Tribological properties of solid lubricant nanocomposite coatings on base of tungsten disulphide nanoparticles

Tungsten disulphide (WS2) and molybdenum disulphide (MoS2), which belong to the family of transition metal dichalcogenides, are well known for their solid lubricating behavior. Thin films of WS2 and MoS2 exhibit extremely low coefficient of friction in dry enviroments, and are typically applied by sputter deposition, pulsed laser ablation, evaporation or chemical vapor deposition, which are essentially either line- of-sight or high temperature processes. In this paper we have investigated the tribological properties of embedded solid lubricant coatings from WS2 nanoparticles and compared them to monolithic and alloy films of the same constituents. The WS2/metal (Ti, W) nanocomposite were deposited on alloy substrate by magnetron sputtering. The patterning methods were used to create two component coatings in which WS2 were embedded in a Ti matrix. Coatings were deposited using sputter deposition, and co-deposition of WS2 and Ti was used to deposit the alloy coatings. A pin-on-disk (POD) test was used to examine the frictional behavior and mechanical stability of the coatings, and was carried out in both low and high humidity conditions. The morphology and microstructure of the coatings were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM). The tribological properties of WS2/metal (Ti, W) nanocomposite coatings were investigated using a POD tribometer in ambient air and in humidity conditions. XRD and SEM was used to examine morphology of the wear track after the POD test. The nanoparticles WS2 can decrease the friction coefficient of lubricant obviously. However the results showed that their friction reductions have not obvious difference by the POD tribometer. The WS2/Ti nanocomposite coating showed lower frictions coefficient and higher wear resistance as compared to the pure WS2 coating, which were caused by the microstructure of the composite coating that serve as perfect intermediate lubricants between the contact surfaces. The analyses of surfaces composition coating conducted by XRD and SEM images showed that nanoparticles form a protective film (WO3) allowing an increase the load capacity of friction (rubbed) pairs. The main advantage of the nanoparticles is ascribed to the release and furnishing of the nanoparticles from the valley onto the rubbing metal surface and their confinement at the interface. Coatings of WS2 alone were found to perform well under low-humidity conditions, but poorly under high- humidity. Alloying of WS2 with Ti was found to provide some improvement under high humidity. The patterned film, which consisted of columns of WS2 embedded in a Ti film was found to exhibit friction and wear properties superior to either Ti or WS2 alone. The coating investigated here have potential applications for cutting tools and metal forming dies that will enhance tool life and reduce the energy expended due to friction forces; as well is used in various tribological fields such as seals, bearings or electrical motor brushes and, also for applications needing excellent lubrication and wear-reducing properties

ESTIMATION ON THE WEAR AND DURABILITY OF THE HEAD OF THE MILLS USING DIFFERENT MODELS

The mathematical model presented in this paper is one of the possible mathematical models to use to estimate the wear and lifespan of the head of the milling cutter, which has an appreciable age and initially modeled a relatively similar phenomenon of aggression or erosion of an entity by a high. The mathematical model of the prey-predator population system, well known in ecology and expressed in a system of differential equations always of the order of AJ Lotka and V. Volterra is successfully applied in other fields: economics, services, prediction of technological evolution, adoption cryptocurrencies, hygiene, communications (security and optimization), medicine, passenger transport forecast, plasma physics. In this wide context of applications, there are also applications used in the paper, of the prey-predator model, Lotka-Volterra, to the interaction phenomenon between the dental milling cutter and the milled material. The application starts from the assimilation of the dental cutter with the predator that extracts material from the body of the milled material, assimilated with the prey. The milling action, the action of the predator, does not remain without negative results for him, the milling material also losing particles. Both parts of this phenomenon cannot grow as a mass, an experimental aspect that turns into an important hypothesi

Results on the use of bacterial biopreparations (biological fertilizers) in agricultural crops in Research and Development Stations for Agriculture, Romania

The development and use of strategies for organic fertilization of agricultural crops will lead to a decomposition of insoluble elements in the soil structure, which will lead to an increase in the number of soluble mineral elements in the soil structure, which will lead to significant plant growth and of agricultural production. Soil pollution with chemical elements has led to an increase in pH from a basic / neutral to an acid one. Soil acidification causes a decrease in agricultural production, a decrease in plant resistance to certain pests of soil structure, but especially soil pollution, groundwater with certain chemical elements found in the structure of fertilizers. Thus, following the research carried out within the research-development stations for agriculture in Romania, it was proved that the lots fertilized with biological fertilizer had a much higher production than the lots fertilized chemically

Economic advantages of using bacterial biopreparations in agricultural crops

The ecological, genetic, biological approach proposed by agricultural specialists in order to protect plants and crops has a role in reducing the impact of pests through the process of selection and improvement of genetic resources in the processes of planting, development and introduction of biological means to combat pests in agricultural ecosystems. The strategies proposed by the specialists in the agricultural field aim not at the total extermination of the pests from the agricultural crops but at keeping the pest populations at the optimal damage threshold. The most important advantages of these biological processes are those of the evolutionary stability of the crop systems, the ecological stabilization of the pest and crop populations as well as the assurance of a superior quality of the resulting agricultural products.The present paper aims to present the main advantages of using bacterial biopreparations in agricultural ecosystems (research conducted in agricultural research stations in Romania), reducing soil pollution, environmental crops, use of alternative fertilization and cultivation technologies as well as obtaining additional, ecological productions.The aim of this paper is to present the economic advantages of using bacterial biopreparations in agricultural research and development stations, reducing costs in agriculture and the processes that these bacterial biopreparations have on the agricultural ecosystem, the environment and humans and animals

Study of Wear Phenomenon of a Dental Milling Cutter by Statistical–Mathematical Modeling Based on the Experimental Results

The wear phenomenon of a dental milling cutter is studied based on experimental results and data and validated by statistical–mathematical modeling. The results of the statistical–mathematical modeling by the interpolation of the experimental results (data) regarding the wear of the dental milling cutter analyzed and obtained in the work process are presented in this paper. These results (data) are important because they lead to polynomial functions which by interpolation approximate very well the dependent parameter, specifically the wear process (mass lost due to dental milling cutter wear, mw), considered in the experimental program. The polynomial interpolation functions are valid, only during the experimental testing range of the dental milling cutter, to describe the wear phenomenon; the extrapolations do not lead to satisfactory results. However, by using a controlled interpolation function with an exponential component, the extrapolation of the results is possible. Therefore, the purpose of this paper is the statistical–mathematical modeling by the interpolation of the experimental results of the mass lost due to dental milling cutter wear, mw, using the deterministic differential model for the work process of it. Thus, interesting conclusions can be drawn relating to the phenomenon. In support of these statements come the results of the statistical–mathematical modeling by the interpolation of the experimental data obtained in the work process of the dental milling cutters, leading to practical applications, such as the extension of the life of dental milling cutter, useful even for its operation optimization; determination of possible criteria for replacing the worn dental milling cutters; the extension of the life of the materials from which dental milling cutters are built; or the provision of ideas for constructive solutions. Based on the modeling results by interpolation, it was found that the dental milling cutter during the milling operation works with high efficiency (mass loss due to wear is very reduced) in the first 11 h of operation, i.e., about a 10% increase in lifetime. After 11 h of operation, mass loss due to wear of the dental milling cutter increases relatively exponentially; thus, it is recommended that, in the normal way, the dental milling cutter be replaced with a new one to ensure high standards of materials processing

Study of organizational culture and organizational change

Organizational culture plays an essential role for a corporation’s efficient operation and development, a reality valid, both small institutions and corporate giants. To illustrate the importance of a strong culture, or on the contrary, the consequences of a weak, undefined one, we have made an overview of the organizational context. Culture is important to an organization, because it influences the employees, customers, management, virtually the entire public of a company. A company with a strong culture, whether it is formal or informal, will create a positive image, and the effects will manifest on the company, both in internal and external results. A strong organizational culture is the one in which there is a strong attachment to the organization’s values and principles. This paper aims to analyze the effect that the organizational culture has on company's development. We tied this analysis of the status of culture in Vodafone Romania, to see to what extent are concepts applicable in Romanian society and the impact their, on company's development. We wish to show that the role of organizational culture is crucial to the evolution of a modern company, because the company’s image reflects cultural strategies. Moreover, we have emphasized the importance of the change and evolution cultural, required for the company’s adjustment to the current financial, economic, social realities and its prosperity

Tribological Properties of the Lubricant Containing Titanium Dioxide Nanoparticles as an Additive

To improve the oil-solubility of nanoparticles, a new technology was used to prepare a kind of lubricant containing titanium dioxide (TiO2) nanoparticles. The microstructures of the prepared nanoparticles were characterized via transmission electron microscope (TEM) and infrared spectroscopy (IR). Tribological properties of TiO2 nanoparticles used as an additive in base oil were evaluated using four-ball tribometer and ball-on-disk tribometer. In addition, the worn surface of the steel ball was investigated via polarized microscopy (PM) and X-ray photoelectron spectroscopy (XPS). The TiO2 nanoparticles can be completely well-dispersed in the base oil under a new process (NP), which has no significantly negative effect on the anti-oxidation property. The results of the tribological tests show that TiO2 nanoparticles under the NP show a better anti-wear property and friction-reducing property in base oil compared to TiO2 nanoparticles under the tradition process (TP). The main aim of this paper lies in solving with the oil-solubility problem through the combination effect of surface modification and special blend process of lubricating oil. This method was first used to prepare lubricant containing TiO2 nanoparticles and then used as additives in engine oil, gear oil, and other industrial lubricants. At the same time, tribological properties of TiO2 nanoparticles in base oil as a lubricating additive were also studied

Chemical-Mechanical Impact of Nanoparticles and pH Effect of the Slurry on the CMP of the Selective Layer Surfaces

This paper provides a tribochemical study of the selective layer surface by chemical mechanical planarization (CMP). CMP is used to remove excess material obtained in the process of selective transfer. The paper aims at a better understanding of the planarization (polishing) and micromachining. The planarization becomes effective if the material removal rate (MRR) is optimal and the surface defects are minimal. The pH of the slurry plays a very important role in removing the selective layer by CMP, and hydrogen peroxide (H2O2) is the most common oxidizer used in CMP slurry. The purpose of this paper is the analysis of the pH effect on the etching rate (ER) and on the behavior of selective layer polishing by a constant concentration of H2O2 and the influence of nanoparticles size and concentration on selective layer surface CMP. The nanoparticle size used is 250 nm. The MRR results through CMP and ER have been shown to be influenced by the presence of oxides on the selective layer surface and have been found to vary with the slurry pH at constant H2O2 concentrations. The CMP slurry plays an important role in the CMP process performance and should be monitored for optimum results and minimal surface defects. The paper analyzes the impact of chemical-mechanical, inter-nanoparticle, and pad-nanoparticle-substrate interactions on CMP performance, taking into account the state of friction at the interface, by measuring the friction force. Selective layer CMP optimization studies were required to control the chemical and mechanical interactions at the interface between the slurry and the selective layer, the slurry chemistry, the properties, and the stability of the suspended abrasive nanoparticles

A Modelling Study of the Correlation between the Layer Obtained by Selective Transfer and the Dislocations Movement at the Friction Surfaces Limit

The selective transfer phenomenon (STP) is based on physico-chemical processes occurring in the contact area of a friction pair, with an element from a copper alloy and allows the metallic transfer of particles of micro/nanometric size, forming a thin superficial tribologically performing layer under energy and relative motion conditions. During the formation of the layer, its crystalline network has an excess of defects and this makes the dislocations to come to the surface. The layer thickness is small, porous, and with comparable dimensions to those of the tensions field of the dislocations. This paper presents a review and analysis of the STP based on dislocations movement to establish and know the tensions field influence, the energy (about 0.25 J/m), and the linear tension of dislocations (~2.42 × 10−9 N) at the contact surfaces zone of a friction pair, by which we can ensure a low wear state (~4.16 × 10−5–2.16 × 10−4 g/min), and a reduced friction coefficient (~0.014–0.034). Therefore, the purpose of the paper is to analyze the STP based on the dislocations movement because is proves the existence (presence), importance, and utility of the dislocations, respectively, the dislocations movements during the conditions’ selective transfer, at the limit of the friction surfaces, under the action of a tensions field, whose components are determined analytically by modelling, together with energy and the linear tension. Also, the layer formed through STP has the property of ensuring during the deformation process an agglomeration of dislocations (structural defects) which protects it from destruction, and therefore, a self-regulation of the equilibrium processes, disturbed during the friction process, to maintain the friction and wear of the friction pairs within reduced limits

A Modelling Study of the Correlation between the Layer Obtained by Selective Transfer and the Dislocations Movement at the Friction Surfaces Limit

The selective transfer phenomenon (STP) is based on physico-chemical processes occurring in the contact area of a friction pair, with an element from a copper alloy and allows the metallic transfer of particles of micro/nanometric size, forming a thin superficial tribologically performing layer under energy and relative motion conditions. During the formation of the layer, its crystalline network has an excess of defects and this makes the dislocations to come to the surface. The layer thickness is small, porous, and with comparable dimensions to those of the tensions field of the dislocations. This paper presents a review and analysis of the STP based on dislocations movement to establish and know the tensions field influence, the energy (about 0.25 J/m), and the linear tension of dislocations (~2.42 × 10−9 N) at the contact surfaces zone of a friction pair, by which we can ensure a low wear state (~4.16 × 10−5–2.16 × 10−4 g/min), and a reduced friction coefficient (~0.014–0.034). Therefore, the purpose of the paper is to analyze the STP based on the dislocations movement because is proves the existence (presence), importance, and utility of the dislocations, respectively, the dislocations movements during the conditions’ selective transfer, at the limit of the friction surfaces, under the action of a tensions field, whose components are determined analytically by modelling, together with energy and the linear tension. Also, the layer formed through STP has the property of ensuring during the deformation process an agglomeration of dislocations (structural defects) which protects it from destruction, and therefore, a self-regulation of the equilibrium processes, disturbed during the friction process, to maintain the friction and wear of the friction pairs within reduced limits