Chemical Composition Of Coatings Research Articles

Effect of thermal spray process on chemical composition, magnetic behaviour, structure and mechanical properties of coatings based on milled Fe, Co and $$\hbox {Al}_{2}\hbox {O}_{3}$$ powder

Coated steel substrate by $$\hbox {FeCo/Al}_{2}\hbox {O}_{3}$$ nanoparticle with various Co concentrations realized by a thermal spraying process, preliminary powder alloy was elaborated by mechanical alloying technique for 20 h of milling time. The aims of this work are to study the effect of thermal spraying process and mechanical alloying on chemical composition, magnetic behaviour, structure and mechanical properties of coating. After mechanical alloying, the crystallite sizes of the powder were decreased from 18 to 7 nm and the lattice strains increased from 0.36 to 0.56%. This is due to the phenomenon of diffusion of cobalt in the iron lattice and the milling effect. After thermal spraying, many different phases appeared in the coating, such as $$\hbox {Al}_{2}\hbox {FeO}_{4}$$, $$\hbox {CoAl}_{2}\hbox {O}_{4}$$, CoFe and $$\hbox {CoFe}_{2}\hbox {O}_{4}$$. Magnetic behaviour was influenced by this change in the chemical composition of coating. The maximum saturation magnetization was found in $$\hbox {Fe}_{40}\hbox {Co}_{20}(\hbox {Al}_{2}\hbox {O}_{3})_{40}$$ sprayed powder, however, the minimum coercivity was found in $$\hbox {Fe}_{50}\hbox {Co}_{10}(\hbox {Al}_{2}\hbox {O}_{3})_{40}$$ sprayed powder. Mechanical properties’ parameters such as microhardeness and Young’s modulus were enhanced by the change in chemical composition during mechanical alloying and thermal spraying process.

Impact of Sequential Treatments with Natural and Na-Exchanged Chabazite Zeolite-Rich Tuff on Pig-Slurry Chemical Composition

Notwithstanding the widespread use of natural and pre-exchanged zeolites for zootechnical effluent treatment, little attention has been dedicated to the variation in the chemical composition of the treated slurries, besides the effects on their NH4+ content. This paper aimed at elucidating the compositional variations in terms of major and trace elements of a raw pig-slurry (PS) after three sequential treatment cycles (TC) with three different grain sizes of natural and Na-exchanged zeolite-rich volcanic tuffs (natural ZTs and NaZTs). A series of laboratory batch experiments revealed that all ZTs had profoundly influenced the final PS chemical composition. As expected, the NaZTs were more efficient in terms of NH4+ removal than the natural ZTs, reaching almost 60% reduction of the initial content after three TCs. A parallel effect of this efficient removal was the remarkable increase in Na+. The Na-forms of ZTs led also to stronger competition with K+ ions, resulting in adsorption of this macronutrient and hence in a reduction of the fertilization value of the PS. In terms of heavy metals and other trace elements, all the treatments with ZTs had significantly increased the Li, Ba, Rb, Sr, Ga, and U content in the PS.

Corrosion resistance of one-step superhydrophobic polypropylene coating on magnesium hydroxide-pretreated magnesium alloy AZ31

Superhydrophobic coating on magnesium (Mg) alloys usually comprises an inner coating with a hierarchical structure and an outer coating with a low surface energy. However, the instability and weak interfacial adhesion of both coatings restricts their use on a larger scale. In this paper, a Mg(OH)2 coating was formed on the AZ31 Mg alloy via hydrothermal process, and subsequently one-step fabricated a micron-sized spherical structure polypropylene (PP) film on the Mg(OH)2 coating to obtain the corrosion-resistant and superhydrophobic coating. Surface morphology and chemical composition of coatings were characterized via field-emission scanning electron microscopy (FE-SEM), Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD) together with X-ray photoelectron spectroscopy (XPS). The contact and sliding angles were measured to determine the coating hydrophobicity. Furthermore, the corrosion resistance was investigated through electrochemical polarization, electrochemical impedance spectroscopy, and hydrogen evolution tests. Results indicated that the Mg(OH)2/PP hybrid coating exhibited superhydrophobicity due to its micron-scale spherical structure with high contact angle (165.5 ± 3.6°), a low sliding angle (4 ± 0.6°) and low surface energy (6.7 mJ/m2). Corrosion current density decreased approximately four orders of magnitude (from 6.15× 10−5 A cm−2 to 3.12 × 10−9 A cm−2) compared with AZ31 substrate, indicating that the proposed coating possessed superior corrosion resistance. Stability tests indicated that the hybrid coating showed excellent physical and chemical stability. Moreover, the scratch tests revealed that the composite coating had better adhesion.

Исследование влияния наночастиц диоксида кремния на поверхностные свойства кремнийорганических покрытий

Изготовлены покрытия на основе метилфенилсилоксанового каучука марки СКТН-ф с различным содержанием полиметилсилоксанового масла марки ПМС-200 и наночастиц белой сажи БС-100. Проведены исследования стойкости к истиранию и гидрофобных свойств (угол смачивания, угол скатывания) покрытий, адгезии льда к их поверхности. Показано, что введение в состав полимерной матрицы полиметилсилоксанового масла приводит к снижению стойкости к истиранию и понижению гидрофобных свойств покрытий и одновременно позволяет понизить адгезию льда к поверхности. Установлено, что введение наночастиц БС-100 позволяет повысить физико-механические характеристики покрытий при сохранении уровня функциональных свойств. Полученные результаты зависимости функциональных свойств от химического состава покрытий объясняются их структурными особенностями, в частности полиметилсилоксановое масло равномерно распределяется по объему полимерной матрицы, обволакивая выходящие на поверхность агломераты наночастиц белой сажи, формируя тем самым многомодальную шероховатость, которая, в свою очередь, способствует повышению гидрофобных свойств покрытия.

Microstructures of La2Ce2O7 coatings produced by plasma spray-physical vapor deposition

La2Ce2O7 (LC) coatings were produced by plasma spray-physical vapor deposition (PS-PVD). To achieve the quasi-columnar microstructure, three spray parameters with different net power, spray distance, and carrier gas flow rate were applied. The relationships between the spray parameters and the microstructures were investigated. It was found that the coatings’ microstructure is more sensitive to the net power and carrier gas flow rate rather than the spray distance. The corresponding phase and chemical compositions of coatings were studied by X-ray diffraction (XRD) and energy dispersive spectrometer (EDS), respectively. The results indicate that the lattice parameters of LC phases have positive correlations with average atomic La/Ce ratios of the coatings. The regional characteristics of the optimized coating were investigated by transmission electron microscope (TEM). Super-lattice diffraction patterns of TEM revealed that the coating is pyrochlore phase. “Particle-interruption” mechanisms in the quasi-columnar coating were proposed and discussed.

Multiparametric reference materials for metrological support in the area of coating parameter control

The present work analyses the state and development prospects of metrological support and standardization of in the field of measuring surface density, thickness and chemical composition of coatings. The main characteristics of the State Primary Measurement Standard GET 168-2015 and developed multiparameter reference materials are described.

Covalently Crosslinked Nanogels: An NMR Study of the Effect of Monomer Reactivity on Composition and Structure.

Covalently crosslinked nanogels are widely explored as drug delivery systems and sensors. Radical polymerization provides a simple, inexpensive, and broadly applicable approach for their preparation, although the random nature of the reaction requires careful study of the final chemical composition. We demonstrate how the different reactivities of the monomers influence the total degree of incorporation into the polymer matrix and the role played by the experimental parameters in maximizing polymerization efficiency. Nanogels based on N-isopropylacrylamide, N-n-propylacrylamide, and acrylamide crosslinked with N,N’-methylenebisacrylamide were included in this study, in combination with functional monomers N-acryloyl-l-proline, 2-acrylamido-2-methyl-1-propanesulfonic acid, and 4-vinyl-1H-imidazole. Total monomer concentration and initiator quantities are determining parameters for maximizing monomer conversions and chemical yields. The results show that the introduction of functional monomers, changes in the chemical structure of the polymerizable unit, and the addition of templating molecules can all have an effect on the polymerization kinetics. This can significantly impact the final composition of the matrices and their chemical structure, which in turn influence the morphology and properties of the nanogels.

Effects of Composition and Post Heat Treatment on Shape Memory Characteristics and Mechanical Properties for Laser Direct Deposited Nitinol

Nitinol structures were synthesized in a fully dense form using a laser direct deposition method. The pure elemental metal powders of nickel and titanium were used and powder ratios were controlled to arrive at the prescribed final chemical compositions of Nitinol. The transformation temperatures of synthesized Nitinol samples with different chemical composition and post heat treatment conditions were systematically analyzed and compared with those of conventional Nitinol. Compared to Nitinol parts produced by other techniques, the laser engineered net shaping (LENS) created the least amount of secondary phase, indicating the possibility of high corrosion resistance. Two step post processing of solution heat treatment and aging heat treatment was carried out to improve the homogeneity of the microstructure and to investigate its effects on phase transformation temperatures. The resultant phase transformation temperatures could be controlled by the heat treatment parameters. Compression test results showed mechanical properties of synthesized Nitinol samples are largely affected by its post heat treatment history while the effect of initial chemical composition was negligible.

Direct-infusion electrospray ionization-mass spectrometry analysis reveals atractyligenin derivatives as potential markers for green coffee postharvest discrimination

Coffee quality is strongly related to postharvest processes. Dry and wet are the most traditional and employed processes. However, more recently, the semi-dry process has been introduced and applied for producing coffees of good quality in a more environmental friendly manner compared to the wet process. In this work, green Arabica coffee cherries from two consecutive crops were submitted to the dry and semi-dry postharvest processes and their methanol:water extracts were characterized by ESI(−) FT-ICR MS followed by chemometric data analysis. Thirty-three compounds were identified in the extracts by their high-resolution and accurate m/z values and MS/MS spectra being nine of them diterpenes related to atractyligenin derivatives. The dry and semi-dry processes led to distinct extracts in which compounds such as atractyloside II, carboxyatractyloside II and carboxyatractyloside III showed the greatest contributions (p < 0.05) based on t-Student's test and PLS-DA statistical analyses. These compounds were able to discriminate the postharvest processes for coffees from two consecutive crops. These results can help to better understand the effects of the postharvest processes in the final chemical composition and coffee quality.

Laser metal deposition of compositionally graded TiZrNbTa refractory high-entropy alloys using elemental powder blends

In the present study, laser metal deposition (LMD) was used to produce compositionally graded refractory high-entropy alloys (HEAs) for screening purposes by in-situ alloying of elemental powder blends. A compositional gradient from Ti25Zr50Nb0Ta25 to Ti25Zr0Nb50Ta25 is obtained by incrementally substituting Zr powder with Nb powder. A suitable strategy was developed to process the powder blend despite several challenges such as the high melting points of the refractory elements and the large differences in melting points among them. The influence of the LMD process on the final chemical composition was analyzed in detail and the LMD process was optimized to obtain a well-defined compositional gradient. Microstructures, textures, chemical compositions and mechanical properties were characterized using SEM, EBSD, EDX, and microhardness testing, respectively. Compositions between Ti25Zr0Nb50Ta25 and Ti25Zr25Nb25Ta25 were found to be single-phase bcc solid solutions with a coarse grain microstructure. Increasing the Zr to Nb ratio beyond the equiatomic composition results in finer and harder multiphase microstructures. The results shown in the present study clearly show for the first time that LMD is a suitable processing tool to screen HEAs over a range of chemical compositions.

Effect of Duty Cycle on Properties of Al₂O₃ Ceramic Coatings Fabricated on TiAl Alloy via Cathodic Plasma Electrolytic Deposition.

In order to study the effect of duty cycle during the cathodic plasma electrolytic deposition (CPED) process, Al2O3 ceramic coatings were fabricated via the CPED technique on prepared TiAl alloy in an Al(NO3)3 electrolyte with different duty cycles. Microstructure, morphology, and chemical compositions of coatings were analyzed by scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), transmission electron microscopy (TEM), and X-ray diffraction (XRD). The mechanical properties, such as thickness, hardness, and binding strength, were also characterized, and heat-resistance and wear-resistance tested. The results indicated that duty cycle mainly affected the relative crystallinity of CPED coatings. As the duty cycle increased, the crystallinity of CPED coatings increased, the content of Al(OH)3 and γ-Al2O3 decreased, and the content of α-Al2O3 increased. The thickness and bonding strength both increased firstly and then decreased, while hardness increased as duty cycle increased. Heat-resistance and wear-resistance of TiAl alloy with CPED coating was highly improved compared to that of TiAl alloy substrate without CPED coating.

Late-Season Shiraz Berry Dehydration That Alters Composition and Sensory Traits of Wine

Late-season berry dehydration (LSD) is a common occurrence in Shiraz grapes, particularly those grown in hot climates. LSD results in significant yield reductions; however, the effects on wine composition and sensory characteristics are not well-documented. Wines made of 100% nonshriveled clusters (control) were related to red fruit flavors by the sensory panel, whereas wines made of 80% shriveled clusters (S-VCT) were perceived as more alcoholic and associated with dark fruit and dead/stewed fruit characters. The latter wines also resulted in higher concentrations of massoia lactone and γ-nonalactone, compounds known to contribute to prune and stewed-fruit aromas. Wines made of shriveled grapes were also characterized by an increase in C6-alcohols and a decrease in esters, whereas wine terpenoids were altered compound-specific. An increase in orange pigments and wine chemical age in S-VCT wines indicated faster oxidative aging compared to the control. LSD appeared to alter final wine composition directly but also appeared to influence yeast metabolism, potentially due to an alteration of the composition of lipids in the grape juice. This study emphasized the relevance of sorting shriveled and nonshriveled berries for final wine chemical composition and wine style.

Influence of soil conditions on the distribution coefficients of 226Ra in natural soils

In order to clarify some of the assumptions and approximations about the use of the distribution coefficient Kd for 226Ra in soils, a systematic study has been performed using centrifugation to extract the soil solution. The separated fractions of the soil solution have different kinetics with respect to the sorption process in the soil, which may in turn condition the final chemical composition and even the speciation of the radionuclides in solution. In the experimental design of this study three factors were considered: the moisture level in the incubation process, incubation time and the speed of centrifugation. Also, three levels were chosen for each factor. In order to analyze the influence of the structural characteristics of the soil, this study was performed with three textural fractions: coarse sand, fine sand, and silt and clay, obtained from an only soil. Also, the soil was naturally enriched with radionuclides of the 238U series. An analysis of variance (ANOVA) was performed in order to assess the influence of the factors studied on the distribution coefficient of 226Ra. The results indicate that different behaviors can be observed depending on the structural characteristic of the soil. In the case of particle size, the soil with the largest grain size showed that the incubation process parameters influence the equilibrium level achieved, while in the case of the smallest edaphic particles, radium is not homogeneously distributed in the soil solution and the Kd value is dependent on the speed of centrifugation.

CHARACTERIZATION OF FLUORIDATED HYDROXYAPATITE (FHA) SOL-GEL COATINGS ON TITANIUM SUBSTRATE

In this paper, FHA coatings [FHA, Ca10(PO4)6(OH)2-x Fx] (wherein 0 ≤ x ≤ 2) were deposited on titanium substrate by sol-gel method with heat treatment at 900 oC for 4 hours. Different concentrations of F- were incorporated into the apatite structure during the sols preparation. The FHA sols were prepared using various amounts of ammonium fluoride [NH4F] with the [P]/[F] molar ratios of 12, 6, 4, 3 in order to have the corresponding compositions of Ca10(PO4)6(F0.5 OH1.5), Ca10(PO4)6 FOH, Ca10(PO4)6(F1.5 OH0.5) and Ca10(PO4)6F2, respectively. The fabricated FHA coatings were assessed by various methods, namely: morphological structure and chemical composition of coatings were studied by scanning electron microscopy (SEM) and Energy dispersive spectrometry (EDS). The anti-corrosion properties of samples were evaluated by Potentiodynamic polarization curves and Nyquist impedance spectrum. The biocompatibility of FHA coatings on titanium substrates were evaluated by in-vitro tests in simulated body fluid (SBF) solution during 21 days, and ICPMS (Inductively Coupled Plasma Mass Spectrometry) analysis method has been used. The results showed that with dense structure, FHA coatings expressed higher anti-corrosion and biocompatibility performance as compared with that of HA coating.

Single-crystal growth, structure refinement and the properties of Bis(glycine) Strontium Chloride

Single crystals of Bis (glycine) Strontium Chloride (BGSC) were grown by means of slow evaporation process by using analar grade Glycine and Strontium Chloride Hexahydrate as a parent compound from its aqueous solution at room temperature. The final chemical composition, formed were metallic light colorless block, about the size of 28 mm × 9 mm × 8 mm. A single-crystal x-ray diffraction study revealed an ordered superstructure with orthorhombic symmetry that could be assigned to the space group Pbcn. The structure in BGSC, revealed in the electron density distribution was analyzed by the direct methods (SHELXS-2014) and refined by least squares full matrix method (SHELXL-2014). The crystal structure, including anisotropic atomic displacement parameters for each atom and isotropic atomic displacement parameters for hydrogen atom, was refined to R1 = 0.0395, wR2 = 0.0776 using 1097 independent reflections. The FTIR spectrum of BGSC confirms the protonation of amino groups and the different molecular groups present in BGSC vibrate in different modes. Reverse Indentation Size Effect (RISE) was revealed in BGSC in the micro-hardness analysis using Vicker’s micro-hardness analysis. DTA and DSC results ruled out the possibility of structural change independent of mass change. The AFM studies shows fine nano size fiber like structure of the grown crystals.

Decoupling the direct and indirect effects of climate on plant litter decomposition: Accounting for stress-induced modifications in plant chemistry.

Decomposition of plant litter is a fundamental ecosystem process that can act as a feedback to climate change by simultaneously influencing both the productivity of ecosystems and the flux of carbon dioxide from the soil. The influence of climate on decomposition from a postsenescence perspective is relatively well known; in particular, climate is known to regulate the rate of litter decomposition via its direct influence on the reaction kinetics and microbial physiology on processes downstream of tissue senescence. Climate can alter plant metabolism during the formative stage of tissues and could shape the final chemical composition of plant litter that is available for decomposition, and thus indirectly influence decomposition; however, these indirect effects are relatively poorly understood. Climatic stress disrupts cellular homeostasis in plants and results in the reprogramming of primary and secondary metabolic pathways, which leads to changes in the quantity, composition, and organization of small molecules and recalcitrant heteropolymers, including lignins, tannins, suberins, and cuticle within the plant tissue matrix. Furthermore, by regulating metabolism during tissue senescence, climate influences the resorption of nutrients from senescing tissues. Thus, the final chemical composition of plant litter that forms the substrate of decomposition is a combined product of presenescence physiological processes through the production and resorption of metabolites. The changes in quantity, composition, and localization of the molecular construct of the litter could enhance or hinder tissue decomposition and soil nutrient cycling by altering the recalcitrance of the lignocellulose matrix, the composition of microbial communities, and the activity of microbial exo-enzymes via various complexation reactions. Also, the climate-induced changes in the molecular composition of litter could differentially influence litter decomposition and soil nutrient cycling. Compared with temperate ecosystems, the indirect effects of climate on litter decomposition in the tropics are not well understood, which underscores the need to conduct additional studies in tropical biomes. We also emphasize the need to focus on how climatic stress affects the root chemistry as roots contribute significantly to biogeochemical cycling, and on utilizing more robust analytical approaches to capture the molecular composition of tissue matrix that fuel microbial metabolism.

Chitosan-Cellulose Multifunctional Hydrogel Beads: Design, Characterization and Evaluation of Cytocompatibility with Breast Adenocarcinoma and Osteoblast Cells.

Cytocompatible polysaccharide-based functional scaffolds are potential extracellular matrix candidates for soft and hard tissue engineering. This paper describes a facile approach to design cytocompatible, non-toxic, and multifunctional chitosan-cellulose based hydrogel beads utilising polysaccharide dissolution in sodium hydroxide-urea-water solvent system and coagulation under three different acidic conditions, namely 2 M acetic acid, 2 M hydrochloric acid, and 2 M sulfuric acid. The effect of coagulating medium on the final chemical composition of the hydrogel beads is investigated by spectroscopic techniques (ATR–FTIR, Raman, NMR), and elemental analysis. The beads coagulated in 2 M acetic acid displayed an unchanged chitosan composition with free amino groups, while the beads coagulated in 2 M hydrochloric and sulfuric acid showed protonation of amino groups and ionic interaction with the counterions. The ultrastructural morphological study of lyophilized beads showed that increased chitosan content enhanced the porosity of the hydrogel beads. Furthermore, cytocompatibility evaluation of the hydrogel beads with human breast adenocarcinoma cells (soft tissue) showed that the beads coagulated in 2 M acetic acid are the most suitable for this type of cells in comparison to other coagulating systems. The acetic acid fabricated hydrogel beads also support osteoblast growth and adhesion over 192 h. Thus, in future, these hydrogel beads can be tested in the in vitro studies related to breast cancer and for bone regeneration.

Spectroscopic monitoring of laser blown powder directed energy deposition of Alloy 718

Experimental explorations of a spectrometer system used for in-process monitoring of the laser blown powder directed energy deposition of Alloy 718 is presented. Additive manufacturing of metals using this laser process experiences repeated heating and cooling cycles which will influence the final microstructure and chemical composition at every given point in the built. The spectrometer system disclosed, under certain process conditions, spectral lines that indicate vaporisation of chromium. Post process scanning electron microscope energy dispersive spectroscopy analysis of the deposited beads confirmed a reduction of chromium. Since the chromium concentration in Alloy 718 is correlated to corrosion resistance, this result encourages to further investigations including corrosion tests.

Chemical characterization of fluorinated/hydrogenated mixed monolayers grafted on gold nanoparticles

Perfluorocarbons are omniphobic compounds as a consequence of their unique properties such as, e.g., high electronegativity, low polarizability, high ionization energy, and low surface tension. The possibility of combining such properties with the features of nanoscale materials promoted a recent upsurge in the production of fluorinated nanoparticles for application in different fields. Attainment of mixed fluorinated/hydrogenated stabilizing layers is also desired in some cases, but often the composition of the ligand mixture used in the exchange reaction is not reflected in the resulting monolayer. Thus, methodologies for determining the resulting chemical composition of the final mixed fluorinated/hydrogenated monolayers grafted on the nanoparticle (NP) surface are needed. Here we propose a combined Fourier Transform Infrared (FTIR) and X-ray Photoemission Spectroscopy (XPS) investigation for assessing the final chemical composition of a mixed monolayer of hydrogenated and fluorinated alkanethiols grafted on the surface of gold NPs obtained through two different synthetic routes. This analysis allowed the evaluation of the exchange efficiency of the two synthetic routes, and also, coupled with UV–vis studies, highlighted that the colloidal stability of the final NPs was not only dependent on the fluorinated/hydrogenated ratio but also on the chosen exchange route, which seems to influence the ligand organization on the mixed monolayer.

Energy and environmental applications of ultrasonically sulfur doped copper-nickel hydroxides with heterostructures

A series of sulfur doped copper-nickel hydroxides with heterojunctions were successfully fabricated on nickel foam by adjusting thiourea volume via a facile sonochemical pathway. The effect of volume of thiourea on the final morphology and chemical composition of the hybrids were also investigated by field-emission scanning electron microscopy, and X-ray photoelectron spectroscopy analyses. Furthermore, the electrochemical performance and catalytic activity of the as-obtained hybrids were also investigated. Among the tested electrode, the hybrid material fabricated using 6 ml of thiourea (TU-6) showed outstanding electrochemical properties comprising a high specific capacitance of about 2708 F g−1 at 5 A g−1. In addition, the TU-6 hybrid (catalyst) material displayed remarkable reductive degradation ability towards azo dyes viz., methyl orange (within 8 min) and congo red (within 20 min) in the presence of sodium borohydride (reducing agent) with fast kinetics and good reproducibility, respectively. The exceptional electrochemical performance and excellent catalytic activity of TU-6 hybrid electrode may be attributed to the formation of catalytically active sulfur doped copper-nickel hydroxides (CuS/Ni3S2/NiOOH) three-interface synergistic effect, and unique porous micro-rosette-like texture which increased the diffusion rate and adsorption capacity. The adopted strategy is a simple and generic way for material fabrication to solve the energy and environmental problems.