A New Sustainable PPT Coating Based on Recycled PET to Improve the Durability of Hydraulic Concrete.

A new, sustainable polypropylene terephthalate (PPT) coating was synthesized from recycled polyethylene terephthalate (PET) and applied onto a hydraulic concrete substrate to improve its durability. For the first step, PET bottle wastes were ground and depolymerized by glycolysis using propylene glycol (PG) in a vessel-type reactor (20-180 °C) to synthesize bis(2-hydroxypropyl)-terephthalate (BHPT), which was applied as a coating to one to three layers of hydraulic concrete substrate using the brushing technique and polymerized (150 °C for 15 h) to obtain PPT. PET, BHPT, and PPT were characterized by FT-IR, PET, and PPT using TGA, and the PPT coatings by SEM (thickness), ASTM-D3359-17 (adhesion), and water contact angle (wettability). The durability of hydraulic concrete coated with PPT was studied using resist chloride ion penetration (ASTM-C1202-17), carbonation depth at 28 days (RILEM-CPC-18), and the absorption water ratio (ASTM-C1585-20). The results demonstrated that the BHPT and PPT were synthetized (FT-IR), and PPT had a similar thermal behavior to PET (TGA); the PPT coatings had good adhesion to the substrate, with thicknesses of micrometric units. PPT coatings presented hydrophilic hydrophilic behavior like PET coatings, and the durability of hydraulic concrete coated with PPT (2-3 layers) improved (migration of chloride ions decreased, carbonation depth was negligible, and the absorption water ratio decreased).

TiNbN Hard Coating Deposited at Varied Substrate Temperature by Cathodic Arc: Tribological Performance under Simulated Cutting Conditions.

This study focused on investigating the adhesion and tribological properties of niobium-doped titanium nitride (TiNbN) coatings deposited on D2 steel substrates at various substrate temperatures (Ts) under simulated cutting conditions. X-ray diffraction confirmed the presence of coatings with an FCC crystalline structure, where Nb substitutes Ti atoms in the TiN lattice. With increasing Ts, the lattice parameter decreased, and the crystallite material transitioned from flat-like to spherical shapes. Nanoindentation tests revealed an increase in hardness (H) with Ts, while a decrease in the elastic modulus (E) resulted in an improved elastic strain limit for failure (H/E) and plastic deformation resistance (H3/E2), thereby enhancing stiffness and contact elasticity. Adhesion analysis showed critical loads of ~50 N at Ts of 200 and 400 °C, and ~38 N at Ts of 600 °C. Cohesive failures were associated with lateral cracking, while adhesive failures were attributed to chipping spallation. The tribological behavior was evaluated using a pin-on-disk test, which indicated an increase in friction coefficients with Ts, although they remained lower than those of the substrate. Friction and wear were influenced by the surface morphology, facilitating the formation of abrasive particles. However, the absence of coating detachment in the wear tracks suggested that the films were capable of withstanding the load and wear.

The Piezoresponse in WO3 Thin Films Due to N2-Filled Nanovoids Enrichment by Atom Probe Tomography.

Tungsten trioxide (WO3) is a versatile n-type semiconductor with outstanding chromogenic properties highly used to fabricate sensors and electrochromic devices. We present a comprehensive experimental study related to piezoresponse with piezoelectric coefficient d33 = 35 pmV-1 on WO3 thin films ~200 nm deposited using RF-sputtering onto alumina (Al2O3) substrate with post-deposit annealing treatment of 400 °C in a 3% H2/N2-forming gas environment. X-ray diffraction (XRD) confirms a mixture of orthorhombic and tetragonal phases of WO3 with domains with different polarization orientations and hysteresis behavior as observed by piezoresponse force microscopy (PFM). Furthermore, using atom probe tomography (APT), the microstructure reveals the formation of N2-filled nanovoids that acts as strain centers producing a local deformation of the WO3 lattice into a non-centrosymmetric structure, which is related to piezoresponse observations.

Hybrid Coatings of SiO2-Recycled PET Unsaturated Polyester Resin by Sol-Gel Process.

Hybrid coatings of SiO2 and recycled unsaturated polyester resin (R-UPR) from recycled polyethylene-terephthalate (PET) were prepared by the sol-gel process on glass substrates. First, SiO2 was synthesized by the sol-gel process using a tetraethyl orthosilicate (TEOS) solution. Next, bis(2-hydroxypropyl-terephthalate) (BHPT) was synthesized from mechanical and chemical recycling (glycolysis) of post-consumer PET bottles in propylene glycol (PG) using ZnA as catalyst, in a Vessel-type reactor (20-200 °C); maleic anhydride (MA) was added and, following the same procedure, the unsaturated polyester (UP) was synthetized, which was cooled to room temperature. Next, styrene (St) and benzoyl-peroxide (PBO)-initiator were added to obtain R-UPR. TEOS (T) and three hybrid solutions were synthesized, with molar ratios of 0:1:0 (T), 1:2:0.25 (H1), 1:1:0.25 (H2), and 1:0:0.25 (H3) for R-UPR:TEOS:3-trimethoxy-(silyl)-propyl-methacrylate (TMSPM), respectively, with which TC, HC1, HC2, and HC3 coatings were elaborated using the immersion technique and polymerized (120 °C for 24 h). The solutions were characterized by FT-IR and TGA, and the coatings by SEM, nanoindentation, AFM, adhesion, and contact angle. The results showed that SiO2 enhanced mechanical (hardness and Young's modulus) and thermal properties of the R-UPR. The coatings adhered perfectly to the substrate, with thicknesses of micrometer units and a flat surface; in addition, hydrophilicity decreased as SiO2 decreased.

The Use of Recycled PET for the Synthesis of New Mechanically Improved PVP Composite Nanofibers.

Polyethylene terephthalate (PET) waste has become a major challenge for the conservation of the environment due to difficult degradation. For this reason, it is important to develop new recycling strategies for reusing this waste. In this work, the electrospinning technique was used to synthesize composite nanofibers of polyvinylpyrrolidone (PVP), recycling PET (RPET) that was obtained from the chemical recycling of postconsumer PET with glycolysis and styrene (ST) as a crosslinking agent. The polymer solutions were analyzed by viscosity and frequency sweeping, while the composite nanofibers were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis/differential scanning calorimetry (TGA/DSC), and nanoindentation to compare their properties. The PVP nanofibers presented an average diameter of 257 nm; the RPET/PVP and RPET/PVP/ST composite nanofibers had average diameters of 361 nm and 394 nm, respectively; and the modulus of elasticity and hardness of the RPET/PVP/ST composite nanofibers were 29 and 20 times larger, respectively, than those of the PVP nanofibers. With the synthesis of these composite nanofibers, a new approach to PET recycling is presented.

Assessing mechanical behavior of ostrich and equine trabecular and cortical bone based on depth sensing indentation measurements.

Guided bone regeneration surgeries are based on grafting a scaffold in the site to be repaired. The main focus of the scaffold is to provide mechanical support to newly formed blood vessels and cells that will colonize the grafted site, achiving bone regenertation. In this regards, the aim of this study was to characterize the anatomy, structular, surface morphologycal, chemical composition, and nanomechanical properties of ostrich and equine trabecular bone. Ostrich and equine specimens were obtained from a local abattoir and bone was obtained by blunt dissection, n = 5. Tissue bone anatomy and trabecular structure were measured using Computerized Axial Tomography (CAT). Atomic Force Microscopy (AFM) and Energy dispersion spectrometry of X-ray (EDS) were used to examine surface morphology and chemical composition of the trabecular ostrich and equine bone. Mechanical behavior was analysted by nanoindentation. Equine specimens were examined as control. CAT results suggest that in terms of anthropometry, ostrich tarsometatarsus bone is more suitable due to its length is 432.56 ± 3.12 mm vs. the highest human bone structures reported, which femur length is 533.66 ± 18.81 mm. Besides, the low radiodensity in the Hounsfield scale exhibits equine trabecular bone more brittle (Av = 1538.4 ± 0.9) than ostrich trabecular bone (Av = 462.1 ± 1.5). EDS showed a slight variation of the element Calcium (Ca2+) ranging from 20% to 25.5% wt in equine bone; the Ca2+ content variation is consistent with the ring-shaped morphology, while in ostrich bone the chemical composition is homogeneous. The elastic modulus, nanohardness (E = 5.3 ± 0.7 GPa, H = 220 ± 10 MPa) and average roughness (Ra = 207 nm) are similar to the human trabecular bone which could reduce the stress shielding, all of these findings suggest that ostrich bone can be promising for native tissue scaffolds for mechanically demanding applications. This research makes innovative contributions to science and provides a framework, which will allow us to address future biomedical tests, and rapidly identify promising organic and sustainable waste for tissue scaffold.

Nano-structured hydroxyapatite and titanium dioxide enriching PENTA /UDMA adhesive as aesthetic coating for tooth enamel.

OBJECTIVES: The aim of this study was to investigate the effect of the nanostructured hydroxyapatite (NHAp) and titanium dioxide nanoparticles (NTiO2) on dispersion in an adhesive containing monomers of Dipenta erythritol penta-acrylate monophosphate (PENTA) and Urethane dimethacrylate (UDMA), as well as evaluating the structural, optical and mechanical behavior of the composite material for dental aesthetic application. METHODS: The NHAp powders were synthesized through the wet chemical methods of hydrothermal and ultrasound-assisted precipitation. The microstructure, morphology and composition analysis of the powder of NHAp and NTiO2 were performed by scanning and transmission electron microscopy. The optical microscopic identification of the different colors was obtained due to varying the amounts of NHAp and NTiO2 in the adhesive. On the other hand, the diffuse reflectance spectra of the coatings were evaluated every 2nm with the wavelength from 400 to 800nm for combined specular and diffuse reflectance. The nanomechanical properties of the aesthetic coating such as (H), elastic modulus (E) and nanoscratching were evaluated by nanoindentation. The roughness of the composite coatings were evaluated by AFM. RESULTS: From different powders combinations, NHAP 75%Wt-NTiO2 %25Wt, at (10Wt %) into a dental adhesive, the resulting mixture manifested the optimum aesthetic white appearance. The scanning and transmission electron microscopy images confirmed that the HAp nanorods and TiO2 nanoparticles sized were 55nm and 20nm respectively prepared by the high-energy ball mixed process. The values of nanomechanical properties of the optimum aesthetic coating were hardness, H=3.2±0.3GPa, elastic modulus, E=78±3GPa, Yield point, Y=107MPa±2 and scratching, maximum wear track deformation 3.7±0.12 µm2. The percentage of reflectance to optimum aesthetic white appearance was of 46.83% at 423nm of wavelength. CONCLUSIONS: The nanocomposite PENTA/UDMA with mixtures of Nanohydroxyapatite and titanium dioxide may be considerate as a mechanical toughened, also an option to modify shade qualities for dental aesthetic applications.

Structural Aspects LiNbO3 Nanoparticles and Their Ferromagnetic Properties.

We present a solid-state synthesis of ferromagnetic lithium niobate nanoparticles (LiNbO3) and their corresponding structural aspects. In order to investigate the effect of heat treatments, two batches of samples with a heat-treated (HT) and non-heat-treated (nHT) reduction at 650 °C in 5% of hydrogen/argon were considered to investigate the multiferroic properties and their corresponding structural aspects; using magnetometry and scanning transmission electron microscopy (STEM). Results indicate the existence of ferromagnetic domains with a magnetic moment per unit cell of 5.24 × 10-3 µB; caused mainly due to voids and defects on the nanoparticle surface, as confirmed by STEM measurements.

Hardness and Elastic Modulus on Six-Fold Symmetry Gold Nanoparticles.

The chemical synthesis of gold nanoparticles (NP) by using gold (III) chloride trihydrate (HAuCl∙3H2O) and sodium citrate as a reducing agent in aqueous conditions at 100 °C is presented here. Gold nanoparticles areformed by a galvanic replacement mechanism as described by Lee and Messiel. Morphology of gold-NP was analyzed by way of high-resolution transmission electron microscopy; results indicate a six-fold icosahedral symmetry with an average size distribution of 22 nm. In order to understand the mechanical behaviors, like hardness and elastic moduli, gold-NP were subjected to nanoindentation measurements-obtaining a hardness value of 1.72 GPa and elastic modulus of 100 GPa in a 3-5 nm of displacement at the nanoparticle's surface.