This study examined the evolution of the microstructure, microhardness, corrosion resistance, and selective leaching properties of oxide films formed on the surface of a Ti-50Zr (%) alloy during heat ...treatment at 600 °C for various time intervals. According to our experimental results, the growth and evolution of oxide films can be divided into three stages. In stage I (heat treatment for less than 2 min), ZrO
was first formed on the surface of the TiZr alloy, which slightly improved its corrosion resistance. In stage II (heat treatment for 2-10 min), the initially generated ZrO
is gradually transformed into ZrTiO
from the top to the bottom of the surface layer. The formation of ZrTiO
significantly improves the microhardness and corrosion resistance of the alloy. In stage III (heat treatment for more than 10 min), microcracks appeared and propagated on the surface of the ZrTiO
film, deteriorating the surface properties of the alloy. The ZrTiO
began to peel off after heat treatment for more than 60 min. The untreated and heat-treated TiZr alloys exhibited excellent selective leaching properties in Ringer's solution, whereas a trace amount of suspended ZrTiO
oxide particles formed in the solution after soaking the 60 min heat-treated TiZr alloy for 120 days. Surface modification of the TiZr alloy by generating an intact ZrTiO
oxide film effectively improved its microhardness and corrosion resistance; however, oxidation should be performed appropriately to obtain materials with optimal properties for biomedical applications.
This study investigates the damping properties of Cu–Al–Mn shape memory alloys (SMAs) with various chemical compositions and the effects of the addition of quaternary alloying elements Ag and Nb on ...the microstructure, martensitic transformation behavior, and damping capacity of SMAs. Compared to other Cu–12Al–xMn (x = 4–7 wt%) SMAs, Cu–12Al–5Mn has a more significant inherent and intrinsic internal friction (IFPT + IFI) peak above room temperature. The addition of Ag or Nb to Cu–12Al–5Mn reduced the grain size, thereby increasing the hardness of the alloys; however, the damping capacity and temperature of the IFPT + IFI peak decreased simultaneously. The addition of Ag to Cu–12Al–5Mn significantly reduced the damping capacity (IFPT+IFI peak) because of the notable decrease in the amount of transformed martensite. Moreover, the addition of Nb to Cu–12Al–5Mn caused the AlNb3 phase to precipitate, limiting the mobility of the martensite variant interfaces and slightly decreasing the damping capacity (IFPT + IFI peak). Among the Ag- and Nb-doped Cu–12Al–5Mn SMAs, Cu–12Al–5Mn–1 Nb showed not only a significantly higher hardness but also a higher IFPT + IFI peak, with tan δ exceeding 0.01 at approximately 50 °C.
Display omitted
•In Cu-based SMAs, damping capacity depends on microstructure and the volume fraction of the transformed martensite.•Alloying elements with different mechanisms affect the damping performance of Cu-based SMAs.•In Cu-based SMAs, both damping capacity and mechanical strength improve by optimizing chemical composition.
This study investigates the effect of Co additions on the damping properties of Cu-13.5Al–4Ni-xCo and Cu-14.0Al–4Ni-xCo (x = 0–2 wt%) shape memory alloys (SMAs). The Cu-14.0Al–4Ni SMA exhibits a ...higher inherent and intrinsic internal friction (IFPT + IFI) peak than the Cu-13.5Al–4Ni SMA, but its (IFPT + IFI) peak temperature is below 0 °C. Adding Co into the Cu-14.0Al–4Ni SMA can effectively increase the (IFPT + IFI) peak temperature and reduce the grain size of the alloys. The grain size of the Cu-14.0Al–4Ni-xCo SMAs decreases from approximately 300 μm to below 50 μm when the Co content increases from 0 to 2 wt%. The (IFPT + IFI) peak temperature for the Cu-14.0Al–4Ni-xCo SMAs increases from −0.1 °C to 77.7 °C when the Co content increases from 0 to 1 wt%, but their tan δ values decrease from 0.0402 to 0.0090 simultaneously. The Cu-14.0Al–4Ni–2Co SMA does not exhibit an observable (IFPT + IFI) peak. The tan δ values of the (IFPT + IFI) peaks decrease with increasing Co content because the movements of the parent/martensite phase interfaces and twin boundaries are impeded by the increased amounts of grain boundaries and γ2 phase precipitates. Among these Cu–Al–Ni–Co SMAs, the Cu-14.0Al–4Ni-0.5Co SMA is more suitable for high-damping applications as it possesses an (IFPT + IFI) peak with tan δ close to 0.02 at approximately 50 °C.
•Adding Co into Cu–Al–Ni SMAs can increase the (IFPT + IFI) peak temperature.•Adding Co into Cu–Al–Ni SMAs can reduce the grain size of the alloys.•The tan δ values of Cu–Al–Ni–Co SMAs decrease with increasing Co content.•Cu-14.0Al–4Ni-0.5Co possesses an (IFPT + IFI) peak with tan δ close to 0.02 at 50°C.
Abstract
In this study, we analyze the influences of carbon nanotube (CNT) addition on the martensite transformation and internal friction of Cu–Al–Ni shape-memory alloys (SMAs). X-ray diffraction ...and differential scanning calorimetry results demonstrate that Cu–13.5Al–4Ni–
x
CNT (
x
= 0, 0.2, 0.4, 0.6, and 0.8 wt%) SMA/CNT composites exhibit a
$${\upbeta }_{1}({\mathrm{DO}}_{3})\rightleftarrows {\upbeta }_{1}^{\mathrm{^{\prime}}}(18\mathrm{R})$$
β
1
(
DO
3
)
⇄
β
1
′
(
18
R
)
martensitic transformation. The martensitic transformation temperatures and transformation enthalpies of the martensitic transformation peaks for the Cu–13.5Al–4Ni–
x
CNT (
x
= 0–0.8 wt%) composites gradually decrease with the increase in the amount of CNT addition. Compared to the Cu–13.5Al–4Ni SMA, the Cu–13.5Al–4Ni–
x
CNT (
x
= 0.2–0.8 wt%) SMA/CNT composites exhibit significant improvements in the amount of dissipation of energy (storage modulus (
$${E}^{\prime}))$$
E
′
)
)
and mechanical strength. However, the tan δ of the internal friction peak gradually decreases with the increase in the CNT content above 0.6 wt%. The reduction in tan
δ
is attributed to the decrease in the magnitude of the austenite-to-martensite transformation and precipitation of γ
2
(Cu
9
Al
4
) phase particles, which impede the interface motion in between the parent/martensitic phase and martensitic phase.
•The HIFP of the Sn-3Ag-0.5Cu increases with increases in the amount of MWCNTs.•The HHTDB of the Sn-3Ag-0.5Cu decreases with increases in the number of MWCNTs.•MWCNT reinforcement deteriorates the ...damping and creep resistance of the solders.
Sn-3Ag-0.5Cu solder exhibits an internal friction peak, which corresponds to the sliding of the grain boundaries, in the heating internal friction curve. The activation energy of the internal friction peak increases with the number of reinforced multiwall carbon nanotubes (MWCNTs) because the Sn-3Ag-0.5Cu solder has a finer grain size and more abundant sliding grain boundaries after reinforcement with MWCNTs. The activation energy of the high-temperature damping background (HTDB) of the Sn-3Ag-0.5Cu solder decreases after reinforcement with MWCNTs, indicating that MWCNT reinforcement accelerates the dislocation diffusion process and creep process at the HTDB temperature of the Sn-3Ag-0.5Cu solder.
In this study, diethoxydimethylsilane (DEDMS) was blended with chitosan (CS) to fabricate DEDMS/CS composite films, which were deposited on the surface of 316L stainless steel to assess their ...anticoagulant properties. A neat CS film exhibits a high concentration of bovine serum albumin (BSA) protein adhesion of 458.3 ± 6.2 μg/L in a bicinchoninic acid protein assay because the carbonyl and amide functional groups on the CS surface easily form hydrogen bonds with the carboxylic acid functional groups of the BSA protein. The DEDMS/CS composite films exhibited lower BSA adhesion concentration than neat CS films because some of the carbonyl and amide functional groups on the surface of CS were replaced by the –Si-O-Si and –Si-(CH3)2 functional groups. Increasing the DEDMS content in the DEDMS/CS composite films led to a higher concentration of –Si-O-Si and –Si-(CH3)2 functional groups on the surface and lower BSA adhesion concentration. Blending excess amounts of DEDMS caused an undesirable rougher surface morphology because of the hydrolysis and self-condensation reactions of DEDMS; this deteriorated the anticoagulant properties of the composite films. The study confirmed that a DEDMS/CS composite film with an appropriate DEDMS/CS content ratio of 8/92 mL/mL possesses hydrophobic characteristics and the lowest BSA protein adhesion of 155.5 ± 1.0 μg/L and has potential for biomedical coating applications.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
•Plasma-modified chitosan exhibit superior hydrophilicity to that of unmodified one.•Plasma-modified chitosan possess enhanced biodegradability than unmodified one.•Plasma-modified chitosan exhibit ...less BSA protein adsorption in BCA protein assays.
This study investigates how plasma surface modification influences chitosan film biodegradability and protein adsorption properties. Plasma-modified chitosan films exhibit significantly more hydroxyl and carboxylic acid absorption bands in infrared spectra, and therefore exhibit superior hydrophilicity to that of unmodified chitosan films. The plasma-modified chitosan films exhibit rougher surface morphologies and higher swelling ratios in comparison to unmodified chitosan films. The plasma-modified chitosan films possess enhanced biodegradability in comparison to unmodified chitosan films, because more hydroxyl and carboxylic acid groups are metabolized during biodegradation. The plasma-modified chitosan films exhibit less bovine serum albumin (BSA) adsorption in bicinchoninic acid protein assays because the carboxylic acid group in bovine serum albumin is charge-charge repulsed from the abundant carboxylic acid group on the film surface. The 120s plasma-modified chitosan film possesses optimal hydrophilicity, swelling property, biodegradability, and the lowest BSA protein adsorption, because prolonged plasma treatment time may cause films surface damage.
The surface and protein adsorption properties of 316L stainless steel (316L SS) modified with polycaprolactone (PCL) films are systematically investigated. The wettability of the PCL films was ...comparable to that of bare 316L SS because the rough surface morphology of the PCL films counteracts their hydrophobicity. Surface modification with PCL film significantly improves the corrosion resistance of the 316L SS because PCL is insulating in nature. A coating of PCL film effectively reduces the amount of adhered bovine serum albumin (BSA) on the surface of 316L SS in a bicinchoninic acid protein assay. PCL is both biodegradable and biocompatible, suggesting the potential for the surface modification of implants used in human bodies; in these applications, excellent corrosion resistance and anticoagulant properties are necessary.
In this study, we firstly investigated the surface and protein adsorption properties of montmorillonite (MMT)/chitosan (CS) composite films with various MMT/CS weight ratios for metallic implants ...coating applications. Bicinchoninic acid (BCA) protein assay results show that the neat CS film exhibits a high concentration of bovine serum albumin (BSA) protein adhesion because the abundant carbonyl and amide functional groups on the surface of the CS film easily form hydrogen bonds with the copious carboxylic acid groups on the surface of the BSA protein. The MMT/CS composite films with MMT/CS = 3, 5, 8, and 10 possess a much lower BSA adhesion concentration than that of the neat CS film, as some of the carbonyl and amide functional groups on the surface of the composite films are replaced by the –Si–O–Si and –Al–O–Al groups. Among these MMT/CS composite films, the film with MMT/CS = 5 exhibits the lowest BSA adsorption concentration because it possesses a higher MMT content than those with MMT/CS = 1 and 3 and a smoother and non-porous surface than those with MMT/CS = 8 and 10. According to our results, MMT/CS composite films with appropriate MMT/CS weight ratios exhibit better surface and protein adsorption properties than neat CS for biomedical applications.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
This study investigated the surface and electrochemical properties of carbon cloth electrodes surface-modified by using atmospheric pressure plasma jets (APPJs) for applications involving microbial ...fuel cells (MFCs). APPJ treatment made the carbon cloth highly hydrophilic and did not introduce any observable cracks or flaws. MFCs configured with APPJ-treated carbon cloth electrodes exhibited electrochemical performance (maximum power density of 7.56 mW m−2) superior to that of MFCs configured with untreated carbon cloth electrodes (maximum power density of 2.38 mW m−2). This boost in performance can be attributed to the formation of abundant carboxyl and ammonium functional groups on the surface of APPJ-treated carbon cloth, which promoted the formation of anodic biofilms and the adhesion of bacteria, while facilitating the transfer of electrons from the bacteria to the electrodes. APPJ surface modification is non-toxic and environmentally friendly (no exogenous chemicals are required), which is particularly beneficial as the introduction of toxins might otherwise inhibit bacterial growth and metabolism. The APPJ surface modification process is rapid, cost-effective, and applicable to substrates covering a large area, making it ideal for the fabrication of large-scale MFCs and bioelectrochemical bioenergy devices.
•APPJs surface-modified carbon cloth electrodes were provided for MFCs.•The surface of carbon cloth became highly hydrophilic after APPJ treatment.•MFC with APPJ-treated carbon cloth exhibited better electrochemical performance.•APPJ process could prevent the risk of introducing biotoxic chemical species.•APPJ process was ideal for the fabrication of large-scale MFCs.
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