In this study, the effect of the sintering time, temperature and graphene amount on titanium properties was examined for the first time in detail. From the results, the highly dense (4.39 g/cm3), ...most hard (from 390 HV to 566 HV) and improved microstructure for 0.15 wt% graphene addition were performed at 1100℃ for 120 min. The titanium composite properties have been reduced with increasing graphene due to damaged graphene and titanium carbide formation above 0.30 wt% graphene. To summarise, when pure titanium is compared with graphene reinforced titanium composites, the properties enhanced due to dislocation and fine grain strengthening mechanisms.
The traditional aluminum matrix composites were fabricated using pure graphene nanoplatelets (GNPs) and silicon carbide (SiC) in aluminum matrix due to the solid lubricant properties of GNPs and high ...hardness, compressive strength of SiC. However, a few studies are available on the effect of the binary SiC-GNPs reinforced aluminum hybrid composites in large scale. In this study, aluminum matrix was reinforced with pure SiC (varying from 0 to 30 wt.%), GNPs (changing from 0.1 to 0.5 wt.%) and their hybrid form (SiC-GNPs) by powder metallurgy method. From the results, hardness was improved to 79 ± 2 HV (Al-30SiC) and 57 ± 2.5 HV (Al-0.1GNPs) from 28 ± 2 HV, respectively. Similarly, compressive strength of the pure SiC and GNPs reinforced aluminum composite was enhanced to 221 ± 6 (Al-30SiC) and 138 ± 4 MPa (Al-0.5GNPs) from 106 ± 4 MPa, respectively. Interestingly, the highest hardness and compressive strength of the hybrid composites were measured as 85 ± 2.6 HV (Al-30SiC-0.5GNPs) and 271 ± 7 MPa (Al-30SiC-0.1GNPs), respectively.
•Aluminum matrix was reinforced with pure GNPs, SiC and synergistic GNPs-SiC particles.•Vickers hardness was improved to 85 ± 2.6 HV (Al-30SiC-0.5GNPs) from 28 ± 2 HV (pure Al).•Compressive strength of SiC-GNPs reinforced composite was enhanced to 271 ± 7 MPa (Al-30SiC-0.1GNPs) from 106 ± 4 MPa.•The properties of Al hybrid composites enhanced due to the dislocation and fine grain strengthening mechanisms.
This study reports on silicon nitride (Si
) and graphene nanoplatelets binary powder reinforced hybrid titanium composites obtained by a powder metallurgy method. Si
powder was added at 3 wt.% and ...graphene nanoplatelets were added in various amounts (0.15, 0.30, 0.45, 0.60 wt.%) in the titanium matrix. Density, micro-Vickers hardness, compressive behavior, wear properties and microstructure of the hybrid composites were evaluated. Addition of different percentages of graphene nanoplatelets and 3 wt.% Si
to the titanium matrix composites significantly enhanced mechanical properties. The highest hardness (634 HV) and compressive strength (1458 MPa) values were measured for 0.15 wt.% graphene nanoplatelets and 3 wt.% Si
added titanium hybrid composite. The lowest mass loss and wear rate (Δm = 4 mg, W = 6.1×10
mm
(N m)
) values were measured for the same 0.15 wt.% graphene nanoplatelets and 3 wt.% Si
added titanium hybrid composite compared with pure Ti.
In this study,
Si
3
N
4
and graphene-reinforced aluminium matrix composites (AMCs) with various contents (
Si
3
N
4
: 1, 3, 6, 9 wt%; graphene: 0.1, 0.3, 0.5 wt%) were produced by the powder ...metallurgy method. The phase and microstructure analyses of the composites were performed by X-ray diffractometry and scanning electron microscopy, respectively. To investigate the tribological behaviour of Al–
Si
3
N
4
and Al–
Si
3
N
4
–graphene composites, pin-on-disc experiments were conducted with different loads (
F
=
10
, 20 and 30 N) at a constant sliding speed (200 rpm). Thus, the effects of
Si
3
N
4
and graphene contents on microstructure, Vickers hardness, apparent density, porosity, wear rate and friction coefficient of AMCs were investigated. Test results reveal that the highest Vickers hardness (
66
±
1
HV
), the lowest porosity (5.6%), wear rate (
3.1
×
10
-
5
mm
3
N
-
1
m
-
1
)
and friction coefficient (0.13) were obtained for Al–9
Si
3
N
4
–0.1 graphene. After attaining 0.1% graphene content, agglomeration was detected from the microstructure images of
Si
3
N
4
–graphene-reinforced AMCs. It was concluded that
Si
3
N
4
had an outstanding wear resistance and graphene was a good solid lubricant for AMCs.
In this work, The hybrid hydroxyapatite (HaP), chitosan (CH) and graphene nanosheets (GNS) mixtures were applied by electrospinning on the surface of GNS and Si3N4 (SN) binary powder reinforced ...hybrid titanium (Ti) metal composites surface to improve composite biosurface functionallity. The surfaces of coated materials were characterized and antibacterial tests were carried on for their suitability in the industry by performing artificial body fluid tests. The hybrid nano fiber coatings formed a homogeneous structure on the composite. According to bioactivity tests and microstructure analysis, it was seen that HaP, which has the best results in the change of pH (pH= 11.80) values. The lowest mass change (0.0005 g) was observed on the 10th day of pure titanium. The highest mass change (0.0210 g) was obtained as on the HaP coated hybrid titanium composite. According to the antibacterial test result the hybrid nanofiber containing silver (Ag+) doped HaP on Ti composites showed the best antibacterial property aganist the E.coli. The fabricated electrospin coated hybrid composites can be a potantial candidate for dental, orthopedic implant applications and tissue engineering.
Currently, graphene is used in aluminum matrix composite manufacturing due to its superior mechanical properties. However, few detailed studies exist on the effect of the process conditions such as ...sintering temperature (TS), time (tS), and a number of graphene nanoplatelets. Therefore, the effects of different sintering times (tS = 60, 120, 180, 300 min), sintering temperatures (TS = 550, 600, 630℃), and graphene addition (0.1, 0.3, 0.5 wt%) on apparent density and hardness were reported in detail in this study. The crystal structure and microstructure of fabricated composites by powder metallurgy method were examined with X-ray diffractometer and scanning electron microscopy. Apparent density and mechanical properties were tested by density meter and micro Vickers hardness tester. The results indicated that the best sintering time, sintering temperature, and graphene addition were determined to be 180 min, 630℃, and 0.1 wt%, respectively, for the best hardness of composite. The hardness of composite increased from 38 to 57 HV when compared with pure aluminum under the best process conditions.
Magnesium-based alloys are promising materials as next generation biodegradable implants, however low corrosion resistance and inadequate mechanical properties are limiting their application as a ...biodegradable implant material. In this study, Mg-Sr-Ca ternary alloys were prepared in a vacuum/atmosphere controlled furnace and coated by microarc oxidation (MAO) process for 5min to decrease the degradation rate and enhance the biocompatibility. Moreover, Ag doped Hydroxyapatite nano powder (Ag-HA) was also added to alkaline MAO solution by amount of 1 and 10g/l to improve the antibacterial properties while enhancing their bioactivity in a one single process. XRD, SEM-EDS, FTIR spectroscopy, simulated body fluid (SBF) immersion and antibacterial tests were employed for the characterization of the coated alloys. The results showed that, the addition of more Ag-HA increased the HA formation both before and after SBF immersion test and enhanced their antibacterial properties. However, Ag-HA addition decreased the corrosion resistance of the coated alloys in SBF compared to Ag-HA free coating. The results indicated that the present Ag-HA nano powder added MAO coating is a good combination to enhance the corrosion resistance, bioactivity and the antibacterial properties of Mg based biodegradable alloys.
•Silver doped Hydroxyapatite (Ag-HA) addition improved antibacterial properties.•HA morphology is related to Ag-HA content in the electrolyte.•The increase of Ag-HA content in the electrolyte increased the HA formation.•Increasing the Ag-HA concentration resulted in the Ca/P ratio approaching to 1.67.
Ni–Ti stents are perceived as foreign substances in the body and cause damage to the cell wall. Therefore, binary PVA/Propolis (PVA/PP) biopolymer nanofibers were spun on commercial Ni–Ti stent ...surfaces with electrospinning method to overcome these problems. In this study, the spun coatings' suspension mixtures were prepared in different ratios as 10 wt% PVA-1 wt% PP, 10 wt% PVA-3 wt% PP, 10 wt% PVA-5 wt% PP. The successively fabricated nanofibers (< 100 nm) were characterized with a stereo microscope, SEM, FTIR, AFM, and TG, dissolution and antibacterial tests. From the results, the best-spun rates and spun amounts were determined as 10 wt% PVA-5 wt% PP composition. The fiber coatings well adhere to the Ni–Ti stent surface and form a fiber structure without gaps. PVA/PP decomposition temperature decreased compared to PVA with increasing propolis from TG analysis. The strong hydrogen bonds were formed between the PVA and PP from FTIR analyses. The antibacterial effect against
Escherichia Coli
. shown for PVA/PP composition. In bioactivity test, the higher pH change (6.98 to 7.65) and mass change (0.0165 to 0.0565 g) were observed for 10 wt% PVA-5 wt% PP coated Ni–Ti stent in Ringer’s solution depends on the immersion day. 10PVA-5PP coated sample had also been found that dissolves in artificial body fluid and more nanofiber structure. More nanofibers (diameter 30–35 nm) and less beadless morphology were fabricated for 10PVA-5PP. The higher surface roughness values (Ra: 68.95 nm) were observed after electrospun 10PVA-5PP fibers compared to uncoated samples (Ra: 22.60 nm) with AFM analyzes.
In this study, pure aluminum was reinforced with pure silicon nitride (varying from 1 to 12 wt%), pure graphene nanoplatelets (changing from 0.1 to 0.5 wt%), and their hybrid form (silicon ...nitride/graphene nanoplatelets) by using powder metallurgy method. The results show that Vickers hardness increased to 57.5 ± 3 HV (Al-9Si3N4) and 57 ± 2.5 HV (Al-0.1GNPs) from 28 ± 2 HV (pure aluminum). Similarly, ultimate compressive strength of the pure silicon nitride and pure graphene nanoplatelet-reinforced aluminum composite was improved to 268 ± 6 MPa (Al-9Si3N4) and 138 ± 4 MPa (Al-0.5GNPs) from 106 ± 4 MPa (pure aluminum), respectively. Interestingly, the highest Vickers hardness, ultimate compressive strength, and ultimate tensile strength of aluminum-silicon nitride-graphene nanoplatelet hybrid composites were determined as 82 ± 3 HV (Al-9Si3N4-0.5GNPs), 334 ± 9 MPa (Al-9Si3N4-0.1GNPs), and 132 MPa (Al-9Si3N4-0.1GNPs), respectively. The Vickers hardness (for Al-9Si3N4-0.5GNPs), ultimate compressive strength (for Al-9Si3N4-0.1GNPs), and ultimate tensile strength (for Al-9Si3N4-0.1GNPs) improved ∼193%, ∼215%, and ∼47% when compared to pure Al, respectively. Above 9 wt% silicon nitride and 0.1 wt% graphene nanoplatelets content, an adverse effect was observed due to the agglomeration of silicon nitride and graphene nanoplatelets in aluminum matrix composites. Also, energy-dispersive X-ray and scanning electron microphotographs confirmed the presence of both silicon nitride and graphene nanoplatelets and uniformly distributed in the aluminum matrix.
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•Novelty, hMSCs were grown on fabricated metal ion (Zn, Ag and Cu) doped HAP nano-coating surfaces.•Nano-powders are biocompatible and have no negative effects on the hMSCs ...proliferation.•Promoted osteogenic differentiation by surfaces without exogenous osteogenic stimulation.•Enhanced cell adhesion.•HAP-Ag, HAP-ZAg and HAP-ZAgCu nano-powders may have good potential in future bone tissue engineering applications.
Accelerated Mesenchymal Stem Cells (MSCs) condensation and robust MSC-matrix and MSC-MSC interactions on nano-surfaces may provide critical factors contributing to such events, likely through the orchestrated signal cascades and cellular events modulated by the extracellular matrix. In this study, human adipose tissue derived mesenchymal stem cells (hMSC)', were grown on metal ion (Zn, Ag and Cu) doped hydroxyapatite (HAP) nano-coated surfaces. These metal ions are known to have different chemical and surface properties; therefore we investigated their respective contributions to cell viability, cellular behavior, osteogenic differentiation capacity and substrate-cell interaction. Nano-powders were produced using a wet chemical process. Air spray deposition was used to accumulate the metal ion doped HAP films on a glass substrate. Cell viability was determined by MTT, LDH and DNA quantitation methods Osteogenic differentiation capacity of hMSCs was analyzed with Alizarin Red Staining and Alkaline Phosphatase Specific Activity. Adhesion of the hMSCs and the effect of cell adhesion on biomaterial biocompatibility were explored through cell adhesion assay, immunofluorescence staining for vinculin and f-actin cytoskeleton components, SEM and microarray including 84 known extracellular matrix proteins and cell adhesion pathway genes, since, adhesion is the first step for good biocompability. The results demonstrate that the viability and osteogenic differentiation of the hMSCs (in growth media without osteogenic stimulation) and cell adhesion capability are higher on nanocoated surfaces that include Zn, Ag and/or Cu metal ions than commercial HAP. These results reveal that Zn, Ag and Cu metal ions contribute to the biocompatibility of exogenous material.
