scholarly journals Key Properties of a Bioactive Ag-SiO2/TiO2 Coating on NiTi Shape Memory Alloy as Necessary at the Development of a New Class of Biomedical Materials

2021 ◽  
Vol 22 (2) ◽  
pp. 507
Author(s):  
Mateusz Dulski ◽  
Robert Gawecki ◽  
Sławomir Sułowicz ◽  
Michal Cichomski ◽  
Alicja Kazek-Kęsik ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Dermal Fibroblast ◽  
Niti Alloy ◽  
Bacterial Biofilm ◽  
Niti Shape Memory Alloy ◽  
Normal Human Dermal Fibroblast ◽  
Water Contact ◽  
Nano Coating

Recent years have seen the dynamic development of methods for functionalizing the surface of implants using biomaterials that can mimic the physical and mechanical nature of native tissue, prevent the formation of bacterial biofilm, promote osteoconduction, and have the ability to sustain cell proliferation. One of the concepts for achieving this goal, which is presented in this work, is to functionalize the surface of NiTi shape memory alloy by an atypical glass-like nanocomposite that consists of SiO2-TiO2 with silver nanoparticles. However, determining the potential medical uses of bio(nano)coating prepared in this way requires an analysis of its surface roughness, tribology, or wettability, especially in the context of the commonly used reference coat-forming hydroxyapatite (HAp). According to our results, the surface roughness ranged between (112 ± 3) nm (Ag-SiO2)—(141 ± 5) nm (HAp), the water contact angle was in the range (74.8 ± 1.6)° (Ag-SiO2)—(70.6 ± 1.2)° (HAp), while the surface free energy was in the range of 45.4 mJ/m2 (Ag-SiO2)—46.8 mJ/m2 (HAp). The adhesive force and friction coefficient were determined to be 1.04 (Ag-SiO2)—1.14 (HAp) and 0.247 ± 0.012 (Ag-SiO2) and 0.397 ± 0.034 (HAp), respectively. The chemical data showed that the release of the metal, mainly Ni from the covered NiTi substrate or Ag from Ag-SiO2 coating had a negligible effect. It was revealed that the NiTi alloy that was coated with Ag-SiO2 did not favor the formation of E. coli or S. aureus biofilm compared to the HAp-coated alloy. Moreover, both approaches to surface functionalization indicated good viability of the normal human dermal fibroblast and osteoblast cells and confirmed the high osteoconductive features of the biomaterial. The similarities of both types of coat-forming materials indicate an excellent potential of the silver-silica composite as a new material for the functionalization of the surface of a biomaterial and the development of a new type of functionalized implants.

EFFECTS OF PARTICLE SIZE AND SINTERING TEMPERATURE ON SUPERELASTICITY BEHAVIOR OF NiTi SHAPE MEMORY ALLOY USING NANOINDENTATION

2021 ◽  
pp. 2150024
Author(s):  
C. VELMURUGAN ◽  
V. SENTHILKUMAR
Keyword(s):  
Particle Size ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Sintering Temperature ◽  
Niti Alloy ◽  
Indentation Load ◽  
Niti Shape Memory Alloy ◽  
Recovery Ratio ◽  
Work Recovery ◽  
Niti Sma

The present study investigates the superelasticity properties of spark plasma sintered (SPS) nickel titanium shape memory alloy (NiTi SMA) with the influence of sintering temperature and particle size. The nanoindentation is conducted on the surface of the NiTi SMA at various loads such as 100, 300 and 500[Formula: see text]mN. The nanoindentation technique determines the quantitative results of elasto-plastic properties such as depth recovery in the form of superelasticity, stiffness, hardness and work recovery ratio from load–depth ([Formula: see text]–[Formula: see text]) data during loading and unloading of the indenter. Experimental findings show that the depth and work recovery ratio increases with the decrease of indentation load and particle size. In contrast, increasing the sintering temperature exhibited a better depth and work recovery due to the removal of pores which could enhance the reverse transformation. The contact stiffness is influenced by [Formula: see text] which leads to attain a maximum stiffness at the highest load (500[Formula: see text]mN) and particle size (45[Formula: see text][Formula: see text]m) along with the lowest sintering temperature (700∘C). NiTi alloy exhibited a maximum hardness of 9.46[Formula: see text]GPa when subjected to indent at the lowest load and particle size sintered at 800∘C. The present study reveals a better superelastic behavior in NiTi SMA by reducing the particle size and indentation load associated with the enhancement of sintering temperature.

scholarly journals Analysis of Surface Roughness and Flank Wear Using the Taguchi Method in Milling of NiTi Shape Memory Alloy with Uncoated Tools

Coatings ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1259
Author(s):  
Emre Altas ◽  
Hasan Gokkaya ◽  
Meltem Altin Karatas ◽  
Dervis Ozkan
Keyword(s):  
Surface Roughness ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Flank Wear ◽  
Cutting Tools ◽  
Dominant Factor ◽  
Niti Shape Memory Alloy ◽  
Machining Parameters ◽  
Nose Radius ◽  
Dry Cutting

The aim of this study was to optimize machining parameters to obtain the smallest average surface roughness (Ra) and flank wear (Vb) values as a result of the surface milling of a nickel-titanium (NiTi) shape memory alloy (SMA) with uncoated cutting tools with different nose radius (rε) under dry cutting conditions. Tungsten carbide cutting tools with different rε (0.4 mm and 0.8 mm) were used in milling operations. The milling process was performed as lateral/surface cutting at three different cutting speeds (Vc) (20, 35 and 50 m/min), feed rates (fz) (0.03, 0.07 and 0.14 mm/tooth) and a constant axial cutting depth (0.7 mm). The effects of machining parameters in milling experiments were investigated based on the Taguchi L18 (21 × 32) orthogonal sequence, and the data obtained were analyzed using the Minitab 17 software. To determine the effects of processing parameters on Ra and Vb, analysis of variance (ANOVA) was used. The analysis results reveal that the dominant factor affecting the Ra is the cutting tool rε, while the main factor affecting Vb is the fz. Since the predicted values and measured values are very close to each other, it can be said that optimization is correct according to the validation test results.

Corrosion Kinetics of Laser Treated NiTi Shape Memory Alloy Biomaterials

1996 ◽  
Vol 459 ◽  
Author(s):  
F. Villermaux ◽  
I. Nakatsugawa ◽  
M. Tabrizian ◽  
D. L. Piron ◽  
M. Meunier ◽  
...  
Keyword(s):  
Corrosion Resistance ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Laser Treatment ◽  
Niti Alloy ◽  
Niti Shape Memory Alloy ◽  
Surgical Implants ◽  
Hank’S Solution ◽  
Kinetics Of ◽  
Human Fluids

ABSTRACTNiTi shape memory alloy presents interesting mechanical properties as surgical implants. However, due to its high amount of Ni which may dissolve and release toxic ions in human fluids, the medical use of this material is a great concern. We have developed a laser treatment which modifies the oxide layer and enhances uniform and localised corrosion resistance of NiTi alloy.In this paper we further analysed the effect of this treatment with potentiostatic and AC impedance measurements in physiological Hank's solution. We conclude that the laser treatment creates a stable passive film which results in improved corrosion resistance of this alloy.

scholarly journals Experimental Analysis of NiTi Alloy during Strain-Controlled Low-Cycle Fatigue

Materials ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4455
Author(s):  
Pedro Cunha Lima ◽  
Patrícia Freitas Rodrigues ◽  
Ana Sofia Ramos ◽  
José D. M. da Costa ◽  
Francisco Manuel Braz Fernandes ◽  
...  
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Low Cycle Fatigue ◽  
Niti Alloy ◽  
Niti Shape Memory Alloy ◽  
Cycle Fatigue ◽  
Maximum Deformation ◽  
Transmission Electron ◽  
Before And After

The interaction between the stress-induced martensitic transformation and resistivity behavior of superelastic NiTi shape memory alloy (SMA) was studied. Strain-controlled low-cycle fatigue up to 6% was monitored by in situ electrical resistivity measurements. The experimental results show that a great motion of martensite fronts results in a significant accumulation of defects, as evidenced by transmission electron microscopy (TEM), before and after the tensile cycles. This gives rise to an overall increase of the resistivity values up to the maximum deformation. Therefore, the research suggests that shape memory alloy wire has great potential as a stress sensor inside bulk materials.

scholarly journals Functional Behavior of Pseudoelastic NiTi Alloy Under Variable Amplitude Loading

2020 ◽  
Vol 14 (3) ◽  
pp. 154-160
Author(s):  
Volodymyr Iasnii ◽  
Petro Yasniy ◽  
Yuri Lapusta ◽  
Oleg Yasniy ◽  
Oleksandr Dyvdyk
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Residual Strain ◽  
Niti Alloy ◽  
Strain Curve ◽  
Niti Shape Memory Alloy ◽  
Dissipation Energy ◽  
Variable Amplitude Loading ◽  
Variable Amplitude ◽  
Lower Amplitude

Abstract Cyclic loading of superelastic NiTi shape memory alloy (SMA) causes forward and reverse austenite–martensіte transformations, and also increases the volume of stabilized martensite. This appears in the change of stress-strain curve form, the decrease of dissipation energy, and increase of residual strain, that is, named transformation ratcheting. In real structures, the SMA components in most cases are under the action of variable amplitude loading. Therefore, it is obvious that the loading history will influence the functional fatigue. In the present work, the effect of stress ratio on the functional properties of superelastic NiTi shape memory alloy under variable amplitude loading sequence with two blocks was investigated. The studies were carried out under the uniaxial tension of cylindrical specimens under load-full unload and load-part unload. The change of residual strain, strain range, dissipation, and cumulative dissipation energy density of NiTi alloy related to load sequences are discussed. Under both stress ratios, the residual strain in NiTi alloy is increased depending on the number of loading cycles on the high loading block that is similar to the tests at constant stress or strain amplitude. An unusual effect of NiTi alloy residual strain reduction with the number cycles is found at a lower block loading. There was revealed the effect of residual strain reduction of NiTi alloy on the number of loading cycles on the lower amplitude block. The amount of decrement of the residual strain during a low loading block is approximately equal to the reversible part of the residual strain due to the stabilized martensite. The decrease of the residual strain during the low loading block is approximately equal to the reversible part of residual strain due to the stabilized martensite. A good correlation of the effective Young’s modulus for both load blocks with residual strain, which is a measure of the volume of irreversible martensite, is observed.

Damping Characteristics of Biomedical Porous NiTi Shape Memory Alloy

2010 ◽  
Vol 97-101 ◽  
pp. 1083-1086
Author(s):  
Hai Chang Jiang ◽  
Shu Wei Liu ◽  
Xiu Yan Li ◽  
Li Jian Rong
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Strain Amplitude ◽  
Niti Alloy ◽  
Small Strain ◽  
Cooling Curve ◽  
Niti Shape Memory Alloy ◽  
Internal Friction Peak ◽  
Porous Niti ◽  
Tan Δ

One internal friction peak associated with the B2↔B19’ transformation appears on the cooling curve of porous NiTi shape memory alloy and the dense NiTi alloy shows the maximum peak. The tan δ value increased with the increasing of strain amplitude and the decreasing of frequency. Tan δ value of porous alloy mainly comes from the energy absorbing of the matrix at the small strain amplitude, however, if the strain amplitude is large, the tan δ value comes from the energy consumption that overcomes the friction between folds and the plastic contribution.

Stress Analysis and Sealing Performance of Pipe Flange Connections With NiTi Shape Memory Alloy Gasket

2007 ◽  
Author(s):  
Yoshio Takagi ◽  
Teruhisa Tatsuoka ◽  
Naoki Kawasaki ◽  
Toshiyuki Sawa
Keyword(s):  
Thermal Expansion ◽  
Elastic Modulus ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Niti Alloy ◽  
Fem Analysis ◽  
Effect Of Temperature ◽  
Niti Shape Memory Alloy ◽  
3D Fem ◽  
Sealing Performance

Due to the long-term durability and the excellent resistance to aging degradation, metal gaskets are expected to give a longer life compared to conventional polymer gaskets. However, the nature of high elastic modulus of the metal reduces the sealing performance at interface. Nickel-Titanium shape memory alloy (NiTi alloy) shows an excellent elasticity and is expected to be applicable as a gasket. The authors have already evaluated the sealing performance of the pipe flange connections with NiTi gaskets. The results revealed that NiTi alloy showed a superior sealing performance to the conventional aluminum gasket. However, the sealing performance of the connection depended on the ambient temperature due to the change in physical properties like the elastic modulus and the thermal expansion coefficient of NiTi alloy. In this paper, the stress distribution was analyzed with 3D FEM and the effect of temperature in the sealing performance was evaluated. In the analysis, the particular element code was adopted for analyzing the deformation behavior of NiTi alloy gasket. The elements worked well in the analysis and helped to evaluate the sealing behavior of the flange connections. According to the analysis, the gasket contact stress decreased as increasing the temperature because of the lower thermal expansion of NiTi alloy than that of austenitic stainless steel of which the flange and bolt material were made. On the other hand, the FEM analysis suggested that the increment of elastic modulus of NiTi alloy compensate the reduction of compression strain of the gasket due to the difference of thermal expansion between gasket and flange. As a result of the ex-experimental study and FE analysis, the recommendable assembling process for NiTi alloy gasket was proposed.

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