The transmissions of mining conveyors are exposed to very harsh conditions. These are primarily related to the contamination of the gear oil with hard particles coming from coal and lignite, which can cause intensive abrasive wear, scuffing, and even pitting, limiting the life of gears. One of the ways to prevent this problem is the deposition of a wear-resistant coating onto gear teeth. However, a proper choice of gear oil is an important issue. The abrasion, scuffing, and pitting tests were performed using simple, model specimens. A pin and vee block tester was employed for research on abrasion and scuffing. To test pitting, a modified four-ball pitting tester was used, where the top ball was replaced with a cone. The test pins, vee blocks, and cones were made of 18CrNiMo7-6 case-hardened steel. A new W-DLC/CrN coating was tested. It was deposited on the vee blocks and cones. For lubrication, three commercial industrial gear oils were used: A mineral oil, and two synthetic ones with polyalphaolefin (PAO) or polyalkylene glycol (PAG) bases. The results show that, to minimize the tendency forabrasion, scuffing, and pitting, the (W-DLC/CrN)-8CrNiMo7-6 tribosystems should be lubricated by the PAO gear oil. MoS 2 /Ti, C/Cr [4], TiN, and CrN [15]. Concerning DLC coatings, they are either doped coatings: W-DLC [2,15-17], Cr-DLC [18], and Si-DLC [19]; or non-doped coatings: a-C:H [ [18][19][20] or ta-C [19]. The review of the literature allows one to state that it is the DLC coating that is currently used in the majority of tribological research works.Apart from testing thin coatings, it is also important to select a proper oil to lubricate the coated parts [15]. For decades, a lot of research works have been devoted to investigating the interaction between the lubricating additives in the oil with the steel surface [21][22][23][24][25][26][27][28][29][30][31][32], and the mechanisms of the interaction between steel surfaces and lubricants are well recognized.Concerning the interaction between the oil and the thin coating, the publications are less frequent [15,18,[33][34][35][36][37][38] and have been mostly issued in the last 20 years. Unlike the oil-steel interactions, when testing coatings, one can find different statements and observations in the literature. Some authors point out an effect of the coating's elemental composition, occurrence of the transfer of material between the samples, forming of protective films on the surface, or even chemical reactions of the coating with the lubricating additives in the oil.In a review paper, Kalin et al.[33] compared oil-coating interactions when lubricating with oils with a mineral, synthetic ester, and polyalphaolefin (PAO) base using various tribosystems. They stated that non-doped DLC coatings can react with different types of additives (e.g., a friction modifier (FM), antiwear (AW), and extreme-pressure (EP) additives), and that the hydrogen content in DLC coatings plays a crucial role in the tribological performance under lubricated conditions.Michalczewski et al.[15...

White and natural base oils are assessed as candidates for the formulation of ecological gear oils. They are compared to ‘classical’ mineral and polyalphaolefins‐based oils in scuffing four‐ball and gear tests. Four fully formulated gear oils were prepared by blending each base oil with the package of extreme pressure (EP) additives, an anti‐foam additive and an anti‐oxidant. It is shown that the resistance to scuffing of the white oil is comparable to the classical oils, but the natural (rapeseed) oil reduces resistance to scuffing, because the used EP additives may not be suited to the rapeseed ‘matrix’ producing adverse effects. Thus, rapeseed‐based gear oils can be used only for the lubrication of gears working under moderate load conditions. It is also indicated that, when comparing the mechanisms of tribochemical action of the EP additives in the four‐ball tribosystem and meshing teeth, care should be taken, because the conditions in the contact zones are different. Copyright © 2014 John Wiley & Sons, Ltd.

The effect of antiwear (AW) commercial additive concentration on the load-carrying capacity (scuffing resistance) of a-C:H:W/steel tribo-system intended for heavy-loaded machine parts was investigated. For comparison, steel/steel contacts were also investigated. The scuffing resistance has been measured as the limiting pressure of seizure ( poz) using the four-ball apparatus. The method with continuously increasing load was applied. The tribo-systems were lubricated with poly-alpha-olefin as base oil mixed with a commercial zinc dialkyldithiophosphates type of AW additive. The AW concentration was varied in the range of 0.1–5.0 wt%. The results of the tribological experiments performed in sliding contact have shown that, by the application of the a-C:H:W coating, the tribological properties of the system were significantly improved compared with the steel friction pairs. It has also been found that it is possible to reduce the concentration of commercial AW additive below 1.0 wt%. The surface topography of the rubbed surface was investigated with optical microscopy and atomic force microscopy; the elemental chemical nature of the AW film generated on the steel counter-surface (a-C:H:W/steel tribosystem) was investigated with energy dispersive spectrometry, glow discharge optical emission spectrometry, and X-ray photoelectron spectroscopy.

Wpływ warunków termicznych procesu pirolizy na jakość biowęgli otrzymanych z odpadów roślinnychAn effective way of managing natural waste, including waste from the agri-food industry or products that are economically useful can be offered by production of biochar. Biochar is used not only as an energy product, but also as a sorption material for e.g. groundwater treatment, sewage treatment, as well as biogas valorization. Therefore, the aim of the study was to determine the effect of the conditions of cascade heating of selected types of vegetable waste in carbon dioxide on the microstructure and chemical composition of the obtained biochar. Wheat straw, corn waste in the form of dried leaves and stems, as well as flax shives and cherry stones were subjected to pyrolysis. Cascading temperature conditions were programmed for a total time of 100 minutes, including 15 minutes of final heating at 500°C in one variant and at 700°C in the other. After final heating, the products were left in the pyrolytic chamber to cool down spontaneously to room temperature. The biochar samples were next subjected to microscopic examinations coupled with X-ray microanalysis (SEM/EDS) and infrared spectral examination (FTIR). It was found that the pyrolysis yielded biochar in the amount from 26 to 32.3% of the initial charge mass, depending on the conditions of the process and the type of waste. Furthermore, the differences observed in the chemical structure of the surface of the biochar concerned mainly the occurrence of organic oxygen functional groups whose type depends on the pyrolysis temperature. An increase in the temperature of pyrolysis leads to a decrease in the oxygen content of the products obtained, which results in a relative increase in the proportion of char in the product. Biochar obtained at temperatures of up to 500°C contains aromatic rings and quinone groups, whereas those obtained at higher temperatures (up to 700°C) have ether groups embedded mainly in aliphatic cyclic groups.

This paper addresses the issue of plasma treatment of the surface of polypropylene (PP) using sputtering of silver (Ag) and copper (Cu) and their oxides with MS-PVD in order to impart antimicrobial activity. It was found that plasma treatment of PP with Cu and Ag based layers allows to provide excellent antimicrobial properties due to a constant release of metal ions. The samples of PP treated with Cu and CuO were characterized by highest antimicrobial properties and stability of the coatings. The most stable and least effective coating against bacteria was Ag-PP sample. In turn, AgO-PP was characterized by the lowest stability in aqueous conditions and strong antimicrobial activity. It was found that leaching of metal ions from the surface of treated PP even in exceptional levels plays a crucial role in bactericidal activity. Plazmowa depozycja antybakteryjnych powłok srebra i miedzi na powierzchni polipropylenuStreszczenie: Niniejsza praca dotyczy plazmowej obróbki powierzchni polipropylenu (PP) przy użyciu miedzi (Cu) i srebra (Ag) oraz ich tlenków. Powłoki Cu, CuO, Ag i AgO, wytworzone na powierzchni PP metodą rozpylania magnetronowego MS-PVD, zbadano pod względem morfologii, składu, stabilności i właściwości antybakteryjnych. Materiały powierzchniowo zmodyfikowane przy użyciu Cu i CuO charakteryzowały się najsilniejszymi właściwościami przeciwbakteryjnymi i najmniejszą stabilnością i trwałością w środowisku wodnym. Powłoka AgO wykazywała najmniejszą stabilność w warunkach wodnych i silną aktywność przeciwbakteryjną, natomiast powłoka Ag wykazywała największą stabilność, a zarazem najsłabsze działanie przeciwbakteryjne. Uzyskane wyniki wskazują, że uwalniane z naniesionych powłok jony, nawet w niewielkim stężeniu, wykazują silne działanie antybakteryjne.Słowa kluczowe: polipropylen, obróbka plazmowa, srebro, miedź, właściwości antybakteryjne.