Poor Lubrication Research Articles

Tribological behaviour of Ti3C2Tx nano-sheets: Substrate-dependent tribo-chemical reactions

MXenes, a newly emerging class of layered two dimensional (2D) materials, are promising solid lubricants due to their 2D structure consisting of weakly-bonded layers with a low shear strength and ability to form beneficial tribo-layers. This work aims at evaluating for the first time MXenes lubrication performance and tribofilm formation ability on different metallic substrates (mirror-lapped Fe and Cu discs). After depositing MXenes via ethanol (1 wt%) on the substrates, pronounced differences in the resulting substrate-dependent frictional evolution are observed. While MXenes are capable to reduce friction for both substrates after the full evaporation of ethanol, MXenes lubricating effect on Cu is long-lasting, with a 35-fold increased lifetime compared to Fe. Raman spectra acquired in the wear-tracks of the substrates and counter-bodies reveal notable differences in the friction-induced chemical changes depending on the substrate material. In case of Fe, the progressive failure of MXenes lubrication generates different Fe oxides on both the substrate and the ball, resulting in continuously increasing friction and a poor lubrication effect. For Cu, sliding induces the formation of a Ti3C2-based tribofilm on both rubbing surfaces, enabling a long-lasting lubricating effect. This work boosts further experimental and theoretical work on MXenes involved tribo-chemical processes.

Comprehensive analysis of properties of green diesel enhanced by fatty acid methyl esters.

This study systematically investigates the lubricating properties of bio-hydrogenated diesel (BHD), a synthetic diesel produced through biomass hydrogenation of vegetable oil. Despite having similar chemical properties to petroleum diesel, BHD has poor lubricating properties due to the removal of sulfur and oxygenated compounds during the hydrogenation process, which could damage the engine. To address this issue, fatty acid methyl esters (FAME) was added as an additive to BHD to enhance its fuel and lubricating properties. FAME is a polar molecule with good lubricating properties that adsorb on the surface to protect against wear. The study found that adding as little as 5% FAME significantly improved the lubricating properties of BHD. The wear scar diameter (WSD) decreased from 609 μm to 249 μm, and the average film was 94% with an average coefficient of friction of 0.138 by only 5% FAME addition investigated by High Frequency Reciprocating Rig with ISO 12156-1: 2018. This shows that blending FAME with BHD could reduce engine wear and improve its lubricating properties. Disc samples were analyzed using a Scanning Electron Microscope (SEM), OLS5100 3D laser microscopy, and Fourier Transform Infrared Microscopy (FTIR) to examine the worn surface both physically and chemically. An increase in the percentage of FAME addition to BHD resulted in a smoother worn surface, exhibiting reduced delamination and debris compared to pure BHD. This effect was attributed to the protective film formed by FAME. The study highlights the potential of FAME as an additive to enhance the lubricating properties of BHD and reduce engine wear.

Estimation of crack initiation and growth of hard coating by uniaxial tensile test and rotating cross-cylinders wear/friction test

Cold forming has required considerably superior hard coating on a die to manufacture net-shaped products. Especially, under poor lubrication conditions or a dry condition, the hard coating is indispensable for the success of manufacturing. Accordingly, the die has required the superior hard coating to prevent adhesion, reduce friction, and control wear. Recently, it has been also necessary to improve die life and product qualities under severe tribological conditions. However, the comprehension of damage such as cracking, flaking, and galling is insufficient for metal forming. This study focuses on initiation and growth of cracking in the hard coating. Assuming the hard coating is subjected to tensile stress, nominal stress, or frictional shear stress, the performances of typical four hard coatings are investigated by two tests. One is a uniaxial tensile test, and another is a rotating cross-cylinders wear and friction test. These tests are applied to estimate the mechanical performance of hard coatings: CrN, TiN, VC, and CrAlN. After the two test and analyses with detail observation, the CrAlN coating collectively exhibits the highest anti-cracking property of the tested four hard coatings.

Low Friction Achieved on Plasma Electrolytic Oxidized TC4 Alloy in the Presence of PAO Base Oil Containing MoDTC

Surface engineering is required to improve the poor lubrication performance of titanium alloys in many applications. In this study, an oxide coating with high-hardness was created on TC4 titanium alloy by using plasma electrolytic oxidation (PEO). The composition and structure of the PEO coatings were analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD), and Raman spectroscopy. The tribological properties of the PEO-treated TC4 were investigated in the presence of a polyalphaolefin (PAO) base oil with addition of molybdenum dialkyldithiocarbamate (MoDTC). The results show that the PEO-treated TC4 exhibits excellent lubrication performance in the presence of MoDTC. The oxide coating on the PEO-treated TC4 sample shows a tribo-induced catalysis effect enabling the decomposition of MoDTC to forms an effective lubricating film containing MoS2, resulting in reduced friction and wear.

Mesoscopic dynamic characteristics and RCF damage evolution of high-speed transmission gear in wind turbine

For the gears utilized in wind turbines, the main reason leading to malfunction is the crack initiation and propagation under cyclic loading. In the gear engagement process, the fatigue damage accumulates gradually and formulate visible microcrack if the fatigue parameter reaches to specified threshold. In order to simulate the fatigue evolution in wind turbine gears, a mesoscopic model is established, in which the Voronoi tessellation and cohesive elements are integrated, such that the crystal structure and grain boundary can be modeled. The dynamic stress distribution and fatigue evolution phenomenon are then investigated under different working conditions. The loading in the meshing region is simplified as moving load on a semi-infinite plane, so the shear stress distributions for per loading cycle are obtained. Furthermore, bilinear traction-separation law (TSL), Jump-in-Cycles (JIC) loading methodology and multi-axial fatigue criterion are involved to fulfill the damage accumulation simulation. As a result, the initiation location and propagation pattern of the fatigue crack are predicted, and the fatigue life curve is also obtained. Thereafter, the influence of wind speed and lubrication condition on fatigue damage evolution is also discussed. The results have shown that the wind loading mainly influences the magnitude of the maximum shear stress, whereas the contact width will determine the location of the maximum shear stress. When the whole fatigue evolution procedure is finished, the first two cracks initiate at the depth of 0.13 mm and 0.27 mm beneath the surface respectively, and then propagate into the substrate. Through comparative analyses of fatigue life curves, it can be concluded that higher wind speeds and poor lubrication conditions will reduce gear service life significantly.

LUBRICATING PROPERTIES OF POLYESTER OILS AND R404A REFRIGERANT MIXTURES UNDER STARVED LUBRICATION CONDITIONS

There has been a dynamic shift towards the use of ecological refrigerants in the refrigeration industry. Until recently, R404A was a quite commonly used HFC refrigerant for commercial refrigeration equipment, in both small and large systems resulting in the need to select appropriate compressor lubricants. In refrigeration compressors, the amount of oil in friction pairs in certain situations may be insufficient. In that event, starved lubrication conditions or lubrication only by refrigerant may occur. The article contains a methodical selection of test parameters for polyester oils allowing one to assess the lubricating properties of the mixtures of oils for refrigeration compressors and refrigerants under the conditions of poor lubrication. The article also includes the results of wear tests which allow one to evaluate the lubricating properties of oil-refrigerant mixtures under starved lubrication conditions for R404A refrigerant and polyester oils.

Laser Com-Texture on Ti6Al4V Surface for Lubricant Transportation to Improve Tribological Properties

Abstract Artificial joint materials often wear out due to poor lubrication, affecting their service life. A compound texture (com-texture) was prepared, to improve the spreading of lubricant at the friction interface and reduce the friction and wear of artificial joint pairs UHMWPE and Ti6Al4V. The com-texture was divided into rough and smooth parts on the surface. The rough area was a hexagonal convex texture with a texture ratio of 66%, and it was covered with a recoagulated layer left by laser processing to absorb and transport lubricant to the friction interface. The smooth area was a convex texture with a texture ratio of 85%, which was the friction contact area. The texture morphology of the rough region was characterized by SEM and laser focusing microscope. It was found that the edge of the texture was covered with recondensed mountains after laser processing and corroded micro-nano pits, which helped to prepare super-hydrophilic surfaces. Besides, the flow law of simulated body fluid (SBF) on a textured surface was explored, and the motion process was recorded by a high-speed camera. The results showed that the com-texture could transport SBF to the friction region smoothly and quickly. The friction test results indicated that the structure had improved tribological properties.

Preparation of polyethylene glycol brush grafted from the surface of nitrile butadiene rubber with excellent tribological performance under aqueous lubrication

The water-lubricated bearing will be in a state of poor lubrication when marine stern shafts operate under low speed and heavy load conditions, which could cause severe wear and vibration, endangering the stealth performance of underwater vehicles. In this study, the grafting of polyethylene glycol brush was carried out on the surface of nitrile butadiene rubber (PEG-g-sNBR) by “grafting from” method. Fourier-transform-infrared-spectroscopy, nuclear-magnetic-resonance, and scanning-electron- microscope results demonstrated that the PEG-g-sNBR brush was successfully synthesized, and the reactive site was found. Using a tribological test machine with a high-precision vibration acceleration sensor, the tribological behaviors of PEG-g-sNBR were studied under aqueous lubrication. The results showed that the coefficient of friction of PEG-g-sNBR was reduced by 73.4% at 100 rpm compared to pure NBR, its microscopic wear and vibrational energy were also lower than pure NBR. Moreover, the lubrication states were revealed by friction, wear, together with the complexity of friction-induced vibration signal time series, and a lubricating film was formed on the friction surface of PEG-g-sNBR at lower rotational speed. In addition, the PEG-g-sNBR could work stably for 12 h at 300 rpm, and still maintain good tribological performance.

Low coefficient of friction hydrogels with fast self-healing properties inspired by articular cartilage

Hydrogels have potential applications in artificial cartilage, soft robotics, and tissue engineering, owing to their excellent wettability, flexibility, and biocompatibility. However, poor lubrication and fragile mechanical properties often limit their applications. In nature, articular cartilage and cornea are coated by brush-like mucous to realize lubrication. Herein, we present a nature-inspired strategy for improving the lubrication properties of hydrogels. A model hydrogel is prepared using poly(vinyl alcohol), borax, and poly(ethylene oxide). The PEO forms a brush-like hydrophilic lubricating layer on the surface of the hydrogel. Thus, the PVA/Borax/PEO hydrogel exhibits a low coefficient of friction (0.08). In addition, after healing for 30 s in the air, the PVA/Borax/PEO hydrogel with a dynamic borate bond exhibit a 93 % cure in strength. Moreover, PVA/Borax/PEO hydrogels also exhibit excellent underwater self-healing ability. With the combination of lubrication and self-healing properties, the PVA/Borax/PEO hydrogels have great potential for use in a wide variety of fields.

Effect of Working Pressure on Tribological Properties of Ce-Ti/MoS2 Coatings Using Magnetron Sputter

In preparing MoS2-based coatings by magnetron sputtering, the working pressure of the vacuum chamber directly affects the number and kinetic energy of sputtering particles, which causes a difference in coatings structure and performance. In this paper, MoS2 composite coatings with Ce and Ti binary doping were prepared by unbalanced magnetron sputtering technology, and the variation of composition, structure, and tribological properties of Ce-Ti/MoS2 coatings under different working pressures was studied. The results demonstrated that Ce and Ti doping improves pure MoS2 coatings. The Ce-Ti/MoS2 coatings reached the hardness of 9.02 GPa and the friction coefficient of 0.065 when working pressure was at 0.6 Pa. It was also observed that the deposition efficiency and wear rate reached the optimal value at 0.9 Pa. With the increase of working pressure, the columnar structure of the coating was coarse due to the change of kinetic energy and quantity of particles in the chamber. The intensity of the MoS2 (002) diffraction peak decreased, which eventually led to a poor lubrication effect and aggravated wear. This study provides technical guidance for preparing metal-doped MoS2 composite coatings with excellent mechanical and tribological properties.

Recycling and Reusing Aspect of Green Circular Economy to Overcome Engineering and Environmental Challenges

The environmental issues of mineral oil-based drilling muds and additives in spite of their excellent technical performance such as good lubricity and high wear protection characteristics and the technical issues of water-based drilling muds such as the poor lubricity and wear resistance characteristics in spite of their excellent environmental traits require the development of high performance water-based drilling muds to overcome the current as well as the future drilling engineering and other oil and gas field challenges. Hence, several value-added green products have been developed adopting the recycling and reusing aspect of green circular economy of waste cook oil (WCO) to develop eco-friendly fluid additives and demonstrate their applications to explore and exploit oil and gas resources without any damage to the terrestrial, coastal and the marine environments and the ecosystems. Analyses of technical performance of the WCO derived green products with respect to the equivalent commercial products indicate similar or superior technical performance with the added benefit of no environmental impact. Hence, the recycling and reusing of the WCO provide a sustainable circular economical route for ecofriendly product development to overcome the technical and the environmental challenges simultaneously. It also provides a potential avenue for the growth and development of local, regional, national and global industries and infrastructures, development and creation of new job opportunities for the local, regional and the global communities, especially in developing and under-developed countries to create a positive societal and economic impact. Although this paper highlights mainly the oil and gas industry applications, WCO has huge potential for other industrial applications to overcome the technical problems without any negative environmental consequences. It can be used as a sustainable raw material for the development of a large variety of value-added green chemicals and polymers such as plasticizers, binders, surfactants, eco-greases, biopolymers, etc for other industrial applications. The renewable, sustainable and locally available source of the raw material have high potential to bring long-term stability to the oil and gas field additive supply chain for continuous and uninterrupted drilling and production operation. The paper highlights the applications of several WCO-based value-added products to overcome the technical and environmental challenges faced by the oil and gas industry.

Understanding and treatment of severe flange wear of metro train wheels

Urban rail transit usually contains many small radius curved tracks, and wheel flange wear is prominent, which greatly reduces the service life and increases the maintenance and replacement costs of wheelsets. Two metro lines in Shanghai of China had suffered from severe flange wear since 2017, and the flange wear rate increased gradually over the next three years. This paper presents the understanding and treatment of severe flange wear through field measurement and numerical simulation. The investigation results indicated that the key factors causing severe flange wear were poor rail gauge face lubrication, the use of a low conicity wheel profile for trains running on the two metro lines containing many small radius curved tracks, and the lack of timely maintenance of low rail profiles. Three countermeasures were proposed to mitigate wheel flange wear, which were evaluated through wheel–rail matching analysis and wheel wear prediction. Then, two countermeasures, i.e. improving rail gauge face lubrication and employing the LM-30 wheel profile, were verified through field tests.

Tribological characteristics and mechanism of nitrile butadiene rubber coated with typical liquid lubricants

When marine stern shafts operate under low speed and heavy load conditions, the metal shaft and water-lubricated bearing will be in a state of boundary lubrication or even dry friction. Poor lubrication can cause severe wear and friction-induced vibration, endangering the stealth performance of underwater vehicles. In this study, several typical liquid lubricants, including liquid paraffin, tung oil (TO), dimethyl silicone oil (DSO), ionic liquid (IL), and hexamethylene diisocyanate (HDI) were selected as the surface coatings for nitrile butadiene rubber (NBR). Using a tribological test machine with a high-precision vibration acceleration sensor, as well as scanning electron microscopy (SEM) and other techniques, the tribological performance and mechanisms of the NBR samples coated with different lubricants were studied under various working conditions. The results showed that the liquid lubricant significantly reduced the coefficient of friction of the NBR at high rotational speeds by over 92.2%. The sample coated with HDI showed obvious tribochemical wear, and coating with the rest of the liquid lubricants decreased the specific wear rate of NBR. According to the friction-induced vibration signals, we found that an increase in loading aggravated friction-induced vibrations, and the vibrational energy was mainly concentrated in the low frequency range. The liquid paraffin and TO coatings barely changed the vibration characteristics of the NBR, while the other three lubricants produced more friction-induced self-oscillations. In conclusion, compared to the other liquid lubricants, TO exhibited the best tribological performance. The finding of this study further our understanding of the friction and vibration behaviours of polymer materials, providing a reliable basis for designing composite materials with good lubrication and vibration damping performance.

Assessment of energy consumption, carbon emissions and cost metrics under hybrid MQL-Dry ice blasting system: A novel cleaner production technology for manufacturing sectors

Modern industries are seeking innovative and clean cooling techniques in the machining domain to reduce the cost and environmental impact of manufacturing. To diminish the environmental impact of machining, cryogenic and minimum quantity lubrication (MQL) are recent known cooling/lubrication techniques to determine a perfect alternative to mineral-based emulsion cooling. The cryogenic has superior cooling capabilities and poor lubrication and MQL is vice versa. In this endeavor, a new hybrid MQL-dry ice blasting lubri-cooling technology is proposed in machining as eco-benign technology to investigate sustainability as well as machinability metrics in the milling of AISI-52100. The findings have shown that cutting speed and cooling/lubrication showed the most substantial effect on machinability and sustainability metrics. The experimental findings showed that the cutting speed has more significant effect on specific energy consumption, carbon emission, and machining cost. At highest level of cutting speed (300 m/min), processing time, specific energy consumption, carbon emission and surface roughness was 2.6%, 2.3%, 2.35%, and 22.6% less under hybrid dry ice blasting compared to MQL medium. The shares of the standby time in total energy consumption, carbon emission, and total cost are noticed to be dominant. The hybrid dry ice blasting shared a small fraction of the total cost compared to MQL, and dry ice blasting.

Structural Design and Lubrication Properties under Different Eccentricity of Magnetic Fluid Bearings

As a lubricant, the viscosity of the magnetic fluid changes with the external magnetic field, which improves the bearing capacity of the oil film and hence the lubrication effect, and has a promising application in bearings. Based on the Roelands viscosity theory, the Shliomis model is used to derive the viscous temperature, viscous pressure, and magnetic viscosity characteristics of magnetic fluids under the influence of an applied magnetic field, and further proposes a structural model of magnetic fluid lubricated bearings to investigate the pressure, temperature and magnetic intensity distribution of magnetic fluids under different eccentricity conditions. The results show that the viscosity of the magnetic fluid decreases exponentially with increasing temperature, rises linearly with increasing pressure, and increases and stabilizes with increasing magnetic induction strength. Because the minimum film thickness point is the dividing point between the convergent wedge and the dispersed wedge, the pressure distribution of the lubricant film separates high pressure from low pressure at the minimum film thickness, and the differential pressure increases with the increase in eccentricity. The temperature distribution of the high-temperature zone is mainly distributed in the middle of the film, and the minimum film thickness zone and the maximum temperature increases with the increase in eccentricity. The magnetic intensity distribution of the strong magnetic field is mainly concentrated in the minimum film thickness zone, and the magnetic induction intensity increases with the increase in eccentricity. The results of this study have certain research significance for solving the problem of the poor lubrication effect of bearing lubricant due to high temperature.

Prevalence of Sexual Dysfunction in Women With Depression: Need for Psychosexual Health Promotion Approach

Introduction: Depression-associated sexual dysfunction (SD) is a pervasive and ignorant problem among the general population. The antidepressant used to treat depression may further alter the sexual response cycle in one way or another. This study aims to assess the prevalence of SD in females with major depressive disorders and the effects of antidepressant therapy after 4 weeks of follow-ups. Material and Methods: In a prospective observational survey, 94 women diagnosed with depression and on antidepressant therapy were purposively enrolled. Female Sexual Functioning Index (FSFI) and Montgomery-Asberg Depression Rating Scale (MADRS) are administered at baseline and 4 weeks of treatment to measure sexual function and depression changes. Relevant descriptive and inferential statistics are applied to compute the results. Results: The mean age of the participants was 35.87 (±5.10) years. A total of 95.7% of participants showed SD at baseline assessment. There was a significant difference (31.87 vs 18.51, P < .001) in depression from baselines to 4 weeks after antidepressant therapy. Further, a significant negative correlation was reported between the MADRS scores and the scores of arousals (r = −0.396, P < .001), lubrication (r = −0.453, P < .001), orgasm (r = −0.342, P < .001), satisfaction (r = −0.407, P < .001), pain (r = −0.362, P < .001), and total domains of FSFI (r = −0.412, P < .001) after 4 weeks. Using cut-off scores of different areas, decreased sexual desire was reported in 97.9%, poor vaginal lubrication (100%), a problem with arousal (100%), reduced satisfaction (96.8%), reduced ability to achieve orgasm (100%), and pain during sexual intercourse in 100% of the participants. Conclusions: There is a high prevalence of SD in women with depression. There is a marked improvement in depression at the end of 4 weeks. However, sexual function status remains unchanged and indicates the need for time to improve, suggesting different study designs.

Oil film lubrication state analysis of piston pair in piston pump based on coupling characteristics of the fluid thermal structure

The axial piston pump will be seriously damaged when the poor oil film lubrication. Therefore, considering the influence of hydraulic oil viscosity on oil film pressure and oil film temperature, oil film heat transfer to the piston and elastic deformation caused by piston thermal expansion, a fluid thermal structure coupling model of piston pair of axial piston pump was established. An experimental platform was built to measure the oil film characteristic data throughout the cycle, and the multi-physical field test, including temperature, pressure and thickness at multiple locations of the oil film of the piston pair was realized. The effects of oil temperature, spindle speed and load pressure on the lubrication of piston pair were studied and analyzed. The working condition parameter range corresponding to the significant reduction of oil film lubrication performance was obtained, which provides a basis for predicting the lubrication failure of the piston pump.

Machine learning calculation model for hydrodynamic lubrication characteristics of a miter gate bottom pivot

The bottom pivot is a vital support device in the miter gate but often subject to poor lubrication and wear failures. Calculating the hydrodynamic lubrication characteristics of the bottom pivot is a complex three-dimensional (3D) problem, and most of existing models adopt simplified assumptions to reduce the calculation difficulty. To solve this issue, this work develops a 3D model to calculate the hydrodynamic lubrication characteristics of the miter gate bottom pivot. The finite difference method is used to solve the oil film thickness and pressure distribution based on the spherical coordinates Reynolds equation. The component forces in three directions are calculated from the pressure distribution and compared with the theoretical values to generate the calculation difference. Then, the genetic algorithm (GA) is used to minimize the difference to determine the optimal initial parameters for the 3D model. The analysis results show that the calculation accuracy can be significantly improved by using the optimal initial model parameters. When our initial pressure is 5.64MPa, the results meet the engineering accuracy requirements.

Tribological Properties of Different Carboxylate in Water-Glycol Hydraulic Fluid

Conventionally, carboxylic acid salts are widely applied as anti-wear additives for water–glycol (W/G) hydraulic fluids. Here, Min-Traction Machine (MTM) was employed to evaluate the friction properties of four carboxylates in W/G fluid. The results indicate that undecylenate salt (CN-3) exhibits the best antifriction capability and the friction coefficient nearly remains stable when its concentration increases from 3 wt% to 6 wt%. However, ball-on-disc tribology tests show that CN-3 as a single lubricant additive cause poor lubrication under severe condition like a high load of 125 N. Fortunately, the combination of CN-3 and a water soluble heterocyclic compound (COMB) lead to the outstanding antiwear and friction-reducing properties. The possible reason is ascribed to the formation of more stable tribofilm containing FeS2 and carbon structures according to XPS analysis of the worn surfaces. Furthermore, a vane pump test was conducted to confirm the results of the simulating tests. The W/G hydraulic fluid formulation based on COMB as the antiwear package performs well in the pump test, giving rise to only slight pump wear loss. The results of the pump test and the simulating test are consistent with each other. Meanwhile, the W/G hydraulic fluid possesses excellent other physic-chemical properties and meets the specification of ISO 12922 requirement.

Machinability Investigation of Nitronic 60 Steel Turning Using SiAlON Ceramic Tools under Different Cooling/Lubrication Conditions.

The machining of nickel-based super alloys is challenging, owing to the generation of high cutting temperatures, as well as difficulty in maintaining dimensional accuracy and minimizing surface roughness, which compels the use of cutting fluids for reducing these issues due to efficient cooling/lubrication strategies. The present work investigates the comparative performance of four cooling/lubrication techniques: dry cutting, wet, minimum quantity lubricant (MQL) and compressed-air modes in turning Nitronic 60 steel using a new-generation SiAlON ceramic inserts. Several machinability parameters were analyzed for performance evaluation. For this purpose, 16 cycles of turning trials were performed based on Taguchi’s L16 orthogonal array experimental design by varying cutting conditions and lubrication modes. MQL exhibits beneficial effects as compared to the other lubrication conditions concerning low cutting force, improved surface finish, decreased cutting temperature, longer tool life, and lower white layer thickness on machined surface. Burr formation on the saw-tooth chip surface, as well as friction, greatly influenced the tool flank wear due to improper cooling and poor lubrication approach in dry, wet, and compressed-air-cooled machining environments in comparison to MQL-machining. From an economical perspective, the tool life in MQL machining improved by 11%, 72%, and 138% in the comparison with flooded, compressed-air, and dry conditions, respectively. The results of the study demonstrate that using the MQL system can help with heat extraction capability, and provide some promising outcomes.