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Shi Wen-jun - One of the best experts on this subject based on the ideXlab platform.

J R Van Horn - One of the best experts on this subject based on the ideXlab platform.

  • electrochemical and surface characterization of a Nickel Titanium Alloy
    Biomaterials, 1998
    Co-Authors: D J Wever, A G Veldhuizen, J De Vries, Henk J Busscher, Donald R A Uges, J R Van Horn
    Abstract:

    Abstract For clinical implantation purposes of shape memory metals the nearly equiatomic Nickel–Titanium (NiTi) Alloy is generally used. In this study, the corrosion properties and surface characteristics of this Alloy were investigated and compared with two reference controls, AISI 316 LVM stainless steel and Ti6Al4V. The anodic polarization curves, performed in Hanks’ solution at 37°C, demonstrated a passive behaviour for the NiTi Alloy. A more pronounced difference between the corrosion and breakdown potential, i.e. a better resistance to chemical breakdown of passivity was found for the NiTi Alloy compared to AISI 316 LVM. X-ray electron spectroscopy (XPS) and scanning electron microscopy (SEM) were undertaken to study the elemental composition and structure of the surface films prior to, and after immersion in Hanks’ solution. The passive film on the NiTi Alloy consists of a mainly TiO 2 -based oxide with minimal amounts of Nickel in the outermost surface layers. After immersion in Hanks’ solution the growth of a calcium-phosphate layer was observed. The passive diffusion of Nickel from the NiTi Alloy, measured by atomic absorption spectrophotometry reduced significantly in time from an initial release rate of 14.5×10 -7  μg cm -2  s -1 to a Nickel release that could not detect anymore after 10 days. It is suggested that the good corrosion properties of the NiTi Alloy and the related promising biological response, as reported in literature, may be ascribed to the presence of mainly a TiO 2 -based surface layer and its specific properties, including the formation of a calcium-phosphate layer after exposure to a bioenvironment.

  • cytotoxic allergic and genotoxic activity of a Nickel Titanium Alloy
    Biomaterials, 1997
    Co-Authors: D J Wever, A G Veldhuizen, M M Sanders, J M Schakenraad, J R Van Horn
    Abstract:

    The nearly equiatomic Nickel-Titanium (NiTi) Alloy is known for its shape memory properties. These properties can be put to excellent use in various biomedical applications, such as wires for orthodontic tooth alignment and osteosynthesis staples. The aim of this study was to evaluate the short-term biological safety of the NiTi Alloy. We carried out an end-point dilution minimal essential medium (MEM) extract cytotoxicity test, a guinea-pig sensitization test and two genotoxicity tests: the Salmonella reverse mutation test and the chromosomal aberration test. The NiTi Alloy showed no cytotoxic, allergic or genotoxic activity, similar to the clinical reference control material AISI 316 LVM stainless steel. This promising biological behaviour was most likely due to a minimal release of ions and in that way a reflection of the good corrosion resistance of the NiTi Alloy. Given these very good results, together with the good tissue compatibility as shown in several implantation studies in the literature, the NiTi Alloy can be regarded as a biologically safe implant material with many promising clinical applications.

Yanyan Ruan - One of the best experts on this subject based on the ideXlab platform.

  • late complications of Nickel Titanium Alloy stent in tracheal stenosis
    Laryngoscope, 2012
    Co-Authors: Wenxian Chen, Yanyan Ruan
    Abstract:

    Objectives/Hypothesis: To investigate and treat the late complications of using Nickel–Titanium Alloy stents in laryngotracheal, bronchial, and esophageal stenosis patients who developed severe laryngotracheal stenosis (SLS). Study Design: Retrospective clinical study. Methods: Thirteen patients with SLS or tracheoesophageal fistula secondary to insertion of a Nickel–Titanium Alloy stent for treatment of laryngotracheal, bronchial, or esophageal stenosis treated between May 2004 and March 2010 were retrospectively analyzed. Of the 13 total patients, nine had one stent placed, and four had two stents placed. The late complications observed were glottic and/or subglottic extension of cervical tracheal stenosis (n = 6), new stricture of the thoracic trachea (n = 4), severe left bronchial stricture with massive left pulmonary collapse (n = 1), and cervical tracheoesophageal fistula (n = 2). Results: Six patients with glottic and/or subglottic to cervical tracheal stenosis underwent successful laryngotracheal reconstruction. Two patients with subglottic and upper thoracic tracheal stenosis were successfully treated by staged operation for the stenosis. Two patients with subglottic and distal thoracic tracheal stenosis are still undergoing treatment. One patient with severe left bronchial stricture and massive left pulmonary collapse has been treated but has not achieved full recovery. One patient with cervical tracheoesophageal fistula underwent successful repair but died later from metastatic disease. One patient with tracheoesophageal fistula died from massive hemorrhage and asphyxiation induced by the stent, which had not been removed. Conclusions: The Nickel–Titanium Alloy stents should be used with extreme caution in patients with laryngotracheal, bronchial, or esophageal stenosis treatment that can be corrected by surgical therapy. Laryngoscope, 2012

Tongxi Yu - One of the best experts on this subject based on the ideXlab platform.

Linmao Qian - One of the best experts on this subject based on the ideXlab platform.

  • Comparison of nano-indentation hardness to microhardness
    Surface & Coatings Technology, 2005
    Co-Authors: Linmao Qian, Zhongrong Zhou, Hui Yang, Xinyu Shi
    Abstract:

    Abstract With a nano-indenter and a microhardness testing machine, nano-indentation hardness and microhardness are measured in a wide load range (0.1–19600 mN) for five materials. Even fused silica and silicon almost have constant hardness during the load range, the nano-indentation hardness of copper, stainless steel and Nickel Titanium Alloy shows obvious indentation size effect, namely that the hardness decreases with the increase of depth. For the measured materials, the nano-indentation hardness is about 10–30% in magnitude larger than the microhardness. The main reasons can be explained as the analysis of the nano-indentation hardness using the projected contact area at peak load A c instead of the residual projected area A r , as well as the purely elastic contact assumption describing the elastic/plastic indentation process. The analysis based on a simple model indicates that A c is always smaller than A r , and the more heavily the indent piles up (or sinks in), the larger the difference between the nano-indentation hardness and microhardness.

  • anomalous relationship between hardness and wear properties of a superelastic Nickel Titanium Alloy
    Applied Physics Letters, 2004
    Co-Authors: Linmao Qian, Xudong Xiao, Tongxi Yu
    Abstract:

    We have studied the behavior of microwear and hardness of a superelastic Nickel–Titanium Alloy using a triboindenter at various temperatures. Wear resistance was found to anomalously decrease with an increase in hardness. The observations are analyzed based on simple contact theory which suggests that the increase of hardness with the temperature is mainly due to an increase in phase transition stress, while the decrease of wear resistance with the temperature is due to an increase of the austenite elastic modulus and a decrease of the amount of phase transition that can be recovered.