Rubber-like PTFE Thin Coatings Deposited by Pulsed Electron Beam Deposition (PED) Method.

PTFE coatings were manufactured using the pulsed electron beam deposition (PED) technique and deposited on Si substrates. The deposition was carried out at constant parameters: temperature 24 °C, discharge voltages 12 kV, and 5000 electron pulses with a pulse frequency of 5 Hz. Nitrogen was used as the background gas. The gas pressure varied from 3 to 11 mTorr. The coating adhesion was evaluated using micro scratch testing and the residual scratch morphology was characterized by atomic force microscopy. Detailed studies of the chemical and physical structure were conducted using infrared spectroscopy and X-ray diffraction. These analyses were then correlated with the mechanical response of the coatings observed during the scratch tests. Drawing upon a review of the literature concerning energetic beam interactions with PTFE material, hypotheses were posed to explain why only specific conditions of the PED process yielded PTFE coatings with rubber-like properties.

High yield and wide lateral size growth of α-Mo2C: exploring the boundaries of CVD growth of bare MXene analogues.

Synthesis of Mo2C bare MXenes, without surface terminations groups, via chemical vapor deposition (CVD) on metal foils is scientifically a very intriguing crystal growth process, and there are still challenges and limited fundamental understanding to overcome to obtain high yield and wide crystal size lateral growth. Achieving large area coverage via direct growth is scientifically vital to utilize the full potential of their unique properties in different applications. In this study, we sought to expand the boundaries of the current CVD growth approach for Mo2C MXenes and gain insights into the possibilities and limitations of large area growth, with a particular focus on controlling Mo concentration. We report a facile modification of their typical CVD growth protocol and show its influence on the Mo2C synthesis, with growth times spanning up to 3 h. Specifically, prior to initiating the CVD growth process, we introduced a holding step in temperature at 1095 °C. This proved to be beneficial in increasing the Mo concentration on the liquid Cu growth surface. We achieved an average Mo2C crystals coverage of approximately 50% of the growth substrate area, increased tendency of coalescence and merging of individual flakes, and lateral flake sizes up to 170µm wide. To gain deeper understanding into their CVD growth behavior, we conducted a systematic investigation of the effect of several factors, including (i) a holding step time on Mo diffusion rate through molten Cu, (ii) the Cu foil thickness over the Mo foil, and (iii) the CVD growth time. Phase, chemical and microstructural characterization by x-ray diffraction, x-ray photon spectroscopy, SEM and scanning/transmission electron microscopy revealed that the grown crystals are single phaseα-Mo2C. Furthermore, insights gained from this study sheds light on crucial factors and inherent limitations that are essential to consider and may help guide future research progress in CVD growth of bare MXenes.

Gallic Acid Based Black Tea Extract as a Stabilizing Agent in ZnO Particles Green Synthesis.

In this work, zinc oxide particles (ZnO NPs) green synthesis with the application of black tea extract (BT) is presented. A thorough investigation of the properties of the extract and the obtained materials was conducted by using Fourier transform infrared spectroscopy (FTIR), liquid chromatography-mass spectrometry (LC-MS), X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and quadrupole mass spectroscopy (QMS). The obtained results indicated that the amount of used BT strongly influenced the morphology, chemical, and crystalline structure of the obtained particles. The investigation demonstrated that the substance present in black tea (BT) extract, which was adsorbed on the ZnO surface, was in fact gallic acid. It was found that gallic acid controls the crystallization process of ZnO by temporarily blocking the zinc cations. Additionally, these organic molecules interact with the hydroxide group of the precipitant. This blocks the dehydration process stabilizing the zinc hydroxide forms and hinders its transformation into zinc oxide. Performed measurements indicated that obtained ZnO particles have great antioxidant and antimicrobial properties, which are significantly correlated with ZnO-gallic acid interactions.

Pectin-organophilized ZnO nanoparticles as sustainable fillers for high-density polyethylene composites.

A series of nanocomposites made of high-density polyethylene (HDPE) and 10 wt% zinc oxide nanoparticles (ZnO NPs) were produced by extrusion and injection molding. The nanoparticles were prepared via a green way using the pectin-based banana peel extract as the stabilizer and a proper dispersion-providing agent. The fillers were well-dispersed in the matrix and the composites exhibited improved functional characteristics such as increased thermal stability and mechanical properties. The presence of the pectin-organophilized filler had a significant impact on the crystallization process of HDPE. The kinetics of the degradation process was also altered in comparison to the pure polymer. The fire properties of the composites were enhanced as the amount of the gas products produced during their degradation was reduced, what was confirmed by thermogravimetric analysis coupled with gas products analyses (TGA/FTIR/QMS). The structure and morphology of the materials were characterized by scanning electron microscope (SEM), infrared spectroscopy (FTIR), X-ray diffraction (XRD), and differential scanning calorimetry (DSC). Additionally, the mechanical properties were tested by tensile tests. An in-depth analysis revealed that the HDPE-pectin-ZnO interactions are crucial for the structural and performance properties of the final composite. The used biopolymer reacts with ZnO via ionic interaction and through hydrogen bond in the case of HDPE.

Pectin based banana peel extract as a stabilizing agent in zinc oxide nanoparticles synthesis.

Various amounts of banana peel extract were successfully used as a stabilizing agent in the co-precipitation of zinc oxide nanoparticles. The obtained materials were characterized by means of Fourier transform infrared spectroscopy (FTIR), gel permeation chromatography (GPC), X-ray diffraction (XRD), photoluminescence spectroscopy (PL), scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDS), N2 physisorption, thermogravimetric analysis (TGA), and quadrupole mass spectroscopy (QMS). On account of using such a broad spectrum of analytic methods, a thorough description of the interactions between the organic ingredients of the extract and ZnO particles was presented. It was indicated that the banana peel extract is based on pectin. These carbohydrate macromolecules adsorb on ZnO surface due to presence of active carboxylic groups. By increasing the concentration of polysaccharides, pectin-pectin interactions were also observed. The amount of the extract used for the synthesis significantly influenced the crystalline structure of zinc oxide particles along with their size and morphology. The shape and size were varying from thin flakes (450 × 24 nm) when the smallest amount of the extract was used, through nanocones with pointed tips (210 × 120 nm) agglomerated in a flower-like structure, until cubic-shaped nanoparticles (20-40 nm) agglomerated in a pinecone-like structure (430 × 180 nm) when the biggest amount of the extract was applied. The obtained particles have displayed apromising antimicrobial activity against Gram-positive (Staphylococcus aureus) and Gram-negative (Pseudomonas aeruginosa) bacteria, and fungus (Candida albicans). The highest activity was demonstrated against S. aureus pathogen.

XPS and FTIR Studies of Polytetrafluoroethylene Thin Films Obtained by Physical Methods.

Two methods-attenuated total reflection Fourier infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS)-have been used to analyze the chemical structure of polytetrafluorethylene (PTFE) thin coatings deposited by pulsed laser (PLD) and pulsed electron beam (PED) ablations. The volume of the analyzed materials is significantly different in these techniques which can be of great importance in the characterization of highly heterogeneous thin films. Optical microscopy, atomic force microscopy (AFM) and scanning electron microscopy (SEM) have been additionally used to examine the coating surface morphology. The studies have shown that in the case of thin polymer coatings deposited by physical methods, the application for chemical structure evaluation of complementary techniques, with different surface sensitivity, together with the use of surface topography imaging, provide unique insight into the film morphology. The results can provide information contributing to an in-depth understanding of the deposition mechanism of polymer coatings.

Chemical Structure of EVA Films Obtained by Pulsed Electron Beam and Pulse Laser Ablation.

Poly(ethylene-co-vinyl acetate) (EVA) films were deposited for the first time using physical methods. The chemical structure of the films obtained using two techniques, pulsed electron beam deposition (PED) and pulsed laser deposition (PLD), was studied by attenuated total reflection Fourier infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS). Whilst significant molecular degradation of the EVA films was observed for the PLD method, the original macromolecular structure was only partially degraded when the PED technique was used, emphasizing the superiority of the PED method over PLD for structurally complex polymers such as EVA. Optical and scanning electron microscopic observations revealed compact and smooth EVA films deposited by pulsed electron beam ablation as opposed to heterogeneous films with many different sized particulates obtained by PLD.

Sugar Alcohol-Based Deep Eutectic Solvents as Potato Starch Plasticizers.

The aim of this work was to prepare sugar alcohol-based deep eutectic solvents (DES) and test them as starch plasticizers. Thermoplastic starch (TPS) films were obtained via a simple and convenient thermocompression method. Influence of starch/DES premixtures conditioning (preheating, storage time) on TPS properties was investigated. TPS/sorbitol (S)-based DES exhibited similar tensile strength (TS) (8.6 MPa) but twice higher elongation at the break (ε) (33%) when compared with TPS plasticized only with S. Extra treatment, i.e., heating or prolonged storage time, facilitated starch/DES plasticizing. Starch with selected DES was also extruded and the influence of preconditioning and extrusion rotational speed were subsequently studied on thermocompressed films. Extrusion at 100 rpm led to films with TS up to ca. 10 MPa and ε up to 52%. Some differences in film samples morphology obtained via two processing methods were observed. X-ray diffractograms revealed that extruded samples exhibited a V-type peak at 18.2°, with intensity depending on plasticizer total molecular size. Applied techniques (mechanical tests, XRD, Dynamic Mechanical Analysis (DMA), FTIR-Attenuated Total Reflection (ATR), and moisture sorption) indicated that S-based DES forms stronger interactions with starch than glycerol (G) only used as conventional plasticizer, thus leading to better mechanical properties and inhibited tendency to starch recrystallization (studied up to one year).

Deep eutectic solvents as simultaneous plasticizing and crosslinking agents for starch.

The aim of this work was to prepare deep eutectic solvents (DES) made with choline salts with α-hydroxylate anions and glycerol and apply them as starch plasticizers. Additionally, crosslinking potential of polyfunctional anions from the salts was investigated. Starch/DES premixtures were rheologically and thermally (DSC, TGA) analyzed. Thermoplastic starch (TPS)/DES films were prepared via thermocompression molding. Influence of choline salt to glycerol molar ratio, type of anion and compression parameters on mechanical, dynamic mechanical, thermal and sorption properties as well as structural morphology (XRD, FTIR analysis) was studied. DES containing citrate anion exhibited parallel crosslinking and plasticizing ability of polysaccharide matrix as applied techniques confirmed. The higher choline citrate (CCit) content in DES the higher tensile strength, more amorphous structure and lower sorption degree to CCit:G 1:6 M ratio. XRD revealed that TPS/CCit-based DES films did not retrograde even after one year of storage. The best compression parameters for studied systems were: 140 °C, 12 tons, 10 min.

Kinetics of the oxidation of iron carbide dispersed in a carbon matrix with water vapor.

The reaction of iron carbide embedded in a carbon matrix with water vapor was studied in the temperature range 300-500 degrees C and the partial pressure of water vapor p(H(2)O) = 0.63-3.26 kPa. At these conditions the superfine magnetite and hematite are the products of this reaction. High oxidation temperature and low partial pressure of water vapor are favorable conditions to obtain only magnetite phase dispersed in a carbon matrix. The oxidation rate of iron and iron carbide is the same for both of them in the initial, kinetic stage of the reaction. It was observed that carbon deposit caused an increase in the reaction rate as a result of spillover effect. The oxidation rate of iron carbide distributed in a carbon matrix increases linearly with the carburization degree of the sample. The reaction rate is also linearly dependent on the partial pressure of water vapor. The apparent activation energy was determined as 110 kJ/mol.