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The spent bleaching clays (SBC) of vegetable oil refining plants have residual vegetable oil contents ranging from 17 to 40 wt%. The common worldwide practice of landfilling such spent clays imposes inevitable environmental hazards. The extraction of oil from a spent clay will not only alleviate this problem, but can also provide an oil source for processes, such as transesterification for the production of alcohol-esters. In-situ transesterification of the residual oil within SBC is an even more attractive idea, as it can eliminate the extraction step from the process. In this study, in-situ transesterification on the spent bleaching clay of a local vegetable oil plant was investigated experimentally. Furthermore, optimum operating conditions were determined for a number of parameters influencing the conversions, including reaction temperature, ethanol-to-SBC ratio, alkali catalyst type, and catalyst-to-SBC mass ratio. The experiments were designed by the response surface method based on the central composite approach (RSM-CCD model). The results were analyzed using the analysis of variance method (ANOVA) to investigate the effect of the parameters on the efficiencies of the biodiesel produced and the oil removed from the initial SBC. Within the ranges investigated, the maximum conversion to ethyl-ester was 72.90% at the optimum conditions of a reaction temperature of 73.2 °C, reaction time of 4.5 h, ethanol/SBC ratio of 4.2 ml/g, while using NaOH alkali catalyst with a catalyst-to-SBC mass ratio of 4.33%.

This work presents a study of the mechanical properties and influence of thermomechanical training conditions on the two-way shape-memory effect (TWSME) (magnitude and stability) in NiTi and NiTiCu alloys. Correlation with a stress-assisted two-way shape-memory effect (SATWSME) was also investigated. A rapid solidification technique was employed for preparation of small-dimension NiTi samples with homogeneous microstructure. Samples were fabricated by melt spinning. The melt-spun ribbons were trained under tensile deformation by thermal cycling through the phase transformation temperature range. Results showed that the tensile trainings under both constant strain and constant stress were effective in developing a TWSME. The SATWSME was comparable in magnitude to the TWSME. Addition of copper was effective in narrowing the transformation hysteresis and transformation temperature dependence on composition.

Practically all metals and alloys survive high-temperature exposure by growing oxide scales and/or by precipitation of the oxide particles in the matrix. Formed products can grow in shape of external oxide layers on surfaces, or as discrete oxide particles precipitated in a metal matrix. The first case represents external oxidation, and the other case is called internal oxidation. These processes are very important, because they determine the properties and applicability of metallic materials. Generally, they are undesired, because they cause deterioration of the mechanical properties and decomposition of metallic material. On the other side, the controlled process of external oxidation could be used for formation of protective coatings and the internal oxidation for dispersion strengthening of materials. In this paper we present monitoring of high-temperature oxidation of X12Cr13 stainless steel by in-situ electrical resistance measurements at different annealing temperatures in the air atmosphere. We determined the kinetics of oxide scale formation and its morphology with additional metallographic examination made by optical and scanning electron microscopy. The results of this research work show that in-situ monitoring and characterization of high-temperature oxidation present a strong tool that will contribute to a better fundamental understanding of the phenomena that occur during high-temperature oxidation of metallic materials.

This paper discusses the application of rapid solidification by the melt-spinning method for the preparation of thin NiTi-based ribbons. Generally, the application of rapid solidification via melt-spinning can change the microstructure, improving the ductility and shape memory characteristics and lead to small-dimensioned samples. Several thousand thermal cycles were performed on the trained ribbons using bending deformation procedure, continuously observing the changes in the shape memory and transformation behaviors. These changes are due to the appearance of an intermediate phase which was stabilized probably by the accumulation of defects introduced by thermomechanical training. The influence of training and thermal cycling on characteristics of ribbons was studied by x-ray diffraction and transmission electron microscopy and differential scanning calorimetry. The results displayed that bending training methods were useful in developing a two-way shape memory effect (TWSME). All samples show a shape memory effect immediately after processing without further heat treatment. The addition of copper in NiTi alloys was effective to narrow the transformation hysteresis. The W addition has improved the stability of the TWSME and mechanical properties. The TWSME of ribbons and its stability are well suited for important applications such as microsensors and microactuators.

In order to get small-dimensioned shape memory alloys (SMAs) with good functional and mechanical properties, a rapid solidification technique was employed. This paper discusses the use of different melt-spinning procedures for the preparation of proper thin NiTi ribbons. Metallographic characterization of SMAs is an important way to evaluate material properties, therefore the effect of alloy composition and different conditions of melt-spinning process (crucible, melting time and temperature) on the various inclusions and microstructure of NiTi alloys was investigated. Specimens for metallographic studies were cut from the longitudinal cross sections of melt-spun ribbons. The microstructures and different phases were examined by optical, scanning and transmission electron microscopy and the influence of the processing methods on microstructures of ribbons will be discussed.

NiTi alloys are the most technologically important medical Shape Memory Alloys in a wide range of applications used in Orthopaedics, Neurology, Cardiology and interventional Radiology as guide-wires, self-expandable stents, stent grafts, inferior vena cava filters and clinical instruments. This paper discusses the use of rapid solidification by the melt spinning method for the preparation of thin NiTi ribbons for medical uses. Generally, the application of rapid solidification via melt-spinning can change the microstructure drastically, which improves ductility and shape memory characteristics and leads to samples with small dimensions. As the increase in the wheel speed led to a reduced ribbon thickness, the cooling rate increased and, therefore, the martensitic substructure became finer. Furthermore, no transition from the crystalline phase to the amorphous phase was obtained by increasing the cooling rate, even at a wheel speed of 30 m/s. Specimens for our metallographic investigation were cut from the longitudinal cross sections of melt-spun ribbons. Conventional TEM studies were carried out with an acceleration voltage of 120 kV. Additionally, the chemical composition of the samples was examined with a TEM equipped with an EDX analyser. The crystallographic structure was determined using Bragg-Brentano x-ray diffraction with Cu-Kα radiation at room temperature.

The present work has been aimed to study the microstructures, functional properties and the influence of different thermomechanical training methods on the two-way shape memory effect in NiTi-based melt-spun ribbons. In order to get small-dimensioned shape memory alloys (SMAs) with good functional and mechanical properties, a rapid solidification technique was employed. Their fracture and elasticity characteristics have been determined, as well as shape memory properties by thermomechanical cycling. The ribbons were trained under tensile and bending deformation by thermal cycling through the phase transformation temperature range. The results displayed that all different training methods were effective in developing a two-way shape memory effect (TWSME). The influence of copper (5–25 at.% Cu) and tungsten (2 at.% W) on the microstructure, and the functional and mechanical behavior of NiTi thin ribbons was also investigated. All samples show a shape memory effect immediately after processing without further heat treatment. The melt-spun ribbons were trained under constant strain (bending and tensile deformation) by thermal cycling through the phase transformation temperature range. The addition of copper was effective to narrow the transformation hysteresis. The W addition has improved the TWSME stability of the NiTi alloys and mechanical properties. Results about microstructures, functional and mechanical properties will be presented.

Shape memory wires were trained under constant stress in order to introduce a uniaxial shape memory effect by a thermomechanical treatment. These investigations were carried out on three different alloy systems (NiTi, NiTiW and CuAlNi) with different microstructures (cold-worked and annealed condition, with and without particles, large and small grain size). Several thousand thermal cycles were performed on the trained shape memory elements, continuously observing the changes in the deformation behaviour. The influence of the microstructure on development and stability of the intrinsic two-way shape memory effect has been discussed. Furthermore, this work deals with the production of thin specimens of shape memory alloys by melt-spinning and splat-cooling, the training procedure and their characterization with respect to microstructure and functional properties.

Quenching rates, in terms of circumferential wheel speed in melt-spinning, play an important role in the resultant characteristics of the ribbons. In this study, the influence of various wheel speeds on ribbon dimensions, cross-sectional microstructures, and crystallographic phases within samples were investigated. The Ni-50.3at.%Ti melt-spun ribbons were produced under 200 mbar He atmosphere at wheel speeds of 5-30 ms−1 using a quartz crucible coated internally with Y2O3. The different wheel speeds led to different sample dimensions and cooling rates. The microstructures of the samples were observed using optical microscopy and TEM, while the shape memory effect of samples and the existing phases were studied by differential scanning calorimetry, x-ray diffraction, and tensile tests.

Carpal tunnel syndrome is the most common peripheral neuropathy. Conventional carpal tunnel surgery has been performed as a primary procedure for the decompression of the median nerve at the wrist in patients who have idiopathic carpal tunnel syndrome. While the results have been excellent, this surgical procedure has been reported to be related to high postoperative morbidity and extended length of recovery time. Over the past decade, endoscopic release of the transverse carpal ligament has been developed as a new, alternative method to the open procedures. Endoscopic carpal tunnel release has been reported to ensure less postoperative morbidity, more rapid recovery of strength, with earlier return to work, reduced disability time and a better cosmetic result. The authors present a surgical series of 200 hands in 164 patients (36 bilaterals) with idiopathic carpal tunnel syndrome, who underwent a single-portal endoscopic carpal tunnel release (Agee technique), with regards to the clinical outcome and complications occurred after 4-months follow-up.

The present work aims to study the influence of thermomechanical training and two-way shape memory effect (TWSME) on the transformation behaviour of Ni-50.3 at. % Ti melt-spun ribbons by differential scanning calorimetry (DSC). The results showed that the transformation temperatures decrease with an increase in the number of thermal cycles. The austenitic transformation remains a one-stage transformation, while the martensitic transformation changes to a two-stage transformation. These changes are due to the appearance of an intermediate phase which was stabilized probably by the accumulation of defects introduced by thermomechanical training. The phase that is present after training was studied by X-ray diffraction and transmission electron microscopy.

The aim of this work was to study the response of human peripheral blood mononuclear cells (PB-MNCs) to Cu-Al-Ni and Ni-Ti shape memory alloys (SMAs). The alloys were prepared as rapidly solidified thin ribbons via melt spinning. It has been shown that the ribbons were non cytotoxic for PB-MNCs as determined by the viability and apoptosis assay. In 18 cultures out of 20 cultures of individual donor PB-MNCs cultivated with Cu-Al-Ni SMAs, no significant changes in the production of Th1 (IFN-γ), Th2 (IL-5 and IL-10) and proinflammatory (IL-1s, TNF-α, IL-6 and IL-8) cytokines were detected compared to controls. In two cultures out of 20, a significant increase in the production of Th1 and proinflammatory cytokines was observed. Microstructural analyses confirmed the formation of thin oxide on the surface of both SMA ribbons.