Abrasive Forces Research Articles

A Study on the Mechanism by Which Graphene Oxide Affects the Macroscopic Properties and Microstructure of Abrasion-Resistant Ultra-High-Performance Concrete (UHPC)

To further enhance the abrasion resistance of UHPC in demanding abrasion environments, this study investigated the effects of graphene oxide (GO) on the workability, mechanical properties, and abrasion resistance of UHPC. Utilizing 27Al Nuclear Magnetic Resonance (NMR), 29Si NMR, microhardness, and BET analysis, the study analyzed the mechanisms through which GO influences UHPC’s microstructure in terms of abrasion resistance. Additionally, molecular dynamics simulations were employed to examine the mechanisms by which GO enhances UHPC’s abrasion resistance at the nano and micron scale. The findings show that an optimal amount of GO can improve the mechanical properties and abrasion resistance of UHPC. When 0.03% of GO (by cementitious material mass) was incorporated, the impact on workability was minimal, yet compressive strength increased by approximately 1.80%, flexural strength by 3.02%, impact wear resistance by 1.78%, the abrasion loss rate decreased by 10.01%, ultimate impact energy increased by 1.76%, and the toughness index improved by 10.10%. GO enhances abrasion-resistant UHPC primarily by increasing hydration, refining pore structure, and improving the microstructure of the interfacial transition zone. While GO increases the hydration degree of the UHPC matrix, it does not alter the silicate chain in C-A-S-H gels within the paste. Additionally, the incorporation of graphene oxide can refine the pore structure of the UHPC cement paste and improve the microstructure of the interfacial transition zone (ITZ) between the aggregate and the cement paste. The molecular dynamics simulation reveals that, under abrasive forces, GO forms strong, stable chemical bonds with the C-A-S-H base atoms, significantly enhancing the abrasion resistance of C-A-S-H.

Negative expansion induced anti-abrasive self-cleaning coatings for enhancing output of solar panels

Pollutants on solar panels impede sunlight absorption, leading to a reduction in their output power. Superhydrophilic coatings exhibit effective self-cleaning performance as droplets fully spread on their surfaces. However, one challenge for the commercial development of transparent superhydrophilic coatings is poor abrasion resistance. Frictional heating on the coatings’ surface causes the abrasion force to rise uncontrollably, which in turn causes the coatings to either fracture or wear catastrophically. A promising alternative is utilizing novel adaptive materials with a negative thermal expansion coefficient in the coating. The compressive stress on the surface of the coating with negative expansion will enhance its abrasion resistance. Here, we demonstrate a method to achieve compressive stress in the coating by incorporating halloysite (HNTs) nanotubes due to their negative expansive behavior. Hydrolyzed tetraethyl orthosilicate (TEOS) combines HNTs nanotubes with SiO2 nanoparticles, thus forming a hard nano-composite unit. Meanwhile, amino resin and acrylic resin as adhesives participate in constructing the coating’s three-dimensional network structure. The surfactant sodium alkenyl sulfonate (AOS) endows the coating with superhydrophilicity. As a result, the nano-composite (NC) coating shows superior superhydrophilicity and anti-abrasive properties. The NC coating retains good hydrophilicity and self-cleaning properties after 2000 cycles of Taber abrasion loading 250 g or 1000-line cycles of steel wool friction loading 500 g. The self-cleaning performance of the robust NC coating on solar panels can improve the output power by up to 33.65 % after 296 days. Hence, introducing shrinkage components such as HNTs may provide a general strategy for developing robust superhydrophilic coatings.

The Effect of Weathering Conditions in Combination with Natural Phenomena/Disasters on Microplastics’ Transport from Aquatic Environments to Agricultural Soils

Concern over microplastics (MPs) in the environment is rising. Microplastics are generally known to exist in aquatic settings, but less is known about their occurrence in soil ecosystems. When plastic waste builds up in agricultural areas, it can have a negative impact on the environment and food sources, as well as have an indirect effect on all trophic levels of the food chain. This paper addresses the relationship between microplastics and the management of plastic waste, which contributes to their accumulation, and it describes the sources and the movement processes of microplastics in agricultural soils as a result of natural events and disasters. Evaluating the impact of weather on coastal microplastic contamination is critical, as extreme weather events have become more frequent in recent years. This study sheds light on how weather patterns affect the dispersion of plastic waste in terrestrial habitats, including the impacts of seasonality and extreme weather. According to the results of this review, typhoons, monsoons, rainfall, and floods contribute significantly more microplastics to the surface sediment through surface runoff and wind transport, particle redistribution caused by agitated waves, and fragmentation under intense abrasion forces. Severe weather conditions have the potential to disperse larger and more varied kinds of microplastics.

Wear properties of acrylic dental material 3D printed via digital light processing: Influence of process settings

The digital light processing (DLP) is one of the additive manufacturing methods, renowned for its precision and efficiency, with wide-ranging applications, notably in dentistry. Recent advancements in photocurable resins and DLP technologies have profoundly influenced dentistry. Despite their common clinical use, some resins lack comprehensive empirical studies on their mechanical and wear properties. In addition, analyzing the wear resistance of dental materials manufactured via additive manufacturing is imperative for ensuring their prolonged durability and dependability within authentic oral settings. Profound comprehension of the manner in which these materials withstand abrasive forces ensures their capability to withstand the mechanical strains imposed by chewing and brushing activities, thereby preserving their structural robustness and functional efficacy. The aims of this research are to investigate the effect of DLP process parameter setting, including: layer thickness, exposure time, and light intensity, on the wear resistance of acrylate dental materials. Using a pin-on-disc apparatus, wear tests were conducted. A steel pin, with a diameter of 5 mm, moved linearly over the specimen surface under the speed of 15 m/min and applying a force of 20 N. Scanning electron microscopy (SEM) was employed to examine the worn surface and wear mechanisms. Additionally, Analysis of Variance (ANOVA) was utilized to assess parameter effects and correlations. The findings indicate that parameter configurations exert a considerable influence on wear resistance and represent a cost-effective avenue for enhancing the wear resistance of components produced through additive manufacturing. The results revealed a direct correlation between resin curing and wear resistance, with inadequate or excessive curing leading to increased wear rates. The samples with a layer thickness of 25 µm, exposure time of 7.2 s, and light intensity of 160 W/m2, exhibited the lowest wear rate (11 × 10−2 mm3/min). Conversely, samples with a layer thickness of 100 µm, exposure time of 2.8 s and light intensity of 160 W/m2, demonstrated the highest wear rate (55 × 10−2 mm3/min). Additionally, the analysis of variance confirmed correlations between parameters, noting a negative correlation between intensity and time parameters, and positive correlations among other inter-parameter correlations.

Comparison of Surface Hardening Processes Applied to AISI 5140 Steel withSide Load Test

AISI 5140 Tempered steel is generally preferred in the joints of vehicles. This steel is a material with high toughness. Its usage areas are quite wide. The purpose of the surface hardening process is to increase the wear resistance of surfaces exposed to wear, as well as to increase the fatigue life of the part and increase corrosion resistance. Since the inner parts of the parts are not affected by surface hardening, the resistance to impacts increases and therefore the formation of cracks on the surface is delayed. Surface hardening processes delay the formation of cracks on the surface and extend fatigue life. In this study, a comparison was made between a part with induction surface hardening, which is one of the methods in which the chemical composition of the surface is not changed, a part with nitration, which is one of the methods in which the chemical composition is not changed, and a part with standard reclamation heat treatment. Side Load test, a static testing method, was used for this comparison. In the Side Load test, the samples were compressed from the conical region and a vertical load was applied corresponding to the center of the joint. According to the results obtained in the tests, the sample with Induction surface hardening process withstood 64500 N, the sample with Nitriding heat treatment withstood 54500 N and the sample with Standard tempering heat treatment withstood 50200 N. According to the results obtained, the sample with the highest durability rate is the sample whose surface was hardened by induction.

Cryogenic assisted femtosecond laser ablation of polycrystalline diamond

Polycrystalline diamond (PCD) tools have gained popularity in machining industry ascribed to superior surface quality and durability at elevated temperature and abrasive forces. A major obstacle for high-speed PCD machining is the excessive heat production that transcend the heat dissipation capacity, resulting in reduced tool life and performance. Surface microstructures on PCD tools can improve thermal performance by increasing the heat transfer area and reducing the thermal contact resistance, therefore enhancement in durability and operation. Femtosecond laser processing is a non-contact, high precision and low thermal effect technique for creating superior quality microstructures. This study investigates the effects of cryogenic-assisted femtosecond laser processing in improvement of diamond microstructures quality. Initially the effects of different laser settings on the performance of the process were investigated by conducting single-factor experiments at ambient conditions. Later, the effects of cryogenic assistance on diamond irradiation, surface quality and chemical changes were investigated utilizing laser confocal scanning microscopy (LCSM), scanning electron microscopy (SEM) and Raman spectroscopy. Cryogenic laser ablation had no effect on the diamond removal rate, on contrary improved the surface quality by reducing the surface roughness and graphite disorderliness. This study reports superior surface quality finish for cryogenic assisted laser ablation than ambient conditions therefore it is recommended to irradiate PCD at low temperatures.

Effect of mechanical activation of natural filler on the properties of elastomeric composites

In this paper, the structure and surface properties of a mechanically activated filler based on rice processing products were studied. The particles of the natural filler were mechanically activated on a vibrating and planetary ball mill with different impact times and abrasion forces. The particles of the filler were characterized by laser diffraction, scanning electron microscopy and X-ray phase analysis. To study the possibility of using rice production waste in rubber products, model elastomeric compositions were made on laboratory rollers according to a standardized method with a complete replacement of industrial low-strength carbon black. It was determined that the mechanical activation of a natural filler in a planetary mill leads to an improvement in the physical-chemical parameters of the particle surface (the average size of the aggregates decreases by 2.2 times, the specific external surface increases by 3.1 times), increases the interfacial interaction of the filler with rubber (up to 33.9%), increases the Mooney viscosity values of rubber mixtures, increases resistance rubber to premature vulcanization (by 23.1%–61.5%) and leads to the production of vulcanizates with higher elastic strength indicators.

Study on Grinding Behavior Characteristics under Low-Speed Grinding Condition

In order to explore the crushing mechanism of minerals, this paper attempts to eliminate the throwing effect of media and study the grinding characteristics of minerals only under the action of abrasion force. In this paper, the method of removing the throwing state of media is to adjust the mill to a lower rotational speed, so that the grinding media are all in a cascading state. Three single-component pure minerals, quartz, pyrrhotite, and pyrite, commonly found in complex ores, were selected as research objects to study the grinding behavior characteristics of the three minerals only under the force of abrasion. The effects of mineral species, feed-particle sizes, grinding time, and other factors on the particle-size distribution and product-generation rate of grinding products are studied. The results show that from the particle-size distribution of grinding products, the yield of coarse particles is the highest, while the yield and t10 value of other fine particles are very low. The feed-particle size and the hardness of the mineral sample affect the grinding behavior. The product particle size is mainly 0.71 times the feed-particle size, and the other fine particle sizes generated are less than 0.5 times the feed-particle size.

Effect of tooth brushing simulation on the surface properties of various resin-matrix computer-aided design/computer-aided manufacturing ceramics.

The purpose was to investigate the alterations in surface properties of different resin-matrix CAD/CAM ceramics following tooth brushing simulation (TBS) and compare them with a direct resin composite and a glass ceramic CAD/CAM material. Four resin-based CAD/CAM restoratives (Brilliant Crios-BR, Lava™ Ultimate-LV, Grandio Blocs-GR and Shofu Block HC-SH), a leucite-reinforced glass ceramic (IPS Empress® CAD-EC) and a resin composite (Filtek™ Z250-FZ) for direct restorations were tested. In particular, surface loss, hardness, roughness and morphology were investigated utilizing confocal microscopy, scanning electron microscopy and nanoindentation tester. TBS was conducted for 4 × 15 min on the surface of the samples and then the changes in their surface properties were evaluated. After TBS, all the experimental groups exhibited surface loss to different extent. FZ and BR presented the highest surface loss, while EC and GR the lowest (p < 0.05). Regarding surface roughness, all the tested materials exhibited increase after TBS (p < 0.05), except LV (p = 0.099). EC presented the lowest Sa values, while FZ and BR the highest (p < 0.05). Changes in surface morphology were in compliance with the results of surface roughness and also surface hardness was correlated with surface loss. The tested resin-matrix CAD/CAM ceramic restorative materials showed a competent behavior against abrasive forces applied during TBS. Surface loss and roughness changes were material dependent and superior compared to a resin composite for direct restorations, while in comparison with a leucite-reinforced glass ceramic exhibited inferior properties. Tooth brushing affected differently the surface of the tested restorative materials. However, the abrasive wear that was induced was negligible. Clinical studies are necessary to ascertain if there is clinical significance of these surface alterations that may demand repair of such restorations.

Effect of wet ball milling on copper ore flotation by fractal geometry

ABSTRACT One of the important parameters in mineral processing is particles morphology, which is a function of the comminution mechanism. Particles morphology has considerable impacts in flotation process. Variations in particles morphology have been studied by different methods, including fractal geometry. This study aims to investigate the ball milling effect on particles flotation using fractal dimension, in which the calculations in the particles morphology has been made using the step-length method. The ore sample of under-investigation was a copper ore. The examined parameters include grinding time, ball load, and solid weight percentage. The collected fractal dimensions for particles ranged from 1 to 2, which is according to the principle of fractal geometry. Based on the results, low (30 minute) or high (50 minute) grinding time reduces fractal dimension and recovery because low grinding time is resulted in a coarse grain product while high grinding time is resulted in fine particles with spherical shapes. If balls load is high (8710 gr), predominant comminution force turns to an abrasive force are resulted in fine and spherical particles due to an increase in the accumulation volume. When the ball load decreased (4690 gr), the coarse particles were produced. Fractal dimensions and recovery are decreased in both cases. Low (40%) and high (60%) solid weight percentages are resulted in ineffective comminution, producing a coarse grain product. As a result, fractal dimensions and recovery are decreased. There is a direct correlation between recovery and fractal dimension.

Mechanical stability of newly-formed soil macroaggregates influenced by calcium concentration and the calcium counter-anion

Aggregate stability, an indicator of soil structural resistance to mechanical forces, depends upon the strength of binding substances within the aggregate. Adhesion of calcium (Ca2+) oxide-based compounds to soil primary particles is expected to create stable aggregates. This occurs because Ca2+ will flocculate clay and silicate minerals, and precipitate with carbonate or as Ca2+ hydrates (calcium-silica-hydrate, calcium-aluminium-silica hydrate), filling the air-filled pore space with solids that resist mechanical rupture. The objective of this work is to determine how the Ca2+ concentration, as well as the type of Ca2+ counter-anion (CO32−, OH−), affects the binding strength of newly formed macroaggregates (0.84–3 mm in diameter) that resist abrasive force. Soil from six arid desert locations was ground (<0.125 mm) and mixed with solutions containing 40 to 2560 mg Ca L−1 made with CaCO3 or Ca(OH)2. The stable aggregate diameter of newly-formed macroaggregates was based on their resistance to abrasion in an erosive chamber. Stable aggregate diameter tended to increase as the log of Ca2+ concentration increased and was similar in the presence of the CO32− and OH− counter-anions. Larger stable aggregate diameter formed as the Ca2+ solution concentration increased from 0.04 to 2.6 g Ca2+ L−1, using CaCO3 or Ca(OH)2 solution, and was enhanced when the soil contained 48–170 g clay kg−1 dominated by montmorillonite clay minerals. We observed Ca2+ accumulation on Al- and Si-rich surfaces, which may indicate formation of flocculants < 20μ m, as well as soil particle adhesion within newly-formed macroaggregates by calcium carbonate or calcium silicate hydrate precipitates. This work highlights the importance of calcium oxide binding for macroaggregate stabilization in arid desert soils.

Research on the Relationship between Multi-Component Complex Ore and Its Component Minerals’ Grinding Characteristics under Abrasion Force

The relationship between the grinding characteristics of polymetallic complex ore and its component minerals, pyrrhotite, sphalerite, and quartz, under the action of abrasion was studied, based on batch grinding experiments and theoretical analysis methods of selective grinding. The results show that when the polymetallic complex ore was subjected to the action of abrasion, the crushing effect of ore was enhanced by the existence of sphalerite, that is, sphalerite plays a positive role in the crushing effect of ore. The crushing effect of ore was reduced by the existence of pyrrhotite and quartz, that is, pyrrhotite and quartz plays a negative role in the crushing effect of ore. In addition, the sphalerite had a more prominent effect on the grinding characteristics of the ore. The grinding speed of ore and its component minerals decreased exponentially with the grinding time, and the instantaneous grinding speed of 0 min was negatively correlated with the feed sizes. The rapidly decreasing trend of the grinding speed reached the threshold when the grinding time reached 4 min. The results can provide some theoretical guidance for the study of grinding characteristics of multi-component complex ores in subsequent grinding process.

Analysis of the kinetics of the eyelids of little owl Athene noctua

AbstractThis study gives a comprehensive description of eyelids movement in little owl and discusses the impact of some surrounding conditions in their kinetic performance. The present study used the video's recording technique to record the kinetic activity of eyelids, besides the anatomical and histological studies of the eyelid's structure. The fundamental eyelid movements can be uniquely and reliably characterized by their anatomical relationship that was confirmed via video recording for their kinetic activity. The levator palpebrae muscle is considered a main generating motor for the upper eyelid; in the little owl, this muscle splits into multiple directions and is distinguished from the levator palpebrae superioris (Lps) and the levator anguli oculi (Lao) muscle. That anatomical pattern of insertion increases the movement of the upper lid. On the other side, the contraction of depressor palpebrae inferioris (Dpi) muscle and the active upward forces of levator palpebrae muscle help in increasing the opening of the eye's fissure. However, the closure process is produced from the passive downward forces and relaxation of the levator palpebrae superioris (Lps), levator anguli oculi (Lao), and depressor palpebrae inferioris muscle, as well as the contraction of retractor anguli oculi lateralis (Raol) and medialis (Raom) muscle. The present results also recorded that nictitating membrane's (Nm) movement is reversely proportionate to the level of kinetic of other eyelids. The mobility of Nm in little owl occurs under the effect of artificial external stress. These anatomical data and sequence video recordings have confirmed that the upper eyelid moves more compared to other eyelids. The authors also suggest that the mobility of eyelids may get stimulated through external pressure force of some surrounding structure like the periorbital sheet. Also, the histological study exhibited that the structure of two eyelids is very similar in the little owl and the variability is showing in the number of cell layers that forms their epithelium of skin and palpebral surfaces, the distribution of pigment granules, and degree of keratinization on their surface. That variability in the histological characters of eyelids may counteract the abrasive forces occurring during the opening and closing processes.

Evaluation of the mechanical resistance of rheophores of the means of initiation for explosive’s materials, on the basis of the resistance to abrasion determined with the OPVA 10 specialized equipment

The scientific paper presents the synthesis of research results undertaken to develop the technical and methodological infrastructure for assessing the safety of means of initiating explosives, on the abrasion resistance of rheophores of electric detonators, in order to increase the safety of their use. The state-of-the-art OPVA 10 equipment is used to test the ability of rheophores insulation to withstand the abrasion forces that may occur during normal use. This equipment with a programmable automatic ensures the testing of the rheophores of the electric detonating staples to determine the abrasion resistance under the operating conditions provided by the harmonized European standard EN 13763-4 and the technical specification of the manufacturer, the operating temperature of this equipment being between 10 ÷ 30 °C ensuring at the highest level the fulfillment of the technical requirements imposed by the European and international regulations in the field.

Influence of Machining Conditions on Friction in Abrasive Flow Machining Process – A Review

This paper presents a rage of variable machining factors which influence substantially friction directly or by the abrasive media wear developed in the cutting zone. Abrasive flow machining is method of machining surfaces of complex holes and curved surface. In the case of traditional stream treatment methods abrasive (AFM) it is difficult to obtain a uniform roughness radial decomposition during polishing complicated openings, which results from uneven distribution of abrasive forces. The group of direct factors include the work piece materials and abrasive media, changes in the fluid pressure, number of flow cycles, the medium flow frequency. In addition, it was proposed modifications in the amount and size of grains abrasives filling the abrasive medium to increase the value of the grain pressure force on the surface to be processed and obtained an even surface of complex holes in the process AFM processing. Special attention was paid to the abrasive media wear evolution and its pronounced effect on changes of the contact conditions. The experiment results also confirm that the rise in the medium flow frequency during the process will not affect the roughness changes work piece surface.

From bottle to microplastics: Can we estimate how our plastic products are breaking down?

Microplastics (MPs) have become an emerging new pollutant of rising concern due to the exponential growth of plastics in consumer products. Most MP and nanoplastic pollution comes from the fragmentation of plastics through mechanical stress, chemical reactions and biological degradation that occurs during use and after disposal. Models predicting the generation and behavior of MP in the environment are developing, however there is lack of data to predict the rates of MP generation as a function of the abrasive forces. A method to deliver scalable, quantitative release rates of MPs during mechanical stress throughout a plastic's life cycle (e.g., sanding, chewing, river and ocean disposal) is described. A custom abrasion machine was built with features to provide data to calculate power input. The generation rate of MPs through abrasion was tested for the following 3D printed polymers: polylactic acid (PLA), polycarbonate (PC), thermoplastic polyurethane 85A (TPU), polyethylene glycol terephthalate (PETG), high-impact polystyrene (HIPS), and nylon. Each material underwent tensile strength material tests to identify which mechanical properties drive their abrasion rate. Abrasion rate was not observed to correlate to macroscopic mechanic properties. Results indicate that the order of abrasion from most to least were HIPS, nylon, PC, PLA, PETG, and then TPU. This study will help comprehend and provide data to understand generation rates of MPs from consumer plastic products and macro-plastic debris. This will be instrumental in helping to better understand the release of MPs and nanoplastics into the environment and to provide data for fate and transport models, especially in order to predict the amount of plastic entering water systems. MP generation rates and power inputs can be correlated with each plastic's use to inform which release the most MPs and how to better change these products in order to reduce pollution in water sources.

Comparative Evaluation of Surface Roughness of Cention N after Brushing Simulation with Herbal and Fluoridated Toothpaste - An In-vitro Study

Introduction: Cention N, a new alternative tooth coloured resin based filling material. Toothbrushing abrasion is a key issue in restorative dentistry. A smooth surface is a crucial factor to be considered for establishing a successful restoration because the surface roughness of a restorative material results in plaque deposition, discoloration of the restoration, microleakage and secondary caries. The present study aims in evaluating the surface roughness of Cention N before and after brushing with herbal toothpaste and fluoridated toothpaste.&#x0D; Materials and Methods: A total of 8 Cention N samples were prepared and randomly divided into two groups into 2 groups as Group A- herbal toothpaste(n=4), Group B- fluoridated toothpaste(n=4). The samples were placed in a brushing simulator for 30000 cycles and their surface roughness was evaluated by using stylus profilometer-Mitutoyo SJ 310 and with the results collected a statistical analysis was performed using the statistical software “SPSS VERSION 23” and its results are demonstrated in the form of bar graph.&#x0D; Results: The Ra values of both the samples before and after brushing simulation was constant and only the Rq and Rz values showed difference between the groups. There was no notable changes in surface roughness parameters between the groups. The statistical “paired t test” analysis depicts that the p value for Rz parameter was 0.359 which is (p&lt;0.05), hence statistically insignificant.&#x0D; Conclusion: Brushing simulation did not influence the surface roughness of Cention N restorative material. There was no significant increase or decrease in surface roughness values after brushing simulation which indicates cention N material can withstand abrasive forces, but the results can vary in oral cavity environment.

Study on magnetic preparation of dual disk based on silica gel magneto-elastic abrasive particles

Magneto-elastic abrasive grains have magnetism, low elastic modulus and excellent abrasive performance, and have the characteristics of bonded abrasive grains and loose abrasive grains. The dual-disk magnetic preparation greatly improves the preparation quality and efficiency. Firstly, the magneto-elastic abrasive particles are introduced into the edge preparation of the dual-disk magnetic tool, and the preparation method of 4035 silica gel magneto-elastic abrasive particles is proposed. According to the microscopic characteristics of the magneto-elastic abrasive particles, the finite element software ABAQUS is used to establish the magneto-elastic abrasive particles. The meso-level representative volume element (RVE) model is built to analyze the stress and strain law of magneto-elastic abrasive particles under tension and compression. Secondly, an experimental platform for magnetic preparation of magneto-elastic abrasive particles with dual disks was built to analyze the force of magneto-elastic abrasive particles. Finally, Through the magnetic preparation experiment of the magneto-elastic abrasive dual-disk magnetic force, the influence of the disk rotation speed, abrasive particle size and relative magnetic permeability on the cutting edge wear is studied. And compared to the magnetic abrasive particles double-disk magnetic and drag finishing method, the magneto-elastic abrasive particle double-disk magnetic preparation method can obtain the maximum edge wear amount and the maximum surface roughness decreasing amplitude. The research results are of great significance to promote the progress of our country's magnetic high-efficiency processing and magneto-finishing processing technology.

Polysilsesquioxane with potent resistance to intraoral stress: Functional coating material for the advanced dental materials

Since the oral cavity is a harsh environment where various germs and chemical and mechanical stress exist simultaneously, well-organized hybrid technology should be considered in the design of cutting-edge dental materials. Although the Clear Overlay Appliance (COA) is widely used as a transparent orthodontic device, it still requires specific modifications to overcome the poor durability and frequent contamination that cause the patient's therapeutic burden. Herein, robust polysilsesquioxane (PSQ) containing quaternary ammonium cations (QACs) and long alkyl chains (LACs) in a durable siloxane matrix are reported as coating materials for the advanced COAs. The PSQ coatings are engineered to have a ladder-like structure that exhibits excellent stability under various pH and enzymatic conditions. Experiments simulating the dynamic intraoral are established to investigate the effects of PSQ coatings for the functional improvement of COA. The QACs and LACs firmly fixed to the siloxane matrix cause bacterial contact killing to prevent the contamination of COAs in the environment exposed to bacteria. The ladder-like siloxane matrix of the coating protects the COAs from intraoral abrasion forces and shearing movements with its flexible adaptability to external stresses. This study clarifies the clinical application potential of the coated COAs via in-vivo experiments using the beagle model.

Tribological properties of duplex coatings of chromium-vanadium carbide produced by thermo-reactive diffusion (TRD)

Carbide coatings are very important in molding industries due to their good anti-wear properties increasing the life of molds of hot and cold forging, extrusion and powder metallurgy exposing to abrasive forces. Diverse processes are applied to produce carbide coatings. One of them is the thermo-reactive diffusion method (TRD) using a molten salt bath. This process has many advantages including cost-effectiveness over other similar surface coating methods. The aim of this study is the formation of carbide-composite coatings using molten salt baths containing oxides of carbide forming elements individually and in a mixed form on SKD-11 cold work tool steel at 1000 °C. For this purpose, two sets of experiments were considered in this study. In experiment A, a chromium oxide bath and then a mixed chromium oxide and vanadium oxide bath with a molar ratio of Cr to V equal to 0.66 were used. In experiment B, at first a mixed chromium oxide and vanadium oxide bath (Cr/V ratio = 0.66) and next a single bath of vanadium oxide were utilized. To evaluate and compare the produced coatings, FE-SEM, EPMA (point, line and map), XRD analysis, nano-indentation and wear tests were performed. The results showed that the coatings include chromium carbides (Cr3C2, Cr7C3 and Cr23C6) and vanadium carbides (V2C, V6C5 and V8C7) as well as a carbon-chromium-vanadium triple phase with the composition of Cr2C2V. Moreover, the best hardness and abrasion resistance were gained for the coating produced in the molten bath containing chromium oxide and vanadium oxide after experiencing a chromium oxide bath. For the sample, the hardness was between 17.2 and 19.6 GPa and the lowest amount of COF was 0.32.