Dialkyl Dithiocarbamate Research Articles

Comparative Study on the Performance of Gel Grease for High-End Equipment Based on the Synergistic Effect of Friction-Reducing Agents.

In the field of high-end equipment, the synergistic effect of friction-reducing agents plays an important role in the performance study of gel grease. Exploring its tribological and rheological properties can not only significantly reduce the coefficient of friction of mechanical components and enhance its viscosity at high temperatures but also effectively reduce energy consumption, thus improving the service life of high-end equipment. In this study, Schaeffler Load 460 gel grease was mixed with polysiloxane viscosity modifier (PV611) and molybdenum dialkyl dithiocarbamate (RFM3000) according to (3:1, 1:1, and 1:3), and its tribological properties and rheological properties were investigated by the MRS-10G friction and wear tester, MCR302 rotational rheometer, and crossover test. Comparative analyses of tribological and rheological properties were carried out. The results showed that the average coefficient of friction of Schaeffler Load 460 grease was reduced by 57.2%, 60%, and 71.9%, respectively, with the addition of two different ratios of friction reducers; the average diameter of abrasive spots was reduced by 44.5%, 55.4%, and 61.3%; and the shear stress and viscosity were increased by 117.94 Pa and 1295.02 mPa∙s, respectively, compared with that of the original grease, which is a good example for the lubrication of gel grease in the high-end equipment industry. This study provides a new direction and idea for the lubrication research of gel grease in the high-end equipment industry.

Synergistic Effect of Acrylate of Dialkyl Dithiophosphoric Acid Combined with Molybdenum Dialkyl Dithiocarbamate as Additives in Gear Oil

With the aim of improving the tribological properties of low-viscosity gear oil for automobiles, an acrylate of dialkyl dithiophosphoric acid (ADDP) with strong polar groups was synthesized. The tribological behavior of ADDP combined with molybdenum dialkyl dithiocarbamate (MoDTC) in gear oil was systematically studied. Tribological performances of gear oil containing different additives were assessed using a four-ball friction and wear tester. The obtained tribological characteristics reveal that ADDP and MoDTC can significantly improve the antiwear and antifriction performance of low-viscosity gear oil. Moreover, compared with using MoDTC or ADDP alone, the average friction coefficient and wear scar diameter of ADDP combined with MoDTC further decreased by 2.41–19.15% and 5.00–18.19%, respectively. Analysis of the worn surface showed that the structural characteristics and physical synergistic lubricating actions of the ADDP with MoDTC additives during the friction process can contribute to the exceptional tribological properties of the hybrid additives.

Revealing the tribological mechanism of synergistic effect between MoDTC and P-containing additives in aluminum-based grease

Purpose This study aims to reveal the tribological mechanism of synergistic effect between MoDTC and P-containing additives in aluminum-based grease. Design/methodology/approach The authors prepared a molybdenum dialkyl dithiocarbamate (MoDTC) and revealed the tribological mechanism of synergistic effect between MoDTC and P-containing additives in aluminum-based grease by combining with ZDDP and P-containing and S-free additives. Findings The MoDTC the authors prepared has good friction-reducing and anti-wear properties in aluminum-based grease and has an obvious synergistic effect with ZDDP. MoDTC and ZDDP have a significant synergistic effect on the tribological properties in aluminum-based grease, mainly because of the formation of phosphates and metaphosphates as well as more MoS2 in the friction film. P element plays a facilitating role in the chemical conversion of MoDTC to MoS2. Originality/value The experiments of MoDTC with tributyl phosphate and trimethylphenyl phosphate confirm that the P element plays a facilitating role in the chemical conversion of MoDTC into MoS2. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-12-2023-0410

Research on the optimization of tribological performance of wind power lubricating grease based on carbon emission

The manufacturing, installation, operation and dismantling of wind turbines can also have environmental impacts such as excessive carbon emissions and consume large amounts of resources. Optimisation of the tribological properties of wind power greases can reduce the energy consumption and carbon emissions of wind power systems, improve their operational efficiency and reliability, thereby slowing down climate change and improving environmental quality, which is not only important for individual wind power projects, but also has a positive impact on reducing carbon emissions, promoting clean energy development and combating climate change on a global scale. However, the higher the grease lubrication performance, the lower the wind turbine failure rate and the lower the carbon emissions. Good tribological properties can significantly reduce the coefficient of friction of mechanical components, reducing surface wear and heat generation, helping to extend the life of mechanical equipment, improve efficiency and reduce unnecessary repairs and replacements. Therefore, in this paper, Mobil SHC 461WT lithium composite grease was mixed with molybdenum dialkyl dithiocarbamate (RFM3000), nano-boronated rare-earth friction modifiers (SK3115), polysiloxane viscosity modifier (PV611), and zinc dialkyl dithiophosphate (ZDDP), and the comparative analysis of their tribological performances was carried out through the method of cross-experimentation. The results showed that the average coefficient of friction of Mobil added with the four antiwear additives was reduced by 74 %, 41 %, 54 % and 48 %, respectively, and the average diameter of wear spots was reduced by 64 %, 63 %, 69 % and 54 %.

Synthesis of diaryl dithiocarbamate complexes of zinc and their uses as single source precursors for nanoscale ZnS

Diaryldithiocarbamate complexes, [Zn(S2CNAr2)2], have been prepared with a view to comparing their structures, reactivity and thermally-promoted degradation with respect to the well-studied dialkyl-derivatives. In the solid-state both [Zn{S2CN(p-tol)2}2] and [Zn{S2CN(p-anisyl)2}2] are monomeric with a distorted tetrahedral Zn(II) centre, but somewhat unexpectedly, the bulkier naphthyl-derivative [Zn{S2CN(2-nap)2}2]2 forms dimeric pairs with five-coordinate Zn(II) centres. Preliminary reactivity studies on [Zn{S2CN(p-tol)2}2] suggests that it binds amines and cyclic amines in a similar fashion to the dialkyl complexes and can achieve six-coordination as shown in the molecular structure of [Zn{S2CN(p-tol)2}2(2,2′-bipy)]. The thermal decomposition of [Zn{S2CN(p-tol)2}2] was studied in oleylamine solution by both heat-up and hot-injection methods. Nanorods of ZnS were produced in both cases with average dimensions of 17 × 2.1 nm and 11 × 3.5 nm respectively, being significantly shorter than those produced from [Zn(S2CNiBu2)2] under similar conditions. This is tentatively attributed to the differing rates of amine-exchange between diaryl- and dialkyl dithiocarbamate (DTC) complexes and/or their differing rates of DTC loss following amine-exchange. The solid-state decomposition of [Zn{S2CN(p-tol)2}2] has also been studied at 450 °C under argon affording irregular and large (10–300 µm) sheet-like particles of wurtzite.

Tribological Properties of Polymer Friction Improvers Combined with MoDTC/ZDDP at Different Temperatures

To expand the applications of polymer friction modifiers in low viscosity oils suitable for hybrid power systems, the tribological properties of five kinds of oil samples at different temperatures were studied, which were compounded with polymer friction modifiers Perfad XG 2500, molybdenum dialkyl dithiocarbamate (MoDTC), zinc dialkyl dithiophosphate (ZDDP). When Perfad XG 2500 is used alone, it forms a brush-like surface film at low temperatures, which can provide lower initial friction. With the rise in temperature, its antifriction effect decreases significantly, which is related to the desorption behavior of physical film. When Perfad XG 2500 is combined with MoDTC, it has the best synergistic antifriction effect, and the average friction coefficient is reduced by a maximum of 20.83% (90 °C). Its friction coefficients decrease significantly with the increase in temperature due to the dissociation process of MoDTC catalyzed by high temperature. However, there are many furrows on the worn surfaces, and the sharp features of the profiles are obvious. When Perfad XG 2500 is combined with ZDDP, it has the best synergistic anti-wear effect, and the total wear depth is reduced by 49.6%. Its worn surface is smooth and defect-free, with minimal residual strain. The friction coefficients are hardly affected by temperature, and the average friction coefficient is reduced by a maximum of 14.4% (30 °C). When Perfad XG 2500, MoDTC and ZDDP are used together, the average friction coefficient is reduced by up to 15.2% (30 °C). Its friction coefficient increases slightly with the rise in temperature. The reason for its moderate tribological performance may be related to the superficial competition of various additives.

Synergistic tribological effect between polyisobutylene succinimide-modified molybdenum oxide nanoparticle and zinc dialkyldithiophosphate for reducing friction and wear of diamond-like carbon coating under boundary lubrication

Organic molybdenum lubricant additive like molybdenum dialkyl dithiocarbamate (MoDTC) can cause wear acceleration of diamond-like carbon (DLC) coating coupled with steel under boundary lubrication, which hinders its industrial application. Therefore, polyisobutylene succinimide (PIBS), an organo molybdenum amide, was adopted to modify molybdenum oxide affording molybdenum polyisobutylene succinimide-molybdenum oxide nanoparticles (MPIBS-MONPs) with potential to prevent the wear acceleration of DLC coating. The thermal stability of MPIBS-MONPs was evaluated by thermogravimetric analysis. Their tribological properties as the additives in di-isooctyl sebacate (DIOS) were evaluated with MoDTC as a control; and their tribomechanism was investigated in relation to their tribochemical reactions and synergistic tribological effect with zinc dialkyldithiophosphate (ZDDP) as well as worn surface characterizations. Findings indicate that MPIBS-MONPs/ZDDP added in DIOS can significantly reduce the friction and wear of DLC coating, being much superior to MoDTC. This is because MPIBS-MONPs and ZDDP jointly take part in tribochemical reactions to form a composite tribofilm that can increase the wear resistance of DLC coating. Namely, the molybdenum amide on MPIBS-MONPs surface can react with ZDDP to form MoS2 film with excellent friction-reducing ability; and MPIBS-MONPs can release molybdenum oxide nanoparticle to form deposited lubrication layer on worn surfaces. The as-formed composite tribofilm consisting of molybdenum oxide nanocrystal, amorphous polyphosphate, and molybdenum disulfide as well as a small amount of Mo2C accounts for the increase in the wear resistance of DLC coating under boundary lubrication.

Synthesis of nano-oxides by preparing metal complexes based on dithiocarbamate derivatives

Metal oxide nanoparticles are a branch of nanoparticles that have high optical properties. Dithiocarbamites are organic sulfur bonds that form stable complexes with metals. There are two types of dithiocarbamate: mono- and di-alkyl dithiocarbamate. In this study, two Schiff bases were prepared, the first Schiff base: [(E)-N-(2-ethylhexyl)-1-Phenyl methanimine] and the second Schiff base: [(E)-N-benzyl-1-Phenyl methanimine ]. From these two bases, the first secondary amine was prepared: N-Benzyl-2-ethylhexyl-1-amine, and the second secondary amine, Di Benzylamine. This was followed by the preparation of ligands from the two prepared secondary amines, which are Potasium benzyl(2-ethyl) Carbamadithioate, and the second ligand: Potasium di benzyl Carbamodithioate. These two ligands were employed in the interaction with the ions: Mn, Cu, Zn. each separately to form the macrocyclic complexes.

Temperature dependence of molybdenum dialkyl dithiocarbamate (MoDTC) tribofilms via time-resolved Raman spectroscopy

Molybdenum dialkyl dithiocarbamate (MoDTC) is a friction reducing additive commonly used in lubricants. MoDTC works by forming a low-friction molybdenum disulphide (MoS2) film (tribofilm) on rubbed surfaces. MoDTC-induced MoS2 tribofilms have been studied extensively ex-situ; however, there is no consensus on the chemical mechanism of its formation process. By combining Raman spectroscopy with a tribometer, effects of temperature and shear stress on MoS2 tribofilm formation in steel-steel contacts were examined. Time-resolved Raman spectra of the tribofilm were acquired, together with the instantaneous friction coefficient. The tribofilm is constantly being formed and removed mechanically during rubbing. Increasing shear stress promotes MoS2 formation. The nature of the tribofilm is temperature-dependent, with high-temperature tribofilms giving a higher friction than lower temperature films. Below a critical temperature Tc, a small amount of MoS2 gives significant friction reduction. Above Tc, a patchy film with more MoS2, together with a substantial amount of amorphous carbon attributed to base oil degradation, forms. The composition of this tribofilm evolves during rubbing and a temporal correlation is found between carbon signal intensity and friction. Our results highlight the mechanochemical nature of tribofilm formation process and the role of oil degradation in the effectiveness of friction modifier MoDTC.

Effect of MoО2(VI), Zn(II), Cu (II) and Mg(II) complexes with N-methyldecanohydroxamic acid on the thermal oxidation stability of biodiesel

General climate changes and catastrophic environmental pollution cause the steadily increasing interest in the world to bio-based technical oils, including lubricants. In order that they bully comply with current environmental requirements, the additives added to them must not contain environmentally harmful components and provide the maximum thermal oxidation stability of the base oil. A significant disadvantage of zinc dialkyl dithiocarbamates and dialkyl dithiophosphates, which are widely used today as highly efficient polyfunctional additives, is that they contain ecotoxic organosulfur and organophosphorus components. In view of this, complexes of biometals with hydroxamic acids are promising. The paper presents the results of a study of the influence of MoO2L2, ZnL2, CuL2, MgL2 coordination compounds with N-methyldecanohydroxamic acid (HL) and mixtures of MoO2L2 with tert-butylcatechol and 2,6-di-tert-butyl-4-methylphenol (ionol) on the oxidation of distilled sunflower fatty acid methyl esters (one of the variants of biodiesel). Procedures for the synthesis of novel homoleptic Mg(II) and Zn(II) bis-hydroxamate complexes and their spectral characteristics are presented. The antioxidation properties of the complexes contained in the model solutions were determined by the method of oxygen absorption in a hermetically sealed system at 110 C. It has been found that the magnesium complex has no effect on the oxidation of the substrate, and that the copper complex decomposes, under experimental conditions, to metallic copper, which is an oxidation promoter. Zinc and molybdenum complexes exhibit antioxidation properties. It has been shown that ionol is an efficient co-component for MoO2L2, but no synergistic effect was detected. In view of the high tribological characteristics, the MoO2L2 complex is a promising prototype for the development of a polyfunctional eco-friendly additive to commercial biodisel-based lubricating compositions.

MoS2 tribofilm distribution from low viscosity lubricants and its effect on friction

The current study analyses the friction performance of low viscosity fully-formulated oils containing the Molybdenum Dialkyl Dithiocarbamate (MoDTC) friction modifier at different concentrations. The MoDTC friction modifier is known to produce MoS2 sheets in the tribocontact providing a low coefficient of friction under boundary lubrication conditions. However, there is a little knowledge around the quantitative relationship between the concentration of MoDTC in the oil and MoS2 amount and distribution in the contact. The study uses Raman spectroscopy mapping capability to characterise the tribofilm formed from different chemistry lubricants and under different tribological conditions as defined by the lambda ratio. After qualitative and quantitative chemical surface characterisation a discussion is presented to highlight some important aspects to relate the formed MoS2 sheets, their spatial distribution in tribofilms and the subsequent tribological performance.

Syntheses, characterizations, and reactivities of new 1,4,7-trimethyl-l,4,7-triazacyclononane (Me3tacn) molybdenum and tungsten complexes

The reported complexes of [(Me3tacn)M0(CO)3] (Me3tacn = 1,4,7-trimethyl-1,4,7-triazacyclononane; M = W, 1a; Mo, 1b), [(Me3tacn)MII(CO)3I](PF6) (M = W, 2a; Mo, 2b), [(Me3tacn)MVOCl2](PF6) (M = W, 3a; Mo, 3b), and [(Me3tacn)MVIO3]·4H2O (M = W, 4a; Mo, 4b) were synthesized as tungsten and molybdenum precursors according to the works by Wieghardt [20,21,24]. Reaction of 2a with sodium dialkyl dithiocarbamate afforded complexes [(Me3tacn)WII(CO)2(S2CNR2)]I (R = Me, 5a; iPr, 6a). Similar reaction using 2b gave rise to the isolations of complexes [(Me3tacn)MoII(CO)2(S2CNR2)](PF6) (R = Me, 5b; iPr, 6b; nPr, 7). Hydrolysis of 3b in acetonitrile gave a dimeric molybdenum complex [{(Me3tacn)MoVO(OH)}2(μ-O)](PF6)2·2MeCN (8). Treatment of 4b with sodium diisopropyl dithiocarbamate in the presence of HPF6 yielded [(Me3tacn)MoVIO2S] (9), while the similar reaction with S8 powder yielded the oxotetrasulfido complex [(Me3tacn)MoIVO(S4)] (10). All complexes are well characterized by electronic, infrared, and NMR spectroscopies, and the solid-state structures of 1a/b, 2a, 3b, 4a/b, 5a/b, 6a/b, and 7–10 have been also established by single-crystal X-ray diffraction. The electrochemical properties of these molybdenum and tungsten complexes were also investigated in the paper.

Dithiocarbamate-modified cellulose-based sorbents with high storage stability for selective removal of arsenite and hazardous heavy metals.

A series of cellulose derivatives bearing dialkyl dithiocarbamate (DTC) groups were synthesized. Their ability of sorption of arsenite (As(iii)) and heavy metals and their storage stability in the solid state were investigated. Among them, DTC-modified cellulose derived from l-proline showed the highest sorption capacity for As(iii) and heavy metals to selectively remove them from aqueous media. It also showed exellent storage stability in air at 40 °C.

Ultrasound-Assisted Synthesis, Antifungal Activity against Fusarium oxysporum, and Three-Dimensional Quantitative Structure–Activity Relationship of N,S-Dialkyl Dithiocarbamates Derived from 2-Amino Acids

A high-yielding, green, and fast synthesis of alkyl 2-substituted {[(alkylsulfanyl)carbonothioyl]amino}acetate-type compounds is described. The one-pot, three-component condensation of alkyl 2-aminoesters, carbon disulfide, and electron-deficient olefins was the key reaction to be developed. The products were obtained easily and efficiently, with good overall yields after two steps (79–91%), employing short reaction times, without the use of a catalyst, and ultrasonic irradiation in water. This procedure was exploited to produce antifungals against the phytopathogenic fungus Fusarium oxysporum. Some synthesized compounds exhibited good performance as mycelial growth inhibitors (IC50 < 80 μM). Structural and antifungal datasets were integrated to explore the comprehensive three-dimensional quantitative structure–activity relationship (3D-QSAR) using comparative molecular field analysis (CoMFA) and explain the observed activity. This integration resulted in an excellent CoMFA model (r2 = 0.812; q2 = 0.771) after substructure-based alignment. According to this model, synthesized compounds possessing steric bulky electron-withdrawing groups in the dithiocarbamate moiety can be considered as promising F. oxysporum inhibitors.

The effect of clearance between tappet insert and camlobe on the tribological and tribochemical performance of cam/follower surfaces

This paper examines the effect of tappet insert clearance on the tribological and tribochemical performance of the camlobe/follower tribopair when lubricated in a fully-formulated oil containing 1 wt% of Molybdenum Dialkyl Dithiocarbamate (MoDTC). Tests were performed on a Single Cam Rig (SCR), taken from 1.25 l FORD Zetec (SE) engine. White Light Interferometry and Talysurf contact profilometry were used to characterise the wear scar on the tappet inserts and camlobes respectively. In addition, Scanning Electron Microscopy (SEM) was used on both (i.e. camlobes and tappet inserts) for wear mechanisms assessment as well as to access the durability of coatings used on tappet inserts. Energy-Dispersive X-ray (EDX) and Raman spectroscopy analyses were also used to understand the tribochemical interactions between oil additives and the cam/follower interface. Results show that the chemistry of the tribofilm derived on camlobes and tappet inserts vary as a function of tappet insert clearance and cam profile. Also, regardless of the type of coating, the smaller clearance of tappet inserts exhibited higher friction and wear. Therefore, based on this work, the use of the thicker tappet insert would be inadvisable as this possibly can cause higher fuel consumption and inefficient performance of the intake/exhaust valves of the engine.

A Study on the Tribofilm Growth and Tribological Properties of Tribofilms Formed from Zinc Dialkyl Dithiophosphate (ZDDP) and Molybdenum Dialkyl Dithiocarbamate (MoDTC)

A Study on the Tribofilm Growth and Tribological Properties of Tribofilms Formed from Zinc Dialkyl Dithiophosphate (ZDDP) and Molybdenum Dialkyl Dithiocarbamate (MoDTC)

Investigation of pure sliding and sliding/rolling contacts in a DLC/Cast iron system when lubricated in oils containing MoDTC-Type friction modifier

Abstract Diamond-like carbon (DLC)/cast iron (CI) systems have been widely investigated due to their important application in engine components such as cylinders, pistons and more specifically for the cam/follower interface. The pure sliding contact of the DLC/CI system has traditionally been the focus of research; consequently less is understood about sliding/rolling contact systems. In addition, the tribological and tribochemical characteristics of the Molybdenum Dialkyl Dithiocarbamate (MoDTC) as a lubricant additive in such sliding/rolling contacts are not fully understood. In this study, a Mini Traction Machine (MTM) was used to run the experiments using alloy steel balls coated with 15 atomic percent (at. %) hydrogenated DLC (a-C: 15H) rubbing against uncoated cast iron discs. Results showed that the sliding/rolling ratio affects friction, wear and tribochemistry in CI/DLC systems; pure sliding enhances MoDTC activation. MoDTC decomposes to form MoS2, FeMoO4 and not MoO3. In addition, it was observed that MoS2/FeMoO4 ratio depends on test conditions and affects to the friction performance.

Measuring tappet rotation in a valvetrain rig when lubricated in a fully formulated oil containing MoDTC-type friction modifier

Abstract In a direct acting valve train configuration, tappet rotation plays a key role in improving lubrication, reducing wear and friction. However, to the best of the authors' knowledge, no studies were found to investigate the rotation of tappet under the effect of different coatings, thicknesses of tappets and formulations with Molybdenum Dialkyl Dithiocarbamate (MoDTC) which has been recently reported to be detrimental to Diamond-Like Carbon (DLC) wear. In this work, a new technique of measuring tappet rotation has been developed. A giant magnetoresistance (GMR) sensor coupled with a split pole ferrite disk magnet was used. The sensor was installed very close to the tappet/bucket while the magnet was mounted into the underside of the tappet. Experiments were performed using standard production steel tappets coated with Mn-phosphate (MnPO4) and diamond-like carbon (DLC) coatings. In general, results showed that the tappet rotation is strongly dependant on oil formulation, clearance, speed/temperature, and surface roughness of the coating. MoDTC promoted the rotation of the tappet under both coatings. In addition, DLC inserts showed an increase in tappet rotation as compared to MnPO4 inserts. Nevertheless, regardless of the type of coating, the thickest tappets showed the highest rotation.

Efficiency improvement in automobile bucket tappet/camshaft contacts by DLC coatings – Influence of engine oil, temperature and camshaft speed

With the aim to fulfill legal regulations concerning energy efficiency and greenhouse gas emissions, diamond-like carbon (DLC) coatings are increasingly used on highly stressed components of internal combustion engines to reduce friction and prolong component lifetime. The valve train is one of a key system of the combustion engine considerably contributing to frictional losses, especially under boundary and mixed lubrication conditions at lower crankshaft speeds. In this regard, the tribological contact bucket tappet/camshaft offers high potential for friction reduction but imposes high demands on DLC coatings due to highly complex kinematics and repetitive loads depending on the cam contours and the camshaft angle and speed. The aim of this work was to analyze the influence of DLC coatings on the frictional and wear behavior within the contact bucket tappet/camshaft. This tribological contact was analyzed in a one tappet/one cam friction test-rig using series-production tappets, cams and valve springs ensuring high transferability of the results into the real application. Two amorphous hydrogen containing carbon based coatings were deposited on series-production bucket tappets. The zirconium based DLC coating a-C:H/ZrCg was compared to a DLC coating system a-C:H:X deposited under industrial conditions. One mineral motor oil of SAE viscosity grade 0W20 and one synthetic motor oil polyalphaolefin (PAO) of SAE viscosity grade 5W30 formulated with different additive packages containing the anti-wear (AW)/extreme pressure (EP) additive zinc dialkyl dithiophosphate (ZDDP) and the friction modifier (FM) additives molybdenum dialkyl dithiocarbamate (MoDTC) and glycerol monooleate (GMO) were used in the test-rig. Special attention was paid to the interactions of the additive packages in the low viscosity oils with the functional surfaces of the a-C:H:ZrCg coated bucket tappets. The frictional behavior determined by time-resolved measurements of friction forces reveals that higher camshaft speeds led to increased lubrication film formation contributing to reduced frictional losses. Higher motor oil temperature resulted in temperature induced reduced viscosity of the motor oils leading to higher frictional losses. The DLC coatings a-C:H:ZrCg and a-C:H:X caused significant reduction of frictional losses under the operating conditions in the test-rig. The a-C:H:ZrCg coated bucket tappets caused higher frictional losses than uncoated bucket tappets at low camshaft in boundary friction conditions. Friction reduction at all operating points was ensured by a-C:H:X regardless of camshaft speed, motor oil temperature and the choice of motor base oil and additive package proving the great potential for application on components under challenging lubricating and loading conditions. The wear of the uncoated and a-C:H:ZrCg coated functional surfaces was analyzed by means of confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM). The a-C:H:ZrCg coating contributed to wear protection in the highly loaded tribological contact despite the different lubricating and loading conditions regardless of the base oil and additive packages. The a-C:H:X coating revealed similar favorable behavior. Comprehensive surface sensitive analysis of the uncoated and a-C:H:ZrCg coated bucket tappets by means of Raman spectroscopy and XPS indicated that no tribo-chemical reaction layer was formed from the motor oil and the additive packages on a-C:H:ZrCg coated bucket tappets under the operating conditions. Moreover, the combination of additives ZDDP and GMO in PAO appears to be disadvantageous in terms of reaction layer formation since no tribo-chemical reaction layer was found on uncoated steel bucket tappets after tribological tests in contrast to the mineral oil containing ZDDP and MoDTC.

Synthesis, characterization and anticancer activity of gold(I) complexes that contain tri-tert-butylphosphine and dialkyl dithiocarbamate ligands

Two new gold(I) complexes that contain tri-ter-butylphosphine and dialkyl dithiocarbamate ligands were synthesized and characterized by FTIR, NMR spectroscopy, Cyclic voltammetry, elemental analysis and X-ray diffraction. The in vitro cytotoxicity of both complexes was examined against A549 (lung cancer), MCF7 (breast cancer), and HeLa (cervical cancer) human cancer cell lines. Both complexes exhibit very strong in vitro cytotoxic effects against A549, MCF7 and HeLa cell lines. The screening of the cytotoxic activity based on IC50 data against the A549, MCF7, and HeLa lines shows that the synthesized gold(I) complexes are highly effective, particularly against HeLa cancer cell line. Based on IC50 data, the cytotoxic activity of both complexes is better than well-known commercial anticancer drug cisplatin against all the three cancer lines tested.