Microhardness Of Composites Research Articles

Effect of nanostructured Cu on microstructure, microhardness and wear behavior of Cu-xGnP composites developed using mechanical alloying

In the present study, Cu-1, 2 and 3 wt.% xGnP composites have been developed by powder metallurgy (PM) route using nanostructured Cu powder and their effect on microstructure, microhardness, sliding wear behaviour has been examined. The crystallite size and lattice strain of Cu after 25 h of mechanical milling have been found to be 16 nm and 0.576%, respectively. Major challenges associated with the development of Cu-xGnP composites is the uniform dispersion of the nanoplatelets in the Cu matrix, which have been dealt out by incorporating the nanostructured Cu- xGnP composites after mechanical alloying leading to the homogenous distribution of nanoplatelets in the Cu-matrix. A significant enhancement in relative density, microhardness and wear resistance of the Cu-3 wt. % xGnP nanofiller composite in particular has been observed due to the uniform distribution of the nanofillers. In Cu-3 wt. % xGnP composite developed using as-milled nanostructured Cu, a microhardness of ∼ 1.1 GPa could be achieved which is about ∼3 times higher than that of the pure sintered Cu sample (∼359 MPa). Nanostructured Cu also leads to enhancement of the hardness and wear property as compared to the as-received Cu. The wear mechanism in the various nanostructured Cu-xGnP composites has been studied in details.

Фізико-механічні характеристики нанокомпозційниих матеріалів на основі фторопласту

In this work, the elastic and strength properties of polymer composites with a polytrifluorochlorethylene matrix and a thermally expanded graphite filler were evaluated by the nanoindentation method, and the effect of the dispersion and concentration of the filler on the mechanical characteristics of nanocomposite materials was considered. It is shown that the microhardness of nanocomposite materials decreases with increasing filler concentration. An increase in the microhardness and Young's modulus with the growth of filler particles was observed for nanocomposite materials with a filler concentration of 3 vol.%. As for nanocomposite materials with a filler volume fraction of 10 vol.%, similar behavior of the mechanical characteristics was observed with an increase in the dispersion of thermally expanded graphite particles to 180 μm. A subsequent increase in the average particle size of thermally expanded graphite leads to a decrease in Young's modulus and microhardness of composites, which may be associated with different degrees of polymer structuring and the formation of different orientational orders from the filler. The observed changes in Young's modulus and H/E ratio indicate a change in the amorphous crystalline behavior of the composite to that characteristic of fine-crystalline materials and depends on the dispersion of thermally expanded graphite.

Characterization of low-cost Brazilian resin composites submitted to tooth brushing.

This in vitro study aimed to evaluate surface microhardness, roughness, color, gloss and topography of low-cost Brazilian resin composites, compared with an international one. All 120 samples (8mm ø x 2mm height) were prepared and divided into 5 groups: Ultrafill (Biodinâmica), Llis (FGM), Fill Magic (Coltene), Applic (Makira), and Filtek Z250XT (3M Oral Care). Surface microhardness (KHN) (n=10) was analyzed at two time periods: before and after simulated tooth brushing (STB). Other standardized samples of each group (n=10) were analyzed for surface roughness (Ra), color (ΔL, Δa, Δb, ΔE, ΔE00) and gloss unit (GU) at the same two periods. The topography of non-brushed and brushed samples of each group (n=4) was evaluated by scanning electron microscopy. Data were analyzed statistically by two-way repeated measures ANOVA with Bonferroni post-hoc test (KHN, Ra, GU), and one-way ANOVA with Tukey post-hoc test (ΔL, Δa, Δb, ΔE, ΔE00) (α=0.05). Topographic images were submitted to descriptive analysis. The low-cost Brazilian resin composites investigated were compared with the international one and revealed: lower KHN, regardless of before or after STB; statistically similar Ra before STB, except Ultrafill, which presented higher values; lower Ra after STB, except Ultrafill, which presented statistically similar values; statistically similar color change in ΔL, Δa, Δb parameters; statistically similar color change in ΔE, ΔE00 parameters, except Fill Magic, which presented lower values; lower gloss before STB; lower gloss after STB, except Ultrafill, which presented statistically similar values. In a situation of scarce resources, low-cost Brazilian composites might be an acceptable cost-effective restorative alternative.

New Experimental Zirconia-Reinforced Rice Husk Nanohybrid Composite and the Outcome of Its Surface Roughness and Microhardness in Comparison with Commercialized Nanofilled and Microhybrid Composite Resins

Background:An ideal composite resin should demonstrate smooth surface after polishing and high hardness value to provide long-term success. Thus, this study aimed to compare the surface roughness and microhardness of new experimental zirconia-reinforced rice husk nanohybrid composite (Zr-Hybrid) with commercialized nanofilled (Filtek-Z350-XT) and microhybrid composite (Zmack-Comp) resins before and after artificial ageing.Methods:One hundred and eighty standardized disc samples were prepared, of which ninety samples each were used for surface roughness and microhardness test, respectively. They were divided equally into: Group 1 (Filtek-Z350-XT), Group 2 (Zmack-Comp), and Group 3 (Zr-Hybrid). For surface roughness test, all samples were polished with aluminium oxide discs and further subdivided into aged and unaged subgroups, in which composite samples in aged subgroups were subjected to 2500 thermal cycles. Next, all the samples were subjected to surface roughness test using a contact stylus profilometer. As for microhardness test, all the aged and unaged samples were tested using a Vickers hardness machine with a load of 300 kgf for 10 s and viewed under a digital microscope to obtain microhardness value. Data were analyzed using two-way ANOVA followed by post hoc Tukey's honestly significant difference and paired sample t-test with significance level set at P = 0.05.Results:In both the aged and unaged groups, Zr-Hybrid showed statistically significantly lower surface roughness (P < 0.05) than Filtek-Z350-XT and Zmack-Comp, but no statistically significant difference was noted between Filtek-Z350-XT and Zmack-Comp (P > 0.05). A similar pattern was noted in microhardness test, whereby Zr-Hybrid showed the highest value (P < 0.05) followed by Filtek-Z350-XT and lastly Zmack-Comp. Besides, significant differences in surface roughness and microhardness were noted between the aged and unaged groups.Conclusion:Zr-Hybrid seems to demonstrate better surface roughness and microhardness value before and after artificial ageing.

Fabrication and characterization of magnesium based surface composites with hybrid reinforcements by friction stir processing: A review

Friction stir processing (FSP) is an eco-friendly process which works on the identical principle as friction stir welding (FSW). FSP is a process for reforming the mechanical properties of the materials by using the stirring motion of the rotating tool against the material whose properties need to be enhanced. FSP was initially used for the fabrication and processing of aluminum surface composites. But after several developments, it is now utilized for the fabrication of several surface composites like magnesium alloys, copper alloys, titanium alloys, ferrous and non-ferrous alloys. Keeping in view of increasing demand of magnesium alloys and composites in automobile, aerospace and transportation industries, the current review is aimed to examine the outcome of using hybrid reinforcement for improvement in micro-hardness, mechanical properties and tribological functioning of magnesium-based surface composites (SCs) manufactured through the FSP. Previous literature reveals that the majority of the work on processing of Mg SC’s by FSP has been executed by using magnesium alloys of AZ series and few studies are available on ZE and WE series of magnesium alloys. Currently ZE and WE series of magnesium alloy are becoming the material of choice for several applications of automobile and aerospace industries due to their enhanced mechanical properties. This requires more work to be done on processing of ZE and WE series magnesium alloys.

Mechanical and Tribological Behavior of Mechanically Alloyed Ni-TiC Composites Processed via Spark Plasma Sintering.

Titanium carbide (TiC) reinforced nickel (Ni) matrix composites were processed via mechanical alloying (MA) followed by spark plasma sintering (SPS) process. Mechanical alloying has gained special attention as a powerful non-equilibrium process for fabricating amorphous and nanocrystalline materials, whereas spark plasma sintering (SPS) is a unique technique for processing dense and near net shape bulk alloys with homogenous microstructure. TiC reinforcement varied from 5 to 50 wt.% into nickel matrix to investigate its effect on the microstructure and mechanical behavior of Ni-TiC composites. All Ni-TiC composites powder was mechanically alloyed using planetary high energy ball mill with 400 rpm and ball to powder ratio (BPR) 15:1 for 24 h. Bulk Ni-TiC composites were then sintered via SPS process at 50 MPa pressure and 900–1200 °C temperature. All Ni-TiC composites exhibited higher microhardness and compressive strength than pure nickel due to the presence of homogeneously distributed TiC particles within the nickel matrix, matrix grain refinement, and excellent interfacial bonding between nickel and TiC reinforcement. There is an increase in Ni-TiC composites microhardness with an increase in TiC reinforcement from 5 to 50 wt.%, and it reaches the maximum value of 900 HV for Ni-50TiC composites.

Investigations on mechanical behavior of hot rolled Al7075/TiO2/Gr hybrid composites

In the present work, influence of titanium dioxide (TiO2) and graphite (Gr) hybrid reinforcement on microstructure and mechanical behavior of Al7075 alloy is studied. Al7075 and its hybrid composite samples were fabricated by using stir-casting and hot rolling technique. Hot rolling was carried out at a temperature of 450 °C with a reduction-ratio of 90%. Microstructure examination showed a good dispersion of titanium dioxide and graphite reinforcement particles with excellent bond with Al7075 matrix alloy. In case of hot rolling, both the reinforcements were found to be aligned in the direction of rolling. The microhardness and tensile strength of hybrid composites were remarkably improved in case of hot rolling compared to that of cast composites.

Role of filler morphology on friction and dry sliding wear behavior of epoxy alumina nanocomposites

Epoxy alumina composite was fabricated by instant cross-linking process containing 0.5, 1.0 and 1.5 wt.% of alumina reinforcement. Ultrasonication process is used to disperse alumina nanoparticles in epoxy. To study effect of particle morphology two types of alumina nanoparticle’s were used, one was of rod shape whose diameter varies from 5–10 nm and length not more than 50 nm. Whereas other type of particle used was spherical in shape with diameter varying from 27-43 nm. Reinforcement of alumina nano particles enhances the micro hardness of epoxy composite. There is no significant effect of reinforcement on water absorption behavior of epoxy composite. Friction and dry sliding wear behavior was experimentally evaluated by pin on disc setup. Infusion of alumina nanoparticles improves friction and wear behavior of epoxy composite. Reduction of 34% in friction coefficient (CoF) was recorded at 1.5 wt.% of spherical alumina particles. Wear rate also decreases with by 74% at 1.0 wt.% inclusion of spherical nano particles. Calculated energy dissipation was in good correlation with wear rate, thus a good method to predict the wear characteristics of epoxy composite. Stable development of tribo-film and surface smoothening are the major phenomena in improvement of tribological behavior of epoxy composite.

Effect of Surface Wetting Resin on the Color Stability and Microhardness of Esthetic Composites

Objective: The aim of this study was to evaluate and compare the effects of the superficial application of two different modeling resins on the surface microhardness and discoloration of composite resins. Material and Methods: The present study used two different composites and modeling resins. The composites were placed in plastic molds. Subsequently, the modeling resins were applied on the surface of the two composite groups. The microhardness and color pertaining to all the groups were evaluated. The current study used the One-Way ANOVA and Kruskal Wallis tests, in order to perform the statistical evaluation (p&lt;0.05). Results: The present study compared the microhardness pertaining to the groups and the highest microhardness values were observed in the Estelite Asteria group (none), whereas the lowest values were observed in the GC Essentia group (Ultradent). Moreover, the current study evaluated the color stability and the greatest discoloration was observed in the control group of the GC Essentia group, whereas the least discoloration was observed in the Estelite Asteria group that included the samples prepared using Ultradent Wetting Resin. Conclusions: The results of the present study demonstrated that the use of modeling resins, which facilitate the placement of composite resins, reduced the microhardness and discoloration of composite resins. The aforementioned effect can be attributed to the variations in the structure of the filling. However, further studies are warranted to support and verify the results of the current study.

Fabricating In Situ Powdered Nickel–Alumina Metal Matrix Composites Through Microwave Heating Process: A Sustainable Approach

The microwave processing of materials is considered as a novel and sustainable process due to the unique heating properties, huge saving of energy and processing time and non-polluting characteristics. The purpose of the present work is to economically process nickel powder-based metal matrix composites reinforced with variable (5% and 10%) volume fraction of alumina powder through microwaves at 2.45 GHz frequency and 900-W power. The concept of microwave hybrid heating is used for heating and melting the nickel-based powders. Developed composites were characterized through phase analysis, microstructural characterizations, mechanical characterizations and wear study. The XRD analysis of alumina-reinforced composites revealed the formation of nickel aluminides (AlNi and NiAl3), intermetallic of nickel such as Ni3Si and FeNi3, oxides of nickel and chromium carbides (Cr3C2, Cr23C6 and Cr2C3). Microstructures revealed formation of equiaxed grains with uniform dispersion of alumina reinforcements. The microhardness of composites was increased due to the presence of uniformly distributed alumina reinforcements and presence of intermetallics. Vickers microhardness for 10% alumina-reinforced MMC was 2.4 times higher than pure EWAC casting. The 10% ceramic reinforcement increased the tensile strength and wear resistance. For 10% alumina composite, wear was reduced by 71.67% in comparison with pure nickel-based casting.

Surface microhardness of a self-adhesive composite in comparison with conventional composite resins.

The surface microhardness of dental composites greatly affects the durability of restorations. The aim of this study was to compare the surface microhardness of a self-adhesive composite with that of other conventional composites. The effect aging has on surface microhardness was also evaluated. In this in vitro experimental study, the composite resins were poured into molds measuring 3 mm × 3 mm × 6 mm and cured for 40 s. The samples were then immersed in distilled water at 37°C for 24 h. After polishing, the surface microhardness of the samples was measured using the Vickers hardness tester. For this purpose, a 100-gram load was applied to 3 points on the surface of each composite sample for 20 s, and the mean value of surface microhardness was used as the Vickers hardness number. The samples were then subjected to 30,000 thermal cycles at 5-55°C in order to age them; after that, their surface microhardness was measured again. The one-way analysis of variance (ANOVA) was used for the statistical analysis. The maximum hardness value before and after aging belonged to Filtek® Z250, followed by Premise™ Flow and Vertise™ Flow, with significant differences between them (p < 0.001). After aging, the surface microhardness of all composites decreased significantly (p < 0.001). The effect of aging on surface microhardness was the same in all groups (p > 0.05). The surface microhardness of composites was significantly different before and after aging. All composites experienced a reduction in their surface microhardness after aging.

Surface modification via in situ formation of titanium carbide in ferrous matrix through TIG arcing

In situ grown titanium carbide (TiC) particle on the surface of low carbon steel was synthesized using tungsten inert gas (TIG) arcing process to enhance its wear resistance. X-ray and electron back scattered diffraction results reveal the formation of only titanium carbide particles as precipitate in the matrix. The modified region shows uniform distribution of the TiC in the matrix having cubical as well as rod like structure with various sizes ranging from micron to nano level. The high resolution transmission electron microscopy analysis reveals that the nano size TiC precipitates were coherent with the misfit of 2.5% with the matrix. Microhardness of the surface composite was increased by 150% than base metal. Gradual decrease in the hardness shows the unique advantage of using TIG arcing process for having a hard surface for resisting material loss with a relatively soft core for absorbing energy.

Effect of SiC on Microstructure, Phase Evolution, and Mechanical Properties of Spark-Plasma-Sintered High-Entropy Ceramic Composite

Ultra-high temperature ceramic composites have been widely investigated due to their improved sinterability and superior mechanical properties compared to monolithic ceramics. In this work, high-entropy boron-carbide ceramic/SiC composites with different SiC content were synthesized from multicomponent carbides HfC, Mo2C, TaC, TiC, B4C, and SiC in spark plasma sintering (SPS) from 1600 °C to 2000 °C. It was found that the SiC addition tailors the phase formation and mechanical properties of the high-entropy ceramic (HEC) composites. The microhardness and fracture toughness of the HEC composites sintered at 2000 °C were improved from 20.3 GPa and 3.14 MPa·m1/2 to 26.9 GPa and 5.95 MPa·m1/2, with increasing SiC content from HEC-(SiC)0 (0 vol. %) to HEC-(SiC)3.0 (37 vol. %). The addition of SiC (37 vol. %) to the carbide precursors resulted in the formation of two high-entropy ceramic phases with two different crystal structures, face-centered cubic (FCC) structure, and hexagonal structure. The volume fraction ratio between the hexagonal and FCC high-entropy phases increased from 0.36 to 0.76 when SiC volume fraction was increased in the composites from HEC-(SiC)0 to HEC-(SiC)3.0, suggesting the stabilization of the hexagonal high-entropy phase over the FCC phase with SiC addition.

Obtaining, microstructure and microhardness of carbon-doped aluminomatrix composites

Composition and formulation effect of aluminomatrix composites, resulting from carbon mechanical alloying, on their microhardness and structure has been investigated. Obtained results justified regression equations and the dependence of the microhardness and dimensions of coherent scattering areas (CSA) of composite specimens-semi-finished products of composites before and after their thermal processing on the carbon content, abundance and time of aluminum powder mechanical alloying PAD-1 by technical carbon K354 in the mechanoreactor (attritor) of the author’s structure.

EFFECT OF TIO2 PARTICLES ON THE MECHANICAL AND MICROSTRUCTURAL EVOLUTION OF HYBRID ALUMINUM-BASED COMPOSITES FABRICATED BY WARB

In this study, the effect of powder particle contents on the mechanical properties of aluminum-based hybrid composites produced by warm accumulative roll bonding (WARB) process was investigated. Three hybrid composite groups with fully annealed AA1060 strips, 1[Formula: see text]wt.% of MnO2 and 0, 7.5 and 15[Formula: see text]wt.% of TiO2 were first roll-bonded and then the ARB process continued up to eight rolling cycles. In the WARB process, the samples were preheated at 300∘C for 5[Formula: see text]min before each rolling cycle. It was realized that increasing the number of ARB cycles with 0 and 7.5[Formula: see text]wt.% of TiO2 particles improved the uniformity of TiO2 particles distribution in the aluminum matrix. Also, in samples with high contents of TiO2 particles (15%), TiO2 clusters converted into small clusters with a better distribution through the aluminum matrix. Also, by increasing the number of cycles and TiO2 wt.% up to 15%, the tensile strength, elongation, tensile toughness and average Vickers microhardness of hybrid composites were increased first and decreased then. Moreover, the effects of ARB cycles and TiO2[Formula: see text]wt.% on the fracture surface of hybrid composites have been studied by scanning electron microscopy (SEM). It was found that all the samples fabricated with one and two ARB cycles exhibited a typical ductile fracture containing deep dimples, whereas by increasing the TiO2[Formula: see text]wt.% and ARB cycles, a combination of ductile and shear ductile fracture have been detected in the fracture behavior.

Influence of Oscillating Packing Instrument on Microhardness of Bulk-Fill Composite: In Vitro Study

AIM: This study aimed to assess Vickers microhardness of Tetric EvoCeram Bulk Fill composite that was packed manually and using oscillating packing device.&#x0D; MATERIALS AND METHODS: Two different packing techniques were applied on Tetric EvoCeram Bulk Fill composite. For each packing technique, ten specimens (6 mm in diameter and 4 mm height) were prepared using a black-shaded Teflon mold. The resin was inserted in a bulk increment either packed manually or using Compothixo oscillating device and then light-cured for 40 s. Microhardness was analyzed at the top and the bottom surfaces.&#x0D; RESULTS: Overall, for both packing techniques, microhardness decreased significantly with the increase of depth. Tetric EvoCeram Bulk Fill composite when packed either manually or using oscillating device, did not show significant difference neither at the top surfaces of both applied techniques nor at the bottom surfaces of both applied techniques.&#x0D; CONCLUSION: Different packing techniques did not influence the microhardness of Tetric EvoCeram Bulk Fill composite.&#x0D;

Color stability, Roughness, and Microhardness of Enamel and Composites Submitted to Staining/Bleaching Cycles

ObjectiveTo compare the effect of two bleaching systems (bleaching gel and whitening strips) on the color change, roughness, and microhardness of enamel and two resin composites. Material and methodsTwo cavities were prepared on bovine enamel specimens (n = 16) and restored with two composites: a nano-hybrid [Herculite Ultra (HU)] and a micro-hybrid composite [TPH Spectra (TS)]. Baseline color (CIE L*a*b*), roughness (μm), and microhardness (kgf/mm2) were measured using a spectrophotometer, optical profilometer, and Vickers microhardness (VHN) tester, respectively. The specimens were stained with coffee for 14 days, and randomized into two bleaching groups: gel and strips (n = 8), then submitted to a 10-day bleaching/staining test. Color, roughness, and microhardness were re-measured. The outcomes were analyzed using two-way ANOVA and Fisher’s-PLSD test (α = 0.05). ResultsGel significantly improved the color (ΔE 4.9–8.3) and increased the roughness (Ra 0.04–0.08 μm) of all substrates (p < 0.0001) compared to strips. Enamel color was significantly improved (ΔE 5.4–8.3) compared to that of HU (ΔE 2.6–4.9) and TS (ΔE 2.0–4.9) with either gels or strips. TS roughness (0.03–0.08 μm) was significantly higher than that of enamel (0.01–0.05 μm) and HU (0.02–0.04 μm). Enamel had significantly reduced microhardness compared to HU (p = 0.0144). ConclusionGels produced the greatest color improvement and roughness compared to strips. Enamel had significant color improvement but had the greatest decrease in microhardness. Clinical significanceThere was unacceptable color change between enamel and the composites after the combined cyclic effects of staining and bleaching.

Effect of Ta content and sintering temperature on characteristics of nanocrystalline Cu-Ta nanocomposite

In this study, the microstructural, physical and mechanical properties of the nanocrystalline Cu-Ta material synthesized by mechanical milling and subsequent sintering were investigated affected by Ta content and sintering temperature. Scanning electron microscope and X-ray diffraction results showed that increasing Ta content from 1 to 5 wt% changed the material behavior during milling and resulted in reduction of powder particle size and crystallite size. For the sintered specimens, addition of Ta decreased the electrical conductivity due to reduced density and increased electron scattering effect while micro-hardness of Cu matrix was promoted. The higher sintering temperature about 850 °C also increased density and provided more segregation of Ta which was led to improvement in both micro-hardness and electrical conductivity of Cu-Ta composite. In addition, a comparison between sintering process at 850 °C by SPS method and conventional cold pressing- sintering revealed that SPS has a high potential to enhance physical and mechanical properties.

Fullerene Soot-Reinforced Al-Based Composites and Their Densification Via Copper Addition

Al-based composite materials reinforced with fullerene soot (FS) have been prepared by ball milling and subsequent hot pressing. The effects of FS and Cu content on microstructures and mechanical properties of the Al-based composites were investigated, and the role of Cu additions in Al-FS composites was shown. The composites have a complex dispersion-strengthened structure comprising an Al matrix and carbon nanoparticles embedded in it. Composites have high mechanical properties and 2-5% of porosity, which increased with an increase in FS content. We showed that an addition of 2% Cu to Al-FS composites decreases their porosity down to 0.1% for Al-2%FS-2%Cu. That was associated with the exothermic effect accompanied Al2Cu phase formation during hot pressing, leading to more active local sintering, and with the dissolution of oxygen adsorbed on the surface of the particles in the Al2Cu phase. Thus, the microhardness of the Al-FS composites reaches 165 HV, while an addition of 2%Cu results in an extra growth of the hardness up to 250 HV.

Microstructural studies on aluminium metal matrix composite (Al7075-SiC) fabricated through stir casting process

In the present work Al7075 metal matrix reinforced with silicon carbide (SiC) powder is fabricated through stir casting route. Metal matrix composites were manufactured by altering percent weight fraction of silicon carbide powder as 5% & 7.5% by weight with average particle size of 50 µm. Microstructural evaluation and Vickers microhardness studies on stir casted Aluminium 7075 alloy which has silicon carbide (SiC) reinforcement are reported in current paper. After stir casting of composites, manufactured composite samples are examined by using optical microscope and scanning electron microscope (SEM) in order to study distribution SiC particles in aluminium matrix. The microstructural observations on metal matrix composites have reported the presence of SiC reinforcement in the matrix which are very much fairly distributed into the matrix phase. Also it can be seen that there is little clustering of SiC particles in Al7075 matrix and porosity in manufactured composites. It is also been found that microhardness of aluminium metal matrix composites was improved with increment in reinforcement content.