The Study of Corrosion and Wear Resistance of Copper Composite Coatings with Inclusions of Carbon Nanomaterials in the Copper Metal Matrix

This paper deals with the peculiarities of the behaviour of copper nanocomposite coatings with CNMs inclusions under the free corrosion conditions in the acidic medium. The parameters of corrosion current density (<em>j</em>_corr), anodic dissolution current density (<em>i</em>_a) and polarization resistance (<em>R</em>_p) have been determined. In the acidic medium a stronger oxidation of nanostructured copper nanocomposites occurred. With longer immersion periods more corrosion products are formed, resulting in a increase in the polarization resistance (<em>R</em>_p) of corrosion. Corrosion products cover the whole surface of the coatings and the corrosion rate (<em>j</em>_corr) tends towards a steady value of 1.7×10^-3¸2.1×10^-3 A·cm^-2 for all copper coatings studied: 1.7×10^-3 A·cm^-2for both Cu and Cu-CNM1, 1.9×10^-3 A·cm^-2 - for Cu-CNM2 and 2.1×10^-3 A·cm^-2 - for Cu-CNM3 composite coatings. It has been established that nanocomposites possess a higher wear resistance as compared to that of pure copper. The damage of metal characterized as a depth scar (<em><span style="font-size: 10.0pt; font-family: &quot;Times New Roman&quot;,&quot;serif&quot;; mso-fareast-font-family: &quot;Times New Roman&quot;; mso-ansi-language: EN-GB; mso-fareast-language: EN-US; mso-bidi-language: AR-SA;" lang="EN-GB">đ</span></em>) is lower. The roughness of the composites studied was found to be the essential factor affecting their wear resistance. Therefore, the wear resistance of nanocomposites is impaired when they are deposited on a hard steel substrate.<p><a href="http://dx.doi.org/10.5755/j01.ms.17.2.481">http://dx.doi.org/10.5755/j01.ms.17.2.481</a></p

Selectivity of tungsten oxide synthesized by Sol-Gel method towards some volatile organic compounds and gaseous materials in a broad range of temperatures

In this research, the investigation of sensing properties of non-stoichiometric WO3 (WO3−x) film towards some volatile organic compounds (VOC) (namely: Methanol, ethanol, isopropanol, acetone) and ammonia gas are reported. Sensors were tested at several temperatures within the interval ranging from a relatively low temperature of 60 up to 270 ◦C. Significant variation of selectivity, which depended on the operational temperature of sensor, was observed. Here, the reported WO3/WO3–x-based sensing material opens an avenue for the design of sensors with temperature-dependent sensitivity, which can be applied in the design of new gas- and/or VOC-sensing systems that are dedicated for the determination of particular gas- and/or VOC-based analyte concentration in the mixture of different gases and/or VOCs, using multivariate analysis of variance (MANOVA)

Monounsaturation effects on low temperature fluidity of ester derivatives

<p>Camelina and Crambe crops are potential sources for medium-chain fatty acids (MCFA) from C8 to C14, which represent an important feedstock for specialty oleochemicals. Their oils can also find utilization as lubricants after conversion into esters, if appropriate viscosity is achieved with good fluidity at low temperatures, usually measured as pour point. While MCFA esters might have fluidity problems, cis-double bonds can reduce pour pt. [1] The most abundant fatty acid (FA) in Camelina oil is gondoic (i.e. 11-eicosenoic a.), while Crambe oil contains up to 60 % erucic a. (i.e. 13-docosenoic a.). Initially dibasic esters with MCFA and oleic a. were synthesized, see Fig. 1, using a previously established method [2] with two major types of polyhydric alcohol derivatives: 1) H-containing β-carbon polyol with R=H in Fig. 1 and 2) tertiary β-carbon polyol. Additional branched moieties were also attached as R’ for better fluidity. Kinematic viscosities were measured at 40 °C using Cannon-Fenske method (ASTM D455) and in some cases estimated from structural data. Pour pt. was measured under the same thermal cooling regime as in ASTM D97, just in smaller sample sizes.</p> <p>Oleates clearly show that higher mol. weight increases viscosity. Since FA moieties were linear, MCFA esters with viscosities over 20 mm²/s could not retain fluidity at -30 °C. However, oleates approached 35 mm²/s viscosity with better pour pt. and showed a remarkable tendency to retain fluidity around -30 °C (with tertiary β-carbon) or -25 °C (when R=H) despite variation of R’ moieties. Further synthesis with gondoic and erucic esters can give even more flexibility in achieving needed viscosities and lead to broader industrial viability of Camelina and Crambe crops.</p

Tribological Effects of Cu, Fe and Zn Nano-Particles, Suspended in Mineral and Bio-based Oils

Many studies focus on nanoparticles as lubricity additives but overlook the fact that wear produces nanosized debris during the field use. In order to simulate the fine metal contaminants, which are the most widespread in various field applications, prefabricated Fe, Cu and Zn nanoparticles were used. Their 0.01–1% suspensions in vegetable and mineral oils with or without ZDDP and ashless AW package were tested on four-ball AW under 150-N load. Tribological effects of nanoparticles were not significant in formulations without AW additives. However, nanoFe addition produced notable lubricity improvement in already excellently performing rapeseed formulation with ZDDP, while such addition reduced performance of the ashless AW pack. Results show that metal nanoparticles can play both positive and negative roles on additive effectiveness and nanosized contaminants can significantly affect the lubricant performanceValstybinis mokslinių tyrimų institutas Fizinių ir technologijos mokslų centrasVytauto Didžiojo universitetasŽemės ūkio akademij

Femtosecond laser-ablated copper surface as a substrate for a MoS2-based hydrogen evolution reaction electrocatalyst

One of the methods to improve the performance of a heterogeneous electrocatalyst is the dispersion of a catalytic material on a suitable substrate. In this study, femtosecond laser ablation was used to prepare very rough but also ordered copper surfaces consisting of vertical, parallel ridges. Then, a molybdenum sulfide coating was electrochemically deposited onto these surfaces. It was observed by profilometry that the average roughness of the surface after coating with MoS2 had decreased, but the developed surface area still remained significantly larger than the projected surface area. The electrodes were then used as an electrocatalyst for the hydrogen evolution reaction in acidic media. These were highly efficient, reaching 10 mA cm−2 of HER current at a −181 mV overpotential and a Tafel slope of ~39 mV dec−1. Additionally, scanning electrochemical microscopy was used to observe whether hydrogen evolution would preferentially occur in certain spots, for example, on the peaks, but the obtained results suggest that the entire surface is active. Finally, the electrochemical impedance spectroscopy data showed the difference in the double-layer capacitance between the ablated and non-ablated surfaces (up to five times larger) as well as the parameters that describe the improved catalytic activity of fs-Cu/MoS2 electrodes

Cesium-Containing Triple Cation Perovskite Solar Cells

Cesium-containing triple cation perovskites are attracting significant attention as suitable tandem partners for silicon solar cells. The perovskite layer of a solar cell must strongly absorb the visible light and be transparent to the infrared light. Optical transmittance measurements of perovskite layers containing different cesium concentrations (0–15%) were carried out on purpose to evaluate the utility of the layers for the fabrication of monolithic perovskite/silicon tandem solar cells. The transmittance of the layers weakly depended on cesium concentration in the infrared spectral range, and it was more than 0.55 at 997 nm wavelength. It was found that perovskite solar cells containing 10% of cesium concentration show maximum power conversion efficiency

Impact of Cesium Concentration on Optoelectronic Properties of Metal Halide Perovskites

Performance of a perovskite solar cell is largely influenced by the optoelectronic properties of metal halide perovskite films. Here we study the influence of cesium concentration on morphology, crystal structure, photoluminescence and optical properties of the triple cation perovskite film. Incorporation of small amount (x = 0.1) of cesium cations into Csx(MA0.17FA0.83)1&minus;x Pb(I0.83Br0.17)3 leads to enhanced power conversion efficiency (PCE) of the solar cell resulting mainly from significant rise of the short-current density and the fill factor value. Further increase of Cs concentration (x &gt; 0.1) decreases the film&rsquo;s phase purity, carrier lifetime and correspondingly reduces PCE of the solar cell. Higher concentration of Cs (x &ge; 0.2) causes phase segregation of the perovskite alongside with formation of Cs-rich regions impeding light absorption

Photoelectric Properties of Planar and Mesoporous Structured Perovskite Solar Cells

The high efficiency of perovskite solar cells strongly depends on the quality of perovskite films and carrier extraction layers. Here, we present the results of an investigation of the photoelectric properties of solar cells based on perovskite films grown on compact and mesoporous titanium dioxide layers. Kinetics of charge carrier transport and their extraction in triple-cation perovskite solar cells were studied by using transient photovoltage and time-resolved photoluminescence decay measurements. X-ray diffraction analysis revealed that the crystallinity of the perovskite films grown on mesoporous titanium dioxide is better compared to the films grown on compact TiO2. Mesoporous structured perovskite solar cells are found to have higher power conversion efficiency mainly due to enlarged perovskite/mesoporous -TiO2 interfacial area and better crystallinity of their perovskite films