface and agglomeration. This was achieved via a hybrid semi-solid stirring of A319, followed by ultrasonic treatment of the liquid melt using a sonication probe. The microstructure and graphene particles were characterized using optical microscopy and scanning electron microscopy. Furthermore, the interfacial products produced with the incorporation of graphene in liquid aluminum were analyzed with X-ray diffraction. The tensile test results exhibited 10, 11 and 32% improvements in ultimate tensile strength, yield strength, and ductility of A319 reinforced with 0.05 wt.% addition of graphene. Analysis of strengthening models demonstrated primary contribution from Hall-Petch followed by CTE mismatch and load bearing mechanism. The results from this research enable the potential for using cost-effective, efficient and simple liquid metallurgy methods to produce aluminum reinforced graphene composites with improved mechanical properties. Full article