Editorial: Biofuels and Bioproducts From Anaerobic Processes: Anaerobic Membrane Bioreactors (AnMBRs)

New biodegradable waste treatment configurations and technologies have arisen to support the transition of treatment plants toward resource recovery facilities. The interest in Anaerobic Membrane Biological Reactor (AnMBR) technology is increasing due to the advantages related to combine anaerobic digestion with membrane filtration. Thanks to the complete retention of anaerobic microorganisms, AnMBRs have the capacity to efficiently recover most of the energy potential in biodegradable waste streams in the form of biogas and produce high-quality effluents with low biomass production

Fatigue bending behavior of cold-sprayed nickel-based superalloy coatings

Cold-sprayed Ni-based superalloy coatings offer new possibilities for manufacturing and repairing damaged components, such as gas turbine blades or other parts of aircraft engines. This development shines a new light on the conventional additive manufacturing technologies and significantly broadens application fields of cold spray. The idea is that cold spray can contribute to improving the fatigue properties of manufacturing and repaired components. This study deals with the analysis of the microstructural and mechanical properties of IN625 cold-sprayed coatings on V-notched carbon steel substrate. Process conditions of 1000 degrees C and 50bar were employed to produce coatings in V-notched (60 degrees and 90 degrees) samples in order to evaluate the fatigue crack behavior of the sprayed material. Bending tests were carried out in order to evaluate the crack propagation in the coatings during cyclic loading. The K factor was quantified for the two different notch geometries. After fatigue tests, the cracking mechanisms were observed through SEM. Optical microscopy, nanoindentation as a function of coating/substrate distance and corrosion tests were performed. Porosity measurements through image analyses were done to characterize the coatings' quality. The results achieved demonstrate that cold spray deposition and repair can contribute to resistance and to the increase in the global fatigue life of cracked structures

Advanced diamond-reinforced metal matrix composites via cold spray: properties and deposition mechanism

Diamond-reinforced metal matrix composites (DMMC) have great potential for wear-resistance applications due to the superior hardness of the diamond component. Cold spray as an emerging coating technique is able to fabricate coatings or bulk materials without exceeding the material melting point, thereby significantly lowering the risk of oxidation, phase transformation, and excessive thermal residual stress. In this paper, thick DMMC coatings were deposited onto aluminum alloy substrate via cold spray of three feedstock powders: copper-clad diamond and pure copper, and their mixtures. It was found that, due to its low processing temperature, cold spray is able to prevent graphitization of the diamond in the DMMC coatings. Further to that, the original diamond phase was almost completely retained in the DMMC coatings. In case of the coatings fabricated from copper-clad diamond powders only, its mass fraction reached 43 wt.%, i.e. value higher than in any previous studies using conventional pre-mixed powders. Furthermore, it was found that the added copper content powders acted as a buffer, effectively preventing the fracture of the diamond particles in the coating. Finally, the wear test on the coatings showed that the cold sprayed DMMC coatings had excellent wear-resistance properties due to the diamond reinforcement

Wear resistant coatings deposited by cold gas spraying

Naukowym i technologicznym celem badań było wytworzenie nanostrukturalnych powłok FeCuAl-Al2O3, WC-CoAl, Ni-Sn, TiC/Ti o grubości od 45 do 500 μm. Nanoproszki charakteryzujące się strukturą krystaliczną i równomiernym rozmieszczeniem składników otrzymywano, stosując wysokoenergetyczną syntezę mechaniczną. Proszek o strukturze nanokrystalicznej był nanoszony na podłoże bez istotnych zmian jego struktury i właściwości, z wykorzystaniem nowej technologii (natryskiwania zimnym gazem – CGS), pozwalającej uzyskiwać powłoki o dużej gęstości. Mikrostrukturę oraz skład chemiczny nanoproszków i nanoszonych powłok analizowano, wykorzystując mikroskopię świetlną, TEM, STEM, SEM/EDS, XPS oraz XRD. Ponadto mierzono współczynnik tarcia oraz odporność na ścieranie powłok. Przeprowadzone badania wykazały, że mikrostruktura powłok odpowiada strukturze nanoszonych proszków. Dzięki nanostrukturalnej budowie powłok, właściwej proporcji faz twardych i miękkich, natryskiwane zimnym gazem powłoki wykazują lepsze właściwości trybologiczne w porównaniu z materiałami standardowo stosowanymi w przemyśle i bioinżynierii.The basic scientific and technological aim of the research was the generation of nano-structured FeCuAl-Al2O3, WC-CoAl, Ni-Sn, TiC/Ti coatings having thicknesses of about 100-500 μm. High energy ball milling synthesis allowed the production of powders characterized by fine and homogeneous chemical distribution of elements, and an "ultrafine" (nanometer scale) crystalline structure. A new powerful deposition technology (Cold Gas Spray – CGS) was used to transfer the nanophased powder onto the substrate in the form of a dense coating with very little or no change of crystal structure and properties. The microstructure and composition of all prepared nano-powders and deposited coatings were investigated using light microscopy, TEM, STEM, SEM/EDS, XPS and XRD techniques. Hardness, and measurement of the coefficient of friction and wear resistance were carried out on the deposited coatings. It was found that the microstructure of the powder is maintained in the deposited coating. The nano phased structure, with an appropriate balance of hard and soft phases, allows the CGS coatings to exhibit better tribological properties than that of the examined benchmark materials

Wear evaluation of nanostructured Ti cermets for joint reconstruction

Nanostructured cermet coatings consisting of titanium carbides dispersed in a titanium matrix were deposited by supersonic spraying. The aim is to develop novel wear resistant materials that can be applied in joint reconstruction. Structural analysis was performed by Scanning Electron Microscopy, Transition Electron Microscopy, and X-ray Diffraction, whereas the mechanical properties of each phase were determined by nanoindentation technique. In addition, in order to evaluate the friction and wear behavior of these Ti-TiC nanostructured cermet coatings, a two-step tribological approach was applied. This approach consists of two test series. First, pre-screening sliding wear tests were performed in order to provide a ranking of the coatings and a comparison with commonly used biomedical benchmarks. Subsequently parallel wear tests that simulate the joint contact conditions were used to evaluate the reliability of these coatings and the wear loss of the actual tribosystem (coatings vs polyethylene). The experimental results indicated that Ti-TiC cermets possess superior tribological properties, thanks to the appropriate balance of hard carbide and soft titanium phases, and the nanostructuring of the titanium matrix. The wear mechanism was investigated in order to establish a 'structure-property' relationship for these coatings.status: publishe

Microstructure and Properties of TiC/Ti Coatings Deposited by the Supersonic Cold Gas Spray Technique

Nanostructured, biocompatible, TiC/Ti Supersonic Cold Gas Sprayed coatings were deposited onto a Ti6Al4V alloy and their microstructure, wear resistance and hardness were investigated. The starting nanostructured powder, containing a varied mixture of Ti and TiC particles, was produced by high energy ball milling. Scanning and transmission electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction were used for structural and chemical analyses of powder particles and coatings. Coatings, 250-350 μm thick, preserving the nanostructure and chemical powder composition, with low porosity and relatively high hardness (~850 HV), were obtained. These nanostructured TiC/Ti coatings exhibited better tribological properties than commonly used biomedical benchmark materials, due to an appropriate balance of hard and soft nano-phases

Structural properties and wear behaviour of supersonic sprayed nanostructured cermets

oral presentation + abstract (NANO-20)status: publishe

Fretting Wear and Scratch Resistance of Cold-Sprayed Pure Cu and Ti

The paper analyses the fretting and wear behavior of pure copper and pure titanium coatings realized through cold spray. The coatings were designed and produced by employing processing conditions leading to minimum porosity and high hardness; these conditions were 700 °C and 40 bar for Ti powders and 400 °C and 30 bar for Cu ones. The low porosity and high strength materials led to high resistance to wear damaging through the optimal energy dissipation upon fretting. Due to the sprayed particles deformation mode, the sprayed materials show non-uniform hardening along the deposition distance. As a matter of fact, hardness varied in the range 3.7–4.2 GPa for Ti coatings and 1.5–2 GPa for the Cu ones depending on the distance from the substrate and on the coatings thickness. This influenced the materials properties and the response to the wear damaging. This was demonstrated by the scratch tests performed on coatings with different thicknesses. Those coatings sprayed in major thickness revealed the best wear resistance due to the deformation hardening. The harder coatings also revealed brittle fracture at the experienced highest loads

Powder properties and processing conditions affecting cold spray deposition

The cold spray coating properties and performances are largely affected by feedstock characteristics and the employed processing parameters. Starting from experimental results obtained from the bibliographic data, the relationships between starting particles, processing conditions, and coating properties obtained by cold gas spray were analyzed. The relationships among these properties and particle velocity were described for various material systems. The effect on particle flattening, hardness, and porosity were largely described. Finally, the influence of the different parameters on the process output and on the coating properties was analytically defined through the employment of the multi-objective simulation tool modeFRONTIER. The analysis of data from the bibliography is a new trend that can also be applied to cold spray in order to analyze the effect of powder properties and spraying parameters on the cold spray (CS) process