SiC Disk Research Articles

Nickel Coatings on Ceramic Materials Using Different Diffusion Techniques

Diffusion bonding is a process that has proven effective for the joining of metal to ceramic, but the differences in coefficient of thermal expansion still pose challenges during and after the bonding process. This work details the exploration of traditional diffusion-bonding processes using two traditional approaches, which include bonding of a 99.9+% pure Ni foil to SiC, Si3N4, and YSZ disks using (1) a hot isostatic press (HIP), with and without added weight to promote interfacial contact, and (2) field-assisted sintering (FAST). Samples were consolidated by heating to 1200 °C and held for 6 h under vacuum before cooling to room temperature during the HIP method. For the FAST technique, bonding experiments were performed at both 800 °C and 1200 °C in a vacuum environment under 10 MPa uniaxial pressure. After the Ni was bonded to the ceramics, diffusion heat treatments were carried out in the HIP. For electroless-plated samples, the heat-treatment temperature was chosen as 825 °C to avoid melting. For electroplated samples, heat treatment occurred at 925 °C or higher. Electroplated YSZ samples were heat-treated at 1150 °C as the Ni-Si eutectic is not a concern in this system. The time at temperature varied from 6 h to 48 h depending on the material combination tested. Post-heat-treatment diffusion characteristics were analyzed using scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDS). A main cause of poor bonding performance in the HIP samples was reduced interfacial contact, while cohesive failures in the FAST samples are likely due to the formation of brittle intermetallic Ni-Si phases. Preliminary results indicate success in bonding Ni to SiC, Si3N4, and YSZ using a diffusion-enhanced approach on electroplated specimens.

Modifying C/C–SiC brake pads with different Fe–Si alloy phases to improve the wear resistance of full-carbon/ceramic brake pair

The full-carbon/ceramic brake pair is designed to meet the increased demands for reliable braking at high speeds, heavy loads and complex service environments for vehicle and power machinery. In this paper, braking performance of different Fe–Si modified C/C–SiC composites have been studied using laboratory scale dynamometer. The phase composition/microstructure and mechanical properties of the material were studied. By mating with C/C–SiC brake disc, the effect of Fe–Si alloy modification on the friction and wear performance of full carbon/ceramic brake pair was investigated. The results indicated that the Fe–Si modification can effectively improve the wear resistance of both C/C–SiC disc and pads, and the disc/pads will have the least amount of wear only when the appropriate type of Fe–Si alloy and the suitable amount of Fe–Si alloy phase are introduced. When FeSi75 was used as the fusion infiltration material, the wear of disc/pad was 115.4 and 13.3 mm, respectively. Compared to the unmodified C/C–SiC disc/pad, the wear of Fe–Si modification disc/pad was reduced by 72.7 % and 87.2 %, respectively.

Structure analysis of friction layer of copper matrix composites reinforced by composite ceramic (TiC-B4C) powder

To alleviate the issues of matrix softening and excessive wear faced by copper-based composites matched with C/C–SiC disc during high-speed braking, the research was conducted to investigate the impact of composite ceramic (TiC–B4C, TB) powder on copper matrix composites prepared through conventional powder metallurgy method. TiC–B4C powder was produced using the high-energy ball milling method, and a suitable milling time (48 h) was established to obtain the maximum disorder degree. The results revealed that TB2 (6% TB) had the highest densification and the best mechanical and thermal performance, as compared to other composites. However, there were differences in tribological properties, with TB4 (10% TB) achieving the maximum friction coefficient, while TB2 (6% TB) exhibited more stable friction performance. As the TB powder content increased, larger tribo-films were formed on the worn surface. However, the influence of TB powder content (less than 10% TB) on friction performance was mainly due to mechanical strength and structural tightness, rather than the formation of tribo-films. The friction layer consisted of three parts: the top nanostructure layer composed of nanoparticles (C, Cu, Fe, B, O, and Ti), the middle tribo-film composed of graphite and B2O3, and the lower elastic deformation zone.

Superlubricity and running-in wear maps of water-lubricated dissimilar ceramics

Water-lubricated ceramic sliding tribosystems, when operating under superlubricity conditions, reduce frictional energy losses in many applications. Aqueous superlubricity of 5 dissimilar ceramic tribopairs (Si3N4–Al2O3, Si3N4-ZTA, Si3N4–SiC, Al2O3–SiC, ZrO2–SiC) was thus studied in a series of ball-on-disk tests, with the identification of wear mechanisms and lubrication regimes, while introducing a running-in wear map approach to elucidate transient tribological phenomena. All pairs presented superlubricity for certain combinations of normal load and sliding speed, after a running-in period where mechanical and thermal severities of contact remained mostly below their respective threshold values, promoting mild wear regimes. Load-carrying capacity of ZrO2–SiC was the highest due to high homogeneity and low roughness of the tribofilm on SiC disk’s wear track.

Braking behaviors of Cu-based PM brake pads mating with C/C–SiC and 30CrMnSi steel discs under high-energy braking

Exploring braking behaviors of powder metallurgy (PM) brake pads mating with different brake discs is conducive to promoting the development of high-speed trains. In this study, the braking behaviors and wear mechanisms of Cu-based PM brake pads mating with C/C–SiC and 30CrMnSi steel disc, respectively, under high-energy braking condition have been investigated. Results show that compared with PM-30CrMnSi brake pair, the coefficient of friction (COF) and stability coefficient of PM-C/C–SiC brake pair are increased by 28.9% and 13.9%, respectively, and the PM pad wear rate and braking time are reduced by 31.0% and 29.5%. Moreover, PM-C/C–SiC brake pair does not exist obvious tail warping in braking curve, which can be attributed to the formation of dense tribo-layer and the lubrication of carbon fibers. TEM analysis shows that the tribo-layer of PM-C/C–SiC brake pair is composed of nanostructured oxide layer and plastic deformation layer. Besides, a ~600 nm thick oxide layer containing nano-sized Cu/Fe oxides and ZrSiO4 particles greatly improves COF and wear resistance of PM pad. The dominant wear mechanisms of PM-C/C–SiC brake pair are delamination and oxidation wear, whilst those of PM-30CrMnSi brake pair are abrasive and adhesive wear.

Effect of double network hydrogel film thickness on the run-in tribological properties of a friction system using DN gel

This study aims to investigate the potential of double network hydrogel (DN gel) in a low friction mechanical system. In this study, the effect of the thickness of DN gel films on the friction property are clarified. An indentation test, contact pressure measurement, and series of friction tests in water using three different thickness (1.5, 3, 6 mm) of DN gel film and a SiC disc were carried out.Friction of DN gel film sliding against SiC in water can be classified into two types as “Friction region I: friction remains substantially unchanged during the test” and “Friction region II: friction decreases due to run-in”. Friction region transition can be related to the Hersey number region, which consists of viscosity of lubricant, sliding speed and apparent contact pressure. Hersey number larger than 1.5 × 10−10 is a necessary condition for friction region II where different lubrication regimes can be found.1.5 and 6 mm thick DN gel films have exhibit super low friction (μ < 0.01) under a wide range of friction conditions as friction region II, and especially 1.5 mm thick DN gel film, super low friction is achieved by twice run-in phenomena.

Effect of process parameters on dry centrifugal granulation of molten slag by a rotary disk atomizer

Dry centrifugal granulation (DCG) experiments for blast furnace slag (BFS) were performed by means of a rotary disk atomizer since water quenching method can create a series of problems. The results showed that the DCG method can granulate the BFS, but the results are easily affected by the slag flow rate, disk rotating speed, disk radius, disk material and slag falling height. The granulating parameters with an excessive flow rate, low rotating speed, SiN–SiC disk, stainless steel disk and low slag falling height are detrimental to the granulation process. The most suitable parameters for granulation are a slag flow rate of 5.1 × 10−5 m3/s, a disk rotating speed of 1500–2300 r/min, a slag falling height of 0.8 m and a smooth graphitic disk with the radius of 0.1 m. In the absence of an off-center flow, the overall best granulating effect produces round particles with mean diameter of 3.43 mm without creating slag fiber. The vitreous content of the BFS particles granulated by graphite disks is 92%, which meets the requirements of cement raw materials. The Bond work index of dry granulated BFS is 18.4 kWh/t, and the grindability of dry granulated slag and water-quenched slag is similar.

The wet braking and recovery behaviors of the P/M pad mated with C/C–SiC disc for high-speed trains

C/C–SiC ceramic is a promising braking material in high-speed trains. The research on wet braking is necessary for its application. In this paper, braking tests of C/C–SiC disc mated with powder metallic (P/M) pads were conducted under dry, wet and recovery braking conditions at initial braking speed (IBS) of 14, 22, 33, 44, 55 m/s. Coefficient of friction (COF) and surface morphologies under different conditions were discussed: The instantaneous COF under wet condition was lower but the instantaneous COF curves became smoother than those under dry condition. The difference between two conditions went smaller as IBS increased. Under recovery condition, it cost 33 stops at 14 m/s to recover to 93.1% of the origin COF. Meanwhile, 8 stops were needed at 55 m/s, and the recovery rate was 98.9%. When the IBS increased, the number of the stop needed was fewer and the recovery rate was higher. The surface morphologies further showed the braking under wet condition resulted in a smoother surface with less ploughing grooves and the disappearance of the friction film. Under the recovery condition, the surface became rough again with grooves and the friction film formed again. The results indicate that the wear debris were washed away by the sprayed water and the formation of friction film was inhibited. In addition, water film subsequently lubricated the friction surface, which reduced COF at low IBS. As IBS increased, high temperature accelerated the dewatering and evaporation of water and thus lead to the decrement of the COF difference between wet and dry friction which, in turn accelerated the recovery process.

Comparison of braking behaviors between iron- and copper-based powder metallurgy brake pads that used for C/C–SiC disc

Powder metallurgy (PM) brake pads with stable friction behavior are one of the ideal choices for the counterparts of C/C–SiC brake disc that are expected to be applied to the future high-speed trains. In this study, iron- and copper-based PM pads were used to mating with the C/C–SiC brake disc. After testing the brake pairs using a lab-scale dynamometer, the C/C–SiC disc generated almost no wear loss. The coefficient of friction of the carbon/ceramic disc-PM pads brake pair varied nearly between 0.35 and 0.6 under different braking conditions. The analysis of friction surface indicated that the wear mechanism of Fe-based PM pads was mainly dominated by abrasion, while that of Cu-based pair mainly relied on adhesion and fatigue peeling.

Effect of pyrolysis temperature on the microstructure and thermal conductivity of polymer-derived monolithic and porous SiC ceramics

The present work investigates the influence of pyrolysis temperature on the microstructure and thermal conductivity (λ) of polymer-derived SiC ceramics. For the study, both monolithic thin ceramic disks and highly porous reticulated foams were considered. The λ of the polymer-derived SiC disks were measured, in the temperature range 100 °C–1000 °C, to amount between 0.5 W.m−1. K−1 and 47 W.m−1. K−1, depending from the maximum pyrolysis temperature. While, the λ measured at RT on the SiC foams (porosity 79.5 %–99.0 %), ranges between 0.03 W.m−1. K−1 and 0.19 W.m−1. K−1. The thermal transport in polymer-derived SiC ceramics was observed to be more significantly governed by the nanocrystalline to crystalline transition which occurs at pyrolysis temperatures above 1200 °C as compared to mesopore formations or the nature and amount of free carbon.

Friction properties of micro/nanogroove patterns in lubricating conditions

Tribological properties can be improved by surface texturing; however, most of the conducted studies used microscale patterns. This study evaluated the lubrication properties of four different micro/nanogroove layouts (i.e., one straight layout and three different types of V-shaped layouts) created using the nanostripe fabrication technology. For each layout, microgrooves were arrayed at a pitch of 4 μm or 6 μm, and nanogrooves were formed on the ridge between these microgrooves. Friction tests were conducted at different loads and speeds using a single-crystal SiC disk as the counter specimen. We showed that patterns with 6 μm pitch microgrooves had a lower friction coefficient than those with 4 μm pitch microgrooves. The layouts with a higher ratio of nanogrooved area obtained a lower friction coefficient in high load and low speed conditions that are considered as boundary or mixed lubrication regimes.

Effect of Hydrophilic Amide Monomers on Dentin Bonding Strength

Objective: The aim of this study was to compare the shear bond strength (SBS) to dentin of one-step bonding agent containing hydrophilic amide monomers (HMA) and 10-Methacryloyloxydecyl dihydrogen phosphate (MDP) with one-step bonding agent containing only MDP. Materials and Methods: 20 human third molar teeth randomly were divided into two groups. Teeth was abraded with a SiC disc (Carbimet, Bisco Inc., Schaumburg, USA) to be under 1 mm of enamel-dentin junction. The dentin surface of each teeth were etched with %37 phosphoric acid for 15 s and then rinsed with water spray for 10 s and after that air dried. Cylinders of composite (Clearfil Majesty Posterior, Kuraray Noritake Inc, Okuyama, Japan) were bonded using 2 dental bonding agents. Group A used bonding agent containing HMA+MDP (Clearfil Universal Quick bond, Kuraray America, Inc. New York/NY, USA) and Group B used bonding agent containing only MDP (Clearfil S3 Bond plus, Kuraray America, Inc. New York/NY, USA) applied in accordance with the manufacturer's instructions. The speciemens were stored for 24 h in 37°C water and thermocycled between 5 and 55 C water with a 20 s dwell time for 5000 cycles. They were then submitted to a shear bond test with a universal testing machine (AGS-X, Shimadzu, Kyoto, Japan) with a 100 N load cell at 1 mm/min. The values of SBS were analyzed with ANOVA/Tukey’s test. Results: Group A was 35,96±5,47 MPa and B was 24,25±7,5 MPa There was a statistical difference between the two bonding agents (p<0.05). Group A was significantly higher than Group B. Conclusions: According to this study, bonding agents containing which type of monomers may be one of the important factors influencing dentin bond strength. When bonding agents with hydrophilic amide monomers are used, it has showed higher shear bond strength.

The braking behaviors of Cu-Based powder metallurgy brake pads mated with C/C–SiC disk for high-speed train

The improvement of braking systems for the high-speed train is driven by the demand for high & stable coefficient of friction (COF) as well as low wear at high speed. Given to the fading COF and severe wear of powder metallurgy (P/M) pad mated steel disk serving high-speed train in present, C/C–SiC ceramic materials are regarded as a strong candidate for braking disk due to the excellent strength, fracture toughness coupled with relatively low density. The fundamental understanding of the braking behavior at different braking speeds should be clarified for optimal application. In this work, P/M pads and C/C–SiC ceramic disk were prepared, braking tests with the initial braking speeds (IBS) of 15, 22, 30, 37, 46, 55, 59, 64, 69 m/s were conducted, and the surface development, friction & wear behavior were analysed. The COF vs. IBS curve shows a three-stage changing based on the turning points due to the contact patches continuously forming, growing and degrading: it went down and reached a low point with a value of 0.443 at 37 m/s, then increased gradually and reached the maximum 0.486 at 55 m/s, then little fell to 0.460 at 69 m/s. In the great scope of braking speeds, P/M pads mated C/C–SiC ceramic disk showed both high mean friction coefficient of 0.469 and high stability coefficient of 0.908, which are higher than the corresponding values of same P/M pads mated with typical steel disk (0.381 for COF and 0.895 for stability coefficient). Furthermore, at the highest speed tested, the wear rate of the pad mated with the ceramic disk is 0.147 cm3/MJ, far lower than that with steel mate: 0.338 cm3/MJ, showing desired properties for the high-speed train, owing to slight adhesion between ceramic disk and metal matrix of the pad.

Monocrystalline Silicon Carbide Disk Resonators on Phononic Crystals with Ultra-Low Dissipation Bulk Acoustic Wave Modes

Micromechanical resonators with ultra-low energy dissipation are essential for a wide range of applications, such as navigation in GPS-denied environments. Routinely implemented in silicon (Si), their energy dissipation often reaches the quantum limits of Si, which can be surpassed by using materials with lower intrinsic loss. This paper explores dissipation limits in 4H monocrystalline silicon carbide-on-insulator (4H-SiCOI) mechanical resonators fabricated at wafer-level, and reports on ultra-high quality-factors (Q) in gyroscopic-mode disk resonators. The SiC disk resonators are anchored upon an acoustically-engineered Si substrate containing a phononic crystal which suppresses anchor loss and promises QANCHOR near 1 Billion by design. Operating deep in the adiabatic regime, the bulk acoustic wave (BAW) modes of solid SiC disks are mostly free of bulk thermoelastic damping. Capacitively-transduced SiC BAW disk resonators consistently display gyroscopic m = 3 modes with Q-factors above 2 Million (M) at 6.29 MHz, limited by surface TED due to microscale roughness along the disk sidewalls. The surface TED limit is revealed by optical measurements on a SiC disk, with nanoscale smooth sidewalls, exhibiting Q = 18 M at 5.3 MHz, corresponding to f · Q = 9 · 1013 Hz, a 5-fold improvement over the Akhiezer limit of Si. Our results pave the path for integrated SiC resonators and resonant gyroscopes with Q-factors beyond the reach of Si.

Structural and microstructural studies on SiC-SiO2 ceramic composites

In this study, SiC ceramic substrates were prepared with 99.5% silicon carbide powders which were came from waste silicon mud during the manufacturing process of solar cells. It is found that a SiO2 layer with 50 nm in thickness is present on the SiC surface by TEM analysis. The relative density of the SiC samples is too low after sintering to 1550 °C, which is only 60% of the relative density. It will cause a poor mechanical strength at lower relative density of samples. To improve the density of SiC samples, an amorphous SiO2 was introduced as a sintering aid. Different amounts of amorphous SiO2 from 1 wt% to 5 wt% were then added into SiC powders and made into discs. We call this modified-SiC. These samples were sintered at high temperatures from 1350 °C to 1500 °C. The SiO2 addition and sintering temperature effects on the density, phase evolution, microstructure and mechanical properties of modified-SiC were investigated. A Y-ZrO2 layer was then coated onto the SiC disc. Sintering temperature can be efficiently decreased and the mismatch between ZrO2 coatings and SiC disc can be reduced when SiO2 is added into SiC. It is found that SiC powders with 3 wt% SiO2 addition shows the most optimum outcome with higher density and stronger mechanical properties.

Production of C/SiC Nanotubes by Arc Plasma Treatment

Abstract Carbon/Silicon Carbide (SiC) nanotubes were found to grow by treating graphite circular disc and silicon carbide grains in an arc plasma reactor/furnace followed by 4 h of in situ furnace cooling. The arc plasma treatment of samples was carried out in a dc extended 50 kW thermal arc plasma reactor. The plasma treatment was carried out from 5-20 min under Ar atmosphere. Typical in situ grown nanotubes were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive spectra (EDS) and micro Raman spectroscopy, and it is established from these evaluations that the nanotubes are made up of silicon carbide and carbon in SiC and graphite circular disc respectively. In this work we have synthesized and studied the growth of C/SiC nanotubes by dc extended thermal arc plasma method.

Shear Strength of Protein Film Formed by Friction of SiC/SiC Sliding Pair in Plasma Environment

This study aimed to clarify the shear strength of a protein film formed by friction of a SiC/SiC sliding pair in a plasma environment. A ball/disk-type tribometer was utilised to obtain the relationship between the friction force in the plasma and the area of protein aggregates formed on the textured SiC disk sliding against the SiC ball in the plasma. To control the area of protein aggregates adsorbed onto the SiC disk surface, different surface textures and ultraviolet (UV) irradiation for the SiC disk were introduced based on past research. Protein aggregates formed owing to protein denaturation and were adsorbed onto the fabricated surface texture of the SiC disk. A broad protein film formed on the SiC disk surface through conjugation of multiple protein films formed from closely distributed concaves. Therefore, the distribution of fabricated concaves determines the conjugation of the protein film formed from each concave, and the trends of frictional force for each SiC/SiC frictional pair in the plasma depends on the area of protein aggregates. In other words, the area of protein aggregates and the frictional force show an almost linear relationship, regardless of the surface texture on the SiC disk or UV irradiation. Finally, the shear strength of the protein aggregates against the sliding SiC ball in plasma was 7.14MPa, as determined from the relationship between the area of the protein aggregates and the frictional force in the plasma environment.

Biosilicate as a dentin pretreatment for total-etch and self-etch adhesives: In vitro study

PurposeTo evaluate the effect of dentin pre-treatment using biosilicate microparticle suspension prior to the application of total-etch and self-etch adhesives on dentin microtensile bond strength. Material and methodsThe labial enamel of forty bovine central incisors was removed using 600-grit SiC disks to expose the flat dentin surface. Six bonding protocols were evaluated (n=10): Group 1 (etching with 35% phosphoric acid+adhesive Adper Single Bond™ 2—Control group); Group 2 (10% biosilicate suspension prior to etching with 35% phosphoric acid+adhesive Adper Single Bond™ 2); Group 3 (10% biosilicate suspension after etching with 35% phosphoric acid+adhesive Adper Single Bond™ 2); Group 4 (self-etch adhesive Adper Easy One™—Control group); Group 5 (10% biosilicate suspension prior to the self-etch adhesive Adper Easy One™); Group 6 (10% biosilicate suspension after the self-etch adhesive Adper Easy One™). Composite build-ups were performed with Filtek™ Z350. The specimens were stored in distilled water for 24h at 37°C and sectioned into sticks with a 1.0mm2 cross-sectional area. Each stick was tested in a Universal testing machine (0.5mm/min), and the mean microtensile bond strength data (MPa) were analyzed by two-way ANOVA and Bonferroni׳s multiple comparisons test (α=0.05). Representative SEM micrographs were taken to compare the microstructure of different treatments of dentin. The relative amounts of calcium (Ca) and phosphorus (P) were determined by EDS. ResultsGroup 3 (10% biosilicate suspension after acid etching with 35% phosphoric acid+adhesive Adper Single Bond™ 2) showed the highest bonding values (p<0.05). Regarding the self-etch adhesive, there was no difference (p>0.05) between Group 5 and Group 6. SEM images demonstrated biosilicate microparticles in groups 2 and 4. EDS data analysis showed higher amounts of Ca and P ions in groups treated with biosilicate than control groups. ConclusionThe application of biosilicate microparticle suspension as dentin pre-treatment positively influenced the bond strength of the total-etch adhesive when used after acid etching; meanwhile, it does not interfere with the bonding ability of self-etch adhesive to dentin.

Friction and surface fracture of a silicon carbide ceramic brake disc tested against a steel pad

Friction coefficients of a SiC ceramic disc were measured on a laboratory-scale dynamometer by testing against a mild steel pad under different initial braking speeds, and its friction surface was investigated with microscopy techniques. At bedding, averaged friction coefficient for a braking stop varied significantly with the initial braking speed; after bedding, it converged to ∼0.6, regardless of braking speed. Surface fracture on the SiC disc was responsible for the transformation from a flat surface into a rough one, making ploughing a dominant friction mechanism at bedded stage. It was found that fracture surface and non-contact regions directly contributed friction coefficient variation at bedding stage. Friction layer composed of iron oxides and plastic deformation with partial dislocations activated appeared on SiC surface, but were unsustainable owing to surface fracture. A quantitative analysis is provided to understand friction coefficient variation and SiC surface fracture during braking.

Effect of defects on graphitization of SiC

Abstract