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The adverse effects of temperature on the lubricating properties of nano magnetorheological grease are reduced by applying of a magnetic field.

Nano magnetorheological grease was prepared via a thermal water bath with stirring. The lubricating properties of the grease were investigated at different temperatures. Then the lubricity of the prepared nano magnetorheological grease was investigated under the effect of thermomagnetic coupling.

As the temperature rises, the coefficient of friction of grease lubrication gradually increases, surface wear gradually increases and lubrication performance gradually decreases. Compared with grease, magnetorheological grease has a decreased coefficient of friction and enhanced lubrication effect under the action of a magnetic field at different temperatures.

A lubrication method using a magnetic field to reduce the effect of temperature is established, thereby providing new ideas for lubrication design under a wide range of temperature conditions.

The purpose of variable loading conditions (392 N-785N-392N-785N) with break-in period were used to study interactions between zinc dialkyl dithiophosphate (ZDDP) 0.1 P% (phosphorus) and fine-grade molybdenum disulfide (MoS₂) 3%, in different mixtures of NLGI 2 lithium stearate grease. Four-ball wear tests were used to evaluate the tribological properties of different grease mixtures such as coefficient of friction and wear. ASTM 2266 as reported by earlier studies is useful, but it is not representative of real-life applications where variable loads and speeds and different break-in periods play a role and could change the results and the nature of tribofilms.

In this study, chemical and mechanical properties of tribofilms were examined. Moreover, design of experiment was used to examine the data and shorten experimentation time. Research described here is investigating variable loading conditions for real-life applications by using a break-in period of 2 min at the start to minimize asperities and establish a clean surface. Design expert (DOE) analyzes responses to reveal those variables that are single factor and those that are multifactor whether synergistically or antagonistically.

The results indicated that spectrum loading with break-in period showed reduction in wear when tested in greases with ZDDP/MoS₂ combinations. Ramping up or down the load every 7.5 min for a rotational speed of 1,200 rpm and a total of 36,000 revolutions or 30-min time slowed the wear properties of lithium-based grease under different MoS₂ and ZDDP concentrations. Experiments indicated that wear was largely dependent on the loading condition and ZDDP additives during specific break-in period at 1,200 rotational speed. It is believed that MoS₂ greases perform better under spectrum loading and under constant loading when mixed with ZDDP phosphorus.

This research indicates that there is a synergistic interaction between ZDDP, MoS₂ and variable loading especially when a break-in period is applied. The results indicated that wear was largely dependent on the specific speed used with spectrum loading as presented in the energy dispersive spectroscopy and the Auger electron spectroscopy analysis, and thus a 3% MoS₂ grease with ZDDP (phosphorus: 0.1 Wt.%) are needed to improve the wear resistance and improve the friction characteristics.

The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-01-2024-0016/

This paper aims to improve the tribological properties of lithium complex greases using nanoparticles to investigate the tribological behavior of single additives (nano-TiO₂ or nano-CeO₂) and composite additives (nano-TiO₂–CeO₂) in lithium complex greases and to analyze the mechanism of their influence using a variety of characterization tools.

The morphology and microstructure of the nanoparticles were characterized by scanning electron microscopy and an X-ray diffractometer. The tribological properties of different nanoparticles, as well as compounded nanoparticles as greases, were evaluated. Average friction coefficients and wear diameters were analyzed. Scanning electron microscopy and three-dimensional topography were used to analyze the surface topography of worn steel balls. The elements present on the worn steel balls’ surface were analyzed using energy-dispersive spectroscopy and X-ray photoelectron spectroscopy.

The results showed that the coefficient of friction (COF) of grease with all three nanoparticles added was low. The grease-containing composite nanoparticles exhibited a lower COF and superior anti-wear properties. The sample displayed its optimal tribological performance when the ratio of TiO₂ to CeO₂ was 6:4, resulting in a 30.5% reduction in the COF and a 29.2% decrease in wear spot diameter compared to the original grease. Additionally, the roughness of the worn spot surface and the maximum depth of the wear mark were significantly reduced.

The main innovation of this study is the first mixing of nano-TiO₂ and nano-CeO₂ with different sizes and properties as compound lithium grease additives to significantly enhance the anti-wear and friction reduction properties of this grease. The results of friction experiments with a single additive are used as a basis to explore the synergistic lubrication mechanism of the compounded nanoparticles. This innovative approach provides a new reference and direction for future research and development of grease additives.

The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-09-2023-0291/

This paper aims to develop a stable gel-type lubricant emulating commercial conditions. This encompassed rheological and tribological assessments, alongside field trials on the Medellín tram system.

The gel-type lubricant with graphite and aluminum powder is synthesized. Rheological tests, viscosity measurements and linear viscoelastic regime assessments are conducted. Subsequently, tribological analyses encompassing four-ball and twin disc methods are executed. Finally, real-world testing is performed on the Medellín tram system.

An achieved lubricant met the stipulated criteria, yielding innovative insights into the interaction of graphite and aluminum powder additives under varying tests.

Novel findings are unveiled regarding the interaction of graphite and aluminum powder additives in tribological, rheological and real-world trials. In addition, the wear behavior of polymers is observed, along with the potential utilization of such additives in tramway systems.

This study aims to probe the applicability of 2-mercaptobenzothiazole (MBT) functionalized ionic liquids (ILs) as additives in lithium complex grease (LCG) by researching the corrosion inhibiting, rheological and tribological performances.

Electrochemical tests such as electrochemical impedance spectroscopy and potentiodynamic polarization curves were used on Gamry electrochemical workstation to research the corrosion inhibition properties of ILs in 1.0 M HCl corrosive solution. The rheological properties of different grease samples were tested on a rheometer. The tribological properties were investigated on SRV-V oscillating reciprocating friction and wear tester. Scanning electron microscope, X-ray spectrometer and X-ray photoelectron spectrometer were used to characterize the lubricating mechanism.

The 2-MBT functionalized ILs have excellent corrosion inhibition properties. When used as additives in LCG, they both exhibited enhancing effects on thermostability, colloid stability and structural recoverability, and furthermore, outstanding friction-reducing and antiwear properties were also obtained. Surface analysis indicated that the superior lubricating performances of 2-MBT functionalized ILs were mainly ascribed to the formation of tribochemical products on wear tracks, including organic compounds with C–O bond, Fe₂O₃ and FeS₂.

The 2-MBT-based ILs synthesized in this study were multifunctional additives with excellent corrosion inhibiting and tribological properties, which would have a very broad application prospect in lubricating grease industry.

This paper aims to determine a suitable anti-wear and friction-reducing compounding additive for lithium greases (LG) by investigating the effects of three single additives potassium borate (PB), zinc dialkyl dithiophosphate and molybdenum dialkyl dithiophosphate (MoDDP) and two compound additives on the friction, wear and extreme pressure properties of LG.

The effects of the above five additives on the friction, wear and extreme pressure properties of LG were investigated using an SRV-5 friction tester. An X-ray photoelectron spectrometer was used to analyze the various elements presented on the wear surface as well as the types of compounds.

The compound additive suitable for grease consists of PB and MoDDP, which have excellent friction reduction, anti-wear and extreme pressure properties. And a boundary protection film consisting of oxide and MoS₂ is formed on the friction surface, thus improving the friction reduction and anti-wear performance of the grease.

This study can improve the anti-wear and friction-reduction performance of greases, which is of great importance in the field of industrial lubrication. The results of this paper are expected to be useful to researchers and academics of grease.

The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-11-2022-0350/

The evaluation of the haptics of water taps and wear-related changes during usage usually involves time- and cost-intensive testing. The purpose of this paper is to abstract the tribo-system between technical ceramic disks of water tap mixer cartridges to the model level and study the tribological behavior.

The friction and wear behavior was studied by means of an alumina ball-on-original alumina disk setup at different temperatures as well as under dry conditions and under lubrication by different greases. Thereby, the frictional behavior was measured in situ, and the wear losses were analyzed by means of laser scanning microscopy.

It was shown that friction and wear can behave in a contrasting way, whereby one grease might lead to low friction, that is, an easy-going movability of the water tap, but to increased wear losses. The latter, in turn, is an indicator for the usability and service life, which cannot be explained from friction alone. Thereby, the viscosity of the base oil, the grease consistency and additives were identified as relevant grease formulation parameters to allow for fluid film (re-)formation and removal of wear particles.

To the authors’ best knowledge, this is the first approach to systematically analyze the friction and wear behavior of technical ceramic disks of water tap mixer cartridges in dependency on the temperature as well as the used lubricating grease. This approach is relevant for developing screening test strategies as well as for the selection of lubricants for water tap applications.

The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-11-2022-0334/

This analysis examines the relationship between corruption and firm productivity in Vietnam.

The authors apply the system generalized method of moments estimation approach on a panel dataset constructed from comprehensive enterprise surveys covering all the sectors over the 2011–2020 period.

The results confirm a non-linear relationship between corruption and firm productivity. Where corruption is severe, leaving corruption alone tends to benefit firm productivity because efforts to control corruption are likely to cause greater delays. In less corrupt provinces, corruption appears to harm firm productivity while efforts to control corruption provide significant productivity gains. This U-shaped relationship is confirmed for small firms and those in the private sector sub-samples. Intriguingly, this study reveals that the U-shaped relationship does not apply to micro, medium, large firms, state-owned firms and foreign-invested firms because corruption is found to have no significant impact on productivity among these sub-samples. Changes in regulations after 2014 toward promoting a transparent business environment are shown to foster the positive impact of lowering corruption on firm productivity.

This study suggests that lowering corruption is beneficial for firm productivity at the micro level. However, where corruption is severe, monitoring corruption alone is likely to cause adverse effects on productivity due to increased bureaucratic delays. Institutional reforms might play an important role in leveraging the effects of lowering corruption on productivity in highly corrupt areas.

This paper sheds new light on the relationship between corruption and firm productivity in the broad existing literature and especially in the limited number of studies for Vietnam.

The purpose of this study is to clarify the mechanism of ambient and transient temperature effects on piezoelectric pressure sensors, and to propose corresponding compensation measures. The temperature of the explosion field has a significant influence on the piezoelectric sensor used to measure the shock wave pressure. For accurate shock wave pressure measurement, based on the actual piezoelectric pressure sensors used in the explosion field, the effects of ambient and transient temperatures on the sensor should be studied.

The compensation method of the ambient temperature is discussed according to the sensor size and material. The theoretical analysis method of the transient temperature is proposed. For the transient temperature conduction problem of the sensor, the finite element simulation method of structure-temperature coupling is used to solve the temperature distribution of the sensor and the change in the contact force on the quartz crystal surface under the step and triangle temperatures. The simulation results are highly consistent with the theory.

Based on the analysis results, a transient temperature control method is proposed, in which 0.5 mm thick lubricating silicone grease is applied to the sensor diaphragm, and 0.2 mm thick fiberglass cloth is wrapped around the sensor side. Simulation experiments are carried out to verify the feasibility of the control method, and the results show that the control method effectively suppresses the output of the thermal parasitic.

The above thermal protection methods can effectively improve the measurement accuracy of shock wave pressure and provide technical support for the evaluation of the power of explosion damage.

This study examines whether institutional quality affects the relationship between income inequality and entrepreneurial activity. The authors specifically examine whether the greasing or sanding effect holds for the relationship between income inequality and entrepreneurship, while moderating for institutional quality. The greasing effects suggest that income inequality can promote entrepreneurial activity, while the sanding effects disincentivise it.

The authors examine this relationship using a sample of 100 advanced and developing countries from 2006 to 2018 using a dynamic panel estimator to control endogeneity and simultaneity. Additionally, the authors include an interaction term to estimate the marginal effects of income inequality, while moderating for institutional quality. Furthermore, the authors differentiate between six measures of institutional quality.

Overall, the authors find that institutional quality and income inequality have a positive and significant impact on entrepreneurial activity. However, when moderating for institutional quality, the findings show that the marginal impact of income inequality is negative for countries with low levels of institutional quality. The authors show that the rule of law and government effectiveness are effective moderators in terms of magnitude. Furthermore, the authors find that the sanding effect of income inequality is observed in developing economies, even when moderating for institutional quality.

The major limitation lies in the estimation of entrepreneurial activity, which is measured using new business formation. While this is commonly used, it focuses on formal entrepreneurial activities and overlooks the informal economy.

This study provides new empirical evidence on whether institutional quality can moderate and explain the puzzling link between entrepreneurial activity and income inequality.